Nonlinear considerations in EEG signal classification

We investigate the effect of incorporating modeling of nonlinearity on the classification of electroencephalogram (EEG) signals using an artificial neural network (ANN). It is observed that the ANN's predictive ability is improved after preprocessing EEG signals using a particular nonlinear modeling technique, viz. a bilinear model, compared with those obtained by using a particular classical linear analysis method, viz. an autoregressive (AR) model. Until recently, linear time-invariant Gaussian modeling has dominated the development of time series modeling and feature extraction. The advantage of such classical models lies in the fact that a complete signal processing theory is available. In the case of EEG signals, where the underlying theory regarding the dynamical law governing the generation of these signals (e,g., the underlying physiological factors) is not completely understood, a case can be made for using improved signal processing models that are not subject to linear constraints. Such models should recognize important features of the observed data that may not be well modeled by a linear time-invariant model. It is known that EEG signals are nonstationary, and it is possible that they may be nonlinear as well. Thus, one way of gaining further insights on the structure of EEG signals is to introduce nonlinear models and higher order spectra. This paper compares the results of classification using a linear AR model with those obtained from a bilinear model. It is shown that in certain cases, the nonlinearity of the EEG signals is an important factor that ought to be taken into consideration during preprocessing of the signals prior to the classification task     

Structural,optical and non-linear investigation of Eu<Superscript>3+</Superscript>: Al(NO<Subscript>3</Subscript>)<Subscript>3</Subscript>-SiO<Subscript>2</Subscript> sol-gel glass

Optical absorption and fluorescence spectra of Eu³⁺ ions in Al(NO₃)₃-SiO₂ sol-gel glass have been investigated using the Judd- Ofelt theory. JO intensity parameters (ω _λ ) and subsequent radiative properties for⁵ D ₀ ↔⁷ F _1,2,4,6 transitions are determined. The lifetime (τ_r) of⁵ D ₀ state is computed and along with JO parameters are compared with their corresponding values in other glasses prepared by conventional technique. A structural analysis, using IR and XRD spectra and non- linear parametrization of the silica gel glass is carried out. The study reveals the glass to be a very good third order non- linear amorphous optical material.     

Studies on some volatile flavour constituents in orthodox black teas of various clones and flushes in North-east India

Volatile flavour constituents (VFC) of orthodox black teas manufactured from various cultivars of different geographical areas were analysed by gas chromatography and mass spectrometry. Well marked variations in VFC, as observed, were due to differences in weather conditions during the growth periods and manufacturing techniques. In general, second flush teas contained a higher amount of monoterpenoids such as linalool, their oxides and geraniol compared to rain flush teas of both low grown and high grown areas. Non-terpenoid products such as hexanol, z-3 hexenol, benzaldehyde and benzyl alcohol were higher in rain flush teas than in second flush teas of only high grown areas.     

Compositional changes in chlorophylls and carotenoids during the four flushes of tea in North East India

The quantitative changes of two pigments, chlorophylls a and b, and four major carotenoids, β-carotene, lutein, violaxanthine and neoxanthine, were investigated during four flushes of North East Indian plain teas from a deep skiffed area between April and October 1982. The tea flushes with different genetic properties were taken fromn from various Tocklai-released clones: TV-1 (Camellia sinensis (L.) O. Kuntze), TV-2 (C. assamica (Masters) Wight), TV-9 (C. assamica ‘Cambod’) and TV-17 (C. sinensis, hybrid). They showed marked changes in these pigment constituents throughout the plucking period, which affected the organoleptic property of the black tea produced.     

Thermal design parameters of a wet T-shaped fin for linear variation of humidity ratio with saturation temperature

Journal of Mechanical Science and Technology - An analytical model based on homotopy perturbation method is developed to analyze the thermal performance and optimum geometric dimensions of a...     

Studies on Thearubigin Pigments in Black Tea Manufacturing Systems

The formation of thearubigin pigments in prevalent commercial manufacturing systems such as orthodox roll, roll followed by curling, tearing, crushing (CTC), rotorvane combined with CTC and CTC alone was studied in the six Tocklai released clones TV-1, TV-2, TV-8, TV-9, TV-17 and TV-18. The contribution of the pigment composition, especially thearubigins of high, intermediate and low molecular weights as separated by a Sephadex LH 20 column, was examined on the basis of the types of leaves, degree of wither and roll, conditions of fermentation and the temperature and type of drying. It was apparent that the biochemical pathway in the black tea processing could be conveniently followed from the thearubigin formation. Further, the amount of high molecular weight thearubigin could determine the quantity of cream formed in a black tea brew. The thearubigin and concomitant pigments such as theaflavin have distinct organoleptic properties and their variation was reflected in the overall quality of the finished product.     

The pachyderm and the pixel: an assessment of elephant habitat suitability in Sonitpur,India

Remote sensing and geographic information systems (GISs) are increasingly being used in protected area monitoring and habitat suitability studies. In this article, Erdas Imagine's Expert Classifier tool was used to assess the specific trajectories of habitat suitability change during 1994–2007 in the Sonitpur elephant habitat, India. Sonitpur has been witness to increasing human–elephant conflict in the past decade. The suitability analysis took into account information relating to forest type and density, elevation, slope, source of water, human activities in terms of settlement, agriculture, tea plantations, roads, and railways. Satellite imagery, data from topographical maps, digital elevation data, and global positioning system readings formed the major data inputs that were incorporated into a GIS. Various decision rules were created and confidence levels assigned to the input layers to generate high, medium, and low habitat suitability. The area witnessed a sharp decline in suitability from 63% in 1994 to less than 38% by 2007. The high-suitability area declined by more than 50% during this period. The unique natural protected areas of Sonitpur, which are a mix of reserved forests, wildlife sanctuaries, and a national park, urgently need to be protected from further habitat degradation.