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دسترسی آزاد مقاله
1 - The spatial damping of electrostatic wave in Hall thruster beam plasma
Saty Bharti Sukhmander SinghThe magnetohydrodynamics model is used to investigate the spatial damping in a Hall thruster beam plasma under the effect of thermal motion and electron beam density. Plasma dispersion equation is derived analytically using the normal mode analysis of the small oscillat چکیده کاملThe magnetohydrodynamics model is used to investigate the spatial damping in a Hall thruster beam plasma under the effect of thermal motion and electron beam density. Plasma dispersion equation is derived analytically using the normal mode analysis of the small oscillations. The dispersion equation is solved numerically to find out the damping modes in a Hall thrusters plasma. The damping length shows dependence on the radial magnetic field, beam density, ion density, electron drift velocity, collision frequency, electron and ion temperature. We investigated that the damping length increases with ion density and electron-ion temperature, whereas it decreases with the radial magnetic field, beam density, electron drift velocity and collision frequency. پرونده مقاله -
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2 - Bohm sheath criterion for electronegative warm plasma carrying seconadary electron emission in an oblique magnetic field
Yetendra Jha Mayank Kumar Hitendra K. MalikThe Bohm sheath criterion is formulated by using Sagdeev potential approach for electronegative warm plasma under oblique magnetic field and secondary electron emission from the wall. In this model the effect of collisions between positive ions and neutral, ionization, چکیده کاملThe Bohm sheath criterion is formulated by using Sagdeev potential approach for electronegative warm plasma under oblique magnetic field and secondary electron emission from the wall. In this model the effect of collisions between positive ions and neutral, ionization, electronegativity, non-extensivity and temperature ratio (positive/negative ion to electron) are also considered to get the exact behavior of velocity of positive ions at the edge of the sheath. Results are compared with the cases of collision-less, ionization-less and absence of electron emission from the wall and it is found that the Bohm velocity for this case is decreased faster with the increase of non-extensivity and the angle of inclination of the applied magnetic field. Also, Bohm velocity gets increased when the electric field at the edge of the sheath increases. Although Bohm velocity does not depend on the strength of the magnetic field, but the slope in the electrostatic potential gets increased and the sheath thickness decreased on raising the strength of the magnetic field. پرونده مقاله -
دسترسی آزاد مقاله
3 - Compressive solitons in a moving e-p plasma under the effect of dust grains and an external magnetic field
Rakhee Malik Hitendra K MalikAbstractA theoretical investigation concerning the propagation of compressive solitons in a plasma comprising electrons, positrons, and dust grains is presented by considering the dust grains of either positive charge or negative charge. Using reductive perturbation tec چکیده کاملAbstractA theoretical investigation concerning the propagation of compressive solitons in a plasma comprising electrons, positrons, and dust grains is presented by considering the dust grains of either positive charge or negative charge. Using reductive perturbation technique, a relevant Korteweg-deVries (KdV) equation is derived and then solved to obtain the expressions of amplitude and width of the solitons. The magnetic field is found to alter the dispersive property of the plasma, and hence, only the width of the solitons is reduced in the presence of higher magnetic field. Soliton amplitude is found to decrease/increase and the width to increase/decrease for the higher densities of negatively/positively charged dust grains. Moreover, the amplitude of such a soliton remains larger in the case of positively charged dust grains in comparison with the negatively charged dust grains. The effect of electron/positron drift velocities of the charged species is not pronounced on the properties of the compressive solitons. Under the limiting cases, our calculations reduce to the calculations by other investigators. This substantiates the generality of the present analysis. پرونده مقاله -
دسترسی آزاد مقاله
4 - Ultrasonic studies of ternary liquid mixtures of N-N-dimethylformamide, nitrobenzene, and cyclohexane at different frequencies at 318 K
Manoj Kumar Praharaj Abhiram Satapathy Prativarani Mishra Sarmistha MishraAbstractThe ultrasonic velocity, density, and viscosity have been measured for ternary mixtures of nitrobenzene, N,N-dimethylformamide, and cyclohexane at temperature T = 318 K at different frequencies such as 2, 4, 6, and 8 MHz. The experimental data have been used to چکیده کاملAbstractThe ultrasonic velocity, density, and viscosity have been measured for ternary mixtures of nitrobenzene, N,N-dimethylformamide, and cyclohexane at temperature T = 318 K at different frequencies such as 2, 4, 6, and 8 MHz. The experimental data have been used to calculate the acoustical and thermodynamical parameters like adiabatic compressibility, free length, free volume, internal pressure, acoustic impedance, Gibbs free energy, and their excess values. In particular, it is seen that the response of these parameters to frequency is less prominent in comparison to that of the ternary mixtures containing N,N-dimethylformamide, cyclohexane, and chlorobenzene. پرونده مقاله -
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5 - Dynamical and transport properties in plasmas including three-particle spatial correlations
Hakima Ababsa Med Tayeb Meftah Thouria ChohraAbstractIn this work, we study the two and triplet static correlation functions in plasma when the ions interact via the Debye screened potential and via the Deutsch screened potential. The latter takes into consideration the possible quantum effects at short distances. چکیده کاملAbstractIn this work, we study the two and triplet static correlation functions in plasma when the ions interact via the Debye screened potential and via the Deutsch screened potential. The latter takes into consideration the possible quantum effects at short distances. The ratio of the mean distance between two ions and the thermal De Broglie wavelength ri/λTdocumentclass[12pt]{minimal} usepackage{amsmath} usepackage{wasysym} usepackage{amsfonts} usepackage{amssymb} usepackage{amsbsy} usepackage{mathrsfs} usepackage{upgreek} setlength{oddsidemargin}{-69pt} egin{document}$$r_{i}/lambda_{mathrm{T}}$$end{document} gives the measure of these effects. Our investigation is developed in the conditions of weak coupling parameter (Γ پرونده مقاله -
دسترسی آزاد مقاله
6 - Study of electromagnetic solitons excited by different profile pulses
Aparna Sharma Hitendra K. Malik Harish KumarAbstractIn the present paper, we see the effect of shapes of perturbing pulses on the evolution of electromagnetic solitons in a plasma having nonrelativistic ions and electrons. For this, we make use of IMEX scheme in our simulations, which is an invariant scheme for t چکیده کاملAbstractIn the present paper, we see the effect of shapes of perturbing pulses on the evolution of electromagnetic solitons in a plasma having nonrelativistic ions and electrons. For this, we make use of IMEX scheme in our simulations, which is an invariant scheme for the two-fluid plasma flow equations. In particular, the impact of ion-to-electron mass ratio, electron-to-ion temperature ratio and the width of perturbing pulse is examined on the phase velocity, peak amplitude and width of the solitons. پرونده مقاله -
دسترسی آزاد مقاله
7 - تحلیل هیدرولیکی شبکه آبیاری بارانی با استفاده از نرم افزار WaterGEMS
یونس شکریان فرد شهرام شاه محمدی کلالقدر این تحقیق، شبکه آبیاری بارانی منطقه سیسان واقع در شهرستان بستان آباد استان آذربایجان شرقی با استفاده از نرم افزار WaterGEMS تحلیل هیدرولیکی گردید. این شبکه براساس موقعیت لوله های اصلی، نیمه اصلی و لترال ها به سه منطقه A، B و C تقسیم بندی شد. سپس با توجه به دور آبیاری چکیده کاملدر این تحقیق، شبکه آبیاری بارانی منطقه سیسان واقع در شهرستان بستان آباد استان آذربایجان شرقی با استفاده از نرم افزار WaterGEMS تحلیل هیدرولیکی گردید. این شبکه براساس موقعیت لوله های اصلی، نیمه اصلی و لترال ها به سه منطقه A، B و C تقسیم بندی شد. سپس با توجه به دور آبیاری، تعداد استقرار و آبپاش های شبکه، 9 سناریو تعریف شد. پارامترهای هیدرولیکی فشار و سرعت به ترتیب در گره ها و لوله ها قبل و بعد از بهینه سازی با نرم افزار WaterGEMS تحلیل شدند. نتایج تحلیل هیدرولیکی نشان داد؛ باتوجه به فشار مورد نیاز کارکرد آبپاش (40 مترآب) و فشار حداکثر تامین پمپ انتخابی شبکه (70 متر آب)، از نظر تامین فشار شبکه مشکلی یا محدودیتی وجود نداشت. به عبارتی، فشار در دامنه مجاز قرار داشت ولی با توجه به دامنه سرعت مجاز در خطوط اصلی و نیمه اصلی سیستم آبیاری بارانی، سرعتهای بحرانی در 4 سناریو در منطقه B و 5 سناریو در منطقه C مشاهده شدند. با اعمال تغییرات لازم در قطر لولهها و البته به شرط تغییرات مجاز در مقدار فشار (کمتر از 20 %)، مقادیر سرعت، بهینه شده و در دامنه مجاز قرار گرفتند. باتوجه به این که پارامترهای هیدرولیکی سامانه با کاهش در اندازه قطر لوله ها بهینه شدند، لذا سیستم طراحی شده بهینه با نرم افزار WaterGEMS، در مقایسه با سیستم طراحی و اجرا شده مورد مطالعه، منتج به کاهش 3/7 درصدی در هزینه های طرح گردید. پرونده مقاله -
دسترسی آزاد مقاله
8 - تأثیر تغییرات دما و سرعت هوا بر فرآیند خشک کردن بادام زمینی درخشک کن هوای داغ
محمد غلامی پرشکوهی الیاس مرزانژاد امیرحسین احمدبیگی مهرداد سلیمی بنیمقدمه: هدف اصلی خشک کردن تولیدات کشاورزی، کاهش محتوای رطوبت به سطحی ایمن برای رسیدن به حداکثر ماندگاری میباشد.پارامترهای دما و سرعت جابجایی هوای عوامل اصلی مؤثر در فرآیند خشک شدن محسوب میشود. مدل سازی ریاضی فرآیند خشککردن برای طراحی، بهبود سیستم های خشک کن موجود و حتی ک چکیده کاملمقدمه: هدف اصلی خشک کردن تولیدات کشاورزی، کاهش محتوای رطوبت به سطحی ایمن برای رسیدن به حداکثر ماندگاری میباشد.پارامترهای دما و سرعت جابجایی هوای عوامل اصلی مؤثر در فرآیند خشک شدن محسوب میشود. مدل سازی ریاضی فرآیند خشککردن برای طراحی، بهبود سیستم های خشک کن موجود و حتی کنترل فرآیند استفاده میشود.مواد و روشها: در این تحقیق تأثیر تغییرات دما ) 40 ، 50 ، 60 و 70 درجه سانتیگراد( و سرعت هوا ) 2 و 3 متر بر ثانیه( بر زمان و آهنگخشک شدن بادام زمینی با استفاده از خشک کن هوای داغ مورد بررسی قرار گرفت. تغییرات رطوبت در حین فرآیند خشک شدن تحتشرایط مختلف با مدلهای مختلف ریاضی شامل نیوتن، دوجملهای، میدیلی، پیج، پیج اصلاح شده و لگاریتمی برازش داده شد.یافتهها: پارامترهای دما و سرعت جابجایی هوا اثرات معنی داری بر روی زمان و آهنگ خشکشدن داشتند) 01 / 0P< .)نتیجهگیری: تاثیر دما بر فرآیند خشککردن بسیار زیاد بود به طوری که افزایش آن از 40 تا 70 درجه سانتی گراد موجب کاهش زمان تا8 / 67 درصد و افزایش آهنگ خشک شدن تا 109 درصد گردید. حداکثر تاثیر سرعت هوا برابر 3 / 37 درصد برای زمان خشک کردن و 9 / 20درصد برای آهنگ خشک شدن بود. تغییرات رطوبت در حین فرآیند خشک شدن به خوبی با مدل دوجملهای) 999 / 0 = R ( مطابقت نمود. پرونده مقاله -
دسترسی آزاد مقاله
9 - مقایسه عملکرد راکتورهای ایرلیفت جریان داخلی و خارجی جهت تصفیه آب به کمک لجن فعال
محمد علی صالحی نسرین حکیم قیاسیزمینه و هدف: در این تحقیق اثر شرایط عملیاتی و پارامترهای طراحی مانند شدت هوادهی، نسبت سطح ناودان به بالارونده و خصوصیات مایع بر هیدرودینامیک و ضریب حجمی انتقال جرم در راکتور های ایرلیفت سه فازی بررسی شده است. روش بررسی: . آزمایشها در راکتور ایرلیفت دارای حلقه خارجی با چکیده کاملزمینه و هدف: در این تحقیق اثر شرایط عملیاتی و پارامترهای طراحی مانند شدت هوادهی، نسبت سطح ناودان به بالارونده و خصوصیات مایع بر هیدرودینامیک و ضریب حجمی انتقال جرم در راکتور های ایرلیفت سه فازی بررسی شده است. روش بررسی: . آزمایشها در راکتور ایرلیفت دارای حلقه خارجی با نسبت سطح ناودان به بالارونده 14/0 و راکتور های ایرلیفت داخلی با نسبت سطح ناودان به بالارونده36/0 و 1 انجام شده است. هوا و آب به ترتیب به عنوان فاز گاز ومایع و و لجن فعال به عنوان فاز جامد استفاده شده اند. یافته ها: نتایج نشان داد سرعت چرخش مایع، نگهداشت گاز و ضریب حجمی انتقال جرم با افزایش سرعت حجمی گاز، کاهش غلظت لجن و کاهش نسبت سطح ناودان به بالا رونده، افزایش یافته است. بیشترین مقدار نگهداشت گازبرابر با 178/0 در راکتور ایرلیفت دارای حلقه خارجی با غلظت 1% وزنی لجن فعال در سرعت حجمی گاز 24/0 متر بر ثانیه مشاهده شد. مدلی برای پیش بینی اثر غلظت لجن فعال، سرعت حجمی گاز و نسب سطح ناودان به بالارونده بر انتقال جرم راکتور های ایرلیفت لجن فعال ارائه شده است که با نتایج تجربی تطابق خوبی دارند. بحث و نتیجه گیری: بهطورکلی بررسی عملکرد راکتورهای ایرلیفت داخلی و راکتورهای ایرلیفت دارای حلقه خارجی در شرایط مختلف غلظت و سرعت حجمی نشان داد راکتور ایرلیفت دارای حلقه خارجی دارای عملکردی بهتر در مقایسه با راکتور ایرلیفت داخلی است. پرونده مقاله -
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10 - بهینه سازی ورودی مخازن ته نشینی ثانویه مستطیلی شکل (مطالعه موردی: تصفیه خانه فاضلاب تهران)
اکبر اکبرپور حسن کیاده علیرضا مردوخ پورزمینه وهدف : یکی از مهمترین قسمتهای تصفیه خانه ها، مخازن رسوبگذار موجود در آنهاست که نقش مهمی را در تصفیه فاضلاب بر عهده دارد. با توجه به این موضوع، درک صحیح از رفتار مخارن رسوبگذار جهت طراحی و عملکرد مخارن امری ضروری است. بنابراین دور از تصور نیست که مهندسان به فکر طرا چکیده کاملزمینه وهدف : یکی از مهمترین قسمتهای تصفیه خانه ها، مخازن رسوبگذار موجود در آنهاست که نقش مهمی را در تصفیه فاضلاب بر عهده دارد. با توجه به این موضوع، درک صحیح از رفتار مخارن رسوبگذار جهت طراحی و عملکرد مخارن امری ضروری است. بنابراین دور از تصور نیست که مهندسان به فکر طراحی هرچه بهتر مخازن جدید و بهبود کارایی آنها هستند. جهت نیل به این اهداف، روش های مختلفی پیشنهاد شده است، که در میان آنها بهبود کارایی مخازن از طریق تغییر هندسه در مخزن نه تنها حائز اهمیت بوده بلکه جزء روش های اقتصادی بوده و نظر مهندسان را از جنبه های مختلف به خود جلب کرده است. هدف از پژوهش بررسی تأثیر تعداد ورودی های جریان بر راندمان هیدرولیکی در حوضچه های مستطیلی شکل رسوبگذار در تصفیه خانه فاضلاب بررسی تأثیر موقعیت و فاصله ورودی های جریان بر بازده هیدرولیکی در حوضچه های مستطیلی شکل رسوبگذار در تصفیه خانه فاضلاب استروش بررسی : مدل مورد مطالعه از روی تصفیه خانه موجود فاضلاب در تهران برداشته شده است. در مقاله پایه ورودی های مختلف جریان به حوضچه ترسیب تحلیل و با مقایسه راندمان ورودی های مختلف ورودی مشخصی به عنوان پیشنهاد ارائه شده است. در پژوهش حاضر از همان ورودی و مخزن استفاده شده است و با اضافه نمودن پارامتر رسوب به عنوان پارامتر جدید ، هیدرولیک و مشخصات جریان و رسوبگذاری در مخزن یاد شده مشخص شده است. مدل مورد مطالعه مخزن مستطیلی شکل با ابعاد 60 متر طول ، 7/13 متر عرض و 4/4 ارتفاع می باشد. به منظور مشاهده شیوه پخش مواد جامد معلق در طول فرآیند ته نشینی ، آب موجود در مخزن در شروع فرآیند بدون رسوب (زلال) می باشد و سپس با ورود فاضلاب حاوی مواد جامد معلق ، می توان شیوه انتشار مواد معلق و سپس ته نشینی مواد جامد را به صورت کامل مشاهده نمود. در مدل موجود در نقاط ورودی ، فواصل 10 ، 20 و ... تا 60 (سرریز خروجی) با ایجاد سنسورهای مجازی اندازه گیری پارامترهای جریان استفاده گردید تا نمودارهای مقایسه ای تولید و تحلیل گردند.این تحقیق در خرداد ماه سال 1400 انجام شده است.یافته ها: یافته ها بیانگر آن است که زمان تحلیل مطابق با زمان ماند آیین نامه 6500 ثانیه می باشد که در محدوده حدود 800 تا 1000 ثانیه از تحلیل(16 دقیقه) شرایط جریان و حرکت رسوبات به تعادل رسیده و تا انتهای زمان ماند ثابت می باشدبحث و نتیجه گیری : نتایج نشان می دهد که بیشترین انرژی آشفتگی در محل سرریز خروجی با فاصله 10 متری از ورودی می باشد که دلیل آن جریان گردابی و چرخشی در این محدوده است. با حرکت به سمت پایین دست جریان آشفتگی کاهش یافته و در نقطه 10 متری از خروجی نزدیک به صفر می باشد که نشان دهنده عملکرد درست مخزن است. پرونده مقاله -
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11 - Magnetic fluid lubrication of porous pivoted slider bearing with slip and squeeze velocity
Rajesh C. Shah Dilip B. PatelIn this paper the problem on “Magnetic fluid lubrication of porous-pivoted slider bearing with slip velocity by N Ahmad et.al.[7]” has been recapitulated using Jenkin’s model [4] with the additional effect of squeeze velocity of the above plate. It is چکیده کاملIn this paper the problem on “Magnetic fluid lubrication of porous-pivoted slider bearing with slip velocity by N Ahmad et.al.[7]” has been recapitulated using Jenkin’s model [4] with the additional effect of squeeze velocity of the above plate. It is found that while discussing the above problem, [7] has stated but ignored the term , where+, in their study (Refer equation(2.2)). This paper reconsiders the above neglected term with , where . Since is the corotational derivative of magnetization vector, so it has an impact on the performance of the problem [9]. With the addition of the above term and under an oblique magnetic field, it is found that the dimensionless load carrying capacity can be improved substantially with and without squeeze effect. The paper also studied in detail about the effects of squeeze velocity and sliding velocity. It is observed that dimensionless load carrying capacity increases when squeeze velocity increases and sliding velocity decreases. پرونده مقاله -
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12 - Investigation on Hot Tearing Susceptibility of A201 Aluminum Alloy in Different Ingate Velocities and Molds
M. H Ayandeh A. A Kashi M. Ghambarian H. Karimi A. Mootabha A. Khoyini E.M. BoushehriIn this research, Hot tearing Behavior and susceptibility of the Al-Cu A201 aluminum alloy in different mold has been investigated. There are a lot of methods that used for hot tear tests but between all of these methods that proposed for this kind of the tests, The Rin چکیده کاملIn this research, Hot tearing Behavior and susceptibility of the Al-Cu A201 aluminum alloy in different mold has been investigated. There are a lot of methods that used for hot tear tests but between all of these methods that proposed for this kind of the tests, The Ring model was employed for testing the hot tearing tendency. In order to increase the investigated parameters, wooden model designated to support different ingate velocities. Some samples that exposed to the Hot Tear were inspected by visual and NDT (None destructive) tests followed by Scanning Electron Microscopy (SEM) to study of the teared surface of the samples. The extracted results show that the number and severity of tears increased by changing the strength of mold from green sand to CO2 sand. The evaluation of the experimental results in this study showed that these results is in good agreement with the other obtained by another researchers پرونده مقاله -
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13 - Investigation on the Simultaneous Effects of Zn Additions and Critical Ingate Velocity on the Hot Tearing Susceptibility of A356 and A206 Aluminum Alloys
M. Ghambarian S.M.A. Boutorabi F. ShahriIn this study, the simultaneous effects of Zn addition and critical gate velocity on hot tearing susceptibility of A356 and A206 aluminum alloys were investigated. In order to investigate these two parameters, ingate velocities of 0.5, 0.75, 1, 1.5 m/s were taken into a چکیده کاملIn this study, the simultaneous effects of Zn addition and critical gate velocity on hot tearing susceptibility of A356 and A206 aluminum alloys were investigated. In order to investigate these two parameters, ingate velocities of 0.5, 0.75, 1, 1.5 m/s were taken into account. After performing the casting process, the samples were investigated by visual examination, and scanning electron microscopy. In order to quantitative evaluation of results, ProCast software were used. The results of the present study showed that increasing the Zn content for alloy A356, had no effect on hot tearing susceptibility of this alloy, while with increasing the Zn content from 0.01 to 2.8 wt%, the number and severity of the tears were increased. پرونده مقاله -
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14 - Effect of Injection Velocity on Heat Transfer of Water/Alumina Nano Fluid in A Rectangular Microchannel
Afshin Ahmadi Nadooshan Afshin Shiriny Morteza BayarehIn this study, forced convection heat transfer of water/alumina Nano fluid in a rectangular microchannel with cross-flow injection is studied. The Nano fluid enters the microchannel with a temperature of 293 K and cools its walls. The upper wall of the microchannel is a چکیده کاملIn this study, forced convection heat transfer of water/alumina Nano fluid in a rectangular microchannel with cross-flow injection is studied. The Nano fluid enters the microchannel with a temperature of 293 K and cools its walls. The upper wall of the microchannel is at constant temperature of 303 K. On the lower wall, there are two holes for injection of Nano fluid flow. Other parts of the microchannel wall are insulated. Slip velocity boundary condition is used for the walls of the microchannel. Simulations are performed for different injection velocities and the results are presented as velocity and temperature fields, and variation of the Nusselt number. The results show that the slip velocity on the channel wall and the Nusselt number increase by increasing the injection velocity. It is revealed that the Nusselt number is maximum at the channel entrance and decreases along the channel. After each injection, local Nusselt number increases due to the increase of the temperature gradient in the microchannel. Moreover, an optimal value for the ratio of the injection velocity to the inlet velocity is achieved using performance evaluation criteria (PEC). It is concluded that is an optimal value of the injection velocity, leading to maximum PEC. پرونده مقاله -
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15 - Fuzzy-GSA Based Control Approach for Developing Adaptive Cruise Control
M. BostanianAdaptive Cruise Control (ACC) controls vehicle speed and its distance to the proceeding vehicle in the same lane. In this paper a two-level control architecture is proposed to control both velocity and distance to the leading vehicle by taking advantage of fuzzy logic c چکیده کاملAdaptive Cruise Control (ACC) controls vehicle speed and its distance to the proceeding vehicle in the same lane. In this paper a two-level control architecture is proposed to control both velocity and distance to the leading vehicle by taking advantage of fuzzy logic control (FLC) approach. Then the control parameters were tuned by Gravitational Search Algorithm (GSA) to ensure achieving the fastest and most accurate control response. To evaluate performance of the proposed scheme, a speed profile was developed in simulation based test platform to measure performance of the proposed ACC in different maneuvers including some velocity tests and a distance control maneuver. The results revealed that the proposed approach had a stable and fast response which satisfied the requirements of an ACC. پرونده مقاله -
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16 - High-Velocity Compaction of Aluminum Powder by Gas Detonation Forming Technique
Tohid Mirzababaie Mostofi Mostafa Sayah Badkhor Hashem BabaeiIn this paper, a large-scale experimental study has been conducted in order to evaluate the high-velocity compaction of aluminum powder using Gas Detonation Forming (GDF) processing technique. In this series of experiments, the effect of the distribution of grain partic چکیده کاملIn this paper, a large-scale experimental study has been conducted in order to evaluate the high-velocity compaction of aluminum powder using Gas Detonation Forming (GDF) processing technique. In this series of experiments, the effect of the distribution of grain particle size, initial powder mass, and loading conditions on green density and strength of compacted products were thoroughly studied. The maximum relative green density and green strength of 97.6% and 17.9% were achieved. Group Method of Data Handling (GMDH)-type neural network in conjunction with Singular Value Decomposition (SVD) method was exerted to model the high-velocity compaction process of aluminum powder. The main objective of this idea is to demonstrate how two characteristics of the high-velocity compaction, namely, the relative green density and strength of products vary with the changing of significant parameters, involved in GDF processing technique. پرونده مقاله -
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17 - Effect of using a Dynamic Absorber On Vibrations of an Opposed-Piston Ultralight Aircraft Engine
Mohammad Reza Najafi Saied Mahjoub Moghadas Mojtaba MoradiIn this paper, vibrations reduction of piston engine of ultralight aircrafts was studied with considering a combination of experimental, analytical and numerical methods. Analytical equations of dynamic absorber were obtained. Afterward, experimental test was used to de چکیده کاملIn this paper, vibrations reduction of piston engine of ultralight aircrafts was studied with considering a combination of experimental, analytical and numerical methods. Analytical equations of dynamic absorber were obtained. Afterward, experimental test was used to determine the system torque. Due to the difficulty of obtaining experimental data, the amount of angular acceleration and then velocity and angular displacement were calculated numerically using MATLAB software and verified with experimental results with a difference of less than 2%. Different components of the system were designed with reverse engineering method using SolidWorks software. After data transmission to Adams software, vibrational analysis of the system was performed and validated with analytical results with a difference of less than 1.91%. A suitable dynamic absorber was selected. The results showed that engine vibrations is reduced up to 40%. پرونده مقاله -
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18 - Non-Destructive Assessment of Concrete Quality Produced with Riverbed Sand and Drainage Sand as Fine Aggregates
Aderemi__A__Alabi Alabi Ayobami__Eniola__Agboola Agboola Joseph__Olawale__Akinyele Akinyele Victor MakindeIn this work, the effect of fine aggregates from two different sources on the quality and strength of concrete was determined using UPV measurements. The concrete samples were produced using a nominal mix ratio of 1: 1½: 3 and water-cement ratio of 0.55, with three diff چکیده کاملIn this work, the effect of fine aggregates from two different sources on the quality and strength of concrete was determined using UPV measurements. The concrete samples were produced using a nominal mix ratio of 1: 1½: 3 and water-cement ratio of 0.55, with three different aggregate sizes (3/8, ½ and ¾ inches) of granite mixed separately with sand obtained from Ogun river and a local drainage in Abeokuta, Southwestern, Nigeria. UPV was measured through each sample on days 1, 7, 14, 21 and 28 after curing using Pundit lab+ equipment. Comparison of the actual compressive strength and estimated compressive strengths from equations generated for each sample type using the crushed samples on the 7th and 28th days respectively shows that most estimations were within the acceptable ±20% variation. Results show that there is no significant difference between the samples made from using either of the two fine aggregates. پرونده مقاله -
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19 - An Analytic Study on the Dispersion of Love Wave Propagation in Double Layers Lying Over Inhomogeneous Half-Space
A Mandi S Kundu P Chandra Pal P PatiIn this work, attempts are made to study the dispersion of Love waves in dry sandy layer sandwiched between fiber reinforced layer and inhomogeneous half space.Inhomogeneity in half space associated with density and rigidity and considered in exponential form. Displacem چکیده کاملIn this work, attempts are made to study the dispersion of Love waves in dry sandy layer sandwiched between fiber reinforced layer and inhomogeneous half space.Inhomogeneity in half space associated with density and rigidity and considered in exponential form. Displacement components for fiber reinforced layer, dry sandy layer and inhomogeneous half-space have been obtained by using method of separable variables. Boundary conditions are defined at the free surface of the fiber reinforced layer and at the interfaces between layers and half space. The dispersion equation has derived in closed form. Numerical calculations for dispersion equation are performed. The study results show the effect of parameters on the velocity of Love waves and presented graphically. Graphs are plotted between wave number and phase velocity to show the effect of reinforced parameter, sandiness parameter and inhomogeneity on the phase velocity of Love waves. From the graphs it can be concluded that phase velocity decreases with respect to wave number. پرونده مقاله -
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20 - Study of Love Waves in a Clamped Viscoelastic Medium with Irregular Boundaries
P Alam M.K SinghA mathematical model is presented to investigate the effects of sandiness, irregular boundary interfaces, heterogeneity and viscoelasticity on the phase velocity of Love waves. Geometry of the problem is consisting of an initially stressed viscoelastic layer with corrug چکیده کاملA mathematical model is presented to investigate the effects of sandiness, irregular boundary interfaces, heterogeneity and viscoelasticity on the phase velocity of Love waves. Geometry of the problem is consisting of an initially stressed viscoelastic layer with corrugated irregular boundaries, which is sandwiched between heterogeneous orthotropic semi-infinite half-space with initial stress and pre-stressed dry sandy half-space. Heterogeneity arises in the upper half-space is due to trigonometric variation in elastic parameters of the orthotropic medium. Inclusion of the concept of corrugated irregular viscoelastic layer clamped between two dissimilar half-spaces under different physical circumstances such as initial stress and heterogeneity brings a novelty to the existing literature related to the study of Love wave. Dispersion equation for Love wave is obtained in closed form. The obtained dispersion relation is found to be in well agreement with classical Love wave equation. Numerical example and graphical illustrations are made to demonstrate notable effect of initial stress, internal friction, wave number and amplitude of corrugations on the phase velocity of Love waves. پرونده مقاله -
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21 - Rigidity and Irregularity Effect on Surface Wave Propagation in a Fluid Saturated Porous Layer
R.K Poonia D.K Madan V KaliramanThe propagation of surface waves in a fluid- saturated porous isotropic layer over a semi-infinite homogeneous elastic medium with an irregularity for free and rigid interfaces have been studied. The rectangular irregularity has been taken in the half-space. The dispers چکیده کاملThe propagation of surface waves in a fluid- saturated porous isotropic layer over a semi-infinite homogeneous elastic medium with an irregularity for free and rigid interfaces have been studied. The rectangular irregularity has been taken in the half-space. The dispersion equation for Love waves is derived by simple mathematical techniques followed by Fourier transformations. It can be seen that the phase velocity is strongly influenced by the wave number, the depth of the irregularity, homogeneity parameter and the rigid boundary. The dimensionless phase velocity is plotted against dimensionless wave number graphically for different size of rectangular irregularities and homogeneity parameter with the help of MATLAB graphical routines for both free and rigid boundaries for several cases. The numerical analysis of dispersion equation indicates that the phase velocity of surface waves decreases with the increase in dimensionless wave number. The obtained results can be useful to the study of geophysical prospecting and understanding the cause and estimating of damage due to earthquakes. پرونده مقاله -
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22 - The Effects of Initial In-Plane Loads on the Response of Composite-Sandwich Plates Subjected to Low Velocity Impact: Using a New Systematic Iterative Analytical Process
K Malekzadeh Fard A AzarniaA new systematic iterative analytical procedure is presented to predict the dynamic response of composite sandwich plates subjected to low-velocity impact phenomenon with/without initial in-plane forces. In this method, the interaction between indenter and sandwich pane چکیده کاملA new systematic iterative analytical procedure is presented to predict the dynamic response of composite sandwich plates subjected to low-velocity impact phenomenon with/without initial in-plane forces. In this method, the interaction between indenter and sandwich panel is modeled with considering the exponential equation similar to the Hertzian contact law and using the principle of minimum potential energy and the energy-balance model. In accordance with the mentioned procedure and considering initial in-plane forces, the unknown coefficients of the exponential equation are obtained analytically. Accordingly, the traditional Hertzian contact law is modified for use in the composite sandwich panel with the flexible core under biaxial pre-stresses. The maximum contact force using the two-degrees-of-freedom (2DOF) spring-mass model is calculated through an iterative systematic analytical process. Using the present method, in addition to reducing the runtime, the problem-solving process is carried out with appropriate convergence. The numerical results of the analysis are compared with the published experimental and theoretical results. The effects of some important geometrical and physical parameters on contact force history are examined in details. پرونده مقاله -
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23 - Axially Symmetric Vibrations of a Liquid-Filled Poroelastic Thin Cylinder Saturated with Two Immiscible Liquids Surrounded by a Liquid
B Sandhyarani J Anand Rao P Malla ReddyThis paper studies axially symmetric vibrations of a liquid-filled poroelastic thin cylinder saturated with two immiscible liquids of infinite extent that is surrounded by an inviscid elastic liquid. By considering the stress free boundaries, the frequency equation is o چکیده کاملThis paper studies axially symmetric vibrations of a liquid-filled poroelastic thin cylinder saturated with two immiscible liquids of infinite extent that is surrounded by an inviscid elastic liquid. By considering the stress free boundaries, the frequency equation is obtained. Particular case, namely, liquid-filled poroelastic cylinder saturated with single liquid is discussed. When the wavenumber is large, the frequency equation is reduced to that of Rayleigh-type surface wave at the plane boundary of a poroelastic half-space. In this case, the asymptotic expressions of Bessel functions and modified Bessel functions are used. In both general and particular cases, the case of the propagation of Rayleigh waves in a poroelastic half-space is obtained. The parameter values of Columbia fine sandy loam saturated with air-water mixture are used for the numerical evaluation. In all the cases, phase velocity as a function of wavenumber is computed and presented graphically. From the numerical results, some inferences are drawn. پرونده مقاله -
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24 - Effect of Micropolarity on the Propagation of Shear Waves in a Piezoelectric Layered Structure
R Kumar K Singh D.S PathaniaThis paper studies the propagation of shear waves in a composite structure consisting of a piezoelectric layer perfectly bonded over a micropolar elastic half space. The general dispersion equations for the existence of shear waves are obtained analytically in the close چکیده کاملThis paper studies the propagation of shear waves in a composite structure consisting of a piezoelectric layer perfectly bonded over a micropolar elastic half space. The general dispersion equations for the existence of shear waves are obtained analytically in the closed form. Some particular cases have been discussed and in one special case the relation obtained is in agreement with existing results of the classical –Love wave equation. The micropolar and piezoelectric effects on the phase velocity are obtained for electrically open and mechanically free structure. To illustrate the utility of the problem numerical computations are carried out by considering PZT-4 as a piezoelectric and aluminium epoxy as micropolar elastic material. It is observed that the micropolarity present in the half space influence the phase velocity significantly in a particular region. The micropolar effects on the phase velocity in the piezoelectric coupled structure can be used to design high performance acoustic wave devices. پرونده مقاله -
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25 - Study of Torsional Vibrations of Composite Poroelastic Spherical Shell-Biot’s Extension Theory
R Gurijala M Reddy PeratiTorsional vibrations of composite poroelastic dissipative spherical shell are investigated in the framework of Biot’s extension theory.Here composite poroelastic spherical shell consists of two spherical shells, one is placed on other, and both are made of differe چکیده کاملTorsional vibrations of composite poroelastic dissipative spherical shell are investigated in the framework of Biot’s extension theory.Here composite poroelastic spherical shell consists of two spherical shells, one is placed on other, and both are made of different poroelastic materials. Consideration of the stress-free boundaries of outer surface and the perfect bonding between two shells leads to complex valued frequency equation. Limiting case when the ratio of thickness to inner radius is very small is investigated numerically. In this case, thick walled composite spherical shell reduces to thin composite spherical shell. For illustration purpose, four composite materials, namely, Berea sandstone saturated with water and kerosene, Shale rock saturated with water and kerosene are employed. The particular cases of a poroelastic solid spherical shell and poroelastic thick walled hollow spherical shell are discussed. If the shear viscosity of fluid is neglected, then the problem reduces to that of classical Biot’s theory. Phase velocity and attenuation are computed and the results are presented graphically. Comparison is made between the results of Biot’s extension theory and that of classical Biot’s theory. It is conclude that shear viscosity of fluid is causing the discrepancy of the numerical results. پرونده مقاله -
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26 - Assessment of Different Mathematical Models for Analysis of Low-Velocity Impact on Composite Plates in Presence of Pre-loads
A Davar A Labbafian Mashhadi J Eskandari Jam M Heydari BeniIn this paper, the low-velocity impact response of composite plates in the presence of pre-loads is investigated using three new models for contact force estimation. The boundary conditions are considered as simply supported and the behavior of the material is linear el چکیده کاملIn this paper, the low-velocity impact response of composite plates in the presence of pre-loads is investigated using three new models for contact force estimation. The boundary conditions are considered as simply supported and the behavior of the material is linear elastic. The equations are based on both classical and first order shear deformation theory and the Fourier series method is used to solve the governing equations. The mass of the impactor is considered to be large mass and therefore the impact response is categorized as quasi-static. In the first impact model, the contact force history is first considered as a half-sine and then the maximum contact force and contact duration are calculated. In the second model, an improved two degree of freedom (ITDOF) spring-mass system is expressed by calculating the effective contact stiffness using a fast-iterative scheme. In the third model, which is expressed for the first time in this paper, the plate is considered as a series of masses and springs constructing a multi degree of freedom (MDOF) spring-mass system and the average forces applied to springs is introduced as the contact force. Validation of these models is done by comparing the results with the analytical, numerical and experimental results and shows good agreement. Results show that the new MDOF spring-mass system is more accurate for calculating the contact force rather than the ITDOF spring-mass system. پرونده مقاله -
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27 - Experimental and Numerical Investigations of the Effect of Impact Angle and Impactor Geometry on the High-Velocity Impact Response of Aluminum Honeycomb Structures
H Alikhani S Derakhshan H KhoramishadIn this study, the effects of impact angle and impactor geometry were investigated on the impact behavior of aluminum honeycombs experimentally and numerically. The high-velocity impact tests were carried out using a gas-gun test machine with flat, spherical and conical چکیده کاملIn this study, the effects of impact angle and impactor geometry were investigated on the impact behavior of aluminum honeycombs experimentally and numerically. The high-velocity impact tests were carried out using a gas-gun test machine with flat, spherical and conical-head impactors and impact angles of 0°, 15° and 30° at different incident velocities ranging from 55.8 to 150.5 m/s. The numerical models were developed in LS-Dyna finite element code and well validated against the experimental results. The results showed that the impact behavior of honeycombs is considerably dependent on the impactor head geometry and the impact angle. The honeycomb panel impacted by the conical projectile experienced the highest absorbed energy and ballistic limit velocity. Moreover, it was found out that increasing the impact angle increased the absorbed energy and ballistic limit velocity of honeycombs. Furthermore, different impactor head geometries resulted in different failure mechanisms in the course of impact loading. پرونده مقاله -
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28 - Vibration and Stability Analysis of Composite Tube Conveying Fluid Flow Equipped with Piezoelectric Ring
M Nazarzadeh Ansarodi H Biglari M.R SavizIn this paper, dynamic behaviour of composite tube equipped with piezoelectric actuator ring and conveying fluid flow is studied. The effects of incompressible Newtonian internal fluid flow with constant velocity are considered. The stiffened composite shell with differ چکیده کاملIn this paper, dynamic behaviour of composite tube equipped with piezoelectric actuator ring and conveying fluid flow is studied. The effects of incompressible Newtonian internal fluid flow with constant velocity are considered. The stiffened composite shell with different boundary conditions is exposed to electro- mechanical loading. The governing equations of motion are obtained based on the classical shell theory and using Hamilton’s principle. Then, these equations are discretized by using differential quadrature (DQ) method in longitudinal direction and harmonic differential quadrature (HDQ) method in circumferential direction. Solving these equations results in eigenvalues and mode shapes of the smart pipe conveying fluid. After comparing results with those existing in the literature, the detailed parametric study is conducted, by concentrating on the effects of fluid flow properties, geometry, material and boundary conditions of composite pipe, temperature, and piezo-actuator ring (size and position) on the vibration behavior of the coupled system, as well as dimensionless critical fluid velocity. It is expected that stability of the coupled system strongly depends on the imposed electric load. The present study can be applied for optimum design of sensors and actuators in active control systems, MEMS and biomechanical applications. پرونده مقاله -
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29 - Analytical and Numerical Investigation of Energy Absorption in Graded Aluminum Open Cell Foam under Low Velocity Impact Loading
S Davari S. A Galehdari A AtrianGiven the significance of energy absorption in various industries, light shock absorbers such as structures made of metal foam have been considered. In this study, analytical equation of plateau stress is presented for an open cell foam based on the Gibson-Ashby model, چکیده کاملGiven the significance of energy absorption in various industries, light shock absorbers such as structures made of metal foam have been considered. In this study, analytical equation of plateau stress is presented for an open cell foam based on the Gibson-Ashby model, which follows elastic perfectly plastic behavior. For comparison of acquired analytical equations, the problem for a cell and then for three cells that make up an aluminum open cell foam is simulated in ABAQUS/CAE. Using the stress strain diagram, plateau stress and densification strain equations, the specific energy absorbed of the open cell metal foam is extracted. The capacity of absorb energy for an aluminum open cell foam with three cell is obtained once using analytical equations and again by using numerical simulation in ABAQUS/CAE. Numerical results retain an acceptable accordance with analytical equations with less than 3% occurred error for absorbed energy. To ensure the accuracy of numerical simulation, the results of simulating are compared with the results of the simulation of the same foam in a reference whose accuracy is verified by the experiment. Based on the results, the effective cross-sectional area of the foam with Gibson-Ashby cell does not follow the cross-sectional that is used for the calculation of plateau stress in adsorbent structures. Then tow equations are extracted to calculate the effective cross-sectional area and the transfer force. Applying sequential quadratic programming method (SQP) and genetic algorithm (GA), to design a graded metal foam with high specific Energy absorption. پرونده مقاله -
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30 - Effect of Rotation and Stiffness on Surface Wave Propagation in a Elastic Layer Lying Over a Generalized Thermodiffusive Elastic Half-Space with Imperfect Boundary
R Kumar V ChawlaThe present investigation is to study the surface waves propagation with imperfect boundary between an isotropic elastic layer of finite thickness and a homogenous isotropic thermodiffusive elastic half- space with rotation in the context of Green-Lindsay (G-L model) th چکیده کاملThe present investigation is to study the surface waves propagation with imperfect boundary between an isotropic elastic layer of finite thickness and a homogenous isotropic thermodiffusive elastic half- space with rotation in the context of Green-Lindsay (G-L model) theory. The secular equation for surface waves in compact form is derived after developing the mathematical model. The phase velocity and attenuation coefficient are obtained for stiffness and then deduced for normal stiffness, tangential stiffness and welded contact. The dispersion curves for these quantities are illustrated to depict the effect of stiffness and thermal relaxation times. The amplitudes of displacements, temperature and concentration are computed at the free plane boundary. Specific loss of energy is obtained and presented graphically. The effects of rotation on phase velocity, attenuation coefficient and amplitudes of displacements, temperature change and concentration are depicted graphically. Some Special cases of interest are also deduced and compared with known results. پرونده مقاله -
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31 - Effect of Initial Stress on Propagation of Love Waves in an Anisotropic Porous Layer
S Gupta A Chattopadhyay D.K MajhiIn the present paper, effect of initial stresses on the propagation of Love waves has been investigated in a fluid saturated, anisotropic, porous layer lying in welded contact over a prestressed, non-homogeneous elastic half space. The dispersion equation of phase veloc چکیده کاملIn the present paper, effect of initial stresses on the propagation of Love waves has been investigated in a fluid saturated, anisotropic, porous layer lying in welded contact over a prestressed, non-homogeneous elastic half space. The dispersion equation of phase velocity has been derived. It has been found that the phase velocity of Love waves is considerably influenced by porosity and anisotropy of the porous layer, inhomogeneity of the half-space and prestressing present in the media, the layer and the half-space. The effect of the medium characteristics on the propagation of Love waves has been discussed and results of numerical calculations have been presented graphically. پرونده مقاله -
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32 - Analysis of Plane Waves in Anisotropic Magneto-Piezothermoelastic Diffusive Body with Fractional Order Derivative
R Kumar P SharmaIn this paper the propagation of harmonic plane waves in a homogeneous anisotropic magneto-piezothermoelastic diffusive body with fractional order derivative is studied. The governing equations for a homogeneous transversely isotropic body in the context of the theory o چکیده کاملIn this paper the propagation of harmonic plane waves in a homogeneous anisotropic magneto-piezothermoelastic diffusive body with fractional order derivative is studied. The governing equations for a homogeneous transversely isotropic body in the context of the theory of thermoelasticity with diffusion given by Sherief et al. [1] are considered as a special case. It is found that three types of waves propagate in one dimension anisotropic magneto-piezothermoelastic diffusive body, namely quasi-longitudinal wave (QP), quasi-thermal wave (QT) and quasi-diffusion wave (QD). The different characteristics of waves like phase velocity, attenuation coefficient, specific heat loss and penetration depth are computed numerically and presented graphically for Cadmium Selenide (CdSe) material. The effect of fractional order parameter on phase velocity, attenuation coefficient, specific heat loss and penetration depth has been studied. پرونده مقاله -
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33 - Wave Propagation in a Layer of Binary Mixture of Elastic Solids
R Kumar M PanchalThis paper concentrates on the propagation of waves in a layer of binary mixture of elastic solids subjected to stress free boundaries. Secular equations for the layer corresponding to symmetric and antisymmetric wave modes are derived in completely separate terms. The چکیده کاملThis paper concentrates on the propagation of waves in a layer of binary mixture of elastic solids subjected to stress free boundaries. Secular equations for the layer corresponding to symmetric and antisymmetric wave modes are derived in completely separate terms. The amplitudes of displacement components and specific loss for both symmetric and antisymmetric modes are obtained. The effect of mixtures on phase velocity, attenuation coefficient, specific loss and amplitude ratios for symmetric and antisymmetric modes is depicted graphically. A particular case of interest is also deduced from the present investigation. پرونده مقاله -
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34 - Nonlinear Finite Element Eccentric Low-Velocity Impact Analysis of Rectangular Laminated Composite Plates Subjected to In-phase/Anti-phase Biaxial Preloads
M Shariyat M Moradi S SamaeeAll impact analyses performed so far for the composite plates, have treated central impacts. Furthermore, investigations on influences of the in-plane biaxial compression, tension, or tension-compression preloads on various responses of the low-velocity impact, especial چکیده کاملAll impact analyses performed so far for the composite plates, have treated central impacts. Furthermore, investigations on influences of the in-plane biaxial compression, tension, or tension-compression preloads on various responses of the low-velocity impact, especially the indentation, have not been performed so far. In the present research, a finite element formulation is presented for response prediction of a low-velocity eccentric impact between a rigid spherical indenter and a laminated composite rectangular plate with asymmetric lamination scheme. Different contact laws are considered for the loading and unloading phases. A parametric study is performed to investigate influence of the specifications of the plates and the indenter, the eccentric value, and the in-plane preloads on the indentation and force time histories. Results show that the compressive and tensile in-plane preloads reduce and increase the contact force (and consequently, the indentation values), respectively. Therefore, the extensive tensile preloads may lead to higher damages. پرونده مقاله -
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35 - Torsional Surface Wave Propagation in Anisotropic Layer Sandwiched Between Heterogeneous Half-Space
P.K Vaishnav S Kundu S.M Abo-Dahab A SahaThe present paper studies the possibility of propagation of torsional surface waves in an inhomogeneous anisotropic layer lying between two heterogeneous half-spaces (upper and lower half-space). Both the half-spaces are assumed to be under compressive initial stress. T چکیده کاملThe present paper studies the possibility of propagation of torsional surface waves in an inhomogeneous anisotropic layer lying between two heterogeneous half-spaces (upper and lower half-space). Both the half-spaces are assumed to be under compressive initial stress. The study reveals that under the assumed conditions, a torsional surface wave propagates in the medium. The dispersion relation of torsional surface wave has been obtained in the presence of heterogeneity, initial stress and anisotropic, and it is observed that the inhomogeneity factor due to quadratic and hyperbolic variations in rigidity, density and initial stress of the medium decreases the phase velocity as it increases. The result also shows that the initial stresses have a pronounced influence on the propagation of torsional surface waves. In the absence of anisotropy, Initial stress, inhomogeneity and rigidity of the upper half-space, then the dispersion relation coincide with the classical dispersion relation of Love wave. پرونده مقاله -
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36 - Dynamic Fracture Analysis Using an Uncoupled Arbitrary Lagrangian Eulerian Finite Element Formulation
A.R Shahani M.R AminiThis paper deals with the implementation of an efficient Arbitrary Lagrangian Eulerian (ALE) formulation for the three dimensional finite element modeling of mode I self-similar dynamic fracture process. Contrary to the remeshing technique, the presented algorithm can c چکیده کاملThis paper deals with the implementation of an efficient Arbitrary Lagrangian Eulerian (ALE) formulation for the three dimensional finite element modeling of mode I self-similar dynamic fracture process. Contrary to the remeshing technique, the presented algorithm can continuously advance the crack with the one mesh topology. The uncoupled approach is employed to treat the equations. So, each time step is split into two phases: an updated Lagrangian phase followed by an Eulerian phase. The implicit time integration method is applied for solving the transient problem in Lagrangian phase with no convective effects. A mesh motion scheme, in which the related equations need not to be solved at every time step, is proposed in Eulerian phase. The critical dynamic stress intensity factor criterion is used to determine the crack velocity. The variation of dynamic stress intensity factor along the crack front is also studied based on the interaction integral method. The proposed algorithm is applied to investigate the dynamic crack propagation in the DCB specimen subjected to fixed displacement. The predicted results are compared with the experimental study cited in the literature and a good agreement is shown. The proposed algorithm leads to the accurate and efficient analysis of dynamic crack propagation process. پرونده مقاله -
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37 - Free Vibration Analysis of Micropolar Thermoelastic Cylindrical Curved Plate in Circumferential Direction
G Partap R KumarThe free vibration analysis ofhomogeneous isotropic micropolar thermoelastic cylindrical curved plate in circumferential direction has been investigated in the context of generalized themoelasticity III, recently developed by Green and Naghdi. The model has been simplif چکیده کاملThe free vibration analysis ofhomogeneous isotropic micropolar thermoelastic cylindrical curved plate in circumferential direction has been investigated in the context of generalized themoelasticity III, recently developed by Green and Naghdi. The model has been simplified using Helmholtz decomposition technique and the resulting equations have been solved using separation of variable method. Mathematical modeling of the problem to obtain dispersion curves for curved isotropic plate leads to coupled differential equations and solutions are obtained by using Bessel functions. The frequency equations connecting the frequency with circumferential wave number and other physical parameters are derived for stress free cylindrical plate. In order to illustrate theoretical development, numerical solutions are obtained and presented graphically for a magnesium crystal. پرونده مقاله -
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38 - Analytical Prediction of Indentation and Low-Velocity Impact Responses of Fully Backed Composite Sandwich Plates
M Hosseini S.M.R KhaliliIn this paper, static indentation and low velocity impact responses of a fully backed composite sandwich plate subjected to a rigid flat-ended cylindrical indenter/impactor are analytically investigated. The analysis is nonlinear due to nonlinear strain-displacement rel چکیده کاملIn this paper, static indentation and low velocity impact responses of a fully backed composite sandwich plate subjected to a rigid flat-ended cylindrical indenter/impactor are analytically investigated. The analysis is nonlinear due to nonlinear strain-displacement relation. In contrast to the existed analytical models for the indentation of composite sandwich plates, the stacking sequence of the face sheets can be completely arbitrary in the present model. Furthermore, the effects of the initial in-plane normal and shear forces on the edges of the sandwich plate are also considered. Based on these modifications, an improved contact law (contact force – indentation relation) is derived. The low velocity impact analysis of the problem is performed using a discrete system of spring-mass-dashpot model. The characteristics of the equivalent spring and dashpot are identified from the derived contact law and by incorporating the effect of the dynamic material properties of the sandwich plate. Analytical predictions of the load-indentation response as well as the impact force history are compared well with the experimental results in the literature. The effects of various parameters on both indentation and impact responses of the sandwich plates are qualitatively and quantitatively investigated. پرونده مقاله -
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39 - Variational Principle and Plane Wave Propagation in Thermoelastic Medium with Double Porosity Under Lord-Shulman Theory
R Kumar R Vohra M.G GorlaThe present study is concerned with the variational principle and plane wave propagation in double porous thermoelastic infinite medium. Lord-Shulman theory [2] of thermoelasticity with one relaxation time has been used to investigate the problem. It is found that for t چکیده کاملThe present study is concerned with the variational principle and plane wave propagation in double porous thermoelastic infinite medium. Lord-Shulman theory [2] of thermoelasticity with one relaxation time has been used to investigate the problem. It is found that for two dimensional model, there exists four coupled longitudinal waves namely longitudinal wave (P), longitudinal thermal wave (T), longitudinal volume fractional wave corresponding to pores (PV1), and longitudinal volume fractional wave corresponding to fissures (PV2), in addition to, a transverse wave (S) which is not affected by the volume fraction fields and thermal properties. The different characteristics of the wave such as phase velocity and attenuation quality factor are computed numerically and depicted graphically. Some special cases are also deduced from the present investigation. پرونده مقاله -
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40 - Analysis of Axisymmetric Extrusion Process through Dies of any Shape with General Shear Boundaries
H Haghighat G.R AsgariIn this paper, a generalized expression for the flow field in axisymmetric extrusion process is suggested to be valid for any dies and the boundary shapes of the plastic deformation zone. The general power terms are derived and the extrusion force is calculated by apply چکیده کاملIn this paper, a generalized expression for the flow field in axisymmetric extrusion process is suggested to be valid for any dies and the boundary shapes of the plastic deformation zone. The general power terms are derived and the extrusion force is calculated by applying upper bound technique for a streamlined die shape and exponential functions for shear boundaries. It is shown that assuming exponential boundaries for deformation zone yields a die shape with smaller extrusion force than that of by assuming spherical shape boundaries is in agreement with the results obtained by the finite element method. پرونده مقاله -
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41 - Response of Two Temperatures on Wave Propagation in Micropolar Thermoelastic Materials with One Relaxation Time Bordered with Layers or Half Spaces of Inviscid Liquid
R Kumar M Kaur S.C RajvanshiThe present study is concerned with the propagation of Lamb waves in a homogeneous isotropic thermoelastic micropolar solid with two temperatures bordered with layers or half spaces of inviscid liquid subjected to stress free boundary conditions. The generalized theory چکیده کاملThe present study is concerned with the propagation of Lamb waves in a homogeneous isotropic thermoelastic micropolar solid with two temperatures bordered with layers or half spaces of inviscid liquid subjected to stress free boundary conditions. The generalized theory of thermoelasticity developed by Lord and Shulman has been used to investigate the problem. The secular equations for symmetric and skew- symmetric leaky and nonleaky Lamb wave modes of propagation are derived. The phase velocity and attenuation coefficient are computed numerically and depicted graphically. The amplitudes of stress, microrotation vector and temperature distribution for the symmetric and skew-symmetric wave modes are computed analytically and presented graphically. Results of some earlier workers have been deduced as particular cases. پرونده مقاله -
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42 - Dispersion of Love Wave in a Fiber-Reinforced Medium Lying Over a Heterogeneous Half-Space with Rectangular Irregularity
R.M Prasad S KunduThis paper concerned with the dispersion of Love wave in a fiber-reinforced medium lying over a heterogeneous half-space. The heterogeneity is caused by the consideration of quadratic variation in density and directional rigidity of lower half-space. The irregularity ha چکیده کاملThis paper concerned with the dispersion of Love wave in a fiber-reinforced medium lying over a heterogeneous half-space. The heterogeneity is caused by the consideration of quadratic variation in density and directional rigidity of lower half-space. The irregularity has been considered in the form of rectangle at the interface of the fiber-reinforced layer and heterogeneous half-space. The dispersion equation of Love wave has been deduced for existing geometry of the problem under suitable boundary conditions using variable separation method. It has also been observed that for a homogeneous layer with rigidity lying over a regular homogeneous isotropic half-space, the velocity equation coincides with the classical results of Love wave. The effect of the medium characteristics on the dispersion of Love waves has been discussed and the results are displayed with graphs by means of MATLAB programming to clear the physical significance. The study of Love wave dispersion with irregular interface helps civil engineers in building construction, analysis of earthquake in mountain roots, continental margins, and so on. It is also beneficial for the study of seismic waves generated by artificial explosions. پرونده مقاله -
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43 - Problem of Rayleigh Wave Propagation in Thermoelastic Diffusion
R Kumar V GuptaIn this work, the problem of Rayleigh wave propagation is considered in the context of the theory of thermoelastic diffusion. The formulation is applied to a homogeneous isotropic thermoelastic half space with mass diffusion at the stress free, isothermal, isoconcentrat چکیده کاملIn this work, the problem of Rayleigh wave propagation is considered in the context of the theory of thermoelastic diffusion. The formulation is applied to a homogeneous isotropic thermoelastic half space with mass diffusion at the stress free, isothermal, isoconcentrated boundary. Using the potential functions and harmonic wave solution, three coupled dilatational waves and a shear wave is obtained. After developing mathematical formulation, the dispersion equation is obtained, which results to be complex and irrational. This equation is converted into a polynomial form of higher degree. The roots of this polynomial equation are verified for not satisfying the original dispersion equation and therefore are filtered out and the remaining roots are checked with the property of decay with depth. Phase velocity and attenuation coefficient of the Rayleigh wave are computed numerically and depicted graphically. Behavior of particle motion of these waves inside and at the surface of the thermoelastic medium with mass diffusion is studied. Some particular cases are also deduced from the present investigation. پرونده مقاله -
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44 - Vibration Analysis of Carotid Arteries Conveying Non-Newtonian Blood Flow Surrounding by Tissues
A.H Ghorbanpour Arani A Rastgoo A. Ghorbanpour Arani R KolahchiThe high blood rate that often occurs in arteries may play a role in artery failure and tortuosity which leads to blackouts, transitory ischemic attacks and other diseases. However, vibration and instability analysis of carotid arteries are lacking. The objective of thi چکیده کاملThe high blood rate that often occurs in arteries may play a role in artery failure and tortuosity which leads to blackouts, transitory ischemic attacks and other diseases. However, vibration and instability analysis of carotid arteries are lacking. The objective of this study is to investigate the vibration and instability of the carotid arteries conveying blood under axial tension with surrounding tissue support. Arteries are modeled as elastic cylindrical vessels based on first order shear deformation theory (FSDT) within an elastic substrate. The elastic medium is simulated with visco-Pasternak foundation. The blood flow in carotid artery is modeled with non-Newtonian fluid based on Carreau, power law and Casson models. Applying energy method, Hamilton principle and differential quadrature method (DQM), the frequency, critical blood velocity and transverse displacement of the carotid arteries are obtained. It can be seen that increasing the tissue stiffness would delay critical blood velocity. The current model provides a powerful tool for further experimental investigation arteries tortuosity. In addition, the dimensionless transverse displacement predicted by Newtonian model is lower than that of non-Newtonian models. پرونده مقاله -
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45 - Influences of Heterogeneities and Initial Stresses on the Propagation of Love-Type Waves in a Transversely Isotropic Layer Over an Inhomogeneous Half-Space
P Alam S KunduIn the present paper, we are contemplating the influences of heterogeneities and pre-stresses on the propagation of Love-type waves in an initially stressed heterogeneous transversely isotropic layer of finite thickness lying over an inhomogeneous half space. The materi چکیده کاملIn the present paper, we are contemplating the influences of heterogeneities and pre-stresses on the propagation of Love-type waves in an initially stressed heterogeneous transversely isotropic layer of finite thickness lying over an inhomogeneous half space. The material constants and pre-stress have been taken as space dependent and arbitrary functions of depth in the respective media. To simplify the problem, we have used Whittaker’s function and separation of variables method. We present a general dispersion relation to describe the impacts on the propagation of Love-type waves in the structure. The present dispersion relation is analyzed case wise and also validated by comparison of the standard Love wave equation. Further, numerical computations are demonstrated graphically for the set of dimensionless parameters between dimensionless phase velocity and dimensionless wave number of the wave. پرونده مقاله -
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46 - Prediction model of limestone rock mass quality, using seismic wave velocity (Case study: Sarvak formation in Bakhtiari dam site)
Mehdi Kianpour Seyed Mahmoud Fatemi Aghda مهدی تلخابلوThe purpose of this study was to develop a model for the estimation of rock mass classification of Sarvak limestone in the Bakhtiari dam site, south-west (SW) Iran. Q system had been used as the starting point for the rock mass classification. This method was modified f چکیده کاملThe purpose of this study was to develop a model for the estimation of rock mass classification of Sarvak limestone in the Bakhtiari dam site, south-west (SW) Iran. Q system had been used as the starting point for the rock mass classification. This method was modified for sedimentary rock mass which is known as Qsrm. Because Qsrm considers a wide range of rock mass properties, it has become a tool for rock mass classification that more correlates with geophysical parameters. This study tried to revise and empower the correlation between P-wave velocity (Vp) with Q and Qsrm in Sarvak limestone. By using data sets of Bakhtiari Dam Site (BDS) in SW Iran and multivariate regression and the Fuzzy Inference System (FIS), models were rendered for prediction of Q and Qsrm. About 700 sets of data were used for modeling and Vp was considered as the input parameter. The regression equations showed the relationship between Vp with Q and Qsrm,under conditions of quadratic relations, obtained coefficients of determination (R2) of 0.49 and 0.66, respectively. The correlation coefficient was calculated as 0.82 for the Qsrm obtained from FIS models. Also, Variance Accounted For (VAF) and Root Means Square Error (RMSE) indexes were also used for evaluation of prediction accuracy of models. Results showed that Vp has better performance in prediction of Qsrm than Q and theFIS model showed the best prediction results. Because these models have accuracy, they could be used in similar conditions. پرونده مقاله -
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47 - Evaluating the performance of ANSYS-CFX software in simulation the velocity and pressure distributions over circular crested weirs
محمدجواد امیری منوچهر حیدرپور مهدی بهرامی رخساره رستمیانANSYS-CFX is an effective and multipurpose software which can be used for simulation the computational fluid dynamics (CFD) solutions at all levels of complexity. This software can be used for numerical solution of two and three dimensional flows, compressible and incom چکیده کاملANSYS-CFX is an effective and multipurpose software which can be used for simulation the computational fluid dynamics (CFD) solutions at all levels of complexity. This software can be used for numerical solution of two and three dimensional flows, compressible and incompressible flows, viscous and non-viscous flows, laminar and turbulent flows, Newtonian and non-Newtonian flows, porous media, steady and unsteady and FIS by finite element method. Hydraulic control structure is one of the major components of irrigation and drainage systems. Circular crested weirs are extensively used in the hydraulic structures due to simple and relatively precise relationships.To evaluate the performance of ANSYS-CFX software in simulation the flow patterns over the weir crest, two different cylindrical weirs with 90 and 45 for up-and downstream angles, respectively, and also with 60 and 45 for up-and downstream angles, respectively were considered. Three different discharge and concequently three are considered for each weir shape. The results showed that the data predicted by the software in a good agreement with experimental data. The results indicate that the up-and downstream weir face angle has no significant effect on the output of the model and this model approaches work well for pressure and velocity distributions with two different cylindrical weirs angles. In general, the results of 45-90 weirs angles is better than the results of 45-60. پرونده مقاله -
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48 - Numerical study, investigation effect of distance and angle of spur dike on average velocity distribution and maximum velocity position at mild 90 degree bend
یاسر اهلی مرتضی بختیاری مسیح مرUse the Spur dike as one of the easiest ways to protect the costal of the river has always been of interest to River engineers.The aim of this study was numerical investigate, the effect of distance and angle of the spur dikes parameters on the pattern of distribution o چکیده کاملUse the Spur dike as one of the easiest ways to protect the costal of the river has always been of interest to River engineers.The aim of this study was numerical investigate, the effect of distance and angle of the spur dikes parameters on the pattern of distribution of average velocity and the location of maximum velocity position at a mild 90 degree bend. For this purpose used ANSYS CFX software for numerical simulation of flow pattern and for calibration of mentioned model used result of Experimental data 3D- velocity data at Bakhtiari et al (2013) research. Variables of this study were 2 length of spur dike equivalent 15 and 25 percent of width of canal, 3 distance equivalent 3,5 and 7 times to spur dike length, 2 angle include of vertical and absorbed spur dike at 3cm to bed which investigated at a flume with R/B=4, width 0.7m and water depth 0.12m. The result of model verification shows good correspondence between the results of numerical models and laboratory. The result show that with increasing the distance between spur dike, the velocities increased too and also caused the increasing the velocity about 75 cm/s on the head of spur dikes. Also the result show that by positioning the absorbent spur dikes the maximum of velocity divert to external bend Therefore, the most destructive is the case for the breakwater. پرونده مقاله -
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49 - بررسی تجربی ضریب اصطکاک و تنش برشی بین سطحی در جریان دوفازی ناهمسو در لوله عمودی
آرش غفوری اشکان غفوری عباس کوثری نیا علیرضا دنه دزفولیدر پژوهش تجربی حاضر، شکلگیری الگوی جریان حلقوی در لوله عمودی با جریان دوفازی ناهمسو به کمک تکنیک ثبت و پردازش تصاویر مورد بررسی قرار گرفته است. پس از تفکیک رژیم جریانهای دو فاز ایجاد شده، محدوده سرعت ظاهری هوا (پایین به بالا) و آب (بالا به پایین) به ترتیب 20.94-3.66 م چکیده کاملدر پژوهش تجربی حاضر، شکلگیری الگوی جریان حلقوی در لوله عمودی با جریان دوفازی ناهمسو به کمک تکنیک ثبت و پردازش تصاویر مورد بررسی قرار گرفته است. پس از تفکیک رژیم جریانهای دو فاز ایجاد شده، محدوده سرعت ظاهری هوا (پایین به بالا) و آب (بالا به پایین) به ترتیب 20.94-3.66 متر بر ثانیه و 0.31-0.06 متر بر ثانیه برای جریان حلقوی میباشد. ضریب اصطکاک بین سطحی (فاز مایع و گاز) بر حسب پارامترهای هیدرودینامیکی جریان مورد ارزیابی قرار گرفته است. مقایسه متوسط انحراف نتایج حاصله از پژوهش حاضر در مقایسه با پژوهشهای پیشین نشان از تطابق مناسب نتایج دارد. همچنین تنش برشی بین سطحی برای دو لوله آزمایش در الگوی جریان دوفازی ناهمسو در رژیم جریان حلقوی محاسبه و ارزیابی شده است. در این پژوهش ضریب اصطکاک بین سطحی (فاز مایع و گاز) نیز در قالب یک رابطه همبستگی جدید وابسته به عدد رینولدز جریان گاز و عدد رینولدز جریان مایع با ضریب همبستگی 0.98R2= ارائه شده است. پرونده مقاله -
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50 - بررسی پارامترهای موثر (قطر لوله و سرعت سیال) در شبیه سازی پدیده ضربه قوچ در خطوط انتقال آب
نیما اسدی ده میراحمدی یوسف اسمعیلینظر به اهمیت بررسی دقیق ضربه قوچ در شبکه های لوله کشی و خطوط انتقال مایعات در تحقیق حاضر دو پارامتر قطر و سرعت سیال در یک خط لوله، به روش آزمایشگاهی و شبیه سازی توسط نرم افزار همر مورد بررسی قرار گرفت. در این تحقیق بر روی شش نوع لوله با جنسهای مختلفی که شامل برنجی، فول چکیده کاملنظر به اهمیت بررسی دقیق ضربه قوچ در شبکه های لوله کشی و خطوط انتقال مایعات در تحقیق حاضر دو پارامتر قطر و سرعت سیال در یک خط لوله، به روش آزمایشگاهی و شبیه سازی توسط نرم افزار همر مورد بررسی قرار گرفت. در این تحقیق بر روی شش نوع لوله با جنسهای مختلفی که شامل برنجی، فولادی، پنج لایه، مسی و PVC و با فرض بر اینکه علت ایجاد ضربه قوچ بسته شدن سریع شیر میباشد، آزمایش انجام شد. آزمایشات نشان دادند که زمان بسته شدن شیر یکی دیگر از عوامل مهم در این پدیده میباشد. با انجام آزمایش در دو حالت آرام بسته شدن و سریع بسته شدن شیر آب نتایج نشان دادند هر چه مدت زمان بسته شدن شیر طولانیتر باشد اثر ضربه قوچ کمتر شده و موجهای حاصل زودتر میرا میشوند .همچنین با بررسی بر روی قطر لولهها نتایج بدست آمده حاکی از آن است افزایش قطر لوله منجر به افزایش دبی شده و به دنبال خود سرعت سیال در خط لوله بیشتر میشود و اثر ضربه قوچ نیز با افزایش قطر شدیدتر میگردد. این پدیده نشان میدهد تأثیر افزایش سرعت سیال نسبت به اثر قطر بیشتر است. پرونده مقاله -
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51 - تحلیل سرعت بحرانی لوله حاوی سیال با شرایط مرزی غیرکلاسیک
شاهرخ شمس سجاد جنگرویمحاسبه سرعت بحرانی لوله حاوی سیال از مسائل مهم در مهندسی است. بدین منظور، سرعت بحرانی لوله حاوی سیال با شرایط مرزی غیرکلاسیک در مقاله حاضر محاسبه گردیده است. معادلات حرکت سازه بر اساس مدل تیر اویلر- برنولی پایه گذاری شده است. شرایط مرزی غیرکلاسیک شامل فنرخطی ، فنرپیچشی چکیده کاملمحاسبه سرعت بحرانی لوله حاوی سیال از مسائل مهم در مهندسی است. بدین منظور، سرعت بحرانی لوله حاوی سیال با شرایط مرزی غیرکلاسیک در مقاله حاضر محاسبه گردیده است. معادلات حرکت سازه بر اساس مدل تیر اویلر- برنولی پایه گذاری شده است. شرایط مرزی غیرکلاسیک شامل فنرخطی ، فنرپیچشی ، جرم متمرکز و میراکننده ها هستند. برای محاسبه سرعت بحرانی، معادله فرکانسی با توجه به شرایط مرزی با روش عددی حل میگردد. زمانی که قسمت حقیقی معادله فرکانسی به صفر برسد، سرعت بحرانی در لوله ظاهر و سیستم ناپایدار می شود. تاثیر پارامترهای مختلف شامل سختی فنر و جرم متمرکز بر سرعت بحرانی بررسی و نمودار های مقایسه ای از سختی های متفاوت فنر و جرم متمرکز ترسیم شده است. نتایج نشان میدهد که سرعت بحرانی در حالت دو سر فنر خطی بیشتر از شرط مرزی فنرپیچشی- فنرخطی و جرم متمرکز-فنرپیچشی است و همچنین کاهش قابل توجه فرکانس در حالت غیرکلاسیک نسبت به کلاسیک هستند. پرونده مقاله -
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52 - بررسی ارتعاشات سازه شناور در اثر تحریک پروانه با استفاده از تحلیل عددی سیال-سازه (FSI)
مهدیه سادات عزیزی یوسف امیریان عبدالحسین فریدونارتعاشات سازه شناور در اثر تحریک پروانه، یکی از مباحث مهم در طراحی سازه شناور است. در صورت عدم توجه به این مساله و قرارگیری سوپراستراکچر در قسمت انتهایی شناور، ارتعاشات ناشی از تحریک پروانه می تواند مشکلاتی را برای خدمه و افراد ایجاد نماید. همچنین ارتعاشات ناشی از پروا چکیده کاملارتعاشات سازه شناور در اثر تحریک پروانه، یکی از مباحث مهم در طراحی سازه شناور است. در صورت عدم توجه به این مساله و قرارگیری سوپراستراکچر در قسمت انتهایی شناور، ارتعاشات ناشی از تحریک پروانه می تواند مشکلاتی را برای خدمه و افراد ایجاد نماید. همچنین ارتعاشات ناشی از پروانه باعث سر و صدا و همچنین کاهش عمر ماشین آلات موجود در موتورخانه و قسمت انتهایی شناور میگردد. در این مقاله ارتعاشات ناشی از تحریک پروانه، با استفاده از تحلیل عددی سیال- سازه روی یک شناور تجاری مورد بررسی قرار گرفته و به بررسی نتایج آن پرداخته شده است. ابتدا برای شناور با توجه به هندسه و شرایط، پروانه ای مناسب انتخاب شده و حل عددی جریان سیال برای سرعت های مختلف شناور و سرعت دورانی پروانه انجام گرفته است. سپس سازه شناور بر اساس استاندارد، طراحی شده و جزبندی آن با استفاده از جزء محدود صفحه ای انجام گرفته است. توزیع فشار روی پروانه و بدنه که از حل عددی جریان سیال به دست آمده است در تحلیل سازه، به سازه شناور اعمال گشته و سازه شناور در اثر بارگذاری هارمونیک ناشی از دوران پروانه، بررسی شده است. تحلیل مودال سازه شناور نیز انجام گرفته و سپس نتایج تحلیل آن، در یک محدوده فرکانسی شامل فرکانس های طبیعی که می تواند در حالت ها و سرعت های مختلف دورانی پروانه به وجود آید، استخراج شده است. نتایج نشان می دهد که در بعضی از سرعت های دورانی پروانه، فرکانس تحریک در سرعت دورانی مربوطه می تواند منجر به تشدید ارتعاش و افزایش دامنه ی ارتعاش گردد. نتایج با محدوده مجاز استاندارد مقایسه شده و نشان می دهد که می توان با دقت در انتخاب پروانه و محدوده سرعت دورانی مجاز و بهینه سازی و اصلاح سازه شرایط را جهت قرارگیری ارتعاشات در محدوده ی مجاز فراهم نمود. پرونده مقاله -
دسترسی آزاد مقاله
53 - Time series modeling of Alborzs crustal velocity by using artificial neural networks
Tohid malekzadeh DilmaghaniArtifitial neural network (ANN) is an information processing system that is formed by a large number of simple processing elements, known as artificial nerves. It is formed by a number of nodes and weights connecting the nodes. Using the trained data, the designed ANN c چکیده کاملArtifitial neural network (ANN) is an information processing system that is formed by a large number of simple processing elements, known as artificial nerves. It is formed by a number of nodes and weights connecting the nodes. Using the trained data, the designed ANN can be adjusted in an iterative procedure to determine optimal parameters of ANN. Then for an unknown input, we can compute corresponding output using the trained ANN. There are many methods for training the network and modifications of the weights. One of the most famous and simplest methods is a back-propagation algorithm that trains the network in two stages: Feed-forward and feed-backward. In the feed-forward process, the input parameters are moved to the output layer. In this stage, the output parameters the next stage is done In this study, a 3-layer perceptron neural network was used with 28 neurons in a hidden layer for modeling the eastern component (VE) and 27 neurons in a hidden layer for modeling the northern component (VN) velocity field of the earth's crust in Iran. The minimum relative error obtained from this evaluation for the eastern component was -3.57% and for the northern component was +0.16%: also the maximum relative error for the eastern component was +38.1 % and for the northern component was +95.3%. In this study, a polynomial of degree 5 with 18 coefficients was used to model the east and north components for the evaluation of artificial neural networks in estimating the velocity rate of geodetic points. A comparison of the relative error from the polynomial model and the relative error from the neural network illustrated the superiority of the neural model with respect to the polynomial model in this region. پرونده مقاله -
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54 - Modeling of time series of Earth crust velocity field in Azarbaijan using multilayer neural network with PSO training algorithm
Tohid malekzadeh DilmaghaniThe coordinates of the stations along with their velocity field and determination of the strain field are the most important parameters in determining the surface deformation of the shell. Preliminary estimation of the Earth's crust velocity field, especially in seismic چکیده کاملThe coordinates of the stations along with their velocity field and determination of the strain field are the most important parameters in determining the surface deformation of the shell. Preliminary estimation of the Earth's crust velocity field, especially in seismic areas and near faults, can provide valuable information on the geodynamic structure as well as how faults operate. Different solutions can be offered to solve such a problem. Paying attention to the reliability of the solution, its accuracy and efficiency, how to do it and most importantly the discussion of time and cost can be important and fundamental factors in this work. The purpose of this paper is to use modern and accurate methods to estimate and determine the velocity field and displacement field as well as strain tensor parameters in 3D. Artificial neural network (ANN) method with particle mass optimization training (PSO) algorithm for spatial estimation of crustal velocity changes in Iran has been studied. GPS measurements of Central Alborz network stations have been used to evaluate the method.The average relative error calculated in 4 test stations for the permanent base network in the VE component of the velocity field is 13%, in the VN component of the velocity field is 10/10% and in the Vz component of the velocity field is 15.18% of the artificial neural networks. For Central Alborz network, these values have been set as 18.41, 5.45 and 21.20% for VE, VN and Vz components, respectively. The results of this study show the high capability and efficiency of artificial neural network method in spatial estimation of the Earth's crust velocity field in this region. پرونده مقاله -
دسترسی آزاد مقاله
55 - Trajectory Planning Using High Order Polynomials under Acceleration Constraint
Hossein Barghi Jond Vasif V. Nabiyev Rifat BenvenisteThe trajectory planning, which is known as a movement from starting to end point by satisfying the constraints along the path is an essential part of robot motion planning. A common way to create trajectories is to deal with polynomials which have independent coefficien چکیده کاملThe trajectory planning, which is known as a movement from starting to end point by satisfying the constraints along the path is an essential part of robot motion planning. A common way to create trajectories is to deal with polynomials which have independent coefficients. This paper presents a trajectory formulation as well as a procedure to arrange the suitable trajectories for applications. Created trajectories aimed to be used for safe and smooth navigation in mobile robots. First, a trajectory problem is formulized by considering a border on the robot’s acceleration as the constraint. Also, initial and final conditions for the robot’s velocity along the straight path are settled. To investigate that suggested trajectories perform motions with continuous velocity and smooth acceleration, three trajectory problems are formulated using 3rd, 4th and 5th degree of polynomials. The high-degree polynomials are used because of providing of smoothness, but there is complexity in the calculation of additional coefficients. To reduce the complexity of finding the high-degree polynomial coefficients, the acceleration constraint is simplified and this process is based on a certain scenarios. Afterwards, the coefficients of the used polynomials are found by taking into account the acceleration constraint and velocity conditions. Additionally, to compare the obtained solutions through proposed scenarios, the polynomials` coefficients are solved numerically by Genetic Algorithm (GA). The computer simulation of motions shows that as well as acceleration constraint, the velocity conditions at the beginning and at the end of motion are fulfilled. پرونده مقاله -
دسترسی آزاد مقاله
56 - The Validity Assessment of Laboratory Shear Modulus Using In-Situ Seismic Piezocone Test Results
Seyed Majdedin Mir Mohammad Hosseini A.A. HajimohammadiSeismic piezocone device (SCPTu) together with Resonant Column and Cyclic Triaxial test apparatus are employed to measure small strain shear modulus (G0) of carbonate sandy and clayey soils of southern coasts of Iran. A large area of southern regions of Iran is formed f چکیده کاملSeismic piezocone device (SCPTu) together with Resonant Column and Cyclic Triaxial test apparatus are employed to measure small strain shear modulus (G0) of carbonate sandy and clayey soils of southern coasts of Iran. A large area of southern regions of Iran is formed from clay, silt and sand. In this study, maximum shear modulus that is derived from both field (by seismic piezocone) and laboratory (by Resonant Column and Cyclic Triaxial) tests on soil samples from the southern region, indicated a meaningful effect of sample disturbance. Results show that in laboratory tests, loose samples tend to become denser and therefore exhibit greater stiffness whereas dense samples tend to become looser, showing a reduction in stiffness. According to the results of the present study, there are narrow limits of soils shear moduli for which the laboratory tests and the field measurements yield approximately the same amounts. This limit of shear moduli is about 30-50(MPa) for clay deposits and 70-100 (MPa) for sandy deposits. Since the shear moduli of soils in small strains can also be computed from the shear wave velocity, also correlations based on parameters derived from SCPTu test for shear wave velocity determination of sandy and clayey soils of the studied area are presented. This study shows that shear wave velocity can be related to both corrected tip resistance and total normal stress. Regarding the shear moduli and the damping ratio, due to the disturbances of the stiff deposits in the sampling process and great deviations of laboratory results from field results, the laboratory measurements of these parameters out of the above limits are not recommended. پرونده مقاله -
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57 - Evaluating the Liquefaction Potential of Soil in the South and Southeast of Tehran based on the Shear Wave Velocity through Empirical Relationships
M Khalili Noutash R Dabiri M Hajialilue BonabThe liquefaction resistance of soil can be evaluated using laboratory tests such as cyclic simple shear, cyclic triaxial, cyclic torsional shear as well as field methods like Standard Penetration Test (SPT), Cone Penetration Test (CPT) and Shear Wave Velocity (Vs). In t چکیده کاملThe liquefaction resistance of soil can be evaluated using laboratory tests such as cyclic simple shear, cyclic triaxial, cyclic torsional shear as well as field methods like Standard Penetration Test (SPT), Cone Penetration Test (CPT) and Shear Wave Velocity (Vs). In this regard, this study attempts to compare the results of the SPT based on the simplified procedure proposed by Seed and Idriss (1985) and those of the Vs on the basis of Andrus et al.’s (2004) process using empirical relationships between them. Iwasaki’s (1982) method is used to measure the liquefaction potential index for both of them. The study area is a part of the south and southeast of Tehran. It is observed that there is not a perfect agreement between the results of the two methods based on five empirical relationships assuming cemented and non-cemented condition for soils. Moreover, the liquefaction potential index (PL) value in the SPT method is more than that of the Vs method. پرونده مقاله -
دسترسی آزاد مقاله
58 - Assessment of Subsurface Explosion caused byTunnel Construction in Urban Areas
Hossein Haghighimanesh Mohammad AzadiNowadays, tunneling in urban areas is a common activity for a variety of transportations such as subways, water supply, lifelines andsewers that may require blast operations. The characteristics of stress waves of the blast are quite different from earthquake waves. The چکیده کاملNowadays, tunneling in urban areas is a common activity for a variety of transportations such as subways, water supply, lifelines andsewers that may require blast operations. The characteristics of stress waves of the blast are quite different from earthquake waves. The blast waves are usually of high frequency content, short duration, equality of amplitudes in horizontal and vertical directions and large range of magnitude from ten to thousands of the gravitational constant. However few papers can be found to discuss about the effect of soil characteristics under blast loading. In this paper, numerical models based on finite element method is used to simulate stress wave at soil sites under explosion effect in an underground linear chamber and then characteristics of the ground movement and the explosion effect on soil-structure interaction is analyzed. In this study, numerical results of area deformations in every region are compared together and parameter sensitivity of the soil is analyzed. Results presented in this paper can be used in a more detailed assessment of ground motion effect on structures. پرونده مقاله -
دسترسی آزاد مقاله
59 - Investigation of oxidation behavior and Thermal spray of mechanically milled CoNiCrAlY–YSZ powders
Mostafa Tahari Morteza Shamanian Esfahani Mehdi SalehiIn this study, the effects of mechanical milling and YSZ reinforcing on oxidation behavior of CoNiCrAlY coatings were investigated. Various amounts of YSZ particles (0%, 5%, 10% and 15 wt.%) were mixed with commercial CoNiCrAlY powder and milled for 24 hrs. Then, the me چکیده کاملIn this study, the effects of mechanical milling and YSZ reinforcing on oxidation behavior of CoNiCrAlY coatings were investigated. Various amounts of YSZ particles (0%, 5%, 10% and 15 wt.%) were mixed with commercial CoNiCrAlY powder and milled for 24 hrs. Then, the mechanically milled and commercial powders were deposited on Inconel 617 substrate using High Velocity Oxygen-Fuel (HVOF) process. Freestanding bodies of nanostructured and conventional HVOF CoNiCrAlY coatings were oxidized at 1000 °C for different times to form the thermally grown oxide layer. X-ray diffraction analysis, scanning electron microscopy and X-ray mapping were used to analyze the scales formed on the surface of the oxidized samples. The results showed that nanostructured coatings exhibited higher porosity due to undesirable morphology of feedstock powders. This factor accelerated diffusion rate of oxygen into coating body. On the other hand, undesireable oxidation of nanostructured particles during spraying leads to increase in the oxidation rate of coatings. پرونده مقاله -
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60 - Effects of Colliding Particle Size and Velocity on Mechanical Properties of AZ31 after Surface Mechanical Attrition Treatment: Molecular Dynamics Simulation
Ali Kazemi Ali Heidari Kamran Amini Farshid Aghadavoudi Mohsen Loh-MousaviIn this study, the molecular dynamics method is used to simulate the SMAT process in the AZ31 workpiece. Molecular dynamics calculations in LAMMPS software have been used to investigate the effect of size, number, and velocity parameters of carbon steel particles on the چکیده کاملIn this study, the molecular dynamics method is used to simulate the SMAT process in the AZ31 workpiece. Molecular dynamics calculations in LAMMPS software have been used to investigate the effect of size, number, and velocity parameters of carbon steel particles on the mechanical and physical properties of the surface including residual stress, hardness, and surface roughness in AZ31 matrix has been investigated at the atomic scale. The simulation results during the SMAT process show that the residual stress in the AZ31 matrix increases with increasing the diameter of carbon steel particles and the particle velocity in the SMAT process has a significant effect on improving the mechanical properties of the simulated magnesium matrix. The highest residual stress and the largest increase in Vickers hardness in the SMAT process were calculated for the largest colliding particle. The maximum surface temperature of AZ31 decreases after SMAT with the increasing size of carbon steel particles. The results show that the roughness parameter increases with increasing colliding particle size. پرونده مقاله -
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61 - Designing and Manufacturing the Multiple Jets Simulator and Experimental Investigation of the Multiple Jets in Crossflow
Saeed Toolani Mohamad HojajiDesigning and manufacturing the multiple jets simulator and experimental investigation of the multiple jets in crossflow at low velocity ratios have been studied Together with design and build a low-speed wind tunnel. A specific rake is used to determine the flow field چکیده کاملDesigning and manufacturing the multiple jets simulator and experimental investigation of the multiple jets in crossflow at low velocity ratios have been studied Together with design and build a low-speed wind tunnel. A specific rake is used to determine the flow field pressure and changes in static pressure measured by pressure taps in the near field of the jets. There are generally three regions on the pressure distributions whose details depend on the velocity ratio. Study the flow field and surface pressure distribution at low velocity ratios shows that by the increase the velocity ratio, the total pressure of the jet stream decreases sharply. The effects of increasing the number of jet injection nozzles showed that the influence on the jet stream in the vertical plane is significant. However, the influence of Normal multiple jets on the plate is reduced. It also increases the number of nozzles reduced the pressure coefficient rather than the single-jet injection. پرونده مقاله -
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62 - ارزیابی پتانسیل روانگرایی خاک منطقه چالوس و نوشهر در اثر وقوع زلزله با استفاده از روش سرعت موج برشیVs ))
نرگس افسری صمید علیزادهروانگرایی یکی از شایع ترین اثرات تغییر شکل زمین در اثر وقوع زمین لرزه است و اغلب علت اصلی آسیب و تخریب ساختمان ها و زیر ساخت ها می باشد. منطقه مورد مطالعه ( گستره چالوس و نوشهر) در نوار ساحلی دریای خزر واقع شده و بر روی مواد سست آبرفتی واقع شده و در طول تاریخ، شاهد زلزل چکیده کاملروانگرایی یکی از شایع ترین اثرات تغییر شکل زمین در اثر وقوع زمین لرزه است و اغلب علت اصلی آسیب و تخریب ساختمان ها و زیر ساخت ها می باشد. منطقه مورد مطالعه ( گستره چالوس و نوشهر) در نوار ساحلی دریای خزر واقع شده و بر روی مواد سست آبرفتی واقع شده و در طول تاریخ، شاهد زلزله های متعددی بوده است. در این تحقیق، روش سرعت موج برشی (Vs) با به کاربردن 5 رابطه تجربی جهت ارزیابی پتانسیل روانگرایی خاک های شهرهای چالوس و نوشهر با فرض شرایط بدون سمنتاسیون و با سمنتاسیون مورد استفاده قرار گرفته است. همچنین با توجه به توزیع گمانه های مورد ارزیابی که در قسمت رسوبی گستره مورد مطالعه با سن کمتر از 10000 سال قرار دارند، جواب های با شرایط بدون سمنتاسیون مورد قبول است؛ آنالیزهای انجام شده نشان می دهد که از میان 46 حلقه گمانه، تحلیل شده، 35 گمانه مستعد روانگرایی هستند که بیشتر آن ها در شهرستان نوشهر واقع شده اند. با توجه به مقادیر شاخص پتانسیل روانگرایی بدست آمده در گستره مورد مطالعه بر اساس روش سرعت موج برشی با فرض شرایط بدون سمنتاسیون خاک، 7/8 درصد گستره مورد مطالعه در محدودة 0PL = ، 2/15درصد در محدودة 5>PL >0، 3/41 درصد در محدود 15>PL>5و 8/34درصد در محدودة 15<PL قرار دارند. نظر به این که عمق سطح ایستابی یک پارامتر مهم در روانگرایی خاک می باشد، با توجه به بالا بودن سطح ایستابی، و با در نظر گرفتن پتانسیل بالای لرزه خیزی منطقه، احتمال روانگرایی بالا می رود. پرونده مقاله -
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63 - تحلیل تیر FGM در اثر ضربه با سرعت کم به روش FEM با آباکوس
مهدی قهیه ئی سید علیرضا مهاجرانی سعید جعفری مهر آبادی بهناز قهیه ئیآسیب ضربه با سرعت کم از مهمترین مسائلی است که در مواد کامپوزیتی صنایع نظامی و عمران بکار گرفته میشود. کامپوزیتهای فیبری ورقهای محکمی هستند که در معرض تنشهای ناشی از بار ضربه استفاده میشوند تا آسیب ضربه را با استفاده از رزینهای سخت و مقاوم کاهش دهند. در این مقاله ب چکیده کاملآسیب ضربه با سرعت کم از مهمترین مسائلی است که در مواد کامپوزیتی صنایع نظامی و عمران بکار گرفته میشود. کامپوزیتهای فیبری ورقهای محکمی هستند که در معرض تنشهای ناشی از بار ضربه استفاده میشوند تا آسیب ضربه را با استفاده از رزینهای سخت و مقاوم کاهش دهند. در این مقاله برخورد گلوله با سرعت کم به 6 تیر با لایهبندی FGM که مدول الاستیسیته در ضخامت تیر از سرامیک تا فلز متغیر است و پاسخ تیر در برابر ضربه با سرعت کم به روش اجزای محدود به کمک نرمافزار آباکوس بررسی شده است. تنشها و خیز و کرنش تیر در دو حالت لایه آخر فلز و سرامیک – فلز تحلیل شده است، نمودارهایی از تنش، خیز و کرنش در طول تیر برای شش تیر بدست آمده و مشاهده گردید در حالتی که درجه خواص فلز نسبت به سرامیک بیشتر باشد، میزان خیز و تنش بالاتر است و کرنش در تیر با افزایش درجه خواص سرامیک نسبت به فلز کاهش مییابد. پرونده مقاله -
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64 - A Study on the Effects of Chilling Period on Sperm Quality of Sannan and Jamunapari Goats
تی. اسواراموهان کا. نیلانی پی. سورکا پی. ماهادوان ک. بالاسوبرامانیامThe objective of the present study was to examine the effects of chilling period on semen quality of Sannan and Jamunapari. Semen of goat breeds were collected with artificial vagina and chilled at 5-9˚C. Volume, colour and pH were determined on fresh semen. After dilut چکیده کاملThe objective of the present study was to examine the effects of chilling period on semen quality of Sannan and Jamunapari. Semen of goat breeds were collected with artificial vagina and chilled at 5-9˚C. Volume, colour and pH were determined on fresh semen. After dilution, microscopic examination was performed for the progressive motility and sperm viability. Diluted semen of both breed was compared by microscopic examination from day 0 to 3 during chilling. Hemocytometer was loaded with 10 µL of semen to evaluate the sperm count. Eosin stain (1%) was used to assess the viable sperm. Although viability and sperm velocity of both goat breed decreased(P<0.05) in a time dependent manner during chilling, the viability between the Sannan and Jamunapari did not differ significantly. However there was a significant difference for means of sperm velocity (P<0.05). Progressive motility and viability decreased gradually during chilling at 5-9˚C.In order to obtain higher successful rate of insemination, chilled goat semen should be supplied to the farmers within a day. پرونده مقاله -
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65 - Capability of f-k and SPAC methods in determining shear wave velocity of subsurface soil
Mehran Esfahanizadeh Mohammad Davoodi Ebrahim Haghshenas Mohammad JafariA series of microtremor array measurement was performed in a site of Tehran (shaghayeg park) with the aim of estimating the shear wave velocity (Vs) profile for near surface layers. The SPAC and f-k array processing technique were used and the results were compared with چکیده کاملA series of microtremor array measurement was performed in a site of Tehran (shaghayeg park) with the aim of estimating the shear wave velocity (Vs) profile for near surface layers. The SPAC and f-k array processing technique were used and the results were compared with other information specially a 200 meters depth borehole and the downhole and PS logging data have been done in this paper. The data of different time, day and night were processed and the results were compared with the actual Vs profile by definition the various criteria. We found that, the SPAC method is probably more convenient compared to the f-k method. SPAC method gives results as good as the f-k method while using smaller number of recording stations and shorter array dimensions. پرونده مقاله -
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66 - Velocity Distribution in the 90-degree Bend based on the Probability and Entropy Concept
S. Sadeghfam Y. Hassanzadeh , M. MoazamniaPractical concept of velocity distribution of pressure flow in the bends is interesting and hence, the professional engineering design has been investigated in the current study. This paper shows that velocity distribution in the bends can be analyzed in terms of the pr چکیده کاملPractical concept of velocity distribution of pressure flow in the bends is interesting and hence, the professional engineering design has been investigated in the current study. This paper shows that velocity distribution in the bends can be analyzed in terms of the probability distributions. The concept of entropy based on the probability is an applied and new approach to achieve velocity profiles in bends, presented by the probability distribution and Tsallis entropy maximization under the importing constraints. Due to the lack of a specific equation of velocity distribution in the bends, the particular equation in the various band sections was obtained through the numerical simulation of three dimensional flow in the 90-degree bend (via Fluent). In this simulation, flow regime was laminar and the Reynolds number was in the range of 100 to 2000. Then, for m=2, the velocity distribution function was obtained. Studies showed that the proposed model for the mentioned range of Reynolds numbers is in a good agreement with other study results. The calculated error values indicated a reasonable accuracy. The model can directly calculate the velocity at each point of the spatial position. The calculated values were also compared with the results obtained from the velocity distribution based on the Shannon entropy. The results showed a reliable estimate of the velocity profiles. پرونده مقاله -
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67 - Water Velocity Measurements in Open Channels Using Volumetric Current Meter (VCM)
Seyyed Ali Akbar Moosavi Mohammad Abdolahipour-Haghighi Gholamreza MohammadiAn innovative Volumetric Current Meter (VCM) was designed in order to allow quick velocity measurements in open channels. At first, the coefficient of velocity (Cv) of the device was determined through calibration under different water velocities in the laboratory. The چکیده کاملAn innovative Volumetric Current Meter (VCM) was designed in order to allow quick velocity measurements in open channels. At first, the coefficient of velocity (Cv) of the device was determined through calibration under different water velocities in the laboratory. The measurement performance was verified by measurements performed in similar flows in irrigation channels using an ordinary current meter. The obtained results showed that the new device can be used to measure the discharge with an acceptable precision (RMSE and MAD equal to 5.353% and 0.027, respectively compared to a digital flow meter). It was shown that velocity computation by using this device will result in a lower precision in higher water velocities. پرونده مقاله -
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68 - CFD and dimensionless parameter analysis of Froude number to determine the flow regime over ogee spillways
H.R Vosoughifar A.R DaneshkhahIn this research, the numerical method of computational fluid dynamics and dimensionless parameter of Froude number have been applied to determine the flow regime over ogee spillways.Froude number is a dimensionless dynamic parameter calculated using the square root of چکیده کاملIn this research, the numerical method of computational fluid dynamics and dimensionless parameter of Froude number have been applied to determine the flow regime over ogee spillways.Froude number is a dimensionless dynamic parameter calculated using the square root of the ratio of inertia force and gravitational force. Considering that the study of the regimes of flow over hydraulic structures especially spillways is of great importance, and as the most applied spillway is ogee one, therefore it is required to study such structures. To study the sensitivity of the dimensionless parameters of Froude number and velocity using in the proper calculation of the profile of the flow over ogee spillway the software of fluent computational fluid dynamics softwarehas been used. Based on Gauss–Seidel convergence condition applied for the convergence and control of equations, the step time of 0.01 second, quad pave meshing and RNG k– turbulence model have been used. The results of this research shows that the decrease of reference designhead by 10, 20, and 30 percent leads to the decrease of reference average Froude number and reference average velocity of the flow over ogee spillway by 7.646, 15.2 18.835, and 6.519, 12.787, and 26.113 percent respectively. Moreover, the increase of the average Froude number of flow by 6.519, 12.787, and 26.113 percent, and average reference velocity by 13.933, 4.211, and 1.839 causes the reference design head to increase by 10, 20, and 30 percent. Whereas p-value of the profile of the flow in SPSS software is around 0.006 and very lower than 5%, it can be claimed that the numeral study is of high precision. In conclusion, the results obtained from numerical simulation have been provided and compared with the existing numerical and laboratory studies. The accuracy of this research is describable. پرونده مقاله -
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69 - Application of Soft Computing Methods in the Analysis of Velocity Field in Dividing Channel
Sohrab Karimi Hossein Bonakdari Hojat Karami Amir Hossein ZajiThe simplest water diversion method in irrigation systems is using intakes. Measuring the mean velocity is one of the essential hydraulic parameters in increasing the efficiency of the intake. In this study, the mean velocity was predicted for different width ratios of چکیده کاملThe simplest water diversion method in irrigation systems is using intakes. Measuring the mean velocity is one of the essential hydraulic parameters in increasing the efficiency of the intake. In this study, the mean velocity was predicted for different width ratios of an intake using ANN-MLP neural network model. In order to do that, the flow field within a 90-degree intake was first simulated three-dimensionally using ANSYS-CFX. The neural network used in this study includes 3 inputs; longitudinal coordinate (Y*), ratio of the branch channel to the main channel (wr), and mean velocity of the middle line of the channel cross section (V*line). V*lineis the average velocity in the vertical column of the branch channel, which has been measured by the ANSYS-CFX model after the validation. Comparison of the ANSYS-CFX results with the experimental ones indicated that this model, with mean Root Mean Squared Error (RMSE) of 0.013, has a proper accuracy in simulating the characteristics of the flow field within the intake. In addition, comparison of the obtained results from ANN-MLP model and the experimental results indicated that this model, with mean determination coefficient (R2) of 0.948, has a high performance in predicting the mean velocity of open channel intakes. پرونده مقاله -
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70 - Discharge Estimation by using Tsallis Entropy Concept
M Moazamnia H BonakdariFlow-rate measurement in rivers under different conditions is required for river management purposes including water resources planning, pollution prevention, and flood control. This study proposed a new discharge estimation method by using a mean velocity derived from چکیده کاملFlow-rate measurement in rivers under different conditions is required for river management purposes including water resources planning, pollution prevention, and flood control. This study proposed a new discharge estimation method by using a mean velocity derived from a 2D velocity distribution formula based on Tsallis entropy concept. This procedure is done based on several factors which reflect the basic hydraulic characteristics such as river bed slope, wetted perimeter, width, and water level that are easily obtained from rivers. This method avoids putting the environment at risk and significantly reduces time and costs. Validation of the method was carried out by comparing the results with measured values in the experimental sites. Predicted results are in good agreement with the measured data in a cross section of the Tiber River, Italy. Extended usage of this method will make it possible to measure discharge and better estimate the flow rate conveyed from rivers under different hydraulic conditions. پرونده مقاله -
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71 - Numerical Simulation of Sediment Distribution and Transmission in Pre-Sedimentation basins Using FV Method and Comparison with the Experimental Results
Mohammad Reza Borna Mohammad Reza PirestaniPre-sedimentation basins are among the most important elements of the conventional water treatment process. In pre-sedimentation basins, due to different velocity gradients, secondary and rotational flows are formed that will create short paths and increase dead and sti چکیده کاملPre-sedimentation basins are among the most important elements of the conventional water treatment process. In pre-sedimentation basins, due to different velocity gradients, secondary and rotational flows are formed that will create short paths and increase dead and still flow zones as well as changes in the flow mixing. This will prevent laminar flow conditions for sedimentation and will reduce the basin efficiency. The first step in optimization of the pre-sedimentation basins is the correct calculation of the velocity field and rotating zones volume. In this study, flow in a rectangular basin was simulated numerically and continuity and Novier-Stokes equations were solved using the Finite Volume method. 3-D flow simulation was performed using standard k-ε turbulence model and flow velocity profiles at different sections of the pre-sedimentation basin were compared with the experimental results and the results were in good agreement. Then, in order to investigate the sedimentation pattern in pre-sedimentation basin, convection-diffusion equation of the sediment concentration was simultaneously solved with the governing equations of the flow hydraulics. Finally, vertical distribution of sediment concentration at different basin sections was compared with the experimental and numerical results of other researchers. The results indicated a good agreement between the numerical and experimental results as well as the model ability to predict sediment distribution profiles in pre-sedimentation basins. پرونده مقاله -
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72 - بررسی وقوع پدیده گرد و غبار روز 27 مارس 2003 ایستگاه کرمانشاه و ارتباط آن با جت استریم
نیره سیدزاده اقدم پری سیما کتیرایی بروجردی عباس رنجبرمطالعه حاضر بررسی همدیدی پدیده گرد و غبار ایستگاه همدیدی کرمانشاه که یکی از مناطق متأثر از این پدیدهی مخرب جوی است، در تاریخ 27 مارس 2003می باشد. نتایج حاصله از بررسی همدیدی نقشه های میانگین روزانه ارتفاع تراز 500 هکتوپاسکال و نقشه های میدان فشاری تراز دریا و نقشههای چکیده کاملمطالعه حاضر بررسی همدیدی پدیده گرد و غبار ایستگاه همدیدی کرمانشاه که یکی از مناطق متأثر از این پدیدهی مخرب جوی است، در تاریخ 27 مارس 2003می باشد. نتایج حاصله از بررسی همدیدی نقشه های میانگین روزانه ارتفاع تراز 500 هکتوپاسکال و نقشه های میدان فشاری تراز دریا و نقشههای میدان باد تراز 250 هکتوپاسکال نشان داد که از ویژگی های جوی مؤثر، علاوه بر همخوانی ناوهتر از میانی جو مستقر روی دریای سیاه و شمال دریای مدیترانه با کم فشارهای حاکم بر عراق، شرق ترکیه و شمال عربستان، واگرایی 2 جت استریم جنب حاره در تراز 200 و جت استریم جبهه قطبی در تراز 250 هکتوپاسکال از مهم ترین عوامل تقویت همگرایی و ایجاد حرکات صعودی روی نواحی بیابانی کشورهای عراق، سوریه و اردن، بین طول های 35 تا 50 درجه شرقی و 30 تا 35 درجه شمالی میباشد. همچنین هرچه زاویه محور فضایی بین مرکز کم فشار سطح زمین و مرکز کم ارتفاع تراز 500 هکتوپاسکالی بیشتر باشد شدت رخداد پدیده نیز بیشتر خواهد بود. پرونده مقاله -
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73 - Analytical and Numerical Consideration of Projectile Density Effect on Its Penetration Ability in Alumina Armor
حسین کیا علی مهدی پور عمرانیIn this paper, penetration of high velocity impact of 4340 steel and tungsten carbide projectiles with specific shapes in to ceramic armor that includes 10 mm alumina (95%) is considered analytically and simulated with Ls-Dyna software. Bernoulli equation used to consid چکیده کاملIn this paper, penetration of high velocity impact of 4340 steel and tungsten carbide projectiles with specific shapes in to ceramic armor that includes 10 mm alumina (95%) is considered analytically and simulated with Ls-Dyna software. Bernoulli equation used to consider the penetration velocity in ceramics, shows that the penetration is better and easier by increasing projectile density. The simulations showed the same results as well. Using the numerical solution, ballistic limit velocity (BLV) of ceramic armor is calculated and the results showed that the increase in projectile density decreased BLV and so the tungsten carbide projectile which is heavier than steel, penetrates alumina target easier and better and with lower velocity (about 100 m/s) with respect to steel projectile in which BLV is about 170 m/s. Also, comparison between the analytical and the numerical method reveals that the compatibility of these solutions are better at higher range of velocity. پرونده مقاله -
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74 - EFFECTS OF MAGNETIC FIELD ON THE RED CELL ON NUTRITIONAL TRANSPORT IN CAPILLARY-TISSUE EXCHANGE SYSTEM
Nirmala P Ratchagar Vijaya KumarA mathematical model for nutritional transport in capillary tissues exchange system in thepresence of magnetic field has been studied. In this case, the cell is deformed. Due to concentrationgradients, the dissolved nutrient in substrate diffuses into surrounding tissue چکیده کاملA mathematical model for nutritional transport in capillary tissues exchange system in thepresence of magnetic field has been studied. In this case, the cell is deformed. Due to concentrationgradients, the dissolved nutrient in substrate diffuses into surrounding tissue. Theanalytical method is based on perturbation technique while the numerical simulation is basedon finite difference scheme. Results concerning the concentration of dissolved nutrients, diffusiveflux, normal component of velocity and skin friction coefficient, indicate that the presenceof magnetic field influences the flow field considerably. پرونده مقاله -
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75 - MATHEMATICAL ANALYSIS OF NEWLY DESIGNED TWO POROUS LAYERS SLIDER BEARING WITH A CONVEX PAD UPPER SURFACE CONSIDERING SLIP AND SQUEEZE VELOCITY USING FERROFLUID LUBRICANT
Rajesh Shah Ramesh C. KatariaThis paper proposes mathematical modeling and analysis of ferrofluid lubricated newly designed slider bearing having convex pad (surface or plate) stator with two porous layers attached to the slider. The problem considers the effect of slip velocity proposed by Sparrow چکیده کاملThis paper proposes mathematical modeling and analysis of ferrofluid lubricated newly designed slider bearing having convex pad (surface or plate) stator with two porous layers attached to the slider. The problem considers the effect of slip velocity proposed by Sparrowet. al.[1] and modified by Shahet. al.[2] at the film-porous interface. The squeeze velocityV=−which appears when the upper impermeable plate approach to the lower one, is also considered here for study. The magnetic field is assumed to be oblique to the lower plate. From the Reynolds’s equation of the above model, expressions for dimensionless form of pressure and load carrying capacity are obtained. The expression for the dimensionless load carrying capacity is then solved numerically to examine its possible effect on the designed bearing system پرونده مقاله -
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76 - Comparing Aerodynamic Terminal Velocity of Open and Closed Mouth Pistachio Nuts Using Wind Column
Kobra Heidarbeigi Sadegh SamadiDetermining the terminal velocity as one of the important aerodynamic properties of particles and grains is essential for pneumatic separation, grading, and handling. A wind tunnel system was used in the present research to measure the aerodynamic terminal velocity of p چکیده کاملDetermining the terminal velocity as one of the important aerodynamic properties of particles and grains is essential for pneumatic separation, grading, and handling. A wind tunnel system was used in the present research to measure the aerodynamic terminal velocity of pistachio nuts. Some physical properties were measured and calculated. The effects of pistachio mouth status at four levels (closed, open, and semi-open mouth, and shell) were investigated on its terminal velocity. The volume, mass and density of that were 1.33±0.37 cm3, 0.97±0.31 g and 0.72±0.18 g cm3-1, respectively. The average aerodynamic terminal velocity of pistachio was 9.43±1.38 m s-1. The aerodynamic terminal velocity of the pistachio had a direct relationship with the studied physical characteristics, except for density. The terminal velocity of open-mouth pistachio nuts (9.50±0.61 m s-1) was significantly lower than that of closed (10.12±0.51 m s-1) and semi-open mouth (10.16±0.62 m s-1) nuts, with the terminal velocity of the shells (6.51±0.65 m s-1) showing the lowest values. The results revealed that terminal velocity can be considered for pneumatic separation of shells from pistachio nuts as well as the separation of open-mouth nuts from closed-mouth ones. پرونده مقاله -
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77 - بررسی ریزساختاری تکاسپلت آلومینایی ایجاد شده با فرآیند پاشش شعلهای سرعت بالای محلول پیشماده
سعید تقی رمضانی ضیاء والفیفرآیندهای پاشش حرارتی محلول پیش ماده (SPTS) روشی مناسب جهت تولید پوشش های با ساختار نانو هستند. بهواسطهی عدم رخداد کامل واکنش هایی نظیر تبخیر حلال و پیرولیز پیشماده، دستیابی به پوشش های با خواص کنترلشده در یک نرخ رسوب دهی رضایتبخش کماکان بهعنوان یک چالش مهم در این چکیده کاملفرآیندهای پاشش حرارتی محلول پیش ماده (SPTS) روشی مناسب جهت تولید پوشش های با ساختار نانو هستند. بهواسطهی عدم رخداد کامل واکنش هایی نظیر تبخیر حلال و پیرولیز پیشماده، دستیابی به پوشش های با خواص کنترلشده در یک نرخ رسوب دهی رضایتبخش کماکان بهعنوان یک چالش مهم در این فرآیندها مطرح است که نیاز به کنترل دقیق پارامترهای پاشش دارد. در این تحقیق، بهمنظور بررسی تأثیر پارامترهای پاشش شعله ای سرعت بالای محلول پیش ماده از جمله مقدار سوخت و اکسیژن، فاصله پاشش و نرخ تزریق محلول از آزمون پاشش تک اسکن بر روی زیرلایه های شیشه ای استفاده شد. مورفولوژی اسپلت های تشکیلشده و مشخصه های ساختاری با استفاده از میکروسکوپ الکترون روبشی (SEM) بررسی شد. مقایسه ی ساختاری در آزمون پاشش تک اسکن که در دو نسبت سوخت به اکسیژن انجام شد، نشان داد که در پارامتر شعله با فشار اکسیژن bar 6 و سوخت bar 3 در نرخ تزریق محلول پیشمادهcm3/min 20 و فاصله پاششcm 5 به عنوان پارامتر بهینه انتخاب شد. در این پارامتر به دلیل پایین بودن نرخ تزریق محلول و انتقال گرمای بیشتر به ازای هر قطره محلول پیش ماده و تکمیل فرآیندهایی که در نتیجه آن ذوب و کریستالی شدن اتفاق می افتد، تعداد اسپلت ها افزایش یافت. همچنین ارزیابی پاشش تک اسکن در شعله با فشار اکسیژن bar 8 و سوخت bar 4 و فاصله پاششcm 5 نشان داد که نرخ تزریق محلول پیشمادهcm3/min 40 به دلیل افزایش تعداد اسپلت های ریز و بهواسطهی بهبود راندمان پوشش دهی مناسب تر خواهد بود. پرونده مقاله -
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78 - Vibration Suppression of Smart FGM Cylindrical Shells Using Magnetostrictive Layers
منصور درویزه رضا انصاری ابوالفضل درویزه رضا رجبیه فردIn the present work, FGM shells integrated with magnetostrictive layers acting as distributed sensors and actuators are modeled to control vibration attenuation of FGM shells with simply supported boundaryconditions. To achieve a mechanism for actively control of the os چکیده کاملIn the present work, FGM shells integrated with magnetostrictive layers acting as distributed sensors and actuators are modeled to control vibration attenuation of FGM shells with simply supported boundaryconditions. To achieve a mechanism for actively control of the oscillation amplitude of the integrated structure, a negative velocity proportional feedback control law is implemented in the study. Theoretical formulation is based on the first order shear deformation shell theory, taking into consideration transverse shear deformation and rotary inertia effects. Material properties are assumed to be temperature-dependent and graded in the thickness direction according to different volume fraction functions. A FGM cylindrical shell made up of a mixture of ceramic and metal is considered. The magnetostrictive layers are also considered to be made of Terfenol-D. The influence of vibration attenuation characteristics of magnetostrictive layers, the location of these layers and control parameters on vibration suppression is investigated. پرونده مقاله -
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79 - An Upper Bound Solution for Analysis of Twist Extrusion Process with Elliptical Die Cross-section
یاسر میرباقری حامد معصومی مجید سیدصالحیTwist extrusion process is a rather new route to produce highly strained materials. In this process, severe plastic deformation is applied by large shear strains. In current article, required energy for twist extrusion by use of admissible velocity field together with t چکیده کاملTwist extrusion process is a rather new route to produce highly strained materials. In this process, severe plastic deformation is applied by large shear strains. In current article, required energy for twist extrusion by use of admissible velocity field together with the upper bound technique is predicted. The proposed model is capable of considering the effect of various parameters such as die geometry and friction conditions. In addition, the model anticipates the critical die design parameters. To verify the proposed model, the predictions were compared with the results of a finite-element analysis and reasonable consistency was observed. پرونده مقاله -
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80 - The comparison of dominant and non-dominant hand velocity during Gyakuzuki technique in elite Karatekas
ُSalar Hariri Vahid Akbaree Rahim Teymuri Ali jahaniBackground: The purpose of this research was to compare the velocity of the dominant hand and the non-dominant hand in the Gyakozuki technique (with hit and without hit) of elite karate men.Methods: 16 Iranian male karatekas with individual characteristics from the nati چکیده کاملBackground: The purpose of this research was to compare the velocity of the dominant hand and the non-dominant hand in the Gyakozuki technique (with hit and without hit) of elite karate men.Methods: 16 Iranian male karatekas with individual characteristics from the national karate team camp participated in this study. The subjects were asked to perform the Gyakuzuki technique with the dominant hand and the non-dominant hand five times with maximum intensity and strength, hit the shoot fist device. The distance of standing from the device was equal to the length of the upper limb, and the best record of all five performances was considered. It was recorded using a Hero3 digital camera made in the United States (240Hz) in two dimensions. It was filmed at a perpendicular angle to the subject. The peak velocity of the joints (shoulder, elbow, wrist) and the velocity at the moment of the collision were evaluated using Skillspector software. After ensuring the normality of the data using the Shapiro–Wilk test, independent t-tests were used at the level of (p ≤ 0.05) with spss version 22 software.Result: The test results showed a significant difference between peak joint velocity shoulder, elbow, and wrist withthe dominant and non-dominant hand in the with-hit and without-hit method ( p ≤0.05). Also, there was a significant relationship between the velocity of the wrist in contact moment with the dominant and non-dominant hand in the with-hit and without-hit methods ( p ≤0.05).Conclusion: According to the fest result, if a karate man wants to reach to velocity peak with the dominant hand in Gyakuzuki Techniques, he should reinforce the antagonist and stabilizer muscles in the non-dominant hand. پرونده مقاله
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