• Proceedings of the Korea Water Resources Association Conference
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• 2021.06a
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• pp.335-335
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• 2021

하천의 홍수터는 평상시 수면위로 노출되어 국민의 여가생활을 위한 공원, 주차장 등으로 활용되다 홍수기 수위가 상승하면 침수되는 하천공간이다. 홍수범람 면적 또는 홍수위 산정을 위한 수치모의 시, 홍수의 평면적인 변화를 분석하기 위해서는 1차원 모의결과와 지형정보를 연계하여 범람면적을 산정하거나 2차원 수치모형의 격자를 대상공간에 대하여 구축한 후 모의를 수행한다. 1차원 수치모형은 계산효율이 우수하고 지류의 합류에 의한 영향을 다수 반영하거나, 긴 구간의 하천단면 구축을 통하여 경계조건이 수치해석 결과에 미치는 영향을 최소화할 수 있는 장점이 있다. 그러나 지형의 영향으로 발생하는 국부적인 유속변화와 유향의 평면적인 분포에 의해 발생하는 범람면적의 변화를 반영하기 어렵다. 홍수범람을 고려하여 제작하는 홍수위험지도는 2차원 수치모형의 결과를 기반으로 한다. 2차원 수치모형은 하도의 만곡, 제방의 형상 등과 같은 지형에 의한 유속장의 변화, 흐름영역의 수축 및 확대에 의한 유속의 변화 등을 자세히 반영할 수 있는 장점이 있다. 반면에 수치격자 생성 및 계산결과 도출에 소요되는 시간이 길고 계산영역 설정의 한계로 인하여 경계조건이 흐름해석결과에 영향을 미칠 수 있는 문제점이 있다. 이와 같은 문제점을 해결하기 위하여 국내외적으로 1차원과 2차원 수치해석기법을 연계하여 하나의 모형으로 구축한 1-2차원 수치해석 모형이 개발 또는 적용되고 있다. 1-2차원 연계해석기법은 1차원 해석영역과 2차원 해석영역을 연계함에 있어서 흐름방향 연계와 횡방향 연계로 구분할 수 있다. 본 연구에서는 1차원과 2차원 수치해석을 연계하는 기법에 따라서 발생하는 수치모의결과를 비교하고 적용성을 검토하였다. 수리실험 관측결과가 있는 사례에 모형을 적용한 후, 한강지형에 수치모형을 적용하고 그 결과를 비교한다. 또한, 계산에 소요되는 시간을 비교하기 위하여 2차원 수치격자의 해상도를 다양하게 적용하여 수치실험을 수행한다. 분석결과를 기반으로 홍수위험지도 제작, 홍수위산정 및 홍수예보 등에 새로운 기술의 적용성을 검토한다.

• Proceedings of the Korea Water Resources Association Conference
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• 2020.06a
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• pp.154-154
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• 2020

최근 국지성 호우가 빈번하게 발생하고 있고, 이로 인해 국내 도시지역 홍수피해 발생빈도와 피해규모가 증가하고 있다. 2010년, 2011년, 2018년에 서울에서는 홍수로 인한 침수피해가 크게 발생하여 많은 인명과 재산의 피해가 있었다. 이렇듯 도시지역은 타 지역에 비해 인구와 재산이 밀집되어 있어 홍수 취약성이 상대적으로 높은 지역이다. 국내에서는 홍수피해 저감을 위해 홍수예보를 발령하고 있다. 하지만 국내 홍수예보는 국가하천 및 지방하천의 주요 하천 구간에서만 실시되고 있어 이러한 하천에 접하지 않는 지역은 국가 홍수예보의 수혜를 받을 수 없다. 그렇기 때문에 각 지역에서는 홍수 대응을 위해 기상청의 호우특보 기준을 사용하고 있으며 이 기준은 전국적으로 동일하다는 특징이 있다. 하지만 각 도시지역은 과거 홍수피해에 따라 방재시설을 추가로 설치하거나 보수하고 있어 각 지역의 방재시설 현황 및 홍수에 대한 취약성 정도가 다른 상황이다. 그러므로 전국적으로 동일한 강우기준이 적용되어 발령되고 있는 호우 특보는 실제 각 도시지역의 방재현황이 고려되지 못한다는 문제가 있다. 이와 관련하여 과거 낙동강 지역을 대상으로 지역별 홍수위험도에 따른 홍수위험지수를 산정하고 검토한 연구가 수행된 바 있다. 본 연구에서는 각 도시지역의 방재 현황을 고려하여 강우기준을 보정할 수 있는 가중치를 산정하는 방안에 대해 제시하였다. 이를 위해 서울 지역 25개 기초지자체를 대상으로 연구를 진행하였으며, 홍수 취약성을 평가하기 위한 세부인자는 노출도, 민감도, 적응도로 구분하였다. 각 세부인자 별 가중치를 산정하기 위해서는 엔트로피 방법을 적용하였고, 산정된 결과를 이용하여 각 지역 별 가중치를 산정하기 위해서는 유클리드 거리 산정법을 적용하였다. 그 결과 각 지역의 방재 특성을 고려한 가중치를 산정할 수 있었으며 향후에는 지역 별 방재특성이 고려된 강우기준을 제시 및 적용성을 검토할 계획이다.

• Journal of Korean Society of Environmental Engineers
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• v.27 no.1
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• pp.101-108
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• 2005

Because the stone cultural properties located outdoors, they have been altered and deteriorated in external appearance due to environmental factors such as acid rain, extreme change in temperature, and salts. Damage to stone cultural properties is accelerated particularly due to recent industrial development and environmental pollution. An experimental study was conducted to evaluate the effect of environmental contaminants on the weathering of granite. And as part of the developing of conservation method, $TiO_2$ catalyst was prepared and tested. When fresh granite was dipped into the salt and acid solutions, dissolution rate of eight minerals (Si, Mg, Ca, Na, K, Fe, Mn, Al) are abruptly increased at initial stage of reaction and then increased steadily until 100 cycles. After salt and acid solution experiments, the mineral compositions of the granite surface were lower then that of the fresh granite and density of the weathered granite was steadily decreased from $2.60\;g/cm^3$ to $2.56\;g/cm^3$, but Poissions ratio and absorption ratio were slightly increased. It was expected at stone cultural assets could be weathered by salts and acid rain. In the case of $TiO_2$ was coated to the granite, the dissolution rate of minerals and absorption ratio of $TiO_2$ coated granite were decreased. Therefore, the $TiO_2$ coating method tested in this study considered to be a viable method to assist in the conservation of stone cultural properties from environmental contaminants.

• Journal of Korea Water Resources Association
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• v.49 no.11
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• pp.931-939
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• 2016

Bangudae Petroglopys of the national treasure No. 285 located in elevation of 53 m to 57 m have been damaged by repetition of submergence and exposure due to the Sayeon-dam of EL.60 m constructed in down stream. In this study, as a preservation plan of the petroglyphs from the contact with water, the construction of eco-levee was suggested and its effect was investigated in the views of hydraulic engineering. It was designed to be located aside of 80 m from Bangudae Petroglyphs with the length of 440 m in streamwise direction, and it was need to construct a new channel maintaining the original hydraulic capacity and conveyance. Hydraulic characteristics such as water surface elevations and velocities near Bangudae Petroglyphs were measured after the eco-levee was installed in the hydraulic model with the scale of 1:50. It showed that there were not much changes of water surface elevations and velocities between sayeon-dam spillway EL. 60 m (Suggestion 1) and EL. 54 m (Suggestion 2). It was concluded the eco-levee could be made of natural materials like soil, pebble, gravel in terms of allowable velocity and shear stresses. The slope of water surface at Suggestion 2 was steeper, and velocities near Bangudae Petroglyphs were also faster than Suggestion 1. As the vorties occured at the left side in Suggestion 2, more detailed study is required.

• Journal of the Institute of Electronics and Information Engineers
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• v.51 no.2
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• pp.55-68
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• 2014

Some infrastructure these days is usually constructed under the ground for it to not interfere the foot-traffic of pedestrians, and thus, it is difficult to visually confirm the accurate location of the site where the establishments must be buried. These technical difficulties increase the magnitude of the problems that could arise from over-reliance on the experience of the worker or a mere blueprint. Such problems include exposure to flood and collapse. This paper proposes a constructor-oriented visualization system via mobile gadgets in general construction sites with occluded structures. This proposal is consisted with three stages. First, "Stage of detecting manhole and extracting features" detects and extracts the basis point of occluded structures which is unoccluded manhole. Next, "Stage of tracking features" tracks down the extracted features in the previous stage. Lastly, "Stage of visualizing occluded constructions" analyzes and synthesizes the GPS data and 3D objects obtained from mobile gadgets in the previous stages. This proposal implemented ideal method through parallel analysis of manhole detection, feature extraction, and tracking techniques in indoor environment, and confirmed the possibility through occluded water-pipe augmentation in real environment. Also, it offers a practical constructor-oriented environment derived from the augmented 3D results of occluded water-pipings.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.19 no.4
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• pp.345-354
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• 2007

A sedimentation analysis has been attempted to figure out sedimentation environment due to construction of coastal jetties, such as fish harbor dike, flow guided dike and jetty in shallow Kusipo area, in which tidal range marks up to 6.6 meters in spring tide. As an initial approach of understanding field measurement were done on several stations along reference lines with total station and photo analysis taken by remote controlled small air craft far one and half years. Also numerical tests were done by 2-D ADCIRC model considering dry-wet treatment to evaluate flow and bottom shear stress variations. According to direct measurement, deposition seems to be dominant on Kusipo beach. Model results show bottom shear stress lessens to $0.10{\sim}0.15\;N/m^2$ on most shadow zone of jetties and the inner zone is suffering sedimentation as a result of dike construction. However this is the first approach with limited analysis, thus it should be dealt further considering physical characteristics of bottom sediments in a complete sediment model on upcoming study.

• Journal of the Korea institute for structural maintenance and inspection
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• v.14 no.5
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• pp.128-135
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• 2010

Polymer-modified cement mortar(PCM) has been widely used for strengthening of the concrete structures due to its excellent physical properties such as high strength and durability. Adhesive strength or behavior, on the other hands, between PCM and concrete is very important in strengthening the concrete member using PCM. Therefore the adhesive failure mechanism between PCM and concrete should be fully verified and understood. This study was performed to evaluate adhesive strength of PCM to the concrete by the direct pull-out test. In the direct pull-out tests, the adhesive strength under the various pre-treatment conditions such as immersion, thunder shower, freezing and thawing are evaluated. Also, the field direct pull-out test are performed to investigate the adhesive strength of mock-up test specimens. In the results of the test, the adhesive strength value by field test are lower than those of the standard curing condition. From these comparison and investigation, field test result was similar with the thunder shower test result. The results of the test was used to evaluate the korean industrial standard of polymer modified cement mortars for maintenance in concrete.

• Journal of the Korea Institute of Building Construction
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• v.19 no.2
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• pp.131-138
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• 2019

Recently, there are many structures exposed to severe outdoor environments, which results in rapid degradation of durability of the concrete structures. there can be rapid deterioration of the concrete structures from early frost damage due to the insufficient curing in low outdoor temperature condition. The objective of this study is to investigate the effect of thickness change conditions and binding material on early frost damage depth of the concrete exposed to cold weather in winter, and is to clearly assess damage depth of the concrete structure due to early frost damage. Specimens with 300x300x(150, 200, 250, 300mm) were prepared. OPC and OPC+FA+BS were adopted for binders. Test results indicate that the depth of the early frost damage was deeper with the decrease of thickness of members. The brightness of specimens were reduced when the member thickness was thinner. When determining the depth of early frost damage, it can be distinguished into dark color and relatively bright color when dried for approximately 30 minutes in the indoors of $20^{\circ}C$ in temperature and 60% in relative humidity after submerging in water for 24 hours. The dark colored part can be determined easily when measured with vernier calipers.

• Journal of IKEEE
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• v.23 no.4
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• pp.1461-1464
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• 2019

In this paper, we propose the development of embedded board for integrated radiation exposure protection fireman's life-saving alarm capable of location tracking and radiation measurement. The proposed techniques consist of signal processing unit, communication unit, power unit, main control unit. Signal processing units apply shielding design, noise reduction technology and electromagnetic wave subtraction technology. The communication unit is designed to communicate using the wifi method. In the main control unit, power consumption is reduced to a minimum, and a high performance system is formed through small, high density and low heat generation. The proposed techniques are equipment operated by exposure to poor conditions, such as disaster and fire sites, so they are designed and manufactured for external appearance considering waterproof and thermal endurance. The proposed techniques were tested by an authorized testing agency to determine the effectiveness of embedded board. The waterproof grade has achieved the IP67 rating, which can maintain stable performance even when flooded with water at the disaster site due to the nature of the fireman's equipment. The operating temperature was measured in the range of -10℃ to 50℃ to cope with a wide range of environmental changes at the disaster site. The battery life was measured to be available 144 hours after a single charge to cope with emergency disasters such as a collapse accident. The maximum communication distance, including the PCB, was measured to operate at 54.2 meters, a range wider than the existing 50 meters, at a straight line with the command-and-control vehicle in the event of a disaster. Therefore, the effectiveness of embedded board for embedded board for integrated radiation exposure protection fireman's life-saving alarm has been demonstrated.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.6 no.3
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• pp.142-151
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• 2001

Detailed interpretation of some high-resolution seismic profiles in Yosu Strait reveals that Late Quaternary deposits consist of three allostratigraphic units (UH, LH, PL) formed by fluvial and tidal controls. The top mud unit, UH, thins onshore, and overlies the backstepping modem Seomjin delta deposits, which is interpreted as a transgressive systems tract (757) related to Holocene relative sea-level rise. The unit LH below the unit UH is composed of delta, valley- and basin-fill facies. The delta facies (Unit $LH_1$) occurs only in Gwangyang Bay and shows two prograding sets retrogradationaly stacked, thus it is also interpreted as a transgressive systems tract(757). On the contrary, the valley- and basin-fill facies (Unit $LH_2$), interpreted as 757, occur between the units UH and PL (Pleistocene deposits) in Yosu Strait. The bounding surface between UH and $LH_2$ can be interpreted as a tidal ravinement surface on the basis of trends thinning toward inner bay and becoming young landward. Furthermore its geomorphological pattern is similar to that of recent tidal channels. This allostratigraphy in'ffsu Strait suggests that two 757 deposits (UH and $LH_2$), divided by tidal ravinement surface, have been formed in Yosu Strait, whereas in Gwangyang Bay backstepping delta deposits ($LH_1$) without tidal ravinement surface have been formed during Holocene sea-level rise. These characteristics indicate that different stacking patterns could be formed in these two areas according to different increasing rate of accommodation space caused by different geomorphology, sediment supply and tidal-current patterns even in the same period of Holocene sea-level rise.