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  • Comparative Studies. Non-European Languages/Literatures  (6)
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  • Comparative Studies. Non-European Languages/Literatures  (6)
RVK
  • 1
    Online Resource
    Online Resource
    Acoustical nonlinearity and its images in biomedicine
    Acoustical Society of America (ASA) ; 1998
    In:  The Journal of the Acoustical Society of America Vol. 103, No. 5_Supplement ( 1998-05-01), p. 3080-3080
    Details
    In: The Journal of the Acoustical Society of America, Acoustical Society of America (ASA), Vol. 103, No. 5_Supplement ( 1998-05-01), p. 3080-3080
    Abstract: Some acoustical nonlinear effects in biological media at medical ultrasonic frequencies and intensities were studied experimentally. These phenomena include wave distortion, harmonic generation, energy transformation, extra-attenuation, departure of intensity response curve from linear relation, etc. The influence of these effects on medical ultrasonic diagnosis and therapy was discussed. As a basic parameter in nonlinear acoustics, the acoustical nonlinearity parameter can describe the above-mentioned nonlinear effects and provide some information on the structure and composition of biological tissues. Thus the imaging method of an acoustical nonlinearity parameter using secondary wave detection was developed and investigated. Nonlinearity parameter tomography for normal and a series of pathological porcine tissues was presented. The results obtained in experiments indicate that the difference between normal and diseased tissue in nonlinearity parameter tomography is more sensitive than that in linear parameter tomography. Therefore, nonlinearity parameter tomography may become a novel imaging method for tissue characterization. [Work supported by NSF of China.]
    Type of Medium: Online Resource
    ISSN: 0001-4966 , 1520-8524
    URL: Article
    DOI: 10.1121/1.422900
    RVK:
    EQ 1000
    Language: English
    Publisher: Acoustical Society of America (ASA)
    Publication Date: 1998
    detail.hit.zdb_id: 1461063-2
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    Online Resource
  • 2
    Online Resource
    Online Resource
    High resolution ultrasound imaging system for soft tissues
    Acoustical Society of America (ASA) ; 1998
    In:  The Journal of the Acoustical Society of America Vol. 103, No. 5_Supplement ( 1998-05-01), p. 2792-2792
    Details
    In: The Journal of the Acoustical Society of America, Acoustical Society of America (ASA), Vol. 103, No. 5_Supplement ( 1998-05-01), p. 2792-2792
    Abstract: The great interest in high resolution (higher than 0.1 mm axially and 0.3 mm laterally) ultrasound imaging systems for application to the skin, eye, intestinal wall, etc., gives rise to the development of a high resolution ultrasound imaging system. In this study, the high resolution ultrasound imaging system with a frequency range from 20 to 40 MHz was developed. In the system described here, the different resolutions were obtained by means of the focused transducers with different center frequencies in the frequency range mentioned above. In designing and fabricating the PVDF transducer, the KLM equivalent circuit including internal loss was developed and the influence of the PVDF film and backing materials on the transducer characteristics were analyzed as well. The experimental results were compared with the analyzed results. High resolution ultrasound imaging of some soft tissue samples was obtained. Besides the ultrasound parameters such as speed of sound, the attenuation coefficient and backscattering coefficient were measured in the frequency range from 20 to 40 MHz. [Work supported by NSF of Jiangsu Province, China.]
    Type of Medium: Online Resource
    ISSN: 0001-4966 , 1520-8524
    URL: Article
    DOI: 10.1121/1.422307
    RVK:
    EQ 1000
    Language: English
    Publisher: Acoustical Society of America (ASA)
    Publication Date: 1998
    detail.hit.zdb_id: 1461063-2
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    Online Resource
  • 3
    Online Resource
    Online Resource
    Nonlinear effects on acoustic field measurement in biomedical frequency range.
    Acoustical Society of America (ASA) ; 1996
    In:  The Journal of the Acoustical Society of America Vol. 99, No. 4_Supplement ( 1996-04-01), p. 2539-2574
    Details
    In: The Journal of the Acoustical Society of America, Acoustical Society of America (ASA), Vol. 99, No. 4_Supplement ( 1996-04-01), p. 2539-2574
    Abstract: It was shown that ultrasound propagation in media is accompanied with nonlinear phenomena and the nonlinear effects on the measurement of acoustic field cannot be neglected. A needle hydrophone was used to receive the signal in the acoustic field for further analysis and the radiation force method was used to measure the total output power of the transmitter. The case of emitting power was constant, the nonlinear phenomena were accumulated due to the distance between the transmitter, and the hydrophone increased from a few centimeter to less than 20 cm. With increasing distance between the transmitter and the hydrophone, the ultrasound energy was gradually transferred from fundamental frequency f0 to high harmonics. Using the spectrum analyzer, the dependence of f0 and nf0 (n=2,3,...) on the distance increased was measured. When the distance between the transmitter and the hydrophone was fixed, the nonlinear phenomena became stronger as the emitting power increased. The acoustic intensity of f0 was no longer linearly increased with the increased emitting power acoustic intensity, and the acoustic intensity of f0 would tend toward a saturation value. [Work supported by NSFC.]
    Type of Medium: Online Resource
    ISSN: 0001-4966 , 1520-8524
    URL: Article
    DOI: 10.1121/1.415832
    RVK:
    EQ 1000
    Language: English
    Publisher: Acoustical Society of America (ASA)
    Publication Date: 1996
    detail.hit.zdb_id: 1461063-2
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  • 4
    Online Resource
    Online Resource
    Acoustical nonlinearity parameter of liquids with microbubbles
    Acoustical Society of America (ASA) ; 1998
    In:  The Journal of the Acoustical Society of America Vol. 103, No. 5_Supplement ( 1998-05-01), p. 2960-2961
    Details
    In: The Journal of the Acoustical Society of America, Acoustical Society of America (ASA), Vol. 103, No. 5_Supplement ( 1998-05-01), p. 2960-2961
    Abstract: The gas bubbles in liquid are the strong scatters of the sound propagation in such liquid. A liquid containing microbubbles is used as an effective ultrasound contrast agent in medical diagnosis to improve the contrast of the ultrasonic image. However, the existence of bubbles in liquid may enhance its nonlinearity parameter. In our previous paper, the preliminary results of some ultrasound contrast agents were reported and their large values of the nonlinearity parameter were obtained. This paper is devoted to an experimental demonstration of the influence of microbubbles on the nonlinearity parameter B/A values. These include measuring the dependence of B/A values of Echovist 300 on time. Results show that B/A values decrease with time (from 2678 to 16 over 45 min). B/A values of human blood with a different portion of Echovist were also studied. Larger B/A values are obtained with more Echovist. B/A values of a kind aqua, such as 76% Injectio Meglumini Diatrizoatis Composita (MDC), were studied before and after sonication with different bubble contents. Results indicate that the values of nonlinearity parameter depend on the presence of microbubbles obviously. Some explanation of this effect is discussed. [Work supported by NSF of China.]  
    Type of Medium: Online Resource
    ISSN: 0001-4966 , 1520-8524
    URL: Article
    DOI: 10.1121/1.421655
    RVK:
    EQ 1000
    Language: English
    Publisher: Acoustical Society of America (ASA)
    Publication Date: 1998
    detail.hit.zdb_id: 1461063-2
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    Online Resource
  • 5
    Online Resource
    Online Resource
    Recent progress on nonuniform fast Fourier transform algorithms and their applications
    Acoustical Society of America (ASA) ; 1999
    In:  The Journal of the Acoustical Society of America Vol. 106, No. 4_Supplement ( 1999-10-01), p. 2135-2135
    Details
    In: The Journal of the Acoustical Society of America, Acoustical Society of America (ASA), Vol. 106, No. 4_Supplement ( 1999-10-01), p. 2135-2135
    Abstract: Recently, nonuniform fast Fourier transform (NUFFT) algorithms have received significant attention [Dutt and Rokhlin, SIAM J. Sci. Stat. Comput. 14, 1368–1393 (1993)]. Unlike the regular fast Fourier transform (FFT) algorithms, the NUFFT algorithms allow the data to be sampled nonuniformly. The leading order of the number of arithmetic operations for these NUFFT algorithms is O(N & lt;th & gt;log2 & lt;th & gt;N). Here, we review the recent progress of the NUFFT algorithms using the regular Fourier matrices and conjugate-gradient method for the forward and inverse NUFFT algorithms [Liu and Nguyen, IEEE Microwave Guid. Wave Lett. 8, 18–20 (1998); Liu and Tang, Electron. Lett. 34, 1913–1914 (1998)]. Because of their least-square errors, these NUFFT algorithms are about one order of magnitude more accurate than the previous algorithms. These NUFFT algorithms have been applied to develop the nonuniform fast Hankel transform (NUFHT) and nonuniform fast cosine transform (NUFCT) algorithms. Both NUFFT and NUFHT algorithms have been used to solve integral equations in computational electromagnetics and acoustics; The NUFCT has been used to solve time-dependent wave equations. Numerical examples will demonstrate the efficiency of the fast transform algorithms, and the applications in computational electromagnetics and computational acoustics.
    Type of Medium: Online Resource
    ISSN: 0001-4966 , 1520-8524
    URL: Article
    DOI: 10.1121/1.427296
    RVK:
    EQ 1000
    Language: English
    Publisher: Acoustical Society of America (ASA)
    Publication Date: 1999
    detail.hit.zdb_id: 1461063-2
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  • 6
    Online Resource
    Online Resource
    A fast method for acoustic imaging of multiple three-dimensional objects
    Acoustical Society of America (ASA) ; 2000
    In:  The Journal of the Acoustical Society of America Vol. 108, No. 1 ( 2000-07-01), p. 31-37
    Details
    In: The Journal of the Acoustical Society of America, Acoustical Society of America (ASA), Vol. 108, No. 1 ( 2000-07-01), p. 31-37
    Abstract: This paper is concerned with the inverse problem for imaging multiple three-dimensional objects using the information of the far-field pattern of the scattered wave. A spatially dependent function, which has noticeably different values inside and outside the obstacle, is derived. A numerical method based on the characterization is developed to obtain a visualization of the obstacle. The most remarkable advantage of this method is that it does not need any prior knowledge about the geometry and physical properties of the scatterer, and requires only the information of the far-field measurements for a finite number of directions of incidence and observation distributed over a limited range. Furthermore, the scheme is very simple and fast since it avoids the use of the iterative procedure and requires only the solution of a linear system. Some numerical examples with synthetic far-field data are given showing the practicality and efficiency of this scheme.
    Type of Medium: Online Resource
    ISSN: 0001-4966 , 1520-8524
    URL: Article
    DOI: 10.1121/1.429441
    RVK:
    EQ 1000
    Language: English
    Publisher: Acoustical Society of America (ASA)
    Publication Date: 2000
    detail.hit.zdb_id: 1461063-2
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