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Controls on the sources and distribution of chalcophile and lithophile trace elements in arc magmasD'Souza, Rameses Joseph 24 January 2018 (has links)
Volcanic arcs have been the locus of continental growth since at least the Proterozoic eon. In this dissertation, I seek to shine more light on arc processes by inferring the lower crustal mineralogy of an ancient arc by geochemical and structural modelling of its exposed levels. Arcs characteristically have high concentrations of incompatible elements, thus I also experimentally assess the ability of alkaline melts and fluids associated with sediment melting to carry lithophile and chalcophile elements in the sub-arc.
I measured the chemical composition of 18 plutonic samples from the Bonanza island arc, emplaced between 203 and 164 Ma on the Wrangellia terrane on Vancouver Island, British Columbia. Models using trace elements with Nd and Sr isotopes indicate < 10% assimilation of the Wrangellia basement by the Bonanza arc magmas. The Bonanza arc rare earth element geochemistry is best explained as two lineages, each with two fractionation stages implicating < 15% garnet crystallization. My inference of garnet-bearing cumulates in the unexposed lower crust of the Bonanza arc, an unsuspected similarity with the coeval Talkeetna arc (Alaska), is consistent with estimates from geologic mapping and geobarometry indicating that the arc grew to > 23 km total thickness. The age distribution of the Bonanza arc plutons shows a single peak at 171 Ma whereas the volcanic rock age distribution shows two peaks at 171 and 198 Ma, likely due to sampling and/or preservation bias. Numerous mechanisms may produce the E-W separation of young and old volcanism and this does not constrain Jurassic subduction polarity beneath Wrangellia.
Although a small component of arc magmatism, alkaline arc rocks are associated with economic concentrations of chalcophile elements. The effect of varying alkalinity on S Concentration at Sulfide Saturation (SCSS) has not been previously tested. Thus, I conducted experiments on hydrous basaltic andesite melts with systematically varied alkalinity at 1270°C and 1 GPa using piston-cylinder apparatus. At oxygen fugacity two log units below the fayalite magnetite quartz buffer, I find SCSS is correlated with total alkali concentration, perhaps a result of the increased non-bridging oxygen associated with increased alkalinity. A limit to the effect of alkalis on SCSS in hydrous melts is observed at ~7.5 wt.% total alkalis. Using my results and published data, I retrained earlier SCSS models and developed a new empirical model using the optical basicity compositional parameter, predicting SCSS with slightly better accuracy than previous models.
Sediment melts contribute to the trace element signature of arcs and the chalcophile elements, compatible in redox-sensitive sulfide, are of particular interest. I conducted experiments at 3 GPa, 950 – 1050°C on sediment melts, determined fluid concentrations by mass balance and report the first fluid-melt partition coefficients (Dfluid/melt) for sediment melting. Compared to oxidized, anhydrite-bearing melts, I observe high Dfluid/melt for chalcophile elements and low values for Ce in reduced, pyrrhotite-bearing melts. Vanadium and Sc are unaffected by redox. The contrasting fluid-melt behaviour of Ce and Mo that I report indicates that melt, not fluid, is responsible for elevated Mo in the well-studied Lesser Antilles arc. / Graduate
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Feeds : En implementation för skapande av RSS-flöden i nya Smartsign PublisherSundin, Anders January 2024 (has links)
In this project assignment, the ability to create RSS feeds for Smartsign's new web application, New Publisher, has been developed. The current version of Publisher has been in its current form for a long time and is beginning to feel somewhat outdated, motivating the need for an update. The development work has been carried out in the JavaScript framework Angular, in combination with SCSS and Angular-Materials. The purpose of the work has been to create this part of the new web application, which upon implementation will provide a new, simpler, and more visually appealing interface for users who want to distribute messages to connected signage screens in the form of RSS feeds, here in New Publisher called feeds. The work has resulted in a fully functional part of the application which is ready to be put into production / I detta projektarbete har RSS-flöden för företaget Smartsigns nya webbapplikation Nya Publisher utvecklats. Publisher används för att ge företagets kunder möjlighet att leverera budskap till signage-skärmar. Den nuvarande versionen av Publisher har funnits i sin nuvarande form en lång tid och börjar nu kännas något omodern, vilket motiverar behovet av en uppdatering. Utvecklingsarbetet har genomförs i JavaScript-ramverket Angular i kombination med SCSS och Angular-Materials. Syftet med arbetet har varit att skapa denna del i den nya webbapplikationen vilket vid implementering kommer att ge ett nytt, enklare och mer visuellt tilltalande gränssnitt för användare som vill nå ut med budskap till anslutna signage-skärmar i form av RSS-flöden vilket i Publisher kallas för feeds. Arbetet har resulterat i en fullt fungerande del av applikationen vilken i sig är redo att sättas i produktion
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Development of a satellite communications software system and scheduling strategyGilmore, John Sebastian 03 1900 (has links)
Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: Stellenbosch University and the Katholieke Universiteit Leuven has a joint undertaking
to develop a satellite communications payload. The goals of the project are:
to undertake research and expand knowledge in the area of dynamically configurable
antenna beam forming, to prove the viability of this research for space purposes and
to demonstrate the feasibility of the development in a practical application.
The practical application is low Earth orbit satellite communication system for
applications in remote monitoring. Sensor data will be uploaded to the satellite,
stored and forwarded to a central processing ground station as the satellite passes
over these ground stations. The system will utilise many low-cost ground sensor
stations to collect data and distribute it to high-end ground stations for processing.
Applications of remote monitoring systems are maritime- and climate change
monitoring- and tracking. Climate change monitoring allows inter alia, for the monitoring
of the effects and causes of global warming.
The Katholieke Universiteit Leuven is developing a steerable antenna to be
mounted on the satellite. Stellenbosch University is developing the communications
payload to steer and use the antenna. The development of the communications
protocol stack is part of the project. The focus of this work is to implement the
application layer protocol, which handles all file level communications and also implements
the communications strategy.
The application layer protocol is called the Satellite Communications Software
System (SCSS). It handles all high level requests from ground stations, including
requests to store data, download data, download log files and upload configuration
information. The design is based on a client-server model, with a Station Server
and Station Handler. The Station Server schedules ground stations for communication
and creates a Station Handler for each ground station to handle all ground
station requests. During the design, all file formats were defined for efficient ground
station-satellite communications and system administration. All valid ground station
requests and handler responses were also defined.
It was also found that the system may be made more efficient by scheduling
ground stations for communications, rather than polling each ground station until
one responds. To be able to schedule ground station communications, the times
when ground stations will come into view of the satellite have to be predicted. This
is done by calculating the positions of the Satellite and ground stations as functions
of time. A simple orbit propagator was developed to predict the satellite distance
and to ease testing and integration with the communications system. The times
when a ground station will be within range of the satellite were then predicted and a
scheduling algorithm developed to minimise the number of ground stations not able to communicate.
All systems were implemented and tested. The SCSS executing on the Satellite
was developed and tested on the satellite on-board computer. Embedded implementations
possess strict resource limitations, which were taken into account during the
development process. The SCSS is a multi-threaded system that makes use of thread
cancellation to improve responsiveness. / AFRIKAANSE OPSOMMING: Die Universiteit van Stellenbosch ontwerp tans ’n satelliet kommunikasieloonvrag in
samewerking met die Katolieke Universiteit van Leuven. Die doel van die projek is
om navorsing te doen oor die lewensvatbaarheid van dinamies verstelbare antenna
bundelvorming vir ruimte toepassings, asook om die haalbaarheid van hierdie navorsing
in die praktyk te demonstreer.
Die praktiese toepassing is ’n satellietkommunikasiestelsel vir afstandsmonitering,
wat in ’n Lae-Aarde wentelbaan verkeer. Soos die satelliet in sy wentelbaan beweeg,
sal sensor data na die satelliet toe gestuur, gestoor en weer aangestuur word. Die
stelsel gebruik goedkoop sensorgrondstasies om data te versamel en aan te stuur na
kragtiger grondstasies vir verwerking.
Afstandsmoniteringstelsels kan gebruik word om klimaatsverandering, sowel as
die posisie van skepe en voertuie, te monitor. Deur oa. klimaatsveranderinge te
dokumenteer, kan gevolge en oorsake van globale verhitting gemonitor word.
Die Katholieke Universiteit van Leuven is verantwoordelik vir die ontwerp en
vervaardiging van die satelliet antenna, terwyl die Universiteit van Stellenbosch verantwoordelik
is vir die ontwerp en bou van die kommunikasie loonvrag. ’n Gedeelte
van hierdie ontwikkeling sluit die ontwerp en implementasie van al die protokolle van
die kommunikasieprotokolstapel in. Dit fokus op die toepassingsvlak protokol van die
protokolstapel, wat alle leêrvlak kommunikasie hanteer en die kommunikasiestrategie
implementeer.
Die toepassingsvlaksagteware word die Satellietkommunikasie sagtewarestelsel
(SKSS) genoem. Die SKSS is daarvoor verantwoordelik om alle navrae vanaf grondstasies
te hanteer. Hierdie navrae sluit die oplaai en stoor van data, die aflaai van
data, die aflaai van logs en die oplaai van konfigurasie inligting in. Die ontwerp
is op die standaard kliënt-bediener model gebasseer, met ’n stasiebediener en ’n
stasiehanteerder. Die stasiebediener skeduleer die tye wanneer grondstasies toegelaat
sal word om te kommunikeer en skep stasiehanteerders om alle navrae vanaf die
stasies te hanteer. Gedurende die ontwerp is alle leêrformate gedefinieer om doeltreffende
adminstrasie van die stelsel, asook kommunikasie tussen grondstasies en die
satelliet te ondersteun. Alle geldige boodskappe tussen die satelliet en grondstasies
is ook gedefnieer.
Daar is gevind dat die doeltreffendheid van die stelsel verhoog kan word deur die
grondstasies wat wil kommunikeer te skeduleer, eerder as om alle stasies te pols totdat
een reageer. Om so ’n skedule op te stel, moet die tye wanneer grondstasies binne
bereik van die satelliet gaan wees voorspel word. Hierdie voorspelling is gedoen deur
die posisies van die satelliet en die grondstasies as funksies van tyd te voorspel. ’n
Eenvoudige satelliet posisievoorspeller is ontwikkel om toetsing en integrasie met die SKSS te vergemaklik. ’n Skeduleringsalgoritme is toe ontwikkel om die hoeveelheid
grondstasies wat nie toegelaat word om te kommunikeer nie, te minimeer.
Alle stelsels is geimplementeer en getoets. Die SKSS, wat op die satelliet loop,
is ontwikkel en getoets op die satelliet se aanboord rekenaar. Die feit dat ingebedde
stelsels oor baie min hulpbronne beskik, is in aanmerking geneem gedurende die
ontwikkeling en implementasie van die SKSS. Angesien die SKSS ’n multidraadverwerkingsstelsel
is, word daar van draadkansellasie gebruik gemaak om die stelsel se
reaksietyd te verbeter.
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