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Extension fractures are typical for the deformation under low or no confining pressure. They can be explained by a phenomenological extension strain failure criterion. In the past, a simple empirical criterion for fracture initiation in brittle rock has been developed. In this article, it is shown that the simple extension strain criterion makes unrealistic strength predictions in biaxial compression and tension. To overcome this major limitation, a new extension strain criterion is proposed by adding a weighted principal shear component to the simple criterion. The shear weight is chosen, such that the enriched extension strain criterion represents the same failure surface as the Mohr–Coulomb (MC) criterion. Thus, the MC criterion has been derived as an extension strain criterion predicting extension failure modes, which are unexpected in the classical understanding of the failure of cohesive-frictional materials. In progressive damage of rock, the most likely fracture direction is orthogonal to the maximum extension strain leading to dilatancy. The enriched extension strain criterion is proposed as a threshold surface for crack initiation CI and crack damage CD and as a failure surface at peak stress CP. Different from compressive loading, tensile loading requires only a limited number of critical cracks to cause failure. Therefore, for tensile stresses, the failure criteria must be modified somehow, possibly by a cut-off corresponding to the CI stress. Examples show that the enriched extension strain criterion predicts much lower volumes of damaged rock mass compared to the simple extension strain criterion.
„Smartes“ Laden an öffentlich zugänglichen Ladesäulen – Teil 2: USER-Verhalten und -Erwartungen
(2021)
Achilles tendon rupture (ATR) patients have persistent functional deficits in the triceps surae muscle–tendon unit (MTU). The complex remodeling of the MTU accompanying these deficits remains poorly understood. The purpose of the present study was to associate in vivo and in silico data to investigate the relations between changes inMTU properties and strength deficits inATR patients. Methods: Elevenmale subjects who had undergone surgical repair of complete unilateral ATR were examined 4.6 ± 2.0 (mean ± SD) yr after rupture. Gastrocnemius medialis (GM) tendon stiffness, morphology, and muscle architecture were determined using ultrasonography. The force–length relation of the plantar flexor muscles was assessed at five ankle joint angles. In addition, simulations (OpenSim) of the GM MTU force–length properties were performed with various iterations of MTU properties found between the unaffected and the affected side. Results: The affected side of the patients displayed a longer, larger, and stiffer GM tendon (13% ± 10%, 105% ± 28%, and 54% ± 24%, respectively) compared with the unaffected side. The GM muscle fascicles of the affected side were shorter (32% ± 12%) and with greater pennation angles (31% ± 26%). A mean deficit in plantarflexion moment of 31% ± 10% was measured. Simulations indicate that pairing an intact muscle with a longer tendon shifts the optimal angular range of peak force outside physiological angular ranges, whereas the shorter muscle fascicles and tendon stiffening seen in the affected side decrease this shift, albeit incompletely. Conclusions: These results suggest that the substantial changes in MTU properties found in ATR patients may partly result from compensatory remodeling, although this process appears insufficient to fully restore muscle function.
Eigenkapitalkosten sind eine wesentliche Determinante bei der Wertbestimmung von Unternehmen und Unternehmensteilen. Die Eigenkapitalkosten werden regelmäßig mittels des CAPM bestimmt. Für sog. konzerninterne Routinefunktionen mit geringem Risiko stellt diese Bestimmung mittels CAPM ein Problem dar, da börsennotierte Peergroups für eine zuverlässige Bestimmung des Beta-Faktors meist nicht identifizierbar sind. Damit ergeben sich bei Bewertungen von Routineunternehmen Unsicherheiten und Konfliktpotenzial in steuerlichen Betriebsprüfungen. Dieser Beitrag gibt einen Überblick der in der Praxis genutzten Ansätze und stellt eine theoretische Fundierung zur Bestimmung der Eigenkapitalkosten von konzerninternen Routinefunktionen vor. Dabei wird verdeutlicht, dass Eigenkapitalkosten von konzerninternen Routinefunktionen nicht denen des Gesamtkonzerns entsprechen und Praktikeransätze eine grundsätzliche Berechtigung besitzen.