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  • 1
    Electronic Resource
    Electronic Resource
    Static analysis of a two-member linkage interacting with a given surface (1999)
    Springer
    Archive of applied mechanics 69 (1999), S. 429-442 
    Details
    ISSN: 1432-0681
    Keywords: Key words statics ; two-member linkage ; Coulomb friction ; robotics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Summary The static interaction of a two-member linkage with a given surface is investigated. Dry friction acts at the point of contact of the linkage with the surface. The linkage has two drives generating torques at its joints. The optimal distribution of the joint torques is determined to maximize the friction force at the point of contact. The dependence of this maximal force on the lengths of the links and on the linkage configuration is investigated. The results obtained can be applied to the analysis and optimization of various robotic systems, in particular, manipulators interacting with rough surfaces and walking machines, especially tube-crawling robots.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004190050232
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  • 2
    Electronic Resource
    Electronic Resource
    Unilateral problems of dynamics (1999)
    Springer
    Archive of applied mechanics 69 (1999), S. 503-527 
    Details
    ISSN: 1432-0681
    Keywords: Key words Unilateral contact ; multibody dynamics ; complementarity ; friction ; impact
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Summary Contact processes may be described by local discretizations, by rigid representation or by mixed methods incorporating both ideas. A rigid body approach is proposed for the dynamics of mechanical systems, achieving good results also for multiple-contact problems. Contacts in multibody systems are mainly considered, with the corresponding contact constraints varying with time, thus generating structure-variant systems. The equations of motion for dynamical systems with such unilateral behavior are discussed, solution methods and applications are presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004190050240
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  • 3
    Electronic Resource
    Electronic Resource
    Dynamics of spatial structure-varying rigid multibody systems (1999)
    Springer
    Archive of applied mechanics 69 (1999), S. 265-285 
    Details
    ISSN: 1432-0681
    Keywords: Key words Multibody system ; contact ; unilateral constraint ; Coulomb friction ; stick-slip ; variational inequality.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Summary Couplings in machines and mechanisms exhibiting backlash and friction phenomena can be modeled as multibody systems with unilateral constraints and Coulomb friction. The structure of the differential-algebraic equations describing the system depends on the state of the constraints. The contact forces occurring at active constraints are taken into account in the equations of motion as Lagrange multipliers. Additionally, the kinematic conditions of all active constraints are formulated on the acceleration level. Contact and friction laws are sufficient conditions for state transitions of active constraints, and are represented by nonsmooth characteristics. Several formulations, like the linear complementarity problem, and two different nonlinear systems of equations are presented together with their solution method. The theory is applied to a mechanical system containing three-dimensional and coupled unilateral constraints with friction.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004190050219
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  • 4
    Electronic Resource
    Electronic Resource
    The principle of virtual work in mechanical and electromechanical systems (1995)
    Springer
    Archive of applied mechanics 65 (1995), S. 390-400 
    Details
    ISSN: 1432-0681
    Keywords: virtual work ; electromechanical systems ; unifying modelling ; constraints ; mechatronics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Summary The principle of virtual work is applied to electromechanical systems as the foundation of a unifying concept for modelling mechatronical systems. After the presentation of an important result in the field of mechanics, the expansion of the principle on electrical networks and electromechanical systems is shown. The use of the principle of virtual work in the domain of electromechanics yields an analogous form to the central equation of mechanics which is valid for holonomic and nonholonomic systems. The electrotechnical part of the system is confined to networks. The derivation of the mathematical model is demonstrated on the example of a simple electromechanical oscillation circuit. In addition, the physical systems are separately treated, taking into account the explicit constraints on the basis of the Lagrangian multiplier method.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00787532
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  • 5
    Electronic Resource
    Electronic Resource
    The complexity of induced minors and related problems (1995)
    Springer
    Algorithmica 13 (1995), S. 266-282 
    Details
    ISSN: 1432-0541
    Keywords: Graph minors ; NP-completeness ; Planar graphs ; Matching problems ; Treewidth
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract The computational complexity of a number of problems concerning induced structures in graphs is studied, and compared with the complexity of corresponding problems concerning non-induced structures. The effect on these problems of restricting the input to planar graphs is also considered. The principal results include: (1) Induced Maximum Matching and Induced Directed Path are NP-complete for planar graphs, (2) for every fixed graphH, InducedH-Minor Testing can be accomplished for planar graphs in time0(n), and (3) there are graphsH for which InducedH-Minor Testing is NP-complete for unrestricted input. Some useful structural theorems concerning induced minors are presented, including a bound on the treewidth of planar graphs that exclude a planar induced minor.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01190507
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  • 6
    Electronic Resource
    Electronic Resource
    Ein Näherungsverfahren für flüssigkeitsgefüllte Kreisel (1974)
    Springer
    Archive of applied mechanics 43 (1974), S. 306-316 
    Details
    ISSN: 1432-0681
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Description / Table of Contents: Summary We consider gyros containing liquid in several completely filled tanks. Averaging the Helmholtz vorticity equations over the liquid volume yields a set of ordinary differential equations with constant coefficients, which describe the problem approximately. The coefficients depend only on a simple boundary value problem. The usefulness of the method is tested by general and numerical comparisons.
    Notes: Übersicht Es werden Kreisel mit vollständig gefüllten Flüssigkeitsbehältern betrachtet. Durch integrale Mittelung der Helmholtzschen Wirbelgleichungen über das Flüssigkeitsvolumen erhält man für das Problem einen Satz gewöhnlicher Differentialgleichungen mit konstanten Koeffizienten, die nur noch von einem einfachen Randwertproblem abhängen. Allgemeine und numerische Vergleiche bestätigen die Brauchbarkeit dieses Näherungsverfahrens.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00537219
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  • 7
    Electronic Resource
    Electronic Resource
    Über die Bewegung eines drehsymmetrischen Kreisels mit beliebig vielen Flüssigkeitsbehältern (1972)
    Springer
    Archive of applied mechanics 41 (1972), S. 329-341 
    Details
    ISSN: 1432-0681
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Description / Table of Contents: Summary The problem of coupling between the nutational oscillation of a gyro containing liquid and the natural oscillation of the rotating liquid itself is investigated for a rotationally symmetric gyro with arbitrarily many rotationally symmetric liquid containers. The linearized equations are treated numerically using the method of Bubnow-Galerkin. The stability of the motion is investigated using the method of residues and the envelopemethod.
    Notes: Übersicht Für einen drehsymmetrischen Kreisel mit beliebig vielen rotationssymmetrischeu Flüssigkeitsbehältern wird das Problem der gekoppelten Nutationsschwingungen des Kreisels und der Eigenschwingungen der rotierenden Flüssigkeiten untersucht. Die zugrunde gelegte linearisierte Theorie wird numerisch mit Hilfe des Verfahrens von Bubnow-Galerkin behandelt. Stabilitätsuntersuchungen werden nach der Residuenmethode und dem Einhüllenden-Verfahren durchgeführt.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00533080
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  • 8
    Electronic Resource
    Electronic Resource
    Über Rasselschwingungen in Kfz-Schaltgetrieben (1986)
    Springer
    Archive of applied mechanics 56 (1986), S. 25-37 
    Details
    ISSN: 1432-0681
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Description / Table of Contents: Summary In gearboxes of motor vehicles all components not being shifted to transmit torque may be excited to perform clattering vibrations. This type of oscillations can be resolved in a more or less stochastic sequence of impacts taking place at the edges of the gear or bearing tolerances. The energy for this impulsive process comes from motor-engine vibrations in connection with a nonlinear behaviour of the clutch. Based on an impulsive theory for multibody systems a method is presented to analyse these clattering vibrations. For optimizing the essential parameters of the system, i.e. excitation form, tolerances, damping, friction, a simulation program is developed. Clattering noise is assumed to be proportional to the energy losses due to impacts at the edges of the plays. Results compare well with practical experiences.
    Notes: Übersicht In Schaltgetrieben für Kraftfahrzeuge führen in allen Gängen diejenigen Schalträder und im Leerlauf oder im direkten Gang auch die Vorgelegewelle innerhalb ihrer Spiele Rasselschwingungen aus, die an der Momentenübertragung nicht beteiligt sind und damit wegen fehlender Verspannung klappern können. Als Erregung für diese durch Stöße verursachten Rasselschwingungen wirkt im wesentlichen die Drehungleichförmigkeit des Antriebsritzels und damit letztlich die zeitliche Schwankung des Motormoments in Verbindung mit der nichtlinearen Kupplungskennlinie. In der vorliegenden Arbeit wird, ausgehend von einer Theorie mechanischer Systeme mit unstetigen Übergängen, ein Verfahren zur praxisnahen Berechnung dieser Rasselschwingungen vorgestellt. In einem Simulationsprogramm lassen Variationen der wesentlichen Parameter, wie etwa der Erregercharakteristik, der Zahn- und Lagerspiele, der Zahn- und Lagerdämpfung sowie der Schleppmomente, Rückschlüsse auf optimale Parameterkombinationen zu. Die leicht zu ermittelnden Energieverluste bei Stößen liefern einen groben Anhaltspunkt für die Rasselgeräusche. Das gewählte Modell entspricht den beobachteten physikalischen Phänomenen.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00533571
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  • 9
    Electronic Resource
    Electronic Resource
    Seltsame Attraktoren in Zahnradgetrieben (1988)
    Springer
    Archive of applied mechanics 58 (1988), S. 113-125 
    Details
    ISSN: 1432-0681
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Description / Table of Contents: Summary Clattering vibrations in gear-boxes may be described as a sequence of impulsive processes [3, 5]. The motion between two impacts during teeth-meshing can be represented analytically. This leads to discrete and invertible mappings for the motion in phase-space. As a result one gets strange attractors or periodical behaviour according to the set of parameters under consideration. Transitions from periodic to chaotic states (and vice versa) are indicated by Ljapunov's exponents. Some parameter influences become visible by applying estimates of the phasespace boundaries. The examples of a one-stage and a two-stage gearing show advantages of the method as compared to usual numerical simulations.
    Notes: Übersicht Rassel- und Klapperschwingungen in Zahnradgetrieben lassen sich als Folgen von Stoßprozessen beschreiben [3, 5]. Dabei kann man die Bewegung von einem Stoß zum nächsten im allgemeinen analytisch darstellen. Dies ermöglicht die Herleitung diskreter und invertierbarer Abbildungsfunktionen und damit eine Darstellung der Bewegung im Phasenraum als eine Art Poincaré-Abbildung. Als Ergebnis erhält man je nach Parametersituation seltsame Attraktoren oder Fixpunkte, die sich verzweigen. Die Übergänge von periodischen zu chaotischen Zuständen und umgekehrt werden vom Verlauf der Ljapunov-Exponenten angezeigt, strukturelle Aussagen werden mit Hilfe von Abschätzungen der Phasenraumgrenzen möglich. Die Anwendungsbeispiele des einstufigen und zweistufigen Stirnradgetriebes zeigen die Vorteile des Verfahrens, insbesondere gegenüber gewöhnlichen numerischen Simulationen.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00536231
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  • 10
    Electronic Resource
    Electronic Resource
    Phytochrome regulation of mRNA levels of ribulose-1,5-bisphosphate carboxylase in etiolated rye seedlings (Secale cereale) (1987)
    Springer
    Plant molecular biology 10 (1987), S. 21-33 
    Details
    ISSN: 1573-5028
    Keywords: mRNA regulation ; phytochrome ; ribulose-1,5-bisphosphate carboxylase ; rye ; transcription
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The effect of red light and far-red light on the appearance of mRNA for the small and large subunit of ribulose-1,5-bisphosphate carboxylase in rye seedlings has been analysed. Irradiation of etiolated seedlings with a pulse of red light increased the mRNA level of the small subunit by a factor of 7–10 and that of the large subunit by a factor of 3. A pulse of far-red light resulted in a much lower, but measurable increase. The effect of red light is reverted by an immediate far-red pulse, demonstrating the classical phytochrome response.In vitro transcription experiments with nuclei isolated from red light-treated seedlings showed that the transcription rate of the small subunit mRNA was increased only by a factor of 1.5–2.5, indicating posttranscriptional as wells as transcriptional regulations of the small subunit of ribulose-1,5-bisphosphate carboxylase.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00014183
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