• Title/Summary/Keyword: Lu 방법

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Evaluation of different methods to remove pore water in an early age cement paste for the degree of hydration measurement and pore structure analysis. (공극수 추출방법에 따른 시멘트 페이스트의 수화도와 공극 특성 분석)

  • Ahn, Yu-Ri;Lu, Yang;Kim, Baek-Joong;Yi, Chong-Ku;Kang, Kyung-In
    • Proceedings of the Korean Institute of Building Construction Conference
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    • 2012.05a
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    • pp.245-246
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    • 2012
  • The analysis of microstructure is essential to understand the material behavior such as shrinkage, strength, and permeability. In this study, three different easy-to-apply specimen preparation methods for the mercury intrusion analysis were chosen, and their effectiveness in removing pore water and thus impeding further hydration was evaluated. As a result, it was found that the direct freeze-drying was the most effective among the three methods.

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Numerical Analysis Methods for Eddy Current Testing for Heat Exchanger Tube with Axi-symmetric Defects (열교환기 전열관의 결함에 대한 와전류 탐상 수치해석방법)

  • Kim, Chang-Wook;Seo, Jang-Won;Kim, Shin;Lee, Hyang-Beom
    • Proceedings of the KIEE Conference
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    • 2000.07b
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    • pp.831-833
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    • 2000
  • In this paper, a numerical analysis algorithm of eddy current testing(ECT) for heat exchanger tube with axi-symmetric defects using finite element method(FEM) is presented. In the ECT FEM analysis, we used trianglular and rectangular elements for exact signal of ECT for variable shape of defects. This paper presents a systematic and efficient numerical analysis algorithm for ECT. We employ the LU decomposition and Cholesky method for solving the system matrix. This numerical analysis algorithm is effectively applied to heat exchanger tube with defects.

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Evaluation Method of Segregation Resistance of Normal Strength Concrete Depending on Various Water Content (단위수량 변화에 따른 보통콘크리트의 재료분리 저항성 평가 방법 제안)

  • ZHAO, YANG;Lu, LiangLiang;Park, Yong-Jun;Jo, Man-Ki;Han, In-Deok;Han, Min-Cheol
    • Proceedings of the Korean Institute of Building Construction Conference
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    • 2014.11a
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    • pp.38-39
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    • 2014
  • In this research, the evaluation method of segregation resistance is suggested using the ratio of maximum and minimum values of concrete slump flow. As a result, in the case of normal concrete range from 80 to 210 mm of slump, it is considered that managing the EIS-N value to less than 1.10 is the most favorable for segregation determination.

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A Numerical Study of Diffusion Flames in Supersonic Flow (초음속 유동장 내의 확산 화염에 관한 수치 연구)

  • 김지호;윤영빈;정인석
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 1997.11a
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    • pp.17-17
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    • 1997
  • 극초음속 여객기와 군사용 항공기에 대한 수요가 증가함에 따라서 새로운 개념의 다양한 추진기관이 연구가 진행되고 개발되어 왔다. 초음속 항공기의 속도 영역은 마하 10-20 정도가 되는데 이 속도 한계를 극복하기 위하여 초음속 연소 램제트 엔진(SCRamjet; Supersonic Combustion Ramjet)이 제안되었다. 스크램 제트를 개발하기 위해서는 연료와 산화제의 혼합 효율 문제, 화염의 안정화 문제, 벽면의 냉각에 관한 문제 등 몇 가지 기본적인 문제들을 해결해야 한다. Univ of Michigan에서 실험한 연소기를 모델로 본 연구에서는 연료와 공기의 혼합에 관한 수치 연구를 수행하였다. 다원 혼합기체에 관한 축대칭 Navier-Stokes 방정식을 지배 방정식을 이용하였고 비평형 화학반응식을 고려하였다. 공간 차분에는 유한 체적법을 이용하였다. 대류 플럭스 항은 Roe의 Upwind FDS 기법을 사용하여 차분하였고 점성항에는 중심 차분법을 이용하였다. 시간 적분법으로는 근사 자코비안과 LU분할 기법을 이용한 완전 내재적 방법이 쓰였다. 난류 모델로는 Mentor에 의해 제안된 2 방정식 k-$\varepsilon$/k-$\omega$ 혼합모델을 사용하였다. 유동장이 실험에서의 찍은 사진과 유사한 모습의 충격파 간섭을 수치 모사하였고 수소가 확산되는 모습과 함께 노즐 lip 주위의 재순환 영역에 대해서 살펴볼 수 있었다.

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Experimental Comparisons of Simplex Method Program's Speed with Various Memory Referencing Techniques and Data Structures (여러 가지 컴퓨터 메모리 참조 방법과 자료구조에 대한 단체법 프로그램 수행 속도의 비교)

  • Park, Chan-Kyoo;Lim, Sung-Mook;Kim, Woo-Jae;Park, Soon-Dal
    • IE interfaces
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    • v.11 no.2
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    • pp.149-157
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    • 1998
  • In this paper, various techniques considering the characteristics of computer memory management are suggested, which can be used in the implementation of simplex method. First, reduction technique of indirect addressing, redundant references of memory, and scatter/gather technique are implemented, and the effectiveness of the techniques is shown. Loop-unrolling technique, which exploits the arithmetic operation mechanism of computer, is also implemented. Second, a subroutine frequently called is written in low-level language, and the effectiveness is proved by experimental results. Third, row-column linked list and Gustavson's data structure are compared as the data structure for the large sparse matrix in LU form. Last, buffering technique and memory-mapped file which can be used in reading large data file are implemented and the effectiveness is shown.

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Numerical Simulation of Axi-Symmetric Supersonic Intake Flow Operating on Design & Off-Design Conditions (축대칭 초음속 공기흡입구의 설계점/비설계점 유동 연구)

  • 김성돈;정인석;최정열
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2000.11a
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    • pp.20-20
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    • 2000
  • 2개의 경사 충격파와 하나의 수직 충격파로 초음속 유동을 압축하는 초음속 공기 흡입구의 수치적 연구를 수행하였다. 지배방정식으로는 Navier-Stokes방정식을 사용하였고 난류모델로는 SST 모델을 사용하였다. 지배방정식의 점성항 계산에는 중심차분법을 사용하였고 대류항 계산에는 풍상차분법인 Roe의 FDS기법을 MUSCL기법과 결합하여 이용하였다. 유한 체적법을 이용하여 차분된 방정식은 LU분할 기법을 이용한 완전 내재적 방법으로 2차 정확도 시간 적분으로 비정상 과정의 연구를 수행하였다. 흡입구 배압을 정해주어야 하는 어려움을 해결하기 위해 흡입구 후면에 노즐을 달고 노즐의 면적을 조절하여 배압이 형성되도록 하였다.(중략)

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Comparison of Longitudinal Liquid Permeability of Pinus koraiensis Sapwood Treated by Steaming and Various Drying Methods (증기 및 여러 가지 건조방법으로 처리된 잣나무 변재의 섬유방향 액체투과율 비교)

  • Kang, Ho-Yang;Lu, Jianxiong
    • Journal of the Korean Wood Science and Technology
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    • v.33 no.6 s.134
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    • pp.17-24
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    • 2005
  • Korean pine (Pinus koraiensis Sieb.et Zucc.) boards of 30 mm thickness were treated by steaming and four different drying methods. Small specimens were taken from the sapwoods of the treated boards and their longitudinal liquid permeability was measured according to Darcy's law. The specimens were also extracted with alcohol and aceton solutions to examine the mechanism of liquid flow in wood. It was observed that specific permeability drastically decreases with measurement time, resulting in violation of Darcy's law. It may be due to that air bubbles formed under vacuum block flow paths in resin canals. The average specific permeabilities of non-extracted and extracted specimens are different from one treatment to another. It is supposed that the properties of residual resin in resin canals change depending on the conditions of treatments. Anatomical examination was conducted with a scanning electron microscope.

Design of a Six-Axis Force/Moment Sensor using Analytical Method for Humanoid Robot Foot Module (인간형 로봇의 발 모듈 개발을 위한 분석적 방법의 6 축 힘 / 모멘트 센서 설계)

  • Yuan, Chao;Lim, Dong Hwan;Luo, Lu Ping;Han, Chang Soo
    • Journal of the Korean Society for Precision Engineering
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    • v.32 no.4
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    • pp.359-367
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    • 2015
  • The forces and moments exerted on humanoid robot foot are important information for controlling or monitoring the robot. Multi-axis force/moment sensor can be installed under humanoid robot foot to measure forces and moments. The sensor should have large stiffness to support the robot weight and small size not to disturb the motion of the robot. In this paper, we designed a 6-aixs force/moment sensor which has good accuracy, large measuring range, and new compact structure. In addition, the proposed sensor is evaluated using analytical method and FEM(Finite Elements Method) method. Finally, it turned out that it has good performance.

Analysis of Radiation Dose on Single Cells Using Therapeutic Radioisotopes Using the Monte Carlo Method (몬테카를로 방법을 이용한 치료용 방사성동위원소 사용 시 단일 세포에 대한 선량 분석)

  • Kim, Jung-Hoon;Kim, Yu-Soo
    • Journal of radiological science and technology
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    • v.45 no.5
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    • pp.433-438
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    • 2022
  • Targeted radionuclides treatment (TRT) requires the establishment of treatment plans that consider various factors, such as the type of radionuclides, target organs, and administration methods. For this reason, in this study, the absorption dose of a single cell was analyzed according to the type of radioisotope used to treat target radionuclides. In this study, a simulation was performed on beta rays used in the treatment of target radionuclides at the cell level using MCNPX (ver. 2.5.0). First, according to the calculation formula, the beam path according to the type of radioisotope for treatment was calculated. Second, the amount of self-radiation by beta rays emitted from cell diameters of 5 ㎛ and 10 ㎛ cell nuclei was evaluated. As a result, it showed a high range proportional to the maximum energy of the beta-ray, and the highest self-dose distribution from 177 Lu radiation sources among therapeutic radioisotopes. This was analyzed as a result that is inversely proportional to the maximum energy of the beta-ray, and it suggests that the selection of a nuclide considering the range of the beta-ray is necessary in the treatment of target radionuclides in the future.

A Study on the Creation of Social Communities in Urban Reconstruction (도심 재구성에서의 사회 커뮤니티조성에 관한 검토)

  • Lu Zhiyan
    • The Journal of the Convergence on Culture Technology
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    • v.9 no.5
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    • pp.815-819
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    • 2023
  • Currently, China's urban space is gradually changing from gradual development to inventory transformation. The planning and development goals of urban communities have also shifted from material space construction to the direction of sustainable development of humanities and society. Currently, community planning and construction at a single latitude, which focuses on residential life, overlooks the multidimensional elements of community life production, causing many problems such as cold relationships between communities and difficulties in forming relationships between humans and the environment. Therefore, this article re-recognizes the sociality of the community in the continuous unification of the community in time and space, clarifies the central and private aspects of the community, and re-explores the dynamic creation and methods of the community as the starting point of daily life.