Preparation and characterization of polysulfonamide statistical copolymers from three aromatic diamines

Various polysulfonamide(PSA) statistical copolymers were synthesized by polycondensation of three aromatic diamines and terephthaloyl chloride.The inherent viscosities of the resulting PSA copolymers range from 1.54 to 1.66 dL/g.The precipitated PSA copolymers with feed content of p-phenylene diamine(PPD) being less than 50%(mole fraction) can be redissolved in N-methyl-2-pryrrolidone(NMP) or N,N-dimethylacetamide(DMAc) with lithium chloride of wLiCl=0.02.All of the PSA copolymers exhibit enhanced tensile s...     

湖北省中小型加工贸易企业的现状及对策

分析了湖北省中小企业加工贸易的现状,对进一步发展中小企业加工贸易提出了一些对策和建议。     

基于VB、Matlab的交通事故现场勘查摄影测量系统的开发与应用

发生交通事故后,如何快速、准确地记录事故现场,目前尚未得到妥善解决。将摄影测量理论应用于交通事故现场勘查,运用VB和Matlab编程软件开发了交通事故现场勘查测量管理系统,并模拟了事故现场,将实际的测量值与使用交通事故现场勘查测量管理系统所计算的理论值相比较,误差较小,表明该系统具有一定的实用性。     

特种车辆发动机油液性能评估指标体系研究

以润滑油的理化性能指标为基础,分析了油液性能衰变的本质原因及对发动机磨损的影响,结合某特种车工作环境的特点,建立了车用发动机润滑油性能评估指标体系.定性分析了评估指标,确定了指标的权重,建立了润滑油的模糊评价模型,并结合实例验证了该评估体系的合理性与准确性.该研究对特种车发动机润滑油性能的及时改善和按质换油具有一定的指...     

基于C8051F310的内燃机活塞温度场测试系统

介绍了由C8051F310单片机组成的温度场测试系统,提出了高速运动状态下测量发动机活塞温度场的方法,利用热电测量原理和无线传输技术,实现了活塞表面多点温度的同时测量.详细阐述了测试系统的硬件电路设计和程序设计,在某活塞温度场测量中的应用表明,该系统具有较高的测试精度和可靠性.     

Establishment of a uremic apolipoprotein E knockout mouse model to explore the mechanism of uremic atherosclerosis

Objective To establish a uremic apoE-/- mouse model to observe serum biochemical parameters and features of aortic root atherosclerosis (AS) in the model. Methods A uremic model was induced surgically in apoE-/- mice: electrocautery of the right kidney at 8 weeks of age and nephrectomy (NX) of the left one 2 weeks later. Control mice were sham-operated. Two weeks after NX, renal functions were detected in the uremic and control mice to evaluate the efficiency of the model. After 10 weeks of NX, blood samples were taken to determine serum biochemical parameters, and aortic root was collected for frozen sections to investigate the lesion features of AS. Results Two weeks after NX, renal functions declined significantly in the uremic mice compared with the control ones, and remained stable 8 weeks later either in males or in females. Ten weeks after NX, serum levels of TCH, TG and LDL-C were dramatically higher in the uremic mice than in the controls, whereas no differences in serum HDL-C or glucose concentration were found between the two groups. Aortic root plaque relative area increased significantly in the uremic mice compared with the controls either in males or in females; more-over, the lesion area was larger in female mice than in male ones. Conclusion We established a uremic apoE-/- mouse model successfully, and this model is characterized by accelerated atherogenesis which is associated with an increase in serum lipid profile. This experimental model can be a useful tool to study the pathogenesis and therapeutic strategies of uremic AS.     

交流变频器的维护要点

随着交流变频器技术的日趋完善,港口起重机械的直流驱动器已逐渐被交流驱动器所取代。交流驱动器维护简便,能适应恶劣工况,对电机的要求低,若使用带PG矢量控制方式,控制精度可达0．002％,在港机应用上还有很高的储备精度,能适应港机对控制要求的不断提高。     

美军军事通信卫星发展趋势分析及启示

文章讨论了美军先进的军事卫星通信系统,分析归纳了美军卫星通信的特点与发展趋势,并针对我国军事通信卫星发展现状阐述了需要解决的关键技术问题及发展思路。     

海商法下海盗赎金的性质

为解决海盗赎金问题,从海盗行为的定义出发,比较我国与伦敦保险人协会相关保险条款的异同,并结合案例分析赎金的性质,对船舶所有人提出就赎金主张共同海损从而得到分摊以弥补损失的方法建议。     

基于二次回归正交设计法的薄壁吸能特性研究

为提供汽车不同区域的吸能特性与薄壁金属结构匹配的理论依据,一方面应用正交设计理论得到多参数影响下最优吸能特性的薄壁结构水平组合。建立了比吸能与试验参数的二次非线性回归方程并进行了比吸能预测值与试验值的比较,得到理想结果;另一方面,通过不同结构碰撞峰值力与加速度比较,完善了汽车不同区域耐撞性要求下薄壁吸能评价体系。