Monte Carlo model of the uncertainty of SEA loss factors

Finite Element Methods are widely used to model vibro-acoustic systems, but as the modal density becomes higher this type of model becomes inaccurate and impractical. This is why in the high modal density region the use of Statistical Energy Analysis (SEA) models has become increasingly popular. SEA has some obvious advantages such as its simple formal expression, being based on linear equation systems or the reduced number of variables involved. But SEA has drawbacks as well, such as the absence of local information or the necessity of frequency averaging. A key quantity in SEA models is the loss factor. This takes into account the energy dissipated within a given subsystem or when power flows from one subsystem to another. Even though analytical expressions exist for a number of subsystems of differing nature, the measurement of the loss factor is still advisable and a necessity for a large number of cases. The most commonly used method of measuring loss factors is the Power Injection Method. This method is based on the injection of power into every single subsystem in sequence while the energy in each subsystem is measured. In spite of its simplicity, there remain a number of problems where the accuracy of the results is influenced by various practical issues. In this paper, a Monte Carlo model is used to describe the uncertainty of a two subsystemproblem consisting of two planar elements connected along one side. The influence of the input variables is studied and the conditioning of the coefficient matrix that model the system is also taken into accoun

Contribución al atlas palinológico de Andalucía Occidental, VI. Caprifoliaceae

En el presente trabajo se l leva a cabo un estudio morfológico de los granos de pol en de Lonicera etrusca G. Santi , L. i mplexa Ai ton , L. pericl ymenum L. , L. splendida Boiss ., Sambucus ebulus L. , S.. nigra L. y Viburnum tinus L., tanto en microscopía óptica como electr ónica de barrido . Se reconocen tres t ipos de polen diferentes , para cuya separación han servido fundamenta lmente las aperturas y la ornamentación.The polleo morphology of Lonicera etrusca G. San t i, L. implexa Ai to'n , L. periclymenum L. , L. splendida Boiss . , Sacumbus ebul us L. , S. nigra L. and Viburnum tinus L. have benn s t udied by light and scanning electron mi croscopy . Three types of pollen are recognized using the apertures a nd the ornamenta ti e

Ediacaran Obduction of a Fore-Arc Ophiolite in SW Iberia: A Turning Point in the Evolving Geodynamic Setting of Peri- Gondwana

The Calzadilla Ophiolite is an ensemble of mafic and ultramafic rocks that represents the transition between lower crust and upper mantle of a Cadomian (peri-Gondwanan) fore arc. Mapping and structural analysis of the ophiolite demonstrates that it was obducted in latest Ediacaran times, because the Ediacaran-Early Cambrian sedimentary series (Malcocinado Formation) discordantly covers it. The ophiolite and emplacement-related structures are affected by Variscan deformation (Devonian-Carboniferous), which includes SW verging overturned folds (D1) and thrusts (D2), upright folds (D3), extensional faults (D4), and later faults (D5). These phases of deformation are explained in the context of Variscan tectonics as the result of the progressive collision between Gondwana and Laurussia. Qualitative unstraining of Variscan deformation reveals the primary geometry of Ediacaran-Cambrian structures and uncovers the generation of east verging thrusts as responsible for the primary obduction of the Calzadilla Ophiolite. Restoration of planar and linear structures associated with this event indicates an Ediacaran, east directed obduction of the ophiolite, that is, emplacement of the Cadomian fore arc onto inner sections of the northern margin of Gondwana. According to regional data, the obduction separates two extension-dominated stages in the tectonic evolution of the African margin of northern Gondwana preserved in southern Europe. Preobduction extension brought about the onset and widening of fore-arc and back-arc basins in the external part of the continent, while postobduction extension facilitated the formation of extensional migmatitic domes, an oceanward migration of back-arc spreading centers across peri-Gondwana, and the eventual opening of a major basin such as the Rheic Ocean

Chiral transition-metal complexes as Brønsted-acid catalysts for the asymmetric Friedel-Crafts hydroxyalkylation of indoles.

The Friedel-Crafts reaction between 3,3,3-trifluoropyruvates and indoles is efficiently catalysed by the iridium complex [(η5-C 5Me5)Ir{(R)-Prophos}(H2O)][SbF 6]2 (1) with up to 84% ee. Experimental data and theoretical calculations support a mechanism involving the Brønsted-acid activation of the pyruvate carbonyl by the protons of the coordinated water molecule in 1. Water is not dissociated during the process and, therefore, the catalytic reaction occurs with no direct interaction between the substrates and the metal. This journal is © the Partner Organisations 2014.The authors acknowledge the Ministerio de Economía y Competitividad (MINECO, Grants CTQ2006-03030/BQU, CTQ2009-10303/BQU, CTQ2011-27033 and Consolider Ingenio 2010 CSD2006-003), Gobierno de Aragón (Grupo Consolidado: Catálisis Homogénea Enantioselectiva), Generalitat de Catalunya (2009SGR0259) and the ICIQ foundation for financial support. A. S. and R. R. acknowledge MINECO for predoctoral fellowships. S. D.-G. acknowledges MINECO for a “Torres Quevedo” contract.Peer Reviewe

A skewer survey of the Galactic halo from deep CFHT and INT images

We study the density profile and shape of the Galactic halo using deep multicolour images from the MENeaCS and CCCP projects, over 33 fields selected to avoid overlap with the Galactic plane. Using multicolour selection and PSF homogenization techniques we obtain catalogues of F stars (near-main sequence turnoff stars) out to Galactocentric distances up to 60kpc. Grouping nearby lines of sight, we construct the stellar density profiles through the halo in eight different directions by means of photometric parallaxes. Smooth halo models are then fitted to these profiles. We find clear evidence for a steepening of the density profile power law index around R=20 kpc, from -2.50 +- 0.04 to -4.85 +- 0.04, and for a flattening of the halo towards the poles with best-fit axis ratio 0.63 +- 0.02. Furthermore, we cannot rule out a mild triaxiality (w>=0.8). We recover the signatures of well-known substructure and streams that intersect our lines of sight. These results are consistent with those derived from wider but shallower surveys, and augur well for upcoming, wide-field surveys of comparable depth to our pencil beam surveys.Comment: 14 pages, 8 figures, 6 table

Finding halo streams with a pencil-beam survey: new wraps in the Sagittarius stream

We use data from two CFHT-MegaCam photometric pencil-beam surveys in the g' and the r' bands to measure distances to the Sagittarius, the Palomar 5 and the Orphan stream. We show that, using a cross-correlation algorithm to detect the turnoff point of the main sequence, it is possible to overcome the main limitation of a two-bands pencil-beam survey, namely the lack of adjacent control-fields that can be used to subtract the foreground and background stars to enhance the signal on the colour-magnitude diagrams (CMDs). We describe the cross-correlation algorithm and its implementation. We combine the resulting main sequence turnoff points with theoretical isochrones to derive photometric distances to the streams. Our results (31 detections on the Sagittarius stream and one each for the Palomar 5 and the Orphan streams) confirm the findings by previous studies, expand the distance trend for the Sagittarius faint southern branch and, for the first time, trace the Sagittarius faint branch of the northern-leading arm out to 56 kpc. In addition, they show evidence for new substructure: we argue that these detections trace the continuation of the Sagittarius northern-leading arm into the southern hemisphere, and find a nearby branch of the Sagittarius trailing wrap in the northern hemisphere.Comment: 16 pages, 15 figures, 2 table

Air gap influence on the vibro-acoustic response of Solar Arrays during launch

One of the primary elements on the space missions is the electrical power subsystem, for which the critical component is the solar array. The behaviour of these elements during the ascent phase of the launch is critical for avoiding damages on the solar panels, which are the primary source of energy for the satellite in its final configuration. The vibro-acoustic response to the sound pressure depends on the solar array size, mass, stiffness and gap thickness. The stowed configuration of the solar array consists of a multiple system composed of structural elements and the air layers between panels. The effect of the air between panels on the behaviour of the system affects the frequency response of the system not only modifying the natural frequencies of the wings but also as interaction path between the wings of the array. The usual methods to analyze the vibro-acoustic response of structures are the FE and BE methods for the low frequency range and the SEA formulation for the high frequency range. The main issue in the latter method is, on one hand, selecting the appropriate subsystems, and, on the other, identifying the parameters of the energetic system: the internal and coupling loss factors. From the experimental point of view, the subsystems parameters can be identified by exciting each subsystem and measuring the energy of all the subsystems composing the Solar Array. Although theoretically possible, in practice it is difficult to apply loads on the air gaps. To analyse this situation, two different approaches can be studied depending on whether the air gaps between the panels are included explicitly in the problem or not. For a particular case of a solar array of three wings in stowed configuration both modelling philosophies are compared. This stowed configuration of a three wing solar arrays in stowed configuration has been tested in an acoustic chamber. The measured data on the solar wings allows, in general, determining the loss factors of the configuration. The paper presents a test description and measurements on the structure, in terms of the acceleration power spectral density. Finally, the performance of each modelling technique has been evaluated by comparison between simulations with experimental results on a spacecraft solar array and the influence on the apparent properties of the system in terms of the SEA loss factors has been analyse

End-pulled polymer translocation through a many-body flexible pore

This paper studies the features of a homopolymer translocating through a flexible pore. The channel is modeled as a monolayer tube composed by monomers with two elastic parameters: spring-like two body interaction and bending three body recall interaction. In order to guarantee the stability of the system, the membrane is compounded by a lipid bilayer structure having hydrophobic body (internal), while the pore is hydrophilic in both edges. The polymer is end-pulled from the cis-side to the trans-side by a cantilever, to which is connected through a spring able to measure the force acting on the polymer during the translocation. All the structure reacts to the impacts of the monomers of the polymer with vibrations generated by the movement of its constituent bodies. In these conditions, the work done by the cantilever shows a nonmonotonic behavior with the elastic constant, revealing a resonant-like behavior in a parameter region. Moreover, the force spectroscopy registered as a function of time, is able to record the main kinetics of the polymer progression inside the pore

Tracing the Evolution of Agglomeration Economies: Spain, 1860-1991

This article attempts to quantify how the effect of agglomeration economies on population growth has evolved over time. Using district population in Spain between 1860 and 1991, recorded approximately every decade, this article examines whether initial population affects subsequent population growth. Our results show that, while the relationship between these two variables hardly existed during the second half of the 19th century, this link increased significantly between 1910 and 1970, although this trend was abruptly interrupted by the Civil War and the autarkic period that followed. The intensity of this relationship debilitated in the 1970s, a process that continued during the 1980s as rural out-migration diminished and de-industrialisation hit traditional manufacturing sectors. Our findings also stress that agglomeration economies were stronger in medium-size districts, especially from 1960 onwards, thus suggesting that congestion costs began to mitigate the benefits arising from agglomeration economies in the largest locations