• 신재생에너지
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• 제5권3호
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• pp.32-39
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• 2009

The Samcheonpo ocean small hydropower plant (SHP) has a special feature of using marginal hydraulic head of circulating water system of fossil fuel power plant as a power source and having the characteristics of general hydropower generation and tidal power generation as well. Also, it contributes to reducing green house gases and developing clean energy source by recycling circulating water energy otherwise dissipated into the ocean. The efficiency of small hydropower plant is directly affected by effective head and flow rate of discharged water. Therefore, the efficiency characteristics of ocean hydropower plant are analyzed with the variation of water level and flow rate of discharged water, which is based on the accumulated operation data of the Samcheonpo hydropower plant. After the start of small hydropower plant operation, definite rise of water level was observed. As a result of flow pattern change from free flow to submerged flow, the instability of water surface in overall open channel is increased but it doesn't reach the extent of overflowing channel or having an effect on circulation system. Performance evaluation result shows that the generating power and efficiency of small hydropower exceeds design requirements in all conditions. Analysis results of CWP's water flow rate verify that the amount of flowing water is measured less and the highest efficiency of small hydropower plant is achieved when the effective head has its maximum value. In conclusion, efficiency curve derived from water flow rate considering tidal level shows the best fitting result with design criteria curve and it is verified that overall efficiency of hydropower system is satisfactory.

• The Korean Journal of Physiology and Pharmacology
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• 제4권2호
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• pp.81-90
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• 2000

The types of $K^+$ channel which determine the pattern of spontaneous action potential (SAP) were investigated using whole-cell variation of patch clamp techniques under current- and voltage-clamp recording conditions in rat clonal pituitary $GH_3$ cells. Heterogeneous pattern of SAP activities was changed into more regular mode with elongation of activity duration and afterhyperpolarization by treatment of TEA (10 mM). Under this condition, exposure of the class III antiarrhythmic agent E-4031 $(5\;{\mu}M)$ to $GH_3$ cells hardly affected SAP activities. On the other hand, the main $GH_3$ stimulator thyrotropin-releasing hormone (TRH) still produced its dual effects (transient hyperpolarization and later increase in SAP frequency) in the presence of TEA. However, addition of $BaCl_2$ (2 mM) in the presence of TEA completely blocked SAP repolarization process and produced membrane depolarization in all tested cells. This effect was observed even in TEA-untreated cells and was not mimicked by higher concentration of TEA (30 mM). Also this barium-induced membrane depolarization effect was still observed after L-type $Ca^{2+}$ channel was blocked by nicardipine $(10\;{\mu}M).$ These results suggest that barium-sensitive current is important in SAP repolarization process and barium itself may have some depolarizing effect in $GH_3$ cells.

• Design & Manufacturing
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• 제17권3호
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• pp.8-14
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• 2023

In this study, basic research was conducted on manufacturing technology of thick-walled light guide a component that controls the light source of automobile lamps. As a preliminary study for manufacturing the final injection molded parts, a model for analyzing the influence of micro patterns on light guides is presented. The optical characteristics of the light guide were analyzed according to the change of the curvature radius of the micro-optical pattern, and the injection molding characteristics of the light guide according to the change of injection molding conditions were analytically evaluated. It was confirmed that the luminance uniformity improves as the R value decreases for changes in the micro-pattern R value, but it was confirmed that there are technical limitations in actual injection mold core processing and high-replication injection molding. Injection molding analysis showed that cooling channel design is very important compared to general injection molding due to thick-wall characteristics and thickness variation. It was also confirmed that the cooling channel has a great influence on the cycle time and birefringence result due to residual stress. As a result of analyzing the influence of filling time, holding condition, and cooling on shrinkage, it was found that the cooling water temperature has a significant effect on the shrinkage of ultra-fine light guide parts, and the holding condition also has a significant effect.

• 인터넷정보학회논문지
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• 제21권2호
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• pp.19-26
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• 2020

This paper analyses the feasibility of using implantable antennas to detect and monitor tumors. We analyze this setting according to the wireless propagation loss and signal fading produced by human bodies and their environment in an indoor scenario. The study is based on the ITU-R propagation recommendations and prediction models for the planning of indoor radio communication systems and radio local area networks in the frequency range of 300 MHz to 100 GHz. We conduct primary estimations on 915 MHz and 2.4 GHz operating frequencies. The path loss presented in most short-range wireless implant devices does not take into account the human body as a channel itself, which causes additional losses to wireless designs. In this paper, we examine the propagation through the human body, including losses taken from bones, muscles, fat, and clothes, which results in a more accurate characterization and estimation of the channel. The results obtained from our simulation indicates a variation of the return loss of the spiral antenna when a tumor is located near the implant. This knowledge can be applied in medical detection, and monitoring of early tumors, by analyzing the electromagnetic field behavior of the implant. The tumor was modeled under CST Microwave Studio, using Wisconsin Diagnosis Breast Cancer Dataset. Features like the radius, texture, perimeter, area, and smoothness of the tumor are included along with their label data to determine whether the external shape has malignant or benign physiognomies. An explanation of the feasibility of the system deployment and technical recommendations to avoid interference is also described.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2005년도 춘계 학술발표회 논문집
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• pp.1211-1218
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• 2005

Temperature variation according to space and time on the inner parts of engineering constructions(e.g.: dam, slope) can be a basic information for diagnosing their safety problem. In general, as constructions become superannuated, structural deformation(e.g.: cracks, defects) could be occurred by various factors. Seepage or leakage of water through these cracks or defects in old dams will directly cause temperature anomaly. Groundwater level also can be easily observed by abrupt change of temperature on the level. This study shows that the position of seepage or leakage in dam body can be detected by multi-channel temperature monitoring using thermal line sensor. For this, diverse temperature monitoring experiments for a leakage physical model were performed in the laboratory. In field application of an old dam, temperature variations for water depth and for inner parts of boreholes located at downstream slope were measured. Temperature monitoring results for a long time at the bottom of downstream slope of the dam showed the possibility that temperature monitoring can provide the synthetic information about flowing path and quantity of seepage of leakage in dam body.

• JSTS:Journal of Semiconductor Technology and Science
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• 제13권4호
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• pp.303-317
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• 2013

Two novel clocking strategies for a high-speed multi-channel serializer-deserializer (SERDES) are proposed in this paper. Both of the clocking strategies are based on groups, which facilitate flexibility and expansibility of the SERDES. One clocking strategy is applicable to moderate parallel I/O cases, such as high density, short distance, consistent media, high temperature variation, which is used for the serializer array. Each group within the strategy consists of a full-rate phase-locked loop (PLL), a full-rate delay-locked loop (DLL), and two fixed phase alignment (FPA) techniques. The other is applicable to more awful I/O cases such as higher speed, longer distance, inconsistent media, serious crosstalk, which is used for the deserializer array. Each group within the strategy is composed of a PLL and two DLLs. Moreover, a half-rate version is chosen to realize the desired function of 1:2 deserializer. Based on the proposed clocking strategies, two representative ICs for each group of SERDES are designed and fabricated in a standard $0.18{\mu}m$ CMOS technology. Measurement results indicate that the two SERDES ICs can work properly accompanied with their corresponding clocking strategies.

• 한국수자원학회논문집
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• 제46권9호
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• pp.909-919
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• 2013

본 연구에서는 실내실험을 통하여 식생의 변화에 따른 하도의 수리학적특성, 저수로의 변화, 사주의 거동, 하안의 안정성 등을 정량적으로 파악하였다. 실내실험은 기존에 인공식생 대신에 수로에서 실제식생인 알팔파를 성장시켜서 수행하였다. 식생대에서는 유속이 매우 느리며, 저수로의 이동이 감소하였다. 2중 퓨리에 해석 결과, 교호사주의 특성을 나타낸 1-1모드의 진폭이 지배적이지만, 시간이 증가하면서 복렬사주의 특성을 나타내는 2-2와 2-3모드의 진폭이 증가하였다. 식생에 의하여 저수로가 고착화 되어 하도의 안정성이 증가하고, 하도 내 사주의 이동속도는 감소하지만, 하상이 불규칙하게 변하면서, 사주의 수는 증가하였다. 식생의 밀도가 증감함에 따라 하안의 안정성은 증가하였다. 식생의 밀도가 증가함에 따라 유사의 유출량과 유출량의 변동성이 감소하였다. 또한 망상화 강도는 감소하지만, 하도의 상관계수와 하상의 기복지수(BRI)는 증가하는 특성을 보여주었다.

• 한국지진공학회논문집
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• 제25권3호
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• pp.145-152
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• 2021

KAERI has planned to carry out a series of dynamic tests using a shaking table and time-history analyses for a channel-type concrete shear wall to investigate its seismic performance because of the recently frequent occurrence of earthquakes in the south-eastern parts of Korea. The overall size of a test specimen is b×l×h =2500 mm×3500 mm×4500 mm, and it consists of three stories having slabs and walls with thicknesses of 140 mm and 150 mm, respectively. The system identification, FE model updating, and time-history analysis results for a test shear wall are presented herein. By applying the advanced system identification, so-called pLSCF, the improved modal parameters are extracted in the lower modes. Using three FE in-house packages, such as FEMtools, Ruaumoko, and VecTor4, the eigenanalyses are made for an initial FE model, resulting in consistency in eigenvalues. However, they exhibit relatively stiffer behavior, as much as 30 to 50% compared with those extracted from the test in the 1st and 2nd modes. The FE model updating is carried out to consider the 6-dofs spring stiffnesses at the wall base as major parameters by adopting a Bayesian type automatic updating algorithm to minimize the residuals in modal parameters. The updating results indicate that the highest sensitivity is apparent in the vertical translational springs at few locations ranging from 300 to 500% in variation. However, their changes seem to have no physical meaning because of the numerical values. Finally, using the updated FE model, the time-history responses are predicted by Ruaumoko at each floor where accelerometers are located. The accelerograms between test and analysis show an acceptable match in terms of maximum and minimum values. However, the magnitudes and patterns of floor response spectra seem somewhat different because of the slightly different input accelerograms and damping ratios involved.

• 대한전자공학회논문지TC
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• 제43권11호
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• pp.141-148
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• 2006

본 논문은 OFDMA 기반의 Wibro 중계국에서 발생되는 루프 간섭 신호의 제거와 위상 보상을 위한 적응 등화기를 사용하여 성능을 개선하기 위한 것이다. Wibro 중계국은 기지국의 통신 가능 영역 확장 및 Throughput 개선을 위하여 사용되는데 송신기와 수신기가 인접해 있으므로 이들간에 루프 간섭의 문제가 성능을 결정하는 중요한 요인이 된다. 논문에서는 먼저 OFDMA 신호를 기저 대역에서 발생시킨 후 Training 시간동안 전송되는 파일롯 톤을 2 가지 삽입 방식으로 조합하여 전송하였다. 또한 부가 잡음 및 루프 간섭 신호에 의한 페이딩파를 발생시켜 수신 신호를 얻은 후 LS (Least Square) 알고리즘을 적용한 채널 추정을 이용을 하여 간섭 신호가 제거된 수신 신호를 복원한 후 적응 등화기를 통과시켜 위상을 보상하였다. 중계기의 성능을 채널 추정 결과, 간섭 제거 후와 등화 출력 신호의 성상도 (Constellation) 및 SNR 변화에 따른 BER 특성 분석을 통하여 개선되었음을 컴퓨터 시뮬레이션을 통해 확인할 수 있었다.

• 태양에너지
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• 제17권2호
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• pp.35-42
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• 1997

열다이오드란 유체의 밀도차에 기인한 대류에 의하여 일방향성 열전달이 주로 일어나며 역방향의 열전달은 미미하도록 고안된 장치이다. 본연구에서는 실용적인 측면에서 평행사변형 형상과 직사각형 형상을 조합하고 좌우에 수직 평판을 설치하였으며, 내부 안내판을 가진 공기식 열다이오드를 제작하여 천이 및 정상상태에 관한 연구를 하였다. 공급된 열속에 따른 $Gr^*$는 $1.11{\times}10^{10}{\sim}1.4{\times}10^{10}$ 사이에 존재하였고 전체 실험 과정에 있어서 $Gr^*$ 값은 ${\pm}3%$ 이내로 유지되었다. $Gr^*$의 증가에 따라 Nu값은 거의 선형적으로 증가하는 경향을 보였으며 guide vane의 유무와 유동통로의 깊이(channel depth)에 따라서는 민감한 경향을 보였다. 경사각의 변화에 따라 온도상태가 무차원시간 $0.5{\sim}0.6$ 에서 나타나는 것으로 보아 시스템의 특성으로 본다.