4,523 research outputs found
Application of spindle speed increaser as sustainable solution to upgrade machine tools
Due to varying machine operations, cutting material and feed motion of the respective milling machine, a wide range of spindle speed is required. Modern machine tools are therefore occasionally equipped with two spindles to cover a wider application scope. Especially while increasing the cutting removal rates for soft materials like aluminium alloys, outdated machine tools fail to provide high spindle speed. Spindle speed increasers (SSI) are possible solutions in order to flexibly increase the cutting removal rates of milling machines. In this paper, the state of the art of SSI is investigated regarding its application in different milling machines and with respect to resource and energy efficiency. Therefore, based on the respective machining operations, spindle input and milling machine, a selection methodology is provided to prove the feasibility of the application of existing SSI. This allows estimating the sustainable benefit on theoretical basis.DFG, 199828953, SFB 1026: Sustainable Manufacturing - Globale Wertschöpfung nachhaltig gestalte
Evaluation of a portable retinal imaging device: towards a comparative quantitative analysis for morphological measurements of retinal blood vessels
This study investigated the possibility of using low-cost, handheld, retinal imaging devices for the automatic extraction of quantifiable measures of retinal blood vessels. Initially, the available handheld devices were compared using a Zeiss model eye incorporating a USAF resolution test chart to assess their optical properties. The only suitable camera of the five evaluated was the Horus DEC 200. This device was then subjected to a detailed evaluation in which images in human eyes taken from the handheld camera were compared in a quantitative analysis with those of the same eye from a Canon CR-DGi retinal desktop camera. We found that the Horus DEC 200 exhibited shortcomings in capturing images of human eyes by comparison with the Canon. More images were rejected as being unevaluable or suffering failures in automatic segmentation than with the Canon, and even after exclusion of affected images, the Horus yielded lower measurements of vessel density than the Canon. A number of issues affecting handheld cameras in general and some features of the Horus in particular have been identified that might contribute to the observed differences in performance. Some potential mitigations are discussed which might yield improvements in performance, thus potentially facilitating use of handheld retinal imaging devices for quantitative retinal microvascular measurements
The case for new academic workspace
Executive summary: This report draws upon the combined efforts of
a number of estates professionals, architects,
academics, designers, and senior managers
involved in the planning of new university buildings
for the 21st century. Across these perspectives,
all would agree – although perhaps for different
reasons - that this planning is difficult and that a
number of particular considerations apply in the
design of academic workspaces. Despite these
difficulties, they will also agree that when this
planning goes well, ‘good’ buildings are truly
transformational – for both the university as a
whole and the people who work and study in them.
The value of well-designed buildings goes far
beyond their material costs, and endures long after
those costs have been forgotten ..
Mexico-UK Sub-millimeter Camera for AsTronomy
MUSCAT is a large format mm-wave camera scheduled for installation on the
Large Millimeter Telescope Alfonso Serrano (LMT) in 2018. The MUSCAT focal
plane is based on an array of horn coupled lumped-element kinetic inductance
detectors optimised for coupling to the 1.1mm atmospheric window. The detectors
are fed with fully baffled reflective optics to minimize stray-light
contamination. This combination will enable background-limited performance at
1.1 mm across the full 4 arcminute field-of-view of the LMT. The easily
accessible focal plane will be cooled to 100 mK with a new closed cycle
miniature dilution refrigerator that permits fully continuous operation. The
MUSCAT instrument will demonstrate the science capabilities of the LMT through
two relatively short science programmes to provide high resolution follow-up
surveys of Galactic and extra-galactic sources previously observed with the
Herschel space observatory, after the initial observing campaigns. In this
paper, we will provide an overview of the overall instrument design as well as
an update on progress and scheduled installation on the LMT.Comment: Accepted for publication in the Journal of Low Temperature Detector
Fluid structure interaction of patient specific abdominal aortic aneurysms: a comparison with solid stress models
BACKGROUND: Abdominal aortic aneurysm (AAA) is a dilatation of the aortic wall, which can rupture, if left untreated. Previous work has shown that, maximum diameter is not a reliable determinant of AAA rupture. However, it is currently the most widely accepted indicator. Wall stress may be a better indicator and promising patient specific results from structural models using static pressure, have been published. Since flow and pressure inside AAA are non-uniform, the dynamic interaction between the pulsatile flow and wall may influence the predicted wall stress. The purpose of the present study was to compare static and dynamic wall stress analysis of patient specific AAAs. METHOD: Patient-specific AAA models were created from CT scans of three patients. Two simulations were performed on each lumen model, fluid structure interaction (FSI) model and static structural (SS) model. The AAA wall was created by dilating the lumen with a uniform 1.5 mm thickness, and was modeled as a non-linear hyperelastic material. Commercial finite element code Adina 8.2 was used for all simulations. The results were compared between the FSI and SS simulations. RESULTS: Results are presented for the wall stress patterns, wall shear stress patterns, pressure, and velocity fields within the lumen. It is demonstrated that including fluid flow can change local wall stresses slightly. However, as far as the peak wall stress is concerned, this effect is negligible as the difference between SS and FSI models is less than 1%. CONCLUSION: The results suggest that fully coupled FSI simulation, which requires considerable computational power to run, adds little to rupture risk prediction. This justifies the use of SS models in previous studies
The Origin of Neutral Hydrogen Clouds in Nearby Galaxy Groups: Exploring the Range Of Galaxy Interactions
We combine high resolution N-body simulations with deep observations of
neutral hydrogen (HI) in nearby galaxy groups in order to explore two
well-known theories of HI cloud formation: HI stripping by galaxy interactions
and dark matter minihalos with embedded HI gas. This paper presents new data
from three galaxy groups, Canes Venatici I, NGC 672, and NGC 45, and assembles
data from our previous galaxy group campaign to generate a rich HI cloud
archive to compare to our simulated data.
We find no HI clouds in the Canes Venatici I, NGC 672, or NGC 45 galaxy
groups. We conclude that HI clouds in our detection space are most likely to be
generated through recent, strong galaxy interactions. We find no evidence of HI
clouds associated with dark matter halos above M_HI = 10^6 M_Sun, within +/-
700 km/s of galaxies, and within 50 kpc projected distance of galaxies.Comment: 35 pages, 10 figures, AJ accepte
Identification of an ADAMTS2 frameshift variant in a cat family with Ehlers-Danlos syndrome.
We investigated four European domestic shorthair kittens with skin lesions consistent with the dermatosparaxis type of the Ehlers-Danlos syndrome (EDS), a connective tissue disorder. The kittens were sired by the same tomcat, but were born by three different mothers. The kittens had easily torn skin resulting in non-healing skin wounds. Both clinically and histologically, the skin showed thin epidermis in addition to inflammatory changes. Changes in collagen fibers were visible in electron micrographs. The complete genome of an affected kitten was sequenced. A one base pair duplication leading to a frameshift in the candidate gene ADAMTS2 was identified, p.(Ser235fs*3). All four affected cats carried the frameshift duplication in a homozygous state. Genotypes at this variant showed perfect co-segregation with the autosomal recessive EDS phenotype in the available family. The mutant allele did not occur in 48 unrelated control cats. ADAMTS2 loss-of-function variants cause autosomal recessive forms of EDS in humans, mice, dogs, cattle and sheep. The available evidence from our investigation together with the functional knowledge on ADAMTS2 in other species allow to classify the identified ADAMTS2 variant as pathogenic and most likely causative variant for the observed EDS
Do High-Velocity Clouds trace the Dark Matter subhalo population?
Within the cosmological concordance model, Cold Dark Matter (CDM) subhalos
form the building blocks which merge hierarchically to more massive galaxies.
Since intergalactic gas is accreted by massive galaxies, observable e.g. as
high- velocity clouds (HVCs) around the Milky Way, with extremely low
metallicities, these can be suggested to represent the baryonic content of
primordial Dark Matter (DM) subhalos. Another possibility of their origin is
that they stem from disrupted satellite galaxies, but in this case, these gas
clouds move unaccompanied by a bound DM structure. Since HVCs are observed with
long gas tails and with irregular substructures, numerical models are performed
aiming at exploring their structure and compare them with observations. If HVCs
are engulfed by DM subhalos, their gas must leave the DM gravitational
potential and reflect this in their dynamics. On the other hand, the evolution
and survival of pure gas models must be tested to distinguish between
DM-dominated and DM-free clouds and to allow conclusions on their origin. The
models demonstrate that purely baryonic HVCs with low masses are disrupted by
ram-pressure stripping and Kelvin-Helmholtz instabilities, while more massive
ones survive, losing their initially spherical shape and develop significant
substructures including cometary elongations in the column density distribution
("head-tail structure"). On the contrary, HVCs with DM subhalos survive with
more than 90% of their gas mass still bound and spherically shaped, approaching
the Galactic disk like bullets. In addition, we find that velocity gradients
along the cometary head-tail structures does not necessarily offer a
possibility to distinguish between DM-dominated and purely gaseous HVCs.
Comparison of models with observations let us conclude that HVCs are not
embedded in a DM substructure and do not trace the cosmological subhalo
population.Comment: Accepted for publication in A&
A peculiar HI cloud near the distant globular cluster Pal 4
We present 21-cm observations of four Galactic globular clusters, as part of
the on-going GALFA-HI Survey at Arecibo. We discovered a peculiar HI cloud in
the vicinity of the distant (109 kpc) cluster Pal 4, and discuss its properties
and likelihood of association with the cluster. We conclude that an association
of the HI cloud and Pal 4 is possible, but that a chance coincidence between
Pal 4 and a nearby compact high-velocity cloud cannot be ruled out altogether.
New, more stringent upper limits were derived for the other three clusters: M
3, NGC 5466, and Pal 13. We briefly discuss the fate of globular cluster gas
and the interaction of compact clouds with the Galactic Halo gas.Comment: Accepted for publication in MNRA
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