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Alkali-metal-induced topological nodal line semimetal in layered XN2 （X=Cr, Mo, W）

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Frontiers of physics 2018年第5期13卷 87-95页

作者： ali ebrahimian Mehrdad Dadsetani Department of Physics Lorestan University Khoramabad Iran

Based on first principles calculations and the K.p effective model, we propose that alkali metal depo- sition on the surface of hexagonal XN2 （X- Cr, Mo, W） nanosheets induces topologically nontrivial phases in these systems. When spin orbit coupling （SOC） is disregarded, the electron-like conduction band from N-pz orbitals can be considered to cross the hole-like valence band from X-d2z orbitals, thereby giving rise to a topological nodal line state in lithium-functionalized XN2 sheets （Li2MoN2 and Li2WN2）. Such band crossing is protected by the existence of mirror reflection and time reversal symmetry. More interestingly, the bands cross exactly at the Fermi level, and the linear dispersion regions of such band crossings extend to as high as 0.9 eV above the crossing. For Li2CrN2, the results reveal the emergence of a Dirac cone at the Fermi level. Our calculations show that lattice compression decreases the thickness of a Li2CrN2 nanosheet, leading to phase transition to a nodal line semimetal. The evolution of the band gap of Li2XN2 at the F point indicates that the nontrivial topological character of Li2XN2 nanolayers is stable over a large strain range. When SOC is included, the band crossing point is gapped out giving rise to quantum spin Hall states in Li2CrN2 nanosheets, while for Li2MoN2, the SOC-induced gap at the crossing points is negligible.

关键词： topological semimetal nodal-line states Dirac cone band inversion

Optimal operation of energy at hydrothermal power plants by simultaneous minimization of pollution and costs using improved ABC algorithm

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Frontiers in Energy 2015年第4期9卷 426-432页

作者： Homayoun ebrahimian Bahman TAHERI Nasser YOUSEFI Department of Engineering Ardabil Branch Islamic Azad University Ardabil 0451 Iran Young Researchers and Elite Club Ardabil Branch Islamic Azad University Ardabil 0451 Iran

The aim of this paper is simultaneous mini- mization of hydrothermal units to reach the best solution by employing an improved artificial bee colony （ABC） algorithm in a multi-objective function consisting of economic dispatch （ED） considering the valve-point effect and pollution function in power systems in view of the hot water of the hydro system. In this type of optimization problem, all practical constraints of units were taken into account as much as possible in order to comply with the reality. These constraints include the maximum and minimum output power of units, the constraints caused by the balance between supply and demand, the impact of pollution, water balance, uneven production curve con- sidering the valve-point effect and system losses. The proposed algorithm is applied on the studied system, and the obtained results indifferent operating conditions are analyzed. To investigate in various operating conditions, different load profiles in 12 h are taken into account. The obtained results are compared with those of the other methods including the genetfc algorithm （GA）, the Basu technique, and the improved genetic algorithm. Fast convergence is one of this improved algorithm features.

关键词： practical constraints of units pollution func-tion inlet steam valve up-ramp rate of units improvedABC algorithm

The Effect of NiAl Coatings on Oxidation Behavior of AISI 403 Stainless Steel

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材料热处理学报 2004年第5B期25卷 666-670页

作者： M. ebrahimian F. Ashrafizadeh Iranian Surface Research & Engineering Centre Isfahan Science & Technology Town Isfahan IranDepartment of Materials Engineering Isfahan University of Technology Isfahan Iran

This paper reports the oxidation behavior of stainless steel type 403 as a substrate material with and without NiAl coating. Evaluation of oxidation resistance was performed on uncoated and coated specimens at 850 and 1050°C. A commercial diffusion process was used for the formation of NiAl intermetallic coatings on the specimens. Before aluminizing, a layer of nickel, about 40 um, was deposited on specimens by electroplating. Various techniques including SEM, EDAX, optical microscopy and micro-hardness testing were employed to investigate the coatings before and after oxidation tests. Nickel-aluminides produced by two stage; plating-aluminizing, treatment with NiAl on the surface increased the performance of stainless steel samples significantly.

关键词： NiAl涂层 AISI403不锈钢氧化热处理

Numerical analysis of nonlinear dynamic behavior of earth dams

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Frontiers of Structural and Civil Engineering 2011年第1期5卷 24-40页

作者： Babak ebrahimian School of Civil Engineering Faculty of EngineeringUniversity of TehranTehranIran Institute of Applied Mechanics Faculty of Civil EngineeringGraz University of TechnologyGraz 8010Austria

A numerical study is conducted to investigate the dynamic behavior of earth *** numerical investigation employs a fully nonlinear dynamic finite difference analysis incorporating a simple elastic perfectly plastic constitutive model to describe the stress-strain response of the soil and the Rayleigh damping to increase the level of hysteretic *** extended Masing rules are implemented into the constitutive model to explain more accurately the soil response under general cyclic *** soil stiffness and hysteretic damping change with loading *** procedures for calibrating the constructed numerical model with centrifuge test data and also a real case history are *** the latter,the Long Valley(LV)earth dam subjected to the 1980 Mammoth Lake earthquake as a real case-history is analyzed and the obtained numerical results are compared with the real measurements at the site in both the time and frequency *** good agreement is observed between computed and measured *** seems that the Masing rules combined with a simple elasto-plastic model gives reasonable numerical ***,a comprehensive parametric study is carried out to identify the effects of dam height,input motion characteristics,soil behavior,strength of the shell materials and dam reservoir condition on the dynamic response of earth *** real earthquake records with different levels and peak acceleration values(PGAs)are used as input *** results show that the crest acceleration decreases when the dam height increases and no amplification is ***,more inelastic behavior and more earthquake energy absorption are observed in higher dams.

关键词： earth dam numerical nonlinear response dynamic analysis earthquake dam height

Hybrid intelligent water drop bundled wavelet neural network to solve the islanding detection by inverter-based DG

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Frontiers in Energy 2015年第1期9卷 75-90页

作者： Mehrdad TARAFDAR HAGH Homayoun ebrahimian Noradin GHADIMI Faculty of Electrical and Computer Engineering University of TabrizTabriz 0411 Iran Department of Electrical Engineering Ardabil Branch Islamic AzadUniversity Ardabil 045 Iran

In this paper, a passive neuro-wavelet based islanding detection technique for grid-connected inverter- based distributed generation was developed. The weight parameters of the neural network were optimized by intelligent water drop （IWD） to improve the capability of the proposed technique in the proposed problem. The proposed method utilizes and combines wavelet analysis and artificial neural network （ANN） to detect islanding. Connecting distributed generator to the distribution net- work has many benefits such as increasing the capacity of the grid and enhancing the power quality. However, it gives rise to many problems. This is mainly due to the fact that distribution networks are designed without any generation units at that level. Hence, integrating distributed generators into the existing distribution network is not problem-free. Unintentional islanding is one of the encountered problems. Discrete wavelet transform （DWT） is capable of decomposing the signals into different frequency bands. It can be utilized in extracting discrimi- native features from the acquired voltage signals. In passive schemes with a large non-detection zone （NDZ）, concern has been raised on active method due to its degrading power quality effect. The main emphasis of the proposed scheme is to reduce the NDZ to as close as possible and to keep the output power quality unchanged. The simulation results from Matlab/Simulink shows that the proposed method has a small non-detection zone, and is capable of detecting islanding accurately within the minimum standard time.

关键词： islanding detection neuro-wavelet intelligent

Novel empirical correlations for estimation of bubble point pressure,saturated viscosity and gas solubility of crude oils

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Petroleum Science 2009年第1期6卷 86-90页

作者： Ehsan Khamehchi Fariborz Rashidi Hanieh Rasouli Amir ebrahimian Faculty of Chemical Engineering Amirkabir University of Technology Faculty of Petroleum Engineering Amirkabir University of Technology

Knowledge of petroleum fluid properties is crucial for the study of reservoirs and their development. Estimation of reserves in an oil reservoir or determination of its performance and economics requires a good knowledge of the fluid physical properties. Bubble point pressure, gas solubility and viscosity of oils are the most important parameters in use for petroleum and chemical engineers. In this study a simple-to-use, straight-forward mathematical model was correlated on a set of 94 crude oil data. Three correlations were achieved based on an exponential regression, which were different from conventional empirical correlations, and were evaluated against 12 laboratory data other than those used for the regression. It is concluded that the new exponential equation is of higher precision and accuracy than the conventional correlations and is a more convenient mathematical formulation.

关键词： Bubble point pressure saturated viscosity gas solubility empirical equation exponential multiple regression

Evaluating and Modeling the Mechanical Properties of the Prepared PLGA/nano-BCP Composite Scaffolds for Bone Tissue Engineering

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Journal of Materials Science & Technology 2011年第12期27卷 1105-1112页

作者： M. ebrahimian-Hosseinabadi F. Ashrafizadeh M. Etemadifar Subbu S. Venkatraman Department of Materials Engineering Isfahan University of Technology Isfahan University of Medical Sciences Orthopedic Departments School of Medicine Isfahan University of Medical Sciences Materials Science & Engineering School Nanyang Technological University

In this paper, preparation of nano-biphasic calcium phosphate （nBCP）, mechanical behavior and load-bearing of poly （lactide-co-glycolide）（PLGA） and PLGA/nBCP are presented. The nBCP with composition of 63/37 （w/w） HA/-TCP （hydroxyapatite/fl-tricalcium phosphate） was produced by heating of bovine bone at 700℃. Composite scaffolds were made by using PLGA matrix and 10-50 wt% nBCP powders as reinforcement material. All scaffolds were prepared by thermally induced solid-liquid phase separation （TIPS） at -60~C under 4 Pa （0.04 mbar） vacuum. The results of elastic modulus testing were adjusted with Ishai-Cohen and Narkis models for rigid polymeric matrix and compared to each other. PLGA/nBCP scaffolds with 30 wt% nBCP showed the highest value of yield strength among the scaffolds. In addition, it was found that by increasing the nBCP in scaffolds to 50 wt%, the modulus of elasticity was highly enhanced. However, the optimum value of yield strength was obtained at 30 wt% nBCP, and the agglomeration of reinforcing particles at higher percentages caused a reduction in yield strength. It is clear that the elastic modulus of matrix has the significant role in elastic modulus of scaffolds, as also the size of the filler particles in the matrix.

关键词： Scaffold Bone tissue engineering Poly (lactide-co-glycolide) (PLGA) Biphasiccalcium phosphate Porous composite

Coronary artery disease in Iranian young adults, similarities and differences

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Open Journal of Epidemiology 2014年第1期4卷 19-24页

作者： Mahnoosh Foroughi Sorena Abbaszadehahranjani Mazaher ebrahimian Mahdieh Saieedi Morteza Safi Zahra Abtahian Cardiovascular Research Center Shahid Beheshti University of Medical Sciences Tehran Iran

Objective: Due to devastating consequences of coronary artery disease (CAD) in young population, this study was designed to evaluate the prevalence of preventable risk factors and severity of atherosclerosis for Iranian young adults (≤45 years) diagnosed with premature CAD. Method: A cross sectional, descriptive study comprised 1093 consecutive patients (≤45 years), with a diagnosis of CAD, who underwent percutaneous intervention (PCI) or coronary bypass graft (CABG) from 2010 to 2012. Data on demographic features, cardiovascular risk factors, and angiographic findings were studied. Result: There were 1093 young patients (234 females, 859 males) with proven CAD;the mean age of 39 ± 3 years and the mean BMI were 28 ± 4.7 kg/m2. According to the treatment plan, patients were classified into two groups: PCI and CABG groups (n = 898,195 respectively). Obesity was the most prevalent risk factor (73.6%). In the risk factor assessment, it was noticed: 27% with diabetes mellitus, 37% with hypertension, 38% with family history, 39% with hyperlipidimia, and 54% smokers. Angiographic study revealed that 10 (1%) had left main coronary disease, 747 (68%) patients had single vessel disease, 181 (17%) had two-vessel disease and that 155 (14%) had three-vessel disease. The most common anatomical involvement was the anterior wall territory. Conclusion: Young CAD patients from Iran have different risk profile. Although atherosclerosis of the coronary arteries is less prominent in young patients, more often it is accompanied by decreased left ventricular function. There is a need for prevention plan to control obesity by targeting young adults in the population.

关键词： Coronary Heart Disease Percutaneous Coronary Intervention Coronary Artery Bypass Graft Prevention Body Mass Index Obesity

Joint Parameter-input Estimation for Digital Twinning of the Block Island Wind Turbine using Output-only Measurements

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Joint Parameter-input Estimation for Digital Twinning of the...