• KSCE Journal of Civil and Environmental Engineering Research
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• v.43 no.1
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• pp.79-89
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• 2023

The inventory of many materials requires a large storage space, and the longer the storage period, the higher the potential maintenance cost. When materials are stored on a construction site, there are also concerns about safety due to the reduction of room for movement and working. On the other hand, construction sites that do not store materials have insufficient inventory, making it difficult to respond to demands such as sudden design changes. Ordering materials is then subject to delays and extra costs. Although securing an appropriate amount of inventory is important, in many cases, material management on a construction site depends on the experience of the site manager, so a reasonable material inventory management plan that reflects the construction conditions of a site is required. This study proposes an economical material management method by reflecting variables such as the status of the preceding and following activities, site size, material delivery cost, timing of an order, and quantity of orders. To this end, we set the appropriate inventory amount while adjusting related activities in the activity network, using float time for each activity, the size of the yard, and the order quantity as the main variables, and applied a genetic algorithm to this process to suggest the optimal order timing and order quantity. The material delivery cost derived from the results is set as a fitness index and the efficiency of inventory management was verified through a case application.

• International Journal of Quality Innovation
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• v.7 no.3
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• pp.15-23
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• 2006

A spare ordering policy is considered for planned maintenance. Introducing the ordering, uptime, downtime, inventory costs and salvage value, we derive the expected cost effectiveness. The problem is to determine jointly the ordering time for a spare and the preventive replacement time for the operating unit which maximize the expected cost effectiveness. Some properties regarding the optimal policy are derived, and a numerical example is included to explain the proposed model.

• Journal of the military operations research society of Korea
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• v.32 no.1
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• pp.113-132
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• 2006

This study suggested a readily applicable model to estimate the proper purchasing amount and the optimal CSP(Concurrent Spare Parts) inventory level based on a supporting echelon. For this model to be implemented, it is determined for studies about Multi-echelon Inventory Model to be divided by issues and utilized in the system Moreover, the model also includes the factors that are to be excluded for a reasearch purpose and to be simply assumed. Compared to previous studies, this model is to be considered the most possible factors, realistically designed, and practically used. It is claimed that the results of this model would raise an issue of improving traditional approaches in CSP acquisition and inventory management.

• IE interfaces
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• v.19 no.1
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• pp.78-85
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• 2006

A centralized inventory system provides a number of stores with cost reduction, information sharing. In this paper, transportation costs are included in the inventory model. To build centralized warehouses, two things should be considered: how many warehouses are required and where these are located. The objective of this paper is to develop efficient heuristics to determine the location and the number of central warehouses by minimizing total costs. Throughout some computational experiments, the results of the heuristics are compared with an optimal solution.

• Journal of Biomedical Engineering Research
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• v.25 no.1
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• pp.77-82
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• 2004

The purpose of this study is to establish a reference for image acquisition for completion of a standard brain for diverse Korean population, and to develop a management system that saves and manage database of the acquired brain image and personal information of those who were tested. 3D MP-RAGE technique, which has excellent SNR and CNR and reduces the times for image acquisition, was selected for anatomical Image acquisition, and parameter values were obtained for the optimal image acquisition. The database management system was devised to obtain not only anatomical image data but also subjects' basic demographic factors, medical history, handedness inventory state-trait anxiety inventory, A-type personality inventory, self-assessment depression inventory questionnaires of Sasang Constitution Mini-Mental State Examination, intelligence test, and personality test via a survey questionnaire and to save and manage the results of the tests. In addition, this system was designed to have functions of saving, inserting, deleting, searching, and Printing of image da a and personal information of subjects, and to have accessibility to them as well as automatic connection setup with ODBC. This newly developed system may have major contribution to the completion of a standard brain of diverse Korean population in that it can save and manage their image date and personal information.

• Journal of Korean Society for Quality Management
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• v.11 no.1
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• pp.2-9
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• 1983

For the optimal achievement of system goals through a systematic analysis of the complex problems, systems engineering provides us the concepts and methodology that include comprehensive interpretability (or understandability), universal applicability, and feasibility. Under this aspect, the main objective of this study is that it introduces mathematical system theory (MST) as the fundamental tool of SE into the Inventory Control among the related parts with IE, and review it's applicability. Through its work, we can find that it has the alternative aspects with which it can replace other existing methods for problem-solving in understanding and analyzing structurally systems in themselves as well as being considerable of the time evolutionary process of a given system.

• Journal of Korean Society for Quality Management
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• v.17 no.2
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• pp.158-167
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• 1989

In this paper, a model is presented which incoporates the possibility of quality control at each of the production stages. We consider the TYPE I error and the TYPE II error in inspection procedures. In addition to alternative quality control configurations, the model integrates the carrying costs of in-process and finished inventory, quality of production process, reprocessing including fixed and variable cost. Our policy determines the value of optimal lot-size and reprocessing batch size in reducing the total costs. A numerical example illustrates the model framework and highlights the role of the decision variables.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2007.11a
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• pp.3-6
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• 2007

In the traditional inventory problem, market parameters such as demand and selling price are exogenous. But incorporating these factors into the model can provide an opportunity for increasing the total profit. So we investigate the joint price-inventory policy in a supply chain consisting of a single retailer and a single manufacturer. Demand at the retailer depends on the retail price. The retailer and the manufacturer cooperate closely each other to maximize overall profit of the supply chain. The mathematical model is presented and the solution procedure is developed in order to jointly determine the optimal policy including the retail price, the production lot sizes, and the delivery frequency from the manufacturer to the retailer.

• Journal of the Korean Operations Research and Management Science Society
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• v.21 no.1
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• pp.71-80
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• 1996

This paper presents a stochastic partial inventory model for the situation in which demand is deterministic, lead time follows normal distribution and backorder ratio during the stockout period decreases exponentially according to the length of backorder period. In this situation, an objective function is formulated to minimize the average annual cost, which is the sum of the ordering, carrying time-proportional backordering, quantity-proportional backordering and lost sales costs. And then the procedure of iterative solution method for the model is developed to find optimal reorder point and order quantity and numerical example to illustrate the proposed method is presented.

• Journal of the Korean Operations Research and Management Science Society
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• v.34 no.1
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• pp.11-28
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• 2009

Intelligent investment in setup cost reduction and process reliability improvement is crucial to an emerging integrated lean six sigma practice today. This study examines a cost-minimizing problem of jointly determining production lot size, setup cost reduction, and process reliability improvement decisions for a manufacturer with an imperfect production process. We develop models for previously untapped discrete shipping in a supply chain context as well as continuous shipping and solve them optimally using differential calculus and nonlinear programming. We also conduct analytic and numerical sensitivity analyses to provide various important managerial insights into practices.