• 제목/요약/키워드: Gas pressure

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가스 하이드레이트의 해리로 발생하는 간극수압의 계산방법 (Excess Pore Water Pressure Calculation Methods due to Gas Hydrate Dissociation)

  • 박성식
    • 한국지반공학회:학술대회논문집
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    • 한국지반공학회 2008년도 추계 학술발표회
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    • pp.888-892
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    • 2008
  • If gas hydrate dissociates due to natural and/or human activities, it generates large amount of gas and water. Upon gas hydrate dissociation, a generated pore water pressure between soil particles increases and results in the loss of an effective stress and degradation of soil stiffness and strength. In order to predict the generated excess pore water pressure due to gas hydrate dissociation, two methods based on small hydrate concept (SHC) and large hydrate concept (LHC) are proposed. An excess pore water pressure generated by the gas hydrate dissociation in the Storegga Slide was calculated using two proposed methods.

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국내 LPG 집단공급시설 환경에 적합한 매몰배관용 과류차단밸브 성능시험 절차 개발 (Development of Performance Test Procedure for the Excess Flow Valve for Buried Piping for the Domestic LPG Mass Supply System)

  • 장찬영;이우귀연;이진한
    • 한국가스학회지
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    • 제22권6호
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    • pp.16-27
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    • 2018
  • 대한민국 정부에서 2014년부터 LPG배관망과 LPG소형탱크를 도시가스 공급망 개설이 어려운 산간이나 도서지역에 보급하는 사업을 시작했다. 마을단위와 군단위로 LPG집단공급시설을 설치하면서 기존의 가스공급 압력이 아닌 10배 이상의 높은 준저압(25kPa~100kPa)으로 소비자에게 공급하게 되면서 가스사고의 위험성이 높아졌다. 기존의 가스공급압력보다 10배 이상 높은 압력이기 때문에 가스가 누출 되었을 때 빠른 속도로 많은 양이 누출하게 된다. 이에 준저압 가스배관의 안전성 확보를 위해 과류차단밸브가 필요하게 되었지만, 국내에서는 준저압 매몰배관용 과류차단밸브가 미개발되어 있으며 보급 또한 되어 있지 않는 상황이다. 이에 한국가스안전공사에서는 과류차단밸브의 국산화를 위해 과류차단밸브를 기개발한 해외의 성능기준과 제품을 조사 중에 있으며, 과류차단밸브의 성능평가를 위해 성능시험설비를 구축하여 준저압 연료가스 매몰배관용 과류차단밸브를 연구 개발 중에 있다.

$H_2$ Formation from HI by the Ram Pressure

  • 정은정;김성은;정애리
    • 천문학회보
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    • 제37권2호
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    • pp.70.2-70.2
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    • 2012
  • Ram pressure is known as one of the most efficient mechanisms to deplete the atomic gas of galaxies in the cluster environment. However, the influence of the ram pressure on the molecular gas is not yet clear. Since the molecular gas resides in the galactic center, thus in the deeper potential well, and has higher surface density than the atomic hydrogen, it has been known as that the molecular gas is not easily affected and/or stripped away by the ICM-ISM interaction. To investigate the influence of the ram pressure on the gas properties of galaxies, we compare HI and $^{12}CO$(J=1-0) distribution of NGC 4654 which is experiencing on-going ram pressure and shows distinct HI, CO, optical, and $H_2$ features due to the ram pressure. We discuss the possibilities of H2 formation from HI by the ram pressure and also the star formation activities.

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가스 하이드레이트가 매장된 해저사면의 붕괴에 관한 기초적 연구 (A Preliminary Study on Submarine Slope Failure of Gas Hydrate-bering Sediments)

  • 박성식
    • 한국지반공학회:학술대회논문집
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    • 한국지반공학회 2008년도 춘계 학술발표회 초청강연 및 논문집
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    • pp.399-404
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    • 2008
  • The influence of gas hydrate dissociation on submarine slope stability was studied in this paper. Gas hydrates are stable under high pressure and low temperature conditions. Once gas hydrate dissociates due to natural or human activities, it generates large amount of gas and water. During gas hydrate dissociation, a pore pressure between soil particles increases and results in the loss of an effective stress and degradation of soil stiffness. A pore pressures model was proposed to calculated excess pore pressures generated by gas hydrate dissociation at the Storegga Slide. A slope stability analysis for the Storegga Slide using a two dimensional finite difference method was carried out by considering excess pore pressures due to gas hydrate dissociation. Since the excess pore pressure calculated by the proposed method resulted in the considerable loss of stiffness and strength in slope, a submarine slope failure occurred at the Storegga slide was well simulated.

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Study on Fault Detection of a Gas Pressure Regulator Based on Machine Learning Algorithms

  • Seo, Chan-Yang;Suh, Young-Joo;Kim, Dong-Ju
    • 한국컴퓨터정보학회논문지
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    • 제25권4호
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    • pp.19-27
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    • 2020
  • 본 논문에서는 정압기의 이상 상태 진단을 위한 기계학습 방법을 제안한다. 일반적으로 설비의 이상 상태 탐지를 위한 기계학습 모델 구현에는 관련 센서의 설치와 데이터 수집 과정이 동반되나, 정압기는 설비 특성상 안전문제에 매우 민감하여 추가적인 센서 설치가 매우 까다롭다. 이에 본 논문에서는 센서의 추가 설치 없이 정압기 설비에서 자체 수집되는 유량과 유압 데이터만을 가지고 정압기의 이상 상태를 조기에 판단하는 기계학습 모델을 제안한다. 본 논문에서는 정압기의 비정상데이터가 충분하지 않은 관계로, 모델 학습 시 오버 샘플링(Over-Sampling)을 적용하여 모델이 모든 클래스에 균형적으로 학습하도록 하였다. 또한, 그레이디언트 부스팅(Gradient Boosting), 1차원 합성곱 신경망(1D Convolutional Neural Networks), LSTM(Long Short-Term Memory) 등의 기계학습 알고리즘을 적용하여 정압기의 이상 상태를 판단하는 분류모델을 구현하였고, 실험 결과 그레이디언트 부스팅 알고리즘이 정확도 99.975%로 가장 성능이 우수함을 확인하였다.

Expansion of Dusty H II Regions and Its Impact on Disruption of Molecular Clouds

  • Kim, Jeong-Gyu;Kim, Woong-Tae;Ostriker, Eve
    • 천문학회보
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    • 제40권1호
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    • pp.58.3-59
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    • 2015
  • Dynamical expansion of H II regions plays a key role in dispersing surrounding gas and therefore in limiting the efficiency of star formation in molecular clouds. We use analytic methods and numerical simulations to explore expansions of spherical dusty H II regions, taking into account the effects of direct radiation pressure, gas pressure, and total gravity of the gas and stars. Simulations show that the structure of the ionized zone closely follows Draine (2011)'s static equilibrium model in which radiation pressure acting on gas and dust grains balances the gas pressure gradient. Strong radiation pressure creates a central cavity and a compressed shell at the ionized boundary. We analytically solve for the temporal evolution of a thin shell, finding a good agreement with the numerical experiments. We estimate the minimum star formation efficiency required for a cloud of given mass and size to be destroyed by an HII region expansion. We find that typical giant molecular clouds in the Milky Way can be destroyed by the gas-pressure driven expansion of an H II region, requiring an efficiency of less than a few percent. On the other hand, more dense cluster-forming clouds in starburst environments can be destroyed by the radiation pressure driven expansion, with an efficiency of more than ~30 percent that increases with the mean surface density, independent of the total (gas+stars) mass. The time scale of the expansion is always smaller than the dynamical time scale of the cloud, suggesting that H II regions are likely to be a dominant feedback process in protoclusters before supernova explosions occurs.

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Colorimetric Effect of Au Nanoparticle Chain/Polymer Film under Mechanical Stress and Gas Pressure

  • Shim, Gowoon;Eom, Kiryung;Lee, Gyuyeon;Seo, Hyungtak
    • 한국재료학회지
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    • 제28권1호
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    • pp.1-5
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    • 2018
  • Gas detection is necessary for various reasons, including the prevention of gas leakages and the creation of necessary environmental conditions. Among the gas detection methods, leakage of gas can be confirmed using materials that undergo color changes that are easily distinguished by the naked eye. Metal nanoparticles (NPs) experience variations in their absorption wavelengths under the localized surface plasmon effect (LSPR) with mechanical stresses, which change the distance between NPs. In this study, we attempted to detect the presence of gas utilizing the LSPR-related color change of a chain of Au NPs. The assembly of Au NPs, arranged in a chain shape, experienced a color change from dark blue to purple with a change in the distance between the NPs by applying a physical force, i.e., compression, stretching, and gas pressure. As the force of compression and the degree of stretching increased, the absorption wavelength shifted from doublet peaks at 650 and 550 nm to a singlet peak at 550 nm. Further, applying gas pressure caused an identical color change. With this result, we propose a method that could be applied to all gases that require detection based on gas pressure.

플라즈마 침질탄화처리된 순철의 화합물층 특성 (The Characteristics of Compound Layers Formed during Plasma Nitrocarburising in Pure Iron)

  • 조효석;이상윤
    • 열처리공학회지
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    • 제13권3호
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    • pp.143-150
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    • 2000
  • Ferritic plasma nitrocarburising was performed on pure iron using a modified DC plasma unit. This investigation was carried out with various gas compositions which consisted of nitrogen, hydrogen and carbon monoxide gases, and various gas pressures for 3 hours at $570^{\circ}C$. After treatment, the different cooling rates(slow cooling and fast cooling) were used to investigate its effect on the structure of the compound layer. The ${\varepsilon}$ phase occupied the outer part of the compound layer and ${\gamma}^{\prime}$ phase existed between the ${\varepsilon}$ phase and the diffusion zone. The gas composition of the atmosphere influenced the constitution of the compound layer produced, i.e. high nitrogen contents were essential for the production of ${\varepsilon}$ phase compound layer. It was found that with increasing carbon content in the gas mixture the compound layer thickness increased up to 10%. In the gas pressure around 3 mbar, the compound layer characteristics were slightly effected by gas pressure. However, in the low gas pressure and high gas pressure, the compound layer characteristics were significantly changed. The constitution of the compound layer was altered by varying the cooling rate. A large amount of ${\gamma}^{\prime}$ phase was transformed from the ${\varepsilon}$ phase during slow cooling.

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대기압이 가스유량측정에 미치는 영향에 관한 연구 (A Study on the Effect of the Atmospheric Pressure in the Gas Flow Measurement)

  • 정종태;하영철;이철구;허재영
    • 유체기계공업학회:학술대회논문집
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    • 유체기계공업학회 2002년도 유체기계 연구개발 발표회 논문집
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    • pp.363-369
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    • 2002
  • Orifice meter is the most widely used flowmeter in custody transfer between KOGAS and city gas companies. Absolute pressure value is needed to calculate the gas flow of orifice metering system, but the gauge pressure transmitters are mainly used in the field. In case that the gauge pressure transmitters are used, the fixed value as standard atmospheric pressure(101.325kPa) is applied for the absolute pressure value. The real, local atmospheric pressures of each metering station are different from the standard condition as the altitude and weather conditions. In this study the flow calculation errors were quantitatively analyzed through examining the atmospheric pressures of 50 stations of KOGAS. The data for analysis are such like the time data of supplied gas amount, the altitude of each metering station, the time data of atmospheric pressures and altitudes of each weather observatory. The results showed that the local atmospheric pressures were different from the standard value and the gas flow calculation errors were distributed between $-0.024\%{\~}0.025\%$ based on the supplied gas amount in the year 1999 and 2000.

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마취기용 인공호흡기의 압력 측정값의 보정을 위한 센서 출력의 데이터 처리 (Data processing of sensor output for correction of pressure measurement value of an anesthesia ventilator)

  • 박영준;이종수;김영길
    • 대한전자공학회:학술대회논문집
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    • 대한전자공학회 1999년도 추계종합학술대회 논문집
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    • pp.1067-1070
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    • 1999
  • Anesthesia gas to pour to patients affects the flow and volume as the pressure difference of an oxygen and an anesthesia gas. An anesthesia gas, being injurious and polluting an environment, must control the pressure of an oxygen gas because of being used by closing up tight. But a pressure sensor to use for measuring an oxygen gas appears other pressure as the characteristic and the error difference of elements to use for implementing an system. A medical machine such as an anesthesia ventilator must be accurate because of using for the person's body. So we intend to implement an system for a sensor pressure measurement not to be change regardless of an environment. This papers is the target that a sensor pressrue measurement to be changed in environment is equal to actual sensor pressure measurement. So an implemented system is using analog filter and digital filter to reduce a noise. And we are using auto-zeroing and calibration to correct a sensor pressure which is changed in environment. Through such a process we increase the accuracy and the confidence of an anesthesia ventilator by controlling the flow of an anesthesia gas.

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