• Journal of applied mathematics & informatics
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• 제19권1_2호
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• pp.311-326
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• 2005

The paper deals with the problem of selective harvesting in a prey-predator model with predator self limitation. Criteria for local stability and global stability for both the exploited and unexploited system are derived. The effort has been considered as a dynamic variable and taxation as a control instrument to protect the fish populations from over exploitation. Finally, the optimal taxation policy is discussed with the help of control theory.

• 보건행정학회지
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• 제18권1호
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• pp.1-20
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• 2008

How health care providers compete and how competition among them affects their behavior are crucial questions in theory and health policy. In ordinary markets, competition improves social welfare, However in health care markets facing uncertainty and information asymmetry, competition can take the form of wasteful quality competition and result in cost increase. The purpose of this study is to examine the characteristics of hospital service markets and examine the impact of hospital competition on hospital behavior, more specifically hospital cost and the size of personnel. Based on patient discharge data of 2002 by the Ministry of Health and Welfare and Korea Institute for Health and Social Affairs, and health insurance EDI claims data of 2002, this study measures the degree of competition in the inpatient service market of hospitals, using variable radius method and Herfindahl index. The result of the study shows that the hospital service market consists of on average 3.13 government administrative units(shi, gun, or gu). Compared with hospitals, general or general specialized hospitals cover larger markets and operate in more competitive markets. Nearly 60% of patients use hospitals, which are not located in their government administrative units, meaning that market definition based on variable radius is better than the conventional method of market definition based on government administrative units. The results of multivariate analysis show that competition is not associated with high cost index of hospitals. But hospitals in more competitive markets employ larger(more intensive) input of personnel per 100 beds, implying that hospital competition in Korea can have the form of quality and cost-increasing competition.

• 아태비즈니스연구
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• 제13권4호
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• pp.135-149
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• 2022

Purpose - The primary objective of this article is to investigate the impact of U.S. monetary policy on institutional / individual / foreign investor reactions in the Korean stock market. Design/methodology/approach - This study employs a high frequency event study methodology to identify U.S. monetary policy shocks and quantify the impact of identified shocks on investor reactions. The dependent variable in the regression model is net stock purchase, while the explanatory variables are U.S. monetary policy shocks. The model is estimated for the period 2000-2019, including 156 FOMC meetings. Findings - Foreign investors immediately sell stocks in response to contractionary U.S. monetary shocks. They do not, however, react to anticipated changes in monetary policy rates, confirming the rationality of foreign investors. Individual investors demonstrate the opposite response, indicating that a non-trivial proportion of individual investors are irrational. Research implications or Originality - This study adds to the current literature on the effect of U.S. monetary policy on the Korean stock market. This study demonstrates a heterogeneous response to U.S. monetary policy shocks, validating the rational investment behavior of foreign investors, while individual investors exhibit a certain degree of irrationality. Methodologically, this study adds to the literature by quantifying the impact of U.S. monetary policy employing a sharper identification method allowing a simple and consistent estimation.

• Journal of Preventive Medicine and Public Health
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• 제46권1호
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• pp.28-38
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• 2013

Objectives: This study aimed to collect information that will help enhance the social networks and improve the quality of life among elderly people by observing the relationship between their social network and health-related quality of life (HRQoL) and by analyzing social network factors affecting HRQoL. Methods: This study was based on the 2008 Community Health Survey in Yeoncheon County. Three hundred elders were included in the study population. We compared the revised Lubben Social Network Scale (LSNS-R) score and Euro quality of life-5 dimensions health status index by demographic characteristics and chronic disease prevalence. We analyzed the data using multiple regression and tobit regression by setting the HRQoL as the dependent variable and social network and other characteristics as the independent variables. We analyzed social network factors by using factor analysis. Results: The LSNS-R score differed significantly according to age and existence of a spouse. According to the results from the hierarchical multiple regression analysis, the LSNS-R explained 0.10 of the variance and LSNS-R friends factor explained 0.10 of the variance. The tobit regression indicated that the contribution of the LSNS-R family size factor to the regression coefficient of the independent variable that affected the HRQoL was $B_T$=2.96, that of the LSNS-R family frequency factor was $B_T$=3.60, and that of LSNS-R friends factor was $B_T$=5.41. Conclusions: Social networks among elderly people had a significant effect on HRQoL and their networks of friends had a relatively higher effect than those of family members.

• ETRI Journal
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• 제25권4호
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• pp.258-265
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• 2003

In our study, we extracted the market, finance, and government factors determining R&D investment of individual firms in the IT industry in Korea. We collected the financial data of 515 individual firms belonging to IT and non-IT industries between 1980 and 1999 from the Korea Investors Service's database and investigated the empirical relationship between the factors using an ordinary regression model, a fixed effects model, and a random effects model. The main findings of our study are as follows: i) The Herfindahl Index variable representing the degree of market concentration is statistically insignificant in explaining R&D expenditures in the IT manufacturing industry. ii) Assets, which is used as a proxy variable for firm size, have a positive and statistically significant coefficient. These two results suggest that the Schumpeterian Hypothesis may be only partially applied to the IT manufacturing industry in Korea. iii) The dividend variable has a negative value and is statistically significant, indicating that a tendency of high dividends can restrict the internal cash flow for R&D investment. iv) The sales variable representing growth potential shows a positive coefficient. v) The subsidy as a proxy variable for governmental R&D promotion policies is positively correlated with R&D expenditure. This suggests that government policy has played a significant role in promoting R&D activities of IT firms in Korea since 1980. vi) Using a dummy variable, we verified that firms reduced their R&D investments to secure sufficient liquidity under the restructuring pressure during Korea's 1998 and 1999 economic crisis.

• 에너지공학
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• 제25권2호
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• pp.37-44
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• 2016

2차 에너지인 전력은 다양한 연료를 발전원으로 하고 있기 때문에, 전력에 대한 수요는 에너지 각 부문에 적지 않은 영향을 미친다. 이에 본 논문에서는 전력수요함수를 추정하여 가격탄력성 및 소득탄력성에 대한 정량적 정보를 도출하고자 한다. 이를 위해 1991년부터 2014년까지의 연간 시계열 자료를 이용하되, 탄력성을 단기와 장기를 구분하여 추정할 수 있는 내생시차변수모형을 적용한다. 종속변수로는 연간 전력수요, 독립변수로는 상수항, 전력실질가격, 실질 국내총생산의 3가지를 이용한다. 분석결과 단기 가격탄력성 및 소득탄력성은 각각 -0.142 및 0.866으로 추정되었으며 유의수준 5%에서 통계적으로 유의하다. 즉 전력수요는 단기적인 관점에서 가격 변화에 대해 비탄력적임과 동시에 소득 변화에 대해서도 비탄력적이다. 장기 가격탄력성 및 소득탄력성을 추정한 결과를 살펴보면 각각 -0.210 및 1.287이며 이 값은 유의수준 5%에서 통계적으로 유의하다. 장기적인 관점에서 보더라도 전력수요는 가격 변화에 대해 여전히 비탄력적인 반면에, 소득 변화에 대해서는 전력수요가 탄력적으로 변한다. 따라서 가격정책 위주의 수요관리정책은 단기 및 장기 모두 효과가 제한적이며, 향후 예상되는 소득 증가에 기인하는 전력수요의 증가는 단기보다는 장기에 보다 두드러질 것으로 예상된다.

• Journal of applied mathematics & informatics
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• 제6권1호
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• pp.127-142
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• 1999

This paper develops a methematical model for growth and exploitation of a schooling fish species using a realistic catch-rate function and imposing a tax on the catch to control harvesting. Fishing effort is assumed to depend on the net revenue. The steady states of the system are determined and their local and global stabil-ity are discussed. Taking the tax as a control variable; the optimal harvest policy is formulated and solved as a control problem. The results are illustrated with the help of a numerical example.

• Journal of the Korean Data and Information Science Society
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• 제18권3호
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• pp.689-696
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• 2007

This paper considers a Bayesian approach to determine an optimal PM policy with random maintenance quality. Thus, we assume that the quality of a PM action is a random variable following a probability distribution. When the failure time is Weibull distribution with uncertain parameters, a Bayesian approach is established to formally express and update the uncertain parameters for determining an optimal PM policy. Finally, the numerical examples are presented for illustrative purpose.

• 보건행정학회지
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• 제24권1호
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• pp.24-34
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• 2014

Background: Bankrupted households have recently been increased due to excessive medical expenditure in Korea. They have not been protected from economic risk when household's member has severe diseases that need a lot of money for treatment. Purpose of this study examines policy effect by comparing unmet needs' change of policy object households and non-object groups. Methods: We used Korea Health panel 2nd 4th data collected by Korea Institute for Health and Social Affairs and National Health Insurance Service. Analysis subjects were 381 households (pre-policy) and 393 households (post-policy) that had cancer and cardiovascular and cerebrovascular diseases. Since it was major concern that estimates benefit strengthening policy started by certain time, we setup comparing households which had diabetes, hypertension disease. Comparison subjects were 393,247 households, respectively and we evaluated policy effect using difference in difference (DID) model. Results: Although unmet needs of policy object households were higher than non-object groups, policy execution variable affected negative direction. But interaction-term which shows pure effect of policy was not statistically significant. We utilized multi-DID model to examine factors affecting unmet needs causes. Copayment assistance policy did not significantly affect households that responded to 'economic reason,' and 'no have time to visit' for unmet needs causes. Conclusion: The second copayment assistance policy did not significantly give positive effect to beneficiary households than non-beneficiary groups. When we consider that primary purpose of public insurance guarantee high medical expenditure occurred by unexpected events, it needs to deliberate on switch of benefit strengthening policy that can assist vulnerable people. Also, we suggest that government forward a policy covering non-reimbursable medical expenses as well as switch of benefit strengthening direction because benefit policy do not affect non-covered medical cost which accounts for quarter of total health expenditure.

• 보건행정학회지
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• 제23권2호
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• pp.124-131
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• 2013

Background: This study aimed to measure the opportunity income by identifying the economic length of stay (ELOS) which is the intersection point of daily revenue and cost on appendectomy and pneumonia cases. Methods: The research subjects were 460 patients of appendectomy and 606 patients of pneumonia, discharged from a general hospital between July 1, 2009 and June 30, 2010. ELOS calculated with both of total revenue on diagnosis-related group (DRG) and fee-for service (FFS). The cost is calculated by activity-based costing system of the hospital. Results: Average length of stay (ALOS) of appendectomy was 4.48 days and its average revenue per case were 1,710,215 (1,989,105) won by DRG (FFS). The variable cost was 491,262 won which was 28.7% (24.7%) of DRG (FFS) total revenue. And 97.2% of the total variable cost was incurred within 2 days from admission. The ELOS was 4 (5) days in DRG (FFS). Shortening three days (two days) would increase opportunity income 52.0% (82.2%) in DRG (FFS). ALOS of pneumonia case was 4.86 days and its average revenue per case were 489,448 (761,426) won by DRG (FFS). The variable cost was 27,230 won which was 5.6% (3.6%) of DRG (FFS) total revenue. Thirty-eight point nine percent of the daily variable cost was incurred in discharge date. The ELOS was 2 (4) days in DRS (FFS). Shortening three days (one day) would increase opportunity income 27.6% (37.2%) in DRG (FFS). Conclusion: The ELOS would be used by strategic index for achieving minimum profit and developing the ways to get there. But we also should not pass over that the opportunity income obtained by the reducing ALOS may cause some problem of quality.