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161.
Using the discrete time approach a model is developed for obtaining the expected queue length of theM(t)/G/1 queue. This type of queue occurs in different forms in transportation and traffic systems and in communications and manufacturing systems. In order to cut down the very high computational efforts required to evaluate the performance measures in such queues by exact methods, the Maximum Entropy Principle is used to approximate the expected queue length which is one of the most commonly used performance measures. A procedure is then developed for reducing the error encountered when this approximation is adopted. The results from this paper will encourage the practitioners to use the appropriate time-varying queueing models when the need arises instead of resorting to very poor approximations. 相似文献
162.
We report the solid-state dye-sensitized solar cell performances of perylene imide using nanoporous TiO2 electrodes. Solid-state dye-sensitized solar cells were fabricated using the organic hole-transporting medium (HTM) 2,2′7,7′-tetrakis-(N,N-di-p-methoxyphenyl-amine)-9,9′-spirobifluorene (spiro-OMeTAD). The experimental ELUMO levels of perylene imide dyes are found to be 3.75 and 3.77 eV, respectively. Therefore, perylene imide dyes can inject electrons to the conduction band of titanium dioxide in organic dye-sensitized solar cells. TiO2 thin films of about 2 μm in thicknesses were prepared. Both preparation and thickness of the compact TiO2 layer were optimized using spray pyrolysis. The studies revealed that an optimum film thickness of 130–150 nm of compact TiO2 yielded the best rectifying behavior and SDSC performance. In this work, our goal was to investigate the performance of perylene sensitizers in connection with spiro-OMeTAD hole transport material. Short-circuit current densities, open circuit voltages and overall conversion efficiencies of the solar cell with 2,2′7,7′-tetrakis-(N,N-di-p-methoxyphenyl-amine)-9,9′-spirobifluorene(spiro-OMeTAD) as a hole conductor and perylene imide as sensitizer on mesoporous TiO2 were investigated. 相似文献