This paper deals with the practical aspects of the design of two active noise control (ANC) systems to attenuate low frequency noise. In the first instance, a hybrid passive-active control system to reduce the noise radiated by a small generator has been designed. A SISO ANC system, in a side branch of the exhaust tube, attenuates some of the harmonics of the lowfrequency exhaust noise as much ...

Seismic ambient noise contains rich information about the physical properties of critical zone. From motor vehicle noise, we extract daily seismic attenuation by quantifying linear relationship between frequency and amplitude ratio paired instantaneous spectra. After verifying reliability proposed method, apply it to data collected at three urban sites. The estimated is compared against environ...

This review presents the basic research and some applications of gamma-ray attenuation, neutron gauges, 137Cs fallout techniques for studying soil physical processes properties. The selected studies aimed to give readers a general idea use these nuclear carried out by Brazilian researchers in past decades. It is expected assist future identifying knowledge gaps opportunities applying methods pr...

In the 20 years since cleanup of contaminated groundwater has been a high priority in the United States, recognition of both the scope of the problem and the technical difficulties involved has grown steadily. Estimates of the number of hazardous waste sites where groundwater may be contaminated vary between 300,000 and 400,000 nationwide [NRC, 1994]. Legislation passed in the 1980s by Congress...

The paper analyzes the dynamic response of an underground main pipe under action a longitudinal wave propagating in soil along pipe. article assumes that elastic is finite length, and linear viscoelastic model “pipe-soil” system interaction considered. problem solved numerically using explicit scheme difference method. A taken as traveling sine wave. presents comparative analysis results for ce...

Background: In this study, a method for linear attenuation coefficient calculation was introduced.Methods: Linear attenuation coefficient was calculated with a new method that base on the physics of interaction of photon with matter, mathematical calculation and x-ray spectrum consideration. The calculation was done for Cerrobend as a common radiotherapy modifier and Mercury.Results: The values...

background: in this study, a method for linear attenuation coefficient calculation was introduced. methods: linear attenuation coefficient was calculated with a new method that base on the physics of interaction of photon with matter, mathematical calculation and x-ray spectrum consideration. the calculation was done for cerrobend as a common radiotherapy modifier and mercury. results: the valu...

introduction: the main goal of spect imaging is to determine activity distribution inside the organs of the body. however, due to photon attenuation, it is almost impossible to do a quantitative study. in this paper, we suggest a mathematical relationship between activity distribution and its corresponding projections using a transfer matrix. monte carlo simulation was used to find a precise tr...