Numerical and experimental investigation of wave propagation in rod-systems with cracks

In this study, the possibility of continuously monitoring load-carrying cables in bridges is considered. A sending/receiving transducer is used to generate an ultrasonic, longitudinal, elastic wave through the cable. The interaction between the L(0, 1)-wave and vertical cracks in a single rod is investigated using the Waveguide-FE-Method to predict the reflection and transmission coefficients. Moreover, this work analyzes how the elastic energy of a propagating wave is distributed between adjacent rods via friction. An energy-based model is developed to approximate the coupling behavior in a two-rod system. Finally, the numerical predictions are verified by experimental data.     

The toughness of epoxy polymers and fibre composites modified with rubber microparticles and silica nanoparticles

The present paper investigates the effect of adding silica nanoparticles to an anhydride-cured epoxy polymer in bulk and when used as the matrix of carbon- and glass-fibre reinforced composites. The formation of ‘hybrid’ epoxy polymers, containing both silica nanoparticles and carboxyl-terminated butadiene-acrylonitrile (CTBN) rubber microparticles, is also discussed. The structure/property relationships are considered, with an emphasis on the toughness and the toughening mechanisms. The fracture energy of the bulk epoxy polymer was increased from 77 to 212 J/m² by the presence of 20 wt% of silica nanoparticles. The observed toughening mechanisms that were operative were (a) plastic shear-yield bands, and (b) debonding of the matrix from the silica nanoparticles, followed by plastic void-growth of the epoxy. The largest increases in toughness observed were for the ‘hybrid’ materials. Here a maximum fracture energy of 965 J/m² was measured for a ‘hybrid’ epoxy polymer containing 9 wt% and 15 wt% of the rubber microparticles and silica nanoparticles, respectively. Most noteworthy was the observation that these increases in the toughness of the bulk polymers were found to be transferred to the fibre composites. Indeed, the interlaminar fracture energies for the fibre-composite materials were increased even further by a fibre-bridging toughening mechanism. The present work also extends an existing model to predict the toughening effect of the nanoparticles in a thermoset polymer. There was excellent agreement between the predictions and the experimental data for the epoxy containing the silica nanoparticles, and for epoxy polymers containing micrometre-sized glass particles. The latter, relatively large, glass particles were investigated to establish whether a ‘nano-effect’, with respect to increasing the toughness of the epoxy bulk polymers, did indeed exist.     

Scalable flame synthesis of SiO2 nanowires: dynamics of growth

Silica nanowire arrays were grown directly onto plain glass substrates by scalable flame spray pyrolysis of organometallic solutions (hexamethyldisiloxane or tetraethyl orthosilicate). The silicon dioxide films consisted of a network of interwoven nanowires from a few to several hundred nanometres long (depending on the process conditions) and about 20 nm in diameter, as determined by scanning electron microscopy. These films were formed rapidly (within 10-20 s) at high growth rates (ca 11-30 nm s(-1)) by chemical vapour deposition (surface growth) at ambient conditions on the glass substrate as determined by thermophoretic sampling of the flame aerosol and microscopy. In contrast, on high purity quartz nearly no nanowires were grown while on steel substrates porous SiO(2) films were formed. Functionalization with perfluorooctyl triethoxysilane converted the nanowire surface from super-hydrophilic to hydrophobic. Additionally, their hermetic coating by thin carbon layers was demonstrated also revealing their potential as substrates for synthesis of other functional 1D composite structures. This approach is a significant step towards large scale synthesis of SiO(2) nanowires facilitating their utilization in several applications.     

The Amsterdam suspension. Balanced suspension after hip surgery

The Amsterdam Suspension is an easily applied, mechanically efficient and inexpensive apparatus for use in postoperative treatment of patients with either hip fractures or arthroplasties. Amsterdam suspension allows lower extremity exercises to be started in the immediate post surgical period by markedly reducing the gravitation load on the extremity.     

Targets and ion sources at the TISOL facility

The TISOL thick target, on-line isotope separator is now operational at the TRIUMF facility with an active experimental program. A series of newly developed, target materials coupled with two different ion sources can now produce a wide range of isotopes. Radioactive beams of isotopes of He, C, N, O, Ne, Cl, Ar, Kr and Xe are now available in significant amounts from the first ECR (electron cyclotron resonance) ion source directly coupled to a multipurpose ISOL device. In addition, a surface ionization source with good yields for radioactive isotopes of Li, Na, Al, Ga, Rb, In, Cs, Yb and Fr is also available. Special emphasis has been given to the development of target materials, in particular light mass powder or pellet targets such as SiC and MgO. In addition, a newly developed zeolite (NaSiAlO₄) target shows properties which make it an optimal choice for producing isotopes near stability for nuclear astrophysics experiments with accelerated radioactive beams. Source and target developments at the upgraded TISOL facility will be presented.     

The ABC-Pyramid Atmospheric Research Observatory in Himalaya for aerosol, ozone and halocarbon measurements

In this work we present the new ABC-Pyramid Atmospheric Research Observatory (Nepal, 27.95 N, 86.82 E) located in the Himalayas, specifically in the Khumbu valley at 5079 m a.s.l. This measurement station has been set-up with the aim of investigating natural and human-induced environmental changes at different scales (local, regional and global). After an accurate instrumental set-up at ISAC-CNR in Bologna (Italy) in autumn 2005, the ABC-Pyramid Observatory for aerosol (physical, chemical and optical properties) and trace gas measurements (ozone and climate altering halocarbons) was installed in the high Khumbu valley in February 2006. Since March 2006, continuous measurements of aerosol particles (optical and physical properties), ozone (O3) and meteorological parameters as well as weekly samplings of particulate matter (for chemical analyses) and grab air samples for the determination of 27 halocarbons, have been carried out. These measurements provide data on the typical atmospheric composition of the Himalayan area between India and China and make investigations of the principal differences and similarities between the monsoon and pre-monsoon seasons possible. The study is carried out within the framework of the Ev-K2-CNR "SHARE-Asia" (Stations at High Altitude for Research on the Environment in Asia) and UNEP-"ABC" (Atmospheric Brown Clouds) projects. With the name of "Nepal Climate Observatory-Pyramid" the station is now part of the Observatory program of the ABC project.     

CADP 2011: a toolbox for the construction and analysis of distributed processes

CADP (Construction and Analysis of Distributed Processes) is a comprehensive software toolbox that implements the results of concurrency theory. Started in the mid-1980s, CADP has been continuously developed by adding new tools and enhancing existing ones. Today, CADP benefits from a worldwide user community, both in academia and industry. This paper presents the latest release, CADP 2011, which is the result of a considerable development effort spanning the last five years. The paper first describes the theoretical principles and the modular architecture of CADP, which has inspired several other recent model checkers. The paper then reviews the main features of CADP 2011, including compilers for various formal specification languages, equivalence checkers, model checkers, compositional verification tools, performance evaluation tools, and parallel verification tools running on clusters and grids. Finally, the paper surveys some significant case studies.     

Demountable 3He melting curve thermometer

We describe a demountable (3)He melting curve thermometer, suitable for use at low temperatures with liquid helium samples at any pressure. The thermometer's resolution is 10 microK below 0.l K. It is designed to be particularly useful for experiments performed in magnetic fields.