The thermodynamic limits of photovoltaic solar energy conversion by fluorescent collectors are examined theoretically and experimaentally. The maximum efficiency of a fluorescent collector corresponds to the Shockley-Queisser limit for a non-concentrating solar cell with a single band gap energy. To achieve this efficiency the collector requires a photonic structure at its surface that acts as an omni-directional spectral band stop filter. Such a band stop filter is also required to achieve the thermodynamic light concentration limit in a fluorescent collector. The potential of photonic structures for the efficiency enhancement of idealized and real fluorescent collectors is highlighted. Analysis of a fluorescent collector system ny spatially resolved light induced current measurements and by quantum efficiency analysis shows that the collection efficiency of a real fluorescent collector system increases by up to 30% with the help of a Bragg stack on top of the collector acting as a band stop filter.
We study a queuing system having a mixture of special semi- Markov process (SSMP) and Poisson arrivals as the input process, where the Poisson arrival is regarded as interfering traffic. It is shown by numerical examples that the SSMP arrivals receive worse service than Poisson arrivals, i.e., the main waiting time of SSMP customers is longer than that of Poisson customers. We also propose a model of Moving Picture Experts Group (MPEG) frame arrivals as an SSMP batch arrival process. This model captures two features of the MPEG coding scheme: (1) the frequency of I, P, and B frames in a Group of Pictures, and (2) distinct size distributions for the three frames. The waiting time of each ATM cell generated from the frames is evaluated in the numerical examples. It is found that the waiting time characteristics are rather different among some real video data.