Browsing by Author "Xiao, Yanyang"

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    Magneto-optical trap and its application to ultra-cold atom collision studies
    (1994) Xiao, Yanyang; Hulet, Randall G.
    We have successfully trapped $\sp7$Li in a vapor cell magneto-optical trap (MOT). The trap is studied in detail and the parameters are measured from the experiment. The trapping mechanism has been understood in terms of the radiation force and a simple one dimensional model is used in interpreting and predicting the experimental results. The cold-cold atom collision rate coefficient is measured in a beam MOT. The two collision mechanisms, fine structure changing and radiative escape, are discussed in a molecular picture. One of the channels, the fine structure changing channel, can be turned on and off by the experimental conditions, namely the laser intensity in this experiment. The rate coefficient for each mechanism has been determined from the experiment.
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    Memory architecture in multi-channel optically interconnected distributed shared memory multiprocessor systems
    (1997) Xiao, Yanyang; Bennett, John K.
    Multi-channel optical networks, although common in telecommunication applications, have only recently found application in computer systems. Multi-channel optical networks offer the potential for high performance interconnects for both local computer networks and multiprocessor systems. In addition to providing high bandwidth, multi-channel optical networks exhibit the capability for efficient broad-cast. The absence of an efficient broadcast mechanism in point-to-point networks has governed the choice of memory subsystem architecture for many parallel computer systems, and has in particular favored cache-coherent non-uniform memory access (CC-NUMA) over cache-only memory access (COMA) architecture. This thesis examined the choice of memory system architecture in the presence of high band-width and efficient broadcast. Using computer simulation, we compared the performance of CC-NUMA and COMA memory architectures in a multi-channel optical network multiprocessing system. Seven well-known parallel benchmarks were used in the study. Our results indicate that COMA consistently and significantly outperforms CC-NUMA in the multi-channel network. We also examined the performance of multi-channel optical networks for a varying-number of optical channels. We found that for the simulated architecture, the sampled benchmarks exhibit significant performance gain using only a small number of channels, relative to the number of nodes in the system. We further found that multiple channels offer better performance than that of a single channel with the same aggregated bandwidth.