Human motion analyses using footstep ultrasound and Doppler ultrasound

Human footsteps generate periodic broadband frequency envelopes of sound due to dynamic friction forces. Also, human body motion when walking is a cyclic temporal process. The individual body parts have different acoustic cross sections and velocities that form unique human Doppler signatures. The paper introduces an approach to analyze this motion using passive and active ultrasound. The passive method employs a narrowband microphone that is sensitive to the sound from footsteps. The active method utilizes continuous-wave ultrasound to measure the Doppler shifted signal from the body appendages. These two methods show time synchronization between Doppler and ultrasonic human footstep signatures.     

Nondestructive testing using air-borne ultrasound

Over the last two decades, more efficient transducers were developed for the generation and reception of air-borne ultrasound, thus enabling the non-contact, non-contaminating inspection of composite laminates and honeycomb structures widely used in the aerospace industry. This paper presents the fundamentals of making air-borne ultrasonic measurement, and point out special considerations unique to propagating ultrasound in air and through solids. Transducer beam profile characterization, thickness dependence and resonance effects in the transmission of air-coupled ultrasound through plates, and the detection and imaging of defects and damage in solid laminates and honeycomb sandwich will be discussed and illustrated with examples. Finally, a manual scan system developed for implementing air-borne ultrasonic imaging in the field and on aircraft will be introduced.     

A positron injector for the LEPTA accumulator

An injector of monochromatic positrons for the low-energy positron accumulator (LEPTA) is being tested at the Joint Institute for Nuclear Research. The source of positrons is the radioactive source ²²Na. At the output of the source, positrons are slowed down in a solid target. Frozen neon is used as a moderator. For this purpose, a system of cryocooling of the source and the neon supply line have been assembled. A method of detection of slow positrons has been developed and tuned. The first experiments with the frozen moderator have been performed. A continuous beam of slow positrons with an average energy of 1.2 eV and spectrum width of 1 eV has been obtained.     

Metal plate testing using airborne ultrasound

A method of exciting plate waves in metal plates is described in which the wave is generated from air without touching the sample. By using this method contactless non-destructive ‘on-line’ testing of metal plates is possible within a thickness range from 0.2 mm up to several millimetres. Defect resolution is best in thin plates.     

Superresolution ultrasound imaging using back-projected reconstruction

An ultrasound technique for imaging objects significantly smaller than the source wavelength is investigated. Signals from a focused beam are recorded over an image plane in the acoustic farfield and backprojected in the wave-vector domain to the focal plane. A superresolution image recovery method is then used to analyze the Fourier spatial frequency spectrum of the signal in an attempt to deduce the location and size of objects in this plane. The physical foundation for the method is rooted in the fact that high spatial frequencies introduced by the object in fact affect the lower (nonevanescent) spatial frequencies of the overall signal. The technique achieves this by using a priori measurements of the ultrasound focus in water, which gives full spectral information about the image source. A guess is then made regarding the size and location of the object that distorted the field, and this is convolved with the a priori measurement, thus creating a candidate image. A large number of candidates are generated and the one whose spectrum best matches the uncorrected image is accepted. The method is demonstrated using 0.34- and 0.60-mm wires with a focused 1.05-MHz ultrasound signal and then a human hair (approximately 0.03 mm) with a 4.7-MHz signal.     

Regeneration of granular activated carbon using ultrasound

To evaluate the feasibility of ultrasonic regeneration of granular activated carbon (GAC), desorption of trichloroethylene (TCE) from GAC by ultrasound was investigated at 20 kHz. About 64% of TCE was desorbed from 5 g of GAC loaded with 6.5 mg TCE for 1 h in ultrasonic field and TCE desorbed to liquid phase were rapidly degraded by ultrasound. 34-43% of stoichiometrically calculated chloride, final degradation product of TCE, was observed in liquid phase during ultrasonic treatment. However, there was desorption limitation at 20 kHz ultrasound. Despite of prolonged ultrasonic irradiation, desorption efficiency of TCE did not exceed critical value. And also, the higher percentage of TCE was desorbed when a sample of 2 mg TCE/4 g GAC was treated ultrasonically than that of 2 mg TCE/g GAC under the same experimental conditions. These results indicate that desorption of TCE by 20 kHz ultrasound occurred mainly at a nearby surface of GAC. In conclusion, the ultrasonic regeneration showed a possibility as an alternative to chemical and thermal regenerations of GAC.     

A portable positron accumulator for antihydrogen formation

A pulsed source of positrons has been developed which may be useful for antihydrogen ( ) formation because it is portable when compared to accelerator-based sources. This positron accumulator uses a Penning-style trap to collect moderated positrons from a radioactive source. The positron pulses may be emitted with repetition rates in the range of 50–1000 Hz, which is appropriate for production schemes involving laser-induced recombination. Bunching techniques may be used to vary the width of the positron pulses over the range 30–120 ns (FWHM) to match the width of the antiproton and/or laser pulses. The efficiency of the accumulator increases from ∼ 10% at 100 Hz to ∼ 50% at 1000 Hz. 250 Hz the efficiency is ∼ 25% and the accumulator has delivered up to 8 e⁺/pulse per mCi of positron activity. This translates into ∼ 1.2 × 10⁵ e⁺/pulse for a 100 Ci⁵⁸Co source.     

Covariant Prolongation Structure of Konno-Asai-Kakuhata Equation

Based upon the covariant prolongation structures theory, we construct the sl（2, R）×R（p） prolongation structure for Konno-Asai-Kakuhata equation. By taking two and one-dimensional prolongation spaces, we obtain the inverse scattering equations given by Konno et al. and the corresponding Riccati equation. The Baecklund transformations are also presented.     

Covariant Prolongation Structure of Konno-Asai-Kakuhata Equation

Based upon the covariant prolongation structures theory, we construct the sl(2,R)×R(ρ) prolongation structure for Konno-Asai-Kakuhata equation. By taking two and one-dimensional prolongation spaces, we obtain the inverse scattering equations given by Konno et al. and the corresponding Riccati equation. The Bäcklund transformations are also presented.     

Selective synthesis of sulfoxides from sulfides using ultrasound

The present work aims at developing a new process to selectively synthesize sulfoxide from sulfides using ultrasound. Methyl phenyl sulfide (MPS) has been taken as a model reactant. The reaction has been carried out in ultrasonic bath with an operating frequency of 22 kHz and maximum power supply of 120 W with an actual power dissipation of approximately 40 W measured using calorimetric studies. Effect of various parameters such as presence and absence of catalyst, type of catalyst (catalysts used were sodium tungstate and ammonium molybdate), temperature, concentration of hydrogen peroxide, effect of molar ratio of MPS to H(2)O(2) has been investigated with an aim of obtaining the optimum conditions for the synthesis of sulfoxides. It was observed that the presence of catalyst is a must to achieve appreciable conversions. It was also observed that the periodic addition of stoichiometric amount of hydrogen peroxide instead of sudden addition of it (total quantity of hydrogen peroxide remains the same) gave better selectivity for sulfoxide. The maximum conversion achieved in the present work was approximately 88.42% with sulfone formation being only 0.4% indicating a 99.6% selectivity for the desired product i.e. sulfoxides.     

Generation of ultrasound in materials using continuous-wave lasers

Generating and detecting ultrasound is a standard method of nondestructive evaluation of materials. Pulsed lasers are used to generate ultrasound remotely in situations that prohibit the use of contact transducers. The scanning rate is limited by the repetition rates of the pulsed lasers, ranging between 10 and 100 Hz for lasers with sufficient pulse widths and energies. Alternately, a high-power continuous-wave laser can be scanned across the surface, creating an ultrasonic wavefront. Since generation is continuous, the scanning rate can be as much as 4 orders of magnitude higher than with pulsed lasers. This paper introduces the concept, comparing the theoretical scanning speed with generation by pulsed laser.     

Detection of chemical damage in concrete using ultrasound

This research deals with a non-destructive method for characterizing the degraded cover of concrete structures using high-frequency ultrasound (0.5-1 MHz). Although such a frequency range is unusual in civil engineering, it is well suited to the kind of defect to be detected, as it corresponds to a thin near-to-surface layer with increased porosity and density of microcracks. In order to assess the feasibility of detecting concrete cover degradation, velocity and attenuation measurements were made on both halves of a concrete slab. One half was immersed into an acid solution for 15-45 days, while the other half remained sound. These measurements were made for longitudinal, transverse and surface waves. The results obtained show a 23% decrease of ultrasonic pulse velocity and a 1000% increase of attenuation in the degraded material relative to the sound material. It is thus possible to detect and characterize concrete cover degradation using high-frequency ultrasound. Although attenuation measurements in heterogeneous media are difficult, their sensitivity to degradation is very high.     

Prolongation structure of a new integrable system

We have obtained the inverse scattering equations associated with a new pair of coupled nonlinear evolution equations in two dimensions. The spectral parameter is introduced by invoking the invariance of the equation set, and imposing those on the Lax pair.     

Sharpening enhancement of ultrasound images using contourlet transform

The furry regions of ultrasound images are to be enhanced for good quality visual perception. This paper proposes a contourlet transform (CT) based sharpening technique (ST) for contrast enhancement in ultrasound (US) images. While sharpening, noise emphasize is the drawback of the classical ST methods. The proposed ST is operated on the multiscale, multidirectional CT decomposition of the underlying US image. The new ST not only sharpens the US image but also control the noise effect with tunable parameters. The results are compared with common unsharp masking and recently proposed nonlinear unsharp masking. The parameters like enhancement measure, structural similarity, and blind image quality measure evaluate the improved performances of the proposed technique.     

超声波对沥青质分散作用的研究进展

本文论述了超声作用原理，并分析了超声波对液体中的化学反应的物理效应和化学效应，指出了超声波对沥青质的作用也可以分为物理效应和化学效应，指出超声作用的一个突出优势是超声的复合作用，即空穴塌陷产生的局部高温、高压对反应的引发作用，冲击波及微相射流对颗粒的分散作用和对传质的改善作用，以及超声对片层的破坏作用等。     

Algorithms for estimating blood velocities using ultrasound

Ultrasound has been used intensively for the last 15 years for studying the hemodynamics of the human body. Systems for determining both the velocity distribution at one point of interest (spectral systems) and for displaying a map of velocity in real time have been constructed. A number of schemes have been developed for performing the estimation, and the various approaches are described. The current systems only display the velocity along the ultrasound beam direction and a velocity transverse to the beam is not detected. This is a major problem in these systems, since most blood vessels are parallel to the skin surface. Angling the transducer will often disturb the flow, and new techniques for finding transverse velocities are needed. The various approaches for determining transverse velocities will be explained. This includes techniques using two-dimensional correlation (speckle tracking), multiple beams, and the new transverse modulation technique. The different advantages and disadvantages of the approaches are explained.     

Incorporation of peptides in phospholipid aggregates using ultrasound

This study presents the highlights of ultrasonic effects on peptides incorporated on phospholipid aggregates (liposomes). These liposomes or vesicles are known as transport agents in skin drug delivery and for hair treatment. They might be a good model to deliver larger peptides into hair to restore fibre strength after hair coloration, modelling, permanent wave and/or straightening. The preparation of liposomes 1,2-dipalmitoyl-sn-glycerol-3-phosphocholine (DPPC) with peptides (LLLLK LLLLK LLLLK LLLLK; LLLLL LCLCL LLKAK AK) was made by the thin film hydration method. The LUVs (uni-lamellar vesicles) were obtained by sonication, applying different experimental conditions, such as depth (mm) and power intensity (%). Photon-correlation spectroscopy (PCS) and electronic microscopy (EM) results confirmed that the incorporation of these peptides, with different sequence of amino acids, presented differences on the diameter, zeta-potential of membrane surface and shape of liposomes. The liposomes that included peptide LLLLK LLLLK LLLLK LLLLK present an increased in zeta-potential values after using ultrasound and an "amorphous" aspect. Conversely, the liposomes that incorporated the peptide LLLLL LCLCL LLKAK AK presented a define shape (rod shape) and the potential surface of liposome did not change significantly by the use of ultrasound.     

Maximum-likelihood approach to strain imaging using ultrasound

A maximum-likelihood (ML) strategy for strain estimation is presented as a framework for designing and evaluating bioelasticity imaging systems. Concepts from continuum mechanics, signal analysis, and acoustic scattering are combined to develop a mathematical model of the ultrasonic waveforms used to form strain images. The model includes three-dimensional (3-D) object motion described by affine transformations, Rayleigh scattering from random media, and 3-D system response functions. The likelihood function for these waveforms is derived to express the Fisher information matrix and variance bounds for displacement and strain estimation. The ML estimator is a generalized cross correlator for pre- and post-compression echo waveforms that is realized by waveform warping and filtering prior to cross correlation and peak detection. Experiments involving soft tissuelike media show the ML estimator approaches the Cramer-Rao error bound for small scaling deformations: at 5 MHz and 1.2% compression, the predicted lower bound for displacement errors is 4.4 microns and the measured standard deviation is 5.7 microns.     

Double Doppler ranging system using FM ultrasound

A new system which detects change in distance between a sound source and a receiver, using FM ultrasound has been developed, the principle of which is based on the Doppler phase shift. The use of FM ultrasound allows simultaneous detection both by carrier signal and by demodulated signal, and by using these methods together, stable measurements with good resolution are possible. Experiments in air and an anechoic water tank confirmed the accuracy of plus or minus half a wavelength for change of distance.