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Search Results: 1 - 10 of 11967 matches for " Hermenegildo Garcia "
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Allotropic Carbon Nanoforms as Advanced Metal-Free Catalysts or as Supports
Hermenegildo Garcia
Advances in Chemistry , 2014, DOI: 10.1155/2014/906781
Abstract: This perspective paper summarizes the use of three nanostructured carbon allotropes as metal-free catalysts (“carbocatalysts”) or as supports of metal nanoparticles. After an introductory section commenting the interest of developing metal-free catalysts and main features of carbon nanoforms, the main body of this paper is focused on exemplifying the opportunities that carbon nanotubes, graphene, and diamond nanoparticles offer to develop advanced catalysts having active sites based on carbon in the absence of transition metals or as large area supports with special morphology and unique properties. The final section provides my personal view on future developments in this field. 1. Introduction: From Active Carbons to Carbon Allotropes In classical heterogeneous catalysis, active carbons (ACs) have been widely used as supports for noble metal and metal oxides [1–3]. ACs are high surface area materials having carbon as predominant element in their composition that are obtained by pyrolysis of available biomass wastes, upon addition of inorganic reagents to promote the carbonisation process. For instance, one popular active carbon comes from coconut shells adequately powdered, pyrolyzed at 600°C under N2, mixed with phosphoric acid for activation, and then baked at temperatures below 300°C [4, 5]. In other recipes, olive seeds or almond shells are used as AC precursors and other mineral acids or oxidizing chemicals are employed as additives [6–8]. The structure of ACs is poorly defined with domains of amorphous carbon and the presence of condensed polycyclic aromatic compounds forming platelets of nanometric dimensions that are interconnected by bridges that can be CH2 and heteroatoms such as O, NH, and S. In certain regions, ACs have graphitic domains when the platelets are large enough and stacking of the imperfect graphene (G) sheets can take place. Besides oxygen and other elements such as nitrogen or sulphur, metal traces such as iron, zinc, and copper, are very frequently present in the final composition of the material because these transition metals have been introduced as additives in the pyrolysis process and they remain in residual, sometimes not negligible, percentages. Understanding the mechanism in heterogeneous catalysis largely depends on the exhaustive characterization of the solid catalyst and on the knowledge on the architecture of the active sites [9]. In this sense, while ACs are available and affordable materials exhibiting high adsorption capacity, this property being suitable for their use as support, they are too complex and
Resource Usage Analysis of Logic Programs via Abstract Interpretation Using Sized Types
Alejandro Serrano,Pedro Lopez-Garcia,Manuel V. Hermenegildo
Computer Science , 2014, DOI: 10.1017/S147106841400057X
Abstract: We present a novel general resource analysis for logic programs based on sized types. Sized types are representations that incorporate structural (shape) information and allow expressing both lower and upper bounds on the size of a set of terms and their subterms at any position and depth. They also allow relating the sizes of terms and subterms occurring at different argument positions in logic predicates. Using these sized types, the resource analysis can infer both lower and upper bounds on the resources used by all the procedures in a program as functions on input term (and subterm) sizes, overcoming limitations of existing resource analyses and enhancing their precision. Our new resource analysis has been developed within the abstract interpretation framework, as an extension of the sized types abstract domain, and has been integrated into the Ciao preprocessor, CiaoPP. The abstract domain operations are integrated with the setting up and solving of recurrence equations for inferring both size and resource usage functions. We show that the analysis is an improvement over the previous resource analysis present in CiaoPP and compares well in power to state of the art systems.
Towards Execution Time Estimation for Logic Programs via Static Analysis and Profiling
Edison Mera,Pedro Lopez-Garcia,German Puebla,Manuel Carro,Manuel Hermenegildo
Computer Science , 2007,
Abstract: Effective static analyses have been proposed which infer bounds on the number of resolutions or reductions. These have the advantage of being independent from the platform on which the programs are executed and have been shown to be useful in a number of applications, such as granularity control in parallel execution. On the other hand, in distributed computation scenarios where platforms with different capabilities come into play, it is necessary to express costs in metrics that include the characteristics of the platform. In particular, it is specially interesting to be able to infer upper and lower bounds on actual execution times. With this objective in mind, we propose an approach which combines compile-time analysis for cost bounds with a one-time profiling of the platform in order to determine the values of certain parameters for a given platform. These parameters calibrate a cost model which, from then on, is able to compute statically time bound functions for procedures and to predict with a significant degree of accuracy the execution times of such procedures in the given platform. The approach has been implemented and integrated in the CiaoPP system.
Angélica y el desencadenamiento de la locura: Lope de Rueda y Tirso de Molina
Hermenegildo, Alfredo
Arbor : Ciencia, Pensamiento y Cultura , 2004,
Abstract: La locura, como recurso dramático, aparece en dos obras separadas por unas cuantas décadas: la Mederà, de Lope de Rueda, y La villana de la Sagra, de Tirso de Molina. En la primera, la presencia destructora y conflictiva de unos hermanos gemelos desencadena la locura de unos individuos, los padres de la protagonista, que alteran con sus andanzas la convivencia social del grupo a que pertenecen. La fiesta carnavalesca está también en la base misma de la construcción de los locos. En la obra de Tirso, la locura del galán, de don Luis, es utilizada para detener, con su fondo libresco, el desarrollo previsible de la fábula.…
Figuras reales en el Códice de autos viejos
Alfredo Hermenegildo
Castilla : Estudios de Literatura , 2009,
Inferring Parametric Energy Consumption Functions at Different Software Levels: ISA vs. LLVM IR
Umer Liqat,Kyriakos Georgiou,Steve Kerrison,Pedro Lopez-Garcia,John P. Gallagher,Manuel V. Hermenegildo,Kerstin Eder
Computer Science , 2015,
Abstract: The static estimation of the energy consumed by program executions is an important challenge, which has applications in program optimization and verification, and is instrumental in energy-aware software development. Our objective is to estimate such energy consumption in the form of functions on the input data sizes of programs. We have developed a tool for experimentation with static analysis which infers such energy functions at two levels, the instruction set architecture (ISA) and the intermediate code (LLVM IR) levels, and reflects it upwards to the higher source code level. This required the development of a translation from LLVM IR to an intermediate representation and its integration with existing components, a translation from ISA to the same representation, a resource analyzer, an ISA-level energy model, and a mapping from this model to LLVM IR. The approach has been applied to programs written in the XC language running on XCore architectures, but is general enough to be applied to other languages. Experimental results show that our LLVM IR level analysis is reasonably accurate (less than 6.4% average error vs. hardware measurements) and more powerful than analysis at the ISA level. This paper provides insights into the trade-off of precision versus analyzability at these levels.
Adorno, arte e educa??o: negócio da arte como nega??o
Fabiano, Luiz Hermenegildo;
Educa??o & Sociedade , 2003, DOI: 10.1590/S0101-73302003000200010
Abstract: the main investigation in this paper aims at understanding that a work of art in its internal form gets a relative autonomy from the empiric reality of which it becomes a critical reflection. as mediation to the social and historical reality that produced it, art is characterized as a negation of this same reality. this principle of determined negation as an antithesis of society is condensed in a work of art as the problem of its internal form, an element to which theodor w. adorno conferred an epistemological dimension. in this category of knowledge, considered through the aesthetics perspective, the instrumental reason as a brutal praxis of surviving is concretely questioned in its restrictive form of knowledge.
Adorno, arte e educa o: negócio da arte como nega o
Fabiano Luiz Hermenegildo
Educa??o & Sociedade , 2003,
Abstract: O eixo temático desta investiga o trata de compreender que a obra de arte corporifica na sua forma interna uma autonomia relativa com rela o à realidade empírica sobre a qual se torna reflex o crítica. Ao se caracterizar como media o com a realidade social que a produziu, a arte é por isso mesmo a sua nega o. é esse princípio de nega o determinada, em que se condensam na obra de arte as antinomias e os antagonismos como antíteses da sociedade enquanto problema de sua forma interna, o elemento ao qual Theodor W. Adorno atribui dimens o epistemológica. Nessa categoria do conhecimento assim concebida, pela perspectiva estética, a raz o instrumental como práxis brutal da sobrevivência é concretamente questionada na sua forma restritiva de conhecimento.
Existence for the steady problem of a mixture of two power-law fluids
Hermenegildo Borges de Oliveira
Physics , 2012,
Abstract: The steady problem resulting from a mixture of two distinct fluids of power-law type is analyzed in this work. Mathematically, the problem results from the superposition of two power laws, one for a constant power-law index with other for a variable one. For the associated boundary-value problem, we prove the existence of very weak solutions, provided the variable power-law index is bounded from above by the constant one. This result requires the lowest possible assumptions on the variable power-law index and, as a particular case, extends the existence result by Ladyzhenskaya dated from 1969 to the case of a variable exponent and for all zones of the pseudoplastic region. In a distinct result, we extend a classical theorem on the existence of weak solutions to the case of our problem.
The Navier-Stokes problem modified by an absorption term
Hermenegildo Borges de Oliveira
Mathematics , 2009,
Abstract: In this work we consider the Navier-Stokes problem modified by the absorption term $|\textbf{u}|^{\sigma-2}\textbf{u}$, where $\sigma>1$, which is introduced in the momentum equation. % For this new problem, we prove the existence of weak solutions for any dimension $N\geq 2$ and its uniqueness for N=2. % Then we prove that, for zero body forces, the weak solutions extinct in a finite time if $1<\sigma<2$, exponentially decay in time if $\sigma=2$ and decay with a power-time rate if $\sigma>2$. % We prove also that for a general non-zero body forces, the weak solutions exponentially decay in time for any $\sigma>1$. In the special case of a suitable forces field which vanishes at some instant, we prove that the weak solutions extinct at the same instant provided $1<\sigma<2$.
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