bluuebunny/crossref_metadata_2025 huggingface dataset:
Murray Hodgson: An appreciation from a practicing acoustical consultant
Authors: O'Keefe John P.
Published: October 2018

So much of what we know about the behaviour of sound in rooms comes from studies in concert halls and reverberation rooms. Hardly everyday architectural geometry. The author first met Murray Hodgson in Cambridge when Dr. Hodgson was doing his early scale model studies on factories. Geometrically and acoustically, factories are much more akin to the day to day built environment that we inhabit. The geometry of a factory is typically long, wide and very flat with scattering elements, typically on the floor. Murray would go on to apply his work on factories to other long, low, and wide rooms. Our understanding of the acoustics of open plan offices, health care facilities, and, of course, classrooms can be traced back to his post-doctoral work in Cambridge. One is impressed how the work on factory acoustics grew to cover so much of the rooms we live in. More impressive was his ability to tackle questions that others wouldn’t. Questions that acoustical consultants are often asked and really don’t have an answer for yet. Noise control in naturally ventilated buildings for example. His legacy will show this work as seminal in the nascent green building type genre.
Concave surfaces and acoustics of performance spaces—Part I— Hybrid ray-image analysis
Authors: Johnston-Iafelice Eva M. , Ramakrishnan Ramani
Published: October 2018

Current acoustic practices deem that concave surfaces do not provide good acoustical performance. However, old cathedrals, churches, and enclosed performance spaces with concave interiors seem to perform well. Part I of the current investigation analyzes the acoustical performance of spaces with curved surfaces. The main focus of the current investigation was to research the uniformity of the sound field produced by curved surfaces by analyzing sound pressure level distribution throughout the audience space. It studied the impact of the focal plane on the overall sound distribution within an enclosed space. To analyze the effect of curved surfaces at different frequencies, three enclosed rooms with curved surfaces were used to measure the sound pressure levels throughout an audience space: the Paul Crocker Gallery in the Ryerson Architecture Building, Toronto; St. Martin-in-the-fields Anglican Church, Toronto; and Wigmore Hall, United Kingdom. The evaluations were achieved with both experimental methods, and computer simulations using hybrid-ray-image methods. Computer simulations were validated by the initial on-site measurements in the Toronto locations. After these evaluations were performed, results showed that in these conditions, the curved surfaces had minimal negative impact as perceived by the audience. The results of the investigation will be presented in this paper.
Clymene dolphin (Stenella clymene) whistles in the Southwest Atlantic Ocean
Authors: Moron Juliana R. , Alves Luiz Cláudio P. , de Assis Carla Viviane , Garcia Felipe C. , Andriolo Artur
Published: October 2018

The Clymene dolphin despite being endemic for the Atlantic Ocean continues to be the least known species in the genus Stenella without available information on their vocal repertoire in Brazilian waters. Data were obtained during mitigation and monitoring work required by IBAMA under the federal environmental licensing as conditions of the license 108/16 for the 3D seismic survey in Pará/Maranhão Sedimentary Basin process 02022.000015/2014. The species record was performed onboard the vessel Polarcus Alima with a Mseis (Night Hawk III) four-element towed array passing signals to a digital M-Audio, recording at 96 kHz/16bits. During visual and acoustic monitoring with the air-guns off, a group of approximate 80 dolphins were sighted and recorded on May 8th, 2016 (00˚38’00” N, 44˚45’25” O) at 3,425 m depth. The wav-files were analyzed through the spectrogram configured as DFT 2048 samples, 70% overlap and Hamming window of 1024 points generated by software Raven Pro 1.5. The results of 14 min recording allowed the extraction of 257 whistles. Minimum frequencies ranged from 5.20 kHz to 15.92 kHz (mean = 10.99 kHz); maximum frequencies ranged from 7.72 kHz to 28.04 kHz (mean = 16.16 kHz); whistle duration ranged from 0.01 s to 1.52 s (mean = 0.43 s). These results are important since they represent the first acoustic record of Clymene dolphins in Brazil.
Low-frequency ambient noise trends of (almost) 2 decades in the northern Pacific Ocean
Authors: Andrew Rex K. , Howe Bruce , Mercer James
Published: October 2018

Nearly two decades of low-frequency (20–500 Hz) ambient noise measurements at seven open-ocean sites in the North Pacific Ocean basin have revealed a complex pattern of long-term trends. The trends in the Northeastern Pacific Ocean show a significant decrease of almost 2 dB/decade. Along the Aleutian archipelago, the levels are either slightly increasing or remaining flat. Levels in two north central Pacific Ocean sites are essentially flat. Comparisons with very sparse measurements made over the last 5 decades suggest that the mid-latitude noise levels may have peaked in the 1990s. These measurements also show, however, that the noise level is still rising elsewhere. The mechanisms driving these trends appear to be more subtle than simply the number of merchant ships or the local wind speed. Climatically-influenced basin-scale acoustic propagation conditions may have an important role.
Model/data comparisons and numerical experiments for the comparison of sandy sediment models
Authors: Bonomo Anthony L. , Isakson Marcia J.
Published: October 2018

Many geoacoustic models have been proposed to study the acoustic behavior of sandy sediments to predict the propagation within the sediment and the reflection loss from waterborne waves. Sandy sediments have been described as a two-phase porous medium using the theoretical framework developed by Biot. Other proposed theories were developed under the assumption that sandy sediments possess no effective skeletal matrix and instead describe the acoustic behavior of the sediments using grain-to-grain contacts. This talk summarizes model/data comparisons and numerical experiments in an attempt to determine which of these two theoretical frameworks is more suitable for the modeling of sandy sediments. Recommendations are made for future experiments that can aid in resolving this issue. [Work supported by ONR, Ocean Acoustics.]
Effective dynamic properties of random complex media
Authors: Alam M. Mahbub , Luppé Francine , Pinfield Valerie J. , Maréchal Pierre
Published: October 2018

In recent years, it has been demonstrated that, as particle concentration in a suspension increases, the viscous nature of the host fluid becomes more and more significant and thereby needs to be taken into consideration when calculating effective properties for acoustic propagation. One approach to the problem is to incorporate wave conversion phenomena, primarily between compressional and shear wave modes, into the models for effective properties. A self-consistent method that includes mode conversion, based on a core-shell model, has been used to determine the effective dynamic bulk modulus and mass density of random complex media consisting of spherical inclusions. The analytical expressions obtained are compared with those obtained from numerical solution of the self-consistent model equations. The contribution of mode conversion on the effective dynamic properties for particles in a viscous liquid are explored. The variation of the effective properties with frequency, volume concentration, and density contrast are also investigated numerically.
Perseverance measured in children’s oral reading
Authors: Bernstein Jared , Cheng Jian , Magooda Ahmed
Published: October 2018

Do struggling readers score lower on reading tests in part because they get discouraged or slow down? Schools track reading progress in grades K-4 by measuring oral reading fluency (ORF) as students read aloud. The usual ORF measure is accurate reading rate, which is reported in words correct per minute (WCPM). Computer recognition and processing of speech has automated the scoring of oral reading and enabled new analyses of reading performance, particularly concurrent scoring of shorter text units such as paragraphs, sentences, and words that occur within a passage that is read for comprehension. Do stronger readers perform more consistently within a passage and across passages during a test, while stuggling readers do not persevere. If true, then some conventional reading tests may conflate perseverance with basic reading skills. We have read-aloud data from 600 students in grades 1–5, but now only compare quintile 2 to quintile 4 in a sample of 100 fourth grade students. We find among both reader groups that passage performance tends not to diminish across passages late in a test, but remains roughly constant. However, within each text passage, the fast readers tend to slow down and the slower readers tend to speed up.
Fricative productions of Mandarin-speaking children with cerebral palsy: The case of five-year-olds
Authors: Liu Chin-Ting , Chen Li-mei , Hustad Katherine C. , Kent Ray D. , Lee Chia-Cheng
Published: October 2018

The age means between cerebral palsy children (CPs) and typically developing children (TDs) were not ideally matched in previous studies targeting the fricative productions of Mandarin-acquiring CPs (Liu et al., 2017, 2016). Therefore, in this study, age-matched CPs (N = 8, Mean = 5;6) and TDs (N = 8, Mean = 5;6) were recruited. Six acoustical parameters (frication duration, rise time, and first to fourth spectral moments) of the five Mandarin Chinese voiceless fricatives (labiodental, alveolar, alveolo-palatal, velar, and retroflex) produced by the participants were compared. The results from Mann-Whitney U tests indicated that, for the labiodental, alveolar, alveolo-palatal, and retroflex fricatives, the values from frication duration, rise time, and first and second spectral moments produced by CPs were generally significantly lower than those produced by TDs. The current results from age-matched groups were different from previous studies and suggested that: 1) CPs tended to have a more posterior constriction site and a more restricted lingual constriction area with the passive articulator; 2) the third and fourth spectral moments were less effective in quantifying the differences between the two groups. Future studies are suggested to observe the fricative productions from older or younger age-matched groups so that the fricative developmental trajectory of Mandarin-acquiring CPs can be faithfully depicted.
Salience of cochlear implant users’ speech rate
Authors: Freeman Valerie
Published: October 2018

Speech rate-matching is a form of rapid accommodation in which speakers adapt their speech rates to match their interlocutor’s previous utterance. Such responsiveness may contribute to rhythmic convergence between speakers throughout a conversation. However, little is known about interactions between typical speakers and those with speech or hearing difficulties. In recent work, prelingually deaf cochlear implant (CI) users were poorer rate-matchers than their peers, but it was unclear whether interlocutors accommodated toward CI users’ speech rates, which can vary widely between individuals. A follow-up study adapted procedures from work in which participants rate-matched toward fast- and slow-talking Parkinson’s patients. Surprisingly, people did not rate-match to either CI users or controls. This study explores one possible explanation: that differences in speech rate were not salient enough for participants to modify their own rates in response. Following previous procedures, participants (a) alternated hearing CI users’ sentences and reading other sentences, (b) rated CI users’ utterances as fast, slow, or neither, and (c) repeated the first task with different stimuli. Results will show whether participants were able to identify differences in speech rate (when prompted) and whether they improved in speech rate-matching after speech rate was brought to their attention.
Application of time-domain near-field acoustical holography to the high-order ambisonics presentation of moving sound sources
Authors: Trevino Lopez Jorge A. , Sakamoto Shuichi , Suzuki Yôiti
Published: October 2018

High-order ambisonics (HOA) is a sound field reproduction method based on results from near-field acoustical holography (NAH). As such, it is formulated in the frequency domain; this assumes a stationary acoustic field. This presentation applies a recent time-domain formulation of NAH by Attendu and Ross. The approach is based on the linear deconvolution along the spatial coordinates and samples the Green's function in the time and spatial domains, as opposed to the Fourier domain. Our contribution is an application of these ideas to overcome the problems inherent in the HOA reproduction of non-stationary sound fields, in particular those of moving sound sources. In practice, the rendering of moving sound sources is approximated by assuming they are stationary within short temporal windows. The approximation, while useful for slow-moving sources, cannot re-create the Doppler shift and results in discontinuities along the temporal structure of the sound field. On the other hand, the proposed method does not impose any constraints on the motion of the sound sources. Unlike conventional HOA, the proposal cannot be formulated as a simple filter bank; however, numerical experiments show that fast moving sources exhibit the expected Doppler shift.
Study on the problem of coherent source resolution with same frequency for the coprime array
Authors: Mei Jidan , Sun Dajun , Zhou Yuyuan , Shi Junjie
Published: October 2018

The coprime sensor array (CSA) can achieve the same resolution capability as an equally spaced half-wave array even using fewer array elements. For single-target, CSA can achieve good anti-grating lobe effect. When there are multiple coherent sources of the same frequency, there still are overlaps between the main lobes and grating lobes of the subarray from different sources, and between the grating lobes and grating lobes of different subarray. In some cases, the strong grating lobes can interfere discriminating the azimuth and quantity of targets. This paper focuses on the multi-targets discrimination problem of CSA for the same frequency coherent source. A processing algorithm of CSA coherent sources is presented. This method uses iterative processing methods to detect and remove strong targets one by one. Then, reconstruct the spatial spectrum of each single target. Finally, recombine the spatial spectrum by each single target spatial spectrum after sidelobe suppression processing. This method can well remove the grating lobe of multiple targets. It is also applicable to the situation when the grating lobe is higher than the weak target peak under strong and weak contrast conditions. The performance of the method was simulated and the results confirmed the feasibility of the method.
Segmentation of underwater acoustic images by FCM with EMD
Authors: Santhanam Sakthivel M. , M. Somasekar
Published: October 2018

In recent years, there is an expanding enthusiasm for studying the seabed structure. The investigation of seabed has numerous applications, for example, protest recognition, exploration of natural resources, angling, analyzing the composition of residues, etc. In oceanic examinations, submerged objects location is a standout amongst the most basic errands. This emphasizes the necessity of image segmentation, which divides an image into parts that have strong correlations with objects to reflect the actual information collected from the real world. Image segmentation is the most practical approach to virtually all automated image recognition systems. Clustering of numerical data forms the basis of many classification and system modelling algorithms. The purpose of clustering is to identify natural groupings of data from a large data set to produce a concise representation of a system's behaviour. In this paper, Empirical Mode Decomposition (EMD) picture upgrade procedure has been utilized to enhance the nature of sonar pictures and Fuzzy C means (FCM) clustering method is used for underwater image segmentation. The result of EMD is compared with histogram equalization and Contrast stretching. EMD with K-means and EMD with FCM is compared and the exploratory outcomes demonstrate that the proposed technique can acquire exact outcomes and enhances operational productivity.
Speech-in-noise research: From classrooms to Canadian Armed Forces operational environments
Authors: Nakashima Ann , Cai Jane , Vartanian Oshin
Published: October 2018

The importance of speech intelligibility in learning and occupational environments is evidenced by the abundance of research in room acoustics and auditory communication. In addition to environmental factors such as background noise and reverberation, individual factors including the presence of hearing loss, wearing of hearing aids and hearing protection devices (HPDs), and language proficiency must be considered. Previous work in these areas has provided a benchmark for the study of communication in complex, high noise environments. For Canadian Armed Forces (CAF) members, the high noise levels inside aircraft, armoured vehicles and sea vessels demand the use of HPDs and integrated radio communication systems. This presentation will summarize our research on speech understanding in noise and multi-talker environments using different communication headsets, simulated hearing loss and language proficiency. We will focus on our recent studies of communication between native (L1) and non-native (L2) English speakers, which is applicable to the CAF due to the relatively high percentage of L2 membership. L2 speakers obtained lower scores on speech-in-noise tests than L1 speakers for both radioed and face-to-face speech, despite having a high level of language proficiency. Preliminary results of an investigation of cognitive load for L2 listeners will also be presented.
Effects of background noise, talker’s voice, and speechreading on speech understanding by primary school children in simulated classroom listening situations
Authors: Rudner Mary , Lyberg-Åhlander Viveka , Brännström Jonas , Nirme Jens , Pichora-Fuller Margaret K. , Sahlén Birgitta
Published: October 2018

In the primary school classroom, children are exposed to multiple factors that combine to create adverse conditions for listening to and understanding what the teacher is saying. Four experiments were conducted to investigate the combined effects of background babble noise (quiet vs. noise), voice quality (normal vs. dysphonic), and speechreading (audio-only vs. audio-visual cues) on speech understanding in 245 eight-year old children. Comprehension was tested using narratives from the test of Clinical Evaluation of Language Fundamentals. Background babble noise was composed of several children talking. Visual speech cues were presented using a digitally animated talker. Vocal loading was used to induce a dysphonic (hoarse) voice. Speech understanding was reduced by even low levels of babble noise, but compensated by visual cues. Dysphonia did not significantly reduce comprehension scores, but it was considered unpleasant. There was some evidence that performance in adverse conditions was positively associated with individual differences in cognitive executive function. Overall, these results suggest that multiple factors combine to influence speech understanding and listening effort for child listeners in the primary school classroom. The constellation of these room, talker, modality, and listener factors should be taken into account in the planning and design of educational and learning activities.
Verification of average absorption coefficients—A follow-up on one of Murray Hodgson’s Classroom Acoustics Projects
Authors: Scherebnyj Katrina
Published: October 2018

Twelve years ago, multivariable linear-regression analysis techniques were used with data from over a hundred UBC classrooms to estimate the “average” absorption coefficient of typical surfaces in classrooms. The purpose of the work was to obtain accurate estimates that could be used in the design of new classrooms, to better predict the early-decay time[1]. The current paper applies the results from the previous work to new classrooms, outside UBC. Detailed information is known regarding the surface types and absorption coefficients used in these classrooms. Measurements of the early decay times have also been taken. Comparisons are made between the early-decay times predicted using standard absorption coefficients, the “average” absorption coefficients from the UBC classrooms, and measurements. [1] Hodgson M., Scherebnyj K. Technical note—Estimation of the absorption coefficients of the surfaces of Classrooms. Applied Acoustics 67 (2006) 936–944.
Antarctic type C killer whale (Orcinus orca) call repertoire from McMurdo Sound, Ross Sea
Authors: Wellard Rebecca , Pitman Robert , Durban John , Erbe Christine
Published: October 2018

Killer whales (Orcinus orca) are found in all oceans of the world. In Antarctic waters, five ecotypes have been described, each displaying distinct differences in morphological features, foraging behaviours, habitat and diet preferences, and genetic structure. Acoustic recordings of Type C killer whales were collected between December 2012 and January 2013 in McMurdo Sound, Ross Sea, Antarctica. Spectrograms of acoustic data were examined for characteristic patterns of Type C vocalizations and a call type catalogue was produced. We measured acoustic parameters of each call type for both whistle and burst-pulse sounds and we then compared call features of Type C animals to those of other killer whales described in the Southern Hemisphere. Analysis of calls revealed that Type C killer whales produce a large number of biphonations and complex calls with multiple frequency-modulated and pulsed components. The limited accessibility of Antarctic regions year-round makes passive acoustic monitoring (PAM) a very effective tool to derive information on ecotype-specific distribution and seasonal occurrence. This study provides new information on the call repertoire of Type C killer whales, investigates the potential use of PAM to study Antarctic ecotypes, and also examines utilising call repertoire as a reliable diagnostic tool for identifying sympatric ecotypes in Antarctic waters.
Description of seasonal acoustic occurrences of humpback and minke whales in South Africa and Antarctica
Authors: Shabangu Fannie W.
Published: October 2018

Seasonal acoustic occurrences and diel singing patterns of humpback whale (Megaptera novaeangliae) songs and Antarctic minke (Balaenoptera bonaerensis) whale are described using acoustic recordings from the west coast of South Africa and Maud Rise, Antarctica. Acoustic data were recorded from early 2014 to early 2017. Acoustic occurrences (i.e., presence) of humpback and minke whale sounds were identified through visual scrutiny of spectrograms of recorded data. Environmental conditions associated with humpback whale song occurrences were ranked according to their model-predicted relative importance. In South Africa, humpback whale songs were detected from June to December but peaked in September. In Antarctica, humpback whale songs were detected from March to May (singing peaked in April). Minke whale sounds were only recorded in 2014, between June and September in Antarctica and between September and November in South Africa. Humpback whales were more vocally active at night in all recording sites whereas minke whales were more vocally active during the day. This is the first study to describe the seasonal acoustic occurrences of humpback and minke whales off the west coast of South Africa. Such knowledge could be essential for the conservation and management of these species in both South Africa and Antarctica.
Laboratory experimental assessment of models for elastic wave propagation in marine sands
Authors: Kimura Masao
Published: October 2018

Laboratory experimental research on the models for elastic wave propagation in marine sands has been performed. The speed dispersion and attenuation of compressional and shear waves using water-saturated unconsolidated glass beads and sands have been measured. The measured compressional wave speed dispersion and attenuation could be predicted by using a gap stiffness model incorporated into the Biot model (the BIMGS model) in the range of kd≤0.5 (k: wavenumber in water, d: grain diameter) and by using the BIMGS model plus multiple scattering effects in the range of kd≥0.5. The temperature and grain size dependence of shear wave speed dispersion and attenuation has been measured. The results showed the validity of the BIMGS model. Furthermore, the empirical equations for the tortuosity, permeability, and pore radius, which are important parameters in the Biot and modified Biot models, were derived. Finally, new laboratory experiments on the dependence of the compressional wave speed and attenuation on the temperature, and the effect of grain size distribution on speed dispersion and attenuation that may shed new light on the validity of the models will be suggested.
Ocean sediments and the Biot theory
Authors: Chotiros Nicholas P.
Published: October 2018

The surficial ocean sediment is usually a granular medium, therefore it is a porous medium and follows Biot’s theory. It predicts one shear wave and two compressional waves, called the fast and slow waves. This sets it apart from the acoustic theories of uniform media (solids or fluids) which permit only one compressional wave. The fast wave is similar to the compressional wave in a solid or fluid. The slow wave is unique to porous media, it is difficult to detect and its presence in the ocean sediment is controversial. There is indirect evidence of the Biot slow wave: The deviation of the acoustic reflection coefficient of the ocean sediment from Rayleigh’s reflection equation, can be explained in terms of the Biot slow wave. Direct detection of the Biot slow wave has been reported in some porous media, particularly sintered glass beads. However, its detection in unconsolidated media such as water saturated sand needs more work. Direct measurement of its properties is desirable. Simulations suggest that it could explain some unusual behavior of finely layered sediments. Finally, due to natural granularity, there should be a continuous conversion between the fast and slow waves that is missing from current models.
Estimating muddy seabed properties using ambient noise coherence
Authors: Barclay David R. , Bevans Dieter A. , Buckingham Michael J.
Published: October 2018

During the Seabed Characterization Experiment, a multi-institutional field effort held at the New England mud patch, the autonomous passive acoustic lander Deep Sound made a series of ambient noise measurements from the seafloor. The instrument platform carried four hydrophones, arranged in an inverted ‘T’ shape with three spaced in the horizontal and two in the vertical, and landed on the seafloor with the bottom phones 30 cm above the interface. Pressure time series, vertical and horizontal noise coherence (directionality), were recorded continuously for periods of 9 hours over the acoustic bandwidth of 5 Hz to 30 kHz, along with the local temperature, conductivity, and depth. An analytical Pekeris waveguide noise model was fitted to the data in order to determine the bulk sound speed, sheer speed, density, and frequency dependent attenuation in the bottom fluid half-space. Acoustic properties of the mud were determined by comparing the data to the output of a range independent noise model, featuring a realistic multi-layered seabed. [Research supported by ONR.]
Acoustic mapping of ocean currents using moving vehicles
Authors: Huang Chen-Fen , Chen KuangYu , Huang Sheng-Wei , Guo JenHwa , Taniguchi Naokazu
Published: October 2018

With the increased availability of highly maneuverable unmanned surface and underwater vehicles, abundant ocean environmental data can now be collected. Most environmental surveys by unmanned vehicles conduct point measurements of the ocean properties along survey lines. This study uses tomographic techniques to extend the survey area covered by the autonomous vehicles and obtain a synoptic ocean current distribution. An acoustic reciprocal transmission experiment was carried out on June 27, 2017, in ChaoJing Bay nearby Keelung City, where the water depth varies from 20 m to 65 m. A total of three tomographic sensors were deployed and they were installed on an AUV, a fishing boat, and a bottom-moored buoy. Reciprocal acoustic transmissions between the mobile platforms were used to estimate ocean currents, which required accounting for the Doppler effects on the acoustic arrival patterns and the resulting differential travel times. The estimated areal currents show consistency with the ADCP current measurement from the boat when the covered area was near the deeper water.
Information content of ship noise on a drifting volumetric array for passive environmental sensing
Authors: Kubicko Jacquelyn S. , Verlinden Christopher M. , Sabra Karim G. , Sarkar Jit , Nichols Brendan , Martin James S. , Fagan Aileen
Published: October 2018

This study investigates the information content of ship noise received on a drifting volumetric array of hydrophones in shallow water marine environments for the purposes of conducting acoustic thermometry or other environmental inversions. Passive inversions for physical oceanographic parameters are conducted using travel time differences, determined by cross-correlating ship noise received on hydrophones suspended beneath drifting buoys. Ships are tracked using the Automatic Identification System (AIS). Information content gained from the inversion is assessed using traditional a-posteriori error analysis. Numerical simulations using a standard normal mode propagation model are used to test limitations of the proposed approach with respect to frequency band, drifting receiver configuration, precision and accuracy of the inversion results, along with sensitivity to environmental and position mismatch. Performance predictions using this model are compared with results from a field experiment using at-sea data collected off the coast of New London, CT in Long Island Sound. Information gathered using passive acoustic inversion methods on drifting arrays can be used to constrain general circulation models (GCMs), in coastal environments, where ship noise is ubiquitous, environmental data are sparse, and the oceanography is dynamic and important for understanding large-scale ocean processes.
Using ships of opportunity for array element localization and relative channel impulse response estimation
Authors: Gemba Kay L. , Sarkar Jit , Cornuelle Bruce , Hodgkiss William S. , Kuperman William A.
Published: October 2018

The uncertainty of estimating relative channel impulse responses (CIRs) obtained using the radiated signature from a ship of opportunity is investigated. The ship observations were taken during a 1.4 km (11 min) transect during the Noise Correlation 2009 (NC09) experiment. Beamforming on the angle associated with the direct ray-path yields an estimate of the ship signature, subsequently used as a matched filter. Relative CIRs are estimated every 2.5 s independently at three vertical line arrays (VLAs) for a total of 270 observations per VLA. The estimated relative arrival-time uncertainty is inversely proportional to source bandwidth and CIR signal-to-noise ratio, and reached a minimum standard deviation of 5 μs (approximately 1 cm). The direct-path relative arrival-times are used to construct time series for each VLA element across the 11 min observation interval. The overall structure of these time series compares favorably with that predicted from an array element localization (AEL) model that exhibits sensitivity on the order of centimeters. The short-term standard deviations calculated on direct-path (7 μs) and bottom-reflected-path (17 μs) time series are in agreement with the estimated arrival-time accuracies. The implication of these observed arrival-time accuracies in the context of making sound speed perturbation and bottom-depth estimates is discussed.
High-resolution space-time spectral estimation method for array signal based on deconvolution
Authors: Guo Wei , Piao Shengchun
Published: October 2018

Conventional beamforming and classical spectral estimation methods are widely used in array signal processing to estimate the angular and frequency spectrum, respectively. But the spectra provided by these algorithms appear as low resolutions and high side lobes because of the limited array aperture and the number of snapshots. Then a multi-dimensional window function is defined, which is composed of the snapshot number and array aperture. Based on the theories of space-time joint spectral estimation, the multi-dimensional power spectrum about the azimuthal angle and frequency of array signal can be deduced as the convolution of the multi-dimensional power spectrum of the true signal and the power spectrum of the multi-dimensional window function. Therefore, the deconvolution algorithm can be introduced to remove the influence from the window function to recover the power spectrum of the true signal which is considered to be received from the infinite time and space. It is illustrated from simulations and experimental data processing that the deconvolution method can greatly improve the angular and frequency resolutions of the multi-dimensional spectrum, suppress the side lobes and provide extra signal-to-noise ratio, which can be applied for multi-target identification and weak signal detection.
Time delay estimation based on cross power spectrum with Doppler compensation
Authors: Han Xue , Guo Wei , Piao Shengchun
Published: October 2018

Time delay estimation is an important topic in underwater acoustic field. However, the Doppler phenomenon caused by relative movement between the source and receivers can arise errors in time delay estimation. In order to deal with this problem, a time delay estimation method based on cross power spectrum with Doppler compensation in frequency domain is proposed in this paper. The proposed method separates the Doppler compensation from the time delay estimation rather than estimates them jointly. The results of simulations and experimental data processing show that this method can improve the estimation accuracy of time delay with the influence of Doppler phenomenon.
Simulated target insertion for automatic target recognition performance estimation
Authors: Abiva Jeannine , Gazagnaire Julia
Published: October 2018

To support automatic target recognition (ATR) algorithm development as well as predict their performance in various operational environments, there is a need for more realistic sonar data that captures environmental effects that are not only difficult to model using physical acoustical models but expensive to measure in the real world. Previous target insertion efforts have focused on high frequency imaging sonar. As such, these efforts effectively combine only the magnitudes of the real and simulated data. This effort will focus on low frequency sonar, and the goal is to retain the phase by combining the complex data where possible. Maintaining the phase allows us to take advantage of the resonant frequency information available in the lower frequency bands, which is lost when the magnitudes are summed. In this effort, several approaches to inserting simulated target data into real sonar data will be investigated. Typically, there are no shadows in the low frequency images; therefore, none of the approaches investigated here take shadows into account. For each method, an analysis will be carried out to evaluate how the simulated targets behave compared to real targets. These analyses will be performed on real and simulated image snippets, gradients of snippets, and the frequency content of the target scattering response or acoustic color plots. The analysis will include several statistical measures which will be used to compare snippets of real and simulated targets as well as backgrounds of their immediate surroundings.
Source localization based on matrix filter and sparse asymptotic minimum variance
Authors: Zhang Yahao , Yang Yixin , Yang Long
Published: October 2018

Wideband direction of arrival (DOA) estimation plays an important role in passive sonar signal processing. Recently, sparsity-based DOA estimation method has attracted considerable attention because of its high resolution in the condition of few snapshots and low signal-to-noise ratio. However, the localization accuracy is seriously affected by the interferences. Matrix filter (MF) has been widely used in passive sonar systems as a useful tool to passband the targets-of-interest while attenuating the interferences, but the output of the MF seriously affected subsequent DOA estimation when the power of the interferences after filtering is still stronger than the weak targets. In this paper, a method based on MF and sparse asymptotic minimum variance (SAMV) is given to localize the weak targets in a strong interference environment. The given method improves the ability of SAMV on weak targets localization and achieves high localization accuracy even in the condition that the power of the interferences after filtering remains stronger than the weak targets, which is verified by simulation and experimental results.
Bottom-laid targets imaging and classification using a synthetic circular array
Authors: Zhang Ting , Yang T. C.
Published: October 2018

Detection and classification of bottom-laid targets in littoral area represents a serious problem for the navies of the world. It has been shown based on past acoustic research that the backscattered field carries a lot of information about the subject in terms of frequency and angular distribution if ensonified over a wide range of distance and can thus be used to different a mine from a stone or one type of mine from the other, referred to as acoustic color image. A circular array is more advantageous compared to a planar array as circular patterns maximize the aperture，and due to its high angular resolution, one can search and classify multiple targets at the same time. While it is difficult to deploy a large circular array since one does not know where is the target and the circular array needs to have a large diameter. Therefore, in this work, one will demonstrate effective bottom-laid targets imaging and classification using a synthetic circular array, which is created by a towed line array. We will study the concept of the proposed system and make simplified assumptions in order to obtain a crude estimate of the system performance.
Scientists who beat the odds seek victory in November
Authors: Mervis Jeffrey
Published: October 2018

Candidates, all Democrats, learned in the primaries that a science background by itself does not sway voters.
DNGR-1 in dendritic cells limits tissue damage by dampening neutrophil recruitment
Authors: del Fresno Carlos , Saz-Leal Paula , Enamorado Michel , Wculek Stefanie K. , Martínez-Cano Sarai , Blanco-Menéndez Noelia , Schulz Oliver , Gallizioli Mattia , Miró-Mur Francesc , Cano Eva , Planas Anna , Sancho David
Published: October 2018

The absence of DNGR-1 is dangerous

Conventional type 1 dendritic cells (cDC1s) can sense tissue damage via DNGR-1, which binds F-actin exposed by necrotic cells. DNGR-1 activation favors cross-presentation, the process by which extracellular antigens are processed and presented to CD8
+
T cells via major histocompatibility complex class I molecules. Del Fresno
et al.
studied mice lacking DNGR-1 and found that DNGR-1 also has anti-inflammatory effects (see the Perspective by Salazar and Brown). It inhibits the secretion of the chemokine CXCL2 by cDC1s, which, in turn, limits neutrophil recruitment. Thus, DNGR-1 connects cell-death sensing with a mechanism of damage control.

Science
, this issue p.
351
; see also p.
292
A family of finite-temperature electronic phase transitions in graphene multilayers
Authors: Nam Youngwoo , Ki Dong-Keun , Soler-Delgado David , Morpurgo Alberto F.
Published: October 2018

Thickness matters in graphene stacks

If you stack graphene monolayers on top of each other, the number of layers will affect the properties of the material. Intuitively, one would expect that as the stack becomes thicker, the results will converge as the sample starts to resemble graphite. Nam
et al.
measured the conductance of graphene multilayers of increasing thickness. Studying samples up to seven layers thick, they found that in all of them, electronic correlations caused a phase transition at a nonzero critical temperature. However, the critical temperature, as well as the nature of the low-temperature state, depended strongly on the number of layers. This unexpectedly persistent dependence showed no signs of slowing down and will motivate further theoretical and experimental work.

Science
, this issue p.
324
Earth's soft heart
Authors: Irving Jessica C. E.
Published: October 2018

A modern seismological method raises questions about the properties of Earth's inner core
Toward human egg-like cells in vitro
Authors: Gill Mark E. , Peters Antoine H. F. M.
Published: October 2018

Human precursor egg-like cells are produced in mouse ovary organoids to study infertility
Corticosteroids for the prevention of bronchopulmonary dysplasia in preterm infants: a network meta-analysis
Authors: Zeng Linan , Tian Jinhui , Song Fujian , Li Wenrui , Jiang Lucan , Gui Ge , Zhang Yang , Ge Long , Shi Jing , Sun Xin , Mu Dezhi , Zhang Lingli
Published: October 2018

Objective

To determine the comparative efficacy and safety of corticosteroids in the prevention of bronchopulmonary dysplasia (BPD) in preterm infants.

Study design

We systematically searched PubMed, EMBASE and the Cochrane Library. Two reviewers independently selected randomised controlled trials (RCTs) of postnatal corticosteroids in preterm infants. A Bayesian network meta-analysis and subgroup analyses were performed.

Results

We included 47 RCTs with 6747 participants. The use of dexamethasone at either high dose or low dose decreased the risk of BPD (OR 0.29, 95% credible interval (CrI) 0.14 to 0.52; OR 0.58, 95% CrI 0.39 to 0.76, respectively). High-dose dexamethasone was more effective than hydrocortisone, beclomethasone and low-dose dexamethasone. Early and long-term dexamethasone at either high dose or low dose decreased the risk of BPD (OR 0.11, 95% CrI 0.02 to 0.4; OR 0.37, 95% CrI 0.16 to 0.67, respectively). There were no statistically significant differences in the risk of cerebral palsy (CP) between different corticosteroids. However, high-dose and long-term dexamethasone ranked lower than placebo and other regimens in terms of CP. Subgroup analyses indicated budesonide was associated with a decreased risk of BPD in extremely preterm and extremely low birthweight infants (OR 0.60, 95% CrI 0.36 to 0.93).

Conclusions

Dexamethasone can reduce the risk of BPD in preterm infants. Of the different dexamethasone regimens, aggressive initiation seems beneficial, while a combination of high-dose and long-term use should be avoided because of the possible adverse neurodevelopmental outcome. Dexamethasone and inhaled corticosteroids need to be further evaluated in large-scale RCTs with long-term follow-ups.
Endoscopic resection of a huge orbital ethmoidal mucocele masquerading as dacryocystocele
Authors: Wong Eugene , Leith Nicholas , Wilcsek Geoff , Sacks Raymond
Published: October 2018

Paranasal mucoceles are cystic masses lined with epithelium thought to result from chronic obstruction of an impaired sinus ostia. If sufficiency large, they can cause ophthalmological sequelae including diplopia, visual acuity, globe displacement as well as the rhinological symptoms of facial pain and headache. We present the case of a 57-year-old man who presented with a 1-year history of epiphora and right globe prominence with associated diplopia. Imaging demonstrated a mass located within the medial aspect of the orbit, closely associated to the lamina papyracea and nasolacrimal duct consistent with a dacryocystocele. An alternate diagnosis of an ethmoidal mucocele was considered preoperatively following rhinologist opinion. Complete endoscopic resection of the cyst was undertaken. Histopathology confirmed diagnosis of an ethmoidal mucocele. Our report highlights mucocele should be considered in patients with chronic symptoms secondary to a mass situated in the nasolacrimal duct without radiological orbital bone destruction.
Development of acquired haemophilia A in a patient treated with alemtuzumab for multiple sclerosis
Authors: Madeley Jarrett , Hodges Georgina , Birchley Andrew
Published: October 2018

This case illustrates a 36-year-old man who presented with a factor VIII (FVIII) inhibitor (acquired haemophilia A) with cutaneous bleeding and a significant thigh haematoma. No traditional risk factors for the development of a FVIII inhibitor were identified. However, previous treatment with alemtuzumab for multiple sclerosis was noted in the patient’s history. Alemtuzumab is an anti-CD52 monoclonal antibody and is known to be associated with the development of a number of autoimmune conditions, with a delay in onset of these conditions as long as 5 years after the cessation of treatment. To our knowledge, there have only been three previously documented cases of a FVIII inhibitor in the setting of alemtuzumab therapy. This case adds further evidence to the current body of literature suggesting alemtuzumab as a causative agent for the development of an FVIII inhibitor.
Impact of prenatal exercise on both prenatal and postnatal anxiety and depressive symptoms: a systematic review and meta-analysis
Authors: Davenport Margie H , McCurdy Ashley P , Mottola Michelle F , Skow Rachel J , Meah Victoria L , Poitras Veronica J , Jaramillo Garcia Alejandra , Gray Casey E , Barrowman Nick , Riske Laurel , Sobierajski Frances , James Marina , Nagpal Taniya , Marchand Andree-Anne , Nuspl Megan , Slater Linda G , Barakat Ruben , Adamo Kristi B , Davies Gregory A , Ruchat Stephanie-May
Published: October 2018

Objective

To examine the influence of prenatal exercise on depression and anxiety during pregnancy and the postpartum period.

Design

Systematic review with random effects meta-analysis and meta-regression.

Data sources

Online databases were searched up to 6 January 2017.

Study eligibility criteria

Studies of all designs were included (except case studies) if they were published in English, Spanish or French and contained information on the Population (pregnant women without contraindication to exercise), Intervention (subjective or objective measures of frequency, intensity, duration, volume or type of exercise), Comparator (no exercise or different frequency, intensity, duration, volume and type of exercise) and Outcome (prenatal or postnatal depression or anxiety).

Results

A total of 52 studies (n=131 406) were included. ‘Moderate’ quality evidence from randomised controlled trials (RCTs) revealed that exercise-only interventions, but not exercise+cointerventions, reduced the severity of prenatal depressive symptoms (13 RCTs, n=1076; standardised mean difference: −0.38, 95% CI −0.51 to –0.25, I2=10%) and the odds of prenatal depression by 67% (5 RCTs, n=683; OR: 0.33, 95% CI 0.21 to 0.53, I2=0%) compared with no exercise. Prenatal exercise did not alter the odds of postpartum depression or the severity of depressive symptoms, nor anxiety or anxiety symptoms during or following pregnancy. To achieve at least a moderate effect size in the reduction of the severity of prenatal depressive symptoms, pregnant women needed to accumulate at least 644 MET-min/week of exercise (eg, 150 min of moderate intensity exercise, such as brisk walking, water aerobics, stationary cycling, resistance training).

Summary/Conclusions

Prenatal exercise reduced the odds and severity of prenatal depression.