• 대한간호학회지
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• 제16권3호
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• pp.78-96
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• 1986

The sympathico-adrenergic system and the hypophyseal-adrenocortical system mediates the regulation of the internal milieu. And the kidneys regulate both water and electrolyte balance of the body fluid. The kidneys are the sites of production of renin which participate indirectly in maintaining renin. angiotensin-aldosterone system. These system de-serve special attention in the context of adjustment the effects on the body function. And so, maximal exercise and work load are associated with home-osthetic function. The nurses working in the hospital have been complained of fatigue and stress by frequent duty changes and overload. In order to define this, the possible changes of hormonal excretion during three-shift nursing practice were investigated. Urine samples were collected at pre-duty and post-duty, and were measured with chemical assay and radioimmunoassay in 30 nursing students, in nursing practice and 43 nursing students, in studying. The results obtained were as follows. 1. In nursing practice, urinary norepinephrine concentration showed a marked increase during day duty, urinary cortisol concentration showed a marked increase during evening duty, and urinary renin concentration was increased in night duty, 2. Corrected ratio of urinary sodium excreted by the urinary excretion of creatinin (UNa/UCr) and UCl/UCr showed a marked decrease during night duty. Nursing practice did not affect on the UK/UCr and urinary concentrating ability. From these results, it is suggested that further studies the define the effects on some physiological function of the three-shift nursing practice against circadian rhythm are needed for better working condition of nurses.

• 전력전자학회논문지
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• 제7권5호
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• pp.443-452
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• 2002

수 백 Watt 급의 통신용 장비 등에 적합하도록 고안된, 직렬 연결된 두 개의 트랜스포머를 갖는 새로운 위상천이 풀 브릿지 컨버터를 제시한다. 제안된 회로의 장점은 넓은 입력 범위를 가지며, 경부하에서도 스위치의 영전압 조건을 보다 쉽게 만족시킬 수 있다는 점, 그리고 작은 출력 변동율을 갖는다는 점 등이다. 뿐만 아니라, 직렬로 연결된 두 개의 트랜스포머가 번갈아 가면서 주 트랜스포머로서의 역할과 출력 인덕터로서의 역할을 함께 수행하므로, 출력측에서는 인덕터없이 필터링이 가능하게 되고, 따라서 고전력밀도의 컨버터를 제작할 수 있게 된다. 모드 해석과 대신호 모델링을 통한 설계식의 유도, 그리고 실험 결과를 보여줌으로써 제안된 컨버터를 검증한다.

• 전기학회논문지
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• 제64권3호
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• pp.384-392
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• 2015

This paper presents an economic assessment of large-scale Li-ion battery energy storage systems applied to Korean power system. There are many applications of the battery energy storage systems (BESSs) and they can provide various benefits to power systems. We consider BESSs to the energy time-shift application to Korean power system and evaluate the benefits from the application of BESS in the social perspective. The mixed integer programming (MIP) algorithm is used to resolve the optimal operation schedule of the BESS. The social benefits can include the savings of the fuel cost from generating units, deferral effects of the generation capacity, delay of transmission and distribution infra construction, and incremental CO2 emission cost impacts, etc. The economic evaluation of the BESS is separately applied into Korean power systems of the Main-land and Jeju island to reflect the differences of the load and generation patterns.

• Journal of Electrical Engineering and Technology
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• 제13권2호
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• pp.752-760
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• 2018

In this paper, interior permanent magnet synchronous motor (IPMSM) design for sensorless drive, considering magnetic neutral point shift according to magnetic saturation, has been proposed. Sensorless control was divided into a method based on inductance and a method based on back induced voltage. Because induced voltage is very small at zero or low speed, error in rotor initial position estimation may occur. Using the ratio of saliency addresses this problem. When using high-frequency injections at low speed, the rotor's initial position is estimated at the smallest portion of the inductance. IPMSM has the minimum inductance at the d-axis. However, if magnetic saturation leads to magnetic neutral point variation, following the load current change, there is a change in the minimum point of inductance. In this case, it can lead to failure of initial rotor position estimation. As a result, it is essential that the blocking design has an inductance minimum point shift. As such, in this study, an IPMSM design method, by blocking magnetic neutral point change, has been proposed. After determining the inductance profile based on the finite element analysis (FEA), the results of proposed method were verified.

• 한국정보통신학회논문지
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• 제2권2호
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• pp.223-230
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• 1998

본 논문은 뉴랄퍼지를 이용한 디지탈식 제어기를 고주파 유도 가열기의 전력 조절을 위해 IGBT를 사용한 위상 전이(Phase-Shift) 펄스폭 변조(PWM)와 펄스 주파수 변조(PFM)가 조절되는 공진 고주파 인버터를 응용한 유도가열기를 설명한다. 이는 실제로 산업 현장에서 20KHz~500KHz 유도 가열 및 유도 용해 전원 장치용으로 쓰인다. 위상 전이(Phase-Shift) PWM 정전력 조절 기술을 바탕으로 한 적응 주파수 추종 기법은 스위칭 손실을 최소화하고 전력조절을 용이하게 하기 위해 소개되어졌다. IGBT를 사용하여 실험적으로 만들어진 실험장치는 성공적으로 논증과 토의가 되어졌다.

• Journal of Power Electronics
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• 제15권1호
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• pp.18-30
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• 2015

This paper focuses on a systematical and in-depth analysis of the reactive power and soft-switching regions of Dual Active Bridge (DAB) converters with dual-phase-shift (DPS) control to achieve high efficiency in a wide operating range. The key features of the DPS operating modes are characterized and verified by analytical calculation and experimental tests. The mathematical expressions of the reactive power are derived and the reductions of the reactive power are illustrated with respect to a wide range of output power and voltage conversion ratios. The ZVS soft-switching boundary of the DPS is presented and one more leg with ZVS capability is achieved compared with the CPS control. With the selection of the optimal operating mode, the optimal phase-shift pair is determined by performance indices, which include the minimum peak or rms inductor current. All of the theoretical analysis and optimizations are verified by experimental tests. The experimental results with the DPS demonstrate the efficiency improvement for different load conditions and voltage conversion ratios.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1997년도 하계학술대회 논문집 F
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• pp.2016-2019
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• 1997

To solve the low efficiency problem of low-voltage power supplies, it has been studied to replace the schottky barrier diode with the MOSFET synchronous rectifier. In this paper, Phase Shift-Controlled Clamp Mode Zero Voltage Switching-Multi Resonant Converter with Synchronous Rectifier (PSC CM ZVS-MRC with SR) is presented to achieve high efficiency in low-voltage power supplies. The characteristics analysis of synchronous rectifier is established by using the MOSFET equivalent circuit and efficiency comparison is established between the Synchronous Rectifier and the schottky barrier diode. To verify the validity of the analysis, 33W(3.3V, 10A) PSC CM ZVS-MRC with self-driven synchronous rectifier at switching frequency of 1MHz is designed and tested. And it is confirmed that the experimental results are well consistent with the theoretical results. The maximum efficiency of the converter is 83.4% at full load, which is 3.3% higher than conventional schottky diode rectification.

• 조명전기설비학회논문지
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• 제21권4호
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• pp.61-72
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• 2007

This study proposed a high efficiency DC-DC converter with a new current doubler rectifier for fuel-cell systems for use with the Nexa(310-0027) PEMFC from the Ballard Co. The proposed high efficiency DC-DC converter for the fuel-cell system generated ZVS by applying partial resonance and using a phase shift PWM control method. Constantly switching frequency, loss of switching, peak current, and peak voltage were reduced by this system. In addition to this system, two inductors were attached to a rectifier circuit allowing it to be able to provide the direct current(DC) and DC voltage safely to a load with reduced ripple components. Also, by using the newly proposed current doubler rectifier, the high frequency DC-DC converter for the fuel cell system was capable of reaching a highest efficiency of 92[%] as compared to 88.3[%] efficiency in previous results, which means that efficiency increased 3.7[%]. The overall results were confirmed by a simulation and laboratory experiment.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2002년도 전력전자학술대회 논문집
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• pp.370-373
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• 2002

A new phase shift full bridge converter(PSFB) with serially connected two transformers is proposed. It is well suited for applications in the communication equipment of a few hundred watts. The main features of the proposed converter are a wide input voltage range, an easiness to meet the requirement for zero voltage switching (ZVS) condition at a light load, and a small output voltage ripple. Furthermore, it features high power density since serially connected two transformers can replace both a main transformer and an output inductor. A mode analysis and experimental results are presented to verify the validity of the proposed converter.

• 대한산업공학회지
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• 제19권4호
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• pp.87-96
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• 1993

Spectrum analysis of surface electromyogram (FMG) signals is an effective approach to the study of localized muscular fatigue during isometric contraction. Many investigators have con firmed the frequency of the EMG signals being lowered during sustained contaction. In this study, the cyclic loading tasks were performed, and a comparison was made for the median power frequency shift pattern of the EMG signals with the sustained contraction of the same load. The median power frequency shift of the EMG signals for the cyclic loading task was found to be a part of that for the sustained contraction. Based on this result, a new muscle fatigue index was computed by normalizing the duration of the sustained contraction. A fatigue index was obtained as a function of exertion level and the work/rest schedule. With the proposed fatigue index, it is possible to evaluate or predict the degree of muscular fatigue for a physically demanding task.