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Carbon nanostructures as thermal field emitters for waste heat recovery

Diamond and Related Materials 2009年第2-3期18卷 563-566页

作者： Wong, Y.M. Kang, W.P. Davidson, J.L. Raina, S. Huang, J.H. Department of Electrical Engineering and Computer Science Vanderbilt University Nashville TN 37235 United States Interdisciplinary Program in Material Science Vanderbilt University Nashville TN 37235 United States Department of Materials Science and Engineering National Tsing Hua University Hsinchu 300 Taiwan

Traditional vacuum-based thermal energy conversion (VTEC) devices with "flat" metal emitters have been compromised by high working temperature mainly due to high work function and electron space charge effect. However, a VTEC system is inherently efficient due to unimpeded flow of electrons through vacuum and reduction of heat conduction by the vacuum medium. Consequently, VTEC devices are attractive in terms of space, weight and energy efficiency for waste heat recovery in a TEC system. Carbon nanostructured emitters including multiwalled carbon nanotubes (CNTs) and "ridge" nanodiamond thin films have shown relatively low threshold fields for electron field emission mainly due to their nanoscaled, high aspect ratio, emitting surfaces. In this study, the field-enhancing features of carbon nanostructures were investigated as thermal-field emitters for waste heat recovery. The turn-on field of CNTs was found to decrease from ~ 1.9V/μm at room temperature to ~ 0.9V/μm at 400°C. A high emission current of ~ 26μA was achieved at relatively low field of ~ 1.5V/μm and low temperature of 400°C. The maximum efficiency of the VTEC device is estimated to be ~ 15% at 300°C with a current density of 54mA/cm2. © 2008 Elsevier B.V.

关键词： Temperature

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Controller design to regulate the DC voltage of a VSC converter

Controller design to regulate the DC voltage of a VSC conver...

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2009 IEEE electrical Power and Energy Conference, EPEC 2009

作者： Hidalgo Mora, Carlos A. Diaz, Nelson L. Universidad Distrital F.J.C. Bogota Colombia Department of Electrical and Computer Engineering Graduate Program in Engineering - Industrial Automation Universidad Nacional de Colombia Bogota Colombia

ISBN: (纸本)9781424445080

The basic function of VSCs is to convert the DC voltage stored in a capacitor into AC voltages or AC voltages into DC voltage. One of the advantages of the VSC is that this kind of electronic converters allow to control the active and reactive power flow with an ac-grid independently. This paper presents a short analysis of the characteristics and dynamic of VSC-HVDC, identification techniques to find transfer function to DC Voltage and Reactive Power in a rectifier station are explored, and finally controller design to regulate the DC voltage is exposed and tested by simulations using Matlab Simulink and its toolbox SimpowerSystems. ©2009 IEEE.

关键词： Reactive power

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Preparing computer engineers for a global economy: A study on effective collaboration practices in global student teams

Preparing computer engineers for a global economy: A study o...

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39th Annual Frontiers in Education Conference: Imagining and engineering Future CSET Education, FIE 2009

作者： Doboli, Alex Doboli, Simona Currie, Edward State University of New York at Stony Brook Department of Electrical and Computer Engineering Stony Brook NY 11794-2350 United States Computer Engineering Program Hofstra University Department of Computer Science Hempstead NY United States Resonance Publications Inc. United States

ISBN: (纸本)9781424447152

This paper discusses our ongoing efforts on developing, and conducting, senior design projects that involve undergraduate students working together on entrepreneurial, innovative projects. The students are from multiple universities, some of which are abroad. The goal is to emulate the main elements of global engineering teams that develop complex, multidisciplinary designs while targeting market-related constraints, such as price, reliability, size and ease-of-use. This paper discusses the goals and organization of the global student teams, and presents our experience in working with such teams. © 2009 IEEE.

关键词： Students

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Ontology engineering

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Nature Biotechnology 2010年第2期28卷 128-130页

作者： Alterovitz, Gil Xiang, Michael Hill, David P. Lomax, Jane Liu, Jonathan Cherkassky, Michael Dreyfuss, Jonathan Mungall, Chris Harris, Midori A. Dolan, Mary E. Blake, Judith A. Ramoni, Marco F. Children's Hospital Informatics Program Harvard-MIT Division of Health Sciences and Technology Harvard Medical School Boston MA United States Partners Healthcare Center for Personalized Genetic Medicine Boston MA United States Department of Electrical Engineering and Computer Science Massachusetts Institute of Technology Cambridge MA United States Jackson Laboratory Bar Harbor ME United States EMBL-EBI Wellcome Trust Genome Campus Hinxton United Kingdom Department of Biology Massachusetts Institute of Technology Cambridge MA United States Lawrence Berkeley National Laboratory Berkeley CA United States

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Fluidic intraocular lens with a large accommodation range

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IEEE Photonics Technology Letters 2009年第5期21卷 304-306页

作者： Qiao, Wen Tsai, Frank S. Cho, Sung Hwan Yan, Huimin Lo, Yu-Hwa for Optical Instrument Zhejiang University Hangzhou 310027 China Department of Electrical and Computer Engineering Jacobs School of Engineering University of California San Diego CA 92093-0407 United States Materials Science and Engineering Program Jacobs School of Engineering University of California San Diego San DiegoCA 92093-0418 United States

Fluidic lenses with tunable focal distances were experimented in a human eye model as intraocular lenses (IOLs). Fluidic IOL shows superior performance to fixed or optic-shift accommodating IOLs because of their much wider accommodation range. Our results demonstrate that fluidic IOL can achieve an accommodation range of eight diopters, equivalent to the performance of young adults. Finite-element analysis shows that the required force for the fluidic IOL to achieve the desired amount of accommodation is comparable to the force generated from ciliary muscles of human eyes, as an initial indication that an implanted fluidic IOL may be controllable by eye muscles. © 2009 IEEE.

关键词： Intraocular lenses

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Design-dimensioning model for grid-connected photovoltaic systems

Design-dimensioning model for grid-connected photovoltaic sy...

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2009 IEEE electrical Power and Energy Conference, EPEC 2009

作者： Hernandez, Johann Diaz, Nelson L. Gordillo, Gerardo Universiudad Nacional de Colombia Bogota Colombia Department of Electrical and Computer Engineering Graduate Program in Engineering - Industrial Automation Universidad Nacional de Colombia Bogota Colombia Universidad Nacional Bogota Colombia

ISBN: (纸本)9781424445080

The main goal in design of grid connected photo voltaic systems is to maximize the energy generation based on local energy requirements, weather conditions, economic and social impact. These factors ought to be taken into account to perform a model that allow design grid-connected photo voltaic systems. In this paper a design-dimensioning model for a small grid-connected photo voltaic systems is developed. This model is based on energy conditions instead of power conditions. There are shown the two main trends that are typically used in the design process and the calculation of the two main components of the system (generator and inverter). An example of the design for a system located in Bogota-Colombia is studied. ©2009 IEEE.

关键词： Design

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Microstructural and pinning properties of YBa2Cu 307-δ thin films doped with magnetic nanoparticles

Microstructural and pinning properties of YBa2Cu 307-δ thin...

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作者： Wang, Jie Tsai, Chen-Fong Bi, Zhenxing Naugle, Donald G. Wang, Haiyan Department of Electrical and Computer Engineering Material Science and Engineering Program Texas A and M University College Station TX 77843 United States Department of Physics Texas A and M University College Station TX 77843 United States

In this paper, we report a strong enhancement in the in-field transport properties of the YBa2Cu307-δ (YBCO) thin films doped with magnetic Fe203 nanoparticles. We incorporated magnetic Fe2o3nanoparticles with two different architectures by laser ablation of the YBCO and dopant targets. YBCO film ' thickness was controlled at around 1 μm for all the samples. We conducted a detailed microstructural characterization on all the doped samples by X-ray diffraction (XRD) and cross-sectional transmission electron microscopy (TEM) and compared with the pure YBCO films. A systematic study on the superconducting properties has been conducted on all the thin film samples. The critical current densities at both self-field and in-field (Jcf and j in-field (h//c)) and the critical transition temperature (Tc) of the doped and un-doped YBCO sample were measured by a Superconducting Quantum Interference Device (SQUID). The Tc of the doped YBCO films varies from 84 K-90 K and the Jc is in the range of 1.2-3.9 MA/cm2 (at 65 K) depending on the doping approach. The pinning properties of these doped YBCO films were explored at different temperatures (5 K, 40 K, and 65 K) and correlated with their microstructural characteristics. © 2009 IEEE.

关键词： Nanoparticles

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System identification of magneto-rheological damper using group method of data handling (GMDH)

System identification of magneto-rheological damper using gr...

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2009 6th International Symposium on Mechatronics and its Applications, ISMA 2009

作者： Assaleh, Khaled Shanableh, Tamer Kheil, Yasmeen Abu Department of Electrical Engineering American University of Sharjah United Arab Emirates Department of Computer Science and Engineering American University of Sharjah United Arab Emirates Mechatronics Graduate Program American University of Sharjah United Arab Emirates

ISBN: (纸本)9781424434817

In this paper Group Method of Data Handling (GMDH) technique is implemented and applied to the system identification problem of a Magneto-Rheological (MR) damper. GMDH networks are used to approximate the forward and inverse dynamic behaviors of a MR damper. The difficulty of this identification problem stems from the inherent hysteretic and highly nonlinear dynamics of MR dampers. The GMDH-based solution exhibits comparable identification accuracy in both the forward and inverse models as compared to state-of-the-art more computationally extensive solutions. © 2009 IEEE.

关键词： Inverse problems

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Effect of nitrogen concentration on nanodiamond film characteristics for electrode application

Effect of nitrogen concentration on nanodiamond film charact...

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作者： Raina, Supil LeQuan, X.C. Kang, W.P. Davidson, J.L. Interdisciplinary Program in Materials Science Vanderbilt University Nashville TN 37235 United States Department of Electrical Engineering and Computer Science Vanderbilt University Nashville TN 37235 United States

ISBN: (纸本)9781607681137

Microwave plasma chemical vapor deposition was used to fabricate nanodiamond films. Nitrogen incorporation was achieved by the introduction of N2 gas along with H2 and CH4 gases in the plasma. SEM studies revealed a change in the microstructure with increase in the N2 flow rate, transitioning from a 'ridge'-like surface morphology to a more 'cauliflower'-like structure. X-ray photoelectron spectroscopy (XPS) analysis showed a general decrease in the sp3 hybridized carbon content while the sp hybridized carbon content increased with N2 flow rate (up to 28.7%) after which it declines. Deconvolution of the C1s XPS spectra indicates incorporation of nitrogen and existence of carbon-nitrogen bonding. Raman spectroscopy shows diamond peak at 1332 cm-1 and the graphite peak, which increases in intensity and shifts towards lower wave number with increase in the N2 flow rate. A diffuse band at 1140 cm -1 indicates presence of a nanocrystalline phase in the films. ©The Electrochemical Society.

关键词： Nitrogen

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Understanding quantification of microvascularity with high-frequency power Doppler ultrasound

Understanding quantification of microvascularity with high-f...

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Medical Imaging 2009: Ultrasonic Imaging and Signal Processing

作者： Pinter, Stephen Z. Lacefield, James C. Biomedical Engineering Graduate Program Departments of Electrical University of Western Ontario London ON Canada Department of Electrical and Computer Engineering University of Western Ontario London ON Canada Department of Medical Biophysics University of Western Ontario London ON Canada Robarts Research Institute University of Western Ontario London ON Canada

ISBN: (纸本)9780819475169

High-frequency power Doppler imaging of angiogenesis can be challenging given the presence of small blood vessels and slow flow velocities. In the presence of substantial Doppler artifacts such as false-positive color pixels or undetected vessels, color pixel density (CPD) and related vascularity metrics do not provide accurate estimates of vascular volume fraction. As a step towards improved microvascular quantification, flow-phantom experiments were performed to establish relationships between CPD and wall filter cut-off velocity for various combinations of vessel size (160, 200, 250, 300, and 360 μm), flow velocity (4, 3, 2, 1, and 0.5 mm/s), and transducer frequency (30 and 40 MHz). Three distinct regions were observed in plots of CPD versus wall filter cut-off velocity: overestimation of CPD at low cut-offs, underestimation of CPD at high cut-offs, and a plateau at intermediate cut-offs. The CPD at the plateau closely matched the phantom's actual vascular volume fraction. The length of the plateau corresponded with the flow-detection performance of the Doppler system, which was assessed using receiver operating characteristic analysis. Color pixel density versus wall filter cut-off curves from analogous in vivo experiments exhibited the same shape, including a distinct CPD plateau. The similar shape of the flow-phantom and in vivo curves suggests that the presence of a plateau can be used to identify the best-estimate CPD value in an in vivo experiment. The ability to identify the best CPD estimate is expected to improve quantification of angiogenesis and anti-angiogenic treatment responses with power Doppler. © 2009 SPIE.

关键词： Flow velocity

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