• Title, Summary, Keyword: Plateau pressure

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Effect of periodic wakes on separated flows over a NACA0012 airfoil (주기적 통과 후류가 익형위 박리 유동에 미치는 영향)

  • Lee, Hui-Kang;Park, Tae-Choon;Jeon, Woo-Pyung;Kang, Shin-Hyoung
    • Proceedings of the KSME Conference
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    • pp.1619-1624
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    • 2004
  • Experimental study of separated flow over a NACA0012 airfoil is conducted at $Re=2{\times}10^5$ when periodic wakes pass over the airfoil. The wakes are periodically generated by circular cylinders upstream of the airfoil. The measurement of surface pressure and surface visualization at various angles of attack are carried out without and with passing wakes. Without passing wakes, a separation bubble at the leading edge of the suction surface is formed at an angle of attack, found from a local plateau in the streamwise pressure distribution and two distinct lines in the surface flow visualization. With passing wakes, however, the bubble disappears. Owing to passing wakes, the lift increases at high angle of attack and the angle of stall also increases.

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Influence of Negative-Pressure Wound Therapy on Tissue Oxygenation of the Foot

  • Shon, Yoo-Seok;Lee, Ye-Na;Jeong, Seong-Ho;Dhong, Eun-Sang;Han, Seung-Kyu
    • Archives of Plastic Surgery
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    • v.41 no.6
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    • pp.668-672
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    • 2014
  • Background Negative-pressure wound therapy (NPWT) is believed to accelerate wound healing by altering wound microvascular blood flow. Although many studies using laser Doppler have found that NPWT increases perfusion, recent work using other modalities has demonstrated that perfusion is reduced. The purpose of this study was to investigate the influence of NPWT on tissue oxygenation of the foot, which is the most sensitive region of the body to ischemia. Methods Transcutaneous partial pressure of oxygen ($TcpO_2$) was used to determine perfusion beneath NPWT dressings of 10 healthy feet. The sensor was placed on the tarso-metatarsal area of the foot and the NPWT dressing was placed above the sensor. $TcpO_2$ was measured until it reached a steady plateau state. The readings obtained at the suction-on period were compared with the initial baseline (pre-suction) readings. Results $TcpO_2$ decreased significantly immediately after applying NPWT, but gradually increased over time until reaching a steady plateau state. The decrease in $TcpO_2$ from baseline to the steady state was 2.9 to 13.9 mm Hg (mean, $9.3{\pm}3.6$ mm Hg; $13.5{\pm}5.8%$; P<0.01). All feet reached a plateau within 20 to 65 minutes after suction was applied. Conclusions NPWT significantly decrease tissue oxygenation of the foot by 2.9 to 13.9 mm Hg. NPWT should be used with caution on feet that do not have adequate tissue oxygenation for wound healing.

Realization of silver fixed-point and application for the high temperature platinum resistance thermometry using the gas-pressure controlled sodium heat-pipe furnace (가스압력조절식 나트륨 열관전기로를 이용한 은 고정점 실현과 고온백금저항온도 계측에의 응용)

  • Gam, K.S.;Choi, I.M.;Yang, I.;Kim, Y.G.
    • Journal of Sensor Science and Technology
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    • v.18 no.2
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    • pp.116-121
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    • 2009
  • Pressure-controlled sodium heat pipe furnace was designed and fabricated, and its characteristics was investigated. Pressure control system was controlled within ${\pm}0.5\;Pa$ at 150 kPa and the stability of pressure was decreased to ${\pm}2.5\;Pa$, when the pressure-controlled system connected with the heat pipe. The melting curve of Ag fixed-point realized well by the adiabatic method using the pressure-controlled sodium heat pipe furnace and its accuracy showed ${\pm}2.27\;mK$ from the calculation of 20% to 80% at the plateau. The freezing curve of Ag fixed-point also realized and its plateau value was 2.23 mK lower than that of the melting curve.

Compatibility and Properties of SIS Pressure Sensitive Adhesives (SIS계 점착제의 상용성과 점착물성)

  • Yoon, J.;Shim, M.J.;Kim, S.W.
    • Applied Chemistry for Engineering
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    • v.5 no.5
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    • pp.851-856
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    • 1994
  • Compatibility and viscoelasticity in non-solvent type pressure sensitive adhesive of styrene-isoprene-styreno(SIS) block copolymer with tackifier resin were investigated. In the isoprene phase of SIS block copolymer, it was found that it's compatibility with $C^5$ petroleum resin was good, but that with Coumarone-indents resin was not so good. The magnitudes of peel strength, tack, and holding power were as follows : $C^5$ petroleum resin>rosin ester resin>coumarone-indene resin. The tackifier resin with good compatibility in rubber phase was also effective. However, with plateau modulus value of $1{\times}10^6-3{\times}10^6dyn/cm^2$, the effect of pressure sensitive adhesives was excellent.

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The Analysis of the Weather Characteristics by Source Region of the Asian Dust Observed in South Korea (한국에 출현한 황사의 발원지별 기상 특성 분석)

  • Kim, Sunyoung;Lee, Seungho
    • Journal of the Korean Geographical Society
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    • v.48 no.2
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    • pp.167-183
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    • 2013
  • This paper aimed to investigate the Asian dust source region and climatic condition of source region by the case of Asian dust in south Korea. In order to analyze the weather condition of source region, observed the Asian dust days data and weather data in China were used. The Asian dust days originating from inner-Mongolia were the most frequent. The Asian dust days originating from all the source regions except Loess plateau were increased recently and occurred over the country. In case of Loess plateau, the frequency of the Asian dust days in 1960s was the highest and only the southern region of the south Korea was mostly affected. The relationship between the Asian dust days of Korea and climatic factors of spring and April of source region was significant. The relationship between the Asian dust days originating from the inner Mongolia and sea level pressure of April and relative humidity of spring was negative. The Asian dust days from Gobi had positive relationship with wind gust days and negative relationship with sea level pressure in April. The Asian dust days from Manchuria had negative relationship with precipitation and sea level pressure in April. The Asian dust days from Loess plateau had positive relationship with maximum wind speed and negative relationship with sea level pressure in April.

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A Study on the Hydrogenation Properties of MmNi4.5Al0.5Zrx(X=0.0-0.2) Alloys Containing the Zr by Excess (Zr을 과잉 첨가한 MmNi4.5Al0.5Zrx(X=0.0-0.2) 합금의 수소화 반응특성에 대한 연구)

  • Na, Young-Sang;Lee, Jai-Young
    • Transactions of the Korean hydrogen and new energy society
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    • v.4 no.1
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    • pp.31-39
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    • 1993
  • In order to improve the hydrogen storage capacity and the activation property of the $MmNi_{4.5}Al_{0.5}$ alloy, the multiphase alloy system are prepared by adding the excess Zr in $MmNi_{4.5}Al_{0.5}$ alloy. It is estimated from the X-ray diffraction pattern and the energy dispersive X-ray analysis that the 2nd phases in $MmNi_{4.5}Al_{0.5}Zr_x$ alloys are $ZrNi_3$, ${\beta}$-Zr. Their morphology is also examined by the scanning electron microscope, and it shows the needle-like precipitation. As the Zr contents increase, the activation time and the plateau pressure decrease, sloping of the plateau pressure increase. Amount of the 2nd phases increase with Zr contents in $MmNi_44.5Al_{0.5}Zr_x$ alloys. The $MmNi_44.5Al_{0.5}Zr_{0.05}$ alloy, which shows the maximum storage capacity and the strong resistance to intrinsic degradation, is considered as a proper alloy for hydrogen storage.

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Heat and Mass Transfer Properties of Mm-Based Metal Hydride upon Co Content (Mm계 금속수소화물의 Co함량에 따른 열 및 물질전달특성)

  • Park, Chan-kyo
    • Transactions of the Korean hydrogen and new energy society
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    • v.15 no.2
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    • pp.144-151
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    • 2004
  • The effect of the cobalt content on the thermodynamic and, heat and mass transfer properties of the $MmNi_{5-y}B_{y-z}C_z(y=0.5{\sim}1.5,\;z=0.5)$hydrogen storage alloys has been studied systematically. The P-C isotherms curves show that with increasing cobalt content in the alloys, the plateau pressure of the hydrogen absorption and desorption and enthalpy(${\Delta}H$) increases steeply and the plateau region becomes flat, while entropy(${\Delta}S$) decreases. Also at the constant cobalt content the hydrogen transfer rate decreases with the reaction temperature, while the initial reaction kinetics increases. But the initial reaction with hydrogen completes within 1min, although the reaction proceeds about 30minutes thereafter.

The Fabrication of MggTi1-(10, 20 wt%)Ni Hydrogen Absorbing Alloys by Hydrogen Induced Mechanical Alloying and Evaluation of Hydrogenation Properties(Part II : Evaluation of Pressure-Composition-Isotherm Properties) (수소 가압형 기계적 합금화법을 이용한 MggTi1-(10, 20 Wt%)Ni 수소저장합금의 제조와 수소화 특성 (제 2보 : 압력-조성-등온 특성 평가))

  • Hong, Tae-Whan;Kim, Gyeong-Bum;Kim, Yeong-Jig
    • Transactions of the Korean hydrogen and new energy society
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    • v.13 no.4
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    • pp.270-278
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    • 2002
  • Mg and Mg alloys are attractive hydrogen storage materials because of their lightweight and high absorption capacity. Their range of applications could be further extended if their hydrogenation properties and degradation behavior could be improved, The main emphasis of this study was to find an economic manufacturing method for Mg-Ti-Ni-H systems, and to investigate their hydrogenation properties, In order to examine hydrogenation behavior, a Sieverts type automatic pressure-composition-isotherm(PCI) apparatus was used and the experiments were performed at 423, 473, 523, 573, 623 and 673K. The results of thermogravimetric analysis(TGA) reveal that the absorbed hydrogen contents are around 2.5 wt% for ($Mg_9Ti_1$)-10 wt% Ni. With increased Ni content, the absorbed hydrogen content decreases to 1.7 wt%, whereas the dehydriding starting temperatures are lowered by some 70-100K. The results of PCI on ($Mg_9Ti_1$)-20 wt% Ni show that its hydrogen capacity is around 5.3 wt% and its reversible capacity and plateau pressure are also excellent at 523K and 573K. In addition, the reaction enthalpy, $\Delta$HD.plateau, is $30.6{\pm}5.7kJ/molH_2$.

Variation of Cardiac Output and Blood Pleasure after Flooding Water into Lungs (폐 침수시의 심장 박출량과 혈압의 변동)

  • Cho, Sung-Doo;Nam, Kee-Yong
    • The Korean journal of physiology & pharmacology
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    • v.1 no.1
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    • pp.57-66
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    • 1967
  • Cold $(0^{\circ}C)$ or warm $(25^{\circ}C)$ fresh and sea water were flooded into the lungs of rabbits through tracheal canule. Respiratory arrest ensued in 19.5 minutes in the warm fresh water flooded rabbits and was the longest survival time among the experimental groups. The survival times in the other groups were: 2.32 minutes in cold fresh water group, 2.75 minutes in .warm sea water group, and 4.57 minutes in cold sea water group. Cardiac output was measured by means of T-1824 dilution technique after 2 or 3 minutes of flooding in 27 rabbits. Blood pressure was observed by mercury manometer throughout the survival time in 40 rabbits. The following results were obtained. 1. Cardiac output in the warm fresh water flooded and sea water flooded animal was smaller than that of control rabbits. In the cold fresh water flooded animal cardiac output was greater than that of the control animal. 2. Time constants of T-1824 dilution curve of experimental group were elongated than the normal curve. 3. Central blood volume showed an increase in the fresh water group, a decrease in cold sea water group and no change in warm sea water group. 4. In all of the experimental groups arterial blood Pressure showed an abrupt and great variations after flooding of lungs and lasted about 30 seconds. Thereafter, arterial pressure remained at a plateau level until the sudden fall to zero and this was almost coincided with the time of respiratory arrest. The Plateau level of arterial Pressure in fresh water group was about 10 mmHg higher than the control value, and it was lower than the control value in warm sea water group. In cold sea water group the plateau was made up by fluctuations around the control value. 5. Osmosis of water through the lung alveolar membrane occured in all animals. Fresh water caused hemodilution and sea water caused hemoconcentration. 6. In sea water flooded animal more volume of water was recovered through the tracheal canule than the volume injected into trachea. This was interpreted as the consequence of the shift of water from plasma to alveolar sac. 7. Relative freight of lung was greater in fresh water group than sea water group. In all animal lung edema ensued. 8. The mechanisms of cardiac output variations were discussed.

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Study on the Application for Hydrogen Storage Tank of MmNi4.5Mn0.5Zrx(x=0, 0.025, 0.05, 0.1) Alloys Containing Excess Zr (과잉 Zr을 첨가한 MmNi4.5Mn0.5Zrx(x=0, 0.025, 0.05, 0.1) 합금의 수소용기 적용에 관한 연구)

  • Kang, Kil-Ku;Park, Sung-Gap;Kang, Sei-Sun;Kwon, Ho-Young
    • Korean Journal of Materials Research
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    • v.12 no.8
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    • pp.624-633
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    • 2002
  • In order to improve the hydrogen storage capacity and the activation properties of the hydrogen storage alloys, the rare-earth metal alloy series, MmN $i_{4.5}$M $n_{0.5}$Z $r_{x}$(x=0, 0.025, 0.05, 0.1), are prepared by adding excess Zr in MmN $i_{4.5}$M $n_{0.5}$ alloy. The various parts in hydrogen storage vessel consisted of copper pipes reached the setting temperature within 4~5 minutes after heat addition, which indicated that storage vessel had a good heat conductivity required in application. The performance test on storage vessel filled with rare-earth metal alloys of 1000 gr was also conducted after hydrogen charging for 10 min at $18^{\circ}C$ under 10 atm. It showed that the average capacity of discharged hydrogen volume was found to be for $MmNi_{4.5}$ $Mn_{0.5}$ and $MmNi_{4.5}$ $Mn_{x}$ 0.5/$Zr_{samples}$ indicated that the released amount of hydrogen for this $AB_{5}$ type alloys was more than 92 % of theoretic value, and also it was found that the optimum discharging temperature for obtaining an appropriate pressure of 3 atm was determined to be $V^{\circ}C$ for $MmNi_{4.5}$ $Mn_{0.5}$$Zr_{x}$(x=0, 0.025, 0.05, 0.1) hydrogen storage alloys. The released amount of these hydrogen storage samples was 125 $\ell$ , 122.4 $\ell$ and 108.15 $\ell$/kg for $MmNi_{4.5}$ $Mn_{0.5}$ $Zr_{0.025}$ $MmNi_{4.5}$M $n_{0.5}$Z $r_{0.05}$, and MmN $i_{4.5}$ Mn_0.5$Zr_{0}$, at $70^{\circ}C$ respectively. Amount of the 2nd phases increase with increase on Zr contents in $MmNi_{4.5}$$Mn_{0.5}$ $Zr_{ 0.1}$/ alloy. This phenomenon indicates that$ ZrNi_3$ in $MmNi_{4.5}$ $Mn_{0.5}$ $Zr_{x}$ / phase, which shows the maximum storage capacity and the strong resistance to intrinsic degradation, is considered as a proper alloy for hydrogen storage. As the Zr contents increase, the activation time and the plateau pressure decreases and sloping of the plateau pressure increases.creases.eases.s.