Functional Reasoning and Functional Modelling

A car that will not start on a cold winter day and one that will not start on a hot summer day usually indicate two very different situations. When pressed to explain the difference, we would give a winter account- Oil is more viscous in cold conditions, and that causes . . .\u27\u27 -and a summer story- Vapor lock is a possibility in hot weather and is usually caused by . . .\u27\u27 How do we build such explanations? One possibility is that understanding how the car works as a device gives us a basis for generating the explanations. But that raises another question: how do people understand devices? Model-based reasoning is a subfield of artificial intelligence focusing on device understanding issues. In any model-based-reasoning approach, the goal is to model\u27\u27 a device in the world as a computer program. Unfortunately, model\u27\u27 is a loaded term-different listeners understand the word to mean very different concepts. By extrapolation, model-based reasoning\u27\u27 can suggest several different approaches, depending on the embedded meaning of model.\u27\u2

Genetic variation in an endangered cedar (Widdringtonia cedarbergensis) versus two congeneric species

Widdringtonia cedarbergensis is a southern African conifer species under threat of extinction. This study explored the genetic status of the species to assess whether loss of genetic variation may be contributing to population declines. Widdringtonia nodiflora and W. schwarzii were used as benchmarks against which to compare genetic diversity in W. cedarbergensis. Isozyme electrophoresis was used to resolve seventeen isozyme loci in seedlings of the three species. Genetic diversity was greatest in W. nodiflora, followed by W. cedarbergensis and W. schwarzii. There is no evidence that W. cedarbergensis has undergone a genetic bottleneck relative to its sister species. Patterns of genetic variation varied between species with most of the variation occurring within populations of W. cedarbergensis, between populations of W. schwarzii, and within population ‘neighbourhoods’ of the more widespread W. nodiflora. The isozyme data indicate inbreeding,probably due to self-pollination, in W. cedarbergensis and W. nodiflora. Populations of W. schwarzii were outbreeding. Selfing in W. cedarbergensis may be caused by a change in population density from dense to sparse stands with potentially deleterious genetic consequences

The 4-Nitro-5-Methyl-2-Sulphobenzoic Acid and Some of Its Derivatives

The 4-nitro-5-methyl-2-sulphobenzoic acid has been investigated to a limited extent as one of the products formed when the 6-nitro-1, 3-dimethyl-4-sulphonic acid is oxidized by potassium permanganate in dilute alkaline solution. Previous to this research, the only record of its preparation was by Limpricht, in which case only a small amount of the neutral potassium salt was isolated. He gives this as occurring with one-half a molecule of water of crystallization, but does not state which of the two methyl groups of the original acid had been oxidized. The neutral potassium salt does not seem to contain any water of crystallization, however, and some doubt is cast upon the value of the observation as made by him

Functional Representation and Reasoning About the F/A-18 Aircraft Fuel System

Functional reasoning, a subfield of model-based reasoning, is discussed. This approach uses abstractions of a device\u27s purpose to index behaviors that achieve that purpose. Functional modeling, a variation on this method, also uses simulation as a core reasoning strategy. The complex causal knowledge of a device along functional lines is decomposed, then a causal story of how the device will operate in a particular situation given stated boundary conditions is composed. The application of the functional approach to modeling the fuel system of a F/A-18 aircraft is described. The representation of the F/A-18 fuel system includes 89 component devices, 92 functions, 118 behaviors, and 181 state variables

Vegetation gradients in Southern Cape mountains

Southern Cape Mountain fynbos has been little studied in the past so that management and planners have had to draw heavily on Western Cape experience. This study arose from the need to define local vegetation patterns and their interdependence with animal life, climate and soil as a necessary prerequisite to vegetation mapping and Fynbos is part of the diverse and complex Cape Floral Kingdom. Field taxonomy in fynbos is often problematic for trained botanists and is an overwhelming obstacle for mapping and monitoring of vegetation by untrained observers. Even the most unsophisticated observer, however, can recognize consistent variation in non-floristic characters such as vegetation height, density and the relative abundance of Proteaceae, small leaved shrubs and graminoid plants. A major aim of the study was thus to test the feasibility of deriving a non-floristic vegetation classification using easily learnt characters which had predictive value and was independent of the complication of high species turnover from one area to the next

Herbivores shape woody plant communities in theKruger National Park: lessons from three long-termexclosures

The role of grazers in determining vegetation community compositions and structuring plant communities is well recognised in grassy systems. The role of browsers in affecting savanna woody plant communities is less clear. We used three long-term exclosures in the Kruger National Park to determine the effect of browsers on species compositions and population structures of woody communities. Species assemblages, plant traits relating to browsing and soil nutrients were compared inside and outside of the exclosures. Our results showed that browsers directly impact plant species distributions, densities and population structures by actively selecting for species with traits which make them desirable to browsers. Species with high leaf nitrogen, low total phenolic content and low acid detergent lignin appeared to be favoured by herbivores and therefore tend to be rare outside of the exclosures. This study also suggested that browsers have important indirect effects on savanna functioning, as the reduction of woody cover can result in less litter of lower quality, which in turn can result in lower soil fertility. However, the magnitude of browser effects appeared to depend on inherent soil fertility and climate. CONSERVATION IMPLICATIONS: Browsers were shown to have significant impacts on plant communities. They have noticeable effects on local species diversity and population structure, as well as soil nutrients. These impacts are shown to be related to the underlying geology and climate. The effects of browsers on woody communities were shown to be greater in low rainfall, fertile areas compared to high rainfall, infertile soils

Classification Characteristics of SOM and ART2

Artificial neural network algorithms were originally designed to model human neural activities. They attempt to recreate the processes involved in such activities as learning, short term memory, and long-term memory. Two widely used unsupervised artificial neural network algorithms are the Self-Organizing Map (SOM) and Adaptive Resonance Theory (ART2). Each was designed to simulate a particular biological neural activity. Both can be used as unsupervised data classifiers. This paper compares performance characteristics of two unsupervised artificial neural network architectures; the SOM and the ART2 networks. The primary factors analyzed were classification accuracy, sensitivity to data noise, and sensitivity of the algorithm control parameters. Guidelines are developed for algorithm selection

Transplant Experiments Point to Fire Regime as Limiting Savanna Tree Distribution

Plant species range shifts are predicted to occur in response to climate change. The predictions are often based on the assumption that climate is the primary factor limiting the distribution of species. However the distribution of grassy biomes in Africa cannot be predicted by climate alone, instead interactions between vegetation, climate and disturbance structure the ecosystems. To test if climatic variables, as predicted by an environmental niche model, determine the distribution limits of two common savanna tree species we established a transplant experiment at a range of latitudes and altitudes much broader than the distribution limits of our study species. We planted seedlings of two common savanna trees, Senegalia nigrescens and Colophospermum mopane, at eight paired high and low elevation sites across an 850 km latitudinal gradient in South African savannas. At each site seedlings were planted in both grassy and cleared plots. After 2 years of growth, rainfall, temperature and location inside or outside their distribution range did not explain species success. Grass competition was the only variable that significantly affected plant growth rates across all sites, but grass competition alone could not explain the distribution limit. Species distributions were best predicted when maximum tree growth rates were considered in relation to local fire return intervals. The probability of sapling escape from the fire trap was the most likely determinant of distribution limits of these two species. As trees grew and survived 100 s of kilometers south of their current range limits we conclude that climate alone does not explain the current distribution of these trees, and that climate change adaptation strategies for savanna environments based only on climatic envelope modeling will be inappropriate

SeMi-Supervised Adaptive Resonance Theory (SMART2)

Adaptive resonance theory (ART) algorithms represent a class of neural network architectures which self-organize stable recognition categories in response to arbitrary sequences of input patterns. The authors discuss incorporation of supervision into one of these architectures, ART2. Results of numerical experiments indicate that this new semi-supervised version of ART2 (SMART2) outperformed ART for classification problems. The results and analysis of runs on several data sets by SMART2, ART2, and backpropagation are analyzed. The test accuracy of SMART2 was similar to that of backpropagation. However, SMART2 network structures are easier to interpret than the corresponding structures produced by backpropagation

Determining Customary International Law Relative to the Conduct of Hostilities in Non-international Armed Conflicts

In 1987, the 6th annual American Red Cross-Washington College of Law Conference on International Humanitarian Law convened to discuss the 1977 Protocols Additional to the 1949 Geneva Conventions. This article outlines the proceedings of the various workshops, serving as a richly detailed scholarly source for a significant historical event