bluuebunny/crossref_metadata_2025 huggingface dataset:
Excitation produced by Schroeder-phase complexes: Evidence for fast-acting compression in the auditory system
Authors: Carlyon Robert P. , Datta A. Jaysurya
Published: July 2002

A series of experiments compared the excitation produced in an auditory filter centered on 1100 Hz by two complexes, both of which consisted of harmonics 2–20 of a 100-Hz fundamental. When the components had a level of 69 dB SPL each, summing them in positive Schroeder phase produced substantially less forward masking of an 1100-Hz signal than when the components were summed in negative Schroeder phase. This difference decreased with decreases in overall masker level. Listeners also reported that the components of the positive-phase masker close to 1100 Hz were quieter than the corresponding components in the negative-phase masker. The data are explained using Kohlrausch and Sander’s [J. Acoust. Soc. Am. 97, 1817–1829 (1995)] finding that the response of an 1100-Hz auditory filter to the positive-phase complex shows marked peaks and dips, whereas that to the negative-phase complex does not. It is argued that the peaks in the response to the positive-phase masker are attenuated by fast-acting compression in the auditory system, thereby reducing the excitation produced by that sound. It is also argued that, compared to the power functions commonly used to model “excess masking” and the growth of loudness, the present data reflect greater compression at high levels but less compression at low levels.
Acoustic axisymmetric radiation and scattering from bodies of revolution using the internal source density and Fourier methods
Authors: Stepanishen Peter R.
Published: July 2002

A brief review is presented of a previously developed mean-square error method to solve the Neumann boundary-value problem corresponding to acoustic axisymmetric harmonic radiation and rigid body scattering from bodies of revolution of arbitrary shape. The method is based on the use of an internal line monopole source distribution along the axis. In contrast to earlier work, the pressures are simply expressed as line integrals of the source distributions which in the far field reduce to Fourier transform relationships. Exact expressions for the source strength distributions for a sphere are developed using the Fourier transform relationships. The source strength distributions involve spatial derivatives of Dirac delta functions and thus have a vanishingly small region of support about the center of the sphere. For cylindrically shaped bodies with large aspect ratios the spatial characteristics of the source strength distributions are shown to be more closely matched to the normal velocity distribution. The use of a discrete series of Dirac delta functions to represent the continuous line source distributions is presented for spherical radiation and scattering problems.
Frequency discrimination of stylized synthetic vowels with a single formant
Authors: Lyzenga Johannes , Horst J. Wiebe
Published: July 2002

Just-noticeable differences (jnd’s) in the center frequency of bandlimited harmonic complexes were measured for normal-hearing subjects. A triangular and a rounded spectral envelope were used. The center frequency ranged from 500 to 600 Hz in a region representing the first formant of vowels, and from 2000 to 2100 Hz in a second formant region. The slope of the spectral envelope was either 50 or 100 dB/oct for the first formant region and 100 or 200 dB/oct for the second formant region. For the fundamental frequency of the complexes 100 and 200 Hz were used. The jnd’s were determined for various phase relations between the individual components of the complexes. For comparison we also determined jnd’s for a Gaussian white noise that was filtered with the same spectral envelopes as the harmonic complexes. A three-interval, three-alternative forced-choice task was used. All measurements were performed with roving stimulus level. The jnd’s found for center frequencies that were halfway between two harmonics were smaller than those found for center frequencies that coincided with a harmonic. The jnd’s for the noise bands were mostly between those of the two aforementioned groups. Except for a small group of stimuli, the phase relations had little effect on the jnd’s. The majority of the results for both the harmonic and the noise band stimuli can be described by a model using a spectral profile comparison. Most of the remaining data can be explained in the temporal domain from changes in the temporal envelope of the stimuli.
A study of materials at high temperature using miniaturized resonant tuning forks and noncontact capacitance transducers
Authors: Schindel David W. , Hutchins David A. , Smith Stuart T.
Published: July 2002

A noncontact acoustical system has been developed which measures Young’s modulus of solid materials at high temperature with ⩽0.05% accuracy. The system employs capacitive (or electrostatic) transducers to excite and detect vibrations of millimeter-sized resonant tuning forks, whose resonance frequencies alter with changing temperature and material properties. The use of tuning forks in their fundamental symmetric modes of vibration provide resonances of high Q’s and eliminate irreversible frequency and drift effects that occur with other forms of resonator. The use of noncontact capacitive transducers reduces the damping and stresses that otherwise occur with contacting transducers, and allows the system to be simply and accurately modeled. Both single crystal silicon tuning forks, and those manufactured from hydrided and unhydrided Zr–2.5%Nb, were investigated at temperatures up to 700 °C. The measured responses of silicon forks confirmed the system accuracy, and suggested that single-crystal silicon be standardized as a calibration material for acoustical measurement systems. Results obtained with Zr–2.5%Nb tuning forks allowed an accurate quantitative analysis of the effects of hydride dissolution and precipitation on Young’s modulus, and confirmed that Young’s modulus of hydrided Zr–2.5%Nb decreases in proportion to free hydrogen concentration. This experimental system should prove valuable for accurate modeling of high-temperature material transformations in solids.
Auditory discrimination of material changes in a struck-clamped bar
Authors: Lutfi Robert A. , Oh Eunmi L.
Published: July 2002

The principles of theoretical acoustics were applied to approximately reconstruct the sound pressure waveform at the ear as would be generated by an idealized struck-clamped bar. The result is an inharmonic sum of damped sinusoids whose individual acoustic parameters (frequency, intensity, and decay modulus) are, for a fixed geometry and fixed driving force, uniquely determined by the material composition of the bar. In the standard 2IFC procedure, listeners were asked to discriminate changes in material composition based on their perception of the acoustic waveform. Listener strategies for discriminating such changes were estimated by perturbing slightly the individual acoustic parameters from trial to trial and computing correlations with the listener’s response [cf. R. A. Lutfi and E. Oh, J. Acoust. Soc. Am. 95, 2963(A) (1994)]. In general, the correlations reveal that listeners fail to make optimal use of the information in the acoustic waveform by tending to give undue weight, for a given material change, to changes in component frequency. In some case, the accompanying reduction in performance efficiency amounted to 80%.
On the effect of a residual stress field on the dispersion of a Rayleigh wave propagating on a cracked surface
Authors: Pecorari Claudio
Published: July 2002

A heuristic model is presented which quantifies the effect of a compressive residual stress of the dispersion on a Rayleigh wave propagating over a cracked surface. The model shows that a residual stress acting on the outermost part of a surface, and extending for about 20% of the crack depth within the sample, reduces the dispersion of the Rayleigh wave by about 70%.
Comparison of relative and absolute sound localization ability in humans
Authors: Recanzone Gregg H. , Makhamra Samia D. D. R. , Guard Darren C.
Published: July 2002

Sound localization ability has traditionally been studied using either a relative localization task, where thresholds to determine a difference in sound source location is approximately 1–10 degrees, or an absolute localization task, where the range of estimates of the source of a sound are 4–30 degrees. In order to directly relate these two psychophysical methods, we compared the psychometric functions from a relative localization task in a human subject to the same subject’s performance on an absolute localization task using three different acoustic stimuli: Gaussian noise, 1-kHz tones, and 4-kHz tones. The results showed that the relative localization threshold was a poor indicator of the range of estimates of the same stimulus in absolute space, however, the width of the relative localization psychometric functions was well correlated with the width of the distribution of estimates made in the absolute localization task. It is concluded that the relative localization psychometric functions, but not threshold, provides a reliable estimate of absolute spatial localization ability in human subjects, and suggested that the same neuronal mechanisms can underlie the psychophysical data using both methods.
Speech recognition of hearing-impaired listeners: Predictions from audibility and the limited role of high-frequency amplification
Authors: Ching Teresa Y. C. , Dillon Harvey , Byrne Denis
Published: July 2002

Two experiments were conducted to examine the relationship between audibility and speech recognition for individuals with sensorineural hearing losses ranging from mild to profound degrees. Speech scores measured using filtered sentences were compared to predictions based on the Speech Intelligibility Index (SII). The SII greatly overpredicted performance at high sensation levels, and for many listeners, it underpredicted performance at low sensation levels. To improve predictive accuracy, the SII needed to be modified. Scaling the index by a multiplicative proficiency factor was found to be inappropriate, and alternative modifications were explored. The data were best fitted using a method that combined the standard level distortion factor (which accounted for decrease in speech intelligibility at high presentation levels based on measurements of normal-hearing people) with individual frequency-dependent proficiency. This method was evaluated using broadband sentences and nonsense syllables tests. Results indicate that audibility cannot adequately explain speech recognition of many hearing-impaired listeners. Considerable variations from audibility-based predictions remained, especially for people with severe losses listening at high sensation levels. The data suggest that, contrary to the basis of the SII, information contained in each frequency band is not strictly additive. The data also suggest that for people with severe or profound losses at the high frequencies, amplification should only achieve a low or zero sensation level at this region, contrary to the implications of the unmodified SII.
On the existence of an age/threshold/frequency interaction in distortion product otoacoustic emissions
Authors: Dorn Patricia A. , Piskorski Pawel , Keefe Douglas H. , Neely Stephen T. , Gorga Michael P.
Published: July 2002

Interactions among age, threshold, and frequency in relation to distortion product otoacoustic emissions (DPOAE) have yet to be resolved. The effects of these variables were explored by analyzing DPOAEs in ears with thresholds not exceeding 20 dB HL. Multivariate regression analyses were performed in two different ways. For data to be included in the first analysis, audiometric threshold had to be 20 dB HL or better only at the particular frequency under study, but might exceed 20 dB HL at other half-octave frequencies. Significant main effects were found for age, threshold, and frequency. There was also an age-by-frequency interaction, but a significant age-by-threshold interaction was not observed. DPOAE amplitudes decreased as either age, frequency, or threshold increased. In the second analysis, when a more stringent inclusion criterion was applied (normal thresholds at all frequencies), the main effects for age, threshold, and frequency were not significant. The significant age-by-frequency interaction remained, whereby DPOAE amplitudes decreased as age and frequency increased, but the age-by-threshold interaction again was not significant. The magnitude of DPOAE amplitude change across age, threshold, and frequency and for the age-by-frequency interaction was small but similar for both groups of subjects. Age in association with threshold did not account for observed changes in DPOAE amplitudes for either group. Importantly, the lack of a significant age-by-threshold interaction indicates that there may be processes intrinsic to aging alone that act on DPOAE generation.
Combined feedback–feedforward active control of sound in a room
Authors: Tseng Wen-Kung , Rafaely B. , Elliott S. J.
Published: July 2002

This paper presents an active noise control system with a combined feedback–feedforward configuration, which may be useful when the location and directivity of the primary source in a room are not known. Using the combined system, the need to choose between a feedforward or a feedback system configuration beforehand is avoided. The optimum performance of feedforward, feedback, and the combined active control systems have been calculated from measurements taken in a 7×6×3 m3 room with various primary source positions. Internal model control (IMC) together with optimal Wiener filtering are used in the design of the optimum controllers, which was performed for each primary source position and also included robust stability to guarantee the stability of the controllers in face of plant uncertainty. The performance of the feedforward controller alone was much more dependent on the position of the primary source than that of the feedback controller alone, but the combined system always performed better than either of those systems. The results also suggested that the combined system could obtain good performance even if the response of its feedback controller was fixed, independently of the primary source location, but the response of its feedforward controller was adapted for different primary source positions.
Auditory-visual spatial integration: A new psychophysical approach using laser pointing to acoustic targets
Authors: Lewald Jörg , Ehrenstein Walter H.
Published: July 2002

The alignment of auditory and visual spatial perception was investigated in four experiments, employing a method of laser pointing toward acoustic targets in combination with various tasks of visual fixation in six subjects. Subjects had to fixate either a target LED or a laser spot projected on a screen in a dark, anechoic room and, while doing so, direct the laser beam toward the perceived azimuthal position of the sound stimulus (bandpass-filtered noise; bandwidth 1–3 kHz; 70 dB sound pressure level, duration 10 s). The sound was produced by one of nine loudspeakers, located behind the acoustically transparent screen between 22° to the left and 22° to the right of straight ahead. Systematic divergences between sound azimuth and laser adjustment were found, depending on the instructions given to the subjects. The eccentricity of acoustic targets was generally overestimated by up to 10.4° with an only slight influence of gaze direction on this effect. When the sound source was straight ahead, gaze direction had a substantial influence in that the laser adjustments deviated by up to 5.6° from sound azimuth, toward the side to which the gaze was directed. This effect of eye position decreased with increasing eccentricity of the sound. These results can be explained by the interactive effects of four distinct factors: the lateral overestimation of the auditory eccentricity, the effect of eye position on sound localization, the effect of the retinal eccentricity on visual localization, and the extraretinal effect of eye position on visual localization.
Experimental verification of the opposite effect of fluid loading on the velocity of dilatational waves in thin plates and rods
Authors: Hassan Waled , Nagy Peter B.
Published: July 2002

In a recent paper [J. Acoust. Soc. Am. 102, 3478 (1997)], it was demonstrated by analytical means that radiation loading increases the velocity of dilatational waves in immersed thin plates, but decreases it in thin rods. The main goal of this paper is to verify experimentally the predicted opposite effect, which is particularly interesting because in almost every respect, the lowest-order dilatational modes of wave propagation in thin plates and rods are very similar. Experimental verification of the predicted small radiation-induced velocity change is rather difficult, partly because of the accompanying strong attenuation effect caused by radiation losses, and partly because of the presence of an additional velocity change caused by viscous drag even in low-viscosity fluids like water. In spite of these inherent difficulties, the presented experimental results provide unequivocal verification of the earlier theoretical predictions.
Continuous monitoring of fish in a shallow channel using a fixed horizontal sonar
Authors: Pedersen Bjarke , Trevorrow Mark V.
Published: July 2002

An acoustic monitoring program of herring migration in Drogden channel, near Copenhagen, Denmark was conducted from June 1996 until the end of May 1997. Fixed 100-kHz side-looking sonars provided nearly continuous surveillance in a 1-km-wide by 12-m-deep navigation channel. Water temperature, salinity, and current profiles were simultaneously monitored at this site. The sonars were positioned to insonify regions near the seabed at ranges up to 800 m, such that the typical reverberation was due to low-grazing angle seabed backscatter. It was found that under normal, weakly stratified flow conditions, fish schools attributable to herring (Clupea harengus) were observed from the 50- to 500-m range. This could be done despite interference from the dense vessel traffic, specifically direct echoes from hulls, propeller cavitation noise, and bubbly wakes. At close ranges (<150 m) hyperbolic trajectories attributable to individual herring were observed, with horizontal advection speeds in close agreement with measured current magnitudes. It was further observed that occasional intrusions of saline bottom waters created strong upward-refracting conditions that significantly limited the range for fish school detection. Ray-tracing analysis is used to define the insonified areas and describe the backscattered reverberation under normal and stratified flow conditions. It is shown using simulations of fish-school echoes that seabed-reflected multipaths can create an upward bias in fish-school densities calculated using echo-integration techniques.
Influence of sound–structure interaction on backscattering amplitude in underwater acoustics
Authors: Peine H.
Published: July 2002

Sea-based backscattering experiments were carried out in the frequency range from Helmholtz numbers (ka) 10 to 30 with a model target. In order to improve target identification, focus here is on separating features related to sound structure interaction from those determined by the target’s shape. At the frequencies under concern generally many overlapping vibration modes of the target are excited. Whereas with specially designed objects, like thin-walled hollow cylindrical or spherical shells, isolated resonance modes can be directly observed in the echo and assigned to surface waves, the model target used here resembles the complex structure of real obstacles. The structural responses measured by accelerometers attached inside the model are recorded simultaneously together with the backscattering amplitude allowing immediate comparison. Narrow-band swept sine and CW pulses were used. At each frequency the target was turned around a fixed axis with angle resolution better than 2 degrees. A novel spectral transfer function is tested modeling the frequency-dependent boundary impedance and therefore the envelope deformation of the scattered pulse due to interaction of the impinging wave with the target’s interior. This model function has rather few parameters to be adjusted.
A perturbation theory for scattering from targets near rough surface sediments: Numerical results
Authors: Bishop Garner C. , Smith Judy
Published: July 2002

A null field T-matrix perturbation theory developed for plane-wave scattering from a fluid loaded elastic spherical shell near a rough fluid elastic interface [J. Acoust. Soc. Am. 101, 767–788 (1997)] is generalized to include scattering from spherical, spheroidal, and endcapped cylindrical targets near rough surface rigid, soft, fluid, and elastic sediments. Numerical results are obtained that demonstrate some of the effects of surface roughness on resonant and nonresonant target-boundary scattering.
A long-range and variable focus phase-conjugation experiment in shallow water
Authors: Hodgkiss W. S. , Song H. C. , Kuperman W. A. , Akal T. , Ferla C. , Jackson D. R.
Published: July 2002

A second phase-conjugation experiment was conducted in the Mediterranean Sea in May 1997 extending the results of the earlier time-reversal mirror experiment [Kuperman et al., J. Acoust. Soc. Am. 103, 25–40 (1998)]. New results reported here include (1) extending the range of focus from the earlier result of 6 km out to 30 km, (2) verifying a new technique to refocus at ranges other than that of the probe source [Song et al., J. Acoust. Soc. Am. 103, 3234–3240 (1998)], and (3) demonstrating that probe-source pulses up to 1 week old can be refocused successfully.
Low frequency passive noise control of a piston structure with a weak radiating cell
Authors: Ross Bradley W. , Burdisso Ricardo A.
Published: July 2002

The concept of a weak sound radiating cell is proposed to reduce the low-frequency radiated noise from structures. The cell consists of two mechanically coupled surfaces such that, when placed on a vibrating structure, the response of the two surfaces are nearly out-of-phase and nearly of the same strength over a wide frequency range. This structure response leads the cell to behave as an acoustic dipole and thus a poor sound-radiating source. The control of low-frequency structurally radiated noise is then achieved by covering the structure with an array of these weak radiating cells, i.e., surface treatment. Thus the surface treatment essentially transforms the response of the structure to that of a distributed array of dipoles yielding a low sound radiating structure. A theoretical model of a single weak radiating cell applied to a simple piston structure was developed and experimental verification was performed. Overall sound power level reductions of over 6 dB were experimentally achieved between 400 and 1600 Hz with maximum reductions of over 30 dB at discrete frequencies.
Scattering from fluid-loaded cylindrical shell with periodic circumferential constraints using analytical/numerical matching
Authors: Loftman R. C. , Bliss D. B.
Published: July 2002

Acoustic scattering from an infinitely long, thin elastic cylindrical shell with axially periodic circumferential constraints leads to the excitation of flexural, longitudinal, and shear waves on the shell. Of interest is the interaction of these structural waves with the discontinuous constraints, and the effect of this interaction on the resultant scattered sound field. This three-dimensional, fully coupled, structural acoustic problem is solved using a method called analytical/numerical matching (ANM). The method combines high-resolution local analytical solutions and low-resolution global numerical solutions to more efficiently model structural discontinuities. The ANM local solutions have been developed to efficiently capture the rapid variation in system response across the discontinuous constraint. The local solutions are combined with a smooth global solution, modeled by modal methods, to form an accurate, uniformly valid composite solution. The ANM composite solution is more accurate and converges much more rapidly than the traditional modal approach. An important observation is that this scattering problem exhibits considerable sensitivity to modeling accuracy and convergence of structural response in the region of the discontinuities. Errors in these regions have an overall effect on the structure and the associated scattered field.
Passive wideband cross correlation with differential Doppler compensation using the continuous wavelet transform
Authors: Ferguson Brian G. , Lo Kam W.
Published: July 2002

An estimate of the time difference for the signal emitted by a stationary source to arrive at two spatially separated sensors is given by the time displacement that maximizes the cross-correlation function. For a fast moving source, however, this estimate is found to be in error because the time scales of the received signals are different for the two sensors. The correct time delay can be extracted by evaluating the continuous wavelet transform, which has the same functional form as the wideband cross-ambiguity function. When the signal-to-noise ratio is high, the coordinates of the ambiguity surface’s global maximum provide reliable estimates of both the differential time of arrival (or time delay) and the ratio of the time scales of the signals received by the two sensors. The continuous wavelet transform is computed using the one-step chirp z-transform method, the cross-wavelet transform method, and the two-step methods where multirate sampled replicas of the sensor waveforms are cross correlated, or else the sensor waveforms are interpolated using the discrete Fourier transform prior to cross correlation. The latter method is applied to real acoustic data recorded from an orthogonal configuration of three microphones during the low-altitude transit of a jet aircraft. The resulting time delay estimates are used to calculate the variation with time of the azimuth and elevation angles of the aircraft during the transit.
Context dependence of fundamental-frequency discrimination: Lateralized temporal fringes
Authors: Gockel Hedwig , Carlyon Robert P. , Micheyl Christophe
Published: July 2002

In a two-interval, two-alternative, forced-choice (2I-2AFC) adaptive procedure, listeners discriminated between the fundamental frequencies (F0s) of two 100-ms harmonic target complexes. This ability can be impaired substantially by the presence of another complex (the “fringe”) immediately before and after each target complex. It has been shown that for the impairment to occur (i) target and fringes have to be in the same frequency region; (ii) if all harmonics of target and fringes are unresolved then they may differ in F0; otherwise, they have to be similar [C. Micheyl and R. P. Carlyon, J. Acoust. Soc. Am. 104, 3006–3018 (1998)]. These findings have been discussed in terms of information about the fringe’s F0 being included in the estimate of the F0 of the target, and in terms of auditory streaming. The present study investigated the role of perceived location and ipsilateral versus contralateral presentation of the fringes on F0 discrimination of the target. Experiment 1 used interaural level differences (ILDs), and experiment 2 used interaural time differences (ITDs) to create a range of lateralized perceptions of the 200-ms harmonic fringes. Difference limens for the F0 of the monaural target complex were measured in the presence and absence of the fringes. The nominal F0 was 88 or 250 Hz and could be the same or different for target and fringes. Stimuli were bandpass filtered between 125–625, 1375–1875, or 3900–5400 Hz. In both experiments, the effect of the fringes was reduced when their subjective location differed from that of the target. This reduction depended on the resolvability of both the fringes and the target. The effect of the fringes was reduced most (but still present), when fringes were presented purely contralaterally to the target. The results are consistent with the idea that the fringes produce interference when the listeners have difficulty segregating the target from the fringes, and that a difference in perceived location enhances segregation of the sequentially presented stimuli.
Temporal integration in the presence of off-frequency maskers
Authors: Bacon Sid P. , Hicks Michelle L. , Johnson Krista L.
Published: July 2002

Temporal integration was measured at a relatively low and a relatively high signal frequency under conditions of off-frequency masking. The masker was typically gated for 300 ms, and the signal was presented 70 ms after masker onset. In experiment 1, the signal frequency was 500 or 2000 Hz. Temporal integration was measured in quiet and in the presence of a masker whose frequency was lower or higher than the signal frequency. In all listening situations, there was less integration at 2000 Hz than at 500 Hz. This effect of frequency was particularly dramatic in the presence of a lower frequency masker, where there was almost no integration at 2000 Hz. Experiment 2 showed that this dramatic effect of frequency cannot be understood in terms of the underlying psychometric functions. Experiment 3 measured temporal integration at 750 and 2000 Hz for a large number of masker-signal frequency separations for both a tonal and a noise masker, and in conditions where the masker was gated or continuous. The results with the gated tonal masker largely confirmed the results of experiment 1. The results with the continuous tonal masker and the gated or continuous noise masker, however, were quite different. In those cases, the amount of temporal integration at both signal frequencies was more or less independent of the masker-signal separation; the masked temporal integration was nearly equal to the integration in quiet. Thus based on the conditions evaluated here, off-frequency masked temporal integration differs substantially from integration in quiet only for gated tonal maskers located considerably lower in frequency than the signal. It is unclear how to account for this finding, although it may be related to attentional factors.
Directional hearing is only weakly dependent on the rise time of acoustic stimuli
Authors: Krahe Rüdiger , Larsen Ole Næsbye , Ronacher Bernhard
Published: July 2002

First-spike latency differences between left and right auditory-nerve fibers have been proposed as one of the physiological cues for sound localization. Since first-spike latency depends not only on stimulus intensity, but also on the steepness of the amplitude rise of a sound stimulus, differences in first-spike latency are not a simple function of interaural level differences but also a function of stimulus rise time. We therefore investigated whether rise time influences human directional hearing in a localization paradigm. Subjects tended to localize a 3-kHz tone pulse with a long (18-ms) rise time further to the side than one with a short (2-ms) rise time delivered from the same source. The small size of this effect and its large inter-individual variability, however, suggest that it is of minor importance for human directional hearing.
The scaling of the wall pressure fluctuations in polymer-modified turbulent boundary layer flow
Authors: Brungart Timothy A. , Holmberg Wayne J. , Fontaine Arnold A. , Deutsch Steven , Petrie Howard L.
Published: July 2002

Wall pressure fluctuations and integrated skin friction were measured beneath a turbulent boundary layer that was modified by adding drag-reducing polymer to the pure water flow. The measurements were performed on an axisymmetric model, equipped with an isolated cylindrical drag balance section, and placed in the test section of the 0.3048-m-diam water tunnel at ARL Penn State. Data were acquired at a free-stream velocity of 10.7 m/s with pure water and with polymer added to the water at concentrations of 1, 5, 10, and 20 weight parts per million. Nondimensionalization of the wall pressure fluctuation frequency spectra with traditional outer, inner, and mixed flow variables failed to adequately collapse the data. The mean square wall pressure fluctuations were found to scale linearly with the wall shear stress. Polymer addition had little effect on the characteristic time scale of the flow. These properties were used to develop a novel form of the nondimensional wall pressure fluctuation spectrum that provided the best collapse of the measured data.
Association Between Psychological Distress and Incident Dementia in a Population-Based Cohort in Finland
Authors: Sulkava Sonja , Haukka Jari , Sulkava Raimo , Laatikainen Tiina , Paunio Tiina
Published: December 2022

Importance

Symptoms of psychological distress have shown association with subsequent dementia, but the nature of association remains unclear.

Objective

To examine the association of psychological distress with etiological risk of dementia and incidence of dementia in presence of competing risk of death.

Design, Setting, and Participants

This cohort study consisted of population-based cross-sectional National FINRISK Study surveys collected in 1972, 1977, 1982, 1987, 1992, 1997, 2002, and 2007 in Finland with register-based follow-up; and the cohort was linked to Finnish Health Register data for dementia and mortality for each participant until December 31, 2017. Participants included individuals without dementia who had complete exposure data. Data were analyzed from May 2019 to April 2022.

Exposures

Self-reported symptoms of psychological distress: stress (more than other people), depressive mood, exhaustion, and nervousness (often, sometimes, never).

Main Outcomes and Measures

Incident all-cause dementia, ascertained through linkage to national health registers. Poisson cause-specific hazard model (emphasizing etiological risk) and Fine–Gray subdistribution hazard model (emphasizing effect on incidence) considering dementia and death without dementia as competing risks. Covariates of age, sex, baseline year, follow-up time, educational level, body mass index, smoking, diabetes, systolic blood pressure, cholesterol, and physical activity. Sensitivity analysis was performed to reduce reverse causation bias by excluding individuals with follow-up less than 10 years.

Results

Among 67 688 participants (34 968 [51.7%] women; age range, 25 to 74 years; mean [SD] age, 45.4 years), 7935 received a diagnosis of dementia over a mean follow-up of 25.4 years (range, 10 to 45 years). Psychological distress was significantly associated with all-cause dementia in a multivariable Poisson model, with incidence rate ratios from 1.17 (95% CI, 1.08-1.26) for exhaustion to 1.24 (95% CI, 1.11-1.38) for stress, and remained significant in sensitivity analyses. A Fine–Gray model showed significant associations (with hazard ratios from 1.08 [95% CI, 1.01-1.17] for exhaustion to 1.12 [95% CI, 1.00-1.25] for stress) for symptoms other than depressive mood (hazard ratio, 1.08 [95% CI, 0.98-1.20]). All the symptoms showed significant associations with competing risk of death in both models.

Conclusions and Relevance

In this cohort study, psychological distress symptoms were significantly associated with increased risk of all-cause dementia in the model emphasizing etiological risk. Associations with real incidence of dementia were diminished by the competing risk of death.
Machine performance and stability of the first clinical self‐shielded stereotactic radiosurgery system: Initial 2‐year experience
Authors: Srivastava Shiv P. , Sorensen Stephen P. , Jani Shyam S. , Yan Xiangsheng , Pinnaduwage Dilini S.
Published: December 2022

This study provides insight into the overall system performance, stability, and delivery accuracy of the first clinical self‐shielded stereotactic radiosurgery (SRS) system. Quality assurance procedures specifically developed for this unit are discussed, and trends and variations over the course of 2‐years for beam constancy, targeting and dose delivery are presented. Absolute dose calibration for this 2.7 MV unit is performed to deliver 1 cGy/MU at dmax = 7 mm at a source‐to‐axis‐distance (SAD) of 450 mm for a 25 mm collimator. Output measurements were made with 2‐setups: a device that attaches to a fixed position on the couch (daily) and a spherical phantom that attaches to the collimating wheel (monthly). Beam energy was measured using a cylindrical acrylic phantom at depths of 100 (D10) and 200 (D20) mm. Beam profiles were evaluated using Gafchromic film and compared with TPS beam data. Accuracy in beam targeting was quantified with the Winston‐Lutz (WL) and end‐to‐end (E2E) tests. Delivery quality assurance (DQA) was performed prior to clinical treatments using Gafchromic EBT3/XD film. Net cumulative output adjustments of 15% (pre‐clinical), 9% (1st year) and 3% (2nd year) were made. The mean output was 0.997 ± 0.010 cGy/MU (range: 0.960–1.046 cGy/MU) and 0.993 ± 0.029 cGy/MU (range: 0.884–1.065 cGy/MU) for measurements with the daily and monthly setups, respectively. The mean relative beam energy (D10/D20) was 0.998 ± 0.004 (range: 0.991–1.006). The mean total targeting error was 0.46 ± 0.17 mm (range: 0.06–0.98 mm) for the WL and 0.52 ± 0.28 mm (range: 0.11–1.27 mm) for the E2E tests. The average gamma pass rates for DQA measurements were 99.0% and 90.5% for 2%/2 mm and 2%/1 mm gamma criteria, respectively. This SRS unit meets tolerance limits recommended by TG‐135, MPPG 9a., and TG‐142 with a treatment delivery accuracy similar to what is achieved by other SRS systems.
Emerging Halide Perovskite Ferroelectrics
Authors: Zheng Weilin , Wang Xiucai , Zhang Xin , Chen Bing , Suo Hao , Xing Zhifeng , Wang Yanze , Wei Han‐Lin , Chen Jiangkun , Guo Yang , Wang Feng
Published: December 2022

Halide perovskites have gained tremendous attention in the past decade owing to their excellent properties in optoelectronics. Recently, a fascinating property, ferroelectricity, has been discovered in halide perovskites and quickly attracted widespread interest. Compared with traditional perovskite oxide ferroelectrics, halide perovskites display natural advantages such as structural softness, low weight, and easy processing, which are highly desirable in applications pursuing miniaturization and flexibility. This review focuses on the current research progress in halide perovskite ferroelectrics, encompassing the emerging materials systems and their potential applications in ferroelectric photovoltaics, self‐powered photodetection, and X‐ray detection. The main challenges and possible solutions in the future development of halide perovskite ferroelectric materials are also attempted to be pointed out.
On the Design of Multibeam Digital Metasurfaces With Multiple Feeds
Authors: Rezaee Rezvan Behrad , Yazdi Mohammad , Hosseininejad Seyed Ehsan
Published: December 2022

In this paper, an analytical design procedure for multibeam metasurfaces with multiple feeds is presented. Considering arbitrary number of input and output beams, the required amplitude and phase distributions on the metasurface plane are theoretically derived without any optimization process. How the limitation of using only passive metasurfaces poses different challenges in the practical implementation of the amplitude profile is discussed. Then, to resolve these problems, a filtering procedure is proposed which effectively produces the desired output pattern. Moreover, the design method is verified through introducing a reflective metasurface with three input beams and sixteen output beams in arbitrary directions. It utilizes a graphene‐based unit cell providing simultaneous 2/2‐bit phase/amplitude modulation, that is, totally 16 states. For validation purposes, the analytical results are compared with numerical full‐wave simulation ones in which a good agreement between them is observed. In addition, by using the proposed design method, three different practical cases for wave manipulation functionalities, including power control, beam steering, and radar cross section (RCS) reduction capabilities are demonstrated. The presented approach paves the way for efficient design of the metasurfaces for a multitude of applications, including reconfigurable intelligent surfaces and multifunctional surfaces.
Experimental solid–liquid equilibria and solid formation kinetics for carbon dioxide in methane for LNG processing
Authors: Sampson Catherine C. , Metaxas Peter J. , Barwood Mark T. J. , Sinclair‐Adamson Rebecca , Falloon Peter E. , Stanwix Paul L. , Johns Michael L. , May Eric F.
Published: December 2022

In cryogenic liquefaction processes, CO2 poses a solid‐formation risk even in trace concentrations. We present solid–fluid equilibrium (SFE) data for CO2 in liquid methane at CO2 concentrations from (52 to 500) ppm, extending the available data and indicating that models tuned to existing data over predict the solubility of CO2 at LNG storage temperatures (~112 K) by nearly a factor of 3. The new data are used to improve the SFE model in the ThermoFAST software package. The formation kinetics of CO2 solids in liquid methane are elucidated at conditions relevant to cryogenic gas processing. Repeated, ramped‐temperature formation measurements provide a statistical basis for quantifying solidification risk. Nucleation rates extracted from the ramped‐temperature data, consistent with those measured at fixed temperature, were used to extract parameters describing CO2 solid formation in methane. These results significantly improve the ability to predict CO2 solid formation risk in cryogenic natural gas processing.
Facile Synthesis of Fully Substituted 1,2,4‐Triazoles via [3+2] Cycloaddition of Nitrileimines with Amidine under Transition Metal‐Free Conditions
Authors: Wang Dahan , Wan Xiaoyuan , Zhou Yazheng , Liu Jinbing , Cai Jinhui , Deng Guo‐Jun
Published: December 2022

An efficient synthesis of densely 1,2,4‐triazoles has been achieved by [3+2] cycloaddition of nitrileimides with amidine hydrochlorides under transition metal‐free conditions. This method features mild reaction conditions, wide substrate scope and good functional group tolerance. A series of aryl, heterocyclic and alkyl substituted 3‐CF3‐1,2,4‐triazoles were synthesized smoothly under the promotion of NaHCO3 and yield up to 96%. In addition, both gram‐scale reaction and synthetic transformations are smoothly elaborated to indicate the utility of this reaction.
Universal Global Cloning of Continuous Variables Entanglement
Authors: Ge Li , Xin Jun , Zhang Lin
Published: December 2022

It is impossible to perfectly duplicate an unknown entangled state while preserving inseparability, which is known as the entanglement no‐cloning principle. Nevertheless, approximate cloning of entanglement is allowed by quantum mechanics. A universal entanglement cloning machine (UECM) duplicates an entangled state such that the quality of its entanglement replicas does not depend on the input. To duplicate entanglement shared between two parties, 1‐to‐N universal local entanglement cloning machine (ULECM) has already been proposed (Weedbrook, et al., Phys. Rev. A, 77, 052313 (2008)), which employs two local UECMs to copy each party of the entangled state. However, the ULECM can never preserve the inseparability in its replicas. Here, a 1‐to‐N universal global entanglement cloning machine (UGECM) that takes the entire entangled state as the input and then globally clone it to produce replicas is proposed. It is demonstrated that the UGECM outperforms the ULECM both in terms of the fidelity and the inseparability preservation. In addition, the UGECM is of more simple and easy structure, compared with the UGECM. Such a UGECM may find its new applications in quantum entanglement broadcasting.
Control of Selectivity in FeCl3‐Catalyzed Aerobic Oxidation of Cycloketones
Authors: Zhao Qi , Wang Yongtao , Wang Yu , Hu Qixuan , Yao Jia , Wen Zeyu , Li Haoran
Published: December 2022

The FeCl3‐catalyzed aerobic oxidation of ketones always gives rise to the α‐C−C cleavage product, having challenges to afford hydroxyl keto compounds. Here we report an effective control of the main product from keto acid to α‐hydroxyl ketone, by reducing the concentration of FeCl3 catalyst, together with the use of DMSO as the solvent. In addition, mechanistic investigations suggested the same FeCl3‐coordinated peroxide intermediate for both hydroxylation and C−C cleavage routes, and emphasize the role of DMSO as both ligand and reductant. This work provides a new approach for selective aerobic oxidation under Lewis acid catalysis.
Rapid Ring‐Opening Polymerization of γ‐Butyrolactone toward High‐Molecular‐Weight Poly (γ‐butyrolactone) by an Organophosphazene Base and Bisurea Binary Catalyst
Authors: Liu Yiming , Xu Jizhe , Zhang Yiming , Shen Yong , Li Zhibo
Published: December 2022

The low temperature condition, long reaction time and associated high energy inputs involved in the polymerization process still hampered the scalable production of poly(γ‐butyrolactone) (PγBL) via ring‐opening polymerization (ROP) of low strained γBL due to its unfavorable thermodynamics. In this contribution, we presented the rapid ROP of γBL using a bisurea in combination with an organophosphazene base as the binary catalyst. Well‐defined PγBL samples with various terminal groups were prepared by using different alcohol initiators. The bisurea as a co‐catalyst exhibited much higher catalytic activity even compared to the most active monourea in previous report as supported by the kinetic experiments. A moderate monomer conversion of 61% was achieved within 10 mins, producing high‐molecular‐weight PγBL with Mn up to 37.5 kDa and good mechanical properties. The short polymerization time considerably reduced the energy cost for the ROP of γBL conducted at low temperature condition. This study may clear away obstacles for the scalable production and practical applications for PγBL.
Highly Active Catalytic CO2 Hydrogenation to Lower Olefins via Spinel ZnGaOx Combined with SAPO‐34
Authors: Yuan Hao , Zheng Heping , Ren Yu , Xiao Daqiang , Ran Longteng , Guo Yujing , Mao Luyao , Tang Jianhua
Published: December 2022

A key primary method for creating a carbon cycle and carbon neutrality is the catalytic hydrogenation of CO2 into high value‐added chemicals or fuels. In this work, ZnGaOx oxides were prepared by parallel co‐precipitation and physically mixed with SAPO‐34 molecular sieves prepared by hydrothermal synthesis to produce ZnGaOx/SAPO‐34 bifunctional catalysts, which were evaluated for the catalytic synthesis of lower olefins (C2=−C4=) from carbon dioxide hydrogenation. It was demonstrated that the reaction process requires oxygen defect activation, synergistic hydrogenation, and CO2 alkaline adsorption of ZnGaOx. The spinel structure of ZnGaOx has more abundant oxygen defects and alkaline adsorption sites than the ZnGaOx solid solution, which effectively enhances the catalytic performance. The CO2 conversion was 28.52%, the selectivity of C2=−C4= in hydrocarbons reached 70.01%, and the single‐pass yield of C2=−C4= was 10.95% at 370 °C, 3.0 MPa, and 4800 mL/gcat/h.
Cosmological bounce in a modified gravity framework
Authors: Chattopadhyay Surajit
Published: December 2022

The present study reports the bouncing cosmology of f(T) gravity with holographic Ricci form of density, that is, . Taking two forms of scale factor, namely exponential and power‐law, we have reconstructed f(T) gravity and accordingly derived expressions for the equation of state parameter in the bouncing scenario. The reconstructed equation of state parameter for the exponential form of scale factor showed a symmetric pattern about the turnaround point or bouncing point. Finally, we checked the stability of the models through the squared speed of sound and demonstrated how the stability depends upon the value of ξ.