Amplitude Waves Research Articles

A quantification and classification framework for water temperature variation features induced by climate change and reservoir construction and operation: Application to the middle Yangtze River

AbstractRiverine water temperature (WT) is a crucial factor affecting habitat quality and ecological effect of aquatic ecosystems. To accurately quantify and classify WT variation features caused by climate change and reservoir construction and operation, a framework was developed that integrates multivariate vine copula model for accurately reconstructing the WT process and general evaluation indicators for comprehensively characterizing of WT variation. In this framework, month‐wise R‐vine copula models were employed to depict the multivariate dependence structure between WT and related hydrometeorological factors, and the change of WT process in the fluctuation range and thermal deviation was analogized as the change of simple harmonic wave in amplitude and phase. A testing‐oriented application of this framework in Yichang section of the Yangtze River highlighted that climate change and the Three Gorges Reservoir (TGR) dominated or participated in the fluctuation range changing and phase deviation of different monthly WT processes, as the ratios of affected months were 1.08:1 and 1.25:1 during the construction phase, and 1:2 and 1:1.28 during the operation phase. WT process also exhibited diverse monthly variation trends during construction and operation phases of the TGR. Therefore, it is inappropriate to neglect the impact of the TGR construction phase and climate change on WT variation. The proposed framework achieved systematic quantification and attribution analysis of WT variation, thereby providing an enhanced understanding of the variation characteristics of river thermal regimes under the individual and combined effects of climate change and artificial reservoir. Considering the significant influence of WT variation on aquatic organism reproduction, the identification of the sources and categories of monthly WT variation can also serve as a foundation for future targeted thermal and hydrological regime regulation, aiming to protecting aquatic species and preventing biodiversity loss.

The Identification of Travelling Waves in a Voltage Sensor Signal in a Medium Voltage Grid Using the Short-Time Matrix Pencil Method

Most of the fault wave localization methods are based on the analysis of line current transformed by current transformers and are limited to high voltage grids. Fault wave localization in medium voltage grids is still being developed. This paper presents a new real-time algorithm for the identification of travelling waves in a distribution grid using voltage signal and the short-time matrix pencil method. To obtain the secondary side voltage waveforms at substation, the model of a resistive voltage sensor based on the broadband measurements from 10 Hz to 20 MHz was developed. The tested sensor amplifies the frequencies associated with travelling waves more than utility frequency allowing for the identification. Short-circuit simulations on the IEEE 34-bus feeder was performed to test the algorithm. The developed method can detect even the waves of low amplitude.

Exponential traveling-wave on a viscous fluid flowing down an inclined plane

An exponential traveling-wave solution of the free surface equation for a viscous film flowing down an inclined plane is presented. The free surface equation, valid for long waves of finite amplitude, is obtained from the general equation for waves of arbitrary amplitude, which is developed by the method of multiple-scales and considering a series solution expanded at two orders higher than the series used by Lin in 1974. Thus, confining ourselves to the case of weakly nonlinear wave motion, we use the Ince transformation method to find an exponential travelling-wave solution that depend of the physical parameters of the viscous fluid , the angle θ of the inclined plane and the wave parameters, which are subjected to three constraints between them. This solution show a free surface with a dynamic gap of thickness between the top and the bottom of the inclined plane. Also, we find a particular numerical example, for laminar flow, that may represent the evolution of the free surface h(x,t) of a viscous film flowing down an inclined plane, when a small quantity, of the same fluid, is added constantly to the primary fluid in the top of the inclined plane. An interesting result of this case show that the final state, when t → ∞, is also stationary and has the same behavior as the unperturbed primary flow, however the final layer of fluid has a greater thickness.

Integrability, conservation laws and exact solutions for a model equation under non-canonical perturbation expansions

In this paper, the non-linear for the small long amplitude waves in two dimensional (2D) shallow water waves propagation with free surface are considered. The shallow water wave problem leads to the non-linear Hamiltonian model equation. Based on the binary Bell-polynomials approach, the bilinear form, bilinear Bäcklund transformation and multiple wave solutions are obtained. The conservation laws are constructed using two different techniques, namely, the Ibragimov's theorem and the multiplier method. The Noether's approach was applied to the non-linear Hamiltonian model equation to obtain the conservation laws. Also, we show that the non-linear Hamiltonian model equation is nonlinearly self-adjoint. Conserved quantities of Hamiltonian model equation are illustrated. Finally, with the help of the extended homogeneous balance method, and an exponential method, a set of new exact solutions for the non-linear Hamiltonian model equation are obtained.

A Novel Low Axis Ratio Double-Circularly Polarized Microstrip Antenna

This article presents a dual circular polarization (CP) microstrip antenna, emitting electromagnetic waves above and below the substrate, which is fed by the double L-probe. Selecting the L-probe feed increases the bandwidth of the antenna, and different probes control the rotation of CP. The antenna could radiate two polarized waves of the same amplitude and vertical through two square radiation patches; meanwhile, adjusting the phase difference between both waves to 90° will produce a CP wave in the far-field. The simulation and measurement results show that the antenna is in 4.3–4.8 GHz band with S11<−10 dB, S22<−10 dB, and AR<3 dB. Furthermore, a lower axis ratio could be obtained in this work compared with similar antennas of the same type.

Plasmalogens Regulate Retinal Connexin 43 Expression and Müller Glial Cells Gap Junction Intercellular Communication and Migration.

Plasmalogens are a specific glycerophospholipid subtype characterized by a vinyl-ether bound at their sn-1 moiety. Their biosynthesis is initiated in the peroxisome by dihydroxyacetone phosphate-acyltransferase (DHAPAT), which is encoded by the DAPAT gene. Previous studies have shown that plasmalogen-deficient mice exhibit major physiological dysfunctions including several eye defects, among which abnormal vascular development of the retina and a reactive activation of macroglial Müller cells. Interestingly, plasmalogen deficiency in mice is also associated with a reduced expression of brain connexin 43 (Cx43). Cx43 is the main connexin subtype of retinal glial cells and is involved in several cellular mechanisms such as calcium-based gap junction intercellular communication (GJIC) or cell migration. Thus, the aim of our work was 1) to confirm the alteration of Cx43 expression in the retina of plasmalogen-deficient DAPAT−/- mice and 2) to investigate whether plasmalogens are involved in crucial functions of Müller cells such as GJIC and cell migration. First, we found that plasmalogen deficiency was associated with a significant reduction of Cx43 expression in the retina of DAPAT−/- mice in vivo. Secondly, using a siRNA targeting DHAPAT in vitro, we found that a 50%-reduction of Müller cells content in plasmalogens was sufficient to significantly downregulate Cx43 expression, while increasing its phosphorylation. Furthermore, plasmalogen-depleted Müller cells exhibited several alterations in ATP-induced GJIC, such as calcium waves of higher amplitude that propagated slower to neighboring cells, including astrocytes. Finally, in vitro plasmalogen depletion was also associated with a significant downregulation of Müller cells migration. Taken together, these data confirm that plasmalogens are critical for the regulation of Cx43 expression and for characteristics of retinal Müller glial cells such as GJIC and cell migration.

Effects of the Rotation on the Mixed Convection Heat Transfer Analysis for the Peristaltic Transport of Viscoplastic Fluid in Asymmetric Channel

In this paper, we study the impact of the variable rotation and different variable on mixed convection peristaltic flow of incompressible viscoplastic fluid. This is investigated in two dimensional asymmetric channel, such as the density, viscosity, rate flow, Grashof number, Bingham number, Brinkman number and tapered, on the mixed convection heat transfer analysis for the peristaltic transport of viscoplastic fluid with consideration small Reynolds number and long wavelength, peristaltic transport in asymmetric channel tapered horizontal channel and non-uniform boundary walls to possess different amplitude wave and phases. Perturbation technique is used to get series solutions. The effects of different values of these parameters for the axial velocity, stream function, stress, temperature and pressure gradient have been obtained. The impact of these parameters is discussed and illustrated graphically through the set of figures. Numerical results have been computed by using MATHEMATICA software.

A continuous-wave method for sound speed measurement based on an infinite-echo model

This paper presents a method for sound speed measurement accounting for the infinite number of echoes of a continuous wave generated between an excitation and a receiving transducer. An infinite-echo model was developed for the output signal sensed by the receiving transducer. From the model, the amplitude of the output signal is shown to be a wave (the amplitude wave) with a periodicity dependent on sound speed, excitation frequency, and pathlength. This yields a method for sound speed measurement. The method was implemented and experimentally demonstrated. Effects of medium material, transducer property, excitation frequency, and pathlength were shown and analyzed for enhancing measurement robustness. Measurement of varied materials showed a high level of consistency with known values or expected variations. More importantly, outstanding signal-to-noise ratios were observed. The method can be used in different fields. Example applications were presented to illustrate the use and usefulness of the method.

A Threshold Model of Tailings Sand Liquefaction Based on PSO-SVM

The liquefaction of tailings sand caused by seismic loads is a major problem in ensuring the safety of tailings ponds. Liquefaction may cause uncontrolled fluidized failure of the dam body, causing considerable damage to the lives, property and environment of people downstream. In this paper, a prototype tailings sand is used as the material to consider the main factors affecting liquefaction (i.e., dynamic load, soil quality, burial and static conditions). By embedding acceleration, pore pressure and earth pressure sensors in the rigid design of the self-designed rigid model box, different types of seismic waves of different ground motion amplitudes (PGA) were induced in a shaking table test of tailings sand liquefaction. The seismic intensity, waveform (class II, III and IV seismic waves) and active earth pressure of the PGA characterizing dynamic factors were obtained, and the static factors were characterized. The dynamic shear stress ratio, the peak acceleration of the earthquake, the pore pressure of the drainage factor and the buried depth (overlying effective pressure) characterize the soil conditions. SPSS software was used to analyze the factor dimension reduction, and the most suitable factors for factor analysis were obtained. Particle Swarm Optimization (PSO) was used to optimize the parameters, and the improved PSO-SVM algorithm was compared with the existing genetic algorithm (GA) and grid node search (GS). The algorithm used in this paper is fast and has a relatively high accuracy rate of 92.7%. The established threshold model method is of great significance to predict the liquefaction of tailings sand soil under the action of ground motions and to carry out safety managemenin advance, which can provide a certain reference for the project.

Mechanism of reduction of aeroacoustic sound by porous material: comparative study of microscopic and macroscopic models

The effects of porous material on the aeroacoustic sound generated in a two-dimensional low-Reynolds-number flow ( $Re=150$ ) past a circular cylinder are studied by direct numerical simulation in which the acoustic waves of small amplitudes are obtained directly as a solution to the compressible Navier–Stokes equations. Two models are introduced for the porous material: the microscopic model, in which the porous material is a collection of small cylinders, and the macroscopic model, in which the porous material is continuum characterized by permeability. The corrected volume penalization method is used to deal with the core cylinder, the small cylinders and the porous material. In the microscopic model, significant reduction of the aeroacoustic sound is found depending on the parameters; the maximum reduction of $24.4$ dB from the case of a bare cylinder is obtained. The results obtained for the modified macroscopic model are in good agreement with those obtained for the microscopic model converted by the theory of homogenization, which establishes that the microscopic and macroscopic models are consistent and valid. The detailed mechanism of sound reduction is elucidated. The presence of a fluid region between the porous material and the core cylinder is important for sound reduction. When the sound is strongly reduced, the pressure field behind the cylinder becomes nearly uniform with a high value to stabilize the shear layer in the wake; as a result, the vortex shedding behind the cylinder is delayed to the far wake to suppress the unsteady vortex motion near the cylinder, which is responsible for the aeroacoustic sound.

Use of 532 nm Potassium Titanyl Phosphate Laser on Vocal Fold Scars Under Topical Anesthesia: A Pilot Study

This pilot study aims to evaluate the efficacy of 532 nm potassium titanyl phosphate (KTP) laser under topical anesthesia in patients with vocal fold scars. A series of 18 patients with vocal fold scars of varying degrees were treated. The KTP laser was used under local anesthesia in the outpatient clinic. It was set to deliver 6 W of power using a continuous output mode. Close-to-contact mode was used for laser irradiation, and contact mode was used for ablation and excision of the lesions. Some of the patients received laser scar ablation on both vocal folds; the scarred vocal fold on one side and the hypertrophic vocal fold on the other. Parameters include glottic closure, amplitude, and mucosal wave pattern were measured using laryngeal stroboscopic examination. Aerodynamic and voice evaluations were carried out using maximum phonation time (MPT), jitter, shimmer, Voice Handicap Index questionnaire (VHI-30), and GRBAS scale. In total, 21 surgeries were performed on 18 patients. Glottic closure, amplitude, and mucosal wave pattern showed improvement 2 months postoperatively (P < .05). There was significant improvement in the postoperative scores for VHI-30, VHI-emotional sub-scale, VHI-physical sub-scale, and GRBAS (P < .05). There was no significant difference in the MPT and VHI-functional sub-scale before and after the operation (P > .05). Re-adhesion of the anterior commissure was observed in 2 patients with Type III scars. The 532 nm KTP laser is an effective tool for the treatment of vocal fold scars. Further research is required to determine if serial laser applications could improve outcomes for this challenging condition. Level IV.

MATHEMATICAL MODELING OF THERMOGASDYNAMIC PROCESSES IN PISTON ENGINES

A method for calculating the non-stationary gas flow in the exhaust pipeline of a piston engine by the method of solitary waves of finite amplitude is presented. The comparison of experimental data and calculation results by the method of characteristics and obtained when considering the process of propagation of solitary waves through the exhaust pipeline of a piston engine equipped with a pulsed turbocharging system is shown.

Detection of Hydrogen Damage in 2.25Cr1Mo0.25V by Ultrasonic Inspection

2.25Cr1Mo0.25V steel has better high temperature strength than ordinary Cr-Mo steel, and has been widely used in nuclear and chemical environments such as nuclear energy and chemical industry. However, vanadium-added steel is still likely to cause hydrogen damage and requires early detection. Ultrasonic inspection has strong penetrating ability. It can detect thin plates with thickness of 1-2mm and steel structure of several meters long. In this paper, ultrasonic longitudinal wave was used to detect the amplitude and longitudinal wave period before and after hydrogen charging, and the change of wave velocity was obtained. The dynamic tensile test of the specimen before and after hydrogen charging was also carried out, and the elastic modulus and elongation of hydrogen before and after hydrogen charging were obtained. The relationship between ultrasonic signal and hydrogen embrittlement was also discussed in this paper.

Compacting nanopowder materials by a pulse pressure generated by expanding plasma channel of a spark ignited by wire electrical explosion

The purpose of the article is to explore the possibilities of powder material compaction by the pressure pulse of an electric explosion of a conductor, establish a functional relationship between the parameters of the pressure pulse and an electrical technological installation for powder material compaction, select the parameters for pulse pressure amplitude and duration adjustment, and specify the design options of the working tool for powder material compaction. Analytical studies have been carried out on the basis of the method of formalized representation of the development of the process of pulse pressure wave formation and propagation where the latter is created by an expanding plasma channel of an electric spark in a transmitting medium initiated by an electric explosion of a wire. The simulation of high-speed de formation of the pipe wall under the action of the pulse pressure is carried out in the MATLAB software package. A scanning electron microscope is used to study the microstructure of the breakage of the compacted material with nanomodifiers. Based on the experimental studies on powder material compaction by the pulse pressure created by the expanding plasma channel of a spark initiated by an electric explosion of a wire when the current pulse f rom an electrotechnological installation is supplied to it, it has been determined that the magnitude and shape of the pressure pulse are most influenced by the parameters of this installation. Based on the obtained model studies, the optimal modes for compaction of nanomodified powders have been selected. The relationship is obtained between the parameters of the pulse pressure (Pm amplitude and pressure wave propagation form) and the electrotechnological installation (voltage, inductance, capacitance). It is proposed to use an acoustic-electric wave model to estimate the pressure that provides high-speed deformation of metal pipes, and to plot a deformation profile of metal pipes used for compaction. Analysis of SEM images of the fractures obtained in compact experiments has showed a high degree of particle compaction with the formation of a solid composite.

Plane Sound Waves of Low Amplitude in a Gas-Dust Environment with Polydispersed Particles

Plane Sound Waves of Low Amplitude in a Gas-Dust Environment with Polydispersed Particles

DETERMINATION OF THE NONLINEAR PARAMETER AND INTERNAL PRESSURE IN A LIQUID BY THE ACOUSTIC METHOD

An acoustic method is proposed for assessing the molecular properties of a liquid, determining the nonlinear parameter of liquids from the ratio of the first and second harmonics when the acoustic wave changes, and using this parameter to measure the internal pressure. In addition, the proposed method measures intermolecular distances for the studied liquids. In organ fluids, the effects of sound scattering and wave interaction are enhanced. In body fluids, at the molecular level, there is a small amount of microscopic bubbles. This leads to the appearance of the phenomenon of cavitation. These phenomena can be harmful, but not always. There are devices for biological and pharmaceutical technologies, medical devices that successfully use these effects. The paper presents a functional diagram of the experiment, identifies the oscillograms of acoustic signals of finite amplitude at different distances from the emitter. The same devices based on quartz plates 25 mm in diameter with a resonance frequency of 3 MHz were used as the emitter and receiver. This difference of approximately three times the resonance frequencies of the sensors and the acoustic signal ensures the linearity of the amplitude-frequency response of both sensors. Nonlinear acoustic methods are a global trend in biomedical research, as they open up new opportunities and prospects in the development of medical devices. The appearance of higher harmonics in the curvature of the initial harmonic wave of finite amplitude can be used for express analysis of the physical properties of pure liquids and especially aqueous solutions of organic substances. This method of experimental determination of the nonlinear parameter and internal pressure in a liquid is more convenient than the static one, since it does not require the use of high excess static pressures. The proposed acoustic method gives less error than the dynamic one. The accuracy of such a determination can be sufficient to judge the change in the intermolecular interaction in liquids.

Power splitter and TE-TM polarization separator based on magneto-photonic crystal fiber

Specifically, this work aims to achieve a power splitter and polarization separator of a guided light, basing on magnetic properties such as gyrotropy, mode coupling and optimization of geometric parameters of a magneto-photonic fiber. This fiber which makes it possible to split and separate the polarizations is characterized by the opto-geometric optimization of an Y junction based on magnetic fluid in a silicon dioxide photonic crystal fiber, able to separate combination of two guided modes TE/TM, into two waves of the same amplitude and in phase between them, an incoming light wave which arrives at the Y-branch input of the fiber.

Characterization and dynamical stability of fully nonlinear strain solitary waves in a fluid-filled hyperelastic membrane tube

We first characterize strain solitary waves propagating in a fluid-filled membrane tube when the fluid is stationary prior to wave propagation and the tube is also subjected to a finite stretch. We consider the parameter regime where all traveling waves admitted by the linearized governing equations have nonzero speed. Solitary waves are viewed as waves of finite amplitude that bifurcate from the quiescent state of the system with the wave speed playing the role of the bifurcation parameter. Evolution of the bifurcation diagram with respect to the pre-stretch is clarified. We then study the stability of solitary waves for a representative case that is likely of most interest in applications, the case in which solitary waves exist with speed c lying in the interval [0, c_1) where c_1 is the bifurcation value of c, and the wave amplitude is a decreasing function of speed. It is shown that there exists an intermediate value c_0 in the above interval such that solitary waves are spectrally stable if their speed is greater than c_0 and unstable otherwise.

Fast accurate seakeeping predictions

ABSTRACT Accurate predictions of ship motions and loads in a steep seaway require to include contributions depending non-linearly on wave amplitude. CFD methods do that routinely, but they require very high computing effort. Previous potential methods neglect either all or at least some nonlinear effects. The present method includes all substantial nonlinear effects amenable to potential flow. Using approximations for effects of flow separation at the aft end of hull and rudder, an accuracy comparable to that of good model experiments and CFD calculations is attained. That is demonstrated for motions and loads in cross sections of a containership sailing in head and quartering waves of large amplitude. Compared are results of model experiments, CFD calculations, a linear and the new nonlinear potential flow method. Another comparison is made for motions and added resistance of a second containership in head waves, where, apparently, an exceptional accuracy of experiments and calculations has been attained. A number of new ideas which were necessary to obtain a robust and accurate, fully nonlinear procedure are described. In typical cases, the method may take only one or a few percent of the computing effort of a comparable CFD computation.

Heat transfer enhancement by localised time varying thermal perturbations at hot and cold walls in a rectangular differentially heated cavity

The objective of this work it is to determine the optimal properties of a thermal disturbance to enhance the heat transfer in a rectangular differentially heated cavity of aspect ratio 4. So, we study numerically the effect on the heat transfer of one or two small thermal actuators (5% of active plate surface) applied at the active walls of this kind of cavity. Thermal disturbances are sine or square waves. Influences of wave characteristics (amplitude, frequency, phase shift) and the vertical location of the disturbance area are investigated for various Rayleigh numbers below its first critical value (RaH=1.02×108). Only a fluid with Prandtl number equal to 0.71 (air) is considered. Flows are calculated solving the 2D unsteady Boussinesq–Navier–Stokes equations using the Spectral Element Method programmed in the Nek5000 opencode. A detailed description of the coupling between one or two thermal disturbances and cavity flow is presented. The main contribution of this work is that the best position to enhance the heat transfer is 70% of the hot plate height or 30% of the cold plate height, and not 0.1 for the hot plate (0.9 for the cold one) which is generally admitted. At this position this increase reaches 5.5% by disturbing at both active walls with local synchronised square waves of amplitude ε=1, of frequency f=0.403 and at a state slightly below the first critical Rayleigh number.