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Joining of Individual Silver Nanowires via Electrical Current

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Nano-Micro Letters 2014年第4期6卷 293-300页

作者： arash Vafaei Anming Hu Irene A.Goldthorpe Department of Electrical and Computer Engineering University of Waterloo Department of Mechanical and Mechatronics Engineering University of Waterloo Department of Mechanical Aerospace and Biomedical Engineering University of Tennessee Knoxville

A procedure for joining polyol-synthesized silver nanowires in air using current-induced Joule heat welding is reported. Using a common probe station and photolithographically patterned gold electrodes, the welding process is completed using a common semiconductor analyzer. A unique two-step procedure eliminates the dielectric barrier at the point of contact without damaging the nanowires away from the junction. This procedure is designed for metal–metal contacts where a strong dielectric intermediate layer might exist, which can occur with metals prone to oxidation or corrosion in air, or as a result of the electrode deposition process. Ohmic connections are also established in cases where there is an initial gap between two nanowires.

关键词： Nanowires Nanowelding Joule heating

Corrosion behavior of composite coatings containing hydroxyapatite particles on Mg alloys by plasma electrolytic oxidation: A review

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Journal of Magnesium and Alloys 2023年第9期11卷 2999-3011页

作者： arash Fattah-alhosseini Razieh Chaharmahali Sajad Alizad Mosab Kaseem Department of Materials Engineering Bu-Ali Sina UniversityHamedan 65178-38695Iran Department of Nanotechnology and Advanced Materials Engineering Sejong UniversitySeoul 05006South Korea

Mg and its alloys have been introduced as promising biodegradable materials for biomedical implant applications due to their excellent biocompatibility, mechanical behavior, and biodegradability. However, their susceptibility to rapid corrosion within the body poses a significant challenge and restricts their applications. To overcome this issue, various surface modification techniques have been developed to enhance the corrosion resistance and bioactivity of Mg-based implants. PEO is a potent technique for producing an oxide film on a surface that significantly minimizes the tendency to corrode. However, the inevitable defects due to discharges and poor biological activity during the coating process remain a concern. Therefore, adding suitable particles during the coating process is a suitable solution. Hydroxyapatite(HAp)has attracted much attention in the development of biomedical applications in the scientific community. HAp shows excellent biocompatibility due to its similarity in chemical composition to the mineral portion of bone. Therefore, its combination with Mg-based implants through PEO has shown significant improvements in their corrosion resistance and bioactivity. This review paper provides a comprehensive overview of the recent advances in the preparation, characterization, corrosion behavior and bioactivity applications of HAp particles on Mg-based implants by PEO.

关键词： Mg and its alloys Hydroxyapatite Corrosion behavior Composite coatings Plasma electrolytic oxidation(peo)

Robust Optimal Higher-order-observer-based Dynamic Sliding Mode Control for VTOL Unmanned Aerial Vehicles

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International Journal of Automation and computing 2021年第5期18卷 802-813页

作者： Yashar Mousavi Amin Zarei arash Mousavi Mohsen Biari Department of Applied Science School of ComputingEngineering and Built EnvironmentGlasgow Caledonian UniversityGlasgow G4 OBAUK Department of Electrical and Computer Engineering University of Sistan and BaluchestanZahedan ***Iran Department Electrical Engineering and Applied Sciences Paradise Research CenterJahrom ***Iran Faculty of Electrical and Robotic Engineering Shahrood University of TechnologyShahrood ***Iran

This paper investigates the precise trajectory tracking of unmanned aerial vehicles(UAV) capable of vertical take-off and landing(VTOL) subjected to external disturbances. For this reason, a robust higher-order-observer-based dynamic sliding mode controller(HOB-DSMC) is developed and optimized using the fractional-order firefly algorithm(FOFA). In the proposed scheme, the sliding surface is defined as a function of output variables, and the higher-order observer is utilized to estimate the unmeasured variables,which effectively alleviate the undesirable effects of the chattering phenomenon. A neighboring point close to the sliding surface is considered, and as the tracking error approaches this point, the second control is activated to reduce the control input. The stability analysis of the closed-loop system is studied based on Lyapunov stability theorem. For a better study of the proposed scheme, various trajectory tracking tests are provided, where accurate tracking and strong robustness can be simultaneously ensured. Comparative simulation results validate the proposed control strategy′s effectiveness and its superiorities over conventional sliding mode controller(SMC) and integral SMC approaches.

关键词： Unmanned aerial vehicle dynamic sliding mode trajectory tracking fractional firefly algorithm vertical take-off and landing system

Parallel Implicit-Explicit General Linear Methods

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Communications on Applied Mathematics and Computation 2021年第4期3卷 649-669页

作者： Steven Roberts arash Sarshar Adrian Sandu Computational Science Laboratory Virginia Polytechnic Institute and State UniversityBlacksburgVA 24060USA

High-order discretizations of partial differential equations(PDEs)necessitate high-order time integration schemes capable of handling both stiff and nonstiff operators in an efficient ***-explicit(IMEX)integration based on general linear methods(GLMs)offers an attractive solution due to their high stage and method order,as well as excellent stability *** IMEX characteristic allows stiff terms to be treated implicitly and nonstiff terms to be efficiently integrated *** work develops two systematic approaches for the development of IMEX GLMs of arbitrary order with stages that can be solved in *** first approach is based on diagonally implicit multi-stage integration methods(DIMSIMs)of types 3 and *** second is a parallel generalization of IMEX Euler and has the interesting feature that the linear stability is independent of the order of *** experiments confirm the theoretical rates of convergence and reveal that the new schemes are more efficient than serial IMEX GLMs and IMEX Runge-Kutta methods.

关键词： Parallel Time integration IMEX methods General linear

Antibacterial activity of bioceramic coatings on Mg and its alloys created by plasma electrolytic oxidation(PEO): A review

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Journal of Magnesium and Alloys 2022年第1期10卷 88-106页

作者： arash Fattah-alhosseini Maryam Molaei Meisam Nouri Kazem Babaei Department of Materials Engineering Bu-Ali Sina UniversityHamedan 65178-38695Iran

Mg and its alloys are suitable choices for implant materials due to their biodegradability and biocompatibility features. However, the high electrochemical activity of this family of biomaterials results in their fast degradation and severe corrosion in the physiological environment,producing hydrogen(H;) gas, and therefore increasing the p H of the environment. To meet the clinical requirements, the degradation rate of Mg biomaterials needs to be reduced. Nevertheless, higher corrosion resistance of Mg results in a low alkaline p H, weakening the antibacterial activity. Therefore, while the rapid degradation problem of Mg-based biomaterials needs to be addressed, good antibacterial properties are also necessary. By using the plasma electrolytic oxidation(PEO) surface modification technique, the antibacterial activity of Mg and its alloys can be enhanced while maintaining their corrosion protection properties at a high level. Throughout the PEO process, introducing antibacterial agents into solutions results in a major increase in antibacterial activity of the coatings. Moreover, post-or pre-processing on PEO coatings can provide better protection against bacteria. In this review, the antibacterial activity of PEO coatings applied on Mg and also its alloys will be discussed in more detail.

关键词： Antibacterial activity Magnesium Plasma electrolytic oxidation(PEO) Gram-positive bacteria Gram-negative bacteria

Probabilistic stability of uncertain composite plates and stochastic irregularity in their buckling mode shapes:A semi-analytical non-intrusive approach

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Frontiers of Structural and Civil Engineering 2023年第2期17卷 179-190页

作者： arash Tavakoli MALEKI Hadi PARVIZ Akbar A.KHATIBI Mahnaz ZAKERI Advanced Structures Research Laboratory K.N.Toosi University of TechnologyTehran 16569-83911Iran Faculty of New Sciences and Technologies University of TehranTehran 16569-83911Iran School of Engineering RMIT UniversityMelbourne VIC 3001Australia

In this study,the mechanical properties of the composite plate were considered Gaussian random fields and their effects on the buckling load and corresponding mode shapes were studied by developing a semi-analytical nonintrusive *** random fields were decomposed by the Karhunen−Loève *** strains were defined based on the assumptions of the first-order and higher-order shear-deformation *** equations of motion were extracted using Euler-Lagrange *** probabilistic response space was obtained by employing the nonintrusive polynomial chaos ***,the effect of spatially varying stochastic properties on the critical load of the plate and the irregularity of buckling mode shapes and their sequences were studied for the first *** findings showed that different shear deformation plate theories could significantly influence the reliability of thicker plates under compressive *** is suggested that a linear relationship exists between the mechanical properties’variation coefficient and critical loads’variation ***,in modeling the plate properties as random fields,a significant stochastic irregularity is obtained in buckling mode shapes,which is crucial in practical applications.

关键词： uncertain composite plate stochastic assume mode method Karhunen−Loève theorem polynomial chaos approach plate buckling irregularity in buckling mode shapes

Weldability and liquation cracking behavior of ZhS6U superalloy during electron-beam welding

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International Journal of Minerals,Metallurgy and Materials 2019年第2期26卷 251-259页

作者： arash Khakzadshahandashti Mohammad Reza Rahimipour Kourosh Shirvani Mansour Razavi Department of Ceramic Materials and Energy Research Center Department of Material and Renewal Energy Iranian Research Organization for Science and Technology (IROST)

The weldability of the ZhS6U nickel-based superalloy, which is prone to solidification cracking during electron-beam welding(EBW) repair processes, was investigated. The effects of two different pre-weld heat-treatment cycles on the final microstructure before and after welding were examined. Welds were made on flat coupons using an EBW machine, and the two heat-treatment cycles were designed to reduce γ′ liquation before welding. Microstructural features were also examined by optical and scanning electron microscopy. The results showed that the change in the morphology and size of the γ′ precipitates in the pre-weld heat-treatment cycles changed the ability of the superalloy to release the tensile stresses caused by the matrix phase cooling after EBW. The high hardness in the welded coupons subjected to the first heat-treatment cycle resulted in greater resistance to stress release by the base alloy, and the concentration of stress in the base metal caused liquation cracks in the heat-affected zone and solidification cracks in the weld area.

关键词： weldability ZhS6U superalloy electron beam welding heat-affected zone liquation cracking pre-weld heat treatment

Precipitation forecasting by large-scale climate indices and machine learning techniques

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Journal of Arid Land 2020年第5期12卷 854-864页

作者： Mehdi GHOLAMI ROSTAM Seyyed Javad SADATINEJAD arash MALEKIAN University of Tehran Tehran ***Iran

Global warming is one of the most complicated challenges of our time causing considerable tension on our societies and on the *** impacts of global warming are felt unprecedentedly in a wide variety of ways from shifting weather patterns that threatens food production,to rising sea levels that deteriorates the risk of catastrophic *** all aspects related to global warming,there is a growing concern on water resource *** field is targeted at preventing future water crisis threatening human *** very first stage in such management is to recognize the prospective climate parameters influencing the future water resource *** prediction models,methods and tools,in this case,have been developed and applied so *** line with trend,the current study intends to compare three optimization algorithms on the platform of a multilayer perceptron(MLP)network to explore any meaningful connection between large-scale climate indices(LSCIs)and precipitation in the capital of Iran,a country which is located in an arid and semi-arid region and suffers from severe water scarcity caused by mismanagement over years and intensified by global *** situation has propelled a great deal of population to immigrate towards more developed cities within the country especially towards ***,the current and future environmental conditions of this city especially its water supply conditions are of great *** tackle this complication an outlook for the future precipitation should be provided and appropriate forecasting trajectories compatible with this region's characteristics should be *** this end,the present study investigates three training methods namely backpropagation(BP),genetic algorithms(GAs),and particle swarm optimization(PSO)algorithms on a MLP *** frameworks distinguished by their input compositions are denoted in this study:Concurrent Model Framework(CMF)and Integrated Model Framework(

关键词： backpropagation genetic algorithms machine learning multilayer perceptron particle swarm optimization Taylor diagram

A Study of Tate Homology via the Approximation Theory with Applications to the Depth Formula

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Acta Mathematica Sinica,English Series 2023年第3期39卷 439-458页

作者： Olgur CELIKBAS Li LIANG arash SADEGHI Tirdad SHARIF Department of Mathematics West Virginia UniversityMorgantownWV 26506-6310USA School of Mathematics and Information Science Guangzhou UniversityGuangzhou 510006P.R.China School of Mathematics and Physics Lanzhou Jiaotong UniversityLanzhou 730070P.R.China School of Mathematics Institute for Research in Fundamental Sciences(IPM)P.O.Box:19395-5746TehranIran

In this paper we are concerned with absolute,relative and Tate Tor *** the first part of the paper we generalize a result of Avramov and Martsinkovsky by using the Auslander-Buchweitz approximation theory,and obtain a new exact sequence connecting absolute Tor modules with relative and Tate Tor *** the second part of the paper we consider a depth equality,called the depth formula,which has been initially introduced by Auslander and developed further by Huneke and *** an application of our main result,we generalize a result of Yassemi and give a new sufficient condition implying the depth formula to hold for modules of finite Gorenstein and finite injective dimension.

关键词： Depth formula homological dimensions absolute relative and Tate Tor modules semidualizing modules