检索结果-南通市图书馆

Journal of Central South University 2017年第9期24卷 2035-2048页

作者： mohammadi mohammad Department of Electrical Engineering Borujerd BranchIslamic Azad UniversityBorujerdIran

Due to development of distribution systems and increase in electricity demand,the use of capacitor banks *** the other point of view,nonlinear loads generate and inject considerable harmonic currents into power *** this condition if capacitor banks are not properly selected and placed in the power system,they could amplify and propagate these harmonics and deteriorate power quality to unacceptable *** attention of disadvantages of passive filters,such as occurring resonance,nowadays the usage of this type of harmonic compensator is *** the other side,one of parallel multi-function compensating devices which are recently used in distribution system to mitigate voltage sag and harmonic distortion,performs power factor correction,and improves the overall power quality as active power conditioner(APC).Therefore,the utilization of APC in harmonic distorted system can affect and change the optimal location and size of shunt capacitor bank under harmonic distortion *** paper presents an optimization algorithm for improvement of power quality using simultaneous optimal placement and sizing of APC and shunt capacitor banks in radial distribution networks in the presence of voltage and current *** algorithm is based on particle swarm optimization(PSO).The objective function includes the cost of power losses,energy losses and those of the capacitor banks and APCs.

关键词： shunt capacitor banks active power conditioner multi-objective function particle swarm optimization (PSO) harmonic distorted distribution system

Nonlinear analysis of cable structures using the dynamic relaxation method

在线全文

学校读者我要写书评

暂无评论

Frontiers of Structural and Civil Engineering 2021年第1期15卷 253-274页

作者： mohammad REZAIEE-PAJAND mohammad mohammadi-KHATAMI Department of Civil Engineering Ferdowsi University of MashhadMashhad ***Iran

The analysis of cable structures is one of the most challenging problems for civil and mechanical *** they have highly nonlinear behavior,it is difficult to find solutions to these *** far,different assumptions and methods have been proposed to solve such *** dynamic relaxation method(DRM)is an explicit procedure for analyzing these types of *** utilize this scheme,investigators have suggested various stiffness matrices for a cable *** this study,the efficiency and suitability of six well-known proposed matrices are assessed using the *** achieve this goal,16 numerical examples and two criteria,namely,the number of iterations and the analysis time,are *** on a comprehensive comparison,the methods are ranked according to the two *** numerical findings clearly reveal the best ***,a variety of benchmark problems are suggested by the authors for future studies of cable structures.

关键词： nonlinear analysis cable structure stiffness matrix dynamic relaxation method

Resilience-oriented intentional islanding of reconfigurable distribution power systems

在线全文

学校读者我要写书评

暂无评论

Journal of Modern Power Systems and Clean Energy 2019年第4期7卷 741-752页

作者： mohammad Hossein OBOUDI mohammad mohammadi mohammad RASTEGAR Department of Power and Control Engineering School of Electrical and Computer EngineeringShiraz UniversityShirazIran

The participation of distributed energy resources in the load restoration procedure,known as intentional islanding,can significantly improve the distribution system *** system reconfiguration can effectively alter islanding procedure and thus provide an opportunity to supply more demanded energy and reduce distribution system *** addition,high-impact events such as hurricanes and earthquakes may complicate the procedure of load restoration,due to the disconnection of the distribution system from the upstream grid or concurrent component *** paper presents a two-level method for intentional islanding of a reconfigurable distribution system,considering high-impact *** thefirst level,optimal islands are selected according to the graph model of the distribution *** the second level,an optimal power flow(OPF)problem is solved to meet the operation constraints of the islands by reactive power control and demand side *** proposed problem in the first level is solved by a combination of depth first search and particle swarm optimization *** OPF problem in the second level is solved in DIgSILENT *** proposed method is implemented in the IEEE 69-bus test system,and the results show the validity and effectiveness of the proposed algorithm.

关键词： Intentional islanding Active distribution system Distributed energy resource Distribution system reconfiguration Distribution system resilience

A fast and accurate dynamic relaxation scheme

在线全文

学校读者我要写书评

暂无评论

Frontiers of Structural and Civil Engineering 2019年第1期13卷 176-189页

作者： mohammad REZAIEE-PAJAND mohammad mohammadi-KHATAMI Department of Civil Engineering Ferdowsi University of MashhadMashhadIran

Dynamic relaxation method (DRM)is one of the suitable numerical procedures for nonlinear structural *** the fictitious inertia and damping forces to the static equation,and turning it to the dynamic system,are the basis of this *** selection of the DRM artificial factors leads to the better convergence rate and efficient *** study aims to increase the numerical stability,and to decrease the analysis *** fulfil this objective,the reduction rate of analysis error for consecutive iterations is *** on this formulation,a new time step is found for the viscous dynamic *** combining this novel relationship with the other DRM factors,various geometrical nonlinear structures,such as trusses,frames,and shells,are *** obtained results verify the efficiency of authors'scheme.

关键词： viscous dynamic relaxation time step displacement error geometric nonlinear analysis

Fuzzy-GA based algorithm for optimal placement and sizing of distribution static compensator (DSTATCOM) for loss reduction of distribution network considering reconfiguration

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Central South University 2017年第2期24卷 245-258页

作者： mohammad mohammadi Mahyar Abasi A.mohammadi Rozbahani Department of Electrical Engineering Borujerd Branch Islamic Azad University

This work presents a fuzzy based methodology for distribution system feeder reconfiguration considering DSTATCOM with an objective of minimizing real power loss and operating cost. Installation costs of DSTATCOM devices and the cost of system operation, namely, energy loss cost due to both reconfiguration and DSTATCOM placement, are combined to form the objective function to be minimized. The distribution system tie switches, DSTATCOM location and size have been optimally determined to obtain an appropriate operational condition. In the proposed approach, the fuzzy membership function of loss sensitivity is used for the selection of weak nodes in the power system for the placement of DSTATCOM and the optimal parameter settings of the DFACTS device along with optimal selection of tie switches in reconfiguration process are governed by genetic algorithm(GA). Simulation results on IEEE 33-bus and IEEE 69-bus test systems concluded that the combinatorial method using DSTATCOM and reconfiguration is preferable to reduce power losses to 34.44% for 33-bus system and to 45.43% for 69-bus system.

关键词： distribution FACTS (DFACTS) distribution static compensator (DSTATCOM) network reconfiguration genetic algorithm fuzzy membership function power loss reduction

Modification of rock mass rating system:Interbedding of strong and weak rock layers

在线全文

学校读者我要写书评

暂无评论

Journal of Rock Mechanics and Geotechnical Engineering 2017年第6期9卷 1165-1170页

作者： mohammad mohammadi mohammad Farouq Hossaini The Alborz Tunnel Site Geodata EngineeringMazandaran ProvinceIran Faculty of Mining Engineering Engineering University CollegeUniversity of TehranTehranIran

Rock mass classification systems are the very important part for underground projects and rock mass rating(RMR) is one of the most commonly applied classification systems in numerous civil and mining projects. The type of rock mass consisting of an interbedding of strong and weak layers poses difficulties and uncertainties for determining the RMR. For this, the present paper uses the concept of rock bolt supporting factor(RSF) for modification of RMR system to be used in such rock mass types. The proposed method also demonstrates the importance of rock bolting practice in such rock masses. The geological parameters of the Shemshak Formation of the Alborz Tunnel in Iran are used as case examples for development of the theoretical approach.

关键词： Rock mass rating(RMR) Strong and weak rock layers Interbedding Rock bolt supporting factor(RSF) Alborz tunnel

Use of fuzzy set theory for minimizing overbreak in underground blasting operations——A case study of Alborz Tunnel,Iran

在线全文

学校读者我要写书评

暂无评论

International Journal of Mining Science and Technology 2015年第3期25卷 439-445页

作者： mohammadi mohammad Hossaini mohammad Farouq Mirzapour Bahman Hajiantilaki Nabiollah General Mechanic Co. Faculty of Mining Engineering Engineering University CollegeUniversity of Tehran

In order to increase the safety of working environment and decrease the unwanted costs related to overbreak in tunnel excavation projects, it is necessary to minimize overbreak percentage. Thus, based on regression analysis and fuzzy inference system, this paper tries to develop predictive models to estimate overbreak caused by blasting at the Alborz Tunnel. To develop the models, 202 datasets were utilized, out of which 182 were used for constructing the models. To validate and compare the obtained results,determination coefficient(R2) and root mean square error(RMSE) indexes were chosen. For the fuzzy model, R2 and RMSE are equal to 0.96 and 0.55 respectively, whereas for regression model, they are 0.41 and 1.75 respectively, proving that the fuzzy predictor performs, significantly, better than the statistical method. Using the developed fuzzy model, the percentage of overbreak was minimized in the Alborz Tunnel.

关键词： Fuzzy model Overbreak Regression analysis Underground blasting Alborz Tunnel

Correction to:Microstructure and mechanical properties of joints welded by friction-stir welding in aluminum alloy 7075-T6 plates for aerospace application

在线全文

学校读者我要写书评

暂无评论

Rare Metals 2024年第11期43卷 6124-6124页

作者： mohammad mohammadi-pour Alireza Khodabandeh Sadegh mohammadi-pour Moslem Paidar Department of Materials Engineering University of Islamic AzadScience and Research BranchTehran 14515775Iran Department of Materials Engineering Amirkabir University of TechnologyTehran ***Iran Department of Materials Engineering University of Islamic AzadSouth Tehran BranchTehran ***Iran

Correction to:Rare Met.D0I10.1007/s12598-016-0692-9 The original version of this article was inadvertently published with incorrect references as below:Section 1:“Friction-stir welding(FSW)technology invented at The Welding Institute,UK,in December 1991 is a solid-state joining process for joining aluminum alloys and used increasingly in aerospace,transportation and car manufacturing industries[1,2].”

关键词： welding welded Microstructure

Bending and stress analysis of polymeric composite plates reinforced with functionally graded graphene platelets based on sinusoidal shear-deformation plate theory

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Defence Technology（防务技术） 2021年第1期17卷 64-74页

作者： mohammad Arefi Ali Tabatabaeian Masoud mohammadi Faculty of Mechanical Engineering Department of Solid MechanicsUniversity of KashanKashan 87317-51167Iran

The bending and stress analysis of a functionally graded polymer composite plate reinforced with graphene platelets are studied in this *** governing equations are derived by using principle of virtual work for a plate which is rested on Pasternak’s *** shear deformation theory is used to describe displacement *** different distribution patterns are employed in our *** analytical solution is presented for a functionally graded plate to investigate the influence of important *** numerical results are presented to show the deflection and stress results of the problem for four employed patterns in terms of geometric parameters such as number of layers,weight fraction and two parameters of Pasternak’s foundation.

关键词： Reinforced composite plate Graphene platelet Sinusoidal shear deformation theory Pasternak’s foundation Stress and deformation analysis

Sol-gel derived nanocrystalline and mesoporous barium strontium titanate prepared at room temperature

在线全文

学校读者我要写书评

暂无评论

Particuology 2011年第3期9卷 235-242页

作者： mohammad Reza mohammadi Derek J.Fray Department of Materials Science & Engineering Sharif University of Technology Department of Materials Science & Metallurgy University of Cambridge

Perovskite-type barium strontium titanate （BST） thin films and powders with nanocrystalline and mesoporous structure were prepared by a straightforward particulate sol-gel route at room temperature. The prepared sol had a narrow particle size distribution of about 20 nm. X-ray diffraction （XRD） revealed that phase composition and preferable orientation growth of BST depended upon the annealing temperature. Transmission electron microscope （TEM） images showed that the crystallite size of the powders decreased with increasing annealing temperature from 8 nm at 25 ℃ down to 5 nm at 800 ℃. Field emission scanning electron microscope （FE-SEM） analysis and atomic force microscope （AFM） images revealed that BST thin films had mesoporous and nanocrystafiine structure with average grain size of 3Onm at 600 ℃. Based on Brunauer-Emmett-Teller （BET） analysis, the synthesized BST showed mesoporous structure containing nnres with needle, and nlate shanes and BET surface area in the range of 49-32 m^2/g at 500-800℃

关键词： Barium strontium titanate Room temperature Sol-gel chemistry Nanostructure