• 한국초전도ㆍ저온공학회논문지
• /
• 제3권1호
• /
• pp.35-39
• /
• 2001

The optimum cross-sectional area profile of gas-cooled high-temperature superconductor(HTS) current lead is analyzed to have minimum helium boil-off rate. The conventional constant area HTS lead has much higher helium consumption than the optimum HTS lead considered in this study. The optimum HTS lead has variable cross-sectional area to have constant satiety factor. An analytical formula of optimum shape of lead and temperature profile are obtained. For multi-stacking HTS current leads, the optimum tape lengths and minimum heat dissipation rate are also formulated. The developed formulations are applied to the Bi-2223 material, and the differences between constant area, constant safety-factor, and multi-stacking current leads are discussed.

• 한국초전도저온공학회:학술대회논문집
• /
• 한국초전도저온공학회 2001년도 학술대회 논문집
• /
• pp.84-88
• /
• 2001

The optimum cross-sectional area Profile of gas-cooled high-temperature superconductor (HTS) current lead is analyzed to have minimum helium boil-off rate. The conventional constant area HTS lead has much higher helium consumption than the optimum HTS lead considered in this study. The optimum HTS lead has variable cross-sectional area to have constant safety factor. An analytical formula of optimum shape of lead and temperature profile are obtained. For multi-step HTS current leads, the optimum tape lengths and minimum heat dissipation rate are also formulated. The developed formulations are applied to the Bi-2223 material, and the differences between constant area, constant safety-factor, and multi-step current leads are discussed.

• Computers and Concrete
• /
• 제10권2호
• /
• pp.149-171
• /
• 2012

The problem of a concrete cross section under flexural and axial loading is indeterminate due to the existence of more unknowns than equations. Among the infinite solutions, it is possible to find the optimum, which is that of minimum reinforcement that satisfies certain design constraints (section ductility, minimum reinforcement area, etc.). This article proposes the automation of the optimum reinforcement calculation under any combination of flexural and axial loading. The procedure has been implemented in a program code that is attached in the Appendix. Conventional-strength or high-strength concrete may be chosen, minimum reinforcement area may be considered (it being possible to choose between the standards ACI 318 or Eurocode 2), and the neutral axis depth may be constrained in order to guarantee a certain sectional ductility. Some numerical examples are presented, drawing comparisons between the results obtained by ACI 318, EC 2 and the conventional method.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 1993년도 하계학술대회 논문집 B
• /
• pp.1286-1288
• /
• 1993

An analytical method for the optimum design of the minimum die size in power MOSFETs is presented. The proposed methodology considers the thermal resistance of the package and gives the minimum die area for desired drain current levels. The results are compared with experimental data and it is found that the die size mar be reduced if it is designed according to the proposed design procedure.

• 한국작물학회지
• /
• 제28권3호
• /
• pp.319-322
• /
• 1983

벼 이앙후에 발생되는 잡초를 조사하여 벼와의 경쟁적 영향을 해석함에 있어 가장 적은 노력으로 전체잡초발생상태를 대표할 수 있는 최소표본크기(minium quadrat size)와 최소표본회수(minimun quadrat number)를 초종일표본변적(species-area) 및 초종일표본회수(species-quadart number) 관계식에 의해 조사하였다. 1. 초종일표본면적, 또는 초종일표본회수 관계식에서 다같이 표본면적, 또는 표본회수가 증가하게 됨에 따라 얻어지는 초종증가는 처음에는 급속도로 증가하고, 서서히 증가속도가 완만해지며, 어느 한계점을 지나면 더 이상의 초종증가는 없이 평형상태를 유지하는 특징적인 곡선을 보였다. 2. 표본추출면적, 또는 표본 추출회수를 10% 증가시킴에 따라 얻어지는 초종 증가율이 10%되는 관계를 고려한 최소표본추출 회수는 3회였다.

• 대기
• /
• 제21권4호
• /
• pp.361-371
• /
• 2011

In this study, characteristics and trends of tropical night (TN) are investigated by using the KMA 14 observation data for the recent 50 years (1958-2007) over South Korea. The TN is defined as a day with a daily minimum temperature exceeds the absolute threshold temperature ($25^{\circ}C$), and the relative deviation from normal temperature, 95th percentile of all observed daily minimum temperature. Although the spatial distribution of TN occurrence depends on the choice of the definitions, the frequency of TN shows strong spatial and interannual variations with the minimum at high land area (Chupungnyeong and wet years) and maximum at southern coastal area and large city area (Jeju, Busan, Seoul, Daegu). Most of TN occurs in August (56%) and July (41%), and the duration date of TN is proportional to the frequency of TN without regard to the definition method. In general, increasing trends are found in the TN time series without regard to the analysis method, but the trends are clearly depending on the analysis period and geographic locations. Decreasing trends are prominent during the most of analysis period, especially until the mid of 1990, whereas strong increasing trends are found during recent 30 years (1988-2007), especially at Jeju, Ulsan, Daegu and Pohang. Also the severity of TN is significantly increased in recent years.

• The Korean Journal of Ecology
• /
• 제21권5_1호
• /
• pp.409-418
• /
• 1998

A molel study was conducted to determine the optimal sample size for the analysis of the aquatic insect community in a stream reach of the Pangtae Creek, Kangwon-do in October 1995 and may 1996. The results showed that the required minimum sample size varied and depended on the purposes of the community analysis. Acoording to the Species: Area Curve method, at least 16 Surber samplings ($30{\times}30cm$) were required in a stream reach in each spring and fall survey. The species diversity index did not vary significantly as the sample size increased. Based on the coefficient of variation analysis, the minimum sample sizes of 10 were required in order to compare seasonal differences of the community in the study area. Considering the static community structure of aquatic insects, including both species numbers and individual numbers of aquatic insects, 11 and 7 samplings were optimal sizes for the fall and spring survey, respectively. We concluded that 12 Surber samplings from 3 riffle-pool sequences (4 samplings at each riffle-pool sequence) would be required in a stream reach (length 1 km) to obtain reliable as well as cost efficient data. Our model showed that the optimal sample size should be determined by interactions between minimum sample size, the degree of data reliability, and cost efficiency.

• 대한전자공학회논문지
• /
• 제24권6호
• /
• pp.1056-1067
• /
• 1987

This paper presents a design procedure for building block integrated circuits that is based on the digraph relaxation model. A set of optimization procedure is prosented for a minimum area and routing-fecsible placement of IC building blocks. Chip area optimization is subject to perimeter and area constraints on the component rectangles in the dissection.

• 대한전자공학회논문지
• /
• 제24권4호
• /
• pp.708-712
• /
• 1987

This paper deals with minimizing layout area of VLSI design. A long wire in a VLSI layout causes delay which can be reduced by using a driver. There can be significant area increase when many drivers are introduced in a layout. This paper describes a method to obtain tight bound on the worst-case increase in area when drivers are introduced along many long wires in a layout. The area occupied by minimum-area embedding for a circuit can depend on the aspect ratio of the bounding rectangle of the layout. This paper presents a separator-based area optimal embeddings for VLSI graphs in rectangles of several aspect ratios.

• 한국항해항만학회지
• /
• 제33권10호
• /
• pp.679-683
• /
• 2009

최근 22년간(1986-2007년)의 기상청 자료를 이용하여 태풍의 발생 해역별(A해역: 캐롤라인 마샬군도 부근 해역, B해역 : 북위 20도 이북 해역, C해역 : 필리핀 근해, D해역 : 남중국해)로, 태풍의 발생 수 및 세기에 관하여 분석하였다. 태풍의 연평균 발생 수는 26.3개로, 모든 해역에서 공통적으로 감소하는 추세를 보인다. 특히, A해역에서 감소 추세가 현저하고, D해역에서는 감소 추세가 미미하다. 태풍이 가장 많이 발생하는 해역은 A해역(연평균 13.8개, 전체의 약 53％)이고, 그 다음은 C해역(5.6개, 약 21％), B해역(3.8개, 약 14％), D해역(3.1개, 약 12％)의 순서이다. 태풍의 세기는 A해역에서 발생하는 것이 가장 강하고(중심최저기압의 평균 951hPa), 그 다음은 C해역(970hPa), B해역(975hPa), D해역(983hPa)의 순서이다. 그리고 전 해역을 대상으로 하여 연평균 중심최저기압의 시계열 분포를 살펴보면, 태풍의 중심최저기압은 미세하게 하강하는 추세를 보인다. 이는 태풍의 세기가 서서히 강해지고 있음을 의미한다. 금번의 연구 결과는 지구 온난화에 따른 태풍의 수와 세기의 변화에 대한 여러 수치실험 결과와 일치한다.