bluuebunny/crossref_metadata_2025 huggingface dataset:
Earnings Announcements and Systematic Risk
Authors: SAVOR PAVEL , WILSON MUNGO
Published: October 2015

Firms scheduled to report earnings earn an annualized abnormal return of 9.9%. We propose a risk‐based explanation for this phenomenon, whereby investors use announcements to revise their expectations for nonannouncing firms, but can only do so imperfectly. Consequently, the covariance between firm‐specific and market cash flow news spikes around announcements, making announcers especially risky. Consistent with our hypothesis, announcer returns forecast aggregate earnings. The announcement premium is persistent across stocks, and early (late) announcers earn higher (lower) returns. Nonannouncers' response to announcements is consistent with our model, both over time and across firms. Finally, exposure to announcement risk is priced.
Field test of canopy cover estimation by hemispherical photographs taken with a smartphone
Authors: Tichý Lubomír
Published: October 2015

Aim

To test the Canopy Cover (CaCo) index for forest vegetation research estimation of canopy cover from hemispherical photographs, and introduce a new Android smartphone application for use of this index.

Methods

The original and modified CaCo index were evaluated using a data set of 234 hemispherical photographs taken in 78 plots in coniferous, mixed and broad‐leaved deciduous forests. The results of the CaCo analysis of these photographs were compared with expert field visual estimation of canopy cover of these plots. For each hemispherical photograph, several CaCo values were calculated based on the photograph being restricted to different degrees by artificial horizon masking. The CaCo index was also tested with respect to precision of canopy cover estimation and sensitivity to different photographic equipment, using a different set of 93 canopy photographs taken in mixed and coniferous forests. Calculation of the CaCo index was done with the newly developed GLAMA – Gap Light Analysis Mobile Application software.

Results

Linear regression showed a close relationship between the CaCo index and visually observed canopy cover data. A proposed calculation modification improved the stability of the CaCo index in cases in which no horizon masking was applied. The best fit, zero‐intercept and a regression slope close to1 were found in cases in which an artificial horizon mask that extended higher than 45° restricted the bottom part of the sky hemisphere. Low sensitivity of the CaCo index to type of photographic equipment used was shown.

Conclusions

The CaCo index is robust and can be used for precise canopy cover estimation, comparable to visual canopy cover estimation and unaffected by observer bias. Not only can it be used on already‐captured photographs, but the index can also be employed on smartphones to rapidly capture hemispherical photographs and immediately calculate their index values. This application is freely available on the Internet and can serve as a powerful research and educational tool that can not only calculate CaCo values, but also standardize forest canopy visual estimates.
Development and function of Foxp3+ regulatory T cells
Authors: Wang Yuan Min , Ghali Joanna , Zhang Geoff Yu , Hu Min , Wang Ya , Sawyer Andrew , Zhou Jimmy Jianheng , Hapudeniya Dhanushka A. , Wang Yiping , Cao Qi , Zheng Guoping , Harris David C. , Alexander Stephen I.
Published: October 2015

Regulatory T cells (Tregs) have been recognized as having a major role in maintaining peripheral tolerance and preventing and limiting autoimmune and chronic inflammatory diseases. Tregs derive from the thymus and also develop peripherally. In this review, we discuss recent progress in our understanding of the basic mechanisms involved in Treg development and function in protecting against autoimmunity in the periphery, including thymic selection, peripheral induction and the many mechanisms of Treg suppression. Specifically in kidney disease, Tregs have been shown to play a role in limiting injury and may potentially have a therapeutic role.
The Distribution Dynamics of Human Development in Mexico 1990–2010
Authors: Villalobos Barría Carlos , Klasen Stephan , Vollmer Sebastian
Published: October 2015

Based on census data linked to household surveys, we analyze the univariate and joint distribution of income, health and education at the municipality level in Mexico from 1990 to 2010 using Gaussian mixture models. The univariate analysis finds an emergence of a low‐income cluster in 2000, which disappears again by 2010. Our trivariate estimation shows an education‐led human development convergence over time while dynamics are mainly affected by fluctuations in health and income. Changes in development clusters have a clear spatial pattern and are closely related to the relative size of the agricultural sector and the proportion of indigenous population groups.
The Sins of the Fathers: Intergenerational Income Mobility in China
Authors: Yuan Weici
Published: October 2015

This paper aims to obtain an accurate estimate of China's intergenerational income mobility and to present evidence on its distributional pattern. Using panel data from the China Health and Nutrition Survey (CHNS) over the period 1989–2009, I find that China is less mobile than most developed countries. Then, I employ five different approaches to investigate the distributional pattern of China's intergenerational mobility across income levels. The results suggest that poor families have relatively high mobility, indicating opportunities for the poor children to escape poverty. Finally, I show that while wealthy fathers are likely to pass on their favorable economic status to their sons, rich sons come from a very wide range of family economic backgrounds.
Maternal Vocal Interactions with Infants: Reciprocal Visual Influences
Authors: Trehub Sandra E. , Plantinga Judy , Russo Frank A.
Published: October 2015

The present study examined the influence of infant visual cues on maternal vocal and facial expressiveness while speaking or singing and the influence of maternal visual cues on infant attention. Experiment 1 asked whether mothers exhibit more vocal emotion when speaking and singing to infants in or out of view. Adults judged which of each pair of audio excerpts (in view, out of view) sounded more emotional. Face‐to‐face vocalizations were judged more emotional than vocalizations to infants out of view. Moreover, mothers smiled considerably more while singing than while speaking to infants. Experiment 2 examined the influence of video feedback from infants on maternal speech and singing. Maternal vocalizations in the context of video feedback were judged to be less emotional than those in face‐to‐face contexts but more emotional than those in out‐of‐view contexts. Experiment 3 compared six‐month‐old infants’ attention to maternal speech and singing with audio‐only versions or with silent video‐only versions. Infants exhibited comparable attention to audio‐only versions of speech and singing but greater attention to video‐only versions of singing. The present investigation is unique in documenting the contribution of infant visual feedback to maternal vocal emotion in contexts that control for infants’ presence, visibility, and proximity.
Teaching Introductory Upper‐Level Religion and Theology Classes
Authors: Clingerman Forrest , O'Brien Kevin J.
Published: October 2015

The undergraduate study of religion is predominantly undertaken by non‐majors who are meeting a general education requirement. This means that, while curricular discussions make important distinctions between the work of lower‐ and upper‐division courses, many religion and theology faculty are teaching hybrid courses that we call “introductory upper‐level courses.” These play an introductory role in general education while also serving the study of religion in a more advanced way. Attention to how these courses fit into multiple curricular goals will be important for the scholarship of teaching and learning in religious studies and theology. This essay draws on scholarship about introductory teaching and a survey of faculty about introductory upper‐level courses to argue that the content of such courses should be understood as serving the study of religion at an advanced level, the context should be understood as introducing general education goals, and the goals for intellectual growth must strike a challenging balance between the two.
Water Transport in a PEMFC Based on the Difference in Capillary Pressure Between the Cathode Catalyst Layer and Microporous Layer
Authors: Nishiyama Enju , Hara Masaya , Murahashi Toshiaki , Nakao Kazushige
Published: October 2015

The water transport behavior of the cathode catalyst layer (CCL) in a proton exchange membrane fuel cell (PEMFC) was investigated by comparing the performance of several cells containing different microporous layers (MPLs). The capillary pressure and effective diffusivity of the cathode gas diffusion layer (GDL) and the CCL play an important role in the transport of water generated in the PEMFC. Experimental data for various inlet humidities and air stoichiometries were evaluated using the modified water vapor activity with the capillary pressure of the MPL. The capillary pressures in the MPLs and CCL are approximated using a polynomial function of liquid saturation. There was a significant increase in the diffusion resistance of oxygen in the CCL, while that in the MPLs and CCL was moderate, which indicates that the CCL is susceptible to flooding.
Systematic and Applied Acarology: introduction, acknowledgements and dedication
Authors: ZHANG ZHI-QIANG
Published: October 2015

For a long time, there has been a lack of a dedicated forum for Chinese acarologists to publish their works. Papers by Chinese acarologists have been published in various zoological and entomological journals in China, and sometimes in obscure journals of the universities or institutes where he or she works. Most papers have been published in Chinese, often with a short English abstract. The language barrier and the lack of Chinese journals and books in libraries outside China make it inevitable that many works published in China are difficult to access and are unknown to many acarologists outside China. The primary aim of this new journal, Systematic and Applied Acarology (SAA), is to make the works by Chinese acarologists more accessible to fellow acarologists throughout the world.
Selection and genetic analysis of fenvalerate resistance in Amblyseius pseudolongispinosus (Acari: Phytoseiidae)
Authors: ZHU KEYAN , KE LISHENG , XIN JIELIU
Published: October 2015

A fenvalerate-resistant strain of Amblyseius pseudolongispinosus Xin, Liang & Ke was selected and evaluated for level of resistance. After 18 selection cycles, the LC50 value was 65 times higher than in wild-type strain. Resistance was partially lost if the selection pressure was removed. Genetic studies indicated that the resistance factor was controlled by a single, incompletely dominant gene. The resistant strain, which had the same intrinsic rate of increase as the wild-type strain, might be a useful biological control agent of spider mites in an IPM system.
Soft 3D acoustic metamaterials
Authors: Brunet Thomas , Poncelet Olivier , Aristégui Christophe , Leng Jacques , Mondain-Monval Olivier
Published: October 2015

One of the current challenges in the field of metamaterials is to extend beyond electromagnetism in other areas such as acoustics [1]. Soft matter techniques coupled with microfluidics provide a unique tool to take up this challenge because they allow for the production of 3D locally resonant (random) materials composed of various soft resonators [2]. The Mie (or cavity) resonators are interesting key elements for acoustic metamaterials since they may induce strong acoustic resonances provided large sound-speed contrasts between the inclusions and the host matrix [3]. For example, the use of “slow” (deformable) ferrofluid-droplets allows for the tuning of sharp Mie resonances, thanks to external magnetic fields [4]. For much higher sound-speed contrasts, we have recently shown that strong Mie resonances of “ultra-slow” beads made of soft porous silicone rubbers [5] could induce strong dispersion effects leading to materials with exotic (zero, negative) values of the acoustic index [6]. [1] Wegener, Science 342, 939–940 (2013). [2] Brunet et al., Science 342, 323–324 (2013). [3] Li and Chan, Phys. Rev. E 70, 055602 (2004). [4] Brunet et al., Phys. Rev. Letters 111, 264301 (2013). [5] Zimny et al., Langmuir 31, 3215–3221 (2015). [6] Brunet et al., Nature Mater. 14, 384–388 (2015).
Fin and humpback whale vocalization classification and localization, northern Georges Bank
Authors: Huang Wei , Wang Delin , Ratilal Purnima
Published: October 2015

Several tens of thousand vocalizations from multiple fin whale individuals were passively recorded by a high-resolution coherent hydrophone array system in the Gulf of Maine in Fall 2006. The recorded fin vocalizations have short durations roughly 0.4 s and frequencies ranging from 15 to 40 Hz. The fin vocalizations were detected via spectrogram intensity thresholding. The horizontal azimuth or bearing of each detected fin whale vocalization was determined by broadband beamforming. Each vocalization was then characterized using numerous features, such as center frequency, upper and lower frequency limits, and duration, obtained from pitch tracking. These vocalizations were then classified using Bayesian-based Gaussian Mixture model feature clustering into several distinct vocal types. The vocalization clustering result was then combined with the bearing-time trajectory and localized by the moving array triangulation and the array invariant techniques. The vocalization types are found be dependent on the geographic region, suggesting a potential application for monitoring different fin whale groups from their vocalization features. A similar approach can be used to monitor humpback whale groups.
Hostile fire detection using a bio-inspired mobile acoustic sensor network
Authors: Cakiades George , Deligeorges Socrates , George Jemin , Núñez Felipe , Wang Yongqiang , Doyle Francis J.
Published: October 2015

Hostile Fire Detection (HFD) sensors play an increasing role in combating asymmetric threats in both military and civilian operations. Bio-inspired advances in acoustic sensor technology have enabled small aperture arrays to localize and identify target sounds on baselines as small as 7.5 cm, making them practical for body worn and mobile applications such as UAVs. The unique approach to acoustic processing reduces acoustic information through a neural transform to key features that allow segregation of multiple targets using spectro-temporal cues creating auditory objects. The sparse representation of targets as auditory objects enables fast computationally efficient localization, identification, and tracking of several acoustic targets nearly simultaneously. The sparse representation is also ideal for information fusion among sensors over limited bandwidth networks for enhanced performance in challenging environments. Through a collaborative effort between Army research groups, the University of California Santa Barbara, and BioMimetic Systems, a prototype acoustic sensor network using biologically inspired sensors and network synchronization for a mobile HFD application has been developed. The network employs body worn PinPoint™ HFD sensors interfaced with smartphones (Android) running net-centric fusion algorithms. The network will be discussed in terms of the biologically inspired components, information fusion, as well as results from preliminary field tests.
Green’s function retrieval for atmospheric acoustic propagation
Authors: Collier Sandra L. , Cain Jericho E. , Noble John M. , Alberts W. C. K. , Ligon David A. , Sim Leng K.
Published: October 2015

There is an extensive classical utilization of the Green's function for wave propagation in many different media. By extracting the Green's function, or medium impulse response, one may obtain information about the medium channel. This information could be used to overcome the medium effects, as is done in time-reversed acoustic localization or acoustic communications; alternatively, it may be used to deduce information about the medium. The use of time-reversal methods has been established for interferometry, phase conjugation, and time-reversal mirrors and cavities. The objective of this research is to determine the feasibility of using a time-reversal method to extract a Green's function for outdoor acoustic propagation utilizing sources in the audible frequency ranges. Initial findings are presented here.
Matched-field source localization with multiple small-aperture arrays
Authors: Tollefsen Dag , Dosso Stan E.
Published: October 2015

This paper considers combining information from multiple small-aperture arrays in matched-field processing (MFP) for source localization. Assuming individual arrays are comprised of calibrated sensors which are synchronized in time, conventional MFP can be applied for each array and the resulting Bartlett processors summed over arrays. However, if the relative calibration and/or time synchronization is known between some or all arrays, more informative multiple-array processors can be derived by maximum-likelihood methods. For example, if the relative calibration between arrays is known, the observed amplitude variations between arrays provide additional information for source localization; if synchronization is known, phase variations provide localization information. Various multiple-array processors are derived and evaluated in terms of the probability of correct localization from Monte-Carlo analyses for a range of signal-to-noise ratios and number of frequencies for simulated shallow-water scenarios with vertical and horizontal arrays. Effects of environmental mismatch in seabed geoacoustic parameters and water depth are also considered. The analysis indicates that, dependent on array configurations, substantial improvements in source localization performance can be achieved when including relative amplitude and/or phase information in the multiple-array processor. The improvement is reduced by environmental mismatch; this degradation can be partially mitigated by including additional frequencies in the processing.
Atmospheric compensation of acoustic signatures of aircraft
Authors: Benyamin Minas , Goldman Geoffrey H.
Published: October 2015

The U.S. Army Research Laboratory is investigating using low size, weight, power, and cost (SWaP-C) acoustic sensors to classify unmanned aircraft systems (UAS). One issue complicating UAS classification using acoustics is that the atmosphere attenuates the signature of the targets in a complex manner. To address this issue, we developed and tested a technique to mitigate the effect of atmospheric attenuation. We used Bass's model with inputs from temperature, relative humidity and range to estimate atmospheric attenuation, then we used techniques based upon a Wiener filter implemented in the frequency domain to adjust the amplitude of the measured signal. The Wiener filter reduced the amplification of the noise while improving the reproducibility of the signature at different ranges, particularly at higher frequencies. The results suggest that preprocessing the data using this technique should improve the performance of acoustic classifier algorithms.
Evaluation of methods for isolating portable loudspeakers during sound transmission testing
Authors: Reuter Eric L.
Published: October 2015

When performing field sound transmission tests, the potential exists for structureborne flanking resulting from poor isolation between the loudspeakers and floor. Many of us resort to using furniture and other creative means of isolation with unpredictable results. This paper will present analysis of a handful mocked up isolation systems with the hope of finding a practical, portable solution.
Change in Canada’s national building code—Assessing flanking sound transmission in steel-framed constructions
Authors: Hoeller Christoph , Zeitler Berndt
Published: October 2015

The proposed 2015 edition of the National Building Code of Canada sees a major change in sound insulation requirements. Instead of prescribing requirements for the separating assembly only (in terms of STC values), the Code now sets requirements for the sound insulation performance of the complete system (in terms of Apparent Sound Transmission Class (ASTC) values), including flanking sound transmission. The National Research Council Canada is actively supporting the change in the Code by conducting various projects with industry associations from different construction sectors, in order to provide tools, guidance, and the necessary data for compliance. This presentation focuses on an ongoing joint project between the National Research Council Canada and the Canadian Sheet Steel Building Institute. In the project, the direct and flanking sound transmission in steel-framed assemblies are being investigated. In the presentation, an overview of the project is given, and updates on the current status of the investigation are provided, including measured data concerning the flanking sound transmission in steel-framed constructions.
Auralization of sound insulation in buildings
Authors: Vorlaender Michael
Published: October 2015

In various surveys, it was found that people living in multi-family dwellings and apartment houses are annoyed by noise of their neighbors. Also, it seems that building regulations, for example, the German standard DIN 4109 “Sound insulation in buildings,” are insufficient. The degree of annoyance is influenced by the personal conditions of the habitants (stress), the value of the dwelling and the duration the habitants live there. The effects on humans include disturbance of conversation or listening to the TV or radio in private dwellings as well as communication in office premises, reduced power of concentration during physical or mental work, and disturbance of sleep. All this strongly depends on the kind of noise signal (speech, music, footfall, etc.) and on the context, and thus, it is highly doubtful if single-number quantities such as the STL sufficiently describe the real situation. In this paper, a technique is presented for auralization of complex virtual acoustic scenes including airborne and structure-borne noise in buildings with particular respect to sound propagation across or between coupled rooms. Based on SEA-like sound propagation models in standardized prediction methods (EN 12354), algorithms are designed for FIR filtering of audio signals and applied in listening tests and for to creation of audio demos. The auralized sounds can be used during building design processes, in studies of human noise perception, and in development of new metrics for future building codes.
Measuring noise level reduction using an artificial noise source
Authors: Robert Rene , Cunefare Kenneth , Ryherd Erica , Irizarry Javier
Published: October 2015

Residences near airports may be subjected to significant noise levels. The impact of aircraft traffic noise imposes a higher level of design consideration for the outdoor-to-indoor transmission of sound for residences. Noise Level Reduction (NLR) is a common metric used to quantify the ability for a building element to reduce the transmission of external sound pressure levels generated by aircraft. The aircraft noise mitigation measure is determined by the estimate of NLR and the building location in the airport’s noise footprint. While NLR may be measured using an actual traffic source (i.e., aircraft fly-overs), another practice is to perform measurements using a loudspeaker. An investigation is underway to better understand the loudspeaker methods of measuring NLR for buildings. Specifically, the study was tasked with quantifying various factors of these measurements such as angular dependency. NLR measurements were taken on the façade of a “test house” that was constructed for the purpose of the research. Although the “test house” is a single-room structure, the same procedures can be applied to buildings such as single family residences and multifamily dwellings, among others. The results of the analysis should provide a more comprehensive understanding of NLR measurement procedures implemented in sound insulation programs.
An approximate model for foliage echoes to study biosonar function in natural environments
Authors: Ming Chen , Gupta Anupam K. , Müller Rolf
Published: October 2015

Natural environments are difficult for current engineered sonars but apparently easy for at least some species of echolocating bats. To better understand the information that foliage echoes provide for biosonar-based sensing, an approximate model of foliage echoes has been developed. The model simplifies the scattering problem through two key assumptions: (i) multi-path scattering was neglected and (ii) all leaves were assumed to be circular disks. Due to the latter, the parameters of the model were reduced to the number of the disks, their positions, sizes, and orientations. The exact far-field scatter from a disk (i.e., simplified leaf) in response to planar incident waves can be obtained by summation over an infinite series of spheroidal wave functions. To reduce the calculation time, the scattered field has been approximated by exponential, polynomial, and cosine fitting functions that also depend on the disk parameters. This allows the simulation of echoes from 100 leaves in 20 s on a standard PC. The model was able to reproduce the echo waveforms from dense and sparse foliages qualitatively. The model should thus be well suited for generation of large echo datasets to explore the existence and utilization of statistical invariants in the echoes from natural environments.
Alternative measurements and processing for extracting seabed information from sea-surface noise correlations
Authors: Siderius Martin , Paddock Joel , Muzi Lanfranco , Gebbie John
Published: October 2015

In recent years, both theoretical and experimental results have shown that the noise generated at the sea-surface from wind and waves contains valuable information about the seabed. A vertical hydrophone array together with beamforming has been a particularly useful configuration for estimating seabed properties. By cross-correlating a vertically upward looking beam with a downward looking beam (the endfire directions), the bathymetry and seabed layering can be determined. However, there may be additional information about the seabed found by cross-correlating beams in directions away from vertical endfire. In this presentation, two new measurement and processing configurations will be considered: noise cross-correlation of beams from a vertical array in directions away from endfire and cross-correlation on a towed horizontal array. For the vertical array, data and modeling show the existence of strong beam correlations coming from a direction consistent with the seabed critical angle. The towed horizontal array configuration, if possible, would provide an alternative to the vertical array for seabed surveying using noise. Measurements from data collected at several sites along with modeling will be used to explain the results from these new measurement and processing configurations.
Improved passive bottom-loss estimation below 10 kHz using arrays deployable on autonomous underwater vehicles
Authors: Muzi Lanfranco , Siderius Martin , Nielsen Peter L.
Published: October 2015

Accurate modeling of acoustic propagation in the ocean waveguide is important for SONAR performance prediction, and requires, among other things, characterizing the reflection properties of the bottom. Recent advances in the technology of autonomous underwater vehicles (AUV) make it possible to envision a survey tool for seabed characterization composed of a short array mounted on an AUV. The bottom power reflection coefficient (and the related reflection loss) can be estimated passively by beamforming the naturally occurring marine ambient-noise acoustic field recorded by a vertical line array of hydrophones. However, the reduced array lengths required by AUV deployment can hinder the process, due to the inherently poor angular resolution. In this paper, data from higher frequencies are used to estimate the noise spatial coherence function at a lower frequency for sensor spacing beyond the physical length of the array. This results in higher angular resolution of the bottom loss estimate, while exploiting the large bandwidth available to current acquisition systems more efficiently than beamforming does. The technique, rigorously justified for a halfspace bottom, proves to be effective also on more complex bottom types, both in simulation and on experimental data.
High-resolution imaging of the San Jacinto fault zone with a dense seismic array and local seismic noise
Authors: Roux Philippe , Lecointre Albanne , Moreau Ludovic , Campillo Michel , Ben-Zion Yehuda , Vernon Frank
Published: October 2015

A highly-dense Nodal array with 1108 vertical (10 Hz) geophone was deployed around the San Jacinto fault zone for ∼4 weeks in 2014 in ∼600 m x 600 m box configuration (nominal instrument spacing 10–30 m) centered on the Clark branch of the fault zone south of Anza. The array continuously recorded local ambient noise from which cross-correlations between each station pair were extracted for imaging purpose between 1 Hz and 20 Hz. Using subarrays made of 25 sensors, double beamforming was applied to separate body waves from surface waves. Focusing solely on surface waves in a first step, dispersion curves for surface wave group velocities are obtained with unprecedented accuracy at each point of a 10-m spacing grid. The data inversion reveals depth- and lateral-variations of local structural properties within and around the San Jacinto fault zone.
Optimizing the ultrasonic imaging of metallic components with high microstructural noise
Authors: Humeida Yousif , Wilcox Paul D. , Drinkwater Bruce W.
Published: October 2015

Ultrasonic arrays are used extensively in a wide range of non-destructive evaluation applications. Many engineering structures are manufactured from polycrystalline metals that result in high levels of microstructural noise making their inspection extremely challenging. In this paper, an optimization framework that uses fast and efficient forward models to simulate the ultrasonic response for both defects and the grains in scattering media is presented. Crucially, these models include both single and multiple scattering effects, and the optimal inspection depends on which type of scattering dominates. For a particular material, simple experimental measurements are used to extract information, such as attenuation and grain scattering coefficients, which is then used to populate models of the microstructural scattering that can be used in an optimization process. As a demonstration, the detectability of small (0.3 mm) defects in copper, a material with high microstructural scatter, is investigated, and the optimal array size, pitch, array location, central frequency, and frequency bandwidth are found. The performance of the optimization system has been evaluated using experimental measurements of receiver operating characteristic (ROC) curves. For the chosen example, the optimal array configuration results in a probability of detection of 90% with a 1% false alarm rate.
A fractional calculus approach to the propagation of waves in an unconsolidated granular medium
Authors: Pandey Vikash , Holm Sverre
Published: October 2015

Our study builds on the work of Buckingham [JASA (2000)] which employed a grain-shearing (GS) model to describe the propagation of elastic waves in saturated, unconsolidated granular materials. He ensemble averages the random stick-slip process which follows the velocity gradient set up by the wave. The stick-slip process is due to the presence of micro-asperities between the contact surfaces of the grains. This is a strain hardening process which is represented by a time-dependent coefficient in the Maxwell element, besides the coefficient also gives the order of the loss term in the wave equations. We find that the material impulse response derived from the GS model is similar to the power-law memory kernel of fractional calculus. The GS model then gives two equations; a fractional Kelvin-Voigt wave equation for the compressional wave and a fractional diffusion equation for the shear wave. These equations have already been analyzed extensively in the framework of fractional calculus. Since the Kelvin-Voigt model is used in biomechanics of living tissue, we believe the GS theory could offer insights into ultrasound and elastography as well. The overall goal is to understand the role of different material parameters which affect wave propagation.
Reconstructing complex thickness variations with guided wave tomography
Authors: Huthwaite Peter , Lowe Michael J. , Cawley Peter
Published: October 2015

Wall thickness mapping is very important for quantifying corrosion within the petrochemical industry. One approach is guided wave tomography, where Lamb-type waves, which travel at different speeds depending on the thickness, due to dispersion, are passed through the region of interest. Wave speed is then reconstructed by a tomographic inversion approach and is converted to thickness by the known dispersion relationship. This approach relies on the assumption that guided waves scatter from the varying thicknesses within the plate in the same way that they would from the equivalent varying velocity field. This talk will investigate the accuracy of this assumption for the complex thickness variations associated with corrosion defects found in industry, and discuss potential approaches to mitigate the effects of any errors associated with this.
Acoustic vector sensors: Principles, applications, and practical experience
Authors: Haege Miriam
Published: October 2015

Acoustic sensors can be applied in both the civilian and military domain in order to detect risky acoustic sources and localize them. In the case of military use, they are of high importance in sniper and gunshot detection as well as in the classification of firearms. On the civil side, acoustic sensors are employed, e.g., in environmental acoustic monitoring. This paper focuses on the usage of a special class of acoustic sensors, the so called acoustic vector sensors. Such sensors measure the scalar acoustic pressure field as well as the vectorial velocity field at a single location. The construction and the functional principle of an acoustic vector sensor will be described. This type of sensor was applied in a series of field trials, e.g., sniper localization and aircraft detection. The paper presents the experimental results received from the corresponding measurements and discusses the experiences gained with this sensor type.
Numerical and experimental study of acoustic horn
Authors: Vitorino Clebe J. , Barbieri Nilson , Lima Key F. , Barbieri Renato
Published: October 2015

Horns are acoustic elements specially designed for maximum transmission of sound pressure and they are used, for example, in sound systems (mainly, external and warning equipment), musical instruments, cleaning apparatus, receivers, and microwave transmitters. The objective of this work is to develop a methodology for obtaining the ideal shape of acoustic horns by comparing numerical data obtained by computational simulation of mathematical model (Finite Element Method—FEM) and experimental data obtained by acoustic tests in laboratory (two microphones method). The main steps to obtain the ideal geometry of acoustic horns are the definition of the objective function, the evaluation of this function and the optimization technique used. The reflection coefficient of the wave is the parameter optimized by the objective function by using the PSO (Particle Swarm Optimization) method. The results obtained for the optimization process were very satisfactory, especially for the correct control of the optimized geometry. The numerical and experimental data showed some differences due to limitations of the numerical model, but the results were good and appear promising.
Teaching the characterization of performance spaces through in-class measurements at Bates Recital Hall at the University of Texas at Austin
Authors: Haberman Michael R. , Spratt Kyle S. , Hemme Dan , Abel Jonathan S.
Published: October 2015

The characterization of a performance space provides an excellent opportunity to provide students with first-hand experience with many fundamental aspects of room acoustics including reverberation, linear time-invariant systems, measurement methods, and post-processing of real-world data to estimate room metrics. This talk reports recent measurements made in Bates Recital Hall at the University of Texas at Austin (UT) as part of the graduate course on architectural acoustics in the acoustics program at UT. For one class period, students participated in acoustical measurements in the 700-seat venue. The measurements consisted of recording the signal at numerous locations within the room resulting from various on-stage excitations including exponential chirps, interrupted pink noise, and balloon-pops. The audio files captured during the experiments were provided to the students for calculation of the impulse response at the measurement positions and associated room metrics such as reverberation time, bass ratio, clarity index, and initial time-delay gap. Learning outcomes from this approach will be discussed in light of the experiential learning model which emphasizes abstract conceptualization, experimentation and experience, and reflective observation.
Development of an educational electro-mechanical model of the middle ear
Authors: Saba Juliana , Ali Hussnain , Lee Jaewook , Hansen John , Ta Son , Nguyen Tuan , Chilson Cory
Published: October 2015

In the United States, 1 in 5 people (20%, or 48.1 M), 12 years or older, have hearing loss in one or both ears,1, 2 and approximately 3 out of 1000 children are born with some degree hearing loss.1, 3Educating the public on potential causes of hearing loss is often overlooked but imperative; like the remedial task of listening to headphones at a high volume. This in part is due to lack of interactive educational tools to demonstrate sound sensation/perception and apparatuses of the natural safety mechanisms against high intensity sounds. This study aids to encourage particularly a younger generation by increasing public health awareness with the design of a standalone, interactive, and educational electro-mechanical model that exhibits middle ear motion. The model includes: (i) anatomical 3-bone configuration (malleus, incus, and stapes), (ii) cochlea fluid environment, (iii) electrical stimulation of auditory nerve fibers, and (iv) an informational display regarding the natural safety mechanism, sound conduction process, the role of the cochlea in sound sensation, and how cochlear implants/hearing aids assist auditory rehabilitation. Since the model encourages hands-on learning, its placement is desired in either a classroom or a museum striving to reduce any ear-damaging habits and negligence by increasing cognizance.
A biomechanically based auditory standard against impulse noise
Authors: Chan Philemon C.
Published: October 2015

This paper addresses two critical issues in developing a damage risk criteria against impulse noise injury, namely, (1) difficulty in setting a threshold for large weapon noise involving hearing protecting devices (HPDs) and small arms noise involving no HPDs; and (2) having a standard procedure to account for the effects of HPDs. The rational way to resolve these issues is to develop biomechanical-based standard using a physics-based model. The Auditory Hazard Assessment Algorithm for the Human (AHAAH) is a biomechanical model that simulates the transmission of sound energy from free field through the ear canal and middle ear to the cochlea. Extensive research has been performed by subjecting the AHAAH to a rigorous verification and validation process. Findings show that the AHAAH middle ear is overly compressive and corrections were made to the annular ligaments parameters. The human data from the historical Albuquerque walk-up study with volunteers wearing HPDs were used to validate the model and develop the dose-response curve for the injury threshold. Calculations were then performed for the German rife noise tests with volunteers not wearing HPDs, and the predictions show excellent comparison with the injury outcomes, hence providing an independent validation of the revised model.
Fluid structure interactions with multicell membrane wings
Authors: Arce Manuel , Perez Raphael , Ukeiley Lawrence
Published: October 2015

Flexible wing surfaces can be observed in many natural flyers and their use in small engineered flying vehicles has translated too many beneficial properties. These benefits have manifested themselves in the aerodynamic forces as well as flight stability which are an effect of how the flow and the membranes interact both statically and dynamically. In this work, time dependent particle image velocimetry and digital image correlation are used to study the fluid structure interaction for flow over a membrane wing. The wings examined here are multi-cell silicon rubber membrane wings which have a scalloped free trailing edge with different levels of pretension. The pretension effects the natural frequencies of the membranes and is shown to affect the extension magnitude and membrane motion frequency which are both also affected by aerodynamic loading. Examinations of the membranes through time based and frequency domain analysis motions shows they are highly correlated with the flow. The velocity measurements demonstrated the effects of membranes motion alter the characteristics of the flow over wing leading to changes in the overall aerodynamic properties such as the stall angle and the wake deficit.
Computational flow noise
Authors: Cox Donald , Perez Daniel , Guarendi Andrew
Published: October 2015

This work focuses on combining the capabilities of computational fluid dynamics with computational structural acoustics to enable the calculation of flow noise primarily for undersea vehicles. The work is limited to the non-coupled problem, where the flow calculations are made over a non-deforming boundary with the goal of calculating wall pressure fluctuations and using them as loads on a finite element structural acoustics model. The ultimate goal of this work is to develop the capability to calculate flow noise for three-dimensional undersea structures for which analytical approaches are not possible. Results will be presented that make use of wall pressure fluctuations calculated using Large Eddy Simulations (LES) and variants of Improved Delayed Detached Eddy Simulations (IDDES).
Individual interaction between hearing and speaking due to aging
Authors: Mizumachi Mitsunori
Published: October 2015

It is well known that a hearing loss is induced by aging in a high frequency range. It is easy to imagine that the aging also alters characteristics of voice, because you can roughly estimate the speaker’s age. In general, those aging phenomena are discussed independently. In speech communication, however, the speech chain [Dense & Pinson, 1993] must dominate the interaction on the aging effects between hearing and speaking. Individual interaction between them is investigated using both his pure-tone audiometry test threshold and his recordings of read utterances. In this study, 21 Japanese elderly males, whose ages ranged from 62 to 85 years old, participated in pure tone audiometry and recording of Japanese sentence and word utterances. Concerning three elderlies with presbycusis, who are aware of hearing loss in daily lives, hearing abilities gradually decrease in proportion to frequency over 2 kHz, and spectral energies increase in the high frequency range over 4.5 kHz. In another case of high-frequency deafness, the spectral energy over 4.5 kHz increases significantly. On the other hand, elderly speakers with normal hearing do not cause energy lift of speech in high frequencies.
Effect of practice type on acquisition and retention of speech motor skills
Authors: Tasko Stephen M.
Published: October 2015

There is a growing literature focused on how speakers acquire and retain speech motor skills. While motor learning experiments provide practical information for improving speech treatment and instructional programs, identifying the specific conditions under which speech skills are enhanced or diminished also offers a window into the underlying organization of the speech motor system. The current study examines how speech motor performance on a challenging speech task varies for different forms of speech practice. Subjects include 40 healthy adult speakers. The challenging speech task is a set of tongue twisters produced at specified speech rates markedly faster than habitual rate. Subjects are assigned to one of three speech practice conditions (imitating an auditory target, listening to an auditory target, or using a magnitude production task) or a control task. Speech motor performance on the challenging speech task is assessed prior to, immediately after, and one day following the speech practice condition. Speech motor performance measures include speech rate accuracy and articulatory accuracy. Improved performance immediately following practice suggests speech skill acquisition while continued improvements during follow up testing suggests speech skill retention. The effect of different practice conditions on speech motor skill acquisition and retention will be described.
Model based comparison of vocal fold dynamics between children and adults
Authors: Döllinger Michael , Dubrovskiy Denis , Beck Eva , Patel Rita
Published: October 2015

In clinical practice, pediatric vocal fold vibration patterns are visualized by methods and standards derived from the adult population. Quantitative evaluations of vocal fold vibratory changes which are connected to growth and development of children are missing, although it is known that the pediatric larynx is not simply a smaller version of the adult one. The aim of this study was to optimize the oscillations of a biomechanical two-mass-model (2MM) for children and adults and to judge whether dynamic differences exist. High speed recordings (4000 fps) at sustained phonation (vowel /i/) were recorded and analyzed. After glottis segmentation, vocal fold trajectories for 11 children and 23 adults (9 men, 14 women) were investigated. Model parameters were achieved by numerical optimization of the 2MM towards the vocal fold trajectories. Differences in oscillating masses, tissue stiffness, and subglottal pressure were identified and quantified. Children showed increased vocal fold stiffness as well as increased subglottal pressure values. Differences between children vs. men were more distinctive than between children vs. women. In summary, the study gives quantitative evidence of differences between pediatric and adult laryngeal dynamics and confirms the applicability of the 2MM towards children. Next steps will include analyses of disordered pediatric voices.