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Numerical analysis of nonlinear dynamic behavior of earth dams

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

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Uncertainty and energy-sector equity returns in Iran:a Bayesian and quasi-Monte Carlo time-varying analysis

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Financial Innovation 2019年第1期5卷 198-217页

作者： babak Fazelabdolabadi Center for Exploration and Production Studies and Research Research Institute of Petroleum Industry(RIPI)P.O.Box 14665-1998TehranIran

This study investigates whether the implied crude oil volatility and the historical OPEC price volatility can impact the return to and volatility of the energy-sector equity indices in *** analysis specifically considers the refining,drilling,and petrochemical equity sectors of the Tehran Stock *** parameter estimation uses the quasi-Monte Carlo and Bayesian optimization methods in the framework of a generalized autoregressive conditional heteroskedasticity model,and a complementary Bayesian network analysis is also *** analysis takes into account geopolitical risk and economic policy uncertainty data as other proxies for *** study also aims to detect different price regimes for each equity index in a novel way using homogeneous/non-homogeneous Markov switching autoregressive *** these methods provide improvements by restricting the analysis to a specific price-regime period,they produce conflicting results,rendering it impossible to draw general conclusions regarding the contagion effect on returns or the volatility transmission between ***,the results indicate that the OPEC(historical)price volatility has a stronger effect on the energy sectors than the implied volatility *** types of oil price shocks are found to have no effect on the drilling sector price pattern,whereas the refining and petrochemical equity sectors do seem to undergo changes in their price patterns nearly concurrently with future demand shocks and oil supply shocks,respectively,gaining dominance in the oil market.

关键词： Quasi-Monte Carlo Bayesian optimization Bayesian network Oil volatility index

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2,4,6-Trichloro-1,3,5-triazine/dimethylformamide as an efficient reagent for one-pot conversion of alcohols into N-alkylphthalimides

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Chinese Chemical Letters 2010年第2期21卷 171-174页

作者： babak Mokhtari Roya Azadi Aseieh Azhdari Department of Chemistry College of ScienceShahid Chamran University

An efficient and mild method for the direct conversion of alcohols into N-alkylphthalimides using 2,4,6-trichloro-1,3,5-triazine and dimethylformamide was *** reaction was preceded via(alcoxymethylene) dimethylammoniu... 详细信息

关键词： Alcohol Potassium phthalimide 2 4 6-Trichloro-1 3 5-triazine Dimethylformamide N-alkylphthalimide

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A hybrid Bayesian-network proposition for forecasting the crude oil price

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Financial Innovation 2019年第1期5卷 520-540页

作者： babak Fazelabdolabadi Center for Exploration and Production Studies and Research Research Institute of Petroleum Industry(RIPI)14665-1998TehranIran

This paper proposes a hybrid Bayesian Network(BN)method for short-term forecasting of crude oil *** method performed is a hybrid,based on both the aspects of classification of influencing factors as well as the regression of the out-ofsample *** the sake of performance comparison,several other hybrid methods have also been devised using the methods of Markov Chain Monte Carlo(MCMC),Random Forest(RF),Support Vector Machine(SVM),neural networks(NNET)and generalized autoregressive conditional heteroskedasticity(GARCH).The hybrid methodology is primarily reliant upon constructing the crude oil price forecast from the summation of its Intrinsic Mode Functions(IMF)and its residue,extracted by an Empirical Mode Decomposition(EMD)of the original crude price *** Volatility Index(VIX)as well as the Implied Oil Volatility Index(OVX)has been considered among the influencing parameters of the crude price *** final set of influencing parameters were selected as the whole set of significant contributors detected by the methods of Bayesian Network,Quantile Regression with Lasso penalty(QRL),Bayesian Lasso(BLasso)and the Bayesian Ridge Regression(BRR).The performance of the proposed hybrid-BN method is reported for the three crude price benchmarks:West Texas Intermediate,Brent Crude and the OPEC Reference Basket.

关键词： Bayesian networks Random Forest Markov chain Monte Carlo Support vector machine

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Aging behavior of a copper-bearing high-strength low-carbon steel

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International Journal of Minerals,Metallurgy and Materials 2018年第4期25卷 429-438页

作者： babak Shahriari Reza Vafaei Ehsan Mohammad Sharifi Khosro Farmanesh Department of Materials Engineering Malek Ashtar University of Technology

The effects of aging temperature and time on the hardness and impact toughness of a copper-bearing high-strength low-carbon steel were investigated. The hardness of the aged samples reached maxima after 1 h and 5 h of aging at 500 and 450℃, respectively; this increase in hardness was followed by a decrease in hardness until a temperature of 700℃, at which secondary hardening was observed. The impact toughness of the aged steel was found to be higher for 5 h of aging. Transmission electron microscopy confirmed the presence of carbide and copper precipitates; also, the secondary hardening could be the result of the transformation of austenite（formed in the aging treatment） to martensite. Differential scanning calorimetry of the steel was performed to better understand the precipitation behavior. The results revealed that the precipitation of the steel exhibited two significant stages of copper precipitate nucleation and coarsening of the precipitates, with corresponding activation energies of 49 and 238 kJ·mol^-1, respectively.

关键词： aging treatment BA-160 steel differential scanning calorimetry precipitation

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Novel decoupled framework for reliability-based design optimization of structures using a robust shifting technique

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Frontiers of Structural and Civil Engineering 2019年第4期13卷 800-820页

作者： Mohammad Reza GHASEMI Charles V. CAMP babak DIZANGIAN Department of Civil Engineering University of Sistan and Baluchestan Zahedan *** Iran Department of Civil Engineering The University of Memphis Memphis TN 38152 USA Department of Civil Engineering Velayat University Iranshahr *** Iran

In a reliability-based design optimization (RBDO), computation of the failure probability (Pf) at all design points through the process may suitably be avoided at the early stages. Thus, to reduce extensive computations of RBDO, one could decouple the optimization and reliability analysis. The present work proposes a new methodology for such a decoupled approach that separates optimization and reliability analysis into two procedures which significantly improve the computational efficiency of the RBDO. This technique is based on the probabilistic sensitivity approach (PSA) on the shifted probability density function. Stochastic variables are separated into two groups of desired and non-desired variables. The three-phase procedure may be summarized as: Phase 1, apply deterministic design optimization based on mean values of random variables;Phase 2, move designs toward a reliable space using PSA and finding a primary reliable optimum point;Phase 3, applying an intelligent self-adaptive procedure based on cubic B-spline interpolation functions until the targeted failure probability is reached. An improved response surface method is used for computation of failure probability. The proposed RBDO approach could significantly reduce the number of analyses required to less than 10% of conventional methods. The computational efficacy of this approach is demonstrated by solving four benchmark truss design problems published in the structural optimization literature.

关键词： reliability-based design optimization trusses sensitivity analysis shifting technique cubic B-splines response surface method

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Computational Analysis of Cysteine Proteases(Clan CA,Family C1) of Leishmania major to Find Potential Epitopic Regions

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Genomics, Proteomics & Bioinformatics 2009年第3期7卷 87-95页

作者： babak Saffari Hassan Mohabatkar Department of Biology College of SciencesShiraz UniversityShirazIran

Leishmania is associated with a broad spectrum of diseases, ranging from simple cutaneous to invasive visceral leishmaniasis. Here, the sequences of ten cysteine proteases of types A, B and C of Leishmania major were obtained from GeneDB database. Prediction of MHC class I epitopes of these cysteine proteases was performed by NetCTL program version 1.2. In addition, by using BcePred server, different structural properties of the proteins were predicted to find out their potential B cell epitopes. According to this computational analysis, nine regions were predicted as B cell epitopes. The results provide useful information for designing peptide-based vaccines.

关键词： bioinformatics,cysteine protease T cell epitope B cell epitope Leishmania major

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Formation mechanism of Al2O3/MoS2 nanocomposite coating by plasma electrolytic oxidation(PEO)

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Plasma Science and Technology 2020年第6期22卷 144-155页

作者： babak GHORBANIAN Mohammad TAJALLY Seyed Mohammad MOUSAVI KHOIE Hossein TAVAKOLI Faculty of Materials and Metallurgical Engineering Semnan UniversityPO Box 35131-19111SemnanIran Faculty of Mining and Metallurgical Engineering Amirkabir University of TechnologyPO Box 15875-4413 TehranIran

In this study,an Al2O3/MoS2 nanocomposite coating was created on an aluminum 1050 substrate using the plasma electrolytic oxidation *** zeta potential measurements showed that small MoS2 particles have negative potential and move toward the anode *** nanoparticles of MoS2 were found to have a zeta potential of-25 mV,which prevents suspension in the ***,to produce an Al2O3/MoS2 nanocomposite,one has to use the microparticles of *** X-ray diffraction analyses showed that the produced coatings containedα-Al2O3,γ-Al2O3,and MoS2,and that the size of MoS2 particles can be reduced to 30 *** was observed that prolonged suspension in the electrolyte results in an enhanced formation of an Al2O3/MoS2 *** the results,it was hypothesized that the mechanism of the formation of the Al2O3/MoS2 nanocomposite coating on the aluminum 1050 substrate is based on electrical energy discharge.

关键词： plasma electrolytic oxidation corrosion Al2O3/MoS2 nanocomposite tribology

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Phosphine-free conversion of alcohols into alkyl thiocyanates using trichloroisocyanuric acid/NH_4SCN

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Chinese Chemical Letters 2012年第1期23卷 77-80页

作者： Roya Azadi babak Mokhtari Mohamad-Ali Makaremi Department of Chemistry College of ScienceShahid Chamran UniversityAhvaz 61357-43337Iran

A convenient and efficient phosphine-free procedure for the one-pot conversion of primary,secondary and tertiary alcohols into the corresponding alkyl thiocyanates or alkyl isothiocyanates is described using trichloro... 详细信息

关键词： Phosphine-free Alcohol Thiocyanate Trichloroisocyanuric acid Thiocyanation

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Comparison of the effects of acute and chronic psychological stress on metabolic features in rats

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Journal of Zhejiang University-Science B(Biomedicine & Biotechnology) 2012年第11期13卷 904-912页

作者： Fatemeh ROSTAMKHANI Homeira ZARDOOZ Saleh ZAHEDIASL babak FARROKHI Neuroscience Research Center Shahid Beheshti University of Medical SciencesTehranIran Department of Biology Shahre-Rey BranchIslamic Azad UniversityTehranIran Department of Physiology Faculty of MedicineShahid Beheshti University of Medical SciencesTehranIran Endocrine Research Center Research Institute for Endocrine SciencesShahid Beheshti University of Medical SciencesTehranIran Department of Immunology Faculty of MedicineShahid Beheshti University of Medical SciencesTehranIran

This study was aimed to compare the effects of acute and chronic psychological stress on metabolic factors. Forty-two male Wistar rats were divided into control and stressed groups. Stress was applied by a communication box acutely (1 d) and chronically (15 and 30 d). Blood sampling was carried out by retro-orbital-puncture method. The plasma levels of glucose, cholesterol, triglyceride, insulin, and corticosterone were measured. In addition, feed and water intake, latency to eat and drink, adrenal and body weights were determined. Acute and chronic psychological stress did not significantly change basal plasma corticosterone levels. However, immediately (1 min) after acute exposure to stress, plasma corticosterone level increased compared to that before stress exposure. Acute stress increased plasma insulin levels significantly. Fifteen days of stress exposure resulted in plasma glucose increase. Chronic stress significantly increased feed intake, latency to eat, and adrenal weight compared to acute stress. The body weights of both control and stressed groups increased markedly during the experiment. Homeostasis model assessment of insulin resistance (HOMA-IR) index did not change significantly in the stressed group. In conclusion, application of acute and chronic psychological stress leads to different metabolic and/or behavioral changes but the metabolic changes resulting from acute exposure to stress seem to be more pronounced.

关键词： Psychological stress Corticosterone Insulin Glucose Cholesterol Triglyceride

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