• Molecules and Cells
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• v.37 no.6
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• pp.435-440
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• 2014

Hemodynamic shear stress, the frictional force acting on vascular endothelial cells, is crucial for endothelial homeostasis under normal physiological conditions. When discussing blood flow effects on various forms of endothelial (dys)function, one considers two flow patterns: steady laminar flow and disturbed flow because endothelial cells respond differently to these flow types both in vivo and in vitro. Laminar flow which exerts steady laminar shear stress is atheroprotective while disturbed flow creates an atheroprone environment. Emerging evidence has provided new insights into the cellular mechanisms of flowdependent regulation of vascular function that leads to cardiovascular events such as atherosclerosis, atherothrombosis, and myocardial infarction. In order to study effects of shear stress and different types of flow, various models have been used. In this review, we will summarize our current views on how disturbed flow-mediated signaling pathways are involved in the development of atherosclerosis.

• Journal of Korean Neurosurgical Society
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• v.39 no.1
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• pp.20-25
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• 2006

Objective : The authors analyze prospectively the result of transcranial doppler[TCD] in normal pressure hydrocephalus and compared its cerebral blood flow parameters to radionuclide cerebrospinal fluid[CSF] flow study, postoperative brain computed tomography[CT] findings and clinical outcome, and studied the relationship between cerebral hemodynamics and clinical performance. Methods : Twenty five patients with hydrocephalus undertook pre- and post-operative TCD but only preoperative CSF flow study was performed. Mean flow velocity[Vm], pulsatility index[PI] and resistance index[RI] were assessed through TCD and changes in ventricle size and cortical gyral atrophy were checked through brain CT. Results : Postoperative hydrocephalus showed an increase in Vm[ACA P=0.037, MCA P=0.034], decrease in PI[ACA P=0.019, MCA P=0.017] and decrease in RI [ACA P=0.017, MCA P=0.021] compared to preoperative TCD parameters in the postoperative improvement group. In the postoperative improvement group, postoperative TCD parameters correlated with CSF flow study grade [Vm : $R^2=-0.75$, PI : $R^2=0.86$, RI : $R^2=0.78$] and ventriculocranial ratio change correlated with PI change [$R^2=0.73$]. The convexity gyral atrophy and initial TCD parameters showed close relationship to outcome. Conclusion : PI and RI can be used as an indicator of post operative prognosis, and with the addition of CSF flow study values, can also be used as a tool to predict pre-op and post-op patient status and successful shunt surgery.

• Bulletin of the Korean Mathematical Society
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• v.48 no.2
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• pp.427-444
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• 2011

In this paper we give some non-existence theorems for Hopf hypersurfaces in the complex two-plane Grassmannian $G_2(\mathbb{C}^{m+2})$ with Lie parallel normal Jacobi operator $\bar{R}_N$ and totally geodesic D and $D^{\bot}$ components of the Reeb flow.

• International Journal of Fluid Machinery and Systems
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• v.6 no.2
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• pp.94-104
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• 2013

This paper describes the design to increase the blade loading factor of a low speed axial flow fan from normal 0.42 to highly loaded 0.55. A three-dimensional viscous solver is used to model the flows in the highly-loaded and normal loaded stages over its operation range. At the design point operation the static pressure rise can be increased by 20 percent with a deficit of efficiency by 0.3 percent. In the highly loaded fan stage, the rotor hub flow stalls, and separation vortex extends over the rotor hub region. The backflow, which occurs along the stator hub-suction surface, changes the exit flow from the prescribed axial direction. Results in this paper confirm that the limitation of the two dimensional diffusion does not affect primarily on the fan's performance. Highly loaded fan may have actually better performance than its two dimensional design. Three dimensional designing approaches may lead to better highly loaded fan with controlled rotor hub stall.

• Journal of the Korean Society of Laryngology, Phoniatrics and Logopedics
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• v.8 no.1
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• pp.27-32
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• 1997

Recently, many people suffering from voice color change visit otolaryngologist. There is no specific data which can be evaluated objectively for voice color change in korean. In aerodynamic study, maximum phonation time, mean air flow rate, phonatory flow volume and subglottal pressure were tested by using Aerophone II voice function analyzer in korean. 112 male and 122 female aged from 10 to 69 years were randomly selected. Maximum phonation time was 20.8${\pm}$6.4sec in male and 17.2${\pm}$4.1sec in female. Mean air flow rate was 167.1${\pm}$61.4ml/sec. in male and 129.6${\pm}$49.3ml/sec in female. Phonatory flow volume was 3184.5${\pm}$646.0ml in male and 2122.1${\pm}$670.5ml in female. Subglottal pressure was 4.1${\pm}$1.8 cmH2O in male and 3.5${\pm}$1.4cm $H_2O$ in female. There was no statistically significant difference among age groups in all above results.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.05a
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• pp.681-687
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• 2001

Two-phase cross-flow exists in many shell-tube heat exchangers such as steam generators, condensers and reboilers. An understanding of flow-induced vibration excitation mechanism is necessary to avoid problems due to excessive tube vibration. This paper presents the results of a series of experiments done on tube bundles of different geometries subjected to two-phase cross-flow simulated by air-water mixtures. Normal(30$^{\circ}$) and rotated (60$^{\circ}$)triangular, and normal(90$^{\circ}$) and rotated (45$^{\circ}$) square tube bundle configurations of pitch-to-diameter ratio of 1.2 to 1.5 were tested over a range of mass fluxes from 0 to 1,000kg/$m^2$ㆍ s and void fraction from 0 to 100%. The effects of tube bundle geometry on vibration excitation mechanism such as fluidelastic instability and random turbulence, and on dynamic parameters such as damping and hydrodynamic mass are discussed. A lower pitch-to-diameter results in a higher hydrodynamic mass. The effect of tube bundle configurations on damping and random turbulence excitation is minor. The effect of pitch-to-diameter on the fluidelastic instability, however, is significant.

• The Korean Journal of Nuclear Medicine
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• v.17 no.2
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• pp.19-24
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• 1983

The purpose of this study was to develop a method by which the sensitivity of radionuclide liver imaging for detection of liver cirrhosis could be enhanced. Dynamic blood flow scan were performed 21 cases of liver cirrhosis patients by using computerized gamma camera named arterialization index. The results were as follows: 1) Arterialization index were higher in liver cirrhosis comparing to normal value 0.33 and its mean is 2. 02. 2) Comparing to static liver scan, higher sensitivity in dynamic hepatic blood flow scan for detection of liver cirrhosis. Sensitivity for detection of liver cirrhosis is over 90%. 3) There are no correlation between arterialization index and serum albumin level. The use of hepatic dynamic blood flow scan proved effective in detection of liver cirrhosis. However, the test may be used as an aid in distinguishing between normal and pathologic livers.

• Asian-Australasian Journal of Animal Sciences
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• v.5 no.1
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• pp.81-90
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• 1992

Five buffaloes kept in normal ambient temperature ($30^{\circ}C$) showed no significant changes in the heart rate, respiratory rate, packed cell volume, plasma constituents and renal hemodymics during intravenous infusion of urea for 4 h. The rate of urine flow, fractional urea excretion, urinary potassium excretion and osmolar clearance significantly decreased while the renal urea reabsorption markedly increased during urea infusion. The decrease of fractional potassium excretion was concomitant with the reduction of the rate of urine flow and urine pH. In animals exposed to heat ($40^{\circ}C$) the rectal temperature heart rate and respiratory rate significantly increased while no significant changes in GFR and ERPF were observed. An intravenous infusion of urea in heat exposed animals caused the reduction of the rate of urine flow with no changes in renal urea reabsorption, urine pH and fractional electrolyte excretions. During heat exposure, there were marked increases in concentrations of total plasma protein and plasma creatinine whereas plasma inorganic phosphorus concentration significantly decreased. It is concluded that an increase in renal urea reabsorption during urea infusion in buffaloes kept in normal ambient temperature depends on the rate of urine flow which affect by an osmotic diuretic effect of electrolytes. The limitation of renal urea reabsorption in heat stressed animals would be attributed to an increases in either plasma pool size of nitrogenous substance or body metabolism.

• The Korean Journal of Food And Nutrition
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• v.14 no.5
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• pp.397-404
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• 2001

The purpose of this study was to investigate effects of inner skin of chestnut on the activation of a living body's function (regional cerebral blood flow and mean arterial blood pressure in Sprague-Dawley rats, proliferation of thymocytes in normal mice and L1210 cells transplanted mice) . We used inner skin of chestnut extract(Sample A : inner skin of chestnut-panbroiled after driedextract (100$\^{C}$ ), Sample B , inner skin of chestnut-panbroiled-extract(100$\^{C}$ ) , Sample C : inner skin of chestnut -panbroiled after dried-extract(80$\^{C}$ ), Sample D : inner skin of chestnut-panbroiled-extract(80$\^{C}$)} Regional cerebral blood flow(rCBF) and Mean arterial blood pressure(MABP) were tested using Leser -Doppler Flowmetry(LDF), and the proliferation of thymcytes was tested using a colorimetric tetrazoliun assay ( MTT assay) The experimental results as follows 1. rCBF was significantly increased by Sample C in a dose-dependent manner. 2. MABP was not changed by Sample C in a 0.1mg/kg∼10.0mg/kg treated group. 3. Proliferation of thymocytes was not changed by Sample C in normal mice. 4. Proliferation of thymocytes was significantly accelerated by Sample C in L1210 cells transplanted mice.

• Journal of The Korean Society of Agricultural Engineers
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• v.60 no.4
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• pp.83-91
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• 2018

Land reclamation, coastal construction, coastline extension and port construction, all of which involve dredging, are increasingly required to meet the growing economic and societal demands in the coastal zone. During the land reclamation, a portion of landfills are lost from the desired location due to a variety of causes, and therefore prediction of sediment transport is very important for economical and efficient land reclamation management. In this study, laboratory disposal tests were performed using an open channel, and suspended sediment transport was analyzed according to flow velocity and grain size. The relationships between the average and standard deviation of the deposition distance and the flow velocity were almost linear, and the relationships between the average and standard deviation of deposition distance and the grain size were found to have high non-linearity in the form of power law. The deposition distribution of sediments was demonstrated to have log-normal distributions regardless of the flow velocity. Based on the experimental results, modeling of suspended sediment transport was performed using deep neural network, one of deep learning techniques, and the deposition distribution was reproduced through log-normal distribution.