• Proceedings of the KOSOMBE Conference
• /
• v.1997 no.11
• /
• pp.528-532
• /
• 1997

X-Ray Angiography has been gold standard or imaging of blood flow. However, patients have to take many risks such as catheterization procedure, iodine contrast agent and ionizing X-rays. MR Angiography has been suggested as a substitute for its non-hazard to patient. But the resolution and contrast was inferior to that of X-ray Angiography. Recently the resolution and the contrast have been much improved due to the development of fast imaging technique.

• Proceedings of the KIEE Conference
• /
• 2000.07d
• /
• pp.3216-3218
• /
• 2000

Projection-type Fast Spin Echo (PFSE) imaging has robustness against motion artifacts due to patient motion during magnetic resonance imaging data acquisition, or reduce flow artifacts. However, it has difficulty in controlling T2 contrast. In this paper, T2 contrast in the PFSE method is analyzed. The contrasts in FSE and PFSE method are compared by computer simulation and experiments with volunteers.

• Proceedings of the Korea Society for Simulation Conference
• /
• 2003.11a
• /
• pp.201-206
• /
• 2003

In clinical practice, CT Angiography is a powerful technique for the visualziation of blood flow in arterial vessels throughout the body. However CT Angiography images of blood vessels anywhere in the body may be fuzzy if the patient moves during the exam. In this paper, we propose a novel technique for removing global motion artifacts in the 3D space. The proposed methods are based on the two key ideas as follows. First, the method involves the extraction of a set of feature points by using a 3D edge detection technique based on image gradient of the mask volume where enhanced vessels cannot be expected to appear, Second, the corresponding set of feature points in the contrast volume are determined by correlation-based registration. The proposed method has been successfully applied to pre- and post-contrast CTA brain dataset. Since the registration for motion correction estimates correlation between feature points extracted from skull area in mask and contrast volume, it offers an accelerated technique to accurately visualize blood vessels of the brain.

• Journal of the Korean Society for Aviation and Aeronautics
• /
• v.18 no.4
• /
• pp.86-91
• /
• 2010

New Design configurations of the fighter aircraft igloo diffuser were studied based on the closed ventilation type in contrast to the conventional open distribution type. To validate the enhanced and safe performance, the exhaust flow patterns of the two igloo diffuser types were simulated by both experimental and computational approaches as design tools. Flow visualizations were conducted to investigate the exhaust flow patterns in experimental approach. In addition, the commercial code called Fluent was used to calculate flow field properties. Computational simulations provided detailed parametric studies that significantly reduced the amount of experimentation necessary to alter the design parameters of the existing fighter igloo diffuser. The closed ventilation type of the igloo diffuser was shown the better results.

• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.6 no.4
• /
• pp.3-7
• /
• 2007

The valve is used on control of flow in a ship. Flow coefficient of valve is very importance in the design of valve. In this paper, three-dimensional computer simulations by commercial code CFX were conducted to observe the valve type and to measure flow coefficient when valves with various angles and uniform incoming velocity were used in a piping system. By contrast, a group of experimental data is used to compare with the data obtained by CFX simulation to investigate the validity of numerical method.

• 한국가시화정보학회:학술대회논문집
• /
• 2003.11a
• /
• pp.83-86
• /
• 2003

Synchrotron X-ray micro imaging technique was employed to non-invasively monitor the water flow inside xylem vessels in a bamboo leaf. The phase contrast X-ray images clearly visualized plant anatomy and the rise of a water front inside the vessels. Consecutive X-ray images taken for 60 seconds revealed water rise kinetics against gravity in the xylem of a cut dry leaf taken from a bamboo tree. For the first time, traces of water rise, variation of contact angle between water and xylem wall as well as the internal structure of xylem were obtained. In xylem vessels, a repeating flow pattern has a typical flow velocity of $30.7{\mu}m/s$ and faster flow is established intermittently. It is concluded that the transmission type of X-ray micro imaging can be used as a powerful tool to investigate the ascent of sap in the xylem vessels at a resolution higher than that of MRI.

• Membrane and Water Treatment
• /
• v.2 no.2
• /
• pp.75-89
• /
• 2011

The predicting equations for mass transfer rate in cross-flow rectangular dialyzers with double flow and recycle, have been derived by mass balances. The recycling operation has two conflicting effects. One is the desirable effect of the increase in fluid velocity, resulting in an increased mass transfer coefficient. The other is the undesirable effect of the reduction in concentration difference due to remixing, resulting in decreased mass-transfer driving force. In contrast a single-pass device without recycling, considerable improvement in mass transfer is achieved if the cross-flow rectangular dialyzer of same size is operated with double pass and external recycling. It is concluded that recycle can enhance mass transfer, especially for larger reflux ratio.

• Proceedings of the IEEK Conference
• /
• 2000.07b
• /
• pp.843-846
• /
• 2000

An optical flow-based motion estimation algorithm is proposed for video coding. The algorithm uses block-matching motion estimation with an adaptive search region. The search region is computed from motion fields that are estimated based on the optical flow. The algorithm is based on the fact that true block-motion vectors have similar characteristics to optical flow vectors. Thereafter, the search region is computed using these optical flow vectors that include spatial relationships. In conventional block matching, the search region is fixed. In contrast, in the new method, the appropriate size and location of the search region are both decided by the proposed algorithm. The results obtained using test images show that the proposed algorithm can produce a significant improvement compared with previous block-matching algorithms.

• Journal of the Korean Ceramic Society
• /
• v.52 no.2
• /
• pp.137-139
• /
• 2015

In this study, we examined the influence of molten $KNO_3$ flow on mechanical properties and their deviation when a chemical toughening process was applied to soda lime silicate glass ($Na_2O-CaO-SiO_2$). $KNO_3$ melt flow was controlled using three methods: (1) glass tray rotation, (2) impeller stirring, and (3) natural convection. DOL and hardness were found to be enhanced by tray rotation because this rotation was able to maintain the concentration around the glass surface, in contrast to other methods. However, there did not appear to be a statistically significant difference in the 3-point bending strength for the three flow conditions due to the ground edge condition.

• Proceedings of the KSME Conference
• /
• 2000.11b
• /
• pp.591-596
• /
• 2000

Flow through compliant tubes with linear taper in wall thickness is numerically simulated by finite element analysis. Two models are examined: a planar two-dimensional channel, and an axisymmetric tube. For verification of the numerical method, flow through a compliant stenotic vessel is simulated and compared to existing experimental data. Computational results for an axisymmetric tube show that as cross-sectional area falls with a reduction in downstream pressure, flow rate increases and reaches a maximum when the speed index (mean velocity divided by wave speed) is near unity at the point of minimum cross-section area, indicative of wave speed flow limitation or "choking" (flow speed equals wave speed) in previous one-dimensional studies. For further reductions in downstream pressure, flow rate decreases. Cross-sectional narrowing is significant but localized. When the ratio of downstream-to-upstream wall thickness is ${\le}$ 2 the area throat is located near the downstream end; as wall taper is increased to ${\ge}$ 3 the constriction moves to the upstream end of the tube. In the planar two-dimensional channel, area reduction and flow limitation are also observed when outlet pressure is decreased. In contrast to the axisymmetric case, however, the elastic wall in the two-dimensional channel forms a smooth concave surface with the area throat located near the mid-point of the elastic wall. Though flow rate reaches a maximum and then falls, the flow does not appear to be choked.