Search results for " surface"
showing 10 items of 2838 documents
Scenery Flow, Conical Densities, and Rectifiability
2015
We present an application of the recently developed ergodic theoretic machinery on scenery flows to a classical geometric measure theoretic problem in Euclidean spaces. We also review the enhancements to the theory required in our work. Our main result is a sharp version of the conical density theorem, which we reduce to a question on rectifiability.
The shakedown load boundary of an elastic-perfectly plastic structure
1995
In the hypothesis of small displacements and combined time-variable/steady loads, the geometrical-mechanical properties of the shakedown load boundary are investigated. It is shown that, in the load space, the shakedown load boundary plays the role of yield surface, and that a certain plastic strain accumulation vector—characterizing some impending inadaptation collapse mechanism—obeys the normality rule, whereas a specific form of the maximum plastic work theorem constitutes an effective tool for the evaluation of the shakedown limit load corresponding to a specified inadaptation collapse mode. The equations governing the state of the structure at the shakedown limit are provided and the r…
Determination of water intrusion heat in hydrophobic microporous materials by high pressure calorimetry
2010
International audience; The understanding of interactions between a solid surface and a non-wetting liquid still remains of fundamental interest in numerous research fields, from chemistry to biology. This work focuses on the mechanisms of water intrusion in hydrophobic microporous materials through the thermal analysis of the phenomenon. A specific calorimetric technique coupled to high pressure equipment has been developed to investigate equilibrium thermal effects in such thermodynamic systems from 0 to 400 MPa under isothermal conditions. First validation tests of this method were carried out by compressing degassed water in a constant volume V with successive small pressure increments …
Phenylene motion in polycarbonate and polycarbonate/additive mixtures
1987
Pulsed deuteron NMR line shapes have been analysed to characterize type and time scale of the phenylene group motion in glassy bisphenol-A polycarbonate. The motional mechanism involvesπ-flips about theC1C4 axis augmented by small angle fulctuations about the same axis, reaching a rms amplitude of ±35‡ at 380 K. The distribution of correlation times for theπ-flips is heterogeneous in nature and can be described either by a log-Gaussian or an asymmetric distribution with a more rapid decay at high correlation times comparable to the Williams-Watts distribution. From both distributions essentailly the same mean activation energy of 37 kJ/mol is obtained, whereas the temperature dependent widt…
Dip Phenomenon in High-Curved Turbulent Flows and Application of Entropy Theory
2018
The estimation of velocity profile in turbulent open channels is a difficult task due to the significant effects of the secondary flow. The present paper investigates the mechanism of the velocity-dip phenomenon, whereby the location of the maximum velocity appears to be below the free surface. Previous studies conducted in straight channels relate the mechanism of the velocity-dip phenomenon to secondary flow induced by anisotropy of turbulence. This work focuses on high-curved channels where the secondary motion, which is also induced by the channel’s curvature, evolves along the bend. The width-to-depth ratio, B/h, is one of the most important parameters that are affecting the secondary …
Layer-Wise Discontinuous Galerkin Methods for Piezoelectric Laminates
2020
In this work, a novel high-order formulation for multilayered piezoelectric plates based on the combination of variable-order interior penalty discontinuous Galerkin methods and general layer-wise plate theories is presented, implemented and tested. The key feature of the formulation is the possibility to tune the order of the basis functions in both the in-plane approximation and the through-the-thickness expansion of the primary variables, namely displacements and electric potential. The results obtained from the application to the considered test cases show accuracy and robustness, thus confirming the developed technique as a supplementary computational tool for the analysis and design o…
COVID-19 Pandemic: Prevention and protection measures to be adopted at the workplace
2020
Introduction: SARS-CoV-2, identified in Wuhan, China, for the first time in December 2019, is a new viral strain, which has not been previously identified in humans; it can be transmitted both by air and via direct and indirect contact; however, the most frequent way it spreads is via droplets. Like the other viruses belonging to the same family of coronaviruses, it can cause from mild flu-like symptoms, such as cold, sore throat, cough and fever, to more severe ones such as pneumonia and breathing difficulties, and it can even lead to death. Since no effective specific drug therapy has been found yet, nor any vaccine capable of limiting the spread of this pathogen, it is important for way…
Security Implications of Using Third-Party Resources in the World Wide Web
2018
Modern web pages have nothing in common with the static connotation coming from the word “page” - it is a dynamic unique experience created by active content and executed within browser, just-in-time assembled from various resources hosted on many different domains. Active content increases attack surface naturally exposing users to many novel threats. A popular security advice has been to deploy active content blocker plugins like NoScript, unfortunately they are not capable to effectively stop the attacks. Content Security Policy (CSP) can be effective against these attacks, but we demonstrate how poor decisions made by website administrators or external resource hosters can render CSP in…
Electronic and magnetic properties of Mn 12 molecular magnets on sulfonate and carboxylic acid prefunctionalized gold surfaces
2012
Structural, electronic, and magnetic properties of [Mn 12O 12(bet) 16(EtOH) 4](PF 6) 14·4CH 3CN·H 2O (in short Mn 12bet, bet = betaine = +N(CH 3) 3-CH 2-COO -) single-molecule magnets (SMMs) deposited on previously functionalized gold surfaces have been investigated. Self-assembled monolayers (SAMs) either of sodium mercaptoethanesulfonate (MES) or mercaptopropionic acid (MPA) are used as functionalization to avoid the direct interaction between the Mn 12bet molecules and the Au surface with the aim of preserving the main functional properties of the molecules. Scanning tunneling microscopy (STM) and X-ray photoemission spectroscopy (XPS) analysis show deposited Mn 12bet SMMs well-isolated …
Thin plastic foil X-ray optics with spiral geometry
2007
Winding a plastic foil ribbon into spiral cylinder or spiral cones we can design and build single or multiple reflection X-ray grazing incidence focusing optics with potential applications in Astronomy as well as experimental physics. The use of thin plastic foils from common industrial applications and of a mounting technique which does not require the construction of mandrels make these optics very cost effective. A spiral geometry focusing optic produces an annular image of a point source with the angular size of the annulus depending mainly on the pitch of the winding and the focal length. We use a ray-tracing code to evaluate the performances of cylindrical, and double conical spiral g…