Low Pitch Research Articles

Effect of Reynolds Number on Five-Hole Probe Performance: Experimental Study of the Open-Access Oxford Probe

Abstract There is relatively little literature concerning the effect of Reynolds number on multi-hole aerodynamic probe performance. In particular, there is almost no discussion in the literature regarding the underlying mechanisms of Reynolds number (Re) sensitivity for such probes. In order to close this gap, detailed investigations of the effect of Re on a five-hole probe have been performed using both particle image velocimetry (PIV) techniques and oil flow visualizations. Wind- and water-tunnels were used to cover a wide range of Re. The open-access Oxford Probe was used for these studies because of the readily available data-sets and processing routines and to allow future comparisons by other authors. Complex flow dynamics including flow separation and re-attachment were identified, which cause Re-sensitivity of the calibration map at low Re even for low yaw or pitch angles. By comparing calibration maps across a wide range of Re, we demonstrate that the Oxford Probe can be employed without much loss of accuracy at lower Re levels than initially (conservatively) suggested, and quantify the errors in the extreme low-Re regime. Overall, we demonstrate the robustness of the Oxford Probe concept across a wide range of Re conditions, we more clearly defined the low-Re limit for the probe design and quantify errors below this limit, and we illustrate the fundamental mechanisms for Re-sensitivity of multi-hole probes.

Deformation and wake of a flexible rotor in water

In this paper, we study experimentally the fluid-structure interaction of a simplified small-scale rotor operating in a water channel. The rotor consists of a single untwisted rectangular blade and is tested with various pitch angles at different rotation speeds and free stream velocities. Flapwise blade deformations are measured using image processing, and flow fields are obtained by Particle Image Velocimetry. The blade exhibits extreme downstream and upstream bending at high negative and positive pitch angles, respectively. In addition, for negative pitch angles, unsteady flapwise fluctuations are observed, accompanied by large-scale recirculation zones. These zones are formed and shed periodically behind the rotor, resembling the dynamics of the Vortex Ring State known for helicopters in steep descent. The induced axial velocity near the blade tip changes direction from upstream to downstream, in accordance with the bending direction, reaching values that exceed twice the free-stream velocity in extreme bending conditions. The blade deformation has a strong dependence on the tip speed ratio for low pitch angles, and a more pronounced dependence on the tip Reynolds number for high pitch angles. Results for a two-bladed rotor are also shown and compared to the behaviour observed for a single blade.

Electroglottographic Analysis of the Voice in Young Male Role of Kunqu Opera

The phonation types used in the young male role in Kunqu Opera were investigated. Two national young male role singers volunteered as the subjects. Each singer performed three voice conditions: singing, stage speech, and reading lyrics. Three electroglottogram parameters, the fundamental frequency, contact quotient, and speed quotient, were analyzed. Electroglottogram parameters were different between voice conditions. Five phonation types were found by clustering analysis in singing and stage speech: (1) breathy voice, (2) high adduction modal voice, (3) modal voice, (4) untrained falsetto, and (5) high adduction falsetto. The proportion of each phonation type was not identical in singing and stage speech. The relationship between phonation type and pitch was multiple to one in the low pitch range, and one to one in the high pitch range. The sound pressure levels were related to the phonation types. Five phonation types, instead of only the two phonation types (modal voice and falsetto) that are identified in traditional Kunqu Opera singing theory, were concomitantly used in the young male role’s artistic voices. These phonation types were more similar to those of the young female roles than to those of the other male roles in the Kunqu Opera.

Damage tolerance and notch sensitivity of bio-inspired thin-ply Bouligand structures

Different bio-inspired Bouligand thin-ply Carbon-Fibre-Reinforced Plastic (CFRP) laminates with a pitch angle as low as 2.07∘ are realised, which is the smallest pitch angle realised in literature. The angle is therefore close angles found in biological microstructures. Low-Velocity Impact (LVI) and residual compressive strength tests determined the damage tolerance of the structures. Investigated were two different interlaminar fracture toughnesses and two different metal-Bouligand-CFRP-layups. The low pitch angle results in significantly higher residual strengths than 45∘ quasi-isotropic (QI) layups, despite the significantly lower proportion of 0∘ fibres. Higher fracture toughness and hybridisation with steel layers lead to reduced matrix damage without increasing residual compressive strength. In-plane plane tension properties are determined with a pitch angle of 2.59∘. The results reveal, that the unnotched tensile strength is significantly lower. However, only helicoidal, sub-critical matrix cracking and no delaminations occur before final failure. The sub-critical matrix cracking leads to almost no notch sensitivity and a similar open-hole-tensile strength to 45∘-QI layups despite the low number of 0∘-fibres.

Computational modeling of thermal characteristics of hybrid nanofluid in micro-pin fin heat sink for electronic cooling

ABSTRACT Emerging technology in the electronic industry has led to miniaturization of electronic devices such as iPhones and laptops. Heat dissipation is required to maintain high performance and long-term reliability of these devices. Micro heat sinks and novel working fluids such as nanofluids are becoming popular. Until recent times the full potential of hybrid nanofluid in heat transfer has not yet been exploited. In order to address the lack of adequate modeling data in this field, the aim of this study is to systematically model and investigate computational heat transfer characteristics of Al2O3-Cu/water hybrid nanofluid in micro heat sink. Volume concentration in the range of 0.1%-0.5% was used for the working fluid. Hexagonal micro-pin fin heat sink with staggered arrangement was simulated in ANSYS Fluent. Reliable experimental result from literature was used to validate the accuracy of the results. The most obvious finding to emerge from this study is that the Nusselt number increases with increase in Reynolds number and this observation is consistently the same at different concentrations and pin spacing. Lower transverse pitch was observed to dominate the enhancement of Nusselt number. There was a 10% increase in heat transfer coefficient at 0.5% nanofluid concentration when compared to 0.1%. This phenomenon is highly influenced by the transition of the Re into turbulent situation which eventually enhances the heat transfer characteristics. Also, lower transverse pitch promotes swirling flow situation. At 0.5% hybrid nanofluid concentration, it was observed that the Nusselt number increased from 14.00 at transverse pitch of 3.81 mm to 17.00 at a transverse pitch of 1.81 mm and this corresponds to 16.05% enhancement of Nusselt number. The pressure drop penalty of the working fluid is a result of increase in viscous effect of the hybrid nanofluid, especially at high concentration.

The Third Mobile Window Effects in Otology/Neurotology.

It has been revealed that the pure-tone audiometry demonstrates large air-bone gaps at low pitches due to the presence of inner ear fistulae. When a third mobile window resulting from an inner ear fistula is present, in addition to the 2 normally present windows consisting of the oval window and the round window, a portion of the air-conducted waves escape from the scala vestibuli through the inner ear fistula. On the other hand, bone-conducted waves traveling to the scala vestibuli are reduced by an inner ear fistula; however, bone-conducted waves traveling to the scala tympani are not affected by an inner ear fistula. This results in a larger gap than usual in compliance between both perilymphatic spaces and leads to a decrease in the bone conduction threshold.This phenomenon, so-called the third mobile window effects, sometimes may lead otology/neuro-otology surgeons to misunderstand the reason why large air-bone gaps still exist after ossicular reconstruction in tympanoplasty. This review article gives good examples regarding the third mobile window effects in otology/neuro-otology diseases and surgeries.

Numerical simulation of chorus-driving acceleration of relativistic electrons at extremely low L-shell during geomagnetic storms* *Project supported by the National Natural Science Foundation of China (Grant Nos. 41904149 and 12173038), Stable-Support Scientific Project of ChinaResearch Institute of Radiowave Propagation (Grant No. A132001W07), and the National Institute of Natural Hazards, Ministry of Emergency Management of China (Grant No. 2021-JBKY-11).

During 2018 major geomagnetic storm, relativistic electron enhancements in extremely low L-shell regions (reaching L∼3) have been reported based on observations of ZH-1 and Van Allen probes satellites, and the storm is highly likely to be accelerated by strong whistler-mode waves occurring near very low L-shell regions where the plasmapause was suppressed. It is very interesting to observe the intense chorus-accelerated electrons locating in such low L-shells and filling into the slot region. In this paper, we further perform numerical simulation by solving the two-dimensional Fokker–Planck equation based on the bounce-averaged diffusion rates. Numerical results demonstrate the evolution processes of the chorus-driven electron flux and confirm the flux enhancement in low pitch angle ranges (20°–50°) after the wave-particle interaction for tens of hours. The simulation result is consistent with the observation of potential butterfly pitch angle distributions of relativistic electrons from both ZH-1 and Van Allen probes.

The Influence of Speaker Pitch on Inferring Semantic Valence

ABSTRACT Research on metaphors has shown that individuals form associations between the verticality, brightness, and distance of stimuli and their valence. Building on the literature on conceptual metaphor theory, the pitch–valence hypothesis predicts an association between the pitch of spoken words and their valence. A study was conducted recording participants’ accuracy and response latencies in identifying positive and negative words that were spoken in high and low pitches to see whether pitch affects the accuracy and speed when choosing words that systematically vary in their semantic valence. The results supported the pitch–valence hypothesis by revealing systematic differences in performance. The observed effects were mainly due to participants’ accuracies when words were presented in a high pitch.

Dynamically varying timbre cues interfere with listeners’ pitch perception

One timbre cue that has been studied psychophysically is the spectral centroid of a steady-state harmonic complex, which corresponds to the “brightness” of the complex. Complexes having higher spectral centroids tend to be perceived as having higher pitches even with a constant fundamental frequency (F0). To further understand pitch-timbre interactions, the current study investigates whether dynamically varying spectral centroids of harmonic complexes affect the pitches. Normal-hearing listeners ranked the pitch of two harmonic complexes on each trial. In some trials the spectral centroid of one complex swept from low to high frequencies across its duration while the centroid of the other complex varied from high to low. Other trials had centroids moving from high to low then low to high across the interval. F0s of the two complexes differed by one just noticeable difference. Results show that a more recent rising spectral centroid tends to bias listeners to generate “higher pitch” responses, while a more recent declining spectral centroid tends to bias listeners to generate “lower pitch” responses, even when the rising and declining stimuli had identical long-term spectra. The results suggest that the spectral centroids at various temporal position of a harmonic complex do not influence pitch perception equally.

Integral perception, but separate processing: The perceptual normalization of lexical tones and vowels

In tonal languages, speech variability arises in both lexical tone (i.e., suprasegmentally) and vowel quality (segmentally). Listeners can use surrounding speech context to overcome variability in both speech cues, a process known as extrinsic normalization. Although vowels are the main carriers of tones, it is still unknown whether the combined percept (lexical tone and vowel quality) is normalized integrally or in partly separate processes. Here we used electroencephalography (EEG) to investigate the time course of lexical tone normalization and vowel normalization to answer this question. Cantonese adults listened to synthesized three-syllable stimuli in which the identity of a target syllable — ambiguous between high vs. mid-tone (Tone condition) or between /o/ vs. /u/ (Vowel condition) — was dependent on either the tone range (Tone condition) or the formant range (Vowel condition) of the first two syllables. It was observed that the ambiguous tone was more often interpreted as a high-level tone when the context had a relatively low pitch than when it had a high pitch (Tone condition). Similarly, the ambiguous vowel was more often interpreted as /o/ when the context had a relatively low formant range than when it had a relatively high formant range (Vowel condition). These findings show the typical pattern of extrinsic tone and vowel normalization. Importantly, the EEG results of participants showing the contrastive normalization effect demonstrated that the effects of vowel normalization could already be observed within the N2 time window (190–350 ms), while the first reliable effect of lexical tone normalization on cortical processing was observable only from the P3 time window (220–500 ms) onwards. The ERP patterns demonstrate that the contrastive perceptual normalization of lexical tones and that of vowels occur at least in partially separate time windows. This suggests that the extrinsic normalization can operate at the level of phonemes and tonemes separately instead of operating on the whole syllable at once.

The encoding of stochastic regularities is facilitated by action-effect predictions

Our brains continuously build and update predictive models of the world, sources of prediction being drawn for example from sensory regularities and/or our own actions. Yet, recent results in the auditory system indicate that stochastic regularities may not be easily encoded when a rare medium pitch deviant is presented between frequent high and low pitch standard sounds in random order, as reflected in the lack of sensory prediction error event-related potentials [i.e., mismatch negativity (MMN)]. We wanted to test the implication of the predictive coding theory that predictions based on higher-order generative models—here, based on action intention, are fed top-down in the hierarchy to sensory levels. Participants produced random sequences of high and low pitch sounds by button presses in two conditions: In a “specific” condition, one button produced high and the other low pitch sounds; in an “unspecific” condition, both buttons randomly produced high or low-pitch sounds. Rare medium pitch deviants elicited larger MMN and N2 responses in the “specific” compared to the “unspecific” condition, despite equal sound probabilities. These results thus demonstrate that action-effect predictions can boost stochastic regularity-based predictions and engage higher-order deviance detection processes, extending previous notions on the role of action predictions at sensory levels.

Voice Assessment in Patients With Obstructive Sleep Apnea Syndrome After Transoral Robotic Surgery.

Objectives: Removal of part of the tongue base, in combination with uvulopharyngopalatoplasty via transoral robotic surgery (TORS), for treating obstructive sleep apnea syndrome (OSAS) results in enlargement of the oropharynx and hypopharynx and change in the size of the resonance chamber. These procedures may also alter the laryngeal-hyoid bone complex, which is linked to vocal fold tension. Thus, there is the potential for change in phonation and pitch after surgery.Study Design: Prospective, nonrandomized, institutional board-approved study.Methods: From January to August 2018, 15 patients with OSAS receiving TORS underwent voice and pitch sampling. The multi-dimensional voice program (MDVP) was applied to the evaluation of preoperative sound parameters. Highest pitch and lowest pitch were obtained with real-time pitch software, with pitch synchronized to electronic organ or tuner. Subjects also completed the Voice Handicap Index-10 scale (VHI-10), to assess their subjective perception and to detect factors affecting the VHI-10 score. The relevant parameters were analyzed again 3 months after the operation.Results: There was an increase in VHI-10 score 3 months after operation that did not reach statistical significance. There were also no significant differences in sound parameters. Increases in highest pitch (353.18 Hz shift to 387.99 Hz), highest semitone ( shift to ), lowest pitch (117.45 Hz shift to 131.42 Hz), and lowest semitone (C3 shift to C3) did not reach statistical significance. The increase in the lowest semitone was significantly related to change in VHI-10 score (r = −0.808, P = 0.028).Conclusion: Patients with OSA undergoing TORS showed a negative correlation coefficient over 0.8 with change in VHI-10 score. That is, increase in the lowest semitone after operation correlated with increase in VHI-10 score which may cause perceive changes in subjective pronunciation.

The Influence of Different Prosodic Cues on Word Segmentation.

A prerequisite for spoken language learning is segmenting continuous speech into words. Amongst many possible cues to identify word boundaries, listeners can use both transitional probabilities between syllables and various prosodic cues. However, the relative importance of these cues remains unclear, and previous experiments have not directly compared the effects of contrasting multiple prosodic cues. We used artificial language learning experiments, where native German speaking participants extracted meaningless trisyllabic “words” from a continuous speech stream, to evaluate these factors. We compared a baseline condition (statistical cues only) to five test conditions, in which word-final syllables were either (a) followed by a pause, (b) lengthened, (c) shortened, (d) changed to a lower pitch, or (e) changed to a higher pitch. To evaluate robustness and generality we used three tasks varying in difficulty. Overall, pauses and final lengthening were perceived as converging with the statistical cues and facilitated speech segmentation, with pauses helping most. Final-syllable shortening hindered baseline speech segmentation, indicating that when cues conflict, prosodic cues can override statistical cues. Surprisingly, pitch cues had little effect, suggesting that duration may be more relevant for speech segmentation than pitch in our study context. We discuss our findings with regard to the contribution to speech segmentation of language-universal boundary cues vs. language-specific stress patterns.

Uvula Manipulation and Resonance (UMAR) Treatment for Puberphonia

Otolaryngologists and speech therapist can be experts in managing specific puberphonia lesions to improve voice. However, not all voice problems have lesions amenable to surgical or medical therapies. Many are associated with maladaptive speech behaviors. We may employ a variety of techniques to improve vocal quality and function in patients with and without structural or neurologic laryngeal pathology. There is an alarming increase in cases of puberphonia and it’s after effects. Otolaryngologists can partner to manage a constellation of puberphonia voice problems with directed voice evaluation and therapy. We, in a small Otorhinolarygolist center in a small city, Chennai has registered and treated 600 cases of puberphonia. We are able to register the devastating problems of puberphonia. Regarding the treatment of puberphonia, in which laryngeal massage, outside the neck, is consistently highlighted as being an effective therapy technique for treating it. In addition, there have been several individual studies conducted to examine the effectiveness of laryngo pharyngeal manipulation inside the vocal tract, which also yielded positive results. A basic review of UMAR techniques and this partnership with yoga breathing trainers is presented which give almost immediate low pitch speech and give a good follow up.

Altered postnatal developmental patterns of ultrasonic vocalizations in Dock4 knockout mice

Ultrasonic vocalization (USV) characterization is useful for evaluating communication in mouse models of autism spectrum disorder (ASD). Here, by categorizing USVs into 12 types using a comprehensive classification method, we obtained the qualitative and quantitative characteristics of USV repertoire emitted by ASD-related Dock4 knockout (KO) mice and their wild-type (WT) littermates during social isolation over early postnatal development. Notably, USVs emitted by WT pups exhibited a developmental switch from a pattern with more multiple-note calls, which have more complex acoustic structure, lower pitch and larger volume, into one with more single-note calls, which have simpler acoustic structure, higher pitch and smaller volume. Comparing with WT pups, USVs emitted by Dock4 KO pups had larger volume and consisted of more multiple-note calls with higher pitch in later developmental stage. These findings collectively reveal a developmental pattern of USV in normal mice and identified a set of alterations in Dock4 KO pups.

Parallel velocity mixing yielding enhanced electron heating during magnetic pumping

Magnetic wave perturbations are observed in the solar wind and in the vicinity of Earth's bow shock. For such environments, recent work on magnetic pumping with electrons trapped in the magnetic perturbations has demonstrated the possibility of efficient energization of superthermal electrons. Here we also analyse the energization of such energetic electrons for which the transit time through the system is short compared with time scales associated with the magnetic field evolution. In particular, considering an idealized magnetic configuration we show how trapping/detrapping of energetic magnetized electrons can cause effective parallel velocity ($v_{\parallel }$-) diffusion. This parallel diffusion, combined with naturally occurring mechanisms known to cause pitch angle scattering, such as whistler waves, produces enhanced heating rates for magnetic pumping. We find that at low pitch angle scattering rates, the combined mechanism enhances the heating beyond the predictions of the recent theory for magnetic pumping with trapped electrons.

Classification of Pitch and Gender of Speakers for Forensic Speaker Recognition from Disguised Voices Using Novel Features Learned by Deep Convolutional Neural Networks

Voice disguise is a major concern in forensic automatic speaker recognition (FASR). Classifying the type of disguise is very important for speaker recognition. Pitch disguise is a very common type of disguise that criminals try to attempt. Among the different types of disguises, high pitch and low pitch voices show more distortion. The features that are robust for high pitch and low pitch voices are different. Moreover, the effect of disguise on male and female voices are also different. In this work, we classified high pitch and low pitch disguised voices for male and female voices using a novel set of features. We arranged Mel frequency cepstral coefficients (MFCC), ΔMFCC, and ΔΔMFCC features as three-dimensional features, and these are given as the RGB equivalent spectrogram inputs to pretrained AlexNet deep convolutional neural network (DCNN). We fused the AlexNet output features with corresponding MFCC correlation features. These fused features are the proposed novel features for disguise classification. Classification using neural network (NN) and support vector machine (SVM) classifiers are performed. Simulation results show that classification with SVM classifier using these novel features gives improved accuracy of 98.89% compared to 95.99% accuracy obtained by using DCNN output features using traditional spectrogram inputs.

Natural Convection Heat Transfer From a Vertical Hollow Cylinder With Surface Holes

Abstract Three-dimensional continuity, momentum, and energy equations have been solved around a perforated vertical hollow cylinder to predict the buoyancy-induced flow field and the temperature distribution around it. Finite volume method (FVM) has been implemented for the discretization of the underlying governing equations. Second-order upwind scheme has been adopted to discretize the convective terms in the momentum and energy equation. Results have been obtained by varying the input parameters like hole diameter to cylinder length ratio (d/L), pitch to length ratio (P/L), angular pitch (θ), cylinder length to diameter ratio (L/D), and Rayleigh number (Ra) spanning from 0.005 to 0.08, 0.1 to 0.3333, 30 deg to 180 deg, 2 to 20, and 104 to 108, respectively. It has been found that the average surface Nusselt number (Nu) for the outer surface increases with the diameter of the hole for Ra of 106, however for Ra of 108, it marginally decreases up to d/L of 0.01 and then increases. Nu for the inner surface increases when d/L is more than 0.04 for all Ra. The cylinder with the staggered holes shows a slightly higher Nu compared to the inline holes. Nu for the inner and outer surface at a lower pitch is less than that of the higher pitch when d/L is less than 0.02 for all Ra. The heat transfer rate of the perforated cylinder is more than the nonperforated cylinder for all the cases when L/D is less than 10 and Ra less than 106. However, for Ra more than 106, the perforated cylinder always loses more heat compared to the nonperforated one for all L/D. Finally, the correlation for Nu has been proposed as a function of the pertinent input parameters for future reference in the academic as well as industrial practices.

Ring Current Proton Dynamics Driven by Wave-Particle Interactions During a Nonstorm Period

Modeling of pitch angle scattering of ring current protons at interaction with electromagnetic ion cyclotron waves during a nonstorm period was considered very seldom. Therefore it is used correlated observation of enhanced electromagnetic ion cyclotron (EMIC) waves and dynamic evolution of ring current proton flux collected by Cluster satellite near the location L = 4.5 during March 26–27, 2003, a nonstorm period (Dst > –10 nT). Energetic (5–30 keV) proton fluxes are found to drop rapidly (e.g., a half hour) at lower pitch angles, corresponding to intensified EMIC wave activities. As mathematical model is used the non-stationary one-dimensional pitch angle diffusion equation which allows to compute numerically density of phase space or pitch angle distribution of the charged particles in the Earth’s magnetosphere. The model depends on time t, a local pitch angle and several parameters (the mass of a particle, the energy, the McIlwain parameter, the magnetic local time or geomagnetic eastern longitude, the geomagnetic activity index, parameter of the charged particle pitch angle distribution taken for the 90 degrees pitch angle at t = 0, the lifetime due to wave–particle interactions). This model allows numerically to estimate also for different geophysical conditions a lifetime due to wave–particle interactions. It is shown, that EMIC waves can yield decrements in proton flux within 30 minutes, consistent with the observational data. The good consent is received. Comparison of results on full model for the pitch angle range from 0 up to 180 degrees and on the model for the 90 degrees pitch angle is lead. For a perpendicular differential flux of the Earth’s ring current protons very good consent with the maximal relative error approximately 3.23 % is received

Properties of graphite blocks consisting of ordered graphite flakes with bimodal particle size distribution

AbstractPetroleum pitch‐based graphite blocks (GBs) attract considerable attention owing to their low cost, high yield, and possible application as heat sink components. However, no studies have systematically investigated the particle size distribution of GBs, their structures, and the relationship between the structures and thermal properties resulting from graphitization. Hence, herein, we present a novel method for fabricating petroleum pitch‐based GBs using natural graphite flakes (GFs) of sizes ranging between 50 and 500 μm and a bimodal particle size distribution. Furthermore, the effects of the mean GF particle size, pitch binder content, and microstructure of the GBs with low GF contents on compression molding with elevated hot‐pressing temperatures after graphitization are investigated. To investigate the effect of packing density with a GF size of 500 μm, we mix a small‐sized GF (50 μm) and low pitch binder content by kneading. In particular, specimens in the in‐plane direction with a bimodal particle size distribution of GFs and 10 wt% pitch binder yield optimum density and thermal conductivity values of 1.74 g m−3 and 384 Wm−1 K−1, respectively, after high‐temperature graphitization at 2600°C. These findings provide insights for developing high‐performance GBs for use in heat sink components with high thermal conductivity.