HEH-BMAC: hybrid polling MAC protocol for WBANs operated by human energy harvesting

This paper introduces human energy harvesting medium access control (MAC) protocol (HEH-BMAC), a hybrid polling MAC suitable for wireless body area networks powered by human energy harvesting. The proposed protocol combines two different medium access methods, namely polling (ID-polling) and probabilistic contention access, to adapt its operation to the different energy and state (active/inactive) changes that the network nodes may experience due to their random nature and the time variation of the energy harvesting sources. HEH-BMAC exploits the packet inter-arrival time and the energy harvesting rate information of each node to implement an efficient access scheme with different priority levels. In addition, our protocol can be applied dynamically in realistic networks, since it is adaptive to the topology changes, allowing the insertion/removal of wireless sensor nodes. Extensive simulations have been conducted in order to evaluate the protocol performance and study the throughput and energy tradeoffs.Peer ReviewedPostprint (author's final draft

Detección y clasificación automática de registros sísmicos en el observatorio vulcanológico y sismológico de pasto utilizando redes neuronales artificiales

En este trabajo se aplica una metodología que combina Análisis de predicción lineal (LPC) y Redes neuronales artificiales (RNA) con el objetivo de detectar y clasificar tres tipos de sismos volcánicos: volcano-tectónicos (VT) tipo A, largo periodo (LP) y tremor (TRE). Se construye una herramienta computacional orientada a la detección y clasificación automática de estas señales sísmicas, generando información en tiempo real. Segmentos cortos de la traza continua se representan utilizando la técnica LPC que también cumple la función de reducir la dimensión del vector que contiene los datos de la forma de onda. Para las fases de detección y clasificación se utilizan RNA tipo perceptrón multicapa con una capa oculta. Entre las ventajas de la metodología está la posibilidad de detectar sismos con arribos emergentes, de corta duración o de bajo nivel energético. La aplicación del método muestra cerca de 100% de acierto para la distinción entre ruido y señal sísmica (fase de detección), 92 % de acierto para la clasificación entre sismos LP y VT y cerca del 100% en la detección de sismos tipo TRE. / Abstract. In this work is applied a methodology that to combine Linear Prediction Coding (LPC) and Artificial Neural Networks (ANN) in order to detect and classify three types of volcanic seismic signals: Type A Volcano-Tectonic events (VT), Long Period (LP) and volcanic Tremor (TRE). It was built a software oriented to detection and automatic classification of these kinds signals, generating information in Real-Time. Short segments of the continuous streams are represented using the LPC technique, also carry out the reduction of the vector containing waveform data. For the detection and classification processing-phases are used ANN type Multi-Layer Perceptron (MLP). Among the advantages of this methodology are the possibility of detect seismic events with emergent arrives, short duration or low energetic level. The application of this method shows near to 100 % of good choices for to distinguish between signal and noise level (detection phase); 92% of good choices for classification between LP and VT events; and near to 100 % for TRE-type seismicity detection.Maestrí

Suitability of different RANS models in the description of turbulent forced convection flows: application to air curtains

The main motivation of this thesis is the analysis of turbulent flows. Turbulence plays an important role in engineering applications due to the fact that most flows in industrial equipment and surroundings are in turbulent regime. The thesis has a double purpose and is divided in two main parts. The first one is focussed on the basic and fundamental analysis of turbulence models. In the second part the know-how acquired in the first part is applied to the study of air curtains.Regarding to the first part, the principal difficulty of computing and modelling turbulent flows resides in the dominance of non-linear effects and the continuous and wide spectrum of time and length scales. Therefore, the use of turbulence modelling employing statistical techniques for high Reynolds numbers or complex geometries is still necessary. In general, this modelization is based on time averaging of the Navier-Stokes equations (this approach is known as Reynolds-Averaged Navier-Stokes Simulations, RANS). As consequence of the average new unknowns, so-called Reynolds stresses, arise. Different approaches to evaluate them are: i) Differentially Reynolds Stress Models (DRSM), ii) Explicit Algebraic Reynolds Stress Models (EARSM), and iii) Eddy Viscosity Models (EVM).Although EVM models assuming a linear relation between the turbulent stresses and the mean rate of strain tensor are extensively used, they present various limitations. In the last few years, with the even-increasing computational capacity, new proposals to overcome many of these deficiencies have started to find their way. Thus, algebraic or non-linear relations are used to determinate the Reynolds stress tensor without introducing any additional differential equation.Therefore, the first part of this thesis is devoted to the study of several EARSM and EVM models involving linear and higher order terms in the constitutive relation to evaluate turbulent stresses. Accuracy and numerical performance of these models is tested in different flow configurations such as plane channel, backward facing step, and both plane and round impinging jets. Special attention is paid to the verification of the code and numerical solutions, and the validation of the mathematical models used. In the impinging plane configuration, improvements of models using higher order terms in the constitutive relation are limited. Whereas, in the rest of studied cases these non-linear models show a reasonably good behaviour.Moreover, taken into account models convergence, robustness and predictive realism observed in the analysis of these benchmark flows, some of them are selected for the study of air curtains and their interaction with the environment where they are placed. Air curtains are generally one or a set of vertical or horizontal plane jets used as ambient separator of adjacent areas presenting different conditions. The jet acts as a screen against energy losses/gains, moisture or mass exchanges between the areas.As was indicated before, the main purpose of the second part of this thesis is to characterize in detail actual air curtains using both experimental and different numerical approaches. Semi-empirical models to design air curtains are presented. Then, an experimental set-up used to study air curtain discharge and jet downstream is explained. Experimental measurements of velocity and temperature are shown. As a result of the experiments carried out, an improved air curtain with a new design of the discharge nozzle is obtained. Furthermore, air curtain experiments are numerically reproduced and predictions validated against the experimental data acquired. Good agreement between numerical and experimental results is observed.Finally, systematic parametric studies of air curtains in heating and refrigeration applications are done. Global energetic balances are specially considered together with global parameters selected in order to evaluate air curtain performance. It is found that discharge velocity, discharge angle and turbulence intensity of the jet are the most sensitive parameters. Inadequate values for these variables can produce undesirable effects and contribute to increase energy gains/losses

Síntese e caracterização das propriedades vibracionais, estruturais e magnéticas de nanopartículas de ZnO dopadas com metais de transição

Dissertação (mestrado)—Universidade de Brasília, Instituto de Física, 2013.Neste trabalho foram estudadas as propriedades magnéticas de nanopartículas de ZnO dopadas com metais de transição (Mn, Fe). As amostras foram sintetizadas pelo método de co-precipitação e suas propriedades vibracionais foram estudadas com espectroscopia infravermelha e espetroscopia Raman. A espetroscopia infravermelha mostrou a evolução da formação da fase desejada através do surgimento de bandas associadas com as ligações Zn - O durante a lavagem. A espetroscopia Raman mostrou a presença de modos vibracionais associados com a estrutura wurtzita do ZnO, após calcinar as amostras a 300ºC. No entanto, modos vibracionais adicionais foram determinados nas amostras dopadas com Mn e Fe, os que foram associados com a presença dos íons dopantes na estrutura. Através de medidas de difração de raios X se determinou a presença de uma única fase cristalina identificada como a estrutura wurtzita em todas as amostras estudadas. O Refinamento dos padrões de difração usando o método de Rietveld mostrou que nas nanopartículas dopadas com Mn os parâmetros de rede não têm uma tendência clara ao aumentar a concentração do dopante, o que sugere que os íons de Mn não substituem íons de Zn, mas provavelmente ocupam posições intersticiais da estrutura. Foram feitos também estudos de estabilidade cristalina da amostra dopada com 10mol% de Mn. Após tratamentos térmicos adicionais da amostra em 500 e 900ºC se determinou a formação de uma fase secundária que pode ser Mn3O4 ou Mn3O4 /ZnMnO3. Nas nanopartículas de ZnO dopadas com Fe, o aumento de volume da célula unitária com a concentração de Fe sugere que nestas amostras acontece a substituição de íons Fe2+ por íons Zn2+. Por outro lado, as medidas de magnetização em função do campo magnético aplicado nas nanopartículas de ZnO sem dopagem, revelam a ocorrência de um ordenamento magnético de intensidade fraca, cuja origem foi associada com o ordenamento de spins de elétrons desemparelhados e armadilhados em vacâncias de oxigênio localizadas na superfície das partículas. A densidade destas vacâncias de oxigênio é grande devido ao tamanho pequeno das partículas. A caracterização magnética das nanopartículas de ZnO dopadas com Mn revela a coexistência de duas fases magnéticas; uma fase paramagnética intensa, na qual os momentos magnéticos dos íons de Mn apresentam interações antiferromagnéticas e outra fase ferromagnética, a qual foi associada com a presença de fases adicionais como Mn3O4. A caracterização magnética das nanopartículas de ZnO dopadas com Fe revela a ocorrência de um comportamento ferromagnético. As curvas de magnetização (M) em função do campo magnético (H) obtidas a 5K mostram campos coercivos que crescem com a concentração do dopante. A 300 K, estes campos coercivos tendem a zero. Curvas de zero-field-cooled (ZFC) e field-cooled (FC) para as amostras dopadas com Fe, mostram características próprias de relaxação térmica de superspins ou de sistemas frustrados. A fim de determinar a origem foram feitas medidas de susceptibilidade AC variando a frequência do campo alternado. A parte real da susceptibilidade em função da temperatura mostra um máximo que se desloca para temperaturas maiores à medida que se aumenta a frequência. Assumindo que esse máximo representa a temperatura de congelamento do sistema, ficou determinado que as propriedades magnéticas das nanopartículas de ZnO dopadas com Fe correspondem a um sistema que mostra comportamento tipo vidro de spin. ______________________________________________________________________________ ABSTRACTIn this work, the magnetic properties of ZnO nanoparticles doped with transition metals (Mn; Fe) were studied. The samples were synthesized by the coprecipitation method and its vibrational properties were analyzed with infrared and Raman spectros-copy. The infrared spectroscopy showed the evolution of the wurtzite phase formation through the arising of the bands associated with Zn O bonds during the washing. The Raman spectroscopy showed the presence of vibrational modes associated with the wurtzite structure of ZnO, after annealing the powders at 300C. Additional vibratio- nal modes were determined in samples doped with Mn and Fe, which were associated with the presence of dopant ions in the structure.Through X-ray di raction measurements, it was determined the presence of a single crystalline phase identi ed as the wurtzite structure in all samples. The Rietveld re nement of di raction patterns showed that in nanoparticles doped with Mn the lattice parameters did not show a clear dependence on the dopant concentration. This result suggests that the Mn ions do not substitute Zn ions, but probably they occupy interstitial sites in the structure. It was also made crystalline stability studies of the sample doped with 10mol% Mn. After additional thermal treatments of the sample at 500 and 900C, it was determined the formation of a secondary phase such as Mn3O4 ou Mn3O4 /ZnMnO3 . For the ZnO nanoparticles doped with Fe, it was determined an increase in unit cell volume as the Fe concentration is increased, which suggests that in 2+ 2+these samples the Fe ions substitute Zn ions. On the other hand, magnetization measurements as a function of applied magnetic eld of undoped ZnO nanoparticles reveal the occurrence of a magnetic ordering which signal is weak and its origin was associated with the coupling of spins of unpaired electrons trapped in the oxygen vacancies located at the surface of the particles. The oxygen vacancy density is large due to the small size of the particles. The magnetic characterization of ZnO nanoparticles doped with Mn reveals the coexistence of two magnetic phases; an intense paramagnetic phase, in which the magnetic moments of Mn ions show antiferromagnetic interactions and another ferromagnetic phase, which was associated with the presence of additional phases such as Mn3O4. The magnetic characterization of ZnO nanoparticles doped with Fe reveals the occurrence of a ferromagnetic behavior. The curves of magnetization (M) vs. magnetic eld (H) obtained at 5K show coercive elds. These coercive elds show an increase with the dopant concentration. At 300K, these coercive elds tend to zero. Zero- eld-cooled (ZFC) and eld-cooled (FC) curves obtained for the Fe-doped ZnO nanoparticles show features of thermal relaxation of superspins or frustrated systems. In order to determine the origin of those relaxations, AC susceptibility measurements were made by varying the frequency of the alternating eld. The real part of the AC susceptibility as function of the temperature shows a maximum, which shifts to higher temperatures when the frequency is increased. Assuming that maximum as the freezing temperature of the system, it was determined that the magnetic properties of the Fe-doped ZnO nanoparticles correspond to a spin glass-like behavior

QoS-Aware energy management in body sensor nodes powered by human energy harvesting

Harvesting energy in the human environment has been identified as an effective way to charge the body sensor nodes in wireless body area networks (WBANs). In such networks, the capability of the nodes to detect events is of vital importance and complements the stringent quality of service (QoS) demands in terms of delay, throughput, and packet loss. However, the scarce energy collected by human motions, along with the strict requirements of vital health signals in terms of QoS, raises important challenges for WBANs and stresses the need for new integrated QoS-aware energy management schemes. In this paper, we propose a joint power-QoS (PEH-QoS) control scheme, composed of three modules that interact in order to make optimal use of energy and achieve the best possible QoS. The proposed scheme ensures that a sensor node is able to detect the medical events and transmit the respective data packets efficiently. Extensive simulations, conducted for different human activities (i.e., relaxing, walking, running, and cycling), have shown that the application of PEH-QoS in a medical node increases the detection efficiency, the throughput, and the energy efficiency of the system.Peer ReviewedPostprint (author's final draft

Efecto de diferentes niveles lipídicos y proteicos en la dieta sobre el desempeño productivo de juveniles del pez ángel o escalar (Pterophyllum scalare)

Antecedentes: Actualmente, en nuestro país los peces ornamentales son un segmento importante de la piscicultura nacional,siendo el pez ángel o escalar (Pterophyllum scalare), una de las especies cultivadas más popular y apetecida en el mundo de acuariofilia, gracias a su belleza, majestuosidad y forma estilizada. Sin embargo, son pocos los autores que han estudiado sus exigencias nutricionales en términos de niveles lipídicos y proteicos. Objetivo: La presente investigación evaluó seis dietas, conformadas por la combinación de dos niveles de extracto etéreo (EE) 9 y 11 % y de tres niveles de proteína bruta (PB) 32, 34 y 36 %, para determinar su efecto sobre el desempeño productivo y la sobrevivencia de juveniles de pez escalar (P. scalare). Metodología: Fueron usados 324 juveniles de P. scalare con peso promedio de 753,5 ± 0,14 mg, los cuales fueron distribuidos en 18 acuarios con volumen de 105L, a una densidad de 18 peces/acuario y alimentados al 6% de la biomasa. Resultados: los hallazgos mostraron que un nivel 32% de proteína bruta en la dieta no afecta la sobrevivencia, pero si el desempeño productivo (p<0,05), y que niveles de 34 ó 36% de PB lo mejoran. También se evidencio que no hubo diferencia estadística (P>0,05) entre los dos niveles (9 y 11%) de extracto etéreo utilizados en las dietas. Conclusión: Se concluye que dietas para juveniles de esta especie, que contengan 32% de PB pueden afectar el desempeño productivo en términos de baja ganancia de peso, alta conver- sión alimenticia y bajas tasas específicas de crecimiento y de eficiencia proteica.PALABRAS CLAVE: Acuariofilia, pez ornamental, requeri- miento nutricional, tasa especifica de crecimiento, tasa de eficiencia proteica.Background: Currently, ornamental fish are an important element of the pisciculture in our country, with Angelfish(Pterophyllum scalare), being one of the most popular and desired cultured species in the fishkeeping field, given its beauty, majesty and stylized form. However, few authors have studied their nutritional requirements in terms of lipid and protein levels. Objective: This research evaluated six diets, formed by the combination of two levels of crude fat (CF) 9 and 11% and three levels of crude protein (CP) 32, 34 and 36%, to determine its effect on productive performance and the survival of juvenile angelfish (P. scalare). Methodology: 324 juveniles of P. scalare with average weight of 753.5 ± 0.14 mg were randomized in 18 aquariums with volume of 105L, a density of 18 fish/aquarium and fed to 6% of the biomass. Results: We found that a 32% level of crude protein in the diet did not affect the survival, but affected the productive performance (p <0.05), and that levels of 34 or 36% of CP improve it. It was also evidenced that there was no statistical difference (P> 0.05) between the two levels (9 and 11%) of the crude fat used in the diets. Conclusion: It is concluded that diets for juveniles of this species, containing 32% PB can affect the productive performance in terms of low weight gain, high feed conversion and low specific growth rates and protein efficiency.KEYWORDS:Fishkeeping, ornamen- tal fish, nutritional requirement, specific growth rate, protein efficiency rat

Comparative-experimental study of different roof types in a tropical climate

Introduction: The implementation of green roofs in buildings has become increasingly common, because it is an ecological construction alternative that provides great benefits, which range from reducing air pollution to improving air conditioning inside of the buildings. Objective: This article aims to evaluate whether extensive green roofs are an energy-valuable option in a tropical climate compared to a thermoacoustic, clay tile, and concrete roof. Methodology: An experimental study was carried out in summer (December) in a tropical climate, where the internal temperature of two identical small buildings was compared except for the roof type. Both small buildings were built with a low construction standard according to buildings of families with low income in this region. Data of internal temperatures and other climatic conditions were analyzed to compare the influence of the roof type on the inner shelter temperature. Results: In these experiments, the average inner shelter temperature of green roofs was lower than the same temperature for thermoacoustic, clay tile and concrete roof and resulted in average temperature differences of 1.8 °C, 0.9 °C and 1.5 °C, respectively (depending on environmental conditions). Conclusions: It was possible to show that the green roof has a greater thermal inertia compared to the others. However, the temperature difference between the green roof and the other roof types was in the same range as in studies conducted in other climatic regions, therefore no special benefit of the green roof has been derived in a warm-tropical climate in this study. However, the low building standard can be of great interest for a final evaluation and the authors recommend to conduct further studies.Resumen Introducción: La implementación de techos verdes en las edificaciones se ha vuelto cada vez más común, debido a que es una alternativa de construcción ecológica que brinda grandes beneficios que van desde la reducción de la contaminación en el aire, hasta la mejora de la climatización dentro de los edificios. Objetivo: Este artículo tiene como objetivo evaluar si los techos verdes extensivos son una opción energéticamente valiosa en un clima tropical en comparación con un techo termoacústico, de tejas de barro y concreto.  Metodología: Se realizó un estudio experimental en verano (diciembre) en clima tropical donde se comparó la temperatura interna de dos cubículos idénticos excepto del tipo de techo. Los cubículos fueron construidos de bajo estándar de construcción como se construyen casas unifamiliares de personas de bajos ingresos. Los datos de temperaturas internas y demás condiciones climáticas se analizaron para comparar la influencia del tipo de techo en la temperatura interna del cubículo.  Resultados: En los experimentos realizados, la temperatura interna promedio en los techos verdes fue menor que la misma temperatura de los techos termoacústicos, de tejas de barro y concreto, con diferencias de 1.8 °C, 0.9 °C y 1.5 °C, respectivamente (dependiendo de las condiciones ambientales). Conclusiones: Se pudo evidenciar que el techo verde presenta una mayor inercia térmica con respecto a los demás. Sin embargo, la diferencia de temperatura entre el techo verde y los otros tipos de techo estuvo en el mismo rango que en los estudios realizados en otras regiones climáticas, por lo tanto, no se ha derivado ningún beneficio especial del techo verde en un clima cálido tropical en este estudio. Sin embargo, el bajo estándar de construcción puede ser de gran interés para una evaluación final y los autores recomiendan realizar más estudios

Detección Temprana de Epilepsia Pediátrica: Progresión de los Electrodos en EEG

Epilepsy is a brain disorder caused by unexpected changes in electrical activity, manifested by unusual behaviors called seizures, which can lead to loss of consciousness and can be repeated several times during the patient's life. Pediatric epilepsy manifests itself in a very varied way with the age of children; since the type of seizures depends on the degree of maturation of the central nervous system the genetics that predominate in the structure and biochemical processes of the developing brain. In this order of ideas, the electroencephalogram (EEG) is a tool that supports the process of diagnosing this disease through the electrical recording of epileptic seizures. The bioelectrical activity of the brain is detected at the level of the scalp by the electrodes, then amplified and finally recorded. This process is known as neuromonitoring. This review describes several investigations done to determine the effectiveness and performance of different EEG electrodes, emphasizing pediatric applications given the difficulty in this type of patient. It is intended to propose emerging technologies that could shortly be used in the early detection of epileptiform events, allowing treatment strategies to be established from the beginning of patients' lives. Although pediatric electroencephalography has been evolving; however, it still lacks effective and comfortable means of monitoring EEG in early stages and long periods. Therefore, emerging technologies that manage to solve this problem continue to be investigated, such as graphene and doped polymers. La epilepsia es un trastorno cerebral producido por cambios inesperados de la actividad eléctrica del cerebro, manifestado por comportamientos inusuales llamados convulsiones, que pueden llevar hasta la pérdida del conocimiento, y pueden repetirse varias veces en el transcurso de vida del paciente. La epilepsia pediátrica se manifiesta en forma muy variada con la edad de los niños; ya que, el tipo de convulsiones depende del grado de maduración del sistema nervioso central, la genética predominante en la estructura y los procesos bioquímicos del cerebro en desarrollo. En este orden de ideas, el electroencefalograma (EEG) es una herramienta que apoya el diagnóstico de esta enfermedad por medio del registro eléctrico de las crisis epilépticas. La actividad bioeléctrica del cerebro es detectada a nivel del cuero cabelludo por los electrodos, luego se amplifica y finalmente, se registra; este proceso es conocido como la neuromonitorización. En esta revisión se describen varias investigaciones que se recopilaron de revisiones de registros existentes en base a ingeniería biomédica, para determinar la efectividad y desempeño de diferentes electrodos de EEG, con énfasis en aplicaciones pediátricas dada la dificultad en este tipo de paciente. Se pretende plantear las tecnologías emergentes que pudieran en un futuro cercano utilizarse en la detección temprana de eventos epileptiformes, permitiendo establecer estrategias de tratamiento desde el inicio de la vida de los pacientes. Aunque ha evolucionado progresivamente, la Electroencefalografía pediátrica todavía carece de medios efectivos y cómodos para monitorizar continuamente el EEG en etapas tempranas. Tecnologías como el grafeno y los polímeros dopados podrían resolver esta problemática

Improving the monitoring of corn phenology in large agricultural areas using remote sensing data series

Aim of study: Mexico's large irrigation areas demand non-structural actions to improve the irrigation service, such as monitoring crop phenology; however, its application has been limited by the large volumes of field information generated, diversity of crop management and climatic variability. The objective of this study was to generate and validate a methodology to monitor corn (Zea mays L.) phenology from the historical relationship of the vegetation indexes (VIs), EVI and NDVI, with the phenological development (PD) of corn grown in large irrigation zones.Area of study: Irrigation District (ID) 075 “Valle del Fuerte”, northern Sinaloa, Mexico.Material and methods: We used a database of 20 years of climate, field crop growth and crop phenology data, and Landsat satellite images. A methodology was proposed on a large scale supported with GIS and remote sensing data series.Main results: The methodology was validated in 19 plots with an acceptable correlation between observed PD and estimated PD for the two VIs, with slightly better values for EVI than for NDVI. NDVI and EVI models agreed with experimental PD observations in 92.1% of the farms used to validate the methodology, in 2.5% only the NDVI model coincided with the real, in 3.1% only the EVI model coincided, and in 2.3% both models disagreed with observation, generated a stage out of phase with respect to the real phenological stage.Research highlights: is possible to generalize the methodology applied to large irrigation zones with remote sensing data and GIS