• Transactions of the Korean Society of Mechanical Engineers B
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• v.28 no.12
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• pp.1521-1527
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• 2004

Thermocapillary migration of a liquid slug is caused by temperature difference between the ends of a slug. The temperature difference induces the difference of the surface tension coefficient and consequently of capillary pressure between the ends of the slug. Presently available model to predict a velocity of thermocapillary migration adopts the Poiseuille equation which is valid only for a very long slug and neglects the shear stress near the contact line. In the present study, a new model has been developed to consider the shear stress near the contact line so that it can be applied to slugs or drops of general configuration. The experiments using mineral oil with the length to diameter ratio being 10 and a glass capillary were performed. It was found that the liquid slug began to move upon overcoming contact angle hysteresis when the temperature difference reached 35$^{\circ}C$. The results indicate that the new model well predicts the velocity of the liquid slug.

• Journal of the Korean Geotechnical Society
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• v.32 no.1
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• pp.55-62
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• 2016

This study presents the numerical results of soil-water characteristic curve for sandy soil by pore network model. The Jumunjin sand is subjected to the high resolution 3D X-ray computed tomographic imaging and its pore structure is constructed by the web of pore body and pore channel. The channel radius, essential to the computation of capillary pressure, is obtained based on the skeletonization and Euclidean Distance transform. The experimentally obtained soil-water characteristic curve corroborates the numerically estimated one. The pore channel radius defined by minimum radii of pore throat results in the slightly overestimation of air entry value, while the overall evolution of capillary pressure resides in the acceptable range. The relative permeability computed by a series of suggested models runs above that obtained by pore network model at high degree of saturation.

• Journal of Soil and Groundwater Environment
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• v.23 no.1
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• pp.1-13
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• 2018

A series of experiments using transparent micromodels with an artificial pore network etched on glass plates was performed to investigate the effects of flow rate on the migration and distribution of resident wetting porewater (deionized water) and injecting non-wetting fluid (n-hexane). Multicolored images transformed from real RGB images were used to distinguish n-hexane from porewater and pore structure. Hexane flooding followed by immiscible displacement with porewater, migration through capillary fingering, preferential flow and bypassing were observed during injection experiments. The areal displacement efficiency increases as the injection of n-hexane continues until the equilibrium reaches. Experimental results showed that the areal displacement efficiency at equilibrium increases as the flow rate increases. Close observation reveals that preferential flowpaths through larger pore bodies and throats and clusters of entrapped porewater were frequently created at lower flow rate. At higher flow rate, randomly oriented forward and lateral flowpaths of n-hexane displaces more porewater at an efficiency close to stable displacement. It may resulted from that the pore pressure of n-hexane, at higher flow rate, increases fast enough to overcome capillary pressure acting on smaller pore throats as well larger ones. Experimental results in this study may provide fundamental information on migration and distribution of immiscible fluids in subsurface porous media.

• Journal of the Korean Geotechnical Society
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• v.24 no.6
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• pp.27-35
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• 2008

At low normal stress levels tensile strength of sand varies with either saturation or suction of soil in an up-and-down manner with a peak tensile strength that can occur at any degree of saturation. A theory that accurately predicts tensile strength of wet sand is presented. A closed form expression for tensile strength unifies tensile strength characteristics in all three water retention regimes: pendular, funicular, and capillary. Three parameters are employed in the theory; namely, the Internal friction angle (at low normal stress) ${\phi}_t$, the inverse value of the air-entry pressure ${\alpha}$, and the pore size spectrum parameter n. It is shown that the magnitude of peak tensile strength is dominantly controlled by the ${\alpha}$ parameter. The saturation at which peak tensile strength occurs only depends on the pore size spectrum parameter n.

• Applied Chemistry for Engineering
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• v.35 no.2
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• pp.115-121
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• 2024

This study analyzed the influence of process variables affecting the thermodynamic equilibrium and fluid dynamics of interfaces such as reverse micelle, salt concentration, interfacial tension, and viscosity of fluids to optimize the microencapsulation process using the W1/O/W2 double emulsion method. The process variable with the greatest impact on encapsulation efficiency was found to be the difference in osmotic pressure between the W1 and W2 phases. It was observed that increasing the salt concentration in the W2 phase or decreasing the ascorbic acid concentration in the W1 phase resulted in higher encapsulation efficiency. Additionally, a larger difference in osmotic pressure led to increased damage to the surface of the microparticles, as confirmed by SEM images. The introduction of reverse micelles, which was anticipated to increase encapsulation efficiency, either had a low contribution or even decreased encapsulation efficiency. The yield of microcapsules was expressed as a universal function, applicable to all process conditions or solution compositions. According to this universal function, no further increase in yield was observed beyond the Ca (capillary number) of approximately 20.

• Journal of Pharmaceutical Investigation
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• v.5 no.3
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• pp.43-49
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• 1975

The rheological properties of seven mixed sugar solutions of glucose, fructose, maltose, sucrose, and two kinds of honey, the chestnut and the acacia, were discussed. The fluidity of the above samples were studied by using the applied pressure horizontal viscometer with which glycerine was confirmed to be a Newtonian flow at $25^{\circ}C$. Time required to pass the constant volume of the sample fluids through the capillary was measured at various pressure differences, ${\Delta}p$, and the ${\Delta}p$ vs ${\Delta}p{\cdot}t$ in the Poiseuille equation was plotted. Shear rate against shearing stress, on the other hand, was plotted for the sample fluids and it was found that all the sample fluids have shown a Newtonian behavior. It was interesting to note that the shear viscosity increased as the concentration of sugar solutions increased, and as the concentration of sucrose became higher than that of maltose, although the total concentration of sugar solution is constant.

• The Korean Journal of Pharmacology
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• v.8 no.1
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• pp.63-65
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• 1972

It is well known that pharmacological actions of bradykinin are smooth muscle dilatation, increase in capillary permeability, accumulation and migration of leucocytes and inducement of pain. The most significant action of bradykinin is the dilatation of blood vessels. The responses of bradykinin (0.5ug/kg, i. v. injection) on blood pressure were observed before and after single i. v. administration of guanethidine (2mg/kg) in the rabbits. The result of experiment was as follows: In the rabbit pretreated with guanethidine, the depressor response of bradykinin was much pronounced in comparison with that of normal rabbit.

• 유체기계공업학회:학술대회논문집
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• 2006.08a
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• pp.305-308
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• 2006

For controlling micro-flows inside a LOC (lab-on-a-chip) a syringe pump or an electronic device for EOF(electro-osmotic flow) have been used in general. However, these devices are so large and heavy that they are burdensome in the development of a portable micro-TAS (total analysis system). In this study, a new flow control system employing pressure chambers, digital switches and speed controllers was developed. This system could effectively control the micro-scale flows inside a LOC without any mechanical actuators or electronic devices We also checked the feasibility of this new control system by applying it to a LOC of micro-mixer type. Performance tests show that the developed control system has very good performance. Because the flow rate in LOC is controlled easily by throttling the speed controller, the flows in complicate microchannels network can be also controlled precisely.

• Journal of Chest Surgery
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• v.40 no.8
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• pp.552-557
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• 2007

Background: B-type natriuretic peptide (BNP) is a cardiac hormone that is primarily synthesized by the ventricular cardiac myocytes. Increased plasma BNP levels have been observed in patients suffering with congestive heart failure, ventricular hypertrophy and myocaridits and also during heart transplantation rejection. We investigated the serum BNP level as a predictive marker for rejection after heart transplantation. Material and Method: To test the usefulness of measuring the BNP level in cardiac transplant patients, consecutive blood samplings for BNP, right ventricular endomyocardial biopsies, hemodynamic measurements and transthoracic echocardiogram were all done in 10 such patients between January 2004 and August 2005 at the Department of Thoracic and Cardiovascular Surgery in Asan Medical Center. Two groups were identified with using the median value: the low BNP group (n=28, BNP: ${\le}290$ pg/mL) and the high BNP group (n=29, BNP: >290 pg/mL). We retrospectively analyzed rejection, the ejection fraction, tricuspid regurgitation, left ventricular hypertrophy, the pulmonary capillary wedge pressure and the right atrial pressure between the 2 groups. Result: There were no differences in age, gender, rejection, the ejection fraction, tricuspid regurgitation, left ventricular hypertrophy and the right atrial pressure between the 2 groups (p>0.05). However, a higher pulmonary capillary wedge pressure and a higher mean pulmonary atrial pressure were observed in the high BNP group (p<0.05). Further, BNP has linear correlation with the pulmonary capillary wedge pressure (r=0.590, p<0.001). Using the cut-off value of 620 pg/mL, the BNP predicted a high PCWP (>12 mmHg) with a sensitivity of 83.3% and a specificity of 91.1% (AUC: $0.900{\pm}0.045$, p<0.001). Conclusion: The BNP level after heart transplantation does not show any significant correlation with rejection, yet it might be a predictive marker of ventricular diastolic dysfunction.

• The Journal of Internal Korean Medicine
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• v.11 no.2
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• pp.1-15
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• 1990

Certain oriental medication have been shown to be effective in decreasing pulmonary vascular resistance and increasing cardiac output in primary pulmonary artery pressure secondary to pulmonary edema. So oleic acid was administered in 14 dogs in order to induce acute lung injury. And we studied the hemodynamics and blood gas changes of Pyengpaetang(50mg, 100mg) with continuous postive pressure was ventilation in pulmonary edema. The pulmonary edema group, arterial oxygenation was improved after 5 and $10cmH_2O$ PEEP(positive end expiratory pressure), but cardiovascular system was depressed. Blood pressure and cardiac output were decreased, and CVP, MP AP, PCWP were increased. In Pyengpaetang(50mg) group, mean aortic pressure was decreased and PCWP(pulmonary capillary wedge pressure) was decreased remarkably, while there was a significant increase in cardiac output. And there was improvement in $PaO_2$ and $PaCO_2$ without hemodynamic changes after applying 5cm $H_2O$ PEEP, but arterial blood gases$(PaO_2,\;PaCO_2)$ were improved, while cardiovascular effects were depressed after cm $H_2O$ PEEP. In Pyengpaetang(100mg) treated group, there was no significant hemodynamic change. But mean pulmonary arterial pressure was significantly increased, and cardiac output was decreased significantly after applying the more degree of PEEP. And blood gases were not changed significantly after applying the more degree of PEEP. The above results suggest that the effects of Pyengpaetang(50mg) group is superior to those of Pyengpaetang(100mg) group on the effects of hemodynamics and gas exchanges in acute lung injury in dogs. So we can conclude that lower degree PEEP 5cm $H_2O$ is more beneficial in Pyengpaetang(50mg) treated group.