Power spectrum estimation from values of noisy autocorrelations

The problem of estimating the power spectrum from noisy autocorrelation values is considered in this paper, and it is proposed that in order to reduce errors, oversampling of the available time domain data should be employed. The oversampling problem is discussed from the frame theory point of view, and it is shown that the frame reconstruction represents an improvement upon the standard correlogram, windowing, and autoregressive modelling approaches.     

Audio-visual active speaker tracking in cluttered indoors environments

We propose a system for detecting the active speaker in cluttered and reverberant environments where more than one person speaks and moves. Rather than using only audio information, the system utilizes audiovisual information from multiple acoustic and video sensors that feed separate audio and video tracking modules. The audio module operates using a particle filter (PF) and an information-theoretic framework to provide accurate acoustic source location under reverberant conditions. The video subsystem combines in 3-D a number of 2-D trackers based on a variation of Stauffer's adaptive background algorithm with spatiotemporal adaptation of the learning parameters and a Kalman tracker in a feedback configuration. Extensive experiments show that gains are to be expected when fusion of the separate modalities is performed to detect the active speaker.     

Audio–Visual Active Speaker Tracking in Cluttered Indoors Environments

We propose a system for detecting the active speaker in cluttered and reverberant environments where more than one person speaks and moves. Rather than using only audio information, the system utilizes audiovisual information from multiple acoustic and video sensors that feed separate audio and video tracking modules. The audio module operates using a particle filter (PF) and an information-theoretic framework to provide accurate acoustic source location under reverberant conditions. The video subsystem combines in 3-D a number of 2-D trackers based on a variation of Stauffer's adaptive background algorithm with spatiotemporal adaptation of the learning parameters and a Kalman tracker in a feedback configuration. Extensive experiments show that gains are to be expected when fusion of the separate modalities is performed to detect the active speaker.     

Photoionization and photoabsorption cross sections of He, O,N2 and O2 for aeronomic calculations

A compilation of experimental and theoretical photoionization and photoabsorption cross sections is presented for He, O, N₂, and O₂ for use in studies of ion and photoelectron production in the terrestrial ionosphere. In wavelength regions where rapid variations occur in the cross sections, averaged cross sections are calculated. When necessary the cross sections have been extrapolated to shorter wavelengths. The cross sections are tabulated at the wavelengths of the solar lines and continua given in the solar reference spectrum of Hinteregger from ～1030 to ～34 Å. For the molecules N₂ and O₂, branching ratios are given for ionization into the ground and electronic states of the molecular ions and for dissociative ionization.     

A THREE DIMENSIONAL NETWORK MODEL FOR CONSOLIDATED POROUS MEDIA. BASIC STUDIES

A three-dimensional porous medium model that pertains to consolidated permeable porous rocks and similar structures is proposed. The porous medium is considered as a network of chambers connected through long narrow throats and it is approximated as a network of unit cells of the constricted tube type. The skeleton of the network can be either regular or randomized, and the throat-to-chamber coordination number can be varied by randomly removing a number of throats. The sizes of contiguous chambers and throats can be cither independent random variables, or they can be correlated. This correlation can be positive (large chambers preferring large throats), or negative (large chambers preferring small throats). The permeability of the network is found to be minimal when the chambers and throats are completely uncorrected. The degree of correlation also affects the throat-to-chamber size ratio, a parameter which is very important in two-phase flows through porous media. A substantial correlation between the local intensity of the flow field on one hand and the local porosity and throat diameter on the other is found. @KEYWORDS: Pore network model, Consolidated porous media.     

Automated Mapping of the MapReduce Pattern onto Parallel Computing Platforms

The MapReduce pattern can be found in many important applications, and can be exploited to significantly improve system parallelism. Unlike previous work, in which designers explicitly specify how to exploit the pattern, we develop a compilation approach for mapping applications with the MapReduce pattern automatically onto Field-Programmable Gate Array (FPGA) based parallel computing platforms. We formulate the problem of mapping the MapReduce pattern to hardware as a geometric programming model; this model exploits loop-level parallelism and pipelining to give an optimal implementation on given hardware resources. The approach is capable of handling single and multiple nested MapReduce patterns. Furthermore, we explore important variations of MapReduce, such as using a linear structure rather than a tree structure for merging intermediate results generated in parallel. Results for six benchmarks show that our approach can find performance-optimal designs in the design space, improving system performance by up to 170 times compared to the initial designs on the target platform.     

Prospects for Non-Rare Earth Permanent Magnets for Traction Motors and Generators

With the advent of high-flux density permanent magnets based on rare earth elements such as neodymium (Nd) in the 1980s, permanent magnet-based electric machines had a clear performance and cost advantage over induction machines when weight and size were factors such as in hybrid electric vehicles and wind turbines. However, the advantages of the permanent magnet-based electric machines may be overshadowed by supply constraints and high prices of their key constituents, rare earth elements, which have seen nearly a 10-fold increase in price in the last 5?years and the imposition of export limits by the major producing country, China, since 2010. We outline the challenges, prospects, and pitfalls for several potential alloys that could replace Nd-based permanent magnets with more abundant and less strategically important elements.     

A multi-technique investigation of the nanoporosity of cement paste

The nanometer-scale structure of cement paste, which is dominated by the colloidal-scale porosity within the C-S-H gel phase, has a controlling effect on concrete properties but is difficult to study due to its delicate structure and lack of long-range order. Here we present results from three experimental techniques that are particularly suited to analyzing disordered nanoporous materials: small-angle neutron scattering (SANS), weight and length changes during equilibrium drying, and nanoindentation. Particular attention is paid to differences between pastes of different ages and cured at different temperatures. The SANS and equilibrium drying results indicate that hydration of cement paste at 20 °C forms a low-density (LD) C-S-H gel structure with a range of gel pore sizes and a relatively low packing fraction of solid particles. This fine structure may persist indefinitely under saturated conditions. However, if the paste is dried or is cured at elevated temperatures (60 °C or greater) the structure collapses toward a denser (less porous) and more stable configuration with fewer large gel pores, resulting in a greater amount of capillary porosity. Nanoindentation measurements of pastes cured at different temperatures demonstrate in all cases the existence of two C-S-H structures with different characteristic values of the indentation modulus. The average value of the modulus of the LD C-S-H is the same for all pastes tested to date, and a micromechanical analysis indicates that this value corresponds to the denser and more stable configuration of LD C-S-H. The experimental results presented here are interpreted in terms of a previously proposed quantitative “colloid” model of C-S-H gel, resulting in an improved understanding of the microstructural changes associated with drying and heat curing.     

Code-aided quasi-maximum SINR algorithms for blind linear multiuser detection

The problem of blind linear data-symbol estimation and data detection for the air- interface adopting the wide-band direct sequence code division multiple access multiuser multiplexing technique with the promising short-code configurations has been addressed. The superior interference-suppression ability of the code-constrained minimum output energy multipath- component estimation is utilised to develop three code-aided quasi-maximum signal-to-interference and noise ratio (SINR) algorithms. These algorithms operate in such a way as to maximise approximate measures of the output SINR, each having variations, especially in the adaptive implementation, because of different criteria employed. The 'quasi-maximum SINR' nature is because of the approximations employed. Extensive simulations indicate that all of these algorithms significantly outperform the existing code-aided blind linear algorithms at considerably low computational complexity. Moreover their adaptive versions exhibit very high level of desirable trade-off between convergence speed and steady-state performance at further reduced computational complexity.