| 241. |
- Karlsson, Johan, et al.
(författare)
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Parameterisation invariant statistical shape models
- 2004
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Ingår i: Proceedings of the 17th International Conference on Pattern Recognition. - 0769521282 ; , s. 23-26
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Konferensbidrag (refereegranskat)abstract
- In this paper novel theory to automate shape modelling is described. The main idea is to develop a theory that is intrinsically defined for curves, as opposed to a finite sample of points along the curves. The major problem here is to define shape variation in a way that is invariant to curve parametrisations. Instead of representing continuous curves using landmarks, the problem is treated analytically and numerical approximations are introduced at the latest stage. The problem is solved by calculating the covariance matrix of the shapes using a scalar product that is invariant to global reparametrisations. An algorithm for implementing the ideas is proposed and compared to a state of the an algorithm for automatic shape modelling. The problems with instability in earlier formulations are solved and the resulting models are of higher quality
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| 242. |
- Karlsson, Karl Göran, et al.
(författare)
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Scientific Literacy and Educational Reforms in Norway and Sweden
- 2006
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Ingår i: Northern Lights on PISA 2003. - 9289313005 ; , s. 267-
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- In December 2004, when results from PISA 2003 were presented, much focus in media was on ranking lists and overall changes since PISA 2000. In Sweden no significant changes between 2000 and 2003 occurred in none of the three test domains in PISA (reading literacy, mathematical literacy and scientific literacy). Moreover, Swedish scores were significantly above the OECD average in all three domains. In Norway results in reading and mathematics showed no significant changes but a considerable drop in science results. The Norwegian science score was also below the OECD average, whereas reading and mathematics scores were close to the international means (OECD 2001, 2004). In this article we will take a closer look at the PISA science results for the two countries in order to discuss some possible links to educational reforms that has been introduced during the last decennium. For that purpose we will also discuss some results from TIMSS (Trends in International Mathematics and Science Study), or more precisely: results for the science grade 8 part of the study. In addition to the national PISA 2003 reports for Sweden (Skolverket 2004c) and Norway (Kjærnsli et al 2004), also the national TIMSS 2003 reports (Skolverket 2004a, Grønmo et al 2004) discuss the achievement drop in science. In addition, Kjærnsli et al (2005) has recently focused quite specifically on the general drop of competencies in the Nordic countries during the last decennium.
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| 243. |
- Kharisov, Evgeny, et al.
(författare)
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Comparison of architectures and robustness of model reference adaptive controllers and L-1 adaptive controllers
- 2014
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Ingår i: International Journal of Adaptive Control and Signal Processing. - : Wiley. - 0890-6327. ; 28:7-8, s. 633-663
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Tidskriftsartikel (refereegranskat)abstract
- The paper compares direct and indirect model reference adaptive controllers (MRAC) with the L-1 adaptive controller. The architectures of the closed-loop systems are first compared in a simple setting that clarifies the similarities and differences of the controllers. The indirect MRAC and the L-1 controller have identical state predictors, but they differ in the computation of the control signal, which in L-1 is carried out by solving a feedback loop. The special case, where the controllers only adapt to a parameter representing input disturbances, is discussed. In this case, the closed-loop system is linear, so it may not be appropriate to call the controllers adaptive. The special case does, however, give good insight into similarities and differences of the controllers and the effects of various modifications. In particular, the analysis gives good understanding of the robustness properties. Copyright (C) 2013 John Wiley & Sons, Ltd.
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| 244. |
- Kharisov, Evgeny, et al.
(författare)
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Comparison of Several Adaptive Controllers According to Their Robustness Metrics
- 2010
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Konferensbidrag (refereegranskat)abstract
- This paper compares the performance and the robustness of several linear adaptive controllers using a linear system with time–varying disturbance in the presence of measurement noise. For the purpose of comparison we select the direct and indirect model reference adaptive controller (MRAC), the direct MRAC with σ–modification, and the L1 adaptive controller. Using tools from linear systems theory we compute the stability margins of these controllers and examine the performance of these closed–loop systems via analysis of several important transfer functions between the system’s inputs and outputs. In this paper we also investigate some properties of the piecewise constant update laws, introduced in recent L1 papers, and provide an interpretation to draw some insights. Finally, we validate the conclusions in simulations.
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| 245. |
- Kjellberg, Tobias, et al.
(författare)
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Tracking the Motion of Box Jellyfish
- 2014
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Konferensbidrag (refereegranskat)abstract
- In this paper we investigate a system for tracking the motion of box jellyfish tripedalia cystophora in a special test setup. The goal is to measure the motor response of the animal given certain visual stimuli. The approach is based on tracking the special sensory structures – the rhopalia – of the box jellyfish from high-speed video sequences. We have focused on a realtime system with simple building blocks in our system. However, using a combination of simple intensity based detection and model based tracking we achieve promising tracking results with up to 95% accuracy.
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| 246. |
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| 247. |
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| 248. |
- Kuang, Yubin, et al.
(författare)
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A Complete Characterization and Solution to the Microphone Position Self-Calibration Problem
- 2013
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Ingår i: A. - 1520-6149. ; , s. 3875-3879
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Konferensbidrag (refereegranskat)abstract
- This paper presents a complete characterization and solution to microphone position self-calibration problem for time-of-arrival (TOA) measurements. This is the problem of determining the positions of receivers and transmitters given all receiver-transmitter distances. Such calibration problems arise in application such as calibration of radio antenna networks, audio or ultra-sound arrays and WiFi transmitter arrays. We show for what cases such calibration problems are well-defined and derive efficient and numerically stable algorithms for the minimal TOA calibration problems. The proposed algorithms are non-iterative and require no assumptions on the sensor positions. Experiments on synthetic data show that the proposed minimal solvers are numerically stable and perform well on noisy data. The solvers are also tested on two real datasets with good results.
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| 249. |
- Kuang, Yubin, et al.
(författare)
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Minimal solvers for relative pose with a single unknown radial distortion
- 2014
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Ingår i: Proceedings of the IEEE Computer Society Conference on Computer Vision and Pattern Recognition. - 1063-6919. - 9781479951178 ; , s. 33-40
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Konferensbidrag (refereegranskat)abstract
- In this paper, we study the problems of estimating relative pose between two cameras in the presence of radial distortion. Specifically, we consider minimal problems where one of the cameras has no or known radial distortion. There are three useful cases for this setup with a single unknown distortion: (i) fundamental matrix estimation where the two cameras are uncalibrated, (ii) essential matrix estimation for a partially calibrated camera pair, (iii) essential matrix estimation for one calibrated camera and one camera with unknown focal length. We study the parameterization of these three problems and derive fast polynomial solvers based on Gröbner basis methods. We demonstrate the numerical stability of the solvers on synthetic data. The minimal solvers have also been applied to real imagery with convincing results.
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| 250. |
- Kuang, Yubin, et al.
(författare)
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Numerically Stable Optimization of Polynomial Solvers for Minimal Problems
- 2012
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Ingår i: Lecture Notes in Computer Science (Computer Vision ECCV 2012, 12th European Conference on Computer Vision, Florence, Italy, October 7-13, 2012, Proceedings, Part III). - Berlin, Heidelberg : Springer Berlin Heidelberg. - 1611-3349 .- 0302-9743. - 9783642337116 - 3642337112 - 9783642337123 ; 7574, s. 100-113
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Konferensbidrag (refereegranskat)abstract
- Numerous geometric problems in computer vision involve the solu- tion of systems of polynomial equations. This is particularly true for so called minimal problems, but also for finding stationary points for overdetermined prob- lems. The state-of-the-art is based on the use of numerical linear algebra on the large but sparse coefficient matrix that represents the original equations multi- plied with a set of monomials. The key observation in this paper is that the speed and numerical stability of the solver depends heavily on (i) what multiplication monomials are used and (ii) the set of so called permissible monomials from which numerical linear algebra routines choose the basis of a certain quotient ring. In the paper we show that optimizing with respect to these two factors can give both significant improvements to numerical stability as compared to the state of the art, as well as highly compact solvers, while still retaining numerical stabil- ity. The methods are validated on several minimal problems that have previously been shown to be challenging
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