فهرس المقالات Shrinkage

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  1 - برآوردیابی بیز انقباضی پارامتر مقیاس توزیع نمایی دو پارامتری مبتنی بر داده‌های سانسور نوع دوم فزاینده و تابع زیان آنتروپی تعمیم یافته
  مهدی بازیار دیزآبادی عین اله دیری عزت اله بالوئی جامخانه
  هدف اصلی ما در این مقاله تحلیل برآوردگرهای بیز انقباضی پارامتر مقیاس توزیع نمایی دوپارامتری تحت تابع زیان آنتروپی تعمیم یافته بر اساس توزیع پیشین مزدوج و داده‌های سانسورشده نوع دوم فزاینده در حضور پارامتر مکان می‌باشد. به همین منظور در این مقاله ابتدا برآوردگر انقباضی پ أکثر

  هدف اصلی ما در این مقاله تحلیل برآوردگرهای بیز انقباضی پارامتر مقیاس توزیع نمایی دوپارامتری تحت تابع زیان آنتروپی تعمیم یافته بر اساس توزیع پیشین مزدوج و داده‌های سانسورشده نوع دوم فزاینده در حضور پارامتر مکان می‌باشد. به همین منظور در این مقاله ابتدا برآوردگر انقباضی پارامتر مقیاس را بر اساس برآوردگر بیزی که تحت تابع زیان تعمیم یافته آنتروپی و توزیع پیشین مزدوج به دست آمده ارائه داده و سپس کارایی برآوردگر پیشنهادی را با سایر برآوردگرها مثل، برآوردگر درستنمایی ماکزیمم ، برآوردگر بیز، برآوردگر بیز تجربی و برآوردگر بیز انقباضی تجربی مورد بررسی قرار می‌دهیم. روشی که ما در این مقاله برای بدست آوردن برآوردگر بیز تجربی و برآوردگر بیز انقباضی تجربی استفاده شده، روش حدسی است. با استفاده از شش طرح مختلف و داده‌های شبیه-سازی شده و توزیع‌های پیشین جفری و هارتیگان، کارایی برآوردگرهای پیشنهادی با هم مقایسه می‌شوند، نهایتا با استفاده از داده‌های واقعی کارایی برآوردگرهای پیشنهادی مورد بررسی قرار می‌گیرد. تفاصيل المقالة
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  2 - بررسی آزمایشگاهی بهسازی یک خاک متورم شونده با استفاده از اعمال چرخه‏‌های مرطوب و خشک شدن متناوب
  امین سلطانی علی رئیسی استبرق
  بهسازی مکانیکی خاک های مشکل ساز در محل احداث شبکه های آبیاری و زهکشی جهت جلوگیری از تخریب ساز ه های هیدرولیکی و در نتیجه تلفات آب همواره یکی از مهم ترین مسائل مربوط به حفاظت منابع آب و خاک است. خاک های رسی متورم شونده منطقه وسیعی از جهان را پوشش داده و همواره موجب بروز أکثر

  بهسازی مکانیکی خاک های مشکل ساز در محل احداث شبکه های آبیاری و زهکشی جهت جلوگیری از تخریب ساز ه های هیدرولیکی و در نتیجه تلفات آب همواره یکی از مهم ترین مسائل مربوط به حفاظت منابع آب و خاک است. خاک های رسی متورم شونده منطقه وسیعی از جهان را پوشش داده و همواره موجب بروز خسارات جدی به سازه های (بخصوص سازه های هیدرولیکی) ساخته شده بر روی آنها می گردد. در این کار تحقیقاتی نتایج آزمایشگاهی اعمال چرخه های مرطوب و خشک شدن بر روی یک نمونه خاک رسی متورم شونده حاوی آب منفذی شور (سدیم کلرید با غلظت 50 گرم بر لیتر) برای بهسازی آن ارائه می گردد. اعمال چرخه های مرطوب و خشک شدن بر روی نمونه های تراکم یافته و تهیه شده از روش تراکم استاتیکی با آب منفذی سدیم کلرید در دستگاه تحکیم اصلاح شده و تحکیم معمولی صورت پذیرفت. نتایج نشان داد که درصد تغییر شکل های محوری ناشی از اعمال چرخه های مرطوب و خشک متوالی با تکرار چرخه ها به مقادیر ثابتی می رسد و مقدار تورم ناشی از مرطوب شدن با مقدار انقباض ناشی خشک شدن تقریباً یکسان می گردد. همچنین نتایج تغییرات نسبت تخلخل در مقابل درصد رطوبت (مسیر های تورمی- انقباضی) طی چرخه های متوالی مرطوب و خشک شدن نشان داد که شکل عمومی مسیر های تورمی و انقباضی تقریباًٌ S شکل بوده و پدیده پسماند رطوبت (هیسترسیس) ایجاد شده در خاک با افزایش تعداد چرخه های متوالی به تعادل می رسد، به طوری که مسیر تورمی و انقباضی در چرخه نهایی (چرخه تعادل) برای خاک مورد آزمایش تقریباً یکسان و بر هم منطبق می گردند. تفاصيل المقالة
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  3 - استفاده از مایکروویو به‌عنوان پیش‌تیمار قبل از خشک‌کردن برش‌های پرتقال توسط پرتو فروسرخ
  فخرالدین صالحی مریم تشکری کیمیا ثمری
  مقدمه: گرمایش مایکروویو شکلی از گرمایش دی‌الکتریک است که به‌وسیله آن تولید گرما در مواد با رسانایی الکتریکی پایین توسط یک میدان الکتریکی با فرکانس بالا امکان‌پذیر است. مواد و روش‌ها: برای اعمال پیش‌تیمار مایکروویو، پرتقال‌ها به مدت 0، 1، 2 و 3 دقیقه داخل دستگاه مایکروو أکثر

  مقدمه: گرمایش مایکروویو شکلی از گرمایش دی‌الکتریک است که به‌وسیله آن تولید گرما در مواد با رسانایی الکتریکی پایین توسط یک میدان الکتریکی با فرکانس بالا امکان‌پذیر است. مواد و روش‌ها: برای اعمال پیش‌تیمار مایکروویو، پرتقال‌ها به مدت 0، 1، 2 و 3 دقیقه داخل دستگاه مایکروویو قرار گرفتند و بعد از تیماردهی، برش‌هایی با ضخامت 5/0 سانتی‌متر از پرتقال‌ها تهیه و سپس برش‌ها توسط لامپ فروسرخ با توان 250 وات خشک شدند. یافته‌ها: با افزایش زمان تیمار مایکروویو از صفر به 3 دقیقه، ضریب نفوذ مؤثر رطوبت افزایش یافت. نتایج مدل‌سازی سینتیکی داده‌های آزمایشگاهی خشک‌کردن برش‌های پرتقال نشان داد که بهترین مدل برای این فرآیند مدل میدیلی است. اعمال مایکروویو تأثیر معنی‌داری بر تغییر چروکیدگی سطحی برش‌های پرتقال خشک‌شده و آبگیری شده داشت (05/0>p) و اعمال این پیش‌تیمار باعث کاهش چروکیدگی سطحی محصول شد. اعمال مایکروویو تأثیر معنی‌داری بر تغییر شاخص‌های رنگ (زردی، قرمزی، روشنایی و تغییر رنگ کل) برش‌های پرتقال خشک و آبگیری ‌شده نداشت (05/0<p). با افزایش زمان تیمار مایکروویو از 0 به 3 دقیقه، میانگین آبگیری مجدد برش‌های پرتقال خشک شده در خشک کن فروسرخ از 25/154 درصد به 85/212 درصد افزایش یافت. نتیجه‌گیری: به‌طورکلی، استفاده از پیش‌تیمار مایکروویو قبل از خشک‌کردن برش‌های پرتقال به دلیل افزایش سرعت انتقال جرم، کاهش چروکیدگی سطحی و افزایش آبگیری مجدد توصیه می‌شود. تفاصيل المقالة
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  4 - Experimental and Numerical Investigation of Injection Molding Main Parameters’ Effects on Shrinkage and Warpage of a Thin Sheet Made of HDPE
  Ali Massah Nathan Jafarian Jam Ehsan Soury
  10.30486/admt.2022.1937988.1306
  Injection molding is one of the common processes for producing plastic parts. In this process, the mold is filled immediately and then the part and mold will be cooled down during the packing time. In the end, the part will be ejected from the mold. In this study, the e أکثر

  Injection molding is one of the common processes for producing plastic parts. In this process, the mold is filled immediately and then the part and mold will be cooled down during the packing time. In the end, the part will be ejected from the mold. In this study, the effects of the most important processing parameters such as packing time, melt and mold temperature have been investigated on shrinkage and warpage of the products experimentally and numerically. According to previous reports, a thin sheet is defined by a length to thickness ratio of at least 100. MOLDFLOW software has been utilized to obtain the numerical results. For the empirical study, 64 specimens have been produced in different production conditions. These samples have been scanned by a 3D scanner and results have been analyzed by CATIA software. The findings show that increasing melt and mold temperature decreases the warpage amount and rises the shrinkage in the specimens. Also increasing the packing time up to 2 seconds increases the warpage and decreases the shrinkage noticeably but in longer packing times the variations will be less remarkable. Moreover, findings show that the general trend in simulated and experimental results are similar in all reported values of shrinkage and warpage, in which the maximum calculated errors for both of them are approximately 10%. تفاصيل المقالة
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  5 - Development of Fiber Reinforced SCM for Sustainable Construction
  Iman Mehdipour Nicolas Ali Libre Mohammad Shekarchia
  The sustainability of the built environment is increasingly coming to the forefront of infrastructure design and maintenance decisions. To address this, development of a new class of more sustainable cement-based materials is needed. Fiber reinforced self-consolidating أکثر

  The sustainability of the built environment is increasingly coming to the forefront of infrastructure design and maintenance decisions. To address this, development of a new class of more sustainable cement-based materials is needed. Fiber reinforced self-consolidating mortar (FRSCM) was developed by optimizing the micromechanical parameters, which control composite properties in the hardened state, and the processing parameters, which control the rheological properties in the fresh state. The addition of fibers may take advantage of its high performance in the fresh state to achieve a more uniform dispersion of fibers, which can help to mitigate the shrinkage of the self-consolidating composite. In other words, fibers can have rheological and mechanical synergistic effects and that optimized fiber combinations can better increase mechanical performance while maintaining adequate flow properties for fiber reinforced self-consolidating mortar. In this study, effects of aspect ratio (l/d) and volume fraction (Vf) of polypropylene (PP) fiber on the free shrinkage and mechanical properties of FRSCM were investigated. Besides, the rheological properties of fiber reinforced SCMs are investigated by mini-slump and mini V-funnel tests. Nine mortar mixtures are prepared containing 0 to 0.7 percent of 6 and 12 mm length polypropylene fibers. The shrinkages of hardened mortar were measured since removing the molds and the measurements were continued up to six months. The results show that, the optimum volume fraction of polypropylene fiber content in SCMs to achieve appropriate rheological and mechanical properties is about 0.3% of the mixture volume. On the other hand, increasing the volume fraction and aspect ratio of PP fibers to about 0.7% causes the mechanical properties to drop considerably. This could be due to balling of fibers or fibers coagulation in the mixtures which decreases the mechanical properties. تفاصيل المقالة
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  6 - Evaluation of Autogenous Shrinkage in High-Performance Concrete
  Jamal Ahmadi Reza Naghdi2
  Recent tendencies in concrete technology have been towards to high- performance concrete with a low water-cement ratio. However, high performance concretes have some problems. One of the problems is early-age cracking due to autogenous shrinkage. This study presents t أکثر

  Recent tendencies in concrete technology have been towards to high- performance concrete with a low water-cement ratio. However, high performance concretes have some problems. One of the problems is early-age cracking due to autogenous shrinkage. This study presents the results of an experimental investigation carried out to evaluate the autogenous shrinkage of high-strength concrete. According to this, effects of water/binder ratio, cement content, fine to coarse aggregate ratio and silica fume content were evaluated. From the results of this investigation, it can be concluded that the autogenous shrinkage strain of high strength concrete increases with reduction of w/b ratio. The results show also that the variation of cement content and fine to coarse aggregate ratio had only a limited effect on the autogenous shrinkage. تفاصيل المقالة
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  7 - EffectofMetakaolin and Nano-SiO2onshort and Long-term shrinkageofself-compactingcement sandmortar
  Hassan Soltanshahi
  The use of cementitious products isincreasing in the world,Thusreplacement part of cement with pozzolanic materials reduced energy consumption and preserve natural resources and the environment and also improve the mechanical properties and durability of the cement mort أکثر

  The use of cementitious products isincreasing in the world,Thusreplacement part of cement with pozzolanic materials reduced energy consumption and preserve natural resources and the environment and also improve the mechanical properties and durability of the cement mortar.Furthermore Nano technology has promptedto tremendous developments in technology of building materials in recent yearsso use of nano-silica has considered by many researchers.On the other hand the use of self-compacting mortar due to high performance and flow ability has increased remarkable in recent years. One of the major issues affecting on durability of cement products is shrinkage of cement mortar.Because of the importance of self-compacting mortar and role of additives pozzolanic, particularly at the nanoscale, in this laboratory study the binary blend of Metakaolinpozzolan and Nano-SiO2as replacement part of the cement have been used. The rate of shrinkage of self-compacting mortar has been investigated.Therefore Metakaolin with percent by weight 10, 15 and 20 and Nano-SiO2with percent by weight 1% and 2% were replaced cement. The results show that using metakaolin,Nano-SiO2 and combination of them reduce the rate of shrinkage of self-compacting cement mortar. تفاصيل المقالة
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  8 - Finite element simulation of pyroplastic deformation, anisotropic shrinkage and heterogeneous densification for ceramic materials during liquid phase sintering process
  Hamed Yaghoubi Esmail Salahi Fateme Taati
  Pyroplastic deformation is a distortion of the ceramic shape during the sintering process. It occurs because the flow of the vitreous phase at high temperature and the applied stress due to the weight of the product during sintering process. The aim of this paper deals أکثر

  Pyroplastic deformation is a distortion of the ceramic shape during the sintering process. It occurs because the flow of the vitreous phase at high temperature and the applied stress due to the weight of the product during sintering process. The aim of this paper deals with describing a numerical-experimental method to evaluate the pyroplastic deformation, to predict the anisotropic shrinkage and heterogeneous densification for ceramic materials during the liquid phase sintering process, as a function of sintering time. For this purpose, three experimental configurations including midpoint deflection, sinter bending and free sintering test were designed; the finite element method are implemented by the CREEP user subroutine code in ABAQUS. The fair accordance between simulation results and experimental data reveals that the shear and bulk viscosity modulus as well as dynamic viscosity used in the simulation are near the real ones. The anisotropic shrinkage factor K_xy has been proposed to investigate the shrinkage anisotropy. It has been shown that the shrinkage along the normal axis of slip casting is about 1.5 times larger than that of casting direction. The inhomogeneity in Von-Misses, pressure, and principal stress intensifies the density non-uniformity in the samples. تفاصيل المقالة
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  9 - Experimental Study of Packing Time and Melt Temperature Effects on Shrinkage of a Thin Sheet Made of Wood-HDPE Composite
  Siavash Sobhani Nathan Jafarian Jam
  Injection molding is one of the most common processes which are used for manufacturing different plastic parts. This method includes 3 continuous steps: filling of the mold, cooling and driving the part out. A wide range of plastic and Non-Plastic materials can be used أکثر

  Injection molding is one of the most common processes which are used for manufacturing different plastic parts. This method includes 3 continuous steps: filling of the mold, cooling and driving the part out. A wide range of plastic and Non-Plastic materials can be used as raw material in this process. One of the most important advantages of this way of production is that it is very economic. In this study packing time &amp; melt temperature effects on shrinkage of a thin sheet made of wood- HDPE composite has been investigated. Based on previous works, defining a thin sheet means the ratio of length to thickness of it should be at least 100. The results were obtained after manufacturing of different pieces and 3D scanning using CATIA software package. Finally the results were represented and compared using EXCEL. Main parameters such as packing time and melt temperature were studied in 4 levels. The method used for designing of experiments is full factorial. The main goals in this study were to reduce the number of defected parts and recommend appropriate process parameters to producethin sheetsmade of wood-HDPE composite. Having this information will result in saving time and reducing the production costs. It has been seen that by increasing the packing time and lowering the temperature, the shrinkage was reduced. تفاصيل المقالة
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  10 - Using Non-Sub sampled Shearlet Transform and Nakagami Model for Ultrasound Image De-Speckling
  Sedigheh Ghofrani
  Ultrasound images suffer of multiplicative noise named speckle. Different de-speckling algorithms run either in spatial domain or in transformed domain. In this paper, an adaptive filter in spatial domain according to assume the Nakagami distribution as the statistic of أکثر

  Ultrasound images suffer of multiplicative noise named speckle. Different de-speckling algorithms run either in spatial domain or in transformed domain. In this paper, an adaptive filter in spatial domain according to assume the Nakagami distribution as the statistic of log-compressed ultrasound images is used. For de-speckling in transformed domain, the non-sub sampled shearlet transform is used. In addition, the Bayesian shrinkage as a well-known method for finding the optimum threshold values in transformed domain is applied. The main contribution of this paper is comparing the performance of two methods that suppress the speckle noise in spatial domain and transformed domain. For this purpose, a synthetic test image and the original ultrasound images are processed and peak signal to noise ratio (PSNR), mean square error (MSE), structural similarity (SSIM), edge keeping index (EKF), noise variance (NV), mean square difference (MSD), and equivalent number of looks (ENL) are obtained. تفاصيل المقالة
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  11 - The use of raw materials available in Yazd province for manufacturing of monoprosa tile
  Fatemeh Mirjalili Sasan Otroj Hossein Badiee
  This study is conducted on the use of raw materials available in Yazd province in order to make monoprosa tile. For this reason, about one hundred various types of raw materials available in Yazd province have been studied and with regard to their chemical analysis, dif أکثر

  This study is conducted on the use of raw materials available in Yazd province in order to make monoprosa tile. For this reason, about one hundred various types of raw materials available in Yazd province have been studied and with regard to their chemical analysis, different bodies were made. Then, the most important properties such as density, shrinkage, green and fired strengths have been measured. Also, present phases in raw materials and the bodies were determined by x-ray diffraction method (XRD) and the thermal analysis of the samples was evaluated by dilatometry and simultaneously thermal analysis (STA). The results show that the properties of the tile samples made of the suitable raw materials in Yazd province and the tile bodies made in the Maryam tile factory are almost similar. The dilatometry and STA curves of both bodies are similar; hence, a good match between glaze used in the factory and tile samples can occur without any problem. تفاصيل المقالة
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  12 - Experimental and Numerical Investigation of Thickness on the Shrinkage and out of Roundness in Cylindrical Parts in Injection Molding Process
  ناتان جعفریان جم پیام سرائیان آیت اله عرب امین ابادی
  Injection molding process is one of the most important methods of forming in the plastics manufacturing industry. Shrinkage and out of roundness are phenomenons that affect the final product quality. In this study, the effect of the thickness of cylindrical parts from p أکثر

  Injection molding process is one of the most important methods of forming in the plastics manufacturing industry. Shrinkage and out of roundness are phenomenons that affect the final product quality. In this study, the effect of the thickness of cylindrical parts from polypropylene material on shrinkage and out of roundness has been investigated. For this purpose, injection molding process is simulated and analyzed with MOLDFLOW software. Then a five-cavity injection mold from hallow cylindrical parts with five different thicknesses is made. Using an injection molding machine least five samples of these parts are made. Then dimensions of samples are measured using 3D optical coordinate measuring machine and the amount of shrinkage of each sample is obtained. It can be concluded that with increasing part thickness, shrinkage and out of roundness are increased. It is because of being slower at melting material cools and having more time to make crystals. More crystallize caused to more shrinkage and more out of roundness. At the end, the simulation results are compared with the experimental results and showed a good agreement. تفاصيل المقالة