2,102 research outputs found
Exploiting the Design Freedom of RM
This paper details how Rapid Manufacturing (RM) can overcome the restrictions imposed by the
inherent process limitations of conventional manufacturing techniques and become the enabling
technology in fabricating optimal products. A new design methodology capable of exploiting
RM’s increased design freedom is therefore needed. Inspired by natural world structures of trees
and bones, a multi-objective, genetic algorithm based topology optimisation approach is
presented. This combines multiple unit cell structures and varying volume fractions to create a
heterogeneous part structure which exhibits a uniform stress distribution.Mechanical Engineerin
Statistical physics of cerebral embolization leading to stroke
We discuss the physics of embolic stroke using a minimal model of emboli
moving through the cerebral arteries. Our model of the blood flow network
consists of a bifurcating tree, into which we introduce particles (emboli) that
halt flow on reaching a node of similar size. Flow is weighted away from
blocked arteries, inducing an effective interaction between emboli. We justify
the form of the flow weighting using a steady flow (Poiseuille) analysis and a
more complicated nonlinear analysis. We discuss free flowing and heavily
congested limits and examine the transition from free flow to congestion using
numerics. The correlation time is found to increase significantly at a critical
value, and a finite size scaling is carried out. An order parameter for
non-equilibrium critical behavior is identified as the overlap of blockages'
flow shadows. Our work shows embolic stroke to be a feature of the cerebral
blood flow network on the verge of a phase transition.Comment: 11 pages, 11 figures. Major rewrite including improved justification
of the model and a finite size scalin
Recommended from our members
Analysis of Droplet Train/Moving Substrate Interactions in Ink-Jetting Processes
Ink-jetting technology has been applied to several processes in solid free-form
fabrication (SFF) wherein droplets impinge onto a substrate to deposit the build material.
Droplet impact behaviour on a surface has been the interest of many researchers; however,
few studies have been undertaken to investigate the interaction of droplets with the moving
substrate. This paper reports the impact behaviour of the droplets jetted at different
frequencies onto a substrate moving over a range of velocities. The phenomena associated
with the interaction were classified into three main regimes.Mechanical Engineerin
Magnetic circular dichroism in X-ray fluorescence of Heusler alloys at threshold excitation
The results of fluorescence measurements of magnetic circular dichroism (MCD)
in Mn L_2,L_3 X-ray emission and absorption for Heusler alloys NiMnSb and
Co2MnSb are presented. Very intense resonance Mn L_3 emission is found at the
Mn 2p_3/2 threshold and is attributed to a peculiarity of the threshold
excitation in materials with the half-metallic character of the electronic
structure. A theoretical model for the description of resonance scattering of
polarized x-rays is suggested.Comment: 3 pages, 2 figures. Discussed at conferences, submitting process in
progres
Highly sensitive alkane odour sensors based on functionalised gold nanoparticles
We deposit dense, ordered, thin films of Au-dodecanethiol core/shell nanoparticles by the Langmuir-Schafer (LS) printing method, and find that their resistance at ambient temperature responds selectively and sensitively to alkane odours. Response is a rapid resistance increase due to swelling, and is strongest for alkane odours where the alkane chain is similar in length to the dodecane shell. For decane odours, we find a response to concentrations as low as 15 ppm, about 600 times below the lower explosive limit. Response is weaker, but still significant, to aromatic odours (e.g. Toluene, Xylene), while potential interferants such as polar and/or hydrogen-bonding odours (e.g. alcohols, ketones, water vapour) are somewhat rejected. Resistance is weakly dependent on temperature, and recovers rapidly and completely to its original value within the error margin of measurement. (C) 2011 Elsevier B.V. All rights reserved
Recommended from our members
Rapid Manufactured Textiles
Rapid Manufacturing (RM) is increasingly becoming a viable manufacturing process due
to dramatic advantages that are achievable in the area of design complexity. Through the
exploration of the design freedom, this paper introduces the concept of manufacturing textiles for
potential smart and high performance textile applications. This paper discusses the current
limitations associated with the manufacture of textiles through RM and presents a novel
methodology for the generation of 3D conformal RM textile articles. The paper concludes that
through RM it is entirely possible to manufacture a structure that incorporates drape and free
movement properties directly comparable to conventional textiles.Mechanical Engineerin
An electrical characterisation system for the real-time acquisition of multiple independent sensing parameters from organic thin film transistors
The presence of multiple independent sensing parameters in a single device is the key conceptual
advantage of sensor devices based on an organic thin film transistor (OTFT) over simple organic chemiresistors.
Practically, however, these multiple parameters must first be extracted from the electrical characteristics of the
OTFTs and, thus, they are not immediately apparent. To exploit the advantage of OTFT sensors, we require a
measurement technology to extract these parameters in real time. Here, we introduce an efficient, cost-effective
system that is a faster and more compact alternative to the expensive and cumbersome laboratory-based instruments
currently available. The characterisation system presented here records the electric behaviour of OTFTs
in the form of its “saturated transfer characteristics” multiple times per second for virtually unlimited periods
of time, with the option to multiplex up to 20 devices in parallel. By applying a bespoke algorithm to the measured
transfer characteristics, the system then extracts, in real time, several underlying transistor parameters
(on- and off-current, threshold voltage, and charge carrier mobility). Tests were conducted on the example of
a poly(thieno[3,2-b]thiophene) (PBTTT) OTFT exposed to ethanol vapour. The system extracts the underlying
OTFT parameters with very low noise without introducing apparent correlations between independent parameters
as an artefact
- …