108 research outputs found
X-TCP: A Cross Layer Approach for TCP Uplink Flows in mmWave Networks
Millimeter wave frequencies will likely be part of the fifth generation of
mobile networks and of the 3GPP New Radio (NR) standard. MmWave communication
indeed provides a very large bandwidth, thus an increased cell throughput, but
how to exploit these resources at the higher layers is still an open research
question. A very relevant issue is the high variability of the channel, caused
by the blockage from obstacles and the human body. This affects the design of
congestion control mechanisms at the transport layer, and state-of-the-art TCP
schemes such as TCP CUBIC present suboptimal performance. In this paper, we
present a cross layer approach for uplink flows that adjusts the congestion
window of TCP at the mobile equipment side using an estimation of the available
data rate at the mmWave physical layer, based on the actual resource allocation
and on the Signal to Interference plus Noise Ratio. We show that this approach
reduces the latency, avoiding to fill the buffers in the cellular stack, and
has a quicker recovery time after RTO events than several other TCP congestion
control algorithms.Comment: 6 pages, 5 figures, accepted for presentation at the 2017 16th Annual
Mediterranean Ad Hoc Networking Workshop (MED-HOC-NET
Structural analysis of sulfate vein networks in Gale crater (Mars)
The Curiosity rover's campaign in the Gale crater on Mars provides a large set of close-up images of sedimentary formations outcrops displaying a variety of diagenetic features such as light-toned veins, nodules and raised ridges. Through 2D and 3D analyses of Mastcam images we herein reconstruct the vein network of a sample area and estimated the stress field. Assessment of the spatial distribution of light-toned veins shows that the basin infillings, after burial and consolidation, experienced a sub-vertical compression and lateral extension coupled with fluid overpressure and cracking. Overall, rock failure and light-toned veins formations could have been generated by an overload produced by infilling material within the basin
MICADO Italian Contribution
Citato dalla notizia media inaf
https://www.media.inaf.it/2020/01/21/micado-elt/The Webpages of the Istituto Nazionale di Astrofisica (INAF) contribution to the MICADO project for the European Southern Observatory (ESO) Extremely Large Telescope (ELT). The Webpages serve as white pages for easy access to information relative to the MICADO and in particular to the Point Spread Function (PSF) reconstruction working group
Study of Different H2/CO2 Ratios as Feed in Fischer-Tropsch Reactor with Iron-Based Nano-Hydrotalcite Catalysts
CO2-FTS is among the most viable methods for converting CO2 into useful chemicals and fuels in order to minimize CO2 emissions. Due to its chemical inertness, however, effective conversion continues to be a difficulty. The challenges in terms of yield and mechanism have attracted the interest of different research groups in the development of a new carbon dioxide hydrogenation catalysts, capable of reaching satisfactory results. In this work, a selection of nano ternary hydrotalcites (HTlc) were synthesized with and without ultrasound in order to develop active Fe-based catalysts for the Fischer–Tropsch synthesis. HTlc consists mostly of metal hydroxides in which different metal atoms are uniformly distributed at the atomic level. The reaction was carried in a lab scale plant in a fixed bed configuration. All fresh and used catalysts were examined and characterized using XRPD, ICP-OES, SEM, TEM, BET. Ternary HTlc composed of Mg, Cu, and Fe was synthesized using an ultrasound-assisted co-precipitation technique (MCF-US). HTlc was tested for carbon dioxide hydrogenation reaction with a study concerning different H2/CO2 ratios in order to evaluate the product distribution as well as the efficiency of the catalyst itself. The CO2 conversion resulted higher and more stable in feeds with higher H2 quantities. The selectivity towards higher chain hydrocarbons was higher for lower H2/CO2 ratios whereas methane and carbon monoxide selectivities were adequately low
BRUTE, PSF Reconstruction for the SOUL pyramid-based Single Conjugate Adaptive Optics facility of the LBT
The astronomical applications greatly benefit from the knowledge of the
instrument PSF. We describe the PSF Reconstruction algorithm developed for the
LBT LUCI instrument assisted by the SOUL SCAO module. The reconstruction
procedure considers only synchronous wavefront sensor telemetry data and a few
asynchronous calibrations. We do not compute the Optical Transfer Function and
corresponding filters. We compute instead a temporal series of wavefront maps
and for each of these the corresponding instantaneous PSF. We tested the
algorithm both in laboratory arrangement and in the nighttime for different
SOUL configurations, adapting it to the guide star magnitudes and seeing
conditions. We nick-named it "BRUTE", Blind Reconstruction Using TElemetry,
also recalling the one-to-one approach, one slope-to one instantaneous PSF the
algorithm applies.Comment: 11 pages, 7 figures, Proceeding of the SPIE Conference 12185,
Adaptive Optics Systems VIII, 1218540 (29 August 2022
LBT SOUL data as a science test bench for MICADO PSF-R tool
Current state-of-the-art adaptive optics (AO) provides ground-based,
diffraction-limited observations with high Strehl ratios (SR). However, a
detailed knowledge of the point spread function (PSF) is required to fully
exploit the scientific potential of these data. This is even more crucial for
the next generation AO instruments that will equip 30-meter class telescopes,
as the characterization of the PSF will be mandatory to fulfill the planned
scientific requirements. For this reason, there is a growing interest in
developing tools that accurately reconstruct the observed PSF of AO systems,
the so-called PSF reconstruction. In this context, a PSF-R service is a planned
deliverable for the MICADO@ELT instrument and our group is in charge of its
development. In the case of MICADO, a blind PSF-R approach is being pursued to
have the widest applicability to science cases. This means that the PSF is
reconstructed without extracting information from the science data, relying
only on telemetry and calibrations. While our PSF-R algorithm is currently
being developed, its implementation is mature enough to test performances with
actual observations. In this presentation we will discuss the reliability of
our reconstructed PSFs and the uncertainties introduced in the measurements of
scientific quantities for bright, on-axis observations taken with the SOUL+LUCI
instrument of the LBT. This is the first application of our algorithm to real
data. It demonstrates its readiness level and paves the way to further testing.
Our PSF-R algorithm is able to reconstruct the SR and full-width at half
maximum of the observed PSFs with errors smaller than 2% and 4.5%,
respectively. We carried out the scientific evaluation of the obtained
reconstructed PSFs thanks to a dedicated set of simulated observations of an
ideal science case.Comment: 10 pages, 3 figures. Proceeding of the SPIE conference Adaptive
Optics Systems VIII, SPIE Astronomical Telescopes + Instrumentation 2022
(paper 12185-12). arXiv admin note: substantial text overlap with
arXiv:2209.0156
Status of the PSF Reconstruction Work Package for MICADO ELT
MICADO is a workhorse instrument for the ESO ELT, allowing first light
capability for diffraction limited imaging and long-slit spectroscopy at
near-infrared wavelengths. The PSF Reconstruction (PSF-R) Team of MICADO is
currently implementing, for the first time within all ESO telescopes, a
software service devoted to the blind reconstruction of the PSF. This tool will
work independently of the science data, using adaptive optics telemetry data,
both for Single Conjugate (SCAO) and Multi-Conjugate Adaptive Optics (MCAO)
allowed by the MORFEO module. The PSF-R service will support the
state-of-the-art post-processing scientific analysis of the MICADO imaging and
spectroscopic data. We provide here an update of the status of the PSF-R
service tool of MICADO, after successfully fulfilling the Final Design Review
phase, and discuss recent results obtained on simulated and real data gathered
on instruments similar to MICADO.Comment: to appear in the Proceedings 12185-149 of the SPIE conference
Adaptive Optics Systems VIII, Astronomical Telescopes+Instrumentation 2022
Montreal, Quebec, Canada; 6 pages, 1 figure, 1 table; updated affiliation
Point spread function reconstruction for SOUL + LUCI LBT data
Here, we present the status of an ongoing project aimed at developing a point spread function (PSF) reconstruction software for adaptive optics (AO) observations. In particular, we test for the first time the implementation of pyramid wave-front sensor data on our algorithms. As a first step in assessing its reliability, we applied the software to bright, on-axis, point-like sources using two independent sets of observations, acquired with the single-conjugated AO upgrade for the Large Binocular Telescope. Using only telemetry data, we reconstructed the PSF by carefully calibrating the instrument response. The accuracy of the results has been first evaluated using the classical metric: specifically, the reconstructed PSFs differ from the observed ones by <2 % in Strehl ratio and 4.5% in full-width at half maximum. Moreover, the recovered encircled energy associated with the PSF core is accurate at 4% level in the worst case. The accuracy of the reconstructed PSFs has then been evaluated by considering an idealized scientific test-case consisting in the measurements of the morphological parameters of a compact galaxy. In the future, our project will include the analysis of anisoplanatism, low signal-to-noise ratio regimes, and the application to multi-conjugated AO observations
In and out star formation in z~1.5 quiescent galaxies from rest-frame UV spectroscopy and the far-infrared
We present a sample of 34 spectroscopically confirmed BzK-selected ~1e11 Msun quiescent galaxies (pBzK) in the COSMOS field. The targets were initially observed with VIMOS on the VLT to facilitate the calibration of the photometric redshifts of massive galaxies at z >~ 1.5. Here we describe the reduction and analysis of the data, and the spectrophotometric properties of these pBzK galaxies. In particular, using a spatially resolved median 2D spectrum, we find that the fraction of stellar populations with ages <1 Gyr is at least 3 times higher in the outer regions of the pBzK galaxies than in their cores. This results in a mild age gradient of ~<0.4 Gyr over ~6 kpc and suggests either the occurrence of widespread rejuvenation episodes or that inside-out quenching played a role in the passivization of this galaxy population. We also report on low-level star formation rates derived from the [OII]3727A emission line, with SFR_OII = 3.7-4.5 Msun/yr. This estimate is confirmed by an independent measurement on a separate sample of similarly-selected quiescent galaxies in the COSMOS field, using stacked far-infrared data (SFR_FIR = 2-4 Msun/yr). This second, photometric sample also displays significant excess at 1.4 GHz, suggestive of the presence of radio-mode AGN activity
MICADO PSF-reconstruction work package description
The point spread function reconstruction (PSF-R) capability is a deliverable of the MICADO@ESO-ELT project. The PSF-R team works on the implementation of the instrument software devoted to reconstruct the point spread function (PSF), independently of the science data, using adaptive optics (AO) telemetry data, both for Single Conjugate (SCAO) and Multi-Conjugate Adaptive Optics (MCAO) mode of the MICADO camera and spectrograph. The PSF-R application will provide reconstructed PSFs through an archive querying system to restore the telemetry data synchronous to each science frame that MICADO will generate. Eventually, the PSF-R software will produce the output according to user specifications. The PSF-R service will support the state-of-the-art scientific analysis of the MICADO imaging and spectroscopic data
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