Mobile Phone Use among Market Traders at Fairs in Rural Peru

We characterize market traders at two rural fairs in Puno, Peru, based on quantitative and qualitative data gathered in 2008, to gain insight into types of traders and the information needs that influence the degree to which they use mobile phones to make decisions regarding which weekly fairs to attend. Using variables such as origin, type of goods sold, means of transportation to the market, and reliance on networks, we identify traders as full-time traders, part-time traders, or subsistence traders, that is, people trading solely to survive. We find that when traders are already familiar with the technology, regularly rely on endogenous networks to make decisions, and have more to lose from failing to trade (e.g., those selling perishable goods), they are more likely to use mobile phones to decide where to sell.

Lossless Image Data Embedding in Plain Areas

This letter presents a lossless data hiding scheme for digital images which uses an edge detector to locate plain areas for embedding. The proposed method takes advantage of the well-known gradient adjacent prediction utilized in image coding. In the suggested scheme, prediction errors and edge values are first computed and then, excluding the edge pixels, prediction error values are slightly modified through shifting the prediction errors to embed data. The aim of proposed scheme is to decrease the amount of modified pixels to improve transparency by keeping edge pixel values of the image. The experimental results have demonstrated that the proposed method is capable of hiding more secret data than the known techniques at the same PSNR, thus proving that using edge detector to locate plain areas for lossless data embedding can enhance the performance in terms of data embedding rate versus the PSNR of marked images with respect to original image.

A Secure Cooperative Sensing Protocol for Cognitive Radio Networks

Cognitive radio networks sense spectrum occupancyand manage themselves to operate in unused bands without disturbing licensed users. Spectrum sensing is more accurate if jointly performed by several reliable nodes. Even though cooperative sensing is an active area of research, the secureauthentication of local sensing reports remains unsolved, thus empowering false results. This paper presents a distributed protocol based on digital signatures and hash functions, and ananalysis of its security features. The system allows determining a final sensing decision from multiple sources in a quick and secure way.

Secure Dynamic MANET On-demand (SEDYMO) Routing Protocol

This paper describes the state of the art of secure ad hoc routing protocols and presents SEDYMO, a mechanism to secure a dynamic multihop ad hoc routing protocol. The proposed solution defeats internal and external attacks usinga trustworthiness model based on a distributed certification authority. Digital signatures and hash chains are used to ensure the correctness of the protocol. The protocol is compared with other alternatives in terms of security strength, energy efficiency and time delay. Both computational and transmission costs are considered and it is shown that the secure protocol overhead is not a critical factor compared to the high network interface cost.

Power supply noise and logic error probability

Voltage fluctuations caused by parasitic impedances in the power supply rails of modern ICs are a major concern in nowadays ICs. The voltage fluctuations are spread out to the diverse nodes of the internal sections causing two effects: a degradation of performances mainly impacting gate delays anda noisy contamination of the quiescent levels of the logic that drives the node. Both effects are presented together, in thispaper, showing than both are a cause of errors in modern and future digital circuits. The paper groups both error mechanismsand shows how the global error rate is related with the voltage deviation and the period of the clock of the digital system.

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.

A performance lower bound for quadratic timing recovery accounting for the symbol transition density

The symbol transition density in a digitally modulated signal affects the performance of practical synchronization schemes designed for timing recovery. This paper focuses on the derivation of simple performance limits for the estimation of the time delay of a noisy linearly modulated signal in the presence of various degrees of symbol correlation produced by the varioustransition densities in the symbol streams. The paper develops high- and low-signal-to-noise ratio (SNR) approximations of the so-called (Gaussian) unconditional Cramér–Rao bound (UCRB),as well as general expressions that are applicable in all ranges of SNR. The derived bounds are valid only for the class of quadratic, non-data-aided (NDA) timing recovery schemes. To illustrate the validity of the derived bounds, they are compared with the actual performance achieved by some well-known quadratic NDA timing recovery schemes. The impact of the symbol transitiondensity on the classical threshold effect present in NDA timing recovery schemes is also analyzed. Previous work on performancebounds for timing recovery from various authors is generalized and unified in this contribution.

Voltage fluctuations in IC power supply distribution

The supply voltage decrease and powerconsumption increase of modern ICs made the requirements for low voltage fluctuation caused by packaging and on-chip parasitic impedances more difficult to achieve. Most of the research works on the area assume that all the nodes of the chip are fed at thesame voltage, in such a way that the main cause of disturbance or fluctuation is the parasitic impedance of packaging. In the paper an approach to analyze the effect of high and fast current demands on the on-chip power supply network. First an approach to model the entire network by considering a homogeneous conductive foil is presented. The modification of the timing parameters of flipflops caused by spatial voltage drops through the IC surface are also investigated.

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

150 aniversari del naixement de Sigmund Freud : presentació

La commemoració del 150 Aniversari del naixement de Sigmund Freud a Barcelona ha estat intensa. Un any ple d’activitats: conferències, taules rodones, poesia, cinema i cursos realitzats a diferents recintes de la ciutat, en bona part organitzades directament per la comissió de l’Any Freud i amb el suport de tots els grups de psicoanàlisi de la ciutat. Grups que van organitzar les seves pròpies activitats entorn de la commemoració, moltes de les quals foren adscrites i impulsades per l’Any Freud. També hi va haver iniciatives dels mitjans de comunicació i de les Universitats.

Europa als ulls dels Annales (1093-1933)

During this first third of this century, the continent of Europe witnessed far-reaching territorial transformations in the nineteenth century model. To some extent, the setting wich had inspired the epistemological structure of the French regional school was being replaced by one in which -at least to externa1 appearances- the relationship between the physical environment and human activities was much less evident. The adaptation of the theoretical and methodological context to the new Europe seems to take the form of a non-lineal evolution, for in the latter years of the period examined, evolutionary tendencies indicate a return to the more classical model. In this way, the growing interest which the publication had shown in Atlantic Europe and topics of a more economic nature, was truncated. The traditional settings --especially the Mediterranean- came to the fore again and interest in rural societies was renewed. Likewise, the monographic studies which had demonstrated distinct functional objectives in the midtwenties, recovered elements of ecological explanation, and the search for the relationship between environment and society

Definir les causes del trastorn vocal : un camí complex però imprescindible

La disfonia és una alteració de les qualitats bàsiques de la veu (timbre, alçada, intensitat) que pot afectar la vida social i professional del pacient. La valoració de la disfonia en els protocols mèdics actuals incideix, d'una banda, en els mitjans tecnics que ajuden a definir les característiques d'aquesta disfonia (anàlisi acústica informatitzada) i, de l'altra, en l'exploració de la laringe que permet una classificació de les lesions orgàniques i de la funcionalitat laríngia (laringoestrobosòpia), així com la valoració subjectiva del pacient del seu handicap vocal. Aquest article aborda la multifactorialitat de la disfonia com a símptoma i no com a causa, valorant especialment els aspectes emocionals, i constata la manca de mitjans simples i significatius per a una valoració d'aquests aspectes. D'aquí se'n deriva la necessitat de l'abordatge multidisciplinari, tant en el diagnòstic com en la intervenció en els trastorns de la veu.

Aplicación de la técnica de espectrometría de fluorescencia de rayos-X en el estudio de la dispersión de metales en áreas mineras

One critical factor for success in characterizing metals polluting mining environments so as to be able to eliminate them and subsequently recover these areas depends upon a speedy and correct response in the analysis of samples. Rapid, simultaneous, multi-element analysis can be undertaken using X-ray fluorescence spectrometry, a versatile, non-destructive analytical technique commonly employed to identify both major and minor elements in samples related to environmental studies. An additional advantage of this technique is the possibility of conducting the analysis directly on solid samples, which is extremely convenient when dealing with environmental samples that are difficult to dissolve, such as soils, sediments and mining wastes. Moreover, in recent years the development of spectrometers equipped with digital-signal processors combined with enlarged X-ray production, using better designs for excitation-detection, has contributed to an improvement in instrumental sensitivity, thus allowing us to detect important polluting elements such as Cd and Pb at trace levels. In this paper the authors describe, on the basis of their own experience, some interesting applications of XRF spectrometry for the analysis of several types of environmental samples related to the study of the dispersion of metals within mining environments: (A) analysis of mining wastes, soils and sediments; (B) analysis of samples of vegetation used as bioindicators or related to phytoremediation studies; and (C) analysis of water samples related to mining operations

Hemerotecas de prensa digital: evolución y tendencias

Se analizan las hemerotecas digitales de los diarios españoles de mayor audiencia y difusión. Es un estudio evaluativo basado en 27 indicadores divididos en 4 grandes secciones: aspectos generales, contenidos, sistema de consulta y presentación de resultados. Se muestran los resultados de un análisis realizado en 2010, y se relacionan con los obtenidos anteriormente en 2007. Se señalan los aspectos mejores y peores de las hemerotecas de prensa digital, se establece un ranking de diarios en el que ocupan las primeras posiciones El mundo, Abc, El país y La vanguardia, y se destacan 5 grandes tendencias observadas: ampliación del fondo temporal online, hemerotecas gratuitas versus hemerotecas de pago, simplificación (y empobrecimiento) de la búsqueda, filtros en la presentación de resultados y productos documentales en la sección Hemeroteca

Nou portal d'accés als materials en obert de la UdG : DUGi 2.0

La Biblioteca de la Universitat de Girona és l'encarregada de coordinar els repositoris digitals de la Universitat. A l'inici el repositori neix de la necessitat de difondre i preservar tota la recerca de la Universitat, però mica en mica el projecte va creixent i es creen diferents repositoris per a diferents tipus de continguts. Així es creen els repositoris DUGiDocs, DUGiMedia i DUGiFonsEspecials.L'objectiu d'aquest PFC és desenvolupar un portal web amb un sistema d'indexació que permeti la cerca per diferents criteris com, per exemple, autor, matèria i títol. L'entorn ha de tenir un disseny agradable per a l'usuari final i ha de permetre obtenir les dades del repositori que se li indiquin. També ha de ser capaç de detectar els possibles duplicats en els criteris de cerca i notificar-ho a l'administrador