检索结果-内蒙古大学图书馆

作者： Him, Kaifu Fu, Jijiang Lu, Bin Ni, Hongwei Hu, Yemin Chu, Paur K. Hu, Zheng Hubei Province Key Lab. of Refractories and Ceramics Key Lab. for Ferrous Metallurgy and Res. Utilization of MOE College of Materials and Metallurgy Wuhan Univ. of Sci. and Tech. Wuhan 430081 China Key Laboratory of Mesoscopic Chemistry of MOE and Jiangsu Provincial Laboratory for Nanotechnology School of Chemistry and Chemical Engineering Nanjing University Nanjing 210093 China Department of Physics and Materials Science City University of Hong Kong Tat Chee Avenue Kowloon Hong Kong Hong Kong

Hierarchical tree-like and jellyfish-like SiOx nanostructures have been synthesized by annealing a mixture of carbon coated Ni nanoparticles (Ni@C) and Si02 powers under argon atmosphere at 1400 °C. The synthesized products were characterized by electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy. The tree-like SiOx nanostructures consisting of the trunks and many branches and subbranches with diminishing diameters have been observed for the first time. The diameters of the trunks are about 150~1000 nm, and the branches become more slender for each branching, ultimately to 20-40 nm in diameter for the ends. The jellyfish-like SiOx nanostructures are constructed by the catalyst heads with sizes of about 1~10 fim and many connected quasi-aligned SiOx nanowires with diameters about 20-40 nm. The Ni species of the Ni@C nanoparticles acts as the catalyst and the surface carbon as the reducing agent for car-bothermal reduction of Si02. The experimental results suggest that the formation of different SiOx nanostructures mainly depend on the dimensions of the congregated Ni catalyst droplets during the reaction process and the growth mechanism is reasonably discussed. Copyright © 2009 American scientific Publishers All rights reserved.

关键词： Nanoparticles

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Field emission and optical properties of ZnO nanowires grown directly on conducting brass substrates

Field emission and optical properties of ZnO nanowires grown...

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作者： Huo, Kaifu Fu, Jijiang Ni, Hongwei Hu, Yemin Qian, Guixiang Chu, Paul K. Hu, Zheng Hubei Province Key Lab. of Refractories and Ceramics Key Lab. for Ferrous Metallurgy and Res. Utilization of MOE College of Materials and Metallurgy Wuhan Univ. of Sci. and Tech. Wuhan 430081 China Key Laboratory of Mesoscopic Chemistry of MOE and Jiangsu Provincial Laboratory for Nanotechnology School of Chemistry and Chemical Engineering Nanjing University Nanjing 210093 China Department of Physics and Materials Science City University of Hong Kong Tat Chee Avenue Kowloon Hong Kong

Large-area and uniform ZnO nanowires have been produced directly on a conducting brass substrate by annealing a Cu0.66Zn0.34 foil under a mixture of argon and oxygen. The morphology, structure, and composition of the ZnO nanowires are characterized by X-ray diffraction, electron microscopy, energy-dispersive X-ray spectrometry, and X-ray photoelectron spectroscopy. The ZnO nanowires with diameters of about 40-70 nm and lengths up to micrometers grow preferentially along the [001] direction. Since the Cu0.66Zn0.34 foil serves as both the Zn source and substrate, the synthesis and assembly of the ZnO nanowires on a conducting substrate is accomplished in one step, and good intrinsic adhesion and robust electrical contact between the ZnO nanowires and conducting substrate are realized. This ZnO configuration forms an ideal field emitter and good field emission properties are corroborated in this study. Photoluminescence studies indicate that these ZnO nanowires have good optical quality exhibiting strong ultraviolet (UV) emission at 383 nm and a weak visible emission band centered around 485 nm at room temperature. The good field emission and optical properties suggest that ZnO nanowires fabricated by this method have promising applications in nano-optoelectronic and field emission *** © 2009 American scientific Publishers All rights reserved.

关键词： Photoluminescence

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Hierarchical finite automation modeling of device automatic polling logic and its implementation

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Jiefangjun Ligong Daxue Xuebao/Journal of PLA university of science and tech.ology (Natural science Edition) 2009年第6期10卷 528-535页

作者： Yang, Qi-Liang Xing, Jian-Chun Wang, Ping Tan, Ming-Jin Department of Computer Science and Technology Nanjing University Nanjing 210093 China Engineering Institute of Corps of Engineers PLA Univ. of Sci. and Tech. Nanjing 210007 China

To settle the problems of complicated polling logic that leads to barriers to the implementation of software, one formal model of hierarchical finite automation (HFA) was setup and discussed. Dynamic behavior characteristics of the device automatic polling were analyzed and modeled with HFA. The core and subsidiary states of the HFA were abstracted according to the process of polling. The main core states were farther subdivided using the principles of HFA. One implementing architecture was also presented for the HFA transformation in to the software system. The HFA model can describe the device automatic polling logic briefly, which ensures the application of the software.

关键词： Automation

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Shielding effectiveness of shielding fabric woven by steel and chemical fiber composites

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Jiefangjun Ligong Daxue Xuebao/Journal of PLA university of science and tech.ology (Natural science Edition) 2009年第4期10卷 366-370页

作者： Yi, Yun Chen, Bin Han, Jian-Jun Engineering Institute of Corps of Engineers PLA Univ. of Sci. and Tech. Nanjing 210007 China School of Electronic Engineering and Optoelectronic Technique Nanjing University of Science and Technology Nanjing 210094 China

To research the relation between the structure of the shielding fabric and the shielding effectiveness for the design of electromagnetic shielding tent, the simplified equivalent model of the shielding fabric was established. The shielding effectiveness of the single-layer and double-layer shielding fabric was calculated with FDTD method. There was a good agreement between the numerical results and the experimental results. The numerical results show that the shielding effectiveness of the double-layer shielding fabric is higher than that of the single-layer shielding fabric in the frequency domain of 10 GHz. The catastrophic resonance phenomenon of the double-layer shielding fabric was analyzed and the measure of the deleting resonance was proposed.

关键词： Resonance

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System modeling and stability design for peak current-mode buck power converter

System modeling and stability design for peak current-mode b...

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IEEE International Conference on Industrial Informatics (INDIN)

作者： Xiao-fei Chen Xue-cheng Zou Jun Cheng Kai Yu Shuang-xi Lin College of Computer Sci. and Tech. Huazhong University of Science and Technology Wuhan P.R. China Department of Electronic Sci. and Tech. Huazhong University of Science and Technology Wuhan China School of Electric and Information Engineering Wuhan Institute of Technology Wuhan P.R. China

In this paper, a small-signal model of a kind of peak current-mode pulse-width-modulation (PWM) control buck converter is presented which uses the circuit state average approach and combines with the consideration of influence by load change, and mutual effect between voltage feedback loop and current feedback loop. Based on the small-signal model, this paper proposes a novel method of systematic stability design. The principle is, firstly, just considering the stability design of current inner loop by cutting off the voltage outer loop; when the current inner loop compensation succeeds; we close the inner loop and complete the design of outer loop compensation. Consequently the stability design of the whole systematic circuit completes. This paper also gives a brief discuss on the issue of input immunity and output immunity. Finally, by using Matlab Simulink, based on system equivalent model which is established in this paper, and Hsipce, based on transistor-level circuit, this paper works out the system transient response simulation. Results from the simulation show that the system small-signal model proposed in this paper is reasonable, and the system-level design based on the model is feasible. Also, it is capable to enhance the system stability and has good input and output immunity.

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New channel assignment strategy based on DCRS in LEO

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Jiefangjun Ligong Daxue Xuebao/Journal of PLA university of science and tech.ology (Natural science Edition) 2007年第1期8卷 1-4页

作者： Feng, Shao-Dong Li, Guang-Xia Li, Su-Dan Institute of Communications Engineering PLA Univ. of Sci. and Tech. Nanjing 210007 China School of Computer Science National University of Defense Technology Changsha 410073 China

In order to increase the channel utility in LEO satellite communication system, a new channel assignment strategy in LEO communication system based on DCRS (dynamic channel reservation scheme) was proposed in light of the unequal distribution of the subscribers. The strategy can assign the guarded channel dynamically according to the proportion of the new calls and handoff calls. The simulation results show that the strategy can reduce the new call blocking probability, improve the channel utilization and QoS while guaranteeing the handoff blocking probability compared with FCRS (fixed channel reservation scheme).

关键词： Satellite communication systems

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Study of photo-sensor candidates for the MEMSTEL project

Study of photo-sensor candidates for the MEMSTEL project

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30th International Cosmic Ray Conference, ICRC 2007

作者： Lee, M.H. Ahn, H.S. Artikova, S. Ganel, O. Garipov, G. Han, J.H. Jeon, J.A. Khrenov, B. Kim, J.E. Kim, M.S. Kim, Y.K. Klimov, P. Lee, J. Lutz, L. Malinin, A. Moon, K.H. Na, G.W. Nam, S. Oh, S.J. Park, I.H. Park, J.H. Park, Y.S. Ryu, H.J. Seo, E.S. Walpole, P. Yang, J. Yoo, B.W. Yoo, J.H. Yoon, Y.S. Inst. for Phys. Sci. and Tech. University of Maryland College Park MD 20742 United States Dept. of Physics Ewha Womans University Seoul 120-720 Korea Republic of DV Skobeltsyn Institute of Nuclear Physics Russia Federation Moscow State University Moscow 119992 Russia School of Electrical Engineering and Computer Science Seoul National University Seoul 151-742 Korea Republic of School of Physics and Astronomy Seoul National University Seoul 151-742 Korea Republic of Dept. of Physics University of Maryland College Park MD 20742 United States

The MEMSTEL (Micro Electro Mechanical Systems Space Telescope) is a space-based experiment being designed to investigate the origin of extreme energy cosmic-ray (EECR) particles above 5 × 1019 eV. The fluorescent light generated in extensive air showers (EAS) when EECRs hit the atmosphere can be detected from low Earth orbit. MEMSTEL will implement a novel idea of a tracking mirror based on semiconductor MEMS tech.ology. The light signal will be focused on a relatively small area of readout photo-sensors using a tracking mirror. One candidate for MEMSTEL photo-sensors is the conventional multi-anode photo multiplier tube (PMT). Recently, a new type of photo-sensor was developed for particle detector readouts - The silicon photo multiplier (Si-PM). This compact photo-sensor is comprised of a large array of micro-cells operating in a limited Geiger mode, and provides high gain (∼ 10 6) with low operating voltage (∼ 50 V). The compact design, light weight and low power consumption make this device an excellent photon-detector candidate for space-based experiments. In this paper, we report on the comparative performance of a 1 × 1mm2 Si-PM, a conventional PMT, and a Hybrid Photo Diode (HPD) in lab tests, reading out light generated by Light Emitting Diode (LED) as well as by scintillating fibers excited with a radioactive source.

关键词： Cosmology

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High Pressure Deuterium Annealing Effect on Nano-Scale Strained CMOS Devices

High Pressure Deuterium Annealing Effect on Nano-Scale Strai...

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2007 IEEE International Reliability Physics Symposium (IRPS 2007), vol.2

作者： Sung-Man Cho Jeong-Hyun Lee M. Chang M. S. Jo H. S. Hwang J. K. Lee S. B. Hwang Jong-Ho Lee School of Electrical Engineering and Computer Science Kyungpook National University Daegu Korea Dept. of Materials Science & Eng. Gwangju Inst. of Sci. & Tech. Korea R&D Center MagnaChip Semiconductor Inc. Cheongju Korea R&D Center MagnaChip Semiconductor Inc. Cheongju Korea

High pressure deuterium annealing was applied to nano-scale strained CMOS devices and its effect was characterized in terms of charge pumping, hot carrier, NBTI and DNBTI stress, and normalized drain current noise spectral density for the first time. The characteristics of tensile stressed NMOS devices were improved by the annealing. But for PMOS, especially compressive stressed devices showed degraded characteristics by the annealing.

关键词： Deuterium Annealing Nanoscale devices Charge pumps Hot carriers Niobium compounds Titanium compounds Compressive stress Tensile stress MOS devices

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Equivalence of Short Circuits between SIRW with Cylinder Wall and Regular Waveguide with Solid Wall

Equivalence of Short Circuits between SIRW with Cylinder Wal...

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IEEE Antennas and Propagation Society International Symposium, APS 2006

作者： Che, W. Deng, K. Wang, D.P. Fu, B. Xu, L. Chow, Y.L. Department of EE Nanjing University of Sci.& Tech. Nanjing China Electrical and Computer Engineering University of Waterloo Canada

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A multi-channel MAC protocol for wireless sensor networks

A multi-channel MAC protocol for wireless sensor networks

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6th IEEE International Conference on computer and Information tech.ology, CIT 2006

作者： Chen, Xun Han, Peng He, Qiu-Sheng Tu, Shi-Liang Chen, Zhang-Long Department of Computer Science and Engineering Fudan University Shanghai 200433 China School of Electronic and Information Jiangsu University of Sci and Tech. Zhenjiang Jiangsu 212003 China

ISBN: (纸本)076952687X

In this paper, we propose a novel multi-channel medium access control protocol for wireless sensor networks. Our protocol can dynamically assign multiple channels to nodes, thereby significantly increasing network energy efficiency, network lifetime and data throughput as well. The protocol requires only one transceiver per node, but solves the multi-channel hidden terminal problem through distributed coordinator node. Finally we evaluate the performance of this protocol through simulations. The performance results show that protocol significantly increase network energy efficiency, network lifetime and data throughput and exhibits prominent ability to utilize multi-channel transceiver among neighboring nodes. © 2006 IEEE.

关键词： Network protocols

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