• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 춘계학술대회
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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.

• Archives of Plastic Surgery
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• 제41권6호
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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.

• 센서학회지
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• 제18권2호
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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.

• 공업화학
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• 제5권5호
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• pp.851-856
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• 1994

무용제 타입의 hot melt계 중 styrene-isoprene-styrene(SIS) 블럭공중합체에 대한 tackifier resin의 상용성과 점탄성, 그에 영향을 미치는 점착물성에 관해 조사하였다. SIS블럭공중합체의 이소프렌상에서는 $C^5$ petroleum resin이 상용성이 우수하며, coumarone-indene resin은 전혀 상용성을 보이지 않았다. 그에 따른 점착력, 초기점착력, 견지력 등의 점착물성은 $C^5$ petroleum resin>rosin ester resin>coumarone-indene resin순으로 나타났으며, 고무상에서 상용성이 우수한 tackifier resin이 효과적임을 알았다. 한편, 이때의 저장탄성률(G')에서, plateau modulus값이 $1{\times}10^6-3{\times}10^6dyn/cm^2$일때 점착력이 가장 우수하였다.

• 말소리와 음성과학
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• 제14권3호
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• pp.11-25
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• 2022

From simultaneous recordings of the external photoglottography, intra-oral air pressure (P_io), airflow and acoustic data from four native Seoul Korean speakers (2 male and 2 female), we have found that the two fricatives are not significantly different in glottal opening peak and airflow peak height either word-initially or word-medially and that the duration of aspiration is significantly reduced in word-medial /s/, compared to those in word-initial /s/, not in /s'/. We have also found that the duration of a high P_io plateau is significantly longer in /s/ than in /s'/ both word-initially and word-medially and that airflow resistance (R=P_io/U) at the onset and offset of a P_io plateau and at the time of airflow peak height is significantly higher in /s'/ than in /s/ across the contexts. However, the differences in P_io peak and F0 are not significant. In addition, the transition time to reach airflow peak height from the offset of a P_io plateau is found to be significantly longer in /s/ than /s'/ in both word-initial and word-medial positions. No significant differences in glottal opening peak and airflow peak height confirm that /s/ is specified as [-spread glottis] like /s'/. As for the other significant differences, we propose that /s/ is [-tense], and /s'/ [+tense].

• 대한지리학회지
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• 제48권2호
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• pp.167-183
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• 2013

본 연구에서는 한국에 출현한 황사 발원지별로 기상 특성을 파악하였다. 이를 위하여 한국의 일별 황사자료와 발원지의 일별 기상자료를 이용하여 한국에 황사 출현 시의 발원지 기상상태를 분석하였다. 한국에 출현한 황사 중 네이멍구에서 발원한 황사의 빈도가 가장 높다. 황토고원을 제외한 발원지에서 출현한 황사 일수가 최근 증가하고 있으며, 한국의 전국에 영향을 미친 빈도가 높았다. 황토고원의 경우 1960년대의 출현빈도가 가장 높았으며, 한국의 남부지방에 영향을 미친 빈도가 높았다. 한국의 황사 발생일수와 발원지의 봄철 및 4월 기상요소와 유의한 관계가 있다. 네이멍구에서 발원한 황사 발생일과 4월 해면기압, 봄철 상대습도와 음의 관계가 있다. 고비에서 발원한 황사 발생일과 4월 돌풍일수와 양의 관계이며, 4월 해면기압과 음의 관계이다. 만주에서 발원한 황사 발생일과 4월 강수량, 해면기압과는 음의 관계이다. 황토고원에서 발원한 황사 발생일과 4월 최대풍속과는 양의 관계이며, 해면기압과는 음의 관계이다.

• 한국수소및신에너지학회논문집
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• 제4권1호
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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.

• 한국수소및신에너지학회논문집
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• 제15권2호
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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.

• 한국수소및신에너지학회논문집
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• 제13권4호
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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 $30.6{\pm}5.7kJ/molH_2$.

• The Korean Journal of Physiology
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• 제1권1호
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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.