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  • Articles  (9)
  • 550 - Earth sciences
  • Electronic structure and strongly correlated systems
  • uncertainty
  • Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition  (5)
  • Chemistry and Pharmacology  (4)
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  • Articles  (9)
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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    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.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    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.
    Type of Medium: Electronic Resource
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  • 3
    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
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    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.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    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.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Microchimica acta 123 (1996), S. 303-309 
    ISSN: 1436-5073
    Keywords: accuracy ; quality assessment ; instrumental neutron activation analysis ; uncertainty
    Source: Springer Online Journal Archives 1860-2000
    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.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Agroforestry systems 13 (1991), S. 63-71 
    ISSN: 1572-9680
    Keywords: Mathematical programming ; portfolio theory ; economics ; nonlinear programming ; linear programming ; quadratic programming ; risk ; uncertainty ; mean-variance analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The ability to use a knowledge of past market price fluctuations to reduce the risk of future financial returns is explored in the context of planning an agroforestry system with a cash crop component. It is demonstrated that if past crop price behavior is indicative of future price behavior, planting crops with stable and/or negatively correlated net revenues can reduce the variance of future net revenues and hence decrease the financial risks of agroforestry systems.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Radiation Physics and Chemistry 42 (1993), S. 731-738 
    ISSN: 0969-806X
    Keywords: Dosimetry ; radiation ; standards ; sterilization ; traceability ; uncertainty
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering , Physics
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 0261-2194
    Keywords: Puccinia recondita ; Sitobion avenae ; Triticum aestivum ; damage threshold ; profitability ; risk ; supervised control ; uncertainty
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Type of Medium: Electronic Resource
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