3,822 research outputs found
Fully Discrete Approximations to the Time-Dependent Navier–Stokes Equations with a Projection Method in Time and Grad-Div Stabilization
This paper studies fully discrete approximations to the evolutionary Navier{
Stokes equations by means of inf-sup stable H1-conforming mixed nite elements
with a grad-div type stabilization and the Euler incremental projection method in
time. We get error bounds where the constants do not depend on negative powers
of the viscosity. We get the optimal rate of convergence in time of the projection
method. For the spatial error we get a bound O(hk) for the L2 error of the velocity,
k being the degree of the polynomials in the velocity approximation. We prove
numerically that this bound is sharp for this method.MINECO grant MTM2016-78995-P (AEI)Junta de Castilla y León grant VA024P17Junta de Castilla y León grant VA105G18MINECO grant MTM2015-65608-
Grad-div stabilization for the time-dependent Boussinesq equations with inf-sup stable finite elements
In this paper we consider inf-sup stable nite element discretizations of the
evolutionary Boussinesq equations with a grad-div type stabilization. We prove
error bounds for the method with constants independent on the Rayleigh numbersMINECO grant MTM2016-78995-P (AEI)Junta de Castilla y León grant VA024P17Junta de Castilla y León grant VA105G18MINECO grant MTM2015-65608-
Freeze-thaw durability of recycled concrete from construction and demolition wastes
Road engineering is one of the most accepted applications for concrete including
recycled aggregates from construction and demolition wastes as a partial replacement of the natural
coarse aggregates. Amongst the durability concerns of such application, the deterioration due to
freeze-thaw cycles is one of the most important causes decreasing the life span of concrete in
countries with a continental climate. Moreover, the use of de-icing salts, which is a common
practice to prevent ice formation on roadways and walkways, increases the superficial degradation
of concrete due to frost-salt scaling. Thus, this paper aims to assess the resistance to frost salt with
de-icing salts of two recycled concrete mixtures containing a 50% replacement of the conventional
gravel by recycled aggregates both of mixed and ceramic nature, i.e. containing ceramic percentages
of 34% and 100%, in comparison to a conventional concrete made with siliceous gravel. Therefore,
the surface scaling was evaluated based on EN 1339 (2004) on 28 days cured cylinders, exposed to
7, 14, 21 and 28 freeze-thaw cycles in the presence of sodium chloride solution. Given that no airentraining
admixture was used in any of the mixtures, the scaling of both conventional and recycled
concretes exceeded the 1 kg/m2 limit established by the European standard. Nonetheless, for the
casting surface, the recycled concrete with low ceramic content exhibited a similar behaviour to the
conventional concrete, whereas the performance of the recycled concrete with high ceramic content
was better. However, as expected, trowelled surfaces showed a worse performance and both
recycled concretes had a lower freeze-thaw durability than the conventional mixture. In any case,
the results suggested that the composition of the recycled aggregates could be used as a factor to
limit the differences in performance between recycled and conventional mixtures
The Postprocessed Mixed Finite-Element Method for the Navier–Stokes Equations: Refined Error Bounds
A postprocessing technique for mixed finite-element methods for the incompressible Navier–Stokes equations is analyzed. The postprocess, which amounts to solving a (linear) Stokes problem, is shown to increase the order of convergence of the method to which it is applied by one unit (times the logarithm of the mesh diameter). In proving the error bounds, some superconvergence results are also obtained. Contrary to previous analysis of the postprocessing technique, in the present paper we take into account the loss of regularity suffered by the solutions of the Navier–Stokes equations at the initial time in the absence of nonlocal compatibility conditions of the data.Ministerio de Educación y Ciencia MTM2006- 0084
Stabilization of Galerkin Finite Element Approximations to Transient Convection-Diffusion Problems
A postprocessing technique to improve Galerkin finite element approximations to linear
evolutionary convection-reaction-diffusion equations is considered. A steady convection-reactiondiffusion
problem with data based on the computed standard Galerkin approximation is solved at
any fixed time. The postprocessing approximation is obtained using the SUPG method over the
same Galerkin finite element space. Error bounds for the method are obtained in the convectiondominated
regime. The numerical experiments we present show a substantial reduction of spurious
oscillations achieved by means of this procedure.Ministerio de Educación y Ciencia MTM2007-6052
Postprocessing finite-element methods for the Navier–Stokes Equations: the Fully discrete case
An accuracy-enhancing postprocessing technique for finite-element discretizations
of the Navier–Stokes equations is analyzed. The technique had been previously analyzed only for
semidiscretizations, and fully discrete methods are addressed in the present paper. We show that
the increased spatial accuracy of the postprocessing procedure is not affected by the errors arising
from any convergent time-stepping procedure. Further refined bounds are obtained when the timestepping
procedure is either the backward Euler method or the two-step backward differentiation
formula
Improving the quality of various types of recycled aggregates by biodesposition
Demand for construction materials has been rising in recent decades in many countries around the
world, placing a heavy burden on the environment in terms of both the natural resources consumed
and the enormous flow of waste generated. In order to obtain a more sustainable construction, it is
often suggested to reintroduce the industry’s own waste as input for the manufacture of new materials.
In this study, the use of construction and demolition waste of concrete or mixed concrete/ceramic
nature is investigated as a replacement of natural aggregates in concrete. The greater affinity of
recycled aggregates for water directly affects the workability and/or the concrete strength and
durability. One possible solution to reduce the aggregates water absorption is to apply a biogenic
treatment with calcium carbonate-precipitating bacteria that consolidate the aggregate surface or the
adhering mortar.
Experimental results show that the biodeposition treatment reduced the recycled aggregate water
absorption by generating precipitation in the pores and an impermeable outer layer, most effectively
on the roughest particle surfaces. The largest decrease happened in the aggregates with the highest
porosity. The biogenic layer had a good cohesion with the aggregates. The results of sonication
indicated that the most effective treatment was on recycled concrete aggregates (RCA) instead of
mixed aggregates (MA). Therefore, the treated RCA was used to make concrete for further
investigation. The concrete made with bio-treated RCA had a denser structure, a decreased water
absorption (around 1%) and an improved compressive strength (25%)
Biofabrication of a tri-layered 3D-bioprinted CSC-based malignant melanoma model for personalized cancer treatment
Conventional in vitro cancer models do not accurately reproduce the tumor microenvironment
(TME), so three-dimensional (3D)-bioprinting represents an excellent tool to overcome their
limitations. Here, two multicellular tri-layered malignant melanoma (MM) models composed by
cancer stem cells (CSCs) isolated from a MM established cell line or a primary-patient derived cell
line, fibroblasts, mesenchymal stem cells, and endothelial cells, embedded within an
agarose-collagen type I hydrogel were bioprinted. Embedded-cells showed high proliferation and
metabolic activity, and actively remodeled their TME. MM hydrogels displayed similar rheological
properties that skin and were able to support an early onset of vascularization. Besides, MM
hydrogels displayed different response to vemurafenib compared with cell cultures, and supported
tumorigenesis in murine xenotransplant achieving more mimetic in vivo models. For the first time
a tri-layered 3D-bioprinted CSC-based human MM model is developed recreating TME in vitro
and in vivo and response to treatment, being useful for precision treatment regimens against MM.Consejería
de Salud y Familias de la Junta de Andalucía (Project
No. PIN-0224-2019)Consejería de Economía,
Conocimiento, Empresas y Universidad de la Junta de
Andalucía (FEDER Funds, Projects PY18-FR-2470,
B-CTS-230-UGR18, A-CTS-180-UGR20, PYC20 RE
015 UGR and P18-FR-2465),Ministry de Economía
y Competitividad, Instituto de Salud Carlos
III (FEDER funds, Projects Nos. DTS19/00145
and DTS21/00098)Chair ‘Doctors
Galera-Requena in cancer stem cell research’ (CMCCTS963)Universidad
de Granada/CBUA.Plan Andaluz de Investigación,
Desarrollo e Innovación (PAIDI 2020—
FEDER funds—Ref: DOC_01574)
Monocapas de ácidos grasos. III. Ácidos paimítico, láurico y oleíco sobre disoluciones acuosas que contienen solutos con grupos funcionales alcohólicos.
Monocapas de ácidos grasos. III. Ácidos palmítico, láurico y oleico sobre disoluciones acuosas que contienen solutos con grupos funcionales alcohólicos. Se ha estudiado la influencia que ejercen la longitud y la insaturación de la cadena acílica sobre las características de las monocapas de ácidos grasos sparcidas sobre medios acuosos que contienen etanol, glicerina, glucosa o sacarosa, utilizando una balanza de superficie de tipo Langmuir. La estabilidad de la monocapa es función de la longitud de la cadena acílica y de la presencia de insaturación. En general, los mismos factores que disminuyen la estabilidad de la monocapa pueden favorecer las transiciones iiacia configuraciones con estructuras más expandidasMonolayers of fatty acids. III. Palmitic, Laurie and Oleic Acids on aqueous solutions containig solutes witli alcoholic functional groups. Tiie influence exerted by the length or the insaturation of acyl chain on characteristics of fatty acid monolayers spread on aqueous solutions containing ethanol, glycerol, glucose or sucrose, is studied using a Langmuir type surface balance. The monolayer stability is function of acyl chain length and presence of insaturarion. Generally, the factors decreasing monolayer stability can help transformations towards configurations with more expanded structures
Monocapas de ácidos grasos I. Ácido esteárico sobre disoluciones acuosas de etanol
Monocapas de ácidos grasos. I. Acido esteárico sobre disoluciones acuosas de etanol. Se ha estudiado la estructura y estabilidad de monocapas de ácido esteárico esparcidas sobre disoluciones acuosas que contienen etanol. Las experiencias se han realizado en una iaalanza de superficie comercial tipo Langmuir y se ha operado en condiciones isotérmicas. Las monocapas presentan estructuras de tipo sólida o de líquido condensado en función de la concentración de etanol en la subíase. La estructura que adopta la monocapa es prácticamente independiente de la temperatura. La pérdida de moléculas de ácido esteárico de la monocapa por disolución en la subíase se incrementa a los valores más elevados de temperatura y de concentración de etanol.Monolayers of fatty acids. I. Stearic acid on aqueous solutions of ethanol. The structure and stability of fatty acid monolayers spread on aqueous solutions with ethanol has been studied. The experiments were carried out isothermically using a commercial Langmuir balance (Lauda). Monolayers exhibit solid or condensed liquid structure depending of the ethanol concentration in the subphase. Temperature has not a significant influence on the monolayer. Structure there is a loss of stearic acid film through solution into the adjacent subphase. This loss is increased with the temperature and ethanol concentration in the subphase
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