Equations describing facies proportions and amalgamation ratios are derived for randomly placed objects belonging to two or three foreground facies embedded in a background facies, as a function of the volume fraction...
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Equations describing facies proportions and amalgamation ratios are derived for randomly placed objects belonging to two or three foreground facies embedded in a background facies, as a function of the volume fractions and object thicknesses of independent facies models combined in a stratigraphically meaningful order. The equations are validated using one-dimensional continuum models. Evaluation of the equations reveals a simple relationship between an effective facies proportion and an effective amalgamation ratio, both measured as a function only of the facies in question and the background facies. This relationship provides a firm analytical basis for applying the compression algorithm to multi-facies object-based models. A set of two-dimensional cross-sectional models illustrates the approach, which allows models to be generated with realistic object stacking characteristics defined independently for each facies in a multi-facies object-based model.
Formalising and automating the software life-cycle processes are key factors in the improvement of software productivity. This paper describes the Project Master Database (PMDB) work, three generations of investigatio...
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Formalising and automating the software life-cycle processes are key factors in the improvement of software productivity. This paper describes the Project Master Database (PMDB) work, three generations of investigations into the modelling and encoding of software life-cycle processes;it briefly describes past activities and concentrates on more recent investigations. It presents an approach to software process modelling based on an object-based model called the PMDB + model, which includes project elements, relationships between those elements and behavioural descriptions of project life-cycle activities. An overview of the model is presented, together with examples to illustrate the application of the model to existing software processes. It also describes a prototyping exercise that implemented the PMDB + model in an object-oriented database management system. Key results of these investigations, the impact of process implementations on the architecture of environments, and lessons learnt from the exercises are described.
A hierarchy of questions and answers about the features of distributed computing systems (DCSs) leads to an overall system description that facilitates system comparisons. The taxonomy uses terminology from an object-...
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A hierarchy of questions and answers about the features of distributed computing systems (DCSs) leads to an overall system description that facilitates system comparisons. The taxonomy uses terminology from an object-based model of DCSs and emphasizes the runtime services the DCS provides to applications. It is based on the division of DCS issues into three distinct categories: threads object properties and separation. The threads subtree explores the creation, the number, and the control of threads in the DCS. The object properties subtree explores DCS features that are defined for objects in isolation. The separation subtree explores issues that arise because there are many objects in the DCS. To describe a specific DCS, a taxonomy user traces paths through the hierarchy
A doubly nonstationary cylinder-basedmodel is built to describe the dispersal of a population from a point source. In this model, each cylinder represents a fraction of the population, i.e., a group. Two contexts are...
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A doubly nonstationary cylinder-basedmodel is built to describe the dispersal of a population from a point source. In this model, each cylinder represents a fraction of the population, i.e., a group. Two contexts are considered: The dispersal can occur in a uniform habitat or in a fragmented habitat described by a conditional Boolean model. After the construction of the models, we investigate their properties: the first and second order moments, the probability that the population vanishes, and the distribution of the spatial extent of the population.
Tree biomass is an integrated measure of net growth and is critical for understanding, monitoring, and modeling ecosystem functions. Despite the importance of accurately measuring tree biomass, several fundamental bar...
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Tree biomass is an integrated measure of net growth and is critical for understanding, monitoring, and modeling ecosystem functions. Despite the importance of accurately measuring tree biomass, several fundamental barriers preclude direct measurement at large spatial scales, including the facts that trees must be felled to be weighed and that even modestly sized trees are challenging to maneuver once felled. Allometric methods allow for estimation of tree mass using structural characteristics, such as trunk diameter. Savanna trees present additional challenges, including limited available allometry and a prevalence of multiple stems per individual. Here we collected airborne lidar data over a semiarid savanna adjacent to the Kruger National Park, South Africa, and then harvested and weighed woody plant biomass at the plot scale to provide a standard against which field and airborne estimation methods could be compared. For an existing airborne lidar method, we found that half of the total error was due to averaging canopy height at the plot scale. This error was eliminated by instead measuring maximum height and crown area of individual trees from lidar data using an object-based method to identify individual tree crowns and estimate their biomass. The best object-based model approached the accuracy of field allometry at both the tree and plot levels, and it more than doubled the accuracy compared to existing airborne methods (17% vs. 44% deviation from harvested biomass). Allometric error accounted for less than one-third of the total residual error in airborne biomass estimates at the plot scale when using allometry with low bias. Airborne methods also gave more accurate predictions at the plot level than did field methods based on diameter-only allometry. These results provide a novel comparison of field and airborne biomass estimates using harvested plots and advance the role of lidar remote sensing in savanna ecosystems.
In this paper we describe the architecture and implementation of a digital library framework for scientific data, particularly imagery, with a focus on support for content-based search. Content is specified by the use...
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