Contribucions a la sociologia de la professió periodística a Catalunya

La realitat professional del periodisme català ha canviat en els darrers anys, tant per adaptar-se als nous contextos de producció informativa (derivats dels canvis organitzacionals, tecnològics, econòmics, etc.), com per trobar la seva funció en el concert social, cultural i polític de la Catalunya de principis del segle XXI. El perfil del periodista, les seves condicions sociolaborals i les seves actituds han variat força tres dècades després del procés de transició política. El desenvolupament d'una nova cultura professional, l'aparició de noves i precàries maneres d'exercir la professió, el creixent poder de les fonts en la difusió d'informació, la pseudopresència de les dones a la professió i la incidència de les noves tecnologies són algunes de les més importants i vistoses transformacions de la tasca periodística a Catalunya.The article analyses the present of journalism profession in Catalonia and its evolution during the last 25 years. The authors gathered data on profession structure from 1992 to 2004 and made 25 in-deep interviews to a sample of journalist. As a results they found that the most important fields where the profession has changed has been a new news culture, bad work conditions, the increasingly influence of news sources, a «pseudofeminization» of the profession and new technologies

Estratègies per a la millora de la regularitat de pas dels autobusos

Aquesta tesina estudia diferents estratègies per a millorar la regularitat de pas dels autobusos, a partir de la simulació d'escenaris característic

Estratègies per a la millora de la regularitat de pas dels autobusos

Aquesta tesina estudia diferents estratègies per a millorar la regularitat de pas dels autobusos, a partir de la simulació d'escenaris característic

A crack-tracking technique for localized damage in quasi-brittle materials

This work presents a procedure to simulate the growth and propagation of localized tensile cracks on quasi-brittle materials. The so-called smeared damage approach, which consists in standard finite elements and local nonlinear constitutive laws, is recovered and improved in order to represent crack localization and avoid spurious mesh-bias dependence in the discrete problem. This is achieved by means of the implementation of a local crack-tracking algorithm which can reproduce individual (discrete) cracks and ensure objectivity of the finite element problem solution. The performance of the localized damage model is stressed by means of the analyses of structural case-studies. Compared to the Smeared Crack Approach in its original form, the presented procedure shows clearly a better capacity to predict realistic collapse mechanisms. The proposed tracking technique is relatively inexpensive

Predicting topology propagation messages in mobile ad hoc networks: The value of history

This research was funded by the Spanish Government under contracts TIN2016-77836-C2-1-R,TIN2016-77836-C2-2-R, and DPI2016-77415-R, and by the Generalitat de Catalunya as Consolidated ResearchGroups 2017-SGR-688 and 2017-SGR-990.The mobile ad hoc communication in highly dynamic scenarios, like urban evacuations or search-and-rescue processes, plays a key role in coordinating the activities performed by the participants. Particularly, counting on message routing enhances the communication capability among these actors. Given the high dynamism of these networks and their low bandwidth, having mechanisms to predict the network topology offers several potential advantages; e.g., to reduce the number of topology propagation messages delivered through the network, the consumption of resources in the nodes and the amount of redundant retransmissions. Most strategies reported in the literature to perform these predictions are limited to support high mobility, consume a large amount of resources or require training. In order to contribute towards addressing that challenge, this paper presents a history-based predictor (HBP), which is a prediction strategy based on the assumption that some topological changes in these networks have happened before in the past, therefore, the predictor can take advantage of these patterns following a simple and low-cost approach. The article extends a previous proposal of the authors and evaluates its impact in highly mobile scenarios through the implementation of a real predictor for the optimized link state routing (OLSR) protocol. The use of this predictor, named OLSR-HBP, shows a reduction of 40–55% of topology propagation messages compared to the regular OLSR protocol. Moreover, the use of this predictor has a low cost in terms of CPU and memory consumption, and it can also be used with other routing protocols.Peer ReviewedPostprint (published version

Single-pixel digital "ghost" holography

Since its discovery, the "ghost" diffraction phenomenon has emerged as a non-conventional technique for optical imaging with very promising advantages. However, extracting intensity and phase information of a structured and realistic object remains a challenge. Here, we show that a "ghost" hologram can be recorded with a single-pixel configuration by adapting concepts from standard digital holography. The presented homodyne scheme enables phase imaging with nanometric depth resolution, three-dimensional focusing ability, and shows high signal-to-noise ratio

Signal-to-noise ratio of single-pixel cameras based on photodiodes

Single-pixel cameras have been successfully used in different imaging applications in the last years. One of the key elements affecting the quality of these cameras is the photodetector. Here, we develop a numerical model of a single-pixel camera, which takes into account not only the characteristics of the incident light but also the physical properties of the detector. In particular, our model considers the photocurrent, the dark current, the photocurrent shot noise, the dark-current shot noise, and the Johnson–Nyquist (thermal) noise of the photodiode used as a light detector. The model establishes a clear relationship between the electric signal and the quality of the final image. This allows us to perform a systematic study of the quality of the image obtained with single-pixel cameras in different contexts. In particular, we study the signal-to-noise ratio as a function of the optical power of the incident light, the wavelength, and the photodiode temperature. The results of the model are compared with those obtained experimentally with a single-pixel camera

Viscoelasticity and damage model for creep behaviour of historical masonry structures

This paper presents a continuum model for the simulation of the viscous effects and the long-term damage accumulation in masonry structures. The rheological model is based on a generalized Maxwell chain representation with a constitutive law utilizing a limited number of internal variables. Thanks to its computational efficiency, this approach is suitable for the analysis of large and complex structures. In the paper, the viscous and damage models are presented and their coupling is discussed. The FE simulation of the construction process of the representative bay of Mallorca Cathedral is presented, together with the analysis of the long-term effects. The parameters of the model are tentatively calibrated on the basis of the time-dependent viscous deformations detected during the cathedral monitoring

Single-Pixel Imaging Using Photodiodes

Single-pixel cameras (SPCs) have been successfully used in different imaging applications during the last decade. In these techniques, the scene is illuminated with a sequence of microstructured light patterns codified onto a programmable spatial light modulator. The light coming from the scene is collected by a bucket detector, such as a photodiode. The image is recovered computationally from the photodiode electric signal. In this context, the signal quality is of capital value. One factor that degrades the signal quality is the noise, in particular, the photocurrent, the dark-current, and the thermal noise sources. In this chapter, we develop a numerical model of a SPC based on a photodiode, which considers the characteristics of the incident light, as well as the photodiode specifications. This model includes the abovementioned noise sources and infers the signal-to-noise ratio (SNR) of the SPCs in different contexts. In particular, we study the SNR as a function of the optical power of the incident light, the wavelength, and the photodiode temperature. The results of the model are compared with those obtained experimentally with a SPC

Single-pixel digital holography with phase-encoded illumination

We demonstrate imaging of complex amplitude objects through digital holography with phase-structured illumination and bucket detection. The object is sampled with a set of micro-structured phase patterns implemented onto a liquid-crystal spatial light modulator while a bucket detector sequentially records the irradiance fluctuations corresponding to the interference between object and reference beams. Our reconstruction algorithm retrieves the unknown phase information from the full set of photocurrent measurements. Interestingly, the sampling functions can be codified onto the reference beam, so they can be nonlocal with respect to the object. Finally, we show that the system is well-fitted for transmission of the object information through scattering media