5,789 research outputs found
Indentation of a free beam resting on an elastic substrate with an internal lengthscale
No full textThe plane strain problem of a slender and weightless beam-plate loaded by a transversal point force in unilateral contact with a couple stress elastic foundation is investigated. The study aims to explore the consequences of the material internal lengthscale on the contact mechanics. In particular, compatibility between the beam and the foundation surface demands that both displacement and rotation match along the contact line. To this aim, couple tractions are exchanged besides the traditional contact pressure until separation between the beam and the foundation occurs. The problem is formulated making use of the Green's functions for a point force and a point couple acting atop of a couple stress elastic half-plane. A pair of coupled integral equations is thus derived, that governs the distribution of contact pressure and couple tractions, with one of them being immediately solved to provide an explicit relation between the two unknowns. In this sense, we retrieve the concept of a mechanically equivalent action, as it is the case of the Kirchhoff shear for plates. The remaining integral equation sets a cubic eigenvalue problem, whose linear term accounts for the microstructure. Its numerical solution is sought by expanding the equivalent contact pressure in series of Chebyshev polynomials vanishing at the contact region ends points, namely the lift-off points, and then applying a collocation strategy. The contact length, the distributions of contact pressure and couple tractions under the beam and the shearing force and bending moment along the beam are then obtained as a function of the material characteristic length. Results clearly indicate that accounting for the material internal lengthscale is mainly realized through exchange of the couple tractions, in the lack of which results much resemble those of the classical solution. Specifically, greater contact lengths and a stronger focusing effect about the loading point are encountered, which become very significant when the contact length approaches the internal lengthscale
Couple stress effects in a thin film bonded to a half-space
No full textThis study investigates the contact mechanics of a thin film laying on an elastic substrate within the context of couple-stress elasticity. It aims to introduce the effects of material internal length scale, which has proven an effective way of modeling structures at micro to nano-scales, allowing to capture their size dependent behavior. Specifically, stress analysis for a thin film bonded to a couple stress elastic half-space is considered under plane strain loading conditions by assuming that both shear stress and couple tractions are exchanged between the thin film and the substrate. The problem is converted to a singular integral equation, which is solved by expanding the shear stress tractions as a Chebyshev series. The results show that the introduction of couple tractions decreases the shear stress tractions and the axial load in the thin film. When the characteristic length is sufficiently small, but still finite, the results for classical elastic behavior are approached
Palynological PV borehole dataset
No full textQuantitative palynological data – proxy data – from the PV borehole (onshore Valdés Basin) together with the statistical treatment of data, offer key information for regional paleoclimatic, paleoenvironmental and paleogeomorphic reconstructions for the Miocene of the southwestern Atlantic Ocean. Data show the stratigraphical distribution of palynomorphs (number of specimens) and environmental variables of 60 samples from a 580 m-thick section. Quantitative changes in the palynological assemblages may indicate shifting of the coastline, related — in part – to fluctuations of the relative sea level and in turn, interpreted as successive regional transgressive - regressive cycles occurred during the Miocene in the southwestern Atlantic margin
A 2D Peridynamic Model for Failure Analysis of Orthotropic Thin Plates Due to Bending
No full textThe present paper deals with the problem of cracks propagating in thin orthotropic flat plates under bending loads. We define the mechanical behavior of an orthotropic lamina in which shear deformation can be neglected (Kirchhoff plate). The formulation follows the main ideas of bond based Peridynamics. Failure criteria limit the maximum curvatures and provide failure values which may be different in different directions. Several numerical examples show that the results obtained with the new approach are in good agreement with those obtained with more classical computational methods. Moreover the numerically computed crack patterns seem to follow in a reasonable way the orthotropic properties of the models. Copyright (C) 2016 The Authors. Published by Elsevier B.V
Probabilistic and Deterministic Safety Analysis: Complementary Use for Safety Performance Evaluation
No full textDeterministic Safety Assessment (DSA) and Probabilistic Safety Assessment
(PSA) are both used for regulatory purposes. In general, PSA and DSA groups
work independently even though the main objective of their analyses is common:
demonstration of the safety of the concerned installation. The objective of the
present paper is to propose an exchange of information between DSA and PSA
with a sample application. The proposed approach was tested by performing
Large Break Loss of Coolant Accident (LBLOCA) analysis for a VVER-1000
with a double-ended break. The RELAP5 code was used for the analysis. Besides
the classical LBLOCA assumptions (e.g. instantaneous guillotine break
occurrence), PSA provides information on the most probable Emergency Core
Cooling (ECC) system failure that needs to be considered. This approach
substitutes for the assumption made in the traditional PSA approach on the
sequencing of events, which is generally based either on engineering judgment or
derived from a set of preliminary deterministic calculations by simply applying a
brute force method. In this view, best estimate analysis is conducted with
boundary conditions derived by not only accounting for plant design (e.g. single
failure assumption) but also by performing systematic analysis, which is accepted
by the scientific community and by regulatory bodies. The paper summarizes the
complementary use of DSA and PSA and their relationship for Level 1 analysis
Secondary transfer effect of contact on solidarity with immigrants: A test of emotion generalization as an alternative mechanism
No full textPresentazione orale al simposio “Host-migrant relations and acceptance of immigrants in novel contexts: An intergroup contact approach
Sol-Gel Synthesis of Nanocomposite Cu-Li4Ti5O12 Structures for Ultrahigh Rate Li-Ion Batteries
No full textIn this study, spinel Li4Ti5O12 materials were successfully synthesized by a simple and facile sol-gel process and electroless copper deposition techniques. The characteristics of the as-prepared Li4Ti5O12 and Cu-Li4Ti5O12 were examined by X-ray diffraction and scanning electronic microscopy, while the electrochemical performances including charge/discharge and rate performance tests were also investigated. Cu-Li4Ti5O12 electrode demonstrated the superior initial discharge capacity and rate capability to Li4Ti5O12 electrode, cycled between 1.0 and 2.5 V. The enhanced rate capability can be attributed to the higher Li+ diffusivity and lower charge-transfer resistance due to the electroless deposition of copper. Moreover, when both electrodes discharged with 80 C state of discharge conditions, the reversible capacities were further increased similar to 70 mAhg(-1) with excellent cycling stability and almost no irreversible capability was observed during cycling
The Octopus Sign-A New HRCT Sign in Pulmonary Langerhans Cell Histiocytosis.
No full textBackground: Fibrosis in pulmonary Langerhans cell histiocytosis (PLCH) histologically comprises a central scar with septal strands and associated airspace enlargement that produce an octopus-like appearance. The purpose of this study was to identify the octopus sign on high-resolution computed tomography (HRCT) images to determine its frequency and distribution across stages of the disease. Methods: Fifty-seven patients with confirmed PLCH were included. Two experienced chest radiologists assessed disease stages as early, intermediate, or late, as well as the lung parenchyma for nodular, cystic, or fibrotic changes and for the presence of the octopus sign. Statistical analysis included Cohen's kappa for interrater agreement and Fisher's exact test for the frequency of the octopus sign. Results: Interobserver agreement was substantial for the octopus sign (kappa = 0.747). Significant differences in distribution of the octopus sign between stages 2 and 3 were found with more frequent octopus signs in stage 2 and fewer in stage 3. In addition, we only found the octopus sign in cases of nodular und cystic lung disease. Conclusions: The octopus sign in PLCH can be identified not only on histological images, but also on HRCT images. Its radiological presence seems to depend on the stage of PLCH
Cr and V Substitution in the LiMn(2)O(4)Spinel Positive Electrode Li-Ion Batteries
No full textIn this study, LiCr0.2V0.4Mn1.4O4 cathode active electrode materials were produced via a facile sol-gel method at 800 degrees C. The surfaces of the LiCr0.2V0.4Mn1.4O4 cathode active electrode materials were then coated with Cu in order to increase the conductivity and suppress the manganese ion dissolution into the electrolyte. The structure and electrochemical properties of the obtained Cr and V substituted LiMn2O4 powders were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), galvanostatic charge-discharge test and electrochemical impedance spectroscopy (EIS). The improvement in the cycling performances attributed to stabilization of spinel structure by bication ion substation and Cu coating on the spinel particles. EIS analysis confirmed that bication doping and conductive Cu coating contributed stability of the spinel electrodes and provided stable electrolyte/electrode interface due to the suppression of electrolyte decompositio
A New Light-to-Frequency Analog Front-End Circuit for Optical Sensing in Biomedical Applications
No full textThis paper reports on a new analog front-end circuit capable of measuring light intensity variations by providing the frequency modulation of a square wave output voltage signal. The circuit design allows for a quasi-digital output that can be measured using a simple digital frequency meter, avoiding the use of transimpedance amplifiers and analog-to-digital converters. Thus, the proposed solution is suitable to be employed, for example, as analog front-end in low-voltage, low-power wearable medical devices that make use of optical electrodes (optrodes) for telemedical diagnostic and therapeutic screening. The analog front-end circuit has been designed at the transistor level in TSMC 180 nm standard CMOS technology, and its main characteristics and properties have been studied both theoretically and numerically. Moreover, a simplified version of the proposed analog frontend circuit, implemented by using commercial off-the-shelf discrete components, is also presented to validate the solution and to demonstrate its performances and capabilities experimentally, especially in terms of sensitivity and resolution, as well as its real-time response to light intensity variations by using a laser operating in both steady-state and pulsed conditions
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