• Journal of the Korea Institute of Information and Communication Engineering
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• v.8 no.4
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• pp.774-781
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• 2004

The HF band SSB communication of coast radio station had operated with principal axis of maritime communication until early in the 1990. But, that is changed with development of data communication and satellite technique, which have operated a few by rapidly decrement of user with accomplishment of the CMDSS. Recently, the radio system of HF band is expanded to globe maritime communication, which is support to maritime safety information and data traffic service by low charge with the SSB high speed modem. This study have proposed the digitalize method for maritime communication system using HF band in domestic.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2004.05b
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• pp.116-122
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• 2004

The HF band communication of roast radio station had operated with principal axis of maritime communication until early in the 1990. But, that is changed with development of data communication and satellite technique, which have operated a few by rapidly decrement of user with accomplishment of the GMDSS. Recently, the radio system of 11u band is expanded to globe maritime communication, which is support to maritime safety information and data traffic service by low charge with the SSB high speed modem. This study have proposed the digitalize method for maritime communication system using HF band in domestic.

• Korean Journal of Agricultural Science
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• v.6 no.2
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• pp.112-118
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• 1979

This experiment was carried out to evaluate the effect of potassium application level for pasture management in Chungnam area. The results obtained were as follows. 1. The seedling establishment of pasture species was slightly depressed by high potassium application. 2. By increasing potassium application level, the winter hardiness of pasture species increased. 3. The forage yield of pasture species was more increased in legume single seeding than grass single and mixed seeding by higher potassium application. 4. The $K_2O$ content in forage was increased markedly by increasing potassium application level on grass single block. 5. The results obtained from this experiment indicated that potassium application level much effective on the winter hardiness of pasture species and forage yield specially in legume single seeding and adequate amount of potassium would be 20kg per 10a in this area.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.28 no.2
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• pp.272-279
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• 1983

Canopy structure and light interception were investigated as related to forage growth and dry matter production in four swards; pure orchardgrass, pure ladino clover, orchard-ladino mixture, and multi-mixture that was consisted of four grasses and three legumes. In spring, multi-mixture stand had the highest LAI, while ladino clover pure stand had low LAI but the highest leaf volume density(L$_{v}$ ). In fall, both pure orchardgrass and orchard-ladino mixture had higher LAI and L$_{v}$ than others. Orchard pure stand was an electophile canopy with K, light extinction coefficient, of 0.29-0.43, pure ladino clover a planophile canopy with K of 0.72, and both mixtures a plagiophile canopy with K of 0.43-0.58. Dry matter yields had highly significant correlation with LAI in all stands. Optimum LAI for pure orchardgrass was estimated above 6.0 and for pure ladino clover, orchard-ladino mixture and multi-mixture were about 3.8,5.0 and 8.0, respectively. Conclusion was made that multi-mixture and orchard-ladino mixture had better canopy structure to improve light penetration and forage yield than pure stands.

• Journal of Korea Water Resources Association
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• v.52 no.5
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• pp.313-323
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• 2019

Deep Tunnel system is a large-scale urban flood control facility installed underground in order to reinforce the lack of drainage systems in developed cities. In a structure like a deep tunnel system, the undular bore generated in the downstream causes a problem in the hydraulic stability of the tunnel. In this study, to investigate the influence of the undular bore on the hydraulic stability at the "Shinwol rainwater storage and drainage system", under construction for the first time in the country, a hydraulic model experiment was conducted on various flooding inflow scenarios. As a result of the hydraulic model experiment carried out in this study, the undular bore generated downstream is trapped in the pipe while moving to upstream, pushes the compressed air. It is judged that overflow occurred by choking the vertical drop shaft in the process when this compressed air is being exhaust through the upstream vertical drop shaft and blocking flood inflow. In addition, the analysis of velocity of undular bore shows that the undular bore transfers energy, and at this time, the pressure rose in the pipe and the velocity increment occurred of the undular bore. Further studies are needed to predict the size and velocity of undular bore, which plays an important role in the hydraulic stability of the tunnel in the deep tunnel system.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.5B
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• pp.575-589
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• 2008

In the present work, we investigate the hydrodynamic behavior of a turbulent bore, such as tsunami bore and tidal bore, generated by the removal of a gate with water impounded on one side. The bore generation system is similar to that used in a general dam-break problem. In order to the numerical simulation of the formation and propagation of a bore, we consider the incompressible flows of two immiscible fluids, liquid and gas, governed by the Navier-Stokes equations. The interface tracking between two fluids is achieved by the volume-of-fluid (VOF) technique and the M-type cubic interpolated propagation (MCIP) scheme is used to solve the Navier-Stokes equations. The MCIP method is a low diffusive and stable scheme and is generally extended the original one-dimensional CIP to higher dimensions, using a fractional step technique. Further, large eddy simulation (LES) closure scheme, a cost-effective approach to turbulence simulation, is used to predict the evolution of quantities associated with turbulence. In order to verify the applicability of the developed numerical model to the bore simulation, laboratory experiments are performed in a wave tank. Comparisons are made between the numerical results by the present model and the experimental data and good agreement is achieved.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• v.9 no.2
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• pp.173-176
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• 2005

본 연구는 2005. 7. 1 시행 공포된 전파법 시행령 개정안 내용 중 전력선통신설비의 주파수 대역이 9kHz${\sim}$450kHz에서 그 상한선 범위가 30MHz까지 확대 시행됨과 관련하여 전력선통신설비가 단파대 무선통신에 혼신을 야기할 수 있음에 따라 그 영향여부를 평가하는 방법을 제시하고 향후 전력선통신설비를 운용함에 있어서 단파대 무선통신에 영향을 회피하기 위한 대책방안을 제안하는데 있다. 전력선통신의 운용주파수 확대와 관련하여 정보통신부 전파연구소에서 전력선통신이 단파대 무선통신의 혼신여부에 대하여 측정 관찰해 왔으며 그 간섭정도를 판단하기 위해 노력해 왔다. 본 연구에서는 전파수신기, 신호발생기 및 SINAD(Signal to Noise and Distortion) Meter를 사용한 측정방법을 제시하고 있으며 이는 무선(RF : Radio Frequency) 환경에 적합한 측정방법으로 기존의 EMC(electromagnetic compatibility) 환경에 의한 한계를 극복할 수 있다. 또한, 본 연구에서는 전력선통신설비가 단파대 해상이동통신에 영향을 최소화하기 위하여 보호구역을 설정 또는 해당 주파수에 대하여 운용금지하는 방안을 제시함으로써 무선통신환경을 보호하는데 그 목적이 있다.

• Proceedings of the Korean Environmental Sciences Society Conference
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• 2002.05b
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• pp.459-460
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• 2002

현재 오염 토양의 복원기술은 여러 가지 문제점들을 안고 있어 보다 경제적이면서 신속하고 실용적인 오염물질 제거방법의 개발이 요구되고 있다. 이에 본 연구에서는 유류에 오염된 토양을 극초단파와 용매를 사용하여 복원하는 것에 관한 기초 조사를 위한 실험을 수행하였다. 그 결과 유류에 오염된 토양을 극초단파를 이용하여 정화를 할 경우 토양 입자의 크기도 고려를 하여야 할 것으로 사료된다. 그리고, soxhlet 추출법과 극초단파 추출법을 비교하였을 경우 soxhlet 추출법에 비하여 약 1/3 정도의 용매로 추출이 가능하며, 1분 내ㆍ외의 추출 시간으로 soxhlet 추출법에 의한 kerosene의 회수율과 유사하거나 또는 그 이상의 회수율을 얻을 수 있는 것으로 조사되었다.

• Proceedings of the Korea Institute of Fire Science and Engineering Conference
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• 2011.11a
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• pp.306-309
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• 2011

본 연구에서는 정확한 화재원인 분석 및 사기범죄 여부 확인을 위하여 극초단파를 직접 휴대전화에 조사하고, 이때 발생되는 휴대전화의 손상형태를 분석하였다. 극초단파 조사를 위하여 전자레인지를 이용하였으며, 전자레인지의 마그네트론에서 발생되는 2.45 GHz의 극초단파가 휴대전화에 인가될 때 휴대전화의 손상형태를 분석하였다. 실험 결과, 휴대전화에 극초단파를 조사하는 경우, 조사 시간이 길어짐에 따라 심하게 손상되는 경향을 나타내었으며, 특히, 폴더의 힌지 부분 및 인테나 부분과 같이 금속이 설치되는 부분이 심하게 열변형되는 결과를 나타내었다. 휴대전화의 배터리 부분은 외함이 열변형되는 것 이외에 배터리의 손상이나 폭발 등은 발생되지 않는 것으로 평가되었다.

• Proceedings of the KSEEG Conference
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• 2001.04a
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• pp.245-246
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• 2001