Improve the performance of interferometer with ultra-cold atoms

Ultra-cold atoms provide ideal platforms for interferometry.The macroscopic matter-wave property of ultra-cold atoms leads to large coherent length and long coherent time,which enable high accuracy and sensitivity to measurement.Here,we review our efforts to improve the performance of the interferometer.We demonstrate a shortcut method for manipulating ultra-cold atoms in an optical lattice.Compared with traditional ones,this shortcut method can reduce the manipulation time by up to three orders of magnitude.We construct a matter-wave Ramsey interferometer for trapped motional quantum states and significantly increase its coherence time by one order of magnitude with an echo technique based on this method.Efforts have also been made to enhance the resolution by multimode scheme.Application of a noise-resilient multi-component interferometer shows that increasing the number of paths could sharpen the peaks in the time-domain interference fringes,which leads to a resolution nearly twice compared with that of a conventional double-path two-mode interferometer.With the shortcut method mentioned above,improvement of the momentum resolution could also be fulfilled,which leads to atomic momentum patterns less than 0.6hkL. To identify and remove systematic noises,we introduce the methods based on the principal component analysis (PCA) that reduce the noise in detection close to the 1/√2 of the photon-shot noise and separate and identify or even eliminate noises.Furthermore,we give a proposal to measure precisely the local gravity acceleration within a few centimeters based on our study of ultracold atoms in precision measurements.     

宽带信道增益平坦度仿真设计

宽带信道的增益平坦度指标好坏是信道宽带性能保证的基础,同时由于影响因素众多,也是设计难点所在.以公式计算与电路仿真、三维电磁场仿真相结合的方式,详细分析了微波电路设计中各种因素对信道增益平坦度的影响,再针对各种影响因素给出了电路解决改善方法,论述了实际电路设计中宽带增益平坦度保证的关键技术和注意事项.     

纵横论集群

80年代末到90年代初，中国成了世界集群产品的博览会，90年代中期有少数厂家开始生产国产设备，但至今尚未出现全面国产化的局面，下一世纪将如何?     

双频共塔中的避雷

本文以比较实际的经验简述了双频共塔中的避雷措施，较详细地分析了避雷电路改进的理由，并介绍了双频共塔避雷电路使用元件的计算方法。     

7050航空铝合金结构材料激光冲击强化处理研究

用自行研制的激光冲击强化处理(LSP)装置对两种重要航空铝合金结构材料7050T7451，7050T7452冲击强化试验，进行了疲劳寿命对比试验。给出了反映疲劳应力水平与结构件寿命对应关系的σm-N曲线。结果表明．在67．3MPa的加载应力水平下，激光冲击处理后7050T7451结构材料的疲劳寿命提高到未经处理的435％，而7050T7452在81．4MPa的应力水平下提高到518%。并对试件进行了激光冲击处理机理的研究。结果显示试件表面具有较大的残余压应力和较高的位错密度。     

Effects of preparation parameters on growth and properties of β-Ga2O3 film

The Ga$_{2}$O$_{3}$ films are deposited on the Si and quartz substrates by magnetron sputtering, and annealing. The effects of preparation parameters (such as argon-oxygen flow ratio, sputtering power, sputtering time and annealing temperature) on the growth and properties ($e.g.$, surface morphology, crystal structure, optical and electrical properties of the films) are studied by x-ray diffractometer (XRD), scanning electron microscope (SEM), and ultraviolet-visible spectrophotometer (UV-Vis). The results show that the thickness, crystallization quality and surface roughness of the $\beta $-Ga$_{2}$O$_{3}$ film are influenced by those parameters. All $\beta $-Ga$_{2}$O$_{3 }$films show good optical properties. Moreover, the value of bandgap increases with the enlarge of the percentage of oxygen increasing, and decreases with the increase of sputtering power and annealing temperature, indicating that the bandgap is related to the quality of the film and affected by the number of oxygen vacancy defects. The $I$-$V$ curves show that the Ohmic behavior between metal and $\beta $-Ga$_{2}$O$_{3}$ films is obtained at 900 ${^\circ}$C. Those results will be helpful for the further research of $\beta $-Ga$_{2}$O$_{3}$ photoelectric semiconductor.     

稀土元素的摩擦学研究发展概况

本文对稀土元素的摩擦学研究发展概况作了综述与讨论,主要涉及的是稀土金属及稀土无机化合物和稀土配合物作为润滑油、脂及润滑涂层的添加剂的摩擦学特性,并对稀土无机化合物的高温润滑特性、稀土金属及其化合物在高温涂层中的应用作了简要讨论,最后还提出了稀土的摩擦学研究中当前值得注意的几个重要课题。