• Nuclear Engineering and Technology
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• 제26권1호
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• pp.9-18
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• 1994

월성 원자력발전소의 안전계통은 비상사태시에만 작동하는 3분의 2논리로 구성되어 있다. 그들의 작동성을 보증하기 위해 이 안전계통은 주기적으로 점검되어진다. 본연구에서 사람의 실수가 고려되어진 3분의 2논리 구성 시스템에서의 불이용도가 계산되어졌다. 그리고 우리는 시험기간중에 사람의 실수또는 기계의 고장으로 인해 발전정지를 일으킬 확률을 구했다. 우리는 이 불이용도와 발전정지를 일으킬 확률을 둘다 고려하여 적정한 최적점검주기를 계산하였다. 이렇게 얻어진 점검주기와 현재 사용되는 점검주기를 비교하면 사람의 실수를 최소(8.24 $\times$ $10^{-6}$ )로 보았을때 최적점검주기는 현재 사용되는 점검주기 보다 조금 짧았고 사람의 실수를 최대 (4.44 $\times$ $10^{-4}$ )로 보았을 때 최적점검주기는 현재 사용하는 점검 주기보다 다소 긴 것으로 계산되어졌다.

• ETRI Journal
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• 제15권3_4호
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• pp.47-59
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• 1994

A capacity expansion planning problem with buy-or-lease decisions is considered. Demands for capacity are deterministic and are given period-dependently at each period. Capacity additions occur by buying or leasing a capacity, and leased capacity at any period is reconverted to original source after a fixed length of periods, say, lease period. All cost functions (buying, leasing and idle costs) are assumed to be concave. And shortages of capacity and disposals are not considered. The properties of an optimal solution are characterized. This is then used in a tree search algorithm for the optimal solution and other two algorithms for a near-optimal solution are added. And these algorithms are illustrated with numerical examples.

• Industrial Engineering and Management Systems
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• 제14권4호
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• pp.372-378
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• 2015

In labor-intensive enterprise, such as garment factory, assembly line is widely used as a manufacturing process for reducing costs and production time. However, for the sake of the various working capacity of worker, idle or delay may happen and influence the rear processes. If these unforeseeable delay happened continuously, it may influence the whole manufacturing process and a model, which is called limited-cycle model with multiple periods (LCMwMP), is assumed to evaluate the influence risk. In order to minimize the risk, the assignment of the workers is focused on. In this paper, we deal with an assembly line as LCMwMP model when two kinds of workers exist, whose efficiency is assumed to two different groups. We consider an optimization problem for finding an assignment of workers to the line that minimizes total expected risk, which is exchanged to expected cost by reset model of LCMwMP. First, reset model as a simple model of LCMwMP is introduced. Then, some hypotheses of the rules of the optimal worker assignment are proposed and some numerical experiments are researched assuming the processing time as Erlang distribution. Finally, the other rules on other certain conditions are discussed.

• 전기학회논문지
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• 제60권1호
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• pp.193-200
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• 2011

This paper presents an optimal checkpoint strategy for fault-tolerance in real-time systems. In our environment, multiple real-time tasks with arbitrary periods are scheduled in the system by Rate Monotonic (RM) algorithm, and checkpoints are inserted at a constant interval in each task while the width of interval is different with respect to the task. We propose a method to determine the optimal checkpoint interval for each task so that the probability of completing all the tasks is maximized. Whenever a fault occurs to a checkpoint interval of a task, the execution time of the task would be prolonged by rollback and re-execution of checkpoints. Our scheme includes the schedulability test to examine whether a task can be completed with an extended execution time. A numerical experiment is conducted to demonstrate the applicability of the proposed scheme.

• 제어로봇시스템학회논문지
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• 제13권6호
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• pp.519-524
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• 2007

The OBC(on-board computer) of a satellite which plays a role of the controller for the satellite should be equipped with preventive measures against transient errors caused by SEU(single event upset). Since memory devices are pretty much susceptible to these transient errors, it is essential to protect memory devices against SFU. A common method exploits an error detection and correction code and additional memory devices, combined with periodic memory scrubbing. This paper proposes an effective memory scrubbing scheme for the OBC of STSAT-2. The memory system of the OBC is briefly mentioned and the reliability of the information stored in the memory system is analyzed. The result of the reliability analysis shows that there exist optimal scrubbing periods achieving the maximum reliability for allowed overall scrubbing overhead and they are dependent on the significance of the information stored. These optimal scrubbing periods from a reliability point of view are derived analytically.

• 한국농공학회논문집
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• 제64권1호
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• pp.39-50
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• 2022

In this study, we suggested the optimal training period for predicting the streamflow using the LSTM (Long Short-Term Memory) model based on the deep learning and CMIP5 (The fifth phase of the Couple Model Intercomparison Project) future climate scenarios. To validate the model performance of LSTM, the Jinan-gun (Seongsan-ri) site was selected in this study. We comfirmed that the LSTM-based streamflow was highly comparable to the measurements during the calibration (2000 to 2002/2014 to 2015) and validation (2003 to 2005/2016 to 2017) periods. Additionally, we compared the LSTM-based streamflow to the SWAT-based output during the calibration (2000~2015) and validation (2016~2019) periods. The results supported that the LSTM model also performed well in simulating streamflow during the long-term period, although small uncertainties exist. Then the SWAT-based daily streamflow was forecasted using the CMIP5 climate scenario forcing data in 2011~2100. We tested and determined the optimal training period for the LSTM model by comparing the LSTM-/SWAT-based streamflow with various scenarios. Note that the SWAT-based streamflow values were assumed as the observation because of no measurements in future (2011~2100). Our results showed that the LSTM-based streamflow was similar to the SWAT-based streamflow when the training data over the 30 years were used. These findings indicated that training periods more than 30 years were required to obtain LSTM-based reliable streamflow forecasts using climate change scenarios.

• 한국식품조리과학회지
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• 제30권1호
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• pp.22-32
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• 2014

This study investigated the spicy hot flavor related quality characteristics of baechu (Kimchi cabbage) Kimchi prepared using hot pepper powder in various capsaicin levels during 8 weeks of storage. The pHs in the Kimchi samples were in the optimum range of the pH 4.2-4.5 due to the relatively low storage temperature of $2^{\circ}C$ during the entire storage periods. The L, a and b values of cap-150 sample group were significantly higher compared to those in the other samples at 8 weeks of storage. Grading hotness of the Kimchi was significantly clearly separated when varied levels of hotness for the hot pepper powder were used at 2-4 weeks of storage (p<0.001). Sensory spicy hotness of the cap-40 showed significantly the lowest with values of 4.57-4.38 representing mild hot:, that of cap-85 was medium hot with values of 5.81-6.00; and finally, that of cap-150 showed the values of 6.86-7.14, representing strong hot flavor at 2-4 weeks of storage (p<0.001). The grading of spicy hotness in the Kimchi increased by about one level at the optimal edible periods due to the leaching out of capsaicin from the hot pepper powder for those storage periods. Thus, the increased hotness of the Kimchi in the optimal edible periods should be considered when the desired hotness of the hot pepper is chosen for the Kimchi preparation. The hotness decreased as the organic acids were generated during ripening by the 8th weeks of storage.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2009년도 제40회 하계학술대회
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• pp.567_568
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• 2009

In the past, pumping-storage generator pumped the water from the lower part storage to the upper part storage during the base load periods. And, it generated during the peak load or when other generator was outage. However, pumping-storage generator will operate different ways in the competitive power markets. It will pump during lower price periods and generate at higher price periods. This paper presents economic analysis of pumping-storage generator using price (or SMP) duration curve.

• Journal of Information Processing Systems
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• 제7권4호
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• pp.613-626
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• 2011

In this paper, we focus on the pinwheel task model with a variable voltage processor with d discrete voltage/speed levels. We propose an intra-task DVS algorithm, which constructs a minimum energy schedule for k tasks in O(d+k log k) time We also give an inter-task DVS algorithm with O(d+n log n) time, where n denotes the number of jobs. Previous approaches solve this problem by generating a canonical schedule beforehand and adjusting the tasks' speed in O(dn log n) or O($n^3$) time. However, the length of a canonical schedule depends on the hyper period of those task periods and is of exponential length in general. In our approach, the tasks with arbitrary periods are first transformed into harmonic periods and then profile their key features. Afterward, an optimal discrete voltage schedule can be computed directly from those features.

• 한국항만학회지
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• 제8권2호
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• pp.1-35
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• 1994

The main arterial which runs through the in City of Pusan, carries about 60% of downtown traffic or more, maintains about 20% yearly increase in traffic is severely suffering from the traffic congestion because of concentrated traffic volumes regardless of peak-time periods. The purpose of this study was to grasp the traffic, geometric, and signal conditions of the main arterial through the Videologging System Techniques, perform the transportation system analyses, and finally suggest the improvements which could increase the travel capacity, reduce the average delay and fuel consumption with the optimal conditions of signal system. The following conclusions were drawn : firstly the traffic system should be shifted for the travel distribution on the arterial during the peak time periods, secondly the roadway system of the arterial reviewed for left-turn traffic during the peak time periods, and thirdly the signal system of intersection reconstructed for signal optimization or progression within the range of cycle length suggested.