• Journal of Korea Water Resources Association
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• v.43 no.12
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• pp.1029-1038
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• 2010

In meteorology Korea has 2/3 of rain of annual total rainfall at the month of Jun through Sept and it has possibility to have serious flood damage because geographically it is composed of mountainous area with steep slope which account for 70% of its country. Also, the increase of impervious layer due to industrialization and urbanization causes direct runoff, which deteriorates contamination of rivers by moving the contaminated material on the surface at the beginning of rain. In particular, the area of leisure facilities needs the management of water quality absolutely because dense population requires space of park function and place to relax and increases moving capability of non-point pollution source. For disposition of rainfall & runoff, the standard of initial rainfall, which is to be used for the computation of disposition volume, is significant factors for the runoff study of non-point pollution source, Until now, a great deal of study has been done by many researchers. However, it is the current reality that the characteristics of runoff varies according to land protection comprising river basin and the standard of initial rainfall by each researcher is not clearly defined yet. Therefore, in this research, it is suggested that, with the introduction of SOM (Self-Organizing Map), the standard of initial rainfall be determined after analyzing each sectional data by executing pattern classification about runoff and water quality data measured at the test river basin for this research.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.29 no.1
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• pp.36-41
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• 2018

This paper presents an implementation of a millimeter-wave(W band) multiflare-angle horn antenna. The proposed antenna is a multimode dual-polarized square horn having equal E- and H-plane beamwidths and consists of a multimode generating section, a four-square-waveguide exciter, orthomode transducers, and power combiners for the sum pattern formation. The antenna structure has been designed to allow for easy fabrication and the designed antenna has been fabricated to a precision of ${\pm}0.02mm$ by layer-by-layer machining and diffusion bonding. The input reflection coefficient and the radiation pattern of the fabricated antenna have been measured using a network analyzer and a far-field test facility. Measurements show that the proposed antenna has 17.7~18.3 dBi gain, $25.2{\sim}28.5^{\circ}$ beamwidth, and an input VSWR between 1.02~1.75, within ${\pm}0.5GHz$ from the center frequency.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.2
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• pp.905-910
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• 2013

Road facility has the high possibility of being damaged or destroyed due to continuous pass of the vehicles, overloaded vehicles, traffic accidents and so on and stormwater manhole, sewerage manhole that are installed on the road may cause the functional degradation in case of periodic pavement of the road. So management through establishing DB of road facility and efficient updating plan are required. Thus, this study used DGPS camera for efficient establishment and improvement of road facility DB. Applicability of DGPS camera could be suggested by satisfying the allowable accuracy required for establishing DB of road facility through the comparative analysis with the result of establishment of existing road facility DB and the process of DB establishment by existing total solution could be improved through process analysis. And the existing DB of road facility was improved so that the present conditions of surrounding topography and road facility can be grasped by developing the module that can add the images of road facility to digital map and Google Earth-based KML Builder. It is expected that road facility service that provides various information can be available if the spatial data of each local self-governing body and study of automation that utilizes DGPS camera images are accomplished hereafter.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.11
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• pp.53-60
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• 2020

The bogies of railway vehicles are one of the most critical components for service. Fatigue defects in the bogie can be initiated for various reasons, such as material imperfection, welding defects, and unpredictable and excessive overloads during operation. To prevent the derailment of a railway vehicle, it is necessary to evaluate and detect the defect of a connection weldment between the car body and bogie accurately. The safety of the bogie weldment was checked using an ultrasonic test, and it is necessary to determine the occurrence of defects using a learning method. Recently, studies on deep learning have been performed to identify defects with a high recognition rate with respect to a fine and similar defect. In this paper, the databases of weldment specimens with artificial defects were constructed to detect the defect of a bogie weldment. The ultrasonic inspection using the wedge angle was performed to understand the detection ability of fatigue cracks. In addition, the convolutional neural network was applied to minimize human error during the inspection. The results showed that the defects of connection weldment between the car body and bogie could be classified with more than 99.98% accuracy using CNN, and the effectiveness can be verified in the case of an inspection.

• Journal of Korea Water Resources Association
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• v.44 no.8
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• pp.653-666
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• 2011

The purposes of this study are to suggest flood vulnerability assessment method on climate change with evaluation of this method over the 5 river basins and to present the uncertainty range of assessment using multi-model ensemble scenarios. In this study, the data related to past historical flood events were collected and flood vulnerability index was calculated. The vulnerability assessment were also performed under current climate system. For future climate change scenario, the 39 climate scenarios are obtained from 3 different emission scenarios and 13 GCMs provided by IPCC DDC and 312 hydrology scenarios from 3 hydrological models and 2~3 potential evapotranspiration computation methods for the climate scenarios. Finally, the spatial and temporal changes of flood vulnerability and the range of uncertainty were performed for future S1 (2010~2039), S2 (2040~2069), S3 (2070~2099) period compared to reference S0 (1971~2000) period. The results of this study shows that vulnerable region's were Han and Sumjin, Youngsan river basins under current climate system. Considering the climate scenarios, variability in Nakdong, Gum and Han river basins are large, but Sumjin river basin had little variability due to low basic-stream ability to adaptation.

• International Journal of Highway Engineering
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• v.12 no.1
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• pp.1-8
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• 2010

Construction of road closed to mountains is inevitable in Korea because the mountainous region in Korea is more than 70% in area. Recently, due to global warming, typhoons or heavy rainfalls frequently occur, and accordingly, mountain roads are seriously damaged by landslides, debris flows, and uplift pressure below pavement. in this study, damage on pavement by uplift pressure was investigated. Various influencing factors such as slope angle, reinforcement of slope surface, thickness of soil cover underlain by rock, and types of drainage system were considered to evaluate uplift pressure acting on the bottom of pavement. Raising of water table up to the surface of slope may depend on the duration and intensity of rainfall. It shows that the installation of subdrain can reduce the uplift water pressure. Therefore, It is concluded that the use of subdrain system is effective to decrease uplift pressure and cement treated base is more endurable than typical crushed-stone base.

• Journal of Korea Water Resources Association
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• v.38 no.10 s.159
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• pp.801-810
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• 2005

The lag time is one of the most important factors for estimating a flood runoff from streams. It is well known to be under the influence of the morphometric properties of basins which could be expressed by catchment shape descriptors. In this paper, the notion of the geometric characteristics of an equivalent ellipse proposed by Moussa(2003) is applied for calculating the lag time of geomorphological instantaneous unit hydrograph(GIUH) at the basin outlet. The lag time is obtained from the observed data of rainfall and runoff by using the method of moments suggested by Nash(1957), and the procedure based on geomorphology is used for GIUH. The relationships between the basin morphometric properties and the hydrological response are discussed as applied to 3 catchments In Korea. Additionally, the shapes of equivalent ellipse are examined how then are transformed from upstream area to downstream one. As a result, the relationship between the hydrological response and descriptors is shown to be comparatively good, and the shape of ellipse is presented to approach a circle along the river downwards. These results may be expanded to the estimation of hydrological response of ungauged catchment.

• Journal of Korea Water Resources Association
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• v.38 no.12 s.161
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• pp.1039-1049
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• 2005

The objective of this study is to produce optimal radar-derived rainfall for hydrologic utilization. The ground clutter and beam blockage effects from Mt. Kwanak station (E.L 608m) are removed from radar reflectivities by POD analysis. The reflectivities are used to produce radar rainfall data in the form of rain rates (mm/h) by the application of the Marshall-Palmer reflectivity versus rainfall relationship. However, these radar-derived rainfall are underestimated in temporal and spatial scale compared with observed one, so it is necessary to hire a correction scheme based on the gauge-to-radar (G/R) statistical adjustment technique. The selected watershed for studying the real-time correction of radar-rainfall estimation is the Soyang dam site, which is located approximately 100km east of Kwanak radar station. The results indicate that adjusted radar rainfall with the gauge measurement have reasonal G/R ratio ranged on 0.95-1.32 and less uncertainty with that mean standard deviation of G/R ratio are decreased by $9-28\%$. Mean areal precipitation from adjusted radar rainfall are well agreed to the observed one on the Soyang River watershed. It is concluded that the real-time bias adjustment scheme is useful to estimate accurate basin-based radar rainfall for hydrologic application.

• Proceedings of the Korean Society of Dyers and Finishers Conference
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• 2012.03a
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• pp.107-107
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• 2012

3종 복합소재인 양모와 나일론, 레이온의 염색공정은 먼저 알칼리 욕에서 반응성염료로 레이온을 염색한 후, 산성욕에서 산성염료로 양모와 나일론을 염색하는 것이 일반적이다. 그런데 양모, 나일론, 레이온은 알칼리에 민감하므로 면 염색 시 적용되는 강알칼리인 수산화나트륨을 사용하면 섬유의 취화로 인하여 강도와 촉감저하 등의 문제가 발생하게 된다. 따라서 본 연구에서는 알칼리 중 탄산나트륨과 중탄산나트륨을 사용하여 염료를 투입하지 않고 염색공정을 거친 후 백도와 인장강도를 측정하여 황변 및 강도 변화 여부를 알아보았다. 레이온 70%, 양모 19%, 나일론 11%의 혼용율을 가지는 전처리 된 편물(130$g/m^2$, 32 inch, 18 gauge)에 탄산나트륨(시약 1급) 20g/l과 중탄산나트륨(시약 1급) 20g/l 각각을 투입하고 반응성염색공정($60^{\circ}C$, 60 min)으로 처리한 경우와 반응성 염색 후 산성염색공정($98^{\circ}C$, 60 min)으로 처리한 경우로 나누어 측색을 통해 백도와 L, a, b값을 측정하고 KS K 0521에 따라 인장강도 시험을 실시하였다. 그 결과, 탄산나트륨 투입시 백도 값이 중탄산나트륨에 비해 10% 정도 낮아지고 L, a, b값도 상대적으로 yellow 방향으로 이동해 있는 것으로 나타났다. 이것은 황변이 일어남을 의미하며 육안으로 확인하였다. 또한 인장강도 측정결과를 통해 소다회 처리 시 중조에 비해 30% 정도의 강도 저하가 일어남을 확인할 수 있었다. 그러나 반응성염색 후 산성염색을 거치게 되면 황변과 강도 저하 현상이 회복되는 경향을 나타내었다. 즉, 천연/나일론 편물을 반응성염색 시 알칼리로 탄산나트륨을 사용하면 염색공정 상에서 중탄산나트륨에 비해 황변이 일어나 염료 고유의 색상 발현에 영향을 줄 수 있고 강도 또한 30% 정도 저하되지만, 후에 산성염색 공정을 거치면 산 조건과 욕중 효과를 통해 일부 개선됨을 확인하였다. 이와 별도로 이번에는 시판되는 반응성염료 5종과 산성염료 3종을 조합하여 탄산나트륨과 중탄산나트륨 투입에 따른 염색실험을 실시하고 측색(DataColor SF600 광원D65, Strength)을 통해 염착량을 비교하였다. 그 결과, 중탄산나트륨으로 염색하면 탄산나트륨에 비해 모두 염착량이 저하되었으며, 염료의 구조적 차이와 컬러별로도 그 차이는 다양하였다. 그 중 저온에너지형 반응성염료는 탄산나트륨 투입에 비해 47~60% 정도로 가장 양호하였으며, 일부 반응성염료는 20%까지 떨어지는 값을 나타내었다. 이것은 탄산나트륨보다 중탄산나트륨의 알칼리 정도가 낮으므로 반응성염료의 염착이 적은 것으로 생각되며, 저에너지형 반응성염료의 경우에는 낮은 온도나 알칼리 조건에서도 상대적으로 높은 고착률을 나타내므로 적절한 반응성염료의 선택을 통해 그 차이를 극복할 수 있을 것으로 사료된다. 이상의 결과를 통해 탄산나트륨과 중탄산트륨의 알칼리 정도가 강도와 염착량에 미치는 영향의 차이를 고려하여 최적의 현장 처방을 선정해야 함을 알 수 있었다.

• Journal of the Korean Society of Hazard Mitigation
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• v.10 no.5
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• pp.159-168
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• 2010

This study investigates the relationships between the maximum freshwater pumping discharge and hydraulic properties of coastal aquifer using a laboratory model. The experiment performed the fresh pumping test in various locations near the saltwedge induced by saltwater intrusion to freshwater over aquifer characteristics of hydraulic conductivity, salinity, and ground surface slope. Saltwater pumping also tested to protest saltwater intrusion to the excessively discharging freshwater well. The maximum freshwater discharges were achieved, and then the optimum saltwater discharges were measured. It is found that greater hydraulic conductivity and ground surface slope produced greater the maximum freshwater pumping discharge. Salinity gave less impact on the pumping discharge relatively. Higher freshwater discharge was found at higher hydraulic conductivity and steeper ground surface slope. The optimum saltwater discharge required 14% more pumping rate than the maximum freshwater discharge to keep saltwater intrusion to the freshwater pumping well. Pumping well located closer to salt-wedge profile promoted less freshwater pumping discharge. Therefore, pumping well location, hydraulic conductivity, ground surface slope, and salinity should be taken into account in freshwater pumping in coastal aquifer.