Wave Curves Research Articles

Digital Photoplethysmography for Assessment of Arterial Stiffness: Repeatability and Comparison with Applanation Tonometry.

IntroductionArterial stiffness is an independent risk factor for cardiovascular morbidity and can be assessed by applanation tonometry by measuring pulse wave velocity (PWV) and augmentation index (AIX) by pressure pulse wave analysis (PWA). As an inexpensive and operator independent alternative, photoelectric plethysmography (PPG) has been introduced with analysis of the digital volume pulse wave (DPA) and its second derivatives of wave reflections.ObjectiveThe objective was to investigate the repeatability of arterial stiffness parameters measured by digital pulse wave analysis (DPA) and the associations to applanation tonometry parameters.Methods and Results112 pregnant and non-pregnant individuals of different ages and genders were examined with SphygmoCor arterial wall tonometry and Meridian DPA finger photoplethysmography. Coefficients of repeatability, Bland-Altman plots, intraclass correlation coefficients and correlations to heart rate (HR) and body height were calculated for DPA variables, and the DPA variables were compared to tonometry variables left ventricular ejection time (LVET), PWV and AIX. No DPA variable showed any systematic measurement error or excellent repeatability, but dicrotic index (DI), dicrotic dilatation index (DDI), cardiac ejection elasticity index (EEI), aging index (AI) and second derivatives of the crude pulse wave curve, b/a and e/a, showed good repeatability. Overall, the correlations to AIX were better than to PWV, with correlations coefficients >0.70 for EEI, AI and b/a. Considering the level of repeatability and the correlations to tonometry, the overall best DPA parameters were EEI, AI and b/a. The two pansystolic time parameters, ejection time compensated (ETc) by DPA and LVET by tonometry, showed a significant but weak correlation.ConclusionFor estimation of the LV function, ETc, EEI and b/a are suitable, for large artery stiffness EEI, and for small arteries DI and DDI. The only global parameter, AI, showed a high repeatability and the overall best correlations with AIX and PWV.

Properties of the Wave Curves in the Shallow Water Equations with Discontinuous Topography

We first establish the monotonicity of the curves of composite waves for shallow water equations with discontinuous topography. Second, a critical investigation of the Riemann problem yields deterministic results for large data on the existence of Riemann solutions made of Lax shocks, rarefaction waves, and admissible stationary contacts. Although multiple solutions can be constructed for certain Riemann data, we can determine relatively large neighborhoods of Riemann data in which the Riemann problem admits a unique solution.

Shear wave velocity analysis of a deep seated gravel landslide structure using the microtremor survey method

The depth and geometry of potential failure surface is the fundamental for evaluating the mechanisms of a landslide. Traditional techniques to acquire information on potential sliding surface are mainly drilling, pitting, and trenching, but these techniques are time consuming and expensive. In this study, microtremor signals and the dispersion curves of surface wave are extracted from the vertical component of microtremor records using the spatial autocorrelation (SPAC) method to estimate shear wave velocity structure. The results suggest that the buried depth of phyllite bedrock is approximately 47.4m, and the thickness of weathered bedrock layer is about 9.9m at about 57.3m deep, which could be interpreted as the potential sliding surface of this landslide, in accordance with borehole data. The microtremor survey method (MSM) is flexible, non-invasive, relatively quick and deployable on the landslide. It clearly demonstrat that it is an effective tool to improve the drilling success rate, and hence allow a large scale and high density investigation of structure characteristics of a deep seated landslide.

Lithospheric shear wave velocity and radial anisotropy beneath the northern part of North China from surface wave dispersion analysis

AbstractRayleigh and Love wave phase velocities in the northern part of the North China are obtained from ambient noise tomography in the period range of 8–35 s and two plane wave earthquake tomography at periods of 20–91 s using data recorded at 222 broadband seismic stations from the temporary North China Seismic Array and permanent China Digital Seismic Array. The dispersion curves of Rayleigh and Love wave from 8 to 91 s are jointly inverted for the 3‐D shear wave structure and radial anisotropy in the lithosphere to 140 km depth. Distinct seismic structures is observed from the Fenhe Graben and Taihang Mountain to the North China Basin. The North China Basin from the lower crust to the depth of 140 km is characterized by high‐velocity anomaly, reflecting mafic intrusion and residual materials after the extraction of melt, and by strong radial anisotropy with Vsh > Vsv, implying horizontal layering of intrusion and alignment of minerals due to vigorous extensional deformation and subsequent thermal annealing. However, low‐velocity anomaly and positive radial anisotropy are observed in the Fenhe Graben and Taihang Mountain, suggesting the presence of partial melt in the lithosphere due to the mantle upwelling and horizontal flow pull.

Sedimentation Rate Rhythms: Evidence from Filling of the Tarim Basin, Northwest China

AbstractVariations of sedimentation rate within a basin over geologic time are a time series that can be filtered into several cyclic wave curves. Based on back‐stripping and the empirical mode decomposition method, the cores from 14 wells in the Tarim Basin were selected to do filtering analysis. Four cycles or quasi‐cycles (33 Ma, 64.4 Ma, 103.6 Ma, and 224 Ma) were obtained. Among these, the 33 Ma period, which was related to the internal earth activity, an external force, or a combination of the two, was the most obvious. The 64.4 Ma period corresponded to the solar system crossing the galaxy plane or the periodic melting of inner‐earth material. The 103.6 Ma period was related with plate collisional tectonism around the Tarim Plate. The 224 Ma period was related to one galaxy year and may also be related to the aesthenospherical convection cycle.

Analysis on the frequency dispersion characteristics of seismic wave caused by low frequency sound source in shallow sea

The elastic wave in seabed caused by low frequency noise radiated from ship is the so-called ship seismic wave which can be used to identify ship target. In order to analyze the wave components and the propagating properties of ship seismic wave, numerical calculation for frequency dispersion curves of seismic wave caused by low frequency sound source in shallow sea has been carried out. According to the numerical example for shallow sea with hard sea bottom, time series of seismic wave at seafloor are mostly composed of normal modes and interface waves. Each normal mode has a well defined low frequency cut-off, on the contrary the interface wave doesn’t have. The frequency dispersion of normal mode is obviously when frequency is lower than 100Hz, while interface wave is dispersive only in the infra-sound frequency range. The time series of seismic wave is dominated by interface wave when the source frequency is less than the minimal cut-off frequency of normal modes. As for shallow sea with soft sea bottom, there is only one real root in the dispersion equation of seismic wave. The root corresponds to the interface wave which propagates along the seafloor at a slow speed. More normal modes appear when the depth of sea water increases and more source energy transmits through the wave-guide of sea water rather than along the seafloor by the interface wave. Normal modes gradually become the significant carriers of source energy and interface wave weak accordingly.

Assessing the Temporal Stability of a Cigarette Purchase Task After an Excise Tax Increase for Factory-Made and Roll-Your-Own Smokers.

Cigarette purchase tasks (CPTs) are used increasingly to measure simulated demand curves for tobacco. However, there is currently limited information about the temporal stability of demand curves obtained from these tasks. We interviewed a sample (N = 210) of smokers in New Zealand both before and after a 10% increase in the tobacco excise tax that took effect on January 1, 2013. Participants were interviewed in November-December 2012 (wave 1) and February-March 2013 (wave 2). At each interview, participants completed a high-resolution CPT with 64 prices ranging from NZ $0.00 to NZ $5.00/cigarette, and questionnaires regarding their smoking habit. Roll-your-own smokers had higher levels of nicotine dependence and tobacco demand based on CPT responses than factory-made smokers. Although demand curves for waves 1 and 2 were similar, intentions to purchase cigarettes were significantly less at wave 2 for three prices (NZ $0.85, NZ $0.90, and NZ $0.95) that were just higher than the actual price after the tax increase, for both roll-your-own and factory-made smokers. Measures of elasticity (α) derived from Hursh and Silberberg's model were significantly greater at wave 2 than wave 1, and there was a significant reduction in smoking habit as measured by cigarettes/day and the Fagerström Test for Nicotine Dependence at wave 2. Purchase tasks can discriminate between smokers based on their tobacco preference, and although results are relatively stable over time, they depend on contextual factors such as the current real price for tobacco.

A Godunov-type scheme for the isentropic model of a fluid flow in a nozzle with variable cross-section

We present a Godunov-type scheme for the isentropic model of a fluid flow in a nozzle with variable cross-section. The model is of nonconservative form, making it hard for standard numerical discretizations of the nonconservative term. In particular, the error for a standard numerical scheme with a usual discretization of the nonconservative term may become larger as the mesh size gets smaller. We first re-investigate the Riemann problem of the model, pointing out several interesting properties of the wave curves, and establishing specific existence domain for each type of solutions. Then, we incorporate local Riemann solutions to build a Godunov-type scheme for the model. The scheme is constructed in subsonic and supersonic regions, where the system is strictly hyperbolic. Tests show that our scheme can capture standing waves, so that it is well-balanced. Furthermore, tests also show that our Godunov-type scheme can give a good accuracy for numerical approximations of exact solutions. Our Godunov-type scheme can resolve the difficulty of other existing schemes for similar models of fluid flows with nonconservative terms.

Observational evidence of electron pitch angle scattering driven by ECH waves

AbstractUsing the plasma wave and electron data obtained from Time History of Events and Macroscale Interactions during Substorms, we show a signature of electron pitch angle scattering driven by Electrostatic Cyclotron Harmonic (ECH) waves in the velocity distribution function (VDF). The diffusion curve of whistler mode waves is used as a proxy to identify changes in VDFs due to wave‐particle interactions. We confirm that the shape of the VDF well agrees with the diffusion curve of whistler mode waves when whistler mode chorus alone is active. On the other hand, we find that the shape of the VDF deviates from the diffusion curves at low pitch angles when ECH waves are active following the inactivation of chorus waves. The result is observational support for electron pitch angle scattering caused by ECH waves and suggests that ECH waves can contribute to generation of diffuse auroras.

Wave propagation in layer with two preferred directions

This article is concerned with overall or macroscopic properties of a composite material with no distinction made between the fibres and the matrix which they are embedded in. All the properties with dimensions larger than the fibre diameter and spacing are regarded as averaged over a volume of material. The systems of particular interest here are in the fibre reinforced composites with the fibres being very much stiffer and stronger than the matrix.Laminated plates of fibre-reinforced material are often fabricated from prepreg tapes, laid up according to some specific arrangement of fibre orientation and then bonded together. An angle-ply laminate is formed by alternating plies so that the families in adjacent laminas are inclined by angle ϕ and −ϕ to given direction alternately. The process of fabricating a multilayered plate of this material gives rise to a laminate in which the plies are separated by resin rich layer, and when this layer is thin enough that its thickness is negligible it may be regarded as plate reinforced by two families of fibres. Problems shall be considered in three dimensions, but attention shall be restricted to linear elasticity theory. The plate under consideration is reinforced by two mechanically equivalent families of fibres, but with no other preferred directions, so that it is locally orthotropic with respect to the plane of the fibres and to the two planes that orthogonally bisect the fibres.In this article linear elastic stress–strain relation is employed to derive dispersion curves for plane harmonic waves propagating in a plate of finite thickness but of infinite lateral extent. Attention is restricted to waves propagating in the plane parallel to stress free plate faces where waves travelling at any angle to one of the families of very strong fibres are examined. The dispersion equations, relating the phase velocity to the wavelength, are obtained. The fundamental modes are examined for symmetric as well as for anti-symmetric deformations. This leads to full understanding of displacement field as well as stress field.

In-Plane Bending of a Drill String During its Compression in a Horizontal Borehole

The stress-strain state of a drill string during its compression in a horizontal borehole is considered. The function of the elastic axis of the drill string as a wave curve is obtained, which enables one to improve the analytical models: evaluation of decrease of axial force depending on the drill string elastic axis shape, determination of the force of pressing of the string to borehole walls, and calculation of normal stresses in the cross section of drill pipes.

Noninvasive potassium determination using a mathematically processed ECG: Proof of concept for a novel “blood-less, blood test”

ObjectiveTo determine if ECG repolarization measures can be used to detect small changes in serum potassium levels in hemodialysis patients. Patients and MethodsSignal-averaged ECGs were obtained from standard ECG leads in 12 patients before, during, and after dialysis. Based on physiological considerations, five repolarization-related ECG measures were chosen and automatically extracted for analysis: the slope of the T wave downstroke (T right slope), the amplitude of the T wave (T amplitude), the center of gravity (COG) of the T wave (T COG), the ratio of the amplitude of the T wave to amplitude of the R wave (T/R amplitude), and the center of gravity of the last 25% of the area under the T wave curve (T4 COG) (Fig. 1). ResultsThe correlations with potassium were statistically significant for T right slope (P<0.0001), T COG (P=0.007), T amplitude (P=0.0006) and T/R amplitude (P=0.03), but not T4 COG (P=0.13). Potassium changes as small as 0.2mmol/L were detectable. ConclusionSmall changes in blood potassium concentrations, within the normal range, resulted in quantifiable changes in the processed, signal-averaged ECG. This indicates that non-invasive, ECG-based potassium measurement is feasible and suggests that continuous or remote monitoring systems could be developed to detect early potassium deviations among high-risk patients, such as those with cardiovascular and renal diseases. The results of this feasibility study will need to be further confirmed in a larger cohort of patients.

Dispersion of SH and Love Waves

A mathematical model for analyzing both Love waves and horizontally polarized shear surface waves (SH-waves) propagating in stratified media with monoclinic symmetry is worked out. Analytic and numerical solutions for SH and Love waves obtained by applying the Modified Transfer Matrix (MTM) method and a special complex formalism, are presented. Displacement fields, specific energy, phase, ray, and group velocities, and dispersion curves for SH and Love waves are compared and analyzed. Plates with different types of boundary conditions imposed on the outer surfaces are considered. Behavior of the leakage Love waves and anomalous SH-waves is discussed.

Weighing Technology for High-Speed Moving Vehicle Based on Wireless Sensor Networks

This paper focuses on the weakening or eliminating low frequency dynamic load of vehicle dynamic weighing, improve the efficiency and accuracy of dynamic weighing system, weighing the purpose of. Wireless sensor network is deployed in the monitoring region of sensor nodes, the nodes achieve interconnectivity through wireless communication protocol, the network system structure. Usually, information without knowing the corresponding node position, often meaningless, positioning plays a very important role in many applications of wireless sensor network. Based on dynamic load model, load WSN-WIM system design, signal processing, in-depth research of sensor fault diagnosis. Methods to investigate the dynamic load processing based on WSN. The cooperation of each sensor nodes through the use of sine fitting algorithm based on three parameter sine wave curve fitting of the dynamic load, a set of linear equations, using efficient algorithm and information processing method of improving weighting precision. Study on sensor fault load based on grey prediction theory. In the WSN-WIM system, sensor calibration is a key problem, which put forward the optimization scheme of weighing sensor fault diagnosis method and grey prediction model based on the grey prediction theory, improving the weighing accuracy and system stability of WSN-WIM system

Riemann problem for Chaplygin gas with combustion

We study the Riemann problem of the Chapman–Jouguet model for an ideal combustible Chaplygin gas. By analyzing the wave curves in the phase plane, we obtain constructively the unique solution of the Riemann problem under the global entropy conditions.

Joint inversion of P- and S-receiver functions and dispersion curves of Rayleigh waves: The results for the Central Anatolian Plateau

The P- and S-wave receiver functions and dispersion curves of the fundamental Rayleigh wave are used to study the lithosphere within the Central Anatolian Plateau. The results for eight broadband seismic stations are presented. It is established that within the plateau, the crust with a thickness of about 35 km is underlain by the mantle lid with its bottom at a depth of about 60 km. The velocities of longitudinal (Vp) and shear (Vs) waves in this layer are at most 7.6 and 4.5 km/s, respectively, and the Vp/Vs ratio is close to 1.7 (i.e., by 6% lower than in the standard IASP91 and PREM models). Such a low velocity ratio is characteristic of rocks having high orthopyroxene content. Beneath the high-velocity mantle lid, the S-wave velocity decreases to 4.0–4.2 km/s and the Vp/Vs ratio is close to its standard value (1.8). At most stations, the P-wave receiver functions do not contain seismic phase P410s, which is formed at the global seismic boundary at a depth of 410 km. The seismic boundary at a depth of 410 km is related to the olivine-spinel phase transformation, and its absence can indicate the anomalously low olivine content and high basalt content. This anomaly is probably associated with the subduction of a large amount of oceanic crust during the closure of the Tethys. The results of the study overall indicate the high informativity of the used method.

Absorbing Boundary Conditions for 2D Tilted Transverse Isotropic elastic media

This work deals with the construction of a low-order absorbing boundary condition (ABC) for 2D elliptic TTI media, preserving the system stability. The construction is based on comparing and then connecting the slowness curves for isotropic and elliptic TTI waves. Numerical experiments illustrate the performance of the new ABC. They are performed by integrating the ABC in a DG formulation of Elastodynamics. When applied in a TTI medium, the new ABC performs well with the same level of accuracy than the standard isotropic ABC set in an isotropic medium. The condition demonstrates also a good robustness when applied for large times of simulation.

Mechanisms of amplification of short electromagnetic pulses in gyroresonance traveling-wave tubes

Traditional gyroresonance traveling-wave tubes (gyro-TWTs) with a smooth waveguide serving as the operating space and gyro-TWTs based on a waveguide with multiturn helical corrugation are considered. A nonstationary nonlinear theory providing for the description of amplification of short pulses in various circuits of such TWTs is proposed. The specific features of amplification of short pulses in helical gyro-TWTs are investigated for the regimes in which the dispersion curves of a normal wave and of an electron flow contact and intersect. In the first case, it is demonstrated that pulses having a spectrum width on the order of the amplification bandwidth can be amplified without distortion of their shapes. In the second case, it is shown that the slip of an extremely short input pulse relative to the electron beam ensures the infeed of one of the fronts of an electromagnetic pulse with an initially unmodulated electron flow. As a result, the pulse amplitude at the output of the interaction space can exceed the saturation amplitude in the regime of stationary amplification of monochromatic radiation.

Electron Bernstein waves in nonextensive statistics

The propagation of electron Bernstein waves in a magnetized plasma is investigated in the context of nonextensive q-distribution of Tsallis statistics. The dispersion relation is expressed as a function of generalized hypergeometric function. It is shown that the generalized dispersion relation significantly depends on the q-parameter, which quantifies the degree of nonextensivity of the system. The reduced number of superthermal particles shifts the Bernstein wave curves to higher wavenumbers. For harmonics whose frequency lies above the upper hybrid frequency, an increase in the value of q increases the maximum frequency and the wavenumber at which the group velocity vanishes. For Bernstein waves which propagate at frequencies lower than the upper hybrid frequency or close to it, diminishing q, or increasing the number of superthermal particles, gives rise to faster frequency fall-off. The generalized electron Bernstein waves are studied in both the strongly and weakly magnetized regimes and for both small and large wavenumbers compared with the Larmor radius. It is found that for the weak magnetic field, the frequency range occupied by the mode spans the complete intraharmonic frequency, and the q value significantly affects the dispersion curves. On the other hand, in strongly magnetized regimes the frequency variation domain is extremely restricted and has little dependence on the q value.

Crustal Velocity Structure of the Northeastern Tibetan Plateau from Ambient Noise Surface-Wave Tomography and Its Tectonic Implications

Abstract Broadband seismic data from the regional seismic network operated by the China Earthquake Administration and 32 temporary seismic stations are used to image the crustal velocity structure in the northeast Tibetan plateau. Empirical Rayleigh‐ and Love‐wave Green’s functions are obtained from interstation cross correlation of continuous seismic records. Group velocity dispersion curves for Rayleigh and Love waves between 10 and 50 s are obtained using the multiple‐filter analysis method with phase‐matched processing. The group velocity variations of Rayleigh and Love waves overall correlate well with the major geologic structures and tectonic units in the study region. Shear‐wave velocity structures were then inverted from Rayleigh‐ and Love‐wave dispersion maps. The results show that the Songpan–Ganzi terrane is associated with a low velocity at depth greater than 20 km. The northern Qilian orogen, with higher elevation and thicker crust compared to the southern Qilian orogen, is also dominated by low velocity at depth greater than ∼25 km. However, there is no clear evidence of the low‐velocity mid‐to‐lower crust beneath the southern Qilian orogen as the crustal flow model predicts. The low‐velocity zone (LVZ) beneath the northern Qilian orogen may suggest that the crustal thickening and surface uplift of the northern Qilian orogen are related to the LVZ, and the LVZ may be considered as an intracrustal response to bear the ongoing deformation in the northern Qilian orogen. Online Material: Figures of crustal topography, number of group velocity measurements, checkerboard tests for NETS stations, and 1D velocity models.