bluuebunny/crossref_metadata_2025 huggingface dataset:
Two Mandarin readers in Taiwan: characteristics of children with higher and lower reading proficiency levels
Authors: Charlene Yau Jia‐ling
Published: May 2005

This study investigated how two readers of Mandarin with differing reading‐proficiency skills interacted with a narrative passage, as well as what knowledge they brought to and made use of while reading the text. The perspectives of reading comprehension, transactional theory and social‐cognitive models of reading served as this study's theoretical framework. Two Sixth‐Grade participants were selected for inclusion through snowball sampling. The data in this study were obtained from interviews and think‐alouds. Qualitative analysis indicated that the skilled Mandarin reader's stance moved along the efferent/aesthetic continuum, while the less‐skilled Mandarin reader's was mainly efferent. The skilled reader employed strategies of inferencing, summarisation and synthesis during and after reading, while the less‐skilled reader applied bridging inferences, paraphrasing and repetition. The findings of this study corroborate previous findings that proficient readers employ more sophisticated approaches to reading than less‐proficient readers.
Beginning readers' use of ‘talking books’ software can affect their reading strategies
Authors: Wood Clare
Published: May 2005

This paper reports on a small‐scale study that considered whether a phonic‐based ‘talking book’ could outperform one‐to‐one reading tuition with an adult with respect to improving beginning readers' phonological awareness over a short period. It also examined whether the children's reading strategies were affected by their use of the software. Two groups of children, one aged five years and one aged six years, used three phonic‐based talking books over six 15‐minute sessions and were assessed on their phonological awareness and reading strategies both before and after this intervention. Their performance was compared to that of matched comparison groups who were given one‐to‐one adult tutoring with the paper versions of the same books. There were no significant differences between the two groups in their phonological awareness attainment, with both groups showing equivalent gains from pre‐ to post‐test. Use of specific features of the software was associated with gains in rhyme detection ability and with changes in the children's reading strategies.
Technological Diversity and Jacobs’ Externality Hypothesis Revisited
Authors: EJERMO OLOF
Published: May 2005

ABSTRACT  Recent empirical evidence strongly supports Jacobs's (1969) externality hypothesis that urban diversity provides a more favorable environment for economic development than urban specialization. In order to correctly gauge Jacobs's hypothesis, economic development should be understood as a result of innovations. Furthermore, a relevant diversity measure should take into account the degree of diversity of the inherent classes (e.g. pharmaceuticals are closer to chemicals than to forestry). These ideas are tested using regionally classified Swedish patent application data as a measure of innovativeness. Patent data are also used to reflect technological diversity. The results show that the number of patent applications in Swedish regions is highly and positively dependent on regional technological specialization, quite the opposite of Jacobs's prediction. This paper raises general questions about earlier empirical results. It is concluded that the size of regions is an important factor to consider, since this in itself may affect patenting intensity and technological diversity.
Natural Amenities and Rural Development: Understanding Spatial and Distributional Attributes
Authors: KIM KWANG‐KOO , MARCOUILLER DAVID W. , DELLER STEVEN C.
Published: May 2005

ABSTRACT  Contemporary resource management practice and rural development planning increasingly emphasize the integration of resource extractive industries with non‐market‐based recreational and amenity values. There is a growing empirical literature which suggests that natural amenities impact regional economies through aggregate measures of economic performance such as population, income, and/or employment growth, and housing development. We maintain that assessing the developmental aspects of amenity‐led regional change requires a more thorough focus on alternative measures of economic performance such as income distribution and spatial organization. In the applied research presented here we investigate relationships between amenities and regional economic development indicators. Results suggest mixed and generally insignificant amenity‐based associations which highlight the need for appropriate regional economic modeling techniques that account for often dramatic spatial autocorrelation of natural amenity attributes. We conclude that with respect to amenity driven economic growth and development “place in space” matters.
Microbiological and clinical outcomes and patient satisfaction for two treatment options in the edentulous lower jaw after 10 years of function
Authors: Quirynen Marc , Alsaadi Ghada , Pauwels Martine , Haffajee Anne , Van Steenberghe Daniel , Naert Ignace
Published: May 2005

Background: Long‐term data on microbiological and clinical outcome as well as on patient satisfaction after implant therapy in the edentulous mandible are limited. Especially comparisons between fixed full prostheses (FFPs) and overdentures (ODs), or between anchoring systems for the latter are scarce.

Aim: This study aimed to evaluate both of these parameters at the 10‐year follow‐up in a group of fully edentulous patients rehabilitated via an OD or a FFP (the latter to allow inter‐group comparison).

Material and methods: A total of 37 fully edentulous patients (25 ODs, 12 FFPs, age at implant installation ranged from 36 to 85 years) participated in this study. All subjects received their implants (Brånemark System®, Nobel Biocare AB, Gothenburg, Sweden) 10 years previously. For the ODs different attachment systems (bar, magnets, ball) had been applied that allowed a further intra‐group comparison. At the follow‐up visit, 10 years after the abutment insertion, a series of periodontal parameters were recorded, long‐cone radiographs were taken and subgingival plaque samples were collected for analysis using checkerboard DNA–DNA hybridization. The clinical and radiographic data were recorded at abutment connection and after 1 and 10 years.

Results: After 10 years of loading, mean plaque and bleeding indices and changes in attachment or marginal bone level were not significantly different, neither between the OD and FFP group, nor within the OD group. The marginal bone loss between abutment connection and year 10 was 0.86 and 0.73 mm for OD and FFP groups, respectively. The subgingival microbiota at implant sites from all (sub)‐groups was comparable, with low numbers of DNA counts (±10 × 105) but high detection frequencies of Actinobacillus actinomycetemcomitans (>90%), Porphyromonas gingivalis (>85%) and Tannerella forsythensis (30%). The composition of the subgingival microbiota was influenced by probing depth and bleeding tendency. Patient satisfaction was very high for both types of prosthetic rehabilitation. The FFP group scored only slightly better for chewing comfort and general satisfaction.

Conclusion: These data indicate that from the clinical and microbiological standpoint, as well as patient satisfaction, both an OD and a FFP offer a favourable long‐term outcome.
Measured Adiabatic Effectiveness and Heat Transfer for Blowing From
the Tip of a Turbine Blade
Authors: Christophel J. R. , Couch E. , Thole K. A. , Cunha F. J.
Published: May 2005

The clearance gap between the tip of a turbine blade and the shroud has an inherent leakage flow from the pressure side to the suction side of the blade. This leakage flow of combustion gas and air mixtures leads to severe heat transfer rates on the blade tip of the high-pressure turbine. As the thermal load to the blade increases, blade alloy oxidation and erosion rates increase thereby adversely affecting component life. The subject of this paper is the cooling effectiveness levels and heat transfer coefficients that result from blowing through two holes placed in the forward region of a blade tip. These holes are referred to as dirt purge holes and are generally required for manufacturing purposes and expelling dirt from the coolant flow when operating in sandy environments. Experiments were performed in a linear blade cascade for two tip-gap heights over a range of blowing ratios. Results indicated that the cooling effectiveness was highly dependent on the tip-gap clearance with better cooling achieved at smaller clearances. Also, heat transfer was found to increase with blowing. In considering an overall benefit of cooling from the dirt purge blowing, a large benefit was realized for a smaller tip gap as compared with a larger tip gap.
Cooling the Tip of a Turbine Blade Using Pressure Side Holes—Part I:
Adiabatic Effectiveness Measurements
Authors: Christophel J. R. , Thole K. A. , Cunha F. J.
Published: May 2005

Durability of turbine blade tips has been and continues to be challenging, particularly since increasing turbine inlet temperatures is the driver for improving turbine engine performance. As a result, cooling methods along the blade tip are crucial. Film-cooling is one typically used cooling method whereby coolant is supplied through holes placed along the pressure side of a blade. The subject of this paper is to evaluate the adiabatic effectiveness levels that occur on the blade tip through blowing coolant from holes placed near the tip of a blade along the pressure side. A range of blowing ratios was studied whereby coolant was injected from holes placed along the pressure side tip of a large-scale blade model. Also present were dirt purge holes on the blade tip, which is part of a commonly used blade design to expel any large particles present in the coolant stream. Experiments were conducted in a linear cascade with a scaled-up turbine blade whereby the Reynolds number of the engine was matched. This paper, which is Part 1 of a two part series, compares adiabatic effectiveness levels measured along a blade tip, while Part 2 combines measured heat transfer coefficients with the adiabatic effectiveness levels to assess the overall cooling benefit of pressure side blowing near a blade tip. The results show much better cooling can be achieved for a small tip gap compared with a large tip gap with different flow phenomena occurring for each tip gap setting.
Modeling of Threshold Strength in Cylindrical Ceramic Structures
Authors: Jo´nsdo´ttir Fjo´la , Beltz Glenn E. , McMeeking Robert M.
Published: May 2005

Recently, three-dimensional structured ceramic composites with large threshold strengths (i.e., stress below which there is zero probability of failure) have been fabricated utilizing an architecture consisting of relatively stress-free, elongated prismatic domains, separated by thin compressive walls. We build upon prior work on laminate architectures, with the common feature that these structures are all susceptible to fracture. Typically, these three-dimensional structures consist of thin shells of mullite that surround alumina. Cracks, originating from large flaws within the ceramic body, are arrested by the surrounding compressive layers until a specific stress level is attained (i.e., the threshold strength), resulting in a truncation of the strength distribution in the flaw region. A preliminary stress intensity solution has shown that this arrest is caused by a reduction of the crack driving force by the residual compression in the compressive walls. This solution also predicts that the threshold strength is dependent not only on the magnitude of the residual compression in the walls but also on the dimensions of both phases. A finite element model is presented that utilizes a penny-shaped crack in the interior of such a structure or half-penny-shaped crack emanating from the edge of such a structure. Ongoing analytical and experimental work that is needed to more fully understand this arrest phenomenon and its application towards the development of reliable, damage-tolerant ceramic components are discussed.
Control of Bending Vibrations Within Subdomains of Thin Plates—Part I: Theory and Exact Solution
Authors: Krommer Michael , Varadan Vasundara V.
Published: May 2005

Control of the surface profile or shape of structures that deform under externally applied dynamical loads is important in many applications where no control can be exercised on the applied loads. The only recourse is to make the structure adaptive by the action of smart actuators that can null or nearly null the resulting deformation. The class of problems, to which shape control may be applied, is huge and in this paper a theoretical approach is presented for a special subset of such problems, wherein, suitable actuation can be applied in order to keep a subdomain of the structure in its nondeformed state under the action of external dynamical loads. A suitable actuation to achieve this goal is the complement of the self-stress. An appropriate distribution of the self-stress should result in an elimination of the motion of the subdomain of the structure. Moreover, we seek a solution of the problem, which only requires the application of the self-stress in the subdomains or in a slightly larger domain. This is also a practical approach to such problems where it would be prohibitively expensive to design and power actuators to control the entire domain. We choose a linear, thin elastic plate to present the basics of our methodology. The main part of the paper is devoted to the theoretical foundation of the method; however, to show its validity, we also present exact results for the simple case of a circular plate in axisymmetric bending.
Efficient Parallel Simulation of Direct Methanol Fuel Cell
Models
Authors: Rajasekaran S. , Ammar R. , Reifsnider K. , Achenie L. , Mohamed A. , Zhang G. , Ahmed M.
Published: May 2005

Fuel cells, as highly efficient and environment-friendly power sources, have attracted ever-increasing research and development in the past few decades. Mathematical modeling and simulation are applied to examine the influence of the different physical and electrochemical phenomena occurring in the structure of the fuel cell during operation. Such simulation programs take a very long time (of the order of days or even weeks) to run, especially when accurate results are called for. To achieve accurate results and more insight, we need even more complex models (two- and three-dimensional models). In this paper, we present techniques for the parallel simulation of a mathematical model of direct methanol fuel cells (DMFC). In particular, we employ a paradigm called LessTalk. LessTalk is a general technique that can be employed to reduce communications in parallel computations. Using LessTalk, we have achieved almost linear speedup in simulating the DMFC model. The results were validated against measurements available from the Connecticut Global Fuel Cell Center (CGFCC).
Effect of Operating Parameters on the DMFC Performance
Authors: Jung Guo-Bin , Su Ay , Tu Cheng-Hsin , Weng Fang-Bor
Published: May 2005

Methanol crossover largely affects the efficiency of power generation in the direct methanol fuel cell. As the methanol crosses over through the membrane, the methanol oxidizes at the cathode, resulting in low fuel utilization and in a serious overpotential loss. In this study, the commercial membrane electrode assemblies (MEAs) are investigated with different operating conditions such as membrane thickness, cell temperature, and methanol solution concentration. The effects of these parameters on methanol crossover and power density are studied. With the same membrane, increasing the cell temperature promotes the cell performance as expected, and the lower methanol concentration causes the concentration polarization effects, thus resulting in lower cell performance. Although higher methanol solution concentration can overcome the concentration polarization, a serious methanol crossover decreases the cell performance at high cell temperature. In this study, the open circuit voltage (OCV) is inversely proportional to methanol solution concentration, and is proportional to membrane thickness and cell temperature. Although increasing membrane thickness lowers the degree of methanol crossover, on the other hand, the ohmic resistance increases simultaneously. Therefore, the cell performance using Nafion 117 as membrane is lower than that of Nafion 112. In addition, the performance of the MEA made in our laboratory is higher than the commercial product, indicating the capability of manufacturing MEA is acceptable.
High Frequency Surface Heat Flux Imaging of Bypass
Transition
Authors: Anthony Richard J. , Jones Terry V. , LaGraff John E.
Published: May 2005

A high-frequency surface heat flux imaging technique was used to investigate bypass transition induced by freestream turbulence. Fundamental experiments were carried out at the University of Oxford using high-density thin film arrays on a flat plate wind tunnel model. Bypass transition was induced by grid-generated turbulence with varying intensities of 2.3%, 4.2%, and 17% with a fixed integral length scale of approximately 12mm. Unique high resolution temporal heat flux images are shown which detail significant differences between unsteady surface heat flux events induced by freestream turbulence and the classical Emmons-type spots which many turbomachinery transition models are based on. The temporal imaging technique presented allows study of unsteady surface heat transfer in detail, and helps elucidate the complex nature of transition in the high-disturbance environment of turbomachinery.
Flow and Heat Transfer in an Internally Ribbed Duct With Rotation: An
Assessment of Large Eddy Simulations and Unsteady Reynolds-Averaged
Navier-Stokes Simulations
Authors: Saha A. K. , Acharya Sumanta
Published: May 2005

Large eddy simulations (LES) and unsteady Reynolds averaged Navier-Stokes (URANS) simulations have been performed for flow and heat transfer in a rotating ribbed duct. The ribs are oriented normal to the flow and arranged in a staggered configuration on the leading and trailing surfaces. The LES results are based on a higher-order accurate finite difference scheme with a dynamic Smagorinsky model for the subgrid stresses. The URANS procedure utilizes a two equation k-ε model for the turbulent stresses. Both Coriolis and centrifugal buoyancy effects are included in the simulations. The URANS computations have been carried out for a wide range of Reynolds number (Re=12,500-100,000), rotation number (Ro=0-0.5) and density ratio (Δρ∕ρ=0-0.5), while LES results are reported for a single Reynolds number of 12,500 without and with rotation (Ro=0.12,Δρ∕ρ=0.13). Comparison is made between the LES and URANS results, and the effects of various parameters on the flow field and surface heat transfer are explored. The LES results clearly reflect the importance of coherent structures in the flow, and the unsteady dynamics associated with these structures. The heat transfer results from both LES and URANS are found to be in reasonable agreement with measurements. LES is found to give higher heat transfer predictions (5–10% higher) than URANS. The Nusselt number ratio (Nu∕Nu0) is found to decrease with increasing Reynolds number on all walls, while they increase with the density ratio along the leading and trailing walls. The Nusselt number ratio on the trailing and sidewalls also increases with rotation. However, the leading wall Nusselt number ratio shows an initial decrease with rotation (till Ro=0.12) due to the stabilizing effect of rotation on the leading wall. However, beyond Ro=0.12, the Nusselt number ratio increases with rotation due to the importance of centrifugal-buoyancy at high rotation.
Pt
3

Cr

(
111
)

Alloy Effect on the Reversible Potential of OOH(ads) Formation from O2(ads) relative to Pt(111)
Authors: Roques Jérôme , Anderson Alfred B.
Published: May 2005

A quantum mechanical study of O2 and OOH adsorption on Pt(111) and on a Pt monolayer on Pt3Cr(111) is presented. The calculated adsorption energies are used to predict the reversible potential for O2 reduction to OOH(ads) on these surfaces. The resulting 0.43V for Pt(111) and 0.49V for the Pt skin on the Pt3Cr(111) are far from the 1.23V reversible potential for the four-electron reduction to water. However, OOH(ads) easily dissociates over Ptn sites (n⩾2) to OH(ads) and O(ads), the latter forming with a reduction potential greater than 1.23V and the resulting heat loss contributes to the overpotential in the four-electron reduction process.
Dynamic Modeling on the Hybrid Molten Carbonate Fuel Cell-Gas Turbine Bottoming Cycle
Authors: Zhang Huisheng , Weng Shilie , Su Ming
Published: May 2005

The intention of this paper is to present the dynamic models for the molten carbonate fuel cell (MCFC)-gas turbine hybrid cycle. This paper analyzes the performance of various components in the hybrid power plant, such as the compressor, turbine, recuperator, generator, fuel cell stack, etc. The modular simulation models of these components are presented. Based on the dynamic simulation modeling principle, one bottoming hybrid MCFC-microturbine cycle was studied to carry out the simulation. The simulation result can reflect the dynamic response of the hybrid power plant.
A New PtRu Anode Formed by Thermal Decomposition for the Direct Method Fuel Cell
Authors: Yang L. X. , Allen R. G. , Scott K. , Christensen P. , Roy S.
Published: May 2005

New PtRu catalyst anodes for methanol oxidation were prepared by a thermal decomposition method on titanium mesh supports. The supports employed were: Single layer (titanium mesh), double layer (two layers of titanium mesh were spot-welded together), and triple layer (two layers of titanium mesh with carbon paper between were spot-welded together). The catalytic activity of such anodes for the oxidation of methanol was characterized using galvanostatic measurements and electrochemical impedance spectroscopy in combination with scanning electron microscopy. The results showed that the PtRu catalyst thermally decomposed on the double-layer mesh support exhibited a higher catalytic activity for methanol electro-oxidation than those supported on carbon powders. Preliminary direct methanol fuel cell (DMFC) data show that the power density of the DMFC with the new anode is higher than that with carbon-supported anodes. A further increase in power density for the DMFC with the new anodes is expected with optimization of the mesh support with regard to structure, mesh material, and catalyst coating methods.
Strain-Modulated Adatom and Surface Vacancy Pair
Interactions
Authors: Liu P. , Kukta R. V. , Kouris D.
Published: May 2005

Adsorbed atoms (adatoms) and vacancies have a significant role to play in the physics of surfaces and the mechanisms of film growth on a substrate. This paper investigates the effect of applied or residual strain on the energetic interaction between pairs of adatoms and vacancies. The analysis is based on a continuum-level point-defect model, where adatoms and vacancies have strain-dependent properties. Atomistic calculations are used to evaluate the defect properties for Si(111). The result is used as input for the defect model in order to investigate the strength and character of the interaction versus strain, separation distance, and relative orientation of the defects. It is found that strain may cause the defects to align in certain direction and modulate their interaction between repulsion and attraction, providing a mechanism for controlled building of nanostructures.
A Comparison of the Structural Response of Clamped and Simply Supported Sandwich Beams With Aluminium Faces and a Metal Foam Core
Authors: Tagarielli V. L. , Fleck N. A.
Published: May 2005

Plastic collapse modes for clamped sandwich beams have been investigated experimentally and theoretically for the case of aluminium face sheets and a metal foam core. Three initial collapse mechanisms have been identified and explored with the aid of a collapse mechanism map. It is shown that the effect of clamped boundary conditions is to drive the deformation mechanism towards plastic stretching of the face sheets. Consequently, the ultimate strength and level of energy absorption of the sandwich beam are set by the face sheet ductility. Limit load analyses have been performed and simple analytical models have been developed in order to predict the postyield response of the sandwich beams; these predictions are validated by both experiments and finite elements simulations. It is shown experimentally that the ductility of aluminium face sheets is enhanced when the faces are bonded to a metal foam core. Finally, minimum weight configurations for clamped aluminium sandwich beams are obtained using the analytical formulas for sandwich strength, and the optimal designs are compared with those for sandwich beams with composite faces and a polymer foam core.
Green’s Function of a Bimaterial Problem With a Cavity on the Interface—Part I: Theory
Authors: Prasad P. B. N. , Hasebe Norio , Wang X. F. , Shirai Y.
Published: May 2005

The problem of a point dislocation interacting with an elliptical hole located on a bimaterial interface is examined. Analytical solution is obtained by employing the techniques of complex variables and conformal mapping. A rational mapping function is used to map a half-plane with a semielliptical notch onto a unit circle. In the first part of this paper, complex potentials for the bimaterial system with an elliptical hole on the interface is derived when a point dislocation is present in the upper half-plane without loss of generality. The solution derived can be used as Green’s function to study internal cracks interacting with an elliptical interfacial cavity.
Application of an Anode Model to Investigate Physical Parameters in an Internal Reforming Solid-Oxide Fuel Cell
Authors: Greene Eric S. , Medeiros Maria G. , Chiu Wilson K. S.
Published: May 2005

A one-dimensional model of chemical and mass transport phenomena in the porous anode of a solid-oxide fuel cell, in which there is internal reforming of methane, is presented. Macroscopically averaged porous electrode theory is used to model the mass transfer that occurs in the anode. Linear kinetics at a constant temperature are used to model the reforming and shift reactions. Correlations based on the Damkohler number are created to relate anode structural parameters and thickness to a nondimensional electrochemical conversion rate and cell voltage. It is shown how these can be applied in order to assist the design of an anode.
Instantaneous frequency decomposition: An application to spectrally sparse sounds with fast frequency modulations
Authors: Gardner T. J. , Magnasco M. O.
Published: May 2005

Classical time–frequency analysis is based on the amplitude responses of bandpass filters, discarding phase information. Instantaneous frequency analysis, in contrast, is based on the derivatives of these phases. This method of frequency calculation is of interest for its high precision and for reasons of similarity to cochlear encoding of sound. This article describes a methodology for high resolution analysis of sparse sounds, based on instantaneous frequencies. In this method, a comparison between tonotopic and instantaneous frequency information is introduced to select filter positions that are well matched to the signal. Second, a cross-check that compares frequency estimates from neighboring channels is used to optimize filter bandwidth, and to signal the quality of the analysis. These cross-checks lead to an optimal time–frequency representation without requiring any prior information about the signal. When applied to a signal that is sufficiently sparse, the method decomposes the signal into separate time–frequency contours that are tracked with high precision. Alternatively, if the signal is spectrally too dense, neighboring channels generate inconsistent estimates—a feature that allows the method to assess its own validity in particular contexts. Similar optimization principles may be present in cochlear encoding.
Pitch strength of regular-interval click trains with different length “runs” of regular intervals
Authors: Yost William A. , Mapes-Riordan Dan , Shofner William , Dye Raymond , Sheft Stanley
Published: May 2005

Click trains were generated with first- and second-order statistics following Kaernbach and Demany [J. Acoust. Soc. Am. 104, 2298–2306 (1998)]. First-order intervals are between successive clicks, while second-order intervals are those between every other click. Click trains were generated with a repeating alternation of fixed and random intervals which produce a pitch at the reciprocal of the duration of the fixed interval. The intervals were then randomly shuffled and compared to the unshuffled, alternating click trains in pitch-strength comparison experiments. In almost all comparisons for the first-order interval stimuli, the shuffled-interval click trains had a stronger pitch strength than the unshuffled-interval click trains. The shuffled-interval click trains only produced stronger pitches for second-order interval stimuli when the click trains were unfiltered. Several experimental conditions and an analysis of runs of regular and random intervals in these click trains suggest that the auditory system is sensitive to runs of regular intervals in a stimulus that contains a mix of regular and random intervals. These results indicate that fine-structure regularity plays a more important role in pitch perception than randomness, and that the long-term autocorrelation function or spectra of these click trains are not good predictors of pitch strength.
The effects of neural synchronization and peripheral compression on the acoustic-reflex threshold
Authors: Müller-Wehlau Matthias , Mauermann Manfred , Dau Torsten , Kollmeier Birger
Published: May 2005

This study investigates the acoustic reflex threshold (ART) dependency on stimulus phase utilizing low-level reflex audiometry [Neumann et al., Audiol. Neuro-Otol. 1, 359–369 (1996)]. The goal is to obtain optimal broadband stimuli for elicitation of the acoustic reflex and to obtain objective determinations of cochlear hearing loss. Three types of tone complexes with different phase characteristics were investigated: A stimulus that compensates for basilar-membrane dispersion, thus causing a large overall neural synchrony (basilar-membrane tone complex—BMTC), the temporally inversed stimulus (iBMTC), and random-phase tone complexes (rTC). The ARTs were measured in eight normal-hearing and six hearing-impaired subjects. Five different conditions of peak amplitude and stimulus repetition rate were used for each stimulus type. The results of the present study suggest that the ART is influenced by at least two different factors: (a) the degree of synchrony of neural activity across frequency, and (b) the fast-acting compression mechanism in the cochlea that is reduced in the case of a sensorineural hearing loss. The results allow a clear distinction of the two subjects groups based on the different ART for the utilized types and conditions of the stimuli. These differences might be useful for objective recruitment detection in clinical diagnostics.
Comparison between distortion product otoacoustic emissions and nerve fiber responses from the basilar papilla of the frog
Authors: Meenderink Sebastiaan W. F. , van Dijk Pim , Narins Peter M.
Published: May 2005

The basilar papilla (BP) is one of the three end organs in the frog inner ear that is sensitive to airborne sound. Its anatomy and physiology are unique among all classes of vertebrates. Essentially, the BP functions as a single auditory filter presumably arising from a mechanically-tuned mechanism. As such, both neural and distortion product otoacoustic emission (DPOAE) tuning may reflect a single mechanical filtering mechanism. Using the Duffing oscillator as a simple model for both neural and DPOAE tuning from the BP, two predictions can be made: [1] the characteristic frequency (CF) of neural tuning and the best frequency (BF) of DPOAE tuning will coincide and [2] the neural tuning curve and DPOAE-audiogram have a similar shape when the neural tuning curve is scaled by a factor of 4 along the y-axis. We recorded both neural tuning curves and DPOAE-audiograms from the BP of the leopard frog. These recordings show good agreement with the model predictions when the stimulus tones are related by relatively small stimulus frequency ratios. For larger stimulus frequency ratios, DPOAE recordings clearly deviate from model predictions. These differences are most likely caused by the oversimplified representation of the frog BP by the model.
Localizing nearby sound sources in a classroom: Binaural room impulse responses
Authors: Shinn-Cunningham Barbara G. , Kopco Norbert , Martin Tara J.
Published: May 2005

Binaural room impulse responses (BRIRs) were measured in a classroom for sources at different azimuths and distances (up to 1 m) relative to a manikin located in four positions in a classroom. When the listener is far from all walls, reverberant energy distorts signal magnitude and phase independently at each frequency, altering monaural spectral cues, interaural phase differences, and interaural level differences. For the tested conditions, systematic distortion (comb-filtering) from an early intense reflection is only evident when a listener is very close to a wall, and then only in the ear facing the wall. Especially for a nearby source, interaural cues grow less reliable with increasing source laterality and monaural spectral cues are less reliable in the ear farther from the sound source. Reverberation reduces the magnitude of interaural level differences at all frequencies; however, the direct-sound interaural time difference can still be recovered from the BRIRs measured in these experiments. Results suggest that bias and variability in sound localization behavior may vary systematically with listener location in a room as well as source location relative to the listener, even for nearby sources where there is relatively little reverberant energy.
Speech intelligibility and spatial release from masking in young children
Authors: Litovsky Ruth Y.
Published: May 2005

Children between the ages of 4 and 7 and adults were tested in free field on speech intelligibility using a four-alternative forced choice paradigm with spondees. Target speech was presented from front (0°); speech or modulated speech-shaped-noise competitors were either in front or on the right (90°). Speech reception thresholds were measured adaptively using a three-down/one-up algorithm. The primary difference between children and adults was seen in elevated thresholds in children in quiet and in all masked conditions. For both age groups, masking was greater with the speech-noise versus speech competitor and with two versus one competitor(s). Masking was also greater when the competitors were located in front compared with the right. The amount of masking did not differ across the two age groups. Spatial release from masking was similar in the two age groups, except for in the one-speech condition, when it was greater in children than adults. These findings suggest that, similar to adults, young children are able to utilize spatial and/or head shadow cues to segregate sounds in noisy environments. The potential utility of the measures used here for studying hearing-impaired children is also discussed.
Acoustic impedance measurements—correction for probe geometry mismatch
Authors: Fletcher N. H. , Smith J. , Tarnopolsky A. Z. , Wolfe J.
Published: May 2005

The effect of evanescent mode generation, due to geometrical mismatch, in acoustic impedance measurements is investigated. The particular geometry considered is that of a impedance probe with an annular flow port and a central microphone, but the techniques are applicable to other geometries. It is found that the imaginary part of the measured impedance error is proportional to frequency, and that the sign of the error is positive for measurements made on tubes with diameter much larger than that of the inlet port, but negative for tubes with diameter close to that of the inlet. The result is a distortion of the measured frequencies of the impedance minima of the duct while the maxima are largely unaffected. There is, in addition, a real resistive component to the error that varies approximately as the square root of the frequency. Experiment confirms the results of the analysis and calculations, and a calibration procedure is proposed that allows impedance probes that have been calibrated on a semi-infinite tube of one diameter to be employed for measurements on components with an inlet duct of some very different diameter.
Effect of pulse characteristics on temperature rise due to ultrasound absorption at a bone/soft-tissue interface
Authors: Myers Matthew R.
Published: May 2005

The transient temperature rise at a bone/soft-tissue interface is an important quantity in the safety evaluation of procedures involving trains of high-intensity ultrasound pulses. Mathematical models based upon the time-averaged intensity of the pulse train can provide rapid estimates of the temperature rise, but are known to underestimate the temperature rise during the on-time of the pulse. This paper extends a previous analytical model to account for pulse shape, and provides error estimates for simulations employing time-averaged intensities. A simple analytic expression for the interface temperature that accounts for both bone and soft-tissue properties is provided. The analytic expression agrees well with temperature rise predictions based upon the finite-element method, when the insonation time is large compared to the pulse repetition period. In this case of large relative insonation time, the pulse shape is found to be inconsequential.
The spatial unmasking of speech: evidence for within-channel processing of interaural time delay
Authors: Edmonds Barrie A. , Culling John F.
Published: May 2005

Across-frequency processing by common interaural time delay (ITD) in spatial unmasking was investigated by measuring speech reception thresholds (SRTs) for high- and low-frequency bands of target speech presented against concurrent speech or a noise masker. Experiment 1 indicated that presenting one of these target bands with an ITD of +500 μs and the other with zero ITD (like the masker) provided some release from masking, but full binaural advantage was only measured when both target bands were given an ITD of +500 μs. Experiment 2 showed that full binaural advantage could also be achieved when the high- and low-frequency bands were presented with ITDs of equal but opposite magnitude (±500 μs). In experiment 3, the masker was also split into high- and low-frequency bands with ITDs of equal but opposite magnitude (±500 μs). The ITD of the low-frequency target band matched that of the high-frequency masking band and vice versa. SRTs indicated that, as long as the target and masker differed in ITD within each frequency band, full binaural advantage could be achieved. These results suggest that the mechanism underlying spatial unmasking exploits differences in ITD independently within each frequency channel.
Detection, direction discrimination, and off-frequency interference of center-frequency modulations and glides for vowel formants
Authors: Lyzenga J. , Carlyon R. P.
Published: May 2005

Vowels are mainly classified by the positions of peaks in their frequency spectra, the formants. For normal-hearing subjects, change detection and direction discrimination were measured for linear glides in the center frequency (CF) of formantlike sounds. A CF rove was used to prevent subjects from using either the start or end points of the glides as cues. In addition, change detection and starting-phase (start-direction) discrimination were measured for similar stimuli with a sinusoidal 5-Hz formant-frequency modulation. The stimuli consisted of single formants generated using a number of different stimulus parameters including fundamental frequency, spectral slope, frequency region, and position of the formant relative to the harmonic spectrum. The change detection thresholds were in good agreement with the predictions of a model which analyzed and combined the effects of place-of-excitation and temporal cues. For most stimuli, thresholds were approximately equal for change detection and start-direction discrimination. Exceptions were found for stimuli that consisted of only one or two harmonics. In a separate experiment, it was shown that change detection and start-direction discrimination of linear and sinusoidal formant-frequency modulations were impaired by off-frequency frequency-modulated interferers. This frequency modulation detection interference was larger for formants with shallow than for those with steep spectral slopes.
The effect of inharmonic partials on pitch of piano tones
Authors: Anderson Brian E. , Strong William J.
Published: May 2005

Piano tones have partials whose frequencies are sharp relative to harmonic values. A listening test was conducted to determine the effect of inharmonicity on pitch for piano tones in the lowest three octaves of a piano. Nine real tones from the lowest three octaves of a piano were analyzed to obtain frequencies, relative amplitudes, and decay rates of their partials. Synthetic inharmonic tones were produced from these results. Synthetic harmonic tones, each with a twelfth of a semitone increase in the fundamental, were also produced. A jury of 21 listeners matched the pitch of each synthetic inharmonic tone to one of the synthetic harmonic tones. The effect of the inharmonicity on pitch was determined from an average of the listeners’ results. For the nine synthetic piano tones studied, pitch increase ranged from approximately two and a half semitones at low fundamental frequencies to an eighth of a semitone at higher fundamental frequencies.
Shallow water sound propagation with surface waves
Authors: Tindle Chris T. , Deane Grant B.
Published: May 2005

The theory of wavefront modeling in underwater acoustics is extended to allow rapid range dependence of the boundaries such as occurs in shallow water with surface waves. The theory allows for multiple reflections at surface and bottom as well as focusing and defocusing due to reflection from surface waves. The phase and amplitude of the field are calculated directly and used to model pulse propagation in the time domain. Pulse waveforms are obtained directly for all wavefront arrivals including both insonified and shadow regions near caustics. Calculated waveforms agree well with a reference solution and data obtained in a near-shore shallow water experiment with surface waves over a sloping bottom.
A theoretical study of the feasibility of acoustical tweezers: Ray acoustics approach
Authors: Lee Jungwoo , Ha Kanglyeol , Shung K. Kirk
Published: May 2005

The optical tweezer has been found to have many biomedical applications in trapping macromolecules and cells. For the trapping mechanism, there has to be a sharp spatial change in axial optical intensity and the particle size must be much greater than the wavelength. Similar phenomenon may exist in acoustics. This work was undertaken to demonstrate theoretically that it is possible to acoustically trap particles near the focal point where most of the acoustic energy is concentrated if certain conditions are met. Acoustic force exerted on a fluid particle in ultrasonic fields is analyzed in a ray acoustics regime where the wavelength of acoustic beam is much smaller than the size of the particle. In order to apply the acoustical tweezer to manipulating macromolecules and cells whose size is in the order of a few microns or less, a prerequisite is that the ultrasound wavelength has to be much smaller than a few microns. In this paper, the analysis is therefore based on the field pattern produced by a strongly focused 100 MHz ultrasonic transducer with Gaussian intensity distribution. For the realization of acoustic trapping, negative axial radiation force has to be generated to pull a particle towards a focus. The fat particle considered for acoustic trapping in this paper has an acoustic impedance of 1.4 MRayls. The magnitude of the acoustic axial radiation force that has been calculated as the size of the fat particle is varied from 8λ to 14λ. In addition, both Fresnel coefficients at various positions are also calculated to assess the interaction of reflection and refraction and their relative contribution to the effect of the acoustical tweezer. The simulation results show that the feasibility of the acoustical tweezer depends on both the degree of acoustic impedance mismatch and the degree of focusing relative to the particle size.
Relative contributions of spectral and temporal cues for phoneme recognition
Authors: Xu Li , Thompson Catherine S. , Pfingst Bryan E.
Published: May 2005

Cochlear implants provide users with limited spectral and temporal information. In this study, the amount of spectral and temporal information was systematically varied through simulations of cochlear implant processors using a noise-excited vocoder. Spectral information was controlled by varying the number of channels between 1 and 16, and temporal information was controlled by varying the lowpass cutoff frequencies of the envelope extractors from 1 to 512 Hz. Consonants and vowels processed using those conditions were presented to seven normal-hearing native-English-speaking listeners for identification. The results demonstrated that both spectral and temporal cues were important for consonant and vowel recognition with the spectral cues having a greater effect than the temporal cues for the ranges of numbers of channels and lowpass cutoff frequencies tested. The lowpass cutoff for asymptotic performance in consonant and vowel recognition was 16 and 4 Hz, respectively. The number of channels at which performance plateaued for consonants and vowels was 8 and 12, respectively. Within the above-mentioned ranges of lowpass cutoff frequency and number of channels, the temporal and spectral cues showed a tradeoff for phoneme recognition. Information transfer analyses showed different relative contributions of spectral and temporal cues in the perception of various phonetic/acoustic features.
Atypical calling by a blue whale in the Gulf of Alaska (L)
Authors: Stafford Kathleen M. , Moore Sue E.
Published: May 2005

Worldwide, calls from blue whales share the characteristics of being long (>20 s), low-frequency (<100 Hz) signals that often exhibit amplitude and frequency modulation. Despite sharing these basic features, the calls of blue whales recorded in different ocean basins are distinct from one another, leading to the suggestion that populations and/or subspecies may be identified based on call characteristics. An example of anomalous calling behavior by a blue whale in the Gulf of Alaska is reported that may complicate this approach, and that suggests that blue whales can mimic each other’s calls.