• Proceedings of the Korea Water Resources Association Conference
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• 2011.05a
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• pp.249-249
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• 2011

본 연구에서 AFDA(Approximate Full Distribution Approach)를 사용하여 하수관의 성능불능확률(Probability of capacity failure)을 정량적으로 산정할 수 있는 신뢰성 모형이 개발되었다. 전국 여러 도시의 연 최대강우강도(Yearly Maximum Rainfall Intensity)를 이용하여 그 확률분포함수를 규명하였고 우수관(Storm sewer)의 성능불능확률 산정을 위한 신뢰성모형에 적용하였다. 본 연구에서는 우수관의 성능불능확률을 산정하여 신뢰성 해석을 수행하였다. 먼저 적용도시의 강우자료를 면밀히 분석하고 연 최대강우강도의 통계적 특성을 분석하여 신뢰함수를 구축하였으며 우수관의 성능불능확률 산정을 위한 신뢰성 모형이 개발되었다. 그리고 우수관에 적체되는 토사의 깊이에 따라 우수관의 용량을 산정하였다. 재현기간별 강우강도를 사용하여 청주와 춘천의 원형우수관의 성능불능확률을 산정한 결과, 재현기간의 증가에 따란 성능불능확률을 급하게 상승하는 것을 알 수 있었다. 5년, 10년, 20년 재현기간에 따른 연 최대강우강도를 사용하여 청주와 춘천의 우수관의 성능불능확률을 산정하였다. 또한 토사의 적체에 따른 우수관 유효면적의 변화를 고려하여 두 도시의 우수관의 성능불능확률을 산정하였다. 원형 우수관의 성능불능확률을 산정한 결과, 토사의 적체에 따라 우수관의 용량은 감소하여 성능불능확률이 크게 증가하는 것을 확인 할 수 있었다. 따라서 우수관의 용량 감소를 막고 성능불능확률을 최소화하기 위해 우수관에 적체된 토사의 양을 예측할 수 있는 연구가 필요하며 적체된 토사와 콘크리트나 강관벽면이 복합된 우수관에 대한 조도계수를 보다 더 정확히 정량화 할 수 있는 연구가 수행되어야 할 것이다.

• Cement
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• s.69
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• pp.23-28
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• 1977

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.47 no.11
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• pp.59-68
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• 2010

In this paper, we present a new method to complete Dynamic Spectrum Access by modifying the reward function. Partially Observable Markov Decision Process (POMDP) is an eligible algorithm to predict the upcoming spectrum opportunity. In POMDP, Reward function is the last portion and very important for prediction. However, the Reward function has only two states (Busy and Idle). When collision happens in the channel, reward function indicates busy state which is responsible for the throughput decreasing of secondary user. In this paper, we focus the difference between busy and collision state. We have proposed a new algorithm for reward function that indicates an additional state of collision which brings better communication opportunity for secondary users. Secondary users properly utilize opportunities to access Primary User channels for efficient data transmission with the help of the new reward function. We have derived mathematical belief vector of the new algorithm as well. Simulation results have corroborated the superior performance of improved reward function. The new algorithm has increased the throughput for secondary user in cognitive radio network.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39C no.7
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• pp.538-545
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• 2014

This paper proposes a coordinated multi-point (CoMP) based dynamic transmission scheme in a downlink multi-ship network, where a central ship selects a ship in order to maximize the utility function. The proposed scheduling scheme dynamically decides to the usage of the coordinated multi transmissions and selects a user to be served for every frame, in order to the utility function on the basis of the throughput and fairness. In particular, the proposed utilify function based scheduling scheme aims to increase the quality of service of ships at the edge of cells. Under the proportional fair scheduling, the simulation results show that the proposed utility function-based scheduling improves the throughput of the ships at the cell edge with the little sacrifice of the system capacity.

• Journal of the Korean Society of Radiology
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• v.15 no.5
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• pp.705-713
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• 2021

The modulation transfer function (MTF) is calculated to analyze the resolution of the spatial frequency of the image acquired from the x-ray imaging system. In general, the response function of the detector acquires a line spread function (LSF) using a slit-camera, and derives a modulation transfer function through a Fourier transform. Because of the fact that the x-ray must always be incident on the center of the slit-camera, the tilt of the detector and slit-camera caused by the experimenter will affect the detector performance. In addition, if the tilt increases, the performance evaluation of the x-ray image system will be problematic. In this study, we analyzed the experimental and analytical models in the modulation transfer function, ie, the Fourier domain, based on the experimental error and analyzed the effect on the spatial frequency. Furthermore, performance evaluation is being carried out for various x-ray imaging systems, and experimental errors are indispensable, and the extent to which they can be tolerated should be reviewed.

• The Journal of the Acoustical Society of Korea
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• v.28 no.5
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• pp.461-470
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• 2009

We investigate and analyze the problems encountered in frame-based estimation of TDOA (Time Difference of Arrival) using CPSP function. Spectral leakage occurring in framing of a speech signal by a rectangular window could make estimation of CPSP spectrum inaccurate. Framing with other windows to reduce the spectral leakage distorts the signal due to the asynchronous weighting around the frame specifically both ends of the frame. These problems degrade the performance of the CPSP-based TDOA estimation. In this paper, we propose a method to alleviate those problems by pre-emphasis of the speech signal. It reduces the influence of the spectral leakage by reducing dynamic range of the spectrum of a speech signal with pre-emphasis. To validate the proposed method of pre-emphasis, we carry out TDOA estimation experiments in various noise and reverberation conditions, Experimental results have shown that the framing of pre-emphasized microphone output by a rectangular window achieves higher success rate of TDOA estimation than any other framing methods.

• Journal of KIISE:Computing Practices and Letters
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• v.16 no.6
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• pp.637-647
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• 2010

Recent embedded systems are being more complicated due to their hierarchical software architecture including operating systems. The performance of such complicated software architecture could not be well analyzed through separate analysis of each software layer; the combined effect and the interactions among the whole software layers should be considered. In this paper, we show the design and implementation of a performance analysis framework that enables hierarchical analysis of performance of Linux-based embedded systems considering interactions among the software layers. By using the proposed framework, we can obtain useful run-time information about a hierarchical software structure which usually consists of user-defined function layer, library function layer, system call layer, and kernel events layer. Experimental results reveal that the proposed framework could accurately identify the performance bottlenecks with the corresponding software layers during executions of target applications through the accompanying sub-steps of the analysis: the actual execution paths, the execution time of each observed event in each software layer, and the control flows across the software layers.

• Proceedings of the Korea Institutes of Information Security and Cryptology Conference
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• 2002.11a
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• pp.211-214
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• 2002

본 논문에서는 loop unrolling 방법을 적용한 해쉬 함수의 하드웨어 구현에 관하여 기술한다. 해쉬 함수는 메시지의 무결성을 보장하기 위한 인증에 사용되는 알고리즘으로 메시지를 처리하는 전처리부, 데이터 압축을 수행하는 반복 프로세싱부, 그리고 처리된 결과를 출력하는 결과 출력부로 기능을 분리할 수 있다. 이때 데이터 연산 처리 속도를 개선하기 위하여 반복 프로세싱부에 loop unrolling 기법을 적용하였다. 본 논문에서는 loop unrolling 기법을 적용한 해쉬 함수의 구현에 관한 것과 이로 인한 성능 개선 효과에 대하여 기술한다.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 1996.10a
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• pp.306-309
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• 1996

본 논문에서는 유전자 알고리즘을 이용하여 퍼지 제어기를 위한 최적 소속함수와 제어 규칙들을 자동으로 생성하는 방법을 제안한다. 제안한 방법은 효과적인 염색체 암호화 방법을 이용하여 소속함수의 표현 해상도가 증가하여도 소속함수의 언어항의 개수를 일정하게 유지하여 제어 규칙을 표현하는 염색체의 길이가 크게 늘어나지 않도록 한다. 또, 소속함수의 언어항의 개수가 서로 다른 염색체에 대해서도 개선된 교배 및 돌연변이 연산자를 이용하여 효과적으로 유전자 연산을 적용할 수 있게 한다. 본 논문에서는 제안된 방법을 퍼지 제어기의 자동 생성 방법의 평가 문제로 널리 이용되는 트럭 후진 주차 문제에 적용하여 성능을 평가한다.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.41 no.10
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• pp.85-94
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• 2004

In this paper, a register allocation techlique that translates memory accesses to register accesses Is presented to enhance embedded software performance. In the proposed method, a source code is profiled to generate a memory trace. From the profiling results, target functions with high dynamic call counts are selected, and the proposed register allocation technique is applied only to the target functions to save the compilation time. The memory trace of the target functions is searched for the memory accesses that result in cycle count reduction when replaced by register accesses, and they are translated to register accesses by modifying the intermediate code and allocating Promotion registers. The experiments where the performance is measured in terms of the cycle count on MediaBench and DSPstone benchmark programs show that the proposed method increases the performance by 14% and 18% on the average for ARM and MCORE, respectively.