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In this paper, a novel programmable-gain amplifier (PGA) with precise dB-linear control is presented for medical ultrasound imaging. To obtain small gain step and wide gain range simultaneously, the pseudo- and the actual-exponential approximation are combined as a hybrid-type. Considering the gain accuracy of each control word, the two type controls are realized in a single stage amplifier in a proper...
Virtualized datacenter (VDC) has become a popular approach to large-scale system consolidation and the enabling technology for infrastructure-as-a-service cloud computing. The consolidation inevitably aggregates the security threats once faced by individual systems towards a VDC, and a VDC operator should remain vigilant of the threats at all times. We envision the need for on-demand mandatory security...
The Nansha (Spratly) Islands are located in the middle of the South China Sea (at about 10°N) near the northwestern margin of the Western Pacific Warm Pool (WPWP). A borehole was drilled at an atoll at Nansha, and cores were taken. The upper 165.4 m of the borehole consists entirely of limestone of reef facies and lagoon facies, which had been influenced by extensive meteoric diagenesis. Petrographic...
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