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A note on identifying a transmission factor in room acoustics

Ohta M., Ogawa H.

Archives of Acoustics

2005

Vol. 30, No. 3

323-331

In this study, as a concrete example of the non-linear inverse problem in indoor sound fields, a complex sound fluctuation leaked through an aperture gap in the partition door of a coupled room under the actual sound environment has been discussed. A probability evaluation theory introducing a simple stochastic inverse system model has been proposed first especially from an object-oriented viewpoint. More concretely, in order to evaluate the output response probability distribution of the acoustic intensity in the sound receiving room, after introducing time-averaged stochastic variables, we have identified functionally the leakage property as some variability of a transmission factor. Then, we have predicted the output response probability distribution for a new arbitrary stochastic input once after establishing a prediction theory for the probability distribution of a multiplicative model. Finally, an effectiveness of the proposed theory has been experimentally confirmed too by an application to actual indoor sound field data.

Multiaxial constitutive modelling for R-phase and M-phase transformations of TiNi shape memory alloys

Kawai M., Ogawa H., Baburaj V., Koga T.

Archives of Mechanics

1999

Vol. 51, nr 6

665-692

A multiaxial constitutive model for describing the pseudoelastic and shape memory behaviour of a titanium-nickel (TiNi) shape memory alloy due to the stress-induced rhombohedral and martensitic transformations has been developed from a phenomenological point of view. First, the existing constitutive models proposed for shape memory alloys are reviewed in brief. On the basis of a comparison between these models, an expression prescribing the transformation strain range is proposed which depends on the applied stress and the current phase volume fraction. Then, the uniaxial Tanaka model for the rhombohedral and martensitic transformations of TiNi shape memory alloys is extended to a multiaxial form using the framework of the Boyd-Lagoudas model and the proposed expression of the transformation strain range. Finally, the capability of the present model to predict the pseudoelastic behaviour of TiNi shape memory alloys is examined through numerical simulations of stress-strain responses under uniaxial and multiaxial proportional/nonproportional loading-unloading conditions.