Porous composites of hydroxyapatite‐filled poly[ethylene‐co‐(vinyl acetate)] for tissue engineering

A novel porous composite of hydroxyapatite/poly[ethylene‐co‐vinyl acetate)] (HAP/EVA) having better osteointegration was fabricated by gas foaming technique using a non toxic gas blowing agent intended for bone replacement applications. Combined techniques of scanning electronic microscopy (SEM) and X‐ray microcomputed tomography (µCT) analysis showed that the pore size and pore volume of the porous composite decrease with the increase of HAP content. The gravimetric analysis evidenced for good pore interconnectivity within the porous composites. Energy dispersive X‐ray analysis (EDX) studies inveterated the even scattering of Ca ions which in turn indicate the uniform dispersion of HAP particles in the composites. The significant gradation in Ca ion concentration seen in EDX studies is well accordance with the amount of HAP loading in the sample. Mechanical properties of the porous composite having different HAP content were measured to have the compressive strength varying from 1.06 to 2.2 MPa. Non‐cytotoxic character of the material was observed by the cytocompatibility studies. The metabolic activity of L929 cells seeded on the material assessed by [3‐(4,5‐dimethylthiazol)‐2‐yl]‐2,5‐diphenyltertrazolium bromide (MTT) assay was found to be 91.8%. The adhesion and migration of the cells inside the pore walls were visualized by confocal microscopy. Copyright © 2010 Society of Chemical Industry     

EFFECT OF STEPWISE CHANGE OF DRYING RATE ON MICROSTRUCTURE EVOLUTION IN POLYMER FILMS

The effect of the drying rate of the solvent on microstructure evolution in thin films of immiscible polystyrene/polycarbonate blends was investigated by applying a stepwise change in air velocity. The polymer blend was dissolved in tetrahydrofuran and cast on a glass substrate to form a thin liquid film. The drying rate of the solvent was measured by a gravimetric technique, and the phase-separated structure in the film was observed by optical microscopy. The results indicated that cellular structures of droplet arrays were formed in the phases evolved primarily during the early stage of drying, and the droplets then coalesced in the intermediate stage to form bigger droplets. The size of the first evolved phase decreased with increasing time at a high drying rate, whereas larger droplets were obtained with longer high drying rate regimes. These results suggested that the droplets were induced by secondary phase separation which was strongly affected by the drying rate of the solvent.     

视地层水电阻率正态分布分析及应用

通过多组随机正态分布序列数据正态频率分布绘图分析，指出正态分布序列数据的方差值越大，即储层段的视地层水电阻率分布范围较大时，正态频率分布曲线的斜率就越大；反之，正态分布序列数据的方差值越小，即储层段的视地层水电阻率分布比较集中时，正态频率分布曲线的斜率就越小。实际数据显示P^1/2 值越大，含气性越好；水层段P^1/2 值小，斜率小；通过该方法计算的地层水电阻率与水分析资料显示一致。     

减少板坯表面纵向裂纹的生产实践

针对板坯投产以来易出现表面纵向裂纹的情况,结合现场实际生产特点,从钢水质量、工艺控制和操作等方面进行分析与改进,铸坯表面纵向裂纹发生率得到了有效控制,板坯表面纵裂发生率由2009年的6.2%降到2010年的3.5%。     

The Mechanism of Crack Formation in Rubbers under the Effect of Ozone

Abstract

The formation and growth of cracks under an effect of ozone were investigated in different types of rubbers, such as NR, PBR, BMSR, SBR and in composite materials based on these rubbers. The study was carried out by the reflection-light optical microscopy method with using the MMP-4 microscope. In the presence of microinhomogeneities in a surface structure the crack formation is shown to start from those defects. In the absence of inhomogeneities the cracks are formed uniformly over the whole surface of a specimen. It is found that even insignificant quantities of low-modulus rubber in the PBR-based composite material may result in changing the shape of a crack during its growth. An attempt is undertaken to describe the shape of formed cracks quantitatively. The calculational and experimental data are presented.

The influence of deformation on the number of cracks per surface unit, on their shape, geometrical size, cracking degree is studied for example of natural rubber specimen.     

大型机床主传动链自动控制数控化改造技术

在某大型机床数控化改造过程中,主要针对主传动链进行技术攻关,改进传动结构设计,达到全自动化控制。对主传动机构进行了分析,阐述了主传动链自动控制数控化改造的方案和实施过程。     

Effect of exposure time on the morphology of corrosion on high chromium white cast iron in high temperature caustic solutions

High chromium white irons are important candidate materials for use in alumina refineries to combat wear and corrosion. The effect of exposure time on the formation of oxide films was studied in a 23% Cr white cast iron exposed at 260 °C in 110 g/l caustic soda solutions. It was found that whilst well‐formed octahedral M(II)O.M(III)₂O₃ spinel type oxides initially formed and spread across the surface of the material, these were gradually replaced by a background oxide with a higher Cr/Fe ratio and the morphology of the octahedral crystals became less well formed. Also, the oxidation was found to be predominantly in the matrix material, leaving carbide particles unsupported on the surface and in the later stages, significant corrosion was found along the carbide/matrix phase boundary.     

Using brazing alloys in resistance spot welding of joints in aluminium–magnesium alloys

The results of mathematical modelling of the process of propagation of heat in the parent metal in submerged-arc surfacing with a composite strip electrode are presented. The mathematical model was constructed by solving the differential equation of heat conductivity by the finite element method. The calculations and plotting of the graphs were carried out using the MSC Patran software. The model was used to determine the main parameters of the composite strip electrode influencing the shape and dimensions of the pool and the non-uniformity of penetration. The comparison of the calculated and experimental data shows that they are in good agreement.     

Investigation of metallurgical processes in pulsed laser welding of nickel alloys of small thickness

Metallurgical processes taking place in pulsed laser welding of nickel alloys of small thickness are described.