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  • 1
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Respiration Physiology 36 (1979), S. 201-216 
    ISSN: 0034-5687
    Keywords: Brain stem ; Pentobarbitone ; Pneumotaxic centre ; Respiratory centres ; Reticular formation
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Medicine
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 16 (1973), S. 383-399 
    ISSN: 1432-1106
    Keywords: Pons ; Respiratory neurons ; Trigeminal system ; Reticular formation ; Respiratory oscillators
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The upper and middle pons and the lower mesencephalon of the cat were explored with extracellular microelectrodes in a search for respiratory related units (RRU). The preparation used, the unanesthetized normocapnic cat, resulted in an “isolated respiratory center” by eliminating input from, as well as output to, lung and thorax. Observations were done in standard experimental conditions which allowed quantitative comparisons of anatomical structures with respect to RRU density (RRUD), RRUD to total unit density (UD) ratio, and a respiratory modulation index (RMI). Units were recorded in 22 anatomical structures; of 3614 units kept for analysis, 46.9% had a definite respiratory rhythm. The phase relations of frequency variation ere classified into five main categories: 1) tonic expiratory (E) or 2) inspiratory (I) patterns, 3) phase spanning inspiratory-expiratory (IE) or 4) expiratoryinspiratory (EI) patterns, and 5) tonic early expiratory depressed (EED) pattern. Densely packed RRU were recorded in anatomical structures known to be involved in the command of respiratory accessory musculature (trigeminal system) or thought to be part of the pneumotaxic machinery (nucleus parabrachialis median's, Kölliker-Fuse nucleus). In these structures, RRU proportion was 57–89% of the total neuronal activity. On the other hand, definite RRU (10–26%) were recorded in structures which are not thought to have a respiratory function (such as inferior colliculus or griseum centralis) where isolate RRU were scattered among non-respiratory tonic units. This group includes nuclei sometimes considered as having a pneumotaxic function. The pontine reticular formation represents an intermediate category (RRU = 35.6%) where clusters of RRU alternate with non-respiratory modulated cells. The possible role of these clusters is discussed in relation to the hypothesis of multiple coupled respiratory oscillators. Variance analysis of RRUD, RRUD to UD ratio and RMI shows highly significant differences between the three preceding categories of structures.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 33 (1992), S. 1251-1267 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: Several old and new tetrahedral elements are tested and compared to some classical hexahedral elements for the solution of three-dimensional incompressible fluid flow problems. The proposed elements are created by adding velocity degrees of freedom to the basic trilinear velocity, constant pressure tetrahedron so as to satisfy the Brezzi condition. Numerical tests carried out for an artificial divergence-free flow problem and the lid-driven cubic cavity up to a Reynolds number of 400 are used to compare the proposed elements and assess their accuracy.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 25 (1997), S. 719-736 
    ISSN: 0271-2091
    Keywords: finite element method ; fictitious domain method ; three-dimensional ; internal parts ; incompressible fluid flow ; constrained optimization ; Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: A new Galerkin finite element method for the solution of the Navier-Stokes equations in enclosures containing internal parts which may be moving is presented. Dubbed the virtual finite element method, it is based upon optimization techniques and belongs to the class of fictitious domain methods. Only one volumetric mesh representing the enclosure without its internal parts needs to be generated. These are rather discretized using control points on which kinematic constraints are enforced and introduced into the mathematical formulation by means of Lagrange multipliers. Consequently, the meshing of the computational domain is much easier than with classical finite element approaches.   First, the methodology will be presented in detail. It will then be validated in the case of the two-dimensional Couette cylinder problem for which an analytical solution is available. Finally, the three-dimensional fluid flow inside a mechanically agitated vessel will be investigated. The accuracy of the numerical results will be assessed through a comparison with experimental data and results obtained with a standard finite element method. © 1997 John Wiley & Sons, Ltd.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 13 (1991), S. 1073-1083 
    ISSN: 0271-2091
    Keywords: Crouzeix-Raviart ; Analytical integration ; Brezzi-Babuška condition ; Navier-Stokes ; Finite element method ; Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: A methodology for the decomposition of the Crouzeix-Raviart finite element into six linear subelements is described. The resulting element is shown to satisfy the Brezzi-Babuška compatibility condition. The error bounds are also established. A comparison in accuracy between this and the standard Crouzeix-Raviart element is presented for driven cavity flows. Other results include the execution time for the DCR element and the Crouzeix-Raviart element along with both analytical and numerical integration. It is shown that the decomposed element results in shorter execution times with only marginal changes in accuracy.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Communications in Applied Numerical Methods 4 (1988), S. 213-217 
    ISSN: 0748-8025
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A new graphical representation for fluid flow is explained. It combines the concepts of classical streamline plot and velocity vector display and enables a more adequate visualization of flow pattern, especially near solid boundaries.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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