Damage Model for Composites Defined in Terms of Available Data

A model to predict stiffness reduction and stress redistribution due to damage of laminated polymer composites is presented. The material properties required by the model are limited to those already available for unidirectional composites. Classical lamination theory is generalized for the case of a continuously damaging material using concepts from continuous damage mechanics. The Tsai-Wu failure criteria can be recovered as a limiting case. The damage model is validated with experimental results for various laminates built with aramid/epoxy, T300/5208, and T300/914 carbon/epoxy.     

Unmanned Aerial System-Based Multispectral Water Quality Monitoring in the Iberian Pyrite Belt (SW Spain)

Few studies have assessed mining-associated water pollution using spectral characteristics. We used high-resolution multispectral data acquired by unmanned aerial drones combined with in situ chemical data to assess water quality parameters in 12 relatively small water bodies located in the Tharsis complex, an abandoned mining area in the Iberian pyrite belt (SW Spain). The spectral bands of Micasense RedEdge-MX Dual and spectral band combinations were used jointly with physicochemical data to estimate water quality parameters and develop reliable empirical models using regression analysis. Physicochemical parameters including pH, ORP, EC, Al, Cu, Fe, Mn, S, Si, and Zn were estimated with high accuracy levels (0.81?<?R²?<?0.99, 4?<?RMSE%?<?75, 0.01?<?MAPE?<?0.97). In contrast, the observed and modelled values for Ba, Ca, and Mg did not agree well (0.42?<?R²?<?0.70). The best-fitted models were used to generate spatial distribution maps, providing information on water quality patterns. This study demonstrated that using empirical models to generate spatial distribution maps can be an effective and easy way to monitor acid mine drainage.

     

Drosophila grim induces apoptosis in mammalian cells

Genetic studies have shown that grim is a central genetic switch of programmed cell death in Drosophila; however, homologous genes have not been described in other species, nor has its mechanism of action been defined. We show here that grim expression induces apoptosis in mouse fibroblasts. Cell death induced by grim in mammalian cells involves membrane blebbing, cytoplasmic loss and nuclear DNA fragmentation. Grim-induced apoptosis is blocked by both natural and synthetic caspase inhibitors. We found that grim itself shows caspase-dependent proteolytic processing of its C-terminus in vitro. Grim-induced death is antagonized by bcl-2 in a dose-dependent manner, and neither Fas signalling nor p53 are required for grim pro-apoptotic activity. Grim protein localizes both in the cytosol and in the mitochondria of mouse fibroblasts, the latter location becoming predominant as apoptosis progresses. These results show that Drosophila grim induces death in mammalian cells by specifically acting on mitochondrial apoptotic pathways executed by endogenous caspases. These findings advance our knowledge of the mechanism by which grim induces apoptosis and show the conservation through evolution of this crucial programmed cell death pathway.     

X-ray photoelectron spectroscopy study of passive layers formed on Pb-Sn and Pb-Sb alloys

In this article, passivated Pb-Sn and Pb-Sb alloys with different compositions were studied by X-ray photoelectron spectroscopy (XPS). The passive films were found to have a double-layer structure. Both Sn and Sb were found to play an important role during the growth of passive film, which resulted in different compositions of passive films. The Pb oxides, Pb sulfate, Sn/Sb oxides, and Pb-Sn/Sb complex oxides (PbO _x ·Sn_1−x O₂, PbSb₂O₆) were present in the passive films. Both Sn and Sb facilitated PbO _x (1<x<2) formation, which was considered to be very helpful to optimize the conductivity of passive films. It was also shown that the positions of peak signals of alloying Sn/Sb, Pb, and O were almost fixed, even though the contents of alloying Sn/Sb oxides were quite different in different specimens.     

Inhibitory effects of terpene alcohols and aldehydes on growth of green algaChlorella pyrenoidosa

The growth of the green algaChlorella pyrenoidosa was inhibited by terpene alcohols and the terpene aldehyde citral. The strongest activity was shown by citral. Nerol, geraniol, and citronellol also showed pronounced activity. Strong inhibition was linked to acyclic terpenes containing a primary alcohol or aldehyde function. Inhibition appeared to be taking place through the vapor phase rather than by diffusion through the agar medium from the terpene-treated paper disks used in the system. Inhibition through agar diffusion was shown by certain aged samples of terpene hydrocarbons but not by recently purchased samples.     

A three-dimensional layer-wise constant shear element for general anisotropic shell-type structures

This paper deals with the development of a new three-dimensional element with two-dimensional kinematic constraints capable of analysing the mechanical behaviour of the laminated anisotropic shell-type structures. This element, originally developed for the linear analysis of plates, is extended for the linear analysis of laminated composite shells. The element can represent arbitrarily curved shells with variable number of layers and thicknesses, including ply drop-off problems. The element was validated in a previous work by the patch test. All the analytical details necessary to make possible the shell analysis are presented here. Examples are reported to show the capability of the element to predict the behaviour of complex structures and a refined computation of the stresses is carried out by integrating the equilibrium equations.     

Finite elements for post-buckling analysis. I—The W-formulation

This paper presents a convenient formulation for the stability analysis of structures using the finite element method. The main assumptions are linear elasticity, a linear fundamental path, and the existence of distinct critical loads (i.e. no coupling between buckling modes occurs). The formulation developed is known as W-formulation, in which the energy is written in terms of a sliding set of incremental coordinates measured with respect to the fundamental path. In the presentation developed here, the only ingredients required to carry out the analysis are the strain-displacement and the constitutive matrices at the element level. The present formulation is compared with the so called V-formulation, in which the displacements refer to the unloaded state. It is shown that under the present assumptions of linear fundamental path, the advantages of the V-formulation are lost and both approaches are similar. An example of a circular plate under in-plane loading illustrates the procedures. Part II of this paper deals with the application to the post buckling analysis of plate assemblies made of composite materials.     

Analysis and optimization of ventilation systems for an underground transport interchange building under regular and emergency scenarios

The work and conclusions gained from the analysis of five new underground interchange buildings ongoing in Madrid, Spain, is presented. An additional study was performed for a typical two-level interchange building, and the methodology and results are presented in this paper.First, different ventilation and air conditioning strategies have been analyzed. The main goal is to find the most efficient design in order to maintain pollutants concentration and temperatures below the designed values, at minimum investment and operation costs. Different strategies have been modelled and compared using a Computational Fluid Dynamics (CFD) code, taking into account the buses circulation and the different pollution and heat sources. The final solution developed is based on a physical separation between the island area and the dock area. Conclusions on the efficiency of the different design strategies and possible pitfalls are presented.Secondly, different fire scenarios are analyzed. The main goal is to check whether the fire fighting measures planned, such as mechanical ventilation and a curtains system to define smoke sectors are able to cope with a fire emergency situation. A model for the bus fire has been developed, including heat release and smoke production. The main results presented are temperature fields, visibility and smoke concentration.     

High-quality few layer graphene produced by electrochemical intercalation and microwave-assisted expansion of graphite

Few-layer graphene is synthesized from electrochemically-produced graphite intercalation compounds in aqueous perchloric acid. Although anodic intercalation is more efficient in terms of time, cathodic pre-treatment is preferred to avoid the formation of graphite oxide. The materials are characterized by high resolution transmission electron microscopy and scanning electron microscopy, UV–visible, infrared and Raman spectroscopy. We demonstrate that the method, under the experimental conditions used in this work, does not produce damage to the sp² carbon lattice. The synthetic approach using electrochemical-potential control is very promising to obtain, in a controllable manner, graphene with different degrees of oxidation.