• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• 제29권1호
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• pp.7-14
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• 2017

This study carried out a numerical analysis of the effects of hot waste water supply on the performance of a Type II absorption heat pump. There are two types of hot waste water supply, regular series flow and reverse series flow. Also it investigated the interaction between each type of flow and heat exchange solutions. As the effectiveness of heat exchange solutions increase, the steam generation and (COP) increase as well. If the effectiveness of a heat exchange solution is lower than 0.566, the steam generation rate of the reverse flow is lower than that of the regular series flow. A high effectiveness of heat exchange solution is therefore required to make a larger amount of steam in reverse series flow than with ordinary series flow. The COP difference between the two types of flow decreases with the increasing effectiveness of the heat exchange solution. Thus, a reverse flow type absorption heat pump can match the high steam generation rate and COP of the ordinary flow type when a highly effective heat exchange solution is applied.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• 제18권1호
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• pp.87-94
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• 2006

In this paper, we investigated a feasibility of applying highest and lowest temperatures of the next day forecasted from a meteorological observatory to operation of an air-conditioning system with thermal storage. First we investigated specific characteristics of the time series of forecasted temperatures and errors in Osaka from 1994 to 1996. Since the forecast error is not always small, it might be difficult to use the forecasted data without correction for the sizing and the control of the thermal storage system. On the other hand, the autocorrelation functions of the forecast errors decrease relatively slowly during high summer season when cooling thermal storage is required. Since the values of the autocorrelation function; for one day are larger than 0.4, not small, the forecast errors can be predicted by proper statistical analysis. Thus, the forecasted values of the highest temperatures for the next day were improved by using the stochastic time series models.

• Journal of Chest Surgery
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• 제10권2호
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• pp.190-194
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• 1977

An analysis of 503 pulmonary resection is presented, with the following points of interest; 1] By using a stapling device, the operation time is shortened, more lung tissue can be saved, and post-operative complications are fewer. 2] By comparison with a previous series, postoperative drainage from the chest is decreased when the stapling device is used. In the present series 82% of patients has less than 500 cc of drainage post-operatively. Average required whole blood replacement was less than 800 cc in this series of patients. 3] Only 13 patients, or 2.6% developed a bronchopleural fistula, and only 8 patients, or 1.5% developed post-operative empyema when the stapling device was used. 4] Because of the decreased air leaks when the stapling device is used, the anterior and posterior tubes can be removed sooner. 5] With careful preservation of lung tissue and paralysis of the phrenic nerve, post operative `dead space" is not a problem after the pulmonary lobectomy. Thus thoracoplasty is not necessary to eliminate "dead space".

• The Transactions of The Korean Institute of Electrical Engineers
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• 제67권2호
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• pp.331-336
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• 2018

In this paper, the life cycle cost of the auxiliary power unit in the conventional 8200 series electric locomotive is evaluated and an effective life cycle cost reduction method is sought. For this, a life cycle cost evaluation model was proposed using IEC 60300-3-3 standard. As a result of analysis, material cost which accounted for a large percentage of preventive maintenance cost, accounted for 64% of total cost, and breakdown maintenance cost was as high as 27%. Except for the cost of preventive maintenance, the breakdown maintenance cost ratio was the highest. In order to reduce the LCC of the auxiliary power unit(APU) of the 8200 series in the future, it is necessary to reduce the material cost in case of development and to secure the high reliability according to the parts manufacturing so as to minimize the maintenance cost.

• The Transactions of the Korean Institute of Power Electronics
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• 제2권2호
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• pp.19-28
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• 1997

A simple AC complex circuit analysis for LCL type series resonant converter with phase shift control is proposed. Based on these analyses, a set of characteristic curves which allows a optimal design procedure for this converter is shown, without increasing the volt-ampere rating of tank circuit. Especially, inverter output peak current can be minimized in both full load and partial load conditions. The presented design considerations can make the load range wide from full loads to light loads achieving turn-on with zero voltage switching (ZVS) operation. The simulation and experimental results show the effectiveness of the proposed design algorithms.

• The Transactions of the Korean Institute of Power Electronics
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• 제8권1호
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• pp.9-16
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• 2003

This paper presents an novel multilevel inverter employing series connected transformers to reduce the harmonics of output voltage. The proposed inverter consists of several full-bridge modules and their corresponding transformers. Continuous output voltage levels can be generated from a suitable selection of turns ratio of transformer. And it appears an integral ratio to input DC source. Because of its series operation of transformers, output filter inductor is not required. The validity of the proposed system is verified through the experimental results using a 1.5 [kW] prototype, which can generate a 220 $[V_ac]$ output voltage from $[V_dc]$ input.

• The Journal of the Korea institute of electronic communication sciences
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• 제13권2호
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• pp.377-382
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• 2018

In order to partially localize the electric locomotive(8200 series) currently being operated, analysis of the inter-device MVB protocol in the electric locomotive should be performed first. Especially, it is necessary to analyze the operation when a newly developed auxiliary power supply is applied. In this paper, when a new auxiliary power supply applied to a conventional electric locomotive through a newly developed communication control unit using the analyzed protocol, a protocol for a failure codes was analyzed.

• Proceedings of the KIPE Conference
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• 전력전자학회 2006년도 전력전자학술대회 논문집
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• pp.200-202
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• 2006

In this paper, a novel type of auxiliary active snubbing circuit assisted quasi-resonant soft-switching pulse width modulation inverter is proposed for consumer induction heating equipments. The operation principle of this high frequency inverter is described using switching modes and equivalent circuits. This newly developed series resonant high frequency inverter can regulate its high frequency output AC power under a principle of constant frequency active edge resonant soft-switching commutation by asymmetrical PWM control system. The high frequency power regulation and actual power conversion efficiency characteristics of consumer induction heating (IH) products using the proposed soft-switching pulse width modulation (PWM) series load resonant high frequency inverter evaluated. The practical effectiveness and operating performance of high frequency inverter are discussion on the basis of simulation and experimental results as compared with the conventional soft-switching high frequency inverter.

• Proceedings of the KIPE Conference
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• 전력전자학회 2003년도 춘계전력전자학술대회 논문집(2)
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• pp.499-502
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• 2003

This paper presents the voltage source type half bridge lossless auxiliary inductor snubber assisted series capacitor compensated resonant high frequency inverter for induction heated fixing roller in copy machines. This high-frequency inverter treated here can completely achieve zero current soft switching (ZCS) commutation for wide power regulation range under its constant frequency pulse density modulation (PDM) scheme. Its transient and steady-state operating principle is originally presented fur a constant frequency PDM control strategy under a ZCS operation commutation, together with its output effective power regulation characteristics-based on the PDM strategy. The experimental operating performances of this ZCS-PDM high frequency inverter using IGBTs are illustrated as compared with computer simulation ones. Its power losses and actual efficiency are evaluated and discussed on the basis of simulation and experimental results.

• The Transactions of the Korean Institute of Power Electronics
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• 제8권5호
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• pp.463-467
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• 2003

This paper describes an AC voltage regulator using AC chopper and auxiliary transformer which is series connected with main input. It has many advantages such as fast voltage control, high efficiency and low THD. A detail study of step down AC voltage regulator is described and two kinds of novel step-up/down voltage regulator for AVR application are proposed. The operation principle and PWM method of the proposed regulator are described. Experimental results show that it can be used as AC voltage regulator for special purpose very efficiently.