bluuebunny/crossref_metadata_2025 huggingface dataset:
A novel type of DNA curvature present in a Clostridium perfringens ferredoxin gene: characterization and role in gene expression
Authors: Kaji Masato , Matsushita Osamu , Tamai Eiji , Miyata Shigeru , Taniguchi Yuki , Shimamoto Seiko , Katayama Seiichi , Morita Shushi , Okabe Akinobu
Published: November 2003

This study has revealed that aClostridium perfringensferredoxin gene (per-fdx) possesses a novel type of DNA curvature, which is formed by five phased A-tracts extending from upstream to downstream of the −35 region. The three A-tracts upstream of the promoter and the two within the promoter are located at the positions corresponding to A-tracts present in aC. perfringensphospholipase C gene (plc) and aClostridium pasteurianumferredoxin gene (pas-fdx), respectively. DNA fragments of the per-fdx, pas-fdxandplcgenes (nucleotide positions −69 to +1 relative to the transcription initiation site) were fused to a chloramphenicol acetyltransferase reporter gene on a plasmid, pPSV, and theirin vivopromoter activities were examined by assaying the chloramphenicol acetyltransferase activity of eachC. perfringenstransformant. Comparison of the three constructs showed that the order of promoter activity is, in descending order, per-fdx, pas-fdxandplc. Deletion of the three upstream A-tracts of the per-fdxgene drastically decreased the promoter activity, as demonstrated previously for theplcpromoter. Substitution of the most downstream A-tract decreased the promoter activities of the per-fdxand pas-fdxgenes. These results indicate that not only the phased A-tracts upstream of the promoter but also those within the promoter stimulate the promoter activity, and suggest that the high activity of the per-fdxpromoter is due to the combined effects of these two types of A-tracts.
3- and 4-alkylphenol degradation pathway in Pseudomonas sp. strain KL28: genetic organization of the lap gene cluster and substrate specificities of phenol hydroxylase and catechol 2,3-dioxygenase
Authors: Jeong Jae Jun , Kim Ji Hyun , Kim Chi-Kyung , Hwang Ingyu , Lee Kyoung
Published: November 2003

The enzymes and genes responsible for the catabolism of higher alkylphenols have not been characterized in aerobic bacteria.Pseudomonassp. strain KL28 can utilize a wide range of alkylphenols, which include the 4-n-alkylphenols (C1–C5). The genes, designated aslap(forlong-chainalkylphenols), encoding enzymes for the catabolic pathway were cloned from chromosomal DNA and sequenced. Thelapgenes are located in a 13·2 kb region with 14 ORFs in the orderlapRBKLMNOPCEHIFGand with the same transcriptional orientation. ThelapRgene is transcribed independently and encodes a member of the XylR/DmpR positive transcriptional regulators.lapB, the first gene in thelapoperon, encodes catechol 2,3-dioxygenase (C23O). ThelapKLMNOPandlapCEHIFGgenes encode a multicomponent phenol hydroxylase (mPH) and enzymes that degrade derivatives of 2-hydroxymuconic semialdehyde (HMS) to TCA cycle intermediates, respectively. ThePlapBpromoter contains motifs at positions −24(GG) and −12(GC) which are typically found inσ54-dependent promoters. A promoter assay using aPlapB : : gfptranscriptional fusion plasmid showed thatlapBpromoter activity is inducible and that it responds to a wide range of (alkyl)phenols. The structural genes encoding enzymes required for this catabolism are similar (42–69 %) to those encoded on a catabolic pVI150 plasmid from an archetypal phenol degrader,Pseudomonassp. CF600. However, thelaplocus does not include genes encoding HMS hydrolase and ferredoxin. The latter is known to be functionally associated with C23O for use of 4-alkylcatechols as substrates. The arrangement of thelapcatabolic genes is not commonly found in othermeta-cleavage operons. Substrate specificity studies show that mPH preferentially oxidizes 3- and 4-alkylphenols to 4-alkylcatechols. C23O preferentially oxidizes 4-alkylcatechols via proximal (2,3) cleavage. This indicates that these two key enzymes have unique substrate preferences and lead to the establishment of the initial steps of the lap pathway in strain KL28.
Koch's Bacillus – a look at the first isolate of Mycobacterium tuberculosis from a modern perspective
Authors: Taylor G. M. , Stewart G. R. , Cooke M. , Chaplin S. , Ladva S. , Kirkup J. , Palmer S. , Young D. B.
Published: November 2003

Using molecular methods the authors have studied mycobacterial DNA taken from a 19th century victim of tuberculosis. This was the case from which Robert Koch first isolated and cultured the organism responsible for tuberculosis. The mycobacteria were preserved within five glass culture tubes as abundant bacterial colonies on slopes of a gelatinous culture medium of unknown composition. Originally presented by Koch to surgical laryngologist Walter Jobson Horne in London in 1901, the relic has, since 1983, been in the care of the Royal College of Surgeons of England. Light and electron microscopy established the presence of acid-fast mycobacteria but showed that morphological preservation was generally poor. Eleven different genomic loci were successfully amplified by PCR. This series of experiments confirmed that the organisms were indeed Mycobacterium tuberculosis and further showed that the original strain was in evolutionary terms similar to ‘modern’ isolates, having undergone the TB D1 deletion. Attempts to determine the genotypic group of the isolate were only partially successful, due in part to the degraded nature of the DNA and possibly also to a truncation in the katG gene, which formed part of the classification scheme. Spoligotyping resulted in amplification of DR spacers consistent with M. tuberculosis but with discrepancies between independent extracts, stressing the limitations of this typing method when applied to poorly preserved material.
Time for a change: co‐operative reader development working in the North West of England
Authors: Spencer Julie , Mathieson Jane
Published: November 2003

This article describes in some detail reader development project work targeting 16‐25 year old young people carried out in 18 library authorities in the North West of England during 2000‐2002. The context of the project is set, focusing on the aim of increasing library use by young people. Key national reading agencies are briefly described, as well as the regional Time To Read partnership. The project description is detailed, including aims and objectives, delivery, training, new partnerships and the impact of the work locally and nationally. Some key conclusions are of significant practical value for future reader centred projects. The article concludes by describing a new co‐ordinator’s post which is taking reader development work forward in the region and offers a model for future cross‐authority working.
Characteristics of product/service process and customer needs of geographical accessibility in electronic commerce
Authors: Cho Sung‐Eui , Park Kwangtae
Published: November 2003

The necessity of geographical accessibility between service provider and the customer has been essential for face‐to‐face contact in many service industries. However, the emergence of electronic commerce (EC) and new technologies has altered the concept of location and geographical accessibility of service industries in a traditional economy. This study developed factors representing characteristics of product/service processes and verified that those factors are significantly related to customer needs of geographical accessibility in the transactions of EC. In addition, it investigated the relationships with the reasons for customer needs of geographical accessibility. Data for analyses were collected through customer surveys and statistically analyzed through exploratory factor analysis, multiple regression analysis, and canonical correlation analysis.
A descriptive model of online shopping process: some empirical results
Authors: Chen Su‐Jane , Chang Tung‐Zong
Published: November 2003

Since early 1990s, tremendous growth of e‐commerce has transformed the world retail infrastructure rapidly. Although the Internet burst between 2000 and 2002 which slowed down the rage in the financial market, the Internet infrastructure continues to grow and becomes an integral part of market strategic portfolio for many organizations. In order to be successful in the Internet niche, many retailers engage in business model reengineering to keep up with changes in how customers acquire goods and services. Based on in‐depth interviews and a follow‐up survey, the present study depicts a common online shopping process and identifies three common online shopping components: interactivity, transaction, and fulfillment. These components and their respective factors form one's online shopping experience. Managerial implications and future research directions are offered.
Cost benefit factor analysis in e‐services
Authors: Lu Jie , Zhang Guangquan
Published: November 2003

This paper first presents a research framework for e‐service evaluation within four categories: cost, benefit, functions and development, each incorporating a number of factors. Through data analysis and hypotheses testing, inter‐relationships among the factors of the four categories are examined. The results show that the development type of an e‐service has a significant effect on the degree of user satisfaction. Expertise, technique and expense are the principle factors limiting current e‐service adoption. The most significant finding is that, in the development of e‐services, certain cost factors are significantly more important than others in relation to certain benefit factors. The finding is presented as a cost‐benefit factor‐relation model. This provides an insight into whether investment in certain areas of e‐service applications is more important than in others for particular business objectives. These results have the potential to improve the strategic planning of companies by determining more effective investment areas and adopting more suitable development activities where e‐services are concerned.
Developing a measure of knowledge management behaviors and practices
Authors: Darroch Jenny
Published: November 2003

Knowledge management has recently emerged as a new discipline and is generating considerable interest among academics and managers. Given its newness, there is still little guidance in the extant literature on how to measure knowledge management. This paper presents the first scale developed to measure knowledge management behaviors and practices and in so doing provides construct boundaries that should enable the development of a theory of knowledge management (Zaltmanet al., 1973).
Third generation R&D and strategies for knowledge management
Authors: Paraponaris Claude
Published: November 2003

The structures of R&D have evolved towards a bigger articulation between the development of the technological potentialities and exploitation of commercial opportunities. The third generation R&D supplies a more rational frame of action to reconcile several objectives which can turn out contradictory: dedicate enough resources to create new technologies, develop a wallet of industrial and academic co‐operation to accelerate the acquisition of new knowledge. The strategies of high‐tech firms succeed to create a great variety of knowledge. It is necessary to organize the diversity of the internal and external sources to use knowledge fully as a true competitive advantage. We show how the memory must be constituted of the firm to reach that point. From a study on several cases of MNC we characterize the difficulties of the capitalization of the knowledge, and then we present how the firms can take advantage of an active management of knowledge flows.
Knowledge‐enabled customer relationship management: integrating customer relationship management and knowledge management concepts[1]
Authors: Gebert Henning , Geib Malte , Kolbe Lutz , Brenner Walter
Published: November 2003

The concepts of customer relationship management (CRM) and knowledge management (KM) both focus on allocating resources to supportive business activities in order to gain competitive advantages. CRM focuses on managing the relationship between a company and its current and prospective customer base as a key to success, while KM recognizes the knowledge available to a company as a major success factor. From a business process manager’s perspective both the CRM and KM approaches promise a positive impact on cost structures and revenue streams in return for the allocation of resources. However, investments in CRM and KM projects are not without risk, as demonstrated by many failed projects. In this paper we show that the benefit of using CRM and KM can be enhanced and the risk of failure reduced by integrating both approaches into a customer knowledge management (CKM) model. In this regard, managing relationships requires managing customer knowledge – knowledge about as well as from and for customers. In CKM, KM plays the role of a service provider, managing the four knowledge aspects: content, competence, collaboration and composition. Our findings are based on a literature analysis and six years of action research, supplemented by case studies and surveys.
Software systems support for knowledge management
Authors: Lindvall Mikael , Rus Ioana , Suman Sinha Sachin
Published: November 2003

Human capital is the main asset of many companies, whose knowledge has to be preserved and leveraged from individual to the company level, allowing continual learning and improvement. Knowledge management has various components and aspects such as socio‐cultural, organizational, and technological. In this paper we address the technological aspect; more precisely we survey available software systems that support different knowledge management activities. We categorize these tools into classes, based on their capabilities and functionality and show what tasks and knowledge processing operations they support.
The correlogram: A visual display of periodicity
Authors: Granqvist Svante , Hammarberg Britta
Published: November 2003

Fundamental frequency (F0) extraction is often used in voice quality analysis. In pathological voices with a high degree of instability in F0, it is common for F0 extraction algorithms to fail. In such cases, the faulty F0 values might spoil the possibilities for further data analysis. This paper presents the correlogram, a new method of displaying periodicity. The correlogram is based on the waveform-matching techniques often used in F0 extraction programs, but with no mechanism to select an actual F0 value. Instead, several candidates for F0 are shown as dark bands. The result is presented as a 3D plot with time on the x axis, correlation delay inverted to frequency on the y axis, and correlation on the z axis. The z axis is represented in a gray scale as in a spectrogram. Delays corresponding to integer multiples of the period time will receive high correlation, thus resulting in candidates at F0, F0/2, F0/3, etc. While the correlogram adds little to F0 analysis of normal voices, it is useful for analysis of pathological voices since it illustrates the full complexity of the periodicity in the voice signal. Also, in combination with manual tracing, the correlogram can be used for semimanual F0 extraction. If so, F0 extraction can be performed on many voices that cause problems for conventional F0 extractors. To demonstrate the properties of the method it is applied to synthetic and natural voices, among them six pathological voices, which are characterized by roughness, vocal fry, gratings/scrape, hypofunctional breathiness and voice breaks, or combinations of these.
Remote sensing of sediment characteristics by optimized echo-envelope matching
Authors: Sternlicht Daniel D. , de Moustier Christian P.
Published: November 2003

A sediment geoacoustic parameter estimation technique is described which compares bottom returns, measured by a calibrated monostatic sonar oriented within 15° of vertical and having a 10°–21° beamwidth, with an echo envelope model based on high-frequency (10–100 kHz) incoherent backscatter theory and sediment properties such as: mean grain size, strength, and exponent of the power law characterizing the interface roughness energy density spectrum, and volume scattering coefficient. An average echo envelope matching procedure iterates on the reflection coefficient to match the peak echo amplitude and separate coarse from fine-grain sediments, followed by a global optimization using a combination of simulated annealing and downhill simplex searches over mean grain size, interface roughness spectral strength, and sediment volume scattering coefficient. Error analyses using Monte Carlo simulations validate this optimization procedure. Moderate frequencies (33 kHz) and orientations normal with the interface are best suited for this application. Distinction between sands and fine-grain sediments is demonstrated based on acoustic estimation of mean grain size alone. The creation of feature vectors from estimates of mean grain size and interface roughness spectral strength shows promise for intraclass separation of silt and clay. The correlation between estimated parameters is consistent with what is observed in situ.
Theory of explosive beam spreading due to ray chaos
Authors: Tappert F. D.
Published: November 2003

In an ocean acoustic situation where rays are known to be chaotic, a theory based on a Gaussian beam approximation is used to show that the width of a narrow-angle beam increases exponentially (explosively) with range at a rate that is given by the Lyapunov exponent that is calculated in the geometric limit. This finite frequency result shows that the phenomenon of “wave chaos” is real, and might be observable experimentally.
Acoustic backscattering by Hawaiian lutjanid snappers. I. Target strength and swimbladder characteristics
Authors: Benoit-Bird Kelly J. , Au Whitlow W. L. , Kelley Christopher D.
Published: November 2003

The target strengths and swimbladder morphology of six snapper species were investigated using broadband sonar, x rays, and swimbladder casts. Backscatter data were obtained using a frequency-modulated sweep (60–200 kHz) and a broadband, dolphinlike click (peak frequency 120 kHz) from live fish, mounted and rotated around each of their three axes. X rays revealed species-specific differences in the shape, size, and orientation of the swimbladders. The angle between the fish’s dorsal aspect and the major axis of its swimbladder ranged from 3° to 12° and was consistent between individuals within a species. This angle had a one-to-one relationship with the angle at which the maximum dorsal aspect target strength was measured (r2=0.93), regardless of species. Maximum dorsal aspect target strength was correlated with length within species. However, the swimbladder modeled as an air-filled prolate spheroid with axes measured from the x rays of the swimbladder predicted maximum target strength significantly better than models based on fish length or swimbladder volume. For both the dorsal and lateral aspects, the prolate spheroid model’s predictions were not significantly different from the measured target strengths (observed power >0.75) and were within 3 dB of the measured values. This model predicts the target strengths of all species equally well, unlike those based on length.
Acoustic backscattering by Hawaiian lutjanid snappers. II. Broadband temporal and spectral structure
Authors: Au Whitlow W. L. , Benoit-Bird Kelly J.
Published: November 2003

The characteristics of acoustic echoes from six species of deep-dwelling (up to 400 m) Hawaiian Lujanid snappers were determined by backscatter measurements at the surface. A broadband linear frequency-modulated signal and a short dolphinlike sonar signal were used as the incident signals. The fish were anesthetized and attached to a monofilament net that was attached to a rotor so echoes could be collected along the roll, tilt, and lateral axes of each fish. The temporal highlight structure of broadband echoes was determined by calculating the envelope of the cross-correlation function between the incident signal and the echoes. The echo waveforms were complex with many highlights and varied with the orientation of the fish. In the tilt plane, the strongest echoes occurred when the incident signal was perpendicular to the long axis of the swimbladder. The number of highlights was the fewest at this orientation. The number of echo highlights and the length of echoes increased as the fish was tilted from this orientation. The highlight structure of the echoes resulted in the transfer function being rippled, with local maxima and minima that changed with fish size and species. The echo structures in both the time and frequency domains were generally consistent within species and were easily distinguishable between species.
High-frequency acoustic scattering from turbulent oceanic microstructure: The importance of density fluctuations
Authors: Lavery Andone C. , Schmitt Raymond W. , Stanton Timothy K.
Published: November 2003

Acoustic scattering techniques provide a unique and powerful tool to remotely investigate the physical properties of the ocean interior over large spatial and temporal scales. With high-frequency acoustic scattering it is possible to probe physical processes that occur at the microstructure scale, spanning submillimeter to centimeter scale processes. An acoustic scattering model for turbulent oceanic microstructure is presented in which the current theory, which only accounts for fluctuations in the sound speed, has been extended to include fluctuations in the density as well. The inclusion of density fluctuations results in an expression for the scattering cross section per unit volume, σv, that is explicitly dependent on the scattering angle. By relating the variability in the density and sound speed to random fluctuations in oceanic temperature and salinity, σv has been expressed in terms of the temperature and salinity wave number spectra, and the temperature-salinity co-spectrum. A Batchelor spectrum for temperature and salinity, which depends on parameters such as the dissipation rates of turbulent kinetic energy and temperature variance, has been used to evaluate σv. Two models for the temperature-salinity co-spectrum have also been used. The predictions indicate that fluctuations in the density could be as important in determining backscattering as fluctuations in the sound speed. Using data obtained in the ocean with a high resolution vertical microstructure profiler, it is predicted that scattering from oceanic microstructure can be as strong as scattering from zooplankton.
Blind estimation of reverberation time
Authors: Ratnam Rama , Jones Douglas L. , Wheeler Bruce C. , O’Brien William D. , Lansing Charissa R. , Feng Albert S.
Published: November 2003

The reverberation time (RT) is an important parameter for characterizing the quality of an auditory space. Sounds in reverberant environments are subject to coloration. This affects speech intelligibility and sound localization. Many state-of-the-art audio signal processing algorithms, for example in hearing-aids and telephony, are expected to have the ability to characterize the listening environment, and turn on an appropriate processing strategy accordingly. Thus, a method for characterization of room RT based on passively received microphone signals represents an important enabling technology. Current RT estimators, such as Schroeder’s method, depend on a controlled sound source, and thus cannot produce an online, blind RT estimate. Here, a method for estimating RT without prior knowledge of sound sources or room geometry is presented. The diffusive tail of reverberation was modeled as an exponentially damped Gaussian white noise process. The time-constant of the decay, which provided a measure of the RT, was estimated using a maximum-likelihood procedure. The estimates were obtained continuously, and an order-statistics filter was used to extract the most likely RT from the accumulated estimates. The procedure was illustrated for connected speech. Results obtained for simulated and real room data are in good agreement with the real RT values.
Interactions between test- and inducer-tone durations in induced loudness reduction
Authors: Nieder Bärbel , Buus Søren , Florentine Mary , Scharf Bertram
Published: November 2003

A tone usually declines in loudness when preceded by a more intense inducer tone. This phenomenon is called “loudness recalibration” or “induced loudness reduction” (ILR). The present study investigates how ILR depends on level, loudness, and duration. A 2AFC procedure was used to obtain loudness matches between 2500-Hz comparison tones and 500-Hz test tones at 60 and 70 dB SPL, presented with and without preceding 500-Hz inducer tones. For 200-ms test and comparison tones, the amount of ILR did not depend on inducer level (set at 80 dB SPL and above), but ILR was greater with 200- than with 5-ms inducers, even when both were equally loud. For 5-ms tones, ILR was as great with 5- as with 200-ms inducers and about as great as when test and inducer tones both lasted 200 ms. These results suggest that (1) neither the loudness nor the SPL of the inducer alone governs ILR, and (2) inducer duration must equal or exceed test-tone duration to yield maximal amounts of ILR. Further analysis indicates that the efferent system may be partly responsible for ILR of 200-ms test tones, but is unlikely to account for ILR of 5-ms tones.
The selection of layer thicknesses to control acoustic radiation force profiles in layered resonators
Authors: Hill Martyn
Published: November 2003

Ultrasonic standing waves can be used to generate radiation forces on particles within a fluid. A number of authors have derived detailed representations of these forces but these are most commonly applied using an approximation to the energy distribution based upon an idealized standing wave within a mode based upon rigid boundaries. An electro-acoustic model of the acoustic energy distribution within a standing wave with arbitrary thickness boundaries has been expanded to model the radiation force on an example particle within the acoustic field. This is used to examine the force profile on a particle at resonances other than those predicted with rigid boundaries, and with pressure nodes at different positions. A simple analytical method for predicting modal conditions for combinations of frequencies and layer thickness characteristics is presented, which predicts that resonances can exist that will produce a pressure node at arbitrary positions in the fluid layer of such a system. This can be used to design resonators that will drive particles to positions other than the center of the fluid layer, including the fluid/solid boundary of the layer, with significant potential applications in sensing systems. Further, the model also predicts conditions for multiple subwavelength resonances within the fluid layer of a single resonator, each resonance having different nodal planes for particle concentration.
Effects of fundamental frequency and vocal-tract length changes on attention to one of two simultaneous talkers
Authors: Darwin Christopher J. , Brungart Douglas S. , Simpson Brian D.
Published: November 2003

Three experiments used the Coordinated Response Measure task to examine the roles that differences in F0 and differences in vocal-tract length have on the ability to attend to one of two simultaneous speech signals. The first experiment asked how increases in the natural F0 difference between two sentences (originally spoken by the same talker) affected listeners’ ability to attend to one of the sentences. The second experiment used differences in vocal-tract length, and the third used both F0 and vocal-tract length differences. Differences in F0 greater than 2 semitones produced systematic improvements in performance. Differences in vocal-tract length produced systematic improvements in performance when the ratio of lengths was 1.08 or greater, particularly when the shorter vocal tract belonged to the target talker. Neither of these manipulations produced improvements in performance as great as those produced by a different-sex talker. Systematic changes in both F0 and vocal-tract length that simulated an incremental shift in gender produced substantially larger improvements in performance than did differences in F0 or vocal-tract length alone. In general, shifting one of two utterances spoken by a female voice towards a male voice produces a greater improvement in performance than shifting male towards female. The increase in performance varied with the intonation patterns of individual talkers, being smallest for those talkers who showed most variability in their intonation patterns between different utterances.
Vibration of prolate spheroidal shells with shear deformation and rotatory inertia: Axisymmetric case
Authors: Hayek Sabih I. , Boisvert Jeffrey E.
Published: November 2003

This paper presents the derivation of the equations for nonaxisymmetric motion of prolate spheroidal shells of constant thickness. The equations include the effect of distributed mechanical surface forces and moments. The shell theory used in this derivation includes three displacements and two thickness shear rotations. Thus, the effects of membrane, bending, shear deformation, and rotatory inertia are included in this theory. The resulting five coupled partial differential equations are self-adjoint and positive definite. The frequency-wave-number spectrum has five branches, two acoustic and three optical branches representing flexural, extensional, torsional, and two thickness shear. For the case of axisymmetric motion, these were computed for various spheroidal shell eccentricities and thickness-to-length ratios for a large number of modes. The axisymmetric dynamic response for damped shells of various eccentricities and thicknesses under point and ring surface forces are presented.
Closed-form expressions for ocean reverberation and signal excess with mode stripping and Lambert’s law
Authors: Harrison C. H.
Published: November 2003

Closed-form expressions for two-way propagation and reverberation in variable depth ducts are derived for isovelocity water by using ray invariants and acoustic flux. These expressions include the transition to single mode propagation at long range. Three surface scattering laws are considered: Lambert, Lommel-Seeliger, and angle independent, and these are compared with a point target to give explicit signal-to-reverberation ratios. In particular, there is interesting and sometimes surprising behavior when the propagation obeys mode-stripping (the high angles are preferentially attenuated by bottom losses) whilst the scattering obeys Lambert’s law (high angles are preferentially back-scattered). There may be conditions where the signal-to-reverberation ratio is independent of range so that there is no reverberation range limit. Bottom slope dependence of both target echo and reverberation is surprisingly weak. The implications of refraction are discussed. The angle dependence for a point or surface scatterer at a given range can be translated into arrival time, so it is possible to calculate the received pulse shape for one-way or two-way paths. Because the tail is exponential with a range-independent half-life that only depends on bottom reflection properties there is scope for extracting geoacoustic information from the pulse shape alone. This environmental time spread is also of use to sonar designers.
Contrast source inversion methods in elastodynamics
Authors: Pelekanos George , Abubakar Aria , van den Berg Peter M.
Published: November 2003

In this paper a nonlinear inversion method is presented for determining the mass density of an elastic inclusion from the knowledge of how the inclusion scatters known incident elastic waves. The algorithm employed is an extension of the multiplicative regularized contrast source inversion method (MR-CSI) to elasticity. This method involves alternate determination of the mass density contrast and the contrast sources (the product of the contrast and the fields) in each iterative step. The simple updating schemes of the method allow the introduction of an extra regularization term to the cost functional as a multiplicative constraint. This so-called MR-CSI method (MR-CSI) has been proven to be very effective for the acoustic and electromagnetic inverse scattering problems. Numerical examples demonstrate that the MR-CSI method shows excellent edge preserving properties by robustly handling noisy data very well, even for more complicated elastodynamic problems.
Measurements of near-surface bubble plumes in the open ocean with implications for high-frequency sonar performance
Authors: Trevorrow Mark V.
Published: November 2003

This study examines near-surface bubble data obtained with a self-contained 200-kHz inverted echo-sounder deployed at Ocean Station Papa (NE Pacific, 1400 km west of Vancouver Is.) over an 81-day period in the spring of 1996. The instrument operated continuously, recording calibrated volume scattering profiles from near-surface bubbles with 3-s and 30-cm resolution. The data show the frequent occurrence of bubbles organized into vertical, plume-like structures, presumably drawn downwards by turbulence and other near-surface circulations. Average bubble plume penetrations of up to 15 m were observed, with maximum penetrations up to 25 m. Within the plumes, the backscatter cross section exhibited an exponential decay with depth, with e-folding scale in the range 0.5 to 3 m, increasing proportionally to the square of average plume depth. Using standard models for bubble scattering, and incorporating recent acoustic resonator measurements of bubble-size distributions along with actual bubble plume data, high-frequency near-surface sonar performance models were developed. These models show that on a ping-to-ping basis the bubble plume structures can induce significant spatial variations in the reverberation level and path-integrated extinction losses to near-surface targets.
Capillary forces in the acoustics of patchy-saturated porous media
Authors: Tserkovnyak Yaroslav , Johnson David Linton
Published: November 2003

A linearized theory of the acoustics of porous elastic formations, such as rocks, saturated with two different viscous fluids is generalized to take into account a pressure discontinuity across the fluid boundaries. The latter can arise due to the surface tension of the membrane separating the fluids. We show that the frequency-dependent bulk modulus K̃(ω) for wavelengths longer than the characteristic structural dimensions of the fluid patches has a similar analytic behavior to the case of a vanishing membrane stiffness and depends on the same parameters of the fluid-distribution topology. The effect of the capillary stiffness can be accounted for by renormalizing the coefficients of the leading terms in the low-frequency limit of K̃(ω).
Modified Szabo’s wave equation models for lossy media obeying frequency power law
Authors: Chen W. , Holm S.
Published: November 2003

Szabo’s models of acoustic attenuation [Szabo, J. Acoust. Soc. Am. 96(1), 491–500 (1994)] comply well with the empirical frequency power law involving noninteger and odd-integer exponent coefficients while guaranteeing causality, but nevertheless encounter the troublesome issues of hypersingular improper integral and obscurity in implementing initial conditions. The purpose of this paper is to ease or remove these drawbacks of the Szabo’s models via the Caputo fractional derivative concept. The positive time-fractional derivative is also introduced to include the positivity of the attenuation processes.
Determination of transport parameters in air-saturated porous materials via reflected ultrasonic waves
Authors: Fellah Z. E. A. , Depollier C. , Berger S. , Lauriks W. , Trompette P. , Chapelon J.-Y.
Published: November 2003

An ultrasonic reflectivity method of evaluating the acoustic parameters of porous materials saturated by air (or any other gas) is discussed. The method is based on experimental detection of waves reflected at normal incidence by the first and second interface of the material. This method is based on a temporal model of direct and inverse scattering problems for the propagation of transient ultrasonic waves in a homogeneous isotropic slab of porous material with a rigid frame [Fellah et al., J. Acoust. Soc. Am. 113, 61–73 (2003)]. Generally, the conventional ultrasonic approach can be used to determine tortuosity, and viscous and thermal characteristic lengths via transmitted waves. Porosity cannot be estimated in transmitted mode because of its very weak sensitivity. First interface use of the reflected wave at oblique incidence leads to the determination of porosity and tortuosity [Fellah et al., J. Acoust. Soc. Am. 113, 2424–2433 (2003)] but this is not possible at normal incidence. Using experimental data of reflected waves by the first and second interface at normal incidence simultaneously leads to the determination of porosity, tortuosity, viscous and thermal characteristic lengths. As with the classic ultrasonic approach for characterizing porous material saturated with one gas, both characteristic lengths are estimated individually by assuming a given ratio between them. Tests are performed using weakly resistive industrial plastic foams. Experimental and numerical results, and prospects are discussed.
Finite-bandwidth effects on the causal prediction of ultrasonic attenuation of the power-law form
Authors: Mobley Joel , Waters Kendall R. , Miller James G.
Published: November 2003

Kramers–Kronig (K–K) relations exist as a consequence of causality, placing nonlocal constraints on the relationship between dispersion and absorption. The finite-bandwidth method of applying these relations is examined where the K–K integrals are restricted to the spectrum of the experimental data. These finite-bandwidth K–K relations are known to work with resonant-type data and here are applied to dispersion data consistent with a power-law attenuation coefficient (exponent from 1 to 2). Bandwidth-restricted forms of the zero and once-subtracted K–K relations are used to determine the attenuation coefficient from phase velocity. Analytically, it is shown that these transforms produce the proper power-law form of the attenuation coefficient as a stand-alone term summed with artifacts that are dependent on the integration limits. Calculations are performed to demonstrate how these finite-bandwidth artifacts affect the K–K predictions under a variety of conditions. The predictions are studied in a local context as a function of subtraction frequency, bandwidth, and power-law exponent. The K–K predictions of the power-law exponent within various decades of the spectrum are also examined. In general, the agreement between finite-bandwidth K–K predictions and exact values grows as the power-law exponent approaches 1 and with increasing bandwidth.
Open cycle traveling wave thermoacoustics: Mean temperature difference at the regenerator interface
Authors: Weiland Nathan T. , Zinn Ben T.
Published: November 2003

In an open cycle traveling wave thermoacoustic engine, the hot heat exchanger is replaced by a steady flow of hot gas into the regenerator to provide the thermal energy input to the engine. The steady-state operation of such a device requires that a potentially large mean temperature difference exist between the incoming gas and the solid material at the regenerator’s hot side, due in part to isentropic gas oscillations in the open space adjacent to the regenerator. The magnitude of this temperature difference will have a significant effect on the efficiencies of these open cycle devices. To help assess the feasibility of such thermoacoustic engines, a numerical model is developed that predicts the dependence of the mean temperature difference upon the important design and operating parameters of the open cycle thermoacoustic engine, including the acoustic pressure, mean mass flow rate, acoustic phase angles, and conductive heat loss. Using this model, it is also shown that the temperature difference at the regenerator interface is approximately proportional to the sum of the acoustic power output and the conductive heat loss at this location.
The ultrasonic weak short-pulse responses of microbubbles based on a two-frequency approximation
Authors: Wu Chung-Yuo , Tsao Jenho
Published: November 2003

The ultrasonic short-pulse responses of microbubbles are of interest in cavitation, transient responses, and contrast imaging. We extend the two-frequency analytic solutions of Newhouse and Shankar [J. Acoust. Soc. Am. 75, 1473–1477 (1984)] to approximate the short-pulse responses of microbubbles in a low-amplitude field. Based on their results, there is an expected component near dc in the spectrum of bubble echoes excited by a short pulse. Here this component is named the low-frequency response, and its theoretical properties are verified experimentally. Including the fundamental and second-harmonic components, the weak short-pulse responses of microbubbles include three types of response. Our work has determined the constraint conditions under which this approximated solution can be used to analyze these short-pulse responses. This paper also provides the amplitude and spectral properties of these responses. The low-frequency response has a special bandwidth-dependent property and has potential applications in imaging and bubble sizing.
Acoustics of native-American ceremonial sites in prehispanic America (Acustica en los espacios escenios rituales prehispanicos)
Authors: Martinez Maria Isabel
Published: November 2003

This thesis establishes a methodology that incorporates the latest procedures used in architectural acoustics for the study of open spaces of this general type, and definitions are given for the acoustic variables of interest. The “Juego de Pelota” (ball game) sites are the only ceremonial sites built specifically for the performance of a fertility ritual, and are ideal for the study of prehispanic architectural topographies. Analysis of the acoustic properties of such sites revealed that the topographical characteristics of the elevation profiles of these architectural structures determine the acoustic behavior of these spaces. Such profiles are classified into three basic types: (i) inclined profile, (ii) terraced profile, and (iii) mixed profile. The terraced profiles are the most efficient, and the mixed profiles are the least efficient, in regard to acoustics. The consideration of the acoustic behavior of architectural structures intended for the “Ball Game,” as the designs evolved over time, leads to the conclusion that acoustical sensations that contributed effectively to the characteristic mystical atmosphere of the ceremonial rituals were characteristic only of those sites constructed in the “classical” period.

Thesis advisors: Jaime Navarro and Juan J. Sendra

Copies of this thesis written in Spanish may be obtained by contacting the advisor, Jaime Navarro, E.T.S. de Arquitectura de Sevilla, Dpto. de Construcciones Arquitectonicas I, Av. Reina Mercedes, 2, 41012 Sevilla, Spain. E-mail address: jnavarro@us.es
Weak sparks, N waves, and the calibration of microphones at ultrasonic frequencies
Authors: Wright Wayne M.
Published: November 2003

A fortuitous situation involving the availability of wide-band condenser microphones, curiosity about acoustic waves generated by sparks, and his own development of nonlinear acoustic theory provided two significant contributions to David Blackstock’s continuing research. Theoretical understanding of the nonlinear distortion experienced by intense acoustic impulses in air, such as those generated by relatively weak sparks, led to a technique for calibration of microphones that have essentially flat frequency response up to almost 1 MHz. These sparks and calibrated microphones, in turn, provided the means to carry out several graduate student thesis projects that were supervised by David. Diffraction at edges, apertures, and discs was studied in the time domain. Model studies related to sonic boom phenomena were carried out, as was the propagation of N waves in waveguides. The most recent application has been a model study of focusing by an ellipsoidal reflector, such as is typically used in lithotripsy. In each case, the various contributions to the received signals were readily identified in the time-domain presentation.
Overview of orthopedic shock wave devices
Authors: Brown Roy , Schultheiss Reiner
Published: November 2003

This presentation will cover the various types of shock wave devices that are known to have completed serious patient studies for orthopedic applications. This will include high energy and low energy instruments, as well as focused and unfocused devices, and the method which each device uses to generate a shockwave. The presentation will not be limited only to those devices that have been FDA approved, but will include those that are currently in trials or are expected to begin trials with the FDA in the near future. The power of the equipment, the applications, and the number of treatment sessions generally used will be examined. Some of the devices which are evaluated in particular are the equipment from HMT, Dornier, Siemens, and Storz.
Discussion of errors in the Green’s function parabolic equation for outdoor sound propagation
Authors: Cooper Jennifer , Swanson David C.
Published: November 2003

As is to be expected of any numerical method, use of the Green’s function parabolic equation (GFPE) does result in small errors that can propagate and increase. The main causes of errors in using the GFPE for outdoor sound propagation with constant sound speeds appear to be inadequate spatial sampling, approximated starting fields, and errors in the numerical integration used to compute the surface wave. The relative significance of these errors as well as a set of appropriate computational parameters for avoiding or minimizing them will be discussed. With the proper parameter selection (for step sizes, attenuation layer depth, etc.), the GFPE produces reliably accurate results for outdoor sound propagation even over finite impedance grounds and beyond barriers or changes in ground height.
Children’s need for favorable acoustics in schools
Authors: Nelson Peggy B.
Published: November 2003

Children continue to improve their understanding of speech in noise and reverberation throughout childhood and adolescence. They do not typically achieve adult performance levels until their late teenage years. As a result, schools that are designed to be acoustically adequate for adult understanding may be insufficient for full understanding by young children. In addition, children with hearing loss, those with attention problems, and those learning in a non-native language require even more favorable signal-to-noise ratios. This tutorial will review the literature gathered by the ANSl/ASA working group on classroom acoustics that shaped the recommendations of the working group. Special topics will include speech perception data from typically developing infants and children, from children with hearing loss, and from adults and children listening in a non-native language. In addition, the tutorial will overview recommendations contained within ANSI standard 12.60-2002: Acoustical Performance Criteria, Design Requirements, and Guidelines for Schools. The discussion will also include issues related to designing quiet classrooms and working with local schools and professionals.