预警卫星大口径拼接组合型二元衍射校正元件制作工艺研究

介绍了一种取代预警卫星红外施密特望远镜折射校正板的二元衍射校正板的设计及工艺制作方法 ,并对该拚接组合型的二元衍射校正板的制作误差进行了分析。     

大口径连续相位板拼接检测误差分析

对大口径连续相位板（CPP）在子孔径拼接检测过程中存在的几种影响检测精度的主要因素, 包括定位误差、系统误差和拼接模式等进行了归纳并分析了其对检测精度的影响权重。通过对子孔径重叠区域分布的均匀性计算,分析了检测误差对拼接质量的影响。结果表明,定位误差是影响CPP拼接精度的主要原因,而对系统误差进行有效处理可以进一步减小重叠区非均匀性,拼接模式的选择对CPP的拼接结果的影响有限。通过CPP深度特性对重叠区域均匀性的统计分析表明,在像素级别的检测中,重叠区域均方根残差随着CPP深度的增加而线性增加,即拼接精度随CPP深度的增加而降低。     

A mathematical model for pattern formation in biological systems

A system of reaction-diffusion equations with applications in biological problems is presented and studied theoretically and numerically. Solutions demonstrating the following types of behaviour have been obtained: (i) time constant, spatially inhomogeneous, (ii) time periodic, spatially homogeneous, and (iii) time periodic, travelling wave-like. Some applications in embryological problems are discussed.     

高变倍比大相对口径长波红外变焦系统设计

针对传统红外连续变焦系统难以同时满足高变倍比和大相对口径的使用要求,通过采用复合变焦光学系统结构,增加传统红外连续变焦光学系统的变焦距范围和相对口径。基于长波红外320×240像元、25 μm×25 μm非制冷焦平面探测器,设计了一款高变倍比大相对口径长波红外变焦光学系统, 光学系统由一个连续变焦部分与两档变焦部分组成,通过引入衍射光学元件校正长焦端色差,工作波段为8 μm~12 μm,焦距变化范围为-9 mm~-272.25 mm,F数为1.4。该系统具有成像质量好、变倍比高、相对口径大、导程小和凸轮曲线平滑等优点。     

大长宽比、变发散角光束二维变焦整形研究

为实现激光束形状的二维整形,同时灵活适应入射光束发散角、尺寸等参数的变化,提高光束质量,提出了一种适用于大长宽比、变发散角的激光束二维变焦整形方法。该方法利用光线变换矩阵方法分析光路,采用柱透镜、球透镜对光束进行二维变焦整形,通过镜片位置和间距的动态调节,实现对光束在x,y两个维度上的尺寸、发散角共四个参数各自独立的调整,实时校正激光束的低阶像差,使出射光束始终保持为预定状态。试验研究表明,该方法具有光路结构简单、综合像差小、调节范围大等优点,能够显著改善高功率激光器的光束质量,尤其适用于具有大长宽比增益区的板条激光器和化学激光器的输出光束整形。     

大长宽比、变发散角光束二维变焦整形研究

为实现激光束形状的二维整形,同时灵活适应入射光束发散角、尺寸等参数的变化,提高光束质量,提出了一种适用于大长宽比、变发散角的激光束二维变焦整形方法。该方法利用光线变换矩阵方法分析光路,采用柱透镜、球透镜对光束进行二维变焦整形,通过镜片位置和间距的动态调节,实现对光束在x,y两个维度上的尺寸、发散角共四个参数各自独立的调整,实时校正激光束的低阶像差,使出射光束始终保持为预定状态。试验研究表明,该方法具有光路结构简单、综合像差小、调节范围大等优点,能够显著改善高功率激光器的光束质量,尤其适用于具有大长宽比增益区的板条激光器和化学激光器的输出光束整形。     

A generalised mathematical model and analysis for integrated multi-channel vibration structure-control interaction systems

A generalised mathematical model and analysis for integrated multi-channel vibration control-structure interaction systems are developed. The governing equations describing the interactions between a generalised elastic structure and a multi-channel electromagnetic excitation and control system are derived. Based on these equations, the stability and dynamic response of the system are analysed. The introduction of an additional dynamic impedance matrix between structure and control system allows vibration structure-control interaction mechanisms to be investigated. The generalised theory provides a basis to measure exactly the dynamic parameters of the structure negating any influence of the excitation and control system. It also allows the design of a more effective control system taking into account the interactions of the control system with structural motions and vice versa. To illustrate the general formulations developed and their applications, simple one- and two-channel systems are investigated using non-dimensional parameters.     

A general local composition and coordination number model for square-well fluids with variable well width and diameter ratio

A radial distribution function for attractive hard-core systems is obtained from the equilibrium of a molecular pair between local and bulk environments. With this function, a general model is established for the coordination number (CN) and local composition (LC) of square-well fluids. It meets the low-density, high-density and high-temperature limit conditions, as well as the unlike pair conservation and quasi-chemical equilibrium conditions. It also has some other features that many other models do not have: (1) its CN and LC expressions contain all pair potentials; (2) it yields temperature-dependent CN and LC for closely packed mixtures with different pair potentials; (3) its energy parameter is the difference of the total potentials of one pair in local and bulk environments, not the difference of two pair potentials. This model can accurately predict the CN, LC and compressibility factors of square-well fluids from computer simulation over a wide range of density, well width (λ?=?1–2) and diameter ratio. For the case λ?=?1.5, this model is better than or comparable with semi-empirical models; in other cases, it is far better than semi-empirical models. It does not need any empirical parameter for LC prediction. For the prediction of CN and compressibility factors, it only needs the smoothed radial distribution function of pure hard-sphere fluids. It also gives excellent results for lattice gases and highly nonideal lattice mixtures.     

A scale model investigation of sound radiation from a large aperture in a building

Measurements were made on a 1:20 scale model of a large aperture in a building. The experimental results were compared with the predictions of a simple theoretical model. Large discrepancies were observed at large aperture widths and high frequencies. The experimental data were used to derive corrections which were applied to the computer predictions to yield design charts suitable for use by the building designer.     

大视场反射式施密特光学系统设计与检测

大视场、低成本、高性能天文望远镜是当前研究和开发的热点。基于像差平衡原理,在正入射施密特矫正板基础上推导出斜入射反射式施密特矫正板方程,针对焦距1 700 mm,成像视场角4°,波段为0.4 μm～0.9 μm,F数为4.25的光学系统,求解出施密特矫正板方程,并作为初始结构参数代入Zemax软件进一步优化。设计结果表明,在全视场范围内,该系统在奈奎斯特频率100 lp/mm处的调制传递函数MTF大于0.35,畸变小于2.5%,成像质量达到了衍射极限。优化设计后施密特矫正板与最近球面最大偏差为0.005 mm,采用特制的补偿器结合干涉仪可完成面形高精度检测。该施密特系统的设计为大视场、宽波段天文望远镜的开发提供了参考。     

Enhancement of laser interaction with vacuum for a large angular aperture

We study the nonlinear interaction of laser light with vacuum for a large angular aperture at electromagnetic field strengths far below the Schwinger limit. The polarization and magnetization in vacuum irradiated by a focused laser beam clearly differ from those in matter. This is due to the dependence on the Lorentz invariant, which results in a ring-shaped radiation distribution in vacuum. The number of the radiated photons increases nonlinearly with increasing angular aperture.     

大口径球面反射镜曲率半径的精确测量

介绍了大口径球面反射镜曲率半径的传统测量方法,提出了利用组合测杆结合激光干涉仪测量球面反射镜曲率半径的新方法。首先利用激光干涉仪检测球面反射镜的面型,调整干涉仪与被测镜的位置,使被测镜达到零条纹干涉状态,然后架设合理长度组合测杆,调整组合测杆靠近干涉仪端测量球头的位置,使之达到零条纹干涉状态,再使组合测杆另一端测头与镜面接触完成测量,通过计算分析即可得到被测球面镜的曲率半径。对该方法的基本测量原理进行了研究分析,并对口径为600 mm的望远镜球面主镜的曲率半径进行了多次测量,测得其曲率半径均值为2 836.774 mm,标准偏差为0.071 mm。最后对该方法的测量不确定度进行了分析,找出了影响测量精度的主要因素,合成标准不确定度为0.061 mm。     

大口径精密光学调整架的优化设计

针对大功率激光检测技术发展中精密光学调整架存在的刚度不足的问题,设计了一种适合装调大口径光学镜片的精密光学调整架结构,并建立其力学模型,分析其动力学性能,通过420 mm大口径球关节调整架结构俯仰模态理论的分析和实验测试数据之间对比,找出导致调整架结构谐振频率变差的原因。采用优化设计后的大口径调整架第一阶俯仰模态的频率为157.788 Hz,能够很好满足在强振源下的工作需要。     

大口径精密光学调整架的优化设计

针对大功率激光检测技术发展中精密光学调整架存在的刚度不足的问题,设计了一种适合装调大口径光学镜片的精密光学调整架结构,并建立其力学模型,分析其动力学性能,通过420 mm大口径球关节调整架结构俯仰模态理论的分析和实验测试数据之间对比,找出导致调整架结构谐振频率变差的原因。采用优化设计后的大口径调整架第一阶俯仰模态的频率为157.788 Hz,能够很好满足在强振源下的工作需要。     

A mathematical model for the dynamics of clustering

The formation of several clusters, arising from attracting forces between nonidentical entities or agents, is a phenomenon observed in diverse fields. Think of people gathered through a mutual interest, swarm behaviour of animals or clustering of oscillators in brain cells.We introduce a dynamic model of mutually attracting agents for which we prove that the long-term behaviour consists of agents organized into several groups or clusters. We have completely characterized the cluster structure (i.e. the number of clusters and their composition) by means of a set of inequalities in the parameters of the model and have identified the intensity of the attraction as a key parameter governing the transition between different cluster structures.The versatility of the model will be illustrated by discussing its relation to the Kuramoto model and by describing how it applies to a system of interconnected water basins.     

A passive network model for large diameter thermoacoustic tube systems and its experimental verification

Linear thermoacoustic theory is currently well accepted for simulating thermoacoustic systems, and correction is used to reduce the discrepancy between calculations and experimental results for turbulent flow. In order to calculate passive tube systems and make linear thermoacoustic theory coincide closely with experiments, a passive network model based on fluid network theory is derived. An amendment method is proposed to further correct for turbulence by amending thermal and viscous penetration depths when the ratio of the tube radius to the viscous penetration depth R/δ_v is large. The experiments have been done to verify the model in the acoustic amplifier, Helmholtz resonator, and inertance tube. In addition, the mechanisms of such tubes are further analyzed based on the model.