• Title/Summary/Keyword: 가상압축성

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Evaluation test of applicability of Compressed Air Foam fire extinguishing system for train fire at rescue station in Subsea tunnel (해저터널 구난역 열차화재시 압축공기포(Compressed Air Foam) 소화설비의 적용성 평가 실험)

  • Park, Byoung-Jik;Shin, Hyun-Jun;Yoo, Yong-Ho;Park, Jin-Ouk;Kim, Hwi-Seong
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.18 no.5
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    • pp.413-418
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    • 2016
  • Recently, a mega project such as Korea-China or Korea-Japan undersea tunnel project has been emerged for detail discussion and the interest in undersea tunnel is on the rise. More severe damage by train fire is expected in undersea tunnel comparing to ground tunnel and thus the study on more efficient fire extinguishing system, besides existing disaster prevention design is underway. To that end, a full-scale fire tests using CAF fire extinguishing system which has been developed by modifying traditional foam fire extinguishing system for fire suppression at rescue station in timely manner were conducted over 7 times. The test was conducted after setting the rescue station in virtual tunnel with a car of KTX. As a result of using compressed air foam directly to the fire source, 30 liter of Heptane combustibles was extinguished within 1 minutes. Applicability of compressed air foam to train fire at rescue station in undersea tunnel was has been proven and further study is considered required while changing the nozzle angle and location so as to achieve quick and easy extinguishing goal, making use of the advantage of CAF, as well as to reduce the fire water and chemicals required.

IMPLEMENTATION OF IMMERSED BOUNDARY METHOD TO INCOMPRESSIBLE NAVIER-STOKES SOLVER USING SIMPLE ALGORITHM (SIMPLE Algorithm기반의 비압축성 Navier-Stokes Solver를 이용한 Immersed Boundary Method의 적용)

  • Kim, G.H.;Park, S.O.
    • Journal of computational fluids engineering
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    • v.17 no.1
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    • pp.44-53
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    • 2012
  • Immersed boundary method(IBM) is a numerical scheme proposed to simulate flow field around complex objectives using simple Cartesian grid system. In the previous studies, the IBM has mostly been implemented to fractional step method based Navier-Stokes solvers. In this study, we implement the IBM to an incompressible Navier-Stokes solver which uses SIMPLE algorithm. The weight coefficients of the bi-linear and quadratic interpolation equations were formulated by using only geometric information of boundary to reconstruct velocities near IB. Flow around 2D circular cylinder at Re=40 and 100 was solved by using these formulations. It was found that the pressure buildup was not observed even when the bi-linear interpolation was adopted. The use of quadratic interpolation made the predicted aerodynamic forces in good agreement with those of previous studies. For an analysis of moving boundary, we smulated an oscillating circular cylinder with Re=100 and KC(Keulegan-Carpenter) number of 5. The predicted flow fields were compared with experimental data and they also showed good agreements.

A Study for the Adaptation of Simulation of Uniaxial Compressive Strength Test for Concrete in 3-Dimensional Particle Bonded Model (3차원 입자 결합 모델에서 콘크리트의 일축압축실험 모사 적용성 연구)

  • Lee, Hee-Kwang;Jeon, Seok-Won
    • Journal of the Korea Concrete Institute
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    • v.20 no.2
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    • pp.147-156
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    • 2008
  • In an uniaxial compressive test of a concrete standard specimen (150$\times$300 mm) the crack initiation and extension with the stress increase are the major reason of the failure, which is similar to the breakage of the particle bonding in the simulation by using particle bonded model, especially particle flow code in 3 dimensions (PFC3D) developed by Itasca Consulting Group Inc. That is the main motive to study the possibility of an uniaxial compressive strength test simulation. It is important to investigate the relationship between the micro-parameters and the macro-properties because the 3-dimensional particle bonded model uses the spherical particles to analyze the physical phenomena. Contact bonded model used herein has eight micro-parameters and there are five macro-properties; Young's modulus, Poisson's ratio, uniaxial compressive strength and the crack initiation stress and the ratio concerning the crack propagation with the stress. To simulate the compressive test we made quantitative relationships between the micro-parameters and the macro-properties by using the fractional factorial design and various sensitivity analyses including regression analysis, which result in the good agreement with the previous studies. Also, the stress-stain curve and the crack distribution over the specimen given by PFC3D showed the mechanical behavior of the concrete standard specimen under the uniaxial compression. It is concluded that the particle bonded model can be a good tool for the analyzing the mechanical behavior of concrete under the uniaxial compressive load.

The Influence of the Application Methods of Direct Analysis Method for the Evaluation of Frame Stability (골조 안정성 평가를 위한 직접해석법의 적용 방법에 따른 영향)

  • Kim, Hee-Dong
    • Journal of Korean Society of Steel Construction
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    • v.22 no.4
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    • pp.293-303
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    • 2010
  • The purpose of this study was to evaluate the influence of the methods of application of the direct analysis method, using the load amplification factor suggested by the KBC 2009 design code, for the evaluation of frame stability. For this purpose, the direct analysis method was performed for three-story-one-bay and five-story-three-bay unbraced steel frames with various notional loads, bending stiffness reductions, and factor B2s. The results of the analyses were compared with the results of the second-order inelastic analysis to evaluate the influence of the applied methods. The scale of the frame, the axial load ratio, and the axial load distribution pattern were added to the main parameters to investigate the external effects. The research results showed that the influence of the methods of application of the direct analysis method is not significant in the case of the required axial strength and the application of the additional notional loads; and that the application of the factor B2 with the story stiffness concept to the direct analysis method is appropriate for the required flexural strength.

Effect of Field of View on Egocentric Distance Perception in Real and Virtual Environment (현실과 가상현실에서 시야각이 자기중심적 거리지각에 미치는 영향)

  • Jin, Seungjae;Kim, Shinwoo;Li, Hyung-Chul O.
    • Science of Emotion and Sensibility
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    • v.24 no.4
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    • pp.17-28
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    • 2021
  • The purpose of the research was to examine the effect of field of view on egocentric distance perception in the real and virtual environment. The replica that mimicked the real environment condition was used to create the virtual environment condition. We manipulated field of view levels equally in both viewing conditions using glasses that limit the field of view in real-world conditions and limiting the field of view in virtual-world conditions in a manner equivalent to real-world conditions via HMD. Eighteen participants observed the target with a limited field of view in a real and virtual environment without head movement. Then, we measured perceived distance using the timed imagined walking method, which measures the time taken by each participant to mentally walk to the target. The target was shown three times at three different distances from the participants: 3, 4, and 5 m. For the analysis, we converted time estimates into distance estimates. Consequently, the estimated distance in the virtual environment condition was less than the estimated distance in the real environment condition. And as the field of view shrank, the estimated distance also decreased. The estimated distance did not vary with field of view levels in real-world conditions. In the virtual environment, the estimated distance decreased as the field of view decreased, whereas in the real environment, the estimated distance increased. The implications of the results and some future research directions are discussed below.

A Study on the Efficient Modularization of Virtual World Creation in Unreal Engine (언리얼엔진에서의 가상세계 창작을 위한 효율적 모듈화 연구)

  • Min-Jun, Oh
    • Journal of Industrial Convergence
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    • v.20 no.11
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    • pp.19-25
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    • 2022
  • In the development of existing games, it is judged that virtual world production was done by arranging game elements one by one. What is noteworthy here is the question of whether quality virtual worlds were efficiently produced in preparation for investment. In this study, we propose a methodology that can build an efficient virtual world based on the concept of modularization in an unreal engine. First, precedents were analyzed and five reference elements for modularization were extracted. In addition, the concept of an instance production pipeline was proposed by dividing it into four stages, and the minimum-unit instance modules for urban virtual world production were compressed into four. Finally, an urban virtual world constructed based on the minimum unit module and reference elements was implemented and presented. In conclusion, research on the production method centered on this efficiency is thought to be able to focus the time that designers or artists had to spend on production only on ideas and creativity. The limitations of the research are that the basic minimum module is limited to the city, and the derived reference elements and production pipelines have not been verified when implementing them with an unreal engine. Therefore, it is expected that various virtual world creation plans will be derived through more advanced modular research.

Implementation of Real-time Data Stream Processing for Predictive Maintenance of Offshore Plants (해양플랜트의 예지보전을 위한 실시간 데이터 스트림 처리 구현)

  • Kim, Sung-Soo;Won, Jongho
    • Journal of KIISE
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    • v.42 no.7
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    • pp.840-845
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    • 2015
  • In recent years, Big Data has been a topic of great interest for the production and operation work of offshore plants as well as for enterprise resource planning. The ability to predict future equipment performance based on historical results can be useful to shuttling assets to more productive areas. Specifically, a centrifugal compressor is one of the major piece of equipment in offshore plants. This machinery is very dangerous because it can explode due to failure, so it is necessary to monitor its performance in real time. In this paper, we present stream data processing architecture that can be used to compute the performance of the centrifugal compressor. Our system consists of two major components: a virtual tag stream generator and a real-time data stream manager. In order to provide scalability for our system, we exploit a parallel programming approach to use multi-core CPUs to process the massive amount of stream data. In addition, we provide experimental evidence that demonstrates improvements in the stream data processing for the centrifugal compressor.

Design and Implementation of the Execution File Format Translator (실행 파일 포맷 변환기의 설계 및 구현)

  • Kim Seong-Jin;Ko Kwang-Man
    • Proceedings of the Korea Information Processing Society Conference
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    • 2004.11a
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    • pp.685-688
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    • 2004
  • 자바 클래스 파일은 플랫폼 독립성을 보장하면서 다양한 애플리케이션의 실행 파일 포맷으로 사용되고 있으며 실행 효율성을 높이기 위해 파일 형식의 변환 연구, 압축 기법 연구 등이 진행되고 있다. 본 연구에서는 임베디드 시스템에 적합한 가상기계(EVM)을 개발하기 위해 기존의 자바 클래스 파일형식을 간결한 형태로 재구성한 실행 파일 포맷($^{\ast}.evm$)에 대한 실행 환경 모델을 구축하기 위해 본 논문에서 자바 클래스 파일을 $^{\ast}.evm$ 형식으로 변환하는 변환기를 설계하고 구현하였다. 자바 클래스 파일로부터 변환된 $^{\ast}.evm$ 형식에 대한 검증은 현재 구현중인 로더/링커 및 실행 시간 엔진 등을 통한 실험 결과의 정확성을 통해 증명하였다.

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The Design and Implementation of the Reliable Network RAM using Compression on Linux (리눅스에서 압축을 이용한 안정적인 네트웍 램의 설계 및 구현)

  • 황인철;정한조;맹승렬;조정완
    • Journal of KIISE:Computer Systems and Theory
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    • v.30 no.5_6
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    • pp.232-238
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    • 2003
  • Traditional operating systems use a virtual memory to provide users with a bigger memory than a physical memory. The virtual memory augments the insufficient physical memory by the swap device. Since disks are usually used as the swap device, the cost of a page fault is relatively high compared to the access cost of the physical memory. Recently, numerous papers have investigated the Network RAM in order to exploit the idle memory in the network instead of disks. Since today's distributed systems are interconnected with high-performance networks, the network latency is far smaller than the disk access latency In this paper we design and implement the Network RAM using block device driver on Linux. This is the first implementation of the Network RAM on Linux. We propose the new reliability method to recover the page when the other workstation's memory is damaged. The system using the Network RAM as the swap device reduces the execution time by 40.3% than the system using the disk as the swap device. The performance results suggest that the new reliability method that use the processor more efficiently has the similar execution time with others, but uses smaller server memory and generates less message traffic than others.

A Robustness of Hierarchic Element Formulated by Integrals of Legendre Polynomial (적분형 르장드르 함수에 의한 계층요소(階層要素)의 통용성(通用性))

  • Woo, Kwang Sung
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.12 no.1
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    • pp.43-50
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    • 1992
  • The purpose of this study is to ascertain the robustness of p-version model with hierarchic intergrals of Legendre shape functions in various applications including plane stress/strain, axisymmetric and shell problems. The most important symptoms of accuracy failure in modern finite elements are spurious mechanisms and a phenomenon known as locking which are exhibited for incompressible materials and irregular shapes which contain aspect ratios(R/t, a/b), tapered ratio(d/b), and skewness. The condition numbers and energy norms are used to estimate numerical errors, convergence characteristics and algorithmic efficiencies for verifying the aforementioned symptoms of accuracy failure. Numerical results from p-version models are compared with those from NASTRAN, SAP90, and Cheung's hybrid elements.

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