Amplitude Plots Research Articles

Hydrodynamic cavitation overall intensity evaluation via noise characterization and its effect on phenol oxidative degradation

In the present research, noise signals generated by Hydrodynamic cavitation (HC) are charcterized to provide an applicable direct measuring for overall intensity estimation of the phenomenon. The signals amplitude plots as well as spectrogram graph and Fast Fourier Transform (FFT) are used for the characterization of the noise generated by the cavitation phenomenon for each experiment. In order to validate the outcomes, results are complied with the chemical activity. For such a purpose, phenol oxidative degradation kinetics is selected. Experiments are performed at various HC inlet pressure (4–7 bar), operating temperature (20–40 °C) and concentration of H2O2 (0–1000 mg L−1). It was found that the amplitude mean square of the cavitation noise signals could be introduced as a quantitative index for HC overall intensity. The results imply a direct correlation of HC overall intensity with chemical reaction at constant temperature. According to the results, it can also be also concluded that H2O2 presence can affect the intensity of HC and facilitate the super cavitation occurrence, as well as its expected beneficial effect on phenol degradation. The optimum values of the signal characterization and chemical experiments are in the same wavelength showing an 88.9 % degradation in the presence of 1000 mg L−1 H2O2 at 5 bar inlet pressure.

Fusion pore flux controls the rise-times of quantal synaptic responses.

The release of neurotransmitter from a single synaptic vesicle generates a quantal response, which at excitatory synapses in voltage-clamped neurons is referred to as a miniature excitatory postsynaptic current (mEPSC). We analyzed mEPSCs in cultured mouse hippocampal neurons and in HEK cells expressing postsynaptic proteins enabling them to receive synaptic inputs from cocultured neurons. mEPSC amplitudes and rise-times varied widely within and between cells. In neurons, mEPSCs with larger amplitudes had longer rise-times, and this correlation was stronger in neurons with longer mean rise-times. In HEK cells, this correlation was weak and unclear. Standard mechanisms thought to govern mEPSCs cannot account for these results. We therefore developed models to simulate mEPSCs and assess their dependence on different factors. Modeling indicated that longer diffusion times for transmitters released by larger vesicles to reach more distal receptors cannot account for the correlation between rise-time and amplitude. By contrast, incorporating the vesicle size dependence of fusion pore expulsion time recapitulated experimental results well. Larger vesicles produce mEPSCs with larger amplitudes and also take more time to lose their content. Thus, fusion pore flux directly contributes to mEPSC rise-time. Variations in fusion pores account for differences among neurons, between neurons and HEK cells, and the correlation between rise-time and the slope of rise-time versus amplitude plots. Plots of mEPSC amplitude versus rise-time are sensitive to otherwise inaccessible properties of a synapse and offer investigators a means of assessing the role of fusion pores in synaptic release.

Theoretical model of femtosecond coherence spectroscopy of vibronic excitons in molecular aggregates.

When used as pump pulses in transient absorption spectroscopy measurements, femtosecond laser pulses can produce oscillatory signals known as quantum beats. The quantum beats arise from coherent superpositions of the states of the sample and are best studied in the Fourier domain using Femtosecond Coherence Spectroscopy (FCS), which consists of one-dimensional amplitude and phase plots of a specified oscillation frequency as a function of the detection frequency. Prior works have shown ubiquitous amplitude nodes and π phase shifts in FCS from excited-state vibrational wavepackets in monomer samples. However, the FCS arising from vibronic-exciton states in molecular aggregates have not been studied theoretically. Here, we use a model of vibronic-exciton states in molecular dimers based on displaced harmonic oscillators to simulate FCS for dimers in two important cases. Simulations reveal distinct spectral signatures of excited-state vibronic-exciton coherences in molecular dimers that may be used to distinguish them from monomer vibrational coherences. A salient result is that, for certain relative orientations of the transition dipoles, the key resonance condition between the electronic coupling and the frequency of the vibrational mode may yield strong enhancement of the quantum-beat amplitude and, perhaps, also cause a significant decrease of the oscillation frequency to a value far lower than the vibrational frequency. Future studies using these results will lead to new insights into the excited-state coherences generated in photosynthetic pigment-protein complexes.

Ultrasensitive vibrational resonance induced by small disturbances.

We have found two kinds of ultrasensitive vibrational resonance in coupled nonlinear systems. It is particularly worth pointing out that this ultrasensitive vibrational resonance is transient behavior caused by transient chaos. Considering a long-term response, the system will transform from transient chaos to a periodic response. The pattern of vibrational resonance will also transform from ultrasensitive vibrational resonance to conventional vibrational resonance. This article focuses on the transient ultrasensitive vibrational resonance phenomenon. It is induced by a small disturbance of the high-frequency excitation and the initial simulation conditions, respectively. The damping coefficient and the coupling strength are the key factors to induce the ultrasensitive vibrational resonance. By increasing these two parameters, the vibrational resonance pattern can be transformed from ultrasensitive vibrational resonance to conventional vibrational resonance. The reason for different vibrational resonance patterns to occur lies in the state of the system response. The response usually presents transient chaotic behavior when the ultrasensitive vibrational resonance appears and the plot of the response amplitude vs the controlled parameters shows a highly fractalized pattern. When the response is periodic or doubly periodic, it usually corresponds to the conventional vibrational resonance. The ultrasensitive vibrational resonance not only occurs at the excitation frequency, but it also occurs at some more nonlinear frequency components. The ultrasensitive vibrational resonance as transient behavior and the transformation of vibrational resonance patterns are new phenomena in coupled nonlinear systems.

A cohesive fatigue model for composite delamination based on a new material characterization procedure for the Paris law

A new cohesive fatigue model (CF22) is proposed after an extensive characterization of experimental data. To minimize the number of parameters required, experimental Paris law data is transformed into a plot of amplitude versus mean relative endurance, where the data is fit using an empirical function. This novel characterization procedure helps identify trends and inconsistencies in the data and provides the values of the model input parameters without requiring inverse analyses. The new fatigue model significantly improves the predictions of crack propagation rates and thresholds compared to CF20, especially under conditions of high stress ratios and high values of mode mixity.

Numerical simulation of flooding characteristics in steam-water countercurrent inside an inclined pipe under condensation conditions

In this paper, a three-dimensional CFD model, which is established on VOF (Volume of Fluid) model, Lee model together with CSF (Continuum Surface Force) model and RNG k − ɛ turbulence model, is adopted for the condensation heat and mass transfer of steam in an inclined circular tube with the occurrence of flooding and liquid bridge. The entire process of liquid bridge formation is depicted with a three-dimensional space-time plot of the wave amplitude of the interfacial wave with time and axial distance. The effects of different pipe inclination angles and different contact angles on the flow behavior and heat transfer characteristics are investigated and the results demonstrate that under high liquid film Reynolds number and condensation conditions, as the inclination angle increases, the liquid bridge begins to form at a position which moves upward along the pipe. The reason is that as the inclination angle increases, the liquid film is more uniformly distributed in the radial direction, and a vortex symmetrical about the axis is formed on the leeward side of the flooding wave.

Calculating Turns/Amplitude peak ratio of EMG interference pattern by using logistic curve fitting

The aim of the study was to test whether logistic curve fitting (LCF) of Turns = f(Amplitude) plots of single muscle contractions can provide a reliable alternative method for peak-ratio calculation. EMG signals from 74 biceps and 62 triceps contractions were analyzed by applying LCF to Turns = f(Amplitude) plots. Peak-ratio (peak-ratio2) could then be calculated as the point of the fitted line with the highest Turn/Amplitude value. LCF yielded R2 values > 0.95 in the vast majority of contractions studied (68/74 biceps and 53/62 triceps). Peak-ratio2 values had a very strong linear relationship with the corresponding values calculated by the traditional method (peak-ratio1) in both normal and neurogenic conditions. Furthermore, ROC curve analysis showed that peak-ratio1 and peak-ratio2 had similar AUC values. Based on the LCF equation, peak-ratio = T2*(p − 1)/A0*p*(p − 1)1/p. Therefore, peak-ratio is proportional to the maximum number of turns (T2), positively correlated to the rate of turns’ increment at the midpoint of the curve (p) and negatively correlated to the mean amplitude at the midpoint of the curve (A0). A0 is the variable that best discriminates between normal and neurogenic conditions. We provide an alternative method for peak-ratio calculation and show the variables that influence this sensitive marker of neurogenic disease.

Graphic Relation Between Amplitude and Sound Intensity Level

We present a simple experiment that allows us to demonstrate graphically that the intensity of sound waves is proportional to the square of their amplitude, a result that is theoretically analyzed in any introductory wave course but rarely demonstrated empirically. To achieve our goal, we use an audio signal generator that, when connected to a loudspeaker, produces sine waves that can easily be observed and measured using an oscilloscope. The measurements made with these instruments allow us to create a plot of amplitude vs. sound intensity level, which verifies the mathematical relationship between amplitude and intensity mentioned above. Among the experimental errors, the plot obtained is in excellent agreement with what is theoretically expected.

The Fault Detection of Gears of Electromechanical Power Transmission System using Frequency Domain Approach

Electric motors are widely used in the industry and convert electrical power to mechanical power. Gears are connected with the motor shaft for frictionless power transmission. The power transmission efficiency is dropped when the gear teeth is damaged. It causes huge financial loss. There are various commercially available condition monitoring tools for the preventive maintenance and condition monitoring of the gearing systems. However, such tools and techniques are intrusive and costly. This paper presents a non-intrusive approach for timely detection of gear damages and can be integrated to existing condition monitoring systems to save time and cost. The proposed method is based on the analysis of power spectra of the frequency amplitude plots. The amplitude difference at gear harmonics gives indication of the presence of the fault. The proposed technique has been tested and validated at 1400 rpm and 1370 rpm of the motor which is operating at 75 % load and full load.

An Aggregation-Induced Emission Optical Highlighter for the Studies of Endoplasmic Reticulum-Lipid Droplet Content Dynamics

An Aggregation-Induced Emission Optical Highlighter for the Studies of Endoplasmic Reticulum-Lipid Droplet Content Dynamics

Static and dynamic characteristics of a compound sphere using Initial Stress Reference Independence

We study the influence of residual stress on the static and dynamic characteristics of a spherical structure. We consider a shrink-fitted compound sphere, where residual stress is developed due to the interference between outer and inner spherical layers. We calculate this residual stress and model the residually stressed material with suitable hyperelastic strain energy satisfying Initial Stress Reference Independence (ISRI). Under the action of inhomogeneous residual stress, the compound sphere behaves as an anisotropic, functionally graded composite sphere, which is reflected by the model. We apply this model to obtain stress distributions and inflation characteristics of the compound sphere. Our results demonstrate the hypothesis that residual stress moderates the stress concentration and reduces the stress gradient in biological/engineering structures. We obtain critical stretch and pressure for spherically symmetric deformations. An increase in interference/residual stress increases the critical stretch/pressure and improves the structural stability. We then apply an analytical approach to calculate the natural frequency of the compound sphere for small amplitude radial vibration. We observe that an increase in residual stress increases the natural frequency and widens the range of stable free vibration. We numerically investigate the free and forced vibration of the compound sphere. Forced vibration amplitude reduces as interference/residual stress increases, which is reflected in the frequency–amplitude plots. The frequency response shows a small hardening non-linearity. We investigate the subharmonic and superharmonic responses for small and large amplitude vibration.

Effect of temperature fluctuation on the localized pattern of action potential in cardiac tissue

Based on the improved FitzHugh–Nagumo myocardial model driven by a constant external current, the effect of temperature fluctuation in a network of electrically coupled myocardial cells are investigated through analytical and numerical computations. Through the technique of multiple scale expansion, we successfully reduced the complex nonlinear system of equations to a more tractable and solvable nonlinear amplitude equation on which the analysis of linear stability is performed. Interestingly from this analysis, a plot of critical amplitude of action potential versus wave number revealed the growth rate of modulational instability (MI) is an increasing function of the thermoelectric couplings; T^{(1)} and T^{(2)}, under fixed conditions of nonlinear electrical couplings. In order to verify our analytical predictions through the study the long-time evolution of the modulated cardiac impulses, numerical computation is finally carried out. Numerical experiment revealed the existence of localized coherent structures with some recognized features of synchronization. Through the mechanism of MI, changes in thermoelectrical couplings promote wave localization and mode transition in electrical activities in the cell lattice. Results could provide new insights in understanding the underlying mechanism of the manifestation of sudden heart disorder subjected to heavily temperature fluctuation.

The influence of mean strain on the high-cycle fatigue of Nitinol with application to medical devices

One of the contentious issues associated with the high-cycle fatigue of Nitinol, a nominally equiatomic alloy of nickel and titanium, is the claim that increasing the applied mean strain can increase, or at least have no negative impact, on the fatigue lifetime, in conflict with reported behavior for the vast majority of other metallic materials. To investigate this in further detail, cyclic fatigue tests in bending were carried out on electropolished medical grade Nitinol at 37 °C for lives of up to 400 million cycles of strain involving various levels of the mean strain. A constant life model was developed through statistical analysis of the fatigue data, with 90% reliability at a confidence level of 95% on the effective fatigue strain. Our results show that the constant life diagram, a plot of strain amplitude versus mean strain, is monotonic yet nonlinear for lives of 400 million cycles of fatigue loading. Specifically, we find that in contradiction to the aforementioned claim, the strain amplitude limit at zero mean strain is 0.55% to achieve a 400 million cycle lifetime, at 90% reliability with 95% confidence; however, to achieve the same lifetime, reliability and confidence level in the presence of a 3% or more mean strain, the required strain amplitude limit is decreased by over a factor of three to 0.16%. Moreover, for mean strains from 3% to 7%, the strain amplitude limit that allows a 400 million cycle lifetime, at 90% reliability with 95% confidence, is ~ 0.16%, and essentially independent of mean strain. We conclude that the debatable claim that an increase in the applied mean strain can increase the fatigue life of Nitinol components is not supported by the current data.

Fabricating D-A type AIE luminogen into film sensor for turn-on detection of methanol vapour

Advances in sensor technique benefit considerably from the donor–acceptor (DA) type aggregation-induced emission (AIE) systems, owing to their sensitive ICT emission together with emission controllability at solid state. In this report, we present a tailor-made D–A type AIE luminogen, DBABN, and study its AIE and ICT natures. Our systematic investigation has observed remarkable enhancement in emission intensity together with hypsochromic shift in emission wavelength in response to methanol vapor, and further confirmed its high selectivity. As supported by DFT calculations, including electrostatic potential map and molecular orbital amplitude plots, hydrogen-bonding between DBABN and methanol molecule would be formed and further stabilized by electrostatic attraction, which weakens the ICT but simultaneously reinforces the AIE. Therefore the mechanism for the stimuli-responsive emission is illustrated. Utilizing such property, a film sensor for methanol was developed, with a detection limit down to 9.65 ppm. Furthermore, the signal can be easily visualized.

Nonlinear rheological characteristics of single species bacterial biofilms

Bacterial biofilms in natural and artificial environments perform a wide array of beneficial or detrimental functions and exhibit resistance to physical as well as chemical perturbations. In dynamic environments, where periodic or aperiodic flows over surfaces are involved, biofilms can be subjected to large shear forces. The ability to withstand these forces, which is often attributed to the resilience of the extracellular matrix. This attribute of the extracellular matrix is referred to as viscoelasticity and is a result of self-assembly and cross-linking of multiple polymeric components that are secreted by the microbes. We aim to understand the viscoelastic characteristic of biofilms subjected to large shear forces by performing Large Amplitude Oscillatory Shear (LAOS) experiments on four species of bacterial biofilms: Bacillus subtilis, Comamonas denitrificans, Pseudomonas fluorescens and Pseudomonas aeruginosa. We find that nonlinear viscoelastic measures such as intracycle strain stiffening and intracycle shear thickening for each of the tested species, exhibit subtle or distinct differences in the plot of strain amplitude versus frequency (Pipkin diagram). The biofilms also exhibit variability in the onset of nonlinear behaviour and energy dissipation characteristics, which could be a result of heterogeneity of the extracellular matrix constituents of the different biofilms. The results provide insight into the nonlinear rheological behaviour of biofilms as they are subjected to large strains or strain rates; a situation that is commonly encountered in nature, but rarely investigated.

NOMERICAL ANALYSIS OF UMBALANCED ROTOR

The article presents the research results of the vibrational characteristics of the designed rotor system, namely, the amplitude-frequency characteristicsare constructed in different frequency ranges and at various unbalanced masses. The main stages of conducting dynamic analysis in ANSYS arehighlighted on the example of harmonic analysis. The critical frequencies for unbalanced rotor are determined at which resonance is observed. Thevalues of the displacement amplitudes at critical frequencies and at the operating frequency under different imbalance values are observed. The plot ofamplitude dependence is constructed on the imbalance magnitude at the pump operating frequency. The obtained values are compared with the maximum allowable gap between the rotor and stator pump parts, and with that in mind, the permissible values of the unbalance values for the designed pump are determined. On the basis of the research, practical recommendations for the pump dynamic balancing have been developed for agiven permissible imbalance magnitude.

Fracture studies on narrow gap welded SA 312 Type 304LN stainless steel straight pipes under quasi-cyclic loading

Fracture studies were carried out on narrow gap welded SA 312 Type 304LN stainless steel straight pipes having circumferential through-wall notch in the weld. Totally six specimens were tested; one specimen was subjected to monotonic loading and the remaining five specimens were subjected to quasi-cyclic loading. Under quasi-cyclic loading, one specimen was tested under incremental displacement-controlled loading and the remaining four specimens were tested constant amplitude load-controlled loading. Based on the load-controlled experimental results, a plot of the cyclic load amplitude versus number of cycles to failure of the specimens was obtained. The experimental results indicate that the piping components subjected to quasi-cyclic loading may fail in very less number of loading cycles even when the load amplitude is sufficiently below the monotonic fracture/collapse load. Crack growth behaviour and cyclic tearing instability in the specimens, which are required for realistic assessment of Leak Before Break applicability, was studied.

Thermal-wave resonant cavity signal processing.

The thermal-wave resonant cavity (TWRC) technique has been used for thermal diffusivity measurements by many researchers. This study aims to reduce the uncertainty associated with TWRC signal processing (curve fitting) by means of numerical simulation and experimental verification. Simulations show that the plot of signal amplitude versus cavity length can be fitted to a simplified model reported previously when the initial fitting position is at least twice the thermal-wave diffusion length (2 μg), and that the uncertainty caused by different end positions is negligible in the range of 6-10 μg. Upon consideration of the simulation results, signal-to-noise ratio, and clearly defined amplitude curve shape, fitting ranges of about 2.2-8.0 μg and 2.2-8.7 μg were chosen for the experimental data. Thermal diffusivity values (1.438 ± 0.001) × 10-7 and (1.436 ± 0.001) × 10-7 m2 s-1, respectively, were obtained for distilled water, in excellent agreement with the accepted literature value. The ratio of standard deviation to the mean value is smaller than 0.07%, one order of magnitude lower than typical results reported in the literature. Similar simulation results were obtained for air and methanol as intra-cavity samples.

Morphological estimation of pitting corrosion on vertically positioned 304 stainless steel using acoustic-emission duration parameter

A morphological estimation of the pitting corrosion of type 304 stainless steel using the acoustic emission (AE) duration parameter is proposed in the present work. The pit morphology depending on Cl− concentration and gravity was investigated. Occluded pits in low-concentration NaCl solution were observed to develop with more long-duration AEs, while elongated pits with ruptured cover in high-concentration NaCl solution were predominantly concurrent with short-duration AEs. The morphological descriptor “η” derived from the AE duration–amplitude plots reflected the morphological transition from occluded to elongated open pits. An AE-based correspondence among the environmental factors and corrosion morphologies was proposed.

Evaluation of Process Parameters in Machining of AA6063 Alloy

The main aim of this work is to analyse the significance of cutting parameters on surface roughness and spindle vibrations while machining the AA6063 alloy. The turning experiments were carried out on a CNC lathe with a constant spindle speed of 1000rpm using carbide tool inserts coated with Tic. The cutting speed, feed rate and depth of cut are chosen as process parameters whose values are varied in between 73.51m/min to 94.24m/min, 0.02 to 0.04 mm/rev and 0.25 to 0.45 mm respectively. For each experiment, the surface roughness parameters and the amplitude plots have been noted for analysis. The output data include surface roughness parameters (Ra,Rq,Rz) measured using Talysurf and vibration parameter as vibration amplitude (mm/sec) at the front end of the spindle in transverse direction using single channel spectrum analyzer (FFT).With the collected data Regression analysis is also performed for finding the optimum parameters. The results show that significant variation of surface irregularities and vibration amplitudes were observed with cutting speed and feed. The optimum cutting speed and feed from the regression analysis were 77.0697m/min and 0.0253mm/rev. for the minimum output parameters. No significant effect of depth of cut on output parameters is identified.