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  • CYBERNETICS  (6)
  • GEOPHYSICS  (5)
  • Chemical Engineering  (4)
  • 2005-2009
  • 1990-1994  (15)
  • 1970-1974
  • 1992  (15)
  • 1
    Electronic Resource
    Electronic Resource
    Two-dimensional finite element analysis of microwave heating (1992)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 38 (1992), S. 1577-1592 
    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: Transient temperature profiles for long rods of lossy dielectric materials with thermally-dependent dielectric properties exposed to uniform plane waves are obtained. Maxwell's equation and the heat equation are simultaneously solved using the finite element method to predict the power absorbed and the resulting temperature rise in samples of square and circular cross-section. Following the method introduced recently, we derive an exact radiation boundary condition which is independent of the rod cross-section. For a cylindrical sample, the boundary condition is imposed on the cylinder itself. For a square rod, the boundary condition is imposed on a cylinder containing the rod. The temperature dependence of dielectric properties and sample dimensions appreciably influence heating patterns. For square samples, the edges focus radiation, causing preferential heating at the edges. This effect is pronounced for larger samples. In addition, the incident wave polarization influences the heating of the rod. For waves where the electric field is polarized along the long axis of the sample (TMz polarization) the power absorbed is higher than when the electric field is perpendicular to the axis (TEz polarization). A case involving runaway heating is also investigated.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690381009
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Unbiased estimation of gross errors in process measurements (1992)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 38 (1992), S. 563-572 
    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: A new approach to gross error detection provides unbiased estimates and 100(1-α)% simultaneous confidence intervals of process variables when biased process measurements and process leaks exist. Presented in this article are estimation equations for process variables, as well as equations that help identify biased measurements and process leaks. These equations include the power function for a global test, and two types of α-level component tests and their power functions. Important strengths and weaknesses of this approach are compared to those of the serial compensation strategy, in particular, by varying the significance level (α), the variance-covariance matrix (Σ), the size of measurement bias (δ), the number of biased variables, and the sample size (N). Accuracy of δ estimation and performance in detecting the presence of process leaks (γ) are also evaluated and compared. The proposed approach has unique features that can provide a basis for improving the reconciliation of variables in process operations.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690380410
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  • 3
    Electronic Resource
    Electronic Resource
    Affinity membranes: Their chemistry and performance in adsorptive separation processes. By Elias Klein, Wiley, New York, 152 pp., 1991 (1992)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 38 (1992), S. 1997-1998 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690381219
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Continuous flow methods in organic synthesis. By P. Tundo, Ellis Horwood Ltd., 310 pp., 3 Appendices, hardback, 1991 (1992)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 38 (1992), S. 1999-2000 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690381222
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  • 5
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    Reduction of Marine Magnetic Data for Modeling the Main Field of the Earth (1992)
    In:  CASI
    Details
    Publication Date: 2014-09-25
    Description: The marine data set archived at the National Geophysical Data Center (NGDC) consists of shipborne surveys conducted by various institutes worldwide. This data set spans four decades (1953, 1958, 1960-1987), and contains almost 13 million total intensity observations. These are often less than 1 km apart. These typically measure seafloor spreading anomalies with amplitudes of several hundred nanotesla (nT) which, since they originate in the crust, interfere with main field modeling. The source for these short wavelength features are confined within the magnetic crust (i.e., sources above the Curie isotherm). The main field, on the other hand, is of much longer wavelengths and originates within the earth's core. It is desirable to extract the long wavelength information from the marine data set for use in modeling the main field. This can be accomplished by averaging the data along the track. In addition, those data which are measured during periods of magnetic disturbance can be identified and eliminated. Thus, it should be possible to create a data set which has worldwide data distribution, spans several decades, is not contaminated with short wavelengths of the crustal field or with magnetic storm noise, and which is limited enough in size to be manageable for the main field modeling. The along track filtering described above has proved to be an effective means of condensing large numbers of shipborne magnetic data into a manageable and meaningful data set for main field modeling. Its simplicity and ability to adequately handle varying spatial and sampling constraints has outweighed consideration of more sophisticated approaches. This filtering technique also provides the benefits of smoothing out short wavelength crustal anomalies, discarding data recorded during magnetically noisy periods, and assigning reasonable error estimates to be used in the least square modeling. A useful data set now exists which spans 1953-1987.
    Keywords: GEOPHYSICS
    Type: NASA. Goddard Space Flight Center, Types and Characteristics of Data for Geomagnetic Field Modeling; p 149-202
    Format: text
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  • 6
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    Rescheduling with iterative repair (1992)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: This paper presents a new approach to rescheduling called constraint-based iterative repair. This approach gives our system the ability to satisfy domain constraints, address optimization concerns, minimize perturbation to the original schedule, and produce modified schedules quickly. The system begins with an initial, flawed schedule and then iteratively repairs constraint violations until a conflict-free schedule is produced. In an empirical demonstration, we vary the importance of minimizing perturbation and report how fast the system is able to resolve conflicts in a given time bound. These experiments were performed within the domain of Space Shuttle ground processing.
    Keywords: CYBERNETICS
    Type: NASA. Ames Research Center, Working Notes from the 1992 AAAI Spring Symposium on Practical Approaches to Scheduling and Planning; p 92-96
    Format: application/pdf
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  • 7
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    Reliable design of H-2 optimal reduced-order controllers via a homotopy algorithm (1992)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Due to control processor limitations, the design of reduced-order controllers is an active area of research. Suboptimal methods based on truncating the order of the corresponding linear-quadratic-Gaussian (LQG) compensator tend to fail if the requested controller dimension is sufficiently small and/or the requested controller authority is sufficiently high. Also, traditional parameter optimization approaches have only local convergence properties. This paper discusses a homotopy algorithm for optimal reduced-order control that has global convergence properties. The exposition is for discrete-time systems. The algorithm has been implemented in MATLAB and is applied to a benchmark problem.
    Keywords: CYBERNETICS
    Type: In: Controls for optical systems; Proceedings of the Meeting, Orlando, FL, Apr. 21, 22, 1992 (A93-34276 13-74); p. 116-127.
    Format: text
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  • 8
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    Learning to improve iterative repair scheduling (1992)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: This paper presents a general learning method for dynamically selecting between repair heuristics in an iterative repair scheduling system. The system employs a version of explanation-based learning called Plausible Explanation-Based Learning (PEBL) that uses multiple examples to confirm conjectured explanations. The basic approach is to conjecture contradictions between a heuristic and statistics that measure the quality of the heuristic. When these contradictions are confirmed, a different heuristic is selected. To motivate the utility of this approach we present an empirical evaluation of the performance of a scheduling system with respect to two different repair strategies. We show that the scheduler that learns to choose between the heuristics outperforms the same scheduler with any one of two heuristics alone.
    Keywords: CYBERNETICS
    Type: NASA-TM-108118 , FIA-92-14 , NAS 1.15:108118
    Format: application/pdf
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  • 9
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    Scheduling and rescheduling with iterative repair (1992)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: This paper describes the GERRY scheduling and rescheduling system being applied to coordinate Space Shuttle Ground Processing. The system uses constraint-based iterative repair, a technique that starts with a complete but possibly flawed schedule and iteratively improves it by using constraint knowledge within repair heuristics. In this paper we explore the tradeoff between the informedness and the computational cost of several repair heuristics. We show empirically that some knowledge can greatly improve the convergence speed of a repair-based system, but that too much knowledge, such as the knowledge embodied within the MIN-CONFLICTS lookahead heuristic, can overwhelm a system and result in degraded performance.
    Keywords: CYBERNETICS
    Type: NASA-TM-108120 , FIA-92-16 , NAS 1.15:108120
    Format: application/pdf
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  • 10
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    A parameterization of minimal plants (1992)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The authors present the input-normal Riccati parameterization which allows a minimal plant (A, B, C, D) to be represented completely by its B, C, and D matrices. In addition to the basic parameterization, they present useful gradient expressions for a cost functional J(A, B, C, D) when the plant is restricted to the input-normal Riccati form. The parameterization is valid for both stable and unstable, and continuous-time and discrete-time systems.
    Keywords: CYBERNETICS
    Type: In: 1992 American Control Conference, 11th, Chicago, IL, June 24-26, 1992, Proceedings. Vol. 1 (A93-22776 07-63); p. 355, 356.
    Format: text
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