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양재환(Jaehwan Yang),여윤경(Yoonkyung Yuh) 한국경영과학회 2010 經營 科學 Vol.27 No.1
This study evaluates life annuity plans based on two different types of measures:financial benefit and utility on consumption. The financial benefit is measured by Money’s Worth (MW) ratio and return on annuity. For the measure of utility, an optimization problem is formulated with the objective of maximizing utility on consumption. To solve the optimization model, we use Dynamic Programming (DP) technique. The both types of measures are applied to cases of Korean pre-retirees at age 40 with different accumulation years of annuity (i.e. level of annuity asset at the age of retirement) and different timings of annuitization. Our results generally indicate that the utility based optimization model is superior to the financial measures in terms of providing a better evaluation of an annuity plan due to its capability to consider an individual’s financial situation during his/her retirement period. Also, they suggest that the level of annuity asset is an important factor when an individual determines the optimal annuitization timing.
양재환(Jaehwan Yang),여윤경(Yoonkyung Yuh) 한국경영과학회 2021 經營 科學 Vol.38 No.3
This study analyzed coping strategies that subscribers can take, assuming the situation in which housing prices surge after their joining the reverse mortgage loan program. In the analysis of the net present value, it was found that the termination (and rejoining)strategy after 3 years was advantageous when the rate of increase in house prices was more than 20%. When the rate of increase in housing prices is more than 20%, for both termination strategies the homepension amount increases significantly compared to the maintaining strategy while the expected inheritance amount decreases significantly. In the analysis of expected utility, it was found that if housing price increases more than 20%, then the termination strategiesbecame more advantageous than the maintaining strategy. If preferential subscription is possible due to low house price such as 100 million won or the subscription starting age is low, then the termination strategy became more advantageous.Also, the shorter the subscription period and the lower the inheritance strength, the more advantageous the termination strategy. Lastly, when the rate of increase in housing prices in the future was very low (-1~1%) or very high (3~4%), the termination strategy was more advantageous. In the end, it was found that the optimal strategy to be selected depends on the subscriber’s preference such as the strength of inheritance motive, and various conditions such as housing price, subscription age, and subscription period.
다중회귀분석을 활용한 국내 산업 및 기업 규모 별 현금화주기와 재무성과와의 상관관계 분석
장금주(Geum-Joo Jahng),양재환(Jaehwan Yang) 한국SCM학회 2011 한국SCM학회지 Vol.11 No.2
This paper studies the relationship between C2C(Cash-To-Cash) cycle time and financial performance of Korean companies. Especially, we focus on the effect of the industry type and the size of companies on this relationship by considering 10 different industries and two different sizes. More specifically, the multiple regression analysis is used to investigate the relationship between the C2C cycle time including its components such as days of inventory, days sales outstanding, and days payable outstanding and financial performance metrics such as ROA(Return On Asset), operating profit rate, and net profit rate. The results indicate that the relationship between the C2C cycle time and financial performance is sensitive to the industry type, and 17 out of 30 cases(combinations of the three financial metrics and 10 industries) result in statistically significant negative relationship. Similarly, on 33 out of 90 cases, the three components of the C2C cycle time have statistically significant relationship with the financial performance of companies. Regarding the size of companies, we find statistically significant relationship between the C2C cycle time and the financial performances regardless of the size of companies. However, the significance is higher with the SME(Small and Medium size Enterprises). Further, ROA and operating profit rate of big companies do not show statistically significant relationship with days of inventory and days sales outstanding.
혼합정수계획법을 이용한 항공기-목표물 최적할당에 관한 연구
이대력(Dae Ryeock Lee),양재환(Jaehwan Yang) 한국경영과학회 2008 經營 科學 Vol.25 No.1
In recent warfare, the performance improvement of air weapon systems enables an aircraft to strike multiple targets on a single sortie. Further, aircrafts attacking targets may carry out an operation as a strike package that is composed of bombers, escort aircrafts, SEAD (Suppression of Enemy Air Defenses) aircrafts and etc. In this paper, we present an aircraft allocation model that allocates multiple targets to a single sortie in the form of a strike package. A mixed integer programming is developed and solved by using a commercially available software. The new model is better than existing ones because not only it allocates aircrafts to multiple targets but also it models the concept of the strike package. We perform a computational experiment to compare the result of the new model with that of existing ones, and perform sensitivity analysis by varying a couple of important parameters.
혼합정수계획법을 이용한 요격미사일의 할당 및 교전 일정계획에 관한 연구
이대력(Dae Ryeock Lee),양재환(Jaehwan Yang) 한국경영과학회 2015 經營 科學 Vol.32 No.4
This paper considers the allocation and engagement scheduling of air defense missiles by using MIP (mixed integer programming). Specifically, it focuses on developing a realistic MIP model for a real battle situation where multiple enemy missiles are headed toward valuable defended assets and there exist multiple air defense missiles to counteract the threats. In addition to the conventional objective such as the minimization of surviving target value, the maximization of total intercept altitude is introduced as a new objective. The intercept altitude of incoming missiles is important in order to minimize damages from debris of the intercepted missiles and moreover it can be critical if the enemy warhead contains an atomic or chemical bomb. The concept of so called the time window is used to model the engagement situation and a continuous time is assumed for flying times of the both missiles. Lastly, the model is extended to simulate the situation where the guidance radar, which guides a defense missile to its target, has the maximum guidance capacity. The initial mathematical model developed contains several non-linear constraints and a non-linear objective function. Hence, the linearization of those terms is performed before it is solved by a commercially available software. Then to thoroughly examine the MIP model, the model is empirically evaluated with several test problems. Specifically, the models with different objective functions are compared and several battle scenarios are generated to evaluate performance of the models including the extended one. The results indicate that the new model consistently presents better and more realistic results than the compared models.