Simultaneous Budget and Buffer Size Computation for Throughput-Constrained Task Graphs

Modern embedded multimedia systems process multiple concurrent streams of data processing jobs. Streams often have throughput requirements. These jobs are implemented on a multiprocessor system as a task graph. Tasks communicate data over buffers, where tasks wait on sufficient space in output buffers before producing their data. For cost reasons, jobs share resources. Because jobs can share resources with other jobs that include tasks with data-dependent execution rates, we assume run-time scheduling on shared resources. Budget schedulers are applied, because they guarantee a minimum budget in a maximum replenishment interval. Both the buffer sizes as well as the budgets influence the temporal behaviour of a job. Interestingly, a trade-off exists: a larger buffer size can allow for a smaller budget while still meeting the throughput requirement. This work is the first to address the simultaneous computation of budget and buffer sizes. We solve this non-linear problem by formulating it as a second-order cone program. We present tight approximations to obtain a non-integral second-order cone program that has polynomial complexity. Our experiments confirm the non-linear trade-off between budget and buffer sizes

Experimental and theoretical investigations of a rectangular grating structure for low-voltage traveling wave tube amplifiers

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Critical Behavior of Disordered Systems with a Free Surface

The behavior of homogeneous and disordered systems with a free boundary is described on the basis of group theory in the two-loop approximation directly in three-dimensional space. The effect of the free boundary on the regime of the bulk critical behavior is revealed. It is shown that the boundedness of the system slightly affects the regime of the bulk critical behavior in the case of the ordinary transition, whereas this effect is more noticeable in the case of the special transition. Surface critical phenomena are described for homogeneous and disordered systems, and the critical exponents are calculated in the two-loop approximation. It is shown that the effect of impurities is insignificant in the special phase transition, whereas it is more noticeable in the ordinary phase transition. The derived critical exponents are compared with the computer-simulation results.Comment: 19 pages, 2 figure

Belowground Consequences of Intracontinental Range-Expanding Plants and Related Natives in Novel Environments

Introduced exotic plant species that originate from other continents are known to alter soil microbial community composition and nutrient cycling. Plant species that expand range to higher latitudes and altitudes as a consequence of current climate warming might as well affect the composition and functioning of native soil communities in their new range. However, the functional consequences of plant origin have been poorly studied in the case of plant range shifts. Here, we determined rhizosphere bacterial communities of four intracontinental range-expanding plant species in comparison with their four congeneric natives grown in soils collected from underneath those plant species in the field and in soils that are novel to them. We show that, when controlling for both species relatedness and soil characteristics, range-expanding plant species in higher latitude ecosystems will influence soil bacterial community composition and nutrient cycling in a manner similar to congeneric related native species. Our results highlight the importance to include phylogenetically controlled comparisons to disentangle the effect of origin from the effect of contrasting plant traits in the context of exotic plant species