• Journal of the military operations research society of Korea
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• v.18 no.1
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• pp.110-127
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• 1992

In the preventive replacement policies of system that the failure can be detected through only periodic inspection, there is a penalty cost associated with the lapsed time between system failure and its detection. The system under study is replaced if the system fails before $n^{th}$ inspection, otherwise, preventive replacement is performed at the $n^{th}$ inspection. The decision variables are the inspection interval and the period of preventive replacement. This study presents the optimal preventive replacement policy that minimizes the long-run expected cost per unit time.

• Korean Journal of Mathematics
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• v.29 no.2
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• pp.371-386
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• 2021

This paper investigates two discrete time queueing inventory models with positive service time and lead time. Customers arrive according to a Bernoulli process and service time and lead time follow geometric distributions. The first model under discussion based on replenishment of order upto S policy where as the second model is based on order placement by a fixed quantity Q, where Q = S - s, whenever the inventory level falls to s. We analyse this queueing systems using the matrix geometric method and derive an explicit expression for the stability condition. We obtain the steady-state behaviour of these systems and several system performance measures. The influence of various parameters on the systems performance measures and comparison on the cost analysis are also discussed through numerical example.

• Journal of Korean Society for Quality Management
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• v.28 no.1
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• pp.57-77
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• 2000

A two-dimensional warranty policy, two types of warranty criteria, such as the age and mileage of an automobile, are employed simultaneously to determine the eligibility of a warranty claim. We deal with the analysis of a variety of combined two-dimensional free replacement warranty(FRW) and pro-rata replacement warranty(PRW). In this paper we also propose the analysis of policies with item failures modelled using the one-dimensional and two-dimensional approach, respectively. We obtain expressions for the expected warranty costs and illustrate through numerical examples.

• Journal of applied mathematics & informatics
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• v.1 no.1
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• pp.1-12
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• 1994

We consider a single channel CSMA/CD system with D homogeneous stations and impeded buffer of infinite size. We find a sufficient condition for the model to be stable under the threshold control policy and derive the limiting distri-bution of the number of messages in the system at the moment of service completion. We also derive the limiting distributing of the number of messages in the system size at arbitrary time by using Markov regenerative processes. Some numerical examples and special cases are also treated.

• Journal of applied mathematics & informatics
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• v.6 no.2
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• pp.539-552
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• 1999

An order-level inventory model for a perishable product with a time-dependent demand is developed for a fixed planning pe-riod allowing backlogging in all cycles within the said period. The market demand is assumed to decrease exponentially as time elapses. The average system cost is derived and its optimization procedure is illustrated with a numerical example. Sensitivity of the optimal so-lution to changes in the values of different parameters of the system is also analysed.

• Journal of applied mathematics & informatics
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• v.6 no.1
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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.

• Proceedings of the Korean Information Science Society Conference
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• 2001.04a
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• pp.217-219
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• 2001

플래쉬 메모리는 데이터 저장 및 변경이 가능한 비휘발성 메모리로 가벼운 무게, 낮은 전력 소모, 충격에 대한 저항성과 빠른 데이터 처리 능력 때문에 이동형 컴퓨터 시스템에서 사용하기에 적당하다. 그러나 플래쉬 메모리는 덮어쓰기(update-in-place)가 불가능하고 각 메모리 셀에 대해 초기화 작업(erasing operation)의 수가 제한되어 있다. 이러한 단점들을 고려하여 세그먼트의 데이터 중 유효 데이터의 비율과 hot 데이터(가까운 시간 안에 update가 될 것이라는 예상되는 data)의 수, 세그멘트가 초기화되었던(easing) 횟수 등을 고려한 새로운 초기화 기법(cleaning policy)을 제안하고자 한다.

• Analyses & Alternatives
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• v.1 no.1
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• pp.31-43
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• 2017

The situation in Korean peninsula, globally and regionally, which followed the global huge uncertainty, changed a lot. Because of the political crisis, ROK falls into a chaos. And DPRK goes into a policy changing period by the internal issues, international sanctions and assassination accident in Malaysia, which is confirmed to be DPRK's Supreme leader, Kim Jong Un's half brother. Under this changing circumstances, the perspectives of regarding China and the Korean peninsula, must be undated accordingly. Only by understanding the Sino-US relations, the DPRK nuclear issue and the regional dilemmas can we formulate reasonable policies to contribute to the peace and stability of the Korean Peninsula.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.6
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• pp.4267-4275
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• 2015

Prefabricated houses are fabricated at the factory for approximately 60 to 80% of the entire construction process, and assembled in the field. In the process of transporting and lifting, internal and external finishes of the unit module are concerned about damages. The purpose of this study is to improve the fixing equipment by analyzing load behavior. The improved fixing equipment would minimize the deformation of internal and external finishes. In order to develop the improved fixing equipment, transporting load on the fixing equipment is analyzed using Monte Carlo simulations, and structural performance is verified by the non-linear finite element analysis. Statistical analysis shows load distribution of unit module is similar with extreme value distribution. Based on the statistical analysis and Monte Carlo simulation, the maximum transporting load is 28.9kN and 95% confidence interval of transporting load is -1.22kN to 9.5kN. The nonlinear structural analysis shows improved fixing equipment is not destructed to the limit load of 35.3kN and withstands the load-bearing in the 95% confidence interval of transporting load.

• Health Policy and Management
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• v.23 no.1
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• pp.52-58
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• 2013

This study was conducted to investigate the responsiveness and its related factors of public health center for novel influenza A (H1N1) epidemic. The data was collected through a web-based survey conducted during February to April 2011. The 182 respondents were team leaders or persons who were responsible for H1N1-related work at public health centers during the H1N1 prevalence. The related factors affecting the responsiveness were different by urban or rural area. In the level of gu (urban) area, cooperation with the public organizations, preparing its own response plan were the significant factors. But, in the level of si or gun (rural) area, cooperation with private organizations (clinic or pharmacy), physical (facilities, equipments, and medicines), and human infrastructures (public health professions, education and knowledge, and motivation) were more important factors. Therefore, how to cope with H1N1 prevalence in the future should be different by local characteristics. As a result, there are several challenges that public health centers should prepare for the further emerging infectious diseases. First, it is needed to make standard manuals which could strengthen education and training in order to respond appropriately, as well as to prepare enough physical infrastructures for the crisis. Next, the public health center should prepare correct media response and cooperation system with public and private organizations.