• Journal of the Korean Crystal Growth and Crystal Technology
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• v.24 no.4
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• pp.145-150
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• 2014

GaN nanorods were grown on the apex of GaN stripes by three dimensional selective growth method. $SiO_2$ mask was partially removed only on the apex area of the GaN stripes by an optimized photolithography for the selective growth. Metallic Au was deposited only on the apex of the GaN stripes and a selective growth of GaN nanorods was followed by a metal organic vapor phase epitaxy (MOVPE). We confirmed that the shape and size of the GaN nanorods depend on growth temperature and flow rates of group III precursor. GaN nanorods were grown having a taper shape which have sharp tip and triangle-shaped cross section. From the TEM result, we confirmed that threading dislocations were rarely observed in GaN nanorods because of the very small contact area for the selective growth. Stacking faults which might be originated from a difference of the crystal facet directions between the GaN stripe and the GaN nanorods were observed in the center area of the GaN nanorods.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.29 no.4
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• pp.381-392
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• 2011

Pollutant loads calculated with unit factor method can not identity seasonal variations of pollutant inputs. Estimation of pollutant loads considering rainfall runoff can overcome these limits. SCS curve number method was applied to estimate runoff of each event of Koeup watershed of Koheung estuary lake. SCS curve numbers were calculated based upon land use, soil types of the catchment using GIS. Point and nonpoint source pollutant loads were summed up for total loads estimation. Those from nonpoint source were estimated by multiplying the calculated runoff and expected mean concentrations (EMC) presented by the Minister of Environment of Korea. DEM can present three dimensional views of a terrain, identity stream networks and flow accumulation. Furthermore, it can examine accumulated pollutant loads of specific point of a catchment. Therefore, cell based pollutant load estimation was attempted using DEM. ArcView was utilized to collect, store and manipulate spatial and attribute data of pollutant sources and features of the catchment. Cell-based DEM which was established by the GRID module of ARC/INFO was employed to estimate flows and pollutant loads.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.31 no.4
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• pp.326-339
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• 1995

In this paper, the validity of the numerical model of fishes' behavior presented in our earlier paper was examined by the whiteness test on the residual of numerical model and by the comparison between experiment and simulation on several indexes represented by fishes' swimming characteristics. The validity of the numerical model was proved statistically by means of the whiteness test of the residual. The similarity was confirmed by comparison between experiment and simulation for the swimming trajectory of fishes, the mean distance of individual from wall, the mean swimming speed and the mean distance between the nearest individuals. These results suggest that the behavior of fishes according to the flow speed in three-dimensional space can be estimated partially by the numerical model presented in our earlier paper. However, a long-term approach to improve the modeling technique on the behavior of fishes may be needed before applying the numerical model presented in our earlier paper to real fishing ground.

• Journal of Korean Society of Environmental Engineers
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• v.32 no.7
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• pp.690-698
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• 2010

Contamination of groundwater resources by organic chemicals has become an issue of increasing environmental concern. Surfactant-enhanced aquifer remediation (SEAR) is widely recognized as one of the most promising techniques to remediate organic contaminations in-situ. Solutions of surfactant or surfactant with polymer are used to dramatically expedite the process, which in turn, may reduce the treatment time of a site compared to use of water alone. In the design of surfactant-based technologies for remediation of organic contaminated aquifers, it is very important to have a considerable analysis using extensive numerical simulations prior to full-scale implementation. This study investigated the formation and flow of microemulsions during SEAR of organic-contaminated aquifer using the finite difference model UTCHEM, a three-dimensional, multicomponent, multiphase, compositional model. The remediation process variables considered in this study were the sequence of injection fluids, the injection and extraction rate, the concentrations of polymer in surfactant slug and chase water, and the duration of surfactant injection. For each variable, temporal changes in injection and production wells and spatial distributions of relative saturations in the organic phase were compared. Cleanup time and cumulative organic recovery were also quantified. The study would provide useful information to design strategies for the remediation of nonaqueous phase liquid-contaminated aquifers.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.8
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• pp.1051-1057
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• 2010

This paper proposes a method that involves a combination of FDM and FEM for analyzing casting process. At present, many numerical analysis methods such as FDM, FEM, and BEM are used for solving engineering problems. For a given problem, a specific method that is suited to the problem is adopted; in general, FDM or FVM is favored for problems related to fluid flow or heat transfer, and FEM is adopted in stress analysis. However, there is an increasing need for using a combined method for complex and coupled phenomena analysis. Hence, we proposed a method in which FDM and FEM are coupled in three-dimensional space, and we applied this method to analyze casting process. In the proposed method, solidification and heat transfer was analyzed by using FDM. The field data such as temperature distribution were converted into a format suitable for FEM analysis that was used for calculating thermal stress distribution. Using the proposed method, we efficiently analyzed the analysis process from the viewpoints of work and time.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.22 no.4
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• pp.215-223
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• 2010

A seasonal circulation patterns in the Chinju Bay (CB) were suggested from the observed data at two channels of the Noryang Channel (NC) and the Daebang Channel (DC) during the period from 2005 to 2008. The water circulation in the CB is mainly controlled through the NC and the DC. In winter, tidal current at the surface layer of the NC flows from the Kwangyang Bay (KB) eastward into the CB, whereas the current at the bottom layer flows from the CB westward into the KB. In summer, tidal current at the surface layer of the NC goes from the CB westward into the KB. The flow system at the NC shows the typical pattern of thermohaline circulation. In spring, tidal current at the surface layer of the eastern part of the DC flows out into southeastern open ocean. However, in summer, the current in the western part of the DC flows into the CB through the DC. Also, the velocity in the western part of DC is 50~70 cm/sec stronger than that in the eastern part. To obtain better understanding on the seasonal circulation pattern in the NC and the DC, additionally the detailed studies on the field measurements and three dimensional numerical modeling are needed.

• Journal of the Korean Wood Science and Technology
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• v.35 no.4
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• pp.1-8
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• 2007

Japanese larch specimens with dimension of 2.5 (radial direction) ${\times}$ 2.5 (tangential direction) ${\times}$ 2.5 cm (longitudinal direction) were prepared to determine 3 different directional internal moisture movement coefficients and surface emission coefficients along the radial-, the tangential-, and the tangential-direction. 4 sides of each cubic specimen were wrapped with paraffin tape and rubber tape, leaving open the 2 opposite surfaces of interest, to provide one dimensional moisture movement during drying. The coefficients were determined at three different temperatures, 70, 50 and $30^{\circ}C$ and at two different relative humidities, 30 and 60%. Internal moisture movement coefficients inclusive of flow of free water and diffusion of bound water and water vapor were increased in the high temperature condition. The internal moisture movement coefficient in the longitudinal direction was about six times of those in transverse directions with radial value being 20% greater than the tangential. Surface emission coefficients were increased with temperature and decreased with surface moisture content. Using this results, moisture content (MC) profile and quantities of moisture evaporating in Japanese larch lumber could be predicted in dynamic drying situations.

• Proceedings of the Korean Environmental Sciences Society Conference
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• 2003.11a
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• pp.177-184
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• 2003

Numerical simulation on marine wind and sea surface elevation was carried out using both three-dimensional hydrostatic and non-hydrostatic models and a simple oceanic model from 0900 LST, August 13 to 0900 LST, August 15, 1995. As daytime easterly meso-scale sea-breeze from the eastern sea penetrates Kangnung city in the center part as basin and goes up along the slope of Mt. Taegullyang in the west, it confronts synoptic-scale westerly wind blowing over the top of the mountain at the mid of the eastern slope and then the resultant wind produces an upper level westerly return flow toward the East Sea. In a narrow band of weak surface wind within 10km of the coastal sea, wind stress is generally small, less than l${\times}$10E-2 Pa and it reaches 2 ${\times}$ 10E-2 Pa to the 35 km. Positive wind stress curl of 15 $\times$ 10E-5Pa $m^{-1}$ still exists in the same band and corresponds to the ascent of 70 em from the sea level. This is due to the generation of northerly wind driven current with a speed of 11 m $S^{-1}$ along the coast under the influence of south-easterly wind and makes an intrusion of warm waters from the southern sea into the northern coast, such as the East Korea Warm Current. On the other hand, even if nighttime downslope windstorm of 14m/s associated with both mountain wind and land-breeze produces the development of internal gravity waves with a hydraulic jump motion of air near the coastal inland surface, the surface wind in the coastal sea is relatively moderate south-westerly wind, resulting in moderate wind stress. Negative wind stress curl in the coast causes the subsidence of the sea surface of 15 em along the coast and south-westerly coastal surface wind drives alongshore south-easterly wind driven current, opposite to the daytime one. Then, it causes the intrusion of cold waters like the North Korea Cold Current in the northern coastal sea into the narrow band of the southern coastal sea. However, the band of positive wind stress curl at the distance of 30km away from the coast toward further offshore area can also cause the uprising of sea waters and the intrusion of warm waters from the southern sea toward the northern sea (northerly wind driven current), resulting in a counter-clockwise wind driven current. These clockwise and counter-clockwise currents much induce the formation of low clouds containing fog and drizzle in the coastal region.

• Investigative Magnetic Resonance Imaging
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• v.18 no.4
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• pp.290-302
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• 2014

Purpose : Susceptibility-weighted magnetic resonance (MR) sequence is three-dimensional (3D), spoiled gradient-echo pulse sequences that provide a high sensitivity for the detection of blood degradation products, calcifications, and iron deposits. This pictorial review is aimed at illustrating and discussing its main clinical applications. Materials and Methods: SWI is based on high-resolution, 3D, fully velocity-compensated gradient-echo sequences using both magnitude and phase images. To enhance the visibility of the venous structures, the magnitude images are multiplied with a phase mask generated from the filtered phase data, which are displayed at best after post-processing of the 3D dataset with the minimal intensity projection algorithm. A total of 200 patients underwent MR examinations that included SWI on a 3 tesla MR imager were enrolled. Results: SWI is very useful in detecting multiple brain disorders. Among the 200 patients, 80 showed developmental venous anomaly, 22 showed cavernous malformation, 12 showed calcifications in various conditions, 21 showed cerebrovascular accident with susceptibility vessel sign or microbleeds, 52 showed brain tumors, 2 showed diffuse axonal injury, 3 showed arteriovenous malformation, 5 showed dural arteriovenous fistula, 1 showed moyamoya disease, and 2 showed Parkinson's disease. Conclusion: SWI is useful in detecting occult low flow vascular lesions, calcification and microbleed and characterising diverse brain disorders.

• Progress in Medical Physics
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• v.10 no.3
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• pp.159-168
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• 1999

Cardiac disease is one of the leading causes of death in Korea. In quantitative analysis of cardiac function and morphological information by three-dimensional reconstruction of magnetic resonance images, left ventricle provides an important role functionally and physiologically. However, existing procedures mostly rely on the extensive human interaction and are seldom evaluated on clinical applications. In this study, we developed a system which could perform automatic extraction of enpicardial and endocardial contour and analysis of cardiac function to evaluate reliability and stability of each system comparing with the result of ARGUS system offered 1.5T Siemens MRI system and manual method performed by clinicians. For various aspects, we investigated reliability of each system by compared with left ventricular contour, end-diastolic volume (EDV), end-systolic volume (ESV), stock volume (SV), ejection fraction (EF), cardiac output (CO) and wall thickness (WT). When comparing with manual method, extracted results of developed process using minimum error threshold (MET) method that automatically extracts contour from cardiac MR images and ARGUS system were demonstrated as successful rate 90% of the contour extraction. When calculating cardiac function parameters using MET and comparing with using correlation coefficients analysis method, the process extracts endocardial and epicardial contour using MET, values from automatic and ARGUS method agreed with manual values within :t 3% average error. It was successfully demonstrated that automatic method using threshold technique could provide high potential for assessing of each parameters with relatively high reliability compared with manual method. In this study, the method developed in this study could reduce processing time compared with ARGUS and manual method due to a simple threshold technique. This method is useful for diagnosis of cardiac disease, simulating physiological function and amount of blood flow of left ventricle. In addition, this method could be valuable in developing automatic systems in order to apply to other deformable image models.