3,033 research outputs found
Estimation in the group action channel
We analyze the problem of estimating a signal from multiple measurements on a
\mbox{group action channel} that linearly transforms a signal by a random
group action followed by a fixed projection and additive Gaussian noise. This
channel is motivated by applications such as multi-reference alignment and
cryo-electron microscopy. We focus on the large noise regime prevalent in these
applications. We give a lower bound on the mean square error (MSE) of any
asymptotically unbiased estimator of the signal's orbit in terms of the
signal's moment tensors, which implies that the MSE is bounded away from 0 when
is bounded from above, where is the number of observations,
is the noise standard deviation, and is the so-called
\mbox{moment order cutoff}. In contrast, the maximum likelihood estimator is
shown to be consistent if diverges.Comment: 5 pages, conferenc
Multiscale Fractal Descriptors Applied to Nanoscale Images
This work proposes the application of fractal descriptors to the analysis of
nanoscale materials under different experimental conditions. We obtain
descriptors for images from the sample applying a multiscale transform to the
calculation of fractal dimension of a surface map of such image. Particularly,
we have used the}Bouligand-Minkowski fractal dimension. We applied these
descriptors to discriminate between two titanium oxide films prepared under
different experimental conditions. Results demonstrate the discrimination power
of proposed descriptors in such kind of application
Characterization of nanostructured material images using fractal descriptors
This work presents a methodology to the morphology analysis and
characterization of nanostructured material images acquired from FEG-SEM (Field
Emission Gun-Scanning Electron Microscopy) technique. The metrics were
extracted from the image texture (mathematical surface) by the volumetric
fractal descriptors, a methodology based on the Bouligand-Minkowski fractal
dimension, which considers the properties of the Minkowski dilation of the
surface points. An experiment with galvanostatic anodic titanium oxide samples
prepared in oxalyc acid solution using different conditions of applied current,
oxalyc acid concentration and solution temperature was performed. The results
demonstrate that the approach is capable of characterizing complex morphology
characteristics such as those present in the anodic titanium oxide.Comment: 8 pages, 5 figures, accepted for publication Physica
Impact of parental cancer in offspring’s psychological development: literature review
O presente artigo engloba uma extensa revisão da literatura sobre a temática do câncer parental e as
consequências pessoais e familiares desta vivência. Nesse sentido, são abordadas as principais consequências
médicas e psicossociais do diagnóstico e tratamento do câncer e, usando o modelo sistémico, é descrita a
influência (negativa e positiva) deste acontecimento no doente e noutros membros da família. É dado
especial enfoque ao desenvolvimento psicológico dos filhos, incluindo os resultados dos estudos referentes
ao stress traumático e crescimento pós-traumático, em particular no câncer da mama. São tecidas algumas
implicações para a investigação nesta área, bem como sugestões para futuras investigações.The present paper includes an extended literature review about parental cancer and personal and family
consequences of such experience. Some of the most important medical and psychosocial issues regarding
the diagnosis and treatment of parental cancer are presented. Using a systemic theory as the background
model it addresses the influences (negative and positive) of the event in the patient and in other family
members. The present paper gives special focus on the offspring’s psychological development, including
the results regarding traumatic stress and posttraumatic growth, particularly on breast cancer. Some implications
and suggestions for future research are addressed.Fundação para a Ciência e a Tecnologia (FCT
On the nature of the (de)coupling of the magnetostructural transition in ErSi
In this report, a successful thermodynamical model was employed to understand
the structural transition in ErSi, able to explain the decoupling of
the magnetic and structural transition. This was achieved by the DFT
calculations which were used to determine the energy differences at 0 K, using
a LSDA+U approximation. It was found that the M structure as the stable phase
at low temperatures as verified experimentally with a 0.262 eV.
Finally, it was achieved a variation of Seebeck coefficient ( 6 V)
at the structural transition which allow to conclude that the electronic
entropy variation is negligible in the transition.Comment: 17 pages, 3 figures, 1 tabl
Recovery of valuable aromas from sardine cooking wastewaters by pervaporation with fractionated condensation: matrix effect and model validation
Due to the lack of studies addressing the influence of real food matrices on integrated organophilic pervaporation/fractionated condensation processes, the present work analyses the impact of the real matrix of sardine cooking wastewaters on the fractionation of aromas. In a previous study, a thermodynamic/material balance model was developed to describe the integrated pervaporation—a fractionated condensation process of aroma recovery from model solutions that emulate seafood industry aqueous effluents, aiming to define the best conditions for off-flavour removal. This work assesses whether the previously developed mathematical model, validated only with model solutions, is also applicable in predicting the fractionation of aromas of different chemical families from real effluents (sardine cooking wastewaters), aiming for off-flavour removals. It was found that the food matrix does not influence substantial detrimental consequences on the model simulations, which validates and extends the applicability of the model.info:eu-repo/semantics/publishedVersio
Bandwidth and memory efficiency in real-time ray tracing
Real time ray tracing has been given a lot of attention in recent years in the academic and research community.
Several novel algorithms have appeared that parallelize different aspects of the ray tracing algorithm through
the use of a GPU. Among these, the creation of Bounding Volume Hierarchies (BVHs). We believe that recent
approaches have failed to consider the performance impact of memory accesses in GPU and how their cost affects
the overall performance of the application. In this work we show that by reducing memory bandwidth and footprint
we are able to achieve significant improvements in BVH traversal times. We do this by compressing the BVH and
the triangle mesh in a parallel manner after its creation, in each frame, and then decompressing it as needed while
traversing the BVH
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