Solar Cell Light Trapping beyond the Ray Optic Limit

In 1982, Yablonovitch proposed a thermodynamic limit on light trapping within homogeneous semiconductor slabs, which implied a minimum thickness needed to fully absorb the solar spectrum. However, this limit is valid for geometrical optics but not for a new generation of subwavelength solar absorbers such as ultrathin or inhomogeneously structured cells, wire-based cells, photonic crystal-based cells, and plasmonic cells. Here we show that the key to exceeding the conventional ray optic or so-called ergodic light trapping limit is in designing an elevated local density of optical states (LDOS) for the absorber. Moreover, for any semiconductor we show that it is always possible to exceed the ray optic light trapping limit and use these principles to design a number of new solar absorbers with the key feature of having an elevated LDOS within the absorbing region of the device, opening new avenues for solar cell design and cost reduction

Beyond the Spoken Word: Examining the Nature of Teacher Gesturing in the Context of an Elementary Engineering Curriculum for English-Learner Students

Our research team performed an exploratory analysis of teacher gesturing via a case study of an elementary teacher. We focused on gesturing, a practice found to support both bilingual English learner students’ linguistic development and mathematics achievement, during the teacher’s engineering and science lessons. The research team systematically analyzed teacher video data using McNeill’s gestural dimensions framework and found variation of gesturing types and rates when comparing engineering and baseline science lessons. Additionally, specific types of teacher-gestures appear to be associated with either behavioral or classroom management practices, procedural instructions, and discussion facilitation. We suggest that teacher-gestures such as these have the potential to facilitate bilingual English learners’ language acquisition, while also developing their STEM literacy in general and engineering capacity in particular. Further exploration of teacher-gestures in elementary engineering curricula could lead to an integrated STEM pedagogy that incorporates gesturing as a fundamental teaching strategy, bridging STEM instruction with linguistically responsive instructional practices.Educatio

The politics of walls: barriers, flows, and the sublime

As Donald Trump’s presidential campaign showed, walls are a hot topic. While ‘globalisation’, with its free flow of capital and goods, characterised world politics after the end of the Cold War, the twenty-first century has witnessed a reassertion of cultural, legal, and physical barriers. It is common to criticise such post-Cold War walls, especially the US-Mexico Barrier and Israel’s West Bank Barrier, as ineffective and immoral. This article problematises such critical discourse by using unlikely juxtapositions (the Great Wall of China) and new conceptual frameworks (gaps, critical aesthetics) to explore: (1) how walls can be a rational security policy; (2) how they are not simply barriers, but can be complex sites of flows; and (3) how walls are not simply texts waiting to be decoded: they are also sites of non-narrative affective experience that can even excite the sublime. This critical juxtaposition of walls first explores what they can tell us about the politics of borders, identity, and foreign policy, and then considers how walls, as concrete visual artefacts, can be examples not simply of ideology, but also of affect. The article aims to understand walls in a different register as active embodiments of political debate – and of political resistanc

Learning guide for the terminal configured vehicle advanced guidance and control system mode select panel

This learning guide is designed to assist pilots in taking the PLATO presimulator training course on the advanced guidance and control system mode select panel. The learning guide is divided into five sections. The first section, the introduction, presents the course goals, prerequisites, definition of PLATO activities, and a suggested approach to completing the course. The remaining four sections present the purpose, learning activities and summary of each lesson of the AGCS PLATO course, which consists of (1) AGCS introduction; (2) lower order modes; (3) higher order modes; and (4) an arrival route exercise

Simulations of solar cell absorption enhancement using resonant modes of a nanosphere array

We propose an approach for enhancing the absorption of thin-film amorphous silicon solar cells using periodic arrangements of resonant dielectric nanospheres deposited as a continuous film on top of a thin planar cell. We numerically demonstrate this enhancement using 3D full field finite difference time domain simulations and 3D finite element device physics simulations of a nanosphere array above a thin-film amorphous silicon solar cell structure featuring back reflector and anti-reflection coating. In addition, we use the full field finite difference time domain results as input to finite element device physics simulations to demonstrate that the enhanced absorption contributes to the current extracted from the device. We study the influence of a multi-sized array of spheres, compare spheres and domes and propose an analytical model based on the temporal coupled mode theory

Structural response and input identification

Three major goals were delineated: (1) to develop a general method for determining the response of a structure to combined base and acoustic random excitation: (2) to develop parametric relationships to aid in the design of plates which are subjected to random force or random base excitation: (3) to develop a method to identify the individual acoustic and base input to a structure with only a limited number of measurement channels, when both types of excitation act simultaneously

Community detection and role identification in directed networks: understanding the Twitter network of the care.data debate

With the rise of social media as an important channel for the debate and discussion of public affairs, online social networks such as Twitter have become important platforms for public information and engagement by policy makers. To communicate effectively through Twitter, policy makers need to understand how influence and interest propagate within its network of users. In this chapter we use graph-theoretic methods to analyse the Twitter debate surrounding NHS Englands controversial care.data scheme. Directionality is a crucial feature of the Twitter social graph - information flows from the followed to the followers - but is often ignored in social network analyses; our methods are based on the behaviour of dynamic processes on the network and can be applied naturally to directed networks. We uncover robust communities of users and show that these communities reflect how information flows through the Twitter network. We are also able to classify users by their differing roles in directing the flow of information through the network. Our methods and results will be useful to policy makers who would like to use Twitter effectively as a communication medium

Individual and community socioeconomic status : impact on mental health in individuals with arthritis

Peer reviewedPublisher PD

Light trapping beyond the 4n^2 limit in thin waveguides

We describe a method for determining the maximum absorption enhancement in thin film waveguides based on optical dispersion relations. For thin film structures that support one, well-confined guided mode, we find that the absorption enhancement can surpass the traditional limit of 4n^2 when the propagation constant is large and/or the modal group velocity is small compared to the bulk value. We use this relationship as a guide to predicting structures that can exceed the 4n^2 light trapping limit, such as plasmonic and slot waveguides. Finally, we calculate the overall absorption for both single and multimode waveguides, and show examples of absorption enhancements in excess of 4n^2 for both cases