• Journal of Environmental Science International
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• v.18 no.9
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• pp.941-952
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• 2009

The urban microscale wind field around the air quality monitoring station was investigated in order to check how a building complex influences it. For this study as the high density areas Jwa-dong and Yeonsan-dong monitoring sites in Busan were chosen. As the direction of inflow which is perpendicular to the building of the monitoring station was expected to cause the considerable variation of the wind field, that direction was selected. The model Envi-met was used as the diagnostic numerical model for this study. It is suitable for this investigation because Envi-met has the microscale resolution. After simulating it, on the leeward side around a building complex the decrease of flow velocity and some of vortexes or circulation area were discovered. In addition, on the edge of the top at the building and at the back of the building the upward flow was developed. If the sampling hole of monitoring site were located in this upward flow, it would be under the influence of upward flow from the near street.

• 한국정보디스플레이학회:학술대회논문집
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• 2003.07a
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• pp.893-896
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• 2003

Plasma polymerized para-xylene (PPpX) thin films deposited by plasma enhanced chemical vapor deposition (PECVD) were used to passivate the organic light emitting diodes (OLEDs). For OLEDs, indium tin oxide (ITO), N,N'-diphenyl-N,N'-bis(3-methylphenyl)-1,1'-diphenyl-4,4'-diamine (TPD), tris(8-hydroxyquinoline) aluminum $(Alq_{3})$ and aluminum (Al) were used as the anode, the hole transport layer (HTL), the emitting layer (EML) and the cathode, respectively. The OLED device with the PPpX passivation film (passivated device) showed similar electrical and optical characteristics to those of the OLED device without the PPpX passivation film (control device), indicating that the PECVD process did not degrade the performance of the OLEDs notably. The lifetime of the passivated device was two times longer than that of the control device. Passivation of OLEDs with PPpX films also suppressed the growth of dark spots. The density and size of dark spots of the passivated device were much smaller than those of the control device.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.03b
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• pp.45-45
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• 2010

Nanoporous anodic alumina membranes (NAAM) with high aspect ratio, self-ordered pore array were fabricated by high-field 2-step anodization method. High voltages of 80, 100, 120 and 140 V as well as 40 V for comparison were applied to an aluminum anode with respect to a Pt cathode immersed both in 0.3M oxalic acid solution in order to investigate the self-ordering characteristics of the nanoporous structure. The pore structures, including interpore distance, pore size, pore density, and porosity as well as the ordering characteristic were analyzed using field-enhanced scanning electron microscopy (FE-SEM) and the corresponding Fourier-transformed images. The nanoporous structure could be produced for all the voltage conditions, but the well-ordered through-hole pore without a branched structure seemed to occur only at 40 and 140 V. It turned out that the growth rate under 140 V high-field anodization was about 40 times higher than under conventional 40 V mild anodization, which enabled the fast fabrication of self-ordered, high aspect ratio NAAMs.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.26 no.9
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• pp.701-706
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• 2013

We have focused on the conversion efficiency of CIGS thin film solar cell prepared by co-evaporation method as well as the optimization of process condition. The total thickness of back electrode was fixed at 1 ${\mu}m$ and the structural, electric and optical properties of CIGS thin film were investigated by varying the thickness of Mo:Na bottom layer from 0 to 500 nm. From the experimental results, the content of Na was appeared as 0.28 atomic percent when the thickness of Mo:Na layer was 300 nm with compactly densified plate-shape surface morphology. From the XRD measurements, (112) plane was the strongest preferential orientation together with secondary (220) and (204) planes affecting to the crystallization. The lowest roughness and resistivity were 2.67 nm and 3.9 ${\Omega}{\cdot}cm$, respectively. In addition, very high carrier density and hole mobility were recorded. From the optimization of Mo:Na layer, we have achieved the conversion efficiency of 9.59 percent.

• ETRI Journal
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• v.18 no.4
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• pp.315-338
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• 1997

We extend our previous theoretical analysis of electronic and optical properties of p-type quantum well structures based on the two heavy- and light-hole system to include all the three valence bands. These theories are then used to clarify the origin of the normal incidence absorption and photo current at photon wavelengths of 2 - 3 ${\mu}m$, which was observed in addition to the absorption around 8 ${\mu}m$ by a recent experimental investigation with heavily doped p-type GaAs/AlGaAs multi-quantum well (MQW) structures. In the theoretical analysis, the Hartree and exchange-correlation many-body interactions are taken into account within one-particle local density approximation, and it is shown that normal incidence absorption occurs in two wavelength regions over the transition energy range higher than barrier height for p-type GaAs/AlGaAs superlattices with well doping of $2{\times}10^{19}\;cm^{-3}$; one region has broad absorption peaks with coefficients of about 5000 $cm^{-1}$ around 8 ${\mu}m$, and the other has two rather sharp peaks at 2.7 ${\mu}m$ and 3.4 ${\mu}m$ with 1800 $cm^{-1}$ and 1300 $cm^{-1}$, respectively. The result indicates that the theory explains the experimental observation well, as the theoretical and experimental results are in close agreement in general absorption features.

• The Bulletin of The Korean Astronomical Society
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• v.42 no.2
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• pp.67.2-67.2
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• 2017

Korea Astronomy and Space Science Institute (KASI) plans to develop a coronagraph to measure the coronal electron density, temperature, and speed using four different filters around 400 nm, where strong Fraunhofer lines from the photosphere are scattered by coronal electrons. During the total solar eclipse occurring on August 21 across USA, KASI will organize an expedition team to demonstrate the coronagraph measurement scheme and the instrumental technology. The observation site is in Jackson Hole, Wyoming, USA. We plan to build two coronagraphs without occulter to improve signal to noise ratio. In addition, images of white light corona, wide field background, and all sky are planned to be taken with DSLR cameras. We will present the preliminary results of the expedition.

• Journal of the Korean Geophysical Society
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• v.4 no.2
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• pp.95-102
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• 2001

As a basic study of characterizing fracture condition in bore hole, conventional geophysical well log data consisting of sonic, gamma-gamma and resistivity logs were compared with geological core log and acousic televiewer log in limestone geology. Discontinuities shown on the acoustic televiewer log and the core log show fairly good correlation. The conventional Geophysical log is also shown to bi effective in locating discontinities in limestone geology; sonic log shows the best result and resistivity shows the worst. Particularly, the combination method of density and sonic logs is shown to be the most effective in delineating discontinuities.

• Tunnel and Underground Space
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• v.1 no.2
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• pp.181-203
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• 1991

The effects of geologic structures such as rock joins and bedding planes on the thermal conductivity of a discontinuous rock mass are studied. The expressions for the equivalent thermal conductivities of jointed rock masses are derived and found to be anisotropic. The degree of anisotropy depends primarily on the thermal properties contrast between the joint phase and surrounding intact rock, the joint density expressed as volume fraction and the inclination angle of the joint. Within the context of 2-dimensional finite element heat transfer scheme, the isotherms around a circular hole are analyzed for both the isotropic and anisotropic rock masses in 3 different thermal boundary conditions. i.e. temperature, heat flux and convection boundary conditions. The temperature in the stratified anisotripic rock mass is greatly influenced by the thermal properties of the rock formation in contact with the heat source. Using the excavation-temperature coupled elastic plastic finite element method, analyzed is the thermo-mechanical stability of a circular opening subjected to 10$0^{\circ}C$ at a depth of 527m. It is found that the thermal stress concentration was enough to deteriorate the stability and form a plastic yield zone around the opening, in contrast to the safety factor greater than 2 resulted form the excavation-only analysis.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.1291-1292
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• 2008

ITO is widely used as an anode material in OLED, because of its good transparency, low electrical resistivity, high work function, and efficient hole injection properties. The interface between the electrode and the organic layer in the OLED effects the charge injection process and may influence the electrical and the luminance properties. Surface treatment of ITO, such as an Aquaregia treatment has been shown to enhance the efficiency, and luminance characteristics of the OLED. In this study, we investigated the effect of Aquaregia treatment. The fundamental structures of the OLED were ITO/NPB/$Alq_3$/LiF/Al. The current density-voltage-luminance, efficiency, and lifetime characteristics were measured with untreated and Aquaregia-treated ITO substrates. The Aquaregia treatment was found to enhance the performance of OLED. For the Aquaregia treated device, the maximum luminance and efficiency were increased by about 2 times compared to the untreated device. The mechanism of the Aquaregia treatment is discussed based on AFM analyses.

• Proceedings of the KIEE Conference
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• 2015.07a
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• pp.1136-1137
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• 2015

The accelerated thermal aging of chlorosulfonated polyethylene (CSPE) was performed for 0 days, 80.82 days, and 161.63 days at $100^{\circ}C$, which is equivalent to 0y, 40y, and 80y of aging, respectively, at $50^{\circ}C$. The volume electrical resistivity of dried CSPE for 570~630 days after seawater and freshwater soaking, are $1.109{\times}10^{14}{\Omega}{\cdot}cm$, $8.546{\times}10^{13}{\Omega}{\cdot}cm$ and $8.466{\times}10^{13}{\Omega}{\cdot}cm$. The applied voltage rising time of 11~12 second and dielectric breakdown time of 9~11 second of the accelerated thermal aged CSPE is shorter than those of 12~13 and 11~13 second of the non-accelerated thermal aged CSPE, respectively. It is shown that oxidation, fragment and crack are formated at hole of dielectric breakdown in CSPE. The apparent density of dried CSPE for 750 days are $1.555g/cm^3$, $1.595g/cm^3$ 및 $1.597g/cm^3$ according to accelerated thermal aging year, respectively.