• Journal of the Chungcheong Mathematical Society
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• v.29 no.1
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• pp.59-71
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• 2016

To obtain more accurate approximation of the true images in the deblurring problems, the weighted global generalized cross validation(GCV) function to the inverse problem with multiple right-hand sides is suggested as an efficient way to determine the regularization parameter. We analyze the experimental results for many test problems and was able to obtain the globally useful range of the weight when the preconditioned global conjugate gradient linear least squares(Gl-CGLS) method with the weighted global GCV function is applied.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.22 no.7
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• pp.956-965
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• 1998

Hot-wire measurement of the longitudinal and radial velocity components and Reynolds stresses are reported for developing turbulent flow in a strongly curved 180 deg. pipe and its tangents. Slanted wire is rotated to 6 directions and the voltage outputs of them are combined to obtain the mean velocities and Reynolds stresses. Significant double maxima in the longitudinal velocity component appear in the bend. V-profiles reveal the development of a strong secondary flow. This secondary flow is induced by the transverse pressure gradient set up between the outer(r$\sub$o/) and inner(r$\sub$i/) wall region of the bend. Another second cross-stream flow develops after .theta.=135 deg. and its direction is opposed to that of main second flow.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.13 no.4
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• pp.52-64
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• 2010

This study was carried out to analyze the occurrence characteristics and the influence of forest environment factors on the debris flow of 3 national parks in korea. The results obtained from this study were summarized as follows; The total number of debris flow occurrence was 125 areas. The average length of the debris flow scar was 144m, average width was 20m. And the average area and sediment were $2,854m^2$ and $3,959m^3$ respectively. The factors influencing the debris flow were highly occurred in Metamorphic rock, mixed forest type. And also, slope gradient was $30{\sim}35^{\circ}$, aspect was NE, altitude was over 1,000m, vertical and cross slope was concave (凹), soil depth was below 15cm, stream order was 0 order. The variables of cross slope (complex), deciduous tree, soil depth (over 46cm), cross slope (concave), mixed forest type and altitude (801~1200m) in correlation analysis were significant at 1 % level. The landslide of high mountain area highly tend to change the debris flow in stream bed of torrent. The debris flow in national parks mainly occurred in high mountain area with long ridge and steep slope.

• Transactions of the Korean Society of Mechanical Engineers
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• v.15 no.1
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• pp.262-273
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• 1991

In the present study, the steady, incompressible, isothermal, developing flow in a 90.deg. rectangular cross sectional strongly curved duct with aspect ratio 1:1.5 and Reynolds number of 9.4*10$^{4}$ has been investigated. Measurements of components of mean velocities, pressures, and corresponding components of the Reynolds stress tensor are obtained with a hot-wire anemometer and pitot tube. In general, flow in a curved duct is characterized by the secondary vortices which are driven mainly by centrifugal force-radial pressure gradient imbalance, and the stress field stabilizing effects near the convex wall and destablizing effects close to the concave wall. It was found that the secondary mean velocities attain values up to 39% of the bulk velocity and are largely responsible for the convections of Reynolds stress in the cross stream plane. Therefor upstream of the bend the Reynolds stress are low. Corresponding to the small boundary layer thickness. At successive planes, large values of Reynolds stress were observed near the concave surface and the side wall.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.21 no.9
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• pp.1139-1148
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• 1997

Compression waves propagating in a high-speed railway tunnel develops large pressure fluctuations on the train body or tunnel structures. The pressure fluctuations would cause an ear discomfort for the passengers and increase the aerodynamic resistance of trains. As a fundamental research to resolve the pressure wave phenomenon in the tunnel, experiments were carried out by using a shock tube with an open end. A blockage to model trains inside the tunnel was installed on the lower wall of shock tube, thus forming a sudden cross-sectional area reduction. The compression waves were obtained by the fast opening gate valve instead of a conventional diaphragm of shock tube and measured by the flush mounted pressure transducers with a high sensitivity. The experimental results were compared with the previous theoretical analyses. The results show that the ratio of the reflected to the incident compression wave at the sudden cross-sectional area reduction increases but the ratio of the passing to the incident compression wave decreases, as the incident compression wave becomes stronger. This experimental results are in good agreements with the previous theoretical ones. The maximum pressure gradient of the compression wave abruptly increases but the width of the wave front does not vary, as it passes over the sudden cross-sectional area reduction.

• Journal of the Korean Ceramic Society
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• v.25 no.3
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• pp.243-250
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• 1988

The cross effect between an ion flux and an electronic current in a nonstoichiometric binary oxide, $A_{1-\delta}O_\mu$, has been analyzed in the light of irreversible thermodynamics. It has been shown that a net flux of the mobile cation vacancy is induced through the system in an electrical potential gradient applied across a pair of the reversible electrodes, which makes the Fick frame shift relative to the laboratory frame. As a consequence, the relative shift is a measure of the effective charge responsible for the cross effect. Two experiments are proposed to measure the shift.

• Journal of the Korean Wood Science and Technology
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• v.36 no.2
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• pp.20-28
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• 2008

This study was carried out to provide the so-called circumferential slicing method for investigating radial distributions of the tangential strains and of moisture contents within the log cross section (LC) of Kalopanax pictus during indoor drying it. While the heartwood showed an almost uniform moisture content distribution in the range of about 50~55% in case of the green wood, it has gradually decreased toward the outer side, showing about 19% of moisture content difference from the innermost slice. Although the moisture gradient along the radial direction has gradually become gentle as drying progresses, the sapwood of the outer side represented the moisture contents below the fiber saturation point after 24 hours of drying while the heartwood in the inner part showed the moisture contents higher than the fiber saturation point. The pith side was laid under the tensile stress after 24 hours of drying, and then gradually decreasing toward the bark side, and showed the distribution being switched again to the tensile stress on the bark side. As the drying has progressed, this trend got more intensified, and finally showed the U-shaped distribution model after 48 hours of drying. The circumferential slice test is considered to be suitable in quantitatively determining the tangential strains and moisture content within a LC.

• Journal of Preventive Medicine and Public Health
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• v.53 no.4
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• pp.211-219
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• 2020

Objectives: The goal of this study was to identify chronic conditions and multimorbidity patterns in patients with coronavirus disease 2019 (COVID-19) and to examine their associations with pneumonia and death. Methods: This cross-sectional study analyzed the official data of COVID-19 patients in Mexico through May 18, 2020 (released by the Secretaría de Salud de México). Adjusted logistic regression models were applied to assess the associations of comorbidities with pneumonia and death. The marginal effects were estimated, and the probability of pneumonia or death according to the number of comorbidities was graphed for each year of age. Results: Of the 51 053 COVID-19 patients enrolled in the final analysis, 27 667 (54.2%) had no chronic conditions, while 13 652 (26.7%), 6518 (12.8%) and 3216 (6.3%) were reported to have 1, 2, and 3 or more simultaneous conditions, respectively. Overall, a significant incremental gradient was observed for the association between multimorbidity and pneumonia (p<0.001); for 2 chronic conditions, the adjusted odds ratio (aOR) was 2.07 (95% confidence interval [CI], 1.95 to 2.20), and for ≥3 conditions, the aOR was 2.40 (95% CI, 2.22 to 2.60). A significant incremental gradient was also found for the relationship between multimorbidity and death (p<0.001); an aOR of 2.51 (95% CI, 2.30 to 2.73) was found for 2 chronic conditions and an aOR of 3.49 (95% CI, 3.15 to 3.86) for ≥3 conditions. Conclusions: Underlying chronic conditions and multimorbidity are associated with pneumonia and death in Mexican COVID-19 patients. Future investigation is necessary to clarify the pathophysiological processes behind this association, given the high burden of chronic diseases in various countries, including Mexico.

• Journal of Korean Society of Forest Science
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• v.96 no.6
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• pp.611-619
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• 2007

This study was carried out to analyze the landslide characteristics and forest environment factors on the landslide area of 7 national parks in korea. The results obtained from this study were summarized as follows; The total number of landslide occurrence was 44 areas. The average length of the landslides scar was 152 m, average width was 17 m. And the average area was $2,818m^2$. The factors influencing landslides were highly occurred in Metamorphic rock, mixed forest type. And also, $30{\sim}35^{\circ}$ in slope gradient, NE in slope aspect, slope higher than 1,000 m, concave (凹) type in vertical and cross slope, 0 ordered stream. The main factors affecting landslide area in stepwise regression analysis were sheet type in landslided shape, NE in slope aspect, 2 ordered stream, SE in slope aspect, slope gradient and complex slope in cross slope type in order of regression coefficient.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.26 no.7
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• pp.996-1003
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• 2022

In this paper, we present a new method for determining the scan line and range for vision-based 1-D barcode recognition. This is a study on how to detect valid barcode representative points and directions by applying the DBSCAN clustering method based on block HOG (histogram of gradient) and determine scan lines and barcode crosslines based on this. In this paper, the minimum and maximum search techniques were applied to determine the cross-line range of barcodes based on the obtained scan lines. This can be applied regardless of the barcode size. This technique enables barcode recognition even by detecting only a partial area of the barcode, and does not require rotation to read the code after detecting the barcode area. In addition, it is possible to detect barcodes of various sizes. Various experimental results are presented to evaluate the performance of the proposed technique in this paper.