• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2003년도 학술회의 논문집 정보 및 제어부문 B
• /
• pp.677-680
• /
• 2003

In this paper, the analysis of practical end-to-end delay in worst case is performed for distributed control system considering the implementation of the system. The control system delay is composed of the delay caused by multi-task scheduling of operating system, the delay caused by network communication, and the delay caused by the asynchronous between them. Through simulation tests based on CAN(Controller Area Network), the proposed end-to-end delay in worst case is validated. Additionally, online clock synchronization algorithm is proposed here for the control system. Through another simulation test, the online algorithm is proved to have better performance than offline one in the view of network bandwidth utilization.

• International Journal of Automotive Technology
• /
• 제5권4호
• /
• pp.269-276
• /
• 2004

There has been considerable activity in recent years in developing timing analysis algorithms for distributed real-time control systems. However, it is difficult for control engineers to analyze the timing behavior of distributed real-time control systems because the algorithms was developed in a software engineer's position and the calculation of the algorithm is very complex. Therefore, there is a need to develop a timing analysis tool, which can handle the calculation complexity of the timing analysis algorithms in order to help control engineers easily analyze or develop the distributed real-time control systems. In this paper, an interactive timing analysis tool, called RAT (Response-time Analysis Tool), is introduced. RAT can perform the schedulability analysis for development of distributed real-time control systems. The schedulability analysis can verify whether all real-time tasks and messages in a system will be completed by their deadlines in the system design phase. Furthermore, from the viewpoint of end-to-end scheduling, RAT can perform the schedulability analysis for series of tasks and messages in a precedence relationship.

• 한국대기환경학회지
• /
• 제19권6호
• /
• pp.647-661
• /
• 2003

For continuous monitoring of atmospheric visibility in the city of Kwanaju, Korea, a transmissometer system consisting of a transmitter and a receiver was installed at a distance of 1.91 km across the downtown Kwanaju. At the transmitter site an integrating nephelometer and an aethalometer were also installed to measure the scattering and absorption coefficients of the atmosphere, respectively. At the receiver site. an URG PM$_{2.5}$ cyclone sampler and an URG-VAPS (Versatile Air Pollutant Sampler) with three filter packs and two denuders were used to collect both PM$_{2.5}$ and PM$_{10}$ samples at a 2-hour or 12-hour sampling interval for aerosol chemical analysis. Sulfate, organic mass by carbon (OMC), nitrate, elemental carbon (EC) components of fine aerosol were the major contributors to visibility impairment. Diurnal variation of visibility during best-case days showed rapid improvement in the morning hours, while it was delayed until afternoon during the worst-case days. Aerosol mass concentration of each aerosol component for the worst-case was calculated to be 11.2 times larger than the best-case for (NH$_4$)$_2$SO$_4$(NHSO), 19.0 times for NH$_4$NO$_3$ (NHNO), 2.2 times for OMC, respectively. Also result shows that elemental carbon and fine soil (FS) were 3.7 and 2.2 times more than those of best-case. respectively- Sum of total contributions of wet NHSO and NHNO to light extinction was calculated to be 301 Mm$^{-1}$ for the worst-case. However, sum of contributions by dry NHSO and NHNO was calculated to be 123 Mm$^{-1}$ for the best case. Mass extinction efficiencies of fine and coarse particles were calculated to be 5.8$\pm$0.3 $m^2$/g and 1.8$\pm$0.1 $m^2$/g, respectively.ely.

• 대한전자공학회:학술대회논문집
• /
• 대한전자공학회 1999년도 추계종합학술대회 논문집
• /
• pp.743-746
• /
• 1999

In this paper, Flyback type DC/DC Switching Converter was designed, analyzed and fabricated. Worst Case Analysis(WCA) was peformed with Mathcad program and presents circuit simulation results for the in-rush current limit circuit. The value of the maximum OFF voltage stress is 131.84V, it is less than device specification(200V). The switching frequency(nominal case) and duty cycle at the wont case analysis are 75KHz and 34.62%, respectively. The maximum in-rush current presents 0.5A Those results show a possibility for use in space

• 한국자동차공학회논문집
• /
• 제13권1호
• /
• pp.194-203
• /
• 2005

The process of guaranteeing that a distributed real-time control system will meet its timing constraints, is referred to as schedulability analysis. However, schedulability analysis algorithm cannot be simply used to analyze the system because of complex calculations of algorithm. It is difficult for control engineer to understand the algorithm because it was developed in a software engineer's position. In this paper we introduce a Response-time Analysis Tool(RAT) which provides easy way far system designer to analyze the system by encapsulating calculation complexity. Based on the RAT, control engineer can verify whether all real-time tasks and messages in a system will be completed by their deadline in the system design phase.

• 항공우주기술
• /
• 제3권2호
• /
• pp.42-49
• /
• 2004

발사단계 중 fairing jettison에서 separation에 이르는 과정에서 위성체의 부품박스가 가지는 온도를 worst hot 조건에 대하여 해석적 방법을 이용하여 구하였다. Fairing jettison 이후에 위성체에 가해지는 외부 열환경과 박스 자체 내부에서의 발열, 박스 자체의 온도에 의한 방사열을 고려하여, 하나의 질량으로 가정할 수 있는 박스에 대한 온도 지배방정식을 해석해가 존재하는 1차 상미분 방정식으로 단순할 수 있었다. 특히, 고려하는 박스의 질량의 변화여부에 따라 해석해가 다른 지배방정식이 유도되었고, 각 경우에 대하여도 단순화된 식 내의 상수항의 조건에 따라 서로 다른 해석해가 존재하였다. 또한, 유도된 해석해를 실제 위성체인 STSAT-1의 worst hot 발사 조건에 대하여 적용하여 위성체 상단에 부착한 부품 박스의 온도를 예측하여 보았고, 이를 통하여 해석해의 유용성을 검증하였다.

• 대한토목학회논문집
• /
• 제31권4D호
• /
• pp.547-553
• /
• 2011

본 연구는 대중교통취약지역 평가척도인 이동성 지표와 잠재수요에 대한 개념을 새로 정립하고 이들 지표를 적용하여 대중교통이동성 취약지역 선정과 이들 지역 간을 연결하는 대중교통 직결노선 선정방법을 제시하였다. 이동성 지표와 잠재수요평가지표를 적용하여 4개 대도시권의 대중교통 취약지역을 선정하고 이들 지역 간을 운행하는 직결 버스 노선을 사례연구를 통해 분석하였다. 분석결과 대중교통 이동성 사각지대는 대중교통통행시간이 승용차에 비해 현저히 높게 소요되거나 대중교통노선의 서비스가 제공되지 않은 지역으로 분석되었다. 또한, 이러한 대중교통취약지역을 해소하기 위한 직결버스노선은 대중교통통행시간을 승용차 통행시간과 동등한 수준을 유지할 수 있도록 자동차 전용도로로 운행하고 승 하차로 인한 통행시간 손실을 최소화 시키고 연계를 극대화 할 수 있는 노선체계가 구축되어야 할 것으로 분석되었다.

• 항공우주시스템공학회지
• /
• 제16권6호
• /
• pp.123-128
• /
• 2022

본 연구는 전개형 SAR 안테나에 적용하기 위한 비폭발 분리장치를 제안하였다. Ni-Cr 와이어를 감아 제작된 분리장치를 이용하여 SAR 안테나의 벨트가 전개되지 않도록 구속한다. 분리 장치를 구속하는 Ni-Cr 와이어는 발열을 통해 절단함으로써 벨트 전개 시 충격량을 최소화한다. 분리장치의 설계를 위해 설계하중(99g)과 preload를 고려하여 AL과 Ti을 대상으로 유한요소 해석을 수행하였다. AL을 이용 시 해석결과, 최대 변형량이 0.256 mm 발생하였고, 안전마진은 +0.09로 확인되었다. 또한 궤도상 열분석을 수행하여 온도분포를 확인한 결과, 최저온 궤도와 최고온 궤도에서 -50~+2℃의 온도분포와 -10~+90℃의 온도분포를 각각 나타내어 우주환경에서도 구속분리장치가 안정적임을 입증하였다.

• 가정과삶의질연구
• /
• 제32권3호
• /
• pp.99-114
• /
• 2014

The purpose of this study is to investigate the relationship between moral cognitive distortion and peer bullying of children and adolescents. For this study, questionnaires on moral cognitive distortion and peer bullying were administered to 678 students in the 4th, 5th, 7th, 8th, 10th and 11th grades in elementary, middle and high schools located in the metropolitan area of Seoul. The data were analyzed through frequency analysis, mean and standard deviation, t-test, two-way ANOVA, Pearson's correlation and stepwise multiple regression analysis using SPSS Win 12.0. The main findings of this study are as follows: 1) While grade had a significant influence on the moral cognitive distortion of children and adolescents, gender did not. On bullying perpetration and bullying victimization, both gender and grade had a significant influence. 2) Moral cognitive distortion had a significant influence on peer bullying. More specifically, for elementary school students, the variables affecting bullying victimization and bullying perpetration were found to be worst-case-scenario thinking and other-blame thinking, respectively. For middle school students, victimization was affected most significantly by worst-case-scenario thinking, followed by gender; perpetration was most significantly affected by worst-case-scenario thinking. For high school students, victimization was affected most significantly by other-blame thinking, followed by gender; perpetration was most significantly affected by other-blame thinking.

• Industrial Engineering and Management Systems
• /
• 제14권1호
• /
• pp.22-31
• /
• 2015

In this paper, a two-stage hybrid flow shop problem is considered. Specifically, there exist identical parallel machines at stage 1 and two dedicated machines at stage 2, and the objective of the problem is to minimize makespan. After being processed by any machine at stage 1, a job must be processed by a specific machine at stage 2 depending on the job type, and one type of jobs can have different processing times on each machine. First, we introduce the problem and establish complexity of several variations of the problem. For some special cases, we develop optimal polynomial time solution procedures. Then, we establish some simple lower bounds for the problem. In order to solve this NP-hard problem, three heuristics based on simple rules such as the Johnson's rule and the LPT (Longest Processing Time first) rule are developed. For each of the heuristics, we provide some theoretical analysis and find some worst case bound on relative error. Finally, we empirically evaluate the heuristics.