Electrical system resilience:a forensic analysis of the blackout in Lancaster, UK

Great Britain’s electricity network is undergoing a major transformation as it moves from a system based on burning fossil fuels in central power stations to one dominated by distributed renewable energy; this brings with it a new set of risks. In parallel, the move to electronic documentation and communication is increasing the dependence of society on an ‘always-on’ electricity supply. Assessing the level of dependence is difficult, as full-scale experimentation is not practicable and a desktop analysis of situations involving a large number of human interactions is unlikely to be representative. In December 2015, Storm Desmond resulted in a blackout affecting more than 100 000 people in Lancaster, UK. This provided a unique case study that allowed researchers to investigate how society responds to a widespread loss of the electricity supply

The feasibility of using megavoltage CT for the treatment planning of HDR cervical brachytherapy with shielded tandem and ovoid applicators

Purpose/Objectives: A drawbackof tandem and ovoid (T&O) ICBT is exposure of the posterior bladder and anterior rectal walls to relatively high isodoses. To mitigate this effect, intra-ovoid shielding may be used to reducedose to these OARs. However, metal artifactspresent in images acquired via kVCT make anatomy segmentation and catheter localization difficult for the purpose of 3D treatment planning. We present a method that combines MVCT-based imaging and applicator modeling to increase the quality of 3D treatment plans for shielded T&O ICBT. Materials/Methods: Using Oncentra’s TPS, 9 participants from multiple institutions performed organ segmentation and catheter reconstruction for KVCT and MVCT data sets acquired of a water phantom containing bladder and rectum surrogatesand various HDR T&O applicators: Nucletron’s CT/MR compatible(CTMR),Nucletron’s shielded Fletcher Williamson (FW) and (3) Varian’s shielded Fletcher-Suit-Delclos style(FSD).The dimensions of OAR structures were determined using in-air kVCT and physical measurements. By comparing the 3D volumes andcentroid-to-perimeter (C2P) measurements of individual OAR contours, segmentation accuracy was assessed in regions exhibiting artifact under kVCT (1cm superior and inferior to shielding). Comparing the TPS-defined coordinate of the most distal dwell position to that of the true position (determined using radiographs of a fiducial affixed to the applicators), assessed catheter reconstruction accuracy. For Nucletron devices, this metricwas also quantified using an applicator-model for localization. Results:The percentage of points for C2P measurements that differ (greater than 2mm) from the true contour extentsdecreased underMVCT for the shielded T&Os (78.4 vs. 71.3%), while the converse is observed for the CTMR. Similarly, the volume of the OAR surrogates follows the same trend. This is attributed to the lack of metal artifacts as well as the decrease in the contrast of low Z materials observed when utilizing MVCT. Catheter reconstruction accuracy improved by 26% under MVCT for shielded T&Os, was invariant for the CTMR and within 2.29mm of the true position using applicator modeling. Conclusions:The quality of MVCT 3D ICBT treatment plans of shielded T&O is comparable to MVCT CTMR treatment plans. Further improvements were observed when using an applicator model for catheter reconstruction

Electrostatic charging of non-polar colloids by reverse micelles

Colloids dispersed in a non-polar solvent become charged when reverse micelles are added. We study the charge of individual sterically-stabilized poly(methyl methacrylate) spheres dispersed in micellar solutions of the surfactants sodium bis(2-ethyl 1-hexyl) sulfosuccinate [AOT], zirconyl 2-ethyl hexanoate [Zr(Oct)$_{2}$], and a copolymer of poly(12-hydroxystearic acid)--poly(methyl methacrylate) [PHSA-PMMA]. Although the sign of the particle charge is positive for Zr(Oct)$_{2}$, negative for AOT, and essentially neutral for PHSA-PMMA the different micellar systems display a number of common features. In particular, we demonstrate that, over a wide range of concentrations, the colloid charge is independent of the number of micelles added and scales linearly with the colloid size. A simple thermodynamic model, in which the particle charge is generated by the competitive adsorption of both positive and negative micelles, is in good agreement with the experimental data

Transport of charged aerosol OT inverse micelles in nonpolar liquids

Surfactants such as Aerosol OT (AOT) are commonly used to stabilize and electrically charge nonpolar colloids in devices such as electronic ink displays. The electrical behavior of such devices is strongly influenced by the presence of charged inverse micelles, formed by excess surfactant that does not cover the particles. The presence of charged inverse micelles results in increased conductivity of the solution, affecting both the energy consumption of the device and its switching characteristics. In this work, we use transient current measurements to investigate the electrical properties of suspensions of the surfactant Aerosol OT in dodecane. No particles are added, to isolate the effect of excess surfactant. The measured currents upon application of a voltage step are found to be exponentially decaying, and can be described by an analytical model based on an equivalent electric circuit. This behavior is physically interpreted, first by the high generation rate of charged inverse micelles giving the suspension resistor like properties, and second by the buildup of layers of charged inverse micelles at both electrodes, acting as capacitors. The model explains the measurements over a large range of surfactant concentrations, applied voltages, and device thicknesses

Charging dynamics of aerosol OT inverse micelles

Aerosol OT (AOT) is a commonly used surfactant and charging agent in nonpolar liquids. Properties such as the conductivity of AOT suspensions in nonpolar liquids and the behavior of charged AOT inverse micelles at interfaces have been studied recently, but still little is known about the generation dynamics of charged AOT inverse micelles. In this article, the generation dynamics of charged AOT inverse micelles in dodecane are investigated with transient current measurements. At low applied voltages, the generation rate is sufficiently fast to maintain the equilibrium concentration of charged inverse micelles, such that the current scales proportionally with the applied voltage. However, above a threshold voltage the current becomes limited by the generation of charged inverse micelles. Al2O3‑coated electrodes are used to achieve these high-voltage current measurements while reducing surface generation currents. The dependency of the resulting generation-limited currents with the micelle concentration and the liquid volume is compatible with a bulk disproportionation mechanism. The measured currents are analyzed using a model based on drift, generation, and recombination of charged inverse micelles and the corresponding generation and recombination rates of charged AOT inverse micelles have been determined

Investigation of various types of inverse micelles in nonpolar liquids using transient current measurements

Transient current measurements are used to characterize a wide variety of charge carriers in nonpolar liquids. The transient current method allows us to obtain both the concentration and mobility of charge carriers and therefore also the hydrodynamic radius using Stokes' law. In this article, five different surfactants in dodecane are investigated: OLOA11K, Solsperse13940, Span80, Span85, and AOT. We show that different types of currents are observed depending on the size of the inverse micelles. For large inverse micelles such as for OLOA11K, Solsperse13940, and Span80, the measurement of the transient current is straightforward because of the low steady-state current level. However, for small inverse micelles such as AOT and Span85, the current from the generation of charges is much larger such that high voltages, a small distance between the electrodes, and dielectric coatings on the electrodes are required to measure the signal related to the initially present charged inverse micelles. The estimated hydrodynamic radii of AOT and Span85, the two smallest inverse micelles, are in good agreement with the values reported in the literature. The comparison of the transient currents with simulations indicates that the dynamics of the charge transport are well-understood

Local Governments in the United States: An Overview of Cities and Counties

America’s local governments, while still evolving over time, trace their roots back to the English shire from centuries ago. The shire had a dual function, serving as the administrative arm of the national government as well as the citizen’s local government. The structural form of the shire was adopted along the eastern seaboard of North America by the original colonists, who adapted it to suit the diverse economic and geographic needs of each of the original colonies. When the United States national government was formed, the framers of the Constitution did not provide for local governments. Rather, they left this matter to the states. Subsequently, early state constitutions generally embraced local governments as arms of the state. Currently, the term county is used in 48 of the 50 states of the United States to describe that tier of government below the state. Louisiana has government entities similar to counties, but they are called parishes. Alaska is divided into boroughs, which typically provide fewer services than most counties, since the state provides most services directly to citizens. Units of government below the county level are often referred to generically as cities, but they are known by a host of different names that vary greatly from state to state. Common terms include towns, townships, boroughs, villages, and municipalities

Iodide-ion transport in methylammonium lead iodide perovskite: Some surprising aspects

Methylammonium lead iodide, CH3NH3PbI3 (= MAPbI3), is a hybrid organic–inorganic perovskite that exhibits excellent photovoltaic properties. In comparison with traditional photovoltaic materials, such as Si or CIGS, MAPbI3 is evidently characterised by one or more highly mobile constituent ions. In photovoltaic devices based on MAPbI3, ion mobility is deemed to be responsible for current–voltage hysteresis, a huge low-frequency dielectric response, and long-term instability. Despite enormous interest in ion transport, debate surrounds almost every aspect. This is evident in the excessive scatter in activation enthalpies reported in the literature for ion conduction in MAPbI3 (see Fig. 1). Please click Additional Files below to see the full abstract

Regulating the safety of autonomous vehicles using artificial intelligence

In the last five years, there has been increasing enthusiasm for autonomous (also called self-driving or driverless) vehicles on public roads in the UK. There are many benefits claimed for them: lower energy consumption, better use of infrastructure, fewer accidents and mobility for all, including those who, for reasons of age or infirmity, are unable to drive. The UK Government has been encouraging, consulting on and facilitating the development and introduction of driverless cars and “connected autonomous vehicles” (CAVs) that can communicate with each other and the infrastructure. In February 2017 they published a draft Bill to legislate for compulsory insurance of CAVs, with explanatory notes showing that the Government expects driverless cars to be introduced in the UK in “five to ten years” – that is, between 2022 and 2027. However, there appears to have been no realistic analysis of how the safety of such vehicles would be regulated or how their interactions with other road users could be controlled. This paper reviews the safety regulatory regime for other automated transport systems and discusses how similar processes might be implemented for CAVs. It concludes that the government’s timescale targets are unrealistically optimistic