• Proceedings of the Korea Water Resources Association Conference
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• 2005.05b
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• pp.1496-1501
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• 2005

최근까지 물 부족을 해소하기 위한 방법으로 용수공급 확대만이 유일한 방법인 양 인식하여 왔다. 그러나 최근에 이르러 우리나라는 가용 수자원의 부족, 댐 개발 적지의 고갈, 지역주민의 집단반발 등으로 용수원의 적기확보가 난관에 봉착하고 있다. 갈수록 어려워지는 용수원 확보로, 급증하는 용수수요를 어떻게 충족시킬 것인가에 대한 진지한 논의가 필요한 시점인 것이다. 수자원의 확보가 심각한 사회문제로 대두되고 있고 물 부족 사태가 언제 올지 모르는 시점에서 앞으로의 용수수요에 대한 추정이 맞지 않고 용수량을 과다측정 또는 과소 측정하는 가장 큰 이유 중의 하나가 과거로부터 축적된 데이터의 부족이라 할 수 있다. 그럼에도 불구하고 기존까지의 용수수요예측에 관한 연구는 부분적인 연구결과만 있을 뿐 전반적인 이론 및 기법에 관한 정립이 되어 있지 않은 실정이다. 용수수급의 효율화는 수요측면과 공급측면을 조화롭게 운용함으로서 가능해지는 것으로 용수수요를 정확하고 신속하게 예측하는 것은 용수공급능력의 확대와 동일한 효과를 나타낸다. 그러나 인구, 생활양식, 문화수준, 산업구조, 용수요금, 소득, 기후조건 등 각종 요인을 종합적으로 분석하여 장래의 용수수요예측을 한다는 것은 현 기술 상태에서 매우 어려운 일이다. 따라서 본 연구에서는 금강유역을 시범유역을 선정하여 금강유역내의 용수수급현황을 직접 현장조사를 통해 파악하고, 현재 용수수급현황 파악에 있어서의 문제점과 향후 체계적이고 정확한 용수수급현황 파악을 위한 방법을 제시하고자 한다. 이를 위해 주요 생활용수, 공업용수 취수장을 직접 방문하여 용수사용실태를 조사함은 물론 금강홍수통제소에서 운영하고 있는 하천유수사용실적 관리시스템의 필요성과 문제점을 동시에 분석해보았다. 더 나아가 지속적인 용수사용실태를 조사하여 표준권역별로 물이용 지표화를 제시함으로써 향후 용수사용실태 분석시 효율성을 극대화 시키는 방안을 제시한다면 용수수요추정 오류에 따른 부작용을 최소화할 수 있을 것으로 판단된다.

• Journal of Wetlands Research
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• v.10 no.2
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• pp.67-79
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• 2008

The one-dimensional (1D) finite-difference method (FDM) with Abbott-Ionescu scheme and the two-dimensional (2D) finite-volume method (FVM) with an approximate Riemann solver (Osher scheme) for unsteady flow calculation in river are described. The two models have been applied to several problems including flow in a straight channel, flow in a slightly meandering channel and a flow in a meandering channel. The uniform rectangular channel was employed for the purpose of comparing results. A comparison is made between the results of computation on 1D and 2D flows including straight channel, slightly meandering channel and meandering channel application. The implementation of the finite-volume method allows complex boundary geometry represented. Agreement between FVM and FDM results regarding the discharge and stage is considered very satisfactory in straight channel application. It was concluded that a 1D analysis is sufficient if the channel is prismatic and remains straight. For curved (meandering) channels, a 2D or 3D model must be used in order to model the flow accurately.

• Journal of Broadcast Engineering
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• v.8 no.3
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• pp.250-258
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• 2003

Recently, the transition from conventional analog broadcasting to digital broadcasting has been proceeding as a result of the advance in digital multimedia broadcasting technique. In radio broadcasting, Eureka-147 DAB(Digital Audio Broadcasting) was decided as the standard system of digital radio broadcasting in Korea. In addition to CD quality audio, a variety of data services and excellent performance in mobile reception can be served by DAB, and DAB was evolved into DMB(Digital Multimedia Broadcasting) in Korea for the purpose of emphasizing moving picture multimedia service by DAB. In case of digital broadcasting, it is absolutely essential to measure the BER(Bit Error Rate) in the received signal in order to evaluate the coverage obtained by a transmitter and the quality of the received signal. In this paper, we propose efficient subchannel data structure and BER measurement algorithm. and then verify it by laboratory experiments. With a proposed method, the synchronization for BER measurement is easily obtained and especially the exact results can be obtained by classifying the lost bits which are included in the reception-failed CIFs(Common Interleaved Frame) into errors. This makes the proposed BER measurement system especially appropriate to DMB in which the frequent changes in channel status caused by mobile reception environment exist.

• Journal of Broadcast Engineering
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• v.15 no.6
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• pp.749-756
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• 2010

The signal space diversity is one of the promising transmission techniques in next generation mobile TV service. However, DVB-T2 does not consider the multiple antennas (MIMO) so that the cyclic Q-delay method, a component interleaver in DVB-T2, causes a critical issue in detecting symbols at the receiver side by increasing the inter-symbol dependency. To solve this problem, the component-swapping technique is proposed, which limits the inter-symbol dependency in order to reduce detection complexity. In this paper, the achievable gain of a component-swapping technique combined with 16K LDPC code defined in DVB-T2 is evaluated by computer simulations. From the results, the gain is confirmed in terms of BER and receive complexity compared to legacy component interleaver methods.

• Korean Journal of Optics and Photonics
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• v.7 no.4
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• pp.419-427
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• 1996

Thermally-stabilized fiber-optic current sensors are proposed and demonstrated. The sensor head is made of two coil formers combined perpendicularly. In this sensor head, bending-induced birefringences can be reduced to the level much smaller than those of the single former type because the eigen-axes of the two perpendicular coil formers are made orthogonal to each other. Moreover, thermal variation of the birefringence is also expected to be minimized by the orthogonality of the two polarization eigen-axes. We changed the temperature slowly in the range of 20~45$^{\circ}C$ during 100 minutes. The overall linearity of the sensor is better than 1.2% in the range of 0~1000A. The long-term fluctuation of the sensor is less than 1% when measured for 3 hours at 500A and room temperature. Two orthogonally-polarized laser diodes are combined together to make the incident beam unpolarized. In the signal processing, the signals are separated by two parts and normalized respectively, which minimize the efects of optical fluctuations coming from sources, connectors, etc.

• Journal of Broadcast Engineering
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• v.11 no.4 s.33
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• pp.541-553
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• 2006

Since DMB on-air was started, not high-qualified audio, video services but various service models have been required. This paper is about systems for one of these services, video associated data service. A terrestrial DMB system to make contents of video associated data services and transmit them on DMB channel is proposed in this paper. This system satisfies standard of the video associated data services for terrestrial DMB; MPEG-4 BIFS (BInary Format for Scene) Core2D scene description profile and graphics profile. This system is designed to support two major features of broadcasting, real-time authoring non automatic transmission and non real-time authoring automatic transmission, and focuses on the abilities to make high-qualified contents efficiently and transmit them to video encoder reliably. This system proved its performance through conformance tests with various receivers, so can be used in future on-air.

• The Journal of the Acoustical Society of Korea
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• v.37 no.4
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• pp.163-173
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• 2018

This paper performed the prediction of the acoustic loads applied to the surface of the flight vehicle during flight. Acoustic loads during flight arise from the pressure fluctuations on the surface of body. The conventional method of predicting the acoustic loads in flight uses semi-empirical method derived from theoretical and experimental results. However, there is a limit in obtaining the flow characteristics and the boundary layer parameters of the flight vehicle which are used as the input values of the empirical equation through experiments. Therefore, in this paper, we use the hybrid method which combines the results of CFD (Computational Fluid Dynamics) with semi-empirical methods to predict the acoustic loads acting on flight vehicle during flight. For the flight vehicle with cone-cylinder-flare shape, acoustic loads were estimated for the subsonic, transonic, supersonic, and Max-q (Maximum dynamic pressure) condition flight. For the hybrid method, two kind of boundary layer edge estimation methods based on CFD results are compared and the acoustic loads prediction results were compared according to empirical equations presented by various researchers.

• Journal of Digital Convergence
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• v.15 no.8
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• pp.195-202
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• 2017

Unmanned Aerial Vehicles (UAV) have mostly been used for military purposes but with the progress in ICT and reduced manufacturing costs, they are increasingly used for various private services. UAVs are expected to carry out autonomous flying in the future. In order to carry out complex tasks, swarm flights are essential. Although the swarm flights has been researched a lot due to its different network and infrastructure from the existing UAV system, There are still not enough study on security threats and requirements for the secure swarm flights. In this paper, to solve these problems, UAV autonomous flight technology is defined based on US Army Corps of Engineers (USACE) and Air Force Research Laboratory (AFRL), and swarm flights and security threat about it are classified. And then we defined and compared security requirements according to security threats of each swarm flights so as to contribute to the development of secure UAC swarm flights in the future.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.36 no.2
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• pp.75-84
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• 2018

The purpose of this study is that the low-cost mobile mapping system using INS (Inertial Navigation System) based on MEMS (Micro Electro Mechanical System) could decipher the interpretation of road facility with the accuracy of x, y 0.546m plane error. Even though the MMS (Mobile Mapping System) technology as a new measurement technology has been used vividly to set up geographic information by some world leading surveying equipment manufacturers, the domestic technology is still in its beginning stage. Several domestic institutes and companies tried to catch up the leading technology but they just produced prototypes which needs more stabilization. Through this thesis, we developed low-cost mobile mapping system installed with INS based on MEMS after time synchronizing sensors for MMS such as LiDAR (Light Detection And Ranging), CCD (Charge Coupled Device), GPS/INS (Global Positioning System / Inertial Navigation System) and DMI (Distance Measurement Instrument).

• Journal of Korea Water Resources Association
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• v.31 no.1
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• pp.45-57
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• 1998

The purpose of this paper is to develop a neural network model in order to forecast flood inflow into the reservoir that has the nature of uncertainty and nonlinearity. The model has the features of multi-layered structure and parallel multi-connections. To develop the model. backpropagation learning algorithm was used with the Momentum and Levenberg-Marquardt techniques. The former technique uses gradient descent method and the later uses gradient descent and Gauss-Newton method respectively to solve the problems of local minima and for the speed of convergency. Used data for learning are continuous fixed real values of input as well as output to emulate the real physical aspects. after learning process. a reservoir inflows forecasting model at flood period was constructed. The data for learning were used to calibrate the developed model and the results were very satisfactory. applicability of the model to the Chungju Mlultipurpose Reservoir proved the availability of the developed model.