• 대한수학회지
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• 제57권6호
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• pp.1573-1590
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• 2020

In this paper, we classify all solutions bounded from below to uniformly elliptic equations of second order in the form of Lu(x) = a_ij(x)D_iju(x) + b_i(x)D_iu(x) + c(x)u(x) = f(x) or Lu(x) = D_i(a_ij(x)D_ju(x)) + b_i(x)D_iu(x) + c(x)u(x) = f(x) in unbounded cylinders. After establishing that the Aleksandrov maximum principle and boundary Harnack inequality hold for bounded solutions, we show that all solutions bounded from below are linear comb_inations of solutions, which are sums of two special solutions that exponential growth at one end and exponential decay at the another end, and a bounded solution that corresponds to the inhomogeneous term f of the equation.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1991년도 하계학술대회 논문집
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• pp.411-416
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• 1991

Operation simulation is a key factor to evaluate investment and operation in a power utility. Probabilistic production simulation is of major concern. With pumped-storage plant, production simulation is not an easy task, because its economy should fully be exploited. In addition, usual operation interval is a week rather than a day. Most existing models are based on approximate production simulation such as adopting simple priority orders of generations. This study is based on the more elaborate model developed by authors. Further, a policy of weekly coordination is established based on the Maximum Principle. Chronological load curve instead of usual load duration curve is used and the accuracy in simulation is enhahced. Resulting economics are compared. Deviation between these two toad curve is shown.

• 대한수학회지
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• 제50권4호
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• pp.829-845
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• 2013

In this paper, we firstly establish a family of curvature invariant conditions lying between the well-known 2-nonnegative curvature operator and nonnegative curvature operator along the Ricci flow. These conditions are defined by a set of inequalities involving the first four eigenvalues of the curvature operator, which are named as 3-parameter ${\lambda}$-nonnegative curvature conditions. Then a related rigidity property of manifolds with 3-parameter ${\lambda}$-nonnegative curvature operators is also derived. Based on these, we also obtain a strong maximum principle for the 3-parameter ${\lambda}$-nonnegativity along Ricci flow.

• Computers and Concrete
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• 제34권1호
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• pp.63-77
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• 2024

In this research, we considered fractional order optimal control models for cancer, HIV treatment and glucose.These models are based on fractional order differential equations that describe the dynamics underlying the disease.It is formulated in term of left and right Caputo fractional derivative. Pontryagin's Maximum Principle is used as a necessary condition to find the optimal curve for the respective controls over fixed time period. The formulated problems are numerically solved using forward backward sweep method with generalized Euler scheme.

• Journal of Biosystems Engineering
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• 제24권5호
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• pp.445-452
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• 1999

This study was conducted to develop a searching algorithm for optimal daily temperature setpoint greenhouse. An algorithm using crop growth and energy models was developed to determine optimum crop growth environment. The results of this study were as follows: 1. Mathematical models for crop growth and energy consumption were derived to define optimal daily temperature setpoint. 2. Optimum temperature setpoint, which could maximize performance criterion, was determined by using Pontryagin maximum principle. 3. Dynamic control of daily temperature using the developed algorithm showed higher performance criterion than static control with fixed temperature setpoint. Performance criteria for dynamic control models were with simulated periodic weather data and with real weather data, increased by 48% and 60%, respectively.

• 대한수학회보
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• 제49권3호
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• pp.647-653
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• 2012

In this paper, we obtain a generalized Lorentzian splitting theorem by weakening the assumption of nonnegative Ricci curvature.

• 대한전자공학회논문지
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• 제12권4호
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• pp.15-20
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• 1975

원자로의 출력을 초기상태에서 요구표적 상태로 증가시켜 주는 과도기간중 출력의 Overshoot가 생기는데 이 Overshoot에 구속조건을 두는 것은 원자로를 제각함에 있어 안전사 매우 중요하다. 따라서 출력이 요구 최대허용 구동영역을 넘지 않도록 반응도를 조절하면서 초기값(no, co)에서 최종같인 요구값(2no,2co) 또는 (1. 5no,1.5co)로 출력을 증가시키는데 최대원리(Maximum principle)를 적용하였다. 그리고 이때의 스위청점, 스위청시간 및 최적제각 반응도를 구하였다. The power overshoot is rises in the output during the transient period when the output of nuclear reactor is increased from the initial state to the desired target state and certain amount of constraint on power level is of primary importance for safety control of nuclear reactor. Therefore, the maximum principle is applied to this process control in transfering its power from the initial state(no, co) to the final target state(2no, 2co or 1.5no, 1.5co), adjusting the reactivity so that its overshoot is limited within the allowable constraint required. In this case, the switching points, switching times, optimal lima and optimal control reactivity are calculated.

• 대한기계학회논문집B
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• 제41권10호
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• pp.631-638
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• 2017

원심펌프와 구조 및 작동 원리가 다른 토네이도 원리를 적용한 슬러리 펌프의 성능특성에 미치는 로터 설계형상의 영향에 대한 실험적 연구를 수행하였다. 십자 구조인 로터의 설계변수는 직경, 높이 및 두께로 설정하였으며, 설계변수에 따라 성능특성을 비교하였다. 로터의 직경과 높이가 커지면 펌프효율이 증가하는 반면에, 로터의 두께가 증가하면 효율은 감소하였다. 본 연구의 설계조건에서 높이가 최대인 로터가 직경이 최대인 경우에 비해 비면적은 약간 작지만 펌프효율은 더 높게 나타났다.

• Structural Engineering and Mechanics
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• 제70권3호
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• pp.367-380
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• 2019

The paper concerns topology and geometry optimization of statically determinate beams with arbitrary number of supports. The optimization problem is treated as a bi-criteria one, with the objectives of minimizing the absolute maximum bending moment and the maximum deflection for a uniform gravity load. The problem is formulated and solved using the Pareto optimality concept and the lexicographic ordering of the objectives. The non-dominated sorting genetic algorithm NSGA-II and the local search method are used for the optimization in the Pareto sense, whereas the genetic algorithm and the exhaustive search method for the lexicographic optimization. Trade-offs between objectives are examined and sets of Pareto-optimal solutions are provided for different topologies. Lexicographically optimal beams are found assuming that the maximum moment is a more important criterion. Exact formulas for locations and values of the maximum deflection are given for all lexicographically optimal beams of any topology and any number of supports. Topologies with lexicographically optimal geometries are classified into equivalence classes, and specific features of these classes are discussed. A qualitative principle of the division of topologies equivalent in terms of the maximum moment into topologies better and worse in terms of the maximum deflection is found.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2004년도 춘계학술대회 논문집
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• pp.451-456
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• 2004

본 연구에서는 장치장 운영규칙의 현실성을 높이기 위해서 트랜스퍼 크레인의 작업운영체계를 분석하고 작업우선순위의 적용을 위한 운영규칙의 적용방법을 설명하였다. 또한 장치장에서 주행로의 특성에 따른 대기 및 주행로 점거형태를 분석하여 블록에 진입하여 대기할 수 있는 최대 대기차량수를 도출할 수 있는 산정식을 정리하고 공간의 제약상태를 분석하였다. 또한 공간의 제약사항 극복하기 위해서 공간자원을 정의할 수 있는 다작업원칙을 제시하고 그 원칙을 위한 해법과 순서도를 묘사하였다.