Comparison of different technologies for improving commutation failure immunity index for LCC HVDC in weak AC systems

Flexible AC Transmission System (FACTS) devices and Voltage Source Converter (VSC) High Voltage Direct Current (HVDC) systems have fast reactive power control capabilities which can be used to increase power system voltage stability. When located near a Line Commutated Converter (LCC) HVDC converter they can be used to support the performance of the LCC HVDC. This paper shows how well VSC HVDC, Static synchronous Compensation (STATCOM) and Static Var Compensators (SVC) are able to support LCC HVDC based on their improvement of the LCC HVDC Commutation Failure Immunity Index (CFII) and presents a comparison of their relative capabilities

Exploring the Risks of Children Engaging with Programmable IoT

This paper reports on IoT4Kids, a study exploring the privacy, security and safety implications of children programming the Internet of Things. The study focuses on the BBC micro:bit as one device that allows children to create rudimentary IoT devices. Prior publications have described the first stage of this study, which involved workshops with child participants. This paper instead focuses on the second stage of the project, which involved conducting key informant interviews with representatives from our project partners in order to understand the risks children face with interacting with programmable IoT devices. We describe themes that emerged from these interviews, along with implications for the study and for future work in this area

Physical computing:A key element of modern computer science education

Policymakers and educators around the globe acknowledge the importance of computer science (CS) education. But traditional CS teaching tools and methodologies do not necessarily address the needs of a diverse, global student population or the latest developments in modern programming and data science. Physical computing – combining software and hardware to build interactive physical systems that sense and respond to the real world – has been shown to result in broad engagement across a spectrum of users. In this paper we review prior research into physical computing in the classroom and combine this with our own experiences. We summarise the reported benefits and show how recent trends in the design and implementation of physical computing devices and systems are resulting in growing adoption. By way of example, we provide a detailed description of a recently developed physical computing system, the BBC micro:bit

Introducing Classroom Cloudlet : a mobile, tangible, and transparent approach to Internet of Things education

Providing a good understanding to children and educators on the Internet of Things (IoT) means to make them aware about where the data goes, how it is stored, and what it is stored on. In this perspective many commercial IoT systems have been shown to be unsuitable for this purpose especially when used in an educational context. They do not create user centric data collection opportunities; many of their IoT sensors that send data offsite to an online cloud create gaps in knowledge; the sensors themselves are not transparent: it's not clear what data they are collecting and how, and they are not easily compatible with school networks. Classroom Cloudlet addresses this issue. This demonstration presents an end-to-end IoT like system that includes a mobile, tangible, and transparent classroom cloudlet. Classroom Cloudlet aims to allow data from multiple devices to be easily shared, collated and analysed without using the Internet, but while still educating students about IoT and cloud concepts. The classroom cloudlet aims to be a physical representation of a cloud in an IoT system; visualise the movement of data around the system; provide a web front-end for students to view and create custom visualisations of their data. Classroom Cloudlet aims to gives the educator and the children full control and ownership of their data

IoT4Kids:Strategies for Mitigating Against Risks of IoT for Children

This paper describes the key outputs of IoT4Kids, a project exploring the privacy, security and safety implications of children programming the Internet of Things.We present our Risk Mitigation Checklist in order to illustrate the need for a multi-pronged approach for attending to risks to children from emergent IoT devices, and we discuss what this may mean in terms of industry practice, policymaking and education

MakeCode and CODAL:Intuitive and Efficient Embedded Systems Programming for Education

Across the globe, it is now commonplace for educators to engage in the making (design and development) of embedded systems in the classroom to motivate and excite their students. This new domain brings its own set of unique requirements. Historically, embedded systems development requires knowledge of low-level programming languages, local installation of compilation toolchains, device drivers, and applications. For students and educators, these requirements can introduce insurmountable barriers. We present the motivation, requirements, implementation, and evaluation of a new programming platform that enables novice users to create software for embedded systems. The platform has two major components: 1) Microsoft MakeCode (www.makecode.com), a web app that encapsulates an entire beginner IDE for microcontrollers; and 2) CODAL, an efficient component-oriented C++ runtime for microcontrollers. We show how MakeCode and CODAL provide an accessible, cross-platform, installation-free programming experience for the BBC micro:bit and other embedded devices

Unusual magnetotransport in twisted bilayer graphene from strain-induced open Fermi surfaces

Anisotropic hopping in a toy Hofstadter model was recently invoked to explain a rich and surprising Landau spectrum measured in twisted bilayer graphene away from the magic angle. Suspecting that such anisotropy could arise from unintended uniaxial strain, we extend the Bistritzer-MacDonald model to include uniaxial heterostrain. We find that such strain strongly influences band structure, shifting the three otherwise-degenerate van Hove points to different energies. Coupled to a Boltzmann magnetotransport calculation, this reproduces previously-unexplained non-saturating $B^2$ magnetoresistance over broad ranges of density near filling $\nu=\pm 2$, and predicts subtler features that had not been noticed in the experimental data. In contrast to these distinctive signatures in longitudinal resistivity, the Hall coefficient is barely influenced by strain, to the extent that it still shows a single sign change on each side of the charge neutrality point -- surprisingly, this sign change no longer occurs at a van Hove point. The theory also predicts a marked rotation of the electrical transport principal axes as a function of filling even for fixed strain and for rigid bands. More careful examination of interaction-induced nematic order versus strain effects in twisted bilayer graphene could thus be in order.Comment: 11 pages main text (4 figures) + 8 pages supplementary material (11 figures