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A novel control strategy for load converter of DC isolated distribution system under unbalanced loading conditions

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2009年第6期10卷 890-899页

作者： R.NOROOZIAN m.abedi G.B.GHAREHPETIAN S.H.HOSSEINI Department of Electrical Engineering Amirkabir University of Technology Department of Electrical and Computer Engineering Tabriz University

A novel control strategy for the load converter supplying the unbalanced AC load in a DC isolated distribution system is presented. The control algorithm results in balanced and sinusoidal load voltages under unbalanced AC loading. The unbalanced load is characterized in the d-q-0 rotating coordinate based on symmetrical sequence components. Also, the mathematical model of the load converter in both a-b-c and d-q-0 coordinates is derived by using the average large signal model. Then, two control strategies for the load converter are presented. The first one uses the conventional d-q-0 controller to ensure the voltage and current regulation. The second one is a newly proposed control strategy based on the decomposition of the voltage and current into in-stantaneous positive, negative, and zero sequences. These three sequences are controlled independently in their own reference frames as DC signals. The performance of the load converter using these two control strategies is compared. Simulation results show the validity and capability of the newly proposed control strategy.

关键词： Unbalanced load Power quality Symmetrical components Control strategy

Axisymmetric and three-dimensional flow simulation of a mixed compression supersonic air inlet

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Propulsion and Power Research 2020年第1期9卷 51-61页

作者： m.abedi R.Askari J.Sepahi-Younsi m.R.Soltani Department of Aerospace Engineering Sharif University of TechnologyTehranIran mechanical Engineering Department Faculty of EngineeringFerdowsi University of MashhadMashhadIran Visiting Professor William E.Boeing Department of Aeronautics and AstronauticsUniversity of WashingtonWashingtonU.S.A.

The flow through an axisymmetric supersonic mixed-compression air inlet has been simulated numerically to investigate the effects and the necessity of the three-dimensional(3D)modeling in comparison with the axisymmetric *** this purpose,a supersonic inlet has been simulated numerically via axisymmetric and 3D CFD solvers,using the steady state Reynolds-averaged Navier-Stokes equations along with the SST k-ωturbulence model,for a free-stream mach number of 2.0 and at zero degrees angle of *** grid for the 3D cases was a 14.4-degree sector,instead of a 360-degree domain one,with rotational periodic boundary condition for the side *** results show that both static and total pressure distributions match well with the experimental data for both the axisymmetric and the 3D *** the prediction of performance parameters is the main goal of simulations,it seems that the axisymmetric simulation provides adequate accuracy,and the 3D simulation one is not the best *** 3D numerical simulation results in an in-depth study on the supersonic inlets,including the shock wave-boundary layer interaction,the location of the terminal normal shock wave,and consequently the separation *** an axisymmetric supersonic inlet in an axisymmetric flow condition,3D effects are not strong enough to have a significant influence on the inlet performance for all operational ***,it seems that 3D effects play an important role in both critical and supercritical operating conditions during the steady state operation.

关键词： Supersonic inlet Axisymmetric simulation Three-dimensional simulation Inlet performance Shock-boundary layer interaction

Some non-linear height–diameter models performance for mixed stand in forests in Northwest Iran

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Journal of mountain Science 2020年第5期17卷 1084-1095页

作者： Roya abedi Tooba abedi Department of Forestry Ahar Faculty of Agriculture and Natural ResourcesUniversity of TabrizAhar ***Iran Environmental Research Institute Academic Center for EducationCulture and ResearchRasht 41635-3114Iran

This study evaluated the total height of trees based on diameter at breast height by using 23 widely used height-diameter non-linear regression models for mixed-species forest stands consisting of Caucasian oak,field maple,and hornbeam from forests in Northwest Iran.1920 trees were measured in 6 sampling plots(every sampling plot has 1 ha area).The fit of the best height–diameter models for each species were compared based on R2,Root mean Square Error(RmSE),Akaike information criterion(AIC),standard error,and relative ranking performance *** the final step,verification of results was performed by paired sample t-test to compare the observed height and estimated *** showed that among 23 height-diameter models,the best models were obtained from the top five ones including modified-logistic,Prodan,Sibbesen,Burkhart,and *** between the actual observed height and estimated height for Caucasian oak showed that modified–Logistic,Prodan,Sibbesen,Burkhart,and Exponential performed better than the others,respectively(There were no statistically significant differences between observed heights and predicted height(p≥0.05)).Prodan,modified-Logistic,Burkhart,and Loetch evaluated field maple tree height correctly,and modified-Logistic,Burkhart,and Loetch had better fitness compared to the others for hornbeam,*** other models were introduced as appropriate criteria,they could not reliably predict the height of *** the Rank analysis,the modified-Logistic model for the Caucasian oak and Prodan model for field maple and hornbeam had the best ***,to complement the results of this study,it is suggested to assess how environmental factors such as elevation,climate parameters,forest protection policy and forest structure will modify height-diameter allometry models and will enhance the prediction accuracy of tree heights prediction in mixed stands.

关键词： Arasbaran Forest inventory Height prediction model validation Non-linear modeling Rank analysis

Parametric study of hexagonal castellated beams in post-tensioned self-centering steel connections

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Frontiers of Structural and Civil Engineering 2019年第5期13卷 1020-1035页

作者： Hassan abedi SARVESTANI Faculty of Water and Environmental Engineering Shahid Beheshti UniversityTehran 16589-53571Iran

The effects o f important parameters (beam reinforcing plates, initial post-tensioning, and material properties o f steel angles) on the behavior o f hexagonal castellated beams in post-tensioned self-centering (PTSC) connections undergone cyclic loading up to 4% lateral drift have been investigated by finite element (FE) analysis using ABAQUS. The PTSC connection is comprised o f bolted top and bottom angles as energy dissipaters and steel strands to provide self-centering capacity. The FE analysis has also been validated against the experimental test. The new formulations derived from analytical method has been proposed to predict bending moment o f PTSC connections. The web-post buckling in hexagonal castellated beams has been identified as the dominant failure mode when excessive initial post-tensioning force is applied to reach greater bending moment resistance, so it is required to limit the highest initial post-tensioning force to prevent this failure. Furthermore, properties o f steel material has been simulated using bilinear elastoplastic modeling with 1.5% strain-hardening which has perfectly matched with the real material of steel angles. It is recommended to avoid using steel angles with high yielding strength since they lead to the yielding o f bolt shank. The necessity o f reinforcing plates to prevent beam flange from local buckling has been reaffirmed.

关键词： finite element analysis hexagonal castellated beam parametric study post-tensioned self-centering steel connection steel moment-resisting frame

The design of electroabsorption modulators with negative chirp and very low insertion loss

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Journal of Semiconductors 2012年第6期33卷 14-19页

作者： Kambiz abedi Department of Electrical Engineering Faculty of Electrical and Computer EngineeringShahid Beheshti University

Electroabsorption modulators（EAms） with negative chirp and very low insertion loss are numerically designed with asymmetric intra-step-barrier coupled double strained quantum wells（AICD-SQWs） based on InGaAlAs *** this purpose,the electroabsorption coefficient is calculated over a range of wells layer strain from compressive（CS） to tensile（TS）.The chirp parameter and insertion loss for TE input light polarization are evaluated from the calculated electroabsorption spectra,and their Kramers-Kronig transformed refractive index *** results of the numerical simulation show that the best range of left and right wells strain for EAms based on AICD-SQWs with negative chirp and very low insertion loss are from 0.032%to 0.05%（TS） and-0.52% to-0.50%（CS）,respectively.

关键词： electroabsorption modulators AICD-SQW strain chirp insertion loss

Some Explicit Constructions of Type-Ⅱ,Ⅲ,Ⅳ,Ⅴ QC-LDPC Codes with Girth 6

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China Communications 2020年第5期17卷 89-109页

作者： Farzaneh abedi mohammad Gholami Department of mathematics Shahrekord UniversityP.O.Box 88186-34141ShahrekordIran School of Computer Sciences Institute for Research in Fundamental Sciences(IPM)P.O.Box 19395-5746TehranIran

multi-type quasi-cyclic(QC) low-density parity-check(LDPC) codes can be considered as multiple-edge protograph QC-LDPC codes having some advantages in the minimum Hamming distance bound over single-edge protograph codes or type-Ⅰ QC-LDPC codes when the base matrices have the same size. In this paper, we investigate a class of multi-type QC-LDPC codes whose parity-check matrices contain just one blockrow of circulants and we obtain the generator matrix of such codes in general form. Using the permutation arrays and defining injection arrays, we present a new approach to construct a class of high-rate type-Ⅰ QC-LDPC codes with girth 6 from the constructed 4-cycle free multi-type QC-LDPC codes. In continue, for 2 ≤ w≤6, some type-w QC-LDPC codes with girth 6 are constructed explicitly such that the constructed codes are flexible in terms of rate and length. To the best of our knowledge, for w = 5,6, this is the first paper which deals with the explicit construction of type-w QC-LDPC codes with girth 6 and high rates. moreover, for w = 3, 4, the constructed type-w QC-LDPC codes have better(6,8)-cycle multiplicities than the codes with minimum achievable length recently constructed by cyclic difference families(CDFs). Simulation results show that the binary and non-binary constructed codes outperform the constituent underlying QC-LDPC codes.

关键词： QC-LDPC codes permutation arrays girth explicit constructions

Particle shape consideration in numerical simulation of assemblies of irregularly shaped particles

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Particuology 2011年第4期9卷 387-397页

作者： Saba abedi Ali Asghar mirghasemi School of Civil Engineering College of Engineering University of Tehran

The mechanical behavior of granular materials depends much on the shape of the constituent particles. Therefore appropriate modeling of particle, or grain, shape is quite important. This study employed the method of direct modeling of grain shape （matsushima ＆ Saomto, 2002）, in which, the real shape of a grain is modeled by combining arbitrary number of overlapping circular elements which are connected to each other in a rigid way. Then, accordingly, a discrete-element program is used to simulate the assembly of grains. In order to measure the effects of grain shape on mechanical properties of assembly of grains, three types of grains-high angular grains, medium angular grains and round grains are considered where several biaxial tests are conducted on assemblies with different grain types, The results show that the angularity of grains greatly affects the behavior of granular soil.

关键词： Discrete element method Granular soil Angularity Confining pressure

Deflection modification factors of multistory buildings considering soil-structure interaction

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Earthquake Engineering and Engineering Vibration 2015年第3期14卷 561-570页

作者： Farhad abedi-Nik Faramarz Khoshnoudian Department of Civil Engineering SADRA Institute of Higher Education Department of Civil Engineering Amirkabir University of Technology

In this investigation,attempts are made to examine the effects of soil-structure interaction on the deflection modification factor of multistory buildings and to clarify the role of deformable soil on this factor.A comprehensive study is conducted to investigate the effect of inertial interaction on displacement demand ratios in soil-structure systems with different structural characteristics and various non-dimensional parameters,using a simplified interacting model.A two-step regression analysis of the nonlinear,dynamic computer simulation results obtained,leads to a reliable and accurate formula for predicting deflection modification factors that incorporate foundation *** results illustrate that the application of deflection modification factors derived from fixed-base structures can lead to unsafe evaluation of the structures on soft *** proposed formula provides a useful tool for design engineers to incorporate the effect of soil-structure interaction into the evaluation of structural deformations.

关键词： defl ection modifi cation factor multistory struct

First investigation of eclipsing binary KIC 9026766:analysis of light curve and periodic changes

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Research in Astronomy and Astrophysics 2021年第11期21卷 55-61页

作者： Somaye Soomandar Abbas abedi Faculty of Sciences University of BirjandIran

We investigate a short-period W Uma binary KIC 9026766 with an orbital period of 0.2721278 d in the Kepler field of *** applying an automated q-search for the folded light curve and producing a synthetic light curve for this object based on the PHOEBE code,we calculate the fundamental stellar *** also analyze the O-C curve of the primary *** orbital period changes can be attributed to the combination of an upward quadratic function and light-travel time effect(LTTE)due to a possible third body with a minimum mass of 0.029 m☉and an orbital period of 972.5866±0.0041 *** relative luminosity of the primary and secondary eclipses(minⅠ-minⅡ)is *** periodogram of the residuals of the LTTE and minⅠ-minⅡshow peaks with the same period of 0.8566 *** background effect of two nearby stars on our target is the possible reason for this *** considering the amplitudes and periods of the remaining signals in the O-C curve of minima,spot motion is possible.

关键词： techniques:photometric stars:individual:KIC 9026766