| 1. |
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| 2. |
- Bergman, Stefan, et al.
(författare)
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Smärta vid artros
- 2007
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Ingår i: Långvarig smärta. - 9789144019741 ; , s. 145-145
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Bokkapitel (övrigt vetenskapligt/konstnärligt)
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| 3. |
- Adalbjörnsson, Stefan, et al.
(författare)
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Conjugate priors for Gaussian emission plsa recommender systems
- 2016
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Ingår i: 2016 24th European Signal Processing Conference, EUSIPCO 2016. - 9780992862657 ; 2016-November, s. 2096-2100
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Konferensbidrag (refereegranskat)abstract
- Collaborative filtering for recommender systems seeks to learn and predict user preferences for a collection of items by identifying similarities between users on the basis of their past interest or interaction with the items in question. In this work, we present a conjugate prior regularized extension of Hofmann's Gaussian emission probabilistic latent semantic analysis model, able to overcome the over-fitting problem restricting the performance of the earlier formulation. Furthermore, in experiments using the EachMovie and MovieLens data sets, it is shown that the proposed regularized model achieves significantly improved prediction accuracy of user preferences as compared to the latent semantic analysis model without priors.
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| 4. |
- Adalbjörnsson, Stefan Ingi, et al.
(författare)
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A Sparse Approach for Estimation of Amplitude Modulated Sinusoids
- 2014
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Konferensbidrag (refereegranskat)abstract
- We consider the problem of spectral analysis of signals composed of sums of multiple amplitude modulated, possibly harmonically related, sinusoids using a sparse approach. By separating the nonlinear frequency variables using a dictionary of possible frequency components as well as a spline basis for the amplitude modulation, results in a convex criterion which can be efficiently solved without worrisome local minima. The resulting method makes no model order assumption and automatically estimates both the signal parameters and their amplitude modulations
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| 5. |
- Adalbjörnsson, Stefan Ingi, et al.
(författare)
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Efficient Block and Time-Recursive Estimation of Sparse Volterra Systems
- 2012
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Ingår i: 2012 IEEE Statistical Signal Processing Workshop (SSP), Proceedings of. - 9781467301831 ; , s. 173-176
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Konferensbidrag (refereegranskat)abstract
- We investigate the application of non-convex penalized least squares for parameter estimation in the Volterra model. Sparsity is promoted by introducing a weighted !q penalty on the parameters and efficient batch and time recursive algorithms are devised based on the cyclic coordinate descent approach. Numerical examples illustrate the improved performance of the proposed algorithms as compared the weighted !1 norm.
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| 6. |
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| 7. |
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| 8. |
- Adalbjörnsson, Stefan Ingi, et al.
(författare)
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Estimating Periodicities in Symbolic Sequences Using Sparse Modeling
- 2015
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Ingår i: IEEE Transactions on Signal Processing. - 1053-587X. ; 63:8, s. 2142-2150
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, we propose a method for estimating statistical periodicities in symbolic sequences. Different from other common approaches used for the estimation of periodicities of sequences of arbitrary, finite, symbol sets, that often map the symbolic sequence to a numerical representation, we here exploit a likelihood-based formulation in a sparse modeling framework to represent the periodic behavior of the sequence. The resulting criterion includes a restriction on the cardinality of the solution; two approximate solutions are suggested—one greedy and one using an iterative convex relaxation strategy to ease the cardinality restriction. The performance of the proposed methods are illustrated using both simulated and real DNA data, showing a notable performance gain as compared to other common estimators.
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| 9. |
- Adalbjörnsson, Stefan Ingi, et al.
(författare)
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High resolution sparse estimation of exponentially decaying two-dimensional signals
- 2014
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Ingår i: European Signal Processing Conference. - 2219-5491.
-
Konferensbidrag (refereegranskat)abstract
- In this work, we consider the problem of high-resolution estimation of the parameters detailing a two-dimensional (2-D) signal consisting of an unknown number of exponentially decaying sinusoidal components. Interpreting the estimation problem as a block (or group) sparse representation problem allows the decoupling of the 2-D data structure into a sum of outer-products of 1-D damped sinusoidal signals with unknown damping and frequency. The resulting non-zero blocks will represent each of the 1-D damped sinusoids, which may then be used as non-parametric estimates of the corresponding 1-D signals; this implies that the sought 2-D modes may be estimated using a sequence of 1-D optimization problems. The resulting sparse representation problem is solved using an iterative ADMM-based algorithm, after which the damping and frequency parameter can be estimated by a sequence of simple 1-D optimization problems.
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| 10. |
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| 11. |
- Adalbjörnsson, Stefan Ingi, et al.
(författare)
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Multi-Pitch Estimation Exploiting Block Sparsity
- 2015
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Ingår i: Signal Processing. - : Elsevier BV. - 0165-1684. ; 109:April, s. 236-247
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Tidskriftsartikel (refereegranskat)abstract
- We study the problem of estimating the fundamental frequencies of a signal containing multiple harmonically related sinusoidal components using a novel block sparse signal representation. An efficient algorithm for solving the resulting optimization problem is devised exploiting a novel variable step-size alternating direction method of multipliers (ADMM). The resulting algorithm has guaranteed convergence and shows notable robustness to the f 0 vs f0/2f0/2 ambiguity problem. The superiority of the proposed method, as compared to earlier presented estimation techniques, is demonstrated using both simulated and measured audio signals, clearly indicating the preferable performance of the proposed technique.
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| 12. |
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| 13. |
- Adalbjörnsson, Stefan Ingi, et al.
(författare)
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Sparse Estimation Of Spectroscopic Signals
- 2011
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Ingår i: European Signal Processing Conference. - 2219-5491. ; 2011, s. 333-337
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Konferensbidrag (refereegranskat)abstract
- This work considers the semi-parametric estimation of sparse spec- troscopic signals, aiming to form a detailed spectral representation of both the frequency content and the spectral line widths of the oc- curring signals. Extending on the recent FOCUSS-based SLIM al- gorithm, we propose an alternative prior for a Bayesian formulation of this sparse reconstruction method, exploiting a proposed suitable prior for the noise variance. Examining three common models for spectroscopic signals, the introduced technique allows for reliable estimation of the characteristics of these models. Numerical sim- ulations illustrate the improved performance of the proposed tech- nique.
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| 14. |
- Adalbjörnsson, Stefan Ingi, et al.
(författare)
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Sparse Localization of Harmonic Audio Sources
- 2016
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Ingår i: IEEE/ACM Transactions on Audio, Speech, and Language Processing. - 2329-9290. ; 24:1, s. 117-129
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, we propose a novel method for estimating the locations of near- and/or far-field harmonic audio sources impinging on an arbitrary, but calibrated, sensor array. Using a joint pitch and location estimation formed in two steps, we first estimate the fundamental frequencies and complex amplitudes under a sinusoidal model assumption, whereafter the location of each source is found by utilizing both the difference in phase and the relative attenuation of the magnitude estimates. As audio recordings often consist of multi-pitch signals exhibiting some degree of reverberation, where both the number of pitches and the source locations are unknown, we propose to use sparse heuristics to avoid the necessity of detailed a priori assumptions on the spectral and spatial model orders. The method’s performance is evaluated using both simulated and measured audio data, with the former showing that the proposed method achieves near-optimal performance, whereas the latter confirms the method’s feasibility when used with real recordings.
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| 15. |
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| 16. |
- Andersson, Björn O, 1982, et al.
(författare)
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A Modified TAB Model for Simulation of Atomization in Rotary Bell Spray Painting
- 2013
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Ingår i: Journal of Mechanical Engineering and Automation. - 2163-2413. ; 3:2, s. 54-61
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Tidskriftsartikel (refereegranskat)abstract
- The Rotary bell spray applicator technique is commonly used in the automotive industry for paint application because of its high transfer efficiency and high-quality result. The bell spins rapidly around its axis with a tangential velocity at the edge in the order of 100 m/s. The paint falls off the edge and enters the air with a large relative velocity, driving the atomization into small droplets where the resulting size distribution depends on the process conditions. Especially the rotation speed of the bell is an important parameter governing the size distribution. The main research question in this work is to investigate if the Taylor Analogy Breakup (TAB) model can be used to predict the resulting droplet size distributions in spray painting. As the paint is a viscous fluid a modification of the TAB model taking non-linear effects of large viscosity into account is proposed. The parameters in the breakup model are tuned by optimization to match droplet size distributions obtained in CFD simulations with measured ones. Results are presented for three cases with rotation speeds from 30 to 50 thousand RPM where the full droplet size distributions are compared with measurements. Good results are obtained for all three cases where the simulated size distributions compare well to measurements over a wide range of droplet sizes. The TAB method is able to quantitatively predict the result of the breakup process and can be used in a preprocessing stage of a full spray painting simulation, thereby reducing the need for costly and cumbersome measurements.
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| 17. |
- Andersson, Björn O, 1982, et al.
(författare)
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Modeling Surface Tension in SPH by Interface Reconstruction using Radial Basis Functions
- 2010
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Ingår i: Proceedings of the 5th International SPHERIC Workshop, 22-25 June 2010, Manchester, U.K., edited by B. D. Rogers. ; , s. 7-14
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- A novel method for reconstructing the interface between two fluids is described and evaluated. The method uses a different basis for approximating the color function than what is common practice in SPH simulations. The key feature of the new method is the ability to omit small length scale structures in order to obtain a smoother representation. A smoother interface is more suitable to derive a surface tension force from, as the magnitude of the force is proportional to the curvature which is related to the second derivative along the interface.
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| 18. |
- Andersson, Björn O, 1982, et al.
(författare)
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Modified TAB Model for Viscous Fluids applied to Breakup in Rotary Bell Spray Painting
- 2012
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Ingår i: ICLASS 2012 - 12th International Conference on Liquid Atomization and Spray Systems.
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Konferensbidrag (refereegranskat)abstract
- The Taylor Analogy Breakup (TAB) model is applied to droplet breakup in rotary bell spray painting commonly used in the automotive industry. The bell spins rapidly around its axis with a tangential velocity at the edge in the order of 100 m/s. The paint falls off the edge and enters the air with a large relative velocity, driving the atomization. The paint is a viscous fluid and a modification of the TAB model taking non-linear effects of large viscosity into account is described. The parameters in the breakup model are tuned to match droplet size distributions obtained in CFD simulations with measured ones. Results are presented for three cases with rotation speeds from 30 to 50 thousand RPM where the full droplet size distributions are compared with measurements. Good results are obtained for all three cases where the simulated size distributions compare well to measurements over a wide range of droplet sizes. The obtained results can be used in a preprocessing stage of a full spray painting simulation thereby reducing the need for costly and cumbersome measurements.
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| 19. |
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| 20. |
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| 21. |
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| 22. |
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| 23. |
- Correa, Maicon Ribeiro, et al.
(författare)
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A transient thermoelastic mathematical model for topology optimization of support structures in additive manufacturing
- 2024
-
Ingår i: Structural and multidisciplinary optimization (Print). - : SPRINGER. - 1615-147X .- 1615-1488. ; 67:3
-
Tidskriftsartikel (refereegranskat)abstract
- This study presents a Topology Optimization (TO) methodology for determining the optimal distribution of support structures in the powder bed fusion Additive Manufacturing (AM) fabrication technology. The support structures enhance thermal dissipation, reducing distortion on overhang surfaces during the build process and improving printability. A novel transient thermoelastic layer-by-layer model simulates the AM process, evaluating temperature and displacement in partially built structures with supports. We propose two new objective functions related to part distortion, perform their adjoint sensitivity analysis, and present a comprehensive set of numerical experiments with different geometries and levels of overhang complexity. The numerical results show non-standard optimal support structures obtained using the proposed TO-AM methodology for different model parameters, including support volume, thermal anisotropy, time discretization method, and building times for each layer.
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| 24. |
- Edelvik, Fredrik, 1972, et al.
(författare)
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An improved method for dipole modeling in EEG-based source localization
- 2009
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Ingår i: International Federation for Medical and Biological Engineering Proceedings. - Berlin, Heidelberg : Springer Berlin Heidelberg. - 1680-0737. - 9783642038884 ; 25:9, s. 146-149
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Konferensbidrag (refereegranskat)abstract
- The inverse problem in EEG-based source localizationis to determine the location of the brain sources that areresponsible for the measured potentials at the scalp electrodes.The brain sources are usually modeled as current dipoles whichlead to a singularity in the right-hand side of the governing Poisson’sequation. Subtraction methods have been proposed as aremedy and in this paper an improved subtraction method formodeling the dipoles is presented. The accuracy is demonstratedfor radial and tangential sources in layered sphere models and isto the best of the authors’ knowledge superior to previous methodsfor superficial sources. An additional advantage is that itproduces a right hand side with few non-zeros which is beneficialfor efficient solution of the inverse problem.
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| 25. |
- Elvander, Filip, et al.
(författare)
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An Adaptive Penalty Multi-Pitch Estimator with Self-Regularization
- 2016
-
Ingår i: Signal Processing. - : Elsevier BV. - 0165-1684. ; 127, s. 56-70
-
Tidskriftsartikel (refereegranskat)abstract
- This work treats multi-pitch estimation, and in particular the common misclassification issue wherein the pitch at half the true fundamental frequency, the sub-octave, is chosen instead of the true pitch. Extending on current group LASSO-based methods for pitch estimation, this work introduces an adaptive total variation penalty, which enforces both group- and block sparsity, as well as deals with errors due to sub-octaves. Also presented is a scheme for signal adaptive dictionary construction and automatic selection of the regularization parameters. Used together with this scheme, the proposed method is shown to yield accurate pitch estimates when evaluated on synthetic speech data. The method is shown to perform as good as, or better than, current state-of-the-art sparse methods while requiring fewer tuning parameters than these, as well as several con- ventional pitch estimation methods, even when these are given oracle model orders. When evaluated on a set of ten musical pieces, the method shows promising results for separating multi-pitch signals.
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| 26. |
- Elvander, Filip, et al.
(författare)
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Robust Non-Negative Least Squares Using Sparsity
- 2016
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Ingår i: 2016 24th European Signal Processing Conference (EUSIPCO). - 2076-1465. - 9780992862657 ; , s. 61-65
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Konferensbidrag (refereegranskat)abstract
- Sparse, non-negative signals occur in many applications. To recover such signals, estimation posed as non-negative least squares problems have proven to be fruitful. Efficient algorithms with high accuracy have been proposed, but many of them assume either perfect knowledge of the dictionary generating the signal, or attempts to explain deviations from this dictionary by attributing them to components that for some reason is missing from the dictionary. In this work, we propose a robust non-negative least squares algorithm that allows the generating dictionary to differ from the assumed dictionary, introducing uncertainty in the setup. The proposed algorithm enables an improved modeling of the measurements, and may be efficiently implemented using a proposed ADMM implementation. Numerical examples illustrate the improved performance as compared to the standard non-negative LASSO estimator.
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| 27. |
- Elvander, Filip, et al.
(författare)
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Using optimal transport for estimating inharmonic pitch signals
- 2017
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Ingår i: 2017 IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP). - : Institute of Electrical and Electronics Engineers (IEEE). - 9781509041176 ; , s. 331-335
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Konferensbidrag (refereegranskat)abstract
- In this work, we propose a novel multi-pitch estimation technique that is robust with respect to the inharmonicity commonly occurring in many applications. The method does not require any a priori knowledge of the number of signal sources, the number of harmonics of each source, nor the structure or scope of any possibly occurring inharmonicity. Formulated as a minimum transport distance problem, the proposed method finds an estimate of the present pitches by mapping any found spectral line to the closest harmonic structure. The resulting optimization is a convex and highly tractable linear programming problem. The preferable performance of the proposed method is illustrated using both simulated and real audio signals.
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| 28. |
- Fridriksson, Steen, 1961-, et al.
(författare)
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Intraoperative complications in aneurysm surgery : a prospective national study
- 2002
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Ingår i: Journal of Neurosurgery. - : Journal of Neurosurgery Publishing Group (JNSPG). - 0022-3085 .- 1933-0693. ; 96:3, s. 515-522
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Tidskriftsartikel (refereegranskat)abstract
- Object. With increasing use of endovascular procedures, the number of aneurysms treated surgically will decline. In this study the authors review complications related to the surgical treatment of aneurysms and address the issue of maintaining quality standards on a national level.Methods. A prospective, nonselected amalgamation of every aneurysm case treated in five of six neurosurgical centers in Sweden during 1 calendar year was undertaken (422 patients; 7.4 persons/100,000 population/year). The treatment protocols at these institutions were very similar. Outcome was assessed using clinical end points. In this series, 84.1% of the patients underwent surgery, and intraoperative complications occurred in 30% of these procedures. Poor outcome from technical complications was seen in 7.9% of the surgically treated patients. Intraoperative aneurysm rupture accounted for 60% and branch sacrifice for 12% of all technical difficulties. Although these complications were significantly related to aneurysm base geometry and the competence of the surgeon, problems still occurred apparently at random and also in the best of hands (17%). The temporary mean occlusion time in the patients who suffered intraoperative aneurysm rupture was twice as long as the temporary arrest of blood flow performed to aid dissection.Conclusions. The results obtained in this series closely reflect the overall management results of this disease and support the conclusion that surgical complications causing a poor outcome can be estimated on a large population-based scale. Intraoperative aneurysm rupture was the most common and most devastating technical complication that occurred. Support was found for a more liberal use of temporary clips early during dissection, regardless of the experience of the surgeon. Temporary regional interruption of arterial blood flow should be a routine method for aneurysm surgery on an everyday basis. A random occurrence of difficult intraoperative problems was clearly shown, and this factor of unpredictability, which is present in any preoperative assessment of risk, strengthens the case for recommending neuroprotection as a routine adjunct to virtually every aneurysm operation, regardless of the surgeon's experience.
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| 29. |
- Gleeson, Daniel, 1988, et al.
(författare)
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Generating Optimized Trajectories for Robotic Spray Painting
- 2022
-
Ingår i: IEEE Transactions on Automation Science and Engineering. - 1558-3783 .- 1545-5955. ; 19:3, s. 1380-1391
-
Tidskriftsartikel (refereegranskat)abstract
- In the manufacturing industry, spray painting is often an important part of the manufacturing process. Especially in the automotive industry, the perceived quality of the final product is closely linked to the exactness and smoothness of the painting process. For complex products or low batch size production, manual spray painting is often used. But in large scale production with a high degree of automation, the painting is usually performed by industrial robots. There is a need to improve and simplify the generation of robot trajectories used in industrial paint booths. A novel method for spray paint optimization is presented, which can be used to smooth out a generated initial trajectory and minimize paint thickness deviations from a target thickness. The smoothed out trajectory is found by solving, using an interior point solver, a continuous non-linear optimization problem. A two-dimensional reference function of the applied paint thickness is selected by fitting a spline function to experimental data. This applicator footprint profile is then projected to the geometry and used as a paint deposition model. After generating an initial trajectory, the position and duration of each trajectory segment are used as optimization variables. The primary goal of the optimization is to obtain a paint applicator trajectory, which would closely match a target paint thickness when executed. The algorithm has been shown to produce satisfactory results on both a simple 2-dimensional test example, and a non-trivial industrial case of painting a tractor fender. The resulting trajectory is also proven feasible to be executed by an industrial robot.
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| 30. |
- Gleeson, Daniel, 1988, et al.
(författare)
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Robot spray painting trajectory optimization
- 2020
-
Ingår i: IEEE International Conference on Automation Science and Engineering. - 2161-8070 .- 2161-8089. ; 2020-August, s. 1135-1140
-
Konferensbidrag (refereegranskat)abstract
- In the manufacturing industry, spray painting is often an important part of the process. Especially in the automotive industry, the perceived quality of the final product is closely linked to the exactness and smoothness of the painting process. For complex products or low batch size production, manual spray painting is often used. But in large scale production with a high degree of automation, the painting is normally performed by industrial robots. There is a need to improve and simplify the generation of robot trajectories used in industrial paint booths. A method for spray paint optimization is presented, which can be used to smooth out an initial trajectory and minimize paint thickness deviations from a target thickness. By fitting a spline function to experimental data, an applicator footprint profile is determined, which is a two-dimensional reference function of the applied paint thickness. This footprint profile is then projected to the geometry and used as a deposition model at each point along the trajectory. The positions and durations of all trajectory segments are used as optimization variables. They are modified with the primary goal to obtain a paint applicator trajectory, which will closely match a target paint thickness when executed. The algorithm is shown to produce satisfactory results on both a simple 2-dimensional test example, and a nontrivial industrial case of painting a tractor render. The final trajectory shows an overall thickness close to the target thickness, and the resulting trajectory is feasible to execute directly on an industrial robot.
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| 31. |
- Gunasekera, Sunithi, 1977-, et al.
(författare)
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Stabilized Cyclic Peptides as Scavengers of Autoantibodies : Neutralization of Anticitrullinated Protein/Peptide Antibodies in Rheumatoid Arthritis
- 2018
-
Ingår i: ACS Chemical Biology. - : American Chemical Society (ACS). - 1554-8929 .- 1554-8937. ; 13:6, s. 1525-1535
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Tidskriftsartikel (refereegranskat)abstract
- The occurrence of autoantibodies is a hallmark of rheumatoid arthritis, specifically those autoantibodies targeting proteins containing the arginine-derived amino acid citrulline. There is strong evidence showing that the occurrence of anticitrullinated protein/peptide antibodies (ACPA) are involved in disease progression, and ACPA was recently shown to induce pain in animals. Here, we explore a novel concept useful for research, diagnostics, and possibly therapy of autoimmune diseases, namely, to directly target and neutralize autoantibodies using peptide binders. A high-affinity peptide-based scavenger of ACPA was developed by grafting a citrullinated epitope derived from human fibrinogen into a naturally occurring stable peptide scaffold. The best scavenger comprises the truncated epitope α-fibrinogen, [Cit573]fib(566-580), grafted into the scaffold sunflower trypsin inhibitor-1, SFTI-1. The final peptide demonstrates low nanomolar apparent affinity and superior stability.
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| 32. |
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| 33. |
- Gustafsson, Christian Jamtheim, et al.
(författare)
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Development and evaluation of a deep learning based artificial intelligence for automatic identification of gold fiducial markers in an MRI-only prostate radiotherapy workflow
- 2020
-
Ingår i: Physics in Medicine and Biology. - : IOP Publishing. - 1361-6560 .- 0031-9155. ; 65:22
-
Tidskriftsartikel (refereegranskat)abstract
- Identification of prostate gold fiducial markers in magnetic resonance imaging (MRI) images is challenging when CT images are not available, due to misclassifications from intra-prostatic calcifications. It is also a time consuming task and automated identification methods have been suggested as an improvement for both objectives. Multi-echo gradient echo (MEGRE) images have been utilized for manual fiducial identification with 100% detection accuracy. The aim is therefore to develop an automatic deep learning based method for fiducial identification in MRI images intended for MRI-only prostate radiotherapy. MEGRE images from 326 prostate cancer patients with fiducials were acquired on a 3T MRI, post-processed with N4 bias correction, and the fiducial center of mass (CoM) was identified. A 9 mm radius sphere was created around the CoM as ground truth. A deep learning HighRes3DNet model for semantic segmentation was trained using image augmentation. The model was applied to 39 MRI-only patients and 3D probability maps for fiducial location and segmentation were produced and spatially smoothed. In each of the three largest probability peaks, a 9 mm radius sphere was defined. Detection sensitivity and geometric accuracy was assessed. To raise awareness of potential false findings a 'BeAware' score was developed, calculated from the total number and quality of the probability peaks. All datasets, annotations and source code used were made publicly available. The detection sensitivity for all fiducials were 97.4%. Thirty-six out of thirty-nine patients had all fiducial markers correctly identified. All three failed patients generated a user notification using the BeAware score. The mean absolute difference between the detected fiducial and ground truth CoM was 0.7 ± 0.9 [0 3.1] mm. A deep learning method for automatic fiducial identification in MRI images was developed and evaluated with state-of-the-art results. The BeAware score has the potential to notify the user regarding patients where the proposed method is uncertain.
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| 34. |
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| 35. |
- Idborg, Helena, et al.
(författare)
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STRATIFICATION OF SLE PATIENTS FOR IMPROVED DIAGNOSIS AND TREATMENT
- 2013
-
Ingår i: Annals of the Rheumatic Diseases. - : BMJ. - 0003-4967 .- 1468-2060. ; 72, s. A80-A80
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Background. Systemic autoimmune diseases (SAIDs) affect about 2% of the population in Western countries. Sufficient diagnostic criteria are lacking due to the heterogeneity within diagnostic categories and apparent overlap regarding symptoms and patterns of autoantibodies between different diagnoses. Systemic lupus erythematosus (SLE) is regarded as a prototype for SAIDs and we hypothesise that subgroups of patients with SLE may have different pathogenesis and should consequently be subject to different treatment strategies.Objectives. Our goal is to find new biomarkers to be used for the identification of more homogenous patient populations for clinical trials and to identify sub-groups of patients with high risk of for example cardiovascular events.Methods. In this study we have utilised 320 SLE patients from the Karolinska lupus cohort and 320 age and gender matched controls. The SLE cohort was characterised based on clinical, genetic and serological data and combined by multivariate data analysis in a systems biology approach to study possible subgroups. A pilot study was designed to verify and investigate suggested subgroups of SLE. Two main subgroups were defined: One group was defined as having SSA and SSB antibodies and a negative lupus anticoagulant test (LAC), i.e., a “Sjögren-like” group. The other group was defined as being negative for SSA and SSB antibodies but positive in the LAC test.i.e. an “APS-like” group. EDTA-plasma from selected patients in these two groups and controls were analysed using a mass spectrometry (MS) based proteomic and metabolomic approach. Pathway analysis was then performed on the obtained data.Results. Our pilot study showed that differences in levels of proteins and metabolites could separate disease groups from population controls. The profile/pattern of involved factors in the complement system supported a division of SLE in two major subgroups, although each individual factor was not significantly different between subgroups. Complement factor 2 (C2) and membrane attack complex (MAC) were analysed in the entire cohort with complementary methods and C2 verifies our results while the levels of MAC did not differ between SLE subgroups. The generated metabolomics data clearly separated SLE patients from controls in both gas chromatography (GC)-MS and liquid chromatography (LC)-MS data. We found for example that tryptophan was lower in the SLE patients compared to controls.Conclusions. Our systems biology approach may lead to a better understanding of the disease and its pathogenesis, and assigning patients into subgroups will result in improved diagnosis and better outcome measures of SLE.
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| 36. |
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| 37. |
- Jacobson, Therese, et al.
(författare)
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Cadmium Causes Misfolding and Aggregation of Cytosolic Proteins in Yeast
- 2017
-
Ingår i: Molecular and Cellular Biology. - : Informa UK Limited. - 0270-7306 .- 1098-5549. ; 37:17
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Tidskriftsartikel (refereegranskat)abstract
- Cadmium is a highly poisonous metal and is classified as a human carcinogen. While its toxicity is undisputed, the underlying in vivo molecular mechanisms are not fully understood. Here, we demonstrate that cadmium induces aggregation of cytosolic proteins in living Saccharomyces cerevisiae cells. Cadmium primarily targets proteins in the process of synthesis or folding, probably by interacting with exposed thiol groups in not-yet-folded proteins. On the basis of in vitro and in vivo data, we show that cadmium-aggregated proteins form seeds that increase the misfolding of other proteins. Cells that cannot efficiently protect the proteome from cadmium-induced aggregation or clear the cytosol of protein aggregates are sensitized to cadmium. Thus, protein aggregation may contribute to cadmium toxicity. This is the first report on how cadmium causes misfolding and aggregation of cytosolic proteins in vivo. The proposed mechanism might explain not only the molecular basis of the toxic effects of cadmium but also the suggested role of this poisonous metal in the pathogenesis of certain protein-folding disorders.
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| 38. |
- Jakobsson, Stefan, 1970, et al.
(författare)
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A method for simulation based optimization using radial basis functions
- 2010
-
Ingår i: Optimization & Engineering. - : Springer Science and Business Media LLC. - 1573-2924 .- 1389-4420. ; 11:4, s. 501-532
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Tidskriftsartikel (refereegranskat)abstract
- We propose an algorithm for the global optimization of expensive and noisy black box functions using a surrogate model based on radial basis functions (RBFs). A method for RBF-based approximation is introduced in order to handle noise. New points are selected to minimize the total model uncertainty weighted against the surrogate function value. The algorithm is extended to multiple objective functions by instead weighting against the distance to the surrogate Pareto front; it therefore constitutes the first algorithm for expensive, noisy and multiobjective problems in the literature. Numerical results on analytical test functions show promise in comparison to other (commercial) algorithms, as well as results from a simulation based optimization problem.
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| 39. |
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| 40. |
- Jakobsson, Stefan, 1970, et al.
(författare)
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A time domain beam propagation method for chirped signals
- 2014
-
Ingår i: XXXV Congresso Nacional de Matemática Aplicada e Computacional, 8-12 September 2014, Natal, Brazil.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Chirped pulses are used in time stretch analog-to-digital converters to stretch high speed electric signals so that they can be measured with conventional detectors. Here a time domain beam propagation method for strongly chirped signals propagating along a specified direction is presented. By examining the propagation of chirped pulses in waveguides we derive a phase factor which captures the rapidly oscillating part of the chirped pulse. We then solve for the slowly varying envelope with respect to this phase factor in a time window moving with the pulse. The new method is applied to simulation of electro-optical modulators for chirped pulses with promising results.
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| 46. |
- Jakobsson, Stefan
(författare)
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The harmonic Bergman kernel and the Friedrichs operator
- 2002
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Ingår i: Arkiv för Matematik. - 0004-2080. ; 40:1, s. 89-104
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Tidskriftsartikel (refereegranskat)abstract
- The harmonic Bergman kernel Q(Omega) for a simply connected planar domain Q can be expanded in terms of powers of the Friedrichs operator F-Omega if parallel toF(Omega)parallel to <1 in operator norm. Suppose that &UOmega; is the image of a univalent analytic function φ in the unit disk with φ '(z)=1+ψ(z) where ψ(0)=0. We show that if the function ψ belongs to a space D-s(D), s>0, of Dirichlet type, then provided that parallel topsiparallel to(infinity) < 1 the series for Q(&UOmega;) also converges pointwise in <(Omega)over bar>x (&UOmega;) over barDelta(partial derivativeOmega), and the rate of convergence can be estimated. The proof uses the eigenfunctions of the Friedrichs operator as well as a formula due to Lenard on projections in Hilbert spaces. As an application, we show that for every s>0 there exists a constant C-s>0 such that if parallel topsiparallel to(Ds(D))less than or equal to C-s, then the bilharmonic Green function for Omega=phi(D) is positive.
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| 47. |
- Jakobsson, Stefan
(författare)
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Weighted Bergman kernels and biharmonic Green functions
- 2000
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The main theme of this thesis is the connection between weighted biharmonic Green functions and weighted Bergman kernels. In the first paper, which is a joint work with H. Hedenmalm and S. Shimorin, we prove that weighted biharmonic Green functions are positive for weights which satisfy a mean-value condition and whose logarithms are subharmonic. To achieve this, we use a variational formula due to J. Hadamard, weighted Hele-Shaw flow, as well as a new structural formula for the analytic Bergman kernel. The result has applications to the factorization theory in weighted Bergman spaces. In the subsequent papers, we continue to investigate Bergman kernels and Green functions. In the second paper, we analyze the singularity of the weighted analytic and harmonic Bergman kernels for a general smooth weight in a domain with smooth boundary. In the third paper, we apply the theory of semigroups to one of the arguments in the first paper. It turns out that if the harmonic Bergman kernel for a starshaped domain satisfies a certain inequality, then the biharmonic Green function for the domain is positive. In the fourth paper, we show how the Friedrichs operator can be used to expand the harmonic Bergman kernel in terms of the analytic counterpart for a simply connected domain. Under certain conditions on the conformal map from the unit disk to the domain, we obtain a pointwise estimate of the harmonic Bergman kernel.
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| 48. |
- Johnson, Tomas, 1979, et al.
(författare)
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A finite volume method for electrostatic three species negative corona discharge simulations with application to externally charged powder bells
- 2015
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Ingår i: Journal of Electrostatics. - : Elsevier BV. - 0304-3886. ; 74, s. 27-36
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Tidskriftsartikel (refereegranskat)abstract
- A three species model for steady-state negative corona discharge is studied. Ionization, attachment, and recombination reactions are modeled. A novel unstructured finite volume algorithm to solve the equations is presented, using the secondary emission of electrons from the cathode to set boundary values for the electrons.To show the usefulness of the method for industrial applications it is used to characterize the electrostatic properties of an externally charged rotary powder bell used in the automotive industry. Experimental current density profiles are reconstructed with good accuracy, which validates the model and the method with real experimental data.
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| 49. |
- Kozakevicius, Alice de Jesus, et al.
(författare)
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Solving a mixture model of two-phase flow with velocity non-equilibrium using WENO wavelet methods
- 2018
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Ingår i: International Journal of Numerical Methods for Heat and Fluid Flow. - 0961-5539. ; 28:9, s. 2052-2071
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Tidskriftsartikel (refereegranskat)abstract
- Purpose The purpose of this work is to present the implementation of weighted essentially non-oscillatory (WENO) wavelet methods for solving multiphase flow problems. The particular interest is gas-liquid two-phase mixture with velocity non-equilibrium. Numerical simulations are carried out on different scenarios of one-dimensional Riemann problems for gas-liquid flows. Results are validated and qualitatively compared with solutions provided by other standard numerical methods. Design/methodology/approach This paper extends the framework of WENO wavelet adaptive method to a fully hyperbolic two-phase flow model in a conservative form. The grid adaptivity in each time step is provided by the application of a thresholded interpolating wavelet transform. This facilitates the construction of a small yet effective sparse point representation of the solution. The method of Lax-Friedrich flux splitting is used to resolve the spatial operator in which the flux derivatives are approximated by the WENO scheme. Findings Hyperbolic models of two-phase flow in conservative form are efficiently solved, as shocks and rarefaction waves are precisely captured by the chosen methodology. Substantial computational gains are obtained through the grid reduction feature while maintaining the quality of the solutions. The results indicate that WENO wavelet methods are robust and sufficient to accurately simulate gas-liquid mixtures. Originality/value Resolution of two-phase flows is rarely studied using WENO wavelet methods. It is the first time such a study on the relative velocity is reported in two-phase flows using such methods.
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| 50. |
- Kronvall, Ted, et al.
(författare)
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An Adaptive Penalty Approach to Multi-Pitch Estimation
- 2015
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Ingår i: Signal Processing Conference (EUSIPCO), 2015 23rd European. - 2076-1465. - 9780992862633
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Konferensbidrag (refereegranskat)abstract
- This work treats multi-pitch estimation, and in particular the common misclassification issue wherein the pitch at half of the true fundamental frequency, here referred to as a sub-octave, is chosen instead of the true pitch. Extending on current methods which use an extension of the Group LASSO for pitch estimation, this work introduces an adaptive total variation penalty, which both enforce group- and block sparsity, and deal with errors due to sub-octaves. The method is shown to outperform current state-of-the-art sparse methods, where the model orders are unknown, while also requiring fewer tuning parameters than these. The method is also shown to outperform several conventional pitch estimation methods, even when these are virtued with oracle model orders.
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