Perfect sampling for multiclass closed queueing networks

International audienceIn this paper we present an exact sampling method for multiclass closed queuing networks. We consider networks for which stationary distribution does not necessarily have a product form. The proposed method uses a compact representation of sets of states, that is used to derive a bounding chain with significantly lower complexity of one-step transition in the coupling from the past scheme. The coupling time of this bounding chain can be larger than the coupling time of the exact chain, but it is finite in expectation. Numerical experiments show that coupling time is close to that of the exact chain. Moreover, the running time of the proposed algorithm outperforms the classical algorithm

Ultrasound technology for examining the mechanics of the muscle, tendon, and ligament

Ultrasound imaging provides a means to look inside the body and examine how tissues respond to mechanical stress or muscle contraction. As such, it can provide a valuable tool for understanding how muscle, tendon, and ligament mechanics influence the way we move, or vice versa, in health and disease, or to understand how and why these tissues might get injured due to chronic or acute loading. This chapter explores the basic concepts of ultrasound and how it can be used to examine muscle, tendon, and ligament structure and mechanical function. It introduces different techniques, like conventional B-mode imaging, threedimensional ultrasound, and various forms of elastography that can be used to quantify geometrical and mechanical properties of the muscle, tendon, and ligament. Furthermore, methods to quantify muscle and tendon mechanical function during dynamic human movement are explored, and recommendations provided on which techniques are most suitable for different biomechanical investigations. Finally, some predictions about how new ultrasound imaging technologies might continue to advance our understanding of human motion are proposed and explored