Using Sparse Semantic Embeddings Learned from Multimodal Text and Image Data to Model Human Conceptual Knowledge

Distributional models provide a convenient way to model semantics using dense embedding spaces derived from unsupervised learning algorithms. However, the dimensions of dense embedding spaces are not designed to resemble human semantic knowledge. Moreover, embeddings are often built from a single source of information (typically text data), even though neurocognitive research suggests that semantics is deeply linked to both language and perception. In this paper, we combine multimodal information from both text and image-based representations derived from state-of-the-art distributional models to produce sparse, interpretable vectors using Joint Non-Negative Sparse Embedding. Through in-depth analyses comparing these sparse models to human-derived behavioural and neuroimaging data, we demonstrate their ability to predict interpretable linguistic descriptions of human ground-truth semantic knowledge.Comment: Proceedings of the 22nd Conference on Computational Natural Language Learning (CoNLL 2018), pages 260-270. Brussels, Belgium, October 31 - November 1, 2018. Association for Computational Linguistic

Nanomechanical testing of bcc micropillars – power laws and lattice resistance correlations

It is now well established that the compression plastic flow stress, sp, of metallic micropillars increases with decreasing sample diameter. With fcc metals, if the pillar flow stress and pillar diameter are normalised by the shear modulus resolved onto the active slip system, m, and Burgers’ vector, b, respectively, the data follows an empirical relation of Please click Additional Files below to see the full abstract

Formation and stability of lines produced by inkjet printing

To produce stable lines with parallel sides through inkjet printing, individual drops are deposited on a surface so that they coalesce; this initial liquid line (or bead) must remain stable until it forms a solid. The stable line width is shown to be bounded by two limits, with the lower bound (minimum line width) determined by the maximum drop spacing for stable coalescence and the upper bound determined by the minimum drop spacing below which a bulging instability occurs. The maximum stable track width is also a function of the velocity at which an inkjet printhead traverses the substrate. These bounds are presented in dimensionless form and are shown to agree well with experiment. To enable easier determination of the stability of an arbitrary ink/substrate combination, both the upper and lower bounds are presented in graphical forms to define a region of bead stability in an appropriate parameter space. © 2010 American Chemical Society

Inkjet Printing Ultra-Large Graphene Oxide Flakes

Graphene oxide 2D materials inks with mean flake diameter 36 µm can be inkjet printed, with no significant blockage of the printer or apparent damage to the flakes, despite the mean flake size being  >50% of the printer nozzle diameter and the ink containing individual flakes considerably larger than the nozzle. Printed flakes show a similar level of wrinkle and fold defects as observed in flakes deposited by drop casting. Polarised light imaging of the ink in the printhead prior to printing shows alignment of the flakes in the shear flow and this is believed to allow passage without agglomeration or blocking of the nozzle. The bulk electrical conductivity of these ultra-large flake printed films is 2.48  ×  104 Sm−1 after reduction, which is comparable to that reported with printed pristine graphene. The conductivity of the printed films increases slightly with increasing flake size indicating that there is no increase in damage to electrical properties as the flakes approach and exceed the nozzle diameter

Graphene-Based Transparent Flexible Strain Gauges with Tunable Sensitivity and Strain Range

Flexible strain gauges with 88% optical transmittance, of reduced graphene oxide (rGO) on poly dimethylsiloxne membranes, are produced form monolayers of graphene oxide assembled into densely packed sheets at an immiscible hexane/water interface and subsequently reduced in HI vapor to increase electrical conductivity. Pre-straining and relaxing the membranes introduces a population of cracks into the rGO film. Subsequent straining opens these cracks, inducing piezoresistivity. Reduction for 30 s forms an array of parallel cracks that do not individually span the membrane and results in a strain gauge with a usable strain range > 0.2 and gauge factor of 20 - 100 at low strain levels that increases with increasing pre-strain. In all cases the gauge facto decreases with increasing applied strain and asymptotes to a value of about 3, as it approaches the pre-strain value. If the rGO is reduced for 60 s, the cracks fully span the width of the membrane, leading to an increased gauge resistance but a much more sensitive strain gauge with GF ranging from 1000 - 16000. However, the usable strain range reduces to < 0.01. A simple equivalent resistor model is proposed to describe the behaviour of both gauge types. The gauges show a repeatable and stable response with loading frequencies up to 1 kHz and have been used to detect human body motion in a simple e-skin demonstration.Comment: 24 Pages, 9 Figures plus Supporting Information 11 page

In-situ bending tests of penta-twinned Ag NWs and their structure analyses

Ag nanowires (NWs) are readily available for applications in flexible electronics because of their excellent electrical and optical performance. Research into the mechanical properties and deformation mechanisms of NWs is important to understand the durability of these devices. The polyol process used to fabricate Ag NWs leads to a penta-twinned structure containing five {111} twin planes sharing a common axis along the [110] direction. Here we study the microstructures of the twinned NWs after plastic deformation in bending (Fig 1 (a)-(c))1. When deformation is highly spatially confined a clear grain boundary is observed under dark filed imaging (Fig 1 (d)). To further characterize the deformed penta-twinned wires, scanning precession nano-beam diffraction was used to map their structure and determine the crystal orientations. The diffraction signal and corresponding physical localization for every sub-crystal were isolated from the data using non-negative matrix factorization (NMF) 2. For example in Fig 1. (e)-(f), the crystal orientation is confirmed to be [110] albeit with an in-plane rotation of the pattern corresponding to the bend in the wire. The same approach was applied to other sub-crystals. The structure of penta-twinned Ag nanowire and the direction of incident electron beam are illustrated in Fig 1. (h). From the outlined shape of the subcrystals in the bent penta-twinned Ag NWs (Fig 1. (e), (f)), it was observed that the sub-crystals can expand or contract when approaching the bending Interface. To explain these behaviors, a coincident site lattice (CSL) was used to model the structure of grain boundaries formed during the bending process3. The change in orientation within a sub-crystal across the bending interface could be assigned in many cases to a particular highly coherent planar interface. This study is a clear example of how nano-materials with complex structure can be explored under advanced TEM experiments to provide insight into the deformation mechanisms of nanostructures. Please click Additional Files below to see the full abstract

Ink-jet printing of zirconia: Coffee staining and line stability

We have prepared a 10 vol% zirconium oxide (ZrO2) powder aqueous ink for ink-jet printing. This ink shows severe segregation or coffee staining during drying on solid substrates. Coffee staining is suppressed by the addition of 10 wt% poly(ethylene glycol) (PEG) to the ink formulation. However, coffee staining occurs with the PEG solution ink when drops are printed onto a substrate made from a preprinted ZrO2 powder layer. The mechanism for this phenomenon remains unknown but may be related to the draining of solvent into the powder. The stability of printed features is controlled by the overlap of printed drops and the range of line stability is shown to be consistent with models in the literature. © 2011 The American Ceramic Society

Influence of gas phase equilibria on the chemical vapor deposition of graphene

We have investigated the influence of gas phase chemistry on the chemical vapor deposition of graphene in a hot wall reactor. A new extended parameter space for graphene growth was defined through literature review and experimentation at low pressures (≥0.001 mbar). The deposited films were characterized by scanning electron microscopy, Raman spectroscopy, and dark field optical microscopy, with the latter showing promise as a rapid and nondestructive characterization technique for graphene films. The equilibrium gas compositions have been calculated across this parameter space. Correlations between the graphene films grown and prevalent species in the equilibrium gas phase revealed that deposition conditions associated with a high acetylene equilibrium concentration lead to good quality graphene deposition, and conditions that stabilize large hydrocarbon molecules in the gas phase result in films with multiple defects. The transition between lobed and hexagonal graphene islands was found to be linked to the concentration of the monatomic hydrogen radical, with low concentrations associated with hexagonal islands. © 2013 American Chemical Society

Inkjet printing and cell seeding thermoreversible photocurable gel structures

We have developed a biocompatible fluid suitable for inkjet delivery that gels by a tandem mechanism of a rapid physical gelation followed by a photoactivated chemical cross-linking. We prepared 20 vol% aqueous solutions of acrylate functionalised Pluronic F127, a poly(ethylene glycol-b-propylene glycol-b-ethylene glycol) (PEO-PPO), with triethanolamine and eosin Y as a photocurable cross-linker combination; poly(ethylene glycol) diacrylate was also added to the solution to improve the sol-gel transition. This fluid has a viscosit

Solution Processing of Two-Dimensional Black Phosphorus

This feature article discusses solution-phase routes to semiconducting two-dimensional black phosphorus (‘phosphorene’) and highlights challenges in processing the material as well as illuminating new avenues and opportunities in the area.</p