• Title, Summary, Keyword: Suppression

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A Study on the Fire Suppression Characteristics of a Flame Arrester with Water Mist System (미분무 시스템이 장착된 화염방지장치의 화재 진화 특성에 관한 연구)

  • Kim, Hae-Ji;Lee, Kyung-Ro
    • Journal of the Korean Society of Manufacturing Process Engineers
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    • v.15 no.5
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    • pp.117-124
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    • 2016
  • In this paper, we developed a breather valve with a water mist system for use near an oil storage tank. Our process applied a water mist system to the flame arrester to evaluate the fire suppression characteristics. For the fire suppression evaluation of the water mist system, we evaluated the angle of the nozzle, fire suppression, spray particle size, flashback, fire suppression time, and fire suppression test of antifreeze. Through the fire suppression test, the best fire suppression nozzle used an angle of $140^{\circ}$, and the flashback phenomenon of flame arrester did not occur. The fire suppression time of water mist system time was within three seconds, and the antifreeze was no problem with the fire suppression.

A Study on the Fire Suppression Characteristics Using a Water Mist (물분무에 의한 화재제어 특성에 관한 연구)

  • 김성찬;유홍선
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.15 no.4
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    • pp.261-267
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    • 2003
  • The present study investigates the fire suppression characteristics using a water mist fire suppression system. Numerical simulations of fire suppression with water mist are performed with considering the interaction of fire plume and water droplet, droplet evaporation, and combustion of pool fire. The predicted temperature fields of smoke layer are compared with that of measured data. Numerical results agree with the experimental results within 5$^{\circ}C$ in the case without water mist In the case of fire suppression with water mist, numerical results dose not predict well lot temperature field in the gradual cooling region after water mist injection. But the predicted results of initial fire suppression are in good agreement with that of measured data. The reason of the discrepancy between predicted and measured data is due to the variation of turning rate during the injection of water mist. The effect of burning rate on the fire suppression is left as future study.

Image Analysis Using Grid Suppression Software to Remove Moire Artifact from Micro Lesions of Sprague Dawley Rat (Sprague Dawley Rat의 미세병변에서 Moire Artifact를 제거하기 위한 Grid suppression software 사용 후 영상분석)

  • Lee, Sang-Ho
    • Journal of radiological science and technology
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    • v.40 no.4
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    • pp.575-580
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    • 2017
  • Because moire artifacts overlap with fine lesions and frequency bands, image processing software that removes moire artifacts can lead to loss of micro lesions. In this study, microscopic lesions such as microcalcification and microfracture were randomly formed on SD (Sprague Dawley) rats and image and optimized grid images were compared and analyzed using reference image and grid suppression software. The images were read by two consecutive radiologists using a McNemar's test. Among the 73 microcalcifications, in the 13 cases after grid suppression, the image of the optimized grid shows the loss of image in 3 cases, and the image after grid suppression shows statistically significant image loss (p=0.021). In all 53 fracture lines, there were 19 cases of image loss after the grid suppression, and only one case of the optimized grid showed no image loss. Therefore, the use of grid suppression software to remove moire artifacts should be carefully considered in the diagnosis of micro lesions.

Suppression for Logistic Regression Model (로지스틱 회귀모형에서의 SUPPRESSION)

  • Hong C. S.;Kim H. I.;Ham J. H.
    • The Korean Journal of Applied Statistics
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    • v.18 no.3
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    • pp.701-712
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    • 2005
  • The suppression for logistic regression models has been debated no longer than that for linear regression models since, among many other reasons, sum of squares for regression (SSR) or coefficient of determination ($R^2$) could be defined into various ways. Based on four kinds of $R^2$'s: two kinds are most preferred, and the other two are proposed by Liao & McGee (2003), four kinds of SSR's are derived so that the suppression for logistic models is explained. Many data fitted to logistic models are generated by Monte Carlo method. We explore when suppression happens, and compare with that for linear regression models.

The Effects of Water Mist on the Compartment Fire

  • Ryou, Hong-Sun;Kim, Sung-Chan
    • International Journal of Air-Conditioning and Refrigeration
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    • v.12 no.1
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    • pp.30-36
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    • 2004
  • The present study investigates the fire suppression characteristics using a water mist fire suppression system. Numerical simulations of fire suppression with water mist are performed with considering the interaction of fire plume and water spray. The predicted temperature fields of smoke layer are compared with those of measured data. Numerical results agree with the experimental results within $10^{\circ}C$ in the case without water mist. In the case of fire suppression with water mist, numerical results do not predict well for temperature field in the gradual cooling region after water mist injection. But the predicted results of initial fire suppression are in good agreement with those of measured data. The reason for the discrepancy between predicted and measured data is due to the poor combustion modeling during the injection of water mist. More elaborate models for numerical simulation are required for better predictions of the fire suppression characteristics using water mist.

Application of CFD Method to Performance Prediction of Fire-Suppression System for Electric Power Utilities (발전설비용 소화시스템의 성능 예측을 위한 CFD기법 적용 연구)

  • Chung, H.T.;Bae, K.Y.;Kim, C.H.;Jeong, I.S.;Bae, J.S.;Han, Y.S.;Kim, J.J.
    • 한국전산유체공학회:학술대회논문집
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    • pp.296-299
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    • 2008
  • In the present research, the exclusive analysis system based on the CFD method were suggested to predict the fire-suppression performance of water mist fire-suppression equipments for design applications. The computing scope is ranged from starting pump to fire-suppression equipments, composed of three parts that calculation of flow rate and pressure distribution at each nozzle, examining of spray performance and predicting of fire-suppression performance in the fire space. Application were done to the fire-suppression system for electric power generation plants. The results were analyzed by comparison between numerical results and initial design conditions in terms of thermal and fluid mechanics.

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CO2 Suppression Characteristics of the Nitrogen-diluted Methane Counterflow Non-premixed Flame (질소로 희석된 대향류 메탄 비예혼합화염에서 CO2에 의한 소화특성)

  • Lee, Ho-Hyun;Oh, Chang Bo;Hwang, Cheol Hong
    • Journal of the Korean Society of Safety
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    • v.28 no.2
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    • pp.42-48
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    • 2013
  • The $CO_2$ suppression characteristics and flame structure of nitrogen-diluted methane counterflow non-premixed flame were studied experimentally and numerically. To mimic a situation where combustion product gases are entrained into a compartment fire, fuel stream was diluted with $N_2$. A gas-phase suppression agent, $CO_2$, was diluted in the air-stream to investigate the suppression characteristics by the agent. For numerical simulation, an one-dimensional OPPDIF code was used for comparison with experimental results. An optically-thin radiation model(OTM) was adopted to consider radiation effects on the suppression characteristics. It was confirmed experimentally and numerically that suppression limit decreased with increasing nitrogen mole fraction in the fuel stream. A turning point was found only when a radiation heat loss was considered and the extinguishing concentration for turning point was differently predicted compared to the experiment result. Critical extinguishing concentration when neglecting radiation heat loss was also differently predicted compared with the experimental result.

A Comparative Quantitative Analysis of IDEAL (Iterative Decomposition of Water and Fat with Echo Asymmetry and Least Squares Estimation) and CHESS (Chemical Shift Selection Suppression) Technique in 3.0T Musculoskeletal MRI

  • Kim, Myoung-Hoon;Cho, Jae-Hwan;Shin, Seong-Gyu;Dong, Kyung-Rae;Chung, Woon-Kwan;Park, Tae-Hyun;Ahn, Jae-Ouk;Park, Cheol-Soo;Jang, Hyon-Chol;Kim, Yoon-Shin
    • Journal of Magnetics
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    • v.17 no.2
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    • pp.145-152
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    • 2012
  • Patients who underwent hip arthroplasty using the conventional fat suppression technique (CHESS) and a new technique (IDEAL) were compared quantitatively to assess the effectiveness and usefulness of the IDEAL technique. In 20 patients who underwent hip arthroplasty from March 2009 to December 2010, fat suppression T2 and T1 weighted images were obtained on a 3.0T MR scanner using the CHESS and IDEAL techniques. The level of distortion in the area of interest, the level of the development of susceptibility artifacts, and homogeneous fat suppression were analyzed from the acquired images. Quantitative analysis revealed the IDEAL technique to produce a lower level of image distortion caused by the development of susceptibility artifacts due to metal on the acquired images compared to the CHESS technique. Qualitative analysis of the anterior area revealed the IDEAL technique to generate fewer susceptibility artifacts than the CHESS technique but with homogeneous fat suppression. In the middle area, the IDEAL technique generated fewer susceptibility artifacts than the CHESS technique but with homogeneous fat suppression. In the posterior area, the IDEAL technique generated fewer susceptibility artifacts than the CHESS technique. Fat suppression was not statistically different, and the two techniques achieved homogeneous fat suppression. In conclusion, the IDEAL technique generated fewer susceptibility artifacts caused by metals and less image distortion than the CHESS technique. In addition, homogeneous fat suppression was feasible. In conclusion, the IDEAL technique generates high quality images, and can provide good information for diagnosis.

Numerical investigation on VIV suppression of marine riser with triangle groove strips attached on its surface

  • Wang, Wei;Song, Baowei;Mao, Zhaoyong;Tian, Wenlong;Zhang, Tingying
    • International Journal of Naval Architecture and Ocean Engineering
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    • v.11 no.2
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    • pp.875-882
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    • 2019
  • The effects of Triangle Groove Strips (TGS) on Vortex-induced Vibration (VIV) suppression of marine riser are numerically investigated using Computational Fluid Dynamics (CFD) method. The range of Reynolds number in simulations is 4.0 × 104 < Re < 1.2 × 105. The two-dimensional unsteady Reynolds-Averaged Navier-Stokes (RANS) equations and Shear Stress Transport (SST) k-ω turbulence model are used to calculate the flow around marine riser. The Newmark-β method is employed for evaluating the structure dynamics of marine riser. The effect of the height ratio (ε) of TGS on VIV suppression is evaluated. The amplitude responses, frequency responses, vortex patterns and the flow around the structures are discussed in detail. With the increase of the height ratio of TGS, the suppression effect of TGS on VIV suppression is improved firstly and then weakened. When ε=0.04, the suppression effect of TGS is the best. Compared with the VIV responses of smooth marine riser, the amplitude ratio is reduced by 38.9%, the peak of the lift coefficient is reduced by 69% and the peak of the drag coefficient is reduced by 40% when Re=6.0 × 104. With the increase of Reynolds number, the suppression effect of TGS on VIV suppression is improved firstly and then weakened. When the Reynolds number is 7.0 × 104, the amplitude ratio can be reduced by 40.1%. As to the large-amplitude vibration cases, the TGS show nice suppression effect on VIV.

Suppression of Turbulence in a Circular Jet Using a Single Frequency Excitation (단일 주파수 가진을 이용한 원형 제트의 난류 억제)

  • Park Jeongyoung;Choi Haecheon
    • Proceedings of the KSME Conference
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    • pp.241-244
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    • 2002
  • Large eddy simulation of a circular jet at the Reynolds number of 10000 is performed to investigate turbulence suppression effect with single frequency excitation at the non-dimensional frequency of 0.017. Instantaneous flow fields show that, with excitation, naturally occurring energetic vortices are suppressed through earlier saturation and breakdown of the shear layer vortices into fine grained turbulence. Due to the excitation, the Reynolds stresses are larger for the excited case near the jet and turbulence suppression begins afterward. The Reynolds normal stresses show largest suppression in the shear layer near the jet and in the centerline further downstream, while the Reynolds shear stress shows largest suppression in the shear layer at all the downstream locations.

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