Explicit solutions for multi-layered wide plates and beams with perfect and imperfect bonding and delaminations under thermo-mechanical loading

Explicit expressions, for efficient application in engineering practice, are derived for generalized displacements and stresses in simply supported multi-layered wide plates and beams subjected to steady-state thermal and mechanical loading. The expressions are general and apply to plates composed of an arbitrary number of layers, of arbitrary thickness and elastic/thermal properties, and where the interfaces between the layers may be imperfect and allow relative sliding. The closed-form solutions are obtained using a multiscale homogenized model which depends on only three displacement variables and overcomes limitations of current approaches based on computationally expensive discrete-layer models. The accuracy of the expressions in predicting the highly complex and discontinuous fields, which characterize the response of thick and highly anisotropic plates with interlayer damage and delaminations, is verified using exact 2D thermo-elasticity solutions. The asymptotic limits of the model/solution correspond to the problems of an intact and a multiply delaminated plate. They are derived using a perturbation technique, which also explains the multiscale dependence of the model on the parameters

Assessment of nitrate hazards in umbria region (Italy) using field datasets: Good agriculture practices and farms sustainability

The Nitrates Directive, EU 91/676/EEC, obliged all European Union member states to introduce laws that guarantee the use of proper agriculture and farm methods, with the aim to reduce pollution resulting from the excessive use of nitrates. In this work, we estimated the potential and effective nitrogen load from agriculture, farms, civil, and industrial sources in Umbria region, Italy, and assessed the previous (and actual) contamination by nitrates at different scales. The adopted methodology uses databases of the sources, such as the type of fertilizer (inorganic or manure), the type of industrial site, the census of livestock and field data at a local, basin, and regional scale. Hydrological and geological models are used to compute infiltration. The study shows that the contribution of farms to nitrate pollution is in the order of swine > cattle > sheep and goats; while the highest agricultural load is due to arable land, followed by olive and grape. The study also shows that municipalities that have values of nitrates over the threshold for both groundwater and surface water can rapidly change their status during consecutive years. This means that rules for farm sustainability, complying with the Nitrates Directive, EU 91/676/EEC, should be defined at a sub-basin scale, where the hydrogeological conditions strongly influence infiltration

Shear Lag And Beam Theories For Structures

Dynamic problems are solved using beam theory and shear lag approximations, and also FEM. For a laminated plate incorporating through-thickness fibers, highlights are: 1) Inertia complicates the fiber pullout problem considerably. 2) Disturbances propagate along frictionally coupled fibers at less than the bar wave speed. 3) Unstable regimes appear in interfacial friction. 4) Large scale bridging creates oscillatory, predominately mode II crack profiles and 5) strongly modifies fracture at low to intermediate velocities. These results imply that dynamic delamination damage evolution will be dominated by distributed (not localized) bridging and friction effects. Solutions for single cracks with small process zones are less relevant than those for multiple cracks with large scale bridging, for which some initial solutions are discussed

New molecular approaches in adipogenesis regulation: The connexin 43 role

Indexación: Scopus; Redalyc.La prevalencia de la obesidad a nivel mundial se ha incrementado rápidamente durante los últimos años debido principalmente a los cambios en el estilo de vida de la población con un aumento significativo en el consumo de energía y disminución de los niveles de actividad física. Es por esto que la comunidad científica está interesada en comprender de forma más profunda los mecanismos que regulan la fisiopatología de la obesidad. Dentro de los diferentes blancos de estudio se encuentra la adipogénesis, cuyo entendimiento es fundamental para comprender el desarrollo de la obesidad y las patologías asociadas a esta. Recientemente ha surgido importantes evidencias que involucran a la proteína de canales de “Gap Junction” conexina 43 (Cx43) en la regulación de los procesos relacionados con adipogénesis, cuyo papel es básicamente anti-adipogénico, sin embargo, nuevas funciones de Cx43 en la regulación de la formación del tejido adiposo siguen descubriéndose.The global prevalence of obesity has been increased rapidly over the past few years mainly due to changes in the lifestyle of the population with a significant increase in energy consumption and decreased levels of physical activity. As a result, the scientific community is interested in a deeper understanding of the mechanisms that regulate the pathophysiology of obesity. In this context, adipogenesis process is an important target of study to understand the obesity and associated pathologies. Recently has been emerged important evidence that involve gap junction channel protein connexin 43 (Cx43) in the regulation of processes related to adipogenesis, whose role is fundamentally anti-adipogenic. However, new functions of Cx43 in the regulation of adipose tissue function also continued to emerge.http://www.redalyc.org/articulo.oa?id=5594990800

MULTISCALE MODELING OF MULTI-LAYERED STRUCTURES

A mechanical model based on a novel multiscale approach has been recently formulated in Massab\uf2 and Campi, Meccanica, 50(4), 2015, to study multi-layered plates with imperfect interfaces and delaminations loaded dynamically. The model couples an equivalent single-layer structural theory and a discrete-layer cohesive-crack model in order to efficiently and accurately describe both the global behaviour and the local perturbations of the fields generated by the inhomogeneous material structure and the presence of interfacial imperfections. The homogenized field equations depend on the global variables only so that problems characterized by a large number of layers and delaminations are conveniently treated and efficient and insightful closed-form solutions can be derived for relevant problems. The model is applied to investigate the effects of the presence of imperfect interfaces on the dynamic characteristics of the plates. Closed form solutions are derived for unidirectionally reinforced wide plates with elastic sliding interfaces. The asymptotic limits, which can be obtained through a perturbation analysis, define the free vibrations of fully-bonded and fully-debonded plates. Changes in the interfacial stiffness strongly affects natural frequencies and modes of vibration: new modes are activated and the cut-off frequency of the second flexural spectrum, which in fully bonded plates is quite large so that the spectrum is usually disregarded, decreases and vanishes for decreasing/vanishing interfacial stiffness

Structural theories in the analysis of dynamic fracture of composite laminates

The problem of the dynamic delamination fracture of composite laminates in the presence of large process zones where nonlinear mechanisms take place is examined within the framework of elastic structural analysis and nonlinear elastic fracture mechanics. A model based on Timoshenko beam theory is formulated to analyze mode I dynamic fracture and investigate the influence of cohesive or bridging mechanisms on crack growth. A close form solution of the problem is obtained for the case of steady state cracking. Transient dynamic fracture is treated numerically through a finite difference approximatio

Integrated air stripping for remediation of soils contaminated by organic compounds

This paper presents the results of a laboratory scale investigation on the remediation of a soil contaminated by a mixture of organic compounds using a two-step process consisting of stripping and biofiltration. The biofilter was packed with the soil under examination in order to use autochthonous microorganisms. To assess the effects of both temperature and superficial velocity of the air stream on process performance different sets of experimental tests were carried out at two air temperatures (50 and 80 degrees C), and at two superficial air velocities (41.0 and 82.0 m h(-1)), corresponding to apparent air residence times in the biofilter column of 38 and 19s respectively. The stripping rate proves to be inversely correlated with the soil-water partitioning coefficient, while no evident correlation was found with the Henry coefficient. It can therefore be concluded that soil-water partitioning is limited by mass transfer while air-water partitioning reaches equilibrium. Temperature influences both stripping rate in the stripping column and degradation capacity in the biofilter. A stripping temperature of 80 degrees C combined with a biofiltration temperature of WC provides the best process performance. (c) 2007 Society of Chemical Industry