Search results for "temes"
showing 10 items of 75 documents
Coordination in a multi-cell multi-antenna multi-user W-CDMA system: a beamforming approach
2008
The problem of designing joint power control and optimal beamforming (JPCOB) algorithms for the downlink of a coordinated multi-cell WCDMA system is considered throughout this paper. In this case, the JPCOB design is formulated as the problem of minimizing the total transmitted power in the coordinated multi-cell system, subject to a certain quality of service requirement for each user. In this paper, the performance of two JPCOB algorithms based on different beamforming approaches is compared over the coordinated multi-cell system. The first one, obtains local beamformers by means of the well-known virtual uplink-downlink duality. In contrast, the second algorithm implements multi-base bea…
La teoria ecològica del desenvolupament: un marc teòric per a la comprensió del comportament humà
2008
L'any 2009 es van complir 30 anys de la publicació del llibre The Ecology of Human Development d'Urie Bronfenbrenner (1917-2005). Aquesta obra va signifi car la síntesi del pensament d'aquest autor, que ja havia esbossat en textos anteriors, i el punt de referència d'una teoria estimulant sobre el comportament humà. La idea bàsica de Bronfenbrenner és que el desenvolupament de l'individu es troba condicionat per les característiques dels entorns en què té lloc, és a dir, l'ésser humà es «fa» en interacció dinàmica amb els seus contextos i en el marc de les relacions entre aquests. Malgrat la rellevància teòrica i metodològica d'aquesta aportació, continua resultant poc coneguda per a una ma…
Mapping Carbon Stocks In Central And South America With Smap Vegetation Optical Depth
2019
Mapping carbon stocks in the tropics is essential for climate change mitigation. Passive microwave remote sensing allows estimating carbon from deep canopy layers through the Vegetation Optical Depth (VOD) parameter. Although their spatial resolution is coarser than that of optical vegetation indices or airborne Lidar data, microwaves present a higher penetration capacity at low frequencies (L-band) and avoid cloud masking. This work compares the relationships of airborne carbon maps in Central and South America with both (i) SMAP L-band VOD at 9 km gridding and (ii) MODIS Enhanced Vegetation Index (EVI). Models to estimate carbon stocks are built from these two satellite-derived variables.…
Sensitivity of L-band vegetation optical depth to carbon stocks in tropical forests: a comparison to higher frequencies and optical indices
2019
Supplementary data to this article can be found online at https://doi.org/10.1016/j.rse.2019.111303. Monitoring vegetation carbon in tropical regions is essential to the global carbon assessment and to evaluate the actions oriented to the reduction of forest degradation. Mainly, satellite optical vegetation indices and LiDAR data have been used to this purpose. These two techniques are limited by cloud cover and are sensitive only to the top of vegetation. In addition, the vegetation attenuation to the soil microwave emission, represented by the vegetation optical depth (VOD), has been applied for biomass estimation using frequencies ranging from 4 to 30¿GHz (C- to K-bands). Atmosphere is t…
Microbubble PhoXonic resonators: Chaos transition and transfer
2022
We report the activation of optomechanical chaotic oscillations in microbubble resonators (MBRs) through a blue-side excitation of its optical resonances. We confirm the sequence of quasi-periodical oscillation, spectral continuum and aperiodic motion; as well as the transition to chaos without external feedback or modulation of the laser source. In particular, quasi periodic transitions and a spectral continuum are reported for MBRs with diameters up to 600 μm, whereas only an abrupt transition into a spectral con- tinuum is observed for larger microbubbles.
An Scalable matrix computing unit architecture for FPGA and SCUMO user design interface
2019
High dimensional matrix algebra is essential in numerous signal processing and machine learning algorithms. This work describes a scalable square matrix-computing unit designed on the basis of circulant matrices. It optimizes data flow for the computation of any sequence of matrix operations removing the need for data movement for intermediate results, together with the individual matrix operations’ performance in direct or transposed form (the transpose matrix operation only requires a data addressing modification). The allowed matrix operations are: matrix-by-matrix addition, subtraction, dot product and multiplication, matrix-by-vector multiplication, and matrix by scalar multiplication.…
Sprawl urbano e bolla inmobiliare (1997-2007) in València (Spagna) Secondo CORINE e SIOSE
2012
During the Spanish housing bubble (1997-2007) artificial surfaces grew in coastal València as never before, due to the construction boom. According to CORINE 2006 they reached 4.8% of the whole Valencian territory (they represented 2.6% in 1990), and almost 7% according to SIOSE 2005 (an accurate and precise Spanish GIS on land cover and use). The most developed growth pattern in that period was urban sprawl, which had been almost totally absent in València before 1990.
Etude numérique d'équations aux dérivées partielles non linéaires et dispersives
2011
Numerical analysis becomes a powerful resource in the study of partial differential equations (PDEs), allowing to illustrate existing theorems and find conjectures. By using sophisticated methods, questions which seem inaccessible before, like rapid oscillations or blow-up of solutions can be addressed in an approached way. Rapid oscillations in solutions are observed in dispersive PDEs without dissipation where solutions of the corresponding PDEs without dispersion present shocks. To solve numerically these oscillations, the use of efficient methods without using artificial numerical dissipation is necessary, in particular in the study of PDEs in some dimensions, done in this work. As stud…
Applying data driven decision making to rank vocational and educational training programs with TOPSIS
2021
Abstract In this paper we present a multi-criteria classification of Vocational and Educational Programs in Extremadura (Spain) during the period 2009–2016. This ranking has been carried out through the integration into a complete database of the detailed information of individuals finishing such studies together with their labor data. The multicriteria method used is TOPSIS together with a new decision support method for assessing the influence of each criterion and its dependence on the weights assigned to them. This new method is based on a worst-best case scenario analysis and it is compared to a well known global sensitivity analysis technique based on the Pearson's correlation ratio.
Paradigms as triggers of semantic change: Demonstrative adverbs in Catalan and Spanish
2015
This paper sets out to analyse the development of demonstrative adverbs of place in Catalan and Spanish. The main questions dealt with in this study are the following: (i) why two-term and three-term deictic systems often display a certain lack of stability so that diachronically two-term systems sometimes become three-term (as in old Catalan and Spanish) or, the other way round, three-term systems become two-term (like in late Latin and in Catalan during the modern era); (ii) if the most normal and expected development is for deictic systems to take on anaphoric values, why in the case of the adverb aquí ('near the speaker and/or addressee') in Catalan and the adverb ahí ('near the address…