Office Online  
    Office Online
    Manuscript Tracking
    Editor Work
    Office Work
    Editor-in-chief
Journal Online
    Current Issue
    Advanced Search
    Archive
    Read Articles
    Download Articles
    Email Alert
Traffic
Quick Search  
  Adv Search
2022 Vol. 43, No. 7
Published: 2022-07-28
 
837 Research on Stitching Method for Segment Straightness Measurement of the Long Guideway
LI Ting,MIAO Dong-jing,LI Lian-fu,LI Jian-shuang,ZHONG Wen
DOI: 10.3969/j.issn.1000-1158.2022.07.01
When using the interferometer to measure the straightness of the ultra-long rail, the stitching may introduce a large error due to the length of the rail exceeding the measurement range of the interferometer, since the straightness of the whole long guide rail needs to be divided into multiple sections and then each straightness is measured separately.By analyzing the influencing factors in the splicing process, and combined with the structural characteristics of long guide rails, a new straightness splicing method for long guide rails is proposed.This method uses common points distributed on two adjacent sub-guide rails for splicing, and uses the stable characteristic of the angle between two adjacent sub-guide rails to realize straightness splicing .Through simulation and experiment, the measurement results of the direct measurement method and the coordinate transformation splicing method in the range of 30m are compared, and the difference of straightness results between the two methods is less than 10μm, which shows that the proposed method can effectively reduce the stitching error.Finally, this method is applied to the straightness measurement of 72m rail, and compared with the electronic level measurement method, the difference of the two results methods is 10μm, which indicated that the proposed method can achieve high-precision straightness stitching.
2022 Vol. 43 (7): 837-843 [Abstract] ( 261 ) HTML (1 KB)  PDF (3304 KB)  ( 185 )
844 Research on the Key Technology of the Automatic Measurement System for Surface Roughness International Comparison
BU Xiang-peng,ZHANG Shu,PI Lei,SHI Yu-shu
DOI: 10.3969/j.issn.1000-1158.2022.07.02
Based on the surface roughness measurement device of NIM, researches on the visual positioning system, automatic operating system and multi-degree-of-freedom displacement system have been carried out, so as to realize the automatic measurement in accordance with the procedures specified in the international comparison agreement.Through experimental verification, the system can effectively realize the automatic measurement of surface roughness and meet the requirements of international comparison.In the measurement experiment on the surface roughness standard specified by the international comparison, the repeatability of the automatic positioning measurement of the system is 4.2nm, which is 2.6 times higher than the manual positioning measurement, and can effectively reduce the introduction of human error in the measurement process.
2022 Vol. 43 (7): 844-850 [Abstract] ( 208 ) HTML (1 KB)  PDF (2281 KB)  ( 221 )
851 Research on Measuring Device and Method of Reflective Grey Scale Test Card
GAO Hong-bo,WU Wei-gang,ZENG Zhi,ZHOU Yan,CAO Xue-ying
DOI: 10.3969/j.issn.1000-1158.2022.07.03
In order to solve the metrological traceability of quantity value of reflective gray-scale test card used for evaluating photographic image quality, an optical test platform is built according to the existing test instruments in the laboratory, a simple and feasible test scheme is proposed.The halogen lamp is equipped with collimator as light source.The automatic control of 45°/0°angle system is realized by using double-axis stepper motor and PCI test card based on PCI interface.The spectral spectroradiometer is selected as the receiving unit, the standard white board with known value is used as the standard, adopting the relative measurement method, the non-contact measurement of reflective optical density is realized.The experimental data analysis shows the device is used to measure the TE-108 reflective gray-scale test card, the maximum error between the measured optical density test data and the factory value is only 0.02, the reliability of the device and the feasibility of the measurement method are high, at the same time, it is proved that the printing quality of the reflective gray-scale test card is good.The results can provide a reference for future research.
2022 Vol. 43 (7): 851-855 [Abstract] ( 162 ) HTML (1 KB)  PDF (671 KB)  ( 127 )
856 Research on Gesture Recognition Algorithm under Multi-channel Fusion and Design of Ship Virtual Interaction Platform
CHENG Shu-hong,YANG Zhen-hao,WANG Chang
DOI: 10.3969/j.issn.1000-1158.2022.07.04
A gesture recognition algorithm based on multi-channel fusion is proposed to promote the intelligent human-computer interaction of ship virtual interaction platform.It collects gesture images from different perspectives and establishes gesture data sets.Based on the YOLOV4 target detection algorithm, a gesture recognition framework is constructed to recognize the multi-angle gesture images, and the final result is determined by a multi-data fusion algorithm.At the same time, the virtual scene of ship navigation based on Unity 3D is designed to realize the operation of virtual ship stability platform by gesture recognition.Experiments were conducted to test the robustness of the gesture recognition algorithm in complex environment, and compare the one-view gesture identification method based on YOLOV4 with the accuracy of this algorithm.Experimental results show that this gesture recognition algorithm can eliminate false candidate results and retain maximum confidence by multi-data fusion.The average recognition accuracy of gesture is 95.06 % in complicated environments.
2022 Vol. 43 (7): 856-862 [Abstract] ( 186 ) HTML (1 KB)  PDF (3664 KB)  ( 515 )
863 Research on Material Counting Method Based on Improved Template Matching Algorithm
HAN Shuo,CHEN Xiao-rong,ZHANG Cai-xia,GUO Rong-rong,WANG Xiao-long
DOI: 10.3969/j.issn.1000-1158.2022.07.05
In order to solve the defects of the material counting method in the production process, an improved template matching algorithm is studied for material quantity detection, and the improved template matching algorithm (TMA) is optimized based on the dual template search method and the position constraint coefficient r. The process of finding the best matching image, obtaining the optimal solution, and then performing image stitching to complete the material count. Through experimental comparison with traditional TMA and Gaussian pyramid transformation (GPT) optimization, it proves that compared with the other two algorithms, the time to process each sample image is shortened from 0.013s, 0.011s to 0.008s, and the counting accuracy is improved from 77.32%, 84.94% to more than 97.36% respectively. The stitching accuracy is also better than the other two algorithms, and the experimental results verify the effectiveness of the algorithm.
2022 Vol. 43 (7): 863-868 [Abstract] ( 202 ) HTML (1 KB)  PDF (1056 KB)  ( 532 )
869 Research on Extrapolation of PPRTs Deviation Equation to -189.3442~156.5985℃
WANG Bo-yang,ZENG Fan-chao,HUANG An-yi,SUN Jian-ping,FU Cheng-yu
DOI: 10.3969/j.issn.1000-1158.2022.07.06
The traceability of precision platinum resistance thermometers (PPRTs) can be improved by using the fixed-points method defined by the International Temperature Scale of 1990 (ITS-90). Due to the small number of fixed-points and the large temperature interval in ITS-90, the extrapolation based on deviation equation is an effective method to solve the problem of thermometer calibration beyond the temperature range. In the experiment, 16 PPRTs were calibrated in the temperature range of -189.3442~156.5985℃ to verify the extrapolation feasibility of the fixed-points method deviation equation and comparison method deviation equation.The experimental results showed that the average maximum difference using the new deviation equation from -38.8344~0.01℃ was 5.2mK when extrapolating to -189.3442℃; the average maximum difference using the deviation equation from 0~29.7646℃ was 2.0mK when extrapolating to 156.5985℃; and the average difference using comparison method deviation equation was less than 3.3mK.All the three equations improved the extrapolation accuracy of PPRTs out of the fixed-points temperature range and provided supporting data for the traceability of spaceborne blackbody radiation source.
2022 Vol. 43 (7): 869-876 [Abstract] ( 150 ) HTML (1 KB)  PDF (4304 KB)  ( 1110 )
877 Calculation of Conductor Temperature and Ampacity of Directly Buried Cable Based on Electromagnetic Thermal Multi Field Coupling
WANG Yan-nan,LI Zheng,YANG Peng-fei,LIU Wei
DOI: 10.3969/j.issn.1000-1158.2022.07.07
In order to study the temperature and current carrying capacity of underground cable conductors and design reasonable cable laying methods, combined with the knowledge of heat transfer and using finite element analysis, a calculation model of electromagnetic thermal coupling for buried power cables is established, and the current carrying capacity of the model is calculated. The calculation result is compared and verified with the calculation result based on the IEC 60287 standard. The influence of cable laying depth, interphase distance, thermal backfill and phase sequence changes on the temperature and current carrying capacity of power cable conductors is discussed, and the degree of influence of different factors on the temperature and current carrying capacity of cable conductors is analyzed through multiple linear regression. The research results show that the cable laying method greatly affects the cable conductor temperature and ampacity. The greater the laying depth, the smaller the interphase distance, the smaller the thermal conductivity of the thermal backfill, the higher the cable conductor temperature, the lower the ampacity. The thermal conductivity of backfill has the most significant effect on the temperature and ampacity of the cable conductor, and the phase sequence has the smallest effect. Therefore, in the direct buried cable laying project, thermal backfill with high thermal conductivity should be used to enhance the heat dissipation effect of the cable, thereby ensuring the safe and economic operation of the cable.
2022 Vol. 43 (7): 877-884 [Abstract] ( 181 ) HTML (1 KB)  PDF (2297 KB)  ( 206 )
885 Exploring the Research Direction of Fluid Flow Measurement in China Based on the Distribution of Calibration and Measurement Capabilities
LI Meng-na,LI Chun-hui
DOI: 10.3969/j.issn.1000-1158.2022.07.08
Based on the calibration and measurement capabilities distribution in fluid flow of the top 10 economics in total number of calibration and measurement capabilities, and according to the key comparisons classification system of the Fluid Flow Working Group (WGFF) of the International Committee for Weights and Measures (CIPM), the principle of flow measurement, flow range, uncertainty are compared and analyzed. In addition, the future research of Chinas calibration and measurement capability in fluid flow is proposed, and it provides a support for the re-evaluation of calibration and measurement capability in fluid flow.
2022 Vol. 43 (7): 885-891 [Abstract] ( 233 ) HTML (1 KB)  PDF (1284 KB)  ( 274 )
892 On-situ Calibration Technology of Force Balance for Helicopter Rotor Aerodynamic Test
TANG Bin,WANG Wen-jian
DOI: 10.3969/j.issn.1000-1158.2022.07.09
Studied the on-situ calibration method of five-component helicopter aerodynamic measurement balance. According to the measurement principle and structural characteristics of the helicopter aerodynamic measurement balance which mounted on the top of a helicopter fullscale rotor test tower, the researchers determined the on-situ calibration technical scheme of the combined loading based on the principle of force superposition. According to its principle, the field calibration device is developed, and the design of key mechanical structure and the control system of adaptive cooperative algorithm are introduced. A high precision micro-deformation measurement system was developed to evaluate the calibration error. Finally, the performance of the calibration device was verified through the on-situ calibration test of the rotor test tower, and the on-situ relative calibration uncertainty of each force element was evaluated to be better than 0.1% (k=2).
2022 Vol. 43 (7): 892-899 [Abstract] ( 181 ) HTML (1 KB)  PDF (3270 KB)  ( 233 )
900 Numerical Modelling of Non-contact Tonometer′s Cornea Applanation Process
LIN Zheng-hao,WANG Can,ZHANG Zhong-li,QIN Ting-ting,LIU Bei-bei,Feng Qi-bin,HONG Bian
DOI: 10.3969/j.issn.1000-1158.2022.07.10
A transient 3D fluid-structure interaction model of non-contact tonometer′s cornea applanation process has been built to study the external flow field of non-contact tonometer and the dynamic corneal deformation with different intraocular pressure. The results show that the flow field satisfies jet flow theory by showing certain characteristics like the potential core and outer jet boundary; the outer jet boundary of the non-contact tonometer air-puff is around 8.4° which does not change over time, while the jet core decrease from 4.9° to 4.6° over time; the applanation time of cornea increase with intraocular pressure while the applanation length remains in 3.2~3.6mm,which is consistent with the data on the applanation diameter of the non-contact tonometer in the relevant literature. Furthermore, an in-house made experimental device for phantom of intraocular pressure is used to compare results with different applanation length. The results show that comparatively small applanation length will cause severe deviation of intraocular pressure measurement up to 665Pa, which also matches with the simulation result.
2022 Vol. 43 (7): 900-906 [Abstract] ( 177 ) HTML (1 KB)  PDF (4165 KB)  ( 169 )
907 Bearing Fault Diagnosis Method Based on Histogram Equalization and Convolutional Neural Network
CHEN Jian,SUN Tai-hua,HUANG Kai-xuan,KAN Dong,CAO Kun-ming,ZHANG Lei,CHENG Ming
DOI: 10.3969/j.issn.1000-1158.2022.07.11
To solve the problem that traditional fault diagnosis methods of rolling bearing rely on artificial feature extraction and expert experience, and it is difficult to self-adapt to extract weak fault features of strong noise signals, an intelligent diagnosis method combining histogram equalization and convolutional neural network (CNN) is proposed. First, the one-dimensional vibration signal collected by the sensor is transformed into a two-dimensional vibration image that is easy to be recognized by the model through Transversal interpolation. Histogram equalization technology is used to stretch the dynamic range of gray value difference between pixels, highlight texture details and contrast, and enhance periodic fault characteristics. Then, a deep CNN model is constructed, and the optimization technology is used to reduce the model parameters, and the complex mapping relationship between monitoring data and fault state is learned layer by layer. The experimental results show that this method has a high accuracy of more than 99%, and still has a high identification accuracy and generalization ability for fault signals under different loads.
2022 Vol. 43 (7): 907-912 [Abstract] ( 158 ) HTML (1 KB)  PDF (3014 KB)  ( 269 )
913 Fault Diagnosis of Rolling Bearing Based on Bayesian Optimization and Improved LeNet-5
TANG Liang,FAN Yan-feng,XU Shi-fei,CAI Kai-yi
DOI: 10.3969/j.issn.1000-1158.2022.07.12
Considering that the network structure is difficult to determine, too many training times and too long training time exist in rolling bearing fault diagnosis by convolutional neural network (CNN), a Bayesian optimization algorithm for improving LeNet-5 is designed, and a bearing fault diagnosis model constructed by this algorithm is presented.The learning rate and other hyperparameters in the Bayesian optimization training process are adopted, the original vibration signals of various fault bearings are directly used as the input of the improved LeNet-5 network, batch normalization is adopted for the pooled output and the activation function of the improved pool layer is adopted to prevent over-fitting, and the global average pool layer is used to replace the full connection layer to improve the generalization ability of the improved LeNet-5 network, the fault classification of rolling bearing is realized by softmax classifier.The experimental results show the accuracy of bearing fault diagnosis model constructed by this algorithm training set is 99.94%, the accuracy of verification set is 99.89%, and the accuracy of test set is 99.65%, compared with 1D-CNN and 2D-CNN, bearing fault diagnosis model based on Bayesian optimization and improved LeNet-5 algorithm has higher accuracy, less training times and training time in the fault diagnosis model of rolling bearings.
2022 Vol. 43 (7): 913-919 [Abstract] ( 179 ) HTML (1 KB)  PDF (1282 KB)  ( 420 )
920 Study on an Improved HVD Signal Feature Extraction Method and Its Application
SHI Pei-ming,FAN Ya-fei,HAN Dong-ying
DOI: 10.3969/j.issn.1000-1158.2022.07.13
Hilbert vibration decomposition (HVD) is widely used in fault diagnosis of rotating machinery such as fans and gearboxes.However, it has two problems to be solved: (1) the parameters of the algorithm need to be set empirically or determined manually; (2) how to avoid modal mixing by selecting sensitive intrinsic mode function (IMF) components.In view of the above two problems, an improved HVD algorithm is proposed, which effectively solves the problem of parameter setting and model aliasing of Hilbert vibration decomposition.The proposed method is described as follows: firstly, two parameters of HVD algorithm are optimized by particle swarm optimization (PSO).In addition, a new evaluation metric-Max envelope kurtosis mean (MEKM) is proposed as the objective function of the PSO optimization algorithm, and Max envelope kurtosis (MEK) is introduced to adaptively select the sensitive IMF component. Finally, the selected reconstructed signals are analyzed by square envelope spectrum and fault characteristic frequencies are extracted to identify wind turbine equipment fault types.The effectiveness of the proposed improved HVD method is verified by a simulated signal, experimental signal and wind turbine applied example analysis.
2022 Vol. 43 (7): 920-926 [Abstract] ( 164 ) HTML (1 KB)  PDF (3252 KB)  ( 200 )
927 Research on Improving the Accuracy of Measuring Acoustic Pressure by Photon Correlation Spectroscopy Based on Interference Angle Microscopy
YANG Rong-yan,ZHAO Jie,WANG Da-yong,ZHU Wei-min
DOI: 10.3969/j.issn.1000-1158.2022.07.14
In the experiment of measuring air-borne sound pressure by photon correlation spectroscopy in free field, the accurate measurement of the angle between two beams has a great influence on the result of sound pressure measurement. By using the magnified imaging of the microscopic objective, the fringe spacing in the interference area is measured and the angle between the two beams is calculated with high accuracy. Firstly, the influence of the interference spot shape and the uniformity of the fringe spacing on the sound pressure measurement is studied to optimize the optical configuration. Then, the USAF test target is employed as the sample to calibrate the amplification factor of the system. Finally, the air-borne sound pressure in free field is measured by the photon correlation technology. The experimental results showed that, compared with the angle obtained by traditional tri-angle method by measuring the spatial propagation distance of light, the angle obtained by this method improved the accuracy of air acoustic pressure measurement.
2022 Vol. 43 (7): 927-933 [Abstract] ( 160 ) HTML (1 KB)  PDF (3760 KB)  ( 133 )
934 Research on Traceability Method of Micro Capacitance Measuring Instrument at 500fF/1MHz
QIAO Yu-e,LIU Xia-mei,JIN Pan,DING Chen,REN Yu-long,WU Ai-hua,XU Yan-jun
DOI: 10.3969/j.issn.1000-1158.2022.07.15
Micro capacitance measuring instrument in fF level has an important role in Military electronic products.In order to solve the no traceability problem of micro capacitance measuring instrument at 500fF/1MHz, a high frequency 500fF standard capacitor encapsulated with inert gas was manufactured as transfer standard.A measurement model of micro capacitance with high frequency was established, and the distributed parameter was estimated using “subjunctive” method.In the end, the uncertainty of a traceability method called “theoretical deduction” achieves 0.15%.Using three micro capacitance measuring instruments in the same level, the uncertainty of a traceability method called “measurement comparison” achieves 0.07%.The two kinds of traceability methods were used to calculate the same instrument, and the test results showed the same effect, which can satisfy users requirements.The above two traceability methods give an effective way for micro capacitance measurement in high frequency with lower capacitance.
2022 Vol. 43 (7): 934-939 [Abstract] ( 183 ) HTML (1 KB)  PDF (1796 KB)  ( 282 )
940 Research on the Technology of AC Voltage Source at mV Level
DING Xiang,HUANG Yan,ZHANG Lei,PAN Xian-lin,SHI Zhao-min,ZHANG Jiang-tao,WANG Rong-yu
DOI: 10.3969/j.issn.1000-1158.2022.07.16
An accurate calibration method of millivolt AC voltage source based on voltage proportional and AC/DC transfer technology is proposed. The binary cascaded voltage proportional device and 792A AC/DC transfer standard are adopted to trace the millivolt AC voltage to a known AC voltage. By using a substitution measurement method,and choosing the combination of different voltage proportion and different range of 792A, the AC voltage in the range of 10~200mV of a 5720A multifunctional calibration source is accurately measured in the frequency range of 55Hz~5kHz. Results show that the relative error of any measured millivolt AC voltage is within ±40μV/V, and the expanded uncertainty is better than 80μV/V, which shows that the proposed method can meet the traceability requirements of millivolt AC voltage source.
2022 Vol. 43 (7): 940-943 [Abstract] ( 181 ) HTML (1 KB)  PDF (713 KB)  ( 143 )
944 Research on Permanent Magnet Brush-less DC Motor with Low Pulsating Torque
LU Jun,ZHAO Hao,ZHU Gao-lin,FENG Hao
DOI: 10.3969/j.issn.1000-1158.2022.07.17
The permanent magnet brush-less DC motor (BLDCM) has obvious pulsating torque during operation, a new low pulsating torque BLDCM is proposed in order to solve this problem. Firstly, the physical analysis of permanent magnet brush-less DC motor pulsating torque is obtained under three factors, which are current commutation, polar arc coefficient less than 1 and armature reaction. Then, a new motor can generate the pulsating torque have same amplitude, same frequency and 180° phase difference is proposed, in order to realize the suppression strategy of the peak and valley complementation of the pulsating torque, and the method of peak and valley complementation of pulsating torque is found through theoretical analysis. Finally, the low ripple permanent magnet brush-less DC motor and its controller are developed, the effectiveness of pulsating torque suppression is verified through experiments. Compared with ordinary brush-less DC motor, the experimental results show that the pulsating torque can be reduced about 70%.
2022 Vol. 43 (7): 944-951 [Abstract] ( 150 ) HTML (1 KB)  PDF (4837 KB)  ( 202 )
952 Numerical Simulation Analysis of Rubidium Lamp Life Prediction and Type Selection Based on ANSYS
YAO Li,WANG Zhou,WANG Xiao-li,GE Jiu-zhi,TAN Li-cheng,ZHU Xi,TAO Hai-zheng
DOI: 10.3969/j.issn.1000-1158.2022.07.18
The consumption of metal rubidium in rubidium lamp is the main factor determining the working life of rubidium atomic clock. In order to predict the working life of rubidium lamp, based on the similarity of transient heat conduction equation and unsteady mass diffusion equation in mathematical form, a rubidium diffusion model was established to predict the working life of Schott 8436 glass rubidium lamp by using the finite element software ANSYS, The accuracy of the model is verified by comparing the predicted results of the finite element model with the seven-year rubidium measurement data of Wuhan Institute of physics and mathematics, Chinese Academy of Sciences. Through the verified finite element model, the influence of Schott 8436 glass rubidium bulb volume and external profile curvature on rubidium consumption under the same diffusion area is discussed. The relevant results provide theoretical support for the selection of glass rubidium bulb.
2022 Vol. 43 (7): 952-959 [Abstract] ( 178 ) HTML (1 KB)  PDF (4541 KB)  ( 195 )
960 The Establishment of Radiation Qualities and Energy Spectra Simulation of X-ray Lead Equivalent Measurement
ZHAO Rui,WEN Yu-qin,WU Jin-jie,HAN Lu,GUO Bin
DOI: 10.3969/j.issn.1000-1158.2022.07.19
The protective performance of medical diagnostic X-ray protective equipment is usually expressed with lead equivalent.According to IEC 61331-1, the measurement of attenuation performance of protective materials is mainly to study the lead equivalent of pure lead, lead-containing and lead-free materials under the conditions of narrow beam, wide beam and reverse wide beam in the range of 40~150kV X-ray. In order to study the shielding performance of protective materials under different measurement methods furtherly, it is necessary to establish the required X-ray reference radiation qualities and simulate or measure the corresponding energy spectrum.Based on the medium energy X-ray radiation device, by adding additional filter, eight X-ray reference radiations qualities in the range of 40～150kV are established and the maximum relative deviation of the HVL is 2.8%. The corresponding X-ray energy spectra are simulated by EGSnrc Monte Carlo simulation program, and the average energy are obtained. The results are consistent with the standard and the maximum relative deviation of average energy is less than 0.4% with IEC. The result can meet the requirements of lead equivalent measurement for X-ray protection materials.
2022 Vol. 43 (7): 960-964 [Abstract] ( 196 ) HTML (1 KB)  PDF (1233 KB)  ( 429 )
965 Evaluation of Measurement Uncertainty in the Determination of Pesticides Residues in Vegetables by Gas Chromatography
ZHANG Li-fang,ZHANG Liang,DU Rui-huan,ZHENG Bai-qin,LIU Yang
DOI: 10.3969/j.issn.1000-1158.2022.07.20
According to NY/T 761—2008, the uncertainty of HCH, pythium, bifenthrin, beta cypermethrin, permethrin and cypermethrin in vegetables were evaluated by gas chromatography. The uncertainty of the detection method was evaluated from seven aspects: standard purity, standard solution, sample weighing, pretreatment process, standard solution peak, sample solution peak and recovery. The results showed that: at the spiking level of 0.08mg/kg, the relative combined standard uncertainty of α-HCH, β-HCH, γ-HCH, δ-HCH, Pythium, bifenthrin, beta Cypermethrin, permethrin and cypermethrin were 2.63%, 3.01%, 2.45%, 2.69%, 2.33%, 1.83%, 2.41%, 3.34% and 2.84%, respectively. The main factors of uncertainty were recovery, sample solution peak and standard solution peak. Standard solution and pretreatment process can not be ignored especially for the target with less measurement uncertainty.
2022 Vol. 43 (7): 965-972 [Abstract] ( 169 ) HTML (1 KB)  PDF (651 KB)  ( 300 )
News
Download
Links
Copyright © Editorial Board of Acta Metrologica Sinica
Supported by:Beijing Magtech