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A Sliding Mode Approach to Enhance the Power Quality of Wind Turbines Under Unbalanced Voltage Conditions

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IEEE/CAA Journal of Automatica Sinica 2019年第2期6卷 566-574页

作者： mohammad javad Morshed Afef Fekih IEEE the Department of Electrical and Computer Engineering University of Louisiana at Lafayette

An integral terminal sliding mode-based control design is proposed in this paper to enhance the power quality of wind turbines under unbalanced voltage conditions. The design combines the robustness, fast response, and high quality transient characteristics of the integral terminal sliding mode control with the estimation properties of disturbance observers. The controller gains were auto-tuned using a fuzzy logic *** effectiveness of the proposed design was assessed under deep voltage sag conditions and parameter variations. Its dynamic response was also compared to that of a standard SMC *** performance analysis and simulation results confirmed the ability of the proposed approach to maintain the active power,currents, DC-link voltage and electromagnetic torque within their acceptable ranges even under the most severe unbalanced voltage conditions. It was also shown to be robust to uncertainties and parameter variations, while effectively mitigating chattering in comparison with the standard SMC.

关键词： Doubly fed induction generators(DFIG) fuzzy approach integral terminal sliding mode control(ITSMC) observer power quality voltage unbalances wind turbines

A novel hybrid algorithm based on a harmony search and artificial bee colony for solving a portfolio optimization problem using a mean-semi variance approach

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Journal of Central South University 2016年第1期23卷 181-188页

作者： Seyed mohammad Seyedhosseini mohammad javad Esfahani Mehdi Ghaffari Department of Industrial Engineering Iran University of Science and Technology Young Researchers and Elite Club Naragh BranchIslamic Azad University Department of Industrial Engineering Naragh BranchIslamic Azad University

Portfolio selection is one of the major capital allocation and budgeting issues in financial management, and a variety of models have been presented for optimal selection. Semi-variance is usually considered as a risk factor in drawing up an efficient frontier and the optimal portfolio. Since semi-variance offers a better estimation of the actual risk portfolio, it was used as a measure to approximate the risk of investment in this work. The optimal portfolio selection is one of the non-deterministic polynomial(NP)-hard problems that have not been presented in an exact algorithm, which can solve this problem in a polynomial time. Meta-heuristic algorithms are usually used to solve such problems. A novel hybrid harmony search and artificial bee colony algorithm and its application were introduced in order to draw efficient frontier portfolios. Computational results show that this algorithm is more successful than the harmony search method and genetic algorithm. In addition, it is more accurate in finding optimal solutions at all levels of risk and return.

关键词： portfolio optimizations mean-variance model mean semi-variance model harmony search and artificial bee colony efficient frontier

Micromechanical simulation and experimental investigation of aluminum-based nanocomposites

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Defence Technology（防务技术） 2021年第1期17卷 196-201页

作者： mohammad javad Ghasemi mohammad Silani Ali Maleki Mostafa Jamshidian Department of Mechanical Engineering Isfahan University of TechnologyIsfahan84156-83111Iran

Ceramic reinforced metal matrix nanocomposites are widely used in aerospace and auto industries due to their enhanced mechanical and physical *** this research,we investigate the mechanical properties of aluminum/Nano-silica composites through experiments and ***/Nanosilica composite samples with different weight percentages of silica nanoparticles are prepared via powder *** this method,Nano-silica and aluminum powders are mixed and compressed in a mold,followed by sintering at high *** tensile testing of the nanocomposite samples shows that adding one percent of Nano-silica causes a considerable increase in mechanical properties of nanocomposite compared to pure aluminum.A computational micromechanical model,based on a representative volume element of aluminum/silica nanocomposite,is developed in a commercial finite element *** model employs an elastoplastic material model along with a ductile damage model for aluminum matrix and linear elastic model for nano-silica *** careful determination of model parameters from the experimental results of pure aluminum samples prepared by powder metallurgy,the proposed computational model has shown satisfactory agreement with *** validated computational model can be used to perform a parametric study to optimize the microstructure of nanocomposite for enhanced mechanical properties.

关键词： Aluminum/nano-silica composites Powder metallurgy Micromechanics

Strengthening of reinforced concrete beams using fiberreinforced cementitious matrix systems fabricated with custom-designed mortar and fabrics

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Frontiers of Structural and Civil Engineering 2023年第7期17卷 1100-1116页

作者： Ahmadreza RAMEZANI mohammad Reza ESFAHANI javad SABZI Faculty of Engineering Ferdowsi University of MashhadMashhadIran

The performance of a new fiber-reinforced cementitious matrix(FRCM)system developed using custom-designed mortar and fabrics is investigated in this *** behavior of this system is evaluated in terms of both the flexural and shear strengthening of reinforced concrete *** beams are designed to assess the effectiveness of the FRCM system in terms of flexural strengthening,and four specimens are designed to investigate their shear *** parameters investigated for flexural strengthening are the number of layers,span/depth ratio,and the strengthening *** previous studies,custom fabrics with similar axial stiffness are used in all strengthening methods in this *** the shear-strengthened specimens,the effects of the span/depth ratio and strengthening system type(fiberreinforced polymer(FRP)or FRCM)are *** proposed FRCM system exhibits desirable flexural and shear strengthening for enhancing the load capacity,provides sufficient bonding with the substrate,and prevents premature failure *** the similar axial stiffness of fabrics used in both FRCM and FRP systems and the higher load capacity of specimens strengthened by the former,cement-based mortar performs better than epoxy.

关键词： fiber-reinforced cementitious matrix flexural strengthening shear strengthening carbon fiber-reinforced polymer shear span

Estimation of photolysis half-lives of dyes in a continuous-flow system with the aid of quantitative structure-property relationship

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Frontiers of Environmental Science & Engineering 2014年第5期8卷 683-692页

作者： Davoud BEIKNEJAD mohammad javad CHAICHI Faculty of Chemistry University of Mazandaran Babolsar 47416-95447 Iron

In this paper the photolysis half-lives of the model dyes in water solutions and under ultraviolet （UV） radiation were determined by using a continuous-flow spectrophotometric method. A quantitative structure- property relationship （QSPR） study was carried out using 21 descriptors based on different chemometric tools including stepwise multiple linear regression （MLR） and partial least squares （PLS） for the prediction of the photolysis half-life （t1/2） of dyes. For the selection of test set compounds, a K-means clustering technique was used to classify the entire data set, so that all clusters were properly represented in both training and test sets. The QSPR results obtained with these models show that in MLR-derived model, photolysis half-lives of dyes depended strongly on energy of the highest occupied molecular orbital （EHoMO）, largest electron density of an atom in the molecule （ED^＋） and lipophilicity （logP）. While in the model derived from PLS, besides aforementioned EHOMO and ED^＋ descriptors, the molecular surface area （Sm）, molecular weight （M-W）, electronegativity （X）, energy of the second highest occupied molecular orbital （EHoMO- 1） and dipole moment （μ） had dominant effects on logt1/2 values of dyes. These were applicable for all classes of studied dyes （including monoazo, disazo, oxazine, sulfo- nephthaleins and derivatives of fluorescein）. The results were also assessed for their consistency with findings from other similar studies.

关键词： dye photolysis half-life quantitative structure-property relationship continuous-flow stepwise multiple linear regression partial least squares

Application of Statistical Methods to Biomarkers for Geochemical Evaluation and Genetic Type Determination of Gas Condensates in the Persian Gulf and Coastal Fars,Southern Iran

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Acta Geologica Sinica(English Edition) 2022年第4期96卷 1246-1256页

作者： mohammad javad SEIDY mohammad Hossein SABERI Petroleum Engineering Department Semnan UniversitySemnanIran The New Technology Campus Petroleum Engineering DepartmentSemnan UniversitySemnanIran

In a comprehensive geochemical study,the genetic relationships among 14 samples of gas condensates from the Persian Gulf were investigated for the purpose of evaluating the respective source rocks in terms of both age and sedimentary *** analysis was used for categorization and determination of a certitude range to determine the genetic type of the condensate families in the studied *** samples were collected from Late Permian-Triassic reservoirs(Dalan and Kangan formations)located in 6 gasfields(gas condensate)hosting some of Iran’s most important gas/gas condensate *** by gas chromatography-mass spectrometry(GC-MS),a total of 16 biomarker parameters(10 maturity-related parameters and 6 sedimentary environment-related parameters)were used to evaluate the samples in terms of thermal maturity(and hence their positions in the maturity chart),the sedimentary environment of the source rock and the *** of Hierarchical Clustering Analysis(HCA)and Principal Component Analysis(PCA)to the collected data led to the categorization of the samples into three main genetic groups,Ⅰ-Ⅲ.GroupsⅠandⅢwere found to be located in the east and the west of the Persian Gulf,respectively,while GroupⅡwas developed between the two other groups.

关键词： gas condensate satistical methods genetic linkage thermal maturation Persian Gulf Coastal Fars

Relative T-Injective Modules and Relative T-Flat Modules

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Chinese Annals of Mathematics,Series B 2011年第4期32卷 497-506页

作者： mohammad javad NIKMEHR Farzad SHAVEISI Department of Mathematics Faculty of Science K. N. Toosi University of Technology Tehran Iran Department of Mathematics Razi University Kermanshah Iran

Abstract Let T be a Wakamatsu tilting module. A module M is called （n, T）-copure injective （resp. （n, T）-copure flat） if εT^1（N, M） = 0 （resp. Г1^T（N, M） = 0） for any module N with T-injective dimension at most n （see Definition 2.2）. In this paper, it is shown that M is （n, T）-copure injective if and only if M is the kernel of an In（T）-precover f ： A → B with A ∈ ProdT. Also, some results on Prod T-syzygies are presented. For instance, it is shown that every nth Prod T-syzygy of every module, generated by T, is （n, T）-copure injective.

关键词： Wakamatsu tilting module (n T)-Copure injective module (n T)-Copure fiat module T-Projective dimension T-Injective dimension

Numerical demonstration of three-dimensional terahertz metamaterials based on the causality principle

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Chinese Physics B 2014年第2期23卷 518-523页

作者： Saeid Jamilan javad Nourinia mohammad Naghi Azarmanesh Department of Electrical Engineering Urmia University

A parameter retrieval algorithm based on the causality principle and Kramers-Kronig （KK） relations is employed to calculate the effective parameters of three-dimensional （3D） metamaterials. Using KK relations, the branch selecting problem, which is the challenge of effective parameter retrieval method, can be removed. To reveal the validity of the proposed algorithm, the constitutive refractive index of a homogeneous polymide cube is extracted. The result is in excellent agreement with the intrinsic refractive index of the polymide. Finally, the two terahertz metamaterials with 3D structures are designed and their effective parameters are then retrieved using the proposed algorithm. Numerical simulations are performed using the fuiI-wave electromagnetic solver, CST Microwave Studio.

关键词： metamaterial three-dimensional causality principle Kramers-Kronig relations

Peak displacement patterns for the performance-based seismic design of steel eccentrically braced frames

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Earthquake Engineering and Engineering Vibration 2019年第2期18卷 379-393页

作者： Ali Fakhraddini Hamed Saffari mohammad javad Fadaee Department of Civil Engineering Shahid Bahonar University of Kerman

Performance-based seismic design(PBSD) aims to assess structures at different damage states. Since damage can be directly associated to displacements, seismic design with consideration of displacement seems to be logical. In this study, simple formulae to estimate the peak floor displacement patterns of eccentrically braced frames(EBFs) at different performance levels subjected to earthquake ground motions are proposed. These formulae are applicable in a PBSD and especially in direct displacement-based design(DDBD). Parametric study is conducted on a group of 30 EBFs under a set of 15 far field and near field accelerograms which they scaled to different amplitudes to adapt various performance levels. The results of thousands of nonlinear dynamic analyses of EBFs have been post-processed by nonlinear regression analysis in order to recognize the major parameters that influence the peak displacement pattern of these frames. Results show that suggested displacement patterns have relatively good agreement with those acquired by an exact nonlinear dynamic analysis.

关键词： performance-based seismic design direct displacement-based design displacement pattern eccentrically braced frames steel building