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We propose a cross-layer based multi-channel Medium Access Control (MAC) protocol to maximize the utilization of the leftover spectrum of primary user channels in cognitive radio networks. This protocol integrates the spectrum sensing at Physical layer and the packet scheduling at the MAC layer for mobile ad-hoc networks. With a TDMA-based control channel,(More)
Because diabetic retinopathy increases fracture risk, we studied the association between bone mineral density (BMD) and diabetic retinopathy in a nationally representative sample. A significant association between the presence of diabetic retinopathy and low BMD was observed. Therefore, diabetic retinopathy might be considered as a marker of low BMD.(More)
Because the rate of bone loss is an important risk factor for fracture, we studied longitudinal changes in bone mineral density (BMD). Although the BMD of the hip decreased over time, spine BMD remained largely stable or increased. Therefore, spine BMD may not be appropriate for assessing BMD change. The rate of age-dependent bone loss has been shown to be(More)
A major problem encountered when designing infinite im-<lb>pulse response (IIR) filters in the complex domain is to ensure thal<lb>the filter is stable. Instability occurs frequently when the IIR filter<lb>approximates the inverse of a nonminimum phase system. This is often1<lb>the case for equalization filters. Addition of delay to the target(More)
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