• Title/Summary/Keyword: Pressure mitigation

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Dynamic Response of Hydraulic Transmission Lines with an Accumulator (축압기를 갖는 유압관로의 동특성에 관한 연구)

  • Lee, Ill-Yeong;Hong, Bong-Ki
    • Journal of the Korean Society of Fisheries and Ocean Technology
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    • v.17 no.1
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    • pp.29-34
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    • 1981
  • More recently, unsteady flow in small-diameter pipes plays a major role in liquid propellantrocket systems, hydraulic and pneumatic control system, and elsewhere. And it has shown that line dynamics can have a marked effect on the hydraulic system characteristics. In this paper, transfer function of hydraulic lines with an accumulator and an outlet orifice is' developed and compared with experimental data from frequency response tests at various airvolume(V.) and the location of accumulator(ld1t), so that their performance may be correctly and easily predicted and the design of the systems incorporating them improved. The obtained results are as follows: 1. The dynamic response of hydraulic lines may be analyzed more accurately by use of the viscous term(22) in unsteady laminar flow. 2. There was good agreement between the theoretical and experimental results of this investigation, and hydraulic systems with liines included an accumulator can be analyzed more accurately by use of the pressure transfer function given by eq. (16). 3. For the mitigation of surge in hydraulic lines, it is more effective that the location ofaccumulator is close to the pipe outlet side. 4. According to the gas volume of accumulator is increased(the sealing pressure is close tomean line pressure), the damping effect of pressure wave is improved.

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An Estimation of Smear Zone Induced by Vertical Drain Construction Based on the Laboratory Model test (실내모형실험을 통한 연직배수재 타설에 의한 스미어존의 평가)

  • Kim, Hong-Taek;Han, Yeon-Jin;Kim, Seong-Wook;Hwang, Jeong-Soon
    • 한국방재학회:학술대회논문집
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    • 2007.02a
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    • pp.279-282
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    • 2007
  • When ground disturbance takes place due to vertical drain construction through mandrel penetration, that affects excess pore water pressure dissipation time because of soft clay coefficient of permeability decreasing. Eventually, consolidation time is influenced. In this research, we measure process of excess pore water pressure dissipation before and after each other different shape's mandrel penetration through model test, and calculates range of smear zone, coefficient of permeability and horizontal coefficient of consolidation after model test. Using of test result, we grasp a degree of drainage ability drop resulting from vertical drain construction.

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Characteristics of the Smear Zone by Vertical Drain on Silt (연직배수재에 의한 실트질 지반에서의 스미어 존 특성 평가)

  • Kang, Yun;Kim, Seong-Wook;Yoo, Chan-Ho;Kim, Hong-Taek
    • 한국방재학회:학술대회논문집
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    • 2007.02a
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    • pp.542-545
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    • 2007
  • The vertical drain method generate the disturbed zone, because the drainage should be penetrated into the in-situ ground. The characteristics of the smear zone generated cause the problems that the coefficient of permeability decreases and the consolidation time anticipated in the design is not properly shortened. In this study, in order to understand such influence, the laboratory test were carried out so as to reasonably determine the coefficient of consolidation in silt. For that procedure, mandrel of a diversity were penetrated into the soil tube with silt, and then the variation of pore water pressure was measured with the pore pressure meter, Then, the range of smear effect on silt was estimated with monitoring data through the laboratory test, and also analyzed with inputting the coefficient of consolidation into the theoretical equation.

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Hexagonal reciprocating pump: advantages and weaknesses

  • Stanko, Milan;Golan, Michael
    • International Journal of Fluid Machinery and Systems
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    • v.6 no.3
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    • pp.121-136
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    • 2013
  • This paper reports the 1-D fluid transient simulation results of the discharge flow conditions in a 6-cylinder reciprocating slurry pump. Two discharge manifold configurations are studied comparatively; a case with a hexagon shaped discharge manifold where each cylinder discharges at a single vertex, and a case where all the cylinders discharges are lumped together into a tank shaped manifold. In addition, the study examines the effect of two pulsation mitigation measures in the case of hexagonal manifold; a single inline orifice in one of the hexagon sides and a volumetric dampener at the manifold outlet. The study establishes the pressure and flow fluctuation characteristics of each configuration and decouples the pulsation characteristics of the pump and the discharge manifold.

Study and Analysis of the Damage by the Storm Surge (폭풍해일에 의한 피해사례 연구 및 분석)

  • Hong, Weon-Sig;Park, Seong-Soo;Cho, Yong-Sik
    • 한국방재학회:학술대회논문집
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    • 2008.02a
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    • pp.447-450
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    • 2008
  • A storm surge is gradually increased in the Korean peninsula. Furthermore, this phenomenon is confined not only the Korean peninsula but also the whole world. A storm surge induced by storm, typhoon, or cyclone is a phenomenon that the water surface elevation is raising by the barometric pressure difference and this water level rising threatens the coastal facilities, settlement, or lives. Most of coastal region in our country are unsafe from this disaster. Even though we are not able to prevent the generation of this phenomenon, we can reduce the damages by investigating the kind of storm surge disaster. Once we finish this investigation, we can reduce the damages by offering the information for risk prior to an invasion of storm surge. This study, we analyzed the previously occurred storm surge damages, and this data can be utilized as a guide for those who live near the coastal region providing the information about the predicting scale of the storm surge

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Numerical Simulation of Wave Deformation due to a Submerged Structure with a Second-order VOF Method (2차 정확도 VOF기법을 활용한 수중구조물에 의한 파랑변화 예측)

  • Ha, Tae-Min;Cho, Yong-Sik
    • Journal of the Korean Society of Hazard Mitigation
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    • v.10 no.1
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    • pp.111-117
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    • 2010
  • A three-dimensional numerical model is employed to investigate wave deformation due to a submerged structure. The three-dimensional numerical model solves the spatially averaged Navier-Stokes equations for two-phase flows. The LES(large-eddy-simulation) approach is adopted to model the turbulence effect by using the Smagorinsky SGS(sub-grid scale) closure model. The two-step projection method is employed in the numerical solutions, aided by the Bi-CGSTAB technique to solve the pressure Poisson equation for the filtered pressure field. The second-order accurate VOF(volume-of-fluid) method is used to track the distorted and broken free surface. A simple linear wave is generated on a constant depth and compared with analytical solutions. The model is then applied to study wave deformation due to a submerged structure and the predicted results are compared with available laboratory measurements.

A Case Study of PC-Culvert Construction with Foundation Plate (기초판 보강형 PC 암거의 시공사례 연구)

  • You, Jun;Choi, Chang-Ho
    • Journal of the Korean Geosynthetics Society
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    • v.10 no.2
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    • pp.13-19
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    • 2011
  • Precast culvert system is generally constructed with a series of process such as excavation, ground mitigation, placement of culverts, anti-leakage packing between adjacent culverts, post-tensioning for PS strands and backfilling. In this process inappropriate ground mitigation often causes differential settlement and, correspondingly, makes water-leakage to be occurred between adjacent boxes. This study was performed to understand the behavioral characteristics of recently proposed precast foundation plate to support precast culvert system through on-site pilot construction. The gap between two adjacent culverts, increment of earth pressure at the bottom of culvert, vertical settlement of top of the culverts were monitored using various sensors. The monitoring results showed that the proposed foundation plate provides better culvert system in the points of less gap development, earth pressure and settlement at the adjacent of two culverts.

Development of New Code Case "Mitigation of PWSCC and CISCC in ASME Code Section III Components by the Advanced Surface Stress Improvement Technology (일차수응력부식균열(PWSCC) 및 염화이온부식균열(CISCC) 저감용 표면개질기술 적용을 위한 코드케이스 개발)

  • Cho, Sungwoo;Pyun, Youngsik;Mohr, Nick;Tatman, Jon;Broussard, John;Collin, Jean;Yi, Wongeun;Oh, Eunjong;Jang, Donghyun;Koo, Gyeong Hoi;Hwang, Seong Sik;Choi, Sun Woong;Hong, Hyun UK
    • Transactions of the Korean Society of Pressure Vessels and Piping
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    • v.15 no.1
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    • pp.28-32
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    • 2019
  • In nuclear power plant operation and spent fuel canisters, it is necessary to provide a sound technical basis for the safety and security of long-term operation and storage respectively. Recently, the peening technology is being discussed and the technology will be adopted to ASME Section III, Division 1, Subsection NX (2019 Edition). The peening is prohibited in current edition, but it will be approved in 2019 Edition and adopted. However, Surface stress improvement techniques such as the peening is used to mitigate SCC susceptible in operating nuclear plants. Although the peening will be approved to ASME CODE, there are no performance criteria listed in the 2019 edition. The Korean International Working Group (KIWG) formed a new Task Group named "Advanced Surface Stress Improved Technology". The task group will develop a CODE CASE to address PWSCC(Primary Water Stress Corrosion Cracking) and CISCC(Chloride Induced Stress Corrosion Cracking) for new ASME Section III components. TG-ASSIT was started to make peening performance criteria for ASME Section III (new fabrication) applications. The objective of TG-ASSIT is to gain consensus among the relevant Code groups that requirements/mitigation have been met.

THE POTENTIAL OF SATELLITE REMOTE SENSING ON REDUCTION OF TSUNAMI DISASTER

  • Siripong, Absornsuda
    • Proceedings of the KSRS Conference
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    • v.1
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    • pp.52-55
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    • 2006
  • It's used to be said that tsunami is a rare event. The recurrence time of tsunami in Sumatra area is approximately 230 years as CalTech Research Group‘s study from paleocoral. However, the tsunami occurred in Indian Ocean on 26 December 2004, 28 March 2005 and 17 July 2006, because the earthquakes still release the energy. To cope with the tsunami disaster, we have to put the much effort on better disaster preparedness. The Tsunami Reduction Of Impacts through three Key Actions (TROIKA) was suggested by Eddie N. Bernard, the director of NOAA/PMEL (Pacific Marine Environmental Laboratory). They are Hazard Assessment, Mitigation and Warning Guidance. The satellite remote sensing has potential on these actions. The medium and high resolution satellite data were used to assess the degree of damage at the six-damaged provinces on the Andaman seacoast of Thailand. Fast and reliable interpretation of the damage by remote sensing method can be used for inundation mapping, rehabilitation and housing plans for the victims. For tsunami mitigation, the satellite data can be used with GIS to construct the evacuation map (evacuation route and refuge site) and coastal zone management. It is also helpful for educational program for local residents and school systems. Tsunami is a kind of ocean wave, therefore any satellite sensors such as SAR, Altimeter, MODIS, Landsat, SPOT, IKONOS can detect the tsunami wave in 2004. The satellite images have shown the characteristics of tsunami wave approaching the coast. For warning, satellite data has potential for early warning to detect the tsunami wave in deep ocean, if there are enough satellite constellation to monitor and detect the first tsunami wave like the pressure gauge, seismograph and tide gauge with the DART buoy can do. Moreover, the new methods should be developed to analyse the satellite data more faster for early warning procedure.

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OVERVIEW ON HYDROGEN RISK RESEARCH AND DEVELOPMENT ACTIVITIES: METHODOLOGY AND OPEN ISSUES

  • BENTAIB, AHMED;MEYNET, NICOLAS;BLEYER, ALEXANDRE
    • Nuclear Engineering and Technology
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    • v.47 no.1
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    • pp.26-32
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    • 2015
  • During the course of a severe accident in a light water nuclear reactor, large amounts of hydrogen can be generated and released into the containment during reactor core degradation. Additional burnable gases [hydrogen ($H_2$) and carbon monoxide (CO)] may be released into the containment in the corium/concrete interaction. This could subsequently raise a combustion hazard. As the Fukushima accidents revealed, hydrogen combustion can cause high pressure spikes that could challenge the reactor buildings and lead to failure of the surrounding buildings. To prevent the gas explosion hazard, most mitigation strategies adopted by European countries are based on the implementation of passive autocatalytic recombiners (PARs). Studies of representative accident sequences indicate that, despite the installation of PARs, it is difficult to prevent at all times and locations, the formation of a combustible mixture that potentially leads to local flame acceleration. Complementary research and development (R&D) projects were recently launched to understand better the phenomena associated with the combustion hazard and to address the issues highlighted after the Fukushima Daiichi events such as explosion hazard in the venting system and the potential flammable mixture migration into spaces beyond the primary containment. The expected results will be used to improve the modeling tools and methodology for hydrogen risk assessment and severe accident management guidelines. The present paper aims to present the methodology adopted by Institut de Radioprotection et de $S{\hat{u}}ret{\acute{e}}$ $Nucl{\acute{e}}aire$ to assess hydrogen risk in nuclear power plants, in particular French nuclear power plants, the open issues, and the ongoing R&D programs related to hydrogen distribution, mitigation, and combustion.