• Structural Engineering and Mechanics
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• v.28 no.1
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• pp.1-18
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• 2008

The conventional design of bridge piers against scour uses scour equations which involve number of uncertain flow, sediments and structural parameters. The inherent high uncertainties in these parameters suggest that the reliability of piers must be assessed to ensure desirable safety of bridges against scour. In the present study, a procedure for the reliability assessment of bridge piers, installed in main and flood channels, against scour has been presented. To study the influence of various random variables on piers' reliability sensitivity analysis has been carried out. To incorporate the reliability in the evaluation of safety factor, a simplified relationship between safety factor and reliability index has been proposed. Effects of clear water (flood channel) and live bed scour (main channel) are highlighted on pier reliability. In addition to these, an attempt has also been made to explain the failure of Black mount bridge of New Zealand based on its pier's reliability analysis. Some parametric studies have also been included to obtain the results of practical interest.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2014.11a
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• pp.154-155
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• 2014

본 논문에서는 TV 시청환경에서의 실내소음의 스트레스 평가를 위한 소음 데이터베이스(database, DB) 설계 방법을 제안한다. 제안된 DB 는 TV 시청공간을 포함하는 실제 주거환경 내에서 binaural recording을 위한 1 개의 dummy head 와 multi-channel recording 을 위한 2 개의 다채널 마이크 배열을 활용하여 TV 콘텐츠 및 실내소음의 음향 정보를 취득한다. 설계된 DB는 TV 시청자의 청각정보에 해당하는 binaural recording 신호와 실내소음의 위치 및 종류 추정을 위한 multi-channel recording 신호를 모두 포함하기 때문에 TV 시청환경에서 실내소음이 시청자에게 유발하는 스트레스의 분석 및 평가 관련 연구에 적합하게 설계되었다. 본 DB 는 5 가지 종류의 TV 콘텐츠 10 시간 분량, 30 가지 종류의 실내소음 2 시간 분량으로 구성되었다.

• Proceedings of the Safety Management and Science Conference
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• 2010.04a
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• pp.371-392
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• 2010

Since the 21st century, to the worldwide computer, broadcasting, communications and other technologies have be developed. because of the Internet allows real-time information delivery, Information Society that was done quickly. In this study, using information technology, Active measures to enable e-commerce in agriculture is discussed. agricultural e-commerce to the consumer satisfaction surveys were conducted, too. In addition to, as a e-commerce features, informance, convenience, interface presented. After research results, I think information, convenience, interface is important to consumers. Consumers will be spent on activities having a new value. To respond to these consumers, Companies must evaluate the internal capabilities. and outside the assessment continuously. E-commerce will give an effective way to companies. And e-commerce will develop further in the future. Therefore, e-commerce will be done by the long-term plan.

• Journal of Communications and Networks
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• v.7 no.1
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• pp.29-35
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• 2005

This paper deals with the problem of multiuser detection over a direct-sequence code-division multiple access (DS-CDMA) channel with incomplete channel state informations (I-CSI). We devise and assess two novel recursive detectors based on the expectation conditional maximization (ECM) algorithm and the generalized likelihood ratio (GLR) principle, respectively. Both receivers entail an affordable computational complexity. Moreover, the performance assessment, conducted via Monte Carlo techniques, shows that they achieve satisfactory performance levels and outperform linear detectors.

• Proceedings of the Korea Information Processing Society Conference
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• 2007.11a
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• pp.899-902
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• 2007

RFID(Radio Frequency IDentification) 시스템에서는 리더와 태그가 무선으로 통신을 하기 때문에 리더와 태그의 수가 많아지게 되면 서로간에 신호의 충돌이 발생한다. 이러한 충돌을 해결하기 위해서는 각각의 리더가 서로 다른 시간에 동작하거나 사용하는 채널을 달리하여 충돌을 해결할 수 있다. 본 논문에서는 셀 분할 기법을 적용하고 각각의 셀이 채널 운용을 다르게 하도록 하여 충돌문제를 해결하였다. 그 방법으로 주파수 호핑(Frequency Hopping) 방식과 CCA(Clear Channel Assessment) 기법을 사용할 것을 제안한다. 그리고 제안한 방법을 시뮬레이션 하기 위해 모델링 하는 방법에 대해 살펴 보겠다.

• The Journal of Engineering Geology
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• v.24 no.4
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• pp.631-641
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• 2014

Characteristics of water-level changes in the Temporary Gulpocheon Discharge Channel were identified by observing and analyzing changes in the subterranean water level induced by hydrological stresses the underground aquifer. The subterranean water level refers to the level at which the pressure of subterranean water passing through the corresponding position has an equipotential value that is in equilibrium with the atmospheric pressure at that location. This water level is not fixed but changes in response to hydrological stress. It can be identified by repeatedly measuring the distance from the observation point to the surface of the subterranean water. The subterranean water-level change equation and the variance range of the hydrological curve of subterranean water over 24 hours at the Gimpo-Gimpo National Groundwater Monitoring Network (NGMN) were used as assessment factors. The variance characteristics of the subterranean water at the 18 monitoring system locations were classified into three impact, observational wish, and non-impact. The impact type accounted for 50% of the subterranean water of and accurately reflected the water-level changes due to hydrological stress, showing that distance is the major controlling factor. The observational wish type accounted for 27.8% of the subterranean water, and one of the two assessment factors did not meet the assessment factors. The nonimpact type accounted for 22.2% of the subterranean water. This type satisfied the two assessment factors and represents subterranean water-level changes response to precipitation.

• Ecology and Resilient Infrastructure
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• v.6 no.3
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• pp.154-162
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• 2019

Lateral connectivity between the channel and the floodplains has been damaged by the levee construction and channelization in most streams of South Korea. The purpose of this study was to develop a technique for easily and remotely assessing lateral connectivity using GIS in the streams and to evaluate the effectiveness of the assessment method by applying it to Cheongmi-cheon Stream, a representative stream in the central Korean Peninsula. The metrics of the lateral connectivity assessment are composed of (1) existence of remaining wetlands and (2) land use property as a habitat quality of the former floodplain outside the levee and (3) existence of levee barrier, (4) connectivity to the stream and (5) connectivity to the upland natural habitats as a connectivity from the channel through floodplain to the upland forest. According to the result of applying the assessment method to Cheongmi-cheon Stream, the lateral connectivity was severely damaged due to the levee construction and land use change in the former floodplain. The GIS-based assessment of the lateral connectivity developed in this study is expected to be used as a useful tool for identifying limitations of current connectivity in various attempts to restore lateral connectivity in riparian ecosystems.

• Korean Journal of Environmental Biology
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• v.38 no.4
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• pp.705-713
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• 2020

The present study investigated the temporal changes of river habitats caused by construction and operation of the three large weirs (Sejong, Gongju, and Baekje) in the Geum River. High resolution satellite imagery taken during three periods (preconstruction, before and after gate operation) were used for habitat analysis. We divided bar area into eight habitat types in addition to water area. Then, we identified the nine habitat types from the satellite imagery and estimated each habitat area. Our results show that after weir construction, large bar areas were dramatically decreased and bareland was nearly absent post gate-operation in all three weirs. However, total bar area and bareland were again increased distinctively soon after weir opening events, especially in the uppermost weir, the Sejongbo. These results suggest that weir opening operations provide a relatively simple channel of more diverse through the process of increasing bar area in a river channel.

• Ecology and Resilient Infrastructure
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• v.10 no.4
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• pp.143-160
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• 2023

This study applied the stream physical habitat assessment system to obtain basic information for river restoration and watershed management in high-gradient and mid-gradient streams in the Naeseongcheon basin. The total length of high-gradient and mid-gradient streams in the Naeseongcheon basin is about 273 km, and as a result of the assessment, it was analyzed that suboptimal reach was about 8.2 km, normal reach was 180.3 km, and marginal reach was 84.7 km. In addition, the physical habitat quality of high-gradient streams was analyzed to be normal condition with an average of 106 points (53%), and in particular, the score of channel/hydraulic category, which is the most important for the habitat of aquatic animals, was analyzed to be normal, close to the limit, with an average of 54 points (45%). The physical habitat quality of mid-gradient streams was found to be in normal condition with an average of 90 points (45%), and the score of channel/hydraulic category was in marginal condition with an average of 39 points (32%). Overall, among 165 reaches of high-gradient and mid-gradient streams in the Naeseongcheon basin, 4 reaches (3%) were evaluated as suboptimal, 119 reaches (72%) were normal, and 42 reaches (25%) were considered marginal. These results showed that the physical habitat of Naeseongcheon was significantly disturbed. Disturbance of stream physical habitat in the Naeseongcheon basin occured due to farmland around stream, urbanization, reservoir construction, and river maintenance.

• Journal of the Korean Geotechnical Society
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• v.24 no.5
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• pp.15-25
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• 2008

Contamination level assessment of harbor dredged materials is carried out for beneficial use, which generated annually due to port construction and maintenance of harbor channel. The basic purpose of environmental risk assessment was a scientific approach to susceptibility of hazard risk to human's health from different dredged materials. And this paper proposes a guideline of safely beneficial use of dredged materials at both industrial area and residental area, generated from major port execution throughout a sound investigation of their contamination levels. Newly proposed guidelines were in general higher levels compared to both current guidelines of treatment and use of dredged materials and soil environment protection levels. Finally, environmental assessment results of dredged material contamination generated in major ports of Korea for beneficial use based on pre-assessment environmental levels show that some port's dredged materials contain heavy metals such as Cd, As, Cr and Zn, more than base levels which requires more precise contamination investigation. Others were found to be very appropriate for beneficial use.