Quality Control for Scalable Media Processing Applications

Many media processing applications create a load that varies significantly over time. Hence, if such an application is assigned a lower processing-time budget than needed in its worst-case load situation, deadline misses are likely to occur. This problem can be dealt with by designing media processing applications in a scalable fashion. A scalable media processing application can run in multiple qualities, leading to correspondingly different resource demands. The problem we consider is to find an accompanying quality control strategy, which minimizes both the number of deadline misses and the number of quality changes, while maximizing the quality of processing. We present an initial approach to the above problem by modeling it as a Markov decision process (MDP). Our model is based on measuring relative progress at milestones. Solving the MDP results in a quality control strategy that can be applied during runtime with only little overhead. We evaluate our approach by means of a practical example, which concerns a scalable MPEG-2 decoder.     

Transalkylation of biphenyl over zeolites: Optimizing the reaction conditions and kinetic modeling

The shape-selective transalkylation of biphenyl with pentamethylbenzene over ultrastable Y-faujasites to produce para-methylated biphenyls was studied in the liquid slurry phase. The reaction was carried out in a discontinuously operated stainless steel autoclave using n-heptane as the solvent with a temperature range of 513 to 533 K and a pressure of 3 MPa. As for the progress of the reaction the presence of strong Brønsted acid sites was essential, an ultrastable faujasite treated with aqueous hydrochloric acid having a high content of those sites was used as the catalyst. Thus, a yield of the target product 4,4′-dimethylbiphenyl of above 11% referring to biphenyl could be achieved. The effect of the operating conditions on the formation of the target product was investigated. The decisive influence was acted out by the molar ratio of biphenyl to alkylating agent, in so far as a surplus of pentamethylbenzene of 7:1 referring to biphenyl enhanced the yield of the target product to 14%. The kinetics of the reaction could be successfully descibed with a lumped reaction scheme, introducing pseudo components, summarizing structural isomers, and pseudo reactions, such as the formation of coke.     

Ultra-fast vapour-liquid-solid synthesis of Si nanowires using ion-beam implanted gallium as catalyst

The feasibility of gallium as a catalyst for vapour-liquid-solid (VLS) nanowire (NW) growth deriving from an implantation process in silicon by a focused ion beam (FIB) is investigated. Si(100) substrates are subjected to FIB implantation of gallium ions with various ion fluence rates. NW growth is performed in a hot wall chemical vapour deposition (CVD) reactor at temperatures between 400 and 500?°C with 2% SiH(4)/He as precursor gas. This process results in ultra-fast growth of (112)- and (110)-oriented Si-NWs with a length of several tens of micrometres. Further investigation by transmission electron microscopy indicates the presence of a NW core-shell structure: while the NW core yields crystalline structuring, the shell consists entirely of amorphous material.