Spectral Moments Research Articles

A WTC suppression algorithm for weather radar based on weighted schatten p-norm minimization

ABSTRACT The Matrix Completion (MC) method can effectively suppress the wind turbine clutter (WTC) of the weather radar, however its recovery accuracy suffers from the low signal-to-noise ratio (SNR) of the real measured weather signal. Moreover, the singular value distribution of the observation matrix constructed by the measured radar data has no sharp cut-off characteristic, which results the rank can not be well approximated and also reduces the recovery accuracy. In this paper, a non-convex MC algorithm based on weighted Schatten p-norm is proposed for the WTC suppression in Doppler frequency domain. Experiments are carried out on the measured signal data, and the results demonstrate that compared with the commonly used nuclear norm minimization (NNM) model, the weighted Schatten p-norm minimization (WSNM) model can further improve the recovery accuracy of weather signal and realizes the superior estimation performance of spectral moment.

Conditional ground-motion model based on RVT spectral moments for converting Fourier amplitude spectra to response spectra

Conditional ground-motion model based on RVT spectral moments for converting Fourier amplitude spectra to response spectra

The role of L1-L2 dissimilarity in L2 segment learning - Implications from the acquisition of English post-alveolar fricatives by Mandarin and Mandarin/Wu speakers.

This study examines how the concept of L1-L2 dissimilarity should be addressed from a two-way perspective in L2 segment learning, and how it relates to the learning outcomes. We achieved this by investigating the productions of the post-alveolar fricatives /ʃ, ʒ/ by Mandarin and Mandarin/Wu speakers, which were subsequently assessed by native English listeners. In the first experiment, we analyzed the spectral moments of /ʃ, ʒ/ produced by Mandarin monolingual and Mandarin/Wu bilingual speakers to find out how the two groups of speakers pronounced the target segments. In the second experiment, native English listeners were tasked with rating the accentedness of the Mandarin- and Mandarin/Wu-accented /ʃ, ʒ/. Results showed native English listeners scored Mandarin/Wu-accented /ʃ/ as having no accent and Mandarin-accented /ʒ/ as having a heavy accent, indicating that English natives perceived the 'native vs. nonnative' segment dissimilarity differently from Chinese learners of English, and that the L1-L2 dissimilarity perceived from both sides may work together in defining the L2 segment learning outcomes.

Length of stationary Gaussian excursions

Given that a stationary Gaussian process is above a high threshold, the length of time it spends before going below that threshold is studied. The asymptotic order is determined by the smoothness of the sample paths, which in turn is a function of the tails of the spectral measure. Two disjoint regimes are studied – one in which the second spectral moment is finite and the other in which the tails of the spectral measure are regularly varying and the second moment is infinite.

Long-Term Averaged Spectrum Descriptors of Dysarthria in Patients With Parkinson's Disease Treated With Subthalamic Nucleus Deep Brain Stimulation.

This study aimed to evaluate whether long-term averaged spectrum (LTAS) descriptors for reading and monologue are suitable to detect worsening of dysarthria in patients with Parkinson's disease (PD) treated with subthalamic nucleus deep brain stimulation (STN-DBS) with potential effect of ON and OFF stimulation conditions and types of connected speech. Four spectral moments based on LTAS were computed for monologue and reading passage collected from 23 individuals with PD treated with bilateral STN-DBS and 23 age- and gender-matched healthy controls. Speech performance of patients with PD was compared in ON and OFF STN-DBS conditions. All LTAS spectral moments including mean, standard deviation, skewness, and kurtosis across both monologue and reading passage were able to significantly distinguish between patients with PD in both stimulation conditions and control speakers. The spectral mean was the only LTAS measure sensitive to capture better speech performance in STN-DBS ON, as compared to the STN-DBS OFF stimulation condition (p < .05). Standardized reading passage was more sensitive compared to monologue in detecting dysarthria severity via LTAS descriptors with an area under the curve of up to 0.92 obtained between PD and control groups. Our findings confirmed that LTAS is a suitable approach to objectively describe changes in speech impairment severity due to STN-DBS therapy in patients with PD. We envisage these results as an important step toward a continuum development of technological solutions for the automated assessment of stimulation-induced dysarthria. https://doi.org/10.23641/asha.21644798.

Development of a new spectral method for fatigue damage assessment in bimodal and trimodal Gaussian random processes

Fatigue damage assessment for marine structures subjected to random environmental loadings is an important issue at the design stage. The bimodal and trimodal Gaussian fatigue damage problems have attracted great attentions from scholars in recent decades. In this paper, several existing spectral methods for fatigue damage assessment are first reviewed, then a new spectral method, named as the improved bands method, is developed based on the spectral decomposition approach. In the present method, the power spectrum of either bimodal or trimodal Gaussian process is split into narrow frequency bands, and the total fatigue damage can then be predicted by means of summing up the damages of each individual band via a linear combination rule. A parameter μ is introduced in order to modify the zero order spectral moments, so that the effect of interaction of high-frequency process superimposed on the low-frequency process can be reflected. Through comprehensive case studies, comparisons with time-domain rain-flow counting method and the other spectral methods are conducted to validate the accuracy and robustness of the proposed method. It is demonstrated that the present method can provide accurate and reasonable fatigue damage estimations for wide ranges of bimodal and trimodal cases for marine structures.

Peak factor estimation method of non‐Gaussian wind pressures on long‐span tri‐centered cylindrical roof structures

SummaryCladdings are susceptible to damage due to underestimation of extreme wind‐induced surface pressures. Commonly accepted methods for estimating the peak factor (an input used to determine cladding design loads) involve complex calculation‐intensive procedures. This research develops a four‐parameter unified auto‐spectral model of wind pressure to simplify peak factor estimation of wind‐induced surface pressure via analysis of wind tunnel wind load data on tri‐centered cylindrical roofs. Values of the model parameters were identified via statistical analysis of wind tunnel wind pressure measurement on two long‐span tri‐centered cylindrical roof structures with different curvatures. The study identified roof regions with non‐Gaussian features by inspecting probabilistic density functions of the standardized wind‐induced roof pressures and the third‐ and fourth‐order statistical moments of wind pressure time histories. The paper ultimately proposed and evaluated a simplified method for estimating the peak factors in the non‐Gaussian regions, the Three‐parameter Hermite Model, derived through the moment‐based Hermite Model, the Revised Hermite Model, and the parameter simplification accomplished in this study. The results show that the auto‐spectral model of wind‐induced roof pressures can accurately estimate the zero‐ and second‐order spectral moments, which reflects the wind pressure fluctuating characteristics and geometric features of spectral curves. Compared with the peak factors of the moment‐based Hermite Model and the Revised Hermite Model, the peak factor errors estimated by the Three‐parameter Hermite Model are all less than 10%. These results suggest that the Three‐parameter Hermite Model simplifies the calculation with acceptable accuracy.

Wind vibration responses of structure with generalized Maxwell model viscoelastic dampers

A new method for analysis of wind vibration response of structures with viscoelastic dampers is presented. Most existing studies focused on the numerical solution, and in this paper, an analytical method based on quadratic orthogonalized power spectral density function (QO-PSDF) was applied to obtain the closed-form solution of the structural dynamic responses with generalized Maxwell model (GMM) viscoelastic damper under Davenport spectral wind excitation. Firstly, the equations in motion of GMM viscoelastic dampers were coupled with the structural dynamic equation, which was decoupled into a linear combination of first-order vibration equations through complex mode method (CMM). Secondly, the frequency response eigenvalue function (FREF) was quadratic orthogonalized, which was combined with power spectral density function (PSDF) of Davenport spectral to obtain a QO-PSDF of the structural dynamic responses, and the exact closed-form solutions of the spectral moments and variances of the dynamic response were successfully acquired using the QO-PSDF. Finally, a 16-storey reinforced concrete building structure equipped with GMM viscoelastic dampers is taken as an example to validate the accuracy and applicability of the closed-form solution through a series of structural responses, including absolute displacements, inter-storey displacements, absolute velocities, inter-storey velocities.

1D van der Waals heterostructures based on single-walled carbon nanotubes encapsulating linear carbon chains: Stability and charge transfer evidence from Raman spectroscopy

The emerging one-dimensional van der Waals heterostructures (1D vdWHTs) are raising a lot of enthusiasm due to the possibilities for creating novel physical properties. In this paper, we focus on single-walled carbon nanotubes (SWCNTs) encapsulating a series of hydrogen-terminated linear carbon chains (LCCs) of lengths ranging from 4 up to 40 carbon atoms as a template for 1D vdWHTs (LCCs@SWCNTs). We explored the structural properties and stability of the LCCs@SWCNTs systems. The optimal SWCNT diameter for which the resulting 1D vdWHTs are stable is determined using Lennard-Jones (LJ) potential. SWCNTs with diameters of around 0.75 nm are found most convenient to accommodate LCCs. Combining the molecular dynamics (MD), the density functional theory (DFT), bond polarizability model (BPM), and the spectral moment’s method (SMM), we computed the Raman spectra of the free LCCs and LCCs@(6,5) 1D vdWHTs. The stability and charge transfer in the LCCs@(6,5) systems are evinced by analyzing the Raman active modes of the LCCs, as well as the radial breathing mode (RBM) and G-band of the (6,5) SWCNT before and after filling. These findings provide benchmark theoretical data to understand both the Raman data of the LCCs and the confinement effect on those of the SWCNTs encasing LCCs which have not been clearly addressed before.

An Acoustic-Phonetic Approach to Effects of Face Masks on Speech Intelligibility.

This study aimed to examine the effects of wearing a face mask on speech acoustics and intelligibility, using an acoustic-phonetic analysis of speech. In addition, the effects of speakers' behavioral modification while wearing a mask were examined. Fourteen female adults were asked to read a set of words and sentences under three conditions: (a) conversational, mask-off; (b) conversational, mask-on; and (c) clear, mask-on. Seventy listeners rated speech intelligibility using two methods: orthographic transcription and visual analog scale (VAS). Acoustic measures for vowels included duration, first (F1) and second (F2) formant frequency, and intensity ratio of F1/F2. For consonants, spectral moment coefficients and consonant-vowel (CV) boundary (intensity ratio between consonant and vowel) were measured. Face masks had a negative impact on speech intelligibility as measured by both intelligibility ratings. However, speech intelligibility was recovered in the clear speech condition for VAS but not for transcription scores. Analysis of orthographic transcription showed that listeners tended to frequently confuse consonants (particularly fricatives, affricates, and stops), rather than vowels in the word-initial position. Acoustic data indicated a significant effect of condition on CV intensity ratio only. Our data demonstrate a negative effect of face masks on speech intelligibility, mainly affecting consonants. However, intelligibility can be enhanced by speaking clearly, likely driven by prosodic alterations.

The Hubbard model: exact constraints on spectral moments in the strong coupling limit

ABSTRACT Exact spectral moment relations are derived and presented for the low temperature, strong coupling limit of the Hubbard model, for any dimension, lattice structure and electron density. These results generate an exact, rigorous and quantitative test for proposed solutions to the Hubbard model that claim to be valid in the strong coupling, low temperature region. The test complements analyses for weak coupling and high temperatures, offering insights into the essential physics of the model, specifically the quasiparticle energy (centroid) and lifetime (width) of the spectral weight function in the infinite coupling, finite hopping limit. Numerical results are given for nearest neighbour hopping in 1, 2 and 3D.

Seismic responses of structure with six-element generalized model viscoelastic dampers

In this paper, the closed-form solution of seismic response of the structure with six-element generalized model (SGM) viscoelastic damper is analytically investigated based on complex model method (CMM) and pseudo excitation method (PEM), named as CM-PEM. Firstly, the damping characteristic of SGM viscoelastic damper is combined into structural dynamic equation which was decoupled into linear combination of first order equations by CMM. And the closed-form solutions of the structural dynamic responses are obtained as follow. Based on PEM, the power spectral density function (PSDF) of the structure is divided into the product of PSDF of the ground excitation and frequency response eigenvalue function. Through mathematical transformation, PSDF of the structural dynamic responses is quadratically orthogonalized, which can be integrated to obtain the closed-form expression of spectral moments. A 20-storey reinforced concrete structure is taken as an example study for verifying the accuracy and efficiency of the proposed CM-PEM method. A comparatively study between increasing column lateral stiffness and installation of SGM damper is finally conducted, and the results indicate installation of SGM damper shows better energy dissipation capacity.

Impacts of anterior-posterior jaw disproportions on speech of dentofacial disharmony patients.

Articulation problems impact communication, development, and quality of life, and are diagnosed in 73-87% of patients with Class II Dentofacial Disharmony (DFD). We evaluated whether differences exist in stop (/t/ or/k/), fricative (/s/ or/ʃ/), and affricate (/tʃ/) consonant sounds of Class II DFD subjects, and whether extent of malocclusion correlates with severity of speech distortion. We hypothesized that Class II patients display milder distortions than Class III and anterior open bite (AOB), as Class II patients can posture into a Class I occlusion. Audio and orthodontic records were collected from DFD patients (N = 53-Class II, 102-Class III, 72-Controls) who were pursuing orthodontics and orthognathic surgery. A speech pathologist perceptually scored speech. Acoustic differences in recordings were measured using Spectral Moment Analysis. When Class II subjects were compared to controls, significant differences were found for the centroid frequency (M1) of the /s/ sound and the spectral spread (M2) of /t/, /tʃ/, and /s/ sounds, with pairwise significance for controls relative to Class II AOB and all Class II subjects. Class II AOB subjects had higher M1 and M2 values than patients with Class II closed bites and Class I controls for most sounds. When comparing across anterior-posterior (AP) groups, differences exist between controls, Class II and III DFD subjects for M1 of /t/, /tʃ/, and/ʃ/ and M2 for /t/, /tʃ/, /s/, and /ʃ/ sounds. Using linear regression, correlations between Class II and III severity and spectral measures were found for /t/ and /tʃ/ sounds. Class II and III patients have a higher prevalence of qualitative distortions and spectral changes in consonants compared to controls, but Class II spectral shifts are smaller and affect fewer sounds than in Class III and AOB cohorts. Linear correlations between AP discrepancy and spectral change suggest causation and that treatment may improve articulation problems.

Syntheses, spectral, thermal and pH-metric studies on bivalent metal ion complexes of N,N’-bis(3-carboxy-1-oxo-z-prop-2-elenyl)ethylenediamine

A novel carboxyamide ligand has been synthesized using maleic anhydride and ethylenediamine. Co(II), Ni(II), Cu(II) and Pd(II) complexes of the ligand, i.e., N,N’-bis(3-carboxy-1-oxo-z-prop-2-elenyl)ethylenediamine [H2L] have been prepared and characterized by elemental analyses, IR, electronic, 1H NMR, EPR spectral and thermal studies. It is revealed by IR and 1H NMR spectral studies that the ligand coordinated to the metal ions through deprotonated carboxylate oxygen and non-deprotonated amide nitrogen in all the complexes. It is suggested by electronic spectral and magnetic moment studies that N2O2 coordination is around each metal center with a strong field square planar chromophore. All the complexes have been studied by TGA and DTA studies done simultaneously. The complex formation between ligand and metal ions [Mn(II), Co(II), Ni(II), Cu(II) and Zn(II)] has also been studied pH metrically in 75% aqueous DMF solution at 298 K in 0.1 M NaClO4. The probable structures of the complexes have also been proposed.

Q-Pearson pair and moments in q-deformed ensembles

The generalisation of continuous orthogonal polynomial ensembles from random matrix theory to the q-lattice setting is considered. We take up the task of initiating a systematic study of the corresponding moments of the density from two complementary viewpoints. The first requires knowledge of the ensemble average with respect to a general Schur polynomial, from which the spectral moments follow as a corollary. In the case of little q-Laguerre weight, a particular \(_3 \phi _2\) basic hypergeometric polynomial is used to express density moments. The second approach is to study the q-Laplace transform of the un-normalised measure. Using integrability properties associated with the q-Pearson equation for the q-classical weights, a fourth-order q-difference equation is obtained, generalising a result of Ledoux in the continuous classical cases.

Computational and theoretical study of B-doped achiral single-walled carbon nanotubes: A nonresonant polarized Raman analysis

Tailoring the unique properties of carbon nanotubes should be studied. However, chemical doping by incorporation of boron atoms into carbon nanotubes (CNTs) has been examined as a powerful tool which provides various advantages. In this paper, we review several recent researches by which to dope carbon nanotubes by boron atoms into the sp2 carbon lattice, the properties induced by boron doping, and promising applications of this type of doping nanomaterials. We envisage that intrinsic boron doping will accelerate both scientific and industrial developments in the area of CNTs and nanotechnology in a later researches. Furthermore, the calculations of the polarized Raman active modes in boron-doped achiral single-walled carbon nanotubes are performed in the framework of the force constants model. Moreover, The spectral moment’s method was used in order to calculate the nonresonant Raman spectra for systems contain several atoms, it is shown that a powerful tool. The variations of the Raman spectra as a function of the rate doping of boron atoms are identified and the relative intensity ratio between Raman active modes of D and G bands has been analyzed. Raman spectroscopy analysis reveals mathematical expressions, it was derived to describe the dependence of the Radial Breathing Modes (RBM) with the diameter and the B-doping rate. It is shown that the diameter scale in Kataura’s plot must be converted into in order to directly compare to the experimental Raman spectra. Such conversion must be performed by using the relation ωRBM=218−1,2τD. Once this adjustment is done, one is ready to associate each pair (ωRBM,τ) to a specific (n, m) if the ωRBM values are well known. For example the RBM modes at 165 cm−1 and 133 cm−1 are assigned to the single walled carbon nanotube (10,10) and BC3 nanotube (5,5) respectively. The results of this work provide the (n, m) dependence of the RBM of SBCNTs, it gives good benchmark for performing (n,m) assignment of doped SWCNTs.

Quantifying errors in wind and wave measurements from a compact, low-cost wave buoy

A yearlong wind and wave dataset derived from a cost-effective GPS wave buoy (Spotter) is compared to waves obtained from an accelerometer wave buoy (Datawell) and winds obtained from a collocated meteorological buoy. Overall, there was a strong correlation in bulk wave parameters obtained from the Spotter buoy and the Datawell buoy (RMSE of 0.06 m, 0.27 s, and 21.89° for significant wave height, mean wave period, and peak wave direction, respectively). Similarly, the bulk characteristics compared well when separating the directional wave spectra into sea and swell components with more scatter in mean wave periods for lower frequencies. Measurements of mean directional spread from the Spotter buoy were 7.51° larger than the Datawell, spreading more wave energy across different directions outside the peak direction. Additional analysis indicates that the increased directional spreading arises from a bias in the a1 and b1 spectral moments. Using the equilibrium frequency range of the wave energy spectrum, the Spotter buoy can derive wind speed and direction. This study found the Spotter buoy can report wind speed and direction with reasonable accuracy but underestimates wind speeds less than 4 m/s and greater than 8 m/s and was less accurate reporting wind directions oriented offshore. A comparison with a Spotter buoy in deeper water revealed the Spotter buoy further offshore was most accurate in reporting wind directions indicating this proxy-based measurement of wind speed and wind direction may be significantly influenced by fetch and local geography (e.g., large-scale cuspate coastlines).

Analyzing time-varying spectral characteristics of speech with function-on-scalar regression

The acoustic characteristics of noise from fricatives and stop releases are difficult to analyze. The spectral characteristics of such noise are multi-dimensional, and popular methods for analyzing them typically rely on reducing this complex information to one or a few discrete numbers, such as spectral moments or coefficients of discrete cosine transformations. In this paper, I propose using function-on-scalar regression models as a method for analyzing and mass-comparing spectra with minimal reduction of the complexity in the signal. The method is further useful for analyzing how spectra change as a function of time. The usefulness of this method is demonstrated with a corpus analysis of Danish aspirated stop releases, using the DanPASS corpus. The analysis finds that /t/ releases are invariably affricated; /k/ releases are highly affected by coarticulatory context; and /p/ releases are almost always dominated by aspiration in the latter half of the release, but are affricated in the first half in certain contexts.

Moment functional based spectral density functional theory

We describe a density-functional method which aims at computing the ground state electron density and the spectral function at the same time. One basic ingredient of our method is the construction of the spectral function from the first four spectral moment matrices. The second basic ingredient is the construction of the spectral moment matrices from density functionals. We call our method moment-functional based spectral density-functional theory (MFbSDFT), because it is based on density-functionals for the spectral moments and because it allows us to compute the spectral function. If it is implemented in second variation our method consumes only a fraction more computer time than a standard DFT calculation with the PBE functional. We show that MFbSDFT captures correlation effects such as the valence-band satellite in Ni and the formation of lower and upper Hubbard bands in SrVO$_3$. For the purpose of constructing the spectral function from the first four $N\times N$ spectral moment matrices we describe an efficient algorithm based on the diagonalization of one hermitean $2N\times 2N$ matrix.

Constraints on ion velocity distributions from fusion product spectroscopy

Recent inertial confinement fusion experiments have shown primary fusion spectral moments which are incompatible with a Maxwellian velocity distribution description. These results show that an ion kinetic description of the reacting ions is necessary. We develop a theoretical classification of non-Maxwellian ion velocity distributions using the spectral moments. At the mesoscopic level, a monoenergetic decomposition of the velocity distribution reveals there are constraints on the space of spectral moments accessible by isotropic distributions. General expressions for the directionally dependent spectral moments of anisotropic distributions are derived. At the macroscopic level, a distribution of fluid element velocities modifies the spectral moments in a constrained manner. Experimental observations can be compared to these constraints to identify the character and isotropy of the underlying reactant ion velocity distribution and determine if the plasma is hydrodynamic or kinetic.