• 한국신뢰성학회지:신뢰성응용연구
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• 제11권2호
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• pp.167-176
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• 2011

This paper introduces models for preventive maintenance policies and considers periodic preventive maintenance policy with minimal repair when the failure of system occurs. It is assumed that minimal repairs do not change the failure rate of the system. The failure rate under prevention maintenance received an effect by a previously prevention maintenance and the slope of failure rate increases the model where it considered. Also the start point of failure rate under prevention maintenance considers the degradation of system and that it increases quotient, it assumed. Per unit time it bought an expectation cost from under this prevention maintenance policy. We obtain the optimal periodic time and the number for the periodic preventive maintenance by using Nakagawa's Algorithm, which minimizes the expected cost per unit time.

• 한국시뮬레이션학회:학술대회논문집
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• 한국시뮬레이션학회 2003년도 춘계학술대회논문집
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• pp.129-134
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• 2003

In this paper, we determine optimal reduction in the lead time and setup cost for some stochastic inventory models. And we propose more general model that allow the backorder rate as a control variable. We first assume that the lead time demand follows a normal distribution. And we assume that the backorder rate is dependent on the length of lead time through the amount of shortages. The stochastic models analyzed in this paper are the classical continuous and periodic review policy models with a mixture of backorders and lost sales. For each of these models, we provide a sufficient conditions for the uniqueness of the optimal operating policy. We also develop algorithms for solving these models and provide illustrative numerical examples.

• 응용통계연구
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• 제28권4호
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• pp.685-701
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• 2015

한국의 지속적인 저출산은 세계적으로 유례가 없을 정도의 급격한 고령화 속도와 맞물려 국가경쟁력 및 사회보장 시스템을 약화시키는 요인이 되었다. 저출산 문제를 해결하기 위하여 정부에서는 각종 출산장려정책을 실시하고 있으나, 현재까지 저출산에서 벗어나지 못하고 있어 정책이 효과적이지 못하였던 것으로 평가된다. 그러므로 본 연구에서는 보다 효과적인 정책개발의 근간을 마련하기 위하여 조건부 순위별 출산율을 제안하고, 이를 이용하여 한국의 출산정책 효과를 파악하였다. 조건부 순위별 출산율을 사용하면 순위별 출산율을 사용하는 것보다 합계출산율의 변화와 효과를 명확히 산출할 수 있으므로, 다양한 순위별 출산율의 시나리오에 따라 합계출산율의 변화를 비교하였다. 이를 통하여 현재 정부의 셋째 아 출산지원 정책으로 도달할 수 있는 합계출산율 및 둘째 아 또는 첫째 아의 출산지원을 하였을 때 도달할 수 있는 합계출산율을 산출할 수 있었다. 또한 지속적인 저출산으로 빠르게 감소하고 있는 가임여성(15-49세)을 고려하여 합계출산율에 따른 출생아수를 함께 제시하여 실질적인 출생아수의 증가를 유도하는 정책개발에 도움이 될 수 있도록 연구결과를 정리하였다.

• East Asian Economic Review
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• 제20권2호
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• pp.229-275
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• 2016

We study the effect of the high-skilled emigration rate on the growth rate of the source countries. We incorporate the foreign direct investment and the policy variables into the panel model and also their interactions with the high-skilled emigration rate, as they are related to the network externality that may be created by the high-skilled emigrants working abroad. We apply the static fixed-effects model and compare it with the results obtained in the dynamic panel model with system generalized methods of moments estimators. We find the negative effect of the high-skilled emigration rate by itself and in its interaction with the foreign direct investment only in the dynamic model. However, we find positive coefficient for the interaction of the high-skilled emigration rate and the civil liberties index, which holds across the static and dynamic specifications. This implies that the effect of the high-skilled emigration rate on the growth rate of the source countries can be positive, and the extent is larger for countries with 'poor' civil liberties. The developing countries with low levels of foreign direct investment inflows and 'poor' civil liberties can best benefit from the high levels of skilled emigration outward. Through finding significant interactions with other variables, we confirm that the high-skilled emigration should be considered along with other related variables in measuring its impact on growth. The implications offer suggestions for the international trade and aid policies.

• 조명전기설비학회논문지
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• 제28권7호
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• pp.97-105
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• 2014

This article examines the causality relationship among SMP, base-load share, LNG import price, and exchange rate in Korean power market during 2002~2012, using unit root test, cointegration test, and vector error correction model(VECM). The cointegration test shows that 4 variables without unit root have been in the long-run causality. As the results of ECM, SMP is analyzed to have been unilaterally caused from LNG import price and base-load share in the shot-run, while it has been unilaterally caused from LNG import price and exchange rate in the long-run. This article has the following policy implications: the adjustment of exchange rate to reduce he risk of LNG import price and the proper securement of base-load share for the long-run stability of SMP.

• 한국신뢰성학회지:신뢰성응용연구
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• 제13권4호
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• pp.229-239
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• 2013

This paper reports a manner to use a Bayesian approach to derive the optimal replacement policy. In order to produce a system with minimal repair warranty, a replacement model with the extended warranty is considered. Within the warranty period, the failed system is minimally repaired by the manufacturer at no cost to the end-user. The failure time is assumed to follow a Weibull distribution with unknown parameters. The expected cost rate per unit time, from the end-user's viewpoints, is induced by the Bayesian approach, and the optimal replacement policy to minimize the cost rate is proposed. Finally, a numerical example illustrating to derive the optimal replacement policy based on the Bayesian approach is described.

• 한국통계학회:학술대회논문집
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• 한국통계학회 2005년도 추계 학술발표회 논문집
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• pp.73-78
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• 2005

This paper considers a preventive maintenance policy following the expiration of renewing warranty, Most preventive maintenance models assume that each PM costs a fixed predetermined amount regardless of the effectiveness of each PM. However, it seems more reasonable to assume that the PM cost depends on the degree of effectiveness of the PM activity. In this paper we consider a periodic preventive maintenance policy following the expiration of renewing warranty when the PM cost is an increasing function of the PM effect. The optimal number and period for the periodic PM policy with effect dependent cost that minimize the expected cost rate per unit time over an infinite time span are obtained.

• KDI Journal of Economic Policy
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• 제39권4호
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• pp.69-94
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• 2017

This paper re-examines the impacts an institutional arrangement may have on labour market outcomes such as the employment and unemployment rates. Based on the results from a generalized econometric model, the generosity of unemployment insurance benefits, organized labour and active labour market policy have effects on a labour market in line with previous findings. However, taxes on labour and the degree of employment protection are found to affect neither the employment rate nor the unemployment rate. Thus, some findings in this paper validate earlier findings, whereas others do not.

• International journal of advanced smart convergence
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• 제11권2호
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• pp.1-6
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• 2022

With the emergence of the new era of the 4th industrial revolution, compute-bound workloads with large memory footprint like big data processing increase dramatically. Even in such compute-bound workloads, however, we observe bulky I/Os while loading big data from storage to memory. Although file I/O cache plays a role of accelerating the performance of storage I/O, we found out that the cache hit rate in such environments is not improved even though we increase the file I/O cache capacity because of some special I/O references generated by compute-bound workloads. To cope with this situation, we propose a new file I/O cache management policy that improves the cache hit rate for compute-bound workloads significantly. Trace-driven simulations by replaying file I/O reference logs of compute-bound workloads show that the proposed cache management policy improves the cache hit rate compared to the well-acknowledged CLOCK algorithm by a large margin.

• KDI Journal of Economic Policy
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• 제29권2호
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• pp.117-133
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• 2007

본 논문은 이자율 준칙에 근거하여 한국의 통화정책의 효율성을 인플레이션과 산출갭의 상대적 안정성을 중심으로 경험적으로 검증하는 데 목적이 있다. 이를 위해 1991년 이후 한국의 주요 거시경제 변수를 설명할 수 있는 구조적 모형이 필요한데, 본고에서는 Ball(1999)의 모형과 유사한 소규모 개방경제모형을 도입한다. 모형의 추정결과, 한국 거시경제 변수를 비교적 잘 설명할 수 있음을 확인할 수 있었고 추정된 모형을 바탕으로 이자율준칙의 범위 내에서 최적 통화정책을 도출하였다. 따라서 최적 이자율 준칙하에서의 인플레이션과 산출갭의 변동성을 실제 데이터와 비교할 수 있다. 실증적 분석의 결과, 중앙은행은 산출갭의 변동성보다 인플레이션의 변동성을 낮추는 데 상대적으로 더 효율적이었음을 알 수 있다. 이는 외환위기 이후 인플레이션이 실제 중앙은행의 목표범위 내에서 하락 안정세를 유지하였고 변동성도 상대적으로 크지 않았음을 고려해 볼 때 타당한 결과라고 해석할 수 있다. 그러나 최적 이자율 준칙과 비교해 볼 때 실제 추정된 이자율 준칙은 인플레이션에 대한 반응 정도가 매우 낮아 인플레이션의 안정성이 이자율 준칙이 효과적이었기 때문은 아닌 것으로 나타났다. 또한 인플레이션을 유발할 수 있는 실질환율 상승의 경우 이자율을 오히려 하락시킨 것으로 나타났는데, 이는 이론 및 최적 이자율 준칙과는 배치되는 결과이다.