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This paper presents the development of a bidomain model of electrical defibrillation and post-shock arrhythmogenesis of the rabbit heart. The model incorporates a realistic representation of cardiac geometry, fiber structure, and membrane ionic processes. Fibrillation is induced in the rabbit heart with burst pacing. Defibrillation shocks of various strengths are delivered to the model in an attempt to terminate the arrhythmia. Two sets of defibrillation simulations are conducted based on the waveform of the defibrillation shock: monophasic and biphasic. The simulations presented here demonstrate the feasibility of modeling realistically the effect of the defibrillation shock on the heart.

In short-fiber composites (SFCs), fiber length distribution (FLD) is complicated and has a considerable impact on the mechanical properties of SFCs. This work proposes a fractal FLD in SFCs on the basis of the fractal theory, and develops a multi-step mean-field homogenization (MSMFH) method to accurately and efficiently predict the mechanical properties of SFCs with fractal FLD. In the developed MSMFH method, SFCs are first decomposed into virtual pseudo-grains (PGs) according to fiber orientation distribution (FOD), followed the further division of the PGs into virtual sub-pseudo-grains (SPGs) according to FLD. The Mori–Tanaka or Double-Inclusion model is adopted to homogenize the mechanical properties of each SPG in the first step, and the Voigt model is implemented to homogenize the mechanical properties of all the SPGs and the PGs, respectively, in the sequential steps. Fiber length and orientation averaging algorithms for the developed MSMFH method are detailed. The developed MSMFH method and the proposed fractal FLD are validated to accurately predict the mechanical properties of SFCs by the means of the comparison with the FE method and the available experimental tests.

Steel fiber-reinforced self-compacting concrete (SCFRC) has been developed in recent decades to overcome the weak tensile performance of traditional concretes. As the flexural strength of SCFRC is dependent on the distribution of steel fibers, a numerical model based on Jeffery’s equation was developed in this study for investigating the effects of the concrete flow on the fiber orientation and distribution in SCFRC. This numerical method shows higher computational efficiency than available particle-based methods like SPH and LBM. The influence of casting parameters like casting method, formwork size and casting velocity on the fiber orientation is investigated from the perspective of the flow field of fresh concrete during casting. The simulation results show that the fiber orientation is largely dominated by the concrete flow during the casting process. Importantly, during casting SCFRC beam, fibers tend to be oriented in parallel along the longitudinal direction at the middle section, while they stick up at the end of the formwork due to the upward concrete flow. In addition, the results from parametric studies show that the formwork size and casting method could significantly affect the concrete flow during the casting process, ultimately the orientation of fibers in a SCFRC beam. Furthermore, it indicates that the casting speed needs to be carefully chosen in order to achieve the optimal fiber alignment.