• Title/Summary/Keyword: 순환영역

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통합 영역의 분류에 따른 EAI 구축 방안

  • 이강일
    • Communications of the Korean Institute of Information Scientists and Engineers
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    • v.22 no.7
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    • pp.41-45
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    • 2004
  • 기업의 IT 환경 순환주기를 보면 업태마다 약간의 차이가 있겠으나 평균 2∼3년, 길게는 5년 정도마다 신규 부문에 대한 대단위의 투자가 이루어지고 있으며, 이런 투자 주기는 2000년 밀레니엄 시대를 맞이하여 더욱 활발하게 이루어졌다. 결과적으로 기업의 IT 자산은 그 동안 질적인 부분보다는 양적인 팽창이 기업 경쟁력 강화, 업무 생산성 향상이라는 명분을 충족시키기 위한 수단으로 행해져 왔다.

The computation of the turn-over time by meteorologically-induced circulation on the East China Sea (계절별 풍성류에 의한 동지나해의 해수 교체시간 산정)

  • 최병호;서경석
    • Proceedings of the Korean Society of Coastal and Ocean Engineers Conference
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    • 1991.07a
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    • pp.77-81
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    • 1991
  • 3차원 수치모형(Choi, 1989)을 이용하여 동지나해의 계절별 및 연평균의 풍성류 순환을 산정하였고, 이률 사용하여 동지나해의 분할된 여러 영역에서 수심별 해수 교체시간(turn-over time)을 계산하였다.(중략)

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Quality Properties of Mortar Using the Recycled Fine Aggregates and Fly Ash Depending on Mixing Factors (순환잔골재와 플라이애시를 사용하는 모르터의 배합요인 변화에 따른 품질특성)

  • Han, Cheon-Goo;Son, Seok-Heon;Park, Kyung-Taek
    • Journal of the Korean Recycled Construction Resources Institute
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    • v.5 no.4
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    • pp.99-105
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    • 2010
  • This study analyzed the effects of changes in mixing factors of zero-cement mortar that only used recycled fine aggregates and fly-ash on quality of mortar, and the results are as follows. To describe the property of fresh mortar, as mix proportion and flow of mortar increased, W/B was highly selected and air content decreased. To describe compressive strength according to age as the property of hardened mortar, it was revealed that the strength did not strength until the 14 day, but strength of about 1 ~ 2 MPa strength during the 14 day through 28 day, and almost similar strength after 28 day. Also, compressive strength according to changes in mix proportion, flow and B/W was generally similar. Summarizing the above experimental results, in case of mortar that used recycled fine aggregates and fly-ash, it secured the strength for the use of landfill even though not for structural use. Especially, poor mix proved to be more useful than rich mix.

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An Analysis of Students' Conceptions on Blood Circulation as Components: A Cross-sectional Study (혈액 순환 요소별 학생들의 개념 분석 : 횡단적 연구)

  • Kim, Mi-Young;Kim, Heui-Baik
    • Journal of The Korean Association For Science Education
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    • v.26 no.6
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    • pp.753-764
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    • 2006
  • The concept of blood circulation is so complex, dynamic and abstract that students have difficulty in understanding it and students' preconceptions hardly change into scientific concepts even after the lessons. The purpose of this study is to examine middle school, high school, and undergraduate students' understanding of blood circulation and to find the reason why the lack of deep understanding is displayed in students' explanations for the blood circulation. The study consists of three parts. First, the test was designed to investigate students' ideas for blood circulation as components of the structure, the function, the behavior and the mechanism. Second, the test was applied to 7th, 10th and 13th graders to investigate the students' understanding of blood circulation and categorize the types of students' blood circulation model according to their academic level. Finally, the concepts the students had little understanding of were analyzed to decide which ontological category they fell into and further to inquire the characteristics of each concept. The results showed that many students comprehend the structure and the function of blood circulation components well, and there was no significant difference in students' understanding according to the academic level. In contrast, understanding the behavior and the mechanism of circulatory components has remarkably improved in high school students and undergraduates majoring in science and engineering. Also, students' blood circulation models were classified into seven different types. High school students and undergraduates majoring in science and engineering demonstrated a significantly higher percentage on the type of double-loop-branch compared to other academic levels. In addition, it was found that the lack of deep understanding was caused by students' misconceiving the 'equilibrium' category as 'event' category.

Measured Effect of Shock Wave on the Stability Limits of Supersonic Hydrogen-Air Flames (충격파가 초음속 수소-공기 화염의 안정한계에 미치는 영향)

  • Hwanil Huh
    • Journal of the Korean Society of Propulsion Engineers
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    • v.3 no.1
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    • pp.86-94
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    • 1999
  • Measured shock wave effects were investigated by changing shock strength and position with particular emphasis on the stability limits of hydrogen-air jet flames. For this purpose, a supersonic nonpremixed, jet-like flame was stabilized along the axis of a Mach 2.5 wind tunnel, and wedges were mounted on the sidewall in order to interact oblique shock waves with the flame. This experiment was the first reacting flow experiment interacting with shock waves. Schilieren visualization pictures, wall static pressures, and flame stability limits were measured and compared to corresponding flames without shock-flame interaction. Substantial improvements in the flame stability limits were achieved by properly interacting the shock waves with the flameholding recirculation zone. The reason for the significant improvement in flame stability limits is believed to be the adverse pressure gradient caused by the shock, which can elongate the recirculation zone.

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A Computational Study of Flowfield for a Vent Mixer in Supersonic Flow (초음속 유동장 내 벤트 혼합기에 관한 수치해석 연구)

  • Kim, Chae-Hyoung;Jeung, In-Seuck
    • Journal of the Korean Society of Propulsion Engineers
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    • v.12 no.2
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    • pp.33-39
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    • 2008
  • To improve the mixing efficiency and to reduce the pressure loss, it is needed to develope a new mixing device for supersonic combustion. The vent mixer is introduced as the new supersonic fuel-air mixer. Computational analyses, that include pressure profile, density contour, and streamline tracing, have been carried out. The expansion wave generates at the end of the extended upper wall of the mixer. And it reduces the shock wave from the hole. Incoming air flow through the hole makes several recirculation regions which increase the mixing efficiency, and the separation region at the downward wall expends the boundary layer which reduces the pressure loss.

Dissipation and Control of Flow Instability in a Rectangular Swirl Combustor using Cooling Flow Injection (사각 스월 연소기에서 냉각 유동을 이용한 연소기 내 유동 불안정 감쇠 및 조종)

  • Yoo, Kwang-Hee;Kim, Jong-Chan;Sung, Hong-Gye
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2009.11a
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    • pp.236-241
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    • 2009
  • To identify turbulent flow characteristics of non-reacting case resulted from cooling flow injection in a rectangular swirl combustor, 3D Large Eddy Simulation(LES) was implemented and Proper Orthogonal Decomposition(POD) analysis was used for post-processing. The combustor of concern is the LM6000, lean premixed dry low-NOx annular combustor, developed by GEAE. It was observed that increase in speed of shear layer resulted from the inflow of cooling flow caused intensified vorticity magnitude in central toroidal recirculation zone. In the case of vorticity magnitude in corner recirculation zone, however, was weakened. In addition, pressure fluctuation in combustor was damped down and longitudinal acoustic mode was significantly dissipated

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Interior Crisis in a Chaotic Band (혼돈띠에서의 내부고비현상)

  • Kim, Chil-Min;Park, Jong-Dae;Jo, Chang-Ho
    • The Journal of Natural Sciences
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    • v.6 no.1
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    • pp.79-87
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    • 1993
  • In the map of period-doubling bifurcation, stable fixed points bifurcate to $2^n$ fixed points, and in the chaotic region, the chaotic bands merge to 1/$2^n$ bands. In a typical map, the chaotic bands expand to a broad chaotic band during the merging process, so called crisis. In this paper, interior crises appearing during the merging process will be discussed by using our map and will be analyzed the characteristics of the phenomenon by obtaining the Lyapunov Exponents.

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Three-dimensional Effects of an Axi-symmetric Pintle Nozzle (축대칭 핀틀노즐의 3차원 효과 분석)

  • Lee, Gang-Min;Sung, Hong-Gye
    • Journal of the Korean Society of Propulsion Engineers
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    • v.22 no.6
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    • pp.47-55
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    • 2018
  • In order to determine whether three-dimensional effects exist in a pintle nozzle of axisymmetric shape, a three-dimensional numerical analysis was performed. The compressibility correction was implemented with the k-${\omega}$ SST turbulence model to predict the complex flow separation transition in acceptable accuracy. Recirculation zones were observed at both the front end and rear faces of the pintle, and the flow through the pintle nozzle conveyed complex shock wave structures. Three-dimensional effects that resulted from the reasonable flow separation location were noted, and a trace of the transient pressure increase was observed, mismatched by a two-dimensional axi-symmetric analysis.

Multi-blockchain System based on Directed Acyclic Graph for Increasing Data Throughput (데이터 처리량 향상을 위한 유향 비순환 그래프 기반의 멀티블록체인 시스템)

  • CHEN, Hao-Tian;Kim, Tae Woo;Park, Jong Hyuk
    • Annual Conference of KIPS
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    • 2021.05a
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    • pp.25-28
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    • 2021
  • 블록체인은 탈집중화, 위변조 방지, 추적 가능, 노드 간 공동 유지 및 보수가 가능한 데이터베이스로서 서로 신뢰하지 않은 노드 간 통신 신뢰 문제를 해결할 수 있는 점 대 점 통신 네트워크를 실현할 수 있다. 최근 몇 년 동안, 블록체인 기술은 지속적으로 발전하여 데이터 보안 문제를 해결하기 위한 중요한 기술로 주목받고 있다. 블록체인의 응용은 최초의 디지털 화폐 영역에서 금융·정무·공업 제조 영역으로 확대되고 있다. 블록체인의 특성에 따라 블록체인의 성능은 분산형 데이터 통신에 비해 크게 떨어지고 처리량이 제한되는 문제점이 존재한다. 본 논문에서는 최근 연구되고 있는 블록체인의 보안 구조 및 성능 분석에 대해 조사하고, 기존에 연구되었던 기술과 비교하여 블록체인의 안전성을 유지하며 성능을 향상시키는 방법에 대해 고찰한다. 이후 유향 비순환 그래프 (DAG: Directed Acyclic Graph) 및 샤딩 (Sharding)을 이용하여 안전성과 성능을 강화시키는 방법에 대해 제안한다. 제안하는 시스템은 DAG를 사용하여 위변조 방지 및 처리 속도 향상의 이점을 가지고 있으며, 샤딩을 사용함으로써 데이터 처리량을 향상시킨다. 마지막으로 제안하는 시스템은 기존 블록체인과 비교하여 안정성과 데이터 처리량 측면에서 비교 분석을 진행한다.