Spatially distributed sea wave measurements

In recent years, there has been growing interest in remote and proximal observation of sea surface waves. This has been partially driven by new technologies allowing the characterization of wave fields in both their spatial and temporal aspects. Typical examples are radar systems and stereo-imaging that permit remote monitoring of oceanic waves (from satellites, platforms, or vessels) with remarkable accuracy and range of use. These new exciting possibilities usually come at the price of being relatively harder to master with respect to traditional “point-like” approaches providing measurements limited to a temporal perspective. This difficulty is not restricted to the technology itself (see, for example, the delicate camera-calibration process required in stereo-imaging) but also on how to properly process, analyze, and assimilate spatio-temporal data. Therefore, in this Special Issue, we decided to embrace a wide range of topics that have led a multitude of multi-disciplinary works in the recent past, including: Wave mechanics and sea surface dynamics; Analysis of the wave climate and its extremes; Data fusion and signal processing; Statistical and probabilistic methods; Assessment of wave models. We did our best to propose recent advancements, not only on the technological aspect of spatially distributed sea waves acquisition but also on the characterization of wave statistics from measured and assimilated data. For the former aspect, we included the work of Vieira et al. [1], proposing the first cheap and simple stereo-based technique to estimate the 3D sea surface elevation from inexpensive smartphones. For the latter, the paper of Serebryany et al. [2] investigates internal waves on a narrow steep shelf of the northeastern coast of the Black Sea using the spatial antenna of line temperature sensors. We also included a discussion on space-time wave extremes in the paper of Benetazzo et al. [3] and a comparison of assimilated coastal wave data by Yukiharu Hisaki [4]. Finally, the work of Ciurana and Aguilar [5] provides an overview of how an ensemble of meteorological buoys and citizen science data can help economic activities to achieve optimal performances (in a case study, to predict optimal surfing days in the Iberian Peninsula). We hope that these works will be interesting both for researchers already working on this topic and for those who want to embrace the new possibilities offered by modern sea wave acquisition techniques

Northern Adriatic general circulation behaviour induced by heat fluxes variations due to possible climatic changes

The thermohaline circulation of the central-north Adriatic basin is investigated by means of a 3D hydrodynamic numerical model. Three different runs — where the surface heat fluxes annual average is respectively negative, slightly positive and slightly negative — are performed; the general circulation patterns are then discussed and depicted, also with the aid of the trajectories of numerical particles released during the integrations. Results confirm that surface heat fluxes can start and trigger the general circulation in the basin (both vertically and horizontally), even without prescribing other forcings. Particularly, when the annual budget of the heat fluxes is negative (i.e. the basin loses heat to the atmosphere)a horizontal cyclonic surface circulation is generated, characterized by a northward flow along the eastern coast and a southward return current system along the western one. From the vertical point of view, an antiestuarine circulation is established. A similar circulation pattern is depicted when the surface fluxes have a slightly negative annual budget. On the other hand, when the annual fluxes balance is positive the vertical circulation switches to estuarine and, as expected, the integrated circulation becomes anticyclonic. A modification in the heat fluxes budget is strictly related to a change in the water column turnover time of the Jabuka pit, the deepest meso-Adriatic depression: when the annual heat fluxes balance is negative but close to zero, the dense-water residence time in the pit becomes minimum and the water has a shorter turnover time, denoting a faster renewal compared to those exhibited in the other experiments

Levantamento de modelos matemáticos aplicados à cana-de-açúcar.

Objetivos da construção de modelos matemáticos para cana-de-açúcar. Modelo, definição e classificaçào. Metodologia da modelagem matemática. Modelos matemáticos e software de simulação descritos para a cana-de açúcar.bitstream/CNPTIA/9209/1/DOCUMENTO1int.pdfAcesso em: 29 maio 2008

One-Shot HDR Imaging via Stereo PFA Cameras

High Dynamic Range (HDR) imaging techniques aim to increase the range of luminance values captured from a scene. The literature counts many approaches to get HDR images out of low-range camera sensors, however most of them rely on multiple acquisitions producing ghosting effects when moving objects are present. In this paper we propose a novel HDR reconstruction method exploiting stereo Polarimetric Filter Array (PFA) cameras to simultaneously capture the scene with different polarized filters, producing intensity attenuations that can be related to the light polarization state. An additional linear polarizer is mounted in front of one of the two cameras, raising the degree of polarization of rays captured by the sensor. This leads to a larger attenuation range between channels regardless the scene lighting condition. By merging the data acquired by the two cameras, we can compute the actual light attenuation observed by a pixel at each channel and derive an equivalent exposure time, producing a HDR picture from a single polarimetric shot. The proposed technique results comparable to classic HDR approaches using multiple exposures, with the advantage of being a one-shot method

A stable graph-based representation for object recognition through high-order matching

Many Object recognition techniques perform some flavour of point pattern matching between a model and a scene. Such points are usually selected through a feature detection algorithm that is robust to a class of image transformations and a suitable descriptor is computed over them in order to get a reliable matching. Moreover, some approaches take an additional step by casting the correspondence problem into a matching between graphs defined over feature points. The motivation is that the relational model would add more discriminative power, however the overall effectiveness strongly depends on the ability to build a graph that is stable with respect to both changes in the object appearance and spatial distribution of interest points. In fact, widely used graph-based representations, have shown to suffer some limitations, especially with respect to changes in the Euclidean organization of the feature points. In this paper we introduce a technique to build relational structures over corner points that does not depend on the spatial distribution of the features

Modelos de transferência de metal pesado na cana-de-açúcar adubada com composto de lixo urbano.

A pesquisa aborda a reciclagem do composto de lixo urbano (CLU) como fertilizante alternativo na cana-de-açúcar e como solução social e ambiental ao acúmulo de resíduos sólidos nos centros urbanos. Utilizou-se da modelagem matemática para conhecer a dinâmica dos metais pesados, visando ao estabelecimento de critérios e procedimentos para o uso seguro do CLU, limitado pela quantidade desses elementos. Foram construídos modelos compartimentais a partir de dados de experimentos em condições controladas e parcialmente validados com dados de campo. Esse modelo descreveu a transferência de metais pesados no sistema solo-raiz-parte aérea para a cana-de-açúcar. Pôde-se concluir, pelas condições desta pesquisa, que o metal mais preocupante foi o níquel, pois demora, aproximadamente, três anos para ser atenuado no solo e chega em maior quantidade na parte aérea. Quanto aos fatores argila, óxidos e pH do solo, notou-se que, nos solos de maior poder tampão, a passagem da maioria dos metais foi mais lenta. Esse modelo pode tornar-se importante aliado na definição de leis de utilização do CLU, visando à não-contaminação ambiental, redução no acúmulo de lixo e de custos de produção

On the correct surface stress for the prediction of the wind wave field and the storm surge in the Northern Adriatic Sea

This paper discusses which formulation of the surface stress over the sea determines the most accurate prediction of the wind wave field and storm surge in the Northern Adriatic Sea. The study shows that the results of the storm surge and wind wave models, when compared to the available observations, can be used for the validation of the surface stress and of the expression adopted for the ssr (sea surface roughness). The results are representative of short fetch and young wind sea conditions. The agreement between the results and the measurements shows the feasibility of the wind wave and storm surge predictions in the Adriatic Sea and supports the dependence of the ssr, and, therefore, of the surface stress, on the spectrum of the surface wave