Fault-dynamic modelling of a phthalic anhydride reactor

A new methodology, fault-dynamic modelling, has been developed for analysis of potentially hazardous situations in the process industries. Traditional fault-tree analysis is used to determine the combinations of component failure that can lead to a particular process upset condition. Realistic dynamic modelling is then used to calculate the time available for corrective action once the upset has started. The method is applied to a phthalic anhydride reactor. The results of the analysis identify three process upsets that can lead to catastrophic failure in 2–5 min if left uncorrected. Other process upsets lead to safe conditions.     

Accidental release: Fuzzy selection of adequate formal model

Risk assessment of a chemical process plant requires the application of a variety of consequence models in order to estimate the potential physical effects of accidental releases. The types of models required vary depending upon the substance under consideration and the circumstances of a release. The objective of this study was the development and application of a system based upon ‘fuzzy logic’, for the selection of a computer model to be used in consequence analysis in specific situations where only certain types of consequence models can be used. The collection of data for modelling purposes from different kinds of computer model and application of fuzzy methods were also important aims of the study.     

Evaluation of guild-indicator species for use in resource management

We followed selection guidelines commonly used by management agencies to select mountain quail (Oreortyx pictus) as an indicator species for an ecological guild of birds. We then evaluated the ability of mountain quail to indicate the presence of other species from the guild and to index the quality of the habitat for other species. The ability of quail to indicate the presence of species from the ecological guild varied widely within and among vegetation types. Species compositions of the ecological guild were more consistent in comparisons of sites within vegetation types than they were in comparisons of sites between vegetation types. Mountain quail habitat was significantly different from the habitats of sympatric species from the guild for 14 of 15 multivariate contrasts. We suggest that managers use indicator species with caution. If indicators are used, they should be applied to guilds composed of species that closely share ecological affinities. The habitat of the indicator species should overlap extensively with those of all other guild members. The use of indicators should be restricted to very similar sites within the same general vegetation type.     

Construction of guilds for habitat assessment

This article outlines a procedure for developing guilds for use in habitat assessment studies. It is based on a matrix constructed around layers of vegetation and other physical features of the environment used by vertebrate species for feeding and breeding. Modifications to permit inclusion of other life requirements such as cover are discussed. Examples are used to illustrate how species are assigned to guild cells based on their use of habitat, and how the association between a species and its environment does not have to be direct to influence the species' placement within the matrix.     

Seasonal food use by white-tailed deer at Valley Forge National Historical Park,Pennsylvania, USA

Food habits of white-tailed deer (Odocoileus virginianus) were examined from January to November 1984 via fecal-pellet analysis at Valley Forge National Historical Park (VFNHP), which represents an island habitat for deer surrounded by extensive urbanization, in southeastern Pennsylvania. In addition, use of fields by deer was compared to food habits. Herbaceous vegetation (forbs, leaves of woody plants, and conifer needles) was the predominant food type in all seasons except fall. Acorns and graminoids (grasses and sedges) were important food resources in fall and spring, respectively. Use of woody browse (twigs) was similar among seasons. Field use was relatively high during fall, winter without snow cover (<20 cm), and spring when food resources in fields were readily available. In contrast, use of fields was lowest in summer when preferred woodland foods were available and in winter with snow cover when food in fields was not readily accessible. Patterns of food-type use by deer at VFNHP indicate the year-round importance of nonwoody foods and field habitats to deer populations on public lands such as national parks in the northeastern United States.     

Habitat classification: A comparison using avian species and guilds

Results of breeding bird censuses in 1979 and 1980 were used to compare the relationships of both species and guilds to forest habitats in the White Mountains of New Hampshire. Several age classes of 11 forest cover types were studied: northern hard-woods (Fagus-Betula-Acer), spruce (Picea), spruce-fir (Picea-Abies), birth (Betula), swamp hardwoods (Acer-Pinus-Tsuga), pine (Pinus strobus andP. resinosa), balsam fir (Abies), aspen (Populus tremuloides andP. grandidentata), northern red oak (Quercus), oak-pine (Quercus-Pinus), and hemlock (Tsuga). All types were even-aged; only northern hardwoods had an additional uneven-aged condition. Forest cover types were also pooled to consider generalized habitats: hardwoods, mixed forest, or softwoods. Results of ordinations based on censuses of 74 bird species indicate that foraging guilds are more related to general cover types than are nesting substrate guilds, but bird species reflect habitat differences to a greater degree than do either guild scheme. Also, considerable overlap occurs in bird species distribution between hardwoods and mixed forests; softwoods show little overlap with other types. Discriminant function and classification analyses revealed that bird species composition can be used to correctly classify general forest habitats more accurately (83.8%) than either foraging (63.2%) or nesting substrate guilds (58.4%). These results indicate that, of the habitats studied, avian species compositions are more characteristic than are foraging or nesting substrate guild composition, which tend to be similar across forest habitats.     

Integrated economic-ecological analysis and evaluation of management strategies on nutrient abatement in the Rhine basin

Management of river basins involves the making of informed choices about the desired levels of economic activities and ecosystem functioning in the catchment. Information on the economic and ecological effects of measures as well as their spatial distribution is therefore needed. This paper proposes the following instruments to support decision-making in river basins: (1) the linking of models and indicators to describe the economic and ecological effects of management actions and their spatial distribution and (2) an extended evaluation framework that aims to evaluate management actions on three objectives for sustainable river management. These are cost-effectiveness, spatial equity, and environmental quality. This paper illustrates the potential of these instruments for river basin management by a case-study on nutrient management in the Rhine basin. In this case-study four nutrient abatement strategies are formulated, based on policies of the International Commission for the Protection of the Rhine and the North Sea Commission. These strategies are analysed and evaluated on their contribution to the three management objectives. Results show that none of these strategies score highest on cost-effectiveness, spatial equity and environmental quality simultaneously. It appears that cost-effectiveness is in conflict with environmental quality, whereas spatial equity and cost-effectiveness show quite close correspondence. This means that a trade-off has to be made between costs and spatial equity on the one hand, and environmental standards on the other hand. This paper offers a framework to make these trade-offs more explicit and provides quantitative information on cause-effect relationships, economic and environmental effects and the spatial distribution of these effects for various management strategies. This information can be particularly useful in the development of compromises required to establish international agreement and co-operation.     

Integrated Assessment of Air Pollution Abatement Strategies in Urban Areas: Application to the Greater Athens Area

This paper presents an integrated system for the assessmentof technical and non-technical measures that are putforward in order to reduce air pollution levels in urbanareas. In contrast to the majority of the currentlyemployed assessment tools, this system allows for theevaluation of any proposed air pollution control measure interms of its combined impact on air quality and socialwelfare, by correlating the environmental and economicaspects of alternative air pollution abatement solutions.Based on the multi-pollutant, multi-effect concept, thesystem presented aims in providing policy-makers with areliable tool for the objective assessment of the mostcost-effective packages of measures, the latter beingallocated according to the particular features and needs ofthe areas examined.     

CFD Prediction of Air Quality in the Area between Two City Vehicular Tunnels Considering Moving Cars

Concentration fields of different pollutants that spread outside two roadtunnels predicted with a CFD code will be presented. The solution domain represents the city area located between two tunnel outlets – tunnel Strahov and tunnel Mrazovka in Prague. The vicinity of both tunnels is a heavily built up area with tall buildings forming typical street canyons. The CFD modelling predicts the situation after the tunnel Mrazovka will be finished and traffic will increase considerably between both tunnels. Namely, an interest was given to the prediction of dispersion of emissions leaving both tunnel and the area touched by the traffic. For the CFD predictions, a method previously developed for moving vehicles was used. The method uses combination of Eulerian and Lagrangian approaches to moving objects and is capable of modeling different speeds and traffic rates of cars as well as traffic-induced turbulence. Influence of several meteorological parameters was studied, namely wind speed and direction and traffic parameters, like traffic rates and speed of cars. The method separates contributions from different sources to the total concentration field, namely from background, tunnel outlet and roadway. Results are presented in the form of horizontal and vertical concentration fields of NO_x.