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An Investigation on Rotating Bending Fatigue Behavior of Nanostructured Low-Temperature Bainitic Steel

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Acta metallurgica Sinica(English Letters) 2014年第2期27卷 233-238页

作者： B.R.Shendy m.N.Yoozbashi B.Avishan S.Yazdani Faculty of materials Engineering Sahand University of Technology University of Applied Science and Technology Faculty of Engineering Azarbaijan Shahid Madani University

The aim of this work is to investigate the fatigue behavior of a new class of nanostructured, low-temperature bainitic steels, where rotating bending fatigue tests were conducted on samples isothermally transformed at 300, 250, and 200 ℃, after which, fracture surfaces were examined using scanning electron microscopy. Results showed that, fatigue limits of about 820, 945, and 1,005 mPa were achieved for the samples transformed at each transformation temperature, respectively. moreover, according to the SEm micrographs, secondary crack initiation was observed in the high carbon retained austenite blocks for samples transformed at 300 ℃ and at the interface of blocky austenite-bainitic ferrite for samples transformed at 250 and 200 ℃.

关键词： Fatigue Bainitic ferrite Retained austenite Fractography

BEST APPROXImATION BY DOWNWARD SETS WITH APPLICATIONS

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Analysis in Theory and Applications 2006年第1期22卷 20-40页

作者： H.mohebi A.m.Rubinov shahid Bahonar University of Kerman Iran University of Ballarat Australia

We develop a theory of downward sets for a class of normed ordered spaces. We study best approximation in a normed ordered space X by elements of downward sets, and give necessary and sufficient conditions for any element of best approximation by a closed downward subset of X. We also characterize strictly downward subsets of X, and prove that a downward subset of X is strictly downward if and only if each its boundary point is Chebyshev. The results obtained are used for examination of some Chebyshev pairs （W,x）, where ∈ X and W is a closed downward subset of X

关键词： best approximation downward set proximinal set Chebyshev set Banach lattice

mONTE CARLO SImULATION FOR mODELING THE EFFECT OF GROUND SEGmENT LOCATION ON IN-ORBIT RESPONSIVENESS OF LEO SUNSYNCHRONOUS SATELLITES

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Journal of Electronics(China) 2011年第2期28卷 239-248页

作者： m.Navabi Hossein Bonyan Khamseh Faculty of New Technologies Engineering-shahid Beheshti University G.C.***TehranIran

Responsiveness is a challenge for space systems to sustain competitive advantage over al-ternate non-spaceborne *** a satellite in its operational orbit,in-orbit responsiveness is defined as the capability of the satellite to respond to a given demand in a timely *** this paper,it is shown that Average Wait Time(AWT) to pick up user demand from ground segment is the ap-propriate metric to evaluate the effect of ground segment location on in-orbit responsiveness of Low Earth Orbit(LEO) sunsynchronous *** metric depends on pattern of ground segment access to satellite and distribution of user demands in time domain.A mathematical model is presented to determine pattern of ground segment access to satellite and concept of cumulative distribution function is used to simulate distribution of user demands for markets with different total demand *** Carlo simulations are employed to take account of uncertainty in distribution and total volume of user *** error and standard deviation are used to ensure validity of AWT metric obtained from monte Carlo *** of the proposed metric in the ground segment site location process results in more responsive satellite systems which,in turn,lead to greater customer satisfaction levels and attractiveness of spaceborne systems for different ***,simula-tion results for a case study are presented.

关键词： Ground segment location In-orbit responsiveness Sunsynchronous satellite

Exergy-energy analysis of full repowering of a steam power plant

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Frontiers in Energy 2015年第1期9卷 54-67页

作者： S. NIKBAKHT NASERABad A. mEHRPANAHI m. R. ALIGOODARZ K. mOBINI Department of mechanical Engineering Shahid Rajaee Teacher TrainingUniversity Tehran *** Iran

A 320 mW old steam power plant has been chosen for repowering in this paper. Considering the technical conditions and working life of the power plant, the full repowering method has been selected from different repowering methods. The power plant repower- ing has been analyzed for three different feed water flow rates： a flow rate equal to the flow rate at the condenser exit in the original plant when it works at nominal load, a flow rate at maximum load, and a flow rate when all the extractions are blocked. For each flow rates, two types of gas turbines have been examined： V94.2 and V94.3A. The effect of a duct burner has then been investigated in each of the above six cases. Steam is produced by a double- pressure heat recovery steam generator （HRSG） with reheat which obtains its required heat from the exhaust gases coming from the gas turbines. The results obtained from modeling and analyzing the energy-exergy of the original steam power plant and the repowered power plant indicate that the maximum efficiency of the repowered power plant is 52.04%. This maximum efficiency occurs when utilizing two V94.3A gas turbines without duct burner in the steam flow rate of the nominal load.

关键词： full repowering exergy analysis V94.2 andV94.3A gas turbines double-pressure HRSG duct burner,Bandarabbas steam power plant efficiency

Synthesis of a New Class of Highly Functionalized Phosphorus Ylides Containing Heterocyclic Compounds

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Chinese Journal of Chemistry 2012年第8期30卷 1893-1900页

作者： Shaabani Ahmad Keshipour Sajjad Aghaei morteza Khodabandeh m. Hassan Zahedi mansour Department of Chemistry Shahid Beheshti University G. C. P. O. Box 19396-4716 Tehran Iran

The zwitterionic intermediate generated from the reaction of triphenylphosphine with electron deficient acety- lenic compounds was trapped by various NH acids. The synthesis resulted in a new class of highly functionalized heterocyclic compounds. Some of the reactions produced E and Z isomers. And the stability and transformation of them were studied by dynamic 1H NmR and density functional theory （DFT） calculations.

关键词： highly functionalized heterocyclic compounds phosphorus ylides triphenylphosphine DFT dynamic 1H NmR

冷轧及退火对310S奥氏体不锈钢的微观结构和组织的影响:基于X射线和电子背散射衍射分析

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Journal of Central South University 2023年第3期30卷 763-785页

作者： R.B.HEIDARI m.ESKANDARI m.YEGANEH Department of materials Engineering Faculty of EngineeringShahid Chamran University of AhvazAhvaz ***Iran

本文研究了热处理对310S奥氏体不锈钢的微观结构和组织的影响。对样品材料进行冷轧,使其厚度分别减少20%、50%和90%,然后在1023、1223和1323 K下退火5、15和30 min。在厚度减少20%后,奥氏体内产生孪晶,且可观察到形变诱发的α’马氏体,... 详细信息

本文研究了热处理对310S奥氏体不锈钢的微观结构和组织的影响。对样品材料进行冷轧,使其厚度分别减少20%、50%和90%,然后在1023、1223和1323 K下退火5、15和30 min。在厚度减少20%后,奥氏体内产生孪晶,且可观察到形变诱发的α’马氏体,孪晶的体积分数大于α’马氏体。当厚度变化由50%增加到90%,α’马氏体的体积分数由11%增加到69%,孪晶被α’马氏体取代。发生形变后奥氏体相主要为Brass、Goss和S织构,α’马氏体的主要纹理为R-Cu、R-cube、F和E组份。随着形变量增大,Brass织构增加,Goss织构减少。退火过程中,马氏体向奥氏体转变,并发生了再结晶,使Goss和Brass再结晶织构的体积分数增加。材料退火后的结构与冷轧后的大致相同。1223 K下退火5 min的马氏体转变速度明显高于1023 K下的。在1023 K下退火5 min,由于马氏体不完全转变和初级再结晶,未能检测到等轴组织。获得超细晶粒组织的最佳退火温度为1023 K,退火时间为15 min。在1173 K和1273 K时出现快速再结晶和晶粒生长。

关键词： 310S不锈钢形变退火电子背散射衍射微观结构组织

A Computationally Hybrid method for Solving a Famous Physical Problem on an Unbounded Domain

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Communications in Theoretical Physics 2019年第1期71卷 9-15页

作者： F.A.Parand Z.Kalantari m.Delkhosh F.mirahmadian Department of mathematics and Computer Science Allameh Tabataba'i University Department of Computer Sciences Shahid Beheshti University Department of mathematics and Computer Science Islamic Azad UniversityBardaskan Branch

In this paper, a hybrid method based on the collocation and Newton-Kantorovich methods is used for solving the nonlinear singular Thomas-Fermi equation. At first, by using the Newton-Kantorovich method, the nonlinear problem is converted to a sequence of linear differential equations, and then, the fractional order of rational Legendre functions are introduced and used for solving linear differential equations at each iteration based on the collocation method. moreover, the boundary conditions of the problem by using Ritz method without domain truncation method are satisfied. In the end, the obtained results compare with other published in the literature to show the performance of the method, and the amounts of residual error are very small, which indicates the convergence of the method.

关键词： fractional order of rational Legendre functions Newton-Kantorovich method collocation method Thomas-Fermi equation

Effect of Co content on electrodeposition mechanism and mechanical properties of electrodeposited Ni-Co alloy

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Transactions of Nonferrous metals Society of China 2016年第2期26卷 484-491页

作者： m.ZAmANI A.AmadEH S.m.LARI BAGHAL School of metallurgy and materials Engineering College of EngineeringUniversity of Tehran Department of materials Science and Engineering Faculty of EngineeringShahid Chamran University

Ni–Co coatings with various cobalt contents were electrodeposited from modified Watts bath. The effect of cobalt content on electrodeposition mechanism of the coatings was studied by electro-chemical impedance spectroscopy method （EIS）. Surface morphology and crystallographic structure of the coatings were investigated by means of SEm and XRD. mechanical properties of the coatings were determined using Vickers microhardness and tensile tests. It was found that with increasing the Co2＋ions in electroplating bath, the charge transfer resistance （Rct）of Ni-Co film increased whereas the Warburg impedence decreased. This may be due to enhancement in coverage of cathode surface by Co（OH）2 and higher diffusion rate of metal ions towards cathode surface, respectively. Also, with increasing the cobalt content in the bath, cobalt content in the alloy coating increased anomalously and （111） texture consolidated gradually. With increasing the cobalt content up to 45% in alloy coating, the grain size decreased and consequently, hardness and strength of the alloy increased. Further enhancement of cobalt content up to 55% led to a little decrease in hardness and strength. The maximum ductility was observed for Ni-25%Co coating due to relatively small grain size and compact structure.

关键词： Ni-Co coating electrodeposition microstructure mechanical properties

Effects of solution treatment on high temperature deformation behavior of extruded mg-0.35Y-2.17Nd-0.36Zr biomedical alloy

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Transactions of Nonferrous metals Society of China 2019年第9期29卷 1842-1853页

作者： Sh.ALIYARI S.m.FATEmI S.m.mIRESmAEILI Department of metallurgy and materials Engineering Shahid Rajaee Teacher Training University

The high temperature deformation behavior of an extruded mg-0.35 Y-2.17 Nd-0.36 Zr(wt.%) alloy was investigated for biomedical application by employing compression tests in temperature range of 225-525 ℃ and strain rate range of 0.0003-0.03 s-1. To study the significance of solute elements, the material was solution-treated before deformation. The low temperature yield strength of the as-extruded material significantly decreased after solutionizing process. A drastic change in the strength of solutionized alloy was recorded as the temperature was raised to 450 ℃, which was attributed to the promotion of grain boundary sliding(GBS). It was evidently shown that the slip-to-twinning transition temperature did not necessarily coincide with the strength-drop temperature. Based on constitutive equations, deformation parameters and related activation energy for the experimental alloy have been determined, incorporating the strain-dependent material constants. The verification of predictability of the developed models indicates a good agreement between experimental and predicted data.

关键词： mg alloy hot deformation constitutive model twinning