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With the development of MEMS and CMOS technologies, the implementation of a huge number of wireless distributed micro-sensors that can be simply and rapidly deployed to form highly redundant, self-configuring, and ad hoc sensor networks. Sensor nodes are generally battery- devices, the critical facets to face concern are how to minimize energy consumption of nodes, so that the lifetime of sensing nodes can be maximized. The first step to achieve this goal is to know completely the sources of energy consumption in wireless sensor networks. In this paper, sources of energy consumption at various communication layers have been studied and investigated. Moreover, the energy consumption for the components of a typical sensor node and the impact of communication protocols stack on the energy consumption are discussed. In the sequel, the sources of energy consumption in each communication layer individually are studied. Then, a survey has been provided for existing energy models and the classification of these models into physical layer, MAC layer and cross-layer energy models

Tissue engineering scaffold is a 3D construction that acts as a template for tissue regeneration. The scaffold should have some basic requirements including biocompatibility, suitable mechanical properties, appropriate surface chemistry, high porosity and interconnectivity. Although several conventional techniques such as solvent casting and gas forming are utilized in scaffold fabrication, these processes show poor interconnectivity and uncontrollable porosity of the produced scaffolds. However, Rapid Prototyping (RP) techniques which are a group of advanced manufacturing processes can produce custom made objects directly from computer data such as Computer Aided Design (CAD), Computed Tomography (CT) and Magnetic Resonance Imaging (MRI) data. Using RP fabrication techniques, constructions with controllable and complex internal architecture with appropriate mechanical properties can be achieved.The present chapter intends to provide an overview of the current state of the art in the area of tissue engineering scaffolds fabrication, using advanced RP processes. The present work highlights also the existing limitations in addition to future prospects in scaffold fabrication via RP techniques.