Probabilistic Interval Perturbation Methods for Hybrid Uncertain Acoustic Field Prediction

2013 ◽  
Vol 135 (2) ◽  
Author(s):  
Baizhan Xia ◽  
Dejie Yu ◽  
Jian Liu

For the hybrid uncertain acoustic field prediction with random and interval variables, the random interval dynamic equilibrium equation is established and two hybrid probabilistic interval perturbation methods, named as hybrid perturbation Monte Carlo method (HPMCM) and hybrid perturbation vertex method (HPVM), are present. In HPMCM, the intervals of expectation and variance of sound pressure are calculated by a combination of the random interval matrix perturbation method, the random interval moment method and Monte Carlo method. In HPVM, the intervals of expectation and variance of sound pressure are calculated by a combination of the random interval matrix perturbation method, the random interval moment method and the vertex method. Numerical results on a 2D acoustic tube, the 2D acoustic cavity of a car and a 3D acoustic cavity verify the effectiveness and the high efficiency of HPVM when compared with HPMCM. HPVM can be considered as an effective engineering method to quantify the effects of parametric uncertainty on the sound pressure response.

2010 ◽  
Vol 118-120 ◽  
pp. 141-146
Author(s):  
Yong Feng Yin ◽  
Jian Guo Zhang

Based on order moment method and improved Monte-Carlo method, this paper mainly studies the importance sampling method which combines with the first-order second-moment method, including how to get the sampling barycenter, how to get the importance distributing function and how to control sampling precision. Finally, the method studied in this paper is applied in actual engineering example and the verification result shows that the method is correct and effective and has higher engineering practical value.


1974 ◽  
Vol 22 ◽  
pp. 307 ◽  
Author(s):  
Zdenek Sekanina

AbstractIt is suggested that the outbursts of Periodic Comet Schwassmann-Wachmann 1 are triggered by impacts of interplanetary boulders on the surface of the comet’s nucleus. The existence of a cloud of such boulders in interplanetary space was predicted by Harwit (1967). We have used the hypothesis to calculate the characteristics of the outbursts – such as their mean rate, optically important dimensions of ejected debris, expansion velocity of the ejecta, maximum diameter of the expanding cloud before it fades out, and the magnitude of the accompanying orbital impulse – and found them reasonably consistent with observations, if the solid constituent of the comet is assumed in the form of a porous matrix of lowstrength meteoric material. A Monte Carlo method was applied to simulate the distributions of impacts, their directions and impact velocities.


Author(s):  
Makoto Shiojiri ◽  
Toshiyuki Isshiki ◽  
Tetsuya Fudaba ◽  
Yoshihiro Hirota

In hexagonal Se crystal each atom is covalently bound to two others to form an endless spiral chain, and in Sb crystal each atom to three others to form an extended puckered sheet. Such chains and sheets may be regarded as one- and two- dimensional molecules, respectively. In this paper we investigate the structures in amorphous state of these elements and the crystallization.HRTEM and ED images of vacuum-deposited amorphous Se and Sb films were taken with a JEM-200CX electron microscope (Cs=1.2 mm). The structure models of amorphous films were constructed on a computer by Monte Carlo method. Generated atoms were subsequently deposited on a space of 2 nm×2 nm as they fulfiled the binding condition, to form a film 5 nm thick (Fig. 1a-1c). An improvement on a previous computer program has been made as to realize the actual film formation. Radial distribution fuction (RDF) curves, ED intensities and HRTEM images for the constructed structure models were calculated, and compared with the observed ones.


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