693 research outputs found
Concurrent constraint programming with process mobility
We propose an extension of concurrent constraint programming with primitives for process migration within a hierarchical network, and we study its semantics. To this purpose, we first investigate a "pure " paradigm for process migration, namely a paradigm where the only actions are those dealing with transmissions of processes. Our goal is to give a structural definition of the semantics of migration; namely, we want to describe the behaviour of the system, during the transmission of a process, in terms of the behaviour of the components. We achieve this goal by using a labeled transition system where the effects of sending a process, and requesting a process, are modeled by symmetric rules (similar to handshaking-rules for synchronous communication) between the two partner nodes in the network. Next, we extend our paradigm with the primitives of concurrent constraint programming, and we show how to enrich the semantics to cope with the notions of environment and constraint store. Finally, we show how the operational semantics can be used to define an interpreter for the basic calculus.
Development and Validation of the Metric-Based Assessment of a Robotic Vessel Dissection, Vessel Loop Positioning, Clip Applying and Bipolar Coagulation Task on an Avian Model
The evolution of robotic technology and its diffusion does not seem to have been adequately accompanied by the development and implementation of surgeon training programs that ensure skilled and safe device use at the start of the learning curve. The objective of the study is to develop and validate performance metrics for vessel dissection, vessel loop positioning, clip applying and bipolar coagulation using an avian model. Three robotic surgeons and a behavioral scientist characterized the performance metrics of the task according to the proficiency-based progression methodology. Fourteen experienced robotic surgeons from different European countries participated in a modified online Delphi consensus. Eight experienced surgeons and eight novices performed the robotic task twice. In the Delphi meeting, 100% consensus was reached on the performance metrics. Novice surgeons took 26 min to complete the entire task on trial 1 and 20 min on trial 2. Experts took 10.1 min and 9.5 min. On average the Expert Group completed the task 137% faster than the Novice Group. The amount of time to reach the vessel part of the task was also calculated. Novice surgeons took 26 min on trial 1 and 20 min on trial 2. Experts took 5.5 min and 4.8 min. On average the experts reached the vessel 200% faster than the novices. The Expert Group made 155% fewer performance errors than the Novice Group. The mean IRR of video-recorded performance assessments for all metrics was 0.96 (95% confidence intervals (CI) lower = 0.94-upper = 0.98). We report the development and validation for a standard and replicable basic robotic vessel dissection, vessel loop positioning, clip applying and bipolar coagulation task on an avian model. The development of objective performance metrics, based on a transparent and fair methodology (i.e., PBP), is the first fundamental step toward quality assured training. This task developed on the avian model proved to have good results in the validation study.info:eu-repo/semantics/publishedVersio
Needle-assisted laparo-endoscopic single-site surgery for radical prostatectomy (LESS-RP) using a new series of Steerable™ instruments : feasible option to overcome current limits?
Decay-assisted collinear resonance ionization spectroscopy: Application to neutron-deficient francium
This paper reports on the hyperfine-structure and radioactive-decay studies
of the neutron-deficient francium isotopes Fr performed with the
Collinear Resonance Ionization Spectroscopy (CRIS) experiment at the ISOLDE
facility, CERN. The high resolution innate to collinear laser spectroscopy is
combined with the high efficiency of ion detection to provide a
highly-sensitive technique to probe the hyperfine structure of exotic isotopes.
The technique of decay-assisted laser spectroscopy is presented, whereby the
isomeric ion beam is deflected to a decay spectroscopy station for alpha-decay
tagging of the hyperfine components. Here, we present the first
hyperfine-structure measurements of the neutron-deficient francium isotopes
Fr, in addition to the identification of the low-lying states of
Fr performed at the CRIS experiment.Comment: Accepted for publication with Physical Review
Laser spectroscopy of francium isotopes at the borders of the region of reflection asymmetry
The magnetic dipole moments and changes in mean-square charge radii of the
neutron-rich isotopes were measured with the
newly-installed Collinear Resonance Ionization Spectroscopy (CRIS) beam line at
ISOLDE, CERN, probing the to atomic
transition. The values for
and follow the observed increasing
slope of the charge radii beyond . The charge radii odd-even
staggering in this neutron-rich region is discussed, showing that
has a weakly inverted odd-even staggering while
has normal staggering. This suggests that both isotopes
reside at the borders of a region of inverted staggering, which has been
associated with reflection-asymmetric shapes. The value supports a shell model configuration for the
ground state. The values support the tentative
spin, and point to a intruder ground state configuration.Comment: Accepted for publication with Physical Review
A theory of normed simulations
In existing simulation proof techniques, a single step in a lower-level
specification may be simulated by an extended execution fragment in a
higher-level one. As a result, it is cumbersome to mechanize these techniques
using general purpose theorem provers. Moreover, it is undecidable whether a
given relation is a simulation, even if tautology checking is decidable for the
underlying specification logic. This paper introduces various types of normed
simulations. In a normed simulation, each step in a lower-level specification
can be simulated by at most one step in the higher-level one, for any related
pair of states. In earlier work we demonstrated that normed simulations are
quite useful as a vehicle for the formalization of refinement proofs via
theorem provers. Here we show that normed simulations also have pleasant
theoretical properties: (1) under some reasonable assumptions, it is decidable
whether a given relation is a normed forward simulation, provided tautology
checking is decidable for the underlying logic; (2) at the semantic level,
normed forward and backward simulations together form a complete proof method
for establishing behavior inclusion, provided that the higher-level
specification has finite invisible nondeterminism.Comment: 31 pages, 10figure
An Algorithm for Stuttering Equivalence and Branching Bisimulation
We provide a new algorithm to determine stuttering equivalence with time
complexity , where is the number of states and is the
number of transitions of a Kripke structure. This algorithm can also be used to
determine branching bisimulation in time
where is the set of actions in a labelled transition system.
Theoretically, our algorithm substantially improves upon existing algorithms
which all have time complexity at best. Moreover, it has better or
equal space complexity. Practical results confirm these findings showing that
our algorithm can outperform existing algorithms with orders of magnitude,
especially when the sizes of the Kripke structures are large. The importance of
our algorithm stretches far beyond stuttering equivalence and branching
bisimulation. The known algorithms were already far more efficient
(both in space and time) than most other algorithms to determine behavioural
equivalences (including weak bisimulation) and therefore it was often used as
an essential preprocessing step. This new algorithm makes this use of
stuttering equivalence and branching bisimulation even more attractive.Comment: A shortened version of this technical report has been published in
the proceedings of TACAS 201
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