1,492 research outputs found
Random Walk Access Times on Partially-Disordered Complex Networks: an Effective Medium Theory
An analytic effective medium theory is constructed to study the mean access
times for random walks on hybrid disordered structures formed by embedding
complex networks into regular lattices, considering transition rates that
are different for steps across lattice bonds from the rates across network
shortcuts. The theory is developed for structures with arbitrary shortcut
distributions and applied to a class of partially-disordered traversal enhanced
networks in which shortcuts of fixed length are distributed randomly with
finite probability. Numerical simulations are found to be in excellent
agreement with predictions of the effective medium theory on all aspects
addressed by the latter. Access times for random walks on these partially
disordered structures are compared to those on small-world networks, which on
average appear to provide the most effective means of decreasing access times
uniformly across the network.Comment: 12 pages, 8 figures; added new results and discussion; added appendix
on numerical procedures. To appear in PR
Analysis of the start to the first hurdle in 110m hurdles at the IAAF World Athletics Championships Beijing 2015
The purpose of this study was to use observational analysis to evaluate the relationships between variables
measured at the start of the men’s 110 hurdles event and race performance itself. Data were obtained for
competitors in 2015 IAAF World Athletics Ch
ampionships, in Beijing, China. The athletes’ start was quantified
by reaction time and time to the first hurdle; their action over the first hurdle was quantified by the take
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off
distance (i.e., the distance from the last step to the first hurdle), the la
nding distance, and the total distance
in the air over the first hurdle. Regression analyses revealed that the combination of one measure of the start
(either reaction time or time to the first hurdle) and the measure of propulsion over the first hurdle (d
istance
in air over the first hurdle) predicted performance (SEE = 0.23 s in the heats, SEE = 0.16 s in the semi
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finals,
SEE = 0.09 s in the finals). In addition, looking at performances in the finals, where all athletes with available
data used a seven
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st
ep approach to the first hurdle, inclusion of stride length data improved the prediction
somewhat (SEE = 0.07 s). The results demonstrate that a combination of a fast start, rapid acceleration, and
strong drive over the first hurdle quantifiably explains a
nd contributes to performance in the men’s 110 m hurdles at the highest level
Rediscovery of the poorly known lichen-mantis Pogonogaster tristani Rehn, 1918 (MANTODEA: THESPIDAE, OLIGONICINAE) in Costa Rica and ecological notes
En el presente trabajo se divulga el redescubrimiento de la poco conocida mantisliquen Pogonogaster tristani Rehn, 1918 para una nueva localidad en Costa Rica, después de 96 años en ser descrita. Se incluyen notas relativas a la diagnosis de la especie, el conocimiento del macho, el hábitat natural y comportamiento.In this paper the rediscovery of the little known Lichen-Mantis Pogonogaster tristani Rehn, 1918 from a new location in Costa Rica, 96 years of being described, is published. Notes concerning the diagnosis of the species, knowledge of the male, the natural habitat and behavior are included
Desarrollo de un métode para identificación de guantes con policloruro de vinilo (pvc)
En un cuerpo hallado en una casa, en las cavidades de la oreja se encontraron ``motas'' plásticas provenientes de guantes
de algodón moteados. Asimismo, se encontraron motas del mismo tipo en los alrededores del cuerpo. En la casa de un sospechoso, se
encontraron guantes a los cuales les faltaban algunas motas. La pregunta es si podemos evaluar si los guantes hallados en la casa del
sospechoso tienen un origen común con las motas encontradas en la escena del crimen. Se hizo un estudio comparativo de los
diferentes tipos de PVC utilizados para hacer guantes moteados, utilizando diferentes guantes habituales en el mercado. Se evalúa la
capacidad discriminatoria del análisis químico por la técnica de EDS (utilizando un SEM) y térmico con técnicas calorimétricas
(DSC). Se analizan además las características morfológicas y cómo varían las texturas dependiendo del proceso de fabricación.
Finalmente, se sugiere una secuencia de análisis para hacer la identificación del plástico, de manera de ir confirmando
progresivamente la posibilidad de un origen común. La secuencia implica realizar estudios progresivamente más complejos. La
utilidad de este esquema es poder detenerse a tiempo en el caso de que la incompatibilidad de las fuentes esté demostrada. Esto
permite reducir costos y evitar la redundancia.In the ears of a corpse found in a house, were found PVC dots of the kind present in a common type of cotton gardening
gloves. These dots were also found in the area surrounding the corpse. On the other hand, cotton gardening gloves whith some PVC
dots missing were found at the house of a suspect. The question raised was whether it could be ascertained if the gloves found at the
suspect's house had a common origin with the PVC dots found at the crime scene. A comparative study was made of different kinds
of PVC used for manufacturing cotton gardening gloves, using different gloves available on the market. The discrimination capacity
of the techniques used for chemical and thermal analysis, using EDS (with a SEM) and DSC, was analyzed. The morphological and
texture characteristics depending on the fabrication process were also analyzed. An sequence of analyses is suggested for
indentifying the plastics, in a way such that the common origin is progressively confirmed. The sequence implies the realization of
studies of increasing complexity. The usefulness of this scheme is the feature it offers of stopping the tests in cases when the
incompatibility of the samples has already been demonstrated. This reduces both costs and time spent on the analyses, avoiding
redundant studies
Equivariant imaging: Learning beyond the range space
In various imaging problems, we only have access to compressed measurements
of the underlying signals, hindering most learning-based strategies which
usually require pairs of signals and associated measurements for training.
Learning only from compressed measurements is impossible in general, as the
compressed observations do not contain information outside the range of the
forward sensing operator. We propose a new end-to-end self-supervised framework
that overcomes this limitation by exploiting the equivariances present in
natural signals. Our proposed learning strategy performs as well as fully
supervised methods. Experiments demonstrate the potential of this framework on
inverse problems including sparse-view X-ray computed tomography on real
clinical data and image inpainting on natural images. Code will be released.Comment: Technical repor
Sensing Theorems for Unsupervised Learning in Linear Inverse Problems
International audienceSolving an ill-posed linear inverse problem requires knowledge about the underlying signal model. In many applications, this model is a priori unknown and has to be learned from data. However, it is impossible to learn the model using observations obtained via a single incomplete measurement operator, as there is no information about the signal model in the nullspace of the operator, resulting in a chicken-and-egg problem: to learn the model we need reconstructed signals, but to reconstruct the signals we need to know the model. Two ways to overcome this limitation are using multiple measurement operators or assuming that the signal model is invariant to a certain group action. In this paper, we present necessary and sufficient sensing conditions for learning the signal model from measurement data alone which only depend on the dimension of the model and the number of operators or properties of the group action that the model is invariant to. As our results are agnostic of the learning algorithm, they shed light into the fundamental limitations of learning from incomplete data and have implications in a wide range set of practical algorithms, such as dictionary learning, matrix completion and deep neural networks
Advertising regulation in the new consumer statute. Implications from the contract theory standpoint
En la contratación masiva contemporánea, el acercamiento entre los productores y/o proveedores de bienes y servicios y los consumidores se hace mayoritariamente a través de la publicidad. Dicha publicidad contiene elementos de información dirigidos al público, que pretenden modificar sus decisiones de consumo, por lo que se permite la inclusión de “elogios subjetivos del anunciante”. Frente a esta situación se plantean dos interrogantes: ¿lo que se dice en la publicidad vincula al anunciante? Y en caso de que la publicidad sea engañosa ¿qué consecuencias jurídicas se derivan de ello? Las respuestas a estos dos interrogantes varían según la naturaleza de la relación jurídica que exista entre las partes, la cual puede ser civil, mercantil o de consumo.In the contemporary mass hiring, the rapprochement between producers and/or suppliers of goods and services and the consumers is achieved mainly through advertising. This advertising has information elements aimed at the audience that intend to modify their consumption decisions, that is why the inclusion of “subjective compliments by the advertiser” is allowed. Two questions arise from this situation: does what is said in the advertisements bind the advertiser? And in the case the advertisements are actually misleading, what juridical consequences branch out from that? The answers to these two questions vary according to the nature of the juridical relation existing between the parties, which can be civil, commercial or of consumption
Tin oxide preparation and characterization and use as a catalyst in the reaction of unsaturated fatty esters epoxidation
La síntesis y la caracterización del óxido de estaño se estudiaron en este trabajo para evaluar su actividad catalítica en
la reacción de epoxidación del metilricinoleato proveniente del aceite de ricino. La obtención del óxido se realiza por
el método de precipitación controlada, encontrándose que se obtienen ventajas significativas al emplear soluciones
acuosas de SnCl2.2H2O como precursor. Su caracterización se efectuó por medio de las técnicas de DTA, TGA, DRX,
encontrándose que para obtener un alto rendimiento hacia el sistema casiterita el valor de pH óptimo fue de 6.25,
mientras que un pH de 8.0 conlleva hacia el sistema romarchita. En el caso de las técnicas de MEB y área superficial,
se determinó que el tamaño de partícula encontrado estaba por debajo de los 50 nm con un área superficial de 19 m2/g.
El ester ricinoleico se obtuvo a partir del aceite empleando metilato de sodio como catalizador y seguidamente se hace
reaccionar con peróxido de hidrógeno como agente oxidante y óxido de estaño para producir un epóxido. Finalmente,
los productos de reacción se identifican por cromatografía de gases, encontrando que los óxidos de estaño son activos
para la obtención de epóxidos con un mejor desempeño del sistema cristalino romarchita (SnO) principalmente hacia
el metil-12-hidroxi-9,10-epoxioctadecanoato (MHEOD). Abstract
Tin oxide synthesis and characterization were studied in the present work in order to evaluate its catalytic activity
in the reaction of methyl ricinoleate from castor oil. Oxide is obtained through the controlled precipitation method,
and significant advantages are obtained when using water solutions of SnCl2.2H2O as precursor. Its characterization
was done using the techniques DTA, TGA, XRD, finding that in order to have high performance for the cassiterite
system the optimum pH value was 6,25 whereas a pH of 8.0 was leading to the romarchite system. When using SEM
techniques and a surface area, the size of the particle found was below 50 nm with a surface area of 19 m2/g. The
ricinoleate ester was obtained from the oil using sodium methylate as catalyst and then making it react with hydrogen
peroxide as oxidant agent and tin oxide to produce an epoxide. Finally, reaction products are identified through gas
chromatography finding that tin oxides are active for obtaining epoxides with better performance of the romarchite
crystal system (SnO) especially towards the methyl-12-hydroxi-9, 10-epoxioctadecanote (MHEOD)
A Sketching Framework for Reduced Data Transfer in Photon Counting Lidar
Single-photon lidar has become a prominent tool for depth imaging in recent
years. At the core of the technique, the depth of a target is measured by
constructing a histogram of time delays between emitted light pulses and
detected photon arrivals. A major data processing bottleneck arises on the
device when either the number of photons per pixel is large or the resolution
of the time stamp is fine, as both the space requirement and the complexity of
the image reconstruction algorithms scale with these parameters. We solve this
limiting bottleneck of existing lidar techniques by sampling the characteristic
function of the time of flight (ToF) model to build a compressive statistic, a
so-called sketch of the time delay distribution, which is sufficient to infer
the spatial distance and intensity of the object. The size of the sketch scales
with the degrees of freedom of the ToF model (number of objects) and not,
fundamentally, with the number of photons or the time stamp resolution.
Moreover, the sketch is highly amenable for on-chip online processing. We show
theoretically that the loss of information for compression is controlled and
the mean squared error of the inference quickly converges towards the optimal
Cram\'er-Rao bound (i.e. no loss of information) for modest sketch sizes. The
proposed compressed single-photon lidar framework is tested and evaluated on
real life datasets of complex scenes where it is shown that a compression rate
of up-to 150 is achievable in practice without sacrificing the overall
resolution of the reconstructed image.Comment: 16 pages, 20 figure
GBIF: mobilising information for adapting agriculture to climate change
Poster presented at Climate Change, Global Risk, Challenges & Decisions, Copenhagen (Denmark), 10-12 March 200
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