Redundancy Analysis of Capacitance Data of a Coplanar Electrode Array for Fast and Stable Imaging Processing

A coplanar electrode array sensor is established for the imaging of composite-material adhesive-layer defect detection. The sensor is based on the capacitive edge effect, which leads to capacitance data being considerably weak and susceptible to environmental noise. The inverse problem of coplanar array electrical capacitance tomography (C-ECT) is ill-conditioning, in which a small error of capacitance data can seriously affect the quality of reconstructed images. In order to achieve a stable image reconstruction process, a redundancy analysis method for capacitance data is proposed. The proposed method is based on contribution rate and anti-interference capability. According to the redundancy analysis, the capacitance data are divided into valid and invalid data. When the image is reconstructed by valid data, the sensitivity matrix needs to be changed accordingly. In order to evaluate the effectiveness of the sensitivity map, singular value decomposition (SVD) is used. Finally, the two-dimensional (2D) and three-dimensional (3D) images are reconstructed by the Tikhonov regularization method. Through comparison of the reconstructed images of raw capacitance data, the stability of the image reconstruction process can be improved, and the quality of reconstructed images is not degraded. As a result, much invalid data are not collected, and the data acquisition time can also be reduced

Data-driven XGBoost model for maximum stress prediction of additive manufactured lattice structures

Abstract Lattice structures created using additive manufacturing technology inevitably produce inherent defects that seriously affect their mechanical properties. Predicting and analysing the effect of defects on the maximum stress is very important for improving the lattice structure design and process. This study mainly used the finite element method to calculate the lattice structure constitutive equation. The increase in defect type and quantity leads to difficulty in modelling and reduces calculation accuracy. We established a data-driven extreme gradient enhancement (XGBoost) with hyperparameter optimization to predict the maximum stress of the lattice structure in additive manufacturing. We used four types of defect characteristics that affect the mechanical properties—the number of layers, thick-dominated struts (oversize), thin-dominated struts (undersizing), and bend-dominated struts (waviness)—as the input parameters of the model. The hyperparameters of the basic XGBoost model were optimised according to the diversity of the inherent defect characteristics of the lattice structure, while the parameters selected by experience were replaced using the Gaussian process method in Bayesian optimization to improve the model’s generalisation ability. The prediction datasets included the type and number of defects obtained via computer tomography and the calculation results of the finite element model with the corresponding defects implanted. The root mean square error and R-squared error of the maximum stress prediction were 17.40 and 0.82, respectively, indicating the effectiveness of the model proposed in this paper. Furthermore, we discussed the influence of the four types of defects on the maximum stress, among which the thick strut defect had the greatest influence

Defect Detection of Adhesive Layer of Thermal Insulation Materials Based on Improved Particle Swarm Optimization of ECT

This paper studies the defect detection problem of adhesive layer of thermal insulation materials. A novel detection method based on an improved particle swarm optimization (PSO) algorithm of Electrical Capacitance Tomography (ECT) is presented. Firstly, a least squares support vector machine is applied for data processing of measured capacitance values. Then, the improved PSO algorithm is proposed and applied for image reconstruction. Finally, some experiments are provided to verify the effectiveness of the proposed method in defect detection for adhesive layer of thermal insulation materials. The performance comparisons demonstrate that the proposed method has higher precision by comparing with traditional ECT algorithms

Mid-long term runoff forecasting model based on RS-RVM

In view of the two key problems in hydrological mid-long term runoff forecasting-the selection of key forecasting factors and the construction of forecasting models, an analysis is made on, taking Danjiangkou Reservoir as an example, the basis of preliminarily identifying the sea-air physical factors such as atmospheric circulation, sea surface temperature and Southern Oscillation, et al. The rough set theory is used to establish the data decision table and reduce the factors, and the relevance vector machine method is adopted to establish the mid-long term runoff forecasting model based on reduced factor set. Meanwhile, this paper simulates and predicts the amount of runoff of the reservoir in September and October during the autumn floods from 1952 to 2008, and makes comparison with the model adopting support vector machine. The result shows that the relevance vector machine has better robustness and generalization performance. According to the standard of 20% annual variation, the simulation accuracy of September and October reaches 93.9% and 95.9%, respectively, and the accuracy of the trial forecasting is all up to standard. Moreover, this model better reflects the characteristics of ample flow period and low water period of the forecasting years

Mid-long term runoff forecasting model based on RS-RVM

In view of the two key problems in hydrological mid-long term runoff forecasting-the selection of key forecasting factors and the construction of forecasting models, an analysis is made on, taking Danjiangkou Reservoir as an example, the basis of preliminarily identifying the sea-air physical factors such as atmospheric circulation, sea surface temperature and Southern Oscillation, et al. The rough set theory is used to establish the data decision table and reduce the factors, and the relevance vector machine method is adopted to establish the mid-long term runoff forecasting model based on reduced factor set. Meanwhile, this paper simulates and predicts the amount of runoff of the reservoir in September and October during the autumn floods from 1952 to 2008, and makes comparison with the model adopting support vector machine. The result shows that the relevance vector machine has better robustness and generalization performance. According to the standard of 20% annual variation, the simulation accuracy of September and October reaches 93.9% and 95.9%, respectively, and the accuracy of the trial forecasting is all up to standard. Moreover, this model better reflects the characteristics of ample flow period and low water period of the forecasting years