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- Brus, Linda, 1977-
(författare)
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Nonlinear Identification and Control with Solar Energy Applications
- 2008
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Nonlinear systems occur in industrial processes, economical systems, biotechnology and in many other areas. The thesis treats methods for system identification and control of such nonlinear systems, and applies the proposed methods to a solar heating/cooling plant. Two applications, an anaerobic digestion process and a domestic solar heating system are first used to illustrate properties of an existing nonlinear recursive prediction error identification algorithm. In both cases, the accuracy of the obtained nonlinear black-box models are comparable to the results of application specific grey-box models. Next a convergence analysis is performed, where conditions for convergence are formulated. The results, together with the examples, indicate the need of a method for providing initial parameters for the nonlinear prediction error algorithm. Such a method is then suggested and shown to increase the usefulness of the prediction error algorithm, significantly decreasing the risk for convergence to suboptimal minimum points. Next, the thesis treats model based control of systems with input signal dependent time delays. The approach taken is to develop a controller for systems with constant time delays, and embed it by input signal dependent resampling; the resampling acting as an interface between the system and the controller. Finally a solar collector field for combined cooling and heating of office buildings is used to illustrate the system identification and control strategies discussed earlier in the thesis, the control objective being to control the solar collector output temperature. The system has nonlinear dynamic behavior and large flow dependent time delays. The simulated evaluation using measured disturbances confirm that the controller works as intended. A significant reduction of the impact of variations in solar radiation on the collector outlet temperature is achieved, though the limited control range of the system itself prevents full exploitation of the proposed feedforward control. The methods and results contribute to a better utilization of solar power.
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- Brus, Linda
(författare)
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Recursive black-box identification of nonlinear state-space ODE models
- 2006
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Nonlinear system identification methods is a topic that has been gaining interest over the last years. One reason is the many application areas in controller design and system development. However, the problem of modeling nonlinear systems is complex and finding a general method that can be used for many different applications is difficult.This thesis treats recursive identification methods for identification of systems that can be described by nonlinear ordinary differential equations. The general model structure enables application to a wide range of processes. It is also suitable for usage in combination with many nonlinear controller design methods.The first two papers of the thesis illustrates how a recursive prediction error method (RPEM) can be used for identification of an anaerobic digestion process and a solar heating system. In the former case the model complexity is significantly reduced compared to a semi-physical model of the system, without loosing much in model performance. In the latter case it is shown that it is possible to reach convergence even for a small data set, and that the resulting model is of comparable quality as a previously published grey-box model of the same system.The third paper consists of a convergence analysis of the studied RPEM. The analysis exploits averaging analysis using an associated ordinary differential equation, and formulates conditions for convergence to a minimum of the criterion function. Convergence to a true parameter set is also illustrated by an example.The fourth, and last, paper of this thesis addresses the problem of finding suitable initial parameters e.g. for the RPEM. With a potentially non-convex criterion function the choice of initial parameters becomes decisive for whether the algorithm converges to the global optimum, or a local one. The suggested initialization algorithm is a Kalman filter based method. Experiments using a simulated example show that the Kalman based method can, under beneficial circumstances, be used for initialization of the RPEM. The result is further supported by successful identification experiments of a laboratory scale cascaded tanks process, where the Kalman based method was used for initialization.
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- Carlsson, Magnus, et al.
(författare)
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A comparative study on the degradation of cotton linters induced by carbonate and hydroxyl radicals generated from peroxynitrite
- 2005
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Ingår i: Holzforschung. - 0018-3830 .- 1437-434X. ; 59:2, s. 132-142
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Tidskriftsartikel (refereegranskat)abstract
- Carbonate (CO3.(-)) and hydroxyl (HO.) radicals were chemically produced in cotton linter suspensions using peroxynitrite as a radical precursor. Both radicals could degrade cotton linters, as shown by viscosity and GPC-SEC measurements. As evidenced by the viscosity measurements, the presence of oxygen during the cotton linter treatments slightly increased cellulose degradation by both radicals. For the carbonate radical, more than 90% of the viscosity losses could be recovered by reductive NaBH4 treatment before measuring the viscosity, whereas only approximately 40% of the viscosity was recovered after hydroxyl radical degradation and subsequent NaBH4 treatment. This indicates that carbonate radicals mainly abstract H-atoms adjacent to hydroxyl groups, i.e., at C-2, C-3 and C-6. This intramolecular selectivity may reflect a polar effect, whereby hydrogen atom abstractions from these positions are favoured. In addition, abstraction at C-6 would be sterically and statistically favoured.
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- Carlsson, Magnus, et al.
(författare)
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The Carbonate Radical as One-Electron Oxidant of Carbohydrates in Alkaline media
- 2005
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Ingår i: Holzforschung. - 0018-3830 .- 1437-434X. ; 59:2, s. 143-146
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Tidskriftsartikel (refereegranskat)abstract
- The mechanism by which the carbonate radical anion reacts with D-glucose in alkaline aqueous solutions has been studied by means of gamma-radiolysis. From the product analysis it is concluded that the reaction sequence is initiated by a one-electron transfer between the carbonate radical anion and deprotonated D-glucose. In the presence of molecular oxygen, the major, if not only products of this reaction sequence are formic acid, arabinose and gluconic acid and reaction schemes are proposed to account for the observed formation of these products.
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- Carlsson, Per-Olof, et al.
(författare)
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Testfasen i miljöklassningsprojekten : Delrapport september 2007
- 2007
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Denna rapport är en redovisning av resultat och underlag i testfasen imiljöklassningsprojekten.I januari 2005 inleddes tre forskningsprojekt med målet att föreslå ettsystem för miljöklassning av byggnader. Forskningsprojekten har engemensam projektgrupp där 27 företag ingår. Syftet med projekten är attta fram förslag till indikatorer och kriterier för klassning inom områdenaenergi, innemiljö och farliga ämnen. Projekten avslutas hösten 2007.Under perioden december 2006 – mars 2007 genomfördes ett test avflera alternativa förslag till indikatorer. Testet utfördes i nära samverkanmed 16 företag från projektgruppen och ytterligare 10 bostadsrättföreningaroch 6 småhusägare. Sammanlagt ingick 46 byggnader av olika typ(flerbostadshus, kontor, sjukhus, småhus etc.).Testet utfördes genom att företag, föreningar och småhusägare samladein nödvändiga data för klassning av ett antal preliminära indikatorer. Defick också svara på frågor om prioritering av aspekter, indikatorer ochvilka resurser som krävdes.Insamlingen av mätdata kompletterades sedan med intervjuer för att fåin ytterligare information och synpunkter.Denna rapport innehåller resultat i form av:Indata från dem som testat.Försök till klassning av respektive byggnad.Synpunkter på genomförandet av testningen.Synpunkter på klassningssystemet.Dessutom ingick en studie av kopplingen mellan energideklarationer ochmiljöklassning. Några av byggnaderna energideklarerades och dessa datajämfördes med vad som behövs för miljöklassning.Rapporten innehåller samtliga dokument från testningen och kommeratt vara ett viktigt underlag i det fortsatta arbetet. Under hösten 2007kommer ett förslag till klassningssystem att presenteras.
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- Enger, Shirin Abbasinejad, et al.
(författare)
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Cross-fire doses from β-emitting radionuclides in targeted radiotherapy : A theoretical study based on experimentally measured tumor characteristics
- 2008
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Ingår i: Physics in Medicine and Biology. - : IOP Publishing. - 0031-9155 .- 1361-6560. ; 53:7, s. 1909-1920
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Tidskriftsartikel (refereegranskat)abstract
- A mathematical model based upon histological findings of cell cluster distributions in primary breast cancers and lymph node metastases was developed. The model is unique because it accounts for tumor cell cluster formations within both primary tumors and metastases. The importance of inter-cell cluster cross-fire radiation dose for beta-emitting radionuclides of different energies was studied. The cell clusters were simulated as spheres with 15, 25 and 50 microm radii having a homogeneous radioactivity distribution. The self-dose as well as the dose distribution around the spheres was calculated for seven radionuclides, (90)Y, (188)Re, (32)P, (186)Re, (159)Gd, (131)I and (177)Lu using the GEANT4 Monte Carlo code. Generally, the self-dose was decreasing with increasing energy of the emitted beta particles. An exception was (188)Re which, compared to (32)P, had higher beta energy as well as higher self-dose. This was due to the higher emission of conversion and Auger electrons in the (188)Re-decay. When the cell clusters had a mean distance that was shorter than the maximum range of beta-particles, then the inter-cluster cross-fire radiation contributed significantly to the absorbed dose. Thus, high-energy beta-particles may, in spite of a low self-dose to single clusters, still be favorable to use due to the contribution of inter-cluster cross-fire radiation.
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