5,929 research outputs found
A branch and cut algorithm for hub location problems with single assignment
The hub location problem with single assignment is the problem of locating hubs and assigning the terminal nodes to hubs in order to minimize the cost of hub installation and the cost of routing the traffic in the network. There may also be capacity restrictions on the amount of traffic that can transit by hubs. The aim of this paper is to investigate polyhedral properties of these problems and to develop a branch and cut algorithm based on these results. © Springer-Verlag 2004
Solving the Uncapacitated Single Allocation p-Hub Median Problem on GPU
A parallel genetic algorithm (GA) implemented on GPU clusters is proposed to
solve the Uncapacitated Single Allocation p-Hub Median problem. The GA uses
binary and integer encoding and genetic operators adapted to this problem. Our
GA is improved by generated initial solution with hubs located at middle nodes.
The obtained experimental results are compared with the best known solutions on
all benchmarks on instances up to 1000 nodes. Furthermore, we solve our own
randomly generated instances up to 6000 nodes. Our approach outperforms most
well-known heuristics in terms of solution quality and time execution and it
allows hitherto unsolved problems to be solved
Survivability in hierarchical telecommunications networks under dual homing
Cataloged from PDF version of article.The motivation behind this study is the essential need for survivability in the telecommunications networks.
An optical signal should find its destination even if the network experiences an occasional fiber cut. We consider
the design of a two-level survivable telecommunications network. Terminals compiling the access layer
communicate through hubs forming the backbone layer. To hedge against single link failures in the network,
we require the backbone subgraph to be two-edge connected and the terminal nodes to connect to the backbone
layer in a dual-homed fashion, i.e., at two distinct hubs. The underlying design problem partitions a given
set of nodes into hubs and terminals, chooses a set of connections between the hubs such that the resulting
backbone network is two-edge connected, and for each terminal chooses two hubs to provide the dual-homing
backbone access. All of these decisions are jointly made based on some cost considerations. We give alternative
formulations using cut inequalities, compare these formulations, provide a polyhedral analysis of the smallsized
formulation, describe valid inequalities, study the associated separation problems, and design variable
fixing rules. All of these findings are then utilized in devising an efficient branch-and-cut algorithm to solve
this network design problem
Star p-hub median problem with modular arc capacities
Cataloged from PDF version of article.We consider the hub location problem, where p hubs are chosen from a given set of nodes, each nonhub node is connected to
exactly one hub and each hub is connected to a central hub. Links are installed on the arcs of the resulting network to route the traffic.
The aim is to find the hub locations and the connections to minimize the link installation cost.We propose two formulations and a
heuristic algorithm to solve this problem. The heuristic is based on Lagrangian relaxation and local search.We present computational
results where formulations are compared and the quality of the heuristic solutions are tested.
2007 Elsevier Ltd. All rights reserved
Regenerator Location Problem and survivable extensions: A hub covering location perspective
Cataloged from PDF version of article.In a telecommunications network the reach of an optical signal is the maximum distance it can traverse before its quality degrades. Regenerators are devices to extend the optical reach. The regenerator placement problem seeks to place the minimum number of regenerators in an optical network so as to facilitate the communication of a signal between any node pair. In this study, the Regenerator Location Problem is revisited from the hub location perspective directing our focus to applications arising in transportation settings. Two new dimensions involving the challenges of survivability are introduced to the problem. Under partial survivability, our designs hedge against failures in the regeneration equipment only, whereas under full survivability failures on any of the network nodes are accounted for by the utilization of extra regeneration equipment. All three variations of the problem are studied in a unifying framework involving the introduction of individual flow-based compact formulations as well as cut formulations and the implementation of branch and cut algorithms based on the cut formulations. Extensive computational experiments are conducted in order to evaluate the performance of the proposed solution methodologies and to gain insights from realistic instances. (C) 2014 Elsevier Ltd. All rights reserved
Network hub locations problems: the state of the art
Cataloged from PDF version of article.Hubs are special facilities that serve as switching, transshipment and sorting points in many-to-many distribution systems. The hub location problem is concerned with locating hub facilities and allocating demand nodes to hubs in order to route the traffic between origin-destination pairs. In this paper we classify and survey network hub location models. We also include some recent trends on hub location and provide a synthesis of the literature. (C) 2007 Elsevier B.V. All rights reserved
A new formulation and branch-and-cut method for single-allocation hub location problems
A new compact formulation for uncapacitated single-allocation hub location problems with fewer variables than the previous Integer Linear Programming formulations in the literature is introduced. Our formulation works even with costs not based on distances and not satisfying triangle inequality. Moreover, costs can be given in aggregated or disaggregated way. Different families of valid inequalities that strengthen the formulation are developed and a branch-and-cut algorithm based on a relaxed version of the formulation is designed, whose restrictions are inserted in a cut generation procedure together with two sets of valid inequalities. The performance of the proposed methodology is tested on well-known hub location data sets and compared to the most recent and efficient exact algorithms for single-allocation hub location problems. Extensive computational results prove the efficiency of our methodology, that solves large-scale instances in very competitive times
Air Taxi Skyport Location Problem for Airport Access
Witnessing the rapid progress and accelerated commercialization made in
recent years for the introduction of air taxi services in near future across
metropolitan cities, our research focuses on one of the most important
consideration for such services, i.e., infrastructure planning (also known as
skyports). We consider design of skyport locations for air taxis accessing
airports, where we present the skyport location problem as a modified
single-allocation p-hub median location problem integrating choice-constrained
user mode choice behavior into the decision process. Our approach focuses on
two alternative objectives i.e., maximizing air taxi ridership and maximizing
air taxi revenue. The proposed models in the study incorporate trade-offs
between trip length and trip cost based on mode choice behavior of travelers to
determine optimal choices of skyports in an urban city. We examine the
sensitivity of skyport locations based on two objectives, three air taxi
pricing strategies, and varying transfer times at skyports. A case study of New
York City is conducted considering a network of 149 taxi zones and 3 airports
with over 20 million for-hire-vehicles trip data to the airports to discuss
insights around the choice of skyport locations in the city, and demand
allocation to different skyports under various parameter settings. Results
suggest that a minimum of 9 skyports located between Manhattan, Queens and
Brooklyn can adequately accommodate the airport access travel needs and are
sufficiently stable against transfer time increases. Findings from this study
can help air taxi providers strategize infrastructure design options and
investment decisions based on skyport location choices.Comment: 25 page
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