A new technique for measuring liquid-level utilizing wedge wave is presented and demonstrated through FEM simulation and a corresponding experiment. The velocities of wedge waves in the air and the water, and the sensitivities for the measurement, are compared with the simulation and the results obtained in the experiments. Combining the simulation and the measurement theory, it is verified that the foundation framework for the methods is available. The liquid-level sensing is carried out using the aluminum waveguide with a 30° wedge in the water. The liquid-level is proportional to the traveling time of the mode 1 wedge wave. The standard deviations and the uncertainties of the measurement are 0.65 mm and 0.21 mm using interface echo, and 0.39 mm and 0.12 mm utilized by end echo, which are smaller than the industry standard of 1.5 mm. The measurement resolutions are 7.68 μm using the interface echo, which is the smallest among all the guided acoustic wave-based liquid-level sensing.
The solid angle, which is closely related to the sky amount and sky factor, has been commonly used to assess urban landscapes. In this paper, we propose a new algorithm to calculate the solid angles of urban landscapes based on computational geometry. This algorithm enables us to incorporate the complicated landscapes which consist of multiple nonconvex polygons. Furthermore, using the algorithms, we assess the public space near Shibuya Station in terms of solid angles. In the analysis, we describe how advertising billboards disturb our visibility. We also develop the algorithm to calculate the sky amount and the sky factor, and evaluate both indexes.
To demonstrate repetitive-intense X-ray source by using pulsed-power discharge, we proposed an innovative Xpinch method using compact pulse generator and liquid metal injection. The compact pulse generator using small pulse-forming-network modules (PFNMs) has been developed. The current rising rate of the PFNMs with X-pinch system is over 0.1 kA/ns at low operation voltage. To suppress the expansion of liquid metal in a vacuum chamber, we have demonstrated liquid metal injection with coaxial supersonic flow generated by an aerospike nozzle. The results indicate that the expansion of liquid metal is suppressed with the coaxial supersonic flow.
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