Papers by Author: Guang Fu Yin

Abstract: Measurement of mechanical properties is very important in material science research area. Shear mechanical properties can be obtained from ultrasound vibromery method. Generally, ultrasound vibrometry is based on Voigt model which cannot describe some viscoelastic material accurately. Our method is based on Zener model, and more precise description of mechanical behavior can be measured. In our work, finite element method and experiment are conducted to validate our approach. Shear wave velocities at harmonics in finite element simulation are very close to the theoretical value and the fitting results from experiment demonstrate that our method has better ability to characterize some materials.

Abstract: Analytic modeling and analog computer simulation techniques are presented to determine the power train transient responses excited by clutch-actuated gear shifts. A method to describe the dynamics of a transmission arrangement having several clutches and interconnected planetary gear sets is considered in detail. Simulation model testing is directed toward optimizing system design parameters and evaluating power train component capability and vehicle shift-feel. Data reduction techniques applied to model responses of torque and speed will yield appropriate spectrums representative of simulated work cycle.

Abstract: Hemocompatibility of a biomaterial is determined by the interactions between its surface and blood. Due to the complicated action mechanism, various effective ways and the multiple affective factors of the hemocompatibility, a comprehensive evaluation needs to be built instead of single index. Therefore, the platelet consumption ratio of 10 kinds of biomaterials including Ti6Al4V-TiC-DLC gradient coat material was studied based on image analysis method. Combined with the kinetic clotting time and the hemolysis ratio, the comprehensive hemocompatibility evaluation of the material is carried out based on the improved principal component analysis. First, linear transformation of negative index is carried out. Second, index is under a dimensionless using the logarithmic treatment, then to acquire all variants’ principal component and their characteristic vectors. Finally, comprehensive evaluation index of hemocompatibility is constructed. The improved principal component analysis avoids the effect of correlativity among indexes during anaphase evaluation, and can more correctly maintain the original information of indexes. Thus, the research provides a new idea to the comprehensive evaluation of Hemocompatibility.

Abstract: The decrease in bone mass caused by wear debris-induced osteolysis could have been compensated through osteoblasts secreting enough new bone matrix. However, the normal osteoblastic population depends on the regular differentiation of their progenitor cells, the bone marrow mesenchymal stem cells (BMSCs). It is not possible to predict whether wear particles will affect the BMSCs’ viability, and subsequently their differentiation. Furthermore, little is known about the extent to which the sizes of the wear particles loading can impact the viability the most. This study has, therefore, concentrated on the potential mechanism for rat BMSCs’ (rBMSCs) viability influenced by different-sized titanium particle (Ti) loading in vitro.rBMSCs were harvested and loaded with circular Ti particles having three different mean diameters, 0.9, 2.7 and 6.9 .m respectively. The results showed that different-sized titanium particles all inhibited rBMSCs’ proliferation and induced rBMSCs’ apoptosis response , but this influence varied with the size of the Ti particles, their concentration and the duration of loading. The smallest Ti particles (0.9.m) exhibited the earliest and largest suppression on the proliferation and the most powerful induction on the apoptotic response of rBMSCs. qRT-PCR analysis demonstrated that those apoptotic effects were association with the abnormal accentuation of inducible nitric oxide synthase(iNOS) activity. The size of titanium particles generated through wear of a prosthetic device and the osteoblastic progenitor BMSCs may be both important considerations in the development of superior implant technology.

Abstract: 5-Fluorouracil-poly(L-lactide) (5-Fu-PLLA) microspheres have been co-precipitated in a process namely solution-enhanced dispersion by supercritical CO2 (SEDS). First, the 5-Fu is successfully micronized and then used to produce the 5-Fu-PLLA microspheres. The 5-Fu-PLLA microspheres synthesized in the SEDS process exhibited a rather spherical shape, smooth surface, and a narrow particle size distribution, where it ranged from 531 nm to 1280 nm, with a mean particle size of 793 nm. The dichloromethane residue in the 5-Fu-PLLA microspheres is 46 ppm. The average drug load of the 5-Fu-PLLA microspheres is 12.7%. The results of this study indicate that the SEDS process is an effective technique to co-precipitate 5-Fu and PLLA as composite microspheres.

Abstract: Poly-L-lactide/β-tricalcium phosphate (PLLA/β-TCP) porous scaffold fabricated by freeze shrinking/particulate leaching was studied. The scaffold was immersed into simulated body fluid (SBF) for 1, 2, 3 and 4 weeks and analyzed by the SEM, XRD and FT-IR spectroscopy. The ability of inducing Ca-P formation was compared among the scaffolds with different content of β- TCP. SEM shows a typical feature of apatite precipitation. Diffraction peak of new crystal structure was detected by x-ray diffraction (XRD). IR Spectrum in which absorption bands arise from newly formed groups of carbonate apatite can be seen. At the same testing point, higher density of Ca-P crystal can be observed by SEM in scaffold with high content of β-TCP than in low group. Until 3 weeks, Ca-P individual crystal started on the wall of inner pore of pure PLLA. Porous PLLA/β-TCP composite scaffolds also indicate good ability of Ca-P formation in vitro, the ability of which to form apatite was enhanced by addition of each other that has different degradable mechanism.

Abstract: In bone tissue engineering, porous scaffolds served as the temporary matrix are often subjected to mechanical stress when implanted in the body. Based on this fact, the goal of this study was to examine the effects of mechanical loading on the in vitro degradation characteristics and kinetics of porous scaffolds in a custom-designed loading system. Porous Poly(L-lactic acid)/β-Tricalcium Phosphate (PLLA/β-TCP) composite scaffolds fabricated by using solution casting/compression molding/particulate leaching technique (SCP) were subjected to degradation in simulated body fluid (SBF) at 37°C for up to 6 weeks under the conditions: with and without static compressive loading, respectively. The results indicated that the increase of the porosity and decrease of the compressive strength under static compressive loading were slower than that of non-loading case, and so did the mass loss rate. It might be due to that the loading retarded the penetration, absorption and transfer of simulated body fluid. These data provide an important step towards understanding mechanical loading factors contributing to degradation.

Abstract: The nano-size silver particles were prepared in polymer-protecting colloidal dispersion with silver nitride as the raw material, hydrazine hydrate as the reduction reagent and polyvinyl pirrolidone (PVP) as the protective solvent. The optimal conditions for the preparation process were studied experimentally as well. The influences from main factors, such as Ag+ concentration and ratio of hydrazine/AgNO3, on the particle size, appearance shape, particle aggregation condition and size distribution of nano-silver particles were also investigated. The results showed that the size of Ag particles prepared in this polymer-protecting system is less than 50 nm, and PVP can reduce the growing tendency of nano-size silver particles. Meanwhile, the antibacterial dope loaded nano-silver particles were prepared by wetting agent, dispersant, defoamer, etc. The antibacterial and bacteriostatic effects of the dope with or without nano-silver particles were tested with bacilli as the tested bacteria. The experiment results showed that the dope loaded nano-silver particles are of high practicality. Its antibacterial ratio is also up to 91.9% in one hour when the added dosage of nano-silver is 0.02%.

Abstract: In this paper, the adsorption of human serum albumin (HSA), human serum fibrinogen (HFG) and human serum immune globulin (IG) on surfaces of diamond like carbon film (DLC), diamond film (DF) and graphite has been studied. The adsorption isotherms of single component protein solution and the competitive adsorption of binary system have been investigated by radioisotope 125 I labeling method. Results showed that (1) the adsorptive amounts of HSA on DLC is more than that of HFG, but the adsorptive amounts of HFG on DF and graphite are apparently more than those HSA; (2) the relative competitive adsorption ability of three proteins on DF and graphite surfaces is HFG > IG > HSA, but that on DLC is HFG ≈ HAS > IG, comparison with HSA, there is no apparent competitive adsorption superiority on DLC for HFG. These results indicated that there is no apparent distinction for the adsorption of three human serum proteins on DLC, but the adsorption of HFG on DF and graphite takes precedence in varying degrees. It probably makes rational explanation for the result of blood-compatibility tests in vitro that DLC is good, but DF and graphite are worse.

Abstract: Silicate fireproof coatings for tunnels (FCT) have many eminent properties. But low adhesion strength and poor water/fire-resistance of this kind of materials largely limit its applications. Here we reported a new kind of FCT based on high alumina cement as principle adhesive, redispersible powder as assisting adhesive, ammonium polyphosphate as fire-retardant material, vermiculite as adiabatic padding, and magnesium hydroxide as assisting reagents. The influence of various experimental conditions on fire resistance, adhesion strength and water resistance were carefully studied. Results showed that dispersible emulsoid powder was a key component affecting adhesion strength and water resistance of FCT, whereas fire-retardant material posed significant effects on the fire resistance.