300GHz超导SIS接收机系统的设计与构建

超导SIS(Superconductor-Insulator-Superconductor)混频技术是新兴的低噪声检测技术.其卓越的低噪声性能已使其成为毫米波和亚毫米波频段灵敏度最高的谱线接收设备,接收机的自动控制和稳定性有更高的要求,研制能够长期稳定工作的接收机有很重要的意义.本文主要讨论了我们自行研究设计工作在4K温度,准光学系统的毫米波超导SIS接收机的组成部件,根据我们制备的超导SIS隧道结器件的特性指标,计算设计了300GHz波段的超导接收机天线和结的集成芯片.     

Joint Reducing Subspaces of Multiplication Operators and Weight of Multi-variable Bergman Spaces

This paper mainly concerns a tuple of multiplication operators defined on the weighted and unweighted multi-variable Bergman spaces, their joint reducing subspaces and the von Neumann algebra generated by the orthogonal projections onto these subspaces. It is found that the weights play an important role in the structures of lattices of joint reducing subspaces and of associated von Neumann algebras. Also, a class of special weights is taken into account. Under a mild condition it is proved that if those multiplication operators are defined by the same symbols, then the corresponding von Neumann algebras are $*$-isomorphic to the one defined on the unweighted Bergman space.     

Demixing of amphiphile–polymer mixtures investigated using density functional theory

We construct a functional for amphiphile–polymer mixtures and investigate the demixing transition by using a proposed version of density functional theory. It is found that increase of the amphiphilic size ratio and polymer length can effectively promote phase separation of the systems. Phase diagrams are plotted to clarify these influences. The results provide an effective way of controlling the stability of the fluid–fluid phase equilibrium of the mixtures.     

对麦克斯韦电磁波传播图像的详解

电磁学的知识是高中物理教学的重要内容,学过的学生会对麦克斯韦电磁场理论深深着迷,“变化的电场产生磁场,变化的磁场产生电场”的规律充分体现了物理规律的对称美、和谐美．     

Estimating color appearance of pearlescent bottles using digital camera

Pearlescent coatings become highly popular to the modern generation of color rendering materials due to their unique color effect. However, it is quite challenging to evaluate its color appearance by traditional color measurement. A low-cost camera is a highly efficient device for multi-geometry color appearance estimation for pearlescent bottles, which has been achieved through the camera characterization, sample image capturing, and then mathematical transforming from RGB （red, green, and blue） values to color appearance attributes based on the color appearance model of CIECAM02. A tele-spectroradiometer for physical measurement together with visual assessment is applied for comparison with the camera method to evaluate the accuracy of camera predictions and discuss the applicability of CIECAM02. The experimental results indicate that the camera data have strong correlation with the physical measurement and also fit well with visual data except for a slight slope shift existing in lightness due to a divinable psychophysical magnitude variation for spatial-dependent color samples. Hence it is feasible to estimate the color appearance of pearlescent bottles using a digital camera.     

Hydrothermal preparation and photoluminescence of bundle-like structure of ZnWO4 nanorods

ZnWO₄ nanorods with a bundle-like structure were synthesized at 180°C for 12 h by a hydrothermal technology from Na₂WO₄⋅2H₂O and ZnSO₄⋅7H₂O in the presence of sodium dodecyl sulfate (SDS). The as-synthesized bundle-like structure of ZnWO₄ nanorods was characterized by various techniques: TEM, XRD and EDS. The luminescence properties of the bundle-like structure of the ZnWO₄ nanorods were investigated by photoluminescence (PL) spectroscopy.     

逐步增加的Ⅱ型截尾下冷贮备串联系统可靠性指标的Bayes估计

在逐步增加的Ⅱ型截尾模型下,运用Bayes方法,研究部件寿命服从双参数指数分布的冷贮备串联系统可靠性指标的近似置信区间问题.在两个参数均未知的情形下,给出了失效率,系统可靠度及平均寿命的Bayes近似置信区间的计算公式;对于超参数的确定,给出一种新的方法;最后进行了随机模拟,并对近似置信区间的精度进行了讨论.     

Single-mode low-loss optical fibers for long-wave infrared transmission

In this Letter, we report single-mode fibers made of chalcogenide glasses with low loss in the 5-12μm range. Glasses from the Ge-As-Te-Se system were optimized to prevent nucleation and to exhibit low density of charge carriers. Single-mode fibers were obtained through the rod-in-tube method by substituting 2% Te/Se between the core and cladding glasses. The resulting single-mode fibers had a core diameter of 30μm and exhibited losses of ~6 dB/m at 10.6μm, and as low as 3-4dB/m in the 6-10μm range.     

Observation of a red-blue detuning asymmetry in matter-wave superradiance

We report the first experimental observation of strong suppression of matter-wave superradiance using blue-detuned pump light and demonstrate a pump-laser detuning asymmetry in the collective atomic recoil motion. In contrast to all previous theoretical frameworks, which predict that the process should be symmetric with respect to the sign of the detuning of the pump laser from the one-photon resonance, we find that for condensates the symmetry is broken. With high condensate densities and red-detuned pump light the distinctive multiorder, matter-wave scattering pattern is clearly visible, whereas with blue-detuned pump light superradiance is strongly suppressed. However, in the limit of a dilute atomic gas symmetry is restored.