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[IEEE 2018 18th International Symposium on Antenna Technology and Applied Electromagnetics (ANTEM) - Waterloo, ON (2018.8.19-2018.8.22)] 2018 18th International Symposium on Antenna Technology and Applied Electromagnetics (ANTEM) - Cavity Perturbation Technique to Characterize Dielectric Materials at Ka-band
摘要： The characterization of permittivity and dielectric loss of dielectric materials using a perturbation technique is conducted in simulation. The working frequency of this technique has been extended to the Ka-band. Simulation results demonstrate this perturbation technique is suitable for characterization of high permittivity dielectric materials for mm-wave and maintains good accuracy.
关键词： dielectric loss measurement,permittivity measurement,cavity perturbation technique,dielectric materials,Ka-band
更新于2025-09-23 15:23:52
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Uncertainty evaluation of an 171Yb optical lattice clock at NMIJ
摘要： We report an uncertainty evaluation of an 171Yb optical lattice clock with a total fractional uncertainty of 3.6 × 10^{-16}, which is mainly limited by the lattice-induced light shift and the blackbody radiation shift. Our evaluation of the lattice-induced light shift, the density shift, and the second-order Zeeman shift is based on an interleaved measurement where we measure the frequency shift using the alternating stabilization of a clock laser to the 6s2 1S0–6s6p 3P0 clock transition with two different experimental parameters. In the present evaluation, the uncertainties of two sensitivity coefficients for the lattice-induced hyperpolarizability shift d incorporated in a widely used light shift model by RIKEN and the second-order Zeeman shift aZ are improved compared with the uncertainties of previous coefficients. The hyperpolarizability coefficient d is determined by investigating the trap potential depth and the light shifts at the lattice frequencies near the two-photon transitions 6s6p3P0–6s8p3P0, 6s8p3P2, and 6s5f3F2. The obtained values are d = ?1.1(4) μHz and aZ = ?6.6(3) Hz/mT2. These improved coefficients should reduce the total systematic uncertainties of Yb lattice clocks at other institutes.
关键词： precise measurement,optical lattice clock,optical frequency comb,Frequency standards,SI second
更新于2025-09-23 15:23:52
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Methodology and implementation of a vision-oriented open CNC system for profile grinding
摘要： CNC systems with the vision function have become very valuable for intelligence machine tools because machine vision is a fast-growing intelligent feature for machines. A novel vision-oriented open CNC system was developed in this study and used in profile grinding machines for the precise machining of parts with contour surfaces, such as complex molds and cutting tools. The system is an innovation to the conventional profile grinding method and enabled the profile error to be visually detected and compensated during the machining process. In this study, a novel design methodology for a machine-vision-oriented CNC system was proposed. An Ethernet-based hardware architecture was constructed for the vision-oriented CNC system. The software characteristics of the developed CNC system were analyzed, including a new type of multi-thread software architecture, a seamless handover approach for multi-thread accessing of the memory space, the integration of the human-machine interface with image processing, and virtual-axis-based online error compensation. The running efficiency test of the software development platforms, time-consumption analysis of the measurement and control in the vision-oriented CNC system, and verification of the effectiveness of the developed vision-oriented CNC system were performed. The results indicate that the proposed vision-oriented open CNC system can effectively fuse image processing with motion control, meet the efficiency requirement, and improve the machining precision of profile grinding. The results are also valuable for developing other machine-vision-based intelligent machine tools.
关键词： Contour error,Profile grinding,Image processing,On-machine measurement,Open CNC,Machine vision
更新于2025-09-23 15:23:52
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Identifying Mangrove Species Using Field Close-Range Snapshot Hyperspectral Imaging and Machine-Learning Techniques
摘要： Investigating mangrove species composition is a basic and important topic in wetland management and conservation. This study aims to explore the potential of close-range hyperspectral imaging with a snapshot hyperspectral sensor for identifying mangrove species under field conditions. Specifically, we assessed the data pre-processing and transformation, waveband selection and machine-learning techniques to develop an optimal classification scheme for eight mangrove species in Qi’ao Island of Zhuhai, Guangdong, China. After data pre-processing and transformation, five spectral datasets, which included the reflectance spectra R and its first-order derivative d(R), the logarithm of the reflectance spectra log(R) and its first-order derivative d[log(R)], and hyperspectral vegetation indices (VIs), were used as the input data for each classifier. Consequently, three waveband selection methods, including the stepwise discriminant analysis (SDA), correlation-based feature selection (CFS), and successive projections algorithm (SPA) were used to reduce dimensionality and select the effective wavebands for identifying mangrove species. Furthermore, we evaluated the performance of mangrove species classification using four classifiers, including linear discriminant analysis (LDA), k-nearest neighbor (KNN), random forest (RF), and support vector machine (SVM). Application of the four considered classifiers on the reflectance spectra of all wavebands yielded overall classification accuracies of the eight mangrove species higher than 80%, with SVM having the highest accuracy of 93.54% (Kappa = 0.9256). Using the selected wavebands derived from SPA, the accuracy of SVM reached 93.13% (Kappa = 0.9208). The addition of hyperspectral VIs and d[log(R)] spectral datasets further improves the accuracies to 93.54% (Kappa = 0.9253) and 96.46% (Kappa = 0.9591), respectively. These results suggest that it is highly effective to apply field close-range snapshot hyperspectral images and machine-learning classifiers to classify mangrove species.
关键词： machine learning,waveband selection,mangrove species classification,close-range hyperspectral imaging,field hyperspectral measurement
更新于2025-09-23 15:23:52
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Design and characterization of the non-uniform solar flux distribution measurement system
摘要： It is important to accurately measure the solar flux distribution on the heated surface for the utilization of solar energy. To this end, in this paper a new measurement system was proposed to measure the solar flux distribution of the absorber tube surface by taking advantage of the end loss effect. The new measurement system does not disturb the collected lights path and influence the operation of the solar collector. The solar flux distribution at different angles can be measured with a few number of heat flux gage by rotating the proposed solar flux measurement system. Compared with existing measurement techniques, the proposed solar flux measurement system has distinct advantages such as simple structure, flexible and reliable operation and easy application. An experimental platform was designed and constructed, and the solar flux distributions on the outer surface of the absorber under different conditions are measured. The feasibility and effectiveness of the proposed measurement method are validated by comparing the experiment results and the numerical simulation results.
关键词： solar flux distribution,solar flux measurement system,parabolic trough solar collector,experimental investigation
更新于2025-09-23 15:23:52
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Estimation of winter time NOx emissions in Hefei, a typical inland city of China, using mobile MAX-DOAS observations
摘要： In this paper, we present a quantitative determination of the NOx emission in Hefei using mobile Multi-Axis Differential Optical Absorption Spectroscopy (MAX-DOAS) measurements. The measurements were carried out during winter time from December 2016 to February 2017. The measured NO2 vertical column densities (VCDs) show a strong spatial gradient with higher values within the city center, indicating the majority of NOx emission sources are located at the city center. A significant 'holiday effect' was found by comparing measurements taken during weekdays and weekend. The weekend reduction is more significant in the suburban (～28%) compared to the city center (～13%). Mobile measurements of NO2 vertical column densities (VCDs) were analyzed together with meteorological data to determine the NOx emission by applying the loop-integral method. Detailed error analysis of the NOx emission shows the variation of wind field and large measurement gap dominated the total error of NOx emission calculation. The result shows the NOx emission in Hefei during winter time varies in a wide range from 10 × 10^24 to 40 × 10^24 molec s^{-1} with an average of 18.44 × 10^24 molec s^{-1}. Our estimation is about 43% lower than the number reported in the previous emission inventory in 2012. The reduction of NOx emission reflects the successful implementation of emission control measures in recent years. Our result also shows about 73% of the total NOx in the city were transported from outside of the city during winter. The impacts of transported NOx are especially large when air masses originated from heavily polluted regions, i.e. North China Plain and Yangtze River Delta. The result presented provides a better understanding of the impacts of local emissions and transportation of pollutants on the local air quality of Hefei.
关键词： Mobile measurement,MAX-DOAS,Regional transport,NOx emission
更新于2025-09-23 15:23:52
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Cuff-less continuous measurement of blood pressure using wrist and fingertip photo-plethysmograms: Evaluation and feature analysis
摘要： Continuous monitoring of blood pressure improves prevention and control of cardiovascular diseases. Currently, cuff-based oscillometric sphygmomanometers are commonly used to monitor the systolic and diastolic blood pressure. However, this technique is discontinuous in nature and inconvenient for repeated measurements. Here we have proposed indirect measurement of blood pressure from photo-plethysmograms (PPG) simultaneously recorded from wrist and fingertip. The signals were recorded from 111 participants and different morphological features were obtained from PPG and its second derivative, acceleration plethysmograms (APG). Moreover, different measures of pulse transit time (PTT) and pulse wave velocity (PWV) were obtained from the recorded PPGs. Multi-layer Neural Networks were used to estimate the non-linear relationship between these features and systolic and diastolic blood pressures (SBP and DBP). Mean absolute errors of 6.77 and 4.82 mmHg were achieved in comparison with measurements from a validated commercial oscillometric sphygmomanometer. Feature analysis provided insight about the importance of features for estimating BP, and demonstrated that these features are not the same for SBP and DBP. Using the highest-ranked 15 and 13 features obtained from moving-backward algorithm the mean absolute errors were reduced to 5.31 and 4.62 mmHg for SBP and DBP. However, the optimum optimal feature sets provided by a genetic algorithm for estimating SBP/DBP led to the lowest mean absolute errors of 4.94/4.03. These results compared to previous studies and the available standards suggest that the method is a promising substitute for oscillometric sphygmomanometers which can be used conveniently for continuous monitoring of blood pressure.
关键词： Genetic algorithms,Non-obstructive blood pressure measurement,Multi-layer neural networks,Photo-plethysmography
更新于2025-09-23 15:23:52
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Research on multi-camera calibration and point cloud correction method based on three-dimensional calibration object
摘要： The single camera measurement system can’t obtain all the surface information of the object limited by the field of view, thus it can’t achieve complete measurement of the object. Multi-camera system can overcome this difficulty. But it is difficult to unify the coordinate system of distinct cameras. In order to solve this problem, a global calibration method of multi-camera system is proposed. A three-dimensional cube calibration object is designed. Every camera is only calibrated on one surface of the cube calibration object. Because different surfaces of the cube calibration object are in a unified world coordinate, the coordinates of the feature points on different surfaces are naturally in the unified world coordinate system. Thus global calibration can be completed by calibrating multiple cameras at the same time. In addition, to minimize the error of calibration, a correction method is proposed. The correction parameters are obtained by the deviation between the world coordinates and the reconstructed coordinates of the feature points on calibration object. The parameters are applied to the measurement to improve the accuracy of the whole point cloud. Experiments are carried out on a multi-camera measurement system, and the results show that the method proposed in this paper is effective and feasible.
关键词： Calibration,Measurement,3D calibration object,Fringe projection,Multi-camera
更新于2025-09-23 15:23:52
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Distribution measurement of permittivity by dividing the sample into multisection in the slotted cylindrical cavity
摘要： There are few papers to introduce the distribution measurement of material’s permittivity in the previous work, but the measurement is an important effort to effectively evaluate the inhomogeneity of material’s permittivity. In order to measure the distribution of the relative permittivity with small interval along sample rod, a multisection measurement model has been introduced. The sample is horizontally inserted into the slotted cylindrical cavity with TM0n0 working modes and passes through it to improve the measurement stability. During the measurement, the sample is divided into many sections, and each section is treated as a subsample for the distribution measurement of the permittivity. The traditional perturbation technology is combined with the field analysis of two subsamples in the cavity to calculate the permittivity of all subsamples from the effective permittivity. Based on the theoretical analysis of the simulation results from HFSS, partial error equation is established, and the absolute error of the multisection measurement model is less than 0.1. Besides, the horizontal movement device for the sample movement, support platform with a groove for the sample placement, and vertical cylindrical cavity for the measurement are employed to make up the test setup. Meanwhile, it can provide a stable and rapid measurement. Thus, a fiber reinforced plastic rod has been measured to verify the feasibility of the developed test setup.
关键词： multisection,cylindrical cavity,distribution measurement,relative permittivity
更新于2025-09-23 15:23:52
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Investigation on formation process of metal atomic filament for metal sulfide atomic switch by electrical measurement
摘要： We have studied the formation process of the metal atomic filament for the metal sulfide atomic switches by the electrical measurement. The switching between ON and OFF states of the atomic switch is controlled by the application of the bias voltage for the atomic switches. The SET (OFF→ON) and RESET (ON→OFF) voltages were investigated for the atomic switch where the Ag2S or Cu2S layer was sandwiched between the Pt and Ag or Cu electrodes. The SET and RESET voltages of the Ag/Cu2S/Pt and Cu/Ag2S/Pt were close to those of the Ag/Ag2S/Pt atomic switch, and different from those of the Cu/Cu2S/Pt atomic switch. These results indicated that the dominant chemical species of the making and breaking part of the metal filament were Ag, and that the source of the metal filament was both the sulfide layer and the metal electrode.
关键词： Atom switch,I-V measurement,Ion migration
更新于2025-09-23 15:23:52