Scalable Model-Based Management of Correlated Dimensional Time Series in ModelarDB+

To monitor critical infrastructure, high quality sensors sampled at a high frequency are increasingly used. However, as they produce huge amounts of data, only simple aggregates are stored. This removes outliers and fluctuations that could indicate problems. As a remedy, we present a model-based approach for managing time series with dimensions that exploits correlation in and among time series. Specifically, we propose compressing groups of correlated time series using an extensible set of model types within a user-defined error bound (possibly zero). We name this new category of model-based compression methods for time series Multi-Model Group Compression (MMGC). We present the first MMGC method GOLEMM and extend model types to compress time series groups. We propose primitives for users to effectively define groups for differently sized data sets, and based on these, an automated grouping method using only the time series dimensions. We propose algorithms for executing simple and multi-dimensional aggregate queries on models. Last, we implement our methods in the Time Series Management System (TSMS) ModelarDB (ModelarDB+). Our evaluation shows that compared to widely used formats, ModelarDB+ provides up to 13.7 times faster ingestion due to high compression, 113 times better compression due to the adaptivity of GOLEMM, 630 times faster aggregates by using models, and close to linear scalability. It is also extensible and supports online query processing.Comment: 12 Pages, 28 Figures, and 1 Tabl

Jurisdictional and Interstate Commerce Problems in the Imposition of Excess on Sales

I denne rapport argumenterer forfatterne for, at der i beskæftigelsespolitikken er behov for at flytte det strategiske fokus fra 'flexicurity' til 'mobication' ('mobility through education'), som indebærer, at man sætter kompetenceudvikling i centrum. Det er forfatternes vurdering, at 'flexicurity' fortsat udgør et vigtigt fundament for fleksibiliteten og sikkerheden for først og fremmest de ledige på arbejdsmarkedet, men at der er behov for en langt mere offensiv satsning på livslang uddannelse af hele arbejdsstyrken, hvis man skal sikre arbejdskraftens konkurrencedygtighed fremover. 'Mobication' sigter netop mod at styrke arbejdskraftens muligheder for at tilpasse sig og bevæge sig i forhold til de skiftende behov på et arbejdsmarked i en stadigt mere konkurrencepræget verdensøkonomi

Boron and nitrogen doping in graphene antidot lattices

Bottom-up fabrication of graphene antidot lattices (GALs) has previously yielded atomically precise structures with sub-nanometer periodicity. Focusing on this type of experimentally realized GAL, we perform density functional theory calculations on the pristine structure as well as GALs with edge carbon atoms substituted with boron or nitrogen. We show that p- and n-type doping levels emerge with activation energies that depend on the level of hydrogenation at the impurity. Furthermore, a tight-binding parameterization together with a Green's function method are used to describe more dilute doping.Comment: 8 pages, 7 figure