• Transactions on Electrical and Electronic Materials
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• v.8 no.4
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• pp.157-160
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• 2007

Lithium-sulphur batteries were fabricated in a dry room, and their electrochemical properties were analyzed by scanning electron microscopy (SEM), cyclic voltammetry (CV), and charge-discharge tests. SEM results showed that sulphur and nanocarbon powders were mixed homogeneously, and sulphur powders were enwrapped by a large amount of carbon powders. The charge-discharge test results demonstrated that the lithium-sulphur battery displayed excellent reversibility and cycling performance, which supplied a discharge capacity of $788.1mAh\;g^{-1}$ at the first cycle and $796.4mAh\;g^{-1}$ after 71 cycles at room temperature, respectively.

• Annual Conference on Human and Language Technology
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• 2013.10a
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• pp.160-162
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• 2013

편리한 블로그 사용과 블로그에서의 정보 탐색을 위해서는 내용에 기반한 분류가 필요하다. 대부분의 블로그 사이트에서는 내용 기반 분류를 제공하고 있으나, 블로거들은 자신이 작성한 블로그에 대한 수동 분류를 입력하지 않는 경우가 많다. 본 논문에서는 분류가 제공되는 블로그 사이트에서 각 분류별 문서를 수집하고, 어휘빈도와 문서빈도, 분류별 빈도를 활용하여 문서 내 어휘의 자질 가중치를 부여하고, 다양한 학습기를 이용하여 분류 모델을 생성한 뒤 블로그의 특성에 적합한 자질 추출 알고리즘과 분류 알고리즘을 찾아낸다. 실험에서는 본 논문에서 고안한 CTF-IECDF와 나이브 베이즈 멀티노미얼로 조합한 분류 모델이 75.40%의 분류 정확률을 보였다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.07a
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• pp.667-670
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• 2000

The electrochemical characterization was conducted by the addition of chemically synthesized polyaniline on LiCoO$_2$electrode. From the results of XRD and SEM, the phase transition and microstructure were not found. Initial electrochemical characteristics of LiCoO$_2$electrode for lithium secondary battery were evaluated through the charge/discharge within the range of 4.3 V to 3.0 V versus Li/Li$^{+}$. Discharge capacity of LiCoO$_2$electrode without addition of Polyaniline were 160.21 mAh/g. But after addition of polyaniline, lower discharge capacities 25.7 mAh/g was found.d.

• Bulletin of the Korean Chemical Society
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• v.18 no.1
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• pp.61-65
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• 1997

The electrochemical properties of LixCoyNi1-yO2 compounds (y=0.1, 0.3, 0.5, 0.7, 1.0) prepared by citrate sol-gel method have been investigated. The LixCoyNi1-yO2 compounds were annealed at 850 ℃ for 20 h after preheating at 650 ℃ for 6 h, in air. The x-ray diffraction (XRD) patterns for LixCoyNi1-yO2 have shown that these compounds have a well developed layered structure (R&bar{3} m). From the scanning electron microscopy of LixCoyNi1-yO2, particle size was estimated less than 5 μm. The Li//LixCoyNi1-yO2 electrochemical cell consists of Li metal anode and 1 M LiClO4-propylene carbonate (PC) solution as the electrolyte. The differences in intercalation rate of the LixCoyNi1-yO2 in the first charge/discharge cycle were less than 0.05 e-. The first discharge capacities of LixCoO2 and LixCo0.3Ni0.7O2 were ∼130 mAh/g and ∼160 mAh/g, respectively.

• Journal of Hydrogen and New Energy
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• v.22 no.5
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• pp.728-734
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• 2011

$LiFePO_4$ is a promising cathode material for secondary lithium batteries due to its high energy density, low cost and safety. $LiFePO_4$ was synthesized by the citrate process under reductive, neutral, and oxidative, atmospheres and the crystal structure was analyzed by X-ray powder diffraction. The samples synthesized under $N_2$ and $H_2$ atmosphere showed a single phase of a olivine structure, where the samples synthesized under $O_2$ atmosphere exhibited second phase of $Fe2O_3$. All the samples synthesized at 400, 600 and $800^{\circ}C$ under $N_2$ atmosphere presented a single phase of olivine. Residual organic material was observed for the sample synthesized at $400^{\circ}C$. There was nearly no intensity difference between the samples synthesized at $600^{\circ}C$ and $800^{\circ}C$. The electrochemical characteristic of the $LiFePO_4$ synthesized at $600^{\circ}C$ in the $N_2$ atmosphere was analyzed. The result exhibited an high discharge capacity of 160 mAh/g at the first cycle, and 155-160 mAh/g after 45 cycles.

• Journal of the Korean Electrochemical Society
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• v.2 no.3
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• pp.123-129
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• 1999

Initial electrochemical characteristics of $LiCoO_2$ electrode for lithium ion battery with various content of super s black as conductive material were evaluated through the charge/discharge with the potential range of 4.3V to 2.0V versus $Li^+/Li^+$. The rate of C/4 and C/2 by the 3 electrode test cell composed with an electrolytic solution of 1 mol/l $LiPF_6/EC+DEC(1:3\;by\; weight)$. Lithium was used as reference electrode. High impedance charge behavior was observed at early stage of charge. In the case of $3\%w/w$ of super s black as conductive material, the specific resistance of the high impedance releasing was $3.82\;{\Omega}\;{\cdot}\;g-LiCoCo_2$ at the current density of $0.5 mA/cm^2$, which corresponds 7 times of the specific resistance of electrode $(0.728 g-LiCoO_2)$. At second charge, the specific resistance of the high impedance releasing was 63 mn · g-Lico02, which corresponds 12eio of the specific resistance of electrode and only $1.7\%$ of that of the first charge. The first charge and discharge specific capacities at C/4 rate were 160-161 and $153\~155mAh/g-LiCoO_2$, respectively, to lead $95.4\~96.4\%$ of coulombic efficiencies and ca. $6 mAh/g-LiCoO_2$ of initial irreversible specific capacity. Specific resistance at the end of charge and rest showed low value at content of super s black between 2 and $7\%w/w$, which agreed with characteristics of irreversible specific capacity. Capacity densities were reduced by the increasing the content of conductive material. They were 447 and 431mAh/ml when 2 and $2.9\%w/w$ of super s black were used, respectively, at the rate of C/4.

• KOREAN JOURNAL OF PACKAGING SCIENCE & TECHNOLOGY
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• v.18 no.1_2
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• pp.9-14
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• 2012

The dried persimmons are susceptible to fungal decay, browning, textural hardening during storage and marketing at ambient temperature. To resolve these problems in commercial storage, chilled storage at $0^{\circ}C$ was tried with cinnamon extract pre-treatment and different packaging conditions measuring the quality changes of dried persimmons for 160 days. Nylon/LDPE package among 6 tested package conditions was the best in maintaining the quality. The rate of weight loss, fungal decay, browning, hardening were the least in this package. Pre-treatment of cinnamon extract in quality of dried persimmons was effective in quality preservation.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.160.2-160.2
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• 2014

Recently silicon has attracted intense interest as a promising anode material of lithium-ion batteries due to its extremely high capacity of 4200 mA/g (for Li4.2Si) that is much higher than 372 mAh/g (for LiC6) of graphite. However, it seriously suffers from large volume change (even up to 300%) of the electrode upon lithiation, leading to its pulverization or mechanical failure during lithiation/delithiation processes and the rapid capacity fading. To overcome this problem, Si nanowires have been considered. Use of such Si nanowires provides their facile relaxation during lithiation/delithiation without mechanical breaking. To design better Si electrodes, a study to unveil atomic-scale mechanisms involving the volume expansion and the phase transformation upon lithiation is critical. In order to investigate the lithiation mechanism in Si nanowires, we have developed a reactive force field (ReaxFF) for Si-Li systems based on density functional theory calculations. The ReaxFF method provides a highly transferable simulation method for atomistic scale simulation on chemical reactions at the nanosecond and nanometer scale. Molecular dynamics (MD) simulations with the ReaxFF reproduces well experimental anisotropic volume expansion of Si nanowires during lithiation and diffusion behaviors of lithium atoms, indicating that it would be definitely helpful to investigate lithiation mechanism of Si electrodes and then design new Si electrodes.

• Transactions on Electrical and Electronic Materials
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• v.7 no.2
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• pp.76-80
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• 2006

Well-defined orthorhombic $LiMnO_2\;and\;LiCo_{0.1}Mn_{0.9}O_2$ were synthesized by a solid-state reaction and quenching process. X-ray diffraction (XRD) results revealed that the as-synthesized powders showed an orthorhombic phase of a space group with Pmnm. The $Li/LiMnO_2\;and\;Li/LiCo_{0.1}Mn_{0.9}O_2$ cells were constituted and cycled galvanostatically in the voltage range of 2.0-4.3 V vs. $Li/Li^+$ at a current density of $0.5\;mA\;cm^{-2}$ at room temperature and $50^{\circ}C$, respectively. The results demonstrated that the highest specific capacity of $Li/LiMnO_2$ cells at room temperature and $50^{\circ}C$ was 95 and $155\;mAh\;g^{-1}$, respectively. As for $Li/LiCo_{0.1}Mn_{0.9}O_2$ cells, the highest specific capacity at room temperature and $50^{\circ}C$ was 160 and $250\;mAh\;g^{-l}$, respectively. It could be seen that the performance of $Li/LiCo_{0.1}Mn_{0.9}O_2$ cells was better than that of $Li/LiMnO_2$ cells.

• Journal of Powder Materials
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• v.24 no.4
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• pp.275-278
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• 2017

In the present work, we apply a technique that has been used for the expansion of graphite to multiwall carbon nanotubes (MWCNT). The nanotubes are rapidly heated for a short duration, followed by immersion in acid solution, so that they undergo expansion. The diameter of the expanded CNTs is 5-10 times larger than that of the as-received nanotubes. This results in considerable swelling of the CNTs and opening of the tube tips, which may facilitate the accessibility of lithium ions into the inner holes and the interstices between the nanotube walls. The Li-ion storage capacity of the expanded nanotubes is measured by using the material as an anode in Li-ion cells. The result show that the discharge capacity of the expanded nanotubes in the first cycle is as high as 2,160 mAh/g, which is about 28% higher than that of the un-treated MWCNT anode. However, the charge/discharge capacity quickly drops in subsequent cycles and finally reaches equilibrium values of ~370 mAh/g. This is possibly due to the destruction of the lattice structures by repeated intercalation of Li ions.