Due to the recent worries about the environment, the transportation companies are incentivized to use Alternative Fuel Vehicles (AFVs) instead of the conventional ones. However, due to the limited ...AFV driving range and since the Alternative Fuel Stations (AFSs) are usually not widespread on the territory, the routes of AFVs have to be properly planned in order to prevent them from remaining without the sufficient fuel to reach the depot or the closest station. The Green Vehicle Routing Problem (G-VRP) aims at determining the AFVs routes, each one serving customers within a maximum duration, minimizing the total travel distance and, if necessary, including stops at AFSs. Contrary to G-VRP, G-VRP with Capacitated AFSs (G-VRP-CAFS) more realistically assumes that each AFS has a limited number of fueling pumps and therefore prevents overlapping in refueling operations. In this paper, we propose a Greedy Randomized Adaptive Search Procedure (GRASP), which properly uses some theoretical results and efficiently solves large-sized instances of G-VRP-CAFS. Computational results carried out on both benchmark instances and large-sized instances show the effectiveness and the efficiency of the proposed GRASP.
•Design of an efficient and effective metaheuristic solution approach.•Route infeasibility management along the search through penalty objective function.•Set up and proof of some theoretical results about the compatibility among routes.•Introduction of a realistic large-sized set of benchmark instances.•Sensitivity analysis on move performances and on station capacity vs AFVs used.
Cluster analysis aims at finding subsets (clusters) of a given set of entities, which are homogeneous and/or well separated.
Starting from the 1990s, cluster analysis has been applied to several ...domains with numerous applications. It has emerged as one of the most exciting interdisciplinary fields, having benefited from concepts and theoretical results obtained by different scientific research communities, including genetics, biology, biochemistry, mathematics, and computer science.
The last decade has brought several new algorithms, which are able to solve larger sized and real-world instances. We will give an overview of the main types of clustering and criteria for homogeneity or separation. Solution techniques are discussed, with special emphasis on the combinatorial optimization perspective, with the goal of providing conceptual insights and literature references to the broad community of clustering practitioners.
A new biased random-key genetic algorithm is also described and compared with several efficient hybrid GRASP algorithms recently proposed to cluster biological data.
•Feature Selection (FS) is modelled as a (mixed) integer optimization problem.•To solve this problem, a new FS algorithm (FSA) with short memory is proposed.•This algorithm has been already ...successfully applied to life science data.•New experiments on randomly generated and real biological datasets are reported.•The results are compared w.r.t. other FSA confirming the validity of our approach.
Feature selection methods are used in machine learning and data analysis to select a subset of features that may be successfully used in the construction of a model for the data. These methods are applied under the assumption that often many of the available features are redundant for the purpose of the analysis. In this paper, we focus on a particular method for feature selection in supervised learning problems, based on a linear programming model with integer variables. For the solution of the optimization problem associated with this approach, we propose a novel robust metaheuristics algorithm that relies on a Greedy Randomized Adaptive Search Procedure, extended with the adoption of short memory and a local search strategy. The performances of our heuristic algorithm are successfully compared with those of well-established feature selection methods, both on simulated and real data from biological applications. The obtained results suggest that our method is particularly suited for problems with a very large number of binary or categorical features.
Summary The frequency of diurnal clenching and/or grinding and nail‐biting habits was assessed in patients affected by temporomandibular disorders (TMDs) and in healthy controls in order to ...investigate the possible association between these oral parafunctions and different diagnostic subgroups of TMDs. The case group included 557 patients (127 men, mean age ± SD = 34·5 ± 15·4 years; 430 women, mean age ± SD = 32·9 ± 14·1 years) affected by myofascial pain or disc displacement or arthralgia/arthritis/arthrosis. The control group included 111 healthy subjects (55 men, mean age ± SD = 37 ± 15·2 years; 56 women, mean age ± SD = 38·2 ± 13·8 years). Multinomial logistic regression analysis was used to assess the association between oral parafunctions and TMDs, after adjusting for age and gender. Daytime clenching/grinding was a significant risk factor for myofascial pain (odds ratio (OR) = 4·9, 95% confidence interval (CI): 3·0–7·8) and for disc displacement (OR = 2·5, 95% CI: 1·4–4·3), nail biting was not associated to any of the subgroups investigated. Female gender was a significant risk factor for myofascial pain (OR = 3·8; 95% CI: 2·4–6·1), whereas the risk factor for developing disc displacement decreased with ageing. No association was found between gender, age and arthralgia/arthritis/arthrosis.
The shortest path tree problem is one of the most studied problems in network optimization. Given a directed weighted graph, the aim is to find a shortest path from a given origin node to any other ...node of the graph. When any change occurs (i.e., the origin node is changed, some nodes/arcs are added/removed to/from the graph, the cost of a subset of arcs is increased/decreased), in order to determine a (still) optimal solution, two different strategies can be followed: a re-optimization algorithm is applied starting from the current optimal solution or a new optimal solution is built from scratch. Generally speaking, the Re-optimization Shortest Path Tree Problem (R-SPTP) consists in solving a sequence of shortest path problems, where the
k
th
problem differs only slightly from the
(
k
-
1
)
th
one, by exploiting the useful information available after each shortest path tree computation. In this paper, we propose an exact algorithm for the R-SPTP, in the case of origin node change. The proposed strategy is based on a dual approach, which adopts a strongly polynomial auction algorithm to extend the solution under construction. The approach is evaluated on a large set of test problems. The computational results underline that it is very promising and outperforms or at least is not worse than the solution approaches reported in the literature.
This paper studies a generalization of the shortest path tour problem with time windows (
GSPTPTW
). The aim is to find a single-origin single-destination shortest path, which has to pass through an ...ordered sequence of not necessarily disjoint node-subsets. Each node has a time window for each node-subset to which it belongs. We investigate the theoretical properties of
GSPTPTW
and propose a dynamic programming approach to solve it. Numerical results collected on a large set of new benchmark instances highlight the effectiveness of the proposed solution approach.
In the last two decades, the study of gene structure and function and molecular genetics have become some of the most prominent sub-fields of molecular biology. Computational molecular biology has ...emerged as one of the most exciting interdisciplinary fields, riding on the success of the ongoing Human Genome Project, which culminated in the 2001 announcement of the complete sequencing of the human genome. The field has currently benefited from concepts and theoretical results obtained by different scientific research communities, including genetics, biochemistry, and computer science. It is only in the past few years that it has been shown that a large number of molecular biology problems can be formulated as combinatorial optimization problems, including sequence alignment problems, genome rearrangement problems, string selection and comparison problems, and protein structure prediction and recognition. This paper provides a detailed description of some among the most interesting molecular biology problems that can be formulated as combinatorial optimization problems and proposes a new heuristic to find improved solutions for a particular class of them, known as the far from most string problem.
Solving the shortest path tour problem Festa, P.; Guerriero, F.; Laganà, D. ...
European journal of operational research,
11/2013, Volume:
230, Issue:
3
Journal Article
Peer reviewed
•We address the shortest path tour problem (SPTP).•Two innovative solution methods for the SPTP are defined and implemented.•An extensive computational phase is performed on a large class of ...instances.•A comparison with the state-of-art algorithm to solve the SPTP is also carried out.•The proposed approaches outperform remarkably the existing solving method.
In this paper, we study the shortest path tour problem in which a shortest path from a given origin node to a given destination node must be found in a directed graph with non-negative arc lengths. Such path needs to cross a sequence of node subsets that are given in a fixed order. The subsets are disjoint and may be different-sized. A polynomial-time reduction of the problem to a classical shortest path problem over a modified digraph is described and two solution methods based on the above reduction and dynamic programming, respectively, are proposed and compared with the state-of-the-art solving procedure. The proposed methods are tested on existing datasets for this problem and on a large class of new benchmark instances. The computational experience shows that both the proposed methods exhibit a consistent improved performance in terms of computational time with respect to the existing solution method.
Understanding changes of right ventricular (RV) geometry and function in repaired Tetralogy of Fallot (rToF) patients can improve decision-making for pulmonary valve replacement. Therefore, we aimed ...to assess the magnitude and clinical correlations of RV changes in rToF patients.
Clinical and MRI data of rToF patients who underwent repeated cardiac magnetic resonance imaging (MRI) at two centers between December 2003 and September 2020 were analyzed together with anatomical factors, including RV outflow tract obstruction, pulmonary artery branch stenosis, and tricuspid regurgitation. Adverse cardiac events and/or NYHA class worsening were documented and correlated with MRI changes. QRS length was reported at each MRI.
Two-hundred-and-nineteen rToF patients (53% males, aged 20.2 ± 10.1 years) were enrolled. An increase of ventricular dimensions, except LVEDVi, and worsening of right and left ejection fractions were found over an average period of 5 years of follow-up. These changes were statistically significant but within 10% of the initial value. No significant changes were reported on a year-to-year basis, except in a small group of patients (6%) in whom no predictive factors were identified. Despite similar RV dimensions at the first examination, younger patients had a higher RV ejection fraction and a different annual rate of change of ventricular dimensions compared to older ones. Patients with arrhythmias (20%) were more frequently older and had larger RV dimensions but showed no significant correlations with MRI changes/years.
Changes in RV dimensions and function occur rarely and very slowly in rToF patients. A small percentage of patients experience a significant worsening in a short time interval without any recognized risk factors. Arrhythmias appear to occur in a small percentage of cases in the late follow-up.
Presence of teeth in a newborn represents a rare finding and a disturbance of biological chronology of teeth. The aim of this paper is to report two cases with neonatal teeth histologically examined.
...In this paper two cases of patients with neonatal teeth are reported and histological examinations of three extracted teeth are described. We report an exceptional finding in one of the neonatal teeth microscopically examined: a massive inflammatory infiltration in the pulp tissue similar to that in pulpitis.
The management of natal and neonatal teeth usually includes the extraction in case of ulceration on the tongue or severe tooth mobility to prevent accidental inhalation or feeding disturbances. The presence of an inflammatory infiltration of pulp tissue in one of teeth histologically examined suggests to review the indications for extraction considered to date.
The management of natal and neonatal teeth should consider the presence of an inflammatory infiltration of pulp tissue. An anamnestic interview is advisable in ordert to deeply investigate about possible behaviours of the child due to pain or discomfort.
