检索结果-内蒙古大学图书馆

2002 IEEE/ACM Conference on Supercomputing, SC 2002

作者： Kikuchi, Hideaki Kalia, Rajiv K. Nakano, Aiichiro Vashishta, Priya Iyetomi, Hiroshi Ogata, Shuji Kouno, Takahisa Shimojo, Fuyuki Tsuruta, Kenji Saini, Subhash Computer Science Department Department of Materials Science Department of Physics and Astronomy Department of Biomedical Engineering University of Southern California United States Concurrent Computing Laboratory for Materials Simulations Department of Computer Science Department of Physics and Astronomy Louisiana State University United States Department of Physics Niigata University Japan Department of Applied Sciences Yamaguchi University Japan Faculty of Integrated Arts and Sciences Hiroshima University Japan Department of Electrical and Electronic Engineering Okayama University Japan IT Modeling and Simulation NASA Ames Research Center United States

ISBN: (纸本)076951524X

A multidisciplinary, collaborative simulation has been performed on a Grid of geographically distributed PC clusters. The multiscale simulation approach seamlessly combines i) atomistic simulation based on the molecular dynamics (MD) method and ii) quantum mechanical (QM) calculation based on the density functional theory (DFT), so that accurate but less scalable computations are performed only where they are needed. The multiscale MD/QM simulation code has been Grid-enabled using i) a modular, additive hybridization scheme, ii) multiple QM clustering, and iii) computation/communication overlapping. The Gridified MD/QM simulation code has been used to study environmental effects of water molecules on fracture in silicon. A preliminary run of the code has achieved a parallel efficiency of 94% on 25 PCs distributed over 3 PC clusters in the US and Japan, and a larger test involving 154 processors on 5 distributed PC clusters is in progress. © 2002 IEEE.

关键词： Density functional theory

来源：评论

学校读者我要写书评

暂无评论

Spin-Orbit Coupling, Antilocalization, and Parallel Magnetic Fields in Quantum Dots

引用

Physical Review Letters 2002年第27期89卷 276803-276803页

作者： D. M. Zumbühl J. B. Miller C. M. Marcus K. Campman A. C. Gossard Department of Physics Harvard University Cambridge Massachusetts 02138 Division of Engineering and Applied Sciences Harvard University Cambridge Massachusetts 02138 Department of Electrical and Computer Engineering University of California Santa Barbara California 93106

We investigate antilocalization due to spin-orbit coupling in ballistic GaAs quantum dots. Antilocalization that is prominent in large dots is suppressed in small dots, as anticipated theoretically. Parallel magnetic fields suppress both antilocalization and also, at larger fields, weak localization, consistent with random matrix theory results once orbital coupling of the parallel field is included. In situ control of spin-orbit coupling in dots is demonstrated as a gate-controlled crossover from weak localization to antilocalization.

关键词： .consistent crossover Spin-Orbit orbital coupling

来源：评论

学校读者我要写书评

暂无评论

Development of Ku-band frequency-doubling coaxial gyroklystrons for accelerator applications

Development of Ku-band frequency-doubling coaxial gyroklystr...

引用

International Conference on Vacuum Electronics

作者： W. Lawson B. Hogan S. Gouveia B. Huebschman V.L. Granatstein Department of Electrical and Computer Engineering and Institute for Research in Electronics and Applied Physics University of Maryland College Park MD USA

ISBN: (纸本)0780372565

Summary form only given. At the University of Maryland, we have been exploring the possibility of using gyroklystrons to drive advanced linear colliders above X-band. We have designed and tested a high-gain four-cavity frequency-doubling system to enable us to use a phase-stable TWT driver. We have also designed an output waveguide system which transforms the power from the output waveguide and equally divides it into two standard WR62 rectangular waveguides. The scheme involves a rippled wall converter to convert the TE/sub 02/ mode to the TE/sub 01/ mode, then a custom converter to produce the TE/sub 20/ mode in the rectangular guide, followed by linear tapers and a standard bifurcation. We hope to use this transport system to energize and test Ku-band accelerator structures. In this paper, we present the experimental results of our four-cavity frequency doubling coaxial gyroklystron. The beam voltage and current are 460 kV and 540 A, respectively, and the applied magnetic field is about 5 kG. The expected interaction efficiency and gain at our design point are 34% and 61 dB, respectively. We also present design and test results for a number of other subsystems. We compare the theoretical calculations with the cold test results for each of the components used in the output waveguide system and present amplitude and phase balance measurements for the two output rectangular waveguides. Finally, we describe efforts to improve beam quality via modifications in emitter design and manufacturing.

关键词： Frequency Coaxial components Klystrons Rectangular waveguides System testing Tellurium Waveguide components Waveguide theory Bifurcation Life estimation

来源：评论

学校读者我要写书评

暂无评论

Frequency dependent characteristics of radiation from a voltage source on a covered microstrip line

Frequency dependent characteristics of radiation from a volt...

引用

Microwave, MTT-S International Symposium

作者： W.L. Langston J.T. Williams D.R. Jackson F. Mesa Department of Electrical and Computer Engineering University of Houston Houston TX USA Department of Applied Physics 1 University of Seville Seville Spain

The fields radiated from the currents induced on a covered microstrip transmission line by a finite-gap voltage source are presented. The character of these radiated fields has been examined in detail as the frequency is varied. It is shown that there is a smooth transition in the total radiation field from the spectral-gap region at lower frequencies to higher frequencies where a physical leaky mode exists. A characteristic leakage beam develops gradually as the frequency increases. When the leakage beam first develops, the observed radiation angle is greater than that predicted by the leaky mode alone. Crosstalk radiation can be significant even before the leaky mode becomes physical.

关键词： Frequency dependence Voltage Microstrip Strips Fourier transforms Crosstalk Stripline Transmission lines Interference Nonhomogeneous media

来源：评论

学校读者我要写书评

暂无评论

The danger of high-frequency spurious effects on wide microstrip line

The danger of high-frequency spurious effects on wide micros...

引用

Microwave, MTT-S International Symposium

作者： F. Mesa D.R. Jackson Department of Applied Physics 1 University of Seville Seville Spain Department of Electrical and Computer Engineering University of Houston Houston TX USA

It has been found that remarkably severe spurious effects can occur in the current excited on microstrip line at moderate to high frequency, when the strip is wide (w/h > 3). This newly observed effect occurs because one or more leaky modes approaches the branch point at k/sub 0/ in the complex longitudinal wavenumber plane. This effect only occurs when the strip is wide. This effect can be disastrous, since the continuous-spectrum part of the current then decays very slowly with distance from the source, so that the total strip current excited by the source exhibits spurious oscillations out to very large distances from the source. An approximate design rule for predicting this effect is given, which is accurate for wide strips (w/h > 6).

关键词： Frequency Strips Interference Voltage Microstrip components physics computing Crosstalk Analytical models Geometry Permittivity

来源：评论

学校读者我要写书评

暂无评论

Acceleration element for femtosecond electron pulse compression

引用

Physical Review E 2002年第4期65卷 046502-046502页

作者： Bao-Liang Qian Hani E. Elsayed-Ali Department of Electrical and Computer Engineering Old Dominion University Norfolk Virginia 23529-0256 Department of Applied Physics National University of Defense Technology Changsha 410073 Hunan People’s Republic of China

An acceleration element is proposed for compressing the electron pulse duration in a femtosecond photoelectron gun. The element is a compact metal cavity with curved-shaped walls. An external voltage is applied to the cavity where a special electric field forms in such a way that the slow electrons in the electron pulse front are accelerated more than the fast electrons, and consequently the electron pulse duration will be compressed. The distribution of the electric field inside the acceleration cavity is analyzed for the geometry of the cavity. The electron dynamics in this acceleration cavity is also investigated numerically. Numerical results show that the electron pulse front and pulse duration can be improved by compensating for the effects of space charge and the initial energy spread of photoelectrons with a Lambertian angular distribution. Depending on the design parameters and the shape of the electron pulse, for a femtosecond electron gun with an electron energy of 30 keV, 103 electrons per pulse, and an electron drift length of 40 cm, the electron pulse duration can be reduced from 550 to 200 fs when using a compensating cavity with an average radius of 1.7 and 5.6 cm in length. Electron pulses shorter than 200 fs can be achieved if the length of the drift region is reduced.

关键词： Electron guns

来源：评论

学校读者我要写书评

暂无评论

A raman scattering study in relaxor Pb(Zn1/3 Nb 2/3)O3-PbTiO3 solid solutions

A raman scattering study in relaxor Pb(Zn1/3 Nb 2/3)O3-PbTiO...

引用

作者： Iwata, M. Tomisato, N. Orihara, H. Ohwa, H. Yasuda, N. Ishibashi, Y. Maeda, M. Suzuki, I. Department of Electrical and Computer Engineering Nagoya Institute of Technology Nagoya 466-8555 Japan Applied Physics Department Nagoya University Nagoya 464-8603 Japan Electric and Information Department Gifu University Gifu 501-1193 Japan Faculty of Communications Aichi Shukutoku University Aichi 480-1197 Japan

The temperature-concentration dependence of the low frequency models below 100cm - 1 in the solid solution system (1 - x ) Pb(Zn 1/3 Nb 2/3 )O 3 - x PbTiO 3 (0 &le x < 1) was measured by means of the Raman scattering experiment. It was found that the mode softening in the vicinity of the transition point is suppressed with increasing the PZN concentration and no softening of the lowest frequency mode is observed in the pure PZN. The temperature-concentration dependence of the lowest frequency optical mode was discussed. © 2002 Taylor & Francis.

关键词： Solid solutions

来源：评论

学校读者我要写书评

暂无评论

Single-Photon Tunneling via Localized Surface Plasmons

引用

Physical Review Letters 2002年第18期88卷 187402-187402页

作者： I. I. Smolyaninov A. V. Zayats A. Gungor C. C. Davis Electrical and Computer Engineering Department University of Maryland College Park Maryland 20742 Department of Pure and Applied Physics Queen's University of Belfast Belfast BT7 1NN United Kingdom Department of Physics Fatih University Istanbul Turkey

Strong evidence of a single-photon tunneling effect, a direct analog of single-electron tunneling, has been obtained in the measurements of light tunneling through individual subwavelength pinholes in a gold film covered with a layer of polydiacetylene. The transmission of some pinholes reached saturation because of the optical nonlinearity of polydiacetylene at a very low light intensity of a few thousand photons per second. This result is explained theoretically in terms of a “photon blockade,” similar to the Coulomb blockade phenomenon observed in single-electron tunneling experiments. Single-photon tunneling may find applications in the fields of quantum communication and information processing.

关键词： Photons

来源：评论

学校读者我要写书评

暂无评论

A Fokker-Planck model for a two-body problem

引用

AIP Conference Proceedings 2002年第1期617卷 340-371页

作者： M. M. Bierbaum R. I. Joseph R. L. Fry J. B. Nelson 1The Johns Hopkins University/Applied Physics Laboratory Laurel Maryland 20723 2Department of Electrical and Computer Engineering The Johns Hopkins University Baltimore Maryland 21218

The evolution of the state-of-knowledge of system regarding the time-varying state of a particle in the two-body problem is deterministically treated in classical mechanics where no uncertainties in initial conditions or acting forces are assumed. When such uncertainties exist, a Fokker-Planck equation can be formulated that describes the propagation in time of the probability density of possible positions and velocities of a particle. Both dissipative and dispersive forces can be present. This approach allows one to infer the coordinates of a particle in phase space as a function of time (both past and future) subject to acknowledged uncertainties. The Fokker-Planck equation is derived from knowledge of both the deterministic equations of motion and the probability distributions of acting forces. In the absence of uncertainties in acting forces, there are three conserved quantities that correspond to energy, total angular momentum, and the component of angular momentum in the direction of the rotation of the larger body (taken as the earth). The solutions for several cases are discussed. In the first case, gravity is absent while dispersive forces are present. An exact solution of the Fokker-Planck equation is given for this case. In a second case, gravity is present while dispersive forces are not. Here, the solution is time-independent, i.e., a conserved quantity and hence can be normalized. In a third case, both gravity and dispersive effects are present. A solution is derived through a perturbation of the functional corresponding to the exponentiated system energy. The perturbation solution is about the first-order moments of the energy function and thus is a temporal perturbation of the maximum entropy equilibrium distribution.

关键词：

来源：评论

学校读者我要写书评

暂无评论

A millimeter wave beam shaping phased antenna array 3

A millimeter wave beam shaping phased antenna array

引用

3rd International Conference on Microwave and Millimeter Wave Technology, ICMMT 2002

作者： Chang, Chia-Chan Liang, Cheng Deng, Bihe Domier, C.W. Luhmann, N.C. Park, Hyeon Munsat, T. Department of Electrical and Computer Engineering University of California DavisCA95616 United States Fodus Communications Inc. SunnyvaleCA94086 United States Department of Applied Science University of California DavisCA95616 United States Princeton Plasma Physics Laboratory Princeton University PrincetonNJ08543 United States

ISBN: (纸本)078037486X

A millimeter wave phased antenna array (PAA) serving as an electrically controlled "lens" is being developed for use in plasma imaging reflectometric diagnostics. To account for the rapid changes of the cutoff layer with plasma density variation, a true time delay (TTD) controlled phased antenna array (PAA) is being developed as an artificial lens with controllable focal length for launching the illumination beam of the microwave imaging reflectometry (NUR) system. Varactor diode loaded transmission lines, also called Nonlinear Delay Lines (NDL), are utilized in this electronic lens to control the time delays between each array element, and subsequently the wavefront of the probe beam. Proof of principle 1-D and 2-D PAAs have previously been demonstrated in beam steering systems. A 45 GHz monolithic NDL-based PAA is currently under development and will be installed on the National Spherical Torus Experiment (NSTX) in the near future. © 2002 IEEE.

关键词： Plasma density

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：