• Journal of the Korean Operations Research and Management Science Society
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• v.11 no.1
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• pp.44-50
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• 1986

In this paper, we find optimal policy for the (Q, r) inventory model under the lead time uncertainty. The (Q, r) inventory model is such that the fixed order quantity Q is placed whenever the level of on hand stock reaches the reorder point r. We first develop the single level inventory model as the basis for the analysis multi-level distribution systems. The functional problem is to determine when and how much to order in order to minimize the expected total cost per unit time, which includes the set up, inventory holding and inventory shortage cost. The model, then, is extended to the multi-level distribution system consisting of the factory, warehouses and retailers. In this case, we also find an optimal policy which minimizes the total cost of the contralized multi-level distribution system.

• Journal of the Korean Home Economics Association
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• v.23 no.4
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• pp.61-68
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• 1985

This study was conducted in a Korean airline catering operation where about 8, 000~10, 000 in flight meals per day were served. Time ad temperature observations were made in an actual airline catering operation to determine critical control points in mushroom and cheese omelet production, and to provide guidelines for the effective quality control programs of the airline catering operation. All data collection was replicated three times. Time and temperature data were collected by using standard instruments throughout the process sequence. Most phases of the food prodct flow were identified as critical control points. Holding phases of after cooking, and before and after reheating need a special attention, since foods were held at room temperature. Several guidelines were suggested for the effective quality control programs for the airline catering operation.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.12 no.5
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• pp.94-101
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• 2013

Injection molding process is one of the most important methods to produce plastic parts with high efficiency and low cost. The objective of this study is to implement the best plastic injection molding process for LED TV speaker frame. Moldflow analysis and simulation of plastic injection molding process were carried out in order to predict optimal modeling operation conditions and then injection molded part was produced various type of resin temperature, filling time and injection pressure variation. the result was that the best injection molding condition is set as 60bar pressure, 2sec filling time and $310^{\circ}C$ degree. The study result would be useful to variety of plastic injection molding process.

• Journal of Korea Foundry Society
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• v.8 no.4
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• pp.459-466
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• 1988

This study was carried out in the austempering temperature and time after Ni, Mo addition in purpose of modification of impact toughness of austempered ductile irons. Addition of alloy element and austempering treatment of $900^{\circ}C$ 60 minutes followed by $300^{\circ}C$, $350^{\circ}C$ and $400^{\circ}C$ for 60 minutes, in this case impact value was increased by ideal mixed structure. But impact value was decreased when holing time is 120minutes, this is attributed to segregation and carbide precipitation from high carbon austenite. Highest impact value was obtained by $350^{\circ}C$ (Mo-addition) and $400^{\circ}C$ (Ni-addition). This phenomena was caused by presence of remained austenite. At all austempering temperature,, Ni-added specimen showed higher impact values than that of Mo-added specimen. And hardness property was affected by austempering temperature and holding time rather than amounts of alloying element.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.17 no.31
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• pp.115-123
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• 1994

Group scheduling, which is a kind of operations scheduling based on the GT concept is analyzed in a multi-stage manufacturing system. The purpose of this research is to develop and evaluate a heuristic algorithm for determining gro up sequence and job sequence within each group to minimize a complex cost function, i.e. the sum of the total pe-nalty cost for tardiness and the total holding cost for flow time, in a multi-stage manufacturing system with group setup time dependent upon group sequence. A heuristic algorithm for group sc heduling is developed, and a numerical example is illustrated. For the evaluation of the pro-posed heuristic algorithm, the heuristic solution of each of 63 problems is compared with that of random scheduling. The result shows that the proposed heuristic algorithm provides better solution in light of the proposed cost function.

• Language and Information
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• v.19 no.1
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• pp.103-117
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• 2015

Not fully satisfied with the treatment of the so-called two nows in Korean by Lee & Choi (2009), this article seeks to furnish the issue with a firmer ground to base on in the relevant conversation. A close comparison between now and cikum appearing in the present perfect and present tense results in the two findings that (i) a crucial difference between the two adverbs is that Korean cikum lacks English now's ability to be identified with the reference time and (ii) further, seeming differences between them are not real but in fact due to tense and aspectual discrepancies between English and Korean. Thus, it claims, contra Lee (1976) and Park (2004), that cikum is a temporal locating adverb which invariably locates the event time of a given eventuality at the utterance time. In particular, it motivates that a past-tensed sentence with cikum should be understood as holding in the recent past mainly from pragmatic inferences rather than semantic entailments.

• Proceedings of the KIEE Conference
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• 2007.04a
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• pp.137-139
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• 2007

In optical disk drives, a conventional control method in the presence of surface defect is holding the previous tracking control command. It is known that the method has a long settling time. This paper proposes a new control method which reduces the settling time. An optical head generally has coupled dynamics between focusing and tracking servo system. We present how to compensate the coupled dynamics so that reduced settling time is achieved. It is verified by experiments that the proposed method brings an improved performance in the presence of surface defect as well as in the normal operating condition.

• Proceedings of the KSME Conference
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• 2008.11a
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• pp.1309-1313
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• 2008

This paper suggests an example of modification of the durability test specifications of electronic control unit for an automotive system in phase of design validation. The basic concept to redefine the specifications of durability test is based on the Arrhenius relationship for accelerated temperature test and the modified Coffin-Manson model for temperature cycle test. The ambient temperature of the powered-event durability test is increased to reduce the required test time of the current specification. Furthermore, the holding time between the events to cool down the temperature of the components is shortened and the resultant temperature rise affects the durability of the components. Thus, the acceleration factor due to the increased temperature range of temperature cycle is also estimated by the modified Coffin-Manson model.

• Journal of the Korean Home Economics Association
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• v.36 no.9
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• pp.139-152
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• 1998

The purpose of this study was to examine interactive effects of gender idelogies on the amount of household work time and the perception of fairness in household work by the couples. The data were collected from 100 couples in Seoul and 142 in Taejon. The Major findings were as follows: Interactive effects of gender idelogies had an important role in explaining household work time and the perception of fairness by husbands. For men holding more egalitarian gender idelogies who were married to women being more egalitarian tend to perform more hours of household work. And husbands who had traditional gender ideologies percept relatively fair to the couples' division of household work. It was approved that wives had a primary role in the division of household work.

• Transactions of the Korean Society of Mechanical Engineers
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• v.12 no.6
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• pp.1320-1326
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• 1988

This paper deals with the behavior of surface crack growth and the characteristics of surface micro-crack distribution under creep and creep-fatigue with 1 min. and 10 min. of load holding times at 593.deg.C, in air. The test specimen is a plate type with a small artificial defect of type 304 the small defect has been carried out by the surface replica method and optical microphotography. The experimental results have been interpreted from the view-point of fracture mechanics. It can be concluded that the longer the hold time the longer the total life time. Most of surface micro-cracks initiate at grain boundaries before the specimen reaches 20% of its total life time, a few of them lead to fracture by coalescence with the main crack.