改进型1-3压电复合材料结构参数对其谐振性能的影响

研究了水声换能器用的1-3改进型(称1-3-2型)压电复合材料的结构参数(陶瓷体积分数)对其谐振性能的影响.1-3-2型压电复合材料是由1-3型复合材料和陶瓷基底两部分组成,利用Newnham串并联理论、均匀场理论和混合定律,得到1-3-2型复合材料的压电方程,从而推导出1-3-2型复合材料的各项等效性能参数,并通过实验对频率常数、机电耦合系数和声阻抗等参数的理论推导进行了验证,实验结果与理论计算符合较好。     

基于M2因子测量的大气湍流参数的确定方法

基于广义惠更斯-菲涅尔原理以及大气湍流理论,推导出部分相干光束在大气湍流中传输的光束传输M ^{2因子的解析表达式.定量分析了表征大气湍流参数的折射率结构常数 C2_n}和涡旋内尺度 l _{0对 M ^{2因子的影响,并由此提出了一种通过实验测量大气湍流中光束的 M 2因子,进而确定出大气湍流参数的新方法.研究结果表明,由于大气湍流对相干性好的光束影响更为明显,在测量中可采用具有高相干性的基模高斯光束作为测量光源,而测量装 关键词： 2因子')" href="#">光束传输 M 2因子 大气湍流参数 湍流折射率结构常数 湍流涡旋内尺度}}     

傅里叶变换中红外光谱法检测脑膜瘤的研究

采用傅里叶变换衰减全反射中红外光谱法检测了24例液氮冻存的脑膜瘤离体样品(其中良性肿瘤12例,有恶性倾向的肿瘤12例),对得到的红外光谱进行整理分析,发现不同类型脑膜瘤组织(如纤维型脑膜瘤和内皮型脑膜瘤)的红外光谱存在着差异,并且同一种类型的脑膜瘤组织,其恶性倾向的程度不同,他们的红外光谱也表现出较为明显的区别,因此,我们可以从各个特征吸收峰的峰位、峰形及峰强等信息的变化来区分脑膜瘤,并可以初步鉴别脑膜瘤的性质;研究结果发现,通过某些特征吸收峰(如1 160cm-1)峰位的变化来鉴别脑膜瘤的性质与病理诊断结果的符合率大于85%,说明傅里叶变换衰减全反射中红外光谱法有可能发展成为一种对样品无损伤、快速的脑肿瘤诊断新方法。     

可见/近红外光谱分析技术快速鉴别航天育种番茄

提出了利用可见/近红外光谱技术快速无损鉴别航天育种番茄品种的方法,采用偏最小二乘法对光谱特征信息进行提取,与神经网络结合建立番茄品种的鉴别模型.该模型将提取后的主成分作为神经网络的输入,加速了神经网络的训练速度.同时采用小波变换对大量光谱数据进行压缩,并结合神经网络建立番茄品种鉴别模型,该模型将压缩后的数据作为神经网络...     

溴到铷的类钠离子能级辐射跃迂几率和能级寿命

本文在多组态Dirac-Fock(MCDF)理论框架下计算了水窗波段(λ:23.3～43.8A,相当于Z:34～46)的溴到铷的类钠离子1s~22s~22p~6nlj(n=3～15,l=0～6)各能级能量及各能级n_il_ij_i—n_kl_kj_k(n_i≤6,n_h≤15)间的电偶极辐射跃迁几率,并由此得出可能产生软X射线激光跃迁(4f-5g,4d-5f,4f-6g,4d-6f)的激光上能级的寿命,把计算得到的跃迁波长与实验测量值进行比较,其相对误差小于0.35％。     

原子吸收光度法测定钢铁及合金中的铌量

本法叙述了一氧化二氮－乙炔火焰原子吸收光度法测定铌量，用鞣酸沉淀分离和在盐酸－氢氟酸介质中加入增感剂三氯化铝，灵敏度１２μｇ／ｍＬ／１％吸收，检出限６．１μｇ／ｍＬ。     

Visible light emission in collisions between O5+ ions and He atoms

Visible light emission spectra during collisions between O⁵⁺ ions and He atoms in the range of 200–800 nm at different projectile energies (4.06–5.31 keV-u⁻¹) have been measured. Emission spectra show that there are three channels of excitation in the O⁵⁺-He collision system: (i) single-electron capture into excited states; (ii) double-electron capture into excited states; (iii) direct excitation of target atoms. There are transitions between states with comparably high quantum numbersnl. The absolute emission cross-sections of every spectral line are calculated. The relations of these cross-sections with the energy of the projectiles are studied. Project supported by the National Natural Science Foundation of China and Chinese Association for Atomic and Molecular Dada.     

一类新的求全局优化问题的填充函数

填充函数方法是一种寻找全局极小解的有效方法.本文首先对现有的填充函数进行研究分析,然后构造出一类新的填充函数,设计算法,并通过数值试验验证了该函数和算法的有效性.     

The Labusch parameter of a driven flux line lattice in YBa Cu O superconducting films

We have investigated the influence of a driving force on the elastic coupling (Labusch parameter) of the field-cooled state of the flux line lattice (FLL) in 400 nm thick YBa₂Cu₃O₇ superconducting films. We found that the FLL of a field-cooled state without driving forces is not in an equilibrium state. Results obtained for magnetic fields applied at and 30 relative to CuO₂ planes, show an enhancement of the elastic coupling of the films at driving current densities several orders of magnitude smaller than the critical one. Our results indicate that the FLL appears to be in a relatively ordered, metastable state after field cooling without driving forces. Received 21 December 1999     

The Quantum-Classical Comparison of the Arrival-Time Distribution Through the Probability Current

We consider the arrival time distribution defined through the quantum probability current for a Gaussian wave packet representing free particles in quantum mechanics in order to explore the issue of the classical limit of arrival time. We formulate the classical analogue of the arrival time distribution for an ensemble of free particles represented by a phase space distribution function evolving under the classical Liouville's equation. The classical probability current so constructed matches with the quantum probability current in the limit of minimum uncertainty. Further, it is possible to show in general that smooth transitions from the quantum mechanical probability current and the mean arrival time to their respective classical values are obtained in the limit of large mass of the particles.