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2020 Vol. 41, No. 1
Published: 2020-01-28
 
1 Research on Leapfrog Measurement Method of Articulated Coordinate Measuring Machine Based on Distance Constraint
LIU Shi-da,ZHAO Hui-ning,YU Lian-dong
DOI: 10.3969/j.issn.1000-1158.2020.01.01
To solve the problem that the measuring range of articulated coordinate measuring machine(ACMM)is limited and the error is large in the large scale measurement, a leapfrog measuring method on ACMM based on the distance constraint is proposed. In the process of coordinate transformation of ACMM, leapfrog balls are used as the public reference points and the spatial position relation between leapfrog balls is calibrated by the high accurate CMM. In the process of calculating coordinate transformation parameters, the distance between any two leapfrog balls is taken as the distance constraint. The gross error existing in measurement result is eliminated and the parameters of coordinate transformation model are optimized to improve the accuracy of coordinate transformation. The experimental results show that the distance constraint can effectively improve the accuracy of coordinate transformation parameters, and the number of public reference points can also greatly improve the accuracy of leapfrog measurement.
2020 Vol. 41 (1): 1-5 [Abstract] ( 391 ) HTML (1 KB)  PDF (1037 KB)  ( 351 )
6 Piecewise Interpolation Measurement in Circular Indexing Angle Measurement Verification
WANG Lei,ZHANG Zhong-wu,WANG Zhen,SUN Fang-jin,WANG Chun-xi,ZANG Tie-li,LIU Xiao-xu
DOI: 10.3969/j.issn.1000-1158.2020.01.02
The circle indexing angle is generally measured by selected a large interval angle when using permutation intercomparison method. In order to measure the deviation of a small angle which is in the range of the large interval angle, a piecewise interpolation measurement is proposed. Considering which have been measured by the permutation intercomparison method, the deviation of the two angle position composing the interval angle can be used as control points. In this interval angle, the small angle deviation can be observed through continuous comparison with small angle inspection tools. In conclusion, the piecewise interpolation measurement is the extension and supplement of the permutation intercomparison method.
2020 Vol. 41 (1): 6-10 [Abstract] ( 332 ) HTML (1 KB)  PDF (596 KB)  ( 232 )
11 Design of Vehicle Distance Detection System Based on Machine Vision
CHENG Yao,ZHAO Lei,CHENG Shan,TIAN You-yuan,MI Zeng-zhen
DOI: 10.3969/j.issn.1000-1158.2020.01.03
In order to detect the front vehicle distance, a monocular imaging system based on CCD was used to collect the vehicle image, and the vehicle distance was measured by detecting the number of pixels in the image.The model including license plate image and vehicle distance information was established by the position and size relationships between object and its image based on the image model of monocular camera.Meanwhile based on the principle of CCD imaging, the model between license plate image and sensor pixels was established.Then the model of ranging detection algorithm was constructed.By building a CCD imaging system, the license plate image of the measured vehicle was acquired.The man-machine interface was designed by using MATLAB, and pre-processings were carried out to improve the image contrast.By matching connected regions and other algorithms, the license plate was located and segmented, and the number of pixels in the horizontal direction of the image was detected.On this basis, the size of vehicle distance was calculated with the principle of small aperture imaging and was displayed on the software platform.Experiments proved that the system can analyze the image of the front vehicle and calculate the distance, the average error of the system is 4% for the distance detection beyond 3 meters.
2020 Vol. 41 (1): 11-15 [Abstract] ( 362 ) HTML (1 KB)  PDF (1320 KB)  ( 1066 )
16 Characteristic Analysis and Optimization Design of Rectangular Array Light Source for Finger Vein Recognition System
ZHU Chao-ping,QIN Hua-feng,LIU Qi-neng
DOI: 10.3969/j.issn.1000-1158.2020.01.04
The quality of vein images collected by finger vein recognition system directly affects the recognition efficiency of finger veins,the design of light source of the system influences the quality of finger veins.Aimed at the illumination uniformity of single near-infrared LED is relatively poor, how to design a high-quality light source by taking advantage of the structure, space, shape and other parameters of multiple near-infrared LED is worth studying.By using sparrow's law to find the optimal solution to the extremum of various parameters, and combining the individual differences of fingers and finger shape characteristics, the illumination surface is designed as a 25mm×25mm rectangular light source array, through comparison experiments, the array light source designed with the optimal parameters can collect high-quality finger vein images.By analyzing the light source parameters of rectangular array, a reference for the development of finger vein acquisition equipment is provided and a foundation for the subsequent finger vein image recognition is laid.
2020 Vol. 41 (1): 16-21 [Abstract] ( 266 ) HTML (1 KB)  PDF (1169 KB)  ( 320 )
22 Optimization of Inclination and Azimuth of Photovoltaic Array
XIE Tong,LI Ke-cheng,MA Zhao-jian,HUANG Ke-yu,LIU Shan-qi
DOI: 10.3969/j.issn.1000-1158.2020.01.05
According to the characteristics of photovoltaic array, the mathematical model of photovoltaic array was established, and the impact of photovoltaic tilt angle and azimuth on capacity and energy value maximization was analyzed.By comparing and studying the data of power generation in 2017, the inclination angle and orientation of capacity and energy value maximization were calculated and verified.The experimental results showed that this method can get the best photovoltaic installation angle, which has high application value.
2020 Vol. 41 (1): 22-25 [Abstract] ( 291 ) HTML (1 KB)  PDF (965 KB)  ( 709 )
26 Study on Isothermal Characteristics of Gravity Cesium Heat Pipe
ZHANG Kai,YUE Kai,YAN Xiao-ke,TONG Wen-yu
DOI: 10.3969/j.issn.1000-1158.2020.01.06
To verify the key technology of the development of the cesium heat pipe, the isothermal performance and the start-up characteristics of the gravity cesium heat pipe were studied under a constant temperature condition by measuring the temperature distribution of the outer wall of the heat pipe. Also, the effects of the length of the condensation section on the isothermal performance of the heat pipe were analyzed. The results showed that, the cesium heat pipe can start normally when the temperature of the heating furnace was in the range from 330℃ to 630℃ and had a good heat transfer ability. Moreover, the higher the temperature of the heating furnace, the faster the start-up of the heat pipe. The temperature of the wall surfaces of the heat pipe showed serrated temperature fluctuations when the length of the condensation section is 300mm. The mechanism of boiling phase transition heat transfer was analyzed in the heat pipe from the perspective of superheat. The selection of a suitable length of condensation section can avoid the occurrence of the phenomena of the periodic intermittent boiling. In addition, the experimental results proved that the cesium heat pipe can be used as a high-efficiency heat transfer element within the temperature range from 330℃ to 630℃, and is suitable for realizing the zinc freezing point of the ITS-90.
2020 Vol. 41 (1): 26-31 [Abstract] ( 429 ) HTML (1 KB)  PDF (1918 KB)  ( 584 )
32 Research on Quantum-voltage-calibrated Superposition Thermometry
XU Xun,ZHOU Kun-li,XU Zhi-peng,HAN Qi-na,LI Jing-hui
DOI: 10.3969/j.issn.1000-1158.2020.01.07
The conventional Johnson noise thermometer with switchs is time-consuming and requires carefully matching of the transmission lines. A quantum-voltage-calibrated superposition thermometer to eliminate the switchs was proposed. In this configuration, matching the transmission lines is not necessary and the sense resistor can be increased to improve the signal to noise ratio. The system included a quantum voltage noise source, low-noise and low-distortion amplifiers, low-pass filters, and high performance analog to digital converters. A fourth-order fitting to eliminate the transmission line effects was used to obtain the thermodynamic temperature. Confirmatory experiments in thermostatic laboratories showed that the relative deviation between the measured temperature value and the nominal temperature value is 0.027% and the uncertainty is 0.16%, which demonstrated the feasibility of the proposed method.
2020 Vol. 41 (1): 32-36 [Abstract] ( 347 ) HTML (1 KB)  PDF (1055 KB)  ( 358 )
37 A Nonlinear Error Correction Method for ADC Based High-precision Resistance Thermometry Readout
DING Jiong,WANG Jia-yin,WANG Xiao-na,XU Qi-yue,YANG Sui-jun,FU Shu-fang,YE Shu-liang
DOI: 10.3969/j.issn.1000-1158.2020.01.08
Due to the complexity of the circuit architecture, high integration and diversity of nonlinear error sources in ADC based resistance thermometry readout, the effect of the existing nonlinear error correction method is not significant. Aiming at these shortcomings, a novel nonlinear error correction method based on the error sources analysis was proposed for ADC based readout. In the method, the influences of the common-mode rejection ratio, the mismatch of the forward and reverse exciting current were analyzed in mathematically. With the resistance bridge calibrator, these two errors were estimated and corrected, Then the residuals were fitted by the linear polynomial. To verify the effect of the proposed correction method, an ADC-based resistance thermometry readout and a resistance bridge calibrators were developed in the study. The experimental results showed that after the correction of the proposed method, the maximum nonlinear error of the readout is -1.77×10-5, while with the correction of the traditional method, the maximum nonlinear error is -3.57×10-5. The circuit schematics and measurement procedures of the ADC based thermometry readout were released, this is helpful for the countrys the ADC based high-precision resistance thermometry readout development and commercialized.
2020 Vol. 41 (1): 37-42 [Abstract] ( 365 ) HTML (1 KB)  PDF (1170 KB)  ( 626 )
43 The Test Facility of the Critical Back-pressure Ratio for Small Sonic Nozzle
ZHOU Li-yuan,LI Chun-hui,XIE Dai-liang
DOI: 10.3969/j.issn.1000-1158.2020.01.09
The back pressure ratio of sonic nozzle at work must be lower than critical back-pressure ratio to realize and maintain the critical flow for the sonic nozzle. Therefore, the back pressure ratio of the sonic nozzle when the Reynolds number Red of throat is less than 2×105 should be no bigger than 0.25, or is subjected to make the actual test, which is suggested in ISO 9300. A test facility was built, which can be used to measure the critical back-pressure ratio for the sonic nozzle with throat diameter of 0.3~3mm, while the flow range of sonic nozzle can be 0.05~5m3/h. The expanded uncertainty is 0.56% (k=2).
2020 Vol. 41 (1): 43-47 [Abstract] ( 296 ) HTML (1 KB)  PDF (409 KB)  ( 497 )
48 Study on Slug Flow Mechanism of Gas-liquid Two-phase Flow based on Long Throat Venturi Tube
FANG Li-de,WANG Pei-pei,WANG Song,LI Sheng-yao,TIAN Ji,LI Xiao-ting,ZHENG Qing-long
DOI: 10.3969/j.issn.1000-1158.2020.01.10
To study the phase holdup of gas-liquid two-phase flow and obtain the relevant model, by combining with the research status of gas-liquid two-phase flow, using the combination of near-infrared spectroscopy and high-speed photography, and using a new structure of the near infrared system located in the position of the Venturi tube of long throat, a simplified model was proposed by divide the slug flow into two parts, the Taylor bubble and the tail bubble, finally measurement model of the phase holdup measurement was obtainted. To some extent, the problem that the two-phase interface at different parts of the slug flow has a great influence on the received light intensity signal of the near-infrared receiving probe was solved. The measurement effect of the new model was better, and the measurement error of the obtained result was small.
2020 Vol. 41 (1): 48-54 [Abstract] ( 333 ) HTML (1 KB)  PDF (946 KB)  ( 264 )
55 Calibration of Piezoelectric Accelerometers Dynamic Characteristics using Primary Vibration Calibration
LU Min,HU Hong-bo
DOI: 10.3969/j.issn.1000-1158.2020.01.11
A novel approach was proposed for calibration of accelerometers by model-based parameter identification, aimed for the problem that mostly used method for accelerometers calibration cant satisfy requirements for dynamic mechanical quantity in reality. The model consisted of a linear, second-order differential equation with unknown coefficients. It was proposed to estimate these model parameters from primary vibration calibration, and an estimation procedure based on linear least-squares was presented. The uncertainties associated with the estimated results were determined utilizing a Monte Carlo simulation technique. The model obtained was used to predict the accelerometers behavior for shock acceleration, measured and predicted results were consistent with difference below 1%, which confirmed the validity of the method.
2020 Vol. 41 (1): 55-59 [Abstract] ( 247 ) HTML (1 KB)  PDF (367 KB)  ( 401 )
60 Dynamic Parameter Identification of Flexible Joint Robot Based on Adaptive Particle Swarm Optimization-genetic Algorithm
WANG Yue-ling,WANG Yue,WANG Qi,WANG Hong-bin
DOI: 10.3969/j.issn.1000-1158.2020.01.12
A method of dynamic parameter identification of flexible joint robot based on adaptive particle swarm genetic algorithm was proposed. The algorithm adopted dynamic adaptive adjustment strategy to improve the convergence speed of particle swarm algorithm. At the same time, a new hybrid genetic algorithm was introduced to avoid particle swarm optimization. Adaptive particle swarm genetic algorithm was compared with the standard particle swarm algorithm, genetic algorithm and artificial swarm algorithm, and the simulation results showed that the algorithm performs parameter identification after about 60 iterations, and the relative error of each parameter was reduced to less than 1%. Finally, the experimental verification was carried out by using the rotating flexible joint experimental platform, and the experimental results showed that the algorithm has better convergence speed and optimization precision.
2020 Vol. 41 (1): 60-66 [Abstract] ( 330 ) HTML (1 KB)  PDF (630 KB)  ( 576 )
67 Sinusoidal Pressure Research Based on Dynamic Mesh Technique
ZHANG Zhong-li,XU Zi-yi,NI Yu-shan,WANG Can,ZHANG Jin-ming
DOI: 10.3969/j.issn.1000-1158.2020.01.13
Sinusoidal pressure is a typical standard signal of periodic dynamic pressure, while the sinusoidal pressure generator is the key to generate sinusoidal pressure signal. A rotating disk type of sinusoidal pressure generator has been carried out for example, to numerically simulate three-dimensional transient flow field through the dynamic mesh technique, the Reynolds-averaged Navier-Stokes equation and the Spalart Allmaras turbulence model, in order to investigate the effect of different cavity size and working frequency. The results show that, firstly in case the working frequency is constant, the dynamic amplitude ratio and the harmonic distortion degree decrease with the increase of cavity width, while the mean pressure increases. Secondly in case the cavity width is constant, as the working frequency increases, the dynamic amplitude ratio decreases, the mean stress increases, meanwhile the harmonic distortion degree decreases at first and then increases. The simulation based on dynamic mesh technique can effectively predict the various structures effects in sinusoidal pressure study.
2020 Vol. 41 (1): 67-72 [Abstract] ( 266 ) HTML (1 KB)  PDF (893 KB)  ( 326 )
73 Determination of Input Parameters of Acoustic Weight Volume Measurement Device Based on Acoustic Simulation
HAN Zhi,WANG Jian
DOI: 10.3969/j.issn.1000-1158.2020.01.14
Aiming at the problem that the selection of the loudspeaker driving signal in the acoustic cavity of the acoustic method weight volume measuring device affects the measurement accuracy, a method for determining the driving signal parameters is proposed, which is a method of using the finite element method to model a simulation of the acoustic cavity, and getting the optimal driver signal amplitude and frequency point of the loudspeaker that minimizes the volume error.At the same time, the acoustic volume measurement device is applied at different amplitudes and frequency points for actual volume measurement verification.The results show that the driving signal parameters that minimize the volume measurement error are in good agreement with the simulation results.The optimal measurement frequency of the above acoustic cavity is 46Hz, and the deviation between the volume measurement value under the driving frequency and the value measured by the hydrostatic method is less than 0.001cm3.In a certain measuring range, the amplitude of driving signal has no effect on the accuracy of the acoustic method.
2020 Vol. 41 (1): 73-78 [Abstract] ( 271 ) HTML (1 KB)  PDF (1408 KB)  ( 250 )
79 Research on Underwater Hull Surface Imaging Method Based on Ultrasonic Phased Array
YE Xiao-tong,ZHAO Peng,ZHENG Ke,WANG Yue-bing,ZHENG Hui-feng
DOI: 10.3969/j.issn.1000-1158.2020.01.15
To solve the problem of lack of equipment, high cost and large errors on underwater hull surface imaging, a method based on ultrasonic phased array technology is proposed. The underwater hull surface is scanned by the focused sound beam emitted by a 1-D linear ultrasonic phased array transducer. Acoustic scattering occurs on the hull surface and echo signal is received by the transducer. The 3-D model of the underwater hull surface is reconstructed using the point cloud data of these scattering points calculated by hyperbolic intersection method. Experiment of underwater hull-model surface imaging is implemented. The result shows that the method has high imaging resolution and can accurately reconstruct the 3-D model of the underwater hull surface with a reconstruction error no more than 5mm.
2020 Vol. 41 (1): 79-84 [Abstract] ( 329 ) HTML (1 KB)  PDF (1703 KB)  ( 973 )
85 Research on New Method of Time Base Error Compensation for Broadband Sampling Oscilloscope
ZHU Jiang-miao,WANG Shi-biao,ZHAO Ke-jia,QIAO Meng-yuan
DOI: 10.3969/j.issn.1000-1158.2020.01.16
Time-based errors seriously affect the accurate measurement of broadband sampling oscilloscopes, but it is extremely difficult to accurately estimate and compensate for time-base errors. For the time-base error of broadband sampling oscilloscope (including time-base distortion and jitter-induced error), the orthogonal time-regression algorithm is used to estimate the time-base error of oscilloscope for the first time. Compared with the multi-phase and multi-frequency least squares method,only to uses a set of approximately orthogonal sinusoidal signals to effectively estimate the time base error of the broadband sampling oscilloscope, and realizes the time base compensation of the measured signals. A time base error of less than 0.3ps is obtained, which significantly improves the measurement accuracy of the broadband sampling oscilloscope.
2020 Vol. 41 (1): 85-89 [Abstract] ( 306 ) HTML (1 KB)  PDF (832 KB)  ( 671 )
90 The Classification of EEG Induced by Motor Imagery Based on Variational Mode Decomposition and Deep Belief Network
HE Qun,DU Shuo,WANG Yu-wen,CHEN Xiao-ling,XIE Ping
DOI: 10.3969/j.issn.1000-1158.2020.01.17
The traditional method of manually determining the optimal periods and frequency bands resulted in the omission of information and the reduction of the recognition rate of motor imagery (MI). Therefore, MI became a challenging issue in brain-computer interface (BCI). Aiming at this issue, variational mode decomposition (VMD) and deep belief network (DBN) were applied to the classification of MI. VMD was proposed to decompose the electroencephalograph (EEG) into multiple narrow band components, then the marginal spectrum, the instantaneous energy spectrum and the joint time-frequency features were extracted by Hilbert transform, then these features were fused. The DBN was proposed to reduce the dimensions of fused high-dimensional features to recognize the pattern of MI, which avoided the omission of information caused by choosing the optimal periods and frequency bands manually. The results showed that the recognition accuracy of MI was improved effectively by the proposed method based on VMD and DBN to automatically extract the optimal period and frequency bands .
2020 Vol. 41 (1): 90-99 [Abstract] ( 369 ) HTML (1 KB)  PDF (2068 KB)  ( 909 )
100 Evaluation of Effective Efficiency Uncertainty in WR-42 Power Standard System
GU Ruo-chen,YUAN Wen-ze,DING Na,CUI Xiao-hai,LI Yong
DOI: 10.3969/j.issn.1000-1158.2020.01.18
The WR-42 power standard is a micro-calorimeter system that uses DC substitution and calorimetry techniques to measure the effective efficiency of the WR-42 thermistor mount. The uncertainty assessment of effective efficiency in WR-42 micro-calorimeter system is introduced, and the measurement results of effective efficiency and uncertainty are given. The development of this power standard fills the gap between 18GHz and 26.5GHz, which help Chinese RF power standard fully cover the frequency band between 10 MHz and 220GHz.
2020 Vol. 41 (1): 100-102 [Abstract] ( 282 ) HTML (1 KB)  PDF (409 KB)  ( 306 )
103 Long-term Constancy Analysis of CT Numbers for Cone-beam CT Images of a Varian OBI System
SHI Fei-yue,TIAN Shu-chang,JIN Xun,QIN Hang,QIN Wei
DOI: 10.3969/j.issn.1000-1158.2020.01.19
The long-term constancy of CT numbers for cone-beam CT images of Varian on-board imager (OBI) system were evaluated, by analyzing the data of CT numbers for seven materials obtained from long-term quality assurance (QA) tests. QA tests for an OBI system equipped by the Varian Clinac iX linear accelerator were carried out with the Catphan504 phantom monthly. CBCT images were obtained with three scan protocols: high-quality head (HQH), standard-dose head (SDH) and Pelvis for the phantom. The DoseLab software was utilized to analyze the 36 series of CBCT images acquired from Mar. 2017 to Feb. 2018, and the CT numbers (Y) and corresponding difference from standard CT numbers (ΔY) for the seves materials were obtained.The datas were analysised by statistical method , and the mean, standard deviation and range values of Y and the mean of ΔY were obtained after calculation for the seven materials with three scan protocols. The results showed that the constancy of CT numbers of the CBCT images from the Varian OBI system was in good condition in 12 months by and large, the scan protocols of SDH and Pelvis were suitable for QA and metering tests of CBCT image quality, the difference between CT numbers of CBCT images with HQH and the standard CT numbers varied greatly with the increasing of relative electron density of material.
2020 Vol. 41 (1): 103-108 [Abstract] ( 272 ) HTML (1 KB)  PDF (1423 KB)  ( 339 )
109 The Grading and Quantitative Testing Method of Cotton Sugar by Chromatic Meter
LI Shuai,Maiheburetiguli Ainiwaer,LIU Rui,JIA Li-Xia,JIA Dong
DOI: 10.3969/j.issn.1000-1158.2020.01.20
In order to obtain a convenient and efficient method for the inspection of cotton sugar, the chromatic meter in textile industry was used to establish chromatic grading testing method (CGTM) and chromatic quantitative testing method (CQTM) of cotton sugar, practical tests have proved that the two methods for cotton sugar were feasible. Based on CGTM, color grades (blue to orange) were digitized description with chromatic parameters (a*, b*, h*), which can replace standard color paper, similar to the quantitative method. The CQTM can be directly used to describe cotton sugar content with the chromatic parameters, such as L*,C*,b*,K/S and dE*, however the fluctuation in fitting data of chromatic parameters for the same batch cotton is larger, and the difference of fitting method for chromatic parameter is significant, which needs to be researched in-depth.
2020 Vol. 41 (1): 109-114 [Abstract] ( 272 ) HTML (1 KB)  PDF (1678 KB)  ( 257 )
115 A Calibration Method for Inner Installed On-line Monitoring Instrument of Pure Water Machine
ZHANG Yao-qi,REN Yun,LI Ya,HE Jun-bin
DOI: 10.3969/j.issn.1000-1158.2020.01.21
To meet with the needs of on-site calibration of monitoring instruments installed in pure water machines, a measurement standard system including high-precision conductivity meter, total organic carbon analyzer and adjustable flow buffer device has been developed.By comparing the indication values of built-in monitoring instruments of pure water machines with the measurement results of the measurement standard system, the on-site calibration of conductivity or resistivity meter and total organic carbon analyzer installed in pure water machines was achieved.The experimental results of eleven pure water machines showed the indication errors of built-in conductivity or resistivity meters ranging from -2.4% to 15% with the expanded uncertainty of 1.7% (k=2) and those of built-in total organic carbon analyzer ranging from -98% to 125% with the expanded uncertainty of 4.8% (k=2).
2020 Vol. 41 (1): 115-120 [Abstract] ( 332 ) HTML (1 KB)  PDF (1311 KB)  ( 483 )
121 Equivalent Simulation and Reference Material of the Bacterial Colonies
CHEN Ling,HUANG Yan-jie,ZHOU Jin-yan,WU Xiang-lei,HUANG Min-han,XU Jun-bin,LUO Xu-dong
DOI: 10.3969/j.issn.1000-1158.2020.01.22
The bacterial colony itself is unstable and inconvenient to carry, so it is not suitable for use as a reference material for calibration of colony counters. Colony simulation images were used to represent colonies. According to the characteristics of colonies, colony images of different sizes and uneven distribution were processed into pictures, and the total number and size of simulated colonies were simulated to simulate standard colony materials. The total number and size of the simulated bacterial colony were equivalent to the simulated bacterial colony reference materials.A stratified random sampling method was used to study the homogeneity and stability of the reference materials.The results showed that the prepared reference materials had good homogeneity and stability.Through rigorous calculation and data processing, the total number and size of the simulated bacterial colony were determined and the uncertainty was calculated.The series of reference materials could be stored and carried easily, so they were suitable for bacterial colony counter calibration and analysis method evaluation, and have been certified as the secondary national certified reference materials with the number of GBW(E) 130586~GBW(E) 130590.
2020 Vol. 41 (1): 121-128 [Abstract] ( 286 ) HTML (1 KB)  PDF (920 KB)  ( 337 )
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