Análise tribo-termodinâmica da aplicação de nanopartículas de Al2O3 como aditivo lubrificante em compressor hermético de refrigeração

The thermodynamic performance of a refrigeration system can be improved by reducing the compression work by a particular technique for a specific heat removal rate. This study examines the effect of small concentrations of Al2O3 (50 nm) nanoparticles dispersion in the mineral oil based lubricant on the: viscosity, thermal conductivity, and lubrication characteristics as well as the overall performance (based on the Second Law of Thermodynamics) of the refrigerating system using R134a or R600a as refrigerants. The study looked at the influences of variables: i) refrigerant charge (100, 110, 120 and 130 g), ii) rotational speed of the condenser blower (800 and 1100 RPM) and iii) nanoparticle concentration (0.1 and 0.5 g/l) on the system performance based on the Taguchi method in a matrix of L8 trials with the criterion "small irreversibility is better”. They were carried pulldown and cycling tests according to NBR 12866 and NBR 12869, respectively, to evaluate the operational parameters: on-time ratio, cycles per hour, suction and discharge pressures, oil sump temperature, evaporation and condensation temperatures, energy consumption at the set-point, total energy consumption and compressor power. In order to evaluate the nanolubricant characteristics, accelerated tests were performed in a HFRR bench. In each 60 minutes test with nanolubricants at a certain concentration (0, 0.1 and 0.5 g/l), with three replications, the sphere (diameter 6.00 ± 0.05 mm, Ra 0.05 ± 0.005 um, AISI 52100 steel, E = 210 GPa, HRC 62 ± 4) sliding on a flat plate (cast iron FC200, Ra <0.5 ± 0.005 um) in a reciprocating motion with amplitude of 1 mm, frequency 20 Hz and a normal load of 1,96 N. The friction coefficient signals were recorded by sensors coupled to the HFRR system. There was a trend commented bit in the literature: a nanolubricant viscosity reduction at the low nanoparticles concentrations. It was found the dominant trend in the literature: increased thermal conductivity with increasing nanoparticles mass fraction in the base fluid. Another fact observed is the significant thermal conductivity growth of nanolubricant with increasing temperature. The condenser fan rotational speed is the most influential parameter (46.192%) in the refrigerator performance, followed by R600a charge (38.606%). The Al2O3 nanoparticles concentration in the lubricant plays a minor influence on system performance, with 12.44%. The results of power consumption indicates that the nanoparticles addition in the lubricant (0.1 g/L), together with R600a, the refrigerator consumption is reduced of 22% with respect to R134a and POE lubricant. Only the Al2O3 nanoparticles addition in the lubricant results in a consumption reduction of about 5%.

Análise tribo-termodinâmica da aplicação de nanopartículas de Al2O3 como aditivo lubrificante em compressor hermético de refrigeração

The thermodynamic performance of a refrigeration system can be improved by reducing the compression work by a particular technique for a specific heat removal rate. This study examines the effect of small concentrations of Al2O3 (50 nm) nanoparticles dispersion in the mineral oil based lubricant on the: viscosity, thermal conductivity, and lubrication characteristics as well as the overall performance (based on the Second Law of Thermodynamics) of the refrigerating system using R134a or R600a as refrigerants. The study looked at the influences of variables: i) refrigerant charge (100, 110, 120 and 130 g), ii) rotational speed of the condenser blower (800 and 1100 RPM) and iii) nanoparticle concentration (0.1 and 0.5 g/l) on the system performance based on the Taguchi method in a matrix of L8 trials with the criterion "small irreversibility is better”. They were carried pulldown and cycling tests according to NBR 12866 and NBR 12869, respectively, to evaluate the operational parameters: on-time ratio, cycles per hour, suction and discharge pressures, oil sump temperature, evaporation and condensation temperatures, energy consumption at the set-point, total energy consumption and compressor power. In order to evaluate the nanolubricant characteristics, accelerated tests were performed in a HFRR bench. In each 60 minutes test with nanolubricants at a certain concentration (0, 0.1 and 0.5 g/l), with three replications, the sphere (diameter 6.00 ± 0.05 mm, Ra 0.05 ± 0.005 um, AISI 52100 steel, E = 210 GPa, HRC 62 ± 4) sliding on a flat plate (cast iron FC200, Ra <0.5 ± 0.005 um) in a reciprocating motion with amplitude of 1 mm, frequency 20 Hz and a normal load of 1,96 N. The friction coefficient signals were recorded by sensors coupled to the HFRR system. There was a trend commented bit in the literature: a nanolubricant viscosity reduction at the low nanoparticles concentrations. It was found the dominant trend in the literature: increased thermal conductivity with increasing nanoparticles mass fraction in the base fluid. Another fact observed is the significant thermal conductivity growth of nanolubricant with increasing temperature. The condenser fan rotational speed is the most influential parameter (46.192%) in the refrigerator performance, followed by R600a charge (38.606%). The Al2O3 nanoparticles concentration in the lubricant plays a minor influence on system performance, with 12.44%. The results of power consumption indicates that the nanoparticles addition in the lubricant (0.1 g/L), together with R600a, the refrigerator consumption is reduced of 22% with respect to R134a and POE lubricant. Only the Al2O3 nanoparticles addition in the lubricant results in a consumption reduction of about 5%.

Métodos de extração de fósforo e micronutrientes em latossolos com uso de energia ultrassônica

Assessing the soil nutrient availability to plants under lab conditions is one of the main challenges to Soil Fertility and Chemistry, due to the complex behavior and the interaction of the soil properties. Many extractant solutions associated with mechanical forms of agitation have been proposed, showing different correlations with plant growth and nutrients absorption. Using ultrasonic energy is a agitation procedure of the soil:extractant solution suspension (based on the cavitation phenomenon). It allows the establishment of relations between the amount of extracted nutrient and the ultrasonic energy level. Thus, this work aims: to evaluate the effect of cavitation intensity on the extraction of P, Zn, Cu, Mn and Fe in soil samples from five Latosols under different uses around Uberlândia and Uberaba, Minas Gerais State; to obtain extracting curves as function of ultrasonic energy levels; and to obtain an index from extracting curves to expresses the nutrient retention by the soil solid phase. A soil-solution suspension (ratio 1:10) was sonicated using a probe ultrasound equipment under different combinations of power and time: i) 30 W for 35, 70, 140 and 280 s; ii) 50 W for 21, 42, 84 and 168 s; and iii) 70 W for 15, 30, 60 and 120 s. The extractant solutions used were Mehlich-1 (for all elements), Olsen and distilled water for P. After each sonication, P concentration was quantified by molybdenum blue colorimetric method and Zn, Cu, Mn and Fe by flame atomic absorption spectrophotometry. The cavitation intensity did not affect the P extraction, only the total energy applied. The P extraction was influenced by extractant solution, decreasing as follows: Mehlich-1>Olsen>water. In cultivated Latosols, the P extraction increased linearly with ultrasonic energy, and the slope of the 1:1 linear regression reflects the P retention in the soil. The Zn and Fe extractions were influenced only by total energy applied. Mn and Cu extractions were influenced by both cavitation intensity and total ultrasonic energy. Soils containing similar amounts of P, Cu, Zn, Mn, and Fe may have a different extraction rate. Likewise, soils containing different amounts of those elements may have the same extraction rate.

Phase coexistence of cluster crystals: beyond the Gibbs phase rule

We report a study of the phase behavior of multiple-occupancy crystals through simulation. We argue that in order to reproduce the equilibrium behavior of such crystals it is essential to treat the number of lattice sites as a constraining thermodynamic variable. The resulting free-energy calculations thus differ considerably from schemes used for single-occupancy lattices. Using our approach, we obtain the phase diagram and the bulk modulus for a generalized exponential model that forms cluster crystals at high densities. We compare the simulation results with existing theoretical predictions. We also identify two types of density fluctuations that can lead to two sound modes and evaluate the corresponding elastic constants.

Statin prescription initiation and lifestyle behaviour: a primary care cohort study

BACKGROUND: Statin prescribing and healthy lifestyles contribute to declining cardiovascular disease mortality. Recent guidelines emphasise the importance of giving lifestyle advice in association with prescribing statins but adherence to healthy lifestyle recommendations is sub-optimal. However, little is known about any change in patients' lifestyle behaviours when starting statins or of their recall of receiving advice. This study aimed to examine patients' diet and physical activity (PA) behaviours and their recall of lifestyle advice following initiation of statin prescribing in primary care.

METHOD: In 12 general practices, patients with a recent initial prescription of statin therapy, were invited to participate. Those who agreed received a food diary by post, to record food consumed over 4 consecutive days and return to the researcher. We also telephoned participants to administer brief validated questionnaires to assess typical daily diet (DINE) and PA level (Godin). Using the same methods, food diaries and questionnaires were repeated 3 months later. At both times participants were asked if they had changed their behaviour or received advice about their diet or PA.

RESULTS: Of 384 invited, 122 (32 %) participated; 109 (89.3 %) completed paired datasets; 50 (45.9 %) were male; their mean age was 64 years. 53.2 % (58/109) recalled receiving lifestyle advice. Of those who did, 69.0 % (40/58) reported having changed their diet or PA, compared to 31.4 % (16/51) of those who did not recall receiving advice. Initial mean daily saturated fat intake (12.9 % (SD3.5) of total energy) was higher than recommended; mean fibre intake (13.8 g/day (SD5.5)), fruit/vegetable consumption (2.7 portions/day (SD1.3)) and PA levels (Godin score 7.1 (SD13.9)) were low. Overall, although some individuals showed evidence of behaviour change, there were no significant changes in the proportions who reported high or medium fat intake (42.2 % v 49.5 %), low fibre (51.4 % v 55.0 %), or insufficient PA (80.7 % v 83.5 %) at 3-month follow-up.

CONCLUSION: Whilst approximately half of our cohort recalled receiving lifestyle advice associated with statin prescribing this did not translate into significant changes in diet or PA. Further research is needed to explore gaps between people's knowledge and behaviours and determine how best to provide advice that supports behaviour change.

Systemische Betrachtung der Zusammenhänge und Auswirkungen von Planungsalternativen auf die Gesamtenergiebilanz von Logistikzentren

Logistikzentren müssen zukünftig eine hohe Gesamtenergieeffizienz aufweisen und zu einem hohen Anteil mit Energie aus erneuerbaren Quellen versorgt werden. Um die Stellschrauben zur Senkung des Energiebedarfs als auch der CO2-Emissionen in Logistikzentren zu identifizieren, werden Auswirkungen von energieeffizienten Planungsalternativen aus den Bereichen Intralogistik, Gebäudetechnik und -hülle auf die Gesamtenergiebilanz untersucht.

Caractérisation de l'impact des conditions opératoires sur l'efficience d'un procédé de concentration du lait par ultrafiltration

Les concentrés de protéines de lait sont couramment utilisés comme ingrédients lors de la standardisation du lait de fromagerie. La concentration des protéines est généralement réalisée par ultrafiltration (UF) à l’aide de membranes polymériques ayant un seuil de coupure de 10 kDa, et ce, jusqu’à un facteur de concentration volumique de 3.5X. Dans l’optique d’améliorer l’efficience du procédé d’UF, l’étude avait pour but de caractériser l’impact du mode opératoire (pression transmembranaire constante (465 et 672 kPa) et flux constant) ainsi que la température (10°C et 50°C) sur la performance du système jusqu’à un facteur de concentration volumique de 3.6X. Le module de filtration à l’échelle pilote comprenait une membrane d’UF en polyéthersulfone de 10 kDa d’une surface de 2,04 m2. La performance du système a été caractérisée sur le flux de perméation, la sélectivité et la consommation énergétique totale. L’étude a montré que le flux de perméation était 1,9 fois plus élevé à une température de 50°C comparativement à 10°C lors de l’UF du lait. Le coefficient de rejet des protéines n’a pas été affecté significativement par la pression transmembranaire et la température (P< 0,05). L’effet de la température a été observé au niveau de la teneur en calcium, laquelle était plus élevée de 12% dans les rétentats générés à 50C. La consommation énergétique totale du système d’UF était plus élevée à 10C comparativement à 50C, représentant 0,32±0,02 et 0,26±0,04 kWh/kg rétentat respectivement. Les résultats montrent que le ratio d’efficience énergétique (rapport entre le flux de perméation et la consommation énergétique) optimal a été obtenu à faible pression transmembranaire constante et à 50C. L’approche développée dans le cadre de ce projet fournira des outils aux industriels laitiers pour améliorer l’éco-efficience de leurs procédés de séparation baromembranaire.

Stratégie d'amélioration de la résistance mécanique des zones de connecteurs

Le bois subit une demande croissante comme matériau de construction dans les bâtiments de grandes dimensions. Ses qualités de matériau renouvelable et esthétique le rendent attrayant pour les architectes. Lorsque comparé à des produits fonctionnellement équivalents, il apparait que le bois permet de réduire la consommation d’énergie non-renouvelable. Sa transformation nécessite une quantité d’énergie inférieure que l’acier et le béton. Par ailleurs, par son origine biologique, une structure en bois permet de stocker du carbone biogénique pour la durée de vie du bâtiment. Maintenant permis jusqu’à six étages de hauteur au Canada, les bâtiments de grande taille en bois relèvent des défis de conception. Lors du dimensionnement des structures, les zones des connecteurs sont souvent les points critiques. Effectivement, les contraintes y sont maximales. Les structures peuvent alors apparaitre massives et diminuer l’innovation architecturale. De nouvelles stratégies doivent donc être développées afin d’améliorer la résistance mécanique dans les zones de connecteurs. Différents travaux ont récemment porté sur la création ou l’amélioration de types d’assemblage. Dans cette étude, l’accent est mis sur le renforcement du bois utilisé dans la région de connexion. L’imprégnation a été choisie comme solution de renfort puisque la littérature démontre qu’il est possible d’augmenter la dureté du bois avec cette technique. L’utilisation de cette stratégie de renfort sur l’épinette noire (Picea Mariana (Mill.) BSP) pour une application structurale est l’élément de nouveauté dans cette recherche. À défaut d’effectuer une imprégnation jusqu’au coeur des pièces, l’essence peu perméable de bois employée favorise la création d’une mince couche en surface traitée sans avoir à utiliser une quantité importante de produits chimiques. L’agent d’imprégnation est composé de 1,6 hexanediol diacrylate, de triméthylopropane tricacrylate et d’un oligomère de polyester acrylate. Une deuxième formulation contenant des nanoparticules de SiO2 a permis de vérifier l’effet des nanoparticules sur l’augmentation de la résistance mécanique du bois. Ainsi, dans ce projet, un procédé d’imprégnation vide-pression a servi à modifier un nouveau matériau à base de bois permettant des assemblages plus résistants mécaniquement. Le test de portance locale à l’enfoncement parallèle au fil d’un connecteur de type tige a été réalisé afin de déterminer l’apport du traitement sur le bois utilisé comme élément de connexion. L’effet d’échelle a été observé par la réalisation du test avec trois diamètres de boulons différents (9,525 mm, 12,700 mm et 15,875 mm). En outre, le test a été effectué selon un chargement perpendiculaire au fil pour le boulon de moyen diamètre (12,700 mm). La corrélation d’images numériques a été utilisée comme outil d’analyse de la répartition des contraintes dans le bois. Les résultats ont démontré une portance du bois plus élevée suite au traitement. Par ailleurs, l’efficacité est croissante lorsque le diamètre du boulon diminue. C’est un produit avec une valeur caractéristique de la portance locale parallèle au fil de 79% supérieure qui a été créé dans le cas du test avec le boulon de 9,525 mm. La raideur du bois a subi une augmentation avoisinant les 30%. Suite au traitement, la présence d’une rupture par fissuration est moins fréquente. Les contraintes se distribuent plus largement autour de la région de connexion. Le traitement n’a pas produit d’effet significatif sur la résistance mécanique de l’assemblage dans le cas d’un enfoncement du boulon perpendiculairement au fil du bois. De même, l’effet des nanoparticules en solution n’est pas ressorti significatif. Malgré une pénétration très faible du liquide à l’intérieur du bois, la couche densifiée en surface créée suite au traitement est suffisante pour produire un nouveau matériau plus résistant dans les zones de connexion. Le renfort du bois dans la région des connecteurs doit influencer le dimensionnement des structures de grande taille. Avec des éléments de connexion renforcés, il sera possible d’allonger les portées des poutres, multipliant ainsi les possibilités architecturales. Le renfort pourra aussi permettre de réduire les sections des poutres et d’utiliser une quantité moindre de bois dans un bâtiment. Cela engendrera des coûts de transport et des coûts reliés au temps d’assemblage réduits. De plus, un connecteur plus résistant permettra d’être utilisé en moins grande quantité dans un assemblage. Les coûts d’approvisionnement en éléments métalliques et le temps de pose sur le site pourront être revus à la baisse. Les avantages d’un nouveau matériau à base de bois plus performant utilisé dans les connexions permettront de promouvoir le bois dans les constructions de grande taille et de réduire l’impact environnemental des bâtiments.

Solar magnetic carpet II: coronal interactions of small-scale magnetic fields

This paper is the second in a series of studies working towards constructing a realistic, evolving, non-potential coronal model for the solar magnetic carpet. In the present study, the interaction of two magnetic elements is considered. Our objectives are to study magnetic energy build-up, storage and dissipation as a result of emergence, cancellation, and flyby of these magnetic elements. In the future these interactions will be the basic building blocks of more complicated simulations involving hundreds of elements. Each interaction is simulated in the presence of an overlying uniform magnetic field, which lies at various orientations with respect to the evolving magnetic elements. For these three small-scale interactions, the free energy stored in the field at the end of the simulation ranges from 0.2 – 2.1×1026 ergs, whilst the total energy dissipated ranges from 1.3 – 6.3×1026 ergs. For all cases, a stronger overlying field results in higher energy storage and dissipation. For the cancellation and emergence simulations, motion perpendicular to the overlying field results in the highest values. For the flyby simulations, motion parallel to the overlying field gives the highest values. In all cases, the free energy built up is sufficient to explain small-scale phenomena such as X-ray bright points or nanoflares. In addition, if scaled for the correct number of magnetic elements for the volume considered, the energy continually dissipated provides a significant fraction of the quiet Sun coronal heating budget.

Effects of mass and body composition on fasting fuel utilisation in grey seal pups (Halichoerus grypus Fabricius): an experimental study using supplementary feeding

This study used supplementary feeding to test the hypothesis that fuel partitioning during the postweaning fast in grey seal pups is affected by size and composition of energy reserves at weaning, and by extra provisioning. Mass and body composition changes were measured during suckling and fasting to investigate the effect of natural differences in energy reserves at weaning on subsequent allocation of fat and protein to energy use. We fed seven pups for 5 days after weaning, to investigate the effect of increased fuel availability, and particularly protein, on fuel utilisation. After correcting for protein used during the moult, the proportional contribution of fat was 86–99% of total energy use. Pups with greater energy reserves, i.e. those that were heavier and fatter at weaning, had higher rates of fat and energy use. There was no significant relationship between adiposity at weaning and proportional contribution of fat to energy use, perhaps due to a limited sample size or range of body masses and adiposity. Supplemented individuals used energy, specifically fat, much faster and utilised proportionally less of their endogenous protein by departure than non-supplemented individuals. Fat metabolism contributed a similar percentage to daily energy use in both groups. These findings show that pups spare protein, even when energy use is dramatically increased. Pups that receive greater maternal provisioning and lay down more protein may have increased survival chances at sea. This study highlights the importance of protein reserves in first year survival of grey seal pups.

Medidas de eficiência energética numa indústria cerâmica

O presente relatório resulta de um estágio realizado no âmbito da eficiência energética assente no programa Galp 20-20-20 que tem por génese uma parceria entre a Universidade de Aveiro e a empresa de coberturas cerâmicas, CS – Coelho da Silva S.A. A Fábrica alvo de estudo é uma consumidora intensiva de energia, despendeu no ano de 2013 cerca de 3.768 tep. Devido aos seus processos de cozedura e secagem, apresenta uma elevada dependência de Gás Natural, representando pouco mais de 78% do consumo global da fábrica. Deste consumo de energia térmica, 83% respeita ao forno e os restantes 17% encontram-se alocados ao secador, pelo que as medidas de eficiência energética presentes neste relatório centram-se da redução deste vetor energético. São então propostas três medidas para a redução da dependência deste vetor. A primeira, incide na recuperação de calor residual presente nos gases de exaustão através da instalação de um permutador de calor. Esta medida permite uma redução do consumo na ordem dos 10% e conta com um payback de 2,3 anos resultante de uma economia anual de 150.000 €. Para este estudo foi desenvolvido um modelo dinâmico em excel que permite a simulação de diversos cenários. São também propostas mais duas intervenções que incidem na alteração do circuito térmico. Estas medidas têm um impacte mais reduzido no que respeita ao percentual de redução energético, ambas com menos de 1% de redução do consumo global da fábrica. Contudo são medidas bastante interessantes dada a sua simplicidade e contam com poupanças anuais na ordem dos 6.000 € que resultam num payback inferior a 2 meses. Paralelamente executaram-se dois estudos para a iluminação, o primeiro sugere a instalação de um modelador de tensão que reduz a potência de iluminação em 36%, implicando uma redução da iluminância de cerca de 5%. A redução da potência resulta numa economia energética na ordem dos 0,4% da energia global da instalação. Este equipamento poderá ser adquirido por completo ou em renting. Ao optar pela compra integral, o investimento será apenas ressarcido em 2,8 anos resultante de uma poupança anula de perto de 6.500 €. Caso seja por renting este não tem qualquer custo adicional e as economias monetárias são partilhadas entre a empresa que fornece o equipamento e a CS-Coelho da Silva, S.A. Por fim é sugerida a substituição de parte da iluminação atual da fábrica por tecnologia LED, com esta medida reduz-se o consumo global em 0,76%. Esta medida gera uma economia monetária na ordem dos 11.500 € sendo ressarcida em 2,1 anos.

Modelling of an efficient dynamic smart solar photovoltaic power grid system

A smart solar photovoltaic grid system is an advent of innovation coherence of information and communications technology (ICT) with power systems control engineering via the internet [1]. This thesis designs and demonstrates a smart solar photovoltaic grid system that is selfhealing, environmental and consumer friendly, but also with the ability to accommodate other renewable sources of energy generation seamlessly, creating a healthy competitive energy industry and optimising energy assets efficiency. This thesis also presents the modelling of an efficient dynamic smart solar photovoltaic power grid system by exploring the maximum power point tracking efficiency, optimisation of the smart solar photovoltaic array through modelling and simulation to improve the quality of design for the solar photovoltaic module. In contrast, over the past decade quite promising results have been published in literature, most of which have not addressed the basis of the research questions in this thesis. The Levenberg-Marquardt and sparse based algorithms have proven to be very effective tools in helping to improve the quality of design for solar photovoltaic modules, minimising the possible relative errors in this thesis. Guided by theoretical and analytical reviews in literature, this research has carefully chosen the MatLab/Simulink software toolbox for modelling and simulation experiments performed on the static smart solar grid system. The auto-correlation coefficient results obtained from the modelling experiments give an accuracy of 99% with negligible mean square error (MSE), root mean square error (RMSE) and standard deviation. This thesis further explores the design and implementation of a robust real-time online solar photovoltaic monitoring system, establishing a comparative study of two solar photovoltaic tracking systems which provide remote access to the harvested energy data. This research made a landmark innovation in designing and implementing a unique approach for online remote access solar photovoltaic monitoring systems providing updated information of the energy produced by the solar photovoltaic module at the site location. In addressing the challenge of online solar photovoltaic monitoring systems, Darfon online data logger device has been systematically integrated into the design for a comparative study of the two solar photovoltaic tracking systems examined in this thesis. The site location for the comparative study of the solar photovoltaic tracking systems is at the National Kaohsiung University of Applied Sciences, Taiwan, R.O.C. The overall comparative energy output efficiency of the azimuthal-altitude dual-axis over the 450 stationary solar photovoltaic monitoring system as observed at the research location site is about 72% based on the total energy produced, estimated money saved and the amount of CO2 reduction achieved. Similarly, in comparing the total amount of energy produced by the two solar photovoltaic tracking systems, the overall daily generated energy for the month of July shows the effectiveness of the azimuthal-altitude tracking systems over the 450 stationary solar photovoltaic system. It was found that the azimuthal-altitude dual-axis tracking systems were about 68.43% efficient compared to the 450 stationary solar photovoltaic systems. Lastly, the overall comparative hourly energy efficiency of the azimuthal-altitude dual-axis over the 450 stationary solar photovoltaic energy system was found to be 74.2% efficient. Results from this research are quite promising and significant in satisfying the purpose of the research objectives and questions posed in the thesis. The new algorithms introduced in this research and the statistical measures applied to the modelling and simulation of a smart static solar photovoltaic grid system performance outperformed other previous works in reviewed literature. Based on this new implementation design of the online data logging systems for solar photovoltaic monitoring, it is possible for the first time to have online on-site information of the energy produced remotely, fault identification and rectification, maintenance and recovery time deployed as fast as possible. The results presented in this research as Internet of things (IoT) on smart solar grid systems are likely to offer real-life experiences especially both to the existing body of knowledge and the future solar photovoltaic energy industry irrespective of the study site location for the comparative solar photovoltaic tracking systems. While the thesis has contributed to the smart solar photovoltaic grid system, it has also highlighted areas of further research and the need to investigate more on improving the choice and quality design for solar photovoltaic modules. Finally, it has also made recommendations for further research in the minimization of the absolute or relative errors in the quality and design of the smart static solar photovoltaic module.

Critical core mass for enriched envelopes: the role of H2O condensation

Context. Within the core accretion scenario of planetary formation, most simulations performed so far always assume the accreting envelope to have a solar composition. From the study of meteorite showers on Earth and numerical simulations, we know that planetesimals must undergo thermal ablation and disruption when crossing a protoplanetary envelope. Thus, once the protoplanet has acquired an atmosphere, not all planetesimals reach the core intact, i.e. the primordial envelope (mainly H and He) gets enriched in volatiles and silicates from the planetesimals. This change of envelope composition during the formation can have a significant effect on the final atmospheric composition and on the formation timescale of giant planets. Aims. We investigate the physical implications of considering the envelope enrichment of protoplanets due to the disruption of icy planetesimals during their way to the core. Particular focus is placed on the effect on the critical core mass for envelopes where condensation of water can occur. Methods. Internal structure models are numerically solved with the implementation of updated opacities for all ranges of metallicities and the software Chemical Equilibrium with Applications to compute the equation of state. This package computes the chemical equilibrium for an arbitrary mixture of gases and allows the condensation of some species, including water. This means that the latent heat of phase transitions is consistently incorporated in the total energy budget. Results. The critical core mass is found to decrease significantly when an enriched envelope composition is considered in the internal structure equations. A particularly strong reduction of the critical core mass is obtained for planets whose envelope metallicity is larger than Z approximate to 0.45 when the outer boundary conditions are suitable for condensation of water to occur in the top layers of the atmosphere. We show that this effect is qualitatively preserved even when the atmosphere is out of chemical equilibrium. Conclusions. Our results indicate that the effect of water condensation in the envelope of protoplanets can severely affect the critical core mass, and should be considered in future studies.

INTEGRATED THRESHOLD-ACTIVATED FEEDBACK MICROSYSTEM FOR REAL-TIME CHARACTERIZATION, SENSING AND TREATMENT OF BACTERIAL BIOFILMS

Biofilms are the primary cause of clinical bacterial infections and are impervious to typical amounts of antibiotics, necessitating very high doses for treatment. Therefore, it is highly desirable to develop new alternate methods of treatment that can complement or replace existing approaches using significantly lower doses of antibiotics. Current standards for studying biofilms are based on end-point studies that are invasive and destroy the biofilm during characterization. This dissertation presents the development of a novel real-time sensing and treatment technology to aid in the non-invasive characterization, monitoring and treatment of bacterial biofilms. The technology is demonstrated through the use of a high-throughput bifurcation based microfluidic reactor that enables simulation of flow conditions similar to indwelling medical devices. The integrated microsystem developed in this work incorporates the advantages of previous in vitro platforms while attempting to overcome some of their limitations. Biofilm formation is extremely sensitive to various growth parameters that cause large variability in biofilms between repeated experiments. In this work we investigate the use of microfluidic bifurcations for the reduction in biofilm growth variance. The microfluidic flow cell designed here spatially sections a single biofilm into multiple channels using microfluidic flow bifurcation. Biofilms grown in the bifurcated device were evaluated and verified for reduced biofilm growth variance using standard techniques like confocal microscopy. This uniformity in biofilm growth allows for reliable comparison and evaluation of new treatments with integrated controls on a single device. Biofilm partitioning was demonstrated using the bifurcation device by exposing three of the four channels to various treatments. We studied a novel bacterial biofilm treatment independent of traditional antibiotics using only small molecule inhibitors of bacterial quorum sensing (analogs) in combination with low electric fields. Studies using the bifurcation-based microfluidic flow cell integrated with real-time transduction methods and macro-scale end-point testing of the combination treatment showed a significant decrease in biomass compared to the untreated controls and well-known treatments such as antibiotics. To understand the possible mechanism of action of electric field-based treatments, fundamental treatment efficacy studies focusing on the effect of the energy of the applied electrical signal were performed. It was shown that the total energy and not the type of the applied electrical signal affects the effectiveness of the treatment. The linear dependence of the treatment efficacy on the applied electrical energy was also demonstrated. The integrated bifurcation-based microfluidic platform is the first microsystem that enables biofilm growth with reduced variance, as well as continuous real-time threshold-activated feedback monitoring and treatment using low electric fields. The sensors detect biofilm growth by monitoring the change in impedance across the interdigitated electrodes. Using the measured impedance change and user inputs provided through a convenient and simple graphical interface, a custom-built MATLAB control module intelligently switches the system into and out of treatment mode. Using this self-governing microsystem, in situ biofilm treatment based on the principles of the bioelectric effect was demonstrated by exposing two of the channels of the integrated bifurcation device to low doses of antibiotics.

Ação de anestésicos gerais em canais iônicos

Dissertação (mestrado)—Universidade de Brasília, Instituto de Ciências Biológicas, Departamento de Biologia Molecular, 2016.