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Edge-Stress-Induced Warping of Graphene Sheets and Nanoribbons

Physical Review Letters 2008年第24期101卷 245501-245501页

作者： V. B. Shenoy C. D. Reddy A. Ramasubramaniam Y. W. Zhang Division of Engineering Brown University Providence Rhode Island 02912 USA Institute of High Performance Computing Singapore 138632 Program in Applied and Computational Mathematics Princeton University Princeton New Jersey 08544 USA Department of Materials Science and Engineering National University of Singapore Singapore 119260

We show that edge stresses introduce intrinsic ripples in freestanding graphene sheets even in the absence of any thermal effects. Compressive edge stresses along zigzag and armchair edges of the sheet cause out-of-plane warping to attain several degenerate mode shapes. Based on elastic plate theory, we identify scaling laws for the amplitude and penetration depth of edge ripples as a function of wavelength. We also demonstrate that edge stresses can lead to twisting and scrolling of nanoribbons as seen in experiments. Our results underscore the importance of accounting for edge stresses in thermal theories and electronic structure calculations for freestanding graphene sheets.

关键词： Nanoribbons

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Motion Planning for a Diesel Oxidation Catalyst Outlet Temperature

Motion Planning for a Diesel Oxidation Catalyst Outlet Tempe...

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2008 American Control Conference (ACC), vol.5

作者： Olivier Lepreux Yann Creff Nicolas Petit Technology Computer Science and Applied Mathematics Division IFP Lyon Vernaison France Centre Automatique et Systèmes Έcole Nationale Supérieure des Mines de Paris Paris France

A simple distributed parameter model is proposed for a Diesel Oxidation Catalyst (DOC). This model focuses on the propagation of the inlet temperature variations. The inlet-to-outlet temperature transfer function is computed. Its inversion allows to derive an open-loop control law corresponding to finite-time transitions of the outlet temperature. However, this straightforward strategy has some shortcomings. In particular, the obtained control histories are, for presented cases of engineering interest, inconsistent with the performance of available actuators. To address this issue, a constrained optimization approach is proposed. The results lead to a surprisingly simple control law.

关键词： Oxidation Temperature control Open loop systems Control systems Automotive engineering Vehicles Chemical analysis Delay Fluid flow Solids

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Parallel Implicit Solution of Diffusion-limited Radiation Transport

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Lecture Notes in Computational science and Engineering 2007年 55卷 579-586页

作者： Gropp, William D. Kaushik, Dinesh K. Keyes, David E. Smith, Barry F. Mathematics and Computer Science Division Argonne National Laboratory Argonne IL 60439 United States Department of Applied Physics and Applied Mathematics Columbia University NY NY 10027 United States

ISBN: (纸本)9783540344681

We present simulations of diffusion-limited transport in an initi ally cold medium of two different materials subjected to an impulsive radiative load, using a Newton-Krylov-Schwarz solver. The spatial discretization employs Galerkin finite elements with linear piecewise continuous basis functions over simplices in 2D and 3D. Temporal integration is via a solution-adaptive implicit Euler method. The code shows excellent domain-decomposed scalability on the Teragrid, BlueGene, and System X platforms. Comparing implementations for this application with. opintensive residual evaluation, we observe that an analytical Jacobian gives better performance (in terms of the overall execution time to solution) than a Jacobianfree approach.

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Optimisation of the antenna placement for an airport surveillance system

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International Journal of Mobile Network Design and Innovation 2007年第3-4期2卷 209-215页

作者： Formella, Arno Aguado-Agelet, Fernando Álvarez-Vázquez, Lino J. Martínez, Aurea Neufeldt, Holger Department of Computer Science University of Vigo Spain Department of Signal Theory and Communications University of Vigo Spain Department of Applied Mathematics University of Vigo Spain Thales ATM Navigation GmbH Air Systems Division Korntal-Münchingen 70825 Germany

We present an optimisation method for the placement of the antennas of a surveillance system on an airport which is based on multilateration. The system takes advantage of a signal sent by an aircraft (for example, SSR Mode S). The measurement error in such a multilateration system is influenced by the Dilution Of Precision (DOP) which reflects the geometry of the surveillance antennas in relation to the position of the aircraft. We derive the mathematical background for the DOP calculation where no timing information is available in the transmitted signal and introduce a gradient free optimisation method to optimise the locations at which to place the antennas. The cost function of the optimisation is based on the distribution of the DOP values in the regions where an aircraft is expected. Further propagation characteristics such as power delay profiles, directions of arrival and received power diagrams, help the engineer to fine tune the design of the system. Copyright © 2007 Inderscience Enterprises Ltd.

关键词： Cost functions

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Performance of a rack of liquid-cooled servers

Performance of a rack of liquid-cooled servers

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2007 Winter Meeting of the American Society of Heating, Refrigerating and Air-Conditioning Engineers

作者： Cader, Tahir McAllister, Herley Westra, Levi Regimbal, Kevin Marquez, Andres Government Computing Group Isothermal Systems Research Liberty Lake WA Applied Computer Science Department Computational Sciences and Mathematics Division Pacific North-west National Laboratory Richland WA

Electronics densification is continuing at an unrelenting pace at the server, rack, and facility level. With increasing facility density levels, airflow management has become a major challenge and concern. In an effort to deal with the resulting thermal management challenges, manufacturers are increasingly turning to liquid cooling as a practical solution. The majority of manufacturers have turned to liquid-cooled enclosed racks or rear-door heat exchangers, in which chilled water is delivered to the racks. Some manufacturers are now looking to cold plate cooling solutions that take the heat directly off problem components, such as the CPUs, to get it directly out of the facility. This paper describes work done at the Pacific Northwest National Labs (PNNL) under a Department of Energy-funded program titled "Energy Smart Data Center." An 8.2 kW (27,980 Btu/h) rack of HP rx2600 2U servers has been converted from air-cooling to liquid spray cooling (CPUs only). The rack has been integrated into PNNL's main cluster and subjected to a suite of acceptance tests. Under the testing, the spray-cooled CPUs ran an average of 10°C (18°F) cooler than the air-cooled CPUs. Other peripheral devices, such as the memory D1MMs, ran an average of 8°C (14.4°F) cooler, and the power pod board was measured at 15°C(27°F) cooler. Since installation in July 2005, the rack has been undergoing a one-year uptime and reliability investigation. As part of the investigation, the rack has been subjected to monthly robustness testing and ongoing performance evaluation while running applications such as High Performance Linpack, parts of the NASA NPB-2 Benchmark Suite, and NW Chem. The rack has undergone three months' worth of robustness testing with no major events. Including the robustness testing, the rack uptime is at 95.54% over 299 days. While undergoing application testing, no computational performance differences have been observed between the liquid-cooled and standard air-cooled racks. A sm

关键词： Electronic equipment

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A language-independent api for unstructured mesh access and manipulation

A language-independent api for unstructured mesh access and ...

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21st International Symposium on High Performance Computing Systems and Applications, HPCS 2007

作者： Ollivier-Gooch, Carl Diachin, Lori Freitag Shephard, Mark S. Tautges, Timothy Advanced Numerical Simulation Laboratory University of British Columbia Center for Applied Scientific Computing Lawrence Livermore National Laboratory Scientific Computing Research Center Rensselaer Polytechnic Institute Mathematics and Computer Science Division Argonne National Laboratory

ISBN: (纸本)0769528139

Software for numerical solution of partial differential equations requires accessing, manipulating, and often modifying information about the geometry of the computational domain, the mesh used for the simulation, and discrete data stored on that mesh. Typically, applications programmers would prefer to avoid the difficulty and complexity of creating their own modules for tasks like interacting with multiple geometric modelers, mesh adaptation, and optimization algorithms, rightly preferring instead to focus on the problem physics and on studying the physical results that the codeproduces. Ideally, these modules would be provided by experts in CAD modeling, meshing, and optimization, and written so that they can use the application's data regardless of the data structures used by the application. This paper describes a language- and data-structure-independent interface supporting query and modification of mesh data conforming to a general abstract data model. © 2007 IEEE.

关键词： Application programming interfaces (API)

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Promoting holistic problem-solving in mechanics pedagogy

Promoting holistic problem-solving in mechanics pedagogy

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114th Annual ASEE Conference and Exposition, 2007

作者： Papadopoulos, Chris Bostwick, Josh Dressel, Andrew University of Wisconsin Milwaukee United States Cornell University United States Department of Civil Engineering and Mechanics University of Wisconsin Milwaukee United States UWM Computer Science Engineering and Mathematics Scholarship Program Brazil Department of Theoretical and Applied Mechanics Cornell University United States

The authors propose three strategies that are designed to enhance students' understanding and problem-solving ability in introductory mechanics courses: (1) employing multiple-method problem-solving, in which students solve a given problem using more than one method;(2) organizing systems of linear equations into a standard "tabular" format which resembles matrix format;and (3) emphasizing the discussion and use of assumptions in problem-solving activities. The authors give a rationale for each strategy, present a review of several mechanics textbooks to determine the prevalence of these strategies, and provide local student performance data that, while as yet inconclusive, suggests a possible method for assessment of the strategies' efficacy. © American Society for Engineering Education, 2007.

关键词： Mechanics

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Algorithm Comparison for Real Time Knock Detection

Algorithm Comparison for Real Time Knock Detection

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International Conference on Acoustics, Speech, and Signal Processing (ICASSP)

作者： Stephan Ker Frederic Bonnardot Laurent Duval IFP Technology Computer Science and Applied Mathematics Division Institut Français du Pétrole Rueil-Malmaison France

This paper addresses the implementation and comparison of algorithms for real-time knock detection. Knock is an unwanted abnormal combustion process that may damage engines and limit their efficiency. For series vehicles, knock detection is generally obtained from knock sensors that capture other noise sources, thus requiring robust algorithms. In order to estimate the performance of time-frequency and Kalman filter based algorithms, a knock signal model is proposed and the algorithms are tested under various noise conditions. Experiments on modelled and real signals show the superiority of the recently developed S-method with respect to the extended Kalman filtering.

关键词： Engines Noise robustness Kalman filters Filtering Combustion Vehicle detection Testing Bandwidth Frequency Amplitude modulation

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Automatic template fit in comprehensive two dimensional gas chromatography images

Automatic template fit in comprehensive two dimensional gas ...

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DaLian Internationall Symposia and Exhibition on Chromatography (大连国际色谱学术报告会(第30届国际毛细管色谱学术报告会、第4届全二维气相色谱学术报告会、第16届全国色谱学术报告会))

作者： Celse, B Bertoncini, F Duval, L Adam, F Institut Frangais du Pétrole (IFP) Technology Computer Science and Applied Mathematics division B Institut Frangais du Pétrole (IFP) Physics and Analysis division BP3 69390 Vernaison-France Institut Francais du Pétrole (IFP) Technology Computer Science and Applied Mathematics division 1

Two-dimensional gas chromatography is a recent technology which is particularly efficient for detailed molecular ***, due to the novelty of the method and the lack of automated analysis tools, quantitative data processing is often performed ***, results are strongly user-dependent, time consuming and, consequently, relatively inaccurate.

关键词： GC × GC Automatic Template Fitting Peak Detection Comprehensive Two-Dimensional Gas Chromatography Quantitative Analysis Van Den Dool index

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Polychrom:a software for semi-automated quantitative GC × GC analysis with identification profiles

Polychrom:a software for semi-automated quantitative GC × G...

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作者： Celse, B Bertoncini, F Adam, F Brodusch, N Esnault, S Duval, L Institut Franc ais du Pétrole (IFP) Technology Computer Science and Applied Mathematics division Institut Francais du Pétrole (IFP) Physics and Analysis division BP3 69390 Vernaison-France Institut Francais du Pétrole (IFP) Technology Computer Science and.Applied Mathematics division 1

Comprehensive two-dimensional gas chromatography (GC × GC) is a recent chemical separation technique with particular efficiency for detailed molecular ***, due to the novelty of the method and the lack of automated analysis tools, quantitative data processing is often performed ***, results are strongly user-dependent and consequently time consuming and relatively *** Polychrom software for GC × GC visualization, quantitative analysis and data edition is proposed to alleviate the former drawbacks and to provide semi-automated product-based peak identification.

关键词： GC×GC Comprehensive two-dimensional gas chromatography Quantitative analysis software GC× GC analysis

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