Enlaces

Web of Science ResearcherID: L-9069-2014
ORCID: 0000-0002-2605-7692
SCOPUS Author ID: 6602849007
Researchgate: https://www.researchgate.net/profile/Jose-Gazquez-Parra
brújula UAL: http://brujula.ual.es/authors/371.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.
• M. E. González-Revuelta, N. Novas, J. A. Gazquez, M. A. Rodríguez-Maresca, J. M. García-Torrecillas «User Perception of New E-Health Challenges: Implications for the Care Process». International Journal of Environmental Research and Public Health, 2022. (10.3390/ijerph19073875) (Abstract)

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  Establishing new models of health care and new forms of professional health-patient communication are lines of development in the field of health care. The onset of the COVID-19 pandemic has accelerated the evolution of information systems and communication platforms to guarantee continuity of care and compliance with social distancing measures. Our objective in this article was, firstly, to know the expectations of patients treated in the healthcare processes “cervical cancer” and “pregnancy, childbirth and puerperium” regarding online access to their clinical history and follow-up in the care process. Secondly, we analyzed times involved in the cervical cancer process to find points of improvement in waiting times when digital tools were used for communication with the patient. A descriptive cross-sectional study was carried out on 120 women included in any of the aforementioned processes using a hetero-administered questionnaire. The analysis of times was carried out using the Business Intelligence tool Biwer Analytics®. Patients showed interest in knowing their results before the appointment with the doctor and would avoid appointments with their doctor if the right conditions were met. Most recognized that this action would relieve their restlessness and anxiety. They were highly interested in receiving recommendations to improve their health status. It was estimated that there was room for improvement in the times involved in the care process, which could be shortened by 34.48 days if communication of results were through digital information access technologies. This would favor the optimization of time, resources and user perception.
• 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.
• J. A. Gazquez, M. Fernandez-Ros, B. Torrecillas, J. Carmona, N. Novas «New approximate analytical solution of the diode-resistance equation». International Journal of Electronics and Communications, 2021. (10.1016/j.aeue.2021.153665) (Abstract)

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  The problem of finding an analytical solution for the circuit formed by a diode with series resistance (D-R circuit) has been investigated for a long time and several authors have proposed approximate solutions. Most solutions use the Lambert function and numerical methods. However, an analytical solution independent of experimental parameters is still missing to replace the D-R circuit with an analytical expression, in which only the diode and circuit parameters appear. In this paper, using a Taylor series expansion of the equation VD = f (VS, R, ID), we propose a new analytical solution that fits the exact solution with more accuracy than all known approximations. The average of the absolute error vector is the best, with an order of magnitude of difference compared to the other 3 approximations studied. This new function can be expressed by voltage analysis, which allows analytical solutions. Our solution may have many applications, such as a simple and accurate way, in circuit simulation programs or numerical calculation programs. In particular, it can be used as well in circuits with D-R branches, exponential amplifiers, logarithmic amplifiers and waveform shapers. On another level, a comparison with other state of the art approximations is presented.
• 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.
• N. Novas, J.A. Álvarez-Bermejo, J.L. Valenzuela, J. A. Gazquez, F. Manzano-Agugliaro «Development of a smartphone application for assessment of chilling injuries in zucchini». Biosystems Engineering, 2019. (10.1016/j.biosystemseng.2019.03.009) (Abstract)

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  Depending on their type and variety, horticultural products are injured by cold when this follows a period of exposure to a range of temperatures above their freezing point. These lesions are a result of tissues having been weakened rendering them unable to conduct normal metabolic processes. Cold stress produces physiological and biochemical alterations and cellular dysfunctions in response to cooling that negatively affect their quality and frequently result in products unsuitable for sale. Currently, evaluation of cold damage is usually carried out qualitatively by experts. This is not particularly accurate and, above all, depends on the observer and is therefore subjective. This study developed an application for a smartphone that automates this process and applied it to one of the most sensitive vegetables, zucchini or courgette. The results provide qualitative values and avoid all subjectivity. To demonstrate their validity, the results were compared to those of the standard method. They were also compared among distinct varieties allowing thresholds of hue and saturation settings to be adapted to these different varieties. These settings allow users to calculate damage in a more reliable manner depending on the specific variety analysed. This application allows for new perspectives in the field of evaluation of cold damage to fruits and vegetables in general and in particular zucchini.
• D. El Khaled, N. Novas, J. A. Gazquez, F. Manzano-Agugliaro «Microwave dielectric heating: Applications on metals processing». Renewable and Sustainable Energy Reviews, 2018. (10.1016/j.rser.2017.10.043) (Abstract)

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  Microwave material processing is a novel energy efficient technology with improved mechanical properties, minimized defects and economical and environmental advantages making it a convenient application for various types of materials. Although, microwave interaction with matter has been largely investigated and published in food processing, ceramics and chemistry, no particular work has been involved in collecting the interactions of microwaves with metals and placing a special emphasis on their interaction with metals and metal-based formulations, and here resides the aim of the review: consolidating the fundamentals of microwave heating applications as a time and energy saving application and addressing its various applications and mechanisms with metal interactions seeking a more sustainable environment. This review reports the latest literature findings on microwave processing fundamentals and highlights the advanced technological improvement applied on metals in this field. It focuses on the relevant industrial applications related to the development of microwave technology on metals and its possible future processing in this specific scope of investigation.
• D. El Khaled, N. Novas, J. A. Gazquez, F. Manzano-Agugliaro «Dielectric and bioimpedance research studies: A scientometric approach using the scopus database». Publications, 2018. (10.3390/publications6010006) (Abstract)

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  This work describes theworldwide applications of dielectric and bioimpedancemeasurements techniques in various fields. Dielectric and bioimpedance spectroscopy are major non-destructive measurement systems with great potential in the technology field. All results produced by the Scopus database were used as the core of the study in hand, with different items from journals, papers and conference proceedings being taken into account. The results of this analysis show that the interest in electrical properties has risen in the last years due to the advanced technological measurements offered on the scientific level. Results show that bioimpedance studies are considerably more recent compared to dielectric studies, and are more directed towards medical purposes while dielectric spectroscopy focuses on physical aspects, and is used mostly in engineering and material science. It can be stated that bioimpendance and dielectric spectroscopy are being increasingly applied and that they have the capacity to deepen and enhance research investigation.
• D. El Khaled, N. Novas, J. A. Gazquez, A. J. Perea-Moreno, F. Manzano-Agugliaro «Dielectric spectroscopy in biomaterials: Agrophysics». Materials, 2016. (10.3390/ma9050310) (Abstract)

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  Being dependent on temperature and frequency, dielectric properties are related to various types of food. Predicting multiple physical characteristics of agri-food products has been the main objective of non-destructive assessment possibilities executed in many studies on horticultural products and food materials. This review manipulates the basic fundamentals of dielectric properties with their concepts and principles. The different factors affecting the behavior of dielectric properties have been dissected, and applications executed on different products seeking the characterization of a diversity of chemical and physical properties are all pointed out and referenced with their conclusions. Throughout the review, a detailed description of the various adopted measurement techniques and the mostly popular equipment are presented. This compiled review serves in coming out with an updated reference for the dielectric properties of spectroscopy that are applied in the agrophysics field.
• J. A. Gazquez, N. Novas, F. Manzano-Agugliaro «Intelligent low cost telecontrol system for agricultural vehicles in harmful environments». Journal of Cleaner Production, 2016. (10.1016/j.jclepro.2015.11.015) (Abstract)

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  The use of vehicles to control pests and crop diseases is needed to maintain agricultural production. This paper describes how to design and implement a low cost intelligent telecontrol system applied for agricultural machinery that are designed for use in places where human presence is not adequate, such as pesticide spraying tasks in farming environments as greenhouses. The intelligent system designed basically consists of these parts: States Encoding, Console Automaton, Vehicle Automaton, Communication System and Security of Communications. This system has been developed with a special-purpose UHF narrow band modem that interchanges digital operative commands/states from the console to the vehicle. The intelligent telecontrol system acts as a security system to protect against outsiders, and loss of communications due to fading or others interference. The originality of this system is based on the fact that it is 10 times cheaper than autonomous systems; those systems need electronic systems, GPS, a complex sensorial system, and a beforehand mapping performed on the new work environment. Related to classic remote control, our system protects from potential oversights of the operator. In addition, in the proposed system, the vehicle state is shown in the console, due the bidirectional communications. The system was successfully applied in prototype vehicle used for spraying tasks, and the result shows that the system operated stably and has confirmed the effectiveness of this intelligent telecontrol system. The proposed technology will help providing solutions for humans and robots working together in agricultural environments considered to be harmful to humans.
• 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.
• N. Novas, J. A. Gazquez, M. Noguerol «Real-time biomedical telemetry system for ambulances». Healthcare Administration: Concepts, Methodologies, Tools, and Applications, 2014.
• J. Clement, N. Novas, J. A. Gazquez, F. Manzano-Agugliaro «An active contour computer algorithm for the classification of cucumbers». Computers and Electronics in Agriculture, 2013. (10.1016/j.compag.2013.01.006) (Abstract)

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  The cucumber is one of the most important crops worldwide and, because it is generally consumed fresh, it must be classified into quality categories. The European classification system includes a parameter that relates the degree of curvature relative to the length. Until now, this classification could not been be achieved with an automatic system due to the difficulty associated with correctly calculating the axis of a cucumber. This article describes a computer algorithm that uses active contours or " snakes" to classify cucumbers by length and curvature. This algorithm demonstrates an advantage in the determination of the central line of each cucumber, based on an iterative process that is quick and carries out the classification process efficiently. The method was validated against human classification for 360. cucumbers and was also compared with an ellipsoid approximation method. The active contour method reduced the classification error by 15% points, compared with the ellipsoid approximation method, to 1%, with no serious errors (i.e., misclassification of Class Extra and I into Class II or vice versa). Meanwhile, the ellipsoid approximation method led to a 16% error rate, of which 2% were serious errors (an error of two classes). The developed approach is applicable to fresh cucumber commercial classification lines to meet the requirements of the European regulations for cucumber classification.
• 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. Clement, N. Novas, J. A. Gazquez, F. Manzano-Agugliaro «High speed intelligent classifier of tomatoes by colour, size and weight». Spanish Journal of Agricultural Research, 2012. (10.5424/sjar/2012102-368-11) (Abstract)

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  At present most horticultural products are classified and marketed according to quality standards, which provide a common language for growers, packers, buyers and consumers. The standardisation of both product and packaging enables greater speed and efficiency in management and marketing. Of all the vegetables grown in greenhouses, tomatoes are predominant in both surface area and tons produced. This paper will present the development and evaluation of a low investment classification system of tomatoes with these objectives: to put it at the service of producing farms and to classify for trading standards. An intelligent classifier of tomatoes has been developed by weight, diameter and colour. This system has optimised the necessary algorithms for data processing in the case of tomatoes, so that productivity is greatly increased, with the use of less expensive and lower performance electronics. The prototype is able to achieve very high speed classification, 12.5 ratings per second, using accessible and low cost commercial equipment for this. It decreases fourfold the manual sorting time and is not sensitive to the variety of tomato classified. This system facilitates the processes of standardisation and quality control, increases the competitiveness of tomato farms and impacts positively on profitability. The automatic classification system described in this work represents a contribution from the economic point of view, as it is profitable for a farm in the short term (less than six months), while the existing systems, can only be used in large trading centers.
• N. Novas, J. A. Gazquez, J. F. L. Rodríguez, F. Manzano-Agugliaro «Telemetry system for transmission data from an ambulance». Dyna, 2012. (Abstract)

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  Currently the transfer of critically patients is carried out through a coordination center for outpatient care and hospital care. Modern wireless communications technologies offer the possibility of improving some systems in the context of critical care emergency; under these situations are many occasions requiring additional examinations. The telemetry system developed in this paper provides real-time communication of patient's blood biochemistry that with a clinical suspicion based on an adequate history taking and physical examination, require this kind of diagnostic tests to better assess the patient's condition. This allows improving attendance at all times and the preparation of all necessary resources for the rapid, and effective patient reception in the hospital without additional cost, since these tests also would be required in the hospital. This allows early detection of conditions that endanger imminent the life of a patient. The results verify the interest of this new service.
• 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.