17,348 research outputs found
Effects of the speed of moving noise sources on the sound visualization by means of moving frame acoustic holography
No full textThe moving frame acoustic holography (MFAH) method [H.-S. Kwon and Y.-H. Kim, J. Acoust. Sec. Am. 1.03, 1734-1742 (1998)] enables the visualization of noise generated by moving noise sources, e.g., moving vehicles, by using a line array of microphones affixed to the ground. However, the sound field of a moving noise source has a moving effect, which produces the wavefront distribution different from what would be generated by the source if it were not moving. The moving effect causes errors on the reconstructed hologram by means of MFAH. This paper studies this effect with regard to the speed of noise sources. A formula, which can show the effect, was derived. This enables the analysis of the effect not only on the hologram plane but also on a prediction plane. It was shown that the phase error is more undesirable than that of magnitude. The phase error, which is proportional to the speed of a noise source, shifts the position of noise sources and distorts radiation pattern. A theoretical investigation explicitly showed that the error is negligible for low Mach number (M < 0.1). Furthermore, the phase error can be reduced by introducing a correction factor. Several numerical examples illustrate the feasibility of the proposed correction method for low Mach number. (C) 2000 Acoustical Society of America. [S0001-4966(00)02412-7]
STORMER-NUMEROV APPROXIMATION FOR NUMERICAL-SOLUTIONS OF ORDINARY AND PARTIAL-DIFFERENTIAL EQUATIONS
No full textAn improved moving frame acoustic holography for coherent bandlimited noise
No full textThe moving frame acoustic holography method, which can increase the aperture size and spatial resolution of a hologram was recently proposed [H. S. Kwon and Y.-H. Kim, J. Acoust. Sec. Am. 103, 1734-1742 (1998)]. This method continuously sweeps a stationary sound field by using a line array of microphones so that the hologram of a scanned plane can be obtained. This method enables us to visualize the noise generated by moving noise sources based on near-field acoustic holography. However, a drawback is that it can be applied only to sinusoidal components. This limits its practical application. In practice, bandlimited and transient noise, as well as a sinusoidal component, must be dealt with in order to effectively control the noise generated by the moving noise sources. This paper addresses a way to improve the moving frame acoustic holography method so that it can be applied not only to sinusoidal components, but also to a coherent bandlimited noise. The practical applicability of the improved method is also verified by experiments. (C) 1998 Acoustical Society ofAmerica. [S0001-4966(98)04111-3]
Visualization of pass-by noise by means of moving frame acoustic holography
No full textThe noise generated by pass-by test (ISO 362) was visualized. The moving frame acoustic holography was improved to visualize the pass-by noise and predict its level. The proposed method allowed us to visualize tire and engine noise generated by pass-by test based on the following assumption; the noise can be assumed to be quasistationary. This is first because the speed change during the period of our interest is negligible and second because the frequency change of the noise is also negligible. The proposed method was verified by a controlled loud speaker experiment. Effects of running condition, e.g., accelerating according to ISO 362, cruising at constant speed, and coasting down, on the radiated noise were also visualized. The visualized results show where the tire noise is generated and how it propagates. (C) 2001 Acoustical Society of America
Crystallization and preliminary X-ray crystallographic studies of the PDZ domain of Shank1 from Rattus norvegicus
No full textShank proteins are a new family of scaffold proteins interacting with various membrane and cytoplasmic proteins. Shank contains multiple protein-protein interaction sites, including ankyrin repeats, an SH3 domain, a PDZ domain, a long proline-rich region and an SAM domain. The PDZ domain of Shank binds to the C-terminus of guanylate kinase-associated protein (GKAP). The PDZ domain of Shank1 from Rattus norvegicus and its complex with the C-terminal octapeptide of GKAP were crystallized at 294 K using polyethylene glycol 20 000 and 6000 as precipitants. Diffraction data sets from a peptide-free crystal and a complex crystal were collected to 1.8 and 3.2 Angstrom resolution, respectively, using synchrotron radiation. The peptide-free crystal belongs to space group P2(1), with unit-cell parameters a = 42.0, b = 50.3, c = 51.8 Angstrom, beta = 106.3degrees. The complex crystal belongs to space group P21 21 21, with unit-cell parameters a = 89.4, b = 97.5, c = 108.3 Angstrom
Calculation and verification of rotation angle of a four-axis hotwire cutter for transfer-type variable lamination manufacturing using expandable polystyrene foam
No full textMost rapid prototyping (RP) processes adopt a solid CAD model sliced into thin layers of constant thickness in the building direction. Each cross-sectional layer is successively deposited and, simultaneously, bonded onto the previous layer; eventually the stacked layers form a physical part of the model. A new RP process called the Transfer-type Variable Lamination Manufacturing process using expandable polystyrene foam sheet (VLM-ST) has been developed to reduce building time and to improve the surface finish of parts with thick layers and sloping surfaces. The objective of this study is to develop a method for calculating the rotation angles (theta(x), theta(y)) of a linear hotwire cutter in the three-dimensional space for the VLM-ST process using inverse kinematics. The method for calculating the rotation angles (theta(x), theta(y)) of the four-axis hotwire cutter to VLM-ST was applied and verified for a variety of free surface bodies
Mechanical properties and anisotropy of expanded polystyrene foam sheet for the VLM-S rapid prototyping process
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