Analysis Of Wave Reflection Research Articles

Sound propagation in the presence of non-isothermal sheared flow refraction and metasurface impedance reflection

Sheared flow can profoundly influence the aeroacoustic performance of near-wall structures like metasurfaces on moving vehicles. In this work, a refractive generalized Snell’s law is developed by combining Snell’s law with the generalized Snell’s law to manipulate anomalous reflections in an idealized sheared flow, comprising a uniform flow region and a stationary air region with velocity and temperature gradients. Theoretical analysis and numerical simulations of planar wave reflection by metasurface impedance under non-isothermal sheared flows are conducted, yielding favorable predictions of the zone of silence, as well as anomalous and total reflection behaviors. The total reflection between the shear layer and the metasurface is analyzed with the objective of confining incident wave below the shear layer. Remarkably, a specific configuration of hot-sheared flow and metasurface length can achieve total absorption over a range of incident wave angles from 0° to almost 90°. Moreover, the refractive generalized Snell’s law, extended to account for directional deflection induced by flow convection, is utilized to regulate sound beam reflection, resulting in satisfactory outcomes under sheared conditions. This study offers a theoretical framework for wave control under non-isothermal and sheared flow conditions, which cannot be resolved by the traditional generalized Snell’s law, and can be implemented in the design of metasurfaces for moving applications.

Wave Reflection Analyses On Laser Scan Data From A Model Salt Marsh

Physical or numerical models are common tools to investigate the interaction between waves and marine structures. The decomposition of the water level into incident and reflected wave components is often required, as most design variables (overtopping, run-up) are linked to the incoming wave characteristics. Also, an accurate solution can provide information on the distribution of energy in the wave spectrum and the spread of energy from the fundamental wave components to the lower and higher frequencies (Lin and Huang, 2004). Thus, utilizing an appropriate wave reflection analysis is critical in the analysis of such experiments.

Time domain analysis of wave reflection in the pulmonary circulation after lung resection in pigs

Time domain analysis of wave reflection in the pulmonary circulation after lung resection in pigs

Buried object localization by spectral analysis of surface wave reflections

A proposed method of buried object localization, based upon spectral analysis of surface wave reflections, is investigated numerically. This arises from a hypothesis to the effect that reflectivity would be maximized at some intermediate wavelength, shorter ones associated with disturbances too shallow to substantially excite the object as a secondary (reflecting) source, and longer ones with disturbances involving such volumes of earth in motion that the object become insignificant as a reflector. Discernment of that intermediate wavelength of maximum reflectivity might, thereby, provide an index of the object’s depth. Horizontal distance from echo return time, and azimuth from phase array techniques, could complete a localization methodology. Presented, accordingly, are 2D FEA simulations, in which narrow-banded surface wave trains are excited by a point source on the surface of an elastic medium, a void provided at some horizontal distance and depth, the strength of reflected surface motions thereafter examined in relation to frequency. These bear out the hypothesis, finding maximal reflectivity for a surface wavelength about two-thirds of the object depth. Proposed is that this could serve as the basis for a horizontal stand-off detection method, especially for applications like landmines, for which it may be undesirable to scan from above.

Moored elastic sheets under the action of nonlinear waves and current

This study is concerned with the interaction between nonlinear water waves and uniform current with moored, floating elastic sheets, resembling floating solar panels, floating airports, tunnels and bridges, and floating energy systems. The Green–Naghdi theory is applied for the nonlinear wave–current motion, the thin plate theory is used to determine the deformations of the elastic sheet and Hooke’s law defines the effect of the mooring lines. The horizontal displacement of the floating sheet is determined by substituting the forces induced by the fluid flow and the tensions generated in the mooring lines into the equations of motion of the floating body. The resulting governing equations, boundary and matching conditions are solved in two dimensions with a finite-difference technique. The results are compared with the available numerical data. Overall, very good agreement is observed. In the model developed here, the sheet is allowed to drift due to the wave–current impact, and hence the mooring lines partially restrict both deformation and the horizontal motions of the sheet. The influence of the mooring lines on the dynamics of the floating sheet is assessed in terms of wave- and current-induced elastic deformations and surge movements of the sheet. It is demonstrated that the mooring lines attached to the leading and trailing edges of the sheet can be highly effective in mitigating the horizontal oscillations and vertical elastic deformations of the floating sheet subjected to the wave and current actions. Special attention is given to the horizontal periodic motions of the sheet, which are analysed by use of a Fourier transform technique. It is shown that the moored elastic sheet can oscillate at a frequency different from its exciting frequency as a result of restoring forces from the mooring lines, exciting resonance when both frequencies meet. Extensive study in a broad range of sheet parameters, mooring stiffnesses and wave–current conditions established the location of resonant regimes of different configurations of the moored systems. Analysis of wave reflection and transmission coefficient revealed that mooring lines of increasing stiffness intensify the wave reflection and, consequently, result in smaller energy transformation downwave.

An analytical approach for the analysis of stress wave transmission and reflection in waveguide systems based on Timoshenko beam theory

The paper presents an analytical continuous solution for the analysis of wave refraction and transmission/reflection caused by arbitrarily complex waveguide subsystems. It allows analyzing the way stress wave components are altered as they go through a substructure. The method is new in that it investigates the wave phenomena which govern the dynamic behavior of a structural system explicitly and studies the effectiveness of different serrated and fractal subsystem designs functioning as wave content filters. Timoshenko beam theory is used to model stress wave propagation in waveguides because of its accuracy and consistency over a wide range of vibration frequencies. The versatility of the method is demonstrated using a number of numerical examples characterizing stress wave refraction in single input/single output and single input/multiple output subsystems to study periodic, fractal, and serrated forms. The low computation cost and stable accuracy of the method over a very wide range of frequencies, make it an effective tool for metaheuristic optimization approaches which require massive calculations over many generations. The method is demonstrated to perform seamlessly in coupling with a genetic algorithm optimization framework to determine the optimal serrated configuration of a wave filter.

Plane-Wave Spectrum Analysis of Spherical Wave Absorption and Reflection by Metasurface Absorber

Plane-Wave Spectrum Analysis of Spherical Wave Absorption and Reflection by Metasurface Absorber

On plane-wave reflection from a two-layer marine sediment: A surficial layer with linear sound speed profile overlying an iso-speed basement.

An analysis of plane wave reflection is developed for a two-layer sediment, the top layer consisting of a fine-grained material (mud) with an upward refracting linear sound speed profile. Beneath is a homogeneous basement, and above is homogeneous seawater. A rather curious, exact analytical expression for the reflection coefficient is derived, involving easy to evaluate integrals over finite limits, of the modified Bessel functions of low-integer order. The expression is generally valid for any linear profile with positive gradient in the surficial mud layer and for any sound speed in the basement, either greater than or less than that in the seawater. For "fast" basements, a critical angle always exists that is independent of the sound speed in the mud layer. With a "slow" basement, a quasi-angle of intromission may exist, which depends only weakly on both frequency and the gradient of the profile in the mud, a conclusion that may be relevant to the conditions of the Seabed Characterization Experiment (2017) performed over the New England Mud Patch. With both types of basement, fast and slow, the reflection coefficient, as a function of grazing angle, exhibits fluctuations that are strongly frequency dependent, associated with resonances and anti-resonances in the mud layer.

Extracellular nucleophosmin is upregulated in psoriasis and correlates with determinants of cardiovascular diseases

Abstract Introduction We previously showed that genotoxic stress induced an active extracellular release of nucleophosmin (NPM) in human cardiac mesenchymal progenitor cells, and that serum deprivation provokes NPM secretion from human endothelial cells, eliciting inflammation via nuclear factor kappa B (NF-kB) transcriptional activation. Purpose The aim of this study was to determine whether NPM was modulated in skin and plasma of psoriatic patients (Pso). Methods 29 Pso were compared to 29 control subjects (Ctrl) age- and sex-matched. All Pso had a severe psoriasis, defined as Psoriasis Area and Severity Index (PASI) >10 and one of the following: at least two systemic psoriasis treatments, psoriasis onset <40 years of age, disease duration >10 years. Exclusion criteria were: diabetes, cardiovascular events, psoriatic arthritis. Total RNA was extracted from plasma and miR-200c levels assayed by quantitative real-time PCR. NPM levels were assayed by ELISA. The clinical parameters were similar between the two groups except for Total Cholesterol (mg/dl) (Ctrl 193.3±6.2; Pso 213.2±6.9; P<0.05). Blood pressure measurement, wave reflection analysis and pulse wave velocity (PWV) were similar between groups, echocardiographic parameters were different for left ventricular (LV) mass index (g/m2) (Ctrl 84.2±5.2; Pso 102.5±4.7; P<0.05) and relative wall thickness (RWT) (Ctrl 0.4±0.0; Pso 0.48±0.0; P<0.01). Total RNA was extracted from biopsies of nonlesional (NLS) and lesional (LS) of 6 Pso and 6 healthy subject skin (HS) from which human fibroblasts (HFs) and primary Keratinocytes (KCs) were extracted. Results NPM was upregulated in LS (1.9+0.3 fold; p=0.05) vs NLS biopsies (2.9+0.1 fold; p<0.01) and was also increased at the transcriptional level in LS vs NLS (8.6+ 1.7fold; p<0.05). Both the innate stimuli, such as lipopolysaccharides and Poly I:C and adaptive stimuli, i.e. cytokine mix, were able to induce extracellular release of NPM in immortalized KCs and HFs. Interestingly, NPM interacts with Toll like receptor (TLR)4 and activates a NF-kB-dependent inflammatory pathway upregulating interleukin IL-6 and COX-2 gene expression. Circulating NPM was increased in the plasma of 29 Pso (1.1+0.1ng/ml; p<0.001) compared to 29 healthy controls (0.78+ 0.03ng/ml) and positively correlates with PASI (Rs=0.44; p=0.05) and with determinants of cardiovascular diseases (CVDs), i.e. PWV (Rs=0.5; p<0.008), PASis (Rs= 0.4; P<0.05) and LV mass (Rs=0.49; p<0.05). Further, NPM positively correlates with miR-200c circulating levels (Rs=0.29; p<0.05), that we previously showed to increase in Pso and to correlate with CVD progression. We found that circulating miR-200c physically associated with NPM, that most probably is responsible for its extracellular release and protection upon cytokine mix via a TLR4-mechanism. Conclusions NPM is increased in psoriasis both in skin and in plasma and could be a novel biologic target to counteract chronic inflammation associated with CVD risk. Funding Acknowledgement Type of funding sources: Public grant(s) – EU funding. Main funding source(s): Italian Ministry of Health and AFM Telethon 22522 grant to AM

Analysis of wave reflection, waveload, and pressure distribution due to a poro-elastic structure in a two-layer fluid over a porous sea-bed

Analysis of wave reflection, waveload, and pressure distribution due to a poro-elastic structure in a two-layer fluid over a porous sea-bed

Large Deformation Hermitian Finite Element Coupled Thermoelasticity Analysis of Wave Propagation and Reflection in a Finite Domain

In the present paper, a finite element nonlinear coupled thermoelasticity formulation is presented for analysis of the wave propagation, reflection, and mixing phenomena in the finite length isotropic solids. The governing equations are derived based on the second Piola-Kirchhoff stress and the full form of Green’s strain-displacement tensors to account for the large deformations and finite strains. In contrast to the available researches, the assumption of very small temperature changes compared to the reference temperature is released in the present research. Galerkin’s method, a weak formulation, and cubic elements are employed to obtain the time-dependent non-linear finite element governing equations. The proposed solution procedure to the resulting highly nonlinear and time-dependent governing equations employs an updating algorithm and Newmark’s numerical time integration method. The wave propagation and reflection phenomena are investigated for both the mechanical and thermal shocks and time variations of distributions of the resulting displacements, temperature rises, and stresses are illustrated graphically and discussed comprehensively. Furthermore, the effects of the non-linear terms are discussed comprehensively. Results reveal that in the non-linear analysis, no fixed speed of wave propagation can be defined.

Analysis of plane wave reflection and transmission phenomenon at the interface of two distinct micro-mechanically modeled rotating initially stressed piezomagnetic fiber-reinforced half-spaces

Analyzed the influence of normal/shear initial stresses and rotation on reflection/transmission characteristics of waves propagating at the interface of two distinct micro-mechanically modeled piezomagnetic fiber-reinforced composite(PMFRC) half-spaces composed of CoFe2O4 fiber-epoxy matrix combination. An incident quasi-longitudinal(qP) wave generates reflected/transmitted quasi-longitudinal(qP), quasi-transverse(qSV), and magneto-acoustic(MA) waves, whose propagation directions are illustrated graphically. Transmitted qP wave has critical angles for considered initial stresses and rotation. Energy ratios of reflected/transmitted waves, interaction energy, and net energy are obtained, which satisfy the Law of Conservation of Energy, thereby validating this problem. Influences of incident angle, initial stresses, and rotation on amplitude/energy ratios are meticulously analyzed.

On the leak-induced transient wave reflection and dominance analysis in water pipelines

The leak-induced reflection information forms the basis of developing and applying transient-based leak detection methods in water-filled pipelines. The transient reflection method (TRM) has been widely incorporated in various leakage problems, and affecting parameters in the process are closely investigated in specific cases. However, the TRM literature lacks a global assessment of the relative importance of each parameter for a general inference on the contribution of each independent variable to the desired reflection criterion, which assists in leakage management. Besides, in the majority of previous studies, the leak-induced reflection wave at the measurement point is approximated by that at the leaky point, i.e., the propagation behavior and process of the reflected wave from the potential leak location to measurement point is ignored, leading to inaccuracy in sizing potential leaks by the TRM. To resolve these issues, this study firstly derives the leak-induced reflection coefficient at the measurement point by incorporating the additional damping effect of the reflection wave propagation process along the pipeline, which is then fully validated by MOC-based numerical and experimental laboratory applications. To further understand the contribution of different factors in the derived reflection coefficient, a systematic analysis is conducted based on dimensional analysis and extensive numerical simulations. The obtained results are characterized by the dominance analysis so as to explore the importance ranking of different dimensionless factors to the leak-induced reflection coefficient in the pipeline system. The analysis results indicate that, amongst all the dimensionless parameters, the leak factor provides the largest influence and contribution to the wave reflection coefficient (with about 40% contribution), followed by the transient intensity (23%) and initial system and flow conditions (20%), and lastly the measurement distance from leak location (17%). The finding of this study is helpful in leakage management as it aims to understand and explain the applicability and effectiveness of the TRM under different conditions.

Field study of wave reflection from permeable rubble mound breakwater of Chabahar Port

The present study analyzes the field measurements of the reflective response of a permeable rubble mound breakwater encountered with a bimodal wave regime. The coexistence of sea and swell wind-driven waves during the measurement program provided directional spreading wave realizations for subsequent bulk and frequency-dependent wave reflection analysis. The directional wave data were acquired near the primary breakwater of Chabahar Port within 28 days, including 643 bursts using an AWAC wave recorder. The available formulae for wave reflection coefficient were evaluated against this data set. Results showed that the equations proposed by Postma (1989) and Zanuttigh and Van der Meer (2007) are in general agreement with the observations of the present study. However, the accuracy of reflection coefficient predictions was improved by developing two new alternative formulations. It was realized that the frequency reflective response differs between sea and swell prevailing conditions. The reflection coefficient decreases drastically within high sea wave predominant periods for the harmonics higher than peak frequency. However, reflection coefficients of high harmonics reduced slightly within swell domination periods. The frequency-dependent reflection coefficients can be even higher than unity due to energy transfer amongst other wave harmonics.

Wave transmission and reflection analysis through complex media based on the second strain gradient theory

The scattering of guided waves through a complex structure is of great importance in predicting vibration energy transmission and reflection across structures. Multi-scale models based on generalized continuum theory have been developed recently to investigate the vibration behavior of complex media in the frame of continuum mechanics. In this study, models based on the second strain gradient theory are employed together with a scattering matrix method to study the wave transmission and reflection through non-classical coupling regions between two waveguides. Numerical results are presented for longitudinal and bending waves through 1-D coupling interfaces. Upon which we discuss the local behavior of the internal heterogeneity in the complex coupling region and its impact on wave scattering properties at coupling interfaces. The results obtained also show that the proposed approach is of great potential in the investigation of vibration transmission control by enriching a waveguide’s internal structure.

A longitudinal analysis of arterial stiffness and wave reflection in preeclampsia: Identification of changepoints

PurposePreeclampsia (PrE) is a leading complication of pregnancy characterized by vascular dysfunction. Characterizing the longitudinal changes in vascular function prior to PrE onset is critical to the identification of optimal timepoints for vascular assessment and the development of effective early screening strategies. MethodsIn this prospective longitudinal study of women with singleton high-risk pregnancies, arterial stiffness and wave reflection parameters were assessed using applanation tonometry at 10–13 weeks' gestation and repeated every 4 weeks throughout pregnancy. Changepoints in carotid-femoral pulse wave velocity (cfPWV), carotid-radial PWV (crPWV), augmentation index (AIx), time to wave reflection (T1R), pulse pressure amplification (PPA), and subendocardial viability ratio (SEVR) were compared between women who did and did not subsequently develop PrE. ResultsA changepoint in cfPWV and crPWV was detected at 14–17 weeks' gestation. cfPWV then increased in women who went on to develop PrE but decreased in women who did not; a 1.2 m/s difference in cfPWV between the groups was observed at 22–25 weeks' gestation. Conversely, crPWV converged in the two groups from a baseline difference of 1.05 m/s (95% credible interval: 0.37, 1.72). Women who subsequently developed PrE demonstrated an increase in AIx at 18–21 weeks' gestation that was not seen in women who did not develop PrE until 30–33 weeks. No differences in T1R, PPA, or SEVR were observed between the groups. ConclusionsAltered vascular adaptations were detected using measures of arterial stiffness and wave reflection in the early second trimester of pregnant women who developed PrE compared to those who did not. These findings demonstrate the potential clinical utility of arterial stiffness and wave reflection parameters as an early screening tool for PrE, which can be used to inform clinical management of high-risk pregnancies.

Vibration Measurement and Wave Reflection Analysis in an Electrified Railway Catenary Based on Analytical Methods

The wave propagation property of the catenary directly affects the pantograph–catenary interaction performance. Specifically, wave reflection and transmission occurring at waveguide discontinuities, particularly at dropper junctions, directly impact the pantograph–catenary interaction performance. In this study, wave reflection occurring at the dropper junctions is investigated using both analytical and experimental approaches. First, a partial catenary model is established to analyze the catenary wave propagation by considering the wave reflections at the dropper junctions. The result indicates that the wave reflection in the contact wire (CW) affects the contact performance more significantly than that in the messenger wire. Two types of experimental tests are performed to analyze the wave reflection in the catenary—single CW and full-scale catenary tests. An analytical method considering back-and-forth reflections between the adjacent droppers is proposed to identify the actual reflection coefficients and extract the wave components from the measured data. The single CW test result shows that the dropper mass has a negligible influence on the wave reflection. The full-scale catenary test result indicates that the catenary reflection coefficient obtained from the measured data can match the design value with an acceptable error using the proposed method. Moreover, the measured data can be decomposed into wave components with different reflection orders, in which less energy is centered in the higher-reflection-order component. The proposed methods have been justified effective in reflection coefficient identification for the actual catenary structure.

Office, central and ambulatory blood pressure for predicting incident atrial fibrillation in older adults.

Recently, more sophisticated blood pressure (BP) measurements, such as central and ambulatory BP (ABP), have proven to be stronger predictors of future cardiovascular disease than conventional office BP. Their predictive value for atrial fibrillation development is not established. We investigated the prognostic impact for incident atrial fibrillation of office, central and ambulatory BP measurements in a predominantly older population-based cohort. Of 1004 participants in the Cardiovascular Abnormalities and Brain Lesions (CABL) study, 769 in sinus rhythm with no history of atrial fibrillation or stroke (mean age 70.5 years) underwent ABP and arterial wave reflection analysis for central BP determination. Fine and Gray's proportional subdistribution hazards models were used to assess the association of BP parameters with incident atrial fibrillation. During 9.5 years, atrial fibrillation occurred in 83 participants. No office BP variable showed a significant association with incident atrial fibrillation. Central SBP and central pulse pressure were marginally associated with incident atrial fibrillation in multivariate analysis. Among ABP variables, 24-h SBP [adjusted hazard ratio per 10 mmHg, 1.24; 95% confidence interval (CI) 1.07--1.44; P = 0.004], daytime SBP (adjusted hazard ratio per 10 mmHg, 1.21; 95% CI 1.04--1.40; P = 0.011) and night-time SBP (adjusted hazard ratio per 10 mmHg, 1.22; 95% CI 1.07--1.39; P = 0.002) were significantly associated with incident atrial fibillation. In a predominantly older, stroke-free community-based cohort, ABP was a better independent predictor of incident atrial fibrillation than central BP, whereas office BP was inadequate for this purpose.

Non-Invasive Ultrasound Detection of Cerebrovascular Changes in a Mouse Model of Traumatic Brain Injury.

Traumatic brain injury (TBI) can induce changes in vascular architecture. Although ultrasound metrics such as pulsatility index (PI) are sensitive to changes in hemodynamic resistance downstream from major arteries, these metrics depend on features unrelated to vessel architecture, such as blood pressure and heart rate. In contrast, input impedance and reflection coefficient that are derived from wave reflection theory seek to minimize the effects of altered cardiac output or heart rate. In this article, we investigate the use of ultrasound to assess changes in vascular impedance and wave reflection in the common carotid arteries of mice exposed to a controlled cortical impact. Focusing on the first harmonics of the reflected waves, the impedance phase was increased ipsilaterally in impacted mice compared with shams, whereas the magnitude of the impedance was unchanged. In contrast, PI was reduced bilaterally. Interestingly, PI and the first harmonic magnitude of input impedance in the carotid artery were correlated on the contralateral but not ipsilateral side. We investigated the use of these metrics to classify mice as sham or TBI, finding an area under the receiver operating characteristic curve ipsilaterally of 0.792 (confidence interval [CI]: 0.648-0.936) for correct classification with first harmonic impedance magnitude and phase as predictors and 0.716 (CI: 0.553-0.879) using carotid artery PI and diameter as predictors. Overall, the findings support the use of wave reflection analysis as a more specific measure of vascular changes following TBI and motivate the translation of this approach for monitoring vascular changes in humans affected by TBI.

Comprehensive analysis of effective reflection distance and its association with wave reflection strength under diverse hemodynamic conditions in anesthetized dogs

Pressure wave reflection is associated with cardiovascular risk. The conceptual distance to a theoretical major reflection site, termed effective reflection distance (ERD), has been associated with aging and augmentation index (AIx) clinically. However, it remains unclear whether and how ERD varies and associates with AIx when the hemodynamic condition is acutely perturbed in a patient. The objective of this study was to address this issue in rigorously controlled animal experiments. In 13 anesthetized dogs, we measured arterial pressure, aortic flow and femoral arterial flow, while altering the hemodynamic condition over wide ranges by administering zatebradine (bradycardic agent), nitroprusside (vasodilator), noradrenaline (vasoconstrictor), dobutamine (inotrope), and dextran (volume-expander). Using the measured data, we determined ERD based on an arterial model comprising a tube with a complex frequency-dependent load (ERDTL), which has been considered a physiologically valid model. We also determined ERD based on wave separation (ERDWSA) and pressure-based analyses (ERDAW). ERDTL was shortened significantly in response to nitroprusside or dobutamine infusion, and was significantly and negatively associated with AIx in multiple regression analysis using pooled data. ERDWSA or ERDAW did not necessarily correlate with ERDTL in terms of responses to drug administration or association with AIx. In conclusion, under diverse hemodynamic conditions, ERDTL changes sensitively and shows physiologically reasonable association with AIx. This result substantiates the importance of paying close attention to medications during clinical analysis of wave reflection. Caution is required when using ERDWSA or ERDAW as an alternative to ERDTL.