Outage thresholds of LDPC codes over nonergodic block-fading channels

This paper derives approximations allowing the estimation of outage probability for standard irregular LDPC codes and full-diversity Root-LDPC codes used over nonergodic block-fading channels. Two separate approaches are discussed: a numerical approximation, obtained by curve fitting, for both code ensembles, and an analytical approximation for Root-LDPC codes, obtained under the assumption that the slope of the iterative threshold curve of a given code ensemble matches the slope of the outage capacity curve in the high-SNR regime.

Optimum pilot overhead in wireless communication: a unified treatment of continuous and block-fading channels

The optimization of the pilot overhead in wireless fading channels is investigated, and the dependence of this overhead on various system parameters of interest (e.g., fading rate, signal-to-noise ratio) is quantified. The achievable pilot-based spectral efficiency is expanded with respect to the fading rate about the no-fading point, which leads to an accurate order expansion for the pilot overhead. This expansion identifies that the pilot overhead, as well as the spectral efficiency penalty with respect to a reference system with genie-aided CSI (channel state information) at the receiver, depend on the square root of the normalized Doppler frequency. It is also shown that the widely-usedblock fading model is a special case of more accurate continuous fading models in terms of the achievable pilot-based spectral efficiency. Furthermore, it is established that the overhead optimization for multiantenna systems is effectively the same as for single-antenna systems with thenormalized Doppler frequency multiplied by the number of transmit antennas.

Gestió de l'aigua i de les conques fluvials

Els dies 14 i 15 de juliol de 2005 es va celebrar a la Facultat deLletres de la Universitat de Girona la sisena edició de l'EscolaInternacional de Medi Ambient, enguany dedicada a la gestió del'aigua i les conques fluvials i organitzada per l'Institut de MediAmbient de la Universitat de Girona i el Consorci Alba-Ter

Aplicación del Libqual+ en el CRAI en la Universidad de Barcelona

La aplicación de la encuesta Libqual+ como herramienta para medir la calidad de los servicios bibliotecarios, a partir de la percepción de los usuarios de los propios servicios. El caso práctico del CRAI de la Universidad de Barcelona.

Aplicación del Libqual+ en el CRAI en la Universidad de Barcelona

La aplicación de la encuesta Libqual+ como herramienta para medir la calidad de los servicios bibliotecarios, a partir de la percepción de los usuarios de los propios servicios. El caso práctico del CRAI de la Universidad de Barcelona.

Carbon and nitrogen partitioning during post-anthesis is conditioned by N fertilization and sink strength in three cereals

Further knowledge of the processes conditioning nitrogen use efficiency (NUE) is of great relevance to crop productivity. The aim of this paper was characterise C and N partitioning during grain filling and their implications for NUE. Cereals such as bread wheat (Triticum aestivum L. cv Califa sur), triticale (× Triticosecale Wittmack cv. Imperioso) and tritordeum (× Tritordeum Asch. & Graebn line HT 621) were grown under low (LN, 5 mm NH4NO3) and high (HN, 15 mm NH4NO3) N conditions. We conducted simultaneous double labelling (12CO2 and 15NH415NO3) in order to characterise C and N partitioning during grain filling. Although triticale plants showed the largest total and ear dry matter values in HN conditions, the large investment in shoot and root biomass negatively affected ear NUE. Tritordeum was the only genotype that increased NUE in both N treatments (NUEtotal), whereas in wheat, no significant effect was detected. N labelling revealed that N fertilisation during post-anthesis was more relevant for wheat and tritordeum grain filling than for triticale. The study also revealed that the investments of C and N in flag leaves and shoots, together with the"waste" of photoassimilates in respiration, conditioned the NUE of plants, and especially under LN. These results suggest that C and N use by these plants needs to be improved in order to increase ear C and N sinks, especially under LN. It is also remarkable that even though tritordeum shows the largest increase in NUE, the low yield of this cereal limits its agronomic value.

Estudio sobre el desarrollo de la identidad en la adolescencia

The aim of this study was to determine how adolescents construct their own identity during this important stage of their lifecycle.We evaluated the identity of a group of 42 adolescents between 11 and 12 years (early adolescence) and between 14 and 15 years (late adolescence), from EOMEIS-II (Extended Version of the Objective Mesure of Ego Identity Estatus created by Adams, Benion and Huh, 1989) which is part of an Ericksonian conceptualization of identity. In the results obtained we can see that students have higher scores on a global level, the most active and mature estatus (identity achieved and moratorium) in the passive and immature estatus (identity foreclosed and diffused). The boys have a higher score than girls in stating the identity moratorium on free time and political identity achieved

Idoneidad didáctica de un protocolo sociocultural de enseñanza y aprendizaje de las matemáticas

En este estudio se evalúa la adecuación de un protocolo para la enseñanza delconcepto de poliedro regular, destinado a alumnos de 14 y 15 años. Este protocolo se ha diseñado desde una perspectiva sociocultural y su evaluación se basa en la aplicación de los criterios deidoneidad didáctica que ofrece el enfoque ontosemiótico. La idoneidad se estudia con la revisión de sus diferentes dimensiones: matemática, cognitiva, interaccional, mediacional, emocional y ecológica. El análisis ha permitido detectar algunos factores que favorecen la validez del protocolo y la adecuación para su empleo en el aula, como el tipo de discurso, el uso de material manipulable o el trabajo cooperativo