• The Bulletin of The Korean Astronomical Society
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• v.43 no.2
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• pp.51.5-52
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• 2018

The origin of dust in the early Universe has been the subject of considerable debate. Core-collapse supernovae (ccSNe), which occur several million years after their massive progenitors form, could be a major source of that dust, as in the local universe several ccSNe have been observed to be copious dust producers. Here we report nine near-infrared (0.8 - 2.5 micron spectra of the Type II-P SN 2017eaw in NGC 6946, spanning the time interval 22 - 205 days after discovery. The spectra show the onset of CO formation and continuum emission at wavelengths greater than 2.1 micron from newly-formed hot dust, in addition to numerous lines of hydrogen and metals, which reveal the change in ionization as the density of much of the ejecta decreases. The observed CO masses estimated from an LTE model are typically 0.0001 Msun during days 124 - 205, but could be an order of magnitude larger if non-LTE conditions are present in the emitting region. The timing of the appearance of CO is remarkably consistent with chemically controlled dust models of Sarangi & Cherchneff.

• Structural Engineering and Mechanics
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• v.81 no.5
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• pp.607-616
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• 2022

In this work, the free vibration problem of a rotating Rayleigh beam is solved using the meshless Petrov-Galerkin method which is a truly meshless method. The Rayleigh beam includes rotatory inertia in addition to Euler-Bernoulli beam theory. The radial basis functions, which satisfy the Kronecker delta property, are used for the interpolation. The essential boundary conditions can be easily applied with radial basis functions. The results are obtained using six nodes within a subdomain. The results accurately match with the published literature. Also, the results with Euler-Bernoulli are obtained to compare the change in higher natural frequencies with change in the slenderness ratio (${\sqrt{A_0R^2/I_0}}$). The mass and stiffness matrices are derived where we get two stiffness matrices for the node and boundary respectively. The non-dimensional form is discussed as well.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.12
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• pp.8654-8664
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• 2015

Beam-type structures with non-uniform cross sections are widely used in mechanical, architectural, and civil engineering fields. This paper deals with dynamic characteristics and vibration problems. Governing equations are first derived by using local coordinates. Their solutions are then assumed by using Galerkin's mode summation method. Bisection method is also applied in solving the determinant of the matrix which can provide natural frequencies. Whereas finite element methods adopt admissible functions satisfying only geometric boundary condition, in this study we apply Galerkin's mode summation method which uses eigen-functions satisfying both governing equations and boundary conditions. Modal analysis and experimental tests are finally performed using simply-supported beams with four different non-uniform cross-sections. Our analytical results then show good agreement with experimental ones.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.15 no.3
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• pp.110-114
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• 2010

A data set of current, wind and wave height measured at the monitoring buoy and sea level at Busan harbor were analyzed to explain the physical conditions during the strong rip current events at Haeundae Beach of Suyeong Bay during 13~15 August 2009. Tidal current, with spring-neap variations, has similar average speed to the short-term non-tidal currents. The common features at the time of rip currents are the strong northeasterly wind and superposition of tidal and non-tidal currents both flowing toward the coast. However on 14 August when the rip current did not occur, tide and wave height were similar to the rip-current cases but the tidal and non-tidal current were to nearly opposite directions. While strong winds produce large waves thus the basic condition for rip current but its influence on the local circulation in the bay is relatively small. Of the three adjacent beaches, only at Haeundae the rip currents are reported. This difference may be due to the unique bottom topography featured by underwater hill in the central region off Haeundae which can decay the incoming waves, tides and currents to intensify the rip current.

• The Journal of Engineering Geology
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• v.10 no.2
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• pp.36-51
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• 2000

Almost every year, Korean suffered from the repetitive natural disasters such as typhoons and floods. During last 10 years, Korea experienced annual average of $50 million property damages caused by inundation. To estabilish the flood disaster counter plan, knowledge for flood damage causes based on the field investigations of inundated area is required. The field investigations is focused on technique to document and analyze the meteorological conditions leading to torrential rains, the causes and patterns of flooding, the performance of flood control structures in affected areas, the extent damages and the effectiveness of local emergency response and recovery actions. We did comparative analysis of field investigation techniques. As a major goal of flood hazard map design, one of non structural disaster countermeasures, it was expected to reduce flood damage losses by requiring local governments to implement land-use regulation that would result in safe building practices in flood hazard areas. This requires local governments to develop flood hazard maps to assess how to manage particularly vulnerable floodplain areas. In this study we suggested a design manual and the management system of flood hazard map.

• Journal of the Korea Society of Computer and Information
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• v.27 no.8
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• pp.177-183
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• 2022

The purpose of this study is to examine the current status of the elderly welfare ordinances currently enacted and operated by local governments, analyze the actual conditions and problems of the contents, and suggest the direction of enactment and revision of the elderly welfare ordinances for actively responding to the demand for various welfare services for the elderly. To this end, the scope of the study was specified by ordinances in Gwangju Metropolitan City, five autonomous districts, Jeollanam-do, and 22 cities and counties, and the criteria for content analysis of the elderly welfare ordinance of these local governments were selected and compared and analyzed in the four major areas of elderly welfare: income and jobs, care, health, leisure activities, and social participation. According to the analysis results, the direction of enacting the ordinance is to secure financial resources for the elderly welfare budget, develop differentiated welfare policies for the elderly that reflect the characteristics of each local government, expand ordinances related to infectious diseases, enact ordinances for medical support for non-infectious diseases, and enact customized ordinances for the elderly living alone. Finally, the limitations on the research subject and analysis scope of this study and future research directions were presented.

• Proceedings of the Korean Society of Organic Agriculture Conference
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• 2009.12a
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• pp.45-56
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• 2009

Current status on the occurrence and the management of the major disease, insect and mite pests were investigated in the organic or non-chemical pest control orchards from 2005 to 2009. Numbers of certified organic or non-chemical apple orchards were increased from 14 in 2005 to 78 in 2008. Severe damages on leaves and fruits occurred by the several diseases such as marssonina blotch, bitter rot, white rot, sooty blotch and flyspeck, and the several insect pests such as apple leaf-curling aphid, woolly apple aphid, oriental fruit moth and peach fruit moth on the almost certified organic or non-chemical pest control orchards. About 10 and 18 environmental-friendly materials were used to control diseases and insect or mite pests respectively. But, lime sulfur and bordeaux mixture to diseases and machine oil, plant oil mixed with egg yolk, and pheromone mating disruptions to insect pests were effective to control under the adequate conditions. At present, it is extremely difficult to produce organic apples in Korea. Growers must consider about and solve so many conditions on the cultivar, weather, local site, marketing and so on, before when they decide to change from conventional or IPM(Integrated Pest Management) to organic or non-chemical pest control orchards.

• Journal of Korean Society on Water Environment
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• v.35 no.6
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• pp.497-509
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• 2019

After the Total Maximum Daily Loads(TMDLs) was applied, it became beyond the limit of concentration management. However, it does not adequately reflect the characteristics of various watersheds, and causes problems with local governments because of the standard flow set. Thus, in this study, the Han River system is organized into four groups in estimating the Pollution Contribution by applying the Flow Duration Curve(FDC) created by the daily flow of data from the HSPF. And the method of this study is expected to be valuable as basic data for the TMDLs. As a result, Group I contains the main watersheds with no large hydraulic structures and tributary watersheds. There is no specificity in the FDC and the Pollution Contribution is estimated as rainfall runoff. Group II contains watersheds near the city where the FDC is maintained above a certain level during the Low Flow Conditions and the Pollution Contribution is estimated as the discharge flow of large scale point pollution facilities. Group III contains the main watersheds in which the large hydraulic structures are installed and FDC is curved in the Low Flow Conditions. So the Pollution Contribution is estimated as the water quality of the large hydraulic structures. Group IV contains the upstream in mainstream watersheds in which the large hydraulic structures are installed and the FDC is disabled before the Low Flow Conditions. As the flow is concentrated in the High Flow Conditions, the non-point pollution sources are estimated as the Pollution Contribution.

• Journal of The Korean Society of Agricultural Engineers
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• v.61 no.4
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• pp.63-73
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• 2019

Coastal and fishing facilities are gradually deteriorating in function due to the continual accumulation of soil sediments, which has affected local economic activities. Currently, there are many methods to remove soil sediments, but these methods are either a temporary solution or require a repetitive removal of the soil sediments, which is a huge financial burden for the maintenance of the facilities. To solve these problems, this study proposed a non-power soil cleaning system and evaluated field applicability by carrying out field model tests. The conditions for the evaluation focused on the drainage-elapsed time and drainage-outflow velocity according to the water level change in the water tank. In the field test, silty clay and sand were separately installed, and sedimentation soil removal test was practiced. As a result, the system was verified to have a sufficient outflow velocity for the removal of soil sediments. In addition, a generalization equation that can be used in different regions of the tide was suggested in this study. These results will greatly contribute to removing soil sediments in ports and dike gate facilities on the southwest coast. Since the system is an eco-friendly technology that does not require additional energy, thus it is expected to contribute to maintenance of sustainable facility performance as well as economic effect in the future.

• Korean Journal of Cognitive Science
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• v.16 no.1
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• pp.17-27
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• 2005

After prolonged viewing of a moving pattern, a stationary pattern can appear to move in the opposite direction, a phenomenon known as motion aftereffect (MAE). Unlike the classical explanation MAE was not confined to an adapted region; instead it can spread to an adjacent region, which was not adapted previously. In order to examine the relative locus of the mechanism responsible for MAE spreading, a rotating harmonic spiral pattern was presented as an adapting stimulus within an annulus window, and then the duration of MAE was measured in both the adapted annulus region and the non-adapted inner region. Two different kinds of test patterns were used: the same and mirror images of the original adapting pattern. An interesting characteristic of a harmonic spiral is that the orientation of a contour at a given location is different from thar of its mirror image by 90 degrees, and consequently the adapting effect of local motion detector is not expected to occur in the mirror image. The results showed that MAE duration in an adapted region was longer in the same image condition than in its mirror image condition, while MAE duration in an non-adapted region was not found to be different between those two different image conditions. These results suggest that MAE spreading might be produced by the adaptation of global motion detectors, not by local motion detectors.