Abstract:Flow direction and specific catchment area were calculated for different flow-routing algorithms using TAPES-G and TauDEM. A fuzzy classification was used along with eight topo-climatic attributes to delineate six landscape classes from a 10-m USGS DEM. A series of maps and tabular outputs were produced to compare flow-routing predictions in different parts of the study area in the Santa Monica Mountains of southern California. The matched pair t-test was used to compare the performance of pairs of specific catchment area grids across six user-defined fuzzy landscape classes. The results show that (1) the 'source' cells predicted with the D1, DEMON, and FD8 algorithms were confined to hilltops; (2) two single flow-routing algorithms (Rho8, D8) produced poor results; and (3) the choice of flow-routing algorithm has potentially important consequences for the calculation of upslope contributing areas, sediment transport capacity, topographic wetness, and several other topographic indices.
This chapter reviews the various flow routing algorithms that simulate the distribution and flow of water across landscapes. The distinguishing characteristics of nine such algorithms and the experiments that have been conducted to evaluate their performance over the past 15 years are discussed. From there, we consider three sets of enduring challenges: (1) the role of scale and feedback between soil and water, and the need to consider these issues when characterizing the properties of both; (2) the need for dynamic flow routing algorithms and related indices in many landscapes; and (3) some of the as yet unrealized opportunities for treating space and time as continuous variables in the representation of soil water properties. The chapter concludes by noting the current state-of-the-art and where we might go from here.
Ion implantation and rapid thermal annealing of Mg, Cd, and Si in AlxGa1−xAs are reported. The dependence of activation on various Al compositions (x=0.15–0.35) and annealing temperatures was investigated. Activations of over 60% were achieved for both Mg and Cd. However, for the same annealing cycle, the activation efficiency of the Mg implants was found to be generally higher than that of Cd implants. No particular dependence of the activation efficiency on Al composition was observed for either ion. For Si29 implants, poor activation was observed in samples with x above 0.2, while for x=0.2 a maximum activation of 80% was achieved with a 1000 °C, 5 s annealing cycle.
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