• Proceedings of the KSME Conference
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• 2007.05b
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• pp.2108-2112
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• 2007

The air and water flow distribution are experimentally studied for a round header-ten microchannel tube configuration. Three different inlet orientations (parallel, side, normal) were investigated. Tests were conducted with downward flow configuration for the mass flux from 70 to 130 kg/$m^2s$, quality from 0.2 to 0.6, non-dimensional protrusion depth (h/D) from 0.0 to 0.5. It is shown that, for almost all the test conditions, normal inlet yielded the best flow distribution, followed by side and parallel inlet. Possible reasoning is provided using flow visualization results.

• Journal of Biomedical Engineering Research
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• v.12 no.1
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• pp.23-28
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• 1991

In this study electrical impedance plethysmograph was developed and each ten digital blood flow was measured for eight nomal males and a patient tvith digital arterial reconstruction surgery. Blood flow of the digit with surgery was approximately fourty percent compared to that of the other normal digit. For the normal subjects, right - handed subjects generally have larger blood flow in right fingers than that in left fingers while it was reverse for the left - handed subjects. The relative average magnitude of the digltal blood flow Is the third, first, second, fourth, and fifth digit in descending order for the left and rich hand, respectively. Blood flow of the fifth digit for all subjec!s except one was the smallest among the five digits.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.33 no.2
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• pp.124-132
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• 2009

Experiments have been performed to investigate fluid-elastic instability of tube bundles, subjected to twophase cross flow. Fluid-elastic is the most important vibration excitation mechanism for heat exchanger tube bundles subjected to the cross flow. The test section consists of cantilevered flexible cylinder(s) and rigid cylinders of normal square array. From a practical design point of view, fluid-elastic instability may be expressed simply in terms of dimensionless flow velocity and dimensionless mass-damping parameter. For dynamic instability of cylinder rows, added mass, damping and the threshold flow velocity are evaluated. The Fluid-elastic instability coefficient is calculated and then compared to existing results given for tube bundles in normal square array.

• Journal of Ship and Ocean Technology
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• v.9 no.4
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• pp.1-10
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• 2005

The effect of buoyancy orientation on turbulent channel flow has been investigated using DNS (direct numerical simulation). Grashof number is kept at 9.6 $\times 10^{5}$ while changing the orientation of the buoyancy vector to be parallel or perpendicular to the channel walls. Four study cases can be distinguished during this research namely; streamwise, wall-normal unstable stratification, wall-normal stable stratification and spanwise oriented buoyancy. The driving mean pressure gradient used in all cases is adjusted to keep mass flow rate constant while friction Reynolds number is around 150. At this Grashof number, the skin friction shows decrement in the unstable and stable stratification and increment in the other two cases. Analyses of the changes of flow structure for the four cases are presented highlighting on the mean quantities and second order statistics.

• The Journal of the Korea Contents Association
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• v.20 no.6
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• pp.439-444
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• 2020

The purpose of this study is to seek an alternative method to prevent the contamination of normal saline caused by the back-flow of Gadolinium Based Contrast Agent(GBCA) by the use of auto-injector for dynamic MRI. The research method is to manufacture the non-return valve as an alternative to the existing, and to examine the usefulness of the normal saline by dividing the state of normal saline into three groups. The signal intensity were compared. As a result, there was no statistically significant difference between normal saline before injection of group 1 and group 3 non-return valve (p> 0.05). It is analyzed that the self-produced non-return valve completely blocked the GBCA back to normal saline when the GBCA was injected. In conclusion, the application of the non-return valve presented in this study for dynamic MRI imaging using the auto injector can prevent normal saline contamination due to GBCA back-flow.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.2 no.1
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• pp.13-22
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• 2004

This study presents the thermal analyses of a spent fuel dry storage cask under normal and off-normal conditions. The environmental temperature is assumed to be 15 $^{\circ}C$ under the normal condition. The off-normal condition has an environmental temperature of 38 $^{\circ}C$. An additional off-normal condition is considered as a partial blockage of the air inlet ducts. Two of the four air inlet ducts are assumed to be completely blocked. The significant thermal design feature of the storage cask is the air flow path used to remove the decay heat from the spent fuel. Natural circulation of the air inside the cask allows the concrete and fuel cladding temperatures to be maintained below the allowable values. The finite volume computational fluid dynamics code FLUENT was used for the thermal analysis. The maximum temperatures of the fuel rod and concrete overpack were lower than the allowable values under the normal and off-normal conditions.

• The Journal of Korean Medicine Ophthalmology and Otolaryngology and Dermatology
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• v.11 no.1
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• pp.300-318
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• 1998

Background : The vasoreactivity of cerebral artery is currently the subject of increasing interest. Transcranial Doppler Sonography(TCD) is an accurate method of monitoring the blood flow velocities of the cerebral artery. We wished to assess the vasoreactivity between age-matched normal and cerebral infarction group. Method : We performed TCD findings in 40 normals and 20 cb-inf. subjects who arrived at hospital during 48 hours after attack. The former were devided into twenties normal group and fifties normal group. Result : 1. Fibrinogen levels showed significant changes between age-matched normal and cb-inf. group. 2. $V^{MEAN}$ of the both side Carotid Siphon during rest state increased significantly in cb-inf. group as compared with the age-matched normal group. 3. $V^{MEAN}and\;V^{MAX}$ of the both side carotid siphon during breath-hold state increased significantly in cb-inf. group as compared with the age-matched normal group. 4. Vasoreactivity of cerebral artery increased significantly in cb-inf. group as compared with the age-matched normal group. 5. $V^{MEAN}and\;V^{MAX}$ of the both side Radial artery during heat-stimuration state increased significantly in cb-inf. group as compared with the age-matched normal group. 6. Vasoreactivity of Radial artery increased significantly in cb-inf. group as compared with the age-matched normal group.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.22 no.9
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• pp.1229-1237
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• 1998

Experiments of shock-wave/turbulent boundary layer interaction were conducted by using a supersonic wind tunnel. Nominal Mach number was varied in the range of 1.6 to 3.0 by means of different nozzles. The objective of the present study is to investigate the effects of boundary layer suction on normal shock-wave oscillations caused by shock wave/boundary layer interaction in a straight duct. Two-dimensional slits were installed on the top and bottom walls of the duct to bleed turbulent boundary layer flows. The bleed flows were measured by an orifice. The ratio of the bleed mass flow to main mass flow was controlled below the range of 11 per cent. Time-mean and fluctuating wall pressures were measured, and Schlieren optical observations were made to investigate time-mean flow field. Time variations in the shock wave displacement were obtained by a high-speed camera system. The results show that boundary layer suction by slits considerably reduce shock-wave oscillations. For the design Mach number of 2.3, the maximum amplitude of the oscillating shock-wave reduces by about 75% compared with the case of no slit for boundary layer suction.

• Nuclear Engineering and Technology
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• v.37 no.6
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• pp.575-586
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• 2005

In a CANDU (CANada Deuterium Uranium) reactor, fuel channel integrity depends on the coolability of the moderator as an ultimate heat sink under transient conditions such as a loss of coolant accident (LOCA) with coincident loss of emergency core cooling (LOECC), as well as normal operating conditions. This study presents assessments of moderator thermal-hydraulic characteristics in the normal operating conditions and one transient condition for CANDU-6 reactors, using a general purpose three-dimensional computational fluid dynamics code. First, an optimized calculation scheme is obtained by many-sided comparisons of the predicted results with the related experimental data, and by evaluating the fluid flow and temperature distributions. Then, using the optimized scheme, analyses of real CANDU-6 in normal operating conditions and the transition condition have been performed. The present model successfully predicted the experimental results and also reasonably assessed the thermal-hydraulic characteristics of a real CANDU-6 with 380 fuel channels. A flow regime map with major parameters representing the flow pattern inside a calandria vessel has also proposed to be used as operational and/or regulatory guidelines.

• Computers and Concrete
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• v.19 no.1
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• pp.99-110
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• 2017

In this paper, the effect of normal load on the failure mechanism of echelon joint has been studied using PFC2D. In the first step, calibration of PFC was undertaken with respect to the data obtained from experimental laboratory tests. Then, six different models consisting various echelon joint were prepared and tested under two low and high normal loads. Furthermore, validation of the simulated models were cross checked with the results of direct shear tests performed on non-persistent jointed physical models. The simulations demonstrated that failure patterns were mostly influenced by normal loading, while the shear strength was linked to failure mechanism. When ligament angle is less than $90^{\circ}$, the stable crack growth length is increased by increasing the normal loading. In this condition, fish eyes failure pattern occur in rock bridge. With higher ligament angles, the rock bridge was broken under high normal loading. Applying higher normal loading increases the number of fracture sets while dilation angle and mean orientations of fracture sets with respect to ligament direction will be decreased.