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A Study on the Stem Angle and Icebreaking Capability of Icebreaking Vessels
Choi,Kyungsik 韓國海洋大學校 附設 海洋科學技術硏究所 1993 硏究論文集 Vol.2 No.1
Among various design factors affecting icebreaking capability of an icebreaker, the stem angle (i.e., angle between bow stem and ice sheet) is the most important one under continuous icebreaking operation. This study focuses on the relationship between the bow stem angle of an icebreaker and its icebreaking capability. Considering relatively high loading-rate conditions with typical advancing speed of 3 to 4 knots, the material properties and deformation characteristics of sea ice are regarded as entirely elastic and brittle. In this paper the dynamic interaction process of icebreaker with level ice is simplified as a beam of finite length supported by Winkler-type elastic foundation simulating water buoyancy. The wedge type ice beam is loaded by the vertical impact forces due to the inclined bow stem of icebreaking vessels. The numerical model provides locations of maximum dynamic bending moment where extreme tensile stress arises and also possible fracture occurs. The model can predict a characteristic length of broken ice sheet given environmental and design parameters.
최경식(Kyungsik Choi) 한국해양대학교 해사산업연구소 1991 海事産業硏究所論文集 Vol.1 No.-
The study focuses the mechanical deformation response predicted by the plasticity model for polycrystalline ice. To describe various deformation characteristics, ice is idealized as a perfectly plastic material using an asymtotic exponential failure criterion. This criterion is suited for describing materials which exhibit brittle deformation at low hydrostatic pressure and ductile deformation at high hydrostatic pressure. The results are compared to those of continuum damage mechanics model. Plasticity model shows good agreement with damage model and experimental results for high confining pressures even. at high strain-rates which is usually considered as a brittle condition under uniaxial compression.
최경식(KYUNGSIK CHOI) 한국해양공학회 2006 韓國海洋工學會誌 Vol.20 No.3
In this study, design parameters of ice-transiting vessels in the world, currently in service or under construction, were collected and a database of principal particulars for each ship was established. To understand the recent design trend, ice-transiting vessels were categorized into four groups, i.e., conventional icebreakers, icebreaking tug/supply/research vessels, ice-strengthened passenger/car ferry and ice-strengthened cargo vessels. Changes in principal particulars for each group were reviewed and summarized. It was found that the most significant change in the design of ice-transiting vessels was the increment of large size commercial cargo vessels. It is believed that the recent hike of oil prices and booming of Russian economy has resulted in the need for year-round operation with bigger ships in the Baltic Sea and in the Sea of Okhotsk and also along the Northern Sea Route in Russian Arctic Sea.
최경식(Kyungsik Choi),강신영(Sin Young Kang),강효진(Hyo Jin Kang),곽한우(Han Woo Kwak) 한국해양공학회 1992 韓國海洋工學會誌 Vol.6 No.1
The motion of a cylindrical object resting on shallow seabed due to wave forces and soil friction is studied. Given environmental conditions such as wave characteristics and seabed soil properties, the equations of motion are derived and the corresponding reponses of the cylinder in two dimensional plane, i.e., translational and rotational displacements, accelerations, are calculated. The motion is substantially restrained by the penetration of a cylinder into seabed and the parametric study focuses on finding out a minimum penetration depth which makes the cylinder motionless.
농업부문 신생 협동조합 사업활성화 요인과 네트워크 영향탐색에 관한 연구 -협동조합 유형별 특성과 사례를 중심으로-
최경식 ( Kyungsik Choi ),남기포 ( Gi Pou Nam ),유형석 ( Hyoungsuk Yoo ) 한국협동조합학회 2015 韓國協同組合硏究 Vol.33 No.2
This study analyzes determinant factors for sustainability of the new agricultural cooperatives established by the Framework Act on Cooperatives of 2012 in Korea. It was found that the most explanatory variable was the business network of cooperatives to increase their business turnovers. Based on this result, the study suggested to build a suitable network model for different kinds of cooperatives. producer cooperatives and employees cooperatives in rural area will do better to build their business networks with same sector cooperatives in urban area to create a firm business relationship in applying the cooperation among cooperatives principle, whilst reducing the asymmetric information between two areas. It was also found that consumer cooperatives and multi-stakeholders cooperatives had their comparative advantages in accessing a lower price and high quality goods from producer cooperatives and employees cooperatives. Therefore, it is recommendable especially for multi-stakeholders cooperatives to be organized by a localized business networks from the startup. Empirically, a business network model established in Hwasung City in Gyeonggi Province provided many implications to interested policy makers, new cooperatives and local agricultural cooperatives who wish to construct a value-chain business network in a region among the three parties. Through the network, the primary production cooperatives can acquire their stable relationships and sustainabilities in the future and contribute to development to the area.
최경식(KYUNGSIK CHOI),이종호(JONG-HO LEE) 한국해양공학회 2002 韓國海洋工學會誌 Vol.16 No.1
The interaction of grounded ice ridges with underlying seabed is one of the major considerations in the design of Arctic pipeline system. Previously several ice scour models were developed by researchers to describe the ice scour-seabed interaction mechanism. In view of possible improvements, a comparative study of those ice scour models is performed and their limitation in modeling is discussed. Simple laboratory tests are carried out and then the shape pattern of deposited soil around the ice model is newly defined. Unlike the rectangular idealization of an ice block, in this modified ice scour model, trapezoidal cross sections are assumed to represent the typical shape of an ice ridge based on the field observation data. With the horizontal and vertical motion of ice model, the ice scour depth and soil reacting forces on seabed are calculated with varying the keel angle of an ice ridge.