空腔中B-dot的低频响应特性北大核心CSCD

针对空腔中B-dot的频响特性开展了分析。当频率低于一定值时,安装在空腔中的B-dot探头的输出信号存在低频分量增益,可以用一个"负时间常数的RC高通滤波器"描述其频响特性,其本质是低频段为增益的高通滤波器。采用不同等效频率的RLC回路连接安装B-dot的传输线,开展了B-dot探头低频响应的实验研究,结果表明,被测信号等效频率不同时,标定得到的磁通穿透特征时间常数以及互感系数有所不同。因此,为得到正确的修正系数,应当使标定波形的等效频率尽量接近实测波形。     

单扩张型Lie Rinehart代数的分类定理

定义单扩张型Lie Rinehart代数,从而给出一种通过导子构造Lie Rinehart代数的途径.指出这是一种特殊的作用Lie Rinehart代数.在系数环是没有零因子的交换代数的前提下,给出单扩张型Lie Rinehart代数的完全分类定理.特别的,证明多项式环上的任何非平凡作用Lie Rinehart代数必然是单扩张型的,并给出其标准型.     

水和氯化铵提取-电感耦合等离子体发射光谱(ICP-AES)法测定石灰性土壤中交换性钾钠钙镁

为了提高石灰性土壤中交换性钾钠钙镁的分析效率及分析准确度,本文创新性采用水和氯化铵对石灰性土壤进行处理,并采用振荡交换、离心分离的方式进行石灰盐清洗、钾钠钙镁离子交换提取,提取液直接在电感耦合等离子体发射光谱仪(ICP-AES)上测定。该方法交换性盐基钙、镁、钾、钠的检出限分别为0.01、0.009、0.004、0.012cmol/kg。用国家一级标准物质GBW07498-新疆棕漠土和新疆地区石灰性土壤进行验证,方法精密度均小于5%,回收率在97％~105%。方法适用于石灰性（碱性）土壤（特别是新疆土壤）样品中交换性钾、钠、钙、镁的分析测定。     

Transverse Inhomogeneous Carrier-Envelope Phase Distribution of Idler Generated through Difference-Frequency-Generation

The transverse inhomogeneous carrier-envelope phase （CEP） distribution of idler generated through difference-frequency-generation （DFG） in quadratic nonlinear crystals is theoretically studied. In practical CEP stabilized DFG setups, the pump and the signal are usually Gaussian beams with non-uniform intensity distribution. Since the idler CEP is dependent on gain, this non-uniform intensity distribution leads to inhomogeneous gain across the aperture of the idler beam, resulting in a varying transverse idler CEP. Simulation results show that in practical settings, in the high-gain regime, transverse inhomogeneous CEP can be much smaller compared with π/2. However, when gain on the propagation axis reaches saturation, CEP difference can well exceed π/2.     

Aharonov-Casher和He-McKellar-Wilkens相位的对偶对称关系

本文首先对电磁理论中的对偶对称性以及对偶变换做了简要回顾.然后讨论了与电磁相互作用相联系的Aharonov-Casher和He-McKellar-Wilkens相位之间的对偶对称性.最后,在宇称不守恒但具有相对论不变性的条件下,给出了一般情况下描述Aharonov-Casher和He-McKellar-Wilkens相位之间对偶对称关系的拉格朗日量,从而建立了统一的、不依赖于模型的描述Aharonov-Casher和He-McKellar-Wilkens相位之间对偶对称关系的方法.     

Wigner Function for Klein-Gordon Landau Problem

First we calculate the Wigner phase-space distribution function for the Klein-Gordan Landau problem on a commmutative space. Then we study the modifications introduced by the coordinate-coordinate noncommuting and momentum-momentum noncommuting, namely, by using a generalized Bopp＇s shift method we construct the Wigner function for the Klein-Gordan Landau problem both on a noncommutative space （NCS） and a noncommutative phase space （NCPS）.     

石英纤维表面低温制备氮化硼涂层

以硼酸和尿素为氮化硼源,氮气气氛下,采用溶液浸涂法在石英纤维表面低温制备了氮化硼涂层.用XRD、SEM、IR、Raman和TEM等测试手段对涂层的结构、形貌进行了表征.结果表明:硼酸和尿素在氮气气氛下于850℃反应5 h,得到的BN涂层为鹅卵石状,产物中含有纳米尺寸的t-BN和无定型BN两种不同形态;纤维表面涂层质量随浸渍次数变化,浸涂一次的纤维表面涂层不连续,存在大量孔洞;浸涂三次的纤维表面光洁,涂层均匀,且无剥落或开裂现象;浸涂大于三次,纤维表面出现大量聚集颗粒,表面不光滑,但亦无剥落或开裂现象.     

Stimulated Raman Scattering of a Modulated Laser Beam in Air： a Perturbation Approach

Stimulated Raman scattering （SRS） of a third-harmonic beam of a high-power laser in air is analysed by using a perturbation approach. It is found that intensity modulations of the third-harmonic beam, resulting from the surface ripple of nonlinear crystal, can be significantly enhanced due to SRS, and the gain of instability increases with the spatial period of modulation. Numerical simulations based on the nonlinear coupled-wave equations verify the validity of the perturbation approach.