摘要：通过分子动力学模拟研究了纳米多晶316L奥氏体不锈钢在不同峰值应力下的高温蠕变变形行为和蠕变机制.数值模拟结果表明纳米多晶316L奥氏体不锈钢的高温蠕变变形是由位错、晶粒内部和晶界扩散以及晶界滑移之间的交互作用引起.在初始蠕变和稳态蠕变阶段,纳米多晶316L奥氏体不锈钢高温蠕变的主导性机制是晶粒内部和晶界的扩散以及晶界的滑移.在加速蠕变阶段,一些晶界被摧毁后,位错滑移成为纳米多晶316L奥氏体不锈钢的主要蠕变机制.这项工作旨在揭示纳米多晶316L奥氏体不锈钢的高温蠕变机理,为增强型抗蠕变316L奥氏体不锈钢的设计和制造提供指导.

摘要：在近空间飞行器、超低轨道航天器和微机电系统(MEMS)等大量工程应用中,对从连续流到自由分子流的跨流域流动实现精确预测在相关气动设计中具有重要价值.跨流域流动的本质是一个由不同尺度和机理组成的复杂科学系统,因此对跨流域流动的建模和数值预测在理论和实践层面都具有很大的挑战性.此外,单一流场中的跨流域流动将使问题变得极其复杂.然而,这种典型的流场在高超声速流动应用中却十分常见,因此,尽快发展并完善跨流域空气动力学具有至关重要的意义.另一方面,建设高焓低密度风洞和进行高空飞行试验在现阶段也非常具有挑战性.因此,对跨流域流动及相关复杂系统的研究在世界范围内遇到了瓶颈.本文回顾了近十年来由我国科研人员主导在跨流域流动计算方法领域取得的突破,这些方法可以作为研究跨流域多尺度流动机理的数值实验工具,并同时为气动设计和热防护工作提供数据.本文重点介绍了近年来建立的统一波-粒子方法的研究进展,此方法被证明对极端高速的跨流域多尺度流动准确且高效.

摘要：Chirped mirrors （CMs） are designed and manufactured. The optimized CM provides a group delay dispersion （ODD） of around -60fs^2 and average reflectivity of 99.4% with bandwidth 200 nm at a central wavelength of 800nm. The CM structure consists of 52 layers of alternating high refractive index Ta2O5 and low refractive index SiO2. Measurement results show that the control of CM manufacturing accuracy can meet our requirement through time control with ion beam sputtering. Because the ODD of CMs is highly sensitive to small discrepancies between the layer thickness of calculated design and those of the manufactured mirror, we analyze the error sources which result in thickness errors and refractive index inhomogeneities in film manufacture.

摘要：A novel single-ring absolute optical shaft encoder is designed by studying the encoding principle of traditional absolute optical shaft encoder in this paper. The description of the orientation algorithm of the encoder is specified, and an example for explaining the orientation arithmetic is given, which indicates that the theory of the encoder works. The visual interface to acquire signals of CCD is shown with VB,which provides reliable foundation to process data. The effective factors of measurement precision of the encoder are analyzed.

摘要：The Lunar-based Ultraviolet Telescope (LUT) is a funded lunar-based ultraviolet telescope dedicated to continuously monitoring variable stars for as long as dozens of days and performing low Galactic latitude sky surveys. The slow and smooth spin of the Moon makes its step by step pointing strategy possible. A flat mirror mounted on a gimbal mount is configured to enlarge the sky coverage of the LUT. A Ritchey-Chrétien telescope with a Nasmyth focus configuration is adopted to reduce the total length of the system. A UV enhanced back illuminated AIMO CCD 47-20 chip together with the low noise electric design will minimize the instrumental influence on the system. The preliminary proposal for astrometric calibration and photometric calibration are also presented.

摘要：Spectral and directional control of thermal emission based on excitation of confined electromagnetic resonant modes paves a viable way for the design and construction of microscale thermal emitters/absorbers. In this paper, we present numerical simulation results of the thermal radiative properties of a silicon carbide（Si C） thermal emitter/absorber composed of periodic microstructures. We illustrate different electromagnetic resonant modes which can be excited with the structure,such as surface phonon polaritons, magnetic polaritons and photonic crystal modes, and the process of radiation spectrum optimization based on a non-linear optimization algorithm. We show that the spectral and directional control of thermal emission/absorption can be efficiently achieved by adjusting the geometrical parameters of the structure. Moreover, the optimized spectrum is insensitive to 3% dimension modification.

摘要：Properties of symmetrical layers as matching layers in multilayer thin film design were analyzed. A calculation method was presented to derive parameters of desired equivalent refractive index. A harmonic beam splitter was designed and fabricated to test this matching method. OCIS codes： 230.1360, 220.0220, 310.6860.

摘要：Designing airfoils according to given pressure (or velocity) distribution is one kind of free boundary problems. Free boundary condition can be coupled with the flow governing equations by variable-domain variational calculus, which makes it possible to calculate simultaneously the flow field and the free boundary. An accurate deduction of the variable-domain variational principles is taken herein to design airfoils in compressible and incompressible flows. Furthermore, two grid types (H and O) are used in the calculation with better results for the O-type grid. It is shown that convergence is accelerated and good results can be obtained even if the initial guessed airfoil shape is a triangle, demonstrating the strong adaptability of this method.

摘要：This Letter presents an optical design method based on the Seidel aberration theory for dynamic refocus systems. The function of a dynamic refocus system is to increase the amount of return photons when a pulsed laser travels over an extended height range. In this study, the dynamic refocus system is a short focal image system. The aberrations of the dynamic refocus system are calculated individually. Aplanatic lenses are used to eliminate the main spherical aberration. A field lens is used to change the stop position in order to eliminate comas and astigmatism. The effectiveness of the initial design results are confirmed, and the designed dynamic refocus objective with an aperture of F-number 0.98 and a focal length of 14.325 mm is achieved. The total motion of the dynamic refocus mirror is approximately 216 pm at heights that ranged from 8 to 18 kin. The optimum result shows that the dynamic refocus system is an ideal optical image system at each conjugating height with 10 km sample thicknesses.

摘要：为降低零级串扰和相移误差对光栅横向剪切干涉仪波前复原精度的影响,进一步提升光栅横向剪切干涉仪检测光刻镜头系统波像差精度,推导出一种设计光栅剪切干涉相移算法的一般表达式,给出相移算法的具体设计方法。根据该表达式和设计方法,可以针对不同的零级串扰和相移误差建立相应的4种相移算法,实现高精度系统波像差检测。同时设计和评价了一种新的13步相移算法,结果证明所推导的一般表达式的有效性和先进性。