Deadlock avoidance with virtual channels

High Performance Computing is a rapidly evolving area of computer science which attends to solve complicated computational problems with the combination of computational nodes connected through high speed networks. This work concentrates on the networks problems that appear in such networks and specially focuses on the Deadlock problem that can decrease the efficiency of the communication or even destroy the balance and paralyze the network. Goal of this work is the Deadlock avoidance with the use of virtual channels, in the switches of the network where the problem appears. The deadlock avoidance assures that will not be loss of data inside network, having as result the increased latency of the served packets, due to the extra calculation that the switches have to make to apply the policy.

The Global Diffusion of Regulatory Agencies: Channels of Transfer and Stages of Diffusion

The autonomous regulatory agency has recently become the ‘appropriate model’ of governance across countries and sectors. The dynamics of this process is captured in our data set, which covers the creation of agencies in 48 countries and 16 sectors since the 1920s. Adopting a diffusion approach to explain this broad process of institutional change, we explore the role of countries and sectors as sources of institutional transfer at different stages of the diffusion process. We demonstrate how the restructuring of national bureaucracies unfolds via four different channels of institutional transfer. Our results challenge theoretical approaches that overemphasize the national dimension in global diffusion and are insensitive to the stages of the diffusion process. Further advance in study of diffusion depends, we assert, on the ability to apply both cross-sectoral and cross-national analysis to the same research design and to incorporate channels of transfer with different causal mechanisms for different stages of the diffusion process.

Cultural leaders and the clash of civilizations

This article builds a micro founded model of the clash of cultures. The clash is defined as the parent's fear of a trait change by their child in an overlapping generations model with intergenerational transmission of cultural traits. The extent of the clash is manipulated by cultural leaders who benefit from the cultural education effort by parents. We identify three channels through which the leaders can affect the clash of cultures: (i) by providing beneficial cultural values, (ii) by claims of cultural superiority and (iii) by cultural alienation, i.e. by inducing cultural dislike towards their own group. We show that all three channels can be in the leader's interest but channels (ii) and (iii) reduce the utility of the leader's goup members. This hints to a strong conflict of interest within groups - between the population at large and the benefactors of radicalization. We further show how the use of alienation relates to the economic opportunities available to a group.

Diseño y fabricación de micro/nanochips para identificación y actuación en células vivas

Este estudio abarca el diseño, desarrollo tecnológico y fabricación, mediante la utilización de tecnologías de Micro y Nanosistemas, de herramientas en el orden de las micras y los nanómetros. Estos dispositivos serán utilizados en el estudio, identificación e interactuación con células vivas, ya que sus pequeñas dimensiones los hacen idóneos para su aplicación en el campo de la Biología Celular. Estas micro y nanoherramientas pueden usarse para el estudio, identificación o actuación de células vivas desde el exterior. Pero también pueden ser microinyectadas, lipofectadas o fagocitadas por parte de la misma célula, y de esta manera hacer estudios o actuar de forma intracelular.

Síntesi i caracterització de micro- i nanoestructures de compostos fotoactius de perilendiimida

En el present treball de recerca s’ha portat a terme la síntesi i caracterització de fibres a escala micro- i nanomètrica mitjançant l’auto-assemblatge dels compostos 1 i 2. Aquests compostos estan formats per una unitat de perilendiimida (PI) i una unitat d’estilbè i, en base a estudis previs desenvolupats al nostre grup de recerca, haurien de comportar-se com a sistemes acceptor-donador d’electrons fotoinduïts. Per tant, les corresponents estructures obtingudes podrien presentar activitat fotovoltaica. En primer lloc, s’ha abordat la síntesi dels compostos 1 i 2, seguint la metodologia posada a punt prèviament al nostre grup de recerca. A continuació, s’han estudiat les propietats òptiques de 1 i 2 en dissolució, la qual cosa ha permès establir que: (a) tal i com es pretenia, tots dos compostos presenten transferència electrònica fotoinduïda entre la unitat electró-acceptora de PI i la unitat electró-donadora de trans-estilbè; (b) la diferent morfologia de la cadena alquílica lateral del grup de PI a 1 i 2 afecta la seva capacitat d’auto-assemblatge mitjançant interaccions intermoleculars de tipus π-π. A continuació, s’han assajat diferents metodologies per a la fabricació de micro- i nanoestructures auto-assemblades de 1 i 2. Els millors resultats s’han obtingut mitjançant l’ús de motlles d’òxid d’alúmina i per al compost 2 degut al menor impediment estèric de la seva cadena alquílica lateral. La caracterització de les estructures resultants en aquest cas mitjançant tècniques microscòpiques i espectroscòpiques han permès demostrar la formació de nanotubs de 200 nm de diàmetre, d’uns 15 μm de longitud i en què les unitats de PI s’ordenen amb els seus sistemes aromàtics de forma co-facial o gairebé co-facial. La possible activitat fotovoltaica d’aquestes estructures s’estudiarà posteriorment.

Análisis del micro-voluntariado (crowdsourcing) en una gran empresa para abordar un problema de salud específico

Este trabajo presenta un análisis del efecto positivo que puede tener el microvoluntariado (crowdsourcing) en las variables psicológicas entre trabajadores de una gran empresa, así como la viabilidad de crear una comunidad práctica para abordar un problema de salud específico. Para el desarrollo de este documento hemos recogido y analizado diferentes tipos de bibliografía, científica y no científica, con el fin de dar una explicación más global de lo que es el crowdsourcing y contextualizar este tipo de voluntariado para lograr una mayor comprensión de esta práctica.

Studying the micro-angels approach to micro-investment decisions

Purpose: The paper analyzes the micro-angels investment behaviour, looking both to the criteria used in the selection of their investment projects and to the characteristics of their guidance role during the investment period. Design/Methodology/Approach: The paper focuses on a double bottom line movement of French micro-angels clubs that has been operating since 1983. Our primary source of data is an online survey carried out during March 2012, asking members of clubs all over France for different aspects of their procedures. Findings: Our findings suggest that micro-angels are interested in small, socially or environmentally friendly projects having the potential to contribute to the development of their neighbourhood. We find that women are even more interested than men in such projects. Educated micro-angels value entrepreneurial motivation and understanding of the project more than less-educated micro-angels. We also point out the factors that micro-angels consider important in accompanying enterprises. Here we find that gender makes little difference. However, retired micro-angels value financial diagnosis made conjointly with entrepreneurs, while both active micro-angels and educated micro-angels value more the use of their network to help micro-entrepreneurs. Practical/Social Implications: Given the potential benefits of micro-angels investing and guiding the development of micro-enterprises, a social micro-angel investment on a major scale in developing countries could help in tackling some of the problems faced by the development of microfinance, such as the over-indebtedness of micro-entrepreneurs. Practitioners and new initiatives would gain from understanding what adaptations need to be made. Originality/value: We expect to add to the venture capital theory to take into account non-economic motives.

A unified treatment of optimum pilot overhead in multipath fading channels

The optimization of the pilot overhead in single-user 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-used block 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 the normalized Doppler frequency multiplied by the number of transmit antennas.

Non-peaky signals in wideband fading channels: achievable bit rates and optimal bandwidth

In the context of fading channels it is well established that, with a constrained transmit power, the bit rates achievable by signals that are not peaky vanish as the bandwidth grows without bound. Stepping back from the limit, we characterize the highest bit rate achievable by such non-peaky signals and the approximate bandwidth where that apex occurs. As it turns out, the gap between the highest rate achievable without peakedness and the infinite-bandwidth capacity (with unconstrained peakedness) is small for virtually all settings of interest to wireless communications. Thus, although strictly achieving capacity in wideband fading channels does require signal peakedness, bit rates not far from capacity can be achieved with conventional signaling formats that do not exhibit the serious practical drawbacks associated with peakedness. In addition, we show that the asymptotic decay of bit rate in the absence of peakedness usually takes hold at bandwidths so large that wideband fading models are called into question. Rather, ultrawideband models ought to be used.

Impact of antenna correlation on the capacity of multiantenna channels

This paper applies random matrix theory to obtain analytical characterizations of the capacity of correlated multiantenna channels. The analysis is not restricted to the popular separable correlation model, but rather it embraces a more general representation that subsumesmost of the channel models that have been treated in the literature. For arbitrary signal-to-noise ratios (SNR), the characterization is conducted in the regime of large numbers of antennas. For the low- and high-SNR regions, in turn, we uncover compact capacity expansions that are valid for arbitrary numbers of antennas and that shed insight on how antenna correlation impacts the tradeoffs between power, bandwidth and rate.

Optimum power allocation for parallel Gaussian channels with arbitrary input distributions

The mutual information of independent parallel Gaussian-noise channels is maximized, under an average power constraint, by independent Gaussian inputs whose power is allocated according to the waterfilling policy. In practice, discrete signalling constellations with limited peak-to-average ratios (m-PSK, m-QAM, etc) are used in lieu of the ideal Gaussian signals. This paper gives the power allocation policy that maximizes the mutual information over parallel channels with arbitrary input distributions. Such policy admits a graphical interpretation, referred to as mercury/waterfilling, which generalizes the waterfilling solution and allows retaining some of its intuition. The relationship between mutual information of Gaussian channels and nonlinear minimum mean-square error proves key to solving the power allocation problem.

Capacity-achieving input covariance for single-user multi-antenna channels

We characterize the capacity-achieving input covariance for multi-antenna channels known instantaneously at the receiver and in distribution at the transmitter. Our characterization, valid for arbitrary numbers of antennas, encompasses both the eigenvectors and the eigenvalues. The eigenvectors are found for zero-mean channels with arbitrary fading profiles and a wide range of correlation and keyhole structures. For the eigenvalues, in turn, we present necessary and sufficient conditions as well as an iterative algorithm that exhibits remarkable properties: universal applicability, robustness and rapid convergence. In addition, we identify channel structures for which an isotropic input achieves capacity.

Sequential estimation of multipath MIMO-OFDM channels

Wireless “MIMO” systems, employing multiple transmit and receive antennas, promise a significant increase of channel capacity, while orthogonal frequency-division multiplexing (OFDM) is attracting a good deal of attention due to its robustness to multipath fading. Thus, the combination of both techniques is an attractive proposition for radio transmission. The goal of this paper is the description and analysis of a new and novel pilot-aided estimator of multipath block-fading channels. Typical models leading to estimation algorithms assume the number of multipath components and delays to be constant (and often known), while their amplitudes are allowed to vary with time. Our estimator is focused instead on the more realistic assumption that the number of channel taps is also unknown and varies with time following a known probabilistic model. The estimation problem arising from these assumptions is solved using Random-Set Theory (RST), whereby one regards the multipath-channel response as a single set-valued random entity.Within this framework, Bayesian recursive equations determine the evolution with time of the channel estimator. Due to the lack of a closed form for the solution of Bayesian equations, a (Rao–Blackwellized) particle filter (RBPF) implementation ofthe channel estimator is advocated. Since the resulting estimator exhibits a complexity which grows exponentially with the number of multipath components, a simplified version is also introduced. Simulation results describing the performance of our channel estimator demonstrate its effectiveness.