Measuring Liquid-Level Utilizing Wedge Wave.

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.

Ultrasonic Lateral Displacement Sensor for Health Monitoring in Seismically Isolated Buildings.

An ultrasonic lateral displacement sensor utilizing air-coupled ultrasound transducers is proposed. The normally-distributed far field of an ultrasound transducer in a lateral direction is taken advantage of for measuring lateral displacement. The measurement system is composed of several air-coupled ultrasound transducers as a receiver and several transmitters. The transmitters are immobilized at a fixed point, whereas the receiver set-up is separately arranged on the opposite side. In order to improve measurement accuracy, a correction method that utilizes polynomial approximation is introduced. The difference between the corrected lateral displacement and the reference displacement is estimated to be 0.2 mm at maximum for the two transmitters system. A good responsiveness is demonstrated by conducting a dynamic response experiment. When five transmitters are arranged, their measurement range is easily extended up to ±60 mm with an accuracy of 0.7 mm. In both cases, the fluctuations to the measurement ranges show less than 1%. These results indicate that the developed sensor system is useful for measuring relative lateral displacement of a seismically isolated building in the field of structural health monitoring.

Unusual variant of the anterior cerebral artery.

A rare abnormality of the A1 segment of the anterior cerebral artery (ACA) is reported. The right ACA bifurcated into two parts at the middle point of the A1 segment, and these segments did not rejoin. The superior right A1 segment connected with the left A1 and formed a single pericallosal artery. The inferior right A1, from which the right ophthalmic artery originated, had no connection with the left A1.

Epilepsy and variation in the frontal lobe artery.

A patient with a rare variation of fronto-orbital artery (FOA) that developed generalized tonic and clonic seizures is reported. The epilepsy focus was in her left frontal region, where blood was supplied by the contralateral fronto-orbital artery. The region was vulnerable to ischemic changes due to a decrease in blood CO2 gas caused by an increase in endogenous progesterone in the luteal period. The anomaly illustrates an important mechanism of ischemia in epilepsy.