Design, Engineering, and Experimental Analysis of a Simulated Annealing Approach to the Post-Enrolment Course Timetabling Problem

The post-enrolment course timetabling (PE-CTT) is one of the most studied timetabling problems, for which many instances and results are available. In this work we design a metaheuristic approach based on Simulated Annealing to solve the PE-CTT. We consider all the different variants of the problem that have been proposed in the literature and we perform a comprehensive experimental analysis on all the public instances available. The outcome is that our solver, properly engineered and tuned, performs very well on all cases, providing the new best known results on many instances and state-of-the-art values for the others

Unified Fock space representation of fractional quantum Hall states

Many bosonic (fermionic) fractional quantum Hall states, such as Laughlin, Moore-Read and Read-Rezayi wavefunctions, belong to a special class of orthogonal polynomials: the Jack polynomials (times a Vandermonde determinant). This fundamental observation allows to point out two different recurrence relations for the coefficients of the permanent (Slater) decomposition of the bosonic (fermionic) states. Here we provide an explicit Fock space representation for these wavefunctions by introducing a two-body squeezing operator which represents them as a Jastrow operator applied to reference states, which are in general simple periodic one dimensional patterns. Remarkably, this operator representation is the same for bosons and fermions, and the different nature of the two recurrence relations is an outcome of particle statistics.Comment: 10 pages, 3 figure

ELECTRIC VEHICLE AND SUSTAINABLE MOBILITY: AN INNOVATIVE INTERFACE

The paper presents a concept of an innovative interaction structure for a digital electric vehicle (EV) dashboard. The structure connects interactions between vehicle, driver and traffic infrastructure, in order to help users driving in a conscious way, informing them about their performances and providing tools able to modify driving behaviour. Through the Systemic Design approach, it is possible to move from a quantitative configuration (set on consumption) to a new one set on resource optimization. The achievement is a new layout for the information visualization system designed for an electric vehicle able to communicate to the driver the environmental impact of its drive style

Selberg integrals in 1D random Euclidean optimization problems

We consider a set of Euclidean optimization problems in one dimension, where the cost function associated to the couple of points $x$ and $y$ is the Euclidean distance between them to an arbitrary power $p\ge1$, and the points are chosen at random with flat measure. We derive the exact average cost for the random assignment problem, for any number of points, by using Selberg's integrals. Some variants of these integrals allows to derive also the exact average cost for the bipartite travelling salesman problem.Comment: 9 pages, 2 figure

Feature-based tuning of simulated annealing applied to the curriculum-based course timetabling problem

We consider the university course timetabling problem, which is one of the most studied problems in educational timetabling. In particular, we focus our attention on the formulation known as the curriculum-based course timetabling problem, which has been tackled by many researchers and for which there are many available benchmarks. The contribution of this paper is twofold. First, we propose an effective and robust single-stage simulated annealing method for solving the problem. Secondly, we design and apply an extensive and statistically-principled methodology for the parameter tuning procedure. The outcome of this analysis is a methodology for modeling the relationship between search method parameters and instance features that allows us to set the parameters for unseen instances on the basis of a simple inspection of the instance itself. Using this methodology, our algorithm, despite its apparent simplicity, has been able to achieve high quality results on a set of popular benchmarks. A final contribution of the paper is a novel set of real-world instances, which could be used as a benchmark for future comparison

Simple Dynamics for Plurality Consensus

We study a \emph{Plurality-Consensus} process in which each of $n$ anonymous agents of a communication network initially supports an opinion (a color chosen from a finite set $[k]$). Then, in every (synchronous) round, each agent can revise his color according to the opinions currently held by a random sample of his neighbors. It is assumed that the initial color configuration exhibits a sufficiently large \emph{bias} $s$ towards a fixed plurality color, that is, the number of nodes supporting the plurality color exceeds the number of nodes supporting any other color by $s$ additional nodes. The goal is having the process to converge to the \emph{stable} configuration in which all nodes support the initial plurality. We consider a basic model in which the network is a clique and the update rule (called here the \emph{3-majority dynamics}) of the process is the following: each agent looks at the colors of three random neighbors and then applies the majority rule (breaking ties uniformly). We prove that the process converges in time $\mathcal{O}( \min\{ k, (n/\log n)^{1/3} \} \, \log n )$ with high probability, provided that $s \geqslant c \sqrt{ \min\{ 2k, (n/\log n)^{1/3} \}\, n \log n}$. We then prove that our upper bound above is tight as long as $k \leqslant (n/\log n)^{1/4}$. This fact implies an exponential time-gap between the plurality-consensus process and the \emph{median} process studied by Doerr et al. in [ACM SPAA'11]. A natural question is whether looking at more (than three) random neighbors can significantly speed up the process. We provide a negative answer to this question: In particular, we show that samples of polylogarithmic size can speed up the process by a polylogarithmic factor only.Comment: Preprint of journal versio

Rate of complications due to neuromuscular scoliosis spine surgery in a 30-years consecutive series

PURPOSE: The aim of this study was to evaluate the rate of intraoperative and postoperative complications in a large series of patients affected by neuromuscular scoliosis. METHODS: It was a monocentric retrospective study. In this study have been considered complications those events that significantly affected the course of treatment, such as getting the hospital stay longer, or requiring a subsequent surgical procedure, or corrupting the final result of the treatment. RESULTS: Of the 358 patients affected by neuromuscular scoliosis treated from January 1985 to December 2010, 185 that met the inclusion criteria were included in the study. There were recorded 66 complications in 55/185 patients. Of that 66 complications, 54 complications occurred in 46/120 patients with Luque's instrumentation, while only 12 complications occurred in 9/65 patients with hybrid instrumentation and this difference was statistically significant (p 0.05). CONCLUSIONS: The surgical treatment in neuromuscular scoliosis is burdened by a large number of complications. An accurate knowledge of possible complications is mandatory to prepare strategies due to prevent adverse events. A difference in definitions could completely change results in good or bad as well as in our same series the adverse events amounted at almost 30% of cases, but complications that due to complete failure would amount at 9.19% of patients. KEYWORDS: Complications; Neuromuscular scoliosis; Scoliosis; Scoliosis surgery PMID: 28314995 DOI: 10.1007/s00586-017-5034-6 Share on FacebookShare on TwitterShare on Google

Ultra-thin clay layers facilitate seismic slip in carbonate faults

Many earthquakes propagate up to the Earth's surface producing surface ruptures. Seismic slip propagation is facilitated by along-fault low dynamic frictional resistance, which is controlled by a number of physico-chemical lubrication mechanisms. In particular, rotary shear experiments conducted at seismic slip rates (1 ms(-1)) show that phyllosilicates can facilitate co-seismic slip along faults during earthquakes. This evidence is crucial for hazard assessment along oceanic subduction zones, where pelagic clays participate in seismic slip propagation. Conversely, the reason why, in continental domains, co-seismic slip along faults can propagate up to the Earth's surface is still poorly understood. We document the occurrence of micrometer-thick phyllosilicate-bearing layers along a carbonate-hosted seismogenic extensional fault in the central Apennines, Italy. Using friction experiments, we demonstrate that, at seismic slip rates (1 ms(-1)), similar calcite gouges with pre-existing phyllosilicate-bearing (clay content ≤3 wt.%) micro-layers weaken faster than calcite gouges or mixed calcite-phyllosilicate gouges. We thus propose that, within calcite gouge, ultra-low clay content (≤3 wt.%) localized along micrometer-thick layers can facilitate seismic slip propagation during earthquakes in continental domains, possibly enhancing surface displacement

Blue Gravity Waves from BICEP2 ?

We present new constraints on the spectral index n_T of tensor fluctuations from the recent data obtained by the BICEP2 experiment. We found that the BICEP2 data alone slightly prefers a positive, "blue", spectral index with n_T=1.36\pm0.83 at 68 % c.l.. However, when a TT prior on the tensor amplitude coming from temperature anisotropy measurements is assumed we get n_T=1.67\pm0.53 at 68 % c.l., ruling out a scale invariant $n_T=0$ spectrum at more than three standard deviations. These results are at odds with current bounds on the tensor spectral index coming from pulsar timing, Big Bang Nucleosynthesis, and direct measurements from the LIGO experiment. Considering only the possibility of a "red", n_T<0 spectral index we obtain the lower limit n_T > -0.76 at 68 % c.l. (n_T>-0.09 when a TT prior is included).Comment: 3 Pages, 4 Figure