• Proceedings of the KIPE Conference
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• 2006.06a
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• pp.203-205
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• 2006

This paper presents a novel soft-switching PWM utility frequency AC to high frequency AC power conversion circuit incorporating boost-half-bridge inverter topology, which is more suitable and acceptable for cost effective consumer induction heating applications. The operating principle and the operation modes are presented using the switching mode and the operating voltage and current waveforms. The performances of this high-frequency inverter using the latest IGBTs are illustrated, which includes high frequency power regulation and actual efficiency characteristics based on zero voltage soft switching (ZVS) operation ranges and the power dissipation as compared with those of the previously developed high-frequency inverter. In addition, a dual mode control scheme of this high frequency inverter based on asymmetrical pulse width modulation (PWM) and pulse density modulation (PDM) control scheme is discussed in this paper in order to extend the soft switching operation ranges and to improve the power conversion efficiency at the low power settings. The power converter practical effectiveness is substantially proved based on experimental results from practical design example.

• Journal of Korean Neurosurgical Society
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• v.30 no.10
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• pp.1241-1244
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• 2001

The authors report a very rare case of tuberculous spondylitis combined with a schwannoma of spinal cord. A 39- year-old man was admitted because of paraparesis(G1/G2). MRI showed severe cord compression at two different levels. One was by the bulged soft tissue and subligamentous abscess extending from T7 to T9 and the other was by an intradural extramedullary cord tumor at the level of T1-2. At first operation, T8 corpectomy and T7-9 plate fixation with autogenous iliac bone graft were performed. After then, Paraparesis was improved(G2/G3) postoperatively. The second operation underwent two weeks later. The tumor was totally removed and shortly after second operation, paraparesis was markedly improved(G3/G4). Histological diagnosis were tuberculous spondylitis and schwannoma, respectively. The authors reviewed this case where good surgical outcome was obtained by two stage operation.

• Journal of Gastric Cancer
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• v.10 no.2
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• pp.63-68
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• 2010

Purpose: Remnant gastric cancer (RGC) are generally detected at advanced stages or infiltration of adjacent organs. We retrospectively reviewed the surgical outcomes and clinicopathologic results of remnant gastric cancers that have operated during fourteen years in one institution of Korea. Materials and Methods: 34 patients who were diagnosed with RGC at Ajou University Hospital from April 1995 to October 2009 were enrolled. We analyzed the features of previous operation, and according to these results, surgical outcomes and clinicopathologic results for RGC were analyzed. Results: Of 34 patients, 20 patients had previously undergone distal gastrectomy for malignant disease, and 14 patients for benign disease. The period between previous operation and surgery for RGC in the patients underwent operation for malignant disease was shorter than that in benign patients (P<0.001). In surgical field, 31 patients (91.0%) were resected and curative resection was possible in 23 patients (67.6%). When 31 patients who underwent resection for RGC were divided into previous malignant and benign disease, there was no significantly different in terms of surgical outcomes and pathologic findings between two groups. Meanwhile, the patients who recently (after 2005) underwent surgery for RGC showed less advanced stage compared with the patients who underwent surgery before 2004. Conclusions: Resection was possible in the higher proportion (91.0%) of patients diagnosed with RGC compared with previous reports. The cause of previous operation did not effect on the surgical outcomes for surgery of RGC. Recent trend of RGC is to increase the proportion of early stage gastric cancer. Therefore, surgeons should consider curatively surgical resection for RGC the regardless of pattern of previous operation.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.05a
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• pp.119-120
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• 2006

Prioritizing the design specifications among many alternatives is necessary at the stage of concept design. Design specifications have trade-offs between cost and performance, and the relationships among them, in the standpoint of various functional requirements, are complex. AHP(Analytic Hierarchy Process) method is one of the most popular ways of solving the priority setting problem. However, it is impossible to monitor the interim findings in the middle of the process, it is hard to predict the difference when changing pairwise comparison conditions, and the operation done by one person makes it hard to share the process simultaneously. This paper shows a new method of priority setting in this kind of decision making problem. This method is designed to support the realtime priority setting among many design specifications with regards to many functional requirements. A new algorithm and visualization methods are introduced, and the usability is verified in an exemplary concept design stage.

• Journal of Gastric Cancer
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• v.2 no.2
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• pp.85-90
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• 2002

Purpose: Perforated gastric cancer (PGC) is rare and occurs in $1\∼4\%$ of all gastric cancers. Possible dissemination of tumor cells at the time of perforation of the gastric carcinoma has been a matter of concern. The intraoperative determination of what kind of operation should be done and how extensive the lymphnode dissection should be still remains controversial. The purpose of this study is to evaluate the factors influencing the survival and to determine the optimal treatment for PGC. Materials and Methods: A total of 42 patients were operated on for a perforated gastric carcinoma at Soonchunhyang University Chunan Hospital from 1983 to 2000. the age and the sexes of the patients, the location of perforation, the diameter of perforation, the histologic type of the tumor, the depth of wall invasion, the absence or presence of lymph node metastasis / distant metastasis, the stage of disease, the type of operation, and the outcomes were examined. Statistically significant differences were analyzed by using Fisher's exact test. Results: The stage distributions according to the UICC classification were 1 case of stage I, 6 cases of stage II, 17 cases of stage III, and 11 cases of stage IV. An emergency gastrectomy was done in 26 patients ($61.9\%$), with a 5-yr survival rate of $44\%$. The survival of patients was significantly influenced by the depth of wall invasion, the lymphnode metastasis, distant metastasis, the stage of disease, and the type of operation. Conclusions: an emergency gastrectomy is the treatment of choice for most patients with resectable PGC. Choosing more a optimistic surgical approach for potentially curative cases of PGC should be one way to increase the patient's survival rate.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.56 no.3
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• pp.223-229
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• 2020

We analyzed the cutting mechanism of laver harvesting machine in the sea area near Gooam Port in Goheung, Jeollanam-do, and investigated the change and efficiency of laver collecting operation in the working ship. The laver working ship slides uniformly from the bow to the upper part of the laver collecting machine on the deck and cuts the wet laver attached to the bottom of the net at the blade of the havesting machine. The laver farming net, which was loaded with laver turrets on the deck by gravity and collected primitives, consisted of a ship structure that led to the stern side and into the sea. The working ship operation is in harvesting process while driving in a S-shape that is separated by one space to efficiently collect the laver net. During laver working ship operation, the speed was 0.51 m/s in the access stage, 0.56 m/s in the havesting stage, and 0.52 m/s in the exit stage. Considering the cutting edge life and production efficiency of the laver harvesting machine, it is appropriate to harvest 1.15 to 1.26 kg/rpm by operating at a rotational speed of about 700 to 800 rpm rather than forcibly harvesting the product at high speed. On the deck of the working ship, 959.7 kg of starboard and 1048.7 kg of center were 964.7 kg of port side. Based on the starboard, 9.3% of the central part and 0.5% of the port side appeared. The reason for this was due to the difference in harvest time according to the turning direction of the working ship.

• Journal of Korea Water Resources Association
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• v.30 no.3
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• pp.269-278
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• 1997

Operating rules, the basic principle of reservoir operation, are mostly developed from maximum or minimum, mean inflow series so that those rules cannot be used in practical operating situations to estimate the expected benefits or provide the operating policies for uncertainty conditions. Many operating rules based on the deterministic method that considers all operation variables including inflows as known variables can not reflect to uncertainties of inflow variations. Explicit operating rules can be developed for improving the weakness. In this method, stochastic trend of inflow series, one of the reservoir operation variables, can be directly method, the stochastic technique was applied to develop reservoir operating rule. In this study, stochastic dynamic programming using the concepts was applied to develop optimal operating rule for the Chungju reservoir system. The developed operating rules are regarded as a practical usage because the operating policy is following up the basic concept of Lag-1 Markov except for flood season. This method can provide reservoir operating rule using the previous stage's inflow and the current stage's beginning storage when the current stage's inflow cannot be predicted properly.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2004.10a
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• pp.527-530
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• 2004

This paper presents an optimization formulation for resource scheduling in Critical Resource Diagramming (CRD) of production scheduling networks. A CRD network schedules units of resources against points of needs in a production network rather than the conventional approach of scheduling tasks against resource availability. This resource scheduling approach provides more effective tracking of utilization of production resources as they are assigned or 'moved' from one point of need to another. Using CRD, criticality indices can be developed for resource types in a way similar to the criticality of activities in Critical Path Method (CPM). In our supply chain model, upstreams may choose either normal operation or expedited operation in resource scheduling. Their decisions affect downstream's resource scheduling. The suggested optimization formulation models resources as CRD elements in a production two-stage supply to minimize the total operation cost

• Journal of Chest Surgery
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• v.30 no.11
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• pp.1062-1068
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• 1997

From August 1989 to January 1996, a total of 105 cases of bidirectional Glean operations have been done as the interim stage for the patien s with some risk of univentricular correction at Sejong General Hospital. From December 1992, we started the conversion to Fontal operations for them, and 42 cases underwent Fontal-stage operation till February 1996. Their diagnoses were univentricular heart in 19(right ventricular type : 14), tricuspid atresia 11, double outlet of right ventricle 9, and others in 3 cases. The median age of bidirectional Glerln-stage operation was 12.5 months(range 2 months to 8 years) and Fontan-stage operation was at 59.6 months of median age(range 1 year 5 months to ,9 year 7 months). The mean waiting interval between the two operations was 33.88 $\pm$ 17.85 months with a range of 10 months to 6 years 3 months. During the waiting periods, 18 patients developed significant systemic-pulmonary collaterals andfor systemic verso-veno collateral channels. There were 5 hospital deaths after operations due to low cardiac output in 4 and sepsis in one. Most of the Fontal-stage operations were done by the late al tunneling with Core-Tex tube graft patch and fenestrated with the size of 2.5 ~6 mm. All the patients were followed-up(7 months to 4 years 2 months, mean 21.97$\pm$10.82 months) and there were 5 late deaths(postoperatively 6 months to 2 years) due to thromboembolism in 1, after heart transplantation 1, plastic bronchitis 1, protein loosing enteropathy 1, and pneumonia in 1. Dividing the patients by the waiting interval of 2 years, the early correction to Fontal group (N=16) showed the better results(hospital mortality 1116, late mortality 1116, significant collateral development 2/16) compared to the other group(N=26) (4/26, 4/26, 16/26). In conclusion, after the bidirectional Glean-stage operation successfully got rid of the previous risk factors, we recommand to do the Fontan-stage operation no later than 2 years of interval.

• Journal of Chest Surgery
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• v.34 no.8
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• pp.604-610
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• 2001

Stanford type A aortic dissection after graft replacement of ascending aorta and/or aortic arch required careful follow-up due to progression of the enlarged false lumen or the recurrence of dissection. From June 1984 to June 200, 124 patients underwent operations for type A aortic dissection. Among them, 6 patients underwent reoperation due to recurred aneurysm or dissection. We evaluated that the causes of reoperation, including Marfan syndrome, the approach and result of reoperation, and strategy to reduce the risk of reoperation. Material and method: The first operation was done on acute stage in 4 cases, and chronic stage in 2 cases. There were Marfan syndromes in 3 cases. The entry site was the ascending aorta for all cases except one who underwent Bentall operation(n=3) or ascending aorta graft replacement(n=2). In one case, Bentall operation and total arch replacement was performed due to chronic type A dissection with multiple fenestrations. Mean interval of reoperation was 67.6months(range 5 months to 14 year 4months) after the first operation. Reoperations were performed with recurrence of dissection(n=4), threatening aneurysmal evolution of persisting dissection(n=1), and false aneurysm with infection(n=1). The redo operation involved the hemiarch in 1 case, distal ascending to total arch and descending thoracic aorta in 4 cases, and only descending thoracic aorta in 1 case. Result: There were Marfan syndromes in 18 patients. The mean age in type A dissection was 56.7 years and that in the first operation of reoperationc ases was 32.2 years. Especially in 3 patients with Marfan syndrome, the mean age was 29 years.