bluuebunny/crossref_metadata_2025 huggingface dataset:
Understorey plant species richness and composition in metropolitan forest archipelagos: effects of forest size, adjacent land use and distance to the edge
Authors: Guirado M. , Pino J. , Rodà F.
Published: January 2006

Aim  To address the relative role of adjacent land use, distance to forest edge, forest size and their interactions on understorey plant species richness and composition in perimetropolitan forests.

Location  The metropolitan area of Barcelona, north‐eastern Spain.

Methods  Twenty sampling sites were distributed in two forest size‐categories: small forest patches (8–90 ha) and large forest areas (> 18,000 ha). For each forest‐size category, five sites were placed adjacent to crops and five sites adjacent to urban areas. Vascular plant species were recorded and human frequentation was scored visually in 210 10 × 10 m plots placed at 10, 50 and 100 m from the forest edge, and additionally at 500 m in large forest areas. Plant species were grouped according to their ecology and rarity categories. A nonmetric multidimensional scaling (NMS) ordination was carried out to detect patterns of variation in species assemblage, and to explore the relationships between these patterns and the richness of the species groups and the studied factors. Factorial anovas were used to test the significance of the studied factors on the richness of species groups. Relationships between human frequentation and the studied variables were assessed through contingency tables.

Results  Forest‐size category was the main factor affecting synanthropic species (i.e. those thriving in man‐made or man‐disturbed habitats). Synanthropic species richness decreased with increasing distance from the forest edge and, when forests were adjacent to crops, it was higher in small forest patches than in large forest areas. Richness of rare forest species was lower in small forest patches than in large forest areas when forests were adjacent to urban areas. Richness of common forest species and of all forest species together were higher close to the forest edge than far from it when forests were adjacent to urban areas. Forests adjacent to urban areas were more likely to experience high human frequentation, particularly in those plots nearest to the forest edge.

Main conclusions  Forest‐size category and adjacent land use were the most important factors determining species richness and composition. The preservation of large forests adjacent to crops in peri‐urban areas is recommended, because they are less frequented by humans, are better buffered against the percolation of nonforest species and could favour the persistence of rare forest species.
Novel ecosystems: theoretical and management aspects of the new ecological world order
Authors: Hobbs Richard J. , Arico Salvatore , Aronson James , Baron Jill S. , Bridgewater Peter , Cramer Viki A. , Epstein Paul R. , Ewel John J. , Klink Carlos A. , Lugo Ariel E. , Norton David , Ojima Dennis , Richardson David M. , Sanderson Eric W. , Valladares Fernando , Vilà Montserrat , Zamora Regino , Zobel Martin
Published: January 2006

We explore the issues relevant to those types of ecosystems containing new combinations of species that arise through human action, environmental change, and the impacts of the deliberate and inadvertent introduction of species from other regions. Novel ecosystems (also termed ‘emerging ecosystems’) result when species occur in combinations and relative abundances that have not occurred previously within a given biome. Key characteristics are novelty, in the form of new species combinations and the potential for changes in ecosystem functioning, and human agency, in that these ecosystems are the result of deliberate or inadvertent human action. As more of the Earth becomes transformed by human actions, novel ecosystems increase in importance, but are relatively little studied. Either the degradation or invasion of native or ‘wild’ ecosystems or the abandonment of intensively managed systems can result in the formation of these novel systems. Important considerations are whether these new systems are persistent and what values they may have. It is likely that it may be very difficult or costly to return such systems to their previous state, and hence consideration needs to be given to developing appropriate management goals and approaches.
NAPECOR's Risk Management Venture
Authors: Fairbanks Stewart , Vance David A. , Chrisman James J.
Published: January 2006

This case focuses on the decisions confronting Sally Bennett, the new Director of Market Risk Management (MRM), a unique department created within the Marketing Division of a large, diversified energy conglomerate. MRM played a crucial role in supporting the trading and marketing operations in a complex, competitive environment. Bennett was facing important challenges as the demand for MRM's service exploded. She wondered if a more formalized approach to risk assessment might be better and if so, who should design the new system. The proper organizational arrangement for MRM was also unclear. Overlaid upon these issues were larger questions of when and how the department should transition from an entrepreneurially oriented to professionally managed department.
Chronic Prostatitis in Premature Ejaculation: A Cohort Study in 153 Men
Authors: Shamloul Rany , Nashaar Abdelrahman el
Published: January 2006

Introduction

Premature ejaculation is a common male sexual dysfunction, affecting 30–40% of sexually active men in an age-dependent manner. Chronic prostatitis has been suggested as an important organic cause of premature ejaculation.

Aim

The aim of this study was to confirm previous data reported on the incidence of chronic prostatitis in a large cohort of patients with primary and secondary premature ejaculation.

Methods

A total of 153 consecutive heterosexual men aged 29–51 years with premature ejaculation and another 100 male healthy subjects were included in this study. Sequential microbiologic specimens were obtained according to the standardized Meares and Stamey protocol. Nonbacterial prostatitis was defined by the evidence of prostatic inflammation but negative cultures of urine and prostatic fluids in men with various genitourinary symptoms.

Results

There was no significant difference between patients and control subjects regarding age, education, or intercourse frequency. Prostatic inflammation was found in 64% and chronic bacterial prostatitis in 52% of the patients with premature ejaculation, respectively, showing statistical significance compared with control subjects (P < 0.05).

Conclusions

Results in our study showed a high prevalence of chronic prostatitis in patients with premature ejaculation. Examination of the prostate, physically and microbiologically, should be considered during assessment of patients with premature ejaculation.
Sexual Communication Skills in Residency Training: The Robert Wood Johnson Model
Authors: Rosen Raymond , Kountz David , Post-Zwicker Tracey , Leiblum Sandra , Wiegel Markus
Published: January 2006

Few medical schools or residency programs offer adequate training in sexual medicine. Using the experience gained in our long-standing program in human sexuality for medical students, we have pilot tested a half-day intensive workshop curriculum for residents that focuses on sexual communication skills and management of sexual problems. Unlike our medical school program, this residency course was offered on an elective, one-day basis. The current report describes the successful implementation of our pilot program with 46 medical residents from subspecialty and primary care residency programs. Before the workshop, 22 (48%) residents indicated that they were uncomfortable with open discussion of sexual issues and would not feel comfortable in addressing the topic with their patients. A number of factors were identified as barriers to communication, including lack of time, inadequate training, and personal discomfort. After the workshop, the participants rated themselves as more comfortable with the topic and as more likely to address sexual issues with their patients. The participants evaluated the workshop positively overall and responded well to the interactive format and audience-response components. Most of the participants showed interest and willingness to participate in further training in sexual medicine skills. Our program offers a model for training of residents in communication skills and management of sexual problems. The difficulties in implementation and overcoming institutional barriers to curriculum reform are addressed.
Peak Systolic Velocities May Be Falsely Low in Young Patients with Erectile Dysfunction
Authors: Shamloul Rany
Published: January 2006

Introduction

Introduction of duplex ultrasonography with color flow Doppler analysis after intracavernous injection of vasoactive drugs has been reported to be a minimally invasive and accurate method, and considered the gold-standard technique for evaluating penile hemodynamics. However, several studies have demonstrated that in some cases Color Doppler Ultrasound (CDU) testing may result in wrong diagnosis because of anxiety and increased sympathetic stimulation.

Aim

This study was carried out to evaluate the impact of age on the decision to repeat CDU in patients with initial low peak systolic velocities (PSVs).

Methods

This is a prospective study involving 71 patients with erectile dysfunction (ED) who presented to the Department of Andrology, Sexology and Sexually Transmitted Diseases at Cairo University between December 2000 and April 2002. An intracavernous pharmacotest and CDU with prostaglandin E1, papaverine, and phentolamine was performed. All patients in the study had poor response to intracavernous pharmacotesting and achieved a low PSV (<30 cm/second) during the initial CDU examination. The CDU was repeated 2 weeks later. The 71 patients were grouped into four according to age: group A (20–29 years old) consisted of 11 patients, group B (30–39 years old) consisted of 19 patients, group C (40–49 years old) consisted of 20 patients, and group D (50–59 years old) consisted of 21 patients.

Results

The group A patients experienced a statistically significant increase (P < 0.05) in their PSV measurements, which reached normal values in the second CDU. None of the patients of groups B, C, or D experienced any statistically significant change (P > 0.05) in their PSV measurements in the second CDU, which remained below normal values. Also, there was a statistically significant difference between the PSV measurements of group A and the other three groups.

Conclusions

Low PSV measurements in young men (less than 30 years old) with ED should be interpreted with caution. The effect of sympathetic overtone because of the environment in the office and anxiety related to penile injection, together with any underlying psychological disturbance, should be taken into consideration during the evaluation of the results of the CDU. Repetition of the CDU is recommended before considering any additional invasive diagnostic or therapeutic modalities.
Educating Physicians to Treat Erectile Dysfunction Patients: Development and Evaluation of a Course on Communication and Management Strategies
Authors: Athanasiadis Loukas , Papaharitou Stamatis , Salpiggidis Georgios , Tsimtsiou Zoi , Nakopoulou Evangelia , Kirana Paraskevi-Sofia , Moisidis Kyriakos , Hatzichristou Dimitrios
Published: January 2006

Purpose

To describe the development and assess the outcome of a workshop on erectile dysfunction (ED) management based on participating physicians evaluations.

Method

The study involved physicians who attended a workshop offered throughout the country, during a 3-year period. The workshop included tutorials, video-based dramatizations, and role-play sessions. A pilot study investigated the workshop's impact on physicians’ attitudes toward patient-centeredness and sexual behavior issues; Patient–Practitioner Orientation Scale (PPOS) and Cross Cultural Attitude Scale (CCAS) were administered before and after the course. New knowledge acquisition, quality of presentation, and workshop's usefulness in their clinical practice were the dimensions used for workshop's evaluation. Analysis used quantitative and qualitative methods.

Results

A total of 194 questionnaires were administered during the pilot study and the response rate was 53.6%. A shift in attitudes toward patient-centeredness and less judgmental attitude toward patients’ sexual attitudes were revealed (total PPOS score and Sharing subscale: P < 0.05, CCAS: P < 0.001). Six hundred physicians were asked to evaluate the workshops and the response rate was 62.3%. The tutorial session for “medical treatment of ED” (P < 0.001) and the role-play on sexual history taking (P < 0.05) received higher evaluation scores. Qualitative analysis showed that the most frequently reported category referred to the appropriateness of role-play as a teaching and awareness-raising technique (31.25%); a need for changes in clinical practice and communication patterns was identified by 20% of the participants who stressed the necessity for multidisciplinary approach, as well as the adoption of a nonjudgmental attitude toward patients.

Conclusion

Training courses on ED management, using a combination of tutorial and interactive sessions, constitute an effective way of providing knowledge, enhancing physicians’ communication skills with ED patients, and influencing attitudes toward patient-centeredness in sexual issues. Such results strongly support the establishment of sexual medicine courses at continuing medical education curricula.
Assessment and monitoring of glycemic control in primary diabetes care: Monitoring techniques, record keeping, meter downloads, tests of average glycemia, and point‐of‐care evaluation
Authors: Rizvi Ali A. , Sanders Michelle B.
Published: January 2006

Purpose: To present a review of glucose monitoring methods useful in primary care.

Data sources: Pertinent publications in the literature, printed materials and resources, and the clinical experience of the authors as a referral center for care of patients with diabetes.

Conclusions: Regular monitoring of glucose control is an integral and important aspect of diabetes care. It allows the advanced practice nurse (APN) to assess whether diabetes goals are being met or not, involves patients in the care of their disease, and assists in making informed treatment decisions.

Implications for practice: A working knowledge of glucose monitoring methods, monitors, testing devices, and laboratory tests is extremely beneficial for the APN in attaining standards of care for patients with diabetes.
Fractional Order Viscoelasticity of the Aortic Valve Cusp: An Alternative to Quasilinear Viscoelasticity
Authors: Doehring Todd C. , Freed Alan D. , Carew Evelyn O. , Vesely Ivan
Published: January 2006

Background: Quasilinear viscoelasticity (QLV) theory has been widely and successfully used to describe the time-dependent response of connective tissues. Difficulties remain, however, particularly in material parameter estimation and sensitivities. In this study, we introduce a new alternative: the fractional order viscoelasticity (FOV) theory, which uses a fractional order integral to describe the relaxation response. FOV implies a fractal-like tissue structure, reflecting the hierarchical arrangement of collagenous tissues. Method of Approach: A one-dimensional (1-D) FOV reduced relaxation function was developed, replacing the QLV “box-spectrum” function with a fractional relaxation function. A direct-fit, global optimization method was used to estimate material parameters from stress relaxation tests on aortic valve tissue. Results: We found that for the aortic heart valve, FOV had similar accuracy and better parameter sensitivity than QLV, particularly for the long time constant (τ2). The mean (n=5) fractional order was 0.29, indicating that the viscoelastic response of the tissue was strongly fractal-like. Results summary: mean QLV parameters were C=0.079, τ1=0.004, τ2=76, and mean FOV parameters were β=0.29, τ=0.076, and ρ=1.84. Conclusions: FOV can provide valuable new insights into tissue viscoelastic behavior. Determining the fractional order can provide a new and sensitive quantitative measure for tissue comparison.
Oscillatory Flow in a Cone-and-Plate Bioreactor
Authors: Chung C. A. , Tzou M. R. , Ho R. W.
Published: January 2006

Motivated by biometric applications, we analyze oscillatory flow in a cone-and-plate geometry. The cone is rotated in a simple harmonic way on a stationary plate. Based on assuming that the angle between the cone and plate is small, we describe the flow analytically by a perturbation method in terms of two small parameters, the Womersley number and the Reynolds number, which account for the influences of the local acceleration and centripetal force, respectively. Working equations for the shear stresses induced both by laminar primary and secondary flows on the plate surface are presented.
Fluid Flow Structure in Arterial Bypass Anastomosis
Authors: Su C. M. , Lee D. , Tran-Son-Tay R. , Shyy W.
Published: January 2006

The fluid flow through a stenosed artery and its bypass graft in an anastomosis can substantially influence the outcome of bypass surgery. To help improve our understanding of this and related issues, the steady Navier-Stokes flows are computed in an idealized arterial bypass system with partially occluded host artery. Both the residual flow issued from the stenosis—which is potentially important at an earlier stage after grafting—and the complex flow structure induced by the bypass graft are investigated. Seven geometric models, including symmetric and asymmetric stenoses in the host artery, and two major aspects of the bypass system, namely, the effects of area reduction and stenosis asymmetry, are considered. By analyzing the flow characteristics in these configurations, it is found that (1) substantial area reduction leads to flow recirculation in both upstream and downstream of the stenosis and in the host artery near the toe, while diminishes the recirculation zone in the bypass graft near the bifurcation junction, (2) the asymmetry and position of the stenosis can affect the location and size of these recirculation zones, and (3) the curvature of the bypass graft can modify the fluid flow structure in the entire bypass system.
Flow Limitation in Liquid-Filled Lungs: Effects of Liquid Properties
Authors: Bull Joseph L. , Reickert Craig A. , Tredici Stefano , Komori Eisaku , Frank Elizabeth L. , Brant David O. , Grotberg James B. , Hirschl Ronald B.
Published: January 2006

Flow limitation in liquid-filled lungs is examined in intact rabbit experiments and a theoretical model. Flow limitation (“choked” flow) occurs when the expiratory flow reaches a maximum value and further increases in driving pressure do not increase the flow. In total liquid ventilation this is characterized by the sudden development of excessively negative airway pressures and airway collapse at the choke point. The occurrence of flow limitation limits the efficacy of total liquid ventilation by reducing the minute ventilation. In this paper we investigate the effects of liquid properties on flow limitation in liquid-filled lungs. It is found that the behavior of liquids with similar densities and viscosities can be quite different. The results of the theoretical model, which incorporates alveolar compliance and airway resistance, agrees qualitatively well with the experimental results. Lung compliance and airway resistance are shown to vary with the perfluorocarbon liquid used to fill the lungs. Surfactant is found to modify the interfacial tension between saline and perfluorocarbon, and surfactant activity at the interface of perfluorocarbon and the native aqueous lining of the lungs appears to induce hysteresis in pressure–volume curves for liquid-filled lungs. Ventilation with a liquid that results in low viscous resistance and high elastic recoil can reduce the amount of liquid remaining in the lungs when choke occurs, and, therefore, may be desirable for liquid ventilation.
Lumped Parameter Model for Computing the Minimum Pressure During Mechanical Heart Valve Closure
Authors: Maines Brant H. , Brennen Christopher E.
Published: January 2006

The cavitation inception threshold of mechanical heart valves has been shown to be highly variable. This is in part due to the random distribution of the initial and final conditions that characterize leaflet closure. While numerous hypotheses exist explaining the mechanisms of inception, no consistent scaling laws have been developed to describe this phenomenon due to the complex nature of these dynamic conditions. Thus in order to isolate and assess the impact of these varied conditions and mechanisms on inception, a system of ordinary differential equations is developed to describe each system component and solved numerically to predict the minimum pressure generated during valve closure. In addition, an experiment was conducted in a mock circulatory loop using an optically transparent size 29 bileaflet valve over a range of conditions to calibrate and validate this model under physiological conditions. High-speed video and high-response pressure measurements were obtained simultaneously to characterize the relationship between the valve motion, fluid motion, and negative pressure transients during closure. The simulation model was calibrated using data from a single closure cycle and then compared to other experimental flow conditions and to results found in the literature. The simulation showed good agreement with the closing dynamics and with the minimum pressure trends in the current experiment. Additionally, the simulation suggests that the variability observed experimentally (when using dP∕dt alone as the primary measure of cavitation inception) is predictable. Overall, results from the current form of this lumped parameter model indicate that it is a good engineering assessment tool.
On the Importance of Considering Porosity When Simulating the Fatigue of Bone Cement
Authors: Jeffers Jonathan R. T. , Browne Martin , Roques Anne , Taylor Mark
Published: January 2006

Fatigue cracking in the cement mantle of total hip replacement has been identified as a possible cause of implant loosening. Retrieval studies and in vitro tests have found porosity in the cement may facilitate fatigue cracking of the mantle. The fatigue process has been simulated computationally using a finite element/continuum damage mechanics (FE/CDM) method and used as a preclinical testing tool, but has not considered the effects of porosity. In this study, experimental tensile and four-point bend fatigue tests were performed. The tensile fatigue S-N data were used to drive the computational simulation (FE/CDM) of fatigue in finite element models of the tensile and four-point bend specimens. Porosity was simulated in the finite element models according to the theory of elasticity and using Monte Carlo methods. The computational fatigue simulations generated variability in the fatigue life at any given stress level, due to each model having a unique porosity distribution. The fracture site also varied between specimens. Experimental validation was achieved for four-point bend loading, but only when porosity was included. This demonstrates that the computational simulation of fatigue, driven by uniaxial S-N data can be used to simulate nonuniaxial loadcases. Further simulations of bone cement fatigue should include porosity to better represent the realities of experimental models.
A measure for predicting audibility discrimination thresholds for spectral envelope distortions in vowel sounds
Authors: Rao Preeti , van Dinther R. , Veldhuis R. , Kohlrausch A.
Published: January 2006

Both in speech synthesis and in sound coding it is often beneficial to have a measure that predicts whether, and to what extent, two sounds are different. This paper addresses the problem of estimating the perceptual effects of small modifications to the spectral envelope of a harmonic sound. A recently proposed auditory model is investigated that transforms the physical spectrum into a pattern of specific loudness as a function of critical band rate. A distance measure based on the concept of partial loudness is presented, which treats detectability in terms of a partial loudness threshold. This approach is adapted to the problem of estimating discrimination thresholds related to modifications of the spectral envelope of synthetic vowels. Data obtained from subjective listening tests using a representative set of stimuli in a 3IFC adaptive procedure show that the model makes reasonably good predictions of the discrimination threshold. Systematic deviations from the predicted thresholds may be related to individual differences in auditory filter selectivity. The partial loudness measure is compared with previously proposed distance measures such as the Euclidean distance between excitation patterns and between specific loudness applied to the same experimental data. An objective test measure shows that the partial loudness measure and the Euclidean distance of the excitation patterns are equally appropriate as distance measures for predicting audibility thresholds. The Euclidean distance between specific loudness is worse in performance compared with the other two.
Sound localization in the presence of one or two distracters
Authors: Langendijk Erno H. A. , Kistler Doris J. , Wightman Frederic L.
Published: January 2006

Localizing a target sound can be a challenge when one or more distracter sounds are present at the same time. This study measured the effect of distracter position on target localization for one distracter (17 positions) and two distracters (21 combinations of 17 positions). Listeners were instructed to point to the apparent position of a train of 30-ms noise bursts, presented at 1 of 85 positions in virtual free field. A harmonic complex and a frequency-swept complex tone served as distracters. The two distracters were turned on 40 and 80 ms after the target onset, had temporal envelopes similar to that of the target, and did not overlap temporally with the target. Virtual sounds were synthesized with individual HRTFs. Localization performance degraded as the number of distracters increased from 0 to 2. When the horizontal distance between target and a single distracter was small (i.e., the interaural differences were almost the same), the influence on the apparent position was greater than when they were far apart. In the vertical dimension, there was not a systematic effect of distracter position on target localizability. However, there was a substantial increase in localization error for targets at high elevations (above 30°) when distracters were present.
Emphasis of short-duration acoustic speech cues for cochlear implant users
Authors: Vandali Andrew E.
Published: January 2006

A new speech-coding strategy for cochlear implant users, called the transient emphasis spectral maxima (TESM), was developed to aid perception of short-duration transient cues in speech. Speech-perception scores using the TESM strategy were compared to scores using the spectral maxima sound processor (SMSP) strategy in a group of eight adult users of the Nucleus 22 cochlear implant system. Significant improvements in mean speech-perception scores for the group were obtained on CNC open-set monosyllabic word tests in quiet (SMSP: 53.6% TESM: 61.3%, p<0.001), and on MUSL open-set sentence tests in multitalker noise (SMSP: 64.9% TESM: 70.6%, p<0.001). Significant increases were also shown for consonant scores in the word test (SMSP: 75.1% TESM: 80.6%, p<0.001) and for vowel scores in the word test (SMSP: 83.1% TESM: 85.7%, p<0.05). Analysis of consonant perception results from the CNC word tests showed that perception of nasal, stop, and fricative consonant discrimination was most improved. Information transmission analysis indicated that place of articulation was most improved, although improvements were also evident for manner of articulation. The increases in discrimination were shown to be related to improved coding of short-duration acoustic cues, particularly those of low intensity.
Visualization of multiple incoherent sources by the backward prediction of near-field acoustic holography
Authors: Nam Kyoung-Uk , Kim Yang-Hann
Published: January 2006

When there are multiple noise sources which share the same frequency bands, a sound field measured or estimated by near-field acoustic holography (NAH) is obviously the combination of the sound fields generated by the multiple sources. The objective of this paper is to estimate the sound field generated by each source when the coherence functions between sources are zeros. This objective can be achieved by obtaining signals coherent to sources. This paper proposes a method to obtain the coherent signals by using the spatial information of NAH. The proposed method obtains the coherent signals from pressure signals at source positions estimated by the backward prediction of NAH. Thus it does not require any prior information on source positions, unlike the conventional method, which placed sensors close to sources in order to obtain the coherent signals. The proposed method was verified by a numerical simulation using two incoherent monopole sources.
Statistical moments of the sound field propagating in a random, refractive medium near an impedance boundary
Authors: Wilson D. K. , Ostashev V. E.
Published: January 2006

Propagation of a monochromatic sound field in a refractive and turbulent medium near an impedance boundary is considered. Starting from the parabolic equation for a moving medium and using the Markov approximation, a closed equation for the statistical moments of arbitrary order of the sound-pressure field is derived. Numerical methods for directly solving the first- and second-moment versions of this equation are formulated. The first-moment formulation is very similar to parabolic equations (PEs) that are now widely used to calculate sound fields for particular realizations of a random medium. The second-moment formulation involves a large, fringed tridiagonal matrix, which is solved using iterative refinement and Cholesky factorization. The solution is computationally intensive and currently restricted to low frequencies. As an example, the first and second moments are directly calculated for upwind and downwind propagation of a sound wave through a turbulent atmosphere. For these cases, predictions from the second-moment PE were statistically indistinguishable from the result of 40 random trials calculated with a standard Crank–Nicholson PE, although the second-moment PE yielded smoother results due to its ensemble-average nature.
Spectral broadening of sound scattered by advecting atmospheric turbulence
Authors: Goedecke G. H. , Wood Roy C. , Auvermann Harry J. , Ostashev V. E. , Havelock David I. , Ting Chueh
Published: January 2006

Scattering and spectral broadening of a monochromatic sound wave by atmospheric turbulence that is flowing with a uniform constant horizontal wind is considered. The acoustic source and a detector are at rest and at different positions in a ground-fixed frame. Analytic expressions are derived for the sound pressure scattered to the detector by a single eddy. Since distances and the scattering angle change with time as the eddy flows through the scattering volume, the detector signal has time-dependent amplitude and frequency, for which general formulas are derived. A computer code is developed that calculates the scattered signal and its Fourier transform from a single eddy, or from a steady-state collection of eddies of many different scale lengths that represents isotropic homogeneous turbulence flowing with the wind. The code utilizes a time-shift algorithm that reduces the calculation time substantially. Several numerical results from this code are presented, including simulations of a recent experiment. The predicted spectral shape, including peak width and jaggedness, are in good agreement with experiment.
Exact solutions for transient spherical radiation
Authors: Hamilton J. A. , Astley R. J.
Published: January 2006

Closed-form, analytic solutions are derived for exterior wave fields generated by the transient, axisymmetric motion of a spherical boundary. These are intended for use as benchmark problems for assessing the accuracy and correctness of transient numerical schemes. Classical Laplace transform methods are used. The derivation of these solutions is presented in sufficient detail to permit their reconstruction by the reader for multipoles of order n where 0⩽n⩽25. Composite solutions can also be obtained by superposition. A novel solution of this type is presented for the wave field generated by the transient motion of a spherical piston in a spherical baffle. The transient wave fields obtained in this way are shown to be consistent with steady time-harmonic solutions for large times, and with high-resolution transient numerical solutions at finite times.
Roughness characterization of porous soil with acoustic backscatter
Authors: Oelze Michael L. , Sabatier James M. , Raspet Richard
Published: January 2006

The use of acoustics to determine the pore properties of soils, such as porosity, permeability, and tortuosity, is well established. A theoretical surface impedance and complex bulk wavenumber was developed by K. Attenborough for porous media that incorporated the soil pore properties as parameters [J. Acoust. Soc. Am. 73, 785–799 (1983)]. Acoustic level difference measurements were used as a noninvasive means of finding the soil pore properties. Acoustic reflection measurements showed that the sound field over porous rough surfaces is modified by the surface impedance and by surface roughness. It is not possible to separate the signal modification due to impedance and the signal modification from roughness scattering in a forward scattering measurement. In order to accurately determine the soil pore properties, the roughness effects must be known independently from the surface impedance. A means of measuring roughness apart from impedance would allow the effects of roughness to be taken out of the level difference measurements. The underwater acoustics community has used acoustic backscatter for many years to examine surface roughness. The feasibility of adapting these acoustic backscatter techniques to outdoor porous soil surfaces is examined.
Revisiting relations between loudness and intensity discrimination
Authors: Hellman William S. , Hellman Rhona P.
Published: January 2006

A comparison is made between the variation of ΔLjnd with L (loudness), based on the beat-detection data of Riesz at 1 kHz [Phys. Rev. 31, 867–875 (1928)], and analogous relations obtained from a cross section of studies. Data analysis shows that only beat detection exhibits the degree of level-dependent variation in slope relating log (ΔLjnd) to log (L) described in a recent paper by Allen and Neely [J. Acoust. Soc. Am. 102, 3628–3646 (1997)]. Moreover, the slope variation determined from beat detection is not dependent on the detailed shape of the loudness function. The results imply that Allen and Neely’s strong conclusions about the dependence of ΔLjnd on L are too tightly coupled to Riesz’s methodology to be generally applicable.
Point load wave excitation in multi-layered solids: Experiments and model verification
Authors: Zhou Chunnan , Popovics John S.
Published: January 2006

Studies of transient wave propagation in a single plate, a two-layer plate structure, and a two-layer-on-a-half-space structure are reported. Experimental results are used to verify the accuracy of a new model for wave propagation in layered solids. The experiments are performed using point load excitation and point detection at the surface of the layered structure. The basis of the new wave propagation model is first introduced. Then, experiments performed on a single plate are described. Results from different wave sources, plate materials, and wave sensors are compared with each other and with computed results from the model. The transient source function for a pencil-lead-break wave source is obtained. Next, the results of experiments performed on a two-layer plate structure (aluminum bonded to stainless steel) are reported. The cases of stainless steel atop aluminum and aluminum atop stainless steel are considered. The effects of the second layer on the transient displacement at the top surface are discussed. Finally, a two-layer-on-a-half-space structure consisting of a stainless steel plate as the top layer, an aluminum plate as the second layer and a thick acrylic resin block as the half-space is studied. The obtained experimental transient measurements agree with the computed results for all cases, thus verifying the accuracy of the model.
Scattering of elastic waves in heterogeneous media with local isotropy
Authors: Turner Joseph A. , Anugonda Phanidhar
Published: January 2006

The scattering of elastic waves in heterogeneous media is discussed. Explicit expressions are derived for the attenuation of longitudinal and transverse elastic waves in terms of the statistics of the density and Lamé parameter fluctuations. The derivation is based upon diagrammatic methods with the problem posed in terms of the Dyson equation. The Dyson equation is solved for the mean field response. The results are given here in a straightforward manner, in which the attenuations reduce to simple integrals on the unit circle. The medium is assumed statistically homogeneous and statistically isotropic. This model, with assumed local isotropic properties, is expected to apply to many materials.
A compressive gammachirp auditory filter for both physiological and psychophysical data
Authors: Irino Toshion , Patterson Roy D.
Published: January 2006

A gammachirp auditory filter was developed by Irino and Patterson [J. Acoust. Soc. Am. 101, 412–419 (1997)] to provide a level-dependent version of the linear, gammatone auditory filter, with which to explain the level-dependent changes in cochlear filtering observed in psychophysical masking experiments. In this ‘analytical’ gammachirp filter, the chirp varied with level and there was no explicit representation of the change in filter gain or compression with level. Subsequently, Carney et al. [J. Acoust. Soc. Am. 105, 2384–2391 (1999)] reviewed Carney and Yin’s [J. Neurophysiol. 60, 1653–1677 (1988)] reverse-correlation (revcor) data and showed that the frequency glide of the chirp does not vary with level in their data. In this article, the architecture of the analytical gammachirp is reviewed with respect to cochlear physiology and a new form of gammachirp filter is described in which the magnitude response, the gain, and the compression vary with level but the chirp does not. This new ‘compressive’ gammachirp filter is used to fit the level-dependent revcor data reported by Carney et al. (1999) and the level-dependent masking data reported by Rosen and Baker [Hear. Res. 73, 231–243 (1994)].
Design and optimization of a noise reduction system for infrasonic measurements using elements with low acoustic impedance
Authors: Alcoverro Benoit , Le Pichon Alexis
Published: January 2006

The implementation of the infrasound network of the International Monitoring System (IMS) for the enforcement of the Comprehensive Nuclear-Test-Ban Treaty (CTBT) increases the effort in the design of suitable noise reducer systems. In this paper we present a new design consisting of low impedance elements. The dimensioning and the optimization of this discrete mechanical system are based on numerical simulations, including a complete electroacoustical modeling and a realistic wind-noise model. The frequency response and the noise reduction obtained for a given wind speed are compared to statistical noise measurements in the [0.02–4] Hz frequency band. The effects of the constructive parameters—the length of the pipes, inner diameters, summing volume, and number of air inlets—are investigated through a parametric study. The studied system consists of 32 air inlets distributed along an overall diameter of 16 m. Its frequency response is flat up to 4 Hz. For a 2 m/s wind speed, the maximal noise reduction obtained is 15 dB between 0.5 and 4 Hz. At lower frequencies, the noise reduction is improved by the use of a system of larger diameter. The main drawback is the high-frequency limitation introduced by acoustical resonances inside the pipes.
Perception of pitch location within a speaker’s F0 range
Authors: Honorof Douglas N. , Whalen D. H.
Published: January 2006

Fundamental frequency (F0) is used for many purposes in speech, but its linguistic significance is based on its relation to the speaker’s range, not its absolute value. While it may be that listeners can gauge a specific pitch relative to a speaker’s range by recognizing it from experience, whether they can do the same for an unfamiliar voice is an open question. The present experiment explored that question. Twenty native speakers of English (10 male, 10 female) produced the vowel /ɑ/ with a spoken (not sung) voice quality at varying pitches within their own ranges. Listeners then judged, without familiarization or context, where each isolated F0 lay within each speaker’s range. Correlations were high both for the entire range (0.721) and for the range minus the extremes (0.609). Correlations were somewhat higher when the F0s were related to the range of all the speakers, either separated by sex (0.830) or pooled (0.848), but several factors discussed here may help account for this pattern. Regardless, the present data provide strong support for the hypothesis that listeners are able to locate an F0 reliably within a range without external context or prior exposure to a speaker’s voice.
Reconstruction of transient acoustic radiation from a sphere
Authors: Wu Sean F. , Lu Huancai , Bajwa Manjit S.
Published: January 2006

Transient near-field acoustical holography (NAH) formulation is derived from the Helmholtz equation least squares (HELS) method to reconstruct acoustic radiation from a spherical surface subject to transient excitations in a free field. To facilitate derivations of temporal solutions, we make use of the Laplace transform and expansion in terms of the spherical Hankel functions and spherical harmonics, with their coefficients settled by solving a system of equations obtained by matching an assumed-form solution to the measured acoustic pressure. To derive a general form of solution for a temporal kernel, we replace the spherical Hankel functions and their derivatives by polynomials, recast infinite integrals in the inverse Laplace transform as contour integrals in a complex s-plane, and evaluate it via the residue theorem. The transient acoustic quantities anywhere including the source surface are then obtained by convoluting the temporal kernels with respect to the measured acoustic pressure. Numerical examples of reconstructing transient acoustic fields from explosively expanding, impulsively accelerating, and partially accelerating spheres, and that from a sphere subject to an arbitrarily time-dependent excitation are depicted. To illustrate the effectiveness of HELS-based transient NAH formulations, all input data are collected along an arbitrarily selected line segment and used to reconstruct transient acoustic quantities everywhere. [Work supported by NSF.]
Concurrent inversion of geo- and bio-acoustic parameters from transmission loss measurements in the Yellow Sea
Authors: Diachok Orest , Wales Stephen
Published: January 2006

This paper describes results of a simultaneous inversion of bio-acoustic parameters of fish (anchovies) and geo-acoustic parameters of the bottom from transmission loss (TL) measurements in the Yellow Sea, which were reported by Qiu et al. [J. Sound Vib. 220, 331–342 (1999)]. This data set was selected because the bio-absorptivity at their site was extremely large, 40 dB at 1.3 kHz at 5 km, and measurements were made between multiple source and receiver depths and ranges. Measurements were made at night when anchovies are generally dispersed. Replica fields were calculated with a normal mode model, which incorporates bio-absorption layers. The inversion was based on minimizing the rms difference, Δ, between measured and calculated values of TL at all ranges and source and receiver depths, and involved a simultaneous search for bio-layer depth, bio-layer thickness, bio-alpha, geo-sound speed, and geo-alpha. The resultant small value of Δ, ±1.7 dB, confirmed that the model, which was assumed in replica field calculations, was realistic, and that inverted parameters were meaningful. In particular, the inverted depth of the bio-absorption layer, 6.9±0.3 m, was consistent with theoretical calculations of the depth, 5.8±1 m, of 10-cm-long anchovies Engraulis japonicus, the dominant species in the Yellow Sea.
Time-reversal imaging for classification of submerged elastic targets via Gibbs sampling and the Relevance Vector Machine
Authors: Dasgupta Nilanjan , Carin Lawrence
Published: January 2006

Time-reversal imaging (TRI) is analogous to matched-field processing, although TRI is typically very wideband and is appropriate for subsequent target classification (in addition to localization). Time-reversal techniques, as applied to acoustic target classification, are highly sensitive to channel mismatch. Hence, it is crucial to estimate the channel parameters before time-reversal imaging is performed. The channel-parameter statistics are estimated here by applying a geoacoustic inversion technique based on Gibbs sampling. The maximum a posteriori (MAP) estimate of the channel parameters are then used to perform time-reversal imaging. Time-reversal implementation requires a fast forward model, implemented here by a normal-mode framework. In addition to imaging, extraction of features from the time-reversed images is explored, with these applied to subsequent target classification. The classification of time-reversed signatures is performed by the relevance vector machine (RVM). The efficacy of the technique is analyzed on simulated in-channel data generated by a free-field finite element method (FEM) code, in conjunction with a channel propagation model, wherein the final classification performance is demonstrated to be relatively insensitive to the associated channel parameters. The underlying theory of Gibbs sampling and TRI are presented along with the feature extraction and target classification via the RVM.
Estimates of auditory filter phase response at and below characteristic frequency (L)
Authors: Oxenham Andrew J. , Ewert Stephan D.
Published: January 2006

Animal studies in basal cochlear regions have shown that basilar-membrane phase curvature (or rate of change of group delay with frequency) is negative around characteristic frequency (CF), but near zero well below CF. This study examined whether psychophysical masking experiments in humans show the same difference between on- and off-CF phase curvature. Masked thresholds were measured for a 2-kHz signal in the presence of harmonic tone complex maskers with a fundamental frequency of 100 Hz, band-limited between 200 and 1400 Hz (off-frequency masker) or between 1400 and 2600 Hz (on-frequency masker). The results from four normal-hearing listeners are consistent with predictions from animal physiological data: negative phase curvature is found for the on-frequency masker, whereas the phase curvature for the off-frequency masker is near zero. The method and results provide a strong test for the temporal response of computational models of human cochlear filtering.
Absorptive properties of rigid porous media: Application to face centered cubic sphere packing
Authors: Gasser S. , Paun F. , Bréchet Y.
Published: January 2006

The classical description of porous media as a homogeneous equivalent fluid is presented, and its foundations on the homogenization method is introduced and applied to the numerical prediction model for a periodic porous medium composed by face centered cubic sphere packing on which measurements have been made. The results are compared with existing numerical results in the literature and with new and experimental data.