边界衍射波理论的两种提法之正误

文献［１］提出“修改的边界衍射波理论”与“π跃变”的观点，本文用它计算了圆孔衍射场，却得不到与实际定量相符的结果。说明“π跃变”提法欠妥。     

全珠光体钢循环应变行为的透射电镜研究

用透射电镜研究了位错在循环应力—应变珠光体组织中的作用机制,探讨了片状珠光体的循环软、硬化机理。结果表明,在循环应变珠光体组织中,渗碳体/铁素体界面弹性不协调应力的发展以及铁素体的屈服,分别是产生界面位错和铁素体位错的原因。珠光体的循环应力—应变行为主要取决于初始可动位错密度及其增殖速率。循环应变后的位错密度随片间距的减小而提高,珠光体的稳态流变应力服从Bailey-Hirsh关系。     

HPLC法测定乳制品中的黄曲霉毒素M1

目的 建立孔制品中黄曲霉毒素M1的HPLC的检测方法.方法 样品经提取、过免疫亲和柱净化后,用高效液相色谱-荧光检测器进行分析.结果 黄曲霉毒素M1在0.1～1 μg/L范围内线性关系良好,γ＞0.999.回收率在90%～110%之间,定量限为5 pg,检测限为2 pg.结论 该方法快速、简便、准确,改善了现有国标GB/T18980-2003操作繁琐,测定结果易受操作影响的缺点.可作为乳制品中黄曲霉毒素M1的定量测定.     

BP神经网络在羊毛品质预测中的应用研究

用BP神经网络方法对加工毛条时所需的羊毛品质进行预测 ,阐述了利用BP神经网络预测羊毛品质的工作原理 ,给出了羊毛品质预测系统的BP神经网络模型 ,并得出了实验结论。     

热学参数在建筑热湿环境营造过程中的适用性分析

比较了两类热学参数--(火用) (或熵)、(火积)在分析建筑热湿环境营造过程时的适用性.(或熵)是研究热功转换过程的热学参数,参考状态的选取对分析所得结论的影响很大.介绍了(火积)的物理概念及其在传热领域的应用,尝试利用(火积)作为热学参数对以热量、质量传递过程为主的热湿环境营造过程进行研究.分析了典型热湿环境营造案例...     

Emission and Absorption Cross Sections at 810 and 860 nm Bands of Er3+ in LiNbO3 Crystal

We have measured the unpolarized and polarized emission spectra of ⁴I_9/2→⁴I_15/2 (810 nm) and ⁴S_3/2→⁴I_13/2 (860 nm) electronic transitions of Er³⁺ in LiNbO₃ crystal under different incident directions and polarization states of excitation beam. From the measured emission spectra, the emission and absorption cross‐section spectra were calculated based upon McCumber theory. It is found that Er³⁺ electronic transition shows interesting excitation beam direction effect in polarization dependence, spectral shape, and cross‐section value. Both transitions are highly π‐polarized as the excitation beam was aligned perpendicular to the optical axis of crystal while being highly σ‐polarized as the excitation beam was oriented parallel to the optical axis of crystal. The spectral shape in the case of the perpendicular excitation is very different from that in the case of parallel excitation. The cross‐section value in the perpendicular excitation case is at least 1.5 times larger than that in the parallel excitation case. These excitation direction effects are independent of the polarization state of excitation light, and are attributed to the selective Er³⁺ site excitation. In addition, the Er³⁺ 860 nm emission lifetime was measured to be 27 ± 5 μs and the quantum efficiency of the emission is 2.5%.     

A Novel Hierarchical Nanostructure for Enhanced Optical Nonlinearity Based on Scattering Mechanism

Surface modification of nonlinear optical materials (NOMs) is widely applied to fabricate diverse photonic devices, such as frequency combs, modulators, and all‐optical switches. In this work, a double‐layer nanostructure with heterogeneous nanoparticles (NPs) is proposed to achieve enhanced third‐order optical nonlinearity of NOMs. The mechanism of modified optical nonlinearity is elucidated to be the scattering‐induced energy transfer between adjacent NPs layers. Based on the LiNbO₃ platform, as a typical example, double layers of embedded Cu and Ag NPs are synthesized by sequential ion implantation, demonstrating twofold magnitude of near‐infrared enhancement factor and modulation depth in comparison with a single layer of Cu NPs. With the elastic collision model and thermolysis theory being considered, the shift of the localized surface plasmon resonance (LSPR) peak reveals the formation mechanism of the double‐layer nanostructure. Utilizing the enhanced optical nonlinearity of LiNbO₃ as modulators, a Q‐switched mode‐locked waveguide laser at 1 µm is achieved with shorter pulse duration. It suggests potential applications to improve the performance of nonlinear photonic devices by using double‐layer metallic nanostructures.