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In order to improve the quality of reconstructed images in electrical capacitance tomography (ECT), the image reconstruction method based on compressed sensing for ECT is studied. First, the traditional discrete Fourier transform and discrete cosine transform are used as a sparsity basis to make the grey vectors of the typical two-phase flow distributions sparse. The energy loss of the sparse signals under different sparsity degrees is calculated, and the effect of energy loss on the quality of reconstructed images is studied. Then, using the natural sparsity of the original signal, an improved orthogonal matching pursuit algorithm for ECT image reconstruction is proposed. There are two main improvements in the proposed algorithm. First, multiple columns instead of one column in each iteration are selected for improving the reconstruction speed. Second, a regularisation solution instead of the least-squares solution is used for improving the adaptability to ill-posed inverse problems. Simulation and experimental tests are carried out and the results show that the proposed method can effectively improve the reconstructed images quality, and on the whole, obtain better reconstruction results than the Landweber iteration algorithm, the Tikhonov regularisation algorithm, and the gradient projection for sparse reconstruction algorithm.

A hotspot in a grain bulk is a localized high temperature zone and normally spoilage begins in this location. The reconstruction strategies of a 3D space are investigated to detect hotspots in grain bulk by acoustic tomography. Since the size of a grain silo is usually large, the whole space to be reconstructed is divided into three blocks and two reconstruction ways: whole reconstruction and block reconstruction, are considered. Three sound ray path selection rules including intra-block, generalized intra-block and unrestricted paths are investigated. These reconstruction ways and path selection rules are combined into four reconstruction strategies. To fully compare the abilities of these strategies in detecting hotspots in grain bulk, 2304 single-hotspot temperature fields and a three-hotspot temperature field are reconstructed by using noise-free and noisy travel-time data. Based on reconstruction results and difficulty in travel-time measurement, the strategy using whole reconstruction way and generalized intra-block paths is the optimal choice.

Image reconstruction of electrical capacitance tomography (ECT) belongs to solving an inverse problem. The first step to solve the inverse problem is to establish a forward problem model which determines the capacitance values for known permittivity distribution. There are three main methods for ECT forward problem modelling. The first is based on the sensitivity definition. The second is based on the multiple linear regression (MLR) method. And the third is based on the electric field strength (EFS). In this study, comparisons of these three modelling methods for the forward problem in three-dimensional ECT are given in terms of modelling error, computational time and reconstruction quality. Comparison results show that the MLR method generates smallest modelling error and better reconstruction quality, especially for the very complex geometry with objects in the shape of letters H and U. However, the EFS method is significantly better than the other two methods in computational time.

The image reconstruction for electrical capacitance tomography is a non-linear, underdetermined and ill-posed inverse problem. It is difficult to obtain a reconstructed image with high quality, especially in the case of three-dimensional (3D) reconstruction. An iterative image reconstruction algorithm with fuzzy thresholding is proposed in this study. The threshold value in each iteration is generated by minimising the measure of fuzziness of current reconstructed image. The algorithm proposed is tested by the noise-free and the noise-contaminated capacitance data. Extensive computer simulations demonstrate that the fuzzy thresholding can reduce low grey-level artefacts effectively. As a result, the spatial error, volume error, permittivity error and scattered artefacts of the reconstructed image are reduced obviously; not only that, the number of iterations needed to obtain a good reconstruction result is decreased greatly. The result of 3D reconstruction of a H-shape object verifies the effectiveness of the fuzzy thresholding further.

Electrical capacitance tomography (ECT) is a relatively mature non-invasive imaging technique that attempts to map dielectric permittivity of materials. Recently, 3D ECT has gained interest because of its potential to generate volumetric images. The study of a fast and accurate image reconstruction algorithm is a challenge task, especially for 3D reconstruction. In this paper, we propose an improved Landweber iteration algorithm. We incorporate an additional acceleration term into the cost function and apply an adaptive threshold operation to the image obtained in each iteration for reducing artefacts. The algorithm proposed is tested by the noise-free and noise-contaminated capacitance data. Sensitivity matrixes and capacitance data of a 3D ECT sensor are obtained by using the finite element (FE) method. Extensive simulations in 3D reconstruction are carried out. The results verify the effectiveness of these improvements. Both the reconstruction time and the artefacts in the reconstructed image are reduced obviously. The experimental results of 3D reconstruction of objects in the shape of letters U and L confirm the effectiveness of the proposed algorithm further.

Acoustic temperature measurement method uses the dependence of sound speed in materials on temperature along the sound propagation path. The measurement of acoustic wave travel-time in grain bulk has been researched in this paper for monitoring grain temperature by acoustic method. A measurement system of sound travel-time based on the virtual instrument is described. Transmitted signals include chirp and maximum length sequence (MLS). Travel-time of sound waves is calculated by cross-correlating the signals received by two microphones. Experiment results show that stable measurement values of sound travel-times in grain can be obtained by MLS combined with cross-correlation. Compared with chirp, MLS can provide much higher measurement accuracy.

Two kinds of sensor structures for 3D direct capacitance imaging are presented. 12 electrodes are arranged in three planes each with four electrodes. Every four electrodes on each plane are rotated 45° (sensor 1) or 0° (sensor 2) with reference to the previous. A comparative study between the two sensors shows that although the difference in sensor’s sensitivities and outputs is obvious, the difference in reconstruction images isn’t apparent, at least for some permittivity distribution. The output range of sensor 1 is smaller than that of sensor 2, thus sensor 1 is better than sensor 2 in terms of the design of a capacitance measuring circuit. Both sensors can achieve 3D direct capacitance imaging with a good axial resolution.

Capacitive grating sensor can be used to measure the length, as its capacitance changes with the shift difference. There are several measuring systems consisting of capacitive sensor, but all their basic principles are capacitive differential sensing. The structure, principles and characteristics of capacitive sensors are introduced in this paper. Especially, we designed a high-resolution electronic length measuring system based on Capacitive Grating Sensor. And the measurement error of the system and the reason are analysed. For this system, the measuring range is from 0 to 500mm, the resolution is 1um, the indication error is 5um, the measuring speed is 1m/s. Accurate measurement on account of large displacement is achieved with the system.

A photoelectric hybrid coupling current transformer has a lot of obvious advantages over a traditional electromagnetic current transformer. It is very valuable in practical application for the electricity protection and signal measurement of power system. This paper will introduce the design of a new type of Rogowski coil, integral and filter circuit, the realization of A / D timing and Manchester decoding with CPLD. The test results have proven that the proposed system design can perform the expected functionality of photoelectric coupling current transformer. It can better meet the power system’s requirements in the high-speed data processing, large data quantity and complex operation. It also has merit of being simple in structure and easier for modification. It is worth of further investigation.

Acoustic temperature field reconstruction is an illposed problem. This means especially that their solution is unstable under data perturbations. Numerical methods that can cope with this problem are the so-called regularization methods. The choice of a regularization parameter has an important influence on reconstruction accuracy. In this paper, a 3D acoustic temperature field reconstruction algorithm is proposed. It uses a new criterion for choosing the regularization parameter, which makes a good compromise between de-noise and detail reconstruction of the temperature field. Reconstructions of a single-peak temperature field by using simulated travel-times corrupted with different level noises demonstrate that the new algorithm has high reconstruction accuracy and good anti-noise ability.

The main work of this paper is to research direct 3D ECT imaging technology. Based on the finite element modeling of a 3D ECT imaging sensor, the sensor sensitivity matrix and simulation data of capacitance measurements were obtained. And then 3D images were reconstructed directly by using linear back projection (LBP), traditional Land Weber iteration and improved Land Weber iteration methods. The reconstruction results show that the images obtained by the improved Land Weber iteration method proposed in this paper are much better than those by LBP and traditional Land Weber iteration method.

—PSD(Position Sensitive Detector) is the sensorwhich can provide continuous data of location, when itssurface is scanned by the laser light. The 3D Spatial Localizingtechnology is achieved by dual 2D PSD sensors. The principleand the characteristics of 2D PSD are described in detail, andthe spatial localizing algorithm of PSD array formed by twoaxis- parallel-placed 2D PSD is researched. Using thealgorithm, we design a reliable system on the targeting Spatiallocation. The measurement error of the system and the reasonare analysed. Through experiments, we know that theLocalizing resolution of the system is 1um and the error is lessthan 5um. The system has many features, such as highresolution, fast responsive time ,strong anti-interference,thecircuit to deal with simply, convenient interface. so it is anideal non-contact Spatial Localizing system.