184 research outputs found
Voltage and active power local PI control of distributed energy resources based on the effective transfer function method
Effect of recycled powder and gear profile into the functionality of additive manufacturing polymer gears
Purpose
Polymer laser powder bed fusion (PBF-LB/P) is an additive manufacturing technology that is sustainable due to the possibility of recycling the powder multiple times and allowing the fabrication of gears without the aid of support structures and subsequent assembly. However, there are constraints in the process that negatively affect its adoption compared to other additive technologies such as material extrusion to produce gears. This study aims to demonstrate that it is possible to overcome the problems due to the physics of the process to produce accurate mechanism.
Design/methodology/approach
Technological aspects such as orientation, wheel-shaft thicknesses and degree of powder recycling were examined. Furthermore, the evolving tooth profile was considered as a design parameter to provide a manufacturability map of gear-based mechanisms.
Findings
Results show that there are some differences in the functioning of the gear depending on the type of powder used, 100% virgin or 50% virgin and 50% recycled for five cycles. The application of a groove on a gear produced with 100% virgin powder allows the mechanism to be easily unlocked regardless of the orientation and wheel-shaft thicknesses. The application of a specific evolutionary profile independent of the diameter of the reference circle on vertically oriented gears guarantees rotation continuity while preserving the functionality of the assembled mechanism.
Originality/value
In the literature, there are various studies on material aging and reuse in the PBF-LB/P process, mainly focused on the powder deterioration mechanism, powder fluidity, microstructure and mechanical properties of the parts and process parameters. This study, instead, was focused on the functioning of gears, which represent one of the applications in which this technology can have great success, by analyzing the two main effects that can compromise it: recycled powder and vertical orientation during construction
Comparative Analysis of Eight Numerical Methods Using Weibull Distribution to Estimate Wind Power Density for Coastal Areas in Pakistan
Shapley Supercluster Survey: mapping the dark matter distribution
We present a 23deg weak gravitational lensing survey of the Shapley
supercluster core and its surroundings using VST images as part of the
Shapley Supercluster Survey (ShaSS). This study reveals the overall matter
distribution over a region containing 11 clusters at that are
all interconnected, as well as several ongoing cluster-cluster interactions.
Galaxy shapes have been measured by using the Kaiser-Squires-Broadhurst method
for the - and -band images and background galaxies were selected via the
colour-colour diagram. This technique has allowed us to detect all of the
clusters, either in the -band or -band images, although at different
levels, indicating that the underlying dark matter distribution is
tightly correlated with the number density of the member galaxies. The deeper
-band images have traced the five interacting clusters in the supercluster
core as a single coherent structure, confirmed the presence of a filament
extending North from the core, and have revealed a background cluster at
. We have measured the masses of the four richest clusters (A3556,
A3558, A3560 and A3562) in the two-dimensional shear pattern, assuming a
spherical Navarro-Frenk-White (NFW) profile and obtaining a total mass of
, which is consistent with dynamical and X-ray studies. Our
analysis provides further evidence of the ongoing dynamical evolution in the
ShaSS region.Comment: 16 pages, 11 figures, 4 tables. Accepted for publication in MNRA
A Mini-Review on Thalidomide: Chemistry, Mechanisms of Action, Therapeutic Potential and Anti-Angiogenic Properties in Multiple Myeloma
Thalidomide is a drug with interesting therapeutic properties but also with severe side effects which require a careful and monitored use. Potential immunomodulatory, anti-inflammatory, anti-angiogenic and sedative properties make thalidomide a good candidate for the treatment of several diseases such as multiple myeloma. Through an increase in the degradation of TNF alpha-mRNA, thalidomide reduces the production of TNF alpha by monocytes and macrophages stimulated by lipopolysaccharide or by T lymphocytes induced by mitogenic stimuli. The decreased level of TNF alpha alters the mechanisms of intracellular transduction by preventing the activation of NF-kB and by decreasing the synthesis of proteins, in particular IL-6, involved in cell proliferation, inflammation, angiogenesis and protection from apoptosis. Furthermore, thalidomide affects VEGF levels by down-regulating its expression. Nowadays, new safer and less toxic drugs, analogs of thalidomide, are emerging as beneficial for a more targeted treatment of multiple myeloma and several other diseases such as Crohn's disease, rheumatoid arthritis, sarcoidosis, erythema nodosum leprosum, graft-versus-host disease
Exploring the low-mass regime of galaxy-scale strong lensing: Insights into the mass structure of cluster galaxies
We aim at a direct measurement of the compactness of three galaxy-scale
lenses in massive clusters, testing the accuracy of the scaling laws that
describe the members in strong lensing (SL) models of galaxy clusters. We
selected the multiply imaged sources MACS J0416.12403 ID14 (), MACS
J0416.12403 ID16 (), and MACS J1206.20847 ID14 ().
Eight images were observed for the first SL system, and six for the latter two.
We focused on the main deflector of each galaxy-scale SL system (identified as
members 8971, 8785, and 3910, respectively), and modelled its total mass
distribution with a truncated isothermal sphere. We accounted for the lensing
effects of the remaining cluster components, and included the uncertainty on
the cluster-scale mass distribution through a bootstrapping procedure. We
measured a truncation radius value of ,
, and
for members 8971, 8785, and 3910, respectively. Alternative non-truncated
models with a higher number of free parameters do not lead to an improved
description of the SL system. We measured the stellar-to-total mass fraction
within the effective radius for the three members, finding ,
, and , respectively. We find that a parameterisation
of the properties of cluster galaxies in SL models based on power-law scaling
relations with respect to the total luminosity cannot accurately describe their
compactness over their full total mass range. Our results agree with modelling
of the cluster members based on the Fundamental Plane relation. Finally, we
report good agreement between our values of the stellar-to-total mass fraction
within and those of early-type galaxies from the SLACS Survey. Our work
significantly extends the regime of the current samples of lens galaxies.Comment: Astronomy & Astrophysics, 679, A124 (2023), 15 pages, 12 figures, 8
table
Time-weighted lactate as a predictor of adverse outcome in acute heart failure
The role of dynamic changes in lactate concentrations on prognosis in acute heart failure has been poorly investigated. The aim of this study was to explore the predictive value of 24Â h time-weighted lactate (LACTW ) in patients with acute heart failure
An Interacting Galaxy Pair at the Origin of a Light Echo
In a low-density region of the Shapley supercluster we identified an interacting galaxy pair at redshift z = 0.04865 in which the Seyfert 2 nucleus of the main galaxy (ShaSS 073) is exciting an extended emission line region (EELR, ∼170 kpc^2) in the disk of the less massive companion (ShaSS 622). New integral-field spectroscopy and the multiband data set, spanning from far-ultraviolet to far-infrared and radio wavelengths, allowed us to obtain a detailed description of the ShaSS 622-073 system. The gas kinematics shows hints of interaction, although the overall velocity field shows a quite regular rotation in both galaxies, thus suggesting that we are observing their first encounter as confirmed by the estimated distance of 21 kpc between the two galaxy centers. The detected ∼ 2-3 kpc active galactic nucleus (AGN) outflow and the geometry of the EELR in ShaSS 622 support the presence of a hollow bicone structure. The status and sources of the ionization across the whole system have been analyzed through photoionization models and a Bayesian approach that prove a clear connection between the AGN and the EELR. The luminosity of the AGN (2.4×10^44 erg/s) is a factor of 20 lower than the power needed to excite the gas in the EELR (4.6 ×10^45 erg/s), indicating a dramatic fading of the AGN in the past 3×10^4 yr. ShaSS 073-622 provides all the ingredients listed in the recipe of a light echo where a highly-ionized region maintains memory of a preceding more energetic phase of a now-faded AGN. This is the first case of a light echo observed between two galaxies
A persistent excess of galaxy-galaxy strong lensing observed in galaxy clusters
Previous studies have revealed that the estimated probability of
galaxy-galaxy strong lensing in observed galaxy clusters exceeds the
expectations from the Cold Dark Matter cosmological model by one
order of magnitude. We aim to understand the origin of this excess by analyzing
a larger set of simulated galaxy clusters and investigating how the theoretical
expectations vary under different adopted prescriptions and numerical
implementations of star formation and feedback in simulations. We perform a
ray-tracing analysis of 324 galaxy clusters from the Three Hundred project,
comparing the Gadget-X and Gizmo-Simba runs. These simulations, which start
from the same initial conditions, are performed with different implementations
of hydrodynamics and galaxy formation models tailored to match different
observational properties of the Intra-Cluster-Medium and cluster galaxies. We
find that galaxies in the Gizmo-Simba simulations develop denser stellar cores
than their Gadget-X counterparts. Consequently, their probability for
galaxy-galaxy strong lensing is higher by a factor of . This increment
is still insufficient to fill the gap with observations, as a discrepancy by a
factor still persists. In addition, we find that several simulated
galaxies have Einstein radii that are too large compared to observations. We
conclude that a persistent excess of galaxy-galaxy strong lensing exists in
observed galaxy clusters. The origin of this discrepancy with theoretical
predictions is still unexplained in the framework of the cosmological
hydrodynamical simulations. This might signal a hitherto unknown issue with
either the simulation methods or our assumptions regarding the standard
cosmological model.Comment: 6 pages, 2 figures, accepted for publication on A&A Letters. See
companion paper Srivastava et al. (2023
The KLEVER Survey: spatially resolved metallicity maps and gradients in a sample of 1.2 < z < 2.5 lensed galaxies
We present near-infrared observations of 42 gravitationally lensed galaxies obtained in the framework of the KMOS Lensed Emission Lines and VElocity Review (KLEVER) Survey, a programme aimed at investigating the spatially resolved properties of the ionized gas in 1.2 3σ) ‘inverted’ gradients are also found, showing an anticorrelation between metallicity and star formation rate density on local scales, possibly suggesting recent episodes of pristine gas accretion or strong radial flows in place. Nevertheless, the individual metallicity maps are characterized by a variety of different morphologies, with flat radial gradients sometimes hiding non-axisymmetric variations on kpc scales, which are washed out by azimuthal averages, especially in interacting systems or in those undergoing local episodes of recent star formation
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