Study of a hot asphalt mixture response based on energy concepts

The main objective of the research reported in this paper is to determine the response of a hot mix asphalt (HMA) in terms of both the tensile strength and energy parameters (based on the assessment of the force-displacement curve) as potential tools for improving the HMA mixture design. The HMAs analyzed were fabricated using a 60-70 penetration asphalt binder, dense-graded aggregate, mineral filler, and different types and contents of mineral filler replacements (i.e., lime, cement, and fly ash). The indirect tensile test was conducted to determine both the HMA tensile strength and force-displacement curve, which allowed for the computation of the HMA toughness as well as the energies involved in the process before and after reaching the tensile strength. Corresponding results suggest that the replacement of mineral filler by cement, lime, and fly ash modified the HMA response in terms of both the tensile strength and energy parameters. In addition, analysis of the energy parameters discussed proved to be useful for determining the optimum mineral filler content of HMA. Consequently, analysis of these energy parameters can benefit the HMA mixture design process. // El objetivo principal de la investigación fue determinar el comportamiento de una mezcla asfáltica en función de la resistencia a la tracción indirecta y parámetros de energía (calculados en función de la curva fuerza-desplazamiento) como herramientas potenciales para mejorar el diseño de mezclas asfálticas. Las mezclas asfálticas analizadas fueron fabricadas con asfalto de penetración 60/70, granulometría cerrada md10 y relleno mineral en diferentes porcentajes y materiales (cal, cemento y ceniza volante). El ensayo de tracción indirecta se utilizó para determinar la resistencia máxima a la tracción y la curva fuerza-desplazamiento, a partir de la cual se calcularon la tenacidad de la mezcla y las energías involucradas en el proceso antes y después de alcanzar la resistencia máxima. Los resultados obtenidos sugieren que reemplazar el relleno mineral por cemento, cal o ceniza volante modifica el comportamiento de la mezcla asfáltica en términos de la resistencia a la tracción y los parámetros de energía. Adicionalmente, el análisis de los parámetros de energía discutidos es útil para establecer el contenido óptimo del relleno mineral. En consecuencia, el análisis de estos parámetros de energía puede beneficiar el proceso de diseño de mezclas asfálticas.Peer ReviewedPostprint (published version

El legado científico de Juan A. Torres-Negrón

Juan A. Torres-Negron (Juan Torres) studied ants, wasps, termites and other insect groups. I reviewed 34 of his publications and grouped them into six subjects: ecological theory, taxonomy, chemistry, ecology, synthesis, and commentaries. Juan Torres used empirical fieldwork, keen observations, and experimentation to advance the understanding of ant taxonomy and ecology in Puerto Rico. His taxonomic work involved the description of new species and genera of various insect groups, as well as revisions of taxonomic groups, and other observations of the ecology and behavior of rare taxa. Juan Torres also published several taxonomic keys in English and Spanish for various insect groups and localities. His work with ant communities advanced ecological niche theory and island biogeography highlighting the non-equilibrium and stochastic nature of ant community dynamics in Puerto Rico and adjacent islands. He also published synthesis summaries of the ants of Puerto Rico, Mona Island, and the Luquillo Mountains. His ecological studies of ants ranged from descriptions of biotic interactions among ants and with other animal species, to the quantification of the role of insects in wood decomposition and nutrient cycling. The research spanned from dry to wet forest and non-forest conditions in Puerto Rico and adjacent islands and cays.Juan A. Torres Negrón (Juan Torres) estudió hormigas, avispas, comejenes y otros grupos de insectos. Revisé 34 de sus publicaciones y las agrupé en seis temas: teoría ecológica, taxonomía, química, ecología, síntesis y comentarios. Juan Torres utilizó trabajo empírico de campo, sagaces observaciones y experimentación para avanzar el campo de la taxonomía y ecología de las hormigas en Puerto Rico. Su trabajo taxonómico resultó en la descripción de nuevas especies y géneros de insectos, revisiones taxonómicas, reportes de presencia de especies en la Isla y la documentación de nuevos aspectos ecológicos y del comportamiento de varios grupos taxonómicos. Además, publicó claves taxonómicas en inglés y español para varios grupos de insectos y distintas localidades. Sus trabajos con comunidades de hormigas ampliaron las teorías de ecología de nicho y la de biogeografía de islas enfatizando el estado de desequilibrio y la naturaleza estocástica de las comunidades de hormigas en Puerto Rico e islas adyacentes. Publicó resúmenes sobre la ecología y taxonomía de hormigas e insectos en Puerto Rico, Isla de Mona y las Montañas de Luquillo. Sus estudios ecológicos cubrieron una amplia gama de tópicos desde las interacciones bióticas entre grupos de hormigas y con otros grupos de plantas y animales, hasta la función de los insectos en la descomposición de la madera y el reciclaje de nutrientes en los bosques. Las investigaciones de Juan Torres incluyeron desde bosques secos a bosques muy húmedos, pastizales y sistemas agrícolas en el archipiélago de Puerto Rico

A low complexity iterative channel estimation and equalisation scheme for (data-dependent) superimposed training

Channel estimation/symbol detection methods based on superimposed training (ST) are known to bemore bandwidth efficient than those based on traditional time-multiplexed training. In this paper we present an iterative version of the ST methodwhere the equalised symbols obtained via ST are used in a second step to improve the channel estimation, approaching the performance of the more recent (and improved) data dependent ST (DDST), but now with less complexity. This iterative ST method (IST) is then compared to a different iterative superimposed training method of Meng and Tugnait (LSST).We show via simulations that the BER of our IST algorithm is very close to that of the LSST but with a reduced computational burden of the order of the channel length. Furthermore, if the LSST iterative approach (originally based on ST) is now implemented using DDST, a faster convergence rate can be achieved for the MSE of the channel estimates

Synchronisation of the superimposed training method for channel estimation in the presence of DC-offset

The superimposed training method estimates the channel from the induced first-order cyclostationary statistics exhibited by the received signal. In this paper, using vector space decomposition, we show that the information needed for training sequence synchronisation, and for DC-offset estimation, can be extracted from the first-order cyclostationary statistics as well. Necessary and sufficient conditions for channel computation and equalisation are derived, when training sequence synchronisation and DC-offset removal are required. The computational burden of the practical implementation of the method presented here is much lighter than for existing algorithms. At the same time, simulation results show that the performance, in terms of the MSE of the channel estimates and BER, is not diminishedwhen compared to these existing algorithms

Holographic phase transition from dyons in an AdS black hole background

We construct a dyon solution for a Yang-Mills-Higgs theory in a 4 dimensional Schwarzschild-anti-de Sitter black hole background with temperature T. We then apply the AdS/CFT correspondence to describe the strong coupling regime of a 2+1 quantum field theory which undergoes a phase transition exhibiting the condensation of a composite charge operator below a critical temperature $T_c$.Comment: 19 pages, 7 figures. Minor corrections, references added. Version published in JHEP

Supertubes and special holonomy

We obtain a $\frac 14$-supersymmetric 6-brane solution of IIA Supergravity by T-dualizing the supertube recently found. The resulting $C_{\it 1}$ electric charge is related to the original $D0$-brane charge. The uplifted solution to eleven dimensions results to be a purely geometrical configuration, which can be interpreted as a bound state of a Taub-NUT space and a pp-wave. Being the non trivial part of the metric pseudo-Riemannian, the resulting reduced holonomy group is non-compact and locally isomorphic to a semidirect product of an Abelian four dimensional group and SU(2).Comment: 11 pages, latex, no figure

SO(3) \times U(1) isometric instantons with non abelian hair in four dimensional string theory

We compute the exact effective string vacuum backgrounds of the level $k = 81/19 SU(2,1)/U(1)$ coset model. A compact SU(2) isometry present in this seven dimensional solution allows to interpreting it after compactification as a four dimensional non-abelian SU(2) charged instanton with a singular submanifold and an $SO(3) \times U(1)$ isometry. The semiclassical backgrounds, solutions of the type II strings, present similar characteristics.Comment: 12 pages, latex fil

COMBINED EFFECT OF LARGE CRABGRASS AND SMOOTH PIGWEED DENSITIES ON SNAP BEAN YIELD

COMBINED EFFECT OF LARGE CRABGRASS AND SMOOTH PIGWEED DENSITIES ON SNAP BEAN YIEL

Gravitating sphalerons and sphaleron black holes in asymptotically anti-de Sitter spacetime

Numerical arguments are presented for the existence of spherically symmetric regular and black hole solutions of the EYMH equations with a negative cosmological constant. These solutions approach asymptotically the anti-de Sitter spacetime. The main properties of the solutions and the differences with respect to the asymptotically flat case are discussed. The instability of the gravitating sphaleron solutions is also proven.Comment: 30 pages, LaTeX, 8 Encapsulated PostScript figure