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Micromachining techniques have been developed and applied in fabricating high frequency piezoelectric composite 2-dimensional ultrasound array transducers. The array has 256 elements with the size of 105 µm by 105 µm. The kerf between elements is 5 µm. The center frequency is 52 MHz with the −6 dB bandwidth of 58%. As many as 98% elements are working. The pulse-echo responses have been measured with...
A fast algorithm for discrete sine transform (DST) is proposed. Through derivation the traditional DST is transformed into the computation of a first-order moment, which can be implemented by a simple parallel structure without multiplications. The comparison with some existing methods on the computation and the hardware complexity shows the advantage of our method under certain conditions. The approach...
Recently, a new concept of rotation scanning synthetic aperture interferometric radiometer (RS-SAIR) has been receiving more and more attentions for its advantage of much simpler configuration with looser requirements of antenna elements. In this article, we investigate the imaging theory of RS-SAIR, and introduce the pseudo-polar FFT algorithm to deal with the polar u-v samples. It only involves...
This paper presents the development of high-frequency ultrasonic annular arrays. A high-frequency six-ring annular array was successfully fabricated with the DRIE dry-etching. The array has a total aperture of 1.3 mm and six equal area (0.25 mm2 ) rings separated by 16-??m kerfs. The simulations prove its capability of dynamic focusing and its improved lateral resolution. The measured results of the...
We have demonstrated a robust magnetic tunnel junction (MTJ) with a resistance-area product RA=8 Omega-mum2 that simultaneously satisfies the statistical requirements of high tunneling magnetoresistance TMR > 15sigma(Rp), write threshold spread sigma(Vw)/<Vw> <7.1%, breakdown-to-write voltage margin over 0.5 V, read-induced disturbance rate below 10-9, and sufficient write endurance, and...
This paper proposes a new method for valuing a major public investment project. The method allows also the study and determination of the optimal time to begin the investment. Such a project needs long-term investment, requires tools of analysis able to collect and systematize the future uncertainty, which is present in the evolution of the problem variables. Valuation is difficult and must take into...
Two approaches to the simulation of photovoltaic arrays are described and compared. The first involves the use of a pilot panel and variable light source. In the second, characteristic array curves are stored in the memory of a microprocessor-based simulator. For the first approach, a stability analysis based on Popov's method is presented. Experimental resul ts are presented for both systems.
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