Vehicle Routing Problems have been extensively analyzed to reduce transportation costs. More particularly, the Vehicle Routing Problem with Time Windows (VRPTW) imposes the period of time of customer availability as a constraint, a common characteristic in real world situations. Using minimization of the total distance as the main objective to be fulfilled, this work implements an efficient algorithm which associates non-monotonic Simulated Annealing to Hill-Climbing and Random Restart. The algorithm is compared to the best results published in the literature for the 56 Solomon instances and it is shown how statistical methods can be used to boost the performance of the method.Keywords Vehicle routing problems · Hybrid systems · Optimization · Simulated annealing Costs with goods transportation have been calling a special attention in the last decades, since logistic expenses minimization is a big concern for many companies. The costs related to people and goods transportation are very significant and are growing rapidly, motivated by the continuing increase of business complexity experienced today (Alvarenga and Mateus 2004). Studies suggest that from 10% to 15% of the final value of the traded goods correspond to its transportation cost (King and Mast 1997). Many studies found in the literature of the Vehicle Routing Problem (VRP) have attempted to contribute to practical advances in this field (Bräysy and Gendreau 2001a;Bräysy et al. 2004). Since in the real world this problem has to consider many constraints and particularities, some parameters have to be considered for a closer approximation to the market situations. One of such constraints is the load capacity of the vehicle and other is the time window within which the customers
Bioisosterism is a technique used in medicinal chemistry to optimize lead compounds in drug research. One can replace a substituent group in original molecule by another with similar physical chemistry properties and then test how this replacement affects biological activity. To help researchers in their bioisosteric replacement choose, computational efforts such as programs and databases was developed. In this article, it is presented MB-Isoster, a software that draws bioisosteric molecules. Starting from an input molecule, user selects a molecular subregion formed by connected atoms to be replaced and MB-Isoster queries an internal library to find bioisosteric substituents for selected subregion, and makes the bioisosteres. Another functionality is receptor-ligand pdb complex reading, in which nonbonded interactions are computed between receptor and ligand in a pdb file, helping in atom/subregion selection to bioisosteric replacement. Physical-chemical properties computing, and virtual screening evaluation is also available. MB-Isoster is freely available at
Vehicle Routing Problems have been analyzed to reduce transportation costs of people and goods. More particularly, the Vehicle Routing Problem with Time Windows (VRPTW) imposes the period of time of customer availability as a constraint, a very common characteristic in real world picking up and delivery problems. Using minimization of the total distance as the main objective to be fulfilled, this work implements an efficient hybrid system which associates a nonmonotonic Simulated Annealing technique to a Hill Climbing Strategy with Random Restart (Multi-Start). The algorithm performance is evaluated by comparing the results achieved with the best published works found in the literature of the 56 Solomon instances. The results outperformed or paired the individual best previous results in 36 out of the 56 instances.
In the last years, the Vehicle Routing Problem (VRP) has been receiving increasing a special attention due its importance in the distribution of products. Considering demands that can appear during the service day, this work solves the Dynamic VRP (DVRP) with support of the environment simulator, capable to emulate the behavior of the vehicular fleet in a geographic 2D space. This work presents two main contributions: (i) the environment simulator that can be used to standardize DVRP test cases; and (ii) a Vehicular Waiting Time Heuristic (VWTH), that delays the attendance of demand with the meaning of reducing the total distance traveled by vehicular fleet. The proposed heuristic is tested by four optimization algorithms (Simulated Annealing, GRASP, Memetic Algorithm and Hill Climbing), and submitted to statistical tests for better conclusions. The tests showed, with 95% of confidence, that the VWTH is able to improve significantly the metaheuristics results.
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