130,794 research outputs found
Una tesis doctoral sobre temas históricos, defendida en la Facultad de Derecho, en la Argentina del Centenario
No full textFil: Cattaruzza, Alejandro. Universidad de Buenos Aires. Facultad de Filosofía y Letras. Buenos Aires, ArgentinaFil: Cattaruzza, Alejandro. CONICET - Universidad de Buenos Aires. Instituto de Historia Argentina y Americana Dr. Emilio Ravignani. Buenos Aires, ArgentinaEstudio preliminar que acompaña la edición electrónica de la tesis del Dr. Emilio Ravignani "Las finanzas argentinas desde 1810 a 1829" publicada por el Instituto de Historia Argentina y Americana Dr. Emilio Ravignani. \nCorresponde al número 1 de la serie Las Tesis del Ravignani
CRONIN EFFECT AND ENERGY CONSERVATION CONSTRAINTS IN HIGH-ENERGY PROTON NUCLEUS COLLISIONS
No full textAbstract: We estimate the Cronin effect in pA collisions at the CERN LHC and at the BNL RHIC, using a Glauber-eikonal model of initial state multiparton interactions. For a correct determination of the initial parton flux, we upgrade the model cross section, taking carefully into account all kinematical constraints of each multiparton interaction process. As compared with previous results, derived with approximate kinematics, we obtain a softer spectrum of produced partons, while improving the agreement of the model with the recent measurements of pi(0) production in d+Au collisions at roots=200A GeV
The Multi-Trip Vehicle Routing Problem with Time Windows and Release Dates
No full textThe multi-trip vehicle routing problem with time windows and release dates is a variant of the multi-trip vehicle routing problem where a time window and a release date are associated with each customer. The release date represents the date when the merchandise requested by a customer becomes available at the depot. The interest for this problem comes from the field of city logistics and the study of delivery systems involving City Distribution Centers (CDC). In these systems, goods are first delivered to a CDC before being transferred to eco-friendly vehicles for final delivery. We propose to address the problem through a population-based algorithm, with a giant tour representation for individuals. An efficient labeling procedure allows turning giant tours into solutions. Experiments demonstrate the effectiveness of the method
Vehicle routing problems with multiple trips
No full textThis paper presents a survey on the multi-trip vehicle routing problem (MTVRP) and on related routing problems where vehicles are allowed to perform multiple trips. The first part of the paper focuses on the MTVRP. It gives an unified view on mathematical formulations and surveys exact and heuristic approaches. The paper continues with variants of the MTVRP and other families of routing problems where multiple trips are sometimes allowed. For the latter, it specially insists on the motivations for having multiple trips and the algorithmic consequences. The expected contribution of the survey is to give a comprehensive overview on a structural property of routing problems that has seen a strongly growing interest in the last few years and that has been investigated in very different areas of the routing literature
A column generation based heuristic for the generalized vehicle routing problem with time windows
No full textThe generalized vehicle routing problem with time windows (GVRPTW) is defined on a directed graph G=(V,A) where the vertex set V is partitioned into clusters. One cluster contains only the depot, where is located a homogeneous fleet of vehicles, each with a limited capacity. The other clusters represent customers. A demand is associated with each cluster. Inside a cluster, the vertices represent the possible locations of the customer. A time window is associated with each vertex, during which the visit must take place if the vertex is visited. The objective is to find a set of routes such that the total traveling cost is minimized, exactly one vertex per cluster is visited, and all the capacity and time constraints are respected. This paper presents a set covering formulation for the GVRPTW which is used to provide a column generation based heuristic to solve it. The proposed solving method combines several components including a construction heuristic, a route optimization procedure, local search operators and the generation of negative reduced cost routes. Experimental results on benchmark instances show that the proposed algorithm is efficient and high-quality solutions for instances with up to 120 clusters are obtained within short computation times
Playing with the enveloping algebra of supersymmetry
No full textIn this paper we show how to obtain from a scalar superfield its first component via a similarity transformation. We prove that in the generators of this similarity transformation live in the enveloping algebra of supersymmetry while for they belong to the basic algebra
The storage location assignment and picker routing problem: A generic branch-cut-and-price algorithm
No full textThe Storage Location Assignment Problem (SLAP) and the Picker Routing Problem (PRP) have received significant attention in the literature due to their pivotal role in the performance of the Order Picking (OP) activity, the most resource-intensive process of warehousing logistics. The two problems are traditionally considered at different decision-making levels: tactical for the SLAP, and operational for the PRP. However, this paradigm has been challenged by the emergence of modern practices in e-commerce warehouses, where decisions are more dynamic. This shift makes the integrated problem, called the Storage Location Assignment and Picker Routing Problem (SLAPRP), pertinent to consider. Scholars have investigated several variants of the SLAPRP, including different warehouse layouts and routing policies. Nevertheless, the available computational results suggest that each variant requires an ad-hoc formulation. Moreover, achieving a complete integration of the two problems, where the routing is solved optimally, remains out of reach for commercial solvers, even on trivial instances. In this paper, we propose an exact solution framework that addresses a broad class of variants of the SLAPRP, including all the previously existing ones. This paper proposes a Branch-Cut-and-Price framework based on a novel formulation with an exponential number of variables, which is strengthened with a novel family of non-robust valid inequalities. We have developed an ad-hoc branching scheme to break symmetries and maintain the size of the enumeration tree manageable. Computational experiments show that our framework can effectively solve medium-sized instances of several SLAPRP variants and outperforms the state-of-the-art methods from the literature
An Iterated Local Search for the Multi Commodity Multi Trip Vehicle Routing Problem with Time Windows
No full textThe Multi-Commodity Multi-Trip Vehicle Routing Problem with Time Windows calls for the determination of a routing planning to serve a set of customers that require products belonging to incompatible commodities. Two commodities are incompatible if they cannot be transported together into the same vehicle. Vehicles are allowed to perform several trips during the working day. The objective is to minimize the number of used vehicles.
We propose an Iterated Local Search that outperforms the previous algorithm designed for the problem. Moreover, we conduct an analysis on the benefit that can be obtained introducing the multi-trip aspect at the fleet dimensioning level. Results on classical VRPTW instances show that, in some cases, the fleet can be halved
A note on the complexity of the picker routing problem in multi-block warehouses and related problems
No full textThe Picker Routing Problem (PRP), which consists of finding a minimum-length tour between a set of storage locations in a warehouse, is one of the most important problems in the warehousing logistics literature. Despite its popularity, the tractability of the PRP in multi-block warehouses remains an open question. This technical note aims to fill this research gap by establishing that the problem is strongly NP-hard. As a corollary, the complexity status of other related problems is settled
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