• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2008년도 춘계학술대회논문집
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• pp.224-227
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• 2008

The present study performs a test of a change in a condenser pressure on two kinds of power plants having different condenser pressure-heat rate correction curve and evaluates the results. According to a result of the test, it is confirmed that a sub-critical drum type steam power plant is optimally operated at the condenser pressure of 38㎜Hga that is designed, even during winters. On the other hand, it can be found that a supercritical once through type steam power plant operated at the condenser pressure that is reduced below a design value, that is, up to 28㎜Hga during winters is advantageous in view of turbine efficiency and is operated without a problem in facility operation such as moisture erosion, turbine vibration, etc. Also, the present study compares and reviews a condenser pressure-heat rate correction curve proposed by a manufacturer and a test value. The present study proposes optimum condenser operation pressure capable of concurrently satisfying the stable operation and efficiency improvement of the power plant facility that is operating, making it possible to support an efficient operation of a power plant.

• 전기학회논문지P
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• 제57권2호
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• pp.121-126
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• 2008

This paper analyzes the losses of a Steinmetz connection three-phase induction motor which is supplied by a single-phase source. The T-type equivalent circuit which is taken no-load losses into account is used to determine phase converter capacitive reactances at starting and rated speed by using the condition of the minimum voltage unbalance. The starting and the operating capacitor are replaced at the slip of the same voltage unbalance factor points which are depicted using two capacitive reactances. The operation characteristics are investigated by comparing with those of three-phase balanced operation to find the feasibility of single-phase operation. To analyze the losses of this motor, the output power decrease factor(OPDF), the loss ratio(LR), the no load loss ratio(NLLR), the copper loss ratio(CLR), the stator copper loss ratio(SCLR), and the rotor copper loss ratio(RCLR) are defined and simulated in the whole slip range. The simulated results show that OPDF is maintained almost uniformly, LR is low at low speed and high at high speed, CLR is higher !ban NLLR, but CLR varies concavely and NLLR varies convexly at high speed, SCLR is low at low speed and high at high speed, but SCLR varies convexly at high speed, and RCLR is nearly opposite to SCLR.

• 전기전자학회논문지
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• 제25권1호
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• pp.218-228
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• 2021

본 논문에서는 다중공진회로를 이용한 고효율 DC-DC 컨버터를 제안한다. 제안한 컨버터는 하프브리지 전력구조이며 컨버터의 고효율화를 위해 2개의 인덕터(LL)와 1개의 커패시터(C)로 구성된 다중공진회로를 이용한다. 이 다중공진회로는 동작모드에 따라, 각각의 공진주파수를 가진 직렬회로 형태의 공진회로를 각각 형성한다. 본 논문에서는 먼저, 동작모드와 정상상태 기본파 근사 모델링에 의해 제안한 컨버터의 동작원리를 설명한다. 그다음 이에 근거하여 제안한 컨버터의 설계예시를 보인다. 그리고 설계된 회로 파라미터에 의해 제작된 프로토타입 컨버터의 실험결과를 통하여 제안한 컨버터의 고효율 DC-DC 전력변환 동작특성을 입증한다.

• 한국초전도저온공학회:학술대회논문집
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• 한국초전도저온공학회 2002년도 학술대회 논문집
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• pp.285-290
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• 2002

Power systems are becoming larger and larger for meeting electric power demand. Therefore, the over-currents resulting from contingencies such short circuits are increasing higher. The Maximum short circuit current of modern power system is becoming so large that circuit breaker are not expected th be able to shut down the current in the future. In order to cut over-currents, a system composed of a superconducting fault current limiter(SFCL) and traditional breaker seems to provide a promising solution for future power operation. In present paper, three line-to-ground fault is assumed to happen at the center of 345kV transmission lines in a large capacity electric power system The superconducting fault current limiter was represented using a commutation type, which consists of a non-inductive superconducting coil and current limiting element(resistor or reactor). The introduction merits of the SFCL were investigated quantitatively by RTDS/EMTDC from the viewpoint of current limiting performance, the prevention of the voltage drop at the load bus and comparison characteristics for two type SFCL. Desired design specification and operation parameters of SFCL were also given qualitatively by the performance evaluation of the two type SFCL in the power system.

• 한국안전학회지
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• 제21권1호
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• pp.86-91
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• 2006

Oil spills caused by the accidents have been occurred from house and factory waste, grounded tanker, the rupture of storage tank and oil pipelines, the deterioration of various industrial facilities, etc. Many oil spills result in contamination of shorelines and workplace. Fire and explosion may happen from these spills. There are several technologies used for clean-up application, which include use of oil dispersing agents, absorbents, solidifiers, booms and skimmers by physical, chemical, and biological methods. Methods for oil spill clean-up operation are classified into the absorption type, gel type and self-swelling type. Porous materials with oil absorptive properties are classified into micropore, mesopore, and macropore depending on their pore sizes. Recently, new porous materials with smaller size have been developed, but the selective oil absorption in water-in-oil interface demonstrates the macro pore size. In this study oil absorption effects were evaluated using the organic porous materials with a complex function of gel type and swelling type. Samples were subjected to analysis by FT-IR spectroscopy and were characterized in terms of gel formation and morphologies. Oil sorption capacity, pressure retention force and gel strength were also measured. From these results, the physicochemical reactivity before and after gelation was verified and the industrial applications of clean-up operation were suggested.

• 전기학회논문지
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• 제60권3호
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• pp.572-576
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• 2011

The operation of permanent magnet synchronous generator (PMSG) type wind power generation system (WPGS) can be affected by the utility condition. Consequently, transient condition of utility should be analyzed for the safe and reliable operation of WPGS. This paper presents transient analysis results of a PMSG type WPGS using real time digital simulator (RTDS). A fault condition was applied to the transient analysis of PMSG type WPGS as the transient grid condition. The simulation results were analyzed to show the operational characteristic of PMSG type WPGS under the transient phenomenon of utility.

• 센서학회지
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• 제27권6호
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• pp.362-367
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• 2018

A complementary metal oxide semiconductor (CMOS) binary image sensor is proposed for low-power and low-noise operation. The proposed binary image sensor has the advantages of reduced power consumption and fixed pattern noise (FPN). A gate/body-tied (GBT) p-channel metal-oxide-semiconductor field-effect transistor (PMOSFET)-type photodetector is used as the proposed CMOS binary image sensor. The GBT PMOSFET-type photodetector has a floating gate that amplifies the photocurrent generated by incident light. Therefore, the sensitivity of the GBT PMOSFET-type photodetector is higher than that of other photodetectors. The proposed CMOS binary image sensor consists of a pixel array with $394(H){\times}250(V)$ pixels, scanners, bias circuits, and column parallel readout circuits for binary image processing. The proposed CMOS binary image sensor was analyzed by simulation. Using the dynamic comparator, a power consumption reduction of approximately 99.7% was achieved, and this performance was verified by the simulation by comparing the results with those of a two-stage comparator. Also, it was confirmed using simulation that the FPN of the proposed CMOS binary image sensor was successfully reduced by use of the double sampling process.

• 한국태양에너지학회 논문집
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• 제33권6호
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• pp.12-18
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• 2013

Domestic solar hot water system can be divided into a passive type and an active type. In a passive type the storage tank is horizontally mounted immediately above the solar collectors. No pumping is required as the hot water naturally rises into the storage tank from the collectors through thermo-siphon flow. While, in an active type the storage tank is ground- or floor-mounted and is below the level of the collectors; a circulating pump moves water or heat transfer fluid between the storage tank and the collectors. We installed two types solar hot water systems consisting of the same storage tank and collectors at the same place, and were measured and compared typical operating characteristics under the same external conditions. In particular, the daily system performance was presented through the stirring test after the sunset. The results show that the amount of solar radiation obtained for an active type were less than a passive type on a cloudy day, because the operation of the circulation pump stops frequently took place on that day. However, on a sunny day, depending on the stable operation of the circulation pump, the amount of solar radiation obtained for an active type were increased than a passive type.

• Journal of Chest Surgery
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• 제15권4호
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• pp.460-466
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• 1982

A analysis of CPK & LDH Isoenzyme was done on the consecutive patients undergoing thoracic operations from July 1982 to October 1982 in the Department of Thoracic and Cardiovascular Surgery, Capital Armed Forces General Hospital. Eighteen patients were analysed by three groups, such as open heart surgery [group A], major thoracic operation [group B] , minor thoracic operation group [group C]. In all patients serial determination of total level and Isoenzyme of CPK, LDH wad done on preoperative operative and up to 8th post-operative day, The results obtained are as follows. 1. The average value of serum CPK before the operation was 61 IU/L. The value of serum CPK was increased following the operation mainly MM portion and reached to the maximal level of 536107 IU/L in A group 1200191 IU/L in B group, 306150 IU/L in C group on the first postoperative day. The enzyme activity was gradually decreased thereafter and returned to the normal range on the 3rd or 4th day after the operation. 2. The average value of serum LDH before the operation was found to be 83 IU/L. The value was increased during the operation and reached to the maximal level of 481108 IU/L in group A, 14827 I U/L in group B, 10035 IU/L in group C on the second day after the operation. The enzyme activity was gradually decreased thereafter and returned to the normal range on the seventh day after the operation. The enzyme activity was dependent to the duration of operation, severity of muscle damage, type of thoracotomy, effect of extracorporeal circulation, state of disease.

• Advances in pediatric surgery
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• 제13권2호
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• pp.135-143
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• 2007

Biliary atresia (BA) is an uncommon neonatal surgical disease that has a fatal outcome if not properly treated. The survival rates of the patients with native liver after Kasai's operation in countries outside Japan are not so good. We reviewed the results of 22 cases of biliary atresia treated in Kosin University Hospital between October 1987 and March 2001. There were 13 males and 9 females aged from 21 to 106 days (mean 52 days). There were 3 cases of Type I (13.6%), and 3 of Type II (13.6%), and 16 Type III (72.7%). The operative methods were resection of the common bile duct remnant and cyst followed by Roux-en-Y hepaticojejunostomy in 3 cases for Type I BA; Kasai I in 15 cases, Kasai II in 1 case, and Ueda's operation in 3 cases for Types II and III BA. There was no death within the first 30 days after operation. We were able to follow 21 of the 22 patients (95.4%) for more than 5 years. The actual 5 year survival rate (YSR) was 40.9%. One Type I case received a living-related liver transplantation at 6 years of age because of the multiple intrahepatic stones and liver cirrhosis. Five YSR after biliostomy group (Kasai II and Ueda op.) was 75 % (3/4) while that of Kasai I was 20% (3/15). One case had no bile duct in the resected fibrotic plaque on microscopic review and died 8 months after Kasai I operation, would have been a strong candidate for early liver transplantation. From the above result, our conclusions are as follows; (1) early liver transplantation should be considered for cases of no bile duct after pathologic examination of the resected specimen, (2) measures to prevent postoperative cholangitis and prevention of postoperative liver cirrhosis are needed, (3) liver transplantation program should be available for failed cases.