大气折射和大气色散的数值计算及结果分析

介绍了大气折射和大气色散的概念，推导了它们的计算公式。通过数值迭代的方法计算了一定条件下各种模型的大气折射和大气色散值。分析得到了各种模型下大气折射和大气色散的差异以及大气压、气温、观测站点海拔和工作波段对大气色散的影响。     

Refraction and geometry in Maxwell's equations

Abstract

Computational studies of Maxwell's equations in complex geometries encountered in photonic band structure calculations run into difficulties when several length scales occur, such as the wavelength of light in free space and the skin depth in metal. These problems are remedied by using an adaptive co-ordinate system which expands or contracts length scales as necessary. Here we show that moving to a general co-ordinate transformation is equivalent to renormalizing ε and μ. This is an huge simplification because now we need only write one computer code in a Cartesian system, and we can use this same code to handle any co-ordinate system by adjusting the ε and μ we feed into the calculation.     

Image Perturbations and Optical Flow in Time-dependent Refraction

Abstract

The ray formulation for light propagation is applied to the problem of image perturbations (‘shimmering’) resulting from perturbations in the refractive index profile of the medium between an object and an observer. Expressions are derived relating the image diagram perturbation and the instantaneous image motion (optical flow) to the change in the refractive index profile, in the paraxial ray approximation. In special circumstances the image perturbation and optical flow can be estimated directly. These results are applied to two simple examples.     

Refraction and diffraction by a metal-dielectric multilayered structure

An optical refraction prism consisting of metal and dielectric, subwavelength, periodic multilayered thin films has been proposed. The multilayered structure of metal and dielectric thin films has a cylindrical dispersion surface for TM polarized light. The light behaviors are very different from those of conventional glass prisms and photonic crystal superprisms. Refraction and diffraction of the light wave for the metal-dielectric multilayered prism has been investigated by numerical simulations and graphical representation based on the dispersion surface. A prism with 0.2 microm period had an angular dispersion of 0.20 degrees /nm for approximately 0.8 microm wavelength light. The finite thick metal-dielectric multilayered structure acted as a slab waveguide.     

油封圈冲压成形

通过分析某油封圈零件的结构特点及技术要求,确定了落料、冲孔-翻边的工艺方案,介绍了每副模具的工作过程及设计要点,大大提高了生产效率,缩短了模具开发周期,优化了工艺方案,使模具运行状态平稳,生产的零件质量可靠。     

The vacuum system of the Low Energy Ion Ring at CERN: Requirements, design, and challenges

For the heavy ion program at CERN's Large Hadron Collider, lead-lead collisions with a design luminosity of 10²⁷ cm⁻² s⁻¹ are foreseen. This will be achieved after an upgrade of the ion injector chain where the Low Energy Antiproton Ring (LEAR) is currently converted into a Low Energy Ion Ring (LEIR). Avalanche-like heavy-ion induced molecular desorption, first observed at LEAR and systematically studied at CERN's Heavy Ion Accelerator (LINAC 3), is the major challenge to achieve the required average dynamic pressure of about 4×10⁻¹² mbar in LEIR. The LEIR vacuum requirements, the technical design, the implementation of non-evaporable getter coatings and low-outgassing collimators, and the concept of ion-beam scrubbing are reviewed in this paper.     

Atmospheric radon levels in Beijing, China

The results of measurement of atmospheric radon concentration in Beijing, China, are reported. Continuous observation was performed hourly throughout 2003 to provide data on annual average radon concentration as well as the variation of radon concentration. An arithmetic annual mean value of 14.1 +/- 5.5 Bq m(-3) was obtained. The value was slightly higher than the world average and the national average. For the monthly average radon concentration, the maximum was 18.5 +/- 5.0 Bq m(-3) in November, while the minimum was 9.9 +/- 4.1 Bq m(-3) in May. Diurnal variation was also observed, and the average daily pattern of radon concentration consisted of a minimum in the late afternoon and a maximum in the early hours of the morning.     

Atmospheric processes and observations

The central role of the atmosphere in abrupt climate change is proposed and discussed. This discussion is given in the context of the poleward transport of energy in the climate system and of climate variability and change. A number of examples based on observational and model data are used to illustrate the ideas.     

全镀铬一道环的工艺改进

根据市场的需求 ,我公司于 1997年推出了全镀铬一道环这一新工艺 ,经全镀铬加工的一道环具有外观洁白、防锈能力强、平面具有一定耐磨性等优点。但本公司原来所采用的生产工艺在大批量生产时合格率很低 (5 0 %左右 ) ,报废的原因是环的开口两端所镀铬层很薄 ,甚至完全镀不上铬 ,使其外观和防锈功能都达不到要求。由于刚推出该工艺时只是进行小批量生产 ,市场的要求也较低 ,所造成的报废量并不太多 ,供求矛盾也不突出 ,因此公司并没有将其作为重点技术问题进行研究。1999年 5月 ,该类产品订单大量增加 ,且客户提出了比以前更高的要求 ,生产部…     

The Waves on the Vortex Ring in HeII

Using the equations of vortex dynamics the waves on a vortex ring are studied both analytically and by computer simulations. At small amplitudes the results coincide. The dispersion relations and the expressions of phase and group velocities are determined. The free and forced oscillations are considered. At large amplitudes the shape of a vortex is strongly distorted and the ring motion changes its direction. The second approximation calculations and computer simulations agree in order of magnitude.     

环同态下连通性的相互影响

对于可换环，考察了环同态下连通性的互相影响，利用环同态给出了环的连通性的若干充要条件，一些已知的结果变成文中定理的推论。     

The Little-Parks Effect in an Inhomogeneous Superconducting Ring

An inhomogeneous superconducting ring (hollow cylinder) placed in a magnetic field is considered. It is shown that the superconducting transition of the section with the lowest critical temperature may be a first order phase transition if the magnetic flux contained within the ring is not divisible by the flux quantum. In the vicinity of this transition, thermal fluctuations can induce the voltage in the ring with rather small sizes.     

DT型大气能见度仪的光学系统

本文介绍了DT型红外大气能见度仪的工作原理,详细描述了其光学结构,给出了各项设计参数。供设计和制造光电测量仪器的工作者参考。     

建筑排水UPVC管阻火圈的原理、结构、试验与安装

对建筑排水UPVC管道阻火圈的结构及阻火原理、工程试验、安装情况等方面作了较详细的阐述。