查看更多>>摘要：We present an approach that allows detecting all three components of the residual magnetic field inside shielding, based on the electron paramagnetic resonance (EPR) of spin-polarized K atoms. The residual field experienced by spin-polarized K atoms dominates Larmor precession frequency, the smaller the frequency is, the more benefits it has to realize spin-exchange relaxation-free (SERF) regime under a definite spin-exchange rate. The measurements are accomplished based on depopulation optical pumping and optically-detected peak of the K EPR spectrum. The EPR-based cross modulation method is employed to determine all three components of the residual field independently by modulating the frequency of transverse field and the strength of longitudinal field. The weighted averages of all measurements with the corresponding uncertainties are (9.60 +/- 0.06) nT, (2.25 +/- 0.03) nT, and (2.83 +/- 0.17) nT along with the negative directions of their related axes, respectively.
Klauenberg, KatyMartens, SteffenBosnjakovic, AlenCox, Maurice G....
8页
查看更多>>摘要：Following the Guide to the expression of uncertainty in measurement (GUM), the slope and intercept in straight-line regression tasks can be estimated and their uncertainty evaluated by defining a measurement model. Minimizing the weighted total least-squares functional appropriately defines such a model when both regression input quantities (X and Y) are uncertain. This paper compares the uncertainty of the straight line evaluated by propagating distributions and by the law of propagation of uncertainty (LPU). The latter is in turn often approximated because the non-linear measurement model does not have closed form. We reason that the uncertainty recommended in the dedicated technical specification ISO/TS 28037:2010 does not fully implement the LPU (as intended) and can understate the uncertainty. A systematic simulation study quantifies this understatement and the circumstances where it becomes relevant. In contrast, the LPU uncertainty may often be appropriate. As a result, it is planned to revise ISO/TS 28037:2010.
查看更多>>摘要：The fusion technology of wide-angle ultrasonic sensor and inclination sensor is applied to the attitude monitoring of advanced hydraulic support in the harsh underground environment. Firstly, the measurement model based on the kinematics of advanced hydraulic support is established, and then the calculation algorithm of yaw angle and roll angle based on ultrasonic ranging data is proposed. Finally, the platform of attitude monitoring system is built to realize the attitude monitoring of advanced hydraulic support based on multi-sensor. The field test results show that the maximum root mean square error of distance measurement is 4.36 mm; the maximum root mean square error of the roll angle is 0.12 degrees; the maximum root mean square error of the yaw angle is 0.20 degrees. The test results verify the accuracy and stability of attitude monitoring system experimental platform for the advanced hydraulic support.
查看更多>>摘要：We have developed a system to determine the position and orientation fast and precisely, by the collaboration measurement of an Unmanned Aerial Vehicle (UAV) and two Robotic Total Stations (RTSs). One RTS is set on the control point, and another is set on the undetermined point. All devices are connected to the control terminal through a wireless network, so that the two RTSs can perform synchronous tracking measurements towards the same 360 degrees prism mounted on the UAV. With an algorithm developed based on the theory of Massive Moving Control Points for Free-stationing (MMCPF), high-accuracy position and orientation can be determined in a onestop mode within several minutes. Results of the simulation experiment and the field experiment validated the feasibility of our system, showing a positioning accuracy of millimetre level and orientation accuracy of angularsecond level. The newly proposed methodology can be applied for limited direct sight conditions and poor GNSS observation environments, especially for under-construction civil engineerings, such as high-rise buildings, dams, railways, and bridges.
查看更多>>摘要：The nanofluidic chips with channels of 100-nm depth and 3-mu m width were employed as molecular flow standard leak elements for vacuum technology applications in this paper. The nanofluidic chips are fabricated by MEMS technologies while the macro-micro connection is achieved using glass fusion bonding and standard Swagelok (R) Fitting. It is found that the choice of annealing temperature and holding time is a key issue regarding fusion bonding and the optimal processing parameters are 780 degrees C, 5 min. Meanwhile, the sealing reliability of fusion bonding and the fitting connection is evaluated. Experiment shows that the flow conductance of the as-fabricated leak can reach 10(-13) m(3).s(-1) magnitude for He, N-2 and Ar. This standard leak has the advantages of controlled dimensions, reliable connection, and constant flow conductance over a range of 10(5) Pa.
查看更多>>摘要：This paper presents the influence of the coordinate system establishment error on the tooth profile deviation with the standard polar coordinate method (SPCM) for a gear measuring center (GMC). The tooth profile deviation measurement model of the SPCM and the coordinate system establishment error model are established. The influences of the coordinate system establishment errors in the X and Y directions on the measurement accuracy of involute tooth profile are simulated on a Digital Twin of GMC (DTGMC) platform, and the model is verified by experiments. The research shows that the influences of the coordinate system establishment errors in different directions on the tooth profile deviation are different, which should be taken seriously. It is found that by changing the error direction, the influence of the measurement error caused by the coordinate system establishment error can be offset, providing a new method to improve the measurement accuracy of the gear tooth profile with the SPCM.
查看更多>>摘要：In this paper, we report a new multi-function servo control dynamic shear test apparatus, DJZ-500. This apparatus consists of five parts, including power system, loading frame, servo control unit, cooling system and PC console. The normal load and shear load are measured by load cells with an accuracy of 0.1 kN; normal and shear displacement are measured by LVDTs with an accuracy of 0.1 mu m. DJZ-500 has the dynamic and static loading modules, which can perform the force and displacement servo control experiments in both vertical and horizontal directions. In addition, the dynamic loading modules can execute the custom waveforms, which can be utilized to investigate the seismic response of rock and soil masses. We presented six sets of representative tests on sands to demonstrate these functions. Moreover, DJZ-500 can also preform the coupled shear-flow test with the pumping system to investigate the flow behavior in sheared rock fractures. This device makes up for the deficiency of the existing equipment, and promotes the study of frictional properties of geomaterials.
查看更多>>摘要：To verify that the density of the material used for weights is within the permissible error range, the masses and volumes of the weights must be measured during the initial verification. Besides the hydrostatic method, the double-weighing in air method is an alternative method to determine the volumes of weights. The principle and feasibility of the double-weighing in air method were described in previous publications, but a comparison of different volume measurement methods for the whole weight series from 1 g to 1 kg is lacking. In this study, we compared the double-weighing in air method and the hydrostatic method. A set of stainless-steel weights were selected as samples, the differences of the volumes/densities determined from both methods were analyzed, and an uncertainty evaluation was performed. The results and the corresponding uncertainties for both methods were compared, and the accuracy and efficiency of the double-weighing in air method were demonstrated.
查看更多>>摘要：In order to realize the in-situ calibration of the large-diameter permanent magnet sodium flowmeter without bluff body based on the cross-correlation method, its serious nonlinearity error must be corrected, and the reduction of the repeatability error is the prerequisite. The analysis shows that the velocity fluctuations near the sidewall are greater than the center, and the signal of low-frequency mainly comes from the sidewall, so the low-frequency signal will cause a large repeatability error of whole. Accordingly, an error correction method based on low-frequency suppression is proposed, and its technical points of the selection of signal electrodes, the filtration of fixed interference and the median filtering are given. The nonlinearity error is corrected by the quadratic function model. The accuracy of in-situ calibration is within +/- 3.0%.
查看更多>>摘要：The empirical wavelet transform (EWT) has made outstanding contributions in the field of fault diagnosis. However, when EWT processes complex signals, there may be modal aliasing or meaningless components. In order to solve the spectral segmentation defect of the EWT method and improve its ability to extract bearing fault features, this paper proposes a new algorithm to improve EWT. In order to weaken the influence of extreme points in the complex Fourier spectrum on modal differentiation, the cycle envelope spectral segmentation method is proposed. The maximum envelope fitting method not only reduces the number of useless extreme points, but also highlights each mode. The number of filters is reduced while suppressing the interference of noise on the modal. The components that contain similar information in the result will be merged based on their correlation. Then sensitive IMFs assessing index (SIAI) is proposed to combine correlation and symmetry of the signal, and obtains the characteristics of time domain, frequency domain, and amplitude domain to extract fault information. Locomotive bearing and wind turbine gearbox bearing fault data verified the effectiveness of the method.
NSTL
Elsevier