• Journal of applied mathematics & informatics
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• 제18권1_2호
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• pp.145-158
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• 2005

We formulate a stochastic control problem on proportional reinsurance that includes impulse and regular control strategies. For the first time we combine impulse control with regular control, and derive the expected total discount pay-out (return function) from present to bankruptcy. By relying on both stochastic calculus and the classical theory of impulse and regular controls, we state a set of sufficient conditions for its solution in terms of optimal return function. Moreover, we also derive its explicit form and corresponding impulse and regular control strategies.

• 한국농공학회논문집
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• 제49권3호
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• pp.11-20
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• 2007

Estimation of crop consumptive use is a key term of agricultural water resource systems design and operation. The 10-year return period drought has special aspects as a reference period in design process of irrigation systems in terms of agricultural water demand analysis so that crop evapotranspiration (ETc) about the return period also has to be analyzed to assist understanding of crop water requirement of paddy rice. In this study, The ETc of 10-year return period drought was computed using frequency analysis by 54 meteorological stations. To find an optimal probability distribution, 8 types of probability distribution function were tested by three the goodness of fit tests including ${\chi}^2$(Chi-Square), K-S (Kolmogorov-Smirnov) and PPCC (Probability Plot Correlation Coefficient). Optimal probability distribution function was selected the 2-parameter Log-Normal (LN2) distribution function among 8 distribution functions. Using the two selected distribution functions, the ETc of 10-year return period drought was estimated for 54 meteorological stations and compared with prior study results suggested by other researchers.

• Management Science and Financial Engineering
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• 제18권2호
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• pp.1-4
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• 2012

We study optimal trading strategy of a market maker with stock inventory. Following Avellaneda and Stoikov (2008), we assume the stock price follows a normal distribution. However, we take a constant expected rate of the stock return and assume that the stock volatility is an inverse function of the stock price level. We show that the optimal bid-ask spread of the market maker is wider for a higher expected rate of stock returns.

• 반도체디스플레이기술학회지
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• 제20권1호
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• pp.48-53
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• 2021

The purpose of this study is to establish a crime prevention system through the Crime Prevention Through Environmental Design (CPTED). The research method went through the double diamond process and discovered the user's needs through the persona analysis. The most representative features are the functions that informs users of the safe and optimal route, checks the presence of streetlights or cctvs in real time to update them, and allows people with similar routs to return home together. It is a function to help safe return home with the help of an autonomous method, and a self-defense function to protect themselves. Therefore, the application presented in this study was intended to be of great help when actually returning home by adding these new functions. In particular, we help users to return home most safely by recommending the best safe route. Through the persona analysis, research method which we had chosen, the needs of users were discovered and implemented in a design that reflected those needs and requirements.

• Journal of Chest Surgery
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• 제24권10호
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• pp.967-972
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• 1991

Between Feb. 1982 and July 1990, 173 patients [male: 89, female: 84] Who underwent heart valve replacement for acquired valvular heart disease on the Department of Thoracic and Cardiovascular Surgery, School of Medicine, Pusan National University, were reviewed for return to work after heart valve replacement. The replaced valve were mitral [128, 74.0%], aortic[10, 5.8%], mitral & aortic[35, 20.2%]. Two tricuspid valve replacement were excluded. Several important factors influencing the return to work were age, the employment status before surgery, the number of replaced valve, the pre - op NYHA functional class and cardiac function [ejection fraction]. These factors were closely related to the optimal time of heart valve replacement. It can be concluded that the rate of return to work and the quality of life would be improved if valve replacement were performed at an earlier stage of valvular heart disease.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2003년도 ICCAS
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• pp.168-173
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• 2003

In this paper, we will present a deeper look on optimal design methods that are related to path-planning for a mobile robot. To control the motion of a mobile robot in a clustered environment, it's necessary to know a suitable trajectory assuming certain start and goal point. Up to now, there are many literatures that concern optimal path planning for an obstacle avoided mobile robot. Among those literatures, we have chosen 2 novel methods for our further analysis. The first approach [4] is based on HJB(Hamilton-Jacobi-Bellman) equation whose solution is the return-function that helps to generate a shortest path to the goal. The later [5] is called polynomial-path-planning approach, in this method, a shortest polynomial-shape path would become a solution if it was a collision-free path. The camera network plays the role as sensors to generate updated map which locates the static and dynamic objects in the space. Therefore, the exhibition of both path planning and dynamic obstacle avoidance by the updated map would be accomplished simultaneously. As we mentioned before, our research will include the motion control of a true mobile robot on those optimal planned paths which were generated by above algorithms. Base on the kinematic and dynamic simulation results, we can realize the affection of moving speed to the stable of motion on each generated path. Also, we can verify the time-optimal trajectory through velocity tuning. To simplify for our analysis, we assumed the obstacles are cylindrical circular objects with the same size.

• 한국정밀공학회지
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• 제29권4호
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• pp.441-448
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• 2012

This paper describes the optimal home positioning algorithm of Eclipse-II, a new conceptual parallel mechanism for motion simulator. Eclipse-II is capable of translation and 360 degrees continuous rotation in all directions. In unexpected situations such as emergency stop, riders have to be resituated as soon as possible through a shortest translational and rotational path because the return paths are not unique in view of inverse kinematic solution. Eclipse-II is man riding. Therefore, the home positioning is directly related to the safety of riders. To ensure a least elapsed time, ZYX Euler angle inverse kinematics is applied to find an optimal home orientation. In addition, the subsequent decrease of maximum acceleration and jerk values is achieved by combining the optimal return path function with cubic spline, which consequently reduces delivery force and vibration to riders.

• Management Science and Financial Engineering
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• 제10권1호
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• pp.25-41
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• 2004

There have been many studies to build a model that can help investors construct optimal portfolio. Most of the previous models, however, are based upon the path-breaking Markowitz model (1959) which is a quantitative model. One of the most important problems with that kind of quantitative model is that, in reality, most of the investors use not only quantitative, but also qualitative information when they select their optimal portfolio. Since collecting both types of information from the markets are time consuming and expensive, making a set of target assets smaller, without suffering heavy loss in the rate of return, would attract investors. To extract only desired assets among all available assets, we need knowledge that identifies investors' preference for the risk of the assets. This study suggests two-layer decision-making rules capable of identifying an investor's risk preference and an architecture applying them to a quantitative portfolio model based on risk and expected return. Our knowledge-based portfolio system is to build an investor's preference-oriented portfolio. The empirical tests using the data from Korean capital markets show the results that our model contributes significantly to the construction of a better portfolio in the perspective of an investor's benefit/cost ratio than that produced by the existing portfolio models.

• 대한수학회보
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• 제48권4호
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• pp.737-757
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• 2011

This work is concerned with an optimal selling rule for a large position of stock in a market. Selling a large block of stock in a short period typically depresses the market, which would result in a poor filling price. In addition, the large selling intensity makes the regime more likely to be poor state in the market. In this paper, regime switching and depressing terms associated with selling intensity are considered on a set of geometric Brownian models to capture movements of underlying asset. We also consider the liquidation strategy to sell much smaller number of shares in a long period. The goal is to maximize the overall return under state constraints. The corresponding value function with the selling strategy is shown to be a unique viscosity solution to the associated HJB equations. Optimal liquidation rules are characterized by a finite difference method. A numerical example is given to illustrate the result.

• 한국정보과학회논문지:정보통신
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• 제36권1호
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• pp.50-56
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• 2009

본 논문에서는 P2P 네트워크 환경에서 유사한 특성을 가진 다른 노드(node)를 찾아 추천자(recommender) 그룹을 형성하고 유지하는 새로운 알고리즘을 제안한다. 두 노드의 유사한 특성을 비교하기 위해 본 논문에서는 두 노드의 특성값(characteristic value. 이하 CV)을 이용한 적합도 검사(fitness evaluation)를 사용하여 유사도(similarity)를 확인한다. 유사도의 크기가 작을수록 두 노드는 매우 유사한 특성을 가지게 된다. 또한, 본 논문에서 제안하는 GORGFM(Globally Optimal Recommender Group Formation and Maintenance) 알고리즘은 최단 기간 내에 최적의 추천자 그룹을 형성하고 사용자의 선호도 변화에 대응할 수 있는 알고리즘이다. GORGFM 알고리즘을 평가하기 위해 본 논문에서는 매칭율(matching rate)과 얼마나 빠르고 정확하게 추천자 그룹을 형성하는가에 대해 시뮬레이션 한다. GORGFM 알고리즘은 네트워크에서뿐만 아니라 인터넷상에서 컨텐츠(contents) 검색 등과 같이 적합도 함수(fitness function)를 이용할 수 있는 모든 시스템에 적용할 수 있다.