• Journal of The Korean Society of Agricultural Engineers
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• v.54 no.2
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• pp.1-6
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• 2012

The objective of this study is to analyze the flood inundation in a low-lying rural area. The study watershed selected for this study includes the Il-Pae and Ahn-Gok watersheds. It is located in the Namyangju, Korea and encompasses $3.64km^2$. A major flood event that occurred in July 2011 was chosen as the case for the flood inundation analysis. The Hydrologic Engineering Center's Hydrologic Modeling System (HEC-HMS) and River Analysis System (HEC-RAS) were used to simulate flood runoff and water surface elevation at each cross-section, respectively. The watershed topographic, soil, and land use data were processed using the GIS (Geographic Information System) tool for the models. The contribution to the total flood volume was estimated based on the results simulated by HEC-HMS and HEC-RAS. The results showed that the overflow discharge from the Il-Pae stream constituted 80% of the total flood volume. The contributions of rainfall falling directly on the inundation area and overflow discharge from the Ahn-Gok stream were 15 % and 5 %, respectively. The simulation results in different levee scenarios for the Ahn-Gok stream were also compared. The results indicated that the levee could reduce the flood volume a little bit.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.13 no.1
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• pp.139-146
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• 2003

In this paper we demonstrate a cryptanalysis of the stream cipher LILI-128. Our approach to analysis on LILI-128 is to solve an overdefined system of multivariate equations. The LILI-128 keystream generato $r^{[8]}$ is a LFSR-based synchronous stream cipher with 128 bit key. This cipher consists of two parts, “CLOCK CONTROL”, pan and “DATA GENERATION”, part. We focus on the “DATA GENERATION”part. This part uses the function $f_d$. that satisfies the third order of correlation immunity, high nonlinearity and balancedness. But, this function does not have highly nonlinear order(i.e. high degree in its algebraic normal form). We use this property of the function $f_d$. We reduced the problem of recovering the secret key of LILI-128 to the problem of solving a largely overdefined system of multivariate equations of degree K=6. In our best version of the XL-based cryptanalysis we have the parameter D=7. Our fastest cryptanalysis of LILI-128 requires $2^{110.7}$ CPU clocks. This complexity can be achieved using only $2^{26.3}$ keystream bits.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2012.05a
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• pp.491-493
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• 2012

소리인식이란 우리 귀에 들리는 모든 소리를 받아 들여 소리의 값과 저장되어 있는 데이터의 값을 비교하여 인식 결과를 도출해내는 과정을 의미한다. 보안 카메라는 현재 다양한 장소에서 설치되어 있어도 여전히 보안의 사각지대는 존재하며, 이를 보완하기 위해서는 여러 방향을 촬영하기 위한 아주 많은 보완 카메라가 설치될 수 밖에 없다. 그렇게 되면 설치비용이 더욱 증가되고, 무수한 카메라는 사람들에게 심적 부담감을 줄 것이다. 본 논문은 보안 카메라에 마이크를 설치하고, 입력되는 소리를 인식하여 발생되는 상황을 판단하는 시스템을 설계하고 구현하기 위한 것이다. 이를 바탕으로 보안 카메라의 사각지대를 소리인식으로 해결할 수 있어서 보완 카메라의 설치 비용을 줄일 수 있다.

• Proceedings of the Korea Information Processing Society Conference
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• 2006.05a
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• pp.885-888
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• 2006

최근 몇 년 동안 센서 네트워크에 보안을 제공하기 위한 여러 연구가 진행되었고 그 결과물로 몇 가지의 보안 프로토콜이 제시되었다. 그러나 지금까지 제시된 보안 프로토콜들은 많은 시스템 자원과 부가적인 통신 횟수들을 필요로 하는 기존의 암호화 방식을 그대로 사용하고 있어 실제 센서 네트워크에 적용하여 사용하기에는 힘들다. 이의 해결 방안으로 본 논문에서는 새로운 암호화 방식을 사용하는 센싱 정보에 기반한 보안 프로토콜 모델인 MKR 프로토콜을 제시한다.

• Proceedings of the IEEK Conference
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• 1998.10a
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• pp.739-742
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• 1998

실시간 동영상의 전송을 위해 본 논문에서는 USB를 전송매체로 하여 구현했다. USB는 키보드, 스태너, 모뎀등 다양하게 사용되고 있는 인터페이스를 한나로 통일하고, 포트의 부족을 해결하기 위해서 개발된 것으로 고속의 데어터전송(12Mbps)을 가능하다. USB의 고속데이터 전송의 특징은 정지화상(JPEG) 뿐만 아니라 실시간 동영상(MPEG1, MPEG2)의 전송을 가능하게 한다. 본 논문에서는 USB로 실시간 동영상 전송을 위한 시스템 구조를 제시하였고 보다 효율적인 데이터 전송을 위한 USB Data Transfer Type에 관해 연구하였다. 720×480의 동영상의 압축을 위해 기존의 널리 이용되는 DCT대신 wevelet 알고리즘을 이용하였고 실시간 압축과 복원을 위해 video compression codec인 adv601를 사용하여 동영상 및 정지화상압축을 하였다. 또한 DSP(TMS320C32)를 이용하여 Quantization Bin Width Calculation을 함으로써 video bit stream의 크기를 가변적으로 제어하려 하였다. 이로서 동영상의 전송시 발생될 수 있는 데이터 병목현상을 해결 하였고 USB뿐만 아니라 다양한 통신망｛ISDN(128Kbps), T1(1.5Mbps) T3(45Mbps)｝에서의 동영상의 실시간 전송이 가능한 시스템 구조를 제시하였다.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.15 no.12
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• pp.1095-1102
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• 2003

Flow characteristics of turbulent steady fluid flow past a cylinder in rectangular duct are measured by 5 W laser doppler velocity meter. The fluid flow is also computed by commercial software of STAR-CD for comparison between the measurement and computation. The turbulent models applied in the computations are standard K-epsilon model, RNG K-epsilon model and Chen K-epsilon model. Acurracy of standard K-epsilon model is a little bit better than acurracies of other models even though those models have almost the same order of error compared to measured data. The computations predict satisfactorily the measured velocity profiles at middle section of the circular cylinder before the fluid flow diverges. However, there are some disagreements between them at down stream from the circular cylinder.

• The Bulletin of The Korean Astronomical Society
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• v.40 no.2
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• pp.44.1-44.1
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• 2015

We set up a project to make spectrometers for single dish observations of the Korean VLBI Network (KVN), a new future multi-beam receiver of the ASTE (Atacama Submillimeter Telescope Experiment), and the total power (TP) antennas of the Atacama Large Millimeter/submillimeter Array (ALMA). Traditionally, spectrometers based on ASIC (Application-Specific Integrated circuit) and FPGA (Field-Programmable Gate Array) have been used in radio astronomy. It is, however, that a Graphics Processing Unit (GPU) technology is now viable for spectrometers due to the rapid improvement of its performance. A high-resolution spectrometer should have the following functions: poly-phase filter, data-bit conversion, fast Fourier transform, and complex multiplication. We wrote a program based on CUDA (Compute Unified Device Architecture) for a GPU spectrometer. We measured its performance using two GPU cards, Titan X and K40m, from NVIDIA. A non-optimized GPU code can process a data stream of around 2 GHz bandwidth, which is enough for the KVN spectrometer and promising for the ASTE and ALMA TP spectrometers.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.11a
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• pp.92-96
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• 2007

Microphone array beamforming method has been recognized as an important aeroacoustic research field and become a standard technique in localizing sound sources. This method also used in flight acoustic measurement, and especially, it is very useful when measure sounds inside the wind tunnel. In measuring sound which is inside the wind tunnel by traditional beamforming method, there are some errors caused by airstream. The speed and the propagation path of the sound changes as it travel through the airstream. This makes the error which the position of sound is changed a little bit to the down stream direction. In this paper, validation test has made about the correction equation for this wind effects of previous researches. And beamforming including shear layer correction was performed about a sound source in the anechoic open-jet windtunnel.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.54 no.8
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• pp.510-516
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• 2005

Rapid advances in telecommunication make emergency telemedicine possible that specialist offers medical care to an emergency case in moving vehicle. Although there were many telemedicine projects delivering the image or video of patient over several wireless networks, none of them considered effective solutions for optimizing video transmission over error-prone environments, such like wireless links. To alleviate the effect of channel errors on compressed video bit-stream, this paper analyzed the error resilient features of MPEG-4 standard and measured the quality of transmitted MPEG-4 encoded video over commercially available CDMA2000 1xEV-DO networks, transmitting different IP packet sizes and RM positions. we propose an error resilient transmission methods for emergency telemedicine over real 3G network.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.2A
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• pp.187-193
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• 2006

Multicarrier systems has major shortcomings due to the large numbers of subcarrier. One of the shortcomings is the high peak-to-average power ratio(PAPR), which causes nonlinearity distortion in the transmitter, and degrades the performance of the system significantly. Partial transmit sequence(PTS) is one of the best approaches that can significantly improve the statistics of the PAPR of an orthogonal frequency division multiplexing(OFDM) signal. Guided scrambling(GS) is an extension of self-synchronizing scrambling. It is also capable of guiding the scrambling process to produce a balanced encoded bit stream. In this paper, we propose a sub-optimal algorithm to optimize the phase factor in PTS. In addition, we integrate GS coding with this method. The proposed Hybrid algorithm can get much more PAPR reduction at the expense of incur a few error extension and do not require transmission of side information.