• Journal of Life Science
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• v.15 no.2 s.69
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• pp.311-315
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• 2005

When paraquat was added to the bacterial membrane or mitochondrial suspension, the mixture turned dark blue, but the color was disappeared by aeration. The same phenomenon was seen when electrons were supplied to the paraquat. Blue color appeared from near the cathode, and then spreaded to whole transit system. Coloration was accelerated by addition of alkali, but the color was reduced by addition of acid or oxygen. Paraquat exhibited absorption at ultraviolet region by electron transfer at the concentrations as low as 1.0 mM which did not exert difficulty in showing color reaction. Paraquat caused the increase of the optical density at 340 nm by electron transit, and an aspect of that had a strong resemblance to NADH. The acute toxic action of paraquat seemes to depend on inhibition of energy metabolism cased by paraquat action of electron donor and acceptor.

• Journal of the Society of Naval Architects of Korea
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• v.34 no.4
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• pp.42-52
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• 1997

The basic principle of underwater ram-jet as a unique marine propulsion concept showing vary high cruise speed range(e. g. 80-100 knots) is the thrust production by the transfer of the potential energy of compressed gas to the operating liquid through kinetic mixing process. This paper is aimed to investigate the propulsive efficiency of the nozzle flow in underwater ram-jet at the speed of 80 knots for the buried type vessel. The basic assumption of the theoretical analysis is that mixture of water and air can be treated as incompressible gas. For an optimized nozzle configuration obtained from the performance analysis, preliminary data for performance evaluation are obtained and effects of nozzle inner wall friction, ambient temperature, ambient pressure, water density, gas velocity, bubble radius, flow velocity, diffuser area ratio, mass flow ratio and water velocity gradient are investigated.

• 한국신재생에너지학회:학술대회논문집
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• 2011.11a
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• pp.99.2-99.2
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• 2011

Transparent conducting oxides (TCOs) supported on glass are widely used as substrates in PEC studies for photovoltaic hydrogen generation applications However, high sheet resistane ($10{\sim}15{\Omega}/cm^2$) and fragileness of glass-supported TCO substrates are the obstacles to produce the large area PEC cells. Such internal sheet resistance is detrimental to efficient collection of photogenerated majority charge carriers at the photoactive material and electrolyte interface. Moreover, these TCO substrates are very expensive and consume about 40~60% cost of the devices. Hence, a low sheet resistance of the substrate is a key point in improving the performance of PEC devices. Metallic substrates coated with a photoactive material would be a good choice for efficient charge collection. Such metal substrates based photanodes are best candidate for large-scale phtoelectrochemical water splitting for hydrogen generation. In this study, we report the enhanced PEC performance of $WO_3$ film on metal(chemical etched, bare) substrate. It is proposed that interface between $WO_3$ and the metal substrate is responsible for efficient charge transfer and demonstrated significant improvement in the photoelectrochmical performance. X-ray diffration and FESEM suduies reveled that $WO_3$ films are monoclinic, porous, polycrystalline with average grain size of ~50nm. Photocurrent of $WO_3$ prepared on metal substrates was measured in 0.5M $H_2SO_4$ electroyte under simulated $100mW/cm^2$ illumination.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.16 no.4 s.109
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• pp.319-328
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• 2006

This paper presents a method for analysis of the mechanical behavior of a crankshaft in a four-cylinder internal combustion engine. The purpose of the analysis was to study the characteristics of the shaft in which the pin and arm parts were assumed to have a uniform section in order to simplify the modal analysis. The results of natural frequency transfer function and mode shape were compared with those obtained by experimental work. The results obtained from the comparison showed a good agreement with each other and consequently verified the analysis model. Furthermore, a prediction of crankshaft characteristics under the firing condition, by using the model, was performed. This study describes a new method for analyzing the dynamic behavior of crankshaft vibrations in the frequency domain based on the initial firing stages. The new method used RMS values to calculate the energy at each bearing journal and counter weight shape modification under the operating conditions.

• Journal of the Korean Society for Nondestructive Testing
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• v.34 no.1
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• pp.38-43
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• 2014

An experimental method based on flexural wave propagation is proposed for identification of structural damage in rail fastening systems. The vibration of a rail clamped and supported by viscoelastic pads is significantly influenced by dynamic support properties. Formation of a defect in the rail fastening system induces changes in the flexural wave propagation characteristics owning to the discontinuity in the structural properties. In this study, frequency-dependent support stiffness was measured to monitor this change by a transfer function method. The sensitivity of wave propagation on the defect was measured from the potential energy stored in a continuously supported rail. Further, the damage index was defined as a correlation coefficient between the change in the support stiffness and the sensitivity. The defect location was identified from the calculated damage index.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.493-494
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• 2011

수 MeV~수십 MeV 양성자빔을 이용해 백금, 은 등의 나노입자 제조실험을 수행하였다. 나노 입자는 의료분야와 산업 분야에서 그 응용성이 다양해 여러 지 방법을 이용한 제조기술이 개발되고 있다. 전자빔, 감마선, 양성자빔 등의 방사선을 이용한 나노입자 제조방법은 가장 널리 이용되고 있는 화학적 제조방법에 비해 비교적 공정이 단순하다는 장점을 가지고 있지만 공정 변수의 제어방법이 확립되어 있지 않아 이에 대한 연구가 필요한 실정이다. 특히, 양성자빔의 경우 에너지에 따른 투과깊이의 조절과 플럭스나 총 선량, LET (Linear Energy Transfer) 등의 변수와 제조된 나노입자의 상관관계 등에 대한 연구가 선행되어야 한다. 본 논문에서는 백금산 용액을 이용한 나노입자 제조 결과와 대면적 양성자빔을 이용하기 위한 초음파 이용 나노입자제조장치의 제작 및 실험결과에 대해 논하고 향후 건설될 100MeV 선형 양성자가속장치의 나노입자 제조실험에의 응용을 위한 이용시설을 소개하고자 한다. 나노입자 제조실험은 한국원자력의학원의 MC-50 싸이클로트론을 이용하여 수행하였으며, 가속기로부터 인출되는 에너지는 35, 45MeV, 빔전류는 수십 nA~수${\mu}A$의 범위 내에서 조절하였다. 제조된 나노입자는 TEM을 이용하여 그 크기와 분포를 관찰하였다. 대면적의 양성자빔을 이용하는 경우, 수mm의 두께와 수십 cm의 직경을 가지는 원반 모양의 시료용기를 사용하여 양성자빔의 에너지와 선량을 정확히 조절할 수 있게 되는데 이 때 용기 내 시료와 양성자빔간의 균일한 반응을 위해 용액을 적절하게 섞어 주어야만 한다. 이러한 목적으로 초음파를 이용하여 나노입자 제조장치를 제작하여 실험을 수행하였다. 나노입자 제조는 현재 교과부의 지원으로 경주 건천지역에 건설되고 있는 100MeV 선형양성자가속기의 주요 이용 분야 중의 하나로 20MeV 빔라인 중 한 개의 빔라인과 표적실을 나노입자 제조 등의 실험을 위한 시설로 구축 중이다. 최대 평균전류 1.6mA 까지 가능하고 펄스폭은 0.05~1.33 msec까지 조절가능하도록 개발되고 있다.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.252-253
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• 2011

ZnO-based thin film transistors (TFTs) are of great interest for application in next generation flat panel displays. Most research has been based on amorphous indium-gallium-zinc-oxide (IGZO) TFTs, rather than single binary oxides, such as ZnO, due to the reproducibility, uniformity, and surface smoothness of the IGZO active channel layer. However, recently, intrinsic ZnO-TFTs have been investigated, and TFT- arrayss have been demonstrated as prototypes of flat-panel displays and electronic circuits. However, ZnO thin films have some significant problems for application as an active channel layer of TFTs; it was easy to change the electrical properties of the i-ZnO thin films under external conditions. The variable electrical properties lead to unstable TFTs device characteristics under bias stress and/or temperature. In order to obtain higher performance and more stable ZnO-based TFTs, HZO thin film was used as an active channel layer. It was expected that HZO-TFTs would have more stable electrical characteristics under gate bias stress conditions because the binding energy of Hf-O is greater than that of Zn-O. For deposition of HZO thin films, Hf would be substituted with Zn, and then Hf could be suppressed to generate oxygen vacancies. In this study, the fabrication of the oxide-based TFTs with HZO active channel layer was reported with excellent stability. Application of HZO thin films as an active channel layer improved the TFT device performance and bias stability, as compared to i-ZnO TFTs. The excellent negative bias temperature stress (NBTS) stability of the device was analyzed using the HZO and i-ZnO TFTs transfer curves acquired at a high temperature (473 K).

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.158-158
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• 2012

A new kind of organic-inorganic hybrid polymer, poly(tetraphenyl)silole siloxane (PSS), was invented and synthesized for realization of its unique charge trap properties. The organic portions consisting of (tetraphenyl)silole rings are responsible for electron trapping owing to their low-lying LUMO, while the Si-O-Si inorganic linkages of high HOMO-LUMO gap provide the intrachain energy barrier for controlling electron transport. Such an alternation of the organic and inorganic moieties in a polymer may give an interesting quantum well electronic structure in a molecule. The PSS thin film was fabricated by spin-coating of the PSS solution in THF organic solvent onto Si-wafer substrates and curing. The electron trapping of the PSS thin films was confirmed by the capacitance-voltage (C-V) measurements performed within the metal-insulator-semiconductor (MIS) device structure. And the quantum well electronic structure of the PSS thin film, which was thought to be the origin of the electron trapping, was investigated by a combination of theoretical and experimental methods: density functional theory (DFT) calculations in Gaussian03 package and spectroscopic techniques such as near edge X-ray absorption fine structure spectroscopy (NEXAFS) and photoemission spectroscopy (PES). The electron trapping properties of the PSS thin film of quantum well structure are closely related to intra- and inter-polymer chain electron transports. Among them, the intra-chain electron transport was theoretically studied using the Atomistix Toolkit (ATK) software based on the non-equilibrium Green's function (NEGF) method in conjunction with the DFT.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.39 no.5
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• pp.474-480
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• 2011

Space Imaging Sensor operated on LEO is affected from the Earth IR and Albedo as well as the Sun Radiation. The Imaging Sensor exposed to extreme environment needs thermal control subsystem to be maintained in operating/non-operating allowable temperature. Generally, units are periodically dissipated on spacecraft panel, which is designed as radiator. Because thermal design of the imaging sensor inside a spacecraft is isolated, heat pipes connected to radiators on the panel efficiently transfer dissipation of the units. First of all, preliminary thermal design of radiating area and heater power is performed through steady energy balance equation. Based on preliminary thermal design, on-orbit thermal analysis is calculated by SINDA, so calculation for thermal design could be easy and rapid. Radiators are designed to rib-type in order to maintain radiating performance and reduce mass. After on-orbit thermal analysis, thermal requirements for Space Imaging Sensor are verified.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.2 no.3
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• pp.119-127
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• 1990

Wave directional spectrum estimation methods for irregular waves were considered in this study. Until now, the Longuet-Higgins Method (LHM) initiated by Longuet-Higgins et al. (1963) has been widely used, but resolutions of the estimation were found to be low. Kobune's Maximum Entropy Method (MEM) for the estimation of wave directional spectrum, bas-ed on the entropy Principle showed higher resolutions comparing with the LHM . If the wave directional spectrum is of Delta functions, the MEM is exact in its estimation. It was also found that for a unimodal spectrum, if the Mitsuyasu's spreading coefficient is above 5, the estimation resolutions were high. In bimodal spectrum, as the angle difference between the two peaks increased, the resolution improved. The energy seems to transfer to the smoother peak in the smoothing of peak's peakedness. LHM has a tendency to estimate bimodal spectrum as a unimodal spectrum ； thus, except for its computational speed, the resolution of LHM falls far below that of MEM.