基于注入半导体激光器的微波副载波相位调制信号产生

光载无线技术是解决终端超宽带无线通信的重要方法,光信号与微波/毫米波信号的融合处理技术在光-无线的数据格式转换中至关重要.提出了一种基于相位调制信号光注入Fabry-Perot型半导体激光器实现微波副载波相位调制信号产生的方法.光学注入半导体激光器的输出光场会产生一周期(P1)振荡效应, P1振荡产生的边带实现了相位调制信号光的调制分量的放大,被放大的调制分量与注入光载波在激光器腔内拍频形成微波副载波.注入光相位的变化导致新产生的微波副载波相位变化, 实现了注入信号光相位信息转化为微波副载波相位信息.本系统完成1.3 Gb/s, 2.7 Gb/s, 2 Gb/s光相位调制信号到微波副载波相位调制信号的转换,并测量了微波的单边带相位噪声. 通过光电转换和电域混频将还原出的光基带信号与原信号进行逻辑对比,证明了数据信息转换的正确性.     

Development of a 170-mm hollow corner cube retroreflector for the future lunar laser ranging

Over the past 50 years, lunar laser ranging has made great contributions to the understanding of the Earth–Moon system and the tests of general relativity. However, because of the lunar libration, the Apollo and Lunokhod corner-cube retroreflector(CCR) arrays placed on the Moon currently limit the ranging precision to a few centimeters for a single photon received. Therefore, it is necessary to deploy a new retroreflector with a single and large aperture to improve the ranging precision by at least one order of magnitude. Here we present a hollow retroreflector with a 170-mm aperture fabricated using hydroxide-catalysis bonding technology. The precisions of the two dihedral angles are achieved by the mirror processing with a sub-arc-second precision perpendicularity, and the remaining one is adjusted utilizing an auxiliary optical configuration including two autocollimators. The achieved precisions of the three dihedral angles are 0.10 arcsecond,0.30 arc-second, and 0.24 arc-second, indicating the 68.5% return signal intensity of ideal Apollo 11/14 based on the far field diffraction pattern simulation. We anticipate that this hollow CCR can be applied in the new generation of lunar laser ranging.     

管道内差压驱动机器人相关流场数值模拟研究

管道内流场对机器人的驱动力是设计管内机器人外形尺寸的基本依据,本文用数值方法计算了管道内检测机器人所受的差压驱动力。在合理提出一些基本假设后,用一阶迎风和中心差分格式离散管道内检测机器人附近流场的控制方程,用SIMPLE算法求得了不同入口流速下机器人附近的流场分布,以及流场对机器人的驱动力。结果表明雷诺数为1875时,机器人下游流场变为湍流;当雷诺数为60000时,机器人下游流场变为非定常流,出现周期性流动;计算数据还表示驱动力只与管内平均流速有关而与运行压力无关。     

一类广义Sierpinski海绵的填充测度

对于m2的任何整数m,本文定义了R~m中的一类广义 Sierpinski海绵,同时给出了该类海绵的填充测度的计算公式.     

Measurement of Eccentricity of the Centre of Mass from the Geometric Centre of a Sphere

The eccentricity of the centre of mass from the geometric centre of a spherical attracting mass in determining the Newtonian gravitational constant G is tested by means of an electronic balance. The experimental result shows that the eccentricity of the sample is about 0.31 μm with uncertainty of 0.05μm. Two density distribution models are discussed to estimate the uncertainty to G by the eccentricities of the attracting masses.     

Improvement of Test of Solar Neutrino Coherent Scattering with Torsion Pendulum

A torsion pendulum containing two sapphire crystals and two lead rings is used to test Weber＇s theory of enhanced solar neutrino coherent scattering. Our experiment gives a null result for the diurnal force with a noise level of 3.8 × 10^-14 N, which is 526 times smaller than the predicted value of Weber＇s theory, and directly rules out Weber＇s theory and the experimental result. This experiment also reveals a test of the weak equivalence principle with η （Al2O3, Pb） （0.8 ± 3.1） × 10^-10 for masses falling toward the Sun.     

Dynamical Behaviour of a Modulated Torsion Pendulum in Test of Weak Equivalence Principle

The dynamic behaviour of a modulated torsion pendulum used to test the weak equivalence principle (WEP) is studied in detail. Theoretical analysis shows that the pendulum will be driven by a force with double-frequency of the rotating turntable no matter whether the WEP is valid or not. This double-frequency effect should be considered for improving the sensitivity of the modulated pendulum in test of the WEP.     

实验检验光子静止质量的研究进展

爱因斯坦狭义相对论的基本假设之一是光速不变性,其直接推论就是光子的静止质量必须为零,因此实验检验光子是否具有非零的静止质量一直备受关注.非零光子静止质量以Proca方程组为基础,其实验检验主要针对真空光速(频率)色散效应、库仑反平方定律和安培环路定律的偏离、寻找纵向电磁波以及磁偶极场的Yukawa势等几个方面.文章作者所在的实验小组采用精密扭秤调制方法将国际上同类实验结果提高了2个数量级,给出光子静止质量上限为mγ≤1.5×10-52g.对光子静止质量的实验检验,也是对光速不变原理的一种检验,即使光子仅有非常微小的静质量,如一旦得到实验的检验,将会对整个物理学的发展产生巨大而深刻的影响.     

拓扑动力系统研究的图像方法(英文)

This paper considers the graph sequence graph （f^n ）={x×f^n ： x ∈X} of the iterates f^n of a continuous map f ： X →X on a compact metric space （X, d）. The main aim is to introduce serval limit sets by using different recurrent time sets, and discuss the relation between dynamics of the underlying compact system （X, f） and the structure of these limit sets, from a topological or fractal viewpoint.     

单原子催化剂在CO2转化中的应用

单原子催化剂(SAC)是由互相隔离分散的原子级活性位点锚定在基底上而形成的一类新兴催化剂材料, 其具有最大化的原子利用率、 可调控的独特电子结构, 因而在热催化、 光催化及电催化等方面展现出良好的应用前景. 通过SAC的热/光/电催化CO₂转化反应(CCR)能将温室气体CO₂转化为燃料或具有附加值的化学品, 为解决严重的全球变暖和能源短缺问题提供了一种有效策略. 本文总结了近年来SAC在CO₂转化领域的研究进展, 讨论了其合成、 调控及催化各类CO₂转化反应的优缺点, 并对其未来的发展进行了展望.