79 research outputs found
New developments in high performance cylinder heads: application of LHIP and SPLIT cylinder head concept
Since specific power output of new engines is increasing, many engine components are facing new challenges. Among these, cylinder heads have to withstand tougher operating conditions in terms of temperatures and loads, which are approaching the limits of present aluminum alloys and of the manufacturing processes currently applied. The paper discusses two approaches to possibly extend the application of Aluminum alloy heads beyond their present limits: the first is the application of the Liquid Hot Isostatic Pressing (LHIP®) process aimed to improve the quality of the castings; the second is a novel design concept, split cylinder head, based on the application of different materials in different parts of the head, in order to achieve locally the required material properties
Trmun (north-eastern Italy): Multi-scale remote and ground-based sensing of a Bronze Age and post-Roman fortification
We have used multi-scale remote sensing to investigate a little known archaeological site in northern Istria (north-eastern Italy). Airborne Laser Scanning (ALS) and archaeological field surveys have allowed us to identify the position and extension of a large Protohistoric hillfort. Its highest and best-preserved sector, corresponding to a modest elevation at the eastern margin of the settlement, has been further investigated through thermal imaging, high-resolution ALS, drone Structure from Motion (SfM) photogrammetry and 3D Ground Penetrating Radar (GPR), leading to a detailed identification of unexpected buried features. An excavation campaign conducted in 2022 has confirmed the remote and ground-based sensing results. This excavation has led to the discovery of a Bronze Age fortification, partially reused and modified with the construction of 2 or 3 square towers during the post-Roman period. Our results demonstrate that the combined analysis of multi-scale remote and ground-based sensing is crucial to planning archaeological exploration in the field. Digital methods provide high-resolution topography and detect buried features that assist in monitoring and managing cultural heritage
Problems With the Vortex-Boson Mapping in 1+1 Dimensions
Using the well known boson mapping, we relate the transverse magnetic
susceptibility of a system of flux vortices in 1+1 dimensions to an
appropriately defined conductivity of a one-dimensional boson system. The tilt
response for a system free of disorder is calculated directly, and it is found
that a subtle order of limits is required to avoid deceptive results.Comment: 4 Pages (REVTeX 3.0). Postscript file for this paper is available on
the World Wide Web at http://cmtw.harvard.edu/~simon/
Vortex-line liquid phases: Longitudinal superconductivity in the lattice London model
We study the vortex-line lattice and liquid phases of a clean type-II
superconductor by means of Monte Carlo simulations of the lattice London model.
Motivated by a recent controversy regarding the presence, within this model, of
a vortex-liquid regime with longitudinal superconducting coherence over long
length scales, we directly compare two different ways to calculate the
longitudinal coherence. For an isotropic superconductor, we interpret our
results in terms of a temperature regime within the liquid phase in which
longitudinal superconducting coherence extends over length scales larger than
the system thickness studied. We note that this regime disappears in the
moderately anisotropic case due to a proliferation, close to the flux-line
lattice melting temperature, of vortex loops between the layers.Comment: 8 pages, Revtex, with eps figures. To appear in Phys. Rev.
Do columnar defects produce bulk pinning?
From magneto-optical imaging performed on heavy-ion irradiated YBaCuO single
crystals, it is found that at fields and temperatures where strong single
vortex pinning by individual irradiation-induced amorphous columnar defects is
to be expected, vortex motion is limited by the nucleation of vortex kinks at
the specimen surface rather than by half-loop nucleation in the bulk. In the
material bulk, vortex motion occurs through (easy) kink sliding. Depinning in
the bulk determines the screening current only at fields comparable to or
larger than the matching field, at which the majority of moving vortices is not
trapped by an ion track.Comment: 5 pages, 5 figures, submitted to Physical Review Letter
Evolutionary Changes in the Complexity of the Tectum of Nontetrapods: A Cladistic Approach
Background: The tectum is a structure localized in the roof of the midbrain in vertebrates, and is taken to be highly conserved in evolution. The present article assessed three hypotheses concerning the evolution of lamination and citoarchitecture of the tectum of nontetrapod animals: 1) There is a significant degree of phylogenetic inertia in both traits studied (number of cellular layers and number of cell classes in tectum); 2) Both traits are positively correlated accross evolution after correction for phylogeny; and 3) Different developmental pathways should generate different patterns of lamination and cytoarchitecture. Methodology/Principal Findings: The hypotheses were tested using analytical-computational tools for phylogenetic hypothesis testing. Both traits presented a considerably large phylogenetic signal and were positively associated. However, no difference was found between two clades classified as per the general developmental pathways of their brains. Conclusions/Significance: The evidence amassed points to more variation in the tectum than would be expected by phylogeny in three species from the taxa analysed; this variation is not better explained by differences in the main course of development, as would be predicted by the developmental clade hypothesis. Those findings shed new light on th
Measurement properties of the Minimal Insomnia Symptom Scale (MISS) in an elderly population in Sweden
<p>Abstract</p> <p>Background</p> <p>Insomnia is common among elderly people and associated with poor health. The Minimal Insomnia Symptom Scale (MISS) is a three item screening instrument that has been found to be psychometrically sound and capable of identifying insomnia in the general population (20-64 years). However, its measurement properties have not been studied in an elderly population. Our aim was to test the measurement properties of the MISS among people aged 65 + in Sweden, by replicating the original study in an elderly sample.</p> <p>Methods</p> <p>Data from a cross-sectional survey of 548 elderly individuals were analysed in terms of assumptions of summation of items, floor/ceiling effects, reliability and optimal cut-off score by means of ROC-curve analysis and compared with self-reported insomnia criteria.</p> <p>Results</p> <p>Corrected item-total correlations ranged between 0.64-0.70, floor/ceiling effects were 6.6/0.6% and reliability was 0.81. ROC analysis identified the optimal cut-off score as ≥7 (sensitivity, 0.93; specificity, 0.84; positive/negative predictive values, 0.256/0.995). Using this cut-off score, the prevalence of insomnia in the study sample was 21.7% and most frequent among women and the oldest old.</p> <p>Conclusions</p> <p>Data support the measurement properties of the MISS as a possible insomnia screening instrument for elderly persons. This study make evident that the MISS is useful for identifying elderly people with insomnia-like sleep problems. Further studies are needed to assess its usefulness in identifying clinically defined insomnia.</p
The Flux-Line Lattice in Superconductors
Magnetic flux can penetrate a type-II superconductor in form of Abrikosov
vortices. These tend to arrange in a triangular flux-line lattice (FLL) which
is more or less perturbed by material inhomogeneities that pin the flux lines,
and in high- supercon- ductors (HTSC's) also by thermal fluctuations. Many
properties of the FLL are well described by the phenomenological
Ginzburg-Landau theory or by the electromagnetic London theory, which treats
the vortex core as a singularity. In Nb alloys and HTSC's the FLL is very soft
mainly because of the large magnetic penetration depth: The shear modulus of
the FLL is thus small and the tilt modulus is dispersive and becomes very small
for short distortion wavelength. This softness of the FLL is enhanced further
by the pronounced anisotropy and layered structure of HTSC's, which strongly
increases the penetration depth for currents along the c-axis of these uniaxial
crystals and may even cause a decoupling of two-dimensional vortex lattices in
the Cu-O layers. Thermal fluctuations and softening may melt the FLL and cause
thermally activated depinning of the flux lines or of the 2D pancake vortices
in the layers. Various phase transitions are predicted for the FLL in layered
HTSC's. The linear and nonlinear magnetic response of HTSC's gives rise to
interesting effects which strongly depend on the geometry of the experiment.Comment: Review paper for Rep.Prog.Phys., 124 narrow pages. The 30 figures do
not exist as postscript file
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