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A Longitudinal Zeeman Slower Based on Ring-Shaped Permanent Magnets for a Strontium Optical Lattice Clock

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Chinese Physics Letters 2015年第10期32卷 22-25页

作者：王强林弋戈高坊林李烨林百科孟飞臧二军李天初方占军 division of Time and Frequency National Institute of Metrology Beijing 100013 Department of Precision Instrument Tsinghua University Beijing 100084 Research Institute of Petroleum Exploration and Development Langfang 065007

We report a longitudinal Zeeman slower based on ring-shaped permanent magnetic dipoles used for the strontium optical lattice clock. The Zeeman slower is composed of 40 permanent magnets with the same outer diameter but different inner diameters. The maximum variation of the axial field from its target values is less than 2%. In most parts of the Zeeman slower, the intensity variations of the field in radial spatial distribution are less than 0.1 roT. With this Zeeman slower, the strontium atoms are slowed down to 95m/s, and approximately 2% of the total atoms are slowed down to less than 50m/s.

关键词： A Longitudinal Zeeman Slower Based on Ring-Shaped Permanent Magnets for a Strontium Optical Lattice Clock

SARS-CoV-2 Aerosol Transmission Through Vertical Sanitary Drains in High-Rise Buildings--Shenzhen,Guangdong Province,China,March 2022

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China CDC weekly 2022年第23期4卷 489-493,I0002,I0003页

作者： Keyang Lyu Siyang Feng Xia Li Qin Wang Xiaoning Zhao Shuyuan Yu Ping Zheng Jiajia Ji Guomin Chen Jing Liang Tao Lan Jinshu Feng Shuai Jiang Jianhua Lu Tianlong Xia Chaoqiong Peng Tiejian Feng Dongqun Xu Key Laboratory of Environment and Population Health National Institute of Environmental HealthChinese Center for Disease Control and PreventionBeijingChina Shenzhen Center for Disease Control and Prevention Shenzhen CityGuangdong ProvinceChina division of Chemical Analysis Biology and MedicineBeijing Institute of MetrologyBeijingChina Futian District Center for Disease Control and Prevention Shenzhen CityGuangdong ProvinceChina

Summary What is already known about this topic?Aerosol transmission of severe acute respiratory syndrome coronavirus 2(SARS-CoV-2)via sanitary pipelines in high-rise buildings is possible,however,there is a lack of ex... 详细信息

关键词： Vertical Guangdong Summary

ALTERABLE INTERVAL OPTICALELECTRONIC AUTOCOLLIMATION METHOD FOR STRAIGHTNESS MEASUREMENT OF PRECISION GUIDE

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Chinese Journal of Mechanical Engineering 2005年第3期18卷 457-460页

作者： Xue Zi Tan Jiubin Zhao Weiqian Zhang Heng Institute of Ultra Precision Optoelectronic Instrument Engineering Harbin Institute of Technology Harbin 150001 China Length division National Institute of Metrology Beijing 100013 China

Optical-electronic autocollimation method is commonly used to measure straightness of precision guides in engineering application. However, the traditional fixed interval optical-electronic autocollimation method is not suitable for measuring straightness of an air-bearing guide with a long air-bearing bush or a precision straight guide with a long slide-carriage, because the air-bearing bush and the slidecarriage are actually taken as a big bridgeboard bigger than the length of the bridgeboard with the reflector, which is about 1/4-1/2 of total length of the measured guide. If straightness is measured according to the traditional method, only a few points are sampled so that the guide straightness can not be evaluated fully or accurately. In order to solve the problem, an alterable measuring interval method is proposed for straightness measurement based on analyzing the mutual relations and effects among the tilting angle of the reflector, the length of the bridgeboard, the measuring interval and the straightness of the guide. A straightness calculation model is also developed using the method, and the errors stemming from the method proposed are introduced in brief. A precision air-bearing guide with a long air-bearing bush is measured and evaluated using the method proposed, and the actual measurement and evaluation results prove that the method is correct in theory and practical in operation. The method proposed gives an effective and flexible solution to the straightness measurement of the precision guide with long slide-carriage or air-bearing bush in application. It is an extension of the traditional optical-electronic autocollimation method for straightness measurement.

关键词： Straightness measurement Optical-electronic autocollimator Alterable interval Autocollimation Air bearing guide Slide carriage

Effect of Hydrolyzing Agents on the Properties of Poly(Ethylene Glycol)-Fe_3O_4 Nanocomposite

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Nano-Micro Letters 2011年第2期3卷 79-85页

作者： E.Karaoglu H.Kavas A.Baykal M.S.Toprak H.Szeri Department of Chemistry~b Fatih University Department of Physics Gebze Institute of Technology Functional Materials division Royal Institute of Technology-KTH TUBITAK-UME National Metrology Institute

Poly(ethylene glycol)(PEG) assisted hydrothermal route has been used to study the influence of the hydrolyzing agent on the properties of PEG-iron oxide(Fe_3O_4) *** oxide nanoparticles(NPs),as confirmed by X-ray diffraction analysis,have been synthesized by a hydrothermal method in which Na OH and NH_3 were used as hydrolyzing *** of PEG-Fe_3O_4 nanocomposite was confirmed by Fourier transform infrared spectroscopy(FTIR).Samples exhibit different crystallite sizes,which estimated based on line profile fitting as 10 nm for NH_3 and 8 nm for Na OH hydrolyzed *** average particle sizes obtained from transmission electron microscopy was respectively 174±3 nm for Na OH and 165±4 nm for NH3 gas hydrolyzed *** characterization results reveal superparamagnetic characteristics despite a large particle size,which indicate the absence of coupling between the nanocrystals due to the presence of polymer in the *** conductivity curve demonstrates that σDC is strongly temperature dependent.

关键词： Magnetite PEG Hydrothermal synthesis Conductivity Magnetization

Influences of cavity dispersion distribution on the output pulse properties of an all-normal-dispersion fiber laser

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Chinese Physics B 2015年第7期24卷 268-274页

作者：李磐时雷孙青冯素娟毛庆和 Anhui Provincial Key Laboratory of Photonics Devices and Materials Anhui Institute of Optics and Fine MechanicsChinese Academy of Sciences Beijing Aerospace Control Instrument Research Institute Optics division National Institute of Metrology

In this paper, the influences of the dispersion distribution in the cavity on the output pulse properties of the all-normaldispersion（ANDi） fiber laser are investigated. Our simulations show that, as the relative length of the dispersion fiber increases, the temporal width and the spectral bandwidth of the output pulse for an ANDi fiber laser with fixed total cavity dispersion or fiber length are decreased, while the pulse energy is enhanced and the compressed pulse width is *** simulation predictions have been proved by our experimental results. The reason may be that the nonlinear phase shift accumulated in the nonlinear fiber is more than that in the dispersion fiber if they have the same length.

关键词： mode-locked lasers fiber lasers dispersion nonlinearity

Direct Spatially Resolved Snapshot Interferometric Phase and Stokes Vector Extraction by Using an Imaging PolarCam

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Chinese Physics Letters 2020年第7期37卷 19-23页

作者： Dahi Ibrahim Daesuk Kim division of Mechanical System Engineering Chonbuk National UniversityJeonju 54896Korea Engineering and Surface metrology Lab National Institute of StandardsTersa St.El haramEl GizaEgypt

We extract the 3 D phase△and the Stokes parameter S3 of a transmissive anisotropic object spatially using an interferometric Polar *** parallel interferograms with a phase shift ofπ/2 between the images are captured in a single snapshot and then reconstructed by the four-bucket algorithm to extract the 3 D phase of the *** S3 is then calculated directly from the obtained 3 D phase△.The extracted results of△and S3 were compared with those extracted from the non-interferometric Polar Cam and the Thorlabs polarimeter,and the results match quite *** merit of using the interferometric Polar Cam is that no mechanical movement mechanisms are included,and hence the△and S3 of the object can be extracted,with high accuracy and within a part of a second(three times faster than non-interferometric Polar Cam and Thorlabs polarimeter methods).Moreover,this method can be applied in the field of the dynamic spectro–interferometric Polar Cam and can be implemented using swept-wavelength approaches.

关键词： hence faster spatially

Phase transformation behaviors and mechanical properties of Ti_(50)Ni_(49)Fe_1 alloy with severe plastic deformation

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Rare Metals 2013年第5期32卷 448-452页

作者： Wen Ma Bin Chen Fu-Shun Liu Qing Xu division of Science and Technology Information General Research Institute for Nonferrous Metals School of Material Science and Engineering Beijing University of Aeronautics and Astronautics metrology and Phsico-Chemical Institute Capital Aerospace Machinery Company

In this work, transformation behaviors and mechanical properties of cold-rolled shape memory alloy TisoNia9Fel by severe plastic deformation （SPD） were intensively investigated. The phase transformation behaviors, phase analysis, and microstructures were characterized by differential scanning calorimetry （DSC）, X-ray diffraction （XRD）, and transmission electron microscopy （TEM）, respectively. Tensile testing was performed to analyze the effect of SPD on the mechanical properties and shape memory of TisoNi49Fel alloy. When the thickness reduction is beyond 30 %, the martensitic transformation is suppressed. After cold-rolling, the alloy is mainly com- posed of B2 parent phases with some stress-induced martensitic B 19t phases, and high density of dislocations are generated and the grains are obviously refined. The yield stress ab significantly raises from 618 MPa of 0 % cold rolling to 1,338 MPa of 50 % SPD. Shape-memory effect increases from 6.5 % without cold rolling to 8.5 % after 30 % SPD, ascribed to the induced defects in cold rolling. Those results indicate that TisoNi49Fel alloy has improved mechanical properties and potential commercial applications after SPD.

关键词： TiNiFe alloy Cold-rolling Severe plasticdeformation (SPD) Shape memory effect

Depth Dependence of Tetragonal Distortion of a ZnO/Mg0.1Zn0.90/ZnO Heterostructure Studied by Rutherford Backscattering/Channeling

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Chinese Physics Letters 2009年第10期26卷 196-199页

作者：王坤丁志博李琳姚淑德 State Key Laboratory of Nuclear Physics and Technology Peking University Beijing 100871 division of metrology in Ionizing Radiation and Medicine National Institute of Metrology Beijing 100013

Rutherford backscattering and channeling are used to characterize the structure of a ZnO/Mg0.1Zn0.90/ZnO heterostructare grown on a sapphire （0001） substrate by rf plasma-assisted molecular beam epitaxy. The results show that the Mg0.1Zn0.90 layer has the same hexagonal wurtzite structure as the underlying ZnO layer, and the heterostructure has a good crystalline quality with xmin = 5%, which is the ratio of the backscattering yields of aligned and random spectra in the near-surface region. Using the channeling angular scan around an off-normal （1213） axis in the {1010} plane of both ZnO and MgZnO layer, the tetragonal distortion εT, which is caused by the elastic strain in the epilayer, is determined. The depth dependence of εT is obtained by using this technique. It can clearly be seen that the elastic strain rapidly decreases with the increase in thickness of the ZnO film in the early growth stage and becomes slightly larger in the region of the Mg0.1Zn0.9O layer.

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Anisotropic Total Variation Regularization Based NAS-RIF Blind Restoration Method for OCT Image

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Journal of Beijing Institute of Technology 2020年第2期29卷 146-157页

作者： Xuesong Fu Jianlin Wang Zhixiong Hu Yongqi Guo Kepeng Qiu Rutong Wang College of Information Science and Technology Beijing University of Chemical TechnologyBeijing 100029China division of Medical and Biological Measurement National Institute of MetrologyBeijing 100029China

Based on anisotropic total variation regularization(ATVR), a nonnegativity and support constraints recursive inverse filtering(NAS-RIF) blind restoration method is proposed to enhance the quality of optical coherence tomography(OCT) image. First, ATVR is introduced into the cost function of NAS-RIF to improve the noise robustness and retain the details in the *** the split Bregman iterative is used to optimize the ATVR based cost function, the ATVR based NAS-RIF blind restoration method is then constructed. Furthermore, combined with the geometric nonlinear diffusion filter and the Poisson-distribution-based minimum error thresholding, the ATVR based NAS-RIF blind restoration method is used to realize the blind OCT image restoration. The experimental results demonstrate that the ATVR based NAS-RIF blind restoration method can successfully retain the details in the OCT images. In addition, the signal-to-noise ratio of the blind restored OCT images can be improved, along with the noise robustness.

关键词： optical coherence tomography(OCT)image blind image restoration cost function nonnegativity and support constraints recursive inverse filtering(NAS-RIF)