• 한국전기전자재료학회논문지
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• 제17권9호
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• pp.988-993
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• 2004

Luminescence characteristics of Ag-doped ZnO as the quantum dot materials to increasing the efficiency on dye-sensitized solar cells (DSC) have been studied. Ag doped ZnO powder was produced by the self-sustaining combustion process using ultrasonic spraying heating method. Luminescence wavelength region of the ZnO by Ag doping was shifted to longer wavelength. Tn the case of the Ag doped ZnO powder, broad luminescence spectrum centered on 600nm was observed. On the other hand, we compared PL data of RTA treated ZnO:Ag film at various temperatures because the front electrode of solar cell was in need of the sintering process. In XRD and PL data for RTA treated film at the 500$^{\circ}C$ showed good property. And, it was found that the grain size wasn't growing but only optical property was changed. According to the result of XRD, PL, absorption, emission spectrum and DV-X${\alpha}$ used in theoretical calculation, it is considered to be possible to use Ag doped ZnO as quantum dot material for improving DSC efficiency.

• 한국연소학회:학술대회논문집
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• 대한연소학회 2003년도 제27회 KOSCO SYMPOSIUM 논문집
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• pp.251-256
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• 2003

The capability of pilot injection with small fuel quantity at all engine operating conditions is one of the main feature of the common rail system. The purpose of the pilot injection is to lower the engine noise and to reduce the NOx emissions. This study describes the pilot spray structure characteristics of the common-rail diesel injectors, solenoid-driven and piezo-driven type, with different electric driving characteristics So, three common-rail injectors with different electric current wave were used in this study. The pilot spray characteristics such as spray speed, spray tip penetration, and spray angle were obtained by spray images, which is measured by the back diffusion light illumination method with optical system for high-speed temporal photography. Also the CFD analysis was carried out for fuel behavior under high pressure in between needle and nozzle of solenoid-driven injector to know the condition of initial injection at experiment test. It was found that pilot injection of common-rail system was effected by rate of injection and temperature of injected fuel and electrical characteristic of the driven injector.

• 동력기계공학회지
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• 제14권3호
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• pp.5-12
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• 2010

The purpose of this study is to analyze heterogeneous distribution of branch-like structure at downstream region of inner spray. The previous many studies about diesel spray structure have yet stayed in the analysis of 2-D structure, and there are very few of informations which are concerned with 3-D analysis of the structure. The heterogeneous distribution of droplets in inner spray affects the mixture formation of diesel spray, and also the combustion characteristics of the diesel engines. Therefore, in order to investigate 3-D structure of evaporative spray the laser beam of 2-D plane was used in this study. Liquid fuel was injected from a single-hole nozzle (l/d=5) into a constant-volume vessel under high pressure and temperature in order to visualize the spray phenomena. The incident laser beam was offset on the central axis. From the images analysis taken by offset of laser beam, we examine formation mechanism of heterogeneous distribution by vortex flow at the downstream of the diesel spray. As the experimental results, the branch-like structure formed heterogeneous distribution of the droplets consists of high concentration of vapor phase in the periphery of droplets and spray tip of branch-like structure. Also the 3-D spatial structure of the evaporative diesel spray can be verified by images obtained from 2-D measurement methods.

• 한국소음진동공학회논문집
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• 제17권9호
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• pp.777-784
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• 2007

With the development of micro electronic circuits and optical equipment, the demand for developing smart munitions with the ability to autonomously search for and attack targets has increased. Since the electronic components within smart munitions are affected by high temperatures, pressure, and impulsive forces upon the combustion of gunpowder, stability and reliability need to be secured for them. Securing those stability and reliability requires soft recovery system which can decelerate smart munitions. A theoretical analysis of flow is performed for the secure recovery of bullets on the basis of Euler equation for compressible fluids. The inner pressure on a pressure tube, the speeds of bullets, and the deceleration of munitions are calculated theoretically. Theoretical results are compared with the data from the experiment with soft recovery system set up at the laboratory.

• 한국정밀공학회지
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• 제20권4호
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• pp.128-135
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• 2003

To decrease environmental damage, the development of environmental friendly fluids provides attractive alternative to the conventional fluids. In this study, the effects of harmful ingredients (Cl, S) contained in the fluids that used in grinding and cutting processes to influence on the nasal cavities of the white rats were measured indirectly. Also, the level of the environmental influence in workshops was graded through analyzing the concentration and chemical ingredients of flying-dust, which generated from the friction and combustion in the cutting process, that for analyzing how harmful the influence of particles to workers then it could be used as the basic data for improving the environment. To improve the conventional machining fluid, which can be harmful on worker's bodies and the environment, the environmental friendly machining method was suggested through analyzing each lubrication properties of vegetable fluid and used-edible oil as alternative fluid. As a result, it was known that an emulsion type fluid might be the main cause leading to some respiratory ailments. Also this paper presents the possibility to use vegetable fluid and used-edible oil as the alternative of cutting fluids.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 춘계학술대회논문집
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• pp.996-1000
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• 2002

A porous tube, comprised of a resin-coated woven fabric has recently been used as an effective component for use in intake systems of internal combustion engines to reduce the intake roaring. For the prediction of the acoustic performance of an engine intake system with a porous woven hose, the acoustic wall impedance of the hose must be known. Because of its peculiar acoustical and structural characteristics, the accurate measurement of the wall impedance ofa porous woven hose is not easy. A new measurement technique is proposed herein, that is valid over the low to mid frequency ranges. The acoustics impedance is inversely estimated from an overdetermined set of measured pressure transmission coefficients for specimens of different lengths and the reflection coefficient of end termination. The method involves only one measurement, and, as a result, it is very simple. The measured TL for samples with arbitrary conditions, arbitrary porous frequency, arbitrary length, and arbitrary mean flow condition, are in reasonably good agreement with values predicted from curve-fitted impedance data.

• 한국재료학회지
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• 제14권12호
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• pp.885-888
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• 2004

$BaMgAl_{10}O_{17}:Eu^{2+}$ for PDP blue phosphor was synthesized using SHS(Self-propagating High temperature Synthesis) method. While Al metal powder was oxidized in this combustion, $Eu_{2}O_3$ was reduced to Eu2+. Therefore the mole ratio of $Al/Al_{2}O_3$ is one of the most important variable of the reaction. When $Al/Al_{2}O_3$ is 2.5/3.75, it has not only appropriate temperature and reaction velocity, but also excellent luminescent property. The sample synthesized in this system has similar characteristics comparing to sample using conventional solid-state reaction.

• 한국자동차공학회논문집
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• 제15권3호
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• pp.183-188
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• 2007

Recently, diesel engine has been frequently applied to RV, SUV and light duty truck due to the good fuel economy and high thermal efficiency. $NO_x$ and PM, environmental pollution materials are basically produced in diesel combustion process. The most important target in diesel engine research is the development of system to reduce the emissions of $NO_x$ and PM. Cooled EGR system is an effective method for the reduction of $NO_x$ emission and PM emission from a diesel engine and EGR cooler is the key component of the system. This study investigates the EGR cooler of oval gas tubes compared with the EGR cooler of shell & tubes to verify the heat exchange efficiency of cooler by means of engine dynamometer tests, rig performance tests and numerical analyses.

• 한국에너지공학회:학술대회논문집
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• 한국에너지공학회 1995년도 추계학술발표회 초록집
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• pp.50-55
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• 1995

향상되어진 93-PCGC-2는 기존의 PCGC-2와 같이 미분탄 연소를 포함하는 다양한 반응성흐름과 비반응성 흐름을 설명하기 위해 2차원 정상상태 모델로 제시되어 졌다. 93-PCGC-2는 실린더형의 축 대칭계에 응용되어질 수 있고, 난류(Turbulence)는 유체역학식과 연소기구 양쪽을 위해 고려되어졌으며, 불연속 세로좌표 방법(Discrete Ordinates Method)을 이용하여 기체, 벽 및 입자들로부터의 복사열(Radiation)을 모사하였다. 입자상은 입자 무리들의 평균 경로들을 따라 해석하는 Lagrangian계의 해석법으로 모델화되어졌다. 석탄의 팽윤(Swelling)과 촤의 반응성에 관한 부모델과 더불어 새롭게 일반화된 석탄 탈휘발화 부모델 (FG-DVC)도 첨가되어졌다. 비균일 반응기구는 확산과 화학반응 둘 모두를 고려하였다. 주요 기상반응은 국부 순간 평형을 가정하여 모델화하였다. 그래서 반응속도는 혼합의 난류속도에 의해 제한되어진다. Thermal NOx과 Fuel NOx의 유한속도 화학론(Finite Rate Chemstry)에 대한 부모델은 화학반응속도론와 난류성의 통계치를 통합하여 만들어져 있다. 기상은 반복적인 line-by-line기교에 의해 풀려지는 elliptic partial differential equation으로 묘사되어진다. 수치적인 안정을 고려하기 위해 under-relaxation이 이용되어졌다. 이렇게 코드화된 93-PCGC-2는 연소를 위해 모사되어졌다. 또한 더 나아가 이 수치모델의 활용범위는 미분탄의 가스화에도 활용되어질 것으로 기대되어진다.

• 한국대기환경학회지
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• 제22권6호
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• pp.940-953
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• 2006

The major source of carbon monoxide (CO) at the Earth's surface is the incomplete combustion of biomass and fossil fuels. Because the global lifetime of CO is about two months, it can be used as a tracer for pollution from anthropogenic activities and biomass hurtling. In this paper, we introduced the principle and algorithm of the Measurement of Pollution in the Troposphere (MOPITT) instrument for global CO monitoring. The MOPITT instrument, which was launched on the Satellite Terra in 1999, measures CO column and mixing ratio based on gas correlation radiometry. CO levels can be determined by a retrieval algorithm based on the maximum likelihood method minimizing the difference between observed and modeled radiances. MOPITT level 2 data (HDF format) can be downloaded through the Earth Observing System (EOS) data gateway of NASA. ASCII files of CO parameters can be extracted from HDF files, and then temporal and spatial distributions can be obtained. Finally, we showed an example of CO monitoring in April 2000. The locations of forest fires and distribution of MOPITT CO clearly indicated that not only anthropogenic emissions but also forest fires play an important role in CO levels and global CO distribution. Our introduction to MOPITT and the example of MOPITT data interpretation would be helpful for scientists who want to use the EOS data.