• 정보처리학회논문지A
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• 제13A권6호
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• pp.517-524
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• 2006

클러스터 컴퓨터에 있어서 I/O 중심적인 응용을 효과적으로 처리하기 위해서는 통합 I/O 하부 구조를 지원하는 단일 I/O 공간(SIOS)이 필수적으로 구현되어야 한다. SIOS 서비스는 클러스터 컴퓨터 내의 어느 노드에서든지 자신 혹은 원격 노드에 위치한 주변기기 및 하드 디스크들을 직접 액세스할 수 있도록 전역 I/O 주소 공간을 구축해준다. 본 논문에서는 리눅스 클러스터에서 프리웨어들만을 이용하여 SIOS를 구현하는 방법을 제안하였다. 이 방법은 ENBD를 이용한 디바이스 드라이버 레벨과 S/W RAID 및 NFS를 이용한 파일 시스템 레벨에서 구현되었다. 이 방법의 주요 장점은 프리웨어들만을 이용하기 때문에 구현이 용이하고 비용이 거의 들지 않는다는 것이다. 또한 본 연구에서 사용한 프리웨어들은 공개 소스이기 때문에 다른 플랫폼에서도 약간의 수정을 통하여 적용이 가능하다는 장점이 있다. 이러한 장점을 가지면서도 실험 결과에서 나타난 I/O 처리율은 커널 수준에서 별도로 개발된 디바이스 드라이버를 사용하는 CDD보다 쓰기 동작에서는 최대 5.5배, 읽기 동작에서는 2.3배정도 더 높게 나타났다.

• 한국정보과학회논문지:컴퓨팅의 실제 및 레터
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• 제9권6호
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• pp.635-645
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• 2003

가격 대 성능비가 좋다는 장점으로 인해 많이 사용되고 있는 클러스터 병렬 컴퓨터 시스템에서는 여러 노드에 산재해 있는 자원들을 사용자들이 투명하게 사용할 수 있도록 지원하는 것이 필수적이다. 본 논문에서는 클러스터 시스템에서 단일 디스크 입출력 공간을 지원하는 효율적인 디스크 공유 기법을 제안한다. 응용 수준이 아닌 운영 체제 내의 블록 장치 드라이버 수준에서 디스크 공유를 지원함으로써 사용자들은 로컬 및 원격 디스크를 구분할 필요 없이 클러스터 시스템 내의 모든 디스크들을 마치 로컬 디스크 인 것처럼 투명하게 사용할 수 있다. 기반 운영체제로는 리눅스를 사용하였으며, 실험 결과 단일 디스크 입출력 공간을 성공적으로 지원함과 동시에 비교적 단순한 전역 캐쉬 일관성 정책을 사용했음에도 성능 면에서 NFS에 비해 읽기 성능은 유사, 쓰기 성능은 월등히 향상됨을 확인할 수 있었다. 본 논문이 기여하는 바는 블록 장치 드라이버 수준에서 단일 디스크 입출력 공간을 지원하는 기법을 제안함으로써 블록 장치 드라이버에 비해 비교적 구현이 쉬운 기타 입출력 장치 드라이버에 대해서도 유사한 방식으로 단일 입출력 공간을 지원할 수 있도록 도움을 줄 수 있다는 점이다.

• 천문학회보
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• 제38권2호
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• pp.63.1-63.1
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• 2013

We present the results of time monitoring observations of $^{28}SiO$ v = 1, 2, J = 1-0, $^{29}SiO$ v = 0, J = 1-0 and $H_2O$ $6_{16}-5_{23}$ maser lines toward radio Source I in Orion KL. The observations have been performed from 2009 June to 2013 April using the 21m single dish radio telescopes of the Korean VLBI Network. Both SiO and $H_2O$ maser lines were simultaneously obtained at 20 epochs. In particular, the third outburst of $H_2O$ maser emission (the first: 1985, the second: 1998) was detected and the flux density variation curve was obtained. The maximum flux density flared up to an order of $10^5$ Jy during 2012 May-July at peak velocity of 7.33 km $s^{-1}$. Hirota et al. (2011) reported that the bursting maser features are located at 8" from Source I and coincident with the interacting region between the outflow from Source I and a dense ambient gas, Orion Compact Ridge. In the case of SiO masers arising from close to the Source I, the peak emission of the v = 1, J = 1-0 maser line appeared in 2010 April. We are investigating the possible relation between this SiO maser peak emission and the third $H_2O$ maser flaring.

• 한국정보과학회논문지:시스템및이론
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• 제36권6호
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• pp.476-487
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• 2009

BSD 가상 메모리 시스템(BSD VM)은 페이지-아웃 시 디스크 I/O 횟수를 줄이기 위해 클러스터링 기법을 사용한다. 이 기법은 페이지-아웃 대상 페이지와 가상 메모리 공간에서 인접한 변경 페이지들을 그 대상 페이지와 함께 클러스터(그룹)를 만들어 한 번의 디스크 I/O로 디스크에 저장한다. 하지만 응용 프로그램이 가상 메모리 공간에서 서로 인접하지 않은 다수의 페이지들을 변경하면 클러스터들의 크기가 작아져 클러스터링의 효과가 감소된다. 이 문제점을 해결하기 위해 본 논문에서는 Multiple-Object Clustering(MOC) 기법을 제안한다. MOC는 클러스터별로 디스크 I/O를 하는 대신 여러 클러스터들을 모아 단일 디스크 쓰기로 페이지-아웃시킨다. 따라서 이 페치지-아웃 방식은 디스크 I/O 횟수를 감소시켜 시스틴 성능을 크게 향상시킨다. MOC는 성능 검증을 위해 FreeBSD 6.2 운영체제 커널에서 구현되었다. NS2, Scimark2 SOR, nbench LU 벤치마크를 통한 MOC 성능 측정 결과 기존 BSD VM보다 MOC의 실행 씨간이 9~45% 단축되었다.

• 한국군사과학기술학회지
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• 제3권1호
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• pp.207-217
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• 2000

A fire fighting characteristic by a single evaporating droplet in the case of a fire of military enclosure space was studied experimentally. Transient cooling of solid surface by water droplet evaporation has been investigated through controlled experiments using a heated brass cylinder. Quantitative predictions of droplet evaporation time and in-depth transient temperature distribution in solid have been made. The particular interest was in the removal of thermal energy from the heated cylinder by evaporative cooling. A $10{\mu}1$ single droplet is deposited on a horizontal brass surface with initial temperatures in the range of $90^{\circ}C{\sim}130^{\circ}C.$ The results can be summarized as follows; Evaporating droplet was divided into three different configuration. Evaporation time was predicted as a function of initial surface temperature ($t_c=492.62-6.89T_{s0}+0.0248T_{s0}^2).$ The contact temperature was predicted as a function of initial surface temperature( $T_{i}$=0.94 $T_{s0}$+1.4), The parameter ${\beta}_o$ was predicted as a function of initial surface temperature( ${\beta}_0$ : 0.O0312 $T_{s0}+0.932$)>)>)

• Bulletin of the Korean Chemical Society
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• 제19권1호
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• pp.63-67
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• 1998

The synthesis and characterization of the monomeric group 13 heterocyclic thiosemicarbazone complexes $Me_2M[SC_4H_3CHNNC(S)SCH_3]$ (M=Al (2), Ga (3)) are described. Compounds 2-3 were prepared using $MMe_3$ (M=Al, Ga) in toluene with 2-thiophenecarboxaldehyde-S-methyldithiocarbazat e under anaerobic conditions. These complexes have been characterized by $^1H\;NMR,\; ^{13}C\; NMR$, elemental analyses, and single-crystal X-ray diffraction. 2 crystallizes in the monoclinic space group $P2_1/c$ with unit cell parameters a=10.2930(5) Å, b=18.564 (1) Å, c=7.3812(6) Å, V=1347.9(2) Å3, $D_{calc}=1.342\; gcm^{-3}$ for Z=4, 9281 reflections with $I_o<3{\sigma}\;(I_o),$ R1=0.0500 and wR2=0.0526. 3 crystalizes in the orthorhombic space group $P_{bca}$ with unit cell parameters a=13.340(3) Å, b=19.9070(5) Å, c=11.3690(2) Å, $V=2673.88(9)\;{\AA}^3$, $D_{calc}=1.511\; gcm^{-3}$ for Z=8, 17004 reflections with $I_o>3{\sigma}\;(I_o),$, R1=0.0480 and wR2=0.0524. Compound 3 is a monomeric gallium compound with a weak interaction between the pendant thiophene and the gallium center.

• 대한화학회지
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• 제57권1호
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• pp.12-19
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• 2013

The single-crystal structure of fully dehydrated partially $Li^+$-exchanged zeolite Y, ${\mid}Li_{50}Na_{25}{\mid}[Si_{117}Al_{75}O_{384}]$-FAU, was determined by single-crystal synchrotron X-ray diffraction techniques in the cubic space group $Fd\bar{3}m$ at 100(1) K. Ion exchange was accomplished by flowing stream of 0.1 M aqueous $LiNO_3$ for 2 days at 293 K, followed by vacuum dehydration at 623 K and $1{\times}10^{-6}$ Torr for 2 days. The structure was refined using all intensities to the final error indices (using only the 801 reflections with ($F_o$ > $4{\sigma}(F_o)$) $R_1/R_2=0.043/0.140$. The 50 $Li^+$ ions per unit cell are found at three different crystallographic sites. The 19 $Li^+$ ions occupy at site I' in the sodalite cavity: the $Li^+$ ions are recessed 0.30 ${\AA}$ into the sodalite cavity from their 3-oxygens plane (Li-O = 1.926(5) ${\AA}$ and $O-Li-O=117.7(3)^{\circ}$). The 20 $Li^+$ ions are found at site II in the supercage, being recessed 0.23 ${\AA}$ into the supercage (Li-O = 2.038(5) ${\AA}$ and $O-Li-O=118.7(3)^{\circ}$). Site III' positions are occupied by 11 $Li^+$ ions: these $Li^+$ ions bind strongly to one oxygen atom (Li-O = 2.00(8) ${\AA}$). About 25 $Na^+$ ions per unit cell are found at four different crystallographic sites: 4 $Na^+$ ions are at site I, 5 at site I', 12 at site II, and the remaining 4 at site III'.

• Bulletin of the Korean Chemical Society
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• 제27권5호
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• pp.679-686
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• 2006

The positions of $PbI _2$ molecule synthesized into the molecular-dimensioned cavities of $\mid K_6 (Pb _4I_2)(PbI_2) _{0.67}-(H_2O)_2\mid [Si _{12}Al _{12}O _{48}]$-LTA have been determined. A single crystal of $\mid Pb _6\mid [Si _{12}Al _{12}O _{48}]$-LTA, prepared by the dynamic ion-exchange of $\mid Na _{12}\mid [Si _{12}Al _{12}O _{48}]$-LTA with aqueous 0.05 M $Pb _(NO _3)_2$ and washed with deionized water, was placed in a stream of flowing aqueous 0.05 M KI at 294 K for three days. The resulting crystal structure of the product $( \mid K_6 (Pb _4I_2)(PbI_2) _{0.67}(H_2O)_2\mid [Si _{12}Al _{12}O _{48}]$-LTA, a = 12.353(1) $\AA$) was determined at 294 K by single-crystal X-ray diffraction in the space group Pm3 m. It was refined with all measured reflections to the final error index $R_1$ = 0.062 for 623 reflections which $F_o$ > 4$\sigma$($F_o$). 4.67 $Pb ^{2+}$ and six $K^+$ ions per unit cell are found at three crystallographically distinct positions: 3.67 $Pb ^{2+}$ and three $K^+$ ions on the 3-fold axes opposite six-rings in the large cavity, three $K^+$ ions off the plane of the eight-rings, and the remaining one $Pb ^{2+}$ ion lies opposite four-ring in the large cavity. 0.67 $Pb ^{2+}$ ions and 1.34 $I^-$ ions per unit cell are found in the sodalite units, indicating the formation of a $PbI _2$ molecule in 67% of the sodalite units. Each $PbI _2$ (Pb-I = 3.392(7) $\AA$) is held in place by the coordination of its one $Pb ^{2+}$ ion to the zeolite framework (a $Pb ^{2+}$ cation is 0.74 $\AA$ from a six-ring oxygens) and by the coordination of its two $I^-$ ions to $K^+$ ions through six-rings (I-K = 3.63(4) $\AA$). Two additional $I^-$ ions per unit cell are found opposite a four-ring in the large cavity and form $Pb _2K_2I^{5+}$ and $Pb _2K_2I^{3+}$ moieties, respectively, and two water molecules per unit cell are also found on the 3-fold axes in the large cavity.

• 분석과학
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• 제20권5호
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• pp.448-451
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• 2007

A new bis(dicyclohexylammonium) chromate dihydrate complex, $[(C_6H_{11})_2NH_2]_2[CrO_4]{\cdot}2H_2O$, (I), has been synthesized and its structure analyzed by FT-IR, EDS, elemental analysis, ICP-AES, and single crystal X-ray diffraction methods. The Cr(VI) complex (I) is tetragonal system, I${\bar{4}}$2d space group with a = 12.5196(1), b = 12.5196(1), c = $17.3796(3){\AA}$, a = ${\beta}$ = ${\gamma}$ = $90^{\circ}$, V = $2724.09(6){\AA}^3$, Z = 4. The crystal structure of complex (I) consists of tetrahedral chromate $[CrO_4]^{2-}$ anion, two organic dicyclohexylammonium $[(C_6H_{11})_2NH_2]^+$ cations and two lattice water molecules. The chromate anion and protonated dicyclohexylammonium cation is mainly constructed through the ionic bond. The cyclohexylammonium rings of the dicyclohexylammonium cation take the chair form and vertical configuration with each other. The N-H${\cdot}$O and O-H${\cdot}$O hydrogen bond networks between the $N_{dicyclohexylammonium}$, $O_{water}$ and $O_{chromate}$ atom lead to self-assembled molecular conformation and stabilize the crystal structure.

• 천문학회보
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• 제38권2호
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• pp.32-32
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• 2013

The Korean VLBI Network (KVN) as a world-first multi-frequency VLBI system is operated at four bands of 22, 43, 86, and 129 GHz simultaneously. The performances of both single dish and VLBI network were already confirmed through single dish researches and VLBI evaluation test observations. The VLBI common use of the KVN at 22/43 GHz bands has been started from this autumn. The combined network of KVN and Japanese VERA (KaVA) will start the common use from the first half of next year. Here we present several observational results in the fields of star forming regions, late-type stars, and active galactic nuclei using the KVN and KaVA. The fringes of 44 GHz $CH_3OH$ (Class I) masers were detected from 26 sources for the first time using the KVN and imaging observations are under performing. Simultaneous observations of SiO and $H_2O$ masers toward about 1000 evolved stars showed the different maser properties between SiO and $H_2O$ masers according to the evolutionary stages of AGB and post-AGB stars. The catalog of correlated flux densities were established from a 43 GHz (Q-band) survey of 637 extragalactic sources. At 22 GHz (K-band), flux density measurement and fringe survey for new sources were performed toward a large number of sources. In addition, the large program of KVN and/or KaVA under planning is introduced.