A quasi-static nonlinear analysis for assessing the fire resistance of 3d frames exploiting time-dependent yield surface

In this work an automatic procedure for evaluating the axial force-biaxial bending yield surface of reinforced concrete sections in fire is proposed. It provides an accurate time-dependent expression of the yield condition by a section analysis carried out once and for all, accounting for the strength reduction of the materials, which is a function of the fire duration. The equilibrium state of 3D frames with such yield conditions, once discretized using beam finite elements, is formulated as a nonlinear vectorial equation defining a curve in the hyperspace of the discrete variables and the fire duration. A generalized path-following strategy is proposed for tracing this curve and evaluating, if it exists, the limit fire duration, that is the time of exposure which leads to structural collapse. Compared to the previous proposals on the topic, which are limited to local sectional checks, this work is the first to present a global analysis for assessing the fire resistance of 3D frames, providing a time history of the fire event and taking account of the stress redistribution. Numerical examples are given to illustrate and validate the proposal

Removal of the center of mass in nuclei and its effects on 4He

Abstract The singular value decomposition of rectangular matrices is shown to provide the recipe for removing the center of mass spurious admixtures from the multiphonon basis generated by an equation of motion method for solving the nuclear eigenvalue problem. It works for any single particle basis without any energy restriction on the selection of the configurations. Its effects on 4He are illustrated

La teoría general del derecho en el marxismo

En el marxismo no existe fundamento para una concepción personalista del orden social y político, que respeten la dignidad de la persona humana, entendida como ente dinámico que tiende a la realización de cada individuo mediante la consecución de su fin personal. Más bien, el sistema marxista es transpersonalista: el individuo es considerado no como un todo con un fin personal, sino como medio para la realización de otros fines, medio para la realización de la humanidad, de la cual es pura parte. El filósofo comunista polaco, A. Schaff, reconoce paladinamente este principio: «Para el marxismo, (el hombre) en cuanto parte específica de la naturaleza animada, es un producto de la sociedad, y, en este sentido, es la totalidad de las relaciones sociales... Esto no tiene nada común con la existencia autónoma del individuo, tal como lo sostiene el personalismo o existencialismo»90. La persona no tiene una realidad propia, no es un ente per se stans; por ello, no tiene fin último propio. El ser humano es un producto social y, como tal, engarzado en el proceso, del cual es parte. A la teoría jurídica de Marx, tomada aisladamente y en abstracto, no se puede llamar positivista. Pero hay que tener en cuenta que Marx nunca tuvo el poder en sus manos, fue un puro teórico. Si Marx hubiera tenido la oportunidad de coger las riendas del gobierno, ¿qué sistema jurídico hubiera impuesto? Naturalmente estamos aquí en el terreno de las puras conjeturas. Pero en el espíritu de Marx existen gérmenes que permiten suponer la utilización de un sistema positivista, adaptado a los fines de la revolución. Personalmente, Marx era un volcán de odio contra sus enemigos, especialmente contra el sistema capitalista. En segundo lugar, él se definía a sí mismo como un revolucionario. Así lo afirmó también Engels en su discurso fúnebre: «El vio en la ciencia una gran palanca, una fuerza revolucionaria en el sentido más verdadero de la palabra... Porque Marx fue realmente un revolucionario como él se llamaba a sí mismo»9 1. En la teoría marxista, el modo de producción cambia en virtud del continuo progreso de las fuerzas productivas. Pero, en realidad, todos los líderes comunistas y de revoluciones postergan el derecho y lo reducen a un simple medio para el logro de sus fines. Esto nos hace suponer que en el espíritu marxista estaban presentes los gérmenes del positivismo, que no pudieron desarrollar porque no alcanzó el poder, como Lenin. Por tanto, la concepción marxista del derecho es esencialmente revolucionaria y, en la praxis, el torrente de la revolución inspira el positivismo e incluso el nihilismo. El derecho es medio y, por ello, cambia en la medida reclamada por las decisiones de sus líderes, que se erigen en fuente de toda norma y rechazan toda normatividad superior a su voluntad. Así nace el puro decisionismo como locomotora de la revolución y de la historia. El lider revolucionario, elevado a la categoría de ser supremo, rechaza toda norma, todo orden jurídico, superior a sus decisiones

An Experimental-Numerical Investigation of the Wake Structure of a Hovering Rotor by PIV Combined with a Γ2 Vortex Detection Criterion

The rotor wake aerodynamic characterization is a fundamental aspect for the development and optimization of future rotary-wing aircraft. The paper is aimed at experimentally and numerically characterizing the blade tip vortices of a small-scale four-bladed isolated rotor in hover conditions. The investigation of the vortex decay process during the downstream convection of the wake is addressed. Two-component PIV measurements were carried out below the rotor disk down to a distance of one rotor radius. The numerical simulations were aimed at assessing the modelling capabilities and the accuracy of a free-wake Boundary Element Methodology (BEM). The experimental and numerical results were investigated by the G2 criterion to detect the vortex location. The rotor wake mean velocity field and the instantaneous vortex characteristics were investigated. The experimental/numerical comparisons show a reasonable agreement in the estimation of the mean velocity inside the rotor wake, whereas the BEM predictions underestimate the diffusion effects. The numerical simulations provide a clear picture of the filament vortex trajectory interested in complex interactions starting at about a distance of z/R = 0.5. The time evolution of the tip vortices was investigated in terms of net circulation and swirl velocity. The PIV tip vortex characteristics show a linear mild decay up to the region interested by vortex pairing and coalescence, where a sudden decrease, characterised by a large data scattering, occurs. The numerical modelling predicts a hyperbolic decay of the swirl velocity down to z/R = 0.4 followed by an almost constant decay. Instead, the calculated net circulation shows a gradual decrease throughout the whole wake development. The comparisons show discrepancies in the region immediately downstream the rotor disk but significant similarities beyond z/R = 0.5

On random flights with non-uniformly distributed directions

This paper deals with a new class of random flights $\underline{\bf X}_d(t),t>0,$ defined in the real space $\mathbb{R}^d, d\geq 2,$ characterized by non-uniform probability distributions on the multidimensional sphere. These random motions differ from similar models appeared in literature which take directions according to the uniform law. The family of angular probability distributions introduced in this paper depends on a parameter $\nu\geq 0$ which gives the level of drift of the motion. Furthermore, we assume that the number of changes of direction performed by the random flight is fixed. The time lengths between two consecutive changes of orientation have joint probability distribution given by a Dirichlet density function. The analysis of $\underline{\bf X}_d(t),t>0,$ is not an easy task, because it involves the calculation of integrals which are not always solvable. Therefore, we analyze the random flight $\underline{\bf X}_m^d(t),t>0,$ obtained as projection onto the lower spaces $\mathbb{R}^m,m<d,$ of the original random motion in $\mathbb{R}^d$. Then we get the probability distribution of $\underline{\bf X}_m^d(t),t>0.$ Although, in its general framework, the analysis of $\underline{\bf X}_d(t),t>0,$ is very complicated, for some values of $\nu$, we can provide some results on the process. Indeed, for $\nu=1$, we obtain the characteristic function of the random flight moving in $\mathbb{R}^d$. Furthermore, by inverting the characteristic function, we are able to give the analytic form (up to some constants) of the probability distribution of $\underline{\bf X}_d(t),t>0.$Comment: 28 pages, 3 figure

Cantharellus lilacinopruinatus Hermitte, Eyssart. & Poumarat, a Catalunya i les Illes Balears

Es descriu , comenta i il·lustra un interessant t áxon de les CantharelI ácies: Cantharellus Iilacinopruinatus Hermitte, Eyssart. & Poumarat, recol·lectat per primer cop a Catalunya i Illes Balears.An interesting taxon of Cantharellaceae: Cantharellus lilacinop ruinatu s Hennitte, Eyssart. & Poumarat, previou sly unrecorded in Catalonia and the Balearic Island s, is described, commented and illustrated.Se describe, comenta e ilustra un interesante taxón de las Cantareláceas: Cantharellus lilacinopruinatus Hennitte, Eyssart. & Poumarat, recolectado por primera vez en Cataluña y Baleares

Empirical vulnerability curves for Italian mansory buildings: evolution of vulnerability model from the DPM to curves as a function of accelertion

In the framework of the emergency management in the case of seismic events, the evaluation of the expected damage represents a basic requirement for risk informed planning. Seismic risk is defined by the probability to reach a level of damage on given exposed elements caused by seismic events occurring in a fixed period and in a fixed area. To this purpose, the expected seismic input, the exposed elements and their vulnerability have to be correctly evaluated. The aim of the research is to define a correct model of vulnerability curves, in PGA, for masonry structures in Italy, by heuristic approach starting from damage probability matrices (DPMs). To this purpose, the PLINIVS database, containing data on major Italian seismic events, has been used and supported by “critical” assumption on missing data. To support the reliability of this assumption, two vulnerability models, considering or not the hypothesis on the missing data, have been estimated and used to calculate the seismic scenario of the L’Aquila 2009 earthquake through the IRMA (Italian Risk MAp) platform. Finally, a comparison between the outcomes elaborated by IRMA platform and the observed damage collected in the AEDES forms, has been done. © 2020, The Author(s)

Dense gas and exciting sources of the molecular outflow in the AFGL 437 star-forming region

We present Very Large Array (VLA) high resolution observations of the NH3(1,1) and NH3(2,2) molecular transitions towards the high mass star forming region AFGL 437. Our aim was to investigate if the poorly collimated CO molecular outflow previously detected in the region is the result of a projection effect, with no intrinsic bipolarity, as suggested by Gomez et al. We complemented our observations with radio continuum archived data from the VLA at 2 and 3.6 cm, and with unpublished public data at 450 {\mu}m taken with Submillimetre Common-User Bolometer Array at the James Clerk Maxwell Telescope. Ammonia emission was found mainly in three clumps located at the south and east of the position of the compact infrared cluster of AFGL 437, where the CO outflow seemed to have its origin. One of the NH3(1,1) clumps coincides with the maximum of NH3(2,2) and with a local peak of emission at 450 {\mu}m. A near infrared source (s11) is also found at that position. Our continuum map at 2 cm shows extended elongated emission associated with the infrared source AFGL 437W. This elongated morphology and its spectral index between 3.6 and 2 cm (\simeq 0.4) suggest the presence of a jet in AFGL 437W. We suggest that several molecular bipolar outflows may exist in the region. The observed CO outflow would be the superposition of those individual outflows, which would explain its low degree of collimation observed at larger scales.Comment: 9 pages, 5 figures, 3 tables, accepted by MNRA