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  • 1990-1994  (4)
  • 1
    Electronic Resource
    Electronic Resource
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Public Health 13 (1992), S. 341-362 
    ISSN: 0163-7525
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Medicine
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Astrophysics and space science 185 (1991), S. 51-61 
    ISSN: 1572-946X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The stellar three-body problem has been approached by directly integrating the equations of motion in the orbital elements. The problem is set up in a barycentric chain with the orbits as perturbed ellipses. The integration was performed using the semi-analytical stroboscopic method, which is particularly useful for solving differential systems that depend on several slow variables and one fast, angular variable. Perturbation theory is applied and the solution for a particular order is obtained by way of successive approximations on the fundamental period of the fast variable.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Structural and multidisciplinary optimization 3 (1991), S. 214-230 
    ISSN: 1615-1488
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract This paper treats the problem of the combined design of structure/control systems for achieving optimal maneuverability. A maneuverability index which directly reflects the time required to perform a given maneuver or set of maneuvers is introduced. By designing the flexible appendages of a spacecraft, its maneuverability is optimized under the constraints of structural properties, and of the postmaneuver spill-over being within a specified bound. The spillover reduction is achieved by making use of an appropriate control design model. The distributed parameter design problem is approached using assumed shape functions and finite element analysis with dynamic reduction. Characteristics of the problem and problem solving procedures have been investigated. Adaptive approximate design methods have been developed to overcome computational difficulties. It is shown that the global optimal design may be obtained by tuning the natural frequencies of the spacecraft to satisfy specific constraints. We quantify the difference between a lower bound to the objective function associated with the original problem and the estimate obtained from the modified problem as the index for the adaptive refinement procedure. Numerical examples show that the results of the optimal design can provide substantial improvement.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Journal of optimization theory and applications 82 (1994), S. 219-251 
    ISSN: 1573-2878
    Keywords: Optimization ; control ; structures ; spacecraft ; fail-safe design
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract A multicriterion design problem for optimal maneuverability and fault tolerance of flexible spacecraft is considered. The maneuverability index reflects the time required to perform rest-to-rest attitude maneuvers for a given set of angles, with the postmaneuver spillover within a specified bound. The performance degradation is defined to reflect the maximum possible attitude error after maneuver due to the effect of faults. The fault-tolerant design is to minimize the worst performance degradation from all admissible faults by adjusting the design of the spacecraft. It is assumed that admissible faults can be specified by a vector of real parameters. The multicriterion design for optimal maneuverability and fault tolerance is shown to be well defined, leading to a minimax problem. Analysis for this nonsmooth problem leads to closed-form expressions of the generalized gradient of the performance degradation function with respect to the fault parameters and structural design variables. Necessary and sufficient conditions for the optimum are derived, and the closed-form expressions of the generalized gradients are applied for their interpretation. The bundle method is applicable to this minimax problem. Approximate methods which efficiently solve this minimax problem with relatively little computational difficulties are presented. Numerical examples suggest that it is possible to improve the fault tolerance substantially with relatively little loss in maneuverability.
    Type of Medium: Electronic Resource
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