Robust S-transform based on L-DFT

Time-frequency representations of signals obtained by the S-transform can be very sensitive to the presence of α- stable noise. An algorithm for the robust S-transform is introduced. The proposed scheme is based on the L-DFT. The results of conducted numerical analysis show a significantly enhanced performance of the proposed scheme compared to the standard S-transform. © 2010 The Institution of Engineering and Technology

Fractional Fourier transform as a signal processing tool: An overview of recent developments

Fractional Fourier transform (FRFT) is a generalization of the Fourier transform, rediscovered many times over the past 100 years. In this paper, we provide an overview of recent contributions pertaining to the FRFT. Specifically, the paper is geared toward signal processing practitioners by emphasizing the practical digital realizations and applications of the FRFT. It discusses three major topics. First, the manuscripts relates the FRFT to other mathematical transforms. Second, it discusses various approaches for practical realizations of the FRFT. Third, we overview the practical applications of the FRFT. From these discussions, we can clearly state that the FRFT is closely related to other mathematical transforms, such as timefrequency and linear canonical transforms. Nevertheless, we still feel that major contributions are expected in the field of the digital realizations and its applications, especially, since many digital realizations of the FRFT still lack properties of the continuous FRFT. Overall, the FRFT is a valuable signal processing tool. Its practical applications are expected to grow significantly in years to come, given that the FRFT offers many advantages over the traditional Fourier analysis. © 2010 Elsevier B.V. All rights reserved

An FEA model study of spectral signature patterns of PM demagnetisation faults in synchronous PM machines

This work reports a finite element analysis (FEA) model study of the stator current spectra of a commercial permanent magnet (PM) AC machine operating with rotor PM demagnetisation faults. A range of PM uniform and local demagnetisation fault scenarios at different severity conditions are examined. The aim of this study is to investigate the extent to which different modes of PM demagnetisation could be distinguished by inspecting the spectral signature patterns these generate in the stator current signal. To this end, a generalised mathematical characterisation of PM fault spectral signature in the stator current is examined and a 2D FEA software used to establish a model of the studied PM machine design. The FEA model was employed to predict the current signal spectral signature patterns of a range of different PM demagnetisation faults. These are then correlated with those arising from the derived expressions to examine whether the predicted and expected spectral trends are in agreement and whether their observation as the potential to provide diagnostic information

On potential to improve DCT-based denoising with local threshold

International audienceThis paper deals with image denoising under standard assumption of additive white Gaussian noise presence. We study potential of denoising effectiveness for a typical representative of orthogonal transform based techniques - a filter based on discrete cosine transform (DCT) with fixed size blocks. It is shown that its performance depends upon many different factors where threshold setting is of prime importance. Possibility of setting individual threshold for each block is considered and it is demonstrated that it opens a certain perspective for further improving performance compared to known versions of DCT-based filter. Performance comparison is done for several denoising techniques including the benchmark BM3D filter. It is shown that potentially DCT-based filter with properly set thresholds adapted to block properties can perform the same or sometimes even better than BM3D filter. © 2018 IEEE

Influence of Irrigation and Application of Kaolin on Canopy Temperature of Peppers Measured by Infrared Thermography

This paper presents measurements of temperature of the above-ground parts of peppers plants using a thermal imager in order to determine the water regime. The experiment was set as a bifactorial block system, with three replications, in the open field on a carbonate chernozem soil in Stara Pazova (40 km North from Belgrade, Serbia). Three treatments of irrigation regimes, with and without the application of 5% kaolin suspension (Surround WP), were monitored. Kaolin (Surround WP) was applied by spraying of the part of the plant above the ground seven times during the vegetation seasons between April and September 2011. All the treatments that have been applied with kaolin have a sign K. Treatment with full irrigation (F, FK) when 100% is covered by ETc (evapotranspiration), a treatment with deficit irrigation (R, RK) with 80% of the ETc and a treatment with deficit irrigation (S, SK) with 70% of ETc. The measurements of plant temperature were carried out with an infrared camera (FLIR, T335) seven times during the vegetation season. From each treatment a sample of 15 measurements was taken and the measurements were used for determination of average temperature of the plant on every level of irrigation. Soil moisture was measured by gravimetric method in 7 day intervals, up to 0.6 m and every 0.2 meters. Temperature measurement data show that the F treatment plants were the coldest with the average temperature of 21.29 degrees C, followed by the R and S treatment with the average temperature of 21.79 degrees C and 22.26 degrees C, respectively. Average temperatures of FK, RK and SK treatments were as follows 21.58 degrees C, 22.11 degrees C and 22.47 degrees C. Plants treated with kaolin had higher temperatures on average, but for the precise conclusion more measurements are needed due to the variability of canopy temperature. Observing the values of soil moisture over all treatments, it can be assumed that kaolin has a role in reducing water consumption. It is also confirmed by CWSI (Crop Water Stress Index). Relationships of available soil water (ASW) and the CWSI show differences between all irrigation and kaolin treatments. The values of CWSI are the lowest and almost never more than zero in fully irrigated treatments (F and FK), in R and RK treatments they are slightly higher, and the highest in S and SK treatments. The values of CWSI are lower in the treatments without kaolin application. Obtained results show an effect of irrigation regime on the canopy temperature of peppers, while the influence of kaolin is small