Reomtly, Coordinate bieasuring Machines （CMMs） are widely used to measure roundness errors. Roundness is calculated from a large number of points collected from the profiles of the parts. According to the Guide to t...Reomtly, Coordinate bieasuring Machines （CMMs） are widely used to measure roundness errors. Roundness is calculated from a large number of points collected from the profiles of the parts. According to the Guide to the Expression of Uncertainty in Measta- meat （GUM）, all measurement results must have a stated uncertainty associated the titan. However, no CMMs give the uncertainty value of the roundness, because no suitable measrement uncertainty calculation procedure exists. In the case of roundness raeasurement in coordinate metrology, this paper suggests the algorithms for the calculation of the measurement uncertainty of the roudness deviation based on the two mainly used association criteria, LSC and MZC. The calculation of the sensitivity coefficients for the uncertainty calculatiion can be done by autnatic differentiation, in order to avoid introducing additional emars by the traditional difference quotient approxima- tions. The proposed methods are exact and need input data only as the nrasured coordinates of the data points and their associated un- certainties.展开更多
Quantitative characterization of the mechanical properties of materials in micro-/nano-scale using depth-sensing indentation technique demands high performance of nanoindentation instruments in use. In this paper, the...Quantitative characterization of the mechanical properties of materials in micro-/nano-scale using depth-sensing indentation technique demands high performance of nanoindentation instruments in use. In this paper, the efforts to calibrate the capacitive force transducer of a commercial nanoindentation instrument are presented, where the quasi-static characteristic of the force transducer has been calibrated by a precise compensation balance with a resolution of ~1 nN. To investigate the dynamic response of the transducer, an electrostatic MEMS (Micro-Electro-Mechanical System) based on nano-force transfer standard with nano-Newton (10-9 Newton) resolution and a bandwidth up to 6 kHz have been employed. Preliminary experimental results indicate that 1) the force transducer under calibration has a probing force uncertainty less than 300 nN (1σ) in the calibration range of 1 mN;2) the transient duration at contact points amounts to 10 seconds;3) the overshoot of engagement is pre-load dependent.展开更多
Silica gel (SG) was synthesized via acidification of sodium silicate solution then doped with Fˉ or Zr(IV) in molar ratios of F/Si 3/100, and Zr/Si 0.75/100 and 3.75/100 and sintered at 500°C, 800°C and 100...Silica gel (SG) was synthesized via acidification of sodium silicate solution then doped with Fˉ or Zr(IV) in molar ratios of F/Si 3/100, and Zr/Si 0.75/100 and 3.75/100 and sintered at 500°C, 800°C and 1000°C. The samples were investigated by X-ray diffractometry, infrared absorption and Raman spectra, surface area measurement, and inductively coupled plasma-optical emission spectrometry-monitored silica hydrolysis. All samples are mesoporous with BET surface areas 181.5 - 523.9 m2·gˉ1. The surface area of the silica samples decreases as the sintering temperature increases. The hydrolysis process of silica decreases as the sintering temperature increases and as the surface area decreases. The pH and the type of buffer solution affect the hydrolysis of silica samples due to a SN2 reaction mechanism favored in basic media using ammonia buffer. Zr(IV) increases the stability of silica samples against the hydrolysis as confirmed by the structural investigation, surface area and silica hydrolysis. Fˉ observably decreases the silica hydrolysis process when presenting on the surface of SG.展开更多
Quantum key distribution(QKD)enables the transmission of information that is secure against general attacks by eavesdroppers.The use of on-demand quantum light sources in QKD protocols is expected to help improve secu...Quantum key distribution(QKD)enables the transmission of information that is secure against general attacks by eavesdroppers.The use of on-demand quantum light sources in QKD protocols is expected to help improve security and maximum tolerable loss.Semiconductor quantum dots(QDs)are a promising building block for quantum communication applications because of the deterministic emission of single photons with high brightness and low multiphoton contribution.Here we report on the first intercity QKD experiment using a bright deterministic single photon source.A BB84 protocol based on polarisation encoding is realised using the high-rate single photons in the telecommunication C-band emitted from a semiconductor QD embedded in a circular Bragg grating structure.Utilising the 79 km long link with 25.49 dB loss(equivalent to 130 km for the direct-connected optical fibre)between the German cities of Hannover and Braunschweig,a record-high secret key bits per pulse of 4.8 x io-5 with an average quantum bit error ratio of~0.65%are demonstrated.An asymptotic maximum tolerable loss of 28.11 dB is found,corresponding to a length of 144 km of standard telecommunication fibre.Deterministic semiconductor sources therefore challenge state-of-the-art QKD protocols and have the potential to excel in measurement device independent protocols and quantum repeater applications.展开更多
The correlation of single-particle imaging and absorption spectroscopy made the development of sizing curves possible and enabled rapid size determination of semiconductor nanocrystals based solely on optical properti...The correlation of single-particle imaging and absorption spectroscopy made the development of sizing curves possible and enabled rapid size determination of semiconductor nanocrystals based solely on optical properties.The increasing demand and production of such materials has resulted in a question of comparability between existing models and adequate volume-weighted size-determining measurement techniques.Small-angle X-ray scattering(SAXS)is a well-established method for obtaining nanostructural information from particle systems while operating sample quantities up to a commercial scale with a large amount of statistically based data.This work utilizes laboratory SAXS to characterize cadmium selenide nanocrystals with band edge energies between 1.97 and 3.08 eV.The evaluation of the scattering patterns is based on an indirect Fourier transformation(IFT),while dimensional parameters are derived from the model-free pair distance distribution functions(Dmode and Dg),as well as the modeled volume(Dv)and number(Dn)-weighted size-density distributions.We find that comparable data from D̅n agree well with existing X-ray diffraction(XRD)and with transmission electron microscopy(TEM)results described in literature;this qualifies SAXS as an equivalent integral characterization method.Although based on an estimate,the radius of gyration yields equivalent accurate results.Additionally,corresponding volume-weighted data are shown that can be useful when transferring information to other techniques.Dmode parametrization represents the largest estimated size of the sample and implies that particles interact and deviate from the spherical morphology,whereas Dv demonstrates results not considering such effects.A full set of the parameters discussed quantifies the quality of a sample.展开更多
A microscope image formation model based on scalar diffraction and Fourier optics has been developed, which takes a slant angle between the optical axis and the observed surface into account. The theoretical investiga...A microscope image formation model based on scalar diffraction and Fourier optics has been developed, which takes a slant angle between the optical axis and the observed surface into account. The theoretical investigations of the imaging of line structures using this model show that reflection type microscopes are much stronger influenced by the slant angle than transmission type microscopes. In addition, the slant angle changes the image contrast and the image shape of a line structure, especially its edge. The larger the slant angle, the stronger the decrease of the image contrast, and the less steep the edge slope in both types of microscopes. Furthermore, the larger the numerical aperture of the objective, the less the effect of the slant angle on the line image shape.展开更多
基金supported by the National Natural Science Foundation of China(No.50705002,50627501)
文摘Reomtly, Coordinate bieasuring Machines （CMMs） are widely used to measure roundness errors. Roundness is calculated from a large number of points collected from the profiles of the parts. According to the Guide to the Expression of Uncertainty in Measta- meat （GUM）, all measurement results must have a stated uncertainty associated the titan. However, no CMMs give the uncertainty value of the roundness, because no suitable measrement uncertainty calculation procedure exists. In the case of roundness raeasurement in coordinate metrology, this paper suggests the algorithms for the calculation of the measurement uncertainty of the roudness deviation based on the two mainly used association criteria, LSC and MZC. The calculation of the sensitivity coefficients for the uncertainty calculatiion can be done by autnatic differentiation, in order to avoid introducing additional emars by the traditional difference quotient approxima- tions. The proposed methods are exact and need input data only as the nrasured coordinates of the data points and their associated un- certainties.
文摘Quantitative characterization of the mechanical properties of materials in micro-/nano-scale using depth-sensing indentation technique demands high performance of nanoindentation instruments in use. In this paper, the efforts to calibrate the capacitive force transducer of a commercial nanoindentation instrument are presented, where the quasi-static characteristic of the force transducer has been calibrated by a precise compensation balance with a resolution of ~1 nN. To investigate the dynamic response of the transducer, an electrostatic MEMS (Micro-Electro-Mechanical System) based on nano-force transfer standard with nano-Newton (10-9 Newton) resolution and a bandwidth up to 6 kHz have been employed. Preliminary experimental results indicate that 1) the force transducer under calibration has a probing force uncertainty less than 300 nN (1σ) in the calibration range of 1 mN;2) the transient duration at contact points amounts to 10 seconds;3) the overshoot of engagement is pre-load dependent.
基金partly funded by the Alexander von Humboldt foundation,Germany,in the frame of a fellowship award.
文摘Silica gel (SG) was synthesized via acidification of sodium silicate solution then doped with Fˉ or Zr(IV) in molar ratios of F/Si 3/100, and Zr/Si 0.75/100 and 3.75/100 and sintered at 500°C, 800°C and 1000°C. The samples were investigated by X-ray diffractometry, infrared absorption and Raman spectra, surface area measurement, and inductively coupled plasma-optical emission spectrometry-monitored silica hydrolysis. All samples are mesoporous with BET surface areas 181.5 - 523.9 m2·gˉ1. The surface area of the silica samples decreases as the sintering temperature increases. The hydrolysis process of silica decreases as the sintering temperature increases and as the surface area decreases. The pH and the type of buffer solution affect the hydrolysis of silica samples due to a SN2 reaction mechanism favored in basic media using ammonia buffer. Zr(IV) increases the stability of silica samples against the hydrolysis as confirmed by the structural investigation, surface area and silica hydrolysis. Fˉ observably decreases the silica hydrolysis process when presenting on the surface of SG.
文摘Quantum key distribution(QKD)enables the transmission of information that is secure against general attacks by eavesdroppers.The use of on-demand quantum light sources in QKD protocols is expected to help improve security and maximum tolerable loss.Semiconductor quantum dots(QDs)are a promising building block for quantum communication applications because of the deterministic emission of single photons with high brightness and low multiphoton contribution.Here we report on the first intercity QKD experiment using a bright deterministic single photon source.A BB84 protocol based on polarisation encoding is realised using the high-rate single photons in the telecommunication C-band emitted from a semiconductor QD embedded in a circular Bragg grating structure.Utilising the 79 km long link with 25.49 dB loss(equivalent to 130 km for the direct-connected optical fibre)between the German cities of Hannover and Braunschweig,a record-high secret key bits per pulse of 4.8 x io-5 with an average quantum bit error ratio of~0.65%are demonstrated.An asymptotic maximum tolerable loss of 28.11 dB is found,corresponding to a length of 144 km of standard telecommunication fibre.Deterministic semiconductor sources therefore challenge state-of-the-art QKD protocols and have the potential to excel in measurement device independent protocols and quantum repeater applications.
基金The authors thank the Laboratory for Nano and Quantum Engineering(LNQE),Leibniz University Hannover,for the access to the TEM instrument and Dr.Brian Pauw from the Bundesanstalt für Materialforschung und-prüfung(BAM)in Berlin for the scientific discussion about SAXS and the provision of the Ag-reference.We also acknowledge the work of David Niedbalka and Marcel Pastuschek who contributed to this research during their time as students.This research was partially funded by Niedersächsisches Ministerium für Wissenschaft und Kultur through the“Quantumand Nano-Metrology(QUANOMET)”initiative(ZN3245)within the scope of the NP-1 project.Furthermore,we acknowledge financial travel support by the DFG Research Training Group GrK1952“Metrology for Complex Nanosystems(NanoMet)”.
文摘The correlation of single-particle imaging and absorption spectroscopy made the development of sizing curves possible and enabled rapid size determination of semiconductor nanocrystals based solely on optical properties.The increasing demand and production of such materials has resulted in a question of comparability between existing models and adequate volume-weighted size-determining measurement techniques.Small-angle X-ray scattering(SAXS)is a well-established method for obtaining nanostructural information from particle systems while operating sample quantities up to a commercial scale with a large amount of statistically based data.This work utilizes laboratory SAXS to characterize cadmium selenide nanocrystals with band edge energies between 1.97 and 3.08 eV.The evaluation of the scattering patterns is based on an indirect Fourier transformation(IFT),while dimensional parameters are derived from the model-free pair distance distribution functions(Dmode and Dg),as well as the modeled volume(Dv)and number(Dn)-weighted size-density distributions.We find that comparable data from D̅n agree well with existing X-ray diffraction(XRD)and with transmission electron microscopy(TEM)results described in literature;this qualifies SAXS as an equivalent integral characterization method.Although based on an estimate,the radius of gyration yields equivalent accurate results.Additionally,corresponding volume-weighted data are shown that can be useful when transferring information to other techniques.Dmode parametrization represents the largest estimated size of the sample and implies that particles interact and deviate from the spherical morphology,whereas Dv demonstrates results not considering such effects.A full set of the parameters discussed quantifies the quality of a sample.
文摘A microscope image formation model based on scalar diffraction and Fourier optics has been developed, which takes a slant angle between the optical axis and the observed surface into account. The theoretical investigations of the imaging of line structures using this model show that reflection type microscopes are much stronger influenced by the slant angle than transmission type microscopes. In addition, the slant angle changes the image contrast and the image shape of a line structure, especially its edge. The larger the slant angle, the stronger the decrease of the image contrast, and the less steep the edge slope in both types of microscopes. Furthermore, the larger the numerical aperture of the objective, the less the effect of the slant angle on the line image shape.
