Browsing by Author "Liu, YS"

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An automatic method to determine mitral annular lines from 2D+1D precordial echocardiogram
(2000)
Liu, YS
;
Ching, YT
;
Chen, SJ
;
資訊工程學系
;
Department of Computer Science
We present a method to determine the sequence of mitral annular lines in 2D + 1D precordial echocardiogram. We first use the optical flow technique a 2-means algorithm to determine a set of possible mitral annular points. A pair of mitral annular points could form the mitral annular line. The problem to determine the sequence of mitral annular lines in 2D + 1D echocardiogram is modeled as a problem to find the shortest path in a graph. The proposed method need very few user inputs. Experimental results show that we can find accurate mitral annular lines.
MAC protocols for multi-channel WLANs
(2005-01-01)
Liu, YS
;
Hsu, TH
;
電信工程研究所
;
Institute of Communications Engineering
Wireless local area networks, in which every station can transmit via any one of the available operating channels, but only one channel at a time. are investigated. Two distributed random access protocols are proposed for these WLANs. The CSMA/CA protocol is similar to the IEEE 802.11 standard but with slight modifications for multiple operating channels. The fuzzy logic controlled protocol employs a simple fuzzy logic controller to tune the size of backoff window. Extensive simulations are provided to evaluate the channel utilization, fairness, and responsiveness of these two protocols. Furthermore, the effects of employing RTS/CTS mechanism with both protocols are considered. Finally, performances of these two protocols are also investigated under conditions of burst traffic and noisy channels. Simulation results show that the fuzzy logic controlled protocol is a great improvement of the CSMA/CA protocol.