Layered Fabrication of Branched Networks Using Lindenmayer Systems

A current challenge impeding the growth of bone tissue engineering is the lack of functional scaffolds of geometric sizes greater than 10mm due to the inability of cells to survive deep within the scaffold. It is hypothesized that these scaffolds must have an inbuilt nutrient distribution network to sustain the uniform growth of cells. In this paper, we seek to enhance the design and layered fabrication of scaffold internal architecture through the development of Lindenmayer systems, a graphical language based theory to create nutrient delivery networks. The scaffolds are fabricated using the Texas Instruments DLP™ system through UV‐photopolymerization to produce polyethylene glycol hydrogels with internal branch structures. The paper will discuss the Lindenmayer system, process planning algorithms, layered fabrication of samples, challenges and future tasks.Mechanical Engineerin

A survey of parallel algorithms for fractal image compression

This paper presents a short survey of the key research work that has been undertaken in the application of parallel algorithms for Fractal image compression. The interest in fractal image compression techniques stems from their ability to achieve high compression ratios whilst maintaining a very high quality in the reconstructed image. The main drawback of this compression method is the very high computational cost that is associated with the encoding phase. Consequently, there has been significant interest in exploiting parallel computing architectures in order to speed up this phase, whilst still maintaining the advantageous features of the approach. This paper presents a brief introduction to fractal image compression, including the iterated function system theory upon which it is based, and then reviews the different techniques that have been, and can be, applied in order to parallelize the compression algorithm

Analysis of ultrasonic transducers with fractal architecture

Ultrasonic transducers composed of a periodic piezoelectric composite are generally accepted as the design of choice in many applications. Their architecture is normally very regular and this is due to manufacturing constraints rather than performance optimisation. Many of these manufacturing restrictions no longer hold due to new production methods such as computer controlled, laser cutting, and so there is now freedom to investigate new types of geometry. In this paper, the plane wave expansion model is utilised to investigate the behaviour of a transducer with a self-similar architecture. The Cantor set is utilised to design a 2-2 conguration, and a 1-3 conguration is investigated with a Sierpinski Carpet geometry

Fractal patterns in fractionated spacecraft

Multi spacecraft architectures have been addressed in response to the demand for flexible architectures with high reliability and reduced costs compared to traditional monolithic spacecraft. A task that can be easily carried out by this kind of systems is the deployment of distributed antennas; these are composed of, typically, receiving elements carried on-board multiple spacecraft in precise formation. In this paper decentralised control means, based on artificial potential functions, together with a fractal-like connection network, are used to produce the autonomous and verifiable deployment and formation control of a swarm of spacecraft into a fractal-like pattern. The effect of using fractal-like routing of control data within the spacecraft generates complex formation shape patterns, while simultaneously reducing the amount of control information required to form such complex formation shapes. Furthermore, the techniques used ensure against swarm fragmentation, while exploiting communication channels anyway needed in a fractionated architecture. In particular, the superposition of potential functions operating at multiple levels (single agents, subgroups of agents, groups of agents) according to a self-similar adjacency matrix produces a fractal-like final deployment with the same stability property on each scale. Considering future high-precision formation flying and control capabilities, this paper considers, for the first time and as an example of a fractionated spacecraft, a decentralised multi-spacecraft fractal shaped antenna. A fractal antenna pattern provides multiple resonance peaks, directly related to the ratios of its characteristic physical lengths. Such a scenario would significantly improve the level of functionality of any multi-spacecraft synthetic aperture antenna system. Furthermore, multi-spacecraft architecture exploiting particular inter agent spacing can be considered to investigate multi-scale phenomena in areas such as cosmic radiation and space plasma physics. Both numerical simulations and analytic treatment are carried out demonstrating the feasibility of deploying and controlling a fractionated fractal antenna in space through autonomous decentralised means