Spectral analysis method of electrophysical non-destructive testing data

A computational method for spectral analysis of the electrophysical test results based on sequential mathematical algorithm transformations using a discrete linear response function has been developed. The procedure for constructing spectral functions has a certain order and is aimed at obtaining adequate results of the experimental sample approximation in the frequency domain. It is shown that use of the low-frequency FIR filter function as part of the convolution, together with the fast Fourier transform, gives accurate results for structural inhomogeneities localization in welded joints.

Study on Precipitation Evolution Characteristics in Tongzhou District of Beijing in Recent 65 Years

Based on the 65a (1956–2020) precipitation series data of 11 rainfall stations and 5 surrounding rainfall stations in Tongzhou District, Beijing, the evolution characteristics of precipitation in Tongzhou District on spatial, interannual and intra annual scales are comprehensively analyzed using cumulative anomaly method, 5a moving average method and spectral analysis method, and the future change trend is predicted using ARIMA model. The results show that: 1) the annual average precipitation in Tongzhou District is higher in the middle and northwest and lower in the southwest, and the precipitation between June to August, accounts for more than 70% of the annual precipitation; 2) In general, the precipitation shows a fluctuating downward trend at the rate of -2.42 mm a-1, in which the precipitation in summer decreases at the rate of -2.68 mm a-1, while the precipitation in spring and autumn increases at the rates of 0.35 mm a-1 and 0.26 mm a-1 respectively; 3) The abrupt change of precipitation occurred in 1959 and 2000, which were 990.2mm and 239.4mm respectively; 4) There are 3∼8a and 14∼16a oscillation periods on the inter annual scale of precipitation, the prediction results of ARIMA model show that the precipitation will increase about 40 mm in the next five years.

Using vertical phase differences to better resolve 3D gravity wave structure

Atmospheric gravity waves (GWs) are a critically important dynamical mechanism in the terrestrial atmosphere, with significant effects on weather and climate. They are geographically ubiquitous in the middle and upper atmosphere, and thus, satellite observations are key to characterising their properties and spatial distribution. Nadir-viewing satellite instruments characterise the short horizontal wavelength portion of the GW spectrum, which is important for momentum transport; however, these nadir-sensing instruments have coarse vertical resolutions. This restricts our ability to characterise the 3D structure of these waves accurately, with important implications for our quantitative understanding of how these waves travel and how they drive the atmospheric circulation when they break. Here, we describe, implement and test a new spectral analysis method to address this problem. This method is optimised for the characterisation of waves in any three-dimensional data set where one dimension is of coarse resolution relative to variations in the wave field, a description which applies to GW-sensing nadir-sounding satellite instruments but which is also applicable in other areas of science. We show that our new “2D + 1 ST” method provides significant benefits relative to existing spectrally isotropic methods for characterising such waves. In particular, it is much more able to detect regional and height variations in observed vertical wavelength and able to properly characterise extremely vertically long waves that extend beyond the data volume.

Mask filtering to the Wigner-Ville distribution

The Wigner-Ville distribution (WVD) is a high-resolution time-frequency spectral analysis method for non-stationary signals, and yet it suffers from cross-term interference among signal components. We proposed applying a masking filter directly to the WVD time-frequency spectrum to suppress the cross-term interference. Conventional methods for suppressing the interference include the smoothed-pseudo WVD (SP-WVD) method, which incorporates smooth filtering in both time and frequency directions. We exploited the SP-WVD spectrum as a reference to design the masking filter, and thus the mask filtered WVD (MF-WVD) procedure is data adaptive. The MF-WVD method preserves the high-resolution energy concentration in the spectrum portrayed by the standard WVD, while suppressing the cross-term interference cleanly like in the SP-WVD method. Applying the MF-WVD method to field 3D seismic data generates high-resolution spectral cubes for various frequencies, and these spectral cubes may be used intuitively for detecting reservoir-related characteristics.

Using Vertical Phase Differences to Better Resolve 3D Gravity Wave Structure

Atmospheric gravity waves (GWs) are a critically-important dynamical process in the terrestrial atmosphere, with significant effects on weather and climate. They are geographically ubiquitous in the middle and upper atmosphere, and thus satellite observations are key to characterising their properties and spatial distribution. Nadir-viewing satellite instruments characterise the short-horizontal-wavelength portion of the GW spectrum, which is important for momentum transport, well; however, these nadir-sensing instruments have coarse vertical resolutions. This restricts our ability to characterise the 3D structure of these waves accurately, with important implications for our quantitative understanding of how these waves travel and how they drive the atmospheric circulation when they break. Here, we describe, implement and test a new spectral analysis method to address this problem. This method is optimised for the characterisation of waves in any three-dimensional dataset where one dimension is of coarse resolution relative to variations in the wave field, a description which applies to GW-sensing nadir-sounding satellite instruments but which is also applicable in other areas of science. We show that this "2D+1 ST" method provides significant benefits relative to existing spectrally-isotropic methods for characterising such waves. In particular, it is much more able to detect regional and height variations in observed vertical wavelength, and able to properly characterise extremely vertically long waves that extend beyond the data volume.

CONNECTING THE FORMATION OF STARS AND PLANETS. I – SPECTROSCOPIC CHARACTERIZATION OF HOST STARS WITH TIGRE

In search for a connection between the formation of stars and the formation of planets, a new semi-automatic spectral analysis method using iSpec was developed for the TIGRE telescope installed in Guanajuato, Mexico. TIGRE is a 1.2m robotic telescope, equipped with an Echelle spectrograph (HEROS), with a resolution R ≃ 20000. iSpec is a synthetic spectral fitting program for stars that allows to determine in an homogeneous way their fundamental parameters: effective temperature, Teff, surface gravity, log g, metallicities, [M/H] and [Fe/H], and rotational velocity, V sin i. In this first article we test our method by analysing the spectra of 46 stars, hosts of exoplanets, obtained with the TIGRE.

Flame temperature and alkali emission in combustion of sugarcane bagasse and straw

This work presents a numerical and experimental study in a laboratorial rig to measure local flame temperature and alkali emission during the combustion of sugarcane bagasse and straw. Tubular combustion chamber to simulate combustion in grate is used. A spectral analysis method in the visible spectrum was used for measurement of local temperatures in a sugarcane bagasse flame and sugarcane straw flame. The two-color method is used to calculate flame temperature. In flame reactive zone, the bagasse and straw flame temperatures in the range of 1420 to 1510 K and in the range of 1450 to 1550 K respectively are calculated. The intensity of alkali emission during the sugarcane bagasse and straw combustion is calculated using data of the spectrum in visible range. It was found that potassium emission is correlated with the instantaneous bagasse flame temperature in the reactive combustion zone. Emission of potassium and sodium during straw combustion is higher than in bagasse combustion. Temperature and alkali emissions along the flame height are measured.

A Full Spectral Analysis Method for the Gamma Spectrum: Weighted Library Least Squares

The traditional library least squares approach (LLS) is affected by the inconsistency of the statistical uncertainties of different channels in a gamma spectrum, which leads to large fluctuations in the...