正态随机矩阵的MTP2性质

给出了正态随机矩阵的定义和一些相关性质,并将正态向量的多元全正二序(MTP2)性质的结论推广到正态随机矩阵.得到随机矩阵和它的任意行向量均满足MTP2的等价关系,以及正态随机样本矩阵为MTP2当且仅当总体的逆协方差阵为M-矩阵等结论.     

磁悬浮控制棒驱动线性能试验研究

为了测试磁悬浮控制棒驱动线的特性,验证其性能的稳定性和可靠性,进行了驱动线的综合性能研究。通过运行特性试验,得到控制棒驱动机构及驱动线的静态、动态性能参数;通过运行寿命考验,验证控制棒驱动线的稳定性、可靠性,并对其综合性能进行检验。     

富氧气氛下受热面改造的经济性分析

富氧气氛下由于烟气量的减少以及锅炉热效率提高所带来的燃料量的减少使得烟气中的粉尘量得到一定的降低,为电站锅炉水平烟道烟气流速的提高带来了可能.增加烟气流速虽然强化了传热,但同时也增大了风机的电耗.采用基于初投资分摊费用和经营成本的动态费用分析法对不同烟气流速下对流受热面的换热进行经济性分析.计算结果表明,最佳工况比空气燃烧方式下的烟道更加紧凑,但是流速超过一定范围之后带来的引风机耗电量的增加超过了流速增加所带来的强化换热的收益,因此是不经济的.采用动态费用法为富氧燃烧方式下对流受热面最佳流速的选择提供依据,对新型富氧燃烧锅炉换热器的设计具有一定的指导意义.     

Formability of Fe-Mn-C Twinning Induced Plasticity Steel

A comparative analysis of formability was investigated between Fe-Mn-C twinning induced plasticity steel with different Mn contents and interstitial-free steel. Tensile test combing with the morphology of fracture reveals that element Mn is helpful for the forming of inclusion or particles with film or rod shapes inducing the crack initiation and propagation. During stamping process, twinning induced plasticity steel without earing shows better anisotropy than interstitial-free steel because a typical <111> fiber texture forms accompanied by a weaker <100> fiber texture. The difference between the two steels is not evident during Erichsen cone cupping test, but the result of cone cupping test indicates that the twinning induced plasticity steel has superior drawing ability compared with interstitial-free steel. The different performances can be attributed to the different deformation mechanism during cupping test. FLD (forming limit diagram) of tested steels further suggests twinning induced plasticity steel has slightly superior deep drawability but low stretchability than that of IF steel, whose FLD₀ value can reach 30%.     

Low Cycle Fatigue Behavior and Deformation Mecha-nism of TWIP Steel

Low cycle fatigue behavior of TWIP （twinning induced plasticity） steel was investigated in axial symmetric tension-compression cyclic loading pattern. Fracture surfaces and microstructures were examined by optical, scanning electron and transmission electron microscopes. It was found that the fatigue life at the strain amplitude of 0.4 % is up to 15 000 cycles, which is much longer than TRIP780 and HSLAS00 steels. The strain hardening and softening features are significant until the strain amplitude comes to 1.25 ~. Persistent slip bands and tiny mechanical twinning layers were observed after fatigue deformation. Deformation mechanism of TWIP steel at low cycle fatigue process is not only twinning, but a complex of both twinning and persistent slip bands.     

剖面浮标变体积油囊式浮力调节系统设计

为精准控制剖面浮标的垂向运动,提出一种可精确控制油量的变体积油囊式浮力调节系统,包含外油囊、增压油箱、密封性能良好的电磁球阀和可调节转速的液压泵等组件。采用拉线位移传感器实时采集增压油箱液面位置实现油量监控,并对外油囊体积进行高精度闭环反馈控制;设计极低泄漏量的液压系统,实现系统在待机状态下浮力保持长期稳定。为精确控制浮力调节系统,构建控制系统数学模型,引入比例积分微分（Proportional Integral Differential,PID）控制算法,并采用Simulink进行稳定性仿真。试验结果表明,系统可实现浮力精确控制,最大超调量低于1%,稳定性与响应速度均符合预期,验证了控制策略的可靠性。     

体表创面修复材料的研究进展

创面修复材料对人体皮肤各种损伤的痊愈尤为重要,一直是临床研究的重要课题.介绍了3个发展阶段划分的新观点,即传统敷料、生物敷料及复合型敷料和组织工程化皮肤,并指出了各阶段存在的问题.其中组织工程原理为研究创面修复材料提供了广阔的前景,目前的研究工作多基于此理论,最后总结了今后的研发方向.     

明胶及其在生物材料中的应用

明胶是一种天然的高分子材料,其理化性质、生物学性能研究表明其是制造生物医用材料的良好基材.总结了明胶的结构和性质,综述了明胶在生物医用材料中的应用,指出了当明胶与其他生物材料复合时,明胶基生物材料在医学领域有着广阔的应用前景.     

基于几何特征与新Haar特征的人脸检测算法

针对普通Adaboost算法训练时间长,对复杂背景下(暗光、多角度、多姿态等)人脸检测识别率较低的问题,提出了一种改进的结合肤色检测及几何特征的Adaboost算法.采用肤色粗检筛选出候选人脸区域,同时采用新的非对称的Haar特征来训练分类器,进一步加强检测性能,提升鲁棒性和复杂背景下的宽容度实验将此算法应用到一个嵌入式系统中,结果表明:在各种复杂背景下的人脸检测中鲁棒性和宽容度均提升很多,误识率进一步降低,并且在嵌入式人脸检测的系统中具有很好的可移植性和实用性.