Improvements and New Evaluation of NIM4 Cesium Fountain Clock and Construction of NIM5 Clock in 2006

The NIM４cesium fountain clock has been operating stably and sub-continually since Aug．２００３．In this paper we present improvements on NIM４in２００５－２００６and the most recent evaluation for its shifts with an uncertainty of５E-１５．A ２２０days comparison between NIM４and GPS showed an agreement offrequency ２E-１４．Finally the construction of a NIM５transportable cesium fountain clock is briefly reported．     

Surface-defect passivation through complexation with organic molecules leads to enhanced power conversion efficiency and long term stability of perovskite photovoltaics

Organic-inorganic hybrid lead halide perovskites(e.g.,CH3NH3PbX3,X=Cl,Br,I)possess a unique combination of excellent electronic and photoelectrochemical properties including suitable and tunable bandgap,low exciton binding energy in the range of 9–80 meV,high extinction coefficient,and long electron and hole diffusion lengths[1],which make them excellent photovoltaic materials.     

NIM频率稳定度测量系统

本文作者按国际建议所推荐,在时域,以双取样标准偏差来表征随机频率不稳定度:在傅里叶频域,推荐以 Y(t)的单边谱密度 S_y(f)表征频率稳定度的方法所建立的测量系统,及其近期已取得的进展。     

量块检定中存在的问题

在量块检定规程 (试行 )ＪＪＧ146- 94 (以下简称为规程 )的实施过程中 ,我们发现某些检定项目和要求难以进行和实施 ,如量块的长度稳定度考核。长度稳定度为规程规定的使用中的量块 5个必检项目之一 ,其结果用长度年变化量的平均值ＬＣ 来表示 :ＬＣ=(Ｌ2 -Ｌ1) /Ｙ ( 1)式中 :Ｌ1为被测量块考察期间首次测得的长度 ;Ｌ2 为被测量块考察期间末次测得的长度 ;Ｙ为以年为单位的考察期限。以按等使用的量块为例 ,规程规定的其长度年变化量的允许值小于 (甚至远小于 )其测量不确定度。如 :3等 10ｍｍ量块 ,其长度年变化量允许值为0 0 6μｍ ,…     

分子泛频谱稳频半导体激光器

利用一阶导数和三阶导数稳频技术，成功地将AlGaAs半导体激光的频率锁定到H2O分子的泛频吸收谱线上，测得1秒和10秒取样时间的频率稳定度分别为1.5-10^-10和4.0×10^-11。     

一种高稳定度的石英晶体微量天平

介绍一种频率稳定度优于０．３ＨＺ的石英晶微量天平，在微量天平的电路中采用了高稳定度的时期振荡器，探头采用丝或半导体致冷器件恒温结构，频率稳定度优于０．３ＨＺ。     

出租车计价器内部时钟稳定性实验及分析

提出了一种利用北斗定位系统所提供的高精度UTC作为参考时钟源,检测出租车计价器(以下称计价器)内部时钟稳定性及环境温度适应性的测量方法。将三台不同晶振的计价器作为实验对象,对其内部晶振时间与北斗定位系统所提供的高精度UTC时间进行比对。在常温25℃下累计110天记录计价器内部时钟差,并通过改变实验温度来分析环境温度对计价器内部时钟的影响。本文对实验数据进行处理分析,得到一组能够客观反映其长期稳定性的实验结果。     

A Distortion-Modified Free Volume Theory for Nonlinear Viscoelastic Behavior

Many polymeric materials, including structural adhesives, exhibit anonlinear viscoelastic response. The nonlinear theory of Knauss and Emri(Polym. Engrg. Sci. 27, 1987, 87–100) is based on the Doolittle conceptthat the free volume controls the mobility of polymer molecules and,thus, the inherent time scale of the material. It then follows thatfactors such as temperature and moisture, which change the free volume,will influence the time scale. Furthermore, stress-induced dilatationwill also affect the free volume and, hence, the time scale. However,during this investigation, dilatational effects alone were found to beinsufficient for describing the response of near pure shear tests of abisphenol A epoxy with amido amine hardener. Thus, the free volumeapproach presented here has been modified to include distortionaleffects in the inherent time scale of the material. The same was foundto be true for a urethane adhesive.The small strain viscoelastic responses of the two materials havebeen determined from master curves of uniaxial and bulk creep testing atvarious temperatures. The nonlinear free volume model, modified toinclude distortional effects in the reduced time, was incorporated inthe ABAQUS finite element code via a user-defined material subroutine.For the epoxy, validation of the modified theory (a strain-basedformulation of free volume) has been achieved through good agreementbetween the computational and experimental results of butterfly-shapedArcan specimens subjected to loadings ranging from near pure shear toshear with various amounts of superposed tension and compression. Inaddition to predicting the response under a variety of multiaxial stressstates, the modified free volume theory also accurately predicts theformation and growth of shear banding, or regions of highly localizeddeformation, which have been found to occur upon continued loading ofthe epoxy. The urethane did not appear to exhibit any localizeddeformation over the range of temperatures at which it was tested.As a result, a stress-based modified free volume approach was requiredto model its multiaxial and temperature-dependent behavior. Althoughfree volume was the unifying parameter for the two materials, the needfor a stress-based and strain-based formulation of the free volume forthe urethane and epoxy, respectively, could not be reconciled at thistime.     

基于开槽管腔的高信噪比铷原子钟物理系统

物理系统提供的原子鉴频信号信噪比是决定铷原子钟频率稳定度的关键因素。借助高频结构仿真软件,设计了一款内径为20 mm的开槽管微波腔。分析和测试表明,该微波腔内微波场磁力线沿腔轴方向均匀密集分布,可激励高强度铷原子微波跃迁。基于这种微波腔,设计出分离滤光物理系统。借助F-P干涉仪光谱测量,优化了滤光效果。测试表明,这种物理系统具备高信噪比,可用于制造频率稳定度为5.0×10^-13t^-1/2的铷原子钟。     

游标时钟数字符合技术研究

微小时间间隔测量是雷达、测距、导航等技术的基础,时间内插是测量微小时间间隔的关键技术.通过游标时钟与主时钟符合可实现游标时间内插,游标时钟符合技术决定了游标时间内插的测时精度.传统的游标时间内插采用微分电路进行时钟符合,测量精度低.为了提高测量精度,本文分析了影响符合精度的多方面因素;在此基础上,建立了离散时间系统中游标内插的数学模型,提出了基于数字电路的游标时钟数字符合方法,仿真结果表明该方法测试精度高于传统方法.     

NIM4#激光冷却-铯原子喷泉钟--新一代国家时间频率基准

中国计量科学研究院NIM4#冷原子喷泉钟自2003 年8月起已经稳定运行6个月,并于2003年9～12月期间完成了系统频率偏差评定.文中介绍NIM4#钟的喷泉实验、微波频率锁定和对其主要频率特性的实验研究.实验和分析表明,NIM4#钟频率稳定性达8×10-13τ-1/2,复现性达5 ×10-15,频偏评定不确定度达8.5 ×10-15.作为旁证,NIM4#与中国计量科学研究院原子时TA(NIM)进行了120天比对,频率偏差在误差范围之内.     

原子钟钟差预测不确定度的建模与分析

钟差预测是原子钟时标产生和原子钟驾驭的关键环节。原子钟作为精准的信号源,其信号由确定信号部分和固有噪声即随机部分组成。氢钟和铯钟主要包含两种噪声,即调频白噪声和调频随机游走噪声,这两种噪声是产生预测不确定度的主要因素。根据原子钟数学模型补充推导出原子钟时差数据预测不确定度的数学表达式,并得出了钟组的最小预测不确定度,分析了钟组的台数对预测不确定度的影响。最后通过数据仿真验证了理论的正确性。     

Synchronization on the basis of pulsar time

A new method of synchronization of atomic timekeepers on the basis of pulsar time that has been synthesized on the basis of observations of the rotation parameters of a pulsar is considered. An analysis of the attainable synchronization precision is presented. __________ Translated from Izmeritel’naya Tekhnika, No. 7, pp. 23–28, July, 2007.     

工业铯钟速率变化主要因素的探讨

上海天文台（ＳＯ）原子时实验室的４台工业铯钟１９８３～１９９０年连续工作了４或７年，它们的速率的长期变化与钟房的环境参数和性能参数的变化有关。本文根据有关数据，用不同的方法进行了分析，得到了一些明晰的结果。１）钟的速率变化受湿度的季节性变化影响：在相对湿度变化１％时，Ｃｓ２（１２６７）和Ｃｓ４（１４５７４）的速率变化分别为１．８９５ｕｓ／ｄ（２．２×１０－１４）和０．６１８ｎｓ／ｄ（７．１×１０－１５）。ＳＯ的原子钟房的相对湿度的年变化为２０％～８５％，引起这两台钟的速率年变化分别为１．４３×１０－１２和４．６５×１０－１４２）钟的速率变化受钟的离子泵电流参数的线性变化（从钟束管寿命的中期开始）影响：在离子泵电流参数变化１μＡ时，Ｃｓ３（１６１８０）和Ｃｓｌ（１２９９７）的速率变化分别为０．４３９ｎｓ／ａ（５．０８×１０－１５）和０．５５２ｎｓ／ａ（６．３９×１０－１５）。这两台钟的离子系电流参数的年变化分别为１６．４７μＡ／ａ和６．５３μＡ／ａ，引起的频率漂移率分别为１．６７×１０－１３／ａ（０．０３９５ｎｓ／ｄ２）和８．３×１０１４／ａ（０．０１９７ｎｓ／ｄ２）     

Mesurement and Calculation Provision for the Creation of Clock Mechanisms

A mathematical model of a clock mechanism is proposed having a free lever escapement movement. The model describes twenty continuously linked stages of operation of the mechanism. The mathematical model implements the possibility, at the development and production stages, of a calculation experiment aimed at investigating and predicting the behavior of a working mechanism in the presence of changes in its geometric and physical parameters and also of changes in its operating conditions. The results of experimental investigations are presented.     

公用IC卡电话机测试仪的研制

 随着公用IC卡电话机的日益普及,在安装IC卡电话机以前以及在其使用过程中,对IC卡电话机的拨号、计费等各项功能的测试,显得日益重要。提出了一种基于单片机的公用IC卡电话机测试仪,以ATMEL公司的AT89C55为核心,加上外围的功能模块,构成测试仪的硬件部分;再按其功能模块进行相应的软件设计。该仪器现已被多家电信局使用,给电信局的测试工作带来了方便。实践证明该仪器具有界面友好、操作简单、功能齐全、测试方便等特点。