• Korean Management Science Review
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• v.29 no.3
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• pp.121-134
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• 2012

In this study, we consider a component procurement planning problem where the procurement amounts of components are determined under assemble-to-order systems with demand uncertainty. In the problem, procurement amount of each component is decided before the demands of finished products are known and after the demands are identified the assembly amounts of the finished products are decided. In this study, the objective function of the problem is minimizing the total costs which are composed of purchase and inventory costs of the components and the backorder costs of the finished products. We assume that the uncertain demand information is given as multiple scenarios of the demands, and we propose procurement planning methods based on stochastic models which considering the multiple demand scenarios. To evaluate the performances of the proposed methods, computational experiments were carried out on the proposed methods as well as benchmarks including a method based on deterministic mathematical model and a heuristic. From the results of the computational tests, the superiorities of the proposed methods were shown.

• Proceedings of the Safety Management and Science Conference
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• 2002.11a
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• pp.227-232
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• 2002

Enormous flocks by the reduced life cycle of products caused by the technological innovation if later 20 century, development of new materials and diversified demands of customers appeared as the pressing element causing the trouble in management of companies, and when considering the logistic costs that are imposed to companies in terms of function, the costs related to the stock topped the list of costs, followed by the transportation ones, and for pallet pool system, inventory of stocks is very difficult by the number of companies. Reducing the logistic cost may be accomplished by numbers of logistic management methods, but the most fundamental and essential one is the accomplishment of the consistent pallet system that is the core of unit load system, and the purpose of consistent pallet system is the treatment of logistic functions such as transportation, storage and unloading with consistent pallet system, and increasing the turnover ratio is required for the improvement of the system. As the turnover ratios is increased, more pallets will be used so, numbers of empty pallets will be increased accordingly by returning the pallet. Therefore, in this study, we will establish the effective stock management system by comparing with the other existing stock management system after looking at the concept and examples of pallet full system in order to resolved this kind of problem.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2002.05a
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• pp.363-370
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• 2002

This paper presents a production planning algorithm for minimizing the costs of production and subcontracting in SCM (supply chain management) environment. In our SCM environment, the several local plants that aye dispersed geographically produce parts and products. In this environment, we have to decide the production volumes of both parts and products considering the BOM (bill-of-material) structure to meet the fixed order quantity or forecasted demand quantity. Each plant produces the specified parts of product with finite production capacity. There exist subcontracting decisions relevant to the production capacity of each plant except the core process plant, and when we use the subcontractor's capacities we should be charged for the fixed subcontracting fees. The objective of this study is to solve the production planning problem, which minimizes the total costs of production, inventory, setup, and subcontracting under constraints of production and subcontracting capacity. For this problem, an integrated production planning model based on the multi-level capacitated lot sizing problem was formulated, and efficient decomposition algorithm was proposed. The experimental investigation shows that the proposed heuristic generates quite good solutions at very low computational costs.

• Journal of the Korea Safety Management & Science
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• v.5 no.1
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• pp.33-43
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• 2003

Enormous stocks by the reduced life cycle of products caused by the technological innovation in later 20 century, development of new materials and diversified demands of customers appeared as the pressing element causing the trouble in management of companies, and when considering the logistic costs that are imposed to companies in terms of function, the costs related to the stock topped the list of costs, followed by the transportation ones, and for pallet pool system, inventory of stocks is very difficult by the number of companies. Reducing the logistic cost may be accomplished by numbers of logistic management methods, but the most fundamental and essential one is the accomplishment of the consistent pallet system that is the core of unit load system, and the purpose of consistent pallet system is the treatment of logistic functions such as transportation, storage and unloading with consistent pallet system, and increasing the turnover ratio is required for the improvement of the system. As the turnover ratios is increased, more pallets will be used so, numbers of empty pallets will be increased accordingly by returning the pallet. Therefore, in this study, we will establish the effective stock management system by comparing with the other existing stock management system after looking at the concept and examples of pallet full system in order to resolved this kind of problem.

• Journal of the Korea Society for Simulation
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• v.29 no.4
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• pp.95-109
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• 2020

In this paper, an optimal manufacturing system design problem in an automotive body assembly lines is introduced when various costs such as equipment investment costs are considered. Meta-model methodology based on simulation results has been used for estimating the performances of the system such as production rate and work-in-process levels. The objective function is minimizing total cost which satisfies the target production rate. The investment costs such as robots, buffers, transportation equipment, and the inventory holding cost of work-in-process have been included in the objective function. Harmony search method has been used for optimization.

• Journal of Institute of Control, Robotics and Systems
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• v.11 no.11
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• pp.956-962
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• 2005

This paper presents an integrated analysis of production and financing decisions. We assume that a cash storage unit is installed to manage the cash flows related with production activities such as raw material procurement, process operating setup, Inventory holding cost and finished product sales. Temporarily financial investments are allowed for more profit. The production plant is modeled by the Batch-Storage Network with Recycle Streams in Yi and Reklaitis (2003). The objective function of the optimization is minimizing the opportunity costs of annualized capital investment and cash/material inventory while maximizing stockholder's benefit. No depletion of all the material and cash storage units is major constraints of the optimization. A novel production and inventory analysis formulation, the PSW(Periodic Square Wave) model, provides useful expressions for the upper/lower bounds and average level of the cash and material inventory holdups. The expressions for the Kuhn-Tucker conditions of the optimization problem can be reduced to two subproblems and analytical lot sizing equations under a mild assumption about the cash flow pattern of stockholder's dividend. The first subproblem is a separable concave minimization network flow problem whose solution yields the average material flow rates through the networks. The second subproblem determines the decisions about financial Investment. Finally, production and financial transaction lot sizes and startup times can be determined by analytical expressions as far as the average flow rates are calculated. The optimal production lot and storage sizes considering financial factors are smaller than those without such consideration. An illustrative example is presented to demonstrate the results obtainable using this approach.

• The Journal of Bigdata
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• v.5 no.2
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• pp.111-120
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• 2020

Despite the recent economic contraction caused by the Corona 19 incident, interest in the residential environment is growing as more people live at home due to the increase in telecommuting, thereby increasing demand for remodeling. In addition, the government's real estate policy is also expected to have a visible impact on the sales of the interior and furniture industries as it shifts from regulatory policy to the expansion of housing supply. Accurate demand forecasting is a problem directly related to inventory management, and a good demand forecast can reduce logistics and inventory costs due to overproduction by eliminating the need to have unnecessary inventory. However, it is a difficult problem to predict accurate demand because external factors such as constantly changing economic trends, market trends, and social issues must be taken into account. In this study, LSTM model and 1D-CNN model were compared and analyzed by artificial intelligence-based time series analysis method to produce reliable results for manufacturers producing furniture components.

• Journal of Families and Better Life
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• v.34 no.1
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• pp.33-47
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• 2016

The purpose of this study was to examine factors which influence maternal parenting stress. The subjects were 182 mothers with toddlers 12 to 36 months old living in Seoul and Gyeonggi-do Province. The instruments used for this study were a self-report questionnaire, PDH(Parenting Daily Hassles), EAS(Emotionality, Activity, Sociability), Value of children by Lee et al., PAI(Parenting Alliance Inventory), and burden of the costs of children. The data were analyzed by descriptive statistics, Pearson's correlation and Hierarchical multiple regression using the SPSS 18.0 program. The main results of this study were as follows: First, the mean score of activity temperament, emotional value of children and husband's support were higher than average. The mean score of Emotionality temperament, instrumental value of children, burden of the costs of children and maternal stress were average. Second, maternal parenting stress was positively correlated with emotionality temperament, mother's age, burden of the costs of children, and negatively correlated with emotional value of children, and instrumental value of children, husband's support. Third, emotionality temperament, husband's support, burden of the costs of children, maternal employment status, and instrumental value of children had an impact on maternal parenting stress. It is expected that the results of this study will contribute to providing basic data for establishing a policy to decrease maternal parenting stress.

• 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.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.38 no.3
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• pp.159-168
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• 2015

Aggregate Production Planning determines levels of production, human resources, inventory to maximize company's profits and fulfill customer's demands based on demand forecasts. Since performance of aggregate production planning heavily depends on accuracy of given forecasting demands, choosing an accurate forecasting method should be antecedent for achieving a good aggregate production planning. Generally, typical forecasting error metrics such as MSE (Mean Squared Error), MAD (Mean Absolute Deviation), MAPE (Mean Absolute Percentage Error), and CFE (Cumulated Forecast Error) are utilized to choose a proper forecasting method for an aggregate production planning. However, these metrics are designed only to measure a difference between real and forecast demands and they are not able to consider any results such as increasing cost or decreasing profit caused by forecasting error. Consequently, the traditional metrics fail to give enough explanation to select a good forecasting method in aggregate production planning. To overcome this limitation of typical metrics for forecasting method this study suggests a new metric, WACFE (Weighted Absolute and Cumulative Forecast Error), to evaluate forecasting methods. Basically, the WACFE is designed to consider not only forecasting errors but also costs which the errors might cause in for Aggregate Production Planning. The WACFE is a product sum of cumulative forecasting error and weight factors for backorder and inventory costs. We demonstrate the effectiveness of the proposed metric by conducting intensive experiments with demand data sets from M3-competition. Finally, we showed that the WACFE provides a higher correlation with the total cost than other metrics and, consequently, is a better performance in selection of forecasting methods for aggregate production planning.