• Journal of Korea Water Resources Association
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• v.54 no.6
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• pp.407-418
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• 2021

In this study, the two-dimensional flow model, Nays2DH, and driftwood dynamics model were combined to analyze the flow and driftwood behavior depending on the characteristics of the inflow of driftwood and the length of the driftwood stem. In particular, the Dashpot-spring model was added to the driftwood dynamics model to simulate the collision motion of the driftwood, and the wood jam characteristics by the collision of the driftwood were compared. As a result of the simulation, the pass rate of the obstacle section, the travel distance of wood jam, and the mean position of the wood pieces were respondent sensitively by the length of the driftwood stem, but the cohort size of the driftwood supply was insignificant excepting for the pass rate. Through this study, we could understand the interaction between hydraulic structures and driftwood, and through this, it is believed that it will be helpful in establishing a durable maintenance plan for hydraulic structures by predicting the transport and jam formation phenomena of driftwood in advance.

• Korean Journal of Remote Sensing
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• v.37 no.6_2
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• pp.1837-1847
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• 2021

This study investigated wind corridors for the entire Suwon-city area using a geographic information system and a computational fluid dynamics model. We conducted numerical simulations for 16 inflow wind directions using the average wind speeds measured at the Suwon automated synoptic observation system (ASOS) for recent ten years. We analyzed the westerly (dominant wind direction) and easterly cases (not dominant but strong wind speed) in detail and investigated the characteristics of a wind speed distribution averaged using the frequencies of 16 wind directions as weighting factors. The characteristics of the wind corridors in Suwon city can be summarized as; (1) In the northern part of Suwon, complicated flows were formed by the high mountainous terrain, and strong (weak) winds and updrafts (downdrafts) were simulated on the windward (leeward) mountain slope. (2) On the leeward mountain slope, a wind corridor was formed along a valley, and relatively strong airflow flowed into the residential area. (3) The strong winds were simulated in a wide and flat area in the west and south part of Suwon city. (4) Due to the friction and flow blocking by buildings, wind speeds decreased, and airflows became complicated in the downtown area. (5) Wind corridors in residential areas were formed along wide roads and areas with few obstacles, such as rivers, lakes, and reservoirs.

• Proceedings of the Korea Water Resources Association Conference
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• 2011.05a
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• pp.194-194
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• 2011

보는 일반적으로 흐르는 하천을 막아 수위를 높여서 취수 용도로 사용되는 저수 시설의 역할을 한다. 그러나 홍수 시 보 구조물은 홍수류 소통의 장애물 역할을 하여 보 상류의 수위를 상승시키고, 이는 곧 보의 상류에서는 침수피해를 발생시키기도 한다. 따라서 홍수 시 보 구조물이 하천흐름을 방해하지 않도록 설계하여 보의 통수능과 안정성을 확보시키는 것은 보 설계 시에 매우 중요한 요인으로 작용한다. 본 연구에서는 낙동강 구미보를 대상으로 보 구조물에 의한 보 상류부의 통수능 및 치수안정성에 대해 분석하기 위하여 수리모형실험을 수행하였다. 가동보의 수문 운영 조건에 따른 보 상류부의 수위 변화, 빈도 홍수량에 의한 구미보 상류의 흐름특성을 유속 및 수위측정을 통하여 비교 분석하였다. 구미보의 수문 2개를 이용하여 수문 2개 개방 조건, 수문 1 개 개방, 수문 1개 폐쇄 조건, 수문 2개 폐쇄 조건으로 구분하여 실험을 진행하여 분석하였다. 연구 결과 수문폐쇄조건에서 수위가 가장 크게 나타났으며 급격히 상승하였다. 수문이 폐쇄된 2년 빈도의 홍수량조건이, 수문이 개방된 100년 빈도 홍수량조건보다 상류수심이 높게 형성되는 것을 확인할 수 있었다. 따라서 실제 계획홍수량보다 작은 유량조건일지라도 수문이 폐쇄됐을 경우에 보 상류부는 홍수범람의 위험이 더욱 커진다고 판단되었다. 가동보 수문을 개방하여 통수하는 경우에 보 상류의 수위저하 영역을 검토한 결과, 유량이 클수록 가동보에 의해 수심저하 영향을 받는 보 상류의 영역이 늘어나며, 보 상류 방향으로 거리에 따른 보 상류의 수심저하가 발생하는 거리의 관계는 유량 크기에 비례하는 것으로 나타났다.

• Korean journal of applied entomology
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• v.56 no.2
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• pp.187-193
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• 2017

The Japanese pine sawyer, Monochamus alternatus Hope, is a representative vector of the pine wood nematode, Bursaphelenchus xylophilus, which causes wilting symptoms in pine trees. A control method using a net has been introduced, which is an alternative method to the fumigation for the control of dead pine trees by pine wilt disease. This study was carried out to investigate the factors that induce gnawing and escaping behaviors of M. alternatus. The behaviors were examined after M. alternatus adult was placed in a confined space at different temperatures. M. alternatus adults could escape through mesh net torn by gnawing when they were confined in a space of 30 mm or less in diameter. The success rate of escape was high at 20 to $30^{\circ}C$, and no adults escaped at $15^{\circ}C$. The enticement of M. alternatus adults by food didn't affect the success rate of escape. In the case of not being confined in a narrow space, the escaping hole could not be formed because the gnawing was not concentrated on one part. M. alternatus moved its body in a narrow space using the tarsus of middle and hind legs, and made an escape hole by concentrically gnawing the obstacle on the front side with mandible, and showed a behavior of getting out while supporting the body by supporting the front legs. The present results will be able to use as an important basic information for evaluating the performance of mesh net which confines M. alternatus adults and suggested by alternative method to fumigation technology.

• International Journal of Highway Engineering
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• v.12 no.3
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• pp.59-70
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• 2010

More than 10 different cases of airline overrun accidents happened annually home and abroad in recent years. So the government put the guidelines to protect that kinds of accidents, which is named 'Runway End Safety Area'. However, the great part of airports are far from the standards, because most of the airports have been built before the guidelines. Moreover, in many cases natural obstacles, ambiance, and local area developments obstruct the extension of the runway to meet the criteria. For these reasons, the Federal Aviation Administration (FAA) recommends that the aviation fields construct 'Aircraft Rapid Arresting System(ARAS)' at the end of the runway. Many airdromes have been constructing the system and some airports have already completed the construction. In this research, our team performed a basic study about low strength perlite concrete to provide the proper material with 'ARAS'. As a result, the unit weight of the low strength perlite concrete was $4.5{\sim}6.4kN/m^3$ and uniaxial compressive strength was measured in the range of $400{\sim}1,470kN/m^2$. In addition, we tested penetration compressive strength by using CBR tester, and we observed that the strength was increased after around 60% of penetration rate. Also, 40% of penetration rate was measured through the penetration test with dump trucks.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.13 no.1
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• pp.30-38
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• 2014

The purpose of this study is to build and manage environment models with line segments from sonar range data on obstacles in unknown and varied environments. The proposed method therefore employs a two-stage data-transform process in order to extract environmental line segments from range data on obstacles. In the first stage, the occupancy grid extracted from the range data is accumulated to form a two-dimensional local histogram grid. In the second stage, a line histogram extracted from a local histogram grid is based on a Hough transform, and matching serves as a means of comparing each of the segments on a global line segments map against the line segments to detect the degree of similarity in the overlap, orientation, and arrangement. Each of these tests is formulated by comparing one of the parameters in the segment representation. After the tests, new line segments can be found at maximum-density cells in the line histogram, and they are composed onto the global line segment map. The proposed technique is demonstrated in experiments in an indoor environment.

• Journal of the Korean Institute of Telematics and Electronics T
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• v.35T no.1
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• pp.111-119
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• 1998

To predict propagation environments of antenna radiation pattern, it is very important for deceision of service area, selection of the best station location and design of cell etc. By analyzing the propagation prediction model that is varied acceding to the kind of antenna, beam angle, terrain and obstacles, we expect that the economic operating of communication networks, calling quality and service of subscriber will be enhanced. It was measured the fields strength to propose the optimal propargation predicted model of the zone of Seji base station in Naju-city. The simulations of field test are 4 types Hata model, the Egri model, the Carey model and the proposed model. Finally the proposed model are more close agreement with experimental test than other models.

• Proceedings of the Korean Society of Computer Information Conference
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• 2021.07a
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• pp.491-492
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• 2021

현대사회의 물류 현장에서 근로자가 직접 물류를 분류하는 작업을 하거나 상하차 작업을 진행하고 있다. 본 논문에서 제안하는 자율주행 로봇을 이용한 물류 분류 시스템은 물류 운반 로봇과 컨베이어 벨트로 구성된다. 물류 운반 로봇은 경로 설정 및 장애물 감지가 가능한 자율주행 기능을 가지며, 컨베이어 벨트는 하차된 물류의 무게 측정과 배송 가격을 표시하는 기능을 가진다. 본 연구의 결과는 근로자들의 노동 강도와 육체적 또는 정신적인 피해로 인해 발생하는 산업재해의 발생률을 감소시킬 수 있는 기대와 심야 시간에 부족한 인력을 보충하여 24시간 물류센터를 가동할 수 있는 가능성을 가진다.

• Proceedings of the Korea Water Resources Association Conference
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• 2022.05a
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• pp.256-256
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• 2022

레이놀즈 분해법은 유속을 비롯한 변수를 평균 성분과 변동 성분으로 분해하는 분석 방법으로, 난류 분석의 기본이 되는 방법이다. 그러나 유체 내에 장애물이 존재할 경우, 흐름에 큰 와류가 존재하여 난류 변동 성분과 구분되는 고유 구조가 형성되는데, 이러한 경우에 레이놀즈 분해법을 적용하면 고유 구조의 변동 성분이 난류로 처리되어 난류 강도가 과다하게 책정될 수 있다는 한계점이 있다. 이에 대한 대안으로 제안된 것이, 변수를 평균 성분, 파동 성분, 변동 성분으로 분해하는 삼중 분해법이다. 삼중 분해법은 흐름 내의 고유 구조를 추출하는 것을 가능하게 하여 다양한 연구에서 사용되어왔다. 삼중 분해법을 구현하기 위해 이용되는 방법론 중 하나로, 공분산 행렬을 이용하여 유속장을 분해하는 방법인 적합 직교 분해법이 많이 사용된다. 본 연구에서는 원기둥 후류에 적합 직교 분해법을 사용하여 삼중 분해법을 시행하고, 후류의 흐름 구조를 분석하는 것을 목표로 하였다. 영상 유속계를 사용하여 실험을 통해 원기둥 후류의 수평 유속장을 측정하였고, 측정 자료에 적합 직교 분해법을 적용한 결과, 첫 두 모드에서 큰 규모의 와류가 파동 형태로 전파되는 것이 관찰되어 고유 구조의 존재를 확인할 수 있었다. 해당 성분을 삼중 분해법의 파동 성분으로 상정하였고, 푸리에 분석을 적용한 결과에서도 원기둥 후류의 고유 진동수가 뚜렷하게 나타나는 것을 확인하였다. 또한, 원기둥 후류의 에너지 전달 구조를 확인하기 위하여 에너지 방정식에 삼중 분해법을 적용하여 식을 유도하고, 실험 자료로부터 각 항을 계산하여 비교해보았다.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.41 no.4
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• pp.365-376
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• 2021

In general, domestic streams and rivers are composed of alluvial rivers consisting of sand and gravel beds. These rivers can cause erosion and riverbed changes due to sudden changes in flow rates, such as floods, torrential rains, and heavy rains. In particular, there are various types of erosion, such as contraction erosion caused by changes in river shape, or local erosion occurring around obstacles such as piers, abutments or embankments. In addition, river changes can occur in various forms, such as static or dynamic periods, due to limitations such as flow rate, velocity, and shear stress. This study focused on the erosions of embankments directly related to human casualties among various river structures, and evaluated limit velocities and critical shear stress in order to identify changes in strength of natural materials by identifying the characteristics of natural hoan materials and resistance to erosions. In particular, the limitations of materials according to the type of materials in the river, characteristics of particles, and size of particles were studied using Soil loss, which is a change in the volume of the revetment material, and it is intended to be used as basic data for river design and restoration.