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Gain enhancement in two-stream free electron laser with a planar wiggler and an axial guide magnetic field

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Chinese Physics B 2012年第9期21卷 247-250页

作者： S.Saviz Z.Rezaei farzin m.aghamir Plasma Physics Research Center Science and Research BranchIslamic Azad University Department of Physics University of Tehran

The theory for a two-stream free electron laser （FEL） consisting of a relativistic electron beam transported alongthe axis of a planar wiggler in the presence of an axial guiding magnetic field is proposed and investigated. The electron trajectories and the small signal gain are derived. The characteristic of the linear gain and the normalized maximum gain are studied numerically. The result shows that the normalized maximum gain is considerably enhanced in comparison with that of the single stream. The effect of the difference between the energies of the two beams in this configuration of FEL is also considered, and we find that the gain is affected by the energy differences between groups 1 and 2.

关键词： wo-stream free-electron laser

The effects of self-fields on the electron trajectory in a two-stream free electron laser with a helical wiggler and an axial guiding magnetic field

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Chinese Physics B 2012年第10期21卷 251-254页

作者： S.Saviz E.Lashani farzin m.aghamir Plasma Physics Research Center Science and Research BranchIslamic Azad UniversityTehranP.O.Box 14665-678Iran Department of Physics University of TehranN.Kargar AveTehran 14399Iran

A theory for the two-stream free-electron laser（TSFEL） with a helical wiggler and an axial guide magnetic field is *** the analysis,the effects of self-fields are taken into *** analysis of the two-stream steady-state electron trajectories is given by solving the equation of *** calculations show that there are seven groups of orbits in the presence of self-fields instead of two groups reported in the absence of *** stability of the trajectories is studied numerically.

关键词： two-stream free electron laser electron trajectory

Effects of self-fields on electron trajectory and gain in two-stream electromagnetically pumped free-electron laser with ion channel guiding

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Chinese Physics B 2011年第7期20卷 158-164页

作者： S.Saviz farzin m.aghamir H.mehdian m.Ghorannevis Plasma Physics Research Center Science and Research BranchIslamic Azad UniversityTehranP.O.Box.14665-678Iran Department of Physics University of TehranN.Kargar AveTehran 14399Iran Department of Physics and Institute for Plasma Research Tarbiat Moallem University49Dr.Mofatteh avenueTehran 15614Iran

A theory for the two-stream free-electron laser with an electromagnetic wiggler （EmW） and an ion channel guiding is developed. In the analysis, the effects of self-fields have been taken into account. The electron trajectories and the small signal gain are derived. The stability of the trajectories, the characteristics of the linear gain and the normalized maximum gain are studied numerically. The dependence of the normalized frequency ω corresponding to the maximum gain on the ion-channel frequency is presented. The results show that there are seven groups of orbits in the presence of the self-fields, which are similar to those reported in the absence of the self-fields. It is also shown that the normalized gains of 2 groups decrease while the rest increase with the increasing normalized ion-channel frequency. Furthermore, it is found that the two-stream instability and the self-field lead to a decrease in the maximum gain except for group 4.

关键词： free electron laser two-stream

magnetohydrodynamic Activity During Limiter Biasing on the CT-6B Tokamak

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Chinese Physics Letters 2001年第3期18卷 393-395页

作者： KHORSHID Pejman WANG Long YANG Xuan-Zong FENG Chun-Hua ZHANG Peng-Yun QI Xia-Zhi ROUHANI Shahriar RAHImITABAR m.Reza aghamir m.farzin GHORANNEVISS mahmud HANTEZADEH m.Reza Institute of Physics Chinese Academy of SciencesBeijing 100080 Plasma Physics Research Centre Azad UniversityTehranIran Institute for Studies in Theoretical Physics and mathematics TehranIran

magnetohydrodynamic phenomena in the CT-6B Tokamak based on mirnov oscillations have been investigated by applying the limiter biasing potentials and changing the vacuum chamber gas pressure and plasma *** results show that setting up a radial electric field at the plasma edge could drive electromagnetic instabilities in the tokamak *** oscillation frequency upon application of a positive bias decreases about 10-15%and then after a delay time,τ_(d)=2.5-3 ms increases about 20-25%with respect to their value without *** the negative bias regime the oscillation frequency increases about 10%in 1 ms after the application of the bias *** poloidal rotation velocity changes during two steps are related to its link with the radial electric field and the time scale of the density *** frequency of oscillations increases with the increasing chamber gas pressure and decreases with the increasing the outward plasma displacement.

关键词： Tokamak oscillation tokamak

Syntheses, Crystal Structures, and Properties of a New Lead(Ⅱ) Complex Involving Holo-and Hemidirected Coordination Spheres with 3,5,6-Tris(2-pyridyl)-1,2,4-triazine Ligand

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Chinese Journal of Structural Chemistry 2014年第8期33卷 1184-1190页

作者： farzin marandi Department of Chemistry Payame Noor University

[Pb（TPT）（μ-I）2PbI2（μ-I）2Pb（TPT）] 1 （TPT is the abbreviation of 3,5,6-tris（2- pyridyl）-1,2,4-triazine ligand） has been synthesized and characterized by elemental analysis, IR, J H- NmR spectroscopy and studied by thermal and electrochemical properties as well as X-ray crystallography. The single-crystal X-ray data show two different kinds of Pb2＋ ions in 1 with coordination numbers of six, Pbl = PbI6, and five, Pb2 = PbN312, with holodirected and hemidirected coordination spheres, respectively. The supramolecular features in 1 are negotiated through the weak but directional Pb...I, C-H...N and C-H...I interactions and aromatic π-π stacking interactions.

关键词： lead(Ⅱ) crystal structure holodirected hemidirected 1,2,4-triazine

multi-objective optimization of molten carbonate fuel cell system for reducing CO2 emission from exhaust gases

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Frontiers in Energy 2015年第1期9卷 106-114页

作者： Ramin ROSHANDEL majid ASTANEHI farzin GOLZAR Department of Energy Engineering Sharif University of TechnologyTehran 14565114 Iran

The aim of this paper is to investigate the implementation of a molten carbonate fuel cell （mCFC） as a CO2 separator. By applying multi-objective optimization （mOO） using the genetic algorithm, the optimal values of operating load and the corresponding values of objective functions are obtained. Objective functions are minimiza- tion of the cost of electricity （COE） and minimization of CO2 emission rate. CO2 tax that is accounted as the pollution-related cost, transforming the environmental objective to the cost function. The results show that the mCFC stack which is fed by the syngas and gas turbine exhaust, not only reduces CO2 emission rate, but also produces electricity and reduces environmental cost of the system.

关键词： molten carbonate fuel cell (mCFC) multi-objective optimization (mOO) Pareto curve geneticalgorithm CO2 separation

Simulation with Fluctuating and Singular Rates

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Communications in Computational Physics 2014年第7期16卷 287-306页

作者： farzin Barekat Russel Caflisch mathematics Department University of California at Los AngelesLos AngelesCA 90095-1555USA.

In this paper we present a method to generate independent samples for a general random variable,either continuous or *** algorithm is an extension of the Acceptance-Rejectionmethod,and it is particularly useful for kinetic simulation in which the rates are fluctuating in time and have singular limits,as occurs for exam-ple in simulation of recombination interactions in a *** it depends on some additional requirements,the new method is easy to implement and rejects less samples than the Acceptance-Rejection method.

关键词： Sampling monte Carlo Acceptance/Rejection method plasma recombination.

Broadband absorption enhancement in hole-transport-layer-free perovskite solar cell by grating structure

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Optoelectronics Letters 2023年第10期19卷 587-592页

作者： Hamideh Talebi farzin Emami Esmat Rafiee Nano-Optoelectronic Research Center Electronic DepartmentShiraz University of TechnologyShirazIran Department of Electrical Engineering Faculty of EngineeringAlzahra UniversityTehranIran

Recently,the hole transport layer-free planar perovskite solar cells(HTL-free PSCs)have attracted intense ***,the poor absorption of light in the wavelengths longer than 800 nm is an important challenge in all configurations of *** this study,the HTL-free PSC with a gold rectangular grating at back contact is *** order to improve the performance of the solar cell,effects of grating dimensions and periodicity on the absorption of the active layer are numerically *** the improved condition,an absorption enhancement of 25%in the range of 300–1400 nm is obtained compared with the flat electrode-based *** improvements are attributed to the coupling of light to surface plasmon polariton(SPP)***,the electrical simulation results of the improved solar cell demonstrated short-circuit current density and power conversion efficiency of 27.72 mA/cm2 and 18%,respectively.

关键词： absorption layer free

NUmERICAL PREDICTIONS AND EXPERImENTAL VALIDATIONS OF DUCTILE DAmAGE EVOLUTION IN SHEET mETAL FORmING PROCESSES

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Acta mechanica Solida Sinica 2012年第6期25卷 638-650页

作者： Farhad Haji Aboutalebi mahmoud farzin mohammad mashayekhi Department of mechanical Engineering University of Isfahan Department of mechanical Engineering Isfahan University of Technology

Prediction of forming limit in sheet metal forming is among the most important challenges confronting researchers. In this paper, a fully coupled elastic-plastic-damage model has been developed and implemented into an explicit code. Due to the adoption of the plane stress and finite strain theories, model can predict deformation and damage of parts quickly and accurately. Also, damage initiation, propagation, and fracture in some operations are predicted and validated with experiments. It is concluded that finite strain combined with continuum damage mechanics can be used as a quick tool to predict ductile damage, fracture, and forming limits in sheet metal forming processes.

关键词： ductile damage finite strain fracture sheet metal forming