5,090 research outputs found
Quantifying structure in networks
We investigate exponential families of random graph distributions as a
framework for systematic quantification of structure in networks. In this paper
we restrict ourselves to undirected unlabeled graphs. For these graphs, the
counts of subgraphs with no more than k links are a sufficient statistics for
the exponential families of graphs with interactions between at most k links.
In this framework we investigate the dependencies between several observables
commonly used to quantify structure in networks, such as the degree
distribution, cluster and assortativity coefficients.Comment: 17 pages, 3 figure
Derivative pricing under the possibility of long memory in the supOU stochastic volatility model
We consider the supOU stochastic volatility model which is able to exhibit
long-range dependence. For this model we give conditions for the discounted
stock price to be a martingale, calculate the characteristic function, give a
strip where it is analytic and discuss the use of Fourier pricing techniques.
Finally, we present a concrete specification with polynomially decaying
autocorrelations and calibrate it to observed market prices of plain vanilla
options
Ătude expĂ©rimentale de la formulation de mortier a base de sable silteux du Togo et de liant de sachets plastiques type « voltic »
La prĂ©sente Ă©tude est destinĂ©e Ă valoriser les dĂ©chets plastiques par la recherche dâune formule optimale de mortier Ă base de sable silteux du Togo et de sachets plastiques fondus du type « voltic » offrant des propriĂ©tĂ©s mĂ©caniques optimales. Trente six (36) Ă©chantillons de mortier Ă base de mĂ©lange de sable silteux et de liant de sachets plastiques Ă des dosages variant de 7% Ă 28% ont Ă©tĂ© prĂ©parĂ©s et soumis aux essais physiques et mĂ©caniques aprĂšs imbibition ou non dans de lâeau. Il ressort des rĂ©sultats que le dosage en liant de sachets plastiques offrant de rĂ©sistance optimale en compression (Ïc), au fendage (Ïd), en traction par flexion (Ïf) et par fendage (Ïd) varient de 16% Ă 22% avec des rĂ©sistances Ă la rupture respectives dâenviron 10,3 MPa (Ă 22%), 2,2 MPa (Ă 16%), 5,3 MPa (Ă 18%) et 1,4 MPa (Ă 16%). Le matĂ©riau prĂ©sente des modules dâĂ©lasticitĂ© en compression (Ec), en flexion (Ef) et au fendage (Gd) respectivement dâenviron 3 800 MPa, 700 MPa et 60 MPa pour des taux de liants de 22%. Pour de faibles taux de liants (8 Ă 10%), la densitĂ© du mortier et son absorption dâeau (en masse) sont optimales (respectivement de 1,95% et 0,29%). Cette absorption dâeau est nulle pour les teneurs en liant supĂ©rieures Ă 18% montrant le comportement Ă©tanche des mortiers. Les mortiers peuvent donc ĂȘtre utilisĂ©s pour les travaux de pavages, dâĂ©tanchement des toitures et de murs pour des taux de liants compris entre 18 Ă 22%.Mots-clĂ©s : mortier, sachets plastiques, sable silteux, eau, propriĂ©tĂ©s physico-mĂ©caniques
Alona kaingang (Crustacea, Cladocera, Aloninae): a new species of the pulchella-group, with identification key to Neotropical species
A Hybrid Approach for Aspect-Based Sentiment Analysis Using Deep Contextual Word Embeddings and Hierarchical Attention
The Web has become the main platform where people express their opinions
about entities of interest and their associated aspects. Aspect-Based Sentiment
Analysis (ABSA) aims to automatically compute the sentiment towards these
aspects from opinionated text. In this paper we extend the state-of-the-art
Hybrid Approach for Aspect-Based Sentiment Analysis (HAABSA) method in two
directions. First we replace the non-contextual word embeddings with deep
contextual word embeddings in order to better cope with the word semantics in a
given text. Second, we use hierarchical attention by adding an extra attention
layer to the HAABSA high-level representations in order to increase the method
flexibility in modeling the input data. Using two standard datasets (SemEval
2015 and SemEval 2016) we show that the proposed extensions improve the
accuracy of the built model for ABSA.Comment: Accepted for publication in the 20th International Conference on Web
Engineering (ICWE 2020), Helsinki Finland, 9-12 June 202
The application of the Raman Spectroscopy Method for Evaluating Implants from the Dura Mater
The results of a comparative spectral evaluation of the component composition of the surfaces of implants from the dura mater manufactured using the Lioplast technology with the use of ultrasound and sterilization are presented. Based on the analysis, coefficients were introduced reflecting the change in the relative concentration of components that determine the quality of the implants. It is established that Raman spectroscopy can be used to assess the change in the composition of implants based on the dura mater during their manufacture.
Keywords: Raman spectroscopy, coefficients, spectral features, implants, dura mater
A Theory of Cheap Control in Embodied Systems
We present a framework for designing cheap control architectures for embodied
agents. Our derivation is guided by the classical problem of universal
approximation, whereby we explore the possibility of exploiting the agent's
embodiment for a new and more efficient universal approximation of behaviors
generated by sensorimotor control. This embodied universal approximation is
compared with the classical non-embodied universal approximation. To exemplify
our approach, we present a detailed quantitative case study for policy models
defined in terms of conditional restricted Boltzmann machines. In contrast to
non-embodied universal approximation, which requires an exponential number of
parameters, in the embodied setting we are able to generate all possible
behaviors with a drastically smaller model, thus obtaining cheap universal
approximation. We test and corroborate the theory experimentally with a
six-legged walking machine. The experiments show that the sufficient controller
complexity predicted by our theory is tight, which means that the theory has
direct practical implications. Keywords: cheap design, embodiment, sensorimotor
loop, universal approximation, conditional restricted Boltzmann machineComment: 27 pages, 10 figure
Defect loops in gauged Wess-Zumino-Witten models
We consider loop observables in gauged Wess-Zumino-Witten models, and study
the action of renormalization group flows on them. In the WZW model based on a
compact Lie group G, we analyze at the classical level how the space of
renormalizable defects is reduced upon the imposition of global and affine
symmetries. We identify families of loop observables which are invariant with
respect to an affine symmetry corresponding to a subgroup H of G, and show that
they descend to gauge-invariant defects in the gauged model based on G/H. We
study the flows acting on these families perturbatively, and quantize the fixed
points of the flows exactly. From their action on boundary states, we present a
derivation of the "generalized Affleck-Ludwig rule, which describes a large
class of boundary renormalization group flows in rational conformal field
theories.Comment: 43 pages, 2 figures. v2: a few typos corrected, version to be
published in JHE
RoboCup 2D Soccer Simulation League: Evaluation Challenges
We summarise the results of RoboCup 2D Soccer Simulation League in 2016
(Leipzig), including the main competition and the evaluation round. The
evaluation round held in Leipzig confirmed the strength of RoboCup-2015
champion (WrightEagle, i.e. WE2015) in the League, with only eventual finalists
of 2016 competition capable of defeating WE2015. An extended, post-Leipzig,
round-robin tournament which included the top 8 teams of 2016, as well as
WE2015, with over 1000 games played for each pair, placed WE2015 third behind
the champion team (Gliders2016) and the runner-up (HELIOS2016). This
establishes WE2015 as a stable benchmark for the 2D Simulation League. We then
contrast two ranking methods and suggest two options for future evaluation
challenges. The first one, "The Champions Simulation League", is proposed to
include 6 previous champions, directly competing against each other in a
round-robin tournament, with the view to systematically trace the advancements
in the League. The second proposal, "The Global Challenge", is aimed to
increase the realism of the environmental conditions during the simulated
games, by simulating specific features of different participating countries.Comment: 12 pages, RoboCup-2017, Nagoya, Japan, July 201
A Rydberg Quantum Simulator
Following Feynman and as elaborated on by Lloyd, a universal quantum
simulator (QS) is a controlled quantum device which reproduces the dynamics of
any other many particle quantum system with short range interactions. This
dynamics can refer to both coherent Hamiltonian and dissipative open system
evolution. We investigate how laser excited Rydberg atoms in large spacing
optical or magnetic lattices can provide an efficient implementation of a
universal QS for spin models involving (high order) n-body interactions. This
includes the simulation of Hamiltonians of exotic spin models involving
n-particle constraints such as the Kitaev toric code, color code, and lattice
gauge theories with spin liquid phases. In addition, it provides the
ingredients for dissipative preparation of entangled states based on
engineering n-particle reservoir couplings. The key basic building blocks of
our architecture are efficient and high-fidelity n-qubit entangling gates via
auxiliary Rydberg atoms, including a possible dissipative time step via optical
pumping. This allows to mimic the time evolution of the system by a sequence of
fast, parallel and high-fidelity n-particle coherent and dissipative Rydberg
gates.Comment: 8 pages, 4 figure
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