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Asghari-Rad, Peyman,Choi, Yeon Taek,Nguyen, Nhung Thi-Cam,Sathiyamoorthi, Praveen,Kim, Hyoung Seop The Korean Powder MetallurgyMaterials Institute 2021 한국분말재료학회지 (KPMI) Vol.28 No.4
In this study, the layered structures of immiscible Fe and Cu metals were employed to investigate the interface evolution through solid-state mixing. The pure Fe and Cu powders were cold-consolidated by high-pressure torsion (HPT) to fabricate a layered Cu-Fe-Cu structure. The microstructural evolutions and flow of immiscible Fe and Cu metals were investigated following different iterations of HPT processing. The results indicate that the HPT-processed sample following four iterations showed a sharp chemical boundary between the Fe and Cu layers. In addition, the Cu powders exhibited perfect consolidation through HPT processing. However, the Fe layer contained many microcracks. After 20 iterations of HPT, the shear strain generated by HPT produced interface instability, which caused the initial layered structure to disappear.
An Integrated Mathematical Model for Supplier Selection
Asghari, Mohammad Korean Institute of Industrial Engineers 2014 Industrial Engineeering & Management Systems Vol.13 No.1
Extensive research has been conducted on supplier evaluation and selection as a strategic and crucial component of supply chain management in recent years. However, few articles in the previous literature have been dedicated to the use of fuzzy inference systems as an aid in decision-making. Therefore, this essay attempts to demonstrate the application of this method in evaluating suppliers, based on a comprehensive framework of qualitative and quantitative factors besides the effect of gradual coverage distance. The purpose of this study is to investigate the applicability of the numerous measures and metrics in a multi-objective optimization problem of the supply chain network design with the aim of managing the allocation of orders by coordinating the production lines to satisfy customers' demand. This work presents a dynamic non-linear programming model that examines the important aspects of the strategic planning of the manufacturing in supply chain. The effectiveness of the configured network is illustrated using a sample, following which an exact method is used to solve this multi-objective problem and confirm the validity of the model, and finally the results will be discussed and analyzed.
Near-DRAM Acceleration with Single-ISA Heterogeneous Processing in Standard Memory Modules
Asghari-Moghaddam, Hadi,Farmahini-Farahani, Amin,Morrow, Katherine,Jung Ho Ahn,Nam Sung Kim IEEE 2016 IEEE micro Vol.36 No.1
<P>THIS ARTICLE PRESENTS A NEAR-DRAM ACCELERATION (NDA) ARCHITECTURE IN WHICH LIGHTWEIGHT PROCESSORS (LWPS) WITH THE SAME ISA AS THEIR HOST PROCESSOR ARE 3D-STACKED ATOP COMMODITY DRAM DEVICES IN A STANDARD MEMORY MODULE TO EFFICIENTLY PROCESS DATA. EXPERIMENTS DEMONSTRATE THAT, ON AVERAGE, THE AUTHORS' NDA-BASED SYSTEM CONSUMES ALMOST 65 PERCENT LESS ENERGY AT NEARLY TWO TIMES HIGHER PERFORMANCE THAN THE BASELINE SYSTEM.</P>
A Driving Scheme Using a Single Control Signal for a ZVT Voltage Driven Synchronous Buck Converter
Asghari, Amin,Farzanehfard, Hosein The Korean Institute of Power Electronics 2014 JOURNAL OF POWER ELECTRONICS Vol.14 No.2
This paper deals with the optimization of the driving techniques for the ZVT synchronous buck converter proposed in [1]. Two new gate drive circuits are proposed to allow this converter to operate by only one control signal as a 12V voltage regulator module (VRM). Voltage-driven method is applied for the synchronous rectifier. In addition, the control signal drives the main and auxiliary switches by one driving circuit. Both of the circuits are supplied by the input voltage. As a result, no supply voltage is required. This approach decreases both the complexity and cost in converter hardware implementation and is suitable for practical applications. In addition, the proposed SR driving scheme can also be used for many high frequency resonant converters and some high frequency discontinuous current mode PWM circuits. The ZVT synchronous buck converter with new gate drive circuits is analyzed and the presented experimental results confirm the theoretical analysis.
Asghari-Rad, Peyman,Sathiyamoorthi, Praveen,Bae, Jae Wung,Moon, Jongun,Park, Jeong Min,Zargaran, Alireza,Kim, Hyoung Seop Elsevier 2019 Materials science & engineering. properties, micro Vol.744 No.-
<P><B>Abstract</B></P> <P>In the present study, V<SUB>10</SUB>Cr<SUB>15</SUB>Mn<SUB>5</SUB>Fe<SUB>35</SUB>Co<SUB>10</SUB>Ni<SUB>25</SUB> (at%) high-entropy alloy (HEA) of a single phase face-centered cubic structure with various grain sizes was fabricated. The influences of grain size on the work-hardening behavior and deformation mechanisms were investigated. The fine-grained and coarse-grained samples showed different work hardening behaviors during room temperature tensile deformation. Microstructural analysis revealed the presence of a high-density tangled dislocation structure without any mechanical twinning in the fine-grained sample, while mechanical twinning was observed to be the additional deformation mechanism in the coarse-grained sample.</P>
Asghari-Rad, Peyman,Kim, Yongju,Nguyen, Nhung Thi-Cam,Kim, Hyoung Seop The Korean Powder Metallurgy Institute 2020 한국분말재료학회지 (KPMI) Vol.27 No.1
In this research, a new medium-entropy alloy with an equiatomic composition of FeCuNi was designed using a phase diagram (CALPHAD) technique. The FeCuNi MEA was produced from pure iron, copper, and nickel powders through mechanical alloying. The alloy powders were consolidated via a high-pressure torsion process to obtain a rigid bulk specimen. Subsequently, annealing treatment at different conditions was conducted on the four turn HPT-processed specimen. The microstructural analysis indicates that an ultrafine-grained microstructure is achieved after post-HPT annealing, and microstructural evolutions at various stages of processing were consistent with the thermodynamic calculations. The results indicate that the post-HPT-annealed microstructure consists of a dual-phase structure with two FCC phases: one rich in Cu and the other rich in Fe and Ni. The kernel average misorientation value decreases with the increase in the annealing time and temperature, indicating the recovery of HPT-induced dislocations.
Investigation of Instability in Multiple Grid-Connected Inverters with LCL Output Filters
Asghari, Fariba,Safavizadeh, Arash,Karshenas, Hamid Reza The Korean Institute of Power Electronics 2018 JOURNAL OF POWER ELECTRONICS Vol.18 No.3
This paper deals with the instability and resonant phenomena in distribution systems with multiple grid-connected inverters with an LCL output filter. The penetration of roof-top and other types of small photovoltaic (PV) grid-connected systems is rapidly increasing in distribution grids due to the attractive incentives set forth by different governments. When the number of such grid-connected inverters increases, their interaction with the distribution grid may cause undesirable effects such as instability and resonance. In this paper, a grid system with several grid-connected inverters is studied. Since proportional-resonant (PR) controllers are becoming more popular, it is assumed that most inverters use this type of controller. An LCL filter is also considered at the inverters output to make the case as realistic as possible. A complete modeling of this system is presented. Consequently, it is shown that such a system is prone to instability due to the interactions of the inverter controllers. A modification of PR controllers is presented where the output capacitor is virtually decreased. As a result, the instability is avoided. Simulation results are presented and show a good agreement with the theoretical studies. Experimental results obtained on a laboratory setup show the validity of the analysis.
A Berry-Esseen Type Bound in Kernel Density Estimation for a Random Left-Truncation Model
Asghari, P.,Fakoor, V.,Sarmad, M. The Korean Statistical Society 2014 Communications for statistical applications and me Vol.21 No.2
In this paper we derive a Berry-Esseen type bound for the kernel density estimator of a random left truncated model, in which each datum (Y) is randomly left truncated and is sampled if $Y{\geq}T$, where T is the truncation random variable with an unknown distribution. This unknown distribution is estimated with the Lynden-Bell estimator. In particular the normal approximation rate, by choice of the bandwidth, is shown to be close to $n^{-1/6}$ modulo logarithmic term. We have also investigated this normal approximation rate via a simulation study.
Reverse Logistics Network Design with Incentive-Dependent Return
Asghari, Mohammad,Abrishami, Salman J.,Mahdavi, Faezeh Korean Institute of Industrial Engineers 2014 Industrial Engineeering & Management Systems Vol.13 No.4
Reverse logistics network design issues have been popularly discussed in recent years. However, few papers in the past literature have been dedicated to incentive effect on return quantity of used products. The purpose of this study is to formulate a dynamic nonlinear programming model of reverse logistics network design with the aim of managing the used products allocation by coordinating the collection centers and recovery facilities to warrant economic efficiency. In the optimization model, a fuzzy approach is applied to interpret the relationship between the rate of return and the suggested incentives. Due to funding constraints in setting up the collection centers, this work considers these centers as multi-capacity levels, which can be opened or closed at different periods. In view of the fact that the problem is known as NP-hard, we propose a heuristic method based on tabu search procedure to solve the presented model. Finally, several dominance properties of optimal solutions are demonstrated in comparison with the results of a state-of-the-art commercial solver.
Reverse Logistics Network Design with Incentive-Dependent Return
Mohammad Asghari,Salman J. Abrishami,Faezeh Mahdavi 대한산업공학회 2014 Industrial Engineeering & Management Systems Vol.13 No.4
Reverse logistics network design issues have been popularly discussed in recent years. However, few papers in the past literature have been dedicated to incentive effect on return quantity of used products. The purpose of this study is to formulate a dynamic nonlinear programming model of reverse logistics network design with the aim of managing the used products allocation by coordinating the collection centers and recovery facilities to warrant economic efficiency. In the optimization model, a fuzzy approach is applied to interpret the relationship between the rate of return and the suggested incentives. Due to funding constraints in setting up the collection centers, this work considers these centers as multi-capacity levels, which can be opened or closed at different periods. In view of the fact that the problem is known as NP-hard, we propose a heuristic method based on tabu search procedure to solve the presented model. Finally, several dominance properties of optimal solutions are demonstrated in comparison with the results of a state-of-the-art commercial solver.