检索结果-内蒙古大学图书馆

IEEE/LEOS International Conference on Optical MEMS

作者： Yen-Sheng Lu Hongyi Xu Hanhong Gao C. Max Hsieh Baile Zhang Handong Sun George Barbastathis Department of Mechanical Engineering Massachusetts Institute of Technology Cambridge MA USA Division of Physics and Applied Physics School of Physical and Mathematical Sciences Nanyang Technological University Singapore Singapore Department of Electrical Engineering and Computer Science Massachusetts Institute of Technology Cambridge MA USA

We present the first ever design of bending adaptor based on transformation optics at near-infrared frequency (1550 nm). The Si-air nanograting structure with period

关键词： Silicon Nanostructures Etching Optical device fabrication Anisotropic magnetoresistance Optical waveguides

来源：评论

学校读者我要写书评

暂无评论

Influence of surface passivation on the friction and wear behavior of ultrananocrystalline diamond and tetrahedral amorphous carbon thin films

引用

Physical Review B 2012年第15期85卷 155448-155448页

作者： A. R. Konicek D. S. Grierson A. V. Sumant T. A. Friedmann J. P. Sullivan P. U. P. A. Gilbert W. G. Sawyer R. W. Carpick Physics & Astronomy Department University of Pennsylvania Philadelphia Pennsylvania 19104 USA Mechanical Engineering Department University of Wisconsin-Madison Madison Wisconsin 53706 USA Center for Nanoscale Materials Argonne National Laboratory Argonne Illinois 60439 USA Sandia National Laboratory Albuquerque New Mexico 87185 USA Physics Department University of Wisconsin-Madison Madison Wisconsin 53706 USA Mechanical and Aerospace Engineering Department University of Florida Gainesville Florida 32611 USA Mechanical Engineering and Applied Mechanics University of Pennsylvania Philadelphia Pennsylvania 19104 USA

Highly sp3-bonded, nearly hydrogen-free carbon-based materials can exhibit extremely low friction and wear in the absence of any liquid lubricant, but this physical behavior is limited by the vapor environment. The effect of water vapor on friction and wear is examined as a function of applied normal force for two such materials in thin film form: one that is fully amorphous in structure (tetrahedral amorphous carbon, or ta-C) and one that is polycrystalline with <10 nm grains [ultrananocrystalline diamond (UNCD)]. Tribologically induced changes in the chemistry and carbon bond hybridization at the surface are correlated with the effect of the sliding environment and loading conditions through ex situ, spatially resolved near-edge x-ray absorption fine structure (NEXAFS) spectroscopy. At sufficiently high relative humidity (RH) levels and/or sufficiently low loads, both films quickly achieve a low steady-state friction coefficient and subsequently exhibit low wear. For both films, the number of cycles necessary to reach the steady-state is progressively reduced for increasing RH levels. Worn regions formed at lower RH and higher loads have a higher concentration of chemisorbed oxygen than those formed at higher RH, with the oxygen singly bonded as hydroxyl groups (C-OH). While some carbon rehybridization from sp3 to disordered sp2 bonding is observed, no crystalline graphite formation is observed for either film. Rather, the primary solid-lubrication mechanism is the passivation of dangling bonds by OH and H from the dissociation of vapor-phase H2O. This vapor-phase lubrication mechanism is highly effective, producing friction coefficients as low as 0.078 for ta-C and 0.008 for UNCD, and wear rates requiring thousands of sliding passes to produce a few nanometers of wear.

关键词： SURFACE passivation FRICTION NANOCRYSTALS DIAMONDS CARBON films MOLECULAR structure WATER vapor

来源：评论

学校读者我要写书评

暂无评论

Towards human-robot teams: Model-based analysis of human decision making in two-alternative choice tasks with social feedback

Towards human-robot teams: Model-based analysis of human dec...

引用

作者： Stewart, Andrew Cao, Ming Nedic, Andrea Tomlin, Damon Leonard, Naomi Department of Mechanical and Aerospace Engineering Princeton University Princeton NJ 08544 United States Applied Physics Laboratory University of Washington Seattle WA 98105-6698 United States University of Groningen 9700 AK Groningen Netherlands Department of Electrical Engineering Princeton University Princeton NJ 08544 United States Princeton Consultants Princeton NJ 08540 United States Neuroscience Institute Princeton University Princeton NJ 08544 United States

With a principled methodology for systematic design of human-robot decision-making teams as a motivating goal, we seek an analytic, model-based description of the influence of team and network design parameters on decision-making performance. Given that there are few reliably predictive models of human decision making, we consider the relatively well-understood two-alternative choice tasks from cognitive psychology, where individuals make sequential decisions with limited information, and we study a stochastic decision-making model, which has been successfully fitted to human behavioral and neural data for a range of such tasks. We use an extension of the model, fitted to experimental data from groups of humans performing the same task simultaneously and receiving feedback on the choices of others in the group. First, we show how the task and model can be regarded as a Markov process. Then, we derive analytically the steady-state probability distributions for decisions and performance as a function of model and design parameters such as the strength and path of the social feedback. Finally, we discuss application to human-robot team and network design and next steps with a multirobot testbed. © 2011 IEEE.

关键词： Decision making

来源：评论

学校读者我要写书评

暂无评论

Model reduction for agent-based social simulation: Coarse-graining a civil violence model

引用

Physical Review E 2012年第6期85卷 066106-066106页

作者： Yu Zou Vladimir A. Fonoberov Maria Fonoberova Igor Mezic Ioannis G. Kevrekidis Department of Chemical and Biological Engineering and Program in Applied and Computational Mathematics Princeton University Princeton New Jersey 08544 USA Aimdyn Inc. 1919 State Street Suite 207 Santa Barbara California 93101 USA Department of Mechanical Engineering University of California Santa Barbara Santa Barbara California 93106 USA

Agent-based modeling (ABM) constitutes a powerful computational tool for the exploration of phenomena involving emergent dynamic behavior in the social sciences. This paper demonstrates a computer-assisted approach that bridges the significant gap between the single-agent microscopic level and the macroscopic (coarse-grained population) level, where fundamental questions must be rationally answered and policies guiding the emergent dynamics devised. Our approach will be illustrated through an agent-based model of civil violence. This spatiotemporally varying ABM incorporates interactions between a heterogeneous population of citizens [active (insurgent), inactive, or jailed] and a population of police officers. Detailed simulations exhibit an equilibrium punctuated by periods of social upheavals. We show how to effectively reduce the agent-based dynamics to a stochastic model with only two coarse-grained degrees of freedom: the number of jailed citizens and the number of active ones. The coarse-grained model captures the ABM dynamics while drastically reducing the computation time (by a factor of approximately 20).

关键词： VIOLENCE SOCIAL dynamics STOCHASTIC models CITIZENS SOCIAL interaction DEGREES of freedom

来源：评论

学校读者我要写书评

暂无评论

A dynamic programming based improvement heuristic for a repetitive routing problem of grasp-and-delivery robots

A dynamic programming based improvement heuristic for a repe...

引用

作者： Shurbevski, Aleksandar Karuno, Yoshiyuki Nagamochi, Hiroshi Graduate School of Science and Technology Kyoto Institute of Technology Matsugasaki Sakyo-ku Kyoto-shi Kyoto 606-8585 Japan Department of Mechanical and System Engineering Kyoto Institute of Technology Matsugasaki Sakyo-ku Kyoto-shi Kyoto 606-8585 Japan Department of Applied Mathematics and Physics Kyoto University Yoshida-honmachi Sakyo-ku Kyoto-shi Kyoto 606-8501 Japan

We consider a repetitive routing problem of a single grasp-and-delivery robot used on a printed circuit board (PCB) assembly line. The robot arranges n identical pins from their current configuration to the next required one by transferring at most one pin at a time. The pins support a PCB from underneath to prevent it from overbending, while an automated manipulator embeds electronic parts in the PCB from above. Given an initial configuration of pins and a sequence of m required configurations, the problem asks to find a transfer route of the robot that minimizes the route length over all m transitions. A polynomial time approximation algorithm with factor two has been proposed by the authors to the problem. In this paper, we design a dynamic programming (DP) procedure to improve its empirical performance, and also conduct numerical experiments to show how well the proposed DP procedure performs. Copyright © 2012 by JSME.

关键词： Approximation algorithms

来源：评论

学校读者我要写书评

暂无评论

Dynamic modelling for thermoelastic Cosserat rod

Dynamic modelling for thermoelastic Cosserat rod

引用

23rd International Congress of Theoretical and applied Mechanics

作者： Dengqing Cao Mitao Song Robin W.Tucker Weidong Zhu Dongsheng Liu Wenhu Huang School of Astronautics Harbin Institute of Technology Department of Physics Lancaster UniversityLancasterUK Department of Mechanical Engineering University of MarylandBaltimore CountyBaltimoreUSA Applied Mathematics Department Nanjing University of Science and Technology

＜正＞A thermoelastic Cosserat rod with a heat flux along the length is modeled based on simple Cosserat rod *** Kirchhoff constitutive relations included thermal effects are obtained using the first law of thermodynamic by defining a free *** thermal dissipation power is estimated by Clausius-Duhem inequality. Nonlinear dynamic equations of thermoelastic Cosserat rod

关键词：

来源：评论

学校读者我要写书评

暂无评论

Studies of Nanomechanical Properties of Pulsed Laser Deposited NbN films on Si Using Nanoindentation

引用

MRS Online Proceedings Library (OPL) 2012年第1期1424卷 mrsf11-1424-ss07-64-mrsf11-1424-ss07-64页

作者： M. A. Mamun A. H. Farha Y. Ufuktepe H. E. Elsayed-Ali A. A. Elmustafa Department of Mechanical and Aerospace Engineering Old Dominion University Norfolk Virginia 23529 USA Applied Research Center Jefferson National Accelerator Facility Newport News Virginia 23606 USA Department of Electrical and Computer Engineering Old Dominion University Norfolk Virginia 23529 USA Department of Physics Cukurova University Adana 01330 TURKEY

Nanomechanical and structural properties of pulsed laser deposited niobium nitride thin films were investigated using X-ray diffraction, atomic force microscopy, and nanoindentation. NbN film reveals cubic δ-NbN structure with the corresponding diffraction peaks from the (111), (200), and (220) planes. The NbN thin films depict highly granular structure, with a wide range of grain sizes that range from 15-40 nm with an average surface roughness of 6 nm. The average modulus of the film is 420±60 GPa, whereas for the substrate the average modulus is 180 GPa, which is considered higher than the average modulus for Si reported in the literature due to pile-up. The hardness of the film increases from an average of 12 GPa for deep indents (Si substrate) measured using XP CSM and load control (LC) modes to an average of 25 GPa measured using the DCM II head in CSM and LC modules. The average hardness of the Si substrate is 12 GPa.

关键词： nano-indentation crystallographic structure grain size

来源：评论

学校读者我要写书评

暂无评论

Laminar flame speeds, flammability limits, and flame/reaction zone thicknesses for a surrogate kerosene fuel at engine operating conditions 50

Laminar flame speeds, flammability limits, and flame/reactio...

引用

50th AIAA Aerospace Sciences Meeting Including the New Horizons Forum and Aerospace Exposition

作者： Colket III, Meredith B. Zeppieri, Stephen P. Smooke, Mitchell D. Kim, Won Wook Thermal Fluid Sciences United Technologies Research Center MS 129-29 East Hartford CT 06108 United States Department of Mechanical Engineering and Materials Science and Applied Physics Yale University New Haven CT 06511 United States Pratt and Whitney East Hartford CT 06108 United States GE Energy Greenville SC United States

ISBN: (数字)9781600869365

Values of laminar flame speed, flame thickness, and reaction zone thickness have been computed for premixed flames of a surrogate kerosene fuel using a detailed chemical kinetics mechanism and associated thermochemistry and transport properties from the literature. Computations were performed at stoichiometric conditions throughout a range of rig and engine operating conditions. In addition, for selected points, computations were performed over the equivalence ratio range of 0.5 to 2.2. Radiation losses were not treated. Literature data on flammability limits were collected for a variety of fuels and used to develop a correlation that was extrapolated to engine conditions. The results for both the lean and rich limits are in reasonable agreement with the computed flame speeds, extrapolated to zero flame speed. From these computed data sets and the flammability limits, correlations were developed for flame speeds, flame (thermal zone) thicknesses, and reaction zone thicknesses as a function of temperature (400-1000K), pressure (1-35 atmospheres), and equivalence ratio (lean to rich limits). Reaction zone thicknesses are found to be about 50% of the thermal zone thickness, significantly larger than those reported in an earlier study. This relatively large reaction zone thickness suggests that the threshold Karlovitz number for flame extinction is closer to 4 rather than 100 as inferred from the earlier estimate of the relative reaction zone thickness. The lower value is consistent with experimental determinations of flame quenching. Copyright © 2012 by United Technologies Corporation.

关键词： Kerosene

来源：评论

学校读者我要写书评

暂无评论

Density-decomposed orbital-free density functional theory for covalently bonded molecules and materials

引用

Physical Review B 2012年第23期86卷 235109-235109页

作者： Junchao Xia Emily A. Carter Department of Mechanical and Aerospace Engineering Princeton University Princeton New Jersey 08544-5263 USA Program in Applied and Computational Mathematics and Andlinger Center for Energy and the Environment Princeton University Princeton New Jersey 08544-5263 USA

We propose a density decomposition scheme using a Wang-Govind-Carter- (WGC-) based kinetic energy density functional (KEDF) to accurately and efficiently simulate various covalently bonded molecules and materials within orbital-free (OF) density functional theory (DFT). By using a local, density-dependent scale function, the total density is decomposed into a highly localized density within covalent bond regions and a flattened delocalized density, with the former described by semilocal KEDFs and the latter treated by the WGC KEDF. The new model predicts reasonable equilibrium volumes, bulk moduli, and phase-ordering energies for various semiconductors compared to Kohn-Sham (KS) DFT benchmarks. The decomposition formalism greatly improves numerical stability and accuracy, while retaining computational speed compared to simply applying the original WGC KEDF to covalent materials. The surface energy of Si(100) and various diatomic molecule properties can be stably calculated and also agree well with KSDFT benchmarks. This linear-scaled, computationally efficient, density-partitioned, multi-KEDF scheme opens the door to large-scale simulations of molecules, semiconductors, and insulators with OFDFT.

关键词： PHYSICAL sciences research MOLECULES SEMICONDUCTORS BENCHMARKING (Management) CRYSTALS SURFACE energy COVALENT bonds (Chemistry)

来源：评论

学校读者我要写书评

暂无评论

Corrosion- and damage-resistant nitride coatings for steel

Corrosion- and damage-resistant nitride coatings for steel

引用

作者： Ahmed, Mohammad Shoeb Munroe, Paul Jiang, Zhong-Tao Zhao, Xiaoli Wajrak, Magdalena Guo, Hua Rickard, William Xie, Zonghan School of Engineering Edith Cowan University Joondalup WA 6027 Australia School of Materials Science and Engineering University of New South Wales Kensington NSW 2052 Australia School of Engineering and Energy Murdoch University Murdoch WA 6150 Australia School of Natural Sciences Edith Cowan University Joondalup WA 6027 Australia Department of Imaging and Applied Physics Curtin University of Technology Bentley WA 6102 Australia School of Mechanical Engineering University of Adelaide Adelaide SA 5005 Australia

Ceramic coatings of distinct microstructures, namely TiSiN and CrN, were deposited on tool steels. The corrosion resistance of the coated steels was measured. Following nanoindentation, immersion tests were conducted in 70% HNO3 solution for 96 h. Deformed CrN, where deformation occurred through shear sliding of columnar grains, was insensitive to corrosion attack. In contrast, open cracks formed in the indented TiSiN coating, serving as pathway for reactive agents to penetrate through the coatings. Finite element analysis was applied to evaluate the damage tolerance of the coatings and its impact on the corrosion resistance of the coated steels. © 2012 The American Ceramic Society.

关键词： Finite element method

来源：评论

学校读者我要写书评

暂无评论

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案：

请选择收藏分类：

通借通还

建议与咨询 留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案： 新增检索档案 确定 取消

请选择收藏分类： 新增自定义分类 确定 取消

通借通还

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

请选择保存的检索档案：

请选择收藏分类：