• Journal of the Institute of Electronics and Information Engineers
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• v.52 no.12
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• pp.124-133
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• 2015

Electro interstitial scan shows potential as a non-invasive screening method. It can discriminate some diseases based on electric current response to induce low intensity direct current to limbs or local area of body. DDFAO was invented in France and it is claimed that multi-channel EIS(Electro Interstitial Scan) is useful for various diseases, especially, diagnoses of endocrine system such as diabetics are very effective. In this study, we verified the repeatability and sensitivity of DDFAO by using a RC phantom model and its clinical usefulness using data obtained from normal and diabetes subject groups. As a result, it showed the repeatability and the output change according to change of phantom characteristic, but it was hard to distinguish normal and patient groups non-invasively with just six surface electrodes of DDFAO. The repeatability and the clinical accuracy was not sufficient for screening or diagnostic purposes, as well. In spite of the results with low repeatability and accuracy conducted in this study, we still need further investigations to improve the EIS-based measurement method; EIS is very convenient and simple and it shows potential as a screening tool of the whole body health conditions rather than localized disease diagnosis.

• Journal of Navigation and Port Research
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• v.26 no.1
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• pp.22-27
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• 2002

The 25 Watt hybrid MIC SSPA has been developed in the frequency rang from 1.6265 GHz to 1.6465 GHz for uplink of INMARST's earth station. To simplify the fabrication process, the whole system is designed of two parts composed of a friving amplifier and a power amplifier. The Motorolas MRF-6401 is used for driving part, the Motorolas MRF-16006 and MRF-16030 is used the power amplifier. We reduced weight and volume of high power amplifier through arranging the bias circuits in the same housing. The realized SSPA has more than 30 dB for gain within 20 MHz bandwidth, and the voltage standing wave ratios(VSWR) of input and output port are less than 1.7, respectively. The output power of 44 dBm is achieved at the 1 dB gain compression point of 106365 GHz These results reveal a high power amplifier of 25 Watt which is the design target. The Proposed SSPA manufacture techniques in this paper can be applied to the implementation of high power amplifiers for some radars and SCPC.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.311-311
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• 2014

III-N계 물질로 이루어진 GaN 기반의 광 반도체는 직접 천이형 넓은 밴드갭 구조를 갖고 있기 때문에 적외선부터 가시광선 및 자외선까지를 포함한 폭 넓은 발광파장 조절이 가능하여 조명 및 디스플레이 관련 차세대 광원으로 많은 관심을 받고 있다. 하지만, GaN기반의 발광 다이오드는 많은 연구기관들의 오랜 연구에도 불구하고 고출력을 내는데 있어 여전히 많은 문제들이 존재한다. 그 중, 주입전류 증가에 따른 효율감소 현상은 출력을 저해하는 대표적인 요소로 알려져 있는데, 이전의 연구 결과에서 알려진 효율감소 현상의 원인으로 결정결함에 의한 누설전류, Auger 재결합, 이송자 넘침 현상 그리고 p-n접합부의 온도 상승 등의 현상이 알려져 있다 [1-2]. 하지만 여전히 주입 전류 증가에 따른 효율 감소 현상의 원인에 대해 명확한 해답은 없으며 아직도 많은 논의가 이루어 지고 있다. 따라서, 본 연구에서는 GaN기반의 청색 및 녹색 LD와 LED소자를 이용하여 주입전류 밀도의 변화에 따른 자발 발광 영역에서의 효율감소 현상의 원인을 규명하고 한다. 유기금속화학증착법(MOCVD)를 이용하여 c면 사파이어 위에 서로 다른 발광파장을 가지는 InGaN/GaN 다중양자우물구조의 질화물계 LED와 LD 박막을 제작하였으며 성장 구조에 의한 특성으로 인해 발생하는 효율 저하 현상을 방지하고자 InGaN/GaN으로 이루어진 다중양자우물층의 조성만 제어하여 청색과 녹색으로 발광하도록 하였다. 청색 및 녹색 LD 웨이퍼들을 이용하여 주입전류 증가에 따른 발광특성을 조사하기 위해 LD와 LED는 표준 팹 공정에 의해 제작되었다. 전계 발광 측정을 위해 상온에서 직류 전류를 주입하여 GaN계 청색 및 녹색 LED와 LD에 각 5 mA/cm2에서 50 mA/cm2까지 전류밀도를 증가시킴에 따라 LD 및 LED칩 형태에 상관없이 청색 LD와 LED의 파장은 약 465nm에서 약 458nm로 감소하였고 녹색 LD와 LED의 파장은 약 521nm에서 약 511~513 nm까지 단파장화가 발생했다. 이는 동일한 웨이퍼에 동일한 전류 밀도를 주입하였기 때문에 발생하는 것으로 판단된다. 그러나, 청색 LED의 효율은 50 mA/cm2에서 약 70%정도로 감소하고 반면 녹색 LED의 경우 동일한 전류밀도 하에 약 52%정도로 감소하였지만, 청색과 녹색 LD의 경우 동일한 전류 밀도의 범위 내에서 더욱 낮은 효율저하 현상을 나타내었다. 또한, 접합 온도를 측정한 바 청색소자가 녹색 소자에 비하여 낮은 접합 온도를 나타낼 뿐아니라, 청색 및 녹색 LD의 경우 LED 보다 낮은 접합 온도를 나타내고 있었다. 이는 InGaN 활성층의 In 조성이 증가할수록 비발광 센터에 의한 접합온도 상승 뿐 아니라, LD ridge 구조에서 더 많은 열이 방출되어 접합 온도가 감소될 수 있는 것으로 판단된다. 우리는 동일한 웨이퍼에 LED와 LD를 제작하였고, 동일한 전류 주입밀도를 인가하였기 때문에 LD와 LED의 효율 감소 현상의 차이는 이송자 넘침 현상, 결정 결함, 오제 재결합 등이 원인보다 활성층의 접합 온도 상승이 가장 큰 영향이 될 수 있을 것으로 판단된다.

• Polymer(Korea)
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• v.29 no.4
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• pp.363-367
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• 2005

The effects of organic solvent on the charge transport behavior of poly (3,4-ethylenedioxythioph one)/p-toluene-sulfonate(PEDOT-OTs) are investigated. The use of different organic solvents during the oxidative chemical polymerization of 3,4-ethylenedioxythiophene (EDOT) with Iron(III) -tosylate can greatly vary the DC conductivity of PEDOT-OTs along with molecular structure and doping concentration. For example, PEDOT-OTs prepared from methanol shows the conductivity of 19.5 S/cm, which is an increase by a factor of $10^8$ compared to PEDOT-OTa prepared from acetone. From the X-ray diffraction (XRD) experiments, it was found that PEDOT-OTs with ketone is amorphous state, while PEDOT-OTs with alcoholic solvent shows the better defined crystalline structure in which the charge transport along and between the PEDOT chains are promoted. Chemical analysis employing X-ray photoelectron spectroscopy (XPS) revealed that the doping concentration of PEDOT-OTs with alcoholic solvent is much higher than that of PEDOT-OTs with ketones. It is proposed that the interactions between the organic solvent and doping anion can cause the variation in doping concentration and, therefore, result in the PEDOT-OTs of different conductivities and chain structures.

• Analytical Science and Technology
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• v.5 no.3
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• pp.249-261
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• 1992

Electrochemical behavior of the heavy lanthanide complexes of alizarin red S(ARS) has been investigated by d. c. polarography, differential pulse polarography and cyclic voltammetry. The reduction mechanism at a mercury electrode of alizarin red S as a complexing ligand showed a one step of two-electron transfer and the electron process is found to be reversible. Alizarin red S forms a 3:1 adsorptive complexes with lanthanides and the complexes are reduced via one step of two-elctron. The reduction potential of complex wave($P_2$) shifted more negatively than the ligand wave($P_1$). The linear calibration curves of the decreacing $P_1$ and increasing $P_2$ is obtained when the lanthanide concentration varies from $2.0{\times}10^{-6}M$ to $6.4{\times}10^{-5}M$ under the condition of pH 9.5, 0.1M LiCl and $1{\times}10^{-3}M$ ARS.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.36 no.4
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• pp.314-321
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• 2000

In order to obtain the fundamental data on the auditory thresholds of fishes for catching method using low frequency sound, the auditory thresholds of coralfish Chromis notatus were measured in the presence of masking noise in the spectrum level range of 73~83dB re l$\mu$Pa/√Hz by heartbeat conditioning technique using pure tones coupled with a delayed electric shock. Critical ratios were about 23~41dB at measurement frequency, The critical ratio increased almost linearly with increasing frequency from 500Hz. The noise spectrum level at the start of masking was about 60~65dB. This suggests that hearing of coralfish is masked in the natural environment with the noise spectrum level above 60dB. The sound pressure level of which the signal sound of 300Hz is recognized by coralfish under the ambient noise is above 88dB and the critical ratio of them is above 23dB. The hearing index of coralfish with ambient noise was 81.

• Fire Science and Engineering
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• v.30 no.4
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• pp.121-127
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• 2016

This study analyzed the structural and electrical characteristics of an iron fittings type Corrugated Stainless Steel Tubing (CSST) damaged by the Primary Current Injection Test System (PCITS). CSST consists of cladding, tube, nuts, clamp ring, flare cap, socket, and ball valve. For an evaluation of the dielectric withstand voltage, the area between the live part and non-live part of the CCST shall withstand a voltage of 220 V AC for one minute. For an evaluation of the insulation performance by 500 V DC, it is required that the insulation exceed more than $1M{\Omega}$ before the temperature rise test, $0.3M{\Omega}$ after the test. Although the average resistance of the product was $11.5m{\Omega}$, that of the product damaged at a current of 130 A by the PCITS was $11.50m{\Omega}$. Furthermore, parts of the cladding were melted and black smoke appeared when a current of 130 A applied for 10 s. After 60 s, most parts were heated and turned red. At 120 s, the parts that turned red had widened. Although it did not form a normal distribution because the P value was 0.019 with a confidential interval of 95%, it revealed outstanding characteristics with an AD (Anderson-Darling) value of 0.896 and a standard deviation of 0.5573.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.9 no.2
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• pp.360-369
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• 2008

The solar cells should be operated at the maximum power point because its output characteristics were greatly fluctuated on the variation of insolation, temperature and load. It is necessary to install an inverter among electric power converts by means of the output power of solar cell is DC. The inverter is operated supply a sinusoidal current and voltage to the load and the interactive utility line. In this paper, the proposes a photovoltaic system is designed with a step up chopper and single phase PWM voltage source inverter. Synchronous signal and control signal was processed by one-chip microprocessor for stable modulation. The step up chopper is operated in continuous mode by adjusting the duty ratio so that the photovoltaic system tracks the maximum power point of solar cell without any influence on the variation of insolation and temperature for solar cell has typical dropping character. The single phase PWM voltage source inverter is consists of complex type of electric power converter to compensate for the defect, that is, solar cell cannot be develop continuously by connecting with the source of electric power for ordinary using. It can be cause the efect of saving electric power, from 10 to 20%. The single phase PWM voltage source inverter operates in situation, that its output voltage is in same phase with the utility voltage. The inverter are supplies an ac power with high factor and low level of harmonics to the load and the utility power system.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.38 no.12
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• pp.1240-1246
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• 2010

Enthalpy probe with the inner and outer diameters of 1.5 mm and 4.8 mm, respectively, is designed and used to measure the temperatures and velocities along the centerline of Ar arc plasma flow until the probe was destroyed. For this purpose, Ar arc plasma flow is generated by non-transferred type DC arc heater with the power level of 17 kW. From this experiment, it is shown that the designed enthalpy probe can measure the temperature and velocity of arc plasma flow up to 12,000 K and 600 m/s, respectively, without destroy of probe tip. In this extreme case, the arc plasma flow is calculated to transfer the heat flux of ${\sim}5{\times}10^7\;W/m^2$ to the probe based on the heat and thermal boundary equations near the forward stagnation point of a body immersed in arc plasma flow. Consequently, the designed enthalpy probe can measure the wide ranges of plasma temperatures, velocities and concentrations simultaneously, which are generated by various types of arc heaters within the heat flux ranges of $0{\sim}5{\times}10^7\;W/m^2$ on the probe tip.

• Journal of the Korean Society for Nondestructive Testing
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• v.30 no.4
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• pp.386-395
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• 2010

The steam generator management program(SGMP) has recently defined the procedures for the qualification of eddy current hardware and technique. These procedures provide two basic methods for qualification. The first way is to qualify the equipment or the probe by using the flaw mechanism and method of the pulled tubes from the heat exchangers or the artificial flawed tubes. The second way is to verify the equivalency with the characteristics of the qualified equipment or probe. In this case, the qualified equipment or probe may be modified to substitute or replace instruments or probes without re-qualification provided that the range of essential variables defined in the examination technique specification sheet are met. This study is to describe the result of the comparative performance evaluation of bobbin coil eddy current probes manufactured by KEPCO Research Institute and probes manufactured by a foreign manufacturer. As a result of this study, although there were minor differences between the two kinds of probes, it was evaluated that the two kinds of probes were almost identical in the significant performance characteristics described in the KEPCO Research Institute guideline.