• 아동복지연구
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• 제16권2호
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• pp.109-135
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• 2018

The purpose of this study was to analyze the longitudinal causal relationship between caregiver relations and peer relations of children in out-of-home care. We analyzed the three years(2011-2013) of longitudinal data from the Panel Study on Korean Children in Out-of-Home Care. The autoregressive cross-lagged model (ARCL) was used to measure the longitudinal causal relationship between caregiver relations and peer relations. As a result, first, caregiver relations and peer relations showed stability over time. In other words, the results of the measurement at three time points showed that the caregiver relations and peer relations at the previous time had a significant effect on the caregiver relations and peer relations at the later time point. Second, the previous caregiver relations had a significant effect on the subsequent peer relations over time. Third, the previous peer relations had a significant effect on the subsequent caregiver relations over time. This study confirmed the interrelationships of caregiver relations and peer relations of children in care by examining the longitudinal data using the longitudinal analysis method.

• 산업공학
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• 제21권3호
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• pp.254-261
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• 2008

Connected-(r,s)-out of-(m,n) : F system is an important topic in redundancy design of the complex system reliability and it's maintenance policy. Previous studies applied Monte Carlo simulation and genetic, simulated annealing algorithms to tackle the difficulty of maintenance policy problem. These algorithms suggested most suitable maintenance cycle to optimize maintenance pattern of connected-(r,s)-out of-(m,n) : F system. However, genetic algorithm is required long execution time relatively and simulated annealing has improved computational time but rather poor solutions. In this paper, we propose the ant colony optimization approach for connected-(r,s)-out of-(m,n) : F system that determines maintenance cycle and minimum unit cost. Computational results prove that ant colony optimization algorithm is superior to genetic algorithm, simulated annealing and tabu search in both execution time and quality of solution.

• Journal of the Korean Data and Information Science Society
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• 제8권2호
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• pp.119-125
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• 1997

We handle the stochastic processes of independent and identically distributed random variables. But random variables are usually dependent among themselves in actual life. So in this paper, we find out a new process not satisfying Markov property. We investigate the probability mass functions and study on the probability of the first-passage time. Also we find out the average frequency of continuous successes in from 0 to n time.

• 대한치과기공학회지
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• 제19권1호
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• pp.5-12
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• 1997

To examine the difference of castability of non -precious porcelain metal according to 2 type of investing method, experiments were carried out using the method of both existing investing method and the investment with spaces to the upper & lower parts of the ring. The following conclusion were obtained from the result. 1. Seperataly using the existing investment and with spaces to the upper & lower parts of the ring, 44 samples resulted in success with the former method and 52 with the latter out of 84 samples. 2. Under the existing investing method, 44 samples out of 56 total resulted in success when the temperature of the ring was $870^{\circ}C$, and all samples failed when the temperature was $800^{\circ}C$. 3. Under the investment that gives space to the ring, when casted with the temperature of the ring fixed at $870^{\circ}C$, 40 samples out of 56 and 17 samples with the temperature fixed at $800^{\circ}C$ resulted in success. 4. Under the existing investing method with the temperaure of the ring fixed at $870^{\circ}C$ and heat soaking time given an hour, 26 out of 28 samples resulted in success and 18 resulted the same with half an hour heat soaking time. 5. Using the investment that gives space to the ring, at ring temperature $870^{\circ}C$ with heat soaking time 1 hour, all of total 28 rusulted insuccess however only 12 smaples succeeded with 30 minutes heat soaking time. 6. Under the existing investing method, samples with heat soaking time 1 hour equally given at ring temperature $870^{\circ}C$, 26 samples out of 28 succeed however at $800^{\circ}C$ all samples failed. 7. In the case of ring's upper and lower parts opened ring temperature is $870^{\circ}C$ and $800^{\circ}C$ and the heat soaking time was fixed at 1 hour, all 28 samples resulted in success and at $800^{\circ}C$ 17 succeed.

• 한국시스템다이내믹스연구
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• 제7권2호
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• pp.21-34
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• 2006

Korean Government has carried out various support policies for small and midium size enterprises(SMEs). However, effect of the policy might not be realized in short term or the policy has turned out in fail. We found out the time of support is also important. Thus we propose that government should figure out the proper time to support funds according to the companies status(Technology, Production, Marketing) based on System Thinking.

• 산업공학
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• 제4권1호
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• pp.63-69
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• 1991

In this paper, the Go-Back-N ARQ protocol with decoding in communication network is considered. The time delay and throughput are respectively analyzed as a function of window size and decoding time out. Packets arrive continuously at the decoder, and are stored in a buffer if the decoder is busy upon its arrival. The decoder devotes no more than a time-out period of predetermined length to the decoding of any single packet. If packet decoding is completed within that period, the packet leaves the system. Otherwise, it is retransimitted and its decoding starts anew. The time delay and throughput are obtained using recursive formula and difference equation. An appropriate time out and window size that satisfies the grade of service can be determined.

• 한국콘텐츠학회논문지
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• 제2권4호
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• pp.76-84
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• 2002

The conventional database evaluation method is carried out by the way in which the person in charge of each specialty database(DB manager) composes the evaluation sheets for corretionㆍrevision on the already-constructed database in a manual method and carries out the measurement and re-education of DB workers based upon it. As a result, that way consumes much time on career information and measurement works about DB workers, causing low time and cost efficiency and lack of systematic management of DB workers, resulting in becoming the hindrance factor of databases quality improvement. This research provides on-line, red-time results of measurements about the efficiency of DB production and DB workers by combining the static measurement with dynamic measurement by DB manager, both of which utilize the System. Therefore, the DB manager can contribute to the improvement of DB quality by determining the continuation of DB production by DB workers or carrying out the re-education of DB workers without being affected by time or spacial constraints.

• 한국국방경영분석학회지
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• 제24권2호
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• pp.43-56
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• 1998

This paper focuses on the optimal replacement time of engine modules of the F16 aircraft. Generally, the optimal replacement time of those should be determined to minimize the replacement cost due to out of order and opportunistic replacement cost of operation cost of remaining period. This paper determined the optimal replacement time by using the opportunistic replacement algorithm that is developed by Forbes and Wyatt. Some real data are utilized but a few data is estimated due to limitation of data. As a result, fan module only reaches to the opportunistic replacement time. The optimal replacement time of the fan module is derived as 1740 cycles. Therefore, the optimal replacement policy of engine modules of the F16 is that fan module should be replaced whenever it is out of order under 1740 cycles and whenever core module is out of order over 1740 cycles.

• 대한전기학회논문지:전력기술부문A
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• 제54권5호
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• pp.217-225
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• 2005

In a power system, an out-of-step condition causes a variety of risk such as serious damage to system elements, tripping of loads and generators, mal-operation of relays, etc. Therefore, it is very important to detect the out-of-step condition and take a proper measure. Several out-of-step detection methods have been employed in relays until now. Most common method used for an out-of-step detection is based on the transition time through the blocking impedance area in R-X diagram. Also, the R-R dot out-of-step relay, the out-of-step prediction method and the adaptive out-of-step relay using the equal area criterion (EAC) and Global Positioning Satellite (GPS) technology have been developed. This paper presents the out-of-step detection algorithm using the time variation of the complex power. The complex power is calculated and the mechanical power of the generator is estimated by using the electrical power, and then the out-of-step detection algorithm which is based on the complex power and the estimated mechanical power, is presented. This algorithm may detect the instant when the generator angle passes the Unstable Equilibrium Point (UEP). The proposed out-of-step algorithm is verified and tested by using Alternative Transient Program/Electromagnetic Transient Program (ATP/EMTP) MODELS.

• 한국정보과학회논문지:컴퓨팅의 실제 및 레터
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• 제8권4호
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• pp.423-429
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• 2002

실시간 프로그래밍에 있어 타임아웃 기능은 매우 중요한 기본적인 기능 중 하나이다. 그러나 내장 실시간 시스템에서 가장 많이 사용하는 C 언어에서는 타임아웃 기능을 지원하지 않는다. 그래서 C언어에서 실시간 프로그래밍 환경을 제공하기 위해 언어 자체를 확장하거나 실시간 엔진(또는 커널)을 지원하는 연구들이 있었다. 그러나 이것은 특정 실시간 커널과 컴파일러가 필요하다는 문제점을 갖고 있다. 본 논문에서는 운영체제에 최소한의 의존성을 갖고 라이브러리와 매크로 함수만으로 C 언어에서 타임아웃 기능을 제공한다. 또한 개발자가 편리하게 타임아웃 기능을 사용할 수 있도록 매크로 정의를 통해 구조화된 _within 문장을 제공한다. 이 기능은 리눅스의 단일 쓰레드 환경과 도스 환경뿐만 아니라 다중 쓰레드 환경인 POSIX 쓰레드에서도 구현하였다.