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  • Chemical Engineering  (3)
  • GEOPHYSICS  (2)
  • 1
    Electronic Resource
    Electronic Resource
    Malfunction diagnosis using quantitative models with non-boolean reasoning in expert systems (1987)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 33 (1987), S. 130-140 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: An approach to chemical plant fault diagnosis is presented that utilizes patterns of violation and satisfaction of the quantitative constraints governing the process. Process knowledge consists of a list of the operational constraints on the plant together with sufficient conditions for violation of each constraint. Interpretation of the pattern of constraint violations is treated by Boolean and non-Boolean techniques. It is shown that non-Boolean reasoning techniques increase the stability and sensitivity of the diagnosis in the presence of noise. The techniques introduced in this paper are easily implemented in rule-based expert systems using certainty factors.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690330115
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    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    A rule-based approach to fault diagnosis using the signed directed graph (1987)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 33 (1987), S. 1067-1078 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Fault diagnosis is the problem of determining the root causes of process upsets. This paper presents a very efficient method of identifying the possible causes of process disturbances using the signed directed graph (digraph) representation of process interactions. The analysis is based on forming logical statements (rules) derived from the process digraph; these are evaluated using on-line data to yield the diagnosis. Evaluation of rule antecedents is more efficient than the previous algorithmic approach of Shiozaki et al. In the rule-based approach, the diagnostic criteria are represented explicitly, not hidden by a complex algorithmic procedure. This allows the diagnostic rules to be tailored to reflect the best available knowledge of plant behavior. The rules generated by this technique can be integrated with other rules on plant operations using an expert systems framework.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690330703
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Narrowing diagnostic focus using functional decomposition (1988)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 34 (1988), S. 25-36 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The problem of diagnosing faults in chemical plants can be efficiently addressed by a hierarchical procedure involving successive narrowing of the space in which the fault search is conducted. A technique is presented for narrowing diagnostic focus useful in the first stages of a diagnostic search. Based on a decomposition of the process according to function, the technique assesses the functionality of process systems based on measurements of controlled and manipulated variables. A procedure for identification of possibly faulty systems and units from the system states is outlined. Detailed diagnosis, not treated in this paper, would be applied after candidate systems or units are located. An example is presented using a hypothetical chemical reaction process.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690340105
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    Paper (German National Licenses)
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  • 4
    facet.materialart.
    Unknown
    Crustal deformation, the earthquake cycle, and models of viscoelastic flow in the asthenosphere (1984)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: The crustal deformation patterns associated with the earthquake cycle can depend strongly on the rheological properties of subcrustal material. Substantial deviations from the simple patterns for a uniformly elastic earth are expected when viscoelastic flow of subcrustal material is considered. The detailed description of the deformation pattern and in particular the surface displacements, displacement rates, strains, and strain rates depend on the structure and geometry of the material near the seismogenic zone. The origin of some of these differences are resolved by analyzing several different linear viscoelastic models with a common finite element computational technique. The models involve strike-slip faulting and include a thin channel asthenosphere model, a model with a varying thickness lithosphere, and a model with a viscoelastic inclusion below the brittle slip plane. The calculations reveal that the surface deformation pattern is most sensitive to the rheology of the material that lies below the slip plane in a volume whose extent is a few times the fault depth. If this material is viscoelastic, the surface deformation pattern resembles that of an elastic layer lying over a viscoelastic half-space. When the thickness or breath of the viscoelastic material is less than a few times the fault depth, then the surface deformation pattern is altered and geodetic measurements are potentially useful for studying the details of subsurface geometry and structure. Distinguishing among the various models is best accomplished by making geodetic measurements not only near the fault but out to distances equal to several times the fault depth. This is where the model differences are greatest; these differences will be most readily detected shortly after an earthquake when viscoelastic effects are most pronounced.
    Keywords: GEOPHYSICS
    Type: Geophysical Journal (ISSN 0016-8009); 78; 735-750
    Format: text
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    NASA TECHNICAL REPORTS
  • 5
    facet.materialart.
    Unknown
    Crustal deformation, the earthquake cycle, and models of viscoelastic flow in the asthenosphere (1983)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The crustal deformation patterns associated with the earthquake cycle can depend strongly on the rheological properties of subcrustal material. Substantial deviations from the simple patterns for a uniformly elastic earth are expected when viscoelastic flow of subcrustal material is considered. The detailed description of the deformation pattern and in particular the surface displacements, displacement rates, strains, and strain rates depend on the structure and geometry of the material near the seismogenic zone. The origin of some of these differences are resolved by analyzing several different linear viscoelastic models with a common finite element computational technique. The models involve strike-slip faulting and include a thin channel asthenosphere model, a model with a varying thickness lithosphere, and a model with a viscoelastic inclusion below the brittle slip plane. The calculations reveal that the surface deformation pattern is most sensitive to the rheology of the material that lies below the slip plane in a volume whose extent is a few times the fault depth. If this material is viscoelastic, the surface deformation pattern resembles that of an elastic layer lying over a viscoelastic half-space. When the thickness or breath of the viscoelastic material is less than a few times the fault depth, then the surface deformation pattern is altered and geodetic measurements are potentially useful for studying the details of subsurface geometry and structure. Distinguishing among the various models is best accomplished by making geodetic measurements not only near the fault but out to distances equal to several times the fault depth. This is where the model differences are greatest; these differences will be most readily detected shortly after an earthquake when viscoelastic effects are most pronounced.
    Keywords: GEOPHYSICS
    Type: NASA-TM-85117 , GSFC-921 , NAS 1.15:85117
    Format: application/pdf
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    NASA TECHNICAL REPORTS
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