左手介质矩形波导导模和表面模的场分布

从麦克斯韦方程组出发,结合电磁场的边界条件,推导出介质矩形波导导模的一般色散方程.对普通介质矩形波导和左手介质矩形波导的导模场分布分别进行了数值模拟.通过对比两种介质矩形波导的导模场分布的模拟结果,发现左手介质矩形波导Ex22模的场分布比普通介质波导Ex00模的场更集中在波导中部.同时,根据处理普通介质矩形波导的Marcatili方法.类比得到左手介质矩形波导表面模的色散方程,并数值模拟了低阶模的场分布,结果表明,能量主要集中在波导的四个角区以及波导的边缘.     

Temporal variation of fundamental constants in 229Th transition

If is there enhanced sensitivity to variations of fine structure constant, nucleon mass and meson masses in the transition between the low energy and long-lived nuclear isomer and ground states? To answer this open problem, we investigate the transition between the long-lived 7.6±0.5 eV isomer and ground states in ²²⁹Th based on the formulae derived from both the Nilsson model and Feynman-Hellmann theorem. Consistent conclusions are drawn by these two method. The sensitivity to relative variation of fine structure constant could be enhanced by 3—4 orders of magnitude, and to variations of nucleon mass and meson masses are enhanced by about 5—6 orders of magnitude in the ²²⁹Th transition.     

Common Features in Electronic Structure of the Oxypnictide Superconductors from Photoemission Spectroscopy

High resolution photoemission measurements are carried out on non-superconducting LaFeAsO parent com- pound and various superconducting RFeAs（O1-ZFx） （R=La, Ce and Pr） compounds. It is found that the parent LaFeAsO compound shows a metallic character. By extensive measurements, several common features are identified in the electronic structure of these Fe-based compounds： （1） 0.2 eV feature in the valence band, （2） a universal 13-16 meV feature, （3） near EF spectral weight suppression with decreasing temperature. These uni- versal features can provide important information about band structure, superconducting gap and pseudogap in these Fe-based materials.     

重自共轭原子核中α凝聚体物理性质的理论研究(英文)

原子核多体系统中可以存在一类被称为α凝聚体的奇异物理态。该奇异态可以被视为玻色-爱因斯坦凝聚在原子核物理中的推广。一般认为,α凝聚体不仅可以存在于12C中,也可以存在于诸如16O,20Ne,24Mg,28Si等质量更重的自共轭原子核中。重自共轭原子核中的α凝聚体的物理性质是核结构理论重要的研究课题,相关理论计算可以为实验研究提供有益参考。主要介绍了该研究方向的基本理论框架,包括Tohsaki-Horiuchi-Schuck-Röpke波函数方法、Yamada-Schuck模型,以及近期提出的半解析近似方法。还讨论了α粒子间四体相互作用对α凝聚体物理性质的影响,并对α凝聚体破裂和一维α凝聚体等可能的研究方向做了简要论述。α condensates are exotic states in nuclear many-body systems, and can be viewed as the generalization of the Bose-Einstein condensate in nuclear physics. It is widely believed that, α condensates exist not only in 12C, but also in heavier self-conjugate nuclei such as 16O, 20Ne, 24Mg, 28Si, etc. It is important to understand the physical properties of these α condensates in heavy self-conjugate nuclei from the theoretical perspective, and the theoretical results could be a useful reference for the experimental studies. This work reviews the basic frameworks to study α condensates, including the Tohsaki-Horiuchi-Schuck-Röpke wave function, the Yamada-Schuck model, and the recently proposed semi-analytic approximation. The impacts of the four-body interactions of α particles on the physical properties of α condensates are reported. The breakup of α condensates and the one-dimensional α condensates are discussed briefly as the possible future directions in this field.     

复合材料修补结构腐蚀扩展特性实验研究

为了研究腐蚀环境对复合材料修补结构疲劳特性的影响,开展以某型飞机加速环境谱为基础的预腐蚀试验,并采用递进式的试验方法分别完成对未修补未腐蚀、修补但未腐蚀、又修补又腐蚀的试样疲劳裂纹扩展试验。利用试验数据计算了复合材料修补构型、腐蚀环境对裂纹尖端应力强度因子影响的修正系数,并确定了通过试验验证的修补结构疲劳裂纹扩展修正模型。该模型预测腐蚀环境下修补结构的疲劳寿命与试验值一致。试验数据和预测模型可为海军飞机复合材料修补结构的损伤容限设计提供参考。     

Theoretical description of improving measurement accuracy for incoherence Mie Doppler wind lidar

For the nonlinearity of Fabry-Perot interferometer(FPI) transmission spectrum,the measurement uncertainty of incoherent Mie Doppler wind lidar based on it increases evidently with the increase of backscattering signal Doppler shift.A method of repeating the use of the approximate linear part of FPI transmission spectra for reducing the high uncertainty of a big Doppler shift is proposed.One of the ways of realizing this method is discussed in detail,in which the characteristics of FPI transmission spectrum changing with thickness and incident angle are utilized simultaneously.Under different atmosphere conditions,it has been proved theoretically that the range of measurement uncertainty drops to one-sixth while its minimum has no serious change.This method can be used not only to guide the new system design,but also as a new working way for the fabricated system.     

考虑均衡性的不确定时间车辆调度问题研究

本文针对车辆调度实际运行过程中时间的不确定性问题,提出了包含时间窗口、车辆容量约束的配送服务线路随机规划模型,以最小化调用的车辆数目和运行距离,降低顾客的不满意度并且尽可能保证每条路线的均衡性。结合模型,给出了基于禁忌搜索的混合启发式算法,并且生成多个算例,依据算例结果说明模型和算法优越性,同时说明可以在不降低顾客满意度和不提高总运输成本的基础上,降低各条线路之间的时间差异。     

不同pH值制备的TiO2和TiO2/SiO2催化剂结构、表面性质及光催化活性

以TiOSO₄和SiO₂溶胶为原料, 采用沉淀法用氨水调节pH值制备TiO₂和TiO₂/SiO₂催化剂. 制备的催化剂用X射线衍射(XRD), 扫描电镜(SEM), N₂吸附(BET), 紫外-可见(UV-Vis)漫反射光谱, 程序升温脱附(NH₃-TPD), 傅里叶变换红外(FT-IR)光谱技术分析. XRD谱图显示纯TiO₂中锐钛型和金红石相共存, 且金红石相含量随pH值升高而增加. 但是, TiO₂/SiO₂催化剂只有锐钛型. 扫描电镜发现制备的催化剂呈类球形, 颗粒间相互交叠, 粒径在10-25 nm之间. TiO₂和TiO₂/SiO₂光催化剂的比表面积随pH值升高略有增大. SiO₂的添加会增大催化剂的比表面积. 程序升温脱附实验结果说明催化剂的表面酸量随pH值升高而增加. TiO₂/SiO₂的表面酸量比相同pH值制备的TiO₂大. 红外光谱分析说明Si掺杂和高pH值有利于催化剂表面生成更多的羟基. TiO₂和TiO₂/SiO₂光催化剂的催化活性随pH值升高而明显增强. TiO₂/SiO₂的光催化活性优于TiO₂. TiO₂/SiO₂催化剂具有较好的耐久性.     

Restrictions on negative energy density for the Dirac field in flat spacetime

This paper investigates the quantum Dirac field in n+1-dimensional flat spacetime and derives a lower bound in the form of quantum inequality on the energy density averaged against spacetime sampling functions. The state-independent quantum inequality derived in the present paper is similar to the temporal quantum energy inequality and it is stronger for massive field than for massless one. It also presents the concrete results of the quantum inequality in 2 and 4-dimensional spacetimes.     

矩阵Hadamard积和Fan积的特征值界的一些新估计式

本文研究了非奇异M-矩阵A与B的Fan积的最小特征值下界和非负矩阵A与B的Hadamard积 的谱半径上界的估计问题.利用Brauer定理,得到了一些只依赖于矩阵的元素且易于计算的新估计式,改进 了文献[4]现有的一些结果.