Terms Of Spectral Parameters Research Articles

Feasibility of Quantitative Tissue Characterization Using Novel Parameters Extracted From Photoacoustic Power Spectrum Considering Multiple Absorbers

Frequency domain analysis of radio frequency signal is performed to differentiate between different tissue categories in terms of spectral parameters. However, due to complex relationship between the absorber size and spectral parameters, they cannot be used for quantitative tissue characterization. In an earlier study, we showed that using linear relationship between absorber size and two new spectral parameters namely number of lobes and average lobe width, absorber size can be successfully recovered from photoacoustic signal generated by single absorber. As actual biological tissue contains multiple absorbers, in this study we extended the application of these two new spectral parameters for computing absorber size from signals generated by multiple PA absorbers. We revisited our analytical model to establish two new linear relationships between the absorber radius and number of lobes as well as average lobe width considering multiple absorbers with bandlimited acquisition. A simulation study was performed to validate these linear relationships. A retrospective ex vivo study, in which the spectral parameters were computed using multiwavelength photoacoustic signals, was performed with freshly exercised thyroid specimens from 38 actual human patients undergoing thyroidectomy after having a diagnosis of suspected thyroid lesions. From statistical analysis it is shown that both the parameters were significantly different between malignant and non-malignant thyroid and malignant and normal thyroid tissue. Performance of the supervised classification with the computed spectral parameters showed that the extracted parameters could be successfully used to differentiate malignant thyroid tissue from normal thyroid tissue with reasonable degree of accuracy.

Design of FIR digital filters using Semi-ellipse window

A fixed window function which is similar in shape to a semi-ellipse is proposed. The semi–ellipse which has its major axis to be equal to the window length and the minor axis at unity produced about 4.2 dB lower ripple ratio than the rectangular window. The proposed window function is derived from the equation of an ellipse in the explicit and parametric forms. First of all, the spectral characteristic of the proposed window is studied in terms of spectral parameters and compared with other fixed windows like Rectangular, Bartlett, Hann, Hamming and Blackman windows. The window simulation results reveal that the proposed window produced comparable spectral characteristic with existing standard fixed windows. Secondly, the paper presents the application of the proposed window in a digital filter design. The filter analysis comparison results with other fixed windows namely Bartlett, Von Hann, Hamming, and Kaiser window, an adjustable window, confirm that filter design with the proposed window exhibits good spectral characteristic, and can be used to design better filter than the Bartlett window using less than half the Bartlett’s filter length for a fixed transition width. The similicity of its coefficients formulation and design algorithm makes it a good choice for digital filter design applications.

Iron rich basaltic eucrites, implication on spectral properties and parental bodies

The Howardites-Eucrite-Diogenite achondrite family is recognized to be the set of extraterrestrial rocks coming from (4) Vesta and Vestoids. In fact, the similar values of oxygen isotopes, and some chemical variation permit to associate these rocks to a system genetically correlated. Reflectance spectral properties permit an association between these achondrites and the (4) Vesta and Vestoids crust. Despite this closer connection, some Eucrites show spectral properties comparable with their pyroxene composition but strongly shifted, in terms of spectral parameters, with respect to the values retrieved for their parental bodies. The results from this work show how these eucrites have an evident shift of the main absorptions without peculiar geochemical variation within the family with respect to the data of the supposed parental body.Here, we evidence how these eucrites show an iron enriched pigeonite indicating these samples underwent a very quick cooling which could be associated to erupting material onto the surface of its parental body. Their distribution on the surface could be then limited to small areas that could be detected only at high spatial resolution on (4) Vesta or Vestoids. Nevertheless, the relationship among band center I and the band area ratio show how these samples could also fit with parental bodies shifted from the typical basaltic achondrites regions and moving closer to the characteristics of other pyroxenes enriched material like SIII-SV type Asteroids.

Analysis of Kaiser and Gaussian Window Functions in the Fractional Fourier Transform Domain and Its Application

Fractional Fourier transform (FRFT) is generalization of Fourier transform. It has an adjustable parameter in the form of $$\alpha$$ rotational angle that makes it more useful in the various fields of science and engineering. In this paper, an analysis of Kaiser and Gaussian window functions is obtained in the FRFT domain. The behavior of these window functions is observed in terms of spectral parameters along with their special cases. The effect of their behavior is applied in FIR filter implementation and tunes its transition band. By changing the order of the FRFT, the variation in the transition width of windowed FIR filter is obtained which makes it possible to vary the stop-band attenuation. While designing a new filter, this tuning method saves significant time to compute filter coefficients. To validate the results, tuning of the FIR filter with Gaussian and Kaiser window functions is achieved in FRFT domain and the performance of the filter is measured in terms of stop-band attenuation.

Low Latency Area-Efficient Distributed Arithmetic Based Multi-Rate Filter Architecture for SDR Receivers

In software defined radio (SDR) receivers, sample rate conversion (SRC) and channelization are two computational intensive tasks. Coefficient-less cascaded-integrator-comb (CIC) filters achieve SRC with low computational complexity, but the design of its gain droop compensation filter involves coefficients. These coefficients vary with the change in radio standards. In this paper, an architecture for variable digital filter (VDF) for gain droop compensation employing a set of fixed coefficient sub-filters and multi-dimensional polynomials in terms of spectral parameters is realized based on distributed arithmetic (DA). As the coefficients in the sub-filters are fixed, the proposed method uses ROM-based LUTs giving rise to low computational complexity. The proposed DA–VDF filter is synthesized on an application specific integrated circuit (ASIC) employing CMOS 90[Formula: see text]nm technology using Synopsis Design Complier. The proposed architecture achieves low latency at a reduced area delay product (ADP) of 78% and an efficiency of 72% in energy per sample (EPS) when compared with the conventional MAC-based architecture.

Spectral Evolution of Short GRBS on sub-millisecond time scale

There has been growing consensus that short and long GRBs are associated with two different populations of astrophysical sources: mergers and SN explosions, respectively. While temporal properties of short and long GRBs could be considered with similar depth and accuracy, patterns of spectral variability of the 2 classes of GRBs are much harder to compare. This is due to the fact, that short GRBs exhibit variability on time scales shorter than 1 ms and count rate, measured at such short time scales, is not sufficient for reliable spectroscopy even for the brightest events. In this situation, any new possibility to look at spectral evolution of short GRBs on sub-millisecond time scales in terms of spectral parameters, may provide more solid background for theoretical analysis. In this paper we present analysis of spectral evolution of short GRBs in terms of Band spectral function parameters, using the earlier developed Global Fit approach (GFA).

Spatial variability of strong ground motion: novel system-based technique applying parametric time series modelling

Spatial variability of strong ground motion within the dimensions of a horizontally extended structure is often described in terms of spectral parameters, such as autospectral densities and cross-spectral densities of motion, recorded at an array of closely spaced sensors. Traditionally, windowed and tapered periodogram techniques have been used in processing strong-motion array data, whereby spectral quantities are estimated. This approach involves large variances in the computed estimates, which can be reduced by decreasing the bandwidth of smoothing windows. A major problem in such applications is the selection of an optimal window, for which, as far as we know, no formal mathematical criteria exist. In this paper we propose a novel technique, based on parametric time series modelling, to replace the periodogram technique for estimating spectral quantities relevant to the description of spatial variability of ground motion. By using actual earthquake data recorded by a strong-motion array, we demonstrate that autoregressive (AR) time series modelling can be used in spectral analysis of strong-motion array data. Such models can easily be calibrated using a variant of least squares techniques, and well-defined statistical criteria are used to identify an optimal model to describe the recorded data. The application of AR modelling eliminates the subjective judgement involved in periodogram techniques and provides stabler estimates of lagged coherencies.

Estimation of the Influence of Soil Moisture on Soil Colour

AbstractSoil colour was expressed in terms of chromaticity coordinates instead of traditional Munsell notations which facilitated correlation with the moisture content of soils. Spectral reflectance of twenty‐one soil samples was measured in the visible region from saturation to air‐dryness from which the colour coordinates for each soil at various moisture levels were calculated. The data were transformed to metric lightness, metric chroma and Munsell values using the tables of Wyszecki and Stiles (1982). All the colour coordinates, metric lightness, metric chroma and Munsell value were negatively correlated with the moisture content. For dark soils, the rate of change of colour parameters with moisture is less compared to red and light coloured alluvial soils. An interesting feature of the study is that all the colour parameters converged to a characteric value for a group of soils at zero moisture level (intercept), which will be useful to assess the moisture status of a soil in that group from the regression equations, if the colour of soil is estimated in terms of spectral parameters.