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71.
The role of physical testing in product development is changing due to the requirements for faster new product development, reduced tolerance of failures in the field and the emergence of computer aided engineering (CAE) technologies. To be used most effectively, testing must be seen as an integral part of the process for reducing risks associated with new product introductions. Quality function deployment (QFD) and failure modes and effects analysis (FMEA) can be used to establish effective test and development plans that integrate the use of virtual and physical testing. By effectively integrating virtual and physical test technologies significant improvements in product performance can be achieved within shorter times and with reduced development and manufacturing costs. The approach was illustrated by a process of reducing in-cab noise during the design of a new truck. 相似文献
72.
J. Kumi
k 《Annalen der Physik》1995,507(8):805-808
Nonlinear generalization of autoregressive sequence of first order is used as basis for construction of mathematical model of bistable burst noise. It is proved that the noise generated using such a model has Lorentzian spectrum after clipping the white noise component. In passing it is demonstrated that random telegraph signal is obtainable by simple iteration. The proposed model suggests that one should expect to observe temperature dependence of frequency of transitions between the two levels of burst noise waveform. 相似文献
73.
Glenn C Gardner 《Applied Acoustics》2003,64(2):229-242
This paper presents a study of neural networks for prediction of acoustical properties of polyurethane foams. The proposed neural network model of the foam uses easily measured parameters such as frequency, airflow resistivity and density to predict multiple acoustical properties including the sound absorption coefficient and the surface impedance. Such a model is quite robust in the sense that it can be used to develop models for many different classes of materials with different sets of input and output parameters. The current neural network model of the foam is empirical and provides a useful complement to the existing analytical and numerical approaches. 相似文献
74.
本文从应用角度,对片式消声器的结构,消声机理,设计原则等作了较为全面的阐述,介绍了应用实例,结合工程实践,提出了一个估算存在气流时消声系数的经验公式。 相似文献
75.
76.
The impact of observational noise on the analysis of scale-free networks is studied. Various noise sources are modeled as random link removal, random link exchange and random link addition. Emphasis is on the resulting modifications for the node-degree distribution and for a functional ranking based on betweenness centrality. The implications for estimated gene-expressed networks for childhood acute lymphoblastic leukemia are discussed. 相似文献
77.
Summary We derive an explicit form for the current correlation function of a Fermi gas in a finite sample at arbitrary degree of degeneracy.
The expression so found enables a continuous investigation from diffusive to ballistic transport regimes to be carried out.
For degenerate one-dimensional conductors under ballistic regime we find that the noise spectral density exhibits characteristic
geometrical resonances and its low-frequency value has the universal formS
I
(0)=8e
2
KT/h, implying a universal conductanceG=2e
2/h. 相似文献
78.
Apartments that are exposed to the same level of road traffic noise on front of the most exposed façade often have very different neighbourhood soundscapes. In the first part of this paper, a neighbourhood soundscape adjusted exposure indicator, NALden, is derived. NALden-values are designed to be used as input to traditional exposure-effect relationships to improve annoyance impact estimates. In the second part, generic spatial procedures are developed and implemented. These produce map presentations in the form of contiguous neighbourhood quality areas. The quality of each neighbourhood is determined from the predicted annoyance impacts for residents. Noise impact maps provide experts, politicians, and the public with high-level impact visualizations of condensed status, “what-if” and scenario information. Results and illustrations are based on data from the Norwegian socio-environmental survey database, and a comprehensive national noise mapping effort. The methodology should work well for mapping Europe’s “black” and “grey” areas. 相似文献
79.
A review of commonly used analytical and empirical formulae for predicting sound diffracted by a thin screen 总被引:2,自引:0,他引:2
This paper reviews some useful analytical and empirical formulae that are used for the calculation of sound diffracted by a barrier. A brief historic overview of the study of spherical waves diffracted by a rigid half plane is presented also. The physical principles of sound diffraction by a thin plane are explained. The mathematical expressions are cast in a convenient form for ease of numerical implementation. Accurate analytical solutions are expressed in terms of standard mathematical functions that can be computed readily. Among the approximate solutions quoted, quite a few empirical formulations are adequate for most engineering purposes. The information presented in this paper should also be helpful for those who are interested in the study of sound diffracted by a barrier in a room or in a long industrial space. 相似文献
80.