Metal magnetic memory testing technology has been effectively used in stress concentration areas and micro-cracks detection of ferromagnetic metal components. However, due to the lack of profound theoretical basis and effective experimental research, the magnetic memory signal characteristics and magnetism quantitative relationship has not yet been determined. In this study, the full electronic potential magneto-mechanical model is established which is using the norm conserving pseudo-potential algorithm based on the first-principle. The quantitative relationship is then calculated between the stress concentration and the magnetic memory signal. The calculation results show that the changes of the wave function, which result from the stress concentration in the solid band, are the fundamental cause of the magnetic memory phenomenon, and atomic magnetic moment, lattice constant and the magnetic flux leakage signal strength linearly changes as a function of stress trend. As the stress concentration reached the critical stress point, the lattice structure was damaged, and the magnetic memory signal had undergone mutation. In this study, the experimental results are consistent with the theoretical calculation results.

The fractional order calculus can represent systems with high-order dynamics and complex non-linear phenomena using fewer coefficients. In this study the extended fractional Kalman filter is developed for the class of non-linear discrete-time fractional order systems using observations with multiple delays contaminated by additive white noise. For a wide class of practical applications, the time delay cannot be neglected. In the time delay integer order systems, a common approach is partial differential equation. This method is very difficult to solve. The authors’ approach is applied the reorganised innovation technique. As a result of the reorganised innovation sequence, the Kalman filtering problem with multiple delayed measurements is converted to filter of a delay-free system. In the rest of paper, the covariance matrix of the prediction error of the states is presented in the form of the novel Riccati equations. Finally, the solution of the Kalman filtering problem is obtained by applying the re-organised innovation sequence and Riccati equations. A numerical example is given to illustrate the effectiveness of the proposed scheme.

Polypropylene (PP), with low loss and high dielectric strength, is widely used as dielectric for the metallised film capacitor (MFC). The electric ageing and dielectric breakdown of the dielectrics under high-voltage stress is a major concern in the research on polymer materials. Surface discharge and flashover may happen on the PP film between the metallised segments in MFCs, which can influence the dielectric property and cause the breakdown of insulation. Fluorination is effective on modifying the surface characteristics of the polymers, meanwhile retaining the bulk properties. The effects of direct fluorination on the surface charge and flashover characteristics of PP films under pulse voltage are experimented in this study. The samples with different fluorination time were prepared. Surface charging was performed by corona discharge using repetitive pulse power, which was applied to measure the surface flashover voltage as well. The experimental results indicated that the surface charge and flashover voltage were strongly correlated with the charge polarity, pulse frequency and fluorination time. It was suggested that the fluorination of certain time could significantly improve the decay rate of the surface charge as well as the surface flashover voltage of PP samples.

The shielding effectiveness (SE) of a small size perforated shielding enclosure is analysed in this study. For an ideal model, the numerical results by modal method of moment (MoM) match well with the simulation results by a finite integration technique simulator CST-MWS. When adding some detailed structures such as reinforcing rib structures to the ideal model, the modal MoM is not suitable. To verify whether the simulation results by CST on the detailed model are correct or not, the physical enclosure is tested in a microwave anechoic chamber. To measure the SE under the height limitation of the enclosure, an L-shaped antenna is designed and used as the receiving antenna. The measurement results and the simulation results by CST on SE are pretty close.

The kinematics of the bearing is erratic and random in nature and requires timely attention to avoid any catastrophic failure. In this study, the authors have proposed and analysed the amplitude and frequency modulated signals emanating from the bearing using four steps, i.e. standardisation, empirical mode decomposition, principal component analysis (PCA), envelope and cepstral envelope techniques. First, the standardised frequency modulated signals are decomposed into stationary non-linear modes called intrinsic mode functions (IMFs). In this approach, PCA is applied on the decomposed IMFs to produce uncorrelated signals. The uncorrelated signals whose value is above the average kurtosis are recombined to form a modified signal. The modified signal incurred from the approach is followed by spectrum, envelope, cepstrum, and cepstral envelope techniques to identify the features. It is observed this proposed combined approach effectively and adaptively identifies the inner/ball faults, shaft rotating frequency and corresponding harmonics in ease with least utilisation of IMFs.

An efficient and simplified procedure is proposed for the reduction of high-frequency oscillations and erroneous magnitude peaks in electromagnetic transient simulations in power transmission systems modelled by the lumped electric parameters approach. This procedure consists of the inclusion of analogue filters in the equivalent representation of multiconductor transmission lines without modifying its electromagnetic propagation characteristics. The analogue filter modelling is conducted as a function of the line length and line parameters. The proposed simulation methodology is applied directly in the line modelling, which means that the filtering/correction process represents a real-time process during simulations, without post-processing filtering techniques using digital filters or variations in the solution methods. The results obtained directly in the time domain by the proposed modelling/simulation methodology are compared with simulations obtained from well-established line models using the numerical Laplace transform and the Bergeron method.

The authors propose an intensity modulation-based fibre optic vibration sensor (FOVS) using an aperture within a proof mass. It consists of an optical collimator, a mass-spring structure, a mirror, and a rectangular aperture. They verify its feasibility via experimental demonstration. For the feasibility test, they implement three lab-based prototype FOVSs with different natural frequencies and measure each FOVS's frequency response according to the base vibration and sensitivity. The experimental results for three lab-based prototype FOVSs show the sensitivities of 163, 183, and 206 mV/g, the minimum detectable accelerations of 0.082, 0.086, and 0.082 mg, and the dynamic ranges of 18–45, 26–52, and 20–120 Hz, respectively. They also experimentally demonstrate its remote sensing and multipoint sensing characteristics. The proposed FOVS has the virtues of easy controllable sensitivity and dynamic range, simple structure, and remote sensing and multipoint sensing characteristics.

The light-addressable potentiometric sensor (LAPS) is one sort of biochemical sensor based on semiconductor principle. To improve the performance of LAPS, a novel designed silicon substrate with micro blind holes structure used for LAPS is presented in this study. In this structure, a great number of micro blind holes are constructed on the back surface of substrate by silicon wet etching technology. When light illuminating the bottom of substrate, because of the light trapping effect, multiple reflection on surface of substrate increases the absorption of light, which will remarkably enhance the photoelectric conversion efficiency. In this research, LAPS chips with 300 μm thick substrate, 270 μm thick substrate, 200 μm thick substrate, and micro blind holes substrate were constructed. The performance of these LAPS, such as amplitude of photocurrent, sensitivity, linearity, signal to noise ratio (SNR) were evaluated, and the results showed that, constructing micro blind holes structure on back surface of substrate illuminated by light can remarkably increase the amplitude of photocurrent, sensitivity, linearity and SNR, and additionally maintain the mechanical strength of substrate, which means the structure is an effective way to improve performance of LAPS.

Capacitive fringing field sensors have been used in some non-contact detections. A lateral displacement measurement method based on fringing field capacitors is investigated by simulations and experiments in this study. For the conventional interdigitated structure, the periodic electric field distribution is obtained because of those alternate electrodes, which produces periodic capacitances along with the target displacement. However, it is inconvenient to construct measurement systems due to the non-linear capacitance output. A dentate structure is proposed to improve the output characteristics of displacement measurement. The periodic uniform electric field is achieved by the dentate electrodes, which brings the linear capacitance variation in every period. Indium–tin oxide film was employed to fabricate a prototype, and the experiment results indicate that the dentate structure can be used in the lateral displacement measurement for its linear output characteristics.

Proper mitigation of power quality disturbances (PQDs) requires a fast, accurate and highly noise immune classification technique. This study, therefore, presents fractional Fourier transform (FRFT) based feature extraction as a new technique for classification of PQDs. FRFT is a generalised version of Fourier transform (FT) with an additional order control and can give time, frequency and intermediate time-frequency representations for a signal. The order control offers multi-domain feature extraction, such that most robust feature matrix is utilised for classification under any condition. An expression is derived for the optimal classification order corresponding to maximum overall accuracy. Based on IEEE-1159 standards, 15 PQDs are simulated and a database of pure and noisy signals is prepared. Features extracted from FRFT processed signals are tested with decision trees (DTs) and bagging predictors (BPs). The proposed technique shows better performance in most of the cases, when compared with Stockwell transform based classification under similar conditions. The classification accuracies of FRFT-DT and FRFT-BP are impressive even with significant reduction in training and features. Further, a validation using real PQDs obtained from an experimental setup is shown. The corresponding results closely resemble the simulation outcomes.

A method is proposed for determining the correlated and uncorrelated parts of phase noise spectra (PNS) of two continuous wave radio signals of different frequencies, ω ₁ and ω ₂. The PNS of the two signals and of mixed signals are measured. The PNS are modelled as having a correlated part that is the same for both signals, except for a multiplicative factor, and uncorrelated parts, that are different for the two signals. A property of the model that the PNS of some mixing products are linear combinations of the PNS of the signals at ω ₁, ω ₂, and ω ₁ − ω ₂ is experimentally verified. The difference of the PNS at ω ₁ + ω ₂ and ω ₁ − ω ₂ is proportional to the correlated part of the PNS and is a part of auxiliary functions that are used for finding the multiplicative factor and the correlated, partly correlated, and uncorrelated phase noise at different offset frequencies. A conventional spectrum analyser was used to characterise two signal generators, a phase-coherent and a non-phase-coherent one. For the phase-coherent generator the phase noise of two signals was found to be correlated for offset frequencies below 10 Hz, partly correlated for 10 Hz–1 kHz and uncorrelated above 1 kHz.

In this study, a graphical modelling approach of the pinched hysteresis loops exhibited by memristors is presented. This method provides a tool to emulate the hysteresis loop pinched at the origin, with the lobe area varying with the excitation frequency. The direction of the pinched hysteresis loop can be controlled. This graphical modelling method provides an alternative to describe the behaviour of memristors without deriving the coupled non-linear differential equations typically required for physical memristors. The method has been successfully applied to model the Hewlett–Packard memristor device.

Plastic deformation may occur in metal structure during the manufacturing and service process which will affect the service life of equipment. This study proposes a radio-frequency method resulting from electromagnetic properties variation for metal plastic deformation monitoring. There is a clearly correlation between the macroscopic electromagnetic properties and the plastic deformation of materials. The energy distribution of radio-frequency varies obviously due to electromagnetic properties variation according to the simulation results. Meanwhile, the reflection features are mainly affected by permeability and electric conductivity of the material. Experiments have been conducted to verify simulation results. The results of the experiments indicate that the reflected radio-frequency signal strength decreases with progressive plastic deformation in metal, which has been in conformity with simulations.

A system-level method to validate previous calibration results for low-precision inertial measurement unit (IMU) in personal navigation system (PNS) is proposed. Micro-electro mechanical systems inertial sensors have gained popularity in PNS because they are small, compact and inexpensive. However, the calibration results of these sensors which belong to low-grade IMU will change as time and environment change. It is significant to know whether previous calibration results are reliable for navigation after a long time. However, users have no devices such as turntable to validate calibration results precisely. Therefore, a triple two-position method without any external aiding is presented to validate the bias errors relative to previous calibration results. If the errors are less than the bias range which is a priori information calculated in previous lab test, previous calibration results are available, otherwise the calibration results is invalid. The two-position method based on the strong tracking filter, which takes velocity and azimuth errors as observations, can estimate the bias and scale factor errors of accelerometers and gyros. The experimental results show that the proposed method is effective, compared with the conventional 24-position calibration method on the turntable and the system-level multi-position method usually used for high-grade IMU.

Ionised field strength on the ground level is one of fundamental electromagnetic environment parameters of high voltage direct current transmission lines. Field mill is generally employed to measure the ground-level ionised field. In order to reduce the field distortion caused by the field mill probe on the ground, a measurement method of the ionised field with a hat-shaped additional electrode is presented in this study. Ionised field distribution on the probe with the hat-shaped electrode is analysed through both calculations and measurements. The ionised field is computed by the upstream finite element method (FEM) and is measured between a corona wire net and a parallel grounded plate. Experimental results demonstrate that the relative error between measurements and calculations is approximately 3%. The field distortion can be ameliorated effectively by the proposed method.

The size measurement of large hot forgings plays an important role during the process of production. In order to realise the size measurement of large forgings in thermal state, an automatic size measurement method for large forgings based on the scattering of rough surface is proposed in this study. In the method, the theory of random facets is applied to research the characteristic of laser scattering on the surface of hot forgings. The model of laser scattering on the random rough surface of cylinder is built. According to the model, the edges of forgings can be detected and the size of forgings can be got. First, the charge coupled device (CCD) camera and the green laser are driven by the motor to move on the guide rail. The real-time images of forgings are captured by CCD camera and the positional information of laser is acquired by pulse coder. Then according to the change of the intensity of the scattered light, whether the laser line is on the edge of forgings is decided. Second, the positional information of two edges is got by pulse coder and the size of forgings is figured out by the positional information. Finally, the feasibility of the method is verified by the experiment of size measurement.

Piezoelectric polymer cellular films have been studied since 1986. In recent years, they have improved the potential applications due to materials progress. Cellular polypropylene (PP) polymers are characterised by its high piezoelectric coefficient d ₃₃ in comparison with other piezoelectric materials such as ceramics. One of the advantages of these films is their elasticity and flexibility. This study is based on the optimisation of the activation process and characterisation results of polymer cellular films. Samples were made of a commercially available PP film which was modified by a thermal biaxial stretching. Coefficient d ₃₃ was measured by a quasi-static method and the frequency characterisation was made for validating all characterisations and their relations. Transducer coefficients around 700 pC/N were obtained with polymer cellular PP films with silver coating electrodes, activated by corona discharge. An approximation of the surface charge density in the polymer voids was obtained with a mathematical model. Thermal stability was checked by thermally stimulated discharge currents (TSDCs) showing a relationship between the TSDC and the coefficient d ₃₃. Time stability was determined after 3000 h ageing, and finally was obtained a resonance frequency by interferometry measurement.

Pinched hysteresis loops (PHLs) can be clockwise, counter-clockwise, self-crossing and non-self-crossing. While it is difficult to differentiate these features from the measured PHLs on the oscilloscope, this study shows that PHL exhibits different forms of symmetry. Self-crossing PHLs display reflection symmetry and non-self-crossing ones display point symmetry. These features are confirmed with practical measurements based on the memristor characteristics of Hewlett-Packard (self-crossing) and of a discharge lamp (non-self-crossing). It is shown that the symmetry graph is a useful tool to identify the features of PHLs.