130 research outputs found
An object based algebra for specifying a fault tolerant software architecture
AbstractIn this paper we present an algebra of actors extended with mechanisms to model crash failures and their detection. We show how this extended algebra of actors can be successfully used to specify distributed software architectures. The main components of a software architecture can be specified following an object-oriented style and then they can be composed using asynchronous message passing or more complex interaction patterns. This formal specification can be used to show that several requirements of a software system are satisfied at the architectural level despite failures. We illustrate this process by means of a case study: the specification of a software architecture for intelligent agents which supports a fault tolerant anonymous interaction protocol
The Galactic neutron star population II -- Systemic velocities and merger locations of binary neutron stars
The merger locations of binary neutron stars (BNSs) encode their galactic
kinematics and provide insights into their connection to short gamma-ray bursts
(SGRBs). In this work, we use the sample of Galactic BNSs with measured proper
motions to investigate their kinematics and predict their merger locations.
Using a synthetic image of the Milky Way and its Galactic potential we analyse
the BNS mergers as seen from an extragalactic viewpoint and compare them to the
location of SGRBs on and around their host galaxies. We find that the
Galactocentric transverse velocities of the BNSs are similar in magnitude and
direction to those of their Local Standards of Rest, which implies that the
present-day systemic velocities are not isotropically oriented and the peculiar
velocities might be as low as those of BNS progenitors. Both systemic and
peculiar velocities fit a lognormal distribution, with the peculiar velocities
being as low as km s. We also find that the observed BNS
sample is not representative of the whole Galactic population, but rather of
systems born around the Sun's location with small peculiar velocities. When
comparing the predicted BNS merger locations to SGRBs, we find that they cover
the same range of projected offsets, host-normalized offsets, and fractional
light. Therefore, the spread in SGRB locations can be reproduced by mergers of
BNSs born in the Galactic disk with small peculiar velocities, although the
median offset match is likely a coincidence due to the biased BNS sample.Comment: 13 pages, 7 figures, accepted for publication in MNRA
Sensory-Glove-Based Open Surgery Skill Evaluation
Manual dexterity is one of the most important surgical skills, and yet there are limited instruments to evaluate this ability objectively. In this paper, we propose a system designed to track surgeons’ hand movements during simulated open surgery tasks and to evaluate their manual expertise. Eighteen participants, grouped according to their surgical experience, performed repetitions of two basic surgical tasks, namely single interrupted suture and simple running suture. Subjects’ hand movements were measured with a sensory glove equipped with flex and inertial sensors, tracking flexion/extension of hand joints, and wrist movement. The participants’ level of experience was evaluated discriminating manual performances using linear discriminant analysis, support vector machines, and artificial neural network classifiers. Artificial neural networks showed the best performance, with a median error rate of 0.61% on the classification of single interrupted sutures and of 0.57% on simple running sutures. Strategies to reduce sensory glove complexity and increase its comfort did not affect system performances substantially
Compact object mergers: exploring uncertainties from stellar and binary evolution with SEVN
Population-synthesis codes are an unique tool to explore the parameter space
of massive binary star evolution and binary compact object (BCO) formation.
Most population-synthesis codes are based on the same stellar evolution model,
limiting our ability to explore the main uncertainties. Our code SEVN overcomes
this issue by interpolating the main stellar properties from a set of
pre-computed evolutionary tracks. With SEVN, we evolved
binaries in the metallicity range , exploring a number
of models for electron-capture, core-collapse and pair-instability supernovae,
different assumptions for common envelope, stability of mass transfer,
quasi-homogeneous evolution and stellar tides. We find that stellar evolution
has a dramatic impact on the formation of single and binary compact objects.
Just by slightly changing the overshooting parameter () and the pair-instability model, the maximum mass of a black hole
can vary from to . Furthermore,
the formation channels of BCOs and the merger efficiency we obtain with SEVN
show significant differences with respect to the results of other
population-synthesis codes, even when the same binary-evolution parameters are
used. For example, the main traditional formation channel of BCOs is strongly
suppressed in our models: at high metallicity () only % of
the merging binary black holes and binary neutron stars form via this channel,
while other authors found fractions %. The local BCO merger rate density
of our fiducial models is consistent with the most recent estimates by the
LIGO--Virgo--KAGRA collaboration.Comment: Submitted to MNRAS, comments welcome! The SEVN code is available at
https://gitlab.com/sevncodes/sevn.git. All the data underlying this article
are available in Zenodo at the link https://doi.org/10.5281/zenodo.7260771.
All the Jupyter notebooks used to produce the plots in the paper are
available in the gitlab repository https://gitlab.com/iogiul/iorio22_plot.gi
Is Digital Image Plethysmographic (DIP) Acquisition a Valid New Tool for Preoperative Body Composition Assessment? A Validation by Dual-energy X-ray Absorptiometry
- …