• 제목/요약/키워드: saturated pressure

검색결과 456건 처리시간 0.023초

Effect of pressure and temperature on bulk micro defect and denuded zone in nitrogen ambient furnace

  • Choi, Young-Kyu;Jeong, Se-Young;Sim, Bok-Cheol
    • 한국결정성장학회지
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    • 제26권3호
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    • pp.121-125
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    • 2016
  • The effect of temperature and pressure in the nitrogen ambient furnace on bulk micro defect (BMD) and denuded zone (Dz) is experimentally investigated. It is found that as pressure increases, Dz depth increases with a small decrease of BMD density in the range of temperature, $100{\sim}300^{\circ}C$. BMD density with hot isostatic pressure treatment (HIP) at temperature of $850^{\circ}C$ is higher than that without HIP while Dz depth is lower due to much higher BMD density. As the pressure increases, BMD density is increased and saturated to a critical value, and Dz depth increases even if BMD density is saturated. The concentration of nitrogen increases near the surface with increasing pressure, and the peak of the concentration moves closer to the surface. The nitrogen is gathered near the surface, and does not become in-diffusion to the bulk of the wafer. The silicon nitride layer near the surface prevents to inject the additional nitrogen into the bulk of the wafer across the layer. The nitrogen does not affect the formation of BMD. On the other hand, the oxygen is moved into the bulk of the wafer by increasing pressure. Dz depth from the surface is extended into the bulk because the nuclei of BMD move into the bulk of the wafer.

R-134a의 열역학적 물성치 계산과 냉동 성능에 관한 연구 (Calculation of the Thermodynamic Properties of R-134a and A Preliminary Study of the Refrigeration Performance)

  • 박영무;이홍원
    • 설비공학논문집
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    • 제3권4호
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    • pp.286-296
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    • 1991
  • The thermodynamic properties of R134a, the prospective R12 alternative, have been computerized using Martin-Hou equation of state and the coefficients given by Willson-Basu. Several experimental results in literatures for PVT data, saturated vapor pressure, saturated liquid density are compared with the calculated results to investigate the accuracy. The average deviation (max. deviation) is 0.13% (0.25%) for saturated liquid density, 0.25% (0.8%) for PVT data. Thermodynamic properties, enthalpy, entropy are compared with the NIST's. The maximum percent difference is 3% for saturated liquid enthalpy, 1.5% for saturated vapor enthalpy, 4% saturated liquid entropy, and 0.7% for saturated vapor entropy. Correction of W-B's coefficients and inclusion of the sixth term of M-H EOS for improvement of accuracy are recommended. R134a and R12 are compared with respect to refrigeration performance. COP's are different from each other within 3%. Refrigeration effect of R134a is superior to that of R12 but refrigeration capacity of R134a is inferior to that of R12 because the volumetric efficiency of the system using R134a is lower than that of the system using R12.

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Frost Heaving in Artificial Ground Freezing

  • 생뢰효박
    • 한국지반공학회:학술대회논문집
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    • 한국지반공학회 1994년도 연약지반처리위원회 봄 학술발표회 논문집 연약지반처리
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    • pp.13-46
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    • 1994
  • Artificial ground freezing methods have been applied to geotechnical construction projects for stabilizing earth materials and controlling water seepage into the ground. However, this can result in frost heaving and causes the same engineering problems as encountered with the natural freezing of soil. In natural freezing, the ground freezes from the surface downward. When artificial ground freezing is applied at a deep location, however, freezing is limited locally. The soil condition differs between them as follows: Natural freezing - unsaturated and without overburden pressure. Artificial freezing -- saturated and under overburden pressure. The authors investigated the practical application of artificial ground freezing and examined the frost behaviour of a saturated soil under overburden pressure. This paper presents the results obtained from experiments concerning frost heaving and discusses frost heaving at the freezing site.

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수구동 액체이젝터를 이용한 농산물의 예냉특성에 관한 연구 (A Study on the Precool Characteristics of Agricultural Products Using the Water-driven Ejector)

  • 박영승;이정혜;김호영;김경근
    • 한국마린엔지니어링학회:학술대회논문집
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    • 한국마린엔지니어링학회 2001년도 추계학술대회 논문집(Proceeding of the KOSME 2001 Autumn Annual Meeting)
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    • pp.45-49
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    • 2001
  • To maintain the freshness of produce, because of stand away between produced and consumer, we need refrigeration system that can supply to consumer at cold chain as soon as gathering. General refrigeration system consist of refrigeration chamber or low temperature store. But the vacuum technology can rapidly refrigeration without refrigerator. This precool system possible to get low precooled temperature, suitable for the fishes, the meat, the vegetables, the fruit etc. Especially get advantage that quality maintain through rapid refrigeration of ferment directly generate heat. Vacuum precool system's principle is that water saturated temperature reduce according to pressure is get to vacuum area, so product temperature reduce as water evaporation at product. In vacuum suction, unit, on early experiment period run the rotary type vacuum pump at purpose pressure, then maintain pressure by water-diven ejector. As the results, cabbage took about 60 minutes to reach from $23.2^{\circ}C$ to $4.5^{\circ}C$at 5mgHg abs.

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포화 및 부분 포화 사질토의 Vp와 Vs 속도 및 과잉간극수압 측정을 위한 비틂전단 시험기의 개발 (Development of Torsional Shear Testing System to Measure P-wave Velocity, S-wave Velocity and Pore Water Pressure Buildup on Fully and Partially Saturated Sands)

  • 김동수;이세현;추연욱
    • 한국지반환경공학회 논문집
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    • 제7권1호
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    • pp.55-66
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    • 2006
  • 사질토의 액상화에 대한 저항 강도는 포화도에 상당히 의존한다. 압축파 속도는 현장에서 쉽게 측정이 가능하고 포화도의 영향을 크게 받기 때문에 현장 지반의 포화도를 예측하고자 할 때 효율적으로 사용될 수 있다. 본 논문에서는 시료의 포화가 가능하고 전단파, 압축파 속도 측정 및 비배수 상태에서 비틂전단 시험을 수행시 유발되는 과잉간극수압을 측정할 수 있는 비틂전단 시험기를 개발하였다. 토요라 모래에 대해 전단파, 압축파 속도 측정이 수행되고, 비배수 비틂전단 시험을 실시하였다. 포화도(B값)에 따른 시료의 전단파 속도 및 압축파 속도를 이론식과 비교하여 개발된 시험기를 검증하였으며, 여러 B값에서 비배수 TS 시험동안 유발되는 과잉 간극수압의 변화를 측정 분석하였다.

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Meshfree consolidation analysis of saturated porous media with stabilized conforming nodal integration formulation

  • Wang, Dongdong;Xie, Pinkang;Lu, Hongsheng
    • Interaction and multiscale mechanics
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    • 제6권2호
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    • pp.107-125
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    • 2013
  • A strain smoothing meshfree formulation with stabilized conforming nodal integration is presented for modeling the consolidation process in saturated porous media. In the present method, nodal strain smoothing is consistently introduced into the meshfree approximation of strain and pore pressure gradient variables associated with the saturated porous media. Meanwhile, in order to achieve a consistent numerical implementation, a smoothing approximation of the meshfree shape function within a nodal representative domain is also proposed in the stiffness construction. The resulting discrete system of equations is all expressed in smoothed nodal measures that are very efficient for numerical evaluation. Subsequently the space-time fully discrete equations are further established by the generalized trapezoidal rule for time integration. The effectiveness of the proposed meshfree consolidation analysis method is systematically illustrated by several benchmark problems.

하천수율원이용 2단압축 열펌프시스템 냉방성능평가 (Cooling Performance Test of 2-stage Heat Pump System Using River Water as a Heat Source)

  • 김종률;이영수;장기창;라호상
    • 대한기계학회:학술대회논문집
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    • 대한기계학회 2004년도 춘계학술대회
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    • pp.2129-2134
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    • 2004
  • The present study has been conducted to develop a heat pump system using river water of temperature energy which not only belongs to unutilized energy but is a kind of good heat source due to maintain its temperature in a certain degree regardless of seasonal variation. The system did not meet the proposed performance after setup. In this paper, the system performance affected by refrigerant Oil, by pressure drop, or by other factors has been discussed. The followings were obtained : (1) Refrigerant Oil mixture rate was 2.5 in weight percentage, (2) Pressure drop through evaporator was 29.1kPa($3.1^{\circ}C$ in saturated tempearture) (3) Pressure drop from the end of evaporator to compressor inlet was 39.8kPa($4.0^{\circ}C$ in saturated tempearture). (4) The system performance can to be improved by modifying a part of pipe line to compressor, and reducing pressure drop through heat exchangers.

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철도노반재료의 동상 팽창압 특성에 관한 연구 (The Characteristics of Frost Heaving Pressure on the Railroadbed Materials)

  • 신은철;박정준;이창섭
    • 한국철도학회:학술대회논문집
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    • 한국철도학회 2002년도 춘계학술대회 논문집
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    • pp.264-270
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    • 2002
  • The frost heaving pressure can be a problem for weakening of the railroadbed material. In this study, upon freezing a saturated soil in a closed-system from the top, a considerable pressure was developed. This pressure is induced as a result of a curved ice-water interface. This study was initiated to investigate the soils frost heaving expansion pressure and physical characteristics resulting from freezing and freezing-thawing cycle process. Weathered granite soils, sandy soil were used in the laboratory freezing test subjected to thermal gradients under closed-systems.

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강우시 불포화토 사면에서의 수리역학적 거동 해석에 관한 연구 (Hydro-mechanical Behavior of Partially Saturated Soil Slopes under Rainfall)

  • 김재홍;임재성;박성완
    • 한국지반공학회논문집
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    • 제28권11호
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    • pp.69-78
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    • 2012
  • 강우로 인한 사면의 안정성 평가를 하기 위한 일반적인 해석 방법들은 강우 침투와 흙의 거동 해석을 개별적으로 구분하여 수행하고 있다. 따라서 상용화된 프로그램과 기 개발된 여러 연구자들의 모델들은 불포화 투수계수를 함수비(또는 흡수력)만의 함수로 정의되어 수리-역학적인 특징을 동시에 고려하지 못하고 있는 실정이다. 그러나 실제 침투수는 사면의 거동을 발생시키고, 지반의 토립자들은 다시 재배열되며 이러한 구성관계에 의해 포화 투수계수 뿐만 아니라 불포화 투수계수도 시간에 따라 변화하게 된다. 강우로 인한 사면의 불안정성은 예측된 불포화 투수계수 값을 근간으로 사면 내 흡수력 감소를 계산함으로써 평가되고 불포화 투수계수는 함수비와 간극률의 함수로 정의되어야 한다. 본 논문에서는 기존의 단계적으로 연결된 해석방법이 불포화 지반에서 침투수를 고려하고 흙의 변형을 예측하는 동시연동해석 결과보다 사면 내부에서 예측되는 흡수력의 변화가 시간에 따라 상대적으로 빠르게 감소함을 보여주고 있다.

포화된 암반에 굴착된 원형공동의 수리-역학적 거동 (Hydro-mechanical Behavior of a Circular Opening Excavated in Saturated Rockmass)

  • 이연규;신희순
    • 화약ㆍ발파
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    • 제23권2호
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    • pp.23-35
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    • 2005
  • 지하수로 포화된 암반내의 공동을 굴착하면 공동 주위에서 응력의 재분배로 인하여 초기 공극수압의 변화가 발생한다. 이러한 공극수압의 변화는 다시 암반의 역학적 거동에 영향을 미치게 된다. 그러므로 공동 주변 암반에서 굴착으로 인해 형성된 공극수압이 소산과정에서 암반의 거동은 공극수압의 변화를 고려하지 않은 해석과 차이를 보이게 된다. 이 연구에서는 굴착직후 짧은 시간 동안에서 공동주변에서 발생하는 응력재분포와 공극수압변화 양상을 수치해석적으로 검토하였다. 공극수압을 고려하지 않는 탄성해석과는 달리 굴착직후 짧은 시간동안에는 공동 벽면의 직후방에서 최대접선응력이 형성되고 있음을 확인할 수 있었다.