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자기공명유속계 해상도 향상을 위한 4.7T MRI용 솔레노이드 RF코일 개발
송시몬(Simon Song),양병권(Byungkuen Yang),조지현(Jee-Hyun Cho) 한국가시화정보학회 2016 한국가시화정보학회 학술발표대회 논문집 Vol.2016 No.4
Magnetic resonance velocimetry (MRV) is a powerful tool to non-invasively measure the velocity of fluid flow in many fields ranging from medicine to engineering and biology. However, since the demands for accurate measurement in the solid/liquid interface for cardiovascular diseases and porous media increase, the improvement of spatial resolution is necessary. In this study, a solenoid RF coil is developed for high spatial resolution measurement. The signal-to-noise ratio in solenoid RF coil is increased seventeen times better than that in commercial coil. Moreover, the velocity distribution of hagen-poiseuille flow is measured with in-plane resolution of 36㎛ by 36㎛.
다양한 헤마토크릿(Hematocrit)치에 대한 혈액 모사 용액 개발
송상민(Sangmin Song),고승빈(Seungbin Ko),송시몬(Simon Song) 대한기계학회 2018 대한기계학회 춘추학술대회 Vol.2018 No.12
As the incidence of vascular disease increases, the need for blood analog fluids for hemodynamic analysis is increasing. Most previous studies have focused on the blood analog fluid for normal hematocrit which is approximately 40%. This study presents an explicit approach to the development of blood analog fluid with various hematocrit values. We use a mixture of xanthan gum, glycerin and deionized water as the blood analog fluid and investigate the effect of mass fraction of each component on the viscosity behavior. As a result, the xanthan gum was found to have an effect on increasing slope of graph by increasing viscosity at low shear rate, and the glycerin was found to have an influence on increasing overall viscosity values. We expect that the results of this study would contribute to wide range of studies that require blood analog fluids.
유기수(KisooYoo),송시몬(Simon Song) 대한기계학회 2005 대한기계학회 춘추학술대회 Vol.2005 No.11
We numerically investigate effects of vorticity on mixing in microchannels. Mixing of two fluids in a Y-shape microchannel is studied using vortex index, mixing index and degree of transverse diffusion. The studies are performed for three geometries: Y-channel, Y-channel with a post array along the centerline, and Y-channel with a zig-zag post array. The results indicate that the high vorticity does not always ensure high performance of mixing in a microchannel. The vorticity of centerline post array and zig-zag post array is about the same, but the zig-zag post array shows significantly better mixing performance than the other.
송호성(Hosung Song),박준홍(Junhong Park),송시몬(Simon Song) 대한기계학회 2008 大韓機械學會論文集B Vol.32 No.9
For a high speed train driving at 300 km/h, aero-acoustic noise is a dominant component among various noise sources. The aeroacoustic noise is mainly due to inter-coach spacings because discontinuities in the train surface significantly disturb turbulent flows. This often leads to the uncomfortableness of passengers. Interestingly, the aero-acoustic noise reduces with decreasing the mud-flap spacing of the inter-couch spacing. We perform numerical simulations to investigate flow characteristics around the inter-coach spacing. We model the inter-coach spacing as a simple 2-D cavity with flaps, and calculate the velocity and pressure field using two equation turbulence models, varying the flap spacing. The results show that a wider flap spacing develops a higher inflection point in mean velocity profiles over the cavity. It is likely that large eddies generated near the inflection point persist longer in the downstream since they are less affected by the wall. This probably induces the more aero-acoustic noises. The wider spacing also results in the larger pressure difference between the inside and outside of the cavity. This is also responsible for the increased noise since the large difference would cause a strong flow oscillations in and out of the cavity.
황현진(Hyunjin Hwang),송시몬(Simon Song) 대한기계학회 2008 대한기계학회 춘추학술대회 Vol.2008 No.11
Polydiacetylenes (PDAs) are very attractive chemical substances which have distinctive features of color change and fluorescence emission by thermal or chemical stress. Especially, when PDAs contact with solutions of a particular pH, such as a strong alkaline sodium hydroxide (NaOH) solution or a strong acidic hydrogen chloride (HCl) solution, PDAs change their color from non-fluorescent blue to fluorescent red. In this study, we propose a novel method to detect alkaline pH using PDAs and NaOH solutions by hydrodynamic focusing on a microfluidic chip. Preliminary results indicate that the fluorescent intensity of PDAs increases in respond to the NaOH solution concentrations. Also, the fluorescence is quenched back when the PDAs are in contact with a HCl solution. These results are useful in a microfluidic PDA sensor chip design for pH detection.