On iterative performance of LDPC and Root-LDPC codes over block-fading channels

This paper presents our investigation on iterativedecoding performances of some sparse-graph codes on block-fading Rayleigh channels. The considered code ensembles are standard LDPC codes and Root-LDPC codes, first proposed in and shown to be able to attain the full transmission diversity. We study the iterative threshold performance of those codes as a function of fading gains of the transmission channel and propose a numerical approximation of the iterative threshold versus fading gains, both both LDPC and Root-LDPC codes.Also, we show analytically that, in the case of 2 fading blocks,the iterative threshold root of Root-LDPC codes is proportional to (α1 α2)1, where α1 and α2 are corresponding fading gains.From this result, the full diversity property of Root-LDPC codes immediately follows.

Fading models and metrics for contemporary wireless systems

The purpose of this paper is to examine (1) some of the models commonly used to represent fading,and (2) the information-theoretic metrics most commonly used to evaluate performance over those models. We raise the question of whether these models and metrics remain adequate in light of the advances that wireless systems haveundergone over the last two decades. Weaknesses are pointedout, and ideas on possible fixes are put forth.

Coupling digital and physical worlds in an AR magic show performance: lessons learned

“Magic for a Pixeloscope” is a one hour show conceived to berepresented in a theater scenario that merges mixed and augmented reality (MR/AR) and full-body interaction with classical magic to create new tricks. The show was conceived by an interdisciplinary team composed by a magician, twointeraction designers, a theater director and a stage designer. Themagician uses custom based hardware and software to createnew illusions which are a starting point to explore new languagefor magical expression. In this paper we introduce a conceptualframework used to inform the design of different tricks; weexplore the design and production of some tricks included in theshow and we describe the feedback received on the world premiere and some of the conclusions obtained.

Student modeling based on fuzzy inference mechanisms

The paper presents a competence-based instructional design system and a way to provide a personalization of navigation in the course content. The navigation aid tool builds on the competence graph and the student model, which includes the elements of uncertainty in the assessment of students. An individualized navigation graph is constructed for each student, suggesting the competences the student is more prepared to study. We use fuzzy set theory for dealing with uncertainty. The marks of the assessment tests are transformed into linguistic terms and used for assigning values to linguistic variables. For each competence, the level of difficulty and the level of knowing its prerequisites are calculated based on the assessment marks. Using these linguistic variables and approximate reasoning (fuzzy IF-THEN rules), a crisp category is assigned to each competence regarding its level of recommendation.

Communication, Coordination, and Efficiency in Evolutionary One-population Models

We analyze the role of commitment in pre-play communication for ensuring efficient evolutionarily stable outcomes in coordination games. All players are a priori identical as they are drawn from the same population. In games where efficient outcomes can be reached by players coordinating on the same action we find commitment to be necessary to enforce efficiency. In games where efficienct outcomes only result from play of different actions, communication without commitment is most effective although efficiency can no longer be guaranteed. Only when there are many messages then inefficient outcomes are negligible as their basins of attraction become very small.

Is confidence in decisions related to feedback? Evidence-and lack of evidence-from random samples of real-world managerial behavior?

Confidence in decision making is an important dimension of managerialbehavior. However, what is the relation between confidence, on the onehand, and the fact of receiving or expecting to receive feedback ondecisions taken, on the other hand? To explore this and related issuesin the context of everyday decision making, use was made of the ESM(Experience Sampling Method) to sample decisions taken by undergraduatesand business executives. For several days, participants received 4 or 5SMS messages daily (on their mobile telephones) at random moments at whichpoint they completed brief questionnaires about their current decisionmaking activities. Issues considered here include differences between thetypes of decisions faced by the two groups, their structure, feedback(received and expected), and confidence in decisions taken as well as inthe validity of feedback. No relation was found between confidence indecisions and whether participants received or expected to receivefeedback on those decisions. In addition, although participants areclearly aware that feedback can provide both confirming and disconfirming evidence, their ability to specify appropriatefeedback is imperfect. Finally, difficulties experienced inusing the ESM are discussed as are possibilities for further researchusing this methodology.

Communication, coordination and efficiency in evolutionary one-population models

We analyze the role of commitment in pre-play communication for ensuringefficient evolutionarily stable outcomes in coordination games. All players are a priori identical as they are drawn from the same population. In games where efficient outcomes can be reached by players coordinating on the same action we find commitment to be necessary to enforce efficiency. In games where efficienct outcomes only result from play of different actions, communication without commitment is most effective although efficiency can no longer be guaranteed. Only when there are many messages then inefficient outcomes are negligible as their basins of attraction become very small.

Promoting rule compliance in daily-life: Evidence from a randomized field experiment in the public libraries of Barcelona

We study how to promote compliance with rules in everyday situations. Having access to unique data on the universe of users of all public libraries inBarcelona, we test the effect of sending email messages with dierent contents.We find that users return their items earlier if asked to do so in a simple email.Emails reminding users of the penalties associated with late returns are more effective than emails with only a generic reminder. We find differential treatmenteffects by user types. The characteristics we analyze are previous compliance,gender, age, and nationality.

What risks do people perceive in everyday life? A perspective gained from the experience sampling method (ESM)

The experiential sampling method (ESM) was used to collect data from 74 parttimestudents who described and assessed the risks involved in their current activitieswhen interrupted at random moments by text messages. The major categories ofperceived risk were short-term in nature and involved loss of time or materials relatedto work and physical damage (e.g., from transportation). Using techniques of multilevelanalysis, we demonstrate effects of gender, emotional state, and types of risk onassessments of risk. Specifically, females do not differ from males in assessing thepotential severity of risks but they see these as more likely to occur. Also, participantsassessed risks to be lower when in more positive self-reported emotional states. Wefurther demonstrate the potential of ESM by showing that risk assessments associatedwith current actions exceed those made retrospectively. We conclude by notingadvantages and disadvantages of ESM for collecting data about risk perceptions.

Xarxa digital multimèdia de pantalles i kioscs interactius

Internet s’ha alçat en poc temps com el mitjà més utilitzat pels turistes per a planificar, organitzar i comprar un viatge, és per això que es proposa donar les mateixes facilitats en el destí. La Publicitat Dinàmica o “Digital Signage” és un nou servei de comunicació que consisteix en un conjunt de tecnologies i aplicacions informàtiques que permeten emetre missatges multimèdia i comunicar-se així d’una manera innovadora amb el públic objectiu de cada empresa, si s’afegeix un sistema independent, multimèdia i interactiu que pot utilitzar-se per a proporcionar informació i/o permetre la realització de transaccions es potencia al màxim el servei. D’aquesta manera es proposa crear una Xarxa Digital Multimèdia de Kioscs Interactius recolzats amb una pantalla de plasma per a la tecnologia Digital Signage. La ubicació escollida estratègicament és en un dels punts de major afluència turística, tal com l’entrada dels hotels. Així es tracta de crear circuits tancats en àrees geogràfiques on es troben els principals nuclis turístics de Mallorca. La possibilitat d’accedir a segments de població altament interessants per al producte o servei es multiplica al ser una manera fàcil, eficaç i altament suggestiva de promocionar el què es pretén. Un avantatge és la simplicitat de la infraestructura tecnològica que es necessita, el dispositiu mitjançant el qual es visualitzaran els missatges serà una pantalla de plasma convencional, i un terminal de punt de venda instal.lat en un lloc de pas. Cada mòdul està connectat a la xarxa ADSL mitjançant un servidor local a Internet. La connexió a la xarxa és imprescindible per a que el manteniment i actualització dels continguts es puguin efectuar remotament. L’objectiu principal d’aquest treball és estudiar la viabilitat de la implantació de la xarxa, mitjançant la realització d’un estudi de mercat on s’analitzen els grups claus per a la implantació: els hotelers, la indústria turística i el Govern Balear. S’identifiquen els beneficis que aportarà al nou servei i les repercussions que tendrà la seva instal.lació. Entre els resultats més destacats d’aquest estudi cal remarcar l’acceptació que ha tengut la idea entre els hotelers entrevistats i la resposta positiva de la indústria turística. Es reconeix: una millora de la imatge del sector, l’ús com a eina de promoció turística pel Govern, i la contribució a la sostenibilitat econòmica pel fet que augmenta la competitivitat de les empreses i això millora la qualitat del servei.

Aproximació al moviment "open access"

[eng] The article describes the background and current state of the open access (OA) movement. Its objectives --with roots in scientists' traditional desire to disseminate their works, in librarians' concerns about the serials crisis, and in technological advances-- were formally articulated in the Budapest Open Access Initiative (BOAI) declaration of 2002. This statement established two strategies for providing access to scientific information without any economic, technical, or legal obstacles: 1) publication of articles in OA journals or 2) deposit by authors of their works in stable institutional or subject-based repositories. The article suggests that this second "route" appears to offer greater possibilities of attaining open access in the short term. However, there still is a lot of work to be done in disseminating the concepts of OA and in training authors regarding procedures for depositing their works: in other words what is needed is a series of promotional activities for overcoming one of today's greatest challenges: author inertia.

The Cave by José Saramago: Platonic image versus metaphysics

The cave by José Saramago has as a certain reference the image of the cave of book VII of Plato's Republic and, however, Saramago is not an idealistic or metaphysical writer. This article, taking advantage of the applicability with which Plato endowed his image, defends the urge to be open to the messages sent by the earth, by matter, the urge not to become prisoners in the golden caves of the Western society and, finally, the urge to find our freedom in Nature, phýsis, and not far or beyond, metá, it.

Training referential communicative skills to individuals with autism spectrum disorder: a pilot study

Summary. The present study reports the effects of referential communication training in individuals formally diagnosed with autism spectrum disorder (ASD). Participants were 20 children with ASD (M age = 14.3 yr., SD = 4.2; 6 girls, 14 boys) in the role of speakers and 20 control children, who acted as listeners. They were all enrolled in mainstream compulsory education. Inclusion/exclusion criteria were defined according to the clinical diagnosis of ASD, the presence or absence of additional or associated disability, previous training in referential communication, and any drug treatment. Speakers were randomly assigned to one of two groups (trained vs untrained). Linguistic age, cognitive level, and autistic symptoms were analyzed, respectively, with the Peabody Picture Vocabulary Test (PPVT), the Wechsler Intelligence Scale (WISCR or WAISIII), and the Autistic Behavior Checklist (ABC). Communicative abilities were analyzed through two indexes related to message complexity and self-regulation. The trained group was trained in referential communication tasks (task analysis, role taking, and task evaluation), while the untrained group took part in a communicative game but without any specific communicative training. The results showed that the complexity of emitted messages had improved statistically significantly in the trained group as an effect of training. Ecological referential communication is shown to be an appropriate paradigm for studying the communicative process and its products and could be used to develop and implement a training program focused on those skills in which individuals with ASD are most deficient.

Statistical modeling of bowing control applied to violin sound synthesis

Excitation-continuous music instrument control patterns are often not explicitly represented in current sound synthesis techniques when applied to automatic performance. Both physical model-based and sample-based synthesis paradigmswould benefit from a flexible and accurate instrument control model, enabling the improvement of naturalness and realism. Wepresent a framework for modeling bowing control parameters inviolin performance. Nearly non-intrusive sensing techniques allow for accurate acquisition of relevant timbre-related bowing control parameter signals.We model the temporal contour of bow velocity, bow pressing force, and bow-bridge distance as sequences of short Bézier cubic curve segments. Considering different articulations, dynamics, and performance contexts, a number of note classes are defined. Contours of bowing parameters in a performance database are analyzed at note-level by following a predefined grammar that dictates characteristics of curve segment sequences for each of the classes in consideration. As a result, contour analysis of bowing parameters of each note yields an optimal representation vector that is sufficient for reconstructing original contours with significant fidelity. From the resulting representation vectors, we construct a statistical model based on Gaussian mixtures suitable for both the analysis and synthesis of bowing parameter contours. By using the estimated models, synthetic contours can be generated through a bow planning algorithm able to reproduce possible constraints caused by the finite length of the bow. Rendered contours are successfully used in two preliminary synthesis frameworks: digital waveguide-based bowed stringphysical modeling and sample-based spectral-domain synthesis.

Quasi-Nonparametric Blind Inversion of Wiener Systems

An e cient procedure for the blind inversion of a nonlinear Wiener system is proposed. We proved that the problem can be expressed as a problem of blind source separation in nonlinear mixtures, for which a solution has been recently proposed. Based on a quasi-nonparametric relative gradient descent, the proposed algorithm can perform e ciently even in the presence of hard distortions.