Amplitude Parameters Research Articles

Influence of Object Physical Properties Instability on Edge Current Method Sensitivity

The article contains results of a study of the eddy current transducer signal parameters from artificial defects against the background of the influence of stray parameters simulated on specially manufactured samples exposed to various external influences. The authors studied the added voltage change of eddy current prob depending on factors affecting the electromagnetic properties of steels. The results of the study were the determination of optimal excitation parameters and threshold values for discrimination levels of phase, amplitude and dynamic parameters when detuning from stray factors. The authors modeled stray parameters of eddy current testing in the form of temperature effects, effects of chemical reagents and plastic deformation of the surface layer. The researchers assessed the distribution of the temperature field, the time of chemical reactions and the composition of the reagents, as well as the geometric parameters of the deformable surface layer of the samples and their effect on eddy current prob added voltage. For the research, artificial defects were made in the form of thin cuts with an opening width of 0.2 mm, located in the stray parameter zone. The geometric dimensions of artificial defects were determined by the requirements for the amplitude of the transducer signals, which should not exceed the change in amplitude under the influence of a stray parameter on the time base, relative to the zero-value installed in the sample area not subject to the influence of external factors. The obtained results of the hodograph analysis when scanning with a clamp-on eddy current transducer made it possible to propose recommendations for detuning from stray parameters of various nature. This was done in order to increase the detectability of defects on objects with significant heterogeneity of the surface structure in the eddy current testing zones.

Measurement of the zodiacal light absolute intensity through Fraunhofer line spectroscopy of the night sky with the Hale telescope

Abstract Measuring the absolute brightness of the zodiacal light (ZL), which is the sunlight scattered by interplanetary dust particles, is important not only for understanding the physical properties of the dust but also for constraining the extragalactic background light (EBL) by subtracting the ZL foreground. We describe the results of high-resolution spectroscopic observations of the night sky in the wavelength range of 300–900 nm with the double spectrograph on the Hale telescope to determine the absolute brightness of the ZL continuum spectra from the Fraunhofer absorption line intensities. The observed fields are part of the fields observed by the Spitzer Space Telescope for the EBL study. Assuming that the spectral shape of the zodiacal light is identical to the solar spectrum in a narrow region around the Fraunhofer lines, we decomposed the observed sky brightness into multiple emission components by amplitude parameter fitting with spectral templates of the airglow, ZL, diffuse Galactic light, integrated starlight, and other isotropic components including EBL. As a result, the ZL component with the Ca ii λλ 393.3, 396.8 nm Fraunhofer lines around 400 nm is clearly separated from the others in all fields with uncertainties around 20%, mainly due to the template errors and the time variability of the airglow. The observed ZL brightness in most of the observed fields is consistent with the modeled ZL brightness calculated by combining the most conventional ZL model at 1250 nm based on the Diffuse Infrared Background Experiment and the observational ZL template spectrum based on the Hubble Space Telescope. However, the ecliptic plane observation is considerably fainter than the ZL model, and this discrepancy is discussed in terms of the optical properties of the interplanetary dust accreted in the ecliptic plane.

Analyzing Vocal Fold Frequency Dynamics Using High-Speed 3D Laser Video Endoscopy.

To examine changes in lateral and vertical vibratory motion along the anterior, middle, and posterior sections of the vocal folds, as a function of vocal frequency variations. Absolute measurements of vocal fold surface dynamics from high-speed videoendoscopy with custom laser endoscope were made on 23 vocally healthy adults during sustained /i:/ production at 10%, 20%, and 80% of pitch range. The 3D parameters of amplitude (mm), maximum velocity opening/closing (mm/s), and mean velocity opening/closing (mm/s) were computed for the lateral and vertical vibratory motion along the anterior, middle, and posterior sections of the vocal folds. Linear mixed model analysis was conducted to evaluate the differences in (a) vocal frequency levels (high vs. normal vs. low pitch), (b) axis level (vertical vs. lateral), (c) position level (anterior vs. middle vs. posterior), and (d) gender differences (male vs. female). Overall, the superior surface vertical motion of the vocal fold is greater compared with the lateral motion, especially in males. Along the superior surface, the mean and maximum closing velocities are greater posteriorly for low pitch. The location (anterior, middle, and posterior) along the superior surface is relevant only for vocal fold closing rather than opening, as the dynamics are different along the various locations. The study highlights the significance of assessing the vertical motion of the superior surface of the vocal fold to understand the complex dynamics of voice production. NA Laryngoscope, 134:3267-3276, 2024.

"Real-Time Neuromonitoring" Increases the Safety and Non-Invasiveness and Shortens the Duration of Idiopathic Scoliosis Surgery.

Introduction: A practical solution to the incidental unreliability of intraoperative neuromonitoring (IONM) may be the simultaneous neurophysiological recording and control of the surgical field through a camera (the concept of "Real-time" IONM). During "Real-time" IONM, the surgeon is immediately warned about the possibility of damage to the neural structures during, but not after, standard idiopathic scoliosis (IS) corrective surgery procedures (the concept of "Surgeon-neurophysiologist" interactive, verbal IONM). This study aimed to compare the advantages, utilities, reliabilities, and time consumption of the two IONM scenarios. Methods: Studies were performed in two similar groups of patients undergoing surgery primarily due to Lenke 2 idiopathic scoliosis (N = 120), when both IONM approaches were applied. Neurophysiological evaluations of the spinal transmission were performed pre- (T0), intra- (before (T1) and after (T2) surgery), and postoperatively (T3), as well as once in healthy volunteers (control, N = 60). Non-invasive and innovative recordings of the motor evoked potentials (MEPs) bilaterally from the peroneal (PER) nerve and tibialis anterior (TA) muscle were performed with surface electrodes as a result of transcranial magnetic stimulation (TMS) or electrical stimulation (TES) at T0-T3. Results: In both groups, the MEP amplitudes and latencies recorded from the PER nerve were approximately 67% lower and 3.1 ms shorter than those recorded from the TA muscle. The MEP recording parameters differed similarly at T0-T3 compared to the control group. In all patients, the MEP parameters induced by TMS (T0) and TES (T1) did not differ. The MEP amplitude parameters recorded from the TA and PER at T1 and T2 indicated a bilateral improvement in the neural spinal conduction due to the surgical intervention. The TMS-induced MEP amplitude at T3 further increased bilaterally. In both IONM groups, an average 51.8 BIS level of anesthesia did not affect the variability in the MEP amplitude, especially in the PER recordings when the applied TES strength was 98.2 mA. The number of fluctuations in the MEP parameters was closely related to the number of warnings from the neurophysiologist during the transpedicular screw implantation, corrective rod implantation, and distraction, derotation, and compression procedures, and it was higher in the "Surgeon-neurophysiologist" IONM group. The average duration of surgery was shorter by approximately one hour in the "Real-time" IONM group. The number of two-way communications between the surgeon and the neurophysiologist and vice versa in the "Real-time" IONM group decreased by approximately half. Conclusions: This study proves the superiority of using "Real-time" IONM over the standard "Surgeon-neurophysiologist" IONM procedure in increasing the safety and non-invasiveness, shortening the time, and lowering the costs of the surgical treatment of IS patients. The modifications of the MEP nerve-conduction-recording technology with surface electrodes from nerves enable precise and reliable information on the pediatric patient's neurological condition at every stage of the applied surgical procedures, even under conditions of slight fluctuations in anesthesia.

Mathematical Modeling of the Bearing Ratio Curve Rmr (50% Rz), through Investigation of the Effect of Process Parameters in Hard Turning of Steel C55 (DIN) with Mixed Ceramics MC2 (Al2O3 + TiC)

The subject of modeling and predicting roughness parameters in hard machining has been discussed in many literature sources. However, most of these sources cover only the amplitude parameters such as Ra and Rz, leaving it unexplored to the right extent compared to its importance the roughness parameter bearing ratio curve (the Abbott–Firestone curve) which is essential in understanding the actual contact area of mating surfaces. To bridge this gap, this research has developed a mathematical model using the design of experiments method through investigation of the effect of process parameters in hard turning of Steel C55 (DIN) with mixed ceramics MC2 (Al2O3 + TiC). The model predicts the bearing ratio curve parameter Rmr (50% Rz), statistically processed using CADEX and Matlab. The research includes the ANOVA as a complementary tool in validating the generated mathematical model. The research analyzes the effects of material properties, cutting forces, and tool geometry as factors that affect the machining process. Additionally, it emphasizes the robustness of hard turning in consistently producing waviness patterns. Overall, this research provides valuable insights into the predictable effects of parameters on machined surfaces, which contributes to a better understanding of surface finish in metalworking.

Point-of-care and traditional erythrocyte sedimentation rate, point-of-care rheometry, and cell-free DNA concentration in dogs with or without systemic inflammation.

RBC aggregation and deformability characteristics are altered by inflammatory, microcirculatory, and hemorheologic disease. These changes can be indirectly evaluated using the erythrocyte sedimentation rate (ESR). Newer point-of-care devices employ syllectometry to evaluate RBC rheology, which can give information beyond the ESR. We evaluated 2 point-of-care rheometers (iSED and MIZAR; Alcor Scientific) in 52 dogs presented to a university teaching hospital. Whole blood samples were analyzed for correlation between the ESR using the Westergren (ESRw) method (measured at 1 h and 24 h) and the predicted ESR using iSED. Plasma fibrinogen and cell-free DNA concentrations were also measured as probable markers of inflammation. The iSED-predicted ESR was positively correlated to the ESRw method at 1 h (r = 0.74; p < 0.001) and 24 h (r = 0.62; p < 0.001). Comparing dogs with or without inflammation (defined as plasma fibrinogen concentration >3.5 g/L [350 mg/dL]), significant differences were seen in the MIZAR parameters of base point, amplitude, integral, and half-time. Median cell-free DNA concentrations were higher in the group of dogs with inflammation (117 [range: 51-266] ng/mL vs. 82.7 [range: 19-206] ng/mL; p = 0.024). The iSED-predicted ESR is a good predictor of the ESRw and was obtained more rapidly. Rheometric parameters measured by MIZAR may be useful in detecting inflammation and monitoring secondary morphologic and functional changes in canine RBCs.

Control of the memory cell magnetization by a combined pulse of local magnetic fields

We study the process of controlling the states of a magnetic memory cell by a pulsed magnetic field. The magnetization dynamics of such a system is described by the Landau-Lifshitz equation. We find the optimal parameters of time dependence, amplitude and duration of magnetic field pulses created by currents in the control system, which provide a fast inertialess process of switching the magnetization of the functional element of the cell.

Abrupt focus and bright spot formation in fractional system with PT-symmetric nonlocal nonlinearity

Abstract We study the dynamics of Gaussian beams in fractional system with PT-symmetric nonlocal nonlinearity. It is found that the Gaussian beam with transverse displacement can abruptly focus to form bright spot in one sub-branch after experiencing a symmetric split, depending on the nonlinear intensity, initial launched amplitude, angle and chirp of the beam, and the initial chirp can shift the time of abrupt focus and bright spot formation. Furthermore, the Talbot-like effect and breather train are explored by setting the initial amplitude parameter of every component of an initial Gaussian beam train. Moreover, for longitudinally periodically modulated nonlinearity, the bright spots can be formed periodically and asymmetrically in two sub-branches for a single Gaussian beam, and Moiré-like lattices can be generated for a Gaussian beam train. Finally, the conical diffraction and crescent-like evolution in the two-dimensional system are investigated in detail. It is found that the direction of crescent-like evolution is determined by the initial launched angles, which may be an inspiration to design channel path through choosing suitable initial launched angles at will.

A theoretical framework for BL Her stars. II. New period-luminosity relations in Gaia passbands

In the era of the Hubble tension, it is crucial to obtain a precise calibration of the period-luminosity ($PL$) relations of classical pulsators. Type II Cepheids (T2Cs; often exhibiting negligible or weak metallicity dependence on $PL$ relations) used in combination with RR Lyraes and the tip of the red giant branch may prove useful as an alternative to classical Cepheids for the determination of extragalactic distances. We present new theoretical $PL$ and period-Wesenheit ($PW$) relations for a fine grid of convective BL Her (the shortest period T2Cs) models computed using mesa-rsp in the $Gaia$ passbands and we compare our results with the empirical relations from $Gaia$ DR3. Our goal is to study the effect of metallicity and convection parameters on the theoretical $PL$ and $PW$ relations. We used the state-of-the-art 1D non-linear radial stellar pulsation tool mesa-rsp to compute models of BL Her stars over a wide range of input parameters:\ metallicity ($-2.0\; dex Fe/H dex $), stellar mass ($0.5M_ odot -0.8M_ odot $), stellar luminosity ($50L_ odot -300L_ odot $), and effective temperature (across the full extent of the instability strip; in steps of 50K). We used the Fourier decomposition technique to analyse the light curves obtained from mesa-rsp and $Gaia$ DR3 and then compared the theoretical and empirical $PL$ and $PW$ relations in the $Gaia$ passbands. The BL Her stars in the All Sky region exhibit statistically different $PL$ slopes compared to the theoretical $PL$ slopes computed using the four sets of convection parameters. We find the empirical $PL$ and $PW$ slopes from BL Her stars in the Magellanic Clouds to be statistically consistent with theoretical relations computed using the different convection parameter sets in the $Gaia$ passbands. There is a negligible effect coming from the metallicity on the $PL$ relations in the individual $Gaia$ passbands. However, there is a small but significant negative coefficient of metallicity in the $PWZ$ relations for the BL Her models using the four sets of convection parameters. This could be attributed to the increased sensitivity of bolometric corrections to metallicities at wavelengths shorter than the $V$ band. Our BL Her models also suggest a dependence of the mass-luminosity relation on metallicity. We found the observed Fourier parameter space to be covered well by our models. Higher mass models ($&gt; 0.6\ odot $) may be needed to reliably model the observed light curves of BL Her stars in the All-Sky region. We also found the theoretical light curve structures (especially the Fourier amplitude parameters) to be affected by the choice of convection parameters.

Average decayed dynamics of one-step transformation process with randomly varying return transition rate

The problem of stochastic averaging of the decayed dynamics of the output state population of a one-step transformation process with constant deterministic forward transition rate and randomly varying return transition rate is solved in approximation where random variation is modeled as a dichotomous stochastic process. The form of the obtained solution represented as a product between bimodal sigmoid rise of average population and its unimodal exponential decay is shown to largely be dependent on the stochastic frequency and amplitude parameters. For example, at high stochastic frequency, the behavior of population is reduced to that of a decayed one-step deterministic system. However, for resonance stochastic amplitude at low stochastic frequency, such behavior coincides with that of three-exponential rise-decay kinetics typical rather of a three-step deterministic slowly decaying process. Thus, there is an equivalence between using a more complex deterministic kinetic model and a less complex stochastic kinetic model for describing the decayed dynamics of different irreversible systems.

The highly nonlinear shallow water equation: local well-posedness, wave breaking data and non-existence of sech2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^2$$\\end{document} solutions

In the context of the initial data and an amplitude parameter ε\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\varepsilon $$\\end{document}, we establish a local existence result for a highly nonlinear shallow water equation on the real line. This result holds in the space Hk\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$H^k$$\\end{document} as long as k>5/2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$k>5/2$$\\end{document}. Additionally, we illustrate that the threshold time for the occurrence of wave breaking in the surging type is on the order of ε-1,\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\varepsilon ^{-1},$$\\end{document} while plunging breakers do not manifest. Lastly, in accordance with ODE theory, it is demonstrated that there are no exact solitary wave solutions in the form of sech and sech2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$sech^2$$\\end{document}.

Influence of quadrature transformation imbalance on the noise immunity of signal reception with amplitude-phase shift keying

Objectives. At the present time, amplitude-phase shift keyed (APSK) signals are actively used in satellite communication systems. In particular, they are applied in systems which operate in a limited radio frequency spectrum with increased data transmission quality requirements. Such systems use multi-channel type receivers with maximum likelihood decision on the received symbol (correlation receiver) or quadrature type receivers. The noise immunity of these receivers is directly dependent on the quality of the formation of reference oscillations. These oscillations are reference signals for correlation receivers and in-phase and quadrature components for quadrature receivers. The aim of the work is to analyze the influence of the amplitude and phase parameter spread of the in-phase and quadrature channels on the noise immunity of receiving APSK signals with a circular shape of the signal constellation.Methods. Methods of statistical radio engineering, theory of optimal signal reception, and computer simulation are used.Results. The study established the characteristics of noise immunity of the APSK signal reception depending on the spread of parameters of the quadrature converter. The theoretical calculations were confirmed by the results of modeling the transmission of APSK signals in a Gaussian communication channel. A comparison with systems using quadrature amplitude modulation (QAM) was carried out, in order to assess system stability in the presence of spread parameters among other similar systems.Conclusions. The studies enabled us to conclude that an imbalance of the quadrature reference oscillations can lead to a significant decrease in the noise immunity of radio systems using APSK signals. The minimum energy loss due to imbalance of quadrature reference oscillations is achieved when the imbalance value is less than 10% in amplitude and 2°–3° in phase. The amplitude imbalance of quadrature reference oscillations when receiving QAM signals is more pronounced than in the case of APSK signals. The phase imbalance affects approximately the same.

APPLICATION OF PHASEOMETRIC COMPENSATION METHOD FOR DETECTION AND LOCALIZATION OF GEODYNAMIC PROCESSES DURING GEOELECTRICAL CONTROL

This work is devoted to considering the issue of using the compensatory method of geoelectric control using the phase characteristics of the field to detect and localize geodynamic processes using the example of the development of a karst-suffusion cavity. The high noise immunity of the phasemetric method for recording geoelectric signals was noted in comparison with the amplitude parameters of the anomalous component of the electromagnetic field, usually used to analyze observation results. A formalized approach to the use of field phase characteristics to interpret monitoring data and the related problem of localizing geodynamic processes has been developed. Within the framework of this approach, it is proposed to determine the section parameters by the minimum sum of the weighted mean square error of interpretation and the regularizing functional containing a priori information about the geoelectric section. To check the possibility of localizing a spherical karst-suffosion cavity, modeling of the amplitude and phase of the anomalous component of the field potential, as well as the root-mean-square error of heterogeneity localization, was carried out when the center of the sphere moves along the installation profile. Modeling showed good differentiation of the potential from the location of the inhomogeneity; the highest localization accuracy was achieved with the combined use of the amplitude and phase components of the field in the problem of localizing the inhomogeneity.

Principle of signal-to-noise ratio direct measurement

The sensitivity of radio receivers and other systems used in all fields of practical applications of electronics is carried out at certain signal-to-noise ratio value. Examples of systems, for which this ratio is one of the important qualitative indicators, are given. The aim of the investigation is to solve the actual problem of signal-to-noise ratio measurement in a wide range of frequencies, simplify instruments and improve their technical and metrological parameters. A principle of signal-to-noise ratio measurement has been proposed, its theoretical foundation has been given. Precise relationship between the signal-to-noise ratio and the parameters of noise amplitude, phase and frequency modulation has been established, thus modulation meters can measure signal-to-noise ratio. There are three options for implementing the developed measurement principle. All of them use one existing industrial modulation meter and provide direct signal-to-noise ratio. For two options there are no restrictions on the origin and type of noise, it may be arbitrary. A pilot test of the measurement principle was conducted, and three implementation options were actually tested. Their discrepancies with the original data of the signal and noise generator lie within error limits of the instrumentation of the former. Mathematical modeling of the principle of signal-to-noise ratio measurement in Mathcad software package was also carried out. Recommendations on the use of the principle are given. The fundamental advantages of the developed principle consist of simple implementation by a single industrial instrument and solving the problem of metrological ensuring of signal-to-noise measuring instruments using the existing state verification plans. The main technical and metrological characteristics obtained by using the principle are determined by parameters of existing modulation meters and are proven to be high, the frequency range is till 26,5 GHz and the measurement error is as low as 8 %.

Optimum stimulus for eliciting masseter vestibular-evoked myogenic potential: a comparative exploration with three different acoustic stimuli

ObjectiveTo compare the EMG rectified amplitude, absolute latencies, interpeak interval, and Interaural asymmetry parameters of masseter vestibular-evoked myogenic potential (mVEMP) elicited using clicks, 500 Hz tone bursts, and 500 Hz NB CE-chirps.MethodTwenty-five young healthy adults in the age range of 18–27 years participated for the study. mVEMP was recorded using three different acoustic stimuli i.e., clicks, 500 Hz tone bursts, and 500 Hz NB CE-chirps. mVEMP was recorded at an intensity of 125 dB peSPL with 5.1/s repetition rate. The potentials were recorded ipsilaterally using zygomatic electrode montage and were filtered between 0.1 and 3000 Hz. EMG rectification of the responses was made prior to analysis.ResultsThe latencies of P1 and N1 were significantly earlier for chirps then followed by click and tone bursts. The EMG rectified amplitude was significantly larger for the potentials obtained using chirps followed by tone bursts and then the clicks. Masseter VEMP obtained using chirps had significantly larger interpeak interval than tone bursts and clicks. The mean amplitude asymmetry ratio was greater in the potentials obtained using chirps than the other two stimuli.ConclusionThe present study reveals that 500 Hz NB CE-chirps tend to produce mVEMP with larger response amplitude and earlier latencies and thus are considered better and constructive stimuli compared to clicks and tone bursts.

Convection and phase change in a lid-driven trapezoidal vented cavity with encapsulated PCM under non-uniform magnetic field by using ternary nanofluid

In this study, a novel configuration of lid-driven vented cavity system equipped with encapsulated phase change materials is studied where applications are relevant in drying, material processing, and electronic cooling. For controlling the convective heat transfer and phase transition, combined utilization of non-uniform magnetic field with ternary nanofluid is offered. Upper wall is inclined and moving with constant speed while ternary nanofluid up to a loading of 0.03 is used. Galerkin weighted residual finite element method is considered as the solution technique. A range of parameters for Reynolds number (Re, 200–1000), wall velocity (Rep, 0–1500), Hartmann number (Ha, 0–30), inclination parameter (yd, 0–0.4H), non-uniform amplitude (Af, 0–0.3), and nanoparticle loading (ϕ, 0–0.03) are considered in the analysis. When Re is increased, transition time (tf) is generally reduced for moving wall case. Reduction of tf up to 65% is obtained at the highest Re when moving wall is used at Rep=1000. For stationary wall case, the behavior of tf with Re is non-monotonic while at the highest Re, tf is reduced. The phase transition process is strongly influenced by the moving wall velocity while first increment and decrement of tf with wall velocity is observed. Thermal performance rises by around 58% and 22%, respectively by using the highest Re for stationary and moving walls. There is a significant increase in heat transfer, of around 211%, as wall velocities rise from Rep=0 (stationary) to Rep=1500. The tf for the moving wall is decreased by around 43.7% at the highest Ha. According to the stationary scenario, tf rises by around 33% until Ha=15 and falls by roughly 39.2% between Ha=15 and Ha=30. Amplitude of non-uniform magnetic field results in variation of tf between 4.5% and 19%. When imposing magnetic field at maximum strength, thermal performance is improved by 44.75% with a moving wall while it is just 5% in a stationary scenario. While raising the value of upper wall’s inclination (yd) increases the thermal performance, it also influences the phase change process. More loading of nanoparticles in base fluid results in a faster transition; the corresponding decreases in tf are 24.5% and 12.7% for stationary and moving wall setups, respectively. The increases in thermal performance for stationary and moving wall cases are 36.3% and 33.7%, respectively.

Analysis of VLF Signal Noise Changes in the Time Domain and Excitations/Attenuations of Short-Period Waves in the Frequency Domain as Potential Earthquake Precursors

In this paper, we complete pioneering research that indicates the very low frequency (VLF) signal amplitude and phase noise reductions, and short-period wave excitations and attenuations as new potential earthquake precursors. We consider changes in the VLF signal broadcast in Italy by the ICV transmitter and recorded in Serbia that start a few tens of minutes before earthquakes. The sampling interval of the analyzed data is 0.1 s. The main objectives of this study are (1) to complete this research in the time and frequency domains during the periods of the four earthquakes analyzed in the previous studies, and (2) to define the parameters of the VLF signal amplitude and phase in both domains that should be further examined in statistical analyses of the aforementioned potential earthquake precursors. In the first part of this study, we analyze the ICV signal amplitude in the frequency domain during the period around three earthquakes that occurred in November 2010 near the considered signal propagation path. Here, we apply the Fourier transform to the relevant recorded data. In the second part, we compare characteristics of the signal amplitude and phase noise reductions in the time domain, and wave excitations and attenuations in the frequency domain. The results of these comparisons indicate the parameters that should be analyzed in subsequent studies to confirm the connection of the considered VLF signal changes with seismic activity before earthquakes, and potentially establish procedures for their detection are: (a) the start and end times of the noise reductions in the time domain and the excited/attenuated waves in the frequency domain, (b) the differences in the corresponding times, and (c) the wave periods of wave excitations of both the signal amplitude and phase.

Chemically reacted blood Cu O nanofluid flow through a non-Darcy porous media with radially varying viscosity

The study investigates the flow of a Newtonian Cu O nanofluid through a non-Darcy porous medium with radially varying viscosity, which is crucial for various industries such as pharmaceuticals, chemicals, nuclear, solar, and solar technologies. The peristaltic motion of the nanofluid is studied with thermal radiation and chemical reaction effects, and the viscosity varies with both radius and axial coordinates. The study assumes low Reynolds and long wavelength assumptions and uses the homotopy perturbation technique to obtain a semi-analytical solution of velocity, temperature, nanoparticle concentration, and skin friction. The results show that axial velocity increases with the increase of slip velocity and viscosity parameters, while wave amplitude and chemical reaction parameters increase while nanoparticle concentration decreases. High viscosity parameters allow fluid nanoparticles to gain more active energy and move more freely, which is the main idea behind crude oil refinement. This physical modeling is essential for physiological flows, such as stomach juice flow during endoscope insertion.

Nonlinear vibration characteristics of virtual mass systems for wind turbine blade fatigue testing

Abstract. The biaxial fatigue test of wind turbine blades is helpful to shorten the test time and is more suitable for the actual operating conditions. Adding tuning masses to the blade is a common method for blade uniaxial testing at present, and its purpose is to adjust the load distribution in one direction of the blade. However, the tuning masses on the blade will affect the load distribution in the direction of the blade flap-wise and edge-wise at the same time in the biaxial test, so the concept of “virtual masses” is proposed to realize the decoupling of the load distribution in the biaxial test. Due to the limitation of the size of the virtual mass mechanism and the complex motion trajectory of the blade, the actual inertial effect provided by the virtual masses is different from the ideal situation, which will affect the resonance characteristics of the test system and the load distribution of the blade. Therefore, in order to evaluate the effect of the nonlinear effect introduced by the virtual masses on the resonance characteristics of the test system and the blade load distribution, the equivalent dynamic model of the bladed virtual mass test system was established by using the Lagrange method. Then, the nonlinear effects of blade amplitude and virtual mass installation parameters on the test system are obtained by a numerical method. Then, based on the nonlinear vibration theory, the approximate nonlinear amplitude–frequency characteristics of the test system are obtained, that is, the resonance frequency of the test system will decrease with the increase in the blade amplitude. Through the simulation analysis of two blades over 80 m in length, the applicability of the theoretical method is verified. It can be seen from the simulation results of the simulated uniaxial test that larger amplitudes of the blade and shorter connection rods will reduce the resonance frequency of the test system. When the vibration amplitude at the excitation point is the same, a lower resonance frequency results in a smaller load distribution level, that is, the area which is actually fully tested will be reduced. In the biaxial simulation test, the resonance frequency of the test system will be further reduced because the virtual masses will be affected by the coupled motion in both directions at the same time. Furthermore, the introduction of an external mechanism of the virtual mass will also cause deformation of the envelope of the blade biaxial trajectory, which will further affect the load distribution of the blade. This work explores the nonlinear influence of virtual masses on the actual fatigue test. The theoretical analysis is helpful to provide the basis and reference for the preliminary preparation work of the test organization, including adjusting the tuning mass scheme, adjusting the load distribution and selecting the appropriate excitation equipment.

Nucleation kinetics, chemical etching, hirshfeld surface, and photoluminescence of Rubidium hydrogen oxalate dihydrate NLO single crystal

The nucleation dynamics of a semi-organic Rubidium hydrogen oxalate dihydrate (RbHOH) crystal were assessed using double-distilled water as a solvent medium to obtain good quality crystal using the solution growth technique. Gravimetric analysis of solubility revealed that it has a positive temperature coefficient of solubility, which is appropriate for bulk growth. Other nucleation parameters such as metastable zonewidth, induction period, and interfacial energy were carried out using the classical theory of nucleation. The photoconductivity experiments reveal that the grown crystal exhibits a positive photoconductivity nature. Chemical etching and atomic force microscopy (AFM) experiments were performed on the produced crystal surface. From AFM experiments, effectively assessed amplitude parameters were calculated. Etching studies showed the presence of etch pit patterns such as tiny hillocks and rectangular shapes. Intermolecular interactions were analysed by using Hirshfeld surface analysis. In the photoluminescence (PL) studies, the grown crystal indicates green emission peaks at 519 nm, and the bandgap energy is found to be 4.8 eV. At room temperature, the refractive index of the RbHOH crystal was determined to be 1.669. The nonlinear optical (NLO) efficiency of the grown crystal was examined using a second harmonic generation efficiency test, and it was determined to be 0.58 times that of KDP.