1,141 research outputs found
Phase growth in bistable systems with impurities
A system of coupled chaotic bistable maps on a lattice with randomly
distributed impurities is investigated as a model for studying the phenomenon
of phase growth in nonuniform media. The statistical properties of the system
are characterized by means of the average size of spatial domains of equivalent
spin variables that define the phases. It is found that the rate at which phase
domains grow becomes smaller when impurities are present and that the average
size of the resulting domains in the inhomogeneous state of the system
decreases when the density of impurities is increased. The phase diagram
showing regions where homogeneous, heterogeneous, and chessboard patterns occur
on the space of parameters of the system is obtained. A critical boundary that
separates the regime of slow growth of domains from the regime of fast growth
in the heterogeneous region of the phase diagram is calculated. The transition
between these two growth regimes is explained in terms of the stability
properties of the local phase configurations. Our results show that the
inclusion of spatial inhomogeneities can be used as a control mechanism for the
size and growth velocity of phase domains forming in spatiotemporal systems.Comment: 7 pages, 12 figure
A Multicultivar Approach for Grape Bunch Weight Estimation Using Image Analysis
The determination of bunch features that are relevant for bunch weight estimation is an
important step in automatic vineyard yield estimation using image analysis. The conversion of 2D
image features into mass can be highly dependent on grapevine cultivar, as the bunch morphology
varies greatly. This paper aims to explore the relationships between bunch weight and bunch features
obtained from image analysis considering a multicultivar approach. A set of 192 bunches from four
cultivars, collected at sites located in Portugal and South Africa, were imaged using a conventional
digital RGB camera, followed by image analysis, where several bunch features were extracted, along
with physical measurements performed in laboratory conditions. Image data features were explored
as predictors of bunch weight, individually and in a multiple stepwise regression analysis, which
were then tested on 37% of the data. The results show that the variables bunch area and visible
berries are good predictors of bunch weight (R2 ranging from 0.72 to 0.90); however, the simple
regression lines fitted between these predictors and the response variable presented significantly
different slopes among cultivars, indicating cultivar dependency. The elected multiple regression
model used a combination of four variables: bunch area, bunch perimeter, visible berry number, and
average berry area. The regression analysis between the actual and estimated bunch weight yielded a
R2 = 0.91 on the test set. Our results are an important step towards automatic yield estimation in the
vineyard, as they increase the possibility of applying image-based approaches using a generalized
model, independent of the cultivarinfo:eu-repo/semantics/publishedVersio
Phase ordering induced by defects in chaotic bistable media
The phase ordering dynamics of coupled chaotic bistable maps on lattices with
defects is investigated. The statistical properties of the system are
characterized by means of the average normalized size of spatial domains of
equivalent spin variables that define the phases. It is found that spatial
defects can induce the formation of domains in bistable spatiotemporal systems.
The minimum distance between defects acts as parameter for a transition from a
homogeneous state to a heterogeneous regime where two phases coexist The
critical exponent of this transition also exhibits a transition when the
coupling is increased, indicating the presence of a new class of domain where
both phases coexist forming a chessboard pattern.Comment: 3 pages, 3 figures, Accepted in European Physics Journa
Multimodal collaborative workgroup dataset and challenges
© 2017, CEUR-WS. All rights reserved. This work presents a multimodal dataset of 17 workgroup sessions in a collaborative learning activity. Workgroups were conformed of two or three students using a tabletop application in a co-located space. The dataset includes time-synchronized audio, video and tabletop system's logs. Some challenges were identified during the collection of the data, such as audio participation identification, and user traces identification. Future work should explore how to overcome the aforementioned difficulties
Simple Quantum Systems in Spacetimes with Closed Timelike Curves
Three simple examples illustrate properties of path integral amplitudes in
fixed background spacetimes with closed timelike curves: non-relativistic
potential scattering in the Born approximation is non-unitary, but both an
example with hard spheres and the exact solution of a totally discrete model
are unitary.Comment: 15 pages, CALT-68-180
Utilización de una nariz electrónica tipo QCM para la evaluación de la calidad aromática en pera y manzana.
The "Libra Nose" electronic nose has eight Quartz Microbalance Sensors. When gas molecules are adsorbed onto the quartz crystal surface, the oscillation frequency changes in proportion to the amount of mass. The response of sensors depends on numerous factors that may be difficult to control, such as the temperature and the humidity of the carrier gas. All these factors cause changes in the selectivity of sensors affecting the reproducibility of measurements. In this paper additive a multiplicative corrections are proposed to be applied to the raw sensors's signal in order to eliminate sources of variations. After these corrections, the sensors' response gives useful information to distinguish between batch of apples and pears with different ripeness stage
Path Integrals, Density Matrices, and Information Flow with Closed Timelike Curves
Two formulations of quantum mechanics, inequivalent in the presence of closed
timelike curves, are studied in the context of a soluable system. It
illustrates how quantum field nonlinearities lead to a breakdown of unitarity,
causality, and superposition using a path integral. Deutsch's density matrix
approach is causal but typically destroys coherence. For each of these
formulations I demonstrate that there are yet further alternatives in
prescribing the handling of information flow (inequivalent to previous
analyses) that have implications for any system in which unitarity or coherence
are not preserved.Comment: 25 pages, phyzzx, CALT-68-188
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