• Clinical and Experimental Reproductive Medicine
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• v.10 no.1
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• pp.1-6
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• 1983

Women were used as their own controls in the comparison of presterilization and poststerilization menstrual patterns. Five parameters were studied: regularity of cycle length, duration and amount of flow and incidence of dysmenorrhea and intermenstrual bleeding. Three parameters in the electrocoagulation group (regularity of cycle length and duration and amount of flow) and one parameter in the tubal ring group (duration of flow) showed significant changes after sterilization. However, by controlling for the effect of previous contraceptive methods used, no significant menstrual pattern changes following sterilization were discerned in either technique group.

• Journal of the Korean Society for Precision Engineering
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• v.26 no.4
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• pp.55-63
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• 2009

This paper reports on the theoretical and experimental study of the pressure ripples in a pressure unbalanced type vane pump which have widespread use in industry. Because they can infinitely vary the volume of the fluid pumped in the system by a control. Pressure ripples occur due to the flow ripples induced by geometry of side plate, leakage flow, reverse flow from the outlet volume produced by pressure difference between pumping chamber and outlet volume when the pumping chamber connected with the outlet volume. In this paper, we measured the pressure variation of a pumping chamber, reaction force on a cam ring, the mathematical model for analyzing the pressure ripples which included vane detachment and fluid inertia effects in notch area has been presented, and was applied to predict the level and the wave form of the pressure ripples according to operating conditions.

• Tribology and Lubricants
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• v.24 no.6
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• pp.343-348
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• 2008

In this paper, a CFD (Computational fluid dynamics) code, FLUENT is adopted to investigate accurate flow characteristics for a slipper bearing which is used swash plate type hydraulic axial piston pump. Static pressure and velocity distributions, and velocity vectors are plotted for different film thickness and slipper rotational velocity. In recess region, there exists a doughnut shaped vortex ring. The static pressure distributions are non-uniform and the flow fields are highly asymmetrical under bearing rotation. Therefore the numerical method adopted in this paper can be use in design of hydrostatic components and further studies are required.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.11a
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• pp.417-420
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• 2005

This paper presents an analytical method to evaluate the dynamic behavior of the scroll compressor. Unbalanced forces and moments act on the compressor body because of the reaction forces acting on rotating components like the orbiting scroll, Oldham coupling ring, and the crank shaft. The vibration of the compressor is induced by the forces and the moments. In this paper, through modeling of the leakage flow, solving the forces from the equations of motion of the moving parts, the analysis of vibration of the compressor was performed. According to the operating condition, the variation of acceleration of the compressor body were calculated and compared.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2020.11a
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• pp.81-82
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• 2020

Cement paste is the basic material constituting concrete and the most basic data of workability. This study quantitatively evaluated the measured data using a ring flow and a rotary viscometer to estimate the flow of cement paste, and also evaluated the flow and rheology over time. For this, the current work has studied admixtures that affect the fluidity of cement paste. As a result of the experiment, since fluidity and plastic viscosity are inversely proportional to each other, more experimental studies are needed to obtain high fluidity and high viscosity at the same time.

• Journal of ILASS-Korea
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• v.29 no.1
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• pp.38-44
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• 2024

This study investigates the flow characteristics of propane-air premixed flames on AC electric field using the Schlieren method. A voltage was applied to the ring electrode and the burner was grounded to form an electric field, and the applied voltage was fixed at 16 kV (V_pp). Results show that under the application of AC electric fields, flow around the flame oscillated only at frequencies below 50 Hz, and no oscillation was observed above this frequency range. Flame height oscillated with frequency in the range of 25 to 300 Hz, with frequency doubling observed in the range of 25 to 150 Hz. The flammability limit increased with frequency up to 250 Hz, but in the high-frequency range above 250 Hz, the flammability limit did not increased and converged.

• Journal of the Korean Society for Marine Environment & Energy
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• v.20 no.2
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• pp.84-90
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• 2017

In this research, a three-dimensional Computational Fluid Dynamics(CFD), scour characteristics around monopile was grasped and the effect of circular ring type scour protection on reducing protection was assessed. When Torsethaugen(1975) found that the scour area and its depth were coincided quantitatively On the ground of previous findings, after scour was assessed in terms of sea current velocity, we also found that the tendency of maximum scour depth and its width were increased as the sea current velocity was increased. The experiments were performed by attaching ring-circular typed scour protection under the bottom in order to reducing scour around the constructs of monopile type and showed reduced scour approximately by 68.5%. In addition, there were reduction of downward flow and bottom velocities, suggesting that scour protection reduce the effect of downward flow on scour.

• The Journal of the Petrological Society of Korea
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• v.7 no.3
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• pp.147-160
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• 1998

The Samrangjin Caldera, a trapdoor-type, formed by the voluminous eruption of the silicic ash-flows of the Samrangjin Tuff which is above 630m thick at the northern inside of the caldera and thinnerly 80m at the southern inside. The caldera volcanism eviscerated the magma chamber by a series of explosive eruptions during which silicic magma was ejected to form the Samrangjin Tuff. The explosive eruptions began with phreatoplinian eruption, progressed through small plinian eruption and transmitted with ash-flow eruption. During the ash-flow eruption, contemporaneous collapse of the roof of the chamber resulted in the formation of the Samrangjin caldera, a subcircular depression subsiding above 550m deep. During postcaldera volcanism after the collapse, flow-banded rhyolite was emplaced as cental plug along the central vent and ring dikes along the caldera margins. Subsequently rhyodacite porphyry and dacite porphyry were emplaced along the inner side of the ring dike. After their emplacement, residual magma was emplaced as a hornblende biotite granite stock into the southwestern caldera margin. In the northeastern part, the eastern dikes were cut final intrusions of granodioritic to granitic composition along the fault zone of $^{\circ}$W trend.

• Economic and Environmental Geology
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• v.48 no.6
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• pp.501-508
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• 2015

The purpose of this study is to provide an inquiry into paleovegetation (paleoenvironment), eruption age and inferred emplacement temperature of pyroclastic deposit using charcoal occurred in the Quaternary Nari Caldera, Ulleung Island. In order to obtain the data, we carried out species identification and tree-ring analysis, radiocarbon dating for the charcoal. This sample was collected from pumiceous deposit in lowermost member(Member N-5) of the Nari Tephra Formation, which corresponds to the wood branch that has well preserved the tree-ring structure. Speciation and outermost tree-ring of wood reveal Picea spp. and $263+{\alpha}$ years. The calibrated ages from the center(pith) to the outermost tree-ring are $20,260{\pm}230$, $19,995{\pm}245$, and $19,975{\pm}265cal\;BP$, respectively, which are accordant with the tree-ring position. The youngest age, <19,710 cal BP would have implications for the eruptive age of Member N-5. Our results indicate that Picea spp. is the paleovegetation representing that Nari Caldera was under cold and wet climate conditions during the late Pleistocene. Based on the silky luster, brittleness, color, and streak of charcoal, etc., the lowest emplacement temperatures of pyroclastic flow are interpreted to have been at least as high as $350{\sim}500^{\circ}C$.

• Journal of the Korean Geotechnical Society
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• v.30 no.7
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• pp.5-15
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• 2014

Abandoned mine deposits are exposed to various physico-chemical geo-environmental hazards and disasters, such as acid mine drainage, water contamination, erosion, and landslides. This paper presents the ring shear characteristics of waste materials. The ring shear box with a rotatable O-ring was used in this study. Three tests were performed: (i) Shear stress-time relationship for given normal stress and shear speed, (ii) shear stress as a function of shear speed, and (iii) shear stress as a function of normal stress. For a given normal stress (50 kPa) and speed (0.1 mm/sec), the materials tested exhibit a strain softening behavior, regardless of drainage condition. The peak and residual shear stresses were determined for each normal stress and shear speed. The shear stress was measured when shear speed is equal to 0.01, 0.1, 1, 10, 50, 100 mm/sec or when normal stress is equal to 20, 40, 60, 80, 100, 150 kPa. From the test results, we found that the shear stress increases with increasing shear speed. The shear stress also increases with increasing normal stress. However, different types of shearing mode were observed in drained and undrained conditions. Under drained condition, particle crushing was observed from the shearing zone to the bottom of lower ring. Under undrained condition, particle crushing was observed only at the shearing zone, which has approximately 1 cm thick. It means that a significant high shear speed under undrained condition can result in increased landslide hazard.