18,721 research outputs found
Applications of Structural Balance in Signed Social Networks
We present measures, models and link prediction algorithms based on the
structural balance in signed social networks. Certain social networks contain,
in addition to the usual 'friend' links, 'enemy' links. These networks are
called signed social networks. A classical and major concept for signed social
networks is that of structural balance, i.e., the tendency of triangles to be
'balanced' towards including an even number of negative edges, such as
friend-friend-friend and friend-enemy-enemy triangles. In this article, we
introduce several new signed network analysis methods that exploit structural
balance for measuring partial balance, for finding communities of people based
on balance, for drawing signed social networks, and for solving the problem of
link prediction. Notably, the introduced methods are based on the signed graph
Laplacian and on the concept of signed resistance distances. We evaluate our
methods on a collection of four signed social network datasets.Comment: 37 page
Cluster Model of Decagonal Tilings
A relaxed version of Gummelt's covering rules for the aperiodic decagon is
considered, which produces certain random-tiling-type structures. These
structures are precisely characterized, along with their relationships to
various other random tiling ensembles. The relaxed covering rule has a natural
realization in terms of a vertex cluster in the Penrose pentagon tiling. Using
Monte Carlo simulations, it is shown that the structures obtained by maximizing
the density of this cluster are the same as those produced by the corresponding
covering rules. The entropy density of the covering ensemble is determined
using the entropic sampling algorithm. If the model is extended by an
additional coupling between neighboring clusters, perfectly ordered structures
are obtained, like those produced by Gummelt's perfect covering rules.Comment: 10 pages, 20 figures, RevTeX; minor changes; to be published in Phys.
Rev.
A Hybrid Genetic Algorithm for the Traveling Salesman Problem with Drone
This paper addresses the Traveling Salesman Problem with Drone (TSP-D), in
which a truck and drone are used to deliver parcels to customers. The objective
of this problem is to either minimize the total operational cost (min-cost
TSP-D) or minimize the completion time for the truck and drone (min-time
TSP-D). This problem has gained a lot of attention in the last few years since
it is matched with the recent trends in a new delivery method among logistics
companies. To solve the TSP-D, we propose a hybrid genetic search with dynamic
population management and adaptive diversity control based on a split
algorithm, problem-tailored crossover and local search operators, a new restore
method to advance the convergence and an adaptive penalization mechanism to
dynamically balance the search between feasible/infeasible solutions. The
computational results show that the proposed algorithm outperforms existing
methods in terms of solution quality and improves best known solutions found in
the literature. Moreover, various analyses on the impacts of crossover choice
and heuristic components have been conducted to analysis further their
sensitivity to the performance of our method.Comment: Technical Report. 34 pages, 5 figure
A gradient system with a wiggly energy and relaxed EDP-convergence
If gradient systems depend on a microstructure, we want to derive a
macroscopic gradient structure describing the effective behavior of the
microscopic effects. We introduce a notion of evolutionary Gamma-convergence
that relates the microscopic energy and the microscopic dissipation potential
with their macroscopic limits via Gamma-convergence. This new notion
generalizes the concept of EDP-convergence, which was introduced in
arXiv:1507.06322, and is called "relaxed EDP-convergence". Both notions are
based on De Giorgi's energy-dissipation principle, however the special
structure of the dissipation functional in terms of the primal and dual
dissipation potential is, in general, not preserved under Gamma-convergence. By
investigating the kinetic relation directly and using general forcings we still
derive a unique macroscopic dissipation potential.
The wiggly-energy model of James et al serves as a prototypical example where
this nontrivial limit passage can be fully analyzed.Comment: 43 pages, 8 figure
Size-effects of metamaterial beams subjected to pure bending: on boundary conditions and parameter identification in the relaxed micromorphic model
In this paper we model the size-effects of metamaterial beams under bending
with the aid of the relaxed micromorphic continuum. We analyze first the
size-dependent bending stiffness of heterogeneous fully discretized
metamaterial beams subjected to pure bending loads. Two equivalent loading
schemes are introduced which lead to a constant moment along the beam length
with no shear force. The relaxed micromorphic model is employed then to
retrieve the size-effects. We present a procedure for the determination of the
material parameters of the relaxed micromorphic model based on the fact that
the model operates between two well-defined scales. These scales are given by
linear elasticity with micro and macro elasticity tensors which bound the
relaxed micromorphic continuum from above and below, respectively. The micro
elasticity tensor is specified as the maximum possible stiffness that is
exhibited by the assumed metamaterial while the macro elasticity tensor is
given by standard periodic first-order homogenization. For the identification
of the micro elasticity tensor, two different approaches are shown which rely
on affine and non-affine Dirichlet boundary conditions of candidate unit cell
variants with the possible stiffest response. The consistent coupling condition
is shown to allow the model to act on the whole intended range between macro
and micro elasticity tensors for both loading cases. We fit the relaxed
micromorphic model against the fully resolved metamaterial solution by
controlling the curvature magnitude after linking it with the specimen's size.
The obtained parameters of the relaxed micromorphic model are tested for two
additional loading scenarios
Partial Strategyproofness: Relaxing Strategyproofness for the Random Assignment Problem
We present partial strategyproofness, a new, relaxed notion of
strategyproofness for studying the incentive properties of non-strategyproof
assignment mechanisms. Informally, a mechanism is partially strategyproof if it
makes truthful reporting a dominant strategy for those agents whose preference
intensities differ sufficiently between any two objects. We demonstrate that
partial strategyproofness is axiomatically motivated and yields a parametric
measure for "how strategyproof" an assignment mechanism is. We apply this new
concept to derive novel insights about the incentive properties of the
probabilistic serial mechanism and different variants of the Boston mechanism.Comment: Working Pape
Wellposedness of the discontinuous ODE associated with two-phase flows
We consider the initial value problem \dot x (t) = v(t,x(t)) \;\mbox{ for
} t\in (a,b), \;\; x(t_0)=x_0 which determines the pathlines of a two-phase
flow, i.e.\ is a given velocity field of the type with denoting the bulk phases
of the two-phase fluid system under consideration. The bulk phases are
separated by a moving and deforming interface . Since we allow for
flows with phase change, these pathlines are allowed to cross or touch the
interface. Imposing a kind of transversality condition at , which
is intimately related to the mass balance in such systems, we show existence
and uniqueness of absolutely continuous solutions of the above ODE in case the
one-sided velocity fields are continuous in and locally Lipschitz continuous in
. Note that this is a necessary prerequisite for the existence of
well-defined co-moving control volumes for two-phase flows, a basic concept for
mathematical modeling of two-phase continua
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