Seguidor solar controlat per microcontrolador

L’objectiu d’aquest projecte és la realització d’un seguidor solar, i per poder tenir la màxima precisió en el control de moviment utilitzarem un microcontrolador (PIC 16F877) per controlar el seu estat en tot moment. Volem aconseguir que aquesta placa electrònica pugui controlar un seguidor i posteriorment ampliar-ho a un camp de seguidor solars per una vivenda estàndard. Quan parlem de controlar els seguidor ens referim a fer la orientació adient a cada moment del dia, aquesta orientació tindrà dos graus de llibertat. També aprofitarem les hores vall per poder fer el reposicionament de totes les plaques solarsAquest sistema microprocessat tindrà el suport d’un sistema d’actualització de calendari solar, per saber en quin moment del dia s’ha de posar en marxa i en quina direcció s’ha de posicionar

Sistematització de la implementació i gestió de sistemes solars a l'Amazònia equatoriana

A l’Amazònia equatoriana existeixen diverses experiències de projectes d’electrificació rural aïllada mitjançant tecnologia solar fotovoltaica els quals estan malmesos i abandonats. Aquest fet no implica que l’energia solar fotovoltaica no sigui una tecnologia apropiada, sinó que mostra que molt sovint no s’han tingut en compte criteris de sostenibilitat i gestió en les etapes de disseny i implementació dels projectes realitzats. El projecte té com a objecte sistematitzar la implementació i gestió de sistemes solars a l’Amazònia equatoriana mitjançant un Manual de Bones Pràctiques. L’abast del projecte comprèn des de la recopilació d’informació sobre l’entorn i problemàtiques dels sistemes solars malmesos, fins a la redacció del propi Manual de Bones Pràctiques. S’estudien tant sistemes d’electrificació individuals com comunitaris

Elevada prevalença d’hipovitaminosi D en pacients amb diabetis mellitus tipus 2: relació amb la ingesta de vitamina D i el temps d’exposició solar

Objectius: Estimar la prevalença del dèficit de VitD en pacients amb DM2; avaluar el compliment de les IDR per la VitD; valorar la influència d’aquest compliment i de l’exposició solar en la 25-OH-D3 i la PTHi. Mètodes: 70 pacients. Es va estimar l’exposició solar i la ingesta de VitD. Es van determinar paràmetres del metabolisme fosfo-càlcic i del control glucèmic. Resultats: El 95,8% presentaven hipovitaminosi D, i el 14,8% una PTHi elevada. La majoria no van assolir el compliment de les IDR. La 25-OH-D3 es va correlacionar amb la PTHi però no amb la ingesta de VitD ni l’exposició solar.

Temporal variability and trends of the downward solar radiation over Europe during the 20th century, with regional focus in the dimming/brightening phenomena on the Iberian Peninsula

Proyecto de investigación elaborado a partir de una estancia en el Institute for Atmospheric and Climate Science, a Alemanya, entre 2010 y 2012. La radiación solar que alcanza la superficie terrestre es un factor clave entre los procesos que controlan el clima de la Tierra, dado el papel que desempeñan en el balance energético y el ciclo hidrológico. Establecer su contribución al cambio climático reciente supone una gran dificultad debido a la complejidad de los procesos implicados, la gran cantidad de información requerida, y la incertidumbre de las bases de datos disponibles en la actualidad. Así, el objetivo principal del proyecto ha consistido en generar una base de datos de insolación incluyendo las series más largas (desde finales del siglo XIX) disponibles en toda Europa. Esta base de datos complementa para nuestro continente el Global Energy Balance Archive (GEBA) que mantiene y gestiona el grupo que ha acogido al receptor de la ayuda postdoctoral, y permite extender espacial (especialmente en países del sur de Europa) y temporalmente las series climáticas disponibles de mediciones de irradiancia solar. Como la insolación es un proxy de la irradiancia solar, el proyecto actual también ha tratado de calibrar de forma exhaustiva ambas variables, a fin de generar una nueva base de datos reconstruida de esta segunda variable que esté disponible desde finales del siglo XIX en Europa. Un segundo objetivo del proyecto ha consistido en continuar trabajando a escala de mayor detalle sobre la Península Ibérica, con el fin de proporcionar una mejor comprensión del fenómeno del “global dimming/brightening” y su impacto en el ciclo hidrológico y balance energético. Finalmente, un tercer objetivo del presente proyecto postdoctoral ha consistido en continuar estudiando los posibles ciclos semanales a gran escala de diferentes variables climáticas, línea de investigación de interés para la detección de posibles efectos de los aerosoles antrópicos en el clima a escalas temporales breves, y consecuentemente estrechamente vinculado al fenómeno del “global dimming/brightening”.

Power Comic Reader : Lector de comics para plataforma iOS

Lector de comics para plataforma iOS para dispositivos iPad.

Interplay of spectral efficiency, power and doppler spectrum for reference-signal-assisted wireless communication

Expressions relating spectral efficiency, power, and Doppler spectrum, are derived for Rayleigh-faded wireless channels with Gaussian signal transmission. No side information on the state of the channel is assumed at the receiver. Rather, periodic reference signals are postulated in accordance with the functioning of most wireless systems. The analysis relies on a well-established lower bound, generally tight and asymptotically exact at low SNR. In contrast with most previous studies, which relied on block-fading channel models, a continuous-fading model is adopted. This embeds the Doppler spectrum directly in the derived expressions, imbuing them with practical significance. Closed-form relationships are obtained for the popular Clarke-Jakes spectrum and informative expansions, valid for arbitrary spectra, are found for the low- and high-power regimes. While the paper focuses on scalar channels, the extension to multiantenna settings is also discussed.

Optimum power allocation for parallel Gaussian channels with arbitrary input distributions

The mutual information of independent parallel Gaussian-noise channels is maximized, under an average power constraint, by independent Gaussian inputs whose power is allocated according to the waterfilling policy. In practice, discrete signalling constellations with limited peak-to-average ratios (m-PSK, m-QAM, etc) are used in lieu of the ideal Gaussian signals. This paper gives the power allocation policy that maximizes the mutual information over parallel channels with arbitrary input distributions. Such policy admits a graphical interpretation, referred to as mercury/waterfilling, which generalizes the waterfilling solution and allows retaining some of its intuition. The relationship between mutual information of Gaussian channels and nonlinear minimum mean-square error proves key to solving the power allocation problem.

High-SNR power offset in multiantenna communication

The analysis of the multiantenna capacity in the high-SNR regime has hitherto focused on the high-SNR slope (or maximum multiplexing gain), which quantifies the multiplicative increase as function of the number of antennas. This traditional characterization is unable to assess the impact of prominent channel features since, for a majority of channels, the slope equals the minimum of the number of transmit and receive antennas. Furthermore, a characterization based solely on the slope captures only the scaling but it has no notion of the power required for a certain capacity. This paper advocates a more refined characterization whereby, as function of SNRjdB, the high-SNR capacity is expanded as an affine function where the impact of channel features such as antenna correlation, unfaded components, etc, resides in the zero-order term or power offset. The power offset, for which we find insightful closed-form expressions, is shown to play a chief role for SNR levels of practical interest.

Optimum power allocation for multiuser OFDM with arbitrary signal constellations

This paper formulates power allocation policies that maximize the region of mutual informationsachievable in multiuser downlink OFDM channels. Arbitrary partitioning ofthe available tones among users and arbitrary modulation formats, possibly different forevery user, are considered. Two distinct policies are derived, respectively for slow fadingchannels tracked instantaneously by the transmitter and for fast fading channels knownonly statistically thereby. With instantaneous channel tracking, the solution adopts theform of a multiuser mercury/waterfilling procedure that generalizes the single-user mercury/waterfilling introduced in [1, 2]. With only statistical channel information, in contrast,the mercury/waterfilling interpretation is lost. For both policies, a number of limitingregimes are explored and illustrative examples are provided.

Per-antenna rate and power control for MIMO layered architectures in the low- and high-power regimes

In a MIMO layered architecture, several codewordsare transmitted from a multiplicity of antennas. Although thespectral efficiency is maximized if the rates of these codewordsare separately controlled, the feedback rate within the linkadaptation loop is reduced if they are constrained to be identical.This poses a direct tradeoff between performance andfeedback overhead. This paper provides analytical expressionsthat quantify the difference in spectral efficiency between bothapproaches for arbitrary numbers of antennas. Specifically, thecharacterization takes place in the realm of the low- and highpowerregimes via expansions that are shown to have a widerange of validity.In addition, the possibility of adjusting the transmit powerof each codeword individually is considered as an alternative tothe separate control of their rates. Power allocation, however,turns out to be inferior to rate control within the context of thisproblem.

Spectral efficiency in reference-signal-assisted low-power wireless communication

Expressions relating spectral efficiency, power and Doppler spectrum are derived for low-power Rayleighfaded wireless channels with proper complex signaling. Noside information on the state of the channel is assumed at the receiver. Rather, periodic reference signals are postulated inaccordance with the functioning of most wireless systems. In contrast with most previous studies, which relied on block-fading channel models, a continuous-fading model is adopted. This embeds the Doppler spectrum directly in thederived expressions thereby imbuing them with practical significance.

Discourse, knowledge, power and politics: towards critical epistemic discourse analysis

Although both are fundamental terms in the humanities and social sciences, discourse and knowledge have seldom been explicitly related, and even less so in critical discourse studies. After a brief summary of what we know about these relationships in linguistics, psychology, epistemology and the social sciences, with special emphasis on the role of knowledge in the formation of mental models as a basis for discourse, I examine in more detail how a critical study of discourse and knowledge may be articulated in critical discourse studies. Thus, several areas of critical epistemic discourse analysis are identified, and then applied in a study of Tony Blair’s Iraq speech on March 18, 2003, in which he sought to legitimatize his decision to go to war in Iraq with George Bush. The analysis shows the various modes of how knowledge is managed and manipulated of all levels of discourse of this speech.

Power transformations in correspondence analysis

Power transformations of positive data tables, prior to applying the correspondence analysis algorithm, are shown to open up a family of methods with direct connections to the analysis of log-ratios. Two variations of this idea are illustrated. The first approach is simply to power the original data and perform a correspondence analysis this method is shown to converge to unweighted log-ratio analysis as the power parameter tends to zero. The second approach is to apply the power transformation to thecontingency ratios, that is the values in the table relative to expected values based on the marginals this method converges to weighted log-ratio analysis, or the spectral map. Two applications are described: first, a matrix of population genetic data which is inherently two-dimensional, and second, a larger cross-tabulation with higher dimensionality, from a linguistic analysis of several books.

Endogenous bargaining power

We present a novel approach to N-person bargaining, based on the idea thatthe agreement reached in a negotiation is determined by how the directconflict resulting from disagreement would be resolved. Our basic buildingblock is the disagreement function, which maps each set of feasible outcomesinto a disagreement point. Using this function and a weak axiom basedon individual rationality we reach a unique solution: the agreement inthe shadow of conflict, ASC. This agreement may be construed as the limitof a sequence of partial agreements, each of which is reached as a functionof the parties relative power. We examine the connection between ASC andasymmetric Nash solutions. We show the connection between the power ofthe parties embodied in the ASC solution and the bias in the SWF thatwould select ASC as an asymmetric Nash solution.