• 한국지구물리탐사학회:학술대회논문집
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• 2005.05a
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• pp.129-136
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• 2005

The groundwater survey was carried out by electrical resistivity and resistivity tomography using several kinds of electrode array to delineate the depth of the saturated zone and basement complex, the aquifer system of fractured rock, and the 2-D resistivity structure was obtained by inversion technique. And the hole-to-surface and crosshole tomography were applied for two boreholes and the inverted resistivity tomogram are obtained. The comparison of those data with core logging data was performed and those results were relatively well correlated. And it was possible to find out the configuration of basement and the fracture zone and the aquifer system from the 2-D resistivity structure and resistivity tomogram.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.14 no.7
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• pp.769-776
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• 2003

This paper presents analysis and design of microstrip Rotman lens operating over wide band and wide steering angle by the contour integral method along with the segmentation method. All mutual coupling, internal reflections between ports and the discontinuity at every junction are taken into account. Equally spaced ports are designed and realized, which make suppress output ripple through the array ports. Impedance matching and mutual coupling between ports are analyzed and optimized using 12 input and 12 output exponential tapers. The measured results of fabricated lens show ${\pm}$ 1.8 dB insertion loss deviation over 6∼18 GHz wide frequency range and beam steering accuracy less than 1$^{\circ}$over ${\pm}$53$^{\circ}$angle and agrees well with the analysis results.

• Journal of Korea Soil Environment Society
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• v.1 no.1
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• pp.29-38
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• 1996

Among many geophysical prospecting methods, GPR(Ground Penetration Radar) and electrical resistivity method have been applied to a open waste dumping landfill for measuring of the site area and depth. The surveying was limited to a boarder of the site and inside area because of the field situation. The data of GPR were recorded by 50MHz antenna, and dipole array was used for electrical resistivity survey in the same survey line for the integrated interpretation. The result of GPR clearly indicated the horizontal boarder of site. However, the data of GPR did not have enough to measure the depth of site clearly. The electrical resistivity method may show the effective information by integrated interpreation. These results coincided with results of the boring test. Therefore, a combination of GPR and electrical resistivity is a good method for surveying of suspective open waste dumping landfill area and it's depth.

• Journal of Advanced Marine Engineering and Technology
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• v.34 no.6
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• pp.846-851
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• 2010

A liquid-air interface sensing system using the flat end surfaces of a fused-silica fiber coupler has been demonstrated. The principle is based on the additional optical loss caused by changing the refractive index of the external material at the boundary of the end face made of a fiber. The immersion characteristics of this system with respect to the different splitting ratios of the couplers were investigated to determine the sensitivity when it responses to water and air. These experimental data are very useful for selecting the coupling ratio of a coupler in order to develop a multiple sensing probe system. In the proposed sensor structure, it can be emphasize that the sensing probe can be appropriately arrayed on the basis of splitting ratio of the coupler. As a result, it is expected that the proposed liquid-air interface sensors can also be applied to monitor flooding that occurs in multiple areas at the same time.

• Journal of the Korean Wood Science and Technology
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• v.12 no.4
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• pp.47-52
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• 1984

본(本) 연구(硏究)는 연필향나무(Juniperus virginiana L.) 지재(技材)내에 형성(形成)된 압축이상재(壓縮異常材)(compression wood) 및 대응재(對應材)(opposite wood)에 관한 주사전자현미경적(走査電子顯微鏡的)인 특성(特性)을 비교(比較)하기 위하여 수행(遂行)되었는데 그 결과(結果)는 다음과 같다. 1. 압축이상재(壓縮異常材)의 가도관(假導管) 이행(移行)은 연륜(年輪)의 경계부(境界部)를 제외하고는 점진적(漸進的)이나 대응재(對應材)의 가도관(假導管) 이행(移行)은 급진적(急進的)이다. 그리고 대응재(對應材)에 있어서 추재율(秋材率)은 변이(變異)가 심하며 추재(秋材) 가도관(假導管)의 배열(排列)은 불균일(不均一)하다. 2. 압축이상재(壓縮異常材) 및 대응재(對應材)의 가도관(假導管)은 그 횡단면(橫斷面)의 모양(模樣)이각각 둥근형 및 모난형이다. 그리고 압축이상재(壓縮異常材)와 대응재(對應材) 모두에서는 큰 가도관(假導管)과 작은 가도관(假導管)이 혼재(混在)되어 있으나 나선상(螺旋狀)의 째짐이 가도관(假導管)의 막(膜)에 존재(存在)하지 않으며 세포간극(細胞間隙)은 경계부(境界部)를 지니는 경우가 있는데 압축이상재(壓縮異常材)에만 존재(存在) 한다. 3. 분야막공(分野膜工)에 있어서 압축이상재(壓縮異常材)의 막공구(膜孔口)는 대응재(對應材)의 것보다 가도관(假導管)측의 막공록(膜孔綠)이 더 넓기 때문에 더 좁으며 경사(傾斜)가 급한 타원형(楕圓形)을 나타낸다.

• Journal of the Korean Society of Marine Environment & Safety
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• v.21 no.5
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• pp.577-582
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• 2015

This paper is the fundamental study for the application of cold storage system to the transportation equipment by sea and land. This numerical study presents the solid-liquid phase change phenomenon of calcium chloride solution of 30wt %. The governing equations are 1-dimensional unsteady state heat transfer equations of $1^{st}$ order partial differential equations. This type of latent heat storage material is often usable in fishery vessel for controlling the temperature of container with constant condition. The governing equation was discretized with finite difference method and the program was composed with Mathcad program. The main parameters of this solution were the initial temperature of heat storage material, ambient temperature of cold air and the velocity of cold air. The data of boundary layer thickness becomes thin with the increasing of cold air flowing velocity and also the heat storage completion time become shorten.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.38 no.12
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• pp.999-1008
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• 2014

In this study, we consider the heat transfer characteristics of channel flow in the presence of an infinite streamwise array of equispaced identical rotating circular cylinders. This flow configuration can be regarded as a model representing a micro channel or an internal heat exchanger with cylindrical vortex generators. A numerical parametric study has been carried out by varying Reynolds number based on the bulk mean velocity and the cylinder diameter, and the gap between the cylinders and the channel wall for some selected angular speeds. The presence of the rotating circular cylinders arranged periodically in the streamwise direction causes a significant topological change of the flow, leading to heat transfer enhancement on the channel walls. More quantitative results as well as qualitative physical explanations are presented to justify the effectiveness of varying the gap to enhance heat transfer from the channel walls.

• The Journal of Engineering Geology
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• v.7 no.2
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• pp.139-149
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• 1997

Electrical resistivity monitoring methods were adopted to detect groundwater table change in alluvium. Numerical modelling test using finite element method(FEM) and field resisfivity monitoring were conducted in the study. The field monitoring data were acquired in the alluvium deposit site in Jeong-Dong Ri, Geum River where pumping test had been conducted continuously for 20 days to make artificial changes of groundwater table. The unit distance of the electrode array was 4m and 21 fixed electrodes were applied in numerical calculation and field data acquisition. "Modified Wenner" and dipole-dipole array configurations were used in the study. The models used in two-dimensional numerical test were designed on the basis of the simplifving geological model of the alluvium in Jeong Dong Ri, Geum River. Numerical test results show that the apparent resistivity pseudosections were changed in the vicinity of the pootion where groundwater table was changed. Furthermore, there are some apparent resistivity changes in the boundary between aquifer and crystalline basement rock which overlays the aquifer. The field monitoring data also give similar results which were observed in numerical tests. From the numerical test using FEM and field resistivity monitoring observations in alluvium site of Geum River, the electrical monitoring method is proved to be a useful tool for detecting groundwater behavior including groundwater table change. There are some limitations, however, in the application of the resistivity method only because the change of groundwater table does not give enough variations in the apparent resistivity pseudosections to estimate the amount of groundwater table change. For the improved detection of groundwater table changes, it is desirable to combine the resistivity method with other geophysical methods that reveal the underground image such as high-resolution seismic and/or ground penetrating radar surveys.

• Korean Journal of Remote Sensing
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• v.37 no.5_2
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• pp.1269-1279
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• 2021

Geostationary Ocean Color Imager II (GOCI-II), which are now operated successfully since its launch in 2020, acquires local area images with 12 Level 1B slot images that are sequentially acquired in a 3×4 grid pattern. The boundary areas between the adjacent slots are prone to discontinuity in radiance, which becomes even more clear in the following Level 2 data, and this warrants the precise analysis and correction before the distribution. This study evaluates the relative radiometric biases between the adjacent slots images, by exploiting the overlapped areas across the images. Although it is ideal to derive the statistics from humongous images, this preliminary analysis uses just the scenes acquired at a specific time to understand its general behavior in terms of bias and variance in radiance. Level 1B images of February 21st, 2021 (UTC03 = noon in local time) were selected for the analysis based on the cloud cover, and the radiance statistics were calculated only with the ocean pixels. The results showed that the relative bias is 0~1% in all bands but Band 1 (380 nm), while Band 1 exhibited a larger bias (1~2%). Except for the Band 1 in slot pairs aligned North-South, biases in all direction and in all bands turned out to have biases in the opposite direction that the sun elevation would have caused.

• Journal of the Korean Society of Radiology
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• v.17 no.1
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• pp.157-165
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• 2023

Ultrasound imaging uses sound waves of frequencies to cause physical actions such as reflection, absorption, refraction, and transmission at the edge between different tissues. Improvement is needed because there is a lot of noise due to the characteristics of the data generated from the ultrasound equipment, and it is difficult to grasp the shape of the tissue to be actually observed because the edge is vague. The edge enhancement method is used as a method to solve the case where the edge surface looks clumped due to a decrease in image quality. In this paper, as a method to strengthen the interface, the quality improvement was confirmed by strengthening the interface, which is the high-frequency part, in each image using an unsharpening mask and high boost. The mask filtering used for each image was evaluated by measuring PSNR and SNR. Abdominal, head, heart, liver, kidney, breast, and fetal images were obtained from Philips epiq5g and affiniti70g and Alpinion E-cube 15 ultrasound equipment. The program used to implement the algorithm was implemented with MATLAB R2022a of MathWorks. The unsharpening and high-boost mask array size was set to 3*3, and the laplacian filter, a spatial filter used to create outline-enhanced images, was applied equally to both masks. ImageJ program was used for quantitative evaluation of image quality. As a result of applying the mask filter to various ultrasound images, the subjective image quality showed that the overall contour lines of the image were clearly visible when unsharpening and high-boost mask were applied to the original image. When comparing the quantitative image quality, the image quality of the image to which the unsharpening mask and the high boost mask were applied was evaluated higher than that of the original image. In the portal vein, head, gallbladder, and kidney images, the SNR, PSNR, RMSE and MAE of the image to which the high-boost mask was applied were measured to be high. Conversely, for images of the heart, breast, and fetus, SNR, PSNR, RMSE and MAE values were measured as images with the unsharpening mask applied. It is thought that using the optimal mask according to the image will help to improve the image quality, and the contour information was provided to improve the image quality.