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2006

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Articles 1231 - 1260 of 5872

Full-Text Articles in Physical Sciences and Mathematics

Hr 1613: A Slowly Rotating A Dwarf Spectroscopic Binary With Solar Abundances, Francis C. Fekel, Michael H. Williamson, Christiane Buggs, Gerald Onuoha, Brittany Smith Aug 2006

Hr 1613: A Slowly Rotating A Dwarf Spectroscopic Binary With Solar Abundances, Francis C. Fekel, Michael H. Williamson, Christiane Buggs, Gerald Onuoha, Brittany Smith

Information Systems and Engineering Management Research Publications

From two sets of radial velocities we have obtained the orbital elements of HR 1613. This single-lined binary has an orbital period of 8.11128 days and a nearly circular orbit. The primary has an A9 V spectral type and a v sin i value of 11 km s-1, while the unseen secondary is likely a K or M dwarf. Spectral classifications and spectrum synthesis analysis indicate that the abundances of the primary are normal. We reject the possibility that the primary of HR 1613 is seen nearly pole-on and instead argue that its rotational inclination is at least 20°, resulting …

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A Fast Algorithm For Color Image Segmentation, L. Dong, P. Ogunbona, Wanqing Li, G. Yu, L. Fan, G. Zheng Aug 2006

A Fast Algorithm For Color Image Segmentation, L. Dong, P. Ogunbona, Wanqing Li, G. Yu, L. Fan, G. Zheng

Faculty of Informatics - Papers (Archive)

Based on K-means and a two-layer pyramid structure, a fast algorithm is proposed for color image segmentation. The algorithm employs two strategies. Firstly, a two-layer structure of a color image is established. Then, an improved K-means with integer based lookup table implementation is applied to each layer. The clustering result on the upper layer (lower resolution) is used to guide the clustering in the lower layer (higher resolution). Experiments have shown that the proposed algorithm is significantly faster than the original K-means algorithm while producing comparable segmentation results.

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Distributed Management Of Oma Drm Domains, Harikrishna Vasanta, Reihaneh Safavi-Naini, Nicholas Paul Sheppard, Martin Jan Surminen Aug 2006

Distributed Management Of Oma Drm Domains, Harikrishna Vasanta, Reihaneh Safavi-Naini, Nicholas Paul Sheppard, Martin Jan Surminen

Faculty of Informatics - Papers (Archive)

Version 2.0 of the Open Mobile Alliance's Digital Rights Management Specification provides for protected content to be shared amongst a collection of devices in a domain. Domains are created and managed directly by the rights issuer that issues rights to the domain. In this paper, we propose to devolve the management of domains to a domain manager known as "Heimdall" that acts as a broker between the devices in an authorised domain and any content providers from which content for the domain can be sourced. We describe and compare three different modes in which Heimdall might operate.

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A Shocking Device For Protection Of Concentrated Food Sources From Black Bears, Stewart W. Breck, Nathan Lance, Peggy Callahan Aug 2006

A Shocking Device For Protection Of Concentrated Food Sources From Black Bears, Stewart W. Breck, Nathan Lance, Peggy Callahan

United States Department of Agriculture Wildlife Services: Staff Publications

Conflicts with American black bears (Ursus americanus) are increasing in rural and suburban areas throughout the United States. Human encroachment on bear range has increased availability of garbage, bird feeders, beehives, and other food sources. Preventing bears from attaining food from anthropogenic sources could mitigate these conflicts. We tested a new shocking mechanism that is being marketed to deter black bears from attaining food from clumped anthropogenic food sources. The Nuisance Bear Controller (NBC) has two 6-volt batteries wired to an automobile vibrator coil/condenser that emits 10,000–13,000 volts through a disk that triggers the device. Activation of the NBC only …

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Customer Lifetime Value : An Integrated Data Mining Approach, Chen Xu Aug 2006

Customer Lifetime Value : An Integrated Data Mining Approach, Chen Xu

Theses & Dissertations

Customer Lifetime Value (CLV) ---which is a measure of the profit generating potential, or value, of a customer---is increasingly being considered a touchstone for customer relationship management. As the guide and benchmark for Customer Relationship Management (CRM) applications, CLV analysis has received increasing attention from both the marketing practitioners and researchers from different domains. Furthermore, the central challenge in predicting CLV is the precise calculation of customer’s length of service (LOS). There are several statistical approaches for this problem and several researchers have used these approaches to perform survival analysis in different domains. However, classical survival analysis techniques like Kaplan-Meier …

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Avian Influenza In Wild Birds: Status As Reservoirs, And Risks To Humans And Agriculture , Larry Clark, Jeffrey Hall Aug 2006

Avian Influenza In Wild Birds: Status As Reservoirs, And Risks To Humans And Agriculture , Larry Clark, Jeffrey Hall

United States Department of Agriculture Wildlife Services: Staff Publications

Influenza A viruses are naturally reservoired in wild bird populations, in which they generally exist as low-pathogenic subtypes. Historically, concern about avian influenza virus (AIV) in wild birds is related to its potential effects on agriculture and human health, and not to health issues of wild bird populations. Several subtypes (primarily H5 and H7) have caused severe outbreaks of disease in domestic bird populations. In some cases, genetic and spatial temporal analyses suggest that these high-pathogenic subtypes may originate in wild bird populations that transmit low-pathogenic forms to domestic birds; after passage in domestic birds, the low-pathogenic subtypes convert to …

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Quantum Entanglement Via Nilpotent Polynomials, Aikaterini Mandilara, Vladimir M. Akulin, Andrei V. Smilga, Lorenza Viola Aug 2006

Quantum Entanglement Via Nilpotent Polynomials, Aikaterini Mandilara, Vladimir M. Akulin, Andrei V. Smilga, Lorenza Viola

Dartmouth Scholarship

We propose a general method for introducing extensive characteristics of quantum entanglement. The method relies on polynomials of nilpotent raising operators that create entangled states acting on a reference vacuum state. By introducing the notion of tanglemeter, the logarithm of the state vector represented in a special canonical form and expressed via polynomials of nilpotent variables, we show how this description provides a simple criterion for entanglement as well as a universal method for constructing the invariants characterizing entanglement. We compare the existing measures and classes of entanglement with those emerging from our approach. We derive the equation of motion …

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Super-Resolution Overlay In Multi-Projector Displays, Christopher O. Jaynes, Divya T. Ramakrishnan Aug 2006

Super-Resolution Overlay In Multi-Projector Displays, Christopher O. Jaynes, Divya T. Ramakrishnan

Computer Science Faculty Patents

A technique, associated system and computer executable program code, for projecting a superimposed image onto a target display surface under observation of one or more cameras. A projective relationship between each projector being used and the target display surface is determined using a suitable calibration technique. A component image for each projector is then estimated using the information from the calibration, and represented in the frequency domain. Each component image is estimated by: Using the projective relationship, determine a set of sub-sampled, regionally shifted images, represented in the frequency domain; each component image is then composed of a respective set …

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The Role Of Enzyme Dynamics And Tunnelling In Catalysing Hydride Transfer: Studies Of Distal Mutants Of Dihydrofolate Reductase, Lin Wang, Nina Goodey, Stephen J. Benkovic, Amnon Kohen Aug 2006

The Role Of Enzyme Dynamics And Tunnelling In Catalysing Hydride Transfer: Studies Of Distal Mutants Of Dihydrofolate Reductase, Lin Wang, Nina Goodey, Stephen J. Benkovic, Amnon Kohen

Department of Chemistry and Biochemistry Faculty Scholarship and Creative Works

Residues M42 and G121 of Escherichia coli dihydrofolate reductase (ecDHFR) are on opposite sides of the catalytic centre (15 and 19 Å away from it, respectively). Theoretical studies have suggested that these distal residues might be part of a dynamics network coupled to the reaction catalysed at the active site. The ecDHFR mutant G121V has been extensively studied and appeared to have a significant effect on rate, but only a mild effect on the nature of H-transfer. The present work examines the effect of M42W on the physical nature of the catalysed hydride transfer step. Intrinsic kinetic isotope effects (KIEs), …

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Design Of Novel Molecular Micelles For Capillary Electrophoresis, Syed Asad Ali Rizvi Aug 2006

Design Of Novel Molecular Micelles For Capillary Electrophoresis, Syed Asad Ali Rizvi

Chemistry Dissertations

The research presented in this dissertation involves the synthesis, characterization, and application of novel anionic and cationic chiral molecular micelles in capillary electrophoresis (CE) for the separation of diverse chiral compounds. Chapter 1 presents brief overview of the surfactants, micelle polymer, CE and micellar electrokinetic chromatography (MEKC). Chapter 2 describes the simultaneous enantioseparation of eight single chiral center â-blockers using two novel leucine and isoleucine based polymeric surfactants. The simultaneous enantioseparation of multichiral center bearing â-blockers, nadolol and labetalol is described in chapter 3. A synergistic approach, using a combination of polysodium N-undecenoxycarbonyl-L-isoleucinate (poly-L-SUCIL) and sulfated â-CD showed dramatic enantioseparation …

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Improved Generalized Estimating Equation Analysis Via Xtqls For Implementation Of Quasi-Least Squares In Stata, Justine Shults, Sarah J. Ratcliffe, Mary Leonard Aug 2006

Improved Generalized Estimating Equation Analysis Via Xtqls For Implementation Of Quasi-Least Squares In Stata, Justine Shults, Sarah J. Ratcliffe, Mary Leonard

UPenn Biostatistics Working Papers

No abstract provided.

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Adjustment Uncertainty In Effect Estimation, Ciprian M. Crainiceanu, Francesca Dominici, Giovanni Parmigiani Aug 2006

Adjustment Uncertainty In Effect Estimation, Ciprian M. Crainiceanu, Francesca Dominici, Giovanni Parmigiani

Johns Hopkins University, Dept. of Biostatistics Working Papers

The selection of confounders and their functional relationship with the out- come affects exposure effect estimates. In practice, there is often substantial uncertainty about this selection, which we define here as “adjustment uncertainty.” We address the problem of estimating the effect of exposure on an outcome with focus on quantifying the effect of unknown confounders from a large set of potential confounders. We propose a general statistical framework for handling adjustment uncertainty in exposure effect estimation, a specific implementation called "Structured Estimation under Adjustment Uncertainty (STEADy)", and associated visualization tools. Theoretical results and simulation studies show that STEADy consistently estimates …

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Essays On Individual And Collective Powers In A Voting Body., Sonali Roy Dr. Aug 2006

Essays On Individual And Collective Powers In A Voting Body., Sonali Roy Dr.

Doctoral Theses

MotivationThe issue of measurement of voting power is a very important topic of discussion in social science these days. The concept of voting power concerns any collective decision making body (or, equivalently, a collectivity) which makes ‘yes’ or ‘no’ decisions on any issue, by the process of voting. Examples of such bodies abound in today’s world. The United Nations Security Council, The Council of Ministers in the European Union, the Parliament of the republic of India, the board room of any corporate house etc., are all examples of such decision making bodies.The voting process of each of these bodies is …

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Studies On Performance And Electrode Materials For All Vanadium Flow Battery, Yuan Jun Aug 2006

Studies On Performance And Electrode Materials For All Vanadium Flow Battery, Yuan Jun

Journal of Electrochemistry

In this paper,cyclic voltammetry has been used to study the electrochemical performance of the treated and untreated graphite,soft graphite and PAN-carbon cloth in vanadium sulfate solution.The results show that: the reversibility of reaction can be improved on the surface of treated electrode,and the current can also increase;the electrochemical performance of treated electrode is remarkably enhanced;in the process of charge/discharge,the charge current can reach up to 20 mA/cm~(2),and discharge current up to 15 mA/cm~(2);surface morphology of the treated and untreated graphite show that the treatment can change the surface structure of electrode and also add the reaction area.

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Electrodeposition Of Nano-Sb-Zn Alloy In Acetamide-Urea-Nabr-Kbr Melt, Peng Liu, Xin-Ai Guo, Ye-Xiang Tong, Qi-Qin Yang Aug 2006

Electrodeposition Of Nano-Sb-Zn Alloy In Acetamide-Urea-Nabr-Kbr Melt, Peng Liu, Xin-Ai Guo, Ye-Xiang Tong, Qi-Qin Yang

Journal of Electrochemistry

The electroreduction of Zn(II) and Sb(III) in acetamide-urea-NaBr-KBr(343 K) were studied by cyclic volatmmetry.The reduction of Zn(II) or Sb(III) to the metals is an irreversible process.The transfer coefficient of Zn(II)+2e→Zn and Sb(III) +3e→Sb were calculated to be 0.231 and 0.319,the diffusion coefficient of Zn(II) and Sb(III) in the melt were determined as 1.70 10~(-6) and 3.21 10~(-6) cm~(2)· s~(-1) respectively.The Zn-Sb films with different Zn content from 29.67 at% to 97.34 at% were electrodeposited in acetamide-urea-NaBr-KBr melt at 343 K by controlling the deposition potential and the Zn(II)/Sb(III) molar ratio.The morphology of Zn-Sb film was observed by SEM.Zn-Sb film comprises …

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The Influence Of Pva As Disperser On Lifepo_(4) Synthesized By Hydrothermal Reaction, Hui-Lin Li, Hui Zhan Aug 2006

The Influence Of Pva As Disperser On Lifepo_(4) Synthesized By Hydrothermal Reaction, Hui-Lin Li, Hui Zhan

Journal of Electrochemistry

LiFePO_(4) was synthesized by means of hydrothermal reaction,in which PVA acts as disperser and glucose as carbon source.The samples were characterized by X-ray diffraction,scanning electron microscopy and electrochemical measurement.SEM results show that the sample is homogeneously composed of grains with a particle size of ca.200nm.In the charge/discharge test,the products exhibited a 3.45V discharge voltage plateau and a maximum specific capacity of 140mAh/g.After 40 cycles,its capacity only declined by 2.1%.Besides these,the mechanism for the influence of the particle size and carbon coating on the electrochemical property of LiFePO_(4)material was discussed in detail.

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Calcined Temperatures Influence On Synthesis And Electrochemistry Charactarization Of Li[Ni_(0.475)Mn_(0.475)Co_(0.05)]O_(2) For Li-Ion Batteries, Li-Qin Wang, Li-Fang Jiao, Hua-Tang Yuan Aug 2006

Calcined Temperatures Influence On Synthesis And Electrochemistry Charactarization Of Li[Ni_(0.475)Mn_(0.475)Co_(0.05)]O_(2) For Li-Ion Batteries, Li-Qin Wang, Li-Fang Jiao, Hua-Tang Yuan

Journal of Electrochemistry

Layered Li[Ni_(0.475)Mn_(0.475)Co_(0.05)]O_(2) materials have been prepared by a solid-state pyrolysis method.Experiments of XRD,SEM,cyclic voltammetry and charge/discharge cycling were carried out.It can be learned that when calclined at 800 ℃,the sample showed the highest first discharge capacity of 178.8 mAh·g~(-1) at a current density of 20 mA/g in the voltage range 2.3~4.6 V.

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Influence Of Crystallinity On The Kinetics Of Li Ion Insertation And Deinsertation In Spinel Limn_(2)O_(4), Rong-Hua Zeng, Dong-Sheng Lv, Wei-Shan Li Aug 2006

Influence Of Crystallinity On The Kinetics Of Li Ion Insertation And Deinsertation In Spinel Limn_(2)O_(4), Rong-Hua Zeng, Dong-Sheng Lv, Wei-Shan Li

Journal of Electrochemistry

Two spinel lithium manganese oxides of different crystallinity were prepared by sol-gel process and were studied by using inducfively coupled plasma,X-ray diffraction,scaning electron micrographs,constant charging and discharging,cyclic voltammetry and electrochemical impedance spectrometry,the results show that the sample treated under 700 ℃ has higher crystallinity than the sample treated under 500 ℃,however,the sample with lower crystallinity has higher discharge capacity and better cyclic performance that due to quicker charge exchange speed and quicker diffusion speed of Li-ion.

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Investigation Of The Direct Electrochemical Reduction Of Cr_(2)O_(3) Powder In Molten Cacl_(2) By A Metallic Cavity Electrode, Guo-Hong Qiu, Di-Hua Wang, Xian-Bo Jin, Xiao-Hong Hu, Zheng Chen Aug 2006

Investigation Of The Direct Electrochemical Reduction Of Cr_(2)O_(3) Powder In Molten Cacl_(2) By A Metallic Cavity Electrode, Guo-Hong Qiu, Di-Hua Wang, Xian-Bo Jin, Xiao-Hong Hu, Zheng Chen

Journal of Electrochemistry

A metallic cavity electrode is used for further investigation of the electrochemical behaviour of(Cr_(2)O_3) powder in molten CaCl_(2)(Na: ~0.02% by mass,Mg: < 0.005% by mass) at 900 ℃.The Cr_(2)O_(3) powder reduction mechanism was confirmed in line with EDX and SEM analysis of the potentiostatic electrolysis products.The correlations between the particle size of metallised product and the electrolysis potential,or electrolysis time were analysed.

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The Electrochemical Study On Self-Assembled Monolayers Of Sodium Stearate Surfactant On Oil/Water Interface, Li-Na Tang Aug 2006

The Electrochemical Study On Self-Assembled Monolayers Of Sodium Stearate Surfactant On Oil/Water Interface, Li-Na Tang

Journal of Electrochemistry

The self-assembled monolayers of sodium stearate surfactant on oil/water interface was investigated by CV with copper ion as probe.The self-assembling process includes four stages,and forms a stable assembly.The electrochemical oxidation of copper ion at assembled surface is a combine controlled process both surface and diffusion with regression equation as i_(p) = 9.214-3.889 v~(1/2) +0.5809v,r=0.9978,compared with the oil covered bared electrode,it is a complete surface controlled.

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Pre-Oxidative Amperometric Glucose Biosensor Incorporated With Carbon Nanotube And Pbo_(2), Hong-Lan Qi, Cheng-Xiao Zhang Aug 2006

Pre-Oxidative Amperometric Glucose Biosensor Incorporated With Carbon Nanotube And Pbo_(2), Hong-Lan Qi, Cheng-Xiao Zhang

Journal of Electrochemistry

A pre-oxidative amperometric glucose biosensor incorporated with carbon nanotube,ferrocenemonocarboxylic acid and PbO_(2) was designed.The interferences coming from reduced substances,such as ascoribic acid and urine acid were eliminated by PbO_(2).The oxidative current is linear at the potential of +0.40 V(vs.SCE) to the concentration of glucose in the range from 0.50 to 20 mmol·L~(-1),and the detection limit of glucose is 0.1 mol L~(-1).The relative standard deviation is 3.3% for seven successive assays at 5.0 mmol·L~(-1)glucose.This biosensors have been applied to determination of the glucose in serum with satisfying results.

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Research Of Explosion Mechanism Of Lithium-Ion Battery, Yu-Hong Chen, Zhi-Yuan Tang Aug 2006

Research Of Explosion Mechanism Of Lithium-Ion Battery, Yu-Hong Chen, Zhi-Yuan Tang

Journal of Electrochemistry

The heat character of Lithium-ion battery materials and explosion mechanism of Lithium-ion cells under the overcharge,short-circuit and other abuse behavior are tested by C_(80) calorimeter,_()DSC and charge-discharge instrument.SEI reactions,Li_xC_(6)/electrolyte and Li_xC_(6)/PVDF reactions take place at the anodes.Electrolyte and solvent reactions happen after 178℃ and Li_(1-x)Co_(1/3)Ni_(1/3)Mn_(1/3)O_(2) decomposes after 230℃.The batteries explode at 150℃ oven test or 1.5C,5.5 V overcharge and do not explode at short-circuit.

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Preparation And Supercapacitor Properties Of Yttrium Doped Nio, Dan-Dan Han Aug 2006

Preparation And Supercapacitor Properties Of Yttrium Doped Nio, Dan-Dan Han

Journal of Electrochemistry

Yttrium doped Nano-NiO were synthesized by chemical precipitation method.Characterization and performance of the samples were studied by X-ray diffraction,the results showed that the doping Yttrium did not change the crystal structure of NiO,but the size of crystalline grain was reduced.The electrochemical properties of the electrode materials were measured in the three electrode system.Electrochemical properties of NiO were researched by cyclic voltammetry,constant current charge/discharge and AC impedance methods.It could be seen that the chemical doping improved the specific capacitance and the utilization of active materials.When the weight ratio of NiO with Y_(2)O_(3)was 1∶0.1,the composite material had the best properties.The maximum discharge …

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Recycling Of The Spent Nickel-Cadmium Batteries Based On Bioleaching Process, Liang-Shu Xia, Shi-Fu Fu, Zhong-Qing Chen Aug 2006

Recycling Of The Spent Nickel-Cadmium Batteries Based On Bioleaching Process, Liang-Shu Xia, Shi-Fu Fu, Zhong-Qing Chen

Journal of Electrochemistry

Less than 1 percent of discarded dry batteries are recovered in china.it is necessary to find an economic,fast and environmentally friendly process to recycle spent dry batteries.Bioleaching is better one of the few technology applied for the recovery of the toxic metals from hazardous spent batteries.In this study,after the acidified sludge made by the inoculated and cultured indigenous sewage sludge was acted as leaching bacteria species,the influence of the different pH values,the different residence time of the sludge in bioreactor(RTB),the leaching time,whether or not adding Fe(iron powder) to the leaching liquid on the leaching rate of Ni,Cd was tested.The results …

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Study On The Microstructure Of Pb-Sn Alloy Obtained From Quasi-Two-Dimensional Electrodeposition, Bin Sun Aug 2006

Study On The Microstructure Of Pb-Sn Alloy Obtained From Quasi-Two-Dimensional Electrodeposition, Bin Sun

Journal of Electrochemistry

A two-layered structure of eutectic-solid sulotion is formed in the microstructure of Pb-Sn alloy obtained from quasi-two-dimensional electrodeposition.It is showed that this unique structure is caused by the variation of the current density on the growth interface.When the interface is located in the front of the whole deposits,the current density is high.So the Pb and Sn can deposit together and the eutectic texture forms.When the interface is in the rear of the whole deposits,the current density is low.At this moment the electrodeposition of Pb is the dominant reaction,and the Pb-based solid solution appears.

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Study On The Preparetion And Electrochemical Beavior Of Nitrogen Doped Tetrahedral Amorphous Carbon Electrode, Ke Liu Aug 2006

Study On The Preparetion And Electrochemical Beavior Of Nitrogen Doped Tetrahedral Amorphous Carbon Electrode, Ke Liu

Journal of Electrochemistry

taC∶N films are a good materials for semiconductor electrodes.But further studies are hampered by the ohmic contact problem,which occurs between the silicon and the lead.By studying the influence of heat treatment on the film's property,it is believed that ohmic contact should be made on the silicon first,and then the film be deposited.A set of taC∶N electrodes with various nitrogen content have been prepared.CV study indicates that the cathodic limits move slowly to positive direction.while the anodic limits are unchanged with the increasing of nitrogen content.As a result,the electrochemical windows get narrow either.

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The Property Study Of Libob-Pc/Dec Electrolyte, Ying-Kun Ning, Bi-Tao Yu, Fu-Shen Li, Wei-Hua Qiu Aug 2006

The Property Study Of Libob-Pc/Dec Electrolyte, Ying-Kun Ning, Bi-Tao Yu, Fu-Shen Li, Wei-Hua Qiu

Journal of Electrochemistry

The new electrolyte salt LiBOB for Li-ion battery was synthesized in laboratory,and series of electrolytes of LiBOB and PC/DEC was compounded.The conductivity of the electrolytes was compared by changing the temperature and concentration.The cycling performance of charging-discharging was also compared by the charging-discharging test,the results showed that the varying regularity of conductivities and cycling stability and capacity were not always identical,but there were a suitable electrolyte for Li/ARG cell.The A.C.impedance and CV were used to test the compatibility of the most suitable electrolyte and ARG anode.Conclusion can be drawn that the ARG anode can be protected very well by SEI …

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Studies On Synthesis And Electrochemical Performance Of Li_(X)Ni_(1/3)Mn_(1/3)Co_(1/3)O_(2) As Cathode Material For Lithium Ion Batteries, Xiao-Jian Guo, Jie Li, Yi-Xiao Li, Yong Yang Aug 2006

Studies On Synthesis And Electrochemical Performance Of Li_(X)Ni_(1/3)Mn_(1/3)Co_(1/3)O_(2) As Cathode Material For Lithium Ion Batteries, Xiao-Jian Guo, Jie Li, Yi-Xiao Li, Yong Yang

Journal of Electrochemistry

A series of LiNi_(1/3)Mn_(1/3)Co_(1/3)O_(2) were synthesized by a combined hydroxides coprecipitation and calcination method.Effects of synthesizing temperature of coprecipitations and the Li∶M ratios on structure and electrochemical performance of the materials were studied.The results showed that materials synthesized with coprecipitation at room temperature(~20 ~(o)C) delivered the best electrochemical performance.Another series of cathode materials Li_(x)Ni_(1/3)Mn_(1/3)Co_(1/3)O_(2) with different Li∶M ratios were synthesized with this method.The results showed that sintering at high temperature could cause loss of LiOH,thus more LiOH should be added.It is demonstrated that Li_(1.08)Ni_(1/3)Mn_(1/3)Co_(1/3)O_(2) had the best electrochemical performance.

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Effects On The Structure And Electrochemical Performance Of Lifepo_(4) By Zr~(4+) Doping, Yan-Li Ruan, Zhi-Yuan Tang Aug 2006

Effects On The Structure And Electrochemical Performance Of Lifepo_(4) By Zr~(4+) Doping, Yan-Li Ruan, Zhi-Yuan Tang

Journal of Electrochemistry

Stoichiometric Zr-doped lithium iron phosphate(LiFePO_(4)) cathode material was synthesized by a solid-state reaction in an inert atmosphere.The effects of doping content on the physical and electrochemical properties of as-synthesized cathode materials were investigated.The samples were characterized by powder X-ray diffraction(XRD),and their electrochemical performance was systematically measured by impedance response and constant current charge/discharge cycling tests.The results indicate that the low concentration Zr~(4+)doping does not affect the structure of the material but considerably improves its kinetics in terms of capacity delivery and cycle performance.At 0.1C discharging rate,the reversible specific capacities of the Li_(0.99)Zr_(0.01)FePO_(4)cathode material is 135.6mAh g~(-1).After 30 cycles,the capacity fade …

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Effect Of Ti Doping On The Structure And Performance Of Lini_(0.75)Co_(0.25)O_(2), Hui He, Xuan Cheng, Zhang Ying Aug 2006

Effect Of Ti Doping On The Structure And Performance Of Lini_(0.75)Co_(0.25)O_(2), Hui He, Xuan Cheng, Zhang Ying

Journal of Electrochemistry

In this study,a series of Co-doped compounds with the formula of LiNi_((0.75-x))Co_(0.25)Ti_(x)O_(2)(x=0,(0.1),0.25)was synthesized by using sol-gel method.Their structure,particle size,electrochemical properties were studied by TG,XRD,SEM and electrochemical tests.It was shown that the structure of materials changed from a hexagonal layered structure to a cubic structure as the x value increased.In particular,a mixture of hexagonal and cubic structure was presented at x =0.25.The electrochemical performance of the materials depended strongly on the amount of Ti doping.Possible effects on the structure and performance of LiNi_((0.75-x))Co_(0.25)Ti_(x)O_(2) due to Ti doping are briefly discussed based upon the experiment and computational results.

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