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The conventional treatment of thermal noise is based on Nyquist’s theorem. This theorem has only been derived for linear, reciprocal (we define “reciprocal networks” as networks that are built of reciprocal network elements) networks. In this paper a description of thermal noise in reciprocal non‐linear RLC networks is presented. This description is derived from first principles, i.e. from a direct application of non‐equilibrium thermodynamics (irreversible thermodynamics) to electrical networks. As an example, the class of “complete” non‐linear networks is considered. Using the idea of equivalent n‐ports, the theory’s extension to certain classes of transistor circuits should be possible.

This article is an edited extract from a new book ‘Image Analysis: Principles and Practice’ about to be published by Joyce Loebl, the image analysis equipment company.

The purpose of this paper is to present an imperceptible and robust watermarking algorithm with high embedding capacity for digital images based on discrete wavelet transform (DWT) domain.

First, the watermark image is scrambled using chaotic sequence and mapped to avoid the block effect after embedding watermark into the host image. Then, the scrambled watermark is inserted in LH₂ and HL₂ sub‐bands of the DWT of the host image to provide a good tradeoff between the transparency and the robustness of watermarks.

This paper presents experimental results and compares the results to other methods. It can be seen from the comparison that this method can obtain a better performance in many cases.

One of the main differences of this technique, compared to other wavelet watermarking techniques, is in the selection of the wavelet coefficients of the host image. When performing second level of the DWT, most methods in the current literature select the approximation sub‐band (LL₂) to insert the watermark. The technique presented in this paper decomposes the image using DWT twice, and then obtains the significant coefficients (LH₂ and HL₂ sub‐bands) of the host image to insert the watermark.

The purpose of this paper is to provide a brief introduction of the finite difference based parabolic equation (PE) modeling to the advanced engineering students and academic researchers.

A three-dimensional parabolic equation (3DPE) model is developed from the ground up for modeling wave propagation in the tunnel via a rectangular waveguide structure. A discussion of vector wave equations from Maxwell’s equations followed by the paraxial approximations and finite difference implementation is presented for the beginners. The obtained simulation results are compared with the analytical solution.

It is shown that the alternating direction implicit finite difference method (FDM) is more efficient in terms of accuracy, computational time and memory than the explicit FDM. The reader interested in maximum details of individual contributions such as the latest achievements in PE modeling until 2021, basic PE derivation, PE formulation’s approximations, finite difference discretization and implementation of 3DPE, can learn from this paper.

For the purpose of this paper, a simple 3DPE formulation is presented. For simplicity, a rectangular waveguide structure is discretized with the finite difference approach as a design problem. Future work could use the PE based FDM to study the possibility of utilization of meteorological techniques, including the effects of backward traveling waves as well as making comparisons with the experimental data.

The proposed work is directly applicable to typical problems in the field of tunnel propagation modeling for both national commercial and military applications.

The purpose of this paper is to present a double‐sided tubular linear machine layout direct‐drive applications, with particular focus on wave‐energy conversion. The paper documents both the computational and mathematical analysis of this novel machine layout.

The selection and finite‐element optimisation of the permanent‐magnet array is presented. The machine is then modelled using magnetic circuit theory. By simultaneously solving the system of equations, a demonstrative design is developed and simulated so as to validate the mathematical model and compare the performance of the new layout with a traditional layout.

A surface‐mounted magnetic array, with unshaped‐poles, is most suitable for the proposed layout. The mathematical model exhibits a suitable level of accuracy for design and analysis purposes. The calculated resultant force differs from the FEA calculation by 1.85 per cent. A higher force‐density is exhibited by the proposed layout, when compared with flat layouts, with a reduction of 36.5 per cent in the spatial footprint and magnetic material of the machine.

Although the research is focused on the application of wave‐energy conversion, the techniques are application‐independent. However, certain design decisions should be reviewed for other applications.

The practical implementation of such a machine poses many mechanical obstacles. These have been solved in theory, and are being implemented at the time of writing.

The combination of a double‐sided and a tubular layout has not previously been researched. This research fills that void and provides designers with the technical background and a mathematical model for development of such devices.

Deep learning (DL) technology is used to design a voice evaluation system to understand the impact of learning aids on DL and mobile platforms on students’ learning behavior.

DL technology is used to design a speech evaluation system.

The experimental results show that the speech evaluation system designed has a high accuracy rate, the highest agreement rate with manual evaluation of pronunciation is 89.5%, and the correct speech recognition rate is 96.64%. The designed voice evaluation system and the manual voice rating system have a maximum error rate of 2%. The experimental results suggest that it is necessary to further optimize the learning aids for mobile platform. The learning aids of the mobile platform need to be further optimized to promote the improvement of student learning efficiency.

The results show that the speech evaluation system designed has good practical application value, and it provides a certain reference value for the future study of learning tools on DL.

The purpose of this paper is to produce a critical history of MP3 technology in an effort to show how its stature as the digital music format of choice had nothing to do with music or associated industries and that its configuration as a product to be bought and sold was unintended.

The approach is reminiscent of Michel Foucault's critical histories, which sought to problematise our current understanding of existing cultural arrangements by unearthing the conditions that made the production of knowledge and their accompanying artefacts possible.

The paper documents how MP3s emerged by outlining the conditions that made its production viable, showing how before MP3s were profiled as commodities to be bought and sold online, the composite of technologies making up the standard MPEG1‐Layer III were objects of knowledge within the fields of electrical engineering and psychoacoustics, and later a process of compression used mainly by audio broadcasting professionals. The paper concludes by examining MPEG1‐Layer III's reconstitution as MP3: its formal configuration and valuation, first as a license for the broadcasting industry to compress sound and then as a “free‐ware” application distributed online.

The paper problematises the taken for granted status of commodities, in this case, MP3s, as digital music to be bought and sold, by revealing how they emerged. At a more parochial level, it produces a competing history of MP3 technology which until now has not been told.

Most systems have a non-linear (NL) behavior and measured signals reflect this non-linearity such that in general they are composed with more than one sinusoidal component. NL analysis methods represent an option for analyzing such signals, however these methods have been developed for single frequency signals, this forces to implement a components separation procedure before performing the signal analysis. The purpose of this paper is to present a new method for analyzing multi-component signals that allows calculating amplitude, frequency and damping constants of the contained sinusoidal components. The method is able to simultaneously identify the different components within a detection bandwidth without previous separation of mono-components, as needed for most methods in used today.

The method proposed in this work characterizes sinusoidal signals determining their amplitude, frequency and damping constant. This method is based on transforming from the time domain to the z-domain an oscillatory signal that may or may not possess damping. Since frequency and damping of a signal can be determined knowing its z-domain poles, using the signal in z-transform domain an equations system to find the signal poles can be written.

From the results it can be concluded that the proposed method is reliable and consistent. One quality of the method is its short delay, when the procedure starts there is a delay equal to the time needed to accumulate four samples for each detectable frequency in order to perform the first calculation, after this, the algorithm can deliver a result at each sampling instant. This short delay and the low complexity of the algorithm can permit using the method in real time applications.

The proposed method is able to determine frequencies, damping constants and amplitudes of the components of a signal without a previous separation of mono-components, in contrast with other methods that require filter banks tuned using a previous knowledge of the signal. Moreover unlike techniques such as the Hilbert-Huang Transform the proposed method can be applied to signals with components having very close frequencies.

Under this heading published regularly abstracts of all Reports and Memoranda of the Aeronautical Research Council, Reports and Technical Memoranda of the United States National Advisory Committee for Aeronautics and publications of other similar Research Bodies as issued.