• International Journal of Automotive Technology
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• 제8권1호
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• pp.39-48
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• 2007

This paper addresses the problem of period and priority assignment in networked control systems (NCSs) using a fixed priority scheduler. The problem of assigning periods and priorities to tasks and messages is formulated as an optimization problem to allow for a systematic approach. The temporal characteristics of an NCS should be considered by defining an appropriate performance index (PI) which represents the temporal behavior of the NCS. In this study, the sum of the end-to-end response times required to process all I/Os with precedence relationships is defined as a PI. Constraints are derived from the task and message deadline requirements to guarantee schedulability. Genetic algorithms are used to solve this constrained optimization problem because the optimization formulation is discrete and nonlinear. By considering the effects of communication, an optimum set of periods and priorities can be holistically derived.

• 산업경영시스템학회지
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• 제33권1호
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• pp.71-79
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• 2010

This paper addresses capacity expansion planning model of distribution center under usability of public distribution center. For discrete and finite time periods, demands for distribution center increase dynamically. The capacity expansion planning is to determine the capacity expansion size of private distribution center and usage size of public distribution center for each period through the time periods. The capacity expansion of private distribution center or lease usage of public distribution center must be done to satisfy demand increase for distribution center. The costs are capacity expansion cost and excess capacity holding cost of private distribution center, lease usage cost of public distribution center. Capacity expansion planning of minimizing the total costs is mathematically modelled. The properties of optimal solution are characterized and a dynamic programming algorithm is developed. A numerical example is shown to explain the problem.

• Pediatric Gastroenterology, Hepatology & Nutrition
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• 제19권1호
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• pp.1-11
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• 2016

Cholestasis results from impairment in the excretion of bile, which may be due to mechanical obstruction of bile flow or impairment of excretion of bile components into the bile canaliculus. When present, cholestasis warrants prompt diagnosis and treatment. The differential diagnosis of cholestasis beyond the neonatal period is broad and includes congenital and acquired etiologies. It is imperative that the clinician differentiates between intrahepatic and extrahepatic origin of cholestasis. Treatment may be supportive or curative and depends on the etiology. Recent literature shows that optimal nutritional and medical support also plays an integral role in the management of pediatric patients with chronic cholestasis. This review will provide a broad overview of the pathophysiology, diagnostic approach, and management of cholestasis beyond the neonatal and infancy periods.

• Journal of Advanced Marine Engineering and Technology
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• 제33권1호
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• pp.166-174
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• 2009

Gijang Sea is located on the southeastern coast of Korea. This study establishes a basic system to identify optimal sites for the wave power generation. To achieve this goal, the field measurements were made at the field site in front of Dong-am fishing port at Gijang. In addition, we analyzed the offshore wave data at the Donghae buoy operated by Korea Meteorological Administration(KMA) and compared the data with the wave characteristics in Gijang Sea. The main results were as follows. In winter, the wave direction in Gijang Sea ranged between east and south($90{\sim}180^{\circ}$). The main wave direction was east($90^{\circ}$). The Significant wave heights and periods were under 2 m and $5{\sim}15$ sec, respectively. A comparison of water depth and wave direction constitutes one(condition) of the important parameters for selecting the optimal site for the wave power generation.

• 대한토목학회논문집
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• 제38권6호
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• pp.793-800
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• 2018

본 연구는 최근 빈번히 발생하는 홍수재해에 대비하고 안정적인 치수대책 수립을 위하여 공학적 판단에 근거한 하천의 적정 설계빈도 결정방안을 제시하였다. 지방하천의 설계빈도는 하천의 중요도 및 지역특성에 따라 최소 50년부터 최대 200년까지 설정되고 있으나, 적용범위가 넓어 하천의 지형적, 치수적 특성을 제대로 반영하지 못하는 실정이다. 본 연구에서는 지방하천의 적정 설계빈도를 결정하기 위하여 7개의 평가인자(시가화 침수면적, 유역면적, 형상계수, 하도경사, 수계 및 하천차수, 배수영향구간, 이상강우 발생빈도)에 대하여 베이즈 이론을 적용하여 가중치를 산정하였다. 또한, 기후변화를 고려한 홍수피해잠재능을 산정하였고, 시군구별 잠재능을 구분하여 적정 설계빈도를 결정하였다. 충청남도 382개 지방하천에 대하여 현행 설계빈도의 적정성을 평가하였다. 382개의 현행 하천설계빈도보다 상향되는 하천은 65개 하천으로 상대적으로 시가화 침수면적이 크게 산정되고 홍수피해잠재능이 큰 지역의 하천이며, 하향되는 하천은 169개로 분석되었다.

• 산업경영시스템학회지
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• 제39권1호
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• pp.81-90
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• 2016

Different from general operating policies to be applied for controllable queueing models, two of three well-known simple N, T and D operating policies are applied alternatingly to the single server controllable queueing models, so called alternating (NT), (ND) and (TD) policies. For example, the alternating (ND) operating policy is defined as the busy period is initiated by the simple N operating policy first, then the next busy period is initiated by the simple D operating policy and repeats the same sequence after that continuously. Because of newly designed operating policies, important system characteristic such as the expected busy and idle periods, the expected busy cycle, the expected number of customers in the system and so on should be redefined. That is, the expected busy and idle periods are redefined as the sum of the corresponding expected busy periods and idle periods initiated by both one of the two simple operating policies and the remaining simple operating policy, respectively. The expected number of customers in the system is represented by the weighted or pooled average of both expected number of customers in the system when the predetermined two simple operating policies are applied in sequence repeatedly. In particular, the expected number of customers in the system could be used to derive the expected waiting time in the queue or system by applying the famous Little's formulas. Most of such system characteristics derived would play important roles to construct the total cost functions per unit time for determination of the optimal operating policies by defining appropriate cost elements to operate the desired queueing systems.

• 산업경영시스템학회지
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• 제17권32호
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• pp.233-242
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• 1994

This study deals with the derivative adverse minimum for inferiority system depends on continuose operating under infinite planning horizon. This planning will be accomplished by maintenance limit renewal policy in consideration of opportunity cost which affects system by failure during operation periods and expected cost under nomal operation states. By the results, we will be expected incresing total efficiency for the system by optimal renewal policy.

• 한국식품영양과학회지
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• 제23권4호
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• pp.618-624
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• 1994

The addition of mustard leaf to kimchi making for extanding the optimum edible period was studied. The quality and sensory characteristics of mustard leaf added kimchi were evaluated . The activity, lactic and acetic acid contents of mustard leaf added kimchi showed lower than that of control kimchi but reducing sugar and vitamin C contents was higher. The duration of optimum edible periods of mustard leaf added kimchi lasted one more weak. While the optimum pH of kimchi for eating lasted, the sensory pannel score for sour taste of mustard leaf added kimchi was lower than that of control but the scoreas for savory taste, carbonated taste and hardness were higher . Especially , the sour taste score between two groups were significantly different (p<0.05). Overall quality score for the mustard leaf added kimchi was higher. There was no differences in texture determined by Penetrometer between mustard leaf added kimchi and control kimchi until the fermentation reached the optimal condition for eating . After that period , the degree of degradation of texture was much delayed in mustard leaf added kimchi.

• 한국경영과학회지
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• 제13권1호
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• pp.10-23
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• 1988

This paper examines a deterministic, discrete-time, finite-horizon, production/distribution problem for a one-plant multi-retailer system. Production may occur at the plant in each time period. Customer demands at each retailer over a finite number of periods are known and must be met without backlogging. The plant as well as the retailers can serve as stocking points. The problem is to find a minimum-cost production/distribution schedule satisfying the known demands. We show that under a certain cost structure a nested policy is optimal, and present an efficient algorithm to find such an optimal policy. Planning horizon results and some computational saving schemes are also presented.

• 제어로봇시스템학회논문지
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• 제8권6호
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• pp.506-513
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• 2002

Distributed control systems(DCS) using fieldbus such as CAN have been applied to process systems but it is very difficult to design the DCS while guaranteeing the given end-to-end constraints such as precedence constraints, time constraints, and periods and priorities of tasks and messages. This paper presents a scheduling method to guarantee the given end-to-end constraints. The presented scheduling method is the integrated one considering both tasks executed in each node and messages transmitted via the network and is designed to be applied to a general DCS that has multiple loops with several types of constraints, where each loop consists of sensor nodes with multiple sensors, actuator nodes with multiple actuators and controller nodes with multiple tasks. An assignment method of the optimal period of each loop and a heuristic assignment rule of each message's priority are proposed and the integrated scheduling method is developed based on them.