Normalized Frequency Spectrum Research Articles

The detection of prostate cancer based on ultrasound RF signal.

The diagnosis of prostate cancer has been a challenging task. Compared with traditional diagnosis methods, the radiofrequency (RF) signal is not only non-invasive but also rich in microscopic lesion information. This paper proposes a novel and accurate method for detecting prostate cancer based on the ultrasound RF signal. Our approach is based on low-dimensional features in the frequency domain and high-throughput features in the spatial domain. The whole process could be divided into two parts: first, we calculate three feature maps from the ultrasound original RF signal, and 1,050 radiomics features are extracted from the three feature maps; second, we extracted 37 spectral features from the normalized frequency spectrum after Fourier transform. We use LASSO regression as the method for feature selection; moreover, we use support vector machine (SVM) for classification 10-fold cross-validation for examining the classification performance of the SVM. An AUC (area under the receiver operating characteristic curve) of 0.84 was obtained on 71 subjects. Our method is feasible to detect prostate cancer based on the ultrasound RF signal with superior classification performance.

An Underwater Acoustic Target Recognition Method Based on Restricted Boltzmann Machine.

This article focuses on an underwater acoustic target recognition method based on target radiated noise. The difficulty of underwater acoustic target recognition is mainly the extraction of effective classification features and pattern classification. Traditional feature extraction methods based on Low Frequency Analysis Recording (LOFAR), Mel-Frequency Cepstral Coefficients (MFCC), Gammatone-Frequency Cepstral Coefficients (GFCC), etc. essentially compress data according to a certain pre-set model, artificially discarding part of the information in the data, and often losing information helpful for classification. This paper presents a target recognition method based on feature auto-encoding. This method takes the normalized frequency spectrum of the signal as input, uses a restricted Boltzmann machine to perform unsupervised automatic encoding of the data, extracts the deep data structure layer by layer, and classifies the acquired features through the BP neural network. This method was tested using actual ship radiated noise database, and the results show that proposed classification system has better recognition accuracy and adaptability than the hand-crafted feature extraction based method.

Translation Invariance-Based Deep Learning for Rotating Machinery Diagnosis

Discriminative feature extraction is a challenge for data-driven fault diagnosis. Although deep learning algorithms can automatically learn a good set of features without manual intervention, the lack of domain knowledge greatly limits the performance improvement, especially for nonstationary and nonlinear signals. This paper develops a multiscale information fusion-based stacked sparse autoencoder fault diagnosis method. The autoencoder takes advantage of the multiscale normalized frequency spectrum information obtained by dual-tree complex wavelet transform as input. Accordingly, the multiscale normalized features guarantee the translational invariance for signal characteristics, and the stacked sparse autoencoder benefits the unsupervised feature learning and ensures accurate and stable diagnosis performance. The developed method is performed on motor bearing vibration signals and worm gearbox vibration signals, respectively. The results confirm that the developed method can accommodate changing working conditions, be free of manual feature extraction, and perform better than the existing intelligent diagnosis methods.

Quantum Storage of Frequency-Multiplexed Heralded Single Photons.

We report on the quantum storage of a heralded frequency-multiplexed single photon in an integrated laser-written rare-earth doped waveguide. The single photon contains 15 discrete frequency modes separated by 261MHz and spanning across 4GHz. It is obtained from a nondegenerate photon pair created via cavity-enhanced spontaneous down-conversion, where the heralding photon is at telecom wavelength and the heralded photon is at 606nm. The frequency-multimode photon is stored in a praseodymium-doped waveguide using the atomic frequency comb (AFC) scheme, by creating multiple combs within the inhomogeneous broadening of the crystal. Thanks to the intrinsic temporal multimodality of the AFC scheme, each spectral bin includes 9 temporal modes, such that the total number of stored modes is about 130. We demonstrate that the storage preserves the nonclassical properties of the single photon, and its normalized frequency spectrum.

Fog backscattering interference suppression algorithm for FMCW laser fuze based on normalized frequency spectrum threshold

Fog backscattering can cause false alarm for laser fuze. The characteristics of the target echo signal and the fog echo signal of FMCW laser fuze are comparatively analyzed. Based on the frequency domain feature of beat signal in these two cases, a fog backscattering suppression method based on the normalized frequency spectrum threshold of beat signal is proposed. Experimental results from simulated laboratory environment showed that the algorithm can identify the target and the fog interference with the correct rate of 91%. This algorithm provides a new method to suppress the fog backscattering for the frequency modulated continuous wave laser fuze.

Theoretical analysis of transmembrane potential of cells exposed to nanosecond pulsed electric field

Purpose: Intracellular electroporation occurs when the cells are exposed to nanosecond pulsed electric field (nsPEF). It is believed the electroporation (formation and extension of pores on the membrane induced by external electric field) is affected significantly by the transmembrane potential. This paper analyzed transmembrane potential induced by nsPEF in the term of pulse frequency spectrum, aiming to provide a theoretical explanation to intracellular bio-effects.Methods: Based on the double-shelled spherical cell model, the frequency dependence of transmembrane potential was obtained by solving Laplace’s equation, while the time course of transmembrane potential was obtained by a method combined with discrete Fourier transform and Laplace transform. First-order Debye equation was used to describe the dielectric relaxation of the cell medium.Results: Frequency-domain analysis showed that when the electric field frequency was higher than 105 Hz, the transmembrane potential on the organelle membrane (ΔΦo) was increasing to exceed the transmembrane potential on the cellular membrane (ΔΦc). In the time-domain analysis, transmembrane potentials induced by four nsPEF (short trapezoid, long trapezoid, bipolar and sine shapes) with the same field strength were compared with each other. It showed that ΔΦo is obviously larger than ΔΦc if the curve of the normalized frequency spectrum of the pulse is more similar with the curve of normalized ΔΦo in frequency domain. Pulses with major frequency components higher than 108 Hz lead to both small ΔΦo and ΔΦc. This may explain why high power pulsed microwave lead to unobvious bio-effects of cells than nsPEF with trapezoid form.Conclusion: Through the pulse frequency spectrum it is clearer to understand the relationship between nsPEF and the transmembrane potential.

Sensing of damage and substrate stress in concrete using electro-mechanical impedance measurements of bonded PZT patches

The influence of stress and induced damage in concrete on the electro-mechanical (EM) impedance response of bonded PZT patches is evaluated for applied compressive loading. Full field displacements obtained from digital image correlation are used to evaluate the level of stress-induced damage in concrete. Stress in the substrate produces an imposed strain on the PZT. A change in the imposed strain produces a rightward frequency shift and an increase in the amplitude of the resonant peak in the EM conductance spectrum of the PZT. An increase in the substrate compliance produces a decrease in the resonant frequency and an increase in the amplitude of the resonant peak. Changes in the resonant peak in the conductance spectrum induced by increasing substrate stress are of a significant magnitude when compared with the changes induced by damage. In the early stages of damage associated with distributed microcracking, the counteracting influences of increasing level of damage and increasing stress on the resonant peak result in no shift in frequency for measurements under applied load. There is however an increase in the amplitude of the resonance peak. When the applied stress is removed, there is a net decrease in frequency resulting from damage in the form of distributed microcracks. Measures of changes in the resonant peak based on root mean square deviation (RMSD), do not show any observable change when measurements are performed under applied loading. There is a consistent increase in RMSD values and frequency shift with increasing damage when the applied stress is removed. The centroidal measure of the normalized frequency spectrum reflects changes in substrate stress. At higher applied stress levels, there is a nonlinear increase in damage, leading to localization and cracking. The influence of damage is dominant in this region and significant changes are obtained in the RMSD values in both loaded and unloaded conditions.

Multi-frequency signal modeling using empirical mode decomposition and PCA with application to mill load estimation

Multi-frequency signals consist of different time-scale components which have different physical interpretations. Normal principal component analysis (PCA) methods and frequency spectrum feature selection techniques do not work well in a multi-scale domain. This paper combines empirical mode decomposition (EMD), PCA, and an optimal feature extraction method to extract, select and model different scale frequency signals. We successfully apply this approach to a laboratory scale wet ball mill. The shell vibration signal produced by the ball mill of the grinding process is used for modeling the mill load. The experimental results demonstrate that this novel approach is effective compared with the other existing methods.

Quantum transport with coupled cavities on an Apollonian network

We study the dynamics of single photonic and atomic excitations in the Jaynes-Cummings-Hubbard (JCH) model where the cavities are arranged in an Apollonian network (AN). The existence of a gapped field normal frequency spectrum along with strongly localized eigenstates on the AN highlights many of the features provided by the model. By numerically diagonalizing the JCH Hamiltonian in the single excitation subspace, we evaluate the time evolution of fully localized initial states, for many energy regimes. We provide a detailed description of the photonic quantum walk on the AN and also address how an effective Jaynes-Cummings interaction can be achieved at the strong hopping regime. When the hopping rate and the atom-field coupling strength is of the same order, the excitation is relatively allowed to roam between atomic and photonic degrees of freedom as it propagates. However, different cavities will contribute mostly to one of these components, depending on the detuning and initial conditions, in contrast to the strong atom-field coupling regime, where atomic and photonic modes propagate identically.

Study of density fluctuation during low hybrid current drive on HT-7 tokamak

An experimental study of medium and high- k density fluctuations has been performed during low hybrid current drive (LHCD) in the HT-7 tokamak. Two series of plasma discharges in different plasma current with a limiter configuration were conducted in which the injected LHW power was gradually increased. The fluctuation level of the mode in channel k θ = 12 cm − 1 and k θ = 20 cm − 1 is related to the q profile, and the normalized frequency spectrum is found to be independent of the LHW power.

Indeterminacy of holographic quantum geometry

An effective theory based on wave optics is used to describe indeterminacy of position in holographic spacetime with a UV cutoff at the Planck scale. Wave functions describing spacetime positions are modeled as complex disturbances of quasimonochromatic radiation. It is shown that the product of standard deviations of two position wave functions in the plane of a holographic light sheet is equal to the product of their normal separation and the Planck length. For macroscopically separated positions the transverse uncertainty is much larger than the Planck length, and is predicted to be observable as a ``holographic noise'' in relative position with a distinctive shear spatial character, and an absolutely normalized frequency spectrum with no parameters once the fundamental wavelength is fixed from the theory of gravitational thermodynamics. The spectrum of holographic noise is estimated for the GEO600 interferometric gravitational-wave detector and is shown to approximately account for currently unexplained noise between about 300 and 1400 Hz. In a holographic world, this result directly and precisely measures the fundamental minimum interval of time.

Resonant scattering of plasma sheet electrons by whistler‐mode chorus: Contribution to diffuse auroral precipitation

A quantitative analysis is presented of the resonant scattering of plasma sheet electrons (∼100 eV–20 keV) at L = 6 due to resonant interactions with whistler‐mode chorus. Using wave parameters modeled from observations under geomagnetically disturbed conditions, it is demonstrated that the rate of pitch angle scattering can exceed the level of strong diffusion over a broad energy range (200 eV–10 keV) containing the bulk of the injected plasma sheet population. Scattering by chorus appears to be more effective than previous analyses of resonant interaction with electrostatic electron cyclotron waves. Chorus scattering is therefore a major contributor to the origin of the diffuse aurora and should also control the MLT distribution of injected plasma sheet electrons. The rates of scattering are sensitive to the distributions of wave power with respect to wave normal direction and wave frequency spectrum. Upper‐band chorus (ω/Ωe > 0.5) is the dominant scattering process for electrons below ≈5 keV while lower‐band chorus (0.1 ≤ ω/Ωe ≤ 0.5) is more effective at higher energies especially near the loss cone.

Scale invariant adaptation in fusiform face-responsive regions

Several functional neuroimaging studies have observed response adaptation in face-sensitive regions when repeating identical face stimuli. To address whether this was due to low-level stimulus properties or facial identity, we decomposed pictures of faces into pictures preserving only the lower or higher parts of the normal frequency spectrum. In an event-related functional neuroimaging study, pairs of such pictures were sequentially presented that showed the same or different persons in the same or different frequency bands. This factorial design allowed to separate effects related to repetition of personal identity from those related to identical stimulus properties. In a random effects group analysis, activation in the right fusiform region was affected by repetition of personal identity regardless of changing or constant spatial scale. Responses in the more medial and posterior fusiform and lingual regions adapted with repetition of the same frequency band. An analysis in regions of interest determined individually as face responsive showed that repetition decreases for the same faces in fusiform face-responsive regions generalized across spatial frequency bands. Our results therefore point to a role of this area in discriminating individual faces at a level of representation that is invariant to changes in low-level stimulus properties, as spatial scale. The same invariance could not be detected in more posterior occipital face-responsive regions.

Quasielastic Neutron Scattering from RbAg4I5 Single Crystal Gives Evidence of Jump Relaxation

AbstractA quasielastic neutron scattering experiment has been performed on a single crystalline sample of the fast ionic conductor rubidium silver iodide (RbAg4I5) in order to study the dynamics of the mobile silver ions in this material. The corrected spectra show broad quasielastic components whose weight increases with increasing momentum transfer in the elastic Q‐range from 1.0 to 1.8 Å−1. The quasielastic broadening is explained by the frequent occurrence of so‐called forward‐backward hopping sequences of the silver ions which are key steps of jump relaxation. A calculation based on the jump relaxation model yields a normalized frequency spectrum of the silver hopping motion that simultaneously fits the dynamic structure factor and the dynamic conductivity spectra of this material.

Effect of three-body interactions on the early stages of atomic cluster growth

The sequence of conformations a cluster assumes as it grows from a trimer into a thirteen-atom aggregrate under a given model potential has been studied. The model potential proposed is a construction composed of a van der Waals pairwise term and a three-body term composed of the triple dipole contribution and the exchange overlap contribution. A parametric study of the thermodynamically preferred structures is given. After reaching a boundary between regions in the parameter space, equilibrium mixtures of isomers with different packings are obtained. The normal frequency spectrum is given for clusters up to thirteen atoms.

Exhaust silencer apparatus for internal combustion engine

A tuned pipe exhaust for a two cycle internal combustion engine for snowmobiles and the like includes a conically shaped converging megaphone section terminating in a small end tube. An absorptive spiral muffler unit is co-axially secured to the end tube and includes an inner radial end wall extending radially from the end tube. The muffler unit attenuates high frequency exhaust noise. The space between such end wall and the upstream conical wall of the tuned pipe is enclosed with a tubular resonator wall to define a resonator cavity with coupling opening in the end tube. The cavity and throat opening defines a Helmholtz resonator which attenuates low frequency exhaust noise. The combination of a low frequency reactive section and a high frequency absorptive section creates an effective balanced silencer operating over the normal frequency spectrum of such engines.

Relaxation Times and Normal Mode Frequencies

Abstract : A simple relationship between normal mode frequencies and relaxation times known to hold for damped one dimensional solids was proved to obtain in all dimensions. Utilizing this relationship, the solution of the relaxation time distribution function problem reduces to the consideration of normal mode frequency spectrum of the array in question, irregardless of dimensionality.

Passive electrical measurements from three Oklahoma tornados

Passive electrical measurement of three tornados in the Oklahoma area have been made and are being reported upon. The measurements made include point discharge current, 18.5-kc/s sferics, along with 10-, 50-, 100-, and 175-kc/s, and 30-Mc/s sferics. The preceding measurements of tornados are compared with a typical local thunderstorm. In this comparison, it is shown that the electrical discharges within the tornados are much more intense than in local thunderstorms, particularly in frequency of occurrence. Data also show that the normal frequency spectrum of sferics radiation is different from the frequency spectrum of the tornados measured. Furthermore, the tornado sferics appear to have a definite aperiodic structure that may be present to a limited extent in the intense portion of a thunderstorm. Similarities between the measurements made on the Oklahoma tornados and Jones's work are pointed out. Finally, it is suggested that a coupling between the electrical and mechanical energies of the tornado may be responsible for the difference noted between tornado sferics and thunderstorm sferics.