A Hierarchical Bayesian Framework for Constructing Sparsity-inducing Priors

Variable selection techniques have become increasingly popular amongst statisticians due to an increased number of regression and classification applications involving high-dimensional data where we expect some predictors to be unimportant. In this context, Bayesian variable selection techniques involving Markov chain Monte Carlo exploration of the posterior distribution over models can be prohibitively computationally expensive and so there has been attention paid to quasi-Bayesian approaches such as maximum a posteriori (MAP) estimation using priors that induce sparsity in such estimates. We focus on this latter approach, expanding on the hierarchies proposed to date to provide a Bayesian interpretation and generalization of state-of-the-art penalized optimization approaches and providing simultaneously a natural way to include prior information about parameters within this framework. We give examples of how to use this hierarchy to compute MAP estimates for linear and logistic regression as well as sparse precision-matrix estimates in Gaussian graphical models. In addition, an adaptive group lasso method is derived using the framework.Comment: Submitted for publication; corrected typo

Investigation of the Load-Induced Cracking and Rutting Performance of Specialty Hot Mix Asphalt Overlay Mixtures

This study was initiated with the aim of investigating the cracking performance, rutting performance, and cost effectiveness of specialty and composite HMA mixtures utilized in New Jersey to rehabilitate deteriorated rigid pavements. As such, four, plant-produced, specialty HMA overlay mixtures currently used in New Jersey were evaluated in this study. These overlay mixtures included: a dense-graded, 9.5-SP mixture, a gap-graded, 12.5-SMA mixture, a dense graded, 4.75-HPTO mixture, and a uniformly graded, 4.75-BRIC mixture. The 9.5-SP, 12.5-SMA, and 4.75-HPTO mixtures were produced using PG 76-22 binder while the 4.75-BRIC was contained a PG 70-28 binder. The laboratory cracking and rutting performance of the mixtures were assessed using the overlay test, the dynamic modulus test, uniaxial cyclic fatigue test, bending beam fatigue test, and asphalt pavement analyzer test. The field reflection cracking performance of the HMA overlay mixtures were assessed by performing accelerated pavement testing on six full-scale, field sections. The field sections contained a similar substructure. However, the overlays utilized on the field sections consisted of a 9.5-SP, 12.5-SMA, 4.75-HPTO, 9.5-SP & 4.75-BRIC, 12.5-SMA & 4.75-BRIC overlay, and 4.75-HPTO & 4.75BRIC. Based on the results of the study it was determined that the use of a 4.75-BRIC interlayer generally improved the reflection cracking performance and overall cost effectiveness of the conventional and specialty overlay mixtures

Evaluating the impact of different types of stabilized bases on the overall performance of flexible pavements

This study was initiated with the aim of evaluating the impact of stabilized and untreated base layers on the performance (i.e., fatigue and rutting) of flexible pavements. Four field sections constructed using stabilized base layers (i.e., bituminous (asphalt emulsion), calcium chloride (CaCl-2), Portland cement, and geogrid stabilized base layers) and a control section constructed using untreated RAP aggregates were analyzed in this study. Falling Weight Deflectometer (FWD) tests were conducted on all the field sections and the collected data was used to backcalculate the elastic moduli for all layers. The influence of the stabilized bases and the untreated RAP base on the mechanical responses (stresses and strains) of the overall pavement structure was also evaluated by conducting layered elastic analyses. Pavement ME simulations were also conducted to determine which of the four stabilized bases enhanced the predicted performance of flexible pavements the most. Based on the results of the study, it was concluded that the Portland cement stabilized base seemed to be more effective than the other stabilized bases at improving the resistance of the pavement sections to fatigue cracking. It was also determined that base layer stabilization appeared to have little effect on the rutting resistance of the pavement sections

Spin adaptation with determinant-based selected configuration interaction

Selected configuration interaction (sCI) methods, when complemented with a second order perturbative correction, provide near full configuration interaction (FCI) quality energies with only a small fraction of the Slater determinants of the FCI space. The selection of the determinants is often implemented in a determinant-based formalism, and therefore does not provide spin adapted wave functions. In other words, sCI wave functions are not eigenfunctions of the $\widehat{S^2}$ operator. In some situations, having a spin adapted wave function is essential for the proper convergence of the method. We propose an efficient algorithm which, given an arbitrary determinant space, generates all the missing Slater determinants allowing one to obtain spin adapted wave functions while avoiding working with configuration state functions. For example, generating all the possible determinants with 6 up-spin and 6 down-spin electrons in 12 open shells takes 21 CPU cycles per generated Slater determinant. We also propose a modification of the denominators in the Epstein-Nesbet perturbation theory reducing significantly the non-invariance of the second order correction with respect to different values of the spin quantum number $m_s$. The computational cost of this correction is also negligible

Complete Sound and Speech Recognition System for Health Smart Homes: Application to the Recognition of Activities of Daily Living

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Age and weathering rate of sediments in small catchments:The role of hillslope erosion

Uranium-series (U-series) isotopes in river material can be used to determine quantitative time constraints on the transfer of erosion products from source to sink. In this study, we investigate the U-series isotope composition of river-borne material in small catchments of Puerto Rico and southeastern Australia in order to improve our understanding of (i) the controls on the U-series isotope composition of river-borne material and (ii) how erosion products acquire their geochemical characteristics. In both regions, thorium isotopes track the origin of sediment and dissolved loads. Stream solutes are mainly derived from the deepest part of the weathering profile, whereas stream sediments originate from much shallower horizons, even in landslide-dominated Puerto Rican catchments. This suggests that in environments where thick weathering profiles have developed, solutes and sediments have distinct origins. The U-series isotope composition of stream sediments was modelled to infer a weathering age, i.e. the average time elapsed since the sediment\u27s minerals have started weathering. In southeastern Australia, the weathering age of stream sediments ranges between 346 ± 12 kyr and 1.78 ± 0.16 Myr, similar to values inferred from weathering profiles in the same catchment. Old weathering ages likely reflect the shallow origin of sediments mobilised via near-surface soil transport, the main mechanism of erosion in this catchment. Contrastingly, in Puerto Rico weathering ages are much younger, ranging from 5.1 ± 0.1 to 19.4 ± 0.4 kyr, reflecting that sediments are derived from less weathered, deeper saprolite, mobilised by landslides. Weathering ages of stream sediments are used to infer catchment-wide, mineral-specific weathering rates that are one to two orders of magnitude faster for Puerto Rico than for southeastern Australia. Thus, the type of erosion (near-surface soil transport vs. landslide) also affects the weathering rate of river sediments, because their weathering ages determine the potential for further weathering during sediment transport and storage in alluvial plains

Impact of an L5 magnetograph on nonpotential solar global magnetic field modeling

We present the first theoretical study to consider what improvement could be obtained in global nonpotential modeling of the solar corona if magnetograph data were available from the L5 Lagrange point, in addition to from the direction of Earth. To consider this, we first carry out a "reference Sun" simulation over two solar cycles. An important property of this simulation is that random bipole emergences are allowed across the entire solar surface at any given time (such as can occur on the Sun). Next we construct two "limited data" simulations, where bipoles are only included when they could be seen from (i) an Earth-based magnetograph and (ii) either Earth- or L5 based magnetographs. The improvement in reproducing the reference Sun simulation when an L5 view is available is quantified through considering global quantities in the limited data simulations. These include surface and polar flux, total magnetic energy, volume electric current, open flux and the number of flux ropes. Results show that when an L5 observational viewpoint is included, the accuracy of the global quantities in the limited data simulations can increase by 26-40%. This clearly shows that a magnetograph at the L5 point could significantly increase the accuracy of global nonpotential modeling and with this the accuracy of future space weather forecasts.Publisher PDFPeer reviewe