Enlaces

Web of Science ResearcherID: L-8551-2014
ORCID: 0000-0003-1157-685X
SCOPUS Author ID: 57190881720
Researchgate: https://www.researchgate.net/profile/Rosa-M-Salvador
brújula UAL: http://brujula.ual.es/authors/357.html

Artículos en revistas indexadas

• F. Portillo, A. Alcayde, R. M. Garcia, N. Novas, J. A. Gazquez, M. Fernandez-Ros «Grid Frequency Measurement through a PLHR Analysis Obtained from an ELF Magnetometer». Sensors, 2022. (10.3390/s22082954) (Abstract)

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  The stability of the power grid’s frequency is crucial for industrial, commercial, and domestic applications. The standard frequency in Europe’s grid is 50 Hz and it must be as stable as possible; therefore, reliable measurement is essential to ensure that the frequency is within the limits defined in the standard EN 50160:2010. In this article, a method has been introduced for the measurement of the grid frequency through a power line harmonics radiation analysis. An extremely low-frequency magnetometer was developed with the specific purpose of monitoring, in real time, the electromagnetic field produced by electrical installations in the range from 0 to 2.2 kHz. Zero-crossing and Fast Fourier transform algorithms were applied to the output signal to calculate the grid frequency as a non-invasive method. As a final step, data for a complete month (May 2021) were compared with a commercial power quality analyzer connected to the main line to validate the results. The zero-crossing algorithm gave the best result on 3 May 2021, with a coefficient of determination (R2) of 0.9801. Therefore, the indirect measurement of the grid frequency obtained through this analysis satisfactorily fits the grid frequency.
• F. Portillo, R. M. Garcia, A. Alcayde, J. A. Gazquez, M. Fernandez-Ros, N. Novas «Prospective environmental and economic assessment of a sensor network». Sustainability (Switzerland), 2021. (10.3390/su131810306) (Abstract)

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  Sustainability is becoming of vital importance in project management, and a life cycle assessment (LCA) can ensure a body of knowledge to bear in mind the environmental burdens the project involves. In this study, two different ways of supplying energy to a sensor network are an-alyzed. Firstly, we analyze the environmental impact of the devices connected to the public grid. Secondly, we analyze the completely full off-grid system, with the sensor connected to a photovol-taic (PV) panel. Our findings show that the off-grid option has a greater number of benefits than the grid-connected option in terms of environmental impacts, although it is less economically advanta-geous. In a detailed analysis of the off-grid scenario, it can be observed that the battery is the com-ponent with the highest impact, so actions to try to reduce consumption, and, therefore, the battery size and its negative impact are taken. After reducing the battery size, the break-even point was reached, providing a net economic benefit of EUR 0.23 sensor/year. However, this analysis refers to a single sensor, and although the environmental and economic benefits seem low, in an economy of scale, this could result in large savings if these types of sensors are massively installed.
• N. Novas, R. M. Garcia, J. M. Camacho, A. Alcayde «Advances in solar energy towards efficient and sustainable energy». Sustainability (Switzerland), 2021. (10.3390/su13116295) (Abstract)

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  Conventional energy resources are not climate sustainable. Currently, engineers and scientists are looking for sustainable energy solutions influenced by climate change. A wide variety of sustainable natural energy resources are available, but they require technical solutions for their implementation. The general trend in energy research is based on renewable resources, amongst which solar energy stands out, being the most mature and widely accepted. In this paper, the current state of the sustainable energy system has been analysed. The main purpose is to provide additional context to assess future scenarios. The study of past contributions allows sustainability planning and increasing the welfare of future society. The aim is to highlight global trends in research on sustainable solar energy from 1995 to 2020 through a bibliometric analysis of 4260 publications. According to their linkages, the analysed articles are distributed in nine clusters: Sustainability assessment, Sustainable energy solutions, Environmental payback time analysis, Sustainability of solar energy in different scenarios, Environmental sustainability, Solar energy applications, Sustainable energy optimisation, Energy transition and Energy and sustainable scenarios. The most repeated keywords are Sustainability, Renewable energy, and Solar energy. Energy research and the exploration of new renewable solar resources are still necessary to meet sustainable energy’s future challenges.
• R. M. Garcia, N. Novas, A. Alcayde, D. El Khaled, F. Gil «Electronics and its worldwide research». Electronics, 2020. (10.3390/electronics9060977) (Abstract)

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  The contributions of researchers at a global level in the journal Electronics in the period 2012–2020 are analyzed. The objective of this work is to establish a global vision of the issues published in the Electronic magazine and their importance, advances and developments that have been particularly relevant for subsequent research. The magazine has 15 thematic sections and a general one, with the programming of 385 special issues for 2020–2021. Using the Scopus database and bibliometric techniques, 2310 documents are obtained and distributed in 14 thematic communities. The communities that contribute to the greatest number of works are Power Electronics (20.13%), Embedded Computer Systems (13.59%) and Internet of Things and Machine Learning Systems (8.11%). A study of the publications by authors, affiliations, countries as well as the H index was undertaken. The 7561 authors analyzed are distributed in 87 countries, with China being the country of the majority (2407 authors), followed by South Korea (763 authors). The H‐ index of most authors (75.89%) ranges from 0 to 9, where the authors with the highest H‐Index are from the United States, Denmark, Italy and India. The main publication format is the article (92.16%) and the review (5.84%) The magazine publishes topics in continuous development that will be further investigated and published in the near future in fields as varied as the transport sector, energy systems, the development of new broadband semiconductors, new modulation and control techniques, and more.
• R. M. Garcia, N. Novas, A. Alcayde, D. El Khaled, M. Fernandez-Ros, J. A. Gazquez «Progress in the knowledge, application and influence of extremely low frequency signals». Applied Sciences (Switzerland), 2020. (10.3390/app10103494) (Abstract)

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  This paper describes the characteristics of contributions made by researchers worldwide in the field of ELF (extremely low frequency) waves from 1957 to 2019. The data were collected through the Scopus database and processed with analytical and bibliometric techniques. The selection of the keywords is an essential step, because ELF has a very different meaning in some areas of medicine, where it is associated with a gene. A total of 12,436 documents were worked on in 12 thematic communities according to their collaborative relationships between authors and documents. Studies included authors publishing in the different thematic areas and the country where the USA stands first with more researchers in this theme than China and Japan. Documents were analyzed from the temporal perspective, their overall contribution, means of publication, and the language of the publication. Research requires extra effort and multidisciplinary collaboration to improve the knowledge, the application, and influence of these fields.
• D. El Khaled, N. Novas, R. M. Garcia, F. Manzano-Agugliaro «Alcohols and alcohols mixtures as liquid biofuels: A review of dielectric properties». Renewable and Sustainable Energy Reviews, 2016. (10.1016/j.rser.2016.08.032) (Abstract)

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  Oils, pure alcohols and alcohols mixtures have a complicated dielectric behavior. The strong electric field of the ions affects intensively the molecular interaction of solvents. Microwave heating resides in the characterization of dielectric properties. Classified as biodiesel precursors, advances in microwave technology of alcohols have a significant potential in improving the biodiesel production. In this context, this review provides basic knowledge on the dielectric properties theory and the heating phenomenon in the microwave fields. The main goal of the paper is to provide an organized summary of the main chemical and physical properties of alcohols and links them to their corresponding research studies dealing with dielectric properties measurements. The review covers the dielectric constant and loss factor variations observed with temperature and frequency, the relaxation time and the tangent loss of various mixtures found in the literature. Moreover, the review provides an updated database for organic solvents and alcohols to account for their abilities to couple in microwave radiation. The aim of the work is building a rigid bridge between chemico-physical and dielectric properties so it can make an essential step towards improving biofuels production. This review opens new perspectives for further investigation of dielectric properties that are interesting for microwave heating studies.
• M. Fernandez-Ros, J. A. Gazquez, R. M. Garcia, N. Novas «Optimization of the periodogram average for the estimation of the power spectral density (PSD) of weak signals in the ELF band». Measurement: Journal of the International Measurement Confederation, 2015. (10.1016/j.measurement.2015.10.006) (Abstract)

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  The frequencies between the ELF, ULF and VLF bands are widely used as indicators of the electrical activity in the atmosphere, as precursors of seismic activity and are of interest in the study of geophysical phenomena. These signal methods of analysis are varied, and among them, we find a method of averaged periodograms, which is based on the Fast Fourier Transform (FFT). In this type of analysis, the optimal number of segments to be averaged must be determined; however, there seems to be no satisfactory method for choosing them. In this paper, we provide a method that will allow us to select the optimal number of segments to be averaged.
• D. El Khaled, N. Novas, J. A. Gazquez, R. M. Garcia, F. Manzano-Agugliaro «Fruit and vegetable quality assessment via dielectric sensing». Sensors (Switzerland), 2015. (10.3390/s150715363) (Abstract)

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  The demand for improved food quality has been accompanied by a technological boost. This fact enhances the possibility of improving the quality of horticultural products, leading towards healthier consumption of fruits and vegetables. A better electrical characterization of the dielectric properties of fruits and vegetables is required for this purpose. Moreover, a focused study of dielectric spectroscopy and advanced dielectric sensing is a highly interesting topic. This review explains the dielectric property basics and classifies the dielectric spectroscopy measurement techniques. It comprehensively and chronologically covers the dielectric experiments explored for fruits and vegetables, along with their appropriate sensing instrumentation, analytical modelling methods and conclusions. An in-depth definition of dielectric spectroscopy and its usefulness in the electric characterization of food materials is presented, along with the various sensor techniques used for dielectric measurements. The collective data are tabulated in a summary of the dielectric findings in horticultural field investigations, which will facilitate more advanced and focused explorations in the future.
• J. A. Gazquez, M. Fernandez-Ros, N. Novas, R. M. Garcia «Techniques for Schumann Resonance Measurements: A Comparison of Four Amplifiers with a Noise Floor Estimate». IEEE Transactions on Instrumentation and Measurement, 2015. (10.1109/TIM.2015.2420376) (Abstract)

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  Schumann resonances are very weak natural electromagnetic signals produced in the earth-ionosphere cavity located in the extremely low frequency (ELF) band (7-60 Hz), and the sensors that measure them produce amplitudes of few microvolts. Strong signals from power lines (50-60 Hz) occur in the same frequency range. Amplification techniques play a key role in acquiring resonance modes with the best signal-To-noise (S/N) ratio. This paper presents a study of the various structures of amplification systems that optimize the S/N ratio for the signal of interest. The aim of this paper is to measure all possible resonance modes with low time acquisition. To this end, we compare four instrumentation amplifiers and design a new indirect method for obtaining the noise floor of the system with sensors manufactured on magnetic cores that are several meters long. We present the measurements of the Schumann resonance achieved using these techniques at the ELF electromagnetic wave observatory at Calar Alto (Spain). The solutions adopted allow measurement of seven resonance modes with an acquisition time of 30 min, where the S/N ratio in the fundamental mode was 39 dB.
• R. M. Garcia, J. A. Gazquez, N. Novas «Characterization and modeling of high-value inductors in ELF band using a vector network analyzer». IEEE Transactions on Instrumentation and Measuremen, 2012. (10.1109/TIM.2012.2215141) (Abstract)

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  Characterization and modeling of high-value inductors (hundreds to thousands of henrys) are complex problems, exacerbated when working in the extremely low frequency (ELF) range. This paper details the measurement and characterization of inductors using a vector network analyzer that has a bottom operating frequency of 5 Hz. Using this device, we establish a strategy for measuring the impedance of high-inductance coils - with or without a high-permeability core - and propose a mathematical model that can explain the behavior of these high-inductance coils, which incorporate long lengths of winding wire, as a function of working frequency. These inductors were constructed as part of a research project on ELF electromagnetic fields. The importance of making a complete characterization derives from the need to exploit the largest possible amount of energy captured by the coil, which acts as a sensor. We propose a mixed model of concentrated and distributed parameters that fits the experimental results with an error of about 2% for the frequency range of 5-500 Hz, as part of the characterization process. The effects of the magnetic core on inductance and winding resistance, as a function of frequency, have been characterized in terms of concentration of the magnetic field.
• J. A. Gazquez, N. Novas, R. M. Garcia, et al. «Rescaled range analysis of ELF natural electromagnetic noise from Antarctica». Progress In Electromagnetics Research Symposium Proceedings, Marrakesh, Morocco,, 2011. (Abstract)

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  We present the results of a statistical rescaled range (R/S) analysis of natural electromagnetic noise in the extremely low frequency (ELF) band. The Hurst exponent was derived from the records of two horizontal magnetic antennas taken in Antarctica with a sample frequency of 512 Hz, to guarantee enough resolution with the small number of samples in the analysis. The study shows that ELF radio noise is a persistent random process, maintaining its value between 0.75 and 0.85 for the different series analyzed. A numerical simulation was performed, in which each discharge was modeled by the radiated field of a wire antenna excited by a Gaussian pulse, demonstrating a way of inferring lightning rates from R/S analysis.