Thermostatistical description of small systems in nonequilibrium conditions: Energy conversion and harvesting

Hysteresis cycles are very important features of energy conversion and harvesting devices, such as batteries. The efficiency of these may be strongly affected by the physical size of the system. Here, we show that in systems which are small enough, the existence of physical boundaries which produce nonhomogeneities of the interaction potential gives rise to inflections and barriers in the associated free energy. This in turn brings on irreversible processes which can be triggered under suitable external conditions imposed by a heat bath. As an example, by controlling the temperature, the state of a small system may be impelled to oscillate between two different structural configurations or aggregation states avoiding equilibrium coexistence and therefore dissipating energy. This cyclical behavior associated with a hysteresis cycle may be prototypical of energy conversion, storage, or generating nanodevices, as exemplified by Li-ion insertion batteries.

Reconocimiento y representación digital de la notación matemática manual

El trabajo muestra un estudio comparativo de las soluciones que plantean diferentes soluciones comerciales y/o libres para la adecuación o no a su integración en un entorno como es el campus virtual de la UOC. Para esto se ha elaborado una lista de indicadores clave y más adelante se ha hecho una valoración de la integración en el entorno UOC, relacionando los indicadores anteriores con los requerimientos de la UOC. Investigando previamente cuales son estos. Por último se ha comprobado y corroborado la posible integración de la solución elegida al campus virtual, con el desarrollo de una pequeña aplicación web.

Positional stability of holographic optical traps

The potential of digital holography for complex manipulation of micron-sized particles with optical tweezers has been clearly demonstrated. By contrast, its use in quantitative experiments has been rather limited, partly due to fluctuations introduced by the spatial light modulator (SLM) that displays the kinoforms. This is an important issue when high temporal or spatial stability is a concern. We have investigated the performance of both an analog-addressed and a digitally-addressed SLM, measuring the phase fluctuations of the modulated beam and evaluating the resulting positional stability of a holographic trap. We show that, despite imparting a more unstable modulation to the wavefront, our digitally-addressed SLM generates optical traps in the sample plane stable enough for most applications. We further show that traps produced by the analog-addressed SLM exhibit a superior pointing stability, better than 1 nm, which is comparable to that of non-holographic tweezers. These results suggest a means to implement precision force measurement experiments with holographic optical tweezers (HOTs).

Realitat de ficció: una recerca en la impressió digital sobre suports rígids

Dins del projecte de recerca I+D Impressió expandida: repercussions dels mitjans digitals en el context de l’art imprès, amb codi: HUM 2007-64757/ARTE i finançat pel Ministerio de Ciencia yTecnologia, l’any 2007 es va constituir un sub-grup que, sota el nom d’Ars Combinatoria, hatreballat en la investigació de la impressió digital sobre diferents suports.Aquest equip investigador està format per les professores M.Mercè Casanovas, Cristina Pastó iEva Vila (col·laboradora) , totes elles vinculades a la pràctica i la docència del gravat, la litografia ila serigrafia .L’interès i la dedicació per aquestes disciplines ha anat ampliant-se i creixent amb l’aportació delsmitjans digitals, que han suposat un canvi en el format, en el projecte i en la concepció de l’obra.Per dur a terme aquesta recerca, hem rebut el suport de l’empresa barcelonina EGM Laboratoriscolor, especialitzada en la impressió digital d’alta resolució.Des d’aleshores s’ha seguit una investigació profunda sobre les diferents possibilitats de laimpressió digital damunt suports convencionals i no convencionals. Tota una recerca que, fins al moment, s’ha concretat en tres exposicions, dues de col·lectives i una d’individual, que mostren els resultats obtinguts.

Creative and Multidisciplinary Etching in the Digital Age

In our capacity as creative artists, researchers and fine arts professors, most part of our activity focuses on the relationships between people and creativity, technology, and resources, and, most frequently, what we aim to offer are new enjoyable and subversive ways of interacting with these three fields. As art teachers, we ask 'why and how' to teach dynamic bearing in mind that digital technology will undoubtedly impact on contemporary art practice.

Projecte Digital Look

Projecte de final de carrera basat en la creació de 3 prototips (aplicació mòbil, web i software d'escriptori) per gestionar un centre d'estudis de perruqueria. El desenvolupament és sempre des del punt de vista del disseny centrat en l'usuari.

La influencia del género en la cultura digital del estudiantado universitario.

The main goal of this paper is to analyse gender differences in the use of ICT among university students. We present the results of a study about the uses and the perception in relation to ICT in everyday life and in academia. The study is based on a statistical simple of 1042 students from 5 different universities. The results show gender differences, both with respect to use as their perception of technology.

Beyond the Net Generation debate: A comparison between digital learners in face-to-face and virtual universities

This paper is based on the hypothesis that the use of technology to support learning is not related to whether a student belongs to the Net Generation, but that it is mainly influenced by the teaching model. The study compares behaviour and preferences towards ICT use in two groups of university students: face-to-face students and online students. A questionnaire was applied to asample of students from five universities with different characteristics (one offers online education and four offer face-to-face education with LMS teaching support).

La brecha digital, una brecha simbólica

Peer-reviewed

Report on theorerical results of power generation and conversion

Experimental results of a new controller able to support bidirectional power flow in a full-bridge rectifier with boost-like topology are obtained. The controller is computed using port Hamiltonian passivity techniques for a suitable generalized state space averaging truncation system, which transforms the control objectives, namely constant output voltage dc-bus and unity input power factor, into a regulation problem. Simulation results for the full system show the essential correctness of the simplifications introduced to obtain the controller, although some small experimental discrepancies point to several aspects that need further improvement.

Error probability in synchronous digital circuits due to power supply noise

This paper presents a probabilistic approach to model the problem of power supply voltage fluctuations. Error probability calculations are shown for some 90-nm technology digital circuits.The analysis here considered gives the timing violation error probability as a new design quality factor in front of conventional techniques that assume the full perfection of the circuit. The evaluation of the error bound can be useful for new design paradigms where retry and self-recoveringtechniques are being applied to the design of high performance processors. The method here described allows to evaluate the performance of these techniques by means of calculating the expected error probability in terms of power supply distribution quality.

Pyroelectric conversion: harvesting energy from temperature fluctuations

Peer reviewed

The Gaussian assumption in second-order estimation problems in digital communications

This paper deals with the goodness of the Gaussian assumption when designing second-order blind estimationmethods in the context of digital communications. The low- andhigh-signal-to-noise ratio (SNR) asymptotic performance of the maximum likelihood estimator—derived assuming Gaussiantransmitted symbols—is compared with the performance of the optimal second-order estimator, which exploits the actualdistribution of the discrete constellation. The asymptotic study concludes that the Gaussian assumption leads to the optimalsecond-order solution if the SNR is very low or if the symbols belong to a multilevel constellation such as quadrature-amplitudemodulation (QAM) or amplitude-phase-shift keying (APSK). On the other hand, the Gaussian assumption can yield importantlosses at high SNR if the transmitted symbols are drawn from a constant modulus constellation such as phase-shift keying (PSK)or continuous-phase modulations (CPM). These conclusions are illustrated for the problem of direction-of-arrival (DOA) estimation of multiple digitally-modulated signals.

Statistical reference criteria for adaptive signal processing in digital communications

A general criterion for the design of adaptive systemsin digital communications called the statistical reference criterionis proposed. The criterion is based on imposition of the probabilitydensity function of the signal of interest at the outputof the adaptive system, with its application to the scenario ofhighly powerful interferers being the main focus of this paper.The knowledge of the pdf of the wanted signal is used as adiscriminator between signals so that interferers with differingdistributions are rejected by the algorithm. Its performance isstudied over a range of scenarios. Equations for gradient-basedcoefficient updates are derived, and the relationship with otherexisting algorithms like the minimum variance and the Wienercriterion are examined.

Disseny d’un circuit analògic reconfigurable

En l’actualitat, l’electrònica digital s’està apoderant de la majoria de camps de desenvolupament, ja que ofereix un gran ventall de possibilitats que permeten fer front a gran quantitat de problemàtiques. Poc a Poc s’ha anat prescindint el màxim possible de l’electrònica analògica i en el seu lloc s’han utilitzat sistemes microprocessats, PLDs o qualsevol altre dispositiu digital, que proporciona beneficis enlluernadors davant la fatigosa tasca d’implementar una solució analògica.Tot i aquesta tendència, és inevitable la utilització de l’electrònica analògica, ja que el mon que ens envolta és l’entorn en el que han de proporcionar servei els diferents dissenys que es realitzen, i aquest entorn no és discret sinó continu. Partint d’aquest punt ben conegut hem de ser conscients que com a mínim els filtres d’entrada i sortida de senyal juntament amb els convertidors D/A A/D mai desapareixeran.Així doncs, aquests circuits analògics, de la mateixa forma que els digitals, han de sercomprovats un cop dissenyats, és en aquest apartat on el nostre projecte desenvoluparà un paper protagonista, ja que serà la eina que ha de permetre obtenir les diferents senyals característiques d’un determinat circuit, per posteriorment realitzar els tests que determinaran si es compleix el rang de correcte funcionament, i en cas de no complir, poder concretar quin paràmetre és el causant del defecte