Influence of thermally induced chemorheological changes on the torsion of elastomeric circular cylinders

When an elastomeric material is deformed and subjected to temperatures above some characteristic value T cr (near 100 ∘ C for natural rubber), its macromolecular structure undergoes time and temperature-dependent chemical changes. The process continues until the temperature decreases below T cr . Compared to the virgin material, the new material system has modified properties (reduced stiffness) and permanent set on removal of the applied load.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/46097/1/161_2006_Article_9.pd

The Great Markarian 421 Flare of 2010 February: Multiwavelength Variability and Correlation Studies

We report on variability and correlation studies using multiwavelength observations of the blazar Mrk 421 during the month of 2010 February, when an extraordinary flare reaching a level of ∼27 Crab Units above 1 TeV was measured in very high energy (VHE) γ-rays with the Very Energetic Radiation Imaging Telescope Array System (VERITAS) observatory. This is the highest flux state for Mrk 421 ever observed in VHE γ-rays. Data are analyzed from a coordinated campaign across multiple instruments, including VHE γ-ray (VERITAS, Major Atmospheric Gamma-ray Imaging Cherenkov), high-energy γ-ray (Fermi-LAT), X-ray (Swift, Rossi X-ray Timing Experiment, MAXI), optical (including the GASP-WEBT collaboration and polarization data), and radio (Metsahovi, Owens Valley Radio Observatory, University of Michigan Radio Astronomy Observatory). Light curves are produced spanning multiple days before and after the peak of the VHE flare, including over several flare "decline" epochs. The main flare statistics allow 2 minute time bins to be constructed in both the VHE and optical bands enabling a cross-correlation analysis that shows evidence for an optical lag of ∼25-55 minutes, the first time-lagged correlation between these bands reported on such short timescales. Limits on the Doppler factor (δ ⪆ 33) and the size of the emission region (δ-1RB≲ 3.8 × 1013cm) are obtained from the fast variability observed by VERITAS during the main flare. Analysis of 10 minute binned VHE and X-ray data over the decline epochs shows an extraordinary range of behavior in the flux-flux relationship, from linear to quadratic to lack of correlation to anticorrelation. Taken together, these detailed observations of an unprecedented flare seen in Mrk 421 are difficult to explain with the classic single-zone synchrotron self-Compton model.</p

An Improved Torsional Method for Determining the Fracture Toughness of Stiff Materials and of Adhesive Joints

11Nsciescopu

Adhesion between Polystyrene and Polymethyl methacrylate

Measurements have been made of the energy required to break through unit area of polystyrene (PS), polymethylmethacrylate (PMMA), and joints prepared by molding the two polymers in contact. The results were: 1.23 ± 0.5 kJ/m2 (PS), 0.46 ± 0.10 kJ/m2 (PMMA), and 0.22 ± 0.04 kJ/m2 for the bonded joint. Thus, the interface was significantly weaker than either adherend, but surprisingly strong for two incompatible materials. Microscopy and selective dyeing revealed that fracture took place at the interface itself, with no appreciable transfer of material from one side to the other. It is concluded that Van der Waals interactions are sufficient to create relatively strong bonds.117Nsciescopu

Thermomechanical Analysis of the Yield Behaviour of a Semicristalline Polymer

This paper first presents the characteristics of a new experimental set-up using digital image correlation and infrared thermography. The kinematical data are used to track the temperature variations of material surface elements. They are then combined to construct local energy balance. To illustrate the interest of such an approach, the paper then describes the calorimetric effects accompanying the propagation of necking in a plasticized PolyAmide 11. A thermodynamic analysis of cyclic loading finally aims to show the existence of an entropic elastic effect generally associated with rubber-like materials

Architettura e Città. Saggi. Con un'antologia di scritti di FAmagazine 2010-2012

Ad ormai sei anni dalla nascita di FAmagazine, Ricerche e progetti sull’architettura e la città, il libro vuole essere un primo bilancio di questa esperienza editoriale, nata in seno al Festival dell’Architettura e progressivamente emancipatasi fino a diventare un luogo autonomo di produzione scientifica. Di questi sei anni è stata selezionata una piccola antologia ragionata di 37 articoli pubblicati tra il 2010 e il 2012 sui primi 20 numeri del magazine, che sembrano stringersi maggiormente intorno al tema del rapporto tra architettura e città. L’Antologia ragionata è preceduta da una serie di saggi degli autori del libro, che devono essere letti da un duplice punto di vista. Da un lato, essi sono semplicemente scritti particolarmente attinenti al tema “architettura e città”, comparsi a diverso titolo, spesse volte come editoriali, sui numeri di FAmagazine fino ad oggi; dall’altro, essi testimoniano la vocazione degli scritti di FAmagazine ad essere assunti come pretesti, ex ante o ex post, per approfondimenti, dibattiti nazionali e internazionali, seminari, call for papers, fino a divenire, in ultima analisi, occasione e strumento di ricerca