1,059 research outputs found
Evaluation of the quantiles and superquantiles of the makespan in interval valued activity networks
This paper deals with the evaluation of quantile-based risk measures for the
makespan in scheduling problems represented as temporal networks with uncer tainties on the activity durations. More specifically, for each activity only the
interval for its possible duration values is known in advance to both the sched uler and the risk analyst. Given a feasible schedule, we calculate the quantiles
and the superquantiles of the makespan which are of interest as risk indicators
in various applications.
To this aim we propose and test a set of novel algorithms to determine rapid
and accurate numerical estimations based on the calculation of theoretically
proven lower and upper bounds. An extensive experimental campaign compu tationally shows the validity of the proposed methods, and allows to highlight
their performances through the comparison with respect to the state-of-the-art
algorithms
An efficient decomposition approach for surgical planning
This talk presents an efficient decomposition approach to surgical planning. Given a set of surgical waiting lists (one for each discipline) and an operating theater, the problem is to decide the room-to-discipline assignment for the next planning period (Master Surgical Schedule), and the surgical cases to be performed (Surgical Case Assignment), with the objective of optimizing a score related to priority and current waiting time of the cases. While in general MSS and SCA may be concurrently found by solving a complex integer programming problem, we propose an effective decomposition algorithm which does not require expensive or sophisticated computational resources, and is therefore suitable for implementation in any real-life setting.
Our decomposition approach consists in first producing a number of subsets of surgical cases for each discipline (potential OR sessions), and select a subset of them. The surgical cases in the selected potential sessions are then discarded, and only the structure of the MSS is retained. A detailed surgical case assignment is then devised filling the MSS obtained with cases from the waiting lists, via an exact optimization model.
The quality of the plan obtained is assessed by comparing it with the plan obtained by solving the exact integrated formulation for MSS and SCA. Nine different scenarios are considered, for various operating theater sizes and management policies. The results on instances concerning a medium-size hospital show that the decomposition method produces comparable solutions with the exact method in much smaller computation time
Coherent 100G Nonlinear Compensation with Single-Step Digital Backpropagation
Enhanced-SSFM digital backpropagation (DBP) is experimentally demonstrated
and compared to conventional DBP. A 112 Gb/s PM-QPSK signal is transmitted over
a 3200 km dispersion-unmanaged link. The intradyne coherent receiver includes
single-step digital backpropagation based on the enhanced-SSFM algorithm. In
comparison, conventional DBP requires twenty steps to achieve the same
performance. An analysis of the computational complexity and structure of the
two algorithms reveals that the overall complexity and power consumption of DBP
are reduced by a factor of 16 with respect to a conventional implementation,
while the computation time is reduced by a factor of 20. As a result, the
proposed algorithm enables a practical and effective implementation of DBP in
real-time optical receivers, with only a moderate increase of the computational
complexity, power consumption, and latency with respect to a simple
feed-forward equalizer for dispersion compensation.Comment: This work has been presented at Optical Networks Design & Modeling
(ONDM) 2015, Pisa, Italy, May 11-14, 201
The Prostacyclin Analogue Iloprost as an Early Predictor of Successful Revascularization in Diabetic Patients Affected by Critical Limb Ischemia and Foot Ulcers
Abstract Purpose The aim of this study is to evaluate the role of Iloprost as an early predictor of successful revascularization in patients affected by ischemic diabetic foot ulcers (DFUs). Methods Consecutive patients with ischemic DFUs with persistent low TcPO2 ( All patients underwent Iloprost infusion and TcPO2 has been recorded at days 3, 14 and 30. According to the TcPO2 reported at day 3, patients were divided into two groups: group A (patients with TcPO2 ≥30mmHg) and group B (patients with TcPO2  Results Twenty-five patients have been included, 12/25 (48%) in Group A and 13/25 (52%) in Group B. There were no significant differences at the baseline and one day after PTA between the two groups while TcPO2 values recorded in Group A at days 3, 14 and 30 after Iloprost infusion were significant higher in comparison to the Group B (χ = 0.005). The rate of re-PTA were respectively 33,3% (Group A) and 53,8% (Group B) (p = 0.03). Conclusions Iloprost may be an early predictor of successful revascularization in patients affected by critical limb ischemia (CLI) and DFUs
An Optimal Control Approach to Learning in SIDARTHE Epidemic model
The COVID-19 outbreak has stimulated the interest in the proposal of novel
epidemiological models to predict the course of the epidemic so as to help
planning effective control strategies. In particular, in order to properly
interpret the available data, it has become clear that one must go beyond most
classic epidemiological models and consider models that, like the recently
proposed SIDARTHE, offer a richer description of the stages of infection. The
problem of learning the parameters of these models is of crucial importance
especially when assuming that they are time-variant, which further enriches
their effectiveness. In this paper we propose a general approach for learning
time-variant parameters of dynamic compartmental models from epidemic data. We
formulate the problem in terms of a functional risk that depends on the
learning variables through the solutions of a dynamic system. The resulting
variational problem is then solved by using a gradient flow on a suitable,
regularized functional. We forecast the epidemic evolution in Italy and France.
Results indicate that the model provides reliable and challenging predictions
over all available data as well as the fundamental role of the chosen strategy
on the time-variant parameters.Comment: 12 pages, 7 figure
On the complexity of the boundary layer structure and aerosol vertical distribution in the coastal Mediterranean regions: A case study
The planetary boundary layer structure in the coastal areas, and particularly in complex orography regions such as the Mediterranean, is extremely intricate. In this study, we show the evolution of the planetary boundary layer based on in situ airborne measurements and ground-based remote sensing observations carried out during the MORE (Marine Ozone and Radiation Experiment) campaign in June 2010. The campaign was held in a rural coastal Mediterranean region in Southern Italy. The study focuses on the observations made on 17 June. Vertical profiles of meteorological parameters and aerosol size distribution were measured during two flights: in the morning and in the afternoon. Airborne observations were combined with ground-based LIDAR, SODAR, microwave and visible radiometer measurements, allowing a detailed description of the atmospheric vertical structure. The analysis was complemented with data from a regional atmospheric model run with horizontal resolutions of 12, 4 and 1 km, respectively; back-trajectories were calculated at these spatial resolutions. The observations show the simultaneous occurrence of dust transport, descent of mid-tropospheric air and sea breeze circulation on 17 June. Local pollution effects on the aerosol distribution, and a possible event of new particles formation were also observed. A large variability in the thermodynamical structure and aerosol distribution in the flight region, extending by approximately 30km along the coast, was found. Within this complex, environment-relevant differences in the back-trajectories calculated at different spatial resolutions are found, suggesting that the description of several dynamical processes, and in particular the sea breeze circulation, requires high-resolution meteorological analyses. The study also shows that the integration of different observational techniques is needed to describe these complex conditions; in particular, the availability of flights and their timing with respect to the occurring phenomena are crucial
Optical Time-Frequency Packing: Principles, Design, Implementation, and Experimental Demonstration
Time-frequency packing (TFP) transmission provides the highest achievable
spectral efficiency with a constrained symbol alphabet and detector complexity.
In this work, the application of the TFP technique to fiber-optic systems is
investigated and experimentally demonstrated. The main theoretical aspects,
design guidelines, and implementation issues are discussed, focusing on those
aspects which are peculiar to TFP systems. In particular, adaptive compensation
of propagation impairments, matched filtering, and maximum a posteriori
probability detection are obtained by a combination of a butterfly equalizer
and four 8-state parallel Bahl-Cocke-Jelinek-Raviv (BCJR) detectors. A novel
algorithm that ensures adaptive equalization, channel estimation, and a proper
distribution of tasks between the equalizer and BCJR detectors is proposed. A
set of irregular low-density parity-check codes with different rates is
designed to operate at low error rates and approach the spectral efficiency
limit achievable by TFP at different signal-to-noise ratios. An experimental
demonstration of the designed system is finally provided with five
dual-polarization QPSK-modulated optical carriers, densely packed in a 100 GHz
bandwidth, employing a recirculating loop to test the performance of the system
at different transmission distances.Comment: This paper has been accepted for publication in the IEEE/OSA Journal
of Lightwave Technolog
SAILenv: Learning in Virtual Visual Environments Made Simple
Recently, researchers in Machine Learning algorithms, Computer Vision
scientists, engineers and others, showed a growing interest in 3D simulators as
a mean to artificially create experimental settings that are very close to
those in the real world. However, most of the existing platforms to interface
algorithms with 3D environments are often designed to setup navigation-related
experiments, to study physical interactions, or to handle ad-hoc cases that are
not thought to be customized, sometimes lacking a strong photorealistic
appearance and an easy-to-use software interface. In this paper, we present a
novel platform, SAILenv, that is specifically designed to be simple and
customizable, and that allows researchers to experiment visual recognition in
virtual 3D scenes. A few lines of code are needed to interface every algorithm
with the virtual world, and non-3D-graphics experts can easily customize the 3D
environment itself, exploiting a collection of photorealistic objects. Our
framework yields pixel-level semantic and instance labeling, depth, and, to the
best of our knowledge, it is the only one that provides motion-related
information directly inherited from the 3D engine. The client-server
communication operates at a low level, avoiding the overhead of HTTP-based data
exchanges. We perform experiments using a state-of-the-art object detector
trained on real-world images, showing that it is able to recognize the
photorealistic 3D objects of our environment. The computational burden of the
optical flow compares favourably with the estimation performed using modern
GPU-based convolutional networks or more classic implementations. We believe
that the scientific community will benefit from the easiness and high-quality
of our framework to evaluate newly proposed algorithms in their own customized
realistic conditions.Comment: 8 pages, 7 figures, submitted to ICPR 202
- …