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Articles 8011 - 8040 of 8897

Full-Text Articles in Physical Sciences and Mathematics

Electron Bernstein Wave-X-O Mode Conversion And Electron Cyclotron Emission In Mast, Josef Preinhaelter, Pavol Pavlo, Vladimir Shevchenko, Martin Valovic, Linda L. Vahala, George Vahala Jan 2003

Electron Bernstein Wave-X-O Mode Conversion And Electron Cyclotron Emission In Mast, Josef Preinhaelter, Pavol Pavlo, Vladimir Shevchenko, Martin Valovic, Linda L. Vahala, George Vahala

Electrical & Computer Engineering Faculty Publications

Electron cyclotron emission (ECE) from overdense plasmas can only occur due to electron Bernstein waves (EBW) mode converting near the upper hybrid region to an electromagnetic wave. Experimental data of ECE observations on MAST are studied and compared with EBW-X-O mode conversion modeling results.

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Compact Supercell Method Based On Opposite Parity For Bragg Fibers, Wang Zhi, Ren Guobin, Lou Shuquin, Liang Weijun, Shangping Guo Jan 2003

Compact Supercell Method Based On Opposite Parity For Bragg Fibers, Wang Zhi, Ren Guobin, Lou Shuquin, Liang Weijun, Shangping Guo

Electrical & Computer Engineering Faculty Publications

The supercell- based orthonormal basis method is proposed to investigate the modal properties of the Bragg fibers. A square lattice is constructed by the whole Bragg fiber which is considered a supercell, and the periodical dielectric structure of the square lattice is decomposed using periodic functions (cosine). The modal electric field is expanded as the sum of the orthonormal set of Hermite-Gaussian basis functions based on the opposite parity of the transverse electric field. The propagation characteristics of Bragg fibers can be obtained after recasting the wave equation into an eigenvalue system. This method is implemented with very high efficiency …

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Protocols For Disease Classification From Mass Spectrometry Data, Michael Wagner, Dayanand Naik, Alex Pothen Jan 2003

Protocols For Disease Classification From Mass Spectrometry Data, Michael Wagner, Dayanand Naik, Alex Pothen

Mathematics & Statistics Faculty Publications

We report our results in classifying protein matrix-assisted laser desorption/ionizationtime of flight mass spectra obtained from serum samples into diseased and healthy groups. We discuss in detail five of the steps in preprocessing the mass spectral data for biomarker discovery, as well as our criterion for choosing a small set of peaks for classifying the samples. Cross-validation studies with four selected proteins yielded misclassification rates in the 10-15% range for all the classification methods. Three of these proteins or protein fragments are down-regulated and one up-regulated in lung cancer, the disease under consideration in this data set. When cross-validation studies …

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Chaotic Free-Space Laser Communication Over Turbulent Channel, N. F. Rulkov, Mikhail Vorontsov, L. Illing Dec 2002

Chaotic Free-Space Laser Communication Over Turbulent Channel, N. F. Rulkov, Mikhail Vorontsov, L. Illing

Electro-Optics and Photonics Faculty Publications

The dynamics of errors caused by atmospheric turbulence in a self-synchronizing chaos-based communication system that stably transmits information over a ∼5  km free-space laser link is studied experimentally. Binary information is transmitted using a chaotic sequence of short-term pulses as a carrier. The information signal slightly shifts the chaotic time position of each pulse depending on the information bit. We report the results of an experimental analysis of the atmospheric turbulence in the channel and the impact of turbulence on the bit-error-rate performance of this chaos-based communication system.

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Supervisory Control And Data Acquisition (Scada) Systems, George H. Baker, Allan Berg Nov 2002

Supervisory Control And Data Acquisition (Scada) Systems, George H. Baker, Allan Berg

George H Baker

Our critical national infrastructure systems have become almost universally dependent upon computer-based control systems technically referred to as supervisory control and data acquisition (SCADA) systems. SCADA systems evolved from the telemetry and event-alarm systems developed in the early days of utilities. With the widespread use of SCADA systems, computers have become the "basis element" for much of our critical infrastructure. Thus, the disruption of controlling computer terminals and networks due to natural disasters, electric power failure, accidents or malicious activity can have catastrophic consequences.

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Properties Of Domestic Natural Graphite Used For Li-Ion Batteries, Cui-Wei Du, Yu-Juan Zhao, Gang Zhang, Yin-Shun Wu, Qing-Guo Liu Nov 2002

Properties Of Domestic Natural Graphite Used For Li-Ion Batteries, Cui-Wei Du, Yu-Juan Zhao, Gang Zhang, Yin-Shun Wu, Qing-Guo Liu

Journal of Electrochemistry

The structure, physical characteristics and electrochemical properties of the natural graphite produced in Shandong province have been studied. The result of X-ray diffraction showed that the graphite consisted of hexagonal structure and rhombic structure (30% rhombic structure). It was fine crystal graphite. Used as a negative material of Lithium ion battery, the natural graphite showed excellent voltage and high energy capacity, but poor compatibility with electrolyte solution containing propylene carbonate (PC) for its own structure limitation.

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Review Of Mathematical Model For Proton Exchange Membrane Fuel Cell, Shan-Hai Ge, Bao-Lian Yi, Hua-Min Zhang Nov 2002

Review Of Mathematical Model For Proton Exchange Membrane Fuel Cell, Shan-Hai Ge, Bao-Lian Yi, Hua-Min Zhang

Journal of Electrochemistry

In the review with 49 references, the mathematical models for proton exchange membrane fuel cell (PEMFC) were summarized. The mechanistic model and empirical model were introduced. Transfer in the membrane, catalyst layer,diffusion layer and flow field of PEMFC were described. The importance of water and heat management was analyzed. The dimension, complexity and solving methods of the PEMFC model were discussed. The importance and validity to develop a model with time dimension are put forward.

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Manufacture Of 1 Kw Molten Carbonate Fuel Cell Stack, Sheng Sui, Xin-Jian Zhu, Zheng-Yu Fan, Cao Guang-Yi And Nov 2002

Manufacture Of 1 Kw Molten Carbonate Fuel Cell Stack, Sheng Sui, Xin-Jian Zhu, Zheng-Yu Fan, Cao Guang-Yi And

Journal of Electrochemistry

A molten carbonate fuel cell stack with an active area of 240 mm×140 mm consisted of 30 cells.The gas feed system works via interior manifolds,and the stack placed in a couple of self-chest,coupled with a heater at the bottom and other fours surrounded,to keep uniformity of temperature.Under ambient pressure and 650 ℃,fed with hydrogen and air as anode and cathode gases respectively,the stack gave a current density of 150 mA/cm 2 at an average cell voltage of 0.7 V.The peak output of the stack was 1.06 kW during its performance of 300 h.

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Preparation And Electrochemical Lithium Intercalation Performance Of Different Shaped Carbon Nanotube, Mao-Hui Chen, Zhen-Cai Huang, Guo-Tao Wu, Jin-Kua You, Zu-Geng Lin Nov 2002

Preparation And Electrochemical Lithium Intercalation Performance Of Different Shaped Carbon Nanotube, Mao-Hui Chen, Zhen-Cai Huang, Guo-Tao Wu, Jin-Kua You, Zu-Geng Lin

Journal of Electrochemistry

In the present work, different shaped carbon nanotubes were produced by the general CVD and the template method at different temperature (600 ℃,700 ℃) with the reaction gas of acetylene. The morphology, structure and the electrochemical lithium intercalation performance were comparatively studied and characterized by TEM, HRTEM, SEM, XRD, Raman techniques and Charge/Discharge Test. It was found that the different preparation methods and temperatures all had an obvious effect on these properties of carbon nanotubes. In our samples, with the increase of preparation temperature, the degree of crystallinity decreased, and the reversible specific capacity increased respectively.

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Lithium Intercalation Performance Of P-Doped Phenolic Resin Pyrolysis Carbon, Bao-Hua Li, Kai-Xi Li, Yonggen Lv, Chun-Xiang Lv, Dong Wu, Li-Cheng Ling Nov 2002

Lithium Intercalation Performance Of P-Doped Phenolic Resin Pyrolysis Carbon, Bao-Hua Li, Kai-Xi Li, Yonggen Lv, Chun-Xiang Lv, Dong Wu, Li-Cheng Ling

Journal of Electrochemistry

Phosphorus-doped phenolic resin carbon was prepared by low temperature(700 ℃)pyrolysis of thermoplastic phenolic resin containing different amounts of phosphorus pentoxide after curing. X-ray diffraction pattern and the constang-current charge-discharge properties of phenolic resin carbon were studied. The results showed that the phenolic resin carbon microstructure became out of order with increasing of content phosphorus pentoxide,otherwise,the first discharge reversible capacities increased firstly and then decreased. The first discharge reversible capacity of phenolic resin carbon containing 9wt% phosphorus pentoxide was 528 mA·h·g -1 which was higher than that of non-phosphorus doped phenolic resin carbon(230 mA·h·g -1 ) did.

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Steady State Simulation Of Ysz Intermediate-Temperature Fuel Cell, Zi-Jing Lin, Ye Gu, Xiao-Hua Zhang Nov 2002

Steady State Simulation Of Ysz Intermediate-Temperature Fuel Cell, Zi-Jing Lin, Ye Gu, Xiao-Hua Zhang

Journal of Electrochemistry

With a coupled 2D electrochemical and thermal modeling software, the characteristics of the steady state operation of the intermediate-temperature fuel cell with thin yttria-stabilized zirconia(YSZ) electrolyte was analyzed. The parameters of I-V equation were obtained from fitting the experiment results and the choice of grid points was determined by balancing the accuracy requirement and computational efficiency. The temperature fields at different operation circumstances such as flow designs, material choices for interconnect, were examined. The dependences of the output power and cell efficiency on the operating voltage at different temperatures were studied. Based upon the analysis of the temperature profile, it …

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Nano-Sized Cobalt-Based Oxides As Negative Electrode For Lithium-Ion Batteries, Feng Huang, Zheng-Yong Yuan, Yun-Hong Zhou, Ju-Tang Sun Nov 2002

Nano-Sized Cobalt-Based Oxides As Negative Electrode For Lithium-Ion Batteries, Feng Huang, Zheng-Yong Yuan, Yun-Hong Zhou, Ju-Tang Sun

Journal of Electrochemistry

Nanosized cobalt-based oxide (Co 3O 4, CoB 1.36 O 2.8 and CoB 0.5 Al 0.1 O 1.5 ) samples were prepared by rheological phase method and were tested as anodes in secondary lithium batteries. The cells were cycled between 0.01V and 3.00 V. The best electrochemical performance was obtained from the Li/Co 3O 4 cell, which retained 95% of its initial capacity (931 mAh/g) after 30 cycles. The doping of B, Al reduced the reversible capacity during the first discharge/charge cycle, and the quantity of reversible capacity reduced with B, A1 increasing. The modifying structures at difference charge and discharge …

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Mechanistic Study Of Oxidation Of Hypophosphite On Pt Electrodes By Sniftirs, Tai-Xiang Jiang, Hui-Huang Wu Nov 2002

Mechanistic Study Of Oxidation Of Hypophosphite On Pt Electrodes By Sniftirs, Tai-Xiang Jiang, Hui-Huang Wu

Journal of Electrochemistry

The oxidation of hypophosphite on a polycrystalline platinum electrode was studied by SNIFTIRS and cyclic voltammetry, the in-situ IR spectra were analyzed as a function of Pt electrode potentials in the solution of 0.5 mol/L H 2SO 4+0.1 mol/L NaH 2PO 2. It was found that the dissociative adsorption of hypophosphite ions occurs on Pt surface, and the oxidation product is H 3PO 4, rather than H 2PO 3 - which was considered to produce on Ni electrodes, thereby a new insight into mechanism of hypophosphite oxidation on Pt in acidic media was provided.

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Preparation And Performance Of Lifeo_2 Coated Nickel Oxide Cathode For Molten Carbonate Fuel Cells, Chun-Ming Wang, Fei Li, Ke-Ao Hu Nov 2002

Preparation And Performance Of Lifeo_2 Coated Nickel Oxide Cathode For Molten Carbonate Fuel Cells, Chun-Ming Wang, Fei Li, Ke-Ao Hu

Journal of Electrochemistry

A novel cathode for molten carbonate fuel cells was prepared by coating LiFeO 2 over the surface of porous NiO cathode by a simple combustion process. The analytical results of X-ray diffraction (XRD), energy dispersive analysis of X-ray (EDAX), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) indicated that the LiFeO 2 coating on the surface of NiO particles consisted of nonometer-sized LiFeO 2 grains and sintered tightly with the NiO particles. The LiFeO 2 coating dramatically reduced the contacting area of NiO with the carbonate melts, thus the solubility of NiO in the carbonate melts was decreased. Meanwhile, …

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Electrocatalytic Oxidation Of Formic Acid On Molybdate-Modified Platinum Electrode, Jun-Hua Du, Xue-Hui Xu, Hong Li, Hong-Yu Cheng, Wei-Shan Li Nov 2002

Electrocatalytic Oxidation Of Formic Acid On Molybdate-Modified Platinum Electrode, Jun-Hua Du, Xue-Hui Xu, Hong Li, Hong-Yu Cheng, Wei-Shan Li

Journal of Electrochemistry

The electrochemical behavior of molybdates on a platinum electrode in H 2SO 4 solutions with different H 2SO 4 concentrations was studied by cyclic voltammetry and double chronoamperometry. Molybdates were reduced to adsorb hydrogen molybdenum bronzes on the platinum electrode in H 2SO 4 solutions during cathodically potential sweep. The hydrogen molybdenum bronzes were oxidized to different forms of hydrogen molybdenum bronzes with less hydrogen, depending on the H 2SO 4 concentration. Platinum electrode was modified by these hydrogen molybdenum bronzes. However, this modified electrode was not stable in H 2SO 4 solutions. The modified electrode was used to study …

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Pattern Recognition For Electric Power System Protection, Yong Sheng Oct 2002

Pattern Recognition For Electric Power System Protection, Yong Sheng

Doctoral Dissertations

The objective of this research is to demonstrate pattern recognition tools such as decision trees (DTs) and neural networks that will improve and automate the design of relay protection functions in electric power systems. Protection functions that will benefit from the research include relay algorithms for high voltage transformer protection (TP) and for high impedance fault (HIF) detection. A methodology, which uses DTs and wavelet analysis to distinguish transformer internal faults from other conditions that are easily mistaken for internal faults, has been developed. Also, a DT based solution is proposed to discriminate HIFs from normal operations that may confuse …

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Study Of Transport Properties Of Inas Using Monte Carlo Simulation, Satyanadh Gundimada Oct 2002

Study Of Transport Properties Of Inas Using Monte Carlo Simulation, Satyanadh Gundimada

Electrical & Computer Engineering Theses & Dissertations

The present research is aimed at ascertaining the usefulness of InAs semiconductor material for single photon avalanche photo detectors operating in the Geiger mode at 2 μm wavelengths. InAs is considered as the material suitable for the purpose because of its less bandgap and lower effective mass of the electrons when compared to other semiconductor materials presently in use. Hence, theoretically transient transport properties of bulk InAs are superior and the velocity overshoot phenomena stronger. InAs is a relatively less explored material when compared to other materials like GaAs. The choice of the material is justified with thorough exploration of …

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Yet Another Algorithm For Pitch Tracking (Yaapt), Kavita Kasi Oct 2002

Yet Another Algorithm For Pitch Tracking (Yaapt), Kavita Kasi

Electrical & Computer Engineering Theses & Dissertations

This thesis presents a pitch detection algorithm that is extremely robust for both high quality and telephone speech. The kernel method for this algorithm is the Normalized Cross Correlation (NCCF) reported by David Talkin [16]. Major innovations include: processing of the original acoustic signal and a nonlinearly processed version of the signal to partially restore very weak F0 components; intelligent peak picking to select multiple F0 candidates and assign merit factors; and, incorporation of highly robust pitch contours obtained from smoothed versions of low frequency portions of spectrograms. Dynamic programming is used to find the ''best" pitch track among all …

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On The Area Of Hypercube Layouts, Ronald I. Greenberg, Lee Guan Sep 2002

On The Area Of Hypercube Layouts, Ronald I. Greenberg, Lee Guan

Computer Science: Faculty Publications and Other Works

This paper precisely analyzes the wire density and required area in standard styles for the hypercube. It shows that the most natural, regular layout of a hypercube of N^2 nodes in the plane, in a NxN grid arrangement, uses floor(2N/3)+1 horizontal wiring tracks for each row of nodes. (In the process, we see that the number of tracks per row can be reduced by 1 with a less regular design, as can also be seen from an independent argument of Bezrukov et al.) This paper also gives a simple formula for the wire density at any cut position and a …

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Modification Of Molybdenum Nitride Electrode For Supercapacitor(I)——The Effect Of Ammonium Vanadate On The Properties Of Molybdenum Nitride Electrode, Xue-Liang Li, Dao-Rong Luo, Hua-Lin Wang, Jian-Bo He, Yun-Guei Zhu Aug 2002

Modification Of Molybdenum Nitride Electrode For Supercapacitor(I)——The Effect Of Ammonium Vanadate On The Properties Of Molybdenum Nitride Electrode, Xue-Liang Li, Dao-Rong Luo, Hua-Lin Wang, Jian-Bo He, Yun-Guei Zhu

Journal of Electrochemistry

The effect of vanadium on the properties of the electrode of molybdenum nitride has been studied by using XRD?SEM and cyclic voltammetry.Modified molybdenum nitride was made as follow:films were coated by dipping titanium sheet in the solution containing different composition of molybdenum oxide,ammonium vanadate,ammonia,glycol and oxalic acid,and coated films are reacted with free ammonia.The results show that the specific capacitance of modified electrode was considerably increased and the operation voltage was broadened with the addition of ammonium vanadate in the dipping solution.The mechanism of these effects generated is the formation of new phase VOMoO 4 in the electrode of molybdenum …

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Research Progress On Electrode Material In All-Vanadium Redox Battery, Hua Li, Shou-Wen Chang, Chuan-Wei Yan Aug 2002

Research Progress On Electrode Material In All-Vanadium Redox Battery, Hua Li, Shou-Wen Chang, Chuan-Wei Yan

Journal of Electrochemistry

An all_vanadium redox flow storage battery possesses many advantages over conventional storage batteries.The development statue of two types electrode materials(metal and compound type)is introduced in this article.

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Study On Modification Of Spinel Limn_2o_4 By Overcoating, Ren-Gang Zhang, Shi-Xi Zhao, Jung-Lei Xia, Han-Xing Liu Aug 2002

Study On Modification Of Spinel Limn_2o_4 By Overcoating, Ren-Gang Zhang, Shi-Xi Zhao, Jung-Lei Xia, Han-Xing Liu

Journal of Electrochemistry

The surface of spinel LiMn 2O 4 was modified by the sol_gel process with LiCoO 2_coated LiMn 2O 4 and studied by XRD,SEM and EPMA.The results have shown that the surface of the coated grains heated at 700 ℃ for 10h,which is cubic spinel,were Co_rich.The amount of Co 3+ in the grains changed owing to different place of the grain and decreased from surface to inner parts. Using the coated as the cathode of Li_ion cells,the initial capacity deceased slightly,but the amount of Mn 2+ solving in electrolyte decreased,Jahn_Teller effect was suppressed to a certain extent.The LiCoO 2_coated LiMn 2O …

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Some Consideration For Lithium-Ion Cells' Safety, Guang-Xia Hu, Jing-Ying Xie Aug 2002

Some Consideration For Lithium-Ion Cells' Safety, Guang-Xia Hu, Jing-Ying Xie

Journal of Electrochemistry

The safety is the most important problem for lithium ion cells, especially for large lithium ion cells. In this paper, some information about lithium ion cells' safety can be learned by discussing several aspects of lithium ion cells, such as, materials of lithium ion cell , manufacturing processes, using conditions and so on.

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Initial Stages Of Copper Electrodeposition On Glassy Carbon Electrode, Ling Huang, Rui Zhang, Min Gu, Fang-Zu Yang, Shu-Kai Xu, Shao-Min Zhou Aug 2002

Initial Stages Of Copper Electrodeposition On Glassy Carbon Electrode, Ling Huang, Rui Zhang, Min Gu, Fang-Zu Yang, Shu-Kai Xu, Shao-Min Zhou

Journal of Electrochemistry

Initial stages of copper electrodeposition on glassy carbon electrode from acid sulphate solutions were studied using cyclic voltammetry and chronoamperometry.The electrolyte solution was a 0.05 mol.L -1 copper sulphate,1.4～1.8 mol.L -1 sulphuric acid containing 1 mg.L -1 2_mercaptobenzoimidazole,Results show that 2_mercaptobenzoimidazole produced an inhibition of the copper deposition,probably related to the adsorption,sulphuric acid promote copper electrodeposition.The initial deposition kinetics corresponded to a model including instantaneous nucleation and diffusion controlled growth.Addition of 2_mercaptobenzoimidazole and sulphuric acid did not change the initial nucleation of copper electrocrystallization,it increased the nucleation rate and the number density of nuclei at the surface.

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Synthesis And Characterization Of Lini_(0.8-X)Al_Xco_(0.2)O_2 As Cathodes For Lithium-Ion Batteries, Jun Zhang, Zhong-Kao Jin, Qing-He Yang, Qing-Mei Song, Xiao-Hua Ma, Xiang-Fu Zong Aug 2002

Synthesis And Characterization Of Lini_(0.8-X)Al_Xco_(0.2)O_2 As Cathodes For Lithium-Ion Batteries, Jun Zhang, Zhong-Kao Jin, Qing-He Yang, Qing-Mei Song, Xiao-Hua Ma, Xiang-Fu Zong

Journal of Electrochemistry

Single_phase solid solution of LiNi 0.8- x Al x Co 0.2 O 2 (0≤ x <0.1)had been synthesized and characterized by X_ray diffraction(XRD) and scanning electron microscopy (SEM). Their electrochemical performance was examined by charge_discharge cycling.The LiNi 0.71 Al 0.09 Co 0.2 O 2 compound showed a discharge capacity of 152 mAh/g after 20 cycles that corresponds to 97.4% capacity retention. The beneficial effect of co_doping with Al and Co elements was corro_borated by slow scanning cyclic voltammograms(SSCV),electrochemical impedance spectrum(EIS)and differential scanning calorimetry(DSC) data on charged cathodes. These results show that the 2D_character of the crystal lattice was stabilized by co_doping with Al and Co, the phase transitions that occur during deintercalation or intercalation of Li_ions were significantly suppressed,and thermal stability in the charged state was also improved.

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Ionic Conduction In Ba_(0.95)Ce_(0.9)Y_(0.1)O_(3-Α)Solid Oxide And Its Performance In Fuel Cell, Gui-Lin Ma, Ding-Xian Jia, Li-Gan Qiu, Hui Shi, Rong Chen Aug 2002

Ionic Conduction In Ba_(0.95)Ce_(0.9)Y_(0.1)O_(3-Α)Solid Oxide And Its Performance In Fuel Cell, Gui-Lin Ma, Ding-Xian Jia, Li-Gan Qiu, Hui Shi, Rong Chen

Journal of Electrochemistry

Using Ba 0.95 Ce 0.9 Y 0.1 O 3-α as a solid electrolyte and porous platinum as electrodes,hydrogen and oxygen concentration cells and hydrogen_air fuel cell were constructed,respectively.Electromotive forces(MEFs)of the gas concentration cells and I_V characteristics of the fuel cell were detdrmined in the temperature range of 600～1 000 ℃.The Ba 0.95 Ce 0.9 Y 0.1 O 3-α exhibited almost the pure protonic conduction under hydrogen gas,and a mixed conduction of oxide_ion and electron hole with oxide_ion transport number of 0.3～0.5 under oxygen gas.It exhibited a mixed conduction of proton and oxide_ion with the total ion transport number above 0.9 …

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Optimum Of Catalyst Layers For Direct Methanol Fuel Cells, Jun Zhang, Lei Li, Li Xu, Yu-Xin Wan Aug 2002

Optimum Of Catalyst Layers For Direct Methanol Fuel Cells, Jun Zhang, Lei Li, Li Xu, Yu-Xin Wan

Journal of Electrochemistry

The performances of membrane electrode assemblies (MEAs)with various Pt loading were compared.The amount of Nafion in a catalytic layer was optimized,and the effect of Nafion loading on the resistance of MEAs was investigated with ac impedance spectroscopy.For a MEA with both Pt 4 mg/cm 2 in the anode and the cathode,suitable Nafion loading was 21.4 wt% in the anode.With 21.4 wt% Nafion loading in the cathode,the Direct Methanol Fuel Cells(DMFC) showed the highest performance at high current density.While,the DMFC performances came down,as Nafion loading increasing,for ohm and concentration polarization.

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Reflection-High Energy Electron Diffraction Study Of Si(100) Homoepitaxy By Femtosecond Pulsed Laser Deposition, Mohammed S. Hegazy Jul 2002

Reflection-High Energy Electron Diffraction Study Of Si(100) Homoepitaxy By Femtosecond Pulsed Laser Deposition, Mohammed S. Hegazy

Electrical & Computer Engineering Theses & Dissertations

The dynamics of femtosecond pulsed laser deposition (fsPLD) of Si(!00)-1 x I and Si(!00)-2x I homoepitaxy are studied by in situ reflection high-energy electron diffraction (RHEED) and ex situ atomic force microscopy (AFM). The effects of substrate temperature, laser fluence and the pressure of a passive gas on the Si(!00)-1 x I growth mode are discussed. It is shown that films grow following the Volmer-Weber (3D) growth mode. The substrate temperature largely affects the morphology of the grown film. Below ~ 400 °C (at laser fluence of~ 1.9 J/cm2), randomly oriented 3D clusters are grown. This is shown …

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Development Of An Efficient Ti:Sapphire Laser Transmitter For Atmospheric Ozone Lidar Measurements, Khaled A. Elsayed Jul 2002

Development Of An Efficient Ti:Sapphire Laser Transmitter For Atmospheric Ozone Lidar Measurements, Khaled A. Elsayed

Electrical & Computer Engineering Theses & Dissertations

The impetus of this work was to develop an all solid-state Ti:sapphire laser transmitter to replace the current dye lasers that could provide a potentially compact, robust, and highly reliable laser transmitter for differential absorption lidar measurements of atmospheric ozone. Two compact, high-energy pulsed, and injection-seeded Ti:sapphire lasers operating at a pulse repetition frequency of 30 Hz and wavelengths of 867 nm and 900 nm, with M2 of 1.3, have been experimentally demonstrated and compared to model results. The Ti:sapphire lasers have shown the required output beam quality at maximum output pulse energy, 115 mJ at 867 nm and …

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Adaptive Predictive Congestion Control Of High-Speed Atm Networks, Sarangapani Jagannathan, Jayasree Talluri Jun 2002

Adaptive Predictive Congestion Control Of High-Speed Atm Networks, Sarangapani Jagannathan, Jayasree Talluri

Electrical and Computer Engineering Faculty Research & Creative Works

This paper proposes an auto regressive moving average (ARMAX)-based adaptive control methodology to prevent congestion in high-speed asynchronous transfer mode (ATM) networks. Adaptive controller is developed to control traffic where sources adjust their transmission rates in response to the feedback information from the network switches. Specifically, the buffer dynamics at a given switch is modeled as a nonlinear discrete-time system and an ARMAX controller is designed so as to predict the explicit values of the transmission rates of the sources so as to prevent congestion. Tuning methods are provided for the unknown coefficients of the ARMAX model to estimate the …

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