bluuebunny/crossref_metadata_2025 huggingface dataset:
Erratum: Herschel/SPIRE observations of the TWA brown dwarf disc 2MASSW J1207334–393254
Authors: Riaz B. , Lodato G. , Stamatellos D. , Gizis J. E.
Published: June 2012

We have revised our analysis of the SPIRE observations of 2MASSW J1207334–393254 (2M1207). Recent PACS observations show a bright source located ∼25 arcsec east of 2M1207. There are issues in terms of the detection/non-detection of the bright source when comparing the Spitzer, WISE and PACS observations. The object's detection/non-detection is apparently inconsistent, perhaps due to variability or low signal-to-noise ratio of the data. We have looked into the possible misidentification of the target, and have revised the measured SPIRE fluxes and the disc parameters for 2M1207. We have also reviewed which among the various formation mechanisms of this system would still be valid.
Highly ionized collimated outflow from HE 0238–1904
Authors: Muzahid S. , Srianand R. , Savage B. D. , Narayanan A. , Mohan V. , Dewangan G. C.
Published: June 2012

We present a detailed analysis of a highly ionized, multiphased and collimated outflowing gas detected through O v, O vi, Ne viii and Mg x absorption associated with the QSO HE 0238–1904 (zem≃ 0.629). Based on the similarities in the absorption-line profiles and estimated covering fractions, we find that the O vi and Ne viii absorption trace the same phase of the absorbing gas. Simple photoionization models can reproduce the observed N(Ne viii), N(O vi) and N(Mg x) from a single phase whereas the low-ionization species (e.g. N iii, N iv and O iv) originate from a different phase. The measured N(Ne viii)/N(O vi) ratio is found to be remarkably similar (within a factor of ∼2) in several individual absorption components kinematically spread over ∼1800 km s−1. Under photoionization this requires a fine-tuning between hydrogen density (nH) and the distance of the absorbing gas from the Quasi Stellar Object (QSO). Alternatively, this can also be explained by collisional ionization in hot gas with T≥ 105.7 K. Long-term stability favours the absorbing gas being located outside the broad-line region. We speculate that the collimated flow of such a hot gas could possibly be triggered by the radio jet interaction.
The Doctrine of Doing and Allowing I: Analysis of the Doing/Allowing Distinction
Authors: Woollard Fiona
Published: June 2012

According to the Doctrine of Doing and Allowing, the distinction between doing and allowing harm is morally significant. Doing harm is harder to justify than merely allowing harm. This paper is the first of a two paper critical overview of the literature on the Doctrine of Doing and Allowing. In this paper, I consider the analysis of the distinction between doing and allowing harm. I explore some of the most prominent attempts to analyse this distinction: Philippa Foot’s sequence account, Warren Quinn’s action/inaction account, and counterfactual test accounts put forward by Shelly Kagan and Jonathan Bennett. I also discuss Jeff McMahan’s account of the removal of barriers to harm. I argue that analysis of the distinction has often been made more difficult by two mistaken assumption: (a) the assumption that when an agent does or allows harm his behaviour makes the difference to whether or not the harm occurs; (b) the assumption that the distinction between doing and allowing and the distinction between action and inaction are interchangeable. I suggest that Foot’s account is the most promising account of the doing/allowing distinction, but that it requires further development.
The Doctrine of Doing and Allowing II: The Moral Relevance of the Doing/Allowing Distinction
Authors: Woollard Fiona
Published: June 2012

According to the Doctrine of Doing and Allowing, the distinction between doing and allowing harm is morally significant. Doing harm is harder to justify than merely allowing harm. This paper is the second of a two paper critical overview of the literature on the Doctrine of Doing and Allowing. In this paper, I consider the moral status of the distinction between doing and allowing harm. I look at objections to the doctrine such as James Rachels’ Wicked Uncle Case and Jonathan Bennett’s argument that any acceptable analysis of the distinction leaves it implausible that the distinction is morally relevant. I consider defences of the Doctrine from Philippa Foot and Warren Quinn. I argue that neither Foot not Quinn provides a satisfactory justification of the Doctrine of Doing and Allowing, but that the idea of self‐ownership discussed by Quinn can be developed to provide a justification of the doctrine.
Roman Ingarden’s Aesthetics
Authors: Mitscherling Jeff
Published: June 2012

While Roman Ingarden remains best known among English‐speaking philosophers and literary theorists for his work in aesthetics, and primarily for his study of the literary work of art, his studies in aesthetics and art belong in fact to the comprehensive program of phenomenological research in ontology and metaphysics that occupied him for his entire career. In this article I briefly describe this program of phenomenological research, then I discuss some of the major features of Ingarden’s analyses of works of art and the aesthetic experience.
Relevant Logic and the Philosophy of Mathematics
Authors: Mares Edwin
Published: June 2012

This paper sets out three programmes that attempt to use relevant logic as the basis for a philosophy of mathematics. Although these three programmes do not exhaust the possible approaches to mathematics through relevant logic, they are fairly representative of the current state of the field. The three programmes are compared and their relative strengths and weaknesses set out. At the end of the paper I examine the consequences of adopting each programme for the realist debate about mathematical objects.
Lack of awareness of neuropsychological deficit in cerebral small vessel disease: The relationship with executive and episodic memory functions
Authors: Brookes Rebecca L. , Hannesdottir Kristin , Markus Hugh S. , Morris Robin G.
Published: June 2012

A common cause of neuropsychological impairment in older adults is cerebral small vessel disease (SVD), but little is known as to whether lack of awareness of neuropsychological impairment is a feature of this clinical condition. In this study, we investigated awareness deficits in a well‐phenotyped population of patients with SVD (n= 45; 21 with defined concomitant neuropsychological impairment) and made comparisons with 24 Alzheimer's disease (AD) patients and a further 80 control participants. Awareness of performance on a range of neuropsychological measures was examined based on the Brief Memory and Executive Test Battery (BMET) (Brookes, Hannesdottir, Lawrence,Morris, & Markus, 2012), exploring the relationship between awareness and memory and executive function. The results revealed significant awareness deficits in both the SVD and AD groups. When splitting the SVD group into those with or without concomitant neuropsychological impairment, only those with neuropsychological impairment showed reduced awareness. For the SVD group, executive function was significantly correlated with awareness but memory was not. By comparison, memory was significantly correlated with awareness in the AD group, with executive function showing a trend but remaining non‐significant. The results show that lack of awareness of deficit is a clinical feature of SVD and indicate that there are distinct neuropsychological associations with awareness deficit for SVD and AD.
Searching for new physics at the frontiers with lattice quantum chromodynamics
Authors: Van de Water Ruth S.
Published: June 2012

Numerical lattice–quantum chromodynamics (QCD) simulations, when combined with experimental measurements, allow the determination of fundamental parameters of the particle‐physics Standard Model and enable searches for physics beyond‐the‐Standard Model. We present the current status of lattice–QCD weak matrix element calculations needed to obtain the elements and phase of the Cabibbo–Kobayashi–Maskawa (CKM) matrix and to test the Standard Model in the quark‐flavor sector. We then discuss evidence that may hint at the presence of new physics beyond the Standard Model CKM framework. Finally, we discuss two opportunities where we expect lattice QCD to play a pivotal role in searching for, and possibly discovery of, new physics at upcoming high‐intensity experiments: raredecays and the muon anomalous magnetic moment. The next several years may witness the discovery of new elementary particles at the Large Hadron Collider (LHC). The interplay between lattice QCD, high‐energy experiments at the LHC, and high‐intensity experiments will be needed to determine the underlying structure of whatever physics beyond‐the‐Standard Model is realized in nature.
Photosynthetic Activity in Marine and Brackish Water Strains of Fucus vesiculosus and Fucus radicans (Phaeophyceae) at Different Light Qualities
Authors: Svahn Carina , Maria Gylle A. , Ekelund Nils G.A.
Published: June 2012

This study investigates the effects of different light qualities on the photosynthetic capacity of the brown algae Fucus vesiculosus, from the Norwegian Sea, and Fucus radicans and F. vesiculosus, from the Bothnian Sea. The electron transport rates (ETR) obtained for F. vesiculosus from the Norwegian Sea showed significantly higher levels of light saturation compared with both species of algae from the Bothnian Sea. The maximum of ETR values for the Norwegian Sea strain showed no significant changes due to varying light quality compared with the initial values. For F. vesiculosus, from the Bothnian Sea, treatment with blue light showed an effect after 1 week of 30 and 90 μmol photons m−2 s−1 (P < 0.01), and for F. radicans from the Bothnian Sea, at the irradiance of 90 μmol photons m−2 s−1 and 1 week (P < 0.01). After 1 week in the Bothnian Sea species and after 2 weeks in F. vesiculosus from the Norwegian Sea, the photosynthetic efficiency (α) was significantly higher regardless of light quality and irradiance compared with the initial values. Variation in light quality and irradiance had minor effects on the Fv:Fm values of the three algal strains studied.
Fragmented red blood cells automated measurement is a useful parameter to exclude schistocytes on the blood film
Authors: Lesesve J.‐F. , Asnafi V. , Braun F. , Zini G.
Published: June 2012

Introduction:  The diagnosis of thrombotic microangiopathies (TMA) or disorders that may mimic their features remains difficult. Mechanical hemolytic anemia with the detection of shistocytes on the blood smear is a cornerstone finding to assess the diagnosis, but microscopic evaluation of shistocytes is still problematic with wide interobserver variations. Some of the latest generation automated blood cell counters (ABCC) propose an original quantitative approach of fragmented red cells (FRC), aiming to be equivalent to the microscopic count. This parameter has been poorly evaluated.

Methods:  To assess the predictive value (PV) of this test, we conducted studies comparing automated and microscopic counts of FRC/schistocytes, based on the analysis of thousands samples in four university hospitals and using the 2 ABCC currently available (Siemens ADVIA series, Sysmex XE‐2100).

Results:  Reference range for FRC was <0.3% for the ADVIA and <0.5% for the XE‐2100. The presence of FRC below a threshold determined at 1% (ADVIA and XE‐2100) had a negative PV close to 100% to exclude the presence of schistocyte on the blood smear, but in relationship with a poor PV value.

Conclusions:  Our study validated the utility of the immediately available FRC parameter on ABCC to exclude schistocytes and the diagnosis of TMA.
Evaluating the Effects of Somatization Disorder for Patients With Severe End‐Stage Lower‐Extremity Osteoarthritis
Authors: HOWARD KRISTA J. , ELLIS HENRY B. , WANG JAMES , VON DER GRUEN JENNIFER K. , BUCHOLZ ROBERT
Published: June 2012

This study examined how somatization disorder relates to physical and psychosocial measures for patients with chronic lower‐extremity osteoarthritis (OA). A cohort of 421 patients with lower‐extremity OA of the hip or knee consented to preoperative evaluations. The Patient Health Questionnaire was administered to identify patients with and without somatization disorder. Analyses were conducted to determine differences between demographic and preoperative physical and psychosocial variables. Patients with somatization disorder scored significantly worse on measures of pain, stiffness, function, perceived disability, and quality of life measures. Somatization disorder can have profound effects on patients' physical and psychosocial measures. Recommended treatment for chronic pain patients often includes using a biopsychosocial approach, which involves treating both the psychological state along with the pain condition.
Comparison of Future Time Perspective and Self‐Determination Theory for Explaining Exercise Behavior
Authors: WININGER STEVEN R. , DESENA THOMAS M.
Published: June 2012

The primary purposes of this study were to compare future time perspective and subtypes of regulation from self‐determination theory as explanatory variables of exercise behavior and to examine potential differences in future time perspective across stages of change. Participants consisted of 317 undergraduates. The two most prominent measures of future time perspective were employed to allow for a comparison. Results revealed numerous significant correlations among future time perspective, self‐regulation subtypes, and exercise behavior. Intrinsic and integrated subtypes of regulation explained the most variance in exercise behavior. Participants in higher stages of change had significantly higher future time perspective scores, lower amotivation scores, and higher scores for internal forms of regulation. Applied implications and suggestions for future research are presented.
Hematologic and IgG responses of heifers experimentally infected with the agent of epizootic bovine abortion
Authors: Coker Michelle R. , Rauw Wendy M. , Nieto Nathan C. , Thain David , Teglas Mike B.
Published: June 2012

Background

Epizootic bovine abortion (EBA) is a tick‐transmitted abortive disease of beef cattle in the westernUnitedStates. Infected cattle do not have clinical signs until abortion occurs, usually within the last trimester of gestation. There is little information on the hematologic response of the dam following infection.

Objective

The purpose of this study was to determine if changes in blood leukocytes and serum IgG concentrations could be detected following experimental infection of pregnant heifers with the etiologic agent of EBA (aoEBA).

Methods

Twelve Angus heifers were infected during gestation with the aoEBAusing an inoculum prepared from the thymus of an infected fetus. Five pregnant heifer controls were given an inoculum prepared from the thymus of an aoEBA‐negative calf.PCVs, total and differential leukocyte counts, and serum IgG concentrations were measured weekly following administration of the inocula until abortion or calving. Gross and microscopic examinations were performed on all aborted fetuses to confirm infection.

Results

Eleven of 12 heifers in the treatment group aborted, and significant findings were decreased lymphocyte counts at weeks 1 and 14 postinoculation and increased monocyte counts at week 4 compared with control animals. Serum IgG concentrations were significantly increased at weeks 6–8 and 11 in the treatment group.

Conclusions

Leukogram changes are subtle in infected cattle. Future research efforts should be aimed at development of an antibody test specific for detection of previously infected animals, which could graze safely onEBA‐endemic pastures.
Emotional reactions to success and failure of collective action as predictors of future action intentions: A longitudinal investigation in the context of student protests in Germany
Authors: Tausch Nicole , Becker Julia C.
Published: June 2012

This research examined how emotional responses to success and failure of collective action relate to willingness to engage in collective action in the future. It was hypothesized that both pride (in relation to a success) and anger (in response to failure) would motivate future collective action. Findings are reported from a two‐wave longitudinal study (N= 98) in the context of student protests against tuition fees in Germany, which was conducted before and after collective action had resulted in both a success and a failure. While anger positively predicted action intentions, over and above baseline action intentions, pride exerted a significant indirect effect on action intentions via increased efficacy perceptions, over and above baseline efficacy and action intentions. Politicized identification positively predicted the intensity of both pride and anger and baseline group efficacy positively predicted the intensity of anger. The theoretical and practical implications of these findings are discussed.
Perturbation Analysis of a Nonlinear Resonator
Authors: Nudehi Shahin S. , Farooq Umar
Published: June 2012

A perturbation analysis of a Helmholtz-type resonator with one of the resonator ends replaced by a membrane is studied in this work. A membrane is known to exhibit nonlinear behavior under certain conditions; thus, when attached to a resonator system, it modifies the dynamic characteristics of the original system. This modified resonator system is modeled by coupled nonlinear differential equations and investigated by using the singular perturbation theory. The resonant frequency of the nonlinear resonator in the primary resonance case is analytically obtained using first-order approximate solutions. A good agreement is seen when the frequency response of the first-order approximate system is compared with the numerically simulated results.
Fixed Point Analytical Method for Nonlinear Differential Equations
Authors: Xu Ding , Guo Xin
Published: June 2012

In this paper, a new analytical method, which is based on the fixed point concept in functional analysis (namely, the fixed point analytical method (FPM)), is proposed to acquire the explicit analytical solutions of nonlinear differential equations. The key idea of this approach is to construct a contractive map which replaces the nonlinear differential equation into a series of linear differential equations. Usually, the series of linear equations can be solved relatively easily and have explicit analytical solutions. The FPM is different from all existing analytical methods, such as the well-known perturbation technique applied in weakly nonlinear problems, because it is independent of any small physical or artificial parameters at all; thus, it can handle more nonlinear problems, including strongly nonlinear ones. Two typical cases are investigated by FPM in detail and the comparison with the numerical results shows that the present method is one of high accuracy and efficiency.
Parametric Resonance Based Piezoelectric Micro-Scale Resonators: Modeling and Theoretical Analysis
Authors: Ghaderi Pooya , Dick Andrew J.
Published: June 2012

In this study, a two-component autoparametric resonator utilizing piezoelectric actuation is proposed. The resonator consists of a plate component which serves as the exciter and a beam component which serves as the oscillator. When an electric signal is applied, the plate component experiences in-plane oscillations which serve to provide axial excitation to the beam component. The system is designed to operate in autoparametric resonance with a plate to beam principal frequency ratio of 1:2. Due to the oscillations of the beam component, a dynamic force and a moment are applied to the plate and can cause out-of-plane oscillations of the plate component. The possibility of internal-resonance between the beam oscillations and the out-of-plane vibrations of the plate component are also considered. A model is derived in order to describe these three motions and the coupling between them. By assuming single mode behavior for each motion, the model is discretized and represented with a three degree-of-freedom model. The model is solved analytically by using the method of multiple scales and results are verified with the numerical simulations. Also, the influence of system parameters on response behavior is studied and the ideal operational conditions and parameter values for nominal performance are obtained.
A Modified Multi-Step Differential Transform Method for Solving Fractional Dynamic Systems
Authors: Shi Min , Wang Zaihua , Du Maolin
Published: June 2012

This paper presents a semianalytical method, the modified multistep differential transform method (MMSDTM), for solving linear and nonlinear fractional-order differential equations with the order between 0 and 2. This method can be considered as a variant of the predictor-corrector method (PCM). The multistep differential transform method (MSDTM), which does not take the memory effect into account and yields unsatisfactory solution very rapidly, is first used to find an estimation as the predictor of the solution. In the corrector procedure, the memory term associated with the fractional-order derivative is decomposed by the subtraction of two integrals; one is abnormal with singularity and the other is normal without singularity and the two integrals are calculated by using the MSDTM and a simple numerical scheme, respectively. Four illustrative examples are given to show that the MMSDTM requires much less computational cost and retains high computational accuracy, compared with the widely used PCM.
Electrocatalytic Reduction of Oxygen on Ni/Graphite Nanoparticles
Authors: Ibrahim M. A. , Al-Solamy Falleh , Al-Hartomy Omar , Al-Ghamdi A. A. , El-Tantawy Farid
Published: June 2012

Ni/Graphite nanocomposite with various compositions were synthesized by a chemical and physical method. These nanocomposites exhibit a 40–60 fold enhancement in O2 reduction activity as compared to the commercial Ni catalyst.
Modeling the Behavior of a 50 MW Direct Steam Generation Plant for Southern Libya Based on the Thermodynamic and Thermophysical Properties of Water Substance
Authors: Aldali Y. , Davison B. , Muneer T. , Henderson D.
Published: June 2012

This paper presents arguments for the use of direct steam generation (DSG) in preference to other forms of generation in particular locations according to the prevailing environmental and economic conditions. In addition, the paper describes the development of a software tool based on Microsoft Excel and Visual Basic for Applications (VBA), which draws upon established physical relationships in the heat transfer literature to perform plant capacity calculations in a fast and convenient manner. The results of the VBA program determine the solar fraction of the plant, assuming that the plant is in operation for 10 h per day (07:30–17:30 hours), the solar fraction is shown to be 76% and the DSG plant achieves a 76% reduction in emissions. Construction costs are also estimated based on formulae from previous work.
Toward an estimation of the clarinet reed pulse from instrument performance
Authors: Smyth Tamara , Abel Jonathan S.
Published: June 2012

In this work, a technique is presented for estimating the reed pulse from the pressure signal recorded at the bell of a clarinet during performance. The reed pulse is a term given to the typically periodic sequence of bore input pressure pulses, a signal related to the volume flow through a vibrating reed by the characteristic impedance of the aperture to the bore. The problem is similar to extracting glottal pulse sequence from recorded speech; however, because the glottis and instrument reeds have very different masses and opening areas, the source-filter model used in speech processing is not applicable. Here, the reed instrument is modeled as a pressure-controlled valve coupled to a bi-directional waveguide, with the output pressure approximated as a linear time invariant transformation of the product of reed volume flow and the characteristic impedance of the bore. By noting that pressure waves will make two round trips from the mouthpiece to the bell and back for each reed pulse, yielding a distinct positive and negative lobe in the running autocorrelation period of the recorded signal, the round-trip attenuation experienced by pressure waves in the instrument is estimated and used to invert the implied waveguide, producing reed pulse estimates.
Comparisons of spectral characteristics of wind noise between omnidirectional and directional microphones
Authors: Chung King
Published: June 2012

Wind noise reduction is a topic of ongoing research and development for hearing aids and cochlear implants. The purposes of this study were to examine spectral characteristics of wind noise generated by directional (DIR) and omnidirectional (OMNI) microphones on different styles of hearing aids and to derive wind noise reduction strategies. Three digital hearing aids (BTE, ITE, and ITC) were fitted to Knowles Electronic Manikin for Acoustic Research. They were programmed to have linear amplification and matching frequency responses between the DIR and OMNI modes. Flow noise recordings were made from 0° to 360° azimuths at flow velocities of 4.5, 9.0, and 13.5 m/s in a quiet wind tunnel. Noise levels were analyzed in one-third octave bands from 100 to 8000 Hz. Comparison of wind noise revealed that DIR generally produced higher noise levels than OMNI for all hearing aids, but it could result in lower levels than OMNI at some frequencies and head angles. Wind noise reduction algorithms can be designed to detect noise levels of DIR and OMNI outputs in each frequency channel, remove the constraint to switch to OMNI in low-frequency channel(s) only, and adopt the microphone mode with lower noise levels to take advantage of the microphone differences.
Scattering measurements from a dissolving bubble
Authors: Kapodistrias George , Dahl Peter H.
Published: June 2012

A laboratory-scale study on acoustic scattering from a single bubble undergoing dissolution in undersaturated fresh water is presented. Several experiments are performed with the acoustic source driven with five-cycle tone bursts, center frequency of 120 kHz, to insonify a single bubble located on axis of the combined beam of the set of transducers. The bubble is placed on a fine nylon thread located in the far field of the transducer set, arranged in bistatic configuration, in a tank filled with undersaturated water. Backscattered waveforms from the bubble target are acquired every few seconds for several hours until the bubble has completely dissolved, and detailed dissolution curves are produced from the acoustic data. The rate of bubble dissolution is calculated using the solution developed by Epstein and Plesset [J. Chem. Phys. 18, 1505–1509 (1950)]. The results of the experiments performed are in agreement with the calculations.
Localization of virtual sound sources with bilateral hearing aids in realistic acoustical scenes
Authors: Mueller Martin F. , Kegel Andrea , Schimmel Steven M. , Dillier Norbert , Hofbauer Markus
Published: June 2012

Sound localization with hearing aids has traditionally been investigated in artificial laboratory settings. These settings are not representative of environments in which hearing aids are used. With individual Head-Related Transfer Functions (HRTFs) and room simulations, realistic environments can be reproduced and the performance of hearing aid algorithms can be evaluated. In this study, four different environments with background noise have been implemented in which listeners had to localize different sound sources. The HRTFs were measured inside the ear canals of the test subjects and by the microphones of Behind-The-Ear (BTEs) hearing aids. In the first experiment the system for virtual acoustics was evaluated by comparing perceptual sound localization results for the four scenes in a real room with a simulated one. In the second experiment, sound localization with three BTE algorithms, an omnidirectional microphone, a monaural cardioid-shaped beamformer and a monaural noise canceler, was examined. The results showed that the system for generating virtual environments is a reliable tool to evaluate sound localization with hearing aids. With BTE hearing aids localization performance decreased and the number of front-back confusions was at chance level. The beamformer, due to its directivity characteristics, allowed the listener to resolve the front-back ambiguity.
Characteristics of noise-canceling headphones to reduce the hearing hazard for MP3 users
Authors: Liang Maojin , Zhao Fei , French David , Zheng Yiqing
Published: June 2012

Three pairs of headphones [standard iPod ear buds and two noise-canceling headphones (NCHs)] were chosen to investigate frequency characteristics of noise reduction, together with their attenuation effects on preferred listening levels (PLLs) in the presence of various types of background noise. Twenty-six subjects with normal hearing chose their PLLs in quiet, street noise, and subway noise using the three headphones and with the noise-canceling system on/off. Both sets of NCHs reduced noise levels at mid- and high-frequencies. Further noise reductions occurred in low frequencies with the noise canceling system switched on. In street noise, both NCHs had similar noise reduction effects. In subway noise, better noise reduction effects were found in the expensive NCH and with noise-canceling on. A two way repeated measures analysis of variance showed that both listening conditions and headphone styles were significant influencing factors on the PLLs. Subjects tended to increase their PLLs as the background noise level increased. Compared with ear buds, PLLs obtained from NCHs-on in the presence of background noise were reduced up to 4 dB. Therefore, proper selection and use of NCHs appears beneficial in reducing the risk of hearing damage caused by high music listening levels in the presence of background noise.
Parameterizing both path amplitude and delay variations of underwater acoustic channels for block decoding of orthogonal frequency division multiplexing
Authors: Xu Xiaoka , Wang Zhaohui , Zhou Shengli , Wan Lei
Published: June 2012

There are no commonly-agreed mathematical models for the input–output relationship of underwater acoustic channels. For each path in a time-varying multipath channel within a short period of time (e.g., one short data block), this paper proposes to use one polynomial to approximate the amplitude variation and another polynomial up to the first order to approximate the delay variation within a block duration. Under such a channel parameterization, the discrete-time channel input–output relationship tailored to zero-padded orthogonal-frequency-division-multiplexing (OFDM) transmissions is then derived, based on which an OFDM receiver is validated using experimental data collected during the 2008 Surface Processes and Acoustic Communications Experiment. For channels with a short coherence time, the numerical results show that incorporating both the amplitude and delay variations improves the system performance.
Beluga whale,Delphinapterus leucas, vocalizations from the Churchill River, Manitoba, Canada
Authors: Chmelnitsky Elly G. , Ferguson Steven H.
Published: June 2012

Classification of animal vocalizations is often done by a human observer using aural and visual analysis but more efficient, automated methods have also been utilized to reduce bias and increase reproducibility. Beluga whale, Delphinapterus leucas, calls were described from recordings collected in the summers of 2006–2008, in the Churchill River, Manitoba. Calls (n=706) were classified based on aural and visual analysis, and call characteristics were measured; calls were separated into 453 whistles (64.2%; 22 types), 183 pulsed/noisy calls (25.9%; 15 types), and 70 combined calls (9.9%; seven types). Measured parameters varied within each call type but less variation existed in pulsed and noisy call types and some combined call types than in whistles. A more efficient and repeatable hierarchical clustering method was applied to 200 randomly chosen whistles using six call characteristics as variables; twelve groups were identified. Call characteristics varied less in cluster analysis groups than in whistle types described by visual and aural analysis and results were similar to the whistle contours described. This study provided the first description of beluga calls in Hudson Bay and using two methods provides more robust interpretations and an assessment of appropriate methods for future studies.
Direction of wave propagation in the cochlea for internally excited basilar membrane
Authors: Li Yizeng , Grosh Karl
Published: June 2012

Otoacoustic emissions are an indicator of a normally functioning cochlea and as such are a useful tool for non-invasive diagnosis as well as for understanding cochlear function. While these emitted waves are hypothesized to arise from active processes and exit through the cochlear fluids, neither the precise mechanism by which these emissions are generated nor the transmission pathway is completely known. With regard to the acoustic pathway, two competing hypotheses exist to explain the dominant mode of emission. One hypothesis, the backward-traveling wave hypothesis, posits that the emitted wave propagates as a coupled fluid-structure wave while the alternate hypothesis implicates a fast, compressional wave in the fluid as the main mechanism of energy transfer. In this paper, we study the acoustic pathway for transmission of energy from the inside of the cochlea to the outside through a physiologically-based theoretical model. Using a well-defined, compact source of internal excitation, we predict that the emission is dominated by a backward traveling fluid-structure wave. However, in an active model of the cochlea, a forward traveling wave basal to the location of the force is possible in a limited region around the best place. Finally, the model does predict the dominance of compressional waves under a different excitation, such as an apical excitation.
Ambient pressure dependence of the ultra-harmonic response from contrast microbubbles
Authors: Sun Tao , Jia Nan , Zhang Dong , Xu Di
Published: June 2012

Sub-harmonic response from ultrasound contrast agent microbubbles has been demonstrated to be an effective modality for noninvasive pressure measurement. In the present study, the dependence of ultra-harmonic response on the ambient overpressure was investigated by both experimental measurements and simulations. In the measurements, the microbubbles were exposed to Gaussian pulses with varied driving frequencies and pulse lengths, at an acoustic pressure of 0.3 MPa. The amplitudes of sub- and ultra-harmonic components were measured when the ambient overpressures varied from 0–25 kPa. At the driving frequency of 1.33 MHz, the ultra-harmonic energy decreased but the sub-harmonic energy increased with the increasing overpressure; while at the driving frequency of 4 MHz, both the sub- and ultra-harmonic components showed the same tendency that the corresponding energy decreased as the overpressure was increased. A 4-MHz Gaussian pulse with 64 cycles could provide an ultra-harmonic response with both good ambient pressure sensitivity and high linearity. Furthermore, the effects of shell parameters of a microbubble on the generation of ultra- and sub-harmonic responses were discussed based on simulations using Marmottant’s model. This study suggests that the ultra-harmonic response from contrast microbubbles might be applicable for noninvasive pressure measurement.
Acoustic reconstruction of the velocity field in a furnace using a characteristic flow model
Authors: Li Yanqin , Zhou Huaichun , Chen Shiying , Zhang Yindi , Wei Xinli , Zhao Jinhui
Published: June 2012

An acoustic method can provide a noninvasive, efficient and full-field reconstruction of aerodynamic fields in a furnace. A simple yet reasonable model is devised for reconstruction of a velocity field in a cross section of a tangential furnace from acoustic measurements based on typical physical characteristics of the field. The solenoidal component of the velocity field is modeled by a curved surface, derived by rotating a curve of Gaussian distribution, determined by six characteristic parameters, while the nonrotational component is governed by a priori knowledge. Thus the inverse problem is translated into determination of the characteristic parameters using a set of acoustic projection data. First numerical experiments were undertaken to simulate the acoustic measurement, so as to preliminarily validate the effectiveness of the model. Based on this, physical experiments under different operating conditions were performed in a pilot-scale setup to provide a further test. Hot-wire anemometry and strip floating were applied to compare with acoustic measurements. The acoustic measurements provided satisfactory consistency with both of these approaches. Nevertheless, for a field with a relatively large magnitude of air velocities, the acoustic measurement can give more reliable reconstructions. Extension of the model to measurements of hot tangential furnaces is also discussed.
Nonequilibrium phenomena in damaged media and their effects on the elastic properties
Authors: Scalerandi M. , Gliozzi A. S. , Bruno C. L. E. , Antonaci P.
Published: June 2012

Concrete, particularly if damaged, exhibits a peculiar nonlinear elastic behavior, which is mainly due to the coupling between nonequilibrium and nonlinear features, the two of which are intrinsically connected. More specifically, the formulation of a constitutive equation able to properly predict the dynamic behavior of damaged concrete is made difficult by the concomitant presence of two mechanisms: The modification of the microstructure of the medium and the transition to a new elastic state caused by a finite amplitude excitation (conditioning). Memory of that new state is kept when the excitation is removed, before relaxation back to the original elastic state takes place. Indeed, besides accounting for linear and nonlinear parameters, a realistic constitutive equation to be used in reliable prediction models should take into account nonequilibrium effects. Specific parameters, sensitive to finite amplitude excitations, should be introduced to provide information about conditioning effects. In this paper, experimental results indicating that nonlinearity of damaged concrete is memory-dependent will be presented and the implications of such findings in the development of physical models, with relevant outcomes for the characterization of hysteretical features, will be discussed.
Speech intelligibility improvements with hearing aids using bilateral and binaural adaptive multichannel Wiener filtering based noise reduction
Authors: Cornelis Bram , Moonen Marc , Wouters Jan
Published: June 2012

This paper evaluates noise reduction techniques in bilateral and binaural hearing aids. Adaptive implementations (on a real-time test platform) of the bilateral and binaural speech distortion weighted multichannel Wiener filter (SDW-MWF) and a competing bilateral fixed beamformer are evaluated. As the SDW-MWF relies on a voice activity detector (VAD), a realistic binaural VAD is also included. The test subjects (both normal hearing subjects and hearing aid users) are tested by an adaptive speech reception threshold (SRT) test in different spatial scenarios, including a realistic cafeteria scenario with nonstationary noise. The main conclusions are: (a) The binaural SDW-MWF can further improve the SRT (up to 2 dB) over the improvements achieved by bilateral algorithms, although a significant difference is only achievable if the binaural SDW-MWF uses a perfect VAD. However, in the cafeteria scenario only the binaural SDW-MWF achieves a significant SRT improvement (2.6 dB with perfect VAD, 2.2 dB with real VAD), for the group of hearing aid users. (b) There is no significant degradation when using a real VAD at the input signal-to-noise ratio (SNR) levels where the hearing aid users reach their SRT. (c) The bilateral SDW-MWF achieves no SRT improvements compared to the bilateral fixed beamformer.
Acoustic scattering from a finite plate: Generation of guided Lamb waves S, A and A
Authors: Cité N. , Chati F. , Décultot D. , Léon F. , Maze G.
Published: June 2012

In the domain of renewable energies, marine current turbines constitute one of the possibilities of producing electrical energy. Naked-eye inspection, or with the aid of video monitoring systems of these machines to ensure their perfect working order, can be difficult in a turbid environment. Acoustic methods are conceivable. The study focuses on the blades of these machines, by considering rectangular plates. The propagation of Lamb waves in a plate is studied by analyzing experimental time signals obtained from acoustic scattering. These signals are analyzed employing the ray theory. In vacuum, the flexural wave is the A0 Lamb wave, whilst in water this wave splits in a bifurcation: the A wave with a phase velocity always smaller than the sound speed in water, and the A0 wave with a phase velocity always higher than the sound speed in water. In the central bandpass of the transducers used in the experiments, mainly the A and S0 waves exist. However, signals observed in the third harmonic bandpass of the transducers are also analyzed. In order to complement these results, resonance frequencies of the plate studied are calculated taking into account the boundary conditions and compared with the resonance frequencies of the experimental spectra.
Acoustic radiation force of a Bessel beam on a porous sphere
Authors: Azarpeyvand Mahdi
Published: June 2012

The possibility of using acoustic Bessel beams to produce an axial pulling force on porous particles is examined in an exact manner. The mathematical model utilizes the appropriate partial-wave expansion method in spherical coordinates, while Biot’s model is used to describe the wave motion within the poroelastic medium. Of particular interest here is to examine the feasibility of using Bessel beams for (a) acoustic manipulation of fine porous particles and (b) suppression of particle resonances. To verify the viability of the technique, the radiation force and scattering form-function are calculated for aluminum and silica foams at various porosities. Inspection of the results has shown that acoustic manipulation of low porosity (<0.3) spheres is similar to that of solid elastic spheres, but this behavior significantly changes at higher porosities. Results have also shown a strong correlation between the backscattered form-function and the regions of negative radiation force. It has also been observed that the high-order resonances of the particle can be effectively suppressed by choosing the beam conical angle such that the acoustic contribution from that particular mode vanishes. This investigation may be helpful in the development of acoustic tweezers for manipulation of micro-porous drug delivery carrier and contrast agents.
Linear and nonlinear Biot waves in a noncohesive granular medium slab: Transfer function, self-action, second harmonic generation
Authors: Legland J-B. , Tournat V. , Dazel O. , Novak A. , Gusev V.
Published: June 2012

Experimental results are reported on second harmonic generation and self-action in a noncohesive granular medium supporting wave energy propagation both in the solid frame and in the saturating fluid. The acoustic transfer function of the probed granular slab can be separated into two main frequency regions: a low frequency region where the wave propagation is controlled by the solid skeleton elastic properties, and a higher frequency region where the behavior is dominantly due to the air saturating the beads. Experimental results agree well with a recently developed nonlinear Biot wave model applied to granular media. The linear transfer function, second harmonic generation, and self-action effect are studied as a function of bead diameter, compaction step, excitation amplitude, and frequency. This parametric study allows one to isolate different propagation regimes involving a range of described and interpreted linear and nonlinear processes that are encountered in granular media experiments. In particular, a theoretical interpretation is proposed for the observed strong self-action effect.
Superresolution imaging of scatterers in ultrasound B-scan imaging
Authors: Parker Kevin J.
Published: June 2012

A number of imaging systems exhibit speckle, which is caused by the interaction of a coherent pulse reflecting off of random reflectors. The limitations of these systems are quite serious because the speckle phenomenon creates a pattern of nulls and peaks from subresolvable scatterers or targets that are difficult to interpret. Another limitation of these pulse-echo imaging systems is that their resolution is dependent on the full spatial extent of the propagating pulse, usually several wavelengths in the axial or propagating dimension and typically longer in the transverse direction. This limits the spatial resolution to many multiples of the wavelength. This paper focuses on the particular case of ultrasound B-scan imaging and develops an inverse filter solution that eliminates both the speckle phenomenon and the poor resolution dependency on the pulse length and width to produce super-resolution ultrasound (SURUS) images. The key to the inverse filter is the creation of pulse shapes that have stable inverses. This is derived by use of the standard Z-transform and related properties. Although the focus of this paper is on examples from ultrasound imaging systems, the results are applicable to other pulse-echo imaging systems that also can exhibit speckle statistics.
Temporal coherence of acoustic rays and modes using the path integral approach
Authors: Yang T. C.
Published: June 2012

Acoustic propagation can be described by rays and normal modes. Applying the path integral to refractive rays in three dimensional space, Dashen et al. [J. Acoust. Soc. Am. 77, 1716–1722 (1985)] derived the mutual coherence function of the acoustic field. For shallow water where sound interacts with boundaries, the acoustic field can be described by vertical modes and horizontal rays. Applying the path integral to the horizontal rays, one obtains the mutual coherence function of the normal modes. This paper applies this formulation to the derivation of the temporal coherence function of individual modes and also that of the acoustic field in the presence of linear internal waves. The effects of mode coupling due to internal waves on temporal coherence loss are illustrated with numerical calculations.
Dispersion of an acoustic pulse passing through a large-grained polycrystalline film
Authors: Every A. G. , Maznev A. A.
Published: June 2012

Propagation of a short acoustic pulse through a polycrystalline film comprised of large randomly oriented elastically anisotropic grains is analyzed theoretically. For average grain size much larger than the film thickness, a short acoustic pulse launched normally into the film will traverse each grain in a time determined by the acoustic slowness in the direction normal to the film, which will depend on the local grain orientation. A typical measurement averages over a large number of grains resulting in the broadening of the composite output pulse. The resulting pulse shape is characterized by distinct features related to stationary values of the directionally dependent acoustic slowness of the crystalline material. Maxima and minima in the slowness yield discontinuities in the pulse shape, while saddle points yield logarithmic singularities. For cubic and hexagonal crystals, power law singularities result from cones of directions in which the slowness is a maximum or minimum. Numerical results, taking into account Gaussian broadening of the input pulse, are presented for thin film materials commonly encountered in picosecond ultrasonic experiments, such as copper, gold, and aluminum.