• Title/Summary/Keyword: modified two-surface model

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Anti-calcification of Bovine Pericardium for Bioprosthetic Heart Valves after Surface Modification with Hyaluronic Acid Derivatives

  • Hahn Sei Kwang;Ohri Rachit;Giachelli Cecilia M.
    • Biotechnology and Bioprocess Engineering:BBE
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    • v.10 no.3
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    • pp.218-224
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    • 2005
  • Surface modification of glutaraldehyde fixed bovine pericardium (GFBP) was success­fully carried out with hyaluronic acid (HA) derivatives. At first, HA was chemically modified with adipic dihydrazide (ADH) to introduce hydrazide functional group into the carboxyl group of HA backbone. Then, GFBP was surface modified by grafting HA-ADH to the free aldehyde groups on the tissue and the subsequent HA-ADH hydrogel coating. HA-ADH hydrogels could be prepared through selective crosslinking at low pH between hydrazide groups of HA-ADH and crosslinkers containing succinimmidyl moieties with minimized protein denaturation. When HA­ADH hydrogels were prepared at low pH of 4.8 in the presence of erythropoietin (EPO) as a model protein, EPO release was continued up to $85\%$ of total amount of loaded EPO for 4 days. To the contrary, only $30\%$ of EPO was released from HA-ADH hydrogels prepared at pH=7.4, which might be due to the denaturation of EPO during the crosslinking reaction. Because the carboxyl groups on the glucuronic acid residues are recognition sites for HA degradation by hyaluronidase, the HA-ADH hydrogels degraded more slowly than HA hydrogels prepared by the crosslinking reaction of divinyl sulfone with hydroxyl groups of HA. Following a two-week subcutaneous implantation in osteopontin-null mice, clinically significant levels of calcification were observed for the positive controls without any surface modification. However, the calcification of surface modified GFBP with HA-ADH and HA-ADH hydrogels was drastically reduced by more than $85\%$ of the positive controls. The anti-calcification effect of HA surface modification was also confirmed by microscopic analysis of explanted tissue after staining with Alizarin Red S for calcium, which followed the trend as observed with calcium quantification.

NEW WEIGHTING COEFFICIENTS FOR CALCULATING MEAN SKIN TEMPERATURE IN RELATION TO THE POSTURE WITH CONSIDERATION TO HEAT CONDUCTION (열전도를 고려한 각 자세에 따른 평균 피부온의 산출)

  • Lee, Ju-Youn;MIYAMOTO, Seiichi;ISODA, Norio
    • Journal of the Ergonomics Society of Korea
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    • v.19 no.2
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    • pp.63-74
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    • 2000
  • This paper is to clarify a thermal physiological index that can account for the effects of local thermal environment. For this purpose two young female subjects exposing themselves to the above while sitting on a chair, sitting on the floor and lying on the floor were measured. These three representative postures accompanied the different contact surface areas, thereby the heat conduction rate between the floor and subject was quantitatively measured for each posture. It made the present study deal with the effect of heat conduction concerning the modified mean skin temperature and finally propose new weighting coefficients for the mean skin temperature calculation based on the Hardy & DuBois' formulas. In order to verify the proposed model, the experiment was carried out using a floor heating system. The comparison between the experimental result and prediction revealed that the proposed model should be about 10% more accurate than the conventional one in the case of lying on the floor which the heat conduction effect becomes important.

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A Study on Dynamic Characteristics by Gearbox of High-speed Pump (고속 펌프용 증속기의 동특성에 관한 연구)

  • Lee, Dong-Hwan;Lee, Hyeong-U
    • 연구논문집
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    • s.31
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    • pp.65-75
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    • 2001
  • A dynamic model of pump having one step gearbox and two step gearbox is developed by the lumped parameter method. The model accounts for shafts, ball bearings and journal bearings flexibilities, gyroscopic effects and the force couplings among the transverse and torsion motions due to gearing. Excitation forces of pump having one step gearbox and two step gearbox are considered as the mass unbalance of the rotors and gear transmission error which comes from the modified tooth surface. A Campbell diagram, in which the excitation sources caused by the mass unbalance of the rotors and the transmitted errors of the gearing are considered, shows that there are no critical speeds at the operating speeds. One step and two step gearboxes are manufactured and are estimated for vibration/noise, lubrication and performance.

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Phase Shift Analysis of 6Li Elastic Scattering on 12C and 28Si at Elab = 318 MeV

  • Kim, Yong Joo
    • New Physics: Sae Mulli
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    • v.68 no.12
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    • pp.1331-1337
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    • 2018
  • We present a three-parameter phase shift model whose form is the same as that of Coulombmodified Glauber model obtained from Gaussian nuclear densities. This model is applied to the $^6Li+^{12}C$ and the $^6Li+^{28}Si$ elastic scatterings at $E_{lab}=318MeV$. The calculated differential cross sections provide quite a satisfactory account of the experimental data. The diffractive oscillatory structures observed at forward angles can be explained as being due to the strong interference between the near-side and the far-side scattering amplitudes. The optical potentials for two systems are predicted by using the method of inversion. The calculated inversion potentials are found to be in fairly good agreements with the results determined from the optical model analysis in the surface regions around the strong absorption radius. We also investigate the effects of parameters in the three-parameter phase shift model on the elastic scattering cross sections.

Numerical Study on the Wind Flow Over Hilly Terrain (언덕지형을 지나는 유동의 수치해석적 연구)

  • 김현구;이정묵;경남호
    • Journal of Korean Society for Atmospheric Environment
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    • v.13 no.1
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    • pp.65-77
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    • 1997
  • A theoretical and numerical investigation on the boundary-layer flow over a two- or three-dimensional hill is presented. The numerical model is based on the finite volume method with boundary-fitted coordinates. The k-$\varepsilon$ turbulence model with modified wall function and the low-Reynolds-number model are employed. The hypothesis of Reynolds number independency for the atmospheric boundary-layer flow over aerodynamically rough terrain is confirmed by the numerical simulation. Comparisons of the mean velocity profiles and surface pressure distributions between the numerical predictions and the wind-tunnel experiments on the flow over a hill show good agreement. The linear theory provides generally good prediction of speed-up characteristics for the gentle-sloped hills. The flow separation occurs in the hill slope of 0.5 and the measured reattachment points are compared with the numerical prediction. It is found that the k- $\varepsilon$ turbulence model is reasonably accurate in predicting the attached flow, while the low- Reynolds-number model is more suitable to simulate the separated flows.ows.

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A Treatment for Truncated Boundary in a Half-Space with 2-D Rayleigh Wave BEM

  • Ju, Tae-Ho;Cho, Youn-Ho;Phan, Haidang;Achenbach, Jan D.
    • Journal of the Korean Society for Nondestructive Testing
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    • v.31 no.6
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    • pp.650-655
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    • 2011
  • Analysis of two-dimensional Rayleigh wave scattering pattern by a surface defect is studied through modified boundary element method. BEM proposed in this paper has special treatment at each end of boundary which should have the Rayleigh wave go away without any generation of virtual reflections. It is shown that treatment for truncated boundary which is used to model two-dimensional Rayleigh waves' behavior in an elastic half-space is successfully implemented. To check numerical results' accuracy, time domain IFFT signal of the displacements is presented. Improvement on getting rid of unwanted influence of truncated boundary induced by 2-D Rayleigh waves on a flat surface of an elastic half-infinite medium is shown. As a final goal, the numerical results of Rayleigh wave scattering trend are plotted and they are compared with theoretical curves to prove its accuracy.

Prediction of the long-term deformation of high rockfill geostructures using a hybrid back-analysis method

  • Ming Xu;Dehai Jin
    • Geomechanics and Engineering
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    • v.36 no.1
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    • pp.83-97
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    • 2024
  • It is important to make reasonable prediction about the long-term deformation of high rockfill geostructures. However, the deformation is usually underestimated using the rockfill parameters obtained from laboratory tests due to different size effects, which make it necessary to identify parameters from in-situ monitoring data. This paper proposes a novel hybrid back-analysis method with a modified objective function defined for the time-dependent back-analysis problem. The method consists of two stages. In the first stage, an improved weighted average method is proposed to quickly narrow the search region; while in the second stage, an adaptive response surface method is proposed to iteratively search for the satisfactory solution, with a technique that can adaptively consider the translation, contraction or expansion of the exploration region. The accuracy and computational efficiency of the proposed hybrid back-analysis method is demonstrated by back-analyzing the long-term deformation of two high embankments constructed for airport runways, with the rockfills being modeled by a rheological model considering the influence of stress states on the creep behavior.

Measurements of Flow Meniscus Movement in a Micro Capillary Tube (마이크로 원형 모세관에서 계면 이동 현상의 측정)

  • Lee, Sukjong;Sung, Jaeyong;Lee, Myeong Ho
    • Journal of the Korean Society of Manufacturing Technology Engineers
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    • v.22 no.1
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    • pp.15-21
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    • 2013
  • In this paper, a high-speed imaging and an image processing technique have been applied to detect the position of a meniscus as a function of time in the micro capillary flows. Two fluids with low and high viscosities, ethylene glycol and glycerin, were dropped into the entrance well of a circular capillary tube. The filling times of the meniscus in both cases of ethylene glycol and glycerin were compared with the theoretical models - Washburn model and its modified model based on Newman's dynamic contact angle equation. To evaluate the model coefficients of Newman's dynamic contact angle, time-varying contact angles under the capillary flows were measured using an image processing technique. By considering the dynamic contact angle, the estimated filling time from the modified Washburn model agrees well with the experimental data. Especially, for the lower-viscosity fluid, the consideration of dynamic contact angle is more significant than for the higher-viscosity fluid.

The wave stability of the nonparallel natural convection flows adjacent to an inclined isothermal surface submerged in water at $4degC$ ($4degC$ 물에 잠겨있는 경사진 등온 벽주위 비평행 자연대류의 파형 안정성)

  • 황영규;장명륜
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.15 no.2
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    • pp.644-653
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    • 1991
  • A wave instability problem is formulated for natural convection flows adjacent to a inclined isothermal surface in pure water near the density extremum. It accounts for the nonparallelism of the basic flow and temperature fields. Numerical solutions of the hydrodynamic stability equations constitute a two-point boundary value problem which are accurately solved using a computer code COLSYS. Neutral stability results for Prandtl number of 11.6 are obtained for various angles of inclination of a surface in the range from-10 to 30 deg. The neutral stability curves are systematically shifted toward modified Grashof number G=0 as one proceeds from downward-facing inclined plate(.gamma.<0.deg.) to upward-facing inclined plate (.gamma.>0.deg.). Namely, an increase in the positive angle of inclination always cause the flows to be significantly more unstable. The present results are compared with the results for the parallel flow model. The nonparallel flow model has, in general, a higher critical Grashof number than does the parallel flow model. But the neutral stability curves retain their characteristic shapes.

Impact of Building Blocks on Inundation Level in Urban Drainage Area (지표 건물이 도시유역의 침수특성에 미치는 영향)

  • Lee, Jeong-Young;Ha, Sung-Ryong
    • Journal of Environmental Impact Assessment
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    • v.22 no.1
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    • pp.99-107
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    • 2013
  • This study is an impact assessment of building blocks on urban inundation depth and area. LiDAR data is used to generate two original data set in terms of DEM with $5{\times}5$ meter and building block elevation layer of the study drainage area in Cheongju and then the building block elevation layer is modified again to the mesh data with same size to DEM. Two-dimensional inundation analysis is carried out by applying 2D SWMM model. The inundation depth calculated by using the building block elevation layer shows higher reliability than the DEM. This is resulted from the building block interference to surface flow. In addition, the maximum flooded area by DEM is two times wider than the area by building block layer. In the case of the surface velocity, the difference of velocity is negligible in either DEM or building block case in the low building impact zone. However, If the impact of building on the surface velocity was increase, the gap of velocity was significant.