• Proceedings of the Korean Operations and Management Science Society Conference
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• 2004.05a
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• pp.23-26
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• 2004

Recently, most of countries in the world are investing huge amount of capital for the infrastructure of logistics and trying to gain dominating position in logistics. To play the role of important hub in logistics, an efficient, flexible, and fault-tolerant transportation process should be developed. Minimization of transportation cost and timely deliveries in the unpredictable environment are a few of the important issues in logistics. This study suggests a way of transporting goods to destinations at the minimal cost and with the minimal delay by optimally allocating transporting resources. Various attributes in transportation such as due date, priority etc. are also considered. Appropriate transporting resources for each work item is selected by calculating the weighted sum of the cost factor and the delay factor assuming that initial sequences of work items are given. A policy to reallocate transporting resources is also suggested when work items or transporting resources are added or deleted because of accidents or disturbances. This policy provides adaptability to the allocation methodology which enables the system to cope with changing environment by controlling various attributes in transportation. Genetic algorithm is used for this approach.

• Journal of Korean Society for Quality Management
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• v.48 no.1
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• pp.201-214
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• 2020

Purpose: The purpose of this paper is to determine an optimal number of cycle times for the replacement under the circumstance where the system is replaced at the periodic time and the multiple number of working cycles whichever occurs first and the system is minimally repaired between the replacements if it fails. Methods: The system is replaced at periodic time () or cycle time, whichever occurs first, and is repaired minimally when it fails between successive replacements. To determine the optimal number of cycle times, the expected total cost rate is optimized with respect to the number of cycle times, where the expected total cost rate is defined as the ratio of the expected total cost between replacements to the expected time between replacements. Results: In this paper, we conduct a sensitivity analysis to find the following results. First, when the expected number of failures per unit time increases, the optimal number of cycle times decreases. Second, when the periodic time for replacement becomes longer, the optimal number of cycle times decreases. Third, when the expected value for exponential distribution of the cycle time increases, the optimal number of cycle times increases. Conclusion: A mathematical model is suggested to find the optimal number of cycle times and numerical examples are provided through the sensitivity analysis on the model parameters to see the patterns for changes of the optimal number of cycle times.

• Journal of the Korean Society of Safety
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• v.17 no.1
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• pp.87-93
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• 2002

In this thesis using FTA technique, the author proposes a new method of analysis of some accidents in construction work. Some efficient plans of safe facility investment are made out. For this study, I referred to 'The Death Accident in Construction Works', which have been published by Korea Industrial Safety Corporation from 1993 to 1999 for 6 years. I selected some of apartment constructions which have caused many deaths for the purpose of analysis in the study. I found that the concrete work using ferro-deck takes more deaths than the conventional construction. After finding this, I selected GANG FORM works using ferro-concrete which is the most widely used but causes many accidents. On the basis of the classification, I try to do some quantitative analyses by adding the death frequency and material factors. In order to draw up the most efficient investment plan, it is imperative that FT diagram be made out and that factors. In order to draw up the most efficient investment plan, it is imperative that FT diagram be made out and that minimal Cut Set be needed. It requires a great deal to labor and time to get Minimal Cut Set. The Minimal Cut Set which is formed of these process is the main factor to analyze disaster in the work. It is desirable that we add calculated percentage of accidents to these factors to these factors in value order, that is to say, from the high cost to low cost.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.29 no.3
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• pp.135-142
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• 2006

Engineers are always concerned with life cycle costs for making important economic decisions through engineering action like reliability of products. Decisions during the reliability growth development of products involve trade-offs between invested costs and its returns. In order to find minimal LCC containing the reliability improvement cost, production cost, repair and replacement costs, and holding cost of spare parts for failure items we suggest in this paper relationship between development cost and sustaining cost in values of growth parameter $\beta$ of AMSAA model. This model is applied to the reliability growth program based on AMSAA model during R&D phase, the warranty activities of items and the block replacement policy for maintenance of items in avionic equipment.

• Journal of Communications and Networks
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• v.11 no.5
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• pp.500-508
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• 2009

We have designed an algorithm for a problem in multicast communication. The problem is to construct a multicast tree while minimizing its cost, which is known to be NP-complete. Our algorithm, which employs new concepts defined as potential cost and spanning cost, generates a multicast tree more efficiently than the well-known heuristic called Takahashi and Matsuyama (TM) [1] in terms of tree cost. The time complexity of our algorithm is O($kn^2$) for an n-node network with k members in the multicast group and is comparable to the TM. Our empirical performance evaluation comparing the proposed algorithm with TM shows that the enhancement is up to 1.25%~4.23% for each best case.

• Proceedings of the Korean Society of Near Infrared Spectroscopy Conference
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• 2001.06a
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• pp.1022-1022
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• 2001

To obtain accurate and repeatable analyses using NIR technology it is important to select an NIR instrument and / or its sample presentation attachments which allow the operator to minimize sampling errors without compromising the benefits of NIR analysis -namely rapid, low cost, minimal sample preparation, minimal structural facilities, minimal hazards. For each sample type and consistency there may be different optimal combinations of instrument, sample presentation attachment, and sample preparation. This paper will consider options available to NIR users in the area of plant and soil analysis and evaluate the potential benefits and disadvantages of crop nutrient diagnoses using laboratory based and airborne imaging techniques.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.29 no.9
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• pp.65-70
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• 2015

Minimal line length enables low-cost construction of the transmission lines and low-loss transportation of electric power. This paper presents a derivation to determine the coordinate and length of the straight line that minimally connects two perpendicular lines x-axis and y-axis via a specific point, using the optimization technique. The author shows a formula to obtain the minimal length, which is represented by the cube root of the coordinate given by the specific point. Case studies have been also discussed to prove the optimal solutions derived by the proposed formula.

• Proceedings of the KIEE Conference
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• 1987.07b
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• pp.1463-1466
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• 1987

The problem of generating minimal area CMOS functional cell layout can be converted to that of decomposing the transistor connection graph into a minimum number of subgraphs, each having a pair of Euler paths with the same sequence of input labels on the N-graph and P-graph, which are portions of the graph corresponding to NMOS and PMOS parts respectively. This paper proposes a heuristic algorithm which yields a nearly minimal number of Euler paths from the path representation formula which represents the give a logic function. Subpath merging is done through a list processing scheme where the pair of paths which results in the lowest cost is successively merged from all candidate merge pairs until no further path merging and further reduction of number of subgraphs are possible. Two examples were shown where we were able to further reduce the number of interlaces, i.e., the number of non-butting diffusion islands, from 3 to 2, and from 2 to 1, compared to the earlier work [1].

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.48 no.4
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• pp.358-364
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• 1999

The auxiliary transformers or start-up/stand-by transformer(s) are installed against the start-up and shut-down of generator and emergency status in fossil power plant. The on-site power supply configuration using these transformers must be determined, considering configuration requirements, site characteristics, reliability and availability severely because it is remarkably important for safety and ecfonomy of plant. The auxiliary or start-up/stand-by power supply configuration has been determined considering only safety requirements and construction cost until now in Korea. This paper presents general theorems for the reliability estimation and proposes 2-unit based 4 alternatives for the start-up power supply stystem of 500㎿ standardized fossil power plant. The reliability and unavailability of equipment, system and configuration are determined using minimal cut-set methodology. The optimized plan of 4 alternatives is determined based on this ultimate reliability and unavailability.

• Proceedings of the Korean Statistical Society Conference
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• 2005.11a
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• pp.73-78
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• 2005

This paper considers a preventive maintenance policy following the expiration of renewing warranty, Most preventive maintenance models assume that each PM costs a fixed predetermined amount regardless of the effectiveness of each PM. However, it seems more reasonable to assume that the PM cost depends on the degree of effectiveness of the PM activity. In this paper we consider a periodic preventive maintenance policy following the expiration of renewing warranty when the PM cost is an increasing function of the PM effect. The optimal number and period for the periodic PM policy with effect dependent cost that minimize the expected cost rate per unit time over an infinite time span are obtained.