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150MPa 150MPa급 초고강도 콘크리트의 섬유 복합 혼입에 따른 휨강도 검토
김성용 ( Sung Yong Kim ),하정수 ( Jung Soo Ha ),김학영 ( Hak Young Kim ),김한식 ( Han Sik Kim ),임남기 ( Nam Gi Lim ),정상진 ( Sang Jin Jeong ) 한국건축시공학회 2013 한국건축시공학회 학술발표대회 논문집 Vol.13 No.2
It is the study on the mechanical properties of the material when mixing hybrid fiber as steel and synthetic fiber to improve fire resistance and toughness of concrete. Finally, The purpose is to identify of mechanical properties of Hybrid Fiber-Reinforced Ultra High Strength Concrete such as flexural strength.
온도응력과 건조수축을 고려한 요소혼입 콘크리트의 품질특성에 관한 연구
김용범(Kim, Yong-Bum),조한병(Cho, Han-Byung),김학영(Kim, Hak-Young),전우철(Jun, Woo-Chul),박희곤(Park, Hee-Gon),정란(Chung, Lan) 대한건축학회 2015 大韓建築學會論文集 : 構造系 Vol.31 No.7
Due to a big difference of temperatures between the inside and outside and a high level of hydration heat on the core, some thermal stress is generated in mass Concrete. In turn, it causes the expansion of the concrete members and some cracks of the concrete joints that become the factors threatening the soundness of a concrete structure. Due to the reason, various kinds of low-heat concrete are being developed in domestic and foreign countries. In this study, some urea for industrial use which is used in microorganism cultivation agents, etc., is applied as a concrete mixing material in order to suppress the hydration heat of mass concrete. This is intended to lower down some levels of hydration heat and drying shrinkage of mass concrete. 21 kinds of concrete mixtures in total were designed at 3 kinds of W/B ratios, that is, 45, 50 and 55%. Thus, the dynamic characteristics, durability and hydration heat properties of urea-mixed concrete were verified through some experiments and the optimum mixing design was suggested. As the results of this study, the compressive strength of urea-mixed concrete at the age of 3 days decreased by 40% compared to that of plain concrete, but it showed the tendency recovering up to 95% at maximum at the age of 56days. On the other hand, the maximum temperature of urea-mixed concrete decreased down to 7.9 ℃at maximum thanks to the hydration heat compared with that of plain concrete and the point of time reaching the highest temperature of the urea-mixed concrete was delayed by 33.9 hours at maximum compared with that of plain concrete. In addition, it resulted that the length change rate of urea-mixed concrete decreased down to 56% at maximum thanks to the expansion characteristics of CaCO₃.
Shack -Hartann 파면분석기와 점광원을 이용한 광학부품의 수차 측정
이진석 ( Jin Seok Lee ),김학영 ( Hak Young Kim ),박영필 ( Yong Pil Park ),박노철 ( No Cheol Park ),한재원 ( Jae Won Hahn ) 정보저장시스템학회 2005 추계학술대회논문집 Vol.2005 No.-
Using a Shack-Hartmann sensor, we construct an optical testing system measuring the wavefront error of small optical components. The systematic error of the sensor is compensated with a reference plane-wave system that produces almost perfect plane waves. Several types of lenses are tested using a point source that generates spherical waves emitted from a pinhole. The results of the optical testing obtained with the ShackHartman sensor are compared with those measured with Zygo interferometer.
SAN 환경에서 공유 디스크 파일 시스템을 위한 전역 버퍼 관리자
손덕주(Duk Joo Son),신범주(Bum-Joo Shin),김학영(Hak-Yong Kim),김명준(Myung-Joon Kim),박선영(Seon-Yeong Park) 한국정보과학회 2004 정보과학회 컴퓨팅의 실제 논문지 Vol.10 No.2
네트워크를 통해 전송되는 데이타의 양이 급속히 증가함에 따라 확장성 있는 저장 시스템에 대한 사용자 요구가 증가하고 있다. 네트워크 연결형 자료 저장 시스템인 SAN(Storage Area Network)은 호스트와 디스크를 광채널 스위치로 연결하는 구조로서 저장 공간과 서버에 대한 확장성을 제공한다. SAN 환경에서는 다수의 호스트가 네트워크에 연결된 저장 장치를 공유하므로 공유 데이타에 대한 일관성 유지가 필요하다. 이를 위해 각 호스트가 수정한 데이타를 즉시 디스크에 반영하는 방법을 사용하고 있지만 이는 느린 디스크 접근 시간(Disk Access Time)으로 인해 시스템의 성능을 저하시키는 요인이 된다. 본 논문에서는 필요한 공유 데이타를 다른 호스트의 메모리를 통해서 직접 전송 받을 수 있도록 하여 공유 데이타의 접근 속도를 향상시킬 수 있는 전역 버퍼 관리자의 설계와 구현에 대해 소개한다. SANtopia 전역 버퍼 관리자는 SAN에 연결된 호스트들이 서로의 버퍼 캐시를 공유하도록 함으로써 블록 데이타로의 빠른 접근을 가능하게 한다. 마이크로 벤치마크를 통한 블록 단위 I/O의 성능 측정 결과, 전역버퍼 관리자를 사용하는 것이 기존의 디스크 I/O를 사용하는 방법에 비해 약 1.8-12.8배 정도 빠른 성능을 보였으며 파일 시스템 벤치마크를 통한 성능 측정 결과, 전역 버퍼 관리자를 사용한 SANtopia 파일 시스템은 사용하지 않은 것과 비교해서 디렉터리 파일 시스템 콜의 경우 약 1.06배 정도 빠르고 일반 파일시스템 콜은 약 1.14배 정도 빠른 성능을 보였다. With rapid growth in the amount of data transferred on the Internet, traditional storage systems have reached the limits of their capacity and performance. SAN (Storage Area Network), which connects hosts to disk with the Fibre Channel switches, provides one of the powerful solutions to scale the data storage and servers. In this environment, the maintenance of data consistency among hosts is an important issue because multiple hosts share the files on disks attached to the SAN. To preserve data consistency, each host can execute the disk I/O whenever disk read and write operations are requested. However, frequent disk I/O requests cause the deterioration of the overall performance of a SAN cluster. In this paper, we introduce a SANtopia global buffer manager to improve the performance of a SAN cluster reducing the number of disk I/Os. We describe the design and algorithms of the SANtopia global buffer manager, which provides a buffer cache sharing mechanism among the hosts in the SAN cluster. Micro-benchmark results to measure the performance of block I/O operations show that the global buffer manager achieves speed-up by the factor of 1.8-12.8 compared with the existing method using disk I/O operations. Also, File system micro-benchmark results show that SANtopia file system with the global buffer manager improves performance by the factor of 1.06 in case of directories and 1.14 in case of files compared with the file system without a global buffer manager.
Finite Element Investigation of Instability in Hot Bar Rolling Process
Muhammad Awais(무하마드 아와이스),Ho-Won Lee(이호원),Hak-Young Kim(김학영),Yong-Taek Im(임용택),Sang-Min Byon(변상민),Hae-Doo Park(박해두) 대한기계학회 2006 대한기계학회 춘추학술대회 Vol.2006 No.6
In this study, the effect of processing parameters on instability of the steel (S10C) during the hot bar rolling process was investigated numerically. Plastic work was used for deriving a criterion to judge a surface nonuniform deformation due to the instability. The processing map was formulated based on the instability criterion derived from the plastic work approach and the experimental observations obtained from the hot compression tests. The effects of roll pass geometry and temperature were examined with the help of a parametric study by employing the processing map with three dimensional rigid thermo-viscoplastic finite element analyses based on the plastic work approach proposed in the present investigation. Based on this approach, processing conditions for reducing the instability were determined. According to this investigation, the roll pass design was determined and the initial processing temperature in the hot bar rolling process recommended for reducing flow instability of the process.