A method for the measurement of flow rate in a pipe is proposed. The method utilizes the vibration signals that are generated using an external excitor. Three accelerometers on the surface of a pipe are used to measure these signals. Applying wave decomposition theory to the measured vibration signal, change of wave number, which is one of the results caused by flow rate change, is estimated. The change of wave number is converted into flow rate using the simple mathematical model of fluid conveying pipe. The main advantage of this method is that it does not require any sensory system inside the pipe, so that the characteristics of flow are not disturbed and the measurement position can be easily moved. All possible errors associated with the proposed measurement system are investigated. Those are due to sensor spacing, relative position of sensor with respect to boundaries, phase mismatch as well as magnitude mismatch between sensors, and measurement noise. To verify the potential of this method, experiments using water conveying steel pipe are accomplished. Finally, the estimated flow rates are within 12% error bounds.

Near-field acoustic holography (NAH) is applied to reconstruct an exterior sound field, as well as an interior sound field. A numerical method is employed to reconstruct the interior sound field of an arbitrary shaped enclosure. Reconstructed sound fields are usually used in identifying noise sources. However, until now, it has not been thoroughly verified whether the reconstructed sound field of an interior also shows source distributions. Interior sound fields have been reconstructed without any thought given to this question. In contrast to an exterior sound field, reflections are added to an interior sound field and therefore, the reconstructed sound field may misrepresent the source distribution. This paper addresses a way to solve this problem. A measurement method is proposed in order to distinguish between reflections and direct radiation from noise sources.

We introduce the notion of R(g, g ′ )-continuity on generalized topological spaces, which is a strong form of (g, g ′ )-continuity. We investigate some properties and relationships among R(g, g ′ )-continuity, (g, g ′ )-continuity and some strong forms of (g, g ′ )-continuity.

Abstract. We introduce the concepts of M -preclosed graph and M * -preopen mapping on spaces with minimal structures and investigate some properties of M * -preopen mapping. We also investigate the relationships between M -precontinuous mappings and several types of m-compactness.

This study proposes a method to identify active sources. The theory itself does not limit the application of the proposed method, but the main aim has been focused on finding the location of active noise sources and their strengths in an enclosure. The acoustic holography method can be applied to identify active sources, primary sources if one prefers to call them. However, it will depict all sources including imaginary sources, which one may call secondary sources, which are due to reflections on the walls of enclosure. In this study, an attempt has been made to distinguish these two different types of sources. First, boundaries are modeled by the inhomogeneous Robin boundary condition. It makes it possible to represent the boundaries as the combination of general ideal sources and passive boundaries; the ideal sources imply the primary sources, while the passive boundaries control the secondary sources. Second, this general boundary condition is combined with the holography method to reconstruct the strength of ideal sources. A technique for estimating surface admittance of passive boundaries is also proposed for a three-dimensional sound field by generalizing that for a duct.