• Title/Summary/Keyword: 지연시간 계산

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An Investigation of the Performance of the Colored Gauss-Seidel Solver on CPU and GPU (Coloring이 적용된 Gauss-Seidel 해법을 통한 CPU와 GPU의 연산 효율에 관한 연구)

  • Yoon, Jong Seon;Jeon, Byoung Jin;Choi, Hyoung Gwon
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.41 no.2
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    • pp.117-124
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    • 2017
  • The performance of the colored Gauss-Seidel solver on CPU and GPU was investigated for the two- and three-dimensional heat conduction problems by using different mesh sizes. The heat conduction equation was discretized by the finite difference method and finite element method. The CPU yielded good performance for small problems but deteriorated when the total memory required for computing was larger than the cache memory for large problems. In contrast, the GPU performed better as the mesh size increased because of the latency hiding technique. Further, GPU computation by the colored Gauss-Siedel solver was approximately 7 times that by the single CPU. Furthermore, the colored Gauss-Seidel solver was found to be approximately twice that of the Jacobi solver when parallel computing was conducted on the GPU.

Performance Analysis for Privacy-preserving Data Collection Protocols (개인정보보호를 위한 데이터 수집 프로토콜의 성능 분석)

  • Lee, Jongdeog;Jeong, Myoungin;Yoo, Jincheol
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.25 no.12
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    • pp.1904-1913
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    • 2021
  • With the proliferation of smart phones and the development of IoT technology, it has become possible to collect personal data for public purposes. However, users are afraid of voluntarily providing their private data due to privacy issues. To remedy this problem, mainly three techniques have been studied: data disturbance, traditional encryption, and homomorphic encryption. In this work, we perform simulations to compare them in terms of accuracy, message length, and computation delay. Experiment results show that the data disturbance method is fast and inaccurate while the traditional encryption method is accurate and slow. Similar to traditional encryption algorithms, the homomorphic encryption algorithm is relatively effective in privacy preserving because it allows computing encrypted data without decryption, but it requires high computation costs as well. However, its main cost, arithmetic operations, can be processed in parallel. Also, data analysis using the homomorphic encryption needs to do decryption only once at any number of data.

A simple approach to refraction statics with the Generalized Reciprocal Method and the Refraction Convolution Section (GRM과 RCS 방법을 이용한 굴절파 정적 시간차를 구하는 간단한 방법)

  • Palmer Derecke;Jones Leonie
    • Geophysics and Geophysical Exploration
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    • v.8 no.1
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    • pp.18-25
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    • 2005
  • We derive refraction statics for seismic data recorded in a hard rock terrain, in which there are large and rapid variations in the depth of weathering. The statics corrections range from less than 10 ms to more than 70 ms, often over distances as short as 12 receiver intervals. This study is another demonstration of the importance in obtaining accurate initial refraction models of the weathering in hard rock terrains in which automatic residual statics may fail. We show that the statics values computed with a simple model of the weathering using the Generalized Reciprocal Method (GRM) and the Refraction Convolution Section (RCS) are comparable in accuracy to those computed with a more complex model of the weathering, using least-mean-squares inversion with the conjugate gradient algorithm (Taner et al., 1998). The differences in statics values between the GRM model and that of Taner et al. (1998) systematically vary from an average of 2ms to 4ms over a distance of 8.8 km. The differences between these two refraction models and the final statics model, which includes the automatic residual values, are generally less than 5 ms. The residuals for the GRM model are frequently less than those for the model of Taner et al. (1998). The RCS statics are picked approximately 10 ms later, but their relative accuracy is comparable to that of the GRM statics. The residual statics values show a general correlation with the refraction statics values, and they can be reduced in magnitude by using a lower average seismic velocity in the weathering. These results suggest that inaccurate average seismic velocities in the weathered layer may often be a source of short-wavelength statics, rather than any shortcomings with the inversion algorithms in determining averaged delay times from the traveltimes.

Analysis of the GPS Error Effect through Simulation (시뮬레이션을 통한 GPS 오차의 영향 분석)

  • Jeon, Jae-Han;Kwon, Jay-Hyoun;Lee, Ji-Sun
    • Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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    • v.26 no.4
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    • pp.397-405
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    • 2008
  • The position accuracy is primarily dependent on the satellite position and signal delay caused by several elements. To know the effect of the delay on the estimated positions, we simulated GPS raw data (RINEX) with GPS errors using Bernese ver5.0. GPS errors used in this paper are Ionospheric delay, Cycle slip, Troposphere, DOP and Random error. If the baseline is short, the position error according to TEC is not large, since the ionospheric delay effect can be removed by ion-free combination. However, if the baseline is long, 3 dimensional position error up to 10cm is occurred. The 3D position error of coordinates with cycle slip is hardly ever changed up to 60% of cycle slip. Because the simulated cycle slips are equally distributed on satellites, the positioning was not seriously affected by the cycle slip. Also, if percentage of cycle slip is 60%, three dimensional error is sharply increased over 1m. The position error is calculated by using the observation data (2 hours) which was selected by DOP less than 3. And its accuracy is more improved about $3{\sim}4cm$.

Optimization of the Empirical Method to the Enhancement Image of the Four Chambers at the Same Time in the Pediatric Cardiac Computed Tomography (소아 심장 전산화단층촬영 검사에서 4 chamber의 동시 조영증강 영상에 대한 최적화 방안)

  • Park, Chanhyuk;Lee, Jaeseung;Im, Inchul
    • Journal of the Korean Society of Radiology
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    • v.8 no.6
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    • pp.279-285
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    • 2014
  • This study is to have dose reduction and minimization of excessive use of contrast medium in the pediatric cardiac computed tomography and to suggest the optimization plan to acquire the enhancement image of the 4 chambers at the same time by formulating scan delay time in empirical method with considering variables such as contrast medium injection velocity and cardiac approaching time. Quantitative, qualitative and dose assessment were carried out for 30 pediatric patients who had taken the cardiac examination. In conclusion, image enhancement in 4 chambers of the cardiac shows over 300 HU which is proper to pediatric cardiac reading by applying the empirical method with calculating scan delay time according to weight and contrast medium volume and injection velocity. Qualitative image assessments in confidence sharpness and noise have excellence qualitatively. Exposure dose to pediatrics also decreases precisely. Therefore this study is judged to take a important role of making optimization images with advantages of dose reduction and less side effects caused by it's excessive use in clinic.

Hydrologic Characterization through Ground Water Monitoring in a Coastal Aquifer (해안 대수층에서 지하수 장기 모니터링을 통한 수리 특성 조사)

  • Shim, Byoung-Ohan;Lee, Chol-Woo
    • Economic and Environmental Geology
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    • v.44 no.3
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    • pp.239-246
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    • 2011
  • Groundwater in small islands is used as main water resource but the overuse of groundwater may cause seawater intrusion and temperature decrease in geothermal wells. This study aimed to characterize the hydrogeology of Maeum-ri area in Seokmo Island of Ganghwagun using long-term monitoring at groundwater wells and geothermal wells. In the monitoring period seasonal water level change, consistent drop or increase of water levels are not detected. The groundwater temperature about 10m below ground surface shows year cycle variation having two to five months difference with ambient temperature cycle. The storativity was calculated by tidal method. The storativity estimated by adapting tidal efficiency factor showed some larger values than that by using tidal time lag. The result suggested that the tidal method assuming several assumptions on aquifer condition may produce broad ranges but the calculated ranges at this application are reasonable. The similar shape of groundwater level change and tidal effects was observed at several wells clustered east-south-east direction which may implicate the distribution of vertical fracture system strongly related with groundwater flow channels. The applied methodology and study results will bc valuable to evaluate optimal pumping rate for the preservation of groundwater resources, and to manage geothermal development.

3D Sound Diffusion Control Using Wavelets (웨이블릿을 이용한 입체음향의 확산감 제어)

  • 김익형;정의필
    • Journal of the Institute of Convergence Signal Processing
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    • v.4 no.4
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    • pp.23-29
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    • 2003
  • In this paper, we propose an idea for the improved 3-D sound system using conventional stereo headphones to obtain a better sound diffusion from the mono-sound recorded at an anechoic chamber. We use the HRTF(Head Related Transfer Function) for the sound localization and the wavelet filter bank with time delay for the sound diffusion. And we test the modified HRTF with the various sampling rate. We investigate the effects of the 3-D sound depending on the length of time delay at lowest frequency band. Also the correlation coefficient of the signals between the left channel and the right channel is measured to identify the sound diffusion. At last we obtain the diffusion sound using Cool Edit for reverberation.

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The VoIP Capacity Analysis of 802.11 WLANS with Propagation Errors (전파 오류가 빈번한 802.11 무선 랜에서의 VoIP 용량 분석)

  • Jung, Nak-Cheon;Ahn, Jong-Suk
    • Journal of KIISE:Computing Practices and Letters
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    • v.14 no.1
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    • pp.101-105
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    • 2008
  • This paper proposes an analytical model to calculate VoIP (Voice of IP) capacity over wireless LANs with frequent bit errors. Since the traditional analytical models for VoIP capacity have not included the effect of bit errors, simulations ould only evaluate VoIP capacity over erroneous channels. For analytically accurate estimation of VoIP capacity over noisy channels, we extend the conventional model to include the effect of propagation errors, end-to-end delay, voice quality, the waiting time in AP(Access Point). The experiments show that our model predicts the VoIP capacity of a given network within the range from 3% to 9% difference comparing with the simulation results.

Analysis and Implementation of Web Based Log System for The Education of Software Developing Process (소프트웨어 개발 프로세스 교육을 위한 웹기반 로그 시스템의 구현 및 분석)

  • Park, Chiyeon;Yoo, Wook-Sung
    • The Journal of Korean Association of Computer Education
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    • v.9 no.4
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    • pp.55-61
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    • 2006
  • The Personal Software Process(PSP) is a rigorous, measurements based process designed to help software developers produce high-quality codes. Learning PSP requires substantial and tedious record keeping including clerical computations with plenty of data occurred at every project. The required task reduces the educational effect and motive by time consuming characteristic and easy occurrence of errors. To alleviate these problems, a web-based PSP log system having streamlined mechanism of data manipulation is designed and implemented at this study. Three years of experiment shows that the system not only improves productivity and accuracy of the process but also allows students and instructors to focus on learning and teaching PSP, rather than PSP data collection.

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Application Layer Multicast Tree Constructing Algorithm for Real-time Media Delivery (실시간 미디어 전송을 위한 응용계층 멀티캐스트 트리 구성 알고리즘)

  • Song Hwangjun;Lee Dong Sup
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.29 no.11B
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    • pp.991-1000
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    • 2004
  • This paper presents an application layer multicast tree constructing algorithm to minimize the average time delay from the sender to end-systems for the effective real-time media delivery. Simultaneously, the proposed algorithm takes into account the computing power and the network condition of each end-system as a control variable and thus avoids the undesirable case that loads are concentrated to only several end-systems. The multicast tree is constructed by clustering technique and modified Dijkstra's algorithm in two steps, i.e. tree among proxy-senders and tree in each cluster. By the experimental results, we show that the proposed algorithm can provide an effective solution.