Wavelet Pulse Research Articles

Small-strain site response of soft soils in the Sacramento-San Joaquin Delta region of California conditioned on VS30 and mHVSR

Sites located in the Sacramento-San Joaquin Delta region of California typically have peaty-organic soils near the ground surface, which are characteristically soft, with shear wave velocities as low as 30 m/s. These unusually soft geotechnical conditions, which are outside the range of applicability of existing ergodic site amplification models, can be anticipated to produce significant site effects during earthquake shaking. We evaluate site response for 36 seismic stations in the Delta region using non-ergodic methods with low-amplitude ground motion data. We model first-order site effects using a period-dependent relation conditioned on the 30 m time-averaged shear wave velocity ( VS30). Relative to extrapolations of global ergodic models, this Delta-specific model provides lower and higher levels of amplification for short and long periods, respectively. While the local model provides unbiased predictions for Delta sites as a whole, it smooths over site-specific effects such as resonant peaks. Microtremor-based horizontal-to-vertical spectral ratios (mHVSRs) were measured for 34 sites, from which additional site parameters such as peak frequency ( fp), peak amplitude ( ap), and average mHVSR amplitude over some frequency bandwidth ([Formula: see text]) are derived. Sites with prominent mHVSR peaks are found to often exhibit site resonance effects, while sites without prominent peak features generally do not. A modified Ricker wavelet pulse function conditioned on fp is used to model resonance effects, while a logistic function whose amplitude is correlated with [Formula: see text] is used to model general broadband amplification that transitions to zero at long periods. These mHVSR-informed models are implemented as additive components to the VS30-scaling model. Relative to a global ergodic model, the VS30-scaling model does not appreciably change the site-to-site aleatory variability ([Formula: see text]) for periods shorter than about 1.5 s but reduces [Formula: see text] by ~0.1 (natural log units) at long periods. When the mHVSR-informed model components are used, [Formula: see text] is reduced by ~0.05 to 0.1 for short-to-intermediate periods (up to ~2 s). A model for nonlinear effects, derived from nonlinear ground response analyses, will be presented in a separate paper.

Excitation of quantum oscillator by electromagnetic wavelet pulses

The excitation of a quantum oscillator at transitions between stationary states by wavelet pulses with zero and nonzero area as a function of their duration and amplitude is studied. The excitation from the ground state is examined in detail, together with the specific features of this process during excitation from excited states. Analytical expressions for the main characteristics of excitation probability under weak and strong perturbation of quantum oscillator were obtained within limits of strict consideration. Particularly, it was found that, on a qualitative and quantitative level, there is no difference between excitation by pulses with zero and non-zero area.

Massive MIMO NOMA with wavelet pulse shaping to minimize undesired channel interference

In this article, wavelet OFDM based non-orthogonal-multiple-access (NOMA) combined with massive MIMO system for 6G networks is proposed. For mMIMO transmissions, the proposed system could enhance the performance by utilizing wavelets to compensate for channel impairments on the transmitted signal. Performance measures include spectral efficiency, symbol error rate (SER), and peak to average ratio (PAPR). Simulation results prove that the proposed system outperforms the conventional OFDM based NOMA systems.

Spontaneous Intrinsic Hepatic Vascular Oscillations

The liver is well known as a large blood reservoir that can shift both stressed and unstressed volumes passively and actively in response to changes in portal venous and hepatic arterial blood flow, inflow and outflow blood pressures, autonomic nervous stimulation, and various humoral and pathophysiological factors. Not described is the characteristic of the liver to intrinsically modulate its own vascular pressure and volume independent of extrinsic factors.METHODSMale Holtzman rats (n=5) were anesthetized (30 mg/kg sodium pentobarbital, i.p.) and heparinized (500 IU/kg, i.v.), the portal vein and inferior vena cava were isolated and cannulated, the liver was flushed with room temperature normal saline, and the liver quickly removed. Each liver was mounted on a scale in a 37°C chamber (95% O2‐5% CO2) and pump‐perfused (Masterflex) with donor rat blood at a baseline 1 ml/min/g of tissue. The hepatic venous pressure (Phv) was regulated by raising and lowering the blood reservoir. At each Time (see table), portal venous oscillations were counted over 3 to 12 min and the portal venous wavelet pulse pressures (Ppv) were measured over at least 40 wavelets.RESULTSThe portal venous pressures of 3 of the 5 livers oscillated spontaneously. One lasted only 26 min while the others went on for over 200 min. The characteristics of these oscillations varied widely from animal to animal, but there usually was an irregular cycle length and uneven wavelet magnitude that tended to degrade to a diminished size with higher frequency over time (see Figure 1). Rat Time (Min) Maneuver Mean Portal Venous Pulse Pressure (mmHg) Frequency (Wavelets/Min) Frequency (Hz) Cycle Length (Sec) 1 0 Baseline 2.1 ± 0.9 (SD) 8.08 0.135 7.42 95 Baseline 1.5 ± 0.8 16.10 0.268 3.73 107 Change Phv 2.5 ± 1.3 17.00 0.283 3.53 (0 to 10 mmHg) (P<0.001 vs. 95 Min Baseline) 180 Baseline 1.3 ± 0.5 18.67 0.311 3.21 2 0 Baseline 0.8 ± 0.4 14.42 0.240 4.16 60 Baseline 0.4 ± 0.3 20.00 0.333 3.00 130 Baseline 0.4 ± 0.2 23.78 0.396 2.52 3 0 Baseline 0.6 ± 0.3 8.67 0.144 6.92 CONCLUSIONSThis is a very limited data set, providing more questions than answers, but it opens a curiosity to much more investigation to understand the function of these intrinsic hepatic vascular oscillations under normal, reflex, and pathophysiological conditions.

Impulse Processing Algorithm for Random Source Signals of Roadheaders That Is Based on Compound Interferometry

The boom-type roadheader is the main equipment for realizing the mechanization of coal drifting in coal mines, and it is an indispensable production equipment in major coal-producing countries. Substantial vibrations are generated during the operation of a roadheader; these vibrations carry substantial energy and, thus, can be regarded as a potential source and used for seismic advance detection purposes in mine drifts. Compared with a conventional exploration source, a roadheader source produces a complex continuous random signal. The shape of a seismic wavelet is uncertain and its duration is relatively long; thus, it must be processed into a conventional pulse signal before it can be used for subsequent processing and analysis. Therefore, based on the advantages of seismic interferometry in random signal processing, two seismic interference techniques, namely, deconvolution and cross-correlation, are introduced for constructing a compound interference algorithm. On the basis of a theoretically derived formula, a random signal impulse processing experiment is conducted using field-acquired source signals from a roadheader; this approach resolves the problem that cross-correlation alone cannot yield ideal results. Hence, a feasible algorithm for the impulse processing of a random signal, namely, the compound interference algorithm, is proposed. The algorithm deconvolves each seismic trace to obtain the reference trace and other receiver traces after compressing the wavelet. Then, the reference trace and each receiver trace are cross-correlated, and the wavelet time delay information of each correlated wavelet pulse, namely, the wavelet time delay information of the receiver trace relative to the reference trace, is obtained. Accordingly, the direct wave and reflected waves are recognized. To evaluate the performance of the algorithm, an algorithm application experiment is conducted for another group of random source signals that were collected by a roadheader under different coal drift conditions. Again, the algorithm processing results are consistent with the single-shot record characteristics of an explosive source. Consequently, the proposed algorithm can satisfy the requirements for engineering exploration and analysis. A comprehensive analysis further demonstrates that the compound interference algorithm is both feasible and effective and that the processed seismic signals can be used for subsequent processing and interpretation.

Imaging With Therapeutic Acoustic Wavelets-Short Pulses Enable Acoustic Localization When Time of Arrival is Combined With Delay and Sum.

Passive acoustic mapping (PAM) is an algorithm that reconstructs the location of acoustic sources using an array of receivers. This technique can monitor therapeutic ultrasound procedures to confirm the spatial distribution and amount of microbubble activity induced. Current PAM algorithms have an excellent lateral resolution but have a poor axial resolution, making it difficult to distinguish acoustic sources within the ultrasound beams. With recent studies demonstrating that short-length and low-pressure pulses-acoustic wavelets-have the therapeutic function, we hypothesized that the axial resolution could be improved with a quasi-pulse-echo approach and that the resolution improvement would depend on the wavelet's pulse length. This article describes an algorithm that resolves acoustic sources axially using time of flight and laterally using delay-and-sum beamforming, which we named axial temporal position PAM (ATP-PAM). The algorithm accommodates a rapid short pulse (RaSP) sequence that can safely deliver drugs across the blood-brain barrier. We developed our algorithm with simulations (k-wave) and in vitro experiments for one-, two-, and five-cycle pulses, comparing our resolution against that of two current PAM algorithms. We then tested ATP-PAM in vivo and evaluated whether the reconstructed acoustic sources mapped to drug delivery within the brain. In simulations and in vitro, ATP-PAM had an improved resolution for all pulse lengths tested. In vivo, experiments in mice indicated that ATP-PAM could be used to target and monitor drug delivery into the brain. With acoustic wavelets and time of flight, ATP-PAM can locate acoustic sources with a vastly improved spatial resolution.

Image Fusion Based on Wavelet Transformation

The article based totally on the MATLAB software program simulation was carried out on the image fusion; to design and develop a MATLAB based image processing application for fusing two images of the similar scene received through other modalities. The application is required to use Discrete Wavelet Transform (DWT) and Pulse Coupled Neural Network (PCNN) techniques. The comparison is to be performed on the results obtained on the above mentioned techniques.

Stochastic Modeling and Synthesis of Near-Fault Forward-Directivity Ground Motions

The stochastic modeling and synthesis of near-fault forward-directivity ground motions for the prescribed seismic scenario is presented in this study. This stochastic model, which is established in the orientation of the strongest pulse, combines the directivity pulse component represented by the Gabor wavelet pulse model and the high-frequency component characterized by the modulated filtered white noise model. In this regard, the pulse feature, evolutionary intensity and frequency contents are reasonably considered. Then, the empirical predictive equations that relate the parameters of the proposed stochastic model to the variables that describe earthquake source, path, site conditions, and near-fault rupture-to-source geometry are developed based on both regression and correlation analysis. The basic procedure for the synthesis of possible forward-directivity ground motions under the prescribed seismic scenario is provided as well. The efficacy of the stochastic model and the simulation procedure is confirmed by comparing the simulated motions with the recorded ones in terms of time-series and response spectra values, which indicate that the synthetic ground motions are capable of reproducing the salient characteristics, as well as the natural variability, of the recorded ones. Therefore, the proposed stochastic modeling and simulation method is expected to be a desirable alternative and complement for recorded ground motions in the near-fault seismic risk assessment.

Forward Analysis of GPR for Underground Pipes Using CUDA-Implemented Conformal Symplectic Euler Algorithm

Ground-penetrating radar (GPR) is widely used in the detection and positioning of underground facilities. Through the inversion analysis of echo signals of GPR, information such as pipe material, burial depth and location of pipelines can be obtained. Unfortunately, underground pipelines are cylindrical, the ladder approximation method used in traditional forward models produces certain errors. In this study, an accurate and efficient numerical model of GPR forward model in underground pipelines is established using symplectic Euler algorithm, graphics processing unit (GPU) acceleration technology and surface conformal technology. With a Ricker wavelet pulse as the GPR source, the convolution perfectly matched layer (CPML) is incorporated in the symplectic Euler algorithm and shown to be effective to truncate the symplectic Euler computational domain. Through the simulation study of different underground pipeline models, GPR image characteristics of the metal pipeline, plastic pipeline and concrete pipeline filled with air and water are obtained. According to the numerical simulation results, parallel conformal symplectic Euler algorithm effectively reduces the false diffracted waves caused by ladder approximation and improves the computational efficiency of the model in metallic and non-metallic media.

Elastic Scattering of Ultrashort Laser Pulses on Noble Gas Atoms

The work deals with a theoretical investigation of elastic scattering of ultrashort electromagnetic pulses (USP) on the noble gas atoms in the far ultra-violet and soft X-ray regions. The investigation is performed within the framework of a dipole approximation and the first-order quantum-mechanics perturbation theory. Major attention is given to the study of the dependence of the total probability of scattering within the pulse time on the USP duration at different carrying frequency values. It is shown that at certain values of the problem parameters this dependence is nonlinear. The calculations are performed for the corrected Gaussian pulses and wavelet pulses without the carrying frequency.

Scattering of Femtosecond Laser Pulses on the Negative Hydrogen Ion

Elastic scattering of ultrashort laser pulses (USLPs) on the negative hydrogen ion is considered. Results of calculations of the USLP scattering probability are presented and analyzed for pulses of two types: the corrected Gaussian pulse and wavelet pulse without carrier frequency depending on the problem parameters.

A pulse-shape discrimination method for improving Gamma-ray spectrometry based on a new digital shaping filter

It is a usual practice for improving spectrum quality by the mean of designing a good shaping filter to improve signal-noise ratio in development of nuclear spectroscopy. Another method is proposed in the paper based on discriminating pulse-shape and discarding the bad pulse whose shape is distorted as a result of abnormal noise, unusual ballistic deficit or bad pulse pile-up. An Exponentially Decaying Pulse (EDP) generated in nuclear particle detectors can be transformed into a Mexican Hat Wavelet Pulse (MHWP) and the derivation process of the transform is given. After the transform is performed, the baseline drift is removed in the new MHWP. Moreover, the MHWP-shape can be discriminated with the three parameters: the time difference between the two minima of the MHWP, and the two ratios which are from the amplitude of the two minima respectively divided by the amplitude of the maximum in the MHWP. A new type of nuclear spectroscopy was implemented based on the new digital shaping filter and the Gamma-ray spectra were acquired with a variety of pulse-shape discrimination levels. It had manifested that the energy resolution and the peak-Compton ratio were both improved after the pulse-shape discrimination method was used.

Photoionization of a Statistic Atom by Ultrashort Wavelet Pulses

Photoionization of atoms by ultrashort electromagnetic wavelet pulses is investigated within the framework of a statistical model. Integral representations of the total probability of atom ionization are obtained within the time over which the pulse acts. It is shown that the dependence of this probability on the pulse duration in the considered case is bell-shaped. The wavelet pulse duration at which the maximum photoionization probability is reached is determined for different charges of atomic nuclii.

Adaptive waveform design based on Morlet wavelet for ultra-wideband MIMO radar

For the issue of deterioration in detection performance caused by dynamically changing environment in ultra- wideband (UWB) multiple input multiple output (MIMO) radar, this paper proposes a novel adaptive waveform design which is aimed to improve the ability of discriminating target and clutter from the radar scene. Firstly, a sequence of Morlet wavelet pulses with frequency hopping and pulse position modulation by Welch-Costas array is designed. Then a waveform optimization solution is proposed which is achieved by applying the minimization mutual-information (MI) strategy. After that, with subsequent iterations of the algorithm, simulation results demonstrate that the optimal waveform design method brings an improvement in the target detection ability in the presence of noise and clutter.

Photoionization of Rydberg States by Ultrashort Wavelet Pulses

Photoionization of Rydberg atomic state by the ultra-short wavelet pulses (USWP) is calculated in the frame of perturbation theory with the use of Kramers ionization cross-section. Two simplest types of USWP are considered, namely, cosine and sine pulses. Analytical expressions containing scaling functions for photoionization probability are derived for above- mentioned USWP.

On the Theory of Hydrogen Atom Ionization by Ultra‐Short Electromagnetic Pulses

AbstractAn investigation of the probability of hydrogen atom ionization by ultra‐short electromagnetic pulses is carried out in the frame of perturbation theory We consider the case when the electric field strength amplitude E0 in a pulse by two orders lower than characteristic atomic field strength Ea (Ea ≅ 5.1 · 109 V/cm). A detailed investigation of the dependence of the probabilities on the pulse duration was performed for Gaussian pulse shapes. In the case where the carrier frequency of the Gaussian pulse is larger than the atomic ionization potential, the probability goes to the standard limit of perturbation per unit time. At the same pulse durations, the probabilities for carrier frequencies less than the ionization potential go to zero. The frequency dependence of the ionization probability becomes equal to the standard threshold dependence with increasing pulse duration time. A comparison between the ionization effects caused by wavelet pulses without carrier frequency and Gaussian pulses with carrier frequency shows that the same ionization probability values are achieved when the pulse carrier frequency is detuned by about 20% from the ionization threshold. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

MHD WAVE REFRACTION AND THE ACOUSTIC HALO EFFECT AROUND SOLAR ACTIVE REGIONS: A 3D STUDY

An enhancement in high-frequency acoustic power is commonly observed in the solar photosphere and chromosphere surrounding magnetic active regions. We perform 3D linear forward wave modelling with a simple wavelet pulse acoustic source to ascertain whether the formation of the acoustic halo is caused by MHD mode conversion through regions of moderate and inclined magnetic fields. This conversion type is most efficient when high frequency waves from below intersect magnetic field lines at a large angle. We find a strong relationship between halo formation and the equipartition surface at which the Alfv\'en speed $a$ matches the sound speed $c$, lending support to the theory that photospheric and chromospheric halo enhancement is due to the creation and subsequent reflection of magnetically dominated fast waves from essentially acoustic waves as they cross $a=c$. In simulations where we have capped $a$ such that waves are not permitted to refract after reaching the $a=c$ height, halos are non-existent, which suggests that the power enhancement is wholly dependent on returning fast waves. We also reproduce some of the observed halo properties, such as a dual 6 and 8 mHz enhancement structure and a spatial spreading of the halo with height.

Sliding Displacement of Flexible Earth Slopes Subject to Near-Fault Ground Motions

AbstractA fully coupled simplified method that incorporates soil nonlinearity is used to conduct sliding-block analysis of slopes subjected to near-fault pulse-like and nonpulse-like ground motions. The effects of the ground motion pulse on the computed sliding displacements are investigated, and the efficiency of various ground motion intensity measures for predicting the sliding displacement of slopes is evaluated. It is shown that the slope is expected to have larger displacements over shorter time intervals when near-fault ground motions have pulse-like characteristics. Results also indicate that for cases in which the natural period of a slope is close to the period of the pulse of a recorded ground motion, an equivalent wavelet pulse appropriately represents the displacement response of slopes. Predictive models are developed for the sliding displacement of near-fault ground motions using spectral acceleration and peak ground velocity as predictive variables. In addition, it is shown that for certai...

Wavelet Pulse를 이용한 다중 사용자 환경에서의 TR-UWB 시스템의 성능 비교

Abstract In this paper, the performance comparison of the TR-UWB System using Wavelet Pulse, DPSS pulse, and second Gaussian pulse in multi-user environment is analyzed. The data signal and the reference signal is sent with some time intervals in TR-UWB system. At this time the two signals are through the same channel. In the receiver the reference signal is used as a template. This advantage results in demodulation without channel estimation and low complexity of it. However the conventional TR-UWB system based on a Gaussian signal in a multi-user environment has the disadvantage of poor performance due to the interferences between the users. To overcome this disadvantage, DPSS (Discrete Prolate Shperoidal Sequence) is used to reduce the interferences between the users. We propose the system with multiresolution function of orthogonal wavelet reducing the interferences, which has a better performance in multi-user environment when they are sent in transmission side. Key Words : Wavelet, Discrete Prolate Shperoidal Sequence, Transmitted Reference Ultra Wide Band, Multiresolution

Effects of near-fault ground motions and equivalent pulses on multi-story structures

The focus of this paper is the structural response of multi-story structures to near-fault ground motions, and whether structural response is dominated by the ground motion pulses present in forward-directivity ground motions. Also considered is whether simplified pulses are capable of representing the effects of these pulses on structural response. Incremental Dynamic Analysis was employed to assess the effects of forward-directivity pulses on the response of near-fault multi-story structures. Three different generic multi-story shear buildings were subjected to fifty four near-fault ground motions including ordinary and forward-directivity records. The Maximum Story Displacement Ductility Demand was selected as the Engineering Demand Parameter. Results showed that pulse-like forward-directivity ground motions impose a larger ductility demand to the structure compared to ordinary ground motions. Moreover, the response of the structures to forward-directivity motions shows higher scatter than the response to ordinary ground motions when correlated with simple intensity measures such as PGA or spectral acceleration at the first mode period. The only intensity measure that appears to be valid for both ordinary and forward-directivity ground motions is the peak ground velocity. The structural response to the forward directivity ground motions was reproduced using an equivalent pulse model based on the modified Gabor Wavelet pulse. It is shown that when the ratio of pulse period to the fundamental structural period falls in a range of 0.5–2.5, the equivalent pulse model appropriately represents the structural response to forward-directivity ground motions. The simplified pulse parameters can be predicted using existing relationships and can be incorporated into probabilistic seismic hazard analysis to develop a seismic reliability analysis. Finally, the effects of damping ratio and P - Δ were investigated for forward-directivity ground motions. The effect of variations in the damping ratio on the ductility demand was insignificant while P - Δ -effects on the ductility demand are significant.