• Journal of Korea Multimedia Society
• /
• v.19 no.2
• /
• pp.224-232
• /
• 2016

The methodology to visualize the shape of blood vessel and its blood flow have been attracting as a very interesting problem to forecast and examinate a disease in thrombus precursor protein. May previous visualization researches have been appeared for designing the blood vessel and also modeling the blood flow using a doppler imaging technique which is one of nondestructive testing techniques. General visualization methods are to depict the blood flow obtained from doppler effects with fragmentary stream lines and also visualize the blood flow model using volume rendering. However, these visualizeation techniques have the disadvantage which a set of small line segments does not give the overall observation of blood flows. Therefore, we propose a visualization system which reconstruct the continuity of the blood flow obtained from doppler effects and also visualize the blood flow with the vector field of blood particles. This system will use doppler phase difference from medical equipments such as OCT with low penetration and reconstruct the blood flow by the curvature estimation from vector field of each blood particle.

• Journal of Korea Society of Digital Industry and Information Management
• /
• v.5 no.3
• /
• pp.87-98
• /
• 2009

This paper discuss secure information flow analysis and its visualization. Information leak is defined as existence of information flow from variables which have user's private informations to variables that anyone can access. Secure information flow analysis has been made to decide of whether the information leak is or not. There are many researches for secure information flow analysis concerning high level programming languages. But actually, programs that user executes don't have program source code represented in high level programming language. Thus there is need for analysis of program represented in low level language. More to analysis, visualization of analysis is very important. So, this paper discuss visualization of secure information flow analysis. In this paper, Mini x86 Assembly Language which is subset of x86 assembly language is defined and secure information flow analysis of program is proposed. In addition, this paper defines transfer function that is used for analysis and shows how to visualize control flow graph.

• Journal of Electrical Engineering and Technology
• /
• v.10 no.2
• /
• pp.647-652
• /
• 2015

A fully coupled finite element analysis (FEA) technique was developed for analyzing the discharge phenomena and dielectric liquid flow while considering surface charge density effects in dielectric flow guidance. In addition, the simulated speed of surface charge propagation was compared and verified with the experimental results shown in the literature. Recently, electrohydrodynamics (EHD) techniques have been widely applied to enhance the cooling performance of electromagnetic systems by utilizing gaseous or liquid media. The main advantage of EHD techniques is the non-contact and low-noise nature of smart control using an electric field. In some cases, flow can be achieved using only a main electric field source. The driving sources in EHD flow are ionization in the breakdown region and ionic dissociation in the sub-breakdown region. Dielectric guidance can be used to enhance the speed of discharge propagation and fluidic flow along the direction of the electric field. To analyze this EHD phenomenon, in this study, the fully coupled FEA was composed of Poisson's equation for an electric field, charge continuity equations in the form of the Nernst-Planck equation for ions, and the Navier-Stokes equation for an incompressible fluidic flow. To develop a generalized numerical technique for various EHD phenomena that considers fluidic flow effects including dielectric flow guidance, we examined the surface charge accumulation on a dielectric surface and ionization, dissociation, and recombination effects.

• Journal of Biomedical Engineering Research
• /
• v.31 no.2
• /
• pp.99-105
• /
• 2010

In order to obtain velocity profile of blood flow with high spatial resolution, a micro PIV technique consisted of a fluorescent microscope, double-pulsed YAG laser, cooled CCD camera was applied to in-vitro blood flow experiment through a micro round tube of a diameter $100{\mu}m$. Velocity distributions of blood flow for rabbit were obtained. The viscosity profiles for shear rate were found at flowing condition. To provide hemorheological characteristics of blood flow, the viscosities for shear rate were evaluated. The viscosity of blood also steeply increase by decreasing shear rate resulting in Non-Newtonian flow, especially in low shear rate region caused by RBC rheological properties. The results show typical characteristics of Non-Newtonian characteristics from the results of velocity profile and viscosity for blood flow. From the inflection points, cell free layer and two-phase flow consisted with plasma and suspensions including RBCs can be separated.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2006.05a
• /
• pp.57-60
• /
• 2006

The instability analysis of submerged gas flow into liquid is studied, which assumes gas and liquid as viscous and irrotational. At low mass flow rate of gas, injected gas plume is collection of bubbles, and increase of gas flow rate makes plume as a jet. It is well known that the transition from bubbling to jetting occurs in the transonic region. But previous works neglect viscous effect of gas flow into liquid. This paper concerns about an application of viscous potential flow theory in cylindrical gas flow into liquid. The growth rate versus wave number and mach number is compared with various condition including inviscid and viscous flow.

• Journal of the Korean Institute of Navigation
• /
• v.17 no.1
• /
• pp.37-48
• /
• 1993

When the vessel is running at the very low Froude numbers, the free-surface is difficult to be disturbed, wave-making is negligible, and the double -model velocity potential gives a very good approximation for calculating the velocity distribution just outside the boundary layer. If the speed of incident flow is gradually increased, the most perceptible change is the rise of the flow surface at stem. With further increase in speed, the nature of the flow at the bow changes completely, The flow ahead of the bow becomes more distrubed, the rise at the stem to stagnation height disappear, and the first wave crest, of less than the stagnation height, appears a small distance downstream from the stem. The present study is concerned with a small region of this flow, mainly in the bow region. The present investigation is primarily an experimental study of the flow in the bow region of s ship model, and it is undertaken in order to investigated systematically, the effect of bow geometry on this flow. The long-range objective is to use these results to guide the development of a mathematical model for predicting the flow about a ship's bow.

• Journal of Korean Society of Water and Wastewater
• /
• v.21 no.5
• /
• pp.581-587
• /
• 2007

In order to suggest the methodology for improving the equality of flow distribution in a distribution channel, wet tests were carried out for pilot plant which was scaled down to 1/8 of full scale distribution channel being operated in domestic K_water treatment plant. The correlation between various hydraulic variables and their effects on the equality of flow distribution was evaluated through wet tests using pilot plant. From the results of wet tests, the longitudinal baffle with orifices was installed in the distribution channel, the equality of flow distribution was improved on the condition that the Froude number in pilot plant was similar with that in the full scale channel. Also, the opening ratio of the orifices on the longitudinal baffled did not have influence on the performance of the equality of flow distribution when the average flow velocity and Froud number were relatively low (Froude number ${\fallingdotseq} 0.01$). In the other hand, the performance of the equality of flow distribution was improved with increasing the opening ration of on the longitudinal baffle under conditions of relatively high average flow velocity and high Froud number(${\gtrsim}0.1$)

• Transactions of the Korean hydrogen and new energy society
• /
• v.20 no.4
• /
• pp.265-273
• /
• 2009

Proton Exchange Membrane Fuel Cell (PEMFC) has low operating temperature and high efficiency. And PEMFC consists of many components as bipolar plate, gas diffusion layer, membrane etc.. Flow-field in bipolar plate roles path for transporting reactants to membrane. Therefore a design of flow-field has an effect on PEMFC's performance. In this study, Computational Fluid Dynamics (CFD) simulations were performed for comparing mixed multiple serpentine (MMS) flow-field and multiple serpentine (MS) flow-field. And we studied an effect according to change mixing region design in MMS flow-field. Finally the applicability of results is verified by performing CFD simulation about fixed MMS flow-field which is combined good designs.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.16 no.1
• /
• pp.16-25
• /
• 2004

The flow and heat/mass transfer in the falling-film of a heat exchanger can be influenced by the motion of the surrounding refrigerant vapor. In this study, the effect of the vapor flow direction on the absorption heat transfer has been investigated for a falling-film helical coil which is frequently used as the absorber of ammonia/water absorption refrigerators. The experiments were carried out for different solution concentration. The heat and mass transfer performance was measured for both parallel and counter-current flow. The effect of vapor flow on the heat and mass transfer is found to be increased with decreasing solution concentration. In the experiments with low solution concentration, whose vapor specific volume is great, the counter-current flow of vapor resulted in uneven distribution of falling-film and reduced the heat transfer performance of the absorber. The direction of the vapor flow hardly affected the thermal performance as the solution concentration became stronger since the specific volume of the ammonia/water vapor was much smaller than that of the water vapor.

• Journal of the Korean Society of Visualization
• /
• v.14 no.2
• /
• pp.18-24
• /
• 2016

This paper presents an experimental investigation to visualize cross-sectional two-phase flow structure and identify liquid-gas interface for condensation of steam at a low mass flux in a slightly inclined tube using the axial-viewing technique, which permits to look directly into flow during condensation of steam. In this technique, two-phase flow is viewed along the axis of a pipe by locating a high-speed video camera in front of a viewer that is fitted at the outlet of the pipe. A short section of the pipe is illuminated and is recorded through the viewer, which is kept free of liquid by mildly introducing air. Experiments were conducted in a pipe of 19.05 mm in inner diameter at atmospheric pressure. Cross-sectional two-phase flow structure is obtained at a steam mass flux of $2.62kg/m^2s$ as a function of steam quality in the range from 0.5 to 0.9. The results show that stratified-wavy flow is a unique flow pattern observed in the scope of the present study. Condensate film thickness, stratification angle and void fraction were measured from the obtained flow structure images. Finally, heat transfer coefficient was calculated using the measurement data and discussed in comparison with existing correlations.