• Water Engineering Research
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• v.6 no.2
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• pp.49-61
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• 2005

This paper presents the numerical study to examine characteristics of fluid flow and solute transport in a rough fracture subject to effective normal stresses. The aperture distribution is generated by using the self-affine fractal model. In order to represent a nonlinear relationship between the supported normal stress and the fracture aperture, we combine a simple mechanical model with the local flow model. The solute transport is simulated using the random walk particle following algorithm. Results of numerical simulations show that the flow is significantly affected by the geometry of aperture distribution varying with the effective normal stress level while it is slightly affected by the fractal dimension that determines the degree of the fracture surface roughness. However, solute transport is influenced by the effective normal stress as well as the fracture surface roughness.

• Proceedings of the KIEE Conference
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• 2004.11c
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• pp.322-324
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• 2004

Up to the present, digital replantation patients has appealed different symptoms due to blood circulatory failure. But, the level of blood circulatory failure has been evaluated only by clinical symptoms, or angiography. According to the cases of digit replantation is increasing, then objective evaluation methods of the level of blood circulation failure is needed other than patient's subjective symptoms and complaints. Although angiography, doppler, electromagnetic flowmeter, laser blood flowmeter, mechanical blood flowmeter has been used for the evaluation of the blood circulatory failure, the result was affected by time, place, surrounding temperature, patient's body temperature, and even emotion. Therefore, it is pointed out with lack of availability, feasibility and reproducibility. Thus, we compared digital blood flow of dominant hand to non dominant hand, and replanted fingers to opposite normal fingers from developed photo-plethysmography. The average digital blood flow showed no difference in normal digits each other, but, replanted digits showed average of 53% (9 - 100 %) compare to opposit normal digits. As it measure relative blood flow for circulatory failure of tissue such as fingers and toes more sensitively, reliably. In conclusion, it is expected that photo- plethysmography will be very useful for diagnosis, curative effect, prognosis of blood circulatory failure in digital replantation patient.

• Korea-Australia Rheology Journal
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• v.20 no.1
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• pp.15-26
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• 2008

It has been known that there is a viscoelastic instability in the channel flow past a cylinder at high Deborah (De) number. Some of our numerical simulations and a boundary layer analysis indicated that this instability is related to the shear flow in the gap between the cylinder and the channel walls in our previous work. The critical condition for instability initiation may be related to an inflection velocity profile generated by the normal stress near the cylinder surface. At high De, the elastic normal stress coupling with the streamline curvature is responsible for the shear instability, which has been recognized by the community. In this study, an instability criterion for the flow problem is proposed based on the analysis on the pressure gradient and some supporting numerical simulations. The critical De number for various model fluids is given. It increases with the geometrical aspect ratio h/R (half channel width/cylinder radius) and depends on a viscosity ratio ${\beta}$(polymer viscosity/total viscosity) of the model. A shear thinning first normal stress coefficient will delay the instability. An excellent agreement between the predicted critical Deborah number and reported experiments is obtained.

• Journal of Oral Medicine and Pain
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• v.25 no.2
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• pp.145-151
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• 2000

The present study was performed to investigate the relationship between the salivary flow rate and the interpretation results of salivary scan in the patients with dry mouth. Twenty-five patients with dry mouth who visited the Dept. of Oral Medicine & Oral Diagnosis, Seoul National University Dental Hospital, were included. The unstimulated whole salivary flow rate was determined by the spitting method and the stimulated whole salivary flow rate was measured with gum-base chewing. Salivary scan was performed after the infusion of $^{99m}technetium$ pertechnetate(Tc) and interpreted. The obtained results were as follows: 1. The unstimulated and stimulated whole salivary flow rate were significantly decreased compared to normal value, which reflected the extensive destruction of salivary gland function in the patients with dry mouth. 2. The unstimulated and stimulated whole salivary flow rate were decreased in the group with decreased function in salivary scan compared with the group with normal function in salivary scan. However, there was no statistical significance between groups. 3. The difference between the stimulated and unstimulated whole salivary flow rates was greater in the group with normal function in salivary scan compared with the group with decreased function in salivary scan. 4. There was significant positive correlation between the stimulated and unstimulated whole salivary flow rates. The level of correlation was higher in the group with decreased function in salivary scan than the group with normal function in salivary scan. Collectively, these data suggested that salivary scan had the limited value. The comprehensive evaluation including history taking, clinical examination, clinical laboratory as well as the measurement of salivary flow rate are need for patients with dry mouth.

• Nuclear Engineering and Technology
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• v.45 no.2
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• pp.257-264
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• 2013

In Canada Deuterium Uranium (CANDU)-type nuclear power plants, the reactor is composed of 380 fuel channels and refueling is performed on one or two channels per day. At the time of refueling, the fluid force of the cooling water inside the channel is exploited. New fuel added upstream of the fuel channel is moved downstream by the fluid force of the cooling water, and the used fuel is pushed out. Through this process, refueling is completed. Among the 380 fuel channels, outer rows 1 and 2 (called the FARE channel) make the process of using only the internal fluid force impossible because of the low flow rate of the channel cooling water. Therefore, a Flow Assist Ram Extension (FARE) tool, a refueling aid, is used to refuel these channels in order to compensate for the insufficient fluid force. The FARE tool causes flow resistance, thus allowing the fuel to be moved down with the flow of cooling water. Although the existing FARE tool can perform refueling in Korean plants, the coolant flow rate is reduced to below 80% of the normal flow for some time during refueling. A Flow rate below 80% of the normal flow cause low flow rate alarm signal in the plant operation. A flow rate below 80% of the normal flow may cause difficulties in the plant operation because of the increase in the coolant temperature of the channel. A new and improved FARE tool is needed to address the limitations of the existing FARE tool. In this study, we identified the cause of the low flow phenomena of the existing FARE tool. A new and improved FARE tool has been designed and manufactured. The improved FARE tool has been tested many times using laboratory test apparatus and was redesigned until satisfactory results were obtained. In order to confirm the performance of the improved FARE tool in a real plant, the final design FARE tool was tested at Wolsong Nuclear Power Plant Unit 2. The test was carried out successfully and the low flow rate alarm signal was eliminated during refueling. Several additional improved FARE tools have been manufactured. These improved FARE tools are currently being used for Korean CANDU plant refueling.

• 한국전산유체공학회:학술대회논문집
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• 2004.03a
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• pp.208-213
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• 2004

The HANARO, multi-purpose research reactor, 30 MWth open-tank-in- pool type, is under normal operation since it reached the initial critical in February 1995. The HANARO is planning to produce a fission moly-99 of radio isotopes, a mother nuclide of Tc-99m, a medical isotope and is under developing a target handling tool for loading and unloading it in a circular flow tube (OR-5). A guide tube is extended from the reactor core to the top of the reactor chimney for easily un/loading a target under the reactor normal operation. But active coolant through the core can be quickly raised up to the top of the chimney through the guide tube by jet flow. This paper is described an analytical analysis to calculate the hole size of a orifice inserted in the circular irradiation hole and to study the flow characteristics through the guide tube under reactor normal operation and loading the target. As results, the results show that the hole size of orifice was 31 mm of the inner diameter to suppress the guide tube jet flow and the coolant safely cooled the target of fission moly after inserting the orifice to the flow tube.

• Proceedings of the SAREK Conference
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• 2009.06a
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• pp.1123-1128
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• 2009

The refrigerant R-134a flow distributions are experimentally studied for a round header/ten flat tube test section simulating a brazed aluminum heat exchanger. Three different inlet orientations (parallel, normal, vertical) were investigated. Tests were conducted with downward flow for the mass flux from 70 to $130\;kg/m^2s$ and quality from 0.2 to 0.6. In the test section, tubes were flush-mounted with no protrusion into the header. It is shown that normal and vertical inlet yielded approximately similar flow distribution. At high mass fluxes or high qualities, however, slightly better results were obtained for normal inlet configuration. The flow distribution was worst for the parallel inlet configuration. Possible explanation is provided based on flow visualization results.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.1835-1840
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• 2004

The HANARO, a multi-purpose research reactor of 30 MWth, open-tank-in-pool type, has been under normal operation since its initial criticality in February, 1995. The HANARO is composed of inlet plenum, grid plate, core channel with flow tubes and chimney. The reactor core channel is located at about twelve meters (12 m) depth of the reactor pool and cooled by the upward flow that the coolant enters the lower inlet of the plenum,. rises up through the grid plate and the core channel and comes out from the outlet of chimney. A guide tube is extended from the reactor core to the top of the reactor chimney for easily un/loading a target under the reactor normal operation. But active coolant through the core can be quickly raised up to the top of the chimney through the guide tube by a jet flow. This paper describes an analytical analysis that is the study of the flow behavior through the guide tube under reactor normal operation and unloading the target. As results, it was conformed through the analysis results that the guide jet is suppressed under the top of the chimney after modifying the orifice diameter of 37.5 mm to 31 mm.

• Korea-Australia Rheology Journal
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• v.11 no.3
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• pp.225-232
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• 1999

This study presents 1-dimensional simple model for sheet casting or rectangular fiber spinning process. In order to achieve this goal, we introduce the concept of force flux balance at the die exit, which assigns for the extensional flow outside the die the initial condition containing the information of shear flow history inside the die. With the Leonov constitutive equation that predicts non-vanishing second normal stress difference in shear flow, we are able to describe the anisotropic swelling behavior of the extrudate at least qualitatively. In other words, the negative value of the second normal stress difference causes thickness swelling much higher than width of extrudate. This result implies the importance of choosing the rheological model in the analysis of polymer processing operations, since the constitutive equation with the vanishing second normal stress difference is shown to exhibit the characteristic of isotropic swelling, that is, the thickness swell ratio always equal to the ratio in width direction.

• Korean Journal of Veterinary Research
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• v.38 no.2
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• pp.413-418
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• 1998

Intracardiac velocities were determined and the wave-forms described for 4 flow areas of the normal canine heart following administration of chemical restraint drugs including xylazine HCl, ketamine HCl, and thiopental sodium using pulsed wave Doppler echocardiography. The result was that xylazine HCl and thiopental sodium reduced intracardiac flow velocities through mitral, tricuspid, aortic and pulmonary valves. It is also thought that precautions are required before using these drugs. Patterns of wave-forms had no changes between control and treatment groups. Doppler echocardiography allows the clinician to determine flow velocities across the different valves and within the various chambers of the heart. It is shown that establishing normal values and those related to chemical restraint administrations and knowing what influences them should allow the clinician to non-invasively diagnose a variety of pathological cardiac conditions.