• Journal of Korea Water Resources Association
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• v.38 no.1
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• pp.59-71
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• 2005

Mountain watersheds are a lot of problems about soil erosion because of frequent wildfire occurrence. Runoff and soil erosion caused by the rain on a hillslope after wildfire are dependent on cover factor. And these has been a decrease by the cover factor recovery following time passage. The present paper defines the dynamic sensitivity of runoff and soil erosion that is the rate of runoff volume and soil erosion weight to rainfall energy and analyzes characteristics of the sensitivity for variation of cover factor, In according to the correlation analysis between other parameters and sensitivities, the sensitivity is the most dependent on the cover factor and the relation is exponential. The sensitivities after wildfire have suitable relation with treatment method for the mitigation of burnt forest and wildfire intensity. It was confirmed that the variation of soil erosion sensitivities come upon the range of stability in 5 years after wildfire.

• Proceedings of the Korea Water Resources Association Conference
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• 2022.05a
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• pp.96-96
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• 2022

가상현실 (Virtual Reality, VR) 기술은 3차원 가상공간 내에서의 높은 몰입감에 기반한 체험을 바탕으로 다양한 분야에서 활용되고 있다. 소방훈련이나 태풍, 지진 등 재해 대응훈련과 같이 인명피해의 위험이 있는 재해에 대한 VR 기술을 활용한 방재교육은 위험성을 동반하지 않으면서도 현장감에 기반한 높은 교육적 효과를 창출할 수 있다. 한국전자통신연구원에서는 VR 기술을 이용하여 소방훈련을 위한 실감 소방훈련 시뮬레이터를 개발한 바 있으며 목동재난체험관에서는 홍수, 태풍, 지진 등 다양한 재해에 대한 안전교육을 위한 자연재해 가상현실체험을 운영하고 있다. 이외에도 전국 지자체 및 교육청에서는 방재교육을 목적으로 VR 기술을 활용하고 있다. 그러나 기존의 VR을 활용한 수재해 방재교육은 범람의 수리학적 특성과 함께 수해지의 지형적 특성을 적절히 반영하지 못하는 단점을 가지고 있다. 이는 방재교육이나 경각심을 부각하는 데엔 효과적이나 실질적인 방재 가이드라인을 제시하는 데엔 한계가 있다. 본 연구는 몰입형 파랑해석모형인 Celeris Base를 기반으로 3차원 가상현실 시각화를 활용한 수리학적 홍수추적 모형을 개발하였다. 3차원 가상현실 시각화는 Unity3D를 이용하여 모의환경 내에 구현되었다. 강우-유출 과정의 수리학적 해석을 위해 동수역학 수치모형의 연속방정식 내에 강우와 침투에 대한 항을 추가하였다. 침투모형으로는 Horton 모형, Green-Ampt 모형과 함께 사면의 기울기를 고려한 Green-Ampt 모형을 적용하였다. 실제 유역에서의 홍수추적 모의결과는 관측값과 비교적 잘 일치함을 확인하였다. 개발된 모형은 VR 방재교육을 통해 일반인의 수재해 대응능력 향상에 기여함과 동시에 정확성 높은 홍수추적 모의결과에 기반한 홍수대책 마련에도 활용 가능할 것으로 기대된다.

• Journal of the Korean association of regional geographers
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• v.22 no.4
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• pp.887-911
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• 2016

The empirical law that transverse dunes migrate inversely with their heights leads logically to the prediction that multiple dune ridges will converse to a single huge dune by merging. This contradicts the existence of the steady state dune fields on the Earth. The recent studies have emphasized dune collisions as a key mechanism to the stability of dunefield. The roles of wind shadow aspect ratio, however, have yet to be fully explored. This research aims to investigate the potential roles of wind shadow aspect ratio in the dynamical behaviors of transverse dune field. The simplified model is established for this, based upon allometric properties of transverse dunes, wind speedup on the stoss slope and sand trapping efficiency. The derived governing equations can be transformed to the zoning criteria and vector field for dune evolution. The dynamics analysis indicates that wind shadow aspect ratios do not produce convergent areas on the behavior space; rather, they just act as one of the factors that affect the trajectories of dune evolution. Though the model cannot represent the stability of dune field, but seem to produce a reasonable exponent for dune spacing-height relations.

• 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.

• The Journal of Engineering Research
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• v.7 no.1
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• pp.61-70
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• 2005

Conventional geological survey utilizes the manual compass for mass amount of measurements of the geologic structure. Portable multifunction digital compass system was required by more detailed geological survey, due to increasing construction for rock slopes and runnels. In this paper, the system was implemented by using Intel PXA 255 embedded board as a system controller, and was composed of tilting sensor, digital azimuth sensor, and Global Positioning System (GPS) module. After the measured location, strike, and the angle of dip with our implemented system were transmitted to Personal Digital Assistant (PDA) or notebook, these data could be used for geologic structure analysis. It is expected that the availability of cheap and improved digital compass will reduce the coast and time of geological survey extensively.

• Current Research on Agriculture and Life Sciences
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• v.29
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• pp.11-19
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• 2011

This research gives weight to establish practical improvement based on analysis of the landscape ecological character and value to realize the importance of small wetland and stream in cultivated areas functioning as a residual landscape element in rural landscape and to deal with ecological depression effectively. The results of summary are as follows. 1) The results of landscape ecological character analysis of wetlands biotop in total of 7 sites, for example, size of surface in site 5 was widely formed about $10,600m^2$, which was assessed satisfactory in terms of slope of waterfront, width of hedgerow, vegetation condition of composition and so on. Also, The number of flexibility showed 2 in site 8-1, the highest, and morphological diversity showed 1.47, the highest. 2) The results of problem analysis of wetland biotop, most of wetlands are analyzed that the width of hedgerow was below 1m. Also, the 4 wetlands in site 8 are appeared that hard to live slope vegetation in there because of slope of waterfronts are above $45^{\circ}$. 3) The results of landscape ecological character analysis of stream in total of 6 sites, for example, width of waterfront in site 4 showed 55m, the widest, and investigated consist of natural ingredients such as soil, rock, gravel. However, width of waterfront in site 2-2 showed 4m, the narrowest, and inclined angle of slope was formed a right angle. 4) The results of problem analysis of stream, width of waterfront hedgerow in site 2-1 showed about 5m, which was very narrower than width of waterfront, and toxic chemicals discharged from near cultivated area without any filtering. Also, all areas of site 2-2 was formed concrete, and was assessed dissatisfactory in terms of capacity of nature purification, flood control, habitat living space because of straight stream. 5) Based on the result above landscape ecological character and problem analysis, main improvement guidelines are set in terms of shape, vegetation, topography in case of wetlands, and which are set in terms of vertical, horizontal structure in case of stream.

• Journal of Korean Society of Forest Science
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• v.105 no.3
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• pp.321-329
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• 2016

To estimate the sediment discharge controlled by sediment-filled check-dam and thereby enhancing factor for check-dam design and dredging criteria, we surveyed slope failures and stream-bed fluctuation caused by geomorphic disturbances (i.e., landslides and debris flows) in Inje, Gangwondo. In general, check-dams play roles for restraining and controlling sediment discharge within a section under the design equilibrium gradient and a section under the design flood gradient, respectively. The results in this study showed same pattern: that is, the closed type check-dam, which has a design restraint sediment discharge of $2,111m^3$, estimated to control a sediment discharge of $3,996m^3$ in the stream section within 250 m right upper area immediately after the disturbances occurred in 2006. As a result, a design control sediment discharge of the check-dam was larger than its design restraint sediment discharge. This represents that the check-dam is still having an own function for controlling sediment discharge although it exceeded the designed capacity by the sediment discharged from upstream during the disturbances. Our finding suggests that the sediment discharge controlling of check-dam may need to be evaluated separately from its sediment discharge restraint. Currently, the country, however, does not consider the design control (or restraint) sediment discharges, based on the actual field survey, as criteria for check-dam design and/or dredging work. Therefore, the accumulation of the quantitative data is required to support that check-dam has functions for both restraining and controlling sediment discharge. This would be a way to develop our erosion control technology to the scientific technology equipped with a more objective and systematic aspects.

• Radiation Oncology Journal
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• v.10 no.2
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• pp.137-145
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• 1992

Three-dimensional dose calculations based on CT images are fundamental to stereotactic radiosurgery for small intracranial tumor. In our stereotactic radiosurgery program, irradiations have been performed using the 6 MV photon beam of linear accelerator after stereotactic CT investigations of the target center through the beam's-eye view and the coordinates of BRW frame converted to that of radiosurgery. Also we can describe the tumor diameter and the shape in three dimensional configuration. Non-coplanar irradiation technique was developed that it consists of a combination of a moving field with a gantry angle of $140^{\circ}$, and a horizontal couch angle of $200^{\circ}C$ around the isocenter. In this radiosurgery technique, we provide the patient head setup in the base-ring holder and rotate around body axis. The total gantry moving range shows angle of 2520 degrees via two different types of gantry movement in a plane perpendicular to the axis of patient. The 3-D isodose curves overlapped to the tumor contours in screen and analytic dose profiles in calculation area were provided to calculate the thickness of $80\%$ of tumor center dose to $20\%$ of that. Furtheremore we provided the 3-D dose profiles in entire calculation plane. In this experiments, measured isodose curves in phantom irradiation have shown very similiar to that of computer generations.

• Journal of the Korean Geotechnical Society
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• v.23 no.11
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• pp.67-76
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• 2007

The characteristics of rockfall are determined by virtually all factors and conditions e.g. the physical figure of the slope such as inclination, height, roughness, the elemental figure of the slope such as vegetation and material deposited, and the shape and weight of the rockfall itself. Although it is one of the major factors to be considered in rockfall simulation, little attention has been given to the weight of the rockfall. And, since the size of the rockfall is dominated by joint spacing, the distribution of the rockfall block weight can be predicted as a function of the joint spacing. In this study, the weight distribution of rockfall was estimated by using the method of volumetric joint count, $J_{\nu}$, based on joint spacing, and $RQD-J_{\nu}$. The results indicate that the weight distributions were analogous in two methods, and the distribution was to be $75.3{\sim}76.7%$ for 200 kilograms or lesser, $15.0{\sim}16.6%$ for $200{\sim}400$ kilograms, and $6.7{\sim}9.7%$ for 400 kilograms or more, which show good matches with the actual on-site weight distribution. Therefore, the weight distribution of rockfall suggested in this paper is able to be considered as appropriate data for rockfall simulation.

• 한국방재학회:학술대회논문집
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• 2011.02a
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• pp.200-200
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• 2011

실제 유역에서 지류유입량(tributary inflow)의 형태로든 사면류의 형태로든 측방유입은 반드시 존재한다. 측방유입이 하도의 지배적인 흐름이 되는 경우 이는 유출수문곡선의 종거값과 형태를 변화시키는데 중요한 역할을 하게 된다. 따라서 측방유입의 형태를 저류상수 및 집중시간과 같은 수문학적 특성으로 적절하게 표현할 수 있다면, 전체 유역 내에서 측방유입의 지체효과 및 저류효과를 파악하는데 크게 기여하게 된다. 측방유입과 관련된 선행연구들을 살펴보면, Saint-Venant 방정식을 근간으로 하는 연구가 주를 이루고, Muskingum 하도추적모형 또는 Muskingum-Cunge 하도추적 모형을 확장한 연구가 나머지 부분을 차지한다(Hayami, 1951; Dooge et al. 1982). 지금까지 수행된 대다수의 연구들은 수치해석적으로 측방유입의 유출량을 모의하거나 혹인 관측값이 존재하는 경우 역으로 측방유입의 특성을 유추한 것들로 다소 복잡하고, 관측값이 존재하지 않는 경우에는 적용이 어려운 문제점을 가지고 있다. 그러나 유역의 물리적인 특성과 주하도의 특성만을 이용하여 측방유입의 특성을 대략적으로 유추하는 것이 가능하다면, 전체유역과 각 소유역의 관계는 전체유역의 물리적인 특성과 주하도의 수문학적 특성만으로 충분히 파악할 수 있게 된다. 다시 말해 유역분할 시 각 소유역 사이의 관계를 고려하여 전체유역의 유출량을 파악하는 것이 가능해진다. 이에 본 연구에서는 Muskingum 하도추적모형을 재해석한 순간단위도를 이용하여 측방유입의 수문학적 해석을 시도하였다. 대상유역으로는 격자형태의 사각형과 삼각형 유역을 임의로 가정하였으며, 각각의 유역에서의 순간단위도를 선형하천모형과 선형저수지모형의 합으로 유도하였다. 이때 저류상수는 하도길이와 비례한다는 가정을 바탕으로 사각형과 삼각형 유역에서의 저류상수 및 집중시간을 유도하였다. 특히 유역 출구에서 최원점에 위치한 격자에서 유출이 발생시간을 집중시간으로 가정하였으며, 이 시점에서의 종거값과 기울기를 이용하여 저류상수를 유도하였다. 그 결과, 선형하천과 선형저수지모형 각각은 집중시간과 저류상수로 특징지어짐을 알 수 있었으며, 결정된 측방유입의 저류상수 및 집중시간이 적절한 것을 확인하였다. 이러한 결과는 향후 대유역에서 유역분할의 효과뿐만 아니라 홍수량 할당문제를 입증하는데 크게 기여할 것으로 기대된다.