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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Journal of Biomedical Engineering Research
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Journal DOI :
The Korea Society of Medical and Biological Engineering
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Volume & Issues
Volume 13, Issue 4 - Dec 1992
Volume 13, Issue 3 - Sep 1992
Volume 13, Issue 2 - Jun 1992
Volume 13, Issue 1 - Mar 1992
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Numerical Simulation of Flow in a Total Artificial Heart
Journal of Biomedical Engineering Research, volume 13, issue 2, 1992, Pages 87~96
In thIns paper, a numerical simulation of steady laminar and turbulent flow in a two dimensional model for the total artificial heart is'presented. A trlleaflet polyurethane valve was simulated at the outflow orifice while the Inflow orifice had a trileaflet or a flap valve. The finite analytic numerical method was employed to obtain solutions to the governing equations in the Cartesian coordinates. The closure for turbulence model was achieved by employing the k-
-E model. The SIMPLER algo rithm was used to solve the problem in primitive variables. The numerical solutions of the slulated model show that regions of relative stasis and trapped vortices were smaller within the ventricular chamber with the flap valve at the Inflow orifice than that with the trileaflet valve. The predicted Reynolds stresses distal to the inflow valve within the ventricular chamber were also found to be smaller wlth the flap valve than with the trlleaflet valve. These resu1ts also suggest a correlation be- tween high turbulent stresses and the presence of thrombus In the vicinity of the valves in the total artificial hearts. The computed velocity vectors and trubulent stresses were comparable with previ ously reported in vitro measurements in artificial heart chambers. Analysis of the numerical solo talons suggests that geometries similar to the flap valve(or a tilting disc valve) results in a better flow dynamics within the total artificial heart chamber compared to a trileaflet valve.
A Simulation Study on Cardiac Activation Process Using the Three Dimensional Ventricular Model
Lee, Kyoung-Joung ; Park, Gum-Soo ; Yun, Hyung-Ro ;
Journal of Biomedical Engineering Research, volume 13, issue 2, 1992, Pages 97~106
The cardiac activation process uslng three dimensional ventricular model is simulated. To study this theme, we constructed a cardiac ventricular model and simulated the cardiac activation process using the action potential duration and the activation time. The cardiac ventricular model is generated by the loglcal combination of the elliptic equations. The action potential duration could be obtained from the fact that It Is linearly distributed between model cells. The cardiac activation process was simulated by the law of "all-or-none". Based on the activation time and the action potential duration the cardiac potential at the arbitrary time after the activation of the model cell was computed. To test the validity of model, the comparison of the results of model simulation with the physiological data was performed. In conclusion, this model shows the simular results which is comparable to the 1 Pal conduction of the cardlac excitation.xcitation.
Design of an Adaptive Filter for Noise Cancdlation of ECG's
Journal of Biomedical Engineering Research, volume 13, issue 2, 1992, Pages 107~114
An adaptive filter for noise cancellation of ECG Is proposed. An adaptive noise canceller using the least mean squares algorithm Is used to reduce unwanted noise. An adaptive filter for nolse cancella lion minimizes the mean-square error between a primary input and a reference input. A primary input is the noisy ECG, and a reference input is a noise that Is correlated in some way with the noise in the primary input or a signal that is correlated only with ECG in the primary input.
Automatic Detection of Left Ventricular Contour from 2-D Echocardiograms using Fuzzy Hough Transform
Journal of Biomedical Engineering Research, volume 13, issue 2, 1992, Pages 115~124
An algorithm has been proposed for the automatic detection of optimal epiand endocardial left ventricular borders from 2-D short axis echocardiogram which is degraded by noise and echo drop out. For the implementation of the algorithm, we modified Ballard's Generalized Hough Transform which can be applicable only for deterministic object border, and newly proposed Fuzzy Hough Transform method. The algorithm presented here allows detection of object whose exact shapes are unknown. The algorithm only requires an approximate model of target object based on anatomical data. To detect the approximate epicardial contour of left ventricle, Fuzzy Hough Transform was applied to the echocardiogram. The optimal epicardial contour was founded by using graph searching method which contains cost function analysis process. Using this optimal epicardial contour and average thickness imformation of left ventricular wall, the approximate endocardial line was founded, and graph searching method was also used to detect optimal endocardial contour.
Power Spectrum Estimation of EEG Signal Using Robust Filter
Journal of Biomedical Engineering Research, volume 13, issue 2, 1992, Pages 125~132
Background EEG signals can be represented as the sum of a conventional AR process and an innovation process. It Is know that conventional estimation techniques, such as least square estimates (LSE) or Gaussian maximum likelihood estimates (MLE-G ) are optimal when the innovation process satisfies the Gaussian or presumed distribution. When the data are contaminated by outliers, however, these assumptions are not met and the power spectrum estimated by conventional estimation techniques may be fatally biased. EEG signal may be affected by artifacts, which are outliers in the statistical term. So the robust filtering estimation technique is used against those artifacts and it performs well for the contaminated EEG signal.
Measurement of Body Fat by Impedance Technique
Kim, Deok-Won ; Song, Chul-Gyu ; Hwang, Soo-Kwan ;
Journal of Biomedical Engineering Research, volume 13, issue 2, 1992, Pages 133~140
Bioelectrical Impedance method for measuring human body composition is based upon the principle that the electrical conductivity of the fat-free mass (FFM) is far greater than that of the (at. Deter- mination o( impedance was nlade in 30 healthy and obese men aged
SD) and 25 healthy and obese women aged
yr. A commercial impedance body fat analyzer was used with a four electrode arrangement that introduced a painless constant current(ImA at 50 kHz) into the body. Linear relationships were found between impudence values and FFM(r=-0.786) and between weight and FFM(r=0.837). Signigicant increases in the correlation coefficients were ob served when the predicator Hta/z was regressed against FFM(r=0.912) where Ht Is height and Z Is impedance. A linear regression equation, FFM=0.586(Htf/z) +0.317(Weight) -1.674(r=0.977), was found. The correlation coefficient of % body fat between the impedance and infrared methods was 0.898. These data Indicate that the bioelectrical impedance technique is a reliable and valld approach for the estimation of human body composition. This method Is safe, noninvasivr, prouides rapld measure menu, requires little operator skill and subject cooperation, and Os portable. Finally measurement of percent body fat was made possible using both the regression equation and a developed impedance measuring device which measures impedance between wrist and ankle.
A Study on the Characteristics of near IR lights for non-restrained Biotelemetry
Journal of Biomedical Engineering Research, volume 13, issue 2, 1992, Pages 141~146
The propagation, reflection and scattering characteristics of the near Infra-red lights were experimented in order to check the feasibility of non-restrained biotelemetry using indirect transmitted light. The results of the experiments show that 3 kinds of walls examined are not specular reflectors but almost perfect diffuse surfaces with slight directivity and that light in a local point is spread out and fills the room uniformly by repeating the reflection and scattering at walls, ceiling, floor. These results also explain the fact that the diffusely reflected light can be utilized as the carrier of biotelemetry even after several scattering and reflections.
Synthesis and Physical Properties of New Biodegradable Polyester-Polypeptide Copolymer
Yong Kiel Sung ; Chu ;
Journal of Biomedical Engineering Research, volume 13, issue 2, 1992, Pages 147~154
Poly (glycolic aclu-co-glycine-L-lactic aclu) has been prepared by rlng opening polymerlzation. The monomer 6-methyl morpholine-2, 5-dlone was synthe-slzed by bromoproplonylation of 2 bromopropionyl bromide with glycine. Glycolide and 6-methyl morpholine-2, 5-dione have been used as starling materials for polydepsipeptides. The synthesized copolymers have been Identlrled by NMR and FT-lR spectrophotometer. The Tg value of poly(glycollc aclu-co glycine-L-tactic acld ) Is In creased with increasing mole fraction of 6-methylmorpholine-2, 5-dlone(60-
). The glass trasltion temperature of poly(glycolic acid-co-glycine-L-lactic-acid) (62-
) is lower than that of poly (L-lactic acrid-co-glycine-L-lactic acid ). The thermal degradation of poly( L-lactic acid-co- glycine-L-lactic acid ) Is decreased with increasing mole fraction of L-lactide. The thermal degrada pion of poly(glycolic acrid-co-91ycine-L-lactic aclu ) is increased with increasing mole Fraction of glycolide.
Attachment of Fibroblast Cells on the Block Copdymer Membrane containing Peptide Segments
Kang, Inn-Kyu ; Kang, Shin-Sung ; Lim, Hak-Sang ;
Journal of Biomedical Engineering Research, volume 13, issue 2, 1992, Pages 155~164
Attachment and growth of mouse flbroblast cells on block copolypeptides were studied in the pres once or absence of serum proteins. Cells are rapidly attached to she polymer surface within 30 min regardless of substrate in the presence of serum. The number of flbroblast cells attached on the poly mer surface coated by collagen was larger than thats on the bare surface. Attachment of cells Is as a whole suppressed to a low level by the addltion of sodium azide in the absence of serum. Thls suE gests that the active attachment of cells requires the biological metabolism taking place on polymer substrates. In the presence of serum protein, flbroblast cells are more rapidly grown on the bolck co polymer consisting of poly(T-benzyl L-glutamate) (PBLG) and polyoxypropylene(POP) than on other block copolymers. These results were in agreement wish the data obatlned by an Inverted ml croscope.
Flow Dynamics Near End-To-End Anastomoses - Part I. In Vitro Compliance Measurement -
Kim, Y.H ;
Journal of Biomedical Engineering Research, volume 13, issue 2, 1992, Pages 165~174
Compliance mismatch across an end-to-end anastomosis was measured In the In vitro experimental setup. A 35mm camera was used and Image process was done in Gould/ DeAnza Image processor. The results showed that compliances of Penrose tubing and synthetic PTFE grafts were In good agreement with the previously reported In vivo data. PTFE grafts exhibited a nonlinear behavior with compliance decreasing with Increasing transmural pressure, whereas the compliance of the Penrose tubing remained relatively constant within the range of the pressures in which data were obtained. The lumen cross sections at the anastomosis were affected by the suture and the mismatch In compliance between the Penrose tubing and vascular grafts. The varla~lons In the lumen dtameter at the anastomosis was more pronounced with increasing transmural pressures. From the present study, it was clearly demonstrated that the compliance of prosthetic grafts Is much lower than that of the arteries. In addition to the hemodynamlc consequences, compliance mismatch across the anastomosis has been known to lead to Increased anastomotlc and suture stresses with resultant suture line dehlscence and false aneurysm formation. Thus, there are good hemodynamic reasons to suppose that Introduction of a less compliant arterial graft Into the arterial circulation wlll be damaging and that grafts should be made to match the elastic behavior of their host arteries as closely possible.