Numerical Simulation Research on Cutting Rock with a PDC Cutter Assisted by an Impact Force

Extensive studies have been carried out on cutting rock with a PDC cutter, but cutting rock assisted by impact force is rarely studied. In this paper, cutting rock using conical and cylindrical PDC cutters assisted by impact force were researched with the explicit dynamic model. The laws of cutting rock using a cylindrical cutter assisted by impact force are the same as those of a conical cutter. There are thresholds of impact frequency and amplitude when they are single variables. When impact frequency is lower than the threshold frequency, the impact frequency is the dominant frequency in the frequency spectrum of weight on bit (WOB), and the amplitude of dominant frequency and removal volume decreases with the increase of impact frequency. When the impact frequency is higher than the threshold frequency, there is no dominant frequency in the frequency spectrum of WOB, and the removal volume behaves the same. When the impact force is lower than the threshold amplitude, there is no dominant frequency in the frequency spectrum of WOB, and it does not affect the removal volume but the removal volume is positively correlated with the impact amplitude. When the impact amplitude is higher than the threshold amplitude, the removal volume is also positively correlated with the impact amplitude, and the removal volume assisted by low-frequency (20 Hz and 40 Hz) impact force is higher. The frequency threshold and amplitude threshold of the conical cutter are smaller than those of the cylindrical cutter. Although the cutting depth and removal volume of the conical cutter are lower than those of the cylindrical cutter, the amplifications of cutting depth and removal volume of the conical cutter are higher than those of the cylindrical cutter when assisted by impact force.

The Influence of Background Ultrasonic Field on the Strength of Adhesive Zones under Dynamic Impact Loads

The influence of background ultrasonic field on the ultimate dynamic strength of adhesive joints is studied using fracture mechanics analysis. Winkler foundation-type models are applied to describe the cohesion zone, and the incubation time fracture criterion is used. The challenging task is to study whether relatively weak ultrasound is able to decrease the threshold values of the external impact load depending on a joint model, such as an “elastic membrane” or “beam” approximation, and various boundary conditions at the ends. The specific task was to investigate the case of short pulse loading through application of time-dependent fracture criterion instead of the conventional principle of critical stress. Three different load cases, namely, step constant force, dynamic pulse, and their combination with ultrasonic vibrations, were also studied. The analytical solution to the problem demonstrates that background vibrations at certain frequencies can significantly decrease threshold values of fracture impact load. Specific calculations indicate that even a weak background sonic field is enough to cause a significant reduction in the threshold amplitude of a dynamic short pulse load. Additionally, non-monotonic dependency of threshold amplitude on pulse duration for weak background field was observed, which demonstrates the existence of optimal regimes of impact energy input. Moreover, this phenomenon does not depend on the way in which the beam edges mount, whether they are clamped or hinged, and it could be applied for micro-electro-mechanical switch design processes as an additional tool to control operational regimes.

456 Esomeprazole Use in Upper Airway Stimulation Patients Associated with Lower Functional Threshold

Introduction Proton pump inhibitors (PPIs) are widely used for gastroesophageal reflux disease (GERD) despite possible side effects including increased susceptibility to infections, secondary hypergastrinemia, and incomplete absorption of micronutrients. Upper airway stimulation (UAS) surgery involves delivering an electrical impulse to the distal hypoglossal nerve for the management of obstructive sleep apnea.. The functional threshold (FT) is the minimum stimulation required to achieve bulk tongue motion. The minimum therapeutic amplitude (MTA) is the lowest voltage required to achieve clinical benefit during titration at postoperative attended overnight polysomnography. We sought to analyze the effect of perioperative PPI use upon patients who had undergone upper airway stimulation (UAS) surgery. We hypothesized that the ion transport-related effects of PPIs would impact the amplitude necessary for tongue protrusion (FT) and clinical benefit (MTA). Methods A retrospective chart review was conducted at a single tertiary care facility. Baseline demographic data, medication history, and comorbidities were collected from December 2014 through August 2019 on patients undergoing UAS surgery. Patients that were taking a PPI at the time of surgery and postoperatively were included. Results 167 patients that underwent UAS surgery between 2014 – 2019 were studied. 74 patients were found to be taking a PPI perioperatively. Specifically, 38 patients were found to be on omeprazole, compared to 17 on pantoprazole, 13 on esomeprazole, 4 on lansoprazole, and 2 on rabeprazole. Overall, esomeprazole was a statistically significant predictor (p=0.0359) of a lower functional threshold amplitude: 1.58 mV in controls as compared to 2.09 mV for omeprazole, 2.12 mV for pantoprazole, 2.14 mV for lansoprazole, and 2.7 mV for rabeprazole. Use of PPI, while associated with lower FT voltage, was not a predictor of statistically significant changes in initial UAS minimum therapeutic amplitude settings. Conclusion The functional threshold amplitude for patients taking esomeprazole was significantly different compared to patients not on a PPI. However, the use of PPI overall was not a statistically significant predictor of initial difference in UAS mean therapeutic amplitude settings. Future studies examining tolerance of therapy and voltage changes over time in patients on proton-pump inhibitors are needed. Support (if any):

Parametric resonance of acoustic and optical phonons in GaAs/GaAsAl quantum well in the presence of laser field

In this paper, we analytically investigated the possibility of parametric resonance of acoustic and optical phonons. We obtained a general dispersion equation for parametric amplification and transformation of phonons. The dispersions of the resonant acoustic phonon modes and the threshold amplitude of the field for acoustic phonon parametric amplification are obtained. The parametric amplification for acoustic phonons in a GaAs/GaAsAl quantum well can occur under the condition that the amplitude of the external electromagnetic field is higher than the threshold amplitude. Full Text: PDF ReferencesB. A. Glavin, V. A. Kochelap, T. L. Linnik, P. Walker, A. J. Kent and M. Henini, "Monochromatic terahertz acoustic phonon emission from piezoelectric superlattices", Journal of Physics: Conference Series, Vol 92, (2007). CrossRef O. A. C. Nunes, "Piezoelectric surface acoustical phonon amplification in graphene on a GaAs substrate", Journal of Applied Physics 115, 233715 (2014). CrossRef Yu. E. Lozovik, S. P. Merkulova, I. V. Ovchinnikov, "Sasers: resonant transitions in narrow-gap semiconductors and in exciton system in coupled quantum wells", Phys. Lett. A 282, 407-414, (2001). CrossRef R.P. Beardsley, A.V. Akimov, M. Henini and A.J. Kent, "Coherent Terahertz Sound Amplification and Spectral Line Narrowing in a Stark Ladder Superlattice", PRL 104, 085501, (2010). CrossRef Pascal Ruello, Vitalyi E. Gusev, "Physical mechanisms of coherent acoustic phonons generation by ultrafast laser action", Ultrasonics 56, 21-35, (2015). CrossRef L. Esaki, in Proc. 17th Int. Conf. Phys. Semiconductors, San Francisco, CA, Aug, J.D. Chadi and W.A. Harrison, Eds, Berlin: Springer- Verlag, 473, (1984). DirectLink W. Xu, F. M. Peeters and J. T. Devreese, "Electrophonon resonances in a quasi-two-dimensional electron system", Phys. Rev. B 48, 1562 (1993). CrossRef Tran Cong Phong, Nguyen Quang Bau, "Parametric resonance of acoustic and optical phonons in a quantum well", Journal of the Korean Physical Society, Vol. 42, No. 5, 647-651, (2003). DirectLink

Stimulation of the pelvic nerve increases bladder capacity in the PGE2 cat model of overactive bladder

Selective electrical stimulation of the pudendal nerve exhibits promise as a potential therapy for treating overactive bladder (OAB) across species (rats, cats, and humans). More recently, pelvic nerve (PelN) stimulation was demonstrated to improve cystometric bladder capacity in a PGE2 rat model of OAB. However, PelN stimulation in humans or in an animal model that is more closely related to humans has not been explored. Therefore, our objective was to quantify the effects of PGE2 and PelN stimulation in the cat. Acute cystometry experiments were conducted in 14 α-chloralose-anesthetized adult, neurologically intact female cats. Intravesical PGE2 decreased bladder capacity, residual volume, threshold contraction pressure, and mean contraction pressure. PelN stimulation reversed the PGE2-induced decrease in bladder capacity and increased evoked external urethral sphincter electromyographic activity without influencing voiding efficiency. The increases in bladder capacity generated by PelN stimulation were similar in the rat and cat, but the stimulation parameters to achieve this effect differed (threshold amplitude at 10 Hz in the rat vs. twice threshold amplitude at 1 Hz in the cat). These results highlight the potential of PGE2 as a model of OAB and provide further evidence that PelN stimulation is a promising approach for the treatment of OAB symptoms.

Numerical modelling of supersonic boundary-layer receptivity to solid particulates

Atmospheric particulates may be a major source of boundary-layer instabilities leading to laminar–turbulent transition on aerodynamically smooth bodies flying at supersonic speeds. Particulates penetrating into the boundary-layer flow can excite wavepackets of the first- and/or second-mode instability. The packets grow downstream, reach the threshold amplitude and ultimately break down to turbulent spots. A numerical model is developed to simulate excitation of unstable wavepackets by spherical solid particulates. As an example, computations are carried out for a $14^{\circ }$ half-angle sharp wedge flying at an altitude of 20 km, Mach number 4 and zero angle of attack. The numerical results agree satisfactorily with the theory developed by Fedorov (J. Fluid Mech., vol. 737, 2013, pp. 105–131). The numerical model opens up an opportunity to investigate receptivity to particulates for practical supersonic and hypersonic configurations such as blunt bodies of revolution.

Multisensory perception reflects individual differences in processing temporal correlations

Sensory signals originating from a single event, such as audiovisual speech, are temporally correlated. Correlated signals are known to facilitate multisensory integration and binding. We sought to further elucidate the nature of this relationship, hypothesizing that multisensory perception will vary with the strength of audiovisual correlation. Human participants detected near-threshold amplitude modulations in auditory and/or visual stimuli. During audiovisual trials, the frequency and phase of auditory modulations were varied, producing signals with a range of correlations. After accounting for individual differences which likely reflect relative temporal processing abilities of participants’ auditory and visual systems, we found that multisensory perception varied linearly with strength of correlation. Diffusion modelling confirmed this and revealed that correlation is supplied to the decisional system as sensory evidence. These data implicate correlation as an important cue in audiovisual feature integration and binding and suggest correlational strength as an important factor for flexibility in these processes.

Technological effect of processing with the organic granular media flows

There has been carried out the analysis of approaches how to model vibrational processing by granulated media. The vibroprocessing model has been developed, that provides effective parts’ surfaces finishing work with granules of stone organic media initially based on the approach of energy impact of the granule flow on the processed surface. Specific volumetric metal scrap has been used as the main characteristic of processing with organic media its physical aim is increase rate of thickness of the material removed from the surface in the frames of definite velocity and pressure of the media. It is shown that metal scrap depends on media flow velocity, granular media height of the loading column, conditions that form stationary circulation motion of the media. Taking into account the analysis of experimental studies results of amplitude-frequency characteristics influence on the metal scrap during of abrasive granules vibroprocessing, there has been disclosed some certain dependence of the specific volume metal scrap while organic media processing, considering threshold amplitude and frequency of oscillations of the working tank that made it possible to observe the effect of surface treatment is. The established dependence describing the effective vibroprocessing conditions with stone organic media that was achieved due to experimental data which allows to assume validity of the obtained model.