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| 2. |
- Chistiakova, Tatiana, et al.
(författare)
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Input–output stability design of an ammonium based aeration controller for wastewater treatment
- 2018
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Ingår i: 2018 Annual American Control Conference (ACC). - : Institute of Electrical and Electronics Engineers (IEEE). - 9781538654286 - 9781538654279 - 9781538654293 ; , s. 2964-2971
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Konferensbidrag (refereegranskat)abstract
- Ammonium feedback is commonly used for controlling the aeration in wastewater treatment plants having biological nitrogen removal. The paper proposes the use of a PI controller tuning method based on a simplified identified model with Hammerstein structure. The Hammerstein model accounts for the delay of the process caused by the settler, the multiple bioreactors dynamics and the main nonlinear process effects. The controller tuning method exploits the Popov inequality for a pre-computation of (a subset of) the stability region of the closed loop system as a function of the PI-controller parameters, quantified in terms of the maximum loop delay of the system. The controller parameters are selected in the computed stability region. In the numerical study, the plant is identified as a Hammerstein model using a recently published method, here extended to identify multiple bioreactor tank dynamics. The identification data is obtained from a high fidelity simulator, which is also used for evaluation of the proposed controller tuning method. The results show that the proposed procedure results in a PI-controller tuning with predictable stability properties and a good performance.
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| 4. |
- Chistiakova, Tatiana, et al.
(författare)
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Nonlinear system identification of the dissolved oxygen to effluent ammonia dynamics in an activated sludge process
- 2017
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Ingår i: IFAC-PapersOnLine. - : Elsevier B.V.. - 2405-8963. ; 50:1, s. 3917-3922
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Tidskriftsartikel (refereegranskat)abstract
- Aeration of biological reactors in wastewater treatment plants is important to obtain a high removal of soluble organic matter as well as for nitrification but requires a significant use of energy. It is hence of importance to control the aeration rate, for example, by ammonium feedback control. The goal of this paper is to model the dynamics from the set point of an existing dissolved oxygen controller to effluent ammonia using two types of system identification methods for a Hammerstein model, including a newly developed recursive variant. The models are estimated and evaluated using noise corrupted data from a complex mechanistic model (Activated Sludge Model no.1). The performance of the estimated nonlinear models are compared with an estimated linear model and it is shown that the nonlinear models give a significantly better fit to the data. The resulting models may be used for adaptive control (using the recursive Hammerstein variant), gain-scheduling control, L2 stability analysis, and model based fault detection.
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| 5. |
- Chistiakova, Tatiana, et al.
(författare)
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Nonlinear system identification of the dissolved oxygen to effluent ammonium dynamics in an activated sludge process
- 2018
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Aeration of biological reactors in wastewater treatment plants is important to obtain a high removal of soluble organic matter as well as for nitrification but requires a significant use of energy. It is hence of importance to control the aeration rate, for example, by ammonium feedback control. The goal of this report is to model the dynamics from the set point of an existing dissolved oxygen controller to effluent ammonium using two types of system identification methods for a Hammerstein model, including a newly developed recursive variant. The models are estimated and evaluated using noise corrupted data from a complex mechanistic model (Activated Sludge Model no.1). The performances of the estimated nonlinear models are compared with an estimated linear model and it is shown that the nonlinear models give a significantly better fit to the data. The resulting models may be used for adaptive control (using the recursive Hammerstein variant), gain-scheduling control, L2 stability analysis, and model based fault detection.
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| 6. |
- Gustavsson, Bengt, 1947, et al.
(författare)
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Phase 1 dose de-escalation trial of the endogenous folate [6R]-5,10-methylene tetrahydrofolate in combination with fixed-dose pemetrexed as neoadjuvant therapy in patients with resectable rectal cancer.
- 2015
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Ingår i: Investigational new drugs. - : Springer Science and Business Media LLC. - 1573-0646 .- 0167-6997. ; 33:5, s. 1078-1085
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Tidskriftsartikel (refereegranskat)abstract
- Background Modufolin® ([6R]-5,10-methylene tetrahydrofolate; [6R]-MTHF) is an endogenous biomodulator that is being developed as an alternative to leucovorin, a folate prodrug used in the treatment of colorectal cancer. The objective of this phase 1 dose de-escalation trial was to estimate the minimum tolerated dose of [6R]-MTHF to be used in combination with pemetrexed 500mg/m(2) in the neoadjuvant treatment of patients with rectal cancer. Methods Adult patients (≥18years) with resectable rectal adenocarcinoma were allocated to [6R]-MTHF doses of 500, 100, 50, and 10mg/m(2) in combination with pemetrexed 500mg/m(2). [6R]-MTHF was administered as an intravenous (i.v.) bolus injection 1week prior to the first dose of pemetrexed and then once weekly for 9weeks; pemetrexed was administered by i.v. infusion once every 21days for three cycles. Results Twenty-four patients (mean [SD] age, 63.1 [12.9] years) were enrolled in the study. A total of 72 treatment-related adverse events (AEs) were reported, of which the most common were fatigue (n=17; 23.6%), nausea (n=10; 13.9%), and diarrhea (n=5; 6.9%). The incidence of treatment-related AEs by [6R]-MTHF dose level (500, 100, 50, 10mg/m(2)) was 11.1% (n=8), 13.9% (n=10), 45.8% (n=33), and 29.2% (n=21), respectively. There were no dose-limiting toxicities, and only two (2.8%) treatment-related AEs were grade 3 in severity. Of the 11 serious AEs reported, none were considered to be related to [6R]-MTHF treatment. Conclusions The results of this phase 1 study indicate that the estimated minimum tolerated dose of [6R]-MTHF was 100mg/m(2) once weekly in combination with pemetrexed 500mg/m(2). The low toxicity profile of [6R]-MTHF supports its further evaluation as a component of systemic chemotherapy in the management of colon and rectal cancer.
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| 7. |
- Holm, Åsa, et al.
(författare)
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Heuristics for Integrated Optimization of Catheter Positioning and Dwell Time Distribution in Prostate HDR Brachytherapy
- 2016
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Ingår i: Annals of Operations Research. - : Springer. - 0254-5330 .- 1572-9338. ; 236:2, s. 319-339
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Tidskriftsartikel (refereegranskat)abstract
- High dose-rate (HDR) brachytherapy is a kind of radiotherapy used to treat, among others, prostate cancer. When applied to prostate cancer a radioactive source is moved through catheters implanted into the prostate. For each patient a treatment plan is constructed that decide for example catheter placement and dwell time distribution, that is where to stop the radioactive source and for how long.Mathematical optimization methods has been used to find quality plans with respect to dwell time distribution, however few optimization approaches regarding catheter placement have been studied. In this article we present an integrated optimization model that optimize catheter placement and dwell time distribution simultaneously. Our results show that integrating the two decisions yields greatly improved plans, from 15% to 94% improvement.Since the presented model is computationally demanding to solve we also present three heuristics: tabu search, variable neighbourhood search and genetic algorithm. Of these variable neighbourhood search is clearly the best, outperforming a state-of-the-art optimization software (CPLEX) and the two other heuristics.
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| 8. |
- Ivert, Torbjörn, et al.
(författare)
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Cardiovascular events in patients under age fifty with early findings of elevated lipid and glucose levels - The AMORIS study
- 2018
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Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 13:8
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: The long-term trajectories of lipid and glucose levels in subjects who experience a major cardiovascular (CV) event at a young age has not been well studied. Our objective was to investigate lipid, lipoprotein, apolipoprotein (apo), and glucose levels in individuals experiencing a CV event before 50 years of age.METHODS AND FINDINGS: A first CV event [non-fatal myocardial infarction (MI), coronary revascularisation, or CV related death] before age 50 was recorded in 2,939 (cumulative incidence 1.2% in males and 0.3% in females) of 361,353 individuals included in the prospective Swedish AMORIS (Apolipoprotein-related MOrtality RISk) study with health examinations 1985-1996 and follow-up through 2011. In a nested case-control analysis, cases with a CV event were matched to randomly selected controls. Population risk factor trajectories were calculated up to 20 years prior to an event. Total cholesterol (TC), triglyceride (TG), and glucose levels were higher in cases than in controls as early as 20 years prior to the event with differences increasing over time. Low density lipoprotein, apoB, and the apoB/apoA-1 ratio were higher and increased over time, while HDL and apoA-1 were lower in cases compared to controls. The odds ratio was 2.5 (95% confidence interval 1.6-3.7) for TC ≥5 mmol/L and TG ≥1.7 mmol/L in cases versus controls. The adjusted population-attributable fractions including lipids, glucose, diabetes, smoking, hypertension, and obesity indicated that about 50% of CV events before age 50 may be associated with elevated lipid and glucose levels.CONCLUSIONS: Elevated TC, TG, LDL, apoB, and glucose levels and high apoB/apo A-1 ratio documented two decades before a CV event in subjects younger than 50 years may account for about half of CV events before age 50, which calls for early recognition and possibly treatment of modifiable CV risk factors in young individuals.
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| 9. |
- Karlsson, Kristian, et al.
(författare)
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Distance Dependent Radiation Patterns in Vehcile-to-Vehicle Communications
- 2015
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Rapport (refereegranskat)abstract
- We present a method for repeatable measurements of antennas integrated on vehicles in vehicle-to-vehicle communications. The method can handle vehicles and heavy vehicles and results in distance dependent radiation pattern measurements, or near-field coverage measurements. The method is exemplified with measurement results. Key words: Channel models, radiation pattern, vehicles, V2V, measurement
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| 10. |
- Morén, Björn, 1987-, et al.
(författare)
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A mathematical optimization model for spatial adjustments of dose distributions in high dose-rate brachytherapy
- 2019
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Ingår i: Physics in Medicine and Biology. - : IOP PUBLISHING LTD. - 0031-9155 .- 1361-6560. ; 64:22
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Tidskriftsartikel (refereegranskat)abstract
- High dose-rate brachytherapy is a modality of radiation therapy used for cancer treatment, in which the radiation source is placed within the body. The treatment goal is to give a high enough dose to the tumour while sparing nearby healthy tissue and organs (organs-at-risk). The most common criteria for evaluating dose distributions are dosimetric indices. For the tumour, such an index is the portion of the volume that receives at least a specified dose level (e.g. the prescription dose), while for organs-at-risk it is instead the portion of the volume that receives at most a specified dose level. Dosimetric indices are aggregate criteria and do not consider spatial properties of the dose distribution. Further, there are neither any established evaluation criteria for characterizing spatial properties, nor have such properties been studied in the context of mathematical optimization of brachytherapy. Spatial properties are however of clinical relevance and therefore dose plans are sometimes adjusted manually to improve them. We propose an optimization model for reducing the prevalence of contiguous volumes with a too high dose (hot spots) or a too low dose (cold spots) in a tentative dose plan. This model is independent of the process of constructing the tentative plan. We conduct computational experiments with tentative plans obtained both from optimization models and from clinical practice. The objective function considers pairs of dose points and each pair is given a distance-based penalty if the dose is either too high or too low at both dose points. Constraints are included to retain dosimetric indices at acceptable levels. Our model is designed to automate the manual adjustment step in the planning process. In the automatic adjustment step large-scale optimization models are solved. We show reductions of the volumes of the largest hot and cold spots, and the computing times are feasible in clinical practice.
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