17,300 research outputs found
Performance of a New Enhanced Topological Decision-Rule Map-Matching Algorithm for Transportation Applications
Indexación: Web of Science; ScieloMap-matching problems arise in numerous transportation-related applications when spatial data is collected using inaccurate GPS technology and integrated with a flawed digital roadway map in a GIS environment. This paper presents a new enhanced post-processing topological decision-rule map-matching algorithm in order to address relevant special cases that occur in the spatial mismatch resolution. The proposed map-matching algorithm includes simple algorithmic improvements: dynamic buffer that varies its size to snap GPS data points to at least one roadway centerline; a comparison between vehicle heading measurements and associated roadway centerline direction; and a new design of the sequence of steps in the algorithm architecture. The original and new versions of the algorithm were tested on different spatial data qualities collected in Canada and United States. Although both versions satisfactorily resolve complex spatial ambiguities, the comparative and statistical analysis indicates that the new algorithm with the simple algorithmic improvements outperformed the original version of the map-matching algorithm.El problema de la ambigüedad espacial ocurre en varias aplicaciones relacionadas con transporte, especÃficamente cuando existe inexactitud en los datos espaciales capturados con tecnologÃa GPS o cuando son integrados con un mapa digital que posee errores en un ambiente SIG. Este artÃculo presenta un algoritmo nuevo y mejorado basado en reglas de decisión que es capaz de resolver casos especiales relevantes en modo post-proceso. El algoritmo propuesto incluye las siguientes mejoras algorÃtmicas: un área de búsqueda dinámica que varÃa su tamaño para asociar puntos GPS a al menos un eje de calzada, una comparación entre el rumbo del vehÃculo y la dirección del eje de calzada asignada, y un nuevo diseño de la secuencia de pasos del algoritmo. Tanto el algoritmo original como el propuesto fueron examinados con datos espaciales de diferentes calidades capturados en Canadá y Estados Unidos. Aunque ambas versiones resuelven satisfactoriamente el problema de ambigüedad espacial, el análisis comparativo y estadÃstico indica que la nueva versión del algoritmo con las mejoras algorÃtmicas entrega resultados superiores a la versión original del algoritmo.http://ref.scielo.org/9mt55
On Galois-Division Multiple Access Systems: Figures of Merit and Performance Evaluation
A new approach to multiple access based on finite field transforms is
investigated. These schemes, termed Galois-Division Multiple Access (GDMA),
offer compact bandwidth requirements. A new digital transform, the Finite Field
Hartley Transform (FFHT) requires to deal with fields of characteristic p, p
\neq 2. A binary-to-p-ary (p \neq 2) mapping based on the opportunistic
secondary channel is introduced. This allows the use of GDMA in conjunction
with available digital systems. The performance of GDMA is also evaluated.Comment: 6 pages, 4 figures. In: XIX Simposio Brasileiro de Telecomunicacoes,
2001, Fortaleza, CE, Brazi
Generalised Umbral Moonshine
Umbral moonshine describes an unexpected relation between 23 finite groups
arising from lattice symmetries and special mock modular forms. It includes the
Mathieu moonshine as a special case and can itself be viewed as an example of
the more general moonshine phenomenon which connects finite groups and
distinguished modular objects. In this paper we introduce the notion of
generalised umbral moonshine, which includes the generalised Mathieu moonshine
[Gaberdiel M.R., Persson D., Ronellenfitsch H., Volpato R., Commun. Number
Theory Phys. 7 (2013), 145-223] as a special case, and provide supporting data
for it. A central role is played by the deformed Drinfel'd (or quantum) double
of each umbral finite group , specified by a cohomology class in
. We conjecture that in each of the 23 cases there exists a rule
to assign an infinite-dimensional module for the deformed Drinfel'd double of
the umbral finite group underlying the mock modular forms of umbral moonshine
and generalised umbral moonshine. We also discuss the possible origin of the
generalised umbral moonshine
Inter- and intra-layer excitons in MoS/WS and MoSe/WSe heterobilayers
Accurately described excitonic properties of transition metal dichalcogenide
heterobilayers (HBLs) are crucial to comprehend the optical response and the
charge carrier dynamics of them. Excitons in multilayer systems posses inter or
intralayer character whose spectral positions depend on their binding energy
and the band alignment of the constituent single-layers. In this study, we
report the electronic structure and the absorption spectra of MoS/WS
and MoSe/WSe HBLs from first-principles calculations. We explore the
spectral positions, binding energies and the origins of inter and intralayer
excitons and compare our results with experimental observations. The absorption
spectra of the systems are obtained by solving the Bethe-Salpeter equation on
top of a GW calculation which corrects the independent particle
eigenvalues obtained from density functional theory calculations. Our
calculations reveal that the lowest energy exciton in both HBLs possesses
interlayer character which is decisive regarding their possible device
applications. Due to the spatially separated nature of the charge carriers, the
binding energy of inter-layer excitons might be expected to be considerably
smaller than that of intra-layer ones. However, according to our calculations
the binding energy of lowest energy interlayer excitons is only 20\%
lower due to the weaker screening of the Coulomb interaction between layers of
the HBLs. Therefore, it can be deduced that the spectral positions of the
interlayer excitons with respect to intralayer ones are mostly determined by
the band offset of the constituent single-layers. By comparing oscillator
strengths and thermal occupation factors, we show that in luminescence at low
temperature, the interlayer exciton peak becomes dominant, while in absorption
it is almost invisible.Comment: 17 pages, 4 figure
Sensitivity of the adjoint method in the inversion of tsunami source parameters
International audienceThis paper tests a methodology for tsunami wave-form inversion, based on the adjoint method. The method is designed to perform the direct optimization of the tsunami fault parameters, from tide-gauge data, imposing strong geophysical constrains to the inverted solutions, leading to a substantial enhancement of the signal-to-noise ratio, when compared with the classical technique based on Green?s functions of the linear long-wave model. A 4-step inversion proce-dure, which can be fully automated, consists (i) in the source area delimitation by adjoint backward ray-tracing, (ii) ad-joint optimization of the initial sea state, from a vanishing first-guess, (iii) non-linear adjustment of the fault model and (iv) final adjoint optimization in the fault parameter space. That methodology is systematically tested with four different idealized bathymetry and coastline setups (flat bathymetry in an open domain, closed conical circular lake, islands in an open domain and submarine mountains in an open domain) and different amounts of synthetic observation data, and of observational and bathymetric errors. Results show that the method works well in the presence of reasonable amounts of error and it provides, as a by-product, a resolution matrix that contains information on the inversion error, identifying the combinations of source parameters that are best and worst resolved by the inversio
Avaliação do termo de ajustamento de conduta da suinocultura amauc/consórcio lambari através de indicadores sociais, econômicos e ambientais.
Projeto: 03.06.05.020
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