Terahertz-wave generation by surface-emitted four-wave mixing in optical fiber

We propose a novel terahertz-wave source through the four-wave mixing effect in a conventional single-mode optical fiber pumped by a dual-wavelength laser whose difference frequency lies in the terahertz range. Surface-emitted geometry is employed to decrease absorption loss. A detailed derivation of the terahertz-wave power expression is presented using the coupled-wave theory. This is a promising way for realizing a reasonable narrow-band terahertz-wave source.     

高速超声加工工具的研究与应用

本文将提供一种设计高速超声加工工具的新方法，并给出了高速超声加工工具的试验结果。     

Adiabatic Passage Based on the Calcium Active Optical Clock

We propose a new application of the optical adiabatic passage effect for the excitation of a thermal atomic beam, which will be used in the calcium active optical clock to produce population inversion. A comparison between the optical adiabatic passage effect and the Rabi π pulse is investigated, 99% of the calcium atoms in the atomic beam that has a wide velocity distribution will be excited to the upper state for population inversion using the adiabatic passage, while 76% at most will be excited to the excited state using the π pulse with suitable parameters.     

一种接近真实评价的选择评价题型(续)——新单选题型之区分效果研究及解疑答问

继<一种接近真实评价的选择评价题型>文之后,就新单选题型对学生的区分效果继续进行研究,并对反馈信息中的主要疑问进行初步探讨.     

斯特林制冷机薄壁气缸加工工艺研究

主要叙述斯特林制冷机中薄壁气缸的加工的工艺方法,加工过程的关键参数、刀具的选择、热处理的方法。提出薄壁件加工精度的技术途径。     

目标红外迷彩伪装技术研究

随着红外迷彩伪装涂料的出现,利用其对目标红外热图像进行分割,破坏目标图像特征的特点,为目标红外对抗提供了一种新的有效手段.首先,以传热模型为基础,模拟出目标的表面温度,并通过实测得出背景的表面瞬态温度.然后,利用随机生成的方法,生成背景的红外纹理图像.最后,以目标与背景的辐射对比度为基础,对红外迷彩涂料的设计参数进行了优化,分析了红外迷彩涂料的设计参数和图案设计对目标伪装效果的影响,达到了较好的红外伪装效果.     

Lattice Boltzmann Simulation of the Cross Flow Over a Cantilevered and Longitudinally Vibrating Circular Cylinder

The multiple-relaxation-time lattice Boltzmann method （MRT-LBM） is implemented to numerically simulate the cross flow over a longitudinal vibrating circular cylinder. This research is carried out on a three-dimensional （3D） finite cantilevered cylinder to investigate the effect of forced vibration on the wake characteristics and the 3D effect of a cantilevered cylinder. To meet the accuracy of this method, the present calculation is carried out at a low Reynolds number Re =100, as well as to make the vibration obvious, we make the vibration strong enough. The calculation results indicate that the vibration has significant influence on the wake characteristics. When the vibrating is big enough, our early works show that the 2D vortex shedding would be locked up by vibration. Contrarily, this phenomenon would not appear in the present 3D case because of the end effect of the cantilevered cylinder.     

Training Effect and Hysteretic Behaviour of Angular Dependence of Exchange Bias in Co/IrMn Bilayers

The training effect and the hysteresis behaviour of the angular dependence of exchange bias are extensively investigated upon the variation of the IrMn layer thickness tXrMn in a series of Co/IrMn bilayers. When tIrMn is very small, both of them are negligible. Then they increase very sharply with increasing tUMn and then reach maxima at almost the same value OftXrMn. Finally they both decrease when tIrMn is further increased. The similar variation trends suggest that these phenomena arise from irreversible change of antiferromagnet spin orientations, according to the thermal activation model.     

材料的微细加工技术研究

在微传感器、执行器、集成光学器件、高分辨探测器等的研究中,材料的非机械微细加工技术是一种必不可少的成型技术。通过相关课题的研究,开展了反应离子刻蚀技术和聚焦离子束精密加工技术研究,进行了金刚石薄膜等材料的微细加工技术实验研究,掌握了基本的实验流程和实验技能。     

反应烧结碳化硅球面反射镜的光学加工与检测

介绍了250mm口径、4200mm曲率半径的反应烧结碳化硅球面反射镜光学加工和检测的工艺流程;并按照流程依次介绍了在研磨成型、细磨抛光和精抛光过程中使用的机床、磨具、磨料及采用的工艺参数和检测方法。介绍了在光学加工和检测各个步骤中应注意的问题。展示了加工后250mm口径反应烧结碳化硅球面反射镜的实物照片,并给出了面形精度和表面粗糙度的检测结果:面形精度(95%孔径)均方根值(RMS)为0.037波长(λ=632.8nm),表面粗糙度RMS值达到1.92nm(测量区域大小为603.6ⅹ448.4μm)。