• Journal of the Institute of Electronics Engineers of Korea SD
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• v.45 no.3
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• pp.86-93
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• 2008

The multi-mode terminal modem which is capable of accommodating a variety of wireless communication standards needs versatile arithmetic units for processing a variety of word lengths and wide range of data rates. Since the target hardware is usually designed to meet the required highest performance, it is often wasteful in power consumption especially when low rate data processing cases. Thus, a speed and power adaptability of the arithmetic unit is a desirable feature for the wireless applications. In this paper, we propose a power efficient versatile adder architecture with carry skip logic as a basic building block constructed in hierarchical manner. The validity of the architecture is shown with respect to size, performance, and power efficiency in diverse operating modes.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.22 no.1
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• pp.89-103
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• 2009

This study investigates the applicability of the time reversal concept in modem acoustics to the Lamb waves, which have been widely studied for defect detection in plate-like structures. According to conventional time reversal acoustics, an input signal can be reconstructed at an excitation point if an output signal recorded at another point is reversed in the time domain and emitted back to the original source point. However, the application of a time reversal process(TRP) to Lamb wave propagations is complicated due to velocity and amplitude dispersion characteristics of Lamb waves and reflections from the boundaries of a structure. In this study, theoretical investigations are presented to better understand the time reversibility of Lamb waves. In particular, the effects of within-mode dispersion, multimode dispersion, amplitude dispersion, and reflections from boundaries on the TRP are theoretically formulated. Simple numerical case studies are conducted to validate the theoretical findings of this study.