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Nonlinear dynamic response of beam and its application in nanomechanical resonator

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Acta Mechanica Sinica 2012年第1期28卷 190-200页

作者： Yin Zhang Yun Liu kevin D.Murphy State Key Laboratory of Nonlinear Mechanics Institute of MechanicsChinese Academy of Sciences100190 BeijingChina Faculty of Information and Automation Kunming University of Science and Technology650051 KunmingChina Department of Mechanical Engineering The University of ConnecticutStorrsCT 06269USA

Nonlinear dynamic response of nanomechanical resonator is of very important characteristics in its application. Two categories of the tension-dominant and curvaturedominant nonlinearities are analyzed. The dynamic nonlinearity of four beam structures of nanomechanical resonator is quantitatively studied via a dimensional analysis approach. The dimensional analysis shows that for the nanomechanical resonator of tension-dominant nonlinearity, its dynamic nonlinearity decreases monotonically with increasing axial loading and increases monotonically with the increasing aspect ratio of length to thickness; the dynamic nonlinearity can only result in the hardening effects. However, for the nanomechanical resonator of the curvature-dominant nonlinearity, its dynamic nonlinearity is only dependent on axial loading. Compared with the tension-dominant nonlinearity, the curvature-dominant nonlinearity increases monotonically with increasing axial loading; its dynamic nonlinearity

关键词： Resonator. Dynamic response. Dynamic nonlinearity - Dimensional analysis

Dynamic Damage Recovery for Web Databases

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Journal of Computer Science & Technology 2010年第3期25卷 548-561页

作者：朱虹付戈冯玉才 kevin Lü School of Computer Science and Technology Huazhong University of Science and Technology Brunel University

In the web context, there is an urgent need for a self-healing database system which has the ability to automatically locate and undo a set of transactions that are corrupted by malicious attacks. The metrics of survivability and availability require a database to provide continuous services during the period of recovery, which is referred to as dynamic recovery. In this paper, we present that an extended read operation from a corrupted data would cause damage spreading. We build a fine grained transaction log to record the extended read and write operations while user transactions are processing. Based on that, we propose a dynamic recovery system to implement the damage repair. The system captures damage spreading caused by extended read-write dependency between transactions. It also retains the execution results for blind write transactions and gives a solution to the issues of recovery conflicts caused by forward recovery. Moreover, a confinement activity is imposed on the in-repairing data to prevent a further damage propagation while the data recovery is processing. The performance evaluation in our experiments shows that the system is reliable and highly efficient.

关键词： dynamic recovery survivability availability

High temperature deformation and recrystallization behavior of magnesium bicrystals with 90°<1010>and 90°<1120>tilt grain boundaries

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Journal of Magnesium and Alloys 2024年第2期12卷 625-638页

作者： kevin Bissa Talal Al-Samman Dmitri A.Molodov Institute of Physical Metallurgy and Materials Physics RWTH Aachen University52056 AachenGermany International Research Organization for Advanced Science and Technology(IROAST) Kumamoto UniversityKumamoto 860-8555Japan

The deformation mechanisms and dynamic recrystallization(DRX)behavior of specifically grown bicrystals with a symmetric 90°and 90°tilt grain boundary,respectively,were investigated under deformation in plane strain compression at 200℃and 400℃.The microstructures were analyzed by panoramic optical microscopy and large-area electron backscatter diffraction(EBSD)orientation *** analysis employed a meticulous approach utilizing hundreds of individual,small EBSD maps with a small step size that were stitched together to provide comprehensive access to orientation and misorientation data on a macroscopic *** slip primarily governed the early stages of deformation at the two temperatures,and the resulting shear induced lattice rotation around the transverse direction(TD)of the *** existence of the grain boundary gave rise to dislocation pile-up in its vicinity,leading to much larger TD-lattice rotations within the boundary region compared to the *** increasing temperature,the deformation was generally more uniform towards the bulk due to enhanced dislocation mobility and more uniform stress *** recrystallization at 200℃was initiated in{1011}-compression twins at strains of 40%and *** 400℃,DRX consumed the entire grain boundary region and gradually replaced the deformed microstructure with progressing *** recrystallized grains displayed characteristic orientations,such that their c-axes were perpendicular to the TD and additionally scattered between 0°and 60°from the loading *** recrystallized grains displayed mutual rotations of up to 30°around the c-axes of the initial grains,forming a discernible basal fiber texture component,prominently visible in the{1120}pole *** is noteworthy that the deformation and DRX behaviors of the two analyzed bicrystals exhibited marginal variations in response to strain and deformation temperature.

关键词： Elevated deformation temperatures Plain strain compression Magnesium bicrystals Panorama EBSD Dynamic Recrystallization

Deformation behaviour of magnesium bicrystals with symmetrical 90°<1120>tilt grain boundaries analysed by large area EBSD mapping

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Journal of Magnesium and Alloys 2023年第5期11卷 1556-1566页

作者： kevin Bissa Talal Al-Samman Dmitri A.Molodov Institute of Physical Metallurgy and Materials Physics RWTH Aachen University52056AachenGermany International Research Organization for Advanced Science and Technology(IROAST) Kumamoto UniversityKumamoto 860-8555Japan

Grain boundaries play a significant role in the deformation of *** response to deformation is however not completely understood,particularly with respect to how they accommodate lattice rotation of adjoining crystallites by changing their structure and *** current study thus investigates the deformation behaviour of Mg bicrystals with 90°symmetric tilt boundary strained in plane-strain compression up to different final *** to the initial soft orientation of the two crystals,activation of basal slip in each crystal gave rise to lattice rotation around the transverse direction towards the compression direction of the *** of single EBSD maps with a small step size were obtained from the GB region and stitched together to produce large panoramic maps of a macroscopic *** very time-consuming,this technique has proven useful in clarifying the origin of the non-uniform deformation zones in the vicinity of the grain boundary and explains the mechanisms,by which the grain boundary was able to cope with the imposed strain before ***,several variants of extension twins were observed as an additional deformation mechanism despite having negative Schmid *** investigation of their resulting combined shear components with respect to the sample coordinate system revealed an alignment along the longitudinal direction of the channel-die,therefore justifying their nucleation.

关键词： Panorama EBSD Plain strain compression Lattice rotation Magnesium bicrystal Anomalous twins

Effect of abutment modeling on the seismic response ofbridge structures

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Earthquake Engineering and Engineering Vibration 2008年第4期7卷 395-402页

作者： Ady Aviram kevin R.Mackie Bozidar Stojadinovic Department of Civil and Environmental Engineering University of CaliforniaBerkeley Department of Civil and Environmental Engineering University of Central Florida

Abutment behavior significantly influences the seismic response of certain bridge structures. Specifically in the case of short bridges with relatively stiff superstructures typical of highway overpasses, embankment mobilization and inelastic behavior of the soil material under high shear deformation levels dominate the response of the bridge and its column bents. This paper investigates the sensitivity of bridge seismic response with respect to three different abutment modeling approaches. The abutment modeling approaches are based on three increasing levels of complexity that attempt to capture the critical components and modes of abutment response without the need to generate continuum models of the embankment, approach, and abutment foundations. Six existing reinforced concrete bridge structures, typical of Ordinary Bridges in California, are selected for the analysis. Nonlinear models of the bridges are developed in OpenSees. Three abutment model types of increasing complexity are developed for each bridge, denoted as roller, simplified, and spring abutments. The roller model contains only single-point constraints. The spring model contains discrete representations of backfill, bearing pad, shear key, and back wall behavior. The simplified model is a compromise between the efficient roller model and the comprehensive spring model. Modal, pushover, and nonlinear dynamic time history analyses are conducted for the six bridges using the three abutment models for each bridge. Comparisons of the analysis results show major differences in mode shapes and periods, ultimate base shear strength, as well as peak displacements of the column top obtained due to dynamic excitation. The adequacy of the three abutment models used in the study to realistically represent all major resistance mechanisms and components of the abutments, including an accurate estimation of their mass, stiffness, and nonlinear hysteretic behavior, is evaluated. Recommendations for abutment modeling

关键词： embankment backfill shear keys bearing pads nonlinear analysis

Influence of 3d transition-metal substitution on the oxygen reduction reaction electrocatalysis of ternary nitrides in acid

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Nano Research 2019年第9期12卷 2307-2312页

作者： kevin E. Fritz Yichen Yan Jin Suntivich Department of Material Science and Engineering Cornell UniversityIthacaNew York 14850USA Kavli Institute at Cornell for Nanoscale Science IthacaNew York 14850USA

The development of non-precious,acid-stable,oxygen reduction reaction(ORR)electrocatalysts can significantly aid the commercialization of proton exchange membrane fuel cells(PEMFCs).We report a survey of the ORR electrocatalysis on 3d metal substituted(M=Mn,Fe,Co)molybdenum and tungsten nitrides in acidic *** find that molybdate catalysts are more active than tungstates,with the specific activity depending on the chemistry of the substituted 3d *** both families,more electronegative 3d metals led to higher ORR activity(i.e.,Co>Fe>Mn).We attribute this result to the ability of the more electro negative 3d metal to withdraw electro ns from the Mo-or W-based active sites,effectively oxidizing the metal centers of the *** on our observation,future nitride ORR electrocatalysts can be further optimized by oxidizing the Mo sites further by,for example,addi ng eve n more electro negative dopa nt metals or in corporati ng anion vaca ncies.

关键词： nitrides electrocatalysis fuel cells oxygen reduction

Autonomic nerve development contributes to prostate cancer progression

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Asian Journal of Andrology 2013年第6期15卷 713-714页

作者： John Bauman kevin McVary Division of Urology Southern Illinois University School ofMedicine Springfield IL 62794 USA

In a significant translational study, Magnon et aL investigated the role that the auto-nomic nervous system plays in the develop-ment and spread of prostate cancer in both mice and human modds. The study shows different roles for both branches of the auto-nomic nervous system, with the sympathetic system promoting early stages of tumorigen-esis, and the parasympathetic system promot-ing cancer dlssemination. This information could lead to important new foundations for treatment, therapies and management of pro-state cancer.

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Overcoming the limitations of gallium oxide through heterogeneous integration

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Science China(Physics,Mechanics & Astronomy) 2021年第1期64卷 118-119页

作者： Yuhao Zhang kevin JChen Center for Power Electronics Systems Virginia Polytechnic and State UniversityBlacksburgVA24060USA Departmnet of Electronic and Computer Engineering The Hong Kong University of Science and TechnologyHong KongChina

Power electronics,processing over 50%of world's electric energy,enables very efficient electric energy conversion for a wide range of applications such as electric vehicles,data centers,autonomous driving,robotics and smart *** availability of low-cost,efficient,and reliable power semiconductor devices that can conduct high current,block high voltage,and switch at high frequencies are key to improving the performance of power electronics systems.

关键词： integration enable autonomous

Uses of probe-based confocal laser endomicroscopy:Responses to a question to practitioners

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World Journal of Gastroenterology 2011年第42期17卷 4739-4740页

作者： Navin Paul kevin A Ghassemi Division of Digestive Diseases Department of MedicineDavid Geffen School of Medicineat UCLA

Confocal laser endomicroscopy is a novel imaging technology,which allows realtime visualization and inter-pretation of microscopic details in live tissues. Although several potential uses have been identified for this technology,no data are available regarding its real-worlduses. We report the results of an email-based survey of experts in North America regarding their use of the technology.

关键词： Confocal laser endomicroscopy Expert opinlon