• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.453-453
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• 2010

In this study, zinc germanate ($Zn_2GeO_4$) thin films has been synthesized by using radio frequency magnetron sputtering and the divalent manganese-activated luminescence was characterized. X-ray diffraction patterns of the as-deposited $Zn_2GeO_4$:Mn films showed only a broad feature, indicative of an amorphous structure. Scanning electron microscopy images revealed that the as-deposited $Zn_2GeO_4$:Mn has a smooth surface morphology. The $Zn_2GeO_4$:Mn films were found to be crystallized by annealing in air ambient at temperatures as low as $700^{\circ}C$. The annealed $Zn_2GeO_4$:Mn possessed a rhombohedral polycrystalline structure. The broad-band photoluminescent emission spectrum from 470 to 650nm was obtained at room temperature from the $Zn_2GeO_4$:Mn films. The emission peak was centered at around 535nm in the green range, which originates from the intrashell transition of manganese $3d^5$ electrons from $^4T_1$ excited-state level to the $^6A_1$ ground state. The PL emission spectrum had an asymmetric line shape, which results from the $^3d_5$ electron transitions of divalent manganese ions located at different sites of the zinc germanate host crystal lattice. Electroluminescent devices were fabricated using $Zn_2GeO_4$:Mn as an emission layer. The fabricated devices showed a green EL emission similar to the PL emission. The CIE chromaticity color coordinates of the EL emission were determined to be x=0.308 and y=0.657.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.10a
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• pp.470-473
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• 2005

Spent nuclear fuels are regarded as a high level radioactive waste and they will be disposed in a deep geological repository. To maintain the safety of the repository for hundreds of thousands of years, the spent fuels are encapsulated in a disposal canister and the canister containing spent fuels should have the structural integrity and the corrosion resistance below the several hundreds meters from the ground surface. In this study, the concept of the spent fuel encapsulation process and the process equipment fur deep geological disposal were established. To do this, the design requirements, such as the functions and the spent fuel accumulations, were reviewed. Also, the design principles and the bases were established. Based on the requirements and the bases, the encapsulation process and the equipment from spent fuel receiving process to transferring canister into the underground repository including hot cell processes was established. The established concept of the spent fuel encapsulation process and the process equipment will be improved continuously with the future studies. And this concept can be effectively used in implementing the reference repository system of our own case.

• Journal of the Korean Society of Hazard Mitigation
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• v.9 no.5
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• pp.69-78
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• 2009

Since the blast vibration induced by explosives of the powder possibly provide damage of the nearby structures adjacent to the tunnel, the stability of the nearby structures should be estimated. In this study, the stability of the tunnel based on the allowable peak particle velocity of the structures as well as allowable stress of the structures presented in the concrete structural design standard was estimated with respect to the stress of the concrete lining and axial force of the rockbolt during the blasting operation at the ground surface of the pre-existing tunnel. The analyses were carried out by using $FLAC^{2D}$ which is one of the programs developed based on the finite difference method. The bending compressive stress and shear stress of the concrete lining and axial force of the rockbolt were rapidly increased when the blasting operation was conducted near the tunnel.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.11a
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• pp.276-279
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• 2004

Plasma enhanced chemical vapor deposition (PECVD) of silicon nitride (SiN) is a proven technique for obtaining layers that meet the needs of surface passivation and anti-reflection coating. In addition, the deposition process appears to provoke bulk passivation as well due to diffusion of atomic hydrogen. This bulk passivation is an important advantage of PECVD deposition when compared to the conventional CVD techniques. A further advantage of PECVD is that the process takes place at a relatively low temperature of 300t, keeping the total thermal budget of the cell processing to a minimum. In this work SiN deposition was performed using a horizontal PECVD reactor system consisting of a long horizontal quartz tube that was radiantly heated. Special and long rectangular graphite plates served as both the electrodes to establish the plasma and holders of the wafers. The electrode configuration was designed to provide a uniform plasma environment for each wafer and to ensure the film uniformity. These horizontally oriented graphite electrodes were stacked parallel to one another, side by side, with alternating plates serving as power and ground electrodes for the RF power supply. The plasma was formed in the space between each pair of plates. Also this paper deals with the fabrication of multicrystalline silicon solar cells with PECVD SiN layers combined with high-throughput screen printing and RTP firing. Using this sequence we were able to obtain solar cells with an efficiency of 14% for polished multi crystalline Si wafers of size 125 m square.

• Wind and Structures
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• v.24 no.6
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• pp.579-611
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• 2017

Bora is a strong, usually dry temporally and spatially transient wind that is common at the eastern Adriatic Coast and many other dynamically similar regions around the world. One of the Bora main characteristics is its gustiness, when wind velocities can reach up to five times the mean velocity. Bora often creates significant problems to traffic, structures and human life in general. In this study, Bora velocity and near-ground turbulence are studied using the results of three-level high-frequency Bora field measurements carried out on a meteorological tower near the city of Split, Croatia. These measurements are analyzed for a period from April 2010 until June 2011. This rather long period allows for making quite robust and reliable conclusions. The focus is on mean Bora velocity, turbulence intensity, Reynolds shear stress and turbulence length scale profiles, as well as on Bora velocity power spectra and thermal stratification. The results are compared with commonly used empirical laws and recommendations provided in the ESDU 85020 wind engineering standard to question its applicability to Bora. The obtained results report some interesting findings. In particular, the empirical power- and logarithmic laws proved to fit mean Bora velocity profiles well. With decreasing Bora velocity there is an increase in the power-law exponent and aerodynamic surface roughness length, and simultaneously a decrease in friction velocity. This indicates an urban-like velocity profile for smaller wind velocities and a rural-like velocity profile for larger wind velocities. Bora proved to be near-neutral thermally stratified. Turbulence intensity and lateral component of turbulence length scales agree well with ESDU 85020 for this particular terrain type. Longitudinal and vertical turbulence length scales, Reynolds shear stress and velocity power spectra differ considerably from ESDU 85020. This may have significant implications on calculations of Bora wind loads on structures.

• Korean Journal of Remote Sensing
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• v.13 no.1
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• pp.57-73
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• 1997

This paper is related to the correction of radiometric distortions induced by topographic relief. RADARSAT SAR image data were obtained over the mountainous area near southern part of Seoul. Initially, the SAR data was geometrically corrected and registered to plane rectangular coordinates so that each pixel of the SAR image has known topographic parameters. The topographic parameters (slope and aspect) at each pixel position were calculated from the digital elevation model (DEM) data having a comparable spatial resolution with the SAR data. Local incidence angle between the incoming microwave and the surface normal to terrain slope was selected as a primary geometric factor to analyze and to correct the radiometric distortions. Using digital maps of forest stands, several fields of rather homogeneous forest stands were delineated over the SAR image. Once the effects of local incidence angle on the radar backscatter were defined, the radiometric correction was performed by an empirical fuction that was derived from the relationship between the geometric parameters and mean radar backscatter. The correction effects were examined by ground truth data.

• Korean Journal of Remote Sensing
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• v.24 no.3
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• pp.223-233
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• 2008

In the mid 90's, the U.S. government released images acquired by the first generation of photo reconnaissance satellite missions between 1960 and 1972. The Declassified Intelligent Satellite Photographs (DISP) from the Corona mission are of high quality with an astounding ground resolution of about 2 m. The KH-4A panoramic camera system employed a scan angle of $70^{\circ}$ that produces film strips with a dimension of $55\;mm\;{\times}\;757\;mm$. Since GPS/INS did not exist at the time of data acquisition, the exterior orientation must be established in the traditional way by using control information and the interior orientation of the camera. Detailed information about the camera is not available, however. For reconstructing points in object space from DISP imagery to an accuracy that is comparable to high resolution (a few meters), a precise camera model is essential. This paper is concerned with the derivation of a rigorous mathematical model for the KH-4A/B panoramic camera. The proposed model is compared with generic sensor models, such as affine transformation and rational functions. The paper concludes with experimental results concerning the precision of reconstructed points in object space. The rigorous mathematical panoramic camera model for the KH-4A camera system is based on extended collinearity equations assuming that the satellite trajectory during one scan is smooth and the attitude remains unchanged. As a result, the collinearity equations express the perspective center as a function of the scan time. With the known satellite velocity this will translate into a shift along-track. Therefore, the exterior orientation contains seven parameters to be estimated. The reconstruction of object points can now be performed with the exterior orientation parameters, either by intersecting bundle rays with a known surface or by using the stereoscopic KH-4A arrangement with fore and aft cameras mounted an angle of $30^{\circ}$.

• Korean Journal of Remote Sensing
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• v.21 no.1
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• pp.73-81
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• 2005

We construct improved geocentric digital elevation model (DEM), estimate tidal dynamics and ice stream velocity over Sulzberger Ice Shelf, West Antarctica employing differential interferograms from 12 ERS tandem mission Synthetic Aperture Radar (SAR) images acquired in austral fall of 1996. Ice, Cloud, and land Elevation Satellite (ICESat) laser altimetry profiles acquired in the same season as the SAR scenes in 2004 are used as ground control points (GCPs) for Interferometric SAR (InSAR) DEM generation. 20 additional ICESat profiles acquired in 2003-2004 are then used to assess the accuracy of the DEM. The vertical accuracy of the OEM is estimated by comparing elevations with laser altimetry data from ICESat. The mean height difference between all ICESat data and DEM is -0.57m with a standard deviation of 5.88m. We demonstrate that ICESat elevations can be successfully used as GCPs to improve the accuracy of an InSAR derived DEM. In addition, the magnitude and the direction of tidal changes estimated from interferogram are compared with those predicted tidal differences from four ocean tide models. Tidal deformation measured in InSAR is -16.7cm and it agrees well within 3cm with predicted ones from tide models. Lastly, ice surface velocity is estimated by combining speckle matching technique and InSAR line-of-sight measurement. This study shows that the maximum speed and mean speed are 509 m/yr and 131 m/yr, respectively. Our results can be useful for the mass balance study in this area and sea level change.

• Korean Journal of Remote Sensing
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• v.26 no.4
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• pp.403-410
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• 2010

NDVI(Normalized Difference Vegetation Index), which is broadly used as short-term data composite, is an important parameter for climate change and long-term land surface monitoring. Although atmospheric correction is performed, NDVI dramatically appears several low peak noise in the long-term time series. They are related to various contaminated sources, such as cloud masking problem and wet ground condition. This study suggests a simple method through harmonic analysis for reducing NDVI noise using SPOT/VGT NDVI 10-day MVC data. The harmonic analysis method is compared with the polynomial regression method suggested previously. The polynomial regression method overestimates the NDVI values in the time series. The proposed method showed an improvement in NDVI correction of low peak and overestimation.

• Proceedings of the Korea Water Resources Association Conference
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• 2016.05a
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• pp.194-194
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• 2016

Gansu, located in the northwestern region, is a typical agricultural province of arid, semiarid in China. The shortage of water resources is the biggest obstacle of Gansu Province's development, and the dry farming water-saving is the eternal theme of Gansu agricultural sustainable development. In recent years, intensify reform in Gansu, has walked out a successful way in the agricultural water-saving. Using the integrated river basin governance as opportunity, the total water-using quantity was regarded as rigidity to retrain, distributed to counties (districts), irrigated areas, towns, associations, groups step by step. Agricultural water price was substantially increased, with the surface water price from about $0.1RMB/m^3$ to more than $0.2 RMB/m^3$, and the ground water from zero to more than $0.1RMB/m^3$. Simultaneously, the difference water prices and over-quota water progression price markup were carried out. The transaction of water rights was encouraged to impel the peasant to establish the consciousness of saving-water. The regulatory documents were formulated to standardize the scope, condition, mode, program etc. of agriculture water-rights transaction, to guarantees the transaction of water rights is carries out in order. The pattern of farming was optimized and adjusted, reducing the high water-consumption crop, increasing economic crops with high benefit and low water-consumption, developing industrialized agricultures such as green house. The relative engineering and measuring facility were comprehensively improved, with the anti-seepage of canal system and the enforcement of dynamo-electric well, developing high-efficient water-saving irrigation and overall metering facilities. The water fine-grained management has realized, and obvious water-saving effect has obtained: water-using rate in the irrigation area by river water has brought up to 0.57 from 0.52, and by well water up to 0.84 from 0.76. Although the water price has increased, the proportion that the water rate expenditure accounted for the cost lasts decline, and the farmers' income has gone up. The peasants express, the used water is few, and it is few to till land, but the income is many, and life is better.