• 전력전자학회논문지
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• 제8권6호
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• pp.504-511
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• 2003

본 연구에서는 네온 변압기를 세라믹 계열의 압전 변압기를 이용한 인버터식 네온관용 변압기를 제안하였다 인버터식 네온관용 압전 변압기의 주요 구성은 정류부, 발진부, 공진형 하프브릿지 인버터회로부 및 압전 변압기부로 구성 제작하였다. 네온관용 변압기는 지금까지 개발된 압전 변압기 용량 보다 대부분 큰 용량을 필요로 하고 있기 때문에 압전 변압기의 용량 증가를 위해 병렬 구동하였다 이때 병렬로 연결된 단층형 압전 변압기간 내부 임피던스 값의 불일치로 발생하는 불평형 전류를 최소화 하기 위하여 압전 변압기별로 LC 필터값을 분석 부착하여 전압의 왜곡율을 최소화 하여 안정된 정현파 출력을 구현하였다. 그리고 이를 컴퓨터 시뮬레이션 실험과 실제 네온관 부착 실험을 통하여 전력 밀도와 절연 레벨이 높고, 누설 자속이 없는 소형, 경량화된, 압전 변압기를 적용한 인버터식 네온관용 변압기가 기존의 자기식 네온관용 변압기 보다 우수함을 비교 입증하였다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2006년도 제37회 하계학술대회 논문집 C
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• pp.1657-1658
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• 2006

An external electrode fluorescent lamps (EEFLs) have the advantage of a long lifetime in the early stages of the study on plasma discharge, interest in the lamp continues. Studies on the operation of external electrode fluorescent lamps have focused mainly on its use of a type of high frequency (MHz). By performing high brightness using a square wave operation method with the low frequency below 100kHz, which is applied to a narrowed tube type lamp that has several mm of lamp diameter. To solve these problems of CCFL, EEFL (External Electrode Fluorescent Lamp) is introduced. Because electrode of EEFL is on the outer surface of discharge tube, the electrode is perfectly prevented from the sputtering by accelerated ions. And it is possible to drive the many CCFLs at the same time, because EEFL shows the positively resistant characteristic. But EEFL has the large non-radiative power loss in sheath. In this study the novel electrode structure was introduced in order to reduce non-radiative power loss in sheath of EEFL. The novel electrode structure comes from the idea to combine conceptually capacitive discharge with inductive discharge. Thus, this study verifies the change in the optical characteristics according to the change in electrode structure through a Maxwell's electromagnetic field simulation and examines the relationship between the change in the EEFL electrode structure and brightness by measuring the optical characteristics.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2006년도 제37회 하계학술대회 논문집 C
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• pp.1621-1622
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• 2006

This paper presents the effect of driving waveform for piezoelectric bend mode inkjet printhead with optimized mechanical design. Experimental and theoretical studies on the applied driving waveform versus jetting characteristic s were performed. The inkjet head has been designed to maximize the droplet velocity, minimize voltage response of the actuator and optimize the firing frequency to eject ink droplet. The head design was carried out by using mechanical simulation. The printhead has been fabricated with Si(100) and SOI wafers by MEMS process and silicon direct bonding method. To investigate how performance of the piezoelectric ceramic actuator influences on droplet diameter and droplet velocity, the method of stroboscopy was used. Also we observed the movement characteristics of PZT actuator with LDV(Laser Doppler Vibrometer) system, oscilloscope and dynamic signal analyzer. Missing nozzles caused by bubbles in chamber were monitored by their resonance frequency. Using the water based ink of viscosity of 4.8 cps and surface tension of 0.025N/m, it is possible to eject stable droplets up to 20kHz, 4.4m/s and above 8pL at the different applied driving waveforms.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 하계학술대회 논문집 C
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• pp.1867-1869
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• 2003

In this paper, chamber(Circuit breaker compartment of C-GIS) made of stainless steel with 4 mm width is used. Artificial defect was made on enclosure or HV conductor of chamber and $SF_6$ gas was injected into it according to pressure. In this experiment, Acoustic emission sensors of different types was used to compare sensitivity to detect acoustic signal occurred by Partial discharge(PD) of according to types and resonance frequency in $SF_6$ gas atmosphere. Sensors used in tests was R6I, R15I and 2/4/6 Pre-Amplifier connected with R6IU without pre. amp. In case of R6IU, gain was adjusted with 40 dB like other sensors and operated by differential mode. Post amplifier(post. amp) and band pass filter(BPF) were developed Gain of post. amp. is 60 dB and BPF has band width of $50{\sim}300$ kHz. Also, envelope circuit developed reduces frequency of AE sensor. As a result, in $SF_6$ atmosphere, R6IU and R6I had resonance frequency of 60 Hz was better than R15I. Also, R6IU was better than R6I because of type property of pre.amp. had differential mode.

• 대한지역사회영양학회지
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• 제11권6호
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• pp.779-784
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• 2006

Several studies about hospital malnutrition have been reported that about more than 40% of hospitalized patients are having nutritional risk factors and hospital malnutrition presents a high prevalence. People in a more severe nutritional status ended up with a longer length of hospital stay and higher hospital cost. Nutrition screening tools identify individuals who are malnourished or at risk of becoming malnourished and who may benefit from nutritional support. For the early detection and treatment of malnourished hospital patients , few valid screening instruments fur Koreans exist. Therefore, the aim of this study was to develop a simple, reliable and valid malnutrition screening tool that could be used at hospital admission to identify adult patients at risk of malnutrition using medical electrical record data. Two hundred and one patients of the university affiliated medical center were assessed on nutritional status and classified as well nourished, moderately or severely malnourished by a Patient-Generated subjective global assessment (PG-SGA) being chosen as the 'gold standard' for defining malnutrition. The combination of nutrition screening questions with the highest sensitivity and specificity at prediction PG-SGA was termed the nutrition screening index (NSI). Odd ratio, and binary logistic regression were used to predict the best nutritional status predictors. Based on regression coefficient score, albumin less than 3.5 g/dl, body mass index (BMI) less than $18.5kg/m^2$, total lymphocyte count less than 900 and age over 65 were determined as the best set of NSI. By using best nutritional predictors receiver operating characteristic curve with the area under the curve, sensitivity and 1-specificity were analyzed to determine the best optimal cut-off point to decide normal or abnormal in nutritional status. Therefore simple and beneficial NSI was developed for identifying patients with severe malnutrition. Using NSI, nutritional information of the severe malnutrition patient should be shared with physicians and they should be cared for by clinical dietitians to improve their nutritional status.

• 한국주조공학회지
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• 제25권6호
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• pp.259-264
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• 2005

The copper clad steel wire is used extensively as lead wires of electronic components such as capacitors, diodes and glass sealing lamp because the wire combines the strength and low thermal expansion characteristic of Fe-Ni steel with the conductivity and corrosion resistance of copper. In order to fabricate the copper clad steel wire, several processes including electro-plating, tubecladding extrusion process and dip forming process have been introduced and applied. The electroplating process for the production of copper clad steel wire shows poor productivity and induces environmental load generation such as electroplating solution. The dip forming process is suitable to mass production of copper clad steel such as trolley wire. and need expensive manufacturing facilities. The present paper describes the improvement of the conventional continuous casting process to fabricate copper clad steel wire, which its core metal is low thermal expansion Fe-Ni alloy and its sheath material is copper. In particular, the formation of intermetallic compound at interface between core and sheath was investigated in order to introduce optimum continuous casting process parameter for fabrication of copper clad steel wire with higher electrical conductivity. The mechanical strength of copper clad steel wire was also investigated through wiredrawing process with of 95% in total reduction ratio.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2006년도 춘계종합학술대회
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• pp.693-696
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• 2006

본 연구에서는 생체 임피던스의 변화를 계측하여 혈류량의 변화를 추정하기 위한 시스템을 구현하였다. 구현된 시스템은 인위적인 압력을 가하여 압력의 변화에 따른 임피던스의 변화량을 측정할 수 있도록 구성하였으며, 크게 압력 측정부와 4 전극법을 이용한 임피던스 측정부로 구분할 수 있다. 압력 측정부는 반도체식 압력센서와 센서의 출력신호를 처리하기 위한 전자회로부로 구성하였고, 임피던스 측정부는 교류 정전류원 회로와 임피던스 신호의 검출을 위한 락인 증폭기로 시스템을 구성하였다. 구현된 시스템의 성능평가를 위하여 표준저항을 이용한 임피던스 측정부의 특성조사 실험을 수행 하였다. 그리고 실제 실험군을 대상으로 임피던스의 계측을 통한 혈류량 변화 추정실험을 수행하였고, 혈류량 변화와 평균 동맥압을 이용한 혈류 저항비를 추정하였다 그 결과 혈류저항비와 혈류량의 변화는 반비례관계를 명확하게 보여 주었으며, 상관분석을 수행한 결과 상관계수가 -0.96776으로 강한 음의 상관관계를 나타내었다.

• 한국정보통신학회논문지
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• 제17권12호
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• pp.2914-2920
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• 2013

본 논문은 동시진공증발법으로 제작된 시편을 $500^{\circ}C$에서 열처리한 시편은 기공이 많이 발생되어 결정결함이 발생 되었어 열처리 시 Se분위기하에서 실행을 해야 된다는 것을 알 수가 있었다. 기판온도를 $430^{\circ}C$, $460^{\circ}C$, $480^{\circ}C$, $500^{\circ}C$로 변화주어 제작된 시편을 열처리 한 결과 결정입자 크기가 증가되어 밀도가 향상되었다. 그리고 XRD 분석결과, 열처리 후에 Cu2Se상이 제거되었으며 열처리 전 후의 흡수지수는 큰 변화가 없었다. 이것은 흡수지수는 열처리보다 시편 두께에 의해 결정된다는 것을 알 수가 있었다.

• 한국구조물진단유지관리공학회 논문집
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• 제20권4호
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• pp.84-93
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• 2016

전자기파가 콘크리트 교량 바닥판을 통과할 때 에너지 손실 메카니즘에 의해 신호의 감쇠가 발생하며, 이는 콘크리트의 상대유전율과 전도도, 그리고 지리적 산란 손실의 영향에 따른 것으로 알려져 있다. 본 연구에서는 건전한 콘크리트에 대해서는 레이더파의 감쇠가 상부철근의 깊이와 선형관계에 있다는 점에 착안하여, 일체식 콘크리트 교량 바닥판에서 상태평가 지표로서의 레이더파의 신호감쇠를 실 교량에 적용하여 그 유용성에 대해 검토하였다. 연구결과, 손상된 콘크리트 교량 바닥판에서는 건전한 상태에 비해 상대적으로 큰 감쇠가 일어나며, 레이더 수신파의 총감쇠량에서 반사체의 깊이에 대해 선형적 관계인 부분을 제거하고 난 보정감쇠량은 일체식 콘크리트 교량 바닥판의 상태평가에 유용한 것으로 나타났다. 실제 공용 중인 손상 교량 바닥판에 적용한 결과, 제안된 방법은 교면에서 상부철근까지의 콘크리트 상태를 신뢰성 있게 평가할 수 있으며, 특히, 일체식 바닥판의 주손상요인인 상부철근의 부식환경을 간접적으로 평가할 수 있는 것으로 판단된다.

• Journal of Power Electronics
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• 제17권4호
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• pp.849-859
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• 2017

This paper illustrates the analysis and design of a multi-resonant converter applied to an electric vehicle (EV) charger. Thanks to the notch resonant characteristic, the multi-resonant converter achieve soft switching and operate with a narrowed switching frequency range even with a wide output voltage range. These advantages make it suitable for battery charging applications. With two more resonant elements, the design of the chosen converter is more complex than the conventional LLC resonant converter. However, there is not a distinct design outline for the multi-resonant converters in existing articles. According to the analysis in this paper, the normalized notch frequency $f_{r2n}$ and the second series resonant frequency $f_{r3n}$ are more sensitive to the notch capacitor ratio q than the notch inductor ratio k. Then resonant capacitors should be well-designed before the other resonant elements. The peak gain of the converter depends mainly on the magnetizing inductor ratio $L_n$ and the normalized load Q. And it requires a smaller $L_n$ and Q to provide a sufficient voltage gain $M_{max}$ at ($V_{o\_max}$, $P_{o\_max}$). However, the primary current increases with $(L_nQ)^{-1}$, and results in a low efficiency. Then a detailed design procedure for the multi-resonant converter has been provided. A 3.3kW prototype with an output voltage range of 50V to 500V dc and a peak efficiency of 97.3 % is built to verify the design and effectiveness of the converter.