• Journal of the Korean Society of Child Welfare
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• no.60
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• pp.25-57
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• 2017

The effects of regular and active leisure activities on positive growth and development in adolescents are widely known. In our society, however, it is challenging to enjoy or expand such activities due to diverse constraints. Under unfavorable circumstances, this study attempted to investigate the application of time availability for liberal leisure activities as a way to help adolescents engage in active leisure activities. Specifically, this study examined the relationship between time availability (both individual and structural) and the time invested in leisure activities at youth training centers which support such leisure activities. The study found the following results: As both individual and structural time availability expanded, the time invested in leisure activities increased as well. Based on these results, this study discussed policy and practice implications regarding the support of adolescents' leisure activities.

• Proceedings of the Korean Information Science Society Conference
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• 2002.04a
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• pp.589-591
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• 2002

본 논문에서는 메쉬 구조의 다중처리시스템을 위한 새로운 할당방법을 제안한다. 이 할당방법은 다른 가용 서브메쉬와 중첩되지 않는 독립 가용 서브메쉬를 유형에 따라 분류하여 유형별 가용 서브메쉬 리스트를 생성한다. 그리고 태스크의 유형에 따라 해당 유형별 가용 서브메쉬 리스트에서 최적할당이 가능한 서브메쉬를 찾음으로써 서브메쉬를 탐색하는데 소요되는 시간을 줄인다. 이 때 서브메쉬를 찾지 못하면 확장지수를 이용하여 더 큰 가용 서브메쉬를 형성한 후 할당함으로써 태스크의 대기 시간을 줄이고, 이 결과로 외적단편화를 줄이는 효과도 얻는다. 또한 할당 해제시 독립 가용 서브메쉬는 다른 가용 서브메쉬의 크기 에 변화를 주지 않기 때문에 그 유형에 따라 유형별 가용 서브메쉬 리스트에 삽입한다. 그럼으로써 할당 해제 후 유형별 가용 서브메쉬 리스트를 재생성하기 위해 전체 메쉬 구조를 탐색 할 필요가 없어진다.

• Journal of KIISE:Computer Systems and Theory
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• v.30 no.9
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• pp.445-453
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• 2003

As cluster systems used for high performance computing consist of large number of running servers, one has to solve the low availability problems occurred by the high chance of the server failures. To handle the problems, it is necessary to have the precise definition of available performance of cluster systems that represents availability and performability of the systems simultaneously. Previous research results that mention availability issues lack for concerning system performance such as waiting time and response time in their availability definition. In this paper, we propose a new availability metric for (n, k)-way cluster systems which compose of n primary servers and k backup servers. With the metric, the change of system performance according to arrival rates is captured and the waiting time of a request can be kept below to a certain level. Using various system operating parameters, we calculate availability and downtime of cluster systems along with waiting tine deadline.

• Journal of the military operations research society of Korea
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• v.35 no.3
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• pp.17-30
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• 2009

In this study, we propose the operational availability computation model that can be used on the weapon system's requirement planning phase. The proposed model consists of the time parameters of Ao(Operational Availability) for a system and each time parameter's estimation method. The time parameters for Ao computation are TT(Total Time) and TDT(Total Down Time). The time parameters are defined by considering OMS/MP(Operational Mode Summary/Mission Profile) elements. TT is a calendar time as a specific mission time at wartime or one year at peacetime. TDT consists of TPM(Total Preventive Maintenance time), TCM (Total Corrective maintenance time), TALDT(Total Administrative and Logistics Down Time). Then the estimation method for these time parameters are presented by the weapon systems types.

• The KIPS Transactions:PartA
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• v.10A no.6
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• pp.643-650
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• 2003

This paper presents a new submesh allocation scheme for mesh-connected multicomputer systems. The key idea in the proposed allocation scheme is to reduce the submesh search time using classified free submesh lists (CFSL). This scheme reduces the submesh search time by classifying independent free submeshes according to their types (square, horizontal rectangle, vertical rectangle) and searching the best-fit submesh from the classified free submesh list. When no suitable submesh is found, the search can be continued by using the expansion index (El), which is stored as an attribute of each submesh, is used to form a larger submesh. Through simulation, we show that the proposed strategy improves the performance compared to previous strategies with respect to submesh search time.

• Tunnel and Underground Space
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• v.32 no.4
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• pp.254-271
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• 2022

The performance of truck haulage operations in an underground mine was evaluated using the time usage model and key performance indicators (KPIs) proposed by Global Mining Guidelines Group (GMG). An underground mine that mainly produces iron and titanium iron was selected as a study area, and truck haulage data were collected using Bluetooth beacons and tablet PCs. The collected data were analyzed to identify unit operations, activities, events, and required time of truck haulage operations, and time categories were classified based on the time usage model. The performance of the haulage operations was evaluated using nine indicators in terms of availability, utilization, and effectiveness. As a result, in terms of availability, uptime was 33.9%, physical availability was 95.7%, and mechanical availability was 94.9%. In the case of utilization, use of availability was 83.1%, asset utilization was 28.1%, and operating and effective utilization were 79.6% and 77.7%, respectively. Also, in terms of efficiency, operating efficiency was high at 97.6%, and production effectiveness was found to be 49%.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.23 no.2
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• pp.201-206
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• 2019

Rejuvenating a system periodically during the most idle time of the system reduces unexpected downtime caused by software aging and increases its availability. In general, software rejuvenation can be largely divided into two broad categories: time-based rejuvenation policy and condition-based rejuvenation policy. In time-based rejuvenation policy the software rejuvenation is triggered at scheduled time epochs with fixed time intervals, while in condition-based rejuvenation policy the software rejuvenation is performed when system state is checked to satisfy a specific condition. Conditionbased policy adds extra cost to the system due to system monitoring and aging estimation. This paper presents a stochastic model for analyzing time-based software rejuvenation mechanism, where the rejuvenation is triggered at scheduled time epochs with fixed time intervals, and provides an analytical solution for the steady-state availability, the user-perceived availability, and the corresponding cost.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.20 no.9
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• pp.1717-1722
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• 2016

Availability, one of the important metrics used to assess the performance of network system, is defined as the probability that a system is operational at a given point in time under a given set of environmental conditions. To improve the availability of the network service, the redundancy models and the rejuvenation schemes are the effective schemes to be typically used. In this paper, we analyse the effect of 2N redundancy model and/or rejuvenation scheme on the availability of network service. The 2N redundancy model consists of one active and one standby component and the performance of time-based rejuvenation scheme mainly depends on its rejuvenation period. We design stochastic reward net model for the 2N redundancy model with time-based rejuvenation scheme and analyse the service availability of the model using stochastic Petri net package. We provide some numerical examples of the service availability, which shows that the system with rejuvenation has higher availability than the system without rejuvenation.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.40 no.6
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• pp.9-21
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• 2003

In this paper, we propose a new submesh allocation scheme which improves the performance of multicomputer systems. The key idea of this allocation scheme is to reduce waiting time of task by minimizing the submesh search time and the submesh a]location delay caused by external fragmentation. This scheme reduces the submesh search time by classifying independent free submeshes according to their types (square, horizontal rectangle, vertical rectangle) and searching a best-fit submesh from the classified free submesh list. If a submesh allocation delay occurs due to external fragmentation, the proposed scheme relocates tasks, executing In allocated submeshes, to another free submeshes and compacts processor fragmentation. This results in reducing the submesh allocation delay. Through simulation, we show that it is more effective to reduce the submesh allocation delay due to external fragmentation than reducing the submesh search time with respect to the waiting time of task. We also show that the proposed strategy improves the performance compared to previous strategies.

• Proceedings of the Korean Information Science Society Conference
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• 2001.04a
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• pp.541-543
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• 2001

일정 수준의 시스템 성능을 제공하기 위해 다수의 서버를 클러스터로 연결하여 동시에 가동할 경우, 서버의 가동 대수가 증가함으로 인해 발생하는 가용도 저하 문제를 해결해야 하며, 이를 위해서는 시스템의 성능 변화를 반영할 수 있는 가용 성능에 대한 명확한 정의가 요구된다. 본 논문에서는 비용 효율적인 결함허용을 위해 n 대의 주서버가 k 대의 여분서버로 구성된 클러스터 시스템에서 대기시간을 일정 수준이하로 만족시키는 새로운 가용도 척도에 근거한 최적 여분 서버 수를 계산하였다.