本地标准时间频率的产生与保持

近年来，地方协调时UTC(BIRM)守时能力稳步提升，截至目前，UTC(BIRM)与UTC的相对频率偏差优于3E-14，时间偏差优于20ns。本文概括介绍了守时系统的组成，本地频率驾驭与主备同步技术，以及TA(BIRM)算法研究等。     

网络分析仪时域测量技术综述

矢量网络分析仪直接测量两端口网络的微波特性，是射频微波测量领域中应用最广泛的仪器之一。网络分析仪时域技术在故障点定位、多路径消除、不连续性测试等应用中有着非常重要的意义，但是如何合理选取时域模式和设置参数是困扰工程研究人员的难点。本文对网络分析仪时域测量模式、离散数据取样、频率截断、窗函数、归一化等时域测量理论进行详细介绍，给出了时域测量范围和分辨力的计算方法，并以开路器的时域响应为例，说明了时域测量相关参数的设置依据。     

Boundary condition modelling and identification for cantilever-like structures using natural frequencies

The actual boundary conditions of cantilever-like structures might be non-ideally clamped in engineering practice, and they can also vary with time due to damage or aging. Precise modelling of boundary conditions, in which both the boundary stiffness and the boundary mass should be modelled correctly, might be one of the most significant aspects in dynamic analysis and testing for such structures. However, only the boundary stiffness was considered in the most existing methods. In this paper, a boundary condition modelling and identification method for cantilever-like structures is proposed to precisely model both the boundary stiffness and the boundary mass using sensitivity analysis of natural frequencies. The boundary conditions of a cantilever-like structure can be parameterized by constant mass, constant rotational inertia,constant translational stiffness, and constant rotational stiffness. The relationship between natural frequencies and boundary parameters is deduced according to the vibration equation for the lateral vibration of a non-uniform beam. Then, an iterative identification formulation is established using the sensitivity analysis of natural frequencies with respect to the boundary parameters. The regularization technique is also used to solve the potential ill-posed problem in the identification procedure.Numerical simulations and experiments are performed to validate the feasibility and accuracy of the proposed method. Results show that the proposed method can be utilized to precisely model the boundary parameters of a cantilever-like structure.     

频率稳定度与守时钟组配置关系研究CSCD

通过对中小型守时实验室对时间尺度稳定度的需求分析,以目前主流守时钟5071A为例,利用国际权度局公布的原子钟数据,研究不同钟组配置与时间尺度稳定度的关系,为中小时间实验室守时钟组的优化配置提供参考依据;权重确定是原子时算法的关键之一,通过对不同数量、不同取权规则的原子时计算结果进行统计分析与比较,提出中小时间实验室原子时尺度算法中的取权原则。     

某型干扰机干扰效果提升研究

通过研究某型干扰机对多普勒雷达速度跟踪系统的干扰方式，分析假多普勒频率产生的干扰工作机理，研究对抗科目训练中该模式干扰效果不佳的具体原因，提出了采用数字移向技术替代行波管移相，增大对雷达回波原载频的抑制度，增强干扰效果。通过对样机的测试验证，给出了两种移相电路的假多普勒干扰比较。     

HORACE: A compact cold atom clock for Galileo

HORACE (HOrloge à Refroidissement d’Atomes en Cellule = clock based on atoms cooled from vapour cell) is a compact cold caesium atom clock developed in SYRTE at Paris Observatory. This clock can operate both on ground and in microgravity environment. Design of HORACE is based on isotropic light cooling, allowing performing the whole clock sequence (cooling, atomic preparation, Ramsey interrogation and detection) at the same place. Compared to more conventional cold atom clocks such as atomic fountains, the use of isotropic light cooling simplifies both the optical part of the setup and the detection sequence, and leads to a drastic size reduction of the physics package. Very good short-term performances have been demonstrated at SYRTE since relative frequency instability of 2.2 × 10⁻¹³ τ^−1/2 has been obtained. Optimization of the long term stability is still under progress and current results show relative frequency instability around 3 × 10⁻¹⁵ in 10⁴ s of integration. With these performances, HORACE appears as a good candidate both for Galileo’s ground segment clock and for onboard Galileo clock.     

特型钝体绕流动态特性的低速实验研究

在低速自由射流风洞上 ,利用热线及相关设备对由半球头部、颈部及旋成体构成的特型钝体周围非定常流动的基本特性、联合特性及湍流度分布进行了测试与分析 ,实验工况为迎角α=- 1 5°～ 1 5°、侧滑角 β =0°～ 1 0°。结果表明 ,在上述工况范围内 ,该钝体周围流场中速度脉动的能量分布平坦 ,属宽频带随机信号 ,流场中没有发生明显的流动分离 ,流场动态品质良好 ;凹陷区内气流的脉动以不同的速度向下游空间传播 ;在上述α、β变化范围内 ,钝体颈部凹陷区的最大湍流度高达 1 0 .9～ 2 4.8%。     

基于随机时隙的RFID读写器防冲突方法

针对密集读写器环境下的无线射频识别(RFID,Radio Frequency Identification)多读写器冲突情况,提出了一种基于随机时隙并通过中央计算机协调的读写器防冲突方法.首先,中央计算机发送每轮起始命令和时隙指令,读写器根据当前利用率随机选择时隙.选择当前时隙的读写器若没有接收到忙信号则发送信标并侦听,若无邻近读写器发送信标则开始读写标签,否则该轮回停止工作.若时隙末存在没有接收到忙信号的读写器则在额外时隙发送二次信标.与现有的分布式防冲突方法相比,该方法具有较好的吞吐量和公平性.     

供距离测量用的光波长度标准

介绍用相位测距仪实现波长标准及在大长度范围内传递长度单位尺寸的情况。其传递精度好于通常采用方法。     

Total electron content monitoring using triple frequency GNSS: Results with Giove-A/-B data

Triple frequency GNSS will be fully operational within the next decade, opening opportunities for new applications. Dual frequency GNSS already allow to study the ionosphere through the estimation of Total Electron Content (TEC). However, the precision is limited by the ambiguity resolution process. This paper studies a triple frequency TEC monitoring technique in which the use of Geometry-Free and Iono-Free linear combinations improves the ambiguity resolution process and therefore the precision of TEC. We have tested it on a set of triple frequency Giove-A/-B data from January and December 2008. The conclusions achieved are (1) TEC values are affected by an error of about 2–2.5 TECU produced through the ambiguity resolution process; (2) the error caused by the Geometric Free phase combination delays (hardware, multipath, noise, antenna phase center) on TEC is about 0.2 TECU; (3) the total error on TEC approximately reach 2–3 TECU.