bluuebunny/crossref_metadata_2025 huggingface dataset:
Student understanding of the first law of thermodynamics: Relating work to the adiabatic compression of an ideal gas
Authors: Loverude Michael E. , Kautz Christian H. , Heron Paula R. L.
Published: July 2002

We report on an investigation of student understanding of the first law of thermodynamics. The students involved were drawn from first-year university physics courses and a second-year thermal physics course. The emphasis was on the ability of the students to relate the first law to the adiabatic compression of an ideal gas. Although they had studied the first law, few students recognized its relevance. Fewer still were able to apply the concept of work to account for a change in temperature in an adiabatic process. Instead most of the students based their predictions and explanations on a misinterpretation of the ideal gas law. Even when ideas of energy and work were suggested, many students were unable to give a correct analysis. They frequently failed to differentiate the concepts of heat, temperature, work, and internal energy. Some of the difficulties that students had in applying the concept of work in a thermal process seemed to be related to difficulties with mechanics. Our findings also suggest that a misinterpretation of simple microscopic models may interfere with student ability to understand macroscopic phenomena. Implications for instruction in thermal physics and in mechanics are discussed.
Circular motion
Authors: Newton Isaac , Henry Richard Conn
Published: July 2002

An extraordinarily simple and transparent derivation of the formula for the acceleration that occurs in uniform circular motion is presented, and is advocated for use in high school and college freshman physics textbooks.
Sources of listener disagreement in voice quality assessment
Authors: Kreiman Jody , Gerratt Bruce R.
Published: July 2002

Traditional interval or ordinal rating scale protocols appear to be poorly suited to measuring vocal quality. To investigate why this might be so, listeners were asked to classify pathological voices as having or not having different voice qualities. It was reasoned that this simple task would allow listeners to focus on the kind of quality a voice had, rather than how much of a quality it possessed, and thus might provide evidence for the validity of traditional vocal qualities. In experiment 1, listeners judged whether natural pathological voice samples were or were not primarily breathy and rough. Listener agreement in both tasks was above chance, but listeners agreed poorly that individual voices belonged in particular perceptual classes. To determine whether these results reflect listeners’ difficulty agreeing about single perceptual attributes of complex stimuli, listeners in experiment 2 classified natural pathological voices and synthetic stimuli (varying in f0 only) as low pitched or not low pitched. If disagreements derive from difficulties dividing an auditory continuum consistently, then patterns of agreement should be similar for both kinds of stimuli. In fact, listener agreement was significantly better for the synthetic stimuli than for the natural voices. Difficulty isolating single perceptual dimensions of complex stimuli thus appears to be one reason why traditional unidimensional rating protocols are unsuited to measuring pathologic voice quality. Listeners did agree that a few aphonic voices were breathy, and that a few voices with prominent vocal fry and/or interharmonics were rough. These few cases of agreement may have occurred because the acoustic characteristics of the voices in question corresponded to the limiting case of the quality being judged. Values of f0 that generated listener agreement in experiment 2 were more extreme for natural than for synthetic stimuli, consistent with this interpretation.
Evidence for a behavioral significance of saccular acoustic sensitivity in humans
Authors: Todd Neil
Published: July 2002

In this article the results are reported of an experiment to provide direct evidence for a perceptual and behavioral significance of human saccular acoustic sensitivity. Ten human subjects were stimulated monaurally with 100-ms trains of 10-ms tone pulses with pulse repetition rate of 40 Hz, and were required to rate the pleasantness of the stimuli on a nine-point scale. The design included three within-subject factors: carrier frequency (two levels, 200 and 4000 Hz), intensity [13 levels from 55 to 115 dB(A) in 5-dB steps] and ear (left and right). For intensities above 90 dB myogenic vestibular evoked potentials (MVEP) were also obtained from the ipsilateral sternocleidomastoid muscle from which it was possible to obtain thresholds by linear regression of MVEP amplitudes against intensity. A further between-subjects factor was added which assessed subjects’ attitude to vestibular sensations. The results indicate that across subjects there is a general trend of decreasing pleasantness with increasing intensity, but for the 200-Hz condition there is a significant positive departure from monotonicity in pleasantness (p<0.05) above the mean saccular threshold. However, when split by the between-subjects factor, the positive departure was only evident for those subjects who have a positive attitude to vestibular sensations (p<0.01). Implications of these results for human responses to loud sound and the possible evolutionary significance of saccular acoustic sensitivity are discussed.
Systematic distortions of auditory space perception following prolonged exposure to broadband noise
Authors: Carlile Simon , Hyams Stephanie , Delaney Skye
Published: July 2002

Perceptual distortions referred to as aftereffects may arise following exposure to an adapting sensory stimulus. The study of aftereffects has a long and distinguished history [Köhler and Wallach, Proc. Am. Philos. Soc. 88, 269–359 (1944)] and a range of aftereffects have been well described in sensory modalities such as the visual system [Barlow, in Vision: Coding and Efficiency (Cambridge University Press, Cambridge, 1990)]. In the visual system these effects have been interpreted as evidence for a population of cells or channels specific for certain features of a stimulus. However there has been relatively little work examining auditory aftereffects, particularly in respect of spatial location. In this study we have examined the effects of a stationary adapting noise stimulus on the subsequent auditory localization in the vicinity of the adapting stimulus. All human subjects in this study were trained to localize short bursts of noise in a darkened anechoic environment. Adaptation was achieved by presenting 4 min of continuous noise at the start of each block of trials and was maintained by a further 15-s noise burst between each trial. The adapting stimulus was located either directly in front of the subject or 30° to the right of the midline. Subjects were required to determine the location of noise burst stimuli (150 ms) in the proximity of the adapting stimulus following each interstimulus period of adaptation. Results demonstrated that following adaptation there was a general radial displacement of perceived sound sources away from the location of the adapting stimulus. These data are more consistent with a channel-based or place-based process of sound localization rather than a simple level-based adaptation model. A simple “distribution shift” model that assumes an array of overlapping spatial channels is advanced to explain the psychophysical data.
Effect of stimulus bandwidth on the perception of /s / in normal- and hearing-impaired children and adults
Authors: Stelmachowicz Patricia G. , Pittman Andrea L. , Hoover Brenda M. , Lewis Dawna E.
Published: July 2002

Recent studies with adults have suggested that amplification at 4 kHz and above fails to improve speech recognition and may even degrade performance when high-frequency thresholds exceed 50–60 dB HL. This study examined the extent to which high frequencies can provide useful information for fricative perception for normal-hearing and hearing-impaired children and adults. Eighty subjects (20 per group) participated. Nonsense syllables containing the phonemes /s/, /f/, and /θ/, produced by a male, female, and child talker, were low-pass filtered at 2, 3, 4, 5, 6, and 9 kHz. Frequency shaping was provided for the hearing-impaired subjects only. Results revealed significant differences in recognition between the four groups of subjects. Specifically, both groups of children performed more poorly than their adult counterparts at similar bandwidths. Likewise, both hearing-impaired groups performed more poorly than their normal-hearing counterparts. In addition, significant talker effects for /s/ were observed. For the male talker, optimum performance was reached at a bandwidth of approximately 4–5 kHz, whereas optimum performance for the female and child talkers did not occur until a bandwidth of 9 kHz.
Evaluation of loudness-level weightings for assessing the annoyance of environmental noise
Authors: Schomer Paul D. , Suzuki Yoiti , Saito Fumitaka
Published: July 2002

Assessment of the annoyance of combined noise environments has been the subject of much research and debate. Currently, most countries use some form of the A-weighted equivalent level (ALEQ) to assess the annoyance of most noises. It provides a constant filter that is independent of sound level. Schomer [Acust. Acta Acust. 86(1), 49–61 (2000)] suggested the use of the equal loudness-level contours (ISO 226, 1987) as a dynamic filter that changes with both sound level and frequency. He showed that loudness-level-weighted sound-exposure level (LLSEL) and loudness-level-weighted equivalent level (LL-LEQ) can be used to assess the annoyance of environmental noise. Compared with A-weighting, loudness-level weighting better orders and assesses transportation noise sources, sounds with strong low-frequency content and, with the addition of a 12-dB adjustment, it better orders and assesses highly impulsive sounds vis-à-vis transportation sounds. This paper compares the LLSEL method with two methods based on loudness calculations using ISO 532b (1975). It shows that in terms of correlation with subjective judgments of annoyance—not loudness—the LLSEL formulation performs much better than do the loudness calculations. This result is true across a range of sources that includes aircraft, helicopters, motor vehicles, trains, and impulsive sources. It also is true within several of the sources separately.
Phased array element shapes for suppressing grating lobes
Authors: Pompei F. Joseph , Wooh Shi-Chang
Published: July 2002

Most techniques for suppressing grating lobes in phased arrays while relaxing the interelement spacing requirement involve redistributing array elements in sparse aperiodic patterns, or varying the transmit-receive beam patterns. An alternative is presented which uses oversized array elements to eliminate grating lobes as a direct consequence of the element shape. It is shown that by using carefully shaped, overlapping elements, maximum scan angle can be exchanged for a reduced interelement spacing requirement.
Smart foam for applications in passive–active noise radiation control
Authors: Gentry C. A. , Guigou C. , Fuller C. R.
Published: July 2002

The development of a smart foam for passive–active noise control is discussed. The smart foam consists of cylindrically curved sections of PVDF film embedded in partially reticulated polyurethane acoustic foam forming a very thin, compact arrangement. The device is designed to reduce sound by the simultaneous action of the passive absorption of the foam (effective at high frequencies) and the active input of the PVDF element driven by an oscillating electrical input (effective at low frequencies). The PVDF actuator is configured to behave in a linear sense and to couple in-plane strain associated with piezoelectric effect with out-of-plane motion needed to radiate sound from the foam surface. The performance of the passive–active device is studied for controlling sound radiation from a vibrating piston. A feedforward LMS controller is used to minimize the signal from a far-field error microphone. Results of harmonic and broadband control are presented. The potential of the smart foam for globally reducing sound radiation in the low- and high-frequency range is demonstrated.
Training Japanese listeners to identify English /r/ and /l/: IV. Some effects of perceptual learning on speech production
Authors: Bradlow Ann R. , Pisoni David B. , Akahane-Yamada Reiko , Tohkura Yoh’ichi
Published: July 2002

This study investigated the effects of training in /r/–/l/ perceptual identification on /r/–/l/ production by adult Japanese speakers. Subjects were recorded producing English words that contrast /r/ and /l/ before and after participating in an extended period of /r/–/l/ identification training using a high-variability presentation format. All subjects showed significant perceptual learning as a result of the training program, and this perceptual learning generalized to novel items spoken by new talkers. Improvement in the Japanese trainees’ /r/–/l/ spoken utterances as a consequence of perceptual training was evaluated using two separate tests with native English listeners. First, a direct comparison of the pretest and post-test tokens showed significant improvement in the perceived rating of /r/ and /l/ productions as a consequence of perceptual learning. Second, the post-test productions were more accurately identified by English listeners than the pretest productions in a two-alternative minimal-pair identification procedure. These results indicate that the knowledge gained during perceptual learning of /r/ and /l/ transferred to the production domain, and thus provides novel information regarding the relationship between speech perception and production.
Fluid–structure interaction of the stereocilia bundle in relation to mechanotransduction
Authors: Zetes D. E. , Steele C. R.
Published: July 2002

Current hypotheses regarding mechanotransduction rely upon motion of the stereocilia relative to the apical surface of the hair cell. The viscosity of the surrounding endolymphatic fluid will, however, attenuate stereocilia motion at higher frequencies of excitation. To investigate stereocilia motion for physiologically reasonable deflections and frequencies of excitation, the fluid–structure interaction of the stereocilia bundle is considered analytically. Solutions in the frequency domain are determined for stereocilia bundle dimensions at several locations along the cochlear duct of the chinchilla. Results indicate that motion of the stereocilia is analogous to that of a low-pass filter. Comparison of these solutions with Greenwood’s frequency-place map demonstrates that motion of the stereocilia bundle exists without substantial attenuation at least up to frequencies appropriate for the location of the corresponding hair cell along the cochlear duct. The variation in stereocilia morphology within the mammalian cochlea thus appears to provide a collection of low-pass mechanoreceptors, arranged in order of increasing corner frequency across the auditory spectrum.
Finite difference predictions of P-SV wave propagation inside submerged solids. II. Effect of geometry
Authors: Dahake Girish , Gracewski S. M.
Published: July 2002

To understand better direct stress wave contributions to stone fragmentation during extracorporeal shock wave lithotripsy (ESWL), the numerical formulation developed in part I is applied to study the time evolution of stress wave fields produced inside submerged isotropic elastic solids having irregular geometries. Cut spheres are used to model stones that have already had an initial fracture. Ellipses are used to approximate other deviations from a spherical geometry. The propagation and focusing of the longitudinal (P) and shear (S) wave fronts are visualized by presenting internal strain contours. Internal strain measurements are obtained from strain gauges embedded inside plaster specimens to confirm the focusing effect obtained from the concave back surfaces of the stones. Fragmentation experiments indicate damage caused by spalling and direct stress wave focusing as well as a front surface pit presumably created by cavitation activity.
Cross-spectral and temporal factors in the precedence effect: Discrimination suppression of the lag sound in free-fielda)
Authors: Yang Xuefeng , Grantham D. Wesley
Published: July 2002

In an anechoic chamber, subjects were required to discriminate a 20° azimuthal change in a lag sound’s position in the presence of a lead sound coming from a different direction. Delay between lead and lag sounds was adaptively varied in several conditions to track discrimination suppression thresholds. In experiment 1, lead and lag stimuli were 5-ms, 1-octave, A-weighted noise bursts (65 dB), with lead and lag parametrically set to center frequencies of 0.5, 2.0, or 3.0 kHz. Discrimination suppression thresholds were higher when lead and lag center frequencies coincided (mean: 11.3 ms) than when they did not coincide (mean: 2.9 ms). These results support the “spectral overlap hypothesis” of Blauert and Divenyi [Acustica 66, 267–274 (1988)], but not the “localization strength hypothesis” later proposed by Divenyi [J. Acoust. Soc. Am. 91, 1078–1084 (1992)]. Spectral overlap and localization strength appear to be two relatively independent factors governing discrimination suppression. It is proposed here that localization strength is weighted more when stimuli are presented via headphones and the only cue to lateral position is the interaural temporal difference, while spectral overlap is weighted more for free-field presented stimuli. In experiment 2, lead and lag stimuli were 8-ms, 1.5-kHz A-weighted tone bursts (65 dB), with lead and lag rise times parametrically set to 0, 2, or 4 ms. In this case the amount of discrimination suppression increased as lead rise time became more abrupt or as lag rise time became more gradual. These results support the localization strength hypothesis: The greater the localization strength of the lead stimulus (independently assessed by measuring its minimum audible angle in isolation), the greater suppression it exerted on discriminability of the lag sound’s position. It appears that for stimuli presented in the free-field, spectral overlap is the primary factor affecting discrimination suppression, but when overlap is held constant, abruptness of stimulus onsets governs the amount of suppression.
Implementation of transparent sources embedded in acoustic finite-difference time-domain grids
Authors: Schneider John B. , Wagner Christopher L. , Broschat Shira L.
Published: July 2002

The finite-difference time-domain (FDTD) method is a simple but powerful numerical method which has been used to perform a wide variety of complex simulations. One of the considerations in using this method is modeling the source of the incident field. When the physical source of acoustic energy is located within the FDTD grid it has typically been modeled as a “hard” source for which a source function determines the field at a source node. One drawback of a hard source is that it acts itself as a scatterer. Moreover, its scattering cross section is dictated by the spatial step size within the grid; thus, scattering is independent of the underlying physical size of the source. In this paper a scheme is presented that permits the creation of completely transparent sources. These sources, although more expensive to implement than traditional hard sources, radiate the same field as a hard source, but do not scatter energy.
Torsional waves in lossy cylinders
Authors: Carcione J. M. , Seriani G.
Published: July 2002

The pure shear problem is one of relative mathematical simplicity and includes the essential physics common to more complicated cases, where multiple and coupled deformations occur. In this sense, the analysis of torsional waves serves as a pilot problem for investigating the influence of anisotropy and/or anelasticity on solution behavior. We obtain the kinematic and dynamic properties of torsional axially symmetric harmonic waves propagating in an infinitely long circular cylinder. The medium is transversely isotropic and dissipative, with its symmetry axis coincident with the axial axis of the cylinder. For an elastic cylinder each mode has a cutoff frequency and below that frequency there is no propagation. For tubes made of quartz and aluminum Lucite, we found that the existence of the cutoff frequencies depend on the degree of anisotropic attenuation, i.e., if the axial quality factor is greater than the transverse quality factor, the modes propagate at all frequencies. In contrast to the elastic case, the Poynting vector and the energy velocity have a component along the radial direction, whose values depend on the transverse attenuation. The presence of intrinsic attenuation confines the energy near the (elastic) cutoff frequencies while the radial distribution of the energy is governed by the geometrical features of the cylinder.
Adaptive feedforward and feedback methods for active/passive sound radiation control using smart foam
Authors: Guigou C. , Fuller C. R.
Published: July 2002

This work investigates and compares the potential of adaptive feedforward and feedback methods for a hybrid active/passive radiation control using smart foam. The radiating structure is a vibrating plate mounted in a rigid baffle in an anechoic chamber. The smart foam, designed to reduce sound by the action of the passive absorption of the foam (which is effective at higher frequencies) and the active input of an embedded PVDF element driven by an oscillating electrical input (which is effective at lower frequencies), is positioned on the plate. The first test consists of using a single-input single-output (SISO) adaptive feedforward LMS controller to minimize the error sensor signal provided by a microphone in the close proximity of the active element under narrow-band excitation and broadband random excitation. For feedforward control, two different reference signals are considered: the voltage sent to the piezoceramic actuator driving the plate (disturbance) and the signal from an accelerometer directly mounted on the plate (more realistic in practice). In the latter case, the effect of the smart foam on the reference signal (or acceleration level) can be taken into account (feedback removal). An adaptive feedback controller is also implemented to avoid the use of a reference signal. In this case, a reference signal is obtained from the error signal using the internal model approach. The results from these three different control methods are compared in terms of the sound attenuation achieved. For broadband excitation, a feedforward adaptive control with an external reference is shown to be more efficient for this arrangement than a feedback adaptive control.
Matched-beam processing: Range tracking with vertical arrays in mismatched environments
Authors: Yang T. C. , Yoo Kwang , Yates T.
Published: July 2002

This paper addresses the problem of range tracking using one or more vertical arrays in certain mismatched shallow-water environments. The objective is to obtain continuous tracking of a target thereby allowing the target to be distinguished from false alarms. It is shown that bottom mismatch can cause large range errors at discrete source ranges as observed in previous experiments. Also, significant range errors (offsets) can result from unknown array tilt. Discrete range errors impede the ability to detect a target by integrating along the target track (track-before-detect) or by a probability based target detection and tracking algorithm. Large range errors impede the ability to localize and track the target from multiple vertical arrays. These problems are addressed using matched-beam processing whereby certain bottom mismatch is minimized by a beam filter and unknown array tilt is estimated by matching the measured beam pattern against the calculated one. Beam filtering and beam matching are simple and convenient methods to implement in practical systems. Comments are also given on other applications using beam domain processing.
Acoustic attenuation performance of circular flow-reversing chambers
Authors: Selamet A. , Ji Z. L.
Published: July 2002

A three-dimensional analytical approach is developed to determine the transmission loss of circular flow-reversing chambers in the absence of bulk flow. The study couples the continuity conditions of the acoustic pressure and particle velocity at the inlet and outlet with the orthogonality relations of Fourier–Bessel functions. The present analytical results are compared with the boundary element predictions to assess the approach, as well as with previous works to examine the effect of nonplanar wave decay in end ducts. The acoustic attenuation due to flow-reversing chamber is then investigated in detail as a function of the length-to-diameter ratio of the chamber and the relative locations of the inlet/outlet.
An equivalent source technique for calculating the sound field inside an enclosure containing scattering objects
Authors: Johnson M. E. , Elliott S. J. , Baek K-H. , Garcia-Bonito J.
Published: July 2002

The equivalent source method has previously been used to calculate the exterior sound field radiated or scattered from bodies in the free-field. In this paper the method is used to calculate the internal pressure field for an enclosure which can have arbitrary boundary conditions and may include internal objects which scatter the sound. Some of the equivalent source positions are chosen to be the same as the first order images of the source inside the enclosure, some are positioned within the scattering objects, and the remainder are positioned on a spherical surface some distance outside the enclosure. The normal velocity on the surfaces of the scattering objects and the enclosure walls is evaluated at a larger number of positions than there are equivalent sources. The sum of the squared difference between this velocity and that expected because of the admittance of the boundary, is minimized by adjusting the strengths of the equivalent sources. The convergence of the method is checked by evaluating the velocity at a larger number of monitoring positions. Example results are presented for the sound field and frequency response inside a damped rectangular enclosure, which compare very well with the conventional modal model. The effect of having rigid spheres inside the enclosure are then investigated, and it is found that the effect is significant even some distance from the spheres and at frequencies for which the size of the sphere is small compared to a wavelength. Finally the effect of a nonlocally reacting boundary condition is illustrated by assuming that one of the walls of the enclosure is an elastic plate.
Utterance rate and linguistic properties as determinants of lexical dysfluencies in children who stutter
Authors: Howell Peter , Au-Yeung James , Pilgrim Lesley
Published: July 2002

Two important determinants of variation in stuttering frequency are utterance rate and the linguistic properties of the words being spoken. Little is known how these determinants interrelate. It is hypothesized that those linguistic factors that lead to change in word duration, alter utterance rate locally within an utterance that then gives rise to an increase in stuttering frequency. According to the hypothesis, utterance rate variation should occur locally within the linguistic segments in an utterance that is known to increase the likelihood of stuttering. The hypothesis is tested using length of tone unit as the linguistic factor. Three predictions are confirmed: Utterance rate varies locally within the tone units and this local variation affects stuttering frequency; stuttering frequency is positively related to the length of tone units; variations in utterance rate are correlated with tone unit length. Alternative theoretical formulations of these findings are considered.
An advanced boundary element/fast Fourier transform axisymmetric formulation for acoustic radiation and wave scattering problems
Authors: Tsinopoulos Stephanos V. , Agnantiaris John P. , Polyzos Demosthenes
Published: July 2002

An advanced boundary element/fast Fourier transform (BE/FFT) methodology for solving axisymmetric acoustic wave scattering and radiation problems with non-axisymmetric boundary conditions is reported. The boundary quantities of the problem are expanded in complex Fourier series with respect to the circumferencial direction. Each of the expanding coefficients satisfies a surface integral equation which, due to axisymmetry, is reduced to a line integral along the surface generator of the body and an integral over the angle of revolution. The first integral is evaluated through Gauss quadrature by employing a two-dimensional boundary element methodology. The integration over the circumferencial direction is performed simultaneously for all the Fourier coefficients through the FFT. The singular and hyper-singular integrals are computed directly by employing highly accurate three-dimensional integration techniques. The accuracy of the proposed boundary element methodology is demonstrated by means of representative numerical examples.
Elastic contact problem of the piezoelectric material in the structure of a bolt-clamped Langevin-type transducer
Authors: Adachi Kazunari , Tsuji Masaharu , Kato Hiroshi
Published: July 2002

Bolt-clamped Langevin-type transducers (BLTs) are widely used in various fields of industrial application of high-power ultrasonics. One of the most crucial points in designing a transducer of this type is estimation of the bearing stress imposed by clamping on the interface between the metal block and the piezoelectric element. This prestress, which compensates for low tensile strength of the piezoelectric materials used, must be larger than the dynamic vibratory stress at the interface between the components in high-amplitude operation. Precise estimation of it is virtually impossible, owing to an intricate elastic contact problem. However, with the use of the unique finite-element-analysis system developed by one of the authors, approximate solutions of the problem have been obtained. A BLT design based on the results of the prestress calculations is proposed. The results of its experimental verification have also been reported.
Passive acoustic methods applied to fin whale population density estimation
Authors: McDonald Mark A. , Fox Christopher G.
Published: July 2002

Assessing the size of cetacean populations in the open ocean has traditionally relied on visual surveys alone. The addition of acoustic monitoring can complement these surveys if reliable protocols can be formulated and calibrated with visual techniques. A study is presented to estimate fin whale population statistics based on near-continuous recording from a single hydrophone. Range to calling animals is estimated by transmission loss and multipath methods to provide a minimum population density estimate. Results are derived from recordings at a hydrophone site north of Oahu, Hawaii that have been the focus of earlier studies. The average calling whale density is 0.027 animals/1000 km2, while the seasonal maximum calling whale density is about three times the average, or 0.081 animals/1000 km2. Over 30 fixed hydrophone sites are available around the Worlds Oceans from which such statistics could be generated.
Acoustic flow perception in cf-bats: Properties of the available cues
Authors: Müller Rolf , Schnitzler Hans-Ulrich
Published: July 2002

Signal design in cf-bats is hypothesized to be commensurate with the evaluation of time-variant echo parameters, imposed by changes in the sound channel occurring as the bat flies by a target. Two such parameters, the proportional changes in Doppler frequency and sound pressure amplitude, are surveyed, employing a simplified acoustic model in order to assess their fitness for target localization given a translational movement within a plane. This is accomplished by considering the properties of the scalar fields given by the value of these putative sensory variables as a function of position in a plane. The considered criteria are: existence and extent of ambiguity areas (i.e., multiple solutions for target position), magnitude of the variables (relevant with regard to perceptual thresholds), as well as magnitude and orthogonality of the gradients (relevant to localization accuracy). It is concluded that these properties render the considered variables compatible with gross judgements of target position. This may be sufficient for behavioral contexts like obstacle avoidance, where adoption of suitable safety margins could compensate for the variance and bias associated with estimates of target location.
Theoretical and experimental studies of surface waves on solid–fluid interfaces when the value of the fluid sound velocity is located between the shear and the longitudinal ones in the solid
Authors: Padilla Frédéric , de Billy Michel , Quentin Gérard
Published: July 2002

The existence of two surface waves propagating on a plane solid–fluid interface is demonstrated when the value of the fluid sound velocity is located between the shear and the longitudinal ones in the solid. First, the Scholte–Stoneley dispersion equation is studied analytically and numerically to find the roots corresponding to the Stoneley and the Rayleigh waves. The anatomy of each one is then described with the formalism of the evanescent plane waves: both waves are unleaky. Finally, the results are confirmed experimentally by measuring the times of flight on a Plexiglas–water interface and on a PVC–water interface.
A probabilistic method for tracking a vocalist
Authors: Grubb Lorin
Published: July 2002

When a musician gives a recital or concert, the music performed generally includes accompaniment. To render a good performance, the soloist and the accompanist must know the musical score and must follow the other musician’s performance. Both performing and rehearsing are limited by constraints on the time and money available for bringing musicians together. Computer systems that automatically provide musical accompaniment offer an inexpensive, readily available alternative. Computer accompaniment requires software that can listen to live performers and follow along in a musical score. An implemented system automatically accompanies a singer given a musical score. The focus is a method for robustly detecting the score position and tempo (performance rate) of the singer in real time. Robust score following requires combining information obtained both from analyzing a complex signal (the signer’s performance) and from processing symbolic notation (the score). The singer’s score position is characterized statistically using a model that combines the available musical information to produce a probabilistic position estimate. By making careful assumptions and estimating statistics from a set of actual vocal performances, a reasonable approximation of this model can be implemented in software and executed in real time during a performance.
A new approach to reflection-transmission between viscoelastic half-spaces
Authors: Caviglia G. , Morro A.
Published: July 2002

Reflection and transmission of time-harmonic waves at the welded boundary between linear, viscoelastic, isotropic half-spaces is examined. A basis consisting of inhomogeneous waves is considered, for wave fields obeying Snell’s law; the basis elements are parameterized by the component k∥ of the wave vector parallel to the interface; incident and reflected-transmitted waves are expressed as superpositions of incoming and outgoing inhomogeneous waves. The characterization of incoming and outgoing inhomogeneous waves through the phase, the amplitude, and the mean energy intensity is shown to provide nonequivalent mathematical models for reflection and transmission. On the basis of the general properties of the energy flux, the energy criterion is regarded as the appropriate one. The resulting approach is developed in connection with the reflection-transmission process. In particular, the incoming or outgoing character of any inhomogeneous wave is shown to depend on k∥. In correspondence with such a dependence, jump discontinuities of the reflection and transmission coefficients are shown to occur.
Psychophysical correlates of contralateral efferent suppression. I. The role of the medial olivocochlear system in “central masking” in nonhuman primates
Authors: Smith David W. , Turner Dennis A. , Henson Miriam M.
Published: July 2002

An extensive physiological literature, including experimental and clinical studies in humans, demonstrates that activation of the medial olivocochlear (MOC) efferent system, by either contralateral sound or electrical stimulation, can produce significant alterations in cochlear function and suggests a role for the MOC system in influencing the auditory behavior of binaural hearing. The present data are from psychophysical studies in nonhuman primates which seek to determine if the noted physiological changes in response to contralateral acoustic stimulation have a perceptual counterpart. Four juvenile Japanese macaques were trained to respond to the presence of 1-s sinusoids, presented to the test ear, in an operant reinforcement paradigm. Thresholds were compared for frequencies ranging from 1.0 to 4.0 kHz in quiet, with thresholds measured when continuous, two octave-band noise, centered on the test tone frequency, was presented in the contralateral ear. Contralateral noise was presented at levels of 10–60 dB above detection threshold for the test-tone frequency. While some variability was evident across subjects, both in the frequency distribution and magnitude (as a function of contralateral noise level), all subjects exhibited an increase, or suppression of thresholds in the presence of contralateral noise. On average, thresholds increased systematically with contralateral noise level, to a peak of 7 dB. In one subject, the threshold increase seen with contralateral noise was significantly reduced when the MOC was surgically sectioned on the floor of the IVth ventricle. The characteristics of the measured shifts in behavioral thresholds, in the presence of contralateral noise reported here, are qualitatively and quantitatively similar to both efferent physiological suppression effects and psychophysical central masking threshold shifts which have been reported previously. These data suggest that at least some aspects of “central masking” are efferent-mediated peripheral processes, and that the term “central masking” may be incorrect.
Difference thresholds for intensity perception of whole-body vertical vibration: Effect of frequency and magnitude
Authors: Morioka Miyuki , Griffin Michael J.
Published: July 2002

Difference thresholds for seated subjects exposed to whole-body vertical sinusoidal vibration have been determined at two vibration magnitudes [0.1 and 0.5 ms−2 root mean square (r.m.s.)] and at two frequencies (5 and 20 Hz). For 12 subjects, difference thresholds were determined using the up-and-down transformed response method based on two-interval forced-choice tracking. At both frequencies, the difference thresholds increased by a factor of five when the magnitude of the vibration increased from 0.1 to 0.5 ms−2 r.m.s. The median relative difference thresholds, Weber fractions (ΔI/I), expressed as percentages, were about 10% and did not differ significantly between the two vibration magnitudes or the two frequencies. It is concluded that for the conditions investigated the difference thresholds for whole-body vibration are approximately consistent with Weber’s Law. A vibration magnitude will need to be reduced by more than about 10% for the change to be detectable by human subjects; vibration measurements will be required to detect reductions of less than 10%.
Rate-dependent plasticity models derived from potential functions
Authors: Houlsby G. T. , Puzrin A. M.
Published: July 2002

In this paper we describe a method for the derivation of the constitutive behavior of rate-dependent materials from two potential functions. Once the potentials have been specified an entirely standardized procedure can be adopted to derive the response, and no additional assumptions are necessary. There is some freedom in the choice of which potential functions to specify: the first is one of four energy potentials, and the second, which specifies the dissipative behavior, is either the force or flow potential. The method allows alternative models to be quickly compared and set within an appropriate hierarchy. This work extends previous work on rate-independent materials, for which the force potentials take a special form. We illustrate the method with four examples of different viscoplastic models.
Approximation of Irregular Loading by Intervals of Constant Stress Rate to Predict Creep and Relaxation of Polyurethane by Three Integral Representations
Authors: Nolte K. G. , Findley W. N.
Published: July 2002

Three integral representations for nonlinear creep were employed to predict from constant-stress creep data the strain resulting from two irregular loading experiments. The stress history for these experiments was approximated by intervals of constant stress rate. By employing this method of approximation and a numerical procedure, the creep representations were inverted to permit predicting from the same constant-stress creep data the stress resulting from prescribed time-varying strains. This procedure was used to predict the tensile stress relaxation of two multiple-step tensile strain tests.
The Measurement of the Elongational Viscosity of Polymer Solutions Using a Viscometer of Novel Design
Authors: Hudson N. E. , Ferguson J. , Mackie P.
Published: July 2002

A prototype viscometer of novel design is described. Experiments using the viscometer with solutions of polybutadiene in decalin were carried out, and measurements were taken of thread tension and filament radius. Using a force-balance equation, these results were used to evaluate the axial stresses in the filament. The effects of gravity, inertia, aerodynamic drag, and stress history on the elongational viscosity are shown. The results are discussed in the light of previous experimental results and theoretical predictions of the elongational viscosity.
Viscosity Rise during Free Radical Crosslinking Polymerization with Inhibition
Authors: González-Romero Victor M. , Macosko Christopher W.
Published: July 2002

A study of the viscosity rise during free radical crosslinking polymerization is presented. Techniques were developed for monitoring isothermal viscosity rise during fast polymerization reactions. The chemical system used was composed of a dimethacrylate resin in styrene monomer, t-butyl perbenzoate initiator, and hydroquinone as the inhibitor. When reduced viscosity is plotted versus conversion, data at all temperatures collapsed into a single curve. A theoretical equation is suggested for the time required to reach the gel point in free radical crosslinking polymerization with inhibition. This equation showed good agreement with experimental observations.
Reliability of dynamic mechanical thermal analyses (DMTA) for the study of frozen aqueous systems
Authors: Blond G. , Ivanova K. , Simatos D.
Published: July 2002

Frozen aqueous solutions were studied using dynamic mechanical spectrometry. DMTA measurements required different devices because of the large evolution of the rheological behavior of the mixtures with temperature, particularly a strong decrease in rigidity during the melting of the ice. For stabilized frozen solutions in which the solutes were not able to crystallize, DMTA showed clearly that the beginning of softening was due to a glass transition of the amorphous fraction. The temperature range, where it is observed, corresponds well to the beginning of the two-step thermal feature observed by differential scanning calorimetry before the ice melting. Compression tests have a better sensitivity at low temperatures but only shear tests allow one to make a full examination of the sample changes during the glass transition of the amorphous phase, and then the ice melting, during the heating process.
Nuclear magnetic resonance imaging investigation of sedimentation of concentrated suspensions in non-Newtonian fluids
Authors: Bobroff Serge , Phillips Ronald J.
Published: July 2002

Nuclear magnetic resonance imaging is used to study rates of sedimentation in several non-Newtonian fluids. It is shown that either shear thinning or elasticity in a fluid can result in a time-dependent sedimentation rate, as measured by the motion of the suspension–supernatant interface. Sedimentation is most rapid at the beginning of the process, and grows steadily slower in time. Two-dimensional images of vertical sections of suspension show clearly the development of a nonhomogeneous microstructure during sedimentation in a viscoelastic fluid. Elongated columns of particles form in the direction of gravity, and these columns are separated by comparably sized regions of pure fluid. Such structures are not present in sedimentation in Newtonian fluids, where the suspension microstructure is homogeneous for the duration of the process.
Long-term Effectiveness Associated With the BNT162b2 Vaccine Against SARS-CoV-2 Infection Among Adolescents in South Korea
Authors: Kim Jia , Choe Young June , Lee Hyunju , Choi Eun Hwa , Jang Eun Jung , Kim Ryu Kyung , Park Young-Joon
Published: August 2022

This cohort study estimates the effectiveness associated with the BNT162b2 vaccine against infection and critical infection of SARS-CoV-2 among adolescents in South Korea.
The Surgical Suite—A Field Laboratory for Sustainability
Authors: Belliveau Sébastien , Gold Morgan S.
Published: August 2022

This Viewpoint discusses the opportunities afforded by modern technological advances and infrastructure that enable health care facilities to develop and rethink approaches to recycling, reducing, and reusing personal protective equipment.
Activity‐Dependent Induction of Younger Biological Phenotypes
Authors: Lissek Thomas
Published: August 2022

In several mammalian species, including humans, complex stimulation patterns such as cognitive and physical exercise lead to improvements in organ function, organism health and performance, as well as possibly longer lifespans. A framework is introduced here in which activity‐dependent transcriptional programs, induced by these environmental stimuli, move somatic cells such as neurons and muscle cells toward a state that resembles younger cells to allow remodeling and adaptation of the organism. This cellular adaptation program targets several process classes that are heavily implicated in aging, such as mitochondrial metabolism, cell–cell communication, and epigenetic information processing, and leads to functional improvements in these areas. The activity‐dependent gene program (ADGP) can be seen as a natural, endogenous cellular reprogramming mechanism that provides deep insight into the principles of inducible improvements in cell and organism function and can guide the development of therapeutic approaches for longevity. Here, these ADGPs are analyzed, exemplary critical molecular nexus points such as cAMP response element‐binding protein, myocyte enhancer factor 2, serum response factor, and c‐Fos are identified, and it is explored how one may leverage them to prevent, attenuate, and reverse human aging‐related decline of body function.