拉曼激光相位噪声对原子干涉重力仪测量分辨力的影响

原子干涉重力仪已获得当今g值测量的最高分辨力，使得其在前沿科学研究和精密计量中有广阔的应用前景，但其分辨力的提高受限于包括拉曼激光相位噪声在内的各种噪声。本文通过对拉曼激光相位噪声模型和原子干涉仪中噪声传递过程的研究，发现微波信号源贡献了拉曼激光相位噪声的主要部分；通过计算常见T，τ条件下拉曼激光相位噪声对干涉仪重力测量分辨力的影响，发现100～300 ms内T越大重力仪测量分辨力越高，其中在T =300 ms、τ=20 μs的条件下，单次测量时拉曼激光相位噪声对原子干涉仪相位波动的影响为19.6 mrad，相应对重力仪分辨力的影响为1.35 μGal（1 μGal=10-8 m/s2）。     

小型化铷原子频标数字锁频环路设计与实现

设计并实现了一种用于铷原子频标的小型化锁频环路。采用数字锁相倍频技术,实现了10MHz信号的45.5645833次倍频。再经过一级15次倍频后获得频率为6834.6875MHz的铷原子频标微波探寻信号。通过数字电路技术实现了455.645833MHz信号的小调频。测量并分析了455.645833MHz信号的相位噪声,结果表明电路系统对铷频标频率稳定度的贡献为3.2×10^-12τ^-1/2。测量了利用该电路得到的铷频标的短期频率稳定度,结果为5×10^-12τ^-1/2（1s≤τ≤100s）,明显高于一般商品小型化铷原子频标。     

微振动的高精度测量

为了测量振幅小于1μm的微振动信号,在传统迈克尔逊干涉仪的基础上,提出了一种大光程差情况下的实时高精度测量系统。该系统使用单频窄线宽光纤激光器来减小长光程差下的相位噪声影响;用零差解调方法来抑制环境影响导致的相位漂移;双路平衡检测的使用将光源强度噪声降低16dB左右。当测量距离为10m时,光源引起的相位噪声仅为5.28×10-rad/Hz1/2;但由于6电路处理上的限制,实际可探测的最小灵敏度约为10-rad/Hz1/2。当被测信号在100Hz~4kHz之间5时,系统具有良好的线性响应度。     

基于微波锁相环的Ka波段锁相信号源

采用鉴相器、变容管压控振荡器(VCO)和毫米波倍频器实现了Ka波段低噪声锁相信号源,其中心频率可在37.6～44 GHz之间设定,在39.8 GHz频点的输出功率为16 dBm,抖动均方根值JRMS≈0.8 ps,相位噪声为-94.4 dBc/Hz(100 kHz频偏).该锁相信号源可作为40Gb/s光纤通信系统中的参考时钟,也可用作毫米波雷达、制导系统中的信号源或本振源.     

用于引力波探测的星间激光干涉测量模拟系统

星间激光干涉仪具有比地面干涉仪更长的干涉臂(10⁶ km),能够探测更低频段0.1 mHz～1 Hz的引力波。星间激光干涉仪具有典型的应答式外差干涉仪结构,其本质是一个光学锁相环。在地面环境下搭建模拟的星间激光干涉仪,成功将从激光器的频率锁定到稳频的主激光器频率上。结果显示：锁相环的锁定时间超过2×10⁴ s,满足了低频信号的探测条件;在较短位移和较长位移的不同条件下,干涉仪无粗大误差。经过分析得出：温度、气压等环境扰动带来的噪声是制约干涉仪精度的关键因素。     

拉曼光反射镜隔振平台设计及性能测试

为提高原子干涉重力仪拉曼光相位稳定性,降低拉曼光反射镜振动噪声对原子干涉仪测量精度的影响,设计并研制了一种适用于小型化原子干涉重力仪拉曼光反射镜隔振平台。通过COMSOL Multiphysics有限元分析和激光干涉仪测试验证了其隔振性能。根据原子干涉重力仪对噪声控制的要求,对隔振平台在60～200 Hz内的减振效果进行仿真,将仿真结果作为试验的指导,用扫描式激光干涉仪配合标准振动台,对装载到隔振平台上的拉曼光反射镜的振动进行了测试,结果符合仿真结论。     

单频激光干涉仪非线性误差修正方法

提出了一种谐波分离的干涉仪信号处理方法,利用傅里叶级数对校准信号进行最小二乘拟合得到修正模型.该方法适合于消除干涉信号中引起非线性误差的各种谐波成分.通过将修正分为初始相位计算和精确相位计算,可以使单频激光干涉仪的非线性误差修正达到最优化.模拟验证结果表明,当噪音信号幅度为基波信号幅度的5%时,残余误差的幅度约为±1 nm;而当噪音为0.5%时,残余误差约为±0.1 nm.     

一种低功耗被动型CPT原子钟

介绍了一款新研制的被动型相干布局囚禁(CPT)原子钟样机及其主要性能.样机功耗约为4 W,频率稳定度达到在τ＜8000s范围内优于6×10-11τ-1/2,10 MHz 输出频率在1Hz范围内的相位噪声达到-79.1dBc/Hz .所研制的CPT原子钟具有小型、低功耗的特点.     

岩巷爆破振动信号的HHT分析与应用

为优化爆破参数,减少对围岩的损伤,以煤矿玄武岩双巷道楔形深孔掏槽爆破的实测爆破振动信号为例,分析对比传统傅里叶变换、小波变换、HHT变换三种变换方法,对爆破地震波信号的时频特性和能量分布特征分析。结果表明:HHT变换能够确保信号被分解后的非平稳性,且自动适应能力较强,分解效率较高。通过HHT变换得到三维图直观展示各分量随时间、频率和能量的分布情况。爆破振动能量主要分布在0.3s¹.0s时间段和01.0s时间段和0⁴00Hz频率段内,频带100Hz400Hz频率段内,频带100Hz²50Hz中爆破振动分量对应的频带能量达到最大。通过分析对比爆破振动信号,得到巷道帮部、底部爆破振动信号的主振方向分别为Y(切向)和Z(垂向)方向。     

地铁车辆段列车动荷载特性实测研究

对车辆段内咽喉区、试车线和运用库的地铁列车荷载进行了实测,获得了其时频特性。基于不同线路条件、行车速度下的实测结果,分析了地铁列车荷载特性的主要影响因素。研究结果表明：地铁列车通过时,咽喉区轨枕的铅垂向加速度幅值为10~15m/s2,荷载以高频成分为主,主频段为60~150Hz;试车线轨枕的铅垂向加速度幅值为5~6m/s2,荷载主频段为60~100Hz;运用库的振动量值较小,实测的铅垂向加速度幅值为1~2 cm/s2,荷载的主频段为30~50Hz。对地铁车辆段列车,与行车速度相比,列车荷载振动量值对线路的平顺度更为敏感。     

Insertion of triangulated surfaces into a meccano tetrahedral discretization by means of mesh refinement and optimization procedures

In this paper, we present a new method for inserting several triangulated surfaces into an existing tetrahedral mesh generated by the meccano method. The result is a conformal mesh where each inserted surface is approximated by a set of faces of the final tetrahedral mesh. First, the tetrahedral mesh is refined around the inserted surfaces to capture their geometric features. Second, each immersed surface is approximated by a set of faces from the tetrahedral mesh. Third, following a novel approach, the nodes of the approximated surfaces are mapped to the corresponding immersed surface. Fourth, we untangle and smooth the mesh by optimizing a regularized shape distortion measure for tetrahedral elements in which we move all the nodes of the mesh, restricting the movement of the edge and surface nodes along the corresponding entity they belong to. The refining process allows approximating the immersed surface for any initial meccano tetrahedral mesh. Moreover, the proposed projection method avoids computational expensive geometric projections. Finally, the applied simultaneous untangling and smoothing process delivers a high‐quality mesh and ensures that the immersed surfaces are interpolated. Several examples are presented to assess the properties of the proposed method.     

The Research of Anti-Wear Properties of Organomolybdenum Compounds in the Engine Oils

A four-ball tester was used to evaluate the anti-wear performance of three kinds of organomolybdemun compounds in the engine oils, i. e., molybdenum dialkyldithiophosphate (MoDDP), molybdenum dialkyldithiocarbamate ( MoDTC), and sulphur and phosphorus freeorganomolybdeum (Molybdate). The results indicate that a low concentration of MoDDP doesn' t improve the anti-wear properties of the commercial engine oils, but a high concentration of MoDDP can obviously improve the anti-wear properties and the load-carrying capacity of the engine oils. MoDTC doesn' t improve the antiwear properties of the engine oils, but worsens the anti-wear properties of the oils. Signifi can timprove ment of frictional and wear characteristics is obtained with Molybdate added in the commercial engine oils and the formulated oils.     

Certification Institutions Expected to Update and Transfer Information on Present Standards

Standards are the basis for production enterprises to organize production, ex-factory inspection, trade (delivery) and technical exchanges, product certification, quality arbitration and supervision.……     

Flow calorimeter for enthalpy increment measurements on condensed gases

A flow calorimeter for enthalpy increment measurements on condensed gases is presented. A better knowledge of the properties of the liquefied natural gas is needed, and therefore a liquid loop has been designed for our flow calorimeter. The fluid loop in the calorimeter is designed in order to avoid the two-phase region, since two phases would give compositional disturbances in the measurements. The avoidance of the two-phase region is made possible by increasing the pressure of the test fluid after the measurement section, then heating the fluid at super-critical pressure past the critical point. Finally, the fluid is throttled to the low-pressure gas state at the inlet condition of the compressor that circulates the fluid. To perform the pressure increase, a new cryogenic pump has been designed. To evaluate the new equipment, measurements were taken on liquid ethane over the temperature range 146–256 K at pressure between 0.9 and 5.1 MPa.     

Refrigerators Enter a New Era of Health Preservation Frestech initiates the establishment of China's first standard for household sterilization refrigerators

On November 30, 2007, the China Association for Standardization (CAS) held a press conference at Beijing Diaoyutai State Guest House. Leaders from the China Household Electric Appliance Research Institute, the China Household Electric Appliance Association, and the China Consumers' Association attended and made speeches.……     

Optimum-Simulation von Ernteprozessen

Zusammenfassung Bei der Gestaltung von Ernteprozessen — beispielsweise des Prozesses Mähdrusch, Körnertransport und -abnahme — als transportverbundene Fließarbeitsverfahren mit mindestens zwei verschiedenen Arbeitsmitteln gibt es einen großen Optimierungsspielraum. Solche Prozesse sind mehrstufige Bedienungsprozesse mit gemischter Anordnung der Bedienungseinrichtungen. Außerdem besitzen sie stark ausgeprägte räumliche Aspekte. Es wird vor allem gezeigt, welche Merkmale solcher Prozesse in Simulationsmodellen abgebildet sein müssen, welche Zielgrößen in Abhängigkeit von welchen Einflußgrößen unter Berücksichtigung welcher Prozeßbedingungen ermittelt werden sollten und wie der Bewertungsprozeß zur Ermittlung der gewünschten Informationen gestaltet werden muß.     

A study of centrifugal cast high boron high speed steel

In the present study a high‐boron high speed steel (HSS) roll material was designed. Many expensive alloy elements have been substituted by cheap boron alloy, and high‐boron high speed steel roll has been manufactured by centrifugal casting method. The microstructures, mechanical properties and wear resistance of centrifugal casting high‐boron high speed steel roll have been investigated by optical microscopy (OM), scanning electron microscopy (SEM), and X‐ray diffraction (XRD) analysis, hardness test, impact test and wear test. The results indicated that the solidification microstructures of high‐boron high speed steel roll consisted of M₂(B,C), (W,Mo)₂(B,C), M₃(B,C), M₂₃(B,C)₆ type borocarbides and martensite, a small amount of retained austenite. Borocarbides were continuously distributed over the grain boundary. After quenching from 1050 °C, local broken network appeared in partial borocarbides, and fine secondary borocarbide precipitated from the matrix. After tempering from 525 °C, the amount of precipitated borocarbide increased significantly. After heat treatment, the hardness of high‐boron high speed steel roll excelled 60 HRC, and its impact toughness excelled 8.0 J/cm². The single groove steel rolling amount of high‐boron high speed steel rolls increases by 500% than that of bainite cast iron roll, when the rolls are used in K₁ mill housing of bar mill.     

Certification Becomes Important for the I Quality; and Safety Supervision of the Chinese Liquor Sector

The end of 2007, over 200 unit products of more than 80 Chinese firms have passed the quality grade certification for liquor products. These products involve distilled spirits, beer, wine, yellow wine, fruit syrup wine and others, and cover over 80% of the national top-branded liquor products.……     

Deposition and Coating Properties on CVD Tungsten

Surface characterization and microstructure studies are performed on chemical vapor deposited (CVD) tungsten coating. There is about 2 μm thickness diffusion layer of tungsten in the molybdenum substrate. The thermal shock test shows tungsten coating has good adhesion with molybdenum substrate, but the elements of oxygen and carbon in the tungsten coating have the bad affection to the adhesion. The result of high-temperature diffusion experiment is the diffusion rate from molybdenum substrate to tungsten coating is faster.