• 한국재료학회지
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• 제4권1호
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• pp.75-80
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• 1994

2-관능성 DGEBA-4-관능성 TGDDM 블렌드를 DDM으로 경화시킨 경호물의 굴곡 특성과 열 안정성을 혼합비에 대하여 조사하였다. 굴곡 탄성율과 유리 전이 온도는 TGDDM이 증가 될수록 증대되었고, 20-40 중량%의 TGDDM조성에서 불연속적으로 변화하는데, 이것은 이 저성 부근에서 ductile/brittle의 구조적 상변화가 일어나고 있기 때문인 것으로 추정된다. TGDDM성분이 증가될수록 최대 열분해 온도는 고온쪽으로 shift되는 경향을 보이지만, 분해에 대한 활성화 에너지는 오히려 감소했다.

• 한국보건간호학회지
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• 제12권1호
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• pp.13-22
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• 1998

This study was conducted to find qualitative approaches to occupational reference to group health practices. In-depth interviewing was done on 8 subjects health monitor members, owners and occupational nurses, respectively). The major findings were as follows; 1. Visiting health management Useful services were 'health counseling', 'medical examination', 'providing informations about managing diseases', 'agency business in relation to Labour Ministry' and 'giving a recognition about occupational health service to owners'. Insufficiencies were 'lack of treatment service after medical examination' and 'lack of follow up services constantly'. 2. Occupational nursing service Useful services were 'providing health information' and 'counselling about health'. Major contents of occupational nursing services were 'management of occupational and adult diseases' and 'explanation of the results after medical examination'. Insufficiencies were 'deficiency of the place where group health education could be performed', 'lack of additional or closer examinations needed in counselling' and 'discontinuous selection of additional or more exact examinations'. 3. Health monitor members Health monitor members in industries were classified into two. Some were selected by owners and the others were selected simply by considering their administrative abilities such as proficient management of documents. Their major tasks were to connect workers with occupational health management agencies. This study suggests that programs should be developed which enable health monitor members to cooperate with occupational nurses.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1994년도 하계학술대회 논문집 A
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• pp.595-602
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• 1994

PERISTOR-3000 loaded with 32 bit DSP(Digital Signal Processor) is a technically advanced versatile dc motor controller in applications with very high requirements for rapid response, control accuracy and reliability. The current controller of PERISTOR-3000 is of the predictive type and gives fast control with both discontinuous and continuous current compared to the conventional PI current control. The speed controller gain is compensated to improve response behavior. PERISTOR-3000 communicates with its host computer, POSTAR-3200, or any IBM or compatible PC and can be controlled. Dedicated monitoring system for MMI is introduced.

• Journal of Power Electronics
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• 제9권6호
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• pp.823-834
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• 2009

This paper proposes a high-efficiency single-stage ac/dc converter. The proposed converter features low voltage stresses and reduced switching losses. It operates at the boundary of discontinuous- and continuous-conduction modes by employing variable switching frequency control. The turn-on switching loss of the switch can be reduced by turning it on when the voltage across it is at a minimum. The voltage across the bulk capacitor is independent of the output loads and maintained within the practical range for the universal line input, so the problem of high voltage stress across the bulk capacitor is alleviated. Moreover, the voltage stress of the output diodes is clamped to the output voltage, and the output diodes are turned off at zero-current. Thus, the reverse-recovery related losses of the output diodes are eliminated. The operational principles and circuit analysis are presented. A prototype circuit was built and tested for a 150 W (50V/3A) output power. The experimental results verify the performance of the proposed converter.

• 전력전자학회논문지
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• 제20권2호
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• pp.130-136
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• 2015

This study describes the structure and operation modes of vertical stabilization (VS) converter for international thermonuclear experimental reactor (ITER) and proposes a protection method. ITER VS converter supplies voltage (${\pm}1000V$)/current (${\pm}22.5kA$) to superconducting magnets for plasma current vertical stabilization. A four-quadrant operation must be achieved without zero-current discontinuous section. The operation mode of the VS converter is separated in 12-pulse mode, 6-pulse mode and circulation current mode according to the magnitude of the load current. Protection measures, such as bypass and discharge, are proposed for abnormal conditions, such as over current, over voltage, short circuit, and voltage sag. VS converter output voltage is controlled to satisfy voltage response time within 20 msec. Bypass operation is completed within 60 msec and discharge operation is performed successfully. The feasibility of the proposed control algorithm and protection measure is verified by assembling a real controller and implementing a power system including the VS converter in RTDS for a hardware-in-loop (HIL) facility.

• Journal of Power Electronics
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• 제18권4호
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• pp.975-984
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• 2018

This work presents a high efficiency phase shifted full bridge (PSFB) DC-DC converter for use in the second stage of a battery charger for neighborhood electrical vehicle (EV) applications. In the design of the converter, Lithium-ion battery cells are preferred due to their high voltage and current rates, which provide a high power density. This requires wide range output voltage regulation for PSFB converter operation. In addition, the battery charger works with a light load when the battery charge voltage reaches its maximum value. The soft switching of the PSFB converter depends on the dead time optimization and load condition. As a result, the converter has to work with soft switching at a wide range output voltage and under light conditions to reach high efficiency. The operation principles of the PSFB converter for the continuous current mode (CCM) and the discontinuous current mode (DCM) are defined. The performance of the PSFB converter is analyzed in detail based on wide range output voltage and load conditions in terms of high efficiency. In order to validate performance analysis, a prototype is built with 42-54 V / 15 A output values at a 200 kHz switching frequency. The measured maximum efficiency values are obtained as 94.4% and 76.6% at full and at 2% load conditions, respectively.

• 대한한의학회지
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• 제25권2호
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• pp.33-40
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• 2004

Objective : This study investigated the apoptotic effect and its mechanism of Radix Aconiti (RA) extract and aconitine, which is a major constituent of RA, in HepG2 human hepatoma cells. Methods : We used MTT and DNA fragmentation assay to investigate cell viability and apoptotic effect on RA extract-treated HepG2 cells. In addition, to clarify the mechanism of RA extract-induced apoptosis, we applied caspase-3 enzyme activity assay and Western blotting method on poly-(ADP-ribose) polymerase (PARP) protein expression. Results : Treatment with RA extract resulted in the decrease of cell viability, and this effect was caused from apoptosis as confirmed by discontinuous fragmentation of DNA in HepG2 cells, but aconitine did not. Also, RA extract-treated HepG2 cells induced the activation of caspase-3 enzyme activity in time- and dose-dependent manners, which was accompanied by the cleavage of 116 kD PARP to 85 kD product. Conclusions : These results suggest that the apoptotic effects of RA extract on HepG2 cells could not be explained by aconitine. Additionally, RA extract induced apoptosis in hepatoma cells through caspase-3 activation and subsequent PARP cleavage.

• 한국도로학회논문집
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• 제14권4호
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• pp.125-131
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• 2012

PURPOSES : Road lighting facilities increase the visibility of road at night in order to improve traffic driver safety and comfort. Generally speaking, current pole lighting has a tendency to create problems of glare and flicker. The phenomenon of glare gives discomfort due to increase of scattered light, when high luminance is in driver's field of view. The phenomenon of flicker occurs due to the driver passing through discontinuous pockets of pole lighting areas. These phenomenon increase eye strain and decrease driver safety. METHODS : Low height line lighting that distributes light lower than driver's eye level has been developed and evaluated to reduce the problems linked to current pole lighting. A test was undertaken with 4 conditions(turn on the general pole lighting, turn off alternate pole lighting, turn on the line lighting and line lighting with 50% dimming). A driver written survey was conducted in order to gain driver feedback. RESULTS : Pupil size and brow frequency compared with degree in pole lighting are reduced. CONCLUSIONS : Low height line lighting environment makes drivers more comfortable than pole lighting environment and is positive lighting method in the energy saving and landscape aspect.

• Journal of Electrical Engineering and Technology
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• 제11권1호
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• pp.143-149
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• 2016

The two-stage converter is widely used in traditional DC/AC inverter. It has several disadvantages such as complex topology, large volume and high loss. In order to overcome these shortcomings, a novel half load-cycle worked dual SEPIC single-stage inverter, which is based on the analysis of the relationship between input and output voltages of SEPIC converters operating in the discontinuous conduction mode (DCM), is presented in this paper. The traditional single-stage inverter has remarkable advantages in small and medium power applications, but it can’t realize boost DC/AC output directly. Besides one pre-boost DC/DC converter is needed between the DC source and the traditional single-stage inverter. A novel DC/AC inverter without pre-boost DC/DC converter, which is comprised of two SEPIC converters, is studied. The output of dual SEPIC converters is connected with anti-parallel and half load-cycle control is used to realize boost and buck DC/AC output directly and work properly, whatever the DC input voltage is higher or lower than the AC output voltage. The working principle, parameter selection and the control strategy of the inverters are analyzed in this paper. Simulation and experiment results verify the feasibility of the new inverter.

• Journal of Electrical Engineering and Technology
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• 제4권4호
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• pp.499-509
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• 2009

Electric vehicles (EV) are developing fast during this decade due to drastic issues on the protection of environment and the shortage of energy sources, so new technologies allow the development of electric vehicles (EV) by means of electric motors associated with static converters. The proposed propulsion system consists of two induction motors (IM) that ensure the drive of the two back driving wheels. The electronic differential system ensures the robust control of the vehicle behavior on the road. It also allows controlling, independently, every driving wheel to turn at different speeds in any curve. This paper presents the study of an hybrid Fuzzy-sliding mode control (SMC) strategy for the electric vehicle driving wheels, stability improvement, in which the fuzzy logic system replace the discontinuous control action of the classical SMC law. Our electric vehicle fuzzy-sliding mode control's simulated in Matlab SIMULINK environment, the results obtained present the efficiency of the proposed control with no overshoot, the rising time is perfected with good disturbances rejections comparing with the classical control law.