| 1. |
- Ohlson, Sten, et al.
(författare)
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Weak affinity chromatography
- 1993. - 1
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Ingår i: Handbook of affinity chromatography. - New York : Marcel Dekker. - 0824789393 ; , s. 299-314
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Bokkapitel (övrigt vetenskapligt/konstnärligt)
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| 2. |
- Wik, Torsten, 1968
(författare)
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Dynamisk modellering av nitrifikation i biobädd
- 1993
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- En kortfattad sammanfattning av teorierna kring nitrifikation i biofilm liksom några resultat från tidigare arbeten inom området presenteras. Försöksdata från en pilotannläggning på Ryaverket i Göteborg har undersökts och några av resultaten redovisas. En dynamisk modell som modellerar de autotrofa nitrifierande bakterierna Nitrosomonas och Nitrobacter har formulerats och ett datorprogram för simuleringar har tagits fram. Modellarbetet har framförallt koncentrerats på dynamiken i biofilmen och transporten av substrat. Inkommande vatten till biobädden innehåller mycket låga halter av organiskt material. Därför har heterotrofa bakterier ej beaktats i modellen. Programmet beskrivs utförligt för att underlätta en utbyggnad av modellen och de numeriska problem som kan uppstå vid lösning av ekvationerna i den här typen av modeller kommenteras. Ett antal simuleringar, bl a ett simulerat faktorförsök, presenteras och kommenteras. Simuleringar som utförts ger anledning att misstänka att nitrithalten i utgående vatten från en nitrifierande biobädd ökar med ökande flöde upp till en viss nivå, varefter den kan tänkas sjunka igen då flödet ökas ytterligare. Stegsvar som genomförts visar att en dålig substrattillgång i bädden under en längre period minskar bakteriekoncentrationerna i biofilmen så mycket att effektiviteten hos bädden märkbart försämras. Studierna av experimentella data visar att inkommande vatten kan anses vara mättat, liksom även i de områden av bädden där nitrifikationen är mycket låg. Den uppmätta kvoten mellan nitrifierad ammonium och minskningen i alkalinitet över bädden stämmer med den teoretiska kvoten som utnyttjas i modellen. Därigenom beaktas även alkalinitetsbegränsning. I stort sett all nitrifierad ammonium övergår i nitrit och nitrat vilket även det stämmer med modellantagandena.
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| 3. |
- Wik, Torsten, 1968, et al.
(författare)
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Modelling the Dynamics of a Trickling Filter for Waste Water Treatment
- 1994
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Ingår i: Preprints of the 5th Nordic Process Control Workshop, Lyngby, Denmark.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- This study concems the dynamics of the nitrifying efficiency of a trickling filter for waste water treatment. In a novel approach, based on minimum plant area usage, a filter will be placed after the secondary sedimentation tanks with recirculation to the activated sludge process stage. The objective of the trickling filter model is to describethe growth of the nitrifying bacteria Nitrosomonas and Nitrobacter in the bio-film. A steady state mass-balance model for the substrates in the film based on Monod kinetics has been formulated. The dynamics of the filter, or the “memory”, is described by a division of the film infour volume fractions, Nitrosomonas, Nitrobacter, inert (non-active) material and water. These fractions are calculated at different depths of the film as well as for various layers of the filter StrUCtUTe. Data from a pilot plant at Rya treatment plant in Gothenburg, Sweden, haveprovided the necessary feedback for calculating model parameters, verifying assumptions etc. A shooting and matching routine in the NAG Fortran library is used for the solution of the model equations. Simulations performed so far have indicated that it can take days and even weeks for changes in the bacteria populations to take place. Thismeans that the working point for the proposed full scale filter at the plant should track the past history of the filter.
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| 4. |
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| 5. |
- Holmberg, Erland, et al.
(författare)
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Reaction conditions for the resolution of 2-methylalkanoic acids in esterification and hydrolysis with lipase from Candida cylindracea
- 1991
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Ingår i: Applied Microbiology and Biotechnology. - 0175-7598. ; 35:5, s. 572-578
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Tidskriftsartikel (refereegranskat)abstract
- We have demonstrated resolution of 2-methylalkanoic acids using lipase from Candida cylindracea as a catalyst. The resolution of 2-methyldecanoic acid was more successful than that of 2-methylbutyric acid both by esterification and hydrolysis. This indicates that the resolution of the acid is dependent on the chain length of the acid moiety. The chain length of the alcohol moiety of the ester affected the resolution of the long-chain acid only. Using esterification, (R)-2-methyldecanoic acid was produced in an enantiomeric excess (e.e.) of 95% (E = 40). If the enantiomeric ratio is low (E = 3.6), as in the resolution of 2-methylbutyric acid, esterification combined with a high equilibrium conversion could be used to yield the remaining acid in a high e.e. In the hydrolytic reactions, the e.e. and the equilibrium conversion were dependent on the pH and the presence of CaCl2. When octyl 2-methyldecanoate was hydrolysed at pH 8.0 in the presence of CaCl2, the (S)-acid was formed with an e.e. of 80% (E = 9), but when the hydrolysis was carried out at pH 7.5 without CaCl2, a very low e.e. and a low equilibrium conversion were observed. The latter conditions allowed the esterification of 2-methyldecanoic acid with 1-octanol even in aqueous medium.
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| 6. |
- Eriksson, Håkan, et al.
(författare)
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A robust correlation receiver for distance estimation
- 1994
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Ingår i: IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control. - New York : Institute of Electrical and Electronics Engineers (IEEE). - 0885-3010 .- 1525-8955. ; 41:5, s. 596-603
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Tidskriftsartikel (refereegranskat)abstract
- Many methods for distance estimation, such as the ultrasonic pulse-echo method, involve the estimation of a time-of-flight (TOF). In this paper, a signal model is developed that, apart from the TOF, accounts for an unknown, linear frequency dependent distortion as well as for additive noise. We derive a TOF estimator for this model based on the criteria of maximum likelihood. The resulting receiver can be seen as an extension or generalization of the well known cross-correlation, or "matched filter", estimator described, e.g., by Nilsson. The novel receiver is found to be more robust against unknown pulse shape distortion than the cross-correlation estimator, giving less biased TOF estimates. Also, bias versus noise sensitivity can be controlled by proper model order selection
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| 7. |
- Sundström, N., et al.
(författare)
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Registration of surface structures using airborne focused ultrasound
- 1991
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Ingår i: Ultrasound in Medicine and Biology. - : Elsevier BV. - 0301-5629 .- 1879-291X. ; 17:5, s. 513-518
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Tidskriftsartikel (refereegranskat)abstract
- A low-cost measuring system, based on a personal computer combined with standard equipment for complex measurements and signal processing, has been assembled. Such a system increases the possibilities for small hospitals and clinics to finance advanced measuring equipment. A description of equipment developed for airborne ultrasound together with a personal computer-based system for fast data acquisition and processing is given. Two air-adapted ultrasound transducers with high lateral resolution have been developed. Furthermore, a few results for fast and accurate estimation of signal arrival time are presented. The theoretical estimation models developed are applied to skin surface profile registrations
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| 8. |
- Axelsson, Jan Peter, et al.
(författare)
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Substrate Control of Biotechnical Fedbatch Processes. Robustness and the Role of Adaptivity
- 1990
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Konferensbidrag (refereegranskat)abstract
- Results from experiments on laboratory scale fedbatch processes are presented as well as analysis and design of the control system. The main reason for control is to track the drastic growth in feed demand during a cultivation. Variations in the amount and quality of the inocculum makes precalculated dosage schemes of limited value to obtain reproducible cultivation conditions. Two processes have been studied on a laboratory scale, production of bakers' yeast, and production of the enzyme salicylate hydroxylase using a strain of bacteria. Direct measurement was used to monitor the feed demand. A regulator structure is proposed based on an observer for the exponentially growing feed demand. It can be viewed as a modified PID regulator around a dosage scheme, but it is less sensitive to errors in the dosage scheme than conventional PID control. The a priori knowledge of the feed profile is further relaxed by introduction of adaptation of the growth rate parameter. The obtained non-linear control system has a simple structure and stability is garanteed for a wide range of initial values using the technique of Liapunov function. The linearized system is analysed in the frequency domain and the adaptation is shown to have negligible influence on the loop phase margin. The adaptive regulator is tested in simulation against real feed profiles and shows good results.
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| 9. |
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