1,263 research outputs found
A robust MPC approach for the rebalancing of mobility on demand systems
A control-oriented model for mobility-on-demand systems is here proposed. The system is first described
through dynamical stochastic state-space equations, and then suitably simplified in order to obtain a controloriented
model, on which two control strategies based on Model Predictive Control are designed. The first
strategy aims at keeping the expected value of the number of vehicles parked in stations within prescribed
bounds; the second strategy specifically accounts for stochastic fluctuations around the expected value. The
model includes the possibility of weighting the control effort, leading to control solutions that may trade off
efficiency and cost. The models and control strategies are validated over a dataset of logged trips of ToBike,
the bike-sharing systems in the city of Turin, Italy
The space density of Compton-thick AGN at z~0.8 in the zCOSMOS-Bright Survey
The obscured accretion phase in BH growth is a key ingredient in many models
linking the AGN activity with the evolution of their host galaxy. At present, a
complete census of obscured AGN is still missing. The purpose of this work is
to assess the reliability of the [NeV] emission line at 3426 A to pick up
obscured AGN up to z~1 by assuming that [NeV] is a reliable proxy of the
intrinsic AGN luminosity and using moderately deep X-ray data to characterize
the amount of obscuration. A sample of 69 narrow-line (Type 2) AGN at
z=0.65-1.20 were selected from the 20k-zCOSMOS Bright galaxy sample on the
basis of the presence of the [NeV] emission. The X-ray properties of these
galaxies were then derived using the Chandra-COSMOS coverage of the field; the
X-ray-to-[NeV] flux ratio, coupled with X-ray spectral and stacking analyses,
was then used to infer whether Compton-thin or Compton-thick absorption were
present in these sources. Then the [NeV] luminosity function was computed to
estimate the space density of Compton-thick (CT) AGN at z~0.8. Twenty-three
sources were detected by Chandra, and their properties are consistent with
moderate obscuration (on average, ~a few 10^{22} cm^-2). The X-ray properties
of the remaining 46 X-ray undetected Type 2 AGN were derived using X-ray
stacking analysis. Current data indicate that a fraction as high as ~40% of the
present sample is likely to be CT. The space density of CT AGN with
logL_2-10keV>43.5 at z=0.83 is (9.1+/-2.1) 10^{-6} Mpc^{-3}, in good agreement
with both XRB model expectations and the previously measured space density for
objects in a similar redshift and luminosity range. We regard our selection
technique for CT AGN as clean but not complete, since even a mild extinction in
the NLR can suppress [NeV] emission. Therefore, our estimate of their space
density should be considered as a lower limit.Comment: 10 pages, 7 figures, 2 tables, A&A, in pres
Short term strength behavior of two-component backfilling in shield tunneling: comparison between standard penetrometer test results and UCS
The two-component backfilling system is the most frequently used method to fill the annular gap created during the shield machine advancement. This gap, due to the head overcut, the shield thickness and conicity and the tail brushes size should be filled continuously in order to avoid mainly surface displacement and linings movements. Nowadays this technology is the most chosen due to operative (both components are chemically and physically stable) and technical (mechanical performance start to grow up just immediately after the injection) advantages that mean money and time saving.The main mechanical parameter used for the two-component grout characterization is the uniaxial compressive strength (UCS). In order to assess this parameter, a laboratory press and suitable hardened samples are needed but, expressly at short curing time, the penetrometer use is also diffused.This research pertains the study of two-component grout uniaxial compressive strength, its evolution in function of time and its correlation with penetrometer tests data
The rest-frame UV-to-optical spectroscopy of APM 08279+5255 - BAL classification and black hole mass estimates
We present the analysis of the rest-frame optical-to-UV spectrum of APM
08279+5255, a well-known lensed broad absorption line (BAL) quasar at . The spectroscopic data are taken with the optical DOLoRes and near-IR
NICS instruments at TNG, and include the previously unexplored range between C
III] 1910 and [O III] 4959,5007. We investigate the
possible presence of multiple BALs by computing "balnicity" and absorption
indexes (i.e. BI, BI and AI) for the transitions Si IV 1400, C IV
1549, Al III 1860 and Mg II 2800. No clear evidence
for the presence of absorption features is found in addition to the already
known, prominent BAL associated to C IV, which supports a high-ionization BAL
classification for APM 08279+5255. We also study the properties of the [O III],
H and Mg II emission lines. We find that [O III] is intrinsically weak
(), as it is typically found in
luminous quasars with a strongly blueshifted C IV emission line (2500 km
s for APM 08279+5255). We compute the single-epoch black hole mass based
on Mg II and H broad emission lines, finding M, with the magnification factor that can
vary between 4 and 100 according to CO and rest-frame UV-to-mid-IR imaging
respectively. Using a Mg II equivalent width (EW)-to-Eddington ratio relation,
the EW \AA\ measured for APM 08279+5255 translates into an
Eddington ratio of 0.4, which is more consistent with . This
magnification factor also provides a value of that is consistent
with recent reverberation-mapping measurements derived from C IV and Si IV.Comment: 10 pages, 4 figures, 4 tables, accepted for publication in A&
Host preferences of phlebotomine sand flies at a hypoendemic focus of canine leishmaniasis in central Italy.
A survey was carried out on phlebotomine sand flies and their feeding habits at a hypoendemic focus of Leishmania infantum in Macerata province, central Italy. During two consecutive years (2000-2001), 1465 sand fly specimens (42.5% of which were males) were collected from a variety of diurnal resting sites in the municipality of Camerino. The most prevalent species was Phlebotomus perniciosus (76.6%), followed by P. papatasi (10.4%), Sergentomyia minuta (9.1%), Phlebotomus perfiliewi (3.3%) and P. mascittii (0.5%). Among the 842 females collected, 578 (68.6%) were blood-fed. Based on the results of blood meal analyses, P. perniciosus fed on man, dogs, equines, sheep and birds; P. perfiliewi on dogs, equines, sheep and birds; P. papatasi on dogs, equines and birds. Two specimens of P. mascittii fed on equines. Forage ratios (FRs) and host selectivity indices gave different results for the large domestic animals. More than 95% of the specimens collected inside a stable, dog kennel, sheep pen and chicken house were found to have fed on the animals housed in the respective shelters. In addition, at one collecting site where almost all the hosts mentioned above were present simultaneously, both P. perniciosus and P. perfiliewi were found to have fed on all five species, indicating that host choice was probably related to its availability (i.e. number and size) rather than specific attractiveness. The feeding habits of the two Leishmania vectors may have implications for the epidemiology of leishmaniasis in urban and peri-urban areas, where sand fly females deprived of other vertebrate hosts (particularly the larger species) may begin to bite humans and dogs more frequently
Analysis of the Parameters Affecting the Stiffness of Short Sisal Fiber Biocomposites Manufactured by Compression-Molding
The use of natural fiber-based composites is on the rise in many industries. Thanks to their eco-sustainability, these innovative materials make it possible to adapt the production of components, systems and machines to the increasingly stringent regulations on environmental protection, while at the same time reducing production costs, weight and operating costs. Optimizing the mechanical properties of biocomposites is an important goal of applied research. In this work, using a new numerical approach, the effects of the volume fraction, average length, distribution of orientation and curvature of fibers on the Young’s modulus of a biocomposite reinforced with short natural fibers were studied. Although the proposed approach could be applied to any biocomposite, sisal fibers and an eco-sustainable thermosetting matrix (green epoxy) were considered in both simulations and the associated experimental assessment. The results of the simulations showed the following effects of the aforementioned parameters on Young’s modulus: a linear growth with the volume fraction, nonlinear growth as the length of the fibers increased, a reduction as the average curvature increased and an increase in stiffness in the x-y plane as the distribution of fiber orientation in the z direction decreased
The multi-phase winds of Markarian 231: from the hot, nuclear, ultra-fast wind to the galaxy-scale, molecular outflow
We present the best sensitivity and angular resolution maps of the molecular
disk and outflow of Mrk 231, as traced by CO observations obtained with
IRAM/PdBI, and we analyze archival Chandra and NuSTAR observations. We
constrain the physical properties of both the molecular disk and outflow, the
presence of a highly-ionized ultra-fast nuclear wind, and their connection. The
molecular outflow has a size of ~1 kpc, and extends in all directions around
the nucleus, being more prominent along the south-west to north-east direction,
suggesting a wide-angle biconical geometry. The maximum projected velocity of
the outflow is nearly constant out to ~1 kpc, thus implying that the density of
the outflowing material decreases from the nucleus outwards as . This
suggests that either a large part of the gas leaves the flow during its
expansion or that the bulk of the outflow has not yet reached out to ~1 kpc,
thus implying a limit on its age of ~1 Myr. We find and erg s.
Remarkably, our analysis of the X-ray data reveals a nuclear ultra-fast outflow
(UFO) with velocity -20000 km s, , and momentum load .We find as predicted for outflows undergoing an energy
conserving expansion. This suggests that most of the UFO kinetic energy is
transferred to mechanical energy of the kpc-scale outflow, strongly supporting
that the energy released during accretion of matter onto super-massive black
holes is the ultimate driver of giant massive outflows. We estimate a momentum
boost . The ratios and agree
with the requirements of the most popular models of AGN feedback.Comment: 16 pages, 17 figures. Accepted for publication in A&
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