• Journal of Advanced Marine Engineering and Technology
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• 제38권10호
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• pp.1340-1346
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• 2014

Previous studies of reliable server assignment considered only to assign the same cost of server, that is, homogeneous servers. In this paper, we generally deal with reliable server assignment with different server costs, i.e., heterogeneous servers. We formulate this problem as a nonlinear integer programming mathematically. Our problem is defined as determining a deployment of heterogeneous servers to maximize a measure of service availability. We propose two metaheuristic algorithms (tabu search and particle swarm optimization) for solving the problem of reliable server assignment. From the computational results, we notice that our tabu search outstandingly outperforms particle swarm optimization for all test problems. In terms of solution quality and computing time, the proposed method is recommended as a promising metaheuristic for a kind of reliability optimization problems including reliable sever assignment and e-Navigation system.

• 패션비즈니스
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• 제18권3호
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• pp.14-28
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• 2014

The purposes of this study are to provide comprehensive reviews on multichannel consumer behaviors published in peer-reviewed academic journals from 2005 to 2014, to develop a conceptual framework that demonstrates multichannel determinants such as psychographics, demographics, social influences, and situational factors on consumers' search and purchase behavior based on customers' profits or costs judgment, and to provide possible direction for future research in multichannel consumer behavior. Three steps were taken in the process of analyzing consumers' channel determinants presented in the 37 studies, and 12 most frequently used factors that appear in the studies were extracted. These factors include convenience, service, trust/risk, saving money, product knowledge, experience, efficacy/usefulness, involvement, shopping environment/situation factors, demographics, product types, and social influence. With 12 determinants of multichannel consumers' search and purchase behavior, a conceptual framework was proposed based on expectancy theory. The directions for future research were also discussed.

• 간호행정학회지
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• 제5권2호
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• pp.297-316
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• 1999

The purpose of this study is searching for hemodialysis nursing bahaviors by hemodialysis room nurses and analyzing them. Then, it estimates hemodialysis nursing costs and obtains basic data for development of proper nursing costs. First, it searched for hemodialysis nursing behaviors at a tertiary hospital hemodialysis room in Seoul and classified them. After the content validity was verified by 6 experts, Tool of hemodialysis nursing behaviors was developed. patients who recived hemodialysis were classified by dialysis patient classification tool. The searcher observed hemodialysis nursing behaviors applied to classified patients per 5 minutes. Then hemodialysis nursing hours spent to classified patients were calculated respectively. The direct expenditures and indirect expenditures were estimated. Ultimately, hemodialysis nursing costs were estimated. The results of the study were as follows ; 1. hemodialysis nursing behaviors were grouped by the same knowledge and skills. then, the content validity of them was verified by evaluation tool of nursing intervention classification by expert groups. They consisted of 9 hemodialysis activity domains and 71 hemodialysis nursing behaviors. The predialysis activity domain included 15 nursing behaviors, the activity domain of start-dialysis included 12 nursing behaviors, the activity domain of during- dialysis included 9 nursing behaviors, the activity domain of finish-dialysis included 5 nursing behaviors, the activity domain of after-dialysis included 5 nursing behaviors, the nursing documentation & undertaking and transfering included 5 nursing behaviors, the supply, drug, equipment & environment management activity domain included 7 nursing behaviors, the patient emotional support & education activity domain included 4 nursing behaviors, the emergency activity domain included 9 nursing behaviors. 2. The acute hemodialysis nursing hours were 106.42 minutes per a dialysis and the chroni hemodialysis nursing hours were 72.23 minutes per a dialysis. 3. The direct expenditure was 11.971 won per hour and indirect expenditure was 288won. 4. Finally, the cost of acute hemodialysis was 21,745 won and that of chronic hemodialysis was 14,759 won. By search of hemodialysis nursing behaviors, they will be used as hemodialysis nursing care standard and will be tended toward high qualitative care. Estimation of hemodialysis nursing costs will be used as fundamental data for development of proper nursing costs.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제18권8호
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• pp.2157-2177
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• 2024

Demand response (DR) refers to the customers' active reaction with respect to the changes of market pricing or incentive policies. DR plays an important role in improving network reliability, minimizing operational cost and increasing end users' benefits. Hence, the integration of DR in the microgrid (MG) management is gaining increasing popularity nowadays. This paper proposes a day-ahead MG scheduling framework in conjunction with DR and investigates the impact of DR in optimizing load profile and reducing overall power generation costs. A linear responsive model considering time of use (TOU) price and incentive is developed to model the active reaction of customers' consumption behaviors. Thereafter, a novel multi-swarm sine cosine algorithm (MSCA) is proposed to optimize the total power generation costs in the framework. In the proposed MSCA, several sub-swarms search for better solutions simultaneously which is beneficial for improving the population diversity. A cooperative learning scheme is developed to realize knowledge dissemination in the population and a competitive substitution strategy is proposed to prevent local optima stagnation. The simulation results obtained by the proposed MSCA are compared with other meta-heuristic algorithms to show its effectiveness in reducing overall generation costs. The outcomes with and without DR suggest that the DR program can effectively reduce the total generation costs and improve the stability of the MG network.

• 물과 미래
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• 제28권2호
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• pp.169-180
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• 1995

관망상배관(Looped networks)시스템에서 관수로시스템의 전체비용은 폐회로유량(Loop flows)에 따라 영향을 받는다. 따라서 관망상배관의 최적설계를 위한 수학적모형을 추계학적 최적화방법에 적용하기 위하여 폐회로유량의 섭동(Perturbations)으로 전체비용이 변하게 하였다. 관망상 배관문제의 분석가능영역은 수많은 국지해(Local optimum)를 갖는 비볼록(Nonconvex)이므로 분석가능영역의 효율적인 심사를 위하여 수정추계학적 심사방법을 제안하였으며 이 방법은 국부심사단계(Global search phase)와 국지심사단계(Local search phase)로 구성되어 있다. 국부탐사에서는 점차적으로 국지해를 증진시키며 국지탐사에서는 국부탐사단계에서 교착상태에 있는 국지해로 부터 벗어나게 하거나 최종국지해를 증진시킨다. 제안한 방법의 효율성을 검정하기 위하여 참고문헌에 있는 기존관수로시스템의 병열관로(Parallel pipe line) 확장문제를 표본으로 채택하여 제안한 방법을 적용한 결과 먼저 발표된 연구자들의 비용보다 적은 비용으로 설계할 수 있었다.

• KIEE International Transactions on Power Engineering
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• 제5A권4호
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• pp.331-338
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• 2005

In this paper, an improved maintenance scheduling approach suitable for the competitive environment is proposed by taking account of profits and costs of generation companies and the formulated combinatorial optimization problem is solved by using Reactive Tabu search (RTS). In competitive power markets, electricity prices are determined by the balance between demand and supply through electric power exchanges or by bilateral contracts. Therefore, in decision makings, it is essential for system operation planners and market participants to take the volatility of electricity price into consideration. In the proposed maintenance scheduling approach, firstly, electricity prices over the targeted period are forecasted based on Artificial Neural Network (ANN) and also a newly proposed aggregated bidding curve. Secondary, the maintenance scheduling is formulated as a combinatorial optimization problem with a novel objective function by which the most profitable maintenance schedule would be attained. As an objective function, Opportunity Loss by Maintenance (OLM) is adopted to maximize the profit of generation companies (GENCOS). Thirdly, the combinatorial optimization maintenance scheduling problem is solved by using Reactive Tabu Search in the light of the objective functions and forecasted electricity prices. Finally, the proposed maintenance scheduling is applied to a practical test power system to verify the advantages and practicability of the proposed method.

• Tuberculosis and Respiratory Diseases
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• 제87권3호
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• pp.234-251
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• 2024

Globally, providing evidence on the economic burden of chronic obstructive pulmonary disease (COPD) is becoming essential as it assists the health authorities to efficiently allocate resources. This study aimed to summarize the literature on economic burden evidence for COPD from 1990 to 2019. This study examined the economic burden of COPD through a systematic review of studies from 1990 to 2019. A search was done in online databases, including Web of Science, PubMed/Medline, Scopus, and the Cochrane Library. After screening 12,734 studies, 43 articles that met the inclusion criteria were identified. General study information and data on direct, indirect, and intangible costs were extracted and converted to 2018 international dollars (Int$). Findings revealed that the total direct costs ranged from Int$ 52.08 (India) to Int$ 13,776.33 (Canada) across 16 studies, with drug costs rannging from Int$ 70.07 (Vietnam) to Int$ 8,706.9 (China) in 11 studies. Eight studies explored indirect costs, while one highlighted caregivers' direct costs at approximately Int$ 1,207.8 (Greece). This study underscores the limited research on COPD caregivers' economic burdens, particularly in developing countries, emphasizing the importance of increased research support, particularly in high-resource settings. This study provides information about the demographics and economic burden of COPD from 1990 to 2019. More strategies to reduce the frequency of hospital admissions and acute care services should be implemented to improve the quality of COPD patients' lives and reduce the disease's rising economic burden.

• 산업경영시스템학회지
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• 제19권40호
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• pp.169-178
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• 1996

Geographically dispersed computing system is made of computers interconnected by a telecommunications network. To make the system operated efficiently, system designer must determine the allocation of data files to each node. In designing such distributed computing system, the most important issue is the determination of the numbers and the locations where database files are allocated. This is commonly referred to as the file allocation problem (FAP)[3]. The proposed model is a 0/l integer programming problem minimizing the sum of file storage costs and communication(query and update) costs. File allocation problem belongs to the class of NP-Complete problems. Because of the complexity, it is hard to solve. So, this paper presents an efficient heuristic algorithm to solve the file allocation problem using Tabu Search Technique. By comparing the optimal solutions with the heuristic solutions, it is believed that the proposed heuristic algorithm gives good solutions. Through the experimentation of various starting points and tabu restrictions, this paper presents fast and efficient method to solve the file allocation problem in the distributed computing system.

• 한국정보기술응용학회:학술대회논문집
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• 한국정보기술응용학회 2005년도 6th 2005 International Conference on Computers, Communications and System
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• pp.13-16
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• 2005

It would be desirable to have methods for specific problems, which have low communication costs compared to the computation costs, and in specific applications, algorithms need to be developed and mapped onto parallel computer architectures. Main memory access for shared memory system or global communication in message passing system deteriorate the computation speed. In this paper, it is found that the m-step generalization of the block Lanczos method enhances parallel properties by forming m simultaneous search direction vector blocks. QR factorization, which lowers the speed on parallel computers, is not necessary in the m-step block Lanczos method. The m-step method has the minimized synchronization points, which resulted in the minimized global communications compared to the standard methods.

• 시스템엔지니어링학술지
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• 제12권2호
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• pp.47-57
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• 2016

As the inventory costs of repairable items in military logistics continue to increase, many studies for optimal inventory level of these items are being carried out in advanced countries, including the US, to reduce these costs. Research on inventory level optimization for repairable items aimed to achieve the availability goal of a system with a MIME(Multi Indenture Multi Echelon) repair policy structure first began with Sherbrooke's METRIC and developed into various types. This research is to analyze and compare recent V-METRIC related studies to search for another variation in this field. This paper mainly looks at how to determine optimum inventory level for each repairable item to achieve a specific availability target within a limited budget, and also how to minimize inventory cost while achieving its availability target by determining optimal inventory level of each repairable item.