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International Journal of Minerals,Metallurgy and Materials 2020年第6期27卷 809-817页

作者： majid Hosseini Mohammad Hossein Paydar Department of Materials Science and Engineering School of EngineeringShiraz UniversityShiraz 71964-84334Iran

Despite the existence of conventional methods for recycling chips,solid-state techniques have become popular,whereby waste metals are directly recycled into consolidated products with the desired shapes and *** investigated the feasibility of recycling phosphor bronze chips through a hot extrusion process using aluminum powder as a metal binder for the fabrication of a metal-fiber-reinforced aluminum matrix *** do so,mixtures containing 20 vol%–50 vol%of chips were prepared,cold-compacted,and *** quality of the consolidated samples was evaluated by determining the density of the fabricated composites and studying their *** addition,we performed tensile and hardness tests to evaluate the mechanical properties of the fabricated *** also analyzed the fracture surfaces of the samples to study the fracture mechanism as a function of the volume fraction of phosphor bronze chips in the fabricated *** results indicated that the most effective consolidation occurred in the sample containing 20 vol%of chips extruded at 465℃in which the chips serve as ideal fibers for improving the mechanical properties,especially the ultimate tensile strength,in comparison with those of Al matrixes that contain no chips but are produced under the same conditions.

关键词： recycling hot extrusion metal–metal composite phosphor bronze chips aluminum powder

Relative Canonical Modules and Some Duality Results

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Algebra Colloquium 2019年第2期26卷 351-360页

作者： majid Rahro Zargar Department of Engineering Sciences Faculty of Advanced Technologies University of Mohaghegh Ardabili Namin Ardabil Iran Department of Engineering Sciences Faculty of Advanced Technologies Sabalan University of Advanced technologies (SUAT) Namin Iran School of Mathematics Institute for Research in Fundamental Sciences (IPM)

Let (R, m) be a relative Cohen–Macaulay local ring with respect to an ideal a of R and set c to be ht a. We investigate some properties of the Matlis dual of the R-module H^ca(R), and we show that such modules behave like canonical modules over Cohen–Macaulay local rings. Moreover, we provide some duality and equivalence results with respect to the module H^ca(R)^∨, and these results lead us to achieve generalizations of some known results, such as the local duality theorem, which have been provided over a Cohen–Macaulay local ring admiting a canonical R-module.

关键词： local cohomology canonical module complex relative Cohen-Macaulay module

Effects of green iron nanoparticles on iron changes and phytoavailability in a calcareous soil

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Pedosphere 2021年第5期31卷 761-770页

作者： Akbar SOLIEMANZADEH majid FEKRI Department of Soil Science College of AgricultureShahid Bahonar University of KermanKerman ***(Iran)

Green iron nanoparticles(Fe NPs)can be a practical solution to combat iron(Fe)deficiency in calcareous agricultural *** main aim of the present work was to assess the effects of green Fe NPs on Fe availability in calcareous *** this purpose,green Fe NPs were synthesized using green tea(G-Fe NPs),Shirazi thyme(T-Fe NPs),walnut green hull(W-Fe NPs),and pistachio green hull(P-Fe NPs)extracts and applied as a source of Fe fertilizer to sorghum(Sorghum bicolor ***)*** of X-ray diffraction(XRD),scanning electron microscopy(SEM),and dynamic light scattering(DLS)indicated that the green Fe NPs were amorphous in nature and the polyphenols obtained from plant-part extracts acted as both capping and reducing *** to the behavior of Fe-ethylenediamine-N,N-bis(2-hydroxyphenyl)acetic acid(Fe-EDDHA)in calcareous soils,G-Fe NPs,T-Fe NPs,W-Fe NPs,and P-Fe NPs increased Fe release compared with the control and FeSO_(4) *** Fe release data fitted well to the power function,intra-particle diffusion,and Elovich kinetic *** to the pot experiment,the increment in soil Fe availability upon Fe-EDDHA and Fe NPs application led to an increase in Fe uptake,growth,and photosynthetic pigment contents of the sorghum *** further research is needed to evaluate the residual effect and environmental impact of green Fe NPs,they may be an appropriate substitute for traditional Fe fertilizers in calcareous soils.

关键词： chlorophyll content Fe fertilizer Fe release green chemistry natural polyphenols sorghum

Numerical simulation of sanding using a coupled hydro-mechanical sand erosion model

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Journal of Rock Mechanics and Geotechnical Engineering 2020年第4期12卷 811-820页

作者： majid Fetrati Ali Pak Department of Civil Engineering Sharif University of TechnologyTehranIran

Mechanical failure of materials adjacent to the production cavity and material disaggregation caused by fluid drag are considered as the most important parameters that affect sand *** light of such factors,the coupling of two mechanisms-mechanical instability and hydrodynamic erosion-is indispensable in order to model this phenomenon *** paper examines the applicability of a coupled hydro-mechanical erosion criterion for simulating sand production using the finite element *** porous medium was considered fully *** onset of sanding and production of sand were predicted by coupling mechanical failure and subsequent erosion of the grain particles utilizing a sanding *** consider the erosion process,the Papamichos and Stavropoulou(1998)’s sand erosion criterion was incorporated into the finite element *** Lagrangian-Eulerian(ALE)adaptive mesh approach was used to account for large amounts of erosive material ***,in order to address the problem of severe mesh distortion,the“mesh mapping technique”was *** production in a horizontal wellbore and in a field case was simulated to demonstrate capabilities of the proposed *** addition,principal parameters affecting sand production,including in situ stresses,cohesion,perforation orientation,and drawdown were *** results indicated the efficiency of the model used in evaluation of sanding in the *** studies indicated that in situ stresses and formation cohesion could be considered as dominant factors affecting the amount of sand production.

关键词： Sand production Finite element method Sanding criterion Hydro-mechanical coupling

Efects of Washing and Drying on Crystal Structure and Pore Size Distribution(PSD) of Zn_4O_(13)C_(24)H_(12) Framework(IRMOF-1)

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Acta Metallurgica Sinica(English Letters) 2013年第5期26卷 597-601页

作者： Mehrzad Arjmandi majid Pakizeh Department of Chemical Engineering Faculty of Engineering Ferdowsi University of Mashhad

In this study, the efects of various methods of washing and drying of MOF-5 nanocrystals on structure formation were investigated. Eight samples of MOF-5 were synthesized under diferent conditions. TGA, XRD and PSD analysis were applied to characterize of the samples. The methods of washing and drying were found to be important in determining the final structure of MOF-5s. MOF-5 with high BET surface area can be obtained by choosing a suitable method of washing and drying. According to the results obtained in this work, it was found that vacuum drying at 425℃ is sufcient to dissolve the MOF-5-DMF. Similar results were obtained by washing method（withCH2Cl2 andCHCl3）, when compared with vacuum drying at 425℃ according to XRD test. The pore size distribution of samples 1-5 and 8 were calculated by SHN1 method and results showed that the samples in which solvent vacuum was DMF, have lower pore volume, uniform pore size distribution and the pore size are smaller than samples 3, 4 and 8. It was also found that activated MOF-5 can be converted to its deactivated form prior to drying of the samples.

关键词： Metal organic framework(MOF) MOF-5 nanocrystal Characterization SHN1 method

Improvement of electrochemical and electrical properties of LiFePO_4 coated with citric acid

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Rare Metals 2016年第4期35卷 303-308页

作者： majid Talebi-Esfandarani Oumarou Savadogo Laboratory of New Materials for Electrochemistry and Energy Polytechnique Montreal

LiFePO4 was synthesized using hydrothermal method and coated with different amounts of citric acid as carbon source. The samples were characterized by X-ray powder diffraction （XRD）, scanning electron microscopy （SEM）, transmission electron microscope （TEM）, surface area measurement--Brunauer-Emmett-Teller （BET）, dis- charge capability, cyclic voltammetry （CV）, and electrochemical impedance spectroscopy （EIS）. The results show that the quality and thickness of the carbon coating on the surface of LiFePO4 particles are very important. The optimum carbon content （about 30 wt%） can lead to a more uniform carbon distribution. Electrochemical results show that the samples containing 20 wt%, 30 wt%, 40 wt%, and 50 wt% carbon deliver a discharge capacity of 105, 167, 151, and 112 mAh.g-1, respectively, at the rate of 0.1C. The increase of carbon content leads to the decrease of discharge capacity of LiFePO4/C, owing to the fact that excess carbon delays the diffusion of Li＋ through the carbon layers during charge/discharge procedure. The LiFePO4/C with low carbon content exhibits poor electrochemical performance because of its low electrical conductivity. Therefore, the amount of carbon must be optimized in order to achieve excellent electrochemical performance of LiFePOjC for its application in a lithium ion battery.

关键词： LiFePO4 Lithium ion batteries Carbon coating

Relativistic symmetries in the Rosen-Morse potential and tensor interaction using the Nikiforov-Uvarov method

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Chinese Physics B 2013年第4期22卷 87-93页

作者： Sameer M Ikhdair majid Hamzavi Department of Electrical and Electronic Engineering Near East University 922022 Nicosia Northern Cyprus Mersin 10 Turkey Department of Physics Faculty of Science An-Najah National University Nablus West Bank Palestine Department of Science and Engineering Abhar Branch Islamic Azad University Abhar Iran

Approximate analytical bound-state solutions of the Dirac particle in the fields of attractive and repulsive Rosen–Morse （RM） potentials including the Coulomb-like tensor （CLT） potential are obtained for arbitrary spin–orbit quantum number κ. The Pekeris approximation is used to deal with the spin–orbit coupling terms κ（κ ± 1）r 2 . In the presence of exact spin and pseudospin （p-spin） symmetries, the energy eigenvalues and the corresponding normalized two-component wave functions are found by using the parametric generalization of the Nikiforov–Uvarov （NU） method. The numerical results show that the CLT interaction removes degeneracies between the spin and p-spin state doublets.

关键词： Dirac equation RM potential CLT potential spin and p-spin symmetries NU method approximation schemes

Conflict-Aware Safe Reinforcement Learning:A Meta-Cognitive Learning Framework

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IEEE/CAA Journal of Automatica Sinica 2022年第3期9卷 466-481页

作者： majid Mazouchi Subramanya Nageshrao Hamidreza Modares Michigan State University East LansingMI 48824 USA Ford Research and Innovation Center Ford Motor CompanyPalo AltoCA 94304 USA IEEE

In this paper,a data-driven conflict-aware safe reinforcement learning(CAS-RL)algorithm is presented for control of autonomous *** safe RL results with predefined performance functions and safe sets can only provide safety and performance guarantees for a single environment or *** contrast,the presented CAS-RL algorithm provides safety and performance guarantees across a variety of circumstances that the system might *** is achieved by utilizing a bilevel learning control architecture:A higher metacognitive layer leverages a data-driven receding-horizon attentional controller(RHAC)to adapt relative attention to different system’s safety and performance requirements,and,a lower-layer RL controller designs control actuation signals for the *** presented RHAC makes its meta decisions based on the reaction curve of the lower-layer RL controller using a metamodel or *** specifically,it leverages a prediction meta-model(PMM)which spans the space of all future meta trajectories using a given finite number of past meta *** will adapt the system’s aspiration towards performance metrics(e.g.,performance weights)as well as safety boundaries to resolve conflicts that arise as mission scenarios *** will guarantee safety and feasibility(i.e.,performance boundness)of the lower-layer RL-based control *** is shown that the interplay between the RHAC and the lower-layer RL controller is a bilevel optimization problem for which the leader(RHAC)operates at a lower rate than the follower(RL-based controller)and its solution guarantees feasibility and safety of the control *** effectiveness of the proposed framework is verified through a simulation example.

关键词： Optimal control receding-horizon attentionalcontroller(RHAC) reinforcement learning(RL)

Nonlinear finite time attitude control of flexible spacecraft based on a novel output redefinition method

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Chinese Journal of Aeronautics 2023年第11期36卷 373-385页

作者： Seyed majid ESMAEILZADEH Mohammad Sadegh ZEYGHAMI Department of Electrical Engineering Iran University of Science and TechnologyNarmakTehran 16846-13114Iran

A finite time attitude controller is designed for a flexible spacecraft based on a novel output redefinition method, in this paper. To make the flexible appendages vibration suppression effective, the appendage tip-point is selected as the output. First, a novel output redefinition method is proposed to overcome the non-minimum phase property of the dynamic model. The proposed method not only makes the system model minimum phase but also improves the attitude control system performance. Consequently, the precise attitude pointing and stabilization are ***, a nonlinear finite time H∞controller is designed based on the backstepping approach. For the situation where the modal variables measurements are not available, a modal observer is also designed. The simulation results show the effectiveness of the proposed method in the presence of the model uncertainties and environmental disturbances.

关键词： Finite time Output redefinition H1 control Attitude control Flexible spacecraft Backstepping Robust

Relativistic symmetries in the Hulthn scalar-vector-tensor interactions

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Chinese Physics B 2013年第8期22卷 257-263页

作者： majid Hamzavi Ali Akbar Rajabi Department of Science and Engineering Abhar Branch Islamic Azad UniversityAbhar Iran Physics Department Shahrood University of TechnologyShahrood Iran

In the presence of spin and pseudospin （p-spin） symmetries, the approximate analytical bound states of the Dirac equation for scalar-vector-tensor Hulth6n potentials are obtained with any arbitrary spin-orbit coupling number using the Pekeris approximation. The Hulth6n tensor interaction is studied instead of the commonly used Coulomb or linear terms. The generalized parametric Nikiforov-Uvarov （NU） method is used to obtain energy eigenvalues and corresponding wave functions in their closed forms. It is shown that tensor interaction removes degeneracy between spin and p-spin doublets. Some numerical results are also given.

关键词： Dirac equation Hulth6n scalar-vector-tensor potential spin and p-spin symmetry NU method