We propose integer-programming formulations for an optimal safety-landing site (SLS) location problem that arises in the design of urban air-transportation networks. We first develop a set-cover based approach for the case where the candidate location set is finite and composed of points, and we link the problems to solvable cases that have been studied. We then use a mixed-integer second-order cone program to model the situation where the locations of SLSs are restricted to convex sets only. Finally, we introduce strong fixing , which we found to be very effective in reducing the size of integer programs.

Abstract We present a two‐phase methodology to address the problem of optimally deploying indoor wireless local area networks. In the first phase, we use Helmholtz's equation to simulate electromagnetic fields in a typical environment such as an office floor. The linear system which results from the discretization of this partial differential equation is solved with a state‐of‐the‐art library for sparse linear algebra. In the second phase, we formulate the network deployment problem in the setting of binary linear programming. This formulation employs the simulator output as input parameters, and jointly optimizes the number of access points, their locations, and their emission channels. We prove that this optimization problem is NP‐Hard, and use mathematical programming based techniques and heuristics to solve it. We present numerical experiments on medium‐sized buildings.

The fundamental problem of distance geometry consists in finding a realization of a given weighted graph in a Euclidean space of given dimension, in such a way that vertices are realized as points and edges as straight segments having the same lengths as their given weights. This problem arises in structural proteomics, wireless sensor networks, and clock synchronization protocols to name a few applications. The well-known Isomap method is a dimensionality reduction heuristic which projects finite but high dimensional metric spaces into the "most significant" lower dimensional ones, where significance is measured by the magnitude of the corresponding eigenvalues. We start from a simple observation, namely that Isomap can also be used to provide approximate realizations of weighted graphs very efficiently, and then derive and benchmark six new heuristics.

The automated real time control of an electrical network is achieved through the estimation of its state using phasor measurement units. Given an undirected graph representing the network, we study the problem of finding the minimum number of phasor measurement units to place on the edges such that the graph is fully observed. This problem is also known as the Power Edge Set problem, a variant of the Power Dominating Set problem. It is naturally modeled using an iteration‐indexed binary linear program, whose size turns out to be too large for practical purposes. We use a fixed‐point argument to remove the iteration indices and obtain a more compact bilevel formulation. We then reformulate the latter to a single‐level mixed‐integer linear program, which performs better than the natural formulation. Lastly, we provide an algorithm that solves the bilevel program directly and much faster than a commercial solver can solve the previous models. We also discuss robust variants and extensions of the problem. © 2016 Wiley Periodicals, Inc. NETWORKS, Vol. 68(2), 104–120 2016