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  • Articles  (155)
  • uncertainty
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  • 1
    facet.materialart.
    Unknown
    University of Tasmania, School of Government
    In:  http://aquaticcommons.org/id/eprint/3328 | 424 | 2011-09-29 17:36:03 | 3328
    Publication Date: 2021-06-27
    Description: “Why does overfishing persist in the face of regulation?” The author argues that over fishing,a fundamental cause of the crisis facing our oceans, is the result of the failure of our fishing management agencies (ultimately our politicians and communities) to embrace a small suite of powerful tools (more correctly strategic approaches) which have been developed to account for uncertainty.Broad success in managing fisheries to achieve sustainability goals will only come if these tools are enthusiastically applied. This will not happen until organisational cultures within fishery management agencies undergo a major shift leading to an asset-based biodiversity conservation, rather than resource exploitation, to be placed at the centre of ocean governance.This thesis examines these issues in the context of case studies covering regional, national and provincial (State) fishery management agencies. With the exception of the case study of a regional fishery (the southern ocean krill fishery) all case studies are drawn from Australianexperiences. The central recommendation of the thesis is that fishery management agencies, worldwide, should be replaced by biodiversity asset management agencies.
    Description: PhD
    Keywords: Fisheries ; Australia ; ocean governance ; overfishing ; uncertainty ; precautionary principle ; precautionary approach ; ecosystem approach ; adaptive management ; krill ; orange roughy ; northern prawns ; western rock lobster ; abalone ; spearfishing
    Repository Name: AquaDocs
    Type: thesis
    Format: application/pdf
    Format: application/pdf
    Format: 440
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  • 2
    Publication Date: 2020-11-12
    Description: Earthquake hypocentral location is perhaps the most classical problem in seismology, the solution of which is often affected by significant uncertainty. In monitoring the effects of underground anthropogenic activities, the earthquake hypocentral location, magnitude, and ground motions are important parameters for managing induced seismicity (as e.g., for operating traffic‐light systems). Such decisional systems define the operative reactions to be enacted once an earthquake, exceeding some magnitude or ground‐motion threshold, occurs within a monitoring volume defined in the neighborhood of a certain anthropogenic underground activity. In this case, a reliable evaluation of the hypocentral location, along with its uncertainty, becomes crucial for rational decision making. In this article, we analyze different sources of uncertainty that can be relevant for the determination of earthquake source locations, and introduce a logic‐tree‐based ensemble modeling approach for framing the problem in a decision‐making context. To demonstrate the performance of the proposed approach, we analyze uncertainties in the location of a seismic event that occurred on 22 July 2019 within the perimeter of the monitoring domain defined in the Val d’Agri oil field (southern Italy). We cast the result as a model ensemble that allows us to obtain samples from a parent distribution that better represents both aleatory and epistemic uncertainties of the earthquake location problem. We find that often‐neglected epistemic uncertainties (i.e., those that arise when considering alternative plausible modeling approaches or data) can be considerably larger and more representative of the state of knowledge about the source location, than the standard errors usually reported by the most common algorithms. Given the consequential repercussions of decision making under uncertainty, we stress that an objective evaluation of epistemic uncertainties associated with any parameter used to support decisional processes must be a priority for the scientific community.
    Description: Centro per il Monitoraggio delle attività di Sottosuolo (CMS).
    Description: Published
    Description: 2423–2440
    Description: 3SR TERREMOTI - Attività dei Centri
    Description: JCR Journal
    Keywords: Earthquake location ; uncertainty ; Traffic light systems ; Decision making ; 04.06. Seismology
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 3
    Publication Date: 2017-04-04
    Description: Accurate detection of time gravity changes attributable to the dynamics of volcanoes requires high-precision gravity measurements. With the aim of improving the quality of data from the Mount Etna gravity network, we used both absolute and relative gravimeters in a hybrid method. In this report, some of the techniques for gravity surveys are reviewed, and the results related to each method are compared. We show how the total uncertainty estimated for the gravity measurements performed with this combined use of absolute and relative gravimeters is roughly comparable to that calculated when the measurements are acquired using only relative gravimeters (the traditional method). However, the data highlight how the hybrid approach improves the measurement capabilities for surveying the Mount Etna volcanic area. This approach enhances the accuracy of the data, and then of the four-dimensional surveying, which minimizes ambiguities inherent in the gravity measurements. As a case study, we refer to two gravity datasets acquired in 2005 and 2010 from the western part of the Etna volcano, which included five absolute and 13 relative stations of the Etna gravity network.
    Description: Published
    Description: 500-509
    Description: 2.6. TTC - Laboratorio di gravimetria, magnetismo ed elettromagnetismo in aree attive
    Description: JCR Journal
    Description: open
    Keywords: absolute and relative gravimeters ; uncertainty ; microgravity ; Etna volcano ; 04. Solid Earth::04.02. Exploration geophysics::04.02.02. Gravity methods
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 4
    Publication Date: 2017-04-04
    Description: Three independent techniques (Bakun and Wentworth, 1997; Boxer from Gasperini et al., 1999; and Macroseismic Estimation of Earthquake Parameters [MEEP; see Data and Resources section, deliverable D3] from R.M.W. Musson and M.J. Jimenez) have been proposed for estimating an earthquake location and magnitude from intensity data alone. The locations and magnitudes obtained for a given set of intensity data are almost always different, and no one technique is consistently best at matching instrumental locations and magnitudes of recent well-recorded earthquakes in Italy. Rather than attempting to select one of the three solutions as best, we use all three techniques to estimate the location and the magnitude and the epistemic uncertainties among them. The estimates are calculated using bootstrap resampled data sets with Monte Carlo sampling of a decision tree. The decision-tree branch weights are based on goodness-of-fit measures of location and magnitude for recent earthquakes. The location estimates are based on the spatial distribution of locations calculated from the bootstrap resampled data. The preferred source location is the locus of the maximum bootstrap location spatial density. The location uncertainty is obtained from contours of the bootstrap spatial density: 68% of the bootstrap locations are within the 68% confidence region, and so on. For large earthquakes, our preferred location is not associated with the epicenter but with a location on the extended rupture surface. For small earthquakes, the epicenters are generally consistent with the location uncertainties inferred from the intensity data if an epicenter inaccuracy of 2–3 km is allowed. The preferred magnitude is the median of the distribution of bootstrap magnitudes. As with location uncertainties, the uncertainties in magnitude are obtained from the distribution of bootstrap magnitudes: the bounds of the 68% uncertainty range enclose 68% of the bootstrap magnitudes, and so on. The instrumental magnitudes for large and small earthquakes are generally consistent with the confidence intervals inferred from the distribution of bootstrap resampled magnitudes.
    Description: Published
    Description: 2712-2725
    Description: 5.1. TTC - Banche dati e metodi macrosismici
    Description: JCR Journal
    Description: reserved
    Keywords: macroseismic data ; uncertainty ; earthquake parameters ; macroseismic magnitude ; macroseismic location ; bootstrap ; 04. Solid Earth::04.06. Seismology::04.06.99. General or miscellaneous
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 5
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    American Geophysical Union
    Publication Date: 2017-04-04
    Description: 28th IUGG Conference on Mathematical Geophysics; Pisa, Italy, 7–11 June 2010; The capabilities and limits of mathematical models applied to a variety of geophysical processes were discussed during the 28th international Conference on Mathematical Geophysics, held in Italy (see the conference Web site (http://cmg2010.pi.ingv.it), which includes abstracts). The conference was organized by the International Union of Geodesy and Geophysics (IUGG) Commission on Mathematical Geophysics (CMG) and the Istituto Nazionale di Geofisica e Vulcanologia and was cosponsored by the U.S. National Science Foundation. The meeting was attended by more than 160 researchers from 26 countries and was dedicated to the theme “Modelling Earth Dynamics: Complexity, Uncertainty, and Validation.” Many talks were dedicated to illustration of the complexities affecting geophysical processes. Novel applications of geophysical fluid dynamics were presented, with specific reference to volcanological and ­subsurface/surface flow processes. In most cases, investigations highlighted the need for multidimensional and multiphase flow models able to describe the nonlinear effects associated with the nonhomogeneous nature of the matter. Fluid dynamic models of atmospheric, oceanic, and environmental systems also illustrated the fundamental role of nonlinear couplings between the different subsystems. Similarly, solid Earth models have made it possible to obtain the first tomographies of the planet; to formulate nonlocal and dynamic damage models of rocks; to investigate statistically the triggering, clustering, and synchronization of faults; and to develop realistic simulators of the planetary dynamo, plate tectonics, and gravity and magnetic fields.
    Description: Published
    Description: 506
    Description: 3.6. Fisica del vulcanismo
    Description: N/A or not JCR
    Description: reserved
    Keywords: mathematical models ; geophysics ; uncertainty ; validation ; 05. General::05.01. Computational geophysics::05.01.99. General or miscellaneous ; 05. General::05.05. Mathematical geophysics::05.05.99. General or miscellaneous
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 6
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    Journal of intelligent and robotic systems 29 (2000), S. 161-189 
    ISSN: 1573-0409
    Keywords: decision making ; entropy ; Markov chains ; multisensor fusion ; uncertainty
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract This paper proposes an entropy based Markov chain (EMC) fusion technique and demonstrates its applications in multisensor fusion. Self-entropy and conditional entropy, which measure how uncertain a sensor is about its own observation and joint observations respectively, are adopted. We use Markov chain as an observation combination process because of two major reasons: (a) the consensus output is a linear combination of the weighted local observations; and (b) the weight is the transition probability assigned by one sensor to another sensor. Experimental results show that the proposed approach can reduce the measurement uncertainty by aggregating multiple observations. The major benefits of this approach are: (a) single observation distributions and joint observation distributions between any two sensors are represented in polynomial form; (b) the consensus output is the linear combination of the weighted observations; and (c) the approach suppresses noisy and unreliable observations in the combination process.
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  • 7
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    Transportation 27 (2000), S. 201-219 
    ISSN: 1572-9435
    Keywords: benefit-cost analysis ; investment timing ; major transportation investments ; net present value ; timing rules ; uncertainty
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying
    Notes: Abstract The timing decision for major transportation investments – when to build – typically is made without an objective approach for considering the economic value of implementation at different times. This paper uses a model of benefit-cost analysis and derives rules for timing major transportation investments. Three sets of conditions are considered, depending on whether annual benefits of an investment are uncertain and whether the objective is to maximize net present value or simply to achieve positive net present value. The timing rules under each set of conditions are stated in three forms: benefit-cost ratio, annual benefits, and implementation time. The paper compares these timing rules analytically, discusses potential applications, and illustrates them with a numerical example. Consequences of incorrectly using the timing rules are also examined with the example.
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  • 8
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    Autonomous robots 9 (2000), S. 261-270 
    ISSN: 1573-7527
    Keywords: mobile robot ; underwater environment ; sonar system ; state estimation ; uncertainty
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Cleaning is a major problem associated with pools. Since the manual cleaning is tedious and boring there is an interest in automating the task. This paper presents methods for autonomous localization and navigation for a pool cleaner to enable full coverage of pools. Path following cannot be ensured through use of internal position estimation methods alone; therefore sensing is needed. Sensor based estimation enable automatic correction of slippage. For this application we use ultrasonic sonars. Based on an analysis of the overall task and performance of the system a strategy for cleaning/navigation is developed. For the automatic localization a Kalman filtering technique is proposed: the Kalman filter uses sonar measurements and a dynamic model of the robot to provide estimates of the pose of the pool cleaner. Using this localization method we derive an optimal control strategy for traversal of a pool. The system has been implemented and successfully tested on the “WEDAB400” pool cleaner.
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  • 9
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    Information retrieval 2 (2000), S. 17-26 
    ISSN: 1573-7659
    Keywords: uncertainty ; information theory ; Bayesian inference ; Ramsey test ; information retrieval model
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract The Logical Uncertainty Principle is re-examined from the point of classical logic. Two interpretations are given, an objective one in terms of an axiomatic theory of information, and a subjective one based on Ramsey's theory of probability.
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  • 10
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    Environmental and resource economics 16 (2000), S. 253-262 
    ISSN: 1573-1502
    Keywords: endogenous future preferences ; stock of the environmental asset ; uncertainty
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Economics
    Notes: Abstract A dynamic optimization model is developed in whichuncertainty about future preferences is endogenous,namely depending on the state of the environment atthe time the change in preferences occurs.Endogeneizing preferences not only provides economicintuition to previous results but also implies thatoptimal policies are less conservative.
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  • 11
    ISSN: 1573-1545
    Keywords: participatory integrated assessment ; methodology ; focus groups ; computer models ; uncertainty
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Integrated assessment (IA) can be defined as a structured process of dealing with complex issues, using knowledge from various scientific disciplines and/or stakeholders, such that integrated insights are made available to decision makers (J. Rotmans, Enviromental Modelling and Assessment 3 (1998) 155). There is a growing recognition that the participation of stakeholders is a vital element of IA. However, only little is known about methodological requirements for such participatory IA and possible insights to be gained from these approaches. This paper summarizes some of the experiences gathered in the ULYSSES project, which aims at developing procedures that are able to bridge the gap between environmental science and democratic policy making for the issue of climate change. The discussion is based on a total of 52 IA focus groups with citizens, run in six European and one US city. In these groups, different computer models were used, ranging from complex and dynamic global models to simple accounting tools. The analysis in this paper focuses on the role of the computer models. The findings suggest that the computer models were successful at conveying to participants the temporal and spatial scale of climate change, the complexity of the system and the uncertainties in our understanding of it. However, most participants felt that the computer models were less instrumental for the exploration of policy options. Furthermore, both research teams and participants agreed that despite considerable efforts, most models were not sufficiently user-friendly and transparent for being accessed in an IA focus group. With that background, some methodological conclusions are drawn about the inclusion of the computer models in the deliberation process. Furthermore, some suggestions are made about how given models should be adapted and new ones developed in order to be helpful for participatory IA.
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  • 12
    ISSN: 1573-1545
    Keywords: climate change ; technology policy ; uncertainty ; agent-based modeling ; exploratory modeling ; social interactions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Many governments use technology incentives as an important component of their greenhouse gas abatement strategies. These “carrots” are intended to encourage the initial diffusion of new, greenhouse-gas-emissions-reducing technologies, in contrast to carbon taxes and emissions trading which provide a “stick” designed to reduce emissions by increasing the price of high-emitting technologies for all users. Technology incentives appear attractive, but their record in practice is mixed and economic theory suggests that in the absence of market failures, they are inefficient compared to taxes and trading. This study uses an agent-based model of technology diffusion and exploratory modeling, a new technique for decision-making under conditions of extreme uncertainty, to examine the conditions under which technology incentives should be a key building block of robust climate change policies. We find that a combined strategy of carbon taxes and technology incentives, as opposed to carbon taxes alone, is the best approach to greenhouse gas emissions reductions if the social benefits of early adoption sufficiently exceed the private benefits. Such social benefits can occur when economic actors have a wide variety of cost/performance preferences for new technologies and either new technologies have increasing returns to scale or potential adopters can reduce their uncertainty about the performance of new technologies by querying the experience of other adopters. We find that if decision-makers hold even modest expectations that such social benefits are significant or that the impacts of climate change will turn out to be serious then technology incentive programs may be a promising hedge against the threat of climate change.
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  • 13
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    Precision agriculture 2 (2000), S. 39-54 
    ISSN: 1573-1618
    Keywords: model selection ; uncertainty ; decision-making
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Models which enable the representation of spatially variable crop performance are central to site-specific management. Rarely have these models been considered in relation to the different sources of uncertainty facing the decision maker. This paper describes various sources of uncertainty (temporal, metrical, structural, and translational) in the context of the site-specific management problem and the model types proposed to solve the problem. An example involving the site specific application of nitrogen fertilizer in dryland wheat production is presented to show how these model types might be evaluated for suitability to a given situation. We conclude that in data poor situations, knowledge-driven models may be less accurate but preferred by the farmer, while in data rich situations data-driven models may be more appropriate.
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  • 14
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    Water resources management 14 (2000), S. 89-109 
    ISSN: 1573-1650
    Keywords: decision making ; fuzzy rules ; reservoir operation ; uncertainty
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Notes: Abstract In this article, a fuzzy rule based model is developed for the operation of a single purpose reservoir. The model operates on an 'if – then' principle, where the 'if' is a vector of fuzzy premises and the 'then' is a vector of fuzzy consequences. The steps involved in the development of the model include, construction of membership functions for the inflow, storage, demand and the release, formulation of fuzzyrules, implication and defuzzification. The methodology is illustrated through the case study of the Malaprabha irrigation reservoir in Karnataka, India. Reservoir storage, inflow, and demands are used as premises and the release as the consequence.Simulated reservoir operation with a steady state policy provides the knowledge base necessary for the formulation of the Fuzzy rules.
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  • 15
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    Autonomous robots 8 (2000), S. 325-344 
    ISSN: 1573-7527
    Keywords: mobile robots ; localization ; multi-robot systems ; uncertainty
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract This paper presents a statistical algorithm for collaborative mobile robot localization. Our approach uses a sample-based version of Markov localization, capable of localizing mobile robots in an any-time fashion. When teams of robots localize themselves in the same environment, probabilistic methods are employed to synchronize each robot's belief whenever one robot detects another. As a result, the robots localize themselves faster, maintain higher accuracy, and high-cost sensors are amortized across multiple robot platforms. The technique has been implemented and tested using two mobile robots equipped with cameras and laser range-finders for detecting other robots. The results, obtained with the real robots and in series of simulation runs, illustrate drastic improvements in localization speed and accuracy when compared to conventional single-robot localization. A further experiment demonstrates that under certain conditions, successful localization is only possible if teams of heterogeneous robots collaborate during localization.
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  • 16
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    Geoinformatica 4 (2000), S. 201-213 
    ISSN: 1573-7624
    Keywords: location referencing ; street networks ; spatial data accuracy ; uncertainty ; error ; datums ; LRMS ; rubber sheeting
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geography
    Notes: Abstract One of the impediments to the implementation of ITS is the lack of map database interoperability. Centreline databases are available from a number of sources, but few were designed specifically for ITS. Consequently there are a variety of problems—coordinate inaccuracy, errors of omission and commission, missing or wrong street names, incorrect topology—that are compounded when communicating parties use databases from different vendors. Many ITS applications (e.g., emergency response, ATIS) rely on the exchange of messages in which location is a component. Map error and interoperability problems can result in a variety of practical difficulties, from inappropriate vehicle routing to delays in delivery of critical services. These problems can be addressed by (a) standards for map databases, (b) intelligent messaging, (c) national integration efforts to improve database quality in the long term. This paper examines the dimensions of the problem, and describes solutions currently under development.
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  • 17
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    Spatial cognition and computation 2 (2000), S. 51-76 
    ISSN: 1542-7633
    Keywords: connectionist learning ; fine motion ; qualitative spatial reasoning ; robotics ; uncertainty
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Psychology
    Notes: Abstract Qualitative spatial reasoning foractual robots in real-world environments mustnecessarily involve perceptive knowledge, sincecomplete a-priori information of the outerworld can never be assumed, not even at aqualitative level. In this paper a contributionis made towards the integration of quantitativedata – namely, sensor signals – into a higherlevel qualitative plan. This integrationincludes the use of neural networks to learnhow to map complex perceptual signals into aqualitative description. Sensors are used toacquire actual knowledge of the environment andproperly identify, with the help of aconnectionist system, the real state of thesystem. The approach is presented in theframework of robotic tasks involving contactfor which the most informative perception comesfrom force/torque sensors. Empirical simulationresults are provided for the chamferlesstwo-dimensional peg-in-hole insertion modelwith friction. The advantages of learningapproaches over geometric model-basedtechniques are discussed: our approach issimple but robust against unpredictable changesof task parameters, and it exhibits agracefully degrading behavior and on-lineadaptation to new task conditions. Anenhancement to incorporate a measure ofconfidence of the network is also presented.
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  • 18
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    Biology and philosophy 15 (2000), S. 493-508 
    ISSN: 1572-8404
    Keywords: complexity ; entropy balance ; environment independence ; evolution ; information fundamental identity ; uncertainty
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Philosophy
    Notes: Abstract Some real objects show a very particular tendency: that of becomingindependent with regard to the uncertainty of their surroundings. This isachieved by the exchange of three quantities: matter, energy andinformation. A conceptual framework, based on both Non-equilibriumThermodynamic and the Mathematical Theory of Communication is proposedin order to review the concept of change in living individuals. Three mainsituations are discussed in this context: passive independence inconnection with resistant living forms (such as seeds, spores, hibernation,...), active independence in connection with the life span of aliving individual (whether an ant or an ant farm), and the newindependence in connection with the general debate of biological evolution.
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  • 19
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    Risk analysis 19 (1999), S. 585-598 
    ISSN: 1539-6924
    Keywords: uncertainty ; threatened plants ; risk ; conservation ; rule sets ; IUCN
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Australian state and federal agencies use a broad range of methods for setting conservation priorities for species at risk. Some of these are based on rule sets developed by the International Union for the Conservation of Nature, while others use point scoring protocols to assess threat. All of them ignore uncertainty in the data. In this study, we assessed the conservation status of 29 threatened vascular plants from Tasmania and New South Wales using a variety of methods including point scoring and rule-based approaches. In addition, several methods for dealing with uncertainty in the data were applied to each of the priority-setting schemes. The results indicate that the choice of a protocol for setting priorities and the choice of the way in which uncertainty is treated may make important differences to the resulting assessments of risk. The choice among methods needs to be rationalized within the management context in which it is to be applied. These methods are not a substitute for more formal risk assessment.
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  • 20
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    Risk analysis 19 (1999), S. 995-1002 
    ISSN: 1539-6924
    Keywords: conditional ; uncertainty ; probability ; intervals ; risk analysis ; conservatism ; Waste Isolation Pilot Plant
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Uncertainty analyses and the reporting of their results can be misinterpreted when these analyses are conditional on a set of assumptions generally intended to bring some conservatism in the decisions. In this paper, two cases of conditional uncertainty analysis are examined. The first case includes studies that result, for instance, in a family of risk curves representing percentiles of the probability distribution of the future frequency of exceeding specified consequence levels conditional on a set of hypotheses. The second case involves analyses that result in an interval of outcomes estimated on the basis of conservative assumptions. Both types of results are difficult to use because they are sometimes misinterpreted as if they represented the output of a full uncertainty analysis. In the first case, the percentiles shown on each risk curve may be taken at face value when in reality (in marginal terms) they are lower if the chosen hypotheses are conservative. In the second case, the fact that some segments of the resulting interval are highly unlikely—or that some more benign segments outside the range of results are quite possible—does not appear. Also, these results are difficult to compare to those of analyses of other risks, possibly competing for the same risk management resources, and the decision criteria have to be adapted to the conservatism of the hypotheses. In this paper, the focus is on the first type (conditional risk curves) more than on the second and the discussion is illustrated by the case of the performance assessment of the Waste Isolation Pilot Plant in New Mexico. For policy-making purposes, however, the problems of interpretation, comparison, and use of the results are similar.
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  • 21
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    Risk analysis 19 (1999), S. 135-152 
    ISSN: 1539-6924
    Keywords: Probability ; uncertainty ; data ; risk assessment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Risk assessors attempting to use probabilistic approaches to describe uncertainty often find themselves in a data-sparse situation: available data are only partially relevant to the parameter of interest, so one needs to adjust empirical distributions, use explicit judgmental distributions, or collect new data. In determining whether or not to collect additional data, whether by measurement or by elicitation of experts, it is useful to consider the expected value of the additional information. The expected value of information depends on the prior distribution used to represent current information; if the prior distribution is too narrow, in many risk-analytic cases the calculated expected value of information will be biased downward. The well-documented tendency toward overconfidence, including the neglect of potential surprise, suggests this bias may be substantial. We examine the expected value of information, including the role of surprise, test for bias in estimating the expected value of information, and suggest procedures to guard against overconfidence and underestimation of the expected value of information when developing prior distributions and when combining distributions obtained from multiple experts. The methods are illustrated with applications to potential carcinogens in food, commercial energy demand, and global climate change.
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  • 22
    ISSN: 1539-6924
    Keywords: Variability ; uncertainty ; maximum likelihood ; bootstrap simulation ; Monte Carlo simulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Variability arises due to differences in the value of a quantity among different members of a population. Uncertainty arises due to lack of knowledge regarding the true value of a quantity for a given member of a population. We describe and evaluate two methods for quantifying both variability and uncertainty. These methods, bootstrap simulation and a likelihood-based method, are applied to three datasets. The datasets include a synthetic sample of 19 values from a Lognormal distribution, a sample of nine values obtained from measurements of the PCB concentration in leafy produce, and a sample of five values for the partitioning of chromium in the flue gas desulfurization system of coal-fired power plants. For each of these datasets, we employ the two methods to characterize uncertainty in the arithmetic mean and standard deviation, cumulative distribution functions based upon fitted parametric distributions, the 95th percentile of variability, and the 63rd percentile of uncertainty for the 81st percentile of variability. The latter is intended to show that it is possible to describe any point within the uncertain frequency distribution by specifying an uncertainty percentile and a variability percentile. Using the bootstrap method, we compare results based upon use of the method of matching moments and the method of maximum likelihood for fitting distributions to data. Our results indicate that with only 5–19 data points as in the datasets we have evaluated, there is substantial uncertainty based upon random sampling error. Both the boostrap and likelihood-based approaches yield comparable uncertainty estimates in most cases.
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  • 23
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    Risk analysis 19 (1999), S. 1193-1204 
    ISSN: 1539-6924
    Keywords: multimedia modeling ; uncertainty ; variability ; exposure efficiency ; toxicity scoring ; toxics release inventory (TRI) ; life cycle assessment (LCA)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract The human toxicity potential, a weighting scheme used to evaluate toxic emissions for life cycle assessment and toxics release inventories, is based on potential dose calculations and toxicity factors. This paper evaluates the variance in potential dose calculations that can be attributed to the uncertainty in chemical-specific input parameters as well as the variability in exposure factors and landscape parameters. A knowledge of the uncertainty allows us to assess the robustness of a decision based on the toxicity potential; a knowledge of the sources of uncertainty allows us to focus our resources if we want to reduce the uncertainty. The potential dose of 236 chemicals was assessed. The chemicals were grouped by dominant exposure route, and a Monte Carlo analysis was conducted for one representative chemical in each group. The variance is typically one to two orders of magnitude. For comparison, the point estimates in potential dose for 236 chemicals span ten orders of magnitude. Most of the variance in the potential dose is due to chemical-specific input parameters, especially half-lives, although exposure factors such as fish intake and the source of drinking water can be important for chemicals whose dominant exposure is through indirect routes. Landscape characteristics are generally of minor importance.
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    ISSN: 1539-6924
    Keywords: risk assessment ; uncertainty ; formaldehyde ; decision analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract A call for risk assessment approaches that better characterize and quantify uncertainty has been made by the scientific and regulatory community. This paper responds to that call by demonstrating a distributional approach that draws upon human data to derive potency estimates and to identify and quantify important sources of uncertainty. The approach is rooted in the science of decision analysis and employs an influence diagram, a decision tree, probabilistic weights, and a distribution of point estimates of carcinogenic potency. Its results estimate the likelihood of different carcinogenic risks (potencies) for a chemical under a specific scenario. For this exercise, human data on formaldehyde were employed to demonstrate the approach. Sensitivity analyses were performed to determine the relative impact of specific levels and alternatives on the potency distribution. The resulting potency estimates are compared with the results of an exercise using animal data on formaldehyde. The paper demonstrates that distributional risk assessment is readily adapted to situations in which epidemiologic data serve as the basis for potency estimates. Strengths and weaknesses of the distributional approach are discussed. Areas for further application and research are recommended.
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  • 25
    ISSN: 1539-6924
    Keywords: compliance certification application ; engineering analysis ; geochemistry ; geohydrology ; performance assessment ; probabilistic systems analysis ; radioactive waste ; scientific validity ; uncertainty ; 40 CFR 191
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Performance Assessment (PA) is the use of mathematical models to simulate the long-term behavior of engineered and geologic barriers in a nuclear waste repository; methods of uncertainty analysis are used to assess effects of parametric and conceptual uncertainties associated with the model system upon the uncertainty in outcomes of the simulation. PA is required by the U.S. Environmental Protection Agency as part of its certification process for geologic repositories for nuclear waste. This paper is a dialogue to explore the value and limitations of PA. Two “skeptics” acknowledge the utility of PA in organizing the scientific investigations that are necessary for confident siting and licensing of a repository; however, they maintain that the PA process, at least as it is currently implemented, is an essentially unscientific process with shortcomings that may provide results of limited use in evaluating actual effects on public health and safety. Conceptual uncertainties in a PA analysis can be so great that results can be confidently applied only over short time ranges, the antithesis of the purpose behind long-term, geologic disposal. Two “proponents” of PA agree that performance assessment is unscientific, but only in the sense that PA is an engineering analysis that uses existing scientific knowledge to support public policy decisions, rather than an investigation intended to increase fundamental knowledge of nature; PA has different goals and constraints than a typical scientific study. The “proponents” describe an ideal, six-step process for conducting generalized PA, here called probabilistic systems analysis (PSA); they note that virtually all scientific content of a PA is introduced during the model-building steps of a PSA; they contend that a PA based on simple but scientifically acceptable mathematical models can provide useful and objective input to regulatory decision makers. The value of the results of any PA must lie between these two views and will depend on the level of knowledge of the site, the degree to which models capture actual physical and chemical processes, the time over which extrapolations are made, and the proper evaluation of health risks attending implementation of the repository. The challenge is in evaluating whether the quality of the PA matches the needs of decision makers charged with protecting the health and safety of the public.
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    Journal of risk and uncertainty 18 (1999), S. 165-188 
    ISSN: 1573-0476
    Keywords: moral hazard ; unemployment insurance ; workers' compensation ; risk ; uncertainty
    Source: Springer Online Journal Archives 1860-2000
    Topics: Economics
    Notes: Abstract This paper examines how the Workers' Compensation (WC) and Unemployment Insurance (UI) programs interact to influence the duration of claims due to workplace accidents. We use longitudinal WC administrative micro-data on more than 30,000 workers in the Canadian construction industry for the period 1976–1986. For the estimations, we use the Meyer (1990) semi-parametric proportional hazard model. Our results show, in particular, that a reduction in the UI replacement ratio is associated with an increase in the duration of claims due to severe accidents that are difficult to diagnose. Moreover, the duration of spells on WC is much higher when an accident occurs in December, a month which corresponds to the beginning of the lay-off season in the construction sector. This result is consistent with the fact that WC benefits are more generous than UI benefits in Canada.
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    Quantitative microbiology 1 (1999), S. 63-88 
    ISSN: 1572-9923
    Keywords: binomial fractions ; microbial counts ; variability ; uncertainty
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In microbiological studies various methods are employed to estimate fractions from paired counts of organisms. When the fraction (second count divided by first count) is constant among the paired counts, the maximum likelihood estimate is the ratio of the arithmetic means. In many practical applications this fraction may however not be constant, but vary substantially between pairs of counts. We discuss a statistical method that estimates the distribution of the fraction from pairs of counts, to allow for this variation. Four real data sets (concerning viability for growth and infection, recovery of a detection method, and removal in a treatment process) are analyzed by this method. Often, pairs of counts are not determined in the same physical sample, but the first count is made in one sample, and the second count in a second sample. We provide parametric models to deal with such a situation: the desired fraction is still estimated as a binomial probability, but the model includes sampling effects. This approach also allows for analysis of two distinct cases: paired observations, where the counts “before” and “after” are related in some way to each other, and unpaired observations, where they are not. The four models for separate samples: paired or unpaired observations, and binomial probability fixed or variable, are used to analyze the removal data. It is concluded that this approach of statistical analysis of fractions is more appropriate than often used calculations based on the ratio between the (geometric) means “before” and “after”. The implications for risk analysis are briefly discussed.
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    Agroforestry systems 45 (1999), S. 395-411 
    ISSN: 1572-9680
    Keywords: adoption of innovations ; sustainability ; uncertainty
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The fundamental challenge in developing a new farming system is to have it adopted and maintained by farmers. The difficulty of achieving widespread adoption is increased if the new farming system is complex and/or radically different to current farming practice. This paper is a review of these issues with a focus on farming systems based on mimicry of natural ecosystems. It is proposed that there are four conditions which are necessary for an individual farmer to adopt an innovative farming-system: awareness of the innovation, perception that it is feasible to trial the innovation, perception that the innovation is worth trialing, and perception that the innovation promotes the farmer's objectives. Challenges involved in meeting each of these conditions are discussed. It is concluded that the most important challenges in developed countries are: (a) developing a farming system that is in fact more profitable than current practice; (b) assessing whether a system is in fact more profitable than current practice; and (c) overcoming the problem of deep uncertainty about the technology. In developing countries one must add the additional challenges of (d) high interest rates/high discount rates; and (e) insecure or inequitable land tenure.
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    Journal of intelligent and robotic systems 26 (1999), S. 1-27 
    ISSN: 1573-0409
    Keywords: nonholonomic systems ; stabilization ; uncertainty ; adaptive control ; robotic systems ; homogeneous feedback ; Lyapunov methods
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract This paper considers the problem of stabilizing nonholonomic robotic systems in the presence of uncertainty regarding the system dynamic model. It is proposed that a simple and effective solution to this problem can be obtained by combining ideas from homogeneous system theory and adaptive control theory. Thus each of the proposed control systems consists of two subsystems: a (homogeneous) kinematic stabilization strategy which generates a desired velocity trajectory for the nonholonomic system, and an adaptive control scheme which ensures that this velocity trajectory is accurately tracked. This approach is shown to provide arbitrarily accurate stabilization to any desired configuration and can be implemented without knowledge of the system dynamic model. Moreover, it is demonstrated that exponential rates of convergence can be achieved with this methodology. The efficacy of the proposed stabilization strategies is illustrated through extensive computer simulations with nonholonomic robotic systems arising from explicit constraints on the system kinematics and from symmetries of the system dynamics.
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    International journal of flexible manufacturing systems 11 (1999), S. 371-377 
    ISSN: 1572-9370
    Keywords: inventory production ; multi-item ; uncertainty
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    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract A variety of manufacturing processes produce parts that have multiple functionalities or uses, that require different degrees of conformity to standards, and with the degree of conformity of an individual part revealed only after it is produced and inspected. If orders for different product grades need to be met in full but demands are upwardly substitutable, we are faced with a complex multiple-lot-sizing problem. We formulate such a decision model and apply it to some structured numerical examples. The implications of inspections and the computation of their expected costs also are discussed.
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    Autonomous robots 6 (1999), S. 131-146 
    ISSN: 1573-7527
    Keywords: mobile robots ; sensor fusion ; terrain mapping ; obstacle avoidance ; uncertainty
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract A method of analyzing three-dimensional data such as might be produced by stereo vision or a laser range finder in order to plan a path for a vehicle such as a Mars rover is described. In order to produce robust results from data that is sparse and of varying accuracy, the method takes into account the accuracy of each data point, as represented by its covariance matrix. It computes estimates of smoothed and interpolated height, slope, and roughness at equally spaced horizontal intervals, as well as accuracy estimates of these quantities. From this data, a cost function is computed that takes into account both the distance traveled and the probability that each region is traversable. A parallel search algorithm that finds the path of minimum cost also is described. Examples using real data are presented.
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    Review of industrial organization 15 (1999), S. 149-163 
    ISSN: 1573-7160
    Keywords: Firm information ; stochastic frontier estimation ; uncertainty
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    Topics: Economics
    Notes: Abstract The role of firm information about product and financial markets is the subject of considerable research. Typically empirical research measures information through price dispersion. However, the dispersion represents an imperfect measure of information. Several studies utilize stochastic frontier estimation techniques to measure worker information about the labor market. This paper determines whether the frontier information measure can be applied to the measurement of firm information about product markets. Several intuitive hypotheses are tested concerning the relationship between firm characteristics and information investments. The results are consistent with expectations and provide support for using stochastic frontier techniques to measure firm information.
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    Environmental and resource economics 13 (1999), S. 435-458 
    ISSN: 1573-1502
    Keywords: bioeconomics ; multiple stocks ; humane values ; Minke whales ; Monte Carlo analysis ; uncertainty
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    Topics: Energy, Environment Protection, Nuclear Power Engineering , Economics
    Notes: Abstract Most bioeconomic models of efficient renewable resource management are constructed for a single harvesting ground. A bioeconomic model is developed in this paper to study the optimal management of renewable resources that are found in spatially distinct harvesting grounds. The model is applied to Minke whale management. Important inter-regional substitution effects are shown to exist. In addition, comparison with previous studies shows that multiple stock management is necessary for efficient management. Finally, the current Minke whale moratorium is shown to be inefficient unless significant nonmarket values exist.
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    Environmental and resource economics 14 (1999), S. 75-94 
    ISSN: 1573-1502
    Keywords: CGE ; Costa Rica ; environmental indicators ; Monte Carlo ; parameter values ; trade policy ; uncertainty
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    Topics: Energy, Environment Protection, Nuclear Power Engineering , Economics
    Notes: Abstract This study explores the role of parameter uncertainty in CGE modeling of the environmental impacts of macroeconomic and sectoral policies, using Costa Rica as a case for study. A CGE model is constructed which includes eight environmental indicators covering deforestation, pesticides, overfishing, hazardous wastes, inorganic wastes, organic wastes, greenhouse gases, and air pollution. The parameters are treated as random variables drawn from prespecified distributions. Evaluation of each policy option consists of a Monte Carlo experiment. The impacts of the policy options on the environmental indicators are relatively robust to different parameter values, in spite of the wide range of parameter values employed.
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    Mitigation and adaptation strategies for global change 4 (1999), S. 267-281 
    ISSN: 1573-1596
    Keywords: societal adaptation ; globalisation ; institutional capacity ; resilience ; uncertainty ; vulnerability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Geography
    Notes: Abstract Institutions in many wealthy industrialised countries are robust and their societies appear to be relatively well insulated against the impacts of climate variability, economic problems elsewhere and so on. However, many countries are not in this position, and there is a growing group of humanity which is not benefiting from the apparent global adaptive trends. Worst case scenarios reinforce the impact of this uneven distribution of adaptive capacity, both between and within countries. Nevertheless, at the broad global scale human societies are strongly adaptive and not threatened by climate change for many decades. At the local level the picture is quite different and the survival of some populations at their present locations is in doubt. In the absence of abatement, the longer term outlook is highly uncertain. Adaptation research needs to begin with an understanding of social and economic vulnerability. It requires a different approach to the traditional IPCC impacts assessment, as human behaviour, institutional capacity and culture are more important than biophysical impacts. This is consistent with the intellectual history of the IPCC which has gradually embraced an increasing range of disciplines.
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    Mitigation and adaptation strategies for global change 4 (1999), S. 319-329 
    ISSN: 1573-1596
    Keywords: uncertainty ; risk ; adaptation ; extreme events ; (credible) information ; integrated assessment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Geography
    Notes: Abstract This paper draws ten lessons from analyses of adaptation to climate change under conditions of risk and uncertainty: (1) Socio-economic systems will likely respond most to extreme realizations of climate change. (2) Systems have been responding to variations in climate for centuries. (3) Future change will effect future citizens and their institutions. (4) Human systems can be the sources of surprise. (5) Perceptions of risk depend upon welfare valuations that depend upon expectations. (6) Adaptive decisions will be made in response to climate change and climate change policy. (7) Analysis of adaptive decisions should recognize the second-best context of those decisions. (8) Climate change offers opportunity as well as risk. (9) All plausible futures should be explored. (10) Multiple methodological approaches should be accommodated. These lessons support two pieces of advice for the Third Assessment Report: (1) Work toward consensus, but not at the expense of thorough examination and reporting of the "tails" of the distributions of the future. (2) Integrated assessment is only one unifying methodology; others that can better accommodate those tails should be encouraged and embraced.
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    Environmental monitoring and assessment 58 (1999), S. 151-172 
    ISSN: 1573-2959
    Keywords: GIS ; ground water vulnerability ; leaching index ; nitrate ; pesticide ; phosphorus ; potassium ; statistical analysis ; uncertainty
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Statistical methods and a Geographic Information System (GIS) were used to investigate potential indicators of ground water vulnerability to agricultural chemical contamination in a representative area of the Mississippi River alluvial aquifer. A total of 47 wells were sampled for analysis of nitrate, phosphorus, potassium, and 13 pesticides commonly-used in the area. Ten soil and hydrogeologic variables and five ground water vulnerability indices were examined to explain the variations of chemical concentrations. The results showed that no individual soil or hydrogeologic variables or their linear combinations could explain more than 25% of the variation of the chemical concentrations. A quadratic response surface model with the values of confining unit thickness, slope, soil permeability, depth to ground water, and recharge rate accounted for 62% of the variation of nitrate, 43% of P, and 83% of K, suggesting that the interactions among soil and hydrogeologic variables were significant. Observed trends of decreasing nitrate and P concentrations with increasing well depth and/or depth to ground water seemed to correlate with carbonate equilibrium in the aquifer and more reduced environment with depth. In view of uncertainties involved, it was recognized that the limitations associated with input data resolution used in GIS and the formulation of leaching indices limited their use for predicting ground water vulnerability. Misuse of pesticides could be another factor that would complicate the relationships between pesticide concentrations and the vulnerability indices.
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    Environmental modeling and assessment 4 (1999), S. 217-234 
    ISSN: 1573-2967
    Keywords: climate change ; climate policy ; integrated assessment ; inverse modeling ; uncertainty
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract The Tolerable Windows Approach (TWA) to Integrated Assessments (IA) of global warming is based on external normative specifications of tolerable sets of climate impacts as well as proposed emission quotas and policy instruments for implementation. In a subsequent step, the complete set of admissible climate protection strategies which are compatible with these normative inputs is determined by scientific analysis. In doing so, minimum requirements concerning global and national greenhouse gas emission paths can be determined. In this paper we present the basic methodological elements of TWA, discuss its relation to more conventional approaches to IA like cost–benefit analyses, and present some preliminary results obtained by a reduced-form climate model.
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    ISSN: 1573-0956
    Keywords: (AGI) ; heat flow ; lithosphere ; thermal conductivity ; thermal diffusivity ; models ; uncertainty
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Measurements on thermal conductivity and diffusivity as functions of temperature (up to 1150 K) and pressure (up to 1000 MPa) are presented for Archaean and Proterozoic mafic high-grade rocks metamorphosed in middle and lower crustal pressures, and situated in eastern Finland, central Fennoscandian Shield. Decrease of 12–20% in conductivity and 40–55% in diffusivity was recorded between room temperature and 1150 K, which can be considered as typical of phonon conductivity. Radiative heat transfer effects were not detected in these samples. Pressure dependencies of the samples are weak if compared to crystalline rocks in general, but relatively typical for mafic rocks. The temperature and pressure dependencies of thermal transport properties (data from literature and the present study) were applied in an uncertainty analysis of lithospheric conductive thermal modellings with random (Monte Carlo) simulations using a 4-layer model representative of shield lithosphere. Model parameters were varied according to predetermined probability functions and standard deviations were calculated for lithospheric temperature and heat flow density after 1500 independent simulations. The results suggest that the variations (uncertainties) in calculated temperature and heat flow density values due to variations in the temperature and pressure dependencies of conductivity are minor in comparison to the effects produced by typical variations in the room temperature value of conductivity, heat production rate or lower boundary condition values.
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    Water, air & soil pollution 110 (1999), S. 313-333 
    ISSN: 1573-2932
    Keywords: Florida Everglades ; Lake Erie ; mercury ; paleoecology ; sediment cores ; uncertainty
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Increased recognition of the ecological damage of mercury (Hg) has focused attention on quantifying spatial and temporal patterns of Hg deposition. Studies are commonly based on core chronologies and use a combination of techniques to measure parameters such as bulk density, percent solids, Hg concentration, and radionuclide activity. Little attention is generally devoted to the propagated error associated with these measurements. We identified the impact of sources of uncertainty on stratigraphic Hg determinations for Florida Everglades and Lake Erie cores. Large errors may be introduced by converting wet sample Hg content to dry-weight concentrations. Drying of sediments at 55 °C caused Hg losses of 18%. Samples, air-dried at room temperature, retained considerable moisture and required corrections for remaining water content. Frozen sediments did not lose Hg during a 72-day storage. Random error in radionuclide analysis of cores resulted in dating uncertainty of ±1.2 yr in 10 yr old deposits. This error increased to ±20 yr in 100 yr old sediments. Propagation of small errors in each step of the analysis (while adhering to strict QA/QC criteria) produced compounded uncertainties of ±11 and ±29% in Hg concentrations under different analytical rigor, and errors of up to ±73% in Hg accumulation rates in older sediments. Enrichment factors, comparing uncertain recent and historic Hg accumulation rates, differed by as much as ±48%. Uncertainty in paleoecological studies of mercury needs to be documented in order to correctly evaluate trends and remediation efforts.
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    Computational economics 14 (1999), S. 237-253 
    ISSN: 1572-9974
    Keywords: cooperative games ; production ; core ; uncertainty ; stochastic programming ; distribution
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    Topics: Computer Science , Economics
    Notes: Abstract The main objects below are transferable-utility games in which each agent faces an optimization problem, briefly called production planning, constrained by his resource endowment. Coalitions can pool members' resources. Such production games are here extended to accommodate uncertainty about events not known ex ante. Planning then takes the form of two-stage stochastic programming. Core solutions are sought, described, and computed via aggregate dual programs. The analysis is motivated by practical applications. Examples include stochastic production and regional distribution with random demand and supply, illustrated by a numerical example.
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    The Geneva risk and insurance review 23 (1998), S. 151-165 
    ISSN: 1554-9658
    Keywords: environmental management ; uncertainty ; public goods ; voluntary contributions ; precaution ; risk
    Source: Springer Online Journal Archives 1860-2000
    Topics: Economics
    Notes: Abstract This article presents a model in which production causes pollution that diminishes the welfare of its agents. Each agent is concerned with the quality of its environment and may voluntary contribute to improve it by financing depollution technology. The effectiveness of this technology on the quality of the environment is uncertain. We show that if an agent is sufficiently risk averse, voluntary contribution is a decreasing function of the average efficiency of depollution technology. If, on the contrary, the pollution effect is weaker than the substitution effect, the opposite holds. We show that precaution about environmental quality has two possible consequences that depend on agents' risk aversion. Therefore, the implications of a precautionary attitude lead us to consider the agents' risk-aversion characterization, which implies knowledge about prudent attitude.
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    Journal of risk and uncertainty 17 (1998), S. 151-167 
    ISSN: 1573-0476
    Keywords: Pari-mutuel game ; uncertainty ; gambler's fallacy
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    Topics: Economics
    Notes: Abstract This paper investigates biases in the perceptions of probabilities using data from the 1989 and 1994 seasons at the Woodlands greyhound park in Kansas City, Kansas. Results reveal consistent evidence that the gambler's fallacy exists. The results also reveal that gamblers overestimate the probability of a win by the favorite and the dog in the “lucky” seven position. However, the comparison also suggests some learning by bettors between the first season of operation in 1989 and the 1994 season.
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    Journal of population economics 11 (1998), S. 1-20 
    ISSN: 1432-1475
    Keywords: JEL classification: D63 ; D71 ; D81 ; Key words: Population ethics ; uncertainty ; critical levels
    Source: Springer Online Journal Archives 1860-2000
    Topics: Sociology , Economics
    Notes: Abstract This paper analyzes variable-population social-evaluation principles in a framework where outcomes are uncertain. We provide characterizations of expected-utility versions of critical-level generalized utilitarian rules. These principles evaluate lotteries over possible states of the world on the basis of the sum of the expected values of differences between transformed utility levels and a transformed critical level, conditional on the agents‘ being alive in the states under consideration. Equivalently, the critical-level utilitarian value functions applied to weighted individual expected utilities can be employed. Weights are determined by the anonymity axiom.
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    Evolutionary ecology 12 (1998), S. 535-541 
    ISSN: 1573-8477
    Keywords: life histories ; scaling ; uncertainty
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    Topics: Biology
    Notes: Abstract Many life-history parameters have condition-dependent optima, but individuals are often required to set the values of such parameters relatively early in development, before the relevant conditions can be assessed with full accuracy. If cues are available that predict such future conditions, then the condition-dependent parameter should evolve to assume values that deviate from the mean in the direction implied by the cues, but these deviations should regress towards the mean to the degree that the cues are less than fully reliable. Under mild assumptions, the slopes of the resulting relationships between condition-dependent life-history parameters and the variable conditions on which their optima depend will be the ‘ideal’ slopes (those that would maximize fitness if the parameter could be chosen on the basis of full information) devalued by the squared correlation between the condition and the parameter.
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    Environmental and resource economics 11 (1998), S. 635-646 
    ISSN: 1573-1502
    Keywords: damages ; global warming ; irreversibility ; optimal stopping ; timing ; uncertainty
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Economics
    Notes: Abstract Although there is widespread agreement about the dangers of global warming and the resulting need to cut down emissions, there does not seem to be general agreement about the exact form the policy should take or the timing of its adoption. Failure to adopt and implement policies against global warming reflects the complexity of the problem, the uncertainties of climate change and the cost of policy adoption. Issues associated with the interactions between uncertainties and irreversibilities in determining the timing of policy adoption are analyzed by using the methodology of optimal stopping rules. Optimal policy functions are derived for cooperative and noncooperative solutions, with differential game representation. Issues associated with the empirical application of the optimal policy rules are also considered.
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    Environmental and resource economics 11 (1998), S. 177-195 
    ISSN: 1573-1502
    Keywords: uncertainty ; externalities ; Pigouvian taxes ; nuclear power
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    Topics: Energy, Environment Protection, Nuclear Power Engineering , Economics
    Notes: Abstract The external effects arising from the use of nuclear power are, in a fundamental way, related to uncertainty. In this paper we locate these external effects and derive a dynamic Pigouvian tax in order to make the decentralized economy support the command optimum. Another interesting result is that a small constant energy tax (which we interpret as a second best policy) can take the decentralized economy reasonably close to the command optimum.
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    International journal of computer vision 27 (1998), S. 127-159 
    ISSN: 1573-1405
    Keywords: model-based vision ; object recognition ; alignment ; noise ; uncertainty ; error propagation ; linear programming ; perspective ; scaled-orthographic ; bounded error ; Gaussian error
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract Robust recognition systems require a careful understanding of the effects of error in sensed features. In model-based recognition, matches between model features and sensed image features typically are used to compute a model pose and then project the unmatched model features into the image. The error in the image features results in uncertainty in the projected model features. We first show how error propagates when poses are based on three pairs of 3D model and 2D image points. In particular, we show how to simply and efficiently compute the distributed region in the image where an unmatched model point might appear, for both Gaussian and bounded error in the detection of image points, and for both scaled-orthographic and perspective projection models. Next, we provide geometric and experimental analyses to indicate when this linear approximation will succeed and when it will fail. Then, based on the linear approximation, we show how we can utilize Linear Programming to compute bounded propagated error regions for any number of initial matches. Finally, we use these results to extend, from two-dimensional to three-dimensional objects, robust implementations of alignment, interpretation-tree search, and transformation clustering.
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    Water, air & soil pollution 101 (1998), S. 289-308 
    ISSN: 1573-2932
    Keywords: emission factor ; emissions ; inventory ; mercury ; operating rate ; sources ; uncertainty
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Estimates of mercury emissions from individual sources and source categories are needed to understand relationships between the emissions and resulting deposition and to evaluate possible approaches to reducing those emissions. We have developed geographically-resolved estimates of annual average mercury emission rates from current anthropogenic sources in the 48 contiguous United States. These estimates were made by applying emission factors to individual facility operating data and to county-wide source activity levels. We apportioned the emissions to an Eulerian modeling grid system using point source coordinates and the fractions of county areas in each grid cell. Point sources account for about 89% of the 48-state total mercury emissions of 146.4 Mg/yr. Most of the emissions in the inventory are from combustion of mercury-containing fossil fuels and municipal waste, located primarily in the mid-Atlantic and Great Lakes states as well as in the Southeast. The major uncertainties in the emission estimates are caused by uncertainties in the emission factors used to develop the estimates. This uncertainty is likely a result of variability in the mercury content of the combusted materials and in the removal of mercury by air pollution control devices. The greatest research need to reduce uncertainties in mercury emission estimates is additional measurements to improve emission factors.
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    Surveys in geophysics 19 (1998), S. 189-203 
    ISSN: 1573-0956
    Keywords: Historical seismology ; historical earthquakes ; intensity ; macroseismic data ; earthquake parameters ; uncertainty
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The principal aim in studies of historical earthquakes is usually to be able to derive parameters for past earthquakes from macroseismic or other data and thus extend back in time parametric earthquake catalogues, often with improved seismic hazard studies as the ultimate goal. In cases of relatively recent historical earthquakes, for example, those of the 18th and 19th centuries, it is often the case that there is such an abundance of available macroseismic data that estimating earthquake parameters is relatively straightforward. For earlier historical periods, especially medieval and earlier, and also for areas where settlement or documentation are sparse, the situation is much harder. The seismologist often finds that he has only a few data points (or even one) for an earthquake that nevertheless appears to be regionally significant. In such cases, it is natural that the investigator will attempt to make the most of the available data, expanding it by making working assumptions, and from these deriving conclusions by inference (i.e. the process of proceeding logically from some premise). This can be seen in a number of existing studies; in some cases extremely slight data are so magnified by the use of inference that one must regard the results as tentative in the extreme. Two main types of inference can be distinguished. The first type is inference from documentation. This is where assumptions are made such as: “the absence of a report of the earthquake from this monastic chronicle indicates that at this locality the earthquake was not felt”. The second type is inference from seismicity. Here one deals with arguments such as “all recent earthquakes felt at town X are events occurring in seismic zone Y, therefore this ancient earthquake which is only reported at town X probably also occurred in this zone”. While in many cases such assumptions may very well be correct, they are usually not testable – or at least untested. Furthermore, it is possible to produce numerous contrary examples. It is concluded that the use of inference to amplify poor data must be made very transparent to the end user of the results, to avoid misleading appearances of accuracy. In many cases it may be best to abandon the quest for parameters altogether and admit that the data are inadequate.
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    Geoinformatica 2 (1998), S. 257-279 
    ISSN: 1573-7624
    Keywords: uncertainty ; vagueness ; rough set ; fuzzy set ; resolution ; spatial reasoning ; data quality
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geography
    Notes: Abstract An important component of spatial data quality is the imprecision resulting from the resolution at which data are represented. Current research on topics such as spatial data integration and generalization needs to be well-founded on a theory of multi-resolution. This paper provides a formal framework for treating the notion of resolution and multi-resolution in geographic spaces. It goes further to develop an approach to reasoning with imprecision about spatial entities and relationships resulting from finite resolution representations. The approach is similar to aspects of rough and fuzzy set theories. The paper concludes by providing the beginnings of a geometry of vague spatial entities and relationships.
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    Journal of economics 68 (1998), S. 271-293 
    ISSN: 1617-7134
    Keywords: H53 ; D81 ; social-welfare programs ; wage distance ; shadow economy ; uncertainty
    Source: Springer Online Journal Archives 1860-2000
    Topics: Economics
    Notes: Abstract It is often argued that low-skilled workers have an incentive to escape to the unofficial sector if welfare benefits come too close to the net wage in the official sector. Upper limits of welfare benefits often serve as an instrument to ensure a sufficiently high income differnetial between sectors. However, if unofficial-sector income is insecure, and if a change of sectors is costly, an option value of working in the official sector has to be taken into account. This option value reduces the incentive for lowly skilled workers to give up official-sector jobs. Upper limits of welfare benefits might therefore be defined less restrictively.
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    ISSN: 1573-5184
    Keywords: anchovy ; decision rule ; management ; objectives ; sardine ; uncertainty
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The pelagic fishery in South Africa targets mainly anchovy, Engraulis capensis, and sardine, Sardinops sagax, both of which have varied substantially in abundance during the history of the fishery. Since 1988, there has been progress in this fishery towards the use of management procedures as the basis for determination of management regulations, where a management procedure is defined as a set of rules, derived by simulation and normally implemented for three to five years, specifying how the regulatory mechanism is set, the data collected for this purpose and how these data are to be analysed and used. Advantages of management procedures include formal consideration of uncertainty, the ability to choose decision rules based on their predicted medium-term consequences and a saving in workload compared with annual assessments. This paper discusses the lessons learned in application of management procedures and their precursors in this fishery. The high variability in abundance of the two stocks, the trend in their relative abundance, the substantial uncertainties in information, strong pressure to meet socio-economic goals and the conflicting objectives which arose between the directed anchovy and directed sardine fishery are identified as major problems in implementation of procedures and management of the resources. However, the use of management procedures is considered to have led to greatly improved communication with the industry and to substantial input by them into the management process. The procedures and the simulations upon which they were based also enabled consideration of the major sources of uncertainty in understanding of the resource dynamics and facilitated the development of procedures that were robust to them. It is argued that biological uncertainty greatly exacerbated the problems in application of the procedures but probably cannot be markedly reduced in the near future. Management procedures must be robust to likely variability and uncertainty. Of equal importance are identification and selection of achievable objectives, and allocation to the political decision makers and not to the scientists, of responsibility for determining acceptable trade-offs between conservation and socio-economic goals. Other issues, including the importance of long-term rights and allowance for flexibility in fishing practice, are also highlighted
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    Biodiversity and conservation 7 (1998), S. 875-894 
    ISSN: 1572-9710
    Keywords: uncertainty ; population viability analysis ; metapopulation model ; human impact
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We demonstrate the effect of uncertainty (resulting from lack of information or measurement error) on the assessment of human impact, with an analysis of the viability of the northern spotted owl throughout its range in the United States. We developed a spatially-explicit, stage-structured, stochastic metapopulation model of the northern spotted owl throughout its range in the United States. We evaluated the viability of the metapopulation using measures such as risk of decline and time to extinction. We incorporated uncertainty in the form of parameter ranges, and used them to estimate upper and lower bounds on the estimated viability of the species. We analysed the effect of this type of uncertainty on the assessment of human impact by comparing the species' viability under current conditions and under an assumed loss of spotted owl habitat in the next 100 years. The ranges of parameters were quite large and resulted in a wide range of risks of extinction. Despite this uncertainty, the results were sensitive to parameters related to habitat loss: under all assumptions and combinations of parameters, the model predicted that habitat loss results in substantially higher risks of metapopulation decline. This result demonstrated that even with relatively large uncertainties, risk-based model results can be used to assess human impact reliably.
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    Accreditation and quality assurance 2 (1997), S. 186-192 
    ISSN: 1432-0517
    Keywords: Key words Traceability ; Quality ; Measurement ; uncertainty ; Clinical reference ; materials ; Clinical photometric ; system
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract  It is well known that erroneous data reported to a physician may strongly affect medical decision making. For routine clinical chemistry purposes, different instrumentation can be used to compare measurements of unknown samples with standard reference materials. Currently, acceptable limits of accuracy and precision are poorly defined in the field of clinical chemistry laboratories. In this article, problems associated with spectrophotometric measurements, both manual and automated, are discussed. The task of the validation of photometric systems for clinical analyses is currently of considerable interest. Some practical aspects of this validation and the use of reference materials for this activity in the national area are discussed.
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    Journal of intelligent and robotic systems 19 (1997), S. 271-298 
    ISSN: 1573-0409
    Keywords: sensor fusion ; planning ; dynamic system ; robotic system ; uncertainty
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Robot intelligence requires a real-time connection between sensing and action. A new computation principle of robotics that efficiently implements such a connection is utmost important for the new generation of robotics. In this paper, a perception–action network is presented as a means of efficiently integrating sensing, knowledge, and action for sensor fusion and planning. The network consists of a number of heterogeneous computational units, representing feature transformation and decision-making for action, which are interconnected as a dynamic system. New input stimuli to the network invoke the evolution of network states to a new equilibrium, through which a real-time integration of sensing, knowledge, and action can be accomplished. The network provides a formal, yet general and efficient, method of achieving sensor fusion and planning. This is because the uncertainties of signals, propagated in the network, can be controlled by modifying sensing parameters and robot actions. Algorithms for sensor planning based on the proposed network are established and applied to robot self-localization. Simulation and experimental results are shown.
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    Landscape ecology 12 (1997), S. 309-320 
    ISSN: 1572-9761
    Keywords: landscape indexes ; landscape diversity ; accuracy assessment ; uncertainty ; classification error ; error matrixes ; bootstrapping
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Many landscape indexes with ecological relevance have been proposed, including diversity indexes, dominance, fractal dimension, and patch size distribution. Classified land cover data in a geographic information system (GIS) are frequently used to calculate these indexes. However, a lack of methods for quantifying uncertainty in these measures makes it difficult to test hypothesized relations among landscape indexes and ecological processes. One source of uncertainty in landscape indexes is classification error in land cover data, which can be reported in the form of an error matrix. Some researchers have used error matrices to adjust extent estimates derived from classified land cover data. Because landscape diversity indexes depend only on landscape composition – the extent of each cover in a landscape – adjusted extent estimates may be used to calculate diversity indexes. We used a bootstrap procedure to extend this approach and generate confidence intervals for diversity indexes. Bootstrapping is a technique that allows one to estimate sample variability by resampling from the empirical probability distribution defined by a single sample. Using the empirical distribution defined by an error matrix, we generated a bootstrap sample of error matrixes. The sample of error matrixes was used to generate a sample of adjusted diversity indexes from which estimated confidence intervals for the diversity indexes were calculated. We also note that present methods for accuracy assessment are not sufficient for quantifying the uncertainty in landscape indexes that are sensitive to the size, shape, and spatial arrangement of patches. More information about the spatial structure of error is needed to calculate uncertainty for these indexes. Alternative approaches should be considered, including combining traditional accuracy assessments with other probability data generated during the classification procedure.
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    Stochastic environmental research and risk assessment 11 (1997), S. 433-448 
    ISSN: 1436-3259
    Keywords: Risk ; uncertainty ; reservoir operation ; sedimentation ; computer application
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Notes: Abstract An attempt of using stochastic hydrologic technique to assess the intrinsic risk of reservoir operation is made in this study. A stochastic simulation model for reservoir operation is developed. The model consists of three components: synthetic generation model for streamflow and sediment sequences, one-dimensional delta deposit model for sediment transport processes in reservoirs, and simulation model for reservoir operation. This kind of integrated simulation model can be used to simulate not only the inflow uncertainty of streamflow and sedimentation, but also the variation in operation rules of reservoirs. It is herein used for the risk assessment of a reservoir, and the simulation is performed for different operation scenarios. Simulation for the 100-year period of sediment transport and deposition in the river-reservoir system indicates that the navigation risk is much higher than that of hydropower generation or sediment deposition in the reservoir. The risk of sediment deposition at the river-section near the backwater profile is also high thereby the navigation at the river-segment near this profile takes high risk because of inadequate navigation depth.
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    Computational & mathematical organization theory 3 (1997), S. 43-66 
    ISSN: 1572-9346
    Keywords: inter-organizational relations ; adaptive learning ; simulation models ; subcontracting ; organizational learning ; uncertainty ; market
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract A model is designed and used to simulate how partners in a supplyrelationship identify and reach a common target in the form of an ideal endproduct. They cooperate fully and share returns. They learn by interaction,as follows. From their different perspectives, they complement each other'sidentification of the target. They adapt their productive competencies tothe target, in order to conform to demand (quality), and to each other, inorder to achieve efficient complementarity in production (efficiency). Asthey approach the target, their accuracy of identifying the targetincreases. Also, their speed of adaptation increases, and thus they can besaid to be learning by doing. The model allows two different patterns ofacceleration: a routine and a radical type of development. At some distancefrom the target they start to produce. A longer distance from the targetyields earlier returns, but also entails a greater compromise on quality andthereby yields lower returns. Unpredictable changes in market and technologyyield random shifts of the target. In the analysis, the returns from singleand dual sourcing are compared under different parameter settings. Thesimulations show that in line with expectations dual sourcing can be moreadvantageous if development is of the radical type. However, the advantageonly arises if conditions of market and technology are neither too volatilenor too stable.
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    Data mining and knowledge discovery 1 (1997), S. 11-28 
    ISSN: 1573-756X
    Keywords: statistics ; uncertainty ; modeling ; bias ; variance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract Data mining is on the interface of Computer Science andStatistics, utilizing advances in both disciplines to make progressin extracting information from large databases. It is an emergingfield that has attracted much attention in a very short period oftime. This article highlights some statistical themes and lessonsthat are directly relevant to data mining and attempts to identifyopportunities where close cooperation between the statistical andcomputational communities might reasonably provide synergy forfurther progress in data analysis.
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    Environmental and resource economics 9 (1997), S. 103-124 
    ISSN: 1573-1502
    Keywords: climate change ; uncertainty ; irreversibility ; intergenerational ; stochastic dynamic programming ; resource extraction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Economics
    Notes: Abstract A three-generation planning model incorporating uncertain climate change is developed. Each generation features a production activity based on capital and an exhaustible resource. An irreversible climate change may occur in period two or three, reducing the productivity for this and the remaining generation. The model is solved by stochastic dynamic programming. If the climate impact and climate change probability is constant, the optimal period one (and two) resource extraction is larger than for the reference case of climate stability. If, however, climate impact and climate change probability increases with increased aggregate resource use, this result is reversed.
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    Geotechnical and geological engineering 15 (1997), S. 145-180 
    ISSN: 1573-1529
    Keywords: information ; site investigation ; rock engineering ; auditing ; uncertainty
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Although there is general awareness that uncertainty, information and decision making are key elements of site investigation, there has previously been little comprehensive attempt to formalize these factors in the site investigation process. In modern design, rock engineering is considered as a system and it is necessary to establish the key variables and interactions between the variables within the system as a precursor to design. Then, questions concerning (i) the information required to characterize the system, (ii) the uncertainty associated with this information, and (iii) the influence that this has on decision making, naturally arise and need to be addressed. We consider the application of information theory to geotechnical engineering through interpretation of informatic concepts in a rock mechanics context. Examples are then given, concentrating on the ideas of information received in sequential phases of site investigation, the information content of rock-mass classification systems, and the information content of scalar and vector quantities using discontinuity frequency as an example. In the concluding section, there are recommendations for making improvements to site investigation using information theory.
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    Environmental and resource economics 9 (1997), S. 451-466 
    ISSN: 1573-1502
    Keywords: global warming ; uncertainty ; learning ; irreversibility ; value of information ; dynamic games ; international agreements
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Economics
    Notes: Abstract In this paper we construct a simple model of global warming which captures a number of key features of the global warming problem: (i) environmental damages are related to the stock of greenhouse gases in the atmosphere; (ii) the global commons nature of the problem means that these are strategic interactions between the emissions policies of the governments of individual nation states; (iii) there is uncertainty about the extent of the future damages that will be incurred by each country from any given level of concentration of greenhouse gases but there is the possibility that at a future date better information about the true extent of environmental damages may become available; an important aspect of the problem is the extent to which damages in different countries may be correlated. In the first part of the paper we consider a simple model with two symmetric countries and show that the value of perfect information is an increasing function of the correlation between damages in the two countries in both the cooperative and non-cooperative equilibria. However, while the value of perfect information is always non-negative in the cooperative equilibrium, in the non-cooperative equilibrium there is a critical value of the correlation coefficient below which the value of perfect information will be negative. In the second part of the paper we construct an empirical model of global warming distinguishing between OECD and non-OECD countries and show that in the non-cooperative equilibrium the value of perfect information for OECD countries is negative when the correlation coefficient between environmental damages for OECD and non-OECD countries is negative. The implications of these results for international agreements are discussed.
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    Environmental and resource economics 9 (1997), S. 451-466 
    ISSN: 1573-1502
    Keywords: global warming ; uncertainty ; learning ; irreversibility ; value of information ; dynamic games ; international agreements
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Economics
    Notes: Abstract In this paper we construct a simple model of global warming which captures a number of key features of the global warming problem: (i) environmental damages are related to the stock of greenhouse gases in the atmosphere; (ii) the global commons nature of the problem means that these are strategic interactions between the emissions policies of the governments of individual nation states; (iii) there is uncertainty about the extent of the future damages that will be incurred by each country from any given level of concentration of greenhouse gases but there is the possibility that at a future date better information about the true extent of environmental damages may become available; an important aspect of the problem is the extent to which damages in different countries may be correlated. In the first part of the paper we consider a simple model with two symmetric countries and show that the value of perfect information is an increasing function of the correlation between damages in the two countries in both the cooperative and non-cooperative equilibria. However, while the value of perfect information is always non-negative in the cooperative equilibrium, in the non-cooperative equilibrium there is a critical value of the correlation coefficient below which the value of perfect information will be negative. In the second part of the paper we construct an empirical model of global warming distinguishing between OECD and non-OECD countries and show that in the non-cooperative equilibrium the value of perfect information for OECD countries is negative when the correlation coefficient between environmental damages for OECD and non-OECD countries is negative. The implications of these results for international agreements are discussed.
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    Environmental and resource economics 9 (1997), S. 103-124 
    ISSN: 1573-1502
    Keywords: climate change ; uncertainty ; irreversibility ; intergenerational ; stochastic dynamic programming ; resource extraction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Economics
    Notes: Abstract A three-generation planning model incorporating uncertain climate change is developed. Each generation features a production activity based on capital and an exhaustible resource. An irreversible climate change may occur in period two or three, reducing the productivity for this and the remaining generation. The model is solved by stochastic dynamic programming. If the climate impact and climate change probability is constant, the optimal period one (and two) resource extraction is larger than for the reference case of climate stability. If, however, climate impact and climate change probability increases with increased aggregate resource use, this result is reversed.
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    Geotechnical and geological engineering 15 (1997), S. 145-180 
    ISSN: 1573-1529
    Keywords: information ; site investigation ; rock engineering ; auditing ; uncertainty
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Summary Although there is general awareness that uncertainty, information and decision making are key elements of site investigation, there has previously been little comprehensive attempt to formalize these factors in the site investigation process. In modern design, rock engineering is considered as a system and it is necessary to establish the key variables and interactions between the variables within the system as a precursor to design. Then, questions concerning (i) the information required to characterize the system, (ii) the uncertainty associated with this information, and (iii) the influence that this has on decision making, naturally arise and need to be addressed. We consider the application of information theory to geotechnical engineering through interpretation of informatic concepts in a rock mechanics context. Examples are then given, concentrating on the ideas of information received in sequential phases of site investigation, the information content of rock-mass classification systems, and the information content of scalar and vector quantities using discontinuity frequency as an example. In the concluding section, there are recommendations for making improvements to site investigation using information theory.
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    Water resources management 11 (1997), S. 339-363 
    ISSN: 1573-1650
    Keywords: estuary ; calibration ; feedback control ; uncertainty ; point-estimate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Notes: Abstract A comprehensive stochastic management methodology is developed for a distributed-parameter estuary system (DPES) which is described by partial differential equations (PDEs). The proposed stochastic management methodology consists of uncertainty-based calibration (i.e. parameter estimation under uncertainty) and uncertainty-based control (i.e. determination of optimal freshwater inflows into the estuary under uncertainty). The technique for uncertainty-based calibration is based on Gauss–Newton minimization method and uncertainty analysis method such as Rosenblueth's point estimate method or Harr's point estimate method. The uncertainty-based calibration technique is used to estimate the optimal parameters such as Manning's roughness coefficient and dispersion coefficient in the PDEs while considering the uncertainties in the boundary conditions or initial conditions for the PDEs. The technique for uncertainty-based control is based on a real-time control method which is discrete-time stochastic linear quadratic feedback control. Real-time control is achieved by feedback control which uses salinities at test stations in the estuary as the state vector and controlled freshwater inflows as the control vector. The feedback control law determines the real-time control vector using observed states in a manner that best approximates desired states and controls (freshwater inflows). This new methodology for real-time control has been applied to the Lavaca–Tres Palacios Estuary in Texas for purposes of testing and illustration.
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    Biotechnology and Bioengineering 53 (1997), S. 320-331 
    ISSN: 0006-3592
    Keywords: numerical modeling ; uncertainty ; statistics ; cometabolism ; trichloroethylene ; methanotroph ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The rates of methane utilization and trichloroethylene (TCE) cometabolism by a methanotrophic mixed culture were characterized in batch and pseudo-steady-state studies. Procedures for determination of the rate coefficients and their uncertainties by fitting a numerical model to experimental data are described. The model consisted of a system of differential equations for the rates of Monod kinetics, cell growth on methane and inactivation due to TCE transformation product toxicity, gas/liquid mass transfer of methane and TCE, and the rate of passive losses of TCE. The maximum specific rate of methane utilization (kCH4) was determined by fitting the numerical model to batch experimental data, with the initial concentration of active methane-oxidizing cells (X0a) also used as a model fitting parameter. The best estimate of kCH4 was 2.2 g CH4/g cells-d with excess copper available, with a single-parameter 95% confidence interval of 2.0-2.4 mg/mg-d. The joint 95% confidence region for kCH4 and X0a is presented graphically. The half-velocity coefficient (KS,CH4) was 0.07 mg CH4/L with excess copper available and 0.47 mg CH4/L under copper limitation, with 95% confidence intervals of 0.02-0.11 and 0.35-0.59 mg/L, respectively. Unique values of the TCE rate coefficients kTCE and KS,TCE could not be determined because they were found to be highly correlated in the model fitting analysis. However, the ratio kTCE/KS,TCE and the TCE transformation capacity (TC) were well defined, with values of 0.35 L/mg-day and 0.21 g TCE/g active cells, respectively, for cells transforming TCE in the absence of methane or supplemental formate. The single-parameter 95% confidence intervals for kTCE/KS,TCE and TC were 0.27-0.43 L/mg-d and 0.18-0.24 g TCE/g active cells, respectively. The joint 95% confidence regions for kTCE/KS,TCE and TC are presented graphically. © 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 53: 320-331, 1997.
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    Computational economics 10 (1997), S. 89-100 
    ISSN: 1572-9974
    Keywords: input-output models ; uncertainty ; interval arithmetic.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Economics
    Notes: Abstract Input-output models are subject to uncertainty. If these models are solved without regard to the effects of the uncertainty the solutions can be substantially in error. Interval arithmetic offers a means by which the effects of this uncertainty can be assessed. They also offer a means of evaluating changes in the technical coefficients and a means of determining inverse important coefficients.
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    Machine learning 23 (1996), S. 121-161 
    ISSN: 0885-6125
    Keywords: machine learning ; robotics ; uncertainty ; planning
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract In executing classical plans in the real world, small discrepancies between a planner's internal representations and the real world are unavoidable. These can conspire to cause real-world failures even though the planner is sound and, therefore, proves that a sequence of actions achieves the goal. Permissive planning, a machine learning extension to classical planning, is one response to this difficulty. This paper describes the permissive planning approach and presents GRASPER, a permissive planning robotic system that learns to robustly pick up novel objects.
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    Machine learning 23 (1996), S. 121-161 
    ISSN: 0885-6125
    Keywords: machine learning ; robotics ; uncertainty ; planning
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract In executing classical plans in the real world, small discrepancies between a planner's internal representations and the real world are unavoidable. These can conspire to cause real-world failures even though the planner is sound and, therefore, “proves” that a sequence of actions achieves the goal. Permissive planning, a machine learning extension to classical planning, is one response to this difficulty. This paper describes the permissive planning approach and presents GRASPER, a permissive planning robotic system that learns to robustly pick up novel objects.
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    The Geneva risk and insurance review 21 (1996), S. 179-189 
    ISSN: 1554-9658
    Keywords: uncertainty ; investment ; newsboy problem ; increase in risk ; optimal capacity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Economics
    Notes: Abstract In this article we study the effect of uncertainty on an entrepreneur who must choose the capacity of his business before knowing the demand for his product. The unit profit of operation is known with certainty, but there is no flexibility in our one-period framework. We show how the introduction of global uncertainty reduces the investment of the risk-neutral entrepreneur and, even more, that of the risk-averse one. We also show how marginal increases in risk reduce the optimal capacity of both the risk-neutral and the risk-averse entrepreneur, without any restriction on the concave utility function and with limited restrictions on the definition of a mean preserving spread. These general results are explained by the fact that the newsboy has a piecewise-linear, and concave, monetary payoff with a kink endogenously determined at the level of optimal capacity. Our results are compared with those in the two literatures on price uncertainty and demand uncertainty, and particularly, with the recent contributions of Eeckhoudt, Gollier, and Schlesinger [1991, 1995].
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    Journal of intelligent and robotic systems 17 (1996), S. 283-308 
    ISSN: 1573-0409
    Keywords: manufacturing ; motion in contact ; force/torque sensors ; error detection ; plan monitoring ; uncertainty ; robotics ; neural networks
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract This paper presents a new approach to error detection during motion in contact under uncertainty for robotic manufacturing tasks. In this approach, artificial neural networks are used for perception-based learning. The six force-and-torque signals from the wrist sensor of a robot arm are fed into the network. A self-organizing map is what learns the different contact states in an unsupervised way. The method is intended to work properly in complex real-world manufacturing environments, for which existent approaches based on geometric analytical models may not be feasible, or may be too difficult. It is used for different tasks involving motion in contact, particularly the peg-in-hole insertion task, and complex insertion or extraction operations in a flexible manufacturing system. Several real examples for these cases are presented.
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    Journal of risk and uncertainty 13 (1996), S. 53-71 
    ISSN: 1573-0476
    Keywords: risk ; uncertainty ; ambiguity ; self-protection ; self-insurance ; framing ; D81
    Source: Springer Online Journal Archives 1860-2000
    Topics: Economics
    Notes: Abstract We build two experimental markets to examine individual valuations of risk reductions with two risk-management tools: self-insurance and self-protection. We find no positive evidence that the risk-reducing mechanisms constitute a “frame.” Ambiguity in the probability on average affects valuation only weakly, and changes in the representation of ambiguity do not alter valuation. Finally, unlike the results obtained by Hogarth and Kunreuther for the case of market insurance, our findings do not provide a strong support for the “Anchoring and Adjustment” ambiguity model.
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    Journal of risk and uncertainty 13 (1996), S. 5-17 
    ISSN: 1573-0476
    Keywords: risk ; uncertainty ; decision weights ; subadditivity
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    Topics: Economics
    Notes: Abstract Professional options traders priced risky prospects as well as uncertain prospects whose outcomes depended on future values of various stocks. The prices of the risky prospects coincided with their expected value, but the prices of the uncertain prospects violated expected utility theory. An event had greater impact on prices when it turned an impossibility into a possibility or a possibility into a certainty than when it merely made a possibility more or less likely, as predicted by prospect theory. This phenomenon is attributed to the subadditivity of judged probabilities.
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    Journal of intelligent and robotic systems 16 (1996), S. 315-385 
    ISSN: 1573-0409
    Keywords: Robotics ; autonomous observation ; observation ; uncertainty ; discrete event systems ; observers ; vision
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract In this work we establish a framework for the general problem of observation, which may be applied to different kinds of visual tasks. We construct ‘intelligent’ high-level control mechanisms for active visual recognition of different processes within a hybrid dynamic system. We address the problem of observing a manipulation process in order to illustrate the ideas and motive behind our framework. We use a discrete event dynamic system as a high-level structuring technique to model the manipulation system. The formulation utilizes the knowledge about the system and the different actions in order to solve the observer problem in an efficient, stable and practical manner. The model uses different tracking mechanisms so that the observer can ‘see’ the workspace of the manipulating robot. An automaton is developed for the hand/object interaction over time and a stabilizing observer is constructed. Low-level modules are developed for recognizing the visual ‘events’ that causes state transitions within the dynamic manipulation system in real time. A coarse quantization of the manipulation actions is used in order to attain an active, adaptive and goaldirected sensing mechanism. The formulation provides high-level symbolic interpretations of the scene under observation. The discrete event framework is augmented with mechanisms for recovering the continuous parametric evolution of the scene under observation and for asserting the state of the manipulation agent. This work examines closely the possibilities for errors, mistakes and uncertainties in the manipulation system, observer construction process and event identification mechanisms. We identify and suggest techniques for modeling these uncertainties. Ambiguities are allowed to develop and are resolved after finite time. Error recovery mechanisms are also devised. The computed uncertainties are utilized for navigating the observer automaton state space, asserting state transitions and developing a suitable tracking mechanism.
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    Applied intelligence 6 (1996), S. 287-309 
    ISSN: 1573-7497
    Keywords: constraint satisfaction problem ; possibility theory ; fuzzy restriction ; softness ; uncertainty ; preference ; priority
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract In classical Constraint Satisfaction Problems (CSPs) knowledge is embedded in a set of hard constraints, each one restricting the possible values of a set of variables. However constraints in real world problems are seldom hard, and CSP's are often idealizations that do not account for the preference among feasible solutions. Moreover some constraints may have priority over others. Lastly, constraints may involve uncertain parameters. This paper advocates the use of fuzzy sets and possibility theory as a realistic approach for the representation of these three aspects. Fuzzy constraints encompass both preference relations among possible instantiations and priorities among constraints. In a Fuzzy Constraint Satisfaction Problem (FCSP), a constraint is satisfied to a degree (rather than satisfied or not satisfied) and the acceptability of a potential solution becomes a gradual notion. Even if the FCSP is partially inconsistent, best instantiations are provided owing to the relaxation of some constraints. Fuzzy constraints are thus flexible. CSP notions of consistency and k-consistency can be extended to this framework and the classical algorithms used in CSP resolution (e.g., tree search and filtering) can be adapted without losing much of their efficiency. Most classical theoretical results remain applicable to FCSPs. In the paper, various types of constraints are modelled in the same framework. The handling of uncertain parameters is carried out in the same setting because possibility theory can account for both preference and uncertainty. The presence of uncertain parameters leads to ill-defined CSPs, where the set of constraints which defines the problem is not precisely known.
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    Autonomous robots 3 (1996), S. 31-48 
    ISSN: 1573-7527
    Keywords: Real-time sensing and planning ; anytime algorithms ; deliberation scheduling ; meta-level reasoning ; uncertainty
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract This paper is concerned with the implications of limited computational resources and uncertainty on the design of autonomous systems. To address this problem, we redefine the principal role of sensor interpretation and planning processes. Following Agre and Chapman's plan-as-communication approach, sensing and planning are treated as computational processes that provide information to an execution architecture and thus improve the overall performance of the system. We argue that autonomous systems must be able to trade off the quality of this information with the computational resources required to produce it. Anytime algorithms, whose quality of results improves gradually as computation time increases, provide useful performance components for time-critical sensing and planning in robotic systems. In our earlier work, we introduced a compilation scheme for optimal composition of anytime algorithms. This paper demonstrates the applicability of the compilation technique to the construction of autonomous systems. The result is a flexible approach to construct systems that can operate robustly in real-time by exploiting the tradeoff between time and quality in planning, sensing and plan execution.
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    Environmental and resource economics 8 (1996), S. 399-416 
    ISSN: 1573-1502
    Keywords: environmental taxes ; tradable permits ; excess burden ; tax revenues ; uncertainty ; secondbest policy
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    Topics: Energy, Environment Protection, Nuclear Power Engineering , Economics
    Notes: Abstract This paper analyses the optimal choice of second-best optimal environmental policies. Using a partial equilibrium model, the paper first reconfirms the well-known result that the existence of a double dividend (in its weak definition) favours environmental policy instruments which maximise tax revenues for a given improvement in environmental quality. Additional revenues can be used to reduce the distortion of existing taxes such as taxes on labour and capital income. Without uncertainty, environmental taxes and auctioned permits are equally appropriate. In the presence of uncertainty, however, the optimal choice of taxes or tradable permits depends on the relative magnitudes of the marginal environmental damage and the marginal benefit from consuming a polluting good. In the second part, the paper, therefore, analyses how the revenue capacity affects the optimal choice of environmental policy instruments in the presence of uncertainty. The paper shows that the first-best choice rule between price and quantity regulation (Weitzman, 1974) remains valid in a second-best world with distortionary taxation.
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    Environmental and resource economics 8 (1996), S. 39-61 
    ISSN: 1573-1502
    Keywords: tropical forests ; irreversibility ; uncertainty ; Thai parks
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    Topics: Energy, Environment Protection, Nuclear Power Engineering , Economics
    Notes: Abstract This paper develops a framework for the valuation and management of tropical forests that reflects their ecological and economic characteristics. The analysis demonstrates the importance of modeling the feasible use patterns and the information structure in tropical forest management decisions. The model predicts that cases exist where the foresighted management of forests leads to more preservation than the traditional expected value approach. An application in Thailand provides evidence that such cases occur in relevant ranges of benefit flows. The model focuses tropical forest management on assessments of sustainability and feasible sequences in light of uncertainty and information flows.
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    Environmental modeling and assessment 1 (1996), S. 71-90 
    ISSN: 1573-2967
    Keywords: Integrated assessment ; uncertainty ; subjectivity in modelling ; perspectives, risk
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    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract In the context of integrated assessment, the authors address the issue of uncertainty and subjectivity in modelling. In relating bias to different perspectives, the authors introduce the methodology of multiple model routes, which are reflections of different perceptions of reality and various policy preferences. As heuristic they use three perspectives, which are distinguished in cultural theory. The article describes case-studies on the population and health controversy in order to illustrate the possibilities of their approach. The article concludes with discussing the lessons learned by applying this methodology.
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    Water resources management 10 (1996), S. 45-79 
    ISSN: 1573-1650
    Keywords: capacity-reliability-yield analysis ; reservoir planning and design ; present value ; value of data ; uncertainty ; opportunity loss ; expected opportunity loss ; streamflow gauging networks
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    Topics: Architecture, Civil Engineering, Surveying , Geography
    Notes: Abstract Streamflow data have economic value because they are used for making decisions in water resources. By quantifying this value, hydrologists should find it much easier to overcome traditional obstacles to investment in streamflow data collection programmes. In this paper, an opportunity loss model is described which enables this to be done. The study has focused on evaluating typical benefits which may arise from more abundant data records for a specific purpose and, through this, provide further evidence which justifies investment in streamflow data collection activities. The specific purpose investigated is the development of reservoir capacity-reliability-yield relationship. Finally, it is argued that, while it is not uncommon for a streamgauging station to be project-specific, the data would invariably be used for other purposes and through these generate additional values. Considerations of such secondary values should make the whole idea of investment in streamflow data collection even more attractive economically.
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    The journal of real estate finance and economics 12 (1996), S. 37-58 
    ISSN: 1573-045X
    Keywords: liability ; uncertainty ; industrial redevelopment
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    Topics: Economics
    Notes: Abstract The paper explores the effects of current liability law on real estate transactions involving properties with potential environmental contamination. Sources of uncertainty and their likely impact on transactions are identified. Liability-driven market distortions are likely to be due less to legal uncertainty than to problems arising from asymmetric information and imperfect detection.
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    Review of quantitative finance and accounting 6 (1996), S. 133-147 
    ISSN: 1573-7179
    Keywords: cost-volume-profit analysis ; uncertainty ; risk aversion ; fixed cost effect
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    Topics: Economics
    Notes: Abstract Cost-volume-profit analysis has focused on the firm's short-run output decision assuming that the manager maximizes the firm's objective function rather than his or her own. This study argues that the decision problem facing the manager is to determine not only the level of output, but also the level of investment in risky assets in such a way that the expected utility of the manager's own end-of-period wealth can be maximized when the manager's wealth function is dependent on vested interests both within and outside of the firm, possibly in competition with the firm. Through analytical work, it is demonstrated that a change in fixed costs of the firm affects not only the production decision of a manager, but also his orher decision to invest in risky assets. The direction of this fixed cost effect depends on the particular type of risk aversion displayed by the manager. From the analytical work, five propositions are developed for empirical investigation in the future.
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  • 85
    ISSN: 1573-8868
    Keywords: heterogeneity ; Monte-Carlo analysis ; uncertainty ; geostatistics ; conditioning ; self-calibrated method
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    Topics: Geosciences , Mathematics
    Notes: Abstract Transmissivity and head data are sampled from an exhaustive synthetic reference field and used to predict the arrival positions and arrival times of a number of particles transported across the field, together with an uncertainty estimate. Different combinations of number of transmissivity data and number of head data used are considered in each one of a series of 64 Monte-Carlo analyses. In each analysis, 250 realizations of transmissivity fields conditioned to both transmissivity and head data are generated using a novel geostatistically based inverse method. Pooling the solutions of the flow and transport equations in all 250 realizations allows building conditional frequency distributions for particle arrival positions and arrival times. By comparing these fresquency distributions, we can assess the incremental gain that additional head data provide. The main conclusion is that the first few head data dramatically improve the quality of transport predictions.
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    Biodiversity and conservation 5 (1996), S. 1143-1167 
    ISSN: 1572-9710
    Keywords: uncertainty ; ecology ; policy ; sustainability ; biodiversity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Using an Australian focus to explore theoretical and policy issues of wider concern, this article examines linkages between public policy and the science of ecology. This is done within the broader framework of sustainability, emphasizing the problem of decision making in the face of ‘uncertainty’. Insights from the ecological, risk, sustainability and policy literatures are used. The sustainability-uncertainty problem is characterized, and the adequacy of existing policy support techniques and approaches noted, particularly the precautionary principle. The problem is further defined using the notion of ignorance. The treatment of ignorance and uncertainty in ecology is discussed. We suggest that the science of ecology has had a limited influence on policy formulation and discuss the basis of this using biodiversity conservation and ecosystem management as examples. We conclude by considering challenges for handling risk, uncertainty and ignorance in ecological science for policy formulation. We emphasize the need for improved communication between the science and policy communities, greater recognition of the limits of quantitative techniques in addressing uncertainty, and contingency planning.
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    Microchimica acta 123 (1996), S. 303-309 
    ISSN: 1436-5073
    Keywords: accuracy ; quality assessment ; instrumental neutron activation analysis ; uncertainty
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    Topics: Chemistry and Pharmacology
    Notes: Abstract Neutron activation analysis is one of the analytical techniques often used for certification of reference materials. The k0-based method of instrumental neutron activation analysis can also be applied in intercomparison runs in the certification process and therefore it is desirable to know its accuracy in advance. Possible systematic errors related to the application of nuclear data at given neutron flux rate parameters, that can affect the uncertainties of the results obtained by this specific method, are elucidated and error propagation factors calculated for a typical irradiation position in the TRIGA Mark II reactor of the Jozef Stefan Institute. It was found that these uncertainties are at the level of 1–2% on the average.
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    Microchimica acta 123 (1996), S. 231-240 
    ISSN: 1436-5073
    Keywords: measurement errors ; reference materials ; validation ; uncertainty ; method evaluation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Quality assurance and method validation are needed to reduce false decisions due to measurement errors. In this context accuracy and standard uncertainty for the analytical method need to be considered to ensure that the performance characteristics of the method are understood. Therefore, analytical methods ought to be validated before implementation and controlled on a regular basis during usage. For this purpose reference materials (RMs) are useful to determine the performance characteristics of methods under development. These performance parameters may be documented in the light of a method evaluation study and the documentation related to international standards and guidelines. In a method evaluation study of Pb in blood using reference samples from the Laboratoire Toxicologie du Quèbec, Canada, a difference between the systematic errors was observed using a Perkin-Elmer Model 5100 atomic absorption spectrometer and a Perkin-Elmer Model 4100 atomic absorption spectrometer, both with Zeeman background correction. For measurement of blood samples, the performance parameters obtained in the method evaluation studies, i.e. slopes and intercepts of the method evaluation function (MEF), were intended to be used for correcting the systematic errors. However, the number of MEF samples was insufficient to produce an acceptable SD for the MEF slopes to be used for correction. In a method evaluation study on valproate in plasma using the SYVA's EMIT assay on COBAS MIRA S a significant systematic error above the concentration 300 mmol dm−3 was demonstrated (slope 0.9541) and consequently the slope was used for correction of results. For analytes, where certified RMs (CRMs) exist, a systematic error of measurements can be reduced by correcting errors by assessment of the trueness as recommended in international guidelines issued by ISO or the National Institute of Standards and Technology (NIST). When possible, the analysis of several RMs, covering the concentration range of interest, is the most useful way to investigate measurement bias. Unfortunately, until recently only few RMs existed and only few had been produced and certified by specialized organizations such as NIST or the Standards, Measurements and Testing (SMT, previously BCR) programme. Due to the lack of such RMs, network organizations are nowadays established with the aim of supporting the correct use and production of high-quality CRMs.
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    Journal of intelligent manufacturing 6 (1995), S. 215-234 
    ISSN: 1572-8145
    Keywords: Possibility theory ; fuzzy constraints ; scheduling ; preference ; uncertainty
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: This paper proposes an extension of the constraint-based approach to job-shop scheduling, that accounts for the flexibility of temporal constraints and the uncertainty of operation durations. The set of solutions to a problem is viewed as a fuzzy set whose membership function reflects preference. This membership function is obtained by an egalitarist aggregation of local constraint-satisfaction levels. Uncertainty is qualitatively described in terms of possibility distributions. The paper formulates a simple mathematical model of job-shop scheduling under preference and uncertainty, relating it to the formal framework of constraint-satisfaction problems in artificial intelligence. A combinatorial search method that solves the problem is outlined, including fuzzy extensions of well-known look-ahead schemes.
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    Journal of risk and uncertainty 10 (1995), S. 15-36 
    ISSN: 1573-0476
    Keywords: ambiguity ; uncertainty ; risk ; ignorance ; cognitive processes
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    Topics: Economics
    Notes: Abstract The metaphor of gambling has had great influence on the topic of choice under uncertainty. However, in many real-world situations, people must make choices when they lack information about the relevant economic features of gambles, i.e., probabilities and outcomes. We refer to this as choice under ignorance as opposed to choice under risk or uncertainty. We propose that people handle these decisions by generating rationales or arguments that allow them to resolve the choice conflict. Moreover, these rationales often do not correspond to principles derived from the cost-benefit framework of economic models. These ideas are explored in two experiments in which subjects simulated the purchase of warranties for consumer durables. Our principal findings are, first, that observable behaviors differ between situations where subjects do and do not have information on probabilities and outcomes. Second, economic cost-benefit models did not yield good descriptions of our subjects' decisions. Third, the nature of arguments used, and thus the processes invoked, differed as a function of the information available to subjects. And fourth, subjects' arguments indicated two types of strategies for reaching decisions. In one, they processed the particular characteristics of each choice option; in the other, they invoked a “meta-rule” or principle that resolved the choice conflict and was insensitive to the particular features of different options. Finally, we discuss the implications of our results. This includes questioning the appropriateness of using the gamble as a metaphor for choice in future research.
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    Journal of risk and uncertainty 10 (1995), S. 143-156 
    ISSN: 1573-0476
    Keywords: uncertainty ; insurance ; renewability ; competition
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    Topics: Economics
    Notes: Abstract We propose a guaranteed renewability (GR) insurance in which a sequence of premiums would enable insurers to break even and would be chosen by both low- and high-risk buyers, whether or not they had suffered a loss. The premium schedule would continually decline over time, as the insurer collects more information to determine who the low-risk buyers are. The highest premiums are charged initially to protect the insurer if low-risk individuals leave for the spot market. The concluding portion of the article discusses the limitations of a GR policy in the health and environmental liability area, the most serious being instability in estimates of underlying loss trends.
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    Journal of risk and uncertainty 10 (1995), S. 37-55 
    ISSN: 1573-0476
    Keywords: uncertainty ; intertemporal choice ; life-cycle ; stochastic dominance ; temporal dominance
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    Topics: Economics
    Notes: Abstract Intertemporal choice has obvious similarities with choice under uncertainty. However, because of technical difficulties in mapping results between the two domains, theoretical analysis of these topics has proceeded independently. In this article, we show that, using Rank Dependent Expected Utility rather than Expected Utility as the basic uncertain choice model, numerous analogies between the two fields may be identified and exploited. The key result is the derivation of a natural analogy between risk-aversion and impatience. This permits the reinterpretation of well-known results on stochastic dominance and comparative risk-aversion in the context of intertemporal choice. It is also possible to reinterpret results on intertemporal optimization in order to derive new results for portfolio choice problems under uncertainty.
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  • 93
    ISSN: 1572-9761
    Keywords: field survey ; vegetation ; land cover type ; mapping ; uncertainty ; error ; change
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Land cover data for landscape ecological studies are frequently obtained by field survey. In the United Kingdom, temporally separated field surveys have been used to identify the locations and magnitudes of recent changes in land cover. However, such map data contain errors which may seriously hinder the identification of land cover change and the extent and locations of rare landscape features. This paper investigates the extent of the differences between two sets of maps derived from field surveys within the Northumberland National Park in 1991 and 1992. The method used in each survey was the ‘Phase 1’ approach of the Nature Conservancy Council of Great Britain. Differences between maps were greatest for the land cover types with the smallest areas. Overall spatial correspondence between maps was found to be only 44.4%. A maximum of 14.4% of the total area surveyed was found to have undergone genuine land cover change. The remaining discrepancies, equivalent to 41.2% of the total survey area, were attributed primarily to differences of land cover interpretation between surveyors (classification error). Differences in boundary locations (positional error) were also noted, but were found to be a relatively minor source of error. The implications for the detection of land cover change and habitat mapping are discussed.
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    Review of industrial organization 10 (1995), S. 269-288 
    ISSN: 1573-7160
    Keywords: Oligopoly ; uncertainty ; fuzzy mathematics ; Herfindahl-Hirschman ; antitrust
    Source: Springer Online Journal Archives 1860-2000
    Topics: Economics
    Notes: Abstract This paper provides a brief sketch of fuzzy mathematics. It employs this relatively new mathematical tool to define and describe oligopoly markets and to quantitatively establish the impacts of uncertainty on the decision making that is intrinsic to oligopolistic industries. It illustrates how the technique would be used, for example, by applying fuzzy mathematics to the Herfindahl-Hirschman Index.
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    Theory and decision 39 (1995), S. 51-77 
    ISSN: 1573-7187
    Keywords: Ambiguity ; competence ; knowledge ; decision making ; uncertainty
    Source: Springer Online Journal Archives 1860-2000
    Topics: Sociology , Economics
    Notes: Abstract Competence has recently been proposed as an explanation for the degree of ambiguity aversion. Using general knowledge questions we presented subjects with simple lotteries in which they could bet on an event and against the same event. We show that the sum of certainty equivalents for both bets depends on the judged knowledge of the class of events. We also elicited the decision weights for events and complementary events. We found a similar effect of knowledge on the sum of decision weights.
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    Environmental and resource economics 5 (1995), S. 71-82 
    ISSN: 1573-1502
    Keywords: Externality ; greenhouse ; estimation ; uncertainty
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Economics
    Notes: Abstract The shadow price of carbon dioxide is the value of the external damage caused by an emission. A shadow price model for calculating the present value of the external damage of a carbon dioxide emission is derived explicitly. Sixteen experts provided subjective high, low and most likely parameter estimates because correct values for the eight model parameters are uncertain. The estimation procedure retains parameter uncertainty while generating the main result, which is a distribution of shadow price estimates. Major assumptions made in the estimation identify the basis for the results. Of the eight model parameters, the discount rate dominates the determination of the shadow price. For comparison, expert estimates of the shadow price itself provide a second distribution of shadow price estimates.
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    Environmental and resource economics 5 (1995), S. 353-374 
    ISSN: 1573-1502
    Keywords: Climate change damage costs ; cost functions ; uncertainty
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    Topics: Energy, Environment Protection, Nuclear Power Engineering , Economics
    Notes: Abstract It is argued that estimating the damage costs of a certain benchmark climate change is not sufficient. What is needed are cost functions and confidence intervals. Although these are contained in the integrated models and their technical manuals, this paper brings them into the open in order to stimulate discussion. After briefly reviewing the benchmark climate change damage costs, region-specific cost functions are presented which distinguish tangible from intangible losses and the losses due to a changing climate from those due to a changed climate. Furthermore, cost functions are assumed to be quadratic, as an approximation of the unknown but presumably convex functions. Results from the damage module of the integrated climate economy modelFUND are presented. Next, uncertainties are incorporated and expected damages are calculated. It is shown that because of convex loss functions and right-skewed uncertainties, the risk premium is substantial, calling for more action than analysis based on best-guess estimates. The final section explores some needs for further scientific research.
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    Journal of aquatic ecosystem stress and recovery 4 (1995), S. 151-156 
    ISSN: 1573-5141
    Keywords: sediment ; toxicity ; uncertainty ; integrated ; bioassays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract During the past few years there has been a tremendous increase in sediment bioassay and toxicity testing and research. The increased activity has paralleled the development of regulatory interest and realization of the role of contaminated sediments in ecosystem degradation. Many critical issues which affect test responses, data interpretation, and extrapolation to in situ conditions, have not been adequately addressed or recognized by the scientific community. Some of these issues may significantly affect contaminant fate and effects and thereby affect the accuracy of data interpretations. Examples of these interferences are disruptive sample collection, extended sample storage, designs which alter exposure routes, improper spiking conditions and sediment dilution, and inadequate validation of laboratory responses against in situ conditions. Over-simplification of complex sediment interactions may lead to erroneous conclusions concerning the significance of moderate to low levels of contamination.
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    Springer
    Water, air & soil pollution 85 (1995), S. 2521-2526 
    ISSN: 1573-2932
    Keywords: Critical loads ; percentiles ; scale ; resolution ; uncertainty ; UK ; UNECE
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Critical loads are estimated in the UK by the Department of Environment's Critical Loads Advisory Group and sub-groups. The Mapping and Data Centre at ITE Monks Wood acts as the National Focal Centre for the UNECE programme for mapping critical loads. The centre is responsible for the generation of UK data sets and their application for national and European purposes. To make effective use of these data, it is necessary to draw upon other environmental data and examine the issues of scale, uncertainty and the way that data are presented. This paper outlines the methodologies which have been employed to derive national maps. Early critical load maps were not vegetation specific, but now critical loads for acidity and for nutrient nitrogen for soils, critical levels maps for ozone and sulphur dioxide, and sulphur deposition maps, have been generated on a vegetation or ecosystem specific basis. These have been used to derive a number of different types of critical load and exceedance maps. The results show the importance of the method selected and the data used for the interpretation. The visualisation of critical loads and the corresponding exceedance data is an important aspect in producing information for pollution abatement strategies.
    Type of Medium: Electronic Resource
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    Electronic Resource
    Electronic Resource
    Springer
    Water, air & soil pollution 85 (1995), S. 2503-2508 
    ISSN: 1573-2932
    Keywords: critical load ; deposition model ; spatial scale ; uncertainty ; probability distribution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract The critical loads approach to quantifying areas at risk of damage requires deposition and critical loads data at the same spatial scale to calculate exceedance. While maps of critical loads for soil acidification are available at a 1 km scale no monitoring networks in Europe measure wet and dry inputs at this scale and, further, the models currently used to estimate deposition incorporate a number of assumptions which are not valid at the 1 km scale. Simulations of 1 km deposition from 20 km data show that the uncertainty introduced by using 20 km scale estimates of deposition is small, except in mountain areas where it can give misleading results, but a major problem is the uncertainty in estimates of deposition at the 20 km scale produced by the current models.
    Type of Medium: Electronic Resource
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