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2021 Vol. 42, No. 2 Published: 2021-02-28

	129	Development of Vacuum Standard Blackbody Radiation Source in Middle Temperature Zone
		YANG Yan-long,HAO Xiao-peng,SONG Jian,LIU Yang,HU You-hua,XIE Chen-yu,LIU Yan,XIE Lin-lin
		DOI: 10.3969/j.issn.1000-1158.2021.02.01
		The structure design, working principle, test results and uncertainty evaluation of the medium temperature vacuum standard blackbody radiation source developed by National Institution of Metrology in China are introduced. The black body radiation source has a working temperature range of 320～500K, the black body cavity aperture diameter is 50mm, the cavity depth is 260mm, the surface is sprayed with high temperature paint, and the cavity emissivity is better than 0.999. The blackbodys axial temperature uniformity, temperature stability and blackbody radiation source brightness temperature were tested in vacuum, and the blackbody temperature uniformity is better than 0.15K, and the temperature stability within 40min is better than 0.03K. The uncertainty sources of black body radiation source are analyzed, and the combined standard uncertainty of the black body radiation source is better than 0.04K.
		2021 Vol. 42 (2): 129-136 [Abstract] ( 344 ) HTML (1 KB) PDF (3733 KB) ( 329 )

	137	Study on active dual-wavelength infrared laser thermometry calibration experiments
		QU Yan,HUAN Ke-wei,AN Bao-lin,DONG Wei,ZHAO Yun-long,SONG Xu-yao,YUAN Zun-dong
		DOI: 10.3969/j.issn.1000-1158.2021.02.02
		Based on active dual-wavelength infrared laser thermometry method, it is possible to measure the true surface temperature when the emissivity is unknown. A high-precision calibration source is an important basis for the accuracy of dual-wavelength infrared thermometry system. However, there is a lack of public reports on such calibration sources in the current research work in the field of dual-wavelength temperature measurement. Therefore, an active infrared laser temperature measuring source is designed and built to study the stability and uniformity of the calibration source, and the dual-wavelength laser thermometry system is calibrated. The results show that the active dual-wavelength infrared laser temperature calibration source has good stability, and the maximum temperature deviation within 20 minutes at 1173K is 0.22K; the surface temperature uniformity is well, and the standard deviation of the surface temperature at 1173K is 0.34K. When the true temperature of the source surface is above 923K, the relative standard deviation of the collected signal is less than 0.7%. The calibration experiment results show that the calibration source has good reliability for the accurate calibration of the active dual-wavelength infrared laser temperature measurement system.
		2021 Vol. 42 (2): 137-143 [Abstract] ( 381 ) HTML (1 KB) PDF (2555 KB) ( 1009 )

	144	Measurement of Micro Transverse Spacing Using Single Frequency-stabilized Laser
		LIU Yu-zhang,GAO Hong-tang,CHENG Yin-bao,WANG Zhong-yu
		DOI: 10.3969/j.issn.1000-1158.2021.02.03
		An interference system for the use of measuring micro transverse spacing is described. A highly frequency-stabilized laser of the wavelength of 532nm and a 633nm wavelength laser of relatively low level of wavelength uncertainty are brought into the system as optical sources. The charge coupled device(CCD) sensor is used in the system to get the interference graph. Some image processing methods are introduced to digitally enhance the interference image and calculate the fractional part of the interference fringe. The transverse distance is calculated by the method of exact fractions. By introducing some software technology to enhance the interference graph, a relatively high accuracy micro transverse spacing measurement can be realized with simple experimental condition.
		2021 Vol. 42 (2): 144-149 [Abstract] ( 321 ) HTML (1 KB) PDF (818 KB) ( 403 )

	150	Measurement Method of Screen Printing Template Size Based on Machine Vision
		LIU Bin,DONG Zheng-tian,HU Chun-hai,LI Pei-hang,GAO Ming-kun
		DOI: 10.3969/j.issn.1000-1158.2021.02.04
		Many types and styles of screen printing samples are used in screen printing plate and there are also many targets to be tested on each sample plate, which make the gradient threshold parameter to locate the edge to perform measurement unsuitable. In addition, the method of using the positioning rectangular frame to establish the measurement coordinate system in the traditional visual inspection can cause measurement error. A method for measuring the size of a screen printing template based on machine vision was proposed. A coarse-to-fine measurement strategy was adopted to analyze the information of each type of target to be measured, and the threshold parameters were set in a targeted manner to improve the measurement accuracy. During the measurement process, a hierarchical matching algorithm based on image pyramid and normalized cross-correlation function was used to achieve rough positioning of multiple targets to be measured, and then the threshold parameters obtained by template information statistics were used to perform fine edge positioning to establish local coordinates to complete the measurement. The experimental results showed that the proposed method can effectively improve the measurement accuracy under the same experimental conditions. The average relative error of the improved algorithm is reduced from 4.02% to 1.47%, and the measurement parameters need not be adjusted by users. It is suitable for flexible measurement of different types of screen printing templates.
		2021 Vol. 42 (2): 150-156 [Abstract] ( 314 ) HTML (1 KB) PDF (4335 KB) ( 500 )

	157	Multi-target Tracking Algorithm Based on YOLOv3 Detection and Feature Point Matching
		TAN Fang,MU Ping-an,MA Zhong-xue
		DOI: 10.3969/j.issn.1000-1158.2021.02.05
		For multiple target tracking algorithm in the traditional pedestrian detection speed is slow, vulnerable to illumination change, the fast moving of pedestrians and the influence of partial occlusion cause the poor performance of pedestrian target tracking. According to the classic Tracking-by-Detection mode, a new pedestrian tracking algorithm is proposed, which uses deep learning YOLOv3 algorithm to detect pedestrian targets, and then uses fast corner detection algorithm and brisk feature point description algorithm to match the feature points of pedestrian targets between adjacent frames to achieve multi-target pedestrian tracking.The experimental results show that the pedestrian target achieves good continuous tracking effect under various complex environments of backlight, fast movement and partial occlusion, with an average accuracy of 87.7% and a speed of 35 frames per second.
		2021 Vol. 42 (2): 157-162 [Abstract] ( 296 ) HTML (1 KB) PDF (2349 KB) ( 1375 )

	163	Research on Detection of Concrete Surface Cracks by Image Processing Based on Smartphone APP
		NI Tong-yuan,ZHOU Ruo-xu,YANG yang,YANG Xue-cheng,ZHANG Wu-yi,LIN Chu-xuan
		DOI: 10.3969/j.issn.1000-1158.2021.02.06
		A nondestructive detection method for the concrete surface crack based on Android APP is proposed, to collect crack area image by using smartphone camera module, and to extract target crack through image processing algorithms such as graying, filtering and denoising, flood filling, etc. The crack length, width and area characteristic value are measured in order to realize the crack nondestructive testing. It is based on the geometric relationship between crack pixel coordinates and the number of pixel points contained in the crack, and combines the unit pixel size of phones camera. The newly developed APP of crack detection technology can measure the width of any point, total crack length, crack area and maximum crack width. The experimental results show that it can effectively improve the accuracy of APP to measure and detect of concrete surface cracks by using smart phone optical zoom to enlarge the target cracks. The accuracy error of APP measurement is less than 5% compared with the crack width meter, and it meets the engineering application requirements.
		2021 Vol. 42 (2): 163-170 [Abstract] ( 343 ) HTML (1 KB) PDF (3338 KB) ( 413 )

	171	Single Fish Tracking under Occlusion and Light Change
		CHENG Shu-hong,WANG Ying
		DOI: 10.3969/j.issn.1000-1158.2021.02.07
		Fish tracking is the basis of fish behavior analysis, when tracking fish in water, the target fish will be difficult to track because of the change of posture and the influence of the occlusion or light of the surrounding fish or object. In order to solve the above problem, a method of tracking fish body by combining Mobilenet-SSD(SSD, single shot multibox detector) with Dlib association tracker was proposed. The fish body in video is accurately detected by SSD algorithm, and then the information is input into Dlib association tracker, which makes the tracking object location more accurate and improves the robustness of fish body tracking when the movement of fish in water occured and the light changes. The experimental results show that the performance of the mentioned method in fish tracking video is obviously better than that of other algorithms, the tracking success rate in different environments is more than 90%.
		2021 Vol. 42 (2): 171-177 [Abstract] ( 318 ) HTML (1 KB) PDF (4493 KB) ( 326 )

	178	A Classroom Population Statistics Algorithm Based on Human Contour Features
		YANG Lu
		DOI: 10.3969/j.issn.1000-1158.2021.02.08
		According to the application scenarios of automatic counting of classrooms, the image processing algorithms based on human contour features and motion detection are studied. The differences in classroom video images, threshold processing, edge extraction, morphological operations, sensitive area identification, human contour feature extraction, etc. The processing steps are used to achieve the result of counting the people number of classroom. At the same time, the layout calculation method of the camera is given in combination with the layout of different classrooms, so as to obtain more effective algorithm effects.The experimental results show that the accuracy of the algorithm is 95.4% in a classroom of 40 people by reasonably arranging the camera positions, which can effectively assist the resource allocation of self-study room.
		2021 Vol. 42 (2): 178-183 [Abstract] ( 310 ) HTML (1 KB) PDF (1518 KB) ( 441 )

	184	Deposition and Characterization of Thin Films for Superconducting Transition Edge Sensor
		LIU Xian-wen,XU Xiao-long,LI Jin-jin,WANG Xue-shen,ZHONG Qing,CAO Wen-hui,BAI Jian-nan,ZHANG Shuo,LIU Xiang-liang,SI Kun-yu,ZHOU Zhe-hai,GAN Hai-yong
		DOI: 10.3969/j.issn.1000-1158.2021.02.09
		Superconductivity transition edge sensors (TES) are single photon detectors which required for quantization of light intensity units, candela.The study of the physical properties of metal superconducting thin films is the basis of TES research. High purity Al and Ti superconducting nano films were prepared by magnetron sputtering with different power supplies. The growth rate of the films was analyzed as a function of pressure and power. The surface stress and electric properties of the films were measured by using surface stress meter and electrical measuring instrument.Finally, the films were tested inside a commercial dilution refrigerator to obtain its superconducting properties, especially the superconducting transition temperature Tc and the transition width ΔT which play an important role in TES energy resolution and time constant.The experimental results will lay the foundation for the fabrication of TES devices.
		2021 Vol. 42 (2): 184-188 [Abstract] ( 355 ) HTML (1 KB) PDF (860 KB) ( 643 )

	189	Research on Analog Drive of Coriolis Mass Flowmeter Based on Characteristic Graph Analysis
		HUANG Ya,XU Ke-jun,LIU Chen-ci,LIU Wen,YUE Jing,XU Hao-ran,ZHANG Lun
		DOI: 10.3969/j.issn.1000-1158.2021.02.10
		Aiming at the problems of easy-to-stop vibration and slow start-up of analog drive flow tube, the characteristic simulation method is used to analyze the drive characteristics of classical analog drive, and two typical analog drive improvement methods are studied. An improved differential drive is proposed. Four kinds of analog drive implementation circuits are developed, and gas-liquid two-phase flow drive experiments and vibration experiments are carried out. The experimental results show that the differential drive significantly increases the driving energy; the driving signal of the new analog driving is more stable and the start-up is faster; Compared with the classical analog drive, the amplitude of drive signal and sensor signal of the improved differential drive are increased by 4.2 times and 3.8 times, the standard deviation of the drive signal amplitude is only 0.08, and the start-up time is reduced to 2.3s.
		2021 Vol. 42 (2): 189-198 [Abstract] ( 267 ) HTML (1 KB) PDF (1848 KB) ( 174 )

	199	High Precision Deep Sea Pressure Simulation Method with Double Pistons
		WANG Huai-yang,HU Shan-shan,LIU Zheng-shi,WANG Yong
		DOI: 10.3969/j.issn.1000-1158.2021.02.11
		In order to develop a high-precision deep-sea pressure environment simulation test platform, a dual-piston high-precision water depth simulation method is proposed based on the compressibility of liquid. Firstly, the working principle of the method and the composition of the pressure simulation system are introduced; secondly, the influence of the main and auxiliary pressure systems on the measurement range and adjustment accuracy of the system is analyzed, and the physical model of the pressure system is further established and simulated. The results show that the system has good pressure following performance. Finally, a prototype experimental platform is built to carry out step-up and “diving-keeping-rising” pressure. Force experiments show that the system can achieve static accuracy of 0.02bar and dynamic accuracy of 0.1bar, which verifies the feasibility and validity of the measurement method.
		2021 Vol. 42 (2): 199-203 [Abstract] ( 304 ) HTML (1 KB) PDF (1589 KB) ( 198 )

	204	Design and Methodology Research of a Sensor Based on Reflection Probe for Focused Ultrasonic Measurement
		XU Ao-xuan,CAO Yong-gang,ZHENG Hui-feng,WANG Yue-bing
		DOI: 10.3969/j.issn.1000-1158.2021.02.12
		Based on the tungsten steel probe and PVDF piezoelectric film material, a new sensor was designed and developed for focused ultrasound measurement. At the same time, the physical model of the sensor was established through theoretical analysis and finite element analysis, and the internal acoustic field and reflection phenomenon of the sensor were simulated to obtain the waveform of the output from the sensor and its amplitude. Finally, the sensor developed was used to detect the acoustic pressure and acoustic intensity in the focal area of the focusing transducer, and the results were compared with the results based on theoretical simulation. Within the acoustical power range of 10W, the feasibility and reliability of the new sensor as well as its measurement theory and method were proved for focused ultrasound measurement. The new reflection probe sensor will provide a new method for the measurement of high intensity focused ultrasonic field.
		2021 Vol. 42 (2): 204-212 [Abstract] ( 282 ) HTML (1 KB) PDF (3869 KB) ( 302 )

	213	Development and Characteristic Analysis of 100kA Fast Response Precision Impulse Shunt
		LONG Zhao-zhi,LI Wen-ting,FAN Jia-wei,XIE Shi-jun,LIU Shao-bo,YU Ye-feng
		DOI: 10.3969/j.issn.1000-1158.2021.02.13
		The impulse current is a transient current waveform, which has a short duration and can not be repeated, so it is difficult to evaluate the influencing factors of measurement errors. A fast response precise impulse shunt is developed. The measuring principle and size design of the shunt are analyzed. The transient response process of the shunt is studied. The output signal is welded to the outside of the resistor to eliminate the skin effect. The steady resistance of the shunt is 0.9697mΩ_and the stray inductance is 32nH. When the rated current is measured, the temperature rise of the resistance is less than 36℃. A step current generator is developed to measure the dynamic characteristics of the shunt. The step response time of shunt is less than 4ns. The convolution integral method is used to calculate the peak value and time parameter measurement error caused by the dynamic characteristics. The linearity, stability of the shunt are tested under 8/20μs. The uncertainty is evaluated by shunt and digital recorder separately. After analyzing the uncertainty components, the measurement uncertainty of the whole system is calculated to be 0.41% (k=2). It shows that the measuring device can be used as a standard measuring device for the calibration of current sensors.
		2021 Vol. 42 (2): 213-220 [Abstract] ( 295 ) HTML (1 KB) PDF (2315 KB) ( 320 )

	221	Parameter Identification of Photovoltaic Cell Engineering Model Based on IHHO Algorithm
		WU Zhong-qiang,LIU Chong-yang
		DOI: 10.3969/j.issn.1000-1158.2021.02.14
		Aiming at the problem that the adjustment of HHO algorithm is not flexible enough in the search process, periodic search cant be carried out pertinently, and sometimes the algorithm falls into the local optimal leading to relatively poor search accuracy, a parameter identification method based on improved harris hawks optimization (IHHO) algorithm is proposed. Two improvements are made to HHO algorithm. The flexible decline strategy is introduced to expand the global search scope at the beginning of the iteration and to extend the local search time at the end of the iteration, which strengthens the global search ability at the initial stage and the local search ability at the later stage. The introduction of golden sine method not only increases the diversity of the population, reduces the possibility of the algorithm falling into local optimization, but also reduces the search space and improves the efficiency of optimization. When applied to the parameter identification of photovoltaic cell engineering model, IHHO algorithm is more accurate than other algorithms, and the identification results are more consistent with the measured data, which shows that IHHO algorithm can accurately identify the parameters of photovoltaic cell engineering model in different environments.
		2021 Vol. 42 (2): 221-227 [Abstract] ( 315 ) HTML (1 KB) PDF (1518 KB) ( 523 )

	228	Detection of Irreversible Flux Loss of Sintered Nd-Fe-B Magnets
		CAO Yu-jie,WU Yu-cheng,LIU You-hao,XU Guang-qing,ZHANG Peng-jie,LIU Jia-qin,CHEN Jing-wu,YI Xiao-fei
		DOI: 10.3969/j.issn.1000-1158.2021.02.15
		The irreversible flux loss is an important performance index of sintered Nd-Fe-B magnets for permanent magnet motor. The accuracy of its measurement results directly affects the design of motor and the selection of magnetic performance. The irreversible flux loss of magnets under different test conditions is studied. The results show that the irreversible flux loss is mainly affected by tray properties (material / specification), magnet spacing and baking temperature. In order to obtain accurate measurement results of irreversible flux loss, these factors should be effectively controlled in the measurement process.
		2021 Vol. 42 (2): 228-231 [Abstract] ( 299 ) HTML (1 KB) PDF (965 KB) ( 606 )

	232	Research on Monitoring Method of AeroengineLubricating Oil Based on CNN-MSLSTM
		MA Min,WANG Tao
		DOI: 10.3969/j.issn.1000-1158.2021.02.16
		Aiming at the defect of traditional data feature extraction method that is difficult to extract the effective features of ECT oil monitoring data,a two-channel network model CNN-MSLSTM based on convolutional neural network (CNN) and multi-scale long-short-term memory (MSLSTM) neural network was proposed. The multi-scale learning was integrated into LSTM. CNN and MSLSTM were used as two channels to learn the characteristics of data in spatial dimension and time dimension. Through the attention mechanism fusion, the wear state of the engine was output by using softmax classifier. The experimental results showed that the classification accuracy of the 3 scale CNN-MSLSTM for ECT data samples is 98%, the F1 score is 98.62%, and the measurement time of single data is only 0.2036ms. The overall performance is better than the single CNN and LSTM networks.
		2021 Vol. 42 (2): 232-238 [Abstract] ( 304 ) HTML (1 KB) PDF (2286 KB) ( 330 )

	239	One Method of the Extraction of the Error Signal Based on the Onboard Hydrogen Maser
		ZHAO Guang-dong,CHEN Peng-fei,LIU Jie,HUANG Yi,LI Si-heng
		DOI: 10.3969/j.issn.1000-1158.2021.02.17
		In view of the high precision positioning requirements of the new generation of satellite navigation system of china, the onboard hydrogen maser has been widely used in the system as a frequency reference because of its excellent long-term stability, drift rate and temperature characteristics. The passive onboard hydrogen maser with dual-frequency scheme consists of physical part and circuit part. The microwave excitation signal excites the microwave cavity of the physical part and generates the error signal of cavity frequency and the error signal of high stability crystal oscillator. For how to extract and process these two kinds of error signal, one separation scheme of amplitude modulation signal by the same time sequence synchronization of error signal and detection signal is proppsed. At the same time, the crystal oscillator error signals are sampled and maintained to realize the downloading of the telemetry parameters of hydrogen maser's locking.
		2021 Vol. 42 (2): 239-244 [Abstract] ( 257 ) HTML (1 KB) PDF (2071 KB) ( 273 )

	245	MC Simulation of the Effect of High Purity Germanium Detector Collimator on X-ray Energy Spectrum Measurement
		WEN Yu-qin,ZHAO Rui,WU Jin-jie,LAI Wan-chang,WANG Er-yan
		DOI: 10.3969/j.issn.1000-1158.2021.02.18
		To study the influence of different beam-limiting aperture collimators on the measurement results, MCNP5 simulation software was used to establish a high-purity germanium detector model with a collimator, and various parameters of the collimator were used to simulate and analyze the impact of the collimator on the high-purity germanium detector. Measuring the influence of the X-ray energy spectrum to establish the optimal size of the collimator, and provide a certain reference basis for the laboratory to use the high purity germanium detector to measure the X-ray energy spectrum. The transmission equivalent aperture (TEA) collimator index was calculated, the detection efficiency of X-ray measured by HPGe detector was analyzed. The results showed that the collimator with small aperture and thick shield should be selected for the low-energy X-ray energy spectrum measurement with energy less than 80keV, and the collimator with larger aperture should be selected for the medium and high-energy X-ray with energy more than 80keV, so as to avoid the influence of the quality of X-ray energy spectrum due to the generation of small angular scattered rays and lead characteristic lines from the lead collimator.
		2021 Vol. 42 (2): 245-249 [Abstract] ( 282 ) HTML (1 KB) PDF (2080 KB) ( 524 )

	250	Rapid and Quantitative Detection of Viable Staphylococcus aureus in Milk Powder Based on Flow Cytometry Technology
		WANG Bin,SUI Zhi-wei,LIU Si-yuan,WANG Jing,FU Bo-qiang,WANG Yi
		DOI: 10.3969/j.issn.1000-1158.2021.02.19
		A flow cytometry (FCM)-based method for rapid and quantitative detection of viable Staphylococcus aureus in milk powder was developed. Staphylococcus aureus was labelled with Fluorescein isothiocyanate (FITC) by reacting with the anti-Staphylococcus aureus polyclonal antibody (FITC), then dead and viable bacteria were distinguished by membrane-impermeable dyes Propidium Iodid (PI). The FCM-based method was established and applied to the quantitative detection for Staphylococcus aureus in milk powder samples. The results showed that the FCM-based method exhibited high specificity towards Staphylococcus aureus. When the concentration of Staphylococcus aureus in artificially contaminated milk powder samples ranged from 2.72×10³~2.80×10⁸CFU/mL, the FCM-based method and plate-based method yielded the same result, and the detection limit of the method is 2.72×10³CFU/mL, and total time is 35min. The method is rapid and efficient, so it has a great application prospect in rapid screening and monitoring of foodborne pathogens.
		2021 Vol. 42 (2): 250-258 [Abstract] ( 275 ) HTML (1 KB) PDF (1982 KB) ( 493 )

	259	Development of Reference Material of SARS-CoV-2 Genomic RNA
		WANG Di,WANG Zhi-dong,WU Xiao,NIU Chun-yan,DONG Lian-hua,DAI Xin-hua,GAO Yun-hua
		DOI: 10.3969/j.issn.1000-1158.2021.02.20
		High and low concentrations of reference material of SARS-CoV-2 genomic RNA were developed(GBW(E)091098 and GBW(E)091099)based on the inactivated RNA extraction of the novel coronavirus from infected patients as the potential material,of which the concentrations of E,ORF1ab and N gene were qualified by digital PCR. The reference values with expanded uncertainty of high concentration of reference material were(1.06±0.11)×10³copy/μL,(8.96±0.61)×10²copy/μL and(1.73±0.1)×10³copy/μL,respectively. And those for the low concentration of reference material were(1.29±0.26)×10²copy/μL,(9.5±1.8)×10¹copy/μL and(2.05±0.31)×10²copy/μL,respectively. The reference material here developed had been widely applied to method establishment of nucleic acid detection for SARS-CoV-2,quality control for detection kits and testing laboratory.
		2021 Vol. 42 (2): 259-264 [Abstract] ( 329 ) HTML (1 KB) PDF (462 KB) ( 605 )

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