bluuebunny/crossref_metadata_2025 huggingface dataset:
Forward-masked intensity discrimination: Duration effects and spectral effects
Authors: Schlauch Robert S. , Lanthier Nicole , Neve Joe
Published: July 2002

Three experiments were completed to examine the effect of masker duration and spectrum on forward-masked intensity discrimination. Four listeners participated in each experiment. Intensity discrimination was measured in quiet and in the presence of forward maskers using adaptive forced-choice procedures. The standard duration was either short (10 ms) or long (250 ms) in experiment 1 and short (10 ms) in experiment 2. The standard always occurred 100 ms after the offset of the masker. In the first experiment employing 1.0-kHz maskers and standards, a short duration masker (10 ms) produced more masking than a long duration masker (250 ms). A mid-level elevation of the Weber fraction was observed for all conditions. To ensure that the results of experiment 1 were not influenced by off-frequency listening, the second experiment employed a broadband noise masker. As before, a short duration (10 ms) masker produced more masking than a long duration masker (100 ms) and a mid-level elevation of Weber fractions was observed. This outcome is inconsistent with a peripheral sensory effect for which an increase in masker duration should result in a greater amount of adaptation, and, as a consequence, more masking. A third experiment employing a broadband noise masker and standard showed the greatest amount of masking for low-level standards, but only when the duration of the masker and standard was short. This result is similar to one seen for a single listener in the first experiment for short duration tonal maskers and standards. For this listener, a second tone presented at 4.133 kHz presented simultaneously with the 1.0-kHz masker reduced significantly the amount of masking for low-level standards, but the mid-level elevation of the Weber fraction remained. Taken together, these results suggest that perceptual similarity plays a role in forward-masked intensity discrimination but does not account entirely for the mid-level elevation of the Weber fraction.
Elastic guided waves in plates with surface roughness. II. Experiments
Authors: Lobkis O. I. , Chimenti D. E.
Published: July 2002

In this artice are reported fundamental experimental measurements on guided waves in plates with surface roughness; the experimental data are critically compared to theoretical calculations presented in Part I. All experiments, in either immersion or contact coupling mode, are modeled by the theory developed in I that exploits the phase-screen approximation. In this theory the effect of the rough surface on the received signal, on a local scale, is assumed to be restricted to the signal phase. The comparisons between experiment and predictions show good agreement in most regimes, despite the rather simplifying approximations contained in the calculation. The model is shown to fail only when the guided wave vector is close to a branch point, that is when the guided wave phase velocity approaches the compressional or shear wavespeeds of the plate. Near these values the internal partial waves comprising the guided wave strike the surfaces at grazing incidence or are evanescent, and a simple phase-screen model cannot account for this behavior. Elsewhere in the guided wave spectrum, agreement is quite good. Of practical significance is the finding that the rough-surface damping contrast can be maximized by configuring the experimental conditions to measure just below and well above the compressional critical angle. Aluminum samples, prepared by indenting or sandblasting and independently profiled to determine rms roughness, are measured in immersion and in contact transduction, the latter with wedge couplers and line sources. The influence of the roughness in immersion experiments is strongly affected by whether the upper or lower plate surface is rough, but only in the interaction zone between specular and nonspecular reflection components.
The effects of two temporal cues on pitch judgments
Authors: Carlyon Robert P.
Published: July 2002

A series of experiments required listeners to judge which of two sequentially presented pulse trains, bandpass filtered to contain only unresolved harmonics, had the higher pitch. The effects of two temporal cues were explored. The “common interval” cue refers to the fact that the interval between any two pulses in each train is an integer multiple of 1/F0, where F0 is the period of the pulse train. The “mean rate” cue arises from the fact that the number of pulses in any period of time is proportional to F0. It was manipulated, independently of the common interval cue, by removing a proportion of the pulses in each of two trains with different F0s. The mean rate cue was removed in one condition of the experiments by deleting more pulses in the stimulus with the higher F0; in other conditions, the number of pulses deleted was either independent of F0, or was higher for the stimulus with the lower F0. The results both of forced-choice and of pitch-matching experiments showed that pitch judgments were affected by the mean rate cue, even though, at least when only a few pulses were deleted, listeners could make consistent judgments using only the common interval cue. Performance in all conditions deteriorated when the number of pulses to be deleted was increased, or when a masking pulse train with a similar spectrum to the targets was mixed with them. Under such circumstances, performance in the absence of the mean rate cue was close to chance.
An analytical investigation of the active attenuation of the plate flexural wave transmission through a reinforcing beam
Authors: Kessissoglou Nicole J. , Pan Jie
Published: July 2002

The transmission of plate flexural waves through a reinforcing beam is related to the coupling between the plate flexural waves and the flexural and torsional waves in the beam. The beam–plate coupling and the energy transmission through the beam can be described in terms of the trace wave matching of the flexural waves in the plate with the flexural and torsional waves in the beam. For a given incident flexural wave from the plate to the beam interface, the amount of trace matching is determined by the flexural and torsional wave numbers in the beam. It is shown in this paper that the reinforcing beam of an infinite beam–plate system serves as a good passive device in attenuating wave transmission except at two coincidences corresponding to the optimal wave trace-matching conditions. The maximum power flow across the beam at the optimal trace wave matching conditions can be reduced by a feedforward active control system using the information on the wave numbers at the coincidence conditions. In this paper, the coupling mechanisms involved with the wave transmission in a coupled beam–plate structure is used to explain the coincidence conditions of the wave transmission. The active control is applied to the reinforcing beam to attenuate the transmitted waves at the coincidences. Results demonstrate that it is possible to achieve a significant reduction of the transmitted energy by using an array of point forces and point moments, and the biologically inspired control strategy for the control actions.
Correlation length of ultrasonic speckle in anisotropic random media: Application to coherent echo detection
Authors: Derode Arnaud , Fink Mathias
Published: July 2002

In a recent paper [Derode and Fink, J. Acoust. Soc. Am. 101, 690–704 (1997)], a technique for studying spatial coherence properties of backscattered speckle noise by means of a transducers array was described. In this paper another approach is presented. Here, a single transducer, focusing inside a scattering medium, is moved in a plane; correlation is studied between signals acquired in two different positions. A study investigates how the correlation function of the medium determines that of the speckle noise. This is applied to fully or partially incoherent media, and media with anisotropic scatterer distribution such as unidirectional and cross-ply composites; we show that it is possible to extract information about the medium from a measurement of the backscattered field correlation length. The influence of correlation length on defect detection is discussed. Experimental as well as theoretical results are presented, they are found in good agreement.
Animations created in Mathematica for acoustics education
Authors: Sparrow Victor W. , Russell Daniel A.
Published: July 2002

One of the unifying assumptions in acoustics and vibrations is that waves and structures move and vibrate. In teaching these topics it makes sense to show students exactly HOW things move. For the last several years the authors have been using the symbolic manipulation program Mathematica [Wolfram Research, Inc., Champaign, IL] to produce brief animations for teaching acoustics. World Wide Web sites have been created for easy access to the animations by all students. The present paper will explain how the animations are created and will demonstrate several including one and two degrees of freedom oscillators, a piston in a tube, reflected waves, doppler effect, elastic waves, circular membranes, and circular plates. The current animations are relatively simple constructions to keep the file sizes to a minimum. However, improved animations containing substantially enhanced graphics will be possible with Internet 2. , for Education Division of Special Session ‘‘Acoustics in Multimedia— Systems issues‘‘
The penetrable wedge as a three-dimensional benchmark
Authors: Deane Grant B.
Published: July 2002

In 1989, members of the Acoustical Society of America developed a suite of range-dependent benchmark geometries, allowing the underwater acoustics community to compare the performance of analytical and numerical solutions to two-dimensional propagation problems. These benchmarks were successful in providing the acoustics community with a set of standards, and continue to be useful as reference geometries. Over the past decade, there have been significant advances in analytical and numerical solutions to three-dimensional propagation problems, and establishing three-dimensional benchmarks is a timely development. A useful benchmark must eliminate the undesired complications of a real-word environment but retain the essential physics of the problem while being tractable to a variety of modelers. A geometry which satisfies these constraints is the ocean wedge with a penetrable basement. The three-dimensional Green’s function for the penetrable wedge has already been studied by a number of investigators, and measured with scale-model tank experiments. The state of modeling and measurement for the wedge will be discussed in the context of its usefulness as a three-dimensional benchmark.
Nonlinear behavior in rock: Experiments show two distinct behaviors
Authors: TenCate James A. , VanDenAbeele Koen E. A. , Shankland Thomas J.
Published: July 2002

The compliant features of rocks—cracks, pores, and the fluids filling them—give rise to a variety of nonlinear elastic effects. As a means of achieving large dynamic strains, longitudinal resonance experiments on thin bars of sandstones were performed. Resonance curves were obtained by measuring acceleration at the end of the bar while sweeping frequency at a fixed drive level. As drive levels increased, resonance curves showed peak bending toward lower frequencies (softening modulus). Two very distinct nonlinear behaviors were observed for several different rock samples. At moderate strain amplitudes (≊10−6), the effects of nonlinearity became quite pronounced: rapid peak shifting and resonance curve shape changes were accompanied by slow dynamics—shapes of the nonlinear resonance curves depend on sweep direction and rate [Geophys. Res. Lett. 23, 3019–3022]. However, even at lower strain amplitudes, nonlinearity remains. Small frequency shifts are observed, even down to the measurement noise of our apparatus. The exact nature of the transition between the two nonlinear behaviors (e.g., effects of temperature or composition) and an explanation for the nonlinearity at very low strain levels are being pursued. [Work supported through the Office of Basic Energy Sciences—Geosciences of the Department of Energy.] a)Currently at Laboratorium Bouwfysica, K.U. Leuven, Belgium. b)Currently at Bayerisches Geoinstitut, Bayreuth, Germany.
Monaural phase discrimination by macaque monkeys: Use of multiple cues
Authors: Moody David B. , Le Prell Colleen G. , Niemiec Andrew J.
Published: July 2002

Research examining the discrimination of monaural phase change has suggested that temporal envelope shape, which varies with phase, may be an important cue. Much of that research employed stimuli consisting of three components, a center frequency (Fc), which is varied in phase, and an upper and lower sideband separated from the carrier by some frequency (ΔF). As the phase of the center component is varied, both temporal envelope and temporal fine structure change. The present research explored the salience of both envelope and fine structure as cues in a phase discrimination task. Monkeys were trained to report detection of a change from a three-tone complex with 90° starting phase for the center component to one in which the starting phase was smaller. In general, for the values of Fc tested, thresholds for phase change decreased as ΔF increased. When tested with comparison stimuli that had a temporal envelope closely matched to that of the standard, but 0° starting phase, subjects had difficulty discriminating these stimuli from the standard for smaller ΔF, but readily discriminated them at larger ΔF values. These findings suggest that temporal envelope is a critical cue in discrimination of three-tone complexes on the basis of the starting phase of the center component at small values of ΔF, but that other cues are used at larger ΔF values.
Sonoluminescence stability for gas saturations down to 0.01 Torr
Authors: Apfel Robert E. , Ketterling Jeffrey A.
Published: July 2002

Water solutions with very small argon partial pressures were investigated. The experiments were performed in a sealed cell. The argon was used in both a pure form and in mixtures with other gases. A regime of stable sonoluminescence was seen at lower driving pressures for argon partial pressures down to 0.01 Torr. Mie scattering, light pulse measurements, and visual observations over tens of thousands of cycles were used to determine if the bubble was stable. As the drive pressure was increased, the bubble moved into a slow time scale instability on the order of several seconds which sometimes caused break up. These experiments are discussed and compared to other published data involving gas mixtures at saturation levels up to 1 atm.
Design and optimization of unipolar pressure pulse generators with a single transducer
Authors: Holé Stéphane , Lewiner Jacques
Published: July 2002

In this paper a broad bandwidth elastic wave generator is described which can produce unipolar (half-oscillation) longitudinal pressure pulses. Such systems are of great interest in many fields: for instance, in nondestructive testing when spatial resolution is needed in lossy materials. The emitter is composed of a thin piezoelectric transducer coupled with a waveguide and a backing medium. Depending on the impedance of each material, both broad proportional and differential bandwidth can be obtained. The theoretical description, which takes into account the connection to an electrical generator, is presented. It allows for optimization of the performance of the system. These developments are in good agreement with the experiments which have been carried out. A bandwidth of 185% of the central frequency and pressure pulses of 1.5-MPa amplitude are obtained.
A field survey on the annoyance caused by sounds from large firearms and road traffic
Authors: Buchta Edmund , Vos Joos
Published: July 2002

Subjective reactions to artillery sounds were determined for over 400 respondents divided among 17 different residential areas. Also, for the same respondents, the subjective effects of road-traffic sounds were determined enabling a comprehensive comparison of the dose-response relations. For the sake of comparison with other field surveys, the noise dose for the shooting sounds was, among other things, expressed as the yearly average C-weighted day–night level (CDNL) and that for the road-traffic sounds was expressed as the A-weighted day–night level (ADNL). Similarly, for both sound types the community response was expressed as the percentage of respondents being “highly annoyed.” From the comparison of the two dose-response relationships it could be concluded that for numerically equal day–night levels, the artillery sounds were more annoying than the road-traffic sounds. Overall, the difference was equivalent to the change in annoyance produced by a 5-dB shift in the yearly average day–night levels of the sounds. With equal day–night levels for “downwind” conditions, the artillery and road-traffic sounds were equally annoying. Results from the present highly controlled field survey provided a new opportunity to optimize the parameter values in Schomer’s rating procedure y=(1/β)(LCE−PNSE)+PNSE, in which the noise exposure for impulsive sounds (y) is expressed as the A-weighted SEL of equally annoying vehicle sounds. PNSE represents the point at which the impulsive and vehicle sounds with numerically equal levels are also equally annoying. With PNSE fixed at 103 dB, an optimal solution was found with slope β set to 1.3. With the previously recommended slope β=0.67, the rating sound level for artillery sounds would be underestimated by almost 12 dB.
Observer weighting of interaural delays in source and echo clicks
Authors: Stellmack Mark A. , Dye Raymond H. , Guzman Sandra J.
Published: July 2002

A correlational analysis was used to assess the relative weight given to the interaural differences of time (IDTs) of source and echo clicks for echo delays ranging from 1–256 ms. In three different experimental conditions, listeners were instructed to discriminate the IDT of the source, the IDT of the echo, or the difference between the IDTs of the source and echo. The IDT of the target click was chosen randomly and independently from trial-to-trial from a Gaussian distribution (μ=0 μs, σ=100 μs). The IDT of the nontarget click was either fixed at 0 μs or varied in the same manner as the IDT of the target. The data show that for echo delays of 8 ms or less, greater weight was given to the IDT of the source than to that of the echo in all experimental conditions. For echo delays from 16–64 ms, the IDT of the echo was weighted slightly more than that of the source and the weights accounted for a greater proportion of the responses when the echo was the target, indicating that the binaural information in the echo was dominant over the binaural information in the source. The data suggested the possibility that for echo delays from 8–32 ms, listeners were unable to resolve the temporal order of the source and echo IDTs. Listeners were able to weight the binaural information in the source and echo appropriately for a given task only when the echo delay was 128 ms or greater.
A mode-based measure of field sensitivity to geoacoustic parameters in weakly range-dependent environments
Authors: Kessel Ronald T.
Published: July 2002

The most sensitive environmental parameters are often deemed most important because errors and uncertainties in their values are among the most likely sources of error in propagation modeling. The usual “snapshot” investigation of sensitivity (overlaying graphs of the modeled sound field before and after the environment is changed) falls short of measuring sensitivity because it fails to assign a physically meaningful quantity to each parameter, signifying its ability to influence the field. Here a new measure of sensitivity is formulated from the adiabatic-mode theory of sound propagation. The measure is practical because it applies as a statistical rule when the propagation scenario is uncertain. It is insightful because it can be explained physically as the combined effect of (1) a uniform change of the long-range phase common to all modes, (2) a nonuniform (jumbling) of the relative phase between modes, and (3) changes in energy loss. All three work together in a single analytic formulation, or they can be isolated to emphasize their particular roles. The measure is demonstrated for shallow-water environments.
Surface waves over bead layers
Authors: Allard Jean-François , Henry Michel , Tizianel Julian , Kelders Luc , Lauriks Walter
Published: July 2002

For thin bead layers saturated by air, a pole of the reflection coefficient related to a trapped mode inside the layer and a surface wave in air is predicted, and detected with the Tamura method [J. Acoust. Soc. Am. 88, 2259 (1990)]. For semi-infinite layers, the Brewster angle is observed with the same method at oblique incidence at 15 kHz. A description of the related Zenneck wave is performed, at high and low frequencies.
Detection of consonant voicing: A module for a hierarchical speech recognition system
Authors: Choi Jeung-Yoon
Published: July 2002

This research describes a module for detecting consonant voicing in a hierarchical speech recognition system. In this system, acoustic cues are used to infer values of features that describe phonetic segments. A first step in the process is examining consonant production and conditions for phonation, to find acoustic properties that may be used to infer consonant voicing. These are examined in different environments to determine a set of reliable acoustic cues. These acoustic cues include fundamental frequency, difference in amplitudes of the first two harmonics, cutoff first formant frequency, and residual amplitude of the first harmonic, around consonant landmarks. Classification experiments are conducted on hand and automatic measurements of these acoustic cues for isolated and continuous speech utterances. Voicing decisions are obtained for each consonant landmark, and are compared with lexical and perceived voicing for the consonant. Performance is found to improve when measurements at the closure and release are combined. Training on isolated utterances gives classification results for continuous speech that is comparable to training on continuous speech. The results in this study suggest that acoustic cues selected by considering the representation and production of speech may provide reliable criteria for determining consonant voicing.
Wideband quantitative ultrasonic imaging by time-domain diffraction tomography
Authors: Mast T. Douglas
Published: July 2002

A quantitative ultrasonic imaging method employing time-domain scattering data is presented. This method provides tomographic images of medium properties such as the sound speed contrast; these images are equivalent to multiple-frequency filtered-backpropagation reconstructions using all frequencies within the bandwidth of the incident pulse employed. However, image synthesis is performed directly in the time domain using coherent combination of far-field scattered pressure waveforms, delayed and summed to numerically focus on the unknown medium. The time-domain method is more efficient than multiple-frequency diffraction tomography methods, and can, in some cases, be more efficient than single-frequency diffraction tomography. Example reconstructions, obtained using synthetic data for two- and three-dimensional scattering of wideband pulses, show that the time-domain reconstruction method provides image quality superior to single-frequency reconstructions for objects of size and contrast relevant to medical imaging problems such as ultrasonic mammography. The present method is closely related to existing synthetic-aperture imaging methods such as those employed in clinical ultrasound scanners. Thus, the new method can be extended to incorporate available image-enhancement techniques such as time-gain compensation to correct for medium absorption and aberration correction methods to reduce error associated with weak scattering approximations.
A model for the horizontal directionality of breaking wave noise in the surf zone
Authors: Deane Grant B.
Published: July 2002

A model is presented for the horizontal directionality of the noise generated by individual breaking waves in the surf zone. The model is based on the interaction between sound radiated by ringing bubbles created in a breaking wave crest and the population of acoustically quiescent bubbles left on the seaward side of the wave in the shallow water waveguide. The effect of the quiescent bubbles is to absorb sound from all but the very ends of the breaking crest, resulting in the formation of “acoustic hot-spots.” The model calculations are in good agreement with observations of the horizontal directionality of noise from individual breaking waves in the surf zone.
Transient acoustic radiation from impulsively accelerated bodies by the finite element method
Authors: Manoj K. G. , Bhattacharyya S. K.
Published: July 2002

Bodies under impulsive motion, immersed in an infinite acoustic fluid, severely put to test any numerical method for the transient exterior acoustic problem. Such problems, in the context of the finite element method (FEM), are not well studied. FE modeling of such problems requires truncation of the infinite fluid domain at a certain distance from the structure. The volume of computation depends upon the extent of this domain as well as the mesh density. The modeling of the fluid truncation boundary is crucial to the economy and accuracy of solution and various boundary dampers have been proposed in the literature for this purpose. The second order damper leads to unsymmetric boundary matrices and this necessitates the use of an unsymmetric equation solver for large problems. The present paper demonstrates the use of FEM with zeroth, first and second order boundary dampers in conjunction with an unsymmetric, out of core, banded equation solver for impulsive motion problems of rigid bodies in an acoustic fluid. The results compare well with those obtained from analytical methods.
Rheo-acoustical study of the shear disruption of reversible aggregates. Ultrasound scattering from concentrated suspensions of red cell aggregates
Authors: Haider L. , Snabre P. , Boynard M.
Published: July 2002

Shear-induced disruption of reversible aggregates or clusters in a concentrated suspension is investigated by ultrasound backscattering in the low shear regime. Fractal aggregates are considered as non-Brownian scatterers much smaller than the wavelength with acoustic properties close to those of the surrounding liquid, so that the attenuation of the coherent field is weak and multiple scattering can be neglected. The concept of variance in local particle volume fraction is used to deduce a first-order expression of the ultrasound scattering cross section per unit volume for Rayleigh scatterers in a dense suspension. On the basis of a scaling law for the shear-induced disruption of aggregates, the shear stress dependence of the ultrasonic scattered intensity from a dense suspension of clusters is derived. In a second part, the shear breakup of hardened red blood cell aggregates is investigated in plane–plane flow geometry by ultrasound scattering. Rheo-acoustical experiments are analyzed within the framework of the self-consistent field approximation and the scaling laws currently used in microrheological models. Finally, the ability of ultrasonic, light reflectometry and viscometry methods to provide quantitative information about red blood cell aggregation and membrane adhesiveness is discussed.
Mathematical modeling of vowel perception by users of analog multichannel cochlear implants: Temporal and channel-amplitude cues
Authors: Svirsky Mario A.
Published: July 2002

A “multidimensional phoneme identification” (MPI) model is proposed to account for vowel perception by cochlear implant users. A multidimensional extension of the Durlach–Braida model of intensity perception, this model incorporates an internal noise model and a decision model to account separately for errors due to poor sensitivity and response bias. The MPI model provides a complete quantitative description of how listeners encode and combine acoustic cues, and how they use this information to determine which sound they heard. Thus, it allows for testing specific hypotheses about phoneme identification in a very stringent fashion. As an example of the model’s application, vowel identification matrices obtained with synthetic speech stimuli (including “conflicting cue” conditions [Dorman et al., J. Acoust. Soc. Am. 92, 3428–3432 (1992)] were examined. The listeners were users of the “compressed-analog” stimulation strategy, which filters the speech spectrum into four partly overlapping frequency bands and delivers each signal to one of four electrodes in the cochlea. It was found that a simple model incorporating one temporal cue (i.e., an acoustic cue based only on the time waveforms delivered to the most basal channel) and spectral cues (based on the distribution of amplitudes among channels) can be quite successful in explaining listener responses. The new approach represented by the MPI model may be used to obtain useful insights about speech perception by cochlear implant users in particular, and by all kinds of listeners in general.
A reduced model of cavitation physics for use in sonochemistry
Authors: Storey Brian D. , Szeri Andrew J.
Published: July 2002

Sonochemistry involves focusing acoustic energy through tiny cavitation bubbles to increase chemical activity. The violent bubble collapses lead to temperatures of several thousand Kelvin which drive chemical reactions. In previous work (B. D. Storey and A. J. Szeri, ‘‘Water vapor, sonoluminescence, and sonochemistry,’’ in review), a very detailed computational model of a single bubble collapse was presented, taking into account phase change, mass diffusion, heat diffusion, nonuniform pressure, and chemical reactions. All of these phenomena are important in determining the conditions at collapse. The present work involves development of a much simpler model that includes all the relevant physics. Comparisons to the more detailed computations are made and the current model is found to provide reasonable results. Further, it is shown that many of the observed trends in sonochemistry are reflected in the results with a single ‘‘representative’’ bubble. [This work was supported by NSF and LLNL.]
Polymers as Structured Continua: Superposed Oscillatory Shear Flows
Authors: Kline Kenneth A.
Published: July 2002

A microstructure model of polymer rheology is applied to study the behavior of the dynamic viscosities under superposed in-line and transverse oscillations. A general solution valid to first order in oscillatory shear rate is obtained, and the limiting cases of small and large values of the frequency of oscillation are examined. The results for these limiting cases are found to be in agreement with results based on the incompressible BKZ and simple fluid models. A solution valid to third order in oscillatory shear rate is obtained, and for this case the shear stress response is found to contain harmonics of the driving frequency.
Curvature-driven shear banding in polymer melts
Authors: Goveas J. L. , Fredrickson G. H.
Published: July 2002

We consider a melt of two chemically identical homopolymers of different lengths. Both species obey Rouse dynamics, and always form a homogeneous mixture at equilibrium. Under shear flow in a wide-gap Couette, such a system exhibits strongly inhomogeneous steady states, that resemble macro-phase separated blends. The corresponding velocity profile is nonmonotonic and exhibits distinct shear bands. These findings may have implications for the processing of polydisperse polymer melts.
Attack detection and mitigation using optimal deep maxout network in cloud computing
Authors: Patil Shubangini , Patil Rekha
Published: June 2022

Cloud computing is a promising technique and the majority of information technology based services function in this infrastructure, which addresses the need of today's data center. There involve privacy and security problems in the cloud, which affected the utility of the cloud. Various mitigation solutions are developed in existing, in which the attacks continue to elevate in frequency and severity. This calls for a model for addressing the needs of challenging security threats. This article devises novel attack detection and mitigation technology using an optimization‐driven deep learning model. Here, the system comprises five modules, like data, data owner, cloud server, cloud user, and thin provision virtual volume. Here, each entity performs its own operations. The proposed technique includes five stages, namely, authentication phase, data sharing and communication phase, recorded log file creation phase, attack detection phase, and attack mitigation phase. An initial phase is the authentication phase where an authentication protocol is modeled using different mathematical functionalities. Once the authentication is done, the data sharing and communication are initiated for sharing the sensitive data. Thereafter the log file creation phase is initiated for storing the log entries. Then the attack detection is performed utilizing deep maxout network that is tuned by the developed gray wolf political optimizer (GWPO). The GWPO is the integration of gray wolf optimizer (GWO) and political optimizer (PO). Finally, attack mitigation is performed by reducing the data rates of attack nodes. The developed GWPO‐enabled deep maxout network provided improved performance with the highest accuracy of 97.9%, true positive rate of 97.3%, and true negative rate of 97.7%.
Strategies for Regenerative Vascular Tissue Engineering
Authors: Wang Yao , Keshavarz Mozhgan , Barhouse Patrick , Smith Quinton
Published: June 2022

Vascularization remains one of the key challenges in creating functional tissue‐engineered constructs for therapeutic applications. This review aims to provide a developmental lens on the necessity of blood vessels in defining tissue function while exploring stem cells as a suitable source for vascular tissue engineering applications. The intersections of stem cell biology, material science, and engineering are explored as potential solutions for directing vascular assembly.
Laser Microfabrication of Janus Tapered Aluminum Foil for Self‐Driven Transportation of Bubbles
Authors: Han Jiang , Tang Jianping , Tian Xiaoqing , You Tongfei , Xia Lian , Yao Yansheng
Published: June 2022

The multidimensional regulation of the directional transport of bubbles is of great importance in the field of subsea gas extraction, with the increased complexity of controlling the direction of underwater bubble transport making it more challenging. Herein, drawing on a variety of bionic technologies, nanosecond laser processing combined with a low surface energy reagent modification to prepare porous hydrophobic/superhydrophobic Janus tapered aluminum foil (JTAF) is used. The wettability gradient of JTAF promotes unidirectionally self‐driven penetration of bubbles, and the shape gradient facilitates self‐driven transport of bubbles from the tip to the root. The synergistic effect of the two gradient forces endows bubbles with unidirectional self‐driven transport capability in both the buoyancy direction and the antibuoyancy direction. Finally, the JTAFs are used as bipolar electrodes in electrolysis cells to achieve gas generation, self‐driven transport, and collection processes by electrolyzing saturated saltwater. This simple, low‐cost, controlled approach to laser processing of the JTAF has tremendous potential for underwater self‐driven gas transport and is a promising tool for solving energy and environmental problems.
In Situ Investigation of Deformation Mechanisms Induced by Boron Nitride Nanotubes and Nanointerphases in Ti–6Al–4V Alloy
Authors: Nautiyal Pranjal , Bustillos Jenniffer , Selvam Tamil , Zhang Cheng , Seal Sudipta , Boesl Benjamin , Agarwal Arvind
Published: June 2022

There is a need to augment the mechanical strength of titanium alloys to take advantage of their low mass density for structural applications. Herein, the reinforcement potential of boron nitride nanotube (BNNT), a high‐aspect‐ratio nanomaterial with exceptional strength and thermal stability, to engineer nanocomposites based on Ti–6Al–4 V alloy, is interrogated. The stress‐transfer behavior at the matrix/filler interface is programmed by tweaking the extent of chemical reactions during sintering. A twofold improvement in indentation resistance after integrating BNNTs in the alloy due to the crack bridging mechanism is reported. There is a further 50% enhancement in hardness and stiffness as the sintering temperature is raised from 750 to 950 °C. This improvement is attributed to the escalated formation of TiN and TiB phases due to matrix–nanotube interfacial reactions at elevated temperatures. A novel indentation‐based in situ trench testing technique is employed to study the subsurface deformation mechanisms activated in the bulk of the composite specimen. The ceramic interphases promote the indentation resistance by acting as crack deflectors in the microstructure, which promotes the dissipation of mechanical work. These insights can be applied to designing Ti‐BNNT microstructures with desired mechanical properties and deformation characteristics.
Activating Oxygen Redox in Layered NaxMnO2 to Suppress Intrinsic Deficient Behavior and Enable Phase‐Transition‐Free Sodium Ion Cathode
Authors: Wang Feng , Peng Bo , Zeng Suyuan , Zhao Liping , Zhang Xiaolei , Wan Guanglin , Zhang Hongli , Zhang Genqiang
Published: June 2022

P2‐type layered NaxMnO2 cathode shows great potential in practical sodium ion batteries, especially for grid‐level applications due to its eco‐friendly and cost‐effective sodium and manganese resources, and high theoretical specific capacity. However, several obstacles including severe phase transitions of P2‐O2 and P2‐P2′, low redox potential of Mn3+/Mn4+, disproportionation reaction and Jahn‐Teller distortion of Mn3+, and deficient behavior have already hindered its practical applications. Herein, a Li, Cu co‐doping strategy to tackle the mentioned obstacles by activating the oxygen redox is presented. The Li, Cu co‐doped material exhibits solid solution reaction without any phase transitions as proved by in situ X‐ray diffraction measurement and reduces the dissolution of active manganese element. With this modification treatment, it can dramatically raise the cycling stability from 30.4% to 80.1% after 150 cycles and simultaneously improves the deficient behavior due to the capacity contribution of oxygen redox at high voltage. More importantly, the coin‐cell type sodium ion full cell assembled with this cathode and commercial hard carbon anode delivers a promising energy density of 225.1 Wh kg–1.
Edge‐Enriched Mo2TiC2Tx/MoS2 Heterostructure with Coupling Interface for Selective NO2 Monitoring
Authors: Zhao Qiuni , Zhou Wenzhe , Zhang Mingxiang , Wang Yang , Duan Zaihua , Tan Chaoliang , Liu Bohao , Ouyang Fangping , Yuan Zhen , Tai Huiling , Jiang Yadong
Published: June 2022

Endowed with rich terminal groups, good electrical conductivity, and controllable structure, transition metal carbides/nitrides (MXenes) have attracted extensive attention for potential application in gas sensor, but long‐standing challenges of the MXenes (titanium carbide as the representative) are their limited selectivity and sensitivity. Herein, a high‐active double transition‐metal titanium molybdenum carbide (Mo2TiC2Tx) with superstrong surface adsorption (−3.12 eV) for NO2 gas molecule is proposed, and it is further coupled with molybdenum disulfide (MoS2) by interface modulation to construct an edge‐enriched heterostructure. Due to the synergistic effect of strong adsorption, rich adsorption sites, and coupling interface of Mo2TiC2Tx/MoS2 composite, the as‐fabricated Mo2TiC2Tx/MoS2 gas sensor exhibits an outstanding response toward NO2 with high selectivity against various interference gases, which is well supported by density functional theory calculations. Meanwhile, the sensor exhibits a sensitivity of 7.36% ppm−1, detection limit of 2.5 ppb, and reversibility at room temperature. A portable, wireless NO2 monitoring system is demonstrated for gas leakage searching and dangerous warning based on Mo2TiC2Tx/MoS2 gas sensor. This work facilitates the gas sensing application of MXenes, and provides an avenue for the development of wireless sensing system in environmental monitoring and safety assurance.
Tunable Ferroelectricity in Van der Waals Layered Antiferroelectric CuCrP2S6
Authors: Cho Kwanghee , Lee Seungyeol , Kalaivanan Raju , Sankar Raman , Choi Kwang‐Yong , Park Soonyong
Published: June 2022

Recent success in experimental and theoretical works on metal thiophosphates (MTPs) paved the way to add multiple functionalities of complex oxides, such as ferroelectricity, in 2D materials. To realize multiferroicity and magnetoelectric coupling on layered van der Waals materials, incorporating magnetic ions in the ferroelectric framework is desirable. Unfortunately, replacing the metal ion with a magnetic one in MTPs results in antiferroelectricity in which spontaneous macroscopic polarization is absent. Herein, the emergence of a tunable local ferroelectric state in antiferroelectric CuCrP2S6 possessing magnetic Cr3+ ion is reported. The spontaneous macroscopic polarization is observed, which is switchable by an external poling field through controlling a defect‐dipole polarization in the quasi‐antipolar state. The observations suggest that the formation of defect dipoles, which is facilitated by an order‐disorder‐type structural transition, is likely related to a metastable Cu site within the van der Waals gap and therefore is a smoking gun of the existence of a uniaxial quadruple potential well. The interaction between the defect‐dipole polarization and dipoles in the antipolar matrix may lead to the emerging local ferroelectricity in antiferroelectric CuCrP2S6. The findings suggest a possibility of utilizing the local ferroelectricity of multiferroic MTPs for novel 2D applications.
Anion‐Induced Catalytic Reaction in a Solution‐Processed Molybdenum Oxide for Efficient Inverted Ternary Organic Photovoltaics
Authors: Ki Taeyoon , Lee Changhoon , Kim Jehan , Hwang In‐Wook , Oh Chang‐Mok , Park Kiyoung , Lee Sanseong , Kim Ju‐Hyeon , Balamurugan Chandran , Kong Jaemin , Jeong Hyeon‐Seok , Kwon Sooncheol , Lee Kwanghee
Published: June 2022

Solution‐processed transition metal oxides (TMOs) prepared from complex ion precursors are developed as promising scalable interfacial layers for non‐fullerene organic photovoltaics (OPVs); however, challenges remain in achieving defect‐free and highly oriented metal‐oxygen networks without post‐deposition treatments due to the presence of residual organic metal‐binding ligands in films. Herein, the novel strategy that the problematic organic metal‐binding ligands in TMO precursors can be successfully eliminated by an anion‐induced catalytic reaction (ACR) at room temperature is demonstrated, in which the low‐level anions induce electron redistribution and instability of TMO precursors, expediting binding ligand removal during the hydrolysis reaction. The subsequent condensation process facilitates a dimensionally confined and continuous metal‐oxygen network with a 20‐fold increase in electrical conductivity (from 8.4 × 10−4 to 1.8 × 10−2 S m−1) and superior work function tunability (from 5.1 to 5.3 eV) compared to the pristine film. The ACR‐derived TMO thin film on top of a ternary PBDB‐TF:Y6:PC71BM photoactive layer enables an inverted device configuration with improved efficiency of 17.6%, as well as enhanced stability over 70% of the initial efficiency for up to 100 h AM 1.5G illumination.
Rashba–Edelstein Effect in the h‐BN Van Der Waals Interface for Magnetization Switching
Authors: Xie Qidong , Lin Weinan , Liang Jinghua , Zhou Hengan , Waqar Moaz , Lin Ming , Teo Siew Lang , Chen Hao , Lu Xiufang , Shu Xinyu , Liu Liang , Chen Shaohai , Zhou Chenghang , Chai Jianwei , Yang Ping , Loh Kian Ping , Wang John , Jiang Wanjun , Manchon Aurelien , Yang Hongxin , Chen Jingsheng
Published: June 2022

Van der Waals materials are attracting great attention in the field of spintronics due to their novel physical properties. For example, they are utilized as spin‐current generating materials in spin–orbit torque (SOT) devices, which offers an electrical way to control the magnetic state and is promising for future low‐power electronics. However, SOTs have mostly been demonstrated in vdW materials with strong spin–orbit coupling (SOC). Here, the observation of a current‐induced SOT in the h‐BN/SrRuO3 bilayer structure is reported, where the vdW material (h‐BN) is an insulator with negligible SOC. Importantly, this SOT is strong enough to induce the switching of the perpendicular magnetization in SrRuO3. First‐principles calculations suggest a giant Rashba effect at the interface between vdW material and SrRuO3 (110)pc thin film, which leads to the observed SOT based on a simplified tight‐binding model. Furthermore, it is demonstrated that the current‐induced magnetization switching can be modulated by the electric field. This study paves the way for exploring the current‐induced SOT and magnetization switching by integrating vdW materials with ferromagnets.
Cluster‐Glass for Low‐Cost White‐Light Emission
Authors: Rojas‐León Irán , Christmann Jan , Schwan Sebastian , Ziese Ferdinand , Sanna Simone , Mollenhauer Doreen , Rosemann Nils W. , Dehnen Stefanie
Published: June 2022

The development of efficient and high‐brilliance white‐light sources is an essential contribution to innovative emission technologies. Materials exhibiting strong nonlinear optical properties, in particular second‐harmonic generation (SHG) or white‐light generation (WLG), have therefore been investigated with great activity in recent times. While many new approaches have been reported until now, the processability of the compounds remains a challenge. Here, a new class of materials, denoted as “cluster‐glass”, which do not only show superior white‐light emission properties upon irradiation by an inexpensive continuous‐wave infrared laser diode, but can be easily accommodated in size and shape by formation of robust glassy solids, is introduced. The cluster‐glass materials are fabricated by mild heating from crystalline powders of adamantane‐type clusters exhibiting a quaternary, inorganic–organic hybrid cluster core [(PhSi)(CH2)3(PhSn)E3] (E  =  S, Se, Te). The process is fully reversible and preserves the integrity of the clusters in the glass, as proven by solution spectroscopy and recrystallization. Theoretical studies corroborate the importance of the quaternary nature of the cluster cores for the observed structural and optical phenomena. Thanks to these findings, high‐brilliance white‐light sources can be synthesized in form of stable, robust glass of any shape, which ultimately renders them suitable for everyday's applications.