• Proceedings of the Korea Water Resources Association Conference
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• 2019.05a
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• pp.373-373
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• 2019

도시화로 인해 인구가 도시로 집중되고, 불투수층이 증가되어 유출율이 지속적으로 커지고 있다. 또한 최근의 기후변화에 의하여 홍수 및 침수가 빈번해짐에 따라, 도시에서 내수침수를 방지하기 위한 새로운 패러다임이 필요한 실정이다. 기존 내수침수 해결방안은 배수능력을 증가시키기 위해 하수관거 용량을 키우고, 펌프장을 증설하였으나, 국지적이고 기습적인 집중호우가 내리는 경우에는 국민의 생명과 재산을 보호하기 어려운 부분이 있다. 이에 따라 지하방수로와 도시물순환 등 중장기계획이 수립되고 있으나, 지하철 출입구, 지하 주차장 출입구, 건물 외부 출입구 등 평상시에는 출입구로 사용하다가 홍수시에 내수침수를 방지하기 위한 차수벽에 대한 다양한 연구는 미흡한 실정이다. 국내 외 차수벽에 대한 조사 및 분석결과 국외의 경우 자동 수동 반자동의 다양한 차수벽이 제시되어 있으나, 국내의 경우에는 이제야 제품개발이 시작되고 있는 것으로 나타났다. 특히, 내수침수 피해가 큰 영국이나 미국의 뉴욕시의 경우 건축법에 의해 내수침수피해를 막을 수 있는 가이드라인이 제시되어 있으며, 실증실험도 진행되고 있으나 국내의 경우에는 미비한 실정이다. 본 연구는 국내 외 차수벽에 대한 조사 및 분석을 수행하고, 자동차수벽을 위한 가이드라인을 제시하며, 수치모의와 수리모형실험을 통해 국내에서 사용가능한 적정 자동차수벽을 제시하고자 한다. 특히, ICT와 연계를 통해 원격제어 및 관리가 되도록 시스템을 구성하도록 한다. 이에 따라 본 연구를 통해 국내에서 사용가능한 내수침수방지가 가능한 자동차수벽이 제시된다면, 기후변화와 도시화에 대응하는 재난대응기술이 되어 내수침수가 빈번한 도시의 홍수복원력을 확보하고 국민의 생명과 안전을 확보할 수 있으리라 판단된다. 또한 기술연구를 통해 상용화된다면 국내 및 국외시장에 진출이 가능하리라 본다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.5A
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• pp.593-601
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• 2000

In a multi-bandwidth CDMA system, the performance of multiple order selection combining rake receivers are analyzed according to the spreading bandwidth of the system and the delay spread of the Rayleigh fading channel. The results for various channel environments indicate a tradeoff between total received signal energy and multipath fading immunity. Increasing the occupied bandwidth of the system(wide-bandwidth spreading) gives better performance for small delay spread environments, while gathering more energy(narrow-bandwidth spreading)gives better performance for large delay spread environments. It is shown that the performance difference between low and high order selection combining grows larger as the spreading bandwidth increases. It is also noted that performance degrades by increasing the bandwidth above a certain point and the optimum spreading bandwidth for each channel environment decreases as the delay spread of the channel increases.

• Journal of Korean Tunnelling and Underground Space Association
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• v.13 no.4
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• pp.291-304
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• 2011

Recently concern for subsea tunnels is increasing, The effect of high water pressure can not be ignored in the case of a deep subsea tunnel. Reinforcement like grouting is necessary for the stability of such a subsea tunnel. In this study, therefore, it was investigated how the water barrier and shear strength increment resulted from grouting had an effect on the stability of a subsea tunnel. To this end, two-dimensional hydromechanical coupled analyses were performed for a sensitivity analysis in terms of different range, permeability coefficient, and cohesion of grouting reinforcement for the rock classes I, III, and V with respect to RMR system. The mutual relationship between strength increment and water pressure increased by barrier effect due to grouting was investigated by analyzing the numerical results.

• Journal of the Korean Geosynthetics Society
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• v.15 no.3
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• pp.39-47
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• 2016

In order to prevent leakage of leachate in offshore landfill, hydraulic barrier is indispensable. In the case of rubble mound revetment at offshore landfill, HDPE sheet in slope should be installed. In this study, seepage analysis were performed to evaluate seepage and flow in the seabed and revetment according to extended length of HDPE sheet by using SEEP/W. Results show that, in the case of low permeability layer is distributed where extended length of HDPE sheet was more than 1m, seepage flux in seabed and revetment was greatly reduced. In order to prevent seepage in seabed and revetment in the case of sand layer of high permeability is existed above low permeable layer, extended length of HDPE sheet and impermeable improvement width of permeable layer should be more than 1m at seabed.

• Journal of the Korean Society for Nondestructive Testing
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• v.27 no.1
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• pp.15-22
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• 2007

A hybrid experimental-numerical method is presented for determining the stresses around a circular hole in a finite-width, tensile loaded plate. Measured fringe orders along straight lines provided the input information on the external boundary of the hybrid element. In order to see the effects of varying stress field, different numbers of terms in a power-series representation of the complex type conformal mapping stress function were tested. For qualitative comparison, actual isochromatic fringes were compared with reconstructed theoretical fringes using stress-optic law. For quantitative comparison, relative errors and standard deviations with respective to relative errors were analyzed for all measured points by changing the number of terms of stress function. The hybrid results are highly comparable with those predicted by FEA. The results show that this approach is effective and promising because isochromatic data along the straight lines in photoelasticity can be conveniently measured by use of phase shifting photoelasticity.

• Journal of the Korean Geosynthetics Society
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• v.23 no.1
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• pp.1-7
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• 2024

In this study, a selecvively block barrier was developed to prevent the spread of contaminants (TPH, Phenol) in the ground only when contamination occurs. The materials were used Jumunjin sand, bentonite, polyolefin elastomer and spill hound marine. First, the properties and environmental hazards characteristics of materials were analyzed for evaluated their usability. Then, the possibility of use as a barrier material was confirmed by analyzing the water permeability characteristics that change after 24 hours of contact with contaminants. As a result of the analysis, the pH of each component was similar to the general groundwater pH range. In addition, the toxicity characteristics and the possibility of dissolution of hazardous substances, it was determined that there was no environmental hazard as the content was below the regulation value. Lastly, when comparing the permeability coefficient before and after contact with the contaminant, the permeability coefficient of approximately α × 10^-3cm/sec before contact was reduced to α × 10^-6cm/sec after contact with the contaminant.

• Journal of Korea Water Resources Association
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• v.41 no.8
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• pp.797-806
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• 2008

The geometric properties of the drainage structures are analyzed through depicting the drainage network which is composed of the whole drainage paths in the natural basin defined at the specific scale. The theoretical consideration is performed on the general structures of networks organized by ramification process based on Fractal tree and Horton's law. The drainage network is generated via ArcGIS, ordered by Strahler's ordering scheme and investigated with Strahler's order. As a results of the Richardson's method it is shown that there may exist the distinct behavioral characteristics between overland-flow and channel flow and the natural stream networks would be space-filling Fractals. As a result, it is shown that the values estimated by considering the overland-flow on being applied to the field data give the different results from the empirical method applied until now. As expected, therefore the results obtained from this study are sure to be devoted further researches on the channel networks.

• Journal of the Korean Geosynthetics Society
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• v.18 no.2
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• pp.1-10
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• 2019

This study was intended to evaluate the water permeability and structure for calcium bentonite-sand mixtures to utilize calcium bentonite as a liner. This study conducted physico-chemical properties tests, compaction tests, permeability test and Scanning Electron Microscopy analysis (SEM) analysis. It was found the higher the ratio of calcium bentonite, the lower the dry density with coefficient of permeability, and the higher the optimum moisture content. In particular, SEM analysis was found the higher the ratio of calcium bentonite, the higher the area of the montmorillonite particles. In conclusion, the optimum coefficient of permeability that finds the landfill liner condition (must be less than $1{\times}10^{-7}cm/sec$) was obtained when the ratio of calcium bentonite was 40% or higher. These findings may improve the understanding of the calcium bentonite as a liner. Calcium bentonite shows a similar permeability to sodium bentonite 7% when mixed at 40% or more. Therefore, it is considered that calcium bentonite can be utilized as a liner.

• Journal of the Korean Recycled Construction Resources Institute
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• v.10 no.1
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• pp.30-39
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• 2022

In this study, laboratory test, program analysis, and test construction in the field were performed to utilize Supplementary Cementitious Material (SCM) developed by recycled resources for slope reinforcement as slope improvement material for aging reservoir, and the results were analyzed. As results of the laboratory test, it was analyzed that the mixing ratio of SCM was appropriate by 9 %, and the coef. of permeability was decreased by about 10,000times, indicating a value close to that of the waterproof material applied in Korea. In addition, as a result of program analysis and test construction, it was analyzed that seepage did not occur in the part of reinforced using SCM and showed a higher safety facto r than domestic criteria. Therefore, since it shows sufficient waterproof and reinforcing effects in aging reservoir, it is judged that the slope improvement using SCM can replace the cement for repair and reinforcement method.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.39 no.1
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• pp.33-41
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• 2002

In this paper, we present a frequency weighted model reduction using LMIs for minimizing the H$\infty$ weighted model error compared with the methods of frequency weighted balanced truncation and frequency weighted Hankel norm approximation. The proposed algorithm, its form is equal to the sufficient condition of performance preserving controller approximation, is based on an iterative two-step LMI scheme induced from bound real lemma. So, it can be applied to the problem of the performance preserving controller approximation. The controller reduction is useful in a practical control design and ensures its easy implementation and high reliability The validity of the proposed algorithm is shown through numerical examples. Additionaly, we extend the proposed algorithm to performance preserving controller approximation by applying to the HIMAT(highly maneuverable aircraft technology) system.