A bayesian approach to classification of multiresolution remote sensing data

Several earth observation satellites acquire image bands with different spatial resolutions, e.g., a panchromatic band with high resolution and spectral bands with lower resolution. Likewise, we often face the problem of different resolutions when performing joint analysis of images acquired by different satellites. This work presents models and methods for classification of multiresolution images. The approach is based on the concept of a reference resolution, corresponding to the highest resolution in the dataset. Prior knowledge about the spatial characteristics of the classes is specified through a Markov random field model at the reference resolution. Data at coarser scales are modeled as mixed pixels by relating the observations to the classes at the reference resolution. A Bayesian framework for classification based on this multiscale model is proposed. The classification is realized by an iterative conditional modes (ICM) algorithm. The parameter estimation can be based both on a training set and on pixels with unknown class. A computationally efficient scheme based on a combination of the ICM and the expectation-maximization algorithm is proposed. Results obtained on simulated and real satellite images are presented.     

Model-driven development using UML 2.0: promises and pitfalls

Experience indicates that effective complexity management mechanisms automate mundane development tasks and provide strong support for separation of concerns. For example, current high-level programming languages and integrated development environments provide abstractions that shield developers from intricate lower-level details and offer automated support for transforming abstract representations of source code into faithful machine-executable forms. The Object Management Group initiated the Unified Modeling Language 2.0 effort to address significant problems in earlier versions. While UML 2.0 improves over earlier versions in some aspects, its size and complexity can present a problem to users, tool developers, and OMG working groups charged with evolving the standard.     

Snow-cover mapping in forests by constrained linear spectral unmixing of MODIS data

A snow-cover mapping method accounting for forests (SnowFrac) is presented. SnowFrac uses spectral unmixing and endmember constraints to estimate the snow-cover fraction of a pixel. The unmixing is based on a linear spectral mixture model, which includes endmembers for snow, conifer, branches of leafless deciduous trees and snow-free ground. Model input consists of a land-cover fraction map and endmember spectra. The land-cover fraction map is applied in the unmixing procedure to identify the number and types of endmembers for every pixel, but also to set constraints on the area fractions of the forest endmembers. SnowFrac was applied on two Terra Moderate Resolution Imaging Spectroradiometer (MODIS) images with different snow conditions covering a forested area in southern Norway. Six experiments were carried out, each with different endmember constraints. Estimated snow-cover fractions were compared with snow-cover fraction reference maps derived from two Landsat Enhanced Thematic Mapper Plus (ETM+) images acquired the same days as the MODIS images. Results are presented for non-forested areas, deciduous forests, coniferous forests and mixed deciduous/coniferous forests. The snow-cover fraction estimates are enhanced by increasing constraints introduced to the unmixing procedure. The classification accuracy shows that 96% of the pixels are classified with less than 20% error (absolute units) on 7 May 2001 when all forested and non-forested areas are included. The corresponding figure for 4 May 2000 is 88%.     

Gas chromatography of monosaccharides as O-isopropylidene derivatives. Analysis of hay,grass silage,and alkali-treated barley straw after mild and strong acid hydrolysis

Samples of hay, silage, untreated and ammonia-or alkali-treated barley straw were subjected to mild and strong acid hydrolysis, and the liberated monosaccharides were analysed by gas-liquid chromatography as their O-isopropylidene derivatives. From the mild acid hydrolysis, the total fructose content of the material and the amount of easily hydrolysed glucose were determined, allowing the content of non-structural carbohydrates to be estimated. In the same operation, the content of mannitol and arabinotol in the feed samples can be determined. From the strong acid hydrolysis, the total amounts of each aldose in the forage materials were determined.     

Models of complex human screening and correcting of social data

National statistical agencies annually spend great budgets in the continuous collection of a huge amount of data on individual persons, households, business activities, etc., to serve the information needs of a number of national and international government and private users. Substantial parts of their budgets are consumed in checking and improving the quality of the data collected. Because of their complexities, these tasks have depended on the handling of specialists. To save both processing time and resources and to improve the processing involved in solving and servicing data requests, these tasks have high priority. The present paper outlines research carried out in Norway on using the neural network paradigm to improve the data quality checking and improvement in large-scale data masses.     

Parameterization and analysis of the optical absorption and scattering coefficients in a western Norwegian fjord: a case II water study

Based on statistical analyses of optical properties measured during a whole year of monthly cruises in a Norwegian fjord, we constructed a two-component model for the absorption and scattering coefficients for visible light. The input to the model is the concentrations of yellow substance and chlorophyll a. Because of the presence of a significant amount of nonalgal particles in coastal water, we assume that the absorption and scattering coefficients approach constant background values when the concentration of chlorophyll a approaches zero. The model works reasonably for a variety of optical conditions encountered throughout the year, with a possible exception during a bloom of the Emiliania huxleyi algae in June.     

Flixborough revisited - an explosion simulation approach

A literature study of explosion estimation reports from the Flixborough accident was performed and commented. The results from this survey were compared to the results obtained from explosion simulations. The simulations were done with a computer model of the Flixborough plant using the EXSIM software simulation tool. The comparison showed that explosion magnitude estimates in the literature based on visual inspection are much lower than the simulated results, while the estimates based on calculations to a large degree conform with the simulations. The simulations also showed that the exact location of the ignition source does not seem to be significant for the magnitude of the explosion.     

Three-phase mixed-wet capillary pressure curves from a bundle of triangular tubes model

We present a bundle of triangular tubes model that simulates three-phase mixed-wet capillary pressure curves for any sequences of gas, oil, and water invasion processes. A diversity of cross-sectional fluid configurations may occur because of pore shape and different combinations of the contact angles. We use expressions for the capillary entry pressures that truly accounts for the mixed wettability condition and the possibility of simultaneous displacement of the fluids occupying the cross-sections. As a consequence, invasion does not necessarily proceed in the order of monotonic increasing or decreasing pore size. We simulate primary drainage and imbibition first. The saturation dependencies of the three-phase capillary pressures are analyzed for the subsequent gas injections and waterfloods and compared with the results from a similar bundle of cylindrical tubes model. Simulations are performed for three sets of contact angles representing oil-wet conditions with variable contact angle hysteresis. It is shown that the capillary pressure at the end of primary drainage, P_cow^max, strongly affects the saturation dependencies in the bundle of triangular tubes. For moderate values of P_cow^max, we have identified regions in the saturation space where two or all three capillary pressures are functions of two saturations, while the corresponding results from the bundle of cylindrical tubes often show that only one of the capillary pressures depends on more than one saturation, regardless of P_cow^max. The differences are caused by the capillary entry pressures in the triangular tubes that are strongly affected by the hinging interfaces in the corners when contact angle hysteresis is assumed. This leads to different bulk pore occupancies in the two bundle models, and hence different saturation dependencies. Furthermore, the level of gas–water and oil–water capillary pressure is higher for the bundle of triangular tubes during the gas and water invasion processes. The saturation dependencies, capillary levels and pore occupancies calculated from triangular tubes approach the corresponding results calculated from cylindrical tubes when P_cow^max is increased.     

Tributyrate as a substrate for the determination of lipase activity in milk.

A procedure is described for the determination of the lipolytic activity in milk using tributyrate as substrate. The method is based on the titration of liberated butyric acid in a diethyl ether: light petroleum (2-75:1, v/v) extract of the incubation mixture. Some of the fundamental factors involved in the procedure are discussed.