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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science Ltd
    Journal of oral rehabilitation 32 (2005), S. 0 
    ISSN: 1365-2842
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: summary  The aim of this study was to investigate (i) whether the masseter muscle shows differential activation under experimental conditions which simulate force generation during clenching and grinding activities; and (ii) whether there are (a) preferentially active muscle regions or (b) force directions which show enhanced muscle activation. To answer these questions, the electromyographic (EMG) activity of the right masseter muscle was recorded with five intramuscular electrodes placed in two deep muscle areas and in three surface regions. Intraoral force transfer and force measurement were achieved by a central bearing pin device equipped with three strain gauges (SG). The activity distribution in the muscle was recorded in four different mandibular positions (central, left, right, anterior). In each position, maximum voluntary contraction (MVC) was exerted in vertical, posterior, anterior, medial and lateral directions. The investigated muscle regions showed different amount of EMG activity. The relative intensity of the activation, with respect to other regions, changed depending on the task. In other words, the muscle regions demonstrated heterogeneous changes of the EMG pattern for the various motor tasks. The resultant force vectors demonstrated similar amounts in all horizontal bite directions. Protrusive force directions revealed the highest relative activation of the masseter muscle. The posterior deep muscle region seemed to be the most active compartment during the different motor tasks. The results indicate a heterogeneous activation of the masseter muscle under test conditions simulating force generation during clenching and grinding. Protrusively directed bite forces were accompanied by the highest activation in the muscle, with the posterior deep region as the most active area.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Zeitschrift für angewandte Mathematik und Physik 37 (1986), S. 150-154 
    ISSN: 1420-9039
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Physics
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Zeitschrift für angewandte Mathematik und Physik 32 (1981), S. 570-581 
    ISSN: 1420-9039
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Physics
    Description / Table of Contents: Zusammenfassung Experimente haben gezeigt, daß die Ausbreitungsrichtung symmetrisch belasteter Risse instabil werden kann. Unter bestimmten Umständen ist dies bei Balken unter Biegung der Fall. Die vorliegende Arbeit befaßt sich mit der Erklärung dieses Phänomens. Mit der Hypothese, daß der Riß sich in die Richtung des maximalen Verlustes an potentieller Energie ausbreitet, wurde ein Stabilitätskriterium für die Rißrichtung gewonnen. Damit konnte gezeigt werden, daß die Richtungsstabilität hauptsächlich von der longitudinalen Druckkraft beeinflußt wird, welche beim spröden Bruch unter Biegung dynamisch erzeugt wird, und daß die Richtungsinstabilität nur im letzten Viertel der Balkendicke auftreten kann.
    Notes: Abstract It has been observed experimentally, that the path of a crack in a brittle beam under bending sometimes becomes unstable. In order to explain this phenomenon a criterion for path-stability is developed, which is based on the hypothesis that the crack will propagate in the direction of maximum loss of potential energy. With this criterion it is shown theoretically and confirmed experimentally that path-instability depends on the amount of the longitudinal compressive stress-resultant, which is generated during brittle fracture, and that path-instability of the crack can only occur in the last quarter of its way.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Mathematische Annalen 268 (1984), S. 379-385 
    ISSN: 1432-1807
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Experimental mechanics 37 (1997), S. 272-277 
    ISSN: 1741-2765
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract An experimental method is presented that enables stress intensity factors due to residual stress to be determined directly, without prior determination of the residual stress. The method is based on the crack compliance method, where a narrow cut is introduced progressively into the considered component, and the resulting strain change is measured by a strain gage. The required mathematical relations to determine stress intensity factors from strain measurements are established by means of some basic relations of linear elastic fracture mechanics. They are derived explicitly for two exemplary geometrical systems, which allowed for analytical treatment. Experimental data obtained in the case of a steel roller are presented and discussed.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    International journal of fracture 25 (1984), S. 95-107 
    ISSN: 1573-2673
    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: Résumé On discute de recherches théoriques sur le chemin parcouru par une fissure produite par l'application à une poutre élastique d'un moment statique de flexion suffisamment grand. Les observations expérimentales ont établi que ce dernier, en général, ne correspond pas à la plus courte distance dans la poutre, à savoir une ligne droite, perpendiculaire à son axe. Le plus souvent, lorsque la fissure s'approche de la face opposée à celle de son démarrage, son chemin s'incurve et se développe parallèlement à l'axe de la poutre. On peut expliquer par la théorie deux aspects de ce comportement: d'une part, la déviation originelle de la ligne droite, qui est à l'évidence un problème de stabilité du parcours, et, d'autre part, la possibilité pour la fissure de se propager ensuite plus ou moins perpendiculairement à la direction initiale. La stabilité du parcours de la fissure est discutée à l'aide d'un critère établi par un calcul de la direction dans laquelle l'énergie libérée passe par un maximum au cours de la propagation de la fissure. Le stade ultérieur de propagation dans la direction parallèle à l'axe de la poutre est discuté par application du critère standard de propagation basé sur la contrainte maximum de membrane.
    Notes: Abstract This paper discusses some theoretical investigations of the path followed by a crack which is produced by applying a sufficiently large static bending moment to an elastic beam. It has been observed experimentally that this path does not, in general, correspond to the shortest distance across the beam, i.e. a straight line perpendicular to the beam axis. Quite often as the path approaches the opposite face of the beam it turns and runs almost parallel to the beam axis. Two aspects of this behavior are theoretically explained: first the initial deviation from the straight line, which obviously is a problem of path-stability, and second the ability of the crack to propagate afterwards more or less perpendicular to the initial direction. Path-stability is discussed by a criterion resulting from a calculation of the direction of maximum released energy during crack-propagation. The subsequent stage of crack-propagation in axial direction is discussed by applying the standard propagation criterion of maximum hoop-stress.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    International journal of fracture 74 (1990), S. R23 
    ISSN: 1573-2673
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    International journal of fracture 82 (1990), S. R3 
    ISSN: 1573-2673
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
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