A polynomial rooting approach for synchronization in multipath channels using antenna arrays

The estimation of the delay of a known training signal received by an antenna array in a multipath channel is addressed. The effect of the co-channel interference is taken into account by including a term with unknown spatial correlation. The channel is modeled as an unstructured FIR filter. The exact maximum likelihood (ML) solution for this problem is derived, but it does not have a simple dependence on the delay. An approximate estimator that is asymptotically equivalent to the exact one is presented. Using an appropriate reparameterization, it is shown that the delay estimate is obtained by rooting a low-order polynomial, which may be of interest in applications where fast feedforward synchronization is needed.Peer ReviewedPostprint (published version

A reduced-complexity and asymptotically efficient time-delay estimator

This paper considers the problem of estimating the time delays of multiple replicas of a known signal received by an array of antennas. Under the assumptions that the noise and co-channel interference (CCI) are spatially colored Gaussian processes and that the spatial signatures are arbitrary, the maximum likelihood (ML) solution to the general time delay estimation problem is derived. The resulting criterion for the delays yields consistent and asymptotically efficient estimates. However, the criterion is highly non-linear, and not conducive to simple minimization procedures. We propose a new cost function that is shown to provide asymptotically efficient delay estimates. We also outline a heuristic way of deriving this cost function. The form of this new estimator lends itself to minimization by the computationally attractive iterative quadratic maximum likelihood (IQML) algorithm. The existence of simple yet accurate initialization schemes based on ESPRIT and identity weightings makes the approach viable for practical implementation.Peer ReviewedPostprint (published version

El Templo de las serpientes: un santuario del Bronce Antiguo I en el poblado de Jebel Al-Mutawwaq (Jordania)

The Bronze Age I architecture of the Jebel al-Mutawwaq settlement (Zarqa, Jordan) always repeats the same designs: isolated buildings built out of large blocks of stone, without any carvings or mortar, put up along side a courtyard which forms an integrate part of the dwelling. However, the site which is known as the "Temple of the Serpents" has a series of anomalies which make it different from the normal modeL Even though the constitutive elements are the same, the main construction is, however, built onto a steep rock which has also been excavated in order to put up the high part of the dwelling and open up a well. In addition the construction of a table or "alter" beside it would indicate that this was not a typical dwelling, but one which had been designed with a different purpose in mind: possibly a sanctuary. The appearance of rooms with peculiar structures built onto the courtyard confirmed this, as did the original decorations on the ceramics which were different from those normally found- in dwellings at the Mutawwaq settlement. The structure of the site leads one to suspect that it could be related to Chalcolithic sanctuaries, like that of En Guedi or that of the Bronze Age (Meguiddo XIX).La arquitectura del Bronce Antiguo I del poblado de Jebel al-Mutawwaq (Zarqa, Jordania), repite siempre los mismos esquemas: edificaciones aisladas construidas con grandes bloques de piedra, sin labrar y sin utilizar ningún tipo de mortero, levantadas junto a un patio que forma parte integrante de la casa. No obstante el conjunto que denominamos 'Templo de las serpientes', presenta una serie de anomalías que la distancian del modelo habitual. Si bien los elementos constitutivos son los mismos, sin embargo la construcción de la estructura principal sobre una roca con fuerte pendiente, la excavación de esa misma roca para levantar la cabecera de la casa y abrir un pozo, así como la construcción de una mesa o "altar" junto a él, hicieron sospechar que no nos encontrábamos ante una vivienda típica, sino ante algo pensado y realizado con un fin distinto: un posible santuario. La aparición de habitaciones construidas en el patio, con estructuras peculiares confirman esa suposición, así como las originales decoraciones de las cerámicas diferentes a las encontradas habitualmente en las casas del poblado de Mutawwaq. La estructura del conjunto hace sospechar que podría estar en relación con santuarios calcolíticos, como el de En Guedi, o del Bronce (Meguiddo XIX)

Supply-Side Policies and the Zero Lower Bound

This paper examines how supply-side policies may play a role in fighting a low aggregate demand that traps an economy at the zero lower bound (ZLB) of nominal interest rates. Future increases in productivity or reductions in mark-ups triggered by supply-side policies generate a wealth effect that pulls current consumption and output up. Since the economy is at the ZLB, increases in the interest rates do not undo this wealth effect, as we will have in the case outside the ZLB. We illustrate this mechanism with a simple two-period New Keynesian model. We discuss possible objections to this set of policies and the relation of supply-side policies with more conventional monetary and fiscal policies.

Bounded and unbounded polynomials and multilinear forms: Characterizing continuity

In this paper we prove a characterization of continuity for polynomials on a normed space. Namely, we prove that a polynomial is continuous if and only if it maps compact sets into compact sets. We also provide a partial answer to the question as to whether a polynomial is continuous if and only if it transforms connected sets into connected sets. These results motivate the natural question as to how many non-continuous polynomials there are on an infinite dimensional normed space. A problem on the \emph{lineability} of the sets of non-continuous polynomials and multilinear mappings on infinite dimensional normed spaces is answered.Comment: 8 page

Analysis the use of the grip with velcro fasteners relating to the effectiveness of volleying in padel tennis

El objetivo de este estudio es investigar si la utilización de un grip con fijaciones, aumenta la efectividad de golpeo de la volea en pádel. Un total de 5 sujetos (5 varones) con una edad media de 22,8±0,84 años, fueron reclutados para participar de una forma voluntaria en este estudio de diseño cuasi- experimental. La elección de la muestra fue intencional, enmarcados dentro de los criterios de inclusión. Todos los sujetos realizaron unas sesiones de familiarización así como el «Test de efectividad de volea en pádel» con y sin el grip con fijaciones. Los resultados obtenidos nos muestran que los sujetos presentan mejores resultados de efectividad de volea cuando usan el grip con fijaciones (p<0,01). Por ello, concluimos que el uso del grip con fijaciones en la mano es más efectivo en la volea en el pádel que el grip cotidiano

Performance of the CMIP6 global climate models over the Iberian Peninsula and relationships with the simulated climate system complexity

Ponencia presentada en: XII Congreso de la Asociación Española de Climatología celebrado en Santiago de Compostela entre el 19 y el 21 de octubre de 2022.[ES]En el presente estudio se muestra una evaluación del rendimiento de las diferentes configuraciones de los modelos climáticos globales que han aportado experimentos históricos a CMIP6 (Coupled Model Intercomparison Project 6) para la Península Ibérica (IB), utilizando un dominio similar al aplicado en iniciativas de downscalling anteriores. La evaluación se basa en los patrones típicos de circulación atmosférica regional definidos por Jenkinson y Collison (1977), que se sabe que están vinculados con un gran número de variables de la física y la química atmosféricas. Los resultados se comparan con los obtenidos de la generación anterior de los modelos (CMIP5) y con los obtenidos de un análisis hemisférico (Brands 2022a), para comprobar 1) si los modelos han mejorado con el tiempo y 2) si los resultados específicos concuerdan con los obtenidos en un dominio más grande, lo que los hace menos propensos a la propagación de errores durante períodos de tiempo no observados.[EN]performance assessment of the global climate model configurations contributing historical experiments to CMIP6 is provided for the Iberian Peninsula (IB), using a spatial domain similar to that applied in previous downscaling initiatives. The evaluation is based on typical recurrent regional atmospheric circulation patterns as defined by Jenkinson & Collison (1977), which are well known to be linked with a large number of variables from atmospheric physics and chemistry. Results are compared to those obtained from the previous model generation (CMIP5), and to those retrieved from a hemispheric-wide analysis (Brands 2022) in order to see 1) if the models have improved over time, and 2) whether the region-specific findings agree with those obtained on a larger domain, thereby making them less prone to error propagation during unobserved time periods. It is found that the model version changes from CMIP5 and 6 lead to slight improvements, mainly associated with an increase in horizontal model resolution, but that the selection of the right model family is more important to obtain good model performance