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دسترسی آزاد مقاله
1 - On optical field driven quantum spin Hall phase in Bi_2Se_3 thin film with magnetic Impurities
Udai Tyagi Partha GoswamiThe normal incidence of circularly polarized optical field (POF) of tunable intensity on the topological insulator Bi2Se3 film is shown to give rise to the quantum spin Hall (QSH) effect, in the presence of the magnetic impurities (MI), starting with a low-energy two-di چکیده کاملThe normal incidence of circularly polarized optical field (POF) of tunable intensity on the topological insulator Bi2Se3 film is shown to give rise to the quantum spin Hall (QSH) effect, in the presence of the magnetic impurities (MI), starting with a low-energy two-dimensional, time-dependent Hamiltonian in the framework of the Floquet theory. The quantized topological number- the KaneMele index Z2 for QSH phase- strongly support this topological state. پرونده مقاله -
دسترسی آزاد مقاله
2 - تبیین اثر بخشی مدل کسبوکار اقتصاد دایرهای در شرکتهای دانش بنیان
فاطمه شهدکار تقی ترابی فریدون رهنمای رود پشتیهدف از پژوهش حاضر بررسی تأثیر به کارگیری مدل کسبوکار اقتصاد دایرهای برای شرکتهای دانش بنیان میباشد. این پژوهش از نظر هدف، در دسته پژوهشهای کاربردی و بر اساس نحوه جمعآوری دادهها، توصیفی- پیمایشی است. جامعه آماری این پژوهش عبارتند از کلیه مدیران شرکتهای دانش بنیان چکیده کاملهدف از پژوهش حاضر بررسی تأثیر به کارگیری مدل کسبوکار اقتصاد دایرهای برای شرکتهای دانش بنیان میباشد. این پژوهش از نظر هدف، در دسته پژوهشهای کاربردی و بر اساس نحوه جمعآوری دادهها، توصیفی- پیمایشی است. جامعه آماری این پژوهش عبارتند از کلیه مدیران شرکتهای دانش بنیان پنج استان کشور که در سال 1400 به خدمت اشتغال داشتهاند؛ که تعداد 354 نفر به عنوان نمونه تحقیق، به روش نمونهگیری تصادفی طبقهای انتخاب شدند. در این پژوهش از پرسشنامه محقق ساخته استفاده شده که روایی و پایایی آن مورد تأیید قرار گرفت. برای تحلیل دادههای گردآوری شده از آزمونهای کولموگروف- اسمیرنف، به منظور نرمال بودن دادهها و همچنین تحلیل عاملی تأییدی و روش معادلات ساختاری از نرمافزار (AMOS24) استفاده شد. یافتهها نشان داد که در بین مؤلفههای مورد مطالعه به ترتیب: فرآیند با ضریب مسیر (0/76)، الزامات اجرای اقتصاد دایرهای (0/88)، رابط کاربری (0/97)، اکوسیستم با ضریب مسیر (0/99)، ساختار مالی (0/99) و ارزش (0/99) بیشترین تأثیر را در مدل کسبوکار اقتصاد دایرهای دارند. مدل حاصل از این پژوهش میتواند راهگشای دستاندرکاران و برنامهریزان معاونت علمی ریاست جمهوری، وزارت علوم، مدیران پارکهای علم و فناوری جهت پیادهسازی و اجرای موفق اقتصاد دایرهای و مدل کسبوکار مربوطه، ارتقای سطح اقتصادی کشور و نیز ایجاد فرصتهای نوآورانه و سازگار با محیطزیست جهت افزایش اشتعال و رونق اقتصادی میباشد. پرونده مقاله -
دسترسی آزاد مقاله
3 - External and Internal Incompressible Viscous Flows Computation using Taylor Series Expansion and Least Square based Lattice Boltzmann Method
E. ShayanThe lattice Boltzmann method (LBM) has recently become an alternative and promising computational fluid dynamics approach for simulating complex fluid flows. Despite its enormous success in many practical applications, the standard LBM is restricted to the lattice unifo چکیده کاملThe lattice Boltzmann method (LBM) has recently become an alternative and promising computational fluid dynamics approach for simulating complex fluid flows. Despite its enormous success in many practical applications, the standard LBM is restricted to the lattice uniformity in the physical space. This is the main drawback of the standard LBM for flow problems with complex geometry. Several approaches have been developed to remove this drawback of standard LBM. One of these methods is the Taylor series expansion and least squares-based LBM (TLLBM). This method is based on the standard LBM combined with the Taylor series expansion and the least squares approach. The prominent feature of the TLLBM is the fact that the final equation is an explicit form and in essence has no limitation on the mesh structure and lattice model. In the present work, the TLLBM with D2Q9 lattice model is used to simulate 2-D steady incompressible viscous flows (both internal and external) on non-uniform meshes. Four test cases are studied: (i) flow past a circular cylinder with a non-uniform O-type mesh; (ii) flow in a rectangular lid driven cavity with a non-uniform H-type mesh; and (iii) flow over a backward- facing step. It was found that this model could give very accurate results for both the internal and external flows. پرونده مقاله -
دسترسی آزاد مقاله
4 - Incompressible smoothed particle hydrodynamics simulations on free surface flows
A. Mahmoud ‎Aly‎‎‎The water wave generation by wave paddle and a freely falling rigid body are examined by using an Incompressible Smoothed Particle Hydrodynamics (ISPH)‎. ‎In the current ISPH method‎, ‎the pressure was evaluated by solving pressure Poisson equation چکیده کامل‎The water wave generation by wave paddle and a freely falling rigid body are examined by using an Incompressible Smoothed Particle Hydrodynamics (ISPH)‎. ‎In the current ISPH method‎, ‎the pressure was evaluated by solving pressure Poisson equation using a semi-implicit algorithm based on the projection scheme and the source term of pressure Poisson equation contains both of divergence free velocity field and density invariance condition‎. ‎Here‎, ‎the fluid-structure interaction is introduced in free surface flows and the structure is taken as a rigid body motion‎. ‎In this study‎, ‎we generated the water waves using the Scott Russell wave generator‎, ‎in which the heavy box sinking vertically into water‎. ‎Also‎, ‎the solitary wave is generated by using the wave paddle and the generated solitary wave profiles are compared with the available results with a good agreement‎. ‎Free falling of torpedo over the water in tank was simulated by using 3D-ISPH ‎method. پرونده مقاله -
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5 - Joining of Ti-6AL-4V to AISI 304 Stainless Steel using Laser Spot Welding with Circular Technique
M Rafi H Sabet V Abouei Mehrizi A AnbarzadehIn this research, dissimilar laser spot welding of the Ti-6Al-4V and AISI 304 (stainless steel) was investigated. The joining of 0.7 and 0.5 mm thickness plates with using a copper interlayer of 0.2 and 0.3 mm in thickness was performed by LSW. A 400-W Nd: YAG laser pul چکیده کاملIn this research, dissimilar laser spot welding of the Ti-6Al-4V and AISI 304 (stainless steel) was investigated. The joining of 0.7 and 0.5 mm thickness plates with using a copper interlayer of 0.2 and 0.3 mm in thickness was performed by LSW. A 400-W Nd: YAG laser pulse welding machine was used to obtain coaxial spot welds of 4 mm in diameter with circular technique. Visual inspection and metallographic examination were used for all samples. If no crack was identified, micro-Vickers hardness test, tensile test, and scanning electron microscopy (SEM) were performed on the samples. The result indicated that with a copper interlayer and 10.7 J heat input on peak power of 1.5 kW, welding frequency 15 Hz, and welding time of 7 ms, leading to an ultimate strength of 160 MPa. In addition the result indicated that applying the circular technique by creating adjacent spot welds can produce a good joint. پرونده مقاله -
دسترسی آزاد مقاله
6 - آنتن چندبانده شانه ای با قطبی شدگی دایروی برای کاربردهای مخابرات بی سیم و اینترنت اشیا
رضا خواجه محمدلو توحید اریبی توحید صدقیدر این پژوهش، نمونه جدیدی از آنتن ریزنوار چندبانده با قطبی شدگی دایروی برای کاربردهای موبایل و اینترنت اشیا معرفی میشود. باندهای فرکانسی کاربردی به طور همزمان و قابل قبولی توسط آنتن اشاره شده تحت پوشش قرار میگیرند که عبارت اند از WLAN(2400 تا 2484 مگا هرتز) WiMAX (IEEE چکیده کاملدر این پژوهش، نمونه جدیدی از آنتن ریزنوار چندبانده با قطبی شدگی دایروی برای کاربردهای موبایل و اینترنت اشیا معرفی میشود. باندهای فرکانسی کاربردی به طور همزمان و قابل قبولی توسط آنتن اشاره شده تحت پوشش قرار میگیرند که عبارت اند از WLAN(2400 تا 2484 مگا هرتز) WiMAX (IEEE 802.16e) 2500 تا 2600 مگاهرتز، اینترنت اشیا (IoT) 2400 تا 2480 مگاهرتز با استاندارد IEEE 802.11.ax، WLAN(5150 تا 5825 مگا هرتز) که استاندارد IEEE802.11ac نامگذاری میگردد. فرایند طراحی آنتن برای دسترسی به باندهای فرکانسی مورد نظر به صورت مرحله به مرحله در متن مقاله اشاره شده است انجام میپذیرد. با استفاده از تکنیک تسهیل چرخش جریان روی آنتن، تحریک دو مود متعامد به راحتی صورت گرفته و در نتیجه قطبی شدگی دایروی محقق می شود. از سوی دیگر تقریبا در کل باندهای کاربردی مورد نظر خصیصه قطبی-شدگی دایروی محقق میشود که به عنوان یک مزیت قابل توجه برای این سیستم تشعشعشی محصوب میشود. ابعاد کلی آنتن مورد نظر 23×34×8/0میلی متر مکعب بوده که روی زیر لایه FR4 با ضریب نسبی دی الکتریک 4/4 و تانژانت تلفات 024/0 محقق میشود. به منظور تصدیق فرایند طراحی، ساختار مورد نظر ساخته شده و مورد تست و اندازه گیری قرار میگیرد. نتایج استخراج شده نشان میدهد که آنتن مورد نظر دارای الگوی تشعشعی همه جهته و بهره مناسبی در باندهای فرکانسی مورد نظر می باشد. پرونده مقاله -
دسترسی آزاد مقاله
7 - آنتن دو قطبی مغناطیسی-الکتریکی با خصیصه قطبش دایروی و الگوی تشعشعی یک جهته با هدف بهبود پهنای باند
سید علی بنی هاشم پژمان محمدی یاشار زهفروشدر این مقاله ساختار جدید و فشرده ای از آنتن یک جهته که از یک دوقطبی الکتریکی صفحه ای و یک المان اتصال کوتاه شده تشکیل شده، معرفی میشود. این آنتن توسط یک خط تغذیه Γ شکل تحریک می گردد. پهنای باند امپدانسی عریضی در بازه فرکانسی 3/1 گیگاهرتز تا 3 گیگاهرتز در عملکرد خ چکیده کاملدر این مقاله ساختار جدید و فشرده ای از آنتن یک جهته که از یک دوقطبی الکتریکی صفحه ای و یک المان اتصال کوتاه شده تشکیل شده، معرفی میشود. این آنتن توسط یک خط تغذیه Γ شکل تحریک می گردد. پهنای باند امپدانسی عریضی در بازه فرکانسی 3/1 گیگاهرتز تا 3 گیگاهرتز در عملکرد خروجی این آنتن مشاهده میشود. الگوهای تشعشعی پایه دار با سطح گلبرگ اصلی بالا و سطح گلبرگ فرعی و پشتی کم از خصایص دیگر آنتن معرفی شده اند. فرایند طراحی آنتن به صورت پله به پله و پارامتریک بر مبنای مقادیر کلیدی هندسه آنتن صورت پذیرفته است. خصیصه اصلی آنتن مورد نظر، تحقق قطبش دایروی در درصد بالایی از پهنای باند کاربردی است. الگوهای تشعشعی صفحات متعامد E و H همراه با الگوهای قطبش دایروی چپگرد و راستگرد برای آنتن مورد نظر استخراج شده و مورد تحلیل قرار گرفته است. شباهت زیادی میان الگوی صفحه ایE و H وجود دارد که نشان دهنده دقت فرایند طراحی است. از سوی دیگر برای مطالعه حالت قطبش دایروی، نمودارهای چپگرد و راستگرد بر مبنای جهت بیم اصلی و سطح قطبش متعامد دارای عملکرد قابل قبولی هستند. بیشینه بهره کلی آنتن در باند فرکانس طراحی شده نزدیک 10 دسیبل است. پرونده مقاله -
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8 - آنتن دوقطبی متعامد دارای المانهای پارازیتیک ترنج شکل با قابلیت قطبش دایروی و کاربرد در سیستم موقعیتیاب جهانی
امیر سیاهچشماین مقاله یک آنتن دوقطبی چاپی متعامد با قطبش دایروی برای گیرنده¬های سیستم موقعیت¬یاب جهانی (Global Positioning System) در باند L1 (1575 مگاهرتز) را ارائه میدهد. ساختار آنتن متشکل از دو عدد دوقطبی چاپی است که بصورت متعامد نسبت به یکدیگر قرار گرفتهاند و شامل دو بالن یک چکیده کاملاین مقاله یک آنتن دوقطبی چاپی متعامد با قطبش دایروی برای گیرنده¬های سیستم موقعیت¬یاب جهانی (Global Positioning System) در باند L1 (1575 مگاهرتز) را ارائه میدهد. ساختار آنتن متشکل از دو عدد دوقطبی چاپی است که بصورت متعامد نسبت به یکدیگر قرار گرفتهاند و شامل دو بالن یکپارچه برای تغذیه دوقطبیها و یک شبکه تغذیه متصل به بالنها است. در این طراحی، شبکه تغذیه از یک تزویجگر شاخهای (Branch-Line Coupler) با دو خروجی مربعی (Quadrature Outputs) تشکیل یافته است. بر این اساس، تغذیه دو دوقطبی متعامد با اختلاف فاز 90 درجه منجر به قطبش دایروی راستگرد میشود که برای کاربردهای سیستم موقعیت¬یاب جهانی امری الزامی است. با هدف بهبود قطبش دایروی آنتن، از چهار عدد المان پارازیتیک ترنج شکل در قسمت فوقانی بازوهای دوقطبی استفاده شده است. طبق نتایج عملی به دست آمده با تکنیک بکار گرفتهشده، پهنای باند نسبت محوری (Axial Ratio) آنتن در حدود 21% افزایش یافته و همزمان خلوص قطبش دایروی آنتن نیز بهبود قابل ملاحظهای داشته است. نتایج تجربی تأیید میکنند که آنتن پیشنهادی برای سیستم موقعیت¬یاب جهانی دارای پهنای باند امپدانسی 28/46% (از 327/1 تا 126/2 گیگاهرتز)، پهنای باند نسبت محوری 36/41% (از 329/1 تا 022/2 گیگاهرتز) و حداکثر بهره 40/6 دسی¬بل است. ابعاد آنتن پیشنهادی کوچک بوده و این آنتن دارای الگوی تشعشعی پایداری است. در گام آخر آنتن پیشنهادی برای سیستم موقعیت¬یاب جهانی در آزمایشگاه آنتن ساخت و تست شده است. پرونده مقاله -
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9 - Flow Study of Wood Plastic Composite Through a Circular Die in an Extrusion Process
N. Jafarian Jam E. SouryThis paper presents a theoretical study on wood plastic composite's (WPC's) flow, based on empirical data provided by a twin screw extruder and experimental data from a rotational rheometer. Four circular extrusion dies were designed and manufactured to produce rod shap چکیده کاملThis paper presents a theoretical study on wood plastic composite's (WPC's) flow, based on empirical data provided by a twin screw extruder and experimental data from a rotational rheometer. Four circular extrusion dies were designed and manufactured to produce rod shaped products with various diameters (D) and length-to-diameter ratios (L/D). Also other parameters such as screw speed (N), polymer matrix type, polymer viscosity (m) and percentage of wood content (W) were selected as the process or material factors to investigate the relationship between the flow characteristics and the above mentioned factors. Moreover, frequency sweep experiments were performed on the selected composites using rotational plate rheometer. The results from these experiments have been studied by using power law and Bingham plastic models which are believed as proper models for WPC in the literature. The results show that Bingham plastic model can explain the flow characteristics of this composite much better. Moreover, although the results of a frequency sweep test can give the required values for parameters in the Bingham plastic model, these quantities will be different with those from empirical experiments. پرونده مقاله -
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10 - Application of Improved Blocked-Off Method to Simulate the Interacting Influences of Obstacle Shape and Wall Velocity on the Turbulent Mixed Convection Flow in a Trapezoidal Cavity
Meysam AtashafroozIn the current research, interaction influences of obstacle shape and top wall velocity on the hydrothermal behaviours of the turbulent mixed convection flow in a trapezoidal cavity are numerically simulated. To achieve this goal, three different shapes of the obstacles چکیده کاملIn the current research, interaction influences of obstacle shape and top wall velocity on the hydrothermal behaviours of the turbulent mixed convection flow in a trapezoidal cavity are numerically simulated. To achieve this goal, three different shapes of the obstacles including semicircular, triangular, rectangular are considered. Dimensions of these obstacles are chosen so that the environment around all three of them is same. The RNG model is chosen to simulate the turbulent flow. To model the inclined or curved walls of trapezoidal cavity and obstacles, the improved blocked-off method is applied. Results show that the obstacle shape and top wall velocity have a significant influence on the thermal and hydrodynamic behaviours. In fact, the highest magnitude of heat transfer rate along the bottom wall occurs in the cavity with the rectangular obstacle and for the highest magnitude of top wall velocity; whilst its lowest magnitude is related to the pure free convection and for the cavity with the semicircular obstacle. Besides, the lowest and highest magnitudes of temperatures fields occur for the cavities with rectangular and triangular obstacles, respectively. پرونده مقاله -
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11 - Performance Improvement of Fractal Microstrip Antenna with Metamaterial
Gohar Varamini Mehdi Khatir Mohammad Naser-MoghadasiThis study was carried out to design, simulate, and develop an ultra wideband (UWB) fractal microstrip patch antenna (MPA). The antenna designed for broadband telecommunications had smaller dimensions, omnidirectional pattern, and good gain/return loss. The miniaturizat چکیده کاملThis study was carried out to design, simulate, and develop an ultra wideband (UWB) fractal microstrip patch antenna (MPA). The antenna designed for broadband telecommunications had smaller dimensions, omnidirectional pattern, and good gain/return loss. The miniaturization was realized through a metamaterial transmission line and antenna power supply by an electromagnetic coupling system. In order to cover the desired frequency bandwidth, a new fractal was designed and combined with the circular polarization of disturbances in certain parts of the fractal structure. Furthermore, the quality of antenna bandwidth was improved deforming the ground plane. Finally, the results of the development, simulation, and measurement of input return losses and radiation patterns were explored. The results demonstrated that the proposed model involves a compact, simple fractal MPA that provides ideal bandwidth and impedance matching. پرونده مقاله -
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12 - A New Three-Dimensional Sector Element for Circular Curved Structures Analysis
H. E Khiouani L Belounar M Nabil HouhouIn this research paper, the formulation of a new three-dimensional sector element based on the strain approach is presented for plate bending problems and linear static analysis of circular structures. The proposed element has the three essential external degrees of fre چکیده کاملIn this research paper, the formulation of a new three-dimensional sector element based on the strain approach is presented for plate bending problems and linear static analysis of circular structures. The proposed element has the three essential external degrees of freedom (Ur, Vθ and W) at each of the eight corner nodes. The displacements field of the present element is based on assumed functions for the different strains satisfying the compatibility equations. The effectiveness of the present element is applied through several tests related to plate bending problems and linear static analysis of circular structures. The results of the developed element have been compared with analytical and other numerical solutions available in the literature. The obtained results show the excellent performances and precision of the present element. It is found that the new three-dimensional sector element is more accurate and efficient than the three-dimensional classical element based on displacement approach. پرونده مقاله -
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13 - Effects of Viscosity on a Thick Circular Plate in Thermoelastic Diffusion Medium
R Kumar Sh DeviThe problem treated here is to determinethe viscosity effect on stresses, temperature change and chemical potential in a circular plate. The mathematical formulation is applied to two theories of thermoelastic diffusion developed by Sherief et al. [27] with one relaxati چکیده کاملThe problem treated here is to determinethe viscosity effect on stresses, temperature change and chemical potential in a circular plate. The mathematical formulation is applied to two theories of thermoelastic diffusion developed by Sherief et al. [27] with one relaxation time and Kumar and Kansal [9]with two relaxation times. Laplace and Hankel transform techniques are used to obtain the expression for the displacement components, stresses, temperature change and chemical potential. The resulting quantities are computed numerically and depicted graphically by using numerical inversion technique for a particular model. Effect of viscosity is shown in the normal stress, tangential stress, temperature change and chemical potential. Some particular cases of interest are also deduced. Viscoelastic materials play an important role in many branches of engineering, technology and, in recent years, biomechanics. Viscoelastic materials, such as amorphous polymers, semicrystalline polymers, and biopolymers, can be modelled in order to determine their stress or strain interactions as well as their temporal dependencies. پرونده مقاله -
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14 - Effect of Winkler Foundation on Radially Symmetric Vibrations of Bi-Directional FGM Non-Uniform Mindlin’s Circular Plate Subjected to In-Plane Peripheral Loading
N Ahlawat R LalAn analysis has been presented of the effect of elastic foundation and uniform in-plane peripheral loading on the natural frequencies and mode shapes of circular plates of varying thickness exhibiting bi-directional functionally graded characteristics, on the basis of f چکیده کاملAn analysis has been presented of the effect of elastic foundation and uniform in-plane peripheral loading on the natural frequencies and mode shapes of circular plates of varying thickness exhibiting bi-directional functionally graded characteristics, on the basis of first order shear deformation theory. The material properties of the plate are varying following a power-law in both the radial and transverse directions. The numerical solutions of the coupled differential equations leading the motion of simply supported and clamped plates acquired by using Hamilton’s principle, is attained by harmonic differential quadrature method. The effect of different plate parameters namely gradient index, heterogeneity parameter, density parameter, taper parameter and thickness parameter is illustrated on the vibration characteristics for the first three modes of vibration for various values of in-plane peripheral loading parameter together with foundation parameter. Critical buckling loads in compression are calculated for both the boundary conditions by putting the frequencies to zero. The reliability of the present technique is confirmed by comparing the results with exact values and results of published work. پرونده مقاله -
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15 - Nonlinear Investigation of Magnetic Influence on Dynamic Behaviour of Non-Homogeneous Varying Thickness Circular Plates Resting on Elastic Foundations
S.A Salawu G.M Sobamowo O.M SadiqIn this work, a nonlinear investigation of non-homogeneous varying thickness circular plates resting on elastic foundations under the influence of the magnetic fieldis investigated. The non-homogeneity of the circular plates’ material is presumed to occur due to l چکیده کاملIn this work, a nonlinear investigation of non-homogeneous varying thickness circular plates resting on elastic foundations under the influence of the magnetic fieldis investigated. The non-homogeneity of the circular plates’ material is presumed to occur due to linear and parabolic changes in Young’s modulus likewise the density along the radial direction in a unique manner. The geometric Von Kármán equations are used in modelling the governing differential equations. The transverse deflection is approximated using an assumed single term mode shape while the central deflection in form of Duffing’s equation is obtained using the Galerkin method. Subsequently, the semi-analytical solutions are provided using the Optimal Homotopy Asymptotic Method (OHAM), the analytical solutions are used for parametric investigation. The results in this work are in good harmony with past results in the literature. From the results, it is realized that the nonlinear frequency of the circular plate increases with an increase in the linear elastic foundation. Also, the results showed that clamped edge and simply supported edge condition produced the same hardening nonlinearity. However, varying taper and non-homogeneity lower the nonlinear frequency ratio. Also, maximum deflection occurs when excitation force is zero, and attenuation of deflection is observed due to the presence of a magnetic field, varying thickness, homogeneity, and elastic foundation. It is anticipated that the discoveries from this research will boost the design of structures subjected to vibration. پرونده مقاله -
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16 - Thermal Buckling Analysis of Temperature Dependent Porous FGM Mindlin Nano Circular Plate on Elastic Foundation
M. M Mohieddin GhomsheiIn the present work, the symmetric thermal buckling behavior of shear deformable heterogonous nano/micro circular porous plates resting on a two parameter foundation is studied. The material behavior of the nano plate is modeled by the modified couple stress theory. The چکیده کاملIn the present work, the symmetric thermal buckling behavior of shear deformable heterogonous nano/micro circular porous plates resting on a two parameter foundation is studied. The material behavior of the nano plate is modeled by the modified couple stress theory. The plate material properties assumed to be graded across the thickness direction according to a simple power law, and has a uniform porosity. Using Mindlin’s plate theory and the nonlinear von-Karman strain field and implementing the energy method, the plate stability equations together with the membrane equilibrium equation are derived and expressed in terms of the displacement field components. Then the nondimensionalized forms of the equations are discretized using differential quadrature method (DQM). The resulting eigenvalue problem is solved to evaluate the plate critical buckling temperature difference. Comparative studies are carried out. Also the influences of some important parameters including length scale factor, porosity factor and Winkler& Pasternak stiffness coefficients are investigated.. پرونده مقاله -
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17 - A Problem of Axisymmetric Vibration of Nonlocal Microstretch Thermoelastic Circular Plate with Thermomechanical Sources
R Kumar R Rani A MiglaniIn the present manuscript, we investigated a two dimensional axisymmetric problem of nonlocal microstretch thermoelastic circular plate subjected to thermomechanical sources. An eigenvalue approach is proposed to analyze the problem. Laplace and Hankel transforms are us چکیده کاملIn the present manuscript, we investigated a two dimensional axisymmetric problem of nonlocal microstretch thermoelastic circular plate subjected to thermomechanical sources. An eigenvalue approach is proposed to analyze the problem. Laplace and Hankel transforms are used to obtain the transformed solutions for the displacements, microrotation, microstretch, temperature distribution and stresses. The results are obtained in the physical domain by applying the numerical inversion technique of transforms. The results of the physical quantities have been obtained numerically and illustrated graphically. The results show the effect of nonlocal in the cases of Lord Shulman (LS), Green Lindsay (GL) and coupled thermoelasticity (CT) on all the physical quantities. پرونده مقاله -
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18 - Elastic Buckling of Moderately Thick Homogeneous Circular Plates of Variable Thickness
S.K Jalali M.H NaeiIn this study, the buckling response of homogeneous circular plates with variable thickness subjected to radial compression based on the first-order shear deformation plate theory in conjunction with von-Karman nonlinear strain-displacement relations is investigated. Fu چکیده کاملIn this study, the buckling response of homogeneous circular plates with variable thickness subjected to radial compression based on the first-order shear deformation plate theory in conjunction with von-Karman nonlinear strain-displacement relations is investigated. Furthermore, optimal thickness distribution over the plate with respect to buckling is presented. In order to determine the distribution of the prebuckling load along the radius, the membrane equation is solved using the shooting method. Subsequently, employing the pseudospectral method that makes use of Chebyshev polynomials, the stability equations are solved. The influence of the boundary conditions, the thickness variation profile and aspect ratio on the buckling behavior is examined. The comparison shows that the results derived, using the current method, compare very well with those available in the literature. پرونده مقاله -
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19 - Vibration Analysis for Rectangular Plate Having a Circular Central Hole with Point Support by Rayleigh-Ritz Method
K Torabi A.R AzadiIn this paper, the transverse vibrations of rectangular plate with circular central hole have been investigated and the natural frequencies of the mentioned plate with point supported by Rayleigh-Ritz Method have been obtained. In this research, the effect of the hole i چکیده کاملIn this paper, the transverse vibrations of rectangular plate with circular central hole have been investigated and the natural frequencies of the mentioned plate with point supported by Rayleigh-Ritz Method have been obtained. In this research, the effect of the hole is taken into account by subtracting the energies of the hole domain from the total energies of the whole plate. To determine the kinetic and potential energies of plate, admissible functions for rectangular plate are considered as beam functions and it has been tried that the functions of the deflection of plate, in the form of polynomial functionsproportionate with finite degrees, to be replaced by Bessel function, which is used in the analysis of the vibrations of a circular plate. Consideration for a variety of edge conditions is given through a combination of simply supported, clamped and free boundary conditions. In this study, the effects of increasing the diameter of the hole and the effects of number of point supported on the natural frequencies were investigated and the optimum radius of the circular hole for different boundary conditions are obtained. The method has been verified with many known solutions. Furthermore, the convergence is very fast with any desirable accuracy to exact known natural frequencies. پرونده مقاله -
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20 - Transverse Vibration of Clamped and Simply Supported Circular Plates with an Eccentric Circular Perforation and Attached Concentrated Mass
S.M Mirkhalaf ValashaniIn this investigation Rayleigh-Ritz variational method has been applied to determine the least natural frequency coefficient for the title problem. Classical plate theory assumptions have been used to calculate strain energy and kinetic energy. Coordinate functions are چکیده کاملIn this investigation Rayleigh-Ritz variational method has been applied to determine the least natural frequency coefficient for the title problem. Classical plate theory assumptions have been used to calculate strain energy and kinetic energy. Coordinate functions are combination of polynomials which satisfy boundary conditions at the outer boundary and trigonometric terms. In the second part of this study ABAQUS software is used to compute vibration natural frequency for some special combinations of geometrical and mechanical parameters. Then results of Rayleigh-Ritz method have been obtained for the mentioned special cases. It can be seen that the agreement between them is acceptable. پرونده مقاله -
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21 - A Semi-Analytical Solution for Free Vibration and Modal Stress Analyses of Circular Plates Resting on Two-Parameter Elastic Foundations
M.M Alipour M Shariyat M ShabanIn the present research, free vibration and modal stress analyses of thin circular plates with arbitrary edge conditions, resting on two-parameter elastic foundations are investigated. Both Pasternak and Winkler parameters are adopted to model the elastic foundation. Th چکیده کاملIn the present research, free vibration and modal stress analyses of thin circular plates with arbitrary edge conditions, resting on two-parameter elastic foundations are investigated. Both Pasternak and Winkler parameters are adopted to model the elastic foundation. The differential transform method (DTM) is used to solve the eigenvalue equation yielding the natural frequencies and mode shapes of the circular plates. Accuracy of obtained results is evaluated by comparing the results with those available in the well-known references. Furthermore, effects of the foundation stiffness parameters and the edge conditions on the natural frequencies, mode shapes, and distribution of the maximum in-plane modal stresses are investigated. پرونده مقاله -
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22 - Thermo-Elastic Analysis of Non-Uniform Functionally Graded Circular Plate Resting on a Gradient Elastic Foundation
A Behravan RadPresent paper is devoted to stress and deformation analyses of heated variable thickness functionally graded (FG) circular plate with clamped supported, embedded on a gradient elastic foundation and subjected to non-uniform transverse load. The plate is coupled by an el چکیده کاملPresent paper is devoted to stress and deformation analyses of heated variable thickness functionally graded (FG) circular plate with clamped supported, embedded on a gradient elastic foundation and subjected to non-uniform transverse load. The plate is coupled by an elastic medium which is simulated as a Winkler- Pasternak foundation with gradient coefficients in the radial and circumferential directions during the plate deformation. The temperature distribution is assumed to be a function of the thickness direction. The governing state equations are derived in terms of displacements and temperature based on the 3D theory of thermo-elasticity. These equations are solved using a semi-analytical method to evaluate the deformation and stress components in the plate. Material properties of the plate except the Poisson's ratio are assumed to be graded continuously along the thickness direction according to an exponential distribution. A parametric study is accomplished to evaluate the effects of material heterogeneity indices, foundation parameters, temperature difference between the top and bottom surfaces of the plate and thickness to radius ratio on displacements and stresses. The results are reported for the first time and the new results can be used as a benchmark solution for the future researches. پرونده مقاله -
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23 - Axi-Symmetric Deformation Due to Various Sources in Saturated Porous Media with Incompressible Fluid
R Kumar S Kumar M.G GourlaThe general solution of equations of saturated porous media with incompressible fluid for two dimensional axi-symmetric problem is obtained in the transformed domain. The Laplace and Hankel transforms have been used to investigate the problem. As an application of the a چکیده کاملThe general solution of equations of saturated porous media with incompressible fluid for two dimensional axi-symmetric problem is obtained in the transformed domain. The Laplace and Hankel transforms have been used to investigate the problem. As an application of the approach concentrated source and source over circular region have been taken to show the utility of the approach. The transformed components of displacement, stress and pore pressure are obtained. Numerical inversion technique is used to obtain the resulting quantities in physical domain. Effect of porosity is shown on the resulting quantities. A particular case of interest is also deduced from the present investigation. پرونده مقاله -
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24 - Free Vibration Analysis of Moderately Thick Functionally Graded Plates with Multiple Circular and Square Cutouts Using Finite Element Method
J Vimal R.K Srivastava A.D Bhatt A.K SharmaA simple formulation for studying the free vibration of shear-deformable functionally graded plates of different shapes with different cutouts using the finite element method is presented. The aim is to fill the void in the available literature with respect to the free چکیده کاملA simple formulation for studying the free vibration of shear-deformable functionally graded plates of different shapes with different cutouts using the finite element method is presented. The aim is to fill the void in the available literature with respect to the free vibration results of functionally graded plates of different shapes with different cutouts. The material properties of the plates are assumed to vary according to a power law distribution in terms of the volume fraction of the constituents. Validation of the formulation is done with the help of convergence studies with respect to the number of nodes and the results are compared with those from past investigations available only for simpler problems. In this paper rectangular, trapezoidal and circular plates with cutouts are studied and the effects of volume fraction index, thickness ratio and different external boundary conditions on the natural frequencies of plates are studied. پرونده مقاله -
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25 - A Zigzag Theory with Local Shear Correction Factors for Semi-Analytical Bending Modal Analysis of Functionally Graded Viscoelastic Circular Sandwich Plates
M Shariyat M.M AlipourFree bending vibration analysis of the functionally graded viscoelastic circular sandwich plates is accomplished in the present paper, for the first time. Furthermore, local shear corrections factors are presented that may consider simultaneous effects of the gradual va چکیده کاملFree bending vibration analysis of the functionally graded viscoelastic circular sandwich plates is accomplished in the present paper, for the first time. Furthermore, local shear corrections factors are presented that may consider simultaneous effects of the gradual variations of the material properties and the viscoelastic behaviors of the materials, for the first time. Moreover, in contrast to the available works, a global-local zigzag theory rather than an equivalent single-layer theory is employed in the analysis. Another novelty is solving the resulted governing equations by a power series that may cover several boundary conditions. To extract more general conclusions, sandwich plates with both symmetric and asymmetric (with a bending-extension coupling) layups are considered. Results are validated by comparing some of them with results of the three-dimensional theory of elasticity, even for the thick plates. Influences of various geometric and material properties parameters on free vibration of the circular sandwich plates are evaluated in detail in the results section. پرونده مقاله -
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26 - Buckling Analysis of Polar Orthotropic Circular and Annular Plates of Uniform and Linearly Varying Thickness with Different Edge Conditions
F Farhatnia A GolshahThis paper investigates symmetrical buckling of orthotropic circular and annular plates of continuous variable thickness. Uniform compression loading is applied at the plate outer boundary. Thickness varies linearly along radial direction. Inner edge is free, while oute چکیده کاملThis paper investigates symmetrical buckling of orthotropic circular and annular plates of continuous variable thickness. Uniform compression loading is applied at the plate outer boundary. Thickness varies linearly along radial direction. Inner edge is free, while outer edge has different boundary conditions: clamped, simply and elastically restraint against rotation. The optimized Ritz method is applied for buckling analysis. In this method, a polynomial function that is based on static deformation of orthotropic circular plates in bending is used. Also, by employing an exponential parameter in deformation function, eigenvalue is minimized in respect to this parameter. The advantage of this procedure is simplicity, in comparison with other methods, while whole algorithm for solution can be coded for computer programming. The effects of variation of radius, thickness, different boundary conditions, ratio of radial Young modulus to circumferential one, and ratio of outer radius to inner one in annular plates on buckling load factor are investigated. The obtained results show that in plate with identical thickness, increasing of outer radius decreases the buckling load factor. Moreover, increase of thickness of the plates results in increase of buckling load factor. پرونده مقاله -
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27 - A Power Series Solution for Free Vibration of Variable Thickness Mindlin Circular Plates with Two-Directional Material Heterogeneity and Elastic Foundations
M.M Alipour M ShariyatIn the present paper, a semi-analytical solution is presented for free vibration analysis of circular plates with complex combinations of the geometric parameters, edge-conditions, material heterogeneity, and elastic foundation coefficients. The presented solution cover چکیده کاملIn the present paper, a semi-analytical solution is presented for free vibration analysis of circular plates with complex combinations of the geometric parameters, edge-conditions, material heterogeneity, and elastic foundation coefficients. The presented solution covers many engineering applications. The plate is assumed to have a variable thickness and made of a heterogeneous material whose properties vary in both radial and transverse directions. While the edge is simply-supported, clamped, or free; the bottom surface of the plate is resting on a two-parameter (Winkler-Pasternak) elastic foundation. A comprehensive sensitivity analysis including evaluating effects of various parameters is carries out. Mindlin theory is employed for derivation of the governing equations whereas the differential transform method is used to solve the resulted equations. In this regard, both the in-plane and rotary inertia are considered. Results show that degradations caused by a group of the factors (e.g., the geometric parameters) in the global behavior of the structure may be compensated by another group of factors of different nature (e.g, the material heterogeneity parameters). Moreover, employing the elastic foundation leads to higher natural frequencies and postponing the resonances. پرونده مقاله -
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28 - Study Of Thermoelastic Damping in an Electrostatically Deflected Circular Micro-Plate Using Hyperbolic Heat Conduction Model
G Rezazadeh S Tayefeh-rezaei A Saeedi Vahdat V NasirzadehThermoelastic damping (TED) in a circular micro-plate resonator subjected to an electrostatic pressure is studied. The coupled thermo-elastic equations of a capacitive circular micro plate are derived considering hyperbolic heat conduction model and solved by applying G چکیده کاملThermoelastic damping (TED) in a circular micro-plate resonator subjected to an electrostatic pressure is studied. The coupled thermo-elastic equations of a capacitive circular micro plate are derived considering hyperbolic heat conduction model and solved by applying Galerkin discretization method. Applying complex-frequency approach to the coupled thermo-elastic equations, TED is obtained for different ambient temperatures. Effects of the geometrical parameters on TED and the critical thickness are investigated. Furthermore, the effect of applied bias DC voltage on TED for an electrostatically deflected micro-plate is also investigated. پرونده مقاله -
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29 - Stress Analysis of Two-directional FGM Moderately Thick Constrained Circular Plates with Non-uniform Load and Substrate Stiffness Distributions
M.M Alipour M ShariyatIn the present paper, bending and stress analyses of two-directional functionally graded (FG) circular plates resting on non-uniform two-parameter foundations (Winkler-Pasternak foundations) are investigated using a first-order shear-deformation theory. To enhance the a چکیده کاملIn the present paper, bending and stress analyses of two-directional functionally graded (FG) circular plates resting on non-uniform two-parameter foundations (Winkler-Pasternak foundations) are investigated using a first-order shear-deformation theory. To enhance the accuracy of the results, the transverse stress components are derived based on the three dimensional theory of elasticity. The solution is obtained by employing the differential transform method (DTM). The material properties are assumed to vary in both transverse and radial directions according to power and exponential laws, respectively. Intensity of the transverse load is considered to vary according to a second-order polynomial. The performed convergence analysis and the comparative studies demonstrate the high accuracy and high convergence rate of the approach. A sensitivity analysis consisting of evaluating effects of different parameters (e.g., exponents of the material properties, thickness to radius ratio, trend of variations of the foundation stiffness, and edge conditions) is carried out. Results reveal that in contrast to the available constitutive-law-based solutions, present solution guarantees continuity of the transverse stresses at the interfaces between layers and may also be used for stress analysis of the sandwich panels. The results are reported for the first time and are discussed in detail. پرونده مقاله -
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30 - Transient Nonlinear Vibration of Randomly Excited Cylindrical Shallow Panels in Non Aging Viscous Medium
A AsnafiIn this paper, the nonlinear transient vibration of a cylindrical shallow panel under lateral white noise excitation is studied. The panel is in contact with a non aging viscoelastic medium. Since the external load is a time varying random wide band process, determinist چکیده کاملIn this paper, the nonlinear transient vibration of a cylindrical shallow panel under lateral white noise excitation is studied. The panel is in contact with a non aging viscoelastic medium. Since the external load is a time varying random wide band process, deterministic and conventional approaches cannot be used. Instead, the evolution of the probability density function of the response is investigated. To compute the density function, the famous Monte Carlo simulation is employed while its correctness for this specific application is validated with another work in literature. The governing equation is rewritten to a non dimensional format; so that the results can be applied to a wide range of panels. Specifically, the transient behavior is investigated with respect to the quasi slenderness ratio and the non dimensional mean value of lateral load. As expected, both the simple damped oscillation and unstable jumping phenomenon are seen relative to the values of prescribed parameters. Finally, the joint probability density function of the response is drawn that give someone an idea about the quality of the response in the phase plane. پرونده مقاله -
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31 - New Method for Large Deflection Analysis of an Elliptic Plate Weakened by an Eccentric Circular Hole
Sh Dastjerdi L YazdanparastThe bending analysis of moderately thick elliptic plates weakened by an eccentric circular hole has been investigated in this article. The nonlinear governing equations have been presented by considering the von-Karman assumptions and the first-order shear deformation t چکیده کاملThe bending analysis of moderately thick elliptic plates weakened by an eccentric circular hole has been investigated in this article. The nonlinear governing equations have been presented by considering the von-Karman assumptions and the first-order shear deformation theory in cylindrical coordinates system. Semi-analytical polynomial method (SAPM) which had been presented by the author before has been used. By applying SAPM method, the nonlinear partial differential equations have been transformed to the nonlinear algebraic equations system. Then, the nonlinear algebraic equations have been solved by using Newton–Raphson method. The obtained results of this study have been compared with the results of other references and the accuracy of the results has been shown. The effect of some important parameters on the results such as the location of the circular hole, the ratio of major to minor radiuses of elliptical plate, the size of circular hole and boundary conditions have been studied. It is concluded that applying the presented method is very convenient and efficient. So, it can be used for analyzing the mechanical behavior of elliptical plates, instead of relatively complicated formulations in elliptic coordinates system. پرونده مقاله -
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32 - Generalized Thermoelastic Problem of a Thick Circular Plate Subjected to Axisymmetric Heat Supply
J.J Tripathi G.D Kedar K.C DeshmukhThe present work is aimed at analyzing the thermoelastic disturbances in a circular plate of finite thickness and infinite extent subjected to constant initial temperature and axisymmetric heat supply. Integral transform technique is used. Analytic solutions for tempera چکیده کاملThe present work is aimed at analyzing the thermoelastic disturbances in a circular plate of finite thickness and infinite extent subjected to constant initial temperature and axisymmetric heat supply. Integral transform technique is used. Analytic solutions for temperature, displacement and stresses are derived within the context of unified system of equations in generalized thermoelasticity in the Laplace transform domain using potential functions. Inversion of Laplace transforms is done by employing a numerical scheme. Temperature, displacement and stresses developed in the thick circular plate are obtained and illustrated graphically for copper (pure) material. پرونده مقاله -
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33 - Analytical and Numerical Modelling of the Axisymmetric Bending of Circular Sandwich Plates with the Nonlinear Elastic Core Material
A Kudin S Choporov Yu Tamurov M.A.V Al OmariHerein paper compares the analytical model with the FEM based numerical model of the axisymmetric bending of circular sandwich plates. Also, the paper describes equations of the circular symmetrical sandwich plates bending with isotropic face sheets and the nonlinear el چکیده کاملHerein paper compares the analytical model with the FEM based numerical model of the axisymmetric bending of circular sandwich plates. Also, the paper describes equations of the circular symmetrical sandwich plates bending with isotropic face sheets and the nonlinear elastic core material. The method of constructing an analytical solution of nonlinear differential equations has been described. The perturbation method for differential equations with small parameters is used to represent nonlinear differential equations as a sequence of linear equations. Linear differential equations are reduced to Bessel’s equation. It is compared results of analytical model with results of other researches using two problems: 1) the problem of axisymmetric transverse bending of a circular sandwich plate, 2) the problem of axisymmetric transverse bending of an annular sandwich plate. The effect of accounting nonlinear elastic core material on the strain state of the sandwich plate is described. پرونده مقاله -
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34 - Nonlocal Bending Analysis of Bilayer Annular/Circular Nano Plates Based on First Order Shear Deformation Theory
Sh Dastjerdi M JabbarzadehIn this paper, nonlinear bending analysis of bilayer orthotropic annular/circular graphene sheets is studied based on the nonlocal elasticity theory. The equilibrium equations are derived in terms of generalized displacements and rotations considering the first-order Sh چکیده کاملIn this paper, nonlinear bending analysis of bilayer orthotropic annular/circular graphene sheets is studied based on the nonlocal elasticity theory. The equilibrium equations are derived in terms of generalized displacements and rotations considering the first-order Shear deformation theory (FSDT). The nonlinear governing equations are solved using the differential quadrature method (DQM) which is a highly accurate numerical method and a new semi-analytical polynomial method (SAPM). The ordinary differential equations (ODE’s) are converted to the nonlinear algebraic equations applying DQM or SAPM. Then, the Newton–Raphson iterative scheme is applied. The obtained results of DQM and SAPM are compared. It is concluded that although, the SAPM’s formulation is considerably simple in comparison with DQM, however, the results of two methods are so close to each other. The results are validated with available researches. The effects of small scale parameter, the value of van der Waals interaction between the layers, different values of elastic foundation and loading, the comparison between the local and nonlocal deflections and linear to nonlinear analysis are investigated. پرونده مقاله -
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35 - Thermo-Mechanical Vibration Analysis of FG Circular and Annular Nanoplate Based on the Visco-Pasternak Foundation
M Goodarzi M Mohammadi M Khooran F SaadiIn this study, the vibration behavior of functional graded (FG) circular and annular nanoplate embedded in a Visco-Pasternak foundation and coupled with temperature change is studied. The effect of in-plane pre-load and temperature change are investigated on the vibrati چکیده کاملIn this study, the vibration behavior of functional graded (FG) circular and annular nanoplate embedded in a Visco-Pasternak foundation and coupled with temperature change is studied. The effect of in-plane pre-load and temperature change are investigated on the vibration frequencies of FG circular and annular nanoplate. To obtain the vibration frequencies of the FG circular and annular nanoplate, two different size dependent theories are utilized. The material properties of the FGM nanoplates are assumed to vary in the thickness direction and are estimated through the Mori–Tanaka homogenization technique. The FG circular and annular nanoplate is coupled by an enclosing viscoelastic medium which is simulated as a Visco- Pasternak foundation. By using the modified strain gradient theory (MSGT) and the modified couple stress theory (MCST), the governing equation is derived for FG circular and annular nanoplate. The differential quadrature method (DQM) and the Galerkin method (GM) are utilized to solve the governing equation to obtain the frequency vibration of FG circular and annular nanoplate. The results are subsequently compared with valid result reported in the literature. The effects of the size dependent, the in-plane pre-load, the temperature change, the power index parameter, the elastic medium and the boundary conditions on the natural frequencies are investigated. The results show that the size dependent parameter has an increasing effect on the vibration response of circular and annular nanoplate. The temperature change also play an important role in the mechanical behavior of the FG circular and annular nanoplate. The present analysis results can be used for the design of the next generation of nanodevices that make use of the thermal vibration properties of the nanoplate پرونده مقاله -
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36 - Numerical and Experimental Study on Ratcheting Behavior of Plates with Circular Cutouts under Cyclic Axial Loading
K Kolasangiani M Shariati Kh Farhangdoost A Varvani-FarahaniIn this paper, accumulation of plastic deformation of AISI 1045 steel plates with circular cutouts under cyclic axial loading is studied. Loading was applied under force-control conditions. Experimental tests were performed using a Zwick/Roell servo hydraulic machine. U چکیده کاملIn this paper, accumulation of plastic deformation of AISI 1045 steel plates with circular cutouts under cyclic axial loading is studied. Loading was applied under force-control conditions. Experimental tests were performed using a Zwick/Roell servo hydraulic machine. Under force-control loading with nonzero mean force, plastic strain was accumulated in continuous cycles called ratcheting. Numerical analysis was carried out by ABAQUS software using nonlinear isotropic/kinematic hardening model. The results of the numerical simulations were compared to experimental data. The results demonstrated that the ratcheting response of plates with circular cutouts could be numerically simulated with a reasonable accuracy. It was observed that the local and global plastic deformation increase with increasing the notch diameter. Also, maximum principal stress was the main parameter for initiation of crack around the notch. Based on numerical results, at notch root, both ratcheting strain and local mean stress relaxation was occur simultaneously and due to relaxation of local mean stress, plastic shakedown was occurred. پرونده مقاله -
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37 - Investigation of Pre-buckling Stress Effect on Buckling Load Determination of Finite Rectangular Plates with Circular Cutout
S Abolghasemi H.R Eipakchi M ShariatiThis paper investigates the buckling of finite isotropic rectangular plates with circular cutout under uniaxial and biaxial loading. The complex potential method is used to calculate the pre-buckling stress distribution around the cutout in the plate with finite dimensi چکیده کاملThis paper investigates the buckling of finite isotropic rectangular plates with circular cutout under uniaxial and biaxial loading. The complex potential method is used to calculate the pre-buckling stress distribution around the cutout in the plate with finite dimensions. To satisfy the in-plane boundary conditions, the generalized complex-potential functions are introduced and a new method based on the boundary integral which has been obtained from the principle of virtual work is used to apply the boundary conditions at the plate edges. The potential energy of the plate is calculated by considering the first order shear deformation theory and the Ritz method is used to calculate the buckling load. The effects of cutout size, type of loading and different boundary conditions on the buckling load are investigated. Comparing of the calculated buckling loads with the finite element results shows the accuracy of the presented method for buckling analysis of the plates. پرونده مقاله -
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38 - Non-Local Thermo-Elastic Buckling Analysis of Multi-Layer Annular/Circular Nano-Plates Based on First and Third Order Shear Deformation Theories Using DQ Method
Sh Dastjerdi M JabbarzadehIn present study, thermo-elastic buckling analysis of multi-layer orthotropic annular/circular graphene sheets is investigated based on Eringen’s theory. The moderately thick and also thick nano-plates are considered. Using the non-local first and third order shea چکیده کاملIn present study, thermo-elastic buckling analysis of multi-layer orthotropic annular/circular graphene sheets is investigated based on Eringen’s theory. The moderately thick and also thick nano-plates are considered. Using the non-local first and third order shear deformation theories, the governing equations are derived. The van der Waals interaction between the layers is simulated for multi-layer sheets. The stability governing equations are obtained according to the adjacent equilibrium estate method. The constitutive equations are solved by applying the differential quadrature method (DQM). Applying the differential quadrature method, the ordinary differential equations are transformed to algebraic equations. Then, the critical temperature is obtained. Since there is not any research in thermo-elastic buckling analysis of multi-layer graphene sheets, the results are validated with available single layer articles. The effects of non-local parameter, the values of van der Waals interaction between the layers, third to first order shear deformation theory analyses, non-local to local analyses, different values of Winkler and Pasternak elastic foundation and analysis of bi-layer and triple layer sheets are investigated. It is concluded that the critical temperature increases and tends to a constant value along the rise of van der Waals interaction between the layers. پرونده مقاله -
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39 - 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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40 - بررسی رفتار ارتعاشی غیرخطی نانو ورق دایره ای از جنس مواد هدفمند با استفاده از مدل دیفرانسیلی غیرمحلی گرادیان کرنش
مرتضی پورعبدی محمد شیشه ساز شهرام شهروئی سیدعلیرضا سیدرکنی زادهدر این مقاله، رفتار ارتعاشی غیرخطی یک نانو ورق با هندسه دایره با فرض شرایط مرزی گیردار مورد بررسی قرار گرفته است. برای این منظور، ترکیبی از شکل دیفرانسیلی نظریه الاستیسیته غیرمحلی، مدل گرادیان کرنش و اصل همیلتون، به همراه روابط کرنش-جابجایی غیرخطی فون کارمان و روش باقیم چکیده کاملدر این مقاله، رفتار ارتعاشی غیرخطی یک نانو ورق با هندسه دایره با فرض شرایط مرزی گیردار مورد بررسی قرار گرفته است. برای این منظور، ترکیبی از شکل دیفرانسیلی نظریه الاستیسیته غیرمحلی، مدل گرادیان کرنش و اصل همیلتون، به همراه روابط کرنش-جابجایی غیرخطی فون کارمان و روش باقیمانده وزنی گالرکین برای گسسته سازی معادلات حاکم استفاده شده است. در ادامه تأثیر اثرات اندازه (اثر غیرمحلی و اثر مادی مدل گرادیان کرنش) و شرایط اولیه بر رفتار ارتعاشی سازه مدنظر بررسی شده است. نتایج نشان می دهند که این پارامترهای غیرمحلی و مادی به ترتیب منجر به کاهش و افزایش رفتار فرکانس های غیرخطی شده اند. در نهایت، افزایش مقدار اولیه جابجابی یک روند افزایشی برای نسبت فرکانسی به ازای هر پارامتر غیرمحلی و پارامتر مادی ایجاد میکند. همچنین، برای تمام پارامترهای غیرمحلی و پارامتر ماده، تفاوت بین نسبت فرکانس با افزایش شرایط اولیه کاهش یافته است. پرونده مقاله -
دسترسی آزاد مقاله
41 - انتقال حرارت جابجائی اجباری روی سه لوله با آرایش مثلثی در نانو سیال آب-آلومینا تحت اثر میدان مغناطیسی
امین نیک الهام ولی انجیل الی نیما وزیری زهرا پولائی موزیرجیدر این تحقیق انتقال حرارت جابجائی اجباری روی لولههای گرم با چیدمان مثلثی در نانوسیال آب-آلومینا در یک میدان مغناطیسی مورد مطالعه قرار گرفته است. معادلات ناویر استوکس و انرژی با استفاده از روش المان محدود در مقاله حاضر گسسته و حل شده است. یک مدل تجربی تابعی از دما، قطر چکیده کاملدر این تحقیق انتقال حرارت جابجائی اجباری روی لولههای گرم با چیدمان مثلثی در نانوسیال آب-آلومینا در یک میدان مغناطیسی مورد مطالعه قرار گرفته است. معادلات ناویر استوکس و انرژی با استفاده از روش المان محدود در مقاله حاضر گسسته و حل شده است. یک مدل تجربی تابعی از دما، قطر نانوذره و کسر حجمی نانوذرات برای برآورد لزجت و ضریب انتقال حرارت هدایتی بکار گرفته شده است. محدوده 100≤Re≤200، 0≤Ha≤100، 0≤fe≤0.06 و gama=0ᵒ,90ᵒ تعریف شده است. نتایج مربوط به خطوط جریان، ناسلت متوسط لولههای ردیف اول و دوم و متوسط ناسلت سه لوله ارائه و مورد بحث قرار گرفته است. وجود نانوذرات موجب افزایش انتقال حرارت و میدان مغناطیسی موجب نظم یافتگی جریان و در ابتدا کاهش انتقال حرارت میشود و پس از آن با افزایش اثر میدان انتقال حرارت افزایش میابد. پرونده مقاله -
دسترسی آزاد مقاله
42 - Novel Circularly Polarized Substrate Integrated Waveguide Slot Antenna By Using A Polarizer Technique
Omid Khodadad Pejman Mohammadicircularly-polarized antenna is built based on new SIW(substrate integrated waveguide)structure which contains cavity-backed resonator and a conventional polarized ring with twosquare slits in inner and outer ring that differ 90° at position and is proposed for righ چکیده کاملcircularly-polarized antenna is built based on new SIW(substrate integrated waveguide)structure which contains cavity-backed resonator and a conventional polarized ring with twosquare slits in inner and outer ring that differ 90° at position and is proposed for right-handedcircular polarization (RHCP) and fabricated in two separate layers. A broadband impedancebandwidth of 13.9% and a RHCP axial ratio of 0.5GHz have been obtained under thecondition of less than VSWR ≤2 and axial ratio≤ 3 dB, respectively. پرونده مقاله -
دسترسی آزاد مقاله
43 - Maraghe Observatory and an Effort towards Retrieval of Architectural Design of Astronomical Units
Javad Shekari NiriMaraghe observatory was built by such engineers as Moayiededdin Orozi etc. under supervision of Khaje Nasireddin Tousi in 7th century AH. The most significant feature associated with Maraghe observatory is the fact that architecture is employed to achieve astronomical p چکیده کاملMaraghe observatory was built by such engineers as Moayiededdin Orozi etc. under supervision of Khaje Nasireddin Tousi in 7th century AH. The most significant feature associated with Maraghe observatory is the fact that architecture is employed to achieve astronomical purposes in this site. The reason for preferring observatory by astronomers was the fact that these units are superior to wooden and metal instruments with respect to accuracy, no size limitations, etc. Architectural design and function of astronomical units of Maraghe observatory site after discovery of its foundation in the course of explorations before Islamic Revolution remained unclear until recent years. After conducting required studies and investigations, the author managed to find significant cues and after some precise comparisons, he succeeded to recover the main design and function of some astronomical units of this international center. Based on these findings these astronomical structures can reliably be rebuilt. This research showed that every circular or polygonal building cannot be considered as an observatory. For example form and function of cemetery structures are completely different with astronomical ones. Following this research also valuable results were obtained in relation to stone architectural structures present on Maraghe observatory hill. In addition, claims about invention of astronomical units of Maraghe observatory by non-Iranian scientists are rejected and rights of Iranian scientists are rationally defended in this regard. پرونده مقاله -
دسترسی آزاد مقاله
44 - Quasi-static Axial Compression of thin-walled Circular Composite Tubes
Mohammad Mahdi Kheirikhah Sajjad Dehghanpour Mohsen RahmaniAssessing the behavior of composite structures which are subjected to impact loads is one of the important subjects in the field of mechanical sciences. Using thin-walled tubes which collapsed and absorbed the impact energy is a well-known method to prevent damages to t چکیده کاملAssessing the behavior of composite structures which are subjected to impact loads is one of the important subjects in the field of mechanical sciences. Using thin-walled tubes which collapsed and absorbed the impact energy is a well-known method to prevent damages to the other parts of the structures. In this paper, deformations, crushing length, peak load, mean force and energy absorption capacity of thin-walled circular composite tubes are investigated both experimentally and numerically. In order to experimental study, three circular composite tubes were fabricated and subjected to quasi-static axial load. Also, a finite element model was constructed and analyzed under same conditions using FEM27 and LS-DYNA software packages. The results of simulations are in good agreement with the experimental data and show that the section geometry has considerable effect on the energy absorption. The circular composite tube has the most energy absorption capacity and the most average force among all investigated sections. پرونده مقاله -
دسترسی آزاد مقاله
45 - استخراج چارچوب ارزیابی مدلهای کسب و کار در صنعت فولاد ایران مبتنی بر رویکرد اقتصاد مدور
مهسا وارسته حسنعلی آقاجانی محمد ولی پور خطیر مجید آقاییامروزه فاصله گرفتن از اقتصاد خطی و حرکت به سمت اقتصاد مدور مورد توجه بسیاری از کشورها و شرکتهای پیشرفته جهان قرار گرفته است. مدلهای کسبوکار مدور از جمله ابزارهایی است که در کاربرد اصول اقتصاد مدور بسیار کارآمد است. در این مطالعه به ارائه چارچوبی جهت ارزیابی مدلهای ک چکیده کاملامروزه فاصله گرفتن از اقتصاد خطی و حرکت به سمت اقتصاد مدور مورد توجه بسیاری از کشورها و شرکتهای پیشرفته جهان قرار گرفته است. مدلهای کسبوکار مدور از جمله ابزارهایی است که در کاربرد اصول اقتصاد مدور بسیار کارآمد است. در این مطالعه به ارائه چارچوبی جهت ارزیابی مدلهای کسبوکار مدور و توسعه یک مدل در صنعت فولاد ایران پرداخته میشود. برای این منظور مطابق با روش تحلیل اسنادی و فراترکیب که یکی از انواع روشهای فرامطالعه است، 562 مقاله لاتین جمعآوری شد که پس از مطالعه و ارزیابی آنها با روش مهارتهای ارزیابی بحرانی درنهایت 28 مقاله برای بررسی نهایی انتخاب شده است. یافتههای تحقیق نشان دادند که چارچوب ارزیابی مدلهای کسبوکار مدور در صنعت فولاد توجه به استراتژی کاهش، استراتژی استفاده مجدد، استراتژی ساخت مجدد، استراتژی بازیافت و استراتژی نگهداری است. همچنین در راستای استراتژیهای مذکور با استفاده از روش دلفی فازی اقدامات اقتصاد مدور بومیسازی شدند. در پایان تحقیق توصیه شده است که مدیران و مسؤولان صنعت فولاد جهت سودآوری بیشتر و پایبندی به اصول پایداری لازم است در قالب مدل کسبوکار مدور به این استراتژیها و اقدامات توجه کنند. پرونده مقاله -
دسترسی آزاد مقاله
46 - ارائه الگوی چالشهای پیادهسازی اقتصاد مدور در صنایع آلاینده:رویکرد فراترکیب و دیمتل-فرآیند تحلیل شبکهای فازی
مهرداد کیانی داود عندلیب اردکانیپژوهش حاضر به دنبال ارائه الگویی نوین از روابط بین چالشهای پیادهسازی اقتصاد مدور در صنایع آلاینده است. این پژوهش از نظر هدف جزو تحقیقات کاربردی-توسعهای و نظر نوع تحقیق، ترکیبی (آمیخته اکتشافی) قلمداد میشود. صنعت شیشهسازی یزد به عنوان یکی از صنایع آلاینده کشور انتخا چکیده کاملپژوهش حاضر به دنبال ارائه الگویی نوین از روابط بین چالشهای پیادهسازی اقتصاد مدور در صنایع آلاینده است. این پژوهش از نظر هدف جزو تحقیقات کاربردی-توسعهای و نظر نوع تحقیق، ترکیبی (آمیخته اکتشافی) قلمداد میشود. صنعت شیشهسازی یزد به عنوان یکی از صنایع آلاینده کشور انتخاب و از 10 خبره این صنعت که به صورت هدفمند انتخاب شدند، نظرخواهی شد. در بخش کیفی تحقیق، جهت شناسایی چالشها و دستهبندی آنها از رویکرد فراترکیب و در بخش کمی جهت ارائه الگوی روابط بین این چالشها و اولویتبندی آنها از روش ترکیبی دیمتل-فرآیند تحلیل شبکهای فازی استفاده شد. یافتههای بخش کیفی شامل شناسایی 27 چالش در 6 بُعد چالشهای اقتصادی، فرهنگی و اجتماعی، مدیریتی، سازمانی، زیرساختی و فناوری، بازار و طراحی بود. در بخش کمی، یافتهها نشان داد که چالشهای اقتصادی تأثیرگذارترین و چالشهای بازار و طراحی تأثیرپذیرترین چالشها در پیادهسازی اقتصاد مدور محسوب میشوند. همچنین، چالشهای سازمانی تعامل بیشتری با سایر چالشها دارد. در تحلیلی کاملتر، چالشهای عدم اطمینان در مورد بازار (بهعنوانمثال، رکود اقتصادی)، وجود ذهنیت خطی در مدیران و عدم تفکر سیستمی و مدور و چالش تقاضای کم مشتریان برای محصولات بازیافتی مهمترین چالشهای موجود در پیادهسازی اقتصاد مدور در صنایع آلاینده همانند صنعت شیشهسازی محسوب میشود. درنهایت، میزان تأثیرپذیری و تأثیرگذاری هر یک از چالشها با یکدیگر شناسایی گردید که میتواند به عنوان نقشه راهی جهت استفاده مدیران و کارشناسان در جهت کاربست اقتصاد مدور در صنایع آلاینده کشور قرار گیرد. پرونده مقاله -
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47 - Detection of the blood hemoglobin using an electro-optical biosensor based on a structurally chiral medium
Amir Madani Nadia Ghorani Samad Roshan EntezarIn this work, a biosensor based on a structurally chiral medium (SCM) under the effect of a low-frequency electric field has been designed to detect blood hemoglobin. The introduced structure is irradiated with a circularly polarized light under an electro-optical Pocke چکیده کاملIn this work, a biosensor based on a structurally chiral medium (SCM) under the effect of a low-frequency electric field has been designed to detect blood hemoglobin. The introduced structure is irradiated with a circularly polarized light under an electro-optical Pockels effect. A photonic band gap is observed in the transmission spectrum of the right-handed circularly polarized waves, which indicates the circular Bragg phenomenon. The sensor consists of a sample layer sandwiched between two identical SCMs. Sensor performance is evaluated using the transfer matrix method (TMM). The results show that the defect mode is sensitive to any change in the refractive index of the defect layer where the defect layer is infiltrated with samples with different concentrations of blood hemoglobin. Also, it is shown that applying a low-frequency electric field increases the sensitivity of the mentioned sensor. It is observed that the sensitivity can be expanded up to 142.66 nm/RIU by changing the various parameters of the SCM. پرونده مقاله -
دسترسی آزاد مقاله
48 - Optimization of laser forming parameters using genetic algorithms
Rasoul Tarkesh Esfahani Sa'id Golabi zahra zojajiThe use of lasers is being considered as a modern method for forming process in recent years. This method has been used in various industries, such as aerospace, marine and oil industry. Extensive research has been done in the field of modeling and optimization of direc چکیده کاملThe use of lasers is being considered as a modern method for forming process in recent years. This method has been used in various industries, such as aerospace, marine and oil industry. Extensive research has been done in the field of modeling and optimization of direct paths parameters with process of laser forming. Although forming in circular paths can be used for producing complex parts, due to some technical reasons, it is considered less. The main purpose of this paper is to detect the proper estimation model and obtain optimal variables conditions for complete circular paths in perforated circular parts by means of genetic algorithms. In this process the outer edges are fixed and the inner edges are being formed by laser. At first, the finite element simulation model is studied then the estimation model has been discussed, after that multi-objective functions have been examined with the least error and energy. Furthermore, the optimization results of the internal hole diameters are reported and analyzed in terms of Pareto charts. In conclusion, optimum forming conditions have been reported in terms of accuracy and energy for different diameters of holes. This study shows with acceptable increasing in the error rate, the required energy could be reduced. Also, increasing in the diameter of inside hole cause to increase energy and decrease of accuracy. پرونده مقاله -
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49 - An Approach Utilizing Epsilon-Constraint and NSGA-II for Circular Manufacturing Supply Chain Networks
Fatemeh Jaferi Arash Shahin Mohammadreza Vasili Omid Boyer HassaniCircular manufacturing supply chains offer a novel and compelling perspective within the realm of supply chain sustainability. Consequently, the development of a suitable solution approach for circular manufacturing supply chains holds significant value. This study pres چکیده کاملCircular manufacturing supply chains offer a novel and compelling perspective within the realm of supply chain sustainability. Consequently, the development of a suitable solution approach for circular manufacturing supply chains holds significant value. This study presents appropriate solution approaches for a mathematical model that has been formulated for a circular supply chain. To address the small-sized problem, the epsilon-constraint method is proposed. This method aids in obtaining a Pareto set of optimal solutions, facilitating the evaluation of trade-offs among three objectives. Given the NP-hard nature of the problem, the non-dominated sorting genetic algorithm (NSGA-II) is employed to approximate the Pareto front for larger problem sizes. A comparative analysis is conducted between the outcomes achieved in smaller dimensions using the epsilon-constraint method and those generated by the metaheuristic algorithm. The results indicate that the error percentage of the objective function, when compared to the epsilon method, remains consistently below 1%, underscoring the effectiveness of the proposed algorithm. These methodologies empower decision-makers to offer efficient, optimal solutions, enabling them to select the most suitable alternative based on budgetary considerations and organizational policies. پرونده مقاله -
دسترسی آزاد مقاله
50 - تخمین زاویه ورودی دوبعدی پهن باند سیگنالهای مدولاسیون فرکانس خطی با استفاده از الگوریتم دچیرپ با تعداد کم فریم زمانی در آرایه دوبعدی دایروی
عباس پرتوی سنگی جاسم جمالی محمدحسین فاتحی دیندارلو محمدمهدی قنبریانسیگنالهای مدولاسیون فرکانس خطی (LFM) پهن باند بهطور گستردهای در سیستمهایی مانند رادار، سونار و موبایل استفاده میشود. الگوریتمهای تخمین زاویه ورود دوبعدی (2D-DOA) سیگنالهای مدولاسیون فرکانس خطی به تعداد زیادی فریم زمانی متکی هستند. به همین دلیل برای کاربردهای با چکیده کاملسیگنالهای مدولاسیون فرکانس خطی (LFM) پهن باند بهطور گستردهای در سیستمهایی مانند رادار، سونار و موبایل استفاده میشود. الگوریتمهای تخمین زاویه ورود دوبعدی (2D-DOA) سیگنالهای مدولاسیون فرکانس خطی به تعداد زیادی فریم زمانی متکی هستند. به همین دلیل برای کاربردهای با توان پایین مناسب نیستند. در این مقاله یک روش برآورد مبتنی بر الگوریتم با محاسبات کم ESPRIT بر مبنای آرایه دوبعدی دایروی با استفاده از تبدیل فوریه فراکتالی (FrFT) ارائه شده است. استفاده از آرایه دایروی، امکان محاسبه دوبعدی زاویه ورود را فراهم مینماید. روش کار به این ترتیب است که ابتدا با استفاده از تبدیل فوریه فراکتالی الگوریتم دچیرپ را برای سیگنالهای مدولاسیون فرکانس خطی توسعه دادهایم، سپس الگوریتم ESPRIT را که برای آرایههای خطی (ULA) استفاده میشود را برای آرایههای دوبعدی دایروی (UCA) گسترش میدهیم، آنگاه محاسبات زاویه ورود را برای تعداد کم فریم زمانی با حجم محاسبات پایین بهدست آوردهایم. نتایج شبیهسازی الگوریتم پیشنهادی MESPRIT (الگوریتم ESPRIT بهبودیافته) در مقایسه با سایر الگوریتمها مانند طبقهبندی سیگنال چندگان (MUSIC) و تخمین زاویه ورود با استفاده از الگوریتم دو مرحلهای سریع (TSFDOA)، بهتر بودن الگوریتم پیشنهادی را نشان میدهد. نشان دادهایم که روش پیشنهادی هم در SNRهای پایین دقت قابل قبولی دارد و هم در SNRهای بالا خطای کمی از خود نشان میدهد. همچنین نشان دادیم برای همه الگوریتمها، دقت زاویه سمت از زاویه ارتفاع بهتر است. پرونده مقاله -
دسترسی آزاد مقاله
51 - طراحی و شبیه سازی یک آنتن شکافی مایکرواستریپی جدید با خاصیت پلاریزاسیون دایروی پهن باند
الهه شیرازی محمدامین هنروردر این مقاله یک آنتن شکافی مایکرواستریپی چاپی جدید با خاصیت پلاریزاسیون دایروی و تغذیه شده با خط CPW طراحی، تحلیل و شبیه سازی شده است. ساختار آنتن شکافی پیشنهادی از یک پچ پله ای شکل اصلاح شده و صفحه زمین مربعی که درون آن یک شکاف پله-ای واقع شده ترکیب بندی شده است. با اس چکیده کاملدر این مقاله یک آنتن شکافی مایکرواستریپی چاپی جدید با خاصیت پلاریزاسیون دایروی و تغذیه شده با خط CPW طراحی، تحلیل و شبیه سازی شده است. ساختار آنتن شکافی پیشنهادی از یک پچ پله ای شکل اصلاح شده و صفحه زمین مربعی که درون آن یک شکاف پله-ای واقع شده ترکیب بندی شده است. با استفاده از پچ پله ای و صفحه زمین مربعی اصلاح شده، رزونانس های اضافی دیگری تحریک شده و پهنای باند امپدانس وسیعی مخصوصا در باند بالاتر به دست میآید. همچنین با استفاده از چنین ساختاری، خصوصا اضافه کردن دو باریکه مستطیلی به صفحه زمین باعث ایجاد پهنایباند پلاریزاسیون دایروی بسیار وسیعی خواهد شد. ساختار پیشنهادی در مقایسه با کارهای مشابه قبلی دارای ابعاد کوچکی می باشد. نتایج شبیه سازی پهنای باند امپدانس در حدود 81.7%و پهنای باند پلاریزاسیون دایروی(3dB AR) در حدود57.6% را نشان میدهد. همچنین نتایج شبیه سازی در تطابق خوبی با ملزومات سیستم های WLAN می باشند. پرونده مقاله -
دسترسی آزاد مقاله
52 - ارزیابی عددی و آزمایشگاهی دیوار برشی فولادی با بازشوهای دایرهای تحت بار چرخهای
علی صاحب جمع حسین شوکتیچکیده سیستم دیوار برشی فولادی یک سیستم باربر جانبی است که به سبب داشتن مزایایی از جمله شکلپذیری مناسب، سختی زیاد، میزان مقاومت برشی و جذب انرژی بالا همواره مورد توجه محققین بوده است. از سال 1980 میلادی که تحقیقات پایه برروی دیوار برشی فولادی بدون سختکننده صورت پذیرفت چکیده کاملچکیده سیستم دیوار برشی فولادی یک سیستم باربر جانبی است که به سبب داشتن مزایایی از جمله شکلپذیری مناسب، سختی زیاد، میزان مقاومت برشی و جذب انرژی بالا همواره مورد توجه محققین بوده است. از سال 1980 میلادی که تحقیقات پایه برروی دیوار برشی فولادی بدون سختکننده صورت پذیرفت، پیوسته پژوهشگران در صدد بهبود رفتار این سیستم، افزایش کارآیی و بهرهوری آن بودهاند. از جمله اقداماتی که در جهت افزایش کارآیی و بهرهوری دیوار برشی فولادی صورت پذیرفت، ایجاد بازشو بر روی ورق درونی بود. تحقیقات بر روی دیوار برشی فولادی دارای بازشو در اوایل دهه ی 90 میلادی با مطالعات صبوری قمی و رابرتز بر روی این سیستم آغاز گردید. در سالهای اخیر یک نمونه دیوار برشی فولادی با بازشوهای منظم دایره ای شکل یا ماتریسی توسط محققان دانشگاه بوفالو آمریکا مطرح شده و مورد آزمایش قرار گرفت. از این نوع بازشو علاوه بر سیستمی جهت عبور تاسیسات در مواردی که ضخامت ورق مورد نیاز طراحی در دسترس نباشد میتوان استفاده نمود، به گونهای که ورق ضخیم همراه با بازشوهای دایره ای شکل جایگزین ورق نازک بدون بازشو میگردد. در این مقاله نیز به جهت مطالعات بیشتر بر روی بازشوهای منظم دایره ای شکل، تاثیر اینگونه بازشو بر روی رفتار سیستم دیوار برشی فولادی مورد ارزیابی قرار میگیرد. بدین منظور یک نمونه دیوار برشی فولادی با بازشوهای دایرهای طراحی و ساخته شده سپس در مرکز تحقیقات سازه دانشگاه ارومیه تحت بارگذاری چرخه ای قرار گرفت. علاوه بر مطالعات آزمایشگاهی رفتار این نوع سیستم به صورت تحلیل عددی و با استفاده از نرم افزار المان محدود ABAQUS بررسی گردیده است. در نهایت نتیجهی هر دو تحلیل آزمایشگاهی و عددی با روش تئوری آنالیز پلاستیک سازه مقایسه شده است. نتایج بدست آمده حاکی از تطابق مناسب پوش منحنی هیسترزیس در دو تحلیل عددی و آزمایشگاهی بوده همچنین نشان دهندهی محافظهکارانه بودن روابط روش آنالیز پلاستیک و یا ضرایب کاهشی اعمال شده بر این روابط به سبب وجود بازشو و کاهش مقطع تیر میباشد. پرونده مقاله -
دسترسی آزاد مقاله
53 - واکاوی نقش عوامل مکانی- فضایی در مهاجرت فصلی نیروی کار روستایی به شهر، مطالعه موردی : شهرستان سروآباد
فرزاد ویسی محمد سلمانی محمدرضا رضوانی مهدی پورطاهریهدف پژوهش حاضر واکاوی نقش عوامل مکانی- فضایی در مهاجرت فصلی نیروی کار روستایی به شهر می باشد. بدین منظور از عوامل مکانی- فضایی، سه موئلفه میانگین زمین خانوار روستایی، فاصله روستا از شهر و ارتفاع روستاها استفاده شده و میزان مهاجرت های فصلی از روستاها بر اساس این سه موءلف چکیده کاملهدف پژوهش حاضر واکاوی نقش عوامل مکانی- فضایی در مهاجرت فصلی نیروی کار روستایی به شهر می باشد. بدین منظور از عوامل مکانی- فضایی، سه موئلفه میانگین زمین خانوار روستایی، فاصله روستا از شهر و ارتفاع روستاها استفاده شده و میزان مهاجرت های فصلی از روستاها بر اساس این سه موءلفه محاسبه گردیده است. جامعه آماری این پژوهش سرپرستان خانوارهای روستایی شهرستان سروآباد تشکیل می دهد. از 65 روستای شهرستان 13 روستا (20 درصد) به صورت تصادفی برای نمونه گیری انتخاب و از جمعیت 11700 خانواری روستاهای شهرستان، براساس فرمول منطقی کوکران 323 سرپرست خانوار انتخاب شدند. سپس با استفاده از ضریب همبستگی پیرسون رابطه میزان مهاجرت با عوامل مکانی- فضایی در نظر گرفته شده یعنی فاصله، ارتفاع و میانگین زمین، بررسی شده است. یافته های توصیفی تحقیق نشان داد که بیشترین تعداد مهاجران فصلی تا 4 ماه در مهاجرت می مانند(54 درصد)، بیشترین آمار مربوط به میانگین تعداد مهاجران فصلی از هر خانوار، مربوط به خانوار های دارای تک مهاجر است(50درصد). فصل انجام مهاجرت برای بیشتر مهاجران فصل بهار می باشد(60 درصد) و فصل برگشت نیز فصل بهار(60درصد) پاییز(39.3) می باشد. شغل مهاجران فصلی برای 57 درصد جامعه نمونه، کارگر ساختمانی است. بر اساس آزمون پیرسون، دو عامل میانگین زمین و فاصله از شهر، با مهاجرت فصلی، دارای همبستگی زیادی بوده و عامل ارتفاع فاقد رابطه است. بر این اساس می توان نتیجه گرفت عوامل مکانی- فضایی در به وجود آمدن مهاجرت فصلی نیروی کار روستایی در شهرستان سروآباد نقش دارند. پرونده مقاله -
دسترسی آزاد مقاله
54 - Contamination Effects on the Bearing Capacity of Circular Shallow Foundation Rested on Sand
Alireza Hajiani BoushehrianThe growth and development of industries have led to expanding suburban factories, complexes, refineries, and oil product transportation lines, causing environmental concerns and repercussions due to the leakage and discharge of pollutions into potable water resources. چکیده کاملThe growth and development of industries have led to expanding suburban factories, complexes, refineries, and oil product transportation lines, causing environmental concerns and repercussions due to the leakage and discharge of pollutions into potable water resources. These contaminations can change the geotechnical characteristics and bearing capacity of soils. This study determined the behavior of circular footings rested on the gasoil and kerosene-contaminated soil. In addition, the obtained results comprised those collected from the uncontaminated soil. The study mainly attempted to determine the effect of oil contamination on the bearing capacity of oil-contaminated sand based on the numerical model created in the PLAXIS. The contaminated sand layers were mixed with varying gasoil and kerosene contaminations levels (1%-4%). Direct shear tests were conducted on the contaminated soil samples to determine the shear strength parameter utilized in numerical analysis. The influences of the contamination depth and type were examined. The numerical model results indicated the negative relationship between the percentage and the depth of contamination with gasoil and Kerosene and the circular foundation bearing capacities; an increase in the first two criteria reduced the later property in the soil. This paper proposed several equations to predict the bearing capacity of a circular foundation based on depth and percentage of contamination. The numerical model used had been verified by recent experimental results. پرونده مقاله -
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55 - Estimating multi-period global cost efficiency and productivity change of systems with network structures
S. Tohidnia G. TohidiThe current paper develops three different ways to measure the multi-period global cost efficiency for homogeneous networks of processes when the prices of exogenous inputs are known at all time periods. A multi-period network data envelopment analysis model is presente چکیده کاملThe current paper develops three different ways to measure the multi-period global cost efficiency for homogeneous networks of processes when the prices of exogenous inputs are known at all time periods. A multi-period network data envelopment analysis model is presented to measure the minimum cost of the network system based on the global production possibility set. We show that there is a relationship between the multi-period global cost efficiency of network system and its subsystems, and also its processes. The proposed model is applied to compute the global cost Malmquist productivity index for measuring the productivity changes of network system and each of its process between two time periods. This index is circular. Furthermore, we show that the productivity changes of network system can be defined as a weighted average of the process productivity changes. Finally, a numerical example will be presented to illustrate the proposed approach. پرونده مقاله -
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56 - An Analytical Solution for Cylindrical Concrete Tank on Deformable Soil
Shirish Vichare Mandar M. InamdarCylindrical concrete tanks are commonly used in wastewater treatment plants. These are usually clarifier tanks. Design codes of practice provide methods to calculate design forces in the wall and raft of such tanks. These methods neglect self-weight of tank material and چکیده کاملCylindrical concrete tanks are commonly used in wastewater treatment plants. These are usually clarifier tanks. Design codes of practice provide methods to calculate design forces in the wall and raft of such tanks. These methods neglect self-weight of tank material and assume extreme, namely ‘fixed’ and ‘hinged’ conditions for the wall bottom. However, when founded on deformable soil, the actual condition at the wall bottom is neither fixed nor hinged. Further, the self-weight of the tank wall does affect the design forces. Thus, it is required to offer better insight of the combined effect of deformable soil and bottom raft stiffness on the design forces induced in such cylindrical concrete tanks. A systematic analytical method based on fundamental equations of shells is presented in this paper. Important observations on variation of design forces across the wall and the raft with different soil conditions are given. Set of commonly used tanks, are analysed using equations developed in the paper and are appended at the end. پرونده مقاله -
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57 - Extraction of the governing equations for steady state and axisymmetric behavior of a porous piezoelectric circular solid plate
علی ابجدی محسن جباری احمد رضا خورشیدوندBased on the available evidence, porous piezoelectric materials have great potential for the development of smart (active) structures with high strength, high stiffness and light weight such as ceramics and composites. Among the ceramic materials with porous piezoelectr چکیده کاملBased on the available evidence, porous piezoelectric materials have great potential for the development of smart (active) structures with high strength, high stiffness and light weight such as ceramics and composites. Among the ceramic materials with porous piezoelectric compounds, can be mentioned Lead-zirconate-titanate (PZT), Lead-titanate (PbTiO2), Lead-zirconate (PbZrO3), Barium-titanate (BaTiO3), Cadmium-selenide (CdSe), etc. This study extracts the governing partial differential equations for steady- state and axisymmetric behavior of a circular solid plate is made of an undrained saturated porous piezoelectric hexagonal material symmetry of class 6 mm. The porosities of the plate vary through the thickness; thus, material properties, except poisson’s ratio, are assumed as exponential functions of axial variable z in cylindrical coordinates. Additionally, piezothermoelastic behavior of a circular plate subject to external thermal, mechanical and electrical loads is considered, so various concepts including three-dimensional linear elasticity theory and dielectric theory are used in combination to create a linear piezoelectric model. The extraordinary and special industrial properties of porous piezoelectric materials, their increasing use and the need to know the behavior of these materials, doubles the importance of this research. پرونده مقاله -
دسترسی آزاد مقاله
58 - تحققپذیری طراحی شهری اکولوژیکی در بافتهای تاریخی براساس ارزشهای بومی-جهانی (موردکاوی: طراحی اکوپارک شهری در محلهی سنگلج تهران)
سمانه محسنی محمود رضاییسهم کلانشهرها در افزایش بی رویه مصرف انرژی، آلودگیهای زیست محیطی و تهدید منابع طبیعی تجدیدناپذیر غیرقابل انکار است. بنابراین ضروری است تا طرح های اکولوژیکی با رویکرد انرژی بهویژه برای بافت های تاریخی شهر تهران تنظیم شود. این بافت ها افزون بر مسائل زیست محیطی، دچار م چکیده کاملسهم کلانشهرها در افزایش بی رویه مصرف انرژی، آلودگیهای زیست محیطی و تهدید منابع طبیعی تجدیدناپذیر غیرقابل انکار است. بنابراین ضروری است تا طرح های اکولوژیکی با رویکرد انرژی بهویژه برای بافت های تاریخی شهر تهران تنظیم شود. این بافت ها افزون بر مسائل زیست محیطی، دچار مهاجرتفرستی شده اند. ازهمینرو، پرسش اصلی این است که در بافتهای ارزشمند تاریخی کشورمان که در سطح میراث تاریخی-اکولوژیکی جهان مطرح بوده اند، چگونه می توان به تحقق طراحی شهری با رویکرد انرژی تجدیدپذیر نائل آمد. هدف پژوهش طراحی تحقق پذیر و کاربردی با تشویق بازگرداندن مردم به این بافتها در راستای تولید و استفاده منابع انرژی تجدیدپذیر، کاهش آلودگی و تأکید به ارزش های تاریخی است. روش پژوهش کیفی، طراحی محور با راهبرد موردکاوی شامل تکنیک هایی از آینده پژوهی مثل چشم اندازسازی، شبیه سازی سه بعدی و دلفی است. محله سنگلج در بافت تاریخی مرکزی تهران در حصار طهماسبی زیر مجموعه حصار ناصری انتخاب شده است. پس از طی مراحل سهگانهی طراحی(سنجشوضعیت، چشماندازسازی و عملیات)، با تکنیک دلفی، تحققپذیری چشمانداز و عملیات در دورهای متوالی، از طریق طراحان و پژوهشگران شهری-معماری کشوربا تخصصهای انرژی، مرمت شهری، محیطزیست، ترافیک و زمین شناسی(قنات) گلچین، سنجیده و به اجماع رسیده است. از یافته های پژوهش این است که چشم اندازسازی مشارکتی یعنی کنشگری مردم و نهادهای مرتبط، امکان تحقق طراحی یک اکوپارک شهری با رویکردهای انرژی، اکولوژیکی و تاریخی را تسهیل می بخشد و آینده ای با اقتصاد و محله چرخهای برای تهران فراهم میسازد. راهبردهایی مثل خیابان کامل، بهره گیری از انرژیهای تجدیدپذیر شامل استفاده از آب های رها، تابش خورشید و باد، بههمراه اقدامات منطبق با پیشینه غنی تاریخی محله مثل باغ ها و قنوات ایرانی بررسی و به حامیان پژوهش پیشنهاد شده است. پرونده مقاله -
دسترسی آزاد مقاله
59 - A generalized cost Malmquist index to compare the productivities of units with negative data in DEA
G. Tohidi S. Razavyan S. TohidniaIn some data envelopment analysis (DEA) applications, some inputs of DMUshave negative values with positive cost. This paper generalizes the global cost Malmquistproductivity index to compare the productivity of dierent DMUs with negative inputs inany two periods of ti چکیده کاملIn some data envelopment analysis (DEA) applications, some inputs of DMUshave negative values with positive cost. This paper generalizes the global cost Malmquistproductivity index to compare the productivity of dierent DMUs with negative inputs inany two periods of times under variable returns to scale (VRS) technology, and then thegeneralized index is decomposed to several components. The obtained components are computed using the nonparametric linear programming models, known as DEA. To illustrate thegeneralized index and its components, a numerical example at three successive periods oftime is given. پرونده مقاله -
دسترسی آزاد مقاله
60 - تاثیر دوازده هفته تمرین مقاومتی دایرهای در سه شدت متفاوت هم حجم بر برخی عوامل همودینامیک مردان چاق
صابر نیازی حمید رجبی صادق امانی شلمزاریچاقی یکی از دلایل بروز بیماری های قلبی عروقی است و فعالیت ورزشی می تواند در تعدیل این خطر نقش داشته باشد لذا هدف از تحقیق حاضر بررسی تاثیر 12 هفته تمرین مقاومتی دایره ای در سه شدت متفاوت هم حجم بر برخی عوامل همودینامیک مردان چاق بود. برای این منظور 44 مرد چاق 23 تا 33 س چکیده کاملچاقی یکی از دلایل بروز بیماری های قلبی عروقی است و فعالیت ورزشی می تواند در تعدیل این خطر نقش داشته باشد لذا هدف از تحقیق حاضر بررسی تاثیر 12 هفته تمرین مقاومتی دایره ای در سه شدت متفاوت هم حجم بر برخی عوامل همودینامیک مردان چاق بود. برای این منظور 44 مرد چاق 23 تا 33 سال (30 BMI ≥ ، 5/0 WHtR >) در چهار گروه کنترل، تمرین مقاومتی دایره ای با شدت کم (Rm1 40%) ، متوسط (Rm1 60%) و بالا (Rm1 80%) (11= تعداد در هر گروه) با حجم برابر انجام دادند. پیش و پس از 12 هفته تمرین ضربان قلب استراحتی، فشار خون سیستولیک و دیاستولیک استراحتی و میزان محصول فشار اندازه گیری شد. جهت بررسی تغییرات درون گروهی از t تست وابسته و مقایسه گرو ه ها، از آنالیز واریانس دو طرفه و آزمون تعقیبی بانفرونی استفاده شد (05/0≥p ). تغییرات درون گروهی نشان داد ضربان قلب استراحتی، فشار خون سیستولی تنها در گروه با شدت بالا، ، فشار خون دیاستولی تنها در گروه با شدت متوسط و میزان محصول فشار در تمام گروه های تمرینی، بعداز دوره نسبت به قبل کاهش معنی داری داشت (05/0≥ p). آزمون تحلیل واریانس نشان داد بین تغییر ضربان قلب استراحتی، فشار خون سیستولی، فشار خون دیاستولی و میزان محصول فشار در گروه با شدت بالا نسبت به سایر گروه ها اختلاف معنی داری وجود دارد (05/0≥p ). یافته ها نشان می دهد احتمالاً دوازده هفته تمرین مقاومتی دایره ای اثر مثبتی بر کاهش فشار خون و بهبود شاخص های مرتبط با عملکرد قلب دارد. احتمالا تمرین با شدت بالا اثر بیشری بر کاهش ضربان قلب استراحتی، فشار خون سیستولی و دیاستولی و میزان محصول فشار داشته باشد. پرونده مقاله -
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61 - Asymmetric buckling analysis of the circular FGM plates with temperature-dependent properties under elastic medium
علیرضا نداف اسکویی هادی محمدی هویه وحید علایی خداداد واحدیIn this paper, Asymmetric buckling analysis of functionally graded (FG) Circular plates with temperature dependent property that subjected to the uniform radial compression and thermal loading is investigated. This plate is on an elastic medium that simulated by Winkler چکیده کاملIn this paper, Asymmetric buckling analysis of functionally graded (FG) Circular plates with temperature dependent property that subjected to the uniform radial compression and thermal loading is investigated. This plate is on an elastic medium that simulated by Winkler and Pasternak foundation. Mechanical properties of the plate are assumed to vary nonlinearly by temperature change. The equilibrium equations are obtained using the classical plate theory (CPT), Von Karman geometric nonlinearity and virtual displacement method. Existence of bifurcation buckling is examined and stability equations are obtained by means of the adjacent equilibrium criterion. The effects of elastic foundation coefficient, thickness to radius, power law index, and temperature-dependency of the material properties on critical buckling load of FG plates are presented. The results of the present work have been compared with the results of other investigator and the results of the comparison are very good. It is found that by increasing temperature, critical buckling load decreases. It is also concluded that the critical buckling load of (FG) Circular plates increases with an increase in the Winkler and Pasternak constants of elastic foundation. پرونده مقاله -
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62 - Free vibration analysis of circular sandwich plates with clamped FG face sheets
یونس محمدی کیوان حسینی صفری محسن رحمانیFree vibration of sandwich plates with temperature dependent functionally graded (FG) face sheets in various thermal environments is investigated. The material properties of FG face sheets are assumed to be temperature-dependent and vary continuously through the thickne چکیده کاملFree vibration of sandwich plates with temperature dependent functionally graded (FG) face sheets in various thermal environments is investigated. The material properties of FG face sheets are assumed to be temperature-dependent and vary continuously through the thickness according to a power-law distribution in terms of the volume fractions of the constituents. Also, the material properties of the core are assumed to be temperature dependent. The governing equations of motion in polar system and in free natural vibration are derived using Hamilton’s principle and Galerkin method is used to solve the equations and obtain the natural frequency. In-plane stresses of the core that usually are ignored in the vibration characteristics of the sandwich structures are considered in this formulation. The results obtained by Galerkin method for symmetric circular sandwich plate with fixed support is compared with finite element method that obtained by ABAQUS and good agreement is found. The results show that varying the power-law index and temperature have important effects on natural frequency. پرونده مقاله -
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63 - Analysis of Roll Wear in Reshaping Using Finite Element Simulation
مهدی سلمانی تهرانی رضا خدابنده شهرکی حسام ولیدیReshaping process is a widely used method for producing tubes with non-circular cross sections. Owing to the friction between pipe and rolls, initial round pipe moves forward and consequently, it gradually formed into square or rectangular one. In practice, geometric pr چکیده کاملReshaping process is a widely used method for producing tubes with non-circular cross sections. Owing to the friction between pipe and rolls, initial round pipe moves forward and consequently, it gradually formed into square or rectangular one. In practice, geometric profile of the rolls will be changed after a while. These changes would be detrimental the production of faultless products. Therefore, in this paper the reshaping process is studied considering wear phenomena on the rolls. This study is a co-operation with a related industry at which square tubes are produced using reshaping process. In order to investigate the production line, considering industrial datasheets, the process is modeled by means of a commercial FEM package, ABAQUS\Explicit. The reshaping process is simulated as a 3D model and subsequently the sustainable regions to wear are investigated. The influences of significant parameters such as material and thickness of strip, as well as friction coefficient on the worn area, are studied. At the end, the FEM reults are comprised with the experiments reults and a good consistency between them is seen. پرونده مقاله -
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64 - Applying Differential Transform Method on the Effect of the Elastic Foundation on the out - Plane Displacement of the Functionally Graded Circular Plates
سمیه عباسی فاطمه فرهت نیا سعید رسولی جزیIn this paper, the effect of elastic foundation on the out of plane displacement of functionally graded circular plates using differential transform method is presented. Differential transform method is a semi-analytical-numerical solution technique that is capable to s چکیده کاملIn this paper, the effect of elastic foundation on the out of plane displacement of functionally graded circular plates using differential transform method is presented. Differential transform method is a semi-analytical-numerical solution technique that is capable to solve various types of differential equations. Using this method, governing differential equations are transformed into recursive relations and boundary conditions are changed into algebraic equations. Since the problem of plates on elastic foundation have a great practical importance in modern engineering structures and Winkler foundation model is widely used, plate is assumed on Winkler elastic foundation. In this article functionally graded plate is considered in which material properties vary through the thickness direction by power-law distribution. Analysis results of out of plane displacement of plate on elastic foundation under uniform transverse loads are obtained in different terms of foundation stiffness, material properties and boundary conditions. In order to validate the solution technique, results obtained are compared with the results of the finite element method (FEM). پرونده مقاله -
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65 - Thermal Buckling Analysis of Circular FGM Plate with Actuator/Actuator Piezoelectric Layer Based on Neutral Plane
محمد مهدی نجفی زاده محسن مالمراد آرش شریفیIn this paper, the thermal buckling analysis of a circular plate made of FGM materials with actuator/actuator piezoelectric layers based on neutral plane, classical plate theory and first order shear deformation plate theory is investigated. Reddy's model is assumed for چکیده کاملIn this paper, the thermal buckling analysis of a circular plate made of FGM materials with actuator/actuator piezoelectric layers based on neutral plane, classical plate theory and first order shear deformation plate theory is investigated. Reddy's model is assumed for material properties of FGM plate. Plate under the thermal loading, nonlinear temperature rise through the thickness and clamped edges is considered. Equilibrium and stability equations are drived using the calculus of variations and applying Euler equations. The obtained results are compared with the numerical values of the critical buckling temperature based on the theories mentioned above, and good agreement is observed between them. پرونده مقاله -
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66 - Nonlocal Mechanical Buckling Analysis of Nano Single Layer Sheets Using Differential Quadrature method
M. Sadeghian M. JabbarzadehThe following article investigates buckling of moderately thick circular Nano plates with an orthotropic property under uniform radial compressive in-plane mechanical load. Taking into account nonlocal elasticity theory (Eringen), principle of virtual work, first order چکیده کاملThe following article investigates buckling of moderately thick circular Nano plates with an orthotropic property under uniform radial compressive in-plane mechanical load. Taking into account nonlocal elasticity theory (Eringen), principle of virtual work, first order shear deformation plate theory (FSDT) and nonlinear Von-Karman strains, the governing equations are obtained based on displacements. The stability equations are derived from the neighbor equilibrium estate. The differential quadrature method (DQM) as a numerical procedure is applied to discretize the derivatives equations with a non-uniform mesh point distribution (Chebyshev-Gauss-Lobatto). The accuracy of the present results is validated by comparing the solutions with those reported by the available literatures. The effect of nonlocal parameter, thickness and radius are investigated on non-dimension buckling loads. From the results, it can be seen that the non-dimension buckling load of Graphene sheets increases by decreasing flexibility of boundary condition and increasing the rate of nonlocal parameter. It can be observed that with increasing the non-dimensional thickness of plate, the non-dimension buckling loa reduces پرونده مقاله -
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67 - Analysis of Free Vibration Sector Plate Based on Elastic Medium by using New Version of Differential Quadrature Method
مسلم محمدی مصطفی غیور علی فرج پورThe new version of differential quadrature (DQ) method is extended to analyze the free vibration of thin sector orthotropic plates on the Pasternak elastic foundation with various sector angles and elastic parameters. Detailed formulations are given. Comparisons are mad چکیده کاملThe new version of differential quadrature (DQ) method is extended to analyze the free vibration of thin sector orthotropic plates on the Pasternak elastic foundation with various sector angles and elastic parameters. Detailed formulations are given. Comparisons are made with existing analytical and/or numerical data. Numerical results indicate that convergence can be achieved with increasing in number of grid points. The accurate results could be obtained with 9x9 or even higher grid. It is found that the results are influenced by grid spacing and for obtaining the accurate and reliable result non-uniform grid should be used. پرونده مقاله -
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68 - شناسایی چالش¬های بکارگیری فناروی صنعت نسل چهارم در زنجیره¬تامین مدور کشاورزی پایدار
حامد کریمی شیرازی Younos Vakil Alroaiaاین مطالعه با هدف شناسایی و تعیین روابط بین چالش¬های بکارگیری فناروی صنعت نسل چهارم در زنجیره¬تامین مدور کشاورزی پایدار به منظور مدیریت و کاهش ضایعات و پسماندهای محصولات کشاورزی از تولید تا مصرف است. بدین منظور، مهم¬ترین چالش¬ها از طریق مرور ادبیات نظری شناسایی و پس از چکیده کاملاین مطالعه با هدف شناسایی و تعیین روابط بین چالش¬های بکارگیری فناروی صنعت نسل چهارم در زنجیره¬تامین مدور کشاورزی پایدار به منظور مدیریت و کاهش ضایعات و پسماندهای محصولات کشاورزی از تولید تا مصرف است. بدین منظور، مهم¬ترین چالش¬ها از طریق مرور ادبیات نظری شناسایی و پس از غربالگری به روش دلفی فازی، با روش مدلسازی تفسیری-ساختاری تحلیل شده است. جامعه آماری خبرگان شامل مدیران ارشد شرکت¬های صنعتی مواد غذایی و کشاورزی به تعداد 15 نفر و به صورت نمونه¬گیری غیراحتمالی هدفمند با تکنیک گلوله برفی انتخاب شدند که به پرسش¬نامه مقایسات زوجی پاسخ دادند. 17 چالش در سه دسته اقتصادی، زیست¬محیطی و اجتماعی شناسایی و تایید شدند، که طبق یافته¬های مدلسازی تفسیری-ساختاری، چالش¬های «تهدیدات شغلی کارکنان و انطباق نشدن کارکنان با فناوری¬های هوشمند» (اجتماعی)، «تامین مالی در زیرساخت دیجیتال» (اقتصادی)، و «انتشار و دفع زباله¬های مضر الکترونیکی و مصرف منابع و انرژی فناوری-های هوشمند» (زیست¬محیطی) تاثیرپذیرترین هستند و چالش¬های «کمبود حمایت¬های مالی دولت از کاربرد فناوری¬های هوشمند» (اقتصادی) و «در دسترس نبودن استانداردها و پروتکل¬های جهانی فناوری¬های هوشمند برای حفاظت از محیط¬زیست» (زیست-محیطی)، « بازده مالی نامشخص سرمایه گذاری در فناوری های صنعت نسل چهارم» و «سرمایه گذاری بالا در فناوری های صنعت نسل چهارم برای عملیات پایدار کشاورزی» تاثیرگذارترین و مهم¬ترین می¬باشند که برای رفع این چالش¬ها نیاز به حمایت-های مالی، قانونی و حقوقی از سوی دولت است. پرونده مقاله -
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69 - تحلیل شاخص های مدل کسب و کار مدور در صنعت فولاد ایران
مهسا وارسته حسنعلی آقاجانیبراساس تحقیقات اخیر انسان تا سال2050 به سه سیاره با ویژگی زمین جهت تامین منابع طبیعی مورد نیاز اقتصاد خطی موجود نیاز خواهند داشت. حرکت به سمت مدل اقتصاد مدور نمونه ای از تغییرات اساسی است که به طرز تفکر و کسب و کار جدید نیاز دارد. صنعت فولاد سازی بعد از نفت و گاز طبیعی چکیده کاملبراساس تحقیقات اخیر انسان تا سال2050 به سه سیاره با ویژگی زمین جهت تامین منابع طبیعی مورد نیاز اقتصاد خطی موجود نیاز خواهند داشت. حرکت به سمت مدل اقتصاد مدور نمونه ای از تغییرات اساسی است که به طرز تفکر و کسب و کار جدید نیاز دارد. صنعت فولاد سازی بعد از نفت و گاز طبیعی دومین صنعت بزرگ دنیا از نظر ارزش اقتصادی و گردش مالی است. با توجه به مشکلات مدیریتی، تشکیلاتی و عدم وجود ساختار تاثیر گذار و منسجم جهت برنامه ریزی و پیگیری امور موبوط به قراضه در کشور هدف این پژوهش بررسی ارتباطات و تحلیل شاخص های مدل کسب و کار مدور صنعت فولاد که از استراتژی ها، اقدامات و خروجی ها تشکیل می شوند با تاکید بر ارائه راهکار کاربردی در سیاست گذاری ها و تصمیمات مدیران در جهت رویکرد اقتصاد مدور می باشد.روش تحقیق این پژوهش توصیفی تحلیلی و ازلحاظ نوع هدف کاربردی است. در این پژوهش از تکنیک دیمتل جهت تحلیل روابط استفاده گردید. جامعه آماری این پژوهش خبرگان ، صاحبنظران و صنعت گران فولادی میباشندکه با توجه به سابقه، مهارت، تخصص از روش نمونه گیری هدفمند استفاده شد. نتایج نشان داد تاثیرگذار ترین شاخص های مدل کسب و کار مدور استراتژی ها و اقدامات و تاثیر پذیر ترین آنها خروجی ها و پیامد ها می باشند. پرونده مقاله