Search results for "scaling"
showing 10 items of 754 documents
A more distinctive representation for 3D shape descriptors using principal component analysis
2015
Many researchers have used the Heat Kernel Signature (or HKS) for characterizing points on non-rigid three-dimensional shapes and Classical Multidimensional Scaling (Classical MDS) method in object classification which we quote, in particular, the example of Jian Sun et al. (2009) [1]. However, in this paper, the main focuses on classification that we propose a concise and provably factorial method by invoking Principal Component Analysis (PCA) as a classifier to improve the scheme of 3D shape classification. To avoid losing or disordering information after extracting features from the mesh, PCA is used instead of the Classical MDS to discriminate-as much as possible-feature points for each…
A non-perturbative study of massive gauge theories
2013
We consider a non-perturbative formulation of an SU(2) massive gauge theory on a space-time lattice, which is also a discretised gauged non-linear chiral model. The lattice model is shown to have an exactly conserved global SU(2) symmetry. If a scaling region for the lattice model exists and the lightest degrees of freedom are spin one vector particles with the same quantum numbers as the conserved current, we argue that the most general effective theory describing their low-energy dynamics must be a massive gauge theory. We present results of a exploratory numerical simulation of the model and find indications for the presence of a scaling region where both a triplet vector and a scalar re…
Yangian Symmetry for Fishnet Feynman Graphs
2017
Various classes of fishnet Feynman graphs are shown to feature a Yangian symmetry over the conformal algebra. We explicitly discuss scalar graphs in three, four and six spacetime dimensions as well as the inclusion of fermions in four dimensions. The Yangian symmetry results in novel differential equations for these families of largely unsolved Feynman integrals. Notably, the considered fishnet graphs in three and four dimensions dominate the correlation functions and scattering amplitudes in specific double scaling limits of planar, gamma-twisted N=4 super Yang-Mills or ABJM theory. Consequently, the study of fishnet graphs allows us to get deep insights into the integrability of the plana…
How light gets through periodically nanostructured metal films: a role of surface polaritonic crystals
2003
The physical origin of the enhanced optical transmission of periodically structured films related to surface plasmon polaritons is discussed from first principles. The enhancement of transmission through smooth, randomly rough and periodically nanostructured films is considered. Analysis shows that any metal (or dielectric) nanostructured film can exhibit enhanced transmission in certain spectral ranges corresponding to surface plasmon (or phonon) polariton Bloch mode states on a periodic structure. Resonant tunnelling via these states is responsible for the transmission enhancement. The properties of surface polaritonic crystals are analogous to those of photonic crystals and can find nume…
High-brilliance double-stage soft x-ray laser pumped by multiple pulses applied in grazing incidence
2014
A new compact scheme for a double-stage seeded x-ray laser is demonstrated. This laser is offering greatly improved beam quality and brilliance making it a useful tool for applications.
Class-B two-photon Fabry–Pérot laser
1998
Abstract We study the stationary operation and stability properties of a class-B two-photon Fabry–Perot laser. We show that, differently from the one-photon laser, the intensity emitted by the two-photon laser is larger in a Fabry–Perot than in a ring cavity. The lasing solution loses stability through a subcritical Hopf bifurcation, as it occurs in the unidirectional ring laser. The stability domain in the parameter space is larger in the Fabry–Perot than in the ring cavity configuration.
Anharmonicity modeling in hydrogen bonded solvent dimers
2021
Abstract Harmonic and anharmonic frequencies of dimers and mixed dimers of water, methanol and benzene were computed and the results were critically analysed to investigate the anharmonicity of the normal mode vibrations within density functional theory (DFT) with empirically included Grimme correction for dispersion (D3). From several options, the B3LYP-D3/6-31++G* level of theory was selected as a good compromise between accuracy and calculation speed, suitable for future modeling of larger solvent clusters. The obtained raw harmonic and anharmonic second-order perturbation theory of vibrational frequencies (VPT2) were additionally scaled using a two-range procedure (below and above 2000 …
Wheat growth simulation and yield prediction with seasonal forecasts and a numerical model
2007
Abstract Wheat is a major winter crop in northern Italy. Italian agricultural markets and government agencies would undoubtedly benefit from the early availability of wheat yield forecasts at the regional and national scales as useful support in decision making. In this study we tested the skill of seasonal weather forecasts, in combination with observed weather data, as input to a crop model working in water limited conditions. The observations were used to simulate wheat growth from sowing up to 2 months before harvest, while seasonal forecasts were used afterwards to predict final yields. Observations included climatic variables and water table levels from a location in the Po river plai…
Application of the SWAP model to predict impact of climate change on soil water balance in a Sicilian vineyard
2012
In Sicily, the increasing scarcity of quality water is leading to irrigation with saline water in soils having a considerable susceptibility to salinization and degradation. In this paper, water flow and solute transport in a Sicilian irrigated soil was simulated by using the SWAP model, and the simulated results compared to measured values of soil moisture and salinity. The investigation was carried out in a vineyard located in Sicily (Mazara del Vallo, Trapani Province) within the framework of the Project: Evolution of cropping systems as affected by climate change (CLIMESCO). The soil hydraulic parameters were obtained by inverse method based on multi-step outflow experiments. The result…
Climate change and Ecotone boundaries: Insights from a cellular automata ecohydrology model in a Mediterranean catchment with topography controlled v…
2014
Abstract Regions of vegetation transitions (ecotones) are known to be highly sensitive to climate fluctuations. In this study, the Cellular-Automata Tree Grass Shrub Simulator (CATGraSS) has been modified, calibrated and used with downscaled future climate scenarios to examine the role of climate change on vegetation patterns in a steep mountainous catchment (1.3 km2) located in Sicily, Italy. In the catchment, north-facing slopes are mostly covered by trees and grass, and south-facing slopes by Indian Fig opuntia and grass, with grasses dominating as elevation grows. CATGraSS simulates solar radiation, evapotranspiration, and soil moisture in space and time. Each model cell can hold a sing…