Delivering Bio-Mems & Microfluidic Education Around Accessible Technologies

Electronic Systems are now being deployed in al-most all aspects of daily life as opposed to being confined to consumer electronics, computing, communication and control applications as was the case in the 90’s. One of the more significant growth areas is medical instrumentation, health care, bio-chemical analysis and environmental monitoring. Most of these applications will in the future require the integration of fluidics and biology within complex electronic systems. We are now seeing technologies emerging together with access services such as the FP6 “INTEGRAMplus” and “MicroBuilder” programs that offer competitive solutions for companies wishing to de-sign and prototype microfluidic systems. For successful deployment of these systems, a new breed of electronic engineers are needed that understand how to deliver bio-chemistry and living cells to transducers and integrate the required technologies reliably into robust systems. This paper will report on initial training initiatives now active under the INTEGRAMplus program

Time-Domain Isolated Phoneme Classification Using Reconstructed Phase Spaces

This paper introduces a novel time-domain approach to modeling and classifying speech phoneme waveforms. The approach is based on statistical models of reconstructed phase spaces, which offer significant theoretical benefits as representations that are known to be topologically equivalent to the state dynamics of the underlying production system. The lag and dimension parameters of the reconstruction process for speech are examined in detail, comparing common estimation heuristics for these parameters with corresponding maximum likelihood recognition accuracy over the TIMIT data set. Overall accuracies are compared with a Mel-frequency cepstral baseline system across five different phonetic classes within TIMIT, and a composite classifier using both cepstral and phase space features is developed. Results indicate that although the accuracy of the phase space approach by itself is still currently below that of baseline cepstral methods, a combined approach is capable of increasing speaker independent phoneme accuracy

Spray Layer-by-Layer Assembled Clay Composite Thin Films as Selective Layers in Reverse Osmosis Membranes

Spray layer-by-layer assembled thin films containing laponite (LAP) clay exhibit effective salt barrier and water permeability properties when applied as selective layers in reverse osmosis (RO) membranes. Negatively charged LAP platelets were layered with poly(diallyldimethylammonium) (PDAC), poly(allylamine) (PAH), and poly(acrylic acid) (PAA) in bilayer and tetralayer film architectures to generate uniform films on the order of 100 nm thick that bridge a porous poly(ether sulfone) support to form novel RO membranes. Nanostructures were formed of clay layers intercalated in a polymeric matrix that introduced size-exclusion transport mechanisms into the selective layer. Thermal cross-linking of the polymeric matrix was used to increase the mechanical stability of the films and improve salt rejection by constraining swelling during operation. Maximum salt rejection of 89% was observed for the tetralayer film architecture, with an order of magnitude increase in water permeability compared to commercially available TFC-HR membranes. These clay composite thin films could serve as a high-flux alternative to current polymeric RO membranes for wastewater and brackish water treatment as well as potentially for forward osmosis applications. In general, we illustrate that by investigating the composite systems accessed using alternating layer-by-layer assembly in conjunction with complementary covalent cross-linking, it is possible to design thin film membranes with tunable transport properties for water purification applications.Center for Clean Water and Clean Energy at MIT and KFUPM (project R5-CW-08

Compressive strength of delaminated aerospace composites

An efficient analytical model is described which predicts the value of compressive strain below which buckle-driven propagation of delaminations in aerospace composites will not occur. An extension of this efficient strip model which accounts for propagation transverse to the direction of applied compression is derived. In order to provide validation for the strip model a number of laminates were artificially delaminated producing a range of thin anisotropic sub-laminates made up of 0°, ±45° and 90° plies that displayed varied buckling and delamination propagation phenomena. These laminates were subsequently subject to experimental compression testing and nonlinear finite element analysis (FEA) using cohesive elements. Comparison of strip model results with those from experiments indicates that the model can conservatively predict the strain at which propagation occurs to within 10 per cent of experimental values provided (i) the thin-film assumption made in the modelling methodology holds and (ii) full elastic coupling effects do not play a significant role in the post-buckling of the sub-laminate. With such provision, the model was more accurate and produced fewer non-conservative results than FEA. The accuracy and efficiency of the model make it well suited to application in optimum ply-stacking algorithms to maximize laminate strength.</jats:p

On positivity of Ehrhart polynomials

Ehrhart discovered that the function that counts the number of lattice points in dilations of an integral polytope is a polynomial. We call the coefficients of this polynomial Ehrhart coefficients, and say a polytope is Ehrhart positive if all Ehrhart coefficients are positive (which is not true for all integral polytopes). The main purpose of this article is to survey interesting families of polytopes that are known to be Ehrhart positive and discuss the reasons from which their Ehrhart positivity follows. We also include examples of polytopes that have negative Ehrhart coefficients and polytopes that are conjectured to be Ehrhart positive, as well as pose a few relevant questions.Comment: 40 pages, 7 figures. To appear in in Recent Trends in Algebraic Combinatorics, a volume of the Association for Women in Mathematics Series, Springer International Publishin

Non-linear finite-element analysis of axially loaded piles driven in chalk

Driven piles are often employed to support onshore and offshore structures at low-density, porous weak carbonate chalk sites, which are encountered across Northern Europe and under the North and Baltic seas. Their efficient design is limited by uncertainties regarding their ultimate axial capacity and load-displacement behaviour. Intensive axial testing has been under- taken recently for the ALPACA Joint Industry Project on piles driven at a UK chalk site, in conjunction with comprehensive chalk characterisation studies. This paper presents PLAXIS-2D numerical simulations of such piles' axial loading behaviour. The simulation accounts for three distinct zones of chalk identified around the pile shafts after installation. These comprise a thin annular zone of de-structured, puttified, chalk and a second, thicker, annular zone of highly fractured chalk; both have different mechanical properties compared to the surrounding parent intact chalk mass. The FE analyses investigate how shaft resistance, axial capacity and load-displacement behaviour develop differently in compression and tension tests