正定矩阵标准型的复合矩阵的一般形式

实对称正定矩阵的复合矩阵正定性的研究已有结论,但对于一般意义下的正定矩阵的复合矩阵是否仍然是正定的研究需要利用一般的正定矩阵的标准形的复合矩阵进行讨论,给出了一般公式及具体算法,为讨论其复合矩阵的正定性提供了基础条件.     

教师课堂教学质量的多元统计分析

应用多元统计分析中的聚类分析法和主成分分析法对教师高等数学的课堂教学质量进行了统计分析,通过对数据的聚类分析结果提出教师应注重启发性教学并善于引导学生解决实际问题.同时利用主成分分析将原先众多的评价指标用三个指标代替,为进一步提高教学质量提供科学的依据.     

石墨-六角氮化硼微晶混合物与水高压反应产物分析

 利用球磨法制备石墨-六角氮化硼微晶混合物，并在6.1 GPa、800~1 500 ℃条件下与水进行高压反应，以便研究用水作触媒合成B-C-N三元化合物的可能性。通过对反应产物的XRD、XPS谱分析发现：高压下随着温度的升高，反应产物中出现再结晶石墨，其晶化程度逐渐提高；但没有出现再结晶六角氮化硼，也未出现立方氮化硼。在球磨不充分条件下，石墨-六角氮化硼混合物的XRD谱没有完全弥散，它们与水高压反应时，能观察到石墨与立方氮化硼分别结晶的现象，但都没有形成B-C-N晶化结构。     

Infrared thermography of masonry structures

The attention of the present paper was devoted to nondestructive evaluation of masonry structures with a Focal Plane Array infrared camera. Tests were carried out in laboratory on specimens, which simulated one- and two-layer structures, with defects of different geometry and nature and located at different depths. The defects detection was analysed through a cause/effect relationship between the characteristics of defects and hosting material and the observed defect thermal signature, or contrast, on the hosting material.     

几种旱生植物水分生理特性的比较研究

本文对梭梭(Halorylon ammodendron)等几种典型荒漠旱生植物在干旱环境下体内含水量、相对合水量、水分饱和亏缺、自由水、束缚水、水势、离体枝叶吸水速率等的变化及其与植物抗旱的关系进行了比较研究。     

基于离差最大化原理的灰色综合评判方法及其应用

在灰色综合隶属度评价方法基础上,按照离差最大化原理,提出了一种品种区域试验的新的确定权重的方法.应用这种方法,对2002-2003年度国家黄淮南片小麦冬水组区域试验进行了分析.结果表明,这种分析方法克服了通常专家调查法和层次分析法主观随意性强的缺点,因而其分析结果更加客观、可靠.大面积生产实践也表明该方法具有一定可行性和有效性.     

Evaluation of gap length fluctuation with harmonic analysis method

Gap length (GL) of reading head is one of the most critical parameters for high-density magnetic recording systems. A novel method is proposed for quantitative evaluation of the GL fluctuation among a batch of magneto-resistive/giant magneto-resistive heads with same structure design. The method works at head-gimbal assembly level and the evaluation can be done with any read/write analysis equipment. The testing process is based on harmonic analysis of the readback signal. The testing system consists of a selected reference head and sample heads for evaluation. A GL variation function is introduced for the evaluation of GL deviation between the reference head and sample head. This method proved to be easy for implementation and results suggest that variation of GL is considerable and has obvious effect on recording performance in high recording density systems.     

中高温工质在蒸发器中的换热模拟分析

本文采用分布参数的方法,建立了水源热泵中普遍采用的壳管式蒸发器稳态数学模型.通过中高温水源热泵试验台的实验数据同模拟计算结果的对比,验证了数学模型的准确性。应用此数学模型对中高温工质HTR01、HTR02及R134a在蒸发器典型制热运行工况,进行了模拟计算。得出了三种工质制冷剂侧换热系数沿管长的变化关系并对三种工质的换热性能进行了对比分析,为采用中高温工质的水源热泵换热器设计提供了参考依据.     

Bending-torsion vibration of a partially submerged cylinder with an arbitrary cross-section

An analytical method is presented to investigate the bending-torsion vibration characteristics of a cylinder with an arbitrary cross-section and partially submerged in water. The compressibility and the free surface waves of the water are considered simultaneously in the analysis. The exact solution of structure–water interaction is obtained mathematically. Firstly, the analytical expression of the velocity potential of the water is derived by using the method of separation of variables. The unknown coefficients in the velocity potential are determined by the longitudinal and circumferential Fourier expansions along the outer surface of the cylinder and are expressed in the form of integral equations including the unknown dynamic bending deflection and torsional angle of the cylinder. Secondly, the force and torque acting on the cylinder per unit length, provided by the water, are obtained by integrating the water dynamic pressure along the circumference of the cylinder. The general solution of bending-torsion vibration of the cylinder under the water dynamic pressure is derived analytically. The integral equations included in the velocity potential of the water can be solved exactly. Finally, the eigenfrequency equation of cylinder–water interaction is obtained by means of the boundary conditions of the cylinder. Some numerical examples for elliptical columns partially submerged in water are provided to show the application of the present method.     

径向剪切干涉法综合诊断光束质量研究

 为了解决高功率激光装置光束质量诊断系统的自验证问题，研究了基于空间相位调制的径向剪切干涉法综合诊断光束质量的实验应用。该方法理论上只需一台干涉仪且从单幅干涉图中获取光束的近场、相位和远场分布信息。实验结果表明，目前可以得到高分辨率的相位分布，由测量近场和相位恢复出的远场同CCD直接测量得到的远场形态相同，环围能量比曲线相当吻合，不足之处在于只能提取近场较低空间频率成分，还达不到CCD直接测量的空间分辨水平。