2,394 research outputs found
A one dimensional model for the prediction of extraction yields in a two phases modified twin-screw extruder
Solid/liquid extraction is performed on raw plant substrate with a modified twin-screw extruder (TSE) used as a thermo-mecanochemical reactor. Visual observations and experimental residence time distributions (RTD) are used to develop a solid transport model based on classical chemical engineering method. Modeled and experimental residence times are compared. The transport model is then coupled with a reactive extraction model in order to predict extraction yields
Further developments in stress initialization in geomechanics via FEM and a two-step procedure involving airy functions
The in-situ stress field in rock masses is a key aspect when a numerical analysis of a rock mass is carried out in any area of geo-engineering, such as civil, mining, or Oil & Gas. A method for the numerical generation of the in-situ stress state in the FE context, based on Airy stress functions was previously introduced. It involves two steps: 1) an estimate of the stress state at each Gauss point is generated, and 2) global equilibrium is verified and re-balancing nodal forces are applied as needed. In this paper, new developments towards improving the accuracy of the stress proposal are discussed. A real application example has been used to illustrate the results achieved with the new implementation
Constraining late-time transitions in the dark energy equation of state
One of the most compelling goals of observational cosmology is the
characterisation of the properties of the dark energy component thought to be
responsible for the recent acceleration of the universe, including its possible
dynamics. In this work we study phenomenological but physically motivated
classes of models in which the dark energy equation of state can undergo a
rapid transition at low redshifts, perhaps associated with the onset of the
acceleration phase itself. Through a standard statistical analysis we have used
low-redshift cosmological data, coming from Type Ia supernova and Hubble
parameter measurements, to set constraints on the steepness of these possible
transitions as well as on the present-day values of the dark energy equation of
state and in the asymptotic past in these models. We have also studied the way
in which these constraints depend on the specific parametrisation being used.
Our results confirm that such late-time transitions are strongly constrained.
If one demands a matter-like pre-transition behaviour, then the transition is
constrained to occur at high redshifts (effectively in the matter era), while
if the pre-transition equation of state is a free parameter then it is
constrained to be close to that of a cosmological constant. In any case, the
value of dark energy equation of state near the present day must also be very
similar to that of a cosmological constant. The overall conclusion is that any
significant deviations from this behaviour can only occur in the deep matter
era, so there is no evidence for a transition associated with the onset of
acceleration. Observational tools capable of probing the dynamics of the
universe in the deep matter era are therefore particularly important.Comment: 9 pages, 7 figures; Astronomy & Astrophysics (in press
A Moment-Based Polarimetric Radar Forward Operator for Rain Microphysics
There is growing interest in combining microphysical models and polarimetric radar observations to improve our understanding of storms and precipitation. Mapping model-predicted variables into the radar observational space necessitates a forward operator, which requires assumptions that introduce uncertainties into model-observation comparisons. These include uncertainties arising from the microphysics scheme a priori assumptions of a fixed drop size distribution (DSD) functional form, whereas natural DSDs display far greater variability. To address this concern, this study presents a moment-based polarimetric radar forward operator with no fundamental restrictions on the DSD form by linking radar observables to integrated DSD moments. The forward operator is built upon a dataset of > 200 million realistic DSDs from one-dimensional bin microphysical rain shaft simulations, and surface disdrometer measurements from around the world. This allows for a robust statistical assessment of forward operator uncertainty and quantification of the relationship between polarimetric radar observables and DSD moments. Comparison of "truth" and forward-simulated vertical profiles of the polarimetric radar variables are shown for bin simulations using a variety of moment combinations. Higher-order moments (especially those optimized for use with the polarimetric radar variables: the 6th and 9th) perform better than the lower-order moments (0th and 3rd) typically predicted by many bulk microphysics schemes
Two phase residence time distribution in a modified twin screw extruder
Biomass fractionation is performed with a modified Clextral twin-screw extruder used as a thermo-mechano-chemical reactor. This new process is firstly analyzed. Visual observations, residence time distributions, and global mass balances are used to obtain information about the process phenomena and their coupling. Residence time distributions (RTD) classical models are adopted to represent the experimental plots. The influence of continuous and discrete process parameters upon the RTD of the solid and liquid phases is analyzed
Conceptos básicos de mecánica en biomecánica
Peer Reviewe
The multidimensional comprehension of Chagas disease. Contributions, approaches, challenges and opportunities from and beyond the information, education and communication field
Chagas is a complex, multidimensional phenomenon in which political, economic, environmental, biomedical, epidemiological, psychological, and sociocultural factors intersect. Nonetheless, the hegemonic conceptualisation has long envisioned Chagas as primarily a biomedical question, while ignoring or downplaying the other dimensions, and this limited view has reinforced the disease's long neglect. Integrating the multiple dimensions of the problem into a coherent approach adapted to field realities and needs represents an immense challenge, but the payoff is more effective and sustainable experiences, with higher social awareness, increased case detection and follow-up, improved adherence to care, and integrated participation of various actors from multiple action levels. Information, Education, and Communication (IEC) initiatives have great potential for impact in the implementation of multidimensional programs of prevention and control successfully customised to the diverse and complex contexts where Chagas disease persists
Nueva plataforma dinamométrica para el análisis y valoración del rendimiento deportivo
Un nuevo modelo de plataforma dinamométrica ha
sido desarrollado por el Instituto de Biomecánica de
Valencia (IBV) y se han fabricado sus primeros prototipos.
Permite la medida de la fuerza de reaccipón tridimensional,
en momento torsor y el punto de aplicación
de la fuerza, a una velocidad de muestre0 de hasta 1000
Hz (500 Hz para dos plataformas).
El nuevo diseño se caracteriza por poseer cuatro captadores
bidimensionales octogonales mecánicamente
desacoplados, placa superior de rigidez optimizada y
sensibilidad cruzada mínima
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