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2023 Vol. 44, No. 7
Published: 2023-07-28
 
1009 Research on Influence of Key Layout Parameters on Measurement Accuracy in Multilateration System
LIANG Chu-yan,MIAO Dong-jing,LI Jian-shuang,KONG Ming,LI Lian-fu,WANG De-li,LIU Yang
DOI: 10.3969/j.issn.1000-1158.2023.07.01
To study the influence of stations mutual position relationship on the measurement accuracy of multilateration system, an error transfer model was derived from the coordinate solution formula.The formula related to the error amplification factor and the station layout parameters in the model are studied and analyzed.From this formula, it can be concluded that increasing two key layout parameters within a certain range can improve the measurement accuracy of the system, which has been verified through simulation and experiments. The experimental results showed that the repeatability error of the system can be reduced from 20μm to 10μm when the key layout parameters were increased from 1m to 3m, and the optimization effect was obvious. Meanwhile, the systems with similar layout parameters had been compared, whose stations were at different locations. The results showed that the different locations of stations in system rarely affected the system precision while systems layout parameters were almost consistent, and suggested that method proposed can improve the measurement accuracy and had flexibility.
2023 Vol. 44 (7): 1009-1018 [Abstract] ( 151 ) HTML (1 KB)  PDF (87140 KB)  ( 73 )
1019 Evaluation of Spatial Straightness Error Based on Differential Bee Colony Algorithm
DONG Zi-yan,XU Xu-song,LI Meng-yuan,TANG Li-yuan
DOI: 10.3969/j.issn.1000-1158.2023.07.02
A differential bee colony algorithm was proposed to evaluate spatial straightness error. Firstly, based on the geometrical product specification and verification(GPS)tolerance standard, the mathematical model of spatial straightness error evaluation conforming to the minimum region is obtained by least square fitting calculation. Secondly, the scaling factor of the differential evolution algorithm was improved, and the improved differential evolution algorithm and artificial bee colony algorithm were mixed and iteratively optimized, through the test function simulation, the differential bee colony algorithm had certain advantages in calculation accuracy and convergence speed. Finally, two evaluation cases are studied and compared. the results show that compared with particle swarm optimization algorithm, hybrid teaching and learning algorithm, least square algorithm and fish swarm hybrid optimization algorithm, the calculation accuracy of spatial straightness evaluation is improved by 83.9%, 54.5% and 54.6%, respectively. compared with differential evolution algorithm and artificial bee colony algorithm, the convergence speed is improved obviously.
2023 Vol. 44 (7): 1019-1026 [Abstract] ( 132 ) HTML (1 KB)  PDF (85599 KB)  ( 44 )
1027 Measurement Method of Large Ring Forgings Based on Point Cloud Simplification
ZHANG Yu-cun,WANG Zhi-yu,FU Xian-bin
DOI: 10.3969/j.issn.1000-1158.2023.07.03
Aiming at the problems of large amount of point cloud data and low quality of point cloud grid in the measurement of large ring forgings, a simplified point cloud measurement algorithm was proposed. Firstly, the target Gaussian curvature of the interior points and boundaries of each vertex on the forging mesh was set to zero.Then, according to the set target curvature, the Ricci flow equation was used to optimize the Ricci flow discrete entropy energy, and the planar target metric was calculated to obtain the parameterized coordinates of each point on the mesh.Finally, the vertex dimension was extended based on the obtained parametric coordinates, and a vertex constraint factor weighted cost function was introduced for mesh simplification measurements.The experimental results showed that the proposed algorithm could handle point cloud models with complex structures, and the simplified point cloud model boundary geometric features were well maintained, which could meet the measurement dimensional accuracy requirements of industrial digital manufacturing.
2023 Vol. 44 (7): 1027-1032 [Abstract] ( 170 ) HTML (1 KB)  PDF (28796 KB)  ( 107 )
1033 The Evaluation of Roundness by Improved Zone Searching Algorithm
KONG Yu-qiang,WANG Shi-qiang,ZHU Yong-gang
DOI: 10.3969/j.issn.1000-1158.2023.07.04
Addressing the issue of numerous ineffective search points in traditional zone search algorithms for roundness error evaluation, an improved zone search (IZS) algorithm is proposed, which incorporates the characteristics of Archimedean spirals to enhance the search area, streamline the number of search points, and boost computational efficiency. Mathematical models for roundness error evaluation based on the minimum zone circle (MZC), maximum inscribed circle (MCC), and minimum circumscribed circle (MIC) are presented, along with a comprehensive description of the algorithm's implementation process.Lastly through experimental comparisons with genetic algorithm (GA), simplex algorithm (SA), and particle swarm optimization (PSO), it has been revealed that IZS algorithm demonstrates superior computational speed and enhanced accuracy. And in comparison to traditional search algorithms (RZS, PZS), the IZS algorithm requires searching only 78points to achieve the same level of accuracy, which is 1.2826μm. Applied in practice, it will improve the detection efficiency of roundness errors in rotary components.
2023 Vol. 44 (7): 1033-1039 [Abstract] ( 115 ) HTML (1 KB)  PDF (95754 KB)  ( 54 )
1040 Determination of the Reflection Loss in the Measurement of UV Output of UV-LED by KI/KIO3 Chemical Actinometer
ZHANG Lian-feng,ZHOU Yu,CHANG Bao-yan,XION Dong,YAN Jian-chang,SHENG Cong-min,WANG Chun-yong
DOI: 10.3969/j.issn.1000-1158.2023.07.05
When measuring the UV output with KI/KIO3, due to the reflection of the liquid surface, part of the photons of the incident light do not enter the liquid, resulting in measurement errors. According to the Fresnel equation, the amount of reflection is closely related to the angle of incidence, and the radiation angle of each beam of light emitted by the UV LED and the angle of incidence into the solution are different.To quantify total reflection amount caused by such complicated emission angles and incident angles, the vortex of the solution of chemical actinometer was photographed, and the mathematical analysis was carried out to establish the method for accurately calculating the reflection loss. The calculated reflection coefficient can compensate the reflection loss to get accurate measurement results. The calculation also can reversely guide the measurement process to control the operating condition to keep smaller reflection. Based on photographed vortexes formed by rotating the liquid, the reflection coefficient can be controlled stably at about 0.025. The stableness of the reflection coefficient indicates that the error due to reflections can be avoided.
2023 Vol. 44 (7): 1040-1045 [Abstract] ( 112 ) HTML (1 KB)  PDF (102205 KB)  ( 44 )
1046 Research on Diopter Measurement Based on Extended Broadband optical Double Grating Interference
LI Tian-hao,HE Yong,HAN Zhi-gang,Xü Hai-fei
DOI: 10.3969/j.issn.1000-1158.2023.07.06
A diopter measurement based on the double grating system with extended broadband light is proposed. Based on Talbot effection and Moire effection, the intensity distribution formula of interference under extended monochromatic light and extended polychromatic light is derived. As it shows that if the distance from the light to the first grating and the distance from the second grating to the screen is equal, the intensity distribution of the interference won’t be related to the wavelength of the light. Besides the influence of double grating system parameters on the contrast of Moire fringe under extended light is analyzed. The results show that when the width of light is 4mm, the grating period is 0.2mm, the angle between two gratings is 1.9°, and the space distance between two gratings is 6.5mm, the clear interference fringe can be obtained. A diopter measurement system is constructed to measure the lens with diopter of -1m-1, -3m-1, 1m-1 and 3m-1. The peak-to-valley deviation of measurements is 0.0064m-1, which is the 0.28% of the average measurement results. The experiment result shows that the lens diopter can be measured with double grating system using extended broadband light source accurately and cheaply.
2023 Vol. 44 (7): 1046-1051 [Abstract] ( 116 ) HTML (1 KB)  PDF (49882 KB)  ( 39 )
1052 A Miniaturized Silicon Microcavity Based Photonic Temperature Measurement System
MEI Ming-cheng,HAN Qi-na,SHI Yang,ZHOU Kun-li,ZENG Jiu-sun,WANG Jin,ZHANG Cheng,GAO Jian-xin,QU Zhi-er,PAN Yi-jie,QU Ji-feng
DOI: 10.3969/j.issn.1000-1158.2023.07.07
The photonic temperature sensing based on silicon microcavity with whispering gallery mode can be applied in extreme environments such as strong electromagnetic field, high irradiation and strong vibration. On the basis of silicon microcavity photonic temperature sensor with mK resolution which is pre-designed, fabricated and validated, a miniaturized microcavity photonic temperature measurement hardware system was developed, which includes modules of signal generation, high-speed digital-to-analog conversion, voltage-to-current conversion, laser diode temperature control, weak signal acquisition and amplification were designed and implemented, as well as the algorithm of synchronous measurement and spectral temperature measurement based on single chip microcomputer. The system performance was verified in a high stable constant temperature bath, the extended uncertainty of the actual temperature measurement results is 115mK (k=2), and the temperature range is 30K.
2023 Vol. 44 (7): 1052-1058 [Abstract] ( 212 ) HTML (1 KB)  PDF (65919 KB)  ( 78 )
1059 The Research on Method for Evaluating the Switching Error in Electrical Thermal Resistance Test
LI Hao,LIU Yan,ZHAI Yu-wei,DING Chen,DING Li-qiang,WU Ai-hua
DOI: 10.3969/j.issn.1000-1158.2023.07.08
During the semiconductor device electrical method thermal resistance testing process, the error caused by current switching is an important factor affecting the accuracy of measurement, which could not be evaluated effectively now.On the basis of error principle analysis, a double-chip circuit was designed to avoid current switching, and a junction temperature reference value without switching error was obtained, achieving effective evaluation of instrument testing results. The results show that this method can quantitatively evaluate the switching process error of thermal resistance testers, and has good practical significance in measuring thermal resistance testers.
2023 Vol. 44 (7): 1059-1063 [Abstract] ( 93 ) HTML (1 KB)  PDF (16914 KB)  ( 41 )
1064 Feasibility Study on the Application of Organic Matter to the Temperature Fixed Point in Marine Warm Zone
GAO Chuan-ji,LING Zhong-qian,LI Ting,SUN Jian-ping,WANG Guang-yao,CHEN Ze-chuan,LI Jia-hao
DOI: 10.3969/j.issn.1000-1158.2023.07.09
The development of a new temperature fixed point suitable for the ocean temperature zone -5～35℃ has become an important means to improve the level of ocean temperature measurement. Aiming at the lower temperature range of ocean temperature zone which gallium base alloy cannot cover, the feasibility of using high purity tridecane and tetradecane as fixed points was explored. The phase transition characteristics were studied by adjusting different preheating and melting temperatures. The results show that the melting temperature plateau of tridecane can last for more than 35h, and the recurrence level of the temperature plateau is better than 1mK. The melting temperature plateau of tetradecane can last for more than 45h, and the recurrence of the temperature plateau is better than 1mK. Both of them have the possibility of becoming the fixed point of temperature. The research results provide supplementary experimental data support for the fixed point of ocean warm zone.
2023 Vol. 44 (7): 1064-1069 [Abstract] ( 135 ) HTML (1 KB)  PDF (85899 KB)  ( 49 )
1070 Design and Experimental Study of Optical Fiber Fabry-Perot Differential Pressure Flow Sensor
ZHANG Bo,YANG Shui-wang,LI Chun-hui,SONG Zhi-qiang,SU Yi-ming
DOI: 10.3969/j.issn.1000-1158.2023.07.10
Based on the principle of fluid flow throttling, a high-precision optical fiber flow sensor was developed, with orifice plate as throttling device and two optical fiber Fabry-Perot pressure sensors as differential pressure signal measuring devices. The flow rate is measured by pressure differential across pressure transducers across the orifice plate In the mass flow measurement range of 0~100g/s, the linear equation of the flow rate and the square root of the pressure difference was obtained, and the linear fitting accuracy reached 0.99995. The developed optical fiber flow sensor has the advantages of high temperature resistance, electromagnetic interference resistance, compact size, passive sensor end and high measurement accuracy.
2023 Vol. 44 (7): 1070-1074 [Abstract] ( 112 ) HTML (1 KB)  PDF (58359 KB)  ( 52 )
1075 Image Reconstruction for Electrical Capacitance Tomography Based on Convolutional Sparse Coding
ZHANG Li-feng,LU Dong-chen
DOI: 10.3969/j.issn.1000-1158.2023.07.11
Aiming at the ill-conditioned inverse problem of electrical capacitance tomography (ECT), a method of introducing convolution sparse coding model into ECT least squares problem as penalty is proposed. The model is solved by pre-trained filter and alternating direction method of multipliersr algorithm (ADMM), and the ECT image reconstruction is completed. The proposed method is simulated and tested experimentally, and compared with LBP, Tikhonov regularization and Landweber iterative algorithm. The results show that the average relative error and correlation coefficient of the reconstructed image obtained by the proposed method are 0.4389 and 0.8968, respectively, which are superior to the other three methods, and the reconstruction quality of central object and multi-object distribution is significantly improved.
2023 Vol. 44 (7): 1075-1079 [Abstract] ( 121 ) HTML (1 KB)  PDF (42630 KB)  ( 38 )
1080 Research on Calibration Technology of Reciprocal Piezoelectric Accelerometer
Lü Si-yao,CAI Chen-guang,KONG Ming,YANG Ming,LIU Zhi-hua,Lü Qi
DOI: 10.3969/j.issn.1000-1158.2023.07.12
A calibration method for piezoelectric accelerometers with internal driving components was introduced. Based on the calibration principle of the reciprocal method, the reciprocal piezoelectric accelerometer can be calibrated by measuring the ratio and product of the two port sensitivities through two experiments. By establishing the vibration equation and mechanical model of the reciprocal piezoelectric accelerometer, the frequency response characteristics of the sensitivity ratio, sensitivity product and self-calibration coefficient are analyzed, and the corresponding measurement methods are explained. The comparison validation experiment between this method and the laser interferometry was carried out, the experimental results show that in the frequency range of 5~4000Hz, the average relative deviation of the sensitivity of the two ports does not exceed 1% and 2%, respectively, and the maximum relative deviation does not exceed 2% and 4%, respectively.
2023 Vol. 44 (7): 1080-1086 [Abstract] ( 107 ) HTML (1 KB)  PDF (70222 KB)  ( 60 )
1087 Calculation Method of Moving Point Coordinates of Tower Multi Lifting Point Constrained Rope System Based on Multi-Scale Retinex Algorithm
WU Jian,LI Yang,HAN Yi-cheng,HUANG Peng
DOI: 10.3969/j.issn.1000-1158.2023.07.13
In order to realize the whole process intelligent management of power transmission and transformation engineering, and ensure the safety of tower hoisting and the use effect after hoisting, a moving point coordinate calculation method based on multi-scale Retinex algorithm was proposed. The multi-scale Retinex algorithm was used to enhance the image quality of tower hoisting, the features were extracted by the least square method, and the categories of tower were identified by feature matching. The moving point coordinate calculation models of different categories of tower hoisting were established by Picard method, and the moving point coordinates of multi-lifting point constraint rope of tower hoisting were calculated. The test results show that this method has good image enhancement effect. The test results of BIQI index and BRISQUE index are more than 4.6. It can complete the distinction of towers in the image, obtain the classification results of towers, calculate the moving point coordinates of lifting point restraint rope system, and ensure the safe lifting of towers. The inclination angle is less than 10 °, and the more uniform the section bending moment is more than 92.5%.
2023 Vol. 44 (7): 1087-1092 [Abstract] ( 106 ) HTML (1 KB)  PDF (24341 KB)  ( 37 )
1093 Traffic Classification Statistics under Video Surveillance in Forest Areas
ZHU Wen-chao,YANG Jie,HE Chao
DOI: 10.3969/j.issn.1000-1158.2023.07.14
In view of the problems such as difficulty in extracting vehicle features and inability to classify statistics by the traditional method of statistical traffic flow through surveillance video in forest environment, a method of traffic flow classification statistics based on YOLOv5 combined with DeepSORT was proposed. The method used the objective detection algorithm YOLOv5 as a detector to classify and detect vehicles. In order to improve the vehicle detection effect in the actual scene, the CBAM attention mechanism was incorporated into the algorithm to enhance the feature extraction ability of the detector for vehicles. In addition, the NMS was improved to DIoU-NMS so as to solve the problem of missed detection caused by mutual vehicle occlusion. The objective tracking algorithm DeepSORT was used to track the detected vehicles, and the reidentification network was retrained on the vehicle re-identification dataset in order to reduce the vehicle identity switching phenomenon. Finally, the tracked vehicles were counted by setting virtual lines in the video. The results of the method were verified in the actual scenario. As shown by the experimental results, the overall traffic flow statistics accuracy was improved by 10.1% compared with that before the improvement. Besides, the traffic flow statistics accuracy of cars, trucks, and buses reached 91.8%, 94.6% and 93.8% respectively.
2023 Vol. 44 (7): 1093-1099 [Abstract] ( 141 ) HTML (1 KB)  PDF (891 KB)  ( 263 )
1100 Scanning Path Planning and Measurement of Focused Transducer Focal area sound field
DUAN Xue-liang,ZHENG Hui-feng,PENG Yuan,GUO Zhong-xiao,ZHU Jie
DOI: 10.3969/j.issn.1000-1158.2023.07.15
The focus area sound pressure scanning of a focused transducer is an important step in the measurement of its acoustic characteristics, while the traditional scanning path measurement is inefficient. A scanning path planning method based on the distribution characteristics of the focused sound field is proposed.First, the experimental scheme and principle are given, the focus area sound field characteristics of the focused transducer sound field are analyzed, and then finite element simulation analysis is carried out for the focusing transducer, according to the concentric circle distribution characteristics of the sound field, the corresponding areas of different sound pressure levels are obtained as the hydrophone scanning characteristic areas with the focus being 0dB sound pressure level. Finally, an experimental system is built,the experimental results show that the parameters such as -6dB focal length and width are consistent with the theoretical values and the measured values of traditional mechanical measuring mechanisms, the measurement accuracy is guaranteed and the measurement efficiency is effectively improved.
2023 Vol. 44 (7): 1100-1106 [Abstract] ( 133 ) HTML (1 KB)  PDF (105660 KB)  ( 62 )
1107 Research on Remote Measurement Method of Off-board Conductive Charger for Electric Vehicle Based on Bayes Theory
ZHOU Di,ZHENG Wen-bin,LI Lin-tong,WEI Ming-chen,QU Xi-song,ZHENG Hui-zeng
DOI: 10.3969/j.issn.1000-1158.2023.07.16
It conducts analysis based on Bayesian theory. The evaluation method of measurement uncertainty for off-board conductive charger is studied. It is proposed of a remote measurement algorithm based on Bayesian method. This algorithm realizes quantity-value transfer based on mesh charging process data. The result of the algorithm is correct in actual experiment. The actual estimate is off by less than 3%. The validity of the algorithm in remote measurement of off-board conductive charger is verified.
2023 Vol. 44 (7): 1107-1112 [Abstract] ( 132 ) HTML (1 KB)  PDF (7323 KB)  ( 69 )
1113 The IEEE 1057 Digital Waveform Recorder Standard Development Review
LIANG Zhi-guo,HE Zhao,FENG Xiu-juan,LIU Yuan,SUN Jing-yu
DOI: 10.3969/j.issn.1000-1158.2023.07.17
The development of technical parameters of the IEEE Std 1057 for digital waveform recorders in previous versions are introduced in detail, the idea of the thirteen parts characteristics of the standard involved is explored, and the six basic methods used are analyzed. At the same time, some problems in the standard are discussed, including time base errors, multi-channel synchronization, absolute delay, trigger parameters error, sinusoidal fitting convergence, and other issues. Future development of the direction about this standard is also prospected.
2023 Vol. 44 (7): 1113-1120 [Abstract] ( 132 ) HTML (1 KB)  PDF (2238 KB)  ( 63 )
1121 Research on Measurement Method of GNSS Receiver Antenna Phase Center Offset Based on Geometric Constraints
LI Jing-jing,LI Lian-fu,WANG De-li,ZENG Jiu-sun,CAI Jin-hui,MIAO Dong-jing,LI Jian-shuang
DOI: 10.3969/j.issn.1000-1158.2023.07.18
By analyzing the relationship between the phase center and the geometric center of the GNSS receiver antenna, a measurement method for the phase center offset of GNSS receiver antenna based on geometric constraints was proposed. The method was measured by a combination of two or more antennas, using the known coordinates of the antenna geometric center in the east-north-top coordinate, the horizontal offset and relative vertical offset of the phase center of all antennas can be solved in only two observation periods. The phase center stability analysis experiment with different observation periods and the phase center offset measurement experiment under different antenna combinations and different antenna position conditions were carried out by using choke antennas. The experimental results show that the observation period of the high-precision GNSS receiver antenna phase center offset measurement is 24h. The repeatability of the horizontal offset of the phase center of the antenna is not more than 0.13mm, and the repeatability of the relative vertical offset is 0.67mm.
2023 Vol. 44 (7): 1121-1127 [Abstract] ( 164 ) HTML (1 KB)  PDF (61267 KB)  ( 90 )
1128 Activity Determination of 131I by Means of Two Coincidence Counting Methods
LUO Li-feng,LIU Hao-ran,LIANG Jun-cheng,FAN Fu-you,ZHANG Ming,XU Qiang
DOI: 10.3969/j.issn.1000-1158.2023.07.19
Activity measurements of 131I were performed by 4πβ(LS)-γ and 4πβ(PC)-γ digital coincidence counting methods, respectively. And the uncertainty of the results obtained by the two methods were also evaluated. The β-ray was detected by a flow-gas proportional counter(PC) operated with a mixture of argon and methane as the working gas and a liquid scintillation counter(LSC) with simple sample preparation, respectively. After that, the digital coincidence counting technique which detects the short-lived nuclides appropriately was used to processed the β、γ list mode file offline. The coincidence counts for efficiency extrapolation were given after dead time correction and coincidence resolution time correction. It shows that the results of 131I obtained by the two methods are consistent in the range of uncertainty, and the relative standard deviation is 0.27%.
2023 Vol. 44 (7): 1128-1133 [Abstract] ( 99 ) HTML (1 KB)  PDF (76503 KB)  ( 61 )
1134 Preparation of Atypical Salmonella Reference Material in Chicken and the Application in the Proficiency Testing
XU Qian,LIU Si-yuan,GAO Ying,WANG Zi-quan,SUI Zhi-wei,CHANG Hai-yan
DOI: 10.3969/j.issn.1000-1158.2023.07.20
In order to solve the problem of the lack of reference material and the development level of Salmonella, atypical Salmonella NIM JZ048 was selected as the target bacteria, and Enterobacter aerogenes CICC 10293 was selected as the interference bacteria to develop atypical Salmonella reference materials in chicken.The results indicated that the quantitative standard value of Salmonella for the reference material is (1.8±0.4)×103CFU/g, the quantitative standard value of total bacterial count is (5.5±0.9)×103CFU/g, the qualitative standard value is Salmonella positive. The reference material has good uniformity and stability, and can be stably stored at -20℃ for six months.In addition, the reference material was used as the test sample for proficiency test of Salmonella qualitative detection participated by twenty-one food inspection agencies. The results of 15 agencies were qualified. Six agencies failed to detect atypical Salmonella, resulting in unqualified results. The atypical Salmonella reference material in chicken can be effectively used for the evaluation of Salmonella detection capability in food inspection agencies.
2023 Vol. 44 (7): 1134-1140 [Abstract] ( 103 ) HTML (1 KB)  PDF (8113 KB)  ( 41 )
1141 Determination of the Mass Fraction of Pure Heart-type Fatty Acid-binding Protein by Pre-column Derivatization UPLC
CUI Hong-en,FENG Su,YE Ren-yuan,LIU Yang,FANG Shuai,ZHU Mao-lin,FAN Xiao-lin
DOI: 10.3969/j.issn.1000-1158.2023.07.21
After the heart type fatty acid binding protein (H-FABP) is hydrolyzed by acid hydrolysis, the amount of four derivatives of aspartic acid, glutamic acid, histidine and arginine can be determined, and then the content of pure H-FABP can be calculated. During the determination process, the national standard substance of amino acid mixed solution was used as the standard, γ-aminobutyric acid was used as the internal standard, and treated with pre column derivatizer. Comparing the results of this method with those of isotope dilution mass spectrometry for the determination of H-FABP content can verify the accuracy of the established method. The experiment showed that under the optimal conditions, the H-FABP content in the established pre column derivatization ultra high performance liquid chromatography (UPLC) method was determined to be 0.1113mg/mL. The relative standard deviation was 2.03%, the expanded uncertainty was 0.0027mg/mL (k=2), and the detection limit and quantification limit were 1.16×10-3mg/mL and 3.86×10-3mg/mL, respectively. In addition, this method has a low cost and clear traceability chain, which may serve as a supplementary validation method for the calibration of pure H-FABP reference materials.
2023 Vol. 44 (7): 1141-1146 [Abstract] ( 110 ) HTML (1 KB)  PDF (15880 KB)  ( 40 )
1147 Research on Motor Imagery EEG Classification Method based on Improved Transformer
LIU Yue-feng,LIU Hao-feng,WANG Yue,LIU Bo,BAO Xiang
DOI: 10.3969/j.issn.1000-1158.2023.07.22
The motor imagery (MI) EEG signal itself is a signal sequence consisting of a set of long and continuous feature values. Traditional Transformers cannot capture dependencies between longer sequences, and setting fixed length sequences can lead to fragmentation issues, so further adjustments and optimization are needed. To address the above issues, a fragment reuse loop mechanism and a relative position encoding mechanism for fragment information have been added to traditional Transformers. This can enable the Transformer to learn feature information from longer feature sequences. At the same time, it can also solve problems such as confusion and reuse of positional encoding information between reused fragments. Subsequently, parallel multi branch CNN was used to further capture local EEG features. Finally, the performance of the improved Transformer model was evaluated using the competition dataset 2008 BCI-Competition 2A. The results showed that, without any manual feature extraction, the average accuracy and kappa value of the improved Transformer model for the four classification dataset were 94.27% and 87.34%, respectively.
2023 Vol. 44 (7): 1147-1153 [Abstract] ( 165 ) HTML (1 KB)  PDF (47348 KB)  ( 83 )
1154 Effect of Sampling Flow Rate and Nozzle-plate Spacing on Collection Efficiency of Plankton Sampler
TIAN Ying,ZHANG Guo-cheng,LIU Jia-qi,WU Dan,SHEN Shang-yi,JING Wen-jie
DOI: 10.3969/j.issn.1000-1158.2023.07.23
As an efficient single-stage Anderson impact sampler, the plankton sampler is easy to operate, small and portable, which is widely used in clean rooms of pharmaceutical factories, sanitation and epidemic prevention. At present, the collection efficiency of plankton sampler in the market lacks scientific and efficient evaluation method. An evaluation method based on aerodynamic particle size spectrometer was used to test the collection efficiency of two kinds of domestic plankton samplers. It was found that sampling flow rate, the height of agar and the distance between nozzle and plate would significantly affect the collection efficiency of phytoplankton sampler. The results show that under a fixed sampling flow rate, the closer the petri dish is to the sampling head, the better the collection efficiency.When the distance between petri dish and sampling head is fixed, the collection efficiency increases first and then decreases with the increase of sampling flow rate, and the collection efficiency is the best when the sampling flow rate is 80L/min. The larger the agar thickness, the higher the sampling efficiency. The study has reference significance for improving the structure design of the plankton sampler, improving the product quality, and helping to improve the accuracy and scientificity of the detection of the plankton sampler.
2023 Vol. 44 (7): 1154-1158 [Abstract] ( 97 ) HTML (1 KB)  PDF (27115 KB)  ( 40 )
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