Adquiridor de dades analògiques

L’empresa TER és una empresa dedicada al disseny i la construcció de projectes electrònics. La necessitat de comprovar el funcionament dels seus dissenys ha motivat a realitzar un projecte capaç de recollir dades significatives de diferents àmbits com pressió, voltatge, intensitat, temperatura etc. En el mercat les dos maneres més freqüents de recollir aquestes dades són per sensors que donen una equivalència d’un paràmetre físic a un rang de voltatge (0 a 10v) o per corrent (4 a 20mA). Aquestes dades seran adquirides i processades periòdicament per un microcontrolador que les emmagatzemarà una a una per posteriorment visualitzar-les en un LCD o en un programa fet per Visual Basic capaç de generar un document que guardi les dades en Excel. Com a conclusions es pot dir que s’han assolit els objectius, tant els personals com els proposats, per tal de tenir un prototip funcional

Adquiridor de dades analògiques

L’empresa TER és una empresa dedicada al disseny i la construcció de projectes electrònics. La necessitat de comprovar el funcionament dels seus dissenys ha motivat a realitzar un projecte capaç de recollir dades significatives de diferents àmbits com pressió, voltatge, intensitat, temperatura etc. En el mercat les dos maneres més freqüents de recollir aquestes dades són per sensors que donen una equivalència d’un paràmetre físic a un rang de voltatge (0 a 10v) o per corrent (4 a 20mA). Aquestes dades seran adquirides i processades periòdicament per un microcontrolador que les emmagatzemarà una a una per posteriorment visualitzar-les en un LCD o en un programa fet per Visual Basic capaç de generar un document que guardi les dades en Excel. Com a conclusions es pot dir que s’han assolit els objectius, tant els personals com els proposats, per tal de tenir un prototip funcional

Estimation of zero-sequence impedance of undergrounds cables for single-phase fault location in distribution systems with electric arc

This paper focus on the problem of locating single-phase faults in mixed distribution electric systems, with overhead lines and underground cables, using voltage and current measurements at the sending-end and sequence model of the network. Since calculating series impedance for underground cables is not as simple as in the case of overhead lines, the paper proposes a methodology to obtain an estimation of zero-sequence impedance of underground cables starting from previous single-faults occurred in the system, in which an electric arc occurred at the fault location. For this reason, the signal is previously pretreated to eliminate its peaks voltage and the analysis can be done working with a signal as close as a sinus wave as possible

Bipolar pulsed excitation of erbium-doped nanosilicon light emitting diodes

High quantum efficiency erbium doped silicon nanocluster (Si-NC:Er) light emitting diodes (LEDs) were grown by low-pressure chemical vapor deposition (LPCVD) in a complementary metal-oxide-semiconductor (CMOS) line. Erbium (Er) excitation mechanisms under direct current (DC) and bipolar pulsed electrical injection were studied in a broad range of excitation voltages and frequencies. Under DC excitation, Fowler-Nordheim tunneling of electrons is mediated by Er-related trap states and electroluminescence originates from impact excitation of Er ions. When the bipolar pulsed electrical injection is used, the electron transport and Er excitation mechanism change. Sequential injection of electrons and holes into silicon nanoclusters takes place and nonradiative energy transfer to Er ions is observed. This mechanism occurs in a range of lower driving voltages than those observed in DC and injection frequencies higher than the Er emission rate.

Current-density-functional approach to large quantum dots in intense magnetic fields

Within current-density-functional theory, we have studied a quantum dot made of 210 electrons confined in a disk geometry. The ground state of this large dot exhibits some features as a function of the magnetic field (Beta) that can be attributed in a clear way to the formation of compressible and incompressible states of the system. The orbital and spin angular momenta, the total energy, ionization and electron chemical potentials of the ground state, as well as the frequencies of far-infrared edge modes are calculated as a function of Beta, and compared with available experimental and theoretical results.

Avalanche-like vortex penetration driven by pulsed microwave fields in an epitaxial LaSrCuO thin film

Different vortex penetration regimes have been registered in the output voltage signal of a magnetometer when single microwave pulses are applied to an epitaxial overdoped La2− x Sr x CuO4 thin film in a perpendicular dc magnetic field. The onset of a significant variation in the sample magnetization which exists below threshold values of temperature, dc magnetic field, and pulse duration is interpreted as an avalanche-type flux penetration. The microwave contribution to the background electric field suggests that the nucleation of this fast vortex motion is of electric origin, which also guarantees the occurrence of vortex instabilities under adiabatic conditions via the enhancement of the flux flow resistivity. Flux creep phenomena and heat transfer effects act as stabilizing factors against the microwave-pulse-induced fast flux diffusion.

Domain matched epitaxial growth of Bi1.5Zn1Nb1.5O7 thin films by pulsed laser deposition

Bi1.5Zn1Nb1.5O7 (BZN) epitaxial thin films were grown by pulsed laser deposition on Al2O3 with a double ZnO buffer layer through domain matching epitaxy (DME) mechanism. The pole figure analysis and reciprocal space mapping revealed the single crystalline nature of the thin film. The pole figure analysis also shows a 60º twinning for the (222) oriented crystals. Sharp intense spots in the SAED pattern also indicate the high crystalline nature of BZN thin film. The Fourier filtered HRTEM images of the BZN-ZnO interface confirms the domain matched epitaxy of BZN with ZnO buffer. An electric field dependent dielectric tunability of 68% was obtained for the BZN thin films with inter digital capacitors patterned over the film.

Chaotic dynamics of electric-field domains in periodically driven superlattices

Self-sustained time-dependent current oscillations under dc voltage bias have been observed in recent experiments on n-doped semiconductor superlattices with sequential resonant tunneling. The current oscillations are caused by the motion and recycling of the domain wall separating low- and high-electric-field regions of the superlattice, as the analysis of a discrete drift model shows and experimental evidence supports. Numerical simulation shows that different nonlinear dynamical regimes of the domain wall appear when an external microwave signal is superimposed on the dc bias and its driving frequency and driving amplitude vary. On the frequency-amplitude parameter plane, there are regions of entrainment and quasiperiodicity forming Arnold tongues. Chaos is demonstrated to appear at the boundaries of the tongues and in the regions where they overlap. Coexistence of up to four electric-field domains randomly nucleated in space is detected under ac+dc driving.

Self-consistent theory of current and voltage noise in multimode ballistic conductors

Electron transport in a self-consistent potential along a ballistic two-terminal conductor has been investigated. We have derived general formulas which describe the nonlinear current-voltage characteristics, differential conductance, and low-frequency current and voltage noise assuming an arbitrary distribution function and correlation properties of injected electrons. The analytical results have been obtained for a wide range of biases: from equilibrium to high values beyond the linear-response regime. The particular case of a three-dimensional Fermi-Dirac injection has been analyzed. We show that the Coulomb correlations are manifested in the negative excess voltage noise, i.e., the voltage fluctuations under high-field transport conditions can be less than in equilibrium.

Current Account imbalances, thriftiness and the real exchange rate in a growing economy

This paper analyses the theoretical relevance of the dynamical aspects of growth on the discussion about the observed positive correlation between per capita real income and real exchange rates. With this purpose, we develop a simple exogenous growth model where the internal, external and intertemporal equilibrium conditions of a typical macroeconomic model are imposed; this last one through the inclusion of a balanced growth path for the foreign assets accumulation. The main result under this consideration is that the relationship defended by the Balassa-Samuelson hypothesis is no more so straightforward. In our particular approach, the mentioned bilateral relationship depends on a parameter measuring thriftiness in the economy. Therefore, the probability of ending up with a positive relationship between growth and real exchange rates -as the classical economic theory predicts- will be higher when the economy is able to maintain a minimum saving ratio. Moreover, given that our model considers a simple Keynesian consumption function, some explosive paths can also be possible.

Sequencing lifeline repairs after an earthquake: an economic approach

Recoveries after recent earthquakes in the U.S. and Japan have shown that large welfare gains can be achieved by reshaping current emergency plans as incentive-compatible contracts. We apply tools from the mechanisms design literature to show ways to integrate economic incentives into the management of natural disasters and discuss issues related to the application to seismic event recovery. The focus is on restoring lifeline services such as the water, gas, transportation, and electric power networks. We put forward decisional procedures that an uninformed planner could employ to set repair priorities and help to coordinate lifeline firms in the post-earthquake reconstruction.

Clean Development Mechanism and Sustainable Development: a discussion on the link between the CDM and Sustainable Development, an analysis of the current status of the CDM portfolio, and an multicriteria evaluation of the effects of additional incentives in order to foster broad local Sustainable Development dividends from the CDM projects

vegeu resum en el fitxer adjunt a l'inici del treball de recerca

Assessment of current anglo-saxon proposals about criminal justice and the justification of legal punishment: Moore, Duff and Finnis on retribution, and the challenging compatibility with the up-and-coming Restorative Justice

Pendent

Dispositius nanoelectrònics a freqüències de THz : estudi de la propagació electromagnètica en les connexions

Per a altes freqüències, les connexions poden tenir un paper rellevant. Atès que la velocitat de propagació dels senyals electromagnètics, c, en el cable no és infinita, el voltatge i el corrent al llarg del cable varien amb el temps. Per tant, amb l’objectiu de reproduir el comportament elèctric de dispositius nanoelectrònics a freqüències de THz, en aquest treball hem estudiat la regió activa del dispositiu nanoelectrònic i les seves connexions, en un sistema global complex. Per a aquest estudi hem utilitzat un nou concepte de dispositiu anomenat Driven Tunneling Device (DTD). Per a les connexions, hem plantejat el problema a partir de tot el conjunt de les equacions de Maxwell, ja que per a les freqüències i longituds de cable considerats, la contribució del camp magnètic és també important. En particular, hem suposat que la propagació que és dóna en el cable és una propagació transversal electromagnètica (TEM). Un cop definit el problema hem desenvolupat un programa en llenguatge FORTRAN que amb l'algoritme de diferències finites soluciona el sistema global. La solució del sistema global s'ha aplicat a una configuració particular de DTD com a multiplicador de freqüència per tal de discutir quins paràmetres de les connexions permet maximitzar la potència real que pot donar el DTD.

Auditoria ambiental de l'edifici de l'Àrea de Territori, Medi Ambient, Paisatge i Espai Urbà de l'Ajuntament de Sitges

Aquest projecte realitza una auditoria ambiental de l’edifici de l’Àrea de Territori, Medi Ambient, Paisatge i Espai Urbà de l’Ajuntament de Sitges, com a primer pas per a la implantació d’un sistema de gestió ambiental (SGA), en acord amb el Reglament (CE) nº 761/2001, i la posterior obtenció d’un certificat de gestió i auditories ambientals (EMAS). L’auditoria s’inicia amb la identificació dels aspectes ambientals de l’edifici, mitjançant la recopilació de dades sobre consums energètics i hídrics, la estimació de la generació de residus i enquestes de mobilitat als treballadors. Aquestes dades són utilitzades per determinar els aspectes ambientals significatius i posteriorment, exposar una sèrie de propostes de millora per tal de corregir-los o minimitzar-los, com ara sistemes d’estalvi d’aigua, d’enllumenat, de producció d’electricitat i l’educació ambiental dels treballadors. Per a la implantació d’un SGA en la situació actual de l’edifici, es necessària, entre altres coses, la implantació d’un sistema de registre que arxivi els consums d’aigua, energia i generació de residus, per tal de dur un control de les despeses de cadascun dels vectors. A més, caldrà implementar un Programa de bones pràctiques ambientals en l’oficina per tal de reduir el consum elèctric, d’aigua i generació de residus, i la seva classificació per part dels treballadors.