提高PCA识别率的新算法

针对基于主元分析(PCA)的识别算法不能最优区分不同种类样本的缺点,提出了一种新的多主元分析(Multi-PCA)识别算法。该算法为每类样本构造单独特征空间,用各个空间的特征向量重建待识别样本。特征空间是基于某类样本图像的共性建立,因此重建该类样本图像时将得到较小重建误差,而重建其它类图像时的误差较大。可以根据重建误差的大小来识别样本图像,将待识别样本分类到具有最小重建误差的特征空间。在ORL、YALE人脸库和标牌压印字符库上的实验结果显示,Multi-PCA的识别率比PCA有较大提高。     

力矩突变时角动量变化规律的实验演示与分析

给出一种演示刚体在定点运动时角动量与角速度方向的关系,及力矩突变为零时角动量变化规律的实验演示与分析.     

一种新的角动量守恒演示实验仪

介绍了新研制成功的一种物理演示实验仪,它是以进动过程中突然除去进动的原因而使进动中止的方式来演示角动量守恒的．实验仪结构简单,操作方便,反映的物理原理深刻．     

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根据能量方法原理,通过单位力法和卡氏定理分析方法,理论计算得出了给定位移变形条件下沿S弯的弯矩、应力分布.分析表明,沿S弯结构的应力主要由热收缩变形产生,但重力影响也不可忽略,考虑重力影响后沿S弯最大应力较不考虑重力时增大了10％.根据该理论原理编程计算发现,在S弯高度受限的条件下,圆弧段半径越小,结构最大应力越小,实际没计中可根据强度要求结合加工工艺选择合适的圆弧半径.该分析方法为有效优化结构设计提供了理论指导.     

基于熵值权重限制的超效率DEA评价模型

为了避免DEA自动分配的权重为零的情况发生,对DEA评价的输入输出指标权重应该加以条件限制.通过利用熵值法分析指标内在的差异性,得到输入输出指标权重的比例关系,将其作为限制条件加入超效率DEA评价模型中,构建基于熵值权重限制的超效率DEA评价模型.此模型既可以客观的揭示指标间的内在关系,又可以使得评价对象实现全排序,评价结果更加符合实际.最后将此模型应用于河北省工程中心的实证分析,结果显示新的模型较传统的DEA模型和超效率DEA模型具有明显的优势.     

对一端固定钢条弯曲振动共振的分析

对一端固定钢条弯曲振动的共振进行了分析,指出它有一系列的振动模式,满足一定条件的策动力若频率接近其某一振动模式的频率时,则可以激发钢条共振．     

关于手摇式静电感应起电机原理

手摇式静电感应起电机,在手柄沿顺时针方向摇动时是一个具有正反馈特征的电荷放大器.若莱顿瓶电容上存在一定的初始电荷,则在电容电极外露部分所带电荷产生的静电场中,在金属电刷上出现静电感应,正负电荷将出现在电刷的两端部,绝缘转盘转动时它上面的导体箔片在滑扫过电刷端部的金属毛刷后即带上了净电荷,带有正负净电荷的导体箔片随绝缘转盘转动,在分别至连接莱顿瓶电容电极的正负极集电叉时,都通过尖端放电向莱顿瓶电容充电,莱顿瓶电容中的电荷越来越多.这就是起电机工作的物理过程.     

Low Threshold Current Density Operation of Strain-Compensated Quantum Cascade Laser

We report the low threshold current density operation of strain-compensated In0.64 Ga0.36As/In0.3sAl0.62As quantum cascade lasers emitting near 4.94 μm. By employing an enlarged strain-compensated structure and optimizing the injector doping density, a rather low threshold current density of 0.57kA/cm^2 at 80 K is achieved/or an uncoated 20-μm-wide and 2.5-mm-long laser.     

Plastic Deformation of Fine-Grained Al-Cu-Fe-（B） Icosahedral Poly-Quasicrystals at Elevated Temperature

Fine-grained Al-Cu-Fe-（B） icosahedral poly-quasicrystals （1QCs） as the main materials and fine-grained Al- Pd-Mn IQCs as the supplements, both prepared by powder metallurgy, are uniaxially deformed at vaNous temperatures and strain rates. The systematic study shows the dependences of curves of the true stress versus true strain on several parameters, such as temperature, strain rate and grain size. For Al-Cu-Fe IQCs with grain sizes of about 10-30μm, QC-specific intra-granular softening drop appears in the deformation curves at lower temperatures and/or faster strain rates, but disappears in those curves at higher temperatures and/or slower strain rates, which suggests that the inter-granular effects such as grain-boundary sliding should be taken into account to interpret the continuous hardening, similarly to conventional poly-crystals. For Al-Cu-Fe-B IQCs with smaller grain sizes of about 1 μm and fine-grained AI-Pd-Mn IQCs with grain sizes of about 10μm, QC- specific intra-granular softening drop is absent for all the deformation curves at the possible lowest temperature and fastest strain rate. This implies that the sma/ler the grain size, the more the inter-granular contribution. At the same time, due to the rapid recovery caused by intense diffusion in small-sized grains, the intra-granular quasicrystal lattice reorders rapidly from disordering, which also inhibits the intra-granular softening drop to some extent.     

Toeplitz矩阵,Hankel矩阵求逆的固有复杂度

对于一类问题P,如果能找到一个算法(对串行计算而言)其计算复杂性为f_1(u),则称f_1(n)为问题P固有复杂度的上界,若问题P的所有算法(对串行计算而言)其计算复杂性不小于f_2(n),则称f_2(u)为问题P固有复杂度下界.问题P的固有复杂度介于上