bluuebunny/crossref_metadata_2025 huggingface dataset:
Computation of edge diffraction for more accurate room acoustics auralization
Authors: Torres Rendell R. , Svensson U. Peter , Kleiner Mendel
Published: July 2002

Inaccuracies in computation and auralization of room impulse responses are related in part to inadequate modeling of edge diffraction, i.e., the scattering from edges of finite surfaces. A validated time-domain model (based on analytical extensions to the Biot–Tolstoy–Medwin technique) is thus employed here to compute early room impulse responses with edge diffraction. Furthermore, the computations are extended to include combinations of specular and diffracted paths in the example problem of a stage-house. These combinations constitute a significant component of the total nonspecular scattering and also help to identify edge diffraction in measured impulse responses. The computed impulse responses are then convolved with anechoic signals with a variety of time-frequency characteristics. Initial listening tests with varying orders and combinations of diffraction suggest that (1) depending on the input signal, the diffraction contributions can be clearly audible even in nonshadow zones for this conservative open geometry and (2) second-order diffraction to nonshadowed receivers can often be neglected. Finally, a practical implementation for binaural simulation is proposed, based on the singular behavior of edge diffraction along the least-time path for a given source–edge–receiver orientation. This study thus provides a first major step toward computing edge diffraction for more accurate room acoustics auralization.
Noncontact quantitative spatial mapping of stress and flexural rigidity in thin membranes using a picosecond transient grating photoacoustic technique
Authors: Rogers John A. , Bogart Gregory R. , Miller Ron E.
Published: July 2002

This paper describes a purely optical technique for measuring and spatially mapping out stress and rigidity in thin membranes. Its application to a membrane of aluminum nitride that has significant spatial nonuniformities in its elastic properties demonstrates the method. The attractive features of this technique—fast, noncontacting measurement, good spatial resolution, ability to quantify in-plane anisotropy—make it potentially useful for characterizing elements of microelectromechanical structures, masks for advanced lithography systems, acoustic filters, and other devices in which the mechanical properties of membranes are important.
Influence of rate of change of frequency on the overall pitch of frequency-modulated tones
Authors: Gockel Hedwig , Moore Brian C. J. , Carlyon Robert P.
Published: July 2002

The mechanism(s) determining pitch may assign less weight to portions of a sound where the frequency is changing rapidly. The present experiments explored the possible effect of this on the overall pitch of frequency-modulated sounds. Pitch matches were obtained between an adjustable unmodulated sinusoid and a sinusoidal carrier that was frequency modulated using a highly asymmetric function with the form of a repeating U (∪∪) or inverted U (∩∩). The amplitude was constant during the 400-ms presentation time of each stimulus, except for 10-ms raised-cosine onset and offset ramps. In experiment 1, the carrier level was 50 dB SPL and the geometric mean of the instantaneous frequency of the modulated carrier, fc, was either 0.5, 1, 2, or 8 kHz. The modulation rate (fm) was 5, 10, or 20 Hz. The overall depth (maximum to minimum) of the FM was 8% of fc. For all carrier frequencies, the matched frequency was shifted away from the mean carrier frequency, downwards for the ∪∪ stimuli and upwards for the ∩∩ stimuli. The shift was typically slightly greater than 1% of fc, and did not vary markedly with fc. The effect of fm was small, but there was a trend for the shifts to decrease with increasing fm for fc=0.5 kHz and to increase with increasing fm for fc=2 kHz. In experiment 2, the carrier level was reduced to 20 dB SL and matches were obtained only for fc=2 kHz. Shifts in matched frequency of about 1% were still observed, but the trend for the shifts to increase with increasing fm no longer occurred. In experiment 3, matches were obtained for a 4-kHz carrier at 50 dB SPL. Shifts of about 1% again occurred, which did not vary markedly with fm. The shifts in matched frequency observed in all three experiments are not predicted by models based on the amplitude- or intensity-weighted average of instantaneous frequency (EWAIF or IWAIF). The shifts (and the pitch shifts observed earlier for two-tone complexes and for stimuli with simultaneous AM and FM) are consistent with a model based on the assumption that the overall pitch of a frequency-modulated sound is determined from a weighted average of period estimates, with the weight attached to a given estimate being inversely related to the short-term rate of change of period and directly related to a compressive function of the amplitude.
An approximate method for determining the maximum amplitude of higher-order duct modes
Authors: Horner J. L. , Lyons R. , Petersson B. A. T.
Published: July 2002

Previous investigations have used Hankel transforms to establish the amplitudes of the wave fields resulting from arbitrary angle impingement on a circular orifice in a baffle. Investigations have also been undertaken on the effects of model coupling between the higher modes in the orifice. In particular, these studies concentrated on establishing the contributions at the cut-on wave number for a particular mode. This work is extended to introduce a method of simply approximating the complex amplitude of the forward and backward waves in the duct at the cut-on wave number, based only on the modal wave number. The interest focuses on the cut-on wave number because the forcing functions for the various fields will be at a maximum at cut-on. This technique is established by observing the relationships between the peak values of the driving functions and the modal wave number. If simple approximations are established for the in-duct field, it is also possible to approximate the maximum amplitude of the scattered field.
Modification of sonic boom wave forms during propagation from the source to the ground
Authors: Bass Henry E. , Raspet Richard , Chambers James P. , Kelly Mark
Published: July 2002

A number of physical processes work to modify the shape of sonic boom wave forms as the wave form propagates from the aircraft to a receiver on the ground. These include frequency-dependent absorption, nonlinear steepening, and scattering by atmospheric turbulence. In the past two decades, each of these effects has been introduced into numerical prediction algorithms and results compared to experimental measurements. There is still some disagreement between measurements and prediction, but those differences are now in the range of tens of percent. The processes seem to be understood. The present understanding of sonic boom evolution will be presented along with experimental justification.
Perceptual fusion and fragmentation of complex tones made inharmonic by applying different degrees of frequency shift and spectral stretch
Authors: Roberts Brian , Brunstrom Jeffrey M.
Published: July 2002

Global pitch depends on harmonic relations between components, but the perceptual coherence of a complex tone cannot be explained in the same way. Instead, it has been proposed that the auditory system responds to a common pattern of equal spacing between components, but is only sensitive to deviations from this pattern over a limited range [Roberts and Brunstrom, J. Acoust. Soc. Am. 104, 2326–2338 (1998)]. This hypothesis predicts that spectral fusion will be largely unaffected either by frequency shifting a harmonic stimulus (because equal spacing is preserved), or by small degrees of spectral stretch (because significant deviations from equal spacing only cumulate over large spectral distances). Complex tones were either shifted by 0%–50% of F0 (200 Hz±10%) or stretched by 0%–12% of F0 (100 Hz±10%). Subjects heard a complex followed by a pure tone in a continuous loop. One of the components 2–11 was mistuned by ±4%, and subjects adjusted the pure tone to match its pitch. Broadly consistent with our hypothesis, frequency shifts had relatively little effect on hit rates and only large degrees of stretch reduced them substantially. The implications for simultaneous grouping are explored with reference to an autocorrelation model of auditory processing.
Low-frequency acoustic scattering by a cube: Experimental measurements and theoretical predictions
Authors: Chinnery Paul A. , Humphrey Victor F. , Zhang Jingdong
Published: July 2002

The acoustic backscattering from a submerged metal (iron) cube has been investigated as a function of frequency and angle of incidence in the low-frequency regime ka<5, where k is the acoustic wave number and a is a characteristic dimension of the cube. The experimental measurements were made in the laboratory using a parametric array as an acoustic source at frequencies between 8 and 120 kHz and a cube of side length 20 mm. The backscattered field is expressed as a dimensionless “form function” and normalized in terms of the average projected cross-sectional area of the cube. The scattered field is seen to vary considerably with the orientation of the cube. The scattering behavior of a rigid cube is modeled numerically using a boundary element code. The results for a cube are compared with calculations of the form function for an elastic sphere. When averaged over cube orientations the form function has characteristics reminiscent of a spherical scatterer, suggesting the propagation of creeping waves.
Relationships between speech intelligibility and objective acoustical parameters for architectural features in Catholic churches
Authors: Carvalho António P. , Morgado António E. , Henrique Luís
Published: July 2002

This study reports on subjective and objective acoustical field measurements made in a major survey of 36 Roman Catholic churches in Portugal built in the last 14 centuries. Monaural acoustical measurements (RT, EDT, C80, D50, TS, L, and RASTI) were taken at several source/receiver locations in each church. A group of college students was asked to judge the intelligibility of speech by evaluating live speech at similar locations in each room. This paper complements those presented at the 1996 Indianapolis and Honolulu ASA Meetings and concentrates exclusively on the relationships of the speech intelligibility averaged values with the objective room acoustics measures and with some architectural features of the churches. The averaged results by church are graphed and analyzedby comparisons. Correlation analyses and statistical modeling identified some relationships among the measures. For instance, squared cor- relation coefficients (R2) of 0.67 were found for the relationships: SPEECH-RT AND SPEECH-TS. Between SPEECH and RASTI only a maximum R2 of 0.50 was found. Regarding the churches’ architectural features, the maximum R2 found was 0.52 between SPEECH and NAVE HEIGHT. A general linear model including several architectural features increased the R2 to 0.72. [Work supported by FEUP and ESMAE/IPP–Portugal.] [See NOISE-CON Proceedings for full paper.]
Dichotic beats of mistuned consonances
Authors: Feeney M. Patrick
Published: July 2002

The beats of mistuned consonances (BMCs) result from the presentation of two sinusoids at frequencies slightly mistuned from a ratio of small integers. Several studies have suggested that the source of dichotic BMCs is an interaction within a binaural critical band. In one case the mechanism has been explained as an aural harmonic of the low-frequency tone (f1) creating binaural beats with the high-frequency tone (f2). The other explanation involves a binaural cross correlation between the excitation pattern of f1 and the contralateral f2 occurring within the binaural critical band centered at f2. This study examined the detection of dichotic BMCs for the octave and fifth. In one experiment with the octave, narrow-band noise centered at f2 was presented to one ear along with f1. The other ear was presented with f2. The noise was used to prevent interactions in the binaural critical band centered at f2. Dichotic BMCs were still detected under these conditions, suggesting that binaural interaction within a critical band does not explain the effect. Localization effects were also observed under this masking condition for phase reversals of tuned dichotic octave stimuli. These findings suggest a new theory of dichotic BMCs as a between-channel phase effect. The modified weighted-image model of localization [Stern and Trahiotis, in Auditory Physiology and Perception, edited by Y. Cazals, L. Demany, and K. Horner (Pergamon, Oxford, 1992), pp. 547–554] was used to provide an explanation of the between-channel mechanism.
The influence of low-frequency instrumentation response on rocket noise metrics
Authors: McInerny Sally A. , Francine Jan K. , Stewart Brent S. , Thorson Philip H.
Published: July 2002

The influence of the low-frequency roll-off and phase distortion of sound level meters (SLMs) on rocket noise metrics based on measured data is studied. Specifically, during the take-off of a space launch vehicle (SLV) called the Taurus, environmental sound pressure was measured with a carrier microphone system. This system has a virtually flat frequency response at low frequencies. In this study, the low-frequency response of SLMs was simulated using high pass filters. Two sets of filters with the same response magnitude were used: with and without phase distortion. It was shown that, for SLVs with small engines (e.g., the Delta, Scout, and Taurus), the low-frequency distortion resulting from measurements with (simulated) SLMs is apparent only in sound pressure power spectral densities (PSDs) of high resolution at frequencies below 10 Hz. This is where PSD levels are already more than 10 dB below the peak levels. There is no significant effect on the skewness of the time domain data nor on the time-energy averaged sound pressure level (SPL). It is shown that for SLVs with large engines the low-frequency response of the typical SLM results in a significant increase in the skewness of the data as peak (positive) shock pressures are increased. Comparisons of the effects of the two high pass filters indicate that the phase of the frequency response is a critical factor in the distortion of the data.
Harmonic Green’s functions of a semi-infinite plate with clamped or free edges
Authors: Gunda R. , Vijayakar S. M. , Singh R. , Farstad J. E.
Published: July 2002

Harmonic Green’s functions for a thin semi-infinite plate with clamped or free edges are developed starting from either simply supported or roller supported solutions and applying corrections to account for boundary excitation. This is achieved by connecting the solutions in terms of polar coordinates with the solutions in Cartesian coordinates. The formal solutions in the form of improper wave-number integrals are numerically evaluated using adaptive Clenshaw–Curtis integration. Alternate solutions obtained for each boundary condition compare well. Only harmonic point loads are considered in this article but the methodology may be extended to moment excitation and distributed loads. The methodology developed here will form the basis for advancing the ray tracing technique for vibration analysis of finite plates.
Modeling interaural-delay sensitivity to frequency modulation at high frequencies
Authors: Saberi Kourosh
Published: July 2002

Interaural-delay sensitivity to high-frequency (⩾3 kHz) sinusoidal-frequency-modulated (SFM) tones is examined for rates from 25 to 800 Hz and depths of −12 to 18 dB. Comparison is made to thresholds obtained for sinusoidal-amplitude-modulated (SAM) tones for the same observers and modulation rates. Both SAM and SFM threshold-by-rate functions are U-shaped with optimum sensitivity to SFM tones occurring at higher rates (fm=200–400 Hz) compared to those for SAM tones (fm=100–200 Hz). Effects of modulation depth were examined for rates from 50 to 300 Hz. In all cases thresholds improved considerably with increasing modulation depth. It is also shown that a hybrid dichotic signal composed of an SFM tone presented to one ear and an SAM tone to the other, can perceptually fuse and be lateralized, with the contingency that both stimuli have equal modulation rates but not necessarily equal carrier frequencies. Using bandpass noise to restrict off-frequency listening, it was shown that for this stimulus, observers can use information from filters either below or above the carrier frequency. Consistent with FM-to-AM conversion from cochlear bandpass filtering, several important differences between the SAM- and SFM-tone data can be predicted from a nonstationary stochastic model of binaural interaction whose parameters are uniquely determined from the SAM-tone data.
An explicit integral formulation for transient acoustic radiation
Authors: Hu Qiang , Wu Sean F.
Published: July 2002

An explicit integral formulation is derived for predicting transient acoustic radiation. The radiated acoustic pressure is shown to be expressible as a sum of integrals over simple and doublet sources and their couplings induced by the normal and tangential components of the particle velocity, which can be measured by a nonintrusive laser velocimeter. Such an integral formulation is computationally advantageous in that solutions thus obtained are unique, and the efficiency of numerical computations is high. This is because the radiated acoustic pressure is expressed as an explicit integral of known quantities, which can be readily implemented numerically by using the Gaussian quadratures. For arbitrary time-dependent excitations, the radiated acoustic pressure can be written as a sum of convolution integrals of impulse response functions over the time history of the particle velocity specified on the control surface. Validations of this integral formulation are demonstrated both analytically and numerically for acoustic radiation from an explosively expanding sphere, sudden accelerating spheres, disks, and right circular cylinders.
The radiating near-field asymptotics of a normal time-harmonic circular ultrasonic transducer in an elastic half-space
Authors: Fradkin Larissa Ju. , Kiselev Aleksei P. , Krylova Eugenia
Published: July 2002

The modern diffraction theory is applied to analyze the radiating near zone of a normal time-harmonic circular transducer directly coupled to a homogeneous and isotropic solid. The two-tier asymptotic approach is used first to find the far-field asymptotics of a point source and then the radiating near-field asymptotics of the circular transducer. All the known ray-theoretical solutions for body waves, such as the plane P wave and the toroidal edge waves, both P and S, are obtained. The non-ray-theoretical solutions, such as the edge waves present in the axial boundary layer and the total field inside the penumbral boundary layer, are also described. The asymptotic formulas produced all have immediate physical interpretation, give explicit dependence on model parameters and involve in geometrical region elementary functions and inside boundary layers, well-known special functions. It is argued that asymptotic results may be used to write computer codes which simulate the radiating near field of the circular transducer orders of magnitude faster than the exact numerical schemes, but more accurately than other known approximations.
Missing-data model of vowel identification
Authors: de Cheveigné Alain , Kawahara Hideki
Published: July 2002

Vowel identity correlates well with the shape of the transfer function of the vocal tract, in particular the position of the first two or three formant peaks. However, in voiced speech the transfer function is sampled at multiples of the fundamental frequency (F0), and the short-term spectrum contains peaks at those frequencies, rather than at formants. It is not clear how the auditory system estimates the original spectral envelope from the vowel waveform. Cochlear excitation patterns, for example, resolve harmonics in the low-frequency region and their shape varies strongly with F0. The problem cannot be cured by smoothing: lag-domain components of the spectral envelope are aliased and cause F0-dependent distortion. The problem is severe at high F0’s where the spectral envelope is severely undersampled. This paper treats vowel identification as a process of pattern recognition with missing data. Matching is restricted to available data, and missing data are ignored using an F0-dependent weighting function that emphasizes regions near harmonics. The model is presented in two versions: a frequency-domain version based on short-term spectra, or tonotopic excitation patterns, and a time-domain version based on autocorrelation functions. It accounts for the relative F0-independency observed in vowel identification.
Report on the second International Round Robin on Room Acoustical Computer Simulation
Authors: Bork Ingolf
Published: July 2002

A Swedish concert hall with a volume of about 11 000 cubic meters served as a test object to compare the performance properties of room simulation software programs. In six octave bands and at 12 source–receiver combinations, nine acoustic parameters defined in ISO 3382 had to be calculated. In the first phase of this round robin only the geometry and a written description of the acoustically relevant properties were given, while in the second phase absorption and diffusion coefficients of the surfaces were prescribed for each octave band. The results obtained by the 16 participants from nine countries will be discussed and compared with measurements performed in the hall. The analysis of the discrepancies and the high variance of the calculated data show that the influence of the software user cannot be neglected and a high degree of practical experience in room acoustics is required to produce optimal results.
On the radiation of ultrasound into an isotropic elastic half-space via wavefront expansions of the impulse response
Authors: Gridin Dmitri
Published: July 2002

The problem of propagation of pulses in the radiating near zone of a large circular normal transducer directly coupled to a homogeneous and isotropic elastic half-space is re-visited. It is shown that for certain observation angles the impulse response approach is computationally inefficient. A new method based on the so-called wavefront expansions of the impulse response is developed instead. The expansions are obtained by the analytical harmonic synthesis of the high-frequency asymptotics of the transducer field. Unlike these asymptotics the wavefront expansions are expressed in terms of elementary functions only. The direct P, edge P and S waves as well as the transition regions (penumbra and axial region) are described. The uniform asymptotic expansions applicable throughout the radiating near zone are derived as well. The code based on the time convolution of the pressure input function with the wavefront expansions is compared to a direct numerical code. It is thousands of times faster but practically just as accurate except that the phenomena related to the head waves are not described. Formulas pertaining to the far field are also offered.
A frequency domain stereophonic acoustic echo canceler exploiting the coherence between the channels
Authors: Benesty Jacob , Gilloire André , Grenier Yves
Published: July 2002

Stereophonic acoustic echo cancellation (AEC) is typically intended for use in high quality teleconferencing systems and multiparticipant desktop conferencing that implement sound transmission through two channels. Because of the high correlation between the two channel signals, rapidly converging adaptive filter algorithms (such as the two-channel fast recursive least-squares—FRLS) are required. In this paper, we propose a new and efficient frequency domain adaptive algorithm that achieves this goal.
Single sensor source tracking and environmental inversion
Authors: Unpingco Jose , Kuperman William A. , Hodgkiss William S. , Hecht-Nielsen Robert
Published: July 2002

A method is introduced for using a single underwater sensor and knowledge of a shallow water environment to track a moving, multi-frequency, acoustic source. The motion of the source creates a synthetic aperture that is adaptively matched against an acoustic propagation model in a manner similar to matched field processing. However, in this case, many more unknowns must simultaneously be determined. Results are presented for tracking using experimental data subject to unknown source speed, heading, level, and initial position. A new parallel adaptive method manages these simultaneous unknowns. Perturbations in the sound speed based on empirical orthogonal functions are used to extend the approach to operating when there also is uncertainty in this parameter. The performance of the tracking process with hydrophone data for various signal-to-noise cases is considered.
Correlated cortical populations can enhance sound localization performance
Authors: Jenison Rick L.
Published: July 2002

Neurons within cortical populations often evidence some degree of response correlation. Correlation has generally been regarded as detrimental to the decoding performance of a theoretical vector-averaging observer making inferences about the physical world—for example, an observer estimating the location of a sound source. However, if an alternative decoder is considered, in this case a Maximum Likelihood estimator, performance can improve when responses in the population are correlated. Improvement in sound localization performance is demonstrated analytically using Fisher information, and is also shown using Monte Carlo simulations based on recordings from single neurons in cat primary auditory cortex.
Directive line source model: A new model for sound diffraction by half planes and wedges
Authors: Menounou Penelope , Busch-Vishniac Ilene J. , Blackstock David T.
Published: July 2002

A new method termed Directive Line Source Model (DLSM) is presented for predicting the diffracted field produced by a sound wave incident on a rigid or pressure release half plane. In the new method the edge of the half plane is modeled as an infinite set of directive point sources continuously distributed along the edge. Because DLSM is fast, simple and intuitive, it is a promising tool for the study of diffraction. It can be applied for several types of incident radiation: omnidirectional cylindrical and spherical waves, plane waves, as well as waves from directional sources. Wedges may also be treated. Finally, DLSM can handle diffraction by an arbitrarily shaped edge profile, for example, a half plane having an edge that is jagged instead of straight. Results for plane, cylindrical and spherical incident waves, as well as for arrays of line and point sources, are presented and their agreement with known analytical solutions is demonstrated. Predictions based on DLSM compare favorably with experimental data.
Approximations for modal coupling in scattered fields from orifices
Authors: Horner J. L. , Lyons R. , Petersson B. A. T.
Published: July 2002

Previous investigations have used Hankel transforms to establish the velocity potentials of the wave fields resulting from arbitrary angle plane wave impingement on a circular orifice in a rigid, thick wall. The scattered field from the orifice is examined, in particular the modal contributions to the amplitude of its velocity potential. For each m,n mode the amplitude is dependent upon the amplitude of the in-orifice waves and a driving term unique to each m,n mode. In establishing the amplitudes of the in-orifice waves, the effects of modal coupling are also considered. In this work these two components of the scattered wave amplitude are investigated on a modal basis and approximations given for coupling effects. These approximations are then used to calculate the scattered field and the results compared with conventional solutions that use full modal coupling.
On acoustic scattering by a shell-covered seafloor
Authors: Stanton Timothy K.
Published: July 2002

Acoustic scattering by the seafloor is sometimes influenced, if not dominated, by the presence of discrete volumetric objects such as shells. A series of measurements of target strength of a type of benthic shelled animal and associated scattering modeling have recently been completed (Stanton et al., “Acoustic scattering by benthic and planktonic shelled animals,” J. Acoust. Soc. Am., this issue). The results of that study are used herein to estimate the scattering by the seafloor with a covering of shells at high acoustic frequencies. A simple formulation is derived that expresses the area scattering strength of the seafloor in terms of the average reduced target strength or material properties of the discrete scatterers and their packing factor (where the reduced target strength is the target strength normalized by the geometric cross section of the scatterers and the averaging is done over orientation and/or a narrow range of size or frequency). The formula shows that, to first order, the backscattering at high acoustic frequencies by a layer of shells (or other discrete bodies such as rocks) depends principally upon material properties of the objects and packing factor and is independent of size and acoustic frequency. Estimates of area scattering strength using this formula and measured values of the target strength of shelled bodies from Stanton et al. (this issue) are close to or consistent with observed area scattering strengths due to shell-covered seafloors published in other papers.
Calculation of the Dynamic Moduli of Linear Viscoelastic Materials from Vibrating Reed Measurements
Authors: Shroff Ramesh N.
Published: July 2002

The direct relation between the complex longitudinal modulus E* and the experimentally measured quantities—the amplitude ratio A and phase angle φ—has been derived for the forced vibrating reed instrument and is given by: exp (iφ)/A=1+∑K=1∞(−ω2ρ/E*)K[AK+BKρ−1+CKρ−2+….], where terms in ρ with negative exponents are not admitted. E* is equal to E′+iE″, where E′ is the longitudinal storage modulus and E″ is the longitudinal loss modulus. A is the ratio of the amplitude of the free end of the reed—either loaded with a pin or unloaded—to that of the clamped sinusoidally driven end and φ is the angle by which the former lags the latter. In practice, the sample dimensions and frequency range are chosen such that the sum in the above equation is rapidly convergent. The dynamic moduli then can be calculated by including only up to the first two or three terms in the sum. Where phase measurements are relatively inconvenient to make and when all but the first term under the sum can be neglected, the equation can be used to calculate dynamic moduli from two amplitude measurements at the same frequency for reeds of two different lengths; or from amplitude at resonance alone, provided E″≪E′. Illustrative examples are given. The procedures for calculating the dynamic moduli are applicable to the data obtained in all experiments where a relation of the form given above is obtained.
Anomalous Heat Transfer and a Wave Phenomenon in Dilute Polymer Solutions
Authors: Ultman J. S. , Denn M. M.
Published: July 2002

The onset of anomalous heat and momentum transfer at low Reynolds Numbers in dilute polymer solutions is shown to occur at the shear wave velocity, in agreement with a simple hydrodynamic model of the flow. The model also predicts the experimentally observed constant transport properties for velocities in excess of the wave velocity.
Some Methods for Estimating the Normal Stress Functions in Viscometric Flows
Authors: Tanner R. I.
Published: July 2002

Two new methods for finding the second normal stress difference are proposed; one depends on an analysis of edge effects in a cone-plate device, the other depends on the shape of the free surface in an open-channel flow. Additionally, the effect of the edge conditions on the total thrust in a cone-plate device is considered carefully. Some possible errors in the interpretation of these measurements is found. For two solutions (polyisobutylene/cetane, polyethylene-oxide/water) the viscometric functions are presented. In both cases the second normal stress difference was found to be negative, in contrast to some earlier conclusions.
Viscoelastic Properties of a Rubber Vulcanizate Under Large Deformations in Equal Biaxial Tension, Pure Shear, and Simple Tension
Authors: Dickie Ray A. , Smith Thor L.
Published: July 2002

Stress-strain data were determined on an unfilled styrene-butadiene rubber vulcanizate in equal biaxial tension (EBT) at deformations up to rupture. Tests were made at temperatures from −43° to 90°C and at extension rates from 0.15 to 4 min−1. The data are represented in terms of a time- and temperature-independent function, Ω(χ), the reduced modulus, T0F(t/aT)/T, and the maximum extensibility, λm(t/aT), the latter two quantities being functions of the temperature-reduced time, t/aT. The function Ω(χ) gives the stress-strain relationship for the material in a reference state for which the modulus is unity and λm=λm0, the equilibrium value. The maximum extensibility equals the extension ratio at which the slope of a stress-strain curve from isochronal data becomes infinite; it cannot be measured directly because rupture always occurs at an extension less than λm. Data from extensive tests in simple tension (ST) have been reported previously, as well as data in pure shear (constrained biaxial tension, CBT) at 1<λ<2.5, where λ is the extension ratio. The three Ω(χ) functions, which represent stress-strain behavior in ST, CBT, and EBT, were considered in terms of the Valanis-Landel theory of finite elasticity, which is based on the assumed validity of the strain-energy function W=ω(λ1)+ω(λ2)+ω(λ3). In this way, the characteristic function λω′(λ)/F was evaluated over the range 0.028<λ<7.5. From this function along with the modulus, the stress-strain behavior in any pure homogeneous deformations can be calculated readily over extended ranges of temperature and extension rate. Because λm(t/aT) depends somewhat on the type of deformation (λm0 in ST is at least 30% greater than in EBT), data at very large deformations under an arbitrary pure homogeneous deformation can be derived only if λm is known as a function of both t/aT and the type of deformation.
Further Studies of Fluid Nonlinearity: The Orthogonal Rheometer and the Oscillating Sphere
Authors: Goldstein Charles , Schowalter W. R.
Published: July 2002

Nonlinear effects have been considered in computations of orthogonal rheometer flow and in flow caused by the oscillation of a sphere in an unbounded fluid. Predictions of fluid response, based on a Bird-Carreau constitutive model, are qualitatively different from those which follow from linear theory. Of particular interest are the corrections to force components in the orthogonal rheometer analysis and the generation of a steady secondary flow in the oscillating sphere problem. Magnitudes of these nonlinear effects are presented for a variety of fluid and flow parameters.
Orientation of long bodies falling in a viscoelastic liquid
Authors: Joseph Daniel D. , Liu Yaoqi Joe
Published: July 2002

New experiments on the orientations of a cylinder settling in viscoelastic and pseudoplastic fluids are described in an attempt to identify the main mechanisms which control the orientation of the cylinder as it falls.
Validity of separable BKZ model for large amplitude oscillatory shear
Authors: Giacomin A. J. , Jeyaseelan R. S. , Samurkas T. , Dealy J. M.
Published: July 2002

Large amplitude oscillatory shear (LAOS) is a useful tool for the study of nonlinear viscoelasticity in polymeric liquids. To concisely describe the response of a material to such a test, it is desirable to make use of a constitutive equation. In this way, the response can be described in terms of the parameters of the rheological model. We have found a separable BKZ model, e.g., Wagner’s equation, to be useful in this regard for LDPE IUPAC X. The damping function determined in step shear experiments does not lead to accurate predictions of the LAOS response. For a given low frequency, however, it is possible to fit the parameters of a simple damping function equation to the LAOS response at one strain amplitude and to use these parameter values to reliably predict the response at other strain amplitudes. Thus, the Wagner equation provides a basis for the concise description of the response of LDPE IUPAC X to large amplitude oscillatory shear experiments at low frequencies. Conversely, it was found that the response of a HDPE melt to large amplitude oscillatory shear cannot be concisely described by the Wagner equation.
Hypercalcemia
Authors: Walker Marcella Donovan , Shane Elizabeth
Published: October 2022

Importance

Hypercalcemia affects approximately 1% of the worldwide population. Mild hypercalcemia, defined as total calcium of less than 12 mg/dL (<3 mmol/L) or ionized calcium of 5.6 to 8.0 mg/dL (1.4-2 mmol/L), is usually asymptomatic but may be associated with constitutional symptoms such as fatigue and constipation in approximately 20% of people. Hypercalcemia that is severe, defined as total calcium of 14 mg/dL or greater (>3.5 mmol/L) or ionized calcium of 10 mg/dL or greater (≥2.5 mmol/L) or that develops rapidly over days to weeks, can cause nausea, vomiting, dehydration, confusion, somnolence, and coma.

Observations

Approximately 90% of people with hypercalcemia have primary hyperparathyroidism (PHPT) or malignancy. Additional causes of hypercalcemia include granulomatous disease such as sarcoidosis, endocrinopathies such as thyroid disease, immobilization, genetic disorders, and medications such as thiazide diuretics and supplements such as calcium, vitamin D, or vitamin A. Hypercalcemia has been associated with sodium-glucose cotransporter 2 protein inhibitors, immune checkpoint inhibitors, denosumab discontinuation, SARS-CoV-2, ketogenic diets, and extreme exercise, but these account for less than 1% of causes. Serum intact parathyroid hormone (PTH), the most important initial test to evaluate hypercalcemia, distinguishes PTH-dependent from PTH-independent causes. In a patient with hypercalcemia, an elevated or normal PTH concentration is consistent with PHPT, while a suppressed PTH level (<20 pg/mL depending on assay) indicates another cause. Mild hypercalcemia usually does not need acute intervention. If due to PHPT, parathyroidectomy may be considered depending on age, serum calcium level, and kidney or skeletal involvement. In patients older than 50 years with serum calcium levels less than 1 mg above the upper normal limit and no evidence of skeletal or kidney disease, observation may be appropriate. Initial therapy of symptomatic or severe hypercalcemia consists of hydration and intravenous bisphosphonates, such as zoledronic acid or pamidronate. In patients with kidney failure, denosumab and dialysis may be indicated. Glucocorticoids may be used as primary treatment when hypercalcemia is due to excessive intestinal calcium absorption (vitamin D intoxication, granulomatous disorders, some lymphomas). Treatment reduces serum calcium and improves symptoms, at least transiently. The underlying cause of hypercalcemia should be identified and treated. The prognosis for asymptomatic PHPT is excellent with either medical or surgical management. Hypercalcemia of malignancy is associated with poor survival.

Conclusions and Relevance

Mild hypercalcemia is typically asymptomatic, while severe hypercalcemia is associated with nausea, vomiting, dehydration, confusion, somnolence, and coma. Asymptomatic hypercalcemia due to primary hyperparathyroidism is managed with parathyroidectomy or observation with monitoring, while severe hypercalcemia is typically treated with hydration and intravenous bisphosphonates.
When Is a Placebo Not a Placebo
Authors: Nissen Steven E.
Published: October 2022

This Viewpoint discusses the concerns about using mineral oil as a placebo.
Estimates of SARS-CoV-2 Omicron BA.2 Subvariant Severity in New England
Authors: Strasser Zachary H. , Greifer Noah , Hadavand Aboozar , Murphy Shawn N. , Estiri Hossein
Published: October 2022

Importance

The SARS-CoV-2 Omicron subvariant, BA.2, may be less severe than previous variants; however, confounding factors make interpreting the intrinsic severity challenging.

Objective

To compare the adjusted risks of mortality, hospitalization, intensive care unit admission, and invasive ventilation between the BA.2 subvariant and the Omicron and Delta variants, after accounting for multiple confounders.

Design, Setting, and Participants

This was a retrospective cohort study that applied an entropy balancing approach. Patients in a multicenter inpatient and outpatient system in New England with COVID-19 between March 3, 2020, and June 20, 2022, were identified.

Exposures

Cases were assigned as being exposed to the Delta (B.1.617.2) variant, the Omicron (B.1.1.529) variant, or the Omicron BA.2 lineage subvariants.

Main Outcomes and Measures

The primary study outcome planned before analysis was risk of 30-day mortality. Secondary outcomes included the risks of hospitalization, invasive ventilation, and intensive care unit admissions.

Results

Of 102 315 confirmed COVID-19 cases (mean [SD] age, 44.2 [21.6] years; 63 482 women [62.0%]), 20 770 were labeled as Delta variants, 52 605 were labeled as the Omicron B.1.1.529 variant, and 28 940 were labeled as Omicron BA.2 subvariants. Patient cases were excluded if they occurred outside the prespecified temporal windows associated with the variants or had minimal longitudinal data in the Mass General Brigham system before COVID-19. Mortality rates were 0.7% for Delta (B.1.617.2), 0.4% for Omicron (B.1.1.529), and 0.3% for Omicron (BA.2). The adjusted odds ratio of mortality from the Delta variant compared with the Omicron BA.2 subvariants was 2.07 (95% CI, 1.04-4.10) and that of the original Omicron variant compared with the Omicron BA.2 subvariant was 2.20 (95% CI, 1.56-3.11). For all outcomes, the Omicron BA.2 subvariants were significantly less severe than that of the Omicron and Delta variants.

Conclusions and Relevance

In this cohort study, after having accounted for a variety of confounding factors associated with SARS-CoV-2 outcomes, the Omicron BA.2 subvariant was found to be intrinsically less severe than both the Delta and Omicron variants. With respect to these variants, the severity profile of SARS-CoV-2 appears to be diminishing after taking into account various factors including therapeutics, vaccinations, and prior infections.
Spillover and crossover effects of exposure to work‐related aggression and adversities: A dyadic diary study
Authors: Herrmann Alexander , Glaser Jürgen , Greitemeyer Tobias
Published: October 2022

The past two decades have produced extensive evidence on the manifold and severe outcomes for victims of aggression exposure in the workplace. However, due to the dominating individual‐centered approach, most findings miss a social network perspective. Consequently, knowledge of negative spillover to different life‐domains or crossover to uninvolved individuals alongside a detailed understanding of the involved transmission processes remains scarce. By integrating social aggression theorizing, the present study investigated transmission routes (emphatic, behavioral) of experienced adversities and aggression at work toward perpetration of aggressive behavior and potential spillover and crossover effects into the private life domain in a diary study of 72 mixed dyads. Analyses of mediation based upon the Actor‐Partner Interdependence Model revealed an association between the frequency of perpetrating aggressive behavior in the work context and a spillover into the private life domain via aggression‐promoting internal states (emotions, cognitions, arousal). Based on the different patterns of mediation, it appears that adversities follow a mental transmission process, whereby experienced aggression displayed behavioral assimilation. In contrast, no crossover effects of exposure to adversities or aggression at work to a study partner at home could be detected. Practical and theoretical implications as well as limitations and ideas for future work are discussed.
Second‐order optimization methods for time‐delay Autoregressive eXogenous models: Nature gradient descent method and its two modified methods
Authors: Chen Jing , Pu Yan , Guo Liuxiao , Cao Junfeng , Zhu Quanmin
Published: October 2022

This article proposes several second‐order optimization methods for time‐delay ARX model. Since the time‐delay in the information vector makes the traditional identification algorithms be inefficient, a redundant rule based method is utilized to transformed the model into a redundant model. Then, the nature gradient descent (NGD) algorithm is developed for such a model. To reduce the computational efforts of the NGD algorithm and to adaptively update each element in the parameter vector, two modified NGD algorithms are also presented. The simulation examples verify the effectiveness of the proposed algorithms.
Effect of Pulsed Laser Irradiation on Microstructure and Evolution of Residual Stress for Gold Film
Authors: Zhou Shujun , Wu Wei , Huang Xiao , Shao Tianmin , Shao Meng
Published: October 2022

Gold film is extensively used in a variety of electronic, optical, and magnetic instruments or devices. Effect of pulsed laser irradiation on microstructure and evolution of residual stress for gold film is studied. Gold film deposited on a silica substrate is irradiated by pulsed laser with different energy densities. Microstructures of the gold film before and after laser irradiation are studied by using scanning electron microscope, scanning transmission electron microscope, and energy‐dispersive X‐ray spectrometry. Recrystallization occurs during laser irradiation. Most of the original defects in the as‐deposited gold film are eliminated, and the films become smooth and more compact after laser irradiation. Curvature‐based technique using Stoney formula is applied to evaluate the residual stress. Pulsed laser irradiation results in the increase in tensile residual stress and stability of the residual stress.
Recent Advances in Lead‐Safe Perovskite Solar Cells
Authors: Gao Yushuang , Hu Yanqiang , Yao Changlin , Zhang Shufang
Published: October 2022

Perovskite solar cells (PSCs) have made unprecedented progress in improving power conversion efficiency in the past decade, and they are considered as one of the most promising photovoltaic technologies. However, the commercialization of PSCs still faces significant challenges, such as the stability issue and toxicity of lead. Recently, pursuing ways to alleviate the toxicity of lead has emerged as an attractive research direction in the community of PSCs. In this review, the discussion is on the toxicity of lead and the impact of lead leakage from perovskites to the environment, the recent progress made to reduce the leakage of lead is presented with an emphasis on the lead sequestration materials applied in encapsulation layers and functional layers of PSCs, and the recovery of lead from damaged or decommissioned PSC devices is concisely summarized. This review may serve as a guide for researchers interested in promoting PSCs from exploitation to application.
Revealing Intrinsic Superconductivity of the Nb/BiSbTe2Se Interface
Authors: Kudriashov Andrei , Babich Ian , Hovhannisyan Razmik A. , Shishkin Andrey G. , Kozlov Sergei N. , Fedorov Alexander , Vyalikh Denis V. , Khestanova Ekaterina , Kupriyanov Mikhail Yu. , Stolyarov Vasily S.
Published: October 2022

Typically, topological superconductivity is reachable via proximity effect by a direct deposition of superconductor (S) on top of a topological insulator (TI) surface. Here, the double critical current in the Josephson junctions based on the topological insulator is observed in the fabricated planar Superconducting Quantum Interference Devicea. By measuring critical currents as a function of temperature and magnetic field, it is shown that the second critical current stems from the intrinsic superconductivity of the S–TI interface, which is supported by the modified Resistively Shunted Junction model and Transmission Electron Microscopy studies. This complex structure of the interface should be taken into account when the technological process involves Ar‐plasma cleaning.