Louisiana State University

About: Louisiana State University is a education organization based out in Baton Rouge, Louisiana, United States. It is known for research contribution in the topics: Population & Poison control. The organization has 40206 authors who have published 76587 publications receiving 2566076 citations. The organization is also known as: LSU & Louisiana State University and Agricultural and Mechanical College.

Effect of spatial and temporal variability in rainfall and watershed characteristics on stream flow hydrograph

Abstract: The shape, timing and peak flow of a stream flow hydrograph are significantly influenced by spatial and temporal variability in rainfall and watershed characteristics. Depending upon the size and shape of a watershed, its hydrological response is closely linked with storm dynamics. On an urban watershed a rain storm moving in the direction of flow produces a higher peak than it would if it were moving in the opposite direction. The effect of storm speed on peak discharge is much less for rapidly moving storms than for storms moving at about the same speed as the flow velocity. In a relatively homogeneous watershed the most important effect of spatial variability of rainfall occurs in the timing and shape of the runoff hydrograph. Temporally variable rainfall leads to higher peak flow than does constant rainfall. Significant errors in the prediction of runoff occur when an equivalent uniform hillslope is used to represent a heterogeneous hillslope. When average soil properties are used instead of spatially variable properties, significant differences are observed in infiltration. Spatially variable roughness alters the flow dynamics significantly. © 1997 John Wiley & Sons, Ltd.

On the online bin packing problem

Abstract: A new framework for analyzing online bin packing algorithms is presented. This framework presents a unified way of explaining the performance of algorithms based on the Harmonic approach. Within this framework, it is shown that a new algorithm, Harmonic++, has asymptotic performance ratio at most 1.58889. It is also shown that the analysis of Harmonic+1 presented in Richey [1991] is incorrect; this is a fundamental logical flaw, not an error in calculation or an omitted case. The asymptotic performance ratio of Harmonic+1 is at least 1.59217. Thus, Harmonic++ provides the best upper bound for the online bin packing problem to date.

Alternative successional pathways in the Amazon Basin

Abstract: Summary 1 Successional pathways were evaluated in two Amazonian secondary forest communities with different land-use histories. Sites which had been clearcut without subsequent use were dominated after 6–10 years by the pioneer genus Cecropia (Moraceae), whereas those used for pasture before abandonment were dominated by the pioneer genus Vismia (Clusiaceae). 2 There were 58 plant families and 300 species identified in Cecropia stands but only 43 families and 147 species were identified in Vismia stands. There were 77 species in common (Sorensen similarity = 0.34). 3 Differences in species number and composition of recruiting individuals between stand types were significant and were a function of the dominant pioneer genus, stem density, distance from primary forest, and land-use history. Regeneration under Vismia canopy was dominated by small Vismia individuals (25% of plants < 2 cm basal diameter), whereas regeneration under Cecropia canopy was more diverse and did not include a single young Cecropia. 4 The number of regenerating plants in both secondary stand types dropped off sharply with distance (5, 25, 50, and 100 m) from primary forest, suggesting that seed dispersal was limiting plant recruitment. Species richness also declined with distance and could be explained by the decline in plant density. Species richness in Cecropia stands increased linearly with plant density, but in Vismia stands the richness increase with density was a decelerating function. 5 For the central Amazon, secondary succession involves a more rapid return of primary forest species if deforestation is not followed by use as pasture before abandonment.