Evaluating the impact of superconducting fault current limiters on distribution network protection schemes

Rising fault levels are becoming increasingly problematic in the UK distribution network, with large sections of the network operating near to its designed fault level capability. With the increase in penetration of distributed generation that is expected in the coming years, this situation is becoming more pressing. Traditional methods of dealing with the issue may not be appropriate - upgrading plant is expensive and disruptive, while network reconfiguration can compromise security of supply. Superconducting Fault Current Limiters (SFCLs) are emerging as a potential solution, with installations now taking place in several locations worldwide. The integration of an SFCL into a network involves a number of challenges, particularly concerning the coordination of protection systems. The operation of existing protection schemes may be compromised due to the increased resistance in the network during a fault (in the case of a resistive SFCL). Furthermore, the reduction in fault levels, although desirable, can have a detrimental impact on protection operating times. This paper will consider an existing medium voltage network in the UK, which incorporates distributed generation capacity. The performance of IDMT overcurrent and distance protection schemes will be examined when an SFCL is installed in this network. In particular, the increased operating time of overcurrent relays will be discussed along with grading implications. The impact on distance protection reach will also be examined. A variety of network operational scenarios including SFCL placement and fault conditions will be considered and compared. Recommendations will be made in terms of protection settings and SFCL placement in order to mitigate the aforementioned issues

College success is for Foster Children too

In 2016, the Adoption and Foster Care Analysis Reporting System reported that 437,465 children were in foster care. Removal of a child from their family typically happens for reasons that pose immediate safety risks, such as abuse, neglect, parental substance abuse, unsuitable living conditions, parental mental illness, family violence, or the absence of parents (Lohr & Jones, 2016). For these reasons, children who are or have been in foster care are at risk of experiencing a variety of negative health and behavior outcomes. One domain where foster children face specific challenges is the education system. Frequent placement changes often result in a change of schools and cause disrupted learning throughout the K-12 education (Morton, 2018). As foster children get older and emancipate from foster care, they are left to make the decision of continuing their education on their own, often without financial or moral support (Courtney, 2009; Morton, 2018). Without support, the transition from primary to secondary education becomes more of an obstacle. In research, former foster care students enrolled in college reported that uncontrolled mental health issues and poor emotion regulation skills were barriers to their success (Morton, 2018). Additionally, research has found that up to 75 percent of college students report adverse childhood experiences (Calmes et al., 2013). These students encounter risks in the academic world such as negative college adjustment and lower academic achievement and are two times as likely to drop out before completing a degree as those with no trauma history (Banyard & Cantor, 2004). The current study sought to explore the relationships between childhood trauma history, foster care history, college enrollment and adjustment, and resilient qualities that contribute to academic success through a mixed-methods approach. Participants completed 2 to 3 online surveys that collected information about childhood experiences (Adverse Childhood Experiences questionnaire), resilience qualities and behaviors (Academic Resilience Scale), and foster care experiences (Foster Care Experience Survey). The questions specifically posed to former foster children inquired about relationships, supports, and protective factors in relation to their foster care experiences and how these things have supported or inhibited their success. A primary goal of this study was to identify specific themes across participant responses to inform what aspects of the college transition were useful and what is needed for future students transitioning from foster care to college. Hearing from former foster children firsthand, as was done in this study, can give educators and policy makers a glimpse into the major struggles they are facing and highlight key areas for improvement. This presentation will help viewers acquire skills to implement strategies that maintain supportive learning environments for students with childhood trauma or foster care experience

De-extinction: A Hopeful Dream or Hopeless Nightmare

This is an essay about de-extinction and what we should and should not do in order to remedy this

Algorithm and Complexity for a Network Assortativity Measure

We show that finding a graph realization with the minimum Randi\'c index for a given degree sequence is solvable in polynomial time by formulating the problem as a minimum weight perfect b-matching problem. However, the realization found via this reduction is not guaranteed to be connected. Approximating the minimum weight b-matching problem subject to a connectivity constraint is shown to be NP-Hard. For instances in which the optimal solution to the minimum Randi\'c index problem is not connected, we describe a heuristic to connect the graph using pairwise edge exchanges that preserves the degree sequence. In our computational experiments, the heuristic performs well and the Randi\'c index of the realization after our heuristic is within 3% of the unconstrained optimal value on average. Although we focus on minimizing the Randi\'c index, our results extend to maximizing the Randi\'c index as well. Applications of the Randi\'c index to synchronization of neuronal networks controlling respiration in mammals and to normalizing cortical thickness networks in diagnosing individuals with dementia are provided.Comment: Added additional section on application

Theorem on the Distribution of Short-Time Particle Displacements with Physical Applications

The distribution of the initial short-time displacements of particles is considered for a class of classical systems under rather general conditions on the dynamics and with Gaussian initial velocity distributions, while the positions could have an arbitrary distribution. This class of systems contains canonical equilibrium of a Hamiltonian system as a special case. We prove that for this class of systems the nth order cumulants of the initial short-time displacements behave as the 2n-th power of time for all n>2, rather than exhibiting an nth power scaling. This has direct applications to the initial short-time behavior of the Van Hove self-correlation function, to its non-equilibrium generalizations the Green's functions for mass transport, and to the non-Gaussian parameters used in supercooled liquids and glasses.Comment: A less ambiguous mathematical notation for cumulants was adopted and several passages were reformulated and clarified. 40 pages, 1 figure. Accepted by J. Stat. Phy

A multistage linear array assignment problem

The implementation of certain algorithms on parallel processing computing architectures can involve partitioning contiguous elements into a fixed number of groups, each of which is to be handled by a single processor. It is desired to find an assignment of elements to processors that minimizes the sum of the maximum workloads experienced at each stage. This problem can be viewed as a multi-objective network optimization problem. Polynomially-bounded algorithms are developed for the case of two stages, whereas the associated decision problem (for an arbitrary number of stages) is shown to be NP-complete. Heuristic procedures are therefore proposed and analyzed for the general problem. Computational experience with one of the exact problems, incorporating certain pruning rules, is presented with one of the exact problems. Empirical results also demonstrate that one of the heuristic procedures is especially effective in practice