| 1. |
- Berezowski, M., et al.
(författare)
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Dynamics of heat-integrated pseudohomogeneous tubular reactors with axial dispersion
- 2000
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Ingår i: Chemical Engineering and Processing. - 0255-2701 .- 1873-3204. ; 39:2, s. 181-188
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Tidskriftsartikel (refereegranskat)abstract
- The study concerns a theoretical analysis of pseudohomogeneous autothermal tubular reactors with axial dispersion of mass and heat. Based on analysis and simulations it is demonstrated that such a system can generate complex oscillatory profiles of temperature and concentration-periodic or chaotic. These profiles, especially those of aperiodic character, can seriously impair the performance of the system. The effect of three parameters on the reactor dynamics is studied, namely, the cooling medium temperature, the Lewis number and the Peclet number. We consider only relatively small values of the Lewis number in this paper.
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| 2. |
- Berezowski, M., et al.
(författare)
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Increased performance through autonomous oscillations in tubular reactors with recycle
- 2001
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Ingår i: In|ynieria Chemiczna i Procesowa. - 0208-6425. ; 22:3B, s. 235-240
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Tidskriftsartikel (refereegranskat)abstract
- The paper treats the dynamics of tubular reactors in which a fraction of the product is recycled and mixed with the fresh feed. The results presented in this paper show that autonomous limit cycles may drastically increase the performance of the reactor, and that limit cycle behavior therefore may be something that should be sought rather than avoid.
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| 6. |
- Cui Carlemalm, Hong, et al.
(författare)
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Performance limitations in decentralized control
- 2002
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Ingår i: Journal of Process Control. - 0959-1524 .- 1873-2771. ; 12:4, s. 485-494
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Tidskriftsartikel (refereegranskat)abstract
- In decentralized control of multivariable systems. the system is decomposed into a number of subsystems and individual controllers are designed for each subsystem. Advantages of such decomposition include reduced modelling requirements and case of implementation. However, a potential disadvantage is a reduction in achievable control performance due to restricted controller structure. In this paper we consider performance limitations from non-minimum phase transmission zeros in decentralized control. In particular, we derive conditions on when closing the loop around one subsystem moves transmission zeros of other subsystems across the imaginary axis. Such zero crossings may occur regardless of the existence of non-minmum phase behavior in the open-loop system, and may, therefore, represent performance limitations specific to the use of decentralized controllers.
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| 7. |
- Cui, H., et al.
(författare)
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Optimal design of buffers in plants with recycling
- 2002
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Ingår i: Pulp & paper Canada. - 0316-4004. ; 103:6, s. 25-29
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Tidskriftsartikel (refereegranskat)abstract
- Buffer tanks are commonly employed to dampen the effect of disturbances in chemical processes. In order to minimize the number and size of tanks, the buffers Should be designed to Mainly handle disturbances that cannot be effectively handled by a feedback Control system. In this paper we consider optimal design of buffers in plants with recycle of material and/or energy. Such recycling is becoming common in process plants, and typically increases the disturbance sensitivity significantly, and hence the potential need for buffers. We Show that the location of the buffer is a crucial decision in recycle systems, and derive simple model-based tools that Call be used to determine both the optimal Size and location of buffers ill recycle systems.
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| 8. |
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| 9. |
- Garcia-Gabin, Winston, et al.
(författare)
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Multilevel model based glucose control for type-1 diabetes patients
- 2013
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Ingår i: 2013 35th Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC). - 9781457702167 ; , s. 3917-3920
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Konferensbidrag (refereegranskat)abstract
- Diabetes is a disease that involves alterationsat multiple biological levels, ranging from intracellular sig-nalling to organ processes. Since glucose homeostasis is theconsequence of complex interactions that involve a numberof factors, the control of diabetes should be based on amultilevel analysis. In this paper, a novel approach to designof closed-loop glucose controllers based on multilevel models ispresented. A control scheme is proposed based on combininga pharmacokinetic/pharmacodynamic model with an insulinsignal transduction model for type 1 diabetes mellitus patients.Based on this, an insulin feedback control schemes is designed.Two main advantages of explicitly utilizing information at theintracellular level were obtained. First, significant reductionof hypoglycaemic risk by reducing the undershoot in glucoselevels in response to added insulin. Second, robust performancefor inter-patient changes, demonstrated through application ofthe multilevel control strategy to a well establishedin silicopopulation of diabetic patients.
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| 10. |
- Garcia-Gabin, Winston, et al.
(författare)
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Multilevel Model of Type 1 Diabetes Mellitus Patients for Model-Based Glucose Controllers
- 2013
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Ingår i: Journal of Diabetes Science and Technology. - : Diabetes Technology Society. - 1932-2968. ; 7:1, s. 193-205
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Tidskriftsartikel (refereegranskat)abstract
- Glucose homeostasis is the result of complex interactions across different biological levels. This multilevel characteristic should be considered when analyzing and designing closed-loop glucose control algorithms. Classic control schemes use only a pharmacokinetic-pharmacodynamic (PKPD) perspective to describe the gluco-regulatory system. A multilevel model combining a PKPD model with an insulin signaling model is proposed for patients with type 1 diabetes mellitus T1DM (T1DM). The PKPD Dalla Man model for T1DM is expanded to include an intracellular level involving insulin signaling to control glucose uptake through glucose transporter type 4 (GLUT4) translocation. A model-based controller is then designed and used as an example to illustrate the feasibility of the proposal. Two significant results were obtained for the controller explicitly utilizing multilevel information. No hypo-glycemic events were registered and an excellent performance for interpatient variability was achieved. Controller performance was evaluated using two indexes. The glucose was kept inside the range (70-180) mg/dl more than 99% of the time, and the intrapatient variability measured using control variability grid analysis was solid with 90% of the population inside the target zone. Multilevel models open new possibilities for designing glucose control algorithms. They allow controllers to take into account variables that have a strong influence on glucose homeostasis. A model-based controller was used for demonstrating how improved knowledge of the multilevel nature of diabetes increases the robustness and performance of glucose control algorithms. Using the proposed multi-level approach, a reduction of the hypoglycemic risk and robust behaviour for intrapatient variability was demonstrated.
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