bluuebunny/crossref_metadata_2025 huggingface dataset:
Location of holes in silicon-rich oxide as memory states
Authors: Crupi I. , Lombardo S. , Rimini E. , Gerardi C. , Fazio B. , Melanotte M.
Published: October 2002

The induced changes of the flatband voltage by the location of holes in a silicon-rich oxide (SRO) film sandwiched between two thin SiO2 layers [used as gate dielectric in a metal–oxide–semiconductor (MOS) capacitor] can be used as the two states of a memory cell. The principle of operation is based on holes permanently trapped in the SRO layer and reversibly moved up and down, close to the metal and the semiconductor, in order to obtain the two logic states of the memory. The concept has been verified by suitable experiments on MOS structures. The device exhibits an excellent endurance behavior and, due to the low mobility of the holes at low field in the SRO layer, a much longer refresh time compared to conventional dynamic random access memory cells.
Type II InAs/GaSb superlattice photovoltaic detectors with cutoff wavelength approaching 32 μm
Authors: Wei Yajun , Gin Aaron , Razeghi Manijeh , Brown Gail J.
Published: October 2002

We report the most recent advance in the area of type II InAs/GaSb superlattice photovoltaic detectors that have cutoff wavelengths beyond 25 μm, with some at nearly 32 μm. The photodiodes with a heterosuperlattice junction showed Johnson noise limited peak detectivity of 1.05×1010 cm Hz1/2/W at 15 μm under zero bias, and peak responsivity of 3 A/W under −40 mV reverse bias at 34 K illuminated by ∼300 K background with a 2π field-of-view. The maximum operating temperature of these detectors ranges from 50 to 65 K. No detectable change in the blackbody response has been observed after 5–6 thermal cyclings, with temperature varying between 15 and 296 K in vacuum.
Food bytes: intelligent systems in the food industry
Authors: Corney David
Published: October 2002

Computers have transformed the design of everything from cars to coffee cups. Now the food industry faces the same revolution, with intelligent computer models being used in the design, production and marketing of food products. The combined market capitalisation of the world’s biggest food, cosmetics, tobacco, clothing and consumer electronics companies is $2 trillion, forming the world’s 500 richest companies. Many of these “fast‐moving consumer goods” companies now apply intelligent computer models to the design, production and marketing of their products. Manufacturers aim to develop and produce high volumes of these commodities with minimum costs, maximum consumer appeal, and of course, maximum profits. Products have limited lifetimes following the fashions of the consumer‐driven marketplace. With food and drink, little is known about many of the underlying characteristics and processes. Product development and marketing must therefore be rapid, flexible and use raw data alongside existing expert knowledge. Intelligent systems, such as neural networks, fuzzy logic and genetic algorithms, mimic human skills such as the ability to learn from incomplete information, to adapt to changing circumstances, to explain their decisions and to cope with novel situations. These systems are being used to tackle a growing range of problems, from credit card fraud detection and stock market prediction to medical diagnosis and weather forecasting. This paper introduces intelligent systems and highlights their use in all aspects of the food and drink industry, from ingredient selection, through product design and manufacture, to packaging design and marketing.
Customer perceptions of services brands: a case study of J.D. Wetherspoons
Authors: Jones Peter , Shears Peter , Hillier David , Clarke‐Hill Colin
Published: October 2002

The service sector has dominated the economy of most advanced capitalist societies for some time but the branding of services has received much less attention than the branding of products in the literature. This case study of J.D. Wetherspoons, the UK’s leading pub brand, offers a simple and exploratory examination of a prominent services brand and as such looks to add to the growing number of studies in this field. The case outlines the development of pub brands within the UK and the origins and growth of J.D. Wetherspoons and its definition of its own brand attributes. The empirical investigation goes on to explore customers’ perceptions of the Wetherspoons brand. The case study suggests that the company has been successful in establishing a distinctive brand identity as a pub that sells a wide range of beers at cheap prices, but that some of the company’s other brand attributes are much less clearly perceived by customers and that staff behaviour is not always very effective in supporting and enhancing the brand.
Researching the social Web: marketing information from virtual communities
Authors: Maclaran Pauline , Catterall Miriam
Published: October 2002

This paper argues that, by focusing on the use of the Internet for one‐to‐one communications, marketers are in danger of ignoring the many‐to‐many communications that are taking place as consumers interact with one another. The authors explore the increasing proliferation of Internet discussion groups and chat rooms that are often market‐orientated in their focus and discuss how the study of virtual communities can provide rich insights for marketers. Detailing how ethnographic research methods can assist the understanding of such online environments, they consider the theoretical and methodological differences between offline and online ethnographic research.
The state of customer management performance in Malaysia
Authors: Starkey Michael W. , Williams David , Stone Merlin
Published: October 2002

First, this paper explores the many varied, and often confusing, definitions of relationship marketing, customer relationship management (CRM) and customer management (CM). Then it reports the results of a survey that examined the CM performance of 34 companies in the consumer banking, credit card, insurance, oil (lubricants) and automotive industries in Malaysia. The research was conducted using the Customer Management Assessment ToolTM (CMATTM) developed by QCi Ltd, a management consultancy that specialises in assessing and improving CM. CM performance was found to be especially poor in insurance and consumer banking. The best performing sector was the credit card industry.
E‐commerce processes: a study of criticality
Authors: Duffy G. , Dale B.G.
Published: October 2002

This paper, based on interviews undertaken with consultants experienced in e‐commerce engagements, has identified ten process which are critical to the success of e‐commerce. The processes are: order fulfilment, revenue generation/collection, financial control, IT/Web changes, business processes, e‐integration, order generation, call centre integration, 24/7 operation, and consumer behaviour. The paper explores the e‐commerce modes and models and relates them to the ten processes. From this analysis the overall challenges facing e‐commerce, with respect to the modes and models, are pinpointed.
Adopting customer relationship management technology
Authors: Xu Yurong , Yen David C. , Lin Binshan , Chou David C.
Published: October 2002

Now customer relationship marketing (CRM) solutions might be the hottest topic in business world. CRM impelled the growth of both B2B and B2C markets. But the issue is how to apply the cutting‐edge CRM solutions. Do people really understand what CRM is and why they should install CRM? The mistaken concept of CRM may have disastrous effects on the company. This paper begins with the basic concepts of CRM, elaborates the characteristics, reviews its brief history and addresses the current status of CRM. Then it develops the extended concepts of CRM from micro‐ and macro‐ perspectives. In the “Implementation and tips” section, it concludes the proper steps to approach CRM and how to bear a right attitude towards CRM solutions. Related Government rules are also covered.
Has MRP run its course? A review of contemporary developments in planning systems
Authors: Kumar Sameer , Meade David
Published: October 2002

The onset of global competition in the 1970s began to change the manufacturing environment drastically. The advent of the computer created an opportunity for the developers of material requirements planning (MRP) concepts to automate many of the manual practices employed in manufacturing for acquiring and tracking of materials. This resulted in more efficient manufacturing operations in terms of labor for planning activities and better material control. Technology was expanded to include capacity planning and production schedule control. The acceptance in industry for the new “tool” was monumental and soon a new industry was born. For some time MRP allowed manufacturers to perform at higher levels of proficiency. However, the demands and expectations of the customers have continued to change and manufacturers wishing to keep pace with competition are beginning to question if MRP is still a valid tool for production planning and control. As a result new concepts have begun to emerge. These new approaches call for an abandonment of some of the foundational components of MRP.
Some aspects of using CASE tools in a Fusion‐based application development project for production optimization
Authors: Bajgoric N. , Altinel I.K. , Draman M. , Ünal A.T.
Published: October 2002

An application development framework for a software project based on fusion as an object‐oriented application development method is presented. An object‐oriented approach has been adopted for the design and implementation of the prototype interactive visual modelling system for building a visual presentation of a refinery process and creation of linear programming model for optimizing production decision variables. The main reason for this selection is the consideration of object‐oriented programming (OOP) as an obvious vehicle for the development of complex visual interactive modelling systems. The main dimensions of the framework are as follows: OO approach, fusion method, computer‐aided software engineering (CASE) tool, application development tool, GUI development tool, and C++ as an implementation language.
The effects of material constants on the micropolar elastic honeycomb structure with negative Poisson's ratio using the finite element method
Authors: Huang Fuang‐Yuan , Yan Biing‐Hwa , Yang Der‐Uei
Published: October 2002

To investigate the relation between the Poisson's ratio of a re‐entrant honeycomb structure by varying the micropolar material constants such as micropolar Young's modulus Em, micropolar Poisson's ratio Vm, characteristic length l, coupling factor N, and micropolar elastic constants in accordance with the micropolar elastic restrictions, a 2‐D triangular finite element formulation including an extra degree of freedom was derived on the basis of Eringen's micropolar elasticity theory by using a linear triangular element. The effects on the structural Poisson's ratio of the honeycomb structure are studied in detail.
Reliability of reinforced concrete structures using stochastic finite elements
Authors: Martins Gomes Herbert , Miguel Awruch Armando
Published: October 2002

In this paper, special emphasis is given to uncertainties in the evaluation of the structural behavior, looking for a better representation of the system characteristics and quantification of the significance of these uncertainties in structural design. The reliability analysis of reinforced concrete structures is performed taking into account the spatial variability of material properties. The finite element method is used to analyze reinforced concrete structures. A multidimensional non‐Gaussian stochastic field generation model (independent of the finite element mesh) is developed and used. The reliability analysis is carried out employing the first order reliability method. Numerical examples are presented to study how to generate correlated non‐Gaussian stochastic fields and determine the reliability of a reinforced concrete structure with respect to a limit state function.
Thermo‐hydro‐mechanical modelling of high performance concrete at high temperatures
Authors: Schrefler Bernhard A. , Majorana Carmelo E. , Khoury Gabriel A. , Gawin Dariusz
Published: October 2002

This paper presents the physical, mathematical and numerical models forming the main structure of the numerical analysis of the thermal, hydral and mechanical behaviour of normal, high‐performance concrete (HPC) and ultra‐high performance concrete (UHPC) structures subjected to heating. A fully coupled non‐linear formulation is designed to predict the behaviour, and potential for spalling, of heated concrete structures for fire and nuclear reactor applications. The physical model is described in more detail, with emphasis being placed upon the real processes occurring in concrete during heating based on tests carried out in several major laboratories around Europe as part of the wider high temperature concrete (HITECO) research programme. A number of experimental and modelling advances are presented in this paper. The stress‐strain behaviour of concrete in direct tension, determined experimentally, is input into the model. The hitherto unknown micro‐structural, hydral and mechanical behaviour of HPC/UHPC were determined experimentally and the information is also built into the model. Two examples of computer simulations concerning experimental validation of the model, i.e. temperature and gas pressure development in a radiatively heated HPC wall and hydro‐thermal and mechanical (damage) performance of a square HPC column during fire, are presented and discussed in the context of full scale fire tests done within the HITECO research programme.
Parallel computation of two‐dimensional rotational flows of viscoelastic fluids in cylindrical vessels
Authors: Baloch A. , Grant P.W. , Webster M.F.
Published: October 2002

The numerical simulation of two‐dimensional incompressible complex flows of viscoelastic fluids is presented. The context is one, relevant to the food industry (dough kneading), of stirring within a cylindrical vessel, where stirrers are attached to the lid of the vessel. The motion is driven by the rotation of the outer vessel wall, with various stirrer locations. With a single stirrer, both a concentric and an eccentric configuration are considered. A double‐stirrer eccentric case, with two symmetrically arranged stirrers, is also contrasted against the above. A parallel numerical method is adopted, based on a finite element semi‐implicit time‐stepping Taylor‐Galerkin/pressure‐correction scheme. For viscoelastic fluids, constant viscosity Oldroyd‐B and two shear‐thinning Phan‐Thien/Tanner constitutive models are employed. Both linear and exponential models at two different material parameters are considered. This permits a comparison of various stress, shear and extensional properties and their respective influences upon the flow fields generated. Variation with increasing speed of vessel and change in mixer geometry are analysed with respect to the flow kinematics and stress fields produced. Optimal kneading scenarios are commended with asymmetrical stirrer positioning, one‐stirrer proving better than two. Then, models with enhanced strain‐hardening, amplify levels of localised maxima in rate‐of‐work done per unit power consumed. Simulations are conducted via distributed parallel processing, performed on work‐station clusters, employing a conventional message passing protocol (PVM). Parallel results are compared against those obtained on a single processor (sequential computation). Ideal linear speed‐up with the number of processors has been observed.
Competitor networks: international competitiveness through collaboration
Authors: Marcela Herrera Bernal Sandra , Burr Caroline , Johnsen Rhona E.
Published: October 2002

The case of the global freight forwarding industry is one example where networks of small‐ to medium‐sized enterprises (SMEs) are playing an increasingly important role. Internationalisation opportunities and competitive advantages may be obtained by SMEs in pooling their resources and exchanging information and expertise. This empirical case study examines horizontal collaboration between SMEs that consider their other network members, first and foremost, as competitors.
Validity of the sonar equation and Babinet’s principle for scattering in a stratified medium
Authors: Ratilal Purnima , Lai Yisan , Makris Nicholas C.
Published: October 2002

The sonar equation rests on the assumption that received sound pressure level after scattering can be written in decibels as a sum of four terms: source level, transmission loss from the source to the target, target strength, and transmission loss from the target to the receiver. This assumption is generally not valid for scattering in a shallow water waveguide and can lead to large errors and inconsistencies in estimating a target’s scattering properties as well as its limiting range of detection. By application of coherent waveguide scattering theory, the sonar equation is found to become approximately valid in a shallow water waveguide when the object’s complex scatter function is roughly constant over the equivalent horizontal grazing angles ±Δψ spanned by the dominant waveguide modes. This is approximately true (1) for all objects of spatial extent L and wavelength λ when 2Δψ<λ/2L and (2) for spheres and certain other rounded objects in nonforward scatter azimuths, even when (1) does not hold. The sonar equation may be made valid by lowering the active frequency of operation in a waveguide. This is often desirable because it greatly simplifies the analysis necessary for target classification and localization. Similarly, conditions are given for when Babinet’s principle becomes approximately valid in a shallow water waveguide.
Spectral and temporal cues to pitch in noise-excited vocoder simulations of continuous-interleaved-sampling cochlear implants
Authors: Green Tim , Faulkner Andrew , Rosen Stuart
Published: October 2002

Four-band and single-band noise-excited vocoders were used in acoustic simulations to investigate spectral and temporal cues to melodic pitch in the output of a cochlear implant speech processor. Noise carriers were modulated by amplitude envelopes extracted by half-wave rectification and low-pass filtering at 32 or 400 Hz. The four-band, but not the single-band processors, may preserve spectral correlates of fundamental frequency (F0). Envelope smoothing at 400 Hz preserves temporal correlates of F0, which are eliminated with 32-Hz smoothing. Inputs to the processors were sawtooth frequency glides, in which spectral variation is completely determined by F0, or synthetic diphthongal vowel glides, whose spectral shape is dominated by varying formant resonances. Normal listeners labeled the direction of pitch movement of the processed stimuli. For processed sawtooth waves, purely temporal cues led to decreasing performance with increasing F0. With purely spectral cues, performance was above chance despite the limited spectral resolution of the processors. For processed diphthongs, performance with purely spectral cues was at chance, showing that spectral envelope changes due to formant movement obscured spectral cues to F0. Performance with temporal cues was poorer for diphthongs than for sawtooths, with very limited discrimination at higher F0. These data suggest that, for speech signals through a typical cochlear implant processor, spectral cues to pitch are likely to have limited utility, while temporal envelope cues may be useful only at low F0.
Comment on “On the complex conjugate roots of the Rayleigh equation: The leaky surface wave” [J. Acoust. Soc. Am. 110, 2867 (2001)] (L)
Authors: Harris John G. , Achenbach Jan D.
Published: October 2002

The authors comment upon the role played by those roots of the Rayleigh equation that are referred to as extraneous, as well as upon the work of the paper given in the title.
A jet engine noise measurement and prediction tool
Authors: Frendi Abdelkader , Dorland Wade D. , Maung Thein , Nesman Tom , Wang Ten-See
Published: October 2002

In this paper, the authors describe an innovative jet engine noise measurement and prediction tool. The tool measures sound-pressure levels and frequency spectra in the far field. In addition, the tool provides predicted results while the measurements are being made. The predictions are based on an existing computational fluid dynamics database coupled to an empirical acoustic radiation model based on the far-field approximation to the Lighthill acoustic analogy. Preliminary tests of this acoustic measurement and prediction tool produced very encouraging results.
Computational aeroacoustics of phonation, Part II: Effects of flow parameters and ventricular folds
Authors: Zhang Cheng , Zhao Wei , Frankel Steven H. , Mongeau Luc
Published: October 2002

The results are described of the second part of an ongoing study aimed at performing direct numerical simulations of translaryngeal flows during phonation. The use of accurate numerical schemes allows the radiated sound to be calculated directly, without the need for acoustic analogy models. The goal is to develop a better understanding of this class of flow, and of the basic sound generation mechanisms involved in phonation. In the present study, the effects of subglottal pressure and of glottal oscillation frequency on the near-field flow and farfield sound were investigated. The effects of the presence of the ventricular folds downstream of the oscillating glottal region were also examined. The results highlighted the effects of subglottal pressure and oscillation frequency on the jet vortical structure, wall pressure and shear stress, and sound radiation. Jet impingement on the ventricular folds introduced additional dipole sources similar to those observed in problems involving grazing flows over cavities.
Underwater audiogram of a Pacific walrus (Odobenus rosmarus divergens) measured with narrow-band frequency-modulated signals
Authors: Kastelein R. A. , Mosterd P. , van Santen B. , Hagedoorn M. , de Haan D.
Published: October 2002

The underwater hearing sensitivity of an 18-year-old male Pacific walrus was measured in a pool by using a go/no-go response paradigm and the up-down staircase method. Auditory sensitivity was measured using narrow-band, frequency-modulated signals (1500 ms duration) with center frequencies ranging from 0.125 to 15 kHz. The resulting underwater audiogram (50% detection thresholds) for this individual walrus shows the typical mammalian U-shape. Maximum sensitivity (67 dB re 1 μPa) occurred at 12 kHz. The range of best hearing (10 dB from the maximum sensitivity) was from 1 to 12 kHz. Sensitivity fell gradually below 1 kHz and dropped off sharply above 12 kHz. The animal showed a peculiar insensitivity for 2 kHz signals. His much higher sensitivity for 1.5- and 3-kHz signals indicated that this is a narrow-band phenomenon. Walrus hearing is relatively sensitive to low frequency sound, thus the species is likely to be susceptible to anthropogenic noise. The thresholds found during a small test with four frequencies with signal durations of 300 ms did not differ significantly from those obtained with signal durations of 1500 ms.
Optimizing the acquisition time of the middle latency response using maximum length sequences and chirps
Authors: Bell Steven L. , Allen Robert , Lutman Mark E.
Published: October 2002

The middle latency response (MLR) may be used as an indicator of anesthetic depth but has been criticized due to its long acquisition time. This study explores methods for optimizing recording of the MLR to maximize signal-to-noise ratio (SNR) and hence reduce acquisition time. The first experiment investigates the effects of increasing stimulation rate beyond conventional values and also using higher rates by means of maximum length sequences (MLS). The second experiment compares the use of click and chirp stimuli to elicit the MLR, both at conventional and MLS stimulation rates. For all conditions total recording duration is fixed at 185 s and stimulation level is fixed at 60 dB SL. It was found that SNR increases progressively with rate using conventional click stimulation until the theoretical rate limit is reached at the reciprocal of the response duration. The SNR improvement is equivalent to increasing test speed by a factor of 3. Using MLS stimulation, the SNR increases further until a maximum is reached at a rate of 167 clicks/s, equivalent to a fivefold test speed improvement relative to a conventional recording at 5 clicks/s. The use of chirp stimuli designed to compensate for the frequency dependent cochlear traveling wave delay produces an increase in wave V–Na amplitude at all recording rates. For the later latency waves of the response an increase in amplitude is seen for MLS, but not for conventional chirp trains. The optimum SNR was obtained using chirp stimuli at a MLS rate of 167 opportunities/s. It is concluded that the combination of chirps and MLS can reduce acquisition time to less than one-tenth of that required for conventional stimulation at 5 clicks/s for the same SNR. This would confer material benefits for estimating anesthetic depth using MLR.
Performance of an underwater acoustic volume array using time-reversal focusing
Authors: Root Joseph A. , Rogers Peter H.
Published: October 2002

Time reversal permits acoustic focusing and beam forming in inhomogeneous and/or high-scattering environments. A volumetric array geometry can suppress back lobes and can fit a large, powerful array of elements into small spaces, like the free-water spaces on submarines. This research investigates applying the time-reversal method to an underwater acoustic volume array. The experiments evaluate the focusing performance of a 27-element volume array when different scattering structures are present within the volume of the array. The array is arranged in a 3×3×3 cubic matrix configuration with 18.75-cm vertical and horizontal element spacing. The system utilizes second-derivative Gaussian pulses to focus on a point 30 cm from the array. Results include a comparison between time-reversal focusing and standard focusing, an evaluation of the volume array’s ability to suppress back lobes, and an analysis of how different scattering environments affect focal region size. Potential underwater applications for a volume array using time reversal include acoustic imaging, naval mine hunting, sonar, and underwater communications.
Measurements and modeling of acoustic scattering from partially and completely buried spherical shells
Authors: Tesei A. , Maguer A. , Fox W. L. J. , Lim R. , Schmidt H.
Published: October 2002

The use of low-frequency sonars (2–15 kHz) is explored to better exploit scattering features of buried targets that can contribute to their detection and classification. Compared to conventional mine countermeasure sonars, sound penetrates better into the sediment at these frequencies, and the excitation of structural waves in the targets is enhanced. The main contributions to target echo are the specular reflection, geometric diffraction effects, and the structural response, with the latter being particularly important for man-made elastic objects possessing particular symmetries such as bodies of revolution. The resonance response derives from elastic periodic phenomena such as surface circumferential waves revolving around the target. The GOATS’98 experiment, conducted jointly by SACLANTCEN and MIT off the island of Elba, involved controlled monostatic measurements of scattering by spherical shells which were partially and completely buried in sand, and suspended in the water column. The analysis mainly addresses a study of the effect of burial on the dynamics of backscattered elastic waves, which can be clearly identified in the target responses, and is based on the comparison of measurements with appropriate scattering models. Data interpretation results are in good agreement with theory. This positive result demonstrates the applicability of low-frequency methodologies based on resonance analysis to the classification of buried objects.
The magnitude of radiation force on ultrasound contrast agents
Authors: Dayton Paul A. , Allen John S. , Ferrara Katherine W.
Published: October 2002

High-speed photography of insonified bubbles with a time resolution of 10 ns allows observations of translation due to radiation force, in addition to the visualization of radial oscillations. A modified version of the Rayleigh–Plesset equation is used to estimate the radius–time behavior of insonified microbubbles, and the accuracy of this model is verified experimentally. The translation of insonified microbubbles is calculated using a differential equation relating the acceleration of the bubble to the forces due to acoustic radiation and the drag imposed by the fluid. Simulations and experiments indicate that microbubbles translate significant distances with clinically relevant parameters. A 1.5 micron radius contrast agent can translate over 5 microns during a single 20-cycle, 2.25 MHz, 380 kPa acoustic pulse, achieving velocities over 0.5 m/s. Therefore, radiation force should be considered during an ultrasonic examination because of the possibility of influencing the position and flow velocity of the contrast agents with the interrogating acoustic beam.
Chaotic vibration induced by turbulent noise in a two-mass model of vocal folds
Authors: Jiang Jack J. , Zhang Yu
Published: October 2002

The contribution of turbulent noise was modeled in symmetric vocal folds. A two-mass model was used to simulate irregular vocal fold vibrations. The threshold values of system parameters to produce irregular vibrations were decreased as a result of turbulent airflow. Periodic vibrations were then driven into the regions of irregular vibrations. Using nonlinear dynamics including Poincaré map and Lyapunov exponents, irregular vibrations were demonstrated as chaos. For the deterministic vocal-fold model with noise free and steady airflow, a fine period-doubling bifurcation cascade was shown in a bifurcation diagram. However, turbulent noise added to the vocal-fold model would induce chaotic vibrations, broaden the regions of irregular vocal fold vibrations, and inhibit the fine period-doubling bifurcations in the bifurcation diagrams. The perturbations from neurological and biomechanical effects were simulated as a random variation of the vocal fold stiffness. Turbulent noise as an external random source, as well as random stiffness perturbation as an internal random source, played important roles in the presence of irregular vocal fold vibrations.
Optimal design of panel speaker array with omnidirectional characteristics
Authors: Bai Mingsian R. , Chung Kuochan
Published: October 2002

A panel speaker system intended for a projection screen is developed. Like other sound sources with large dimension, the panel speaker has a beaming problem in high frequencies. To alleviate the problem, panel speakers are integrated into an array, with optimal electronic compensation for omnidirectional response and array efficiency. The heart of the design procedure is a three-stage optimization scheme involving two nonlinear and nonconvex objectives. The process is interactive, allowing the array coefficients to be tailored so that the specifications of directional response can be met. The optimal design of panel speaker array is then implemented by using a multichannel digital signal processor. In addition, a Hilbert transformer is required to produce the quadrature components of the array coefficients. A small array and a large matrix were constructed to validate the implemented array signal processing system. The experimental results indicate that, without degradation of efficiency, the proposed optimization technique in conjunction with electronic compensation is effective in attaining omnidirectional radiation property.
Sound-wave propagation in a membrane–duct (L)
Authors: Choi Sunghoon , Kim Yang-Hann
Published: October 2002

Theoretical analysis for sound waves in a flexible membrane mounted in an otherwise rigid duct is presented. It has been shown that supersonic fluid-dominant waves and subsonic membrane-dominant waves exist. The latter provides powerful mechanism of transmission loss through the membrane damping and destructive reflections at the edges of the membrane, while the cross-sectional area remains constant. The effect of mean flow and external fluid is also considered.
The effect of spatial separation on informational and energetic masking of speech
Authors: Arbogast Tanya L. , Mason Christine R. , Kidd Gerald
Published: October 2002

The effect of spatial separation of sources on the masking of a speech signal was investigated for three types of maskers, ranging from energetic to informational. Normal-hearing listeners performed a closed-set speech identification task in the presence of a masker at various signal-to-noise ratios. Stimuli were presented in a quiet sound field. The signal was played from 0° azimuth and a masker was played either from the same location or from 90° to the right. Signals and maskers were derived from sentences that were preprocessed by a modified cochlear-implant simulation program that filtered each sentence into 15 frequency bands, extracted the envelopes from each band, and used these envelopes to modulate pure tones at the center frequencies of the bands. In each trial, the signal was generated by summing together eight randomly selected frequency bands from the preprocessed signal sentence. Three maskers were derived from the preprocessed masker sentences: (1) different-band sentence, which was generated by summing together six randomly selected frequency bands out of the seven bands not present in the signal (resulting in primarily informational masking); (2) different-band noise, which was generated by convolving the different-band sentence with Gaussian noise; and (3) same-band noise, which was generated by summing the same eight bands from the preprocessed masker sentence that were used in the signal sentence and convolving the result with Gaussian noise (resulting in primarily energetic masking). Results revealed that in the different-band sentence masker, the effect of spatial separation averaged 18 dB (at 51% correct), while in the different-band and same-band noise maskers the effect was less than 10 dB. These results suggest that, in these conditions, the advantage due to spatial separation of sources is greater for informational masking than for energetic masking.
Sound propagation in concentrated emulsions: Comparison of coupled phase model and core-shell model
Authors: Evans Jonathan M. , Attenborough Keith
Published: October 2002

The predictions of two models of sound propagation in concentrated emulsions are compared with experimental measurements of ultrasonic velocity and attenuation in emulsions with volume fractions up to 0.7. The core-shell model includes irreversible heat transfer, viscoinertial forces, and multiple scattering [McClements et al., J. Acoust. Soc. Am. 105, 915–918 (1999)]. This model accounts for the effect of thermal interactions between neighboring particles by introducing an effective medium, and is valid for all volume fractions. The coupled phase model includes irreversible heat transfer and viscoinertial forces, and also is valid for all volume fractions, since it is derived from volume-averaged balance equations [J. M. Evans and K. Attenborough, J. Acoust. Soc. Am. 102, 278–282 (1997)]. This model has a significantly simpler formulation than the core-shell model and does not require the assumption of an effective medium. The coupled phase model is shown to be a good approximation to the core-shell model when the acoustic radius is small. Despite the fact that it does not include thermal interactions, the coupled phase model is shown to give at least as good agreement as the core-shell model with the experimental data, for all volume fractions, as long as the acoustic radius is less than 0.01.
Topology optimization of the kerf fillings in linear phased arrays for therapy
Authors: Lin Yuan , Grosh Karl
Published: October 2002

Cross talk in ultrasonic arrays is an important problem that affects the array performance. For therapy arrays, cross talk decreases the acoustic power efficiency and array steering capabilities. Since arrays used for therapy are generally air-backed, structure-borne cross talk from the kerf fillings that connect the elements is predominant. In this paper, design strategies are developed to reduce the cross talk in linear phased arrays by optimizing the topology of kerf fillings. Two topology optimization schemes, an element-by-element design and layer-by-layer design, are developed. Sequential linear programming is used to solve the nonlinear optimization problem. Using an array subset technique as the basis for the design, an objective function based on maximizing the normal velocity response of the wet surface of an electrically driven element is shown to improve both the power output and steering of the array.
Hearing loss in shoemakers exposed to noise and solvent in Porto Alegre, Brazil
Authors: Steffen Vera , Ponte Cynthia , Alano Aleteia , Limberger Renata , Simoes Flavio , Abella Hudson , Sebben Viviane , Marques Vera , Pereira Denise , Gerges Samir
Published: October 2002

Clinical and experimental studies indicate a possible harmful effect of chemicals, especially organic solvents, on the hearing system. In combined exposure to noise and solvents, very common in industry, it is most likely that a synergetic action of these factors enhances the traumatizing effect of exposure to noise. The aim of this study was to access the incidence and the risk of hearing impairment in 80 shoemakers. In this work we studied the effects of occupational exposure to solvent and noise in the hearing of workers of a factory in Porto Alegre, Brazil. In the studied group we analyzed solvents concentration in the air, biological marker for toluene in urine (hippuric acid), and levels of environmental noises. We analyze too the flow sheet of industrial production. The analysis of these results showed the bilateral hearing loss of 22.45%, and 18.37% in unilateral loss, in the workers of occupational exposure to toluene and noise, with levels allowed by the Brazilian legislation. The findings suggest that exposure to toluene and noise has a toxic effect on the auditory system. Further research is needed for the better understanding of the interaction of these and other agents in the auditory systems. [Work supported by CNq/FEPPS.]
Linguistically informed automatic speech recognition
Authors: Espy-Wilson Carol Y.
Published: October 2002

The development of an automatic event-based speech recognition system (EBS) that relies heavily on acoustic phonetics (to guide the recognition process and to extract relevant information) and combines a phonetic-feature hierarchy with a uniform statistical framework (at present, Support Vector Machines) to provide adaptability and flexibility is currently under way. This recognition framework allows for easy assessment and distinction of the performances of the acoustic parameters versus that of the pattern recognizer. The overall structure of EBS involves (1) landmark detection based on acoustic parameters that are related to the source and manner-of-articulation phonetic features and (2) use of the landmarks in the extraction of other acoustic parameters related to the place-of-articulation phonetic features. This talk will focus on the development of the acoustic parameters and the need for relative parameters for speaker independence, multi-time-scale processing to capture the dynamics of phonetic segments and extensive evaluation of the parameters to hone in on direct measures of the relevant acoustic properties. [Work supported by NSF and NIH.]
An experimental study for scale prevention in boiler by use of ultrasonic waves
Authors: Heo Pil Woo , Lee Yang Lae , Lim Eui Su , Koh Kwang Sik
Published: October 2002

In case of a boiler, scale is made on the surface of tube by the chemical reactions of Ca and Mg ions contained in the water and heat transfer rate is reduced because of the increment of heat resistance. Thus, it brings about the reduced energy transfer efficiency and also environmental pollution due to the use of chemicals for scale removing. In this paper, we have first investigated the effects of irradiated ultrasonic wave on water with impurities in a beaker. The experiments show that exposed water is less transparent and has finer particles as compared to unexposed water. This means that the ultrasound shakes water in the beaker and breaks out particles, and so broken fine particles are suspend in the state of less precipitation. Second, the laboratory experiment with an exposed sample in the similar condition to the boiler shows better scale prevention effects as compared to the unexposed one. And also 20 kHz ultrasound represents about 3 times better scale prevention effects than 40 kHz. Finally, scale prevention experiments in the real small boiler tell us exposed sample results in 3659% less scale formation than an unexposed one.
Advanced Technology Paths to Global Climate Stability: Energy for a Greenhouse Planet
Authors: Hoffert Martin I. , Caldeira Ken , Benford Gregory , Criswell David R. , Green Christopher , Herzog Howard , Jain Atul K. , Kheshgi Haroon S. , Lackner Klaus S. , Lewis John S. , Lightfoot H. Douglas , Manheimer Wallace , Mankins John C. , Mauel Michael E. , Perkins L. John , Schlesinger Michael E. , Volk Tyler , Wigley Tom M. L.
Published: October 2002

Stabilizing the carbon dioxide–induced component of climate change is an energy problem. Establishment of a course toward such stabilization will require the development within the coming decades of primary energy sources that do not emit carbon dioxide to the atmosphere, in addition to efforts to reduce end-use energy demand. Mid-century primary power requirements that are free of carbon dioxide emissions could be several times what we now derive from fossil fuels (∼10
13
watts), even with improvements in energy efficiency. Here we survey possible future energy sources, evaluated for their capability to supply massive amounts of carbon emission–free energy and for their potential for large-scale commercialization. Possible candidates for primary energy sources include terrestrial solar and wind energy, solar power satellites, biomass, nuclear fission, nuclear fusion, fission-fusion hybrids, and fossil fuels from which carbon has been sequestered. Non–primary power technologies that could contribute to climate stabilization include efficiency improvements, hydrogen production, storage and transport, superconducting global electric grids, and geoengineering. All of these approaches currently have severe deficiencies that limit their ability to stabilize global climate. We conclude that a broad range of intensive research and development is urgently needed to produce technological options that can allow both climate stabilization and economic development.
Microbial Dehalorespiration with 1,1,1-Trichloroethane
Authors: Sun Baolin , Griffin Benjamin M. , Ayala-del-Rı́o Héctor L. , Hashsham Syed A. , Tiedje James M.
Published: October 2002

1,1,1-Trichloroethane (TCA) is a ubiquitous environmental pollutant because of its widespread use as an industrial solvent, its improper disposal, and its substantial emission to the atmosphere. We report the isolation of an anaerobic bacterium, strain TCA1, that reductively dechlorinates TCA to 1,1-dichloroethane and chloroethane. Strain TCA1 required H
2
as an electron donor and TCA as an electron acceptor for growth, indicating that dechlorination is a respiratory process. Phylogenetic analysis indicated that strain TCA1 is related to gram-positive bacteria with low DNA G+C content and that its closest relative is
Dehalobacter restrictus
, an obligate H
2
-oxidizing, chloroethene-respiring bacterium.
Hijacking of Host Cell IKK Signalosomes by the Transforming Parasite
Theileria
Authors: Heussler Volker T. , Rottenberg Sven , Schwab Rebekka , Küenzi Peter , Fernandez Paula C. , McKellar Susan , Shiels Brian , Chen Zhijian J. , Orth Kim , Wallach David , Dobbelaere Dirk A. E.
Published: October 2002

Parasites have evolved a plethora of mechanisms to ensure their propagation and evade antagonistic host responses. The intracellular protozoan parasite
Theileria
is the only eukaryote known to induce uncontrolled host cell proliferation. Survival of
Theileria
-transformed leukocytes depends strictly on constitutive nuclear factor kappa B (NF-κB) activity. We found that this was mediated by recruitment of the multisubunit IκB kinase (IKK) into large, activated foci on the parasite surface. IKK signalosome assembly was specific for the transforming schizont stage of the parasite and was down-regulated upon differentiation into the nontransforming merozoite stage. Our findings provide insights into IKK activation and how pathogens subvert host-cell signaling pathways.
RNA Polymerase II Transcription in Murine Cells Lacking the TATA Binding Protein
Authors: Martianov Igor , Viville Stephane , Davidson Irwin
Published: October 2002

Inactivation of the murine TATA binding protein (TBP) gene by homologous recombination leads to growth arrest and apoptosis at the embryonic blastocyst stage. However, after loss of TBP, RNA polymerase II (pol II) remains in a transcriptionally active phosphorylation state, and in situ run-on experiments showed high levels of pol II transcription comparable to those of wild-type cells. In contrast, pol I and pol III transcription was arrested. Our results show a differential dependency of the RNA polymerases on TBP and provide evidence for TBP-independent pol II transcriptional mechanisms that allow reinitiation and maintenance of gene transcription in vivo.
Role of Histone H3 Lysine 27 Methylation in Polycomb-Group Silencing
Authors: Cao Ru , Wang Liangjun , Wang Hengbin , Xia Li , Erdjument-Bromage Hediye , Tempst Paul , Jones Richard S. , Zhang Yi
Published: October 2002

Polycomb group (PcG) proteins play important roles in maintaining the silent state of HOX genes. Recent studies have implicated histone methylation in long-term gene silencing. However, a connection between PcG-mediated gene silencing and histone methylation has not been established. Here we report the purification and characterization of an EED-EZH2 complex, the human counterpart of the
Drosophila
ESC-E(Z) complex. We demonstrate that the complex specifically methylates nucleosomal histone H3 at lysine 27 (H3-K27). Using chromatin immunoprecipitation assays, we show that H3-K27 methylation colocalizes with, and is dependent on, E(Z) binding at an
Ultrabithorax
(
Ubx
) Polycomb response element (PRE), and that this methylation correlates with
Ubx
repression. Methylation on H3-K27 facilitates binding of Polycomb (PC), a component of the PRC1 complex, to histone H3 amino-terminal tail. Thus, these studies establish a link between histone methylation and PcG-mediated gene silencing.
Empiricism, Realism, and Religion
Authors: Thagard Paul
Published: October 2002

The Empirical Stance
. Bas C. van Fraassen. Yale University Press, New Haven, CT, 2002. 302 pp. $30, £22.50, €36. ISBN 0-300-08874-4.

In these lectures prepared for a general audience, van Frassen highlights the philosophical problems that surround the scientific revolution's shift from religious to secular "ways of seeing or conceiving of ourselves."
MAGNETIC DEPENDENCE OF HALL SIGN REVERSAL FOR Gd1-xPrxBa2Cu3O7-δ IN A VORTEX STATE
Authors: DAADMEHR V. , NAGHSHARA H. , AKHAVAN M.
Published: October 2002

We have investigated the sign reversal of Hall effect in high-temperature superconductors in the vortex state as a function of temperature for several samples of Gd 1-x Pr x Ba 2 Cu 3 O 7-δ with 0.2 ≥ x ≥ 0 in a magnetic field of 0–2 T. Multiple sign reversals of Hall resistivity have been observed in under-doped and partially over-doped samples. The Gd 1-x Pr x Ba 2 Cu 3 O 7-δ sample with x = 0.1 shows double sign change in Hall resistivity with variation of magnetic field, and a single sign reversal with variation of temperature. While for the x = 0.15 and x = 0.2 samples, no sign reversal is observed, for the x < 0.1 sample, one sign change of Hall resistivity with temperature over the magnetic field region is observed. The tan (θ H ) also shows a similar double sign reversal of Hall resistivity. This can be related to the particle-hole asymmetry and the complex nature of the Fermi surface.