• Proceedings of the Korea Water Resources Association Conference
• /
• 2018.05a
• /
• pp.452-452
• /
• 2018

최근에는 지구온난화의 영향으로 집중 호우, 가뭄 등 기상 이변이 빈번하게 발생하고 있어서 물 관리의 복잡성과 불확실성이 매우 높아지고 있다. 특히 중소하천은 하천의 경사가 급하고 하천길이가 짧아 홍수파의 이동시간이 짧기 때문에 홍수대비를 위한 시간이 매우 짧다. 국회예산정책처(2012)에 따르면 과거 5개년간(2007~11) 발생한 자연재해 피해 중 87%가 집중 호우 및 태풍에 의한 피해이며, 이 중 98.7%가 중 소규모 하천에서 발생하였다. 그러나, 중소하천 관리를 담당하는 지자체는 열악한 재정 여건으로 인해 예방보다 사후복구에 집중할 수밖에 없는 상황이다. 또한 최근 하천 고수부지에 주차장, 위락시설 등 공간적 활용이 증가함에 따라 홍수발생시 위험성도 증가하고 있어 예방 및 대응 중심의 홍수대응기준 수립이 시급하다. ICT 인프라를 이용하여 유관기관의 실시간 수문자료를 공유하고, 수집된 실시간 수문자료를 활용한 홍수분석 및 홍수대응 기준 대응기준 수립을 통한 예방적 재난대응 체계를 마련해야 한다. 이에 본 연구에서는 A지자체를 대상으로 홍수분석 모형을 구축하고, 구축된 모형의 계산결과를 활용하여 예상강우별 도달시간, 수위상승 등을 예측하고, 하천수위별 홍수대응기준을 수립하였다. 수위별 대응기준은 현장에서 계측되는 수위값을 기준으로 홍수예보기준, 하천기본계획의 제방고 및 주변 제약 사항을 고려하여 직접알람 기준으로 활용하였다. 특히 A지자체는 상류에 B댐이 위치하여 홍수시 B댐 수위 및 운영의 영향을 반영하는 홍수대응기준의 수립이 요구된다. 본 연구에서는 강우 시나리오별 모형분석을 통하여 예상되는 호우사항에 대한 홍수대응기준을 제시하였다. 향후 본 연구로 산정된 홍수대응기준의 지속적인 보완, 실시간 수문자료 공유체계 확대, 재해관련 책임기관과의 유기적인 기술교류 등을 통해 지자체 및 중소하천 홍수피해 저감을 위한 능동적인 홍수대응 체계 구축이 수행되어야 할 것이다.

• Journal of Broadcast Engineering
• /
• v.24 no.4
• /
• pp.643-659
• /
• 2019

In this paper, the technology verification of next generation broadcasting technology and service suitable for domestic broadcasting environment was carried out to build and activate domestic terrestrial UHD broadcasting. ATSC 3.0-based mobile HD broadcasting is currently conducting experiments with various parameters from broadcasting companies, research institutes and others. However, experiments on integrated transmissions, including audio services, have not been carried out. Through this experiment, we first performed the theory and experiment on the maximum number of ATSC 3.0 based UHD broadcasting service, maximum service number of HD broadcasting considering mobility, and maximum service number of audio broadcasting within one channel (6MHz). Second, parameters for integrated transmission of each service (UHD broadcasting, mobile HD and audio broadcasting) in one channel were derived. Finally, we studied technical possibilities through field tests that we receive while moving directly in the field.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.47 no.3
• /
• pp.169-176
• /
• 2019

In the present study, a CFD/DSMC hybrid method performed by a coupled analysis between the CFD method and the DSMC method was developed to obtain the flow information on the rarefied gas flows effectively. Flow simulations around the high speed vehicles on the transition flow regimes were conducted by using the developed method. The FRESH-FX vehicle made of cone and cylinder shapes was considered for the simulations. The results of the hybrid method were compared with the results of the pure CFD and the pure DSMC method to confirm the reliability and efficiency of the hybrid method. It was found that the gradient and the intensity of the shock waves were weakened due to the relatively low density on the transition flow regime. It was confirmed that the results of the hybrid analysis were different to those of the pure CFD analysis and almost identical to those of the pure DSMC analysis. In addition, the computational time of the hybrid method was reduced than that of the pure DSMC method. As a result, it was obtained that the validity and the efficiency of the CFD/DSMC hybrid method.

• The Journal of the Acoustical Society of Korea
• /
• v.38 no.4
• /
• pp.467-475
• /
• 2019

A high-intensity ultrasound wave generates acoustic streaming and acoustic radiation forces when propagating through a medium. An acoustic radiation force generated in a three-dimensional space can produce a solid tactile sensation, delivering spatial information directly to the human skin. We placed 154 ultrasound transmit elements with a frequency of 40 kHz on a concave circular dish, and generated an acoustic radiation force at the focal point by transmitting the ultrasound wave. To feel the tactile sensation better, the transmit elements were excited by sine waves whose amplitude was modulated by a 60 Hz square wave. As an application of ultrasonic tactile sensing, a region where tactile sense is formed in the air is used as an indicator for the position of the hand. We confirmed the utility of ultrasonic tactile feedback by implementing a system that provides the number of fingers to a machine by receiving the shape of the hand at the focal point where the tactile sense is detected.

• The Journal of the Korea Contents Association
• /
• v.21 no.5
• /
• pp.259-267
• /
• 2021

Machine translators first appeared in the 1950s and made a leap in translation accuracy by applying the neural translation system in the 2010s. However, it is still having difficulty in translating complex sentences, which made it inconvenient to use machine translators as an English learning tool. Therefore, this study analyzed the usability of a machine translator as an English learning tool through a backtranslation experiment of as phrases. As analysis tools, Google Translator, Naver Papago, and Microsoft Translator, were used since they are representative machine translators using a neural translation system. As a result of the study, findings are: The usability was significantly different according to each as usage when using a machine translator. Accordingly, as usages in sentences were classified into high, ordinary, and low usability. Unlike previous studies, this study has a research contribution in analyzing the machine translator as a direct learning tool and quantifying the usability of the conjunction as.

• The Journal of the Korea institute of electronic communication sciences
• /
• v.16 no.6
• /
• pp.1195-1204
• /
• 2021

In this paper, we present an optimal design method for wave power generators using the response surface analysis. Especially, in our method, we reduce the mechanical loss by selecting the linear generator whose linear movement can be converted to the electrical energy directly with the vertical movement of waves. Therefore, we calculate the exciting force acting on the drive device in a slow-wave condition and determine the winding process with a ratio of the slots and poles for the improvement of energy conversion efficiency. In addition, we employ the regression analysis for deriving the shape factors of the stator and the translator, which have a significant effect on the performance of a generator. We choose the best design variables through the response surface analysis, and then we study the optimization method for designing the efficient experiment using the analysis results. Finally, we show the validity of the proposed method through the simulation results.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2021.06a
• /
• pp.336-336
• /
• 2021

기후변화와 도시화로 인한 집중 호우와 불투수층 증가로 도시 홍수의 발생 빈도와 규모가 증가하고 있다. 인적, 물적 자원이 집중되어 있는 도시유역의 특성상 침수가 발생하면 이로 인한 직접적 피해 뿐만 아니라 사회경제적 2차 피해를 발생한다. 도시 홍수로 인한 피해를 줄이고 도시의 재해에 대한 회복력을 키우기 위해서는 관측과 더불어 정확한 모의 기술이 중요하다. 한편, 격자 기반 도시 홍수 모의는 집중 호우에 따른 침수의 시공간적 발생 양상을 물리적으로 해석하는 방법으로, 지표수-우수관거 이중배제 통합 모의, 수치기법, 병렬컴퓨팅, 수질 연계 모의 등의 측면에서 지금까지 많은 발전이 이루어져 왔다. 최근들어 원격탐사 기술의 발달로 공간해상도 1미터 수준 혹은 그 이상의 초고해상도 지형자료가 많은 지역에서 대해 가용해지고 있으며, 도시 홍수 해석에 이와 같은 초고해상도 자료를 적용하기 위한 연구가 활발히 진행되고 있다. 본 연구에서는 초고해상도 지형 및 토지 피복 자료의 공간해상도가 침수해석에 미치는 영향을 분석한다. 도시침수의 두가지 주요 요인인 내수침수와 외수범람 중에서 극한 강우에 의한 내수침수해석 사례만을 주요 연구 범위로 한다. 초고해상도 입력자료의 격자기반 도수 해석 모형으로는 운동파 기반의 2차원 지표 흐름 해석 모형을 적용하고, 초고해상도 모의의 효율적 계산을 위해 하이브리드 병렬 컴퓨팅 기술을 이용한다. 초고해상도 입력자료 적용 사례 대비, 공간해상도 저하에 따라 침수 면적이나 깊이 등에서 어떤 변화가 있는지 정량적으로 검토한다. 또한, 강우의 강도 및 공간분포가 초고해상도 도시 홍수 해석에 미치는 영향에 대해서 분석한다. 모의 결과로부터 도시 홍수 해석시 거리 단위(street-level) 정확도의 재현을 위해 적정한 공간해상도를 분석하고, 초고해상도 도시 홍수 모의를 이용한 기후변화에 따른 극한 홍수의 도시지역 영향 분석 및 회복력 개선 관련 연구의 가능성에 대해 논의한다.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.28 no.4B
• /
• pp.429-439
• /
• 2008

The purpose of this study is to examine the characteristics of run-up height over sandy beach due to the shape of submerged breakwater. For the discussion on it in detail, 3-Dimensional numerical model with Large Eddy Simulation, which is able to simulate directly interaction of Wave Structure Sandy beach (hereafter, LES-WASS-3D; Hur and Lee, 2007) has been used to simulate run-up height over sandy beach as well as wave field around submerged breakwaters. Using the results obtained from numerical simulation, the effects of the shape of submerged breakwaters (crown height, crown width, crown length and submerged breakwater's slope gradient) on run-up height over sandy beach have been discussed related to the wave height distribution and characteristics of up-layer flow around ones.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.28 no.5B
• /
• pp.591-594
• /
• 2008

Present study aims at the development of a reasonable boundary condition for a structure over inclined seabed in case of the numerical model with quadrilateral mesh system. The technique for the inclined impermeable/permeable boundary in the quadrilateral mesh is newly proposed. The new technique and LES-WASS-3D model (Hur and Lee, 2007) have been used for the investigation of the dynamics of fluid field, and validated through the comparison with a typical stair-type boundary condition. 3-Dimensional numerical model with Large Eddy Simulation is called LES-WASS-3D, and is able to simulate directly interaction of WAve Structure Sea bed/Sandy beach.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.28 no.3B
• /
• pp.345-354
• /
• 2008

In this present study, we made a first attempt to investigate physical transformations of incident waves in surf and swash zone and hydrodynamic phenomena of detached and submerged breakwaters. For an accurate simulation of the complicated wave deformation, Three-Dimensional numerical model with Large Eddy Simulation has been developed recently and expanded properly for the current applications, which is able to simulate an accurate and direct WAve Structure Sandy seabed interaction (hereafter, LES-WASS-3D). LES-WASS-3D has been validated through the comparison with experimental results for limited cases, and has been used for the simulation of wave run-up on sandy beach, mean fluid flows over and around submerged structures and swash zone (alongshore/rip current), and spatial distribution of wave height in wide fluid regions. In addition, a strategy of efficient deployment ($Y/L_i=1.50{\sim}1.75$, $W/L_r=0.50$) of the submerged breakwaters has been discussed.