• 한국수자원학회:학술대회논문집
• /
• 한국수자원학회 2009년도 학술발표회 초록집
• /
• pp.905-908
• /
• 2009

In the management of groundwater in coastal areas, saltwater intrusion associated with extensive groundwater pumping, is an important problem. The groundwater optimization model is an advanced method to study the aquifer and decide the optimal pumping rates or optimal well locations. Cheng and Park gave the analytical solutions to the optimization problems basing on Strack's analytical solution. However, the analytical solutions have some limitations of the property of aquifer, boundary conditions, and so on. A simulation-optimization numerical method presented in this study can deal with non-homogenous aquifers and various complex boundary conditions. This simulation-optimization model includes the sharp interface solution which solves the same governing equation with Strack's analytical solution, therefore, the freshwater head and saltwater thickness should be in the same conditions, that can lead to the comparable results in optimal pumping rates and optimal well locations for both of the solutions. It is noticed that the analytical solutions can only be applied on the infinite domain aquifer, while it is impossible to get a numerical model with infinite domain. To compare the numerical model with the analytical solutions, calculation of the equivalent boundary flux was planted into the numerical model so that the numerical model can have the same conditions in steady state with analytical solutions.

• 대한교통학회지
• /
• 제17권5호
• /
• pp.111-122
• /
• 1999

소화물 일관 운송 과정에서 발생하는 직접비용을 최소화하는 수리 모형과 해법이 제안되었다. 고려되는 비용으로는 화물 운송을 위한 차량 운행에 필요한 제반 비용인 링크 비용과 터미널에서 일어나는 하차, 분류, 재적 재등 하역 작업에서 발생하는 노드 비용을 감안하였고 총비용을 줄이기 위한 화물의 운송 경로가 모형의 결정변수이다. 해법으로는 최종해의 품질은 다소 미흡하나 계산 시간이 짧은 Steepest Descent Method와 최종해의 품질이 우수하나 계산 시간이 많이 소요되는 Simulated Annealing Method를 활용한 두개의 알고리즘이 고안되었다. 최적해를 찾아가기 위한 탐색의 출발점이 되는 초기해는 Dijkstra의 최단경로 알고리즘을 수정하여 찾는다. 예제를 통하여 알고리즘의 계산 과정을 설명하였고 제시된 두 방법의 최종해는 초기해에 비하여 비용 측면에서 각각 12%. 15%의 절감 효과가 있음을, 적재율 측면에서 초기해의 62.6%에서 각각 774%. 87.4% 향상됨을 확인하였다.

• 제어로봇시스템학회논문지
• /
• 제15권12호
• /
• pp.1216-1222
• /
• 2009

This article describes a simple method for generating the walking trajectory for the biped humanoid robot. The method used a simple inverted model instead of complex multi-mass model and a reasonable explanation for the model simplification is included. The problem of gait trajectory generation is to find the solution from the desired ZMP trajectory to CoG trajectory. This article presents the analytic solution for the bipedal gait generation on the bases of ZMP trajectory. The presented ZMP trajectory has Fourier series form, which has finite or infinite summation of sine and cosine functions, and ZMP trajectory can be designed by calculating the coefficients. From the designed ZMP trajectory, this article focuses on how to find the CoG trajectory with analytical way from the simplified inverted pendulum model. Time segmentation based approach is adopted for generating the trajectories. The coefficients of the function should be designed to be continuous between the segments, and the solution is found by calculating the coefficients with this connectivity conditions. This article also has the proof and the condition of solution existence.

• 한국컴퓨터정보학회논문지
• /
• 제24권1호
• /
• pp.137-143
• /
• 2019

As the performance of computers increases, the use of deep learning, which has faced technical limitations in the past, is becoming more diverse. In many fields, deep learning has contributed to the creation of added value and used on the bases of more data as the application become more divers. The process for obtaining a better performance model will require a longer time than before, and therefore it will be necessary to find an optimal model that shows the best performance more quickly. In the artificial neural network modeling a tuning process that changes various elements of the neural network model is used to improve the model performance. Except Gride Search and Manual Search, which are widely used as tuning methods, most methodologies have been developed focusing on heuristic algorithms. The heuristic algorithm can get the results in a short time, but the results are likely to be the local optimal solution. Obtaining a global optimal solution eliminates the possibility of a local optimal solution. Although the Brute Force Method is commonly used to find the global optimal solution, it is not applicable because of an infinite number of hyper parameter combinations. In this paper, we use a statistical technique to reduce the number of possible cases, so that we can find the global optimal solution.

• Korean Journal of Mathematics
• /
• 제16권3호
• /
• pp.259-269
• /
• 2008

The non-existence and existence of the positive solution for the generalized cooperation biological model for two species of animals $${\Delta}u+u(a-bu+g(v))=0\;in\;{\Omega}\\{\Delta}v+v(d+h(u)-cv)=0\;in\;{\Omega}\\u=v=0\;on\;{\partial}{\Omega}$$ are investigated. The techniques used in this paper are elliptic theory, upper-lower solutions, maximum principles and spectrum estimates. The arguments also rely on some detailed properties for the solution of logistic equations.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 2003년도 봄 학술발표회 논문집
• /
• pp.853-858
• /
• 2003

A new method is proposed to obtain bond-slip model for an adhesive joint between FRP and concrete. Interface element, which can describe the bond behavior, is developed in order to overcome the restriction that complex constitutive relations cannot be modeled in analytic solution. Calibrating numerical bond-slip model to experimental results, multi-objective optimization problem is constructed by physical programming method, and is solved using genetic algorithm. The validity of proposed method is demonstrated by comparing known analytic solution and numerically optimized solution.

• 한국지반공학회지:지반
• /
• 제13권2호
• /
• pp.169-184
• /
• 1997

Drucker-Prayer의 항복기준을 이용한 원형터널의 해석을 위하여 간략한 수치해석 기법이 유도되었다. 유도된 이론해를 근거로 컴퓨터 프로그램 FDAXP가 개발되었구 예제 해석을 통하여 프로그램의 신뢰도를 검증하여 만족한 결과를 얻었다. 소개된 프로그램 FDAXP는 깊은 터널과 쉽게 소성변형이 발생되는 지반 및 암반에서의 초기 터널해석에 손쉽게 적용될 수 있으며, 기존의 상용 프로그램들에서 Drunker-Prayer model을 검증하는데에 매우 유용하게 사용되리라 사료된다.

• 대한산업공학회지
• /
• 제32권1호
• /
• pp.9-17
• /
• 2006

This paper deals with a discrete simulation optimization method for designing a complex probabilistic discrete event simulation. The developed algorithm uses the configuration algorithm that can change decision variables and the stopping algorithm that can end simulation in order to satisfy the given objective value during single run. It tries to estimate an auto-regressive model for evaluating correctly the objective function obtained by a small amount of output data. We apply the proposed algorithm to M/M/s model, (s, S) inventory model, and known-function problem. The proposed algorithm can't always guarantee the optimal solution but the method gives an approximate feasible solution in a relatively short time period. We, therefore, show the proposed algorithm can be used as an initial feasible solution of existing optimization methods that need multiple simulation run to search an optimal solution.

• 대한교통학회지
• /
• 제9권2호
• /
• pp.121-126
• /
• 1991

Wilson made an importent contribution to develop a trip distribution model with the general form of gravity model which is an entropy maximization program. Also Wilson suggested a technique which is called the "iterative balancing method" for soving the model. This te-chnique however is not stable to find solution because it is a heuristic method and sometimes does not converge to the correct solution. In this paper a new solution method using a numerical method for solving the non-linear simultaneous equation system is developed and evaluated in both computers VAX 8700 and PC/AT 286 The result of this method and Wilson's method are compared with each other. Wilson's method resulted in inferior solutions measured by the final norm of residuals.

• 대한교통학회:학술대회논문집
• /
• 대한교통학회 2002년도 제41회 학술발표회논문집
• /
• pp.97-139
• /
• 2002

The aim of the present study is to find a good quality user equilibrium assignments under time varying condition. For this purpose, this study introduces a dynamic network loading method that can maintain correct flow propagation as well as flow conservation, and it develops a novel solution algorithm that does not need evaluation of the objective function by modifying the Schittenhelm (1990)'s algorithm. This novel algorithm turns out to be efficient and convenient compared to the conventional Frank-Wolfe (1956) algorithm because the former finds solutions based on routes rather than links so that it can maintain correct flow propagation intrinsically in the time-varying network conditions. The application of dynamic user equilibrium (DUE) assignment model with this novel solution algorithm to test networks including medium-sized one shows that the present DUE assignment model gives rise to high quality discrete time solutions when we adopt the deterministic queuing model for a link performance function, and we associate flows and costs in a proper way.