Use of log polar space for foveation and feature recognition

The finding and maintaining of high accuracy foveation points for several types of recognised feature in log polar space such as a line, circular or elliptical arc is considered. Log polar space is preferred over cartesian space as it provides a high resolution and a wide viewing angle; feature invariance in the fovea simplifies foveation; it allows multi-resolution analysis; and rotation and scale are linear translations in log polar space.

Human saccadic eye movements and tracking by active foveation in log polar space

One of the possible models of the human visual system (HVS) in the computer vision literature has a high resolution fovea and exponentially decreasing resolution periphery. The high resolution fovea is used to extract necessary information in order to solve a vision task and the periphery may be used to detect motion. To obtain the desired information, the fovea is guided by the contents of the scene and other knowledge to position the fovea over areas of interest. These eye movements are called saccades and corrective saccades. A two stage process has been implemented as a mechanism for changing foveation in log polar space. Initially, the open loop stage roughly foveates on the best interest feature and then the closed loop stage is invoked to accurately iteratively converge onto the foveation point. The open loop stage developed for the foveation algorithm is applied to saccadic eye movements and a tracking system. Log polar space is preferred over Cartesian space as: (1) it simultaneously provides high resolution and a wide viewing angle; and (2) feature invariance occurs in the fovea which simplifies the foveation process.

Predicting future purchases with the Poisson log-normal model

The negative binomial distribution (NBD) has been widely used in marketing for modeling purchase frequency counts, particularly in packaged goods contexts. A key managerially relevant use of this model is Conditional Trend Analysis (CTA)—a method of benchmarking future sales utilizing the NBD conditional expectation. CTA allows brand managers to identify whether the sales change in a second period is accounted for by previous non-, light, or heavy buyers of the brand. Although a useful tool, the conditional prediction of the NBD suffers from a bias: it under predicts what the period-one non-buyer class will do in period two and over predicts the sales contribution of existing buyers. In addition, the NBD's assumption of a gamma-distributed mean purchase rate lacks theoretical support—it is not possible to explain why a gamma distribution should hold. This paper therefore proposes an alternative model using a log-normal distribution in place of the gamma distribution, hence creating a Poisson log-normal (PLN) distribution. The PLN distribution has a stronger theoretical grounding than the NBD as it has a natural interpretation relying on the central limit theorem. Empirical analysis of brands in multiple categories shows that the PLN distribution gives better predictions than the NBD.

Arranjos Log-Periódicos Compactos em Microfita com Elementos Fractais de Koch

This work aims to present how the application of fractal geometry to the elements of a log-periodic array can become a good alternative when one wants to reduce the size of the array. Two types of log-periodic arrays were proposed: one with fed by microstrip line and other fed by electromagnetic coupling. To the elements of these arrays were applied fractal Koch contours, at two levels. In order to validate the results obtained some prototypes were built, which were measured on a vector network analyzer and simulated in a software, for comparison. The results presented reductions of 60% in the total area of the arrays, for both types. By analyzing the graphs of return loss, it was observed that the application of fractal contours made different resonant frequencies appear in the arrays. Furthermore, a good agreement was observed between simulated and measured results. The array with feeding by electromagnetic coupling presented, after application of fractal contours, radiation pattern with more smooth forms than the array with feeding by microstrip line

Lumber quality of Eucalyptus grandis as a function of diametrical position and log steaming

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Simetria de invariância de escala discreta, log-periodicidade e singularidades em tempo finito

Conselho Nacional de Desenvolvimento Científico e Tecnológico

Log smoldering after an Amazonian deforestation fire

The characteristics of log smoldering after an Amazonian deforestation fire are described. The experiment was carried out in 2001 at the Caiabi farm, near the city of Alta Floresta, state of Mato Grosso, Brazil, as part of a set of tests that have been performed in the same area since 1997. A 200 x 200m(2) test area was slashed in the beginning of June and burned on 20 August. The area contained 507 logs with diameter at breast height (DBH) higher than 10 cm, per hectare. In the day following the main burn 59 logs were found to remain smoldering, a number that corresponds to 2.9% of the total in the area. We chose 11 of the 59 logs to have their smoldering process monitored. Their diameter, moisture content and CHN dry biomass composition after the plot burn and before smoldering were determined. Other parameters such as temperature distribution while smoldering, porosity, density and mass volatilized during thermogravimetric test were also determined. Average smoldering speeds were in the range from 0.8 to 1.5 cm h(-1) for logs that smoldered without transition to the flaming regime. The average speed increased to 2.1 cm h(-1) for those logs that oscillated between smoldering and flaming. The speeds were lower overnight as compared to values determined during daytime for the same log. Higher log moisture contents were found to produce decreased speeds. Micro-porous biomass was not observed in the set of the 11 selected logs. Smoldering was observed to occur at substantial intensity in crossing of logs, with no longitudinal propagation. (C) 2003 Elsevier Ltd. All rights reserved.

A Generalized Log-Normal Model for Grouped Survival Data

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)