Electromagnetic coupling simulagions for a magnetic induction sensor for sleep monitoring

Magnetic induction (MI) method has been extensively used in non-destructive testing of materials. In biomedical applications, it attracted lots of attention for the contact-less advantages it provides. Sleep monitoring through detecting conductivity changes in lungs and heart during breathing and cardiac activity is the purpose of our studies. The low conductivity of biological tissues increase the complexity of the design of such systems. One challenge is to separate the effects of magnetic field from the electric field; achieving a pure magnetic contribution is difficult since the received signal is contaminated by the unwanted capacitive coupling. Our hypothesis is that for a periodic vital sign monitoring like breathing and heart activity, part of this secondary coupling could be considered as a desired effect to take the advantage of both contributions. In this paper, the coupling mechanisms existed in our system have been simulated and studied using finite element and Orcad simulations to estimate different contributions we would have in the developed MI system.Peer ReviewedPostprint (author’s final draft

Usefulness of bioelectrical impedance analysis for monitoring patients with refractory ascites

Background: bioelectrical impedance analysis is a technique for the determination of the hydropic component. The hydropic component, determined by blood volume, could be a reflection of the hemodynamic situation. This study aimed to evaluate the usefulness of peripheral bioelectrical impedance analysis (BIA) for the prediction of hemodynamic changes in large-volume paracentesis and prognosis. Methods: this was a proof-of-concept prospective study of 14 patients with liver cirrhosis and refractory ascites. Peripheral bioimpedance was measured three times using a portable device, IVOL®, before and after large-volume paracentesis, at different frequencies (5, 10, 20, 50, 100 and 200 kHz). Consequently, resistance, reactance and phase angle were obtained, both pre- and post-paracentesis (the difference between them was defined as Δ). Results: the mean age of patients was 62.2 ± 9.6 years, the Child-Pugh was 8.4 ± 1.3 and the MELD score was 15.2 ± 3.9. A direct correlation between the extraction of ascitic fluid and Δresistance (10 kHz [r = 0.722; n = 12; p = 0.008], 20 kHz [r = 0.658; n = 12; p = 0.020] and 50 kHz [r = 0.519; n = 14; p = 0.057]) was observed. The presence of edema was related to lower values of both pre-paracentesis resistance (10 Hz [23.9 ± 8 vs 32.2 ± 4; p = 0.043]) and phase angle (5 kHz [-1.9 ± 2.8 vs 5.9 ± 7.3; p = 0.032]). Pre-paracentesis phase angle was directly correlated with the decline in blood pressure after paracentesis at lower frequencies (5 kHz [r = 0.694; n = 13; p = 0.008] and 10 kHz [r = 0.661; n = 13; p = 0.014]). Lower frequencies of Δphase-angle impacted on patient prognosis (5 kHz [-8.6 ± 5 vs -2.5 ± 2.7; p = 0.021]), patients with Δphase-angle 5 kHz > -4 had a higher rate of mortality (83.3% [5/6] vs 0% [0/6]; logRank 7.306, p = 0.007). Δresistance values were associated with overt HE at six months (10 kHz [4.9 ± 2.5 vs -0.4 ± 4.7; p = 0.046]). Conclusions: in conclusion, a significant correlation between peripheral impedance and hemodynamic changes was found. Impedance was also significantly related to prognosis and overt hepatic encephalopathy

Simulation of a magnetic induction method for determining passive electrical property changes of human trunk due to vital activities

Postprint (published version

Simulation of a magnetic induction method for determining passive electrical property changes of human trunk due to vital activities

Determining the changes in passive electrical properties of human tissues and the geometry changes of the body parts due to breathing and cardiac activity could be a method for monitoring these vital signs. We have designed a model with COMSOL Multiphysics to simulate a magnetic induction method for determining changes of these characteristics. Given the large number of parameters and variables, difficulties of anatomical modeling and various tissue properties, we are facing some numerical challenges. In addition, using magnetic induction method, we have to consider safety issues, standards and limitations. We used COMSOL to simulate the induced currents in the human body and the resulting perturbation in the magnetic field for different tissue properties and geometries. As a result, we obtained the expected changes during breathing and we know the minimum distances and maximum excitation currents that could be used to meet the international safety standards.Postprint (published version

Transmural versus non-transmural in situ electrical impedance spectrum for healthy, ischemic, and healed myocardium

Electrical properties of myocardial tissue are anisotropic due to the complex structure of the myocardial fiber orientation and the distribution of gap junctions. For this reason, measured myocardial impedance may differ depending on the current distribution and direction with respect to myocardial fiber orientation and, consequently, according to the measurement method. The objective of this study is to compare the specific impedance spectra of the myocardium measured using two different methods. One method consisted of transmural measurements using an intracavitary catheter and the other method consisted of nontransmural measurements using a four-needle probe inserted into the epicardium. Using both methods, we provide the in situ specific impedance spectrum (magnitude and phase angle) of normal, ischemic, and infarcted pig myocardium tissue from 1 kHz to 1 MHz. Magnitude spectra showed no significant differences between the measurement techniques. However, the phase angle spectra showed significant differences for normal and ischemic tissues according to the measurement technique. The main difference is encountered after 60 min of acute ischemia in the phase angle spectrum. Healed myocardial tissue showed a small and flat phase angle spectrum in both methods due to the low content of cells in the transmural infarct scar. In conclusion, both transmural and nontransmural measurements of phase angle spectrum allow the differentiation among normal, ischemic, and infarcted tissue.Peer Reviewe

Signal-to-motion artifact ratio versus frequency for impedance pneumography

We measured transthoracic impedance between 12.5 and 185 kHz in nine adults. We used a system with two impedance channels, both simultaneously detecting the real part of impedance at two different frequencies. We used only two electrodes in the midaxillary line, connecting both channels in parallel. The amplitude relation between the two channels was measured for different maneuvers and frequencies. Results show for normal breathing an increase of the signal of 20% and a decrease in motion artifacts from 12.5 to 185 kHz. We conclude that, for the maneuvers studied, it is better to work at higher frequencies than the ones commonly used. Also, we suggest a method to further increase the signal-to-motion artifact ratio based on measurement at two frequencies.Peer Reviewe

Monitoring cell monolayers during electroporation: Electrical impedance spectroscopy measurements

Peer Reviewe

Estimación a carga parcial del rendimiento de torres de refrigeración secas de tiro natural

La finalidad de este proyecto es el desarrollo de un nuevo método de cálculo teórico del rendimiento de torres de refrigeración secas de tiro natural propuesto recientemente por investigadores de la Southeast University en Nanjing y del CPI Shentou Power Generation Co. de Shuozhou, China [22]. La novedad en este método es la consideración del efecto de la temperatura ambiente y del viento cruzado sobre el rendimiento de la torre y su posibilidad de análisis. Este método es muy rápido, simple y permite estimar de forma sencilla el funcionamiento de la torre. Tras el desarrollo del método teórico, se ha realizado una implementación en Matlab que permitirá disponer de una aplicación informática para el cálculo de este tipo de torres. Esta aplicación se ha diseñado con la herramienta GUIDE de Matlab. Por último, se realizarán una serie de análisis del método propuesto para comprobar la veracidad de las hipótesis que propone y comprobar los efectos de estos factores meteorológicos en el rendimiento de una torre de refrigeración seca de tiro natural. Al tratarse un tipo concreto de torre, sería deseable que en un futuro formara parte de un conjunto que incluyera los restantes tipos de torres de refrigeración, para así realizar un estudio completo de este tipo de sistemas. Por tanto, el objetivo del proyecto es el desarrollo de una aplicación informática para este nuevo modelo teórico de cálculo que permita conocer, con mayor rapidez, el funcionamiento de una torre según las condiciones ambientales y de operación a partir de otra de referencia, teniendo en cuenta los efectos meteorológicos mencionados y que nos permita saber si cumple los requerimientos específicos.Ingeniería en Tecnologías Industriale

Ataques DDoS con IoT, Análisis y Prevención de Riesgos

La tecnología del Internet de las cosas (IoT) continúa creciendo a diario, lo que en el ámbito de la ciberseguridad aumenta las preocupaciones sobre la implicación de estos dispositivos en ataques informáticos a empresas e instituciones. Entre ellos los ataques de denegación del servicio distribuido (DDoS), que utilizan el envío de una gran cantidad de peticiones a un servidor para saturarlo. Este trabajo tiene tres objetivos: desarrollar un software capaz de leer el tráfico entrante en una red y permitir analizarlo, determinar la capacidad de los dispositivos IoT de participar en un ataque DDoS y valorar los daños que pueden causar estos ataques para precisar si a las empresas les es recomendable contratar servicios anti-DDoS. En primer lugar se desarrolló un software para leer el tráfico de datos entrante en una red, tras lo cual se realizaron diversas pruebas con dos dispositivos IoT (Raspberry pi 3 y Node MCU) en un entorno controlado. Estas pruebas constituían diferentes ataques DoS contra un servidor en el que estaba instalado el software de lectura de datos. Los resultados de las pruebas mostraban un elevado potencial destructivo de ambos dispositivos en relación a su precio y tamaño, y que efectivamente estos dispositivos pueden suponer una amenaza si participan en ataques DDoS. La valoración de los daños de los ataques DDoS a las empresas se realizó mediante el análisis de informes publicados por grandes empresas del sector de la ciberseguridad y otras instituciones relacionadas. Se concluyó que el coste de sufrir un ataque DDoS es muy elevado para todo tipo de empresas, superando el coste medio los 200.000$por ataque, y que tanto el tamaño como la duración y la cantidad de los ataques aumenta año a año. El crecimiento de los dispositivos IoT, junto con su capacidad para participar en ataques DDoS y el elevado daño causado por estos ataques presentan la necesidad de buscar soluciones contra estos ataques. Es necesario reducir la vulnerabilidad de los dispositivos IoT. Además, es recomendable que las empresas hagan frente a estas amenazas y contraten servicios anti-DDoS para protegerse de estos ataques cada vez más comunes y potentes.The Internet of things (IoT) technology continues to grow daily, which raises concerns in the field of cybersecurity about the involvement of these devices in computer attacks on companies and institutions. Among these attacks are found the distributed denial of service attacks (DDoS), which send a huge amount of petitions to a server in order to saturate it. This investigation has three goals: to develop a software capable of reading incoming traffic on a network and allow analyzing it, to determine the capacity of IoT devices to participate in a DDoS attack, and to assess the damages that these attacks can cause to determine if it is advisable for companies to hire anti-DDoS services. Firstly, a software was developed to enable the reading and analysis of the incoming traffic on a network. Then, several tests were done with two IoT devices (Raspberry pi 3 and NodeMCU), in a controlled environment. These tests were different DoS attacks against a server in which the developed software was installed. The results of these tests show a big destructive potential of both devices in relation to their price and size, and that they can consitute a considerable threat if they take part in a DDoS attack. The damage assessment of DDoS attacks on companies was carried out by analyzing several reports published by large companies in the cybersecurity sector and other related institutions. The conclusion obtained is that the cost of suffering a DDoS attack is very high for all types of companies. In fact, the average cost reported exceeds$200.000 per attack. Furthermore, it is also inferred that both the size and duration and the number of DDoS attacks increase yearly. The growth of IoT devices, together with their ability to participate in DDoS attacks and the high damage caused by these attacks present the need to find a solution to reduce the vulnerability of IoT devices to hackers. Furthermore, it is advisable that companies address these threats and hire anti-DDoS services to protect themselves from DDoS attacks.Doble Grado en Ingeniería Informática y Administración de Empresa

Design and characterization of new tunable devices based on liquid crystal technology for microwave applications

Mención Internacional en el título de doctorThe PhD. Thesis work presented in this document has been made in the research group Grupo de Displays y Aplicaciones Fotónicas (GDAF) of Departamento de Tecnología Electrónica from Universidad Carlos III de Madrid. One of the most traditional GDAF research interest is the study of new devices based on liquid crystals (LC). In this specific research subject, this Thesis work has been focused, including several studies about tunable devices at microwave frequencies based on LC technology. The previous experience of the Group in this field includes the devising of some preliminary approaches related to LC tunable devices, specifically phase retarders. However, no previous systematic study similar to this was made in the scope of this research Group. The main aim of this Thesis work is, indeed, to contribute to the development of new tunable devices at microwave frequencies based on new and advanced LC mixtures with electrical properties that match the requirements at GHz bands. In particular, this work has focused on the design of passive tunable filters, due to the rich functionality of these devices in telecommunication systems at microwave frequencies. The document is structured in several parts. It begins with a revision of the different available technologies used in tunable devices at GHz frequencies. Then, the main theoretical fundamentals and concepts of passive filters, notch filters and band-pass filters, are treated. In the third chapter the general processes that are involved in the manufacturing of the devices are presented. A depth study of LC-based notch filters, using a microstrip spurline structure, is detailed in chapter 4. The different steps with the restrictions that concern the design and the characterization of the manufactured devices are presented. The optimization of the devices configurations and the prediction of the filters frequency response have been made by using commercial electromagnetic software tools. Additionally, the dielectric properties at microwave frequencies of the LC mixtures used in the different devices have been estimated. Chapter 5 is devoted to tunable LC-based band-pass filters based on microstrip dual-mode technology. In the same way, the optimization of the different filter configurations, as well as the design, simulation and measurement of the frequency response of the filters are described in this chapter. Finally, in the last chapter, the main conclusions of this Thesis work and the future research lines are presented.El Trabajo de Tesis Doctoral presentado en esta memoria se ha realizado dentro del Grupo de Displays y Aplicaciones Fotónicas del Departamento de Tecnología Electrónica de la Universidad Carlos III de Madrid. Entre las principales líneas de investigación del GDAF se encuentra el estudio de nuevos dispositivos cuya implementación práctica se basa en el empleo de cristales líquidos (CL). Dentro de esta línea de investigación se han realizado previamente algunos estudios acerca del empleo de CL para el diseño de dispositivos sintonizables a frecuencias de microondas. Así, previamente a la realización de este trabajo, se diseñó y caracterizó experimentalmente un desfasador sintonizable basado en las propiedades de estos materiales. Sin embargo, no se había realizado dentro del grupo un estudio sistemático acerca de dispositivos sintonizables a estas frecuencias similar al presentado en este trabajo de Tesis. El objetivo de este Trabajo de Tesis Doctoral es contribuir al desarrollo de dispositivos sintonizables a frecuencias de GHz basados en CL. Principalmente, el presente trabajo se ha centrado en el diseño de filtros, dada la importancia que estos dispositivos tienen en sistemas de comunicaciones de la citada banda de frecuencias. El documento se estructura en varias partes. Comienza con una revisión del estado del arte de los dispositivos sintonizables a frecuencias de microondas, realizando un barrido de las diferentes tecnologías que se vienen utilizando hasta la fecha de hoy, para posteriormente presentar los principales conceptos teóricos y la fabricación de dispositivos. En particular, los filtros pasivos, concretamente filtros notch y paso banda, son el ámbito central de discusión y el núcleo del presente trabajo. En el cuarto capítulo se presenta un estudio exhaustivo sobre filtros notch con estructura microstrip spurline basados en CL, abordando las distintas fases desde el estudio de las distintas configuraciones y variantes de la tecnología empleada, hasta la implementación de los dispositivos finales. Concretamente, se han diseñado, simulado y caracterizado experimentalmente la respuesta espectral de dos filtros notch basados en CL. La elección de la configuración óptima de cada dispositivo, así como la predicción de la respuesta en frecuencia del mismo, se ha llevado a cabo utilizando herramientas de simulación software comerciales. Por otro lado, la caracterización de las propiedades de los CL a las frecuencias de interés, es otra de las principales aportaciones de este trabajo. De la misma manera, el quinto capítulo está dedicado al diseño de filtros sintonizables paso-banda con tecnología microstrip dual-mode basados en CL. La optimización de las distintas configuraciones para filtros dual-mode, así como el diseño, implementación, simulación y caracterización experimental de la respuesta espectral de los distintos dispositivos fabricados, son los principales puntos a tratar en dicho capítulo. Adicionalmente se incluyen, en la parte final de la memoria, las principales conclusiones del presente trabajo, así como las líneas de investigación para el futuro inmediato.Apoyo financiero del Ministerio de Economía y Competitividad (proyectos TEC2009-13991-C02-01, TEC2014/00354/001) y de la Comunidad de Madrid (proyecto FACTOTEM2 S2009/ESP/1781).Programa Oficial de Doctorado en Ingeniería Eléctrica, Electrónica y AutomáticaPresidente: José Manuel Otón Sánchez.- Secretario: Ricardo Vergaz Benito.- Vocal: Antigone Marin