Development of antimicrobial polypropylene sutures by graft copolymerization. II. Evaluation of physical properties,drug release,and antimicrobial activity

Polypropylene (PP) sutures are prepared by the simultaneous radiation grafting of 1‐vinylimidazole (VIm) onto PP monofilament sutures. The tenacity slightly decreases whereas the elongation increases with the increase in the degree of grafting. Thermogravimetric analysis shows that the stability of the sutures is enhanced by the grafting process. The grafted sutures have reasonably good water uptake. They are subsequently immobilized with an antimicrobial drug, ciprofloxacin. The modified suture releases the drug over a period of 4–5 days. The antimicrobial activity of the modified suture is determined against Esherichia coli by the zone of inhibition technique. A clear zone of inhibition is observed around the drug‐containing suture. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3534–3538, 2007     

微波辐射干燥氟化铝的工艺研究

介绍了微波干燥的原理和主要特点，研究了利用微波辐射干燥氟化铝工艺，探讨了微波功率、微波辐射时间、物料质量、物料厚度对氟化铝脱水率的影响。实验的最佳条件为微波功率2．0kW、干燥时间80s、物料质量400g、物料厚度2．0cm。实验结果表明，利用微波辐射干燥，氟化铝含水质量分数小于1％，且干燥时间短、能耗低，实验为工业化提供了必要的参考数据。     

无线通信基站建设中电磁辐射缓解技术应用实践

无线通信基站电磁辐射缓解技术包括增加发射天线架设高度、增加天线增益、降低发射器功率、减小VRP下倾角度和改变垂直辐射图VRP等。结合案例分析了无线通信基站建设过程中电磁辐射缓解技术的应用实践。     

Dynamic mechanical properties of styrene‐butadiene rubber vulcanizate filled with electron beam modified surface‐treated dual‐phase filler

The influence of the electron beam modification of a dual‐phase filler on the dynamic mechanical properties of styrene‐butadiene rubber (SBR) is investigated in the presence and absence of trimethylol propane triacrylate or triethoxysilylpropyltetrasulfide. Electron beam modification of the filler results in reduction of the tan δ at 70°C, a parameter for rolling resistance, and an increase in the tan δ at 0°C, a parameter for wet skid resistance of SBR vulcanizates. These modified fillers give significantly better overall performance in comparison with the control dual‐phase filler. This variation in properties is explained in terms of filler parameters such as the filler structure that leads to rubber occlusion and filler networking. These results are further corroborated using the master curves obtained by the time–temperature superposition principle. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2992–3004, 2003     

基于LQR方法的巡航导弹BTT控制器设计

基于LQR最优控制思想提出一种针对巡航导弹BTT控制的设计方法。首先基于巡航导弹的气动外形及飞行特点建立数学模型,然后根据导弹控制器设计要求,合理选取状态变量,采用积分型LQR控制设计最优控制律,最后的仿真结果表明,导弹能够无静差的跟踪过载及滚转指令,并有效的抑制了侧滑角的产生。     

防空导弹拦截目标的建模与仿真

利用simulink构造防空导弹抗击目标的模型.在比例导引的基础上,建立导弹和目标的运动轨迹方程,模拟两者运动轨迹对抗击过程进行仿真.模型结构简单,能够实现对航向角和航迹角的实时跟踪,同时可以利用简单的参数调整模拟不同类型目标.最后,对拦截过程多个相关因素的影响给予对比,仿真结果理想可靠.     

光纤黑体腔高温传感器感温腔体的ANSYS分析

为了提高光纤黑体腔式高温传感器感温腔体的辐射性能,使腔体接近于理想黑体辐射状态,计算了腔体的有效发射率。基于ANSYS有限元方法对感温腔进行热辐射分析,讨论了腔底的形状、腔体温度、腔长、材料表面发射率、腔体的不等温分布对有效发射率的影响关系。结果表明,有效发射率会随着腔长的增加而增大,但会存在一个饱和值。同时当腔体处于非等温时,有效发射率随非等温程度近似呈直线下滑。综合分析结果,可以得出感温腔的优化构造参数,对传感器的制作以及提高传感器的测温准确性、分辨力和灵敏度有指导意义。     

辐照改性聚丙烯拉伸流变行为及其挤出发泡的研究

通过在线形聚丙烯中加入双官能团丙烯酸酯类单体,经小剂量γ射线高能辐照,制备了高熔体强度聚丙烯,研究了其拉伸流变行为及其在挤出发泡方面的应用。Rheotens拉伸流变测试表明,辐照改性后由于形成了长支化分子结构,聚丙烯的熔体强度、拉伸黏度显著提高,具有明显的应变硬化特征。实验表明,ZnO可明显降低AC发泡剂分解温度,缓和分解放热;在辐照改性制备的高熔体强度聚丙烯中加入AC／ZnO复合发泡剂,可挤出发泡得到泡孔尺寸较为均一、分布均匀、具有闭孔结构的发泡材料。     

Tocopherol oil concentration in field-grown sunflower is accounted for by oil weight per seed

Tocopherols are natural antioxidants that increase the stability of fat-containing foods and perform important biological activities. Significant variations (389 to 1873 μg g oil⁻¹) in the total tocopherol concentration of sunflower seed oil have been reported. The main objectives of this work were to determine the influence of intercepted photosynthetically active radiation on tocopherol concentration during seed filling and to establish and validate relationships between tocopherol concentration in oil and other quality variables of the seed. Seven sunflower hybrids were grown under good water and nutritional conditions in two similar experiments carried out in two contrasting environments. Treatments were applied to modify the amount of radiation intercepted per plant during seed filling in order to obtain a range in oil yield per plant and its components. Greater per plant intercepted radiation decreased the tocopherol concentration in oil. Tocopherol concentration decreased when oil weight per seed increased. Tocopherol concentration stabilized for oil weight per seed higher than 23 mg oil seed⁻¹. This exponential relationship accounted for 73% of the variability in tocopherol concentration (507 to 1203 μg g oil⁻¹) despite differences in hull type, locations, hybrids, and radiation treatments. The proposed relationship acceptably predicted independent results. Crop management techniques could lead to seeds with greater concentrations of tocopherols.     

Comparative study on the preparation and properties of radiation‐grafted polymer electrolyte membranes based on fluoropolymer films

In this study the fluoropolymers, poly(ethylene‐co‐tetrafluoroethylene) (ETFE) and poly(vinylidene fluoride) (PVDF) films, together with the radiation‐induced crosslinked polytetrafluoroethylene (cPTFE) film were compared on the basis of their preparation and properties of radiation‐grafted polymer electrolyte membranes. The polymer electrolyte membranes were prepared by radiation grafting of styrene into the base films and subsequent sulfonation. The proton conductivity and chemical stability of the three types of membranes with a similar ion exchange capacity (IEC) near 1.0 mmol/g were investigated and are discussed in detail. Although the ETFE‐based polymer electrolyte membrane was relatively more stable, its proton conductivity was lower than those of the PVDF‐ and cPTFE‐based membranes. On the other hand, the cPTFE‐based membrane showed a significantly higher proton conductivity, but its chemical stability was shorter than that of the ETFE‐based membrane. It is considered that the difference in the preparation and properties of the polymer electrolyte membranes was due to the difference in the degree of crystallinity as well as in the chemical structure of the fluoropolymer base films. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1966–1972, 2007