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김대철,박맹언 한국수산학회 1987 한국수산과학회지 Vol.20 No.4
태평양 심해저로부터 채취된 망간단괴는 미세구조의 특징을 기준으로 하여 세가지 유형(Type A, B 및 C)으로 분류되며, 이들 미세구조들은 단일 단괴에서도 혼합구조로서 흔히 산출된다. 각 유형은 상이한 화학성분과 구성광물 및 결정도를 나타내며 이 중 A형은 조립질 조직을 갖고있고 다른 유형에 비해 결정도가 높은 Todorokite로 주로 구성되고 Mn의 함량도 높은 반면에 B와 C형은 중간 내지는 세립질 조직을 갖고 있다(Mn=30.6%). 또한 A형은 상대적으로 빠른 성장속도를 나타내며, 보트리오이드 사이의 공극에서 Smectite와 규질화석이 나타난다. 이러한 특징을 A형 구조를 갖는 미세한 층(micro layer)의 성인이 해저에서의 열수작용과 관련된 것으로 생각되며. 열수용액은 주변 단열대와 해저확장대로부터 공급된 것으로 추정된다. Texture and mineralogy of different microlayers of deep-sea manganese nodules are investigated to reveal the environmental changes of nodules during a nodule formation. Basieally a nodule can have three types (A, B and C) of microlayer. Some nodules show only one or two types of microlayer. The classification is based primarily on the texture. The surface texture of type A is coarsely porous globular microstructure whereas type B and C are intermediate to finely porous textures. The type A is characterized by its highest Mn content (30.6%) and relatively well-crystallized todorokite as well as the rapid growth rate. Smectite and biogenic silica (radiolaria) are also easily observed in the type A layer. It appears that the hydrothermal activity is one of the favorable mechanism of formation for the type A layer. The hydrothermal solution is possibly supplied from nearby fracture zone and spreading center.
김대철,강영선 한국농업기계학회 2009 바이오시스템공학 Vol.34 No.5
This study was performed to develop accelerated life test methods for agricultural tractor transmission that receives variable load. To acquire the parameters for calculation of accelerated life test, endurance tests were performed on different torque conditions. As a result of test, the shape factor of Weibull distribution was 1.5 and fatigue damage exponent was 5.4. The calculated test time was 5,877hr under the conditions of average life (MTBF) 3,000 hours and 90% reliability for one test sample. According to the linear cumulative damage rule, because test time can shorten in case increase test load, test time could be reduced by 252 hours when we put the load 1.2 times of rated load than 0.67 times of rated load that is equivalent load calculated by load spectrum of the agricultural tractor. This time, acceleration coefficient was 23.3.
김대철,이재규,강영선,이재천 사단법인 유공압건설기계학회 2009 드라이브·컨트롤 Vol.6 No.3
The major system of an agricultural power-shift tractor is the transmission, using power-shift. Because the transmission performance depends on the hydraulic control system, the most important aspect of the optimization is the design of the hydraulic control system. This study was conducted to improve a pressure modulation characteristics of the power-shift transmission hydraulic system. It has been tried to replace an existing pressure modulation method with a digital control by using HSSV(High Speed Solenoid Valve). The performance of the PWM control system in power-shift hydraulic transmission has been evaluated by means of experiment.
김대철,김진영,이만우 한국은행 2008 經濟分析 Vol.14 No.2
This paper focuses on a type of individuals' economic behavior that National Pension System is likely to change, particularly their saving. This paper empirically analyzes the whole and different income groups' crowding out effect of the National Pension System(NPS) on household's non pension wealth by estimating Pension Wealth(PW) elasticity using the Korea Labor and Income Panel data(1999 2005). The estimation ~ result shows that 10% increase in the PW decreases the household's non pension wealth by 1% and the lower income household is, the more degree of decreasing it is. This is to say that current National Pension would give a contribution to downward trend of private saving rate and produce large differences in saving rates across income groups since 1998 IMF Currency Crisis. 본 연구에서는 노동패널조사자료를 이용하여 국민연금제도가 가계저축을 구축하는 효과를 살펴보았다. 분석 결과, 생애 연금급여의 현가에서 생애 보험료의 현가를 뺀 순연금액인 국민연금기대자산(PW)이 10% 증가할 경우 가계순자산은 약 1% 정도 감소하는 것으로 제시되어 국민연금제도가 가계저축을 구축하고 있는 것으로 나타났다. 또한 국민연금기대자산이 증가할 경우 저소득층일수록 가계순자산을 더 크게 감소시킴으로써 가계저축의 구축효과는 고소득층보다 저소득층에서 더 크게 나타났다. 이상의 분석결과는 1990년 이후 우리나라의 가계 저축률이 하락하고 IMF 외환위기 이후 소득계층별로 가계저축률 격차가 확대되는데 국민연금제도가 하나의 원인으로 작용했음을 시사한다.
김대철,김기현,Kim, Dae Choul,Kim, Kee Hyun The Korean Society of Oceanography 1988 韓國海洋學會誌 Vol.23 No.3
Properties of porosity, compressional wave velocity, velocity anisotropy, electrical resistivity, and resistivity anisotropy are measured and calculated for two DSDP clay-rich hemipelagic sequences in the northwestern Pacific. Velocity and resistivity increase with burial depth at the expense of decreasing porosity. Profiles of velocity anisotropy and resistivity anisotropy show almost the same trend. Horizontally developed low aspect ratio pores may generate velocity and resistivity anisotropy. The preferred orientation of clay minerals is also believed to be responsible for the observed anisotropy.