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Journal of Modern Power Systems and Clean Energy 2019年第1期7卷 78-87页

作者： bahram SHAKERIGHADI Farrokh AMINIFAR Saeed AFSHARNIA School of Electrical and Computer Engineering College of Engineering University of Tehran

This paper reveals that the existing techniques have some deficiencies in the proper estimation of voltage stability margin(VSM) when applied to a power system with different load change *** problem gets worse when credible contingencies *** paper proposes a real-time wide-area approach to estimate VSM of power systems with different possible load change scenarios under normal and contingency operating *** new method is based on an artificial neural network(ANN) whose inputs are bus voltage phasors captured by phasor measurement units(PMUs) and rates of change of active power loads.A new input feature is also accommodated to overcome the inability of trained ANN in prediction of VSM under N-1 and N-2 *** a new algorithm, the number of contingencies is reduced for the effective training of *** of the proposed technique is assured through adding a random noise to input *** deal with systems with a limited number of PMUs, a search algorithm is accomplished to identify the optimal placement of *** proposed method is examined on the IEEE 6-bus and the New England 39-bus test *** show that the VSM could be predicted with less than 1% error.

关键词： Artificial neural network(ANN) Phasor measurement unit(PMU) Voltage stability margin(VSM)

ANALYTICAL ANALYSIS OF MEMS CAPACITIVE PRESSURE SENSOR WITH CIRCULAR DIAPHRAGM UNDER DYNAMIC LOAD USING DIFFERENTIAL TRANSFORMATION METHOD(DTM)

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Acta Mechanica Solida Sinica 2015年第4期28卷 400-408页

作者： Marzieh Molla-Alipour bahram Azizollah Ganji Department of Engineering South Tehran Branch Islamic Azad University Department of Electrical Engineering Babol University of Technology

In this paper, first a circular diaphragm is modeled using the classical plate theory. An analytical solution based on differential transformation method （DTM） and Runge-Kutta method is employed for solving the governing differential equation for the first time. Then the influences of various parameters on central deflection of the diaphragm, stress distribution and capacitance of pressure sensor with a time-dependent pressure are examined. Several case studies are compared with simulations to confirm the proposed method. The analytical results compared with ABAQUS simulation show excellent agreement with the simulation results. This method is very promising for time saving in calculating micro-device characteristics.

关键词： MEMS capacitive pressure sensor circular diaphragm deflection analytical model,theoretical analysis

Influence of random heterogeneity of shear wave velocity on sliding mass response and seismic deformations of earth slopes

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Earthquake Engineering and Engineering Vibration 2020年第2期19卷 269-287页

作者： Pourya Kazemi Esfeh bahram Nadi Nicholas Fantuzzi Department of Civil ChemicalEnvironmentaland Materials EngineeringUniversity of BolognaItaly Department of Civil Engineering Azad University of NajafabadIran

Soil shear wave velocity has been recognized as a governing parameter in the assessment of the seismic response of *** spatial variability of soil shear wave velocity can influence the seismic response of sliding mass and seismic ***,most analyses of sliding mass response have been carried out by deterministic *** paper stochastically investigates the effect of random heterogeneity of shear wave velocity of soil on the dynamic response of sliding mass using the correlation matrix decomposition method and Monte Carlo simulation(MCS).The software FLAC 7.0 along with a Matlab code has been utilized for this *** influence of statistical parameters on the seismic response of sliding mass and seismic displacements in earth slopes with different inclinations and stiffnesses subject to various earthquake shakings was *** results indicated that,in general,the random heterogeneity of soil shear modulus can have a notable impact on the sliding mass response and that neglecting this phenomenon could lead to underestimation of sliding deformations.

关键词： random heterogeneity random fields Monte Carlo simulation sliding mass response seismic deformations

Estimation of froth flotation recovery and collision probability based on operational parameters using an artificial neural network

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International Journal of Minerals,Metallurgy and Materials 2010年第5期17卷 526-534页

作者： Saeed Chehreh Chelgani Behzad Shahbazi bahram Rezai Surface Science Western Research Park University of Western Ontario Mining Engineering Department Science and Research Branch Islamic Azad University Amirkabir University of Technology

An artificial neural network and regression procedures were used to predict the recovery and collision probability of quartz flotation concentrate in different operational conditions. Flotation parameters, such as dimensionless numbers （Froude, Reynolds, and Weber）, particle size, air flow rate, bubble diameter, and bubble rise velocity, were used as inputs to both methods. The linear regression method shows that the relationships between flotation parameters and the recovery and collision probability of flotation can achieve correlation coefficients （R2） of 0.54 and 0.87, respectively. A feed-forward artificial neural network with 3-3-3-2 arrangement is able to simultaneously estimate the recovery and collision probability as the outputs. In testing stages, the quite satisfactory correlation coefficient of 0.98 was achieved for both outputs. It shows that the proposed neural network models can be used to determine the most advantageous operational conditions for the expected recovery and collision probability in the froth flotation process.

关键词： flotation recovery collision probability neural networks

Hydrological alteration and biodiversity change along the river network caused by anthropogenic activities and climate variability

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Ecological Processes 2022年第1期11卷 189-205页

作者： Farshid Zolfagharpour bahram Saghafian Majid Delavar Department of Civil Engineering Science and Research BranchIslamic Azad UniversityTehranIran Department of Water Resources Engineering Tarbiat Modares UniversityTehranIran

Background:Population growth and intensified human activities in conjunction with climate variability continue to affect the hydrologic cycle,aquatic and terrestrial flora and *** this regard,understanding interactions among ecosystem functions,impacts of anthropogenic interventions and those of climate variability is vital for projecting future ecosystem responses to human activities and climate *** objectives of this study are to determine the ecological flow state via eco-flow index based on discharge hydrograph,to model the ecological diversity through the Shannon diversity index,and to assess the degree of hydrologic alteration using indicators of hydrologic alteration and range of variability approach in six hydrometric stations along the Zayandeh-Rud River in central *** river drains into Gavkhuni ***,the streamflow-induced potential changes for Capoeta damascina(a cyprinid fish species of the genus Capoeta),Petroleuciscus esfahani(a small cyprinid fish)and Aphanius isfahanensis(a Cyprinodontid fish)are *** outcome is expected to assist managers with understanding the effects of anthropogenic activities and climate variability on Gavkhuni aquatic ecosystems so that management options that enhance species resilience and adaptability are ***:Human activities,a primary factor influencing the natural flow regime,caused a significant increase in the minimum flow,July to March streamflow,low pulse number,and the number of reversals in most studied *** the contrary,some other hydrologic indices declined in *** impoundment,the most prominent factor among human interventions,resulted in an overall alteration degree of 74.8%in *** variability impacted the natural flow regime in the range of low degree hydrologic alteration(27.3%).In addition,the biodiversity of the study basin,as modeled by the Shannon diversity index,had strong relevance to the annual eco-surplus and was more sensitive

关键词： Eco-flow Shannon diversity index Human activity Indicators of hydrologic alteration Natural flow regime Range of variability Zayandeh-Rud River

Microstructure and Impression Creep Properties of Ca-Containing AS31 Magnesium Alloy

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Acta Metallurgica Sinica(English Letters) 2016年第12期29卷 1089-1097页

作者： Mohammad Badri Seyyed Mehdi Miresmaeili bahram Nami Shahid Rajaee Teacher Training University Lavizan TehranIran

The effect of Ca addition on the microstructure and impression creep properties of AS31 magnesium alloy was investigated in the current study. The results showed that the microstructure of AS31 alloy is composed of α（Mg） phase, massive Mg17Al12 and some Chinese script Mg2Si compounds. Addition of 2 wt% Ca to AS31 alloy resulted in complete elimination of MglTAl12 phase and formation of Al2Ca compound. Ca improved the alloy＇s creep properties especially at higher temperature. Improvement in the creep properties was attributed to the elimination of soft Mg17Al12 and formation of thermally stable Al2Ca compound. According to the obtained stress exponent and creep activation energy, pipe diffusion climb-controlled creep was estimated as the dominant creep mechanism and Ca had no influence on the dominant mechanism.

关键词： Magnesium-aluminum-silicon alloy Calcium Microstructure Creep Mechanism

Skill Assessment of Copernicus Climate Change Service Seasonal Ensemble Precipitation Forecasts over Iran

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Advances in Atmospheric Sciences 2021年第3期38卷 504-521页

作者： Masoud NOBAKHT bahram SAGHAFIAN Saleh AMINYAVARI Department of Civil Engineering Science and Research BranchIslamic Azad UniversityTehran ***Iran Department of Civil Engineering Chalous BranchIslamic Azad UniversityChalous 46615/397Iran

Medium to long-term precipitation forecasting plays a pivotal role in water resource management and development of warning ***,the Copernicus Climate Change Service(C3S)database has been releasing monthly forecasts for lead times of up to three months for public *** study evaluated the ensemble forecasts of three C3S models over the period 1993-2017 in Iran’s eight classified precipitation clusters for one-to three-month lead *** and non-probabilistic criteria were used for ***,the skill of selected models was analyzed in dry and wet periods in different precipitation *** results indicated that the models performed best in western precipitation clusters,while in the northern humid cluster the models had negative skill *** models were better at forecasting upper-tercile events in dry seasons and lower-tercile events in wet ***,with increasing lead time,the forecast skill of the models *** terms of forecasting in dry and wet years,the forecasts of the models were generally close to observations,albeit they underestimated several severe dry periods and overestimated a few wet ***,the multi-model forecasts generated via multivariate regression of the forecasts of the three models yielded better results compared with those of individual *** general,the ECMWF and UKMO models were found to be appropriate for one-month-ahead precipitation forecasting in most clusters of *** the clusters considered in Iran and for the long-range system versions considered,the Météo France model had lower skill than the other models.

关键词： ensemble forecasts Copernicus Climate Change Service long-term forecasting model evaluation Iran

Seismic reliability assessment of a steel moment-resisting frame with two different ductility levels using a cloud analysis approach

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Earthquake Engineering and Engineering Vibration 2019年第1期18卷 171-185页

作者： Seyed bahram Beheshti Aval Amir Masoumi Verki Department of Civil Engineering K.N.Toosi University of Technology

A cloud method for generating percentile engineering demand parameter versus intensity measure(EDP-IM) curves of a structure subjected to a set of synthetic ground motions is presented. To this end, an ensemble of synthetic ground motions based on available real ones is generated. This is done by using attenuation relationships, duration and suitable Gutenberg-Richter relations attributed to the considered seismic hazard at a given site by estimating a suitable distribution of magnitude and site to source distance. The study aims to clarify the significance of the duration and frequency content on the seismic performance of structures, which were not considered in developing percentile incremental dynamic analysis(IDA) curves. The collapse probabilities of two steel moment-resisting frames with different ductility levels generated by IDA and the proposed cloud method are compared at different intensity levels. When compared with conventional IDA, the suggested cloud analysis(SCA) methodology with the same run number of dynamic analyses was able to develop response hazard curves that were more consistent with site-specific seismic hazards. Eliminating the need to find many real records by generating synthetic records consistent with site-specific seismic hazards from a few available recorded ground motions is another advantage of using this scheme over the IDA method..

关键词： cloud analysis (CA) multiple-strip analysis (MSA) incremental dynamic analysis (IDA) synthetic ground motions

Dynamic simulation of pilot thickener operation using phenomenological model with results validation for continuous and discontinuous tests

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Journal of Central South University 2017年第5期24卷 1207-1216页

作者： Rahimi Mehdi Unesi Majid Rezai bahram Abdollahzadeh Ali Department of Mining and Metallurgical Engineering Amirkabir University of Technology Young Researchers and Elites Club Science and Research Branch Islamic Azad University Department of Mining Engineering University of Kashan

The phenomenological theory of sedimentation-thickening processes predicts the settling behavior of a flocculated suspension in dependence of two functions, the batch flux density function and the effective solid stress. These functions were determined using batch settling tests. The governing equations for sedimentation were then solved numerically for these functions and the predictions were compared to the experimental results from pilot scale thickener tests. Firstly, the continuous tests were performed in the plexiglass pilot thickener at different feed flow rates and discharge rates and the solid volume fraction of discharge, the bed height and the time were recorded for each condition. These tests were also simulated and it was observed that there is a good agreement between the results of continuous tests and the results of dynamic simulation. Secondly, the discontinuous tests were performed in the plexiglass pilot thickener at different feed flow rates with a discharge rate of zero. The bed formation rate was determined for each condition. These tests were also simulated and it was observed that there is a good agreement between the results of discontinuous tests and the results of simulation.

关键词： dynamic simulation dewatering thickener behavior pilot thickener validation

Fe^(3+)-Doped Anatase TiO_2 Study Prepared by New Sol-Gel Precursors

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Chinese Physics Letters 2018年第2期35卷 102-106页

作者： bahram Khoshnevisan Mohammad Bagher Marami Majid Farahmandjou Department of Physics Faculty of ScienceUniversity of Kashan Departments of Physics Varamin Pishva BranchIslamis Azad University

FeTi_1-O_2（= 0.00,0.05,0.10） nanocomposites are synthesized using a sol-gel method involving an ethanol solvent in the presence of ethylene glycol as the stabilizer,and acetic acid as the chemical *** structural and optical analyses are studied to reveal their physicochemical *** the x-ray diffractometer（XRD）analysis,the size of the nanoparticles（NPs） is found to be 18-32 nm,where the size of the NPs decreases down to 18 nm when Fe impurity of up to 10% is added,whereas their structure remains *** results also indicate that the structure of the NPs is tetragonal in the anatase *** Fourier transform infrared spectroscopy analysis suggests the presence of a vibration bond（Ti-O） in the *** photoluminescence analysis indicates that the diffusion of Fe^（3＋） ions into the TiO_2 matrix results in a decreasing electron-hole recombination,and increases the photocatalytic properties,where the best efficiency appears at an impurity of10%.The UV-diffuse reflection spectroscopy analysis indicates that with the elevation of iron impurity,the band gap value decreases from 3.47 eV for the pure sample to 2.95 eV for the 10 mol% Fe-doped TiO_2 NPs.

关键词： Fe Doped Anatase TiO2 Study Prepared by New Sol-Gel Precursors TiO