bluuebunny/crossref_metadata_2025 huggingface dataset:
A new aircraft interior noise simulator for psychoacoustic testing
Authors: Sullivan Brenda M. , Powell Clemans A.
Published: July 2002

NASA is conducting a research program in passenger response to aircraft interior noise to develop tools for use in design decisions for interior noise treatments. A new interior simulator has been built at NASA–Langley to be used in this program. The simulator is a shell fitted with interior trim and seats from 737/727 aircraft. It contains five listening stations, each having a pair of headphones for binaural signal presentation. Binaural recordings made in interiors of a number of aircraft were processed on a workstation into 50 sound stimuli. These were played back over the headphones and analyzed for repeatability within and between headphones. Initial results indicated that ranges averaged within headphones were 0.3 dB (A weighted), 0.3 phons and 0.7 dB (unweighted). When averaged between headphones, ranges were 1.0 dB (A weighted), 0.9 phons and 1.4 dB (unweighted). A first test in the simulator presented stimuli from propeller airplanes digitally modified to reduce the tonal components. Regressions between subjects’ preference responses and measured metrics indicate that the subjective response correlates as well with the arithmetic mean of measurements from the left and right ears of the headphones as with the energy or pressure sums, and better than with measurements from the worse ear.
Statistics of very deep ocean noise
Authors: Walkinshaw H. M.
Published: July 2002

Sea noise was measured continually over a period of 1 year on experimental installations 40 miles south of Bermuda. One-hour stretches of data were recorded daily on four hydrophones, two on the seafloor and two suspended off bottom in 2420 fm s. Analysis of spectrum levels at six frequencies from 0.1 to 1.5 kHz included computation of means, standard deviations, distributions, and higher-order statistical moments. Spectral shape, levels, and variability closely resembled sea noise measured at shallower receivers throughout the western North Atlantic. The suspended very deep hydrophones were 2 to 3 dB noisier than those on the bottom; other statistical properties of both suspended and bottomed receivers were alike. The mean monthly noise migrated through an annual cycle of frequency-dependent change, from 7 dB at 0.1 kHz to 12 dB at 1.5 kHz. This seasonal trend progressed smoothly from winter high to midsummer low, though not at a constant rate. Monthly probability distributions changed form correspondingly, becoming skewed for months with a rapidly shifting mean and tightly peaked for seasons of relative climatic stability. [Work supported by NavElecs.]
Phantom echo generation in dolphin echolocation experiments
Authors: Aubauer Roland , Au Whitlow W. L.
Published: July 2002

In behavioral experiments where real targets are used to investigate dolphin echolocation, it is often very difficult to extract the relevant echo parameters that the animals use to discriminate or classify. The complex relationship between the physical dimensions and the reflection characteristic of real targets prevents separate control of various echo parameters of the stimuli presented in an echolocation experiment. A new echo simulation method presented in this paper avoids this problem. Dolphin echolocation sounds are transformed with the target impulse response into artificial echoes, which are played back to the animal. The developed phantom echo system is implemented on a digital signal processing board and gives an experimenter fully programmable control over the echo generating process and the echo structure itself. Echoes of several underwater targets are simulated to evaluate the quality of the method. A comparison of simulated echoes with the original echoes demonstrated a very good agreement independent of the incident signal (cross-correlation coefficient >0.98). [Work supported by DAAD and DFG.]
A portable virtual instrument for collection of cetacean auditory evoked potentials
Authors: Helweg David A. , Carder Donald A. , Ridgway Sam H.
Published: July 2002

Currently, there are no direct measurements of the frequency-dependent hearing sensitivity of any threatened or endangered cetacean species. Auditory-evoked potentials (EP) allow rapid measurement of cetacean audiograms without the need for the training required to collect behavioral audiograms. A portable EP virtual instrument (VI) has been created that runs on a laptop computer using a commercial PCMCIA DSP card. The VI provides user control over stimulus design, stimulus projection schedules, and collection of evoked potentials via an intuitive graphic user interface. Audiograms can be generated for frequencies up to 8 kHz. EP audiometric methods and the portability of the EP VI makes this system an ideal component of a stranding toolkit for Stranded Whale Auditory Action teams.
Extension of near-field acoustical holography to measurements in a moving medium
Authors: Ruhala Richard J. , Swanson David C. , Burroughs Courtney B.
Published: July 2002

Near-field acoustical holography (NAH) has been widely used to study acoustic radiation from stationary sources. Recently, it has been applied to study tire noise on a vehicle in which the source and receiver are both moving in the medium. Since the source and the measurement plane are moving at the same speed, the frequency Doppler effect is absent. However, a wave-number Doppler effect exists. This leads to errors when reconstructing the acoustic field both toward and away from the source, even at low Mach number speeds. To investigate these errors, a point source is studied analytically using planar NAH with flow in one direction. The effect of the moving medium is noted by a shift in the radiation circle in the wave-number spectrum. From the nonlinear wave equation, a k-space Green’s function and a k-space filter are developed that includes the effects of the moving medium. The newly developed methods are then applied to tire noise using measured data. [Work supported by DOT.]
Military aircraft noise and the outdoor recreationalist
Authors: Elias Bartholomew
Published: July 2002

In response to growing concerns over aircraft noise impacts on outdoor recreationalists, the Department of Defense has initiated a collaborative research program with the National Park Service to study this issue. There are three main objectives to this project. The first objective is to assess park and wilderness land usage by outdoor recreationalists and utilization of military training routes and operations areas within park and wilderness boundaries. The second goal is to assess the response of outdoor recreationalists to military overflights. Recent Air Force sponsored research has examined park visitor reactions to military overflights along a short-hike interpretive trail. However, further research is needed to assess whether outdoor recreationalists seeking more remote back-country wilderness experiences are less tolerant of aircraft overflights. The final goal is to recommend, implement, and assess the effectiveness of various mitigation strategies. Promising mitigation strategies include remapping airspace and establishing operational procedures to minimize overflights of specific noise-sensitive park and wilderness areas, scheduling aircraft operations to minimize the temporal congruence of aircraft and outdoor recreationalists within a given area, and informing outdoor recreationalists of potential overflights within a given area while providing alternative recreational areas where aircraft noise is minimal.
Early use of pitch accent in Japanese spoken-word recognition
Authors: Otake Takashi , Cutler Anne
Published: July 2002

A gating experiment addressed the question of how early in the process of recognizing spoken Japanese words pitch–accent information may be exploited. Twenty-four pairs of Japanese words such as nimotsu/nimono, beginning with the same bimoraic CVCV sequence but with the accent pattern of this initial CVCV being HL in one word and LH in the other, were presented, in increasingly large fragments, to 36 native speakers of Tokyo Japanese. After presentation of each fragment, which was incremented in each case by one phoneme transition from the previous fragment, listeners recorded a guess regarding the word’s identity and a confidence rating for that guess. The results showed that the accent patterns of the word guesses corresponded to the accent patterns of the actually spoken words with a probability significantly above chance from the second fragment onwards, i.e., from the middle of the vowel in the first mora of the word. Accent correspondence averaged 79.6% at this point, rising to 89% by the fourth fragment (vowel of second mora). This demonstrates that Japanese listeners can exploit pitch–accent information effectively at an early stage in the presentation of a word, and use it to constrain selection of lexical candidates.
LF source model adequacy for pathological voices
Authors: Gabelman Brian , Kreiman Jody , Gerratt Bruce R. , Antonanzas-Barroso Norma , Alwan Abeer
Published: July 2002

The adequacy with which source models describe pathological phonation has been little studied, and the perceptual importance of deviations from a perfect model fit remains unknown. To address these issues, pathological voices were selected randomly from a library of samples. Glottal source waveforms were estimated by inverse filtering airflow signals. Formant frequencies and bandwidths were estimated using combined LPC and spectrographic analyses. Source functions were synthesized by least-squares fitting a simplified LF model [Y. Qi and N. Bi, J. Acoust. Soc. Am. 96, 1182–1185 (1994)] to the glottal flow derivative. Three versions of each voice were created. The first was constructed by extracting one cycle from the original voice and repeating it to form a 1-s signal. The second was constructed by recombining the inverse filtered source and estimated vocal tract resonances. The third version comprised the LF-modeled source combined with the estimated vocal tract resonances. Expert listeners compared the three versions of each voice, and results were interpreted in terms of the specific differences among stimuli. This procedure allowed evaluation of the extent and perceptual importance of information lost first by inverse filtering and then by fitting the LF model to the resulting volume velocity signal. [Research supported by NIH.]
Insights on normal vocal-fold oscillation from the acoustic dissection of single glottic pulses in vocal fry
Authors: Elder S. A. , Castellanos P. F.
Published: July 2002

Vocal-fold oscillation has been investigated from the viewpoint of kinematics and dynamics of single glottal pulse at normal intensity vocal fry frequencies, using a modified Sondhi tube. Key moments in the cycle are opening and closing actions, which appear to be very sudden. These events may be noted in two ‘‘kinks’’ which appear along traces of the EGG and glottal cross-sectional area functions. Between opening and closing boundary encounters, vocal folds seem to travel in quasiballistic fashion, being slingshotted out by feedback from the subglottal pressure wave and ending their traverse across the glottal opening with mutual collision The abrupt opening and closing gestures of the glottis permit the glottal valve to modulate subglottal volume flow against the inertia of tracheal air. Acoustic emissions from the glottis may be thought of as flow fluctuations which compensate for changes in fluctuating glottal area, thereby maintaining approximately incompressible flow. Fluctuations of glottal area generate the bulk of F0 energy while upper formants owe their spectral energy to boundary layer events that happen near the violent endpoints of glottal motion.
Characteristics of roughness in esophageal speech
Authors: Javkin Hector , Niedzielski Nancy , Reed James
Published: July 2002

Esophageal voice, produced by the vibration of the superior sphincter of the esophagus by persons who have been laryngectomized, is almost invariably associated with voice source roughness. Using inverse filtering of speech recorded to minimize phase distortion, the source characteristics of six esophageal speakers with different levels of proficiency were examined. With our three less proficient speakers, the roughness is clearly evident in the volume velocity waveform. Highly proficient esophageal speakers, however, although they have a voice quality which is perceived as rough, nevertheless produce a volume velocity waveform surprisingly similar to that of laryngeal speakers. The characteristics that produce this perceived roughness, other than jitter and shimmer, are difficult to detect in the volume velocity waveform. They are noise components of low amplitude and relatively high frequency, which are attenuated in the (integrated) volume velocity. They are best observed in the differentiated volume velocity waveform or in spectral measures. Our results suggest that the volume velocity waveform may not be a very effective measure for evaluating the speech of highly proficient esophageal speakers.
Modeling and analysis of speakers with vocal-fold nodules
Authors: Kuo Jeff , Hillman Robert E. , Holmberg Eva B.
Published: July 2002

Speakers with vocal-fold nodules commonly use higher than normal subglottal pressures to produce a particular sound pressure level (SPL). The SPL may be low because of a decreased maximum flow declination rate (MFDR) of the glottal flow waveform, increased first formant bandwidth, or increased spectral tilt. A modified two-mass model of vocal-fold vibration is proposed, which suggests that the MFDR can be decreased because of increased coupling stiffness between the masses, altered equilibrium positions for the masses, and the presence of nodules that interfere with the normal closure activity of the vocal folds. A parallel acoustic and aerodynamic study of selected patients with vocal nodules was conducted. Preliminary findings show higher than normal calibrated amplitudes of the first harmonic (H1) normalized by the SPL, as well as larger amplitude differences between the first harmonic and first formant (H1–A1). These results agree with the previous finding of a larger ac component of the glottal flow waveform [Hillman et al., J. Speech Hear. Res. 32, 373–392 (1989)]. The presence of a glottal chink may also widen the first formant bandwidth. Relationships between modeling results and experimental data will be discussed. [Work supported by NIH Grants DC00075 and DC00266.] a)Presently at Stockholm Univ., Sweden.
Interference in short-term pitch and timbre memory due to the structure of a tone sequence
Authors: Starr Gary E.
Published: July 2002

A number of studies have investigated memory for pitch and timbre using a tone discimination task [e.g., G. Starr and M. Pitt, J. Acoust. Soc. Am. 102, 486–494 (1997)], where standard and comparison tones are separated by a retention interval filled with interference tones. These studies found same-dimension similarity to be the primary source of interference. However, the organizational structure of the tone sequence may also affect interference. The present project used two different tasks to evaluate the role of organization on interference in memory for pitch and timbre. The first task was identical to that of previous research. In the second task, listeners discriminated either the pitch or timbre of standard and comparison tones when the standard was presented as the sixth tone of an 11-tone sequence. In both tasks, sequences were constructed that varied the organizational structure of the sequences, while same-dimension similarity was kept constant. The organizational structure of the tone sequences was found to influence interference in both tasks, suggesting that factors other than same-dimension similarity disrupt memory.
Microphone array sensor placement optimization in reverberant environments
Authors: Rabinkin Daniel V. , Renomeron Richard J. , Flanagan James L.
Published: July 2002

Microphone arrays can be used for high-quality sound pickup in reverberant and noisy environments. The beamforming capabilities of microphone array systems allow highly directional sound capture, providing a superior signal-to-noise ratio (SNR) when compared to single microphone performance. Recent work [Rabinkin et al., ‘‘Optimum microphone placement for array sound capture,’’ Proc. SPIE 8/97] has addressed the issue of microphone placement for optimized array performance. A Monte Carlo procedure was described to evaluate average sound capture SNR for a given microphone configuration based on geometry-related array performance statistics. Numerical optimization was performed for particular classes of sensor geometries based on the evaluated SNR. A uniformly distributed uncorrelated additive noise model was used to evaluate performance. An improved performance model is described which accounts for the correlated nature of additive noise generated by acoustic reflections of the source in a reverberant environment. The Allen and Berkley image method is used to generate the reflective noise portion. Optimization is performed for various acoustic conditions and array performance is compared for different reverberation levels.
Passive acoustic tracking of echolocating harbor porpoise (Phocoena phocoena). I. Fisheries management requirements and biological basis
Authors: Potter David C. , Quintal Janeen M. , Miller James H. , Gampert Robert , Lashkari Khosrow
Published: July 2002

Harbor porpoises are incidentally taken in various sink gillnet fisheries nationally. Little is known about the mechanism of these entanglements. To protect these animals as required by the Marine Mammal Protection Act (MMPA), fishery managers use time area closures and/or permit the use of acoustic deterrent devices (pingers) to reduce bycatch. To understand how an entanglement occurs and how the pingers function, one must understand the underwater behavior of the animals. Studies of captive porpoises, and using mounted instrumentation on released animals, have shown some aspects of porpoise life history but may or may not reveal natural behavior. A research program was initiated to determine the feasibility of passively tracking wild harbor porpoise using their echolocation signals (clicks) and observing their underwater movements in three dimensions. Additionally, details of these movements during feeding, traveling, and social events may provide an insight into their behavior that makes them prone to entanglement. Preliminary results demonstrate that the underwater tracking of harbor porpoises can be accomplished using this technique and several aspects of the animal’s natural behavior and communication are presented. A next generation autonomous system, to be deployed near actively fishing sink gillnets being developed, is described. [Work supported by NMFS and the URI/NOAA CMER Program.]
Small-scale roughness and the parabolic equation
Authors: Wurmser Daniel , Gragg Robert F.
Published: July 2002

When the Foldy–Wouthuysen transformation is used to derive the parabolic equation (PE) for a range-dependent environment, a new physical effect associated with small-scale fluctuations of the field is predicted [Wurmser et al., J. Acoust. Soc. Am. 101, 1309–1327 (1997)]. In this presentation, the formalism is applied to the problem of scattering from a rough surface, which is treated as a type of range dependence. The theory predicts the effective impedance boundary conditions proportional to the curvature of the surface, essentially unifying the Biot–Tolstoy theory of scattering from a bossed surface with other modern scattering and propagation theories. The result has been obtained for the two-fluid, Neumann and Dirichlet boundary conditions. The related physical effect is associated with the small-scale cutoff of the field, implying that the wave cannot resolve a surface structure smaller than about 1/12 of a wavelength. The theory also predicts related effects; for example, roughness-induced interface waves for the Neumann and two-fluid boundary conditions. Since the effect on the scattered field is cumulative, its incorporation should improve PE modeling of propagation in waveguides with rough boundaries. [Work supported by ONR.]
Effects of cross correlation between different types of medium perturbations on seabed scattering
Authors: Ivakin Anatoliy N.
Published: July 2002

Sound scattering from the seabed can be generally attributed to two major mechanisms connected with seabed roughness and volume inhomogeneities. Each of these two mechanisms in turn can contain different components. For unconsolidated (fluid) sediments, volume inhomogeneities are due to spatial fluctuations of two different parameters, the density and compressibility, or the density and compressional wave speed, with respect to their mean values. For elastic bottoms, one more fluctuating parameter, shear wave speed, is to be considered. The roughness component can be attributed to the water–sediment interface and to various internal interfaces in the seabed medium as well. In this paper, the effects of cross correlations between the roughness of different interfaces and between the volume fluctuations of different parameters, as well as possible volume–roughness correlations, are examined using a first-order perturbation model. Expressions for the bottom scattering cross section involve corresponding cross-correlation and cross-spectral matrices of seabed medium perturbations. Frequency-angular dependencies of the scattering strength in monostatic and bistatic cases are analyzed for various types of seabed stratification and correlated irregularities. Comparisons are presented for the cases of strongly correlated, anticorrelated, and partially correlated perturbations. Examples are given where the cross-correlation effects are important and should be taken into account in development of methods for inversions of seabed properties. [Work supported by ONR.]
A recovery model for coincidence neurons
Authors: Wilson Timothy A. , Thongprasirt Rachod , Khanifar Aziz A.
Published: July 2002

A new model for firings of coincidence neurons in the MSO is presented. The model is similar to one by Colburn et al. [Hearing Res. 49, 335–346 (1990)]: Both are point processes, both have inputs which are impulse-train representations of the firing events of primarylike neurons, both operate on a low-pass filtered sum of those inputs, and both output a sequence of impulses at the event times of the coincidence neuron’s firings. In this model, their threshold-crossing neuron model is replaced by a recovery model similar to that modeling the input firings. The coincidence neuron’s drive function is a nonlinearly distorted version of the filtered sum of inputs; for simplicity, its recovery function is the same as that of the input neurons. The model’s firing rates, vector strengths, period histograms, and interval histograms are compared to data from dog and cat and with similar responses of the Colburn et al. model.
Double-evoked otoacoustic emissions. II. Intermittent noise rejection, calibration and ear-canal measurements
Authors: Keefe Douglas H. , Ling Robert
Published: July 2002

Measurements of double-click-evoked otoacoustics emissions (2CEOAEs) and double-chirp distortion products (2ChDPs) are reported for normal-hearing adults based upon theory presented in an earlier report [Keefe, J. Acoust. Soc. Am. 103, 3489–3498 (1998)]. The nonlinear acoustic response of a probe assembly used in ear-canal measurements is tested in a calibration cavity to compare the double-evoked (2E) technique with existing OAE techniques. The 2E technique reduces the peak distortion by approximately 30 dB relative to existing click-evoked techniques. The 2E subtraction of click responses is partially analogous to current techniques in that the linear response is eliminated, but differs in that high-frequency measurements are improved by eliminating time gating of the cochlear response, and low-frequency measurements are improved by reducing probe distortion, especially when two acoustic sources are used. Because time gating is eliminated, it is straightforward to measure the onset of a click-evoked OAE. The nonlinear coherence function is used to measure the nonlinear distortion signal-to-noise ratio (DNR) for the 2ChDPs and 2CEOAEs. The DNR is typically 20–30 dB. An intermittent noise rejection technique is implemented in real time that compares a currently acquired ear-canal response with a stored response. Dissimilar responses indicate the presence of intermittent noise, and the noise-contaminated responses are thereby discarded before ensemble averaging.
The perception of speech gestures
Authors: Surprenant Aimée M. , Goldstein Louis
Published: July 2002

Two experiments examined the effects of temporal overlap of speech gestures on the perception of stop consonant clusters. Sequences of stop consonant gestures that exhibit temporal overlap extreme enough to potentially eliminate the acoustic evidence of (at least) one of the consonants were obtained from x-ray microbeam data. Subjects were given a consonant monitoring task using stimuli containing stop sequences as well as those containing single stops. Results showed that (1) the initial consonant in the stop sequences was detected significantly less often than in the single stops; (2) bilabial gestures were considerably more effective at obscuring a preceding alveolar than the reverse; and (3) the detection rate correlated with an index of overlap between lip and tongue tip gestures. Experiment 2 employed stimuli that were truncated during the closure for the critical stop or stop sequence, so as to eliminate any information occurring in the acoustic signal at the stop release. This experiment showed that removing release information decreased detectability of the consonants generally. However, consistent with the observed gestural patterns, removing the release did not decrease detection of the alveolar stop when it was the first consonant of a sequence, indicating that there was no information about the alveolar stop present in acoustic realization of the second stop release. These experiments show that certain gestural patterns actually produced by English speakers may not be completely recoverable by listeners, and further, that it is possible to relate recoverability to particular metric properties of the gestural pattern.
Masking patterns for sinusoidal and narrow-band noise maskers
Authors: Moore Brian C. J. , Alcántara Joseph I. , Dau Torsten
Published: July 2002

The masking patterns produced by narrow-band maskers can show distinct irregularities. These experiments attempted to clarify the relative importance of factors contributing to these irregularities. A three-alternative adaptive forced-choice method with feedback was used, to promote use of the optimal detection cues. The masker and signal were either a sinusoid or a band of noise that was 80 Hz wide, giving four possible combinations of masker and signal type. In experiment 1, masking patterns were measured for maskers centered at 1 kHz, for all combinations of masker and signal type (tone or noise). The masking patterns showed irregularities (dips or “shoulders”) above the masker frequency, and the irregularities were larger for the sinusoidal than for the noise masker. Experiment 2 was similar to experiment 1, except that low-pass noise was added to mask combination products. For the noise masker, the low-pass noise slightly increased thresholds, and largely eliminated the irregularities in the patterns, but for the tone masker, the irregularities persisted. Experiment 3 used a noise signal with tone and noise maskers centered at 250, 1000, and 4000 Hz. The tone masker produced less masking than the noise masker for masker-signal frequency separations of 150–250 Hz, regardless of masker frequency. Experiment 4 used an additional masker tone to introduce beats similar to those produced by the interaction of the signal and (main) masker, and to mask combination products. This largely eliminated the dips in the masking patterns for both the noise and tone maskers. Experiment 5 used an additional pair of high-frequency tones to introduce beats, with similar results. We conclude that temporal fluctuations (beats) have a strong influence on the masking patterns for sinusoidal maskers, for masker-signal frequency separations up to a few hundred Hz. Beats may also have some influence on the masking patterns for noise maskers. The detection of combination products also plays a role.
Range dependence of the response of a spherical head model
Authors: Duda Richard O. , Martens William L.
Published: July 2002

The head-related transfer function (HRTF) varies with range as well as with azimuth and elevation. To better understand its close-range behavior, a theoretical and experimental investigation of the HRTF for an ideal rigid sphere was performed. An algorithm was developed for computing the variation in sound pressure at the surface of the sphere as a function of direction and range to the sound source. The impulse response was also measured experimentally. The results may be summarized as follows. First, the experimental measurements were in close agreement with the theoretical solution. Second, the variation of low-frequency interaural level difference with range is significant for ranges smaller than about five times the sphere radius. Third, the impulse response reveals the source of the ripples observed in the magnitude response, and provides direct evidence that the interaural time difference is not a strong function of range. Fourth, the time delay is well approximated by well-known ray-tracing formula due to Woodworth and Schlosberg. Finally, except for this time delay, the HRTF for the ideal sphere appears to be minimum-phase, permitting exact recovery of the impulse response from the magnitude response in the frequency domain.
Are individualized head-related transfer functions required for auditory information displays?
Authors: Wenzel Elizabeth M. , Begault Durand R.
Published: July 2002

In aerospace applications, spatial cues in auditory displays can allow an astronaut, ground-controller, or other human operator to take advantage of their natural ability to localize sounds in three-dimensional space. Synthetic localization of acoustic images can be used to enhance situational awareness, improve segregation of multiple audio signals through selective attention, and provide a means of detecting a desired signal against noise for enhanced speech intelligibility. A number of studies in the literature have suggested that individualized head-related transfer functions (HRTFs) produce the best localization performance for a given listener in a spatial auditory display. However, it is often impractical to measure the HRTFs for each potential user of an aerospace display. Further, whether or not individualized cues are required may depend upon the nature of the task that is being aided. For example, a communications display may not require individualized cues to enhance speech intelligibility, while a display that represents the direction of incoming aircraft to an air traffic controller may benefit from individualized HRTFs. This paper describes some of the spatial auditory displays that have been investigated at NASA Ames and discusses the efficacy of using nonindividualized cues in the context of various aerospace tasks.
Variational formulations for the vibration of a micropolar piezoelectric body
Authors: Ciumasu Silvia G. , Vieru Dumitru
Published: July 2002

This work is a continuation of the previous study ‘‘Polarization gradient in micropolar piezoelectricity,’’ which was presented at The 5th International Conference on Integral Methods in Science and Engineering, IMSE’98, 10–13 August 1998, Michigan Tech, Houghton, MI. The present paper is concerned with the variational formulation for the free vibration of a micropolar piezoelectric body. These variational principles can be considered as generalizations of the corresponding variational formulations in classical piezoelectricity. It is shown that there exist types of variational formulations depending on the internal energy, electric enthalpy, mechanical enthalpy, and enthalpy, respectively.
Elastic waves in monoclinic incompressible materials and reflection from an interface
Authors: Sotiropoulos Dimitrios A. , Nair Sudhakar
Published: July 2002

The reflection of plane elastic waves from a free surface of monoclinic incompressible materials is examined under plane strain conditions in a plane of material symmetry. It is found that this problem can be equivalently treated by elastic wave reflection in orthotropic incompressible materials if the material constants of the monoclinic material are properly related to those of the orthotropic material. Thus the range of existence of the two (one homogeneous and the other homogeneous or inhomogeneous) reflected waves in a monoclinic material, including points corresponding to zero amplitude reflected waves, can be obtained from that given in a previous paper [Nair and Sotiropoulos, J. Acoust. Soc. Am. 102, 102–109 (1997)] where an orthotropic material was treated.
Variation in the dispersion of axisymmetric waves in infinite circular rods with crystallographic wire texture
Authors: Mason T. A.
Published: July 2002

This paper presents the solution to the frequency equation for a number of polycrystalline, textured circular rods having transverse isotropy. The effective, second-order elastic stiffness tensors were estimated using the recursive general Hill arithmetic mean (GHAM). The velocity dispersion curves for a number of combinations of materials and crystallographic fiber or wire textures were calculated and the variation due to texture displayed. At large wavelengths, the velocity dispersion of fiber textured materials exhibits a lowest-order axisymmetric mode which varies only with the directional Poisson’s ratios in a manner similar to that of isotropic aggregates. In this wavelength regime, the waves propagate nondispersively at the wave speed, C0, as dictated by the directional Young’s modulus. At wavelengths smaller than the rod radius, the dispersion curves were more influenced by the full anisotropy of the wire textures. At these wavelengths, the dispersion curves for the anisotropic materials deviated significantly from those of the isotropic materials and one another with the higher axisymmetric vibration modes exhibiting extreme differences. This deviation is a function of the single crystal anisotropy and nature of the wire textures.
Method for the selection of sentence materials for efficient measurement of the speech reception threshold
Authors: Versfeld Niek J. , Daalder Laura , Festen Joost M. , Houtgast Tammo
Published: July 2002

A method is described to select sentence materials for efficient measurement of the speech reception threshold (SRT). The first part of the paper addresses the creation of the sentence materials, the recording procedure, and a listening experiment to evaluate the new speech materials. The result is a set of 1272 sentences, where every sentence has been uttered by two male and two female speakers. In the second part of the paper, a method is described to select subsets with properties that are desired for an efficient measurement of the SRT. For two speakers, this method has been applied to obtain two subsets for measurement of the SRT in stationary noise with the long-term average spectrum of speech. Lastly, a listening experiment has been conducted where the two subsets (each comprising 39 lists of 13 sentences each) are directly compared to the existing sets of Plomp and Mimpen [Audiology 18, 43–52 (1979)] and Smoorenburg [J. Acoust. Soc. Am. 91, 421–437 (1992)]. One of the outcomes is that the newly developed sets can be considered as equivalent to these existing sets.
Phonological conditioning of peak alignment in rising pitch accents in Dutch
Authors: Ladd D. R. , Mennen Ineke , Schepman Astrid
Published: July 2002

This paper deals with the factors that influence the alignment of F0 movements with phonetic segments. It reports two experiments on the alignment of rising prenuclear pitch accents in Dutch. In experiment 1, it is shown that the final peak of the rise is aligned at the end of the vowel if the accented syllable contains a long vowel, but during the following consonant if the accented syllable contains a short vowel. The beginning of the rise is consistently aligned at the beginning of the accented syllable. Experiment 2 attempts to distinguish between two explanations for this finding: (1) a durational account, in which the F0 rise takes a certain amount of time and overruns into the following consonant if the vowel is short; and (2) a structural account, in which the peak of the rise is seen as a tonal target aligned with the end of the syllable (which is structurally earlier for long vowels than for short vowels). The data partially support both accounts. There is an alignment difference despite a lack of durational difference, which supports the structure-based account. However, the effect is reduced compared to experiment 1, showing that time pressure may work against the ideal alignment.
Generalized thermoelastic waves in homogeneous isotropic plates
Authors: Sharma J. N. , Singh Devinder , Kumar Rajneesh
Published: July 2002

The propagation of thermoelastic waves in homogeneous isotropic plate subjected to stress-free and rigid insulated and isothermal conditions is investigated in the context of conventional coupled thermoelasticity (CT), Lord–Shulman (LS), Green–Lindsay (GL), and Green–Nagdhi (GN) theories of thermoelasticity. Secular equations for the plate in closed form and isolated mathematical conditions for symmetric and skew-symmetric wave mode propagation in completely separate terms are derived. It is shown that the motion for SH modes gets decoupled from the rest of the motion and remains unaffected due to thermo-mechanical coupling and thermal relaxation effects. The phase velocities for SH modes have also been obtained. The results for coupled and uncoupled theories of thermoelasticity have been obtained as particular cases from the derived secular equations. At short wavelength limits the secular equations for symmetric and skew-symmetric waves in a stress-free insulated and isothermal plate reduce to Rayleigh surface waves frequency equations. Finally, the numerical solution is carried out for aluminum–epoxy composite material and the dispersion curves for symmetric and skew-symmetric wave modes are presented to illustrate and compare the theoretical results.
Discussing Code Status—Balancing Obligations to Respect Patient Autonomy While Avoiding Harm
Authors: Inglis Sara S.
Published: March 2023

This essay describes a physician’s experience of completing medical education and postgraduate clinical training in Ireland vs adjusting to residency in the US.
Fast and efficient molecule delivery into Euglena gracilis mediated by cell‐penetrating peptide or dimethyl sulfoxide
Authors: Gao Pingwei , Sun Chengfu
Published: March 2023

This study describes the development of two methods for delivering exogenous materials into Euglena gracilis, a unicellular flagellate organism. We report that the use of Pep‐1, a short cell‐penetrating peptide (CPP), or dimethyl sulfoxide (DMSO) can mediate fast and efficient intracellular delivery of exogenous materials into E. gracilis, achieving cellular entry efficiency as high as 70–80%. However, compared with human cells, the penetration of this algal cell with CPP requires a much higher concentration of purified proteins. In addition, upon convenient treatment with DMSO, E. gracilis cells can efficiently adsorb exogenous proteins and DNA with 10% DMSO as the optimal concentration for Euglena cells. Our results provide more options for the E. gracilis transformation ‘toolkit box’ and will facilitate future molecular manipulations of this microalgal organism.
Pre‐fire grazing and herbicide treatments can affect post‐fire vegetation in a Great Basin rangeland
Authors: Gornish Elise S. , Guo Jessica S. , Porensky Lauren M. , Perryman Barry L. , Leger Elizabeth A.
Published: March 2023

Management of wildfire associated with spread of the highly invasive annual grassBromus tectorum(cheatgrass) is a critical need in the western U.S.

We investigated the utility of coupling common rangeland management strategies pre‐fire to modify post‐fire plant community outcomes. We used a long‐term, large‐scale experiment to test the separate and combined effects of pre‐fire targeted grazing (spring and fall), native plant seeding (seeding rate, seed coating and spatial seeding arrangement) and herbicide (glyphosate followed by 2 years of imazapic) on post‐fire plant community outcomes in a highly invaded system in the Great Basin, U.S.

We found grazing and herbicide effects were consistent across cheatgrass biomass, count, and cover. Spring grazing reduced cheatgrass more effectively than fall grazing; however, this effect was detected primarily outside of the seeding treatments. Herbicide overall and in conjunction with grazing reduced cheatgrass and fuel loads. Among seeding treatments, seed mixtures proved more effective than monocultures for reducing both cheatgrass count and cover, particularly when combined with low seed rate. However, many seeding approaches resulted in higher cheatgrass dominance, and thus higher fuel loads.

This work suggests that effects of pre‐fire herbicide for reducing cheatgrass abundance can persist post‐fire. Grazing, however, might not produce consistent results, and season of grazing can affect outcomes. Employing pre‐fire management strategies to interrupt the cheatgrass‐fire cycle may have utility. Some of our treatments were able to reduce cheatgrass abundance after fire, but despite our intensive interventions, we did not find a strategy that led to full restoration of native perennial species.
Design and Applications of Low‐Temperature Hydrogen‐Fed Fuel Cell Stacks
Authors: Barbera Orazio , Giacoppo Giosuè
Published: March 2023

Designing a low‐temperature hydrogen fuel cell stack is a multidisciplinary activity. It involves knowledge of electrochemistry, mechanics, and thermodynamics. To explain the conceptual path that leads from a single cell to a complete power system, however, it is necessary to make a historical excursus and then show the essential information regarding thermodynamics, the components of a fuel cell stack system, and its applications. These are the keys to this article. The historical excursus helps understand how much time this technology needed and the steps necessary so far to reach today's level of maturity. A review of electrochemistry and thermodynamics is essential for understanding the design process. It starts with the choice of the stack architecture, which determines the characteristics and functions of the main components: electrochemical components (electrode and polymer electrolyte) and hardware components (bipolar plates, clamping plates, current collectors, and gaskets). Once the architecture is defined, it is possible to calculate the electrical parameters of the fuel cell stack (voltage and current), the active area of the single cell, the number of cells, and the cell voltage. However, this is not enough for an exhaustive discussion. It is necessary to illustrate the transition from the stack to the fuel cell system. Therefore the most significant components to support the operation of the stack (the “balance of plant”); and the applications of fuel cell systems in automotive, stationary, and portable contexts are the last and no less significant arguments.
A hybrid deep learning framework driven by data and reaction mechanism for predicting sustainable glycolic acid production performance
Authors: Zhou Xin , Li Zhiyang , Feng Xiang , Yan Hao , Chen De , Yang Chaohe
Published: March 2023

Selective oxidation at low temperatures without alkali of biomass is a promising and sustainable avenue to manufacture glycolic acid (GA), a biodegradable functional material to protect the environment. However, producing glycolic acid with high selectivity and yield using the traditional research and development approach is time‐consuming and labor‐intensive. To this context, a hybrid deep learning framework driven by data and reaction mechanisms for predicting GA production was proposed, considering the lack of related reaction mechanisms in the machine learning algorithms. The proposed hybrid deep learning framework involves the kinetic reaction mechanism, catalyst properties, and reaction conditions. Results showed that the fully connected residual network exhibited superior performance (average R2 = 0.98) for the prediction of conversion rate and product yields. Then, the multi‐objective optimization and experimental verification guided the research are carried out. The experimental verification is comparable to the modeling results, with errors of less than 4% for conversion rate and GA yields. The life cycle assessment further identifies that using the optimized operating parameters, the fossil energy demand and greenhouse emissions have decreased by 2.96% and 3.00%, respectively. This work provides new insight and strategy to accelerate the engineered selective oxidation for desired GA production.
DFT Studies on Ligand Controlled Highly Selective Copper‐Catalyzed Borylations of Allenes
Authors: Hong Shichao , Zhang Xue
Published: March 2023

The mechanism of the Cu‐catalyzed borylations of allenes with bis (pinacolato) diboron has been studied by DFT calculations. The possible pathways involve two key steps, borylcupration and γ‐protonolysis. Computed results show that the γ‐protonolysis step is not only the rate‐limiting step but also determines the regioselectivity. When employing monophosphine P(p‐MeOC6H4)3 as the ligand, the electronic and steric effects are both effective in the control of regio‐ and stereoselectivity; however, for sterically hindered bulky bisphosphine ligand BIPHEP, it is the steric hindrance that reverses the regioselectivity of the γ‐protonolysis process.
Catalytic Homologation‐Allylboration Sequence for Diastereo‐ and Enantioselective Synthesis of Densely Functionalized β‐Fluorohydrins with Tertiary Fluoride Stereocenters
Authors: Wang Qiang , Eriksson Lars , Szabó Kálmán J.
Published: March 2023

Homologation of trisubstituted fluoroalkenes followed by allylboration of aldehyde, ketone and imine substrates is suitable for synthesis of β‐fluorohydrin and amine products. In the presence of (R)‐iodo‐BINOL catalyst enantioselectivities up to 99 % can be achieved by formation of a single stereoisomer with adjacent stereocenters, of which one is a tertiary C−F center.
A facile fabrication of zinc oxide‐doped carbon aerogel by cellulose extracted from coconut peat and sodium alginate for energy storage application
Authors: Duy Pham Hoang Anh , Tu Phan Minh , Son Tran Thanh , Dat Nguyen Minh , Nam Nguyen Thanh Hoai , Cong Che Quang , Hai Nguyen Duy , An Hoang , Huyen Nguyen Thi Thanh , Minh Phan Pham Duc , Son Nguyen Truong , Phong Mai Thanh , Hieu Nguyen Huu
Published: March 2023

In this study, ZnO‐doped carbon aerogel is synthesized from cellulose in coconut peat with sodium alginate as a binder via both freeze‐drying and pyrolysis processes. Of those, zinc nitrate is used as not only a crosslinking agent to form gel but also a precursor source to dope ZnO in the carbon aerogel matrix. The effect of precursor ratios on the characterization and energy storage capacity of composite aerogel is investigated. As a result, it is indicated that the formed ZnO‐doped carbon aerogel possesses a highly porous structure which is typical for aerogel structure shown by SEM images, density, and porosity. Besides, via the XRD patterns, the confirmation of the ZnO crystal structure is found within the carbon aerogel lattice. In terms of energy storage, based on the specific capacitance results, the ZCA‐4 sample with a sodium alginate and cellulose weight ratio of 1:20 shows the best energy storage with a specific capacitance of 105 F/g in the voltage range of 0–0.5 V and scan‐rate speed of 0.005 V. Therewithal, the ZCA‐4 also performs high durability, high scanning speed tolerance, and stable storage performance with efficiency reaching more than 99% after 500 consecutive scan cycles. These results demonstrate that the ZnO‐doped carbon aerogel has potential applications as electrode materials in supercapacitors.