检索结果-南通市图书馆

Diversity of woody plant species and their relationship to physiographic factors in central Zagros forests (Case study： Perc forest, Khorramabad, Iran)

在线全文

学校读者我要写书评

暂无评论

Journal of Forestry Research 2016年第5期27卷 1137-1141页

作者： Ramin Hosseinzadeh javad Soosani vahid Aiijani Sheyda Khosravi Hamdieh Karimikia Department of Forestry Agriculture Faculty Lorestan University Lorestan Iran Natural Resources Faculty Tehran University Tehran Iran Kurdistan University Sanandaj Iran

Topography is the most factor that has the greatest impact of all factor that affect the distribution. To study the diversity of trees and shrub species in the Perc forest situated in Khorramabad, Lorestan, 140 circular plots of 1200 m2 in a grid of 300 m × 250 m were surveyed, using a systematic random sampling method. In each plot, the Margalef richness index, Shannon-Wiener diversity index, Hill＇s N1 and Simpson indices and the evenness index of Simpson and Smith-Wilson were calculated and ordered on the basis of different classes of elevation, exposition and slope. The results indicated that slope did not have any significant effect on the indices. Exposition and elevation classes significant impacted the richness and diversity indices, but did not influence evenness. In general, the highest plant diversity was observed for slopes less than 15 %, northern aspects, without geographical direction, and elevations of 2100-2200 m. This information can be very useful in achieving the goals for sustainable management of forests. In addition to greater protection for regions with high diversity and reforestation （compatible species） in degraded area, we can help increase diversity in forests.

关键词： Plant diversity Richness Evenness Physiography Zagros

Finite element analysis of controlled low strength materials

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5期13卷 1243-1250页

作者： vahid ALIZADEH Gildart Haase School of Computer Sciences & Engineering Fairleigh Dickinson UniversityTeaneckNJ 07666USA

Controlled low strength materials (CLSM) are flowable and self-compacting construction materials that have been used in a wide variety of applications. This paper describes the numerical modeling of CLSM fills with finite element method under compression loading and the bond performance of CLSM and steel rebar under pullout loading. The study was conducted using a plastic-damage model which captures the material behavior using both classical theory of elasto-plasticity and continuum damage mechanics. The capability of the finite element approach for the analysis of CLSM fills was assessed by a comparison with the experimental results from a laboratory compression test on CLSM cylinders and pullout tests. The analysis show's that the behavior of a CLSM fill w'hile subject to a failure compression load or pullout tension load can be simulated in a reasonably accurate manner.

关键词： CLSM finite element method compressive strength pullout numerical modeling plastic damage model

A Nonlinear Coordinated Approach to Enhance the Transient Stability of Wind Energy-Based Power Systems

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

IEEE/CAA Journal of Automatica Sinica 2020年第4期7卷 1087-1097页

作者： Mohammad javad Morshed the Department of Electrical and Computer Engineering University of Louisiana at LafayetteLafayetteLA 70504 USA

This paper proposes a novel framework that enables the simultaneous coordination of the controllers of doubly fed induction generators(DFIGs) and synchronous generators(SGs).The proposed coordination approach is based on the zero dynamics method aims at enhancing the transient stability of multi-machine power systems under a wide range of operating conditions. The proposed approach was implemented to the IEEE39-bus power systems. Transient stability margin measured in terms of critical clearing time along with eigenvalue analysis and time domain simulations were considered in the performance assessment. The obtained results were also compared to those achieved using a conventional power system stabilizer/power oscillation(PSS/POD) technique and the interconnection and damping assignment passivity-based controller(IDA-PBC). The performance analysis confirmed the ability of the proposed approach to enhance damping and improve system’s transient stability margin under a wide range of operating conditions.

关键词： Doubly fed induction generator(DFIG) excitation controller multi-machine power system synchronous generator(SG) transient stability zero dynamics

Scale adaptive simulation of vortex structures past a square cylinder

在线全文

学校读者我要写书评

暂无评论

Journal of Hydrodynamics 2018年第4期30卷 657-671页

作者： javad Aminian Faculty of Mechanical and Energy Engineering Shahid Beheshti University

The scale adaptive simulation（SAS） turbulence model is evaluated on a turbulent flow past a square cylinder using the open-source CFD package OpenF OAM 2.3.0. Two and three-dimensional simulations are performed to determine global quantities like drag and lift coefficients and Strouhal number in addition to mean and fluctuating velocity profiles in the recirculation and wake regions. SAS model is evaluated against the Shear Stress Transport k-ω（SST） model and also compared with previously reported results based on DES, LES and DNS turbulence approaches. Results show that global quantities along with mean velocity profiles are well-captured by 2-D SAS model. The 3-D SAS model also succeeded in providing comparable results with recently published DES study on Reynolds shear stress and velocity fluctuation components using about 12 times lower computational cost. It is shown that large values of the SAS model constant result in too dissipative behavior, so that proper calibration of the SAS model constant for different turbulent flows is vital.

关键词： Scale adaptive simulation (SAS) turbulence model bluff body mean and fluctuating properties anisotropic turbulence computational costs

Iterative Algorithm with Mixed Errors for Solving a New System of Generalized Nonlinear Variational-Like Inclusions and Fixed Point Problems in Banach Spaces

在线全文

学校读者我要写书评

暂无评论

Chinese Annals of Mathematics,Series B 2013年第4期34卷 593-622页

作者： javad BALOOEE Department of Mathematics Sari Branch Islamic Azad University

A new system of generalized nonlinear variational-like inclusions involving A- maximal m-relaxed η-accretive （so-called, （A, η）-accretive in [36]） mappings in q-uniformly smooth Banach spaces is introduced, and then, by using the resolvent operator technique associated with A-maximal m-relaxed ~/-accretive mappings due to Lan et al., the exis- tence and uniqueness of a solution to the aforementioned system is established. Applying two nearly uniformly Lipschitzian mappings 81 and 82 and using the resolvent operator technique associated with A-maximal m-relaxed ~？-accretive mappings, we shall construct a new perturbed N-step iterative algorithm with mixed errors for finding an element of the set of the fixed points of the nearly uniformly Lipschitzian mapping Q = （S1, S2） which is the unique solution of the aforesaid system. We also prove the convergence and stability of the iterative sequence generated by the suggested perturbed iterative algorithm under some suitable conditions, The results presented in this paper extend and improve some known results in the literature.

关键词： A-Maximal m-relaxed η-accretive mapping System of generalized non-linear variational-like inclusion Resolvent operator technique Conver-gence and stability Variational convergence

Dimeric quinacridone cyclophanes: Synthesis,structures,and photophysical properties

在线全文

学校读者我要写书评

暂无评论

Science China Chemistry 2011年第2期54卷 314-319页

作者： javad Iqbal State Key Laboratory of Supramolecular Structure and Materials College of Chemistry Jilin University

Two novel quinacridone (QA) cyclophanes with intrinsic intramolecular dye-dye interactions have been designed and synthesized.X-ray crystal structures as well as detailed photophysical properties have been well *** two dyes have a major advantage that efficient fluorescence quenching can be observed even in their dilute solutions.A comparison of photophysical properties between the dimeric QA cyclophane and its reference monomeric counterpart indicates that the dimerization is predominant for the fluorescence quenching of QA dyes in *** study provided some model QA derivatives with dimeric structures for understanding the fluorescence quenching of QA dyes in solutions.

关键词： quinacridone cyclophanes dye-dye interactions photophysics fluorescence quenching

Highly efficient [C8mim][Cl] ionic liquid accompanied with magnetite nanoparticles and different salts for interfacial tension reduction

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Chemical Engineering 2020年第1期28卷 46-53页

作者： Sajjad Hashemi javad Saien Department of Applied Chemistry Bu-Ali Sina UniversityHamedanIran

The 1-octyl-3-methylimidazolium chloride, [C8 mim][Cl] ionic liquid(IL) was used as a novel surfactant in n-heptane/water system. The interfacial tensions(IFT) were measured and corresponding variations were investigated. An IFT reduction of 80.8% was appropriate under the IL CMC of about 0.1 mol·L^-1 and stronger effects were achieved when magnetite nanoparticles and salts were present profoundly under alkaline p *** equilibrium IFT data were accurately simulated with the Frumkin adsorption model. Hereafter, the saturated surface concentration, equilibrium constant and interaction parameter were obtained and their variations were demonstrated. Further, emulsion stability and contact angle of oil/water interface over quartz surface were studied. The oil/water emulsion stability was hardly changed with nanoparticles;however, the stability of oil/water + IL emulsions was significantly improved. It was also revealed that the presence of sodium and calcium chloride electrolytes fortifies the IL impact, whereas sodium sulfate weakens. From dynamic IFT data and fitting with kinetic models, it was found that the IL migration toward interface follows the mixed diffusion–kinetic control model. Consequently, the IL diffusion coefficient and the appropriate activation energy were determined.

关键词： Imidazolium ionic liquids Interfacial tension Magnetite nanoparticle Emulsion stability Frumkin adsorption model Adsorption kinetic model

Hybrid algorithms for handling the numerical noise in topology optimization

在线全文

学校读者我要写书评

暂无评论

Acta Mechanica Sinica 2020年第2期36卷 536-554页

作者： Pooya Rostami javad Marzbanrad Vehicle Dynamical Systems Research Laboratory School of Automotive EngineeringIran University of Science and TechnologyNarmakTehranIran

This paper presents new hybrid methods for the identification of optimal topologies by combining the teaching-learning based optimization(TLBO)and the method of moving asymptotes(MMA).The topology optimization problem is parameterizing with a low dimensional explicit method called moving morphable components(MMC),to make the use of evolutionary algorithms more ***-based solvers have good performance in solving large-scale topology optimization ***,in unconventional cases same as crashworthiness design in which there is numerical noise in the gradient information,the uses of these algorithms are *** standard evolutionary algorithms can solve such problems since they don’t need gradient ***,they have a high computational *** paper is based upon the idea of combining metaheuristics with mathematical programming to handle the probable noises and have faster convergence *** to the ease of computations,the compliance minimization problem is considered as the case study and the artificial noise is added in gradient information.

关键词： Topology optimization Teaching-learning based optimization Method of moving asymptotes Moving morphable components

Experimental and modeling study of the kinetics of methane hydrate formation and dissociation

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

Chinese Journal of Chemical Engineering 2021年第1期34卷 365-374页

作者： Vafa Feyzi vahid Mohebbi Ahvaz Petroleum Faculty Petroleum University of Technology(PUT)AhvazIran

In this work,several experiments were conducted at isobaric and isothermal condition in a CSTR reactor to study the kinetics of methane hydrate formation and *** were performed at five temperatures and three pressure levels(corresponding to equilibrium pressure).Methane hydrate formation and dissociation rates were modeled using mass transfer limited kinetic models and mass transfer coefficients for both formation and dissociation were *** of results,shows that mass transfer coefficients for methane hydrate dissociation are one order greater than formation *** transfer coefficients were correlated by polynomials as relations of pressure and *** results and the method can be applied for prediction of methane production from naturally occurring methane hydrate deposits.

关键词： Methane hydrate Kinetics Formation Dissociation Mass transfer