An Empirical Study of Real-World SPARQL Queries

Understanding how users tailor their SPARQL queries is crucial when designing query evaluation engines or fine-tuning RDF stores with performance in mind. In this paper we analyze 3 million real-world SPARQL queries extracted from logs of the DBPedia and SWDF public endpoints. We aim at finding which are the most used language elements both from syntactical and structural perspectives, paying special attention to triple patterns and joins, since they are indeed some of the most expensive SPARQL operations at evaluation phase. We have determined that most of the queries are simple and include few triple patterns and joins, being Subject-Subject, Subject-Object and Object-Object the most common join types. The graph patterns are usually star-shaped and despite triple pattern chains exist, they are generally short.Comment: 1st International Workshop on Usage Analysis and the Web of Data (USEWOD2011) in the 20th International World Wide Web Conference (WWW2011), Hyderabad, India, March 28th, 201

Numerical simulations of impact behaviour of thin steel plates subjected to cylindrical, conical and hemispherical non-deformable projectiles

In this paper, a numerical study of normal perforation of thin steel plates impacted by different projectile shapes is reported. The numerical simulations of this problem have been performed using a finite element code, ABAQUS-Explicit with a fixed and an adaptive mesh for the plate. To define the thermoviscoplastic behaviour of the material constituting the plate, the Johnson-Cook model has been used. This homogeneous behaviour has been coupled with the Johnson-Cook fracture criterion to predict completely the perforation process. Three kinds of projectile shape (blunt, conical and hemispherical) have been simulated with a large range of impact velocities from 190 to 600 m/s. The analysis considers the influence of adiabatic shear bands, plastic work and the gradient of temperature generated in the plate. The numerical results predict correctly the behaviour projectile-plate in agreement with experimental data published by other authors.Publicad

Thermo-viscoplastic behaviour of 2024-T3 aluminium sheets subjected to low velocity perforation at different temperatures

This paper deals with the mechanical behaviour of the aluminium alloy 2024-T3. This alloy has particular relevance since it is widely used in the aeronautical industry for building aircraft structures. The deformation behaviour of this material has been characterised in tension under wide ranges of strain rate and temperature. Among the aluminium alloys, the AA 2024-T3 highlights due to its high flow stress and strain hardening. Moreover, the material temperature sensitivity has been found dependent on plastic strain. The Modified Rusinek-Klepaczko constitutive description [Rusinek A, Rodriguez-Martinez JA, Arias A. A thermo-viscoplastic constitutive model for FCC metals with application to OFHC copper. Int. J. Mech. Sci. 52 (2010) 120-135], which takes into account such dependence of the temperature sensitivity on plastic strain, has been applied for modelling the thermo-viscoplastic response of the material. Satisfactory agreement between experiments and analytical predictions provided by the Modified Rusinek-Klepaczko model has been found. In order to study the material behaviour under impact loading, low velocity perforation tests on AA 2024-T3 sheets have been performed at different initial temperatures using a drop weight tower. Plastic instabilities formation and progression are identified as the cause behind the target collapse for all the impact tests conducted. The results from these perforation tests are compared with those reported in [Rodriguez-Martinez JA, Pesci R, Rusinek A, Arias A, Zaera R, Pedroche DA. Thermo-mechanical behaviour of TRIP 1000 steel sheets subjected to low velocity perforation by conical projectiles at different temperatures. Int. J. Solids Struct. 47 (2010) 1268-1284.] for TRIP 1000 steel sheets. The comparison reveals that the amount of specific energy absorbed by the aluminium targets is much lower than that corresponding to the steel targets. The role played by inertia on delaying plastic instabilities formation is determined as potential responsible for such behaviour.Publicad

A thermo-viscoplastic constitutive model for FCC metals with application to OFHC copper

In this paper a physical-based constitutive relation for defining the thermo-viscoplastic behaviour of FCC metals with dependence on strain on thermal activation processes is presented. The model, based on previous considerations reported by Rusinek and Klepaczko [Rusinek A, Klepaczko JR. Shear testing of sheet steel at wide range of strain rates and a constitutive relation with strain-rate and temperature dependence of the flow stress. Int J Plasticity 2001;17:87-115], is founded on physical aspects of the material behaviour. The proposed constitutive relation is applied to define the behaviour of oxygen-free high conductivity (OFHC) copper using the experimental data reported in Nemat-Nasser and Li [Nemat-Nasser S, Li Y. Flow stress of FCC polycrystals with application to OFHC copper. Acta Mater 1998;46:565-77]. The description of the material behaviour provided by the model gets satisfactory agreement with the experiments. The analytical predictions of this constitutive description are compared with those obtained from the models due to Voyiadjis and Almasri [Voyiadjis GZ, Almasri AH. A physically based constitutive model for fcc metals with applications to dynamic hardness. Mech Mater 2008;40:549-63], and Nemat-Nasser and Li. This comparison reveals that the original formulation proposed in this paper is a suitable alternative to other physically based relations for modeling OFHC copper.The researchers of the University Carlos III of Madrid are indebted to the Comunidad Autónoma de Madrid (ProjectCCG08UC3M/MAT4464) and to the Ministerio de Ciencia e Innovación de España (ProjectDPI/200806408)Publicad

A little garbage in, lots of garbage out: Assessing the impact of careless responding in personality survey data

[EN]In self-report surveys, it is common that some individuals do not pay enough attention and effort to give valid responses. Our aim was to investigate the extent to which careless and insufficient effort responding contributes to the biasing of data.We performed analyses of dimensionality, internal structure, and data reliability of four personality scales (extroversion, conscientiousness, stability, and dispositional optimism) in two independent samples. In order to identify careless/insufficient effort (C/IE) respondents, we used a factor mixture model (FMM) designed to detect inconsistencies of response to items with different semantic polarity. The FMM identified between 4.4% and 10% of C/IE cases, depending on the scale and the sample examined. In the complete samples, all the theoretical models obtained an unacceptable fit, forcing the rejection of the starting hypothesis and making additional wording factors necessary. In the clean samples, all the theoretical models fitted satisfactorily, and the wording factors practically disappeared. Trait estimates in the clean samples were between 4.5% and 11.8% more accurate than in the complete samples. These results show that a limited amount of C/IE data can lead to a drastic deterioration in the fit of the theoretical model, produce large amounts of spurious variance, raise serious doubts about the dimensionality and internal structure of the data, and reduce the reliability with which the trait scores of all surveyed are estimated. Identifying and filtering C/IE responses is necessary to ensure the validity of research result

The deterministic nature of the fracture location in the dynamic tensile testing of steel sheets

This paper investigates the key mechanisms which determine the fracture location in the dynamic tensile testing of steel sheets. For that purpose we have conducted experiments and finite element simulations. Experiments have been performed using samples with six different gauge lengths, ranging from 20 mm to 140 mm, that have been tested within a wide spectrum of loading velocities, ranging from 1 m/s to 7.5 m/s. Three are the key outcomes derived from the tests: (1) for a given gauge length and applied velocity, the repeatability in the failure location is extremely high, (2) there is a strong interplay between applied velocity, gauge length and fracture location and (3) multiple, and largely regular, localization patterns have been observed in a significant number of the experiments performed using the samples with the shorter gauge lengths. Our experimental findings are explained using the finite element simulations. On the one hand, we have shown that variations in the applied velocity and the gauge length alter the processes of reflection and interaction of waves taking place in the sample during the test, which leads to the systematic motion of the plastic localization along the gauge (as experimentally observed). On the other hand, we have detected that the emergence of multiple localization patterns requires short and equilibrated specimens with uniform stress and strain distributions along the gauge. We conclude that the experimental and numerical results presented in this paper show that, in the absence of significant material and/or geometrical defects, the location of plastic strain localization in the dynamic tensile test is deterministic.The authors are indebted to the Ministerio de Ciencia e Innovación de España (Project DPI/2011-24068) for the financial support received which allowed conducting this work.Publicad

Toward a better “Person–Environment Fit” through items calibration of the SIS-C

Producción CientíficaThe Supports Intensity Scale–Children’s Version (SIS-C) is the only available tool to assess extraordinary support needs for children and adolescents with intellectual disability. In past years, several works have proclaimed the need for its ongoing improvement as a measurement instrument. To contribute to this line of research, the goal of this work is to analyze the reliability of the SIS-C and its usefulness to distinguish between different levels of intensity of support needs. To address this, 814 children and adolescents with intellectual disability (M = 11.13 years; SD = 3.41) were assessed using the SIS-C Spanish version. Item response theory analyses were conducted to estimate latent scores and assess measurement quality along the support needs continuum. The SIS-C items showed good overall discrimination and information values, and none showed problems that required their removal or modification. However, all the scales composing the SIS-C showed problems in discerning high levels of intensity of support needs, especially for children and adolescents with severe/profound intellectual disability. This ceiling effect may be an obstacle for both research and practice involving the SIS-C. Implications for research and practice are discussed, and future lines of research for improving the SIS-C are provided.Ministerio de Economía y Competitividad (PSI2015-65193-P y BES-2016-078252

Sistemas transportadores de fármacos basados en el polímero poly(e- caprolactona) para el tratamiento del cáncer

Chemotherapy agents have little or no specificity over cancer cells, resulting in low therapeutic concentrations at the tumor site (a consequence of a broad systemic distribution), and severe side effects. With the aim of avoiding cancer therapy failure, several approaches such as design of new anticancer drugs, chemical engineering of conventional drugs and development of drug delivery systems have been proposed. The objective is to enhance drug localization at the tumor region (by controlling its biodistribution profile) and, therefore, to increase the anti-tumor efficacy (even in multi-drug resistant tumors), while reducing systemic side effects. One of the most promising approaches to the problem is the development of drug nanocarriers based on the polymer poly(e-caprolactone). In this review we will focus our attention on these polymeric colloids, particularly on the most significant characteristics and formulation procedures, and on their use as nanoplatforms for the delivery of chemotherapy agents to the tumor site. Furthermore, the most recent in vitro and in vivo investigations on the subject are extensively reviewed

A dislocation-based constitutive description for modeling the behavior of FCC metals within wide ranges of strain rate and temperature

In this work a dislocation based constitutive description for modeling the thermo visco plastic behavior of FCC metals has been developed. The constitutive description, which is founded on the concepts of thermal activation analysis and dislocation dynamics, assumes the plastic flow additively decomposed into internal stress and effective stress. The internal stress represents the applied stress required for the transmission of plastic flow between the polycrystal grains and it is defined by the Hall Petch relationship. The effective stress formulation, which is the main innovative feature of this work, represents the thermally activated deformation behavior. This is defined taking into account the interrelationship between strain rate and temperature, and gathers structural evolution dependence. This structural evolution is described as a function of dislocations density, which acts as internal state variable in the material deformation behavior. A systematic procedure for identifica tion of the material parameters is developed and the model is applied to define the behav ior of annealed OFHC copper. The analytical predictions of the constitutive description are compared with the experimental data reported by Nemat Nasser and Li (Nemat Nasser, S., Li, Y., (1998). Flow stress of FCC polycrystals with application to OFHC Copper. Acta Mater. 46, 565 577). Good correlation between experiments and analytical predictions is found within wide ranges of strain rate and temperature.The researchers of the University Carlos III of Madrid are indebted to the Comunidad Autónoma de Madrid (Project CCG10 UC3M/DPI 5596) and to the Ministerio de Ciencia e Innovación de España (Project DPI/2008 06408) for the financial support received which allowed conduct ing part of this work.Publicad

Geología y mineralogía del yacimiento polimetálico de Au-As (Ag-Pb-Zn-Cu-Sb) de Valiña-Azúmara (Lugo, NO de España)

Valiña-Azúmara is a polymetallic Au-As (Ag-Pb-Zn-Cu-Sb) deposit, located in the province of Lugo (NW Spain), that was mined for arsenic at the beginning of the 20th century. The mineralization is hosted in a Variscan thrust fault with a dip direction of N247-261ºE, and N-S and NE-SW Late-Variscan faults. These structures are hosted in black slates, Cambrian in age. To a lesser extent, the mineralization also occurs disseminated within narrow, weakly silicified and sericited selvages. Mineralization is divided into two hypogene stages. The first consists of quartz, calcite, rutile, sericite, arsenopyrite and pyrite. Two types of pyrite (Py-I and Py-II) are defined according to their chemical and textural characteristics. Py-II occurs as overgrowth of previous Py-I crystals. Py-II is As-rich (≤1.7 wt.%) and often contains traces of Te, Zn, Cu, Bi, Sb and Au. The mineralized drill core sections show a significant correlation between Au and As. This is due to Au occurring as invisible Au within the Py-II grains, with contents of up to 176 ppm. The Au/As ratios of Py-II indicate that Au was deposited as Au1+, as solid solution within the pyrite structure. The second stage of mineralization is enriched in Ag-Pb-Zn-Cu-Sb, replacing the first stage, and consists of quartz, calcite, chlorite, sphalerite, jamesonite, Ag-rich tetrahedrite, freibergite, chalcopyrite, pyrrhotite and galena. Although jamesonite shows traces of Ag, the Cu-Ag sulfosalts are the main carriers of the Ag mineralization in the deposit, with contents that vary from 13.7 to 23.9 wt.% of Ag. In the most superficial levels of the area, secondary Fe oxide and hydroxide, scorodite and anglesite developed due to the oxidation of the ore.Valiña-Azúmara es un yacimiento filoniano de Au-As (Ag-Pb-Zn-Cu-Sb) situado en la provincia de Lugo (NO España), que fue explotado por arsénico a principios del siglo XX. La mineralización se encuentra encajada en un cabalgamiento Varisco de dirección de buzamiento N247-261°E y en fracturas tardivariscas de dirección N-S y NE-SO que cortan a filitas negras de edad Cámbrica. En menor medida la mineralización también se encuentra diseminada en el encajante, en finas salbandas levemente sericitizadas y silicificadas. La mineralización se divide en dos etapas hipogénicas. La primera está constituida por cuarzo, calcita, rutilo, sericita, arsenopirita y pirita. En base a su composición y textura, se diferencian dos tipos de pirita, Py-I y Py II. La Py-II suele encontrarse recrecida sobre la Py I, formando bandas poligonales. Esta pirita está enriquecida en As (≤1,7% en peso) y contiene trazas de otros metales como Te, Zn, Cu, Bi, Sb y Au. Los tramos mineralizados de sondeo del yacimiento presentan correlación geoquímica entre los elementos Au y As, debido a que el Au se halla en forma de oro refractario dentro de los cristales de pirita arsenical (Py-II), los cuales llegan a presentar concentraciones en Au de hasta 176 ppm. La relación Au/As de la Py-II sugiere que el oro se encuentra en forma de Au+1, en solución sólida dentro de la estructura cristalina del mineral. La segunda etapa de mineralización está enriquecida en Ag-Pb-Zn-Cu-Sb y consiste en cuarzo, calcita, clorita, esfalerita, jamesonita, cobres grises (tetraedrita argentífera y freibergita), calcopirita, pirrotina y galena. Esta etapa se encuentra rellenando fracturas y cavidades intersticiales en los minerales de la etapa anterior, reemplazándolos en parte. Los principales minerales portadores de Ag son los cobres grises, con contenidos que varían entre 13,7 y 23,9% en peso. En la parte más superficial del yacimiento, la alteración supergénica de la mena primaria dio como resultado la formación de óxidos e hidróxidos de hierro, escorodita y anglesita