• 전력전자학회논문지
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• 제26권4호
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• pp.285-293
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• 2021

An optimal operation method based on weighted efficiency for a two-stage boost converter is proposed in this study. Detailed loss analysis of the converter is performed to derive the optimal operation method according to the load and input voltage fluctuations, and the optimal DC-bus voltage is derived by applying the weighted efficiency method. The proposed method can satisfy optimal efficiency in the main operation region without a complicated control method. Using 1kW typical two-stage boost converter and is verified three types of weighted efficiency formulas and loss analysis are utilized to derive high-efficiency optimal DC-bus voltage from each load range.

• Journal of Power Electronics
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• 제7권1호
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• pp.44-54
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• 2007

Ac-dc power conversion can either be done with two separate converter stages or with a single converter stage. Two-stage ac-dc converters, however, can be costly and complex, while the performance of single-stage converters is compromised due to a reduced number of components. Several researchers have therefore proposed adding some sort of auxiliary circuit consisting of a second switch and some passive elements to single-stage converters to improve their performance. Although these modified single-stage converters may have two converters, they are not two-stage converters as they do not have two separate and independently controlled converters that are always operating to convert power from one form to another. In this paper, the operation of ac-dc single-stage converters is first reviewed and their strengths and weaknesses are noted. The operation of several modified single-stage converters, including one proposed by the authors, is then discussed, and the paper concludes by presenting experimental results that confirm the feasibility of the proposed converter.

• 전자공학회논문지B
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• 제30B권9호
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• pp.76-83
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• 1993

A morphological filtering algorithm using directional information is presented. Directional filtering technique is effective in reducing noises and preserving edges. The proposed directional filtering is composed of two stage filtering processes. The opening and closing operations in the lst stage are performed for the pixels is aligned to the vertical, horizontal, and two diagonal directions, respectively. The opening operation supresses the positive impulse noises, while the closing operation the negative ones. Then, each directional result and their average value are filtered by the opening or closing operations in the 2nd stage. The averaging operation diminishes the effects of Gaussian noises in the homogeneous regions. Thus, the morphological operation in the 1 st stageremoves the impulse noises and in 2nd stage reduces. Gaussian ones. The experimental results show that the proposed filtering is superior to the existing nonlinear filtering in the aspects of the subjective quality. Also, the morphological filtering method reduces the computational loads.

• Journal of Korean Neurosurgical Society
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• 제41권3호
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• pp.166-170
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• 2007

Objective : The purpose of this study is to evaluate the clinical outcome of the two-stage operation for thoracic tuberculous spondylitis. Methods : Eleven patients [4 male, 7 female] with thoracic tuberculous spondylitis were treated with two-stage operation. First stage consisted of anterior debridement and interbody fusion using rib graft and second with posterior instrumentation with fusion. Mean age was 46 years, and mean follow-up period was 18 months. All patients were treated with 12 months of antituberculotic medication postoperatively, and evaluated before and after surgery with respect to pain level, neurological status, associated lesions, hematological parameters and change of kyphotic angle. Results : The associated lesions were pulmonary tuberculosis in 4 cases. There were no recurrences of infection and bone union was obtained within 6 months of the operation in all cases. Changes in the pain severity, neurological status, and hematological parameters demonstrated significant clinical improvement in all patients. The mean kyphotic angle was corrected from $17.8^{\circ}$ to $9.8^{\circ}$ after surgery. The most recent follow-up of the mean kyphotic angle was $12.3^{\circ}$, with a loss of correction of $2.5^{\circ}$. The preoperative VAS averaged to be 7.18 [range, 4-10]. It decreased significantly an average of 1.45 [p <0001]. Conclusion : These results indicate that two-stage surgical treatment for thoracic tuberculous spondylitis provid safe and satisfactory results. Spine instability and kyphosis can be also prevented by two-stage operation.

• Journal of Electrical Engineering and Technology
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• 제12권6호
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• pp.2196-2207
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• 2017

This paper presents a two-stage market auction model in a pool-based electricity market, which explicitly takes into account the system network security. The security network-constrained market auction model considers the use of corrective control to yield economically efficient actions in the post-contingency state, while ensuring a certain security level. Under this framework, the proposed model shows not only for quantifying the correlation between secure system operation and efficient market operation, but also for providing transparent information on the pricing system security for market participants. The two-stage market auction procedure is formulated using Benders decomposition (BD). In the first stage, the market participants bid in the market for maximizing their profit, and the independent system operator (ISO) clears the market based on social welfare maximization. System network constraints incorporating post-contingency control actions are described in the second stage of the market auction procedure. The market solutions, along with the BD, yield nodal spot prices (NSPs) and nodal congestion prices (NCPs) as byproducts of the proposed two-stage market auction model. Two benchmark systems are used to test and demonstrate the effectiveness of the proposed model.

• 산업경영시스템학회지
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• 제20권43호
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• pp.249-263
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• 1997

This paper addresses the parts route selection and economic design in flexible manufactuirng system (FMS). Parts are processed through several stage workstations according to operation sequences. The machine of each workstation can do multiple operation functions. And the operation stage of a part can be processed in several workstations, which are non-identical in functional performance. The objective of this paper is to determine the processing routes of parts, number of machine at each workstation, number of vehicle and makespan time. Two models are suggested. One is assumed that the operation stage of parts can be processed at the only one among several available workstations. Other is assumed that the operation stage of parts is allowed to be processed at several workstations. Parts are transported by automated guided vehicles (AGVs). The decision criteria is to minimize the sum of processing cost, travel cost, setup cost and overhead cost. The formulation of models is represented. A solution algorithm is suggested, and a numerical example is shown.

• Advances in pediatric surgery
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• 제13권1호
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• pp.61-65
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• 2007

Conventional treatment of Hirschsprung's disease consists of initial colostomy followed by pull-through operation. But, the treatment of Hirschsprung's disease has been changed along with the development of new surgical technique. Since 1995, endo-GIA has been available at our hospital and one stage Duhamel operation has been performed for neonatal Hirschsprung's disease. Between May 1995 and April 2006, 26 neonates have been treated with one stage pull-through operation by one pediatric surgeon at HanYang University Hospital. The sex ratio was 4.2:1 with male predominance. Clinical findings included abdominal distension (96.2 %), vomiting (50.0 %), delayed passage of meconium (46.2 %), constipation (23.1 %), and enterocolitis (15.4 %). Twenty two cases (84.6 %) were short-segment and 4 cases (15.4 %) were long-segment disease, of which 2 cases were total colon aganglionosis. One of the two patients with total colonic aganglionosis had double transition zones - distal ileum and hepatic flexure of the colon. The average age at operation was $14.56{\pm}8.77$ days and the average weight at operation was $3.26{\pm}0.66kg$. Primary Duhamel operations were performed in 25 patients and Soave-Boley operations was performed in one patient. The endo-GIA 35 (Ethicon, USA) was used from 1995 until 1997, and after that endo-GIA 60 (USSC, USA) was used. The average Duhamel operation time was $88.57{\pm}22.80$ minutes. Wound abscess (n = 2) and septum formation (n =1) occurred after Duhamel operation. Bowel function was normalized in 59 % within 3 months and in 95% within 1 year after operation. There was no mortality after one stage pull-through operation in neonate.

• Journal of Chest Surgery
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• 제33권1호
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• pp.68-72
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• 2000

Background: The resection of recurrent non-small cell lung cancer can be performed very rarely. There has been many arguments for longterm result and therapeutic role in surgical management of recurrent non-small cell lung cancer(NSCLC). We analyze our result of surgical re-resection of recurrent NSCLC for 10 years retrospectively. Material and Method: In the period from 1987 to 1997, 702 patients who had been confirmed for NSCLC had undergone complete resection in Seoul National University Hospital. As December 1997, 22 of these patients have been operated on the diagnosis of recurrent lung cancer. In these patients one has revealed for benign nodule at postoperative pathologic pathologic was unresectable. and two had revealed other cell type on postoperative pathologic examination. Analysis about postoperative survival rate and the factors that influence postoperative survival rate - sex, age, pathologic stage, cell type, operation adjuvant therapy after first and second operation location of recurrence disease free survival-was 59.1$\pm$10.9 year. There were 14 men and 3 women. Four patients was received radiation therpy after first opration and two patients was received postoperative chemotherapy. At first operation 2 patients was stage Ia, 8 was stage Ib, 1 was stage IIa 6 was stage IIb. Eleven patients had squamous. cell carcinoma at postoperatrive pathologic examination five had adenocarcinoma and one had bronchioalveolar carcinoma. In second operation 8 patients were received limited resection. 9 were received lobectomy or pneumonectomy. One-year survival rate was 82.4% and five-year survival rate was 58.2% Non-adjuvant therapy group after initial operation was more survived than adjuvant therapy group statistically. Conclusion: operation was more survived than adjuvant therapy group statistically. Conclusion : Operation was feasible treatment modality for re-resectable non-small cell lung cancer. But we cannot rule out possibility of double primary lung cancer for them. Postoperative prognostic factor was adjuvant therapy or nor after first oepration but further study of large scale is needed for stastically more valuable result.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2009년도 정기총회 및 추계학술대회 논문집
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• pp.206-208
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• 2009

In this paper, a systematical controller design method for a twostage grid-connected photovoltaic power conditioning system is proposed. For a pre-stage boost converter to achieve the stable operation in the entire region of solar array, the digital resistive current mode controller is used. This algorithm is very simple to implement with a digital controller and there is no power stage parameter dependency in the controller design. For a post-stage single-phase full-bridge inverter, a PI controller with a feedforward compensation for the inner current control is employed. Furthermore, in case that the operating point of the solar array under varying environmental conditions is higher than the required voltage for the inverter current control, the bypass mode for the boost converter is possible for the more efficient operation. The proposed control scheme is validated through the experiment of the prototype two-stage power conditioning system hardware with a 200W solar array.

• 한국경영과학회지
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• 제4권1호
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• pp.51-67
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• 1979

This paper considers the problem of determining an optimal dynamic operating policy for a two-stage tandem queueing service system in which the service facilities (or stages) can be operated at more than one service rate. At each period of the system's operation, the system manager must specify which of the available service rates is to be employed at each stage. The cost structure includes an operating cost for running each stage and a service facility profit earned when a service completion occurs at Stage 2. We assume that the system has a finite waiting capacity in front of each station and each customer requires two services which must be done in sequence, that is, customers must pass through Stage 1 and Stage 2 in that order. Processing must be in the order of arrival at each station. The objective is to minimize the total discounted expected cost in a two-stage tandem queueing service system, which we formulate as a Discrete-Time Markov Decision Process. We present analytical and numerical results that specify the form of the optimal dynamic operating policy for a two-stage tandem queueing service system.