Search results for "Geometric"
showing 10 items of 652 documents
Stochastic dynamical modelling of spot freight rates
2014
Based on empirical analysis of the Capesize and Panamax indices, we propose different continuous-time stochastic processes to model their dynamics. The models go beyond the standard geometric Brownian motion, and incorporate observed effects like heavy-tailed returns, stochastic volatility and memory. In particular, we suggest stochastic dynamics based on exponential Levy processes with normal inverse Gaussian distributed logarithmic returns. The Barndorff-Nielsen and Shephard stochastic volatility model is shown to capture time-varying volatility in the data. Finally, continuous-time autoregressive processes provide a class of models sufficiently rich to incorporate short-term persistence …
Real Options: an Application to RMS Investment Evaluation
2007
Further evidence of length- and sex-dependent variation of some morphological characters in Bathyporeia guilliamsoniana (Bate, 1857) (Crustacea: Amph…
2011
Explorative 3D geometric morphometrics on crania and mandibles of Cercopithecini (1024 specimens)
2015
A dataset of crania and mandibles from Old World primates was investigated through the use of 3D Geometric Morphometrics. We focused the attention on the tribe Cercopithecini, sampling 1024 specimens preserved in 9 different museums and related to a total of 31 species. Other 102 specimens belonging to 10 species of the same family Cercopithecidae were added as outgroup. Our sampling campaign was carried on with a 3D-digitizer Microscribe G2X and the data were processed through the softwares Morphologika and MorphoJ. We conducted both PCA and CVA analyses to investigate the power of resolution of the morphometric method and to understand the role of a-priori groups in the discrimination of …
Periods of Varieties
2017
A period, or more precisely, a period number may be thought of as the value of an integral that occurs in a geometric context. In their papers [Kon99, KZ01], Kontsevich and Zagier list various ways of defining a period. We show that all these variants give the same notion.
Why Magnus expansion
2021
A short story about the origins of Magnus Expansion, why we got involved and how it led us to meet Geometric Integration. We present a biographical draft of Wilhelm Magnus, a sketchy discussion of ...
The isoperimetric profile of a smooth Riemannian manifold for small volumes.
2009
On Upper Conical Density Results
2010
We report a recent development on the theory of upper conical densities. More precisely, we look at what can be said in this respect for other measures than just the Hausdorff measure. We illustrate the methods involved by proving a result for the packing measure and for a purely unrectifiable doubling measure.
Differentiation of Trichuris species eggs from non-human primates by geometric morphometric analysis
2020
Human trichuriasis is a neglected tropical disease which affects millions of people worldwide, mostly living in low socio-economic conditions. Numerous studies have been conducted over the past 10 years to compare the different techniques for T. trichiura eggs detection. Our study provides the first geometric morphometric analysis for the specific detection of eggs of Trichuris sp. isolated from stools of macaque (M. sylvanus), colobus (C. g. kikuyensis), grivets (C. aethiops) and the Brazza's monkey (C. neglectus) from zoos in Spain. Principal Component Analysis (PCA) arises as an efficient method to determine Trichuris spp. eggs. The selected measurements to be included in the PCA were pr…
Ecomorphological inferences in early vertebrates: reconstructing
2017
Our knowledge about the body morphology of many extinct early vertebrates is very limited, especially in regard to their post-thoracic region. The prompt disarticulation of the dermo-skeletal elements due to taphonomic processes and the lack of a well-ossified endoskeleton in a large number of groups hinder the preservation of complete specimens. Previous reconstructions of most early vertebrates known from partial remains have been wholly based on phylogenetically closely related taxa. However, body design of fishes is determined, to a large extent, by their swimming mode and feeding niche, making it possible to recognise different morphological traits that have evolved several times in no…