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- Carvalho Bittencourt, André
(författare)
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On Modeling and Diagnosis of Friction and Wear in Industrial Robots
- 2012
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Industrial robots are designed to endure several years of uninterrupted operation and therefore are very reliable. However, no amount of design effort can prevent deterioration over time, and equipments will eventually fail. Its impacts can, nevertheless, be considerably reduced if good maintenance/service practices are performed. The current practice for service of industrial robots is based on preventive and corrective policies, with little consideration about the actual condition of the system. In the current scenario, the serviceability of industrial robots can be greatly improved with the use of condition monitoring/diagnosis methods, allowing for condition-based maintenance (cbm).This thesis addresses the design of condition monitoring methods for industrial robots. The main focus is on the monitoring and diagnosis of excessive degradations caused by wear of the mechanical parts. The wear processes may take several years to be of significance, but can evolve rapidly once they start to appear. An early detection of excessive wear levels can therefore allow for cbm, increasing maintainability and availability. Since wear is related to friction, the basic idea pursued is to analyze the friction behavior to infer about wear.To allow this, an extensive study of friction in robot joints is considered in this work. The effects of joint temperature, load and wear changes to static friction in robot a joint are modeled based on empirical observations. It is found that the effects of load and temperature to friction are comparable to those caused by wear. Joint temperature and load are typically not measured, but will always be present in applications. Therefore, diagnosis solutions must be able to cope with them.Different methods are proposed which allow for robust wear monitoring. First, a wear estimator is suggested. Wear estimates are made possible with the use of a test-cycle and a friction model. Second, a method is defined which considers the repetitive behavior found in many applications of industrial robots. The result of the execution of the same task in different instances of time are compared to provide an estimate of how the system changed over the period. Methods are suggested that consider changes in the distribution of data logged from the robot. It is shown through simulations and experiments that robust wear monitoring is made possible with the proposed methods.
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- Edgren, Gustaf, et al.
(författare)
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Aktiv hälsostyrning kan ge utsatta patienter stöd ["Active health management" can provide support for vulnerable patients. New model for the prevention of unplanned healthcare].
- 2016
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Ingår i: Läkartidningen. - 0023-7205 .- 1652-7518. ; 113
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Tidskriftsartikel (refereegranskat)abstract
- A small group of frequent emergency department visitors account for a disproportionally large fraction of health care consumption, including unplanned hospitalizations and overall healthcare costs. In response, case and disease management programs aimed at reducing health care consumption in this group have been tested, however results vary widely. In this study, we aimed to investigate if a telephone-based, nurse led case management intervention can reduce health care consumption for frequent emergency department visitors in a large-scale set-up. A total of 12,181 frequent emergency department users in three counties in Sweden were randomized either using Zelen's design or a traditional randomized design to receive a nurse led case management intervention or no intervention. Patients were followed for health care consumption for up to 2 years. The results of the study with traditional design showed an overall 12% (95% confidence interval [CI], 4-19%) decreased rate of hospitalization, which was mostly driven by effects among patients included in the last year. Similar results were achieved in the Zelen studies, with significant reduction of hospitalization, again in the last year, but mixed results in the early development of the project. Our study provides evidence that a carefully designed telephone-based intervention with accurate and systematic patient selection and appropriate staff training in a centralized set-up can lead to significant decreases in health care consumption and costs. However, we also demonstrate that the effects are sensitive to the delivery model chosen.
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- Kågedal, Matts, et al.
(författare)
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A positron emission tomography study in healthy volunteers to estimate mGluR5 receptor occupancy of AZD2066-Estimating occupancy in the absence of a reference region
- 2013
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Ingår i: NeuroImage. - : Elsevier BV. - 1053-8119 .- 1095-9572. ; 82, s. 160-169
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Tidskriftsartikel (refereegranskat)abstract
- AZD2066 is a new chemical entity pharmacologically characterized as a selective, negative allosteric modulator of the metabotropic glutamate receptor subtype 5 (mGluR5). Antagonism of mGluR5 has been implicated in relation to various diseases such as anxiety, depression, and pain disorders. To support translation from preclinical results and previous experiences with this target in man, a positron emission tomography study was performed to estimate the relationship between AZD2066 plasma concentrations and receptor occupancy in the human brain, using the mGluR5 radioligand [C-11]-ABP688. The study involved PET scans on 4 occasions in 6 healthy volunteers. The radioligand was given as a tracer dose alone and following oral treatment with different doses of AZD2066. The analysis was based on the total volume of distribution derived fro m each PET-assessment. A non-linear mixed effects model was developed where ten delineated brain regions of interest from all PET scans were included in one simultaneous fit. For comparison the analysis was also performed according to a method described previously by Lassen et al. (1995). The results of the analysis showed that the total volume of distribution decreased with increasing drug concentrations in all regions with an estimated Kipl of 1170 nM. Variability between individuals and occasions in non-displaceable volume of distribution could explain most of the variability in the total volume of distribution. The Lassen approach provided a similar estimate for Kipl, but the variability was exaggerated and difficult to interpret.
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| 5. |
- Kågedal, Matts, et al.
(författare)
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Non-linear mixed effects modelling of positron emission tomography data for simultaneous estimation of radioligand kinetics and occupancy in healthy volunteers
- 2012
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Ingår i: NeuroImage. - : Elsevier BV. - 1053-8119 .- 1095-9572. ; 61:4, s. 849-856
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this work was to develop a model simultaneously estimating (11)C-AZD9272 radioligand kinetics and the relationship between plasma concentration of AZD9272 and receptor occupancy in the human brain.AZD9272 is a new chemical entity pharmacologically characterised as a noncompetitive antagonist at the metabotropic glutamate receptor subtype 5 (mGluR5). Positron emission tomography (PET) was used to measure the time course of ((11)C-AZD9272) in the brain. The study included PET measurements in six healthy volunteers where the radioligand was given as a tracer dose alone as well as post oral treatment with different doses of unlabelled AZD9272. Estimation of radioligand kinetics, including saturation of receptor binding was performed by use of non-linear mixed effects modelling. Data from the regions with the highest (ventral striatum) and lowest (cerebellum) radioligand concentrations were included in the analysis. It was assumed that the extent of non-displaceable brain uptake was the same in both regions while the rate of CNS uptake and the receptor density differed.The results of the analysis showed that AZD9272 binding at the receptor is saturable with an estimated plasma concentration corresponding to 50% occupancy of approximately 200nM. The density of the receptor binding sites was estimated to 800nM and 200nM in ventral striatum and cerebellum respectively. By simultaneously analysing data from several PET measurements and different brain regions in a non-linear mixed effects framework it was possible to estimate parameters of interest that would otherwise be difficult to quantify.
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| 8. |
- Larsson, Ulf, et al.
(författare)
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Phytoplankton primary production : 14C-in situ and 14C-incubator methods compared
- 2021
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Ingår i: ICES Journal of Marine Science. - : Oxford University Press (OUP). - 1054-3139 .- 1095-9289. ; 78:10, s. 3592-3602
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Tidskriftsartikel (refereegranskat)abstract
- We estimated phytoplankton depth-integrated primary production rates at an open sea station in the northern Baltic Proper in 2004–2009 by parallel in situ and ship-board incubations in an “ICES incubator”. Observations were strongly linearly related (r2 = 0.67, p < 0.00001) and produced similar seasonal signals, but incubator estimates were significantly lower in spring (∼5–20%, March–May) and summer (∼30%, June–August), but not in autumn (September–October). Incubator PBmax was significantly lower in all seasons (∼10, 23, and 14% in spring, summer, and autumn), and the initial slope of the PB/E-curve (αB) was two-thirds of in-situ αB in spring and autumn, and half in summer, but not significantly different in autumn, and had an order of magnitude lower standard deviation. Parallel incubations of mixed 0–10 m hose samples at discrete depths in situ and in the incubator gave similar differences in PBmax and αB. This strongly suggests that the main factor causing the lower photosynthesis rates in the incubator was light quality, since all other potential sources of variability were similar. However, we cannot rule out that the lower incubator PBmax was partly due to insufficient light compared to in situ, particularly in summer. Our results suggest that a major challenge to the harmonization of 14C in situ, and artificial light and deck incubator measurements, is to simulate spectral composition changes with depth or, alternatively, use phytoplankton action spectra or constructed action spectra that are less complicated and time-consuming to establish (Kyewalyanga et al., 1997).
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| 9. |
- Larsson, Ulf, et al.
(författare)
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Växtplanktonproduktion : mätningar med problem
- 2010
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Ingår i: Havet. - Stockholm : Naturvårdsverket och Havsmiljöinstitutet. - 9789162012816 ; , s. 26-29
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Bokkapitel (övrigt vetenskapligt/konstnärligt)
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| 10. |
- Nielsen, Lars, 1955-, et al.
(författare)
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Issues in Diagnosis, Supervision, and Safety
- 1996
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Issues concerning diagnosis, supervision and saftey are found in many technologically advanced products. There is now a trend to extend the functionality of diagnosis and supervision systems to handle more advanced situations. This report collects some of the initiatives taking place in research and some of the developments taking place in the industry.
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| 11. |
- Nyberg, Svante, et al.
(författare)
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Detection of amyloid in Alzheimer's disease with positron emission tomography using [11C]AZD2184
- 2009
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Ingår i: European Journal of Nuclear Medicine and Molecular Imaging. - : Springer. - 1619-7070 .- 1619-7089. ; 36:11, s. 1859-1863
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Tidskriftsartikel (refereegranskat)abstract
- PURPOSE: Current positron emission tomography (PET) radioligands for detection of Aβ amyloid in Alzheimer's disease (AD) are not ideal for quantification. To improve the signal to noise ratio we have developed the radioligand [11C]AZD2184 and report here the first clinical evaluation.METHODS: Eight AD patients and four younger control subjects underwent 93-min PET measurements with [11C]AZD2184. A ratio approach using the cerebellum as reference region was applied to determine binding parameters.RESULTS: Brain uptake of [11C]AZD2184 peaked within 1 min at 3-4% of injected radioactivity. AD patients had high radioactivity in cortical regions while controls had uniformly low radioactivity uptake. Specific binding peaked within 30 min at which time standardized uptake value ratios (SUVR) ranged between 1.19 and 2.57.CONCLUSION: [11C]AZD2184 is a promising radioligand for detailed mapping of Aβ amyloid depositions in Alzheimer's disease, due to low non-specific binding, high signal to background ratio and reversible binding as evident from early peak equilibrium.
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