• Journal of Korean Institute of Industrial Engineers
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• v.29 no.4
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• pp.253-258
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• 2003

We consider the problem of grouping orders into lots. The problem is modelled by a graph G=(V,E), where each node ${\nu}{\in}V$ denotes order specification and its weight ${\omega}(\nu)$ the orders on hand for the specification. We can construct a lot simply from orders of single specification. For a set of nodes (specifications) ${\theta}{\subseteq}V$, if the distance of any two nodes in $\theta$ is at most d, it is also possible to make a lot using orders on the nodes. The objective is to maximize the number of lots with size exactly $\lambda$. In this paper, we prove that our problem is NP-Complete when $d=2,{\lambda}=3$ and each weight is 0 or 1. Moreover, it is also shown to be NP-Complete when $d=1,{\lambda}=3$ and each weight is 1,2 or 3.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2020.06a
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• pp.161-162
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• 2020

Cracks are caused by drying shrinkage between the upper part of the underground parking lot and the apartment wall. As a result of the investigation, the distance between the apartment and the apartment is more than 45m, and the top slab of the underground parking lot is usually flat when there is not with steps. Therefore, the crack occurs more when the underground parking lot is a PC slab than a RC slab. In this study, the reduction of cracks was conducted by extending the slab, expanding the beam size, increasing the wall thickness, and installing a delay joint on slab. In each case, a finite element analysis was performed to examine the crack reduction method.

• Journal of Institute of Control, Robotics and Systems
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• v.3 no.5
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• pp.532-541
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• 1997

This article derives an analytic solution to determine the optimal size of multiple noncontinuous process and storage units. The total cost to be minimized consists of the setup cost of noncontinuous processing units and the inventory holding cost of feedstock/product storages. A novel approach, which is called PSW(Periodic Square Wave) model, is applied to represent the material flow among non-continuous units and storages. PSW model presumes that the material flow between unit and storage is periodic square wave shaped. The resulting optimal unit size has similar characteristics with the classical economic lot sizing model such as EOQ(Economic Order Quantity) or EPQ(Economic Production Quantity) model in a sense that the unit size is determined as the balance between setup and inventory holding cost. However, the influence of inventory holding cost of PSW model is different from that of EOQ/EPQ model. EOQ/EPQ model includes only the product inventory holding cost but PSW model includes all inventory holding costs around the non-continuous unit with proportional contribution. PSW model is suitable for analyzing interlinked process-storage system. The optimal lot size of PSW model is smaller than that of EOQ/EPQ model. This is quitea remarkable result considering that the EOQ/EPQ model has been is widely used since last half century.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.32 no.3
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• pp.110-117
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• 2009

This paper introduces a case study for efficient generation of production schedules in a tube manufacturing system. The considered scheduling problem consists of two sub problems : lot sizing for a job and Job sequencing. Since these problems require simulation optimization in which the performance measures are obtained by simulation execution, the trade-off between solution quality and computation time is an important issue. In this study, the optimal lot size for every product type is determined from simulation experiments. Then, target production quantity for each product type is transformed to several jobs such that a Job consists of determined lot size. To obtain the good solution for a Job sequence in a reasonable time, a number of alternatives are generated from heuristic rules developed by intuition and analysis of the considered system, and a job sequence is selected from simulation experiments.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2000.04a
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• pp.111-117
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• 2000

경제적 로트 일정계획 문제(Economic Lot Scheduling Problem : ELSP)는 지난 수십 여 년간 많은 연구가 이루어진 생산일정계획 문제 중의 한 분야이다. 이 문제는 NP-hard 문제이기 때문에 수많은 발견적 기법이 제안되고, 사용되어져 왔다. 그 중에서도 Dobson［1］의 발견적 기법이 그 수행도의 우수성으로 보아 최고의 기법으로 여겨지고 있는데, 본 연구에서는 Dobson［1］의 시변 로트 크기(time varying lot size) 접근방법에 유전자 알고리즘을 이용한 새로운 발견적 기법을 제안하고, 수치실험을 통해서 새로운 기법이 기존의 Dobson［1］의 기법보다 더 우수하다는 것을 보이고자 한다.

• Journal of the Korean Operations Research and Management Science Society
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• v.34 no.4
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• pp.139-151
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• 2009

Based on single-vendor single-buyer integrated production-inventory problem, a model considering freight costs discounts is suggested when the cargo capacity is constrained. With the cost function formulated, several properties of the model are derived and analyzed. An efficient algorithm to find solutions such as shipment lot size, number of shipments and number of full truckloads using properties derived is suggested. Numerical results are provided to illustrate the proposed solution procedures and to provide additional insights.

• Journal of Korean Society for Quality Management
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• v.19 no.2
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• pp.86-95
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• 1991

Empirical Bayes estimation of the binomial parameter ${\theta}$ is considered when the sample size in each component problem is random. The result is applied to the lot acceptance sampling problem in the presence of various kinds of costs including cost for sampling.

• Proceedings of the Safety Management and Science Conference
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• 2012.04a
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• pp.573-577
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• 2012

Based on latest research, the parametric quality statistics cannot be used in non-normal process with demand pattern of many-variety and small-volume, since it involves extremely small sample size. The research proposes nonparametric quality statistics according to the number of lot or batch in the non-normal process. Additionally, the nonparametric Process Capability Index (PCI) is used with 14 identified non-normal distributions.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.7
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• pp.2955-2963
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• 2012

This study presents a column generation approach for multiple product dynamic lot-sizing problem. The basic idea of this approach is to have a master problem which allocates limited capacity among n different products and a sub-problem that performs the optimal lot sizing for each product subject to capacity allocation given by the master problem. In the sub-problem, we develop M/G/1 queuing model based clearing function which captures nonlinear relationship between the lot size, the work in process level and the throughput. A large number of test problems are randomly generated to evaluate the performance. Computational results show that the proposed model can find better solutions within reasonable CPU times.

• Proceedings of the Korea Concrete Institute Conference
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• 1998.10a
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• pp.301-306
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• 1998

Aggregate as the component of High Flowing Concrete has much influence on the properties of High Flowing Concrete according to the quality and condition because the aggregate occupy a lot of concrete volume. The shape and size of aggregate affect a lot spatial passibility and fillingability. The segregation is easy to occur when the rate of Fine aggregate is high so that Fluidity is much affected by aggregate factor. In this study, therefore, we try to understand the various fluidity according to the fine aggregate of standard grade rang, the size of Coarse aggregate and the rate of fine aggregate to confirm the manufacturing possibility of High Flowing Concrete by examination on the influence of fresh state of high flowing concrete such as flowability, reinforcement passibility, fillingability, segregation resistance.