Bounce Phenomenon Research Articles

Effect of Characteristic Phenomena and Temperature on Super-Cooled Large Droplet Icing on NACA0012 Airfoil and Axial Fan Blade

Icing simulations involving super-cooled large droplets (SLDs) on a NACA0012 airfoil and a commercial axial fan were performed considering the characteristic behavior of SLD icing (i.e., splash-bounce, deformation, and breakup). The simulations were performed considering weak coupling between flow field and droplet motion. The flow field was computed using the Eulerian method, wherein the droplet motion was simulated via the Lagrangian method. To represent the ice shape, an extended Messinger model was used for thermodynamic computation. The ice shape and collection efficiency of the NACA0012 airfoil derived using the icing simulation exhibited a reasonable agreement with the existing experimental data. The icing simulation results for the axial fan, in terms of distribution of ice on the blade and its influence on the flow field, indicated that flow separation occurred, and the mass flow rate of the flow passage decreased. Moreover, the splash and bounce phenomena considerably influenced the icing process; however, the effect of the deformation and breakup phenomena was negligibly small. In terms of the effect of the SLDs on the icing phenomena, it was noted that, with the decrease in the SLD temperature (from −5 °C to −15 °C), the number of adhering SLDs increased, whereas the number of splashing and bouncing SLDs decreased.

Prostate-specific antigen (PSA) bounce following salvage radiotherapy to the prostate bed in a patient with prostate cancer post-prostatectomy.

We present a case of prostate-specific antigen (PSA) bounce in a 76year old man who underwent salvage radiotherapy to the prostate bed following biochemical relapse 6years post-radical prostatectomy for a T2N0 Gleason grade 3 + 3 prostate adenocarcinoma; 10months following completion of salvage radiotherapy for biochemical PSA recurrence of 0.2μg/L. Following undetectable results (<0.03μg/L), his PSA rose from 0.04 to 0.3μg/L with no evidence of prostate cancer recurrence before returning to undetectable levels without medical intervention. This PSA 'bounce phenomenon' is well described following radiotherapy to an intact prostate and has been proposed to be the result of a late fibrotic effect on irradiated prostate tissue. To our knowledge, this is the first case published describing the effect in the post-prostatectomy setting. It highlights the importance of serial PSA monitoring to confirm biochemical relapse before committing the patient to androgen deprivation therapy (with its inherent risks and side effects).

The Application of Overset Grid in the Analysis of Impact Loads of Amphibious Aircraft during Landing on the Water

In view of the complex three-phase coupling problem of gas, liquid and solid when amphibious aircraft landed on the water surface, based on the finite volume method, the overset grid technology was used to simulate the landing load characteristics of amphibious aircraft; firstly, the overset grid technology was used to establish the landing model of amphibious aircraft, and the load characteristics under different landing conditions were obtained, and compared with the model test results. The results show that, firstly, the larger the sinking speed is, the larger the load is, and the more obvious bounce phenomenon occurs; secondly, the transverse distribution of the bottom pressure gradually increases along the keel to bilge; thirdly, the load characteristics obtained by numerical simulation are basically consistent with the model test. Therefore, the overset grid technology can simulate the landing load characteristics of amphibious aircraft and provide an effective method for the landing load design of amphibious aircraft.

Numerical Simulation of Wave Landing Loads Characteristics of Twin-Float Seaplane

The coupled Euler-Lagrangian method is used to simulate the load characteristics of a Twin-Float seaplane when it is landing in waves. The fluid domain is described by Euler, the structure is described by Lagrangian, and the coupling interaction between the Euler material and the Lagrangian element is simulated by the enhanced immersion boundary method. Firstly, a three-dimensional numerical wave tank is established, and the accuracy of numerical wave-making is verified by linear wave theory. Then, the numerical calculation of seaplane wave landing load at different wave heights with the same wave length is carried out, Lastly the numerical results compared with the model experiment of towing tank. The numerical simulation results are in good agreement with the model experiment results. The results show that there will be obvious bouncing phenomena when the seaplane landed in the wave, and the higher the wave height is, the greater the load will be generated when the wave length is the same.

A case report: multiple right ventricular diverticula with constrictive pericarditis and right heart failure.

BackgroundRight ventricular diverticula (RVD) are very rare congenital anomalies and their association with constrictive pericarditis is even rarer. So far, only one case has been published in literature.Case summaryWe report a case of multiple congenital RVD with constrictive pericarditis and right heart failure which was incidentally identified on surveillance computed tomography (CT) for abdominal lymphangioma. Interval CT, echocardiography, and cardiac magnetic resonance imaging (CMR) studies were performed and reviewed. Computed tomography abdomen showed hepatic congestion with features of portal hypertension, increasing size of the RVD on review of serial CTs, and eccentric foci of pericardial calcification. Echocardiography performed for breathlessness demonstrated supranormal early diastolic tissue velocities with average of 19.8 cms−1 and a septal bounce phenomenon on m-mode imaging suggesting constrictive physiology, which triggered a CMR referral. Cardiac magnetic resonance imaging HASTE and right ventricular (RV) outflow tract imaging showed four outpouchings along RV free wall, the largest measuring 4.5 × 2 cm with a sizeable neck. These outpouchings displayed a trabecular network and/or were contractile aiding the diagnosis of diverticula as opposed to aneurysms. Right ventricular function was moderately compromised, whereas left ventricular function was preserved.DiscussionRight ventricular diverticula can be associated with, and potentially be causative of, pericardial thickening and calcification eventually leading to constrictive pericarditis and heart failure.

Slow oscillatory changes of DPOAE magnitude and phase after exposure to intense low-frequency sounds.

Sensitive sound detection within the mammalian cochlea is performed by hair cells surrounded by cochlear fluids. Maintenance of cochlear fluid homeostasis and tight regulation of intracellular conditions in hair cells are crucial for the auditory transduction process but can be impaired by intense sound stimulation. After a short, intense low-frequency sound, the cochlea shows the previously described "bounce phenomenon," which manifests itself as slow oscillatory changes of hearing thresholds and otoacoustic emissions. In this study, distortion product otoacoustic emissions (DPOAEs) were recorded after Mongolian gerbils were exposed to intense low-frequency sounds (200 Hz, 100 dB SPL) with different exposure times up to 1 h. After all sound exposure durations, a certain percentage of recordings (up to 80% after 1.5-min-long exposure) showed oscillatory DPOAE changes, similar to the bounce phenomenon in humans. Changes were quite uniform with respect to size and time course, and they were independent from sound exposure duration. Changes showed states of hypo- and hyperactivity with either state preceding the other. The direction of changes was suggested to depend on the static position of the cochlear operating point. As assessed with DPOAEs, no indication for a permanent damage after several or long exposure times was detected. We propose that sensitivity changes occur due to alterations of the mechanoelectrical transduction process of outer hair cells. Those alterations could be induced by different challenged homeostatic processes with slow electromotility of outer hair cells being the most plausible source of the bounce phenomenon. NEW & NOTEWORTHY Low-frequency, high-intensity sound can cause slowly cycling activity changes in the mammalian cochlea. We examined the effect of low-frequency sound duration on the degree of these alterations. We found that cochlear changes showed a stereotypical biphasic pattern independent of sound exposure duration, but the probability that significant changes occurred decreased with increasing sound duration. Despite exposure durations of up to 1 h, no permanent or transient impairments of the cochlea were detected.

Directed continuous-time random walk with memory

In this paper, we are addressing the old problem of long-term nonlinear autocorrelation function versus short-term linear autocorrelation function. As continuous-time random walk (CTRW) can describe almost all possible kinds of diffusion, it seems to be an excellent tool to use. To be more precise, for instance, CTRW can successfully describe the short-term negative autocorrelation of returns in high-frequency financial data (caused by the bid-ask bounce phenomena). We observe long-term autocorrelation of absolute values of returns. Can it also be described by the CTRW model? And maybe more importantly, to what extent can it be explained by the same phenomena? To refer to these questions, we propose a new directed CTRW model with memory. The canonical CTRW trajectory consists of spatial jumps preceded by waiting times. In directed CTRW, we consider the case with positive spatial jumps only. We take into account the memory in the model as each spatial jump depends on the previous one. This model, based on simple assumptions, allowed us to obtain the general formula covering most popular types of nonlinear autocorrelation functions.Graphical abstract

The Elastic Contact and Stability Analysis of an Inertial Micro-Switch with a Spring Stationary Electrode.

A mechanical trigger inertial micro-switch with spring stationary electrode is proposed and fabricated by surface micromachining. The elastic contact process and stability performance are evaluated through experimental tests performed using a drop hammer. The test results show that the contact time is about 110 μs and 100 μs when the threshold acceleration is 480 g and the overload acceleration is 602 g, respectively. The vibration process of the electrodes is explained through an established physical mode. The elastic contact process is analyzed and discussed by Finite Element Analysis (FEA) simulations, which indicated that the contact time is about 65 μs when the threshold acceleration is 600 g. At the same time, this result also proved that the contact time could be extended effectively by the designed spring stationary electrode. The overload acceleration (800 g) has been applied to the Finite-Element model in ANSYS, the contact process indicated that the proof mass contacted with stationary electrode three times, and there was no bounce phenomenon during contact process, which fully proved that the stable contact process can be realized at high acceleration owing to the designed elastic stationary electrode.

Evolution of inhomogeneous LTB geometry with tilted congruence and modified gravity

The goal of this paper is to shed some light on the significance of congruence of observers, which seems to affect the dynamics of the universe under Palatini f(R) formalism. Starting by setting up the formalism needed, we have explored the field equations using Lemaitre–Tolman–Bondi geometry as an interior metric. We have formulated the relationship between the matter variables as seen by the observers in both co-moving and non-co-moving frames. The dynamical equations are evaluated to study the dynamics of inhomogeneous universe by exploring conservation equations along with the Ellis equations. We have also explored a collapsing factor describing the bouncing phenomena via transport equation and conclude the stability region.

Bouncing of a bubble at a liquid–liquid interface

Significant industrial relevance of gas–liquid–liquid flows calls for understanding of their various aspects. This study focusing on one of the aspects, i.e., interaction of a single bubble with a liquid–liquid interface, is aimed at providing the experimental evidence of a hitherto unreported phenomenon of conditional bouncing of a bubble at the interface between two immiscible, initially quiescent liquids. Bouncing of the bubble is observed for two of the six pairs of the immiscible liquids used in the experiments. The data, obtained by conducting experiments with different pairs of the lighter and heavier liquid bubble diameters and rise heights, suggest that a bubble crossing a liquid–liquid interface is expected to bounce when its average velocity is less than a threshold value that depends on the interfacial tension between the two liquids and the viscosity of the heavier liquid. © 2017 American Institute of Chemical Engineers AIChE J, 63: 3150–3157, 2017

Simulation of seed motion in seed feeding device with DEM-CFD coupling approach for rapeseed and wheat

A numerical study of gas-solid flow in seed feeding device of air-assisted centralized metering system was carried out by means of Discrete Element Method (DEM) and Computational Fluid Dynamics (CFD) coupling approach. In this model, discrete particles phase was applied by EDEM software and continuum gas phase was described by ANSYS Fluent software. Effects of throat’s area, throat length, airflow inlet velocity and seed feed rate were studied and analyzed in terms of gas field and seed movement. Simulation results showed that, throat’s area and airflow inlet velocity mainly affected airflow outlet velocity and seed velocity of airflow direction which resulted from drag force, while seed movement was affected by throat length and seed feed rate slightly. The increase of throat area resulted in the decrease of seed velocity and pressure loss in a certain range. Seeds moved slowly and generated the phenomenon of bounce and concentration for low airflow inlet velocities. With the airflow inlet velocity increased, resultant force and seed velocity developed. The proper airflow inlet velocity was 16–20m/s and 20–24m/s for rapeseed and wheat, respectively. It showed that DEM-CFD coupling approach is reliable as a tool for understanding the physical phenomenon of seed movement in airflow field. Numerical simulation of seed motion based on DEM-CFD coupling approach can provide theoretical basis for developing operating performance of seed feeding device.

Aftereffects of Intense Low-Frequency Sound on Spontaneous Otoacoustic Emissions: Effect of Frequency and Level.

The presentation of intense, low-frequency (LF) sound to the human ear can cause very slow, sinusoidal oscillations of cochlear sensitivity after LF sound offset, coined the "Bounce" phenomenon. Changes in level and frequency of spontaneous otoacoustic emissions (SOAEs) are a sensitive measure of the Bounce. Here, we investigated the effect of LF sound level and frequency on the Bounce. Specifically, the level of SOAEs was tracked for minutes before and after a 90-s LF sound exposure. Trials were carried out with several LF sound levels (93 to 108dB SPL corresponding to 47 to 75 phons at a fixed frequency of 30Hz) and different LF sound frequencies (30, 60, 120, 240 and 480Hz at a fixed loudness level of 80 phons). At an LF sound frequency of 30Hz, a minimal sound level of 102dB SPL (64 phons) was sufficient to elicit a significant Bounce. In some subjects, however, 93dB SPL (47 phons), the lowest level used, was sufficient to elicit the Bounce phenomenon and actual thresholds could have been even lower. Measurements with different LF sound frequencies showed a mild reduction of the Bounce phenomenon with increasing LF sound frequency. This indicates that the strength of the Bounce not only is a simple function of the spectral separation between SOAE and LF sound frequency but also depends on absolute LF sound frequency, possibly related to the magnitude of the AC component of the outer hair cell receptor potential.

Simulation of inertial behavior of dilute particle flow in horizontal channel with Eulerian method of velocity-reassociated quadrature-based method of moments

The velocity reassociated two-node quadrature-based method of moments (VR-QMOM) is a robust Eulerian method which is able to predict the crossing trajectory and surface bouncing phenomena for dilute particle flow. It is used here to predict the particle-laden flow in the dilute particle concentration in a horizontal channel. The multiphase simulation was carried out in the Eulerian-Eulerian two-phase model with VR-QMOM for the particle phase and for comparison with the more established Eulerian-Lagrangian two-phase flow method. The gas phase is simulated with RANS equations and discretised with second-order upwind spatial numerical schemes. Comparing the predicted particle flows obtained using the VR-QMOM and Eulerian-Lagrangian approaches, the conclusion can be made that the VR-QMOM can successfully predict bouncing multiphase flows with dilute particle phase. Both trajectory crossing and bouncing behavior and the trend with increasing particle size are reproduced. The two-node VR-QMOM is seen to be an alternative methodology for the prediction of dispersed particle flow problems.

Bounce regime of droplet collisions: A molecular dynamics study

Droplet collisions have complex dynamics, which can lead to many different regimes of outcomes. The head-on collision and bounce back regime has been observed in previous experiments but numerical simulations using macro- or mesoscale approaches have difficulties reproducing the phenomena, because the interfacial regions are not well resolved. Previous molecular dynamics (MD) simulations have not reproduced the bounce regime either but have reported the coalescence and/or shattering regimes. To scrutinize the dynamics and mechanisms of binary collisions especially the interfacial regions, head-on collision processes of two identical nano-droplets with various impact velocities both in vacuum and in an ambient of nitrogen gas are investigated by MD simulations. With the right combination of the impact velocity and ambient pressure, the head-on collision and bounce back phenomenon is successfully reproduced. The bounce phenomena are mainly attributed to the “cushion effect” of the in-between nitrogen molecules and evaporated water molecules from the two nano-droplets. The analysis has verified and also extended the current gas film theory for the bounce regime through including the effects of evaporated water molecules (vapour). Some similarities and some dissimilarities between nanoscale and macro-/meso-/microscale droplet collisions have been observed. The study provides unprecedented insight into the interfacial regions between two colliding droplets.

Responses of the Human Inner Ear to Low-Frequency Sound.

The perceptual insensitivity to low frequency (LF) sound in humans has led to an underestimation of the physiological impact of LF exposure on the inner ear. It is known, however, that intense, LF sound causes cyclic changes of indicators of inner ear function after LF stimulus offset, for which the term "Bounce" phenomenon has been coined.Here, we show that the mechanical amplification of hair cells (OHCs) is significantly affected after the presentation of LF sound. First, we show the Bounce phenomenon in slow level changes of quadratic, but not cubic, distortion product otoacoustic emissions (DPOAEs). Second, Bouncing in response to LF sound is seen in slow, oscillating frequency and correlated level changes of spontaneous otoacoustic emissions (SOAEs). Surprisingly, LF sound can induce new SOAEs which can persist for tens of seconds. Further, we show that the Bounce persists under free-field conditions, i.e. without an in-ear probe occluding the auditory meatus. Finally, we show that the Bounce is affected by contralateral acoustic stimulation synchronised to the ipsilateral LF sound. These findings clearly demonstrate that the origin of the Bounce lies in the modulation of cochlear amplifier gain. We conclude that activity changes of OHCs are the source of the Bounce, most likely caused by a temporary disturbance of OHC calcium homeostasis. In the light of these findings, the effects of long-duration, anthropogenic LF sound on the human inner ear require further research.

Quasi-molecular modeling of a single supercooled large droplet impact

A mesoscale model for droplet dynamics based on a quasi-molecular approach is proposed. It considers the interaction between quasi-molecules within a single liquid droplet, each quasi-molecule representing an agglomeration of a large number of actual water molecules. The goal is to improve the understanding of the dynamics of large droplet collisions over dry or wet surfaces at velocities typical of aeronautical applications. This detailed analysis will eventually be used to refine the macroscopic Eulerian description of the water impingement process by providing numerical correlations for splashing and bouncing phenomena relevant for in-flight icing applications. Based on the Equipartition Theorem, approaches for extracting macroscopic quantities such as temperature and transport coefficients from the quasi-molecular method are discussed. A proper choice of the free parameters of the model that leads to accurate values of the macroscopic properties is also addressed.

Concurrent Acoustic Activation of the Medial Olivocochlear System Modifies the After-Effects of Intense Low-Frequency Sound on the Human Inner Ear.

>Human hearing is rather insensitive for very low frequencies (i.e. below 100 Hz). Despite this insensitivity, low-frequency sound can cause oscillating changes of cochlear gain in inner ear regions processing even much higher frequencies. These alterations outlast the duration of the low-frequency stimulation by several minutes, for which the term 'bounce phenomenon' has been coined. Previously, we have shown that the bounce can be traced by monitoring frequency and level changes of spontaneous otoacoustic emissions (SOAEs) over time. It has been suggested elsewhere that large receptor potentials elicited by low-frequency stimulation produce a net Ca(2+) influx and associated gain decrease in outer hair cells. The bounce presumably reflects an underdamped, homeostatic readjustment of increased Ca(2+) concentrations and related gain changes after low-frequency sound offset. Here, we test this hypothesis by activating the medial olivocochlear efferent system during presentation of the bounce-evoking low-frequency (LF) sound. The efferent system is known to modulate outer hair cell Ca(2+) concentrations and receptor potentials, and therefore, it should modulate the characteristics of the bounce phenomenon. We show that simultaneous presentation of contralateral broadband noise (100 Hz-8 kHz, 65 and 70 dB SPL, 90 s, activating the efferent system) and ipsilateral low-frequency sound (30 Hz, 120 dB SPL, 90 s, inducing the bounce) affects the characteristics of bouncing SOAEs recorded after low-frequency sound offset. Specifically, the decay time constant of the SOAE level changes is shorter, and the transient SOAE suppression is less pronounced. Moreover, the number of new, transient SOAEs as they are seen during the bounce, are reduced. Taken together, activation of the medial olivocochlear system during induction of the bounce phenomenon with low-frequency sound results in changed characteristics of the bounce phenomenon. Thus, our data provide experimental support for the hypothesis that outer hair cell calcium homeostasis is the source of the bounce phenomenon.

High-dose-rate brachytherapy as a monotherapy for prostate cancer--Single-institution results of the extreme fractionation regimen.

We report a single-institution retrospective analysis of the outcomes, disease control, and toxicity of high-dose-rate (HDR) brachytherapy used as the only treatment modality (monotherapy) for localized prostate cancer. Between 2006 and 2012, 77 patients with diagnosed prostate cancer were treated with HDR brachytherapy as a monotherapy. The prescribed dose was 45Gy in three separate implants 21days apart, with single fraction per implant. Of the 77 patients, 67 (87%) received hormonal therapy. Prostate-specific antigen failure was defined according to Phoenix consensus, as nadir+ 2ng/mL. Toxicity was scored according to Common Terminology Criteria for Adverse Events, version 4.03. The median followup time was 57 months (4.75 years). The 5-year actuarial overall survival was 98.7%, biochemical control 96.7%, local control 96.9%, and metastasis-free survival 98.4%. Younger age at the beginning of brachytherapy predicted the onset of bounce phenomenon. There were no Grade 3 or higher acute toxicities detected, and Grade 2 genitourinary acute toxicity developed in 19 patients (24.6%). There were no Grade 2 gastrointestinal complications. No Grade 4 or 5 late toxicity was detected. There were also no Grade 3 gastrointestinal toxicities detected. One patient (1.3%) underwent transurethral resection of the prostate because of Grade 3 urethral stenosis and urinary retention. A total of 26 patients (33.8%) developed Grade 2 late toxicity. HDR brachytherapy as monotherapy for localized prostate cancer was feasible, effective, and had acceptable toxicity profile.

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Cosmological bounces in spatially flat FRW spacetimes in metric f(R) gravity

The present work analyzes the various conditions in which there can be a bouncing universe solution in f(R) gravity. In the article an interesting method, to analyze the bouncing FRW solutions in a spatially flat universe using f(R) gravity models using an effective Einstein frame description of the process, is presented. The analysis shows that a cosmological bounce in the f(R) theory need not be described by an equivalent bounce in the Einstein frame description of the process where actually there may be no bounce at all. Nevertheless the Einstein frame description of the bouncing phenomena turns out to be immensely important as the dynamics of the bounce becomes amenable to logic based on general relativistic intuition. The theory of scalar cosmological perturbations in the bouncing universe models in f(R) theories has also been worked out in the Einstein frame.