Main Wave Research Articles

Study on ultrasonic wave propagation in equine leg bone for screening bucked shin.

For simple, safe, portable, and inexpensive evaluation suitable for leg bone diseases of racehorses in the field, an ultrasonic measurement technique was applied to evaluate wave velocities. A digital model of the third metacarpal bone with the bucked shin was fabricated using high-resolution peripheral quantitative computerized tomography data of a racehorse. This model was anisotropic and heterogeneous, and was constructed using the measured ultrasonic wave velocities in the bone. With this model, ultrasonic wave propagation along the bone axis was simulated using the elastic finite-difference time-domain method. We found two main waves with different propagation velocities. The fast-waves showed a wave velocity close to the longitudinal wave in the axial direction. However, the apparent velocities changed dramatically owing to bone surface irregularities (changes of the shape) in the area of bucked shin. The slow-waves showed a wave velocity close to the shear wave, which was unaffected by the bone surface irregularities. The simple comparison of different wave behaviors may be a suitable parameter for the initial in vivo screening of bucked shin in the legs of racehorses, which can be performed in the field.

Regional disparities in SARS-CoV-2 infections by labour market indicators: a spatial panel analysis using nationwide German data on notified infections

BackgroundRegional labour markets and their properties are named as potential reasons for regional variations in levels of SARS-CoV-2 infections rates, but empirical evidence is missing.MethodsUsing nationwide data on notified laboratory-confirmed SARS-CoV-2 infections, we calculated weekly age-standardised incidence rates (ASIRs) for working-age populations at the regional level of Germany’s 400 districts. Data covered nearly 2 years (March 2020 till December 2021), including four main waves of the pandemic. For each of the pandemic waves, we investigated regional differences in weekly ASIRs according to three regional labour market indicators: (1) employment rate, (2) employment by sector, and (3) capacity to work from home. We use spatial panel regression analysis, which incorporates geospatial information and accounts for regional clustering of infections.ResultsFor all four pandemic waves under study, we found that regions with higher proportions of people in employment had higher ASIRs and a steeper increase of infections during the waves. Further, the composition of the workforce mattered: rates were higher in regions with larger secondary sectors or if opportunities of working from home were comparatively low. Associations remained consistent after adjusting for potential confounders, including a proxy measure of regional vaccination progress.ConclusionsIf further validated by studies using individual-level data, our study calls for increased intervention efforts to improve protective measures at the workplace, particularly among workers of the secondary sector with no opportunities to work from home. It also points to the necessity of strengthening work and employment as essential components of pandemic preparedness plans.

A First Reliable Gravity Tidal Model for Lake Nasser Region (Egypt)

In the framework of the French–Egyptian Imhotep Project, two spring gravimeters have been installed in the area of Lake Nasser (Egypt) with the aim to establish a first reliable gravity tide model for the region. The two tidal gravity stations are located in Aswan, on the northern edge of the lake and in Abu Simbel in the south, respectively. This study was mainly aimed to obtain a reliable model of the crustal response to tidal forces and, consequently, to increase the accuracy of the geodetic observations, to be used in future geophysical studies in this region as well as to investigate the effect of the Lake level variations on the crustal deformation and related gravity changes. Nearly 3 years of gravity records (from May 2018 to April 2021) were collected. Since no scale factor was available for the two gravimeters, the first step of this study was to achieve a reliable calibration for each of the two collected gravity signals. After removing the instrumental drift, spikes, steps and tares, both gravimeters have been calibrated by fitting the output signal against a synthetic reference signal based on the body tidal gravity response due to Wahr-Dehant Earth model and FES2014 ocean tidal loading model. The calibrated signals have been analyzed with ET34-X-V80 software for tidal analyses. This enabled us to retrieve a set of frequency-dependent gravity factors (amplitude and phase) for the main tidal waves, as well as to obtain gravity residuals. It turns out that the accuracy of the amplitude estimates for the main tidal waves is 0.2 ÷ 1% for LCR_ET16 in Aswan and 1 ÷ 10% for the LCR_D-218 in Abu Simbel. To improve the tidal model at Abu Simbel, LCR_ET16 was stopped in Aswan and relocated there. The first 90 days of gravity recordings from ET16 at Abu Simbel provide promising results, with an accuracy of the order of 0.1% for the main tidal waves, even better than the results obtained in Aswan. The residual gravity signal after tidal subtraction at Aswan is in the range of ± 50 µGal. Further analyses of the instrumental contribution are however needed before to be able to interpret this gravity signal in terms of surface loading (i.e. changes in the water level of Lake Nasser) or underground hydrology.

An Improved Model for Five-Phase Induction Motor Based on Magnetic Noise Reduction Part I: Slot Opening Width

Based on the winding function considering the slot width and the air-gap permeability considering the slot opening width, the main radial electromagnetic force wave expressions of the induction motor are determined. The electromagnetic force-vibration prediction model of the induction motor is established. The natural frequency and acoustic radiation model of a finite-length cylindrical shell with two ends clamped is deduced. On this basis, an improved magnetic noise prediction model of cage induction motor is improved, which can calculate the combined effects of electromagnetic force on the axis and circumferential modes of the stator system. Aiming at two different noise reduction targets, an optimization method is proposed to reduce the overall electromagnetic noise of the motor without sacrificing efficiency and output torque. The feasibility of the model for electromagnetic noise prediction is verified by finite element simulation and experiments. For a 30/26 slots five-phase induction motor, low-noise analysis and optimization schemes of the opening width for two different targets are given. The results show that the larger slot opening scheme can also result in less magnetic noise for the right selection, which is contrary to the common design rule that recommends minimizing slot opening to reduce magnetic noise.

Ocean Wave Inversion Based on a Ku/Ka Dual-Band Airborne Interferometric Imaging Radar Altimeter

Ocean wave parameters (OWPs), including wave propagation direction (WPD), significant wave height (SWH), and main wave wavelength (MWW) can be typically retrieved using an interferometric imaging radar altimeter (InIRA). However, the inversion accuracy of ocean waves in Ku (15.8 GHz) and Ka (35.8 GHz) bands has not yet been evaluated due to the lack of field observation data. In this paper, to assess the inversion accuracy of OWPs in Ku and Ka bands, an airborne observation experiment using simultaneous Ku and Ka bands was carried out for the first time in Rizhao, Shandong Province, China. A dual-band InIRA (DInIRA) was configured with small incidence angles (4°–18°) and a Global Navigation Satellite System (GNSS) buoy; a mobile weather station was placed at the intersection of the plane routes for validation. Afterward, the WPD, SWH, and MWW were retrieved based on the imaging of sea surface height. As compared with the field in situ data, the WPD inversion results of main wind wave were found to be consistent with the measurement environmental wind direction. The SWH inversion biases, retrieved by the Ku and Ka bands, were 0.38 m and 0.27 m; the MWW inversion biases for the swells were equal to 16.75 m and 3.67 m; and the MWW inversion biases about the wind waves were 2.32 m and 0.57 m. Ultimately, it was established that the OWPs could be effectively retrieved by the DInIRA, and the inversion accuracy of the SWH and the MWW in the Ka band outperformed that in the Ku band.

Risk of hospitalization and death for COVID-19 in persons with epilepsy over a 20-month period: The EpiLink Bologna cohort, Italy.

ObjectiveData on COVID‐19 outcomes in persons with epilepsy (PWE) are scarce and inconclusive. We aimed to study the risk of hospitalization and death for COVID‐19 in a large cohort of PWE from March 1, 2020 to October 31, 2021.MethodsThe historical cohort design (EpiLink Bologna) compared adult PWE grouped into people with focal epilepsy (PFE), idiopathic generalized epilepsy (PIGE), and developmental and/or epileptic encephalopathy (PDEE), and a population cohort matched (ratio 1:10) for age, sex, residence, and comorbidity (assessed with the multisource comorbidity score), living in the local health trust of Bologna (approximately 800 000 residents). Clinical data were linked to health administrative data.ResultsIn both cohorts (EpiLink: n = 1575 subjects, 1128 PFE, 267 PIGE, 148 PDEE, 32 other; controls: n = 15 326 subjects), 52% were females, and the mean age was 50 years (SD = 18). Hospital admissions for COVID‐19 in the whole period were 49 (3.1%) in PWE and 225 (1.5%) in controls. The adjusted hazard ratio (aHR) in PWE was 1.9 (95% confidence interval [CI] = 1.4–2.7). The subgroups at higher risk were PFE (aHR = 1.9, 95% CI = 1.3–2.8) and PDEE (aHR = 3.9, 95% CI = 1.7–8.7), whereas PIGE had a risk comparable to the controls (aHR = 1.1, 95% CI = .3–3.5). Stratified analyses of the two main epidemic waves (March–May 2020, October 2020–May 2021) disclosed a higher risk of COVID‐19‐related hospitalization during the first epidemic wave (March–May 2020; aHR = 3.8, 95% CI = 2.2–6.7). Polytherapy with antiseizure medications contributed to a higher risk of hospital admission. Thirty‐day risk of death after hospitalization was 14% in both PWE and controls.SignificanceDuring the first 20 months since the outbreak of COVID‐19 in Bologna, PWE had a doubled risk of COVID‐19 hospital admission compared to a matched control population. Conversely, epilepsy did not represent a risk factor for COVID‐19‐related death.

Method for Solving the Microwave Heating Temperature Distribution of the TE10 Mode

Microwave heating is a process in which the electric, magnetic, and temperature fields are coupled with each other and are characterised by strong non-linearity, high time variability, and infinite dimensionality. This paper proposes a method for predicting the microwave heating temperature distribution of the TE10 mode, because the traditional numerical calculation method is not conducive to designing microwave controllers. First, the spatial distribution of the main electromagnetic mode TE10 waves in a rectangular waveguide was analysed using the principal mode analysis method. An expression for the transient dissipated power and a heat balance equation with infinite-dimensional characteristics were constructed. Then, the microwave heating model was decomposed into electromagnetic and temperature field submodels. A time discretization approach was used to approximate the transient constant dielectric constant. The heating medium was meshed to solve the electric field strength and transient dissipated power in discrete domains, and the temperature distribution was obtained by substituting this value into the finite-dimensional temperature field submodel. Finally, the validity of the proposed numerical model was verified by comparing the results with the numerical results obtained with the conventional finite element method. The methodology presented in this paper provides a solid basis for designing microwave heating controllers.

Cascade downshifting of peak frequency at wave spectra evolution on mild bottom slope: Experimental investigations

The evolution of the wave spectrum is important, because often initial wave parameters necessary for modeling and coastal engineering tasks are obtained on the basis of spectral characteristics. The wave spectra evolution over mild sloping bottom was studied. The data of laboratory experiments were used for spectral and bispectral analysis. The spectrum maximum frequency downshifting with discrete step (i.e. the cascade downshifting) was revealed. Its peculiarities depending on initial wave parameters and spectrum width were investigated. The cascade frequency downshifting occurs due to nonlinear processes and difference triad interactions between a) main frequencies of wave spectrum and infragravity frequencies and b) the frequencies of second harmonics and the new forming low-frequency peak in the main frequency range. According to laboratory experimental data the initial spectrum width determines the frequency step of downshifting and the number of cascades. The wider the initial wave spectrum, the less numbers of cascades are observed. It was shown that wave energy dissipation due to wave breaking is not a main reason for peak frequency downshifting and it has no direct influence on this process. The variability of the main wave period due to the cascade peak frequency downshifting can be important for engineering models because many calculations assume a constant wave period in the coastal zone.

Fedor Sologub in English-Language Anthologies: 1915-1950

The history of the reception of the Russian Symbolist movement in English begins in the 1890s. Readers in Great Britain and the United States could read about the Russian Symbolist Fedor Sologub long before any of his works were translated into English. During World War I and a parallel wave of interest in Russia, Sologub is one of the most popular Russian writers in the English-speaking world. Some of his poetry and prose works are translated into English and during the years 1915-1950 are included in no fewer than 28 Englishlanguage anthologies. During the first years of this period, almost all of his prose that is accessible to English readers is selected and translated by two translators, John Cournos and Stephen Graham. His poetry, on the other hand, is selected and translated by several translators over the course of this entire period. Anthologies with works by Sologub appear in two main waves: from 1915 until the middle of the 1920s, and in the 1940s after the outbreak of WWII. These anthologies demonstrate how Sologub was presented to English-speaking audiences during these years. This article examines English-language anthologies from this period, comparing what, if anything, is said about Sologub in their introductions to the works by Sologub they include. Some presented him as the quintessential decadent, while others tried to show the various sides of Sologub’s works. It is often the case in anthologies that the opinions of Sologub presented by editors are not supported by the works by Sologub these same editors selected for inclusion. The article ends with three bibliographical appendices listing Sologub’s anthologized poetry and prose and the anthologies that included them.

Numerical Analysis of the Main Wave Propagation Characteristics in a Steel-CFRP Laminate Including Model Order Reduction

Guided ultrasonic waves are suitable for use in the context of structural health monitoring of thin-walled, plate-like structures. Hence, observing the wave propagation in the plates can provide an indication of whether damage has occurred in the structure. In this work, the wave propagation in fiber metal laminate consisting of thin steel foils and layers of carbon fiber-reinforced polymer is studied, focusing on the main propagation characteristics like dispersion diagrams and displacement fields. For this purpose, the dispersion diagrams derived from the analytical framework and numerical simulations are first determined and compared to each other. Next, the displacement fields are computed using the global matrix method for two excitation frequencies. The results derived from the analytical framework is used to validate the numerically determined displacement fields based on a 2D and a 3D modeling approach. For both investigations the results of the analytical treatment and the numerical simulation show good agreement. Furthermore, the displacement field reveals the typical and well-known characteristics of the propagation of guided waves in thin-walled structures. Since the use of full 3D models involves a very high computational cost, this work also successfully investigates the possibility for model order reduction to decrease the computational time and costs of the simulation without the loss of accuracy.

Impact of physico-chemical properties on falling liquid films flow over flat and corrugated surfaces

In this paper, an optical technique based on fluorescence intensity is applied and calibrated to simultaneously measure film thickness (up to 8 mm) and interfacial velocity of the liquid film flow. Thus, thin-film flows at intermediate and low Reynolds number (13 < Re < 290) are experimentally studied with special attention given to the spatial variation, the frequency of the waves, and interfacial liquid velocity associated with global visual observation. Two fluids (water-ethanol mixture) characterized by low surface tension (σ = 35 and 50 mN/m) and three fluids (water-glycerin mixture) with high viscosity (µ = 5, 10, and 15 mPa.s) are used to investigate the influence of physico-chemical properties on thin-film flow on flat and corrugated plate topologies. First, the effect of physico-chemical properties on the global variation of waves shape and instability evolution has been investigated. Different work fluids were used in the same experimental conditions on a flat plate. Results showed that decreasing surface tension has a stabilizing effect on the flow, dampening the capillary waves that should otherwise arise. At high viscosity, solitary waves with high thickness followed by an undisturbed thin-film with a constant thickness appear. The impact of liquid flow rate and inclination (θ = 10° and 20°) was also studied. It shows that at higher inclination the film thickness decreases and then increases as the liquid flow rate increases. Next, the impact of counter-current gas was studied and we demonstrated that the amplitude of the main waves significantly increases even at low gas velocity while the effect on the velocity of the wave starts to be significant at a counter-current gas velocity of 3 – 4 m/s. Finally, the effect of the corrugation of the solid plate at a high inclination angle (θ = 60°) shows the onset of the breaking waves phenomenon, especially for fluids with low surface tension.

Surface waves in a linearly graded-index and an intensity-dependent index layered structure.

A new type surface wave is found that propagates in a linearly graded-index and an intensity-dependent index layered structure characterized by an abrupt change in the dielectric constant. The main surface wave characteristics are calculated analytically. The optical domain, the thickness of which increases with an increasing effective refractive index and decreases with an increasing characteristic distance, is formed. It is discovered that the characteristic distance of the graded-index medium and effective refractive index can control wave energy redistribution between the semiconductor layers.

The effect of climate change on wind-wave directional spectra

Through assessment of wind-wave directional spectra, we provide a comprehensive explanation of the projected 21st Century changes in the global wind-wave climatology under a high green-house emissions scenario. Using a seven-member wave climate projection ensemble, we estimate wave climate changes by comparing present and projected climatologies. Clustering techniques are applied to define regional patterns of change with homogenous behavior. The underlying mechanisms behind the changes are also explored by exploiting the relationship between the wave generation area and the effective energy flux propagating toward a target location. A robust transition from positive to negative trends in Southern Ocean westerly swells is observed around 45°S. The increasing signal found in the southernmost swells propagates north beyond 30°N, contributing significantly to the projected changes in tropical regions such as the tropical southern Atlantic and tropical southeastern Pacific. Results highlight the great complexity of the Pacific Ocean due to the convergence of multiple wave systems with different geneses. In the northern basins, the combined effect of the ice melting and a poleward shift of the storm track drives an increase of the northernmost westerly swells. This is countered by a decreasing trend projected in the main wave systems propagating in the North Atlantic Ocean. A poleward shift of trade-induced waves due to the Hadley cell expansion can also be observed globally, causing a clear dipole change pattern in the tropical southern Atlantic and tropical Indian oceans. • The effect of climate change on wave climate is assessed based on directional spectra. • The climate change signals of the main swell systems are described. • Sixteen ocean regions with a similar pattern of change are found.

Reading the History of the Roman Fort in Apsaros (Autonomous Republic of Adjara, Georgia) from a Numismatic Perspective / Odczytując historię rzymskiego fortu w Apsaros (Adżarska Republika Autonomiczna, Gruzja) z perspektywy numizmatycznej

An analysis of coin finds recovered in recent years from the area of the former Roman fort in Apsaros (Gonio, Georgia), allows us to look at the periodization of the history of the Roman military presence in this place from a new perspective. The chronological structure of silver and bronze coins, including those found individually, in hoards and in small foundation deposits, clearly indicates the existence of only a few stages of increased coin inflow in the almost two-hundred-year history of the presence of Roman army units in Apsaros. All of them coincide with important military events in the East and seem to be a testimony to the periodic concentration of Roman troops in the fort. Between the waves of monetary inflow, one can easily observe periods in which coins only reached Apsaros to a limited extent. The aim of the paper is an attempt to interpret the main waves of coins entering the fort in Apsaros in a historical context.

Long-term study on electrophysiological characteristics and catheter ablation of idiopathic ventricular arrhythmias originating from the left ventricular posterior papillary muscles guided by intracardiac ultrasound.

BackgroundThis study aimed to investigate the electrophysiological characteristics of idiopathic ventricular arrhythmias (VAs) originating from the left ventricular posterior papillary muscles (LPPM) and explore the efficiency of catheter ablation using three‐dimensional intracardiac ultrasound technology.MethodsTwenty‐seven cases of premature ventricular contraction/ventricular tachycardia (PVC/VT) originating from the left ventricular posterior papillary muscles were recorded from July 2015 to June 2019 in the Central Hospital of Shengli Oil Field and the First Affiliated Hospital of Zhengzhou University. Electrophysiological mapping and radiofrequency catheter ablation (RFCA) were performed using three‐dimensional intracardiac ultrasound technology. The characteristics of the body surface and intracavity electrocardiogram were analyzed. All cases were followed up for 24 months after the operation.ResultsThe VAs of all 27 cases were successfully eliminated by catheter ablation. QRS complexes were observed with a right bundle branch block (RBBB) pattern and a steep slope in the initial segment. Lead I appeared with an Rs pattern, and inferior leads (lead II, III, and aVF) were usually with an S wave. The lead aVR appeared with a qR pattern, while the R wave was commonly found in aVL. The main wave in leads V1‐V3 was positive but negative in V5 and V6.ConclusionVentricular arrhythmias originating from the left ventricular posterior papillary muscles have similar electrophysiological characteristics. The origin site was accurately located using three‐dimensional intracardiac ultrasound technology. Catheter ablation effectively eliminated VAs.

Study of growth rate of backward Raman scattering in plasma with density ripple

The recent studies proved that stimulated backward Raman scattering of a laser is affected significantly by the existence of magnetic field and density rippled plasma. At lower hybrid frequencies, the localized radial and azimuthal modes can be supported by the magnetized plasma. The density ripple interacts with the Raman process’s main Langmuir wave, producing in a secondary Langmuir wave with a higher wave number that is highly Landau damped on the electrons. Numerically, the influence of various modes on the growth rate revealed that the ripple and local effects greatly decrease the growth rate of stimulated Raman backscattering. As a result, the Raman process is controlled by the magnetized density rippled plasma and the growth rate is reduced significantly.

Impedance matching strategy boost excellent wave absorption performance of zinc-Aluminosilicate cladded short carbon fiber core-sheath structure

Excellent impedance matching and practical material design are the keys to obtaining excellent microwave absorption performance and application. In this paper, a zinc aluminosilicate (ZAS) glass-ceramic precursor was prepared by a sol-gel method, short carbon fiber (SCF) was used as the main wave absorber, and a silane coupling agent (KH-550) was used to combine the ZAS and SCF. The oxidation concentration of short carbon fibers affects the load of KH-550, which changes the concentration of oxygen-containing groups on the SCF, affecting the thickness of the ZAS coated on the SCF to adjust the impedance matching of the material. In short, through simple experimental methods and adjustment methods, we can obtain the target's absorption performance and corresponding bandwidth. Our work provides a new idea for obtaining impedance matching adjustment of high-performance carbon fiber, and glass-ceramic composite electromagnetic (EM) wave absorbing materials.

20th Century revolutions: characteristics, types, and waves

The 20th century revolutionary process had a big impact on the World System and significantly changed its entire configuration. However, there are essential gaps in terms of theoretical approaches, in particular, in terms of the typology of revolutions. Moreover, there is clearly insufficient research related to qualitative and quantitative analysis and consideration of the revolutions of the 20th century in their entirety. This article aims to fill those gaps by pursuing three main goals: (1) comparison of revolutions of the 20th and 19th centuries, highlighting the important characteristics of the former; (2) classification of revolutions of the 20th century; (3) identification of the main revolutionary waves of the 20th century and their essential characteristics.

Characteristics of iceberg calving-generated waves based on three-dimensional SPH simulations

Large-scale icebergs calving into water often generate waves that may threaten human lives or passing ships. The formation and evolution of such three-dimensional (3D) waves in the near field are still not fully understood. In this paper, a 3D numerical model based on the Smoothed Particle Hydrodynamics (SPH) open source code DualSPHysics was established to simulate the generation and evolution processes of waves caused by icebergs calving into water. The model is validated with available large-scale laboratory tests. The 3D characteristics in the near field of the waves are presented and analyzed in detail. The results indicate that iceberg calving can generate three main waves: a leading wave produced by the initial entry of the iceberg into the water; a second wave induced by the collapse of the water jet; and a third wave caused by the resurfacing of the iceberg. The reflux tail blocked by the reflux front may appear prior to the second wave, which can develop into a constantly changing wavefront, and then form a step-like flow structure in the near field by linking these two wavefronts. The shapes of the multiple wavefronts outlined by the leading wave and the trailing waves in the near field are closely related to the iceberg geometry. However, the wavefronts gradually develop into a semicircular shape in the far field irrespective of the iceberg geometry. These findings are helpful for hazard assessments of iceberg calving-generated waves. • A rigid body–fluid coupled SPH model is established to simulate three-dimensional iceberg calving-generated waves (ICGW). • The three-dimensional characteristics of ICGWs in the near field are presented. • ICGW consists of three main waves: a leading wave; a second wave by water jet; and a third wave by resurfacing. • The generation and evolution processes of the multiple wavefronts are outlined.

Fingertip pulse rate variability extraction based on extreme-point symmetric mode decomposition

To solve shortcomings of being sensitive to noise and waveform when using threshold method to extract pulse rate variability (PRV) at this stage, a method using extreme-point symmetric mode decomposition to extract PRV signals from pulse waves with noise is proposed. A Butterworth filter is used to remove the baseline drift, the DC mode and power frequency noise, which can effectively avoid noise interference when identifying peak points. The pre-processed data is decomposed by extreme-point symmetric mode decomposition to select the corresponding mode of the main wave, thereby reducing the difficulty of feature point extraction. Compared with the threshold method, the extraction method proposed in this paper is more intuitive and can self-adaptively select the best decomposition layer. This method is suitable for the extraction of fingertip PRV under complex noise and some disease statuses.