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Application of consistent geometric decomposition theorem to dynamic finite element of 3D composite beam based on experimental and numerical analyses

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Frontiers of Structural and Civil Engineering 2020年第3期14卷 675-689页

作者： Iman FATTAHI hamid reza MIRDAMADI hamid ABDOLLAHI Department of Mechanical Engineering Isfahan University of TechnologyIsfahan ***Iran

Analyzing static and dynamic problems including composite structures has been of high significance in research efforts and industrial applications.In this article,equivalent single layer approach is utilized for dynamic finite element procedures of 3D composite beam as the building block of numerous composite structures.In this model,both displacement and strain fields are decomposed into cross-sectional and longitudinal components,called consistent geometric decomposition theorem.Then,the model is discretized using finite clement procedures.Two local coordinate systems and a global one are defined to decouple mechanical degrees of freedom.Furthermore,from the viewpoint of consistent geometric decomposition theorem,the transformation and element mass matrices for those systems are introduced here for the first time.The same decomposition idea can be used for developing element stiffiness matrix.Finally,comprehensive validations are conducted for the theory against experimental and numerical results in two case studies and for various conditions.

关键词： composite beam dynamic finite element degrees of freedom coupling experimental validation numerical validation

An incremental ant colony optimization based approach to task assignment to processors for multiprocessor scheduling

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Frontiers of Information Technology & Electronic Engineering 2017年第4期18卷 498-510页

作者： hamid reza BOVEIRI Sama Technical and Vocational Training College Islamic Azad University Shoushtar Branch Shoushtar Iran

任务调度优化是多处理器环境(如并行和分布式系统)取得良好性能所面临的最重要挑战之一。目前大多数任务调度算法基于列表调度法,该方法的基本思路是,以列表的形式准备一系列待调度的节点,赋予这些节点不同优先级,然后不断去除列表中优... 详细信息

任务调度优化是多处理器环境(如并行和分布式系统)取得良好性能所面临的最重要挑战之一。目前大多数任务调度算法基于列表调度法,该方法的基本思路是,以列表的形式准备一系列待调度的节点,赋予这些节点不同优先级,然后不断去除列表中优先级最高的节点,并将其分配给具有最早开始时间(Earliest start time,EST)的处理器。由此可见,该算法的完成时间主要由两大因素决定:(1)任务分配顺序的选择(次序子问题);(2)选定顺序的任务如何分配给处理器(分配子问题)。已有文献提出了许多解决次序子问题的好办法,但分配子问题少有人涉及。本文研究结果显示:传统的按照最早开始时间分配任务的方法并非最优;基于蚁群优化算法,得到一种新的方法,可以获得高效得多的调度方案。

关键词：蚁群优化列表调度多处理器任务图调度并行与分布式系统

Characteristics of turbulent flow in 3-D pools in the presence of submerged rigid vegetation in channel bed

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Journal of Hydrodynamics 2024年第1期36卷 158-169页

作者： Kourosh Nosrati Hossein Afzalimehr Jueyi Sui hamid reza Reisifar Natural Disasters Prevention Research Center Faculty of Civil EngineeringIran University of Science and TechnologyTehranIran School of Engineering University of Northern British ColumbiaPrince GeorgeCanada

In this study,the interaction between 3-D bedforms and submerged rigid vegetation has been investigated.Various laboratory experiments were conducted to study the distribution of flow velocity,Reynolds shear stress,turbulent kinetic energy,and skewness coefficients for a constant density of vegetation.Results showed that the velocity profile in the pool section deviates from those in the upstream section of the pool.It has been found that the dip parameter varied between 0.6H and 0.9H depending on various factors including bed roughness,vegetation distribution,and pool entrance/exit slopes.However,scattered vegetation in the pool and differences in slopes created non-uniform flow conditions.Also,in the wake region behind each vegetated element,flow velocity reduced significantly,and small-scale eddies are formed,causing increased perturbations.By decreasing the entrance slope and bed roughness,relatively uniform flow and weaker turbulence was resulted,but the random distribution of vegetated elements counteracted this balance and intensified turbulence.With the decrease in the pool entrance slope,the contribution of sweep event decreased and the contribution of ejection event increased.

关键词： Submerged rigid vegetation 3-D pool Reynolds shear stress skewness coefficients

How do machine learning techniques help in increasing accuracy of landslide susceptibility maps?

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地学前缘：英文版 2020年第3期11卷 871-883页

作者： Yacine Achour hamid reza Pourghasemi Department of Civil Engineering Bordj Bou Arreridj University34030El AnnasserAlgeria Department of Natural Resources and Environmental Engineering College of AgricultureShiraz UniversityShirazIran

Landslides are abundant in mountainous regions.They are responsible for substantial damages and losses in those areas.The A1 Highway,which is an important road in Algeria,was sometimes constructed in mountainous and/or semi-mountainous areas.Previous studies of landslide susceptibility mapping conducted near this road using statistical and expert methods have yielded ordinary results.In this research,we are interested in how do machine learning techniques help in increasing accuracy of landslide susceptibility maps in the vicinity of the A1 Highway corridor.To do this,an important section at Ain Bouziane(NE,Algeria) is chosen as a case study to evaluate the landslide susceptibility using three different machine learning methods,namely,random forest(RF),support vector machine(SVM),and boosted regression tree(BRT).First,an inventory map and nine input factors were prepared for landslide susceptibility mapping(LSM) analyses.The three models were constructed to find the most susceptible areas to this phenomenon.The results were assessed by calculating the receiver operating characteristic(ROC) curve,the standard error(Std.error),and the confidence interval(CI) at 95%.The RF model reached the highest predictive accuracy(AUC=97.2%) comparatively to the other models.The outcomes of this research proved that the obtained machine learning models had the ability to predict future landslide locations in this important road section.In addition,their application gives an improvement of the accuracy of LSMs near the road corridor.The machine learning models may become an important prediction tool that will identify landslide alleviation actions.

关键词： Spatial modelling Support vector machine Random forest Boosted regression tree Validation measures Algeria

两步电沉积微/纳米结构表面的滴状冷凝的热传递（英文）

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Journal of Central South University 2019年第5期26卷 1065-1076页

作者： hamid reza TALESH BAHRAMI Alireza AZIZI hamid SAFFARI School of Mechanical Engineering Iran University of Science and Technology

冷凝是一种重要的传热机制,在发电厂、采暖、通风、空调、制冷等行业有着广泛的应用。冷凝以两种不同的模式发生,包括膜状冷凝(FWC)和滴状冷凝(DWC)。在疏水和超疏水表面上发生的滴状冷凝热传递容量远高于膜状冷凝。因此,近年来对滴状... 详细信息

冷凝是一种重要的传热机制,在发电厂、采暖、通风、空调、制冷等行业有着广泛的应用。冷凝以两种不同的模式发生,包括膜状冷凝(FWC)和滴状冷凝(DWC)。在疏水和超疏水表面上发生的滴状冷凝热传递容量远高于膜状冷凝。因此,近年来对滴状冷凝进行了广泛的研究。超疏水表面具有低表面能的微纳米结构。在本研究中,采用两步电沉积法在铜表面沉积出微/纳米结构。用乙醇和1-十八硫醇溶液自组装单分子层来降低试样的表面能。结果表明,电沉积工艺具有最佳的条件。例如,当第二步电沉积时间为2000s时,滴状冷凝的热传递量是膜状冷凝的5倍,而当第二步电沉积时间为4000s时,滴状冷凝(DWC)与膜状冷凝(FWC)热传递几乎相同。使用XRD和SEM分析检测制备的试样表面。SEM分析显示,在试样表面上存在一些微结构,通过延长第二步电沉积时间,可以降低表面孔隙率。

关键词：冷凝热传递电沉积微/纳米结构孔隙率

Fault ride-through capability improvement in a DFIG-based wind turbine using modified ADRC

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Protection and Control of Modern Power Systems 2022年第1期7卷 751-787页

作者： Seyed reza Mosayyebi Seyed hamid Shahalami Hamed Mojallali Electrical Engineering Department Faculty of EngineeringUniversity of GuilanRashtIran

In this paper,an overview of several strategies for fault ride-through(FRT)capability improvement of a doubly-fed induction generator(DFIG)-based wind turbine is presented.Uncertainties and parameter variations have adverse effects on the performance of these strategies.It is desirable to use a control method that is robust to such distur-bances.Auto disturbance rejection control(ADRC)is one of the most common methods for eliminating the effects of disturbances.To improve the performance of the conventional ADRC,a modified ADRC is introduced that is more robust to disturbances and offers better responses.The non-derivability of the fal function used in the conventional ADRC degrades its efficiency,so the modified ADRC uses alternative functions that are derivable at all points,i.e.,the odd trigonometric and hyperbolic functions(arcsinh,arctan,and tanh).To improve the effciency of the proposed ADRC,fuzzy logic and fractional-order functions are used simultaneously.In fuzzy fractional-order ADRC(FFOADRC),all disturbances are evaluated using a nonlinear fractional-order extended state observer(NFESO).The performance of the suggested structure is investigated in MATLAB/Simulink.The simulation results show that during disturbances such as network voltage sag/swell,using the modified ADRCs leads to smaller fluctuations in stator flux amplitude and DC-link voltage,lower variations in DFIG velocity,and lower total harmonic distortion(THD)of the stator current.This demonstrates the superiority over conventional ADRC and a proportional-integral(PI)controller.Also,by chang-ing the crowbar resistance and using the modified ADRCs,the peak values of the waveforms(torque and currents)can be controlled at the moment of fault occurrence with no significant distortion.

关键词： Doubly-fed induction generator(DFIG) Auto disturbance rejection control(ADRC) Fault ride-through(FRT) Wind turbine Nonlinear fractional-order extended state observer(NFESO)

Landslide susceptibility mapping using machine learning algorithms and comparison of their performance at Abha Basin,Asir Region,Saudi Arabia

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Geoscience Frontiers 2021年第2期12卷 639-655页

作者： Ahmed Mohamed Youssef hamid reza Pourghasemi Geology Department Faculty of ScienceSohag UniversityEgypt Geological Hazards Department Applied Geology SectorSaudi Geological SurveyP.O.Box 54141Jeddah21514Saudi Arabia Department of Natural Resources and Environmental Engineering College of AgricultureShiraz UniversityShirazIran

The current study aimed at evaluating the capabilities of seven advanced machine learning techniques(MLTs),including,Support Vector Machine(SVM),Random Forest(RF),Multivariate Adaptive Regression Spline(MARS),Artificial Neural Network(ANN),Quadratic Discriminant Analysis(QDA),Linear Discriminant Analysis(LDA),and Naive Bayes(NB),for landslide susceptibility modeling and comparison of their performances.Coupling machine learning algorithms with spatial data types for landslide susceptibility mapping is a vitally important issue.This study was carried out using GIS and R open source software at Abha Basin,Asir Region,Saudi Arabia.First,a total of 243 landslide locations were identified at Abha Basin to prepare the landslide inventory map using different data sources.All the landslide areas were randomly separated into two groups with a ratio of 70%for training and 30%for validating purposes.Twelve landslide-variables were generated for landslide susceptibility modeling,which include altitude,lithology,distance to faults,normalized difference vegetation index(NDVI),landuse/landcover(LULC),distance to roads,slope angle,distance to streams,profile curvature,plan curvature,slope length(LS),and slope-aspect.The area under curve(AUC-ROC)approach has been applied to evaluate,validate,and compare the MLTs performance.The results indicated that AUC values for seven MLTs range from 89.0%for QDA to 95.1%for RF.Our findings showed that the RF(AUC=95.1%)and LDA(AUC=941.7%)have produced the best performances in comparison to other MLTs.The outcome of this study and the landslide susceptibility maps would be useful for environmental protection.

关键词： Landslide susceptibility Machine learning algorithms Variables importance Saudi Arabia

Numerical and experimental study of an innovative pipeline design in a granular pneumatic-conveying system

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Particuology 2018年第3期16卷 196-203页

作者： Hasan Ghafori hamid reza Ebrahimi Department of Mechanical Engineering MaJlesi Branch Islamic Azad University lsfilhan Iran Department of Chemical Engineering Majlesi Branch Islamic Azad University lsfahan Iran

During gas-solid mixture conveying in a dense phase, material is conveyed in dunes on the bottom of the pipeline, or as a pulsating moving bed. This phenomenon increases the pressure drop and power consumption. We introduce a new technique to reduce the pressure drop, which is termed the perforated double tube. To validate this new model, the gas-solid flow pattern and pressure drop were studied numerically and experimentally. The power consumption was also studied experimentally. Numerical studies were performed by the Eulerian-Lagrangian approach to predict gas and particle movement in the pipeline, Comparisons between the numerical predictions and the experimental results for the gas-solid flow patterns and pressure drop show good agreement.

关键词： Computational fluid dynamics Power consumption Perforated double tube Pneumatic conveying

In vitro bioactivity and corrosion of PLGA/hardystonite composite-coated magnesium-based nanocomposite for implant applications

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International Journal of Minerals,Metallurgy and Materials 2021年第1期28卷 168-178页

作者： Mahmood Razzaghi Masoud Kasiri-Asgarani hamid reza Bakhsheshi-Rad hamid Ghayour Advanced Materials Research Center Department of Materials EngineeringNajafabad BranchIslamic Azad UniversityNajafabadIran

A type of polymer/ceramic coating was introduced on a magnesium-based nanocomposite, and the nanocomposite was evaluated for implant applications.The microstructure, corrosion, and bioactivity of the coated and uncoated samples were assessed.Mechanical alloying followed by sintering was applied to fabricate the Mg–3Zn–0.5Ag–15NiTi nanocomposite substrate.Moreover, different contents of poly(lactic-co-glycolic acid)(PLGA) coatings were studied, and 10 wt% of PLGA content was selected.The scanning electron microscopy(SEM) images of the bulk nanocomposite showed an acceptable homogenous dispersion of the Ni Ti nanoparticles(NPs) in the Mg-based matrix.In the in vitro bioactivity evaluation, following the immersion of the uncoated and coated samples in a simulated body fluid(SBF) solution, the Ca/P atomic ratio demonstrated that the apatite formation amount on the coated sample was greater than that on the uncoated nanocomposite.Furthermore, assessing the corrosion resistance indicated that the coatings on the Mg-based substrate led to a corrosion current density(icorr) that was considerably lower than that of the substrate.Such a condition revealed that the coating would provide an obstacle for the corrosion.Based on this study, the PLGA/hardystonite(HT) composite-coated Mg–3Zn–0.5Ag–15NiTi nanocomposite may be suitably applied as an orthopedic implant biomaterial.

关键词： magnesium nanocomposite corrosion biocompatibility poly(lactic-co-glycolic acid) hardystonite