26,133 research outputs found
Modeling of Induced Hydraulically Fractured Wells in Shale Reservoirs Using Branched Fractals
Imperial Users onl
Analogy between turbulence and quantum gravity: beyond Kolmogorov's 1941 theory
Simple arguments based on the general properties of quantum fluctuations have
been recently shown to imply that quantum fluctuations of spacetime obey the
same scaling laws of the velocity fluctuations in a homogeneous incompressible
turbulent flow, as described by Kolmogorov 1941 (K41) scaling theory. Less
noted, however, is the fact that this analogy rules out the possibility of a
fractal quantum spacetime, in contradiction with growing evidence in quantum
gravity research. In this Note, we show that the notion of a fractal quantum
spacetime can be restored by extending the analogy between turbulence and
quantum gravity beyond the realm of K41 theory. In particular, it is shown that
compatibility of a fractal quantum-space time with the recent Horava-Lifshitz
scenario for quantum gravity, implies singular quantum wavefunctions. Finally,
we propose an operational procedure, based on Extended Self-Similarity
techniques, to inspect the (multi)-scaling properties of quantum gravitational
fluctuations.Comment: Sliglty modified version of the article about to appear in IJMP
Structure of interacting aggregates of silica nanoparticles in a polymer matrix: Small-angle scattering and Reverse Monte-Carlo simulations
Reinforcement of elastomers by colloidal nanoparticles is an important
application where microstructure needs to be understood - and if possible
controlled - if one wishes to tune macroscopic mechanical properties. Here the
three-dimensional structure of big aggregates of nanometric silica particles
embedded in a soft polymeric matrix is determined by Small Angle Neutron
Scattering. Experimentally, the crowded environment leading to strong
reinforcement induces a strong interaction between aggregates, which generates
a prominent interaction peak in the scattering. We propose to analyze the total
signal by means of a decomposition in a classical colloidal structure factor
describing aggregate interaction and an aggregate form factor determined by a
Reverse Monte Carlo technique. The result gives new insights in the shape of
aggregates and their complex interaction in elastomers. For comparison, fractal
models for aggregate scattering are also discussed
Recommended from our members
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
- …