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Ab-initio Study of Silicon and Tin as a Negative Electrode Materials for Lithium-ion Batteries
문장혁,조맹효,조경재 한국정밀공학회 2012 International Journal of Precision Engineering and Vol. No.
An investigation of Li-M (M: Si, Sn) components using density functional theory (DFT) is presented. Calculation of total energy, structural optimizations, bulk modulus and elastic constants with Li-Sn, Li-Si are performed through DFT calculations. From the comparable study of Li-Sn and Li-Si, it is found that silicon experience drastic mechanical degradation during lithiation than tin-based Li-Sn components. With increasing lithium net charge transfer to metals, the filling of anti-bonding orbital makes M-M covalent bonding weak ionic bonding in both Li-Si and Li-Sn. However, the difference of change of mechanical degradation during lithiation in Li-Si and Li-Sn results from the sensitivity of transition of covalent bonding. We check this from sharp decreasing of yield stress in Li-Si case. Furthermore, we simply make up amorphous Si cell with an additional Li atom at the center of the largest void to simulate the lithiation of amorphous silicon. Volume expansion of amorphous silicon cell agrees with the experiment observation and theoretical data of Li-Si compounds.
고혈압(高血壓) 뇌졸중(腦卒中) 환자(患者)에 대한 사혈(瀉血)의 강압효과(降壓效果)
문장혁,안호진,정동화,윤형선,장재원,김경선,문익렬,백종엽,이상무,Mon, Jang-hyuk,Ahn, Ho-jin,Jeong, Dong-hwa,Yoon, Hyung-sun,Jang, Jae-won,Kim, Kyung-sun,Moon, Ik-ryoul,Baek, Jong-yeob,Lee, Sang-moo 대한침구의학회 2003 대한침구의학회지 Vol.20 No.2
Objective : The aim of this research was to investigate the depressive effect of depletion of B15(心兪), B23(腎兪), L5(尺澤), B40(委中) in hypertentive stroke patients. Methods : Depletion on B15(心兪), B23(腎兪), L5(尺澤), B40(委中) in hypertentive stroke patient who were admitted in Dong-Seo Oriental Medical Hospital every other day form 4 weeks, without western antihypertensive drug. Results : After treatment in 2nd week, depletion on B15(心兪), B23(腎兪), L5(尺澤), B40(委中) without western antihypertensive drug increased the systolic and diastolic blood pressure. After treatment in 4th week, depletion on B15(心兪), B23(腎兪), L5(尺澤), B40(委中) without western antihypertensive drug decreased the systolic and diastolic blood pressure. After treatment in 4th week, values of RBC and hemoglobine were not significantly changed. Conclusions : Continous depletion on B15(心兪), B23(腎兪), L5(尺澤), B40(委中) in hypertentive stroke patient without western antihypertensive drug implies decreasement of blood pressure, without change of values of RBC and hemoglobine.
공공임대주택이 커뮤니티 지가에 미치는 영향에 관한 연구
문장혁,서경천,이성호 대한국토·도시계획학회 2006 國土計劃 Vol.41 No.4
The purpose of the present study is to examine the influence of public housing on nearby community land price. In doing so, the study investigates 9 streets in which 5 public housing complexes are located. The findings are as follows; generally, public housing is regarded as a reason of negative effects such as ‘the fall of the land price' and ‘deterioration'. In correlation-analysis, there is no absolute correlation between public housing and the land price. However, when the correlation was investigated focusing on the built-age of public housing and the use-district of neighbor plots, there is meaningful result between them. The land price of ‘high-density residential district' plots is decreased by public housing. On the contrary, the land price of ‘general-commercial district' plots is increased. And the public housing whose built-age is less than 10 years makes positive effects on the land price of nearby plots. Consequently, common opinion that public housing undermines the land price of their community appears not to be precise. The land price of community seems to be influenced by the characters of public housing and respective plot.키 워 드 주택, 공공임대주택, 커뮤니티, 지가Keywords Housing, Public Housing, Community, Land Price
멀티스케일 해석을 이용한 고용량 리튬이차전지의 전기화학적-기계적 거동 연구
문장혁 한국공업화학회 2020 한국공업화학회 연구논문 초록집 Vol.2020 No.-
The mechanical issues on high capacity energy materials (i.e. silicon) prevents their usage as electrode for lithium ion batteries. As alternative, the oxides (i.e. silicon dioxide) are used for a high-expected capacity and strong mechanical stability during cycles. However, the mechanical behavior of amorphous SiO2 during electro-chemical reaction remains largely unknown. Based on the study of the electrochemo- mechanical coupling analysis, we systematically investigate the stress evolution, the electronic structure and the mechanical deformation of lithiated silicon dioxide through first-principles computation and finite element method. The role of oxygen in amorphous silicon oxide was investigated in structural and thermodynamics point of view. The mechanical strength and brittle behavior of SiO2 due to strong Si-O bonds are also studied. These results would provide fundamental perspectives on the chemo-mechanical behavior of silicon dioxide for the practical use.
제일원리 계산법을 이용한 비정질 실리콘 내에서의 리튬 이온 확산 예측
문장혁(Janghyuk Moon),조경재(Kyeongjae Cho),조맹효(Maenghyo Cho) 대한기계학회 2012 대한기계학회 춘추학술대회 Vol.2012 No.11
We have studied the lithium absorption in crystalline silicon with the strain effects on unit cell using density functional theory calculation. We have concluded that the dependences of the lithium diffusion were on the local volume and environmental. In the various strained cells, the effect of the lattice deformation about migration barriers for the motion of the lithium atom has been fit on the linear regression equation based on the volume of silicon surrounding lithium impurity and the migration distance of lithium atom. This result has applied to the calculation of diffusion coefficient in amorphous silicon which was generated by annealing from crystalline structure at 3000K. The migration barriers and attempt frequency, by Arrhenius formula, of lithium in the amorphous silicon structures has been determined by local environment using the linear regression equation. Then, the statistical method, kinetic Monte Carlo method, has been demonstrated for the diffusion coefficient of lithium. Finally, we have parameterized in terms of the amorphous effects into Arrhenius diffusion formula. This study have supported that the diffusion of lithium in amorphous silicon is faster than that in crystalline silicon.