Wave Shape Research Articles

Influence of dam break scenarios on flood wave characteristics. Case study – Paltinu Dam, Romania

Among the various constructive types of dams, the arch dams breaches are the largest and the quickest to occur, leading to the most catastrophic flood waves. Therefore, prediction of the shape, magnitude and arrival time of the breach waves is of utmost importance for flood risk management. The study analyses in GIS environment the influence of different dam breach scenarios on the evolution in time and space of the flood wave. As a study case it was chosen the 108m in height, Paltinu arch-dam (Romania), built on Doftana River and its about 19km river reach down to the confluence with Prahova River. Several breach widths and depths are considered in the analysed scenarios, coupled with selected inflow hydrographs and initial reservoir water elevation, to assess their influence on the dam break wave characteristics and downstream flooded areas. To model the flood wave routing following the dam brake, HEC-RAS software is used. Inundation boundaries, characteristic depths and velocities, as well as arrival time in selected control sections are compared and conclusions are drawn.

Active Vibration Control Strategy for Online Application in a Range Extender

Noise, vibration and harshness are a big issue for hybrid vehicles especially in range extenders. Traditional vibration control and active damping control are generally used for suppressing vibration. Compared with traditional vibration control, active damping control is more flexible and effective in suppressing vibration. The basic idea of active damping control is controlling electric motor compensating for the torque of engine and reducing the vibration from the source. The reduction of vibration is highly depended on the compensation torque of the electric motor. A differently designed compensation torque has a significant impact on the active damping control effect. In this paper, an active damping control method for online application is proposed. And several kinds of compensation torque are designed for this method. Experiments on vibration performance are conducted to compare the effect of different compensation torque design in reducing vibration. And the results show that the compensation torque in the shape of square wave has potential for reducing vibration in all directions. Finally, a guiding tool for compensation design is proposed by correlation analysis and the relationship between designing factors and vibration is revealed.

РАЗВИТИЕ СЛУХОВОГО ВОСПРИЯТИЯ МУЗЫКАНТОВ-ИНСТРУМЕНТАЛИСТОВ С НАРУШЕНИЯМИ ЗРЕНИЯ

The article focuses on the auditory perception of students with profound visual impairments. The category of "perception" is considered in psychology as a process of reflection in the consciousness of an integral sensual image of an object or phenomenon. In the musical-aural perception of musicians with visual impairments, the subjective image of an object, phenomenon or process directly affects the auditory analyzer, and in a latent form the system of motor and tactile analyzers. Musical sound is understood as a pitch or noise sound, carrying the function of a means of a specific semantic expression. The auditory sensations appear due to the effects of periodic oscillations of sound waves on the auditory receptor. The shape of a sound wave's oscillations is reflected in a specific quality — the timbre of sound. When playing a musical instrument, the performer extracts a sound with a certain pitch, dynamics, timbre and duration. The article emphasizes that the development of musical ear of visually impaired musicians, as the ability to perceive and represent musical images, are inextricably linked to the images of memory. It is important that perceptual skills at the level of sensations and auditory perception are formed and developed under the influence of living conditions, training and the requirements of musical and practical activity.

Mathematical model of the photoplethysmogram for testing methods of biological signals analysis

The purpose of this study was to develop a mathematical model of the photoplethysmogram, which can be used to test methods that introduce the instantaneous phases of the modulating signals. The model must reproduce statistical and spectral characteristics of the real photoplethysmogram, and explicitly incorporate the instantaneous phases of the modulating signals, so they can be used as a reference during testing. Methods. Anacrotic and catacrotic phases of the photoplethysmogram pulse wave were modeled as a sum of two density distributions for the skew normal distribution. The modulating signals were introduced as harmonic functions taken from the experimental instantaneous phases of the VLF (0.015...0.04 Hz), LF (0.04...0.15 Hz) and HF (0.15...0.4 Hz) oscillations in the real photoplethysmogram. The spectral power in the VLF, LF, and HF frequency ranges was calculated to compare the model and experimental data. Results. The model qualitatively reproduces the shape of the experimental photoplethysmogram pulse wave and shows less than 1% error when simulating the spectral properties of the signal. Conclusion. The proposed mathematical model can be used to test the methods for introduction of the instantaneous phases of the modulating signals in photoplethysmogram time-series.

Enhancing Security via Speaker Recognition

In this era of globalization, networking, and the bulk of the information they demand reliable identity verification is quintessential. An efficient means to do this is using biometrics as a method of identification. The current biometric method, voice biometrics, may be an inexpensive and precise confirmation technology widely utilized in recent decades. Voiceprint, human biological characteristics, possess unique physiognomic features for every individual who is difficult to counterfeit, imitate, and replace. As a non-contact identification technology, the users are accepting Voice Recognition Technology and extensively deployed in authentication and assisting systems. The procedure of recognizing or refusing the individuality claim of a user is established on the individual’s exclusive information present in the speech wave shape. Recently it received expanding interest in the past two decades, as an accessible, comprehensible way of substituting (supplementing) basic password-type matching.

Demonstration of Scalable Series-Connected Submodule of Modular-Multilevel-Converter- Based Arbitrary Wave Shape Generator Used for High-Voltage Testing From Off-the-Shelf Component

Demonstration of Scalable Series-Connected Submodule of Modular-Multilevel-Converter- Based Arbitrary Wave Shape Generator Used for High-Voltage Testing From Off-the-Shelf Component

The Peristaltic Flow of Jeffrey Fluid through a Flexible Channel

The purpose of this study is to calculate the effect of the elastic wall of a hollow channel of Jeffrey's fluid by peristaltic flow through two concentric cylinders. The inside tube is cylindrical and the outside is a regular elastic wall in the shape of a sine wave. Using the cylindrical coordinates and assuming a very short wavelength relative to the width of the channel to its length and using governing equations for Jeffrey’s fluid in Navier-Stokes equations, the results of the problem are obtained. Through the Mathematica program these results are analysed.

Thermal performance analysis of artificially roughened solar air heater under turbulent pulsating flow with various wave shapes

This paper presents a numerical investigation of the operation of a solar air heater (SAH) with cylindrical shape ribs under turbulent pulsating flow based on thermal and frictional considerations. Turbulence and thermal natures of flow physics are modeled by taking the relevant governing equations into the account using RNG k−ε turbulence model and transient state Reynolds-Averaged Navier-Stokes (RANS) equations. The pulsating flow is modeled with four different wave shapes including rectangular, sinusoidal, triangular, and sawtooth functions. The influence of various factors such as wave shape, Reynolds number (Re), frequency, and amplitude of pulsating flow on the thermal and hydraulic performance of SAH has been evaluated. Results indicated that the SAH with ribbed absorber section under pulsed flow has a larger Nu number compared to the air heater with smooth duct under steady flow. Moreover, the pulsating flow with a sawtooth velocity profile leads to the greatest value of the thermo-hydraulic performance parameter (THPP). The growth of pulsation frequency up to 200 enhances the heat transfer coefficient of the air heater while for frequencies larger than 200, the thermal performance declines. In addition, the increase in pulsation amplitude has a negative effect on the THPP. It was proved that the increment of the Re number enhances the THPP. Up to 53.3% improvement of THPP can be achieved by applying pulsed flow with sawtooth wave shape and ribbed absorber section compared to air heat with smooth duct under steady flow.

An Effective Method of Detecting Characteristic Points of Impedance Cardiogram Verified in the Clinical Pilot Study.

Accurate and reliable determination of the characteristic points of the impedance cardiogram (ICG) is an important research problem with a growing range of applications in the cardiological diagnostics of patients with heart failure (HF). The shapes of the characteristic waves of the ICG signal and the temporal location of the characteristic points B, C, and X provide significant diagnostic information. On this basis, essential diagnostic cardiological parameters can be determined, such as, e.g., cardiac output (CO) or stroke volume (SV). Although the importance of this problem is obvious, we face many challenges, including noisy signals and the big variability in the morphology, which altogether make the accurate identification of the characteristic points quite difficult. The paper presents an effective method of ICG points identification intended for conducting experimental research in the field of impedance cardiography. Its effectiveness is confirmed in clinical pilot studies.

Electrochemical Behaviour of Organic Explosive Compounds in Ionic Liquids: Towards Discriminate Electrochemical Sensing

AbstractThe electrochemical reduction of four organic explosive compounds, 1,3,5,7‐tetranitro‐1,3,5,7‐tetrazocane (HMX), 1,3,5‐trinitro‐1,3,5‐triazinane (RDX), pentaerythritol tetranitrate (PETN) and 2,4,6‐trinitrophenylmethylnitramine (tetryl), is studied in eight room temperature ionic liquids (RTILs). In all RTILs, the reduction peaks were highly complicated, but much better resolved than in previous studies in conventional solvents. HMX typically showed broad overlapping peaks in RTILs with distinctly different voltammetric wave shapes. The voltammetry of RDX also varied dramatically, ranging from one to four reductive peaks with broad features. PETN showed one large reduction peak owing to the overlapping reduction processes for all the nitro‐ groups. Tetryl produced the most complex voltammetry with the largest number of cathodic peaks, likely due to the structure that contains both nitramine and nitroaromatic groups. For all explosives, an electrogenerated product was oxidized on the reverse scan. The reduction potentials and voltammetric wave shapes were found to vary significantly in the different RTILs, allowing the possibility to ‘fingerprint’ the different explosives using their distinct signatures, suggesting that discriminative sensing may be possible by careful tuning of the RTIL structure. Exploring the electrochemical behaviour of these explosives is a first step towards utilising RTILs as favourable solvents for the electrochemical detection of such compounds.

Condition Assessment of HVDC Cables during their Lifecycle

Recent market developments towards power generation in remote renewable power plants such as concentrated solar power plants in deserts or large off-shore wind parks, raise an interest for long distance power transmission via extruded HVDC cables. HVDC cables require quality assurance during the complete product lifecycle, mainly: a) R&D activities for design verification and - validation b) routine tests in the factory for confirmation of proper manufacturing c) acceptance test after erection and commissioning to exclude defects caused during transport and installation d) ageing monitoring and quick fault detection and location detection during service life. Considering increasing voltage levels, increasing cable lengths and ground or even offshore installation, the dielectric testing of extruded HVDC cables in the factory and on site remains challenging. The long-term validation of insulation coordination requires high voltages for quality assurance tests which represent typical expectable stresses during service. Typical examples are wave shape, partial discharge behavior and dielectric field stress in the insulation medium. Hence, different technical solutions are available to generate these required high voltages for testing of HVDC cables. This paper discusses essential technical and commercial aspects of HVDC cable quality assurance and presents suitable methods for HVDC cable testing.

Localized wave solutions to a variable-coefficient coupled Hirota equation in inhomogeneous optical fiber

The first- and second-order localized waves for a variable-coefficient coupled Hirota equation describe the vector optical pulses in inhomogeneous optical fiber and are investigated via generalized Darboux transformation in this work. Based on the equation’s Lax pair and seed solutions, the localized wave solutions are calculated, and the dynamics of the obtained localized waves are shown and analyzed through numerical simulation. A series of novel dynamical evolution plots illustrating the interaction between the rogue waves and dark-bright solitons or breathers are provided. It is found that functions have an influence on the propagation of shape, period, and velocity of the localized waves. The presented results contribute to enriching the dynamics of localized waves in inhomogeneous optical fiber.

Hydro-optic interaction study on submerged unmanned underwater vehicles regarding to Snell's window

The underwater creatures have always desired to collect information about what is in beyond, for instance, the fishes that hunt birds with precise calculations. Possessing a subsurface device capable of imaging the outside area of water without any distortion can be notified of modern demand. To be acquainted with this phenomenon, a series of submerged hydrofoils with various geometrical properties are mentioned in different submerged distance and incidence angles to recognize the recondite limits upon its aberrated eyesight. The behavioral changes of the wave's surface have been numerically discussed in detail by ray length. The primary outcomes reveal that Snell's window varies under different conditions. In brief, the emitted ray undergoes more severe distortions when the hydrofoil is positioned near the water's surface. However, interestingly enough, other parameters such as hydrofoil's geometry, the angle of attack, and the flow's velocity affect the wave's shape, and that wave's geometry sets different distortions patterns in different areas that the camera spots.

Analysis of an hypersonic magnetohydrodynamic shock layer

A plane hypersonic flow collides against a body possessing a magnetic field, creating a bow shock and a shock layer where an enhanced density and temperature generate a positive electrical conductivity; therefore the Lorentz force influences the flow within the layer. A number of approximations of the magnetohydrodynamics equations, appropriate for the hypersonic case, simplify the system enough to allow us to obtain the values of pressure and velocity at any point of the layer, and in particular at the body itself, provided we know the values of these quantities at a section of the layer and at the shock wave. The last ones are provided by the Newtonian approximation. The inverse problem, to find the shape of the shock wave knowing the values of pressure and magnetic field at the body, may also be solved by this procedure.

A unique cardiac electrocardiographic 3D model. Toward interpretable AI diagnosis.

Mathematical models of cardiac electrical activity are one of the most important tools for elucidating information about heart diagnostics. In this paper, we present an efficient mathematical formulation for this modeling simple enough to be easily parameterized and rich enough to provide realistic signals. It relies on a five dipole representation of the cardiac electric source, each one associated with the well-known waves of the electrocardiogram signal. Beyond the physical basis of the model, the parameters are physiologically interpretable as they characterize the wave shape, similar to what a physician would look for in signals, thus making them very useful in diagnosis. The model accurately reproduces the electrocardiogram signals of any diseased or healthy heart. This new discovery represents a significant advance in electrocardiography research. It is especially useful for diagnosis, patient follow-up or decision-making on new therapies; is also a promising tool for well-performing, transparent and interpretable AI approaches.

Tidally induced spiral arm wraps encoded in phase space

Context. The impact of Sagittarius and other satellite galaxies such as the Large Magellanic Cloud on our Galaxy and in particular its disc is gradually being disclosed. Simulations tailored to the interaction of the Milky Way (MW) and Sagittarius show rings and spiral arms appearing in the Galaxy disc. However, spiral arms can also be induced by the bar or by disc instabilities. Aims. We aim to study the dynamics of tidally induced spiral arms in the context of the different encounters with Sagittarius and determine their kinematic signatures in the shape of ridges and waves in angular momentum, similar to those detected with Gaia DR2. Methods. We built toy models of the interaction between a host and a satellite galaxy using orbital integrations after a tidal distant encounter. We derived analytically the shape of the structures seen in phase space as a function of time for simple power-law potential models. We compared these models to a more realistic N-body simulation of the MW Sagittarius-like interaction and also to real data from Gaia DR3. Results. As previously found, an impulsive distant tidal approach of a galactic satellite generates a kick in velocities that leads to a two-armed spiral structure. The arms are made of orbits in between their apocentres and pericentres, thus, they correspond to regions with average negative galactocentric radial velocity. The two-arm pattern rotates at an angular speed of ω − 1/2κ which depends on Galactocentric radius, thus causing winding with time range of 0.8–2.1 Gyr, respectively. This winding produces ridges in the R − Vϕ projection with alternating signs of VR and oscillations of VR in the LZ − ϕ space, similar to those observed in the Gaia data. The frequency of these kinematic features increases with time, offering a powerful means to infer the potential and the perturbation’s onset time and azimuthal phase. Fourier analysis allows us to date the impact times of simple models and even to date perturbations induced from subsequent pericentric passages that appear as simultaneous waves. For the MW, the Fourier analysis indicates a superposition of two different frequencies, confirming previous studies. Assuming that both are due to impulsive and distant pericentre passages, we find perturbation times < 0.6 Gyr and in the range of 0.8–2.1 Gyr. The latter is compatible with a previous pericentre of Sagittarius and would be associated to about four wraps of the spiral arms in the observed radial range. Conclusions. Further work on the self-gravitating response of galactic discs and possible degeneracies with secular processes induced by the bar is necessary. Our study is a first step towards shedding more light on the elusive structure and dynamics of the spiral arms of the Galaxy.

Evaluating the Window Size’s Role in Automatic EEG Epilepsy Detection

Electroencephalography is one of the most commonly used methods for extracting information about the brain's condition and can be used for diagnosing epilepsy. The EEG signal's wave shape contains vital information about the brain's state, which can be challenging to analyse and interpret by a human observer. Moreover, the characteristic waveforms of epilepsy (sharp waves, spikes) can occur randomly through time. Considering all the above reasons, automatic EEG signal extraction and analysis using computers can significantly impact the successful diagnosis of epilepsy. This research explores the impact of different window sizes on EEG signals' classification accuracy using four machine learning classifiers. The machine learning methods included a neural network with ten hidden nodes trained using three different training algorithms and the k-nearest neighbours classifier. The neural network training methods included the Broyden-Fletcher-Goldfarb-Shanno algorithm, the multistart method for global optimization problems, and a genetic algorithm. The current research utilized the University of Bonn dataset containing EEG data, divided into epochs having 50% overlap and window lengths ranging from 1 to 24 s. Then, statistical and spectral features were extracted and used to train the above four classifiers. The outcome from the above experiments showed that large window sizes with a length of about 21 s could positively impact the classification accuracy between the compared methods.

Using BHR to detect coal seam interface in coal mine

The geological transparency of working face is the premise and guarantee to realize the intelligent and accurate mining for coal resources. A large number of gas drainage holes, water exploration holes and other boreholes are constructed before and during coal mining. In this paper, the borehole radar (BHR) is used to detect the coal bedding interface in boreholes along the coal seam. With gprMax, we analyze the conditions of the top and bottom interface of coal bedding with 100 MHz and 200 MHz BHR at an dip angle of 0°;analyze the response characteristics of the 200 MHz BHR when the dip angle is 15°, 30°, 45°, and 60°;analyze the influencing characteristics of roadways and bolts during BHR detection.Practical applications are carried out.The result shows that 1) when the borehole inclination is 0°, to distinguish the reflected wave of roof from that of floor, for 100 MHz borehole radar, ΔD needs to be greater than 1 m, and for 200 MHz borehole, it needs to be greater than 0.5 m. 2)When the drilling inclination angle is not 0°, the reflection profile of the top and bottom interface will have a cross feature, and the greater the dip angle, the greater the crossing angle. 3) BHR multiples in boreholes along coal seam have nothing to do with borehole position and inclination angle, but are related to dominant frequency of BHR;4)The change of aperture mainly affects the in-phase axis shape of direct wave. 5)the roadways and bolts have an impact on the detection of coal -rock interface.6)The position of roadway reflection event axis is only related to the nature of coal seam. Therefore, the electromagnetic wave velocity of the coal seam can be calculated by calculating the slope of the event axis. The actual detection of coal seam thickness of about 3 m using 200 MHz in a mine in Shanxi province shows that the electromagnetic wave propagation speed in the coal seam in this area is 0.1342 m/ns. With the proposed processing method,the accuracy of BHR results is high, the error is within 0.5 m.Combined with the borehole trajectory, the BHR can provide accurate coal seam interface position information for the transparent working face.

Clinical Applications of Low-Intensity Pulsed Ultrasound and Its Underlying Mechanisms in Dentistry

Low-intensity pulsed ultrasound (LIPUS) serves as a non-invasive treatment tool that reaches the lesion site in the form of ultrasound. Due to its low toxicity, low thermal effect, and low immunogenicity, LIPUS has attracted wide interest in disease treatment. It has been demonstrated that LIPUS can activate multiple signal pathways in the shape of sound wave and one of the most acknowledged downstream response components is integrin/focal adhesion kinase (FAK) complex. In recent years, the functions of LIPUS in bone regeneration, bone healing, bone mass maintenance, and cellular metabolism were found. Various oral diseases and their treatments mainly involve hard/soft tissue regeneration and reconstruction, including periodontitis, orthodontic tooth movement (OTM), dental implant, mandibular deficiency, and dentin-pulp complex injury. Thus, more and more researchers pay close attention to the application prospects of LIPUS in stomatology. We searched these articles in PubMed with keywords LIPUS, temporomandibular joint (TMJ), periodontitis, orthodontics, and pulp, then classified the retrieved literature in the past five years by disease type. In this review, the function effects and possible mechanisms of LIPUS in periodontal tissue regeneration, orthodontic treatment, implant osseointegration, TMJ bone formation/cartilage protection, and dentin-pulp complex repair after injury will be summarized. The challenges LIPUS faced and the research limitations of LIPUS will also be elucidated. Therefore, this paper intends to provide new insights into oral disease treatments, explore the optimal application specification of LIPUS, and probe the future research orientation and the prospect of LIPUS in the dental field.

Propagation and intensity of blast wave from hydrogen pipe rupture due to internal detonation

The coupled fluid-structure-rupture model was developed to study the propagation and intensity of blast wave from hydrogen pipe rupture due to internal detonation. The dynamic rupture of pipe and propagation of blast wave were well coupled together in every timestep during the simulation. The numerical model was validated with experiments in terms of both typical rupture profiles and blast overpressures. Results reveal that crack branching of pipe can dramatically increase the rupture opening rate which controls the intensity and shape of the resultant blast wave. Due to the process of crack initiation and extension, the blast wave out of the pipe first forms and then is strengthened by the subsequent compression waves. This makes the maximum peak overpressure appears at a certain standoff distance above the rupture. Despite consuming some percentages of energy, the dynamic rupture of pipe generally presents positive effects (up to 2–3 times) on the blast wave intensity along the jetting direction due to the convergence effect of rupture opening on the release of internal high-pressure gas. Finally, through defining normalized overpressure and impulse based on the same hydrogen detonation in open spaces, the quantitative influences of pipe rupture on the blast wave intensity in cases of different detonation pressures and standoff distances are clarified.