Acoustic Propagation Speed Research Articles

Research progress of optoelectronic devices based on diamond materials

Diamond has a variety of unique characteristics, including integrates mechanics, electricity, heat, optics and other excellent properties, so that it is widely focus on the field of high and new technology, especially in the optoelectronic technology. Because diamond has the characteristics of high thermal conductivity, high breakdown field (10 mV/cm), high electron and hole mobility, it has a wide application prospect in high temperature, high power and high frequency photoelectric equipment. The wide bandgap (5.47 eV) makes diamond an ideal material in ultraviolet detectors (UV). Its high carrier mobility and breakdown field strength make it an ideal choice for field emission materials, which are expected to be used in high-power electronic devices in the next few years. At the same time, in addition to high hardness, it also has various of excellent physical properties, such as low coefficient of thermal expansion, low coefficient of friction, high acoustic propagation speed and high optical transmittance, so that it has broad application prospects in many fields such as machining, microelectronic devices, optical windows and surface coatings. In addition, diamond also has a high exciton binding energy (80 meV), which plays an important development in deep ultraviolet and high-energy particle detectors. In this article, the latest progress in the application of diamond-based optoelectronic devices is reviewed. A variety of advanced devices and physical phenomena are considered, for example, sensors, transistors, memory, Light-emitting diode (LEDs), ultraviolet detectors and field emission. This review will provide a new idea to promote the development of photoelectric applications based on diamond structure.

Self-compensation methodology for ultrasonic thickness gauges

There are many causes for the reduction of the thickness in pipelines, tanks and other mechanical structures. Corrosion, erosion, and abrasive wear cause degradation of mechanical structures and decrease their lifespan. These can be very slow processes that are difficult to track over time. Thickness gauging monitoring is commonly used as a way of preventive maintenance. The pulse-echo ultrasound can be a suitable technique to measure the thickness diminution in industrial facilities. Although ultrasound is considered a robust technique, in this particular application it presents two main difficulties: the mechanical stability of the assembly and the variation of the ultrasonic speed over time. Both mechanical assembly and acoustic propagation speed are strongly influenced by the temperature. In this paper, the implementation of a methodology that compensates for the temperature influences on the ultrasonic speed and the mechanical assembly is presented. The methodology can be applied in metallic structures to evaluate corrosion over long time periods. The temperature compensation data is obtained from the analysis of the ultrasonic signals. In this sense, the method can be called self-compensated. As initial data for the determination of thickness changes, the ultrasonic speed in the material at a reference temperature must be known. All results are evaluated at this temperature. An analysis of the uncertainty sources and limitations of the methodology is also included. To show the experimental application of the proposed technique, a rigid sample was designed in order to avoid mechanical instability. The results show that the methodology can compensate for the temperature, detecting a thickness reduction in the order of a few micrometers.

Evaluating acoustic and thermal properties of a plaque phantom.

The aim of this study is to evaluate the acoustic and thermal properties of a plaque phantom. This is very important for the effective implementation of ultrasound not only in diagnosis but especially in treatment for the future. An evaluation of acoustic and thermal properties of plaque phantoms to test their suitability mainly for ultrasound imaging and therapy was presented. The evaluation included measurements of the acoustic propagation speed using pulse-echo technique, ultrasonic attenuation coefficient using through transmission immersion technique, and absorption coefficient. Moreover, thermal properties (thermal conductivity, volumetric specific heat capacity and thermal diffusivity) were measured with the transient method using a needle probe. It was shown that acoustic and thermal properties of atherosclerotic plaque phantoms fall well within the range of reported values for atherosclerotic plaque and slightly different for thermal diffusivity and volumetric specific heat capacity for soft tissues. The mean value of acoustic and thermal properties and their standard deviation of plaque phantoms were 1523 ± 23m/s for acoustic speed, 0.50 ± 0.02W/mK for thermal conductivity, 0.30 ± 0.21db/cm-MHz for ultrasonic absorption coefficient and 1.63 ± 0.46db/cm-MHz for ultrasonic attenuation coefficient. This study demonstrated that acoustic and thermal properties of atherosclerotic plaque phantoms were within the range of reported values. Future studies should be focused on the optimum recipe of the atherosclerotic plaque phantoms that mimics the human atherosclerotic plaque (agar 4% w/v, gypsum 10% w/v and butter 10% w/v) and can be used for HIFU therapy.

Leak Localization Method of Jet Fuel Pipeline Based on Second-Generation Wavelet Transform and Short-Time Energy Time Delay Estimation

There is a large error in the acoustic propagation speed of jet fuel pipeline based on cross correlation analysis, which leads to poor positioning accuracy of the leak location. Therefore, a new leak localization method of jet fuel pipeline based on second-generation wavelet (SGW) transform and short-time energy time delay estimation is proposed. Using SGW transform to extract the leak acoustic signal to reduce the interference of external noise in this method, the short-time energy function is estimated to calculate the sudden change time range of leak acoustic signal in the time window, so as to find the sudden change time range containing the sudden change point information of leak acoustic signal. According to the threshold of short-time energy function, the accurate sudden change time of leak acoustic signal is determined. When the accurate sudden change times of three acoustic sensors are obtained, the leak position of pipeline is calculated by a leak localization formula. The proposed method does not need to estimate the acoustic propagation speed, and it can obtain more accurate leak localization accuracy of pipeline leak. The field experimental pipeline results show that the average error rate of jet fuel pipeline leak localization is reduced from 1.25% of the cross correlation analysis method to 0.1% of the proposed method.

Design and Analysis of Handshake-Based MAC with Delay Variations in Underwater Acoustic Networks.

The long propagation delay in underwater acoustic channels has attracted tremendous attentions in designing Medium Access Control (MAC). The low acoustic propagation speed and wide area of the acoustic communication range led to a wide range of variations in the propagation delay. This paper identifies an important characteristic of two-scale delay variations by field test results. We carry out simulations to study the impact of delay variations on MAC, and the results suggest a slot length adaptation scheme for the handshake and slotting based MAC. We further model an absorbing Markov chain to derive the closed-form equation for the throughput of MAC with adaptive slot length. Both the analytical and simulation results show that our proposed slot length adaptation improves significantly the throughput of MAC in underwater acoustic networks. Particularly, the Slotted-FAMA with an adaptive slot length achieves more than double the throughput than the Slotted-FAMA with a fixed slot length in a network with six nodes.

Multiuser communication using adaptive time reversal with moving transmitter

The effect of transmitter movement in multiuser underwater acoustic communication using adaptive time reversal is studied in this paper. In an underwater acoustic channel, Doppler frequency shifts are very large owing to the low acoustic propagation speed, and they have different values depending on the propagation angle of each multipath. These problems are critical to orthogonal frequency division multiplexing (OFDM), which is widely used as the representative method. On the other hand, by time reversal, different frequency shifts are converged to one frequency shift by wave focusing. This advantageous characteristic was confirmed by normal mode simulation. At-sea experiments for multiuser communication with two transmitters taking into consideration transmitter movement were also carried out. As a result, it was found that adaptive time reversal enables multiuser communication independently of the velocity of the moving transmitter even under multiuser interference.

A Novel Cross-Layer Routing Protocol Based on Network Coding for Underwater Sensor Networks.

Underwater wireless sensor networks (UWSNs) have attracted increasing attention in recent years because of their numerous applications in ocean monitoring, resource discovery and tactical surveillance. However, the design of reliable and efficient transmission and routing protocols is a challenge due to the low acoustic propagation speed and complex channel environment in UWSNs. In this paper, we propose a novel cross-layer routing protocol based on network coding (NCRP) for UWSNs, which utilizes network coding and cross-layer design to greedily forward data packets to sink nodes efficiently. The proposed NCRP takes full advantages of multicast transmission and decode packets jointly with encoded packets received from multiple potential nodes in the entire network. The transmission power is optimized in our design to extend the life cycle of the network. Moreover, we design a real-time routing maintenance protocol to update the route when detecting inefficient relay nodes. Substantial simulations in underwater environment by Network Simulator 3 (NS-3) show that NCRP significantly improves the network performance in terms of energy consumption, end-to-end delay and packet delivery ratio compared with other routing protocols for UWSNs.

REALIZATION OF OFDM BASED UNDERWATER ACOUSTIC COMMUNICATION

Nowadays underwater communication plays a vital role in applications from commercial extends to military purposes. Present underwater communication systems involve the transmission of information in the form of sound, electromagnetic (EM), or optical waves. All these techniques has their own benefits and limitations. Acoustic communication is the most versatile and widely used technique in underwater environments because of its low attenuation compared with others. Acoustic waves are more applicable for thermally stable, deep water settings. But acoustic waves in shallow water can be adversely affected by temperature gradients, surface ambient noise, and multipath propagation due to reflection and refraction. The much slower speed of acoustic propagation in water, about 1500 m/s (meters per second), compared with that of electromagnetic and optical waves, and is another limiting factor for efficient communication and networking. Nevertheless, the currently favorable technology for underwater communication is upon acoustics. In this paper, we are planning to design a simple underwater acoustic system. We first discuss about the problems of underwater communication. Then we are designing a data transmission system in underwater and its analysis is done in the next step.

Simplified Scheduling for Underwater Acoustic Networks

The acoustic propagation speed under water poses significant challenges to the design of underwater sensor networks and their medium access control protocols. Similar to the air, scheduling transmissions under water has significant impact on throughput, energy consumption, and reliability. In this paper we present an extended set of simplified scheduling constraints which allows easy scheduling of underwater acoustic communication. We also present two algorithms for scheduling communications, i.e. a centralized scheduling approach and a distributed scheduling approach. The centralized approach achieves the highest throughput while the distributed approach aims to minimize the computation and communication overhead. We further show how the centralized scheduling approach can be extended with transmission dependencies to reduce the end-to-end delay of packets. We evaluate the performance of the centralized and distributed scheduling approaches using simulation. The centralized approach outperforms the distributed approach in terms of throughput, however we also show the distributed approach has significant benefits in terms of communication and computational overhead required to setup the schedule. We propose a novel way of estimating the performance of scheduling approaches using the ratio of modulation time and propagation delay. We show the performance is largely dictated by this ratio, although the number of links to be scheduled also has a minor impact on the performance.

Hamiltonian formalism and cellular algorithm for modeling large numbers of interacting bubbles.

Large, dense clusters of bubbles play an important role in the efficacy of shock-wave lithotripsy. Although methods exist for simulating bubble interaction dynamics within a cluster, for moderately sized clusters (∼1000 bubbles), they are computationally expensive and scale poorly to larger clusters. Currently under development is a method to reduce the computational complexity of the problem and permit direct simulation of large bubble clusters. The algorithm functions by partitioning the cluster into small cells. Bubble interaction within each cell is assumed to be instantaneous and is modeled using a Hamiltonian formulation [Ilinskii et al. J. Acoust. Soc. Am. 121, 786 (2007)] that has been extended to include a correction for radiation damping. The cellular sub-clusters are coupled via the pressure field they generate, and the time delays associated with finite acoustic propagation speed are taken into account. Use of the Hamiltonian formulation reduces computational complexity and numerical error for clusters containing large numbers of bubbles, and it is thus well suited for application to lithotripsy. The accuracy of the method will be validated by comparison with results obtained from an existing model obtained using Lagrangian formalism. [Work supported by the ARL:UT McKinney Fellowship in Acoustics and NIH DK070618.]

On the unsteady inviscid force on cylinders and spheres in subcritical compressible flow

The unsteady inviscid force on cylinders and spheres in subcritical compressible flow is investigated. In the limit of incompressible flow, the unsteady inviscid force on a cylinder or sphere is the so-called added-mass force that is proportional to the product of the mass displaced by the body and the instantaneous acceleration. In compressible flow, the finite acoustic propagation speed means that the unsteady inviscid force arising from an instantaneously applied constant acceleration develops gradually and reaches steady values only for non-dimensional times c(infinity)t/R approximately >10, where c(infinity) is the freestream speed of sound and R is the radius of the cylinder or sphere. In this limit, an effective added-mass coefficient may be defined. The main conclusion of our study is that the freestream Mach number has a pronounced effect on both the peak value of the unsteady force and the effective added-mass coefficient. At a freestream Mach number of 0.5, the effective added-mass coefficient is about twice as large as the incompressible value for the sphere. Coupled with an impulsive acceleration, the unsteady inviscid force in compressible flow can be more than four times larger than that predicted from incompressible theory. Furthermore, the effect of the ratio of specific heats on the unsteady force becomes more pronounced as the Mach number increases.

Concomitant speed-of-sound tomography in photoacoustic imaging

We present a method to generate quantitative cross-sectional maps of acoustic propagation speed in tissue using the photoacoustic principle. The method is based on the interaction of laser-induced ultrasound from an extraneous absorber with the object under photoacoustic investigation. The propagation times of the ultrasound transients through the object at angles around 360° are measured using a multielement ultrasound detector. The geometry lends itself to fan-beam reconstruction allowing speed-of-sound tomograms to be generated. Simultaneously, conventional photoacoustic computed tomography can be performed as well. We demonstrate the concept showing results on phantoms carrying speed-of-sound distributions.

Evaluation by scanning acoustic microscopy (SAM) on glomerular lesion of IgA nephropathy

IgA nephropathy (IgAN) is known to commonly cause of end‐stage renal failure in Japan. The glomerular lesions of IgAN have histological variations. The determination of prognosis and therapeutic strategy should be carefully done by experts because morphological information from renal biopsies using ordinary optical microscopy is usually qualitative and subjective. Moreover, the histological items for the evaluation of glomerular lesions seems to be unsatisfactory for expression of the disease condition of IgAN. The beneficial properties of scanning acoustic microscopy (SAM) include not only observation of microstructure but also quantitative measurement of acoustic propagation speed (APS), indicating the tissue elasticity. In the present study we compared the APS of glomeruli with the pathological scores that were determined by ordinary light microscopy. We used stocked human renal biopsy specimens diagnosed as IgAN (n = 12) and normal/minimal changes (n = 5). All samples were taken by renal biopsy in Kagawa Medical University Hospital during 1997–2000 under informed consent of the patients. The obtained renal tissue were immersed in 10% formalin and embedded in paraffin. A fixed specimen was consecutively cut into 4 μm slices. One of the deparaffinized 4 μm‐specimens was directly utilized for SAM without any staining, and the others were stained with haematoxylin‐eosin and Masson Trichrome for counting cell number and evaluation of collagen accumulation. For the measurement of glomerular APS, the sample line was set on the equator of the glomerulus and then scanning of the X–Z axis was carried out to obtain the interference fringes that were analysed with a computer imaging software in order to calculate the APS. In light microscopic study, pathological scores were evaluated semiquantitatively by two independent investigators who were unaware of the sample number. Glomerular lesions were scored into five grades and glomerular cell number was also counted in individual glomerulus. The computer‐assisted imaging analyser Win ROOF (Mitani, Fukui, Japan) was also used for the determination of glomerular collagen content in specimens stained by Masson Trichrome. A two‐dimensional image (C‐mode scanning) of SAM enabled imaging of glomerulus in renal biopsy specimen compatible with findings of ordinary light microscopy without staining dye. The glomerular APS in IgAN was significantly higher than in normal/minimal changes. This alteration of glomerular APS in IgAN was positively correlated to both semiquantitative pathological scores and glomerular collagen content determined by light microscopy. However, the cell number of glomelurus did not change between IgAN and normal/minimal change. As a result, we conclude that the glomerular lesion, especially matrix expansion in IgAN, was comparable with the absolute value among specimens. Therefore, it is suggested that SAM method is a novel and useful technique for quantitative evaluation of glomerular lesion in IgAN.

Evaluation of progression in nonrheumatic aortic valvular stenosis by scanning acoustic microscopy

To investigate distributions of hardness and thickness in nonrheumatic aortic stenosis (AS), scanning acoustic microscopy was used. The acoustic propagation speed (APS: m/s) and thickness at three sites (tip, middle and base) of aortic valve were measured in 18 cusps from 7 surgical patients with AS (late lesion), 27 showing mild lesions from 9 autopsy cases (early lesion) and 18 healthy from 6 autopsy cases (healthy). These were measured in each layer of cusps: fibrosa (F), spongiosa (S) or ventricularis (V). In early lesions, an increase in APS preceded the thickening and distributed in the tip (1666 ± 107), the three layers of the middle (F: 1782 ± 121; S: 1590 ± 38; V: 1636 ± 59) and the fibrosa of the base (1736 ± 203). In late lesions, APS of the tip and three layers of the base were markedly increased. Progressive nonrheumatic AS is characterized by increased hardness that precedes the thickening, and its distribution may be related to mechanical stress.

A new approach for glomerular lesions: evaluation of scanning acoustic microscopy (SAM) for experimental glomerular disease in rats

Most pathological evaluations using ordinary optical microscopy are usually qualitative and subjective. The beneficial properties of scanning acoustic microscopy (SAM) include not only observation of microstructure but also quantitative measurement of acoustic propagation speed, indicating the tissue elasticity. In this study, we examined the capability of SAM to evaluate pathological findings in glomeruli using anti-Thy.1 glomerulonephritis. Light microscopic observations of the glomeruli showed severe cell proliferation and mesangial matrix expansion at 10 days after induction of glomerulonephritis and, yet, to a lower extent at day 21 with onset of healing. C-mode scanning of SAM enabled imaging of glomerular structure compatible to findings of ordinary light microscopy. In addition, glomerular propagation speed in nephritic rats was significantly increased at day 10, and then decreased at day 21. These results indicate that SAM evaluation may be a new, useful technique for quantitative evaluation of proliferative glomerular lesions.

Azimuth ambiguities in broadside and squint mode synthetic aperture sonar

Synthetic aperture sonar (SAS) mapping rates are limited by acoustic propagation speed in relation to feasible platform velocity and the desired swath coverage. Such limitations result in azimuth undersampling and the appearance of ambiguities in SAS imagery. The position, spreading and ambiguity to signal ratio (ASR) of image aliases caused by grating lobes are discussed from a geometric and a Doppler point of view. Simulation and experimentation for sidelooking SAS imaging show the variation in ASR with along track sampling, processed aperture, target range, and transmitted signal bandwidth. ASR is also shown to improve with increasing SAS squint angle considered up to 60° from broadside.

Evaluation of acoustic properties of the live human smooth-muscle cell using scanning acoustic microscopy

This study was performed to measure the acoustic propagation speed in live human aortic smooth-muscle cells (HASMC), using scanning acoustic microscopy (SAM) and a novel measurement theory that permits the measurement of the acoustic propagation speed in biological samples of unknown thickness. C-mode and X–Z-mode images of HASMC under three different conditions: growing (G); differential (D); and on hypotonic loading (H), were acquired using 100-MHz, 450-MHz and 600-MHz ultrasound. The images exhibit features related to the cell surface curvature and intracellular structure. The theory supporting the methodology is derived in this article and makes use of the interference fringes within the focusing lens of the high-frequency transducer. The propagation speed in the cells was calculated from the location of the interference fringe on the C-mode images and the fringe shift on the X–Y-mode images with 450-MHz ultrasound. The propagation speed in D (1624 ± 16 m/s) was significantly higher than those in G (1571 ± 14 m/s, p < 0.05) and H (1585 ± 8 m/s, p < 0.05). Scanning acoustic microscope measurements, along with the described theory, are useful for studying the acoustic properties of live cells ex vivo and have applications in both pathophysiology and biomechanics.

An equation set for non-equilibrium two phase flow, and an analysis of some aspects of choking, acoustic propagation, and losses in low pressure wet steam

An equation set for multidimensional, time variant, inviscid flow of a condensing vapour is presented. The equations include the effects of relative motion between the primary gas phase and the suspended liquid droplets. They have been formulated with steam turbine applications in mind but are also relevant to problems of gas-particle and liquid bubble flow. It is shown that the critical velocity in one dimensional choking of low pressure wet steam is identical with the “frozen” speed of acoustic propagation, and the variation of choking mass flow with respect to equilibrium based calculations is described. Results obtained with two different models of droplet growth are compared, and simple formulae for calculating limiting values of choking flow are given. A generalised loss coefficient including the effects of thermodynamic and kinematic non-equilibrium is introduced.