• Journal of the Korean Operations Research and Management Science Society
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• v.31 no.4
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• pp.69-87
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• 2006

This paper proposes an effective approach for the part-machine grouping(PMG) based on the non-binary part-machine incidence matrix in which real manufacturing factors such as the operation sequences with multiple visits to the same machine and production volumes of parts are incorporated and each entry represents actual moves due to different operation sequences. The proposed approach adopts Fuzzy ART neural network to quickly create the Initial part families and their machine cells. A new performance measure to evaluate and compare the goodness of non-binary block diagonal solution is suggested. To enhance the poor solution due to category proliferation inherent to most artificial neural networks, a supplementary procedure reassigning parts and machines is added. To show effectiveness of the proposed approach to large-size PMG problems, a psuedo-replicated clustering procedure is designed. Experimental results with intermediate to large-size data sets show effectiveness of the proposed approach.

• Proceedings of the KIEE Conference
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• 1994.07a
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• pp.509-511
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• 1994

Cycloconverters can be classified into two types by the main circuit configuration. One is the non- circulating current type required the dead time the other is circulating current type which has the circulating current reactors. The switching devices were highly stressed by the load voltages during dead time on non-circulating current type operation and the circulating currents on circulating current type operation. The overcome those problems, this paper proposes the switching patterns for the partial and the non circulation current type. The PWM methods, which are saw wave comparing method and load current integrating value comparing method, are presented.

• Journal of Chest Surgery
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• v.14 no.2
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• pp.153-160
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• 1981

Within the group of congenital cardiac anomalies manifesting dextrocardia and double-outlet right ventricle, ventricular non-inversion [S.D.L] is extremely rare. Recently, a 5 year-old boy underwent a successful surgical correction of dextrocardia associated with double-outlet right ventricle, ventricular non-inversion [S.D], ventricular septal defect, pulmonary stenosis, and patent foramen ovale. The operation consisted of construction of an internal baffle connecting the left ventricle to the aorta through the large ventricular septal defect [subaortic]. The pulmonary stenosis was managed by infundibulectomy and patch enlargement of the right ventricular wall. The patient`s postoperative recovery has been uneventful, and 2 months after the operation, he is doing well.

• Proceedings of the KSR Conference
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• 2003.10c
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• pp.151-156
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• 2003

The Communication Based Train Control(CBTC) System generally used to improving existing lines in the world is efficient and stable for improvement. Also it is efficient for improvement because it does not cause any problems in operation of existing lines. We examined the mixed operation scheme for more efficient and stable improvement when improvement is implemented depending on aged equipment and the increased number of passengers in the Korean city railroad. The biggest point in the mixed operation is to implement a stable test without interfering with the operation of the existing lines. For this purpose, we deduced a method of installing the equipment, a method of testing depending on the installed equipment, and the types of mixed operation, and presented a scheme of execution of the methods depending on the mixed operation.

• Journal of Korea Water Resources Association
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• v.51 no.spc
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• pp.1135-1148
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• 2018

Previous studies on reservoir operation have been assumed that the climate in the future would be similar to that in the past. However, in the presence of climate non-stationarity, Robust Optimization (RO) which finds the feasible solutions under broader uncertainty is necessary. RO improves the existing optimization method by adding a robust term to the objective function that controls the uncertainty inherent due to input data instability. This study proposed Robust-SDP that combines Stochastic Dynamic Programming (SDP) and RO to estimate dam operation rules while coping with climate non-stationarity. The future inflow series that reflect climate non-stationarity were synthetically generated. We then evaluated the capacity of the dam operation rules obtained from the past inflow series based on six evaluation indicators and two decision support schemes. Although Robust-SDP was successful in reducing the incidence of extreme water scarcity events under climate non-stationarity, there was a trade-off between the number of extreme water scarcity events and the water scarcity ratio. Thus, it is proposed that decision-makers choose their optimal rules in reference to the evaluation results and decision support illustrations.

• Journal of Electrical Engineering and Technology
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• v.10 no.2
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• pp.452-464
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• 2015

This paper proposes a DC microgrid operational strategy and control method for improved service reliability. The objective is to supply power to as many non-critical loads as possible, while providing an uninterrupted power supply to critical loads. The DC bus signaling method, in which DC voltage is an information carrier, is employed to implement the operational strategy in a decentralized manner. During grid-connected operation, a grid-tied converter balances the power of the microgrid by controlling the DC voltage. All loads are connected to the microgrid, and operate normally. During islanded operation, distributed generators (DGs), a backup generator, or an energy storage system balances the power. However, some non-critical loads may be disconnected from the microgrid to ensure the uninterrupted power supply to critical loads. For enhanced service reliability, disconnected loads can be automatically reconnected if certain conditions are satisfied. Control rules are proposed for all devices, and detailed microgrid operational modes and transition conditions are then discussed. Additionally, methods to determine control parameter settings are proposed. PSCAD/EMTDC simulation results demonstrate the performance and effectiveness of the proposed operational strategy and control method.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.17 no.12
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• pp.1139-1144
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• 2005

This study has been performed to investigate the thermal performance of variable conductance heat pipe (VCHP) with meshed wick. The length of condenser portion in a VCHP is varied by the expansion of inert gas with the operation temperature, and the heat transport capacity is thus varied with the operating temperature. In this study, numerical evaluation of the VCHP is made for the thermal performance of VCHP, based on the diffusion model of inert gas. Water is used as a working fluid and nitrogen as a control inert gas in the copper tube. As a result, the thermal performance of VCHP has been compared with that of constant conductance heat pipe (CCHP) according to the variation of operation temperature. Maximum heat transport capacity of VCHP is mainly presented for operation temperature and the variation of operation temperature is also presented for heat transfer rate of VCHP.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2023.05a
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• pp.162-163
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• 2023

As the development of the 4^th industiral revolution in the maritime industry has progressed, the technical development of autonomous ships, and the development of international regulations have been accelerated. In particular, the IMO Maritime Safety Committee(MSC) has established a road-map for the development of the non-mandatory goal-based MASS instrument(MASS Code) and started developing a non-mandatory MASS Code at MSC 105^th meeting. Many countries are actively participating in the Correspondence Group on the development of MASS Code, and the development of detailed requirements for MASS functions in the MASS Code is underway. Especially, the concept of "Mode of Operation" for MASS functions was mentioned in the Correspondence Group for the first time, and it is expected that discussions on these modes will be conducted from the IMO MASS JWG meeting to held in April 2023. The concept of "Mode of Operation" will be useful in explaining MASS and MASS functions and will be discussed in the future for the development of MASS Code. This paper reviews the contents of the IMCA M 220 document, which provides guidelines on operating modes, to conduct research on the benchmark for setting the operating modes of MASS.

• Fire Science and Engineering
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• v.31 no.1
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• pp.50-57
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• 2017

The present article discusses the response characteristics of smoke detector chamber due to dust and wind velocity. Although situations have improved in terms of early sensing of fires as the smoke detectors are applied indoors, studies tend to place insufficient focus on the side effects and malfunction that can be caused by diversified life dust produced indoors and environmental requirements, etc. Therefore, in the present study, 4 types of photoelectric smoke detectors with different forms and structures of smoke chamber were selected as the experimental objects, and dust test was conducted with fly ash, talcum powder and fiber dust as experiment samples to study indoor applicability of the smoke detectors in terms of their response to diversified dust and wind velocity. Also, to observe response characteristics due to pollution level inside the smoke chamber, wind velocity for dust test were set additionally at 0.25 m/s, 0.5 m/s, and 1.0 m/s. Based to the experimental results, fly ash, talcum powder, and fiber dust (black hair powder) were found to be suitable at the dust test reference wind velocity conditions of 0.25 m/s for both operation test and non-operation test after dust application. On the other hand, under the harsh wind velocity conditions of 0.5 m/s and 1.0 m/s, malfunction of unwanted alarm was observed in non-operation tests in the case of fly ash and talcum powder, and non-operation was confirmed to occur in the case of fiber dust as the alarm failed to operate normally in operation tests.

• Journal of Chest Surgery
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• v.28 no.6
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• pp.571-578
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• 1995

Rastelli operation in which right ventricle[RV and pulmonary artery[PA is connected with an artificial graft is effective in increasing the pulmonary blood flow in certain types of congenital heart disease but, in many, it requires a reoperation because of the relative stenosis of graft that develops as the patients become old. The purpose of this study is to evaluate the various factors which many influence the long term outcome of such patients following a Rastelli operation. A total of 47 patients underwent a Rastelli operation during a 15 year period between November, 1978 and October 1993. The mean follow-up period is 76.1 51.3 months.1 Among the 47 patients, a valved conduit was used in 30[63.8% , and non-valved conduit in 17[36.2% patients. In the 8 patients[17.0% who died postoperatively, a valved conduit was used in 5 [16.6% and a non-valved conduit in 3[17.6% . There was no statistical difference in mortality between the 2 groups. There was a good linear correlation between the body surface area[X and the conduit size[Y [Y=3.86X + 14.6, R=0.55, P=0.01 .2 Ten patients underwent replacement of the conduit during the follow-up period. The type of conduit used and the frequency of subsequent replacement were as follows: Ionescu-Shiley, valved-33.3%, Carpentier-Edwards, valved-30.8%, Hancock, valved-80% and non-valved conduit-9.1%. The median period free of reoperation was 110 months for the valved and 79 months for the non-valved group, there being no statistical difference between the 2 groups. 3 The patients who did not require reoperation are all doing well [New York Heart Association Functional Classification: Class I . Pressure gradient between the RV and the PA was 20 mmHg in 10 randomly selected patients who did not require reoperation and 92 9 mmHg in 10 patients who did require reoperation.4 In the 10 patients who underwent a conduit replacement procedure.5 Among patients undergoing reoperation, 2 died from endocarditis.The remaining 8 patients are doing well without limitation in physical activity at a mean follow-up period of 32.7 33.9 months [range 2 to 89 months . 6 At 5, 7, and 10 years, the reoperation-free rates among all patients were 96%, 91% and 29% and the survival rates were 82%, 82% and 71%. In conclusion, Rastelli operation is an effective procedure in ameliorating symptoms in a select group of patients with congenital heart disease. Because of the inherent nature of relative graft stenosis and degeneration, a long-term follow-up is required under the proper selection of the graft material.