16 research outputs found
Mathematical modelling of a nordic hydrological system, and the use of a simplified run-off model in the stochastic optimal control of a hydroelectrical power system
Reaction Invariants and Their Importance in the Analysis of Eigenvectors, State Observability and Controllability of the Continuous Stirred Tank Reactor
Inventory control of particulate processes
Abstract In this work we address the problem of designing model-based controllers for particulate processes described by population balance (PB) models. We focus on PB models that are solved by numerical discretization, for which many standard control methodologies are not suitable due to the high order of these models. We interpret discretized PB models as chemical reaction networks and suggest to combine inventory control with techniques of stability of chemical reaction networks to design the controller. Inventory control is based on the idea of manipulating process flows so that certain extensive variables defining the system, called inventories, follow their setpoints. The whole system is stabilized by controlling the dominant inventories. The discretized PB is exploited in all aspects of controller design, from determining the controlled inventories to the final implementation of the control law. The methodology is illustrated with an industrial leaching reactor, the Silgrain Âź process. We show that the discretized PB model takes the form of a Feinberg-Horn-Jackson zero-deficiency network, allowing us to prove stabilization of the whole system. The performance of standard inventory control and robust inventory control are investigated by simulation, with satisfactory results even in the presence of modeling errors
âItâs hard to imagine what itâs like to be a leader before you stand thereâ: A study of studentsâ experiences as school leaders in school adoption
Denne artikkelen undersÞker hvordan skoleovertakelse bidrar til forstÄelse av og innsikt i skolen som organisasjon og skoleledelse hos lÊrerstudenter med l. Studien baserer seg pÄ data fra sju gruppeintervjuer. Sentrale funn er at studentene opplevde Ä fÄ et innblikk i hva det innebÊrer Ä vÊre skoleledere og en mer systemisk forstÄelse av skolen. Konklusjonen lÞfter fram forslag til enkelte forbedringer av praksisformen.This article examines how school adoption contributes to insight into the school as an organisation and school leadership among student teachers with leadership responsibilities. The study is based on data from seven group interviews. Central findings are that the students experienced an insight into what it means to be school leaders and a more systemic understanding of the school. The conclusion highlights proposals for some improvements in the form of practice.acceptedVersio
Model Reduction in Large Chemical Systems- an Alternative Method Applying Discrete Approximation
No numerical data.
Dynamic model reduction techniques based on the
decomposition of the stoichiometric matrix to find the chemical invariant, break
down if axial diffusion is present in a tubular reactor.
Straightforward discretization of the partial
differential operator does indeed show that the resulting discrete dynamic
model cannot generally be partioned to obtain the reaction variant vector and
the reaction invariant (asymptotic) vector. However, the paper demonstrate
that, if the diffusional tubular reactor is discretely and approximatively represented
by tanks-in-series, then matrix approaches to successfully find the chemical variant
and invariant vectors of the resulting chemical process model is possible. </p
Model Reduction in Chemical Systems- an Alternative Method Applying Discrete Approximation
This paper addresses model reduction in large or spatially distributed systems including diffusion of matter and chemical reactions. If diffusion is present, it would be represented by a diffusion operator (always including a spatial second derivative term). If diffusion is not present, spatial discretization is straightforward. In the latter case, applying the concept of chemical invariants, or the concept of asymptotic chemical invariants, paves the way for model reduction through elimination of the invariants. Inclusion of diffusion destroys the opportunity to obtain invariants , when numerical discretization of the diffusion term is applied. However, the paper demonstrates that application of the invariant concept may be applied even in the case of diffusion of matter in a chemical tubular reactor, if relying on an approximation in modelling of a tubular reactor by a tank-in-the series model. For nonreacting matter, the quality and numerical properties of the tanks-in-the-series model approximation of a tubular reactor is well documented in the literature. However, there is no general proof available for the quality and effectiveness of such an approximation when chemical reactions are present, although example cases show good approximation.</div
Norsk atompolitikk i nord : en analyse av norske oppfatninger av atomspÞrsmÄl i Nordvest-Russland etter den kalde krigens slutt
NordomrÄdene har etter den kalde krigen opplevd et ulikt interessefokus i norsk politikk. Dette gjenspeiler seg blant annet i hvordan ulike atomutfordringer i nord har blitt oppfattet.
Denne oppgaven ser pÄ hvordan atomspÞrsmÄl i Nordvest-Russland har blitt gjort til sikkerhetspolitikk etter den kalde krigen. Det er materiale fra den norske regjering og Stortinget som ligger til grunn for analysen. Den tar utgangspunkt i hva KÞbenhavnerskolen, kaller en sikkerhetiseringsprosess. Det vil si den prosess som fÞrer til at et tema blir lÞftet fra den alminnelige politiske debatt og opp pÄ det sikkerhetspolitiske plan. I denne prosessen pÄstÄr en talehandling at noe er eksistensielt truet. Om dette blir godtatt av den mÄlgruppen som det er rettet mot, er uavhengig av om det faktisk er truet eller ikke. Dette fordi det ikke finnes noe objektivt mÄl pÄ hva som kan defineres som sikkerhet.
Det finnes eksempler pÄ at atomspÞrsmÄl settes som sikkerhetspolitikk. For eksempel i forhold til atomforurensing. KÞbenhavnerskolens krav til at noe kan anses som fullstendig sikkerhetisert, oppfylles imidlertid ikke.
Utviklingen i hvordan atomtrusselen oppfattes er imidlertid klar. Den gÄr fra Ä se pÄ atomspÞrsmÄl hovedsakelig som en sikkerhetspolitisk utfordring fÞr 1990, over i Ä se den som en miljÞ- og sikkerhetspolitisk utfordring for deretter igjen Ä havne som en sikkerhetspolitisk utfordring
Mathematical modelling of a nordic hydrological system, and the use of a simplified run-off model in the stochastic optimal control of a hydroelectrical power system
An Implementation of Estimation Techniques to a Hydrological Model for Prediction of Runoff to a Hydroelectric Power-Station
Parameter and state estimation algorithms have been applied to a hydrological model of a catchment area in southern Norway to yield improved control of the household of water resources and better economy and efficiency in the running of the power station, as experience proves since the system was installed on-line in the summer of 1978
«Vanskelig Ä forestille seg hvordan det er Ä vÊre i ledelsen fÞr man stÄr der»: En studie om studenters erfaringer som skoleledere i skoleovertakelse
Denne artikkelen undersÞker hvordan skoleovertakelse bidrar til forstÄelse av og innsikt i skolen som organisasjon og skoleledelse hos lÊrerstudenter med l. Studien baserer seg pÄ data fra sju gruppeintervjuer. Sentrale funn er at studentene opplevde Ä fÄ et innblikk i hva det innebÊrer Ä vÊre skoleledere og en mer systemisk forstÄelse av skolen. Konklusjonen lÞfter fram forslag til enkelte forbedringer av praksisformen