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Asperity-based modification on theory of contact mechanics and rubber friction for self-affine fractal surfaces

Friction 2021年第6期9卷 1707-1725页

作者： Anahita EMAMI Seyedmeysam KHALEGHIAN saied taheri Texas State University 601 University DriveSan MarcosTexas 78666USA Virginia Polytechnic Institute and State University 460 Old Turner Street BlacksburgBlacksburgVirginia 24061USA

Modeling the real contact area plays a key role in every tribological process,such as friction,adhesion,and *** between two solids does not necessarily occur everywhere within the apparent contact *** the multiscale nature of roughness,Persson proposed a theory of contact mechanics for a soft and smooth solid in contact with a rigid rough *** this theory,he assumed that the vertical displacement on the soft surface could be approximated by the height profile of the substrate *** this assumption gives an accurate pressure distribution at the interface for complete contact,when no gap exists between two surfaces,it results in an overestimation of elastic energy stored in the material for partial contact,which typically occurs in many practical *** issue was later addressed by Persson by including a correction factor obtained from the comparison of the theoretical results with molecular dynamics *** paper proposes a different approach to correct the overestimation of vertical displacement in Persson’s contact theory for rough surfaces with self-affine fractal *** results are compared with the correction factor proposed by *** main advantage of the proposed method is that it uses physical parameters such as the surface roughness characteristics,material properties,sliding velocity,and normal load to correct the *** method is also implemented in the theory of rubber *** results of the corrected friction model are compared with *** results confirm that the modified model predicts the friction coefficient as a function of sliding velocity more accurately than the original model.

关键词： contact area rubber friction self-affine fractals tribology surface roughness

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A technical survey on tire-road friction estimation

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Friction 2017年第2期5卷 123-146页

作者： Seyedmeysam KHALEGHIAN Anahita EMAMI saied taheri Center for Tire Research(CenTiRe) Department of Mechanical Engineering Virginia Tech Blacksburg VA 24061 United States Department of Biomedical Engineering and Mechanics Virginia Tech Blacksburg VA 24061 United States

Lack of driver's knowledge about the abrupt changes in pavement's friction and poor performance of the vehicle's stability,traction,and ABS controllers on the low friction surfaces are the most important factors affecting car *** to its direct relation to vehicle stability,accurate estimation of tire-road friction is of interest to all vehicle and tire *** studies have been conducted in this field and researchers have used different tools and have proposed different *** literature survey introduces different approaches,which have been widely used to estimate the friction or other related parameters,and covers the recent literature that contains these *** emphasize of this review paper is on the algorithms and studies,which are more popular and have been repeated several *** focus has been divided into two main groups:experiment-based and model-based *** of these main groups has several sub-categories,which are explained in the next few *** summary tables are provided in which the overall feature of each approach is reviewed that gives the reader the general picture of different algorithms,which are widely used in friction estimation studies.

关键词： tire-road friction friction estimation model-based approach experiment-based approach

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基于半主动悬架侧倾力矩分配的侧向稳定性控制

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汽车工程 2016年第8期38卷 974-980,988页

作者：姚嘉凌任杉李智宏孙宁沈亮 saied taheri 南京林业大学汽车与交通工程学院南京210037 美国弗吉尼亚理工大学机械工程系美国布莱克斯堡24060

鉴于利用阻尼可调半主动悬架进行侧倾力矩分配控制缺乏完善的理论依据,根据调节阻尼以实现变刚度变阻尼悬架的思路,将磁流变减振器(MRD)半主动悬架视为变刚度变阻尼的悬架系统,无需对结构进行修改。建立了整车转向和悬架综合非线性模型... 详细信息

鉴于利用阻尼可调半主动悬架进行侧倾力矩分配控制缺乏完善的理论依据,根据调节阻尼以实现变刚度变阻尼悬架的思路,将磁流变减振器(MRD)半主动悬架视为变刚度变阻尼的悬架系统,无需对结构进行修改。建立了整车转向和悬架综合非线性模型,采用二次非线性轮胎模型以构建转向和悬架的关联,以中性转向为控制目标设计了侧倾力矩分配系数ε的非线性控制器,同时设计了3个模糊控制器以控制车身姿态,并将ε和车身姿态控制相结合,通过解耦运算得到控制4个车轮处磁流变减振器的控制力。仿真结果证实了所提控制策略的有效性。进行侧倾力矩分配控制的MRD半主动悬架不仅实现了良好的操纵稳定性,同时也保持了较好的平顺性。

关键词：半主动悬架磁流变减振器侧向稳定性变刚度变阻尼侧倾力矩分配

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基于车载导航的半主动悬架路况协调控制

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机械强度 2015年第4期37卷 587-592页

作者：姚嘉凌史文库陈志勇孙羽 saied taheri 南京林业大学汽车与交通工程学院南京210037 吉林大学汽车工程学院长春130022 美国弗吉尼亚理工大学机械工程系

难以获得路况信息是影响半主动悬架控制性能的重要因素。进行了依据车载导航系统探测和记忆路况信息,半主动悬架据此信息提前切换到相应控制策略或阻尼的初步研究。设计了半车天棚控制器,在随机路面采用天棚控制,当导航仪探测到前方障碍... 详细信息

难以获得路况信息是影响半主动悬架控制性能的重要因素。进行了依据车载导航系统探测和记忆路况信息,半主动悬架据此信息提前切换到相应控制策略或阻尼的初步研究。设计了半车天棚控制器,在随机路面采用天棚控制,当导航仪探测到前方障碍时,则提前通知悬架控制器切换到小阻尼状态,从而降低振动的峰值,提高行驶的平顺性。仿真计算证明了这种思路的有效性。研制了车载导航系统并设计了路况等级探测和记忆查找的策略,实车试验取得了和仿真相近的效果。

关键词：半主动悬架车载导航系统协调控制天棚控制控制切换

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Design, Construction and Validation of a Portable Tire Test Rig

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材料科学与工程（中英文A版） 2011年第5X期1卷 616-626页

作者： Brad Hopkins Derek Fox Josh Caffee Bryan Sides William Burke Michael Craft saied taheri Department of Mechanical Engineering Virginia Polytechnic Institute and State University Blacksburg VA USA Magneti Marelli Sanford NC USA General Motors MilJord MI USA Force Protection Industries Inc. Ladson SC USA Marine Advanced Research Inc. Richmond CA USA

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Microstructural evolution,mechanical properties,and corrosion resistance of a heat-treated Mg alloy for the bio-medical application

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Journal of Magnesium and Alloys 2019年第1期7卷 80-89页

作者： Mohammad Janbozorgi Kimia Karimi taheri Ali Karimi taheri Department of Materials Science and Engineering Sharif University of TechnologyAzadi Ave.TehranIran School of Medicine Shahid Beheshti University of Medical ScienceTehranIran

During the recent years,some Mg based alloys have extensively been considered as a new generation of degradable and absorbable bio-medical *** this work,the Mg-2Zn-1Gd-1Ca(wt%)alloy as a new metallic bio-material was produced by the casting process followed by the heat *** samples of the alloy were solution treated at temperatures of 500,550,and 600°C and then quench aged at temperatures of 125,150,and 175°*** results of SEM-EDS examinations indicated that the alloy microstructure consists ofα-Mg matrix and the Ca_(2)Mg_(6)Zn_(3)and Mg_(3)Gd_(2)Zn_(3)secondary *** regard to the results of Vickers hardness test,the temperatures of 500°C and 150°C were selected as the optimum solutionizing and aging temperatures,***,the dissolution of casting precipitates and production of lattice distortion occurring after the solution treatment led to the reduction in ultimate shear strength up to 21%.But,the precipitation hardening and morphological changes taking place during the aging treatment improved the ultimate shear strength up to 32%.Furthermore,the results of electro-chemical and weight-loss measurements in a simulated body fluid indicated that the heat-treated alloy is a promising candidate for the Mg based alloys recently considered for the bio-medical applications.

关键词： Mg alloys Bio-medical applications Microstructural evolution Mechanical properties Corrosion resistance

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Partial oxidation of methane in Ba_(0.5)Sr_(0.5)Co_(0.8)Fe_(0.1)Ni_(0.1)O_(3-δ) ceramic membrane reactor

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Journal of Natural Gas Chemistry 2012年第5期21卷 519-525页

作者： Ensieh Ganji Babakhani Jafar Towfighi Zahra taheri Ali Nakhaei Pour Majid Zekordi Ali taheri Gas Department Research Institute of Petroleum Industry(RIPI)14665-137TehranIran Chemical Engineering Department Engineering FacultyUniversity of Tarbiat Modares14115-111TehranIran Chemistry and petrochemical Department Research Institute of Petroleum Industry(RIPI)14665-137TehranIran

Ba0.5Sr0.5Co0.8Fe0.1Ni0.1O3δ（BSCFNiO） perovskite oxides were synthesized using a combined EDTA-citrate complexation method,and then pressed into disk and applied in a membrane *** performance of the BSCFNiO membrane reactor was studied for partial oxidation of methane over Ni/α-Al 2 O 3 *** time dependence of oxygen permeation rate and catalytic performance of BSCFNiO membrane during the catalyst initiation stage were investigated at 850 *** unsteady state,oxygen permeation rate,methane conversion and CO selectivity were closely related to the state of the *** 300 min from the initial time,the reaction condition reached to steady state and oxygen permeation rate were obtained about 11.7cm 3 cm 2 min ***,the performance of membrane reactor was studied at the temperatures between 750 and 950 *** results demonstrated good performance for the membrane reactor,as CH 4 conversion and CO selectivity permeation rate reached 98% and 97.5%,respectively,and oxygen permeation rate was about 14.5 cm 3 cm 2 min 1 which was 6.8 times higher than that of air-helium *** of membrane surface by SEM after reaction showed that the original grains disappeared on both surfaces exposed to the air and reaction side,but XRD profile of the polished surface membrane indicated that the membrane bulk preserved the perovskite structure.

关键词： perovskite membrane reactor partial oxidation of methane

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On Zero Dynamics and Controllable Cyber-Attacks in Cyber-Physical Systems and Dynamic Coding Schemes as Their Countermeasures

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IEEE/CAA Journal of Automatica Sinica 2024年第11期11卷 2191-2203页

作者： Mahdi taheri Khashayar Khorasani Nader Meskin the Department of Electrical and Computer Engineering Concordia University the Department of Electrical Engineering Qatar University

In this paper, we study stealthy cyber-attacks on actuators of cyber-physical systems(CPS), namely zero dynamics and controllable attacks. In particular, under certain assumptions, we investigate and propose conditions under which one can execute zero dynamics and controllable attacks in the CPS. The above conditions are derived based on the Markov parameters of the CPS and elements of the system observability matrix. Consequently, in addition to outlining the number of required actuators to be attacked, these conditions provide one with the minimum system knowledge needed to perform zero dynamics and controllable cyber-attacks. As a countermeasure against the above stealthy cyber-attacks, we develop a dynamic coding scheme that increases the minimum number of the CPS required actuators to carry out zero dynamics and controllable cyber-attacks to its maximum possible value. It is shown that if at least one secure input channel exists, the proposed dynamic coding scheme can prevent adversaries from executing the zero dynamics and controllable attacks even if they have complete knowledge of the coding system. Finally, two illustrative numerical case studies are provided to demonstrate the effectiveness and capabilities of our derived conditions and proposed methodologies.

关键词： Controllable attacks cyber-physical systems(CPS) dynamic coding zero dynamics attacks stealthy cyber-attacks

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Specimen aspect ratio and progressive field strain development of sandstone under uniaxial compression by three-dimensional digital image correlation

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Journal of Rock Mechanics and Geotechnical Engineering 2017年第4期9卷 599-610页

作者： H. Munoz A. taheri Deep Exploration Technologies Cooperative Research Centre (DET CRC) Export Park Adelaide Airport Adelaide SA 5950 Australia School of Civil Environmental & Mining Engineering The University of Adelaide Adelaide SA 5005 Australia

The complete stress-strain characteristics of sandstone specimens were investigated in a series of quasistatic monotonic uniaxial compression *** patterns development during pre-and post-peak behaviours in specimens with different aspect ratios was also *** stress,post-peak portion of stress-strain,brittleness,characteristics of progressive localisation and field strain patterns development were affected at different extents by specimen aspect *** patterns of the rocks were obtained by applying three-dimensional(3D) digital image correlation(DIC) *** conventional strain measurement using strain gauges attached to specimen,3D DIC allowed not only measuring large strains,but more importantly,mapping the development of field strain throughout the compression test,*** pre-and post-peak *** strain development in the surface of rock specimen suggests that strain starts localising progressively and develops at a lower rate in pre-peak ***,in post-peak regime,strains increase at different rates as local deformations take place at different extents in the vicinity and outside the localised *** extent of localised strains together with the rate of strain localisation is associated with the increase in rate of strength *** localisation and local inelastic unloading outside the localised zone both feature post-peak regime.

关键词： Uniaxial compression test Aspect ratio Strain patterns Digital image correlation(DIC)

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Quantification of grain boundary effects on the geometrically necessary dislocation density evolution and strain hardening of polycrystalline Mg-4Al using in situ tensile testing in scanning electron microscope and HR-EBSD

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Journal of Magnesium and Alloys 2024年第5期12卷 1815-1829页

作者： Eunji Song Mohsen taheri Andani Amit Misra Department of Materials Science and Engineering University of MichiganAnn ArborMI 48109USA Department of Mechanical Engineering University of MichiganAnn ArborMI 48109USA Department of Mechanical Engineering Texas A&M UniversityCollege StationTX 77843USA

In situ tensile testing in a scanning electron microscope(SEM)in conjunction with high-resolution electron backscatter diffraction(HR-EBSD)under load was used to characterize the evolution of geometrically necessary dislocation(GND)densities at individual grain boundaries as a function of applied strain in a polycrystalline Mg-4Al *** increase in GND density was investigated at plastic strains of 0%,0.6%,2.2%,3.3% from the area including 76 grains and correlated with(i)geometric compatibility between slip systems across grain boundaries,and(ii)plastic *** develop expressions for the grain boundary GND density evolution as a function of plastic strain and plastic incompatibility,from which uniaxial tensile stress-strain response of polycrystalline Mg-4Al are computed and compared with experimental *** findings in this study contribute to understanding the mechanisms governing the strain hardening response of single-phase polycrystalline alloys and more reliable prediction of mechanical behaviors in diverse microstructures.

关键词： Mg-Al alloys Grain boundaries Geometrically necessary dislocations Strain gradient plasticity HR-EBSD

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