• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.44 no.2
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• pp.108-115
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• 2016

In this paper, fluid-structure of interaction behavior of a fluid-filled cylindrical polymer container impacted by a high speed spherical projectile was studied using ALE(Arbitrary Lagrangian Eulerian) method. The hydrodynamic ram phenomenon occurred by the impact projectile penetrating through the container was investigated by examining time histories of projectile velocity and fluid pressure and density. The analysis results were agreed reasonably well compared to those by experiments.

• Journal of Internet Computing and Services
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• v.6 no.1
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• pp.65-72
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• 2005

Flash memories are one of best media to support portable computers in mobile computing environment. The features of non-volatility, low power consumption. and fast access time for read operations are sufficient grounds to support flash memory as major database storage components of portable computers. However. we need to Improve traditional transaction management scheme due to the relatively slow characteristics of flash operation as compared to RAM memory. In order to achieve this goal. we devise a new scheme called flash-aware transaction management (FATM). FATM improves transaction performance by exploiting SRAM and W-Cache, We also propose a simulation model to show the performance of FATM. Based on the results of the performance evaluation, we conclude that FATM scheme outperforms the traditional scheme.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.45 no.1
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• pp.31-40
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• 2008

This paper presented the development and real-time control of a magnetostrictive micro actuator. Magnetostrictive material has many advantages such as high response time, precision displacement and powerful output force. But Magnetostrictive material has characteristic of hysteresis. Conventional Preisach model which based on experimental data is not suitable to the real-time control because of controlling a magnetostrictive system by Preisach model costs a lot of calculating time. And, we prove the validity of proposed model through the experimental comparison between the classical Preisach model and the proposed one.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2011.11a
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• pp.321-324
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• 2011

본 논문에서는 contourlet 변환을 이용하여 잡음을 제거하는 방법을 제안한다. 영상 센서의 발전으로 이미지의 해상도가 좋아지는 반면 잡음에 민감해진다. 그러므로 이를 전처리 단계에서 처리해주는 것이 필요하다. 잡음은 주로 자연 영상의 윤곽선에서 민감하게 반응하기 때문에 고주파대의 잡음을 최대한 정확하게 제거하는 과정이 중요하다. Contourlet 변환은 기존의 wavelet 변환의 다중 스케일과 더불어 다양한 방향 필터뱅크를 이용하여 방향 성분에 대하여 풍부한 정보를 얻을 수 있는 변환이다. 영상의 화이트 가우시안 잡음을 제거하기 위해 contourlet 변환 영역에서의 계수를 이변수 가우스 확률 모델로 설정하고 Bayes 추정법을 사용한다. Bayes 추정법에 필요한 파라미터들은 근사적으로 추정한다. 제안한 방식을 통하여 잡음이 제거된 영상에 추가적으로 Wiener filter와 cycle-spinning을 적용하여 더 높은 PSNR (peak signal-to-noise ratio)값을 얻을 수 있다. 모의실험을 통해 제안한 방식의 PSNR 값과 결과영상으로 성능이 우수함을 확인하였다.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2019.05a
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• pp.43-44
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• 2019

Major construction projects will be directly related to construction costs and disclosure period depending on the selection of the construction method. However, there are some sites that choose without taking into account sufficient conditions. Therefore, the company wants to present a quality model that suits the characteristics of major engineering fields.

• Proceedings of the Korea Society for Simulation Conference
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• 2000.11a
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• pp.34-40
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• 2000

통합 생산시스템의 성능평가문제는 많은 요소들이 고려되어야하며 수리모델을 위하여 많은 가정사항들이 주어진다. 실제 제생산시스템의 운영환경을 고려한 성능평가를 위하여 Simulation Model들이 많이 연구되어 오고있으나, 실제 활용의 용이성 및 관련 data 및 출력의 이해가 실무자들에게는 매우 어려운 문제로 남아 있다 본 연구에서는 사용자의 요구 수준과 System의 환경 여건에 따른 각종 Simulation Model들을 비교 조사 연구하여 수요자의 요구와 System의 특성에 적절한 방법을 활용할 수 있도록 하였다. 본 연구에 다음과 같은 Simulation Model들을 비교 연구하였다 : 1) CAN-WIP Model, 2) RAM-Cost Model, 3) FACTOR/AIM 응용, 및 4) AutoMod의 응용, 본 연구에 고려된 Simulation Model들의 관련 응용 Program을 개발하고 Sample 예제를 통하여 결과를 비교 분석하였다.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2011.05a
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• pp.137-140
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• 2011

A systemic building maintenance management is necessary to supply an convenience and safety environment by maintain the origin features for a building's life. However, the exist maintenance management system has some problems such as interoperability of information or standardization of data. In those reasons, a critical information for maintenance a building may be lost and changed. In addition, the data could be crashed or lost on a process of re-input or re-produce. This paper purpose the interoperability in exchanging data between design/construction and operation phases. In addition, this model will enhance the efficiency of building maintenance tasks through information quality improvement and data reproduction prevention.

• Journal of the Korean Society of Propulsion Engineers
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• v.1 no.1
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• pp.8-23
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• 1997

Steady and unsteady numerical simulations are conducted for the comparison with the experiments performed to investigate the ram accelerator flow field by using an expansion tube facility in Stanford University. Wavier-Stokes equations for chemically reacting flows are analyzed by fully implicit and time accurate numerical methods with Jachimowski's detailed chemistry model for hydrogen-air combustion involving 9 species and 19 reaction steps. Although the steady state numerical simulation shows a good agreement with the experimental schlieren and OH PLIF images for the case of $2H_2$＋$O_2$＋$17N_2$ fails in reproducing the combustion region behind the shock intersection point shown in the case of $2H_2$＋$O_2$＋$12N_2$ mixture. Therefore, an unsteady numerical simulation is conducted for this case and the result shows all the detailed flow stabilization process. From the result of unsteady numerical simulation, the experimental result seems to be an instantaneous state during the flow stabilization process. The combustion behind the shock intersection point is the result of a normal detonation formed by the intersection of strong oblique shocks that exist at early stage of the stabilization process. At final stage, the combustion region behind the shock intersection point disappears and the steady state result is retained. The time required for stabilization of the reacting flow in the model ram accelerator is found to be very long in comparison with the experimental test time.

• Journal of Internet Computing and Services
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• v.15 no.4
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• pp.125-133
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• 2014

The column-oriented database storage is a very advanced model for large-volume data analysis systems because of its superior I/O performance. Traditional data storages exploit row-oriented storage where the attributes of a record are placed contiguously in hard disk for fast write operations. However, for search-mostly datawarehouse systems, column-oriented storage has become a more proper model because of its superior read performance. Recently, solid state drive using MLC flash memory is largely recognized as the preferred storage media for high-speed data analysis systems. The features of non-volatility, low power consumption, and fast access time for read operations are sufficient grounds to support flash memory as major storage components of modern database servers. However, we need to improve traditional transaction management scheme due to the relatively slow characteristics of column compression and flash operation as compared to RAM memory. In this research, we propose a new scheme called Column-aware Multi-Version Locking (CaMVL) scheme for efficient transaction processing. CaMVL improves transaction performance by using compression lock and multi version reads for efficiently handling slow flash write/erase operation in lock management process. We also propose a simulation model to show the performance of CaMVL. Based on the results of the performance evaluation, we conclude that CaMVL scheme outperforms the traditional scheme.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.3 no.4
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• pp.779-785
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• 1999

The satellite signals have attenuation when Satellite path have rain. The signal attenuation by rain is effected over 100Hz and higher frequency signal have very serious attenuation. The rain attenuation is due mostly to rain rate and rain rate data over 10 years need to estimate characteristics of distribution of ram rate. In this paper, We have obtained the rain characteristics from on the recent data(1988-1997) for Changwon-Masan approximated with Moupfouma New Model, and then estimated the rain attenuation using ITU-R, Global and SAM methods, and finally, Effect of rain was analyzed.