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本刊讯(记者杨学功通讯员卢敬叁)中国首台冷原子喷泉钟时间频率基准NIM4#2003年12月24日在中国计量科学研究院通过专家鉴定。新研制的激光冷却铯原子喷泉钟时间频率基准NIM4#准确度达到了8.5×10-15,相当于350万年不差1秒,具有国际先进水平。这一时间基准的建立,使我国时间频率基准重新步入世界先进行列,将满足我国独立自主的双星定位系统和现代通讯、大地测量、天文观测、导弹发射、卫星测控、计量科学、交通运输及基础科学研究等领域对时间频率准确度越来越高的要求,为我国更准确地守时和授时奠定技术基础。该成果鉴定专家委员会由13位… 相似文献
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报道了中国计量科学研究院(NIM)在复现国际单位制(SI)长度单位米和时间单位秒的研究进展,包括稳频激光、NIM4铯原子喷泉钟和飞秒光学频率梳.NIM4钟不确定度达4.4×10-15,NIM在研的飞秒光梳将以优于1×10-13的不确定度实现光学波长向微波频率的溯源.文中还讨论了127I2饱和吸收633nm 3次谐波稳频的HeNe激光波长比5次谐波稳频的更"准确";指出飞秒光梳是从动跟踪系统,描述它的性能指标应当是它的跟踪精度;估计了用"吸收室-原子束-原子喷泉-原子/离子存储"4种不同原理所建频标可能达到的不确定度极限.最后简略展望时间频率基准研究的新动向--光钟. 相似文献
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报道中国计量科学研究院(NIM)在微波-光学频率计量研究的新进展:用NIM4激光冷却-铯原子喷泉钟复现国际单位制(SI)时间单位秒(s),用飞秒(FS)光学频率梳间接复现长度单位米(m)并标定稳频激光波长实际实施米定义.NIM4铯原子喷泉钟的不确定度达到5×10-15,飞秒(FS)光梳锁定到NIM4钟控制的氢钟后,其频率不确定度为2.2×10-14.在此基础上讨论铯原子喷泉钟、稳频激光、FS光梳的作用、意义和相互关系.最后简要介绍NIM5铯原子喷泉钟的研究进展和2006年起NIM立题研制锶原子存储光钟. 相似文献
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报道中国计量科学研究院(NIM)在微波-光学频率计量研究的新进展:用NIM4激光冷却-铯原子
喷泉钟复现国际单位制(SI)时间单位秒(s),用飞秒(FS)光学频率梳间接复现长度单位米(m)并标定稳频
激光波长实际实施米定义。NIM4铯原子喷泉钟的不确定度达到5×10-15,飞秒(FS)光梳锁定到NIM4钟控制的
氢钟后,其频率不确定度为2畅2×10-14。在此基础上讨论铯原子喷泉钟、稳频激光、FS光梳的作用、意义和相互
关系。最后简要介绍NIM5铯原子喷泉钟的研究进展和2006年起NIM立题研制锶原子存储 相似文献
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本刊讯2010年11月30日,由中国计量科学研究院(NIM)自主研制的"NIM5可搬运激光冷却-铯原子喷泉时间频率基准"通过了国家质检总局组织的专家鉴定。经鉴定,NIM5铯原子喷泉钟的频率不确定 相似文献
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正8月7日,国际时间频率咨询委员会频率基准工作组通知中国计量科学研究院(NIM,以下简称"中国计量院"),由该院研制并运行的"NIM5激光冷却-铯原子喷泉钟"(以下简称"NIM5")通过评审,被接收为国际计量局(BIPM)认可的基准钟之一,参与驾驭国际原子时。8月8日,BIPM正式 相似文献
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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。 相似文献
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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. 相似文献
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工业铯钟速率变化主要因素的探讨 总被引:1,自引:0,他引:1
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) 相似文献
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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. 相似文献
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Grigory Bordyugov Ute Abraham Adrian Granada Pia Rose Katharina Imkeller Achim Kramer Hanspeter Herzel 《Journal of the Royal Society Interface》2015,12(108)
The circadian clock coordinates daily physiological, metabolic and behavioural rhythms. These endogenous oscillations are synchronized with external cues (‘zeitgebers’), such as daily light and temperature cycles. When the circadian clock is entrained by a zeitgeber, the phase difference ψ between the phase of a clock-controlled rhythm and the phase of the zeitgeber is of fundamental importance for the fitness of the organism. The phase of entrainment ψ depends on the mismatch between the intrinsic period τ and the zeitgeber period T and on the ratio of the zeitgeber strength to oscillator amplitude. Motivated by the intriguing complexity of empirical data and by our own experiments on temperature entrainment of mouse suprachiasmatic nucleus (SCN) slices, we present a theory on how clock and zeitgeber properties determine the phase of entrainment. The wide applicability of the theory is demonstrated using mathematical models of different complexity as well as by experimental data. Predictions of the theory are confirmed by published data on Neurospora crassa strains for different period mismatches τ − T and varying photoperiods. We apply a novel regression technique to analyse entrainment of SCN slices by temperature cycles. We find that mathematical models can explain not only the stable asymptotic phase of entrainment, but also transient phase dynamics. Our theory provides the potential to explore seasonal variations of circadian rhythms, jet lag and shift work in forthcoming studies. 相似文献
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异步应答激光测距技术 总被引:1,自引:1,他引:0
异步应答激光测距可实现卫星距离及星地时差测量.本文给出的主波时差公式与经典公式,以及一种拟工程实现、且与异步应答激光测距原理相同的无线电测距方法给出的工程应用公式不同.为了探求正确的主波时差公式,掌握这种测距体制的测距精度,进而验证异步应答激光测距体制的工程可行性,本文设计并开展了异步应答激光测距技术验证实验,利用两个地面测距终端对卫星反射测距模拟了星地异步应答激光测距过程.该实验是我国对异步应答激光测距体制的首次实践.实验研究结果表明,异步应答激光测距可用于两终端之间距离和主波时差的精确测量,且本文给出的主波时差公式正确,经典公式与应用公式存在不妥之处. 相似文献