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DYNAMICs OF KNOWLEDGE ACCUMULATION IN TECHNOLOGY FOLLOWER COUNTRIEs: A sYsTEM DYNAMICs APPROACH

第二十七届中国控制会议

作者： Ataei Mohammad shafiei s.ehsan Electronic Department Engineering FacultyUniversity of Isfahan Electrical and Robotic Engineering Faculty Shahrood University of Technology

In this paper a fuzzy sliding mode control（FsMC） for spacecraft attitude tracking in terms of quaternion is designed. For this purpose,at first,the spacecraft dynamic and kinematic equations based on quaternion are ***,the design procedure of related variable structure controller is *** prove the system stability in sliding mode and also to guarantee the convergence of quaternion vectors to desired state,a lemma is presented which is proved by using Lyapunov direct *** continuation,in order to improve the controller performance,tuning of the sliding mode gain is accomplished by using fuzzy logic ***,the proposed controller design is simulated on an assumed case study with uncertain parameters and external *** simulation results are provided to show the effectiveness of the method and its robustness to parameter uncertainties and disturbances.

关键词： sliding mode control Fuzzy logic Lyapunov stability spacecraft attitude tracking Quaternion

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Journal of systems science and systems Engineering 2009年第3期18卷 312-340页

作者： ehsan shafiei Mohammad-Bagher GHOFRANI Yadollah sABOOHI Power and Energy Planning Department Ministry of Energy TehranIran Department of Energy Engineering Sharif University of Technology TehranIran sharif Energy Research Inst. Sharif University of Technology TehranIran

In this paper the process of knowledge accumulation for a particular technology is studied. Two countries, say the technology follower and the technology frontier, are considered. The frontier＇s knowledge growth is determined by its R＆D efforts on the technology. The level of knowledge stock for the follower country is augmented by its R＆D activities for the technology and absorbing some of the external knowledge through spillover from the frontier. The extent to which the follower is able to exploit the external knowledge depends on technological gap, absorptive capacity, absorption time and degree of spillover. New concepts such as natural and enhanced degree of spillover, background and innovative knowledge and absorption speed are introduced in the present work to deeply explore the process of knowledge spillover. The factors influencing the knowledge development in the long term are simultaneously studied in an integrated structure provided by the system Dynamics approach. This framework shows the responses to the changes and provides the basis for examining the interactions among the variables over time.

关键词： Knowledge spillover technology follower absorptive capacity absorption speed,knowledge complexity system dynamics

Dynamic crack propagation in plates weakened by nclined cracks:an investigation based on peridynamics

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Frontiers of structural and Civil Engineering 2018年第4期12卷 527-535页

作者： A.shafiei Department of Mechanical Engineering Yazd UniversityIran Institute of structural Mechanics Bauhaus UniversityWeimarGermany

Peridynamics is a theory in solid mechanics that uses integral equations instead of partial differential equations as governing equations. It can be applied to fracture problems in contrast to the approach of fracture mechanics. In this paper by using peridynamics, the crack path for inclined crack under dynamic loading were investigated. The peridynamics solution for this problem represents the main features of dynamic crack propagation such as crack bifurcation. The problem is solved for various angles and different stress values. In addition, the influence of geometry on inclined crack growth is studied. The results are compared with molecular dynamic solutions that seem to show reasonable agreement in branching position and time.

关键词： peridynamics inclined crack dynamic fracture crack branching

New approach to model the yield strength of body-centered cubic solid solution refractory high-entropy alloys

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Tungsten 2020年第3期2卷 307-320页

作者： Ali shafiei Metallurgy Group Niroo Research Institute(NRI)Tehran 14665-517Iran

A data fitting approach is used in the present work for modeling the yield strength of single-phase body-centered cubic(bcc)refractory high-entropy alloys(RHEAs)in the Al-Hf-Nb-Mo-Ta-Ti-V-Zr *** is suggested that a polynomial equation could be used for modeling the strength of solid solution alloys where an experimental dataset containing more than 80 data is used for fitting and obtaining optimized polynomial *** comparison results show that the predictions are in good agreement with experimental data indicating that the proposed polynomial could be used for modeling the strength of *** show how the developed polynomial can be applied in designing of RHEAs,the alloy system Hf-Mo-Nb-Ta-Ti-V-Zr is selected as an example and the strength of designed RHEAs within this system is investigated by the developed *** results show that the strength of alloys within this system increases by increasing the amount of Mo and Zr,while the strength of alloys decreases by increasing the amount of ***,the results indicate that the strength of alloys increases with increasing the values of parameters atomic size difference(AsD)and valence electron concentration(VEC).The developed polynomial can be considered as a straightforward method for assessing the strength of solid solution RHEAs,although it does not explain the mechanisms involved in the strengthening of alloys.

关键词： High entropy alloys Refractory high entropy alloys Mechanical properties Modelling

Design feasibility of gamma camera without collimator based on specific arrangement of the detectors

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Nuclear science and Techniques 2016年第4期27卷 120-126页

作者： Hossein Akbari-Lalimi seyed Ali shafiei Geriatric Care Research Center Rafsanjan University of Medical Sciences Department of Medical Physics Mashhad University of Medical Sciences Department of Physiology and Pharmacology School of Medicine Qom University of Medical Sciences

In gamma camera and single-photon emission computerized tomography, the collimator removes most photons. Here, a gamma camera without collimator utilizes a specific arrangement of detectors. Instead of bending beams(like a lens) or directing beams(by parallel hole collimator), changes are created in detectors' field of view(FOV), so that each detector's FOV looks different from others. simulation proved this theory, with 98 detectors(2 cm 9 1.41 cm) arranged in a zigzag manner for Monte Carlo simulation. A radioactive source with energy of140 ke V was situated on the detectors' faces. sixty projections, each 3(0 –179) apart, were simulated by Monte Carlo N-Particle(MCNP) 4C code, rotating detectors around a radioactive point. The band containing the radioactive source is clearly visible in each *** obtained after simulation in different projections were reconstructed, and point source location emerged correctly. simulation of gamma camera with zigzag arrangement of detectors and MCNP-4C code demonstrated that one could string the space and determine radioactive source by image reconstruction without using collimators, solely through these special detectors' distribution.

关键词：探测器准直器 γ相机蒙特卡洛模拟计算机断层扫描单光子发射设计布置

Damaging of cemented carbide end mill with different grain sizes:experimental and simulation

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Rare Metals 2021年第3期40卷 671-678页

作者： Ali Amirnasiri Mahdi shafiei Haghshenas Nader Parvin Department of Mining and Metallurgical Engineering Amirkabir University of Technology(AUT)Tehran ***Iran

The main purpose of the current study was to investigate the effects of the size of WC grains on the damage evolution of WC-Co junk *** finite element method(FEM) simulation results showed that the finegrain(FG) tool retained its cutting edges radii longer than the coarse-grain(CG) *** event leads to the larger wear rate in the CG ***,FEM analysis indicated that through increasing the feeding rate,the wear rate and the cutting forces increased as *** observation of worn tool surface revealed that the formation of micro-pits,micro-cracks,scratching grooves and broken WC grains was among the common signs of the damage for both CG and FG ***,it was found that the defects are more intensive in the CG *** can be due to the lower boundary strength and less WC connectivity in the CG milling *** finer grains also decreased the mean free path in the Co binder and impeded the micro-cracks propagation in the material.

关键词： Cemented carbide Junk mill FEM simulation Wear Grain size

Process−microstructure−properties relationship in Al−CNTs−Al2O3 nanocomposites manufactured by hybrid powder metallurgy and microwave sintering process

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Transactions of Nonferrous Metals society of China 2020年第9期30卷 2339-2354页

作者： Meysam TOOZANDEHJANI Farhad OsTOVAN Khairur Rijal JAMALUDIN Astuty AMRIN Khamirul Amin MATORI ehsan shafiei Razak Faculty of Technology and Informatics Universiti Teknologi Malaysia Kuala Lumpur54100 Jalan SemarakKuala LumpurMalaysia Department of Material science and Engineering Islamic Azad UniversityBandar Abbas BranchBandar AbbasHormozganIran Department of Physics Faculty of ScienceUniversiti Putra Malaysia43400SerdangSelangorMalaysia

Al−2CNTs−xAl2O3 nanocomposites were manufactured by a hybrid powder metallurgy and microwave sintering *** correlation between process-induced microstructural features and the material properties including physical and mechanical properties as well as ultrasonic parameters was *** was found that physical properties including densification and physical dimensional changes were closely associated with the morphology and particle size of nanocomposite *** maximum density was obtained by extensive particle refinement at milling time longer than 8 h and Al2O3 content of 10 wt.%.Mechanical properties were controlled by Al2O3 content,dispersion of nano reinforcements and grain *** optimum hardness and strength properties were achieved through incorporation of 10 wt.%Al2O3 and homogenous dispersion of CNTs and Al2O3 nanoparticles(NPs)at 12 h of milling which resulted in the formation of high density of dislocations and extensive grain size *** both longitudinal and shear velocities and attenuation increase linearly by increasing Al2O3 content and milling *** variation of ultrasonic velocity and attenuation was attributed to the degree of dispersion of CNTs and Al2O3 and also less inter-particle spacing in the *** larger Al2O3 content and more homogenous dispersion of CNTs and Al2O3 NPs at longer milling time exerted higher velocity and attenuation of ultrasonic wave.

关键词： hybrid composite aluminum composites powder metallurgy microwave sintering microstructure mechanical properties ultrasonic velocity ultrasonic attenuation

Geochemistry of Rhenium and Other Trace Elements in Molybdenite,sar Cheshmeh Porphyry Cu-Mo Deposit,Iran

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Acta Geologica sinica(English Edition) 2021年第4期95卷 1217-1235页

作者： Behnam shafiei BAFTI Martin sVOJTKA Mehdi ABDOLAHI Department of Geology Faculty of ScienceGolestan UniversityGorganIran Department of Geology Faculty of ScienceShahid Bahonar University of KermanKermanIran Institute of Geology of the Czech Academy of sciences PragueCzech Republic Geology Office Mining AffairsSar Cheshmeh Copper ComplexRqfsanjanIran

LA-ICP-Ms analysis of molybdenite from the sar Cheshmeh porphyry Cu-Mo deposit(PCD),Iran,shows moderate concentration of Re(average~207 ppm)and low concentration of chalcogenides(average of Pb+Te+Bi,~31 ppm)as well as metalloids(average of As+sb+Ge,~4.5 ppm).The early-formed quartz–molybdenites associated with potassic alteration are characterized by moderately low concentration of Re(21–215 ppm with an average of 83 ppm),whereas the transitional quartz–molybdenite veins related to the sericitic stage of mineralization contain more Re(62–465 ppm,with an average of 207 ppm).In contrast,the late-formed quartz–molybdenite veins associated with phyllic alteration show the highest concentration of Re(up to 1273 ppm with an average of 395 ppm).Gradual increase in Re content of molybdenites deposited throughout the evolution of the porphyry system is probably related to elevated fO_(2) and acidic conditions of the ore fluids governing the transitional and late stage of mineralization,when compared to the moderately low fO_(2) and basic conditions of the ore fluids precipitating the low-Re molybdenites associated with potassic *** mixed mantle/crustal source of the ore-related magma and its fractionated composition in sar Cheshmeh are consistent with magmatic conditions for the formation of Mo-rich and Re-poor PCDs in the world.

关键词： rhenium molybdenite LA-ICP-Ms porphyry Cu sar Cheshmeh Iran

structure stability and Oxygen Permeability of Perovskite-type Oxides of Ba_(0.5)sr_(0.5)Co_(0.8)Fe_(0.1)R_(0.1)O_ (3-δ)(R=Al,Mn,Fe,Ce,Cr,Ni,Co)

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Journal of Materials science & Technology 2012年第2期28卷 177-183页

作者： Ensieh Ganji Babakhani Jafar Towfighi Laleh shirazi Ali Nakhaeipour Akbar Zamaniyan Zahra shafiei Gas Department Research Institute of Petroleum Industry (RIPI) Chemical Engineering Department Engineering FacultyUniversity of Tarbiat Modares

Perovskite-type a0.5sr0.5Co0.8Fe0.1R0.1O3-δ （R=Al, Mn, Fe, Ce, Cr, Ni, Co） oxide membranes were ex- ploited and synthesized. Oxygen behavior, order-disorder transition and phase stability of these composite oxides were investigated by combined analysis of X-ray diffraction （XRD）, temperature programmed desorp- tion （TPD）, thermogravimetric-differential thermal analysis （TG-DTA）. Oxygen permeation through these membranes was studied by the gas chromatography （GC） method using a high-temperature permeation cell in a wide temperature range from 700 to 950℃. High permeation fluxes were observed for these materials. The high permeation flux was about 3.19 ***-2 under air/He gradients at 950℃, which was achieved for a0.5sr0.5Co0.8Fe0.1R0.1O3-δ（BsCFNiO） membrane. The results of analysis showed no phase transition for BsCFNiO oxide with increasing temperature and XRD pattern of this material after O2-TPD indicated to sustain a pure perovskite structure after oxygen permeation process.

关键词： Perovskite Ceramic membrane Oxygen separation Phase stability