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Effects of deposition and synthesis parameters on size, density, structure, and field emission properties of Pd-catalyzed carbon nanotubes synthesized by thermal chemical vapor deposition

Journal of Vacuum Science & Technology B: Microelectronics a...

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Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures Processing, Measurement, and Phenomena 2005年第2期23卷 793-799页

作者： S. Wei W. P. Kang W. H. Hofmeister J. L. Davidson Y. M. Wong J. H. Huang Interdisciplinary Program in Materials Science Vanderbilt University Nashville Tennessee 37235 USA Department of Electrical and Computer Engineering Vanderbilt University Box 1661-B Vu Station B Nashville Tennessee 37235 USA Department of Chemical Engineering Vanderbilt University Nashville Tennessee 37235 USA Department of Materials Science and Engineering National Tsing Hua University Hsinchu 300 Taiwan Republic of China

The effects of deposition parameters and NH3 pretreatment on the size and distribution of Pd catalytic particles and subsequently their effects on the characteristics of the synthesized carbon nanotubes (CNTs) were systematically investigated. It was found that the size of Pd particles decreases and the particle density (total number of Pd particles per unit area) increases as the Pd film thickness decreases. Moreover, pretreatment of Pd film in NH3 gas promotes smaller Pd particles and higher particle density which is beneficial for CNT growth. The CNTs were synthesized by thermal chemical vapor deposition at 750 °C using methane (CH4) as the carbon source, and a mixture of Ar/H2 (80 vol %: 20 vol %) as a carrier gas with NH3 serving as a processing reagent. The incorporation of NH3 in CNT synthesis, per the specific pretreatment of catalytic film, has a distinct effect on the size and morphology of CNTs produced. The interrelation between processing, structure and emission behavior of CNTs produced with different synthesis conditions was examined by scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, and field emission measurements.

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Wireless Hearing Aids System Simulation

Wireless Hearing Aids System Simulation

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Asilomar Conference on Signals, Systems & computers

作者： H.K. Garg Tang Bin Zhang Liang R.S. Rana Department of Electrical & Computer Engineering National University of Singapore Singapore 11 Science Park Road Institute of Microelectronics Singapore Graduate Program in Bioengineering National University of Singapore Singapore

Although wireless hearing aid systems have been proposed by several research groups, no viable whole-system simulation results have been reported so far for better evaluation of this advanced hearing device. In this paper, a system-level simulation using ADStrade is presented based on one of the typical wireless hearing aid architecture. The results show that the wireless hearing aid system function can be simulated and verified. And from these results, we can get a very promising performance which can be used for further design

关键词： Hearing aids Auditory system Circuit simulation Radio frequency Noise cancellation Mathematical model Costs RF signals Signal processing Computational modeling

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A Formal Approach for Component Based Embedded Software Modelling and Analysis

A Formal Approach for Component Based Embedded Software Mode...

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IEEE International Symposium on Industrial Electronics (ISIE)

作者： H.O. Almeida L. Dias da Silva E. Oliveira A. Perkusich Department of Electrical Engineering Federal University of Campina Grande Campina Grande Paraiba Brazil Graduate Program in Computer Science Federal University of Campina Grande Campina Grande Paraiba Brazil

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ONLINE TRAFFIC LIGHT CONTROL THROUGH GRADIENT ESTIMATION USING STOCHASTIC FLUID MODELS

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IFAC Proceedings Volumes 2005年第1期38卷 90-95页

作者： Christos G. Panayiotou William C. Howell Michael Fu Department of Electrical and Computer Engineering University of Cyprus Nicosia Cyprus Department of Mathematics Applied Mathematics Scientific Computation Program University of Maryland College Park MD 20742 USA Smith School of Business and Institute for Systems Research University of Maryland College Park MD 20742 USA

In this paper, we consider the problem of dynamically regulating the timing of traffic light controllers in busy cities. We use a Stochastic Fluid Model (SFM) to model the dynamics of the queues formed at an intersection. Based on this model, we derive gradients of the queue lengths with respect to the green/red light lengths within a signal cycle. We report preliminary numerical results comparing the performance of the estimates with finite-difference and smoothed perturbation analysis estimates. Then all estimators are used to optimize the traffic system via Stochastic Approximation.

关键词： Traffic control perturbation analysis stochastic approximation

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Molecular dynamics simulations of the mechanical strength of Si∕Si3N4 interfaces

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Physical Review B 2005年第9期72卷 094115-094115页

作者： Martina E. Bachlechner Jennifer Zhang Ye Wang Jarrod Schiffbauer Steven R. Knudsen Dimitris Korakakis Physics Department West Virginia University Morgantown West Virginia 26506 USA NASA Independent Verification and Validation Facility Science and Engineering Apprenticeship Program—Morgantown High School Morgantown West Virginia 26501 USA Institute for Scientific Research Inc. Fairmont West Virginia 26555 USA Lane Department for Computer Science and Electrical Engineering West Virginia University Morgantown West Virginia 26506 USA

Molecular dynamics simulations are performed on parallel computers to investigate the crystalline Si(111)∕Si3N4(0001) interface that is modeled as an eight-component system. The average total energy per particle and the average kinetic energy per particle of the subsystems are monitored during the preparation of the system. The Young’s modulus of the interface is compared with that of the silicon part alone and that of the silicon-nitride film, respectively. The results for one extended simulation feature a crack in the silicon-nitride film and dislocated atoms in silicon below the crack. Simulations at rates of strain ranging from 0.00125to0.05ps−1 show that for lower strain rates, the systems stretched faster reach their ultimate strength at a higher strain value than those that were stretched more slowly. At the highest strain rates, however, the failure mechanisms change qualitatively indicative of a more ductile behavior.

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Complete pose determination for low altitude unmanned aerial vehicle using stereo vision

Complete pose determination for low altitude unmanned aerial...

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2005 IEEE/RSJ International Conference on Intelligent Robots and Systems

作者： L.K. Wang S.-C. Hsieh E.C.-W. Hsueh Fei-Bin Hsaio Kou-Yuan Huang Department of Electrical Engineering National Kaohsiung University of Applied Sciences Kaohsiung Taiwan National Space Program Office Hsinchu Taiwan Institute of Aeronautics and Astronautics National Cheng Kung University Tainan County Taiwan Department of Computer and Information Science National Chiao Tung University Hsinchu Taiwan

A well-developed pose estimation scenario suitable for low altitude unmanned aerial vehicle (UAV) is proposed. By employing dual CCD cameras onboard, the instant pose of UAV can be determined without any use of expensive sensor like gyro. The unscented Kalman filter (UKF) is hereafter introduced to resolve the highly nonlinear system dynamics as well as the measurement process of the pose estimation system. The only measurements recorded are those snapshots of ground targets/landmarks taken by two CCD cameras. The proposed scenario can also detect large angle rotation of UAV. Simulation is conducted via a simple case, both UAV and ground targets are stationary, to show the feasibility and applicability of the proposed scheme. Actual GPS measurement data of ground targets coordinates was recorded for UKF processing. A highlight phenomenon, implied by simulation, reveals that a sudden transition of estimation errors arises at the epoch when the UAV is experiencing a large angle maneuvering up to 180/spl deg/ per second.

关键词： Unmanned aerial vehicles Stereo vision Charge coupled devices Charge-coupled image sensors Nonlinear systems Nonlinear dynamical systems Vehicle dynamics Global Positioning System Coordinate measuring machines Estimation error

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Journal of Information Science and engineering: Editorial notice

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Journal of Information Science and engineering 2005年第5期21卷 i-ii页

作者： Lee, Der-Tsai Amato, Nancy M. Chang, Shih-Fu Chen, Homer H. Chen, Tsuhan Hsu, Tsan-Sheng Hwang, Jenq-Neng Kuo, Sy-Yen Kuo, Tei-Wei Li, Chung-Sheng Tokuyama, Takeshi Wing, Jeannette Wu, Tzong-Chen Yen, John Computer Science at Texas A and M University United States Parasol Laboratory United States IEEE Transactions on Parallel and Distributed Systems Computing Research Association's Committee on the Status of Women in Computing Research CRA-W's Distributed Mentor Program United States Department of Electrical Engineering Columbia University United States Lab. United States College of Electrical Engineering and Computer Science National Taiwan University Taiwan IEEE Transactions on Circuits and Systems for Video Technology IEEE Department of Electrical and Computer Engineering Carnegie Mellon University Pittsburgh PA United States ACM ACM SIGACT IEEE Computer Society IICM Austria Research and Development of the Department Multimedia Signal Processing Technical Committee IEEE Signal Processing Society United States IEEE Transactions on Circuits and systems for Video Technology College of Electrical Engineering and Computer Science National Taiwan Ocean University Keelung Taiwan Department of Electrical Engineering National Taiwan University Taiwan Department of Computer Science and Information Engineering National Taiwan University Taipei Taiwan IEEE Technical Committee on Real-Time Systems Computer Science Division IBM T.J. Watson Research Center United States IBM Research Division Graduate School of Information Sciences Tohoku University Japan ACM IPSJ Mathematical Society of Japan Japan Department of Computer Science Computer Science Department Carnegie Mellon University United States National Academies of Science's Computer Science and Telecommunications Board United States Microsoft's Trustworthy Academic Advisory Board Intel Research Pittsburgh's Advisory Board United States Dartmouth's Institute for Security Technology Studies Advisory Committee Canada Sloan Research Fellowships Program Committee United States ACM Taiwan China Information Sciences and Technology Pennsylvania State University United States Laboratory for Intelligent Agents Penn State's School of Info

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Carbon nanotubes: Anomalous photo-galvanic effect, electromechanical instability, and IR detection

Carbon nanotubes: Anomalous photo-galvanic effect, electrome...

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Frontiers in Optics, FiO 2005

作者： Rakitin, A. Meĺnikov, I.V. Haus, J.W. Aitchison, J.S. Department of Physics and Astronomy York University 4700 Keele Street North York Ontario M3P 1P3 Canada Comtex Consulting Inc 162 Princess Margaret Boulevard Etobicoke Ontario M9B 2Z5 Canada Electro-Optics Program School of Engineering University of Dayton 300 College Park Dayton Ohio 45469-0245 United States The E. S. Rogers Sr. Department of Electrical and Computer Engineering University of Toronto 10 King's College Road Toronto. Ontario M5S 3G4 Canada

ISBN: (纸本)1557527970

Carbon nanotubes (CNTs) are hollow cylinders composed of one or more concentric layers of carbon atoms arranged in a honeycomb lattice. CNTs are widely considered as an elemental material for a future nanoelectronic technology. This is not simply due to their small size but rather to their overall properties: CNTs are known to exhibit either metallic or semiconducting behaviour, with the band gap being dependent on the nanotube diameter. Both active devices (transistors) and interconnects can be made out of semiconducting and metallic nanotubes, respectively. The key nanotube dimension, their diameter, is controlled by chemistry, not conventional fabrication. The strong covalent bonding gives the CNTs high mechanical and thermal stability and ability to sustain current densities as high as 10 A/cm2.

关键词： Atoms Carbon nanotubes Chemistry Curvature Infrared detection Scattering

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Joint time-frequency properties of freak waves

Joint time-frequency properties of freak waves

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The Fourteenth International Offshore and Polar engineering Conference - ISOPE 2004

作者： Kim, Taekhyun Shin, Yong-June Powers, Edward J. Kim, Nungsoo Kim, Cheung Hun Department of Electrical and Computer Engineering University of Texas at Austin Austin TX United States Ocean Engineering Program Civil Engineering Department Texas A and M University College Station TX United States

In this paper, we discuss the joint time-frequency properties of a transient freak wave in order to distinguish the freak wave from non-freak waves in a quantitative manner. Exploring the use of an alternative to wavelet-based approaches, joint time-frequency distributions (TFDs), we portray the simultaneous time- and frequency-localized nature of freak waves vs. that of non-freak waves. The knowledge of the TFD, which represents the transient energy distribution over time and frequency in a joint manner, is very powerful as it allows one to calculate various moments and conditional moments in the time and frequency domains. Based on the experimental time series data collected at Texas A&M University, we calculate the instantaneous frequency center, frequency bandwidth and time duration. The instantaneous power spectrum of the freak wave, where the second harmonic component is observed, allows one to interpret the abnormal wave elevation of the freak wave in time domain. Also, the freak wave is characterized by impulsive joint time-frequency properties, i.e., wider instantaneous frequency bandwidth and shorter time duration than the non-freak waves. Copyright © 2004 by The International Society of Offshore and Polar Engineers.

关键词： Water waves

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Adaptive source and channel re-encoding to maximize tandem link performance

Adaptive source and channel re-encoding to maximize tandem l...

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2004 First International Symposium on Control, Communications and Signal Processing, ISCCSP 2004

作者： Gibson, Jerry D. Wei, Bo Media Arts Technology Program Electrical and Computer Engineering Univ. of California Santa Barbara Santa Barbara CA 93106-6065 Department of Electrical Engineering Southern Methodist University Dallas TX 75275

ISBN: (纸本)0780383796

We investigate the issues in voice communications over tandem heterogeneous network connections which require multiple source decoding/encoding operations. While it is known from speech coding research that tandem connections of different speech coders can extract a substantial performance penalty, it is shown that the use of error concealment and source re-encoding can improve system performance in the presence of channel impairments such as bit errors and packet losses. A new protocol is proposed for wireless LANs that reduces retransmissions and discarded packets, and hence reduces system delay and facilitates packet loss concealment.

关键词： Signal encoding

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