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The gas centrifuge and nuclear weapons proliferation

AIP Conference Proceedings 2014年第1期1596卷 210-218页

作者： Houston G. Wood Alexander Glaser R. Scott Kemp Mechanical and Aerospace Engineering Department University of Virginia Charlottesville Virginia USA Woodrow Wilson School of Public and International Affairs Program on Science Technology and Environmental Policy Princeton University Princeton New Jersey USA Nuclear Science and Engineering Department Massachusetts Institute of Technology Cambridge Massachusetts USA

Uranium enrichment by centrifugation is the basis for the quick and efficient production of nuclear fuel-or nuclear weapons.

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Use of spectroscopy for assessment of color discrimination in animal vision

Use of spectroscopy for assessment of color discrimination i...

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作者： Akkaynak, Derya Department of Mechanical Engineering Massachusetts Institute of Technology 77 Massachusetts Avenue Cambridge MA 02139 United States Applied Ocean Science and Engineering Woods Hole Oceanographic Institution 266 Woods Hole Road Woods Hole MA 02543 United States Program in Sensory Physiology and Behavior Marine Biological Laboratory 7 MBL Street Woods Hole MA 02543 United States

Animals use color vision for a number of tasks including food localization, object recognition, communication, and mate selection. For these and other specific behaviors involving the use of color cues, models that quantify color discriminability have been developed. These models take as input the photoreceptor spectral sensitivities of the animal and radiance spectra of the surfaces of interest. These spectra are usually acquired using spectroscopic instruments that collect point-by-point data and can easily yield signals contaminated with neighboring colors if not operated carefully. In this paper, I present an equation that relates the optical fiber diameter and numerical aperture to the measurement angle and distance needed to record uncontaminated spectra. I demonstrate its utility by testing the discriminability of two solid colors for the visual systems of a dichromatic ferret and a trichromatic frog in (1) a conspicuous scenario where the colors have little spectral overlap and (2) a perfect camouflage scenario where the spectra are identical. This equation is derived from geometrical optics and is applicable to spectroscopic measurements in all fields. © 2013 Optical Society of America.

关键词： Color

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Plasmofluidics: Plasmofluidics: Merging Light and Fluids at the Micro-/Nanoscale (Small 35/2015)

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Small 2015年第35期11卷

作者： Mingsong Wang Chenglong Zhao Xiaoyu Miao Yanhui Zhao Joseph Rufo Yan Jun Liu Tony Jun Huang Yuebing Zheng Department of Mechanical Engineering Materials Science and Engineering Program Texas Materials Institute The University of Texas at Austin Austin Texas 78712 USA Department of Physics Electro-Optics Graduate Program University of Dayton Dayton Ohio 45469 USA Google Inc. 1600 Amphitheatre Pkwy Mountain View CA 94043 USA Department of Engineering Science and Mechanics Department of Biomedical Engineering Materials Research Institute Huck Institute of Life Sciences The Pennsylvania State University University Park Pennsylvania 16802 USA Institute of Materials Research and Engineering Agency for Science Technology and Research (A*STAR) 3 Research Link Singapore 117602 Singapore

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Analysis of Magnet Layout in Circumferential and Axial Direction for Halbach PM Arrays

Analysis of Magnet Layout in Circumferential and Axial Direc...

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2014中国制导、导航与控制学术会议

作者： Ping He Zongxia Jiao Liang Yan Huisheng Liang Chin-Yin Chen I-Ming Chen Department of Automation Science and Electrical Engineering Beihang UniversityBeijing100191 China Institute of Advanced Manufacturing TechnologyNingbo Institute of Material Technology and EngineeringNingbo315201 China School of Mechanical and Aerospace EngineeringNanyang Technological University50 Nanyang AvenueSingapore

ISBN: (纸本)9781479946983

Permanent magnet (PM) array has great influence on flux field distribution of motor.A Halbach PM array is used in the motor of this paper,which not only increases the thrust output,but also decreases the mover mass.A new analytical model for magnetic flux density in circumferential direction is proposed in this paper based on equivalent surface current method,which could solve the flux density of X and Y component *** magnetic flux density in axial direction is formulated based on equivalent circuit *** two methods are both simple and convenient to analyze air-gap flux density in different *** finite element methods (FEM) and experimental results validate the analytical *** study is useful for quick analysis and design optimization of PM array in motor.

关键词： air gaps equivalent circuits finite element analysis magnetic flux permanent magnet motors permanent magnets FEM Halbach PM array air-gap flux density axial direction circumferential direction equivalent circuit method equivalent surface current method finite element method magnet layout analysis magnetic flux density motor flux field distribution permanent magnet array Air gaps Iron Magnetic circuits Magnetic flux density Magnetic levitation Stators

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Brownian motion of tethered nanowires

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Physical Review E 2014年第5期89卷 053010-053010页

作者： Sadao Ota Tongcang Li Yimin Li Ziliang Ye Anna Labno Xiaobo Yin Mohammad-Reza Alam Xiang Zhang NSF Nano-scale Science and Engineering Center (NSEC) 3112 Etcheverry Hall University of California Berkeley California 94720 USA Department of Mechanical Engineering University of California Berkeley California 94720 USA Material Sciences Division Lawrence Berkeley National Laboratory 1 Cyclotron Road Berkeley California 94720 USA

Brownian motion of slender particles near a boundary is ubiquitous in biological systems and in nanomaterial assembly, but the complex hydrodynamic interaction in those systems is still poorly understood. Here, we report experimental and computational studies of the Brownian motion of silicon nanowires tethered on a substrate. An optical interference method enabled direct observation of microscopic rotations of the slender bodies in three dimensions with high angular and temporal resolutions. This quantitative observation revealed anisotropic and angle-dependent hydrodynamic wall effects: rotational diffusivity in inclined and azimuth directions follows different power laws as a function of the length, ∼L−2.5 and ∼L−3, respectively, and is more hindered for smaller inclined angles. In parallel, we developed an implicit simulation technique that takes the complex wire-wall hydrodynamic interactions into account efficiently, the result of which agreed well with the experimentally observed angle-dependent diffusion. The demonstrated techniques provide a platform for studying the microrheology of soft condensed matters, such as colloidal and biological systems near interfaces, and exploring the optimal self-assembly conditions of nanostructures.

关键词： Brownian movement

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Design and Modeling of Tubular Flux-Switching Permanent Magnet Linear Motor

Design and Modeling of Tubular Flux-Switching Permanent Magn...

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2014中国制导、导航与控制学术会议

作者： Liang Yan Wei Li Zongxia Jiao Hongjie Hu Chin-Yin Chen I-Ming Chen School of Automation Science and Electrical Engineering Beihang UniversityBeijing100191 School of Automation Science and Electrical EngineeringBeihang UniversityBeijing100191China Institute of Advanced Manufacturing TechnologyNingbo Institute of Material Technology and EngineeringNingbo315201 China School of Mechanical and Aerospace EngineeringNanyang Technological University 50 Nanyang Avenue639798Singapore

ISBN: (纸本)9781479946983

A novel tubular flux-switching permanent magnet (PM) linear motor is proposed in this *** takes the hybrid operating principle of conventional flux switching machines and excitation of permanent magnet *** helps to increase the magnetic flux density in air gaps,and improve the force *** complementary phase is employed to reduce force *** design methodology is utilized to improve the system *** design concept and working principle are *** magnetic field distribution and thrust output are formulated analytically based on equivalent magnetic *** analysis is conducted on the magnetic field and thrust output to validate the operating principle of the proposed tubular flux-switching PM linear *** shows that the system can improve the thrust force density compared with conventional flux-switching *** addition,the proposed design helps to depress the force ripple and thus benefit the motion control of linear machines.

关键词： air gaps linear motors machine control magnetic fields magnetic flux motion control permanent magnet motors equivalent magnetic circuits flux switching machines flux-switching machines linear machines motion control magnetic field distribution magnetic flux density permanent magnet poles excitation system interchangeability thrust force density tubular flux-switching permanent magnet linear motor Force Magnetic circuits Magnetic cores Magnetic flux Permanent magnet motors Reluctance motors Windings

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Bayesian estimation of methane emission rates from a single high-frequency gas sensor

Bayesian estimation of methane emission rates from a single ...

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作者： Albertson, John D. Foster-Wittig, Tierney A. Ferrari, Silvia Katul, Gabriel Thoma, Eben Department of Civil and Environmental Engineering Duke University DurhamNC United States Department of Mechanical Engineering and Material Science Duke University DurhamNC United States Nicholas School of the Environment Duke University DurhamNC United States U.S. EPA Office of Research and Development National Risk Management Research 67 Laboratory Research Triangle ParkNC United States

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Influence of growth time on crystalline structure,conductivity and optical properties of ZnO thin films

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Journal of Semiconductors 2013年第2期34卷 11-14页

作者： Said Benramache Foued Chabane Boubaker Benhaoua Fatima Z.Lemmadi Material Sciences Laboratory Faculty of ScienceUniversity of Biskra Mechanical Engineering Faculty of TechnologyUniversity of Biskra Physics Laboratory

This paper examines the growth of ZnO thin films on glass substrate at 350 ℃ using an ultrasonic spray technique. We have investigated the influence of growth time ranging from 1 to 4 min on structural, optical and electrical properties of ZnO thin films. The as-grown films exhibit a hexagonal structure wurtzite and are （002） oriented. The maximum value of grain size G = 63.99 nm is attained for ZnO films grown at 2 min. The average transmittance is about 80%, thus the films are transparent in the visible region. The optical gap energy is found to increase from 3.26 to 3.37 eV with growth time increased from 1 to 2 min. The minimum value of electrical resistivity of the films is 0.13 Ω.cm obtained at 2 min. A systematic study on the influence of growth time on the properties of ZnO thin films deposited by ultrasonic spray at 350 ℃ has been reported.

关键词： ZnO thin film growth time ultrasonic spray technique

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Full-Field Subwavelength Imaging Using a Scattering Superlens

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Physical Review Letters 2014年第11期113卷 113901-113901页

作者： Chunghyun Park Jung-Hoon Park Christophe Rodriguez HyeonSeung Yu Minkwan Kim Kyoungsuk Jin Seungyong Han Jonghwa Shin Seung Hwan Ko Ki Tae Nam Yong-Hee Lee Yong-Hoon Cho YongKeun Park Department of Physics Korea Advanced Institute of Science and Technology Daejeon 305-701 Republic of Korea Graduate School of Nanoscience and Technology and KI for the NanoCentury Korea Advanced Institute of Science and Technology Daejeon 305-701 Republic of Korea Department of Material Science and Engineering Seoul National University Seoul 151-742 Republic of Korea Department of Mechanical Engineering Seoul National University Seoul 151-742 Republic of Korea Department of Materials Science and Engineering Korea Advanced Institute of Science and Technology Daejeon 305-701 Republic of Korea

Light-matter interaction gives optical microscopes tremendous versatility compared with other imaging methods such as electron microscopes, scanning probe microscopes, or x-ray scattering where there are various limitations on sample preparation and where the methods are inapplicable to bioimaging with live cells. However, this comes at the expense of a limited resolution due to the diffraction limit. Here, we demonstrate a novel method utilizing elastic scattering from disordered nanoparticles to achieve subdiffraction limited imaging. The measured far-field speckle fields can be used to reconstruct the subwavelength details of the target by time reversal, which allows full-field dynamic super-resolution imaging. The fabrication of the scattering superlens is extremely simple and the method has no restrictions on the wavelength of light that is used.

关键词： Diffraction

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Establishment of Process Model for Rapid Prototyping Technique (Stereolithography) to Enhance the Part Quality by Taguchi Method

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Procedia Technology 2014年 14卷 380-389页

作者： B.S. Raju U. Chandra Shekar K. Venkateswarlu D.N. Drakashayani Associate Professor Department of Mechanical Engineering REVA ITM Bangalore:560064 India Additional Director Scientist G GTRE DRDO C.V.Raman Nagar Bangalore:560093 India Principal scientist Material Science Division NAL Bangalore: 560017 India Professor Department of Mechanical Engineering Sir.M.VIT Bangalore:562157 India

Rapid prototyping (RP) has evolved as frontier technology in the recent times, which allows direct transformation of CAD files into functional prototypes where it tremendously reduces the lead-time to produce physical prototypes necessary for design verification, fit and functional analysis by generating the prototypes directly from the CAD data. Part quality in the rapid prototyping process is a function of build parameters such as hatch cure depth, layer thickness, orientation, hatch file, hatch spacing and part characteristics. Thus an attempt was made to identify study and optimize the process parameters governing the system which are related to part characteristics using Taguchi experimental design techniques-quality. The part characteristics can be divided into part physical characteristics and mechanical characteristics. The physical characteristics are surface finish, dimensional accuracy, distortion, layer thickness, hatch cure, and hatch file whereas, mechanical characteristics are flexural strength, ultimate tensile strength and impact strength. Thus, the paper proposes to characterize the influence of the physical build parameters over the part quality. An orthogonal array of experiment was developed which has the least number of experimental runs with desired process parameter settings and also by analysis tools such as ANOVA (Analysis of Variance). Establishment of experimentally verified correlations between the physical part characteristics and mechanical part characteristics to obtain an optimal process parameter level for betterment of part quality is obtained. The process model obtained by the empirical relation can be used to determine the strength of the prototype for the given set of parameters that shows the dependency of strength, which are essential for designers and RP machine users.

关键词： Rapid prototyping Stereolithography Process parameter tuning orthogonal array Taguchi Method ANOVA.

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