Pellet—clad bonding during PCMI

Pellet—clad mechanical interaction adjacent to the mouths of radial cracks in the pellet can lead to local clad strain intensification. in particular, if during operation bonding has occurred between the pellet and the clad, preventing relative azimuthal motion, very high strains would result and many clad failures would be expected. These are however not observed. We present here the results of a detailed analysis of the stress field in the region of the mouth of the pellet crack. These show there to be very high radial tensile stresses, not previously predicted, acting on the bond. Such stresses provide a highly plausible mechanism for the failure of the bond. These will permit the strain associated with the opening of pellet cracks during power ramps to be distributed over a relatively large arc of the cladding, and thus explain the low failure rate observed.     

纤维缠绕增强复合管爆破强度试验及理论分析

为了提高涤纶纤维缠绕增强复合管爆破载荷预测的准确性,基于管材特征及缠绕结构特性,以涤纶纤维达到极限强度为失效判据,推导出了爆破载荷理论方程.并开展了复合管水压爆破试验,考虑到HDPE与涤纶纤维非线性力学性能影响,对理论方程进行修正后验证了其准确性.结果表明:修正后理论方程将相对误差降至1.12％,最佳缠绕角度为55.0...     

Positively charged nanomicelles in water of amphiphilic copolymer chitosan-g-polylactide as drug carrier of photoporphyrin IX for photodynamic therapy

Preparation of amphiphilic graft copolymers of chitosan-g-methacrylate-terminated poly(lactic acid) (CS-g-MPLA_n) with various chain length of lactic acid monomers in the copolymers (n = 20, 40, and 70) has been successfully carried out by “grafting on” free radical polymerization. Beside to offer a tunable and easy preparation of chitosan (CS)-based amphiphilic copolymers, the specific purpose is to study the effects of poly(lactic acid) chain length on the micelle properties of the copolymers in water. First, oligomer CS was synthesized by partial oxidation. Second, the methacrylate-terminated poly(lactic acid) with different chain length were synthesized by ring opening polymerization of lactide monomer using 2-hydroxyethyl methacrylate and Sn(Oct)₂ as initiator and catalyst, respectively. Finally, the grafting process was carried out by free radical copolymerization using cerium(IV) sulfate as initiator at 70°C for 24 h. The CS-g-MPLA_n amphiphilic copolymers were characterized by Fourier transform infrared and proton nuclear magnetic resonance. The hydrophobic drug nanomicelles in water with a narrow-size distribution, positively charged and high stability have been confirmed. The micelle size is significantly bigger on longer chain of poly(lactic acid); however, the stability, loading capacity, and encapsulation efficiency are independent on the chain length. The high-loading capacity and encapsulation efficiency for hydrophobic drug protoporphyrin IX as the model are ensuring the hydrophobic drugs efficacy in photodynamic therapy applications.     

螺旋埋弧焊管焊接接头冲击韧性试样缺口位置的确定

基于日常管线钢焊接接头V形缺口冲击韧性试验,分析了螺旋埋弧焊管焊接接头冲击韧性的分布特点,计算机模拟缺口处应力情况,论述了双面埋弧焊管焊接接头冲击韧性试样缺口加工过程中容易出现的问题。结合现行管线钢规范API SPEC 5L对缺口位置和冲击试验的标准要求,分析了几种异常缺口出现的原因及其造成的冲击值变化情况,提出了相应缺口定位问题的预防思路和生产中应采取的解决方法。     

Improving biocompatibility of cobalt based alloy using chemical etching and mechanical treatment

Biomedical grade of cobalt based alloy have found a plethora of applications as medical devices especially in dental and articulation joints like in total ankle, knee and hip arthroplasty. However, the long‐term performance of this material is highly dependent on their ability to withstand in harsh aqueous environment effects such as corrosion and wear once they are used inside a human body. Loss of surface integrity and subsequent leaching of toxic metal ions as well as particles to the surrounding tissues may undermine biocompatibility of metallic implants, also potentially causing untimely loss of mechanical function and device failure. In this study, a biomedical grade of Co?Cr?Mo alloy surface was treated with various surface modification techniques such as chemical etching and mechanical roughening in order to improve its biocompatibility. Investigation was done to study which surface modification techniques possesses the positive effect in cell growth and exhibit excellent cell response on Co?Cr?Mo alloy. In‐vitro study showed that human osteoblast cells grown with good adherence and spread out with an intimate contact on the chemical treated surface after 14 days of incubation. It is believed that porous structure with grooves owned by chemical treated surface helps in anchoring the cells to the substrate surface and facilitates cells growth since more protein molecules expected to have more sites on this surface. Whilst on mechanical roughened surface, the cells appeared to show slightly less extended cell membranes and the cells remained retarded.     

The performance analysis of dual-inverter three phase fed induction motor with open-end winding using various PWM schemes

Wireless Networks - Induction motor with scheme open end winding (OEW) has attract many attention in the recent time as a compromising alternative of multi-level inverter. The structure contains of...     

LLDPE流延膜专用树脂QLLF20的开发与应用

论述流延膜用树脂QLLF20的生产工艺及技术指标,对产品进行性能测试,并与国内外同类树脂进行了对比。QLLF20树脂的熔体质量流动速率为1.8～2.2 g/(10 min),密度为0.918～0.922 g/cm3。薄膜的透光率不小于92.6%、雾度不大于2.0%。加工应用表明,QLLF20树脂适用于流延膜的生产,满足用户的要求。