Fourier-based registration for robust forward-looking sonar mosaicing in low-visibility underwater environments

Vehicle operations in underwater environments are often compromised by poor visibility conditions. For instance, the perception range of optical devices is heavily constrained in turbid waters, thus complicating navigation and mapping tasks in environments such as harbors, bays, or rivers. A new generation of high-definition forward-looking sonars providing acoustic imagery at high frame rates has recently emerged as a promising alternative for working under these challenging conditions. However, the characteristics of the sonar data introduce difficulties in image registration, a key step in mosaicing and motion estimation applications. In this work, we propose the use of a Fourier-based registration technique capable of handling the low resolution, noise, and artifacts associated with sonar image formation. When compared to a state-of-the art region-based technique, our approach shows superior performance in the alignment of both consecutive and nonconsecutive views as well as higher robustness in featureless environments. The method is used to compute pose constraints between sonar frames that, integrated inside a global alignment framework, enable the rendering of consistent acoustic mosaics with high detail and increased resolution. An extensive experimental section is reported showing results in relevant field applications, such as ship hull inspection and harbor mapping

Filtros digitais por transformadas de Fourier aplicados em eletroquímica

The electrochemical properties of micro and nano-electrodes are widely investigated due to their low faradaic and capacitive currents, leading to a new generation of smart and implantable devices. However, the current signals obtained in low-dimensional devices are strongly influenced by noise sources. In this paper, we show the evaluation of filters based on Fast Fourier Transform (FFT) and their implementation in a graphical user interface (GUI) in MATLAB®. As a case study, we evaluated an electrochemical reaction process of charge transfer via outer-sphere. Results showed successful removal of most of the noise in signals, thus proving a promising tool for low-scale measurement.

Fourier transform infrared-attenuated total reflectance (FTIR-ATR) spectroscopy and chemometric techniques for the determination of adulteration in petrodiesel/biodiesel blends

We propose an analytical method based on fourier transform infrared-attenuated total reflectance (FTIR-ATR) spectroscopy to detect the adulteration of petrodiesel and petrodiesel/palm biodiesel blends with African crude palm oil. The infrared spectral fingerprints from the sample analysis were used to perform principal components analysis (PCA) and to construct a prediction model using partial least squares (PLS) regression. The PCA results separated the samples into three groups, allowing identification of those subjected to adulteration with palm oil. The obtained model shows a good predictive capacity for determining the concentration of palm oil in petrodiesel/biodiesel blends. Advantages of the proposed method include cost-effectiveness and speed; it is also environmentally friendly.

Análise exploratória aplicada a espectros de reflexão total atenuada no infravermelho com transformada de Fourier (ATR-FTIR) de blendas de biodiesel/diesel

In this study, hierarchical cluster analysis (HCA) and principal component analysis (PCA) were used to classify blends produced from diesel S500 and different kinds of biodiesel produced by the TDSP methodology. The different kinds of biodiesel studied in this work were produced from three raw materials: soybean oil, waste cooking oil and hydrogenated vegetable oil. Methylic and ethylic routes were employed for the production of biodiesel. HCA and PCA were performed on the data from attenuated total reflectance Fourier transform infrared spectroscopy, showing the separation of the blends into groups according to biodiesel content present in the blends and to the kind of biodiesel used to form the mixtures.

Application of fourier transform infrared spectroscopy, chemical and chemometrics analyses to the characterization of agro-industrial waste

Agroindustrial waste in general presents significant levels of nutrients and organic matter and has therefore been frequently put to agricultural use. In this context, the objective of this study was to determine the chemical composition, nitrogen, phosphorus, potassium, calcium, magnesium and carbon content, as well as the qualitative characteristics through Fourier transform infrared spectroscopy of four samples of poultry litter and one sample of cattle manure, from the southwestern region of Paraná, Brazil. Results revealed that, in general, the poultry litter presented higher amount of nutrients and carbon than the cattle manure. The infrared spectra allowed identification of the functional groups present and the differences in degree of sample humification. The statistical treatment confirmed the quantitative and qualitative differences revealed.

Epistemological anarchism of Paul Karl Feyerabend and medical education

The thoughts of the philosopher Paul Karl Feyerabend brought important contributions to the debate on Science in the 20th century. Most recently his views about non-existence of a single method for doing science have been employed to rethink science education and propose the use of multiple methods for effective teaching-learning process. This article employs the theoretical framework of the author expressed in the book Against Method, 1977, about the epistemological anarchism and the methodological pluralism and uses it in the contemporary discussion of medical education.

Aplicação da análise harmônica por séries de Fourier para a previsão de produtividade da cultura do café no Estado de Minas Gerais

O objetivo deste trabalho foi obter um modelo de previsão de produtividade para a cultura do café, em sete municípios do Estado de Minas Gerais. Submeteram-se à análise harmônica por séries de Fourier, séries de produtividades representativas de cada município, das quais se extraíram os coeficientes até o sétimo harmônico, submetendo-os à regressão linear múltipla nos três primeiros componentes principais de um conjunto de 33 variáveis inerentes à produção cafeeira. Essas variáveis foram médias de 15 anos correspondentes aos mesmos anos das produtividades e subdivididos em quatro períodos trimestrais, ao longo do ciclo produtivo da cultura (julho a junho). O modelo mostrou-se inconsistente, apresentando erros das estimativas bastante discrepantes, evidenciando a complexidade de modelagem de previsão de safras para a cultura do café.

Arkistoluettelo 482: Karl Collan

Luettelo Kansalliskirjastossa olevan Karl Collanin, Maria Elisabeth Collan-Beaurainin ja Agda Salmelan arkiston sisällöstä. Karl Collanin sävellyskäsikirjoitukset on luetteloitu erikseen Viola-tietokantaan (sanahaku: collan käsikirjoitukset)

Tavaststjerna, Karl August

f. 13.5.1860 i S:t Michel, d. 30.3.1898 i Björneborg. K.A. Tavaststjerna är en av de tidigaste realistiska och moderna författarna i Finland, särskilt i den finlandssvenska litteraturen. I hans produktion, som tillkom under 1880- och 1890-talen, ifrågasätts konventionell idealism och nationalism mot bakgrund av en mörkare, mera desillusionerad skildring av den finländska verkligheten och av mänsklig falskhet. Återkommande ideal i hans verk är den fria tanken och ett kompromisslöst konstnärsliv och världsmedborgarskap, som kontrasteras mot tristessen i ett slutet och inskränkt Finland. Till hans mest betydande verk hör romanerna Barndomsvänner. Ett nutidsöde (1886) samt Hårda tider. Berättelse från Finlands sista nödår (1891), men i produktionen ingår även lyrik och dramatik. Tavaststjerna har också uppfattats som den första finlandssvenska författaren, dvs. en författare vars verk ger uttryck för känslan att som svenskspråkig i Finland tillhöra en minoritet.

Arkistoluettelo 051: Karl Ekman

Luettelo Kansalliskirjastossa olevan Karl Ekmanin arkiston sisällöstä (arkistoluettelo 51)