Electro-optical switching by liquid-crystal controlled metasurfaces

We study the optical response of a metamaterial surface created by a lattice of split-ring resonators covered with a nematic liquid crystal and demonstrate millisecond timescale switching between electric and magnetic resonances of the metasurface. This is achieved due to a high sensitivity of liquid-crystal molecular reorientation to the symmetry of the metasurface as well as to the presence of a bias electric field. Our experiments are complemented by numerical simulations of the liquid-crystal reorientation.Comment: 6 pages, 3 figure

Visualizing Diffusion Tensor Images of the Mouse Spinal Cord

Within biological systems water molecules undergo continuous stochastic Brownian motion. The rate of this diffusion can give clues to the structure of underlying tissues. In some tissues the rate is anisotropic - faster in some directions than others. Diffusion-rate images are second-order tensor fields and can be calculated from diffusion-weighted magnetic resonance images. A 2D diffusion tensor image (DTI) and an associated anatomical scalar field, created during the tensor calculation, define seven dependent values at each spatial location. Understanding the interrelationships among these values is necessary to understand the data. We present two new methods for visually representing DTIs. The first method displays an array of ellipsoids where the shape of each ellipsoid represents one tensor value. The novel aspect of this representation is that the ellipsoids are all normalized to approximately the same size so that they can be displayed in context. The second method uses concepts from oil painting to represent the seven-valued data with multiple layers of varying brush strokes. Both methods successfully display most or all of the information in DTIs and provide exploratory methods for understanding them. The ellipsoid method has a simpler interpretation and explanation than the painting-motivated method; the painting-motivated method displays more of the information and is easier to read quantitatively. We demonstrate the methods on images of the mouse spinal cord. The visualizations show significant differences between spinal cords from mice suffering from Experimental Allergic Encephalomyelitis (EAE) and spinal cords from wild-type mice. The differences are consistent with pathology differences shown histologically and suggest that our new non-invasive imaging methodology and visualization of the results could have early diagnostic value for neurodegenerative diseases

Action horizon : on the controllability of complex systems, moving towards management for energy systems

Building robust and resilient systems is a major challenge for engineering. To this end, analytical indicators may be useful for managers in making decisions. In this paper, a new analytical construct is presented: the action horizon. This construct is devoted to assisting in the control of a system when an event driving the system to its collapse is detected. This construct is useful for analysing the best moment to start executing a corrective action. In this paper, the action horizon is experimentally evaluated in the predator-prey system and we discuss how it could help with managing power systems

Reluctance network model for the in-wheel motor of a series-hybrid truck using Tooth Contour Method

Recently, series-hybrid drivetrains are given more emphasis over parallel-hybrid drivetrains due to their simplicity, freedom in implementation and higher efficiency. However, the modeling phase of such machines takes either long calculation time with numerical methods such as Finite Element Analysis (FEA) or produces low accurate results with Magnetic Equivalent Circuit (MEC) models. In this paper a method is used to build a reluctance network where high accuracy is obtained yet still with acceptable calculation time

Local school policies increase physical activity in Norwegian secondary schools

The implementation of school policies to support the adoption of physical activity is one of the main strategies recommended to increase physical activity levels among this age group. However, documentation of the effect of such policies is so far limited. The purpose of this study was to explore policy-related practices to support physical activity in Norwegian secondary schools and their association with recess physical activity. Emphasis was given to examine the association between policies and physical activity, over and beyond, individual level interests and environmental factors and to examine cross-level interaction effects. This cross-sectional study was based on a nationally representative sample of Norwegian secondary schools and grade 8 students who participated in the Health Behaviour in School-aged Children (HBSC) 2005/06 study. The final sample comprised 68 schools and 1347 students. Data were collected through questionnaires. The results showed that schools with a written policy for physical activity and schools offering organized non-curricular physical activity several times a week had a higher proportion of students reporting daily participation in recess physical activity. Multilevel logistic regression analysis demonstrated a cross-level main effect of the policy index after controlling for sex, socio-economic status, individual-level interests and the physical environment. A significant contribution of adding the policy index to the prediction of recess physical activity above that provided by the individual-level interests and the physical environment was demonstrated. The results are encouraging and give scientific support to policy documents recommending the implementation of school policies to increase physical activity

Techno-enviro-economic assessment of household and community energy storage in the UK

Residential electricity demand is expected to rise in the next few decades due to the electrification of heating and transport. Both European and UK national policies suggest that efforts should be made to reduce carbon emissions and increase the share of renewable energy, an important element of which is encouraging generation, typically PV, in partnership with energy storage systems in the residential sector. The scale of the energy storage system is important, i.e. in individual properties or as a community resource. Many advantages of community energy storage (CES) over household energy storage (HES) have been identified, but the design and operation of CES has received significantly less attention. Most existing research has analysed CES at community level only, but the performance and impact on individual households has yet to be fully explored. In this study an agent-based model is proposed to investigate and analyse CES based on a range of criteria. Results indicate that both HES and CES can significantly reduce the grid peak power import and export, improve the community self-consumption rate (SCR) and self-sufficiency rate (SSR), and contribute to much higher energy saving. Furthermore, optimising the CES capacity leads to more effective use of PV power and better demand localisation during high PV-generation periods. It is found that an important challenge for CES systems is to realise the value of the shared electricity equitably amongst the participants and potentially to seek other revenue streams

Residential PV-BES systems: Economic and grid impact analysis

The energy industry has seen a revolutionary transformation in the growth of renewables over the past decade. With recent advances in battery storage performance, solar energy is fast becoming the focus of the global energy shift towards a more sustainable future. Photovoltaic (PV) systems integrated with Battery Energy Storage (BES) systems are expected to play an important role in the UK’s future energy industry, aided in part by manufacturing cost reductions. For energy consumers, these systems can deliver considerable savings in utility costs and potentially bring a financial return via a feed-in-tariff (FIT) scheme. Such a system could also help energy suppliers and network operators ease the burden of a huge surge of future energy demand, mitigate network congestion and improve system resilience and autonomy. There is, however, limited literature that utilises simulation to investigate the influence of PV-BES system deployment at urban scale on the grid based on economic and technical analysis. In this work, a household-level model is developed that includes load demand heterogeneities, as well as BES and PV systems. The single household model can be scaled to higher levels, such as streets and community, hence the model can be applied to study the interaction between households, the wider community and the grid, in terms of electricity im/export, BES usage and network injection impact. A comprehensive analysis of both technical and economic perspectives is presented based on several key performance indicators (KPIs), such as self-consumption rate (SCR), self-sufficiency rate (SSR) and reduction in peak charges. The addition of a BES system can significantly increase the self-consumption of a home PV system, by at least 15%, however the expensive upfront cost of the BES system leads to a much longer payback time