• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.4
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• pp.1031-1038
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• 1994

Characteristics of pulsatile flow and heat transfer have been studied numerically in the constant heat flux curved tube with periodic pressure gradient. As the Womersley number increases, the phase difference between the pressure gradient and the cross section averaged axial velocity becomes larger. In case of the Womersley number $\beta = 2$, when cross section averaged axial velocity reaches periodic state with time, the reverse and the natural flow coexist at phase angle, $\lambda = 1.44\pi$ and $\lambda =1.96\pi$. For all the Womersley numbers of present investigation, the time variation of wall temperature near inner wall is higher than that of near outer wall, independent of phase angle.

• 한국전산유체공학회:학술대회논문집
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• 2005.04a
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• pp.85-90
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• 2005

The heat transfer enhancement by pulsatile flow in plate heat exchanger has been investigated numerically in the present study. The numerical study was performed ill the range of the Strouhal number from 0.04 to 2 and the Reynolds number from 370 to 730. The results showed that the pulsatile flow produces resonating vortex shedding at the groove sharp edges and a strong transient vortex rotation within the grooved channels. As a result, the mixing between the trapped volume in the grooved cavity and the main stream was enhanced. Good agreements between the predictions and measured data are obtained for the optimum frequency of pulsation and corresponding heat transfer enhancement

• Korea-Australia Rheology Journal
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• v.20 no.4
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• pp.189-196
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• 2008

The pulsatile flow of blood through a stenosed artery under the influence of external periodic body acceleration is studied. The effect of non-Newtonian nature of blood in small blood vessels has been taken into account by modeling blood as a Casson fluid. The non-linear coupled equations governing the flow are solved using perturbation analysis assuming that the Womersley frequency parameter is small which is valid for physiological situations in small blood vessels. The effect of pulsatility, stenosis, body acceleration, yield stress of the fluid and pressure gradient on the yield plane locations, velocity distribution, flow rate, shear stress and frictional resistance are investigated. It is noticed that the effect of yield stress and stenosis is to reduce flow rate and increase flow resistance. The impact of body acceleration is to enhance the flow rate and reduces resistance to flow.

• Proceedings of the KOSOMBE Conference
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• v.1996 no.11
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• pp.281-285
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• 1996

Pulsatile swelling behaviors and their application to drug delivery system were studied by using interpenetrating polymer networks(IPN) hydrogels constructed with poly(vinyl alcohol) and poly(acrylic acid). The PVA/PAAc IPNs hydrogels were symthesized by UV irradiation tallowed by repetitive freezing and thawing method. These hydrogels showed pH and temperature sensitive swelling behaviors. From the release experiment, the release amount of model drug incorporated into these hydrogels showed pulsatile patterns. Permeability coefficients obtained by various solutes differed in response to changes of permeation conditions.

• Journal of Chest Surgery
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• v.38 no.2 s.247
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• pp.101-109
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• 2005

Background: In sudden cardiac arrest, the effective maintenance of coronary artery blood flow is of paramount importance for myocardial preservation as well as cardiac recovery and patient survival. The purpose of this study was to directly compare the effects of pulsatile and non-pulsatile circulation to coronary artery flow and myocardial preservation in cardiac arrest condition. Material and Method: A cardiopulmonary bypass circuit was constructed in a ventricular fibrillation model using fourteen Yorkshire swine weighing $25\~35$ kg each. The animals were randomly assigned to group I (n=7, non-pulsatile centrifugal pump) or group II (n=7, pulsatile T-PLS pump). Extra-corporeal circulation was maintained for two hours at a pump flow of 2 L/min. The left anterior descending coronary artery flow was measured with an ultrasonic coronary artery flow measurement system at baseline (before bypass) and at every 20 minutes after bypass. Serologic parameters were collected simultaneously at baseline, 1 hour, and 2 hours after bypass in the coronary sinus venous blood. The Mann-Whitney U test of STATISTICA 6.0 was used to determine intergroup significances using a p value of < 0.05. Result: The resistance index of the coronary artery was lower in group II and the difference was significant at 40 min, 80 min, 100 min and 120 min (p < 0.05). The mean velocity of the coronary artery was higher in group II throughout the study, and the difference was significant from 20 min after starting the pump (p < 0.05). The coronary artery blood flow was higher in group II throughout the study, and the difference was significant from 40 min to 120 min (p < 0.05) except at 80 min. Serologic parameters showed no differences between the groups at 1 hour and 2 hours after bypass in the coronary sinus blood. Conclusion: In cardiac arrest condition, pulsatile extracorporeal circulation provides more blood flow, higher flow velocity and less resistance to coronary artery than non-pulsatile circulation.

• Journal of Veterinary Clinics
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• v.23 no.3
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• pp.320-324
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• 2006

The purpose of the present study was to compare pulsatile type(Twin Pulse Life Support; TPLS) with rotary type hemodialyzer(AK95) in order to reduce the dialysis time and to improve dialysis effect. Three healthy dogs(about 30 kg BW) were used. Experimental renal failure was induced by the ligation of bilateral renal artery. A pair of catheters were implanted in jugular vein for dialysis. Daily investigated parameters included clinical signs such as vomiting, fecal appearance and activity, and also laboratory data such as PCV, TP, BUN and creatinine. Hemodialysis was started above 90 mg/100 ml BUN level and, laboratory data were measured every an hour for 4 hours. Heparin was administered 300 IU/Kg before dialysis and 150 IU/Kg via IV route every 90 minutes during dialysis. Clinical signs after induction renal failure were shown severe vomiting, anorexia, diarrhea, mucous feces, ataxia, dilated pupil and episcleral hyperemia. The average of BUN value decreased hourly $99{\pm}12.1,\;84{\pm}12.2,\;72{\pm}8.0,\;58{\pm}7.1,\;48{\pm}5.2,\;and\;39{\pm}3.2mg/100ml$ by hemodialysis. The average of creatinine value decreased $7.8{\pm}0.61,\;6.4{\pm}0.40,\;5.3{\pm}0.42,\;4.5{\pm}0.23,\;4.0{\pm}0.41,\;and\;3.4{\pm}0.42mg/100ml$ according to hemodialysis an hour. There are not significantly differences BUN, creatinine, PCV and TP values between pulsatile and rotary type hemodialysis. These results suggested that effects of hemodialysis with Pulsatile type(TPLS) are not significantly difference as compared with hemodialysis of rotary type(AK95). Further research is needed in order to estimate the influence of cardiovascular and pulmonary system in hemodialysis of pulsatile type.

• 한국전산유체공학회:학술대회논문집
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• 2006.05a
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• pp.412-412
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• 2006

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.1987-1992
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• 2004

Hemodynamics behavior of the blood flow is influenced by the presence of the arterial stenosis. If stenosis is present in an artery, normal blood flow is disturbed. In the present study, characteristics of steady and pulsatile flow of non-Newtonian fluid, the effects of stenosised geometry are analyzed by numerical simulation. One interesting point is that non-symmetric solutions were obtained at severity stenosis, although the stenosis and the boundary condition were all axisymmetric.

• Clinical and Experimental Reproductive Medicine
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• v.19 no.1
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• pp.81-85
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• 1992

The effects of pulsatile GnRH therapy have been studied for the treatment of different forms of hypogonadotropic hypogonadism, including idiopathic hypogonadotropic hypogonadism and hypogonadism developed as a result of treatment with combination of surgery and irradiation for pituitary or hypothalamic tumor. GnRH was administered subcutaneously in a dose of $10{\mu}g$ every 2 hours with the pulsatile infusion pump. With GnRH therapy, all patients improved secretion of LH, FSH and testosterone. Testicular volumes increased. Spermatogenesis was induced in 8 patients. Pulsatile GnRH therapy is an effective treatment for idiopathic hypogonadotropic hypogonadism and can have a role in hypogonadism previously treated with combination of surgery and irradiation for pituitary or hypothalamic tumor.

• Coupled systems mechanics
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• v.1 no.4
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• pp.361-379
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• 2012

This paper presents a fully coupled three-dimensional solver for the analysis of interaction between pulsatile flow and large deformation structure. A partitioned time marching algorithm is employed for the solution of the time dependent coupled discretised problem, enabling the use of highly developed, robust and well-tested solvers for each field. Conservative transfer of information at the fluid-structure interface is combined with an effective multi-predict-correct iterative scheme to enable implicit coupling of the interacting fields at each time increment. The three-dimensional unsteady incompressible fluid is solved using a powerful implicit time stepping technique and an ALE formulation for moving boundaries with second-order time accurate is used. A full spectrum of total variational diminishing (TVD) schemes in unstructured grids is allowed implementation for the advection terms and finite element shape functions are used to evaluate the solution and its variation within mesh elements. A finite element dynamic analysis of the highly deformable structure is carried out with a numerical strategy combining the implicit Newmark time integration algorithm with a Newton-Raphson second-order optimisation method. The proposed model is used to predict the wave flow fields of a particular flow-induced vibrational phenomenon, and comparison of the numerical results with available experimental data validates the methodology and assesses its accuracy. Another test case about three-dimensional biomedical model with pulsatile inflow is presented to benchmark the algorithm and to demonstrate the potential applications of this method.