Spectral Ensemble Research Articles

Detecting of transient vibration signatures using an improved fast spatial–spectral ensemble kurtosis kurtogram and its applications to mechanical signature analysis of short duration data from rotating machinery

Detecting transient vibration signatures is of vital importance for vibration-based condition monitoring and fault detection of the rotating machinery. However, raw mechanical signals collected by vibration sensors are generally mixtures of physical vibrations of the multiple mechanical components installed in the examined machinery. Fault-generated incipient vibration signatures masked by interfering contents are difficult to be identified. The fast kurtogram (FK) is a concise and smart gadget for characterizing these vibration features. The multi-rate filter-bank (MRFB) and the spectral kurtosis (SK) indicator of the FK are less powerful when strong interfering vibration contents exist, especially when the FK are applied to vibration signals of short duration. It is encountered that the impulsive interfering contents not authentically induced by mechanical faults complicate the optimal analyzing process and lead to incorrect choosing of the optimal analysis subband, therefore the original FK may leave out the essential fault signatures. To enhance the analyzing performance of FK for industrial applications, an improved version of fast kurtogram, named as “fast spatial–spectral ensemble kurtosis kurtogram”, is presented. In the proposed technique, discrete quasi-analytic wavelet tight frame (QAWTF) expansion methods are incorporated as the detection filters. The QAWTF, constructed based on dual tree complex wavelet transform, possesses better vibration transient signature extracting ability and enhanced time-frequency localizability compared with conventional wavelet packet transforms (WPTs). Moreover, in the constructed QAWTF, a non-dyadic ensemble wavelet subband generating strategy is put forward to produce extra wavelet subbands that are capable of identifying fault features located in transition-band of WPT. On the other hand, an enhanced signal impulsiveness evaluating indicator, named “spatial–spectral ensemble kurtosis” (SSEK), is put forward and utilized as the quantitative measure to select optimal analyzing parameters. The SSEK indicator is robuster in evaluating the impulsiveness intensity of vibration signals due to its better suppressing ability of Gaussian noise, harmonics and sporadic impulsive shocks. Numerical validations, an experimental test and two engineering applications were used to verify the effectiveness of the proposed technique. The analyzing results of the numerical validations, experimental tests and engineering applications demonstrate that the proposed technique possesses robuster transient vibration content detecting performance in comparison with the original FK and the WPT-based FK method, especially when they are applied to the processing of vibration signals of relative limited duration.

A pseudo wavelet system-based vibration signature extracting method for rotating machinery fault detection

The rotating machinery, as a typical example of large and complex mechanical systems, is prone to diversified sorts of mechanical faults, especially on their rotating components. Although they can be collected via vibration measurements, the critical fault signatures are always masked by overwhelming interfering contents, therefore difficult to be identified. Moreover, owing to the distinguished time-frequency characteristics of the machinery fault signatures, classical dyadic wavelet transforms (DWTs) are not perfect for detecting them in noisy environments. In order to address the deficiencies of DWTs, a pseudo wavelet system (PWS) is proposed based on the filter constructing strategies of wavelet tight frames. The presented PWS is implemented via a specially devised shift-invariant filterbank structure, which generates non-dyadic wavelet subbands as well as dyadic ones. The PWS offers a finer partition of the vibration signal into the frequency-scale plane. In addition, in order to correctly identify the essential transient signatures produced by the faulty mechanical components, a new signal impulsiveness measure, named spatial spectral ensemble kurtosis (SSEK), is put forward. SSEK is used for selecting the optimal analyzing parameters among the decomposed wavelet subbands so that the masked critical fault signatures can be explicitly recognized. The proposed method has been applied to engineering fault diagnosis cases, in which the processing results showed its effectiveness and superiority to some existing methods.

The rest-frame ultraviolet properties of radio-loud broad absorption line quasars

We recently presented radio observations of a large sample of radio-loud broad absorption line (BAL) quasars from the SDSS and FIRST surveys, as well as a well matched sample of unabsorbed quasars, primarily to measure their radio spectral indices and estimate ensemble orientations. Here, we analyze the SDSS spectra of these samples and compare the rest-frame ultraviolet properties of radio-loud BAL and non-BAL quasars. Ultraviolet properties include the continuum shape, emission-line measurements of C IV, Al III, C III], Fe II, and Mg II, and BAL properties including the balnicity index (BI), absorption index (AI), and minimum and maximum outflow velocities. We find that radio-loud BAL quasars have similar ultraviolet properties compared to radio-loud non-BAL sources, though they do appear to have redder continua and stronger Fe II emission, which is consistent with what is found for radio-quiet BAL sources. No correlations exist between outflow properties and orientation (radio spectral index), suggesting that BAL winds along any line of sight are driven by the same mechanisms. There are also few correlations between spectral index and other properties. We conclude that BAL outflows occur along all lines of sight with similar strengths and velocities.

Dynamics of cellular activation as revealed by attenuated total reflectance infrared spectroscopy

We report the application of attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) to interrogate live cells, resting and stimulated with lipopolysaccharide (LPS) and gamma-interferon (INF-γ) over the course of 1 h from a murine macrophage-like cell line. Sub-culturing of the cells directly on the ATR crystal results in improved surface coverage and adhesion compared to previous investigations. In as little as 17 min post-activation we classify spectra with 80% classification accuracy using a Linear discriminant model developed from 20 spectra at the same time point extracted from multiple kinetic experiments. The loading vector is indicative of changes in the phosphate stretching region arising from an increase in RNA synthesis and protein phosphorylation. We employ factor analysis methods, specifically principal component analysis (PCA) and multivariate curve resolution (MCR), on the entire spectral ensemble consisting of multiple kinetic data sets of resting and stimulated cells to identify molecular changes associated with the dynamic cellular activation process. MCR extracts three distinct spectral signatures arising primarily from phosphodiester and carbonyl vibrations from nucleic acids and cellular proteins that possess distinct temporal patterns during cellular activation. The combination of ATR sampling method and multivariate analysis of FTIR spectra reported has implications in the early diagnosis of disease and infection because it permits unprecedented investigation of kinetic behavior in living cells without the need for extravagant sample preparation or labeling.

Can spectroscopy in combination with chemometrics replace minks in digestibility tests?

One of the most relevant but expensive methods of assessing the quality of fish meal is the physiological digestibility test with minks. The purpose of this study was to determine whether spectroscopic and chemical analyses evaluated with chemometrics can replace minks in digestibility tests. The spectroscopic methods used were the two complementary techniques of fluorescence emission and near-infrared reflectance. The investigation included 54 samples of high-quality fish meal ranging from 89.6 to 93.9 on the mink digestibility index. The investigation also included determination of seven quality parameters in the fish meal to substantiate the spectroscopic models on the mink digestibility. These quality parameters include the content of protein, oil, water, water-soluble protein, ash and the biogenic substance cadaverine as well as the titration value. The study demonstrates that the mink digestibility could be predicted from combining the two reference quality parameters oil and ash with a correlation coefficient of 0.89. The best spectroscopic calibration models on the mink digestibility resulted in a correlation coefficient of 0.94 and a prediction error of 0.5 using the near-infrared spectral ensemble and a correlation coefficient of 0.92 and a prediction error of 0.5 using the fluorescence spectral ensemble. In addition, the seven reference quality parameters could be predicted from the spectroscopic ensembles with good precision. © 2000 Society of Chemical Industry

The Macroscopic Entrainment Processes of Simulated Cumulus Ensemble. Part II: Testing the Entraining-Plume Model

Abstract According to Part I of this paper, it seems that ignoring the contribution from descendent cloud air in a cloud model for cumulus parameterization (CMCP), such as the spectral cumulus ensemble model in the Arakawa–Schubert parameterization, is an acceptable simplification for tropical deep convection. Since each subensemble in the spectral cumulus ensemble model is formally analogous to an entraining plume, the latter is examined using the simulated data from a cloud-resolving model (CRM). The authors first follow the analysis procedure of Warner. With the data from a nonprecipitating experiment, the authors show that the entraining-plume model cannot simultaneously predict the mean liquid water profile and cloud top height of the clouds simulated by the CRM. However, the mean properties of active elements of clouds, which are characterized by strong updrafts, can be described by an entraining plume of similar top height. With the data from a precipitating experiment, the authors examine the spec...

Belt‐zone variations in the Jovian cloud structure

Voyager IRIS observations of Jupiter in the far infrared (180–1200 cm−1) are sensitive to emission originating from pressures less than 2 bars, while the 5‐μm (1800–2300 cm−1) observations are primarily sensitive to emission originating from pressures greater than 2 bars. We use these differences in the location of the peak emission level to constrain the properties of the upper tropospheric cloud structure from the far‐infrared observations and then use the 5‐μm observations, with the upper tropospheric cloud structure fixed, to constrain the deep cloud structure. The relationship between observed 45‐ and 5‐μm brightness temperatures reveals three distinct regions between ±25° latitude: North Equatorial Belt hot spots, which are “hot” at both 45 and 5 μm; Equatorial Zone spectra, which are “warm” at 45 μm and “cold” at 5 μm; and North Tropical Zone spectra, which are “cold” at both 45 and 5 μm. We find that the hot extreme spectral ensemble is unique to belts, and the cold extreme spectral ensembles are unique to zones, but that all other intermediate spectral ensembles are common to both regions. Analyses of these spectra using an anisotropic multiple scattering radiative transfer model reveal that the primary difference between belts and zones is the increased opacity and vertical extent of clouds in zones relative to their belt counterparts. In addition, we find a shift in the location of the para hydrogen gradient toward lower pressures in zones, with an increase in the “equilibrated” cloud‐top para fraction. We suggest that all of the variations in gas abundance profiles, temperature, and cloud structure are consistent with the effects of a simple mean circulation and large‐scale wave motions.

Tropospheric gas composition and cloud structure of the Jovian north equatorial belt

High spatial resolution Voyager infrared interferometer spectrometer spectra of the North Equatorial Belt (NEB) reveal longitudinal variability of 5‐μm brightness temperatures of order 100°C. These observations are used to investigate spatial variations in the gas composition and cloud structure of the NEB. We use an anisotropic multiple scattering radiative transfer model to calculate synthetic spectra for comparison with the IRIS observations. The spectral dependence of cloud extinction from 180 to 2300 cm−1 is modeled using Mie theory. The entire spectral range of the IRIS observations (180–2300 cm−1) is used to constrain the cloud properties and vertical structure of the NEB. Within the model, cloud base locations vary with assumed gas abundances according to thermochemical equilibrium. We find that spatial variations in the abundance profiles of the condensible species, para hydrogen profiles and cloud optical depths can be used as tracers of the local and large‐scale dynamics. Based on the spectral dependence of NH3 cloud extinction that is required to fit the IRIS observations, we conclude that the bulk of the NH3 cloud extinction is provided by large particles, effective radii ≈100 μm; however, a small particle mode may also be present. We find that the observed 5‐μm brightness temperature structure can be reproduced by spatial variations in cloud opacity and water relative humidity. NEB hot spots, due to their low cloud opacity, provide a unique opportunity to study the deep cloud structure in the Jovian atmosphere. Cloud opacity is required at P > 4 bars (coincident with the location of the thermochemically predicted H2O cloud) to reproduce the observed continuum level near 2130 cm−1, as well as to model the overall shape of the continuum between 2100 and 2300 cm−1. Water relative humidity is found to vary spatially above the base of the water cloud increasing from ≈15% in hot spots to 100% in colder spectral ensembles. The variation of relative humidity is strongly correlated with the variation of cloud opacity, suggesting dynamic depletion of water vapor above the cloud forming level as the most plausible model to explain the spatial variation in the water profile within the NEB.

Impact of lateral detrainment and downdraft on the Summer monsoon cloud clusters

A spectral cumulus ensemble model has been used to determine the impact of lateral detrainment and convective downdraft on the cloud clusters, during, different phases of the, summer monsoon, the model consists of a population of clouds of different sizes which are In different stages of their life cycle. Entrainment and detrainment is considered to take place at all levels, Each cumulus cell has an updraft and a corresponding down draft which originates at a level below the cloud top depending upon the depth of the cloud, Upper, air observations collected from stationary ships forming polygons over the Arabian Sea and the Bay of Bengal during MONEX- 79 have been used for the study

A Comprehensive Mass Flux Scheme for Cumulus Parameterization in Large-Scale Models

Abstract Observational studies indicate that a mass flux approach may provide a realistic framework for cumulus parameterization in large-scale models, but this approach, through the introduction of a spectral cloud ensemble, leads normally to rather complex schemes. In this paper the question is addressed whether much simpler schemes can already provide realistic values of the thermal forcing by convection under various synoptic conditions. This is done through verifying such a scheme first on data from field experiments for periods of tropical penetrative convection (GATE, Marshall Islands), tradewind cumuli (ATEX, BOMEX) and extratropical organized convection (SESAME-79) and then in a NWP model. The scheme considers a population of clouds where the cloud ensemble is described by a one-dimensional bulk model as earlier applied by Yanai et al. in a diagnostic study of tropical convection. Cumulus scale downdrafts are included. Various types of convection are represented, i.e., penetrative convection in c...

Cumulus Ensemble Effects on the Large-Scale Vorticity and Momentum Fields of GATE. Part II: Parameterization

Abstract A parameterization of cumulus ensemble effects on the large-scale vorticity is tested to interpret the vorticity budget residual, Z, observed during Phase III of GARP Atlantic Tropical Experiment (GATE). The parameterization is derived consistently from the parameterization of cumulus ensemble effects on the momentum equation. Values of the parameterized Z are computed using the cumulus properties (mass flux, mass detrainment and cloud momentum) diagnosed by a spectral cumulus ensemble model. The results confirm the inferences made in Part I of this paper that organized cumulus convection produces significant residuals in the large-scale vorticity budget mainly through 1) the detrainment of excess momentum from clouds, and 2) the vertical advection of the large-scale vorticity due to the subsidence of environmental air compensating the convective mass flux. In addition, the twisting of the horizontal component of the large-scale vorticity into the vertical component due to nonuniform spatial dist...

The quantitation of arterial elasticity from Doppler flow measurements.

The pattern of phasic pressure and flow in an artery is related to the components of the impedance of that artery and hence to its compliance. Phasic patterns of velocity in peripheral arteries have been recorded by using continuous wave ultrasound Doppler flowmeters coupled to high-speed spectrum analysers; this has enabled display of the stored spectral ensembles as 'sonograms'. Simultaneous recordings at proximal and distal sites in each limb of a variety of subjects were made under standard resting conditions; characteristic patterns of change in the sonogram are recognized where gross abnormalities of arterial anatomy are present. A technique is under development whereby the mean values of velocity for each 7.4 ms time slice are derived, smoothed, and the pulse described by standard Fourier transform analysis. The change of the waveform occurring during passage through the relevant arterial segment is then described by comparing the amplitude/frequency and time-delay/frequency plots at proximal and distal sites. Although results are at present preliminary, changes relating to age and known vascular abnormality are becoming apparent. Further development is in progress to determine the significance of these findings.