On Identification of Distribution Grids

Large-scale integration of distributed energy resources into distribution feeders necessitates careful control of their operation through power flow analysis. While the knowledge of the distribution system model is crucial for this analysis, it is often unavailable or outdated. The recent introduction of synchrophasor technology in low-voltage distribution grids has created ample opportunity to learn this model from high-precision, time-synchronized measurements of voltage and current phasors at various locations. This paper focuses on joint estimation of admittance parameters and topology of a polyphase distribution network from the available telemetry data via the lasso, a method for regression shrinkage and selection. We propose tractable convex programs capable of tackling the low-rank structure of the distribution system and develop an online algorithm for early detection and localization of critical events that induce a change in the admittance matrix. The efficacy of these techniques is corroborated through power flow studies on four three-phase radial distribution systems serving real and synthetic household demands

Event detection and localization in distribution grids with phasor measurement units

The recent introduction of synchrophasor technology into power distribution systems has given impetus to various monitoring, diagnostic, and control applications, such as system identification and event detection, which are crucial for restoring service, preventing outages, and managing equipment health. Drawing on the existing framework for inferring topology and admittances of a power network from voltage and current phasor measurements, this paper proposes an online algorithm for event detection and localization in unbalanced three-phase distribution systems. Using a convex relaxation and a matrix partitioning technique, the proposed algorithm is capable of identifying topology changes and attributing them to specific categories of events. The performance of this algorithm is evaluated on a standard test distribution feeder with synthesized loads, and it is shown that a tripped line can be detected and localized in an accurate and timely fashion, highlighting its potential for real-world applications

Hiker’s attitudes towards traceless travel – a comparative study from Lysefjorden in Norway and Laugavegur in Iceland

Lysefjorden er en av de mest populære naturattraksjonene i Norge med godt over seks hundre tusen besøkende hvert år. Det har tidligere blitt uttrykt bekymring for at naturattraksjoner i Norge ikke er rustet for å møte et stigende antall besøkende, og at besøkende ofte har uansvarlig atferd. Norge opplever for tiden lignende problemer som på Island, hvor store antall besøkende til naturattraksjoner fører til overbelastning og påfølgende behov for regulering. Sporløs ferdsel er en viktig norm innen friluftsliv og handler om at naturen skal være like fin når vi forlater den, som da vi kom. Det finnes imidlertid ingen tidligere forskning som undersøker holdninger til sporløs ferdsel. Hensikten med denne forskningen var å måle og sammenligne holdninger til sporløs ferdsel blant turgåere i Lysefjorden i Norge og Laugavegur på Island. Data ble samlet inn gjennom spørreundersøkelser, og utforsket gjennom deskriptiv analyse. Forskjeller ble utforsket gjennom Mann-Whitney U test. Resultatene indikerte at holdninger til turgåere ved begge destinasjoner generelt var i tråd med sporløs ferdsel. Det ble imidlertid funnet flere signifikante forskjeller mellom de to destinasjonene, hvor turgåerne fra Lysefjorden viste holdninger mindre i tråd med sporløs ferdsel sammenlignet med turgåere fra Laugavegur. Denne studien antyder at fordi Laugavegur er mindre tilgjengelig og mer regulert, i tillegg til få begrensninger til allemannsretten i Lysefjorden kan forklare hvorfor holdningene til turgåere fra Laugavegur virker mer i tråd med sporløs ferdsel sammenlignet med turgåere fra Lysefjord.Lysefjord is one of the most popular nature destinations in Norway with well over six hundred thousand visitors coming to hike and enjoy the nature each year. However, recent concerns have been made that nature destinations in Norway are not equipped to deal with increasingly large visitor numbers, and that visitors often have irresponsible behavior. Norway is currently experiencing similar issues to Iceland, as vast visitor numbers to nature attractions leads congestion and subsequent need for regulation. Traceless travel is an important norm in outdoor recreation and involves leaving nature as beautiful as it was when first arriving. However, there seems to be no previous research examining attitudes towards traceless travel in the current literature. The purpose of this research was to measure and compare attitudes towards traceless travel among hikers visiting Lysefjord in Norway and Laugavegur in Iceland. Results indicate that attitudes of hikers at both destinations were generally in line with traceless travel. However, several significant differences between the two destinations were revealed, as the hikers from Lysefjord generally displayed attitudes less in line with traceless travel compared to hikers from Laugavegur. This study suggests that the Laugavegur being less accessible and more regulated, as well as limited restrictions to right to roam in Lysefjord may explain why attitudes of hikers from Laugavegur seem more in line with traceless travel compared to hikers from Lysefjord

Ex vivo culture of adult CD34+ stem cells using functional highly porous polymer scaffolds to establish biomimicry of the bone marrow niche

Haematopoiesis, the process of blood production, occurs from a tiny contingent of haematopoietic stem cells (HSC) in highly specialised three-dimensional niches located within the bone marrow. When haematopoiesis is replicated using in vitro two-dimensional culture, HSCs rapidly differentiate, limiting self-renewal. Emulsion-templated highly porous polyHIPE foam scaffolds were chosen to mimic the honeycomb architecture of human bone. The unmodified polyHIPE material supports haematopoietic stem and progenitor cell (HSPC) culture, with successful culture of erythroid progenitors and neutrophils within the scaffolds. Using erythroid culture methodology, the CD34+ population was maintained for 28 days with continual release of erythroid progenitors. These cells are shown to spontaneously repopulate the scaffolds, and the accumulated egress can be expanded and grown at large scale to reticulocytes. We next show that the polyHIPE scaffolds can be successfully functionalised using activated BM(PEG)2 (1,8-bismaleimido-diethyleneglycol) and then a Jagged-1 peptide attached in an attempt to facilitate notch signalling. Although Jagged-1 peptide had no detectable effect, the BM(PEG)2 alone significantly increased cell egress when compared to controls, without depleting the scaffold population. This work highlights polyHIPE as a novel functionalisable material for mimicking the bone marrow, and also that PEG can influence HSPC behaviour within scaffolds