A model-based inversion scheme was used to determine absolute chromophore concentrations from multiwavelength photoacoustic images. The inversion scheme incorporated a forward model, which predicted 2D images of the initial pressure distribution as a function of the spatial distribution of the chromophore concentrations. It comprised a multiwavelength diffusion based model of the light transpor...

The effect of evanescent mode generation, due to geometrical mismatch, in acoustic impedance measurements is investigated. The particular geometry considered is that of a impedance probe with an annular flow port and a central microphone, but the techniques are applicable to other geometries. It is found that the imaginary part of the measured impedance error is proportional to frequency, and t...

in recent years, need to increase the convenience of trips in railway vehicles causes that train operators and manufacturers focus on reducing the noise level which is sensed by passengers. in this paper, first the state of modeling acoustic noise in cab train is discussed and natural frequencies and acoustic mode shapes are derived and then formulation of acoustic pressure in the cab will be o...

Forced nonlinear acoustic oscillations near the resonant frequency of closed and open tubes are studied experimentally. In particular, the motion in tubes terminated with different orifice plates is studied, and comparison is made with secondand third-order theories of the motion which contain an adjustable endwall reflexion coefficient. It is found that oscillations at resonance in an open tub...

To solve the problem of low-frequency noise in environment, a Helmholtz-type phononic crystal with adjustable cavity structure and labyrinth tubes was designed. The unique design tube greatly increases length tube, improving sound insulation performance, realizes active regulation band structure. gap characteristics were analyzed by finite element method (FEM) electro-mechanical-acoustic analog...

background: the primary goal of antenatal testing is to identify fetuses at risk of intrauterine neurologic injury or death so that these adverse outcomes can be prevented. we want to assess nonstress test (nst) results and some parameters before and after vibro-acoustic stimulation and acupressure. we did a randomized controlled clinical trial in shahid-beheshti hospital in isfahan in 2011. ma...

in this study, the disadvantages of wood, which is widely employed in producing music instruments, are discussed. for example, high moisture sensitivity, low impact resistance, and time-consuming procedure as well as various properties of different species or in several parts of one specimen which are the main problems of wooden music instruments are extensively discussed in this paper. many ma...

Heat exchanger tube rows can influence the thermoacoustic instability behaviour of combustion systems since they act as both acoustic scatterers and unsteady heat sinks. Therefore, with careful tuning their properties, exchangers have potential to passive control devices. In this work, we focus on (only) scattering tubes. We present a comparison existing models for slits, latter having advantag...