Forslag om bruk av Dynamo for en effektiv arbeidsflyt mellom Revit og FEM-Design

Byggebransjen er under en enorm teknologisk utvikling som åpner opp for nye metoder som bidrar til en mer effektiv prosjektering. Her er parametrisk design et fremadstormende verktøy som benyttes til dette formålet. Denne masteroppgaven tar for seg hvordan parametrisk design kan benyttes for å bidra til en mer effektiv prosjektering. Det skal brukes et visuellt programmeringsverktøy, Dynamo, for å etablere en arbeidsflyt mellom tegningsprogrammet Revit og beregningsprogrammet FEM-Design. Her skal det settes søkelys på overføring av elementer mellom programmene, der armeringsprosessen er sentral. Med bakgrunn i dette er det utarbeidet to script i oppgaven. Det første scriptet tar for seg overføring av en analytisk modell fra Revit til FEM-Design. Scriptet vil også etablere laster, lastkombinasjoner opplagerbetingelser, etasjer, akse og forbindelse mellom elementer. Til slutt vil det utføre en analyse som gir krefter på konstruksjonen i ULS og SLS. Det andre scriptet overfører en armeringsmodell fra FEM-Design til Revit, samt gir mulighet for å overføre strukturelle elementer. Det eksisterer i dag verktøy som utfører en tilsvarende overføring som scriptene, StruXML. Resultat fra scriptene sammenlignes opp mot dette verktøyet, for å se hvordan scriptene presterer i forhold til dagens muligheter. Til tross for at scriptene har sine begrensninger, eksisterer det fordeler som ikke StruXML kan tilby. Det er noen forutsetninger for at en overføring skal være vellykket, men disse er minimale sett opp mot manuelt arbeid. Resultatene anses å være nøyaktige og tidsbesparende. Med bakgrunn i dette, konkluderes det at implementering av parametrisk design i en prosjekteringsfase vil bidra til et mer effektivt resultat

Modulation of Magnetospheric Substorm Frequency: Dipole Tilt and IMF By Effects

Substorm activity is heavily influenced by the Interplanetary Magnetic Field (IMF) Bz component and magnetospheric substorms occur most frequently when Bz is strongly negative. The substorm occurrence rate is also affected by the magnitude of the By component, but it is usually presumed that this contribution is independent of the sign of By. Using five independent substorm onset lists, we show that substorm activity does depend on the sign of By near the solstices. Specifically, we show that substorms occur more frequently when By and the dipole tilt angle Ψ have different signs as opposed to when they have the same sign. These results confirm that the magnetosphere exhibits an explicit dependence on the polarity of By for nonzero Ψ, as other recent studies have suggested, and imply variation in the dayside reconnection rate and/or the magnetotail response. On the other hand, we find no clear relationship between substorm intensity and By regardless of Ψ. Last, for the onset list based on identifying negative bays at auroral latitudes, we observe an overall trend of more frequent onsets for positive By, regardless of season. However, substorm frequency in the other four substorm lists does not exhibit an overall preference for positive By. We show that this phenomenon is very likely a consequence of the particular substorm identification method (i.e., identification of negative bays), which is affected by local ionospheric conditions that depend on By and Ψ.publishedVersio

Evolution of IMF By induced asymmetries during substorms: Superposed epoch analysis at geosynchronous orbit

The By component of the magnetic field inside the magnetosphere is positively correlated with the By component of the Interplanetary Magnetic Field (IMF). This leads to asymmetries in aurora, plasma convection and electric currents between the northern and southern hemispheres It has been demonstrated that magnetic conjugate locations in the northern and southern ionosphere become less displaced during magnetospheric substorms, which are associated with enhanced reconnection in the near-Earth tail. Here we directly address how the average By component in the magnetotail evolves relative to substorm onset by performing a superposed epoch analysis of the magnetic field observed at nightside geosynchronous orbit during periods with dominant IMF By. The observations demonstrate that the average |By| in the magnetotail increases during the loading phase prior to onset. |By| maximizes in the expansion phase and is subsequently reduced during the remaining unloading phase. The observed trends become more pronounced using substorm onset lists that on average identify stronger substorms. Since dayside reconnection dominates over tail reconnection during the loading phase, whereas tail reconnection dominates during the unloading phase, the results demonstrate how asymmetries build up during periods with low tail reconnection and are reduced during periods with enhanced tail reconnection in agreement with previous case studies of conjugate auroral substorm features.publishedVersio

An explicit IMF By dependence on solar wind ‐ magnetosphere coupling

Presently, all empirical coupling functions quantifying the solar wind—magnetosphere energy—or magnetic flux conversion assume that the coupling is independent of the sign of the dawn-dusk component (B) of the Interplanetary Magnetic Field (IMF). In this paper we present observations strongly suggesting an explicit IMF B effect on the solar wind-magnetosphere coupling. When the Earth's dipole is tilted in the direction corresponding to northern winter, positive IMF B is found to on average lead to a larger polar cap than when IMF B is negative during otherwise similar conditions. This explicit IMF B effect is found to reverse when the Earth's dipole is inclined in the opposite direction (northern summer) and is consistently observed from both hemispheres. We interpret the different responses of the polar cap size due to the sign of IMF B to likely be a result of differences in the dayside reconnection rate.publishedVersio

The Magnitude of IMF By Influences the Magnetotail Response to Solar Wind Forcing

Under embargo until: 2022-04-21The dynamics of substorms are known to be dominated by the North-South (Bz) component of the Interplanetary Magnetic Field (IMF), which is the most important driver of the dayside reconnection. Even though the dawn-dusk (By) component is also known to play a role in substorm dynamics, its effects are not yet fully understood. In this paper we study how IMF By modulates the onset latitude, strength and occurrence frequency of substorms as well as the isotropic boundary (IB) latitude of energetic protons. We show that the substorm onset latitude and the IB latitude are about one degree lower for large magnitude By (>|By>|>3 nT) than for small By. In contrast, the substorm occurrence frequency is larger for small >|By>|. We suggest that the magnetotail is more stable during large >|By>|, requiring the magnetotail lobes (and hence the polar cap) to contain more flux to initiate a substorm compared to the situation when By is small.publishedVersio

The relationship between interhemispheric asymmetries in polar ionospheric convection and the magnetic field line footpoint displacement field

Polar electrodynamics is largely controlled by solar wind and magnetospheric forcing. Different conditions can make plasma convection and magnetic field disturbances asymmetric between hemispheres. So far, these asymmetries have been studied in isolation. We present an explanation of how they are linked via displacements of magnetic field line footpoints between hemispheres, under the assumption of ideal magnetohydrodynamics. This displacement has so far been studied only on a point by point basis; here we generalize the concept to a 2D displacement vector field. We estimate displacement fields from average patterns of ionospheric convection using the Weimer et al. (J. Geophys. Res., 2005a, 110, A05306) model. These estimates confirm that the influence of the interplanetary magnetic field extends deep into the magnetosphere, as predicted by models and in-situ observations. Contrary to predictions, the displacement associated with dipole tilt appears uniform across the nightside, and it exceeds the effect of IMF By. While more research is needed to confirm these specific findings, our results demonstrate how ionospheric observations can be used to infer magnetospheric morphology, and that the displacement field is a critical component for understanding geospace as a coupled two-hemisphere system.publishedVersio

Transient high latitude geomagnetic response to rapid increases in solar wind dynamic pressure

Rapid changes in solar wind dynamic pressure can produce a transient geomagnetic response in the high latitude ionosphere. In this study we carry out a superposed epoch analysis of the geomagnetic response based on 2,058 events. The events are divided into 12 groups based on interplanetary magnetic field clock angle and dipole tilt and the magnetic perturbation field is modeled using spherical harmonics. We find that the high latitude transient current vortices associated with a sudden commencement are most clearly observed when the interplanetary magnetic field is northward during equinox and winter in the northern hemisphere. The high latitude geomagnetic response during northward interplanetary magnetic field is decomposed into a preliminary and main impulse. The preliminary impulse onset is 1–2 min prior to the onset of the low/mid latitude geomagnetic response and its rise time is 4–6 min. The main impulse onset is around 2 min after the low/mid latitude geomagnetic response and has a rise time of 6–11 min. When examining the change relative to pre-onset conditions a coherent transient geomagnetic response emerges for all IMF clock and dipole tilt angles. The current vortex associated with the main impulse on the dawnside appears at (9.3 ± 0.5 mlt, 64.8° ± 1.5° mlat) and moves westward with a velocity of 5 ± 1.4 km/s. The vortex on the duskside appears at (15.3 ± 0.9 mlt, 65.8° ± 2.5° mlat) and does not move significantly. In addition, the models were used to recreate the SMR index showing a significant mlt dependence on the magnetic perturbation above 40° mlat and below 10° mlat. The former is thought to be caused by high latitude ionospheric currents. The latter is potentially a combination of the event occurrence probability being skewed toward certain UT ranges for large dipole tilt angles and a UT dependence of the equatorial electrojet magnitude caused by the south atlantic magnetic anomaly.publishedVersio

Utvikling av autonomt system på landbasert plattform - GPS-uavhengig navigering i trange miljøer

I den teknologiske utviklingen er det et større fokus på hvordan autonome systemer fungerer enn tidligere. Forsvaret har økt sin satsing innen autonomi som endrer måten operasjoner planlegges og gjennomføres på. Med bakgrunn i denne utviklingen forsøker oppgaven å gi en større forståelse rundt hvordan et konkret autonomt system kan fungere. Gjennom arbeidet av plattformen er det forsøkt å videreføre modulariteten i konstruksjonen, ved å gi en enkel og oversiktlig enhet å jobbe med. Etter anbefaling fra plattformens utviklere ble motorkontrollene erstattet med en mer robust type. Det er også fjernet moduler fra PLS og ultralyd-baserte avstandsmålere som ble overflødige, grunnet oppgradering av sensorpakken. Disse ble erstattet med en Lidar som brukes til hurtig skanning av plattformens miljø. Raspberry Pi, PLS og ROS er brukt som styrings – og kommunikasjonsenheter. ROS er en linuxbasert programvare for utvikling av software til roboter. Videre er plattformen utvidet på hardwaresiden med en Arduino, som primært benyttes gjennom puls bredde modulasjon for å styre motorene. Disse motorkontrollsignalene blir sendt via programmeringsspråket Node-Red som fungerer som et bindeledd mellom plattformens ulike enheter. Det implementerte Lidar systemet er kompatibelt med en rekke programmeringsspråk. Etter flere vurderinger av ulike språk falt valget på Python, da det er et utbredt programmeringsspråk som er lett å integrere i ROS. Siden oppstarten av bachelorperioden, har tanken vært å bruke systemer som brukes i utdannelsen ved Sjøkrigsskolen. Gjennom arbeidsprosessen har det blitt identifisert flere områder hvor plattformen kan videreutvikles. Det har vært en prioritet å begrense bruken av ukjente programmeringsspråk, slik at fokuset kan legges på integreringen av nye komponenter. Plattformen kan styres på tre ulike måter, gjennom Dualshock PS4 kontroller, gjennom PLS og via ROS. Dette gjør at brukere har mulighet til selv å kunne velge hvordan plattformen skal komme seg fra A til B, og åpner muligheten til å utvide systemet fra forskjellige innfallsvinkler. Oppgaven tar utgangspunkt i Sheridan og Verplank (Hareide, 2018) sin rangering av hvor autonomt et system er, i den hensikt å få et bilde over hva som kreves i et autonomt system. Datamaskinen utfører plattformens handlinger automatisk, og informerer brukeren i etterkant om hva den har gjort. Oppgaven har lyktes med å få plattformen til å kjøre autonomt innendørs. Muligheten til å kjøre autonomt utendørs med GPS-støtte ble også undersøkt. Navio2 anses å ha relevant sensorpakke og brukersystem for videreutvikling av plattformen

Substorm Impact on Dayside Ionospheric Currents

Ionospheric dayside dynamics is strongly controlled by the interaction between the Interplanetary Magnetic Field (IMF) and the Earth's magnetic field near the dayside magnetopause, while nightside ionospheric dynamics depends mainly on magnetotail activity. However, we know little about the influence of magnetotail activity on the dayside ionospheric dynamics. We investigate this by performing superposed epoch analyses of ground magnetic field data for substorms occurring during northward IMF. In such substorms, dayside reconnection is minimized, allowing us to separate the effects of the magnetotail activity on the dayside current system. We find that as nightside activity elevates, the dayside ionospheric current elevates. Our analyses indicate that the lobe cells are less distinct before onset than during non-substorm northward IMF conditions. They become more pronounced after onset, possibly due to magnetospheric reconfiguration or a remote effect of the nightside current. We discuss possible mechanisms that may explain our observations.publishedVersio