All-sky search algorithms for monochromatic signals in bar gravitational wave detector data

In this paper we design and develop several filtering strategies for the analysis of data generated by a resonant bar gravitational wave (GW) antenna, with the goal of assessing the presence (or absence) therein of long-duration monochromatic GW signals, as well as the eventual amplitude and frequency of the signals, within the sensitivity band of the detector. Such signals are most likely generated in the fast rotation of slightly asymmetric spinning stars. We develop practical procedures, together with a study of their statistical properties, which will provide us with useful information on the performance of each technique. The selection of candidate events will then be established according to threshold-crossing probabilities, based on the Neyman-Pearson criterion. In particular, it will be shown that our approach, based on phase estimation, presents a better signal-to-noise ratio than does pure spectral analysis, the most common approach.

Bump time-frequency toolbox: a toolbox for time-frequency oscillatory bursts extraction in electrophysiological signals

Background: oscillatory activity, which can be separated in background and oscillatory burst pattern activities, is supposed to be representative of local synchronies of neural assemblies. Oscillatory burst events should consequently play a specific functional role, distinct from background EEG activity – especially for cognitive tasks (e.g. working memory tasks), binding mechanisms and perceptual dynamics (e.g. visual binding), or in clinical contexts (e.g. effects of brain disorders). However extracting oscillatory events in single trials, with a reliable and consistent method, is not a simple task. Results: in this work we propose a user-friendly stand-alone toolbox, which models in a reasonable time a bump time-frequency model from the wavelet representations of a set of signals. The software is provided with a Matlab toolbox which can compute wavelet representations before calling automatically the stand-alone application. Conclusion: The tool is publicly available as a freeware at the address: http:// www.bsp.brain.riken.jp/bumptoolbox/toolbox_home.html

Continuous phase shift of sinusoidal signals using injection locked oscillators

This work presents an alternative to generate continuous phase shift of sinusoidal signals based on the use of super harmonic injection locked oscillators (ILO). The proposed circuit is a second harmonic ILO with varactor diodes as tuning elements. In the locking state, by changing the varactor bias, a phase shift instead of a frequency shift is observed at the oscillator output. By combining two of these circuits, relative phases up to 90 could be achieved. Two prototypes of the circuit have been implemented and tested, a hybrid version working in the range of 200-300 MHz and a multichip module (MCM) version covering the 900¿1000 MHz band.

Ellipsometric study of a-Si:H thin films deposited by square wave modulated rf glow discharge

Thin films of hydrogenated amorphous silicon (a‐Si:H), deposited by square wave modulated (SQWM) rf silane discharges, have been studied through spectroscopic and real time phase modulated ellipsometry. The SQMW films obtained at low mean rf power density (19 mW/cm2) have shown smaller surface roughness than those obtained in standard continuous wave (cw) rf discharges. At higher rf powers (≥56 mW/cm2), different behaviors depending on the modulating frequency have been observed. On the one hand, at low modulating frequencies (<40 Hz), the SQWM films have shown a significant increase of porosity and surface roughness as compared to cw samples. On the other, at higher modulating frequencies, the material density and roughness have been found to be similar in SQWM and cw films. Furthermore, the deposition rate of the films show more pronounced increases with the modulating frequency as the rf power is increased. Experimental results are discussed in terms of plasma negative charged species which can be relatively abundant in high rf power discharges and cause significant effects on the deposited layers through polymers, clusters, and powder formation.

Influence of pressure and radio frequency power on deposition rate and structural properties of hydrogenated amorphous silicon thin films prepared by plasma deposition

The influence of radio frequency (rf) power and pressure on deposition rate and structural properties of hydrogenated amorphous silicon (a-Si:H) thin films, prepared by rf glow discharge decomposition of silane, have been studied by phase modulated ellipsometry and Fourier transform infrared spectroscopy. It has been found two pressure regions separated by a threshold value around 20 Pa where the deposition rate increases suddenly. This behavior is more marked as rf power rises and reflects the transition between two rf discharges regimes. The best quality films have been obtained at low pressure and at low rf power but with deposition rates below 0.2 nm/s. In the high pressure region, the enhancement of deposition rate as rf power increases first gives rise to a reduction of film density and an increase of content of hydrogen bonded in polyhydride form because of plasma polymerization reactions. Further rise of rf power leads to a decrease of polyhydride bonding and the material density remains unchanged, thus allowing the growth of a-Si:H films at deposition rates above 1 nm/s without any important detriment of material quality. This overcoming of deposition rate limitation has been ascribed to the beneficial effects of ion bombardment on the a-Si:H growing surface by enhancing the surface mobility of adsorbed reactive species and by eliminating hydrogen bonded in polyhydride configurations.

Rockfall induced seismic signals: case study in Montserrat, Catalonia

After a rockfall event, a usual post event survey includes qualitative volume estimation, trajectory mapping and determination of departing zones. However, quantitative measurements are not usually made. Additional relevant quantitative information could be useful in determining the spatial occurrence of rockfall events and help us in quantifying their size. Seismic measurements could be suitable for detection purposes since they are non invasive methods and are relatively inexpensive. Moreover, seismic techniques could provide important information on rockfall size and location of impacts. On 14 February 2007 the Avalanche Group of the University of Barcelona obtained the seismic data generated by an artificially triggered rockfall event at the Montserrat massif (near Barcelona, Spain) carried out in order to purge a slope. Two 3 component seismic stations were deployed in the area about 200 m from the explosion point that triggered the rockfall. Seismic signals and video images were simultaneously obtained. The initial volume of the rockfall was estimated to be 75 m3 by laser scanner data analysis. After the explosion, dozens of boulders ranging from 10¿4 to 5 m3 in volume impacted on the ground at different locations. The blocks fell down onto a terrace, 120 m below the release zone. The impact generated a small continuous mass movement composed of a mixture of rocks, sand and dust that ran down the slope and impacted on the road 60 m below. Time, time-frequency evolution and particle motion analysis of the seismic records and seismic energy estimation were performed. The results are as follows: 1 ¿ A rockfall event generates seismic signals with specific characteristics in the time domain; 2 ¿ the seismic signals generated by the mass movement show a time-frequency evolution different from that of other seismogenic sources (e.g. earthquakes, explosions or a single rock impact). This feature could be used for detection purposes; 3 ¿ particle motion plot analysis shows that the procedure to locate the rock impact using two stations is feasible; 4 ¿ The feasibility and validity of seismic methods for the detection of rockfall events, their localization and size determination are comfirmed.

Production of nanometric particles in radio frequency glow discharges in mixtures of silane and methane

The formation of silicon particles in rf glow discharges has attracted attention due to their effect as a contaminant during film deposition or etching. However, silicon and silicon alloy powders produced by plasma¿enhanced chemical vapor deposition (PECVD) are promising new materials for sintering ceramics, for making nanoscale filters, or for supporting catalytic surfaces. Common characteristics of these powders are their high purity and the easy control of their stoichiometry through the composition of the precursor gas mixture. Plasma parameters also influence their structure. Nanometric powders of silicon¿carbon alloys exhibiting microstructural properties such as large hydrogen content and high surface/volume ratio have been produced in a PECVD reactor using mixtures of silane and methane at low pressure (-1 Torr) and low frequency square¿wave modulated rf power (13.56 MHz). The a¿Si1¿xCx:H powders were obtained from different precursor gas mixtures, from R=0.05 to R=9, where R=[SiH4]/([SiH4]+[CH4]). The structure of the a¿Si1¿xCx:H powder was analyzed by several techniques. The particles appeared agglomerated, with a wide size distribution between 5 and 100 nm. The silane/methane gas mixture determined the vibrational features of these powders in the infrared. Silicon-hydrogen groups were present for every gas composition, whereas carbon¿hydrogen and silicon¿carbon bonds appeared in methane¿rich mixtures (R-0.6). The thermal desorption of hydrogen revealed two main evolutions at about 375 and 660¿°C that were ascribed to hydrogen bonded to silicon and carbon, respectively. The estimated hydrogen atom concentration in the sample was about 50%.

Properties of amorphous silicon thin films grown in square wave modulated silane rf discharges.

Hydrogenated amorphous silicon (a‐Si:H) thin films have been obtained from pure SiH4 rf discharges by using the square wave modulation (SQWM) method. Film properties have been studied by means of spectroellipsometry, thermal desorption spectrometry, photothermal deflection spectroscopy and electrical conductivity measurements, as a function of the modulation frequency of the rf power amplitude (0.2-4000 Hz). The films deposited at frequencies about 1 kHz show the best structural and optoelectronic characteristics. Based upon the experimental results, a qualitative model is presented, which points up the importance of plasma negative ions in the deposition of a‐Si:H from SQWM rf discharges through their influence on powder particle formation.

Diagnosis of Alzheimer’s Disease from EEG by Means of Synchrony Measures in Optimized Frequency Bands

Several clinical studies have reported that EEG synchrony is affected by Alzheimer’s disease (AD). In this paper a frequency band analysis of AD EEG signals is presented, with the aim of improving the diagnosis of AD using EEG signals. In this paper, multiple synchrony measures are assessed through statistical tests (Mann–Whitney U test), including correlation, phase synchrony and Granger causality measures. Moreover, linear discriminant analysis (LDA) is conducted with those synchrony measures as features. For the data set at hand, the frequency range (5-6Hz) yields the best accuracy for diagnosing AD, which lies within the classical theta band (4-8Hz). The corresponding classification error is 4.88% for directed transfer function (DTF) Granger causality measure. Interestingly, results show that EEG of AD patients is more synchronous than in healthy subjects within the optimized range 5-6Hz, which is in sharp contrast with the loss of synchrony in AD EEG reported in many earlier studies. This new finding may provide new insights about the neurophysiology of AD. Additional testing on larger AD datasets is required to verify the effectiveness of the proposed approach.

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.

Creación de una radio musical participativa con difusión online y FM

Este proyecto propone crear un sistema inteligente y autónomo de emisión conjunta por Internet y FM. A través de una interfaz Web cómoda y sencilla, el oyente podrá interactuar con la emisora e influir en la emisión, exponiendo sus preferencias. El sistema tomará de forma autónoma y dinámica las decisiones pertinentes que garantizarán que la emisión cumple las preferencias definidas.

On the existence of hysteresis in the Kuramoto model with bimodal frequency distributions

We investigate the transition to synchronization in the Kuramoto model with bimodal distributions of the natural frequencies. Previous studies have concluded that the model exhibits a hysteretic phase transition if the bimodal distribution is close to a unimodal one, due to the shallowness the central dip. Here we show that proximity to the unimodal-bimodal border does not necessarily imply hysteresis when the width, but not the depth, of the central dip tends to zero. We draw this conclusion from a detailed study of the Kuramoto model with a suitable family of bimodal distributions.

Creació d'una ràdio musical participativa amb difusió online i FM

Aquest projecte té com a propòsit crear una ràdio musical participativa amb difusió online i FM on a partir d’una interfície web l’usuari pugui participar-hi activament votant les cançons que hi sonaran. A més a més els usuaris registrats gaudiran d’una xarxa social on podran fer amistats i deixa’ls-hi comentaris. Primer de tot faig una ràpida introducció a l’estat de l’art de les ràdios actuals, a continuació analitzo els requeriments, especifico el comportament desitjat del sistema, explico detalladament el disseny i l’ implementació i, per últim, faig un seguit de proves de les quals n’extrec les conclusions.

A Folk Theorem for Games when Frequent Monitoring Decreases Noise

This paper studies frequent monitoring in an infinitely repeated game with imperfect public information and discounting, where players observe the state of a continuous time Brownian process at moments in time of length _. It shows that a limit folk theorem can be achieved with imperfect public monitoring when players monitor each other at the highest frequency, i.e., _. The approach assumes that the expected joint output depends exclusively on the action profile simultaneously and privately decided by the players at the beginning of each period of the game, but not on _. The strong decreasing effect on the expected immediate gains from deviation when the interval between actions shrinks, and the associated increase precision of the public signals, make the result possible in the limit. JEL: C72/73, D82, L20. KEYWORDS: Repeated Games, Frequent Monitoring, Public Monitoring, Brownian Motion.

Design of Novel Frequency Generation Circuit with Application to Ultra-Wideband Distributed Oscillators

Given the urgence of a new paradigm in wireless digital trasmission which should allow for higher bit rate, lower latency and tigher delay constaints, it has been proposed to investigate the fundamental building blocks that at the circuital/device level, will boost the change towards a more efficient network architecture, with high capacity, higher bandwidth and a more satisfactory end user experience. At the core of each transciever, there are inherently analog devices capable of providing the carrier signal, the oscillators. It is strongly believed that many limitations in today's communication protocols, could be relieved by permitting high carrier frequency radio transmission, and having some degree of reconfigurability. This led us to studying distributed oscillator architectures which work in the microwave range and possess wideband tuning capability. As microvave oscillators are essentially nonlinear devices, a full nonlinear analyis, synthesis, and optimization had to be considered for their implementation. Consequently, all the most used nonlinear numerical techniques in commercial EDA software had been reviewed. An application of all the aforementioned techniques has been shown, considering a systems of three coupled oscillator ("triple push" oscillator) in which the stability of the various oscillating modes has been studied. Provided that a certain phase distribution is maintained among the oscillating elements, this topology permits a rise in the output power of the third harmonic; nevertheless due to circuit simmetry, "unwanted" oscillating modes coexist with the intenteded one. Starting with the necessary background on distributed amplification and distributed oscillator theory, the design of a four stage reverse mode distributed voltage controlled oscillator (DVCO) using lumped elments has been presented. All the design steps have been reported and for the first time a method for an optimized design with reduced variations in the output power has been presented. Ongoing work is devoted to model a wideband DVCO and to implement a frequency divider.