检索结果-南通市图书馆

A new five-level inverter with reduced leakage current for photovoltaic system applications

在线全文

学校读者我要写书评

暂无评论

Protection and Control of Modern Power Systems 2022年第1期7卷 287-299页

作者： vahid Hosseinkhani Mohammad Sarvi Department of Electrical Engineering Imam Khomeini International UniversityQazvinIran

A general growth is being seen in the use of renewable energy resources,and photovoltaic cells are becoming increasingly popular for converting green renewable solar energy into *** the voltage produced by pho-tovoltaic cells is DC,an inverter is required to connect them to the grid with or without *** inverters are often used for their low cost and low power loss,and light ***,these inverters suffer from leakage current in the system,a challenge that needs to be *** this paper,a topology with two alternative connection models is presented to stabilize the common mode voltage and reduce the leakage *** output voltage characteristic of the proposed inverter is five-level,which reduces the harmonic distortion in the output cur-rent compared to the two-and three-level *** operation modes and output of the proposed topology are described and *** structures of the proposed inverter are simulated in MATLAB/Simulink and are compared with some well-known *** show that the proposed structure with both connection models effectively reduces leakage current and improves grid current THD.

关键词： Grid-connected inverters Multilevel inverters Common mode voltage Leakage current

Composition, environment, and economic value of the Permian to Cretaceous coated grains from Zagros and the Persian Gulf

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

International Journal of Sediment Research 2023年第3期38卷 316-334页

作者： Mehrangiz Naderi-Khujin vahid Tavakoli Pars Oil and Gas Company School of Geology College of Science University of Tehran

Ooid grainstone/packstone carbonate facies of the Dalan, Kangan, and Arab formations are the main hydrocarbon reservoirs in the Persian Gulf. Based on detailed petrographic and petrophysical analyses,sedimentological and mineralogical features of the Permian to Late Cretaceous carbonate and iron-rich coated grains from Zagros and the Persian Gulf were investigated. Frequent ooids in these formations indicate a high-energy environment and a wave-dominated shallow carbonate platform. Because of wide-spread Permian-Triassic epiric seas and long-lasting periods of arid and hot climate, Permian-Triassic carbonate ooids have more vertical and lateral distribution in comparison with Late Jurassic carbonate ooids. Dolomite, calcite, and anhydrite are the major minerals of carbonate ooid grains. Early Cretaceous iron-rich ooids have been deposited above a major Late Aptian disconformity during the highstand systems tract. Ooid ironstone bulk sample X-ray diffraction(XRD) analysis shows that goethite,siderite, fluorapatite, calcite, quartz, and pyrite are the major phases of ooid ironstone deposits. This layer of iron bearing ooids could have economic importance in its outcrops in the Zagros area. Late Cretaceous iron-rich coated grains(pisoid-oncoids) were deposited above the Sarvak exposure surface during the Late Cretaceous, long-lasting sea-level fall on the Arabian Plate. Boehmite, diaspore, hematite, and goethite are the main minerals of these kind of iron-rich deposits. Late Cretaceous karst-type bauxite deposits have also been reported from different sections of the Zagros area and have economic value for mining.

关键词： Coated grains Depositional conditions Permian Cretaceous Bauxite

Daily and Monthly Suspended Sediment Load Predictions Using Wavelet Based Artificial Intelligence Approaches

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Journal of Mountain Science 2015年第1期12卷 85-100页

作者： vahid NOURANI Gholamreza ANDALIB Department of Water Resources Engineering Faculty of Civil Engineering University of Tabriz

In the current study, the efficiency of Wavelet-based Least Square Support Vector Machine （WLSSVM） model was examined for prediction of daily and monthly Suspended Sediment Load （SSL） of the Mississippi River. For this purpose, in the first step, SSL was predicted via ad hoc LSSVM and Artificial Neural Network （ANN） models; then, streamflow and SSL data were decomposed into sub- signals via wavelet, and these decomposed sub-time series were imposed to LSSVM and ANN to simulate discharge-SSL relationship. Finally, the ability of WLSSVM was compared with other models in multi- step-ahead SSL predictions. The results showed that in daily SSL prediction, LSSVM has better outcomes with Determination Coefficient （DC）=o.92 than ad hoc ANN with DC=o.88. However unlike daily SSL, in monthly modeling, ANN has a bit accurate upshot. WLSSVM and wavelet-based ANN （WANN） models showed same consequences in daily and different in monthly SSL predictions, and adding wavelet led to more accuracy of LSSVM and ANN. Furthermore, conjunction of wavelet to LSSVM and ANN evaluated via multi-step-ahead SSL predictions and, e.g., DCLssVM=0.4 was increased to the DCwLsSVM=0.71 in 7- day ahead SSL prediction. In addition, WLSSVM outperformed WANN by increment of time horizon prediction.

关键词： Suspended Sediment Load Least SquareSupport Vector Machine (LSSVM) Wavelet ArtificialNeural Network (ANN) Mississippi River

Distributed output feedback stationary consensus of multi-vehicle systems in unknown environments

在线全文

学校读者我要写书评

暂无评论

Control Theory and Technology 2018年第2期16卷 93-109页

作者： vahid REZAEI Margareta STEFANOVIC Department of Electrical and Computer Engineering University of Denver Denver CO 80208 U.S.A.

In the traditional distributed consensus of multi-vehicle systems, vehicles agree on velocity and position using limited information exchange in their local neighborhoods. Recently, distributed leaderless stationary consensus has been proposed in which vehicles agree on a position and come to a stop. The proposed stationary consensus schemes are based on all vehicles＇ access to their own absolute velocity measurements, and they do not guarantee this collective behavior in the presence of disturbances that persistently excite vehicles＇ dynamics. On the other hand, traditional distributed disturbance rejection leaderless consensus algorithms may result in an uncontrolled increase in the speed of multi-vehicle system. In this paper, we propose a dynamic relative-output feedback leaderless stationary algorithm in which only a few vehicles have access to their absolute measurements. We systematically design the distributed algorithm by transforming this problem into a static feedback robust control design challenge for the low-order modified model of vehicles with fictitious modeling uncertainties. We further propose dynamic leader-follower stationary consensus algorithms for multi-vehicle systems with a static leader, and find closed-form solutions for the consensus gains based on design matrices and communication graph topology. Finally, we verify the feasibility of these ideas through simulation studies.

关键词： Multi-vehicle system distributed control stationary consensus disturbance accommodation

A Novel Investigation on Using Strain in Barriers of 1.3 μm AlGaInAs-InP Uncooled Multiple Quantum Well Lasers

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

Communications in Theoretical Physics 2010年第9期54卷 529-535页

作者： vahid BahramiYekta Hassan Kaatuzian Photonics Research Laboratory(P.R.L) Department of Electrical EngineeringAmirkabir University of Technology

In this study we investigate strain effect in barriers of 1.3 μm AlCalnAs-InP uncooled multiple quantum well lasers. Single effective mass and Kohn-Luttinger Harniltonian equations have been solved to obtain quantum states and envelope wave functions in the structure. In the case of unstrained barriers, our simulations results have good agreement with a real device fabricated and presented in one of the references. Our main work is proposal of 0.2% compressive strain in the structure Barriers that causes significant reduction in Leakage current density and Auger current density characteristics in 85 ℃. 20% improvement in mode gain-current density characteristic is also obtained in 85 ℃.

关键词： multiple quantum well laser semiconductor laser strain in barrier uncooled

On braced trapezoidal corrugated steel shear panels: An experimental and numerical study

在线全文

学校读者我要写书评

暂无评论

Frontiers of Structural and Civil Engineering 2023年第3期17卷 396-410页

作者： vahid AMIRI Arash AKBARI HAMED Karim ABEDI Faculty of Civil Engineering Sahand University of TechnologyTabriz ***Iran

In this study,a new system consisting of a combination of braces and steel infill panels called the braced corrugated steel shear panel(BCSSP)is *** obtain the hysteretic behavior of the proposed system,the quasistatic cyclic performances of two experimental specimens were first *** finite element modeling method was then verified based on the obtained experimental *** numerical evaluations were carried out to investigate the effects of different parameters on the ***,a relationship was established to estimate the buckling shear strength of the system without considering residual *** results obtained from the parametric study indicate that the corrugated steel shear panel(CSSP)with the specifications of a=30 mm,t=2 mm,andθ=90°had the highest energy dissipation capacity and ultimate strength while the CSSP with the specifications of a=30 mm,t=2 mm,andθ=30°had the highest initial *** can thus be concluded that the latter CSSP has the best structural performance and that increasing the number of corrugations,corrugation angle,and plate thickness and decreasing the sub-panel width generally enhance the performance of CSSPs in terms of the stability of their hysteretic behaviors.

关键词： trapezoidal corrugated plate steel shear panel braced steel shear panel experimental study buckling resistance

Three-Dimensional Simulation of Plasma Deformation During Contact Opening in a Circuit Breaker,Including the Analysis of Kink Instability and Sausage Instability

在线全文

学校读者我要写书评

暂无评论

Plasma Science and Technology 2012年第11期14卷 996-1001页

作者： vahid ABBASI Ahmad GHOLAMI Kaveh NIAYESH High Voltage and Magnetic Material Research Center Electrical Engineering DepartmentIran University of Science and Technology School of Electrical and Computer Engineering University of Tehran

A three-dimensional （3-D） transient model has been developed to investigate plasma deformation driven by a magnetic field and its influence on arc stability in a circuit breaker. The 3-D distribution of electric current density is obtained from a current continuity equation along with the generalized Ohm＇s law; while the magnetic field induced by the current flowing through the arc column is calculated by the magnetic vector potential equation. When gas interacts with an arc column, fundamental factors, such as Ampere＇s law, Ohm＇s law, the turbulence model, transport equations of mass, momentum and energy of plasma flow, have to be coupled for aria- lyzing the phenomenon. The coupled interactions between arc and plasma flow are described in the fl＇amework of time-dependent magnetohydrodynamic （MHD） equations in conjunction with a K-~ turbulence model. Simulations have been focused on sausage and kink instabilities in plasma （these phenomena are related tO pinch effects and electromagnetic fields）. The 3-D sjm- ulation reveals the relation between plasma deformation and instability phenomena, which affect arc stability during circuit breaker operation. Plasma deformation is the consequence of coupled interactions between the electromagnetic force and plasma flow described in simulations.

关键词： magnetohydrodynamic (MHD) plasma deformation electromagnetic force kink instability sausage instability

Effect of CNTs and nano ZnO on physical and mechanical properties of polyaniline composites applicable in energy devices

在线全文

学校读者我要写书评

暂无评论

Progress in Natural Science:Materials International 2016年第6期26卷 517-522页

作者： vahid Saadattalab Alireza Shakeri Hamid Gholami School of Chemistry University College of Science University of Tehran

Polyaniline was synthesized chemically in an acidic medium in the presence of Ammonium Peroxydisulphate(APS) as an oxidizing agent. PANI(Polyaniline) nanocomposites were prepared in the presence of various amount of carbon nanotube and zinc oxide(from 1 to 5 wt%) by solution casting method. The free-standing film of polyaniline and its nanocomposites were obtained by vaporization of solvent content. The composition,morphology and structure of the polymer and the nanocomposites were characterized by Fourier transform infrared spectroscopy FT-IR spectra, scanning electron microscopy(SEM) image and XRD pattern. In addition,thermal stability was studied by TGA analysis, electrical conductivity was measured by four-point probe technique and mechanical properties were studied by tensile strength test. The characteristic FTIR peaks of PANI were found to shift to lower wave number in nanocomposites due to the formation of H-bonding. XRD results revealed that the crystallinity of PANI was more noticeable after addition of nano-ZnO, while the intensity of the peaks increased by the addition of ZnO nanoparticles. Furthermore, TGA results showed that the decomposition of the nanocomposite was less than that of pure polyaniline which confirms the successful fabrication of products. Young's modulus and strength at break point were increased in the case of the nanocomposite, in addition, the electrical conductivity of the PANI/ZnO nanocomposite film was found to be smaller than that of the PANI film while CNTs increase the conductivity of polyaniline.

关键词： Conductive polymer Polyaniline Nanocomposite Zinc oxide CNT

Towards automated software model checking using graph transformation systems and Bogor

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2009年第8期10卷 1093-1105页

作者： vahid RAFE Adel T.RAHMANI Department of Computer Engineering Iran University of Science and Technology

Graph transformation systems have become a general formal modeling language to describe many models in software development *** modeling of dynamic systems and model-to-model transformations are only a few examples in which graphs have been used to software *** even the perfect graph transformation system must be equipped with automated analysis capabilities to let users understand whether such a formal specification fulfills their *** this paper,we present a new solution to verify graph transformation systems using the Bogor model *** attributed graph grammars(AGG)-like graph transformation systems are translated to Bandera intermediate representation(BIR),the input language of Bogor,and Bogor verifies the model against some interesting properties defined by combining linear temporal logic(LTL) and special-purpose graph *** results are encouraging,showing that in most cases our solution improves existing approaches in terms of both performance and expressiveness.

关键词： Graph transformation Verification Bogor Attributed graph grammars (AGG) Software model checking