3,552 research outputs found
Experimental investigation of the elastoplastic response of aluminum silicate spray dried powder during cold compaction
Mechanical experiments have been designed and performed to investigate the
elasto-plastic behaviour of green bodies formed from an aluminum silicate spray
dried powder used for tiles production. Experiments have been executed on
samples obtained from cold compaction into a cylindrical mould and include:
uniaxial strain, equi-biaxial flexure and high-pressure triaxial
compression/extension tests. Two types of powders have been used to realize the
green body samples, differing in the values of water content, which have been
taken equal to those usually employed in the industrial forming of traditional
ceramics. Yielding of the green body during compaction has been characterized
in terms of yield surface shape, failure envelope, and evolution of cohesion
and void ratio with the forming pressure, confirming the validity of previously
proposed constitutive models for dense materials obtained through cold
compaction of granulates.Comment: 17 pages; Journal of the European Ceramic Society, 201
A study of German printing inks from the early 20th century
Various coulorful printing inks were developed and widely distributed during the 19th and 20h centuries. However, in comparison to artists' paints from that period, printing inks are not studied in depth. This paper provides a first insight into materials in common German printing inks used at the time to understand the artists' opportunities, predict properties such as light fastness and possible colour alterations. The study is based on literature research and the analysis of two printing ink sample books from the 1920s and 1930s. Complementary analytical techniques were employed to characterise the ink samples, namely Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, Gas Chromatography-Mass Spectrometry (GC-MS) and Scanning Electron Microscopy-energy dispersive X-ray spectroscopy (SEM-EDS). Twenty modern synthetic organic pigments (SOPs) and several traditional pigments as well as metallic pigments were identified in the catalogues. Linseed oil, semi-drying oils and resins (such as Copal and Dammar) were used as binding media. The results will aid decision-making in preservation and conservation of printed works
Nanographitic coating enables hydrophobicity in lightweight and strong microarchitected carbon
Metamaterials that are lightweight, stiff, strong, scalable and hydrophobic have been achieved separately through different materials and approaches, but achieving them in one material is an outstanding challenge. Here, stereolithography and pyrolysis are employed to create carbon microlattices with cubic topology and a strut width of 60–70 µm, with specific strength and stiffness of up to 468.62 MPa cm3 g−1 and 14.39 GPa cm3 g−1 at a density of 0.55 g cm−3, higher than existing microarchitected materials and approaching those of the strongest truss nanolattices. Subsequent fast Joule-heating then introduces a hierarchical nanographitic skin that enables hydrophobicity, with a water contact angle of 135 ± 2°, improving the hydrophilic response of pyrolytic carbon. As the Joule heating induced sp2-hybridization and nano-texturing predominantly affect the strut sheath, the effect on mechanical response is limited to a reduction in the distribution of compressive strength of as-pyrolyzed architectures by ~80% and the increase of the mean effective stiffness by ~15%. These findings demonstrate a technique to fabricate high strength, low density, and hydrophobic nanographite-coated carbon microlattices
Rotational sensitivity of the "G-Pisa" gyrolaser
G-Pisa is an experiment investigating the possibility to operate a high
sensitivity laser gyroscope with area less than for improving the
performances of the mirrors suspensions of the gravitational wave antenna
Virgo. The experimental set-up consists in a He-Ne ring laser with a 4 mirrors
square cavity. The laser is pumped by an RF discharge where the RF oscillator
includes the laser plasma in order to reach a better stability. The contrast of
the Sagnac fringes is typically above 50% and a stable regime has been reached
with the laser operating both single mode or multimode. The effect of hydrogen
contamination on the laser was also checked. A low-frequency sensitivity, below
, in the range of has been
measured.Comment: 6 pages, 6 figures, presented at the EFTF-IFCS joint conference 200
Tos persistente en la infancia
Presentamos el caso de una niña de 11 años con tos persistente de 2 años de evolución. El estudio broncoscópico, en el cual se halló un cuerpo extraño en la tráquea, resultó crÃtico para definir el diagnóstico y efectuar el tratamiento.We are reporting the case of an 11-years-old girl with persistentcough of two years' evolution. The bronchoscopic procedure,through which a tracheal foreign body was found, wasthe key for accurate diagnosis and treatment
La coltura della Reseda Biondella. Un primato nell'area di Mutina?
The Ex Cassa di Risparmio site is a reclaimed channel - first Imperial age - located in the center of the city of Modena and it is unique in Emilia Romagna for the archaeobotanical information provided on urban area. The study of seeds/fruits remains produced a framework which can be considered representative for reconstructing the vegetal environment of Mutina at the moment of maximum splendor of the Roman empire and of the city; some species appeared particularly worthy of insights, such as weld - Reseda luteola L., grass species that produces a very stable yellow pigment used since ancient times for dyeing fabrics like wool, linen and silk. The abundance of seeds found in the drained canal suggests agricultural practices implemented in peri-urban area of the city and presumably related to the economy of this prosperous Roman colony. Agriculture should have been a strong element of its economy in addition to ceramic production, sheep farming and the textile industry
Human Time-Frequency Acuity Beats the Fourier Uncertainty Principle
The time-frequency uncertainty principle states that the product of the
temporal and frequency extents of a signal cannot be smaller than .
We study human ability to simultaneously judge the frequency and the timing of
a sound. Our subjects often exceeded the uncertainty limit, sometimes by more
than tenfold, mostly through remarkable timing acuity. Our results establish a
lower bound for the nonlinearity and complexity of the algorithms employed by
our brains in parsing transient sounds, rule out simple "linear filter" models
of early auditory processing, and highlight timing acuity as a central feature
in auditory object processing.Comment: 4 pages, 2 figures; Accepted at PR
Vibrational properties of phonons in random binary alloys: An augmented space recursive technique in the k-representation
We present here an augmented space recursive technique in the
k-representation which include diagonal, off-diagonal and the environmental
disorder explicitly : an analytic, translationally invariant, multiple
scattering theory for phonons in random binary alloys.We propose the augmented
space recursion (ASR) as a computationally fast and accurate technique which
will incorporate configuration fluctuations over a large local environment. We
apply the formalism to , Ni_{88}Cr_12} and
alloys which is not a random choice. Numerical results on spectral functions,
coherent structure factors, dispersion curves and disordered induced FWHM's are
presented. Finally the results are compared with the recent itinerant coherent
potential approximation (ICPA) and also with experiments.Comment: 20 pages, LaTeX, 23 figure
A device to characterize optical fibres
ATLAS is a general purpose experiment approved for the LHC collider at CERN.
An important component of the detector is the central hadronic calorimeter; for
its construction more than 600,000 Wave Length Shifting (WLS) fibres
(corresponding to a total length of 1,120 Km) have been used.
We have built and put into operation a dedicated instrument for the
measurement of light yield and attenuation length over groups of 20 fibres at a
time.
The overall accuracy achieved in the measurement of light yield
(attenuation length) is 1.5% (3%).
We also report the results obtained using this method in the quality control
of a large sample of fibres.Comment: 17 pages 20 figeres submitted to NIM journa
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