• 한국환경복원기술학회지
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• 제9권6호
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• pp.162-167
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• 2006

The urban stream includes the channel and sandbars. The sandbar plays a key role in the riparian ecosystem. For birds and insects the sandbar offers a small strip of habitat and fish and other fauna feed in the boundary of sandbar where eddies occur. So, it is important habitat and source for the flow of energy, matter and organisms through the landscape and act as ecotone between the terrestrial and stream corridors. However, the sandbar changes continuously by the natural process. Thus, it is necessary to measure the shape and area of the sandbar accurately for the efficient urban stream management for the amenity of urban residents and stream protection. The study site is Yangjae Stream where the first natural-style urban stream restoration projected was impelemented by the support of Ministry of Education in Korea. The measurement was taken by the beacon Differential Global Positioning System (DGPS) and the data were stored and analyzed using ArcView Geographic Information System (GIS) program. Therefore, the purpose of this study is to measure the change of sandbars in the urban stream after concentrated stormwater during summer.

• Journal of Communications and Networks
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• 제12권2호
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• pp.140-149
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• 2010

Green communication is a new paradigm of designing the communication system which considers not only the processing performance but also the energy efficiency. Power control management is one of the approaches in green communication to reduce the power consumption in distributed communication system. In this paper, we propose improved power control schemes for mobile satellite systems with ancillary terrestrial components (ATCs). In order to increase system capacity and reduce the transmitting power of the user's equipment, we propose an efficient channel estimation method consisting of a modified open-loop power control (OLPC) and closed-loop power control (CLPC). The OLPC works well if the forward and reverse links are perfectly correlated. The CLPC is sensitive to round-trip delay and, therefore, it is not effective in a mobile satellite system. In order to solve the above problem, we added monitoring equipment to both the OLPC and CLPC to use information about transmitting power that has not yet been received by the receiver over the satellite/ATC channel. Moreover, we adapted an efficient pilot diversity of both OLPC and CLPC in order to get a better signal to interference plus noise ratio estimation of the received signal.

• 해양환경안전학회지
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• 제8권2호
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• pp.53-60
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• 2002

Marine biotechnology is one of the promising frontier of scientific exploration and commercial utilization for the next century. Compared with the terrestrial environment, the oceans of the world remain largely unexplored and include a major portion of bio-resources. Using the tools of biotechnology, the vast and diverse marine resources can be applied to produce new products and foods. Marine biotechnology has the characteristics of pro-environment, saying energy, and intensive knowledge. Therefore, we can take advantage of the marine biotechnology industry under our situation with the poor natural resources. The study focuses on the current status and administrative supports on marine biotechnology industry for upgrading the economic value of output. The status of our marine biotechnology industry is beginning stage in the economic aspects. Manpower and the level of most technologies are weaker than the ones of the advanced countries. More investment and recruiting skilled specialists are necessary because the improvement of marine biotechnology is depend on the technology and scientists. This study suggests the ways of administrative supports for domestic marine biotechnology: Efficient information network and supporting system for the development of marine biotechnology should be interrelated with other technical and scientific fields; The government should provide sustainable fund for the long-term research project and the infrastructure in the marine biotechnology.

• 한국전자통신학회논문지
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• 제12권6호
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• pp.997-1002
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• 2017

무선전파를 사용하는 지상통신과는 달리 1500[m/s] 속도의 음향채널이 사용되는 수중통신은 수중온도, 염도를 비롯한 통신환경에 민감할 뿐 아니라 3D 공간의 영향을 받는다. 3D 수중통신은 통신공간의 복잡성과 더불어 음파의 전파손실, 해저환경에서 발생되는 음향잡음 등에 민감하다. 본 연구에서는 이와 같은 3D 수중통신환경의 특성을 고려하여 3D 수중통신환경에서 운용되는 MANET을 대상으로 전송성능을 측정 분석하고 이를 토대로 수중 MANET 운용조건을 제시한다. 본 연구는 NS-2를 기반으로 구축한 수중통신 시뮬레이터를 사용하여 수행하며, 성능파라미터로는 처리율, 전송지연, 패킷손실율 및 소비에너지를 사용한다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회B
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• pp.2381-2384
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• 2008

The heat exchange between the Borehole Heat Exchanger(BHE) and the surrounding ground depends directly on ground thermal conductivity k at the certain site. The k is thus a key parameter in designing BHE and coupled geothermal heat pump systems. Currently, although a thermal hydraulic Response Test(TRT) is mostly used in practice, the thermal hydraulic TRT needs additional power and is generally time-consuming. A new, simple wireless probe for hi-speed k determination was introduced in this paper. This technique using a wireless probe is less time-consuming and requires no external source of energy for measurement and predicts local thermal properties by measuring soil temperatures along the depth. Measured temperature data along the depth was analyzed. As a result, the electronic wireless probe can replace the conventional hydraulic TRT method after carrying out the additional research on a lot of local heat flow, etc.

• 한국인터넷방송통신학회논문지
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• 제11권4호
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• pp.17-22
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• 2011

수중 환경은 육상 환경과 많은 차이를 보이며 무선 통신에 사용되는 자원과 제약 조건들도 다르다. 일반적으로 수중 통신 환경은 육상 통신 환경보다 열악하고, 파도, 조류와 같은 해수의 흐름으로 인한 노드의 이동성 때문에 오류 발생 가능성이 기존의 지상 무선 센서 네트워크 보다 높다. 따라서 수중 무선 센서 네트워크의 통신 환경을 고려하여 노드 간 데이터 전송률을 향상시키기 위한 기법들에 대한 요구가 높아지고 있다. 본 논문에서는 수중 무선 센서 네트워크의 통신 환경을 고려하여 클러스터 헤드 노드의 오류 발생 시 이를 빠른 시간 내에 복구하기 위한 체크포인팅 기법을 제안한다. 또한 실험을 통해 제안 기법이 네트워크 운영의 신뢰도를 향상 시킬 수 있을 뿐만 아니라, 에너지 소모량과 오류 복구 지연 시간 측면에서 제안 기법을 적용하지 않았을 때보다 좋은 성능을 보인다는 것을 검증한다.

• Journal of Radiation Protection and Research
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• 제8권2호
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• pp.41-46
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• 1983

방사성핵종의 대기방출로 인한 인근주민의 연간 집단선량을 대기확산모델과 USNRC에서 제안된 지상먹이연쇄모델을 결부시켜 AIRDOS-EPA전산코드를 사용하여 평가하였다. 평가결과는 전신의 경우, $3.348{\times}10^{-1}manrem$으로 GASPAR전산코드에 의해 계산된 값과 다소 차이가 있었으나 갑상선의 경우, 84.95manrem으로 아주 낮게 평가되었다.

• 한국지구과학회지
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• 제43권4호
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• pp.520-531
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• 2022

The Yellow Sea experienced glacio-eustasy sea-level fluctuations during the Quaternary period. In the middle part of the Yellow Sea, the Quaternary successions were accumulated by alternating terrestrial, paralic, and shallow marine deposits that reflected the fluctuating sea levels. A long core of 69.2 m was acquired at the YMGR-102 site (33°50.1782'N and 123°48.3019'E) at a depth of 72.5 m in the middle of the Yellow Sea. A four-layered geoacoustic model was reconstructed for the sedimentary succession. It was based on seismic characteristics from 3.5 kHz SBP and air-gun seismic profiles and 96 grain-size properties in the core sample from YMGR-102. For the underwater simulation and experiments, the in-situ P-wave speeds were calculated using the sound speed ratio of the Hamilton method. The geoacoustic model of YMGR-102 can contribute to the reconstruction of geoacoustic models, reflecting the vertical and lateral variability of the acoustic properties in the continental shelf of the middle Yellow Sea.

• 대한토목학회논문집
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• 제26권6B호
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• pp.583-596
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• 2006

증발은 자연생태계의 에너지 및 물수지에서 중요한 역할을 담당하고 있고, 증발량의 변화에 관한 연구는 수자원의 계획 및 운영에 있어 중요한 요소이다. 본 연구에서는 1973-2004년, 32년간의 4월-10월 사이 7개월 동안의 증발량 평균값과 각 월별 증발량의 변화경향을 파악하고 추세 분석을 위해서 Mann-Kendall 검정을 실시하였다. 또한 증발과 관련된 기상요소들 즉 기온, 강수량, 습도, 전운량, 풍정합 등과의 상관관계도 분석하였다. 전 세계 여러 지역에서 관측된 바와 동일하게 기온 및 강수량이 증가함에도 불구하고 여수와 진주를 제외하고는 모든 관측지점에서 증발량은 감소경향을 나타내었다. 연구 결과는 팬 증발량의 감소가 실제 증발량의 증가를 나타낸다는 Brutsaert와 Parlange(1998)의 해석처럼 우리나라의 팬 증발량의 감소 경향은 실제 증발량의 증가를 나타낸다고 판단된다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2014년도 제46회 동계 정기학술대회 초록집
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• pp.320-320
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• 2014

Amorphous silicon alloy (a-Si) solar cells and modules have been receiving a great deal of attention as a low-cost alternate energy source for large-scale terrestrial applications. Key to the achievement of high-efficiency solar cells using the multi-junction approach is the development of high quality, low band-gap materials which can capture the low-energy photons of the solar spectrum. Several cell designs have been reported in the past where grading or buffer layers have been incorporated at the junction interface to reduce carrier recombination near the junction. We have investigated profiling the composition of the a-SiGe alloy throughout the bulk of the intrinsic material so as to have a built-in electrical field in a substantial portion of the intrinsic material. As a result, the band gap mismatch between a-Si:H and $a-Si_{1-x}Ge_x:H$ creates a barrier for carrier transport. Previous reports have proposed a graded band gap structure in the absorber layer not only effectively increases the short wavelength absorption near the p/i interface, but also enhances the hole transport near the i-n interface. Here, we modulated the GeH4 flow rate to control the band gap to be graded from 1.75 eV (a-Si:H) to 1.55 eV ($a-Si_{1-x}Ge_x:H$). The band structure in the absorber layer thus became like a U-shape in which the lowest band gap was located in the middle of the i-layer. Incorporation of this structure in the middle and top cell of the triple-cell configuration is expected to increase the conversion efficiency further.