• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2001.10a
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• pp.684-687
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• 2001

본 논문에서는 이동통신 시스템에서 성능 열화의 주요 원인인 주파수 선택성 페이딩과 전자기기에서 발생하는 임펄간 간섭 환경에서 DS/CDMA 시스템의 성능 개선을 정량적으로 분석하였다 시스템으로 고려한 변식은 비동기식 MFSK와 MDPSK를 이용한 MFSK-MBPSK 결합변조 방식이다. 분석 결과, 선택성 페이딩에서 합성변조 시스템에 대하여 E$_{b}$/Nn$_{o}$ =20일 때를 기준으로 한 경우, M$_{f}$ =4, M$_{p}$=2인 경우가 가장 성능이 좋았으며, 그 다음으로 M$_{f}$ =2, M$_{p}$=4인 경우, 그리고 M$_{f}$ =4, M$_{p}$=4인 순서대로 오율 성능이 좋았다. 그리고 MRC 다이버시티 기법 및 부호화 기법을 채용한 경우 효과적으로 시스템 성능의 열화를 보상할 수 있었다. 또한, 합성변조기법을 사용함으로써 강한 임펄스 환경에서도 만족할 만한 시스템 성능을 얻을 수 있었다.

• Journal of Soil and Groundwater Environment
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• v.12 no.5
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• pp.105-114
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• 2007

The most advanced oxidation processes (AOPs) are based on reactivity of strong and non-selective oxidants such as hydroxyl radical (${\cdot}OH$). Decomposition of typical DNAPL chlorinated compounds (TCE, PCE) using various advanced oxidation processes ($UV/Fe^{3+}$-chelating agent/$H_2O_2$ process, $UV/H_2O_2$ process) was approached to develop appropriate methods treating chlorinated compound (TCE, PCE) for further field application. $UV/H_2O_2$ oxidation system was most efficient for degrading TCE and PCE at neutral pH and the system could remove 99.92% of TCE after 150 min reaction time at pH 6($[H_2O_2]$ = 147 mM, UVdose = 17.4 kwh/L) and degrade 99.99% of PCE within 120 min ($[H_2O_2]$ = 29.4 mM, UVdose = 52.2 kwh/L). Whereas, $UV/Fe^{3+}$-chelating agent/$H_2O_2$ system removed TCE and PCE ca. > 90% (UVdose = 34.8 kwh/L, $[Fe^{3+}]$ = 0.1 mM, [Oxalate] = 0.6 mM, $[H_2O_2]$ = 147 mM) and 98% after 6hrs (UVdose = 17.4 kwh/L, $[Fe^{3+}]$ = 0.1 mM, [Oxalate] = 0.6 mM, $[H_2O_2]$ = 29.4 mM), respectively. We improved the reproduction system with addition of UV light to modified Fenton reaction by increasing reduction rate of $Fe^{3+}$ to $Fe^{2+}$. We expect that the system save the treatment time and improve the removal efficiencies. Moreover, we expect the activity of low molecular organic compounds such as acetate or oxalate be effective for maintaining pH condition as neutral. This oxidation system could be an economical, environmental friendly, and practical treatment process since the organic compounds and iron minerals exist in nature soil conditions.

• Journal of Digital Convergence
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• v.12 no.10
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• pp.385-390
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• 2014

This research is conducted to identify whether an m-DIXON technique which is useful for an abdomen MRI examination compared with an existing e-THRIVE technique is a clinically useful or not. There was evaluated quantitative and qualitative to 84 subjects who had abdomen MRI exam due to their liver disease were conducted during a period from September in 2013 to February in 2014. First of all the quantitative evaluation, the m-DIXON technique's SNR was $90.42{\pm}16.90$ and the e-THRIVE technique was $60.42{\pm}11.54$ and the m-DIXON technique's CNR was $52.38{\pm}22.58$ and the e-THRIVE technique was $46.31{\pm}20.25$. Secondly in the qualitative evaluation, the m-DIXON technique's image quality was $4.06{\pm}0.34$, a artifact was $3.64{\pm}0.22$, and fat suppression was $4.16{\pm}0.15$, the e-THRIVE technique's image quality was $3.14{\pm}0.35$, a artifact was $3.06{\pm}0.38$, fat suppression was $3.14{\pm}0.30$. In conclusion, m-DIXON technique for abdomen MRI examination showed superiority over both SNR as a quantitative anaylsis, CNR and a qualitative analysis.

• Proceedings of the Korea Water Resources Association Conference
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• 2022.05a
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• pp.302-302
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• 2022

최근 태풍, 집중호우로 인한 홍수피해가 빈번히 발생함하고 있다. 특히 상류에 저수지가 있을 경우 홍수조절을 통해 하류지역의 홍수피해를 저감하기도 하지만 급작스런 방류량의 증가 등으로 인해 하류지역의 피해가 증가되는 경우도 있다. 따라서 하류지역 홍수피해 저감을 위해 저수지의 홍수관리기능에 대한 관심도가 높아지고 있다. 대규모 다목적댐의 경우 다양한 저수지운영룰을 통해 수문을 운영하고 있어 홍수조절기능을 충분히 수행하고 있지만, 농업용저수지는 홍수관리에 있어 수문조작 전문성의 부족과 운영룰의 미정립 등으로 인해 취약성을 가지고 있는 상황이다. 본 연구에서는 수문이 설치된 1백만m³이상의 저수지 중 성주저수지를 연구대상저수지로 선정하였다. 비상수문을 통한 사전방류방안과, 저수지운영을 연구하여 농업용저수지의 홍수조절용량 확보를 위한 사전방류방안에 대해 연구하였다. 저수지운영은 Auto ROM을 적용하였고 홍수조절용량 확보를 위하여 홍수기 수위관리기법 중 사전방류기법을 채택하였다. 사전방류기법은 모의기법에 의한 사전방류와 최적화기법에 의한 최적사전방류량을 결정하는 방법으로 연구하였다. 홍수기의 제한수위는 유효저수량의 70%인 EL.179.7m, 65%인 EL.178.8m, 60%인 EL.177.8m로 설정하여 분석하였다. 모의기법에 의한 사전방류방법은 초기수위는 만수위에서부터 1.0m씩 감소하였고, 비상수문은 0.5m씩 개방하여 4.0m까지 개방 하였다. 사전방류의 시간은 24hrs, 48hrs를 적용하였다. 최적화기법에 의한 사전방류방법은 초기수위는 모의기법과 동일하고 목표수위를 제한수위(70%, 65%, 60%)가 되는 최적방류량을 산정하고 최적방류량을 방류할 수 있는 수문의 개방높이를 분석하였다. 2012년, 2020년의 호우사상에 대해 사전방류가 없는 경우와 모의기법, 최적화기법에 의한 사전방류결과를 적용한 경우를 비교하여 검토하였다. 그 결과 제한수위 70%를 유지할 경우 2012년은 모의기법이 5.6%, 최적화기법이 5.4%의 방류량 감소효과가 있으며 2020년은 모의기법이 9.0%, 최적화기법이 8.8%의 방류량 감소효과가 있는 것으로 검토되었다.

• Korean Journal of Remote Sensing
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• v.27 no.5
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• pp.507-520
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• 2011

Conventional radar altimeter system measured directly the distance between the satellite and the ocean surface and frequently used by aircraft for approach and landing. The radar altimeter is good at flat surface like sea whereas it is difficult to determine precise three dimensional ground coordinates because the ground surface, unlike ocean, is very indented. To overcome this drawback of the radar altimeter, we have developed and validated the interferometric radar altimeter signal processing which is combined with new synthetic aperture and interferometric signal processing algorithm to extract precise three-dimensional ground coordinates. The proposed algorithm can accurately measure the three dimensional ground coordinates using three antennas. In a set of 70 simulations, the averages of errors in x, y and z directions were approximately -0.40 m, -0.02 m and 4.22 m, respectively and the RMSEs were about 3.40 m, 0.30 m and 6.20 m, respectively. The overall results represent that the proposed algorithm is effective for accurate three dimensional ground positioning.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.23 no.10
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• pp.1290-1297
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• 2019

The paper proposes a distance estimation technique for ultra-wideband (UWB) systems using convolutional neural network (CNN). To estimate the distance from the transmitter and the receiver in the proposed method, 1 dimensional vector consisted of the magnitudes of the received samples is reshaped into a 2 dimensional matrix, and by using this matrix, the distance is estimated through the CNN regressor. The received signal for CNN training is generated by the UWB channel model in the IEEE 802.15.4a, and the CNN model is trained. Next, the received signal for CNN test is generated by filed experiments in indoor environments, and the distance estimation performance is verified. The proposed technique is also compared with the existing threshold based method. According to the results, the proposed CNN based technique is superior to the conventional method and specifically, the proposed method shows 0.6 m root mean square error (RMSE) at distance 10 m while the conventional technique shows much worse 1.6 m RMSE.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.27 no.4
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• pp.943-949
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• 2017

Cryptography implementation over lightweight Internet of Things (IoT) device needs to provide an accurate and fast execution for high service availability. However, adversaries can extract the secret information from the lightweight device by analyzing the unique features of computation in the device. In particular, modern ARM Cortex-M3 processors perform the multiplication in different execution timings when the input values are varied. In this paper, we analyze previous multiplication methods over ARM Cortex-M3 and provide optimized techniques to accelerate the performance. The proposed method successfully accelerates the performance by up-to 28.4% than previous works.

• Journal of the Korean Society of Hazard Mitigation
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• v.10 no.1
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• pp.1-7
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• 2010

Rural facilities need to be changed to be industrialized and long span structures due to accelerating aging of the rural population. In this study, the optimized structure was developed by applying Pre-Engineered Building System using the tapered member to make that the Korea standard green house has a long span. When considering design load, reasonable values were adapted by reviewing existing design codes. As a result, applying pre-engineered building system was efficient in structural system that has span longer than 16 m. And it was concluded that the increase with the longitudinal span from 4 m to 12 m was more efficient in aspect of steel amount.

• Journal of the Korean Society of Safety
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• v.27 no.5
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• pp.164-170
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• 2012

In this study, a new technique for detecting near miss using 4M risk assessment method is suggested. Until now, the safety education with instances of near miss has just been progressed in most industrial settings, without any systematic guideline. By menas of appling 4M risk assessment method, the organized technique, which could effectively manage the fundamental prevention of industrial accident in advance, is developed. The organized technique of near miss-management suggested in this study will take an effective role in basically expanding the application of risk assessment method, as well as in contributing the activity of zero-accident as a safety guideline in hazardous workshops.

• Journal of KIISE:Information Networking
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• v.35 no.4
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• pp.355-366
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• 2008

This paper proposes a mobile SCTP (mSCTP) handover scheme for vertical handover between 3G wireless and WiBro networks. To evaluate the proposed mSCTP vertical handover scheme, we implement the mSCTP handover supporting system over Linux platform in which the movement of a mobile node is automatically detected and the mSCTP vertical handover is performed by the mobile node. We analyze and compare the performance of mSCTP handover and Mobile IP handover over the preconfigured testbed. From the numerical results, we can see that the handover latency of mSCTP could be much more reduced, compared to the Mobile IP handover, if the mobile node would sojourn long enough in the overlapping region between the two heterogeneous networks.