• Journal of Environmental Science International
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• v.17 no.7
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• pp.767-774
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• 2008

This study was carried out to evaluate the characteristics of atmospheric concentrations of volatile organic compounds(VOCs) and aldehydes for near a large shipyard. Most of the painting work in marine coating is performed indoor and outdoor. Most of the VOCs are emitted to the atmosphere as the paint is applied and cures. The massive scale of a ship makes it difficult to capture the emissions from outdoor painting. The VOCs are an important health and contributors to photochemical smog. The VOCs and aldehydes samples were collected using adsorbent tube and 2,4-DNPH cartridge, and were determined by an automatic thermal desorption coupled with GC/MS and HPLC-UV analysis, respectively. A total of 16 aromatic VOCs and 12 aldehydes of environmental concern were determined. At indoor coating facilities, the most abundant compound among 16 target VOCs appeared to be m,p-xylene, being followed by o-xylene. But most of the aldehydes were extremely lower concentrations. The atmospheric concentration of VOCs, m,p-xylene concentrations were the highest and the mean value were outdoor workshop 11.323 ppb, residental area 5.134 ppb, and green area 2.137 ppb, respectively. However, the most aldehydes were extremely lower concentrations such as formaldehyde, acetaldehyde and non-detection such as iso-valeraldehyde, n-valeraldehyde and o-tolualdehyde.

• Korean Chemical Engineering Research
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• v.47 no.2
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• pp.208-212
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• 2009

The nano-clay is widely used in polymer-nanocomposites due to the high aspect ratio, heat resistance and nano-scale dimension. In recent researches, the thermal and mechanical properties of polyurethane foam were improved with introducing the nano-clay. In this study, we describe the influence of ultrasonic treatment and content of nano-clay on properties of polyurethane foam. The nano-clay/polyurethane foam were characterized using their recovery time, compressive deflection, cell morphology and tensile test. The ultrasonic treatment was very effective for dispersion of nano-clay. Moreover, we found that introducing over 3 wt% of nano-clay bring the decrease of properties due to the poor dispersion. Expecially, ultrasonically treated 20A/polyurethane foam(1 wt%) showed greatly improved properties, such as homogeneous cell size and good dimension stability. We expect that our results could be applied to insulating materials for construction.

• 한국정보디스플레이학회:학술대회논문집
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• 2006.08a
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• pp.529-529
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• 2006

Several laboratories worldwide have demonstrated the feasibility of producing amorphous silicon thin film transistor (TFT) arrays at temperatures that are sufficiently low to be compatible with flexible foils such as stainless steel or high temperature polyester. These arrays can be used to fabricate flexible high information content display prototypes using a variety of different display technologies. However, several questions must be addressed before this technology can be used for the economic commercial production of displays. These include process optimization and scale-up to address intrinsic electrical instabilities exhibited by these kinds of transistor device, and the development of appropriate techniques for the handling of flexible substrate materials with large coefficients of thermal expansion. The Flexible Display Center at Arizona State University was established in 2004 as a collaboration among industry, a number of Universities, and US Government research laboratories to focus on these issues. The goal of the FDC is to investigate the manufacturing of flexible TFT technology in order to accelerate the commercialization of flexible displays. This presentation will give a brief outline of the FDC's organization and capabilities, and review the status of efforts to fabricate amorphous silicon TFT arrays on flexible foils using a low temperature process. Together with industrial partners, these arrays are being integrated with cholesteric liquid crystal panels, electrophoretic inks, or organic electroluminescent devices to make flexible display prototypes. In addition to an overview of device stability issues, the presentation will include a discussion of challenges peculiar to the use of flexible substrates. A technique has been developed for temporarily bonding flexible substrates to rigid carrier plates so that they may be processed using conventional flat panel display manufacturing equipment. In addition, custom photolithographic equipment has been developed which permits the dynamic compensation of substrate distortions which accumulate at various process steps.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.150-150
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• 2010

Carbon nanotubes have drawn attention as one of the most promising emitter materials ever known not only due to their nanometer-scale radius of curvature at tip and extremely high aspect ratios but also due to their strong mechanical strength, excellent thermal conductivity, good chemical stability, etc. Some applications of CNTs as emitters, such as X-ray tubes and microwave amplifiers, require high current emission over a small emitter area. The field emission for high current density often damages CNT emitters by Joule heating, field evaporation, or electrostatic interaction. In order to endure the high current density emission, CNT emitters should be optimally fabricated in terms of material properties and morphological aspects: highly crystalline CNT materials, low gas emission during electron emission in vacuum, optimal emitter distribution density, optimal aspect ratio of emitters, uniform emitter height, strong emitter adhesion onto a substrate, etc. We attempted a novel approach to fabricate CNT emitters to meet some of requirements described above, including highly crystalline CNT materials, low gas emission, and strong emitter adhesion. In this study, CNT emitters were fabricated by filtrating an aqueous suspension of highly crystalline thin multiwalled CNTs (Hanwha Nanotech Inc.) through a metal mesh. The metal mesh served as a support and fixture frame of CNT emitters. When 5 ml of the CNT suspension was engaged in filtration through a 400 mesh, the CNT layers were formed to be as thick as the mesh at the mesh openings. The CNT emitter sample of $1{\times}1\;cm^2$ in size was characteristic of the turn-on electrical field of 2.7 V/${\mu}m$ and the current density of 14.5 mA at 5.8 V/${\mu}m$ without noticeable deterioration of emitters. This study seems to provide a novel fabrication route to simply produce small-size CNT emitters for high current emission with reliability.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.22 no.4
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• pp.551-561
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• 1998

This paper was studied to understand the characteristics of heat transfer coefficients and surface temperature distributions around a circular combustion chamber within the heat-intercept duct of kerosene fan heater. The experiment was carried out in the heat-intercept duct of kerosene fan heater attached to the blow-down-type subsonic wind tunnel with a test section of 240 mm * 240 mm * 1200 mm. The purpose of this paper was to obtain the basic data related with normal combustion for new design from conventional kerosene fan heater, and to investigate the effect of surface temperature, local and mean heat transfer coefficients versus flow-rate of convection axial fan according to the variations of heat release conditions from kerosene fan heater during normal combustion. Consequently it was found that (i) the revolution of convection axial fan during combustion had a smaller value than that of non-combustion because of the thermal resistance due to the high temperature in the heat-intercept duct, (ii) the pressure ratio P$_{2}$/P$_{1}$ had a comparatively constant value of 0.844 according to the revolution increase of turbo fan and the heating performance of kerosene fan heater had a range of 1,494 ~ 3,852 kcal/hr, (iii) the local heat transfer coefficient around a circular combustion chamber had a comparatively larger scale in the range of 315 deg. < .theta. < 45 deg. than that in the range of 90 deg. < .theta. < 270 deg. as a result of heat transfer difference between front and back of a circular combustion chamber, and (iv) the mean heat transfer coefficient around a circular combustion chamber increased linearly like a H$_{m}$=95.196Q+104.019 in condition of high heat release according to the increase of flow-rate of axial fan.n.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.17 no.1
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• pp.213-218
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• 2017

High-voltage power systems operate in order to generate and transmit electric power at power stations. Compared to low-power systems, high-power systems are complex in structure, large-scale, and expensive. When high-power cable accidents occur, most facilities are incapacitated-including low-power systems-causing huge economic losses. Great care must therefore be taken in designing, installing and managing power systems. Although dependent on installation circumstances and usage conditions, in some cases the cross-sectional areas of cables fall short of the critical area due to the expansion of and improper design and installation of power facilities. In this situation, the exceeded ampacity (allowable current) above the critical value caused by the operating current initiates the deterioration processes of power cables. In order to systematically monitor power cables operating at power stations, we have developed the first device of its kind in Korea. In this paper, we present the analyzed characteristics of expected temperatures of cables based on the load current of high-voltage cables operating at Korean Western Power Co. Ltd. We can predict the lifetime of cables by analyzing the temperature obtained from our device.

• Nuclear Engineering and Technology
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• v.24 no.3
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• pp.243-251
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• 1992

Behavior of loop seal formation and clearing during small break loss of coolant accident is investigated using the RELAP5/MOD 2 and /MOD3 codes with the test of SB-CL-18 of the LSIF (Large Scale Test Facility）. The present study examines the thermal-hydraulic mechanisms responsible for early core uncovery including the manometric effect due to an asymmetric coolant holdup in the steam generator upflow and downflow side. The analysis with the RELAP5/MOD2 demonstrates the main phenomena occuring in the depressurization transient including the loop seal formation and clearing with sufficient accuracy. Nevertheless, several differences regarding the evolution of phenomena and their timing have been pointed out in かe base calculations. The RELAP5/MOD3 predicts overall phenomena, particularly the steam generator liquid holdup better than the RELAP5/MOD2. The nodalization study in the components of the steam generator U-tubes and the cross-over legs wiか the RELAP5/MOD3 results in good prediction of the loop seal clearing phenomena and their timing.

• Proceedings of the Korean Society of Crop Science Conference
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• 2017.06a
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• pp.60-60
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• 2017

It is important to measure the gas exchange activity of the crops in canopy scale to understand the process of biomass production and yield formation. Thermal imaging of the canopy surface temperature is a powerful tool to detect the gas exchange activity of the crop canopy. The simultaneous measurement of the canopy temperature and the meteorological data enables us to calculate the canopy diffusive conductance ($g_c$) based on the heat flux model (Monteith et al. 1973, Horie et al. 2006). It is, however, difficult to realize the long-term and continuous monitoring of $g_c$ due to the occurrence of the calculation error caused by the fluctuation of the environmental condition. This is partly because the model assumption is too simple to describe the meteorological and aerodynamic conditions of the crop canopy in the field condition. Here we report the novel method of the direct measurement of the aerodynamic resistance ($r_a$) of the crop canopy, which enables us the stable and continuous measurement of the gas exchange capacity of the crop plants. The modified heat balance model shows the improved performance to quantify $g_c$ under the fluctuating meteorological condition in the field. The relationship between $g_c$ and biomass production of rice and soybean varieties is also discussed in the presentation.

• Proceedings of the Korean Vacuum Society Conference
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• 1999.07a
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• pp.163-163
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• 1999

MOSFET, MESFET 그리고 MODFET는 Logic ULSIs, high speed ICs, RF MMICs 등에서 중요한 역할을 하고 있으며, 그것의 gate electrode, contact, interconnect 등의 물질로는 refractory metal을 이용한 CoSi2, MoSi2, TaSi2, PtSi2, TiSi2 등의 효과를 얻어내고 있다. 그중 TiSi2는 비저항이 가장 낮고, 열적 안정도가 좋으며 SAG process가 가능하므로 simpler alignment process, higher transconductance, lower source resistance 등의 장점을 동시에 만족시키고 있다. 최근 소자차원이 scale down 됨에 따라 TiSi2의 silicidation 과정에서 C49 TiSi2 phase(high resistivity, thermally unstable phase, larger grain size, base centered orthorhombic structure)의 출현과 그것을 제거하기 위한 노력이 큰 issue로 떠오르고 있다. 여러 연구 결과에 따르면 PAI(Pre-amorphization zimplantation), HTS(High Temperature Sputtering) process, Mo(Molybedenum) implasntation 등이 C49를 bypass시키고 C54 TiSi2 phase(lowest resistivity, thermally stable phase, smaller grain size, face centered orthorhombic structure)로의 transformation temperature를 줄일 수 있는 가장 효과적인 방법으로 제안되고 있지만, 아직 그 문제가 완전히 해결되지 않은 상태이며 C54 nucleation에 대한 physical mechanism을 밝히진 못하고 있다. 본 연구에서는 증착 시 기판온도의 변화(400~75$0^{\circ}C$)에 따라 silicon 위에 DC/RF magnetron sputtering 방식으로 Ti/Si film을 각각 제작하였다. 제작된 시료는 N2 분위기에서 30~120초 동안 500~85$0^{\circ}C$의 온도변화에 따라 RTA법으로 각각 one step annealing 하였다. 또한 Al을 cosputtering함으로써 Al impurity의 존재에 따른 영향을 동시에 고려해 보았다. 제작된 시료의 분석을 위해 phase transformation을 XRD로, microstructure를 TEM으로, surface topography는 SEM으로, surface microroughness는 AFM으로 측정하였으며 sheet resistance는 4-point probe로 측정하였다. 분석된 결과를 보면, 고온에서 제작된 박막에서의 C54 phase transformation temperature가 감소하는 것이 관측되었으며, Al impuritydmlwhswork 낮은온도에서의 C54 TiSi2 형성을 돕는다는 것을 알 수 있었다. 본 연구에서는 결론적으로, 고온에서 증착된 박막으로부터 열적으로 안정된 phase의 낮은 resistivity를 갖는 C54 TiSi2 형성을 보다 낮은 온도에서 one-step RTA를 통해 얻을 수 있다는 결과와 Al impurity가 존재함으로써 얻어지는 thermal budget의 효과, 그리고 그로부터 기대할 수 있는 여러 장점들을 보고하고자 한다.

• Journal of The Korean Astronomical Society
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• v.48 no.5
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• pp.313-323
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• 2015

Active galactic nuclei (AGN) are known for irregular variability on all time scales, down to intra-day variability with relative variations of a few percent within minutes to hours. On such short timescales, unexplored territory, such as the possible existence of a shortest characteristic time scale of activity and the shape of the high frequency end of AGN power spectra, still exists. We present the results of AGN single-dish fast photometry performed with the Korean VLBI Network (KVN). Observations were done in a “anti-correlated” mode using two antennas, with always at least one antenna pointing at the target. This results in an effective time resolution of less than three minutes. We used all four KVN frequencies, 22, 43, 86, and 129 GHz, in order to trace spectral variability, if any. We were able to derive high-quality light curves for 3C 111, 3C 454.3, and BL Lacertae at 22 and 43 GHz, and for 3C 279 at 86 GHz, between May 2012 and April 2013. We performed a detailed statistical analysis in order to assess the levels of variability and the corresponding upper limits. We found upper limits on flux variability ranging from ~1.6% to ~7.6%. The upper limits on the derived brightness temperatures exceed the inverse Compton limit by three to six orders of magnitude. From our results, plus comparison with data obtained by the University of Michigan Radio Astronomy Observatory, we conclude that we have not detected source-intrinsic variability which would have to occur at sub-per cent levels.