bluuebunny/crossref_metadata_2025 huggingface dataset:
Real-Time Machinability Analysis of Free Form Surfaces on the GPU
Authors: Lysenko Mikola , D’Souza Roshan , Rahmani Keyvan
Published: June 2009

In this paper a new hardware accelerated method is presented to evaluate the machinability of free-form surfaces. This method works on tessellated models that are commonly used by computer aided design (CAD) systems to render three-dimensional shaded images of solid models. Modern graphics processing units (GPUs) can be programed in hardware to accelerate specialized rendering techniques. In this research, we have developed new algorithms that utilize the programmability of GPUs to evaluate the machinability of free-form surfaces. The method runs in real-time on fairly inexpensive hardware (<$600), and performs well regardless of the surface type. The complexity of the method is dictated by the size of the projected view of the model. The proposed method can be used as a plug-in in a CAD system to evaluate the manufacturability of a part at early design stages. The efficiency and the speed of the proposed method are demonstrated on some complex objects.
Generating Simplified Trapping Probability Models From Simulation of Optical Tweezers System
Authors: Banerjee Ashis Gopal , Balijepalli Arvind , Gupta Satyandra K. , LeBrun Thomas W.
Published: June 2009

This paper presents a radial basis function based approach to generate simplified models to estimate the trapping probability in optical trapping experiments using offline simulations. The difference form of Langevin’s equation is used to perform physically accurate simulations of a particle under the influence of a trapping potential and is used to estimate trapping probabilities at discrete points in the parameter space. Gaussian radial basis functions combined with kd-tree based partitioning of the parameter space are then used to generate simplified models of trapping probability. We show that the proposed approach is computationally efficient in estimating the trapping probability and that the estimated probability using the simplified models is sufficiently close to the probability estimates from offline simulation data.
Unsteady Separation on Lifting Surfaces
Authors: Gad-el-Hak Mohamed
Published: June 2009

This article presents a review of some recent work that deals with the phenomenon of unsteady separation on two- and three-dimensional lifting surfaces. The presently available experimental data are interpreted in light of the recent idea advanced by Ho (1986), in which unsteady separation is associated with a spatially developing local shear layer. No attempt is made to give a complete account of the vast number of papers written in the subject area. Instead, reference is made to a few excellent review articles available in the open literature. The unsteady motions considered include change of angle of attack, impulsive start from rest, and change of freestream velocity. The lifting surfaces studied are bodies of revolution and wings of different aspect ratios, planforms, and leading edge bluntness. Other, nonlifting surfaces are briefly considered. Velocity probe measurements in such complex flow fields are sparse. However, flow visualization results are ample and are extensively reviewed in this paper.
Constitutive Behavior and Testing of Structural Adhesives
Authors: Sancaktar Erol
Published: June 2009

Material characterization of structural adhesives in the bulk and bonded forms is discussed. Constitutive relations used for describing stress–strain data are reviewed. The difficulties associated with adhesive characterization in the bonded form are cited. Common testing procedures for adhesive characterization in the bulk and bonded forms are reviewed. In presenting the constitutive relations used in material characterization of structural adhesives, deformation theories introduced by Hencky are reviewed first. The modifications made in this theory to render it rate dependent and bilinear are discussed and applications to adhesive characterization are cited. Application of linear viscoelasticity, mechanical model characterization, and its use in describing the dependence of adhesive and cohesive strengths on rate, temperature, and bond thickness are presented. The time–temperature superposition principle and three-dimensional stress–strain relations in integral and differential operator forms are reviewed. Frequent assumptions for dilatation and distortion operations are presented. Procedures for describing nonlinear viscoelastic behavior are reviewed. It is pointed out that the extent of nonlinearity is dependent on both the stress level and the time scale. The use of nonlinear spring and dashpot elements, nonlinear differential operators, and perturbation of elastic and viscous coefficients are cited. Prandtl’s incremental theory of plasticity and its extension in the form of over-stress theory is presented. The incorporation of this over-stress idea into the viscoelastic mechanical model characterization is discussed. The modified Bingham model and the Chase–Goldsmith model developed in this fashion and their application to adhesive material characterization are presented. The use of empirical relations for the description of creep behavior is discussed. Prediction of shear behavior based on bulk tensile data is demonstrated. It is suggested that characterization of adhesive behavior in the bonded form should include the application of stress analysis, fracture mechanics, polymer chemistry and surface analysis techniques. In testing bonded samples the use of thick adherend symmetric single lap geometry or napkin ring test geometry is advised and it is suggested that the specimens should be prepared with the same surface preparation and cure techniques.
Topics in Finite Elasticity: Hyperelasticity of Rubber, Elastomers, and Biological Tissues—With Examples
Authors: Beatty Millard F.
Published: June 2009

This is an introductory survey of some selected topics in finite elasticity. Virtually no previous experience with the subject is assumed. The kinematics of finite deformation is characterized by the polar decomposition theorem. Euler’s laws of balance and the local field equations of continuum mechanics are described. The general constitutive equation of hyperelasticity theory is deduced from a mechanical energy principle; and the implications of frame invariance and of material symmetry are presented. This leads to constitutive equations for compressible and incompressible, isotropic hyperelastic materials. Constitutive equations studied in experiments by Rivlin and Saunders (1951) for incompressible rubber materials and by Blatz and Ko (1962) for certain compressible elastomers are derived; and an equation characteristic of a class of biological tissues studied in primary experiments by Fung (1967) is discussed. Sample applications are presented for these materials. A balloon inflation experiment is described, and the physical nature of the inflation phenomenon is examined analytically in detail. Results for the different materials are compared. Two major problems of finite elasticity theory are discussed. Some results concerning Ericksen’s problem on controllable deformations possible in every isotropic hyperelastic material are outlined; and examples are presented in illustration of Truesdell’s problem concerning analytical restrictions imposed on constitutive equations. Universal relations valid for all compressible and incompressible, isotropic materials are discussed. Some examples of non-uniqueness, including that of a neo-Hookean cube subject to uniform loads over its faces, are described. Elastic stability criteria and their connection with uniqueness in the theory of small deformations superimposed on large deformations are introduced, and a few applications are mentioned. Some previously unpublished results are presented throughout.
Modeling of Seismic Isolation Bearings Including Shear Deformation and Stability Effects
Authors: Koh Chan Ghee , Kelly James M.
Published: June 2009

Elastomeric bearings designed for aseismic base isolation typically have a low shear rigidity in order to achieve a low isolation frequency and are thus modeled by a flexural-shear column on the basis of Haringx’s theory. The buckling load of a flexural-shear column is considerably reduced by the shear effect. It is therefore essential to account for the stability effect due to a compressive load on the dynamic performance of these bearings. In this paper, an exact viscoelastic model consistent with Haringx’s theory is first reviewed. A simplified symmetric model consisting of springs and rigid plates is then discussed. Experimental results for four different sets of natural rubber bearings are presented. It is shown that both models can describe with good accuracy the stability effects on the dynamic stiffness, damping factor and height reduction of bearings. In spite of its simplicity, the simplified model is found to agree very well with the exact model. Lastly, using the simplified model, the applicability of the Southwell plot to predict the buckling load of elastomeric isolation bearings is examined.
Recent Thoughts on Probabilistic Fatigue Crack Growth
Authors: Kozin F. , Bogdanoff J. L.
Published: June 2009

The probabilistic modeling of fatigue crack growth is reviewed, primarily from 1980 to the present. Attention is directed to evolutionary models that start with the randomization of a deterministic differential equation by the introduction of random variables or random functions, and to models that directly generate the evolution of distributions. As a result of the statistical analysis of data, reasons are advanced in favor of increasing the dimension of the observables employed.
Recent Applications of the Optimized Rayleigh Method
Authors: Laura P. A. A.
Published: June 2009

Lord Rayleigh suggested, in 1894, the inclusion of an unknown exponential parameter in the coordinate functions which are used in connection with his now classical method. Since the calculated eigenvalues constitute upper bounds, one is able to optimize the results by minimizing the eigenvalues with respect to the undetermined exponential parameter. This review presents some recent applications of the approach to finite element algorithmic procedures and an extension of the Kantorovich method made possible by Rayleigh’s optimization concept.
Vibration of Nonlinear Systems Under Additive and Multiplicative Random Excitations
Authors: Lin Y. K. , Cai G. Q.
Published: June 2009

Exact probabilistic solutions in the stationary state are obtained for some nonlinear systems under the excitations of Gaussian white noises. The excitation can be additive, appearing in the inhomogeneous terms in the equations, or multiplicative, appearing in the coefficients for the unknowns. The possibility for different systems sharing an identical probabilistic solution is pointed out.
Modal Interactions in Dynamical and Structural Systems
Authors: Nayfeh A. H. , Balachandran B.
Published: June 2009

We review theoretical and experimental studies of the influence of modal interactions on the nonlinear response of harmonically excited structural and dynamical systems. In particular, we discuss the response of pendulums, ships, rings, shells, arches, beam structures, surface waves, and the similarities in the qualitative behavior of these systems. The systems are characterized by quadratic nonlinearities which may lead to two-to-one and combination autoparametric resonances. These resonances give rise to a coupling between the modes involved in the resonance leading to nonlinear periodic, quasi-periodic, and chaotic motions.
Diffraction of Rayleigh Waves at Surface Irregularities
Authors: Rossmanith H. P. , Knasmillner R. E.
Published: June 2009

The effect of topography and subsurface inhomogeneity on surface stress amplification during Rayleigh wave interaction is experimentally investigated. Several types of canyon topographies and arrays of surface-breaking, as well as embedded cracks, are considered. Sequences of dynamic photoelastic fringe pattern and caustic recordings yield surface stress data and stress intensity factor data for practical application in various fields of engineering.
On the Theory of Isotropic Turbulence
Authors: Trevin˜o George
Published: June 2009

The theory of isotropic turbulence is investigated. In particular it is established that, for self-similar turbulence, energy transfer occurs in two distinct invariant modes. Implications of this result are discussed. The related decay of turbulence intensity is determined.
Dynamic Stability of Unidirectional Fiber-Reinforced Viscoelastic Composite Plates
Authors: Chandiramani N. K. , Librescu L.
Published: June 2009

This paper deals with a dynamic stability analysis of unidirectional fiber-reinforced composite viscoelastic plates subjected to compressive edge loads. The integrodifferential equations governing the stability problem are obtained by using, in conjunction with a Boltzmann hereditary constitutive law for a 3-D viscoelastic medium, a higher-order shear deformation theory of orthotropic plates. Such a theory incorporates transverse shear deformation, transverse normal stress, and rotatory inertia effects. The solution of the stability problem as considered within this paper concerns the determination of the critical in-plane edge loads yielding the asymptotic instability. Numerical applications, based on material properties derived within the framework of Aboudi’s micromechanical model, are presented and pertinent conclusions concerning the nature of the loss of stability and the influence of various parameters are outlined.
Response of Composite Shells Containing a Delamination
Authors: Chang Fu-Kuo , Kutlu Zafer
Published: June 2009

The objective of the study was to evaluate the mechanical response of composite shells containing a delamination. An analytical model was developed which consists of a structural analysis for calculating the global deformations of the structures and a fracture mechanics analysis for determining the delamination growth in the structures. In order to accurately predict the response of the delaminated shells during loading, a contact-slip condition along the delamination interface was introduced in the model through a Lagrangian multiplier technique. Based on the model, a nonlinear finite element code was developed. Numerical solutions were generated to evaluate the effect of delamination on cylindrical composite shells. From the calculations, it can be concluded that delamination significantly influences the response of composite shells. Such an effect strongly depends upon the initial length and location of the delamination, the laminate ply orientation and its curvature.
The Hybrid Boundary Element Method: An Alliance Between Mechanical Consistency and Simplicity
Authors: Dumont N. A.
Published: June 2009

The most important features of a new numerical method are outlined. The mechanical, or variational consistency of the hybrid finite element method is extended to the conventional boundary element formulation, giving rise to naturally established symmetric force-displacement relations. The computational effort for the complete solution of a given problem, according to this method, is in some cases only a small fraction of the effort needed with traditional methods. This paper also outlines briefly the types of analyses which may be advantageously performed with this new method, many of which are already being implemented by the author and co-workers. Some numerical examples are provided.
Finite Element Approximation of a New Variational Principle for Compressible and Incompressible Linear Isotropic Elasticity
Authors: Franca Leopoldo P. , Stenberg Rolf
Published: June 2009

Stability conditions are described to analyze a variational formulation emanating from a variational principle for linear isotropic elasticity. The variational principle is based on four dependent variables (namely, the strain tensor, augmented stress, pressure, and displacement) and is shown to be valid for any compressibility including the incompressible limit. An improved convergence error analysis is established for a Galerkin-least-squares method based upon these four variables. The analysis presented establishes convergence for a wide choice of combinations of finite element interpolations.
Analysis of Nonlinear Systems by Truncated Point Mappings
Authors: Guttalu Ramesh S. , Flashner Henryk
Published: June 2009

This paper summarizes results obtained by the authors regarding the utility of truncated point mappings which have been recently published in a series of papers. The method described here is applicable to the analysis of multidimensional, multiparameter, periodic nonlinear systems by means of truncated point mappings. Based on multinomial truncation, an explicit analytical expression is determined for the point mapping in terms of the states and parameters of the system to any order of approximation. By combining this approach with analytical techniques, such as the perturbation method employed here, we obtain a powerful tool for finding periodic solutions and for analyzing their stability. The versatility of truncated point mapping method is demonstrated by applying it to study the limit cycles of van der Pol and coupled van der Pol oscillators, the periodic solutions of the forced Duffing’s equation and for a parametric analysis of periodic solutions of Mathieu’s equation.
Optimization in the Design and Control of Robotic Manipulators: A Survey
Authors: Rao S. S. , Bhatti P. K.
Published: June 2009

Robotics is a relatively new and evolving technology being applied to manufacturing automation and is fast replacing the special-purpose machines or hard automation as it is often called. Demands for higher productivity, better and uniform quality products, and better working environments are primary reasons for its development. An industrial robot is a multifunctional and computer-controlled mechanical manipulator exhibiting a complex and highly nonlinear behavior. Even though most current robots have anthropomorphic configurations, they have far inferior manipulating abilities compared to humans. A great deal of research effort is presently being directed toward improving their overall performance by using optimal mechanical structures and control strategies. The optimal design of robot manipulators can include kinematic performance characteristics such as workspace, accuracy, repeatability, and redundancy. The static load capacity as well as dynamic criteria such as generalized inertia ellipsoid, dynamic manipulability, and vibratory response have also been considered in the design stages. The optimal control problems typically involve trajectory planning, time-optimal control, energy-optimal control, and mixed-optimal control. The constraints in a robot manipulator design problem usually involve link stresses, actuator torques, elastic deformation of links, and collision avoidance. This paper presents a review of the literature on the issues of optimum design and control of robotic manipulators and also the various optimization techniques currently available for application to robotics.
Individual talker differences in voice-onset-time: Contextual influences
Authors: Theodore Rachel M. , Miller Joanne L. , DeSteno David
Published: June 2009

Previous research indicates that talkers differ in phonetically relevant properties of speech, including voice-onset-time (VOT) in word-initial stop consonants; some talkers have characteristically shorter VOTs than others. Previous research also indicates that VOT is robustly affected by contextual influences, including speaking rate and place of articulation. This paper examines whether these contextual influences on VOT are themselves talker-specific. Many tokens of alveolar ∕ti∕ (experiment 1) or labial ∕pi∕ and velar ∕ki∕ (experiment 2) were elicited from talkers across a range of rates. VOT and vowel duration (a metric of rate) were measured for each token. Hierarchical linear modeling analyses showed that (1) VOT increased as rate decreased for all talkers, but the magnitude of the increase varied significantly across talkers; thus the effect of rate on VOT was talker-specific; (2) the talker-specific effect of rate was stable across a change in place of articulation; and (3) for all talkers VOTs were shorter for labial than velar stops, and there was no significant variability in the magnitude of this displacement across talkers; thus the effect of place on VOT was not talker-specific. The implications of these findings for how listeners might accommodate talker differences in VOT during speech perception are discussed.
Analysis of parameters for the estimation of loudness from tone-burst otoacoustic emissions
Authors: Epstein Michael , Silva Ikaro
Published: June 2009

There is evidence that tone-burst otoacoustic emissions (TBOAEs) might be useful for estimating loudness. However, within-listener comparisons between loudness and TBOAE measurements are an essential prerequisite to determine appropriate analysis parameters for loudness estimation from TBOAE measurements. The purpose of the present work was to collect TBOAE measurements and loudness estimates across a wide range of levels in the same listeners. Therefore, TBOAEs were recorded for 1- and 4-kHz stimuli and then analyzed using a wide range of parameters to determine which parameter set yielded the lowest mean-square-error estimation of loudness with respect to a psychoacoustical, cross-modality-matching procedure and the inflected exponential (INEX) loudness model. The present results show strong agreement between 1-kHz loudness estimates derived from TBOAEs and loudness estimated using cross-modality matching (CMM), with TBOAE estimation accounting for almost 90% of the CMM variance. Additionally, the results indicate that analysis parameters may vary within a reasonable range without compromising the results (i.e., the estimates exhibit some parametric robustness). The lack of adequate parametric optimization for TBOAEs at 4 kHz suggests that measurements at this frequency are strongly contaminated by ear-canal resonances, meaning that deriving loudness estimates from TBOAEs at this frequency is significantly more challenging than at 1 kHz.
Rough surface scattering in a Born approximation from a two-way coupled-mode formalism
Authors: Stotts Steven A. , Koch Robert A.
Published: June 2009

Scattering from a rough surface in an ocean waveguide is described in a new derivation from a two-way coupled-mode representation. The general formalism, which contains scattering effects to all orders, is truncated to the first-order terms of an iterative (Born) expansion. Both two- and three-dimensional ocean waveguide geometries are discussed. By reducing the mode functions in terms of plane wave reflection coefficients, the off-diagonal components of the scattering kernel that is derived are shown to be consistent with a standard solution, but the diagonal components are different from the standard solution.
Temporary shift in masked hearing thresholds in a harbor porpoise (Phocoena phocoena) after exposure to seismic airgun stimuli
Authors: Lucke Klaus , Siebert Ursula , Lepper Paul A. , Blanchet Marie-Anne
Published: June 2009

An auditory study was conducted to derive data on temporary threshold shift (TTS) induced by single impulses. This information should serve as basis for the definition of noise exposure criteria for harbor porpoises. The measurements of TTS were conducted on a harbor porpoise by measuring the auditory evoked potentials in response to amplitude-modulated sounds. After obtaining baseline hearing data the animal was exposed to single airgun stimuli at increasing received levels. Immediately after each exposure the animal’s hearing threshold was tested for significant changes. The received levels of the airgun impulses were increased until TTS was reached. At 4 kHz the predefined TTS criterion was exceeded at a received sound pressure level of 199.7 dBpk-pk re 1 μPa and a sound exposure level (SEL) of 164.3 dB re 1 μPa2 s. The animal consistently showed aversive behavioral reactions at received sound pressure levels above 174 dBpk-pk re 1 μPa or a SEL of 145 dB re 1 μPa2 s. Elevated levels of baseline hearing sensitivity indicate potentially masked acoustic thresholds. Therefore, the resulting TTS levels should be considered masked temporary threshold shift (MTTS) levels. The MTTS levels are lower than for any other cetacean species tested so far.
Multitalker speech perception with ideal time-frequency segregation: Effects of voice characteristics and number of talkers
Authors: Brungart Douglas S. , Chang Peter S. , Simpson Brian D. , Wang DeLiang
Published: June 2009

When a target voice is masked by an increasingly similar masker voice, increases in energetic masking are likely to occur due to increased spectro-temporal overlap in the competing speech waveforms. However, the impact of this increase may be obscured by informational masking effects related to the increased confusability of the target and masking utterances. In this study, the effects of target-masker similarity and the number of competing talkers on the energetic component of speech-on-speech masking were measured with an ideal time-frequency segregation (ITFS) technique that retained all the target-dominated time-frequency regions of a multitalker mixture but eliminated all the time-frequency regions dominated by the maskers. The results show that target-masker similarity has a small but systematic impact on energetic masking, with roughly a 1dB release from masking for same-sex maskers versus same-talker maskers and roughly an additional 1dB release from masking for different-sex masking voices. The results of a second experiment measuring ITFS performance with up to 18 interfering talkers indicate that energetic masking increased systematically with the number of competing talkers. These results suggest that energetic masking differences related to target-masker similarity have a much smaller impact on multitalker listening performance than energetic masking effects related to the number of competing talkers in the stimulus and non-energetic masking effects related to the confusability of the target and masking voices.
The directivity of the sound radiation from panels and openings
Authors: Davy John L.
Published: June 2009

This paper presents a method for calculating the directivity of the radiation of sound from a panel or opening, whose vibration is forced by the incidence of sound from the other side. The directivity of the radiation depends on the angular distribution of the incident sound energy in the room or duct in whose wall or end the panel or opening occurs. The angular distribution of the incident sound energy is predicted using a model which depends on the sound absorption coefficient of the room or duct surfaces. If the sound source is situated in the room or duct, the sound absorption coefficient model is used in conjunction with a model for the directivity of the sound source. For angles of radiation approaching 90° to the normal to the panel or opening, the effect of the diffraction by the panel or opening, or by the finite baffle in which the panel or opening is mounted, is included. A simple empirical model is developed to predict the diffraction of sound into the shadow zone when the angle of radiation is greater than 90° to the normal to the panel or opening. The method is compared with published experimental results.
Effects of center frequency and rate on the sensitivity to interaural delay in high-frequency click trains
Authors: Majdak Piotr , Laback Bernhard
Published: June 2009

The effects of center frequency and pulse rate on the sensitivity to ongoing envelope interaural time differences (ITDs) were investigated using bandpass-filtered pulse trains. Three center frequencies (4.6, 6.5, and 9.2kHz) were tested with bandwidths scaled to stimulate an approximately constant range on the basilar membrane. The pulse rate was varied from 200to588pps (pulses per seconds). Five normal-hearing (NH) subjects were tested. Averaged over all rates, the results show a small decrease in sensitivity with increasing center frequency. For all center frequencies, sensitivity decreases with increasing pulse rate, yielding a rate limit of approximately 500pps. The lack of an interaction between pulse rate and center frequency indicates that auditory filtering was not the rate limiting factor in ITD perception and suggests the existence of other limiting mechanisms, such as phase locking or more central processes. It is concluded that the comparison of the rate limits in ITD perception between cochlear-implant listeners and NH subjects listening to high-frequency bandpass-filtered pulse trains is not confounded by the choice of center frequency of stimulation in NH listeners.
Hidden Markov and Gaussian mixture models for automatic call classification
Authors: Brown Judith C. , Smaragdis Paris
Published: June 2009

Automatic methods of classification of animal sounds offer many advantages including speed and consistency in processing massive quantities of data. Calculations have been carried out on a set of 75 calls of Northern Resident killer whales, previously classified perceptually (human classification) into seven call types, using, hidden Markov models (HMMs) and Gaussian mixture models (GMMs). Neither of these methods has been used previously for classification of marine mammal call types. With cepstral coefficients as features both HMMs and GMMs give over 90% agreement with the perceptual classification, with the HMM over 95% for some cases.
Sound source segregation by goldfish: Two simultaneous tones
Authors: Fay Richard R.
Published: June 2009

The perception of two simultaneous tones was investigated in goldfish using classical respiratory conditioning and a stimulus generalization paradigm. Pairs of tones were used to make up a mixture of 150 Hz and a higher harmonic or a mistuned harmonic. Fish were conditioned to the two-tone mixture and then tested for generalization to several pure tones. The simultaneous tones tended to be segregated in perception, with the generalization gradient for single tones having two peaks corresponding to the frequencies of the tone pairs. There were no consistent differences in the generalization gradients following conditioning to harmonic or inharmonic tone pairs. In addition, experiments were carried out in which the two tones of the pair were heard on alternate trials, always as single tones, followed by generalization tests to single tones. There was more generalization in this experiment, reflecting the fact that conditioning and generalization test stimuli were both single tones. However, the shapes of the generalization gradients were similar to those in which fish were conditioned to two simultaneous tones, indicating that the simultaneity of the tones did not make them harder to segregate. As the frequency separation between the two components narrowed, segregation tended to fail.
State-space models of head-related transfer functions for virtual auditory scene synthesis
Authors: Adams Norman H. , Wakefield Gregory H.
Published: June 2009

This study investigates the use of reduced-order state-space models of collections of head-related transfer functions (HRTFs). Recent head-phone applications have motivated interest in binaural displays that can render multiple simultaneous virtual sound sources, acoustic reflections, and source and listener motion. In the present study, a multi-direction framework is considered that can render such phenomena by filtering source signals with a collection of HRTFs rather than individual HRTFs. The collection of HRTFs is implemented in the state-space, and approximation techniques are applied to construct low-order approximants that are indiscriminable from full-order HRTFs. Two experiments are described in which five observers are asked to discriminate between state-space and full-order renderings. Depending on the stimulus conditions and discrimination task, order thresholds of 7≤N≤24 are sufficient for an array of 50 HRTFs surrounding the listener. For comparison, a reference system of truncated minimum-phase impulse responses is also considered.
The rumble sound generated by a tidal bore event in the Baie du Mont Saint Michel
Authors: Chanson Hubert
Published: June 2009

A tidal bore is a sharp rise in free-surface elevation propagating upstream in an estuarine system at the leading edge of the flood tide. It generates a powerful noise that was sometimes compared to the sounds of a horse cavalcade. Herein the sounds generated by a tidal bore event in the Baie du Mont Saint Michel were carefully recorded. The data showed three distinct periods. These were the incoming tidal bore when the sound amplitude increased with the approaching bore front, the passage of the tidal bore in front of the microphone where the impacts of the bore on the bank, rocks, or jetty generated powerful noises, and the upstream propagation of the bore when the flood flow motion caused additional loud noises. During the arrival of the tidal bore, the sound levels were less energetic and a lower-pitch sound was noted than during the subsequent record. For the breaking bore process, the analysis of the sound record indicated a dominant frequency around 76–77 Hz. The low-pitch rumble had a frequency comparable to the collective bubble oscillations, suggesting that air entrapment in the bore roller might play a major role in the acoustic signature.
On the relationship between palate shape and articulatory behavior
Authors: Brunner Jana , Fuchs Susanne , Perrier Pascal
Published: June 2009

In this study the acoustic and articulatory variabilities of speakers with different palate shapes were compared. Since the cross-sectional area of the vocal tract changes less for a slight change in tongue position if the palate is domeshaped than if it is flat, the acoustic variability should be greater for flat palates than for domeshaped ones. Consequently, it can be hypothesized that speakers with flat palates should reduce their articulatory variability in order to keep the acoustic output constant. This hypothesis was tested on 32 speakers recorded via electropalatography (EPG) and acoustics. The articulatory and acoustic variability of some of their vowels and /j/ was measured. Indeed, the results show that the speakers with flat palates reduce their variability in tongue height. There is no such trend in acoustic variability.
Ensemble averaged surface normal impedance of material using an in-situ technique: Preliminary study using boundary element method
Authors: Otsuru Toru , Tomiku Reiji , Din Nazli Bin Che , Okamoto Noriko , Murakami Masahiko
Published: June 2009

An in-situ measurement technique of a material surface normal impedance is proposed. It includes a concept of “ensemble averaged” surface normal impedance that extends the usage of obtained values to various applications such as architectural acoustics and computational simulations, especially those based on the wave theory. The measurement technique itself is a refinement of a method using a two-microphone technique and environmental anonymous noise, or diffused ambient noise, as proposed by Takahashi et al. [Appl. Acoust. 66, 845–865 (2005)]. Measured impedance can be regarded as time-space averaged normal impedance at the material surface. As a preliminary study using numerical simulations based on the boundary element method, normal incidence and random incidence measurements are compared numerically: results clarify that ensemble averaging is an effective mode of measuring sound absorption characteristics of materials with practical sizes in the lower frequency range of 100–1000 Hz, as confirmed by practical measurements.
Effects of envelope discontinuities on perceptual restoration of amplitude-compressed speech
Authors: Başkent Deniz , Eiler Cheryl , Edwards Brent
Published: June 2009

An interrupted signal may be perceptually restored and, as a result, perceived as continuous, when the interruptions are filled with loud noise bursts. Additionally, when the signal is speech, an improvement in intelligibility may be observed. The perceived continuity of interrupted tones is reduced when the signal level is ramped down and up before and after the noise burst, respectively—an effect that has been attributed to envelope discontinuities at the tone-noise interface [Bregman, A. S., and Dannenbring, G. L. (1977). Can. J. Psychiatry 31, 151–159]. The hypothesis of the present study was that the perceptual restoration of speech would also be reduced with similar envelope discontinuities that may occur in real life due to the release time constants of hearing-aid compression. In an effort to make the conditions more relevant to hearing aids, speech was amplitude-compressed and normal-hearing listeners of varying ages were recruited. Envelope amplitude ramps were placed at the onsets/offsets of speech segments of interrupted sentences and the restoration effect was measured in two ways: objectively as the improvement in intelligibility when noise was added in the gaps and subjectively through the perceived continuity measured by subjects’ own reporting. Both measures showed a reduction as the ramp duration increased—a trend observed for subjects of all ages and for all ramp configurations. These findings can be attributed to envelope discontinuities, with an additional contribution from reduced speech information due to ramping and temporal masking from loud noise bursts.
Modeling the dynamics of a compliant piano action mechanism impacting an elastic stiff string
Authors: Vyasarayani Chandrika P. , Birkett Stephen , McPhee John
Published: June 2009

A realistic model of the piano hammer-string interaction must treat the action mechanism and string as a single system. In this paper an elastic stiff string model is integrated with a dynamic model of a compliant action mechanism with flexible hammer shank. Action components represented as rotating bodies interact through felt-lined interfaces for which a specialized contact model with hysteretic damping and tangential friction was developed. The motion of the hammer during string contact is governed by the dynamics of the action mechanism, thereby providing a more sophisticated hammer-string interaction than a simple transverse impact hammer model with fixed contact location. Simulations have been used to compare mechanism response for impact on the elastic string as compared to a rigid stop. Hammer head scuffing along the string and time in contact were predicted to increase, while hammer shank vibration amplitude and peak contact force were decreased. Introducing hammer-string friction decreases the duration of contact and reduces the extent of scuffing. Finally, significant differences in hammer and string motion were predicted for a highly flexible hammer shank. Initial contact time and location, length of contact period and peak force, hammer vibration amplitude, scuffing extent, and string spectral content were all influenced.
The objective measurement of individual earplug field performance
Authors: Voix Jérémie , Laville Frédéric
Published: June 2009

This paper presents a field-microphone-in-real-ear (MIRE) method for the objective measurement of individual earplug field attenuation. This development was made possible by using a recently designed instrumented expandable custom earplug. From the measurement of the noise reduction (NR) through the earplug, this method predicts the attenuation that would be experienced by the wearer and that would be measured using the real-ear attenuation at threshold (REAT) method. Formulations presented include establishing the relationship between NR, insertion loss, and REAT, as well as defining the laboratory and field calibration procedures required to determine the correction factors to be applied to the measured NR. This method was validated experimentally by comparing the predicted field-MIRE attenuation values to the REAT values measured on a group of test-subjects. This method offers fast and accurate measurement of earplug field performance on an individual basis and could lead to further developments for effective hearing protection practices as well as for hearing protection device rating and labeling.
Comparing two methods to measure preferred listening levels of personal listening devices
Authors: Worthington Darrin A. , Siegel Jonathan H. , Wilber Laura Ann , Faber Benjamin M. , Dunckley Kathleen T. , Garstecki Dean C. , Dhar Sumitrajit
Published: June 2009

The potential risk to hearing that mass-storage personal listening devices (PLDs) pose remains unclear. Previous research in this area has either focused on maximum outputs of these devices or on ear-canal measurements of listening levels that could not be compared to standards of occupational noise exposure. The purpose of this study was to compare two standard measurement protocols [ISO 11904-1 (2002), Switzerland; ISO 11904-2 (2004), Switzerland] for the measurement of preferred listening levels of PLD. Noise measurements, behavioral thresholds, and oral interviews were obtained from 30 (18–30 years) PLD users. Preferred listening levels for self-selected music were determined in quiet and background noise using a probe microphone, as well as in the DB-100 ear simulator mounted in KEMAR. The ear-canal measurements were compensated for diffuse-field. Only one of the subjects was found to be listening at hazardous levels once their reported daily usage was accounted for using industrial workplace standards. The variance across subjects was the smallest in the ear-canal measurements that were compensated for diffuse-field equivalence [ISO 11904-1 (2002), Switzerland]. Seven subjects were found to be listening at levels above 85 dBA based on measurements obtained in the KEMAR and then compensated for diffuse-field equivalence.
Effect of a stack on Rayleigh streaming cells investigated by laser Doppler velocimetry for application to thermoacoustic devices
Authors: Moreau Solenn , Bailliet Hélène , Valière Jean-Christophe
Published: June 2009

A preliminary study was conducted to observe the influence of a stack on the Rayleigh streaming pattern for application to thermoacoustic devices. The velocity field was estimated from laser Doppler velocimetry measurements in a resonator first without a stack; then a stack was placed at various positions along the resonator axis for various acoustic levels. It was observed that adding a stack locally modifies the streaming pattern and that new streaming vortices appear. When the stack position approaches the location of the streaming velocity maximum or when the acoustic velocity amplitude is increased, the amplitude of additional acoustic streaming vortices at the ends of the stack increases.
Truncated aperture extrapolation for Fourier-based near-field acoustic holography by means of border-padding
Authors: Scholte Rick , Lopez Ines , Bert Roozen N. , Nijmeijer Henk
Published: June 2009

Although near-field acoustic holography (NAH) is recognized as a powerful and extremely fast acoustic imaging method based on the inverse solution of the wave-equation, its practical implementation has suffered from problems with the use of the discrete Fourier transformation (DFT) in combination with small aperture sizes and windowing. In this paper, a method is presented that extrapolates the finite spatial aperture before the DFT is applied, which is based on the impulse response information of the known aperture data. The developed method called linear predictive border-padding is an aperture extrapolation technique that greatly reduces leakage and spatial truncation errors in planar NAH (PNAH). Numerical simulations and actual measurements on a hard-disk drive and a cooling fan illustrate the low error, high speed, and utilization of border-padding. Border-padding is an aperture extrapolation technique that makes PNAH a practical and accurate inverse near-field acoustic imaging method.
The use of fundamental frequency for lexical segmentation in listeners with cochlear implants
Authors: Spitzer Stephanie , Liss Julie , Spahr Tony , Dorman Michael , Lansford Kaitlin
Published: June 2009

Fundamental frequency (F0) variation is one of a number of acoustic cues normal hearing listeners use for guiding lexical segmentation of degraded speech. This study examined whether F0 contour facilitates lexical segmentation by listeners fitted with cochlear implants (CIs). Lexical boundary error patterns elicited under unaltered and flattened F0 conditions were compared across three groups: listeners with conventional CI, listeners with CI and preserved low-frequency acoustic hearing, and normal hearing listeners subjected to CI simulations. Results indicate that all groups attended to syllabic stress cues to guide lexical segmentation, and that F0 contours facilitated performance for listeners with low-frequency hearing.
Head related transfer functions for KEMAR.
Authors: Rasmussen Gunnar
Published: June 2009

The head related transfer functions (HRTFs) for KEMAR for a number of ear pinnas of different sizes and hardnesses have been measured. Right and left ear differences on KEMAR as well as change in HRTFs over the last 40 years will be reported along with data for the ITU - Type 3 and the IEC 60959 standardized pinna. The influencing factors on the uncertainty budget will be discussed.
Dealing with Decoherence
Authors: Fischer Jan , Loss Daniel
Published: June 2009

For quantum computers to be a reality, the effects of interactions of qubits with their environment must be minimized.
Halofuginone Inhibits T
H
17 Cell Differentiation by Activating the Amino Acid Starvation Response
Authors: Sundrud Mark S. , Koralov Sergei B. , Feuerer Markus , Calado Dinis Pedro , Kozhaya Aimee ElHed , Rhule-Smith Ava , Lefebvre Rachel E. , Unutmaz Derya , Mazitschek Ralph , Waldner Hanspeter , Whitman Malcolm , Keller Tracy , Rao Anjana
Published: June 2009

Starving T Cells

The T
H
17 lineage of CD4
+
helper T cells, characterized by the ability to secrete IL-17, is an important mediator of inflammation and autoimmunity. Dampening the responses of these cells or inhibiting their differentiation is of great therapeutic interest.

Sundrud
et al.

(p.
1334
; see the Perspective by

Blander and Amsen

) now show that the small molecule halofuginone inhibits the differentiation of T
H
17 cells but not other CD4
+
T cell helper lineages both in vitro and in a mouse model of multiple sclerosis. This selective inhibition was mediated by activation of the amino acid starvation response. Amino acid depletion mimicked the effects of halofuginone, whereas excess amino acids rescued T
H
17 differentiation. The results highlight the importance of amino acid metabolism in regulating inflammation.
On Becoming Modern
Authors: Mace Ruth
Published: June 2009

Human social evolution is determined by demography.
Science for Future Physicians
Authors: Long Sharon , Alpern Robert
Published: June 2009

Biomedical research is rapidly transforming our understanding of health and disease, with major implications for medical practice. But the science education of physicians has not kept pace with these advances. Today, the Association of American Medical Colleges (AAMC) and the Howard Hughes Medical Institute release a report that addresses this issue.
*
The analysis, by a committee of U.S. undergraduate and medical school faculty that we co-chaired, comes 6 years after the U.S. National Academies report
BIO 2010
, which noted that undergraduate premedical course requirements and the content of the Medical College Admissions Test (MCAT) constrain innovation in undergraduate science education.
The Quaternary Period Wins Out in the End
Authors: Kerr Richard A.
Published: June 2009

Geoscientists are making room for an interval of time that is uniquely human.
Some RNA May Play Key Role in Repressing Genes, Slowing Cancer
Authors: Pennisi Elizabeth
Published: June 2009

Just as junk DNA proved to be more than junk, at least some non-protein-coding RNA translates into meaningful molecules that may play key roles in turning genes on and off, scientists reported at the Biology of Genomes meeting.