bluuebunny/crossref_metadata_2025 huggingface dataset:
Amplitude and time fluctuations and their relationship to temperature variations
Authors: Lutz Steven D. , Culver R. Lee , Bradley David L.
Published: October 2013

Amplitude and time fluctuations of direct and refracted paths measured during a field test near San Clemente Island in August 2002 are presented. Signals used include 20 and 40 kHz CW pulses with 0.14 ms and 1.0 ms durations. The transmitters were suspended from a buoy with a bungee section in the mooring to minimize the watch circle. The receive hydrophone array was suspended from a research vessel in a three point moor. The source to receiver separation was 714 m. Towed CTD data, also collected during the experiment, is presented. A relationship between the amplitude and phase fluctuation in the acoustic arrivals and temperature variations in the water column is developed and compared to existing theory. Acoustic signals will be analyzed using a matched filter, fluctuations will be computed in normalized level and variance of time of arrival. Temperature variations will be computed as mean-square fluctuations of the index of refraction. Other physical mechanisms contributing to acoustic fluctuations including source/receiver motion, turbulence, and internal waves are also investigated.
High frequency acoustic scattering by a gas bubble
Authors: Gumerov Nail A.
Published: October 2013

A problem of acoustic scattering by a gas bubble when the length of the incident acoustic waves can be comparable with or smaller than the bubble size is considered. For such waves pressure and temperature distributions inside and outside the bubble are not spherically symmetrical even though the bubble is spherical in the absence of the acoustic field and the amplitude of the acoustic field is small. This case is considered in the present study. Genearal three-dimensional pressure and temperature distributions together with capillary effects are taken into account by expansion of solutions for coupled thermal and acoustic problems in series of spherical multipoles. The acoustic response of the bubble including volume and surface oscillations is analyzed. Limits for modeling of the bubble as a sound-soft sphere in acoustic scattering problems are discussed.
The effects of the ocean environmental variability on sound propagation and reverberation from ASIAEX (ECS)
Authors: Li Fenghua , Zhang Renhe , Li Zhenglin , Liu Jianjun
Published: October 2013

During the duration of the Asian Seas International Acoustics East China Sea Experiment, the ocean environment (e.g., wind speed, sea state, internal wave) varied significantly. Propagation and reverberation data from explosive charges recorded by a vertical line array and horizontal line array at different times during the experiment show that the acoustic data have a strong fluctuation. In this paper, the recorded data are analyzed to estimate the relationship between the acoustic signal fluctuation and the environmental variability. A PE code is used to simulate the effect of the recorded ocean environmental variability on the sound signal fluctuation. The experimental data and numerical results indicate the strong dependence between the acoustic fluctuation and ocean environmental variability. A coupled normal-mode-based model is also used to explain some of the acoustic fluctuation. [Work supported by the National Natural Science Foundation of China and ONR.]
Neural mechanisms of call recognition in Pacific treefrogs
Authors: Rose Gary J.
Published: October 2013

Pacific treefrogs, Hyla regilla, use advertisement and encounter calls in their acoustic communication. These two call types differ primarily in the rate that pulses are repeated; at 17°C, pulse repetition rates (PRRs) for advertisement and encounter calls are about 100 pulses/s and 30 pulses/s, respectively. Behavioral studies indicate that two discrete channels exist for processing these communication signals. Because sound pulses in these two call types are highly similar in spectral and temporal structure, the PRR selectivity of the advertisement filter is likely to result from an analysis of interpulse interval. Behavioral studies support the hypothesis that temporal integration might underlie this analysis. As a neural correlate to the behavioral studies, toral neurons have been recorded that respond selectively to PRRs found in the advertisement call. These cells fail to respond to encounter call PRRs. In support of the integration hypothesis, these units only respond after a threshold number of correct interpulse intervals have been presented; the average PRR is largely irrelevant. The interval-counting process can be reset by a single inappropriate interval. In the most selective cases, a single interval that is slightly longer or shorter than the optimal interval can reset the integration process. [Work supported by NIDCD.]
Three applications of David Weston’s work to studies of scattering from fish
Authors: Feuillade C. , Nero R. W. , Thompson C. H. , Love R. H.
Published: October 2013

The Naval Research Laboratory has for many years conducted a program, comprising both experimental and theoretical components, to determine the low- to mid-frequency acoustic scattering characteristics of individual fish and fish schools. This paper discusses three procedures, developed during the course of our work, whose intellectual genesis can be traced directly from David Weston. First, we discuss the ‘‘Weston correction’’ to the monopole resonance frequency of a prolate spheroidal air bubble. This is used to model variations in the resonance frequency of a fish swimbladder as its aspect ratio changes under compression, and to facilitate fish species identification and abundance estimation through the water column. Second, we discuss a scattering model, inspired by Weston’s work on arrays of air bubbles, which incorporates coherence and multiple scattering effects between swimbladders of comparable size to investigate the levels and fluctuations of scattering from fish schools. Third, we discuss an acoustic reference target, constructed from sheets of ‘‘Bubble-Wrap®’’ packaging material and successfully deployed and tested, which is a practical implementation of Weston’s theory for the scattering response of planar arrays of identical bubbles. [Work supported by ONR.]
Monostatic and bistatic scattering from a density contrast surface
Authors: Feuillade C. , Clay C. S.
Published: October 2013

Chu’s formalism for the impulse response of a point source to a density contrast isovelocity wedge [J. Acoust. Soc. Am. 86, 1883–1896 (1989)] is of significant practical importance, since it facilitates the extension of wedge diffraction boundary scattering models to rough penetrable surfaces. The method is used here to study scattering from an experimental surface described by Li et al. [J. Acoust. Soc. Am. 96, 3715–3720 (1994)]. The geometry contains both interior and exterior wedges, and allows the diffracted scattering component to be studied independently of the reflected component. For density contrast values which emulate rigid boundary conditions, the formalism correctly models the experimental results, and duplicates predictions of the Biot–Tolstoy solution for a rigid wedge [J. Acoust. Soc. Am. 29, 381–391 (1957)]. The formalism is then used to investigate an assumption commonly made in boundary scattering work, i.e., that scattering levels can be effectively estimated by scaling the predictions of a rigid surface scattering model by the reflectivity of the surface. The results suggest that the assymption is most valid for monostatic (backscattering) configurations, and less good for bistatic cases, with increasing differences occurring between interior and exterior wedge geometries. [Work supported by ONR.]
Ambient noise level on vertical array in ASIAEX South China Sea experiment
Authors: Wei Ruey-Chang , Chen Yung-Chien
Published: October 2013

Previous literatures show that ambient noise in deep water should decrease with depth, but would it be the same in the shallow? The ASIAEX 2001 South China Sea experiment is on the continental shelf-break, with water depth from 100 m to 400 m, so the depth effect of ambient noise in shallow water can be explored. In this study, acoustic signal of ambient noise was collected on vertical line array, which has 16 elements, from 700 to 1200 Hz. From the results of this study, ambient noise has insignificant change with depth, however it is much affected by the variation of temperature, frequency, and occurrence of internal wave. Higher frequency tends to have lower SPL and the decay is of 5 dB/octave approximately. The temperature profile controls the vertical distribution of ambient noise level, so the internal wave effect can be significant. Moreover, the serious weather condition, like the typhoon during the experiment, can greatly increase the ambient noise level and change its distribution.
Assessment of language impact to speech privacy in closed offices
Authors: Ma Yong Ma , Caswell Daryl J. , Dai Liming , Goodchild Jim T.
Published: October 2013

Speech privacy is the opposite concept of speech intelligibility and can be assessed by the predictors of speech intelligibility. Based on the existing standards and the research to date, most objective assessments for speech privacy and speech intelligibility, such as articulation index (AI) or speech intelligibility index (SII), speech transmission index (STI), and sound early-to-late ratio (C50), are evaluated by the subjective measurements. However, these subject measurements are based on the studies of English or the other Western languages. The language impact to speech privacy has been overseen. It is therefore necessary to study the impact of different languages and accents in multiculturalism environments to speech privacy. In this study, subjective measurements were conducted in closed office environments by using English and a tonal language, Mandarin. Detailed investigations on the language impact to speech privacy were carried out with the two languages. The results of this study reveal the significant evaluation variations in speech privacy when different languages are used. The subjective measurement results obtained in this study were also compared with the objective measurement employing articulation indices.
Wind noise reduction research: Possible lessons for infrasound?
Authors: Raspet Richard , Hedlin Michael A. H.
Published: October 2013

Morgan [Ph.D. dissertation, University of Mississippi, 1992] extended the theory of wind noise reduction by spherical screens proposed by Phelps [RCA Rev. 3, 203–212 (1938)] to modern porous foam windscreens and achieved good predictions of the large (>12 dB) low frequency reduction afforded by spherical screens even when the turbulence scale is much greater than the wind screen size. In this paper the findings of Morgan are reviewed as background for recent measurements of the infrasonic wind noise reduction of a wind barrier design suggested by Ludwik Liska. The data suggest that significant reductions in infrasonic wind noise can be achieved with devices smaller than a turbulence scale size.
Pressure and velocity profiles in a static mechanical hemilarynx model
Authors: Alipour Fariborz , Scherer Ronald C.
Published: October 2013

This study examined pressure and velocity profiles in a hemilarynx mechanical model of phonation. The glottal section was fabricated from hard plastic. Twelve pressure taps were mounted in the vocal-fold surface and connected to a differential pressure transducer through a pressure switch. The glottal gap was measured with a filter gauge and the glottal angle was well specified by use of a laser system. Eight pressure transducers were placed in the flat Plexiglas wall opposite the vocal fold. Hot-wire anemometry was used to obtain velocity profiles upstream and downstream of the glottis. The results indicate that the pressures were asymmetric in the glottis: the pressure distribution on the vocal fold was consistent with pressure change along a parallel duct, whereas the pressures on the opposite flat wall typically were lower. The upstream velocity profiles were symmetric regardless of the constriction shape and size. The jet velocity downstream of the glottis was turbulent even for laminar upstream conditions. The narrower the glottis, the closer the jet stayed to the upper wall and traveled further before expanding. The turbulence ratio was greater on the skirt of the jet and reached as high as 25% of the maximum jet velocity.
Auditory organs in Xenopus laevis and Xenopus tropicalis
Authors: Serrano Elba E. , Quick Quincy A.
Published: October 2013

The genus Xenopus is comprised of over 20 genetically divergent species that occupy aquatic habitats such as lakes, rivers, and swamps south of the African Sahara. Like other anurans, advertisement calls are important signals for reproductive behavior and Xenopus have a vocal apparatus adapted for underwater sound production. The tetraploid Xenopus laevis is a well-established model organism for cell and developmental biology. Xenopus tropicalis, a diploid member of the Silurana group, is a newer Xenopus model for molecular genetics that is suited for transgenic studies. Both species are being used for investigations of inner ear organogenesis. Results presented here use light and confocal microscopy to examine the structure of the auditory organs of X. laevis and X. tropicalis. Images gathered from sectioned tissue stained with hematoxylin/eosin or microdissected organs labeled with Alexa 488 phalloidin (Molecular Probes) and propidium iodide illustrate the organization and innervation of the sensory epithelia of the sacculus, amphibian papilla and basilar papilla of the two species. The data show the similarities between the sensory fields and highlight the size differences of the organs in the two species. [Work supported by grant to EES (NIGMS, NIDCD) and awards to QQ (NASA NMSGC, NIGMS RISE).]
Initial reference level of the absolute reverberation intensity in shallow water
Authors: Zhou Ji-Xun , Zhang Xue-Zhen
Published: October 2013

A quality database of reverberation is absolutely essential if one is to understand the shallow water reverberation problem. To develop a practical prediction model, invert seabottom scattering strength (and acoustic parameters), or to develop a seabottom scattering model, all require a reliable reverberation database either for comparison or justification. It is relatively easy to get nonabsolute intensity curves from at-sea measurements. However, to get wideband absolute reverberation level (ARL) for both short and long range is a very delicate task that can be prone to errors. It often requires a measurement system that can cover a large dynamic range up to 150 dB and avoid signal overflow and saturation. It may need to precisely measure source level (SL) and calibrate measurement system. In this paper, a traditional method to get ARL frequently used by Chinese scientists is introduced by showing the results from the recent ASIAEX and 1996 Yellow Sea experiments. The ARL (relative to SL) at 1 second (after an explosive source is detonated) is defined as the initial reference level (IRL). The IRL from the ASIAEX and Yellow Sea experiments as a function of frequency will be given to compare with the data from other ‘‘natural laboratories’’ with different sediments, and with our theoretical prediction. The advantage of introducing a concept of IRL will be discussed. [Work supported by ONR and CAS.]
Cramer–Rao lower bounds on the angle-of-arrival estimates for a wave propagating in a random medium: Geometric acoustics regime
Authors: Collier Sandra L. , Wilson D. Keith
Published: October 2013

In the geometric acoustics regime, a propagating wave is weakly diffracted and weakly scattered by the medium. The variance of the real component of the signal is much less than the variance of the imaginary component, thus the signal may not be modeled as a complex Gaussian random variable (whose real and imaginary components have equal variance), as is often done in the Rytov extension region, where both scattering and diffraction are strong. A statistical model for a signal in the geometric acoustics regime has been previously developed [S. L. Collier and D. K. Wilson, J. Acoust. Soc. Am. 111, 2379 (2002)] and its properties have been further investigated [S. L. Collier and D. K. Wilson, ASA April 2003 Meeting on Signal Processing (submitted)]. This statistical model is applied here to an acoustic wave propagating in a random medium with fluctuations described by von Kármán’s spectrum. Additive white Gaussian noise is also considered. The correlation functions of the phase and log-amplitude fluctuations for a von Kármán spectrum are derived in the geometric acoustics limit. The Cramer–Rao lower bounds (CRLBs) on the angle-of-arrival estimates are calculated assuming multiple unknown parameters. The range dependence of the CRLBs is studied in detail.
Modeling scattering enhancements at isolated resonances using energy conservation, reciprocity, symmetry, and the optical theorem
Authors: Marston Philip L. , Osterhoudt Curtis F.
Published: October 2013

Sound scattered by some objects in water exhibits isolated narrow resonances that are sufficiently large in amplitude to dominate the low-frequency scattering. Examples include the quadrupole mode of thin spherical shells and of solid plastic spheres [B. T. Hefner and P. L. Marston, J. Acoust. Soc. Am. 107, 1930–1936 (2000)] and organ-pipe modes of water-filled pipes [C. F. Osterhoudt and P. L. Marston, J. Acoust. Soc. Am. 110, 2773 (2001)]. This presentation concerns simple methods for approximating the scattering. In the case of spheres, ray theory for the backscattering reduces to a simple form for high-Q modes: Eq. (58) of Marston [J. Acoust. Soc. Am. 83, 25–37 (1988)]. This result gives the backscattering form function at resonance (in the usual normalization) to have the magnitude 2(2n+1)/ka. Here n is the partial wave index associated with the mode of the sphere and ka is the product of the wave number and the sphere radius. This result may also be derived directly from energy conservation and the optical theorem. Scattering amplitudes associated with high-Q organ pipe resonances of open cylindrical pipes are also derived here by a related method using the energy conservation, reciprocity, symmetry, and the optical theorem.
Scattering of plane evanescent waves by buried cylinders: Modeling the coupling to guided waves and resonances
Authors: Marston Philip L.
Published: October 2013

The coupling of sound to buried targets can be associated with acoustic evanescent waves when the sea bottom is smooth. To understand the excitation of guided waves on buried fluid cylinders and shells by acoustic evanescent waves and the associated target resonances, the two-dimensional partial wave series for the scattering is found for normal incidence in an unbounded medium. The shell formulation uses the simplifications of thin-shell dynamics. The expansion of the incident wave becomes a double summation with products of modified and ordinary Bessel functions [P. L. Marston, J. Acoust. Soc. Am. 111, 2378 (2002)]. Unlike the case of an ordinary incident wave, the counterpropagating partial waves of the same angular order have unequal magnitudes when the incident wave is evanescent. This is a consequence of the exponential dependence of the incident wave amplitude on depth. Some consequences of this imbalance of partial-wave amplitudes are given by modifying previous ray theory for the scattering [P. L. Marston and N. H. Sun, J. Acoust. Soc. Am. 97, 777–783 (1995)]. The exponential dependence of the scattering on the location of a scatterer was previously demonstrated in air [T. J. Matula and P. L. Marston, J. Acoust. Soc. Am. 93, 1192–1195 (1993)].
Basilar-membrane nonlinearity effects on tones and speech
Authors: Dubno Judy R. , Horwitz Amy R. , Ahlstrom Jayne B.
Published: October 2013

The contribution of nonlinearities in the basilar-membrane response to the understanding of speech in noise was estimated by measuring growth of simultaneous masking for tones and speech. Speech signals were bandpass-filtered nonsense syllables; consonant recognition and pure-tone thresholds were measured as a function of masker level in two conditions: (1) masker within the passband of the speech and (2) masker below the passband of the speech. With this low-frequency masker, the effect of the masker at the ‘‘signal’’ place is assumed to grow linearly whereas the growth of response to the speech at the ‘‘signal’’ place is compressed. Growth-of-masking functions were also measured for short-duration tones in narrowband maskers centered at or below the signal frequency. Subjects were younger and older adults with normal hearing; these older adults were included given that age-related changes in nonlinearities may occur even with minimal threshold elevation. For both subject groups, large individual differences were observed in upward spread of masking and in the extent to which the subsequent variance in audibility accounted for the variance in speech-recognition scores. These results will be discussed along with estimates of basilar-membrane nonlinearities obtained from subject’s growth-of-masking functions and otoacoustic emissions. [Work supported by NIH/NIDCD.]
Inversion of sediment property using ambient noise
Authors: Tang Dajun
Published: October 2013

Recently, there have been a couple of groups started using ambient noise and a vertical array to invert for bottom geo-acoustic properties. The basic idea is to select beam outputs from the array of the noise field which is generated near the ocean surface. The ratio of the two beams with angles symmetrical to the horizontal gives the reflection loss of the bottom. The reflection loss can be obtained in large and small grazing angles and over a frequency band limited only by the array length and spacing. In this paper, both modeling and data are presented to demonstrate the applicability and limitations of the approach. Emphasis will be on the resolution and uncertainty of the method when the array is of finite length and has a tilt angle relative to the vertical. The noise field will be generated using numerical methods based on Kraken. Wind as well as shipping noise is considered.
Does an infant-directed speaking style aid in the separation of different streams of speech?
Authors: Newman Rochelle S. , Weppelman Tammy , Hussain Isma
Published: October 2013

This work explores whether an infant-directed speaking style (IDS) may be easier to separate from background speech noise than is adult-directed speech (ADS). Many of the acoustic cues found in infant-directed speech are similar to ones shown to be important in adult stream segregation (such as differences in voice pitch and pitch variability). In addition, using an infant-directed speech style may serve to make the talker’s voice more dissimilar from any background speech (which is likely to be adult-directed). We explored this issue in three different ways: by examining adults’ ability to separate two different streams of speech varying in register, by examining whether adult speakers use IDS to a greater extent when in the context of noise, and by examining whether infants’ preference for IDS over ADS might be greater in the context of background noise. Implications of these three lines of work will be discussed. [Work supported by NSF and NICHD.]
Nonlinear acoustics in the pant-hoot vocalization of common chimpanzees (Pan troglodytes)
Authors: Riede Tobias , Arcadi Adam Clark , Owren Michael J.
Published: October 2013

Pant-hoots produced by chimpanzees are multi-call vocalizations. While predominantly harmonically structured, pant-hoots can exhibit acoustic complexity that has recently been found to result from inherent nonlinearity in the vocal-fold dynamics. This complexity reflects abrupt shifts between qualitatively distinct vibration patterns (known as modes), which include but are not limited to simple, synchronous movements by the two vocal folds. Studies with humans in particular have shown that as the amplitude and vibration rate increase, vocal-fold action becomes increasingly susceptible to higher-order synchronizations, desynchronized movements, and irregular behavior. We examined the occurrence of these sorts of nonlinear phenomena in pant-hoots, contrasting quieter and lower-pitched introduction components with loud and high-pitched climax calls in the same sounds. Spectrographic evidence revealed four classic kinds of nonlinear phenomena, including discrete frequency jumps, subharmonics, biphonation, and deterministic chaos. While these events were virtually never found in the introduction, they occurred in more than half of the climax calls. Biphonation was by far the most common. Individual callers varied in the degree to which their climax calls exhibited nonlinear phenomena, but we are consistent in showing more biphonation than any of the other forms. These outcomes demonstrate that understanding these calls requisitely requires an understanding of such events.
Phase rotation thresholds and its use in watermarking technique
Authors: Sek Aleksander , Suzuki Yoiti , Nishimura Ryouichi , Sonoda Kotaro
Published: October 2013

Strong demands for the protection of copyrights for high fidelity audio recordings as well as broadcasting signals via a network brought about a development of so-called watermarking techniques. One of them is based on a phase modulation referred to in here as a phase rotation (PR). This method assumes a poor sensitivity of the auditory system to the phase changes in a signal and embeds a watermark in the recording by means of a filter with linear phase characteristics. However, the sensitivity of the auditory system to the phase rotation has not been studied in detail, especially for complex signals. In this paper we present a preliminary result of threshold measurements of the phase rotation applied to different types of signals. It appears that the thresholds for detecting the phase rotation, when expressed by means of a time group delay, depend on the type of the signal and the frequency region that the phase rotation is applied for. The detection of the phase rotation is approximately independent on the rotation rate up to 120 Hz. When the phase rotation was applied to several components of a harmonics complex, the highest values of the thresholds were observed in the low frequency region.
Recognizing focus in noise filled sentences
Authors: Xu Ching X. , Xu Yi
Published: October 2013

This study is designed to help identify the intrinsic constituents of focus. Twelve four-word Mandarin sentences were recorded by a native speaker five times, each time either with focus on one of the words, or without any focus. Then, one, two or three words in each sentence produced by the speaker were replaced by pink noise. The noise-filled sentences were presented to subjects along with the text. The subjects’ task was to determine if the sentence had a focus, and if yes, on which word. Ten native Mandarin speakers participated as subjects. Their performance was compared across noise replacement conditions. It was found that, when both on-focus and post-focus words were present, focus could be recognized consistently. When only the focused word was present, focus could be recognized fairly well unless the focus position was sentence final, in which case it was not very distinct from no focus. When post-focus word(s) was(were) left intact while focused words were replaced by noise, focus could still be detected successfully, but its exact localization was sometimes judged wrong. These results seem to support the dual-component hypothesis about focus. Further implications of the findings will be discussed.
A comparison of the rational fraction polynomial method and the algorithm of mode isolation for fitting noisy data
Authors: Allen Matthew S. , Ginsberg Jerry H.
Published: October 2013

A multitude of methods exist for fitting linear, modal models to mechanical system response data. Many of these methods involve rearranging the modal equations of motion of the system so that a linear-least-squares solution is possible. Some methods require simplifying assumptions, such as light damping, while most popular methods are exact for clean data. Because the overall process is nonlinear, two different exact, linear-least-squares methods, can give different results for noisy data. This work compares two methods which are exact for linear, viscous, state-space (or nonproportionally damped) systems, the well known Rational Fraction Polynomial Method (RFP) and the Algorithm of Mode Isolation (AMI). It is shown that while RFP performs exceptionally for clean data, it is much less robust than AMI for noisy data. The performance of both algorithms is compared when applied to noise contaminated analytical data for a multi-degree of freedom frame structure. The frame can be tuned so that high damping ratios and heavy modal coupling are present. [Work supported under a National Science Foundation Graduate Research Fellowship.]
Practical considerations for a second-order directional hearing aid microphone system
Authors: Thompson Stephen C.
Published: October 2013

First-order directional microphone systems for hearing aids have been available for several years. Such a system uses two microphones and has a theoretical maximum free-field directivity index (DI) of 6.0 dB. A second-order microphone system using three microphones could provide a theoretical increase in free-field DI to 9.5 dB. These theoretical maximum DI values assume that the microphones have exactly matched sensitivities at all frequencies of interest. In practice, the individual microphones in the hearing aid always have slightly different sensitivities. For the small microphone separation necessary to fit in a hearing aid, these sensitivity matching errors degrade the directivity from the theoretical values, especially at low frequencies. This paper shows that, for first-order systems the directivity degradation due to sensitivity errors is relatively small. However, for second-order systems with practical microphone sensitivity matching specifications, the directivity degradation below 1 kHz is not tolerable. A hybrid order directive system is proposed that uses first-order processing at low frequencies and second-order directive processing at higher frequencies. This hybrid system is suggested as an alternative that could provide improved directivity index in the frequency regions that are important to speech intelligibility.
Cascade thermoacoustic engine
Authors: Gardner D. L. , Swift G. W.
Published: October 2013

Over the past several years, Los Alamos has successfully fabricated and tested traveling wave thermoacoustic heat engines having efficiencies much greater than those of traditional standing wave thermoacoustic engines. Unfortunately, Gedeon streaming effects present in these traveling wave engines has required using fluid flow ‘‘diodes’’ having greater complexity than desired. The cascade thermoacoustic engine recently fabricated and tested at Los Alamos uses three stages in series, one standing wave and two traveling wave, yielding a configuration in which Gedeon streaming is eliminated and efficiency can still be high. The cascade engine will be described and experimental data will be presented. [Work supported by the U.S. DOE Office of Science and Praxair, Inc.]
An active flow control scheme for the reduction of cavity pressure in flow-excited Helmholtz resonators
Authors: Park Jong Beom , Mongeau Luc
Published: October 2013

Flows over cavities acting as flow-excited Helmholtz resonators feature the formation of strong vortices over the cavity orifice, which strength regulates the amplitude of the cavity pressure oscillations. Much is already known about this phenomenon, and models for predicting the magnitude and the frequency of the pressure oscillations are available. Various control devices and schemes have been developed to suppress the oscillations. In particular, active flow control using oscillated leading edge spoilers has been proposed as an alternative to passive spoilers, or flow injection systems. Little is known, however, about the detailed effects of such an active flow control system on the flow field. In the present study, a simple control loop was implemented to adjust the phase between the leading edge spoiler motion and the cavity pressure. The sound pressure inside a resonator was measured over a range of phase differences and spoiler motion amplitudes. It was found using flow visualization that optimally synchronized spoiler motion caused the vortices over the cavity orifice to be less concentrated. The suppression mechanisms were explained using a model based on vortex sound theory.
Response of a viscoelastic halfspace to subsurface distributed acoustic sources with application to medical diagnosis
Authors: Royston Thomas J. , Yazicioglu Yigit , Loth Francis
Published: October 2013

The response within and at the surface of an isotropic viscoelastic medium to subsurface distributed low audible frequency acoustic sources is considered. Spherically and cylindrically distributed sources are approximated as arrays of infinitesimal point sources. Analytical approximations for the acoustic field radiating from these sources are then obtained as a summation of tractable point source expressions. These theoretical approximations are compared to computational finite element predictions and experimental studies in selected cases. The objective is to better understand low audible frequency sound propagation in soft biological tissue caused by subsurface sources. Distributed acoustic sources could represent vibratory motion of the vascular wall caused by turbulent blood flow past a constriction (stenosis). Additionally focused vibratory stimulation using a dynamic radiation force caused by interfering ultrasound beams effectively creates a distributed subsurface acoustic source. A dynamic radiation force has been investigated as a means of probing subsurface tissue anomalies, including calcified vascular plaque and tumorous growths. In these cases, there is an interest in relating acoustic measurements at the skin surface and within the medium to the underlying flow/constriction environment or tissue anomaly. [Research supported by NIH NCRR 14250 and Whitaker Foundation BME RG 01-0198.]
Differentiating the effects of pot size and nutrient availability on plant biomass and allocation
Authors: Murphy Guillermo P. , File Amanda L. , Dudley Susan A.
Published: October 2013

L. Hess and H. de Kroon (2007. J. Ecol. 95: 241–251) hypothesize that apparent plant responses to neighbour presence could be artifacts of pot-size manipulations. They posit that root size increases with pot size, regardless of nutrient concentration, while plant size increases with nutrient amount in the pot. Simple manipulations of pot size do not test this hypothesis, because larger pots contain more nutrients when nutrients are applied in solution at constant rate. We tested the effects of pot size on growth and allocation in two life stages of Cakile edentula (Bigel.) Hook. subsp. edentula var. lacustris while manipulating nutrient amount and concentration. Although pot size did affect growth and allocation, the patterns were not those predicted by the Hess and de Kroon hypotheses. In several treatments, total plant mass decreased with pot size. Root mass did not increase with pot volume independently of nutrients. Root mass increased with pot volume only when plants were given soluble fertilizer, and to a much greater extent in older plants. Contrary to predictions, root mass increased with pot size only in the treatment with high water-soluble fertilizer where plant size increased greatly with pot size. Root allocation showed a complex pattern of responses with plant life stage and nutrient treatments that were not predicted by the Hess and de Kroon hypotheses.
Evidence of discharging saline formation water to the Athabasca River in the oil sands mining region, northern Alberta
Authors: Gibson J.J. , Fennell J. , Birks S.J. , Yi Y. , Moncur M.C. , Hansen B. , Jasechko S.
Published: October 2013

This paper summarizes various lines of evidence, including new geophysical and geochemical surveys indicating the discharge of naturally occurring saline formation water from Cretaceous and Devonian formations to the Athabasca River downstream of Fort McMurray — an active oil sands extraction area. The following features are indicative of saline water discharge: (i) the hydrogeological setting of the reach which is situated near the western, up-dip, and subcropping, edge of the Western Canada Sedimentary Basin; (ii) springs and seepage along area rivers and tributaries that have been observed and reported in previous studies; and (iii) a significant increase in dissolved solids in the river, particularly chloride, occurring in a downstream direction from Fort McMurray. Further evidence of the saline groundwater discharge was obtained from electromagnetic surveys conducted along a 125 km reach from the Clearwater River to the Firebag River. This technique was used to map the distribution of saline water in the riverbed hyporheic zone, and revealed broad zones of generally high terrain electrical conductivity values in deeply incised Cretaceous- and Devonian-aged subcrop areas, but with numerous point-source and lineal anomalies attributed to occurrence of saline water discharge in less incised areas. Porewater sampling using drive-point piezometers was then used to confirm the presence of saline water in selected zones. Depth-wise gradients in chemical parameters observed in the riverbed porewaters in these zones are interpreted as evidence of upward movement of saline formation water mixing with the Athabasca River. Geochemical properties of the porewater are consistent with natural sources of groundwater flow from the Cretaceous- and Devonian-aged formations discharging along various reaches of the river.
PARTITION FUNCTION OF THE REISSNER–NORDSTRÖM BLACK HOLE
Authors: MÄKELÄ JARMO
Published: October 2013

We consider a microscopic model of a stretched horizon of the Reissner–Nordström black hole. In our model, the stretched horizon consists of discrete constituents. Using our model we obtain an explicit, analytic expression for the partition function of the hole. Our partition function implies, among other things, the Hawking effect, and provides it with a microscopic explanation as a phase transition taking place at the stretched horizon. The partition function also implies the Bekenstein–Hawking entropy law. The model and its consequences are similar to those obtained previously for the Schwarzschild black hole.
VALUE CREATION POTENTIAL OF WEB 2.0 FOR SME — INSIGHTS AND LESSONS LEARNT FROM A EUROPEAN PRODUCER OF CONSUMER ELECTRONICS
Authors: LEHMKUHL TOBIAS , JUNG REINHARD
Published: October 2013

Web 2.0 as a contemporary phenomenon receives considerable attention by IS scholars due to its perceived transformational impact on businesses. This paper critically elaborates on the value creation potential of Web 2.0 for small and medium enterprises (SME). By conducting an inductive study we reveal that SMEs can effectively use Web 2.0 as a means to support customer acquisition, alleviate resource limitations and to maintain customer enthusiasm associated with the customer purchasing process. In case that a high customer convenience is required which is based on the involvement of different parties or on personal service support, there is hardly any Web 2.0 value creation potential. This research contributes to the domain of business modeling by assessing the notion of value in a Web 2.0 setting. It also contributes to IS research on Web 2.0 adoption.
ESTIMATION OF MUSCLE FORCE DERIVED FROM IN VIVO MR ELASTOGRAPHY TESTS: A PRELIMINARY STUDY
Authors: Bensamoun Sabine F. , Dao Tien Tuan , Charleux Fabrice , Ho Ba Tho Marie-Christine
Published: October 2013

The objective is to estimate the vastus medialis (VM) muscle force from multifrequency magnetic resonance elastography (MMRE) tests and two different rheological models (Voigt and springpot). Healthy participants (N = 13) underwent multifrequency (70, 90 and 110 Hz) magnetic resonance elastography MMRE tests. Thus, in vivo experimental elastic (μ) properties of the VM in passive and active (20% MVC) conditions were characterized. Moreover, the muscle viscosity (η) was determined with Voigt and springpot rheological models, in both muscle states. Subsequently, the VM muscle forces were calculated with a generic musculoskeletal model (OpenSIM) where the active and passive shear moduli (μ) were implemented. The viscosity measured with the two rheological models increased when the muscle is contracted. During the stance and the swing phases, the VM tensile forces decrease and the VM force was lower with the springpot model. It can be noted that during the swing phase, the muscle forces estimated from springpot model showed a higher standard deviation compared to the Voigt model. This last result may indicate a strong sensitivity of the muscle force to the change of active and passive contractile components in the swing phase of gait. This study provides for the first time an estimation of the muscle tensile forces for lower limb, during human motion, from in vivo experimental muscle mechanical properties. The assessment of individualized muscle forces during motion is valuable for finite element models, increasing the patient specific parameters. This novel muscle database will be of use for the clinician to better elucidate the muscle pathophysiology and to better monitor the effects of the muscle disease.
Progressive Multi-Objective Optimization
Authors: Sörensen Kenneth , Springael Johan
Published: October 2013

This paper introduces progressive multi-objective optimization (PMOO), a novel technique to include the decision maker's preferences into the multi-objective optimization process. PMOO integrates a well-known method for multi-criteria decision making (PROMETHEE) into a simple multi-objective metaheuristic by maintaining and updating a small reference archive of nondominated solutions throughout the search. By applying this novel technique to a set of instances of the multi-objective knapsack problem, the superiority of PMOO over the commonly accepted sequential approach of generating a Pareto set approximation first and selecting a single solution afterwards is demonstrated.
MULTI-RESOLUTION-TEST FOR CONSISTENT PHENOTYPE DISCRIMINATION AND BIOMARKER DISCOVERY IN TRANSLATIONAL BIOINFORMATICS
Authors: HAN HENRY , LI XIAO-LI , NG SEE-KIONG , JI ZHOU
Published: October 2013

While high-throughput technologies are expected to play a critical role in clinical translational research for complex disease diagnosis, the ability to accurately and consistently discriminate disease phenotypes by determining the gene and protein expression patterns as signatures of different clinical conditions remains a challenge in translational bioinformatics. In this study, we propose a novel feature selection algorithm: Multi-Resolution-Test (MRT-test) that can produce significantly accurate and consistent phenotype discrimination across a series of omics data. Our algorithm can capture those features contributing to subtle data behaviors instead of selecting the features contributing to global data behaviors, which seems to be essential in achieving clinical level diagnosis for different expression data. Furthermore, as an effective biomarker discovery algorithm, it can achieve linear separation for high-dimensional omics data with few biomarkers. We apply our MRT-test to complex disease phenotype diagnosis by combining it with state-of-the-art classifiers and attain exceptional diagnostic results, which suggests that our method's advantage in molecular diagnostics. Experimental evaluation showed that MRT-test based diagnosis is able to generate consistent and robust clinical-level phenotype separation for various diseases. In addition, based on the seed biomarkers detected by the MRT-test, we design a novel network marker synthesis (NMS) algorithm to decipher the underlying molecular mechanisms of tumorigenesis from a systems viewpoint. Unlike existing top–down gene network building approaches, our network marker synthesis method has a less dependence on the global network and enables it to capture the gene regulators for different subnetwork markers, which will provide biologically meaningful insights for understanding the genetic basis of complex diseases.
STOCHASTIC VISCOUS-DAMAGE CONSTITUTIVE MODEL FOR CONCRETE
Authors: LI JIE , HUANG QIAOPING
Published: October 2013

A new rate-dependent stochastic damage model for the dynamic modeling of concrete is presented in the paper. This model is formulated on the basis of the stochastic damage model, from which, the static stochastic evolution of damage is strictly derived. Then, rate dependency of concrete is included by means of viscous-damage mechanism. The model predictions are tested against experimental results on concrete specimens that cover different strain rates. The results demonstrate the proposed model may predict dynamic failure behavior of concrete quite well.
Multimodal label-free microscopy
Authors: Pavillon Nicolas , Fujita Katsumasa , Isaac Smith Nicholas
Published: October 2013

This paper reviews the different multimodal applications based on a large extent of label-free imaging modalities, ranging from linear to nonlinear optics, while also including spectroscopic measurements. We put specific emphasis on multimodal measurements going across the usual boundaries between imaging modalities, whereas most multimodal platforms combine techniques based on similar light interactions or similar hardware implementations. In this review, we limit the scope to focus on applications for biology such as live cells or tissues, since by their nature of being alive or fragile, we are often not free to take liberties with the image acquisition times and are forced to gather the maximum amount of information possible at one time. For such samples, imaging by a given label-free method usually presents a challenge in obtaining sufficient optical signal or is limited in terms of the types of observable targets. Multimodal imaging is then particularly attractive for these samples in order to maximize the amount of measured information. While multimodal imaging is always useful in the sense of acquiring additional information from additional modes, at times it is possible to attain information that could not be discovered using any single mode alone, which is the essence of the progress that is possible using a multimodal approach.