具有非局部扩散的三种群捕食竞争系统的渐近传播速度（英文）

本文研究了一类具有非局部扩散效应的三种群捕食-食饵模型.我们主要关注的问题是当捕食者被引入两食饵物种栖息地时,在栖息地中入侵的渐近传播速度.通过利用反应扩散方程的比较原理和半群理论等理论,确定了捕食者入侵的渐近传播速度.     

3—氨丙基三乙氧基硅烷对溶胶—凝胶法苯乙烯—顺丁烯二酸酐共聚物／Sio2杂化

用３－氨丙基三乙氧基硅烷（ＡＰＴＥＳ）作为偶联剂，通过溶胶－凝胶（ｓｏｌ－Ｇｅｌ）过程制得两相以共价键结合的透明苯乙烯－顺丁烯二酸酐共聚物／ＳｉＯ２杂化材料。通过ＦＴＩＲ分析等证实了材料有机相与无相相间是以共价键结合的。分析了材料热处理温度和分别用盐酸或氨水作催化剂时对材料溶胶分数的影响、偶联剂及其用量对溶胶－凝胶体系凝胶时间的影响、并研究了杂化材料中无机含量对材料折射率和Ｔｇ的影响。     

用于FLTD的陶瓷封装多间隙气体开关

为了提高多间隙气体开关壳体的寿命、绝缘可靠性和装配的一致性,基于堆栈式多间隙气体开关开展了陶瓷封装多间隙气体开关工艺及击穿特性的研究。对比分析了不同封接工艺对陶瓷金属界面场分布的影响,优选了合理的封接结构。研制了用于FLTD的陶瓷封装多间隙气体开关并对其自击穿特性和触发特性开展了测试,结果表明：开关充干燥空气气压0.3 MPa、耐压±100 kV、峰值电流约30 kA条件下,5 000次放电的触发平均时延36.4 ns,抖动2.8 ns。该结果展示了陶瓷封装气体开关在产品化和免维护方面的优势,在FLTD模块中具有广阔应用前景。

     

石榴子石族矿物状态方程研究进展

石榴子石是重要的造岩矿物,是上地幔、地幔转换带以及(超)高压变质岩中最重要的造岩矿物之一,研究其状态方程对于约束地球内部物质组成和状态、正确理解大洋岩石圈俯冲板块和地幔动力学过程具有重要意义。文中综述了20世纪70年代以来石榴子石p-V(压强-晶胞体积)和p-V-T(压强-晶胞体积-温度)状态方程的研究进展,重点讨论高温高压条件下石榴子石的稳定性以及组分变化和含水对热弹性参数的影响。最后简略概括石榴子石状态方程研究存在的问题,并指出发展方向。

     

192Tl高自旋态能级结构研究

通过熔合蒸发反应181Ta（16O,5n）192Tl,在入射束流为97 MeV能量下,布居192Tl的高自旋态,更新了192Tl的能级纲图。共增加8条新能级,尝试性地指定了能级自旋,将负宇称晕带的能级推高到23-?。讨论了192Tl与相邻同位素奇奇核194,196,198Tl负宇称晕带的旋称劈裂与反转现象,发现随着中子数增加,196,198Tl在高自旋处出现了旋称反转,其原因可能是由于中子质子相互作用与科里奥利力相互竞争所致。High spin states of 192Tl were populated by the 181Ta(16O, 5n)192Tl heavy ion fusion evaporation reaction at 97 MeV beam energy. A new level scheme with 8 new levels was constructed and the level spins were tentatively assigned. The negative yrast band was extended up to 23-?. Systematics of signature of inversion were also discussed for the negative yrast band of odd-odd Tl istopes. Signature inversion has been found in 196,198Tl with neutron number increasing in these four Tl isotopes, and it is explained by the competition between the strength of n-p interaction and Coriolis force.     

Importance of ligands on TiO_2 nanocrystals for perovskite solar cells

The fabrication of high-quality electron-selective layers at low temperature is a prerequisite to realizing efficient flexible and tandem perovskite solar cells(PSCs). A colloidal-quantum-dot ink that contains TiO_2 nanocrystals enables the deposition of a flat film with matched energy level for PSCs; however, the selection of ligands on the TiO_2 surface is still unexplored. Here, we systematically studied the effect of the titanium diisopropoxide bis(acetylacetonate)(TiAc_2)ligand on the performance of PSCs with a planar n-i-p architecture. We prepared TiO_2 nanocrystals from TiCl4 and ethyl alcohol with Cl~- ligands attached on its surface and we found that a tiny amount of TiAc_2 treatment of as-prepared TiO_2 nanocrystals in a mixed solution of chloroform and methyl alcohol can enhance PSC power conversion efficiency(PCE)from 14.7% to 18.3%. To investigate the effect of TiAc_2 ligand on PSCs, TiO_2 samples with different TiAc_2 content were prepared by adding TiAc_2 into the as-obtained TiO_2 nanocrystal solution. We use x-ray photoelectron spectroscopy to identify the content of Cl so as to reveal that Cl ligands can be substituted by TiAc_2. We speculate that the improvement in PCE originates from amorphous TiO_2 formation on the TiO_2 nanocrystal surface, whereby a single-molecule layer of amorphous TiO_2 facilitates charge transfer between the perovskite film and the TiO_2 electronic transport layer, but excessive TiAc_2 lowers the PSC performance dramatically. We further prove our hypothesis by x-ray diffraction measurements. We believe the PCE of PSCs can be further improved by carefully choosing the type and changing the content of surface ligands on TiO_2 nanocrystal.     

双波长偏振干涉型应变与温度同时测量的光纤传感器

针对保偏光纤给出了利用双波长偏振干涉型传感器同时测量应变和温度的一般理论，并通过实验证明了这一理论的可行性。对３０ｃｍ长的ｂｏｗ－ｔｉｅ型光纤的实验结果表明，在温度变化７０℃，光纤长度变化５００μｍ测量范围内，最大误差分别为±２．５℃和±８μｍ。由于这一传感器只利用了正交基模的偏振干涉，因此具有较好的稳定性。     

用扫描近场光学显微镜技术研究金膜表面等离体子共振

表面等离体子波(SPW)可与入射光横磁波极化能量耦合并被共振激发,这种现象被称为表面等离体子共振现象(SPR)。主要利用扫描近场光学显微镜(SNOM)技术和表面等离体子共振现象技术相结合,来研究金膜表面等离体子共振。设计并建立了结构独特的新型Kretschmann型表面等离体子共振现象耦合装置,同时又设计了具有厚度梯度的表面等离体子的制备方法。在此基础上,测量了改变入射角条件下的表面等离体子共振曲线,测得该装置的等离体子共振角灵敏度为1°。并且对金膜表面进行表面等离体子共振条件下的扫描近场光学显微成像。实验结果表明,在共振时金膜表面的扫描成像比不共振时清晰,而且增加了很多细节。应用表面等离体子共振现象技术将可以明显提高扫描近场光学显微镜的信噪比、分辨力等性能。     

前驱溶液的pH值对制备Ca2Zn4Ti16O38:Pr3+,Na+发光粉物相、形貌和发光性质的影响

以钛酸丁酯、醋酸钙、醋酸锌、柠檬酸和乙二醇为原料,采用溶胶-凝胶法制备Ca2Zn4Ti16O38:Pr3+,Na+发光粉.研究了前驱溶液的pH值对溶胶-凝胶转变过程、发光粉物相组成、样品形貌和发光性质的影响.通过热重-差热分析(TG/DTA)、X射线衍射(XRD)分析、扫描电子显微镜(SEM)对前驱物分解、发光粉物相和颗粒大小进行了研究.采用荧光光谱对材料的光谱性质进行了表征.研究发现前驱溶液pH≤3时,所得发光粉样品为蓬松的、颗粒均匀的单相Ca2Zn4Ti16O38粉末,红色余辉时间较长;随着pH值增大,逐渐有杂质相TiO2、CaTiO3和Zn2TiO4生成,并且样品颗粒逐渐变大,颗粒团聚呈现不规则形状,余辉时间变短.结果表明,只有在pH≤3条件下以溶胶-凝胶法制备Ca2Zn4Ti16O38:Pr3+,Na+发光粉下才能获得被日光有效激发,并呈现余辉衰减慢的红色长余辉(644 nm)发光.     

Z—Scan Characteristics of Cascading Nonlinear Media

We present a method,which combines the Gaussian decomposition method and the “distributed-lens“ method,for analysing Z-scan curves of cascading nonlinear medium layers or a complicated cascading structure.A good agreement with the experimental data is obtained.The method would be useful to design optical limiters and to determine the nonlinearities of cascading medium layers.