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this paper endeavours to study aspects of wave propagation in a random generalized-thermal micropolar elastic medium. the smooth perturbation technique conformable to stochastic differential equations has been employed. six different types of waves propagate in the random medium. the dispersion equations have been deri... | on wave propagation in a random micropolar generalized thermoelastic medium |
in modern physics it has become common to find the solution of a problem by solving numerically a set of pdes. whether solving them on a finite difference grid or by a finite element approach, the main calculations are often applied to a stencil structure. in the last decade it has become usual to work with so called b... | hybrid multicore/vectorisation technique applied to the elastic wave equation on a staggered grid |
in this paper, modal parameters of a layered soil system comprising of a soft clay layer overlying a dense sand layer are identified from accelerometer recordings in a centrifuge test. for the first time, the subspace state space system identification (4sid) method was employed to identify the natural frequencies, damp... | modal identification of a centrifuge soil model using subspace state space method |
coda wave interferometry (cwi) is largely employed in geotechnical applications to monitor changes due to cracks in materials but it is still not used for composite materials. in this paper, the technique is proposed to study internal stresses in a composite laminate [0°/90°]63 and was compared with the traditional aco... | internal stress determination in a polymer composite by coda wave interferometry |
the aim here is to model torsional waves in homogeneous and expanding twisted flux tubes of solar coronal magnetic plasma structures. for the sake of simplicity, a force-free condition applicable to solar magnetic structures is presented to determine the existing three-dimensional equilibrium magnetic fields. the deter... | torsional waves with force-free magnetic fields in solar plasma structures |
grating-based phase contrast mammography can help facilitate breast cancer diagnosis, as several research works have demonstrated. to translate this technique to the clinics, it has to be adapted to cover a large field of view within a limited exposure time and with a clinically acceptable radiation dose. this indicate... | design of a sensitive grating-based phase contrast mammography prototype (conference presentation) |
we extend our recently developed beam-deflection (bd) method which we used to determine the sign, magnitude, and ultrafast dynamics of bound electronic and nuclear nonlinear optical responses, to measure elements of the third-order nonlinear optical susceptibility tensor with longitudinal field components. in these mea... | cross-propagating beam-deflection measurements of third-order nonlinear optical susceptibility |
a method is described for the prediction of site-specific surface ground motion due to induced earthquakes occurring in predictable and well-defined source zones. the method is based on empirical green's functions (egfs), determined using micro-earthquakes at sites where seismicity is being induced (e.g., hydraulic fra... | a hybrid empirical green's function technique for predicting ground motion from induced seismicity: application to the basel enhanced geothermal system |
a traditional penetrometer measurement of soil strength in terms of penetration resistance, a useful indicator of a soil's mechanical property, is invasive and manually laborious. an alternative non‑invasive technique uses an acoustic source, two microphones and a laser doppler vibrometer to obtain acoustic‑to‑seismic ... | non‑invasive estimation of the depth profile of soil strength with acoustic‑to‑seismic coupling measurement in the presence of crops |
in general, the ultrasonic techniques have been used to determine the mechanical properties of materials based on their relationship with metallurgical characteristics. in this research work, the relationship between ultrasonic wave velocity, hardness and the microstructure of steel pipeline welded joints is investigat... | relation between hardness and ultrasonic velocity on pipeline steel welded joints |
a growing acceptance of fiber-reinforced composite materials imparts some relevance to exploring the effects which a predominantly linear scattering lattice may have upon interior radiative transport. indeed, a central feature of electromagnetic wave propagation within such a lattice, if sufficiently dilute, is ray con... | radiative albedo from a linearly fibered half-space |
for many years sound has been used as a primary method for underwater communication. however, data transmission rate of acoustic systems is low because typical frequencies associated with underwater acoustics are between tens of hertz and hundreds of kilohertz. a higher bandwidth can be achieved with visible light to t... | characterization of underwater optical turbulence on the example of the rayleigh-benard water tank |
an experimental study was conducted on the specific features of instability wave propagation in the mixing layer of a turbulent jet when the jet is excited by an external acoustic wave. we used the technique of conditional phase averaging of data obtained by particle image velocimetry using the reference signal of a mi... | experimental study of propagation of instability waves in a submerged jet under transverse acoustic excitation |
the earliest attempt of seismic characterization of the subsurface using controlled sources date from the mid 1800's [mallet, 1852]. this initial experiment, carried out in ireland, was followed by increasing efforts in the development of the theory of seismic wave propagation through heterogeneous media. in the early ... | preface to the "deep seismix-2014" special issue |
shear wave oce (sw-oce) is a novel technique that relies on the detection of the localized shear wave speed to map tissue elasticity. in this study, we demonstrate high speed imaging to capture single-shot transient shear wave propagation for sw-oce. the fast imaging speed is achieved using a fourier domain mode-locked... | optical coherence elastography based on high speed imaging of single-hot laser-induced acoustic waves at 16 khz frame rate |
the biomechanical properties of the sclera could provide key information regarding the progression and etiology of ocular diseases. for example, an elevated intraocular pressure is one of the most common risk factors for glaucoma and can cause pathological deformations in the tissues of the posterior eye, such as the s... | evaluation of posterior porcine sclera elasticity in situ as a function of iop |
approaches to the modeling of the acoustic field, provided by the through type ultrasound transducers in a cylindrical object, by the finite element technique are introduced in this paper and the developed model is described. the calculation results of the acoustic wave propagation over a rod section are shown, an osci... | mathematical modeling of the acoustic wave propagation generated by the through-type transducer in a cylindrical object |
static time-delay corrections are frequency independent and ignore velocity variations away from the assumed vertical ray path through the subsurface. there is therefore a clear potential for improvement if the finite frequency nature of wave propagation can be properly accounted for. such a method is presented here ba... | surface consistent finite frequency phase corrections |
this work is devoted to the asymptotic analysis of high frequency wave propagation in random media with long-range dependence. we are interested in two asymptotic regimes, that we investigate simultaneously: the paraxial approximation, where the wave is collimated and propagates along a privileged direction of propagat... | fractional white-noise limit and paraxial approximation for waves in random media |
in this paper, we investigated transducer placement strategies for detecting cracks in primary aircraft structures using ultrasonic structural health monitoring (shm). the approach developed is for an expected damage location based on fracture mechanics, for example fatigue crack growth in a high stress location. to as... | transducer placement option of lamb wave shm system for hotspot damage monitoring |
sunspot is the most significant feature in solar disk, and the earliest record of the solar activities. it has been systematically observed for about 400 years after the invention of telescopes. the long-term evolution of solar activities, especially the 11 year solar cycle, has been obtained based on these data to a g... | accuracy analysis for digitized sunspot hand-drawing records of purple mountain observatory |
in this paper, we introduce a method for estimating human left/right walking gait balance using footstep-induced structural vibrations. understanding human gait balance is an integral component of assessing gait, neurological and musculoskeletal conditions, overall health status, and risk of falls. existing techniques ... | characterizing left-right gait balance using footstep-induced structural vibrations |
an efficient and robust restart strategy is important for any krylov-based method for eigenvalue problems. the tensor infinite arnoldi method (tiar) is a krylov-based method for solving nonlinear eigenvalue problems (neps). this method can be interpreted as an arnoldi method applied to a linear and infinite dimensional... | restarting for the tensor infinite arnoldi method |
pulse thermography or thermal wave imaging are commonly used as nondestructive evaluation (nde) method. while the technical aspect has evolve with time, theoretical interpretation is lagging. interpretation is still using curved fitting on a log log scale. a new approach based directly on the governing differential equ... | analysis of pulse thermography using similarities between wave and diffusion propagation |
we present a seismological method for probing the solar atmosphere above sunspot umbrae with three-minute oscillations. our technique allows us to estimate both the vertical distance between atmospheric layers and the wave-propagation speed, without specifying any additional parameters, in particular, the phase speed o... | probing the sunspot atmosphere with three-minute oscillations |
to operate safely, structures and components need to be inspected or monitored either periodically or in real time for potential failure. for this purpose, ultrasonic nondestructive evaluation (nde) techniques have been used extensively. most of these ultrasonic nde techniques utilize only the linear behavior of the ul... | nonlinear wave mixing technique for nondestructive assessment of infrastructure materials |
we review modern hf-x band radars covering over-the-horizon problems. the ionosphere significantly affects wave propagation in all the bands. we describe available correction techniques, which use additional evidence on the ionosphere, as well as models of different degrees of complexity. the fact that the field of vie... | analyzing existing applied models of the ionosphere for calculating radio wave propagation and possibility of their use for radar systems. i. classification of applied models and the main requirements imposed on them for radar aids |
seismic interferometry is a technique that enables the extraction of the seismic impulse response (green's function) between two receivers. the retrieved response is generally dominated by surface waves when sources are located at or near the surface of the earth. in onshore seismic exploration, dealing with complex ne... | reconstruction of surface waves using super virtual interferometry: an example from the forsmark site, sweden |
the purpose of deep-focusing time-distance helioseismology is to construct seismic measurements that have a high sensitivity to the physical conditions at a desired target point in the solar interior. with this technique, pairs of points on the solar surface are chosen such that acoustic ray paths intersect at this tar... | comparison of travel-time and amplitude measurements for deep-focusing time-distance helioseismology |
wave propagation simulation, as an essential part of many algorithms in seismic exploration, is associated with high computational cost. reduced order modelling (rom) is a known technique in many different applications that can reduce the computational cost of simulation by employing an approximation of the model param... | acoustic wave propagation simulation by reduced order modelling |
a well-known optimal velocity (ov) model describes vehicle motion along a single lane road, which reduces to a perturbed modified korteweg-de vries (mkdv) equation within the unstable regime. steady travelling wave solutions to this equation are then derived with a multi-scale perturbation technique, where the travelli... | travelling wave solutions of the perturbed mkdv equation that represent traffic congestion |
in this work, we investigate mathematical models for electromagnetic wave propagation in dispersive isotropic media. we emphasize the link between physical requirements and mathematical properties of the models. a particular attention is devoted to the notion of non-dissipativity and passivity. we consider successively... | mathematical models for dispersive electromagnetic waves: an overview |
jointed composite structures (jcss) are often used in the marine, automotive and civil engineering industries. in jcs, thin carbon-fiber-reinforced composite laminates are bonded with epoxy adhesives. but, disbonds can occur at the bondinterphase due to variable environmental conditions, cyclic loading, aging, fatigue,... | study of disbond effects in a jointed composite structure under variable ambient temperatures |
vibration based methods are commonly deployed to detect structural damage using sensors placed remotely from potential damage sites. whilst many such techniques are modal based there are advantages to adopting a wave approach, in which case it is essential to characterise wave propagation in the structure. the wave fin... | application of the wave finite element method to reinforced concrete structures with damage |
by using relationships between wave propagation and thermal diffusive propagation, it was shown that that one can transform from diffusive propagation into an equivalent wave field. the transformation results in sharp reflections with time delay proportional to the distance. the performance of the transform was tested ... | equivalent wave field transform applied to pulse thermography in carbon composite samples |
various non-destructive testing (ndt) methods have been developed to extract information about state of a structure. two of them: vibration-based and guided wave-based techniques are one of the most commonly used and well developed. both approaches can be implemented using scanning laser doppler vibrometer measurements... | combined vibration and guided wave-based approach for composite panels health assessment |
the aim of this study is to develop an efficient numerical technique using the non-hypersingular, traction boundary integral equation method (biem) for solving wave propagation problems in an anisotropic, viscoelastic plane with cracks. the methodology can be extended from the macro-scale with certain modifications to ... | dynamic response of a cracked viscoelastic anisotropic plane using boundary elements and fractional derivatives |
the determination of physical and mechanical properties of rocks such as attenuation coefficient, bulk density, young's modulus and poisson's ratio in laboratory or in situ conditions is time consuming, tedious and requires special equipment and expertise. however, the use of new technologies based on the propagation o... | a new ultrasound method for measuring the physical and mechanical properties of rocks |
a number of techniques are available for acoustic source localization in isotropic plates without knowing the material properties of the plate. however, for a highly anisotropic plate acoustic source localization requires some knowledge of the plate material properties or its group velocity profile. in absence of this ... | acoustic source localization in an anisotropic plate without knowing its material properties: a new approach |
the characterization of the fade dynamics on earth-satellite links is an important subject when designing the so called fade mitigation techniques that contribute to the proper reliability of the satellite communication systems and the customers' quality of service (qos). the interfade duration, defined as the period b... | characterization of interfade duration for satellite communication systems design and optimization in a temperate climate |
in this work, the theory of coupled plasma, thermal and elastic waves were used to investigate the wave propagation on semiconductor material during photo-thermo-elastic process. a thin slim strip (tss) medium, elastic semiconductor with isotropic and homogeneous thermal and elastic properties have been considered. the... | a study on photothermal waves in a semiconductor material photogenerated by a focused laser beam |
the longitudinal field avoided level crossing (alc) muon spectrum of crystalline benzene is found to exhibit multiple complex features that strongly depend on temperature. in this work, a number of different computational techniques were used in conjunction to explain this behavior. an overall picture emerges in which ... | exploring the temperature dependent solid-state alc spectrum of the c6h6mu• radical with ab-initio simulation techniques |
solar flares are known to generate seismic waves in the sun. we present a detailed analysis of seismic emission in sunspots accompanying m- and x-class solar flares. for this purpose, we have used high-resolution dopplergrams and line-of-sight magnetograms at a cadence of 45 s, along with vector magnetograms at a caden... | on the seismic emission in sunspots associated with lorentz force changes accompanying major solar flares |
peridynamic based elastodynamic computation tool named peri-elastodynamics is proposed herein to simulate the three-dimensional (3d) lamb wave modes in materials for the first time. peri-elastodynamics is a nonlocal meshless approach which is a scale-independent generalized technique to visualize the acoustic and ultra... | peri-elastodynamic simulations of guided ultrasonic waves in plate-like structure with surface mounted pzt |
the sun's polar regions remain largely unobserved and yet understanding and monitoring of the magnetic field, convective flows, and coronal outflow conditions in the solar polar regions are the keys to accurately modeling and forecasting the solar cycle, solar wind conditions, and cme arrival times at earth. we describ... | the solar polar observing constellation (spoc) mission: research and operational monitoring of space weather from polar heliocentric orbits |
helioseismic holography is a powerful technique used to probe the solar interior based on estimations of the 3d wavefield. the porter-bojarski holography, which is a well-established method used in acoustics to recover sources and scatterers in 3d, is also an estimation of the wavefield, and hence it has the potential ... | ghost images in helioseismic holography? toy models in a uniform medium |
lamb wave based structural health monitoring (shm) has received much attention during the past decades for its broad coverage and high sensitivity to damage. lamb waves can be used to locate and quantify damage in static structures successfully. nonetheless, structures are usually subjected to various external vibratio... | lamb wave propagation in vibrating structures for effective health monitoring |
temperature variations affect lamb wave propagation and therefore in this way they can severely limit application of baseline signals in shm systems. various techniques are proposed in the paper to solve this problem. new method based on an interpretation of multiple signals acquired in distinct points of the structure... | data fusion for compensation of temperature variations in lamb-wave based shm systems |
graphics processing units (gpus) have become increasingly powerful in recent years. programs exploring the advantages of this architecture could achieve large performance gains and this is the aim of new initiatives in high performance computing. the objective of this work is to develop an efficient tool to model 2d el... | gpu computing with opencl to model 2d elastic wave propagation: exploring memory usage |
this research considers the effects of diffraction, attenuation, and the nonlinearity of generating sources on measurements of nonlinear ultrasonic rayleigh wave propagation. a new theoretical framework for correcting measurements made with air-coupled and contact piezoelectric receivers for the aforementioned effects ... | measurement and fitting techniques for the assessment of material nonlinearity using nonlinear rayleigh waves |
for dynamic rupture problems, numerical simulation methods, such as the finite-difference method, the finite-element method and the boundary integral element method, usually produce spurious high-frequency oscillations that are mainly generated by discontinuities in the friction law and poor resolution of the breakdown... | a new time-marching scheme that suppresses spurious oscillations in the dynamic rupture problem of the spectral element method: the weighted velocity newmark scheme |
precision doppler tracking supports many investigations, especially determinations of gravity fields and interior structures of solar system bodies. analysis of past measurements, acquired on a 34m diameter antenna and calibrated with an external, co-pointing, water vapor radiometer, reveals that errors are dominated b... | in-line water vapor radiometer for precision deep space doppler tracking |
composite materials are susceptible to hidden defects that may occur during manufacturing and service (e.g., foreign object impact) and may grow to a critical size, jeopardizing the integrity of the structure. among the various existing techniques, guided wave methods provide a good compromise in terms of sensitivity t... | guided waves for detection of delamination and disbonding in stiffened composite panels |
this book reviews the field of helioseismology and its outstanding challenges and also offers a detailed discussion of the latest computational methodologies. the focus is on the development and implementation of techniques to create 3-d images of convection and magnetism in the solar interior and to introduce the late... | imaging convection and magnetism in the sun |
the conventional finite-difference time-domain (fdtd) method for elastic waves suffers from the staircasing error when applied to model a curved free surface because of the structured grid. this is similar to the situation for the fdtd method in electromagnetics when it is applied to model a curved perfect conductor su... | a 2-d enlarged cell technique (ect) for elastic wave modelling on a curved free surface |
in structural health monitoring (shm), classical imaging techniques rely on the use of analytical formulations to predict the propagation and interaction of guided waves generated using piezoceramic (pzt) transducers. for the implementation of advanced imaging approaches on composites structures, analytical formulation... | semi-analytical modelling of guided waves generation on composite structures using circular piezoceramics |
conventional non-destructive inspection of a pipe by ultrasonic wave has difficulty with inspection efficiency because it is a technique to apply by using longitudinal wave or transverse wave which propagates to the thickness direction of a pipe for smaller area than an ultrasonic sensor. however, a guide wave is provi... | pipe inspection system of a pipe by three-modes guide wave using polarized-transverse wave emats |
synoptic map of magnetic field is an important piece of data used for many space weather models. currently solar observation can only provide magnetic field measurement on the earth-side surface. to generate magnetic field synoptic maps, the magnetic field measured about 13 days ago is used for the far-side surface whe... | using sun's far-side images inferred by the time-distance helioseismic imaging to improve synoptic maps of magnetic field: importance and methodology |
this paper aimed to investigate propagation characteristics of the pressure wave in gas flow through pipes and the potential application of the pressure wave propagation theory in the early detection of gas influxes due to encountering gas-bearing fractures in gas drilling. in this work, a simpler and reliable analytic... | investigation on propagation characteristics of the pressure wave in gas flow through pipes and its application in gas drilling |
long-range guided wave testing (gwt) is routinely used for the monitoring and detection of corrosion defects in above ground pipelines in various industries. the gwt test range in buried, coated pipelines is greatly reduced compared to aboveground pipelines due to energy leakage into the embedding soil. in this study, ... | guided wave attenuation in coated pipes buried in sand |
a process of diffusion of small-scale magnetic elements inside four active regions (ars) was analysed. line-of-sight magnetograms acquired by the helioseismic and magnetic imager (hmi) onboard the solar dynamic observatory during a two-day time interval around the ar culmination time were utilized. small magnetic eleme... | dispersion of small magnetic elements inside active regions on the sun |
coalbed methane can be detected employing the amplitudevariation-with-offset technique. however, there are two issues in applying this technique to a coalbed: strong azimuthal anisotropy resulting from high-density fractures, and the seismic response being composed of many or several individual reflections within the c... | wave propagation modeling and amplitude-variation-with-offset response in a fractured coalbed |
in this paper we consider narrow band, active array imaging of weak localized scatterers when only the intensities are recorded at an array with n transducers. we consider that the medium is homogeneous and, hence, wave propagation is fully coherent. this work is an extension of our previous paper, where we showed that... | coherent imaging without phases |
we investigated the strength of the spin orbit interaction induced effective magnetic fields originating from two distinct mechanisms of different symmetry in pt/co/alo trilayer films with varying pt and co thicknesses. films are deposited by rf magnetron sputtering and effective magnetic fields are measured using an a... | layer thickness dependence of spin orbit torques and fields in pt/co/alo trilayer structures |
interpretation of lamb waves signals can rise serious difficulties due to their multi-modal nature. different modes propagating with different velocities can be misleading with damage reflected components. as a solution to this problem we propose a technique capable of modes separation based on a polarization filter. b... | separation of lamb waves modes using polarization filter of 3d laser measured signals |
prompted by a recent finding that the magnitude of the acoustic radiation force (arf) in isotropic tissue-like solids depends linearly on a particular third-order modulus of elasticity—hereon denoted by c, this study investigates the possibility of estimating c from the amplitude of the arf-generated shear waves. the f... | the ‘sixth sense’ of ultrasound: probing nonlinear elasticity with acoustic radiation force |
as the earth's inhomogeneous and viscoelastic properties, seismic signal attenuation we are trying to mitigate is a long-standing problem facing with high-resolution techniques. for addressing such a problem in the fields of time-frequency transform, gabor transform methods such as atom-window method (awm) and molecula... | resolution enhancement of non-stationary seismic data using amplitude-frequency partition |
the inspection possibilities of ground anchors are limited to destructive test such as pull-out test. guided wave propagation gives an opportunity to develop an inspection system dedicated to determine the condition of inspected element without violation of their integrity. in this paper the experimental study on wave ... | wave propagation in damage assessment of ground anchors |
purpose:this paper discusses an application of particle filtering for estimating shear wave velocity in tissue using ultrasound elastography data. shear wave velocity estimates are of significant clinical value as they help differentiate stiffer areas from softer areas which is an indicator of potential pathology.metho... | ultrasonic tracking of shear waves using a particle filter |
breakthroughs in understanding the structure and dynamics of our planet will strongly depend upon instrumenting deep oceans. progress has been made these last decades in ocean-bottom seismic observations, but ocean-bottom seismometer (obs) temporary deployments are still challenging and face set-up limitations. launche... | orienting and locating ocean-bottom seismometers from ship noise analysis |
the mechanism generating the array-distributed atmospheric refractivity fluctuation by a coherent acoustic source is analyzed. the theoretical model is established, which is used to quantifiably analyze the array structure of the artificial dielectric irregularities. it is qualitatively validated that the array-distrib... | a novel idea of purposefully affecting radio wave propagation by coherent acoustic source-induced atmospheric refractivity fluctuation |
acoustic emission (ae) technique is a powerful and potential nondestructive testing method in civil engineering. the ae behavior of concrete beams tested under flexural loading was investigated to characterize and identify cracking damages. the ae signal characteristics were analyzed by hilbert-huang transform (hht) wh... | characteristic identification of cracking acoustic emission signals in concrete beam based on hilbert-huang transform |
wave propagation can be an accurate method for determining material properties. high frequency whistler mode waves (0.7 < ω/|ωce| < 1) in an overdense plasma (ωpe > |ωce|) are damped primarily by doppler-shifted electron cyclotron resonance. a kinetic description of whistler mode propagation parallel to the ba... | alfvénic oscillations of the electron distribution function: linear theory and experimental measurements |
some uk and us nuclear power stations have begun introducing high-density polyethylene (hdpe) pipes to certain cooling water circuits. hdpe offers improved performance over existing pipe materials, such as cast iron, by not corroding in-ternally or externally, yet occasional defects form in hdpe pipe fusion joints at t... | improved fe simulation of ultrasound in plastics |
guided waves based damage detection techniques are popular for their ease of generation and detection along with their ability to travel long distances. accurate and efficient modeling is a key for successful implementation of guided waves for nde/shm. however, efficient prediction of scattering from various damage is ... | physics based modeling of guided waves for detection and characterization of structural damage in nde and shm |
glasses doped with rare earth elements (lanthanide series) are the most popular materials used in upconversion devices. the main aspect to develop these devices is to find suitable host materials for rare earth ions. the host material should have a high transmission of the upconverted photons, high thermal stability, g... | ultrasonic study on complex glass system doped with erbium oxide |
shear wave optical coherence elastography (sw-oce) uses the speed of propagating shear waves to provide a quantitative measurement of localized shear modulus, making it a valuable technique for the elasticity characterization of tissues such as skin and ocular tissue. one of the main challenges in shear wave elastograp... | quantitative shear wave optical coherence elastography (sw-oce) with acoustic radiation force impulses (arfi) induced by phase array transducer |
composite materials are being increasingly used to replace metals, partially or completely, in aerospace, shipping and automotive industries because of their light weight, corrosion resistance, and mechanical strength. integrity of these materials may be compromised during manufacturing or due to impact damage during u... | nde of composite structures using microwave time reversal imaging |
ultrasonic wave propagation decreases as a material is heated. two factors that can characterize material properties are changes in wave speed and energy loss from interactions within the media. relatively small variations in velocity and attenuation can detect significant differences in microstructures. this paper dis... | wave speed propagation measurements on highly attenuative heated materials |
we apply a new technique, the mutual information (mi) from information theory, to time-distance helioseismology, and demonstrate that it can successfully reproduce several classic results based on the widely used cross-covariance method. mi quantifies the deviation of two random variables from complete independence and... | application of mutual information methods in time-distance helioseismology |
the polarimetric and helioseismic imager instrument for the solar orbiter mission from the european space agency requires a high stability while capturing images, specially for the polarimetric ones. for this reason, an image stabilization system has been included in the instrument. it uses global motion estimation tec... | subpixel real-time jitter detection algorithm and implementation for polarimetric and helioseismic imager |
this book gives guidance to solve problems in electromagnetics, providing both examples of solving serious research problems as well as the original results to encourage further investigations. the book contains seven chapters on various aspects of resonant wave scattering, each solving one original problem. all of the... | electromagnetic waves in complex systems: selected theoretical and applied problems |
emc requirements for scientific satellites are usually very stringent and much more demanding than terrestrial standards, mainly because ad-hoc scientific instruments developed for the mission require very quiet electromagnetic environments to perform their science. these requirements will assure the compatibility of a... | radiated emissions of the power converter module of the polarimetric and helioseismic imager instrument on board of solar orbiter: a case study |
the base of the convection zone and the tachocline play a major role in the study of the dynamics of the sun, especially in the solar dynamo. here, we present a phase-sensitive helioseismic holography method to infer changes in the sound-speed profile of the solar interior. we test the technique using numerically simul... | seismic holography of the solar interior near the maximum and minimum of solar activity |
we introduce the complex-step-finite-difference method (csfdm) as a generalization of the well-known finite-difference method (fdm) for solving the acoustic and elastic wave equations. we have found a direct relationship between modelling the second-order wave equation by the fdm and the first-order wave equation by th... | the complex-step-finite-difference method |
when applying the ray tracing in ionospheric propagation, the electron density modelling is the main input of the algorithm, since phase refractive index strongly depends on it. also the magnetic field and frequency collision modelling have their importance, the former as responsible for the azimuth angle deviation of ... | correction's method of the electron density model in ionosphere by ray tracing techniques |
to limit the computation time and the computer resource, 2-d numerical approaches such as 2-d parabolic wave equation (2-d pwe) associated with 1-d multiple phase screens (1-d mps) are classically used to estimate ionospheric scintillation effects on radio wave propagation. however, in the ionosphere, the turbulent flu... | validity of 2-d electromagnetic approaches to estimate log-amplitude and phase variances due to 3-d ionospheric irregularities |
this article aims to address the exact solution of the prestigious partial differential equation, namely, a double dispersive equation. here, we are obtaining some new traveling wave solutions of the double dispersive equation with the more general mathematical technique, which is a direct algebraic extended method. th... | propagation of some new traveling wave patterns of the double dispersive equation |
the propagation of magnetostatic surface spin waves in permalloy stripes was observed by high-resolution wide-field magneto-optical kerr microscopy using the stroboscope technique. a long-time stable semiconductor-laser light source was employed and uniform illumination using a fiber speckle reducer and active stabiliz... | time-resolved vector-field imaging of spin-wave propagation in permalloy stripes using wide-field magneto-optical kerr microscopy |
materials with spatiotemporally varying properties exhibit nonreciprocal wave propagation characteristics. nonreciprocity is predominantly identified by a left-to-right (l-r) transmission amplitude that is different from the right-to-left (r-l) transmission amplitude; a significant difference in the transmitted amplitu... | nonreciprocal phase shifts in spatiotemporally varying materials |
high-melt areas of glaciers generate a rich spectrum of ambient seismicity. these signals do not only contain information about the source mechanisms (e.g. englacial fracturing, water flow, iceberg detachment, basal stick-slip motion) but also carry information about seismic wave propagation within the glacier ice and,... | rayleigh wave is the coolest - resolving microseismicity of a tidewater glacier in svalbard |
this paper aims to present a calibration optimization method for radar cross section measurement setup using time domain measurements. the proposed method requires a measurement of s21 parameter of a metallic plate with a known rcs at 13 different distances. a post processing technique reveals the correlations between ... | improvement of setup calibration for radar cross section measurements |
sound radiation from structures in an underwater waveguide presents a challenging underwater acoustics problem typically resolved with numerical methods. this can be computationally inefficient and limited to low-frequency analysis. hybrid approaches improve on these limitations by combining numerical methods with anal... | predicting the acoustic response of a cylindrical shell immersed in an underwater waveguide using a substructuring technique |
utilizing the shallow water acoustic interference phenomenon in the range-frequency domain, striation-based beamforming (sbf) was proposed to estimate waveguide invariant and enhance active sonar output. in the past decade, sbf has also been applied to enhance lofargrams to improve tracking performance. in this paper, ... | understanding and applications of striation-based beamforming in underwater acoustics |
the guided wave technique is well known for long range pipe inspection. guided wave scattered signal analysis is difficult due to the complex geometry such as corrosion. reciprocity relation is well established theorem to convert complicate mathematical expression to simpler manner. wave signal analysis is performed fo... | a study on closed form solution of guided waves scattering amplitude by the use of reciprocity theorem in the cylindrical coordinate |
the devastating signature of the mw7.8 nepal earthquake in the kathmandu valley still exists in the form of a large number of damaged and tilted buildings at several locations. the study of the main shock and nearly 500 aftershocks that have occurred as far as about 130 km east of the main shock epicenter suggest that ... | 3d-sem ground response analysis of kathmandu valley during the 2015 nepal earthquake |
the practicality of laser ultrasonic scanning is limited because scanning at a high spatial resolution demands a prohibitively long scanning time. inspired by binary search, an accelerated defect visualization technique is developed to visualize defect with a reduced scanning time. the pitch-catch distance between the ... | accelerated defect visualization of microelectronic systems using binary search with fixed pitch-catch distance laser ultrasonic scanning |
the boundary element method (bem) is a powerful algorithm to solve the helmholtz equation for harmonic acoustic waves. the explicit use of green's functions avoids domain truncation of unbounded regions and accurately models wave propagation through homogeneous materials. furthermore, fast multipole and hierarchical co... | fast and accurate boundary element methods for large-scale computational acoustics |
typically, material properties originate from destructive tensile tests and are used in computational models in the design and analysis process of structures. this approach is well-established in relation to isotropic homogeneous materials. however, if this approach is used for composite laminates, inaccuracies can ari... | parametric studies of composite material properties influence on dispersion curves of lamb waves |
distinguishing between competing formation theories for our solar system requires revealing the deep internal structure of the gas giants. helioseismology has been remarkably successful in probing the deep internal structure of the sun, and the gas giants also consist primarily of hydrogen and helium with deep convecti... | taking the pulse of the gas giants from antarctica |
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