• Journal of computational fluids engineering
• /
• v.12 no.4
• /
• pp.61-67
• /
• 2007

Numerical simulation of laminar flow over two spheres in a side-by-side arrangement is carried out to investigate the effect of the inter-sphere spacing on the flow characteristics. The Reynolds numbers considered are 100, 250, and 300, covering the steady axisymmetric, steady planar-symmetric, and unsteady planar-symmetric flows in the case of a single sphere. Results show that the drag and lift coefficients and wake structures are significantly modified depending on both the Reynolds number and the spacing between the spheres. At Re=100, the flow is steady planar-symmetric irrespective of the spacing, but it shows some variation according to the spacing at Re=250 and 300. That is, the flow maintains planar symmetry of the single-sphere wake at large spacings, while it loses the symmetry at small spacings due to the generation of new asymmetric vortical structures. It is also shown that the drag and lift coefficients generally increase with decreasing inter-sphere spacing because the high pressure region is formed near the gap between the spheres.

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

• The Journal of Internal Korean Medicine
• /
• v.21 no.1
• /
• pp.7-12
• /
• 2000

Objectives : This studies were performed to investigate the correlation between the treatment effects and the changes of the thermal differences at the pre and post-treatment by using the digital infrared computer thermographic imaging (D.I.T.I) to the irritable colon syndrome 30 patients. Methods : The extracts of the gwakhyangjunggisan were administerd to the patients by oral method three times per day during four weeks. we selected the Chung-Wan($CV_{12}$), Chunchu($S_{25}$). Hapkok($LI_4$), Naegwan($P_6$), Yongdo($H_4$) acupoints and treated the patients two times per week during four weeks. One week later, we investigated the changes of the pressure pain around left side Pokkyol($SP_{14}$), the symptoms. and the skin temperature changes on Pokkyol($SP_{14}$) and Kimun($LR_{14}$) around, by using the D.I.T.I. Results : In the correlation between the severity of the pressure pain around left side Pokkyol($SP_{14}$) and the thermal differences on Pokkyol($SP_{14}$) and Kimun($LR_{14}$) around, before the treatment, the more the pain was severe, the more the skin temperature was differential significantly. In the correlation between the severity of the symptoms and the thermal differences on Pokkyol($SP_{14}$) and Kimun($LR_{14}$) around, before the treatment, the more the symptom was severe, the more the skin temperature was differential significantly. In the changes of the pressure pain around left side of Pokkyol($SP_{14}$), the improved were significantly higher than the unimproved. In the changes of the symptoms, the improved were significantly higher than the unimproved. In the correlation between the changes of the pressure pain around left side Pokkyol($SP_{14}$) and the changes of the thermal differences at the pre and post- treatment, the more the pain was improved, the more the thermal change was widened significantly. In the correlation between the changes of the symptoms and the changes of thermal differences at the pre and post-treatment, the more the symptom was improved. the more the thermal change was widened significantly. Conclusions : Above the results, the treatments was effective and the digital infrared computer thermographic imaging (D.I.T.I) was useful to prove the improvements of the pressure pain and the symptom with the irritable bowel syndrome patients.

• Journal of Adhesion and Interface
• /
• v.10 no.3
• /
• pp.134-140
• /
• 2009

The acrylic copolymers with variation in side chain were synthesized based on molecular design. Wettability and adhesion properties on the wafer surface were investigated for these acrylic copolymer pressure sensitive adhesives. Three-dimensional networks of linear acrylic copolymers were produced with epoxy-type Tetra-DX cross-linking agent. The effect of cross-linking on adhesion characteristics was investigated. The side chain of acrylic copolymer played more important role in wettability than the interfacial interaction. As the degree of cross-linking increased, both probe tack and peel strength decreased. Also, heat resistance measured by SAFT increased with cross-linking; however, it showed the deterioration when excess cross-linking agent was added.

• Journal of IKEEE
• /
• v.11 no.3
• /
• pp.108-116
• /
• 2007

This paper proposed an analyzable parameter and its analytic method to provide more accurate information than currently employed 4 channels system which uses pulse wave velocity (PWV) information of the volume pulse wave measured from 4 arterial channels for the characterization of arterial vessel. In order to verify the volume pulse waves on 4 sites were simultaneously acquired subjects aged from 12 to 81 years old. and the proposed parameters were extracted from time (UT) was then compared with blood pressure. Then, the regression analyses were done relationships among the proposed parameter and others, such as aging, pulse transit time pressure (BP). The followings are the results of linear regression analysis of the proposed parameter for total 50 normal subjects. We selected any two subjects (58 years and 27 years) and measured PPG (photoplethysmogram) and BP of before and after exercise. The coefficient of correlations between BP and UT observed was -0.928 for 50 years subject, and -0.922 for 20 years subject. For total 50 normal subjects, in case of correlation between the pulse transit time and BP, the result showed -0.170 on left side and -0.233 on right side, and the coefficient value of correlation between the pulse transit time and UT was -0.607 on left side and -0.510 on right side. UI is strongly correlated with the pulse transit time than BP. Hence, we believe that the proposed parameter is related with the index of arterial stiffness.

• Archives of Reconstructive Microsurgery
• /
• v.1 no.1
• /
• pp.51-55
• /
• 1992

Problems of composite tissue transfer commonly arise when a single indispensable recipient vessel receives the graft vssel, and the graft vessel must be sutured in end-to-side fashion so as not todisturb the vascularity of the recipient vessel. The triangular flap in the recipient vessel wall gives an intact endothelial surface when the flow of blood stream is presented and may reduce the chance of anastomosis. We selected mature Wistar rats weighing over 450 grams to compare the conventional longitudinal slit from the triangular flap in the recipient carotid artery over bloood pressure and blood flow when the donor carotid artery was anastomosed in end-to-side fashion. In 30 minutes after anastomosis, maximum blood pressure measured in the donor carotid arterial side when the recipient arterial wall was fasioned with the longitudinal slit was recorded 114 mmHg and with the triangular flap 100mmHg. Minimum blood pressure with the longitudinal slit was 98mmHg and with the triangular flap 88mmHg. The amount of blood collected for 30 seconds in the conventional longitudinal slit was 1.18mg and in the triangular flap 0.78mg. Histology study in 30 minutes, the conventional longitudinal slit demonstrated the more hemorrhagic features around the suture material compared to that of the triangular. flap and, in the 7th day, the conventional longitudinal slit demonstrated the more prominent granulomatous reactions and vascular proliferations around the suture material compared to that of the triangular flap.

• Journal of the Korean Society of Physical Medicine
• /
• v.9 no.3
• /
• pp.315-324
• /
• 2014

PURPOSE: This study aimed to determine the correlation of weight bearing ability at the affected side with balance and gait abilities for the development of pressure biofeedback based equipment to stroke patients. METHODS: This study included 35 patients with stroke patient. The tests were conducted to determine the weight bearing ratio while pushing a step forward the affected side, static balance ability using the total length of COP(Center of pressure), sway velocity of COP, COP velocity at the X and Y axis. Functional reaching test (FRT), berg balance scale (BBS) were used to assess the dynamic balance ability and timed up and go test (TUG), 10m walk test (10mWT) were used assess the gait ability respectively. In order to determine the correlation between measured variables, bivariate correlation analysis was conducted. RESULTS: A significant correlation of the weight bearing ratio were shown with COP total length and velocity(r=-.34), Y-axis velocity(r=-.39), FRT(r=.42), BBS(r=.54), TUG (r=-.39), and 10m walking test (r=-.42). CONCLUSION: This study result showed that as patients with stroke had more weight bearing ratio at the affected side, not only their static and dynamic balance abilities increased more but also functional gait ability improved more. These results mean that, to improve stroke patients' static, dynamic balance ability and gait ability, weight bearing training with the affected side foot placed one step forward necessary for gaits are important.

• Wind and Structures
• /
• v.23 no.5
• /
• pp.465-483
• /
• 2016

This study aims to enhance the understanding of the surface pressure distribution around rectangular bodies, by considering aspects such as the suction pressure at the leading edge on the top and side faces when the body aspect ratio and wind direction are changed. We carried out wind tunnel measurements and numerical simulations of flow around a series of rectangular bodies (a cube and two rectangular bodies) that were placed in a deep turbulent boundary layer. Based on a modern numerical platform, the Navier-Stokes equations with the typical two-equation model (i.e., the standard $k-{\varepsilon}$ model) were solved, and the results were compared with the wind tunnel measurement data. Regarding the turbulence model, the results of the $k-{\varepsilon}$ model are in overall agreement with the experimental results, including the existing data. However, because of the blockage effects in the computational domain, the pressure recovery region is underpredicted compared to the experimental data. In addition, the $k-{\varepsilon}$ model sometimes will fail to capture the exact flow features. The primary emphasis in this study is on the flow characteristics around rectangular bodies with various aspect ratios and approaching wind directions. The aspect ratio and wind direction influence the type of wake that is generated and ultimately the structural loading and pressure, and in particular, the structural excitation. The results show that the surface pressure variation is highly dependent upon the approaching wind direction, especially on the top and side faces of the cube. In addition, the transverse width has a substantial effect on the variations in surface pressure around the bodies, while the longitudinal length has less influence compared to the transverse width.

• Journal of the Korean Geotechnical Society
• /
• v.16 no.1
• /
• pp.243-250
• /
• 2000

The mechanical behavior of the underground box culvert constructed by the open cut method depends mainly on the earth pressure acting on it. In this study, the earth pressure on the underground box culverts constructed by the open cut method during and after the construction sequence was numerically analysed by using FLAC. The results are compared with those of the Marston-Spangler's theory, silo theory, and the model tests. The results showed that the vertical earth pressure on the upper slab of the box structure was not uniform. It was as large as the overburden in the middle part of the slab but was smaller or larger than that at its end part depending on the slope of the excavation, the depth of the cover, and the width of the side refill. The horizontal earth pressure on the side wail was much smaller than the earth pressure at rest and grew nonlinearly with the depth.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.22 no.1
• /
• pp.12-24
• /
• 1998

The paper presents the mechanism of secondary flows and the associated total pressure losses occurring in turbine cascades with turning angle of about 127 and 77 degree. Velocity and pressure measurements are taken in seven traverse planes through the cascade passage using a prism type five hole probe. Oil-film flow visualization is also conducted on blade and endwall surfaces. The characteristics of the limiting streamlines show that the three dimensional separation is an important flow feature of endwall and blade surfaces. The larger turning results in much stronger contribution of the secondary flows to the loss developing mechanism. A large part of the endwall loss region at downstream pressure side is found to be very thin when compared to that of the cascade inlet and suction side endwall. Evolution of overall loss starts quite early within the cascade and the rate of the loss growth is much larger in the blade of large turning angle than in the blade of small turning angle.