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21.
Towards the end of 1999, the building of one of the main communication routes in Spain was finished, the A-3 motorway, which connects Madrid and Valencia. So far, this road was running through the town Motilla de Palancar, province of Cuenca. The opening of the last section of the motorway on 3 December 1999, re-routes all the traffic passing through the town. This study makes a comparative of the noise levels before and after the opening of the motorway that goes through Motilla de Palancar. 相似文献
22.
R. Wilfinger J. Lettry A. Fabich H. Aiginger K. Poljanc R. Catherall M. Eller 《The European physical journal. Special topics》2007,150(1):373-378
Thermal stress-waves are generated in the solid target
material when the proton beam interacts. These stress waves excite
natural oscillations of the target or cause plastic deformations.
Hence, an experimental setup with a laser Doppler vibrometer
[CITE] was developed to investigate free surface
vibrations of cylindrical targets. The target configurations for
RIB and conventional neutrino beams (CNGS project) were
investigated to analyze proton induced thermal stress-wave
generation and propagation. 相似文献
23.
24.
Zhi-Chi Zhu 《Acta Mechanica Solida Sinica》1990,3(4):457-468
Researches on sound propagation problems in ducts done by the author and other investigators in recent years are briefly discussed in this paper. The finite difference method used in fluid mechanics is used for solving these problems thus presenting an aspect of the development of research work in this field at home and abroad.The project supported by National Natural Science Foundation of China. 相似文献
25.
目标强度特性是海洋生物声学识别与资源量评估的重要依据,其中,基于近似几何体和声阻抗特性的理论模型法是研究海洋生物目标强度的重要手段。由于对几何形态近似处理以及数值求解方法的限制,传统理论模型对声波频率、入射方位以及目标声阻抗、形态尺寸等均有各自不同的适用范围,单一模型难以满足不同种类或同一种类但不同尺寸海洋生物的目标强度求解。本文尝试将逐渐见诸应用的有限元/边界元耦合方法用于海洋生物目标强度特性研究,分别以球形生物、纺锤形鱼类尾明角灯鱼(Ceratoscopelus warmingii)和细长形浮游动物南极大磷虾(Euphausia superba)为例进行仿真计算,并与相适应的经典理论模型进行对比分析。结果表明,对于球形生物,有限元/边界元耦合方法与解析模型的目标强度频响曲线完全吻合;对于纺锤形鱼类,有限元/边界元耦合方法可有效弥补基于模态级数解的形变圆柱体模型在中低频和两端入射时的准确性问题;对于细长形浮游动物,有限元/边界元耦合方法与畸变波玻恩近似模型高度吻合。综上,有限元/边界元耦合方法对多种海洋生物目标强度求解均具有较好的适用性,未来有待进一步结合实验测定进行验证。 相似文献
26.
The effect of sound on the flow around plates with semicircular or square leading edges and square trailing edges located in a low turbulence open jet has been studied. In all circumstances the length of the leading edge separation bubbles associated with square leading edge plates was found to oscillate. When sound was applied to the flow around these plates, the leading edge shear layers reattached closer to the leading edge and the oscillations in bubble length occurred at the applied sound frequency, generating patches of concentrated vorticity in the boundary layers. These vorticity patches moved downstream near the plate surface and then beyond the trailing edge to form vortex cores in a street with a Strouhal number equal to the applied sound value. Sometimes these vortex streets are unstable and break down into streets with Strouhal numbers approaching those observed without sound. These effects of sound were not observed in the flow around plates with semicircular leading edges. Without sound, square leading edge plates of intermediate length did not shed regular vortex streets. 相似文献
27.
T. Yano 《Shock Waves》1996,6(6):313-322
A weakly nonlinear plane acoustic wave is emitted into an ideal gas of semi-infinite extent from an infinite plate by its
sinusoidal motion of single period. The wave develops into anN wave in the far field, as long as the energy dissipation is negligible everywhere except for discontinuous shock fronts.
The third-order effects at shock fronts are evaluated, i.e., the generation of reflected acoustic wave as a result of the
interaction of shock and expansion wave and the production of entropy by the energy dissipation at shock fronts. Consideration
of these effects enables one to estimate the whole mass, momentum and total excess energy (sum of the kinetic energy and excess
of internal energy over an initial undisturbed value) transported by theN wave to the accuracy of third order of wave amplitude. It is shown that the mass and total excess energy transported by theN wave increase and the momentum decreases to asymptotic limits as the wave propagates. The result shows good agreement with
a numerical result obtained by solving the Euler equations with a high-resolution TVD upwind scheme. 相似文献
28.
Jeremiah Rushchitsky 《Comptes Rendus Mecanique》2002,330(3):175-180
The problem of self-switching plane waves in elastic nonlinearly deformed materials is formulated. Reduced and evolution equations, which describe the interaction of two waves the power pumping wave and the faint signal wave are obtained. For the case of wave numbers matching the pumping and signal waves, a procedure of finding the exact solution of evolution equations is described. The solution is expressed by elliptic Jacobi functions. The existence of the power wave self-switching is shown and commented. To cite this article: J. Rushchitsky, C. R. Mecanique 330 (2002) 175–180. 相似文献
29.
30.