Hybrid evolutionary search for the traveling repairman problem with profits

The Traveling Repairman Problem with Profits is a node routing problem, where a repairman visits a subset of nodes of a weighted graph in order to maximize the collected time-dependent profits. In this work, we present the first population-based hybrid evolutionary search algorithm for solving the problem that combines: (i) a randomized greedy construction method for initial solution generation, (ii) a dedicated variable neighborhood search for local optimization, (iii) two crossover operators for solution recombination with an adaptive rule for crossover selection. Computational results on six sets of 120 benchmark instances from the literature demonstrate that the proposed algorithm achieves a high performance - it improves the best-known results (new lower bounds) for 39 instances, while matching the best-known results for the remaining cases. We investigate several main algorithmic ingredients to understand their impacts on the performance of the algorithm

Stagnation-aware breakout tabu search for the minimum conductance graph partitioning problem

The minimum conductance graph partitioning problem (MC-GPP) is to partition the vertex set of a graph into two disjoint subsets while minimizing the ratio between the number of the edges crossing the two subsets and the smallest volume of the two subsets, the volume of a vertex set being the sum of degrees of its vertices. MC-GPP has a variety of relevant applications, and however, is known to be NP-hard. In this work, we present a novel metaheuristic algorithm called “stagnation-aware breakout tabu search” for approximating MC-GPP. The algorithm combines a dedicated tabu search procedure to discover high-quality solutions and a self-adaptive perturbation procedure to overcome hard-to-escape local optimum traps. We perform extensive evaluations of the algorithm on five datasets of 110 benchmark instances in the literature. The key components of the proposed algorithm are analyzed to illustrate their influences on the performance of the algorithm

The Use of Dispersion Relations in the ππ\pi\pi and KKˉK\bar K Coupled-Channel System

Systematic and careful studies are made on the properties of the IJ=00 $\pi\pi$ and $K\bar K$ coupled-channel system, using newly derived dispersion relations between the phase shifts and poles and cuts. The effects of nearby branch point singularities to the determination of the $f_0(980)$ resonance are estimated and and discussed.Comment: 22 pages with 5 eps figures. A numerical bug in previous version is fixed, discussions slightly expanded. No major conclusion is change

Controlling the direction, topological charge, and spectrum of transition radiation with holographic metasurfaces

We show experimentally that wavefront - the direction, spectral composition and phase profile of light emission - stimulated by free electron injection into plasmonic and dielectric media can be controlled with high finesse using holographic nanostructures

The friction reducing effect of square-shaped surface textures under lubricated line-contacts - an experimental study

Surface texturing has been shown to be an effective modification approach for improving tribological performance. This study examined the friction reduction effect generated by square dimples of different sizes and geometries. Dimples were fabricated on the surface of ASP2023 steel plates using femtosecond laser-assisted surface texturing techniques, and reciprocating sliding line contact tests were carried out on a Plint TE77 tribometer using a smooth 52100 bearing steel roller and textured ASP2023 steel plates. The tribological characterization of the friction properties indicated that the textured samples had significantly lowered the friction coefficient in both boundary (15% improvement) and mixed lubrication regimes (13% improvement). Moreover, the high data sampling rate results indicated that the dimples work as lubricant reservoirs in the boundary lubrication regim

X-wave mediated instability of plane waves in Kerr media

Plane waves in Kerr media spontaneously generate paraxial X-waves (i.e. non-dispersive and non-diffractive pulsed beams) that get amplified along propagation. This effect can be considered a form of conical emission (i.e. spatio-temporal modulational instability), and can be used as a key for the interpretation of the out of axis energy emission in the splitting process of focused pulses in normally dispersive materials. A new class of spatio-temporal localized wave patterns is identified. X-waves instability, and nonlinear X-waves, are also expected in periodical Bose condensed gases.Comment: 4 pages, 6 figure