Evolución geoquímica de las rocas gabroicas de Galicia durante su meteorización

[Resumen] Se realiza un estudio de la evolución geoquímica de las rocas gabroicasdel macizo de Monte Castelo (La Coruña) en el curso de su meteorización .En medios bien drenados se produce una fuerte pérdida de bases, y en menor medida de Si, ya desde las primeras fases de la alteración, por el, contrario, en tos medios donde la hidromorfia es permanente la lixiviación de bases decrece, la movilidad del Si se aproxima a la del Al y se incrementa la del Fe y el Mn.[Abstract] This paper is a study of the geochemical evolution of the gabbroic rocks of Monte Castelo (La Coruña) in the progress of their üJeathering •In üJell drained envirorunents there are an intense l03S of bases and, in a minor level, of Si, even in the first phases of the üJeathering; but in hydromorphic énvironments , the leach of bases decreases ; the movitity of Si comes near of the Al and that of Fe and Mn increases

Closed-form solutions for the piezoresistivity properties of short-fiber reinforced composites with percolation-type behavior

A new analytical formulation for the modeling of piezoresistive fiber-reinforced composites with percolation-type behavior is presented in this work. Firstly, we develop a closed-form solution of the electrical conductivity of oriented short-fiber reinforced composites by using generalized spherical harmonics series expansions of a Mori-Tanaka (MT) model. Piezoresistive effects are accounted for by means of three distinct mechanisms, namely filler reorientation, volume expansion, and breakage/formation of conductive paths. Then, this solution is used to derive simple analytical formulas to estimate the linear piezoresistivity coefficients. To illustrate the potentials of the proposed formulation, numerical results and discussion are presented on its application to the modeling of the piezoresistive composites doped with carbon nanotubes (CNTs). The presented formulation is also inlaid in a standard 3D finite element code to simulate the electromechanical response of full-scale CNT-based structural elements. The reported results demonstrate the capabilities of the proposed formulation to link the microstructural properties of short-fiber composites with the macroscopic response of structural systems with extraordinarily fast computation times and accuracy.A new analytical formulation for the modeling of piezoresistive fiber-reinforced composites with percolation-type behavior is presented in this work. Firstly, we develop a closed-form solution of the electrical conductivity of oriented short-fiber reinforced composites by using generalized spherical harmonics series expansions of a Mori-Tanaka (MT) model. Piezoresistive effects are accounted for by means of three distinct mechanisms, namely filler reorientation, volume expansion, and breakage/formation of conductive paths. Then, this solution is used to derive simple analytical formulas to estimate the linear piezoresistivity coefficients. To illustrate the potentials of the proposed formulation, numerical results and discussion are presented on its application to the modeling of the piezoresistive composites doped with carbon nanotubes (CNTs). The presented formulation is also inlaid in a standard 3D finite element code to simulate the electromechanical response of full-scale CNT-based structural elements. The reported results demonstrate the capabilities of the proposed formulation to link the microstructural properties of short-fiber composites with the macroscopic response of structural systems with extraordinarily fast computation times and accuracy

Meteorización de las granulitas de Cabo Ortegal

[Resumen] Se realiza el estudio químico y mineralógico del proceso de alteración, en medios sustractivos, de las granuli tas de Cabo Ortegal, la precipi tación media anual supera los 1.300 mm. y las temperaturas medias mensuales extremas son 23ºC y 4,7ºC. Durante el proceso de meteorizaciór se origina una fuerte pérdida de Ca, Na y Mg y,en menor proporción, de Si con acumulación relativa de Fe y Al. Como productos de alteración aparecen filosilicatos 1:1 dioctaédricos, gibbsita, oxihidróxidos de hierro y micas y cloritas degradadas. La edafogénesis es de tipo fermonosialítico con una tendencia ferralítica, al menos en sus fases iniciales.[Abstract] This paper is a chemical and mineralogical study about the weathering process, in subtr&ctive environments, of the granul i tes in Cabo Ortegal. The mean annual precipitation is over 1.300 mm. and the mean monthly extreme temperatures are 23ºC and 4,7ºC . In the process of weathering there is an intense 10S8 of Ca, Na and Mg and, in a minar level , of Si, with a relative accumulation of Fe and Al. Proqucts of the weathering are 1: 1 dioctahedral phyllosilicates, gibbsi teiron oxyhydroxides and degraded micas and chlorites. The pedogenesis is of fermonosialli tic type wi th a ferrallitic tendence, in the first phases at least

Mineralogía de las arcillas en suelos y alteraciones sobre materiales graníticos de Galicia

[Resumen] Se realiza un estudio de la naturaleza de la fracción arcilla en suelos y capas de alteración de.rocas graníticas de Galicia (58 perfiles) encontrando un predominio de minerales propios de "sistemas abiertos" como filosilicatos 1:1 y gibbsita acompañados .de minerales de tipo mica más o menos degradados. Las esmectitas son muy poco abundantes y en general no parecen formarse en procesos edáficos. Dentro del perfil se diferencian dos zonas, una de escasa actividad de la materia orgánica en la que las plagioclasas son los minerales más lábiles, originándose gibbsita por mecanismos de hidrólisis o acidolisis moderada. Otra en las capas superficiales con un mayor ataque a los minerales de tipo mica por mecanismos acidolíticos o de ácido-complexolisis moderada[Abstract] The nature of the clay fraction of saprolites and soils developed on granitic rocks of Galicia (58 profiles) is studied. It is found a predominance of minerais typical of "open systems" like hyllosilicats 1: 1 and gibbsite, acompamed by mica type minerals with different levels of degradation . The smectits are rare and its origin, sems to have no relation with the processes of soil formation. In the profile two zones can be differentiated, at one of them, with very low activity of organic matter, the plagioclases are the most labile minerals '1' and the dominant process is the formation of gibbsite by means of mechanisms of hydrolysis or moderate acidolysis · The upper zone, with high activity of organic matter, is characterized by a stronger attack to the mica type minerals by acidolytic or oderate acido-coplexolytic mechanisms

Independent Component Analysis to Detect Clustered Microcalcification Breast Cancers

The presence of clustered microcalcifications is one of the earliest signs in breast cancer detection. Although there exist many studies broaching this problem, most of them are nonreproducible due to the use of proprietary image datasets. We use a known subset of the currently largest publicly available mammography database, the Digital Database for Screening Mammography (DDSM), to develop a computer-aided detection system that outperforms the current reproducible studies on the same mammogram set. This proposal is mainly based on the use of extracted image features obtained by independent component analysis, but we also study the inclusion of the patient's age as a nonimage feature which requires no human expertise. Our system achieves an average of 2.55 false positives per image at a sensitivity of 81.8% and 4.45 at a sensitivity of 91.8% in diagnosing the BCRP_CALC_1 subset of DDSM

Mineralogía de la fracción arcilla de suelos y sedimentos de la Cuenca de Maceda

[Resumen] Se estudia la mineralogía de la fracción arcilla de los sedimentos terciarios y cuaternarios que rellenan la depresión de Maceda,así como de las rocas que constituyen el marco y sus productos de alteración. Las rocas que rodean la cuenca están sometidas actual mente a un proceso de alteración de tipo hidrólisis ácida (caolinita, gibbsita y oxihidróxidos de hierro son los productos de alteración más significativos) Los sedimentos terciarios presentan en su fracción arcilla un filosilicato 1:1 dioctaédrico(haloisítico o caolinítico) como mineral más ahlndante, micas, micas degradadas, goethita y, ocasionalmente, hematita,observándose la presencia de vermiculitas de baja carga en las capas mas profundas. Los depósitos más recientes contienen abundante filo silicato 1:1 dioctaédrico de bajo grado de orden y gibbsita, micas degradadas en cantidades variables y goethita.[Abstract] The igneous and metamorphic rocks that surround the Maceda depressian are subjected to a weathering of acidic hydrolysis type (kaol inite, gibbsite and Fe-oxihydroxides are the more repl'esenta"LJ.ve weathering products). The tertiary sediments have as principal component a 1:1 diocthaedral phyllosilicate (halloysite or kaolini te) associated wi th micas, degradated micas, goethita-:occasionally hematite and in the deepest layers, low charge vermiculites • - The newest deposits have disordered 1:1 diocthaedral phyllosilicate and gibbsite, changing proportions of degradated micas and goethit

Determinación de familias mineralógicas en suelos sobre rocas graníticas de la provincia de La Coruña

[Resumen] La aplicación de la metodología propuesta por la Soil Taxonomy (1975) para la determinación de familias mineralógicas a un conjunto de suelos desarrollados sobre diversos tipos de rocas graníticas, permite observar que, generalmente, estos suelos pueden clasificarse como pertenecientes a las familias mixtas, existiendo una tendencia micácea o incluso verdaderas clases micáceas en el caso de aquellas rocas que contienen una alta proporción de moscovi ta (en general granitos de dos micas).Cuando la mica dominante es la biotita los suelos se incluyen en las familias mixtas,debido a la fácil alteración de este mineral, en los medios ácidos ricos en materia orgánica, hacia materiales ver miculíticos.[Abstract] The application of the Soil Taxonomy methodology (1975) for the determination of mineralogical families in several soils developped on granitic rocks, shows that, generally, these soils are incl~ded in mi xed classes with a micaceous tendence, or even pure micaceous classes, in thouse soils developped on rocks with a high proportion of muscovite (generally two mica granites). If the predominant mica is bioti te, the soils belong to mixed classes as a consecuence of the weatherability of this mineral towards vermiculitic materials (in acid and organic matter rich environments)

Multielement polynomial chaos Kriging-based metamodelling for Bayesian inference of non-smooth systems

This paper presents a surrogate modelling technique based on domain partitioning for Bayesian parameter inference of highly nonlinear engineering models. In order to alleviate the computational burden typically involved in Bayesian inference applications, a multielement Polynomial Chaos Expansion based Kriging metamodel is proposed. The developed surrogate model combines in a piecewise function an array of local Polynomial Chaos based Kriging metamodels constructed on a finite set of non-overlapping subdomains of the stochastic input space. Therewith, the presence of non-smoothness in the response of the forward model (e.g.~ nonlinearities and sparseness) can be reproduced by the proposed metamodel with minimum computational costs owing to its local adaptation capabilities. The model parameter inference is conducted through a Markov chain Monte Carlo approach comprising adaptive exploration and delayed rejection. The efficiency and accuracy of the proposed approach are validated through two case studies, including an analytical benchmark and a numerical case study. The latter relates the partial differential equation governing the hydrogen diffusion phenomenon of metallic materials in Thermal Desorption Spectroscopy tests

Weathering in granite and lamprophyre contact

[Resumen] Se realiza el estudio microestructural, mineralógico y geoquímico del proceso de meteorización en una zona de contacto granito-lamprófido. En la roca granítica se observa gibbsita, en los medios muy lixiviados, y filosilicatos 1: 1 en los menos drenados. En ellamprófido los productos son filosilicatos 1: 1, integrados vermiculíticos y oxi-hidróxidos de hierro; la abundancia de estos óxidos permite la conservación de la estructura original hasta etapas muy avanzadas dé la meteorización. El proceso global es de tipo monosialítico (fermonosialítico en las rocas básicas) con una tendencia inicial alitizante en las rocas graníticas. El pH de abrasión constituye un buen índice del grado de meteorización de estas rocas.[Abstract] In this paper is developed a microstructural, mineralogical and geochemical study of the weathering process in a contact between a granitic rock and a lamprophyre. In the granitic rack the main weathering products are gibbsite, under strongly leaching conditions, and 1: 1 phyllosilicates when the drainage is lesser. In the lamprophyre the products are 1: 1 phyllosilicates, vermiculitic integrades and iron oxides; the abundance of this oxides permit the conservation of rock structure till advanced stages of weathering. The overall process is moniosiallitic (fermonosiallitic in the basic rock), although an allitic tendency can be appreciated during the initial stages of the granitic rock weathering. The abrasion pH is good index to asses the weathering degree of these rocks

Abrasion pH use as an index ofweathering and pedogenesis degree in granitic soils of A Coruña (Spain).

[Resumen] En este trabajo se determina el pH de abrasión de las fracciones arenosas de un conjunto de perfiles de alteración y suelos desarrollados sobre rocas graníticas de la provincia de A Coruña (Galicia, NW de España). Se observa que tanto estos valores como el del pH de ·abrasión de la muestra total, sin materia orgánica, constituyen un buen índice del grado de evolución del material, presentando la ventaja, sobre otros índices, de su fácil y rápida determinación, por lo que parece un dato a tener en cuenta especialmente en los estudios a gran escala de cartografía y usos potenciales del suelo.[Abstract] In this paper were studied the abrasion pH in samples of several soils and veathering profiles developped on granitic rocks in A Coruña (Galicia, NW Spain). The abrasion pH values of sands and of the whole sample (organic matter free) are a good index to assess the evolution degree of the materials. This index is an esay and no time consuming test; so its use can be considered in large scale cartographic works and in studies on potential soil fertility