摘要:

AbstractAn interactive hybrid expert system is developed to classify polar scenes using AVHRR LAC imagery. A total of 183 spectral and textural signatures are generated from which the 20 “best” are chosen using the Sequential Forward Selection procedure. These 20 features are used to populate the working memory of the expert system. A probabilistic neural network is used as the inference engine to make probabilistic estimates of class membership. As part of the inference engine, a sophisticated outlier test is performed to provide a measure of classification confidence.During a session, the user is provided with an extensive set of on‐screen aids to assist in labelling. The user may modify the knowledge base by adding new samples to existing classes or by including new classes. The expert system provides confidence measures and a distance measure from the proposed class cluster centre. The interactive environment allows the user to test the impact of class labelling upon the knowledge base before new data is entered. For users working with very large datasets and very complex scenes, the integrity of the knowledge base is the primary concern.A bootstrap method is used to validate classification accuracy. On the basis of 100 bootstrap samples, an overall classification accuracy of 87% is achieved, with a standard deviation of 1%. The result is that much more accurate cloud classification in polar regions now can be made, which will aid us in our monitoring of global climate ch

ISSN:1180-4009    

DOI:10.1002/env.3170030201

出版商:John Wiley&Sons, Ltd.    

年代:1992

数据来源: WILEY

摘要:

AbstractAccurate monitoring of contaminated groundwater is one of the most important issues in environmental technology. This paper, composed of two main sections, presents an efficient method of computing plume concentration.In the first section, reservoir rock properties such as permeability are characterized by geostatistical methods for generating spatial property distributions, such as the source point method (SPM), augmented with conditional simulation from the known sample data. In case the data are not available the permeability field is generated from the SPM alone.In the second section of the paper, the generated random field along with source/sink flow data is used as input in the pressure equation to solve for the Darcy velocity. The Darcy velocity is then used in the convectivedispersion (C‐D) equation to solve for the flow of contaminant in the aquifer. A newly developed numerical method of solving the C‐D equation is used to follow the movements of the front. The numerical scheme recognizes both convection and dispersion. The physical dispersion includes both longitudinal and transverse dispersion along with the molecular diffusion. The new method is numerically stable and avoids any numerical dispersion. The fronts are displaced according to the direction and magnitude of the concentration gradient, rather than merely from the streamlines. There are two main advantages of this model. Firstly, the tracking of fronts gives a better representation of the contaminant movement in the heterogeneous reservoir. Secondly, the time record of the output concentration at the production wells will enhance the prediction of contaminant migrat

ISSN:1180-4009    

DOI:10.1002/env.3170030202

出版商:John Wiley&Sons, Ltd.    

年代:1992

数据来源: WILEY

摘要:

AbstractIn this paper, we provide an example demonstrating a means of modelling the interaction of species in an ecosystem which will enable us to determine long term growth trends of the various species. In most cases, the type of interaction between species in an ecosystem is unknown. Therefore it is useful to use a mathematical structure which makes almost no assumptions as to the form of this interaction. We use a topological semigroup to model the behavior interaction. To do this, it will be shown how to define the multiplicative structure of the semigroup. Also, it will be demonstrated how to use kernel density estimation to predict these interactions.

ISSN:1180-4009    

DOI:10.1002/env.3170030203

出版商:John Wiley&Sons, Ltd.    

年代:1992

数据来源: WILEY

摘要:

AbstractThis paper is inspired by recent work of G.A. Barnard, who treats the Behrens‐Fisher problem from a Bayesian point of view, and provides calculator programs to implement the solutions (including the classical fiducial solution). We review Barnard's work, and generalize his family of priors in a manner that makes it convenient to estimate the form of the prior from the observed variance ratio. A calculator program is provided to give an empirical estimate (based on marginal maximum likelihood), in an interesting special case, of a parameter of the prior distribution. In addition, programs similar to Barnard's are provided to calculate Bayes or Empirical Bayes p‐values and confidence interv

ISSN:1180-4009    

DOI:10.1002/env.3170030204

出版商:John Wiley&Sons, Ltd.    

年代:1992

数据来源: WILEY

摘要:

AbstractIn response to California Assembly Bill No. 2070 (1986), an Asbestos Assessment Task Force was created to analyze the magnitude of the asbestos problem in public buildings in the State of California. A survey of 207 city‐owned and county‐owned buildings was carried out to determine the presence and condition of asbestos‐containing material. In addition, a ranking and priority system was developed to rank buildings according to the degree of asbestos hazard, and to estimate the costs of abatement and/or management according to this system. This information was then extrapolated to the universe of city/county buildings using bootstrapping procedures. It was estimated that the average cost for recommended asbestos abatement was $194 million (range $146–254 million). The average cost for total removal of all asbestos increased to $379 million (range $312–470

ISSN:1180-4009    

DOI:10.1002/env.3170030205

出版商:John Wiley&Sons, Ltd.    

年代:1992

数据来源: WILEY

摘要:

AbstractIn this article, nonlinear regression models for correlated count data are examined. Correlation within clusters is modelled by a multivariate Gaussian mixing process on the log‐expectation scale. The regression parameters and the variance‐covariance parameters of the mixing process are estimated using quasi‐likelihood methods. An example involving temporal trends in hospital admissions for respiratory disease is used to illustrate the methods pro

ISSN:1180-4009    

DOI:10.1002/env.3170030206

出版商:John Wiley&Sons, Ltd.    

年代:1992

数据来源: WILEY

摘要:

AbstractMultistate survival models for partially censored data are of great interest for investigating factors attributing to transitions from one state of survival to other states of survival or death. Kay (1982) extended the proportional hazards model for a multistate framework with several transient states. However, in his framework, Kay did not incorporate reverse transitions. This paper discusses an extension of the proportional hazards model for several transient states under a competing risk framework for transitions and reverse transitions. The relationship with the multistate product‐limit method is also shown in this pape

ISSN:1180-4009    

DOI:10.1002/env.3170030207

出版商:John Wiley&Sons, Ltd.    

年代:1992

数据来源: WILEY