• 한국지반공학회지:지반
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• 제4권3호
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• pp.43-52
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• 1988

반복하중을 받는 정토의 거동은 단일하중에 의한 결과와 매우 상리하게 나타나며, 그중에서도 특히 간극수려의 거동은 상당히 중요하다. 본 연구는 반복하중 하에서의 점토에 대한 응력-변형 특성을 규명하기 위한 실험적 연구로서 하 중을 가하는 동안에 발생하는 간극수려에 대하여도 언급하였다. 시료는 삼축용기 안에서 24시간동안 등방려밀시켰으며, 삼축시험은 비배수상태 하에서 재성형된 시료에 때하여 압축파괴, 파괴반복, 비파괴 평형시험을 변형제어방법으로 수행하였다. 이에 따라 어느 특정한 시료의 거동을 뚜렷하게 서로 다른 두가지 양상으로 구분하는 반복응력의 한계치가 존재 함을 확인할 수 있었다.

• 셀메드
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• 제2권3호
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• pp.23.1-23.7
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• 2012

The healing properties of medicinal maggots (larval stage of Lucilia sericata) are widely used in the chirurgical debridement of non-healing wounds including diabetic foot ulcers, venous and pressure ulcers, where classical approaches have failed. Several kinds of wounds are prone to complications coming out of a specific wound bed environment. There are multi-resistant bacterial species present, their pathogenic impact is multiplied by their ability to form a biofilm. Moreover, immunological events in chronic wounds differ from those in acute wounds. Non-healing wounds are cycled in the early inflammation phase with increased levels of inflammation attributes like inflammation cytokines and matrix metalloproteinases produced by inflammation phase cells. Application of larval therapy promotes progress in the healing process to the next stages involving tissue granulation and re-epithelisation. Larval debridement is an effective method of cleaning the wound of cell debris, necrotic tissue and bacterial load. This happens in a mechanical and biological manner, but the whole complex mechanism of the maggot healing activity is still not fully elucidated. Centuries of clinical practice brings noticeable proof of the maggots' beneficial effect in wound healing management. This long history led to the investigation of the bioactive components of the larval body and its extracts in vitro. We introduce a review which describes the immunomodulation impact of maggot body components on the cellular and molecular levels of the wound healing process.

• Journal of Electrochemical Science and Technology
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• 제2권1호
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• pp.8-13
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• 2011

Interfacial compatibility between the Si-Cu electrode and diluted ionic liquid electrolyte containing 50 vol.% of 1M lithium bis(trifluoromethanesulfonyl)imide (LiTFSI)/1-methyl-1-propylpyrrolidinium bis(trifluoromethylsulfonyl)imide (MPP-TFSI) and 50 vol.% dimethyl carbonate (DMC) in a lithium cell and dilution effect on surface chemistry are examined. ex-situ ATR FTIR analysis results reveal that the surface of the Si-Cu electrode cycled in the diluted ionic liquid electrolyte is effectively passivated with the SEI layer mainly composed of carboxylate salts-containing polymeric compounds produced by the decomposition of DMC. Surface species by the decomposition of TFSI anion and MPP cation are found to be relatively in a very low concentration level. Passivation of electrode surface with the SEI species contributes to protect from further interfacial reactions and to preserve the electrode structure over 200 cycles, delivering discharge capacity of > 1670 $mAhg^{-1}$ and capacity retention of 88% of maximum discharge capacity.

• 대한금속재료학회지
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• 제50권2호
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• pp.171-175
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• 2012

By measuring the absorbed hydrogen quantity as a function of the number of cycles, the cycling properties of the Mg-15 wt%Ni-5 wt%$Fe_2O_3$ alloy were investigated. The absorbed hydrogen quantity decreased as the number of cycles increased. The $H_a$ value varied almost linearly with the number of cycles. The maintainability of absorbed hydrogen quantity at n=100 was 89.0% for the hydriding reaction time of 10 min. After the $150^{th}$ hydriding-dehydriding cycle, Mg, $Mg_2Ni$, $Mg(OH)_2$, MgO, and Fe were observed. The phases were analyzed by Rietveld analysis from the XRD patterns of the Mg-15 wt%Ni-5 wt%$Fe_2O_3$ alloy after 150 hydriding-dehydriding cycles. The crystallite size and strain of Mg were then estimated with the Williamson-Hall technique.

• 한국수소및신에너지학회논문집
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• 제32권6호
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• pp.592-611
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• 2021

In this study a rarely available high-throughput cycling data set of 124 commercial lithium iron phosphate/graphite cells cycled under fast-charging conditions, with widely varying cycle lives ranging from 150 to 2,300 cycles including in-cycle temperature and per-cycle IR measurements. We worked out own Python codes which reproduced the various data plots and machine learning approaches for cycle life prediction using early cycles and more details not presented in the article and the supplementary information. Particularly, we applied regularized ridge, lasso and elastic net linear regression models using features extracted from capacity fade curves, discharge voltage curves, and other data such as internal resistance and cell can temperature. We found that due to the limitation in the quantity and quality of the data from costly and lengthy battery testing a careful hyperparameter tuning may be required and that model features need to be extracted based on the domain knowledge.

• KIEE International Transactions on Electrophysics and Applications
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• 제4C권1호
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• pp.21-25
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• 2004

From the gradual increasing state of charge (GISOC) observations, electrochemical behavior of multi-walled carbon nanotube│(lM LiP $F_{6}$ , EC,DEC,DME 3:5:5 volume ratio)│lithium cells was evaluated using the galvanostatic charge-discharge process. A MWCNT delivers a specific charge capacity of 1,300 mAh/g in a Li cell when cycled up to an end voltage of 0 V (vs. Li/L $i^{＋}$ )at a constant current rate every 10 hours. However, in the present study, the specific discharge capacity obtained is 338 mAh/g, thus amounting to a coulombic efficiency of only 26％. Further, when the MWCNT│Li cells were tested using the GISOC method, two distinguishable linear-fit ranges were observed due to the intercalation/deintercalation of lithium, which were found to have II $E_1$, IIC $s_1$ and II $E_2$of 27.3％, 372 mAh/g, and 25.5％, respectively. Q $c_1$, could be calculated from the data of IIE and IICs of each range by the modified equation "II $C_{sum}$= $\Sigma$( $Q_{C}$- $Q_{D}$)=(II $E_{1}$$^{-1}$ ) $Q_{Dl}$ ＋(II $E_2$$^{-1}$ -1) ( $Q_{D2}$- $Q_{Dl}$ ) ＋ IIC $s_1$= $Q_{Cl}$ - $Q_{Dl}$ ". Results of the GISOC method could be converted to the results of galvanostatic charge-discharge process, irrespective of the state of charge of the cell or battery.ery.y.y.

• Geomechanics and Engineering
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• 제34권5호
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• pp.481-489
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• 2023

Drained cyclic triaxial tests were conducted on a saturated sand to examine its deformation characteristics under either axial or lateral cyclic loading condition. To apply lateral cyclic loading, the cell pressure was cycled while maintaining a constant vertical stress. The strain accumulations and flow direction in the soil were presented and discussed considering various initial stress ratios (η₀), cyclic stress amplitudes and cyclic stress paths. The results indicate that axial strain accumulation shows an exponential increase with the maximum stress ratio (η^max). The initial deviatoric stress has comparable effects with lateral cyclic stress amplitude on the accumulated axial strain. In contrast, the accumulated volumetric strain is directly proportional to the lateral cyclic stress amplitude but not much affected by η₀ values. Due to the anisotropy of the soil, the accumulated axial and lateral bulging strains are greater in lateral cyclic loading when compared to axial cyclic loading even though η^max is the same. It is also found that η^max affects soil's lateral deformation and increasing the ratio could change the lateral deformation from contraction to bulging. The flow direction depends on η^max in the sand under lateral cyclic loading, regardless of η₀ values and the cyclic stress amplitudes, and a large η^max could lead to great deviatoric strain but a little volumetric strain accumulation.

• 공업화학
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• 제10권3호
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• pp.415-418
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• 1999

튜브식 양극판과 겔전해액을 사용한 VRLA (valve regulated Iead-acid) 전지에 있어서 양극 활물질 (active material)의 충전 밀도에 따른 충 방전 싸이클 특성을 고찰하였다. VRLA전지에 사용된 양극 활물질의 밀도는 각각 3.2g/mL, 3.4g/mL 및 3.6g/ml 이었다. VRLA전지는 IU 방식 ($I_{max}=0.2C_{10}/10$, 상한 전압 2.40 v/cell)의 충전과, D.O.D 100%/C5의 방전 방법으로 충 방전 싸이클 수명 시험을 실시하였다. 시험은 $25{\pm}1^{\circ}C$의 항온항습기에서 실행하였다. 시험 결과 활물질 밀도별 VRLA전지의 초기 용량은 밀도와 무관하였다. 즉 3.4g/mL에서 가장 우수하였고, 3.6g/mL에서 가장 낮았다. 충 방전 싸이클에서의 특성은 3.6g/mL인 전지는 3.4g/mL와 거의 유사하였고, 3.2g/mL보다는 크게 우수하였다. 또한 VRLA 전지의 수분고갈 및 열화는 양극 활물질의 충전 밀도가 높을수록 적었다. 이상으로 충 방전 싸이클용 VRLA전지의 양극 활물질의 밀도는 3.4~3.6g/mL이 적절한 것으로 판단되었다.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2011년도 춘계학술발표대회
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• pp.5-5
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• 2011

The research and development of hybrid electric vehicle (HEV), plug-in hybrid electric vehicle (PHEV) and electric vehicle (EV) are intensified due to the energy crisis and environmental concerns. In order to meet the challenging requirements of powering HEV, PHEV and EV, the current lithium battery technology needs to be significantly improved in terms of the cost, safety, power and energy density, as well as the calendar and cycle life. One new technology being developed is the utilization of composite cathode by mixing two different types of insertion compounds [e.g., spinel $LiMn_2O_4$ and layered $LiMO_2$ (M=Ni, Co, and Mn)]. Recently, some studies on mixing two different types of cathode materials to make a composite cathode have been reported, which were aimed at reducing cost and improving self-discharge. Numata et al. reported that when stored in a sealed can together with electrolyte at $80^{\circ}C$ for 10 days, the concentrations of both HF and $Mn^{2+}$ were lower in the can containing $LiMn_2O_4$ blended with $LiNi_{0.8}Co_{0.2}O_2$ than that containing $LiMn_2O_4$ only. That reports clearly showed that this blending technique can prevent the decline in capacity caused by cycling or storage at elevated temperatures. However, not much work has been reported on the charge-discharge characteristics and related structural phase transitions for these composite cathodes. In this presentation, we will report our in situ x-ray diffraction studies on this mixed composite cathode material during charge-discharge cycling. The mixed cathodes were incorporated into in situ XRD cells with a Li foil anode, a Celgard separator, and a 1M $LiPF_6$ electrolyte in a 1 : 1 EC : DMC solvent (LP 30 from EM Industries, Inc.). For in situ XRD cell, Mylar windows were used as has been described in detail elsewhere. All of these in situ XRD spectra were collected on beam line X18A at National Synchrotron Light Source (NSLS) at Brookhaven National Laboratory using two different detectors. One is a conventional scintillation detector with data collection at 0.02 degree in two theta angle for each step. The other is a wide angle position sensitive detector (PSD). The wavelengths used were 1.1950 ${\AA}$ for the scintillation detector and 0.9999 A for the PSD. The newly installed PSD at beam line X18A of NSLS can collect XRD patterns as short as a few minutes covering $90^{\circ}$ of two theta angles simultaneously with good signal to noise ratio. It significantly reduced the data collection time for each scan, giving us a great advantage in studying the phase transition in real time. The two theta angles of all the XRD spectra presented in this paper have been recalculated and converted to corresponding angles for ${\lambda}=1.54\;{\AA}$, which is the wavelength of conventional x-ray tube source with Cu-$k{\alpha}$ radiation, for easy comparison with data in other literatures. The structural changes of the composite cathode made by mixing spinel $LiMn_2O_4$ and layered $Li-Ni_{1/3}Co_{1/3}Mn_{1/3}O_2$ in 1 : 1 wt% in both Li-half and Li-ion cells during charge/discharge are studied by in situ XRD. During the first charge up to ~5.2 V vs. $Li/Li^+$, the in situ XRD spectra for the composite cathode in the Li-half cell track the structural changes of each component. At the early stage of charge, the lithium extraction takes place in the $LiNi_{1/3}Co_{1/3}Mn_{1/3}O_2$ component only. When the cell voltage reaches at ~4.0 V vs. $Li/Li^+$, lithium extraction from the spinel $LiMn_2O_4$ component starts and becomes the major contributor for the cell capacity due to the higher rate capability of $LiMn_2O_4$. When the voltage passed 4.3 V, the major structural changes are from the $LiNi_{1/3}Co_{1/3}Mn_{1/3}O_2$ component, while the $LiMn_2O_4$ component is almost unchanged. In the Li-ion cell using a MCMB anode and a composite cathode cycled between 2.5 V and 4.2 V, the structural changes are dominated by the spinel $LiMn_2O_4$ component, with much less changes in the layered $LiNi_{1/3}Co_{1/3}Mn_{1/3}O_2$ component, comparing with the Li-half cell results. These results give us valuable information about the structural changes relating to the contributions of each individual component to the cell capacity at certain charge/discharge state, which are helpful in designing and optimizing the composite cathode using spinel- and layered-type materials for Li-ion battery research. More detailed discussion will be presented at the meeting.

• 생명과학회지
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• 제23권2호
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• pp.324-331
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• 2013

O-GlcNAc 화(O-GlcNAcylation)는 단백질의 serine이나 threonine에 N-acetylglucosamine (GlcNAc) 분자가 결합하는 것으로, 기존의 당단백질과 달리 세포질 및 핵단백질 모두에 일어난다. 또한 수정의 속도가 빠르고 가역적으로 일어남이 인산화 수식과 유사하다. 그러나 수많은 인산화효소와 탈인산화효소가 관여하는 것과 달리 O-GlcNAc 수식은 O-GlcNAc transferase (OGT)와 O-GlcNAcase (OGA) 단 두 개의 효소에 의하여 이루어진다. 이러한 단순한 조절기전은 세포가 내외환경에 즉시 적응할 수 있도록 진화한 것으로 해석된다. 즉, O-GlcNAc 수식은 특정한 단백질 하나 하나의 활성을 켜거나 끄는 것이 아니라, 세포의 신호전달과정의 효율을 전반적으로 조절하는 '가변저항기(rheostat)' 역할을 한다. O-GlcNAc 수식은 흔히 같은 아미노산 혹은 그 주변의 아미노산이 인산화되는 것을 수반하는데, 이는 인산화와 함께 서로 조화를 이루어 세포활성을 조절하는 것으로 해석된다. 최근 O-GlcNAc이 더 나아가 O-GlcNAc-P로 인산화될 가능성이 제시되고 있는 바, 본 총설에서는 이의 가능성을 이론적으로 설명하고, 실제 실험결과를 소개한다.