| 1. |
- Bergion, Viktor, 1986, et al.
(författare)
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Hydrological modelling in a drinking water catchment area as a means of evaluating pathogen risk reduction
- 2017
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Ingår i: Journal of Hydrology. - : Elsevier BV. - 0022-1694. ; 544, s. 74-85
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Tidskriftsartikel (refereegranskat)abstract
- Waterborne outbreaks of gastrointestinal diseases are of great concern to drinking water producers and can give rise to substantial costs to the society. The World Health Organisation promotes an approach where the emphasis is on mitigating risks close to the contamination source. In order to handle microbial risks efficiently, there is a need for systematic risk management. In this paper we present a framework for microbial risk management of drinking water systems. The framework incorporates cost-benefit analysis as a decision support method. The hydrological Soil and Water Assessment Tool (SWAT) model, which was set up for the Stäket catchment area in Sweden, was used to simulate the effects of four different mitigation measures on microbial concentrations. The modelling results showed that the two mitigation measures that resulted in a significant (p
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| 2. |
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| 3. |
- Boettcher, Johanna, et al.
(författare)
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Internet-Based Mindfulness Treatment for Anxiety Disorders : A Randomized Controlled Trial
- 2014
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Ingår i: Behavior Therapy. - New York : Association for advanced behavior therapy. - 0005-7894 .- 1878-1888. ; 45:2, s. 241-253
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Tidskriftsartikel (refereegranskat)abstract
- Mindfulness-based interventions have proven effective for the trans diagnostic treatment of heterogeneous anxiety disorders. So far, no study has investigated the potential of mindfulness-based treatments when delivered remotely via the Internet. The current trial aims at evaluating the efficacy of a stand-alone, unguided, Internet-based mindfulness treatment program for anxiety. Ninety-one participants diagnosed with social anxiety disorder, generalized anxiety disorder, panic disorder, or anxiety disorder not otherwise specified were randomly assigned to a mindfulness treatment group (MTG) or to an online discussion forum control group (CG). Mindfulness treatment consisted of 96 audio files with instructions for various mindfulness meditation exercises. Primary and secondary outcome measures were assessed at pre-, post-treatment, and at 6-months follow-up. Participants of the MTG showed a larger decrease of symptoms of anxiety, depression, and insomnia from pre- to postassessment than participants of the CG (Cohen's d(between) = 0.36-0.99). Within effect sizes were large in the MTG (d = 0.82-1.58) and small to moderate in the CG (d = 0.45-0.76). In contrast to participants of the CG, participants of the MTG also achieved a moderate improvement in their quality of life. The study provided encouraging results for an Internet-based mindfulness protocol in the treatment of primary anxiety disorders. Future replications of these results will show whether Web-based mindfulness meditation can constitute a valid alternative to existing, evidence-based cognitive-behavioural Internet treatments.
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| 4. |
- Ding, Yaqing, et al.
(författare)
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Revisiting the P3P Problem
- 2023
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Ingår i: Proceedings of the IEEE Computer Society Conference on Computer Vision and Pattern Recognition. - 9798350301298 ; , s. 4872-4880
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Konferensbidrag (refereegranskat)abstract
- One of the classical multi-view geometry problems is the so called P3P problem, where the absolute pose of a calibrated camera is determined from three 2D-to-3D correspondences. Since these solvers form a critical component of many vision systems (e.g. in localization and Structure-from-Motion), there have been significant effort in developing faster and more stable algorithms. While the current state-of-the-art solvers are both extremely fast and stable, there still exist configurations where they break down. In this paper we algebraically formulate the problem as finding the intersection of two conics. With this formulation we are able to analytically characterize the real roots of the polynomial system and employ a tailored solution strategy for each problem instance. The result is a fast and stable solver, that is able to correctly solve cases where competing methods might fail. Our experimental evaluation shows that we outperform the current state-of-the-art methods both in terms of speed and success rate.
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| 5. |
- Larsson, Viktor, et al.
(författare)
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Efficient Solvers for Minimal Problems by Syzygy-based Reduction
- 2017
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Ingår i: IEEE Conference on Computer Vision and Pattern Recognition (CVPR), 2017. - 9781538604588 - 9781538604571 ; , s. 2383-2392
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Konferensbidrag (refereegranskat)abstract
- In this paper we study the problem of automatically generatingpolynomial solvers for minimal problems. The maincontribution is a new method for finding small eliminationtemplates by making use of the syzygies (i.e. the polynomialrelations) that exist between the original equations. Usingthese syzygies we can essentially parameterize the setof possible elimination templates.We evaluate our method on a wide variety of problemsfrom geometric computer vision and show improvementcompared to both handcrafted and automatically generatedsolvers. Furthermore we apply our method on two previouslyunsolved relative orientation problems.
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| 6. |
- Larsson, Viktor, et al.
(författare)
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Polynomial Solvers for Saturated Ideals
- 2017
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Ingår i: 2017 IEEE International Conference on Computer Vision (ICCV). - 9781538610329
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Konferensbidrag (refereegranskat)abstract
- In this paper we present a new method for creating polynomialsolvers for problems where a (possibly infinite) subsetof the solutions are undesirable or uninteresting. Thesesolutions typically arise from simplifications made duringmodeling, but can also come from degeneracies which areinherent to the geometry of the original problem.The proposed approach extends the standard action matrixmethod to saturated ideals. This allows us to add constraintsthat some polynomials should be non-zero on thesolutions. This does not only offer the possibility of improvedperformance by removing superfluous solutions, butmakes a larger class of problems tractable. Previously,problems with infinitely many solutions could not be solveddirectly using the action matrix method as it requires azero-dimensional ideal. In contrast we only require thatafter removing the unwanted solutions only finitely manyremain. We evaluate our method on three applications, optimaltriangulation, time-of-arrival self-calibration and optimalvanishing point estimation.
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| 7. |
- Larsson, Viktor, et al.
(författare)
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Uncovering symmetries in polynomial systems
- 2016
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Ingår i: Computer Vision – ECCV 2016 14th European Conference, Amsterdam, The Netherlands, October 11-14, 2016, Proceedings, Part III. - Cham : Springer International Publishing. - 1611-3349 .- 0302-9743. - 9783319464862 - 9783319464879 ; 9907, s. 252-267
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Konferensbidrag (refereegranskat)abstract
- In this paper we study symmetries in polynomial equation systems and how they can be integrated into the action matrix method. The main contribution is a generalization of the partial p-fold symmetry and we provide new theoretical insights as to why these methods work. We show several examples of how to use this symmetry to construct more compact polynomial solvers. As a second contribution we present a simple and automatic method for finding these symmetries for a given problem. Finally we show two examples where these symmetries occur in real applications.
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| 8. |
- Tegler, Erik, et al.
(författare)
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The Multi-view Geometry of Parallel Cylinders
- 2023
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Ingår i: Image Analysis : 23rd Scandinavian Conference, SCIA 2023, Sirkka, Finland, April 18–21, 2023, Proceedings - 23rd Scandinavian Conference, SCIA 2023, Sirkka, Finland, April 18–21, 2023, Proceedings. - 0302-9743 .- 1611-3349. - 9783031314377 - 9783031314384 ; 13886, s. 482-499
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Konferensbidrag (refereegranskat)abstract
- In this paper we study structure from motion problems for parallel cylinders. Using sparse keypoint correspondences is an efficient (and standard) way to solve the structure from motion problem. However, point features are sometimes unavailable and they can be unstable over time and viewing conditions. Instead, we propose a framework based on silhouettes of quadric surfaces, with special emphasis on parallel cylinders. Such structures are quite common, e.g. trees, lampposts, pillars, and furniture legs. Traditionally, the projection of the center lines of such cylinders have been considered and used in computer vision. Here, we demonstrate that the apparent width of the cylinders also contains useful information for structure and motion estimation. We provide mathematical analysis of relative structure and relative motion tensors, which is used to develop a number of minimal solvers for simultaneously estimating camera pose and scene structure from silhouette lines of cylinders. These solvers can be used efficiently in robust estimation schemes, such as RANSAC. We use Sampson-approximation methods for efficient estimation using over-determined data and develop averaging techniques. We also perform synthetic accuracy and robustness tests and evaluate our methods on a number of real-world scenarios.
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