Soft-lithographic processed soluble micropatterns of reduced graphene oxide for wafer-scale thin film transistors and gas sensors

PDMS based imprinting is firstly developed for patterning of rGO on a large area. High quality stripe and square shaped rGO patterns are obtained and the electrical properties of the rGO film can be adjusted by the concentration of GO suspension. The arrays of rGO electronics are fabricated from the patterned film by a simple shadow mask method. Gas sensors, which are based on these rGO electronics, show high sensitivity and recyclable usage in sensing NH 3. © 2012 The Royal Society of Chemistry.

Faecal pellets in deep marine soft clay crusts: Implications for hot-oil pipeline design

In recent years, the presence of crusts within near surface sediments found in deep water locations off the west coast of Angola has been of interest to hot-oil pipeline designers. The origin for these crusts is considered to be of biological origin, based on the observation of thousands of faecal pellets in natural crust core samples. This paper presents the results of laboratory tests undertaken on natural and faecal pellet-only samples. These tests investigate the role faecal pellets play in modifying the gemechanical behaviour of clayey sediments. It is found that faecal pellets are able to significantly alter both the strength and the average grain-size of natural sediments, and therefore, influence the permeability and stiffness. Hot-oil pipelines self-embed into and subsequent shear on crusts containing faecal pellets. Being able to predict the time required for installed pipelines to consolidate the underlying sediment and thus, how soon after pipe-laying, the interface strength will develop is of great interest to pipeline designers. It is concluded from wet-sieving samples before and after oedometer tests, that the process of pipe laying is unlikely to destroy pellets. They will therefore, be a major constituent of the sediment subject to soil-pipeline shearing behaviour during axial pipe-walking and lateral buckling. Based on the presented results, a discussion highlighting the key implications for pipeline design is therefore provided. Copyright © 2011 by ASME.

Case study on a deep excavation in soft ground by centrifuge model tests

This paper provides a case study on the deepest excavation carried out so far in the construction of the metro network in Shanghai, which typically features soft ground. The excavation is 38 m deep with retaining walls 65 m deep braced by 9 levels of concrete props. To obtain a quick and rough prediction, two centrifuge model tests were conducted, in which one is for the 'standard' section with green field surrounding and the other with an adjacent piled building. The tests were carried out in a run-stop-excavation-run style, in which excavation was conducted manually. By analyzing the lateral wall displacement, ground deformation, bending moment and earth pressure, the test results are shown to be reasonably convincing and the design and construction were validated. Such industry orientated centrifuge modeling was shown to be useful in understanding the performance of geotechnical processes, especially when engineers lack relevant field experience. © 2010 Taylor & Francis Group, London.

Seismically-induced displacements of a suction caisson in soft clay

The seismic design for offshore foundations is based predominantly on experience onshore. This paper describes the results of dynamic centrifuge tests performed to validate the performance of a suction caisson installed in normally consolidated clay. The main objective is to evaluate the likely plastic displacement under different shaking levels. Permanent displacement results indicate that the displacements experienced are well within the allowable movement for the foundation considered, even though a strength based design approach would consider this to be a failure. Larger earthquakes are seen to produce comparatively smaller displacements. It is concluded that the when designing for seismic loading, if some displacement is permissible then a performance-based approach allowing some displacement proves significantly less conservative than a purely strength-based design. It is also concluded that dynamic response analyses should consider the strength of soil, as this can act as a fuse against large amplitude shear waves. © 2011 Taylor & Francis Group, London.

The soft impact of composite sandwich beams with a square-honeycomb core

The dynamic response of end-clamped monolithic beams and sandwich beams of equal areal mass have been measured by loading the beams at mid-span with metal foam projectiles to simulate localised blast loading. The sandwich beams were made from carbon fibre laminate and comprised identical face sheets and a square-honeycomb core. The transient deflection of the beams was determined as a function of projectile momentum, and the measured response was compared with finite element simulations based upon a damage mechanics approach. A range of failure modes were observed in the sandwich beams including core fracture, plug-type shear failure of the core, debonding of the face sheets from the core and tensile tearing of the face sheets at the supports. In contrast, the monolithic beams failed by a combination of delamination of the plies and tensile failure at the supports. The finite element simulations of the beam response were accurate provided the carbon fibre properties were endowed with rate sensitivity of damage growth. The relative performance of monolithic and sandwich beams were quantified by the maximum transverse deflection at mid-span for a given projectile momentum. It was found that the sandwich beams outperformed both monolithic composite beams and steel sandwich beams with a square-honeycomb core. However, the composite beams failed catastrophically at a lower projectile impulse than the steel beams due to the lower ductility of the composite material. © 2011 Elsevier Ltd. All rights reserved.

Performing quantitative MFM measurements on soft magnetic nanostructures.

We have extended our previous work (Rawlings et al 2010 Phys. Rev. B 82 085404) on simulating magnetic force microscopy (MFM) images for magnetically soft samples to include an accurate representation of coated MFM tips. We used an array of square 500 nm nanomagnets to evaluate our improved MFM model. A quantitative comparison between model and experiment was performed for lift heights ranging from 20 to 100 nm. No fitting parameters were used in our comparison. For all lift heights the qualitative agreement between model and experiment was significantly improved. At low lift heights, where the magnetic signal was strong, the difference between theory and experiment was less than 30%.

Understanding ground deformation mechanisms during multi-propped excavation in soft clay

To maximize the utility of high land cost in urban development, underground space is commonly exploited, both to reduce the load acting on the ground and to increase the space available. The execution of underground constructions requires the use of appropriate retaining wall and bracing systems. Inadequate support systems have always been a major concern, as any excessive ground movement induced during excavation could cause damage to neighboring structures, resulting in delays, disputes and cost overruns. Experimental findings on the effect of wall stiffness, depth of the stiff stratum away from the wall toe and wall toe fixity condition are presented and discussed. © 2012 Taylor & Francis Group.

Direct-write conductive fibres for soft electronics

We report the use of near-field electrospinning (NFES) as a route to fabricate composite electrodes. Electrodes made of composite fibers of carbon nanotubes in polyethylene oxide (PEO) are formed via liquid deposition, with precise control over their configuration. The electromechanical properties of free-standing fibers and fibers deposited on elastic substrates are studied in detail. We then examine the elastic deformation limit of the resulting free-standing fibers and find, similarly to bulk PEO composites, that the plastic deformation onset is below 2% of tensile strain. In comparison, the apparent deformation limit is much improved when the fibers are integrated onto a stretchable, elastic substrate. It is hoped that the NFES fabrication protocol presented here can provide a platform to direct-write polymeric electrodes, and to integrate both stiff and soft electrodes onto a variety of polymeric substrates. © 2012 IEEE.

The most persistent soft-clique in a set of sampled graphs

When searching for characteristic subpatterns in potentially noisy graph data, it appears self-evident that having multiple observations would be better than having just one. However, it turns out that the inconsistencies introduced when different graph instances have different edge sets pose a serious challenge. In this work we address this challenge for the problem of finding maximum weighted cliques. We introduce the concept of most persistent soft-clique. This is subset of vertices, that 1) is almost fully or at least densely connected, 2) occurs in all or almost all graph instances, and 3) has the maximum weight. We present a measure of clique-ness, that essentially counts the number of edge missing to make a subset of vertices into a clique. With this measure, we show that the problem of finding the most persistent soft-clique problem can be cast either as: a) a max-min two person game optimization problem, or b) a min-min soft margin optimization problem. Both formulations lead to the same solution when using a partial Lagrangian method to solve the optimization problems. By experiments on synthetic data and on real social network data we show that the proposed method is able to reliably find soft cliques in graph data, even if that is distorted by random noise or unreliable observations. Copyright 2012 by the author(s)/owner(s).

Market-pull and technology-push in manufacturing start-ups in emerging industries

Purpose - As traditional manufacturing, previously vital to the UK economy, is increasingly outsourced to lower-cost locations, policy makers seek leadership in emerging industries by encouraging innovative start-up firms to pursue competitive opportunities. Emerging industries can either be those where a technology exists but the corresponding downstream value chain is unclear, or a new technology may subvert the existing value chain to satisfy existing customer needs. Hence, this area shows evidence of both technology-push and market-pull forces. The purpose of this paper is to focus on market-pull and technology-push orientations in manufacturing ventures, specifically examining how and why this orientation shifts during the firm's formative years. Design/methodology/approach - A multiple case study approach of 25 UK start-ups in emerging industries is used to examine this seldom explored area. The authors offer two models of dynamic business-orientation in start-ups and explain the common reasons for shifts in orientation and why these two orientations do not generally co-exist during early firm development. Findings - Separate evolution paths were found for strategic orientation in manufacturing start-ups and separate reasons for them to shift in their early development. Technology-push start-ups often changed to a market-pull orientation because of new partners, new market information or shift in management priorities. In contrast, many of the start-ups beginning with a market-pull orientation shifted to a technology-push orientation because early market experiences necessitated a focus on improving processes in order to increase productivity or meet partner specifications, or meet a demand for complementary products. Originality/value - While a significant body of work exists regarding manufacturing strategy in established firms, little work has been found that investigates how manufacturing strategy emerges in start-up companies, particularly those in emerging industries. © Emerald Group Publishing Limited.

Application of gel-casting to the fabrication of 1-3 piezoelectric ceramic-polymer composites for high-frequency ultrasound devices

A modified gel-casting technique was used to fabricate a 1-3 piezoelectric ceramic/polymer composite substrate formed by irregular-shaped pillar arrays of small dimensions and kerfs. This technique involves the polymerization of aqueous piezoelectric (PZT) suspensions with added water-soluble epoxy resin and polyamine-based hardener that lead to high strength, high density and resilient ceramic bodies. Soft micromoulding was used to shape the ceramic segments, and micropillars with lateral features down to 4 m and height-to-width aspect ratios of ∼10 were achieved. The composite exhibited a clear thickness resonance mode at approximately 70 MHz and a k eff ∼ 0.51, demonstrating that the ceramic micropillars possess good electrical properties. Furthermore, gel-casting allows the fabrication of ceramic structures with non-conventional shapes; hence, device design is not limited by the standard fabrication methods. This is of particular benefit for high-frequency transducers where the critical design dimensions are reduced. © 2012 IOP Publishing Ltd.