• Journal of the Korean Operations Research and Management Science Society
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• v.31 no.3
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• pp.81-96
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• 2006

We consider a rental company that dynamically manages Its capacity level through capacity addition and return While serving customer with its own capacity, the company expands its capacity by renting items from an outside source so that it can avoid lost opportunities of rental which occur when stock is not sufficient. If stock becomes sufficiently large enough to cope with demands, the company returns expanded capacity to the outside source. Formulating the model into a Markov decision problem, we identify an optimal capacity management Policy which states when the company should expand its capacity and when it should return expanded capacity after capacity addition. Since it is intractable to analytically find the optimal capacity management policy and the optimal size of capacity expansion, we present a numerical procedure that finds these optimal values based on the value iteration method. Numerical analysis is implemented and we observe monotonic properties of the optimal performance measures by system parameters, which are meaningful in developing effective heuristic policies.

• Journal of the Korean Operations Research and Management Science Society
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• v.36 no.4
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• pp.17-27
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• 2011

The coupon issued by Korail (Korail's coupon) is characterized by the properties such as a discount rate, an issuing region, a selling region, and a practically discounted rate. The purpose of this study is to investigate their impacts on the redemption time using Log-Normal distribution, and to derive managerial implications for improving Korail's discount program. The result showed that the redemption time was shorter or longer depending a discount rate, an issuing region, a selling region, and a practically discounted rate.

• Journal of the Korean Operations Research and Management Science Society
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• v.31 no.1
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• pp.105-115
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• 2006

In this paper, we investigate the problem of minimizing average inventory costs subject to a fill rate constraint in a two-stage serial inventory model with a normally distributed demand. Fill rate is the fraction of demand that is satisfied immediately from on-hand inventory. We first find the lower bounds of base-stock levels in each node by using the exact base-stock level that satisfies a fill rate in a single node model proposed by Sobel. And then, we extensively analyze the system and show that the cost function is convex. Using such convexity and some other useful properties, we can easily find optimal base-stock levels numerically.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 2000.10a
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• pp.458-465
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• 2000

Although Fly ash possess viable engineering properties, an overwhelming majority of the fly ash from coal combustion is still placed in storage or disposal sites. Similarly, sludges generated from various water treatment operations are predominantly subject to the fate of land disposal. To prepare sludges for land disposal typically requires time consuming dewatering schemes, which can become extremely difficult to execute dependent upon the composition of the sludge and its affinity for water. This test was undertaken to reuse of fly ash and sludge with mix. In this paper includes of geotechnical properties of fly ash and fly ash-sludge mixture and results of compaction test, unconfined test, falling head test and CBR test and it was analyzed the effect on mixing fly ash with sludge.

• Magazine of the Korean Society of Agricultural Engineers
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• v.44 no.3
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• pp.122-135
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• 2002

Although fly ash possesses viable engineering properties, an overwhelming majority of fly ash from coal combustion is still placed in storage or disposal sites. Similarly, sludges generated from various water treatment operations are predominantly subjected to the fate of land disposal. To prepare sludges fur land disposal typically requires time consuming dewatering schemes, which can become extremely difficult to execute depending upon the composition of the sludge and its affinity for water. This study was undertaken to reuse fly ash and sludge as construction materials. This paper includes geotechnical properties of fly ash and fly ash-lime-sludge mixture and results of compaction test, UU-test, falling head test, leaching test and CBR test. The effect on mixing fly ash with sludge and lime and the effect of curing period and the results are obtained from this test.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2004.10a
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• pp.221-224
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• 2004

본 논문에서는 볼록이차계획법을 위한 감도분석의 특성을 분석한다. 이를 위해, 볼록이차계획법을 위한 ${\epsilon}$-감도분석 방법, 최적분할에 의한 감도분석 방법, Yildirim-Todd의 감도분석 방법 등을 유도한다. ${\epsilon}$-감도분석의 경우, 내부점방법의 전개상 얻어지는 계산량을 활용할 수 있도록 유도하여 실용성을 높인다. 또한, 선형계획법을 위한 Yildirim-Todd의 감도분석 방법을 볼록이차계획법에 적합하도록 확장하고, ${\epsilon}$-감도분석의 범위와의 관계성을 분석한다. 마지막으로 Yildirim-Todd의 방법과 최적분할에 의한 감도분석 방법 간의 관계를 규명한다.

• Journal of Korea Society of Digital Industry and Information Management
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• v.9 no.3
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• pp.13-20
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• 2013

In this paper, we propose a multi-scale crack detection method. This method uses decomposition, composition, and shape properties. It is based on morphology algorithm, crack features. We use a morphology operator which extracts patterns of crack. It segments cracks and background using opening and closing operations. Morphology based segmentation is better than existing integration methods using subtraction in detecting a crack it has small width. However, morphology methods using only one structure element could detect only fixed width crack. Thus, we use decomposition and composition methods. We use a decimation method for decomposition. After decomposition and morphology operation, we get edge images given by binary values. Our method calculates values of properties such as the number of pixels and the maximum length of the segmented region. We decide whether the segmented region belongs to cracks according to those data. Experimental results show that our proposed multi-scale crack detection method has better results than those of existing detection methods.

• Smart Media Journal
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• v.11 no.9
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• pp.81-93
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• 2022

In an era where non-face-to-face meetings become common, eXtended Reality(XR) is rapidly developing and filling areas that are not satisfied in online meetings based on existing photos/video method. In particular, general users are also able to easily access and use HMD-type mixed reality devices. However, the basic operations applied in HMD-type in Mixed Reality(MR) with hands as the main input tool do not have a standardized system, and each manufacturer operates in a separate response to each other's hand movements. Therefore, this study considered that a systematic hand motion matching system considering the usability and efficiency of operations performed in mixed reality was necessary, and conducted a study to clarify this. First, the basic operation performed in the MR environment and its attributes were investigated, and at the same time, the structure of the hand and the attributes of the possible hand movements were identified. Based on the identified properties, it is intended to present a system that can intuitively and efficiently match basic operation properties in the MR environment with subtle operation properties according to the structure/context of the hand.

• The KIPS Transactions:PartC
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• v.15C no.3
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• pp.199-204
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• 2008

Controller Area Network was developed originally for in-vehicle communication network. But it is now widely used for factory automation because of its properties such as strong noise resistance and high reliabilities. With changing communication environments from peer to peer topology to bus topology, we should check each devices about not only mechanical operations but also electronic or software operations. In this paper, we suggest reliability test environment for CAN based system, which is divided two parts, data correctness and timely delivery.

• Management Science and Financial Engineering
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• v.18 no.1
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• pp.13-20
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• 2012

This paper considers a revenue maximization problem on a single processor. Each job is identified as its processing time, initial reward, reward decreasing rate, and preferred start time. If the processor starts a job at time zero, revenue of the job is its initial reward. However, the revenue decreases linearly with the reward decreasing rate according to its processing start time till its preferred start time and finally its revenue is zero if it is started the processing after the preferred time. Our objective is to find the optimal sequence which maximizes the total revenue. For the problem, we characterize the optimal solution properties and prove the NP-hardness. Based upon the characterization, we develop a branch-and-bound algorithm for the optimal sequence and suggest five heuristic algorithms for efficient solutions. The numerical tests show that the characterized properties are useful for effective and efficient algorithms.