Sine wave

About: Sine wave is a research topic. Over the lifetime, 12183 publications have been published within this topic receiving 93013 citations. The topic is also known as: sinusoid.

Theory of Series Inductance Matching to Transducer at Premechanical Resonance Zone in Ultrasonic Vibration Cutting

Abstract: In order to obtain large vibration amplitude in ultrasonic vibration cutting, the transducer demands an additional inductance to match its native capacitance. The objective of this paper is to determine the optimum oscillation frequency of the resonant tank constructed using additional inductance and the transducer's native capacitance. By analyzing the transducer impedance matching on the impedance circle deduced from the transducer equivalent circuit model, the optimum oscillation frequency is found to be not equal to the transducer mechanical resonance frequency, but below it. Frequencies near the optimum oscillation frequency are referred to as the optimum premechanical resonance zone. Consequently, the Theory of Ultrasonic Transducer Impedance Matching at Premechanical Resonance Zone is proposed. Comparative experiments are conducted at different frequency zones. The results reveal that when the transducer is excited at the premechanical resonance zone, the vibration amplitude increases and the excitation voltage signal is the desired sine wave, compared to that when excited at the mechanical resonance frequency and the postmechanical resonance zone. The experimental results confirm the feasibility of this proposed theory.

Design, Operation, and Control of S3 Inverter for Single-Phase Microgrid Applications

Abstract: A single-phase voltage source inverter with a front-end dc–dc conversion stage followed by a synchronized push–pull configuration operating at a desired fundamental frequency (FF) is presented. The duty cycle of the dc–dc conversion stage is varied in the form of a unidirectional sine wave to produce a similar output voltage across the dc-link capacitor. The unidirectional voltage is made into an alternating voltage by the synchronized push–pull configuration. This inverter employs three semiconductor switches, in which one is operating at a high frequency and the rest are operating at an FF. Hence, it is named as the S3 inverter. Furthermore, simple and cost-effective analog circuits are presented for the generation of switching pulses and the control of the amount of power fed to the grid. The hardware prototype of the S3 inverter has been built in a laboratory, and its performance during the stand-alone and grid-connected modes of operation is validated.

Stable closed-loop fiber-optic delay of arbitrary radio-frequency waveforms.

Abstract: Thermal drifts in long fiber-optic delay lines are compensated based on chromatic dispersion. An arbitrary input radio-frequency (RF) waveform and a control RF sine wave modulate two different tunable laser sources and are coupled into the fiber delay line. The RF phase of the control tone at the output of the delay line is monitored and used to adjust the wavelengths of both sources, so that the effects of thermal drifts and dispersion cancel out. The input and control waveforms are separated in the optical domain, and no restrictions are imposed on their RF spectra. A figure of merit is proposed, in terms of the fiber delay, range of temperature changes that may be compensated for, and residual delay variations. An upper bound on performance is established in terms of the specifications of the tunable lasers. The principle is used in the stable distribution of sine waves and of broadband linear frequency-modulated (LFM) waveforms, which are commonly employed in radar systems. Lastly, the method is incorporated in stable interrogation of a localized hot-spot within a high-resolution, distributed Brillouin fiber sensing setup. The results demonstrate the applicability of the proposed protocol in the processing of arbitrary waveforms, as part of larger, more complex systems.

Ultrasonic brain infarction treating device

Abstract: Ultrasonic brain infarction treating device in which formation of a standing wave due to interference of between an ultrasonic beam projected into the skull and a reflected beam is avoided and side effects, e.g. destruction of brain cells, occurrence of intracerebral hemorrhage, destruction of nerve tissue, and the like are prevented. An ultrasonic probe cap (20A) is constituted by arranging a plurality of multilayer small transducers (21) composed of a PVDF film, PZT ceramic, and the like on the inner surface of the cap in a mosaic or another pattern. As a high frequency for driving the transducers a continuous sine wave, a burst wave or a pulse wave is used. In order to prevent generation of a standing wave in the skull, the frequency modulation rate is set at 1 ms or less and the repetition period is set at 1 ms or less for the continuous sine wave, and one excitation period is set at 1 ms or less and the repetition period is set at 1 ms or less for the burst wave and the pulse wave. The plurality of multilayer small transducers (21) are driven selectively depending on the location of a thrombus. A cooling jacket is disposed between the cap and the head in order to suppress temperature rise in the skull and to cool the transducer.

Signal processing system

Abstract: A signal processing system and technique is disclosed for detecting the pence of a desired frequency signal particularly that of a sine wave, in a noisy environment. The signal mixed with noise is received and analyzed by a Fast Fourier Transform spectrum analyzer the output of which is indicative of instantaneous signal phase. The output of the spectrum analyzer is digitally processed to produce a series of average instantaneous signal values based upon the instantaneous signal phase and a statistical estimate of its rate of change, the values being representative of the relative signal strengths for a progression of phase reference values between 0° and 360°. The desired signal is detected when an average instantaneous signal value exceeds a threshold value determined empirically based upon a certain probability of detection and false alarm rate.