Low Sound Speed Research Articles

Abstract P1-02-05: Breast cancer development at the fat-gland interface (FGI): Importance of coronal imaging and ultrasound tomography

Abstract PURPOSE. Recent analyses of tumor location by breast magnetic resonance (MR) imaging have shown that breast cancers were significantly more likely to be located, at or near the fat-gland interface (FGI). However, these analyses did not include benign masses or coronal evaluations. Ultrasound tomography (UST) is a novel multi-sequence tomographic form of sonography with anatomic and physiologic information that can improve the sensitivity of breast cancer detection, particularly in women with dense breasts. The purpose of this study was to use the native coronal imaging plane of UST SoftVue (Delphinus Medical Technologies, Inc.) to map the locations of cancers, fibroadenomas and cysts, relative to the FGI, in order to facilitate the detection and characterization of breast masses in future UST screening. METHODS AND MATERIALS. Mass location in coronal UST images was determined by a MQSA certified radiologist with extensive UST imaging experience. The relationship of the lesion to the FGI was noted for a total of 427 breast masses (117 cancers, 135 fibroadenomas, 135 cysts and 40 other benign findings), confirmed by biopsy or by hand-held ultrasound for masses that fulfilled all criteria for a simple cyst. The FGI was defined as the circumferential interface between the peripheral fat and parenchyma as determined by examining sound speed (SS) images, which reliably differentiate the much lower SS of fat compared to that of dense tissue. Mass location was placed into three groups: (i) completely surrounded by dense fibroglandular tissue, (ii) completely surrounded by fat or (iii) partially surrounded by both (i.e., the FGI). Lesion locations relative to FGI were compared using the chi-squared test. RESULTS. Cancers were located at the FGI in 93.2% (109/117) of the cases and were surrounded by fat in 6.0% (7/117) or parenchyma in 0.9% (1/117) (p<0.001) of the cases, respectively (Table 1). For fibroadenomas, 63.0% (85/135) were found at the FGI while 29.9% of cysts were found at the FGI. Moreover, 68.9% of cysts and 31.1% of fibroadenomas were fully surrounded by dense tissue which was dramatically more than cancers (0.9%). DISCUSSION. Coronal imaging by UST provides reliable circumferential evaluation of the FGI, which can be augmented by axial/sagittal reconstructions as needed for additional confirmation of anterior/posterior aspects of the FGI. Our results confirm the previously reported MRI findings that cancers have a very strong tendency to be located at the FGI and extend these findings by demonstrating that benign masses have a weaker tendency in that regard. With the introduction of UST, our finding that breast cancers occur more frequently at the fat-gland interface may facilitate the conspicuity, rapid search and localization of cancers during screening of women with dense breasts. Perhaps equally important for future specificity of screening women with dense breasts, fibroglandular tissue surrounded only 0.9% of cancers and was much more commonly associated with benign masses. CONCLUSIONS. The native coronal imaging plane by SoftVue UST facilitated detection and localization of cancers, which were much more likely to be found at the FGI (p<0.001), compared to masses surrounded by fibroglandular tissue were much more likely to be benign. UST is a novel new technology that has the potential for improved breast cancer detection. This study supports its possible integration into clinical practice. Table 1Type of massAt FGIIn Dense tissueIn FatCancer109 (93%)1 (1%)7 (6%)Fibroadenoma85 (63%)42 (31%)8 (6%)Cyst39 (29%)93 (69%)3 (2%) Citation Format: Peter Littrup, Mark Sak, Neb Duric, Rachel Brem. Breast cancer development at the fat-gland interface (FGI): Importance of coronal imaging and ultrasound tomography [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P1-02-05.

Research on Wind Noise Estimation Method by Synchronous Measurement of Low Frequency Sound and Wind Speed

Research on Wind Noise Estimation Method by Synchronous Measurement of Low Frequency Sound and Wind Speed

Aqueous acoustic metasurface for the anomalous reflection of sound

Ultrathin structures known as acoustic metasurfaces offer the same ability to achieve extreme properties as acoustic metamaterials, yet have the added potential benefit of being very thin (much less than a wavelength in thickness). In this work, we discuss an aqueous acoustic metasurface that utilizes subwavelength non-resonant embedded cavities to achieve anomalous reflection of incident acoustic waves impinging over a wide range of angles. The metasurface was constructed using air-filled cavities in a low-shear matrix material and designed to shift the angle of the reflected wave by 30 deg. The use of a low sound speed matrix material and non-resonant cavities enabled operation over a wider range of frequencies and incident angles while maintaining subwavelength thickness. The cavity heights were varied to achieve 0 to 2π phase shifts in a unit cell according to the generalized form of Snell’s Law. The fabricated structure was mounted on a brass plate and experimentally tested in water. Very good agreement was found between finite element models and the experimental ultrasonic tank tests of the aqueous acoustic metasurface. [Work supported by the Office of Naval Research.]

Direction for High-Performance Supercritical CO2 Centrifugal Compressor Design for Dry Cooled Supercritical CO2 Brayton Cycle

To overcome the degradation of the cycle efficiency of a supercritical carbon dioxide (S-CO2) Brayton cycle with dry cooling, this study proposes an improved design of an S-CO2 centrifugal compressor. The conventional air centrifugal compressor can achieve higher efficiency as backsweep angle increases. However, the structural issue restricts the maximum allowable angle (−50~−56°). In this study, an S-CO2 centrifugal compressor performance was examined while changing the backward sweep angle at impeller exit to study if the previous optimum backsweep angle for an air centrifugal compressor is still valid when the fluid has changed. It is shown through an analysis that an S-CO2 centrifugal compressor can achieve the highest efficiency at −70° backsweep angle, which is greater than the typical design value. The S-CO2 centrifugal compressor is less restricted from a structural integrity issue because it has low relative Mach number regardless of the low sound speed near critical point (Tc = 304.11 K, Pc = 7377 kPa). It is also shown in the paper that the variation of compressibility factor does not impact on its total to total efficiency since its Mach number is still lower than unity. Finally, it is also shown that a backward sweep impeller can achieve higher pressure ratio and operate stably in wider range as the mass flow rate is decreased. As further works, the suggested concept will be validated by the structural analysis and the compressor performance test.

Ship-of-Opportunity Noise Inversions for Geoacoustic Profiles of a Layered Mud-Sand Seabed

This paper considers the use of broadband noise from a ship-of-opportunity in statistical inference for estimating geoacoustic parameters of a layered mud-sand seabed model via trans-dimensional (trans-D) Bayesian matched-field inversion, with applications to data collected with a bottom-moored horizontal array in the 2017 Seabed Characterization Experiment conducted on the New England Shelf. The trans-D approach applied here samples probabilistically over possible model parameterizations (different numbers of seabed layer interfaces), and provides quantitative uncertainty estimates of seabed geoacoustic profiles. Inversions are carried out for acoustic data sets collected both when the ship-of-opportunity (a container ship) was oriented with its bow and with its stern towards the array. A third inversion involved combining data from a series of segments along the ship track. Inversion results image an upper sediment layer 3–7 m thick with low-sound speed (close to the water sound speed) over higher speed sediment, with indication of a transition layer above the interface. Sediment parameter estimates from the inversions are in good agreement with direct measurements from sediment cores and other geophysical data collected in the experiment area.

Geoacoustic provinces of the northern South China Sea based on sound speed as predicted from sediment grain sizes

The determination of geoacoustic provinces has important applications in assessing the responses of sedimentary environment and processes. Suitable geoacoustic provinces have not yet been identified in the northern South China Sea, which is an excellent study site for examining sediment acoustic properties. To determine the geoacoustic provinces of sediments in the northern South China Sea, 270 position samples were collected and analysed. Two-parameter empirical equations linking sediment grain-size components to sound speed were applied to sediments from the continental shelf and slope to accurately calculate sound speed in seafloor sediments, especially in the absence of site-specific acoustic data. Based on the ratios of sound speed within the sediments, two geoacoustic provinces are identified. Province I, which is characterized by low sound speed, primarily consists of fine-grained sediments discharged from the Pearl River. Province II, which is characterized by high sound speed, can be further divided into Province II-A and Province II-B. Province II-A is composed of mixed modern and relict sediments originating from the Pearl River and the southwest coast of Taiwan during a Pleistocene drop in sea level. Province II-B consists of coarser relict sediments caused by sea level change during the late Quaternary.

Gas propellant dependency of plasma structure and thrust performance of microwave rocket

To identify the characteristics of a suitable gas propellant for a microwave rocket, the discharge physics induced by an intense microwave in nitrogen, hydrogen, and helium was numerically reproduced by coupling a plasma fluid model with an electromagnetic wave propagation model. A discrete plasma structure was induced in nitrogen and hydrogen, because the ionization region was smaller than the incident-beam quarter wavelength. However, a diffusive plasma pattern was generated in helium, because the electron temperature increased and the electron-impact ionization was maintained even in the low-electric-field region. The shock wave propagation inside the rocket nozzle was numerically reproduced to evaluate the thrust performance dependence on the propellant species; this was achieved by solving the two-dimensional axisymmetric Euler equation with an energy source term for the microwave heating. The simple shock-tube theory indicated that the momentum coupling coefficient is proportional to the energy stored inside the rocket nozzle and inversely proportional to the propellant sound speed. The smallest momentum coupling coefficient was obtained for the helium case, although the sound speed in helium is faster than that in hydrogen. This was because insufficient energy was stored inside the rocket nozzle when helium was used, owing to the faster plasma propagation and lower energy absorption rate. The findings of this work indicate that to obtain a large thrust for a microwave rocket, selection of a gas propellant with a high energy absorption rate, small electron diffusion coefficient, low sound speed, and low specific heat ratio are preferable.

Advanced Glycation End Product Accumulation Is Associated With Low Skeletal Muscle Mass, Weak Muscle Strength, and Reduced Bone Density: The Nagahama Study.

The accumulation of advanced glycation end product (AGE) might exert deleterious effects on musculoskeletal properties. Our study aims to clarify this possible association in a large general population. This study investigated a general population of 9,203 patients (mean age, 57.8 years). Skeletal muscle mass was measured by bioelectrical impedance analysis, whereas accumulation of AGEs was assessed by skin autofluorescence (SAF-AGE). The muscle strength of upper and lower limbs and usual gait speed were measured in a portion of older (≥60 years of age) participants (n = 1,934). The speed of sound (SOS) in the calcaneal bone was assessed via a quantitative ultrasound technique. In the total population, the frequency of low skeletal muscle mass linearly increased with the SAF-AGE quartiles (Q1: 14.2%, Q2: 16.1%, Q3: 21.1%, Q4: 24.8%; p < .001), and this association was independent of covariates including glycemic traits (Q4: odds ratio [OR] = 1.48, p < .001). The association between the highest SAF-AGE quartile and low skeletal muscle mass remained significant in the older subpopulation (OR = 1.85, p = .002). A similar but weak association was observed for low SOS (Q1: 8.9%, Q2: 8.3%, Q3: 10.4%, Q4: 12.2%; p < .001). Similar inverse associations were also observed with grip strength (OR = 1.98, p = .003), hip flexion strength (OR = 1.50, p = .012), and hip abduction strength (OR = 1.78, p = .001), but not with usual gait speed. Accumulation of AGEs might be a deleterious factor for musculoskeletal properties.

Underwater Distributed Antenna Systems: Design Opportunities and Challenges

Underwater systems for ocean exploration and monitoring consist of a mix of geographically distributed stationary infrastructure and mobile units. The stationary infrastructure could be bottom-anchored nodes and surface buoys that are connected to a control center via cables and in-air radio links. Both the stationary and mobile units can be equipped with acoustic communication modules for underwater wireless data transmission. With the backbone (cable or radio) connection, those acoustic communication modules naturally form an underwater DAS. Similar to the DAS in terrestrial radio networks, the underwater DAS supports larger acoustic communication coverage and higher network throughput compared to the CAS. Furthermore, the characteristics of underwater acoustic channels, such as the frequency-dependent signal absorption loss and the low sound speed in water, lead to unique design challenges and unforeseen opportunities in the underwater DAS. This article examines both theoretical and system design issues pertaining to the underwater DAS, including operation strategies, communication algorithms and mobile node positioning, and pinpoints future research directions to fully realize its potentials.

Experimental research on high energy initiation technology for detonation driver

A shock tunnel with gaseous detonation driver is fit for simulating test gas with high total temperature and pressure, since the sound speed of the driving gas is comparatively high. Decreasing the sound speed of the driving gas can lead to initial detonation difficulties and is therefore deficient in low total temperature and high total pressure gas simulations. In this study, a new high-energy detonation initiation method, the closed-type ignition tube, is proposed, in which initial detonation is achieved in high-concentration nitrogen-diluted hydrogen-oxygen mixed gas and a low-sound speed driving gas is successfully obtained. By experiment, the dominant factors of igniter tube initiation energy are defined, and the design principles of closed igniter tube are given. Through experiments and calculation, the influence mechanism of the new method on the flow process of shock tubes/tunnels is clarified, and the principle of using the new initiation tube is identified. Using this new method, low total temperature and high total pressure test gas could be obtained, which provides a feasible method for expanding the ground test capability of hypersonic flight conditions.

Asymmetric Propagation Delay-Aware TDMA MAC Protocol for Mobile Underwater Acoustic Sensor Networks

The propagation delay in mobile underwater acoustic sensor network (MUASN) is asymmetric because of its low sound propagation speed, and this asymmetry grows with the increase in packet travel time, which damages the collision avoidance mechanism of the spatial reuse medium access control (MAC) protocols for MUASN. We propose an asymmetric propagation delay-aware time division multiple access (APD-TDMA) for a MUASN in which periodic data packet transmission is required for a sink node (SN). Collisions at the SN are avoided by deferring data packet transmission after reception of a beacon packet from the SN, and data packets are arrived at the SN in a packet-train manner. The time-offset, which is the time for a node to wait before the transmission of a data packet after reception of a beacon packet, is determined by estimating the propagation delay over two consecutive cycles such that the idle interval at the SN is minimized, and this time-offset is announced by the beacon packet. Simulation results demonstrate that the APD-TDMA improves the channel access delay and the channel utilization by approximately 20% and 30%, respectively, compared with those of the block time bounded TDMA under the given network conditions.

Violent flows in aqueous foams III: physical multi-phase model comparison with aqueous foam shock tube experiments

Mitigation of blast waves in aqueous foams is a problem that has a strong dependence on multi-phase effects. Here, a simplified model is developed from the previous articles treating violent flows (D’Alesio et al. in Eur J Mech B Fluids 54:105–124, 2015; Faure and Ghidaglia in Eur J Mech B Fluids 30:341–359, 2011) to capture the essential phenomena. The key is to have two fluids with separate velocities to represent the liquid and gas phases. This allows for the interaction between the two phases, which may include terms for drag, heat transfer, mass transfer due to phase change, added mass effects, to be included explicitly in the model. A good test for the proposed model is provided by two experimental data sets that use a specially designed shock tube. The first experiment has a test section filled with spray droplets, and the second has a range of aqueous foams in the test section. A substantial attenuation of the shock wave is seen in both cases, but a large difference is observed in the sound speeds. The droplets cause no observable change from the air sound speed, while the foams have a reduced sound speed of approximately 50–75 $$\hbox {m}/\hbox {s}$$ . In the model given here, an added mass term is introduced in the governing equations to capture the low sound speed. The match between simulation and experiment is found to be satisfactory for both droplets and the foam. This is especially good when considering the complexity of the physics and the effects that are unaccounted for, such as three-dimensionality and droplet atomisation. The resulting statistics illuminate the processes occurring in such flows.

Estimation of parameters of gassy layer in sediment in shallow water using measurement of angular dependence and spectrum of reflection coefficient of wide-band signals

Method of estimation of gassy layer parameters in sediment (sound speed and thickness) on the base of measurement of angular and frequency dependencies reflection coefficient of wideband signals is presented. Experiments were carried out in Lake Kinneret (Israel), which is characterized by remarkable organic content in sediment producing methane bubbles. Direct chemical, biological analysis and usage of frozen cores show comparatively narrow layer (a few tens of cm) changing in dependence on season. Principal point for acoustical method is low sound speed in bubble layer (up to 300–400 m/s) and big reflection coefficient from the corresponding half-space (0.6–0.7 for vertical incident). Due to narrow gassy layer, there should be half wavelength resonances at the corresponding frequencies. In experiments, wideband signals were used (500–2500 Hz) and receiving system: single hydrophone (1 m from source) and vertical line array. Estimation of layer’s parameters was carried out using measured reflection coefficient as a function of frequency and angle of reflection. Resonance frequencies were 800 Hz and 1600 Hz. The corresponding analysis of data give values of thickness 25–30 cm, with the sound speed in layer 400–450 m/c. Results are compared with experimental data obtained by direct measurements. [Work was supported by ONRG and ISF.]

Blast mitigation with fluid Containers: Effect of mitigant type

The effect of filled external containers on the deformation induced in a steel plate under near-field blast loading has been investigated through a combined numerical and experimental study. Six different fill materials (mitigants) were considered for inducing near-field blast mitigation. The mitigants evaluated were bulk water, aerated water, sand, expanded polystyrene (EPS), a combination of EPS and water, and shear thickening fluid. The performance of the mitigants depended on their mass, with sand providing the best mitigation and EPS the worst for a given volume. Bulk water provided the greatest reduction of the peak deformation per unit of added mass. The mitigant material also had a significant effect on the deformation-time history of the steel plate. The sand and ½ EPS + ½ water containers were found to significantly delay the arrival of the pressure wave at the target surface due to their compressibility and low sound speed. Numerical analysis reveals that different mechanisms induce blast mitigation, and these are identified for each of the different mitigant materials.

Experimental realization of enhancing low-frequency sound emission by metamaterial enclosure

A solution to the low radiation rate of a sound source has been proposed by using metamaterial enclosures of degenerated Mie resonances [J. Zhao, L. Zhao, and Y. Wu, J. Acoust. Soc. Am. 142(1), EL24–29, July 2017]. This talk presents our experimental realization of this enhancement for a monopole source. The enclosure with a low sound speed is created by a coiling-space structure fabricated by 3D printing. A small balanced-armature speaker with a 1 mm speaker mouth is placed at the enclosure center to radiate impulsive sound signals. The diameter of the structure is only one seventh of the wavelength of the sound at the maximum enhancement, corresponding to the lowest resonance. The enhanced sound pressure is more than two orders of magnitude larger than the sound pressure without the enclosure. The measurements of sound pressure at different angles in the space show the omnidirectionality of the enhancement. This enhancement is demonstrated as a result of enhanced density of states, i.e., the increased number of modes per unit frequency range and per unit volume, which we relate to Fermi's Golden rule and Purcell effect in quantum systems and find the analog in acoustics.

A diverse group of echogenic particles observed with a broadband, high frequency echosounder

Abstract In 1980, Holliday and Pieper stated: “Most sound scattering in the ocean volume can be traced to a biotic origin.” However, most of the bioacoustics research in the past three decades has focused on only a few groups of organisms. Targets such as small gelatinous organisms, marine snow, and phytoplankton, e.g. have been generally to be considered relatively transparent to acoustic waves due to their sizes and relatively low sound speed and density contrasts relative to seawater. However, using a broadband system (ZOOPS-O2) we found that these targets contributed significantly to acoustic returns in the 1.5–2.5 MHz frequency range. Given that phytoplankton and marine snow layers are ubiquitous features of coastal regions; this works suggests that they should be considered as potential sources of backscatter in biological acoustic surveys.

Enhancing monochromatic multipole emission by a subwavelength enclosure of degenerate Mie resonances.

Sound emission is inefficient at low frequencies as limited by source size. This letter presents enhancing emission of monochromatic monopole and multipole sources by enclosing the source with a subwavelength circular enclosure filled of an anisotropic material of a low radial sound speed. The anisotropy is associated with an infinite tangential density along the azimuth. Numerical simulations show that emission gain is produced at frequencies surrounding degenerate Mie resonant frequencies of the enclosure, and meanwhile the radiation directivity pattern is well preserved. The degeneracy is theoretically analyzed. A realization of the material is suggested by using a space-coiling structure.

Ultrahigh thermoelectric performance in Cu2−ySe0.5S0.5 liquid-like materials

Liquid-like thermoelectric materials have recently received heightened attentions due to their exceptional thermal and electrical transport properties. As a typical example, Cu2−ySe has good electrical transport properties while Cu2−yS has extremely low lattice thermal conductivity. Combining these stirring characters into one material is expected to result in excellent thermoelectric performance. In this study, we found that Cu2−ySe and Cu2−yS can form a solid solution in the composition range down to half Se and half S. XRD, SEM and TEM reveal that Cu2−ySe0.5S0.5 possesses a unique hierarchical microstructure composed of mesoscale polymorphs, nanoscale domains and modulations. Besides, the liquid-like copper ions at high temperature not only strongly scatter lattice phonons but also eliminate some of the transverse phonon vibrations. Combining with the extraordinarily low sound speeds, an overall ultralow thermal conductivity is achieved in Cu2−ySe0.5S0.5 with the values similar to that in Cu2S. Furthermore, the electrical transport performance of Cu2−ySe0.5S0.5 is significantly improved through tuning its native Cu vacancies. High electrical power factors similar to or even superior to Cu2−ySe are observed due to the high weighted mobility. All these favorable factors lead to much enhanced quality factor and thus remarkably high thermoelectric performance in Cu2−ySe0.5S0.5, which reaches a ZT of 2.3 at 1000 K, among the highest values in bulk materials.

Soft porous materials with ultra-low sound speeds in acoustic metamaterials

Porous media have unique acoustic properties that have been intensively studied for many decades and found many applications in various areas. Owing to their low sound speed, porous materials have proven to be interesting key elements for the realization of acoustic metamaterials since they may act as strong Mie-type resonators, when shaped as spherical particles [1]. In that context, soft porous silicone rubbers are ideal “ultra-slow” materials since a sudden drop of the longitudinal sound speed cL with the porosity Φ has been observed in these porous materials (cL < 100 m/s for Φ < 10%). Such unusual behavior is well captured by simple models based on low-frequency approximations of multiple scattering theories [2]. Then, I will discuss the interest of these “ultra-slow” particles for acoustic metamaterials of which the acoustic index has been shown to be negative [3]. At last, I will demonstrate that the exotic values of the acoustic index may be tuned by using other porous particles such as xerogel be...

Highly efficient isolation of waterborne sound by an air-sealed meta-screen

Underwater sound isolation has been a long-standing fundamental issue in industry and military fields. Starting from a simple theoretical model, here an air-sealed meta-screen is proposed to overcome this problem. Comparing with the sample without filling air, the effective impedance of the air-sealed one is greatly reduced and strikingly mismatch with water, accompanying another merit of low sound speed. Deeply suppressed sound transmission (∼50 dB) through such a meta-screen is observed experimentally over a wide range of ultrasonic frequencies and incident angles.