| 1. |
- Andersson, Christian, et al.
(författare)
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A Workbench for Multibody Systems ODE and DAE Solvers
- 2012
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Ingår i: Proceedings of the IMSD2012 - The 2nd Joint International Conference on Multibody System Dynamics. - 9783927618329
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Konferensbidrag (refereegranskat)abstract
- During the last three decades, a vast variety of methods to numerically solve ordinary differential equations (ODEs) and differential algebraic equations (DAEs) has been developed and investigated. Few of them met industrial standards and even less are available within industrial multibody simulation software. Multibody Systems (MBS) offer a challenging class [5] of applications for these methods, since the resulting system equations are in the unconstrained case ODEs which are often stiff or highly oscillatory. In the constrained case the equations are DAEs of index-3 or less. Friction and impact in the MBS model introduce discontinuities into these equations while coupling to discrete controllers and hardware-in-the-loop components couple these equations to additional time discrete descriptions. Many of the developed numerical methods have promising qualities for these types of problems, but rarely got the chance to be tested on large scale problems. One reason is the closed software concept of most of the leading multibody system simulation tools or interface concepts with a high threshold to overcome. Thus, these ideas never left the academic environment with their perhaps complex but dimensionally low scale test problems. In this paper we will present a workbench, ASSIMULO, which allows easy and direct incorporation of new methods for solving ODEs or DAEs written in FORTRAN, C, Python or even MATLAB and which indirectly interfaces to multibody programs such as Dymola and Simpack, via a standardized interface, the functional mock-up interface. The paper is concluded with industrial relevant examples evaluated using industrial and academic solvers.
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| 2. |
- Blomé, Mikael, et al.
(författare)
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Course Supervision Challenges in PhD Education
- 2012
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Ingår i: 7:e Pedagogiska Inspirationskonferensen 2012. - 2003-3761 .- 2003-377X. ; 7
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Konferensbidrag (refereegranskat)abstract
- A large portion of the PhD education in Sweden is dedicated to courses. This made it interesting to explore potential course supervision challenges in the PhD programme. A multiple-case study was conducted to identify such challenges and explore how these are perceived by students and supervisors at the Faculty of Engineering of Lund University. By interviewing students and supervisors in five different research groups, insights were gained into how the main stakeholders reason about courses. The findings indicate that courses that are to be included in the education are characterized by a large degree of freedom tailored to individual student needs and preferences. However, the type, timing, availability, value, and convalidation of courses are challenges that limit this freedom.
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| 3. |
- Fransson, Åsa, 1971, et al.
(författare)
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Characterization of fractured crystalline rock: two Swedish in situ field experiments
- 2014
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Ingår i: 1st International Discrete Fracture Network Engineering Conference, 20-22 oct 2014, Vancouver, Canada.
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Konferensbidrag (refereegranskat)abstract
- Construction of a nuclear waste repository requires information and an understanding of the fractured rock. The Swedish concept for nuclear waste deposition that is currently being developed by the Swedish Nuclear Fuel and Waste Management Co (SKB) includes a natural barrier in the form of crystalline rock, and engineered barriers in the form of bentonite and a copper canister. This paper aims to present two in situ field experiments: the first is the Large fractures experiment and the second is BRIE, the Bentonite Rock Interaction Experiment. Important issues include possible deformation (shearing) of fractures and deformation zones influencing the localization of canisters, and fluid flow, resulting in hydration of the bentonite. The aim of Large fractures is to further develop strategies and integrated investigation and modelling methodology for the identification and characterization of geological structures to ensure that (size) determination of large fractures or minor deformation zones to a greater extent can be based on real properties and to a lesser degree on a criterion related to the existence of a full perimeter fracture – tunnel intersection. BRIE is a field experiment which addresses the hydraulic interaction between the system components of compacted bentonite and the near-field host rock composed of hard and fractured bedrock. The above experiments are presented in terms of investigations performed to obtain discrete fracture descriptions. Grouting of fractures intersecting the investigation borehole of the Large fractures experiment was designed based on field data and a decrease in flow from above 200 liters/min to below 1 liter/min was achieved. The magnitude of the transmissivity of the fracture/deformation zone that was grouted indicates a large fracture size. This is also indicated by the ongoing integrated interpretation (geology, hydrogeology and geophysics). Results from BRIE show that hydration is uneven and is controlled by the main conductive fracture, highlighting the need for a relevant fracture description.
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| 4. |
- Hansson, L-A, et al.
(författare)
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A synthesis of animal movement across scales
- 2014
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Ingår i: Animal Movement Across Scales. - : Oxford University Press. - 9780199677184 ; , s. 259-267
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Bokkapitel (refereegranskat)abstract
- This chapter aims at synthesizing the knowledge presented in the chapters of the book’s three sections by addressing evolutionary compromises, dispersal, gene flow, and assisted movements. How climate change and other environmental changes at different scales may affect animal movement, migration, and dispersal in the future are also summarized here. Moreover, how the different senses are utilized for navigation and orientation and how these may lead to different movement and migration patterns are also discussed. Finally, how the recent technical revolution has affected animal movement research is addressed and the view on future perspectives of animal movement research is also provided.
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| 5. |
- Iwase, Masami, et al.
(författare)
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Analysis of safe manual control by using Furuta pendulum
- 2006
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Ingår i: 2006 IEEE Conference on Computer Aided Control System Design.
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Konferensbidrag (refereegranskat)abstract
- This paper focuses on the interaction of manual and automatic control in a demanding task where the process is unstable and has actuator limitation. The problem is inspired by control of high performance aircrafts but which is similar to controlling the arm of a Furuta pendulum while maintaining the stability of the pendulum. The task is to control the position of the pendulum arm manually while maintaining the pendulum in the upright position. The analysis of regions for safe maneuvers is important to realize the desired control system.
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| 6. |
- Malmgren, Linnea, et al.
(författare)
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The complexity of kidney disease and diagnosing it - Cystatin C, selective glomerular hypofiltration syndromes and proteome regulation.
- 2023
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Ingår i: Journal of Internal Medicine. - : John Wiley & Sons. - 0954-6820 .- 1365-2796. ; 293:3, s. 293-308
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Tidskriftsartikel (refereegranskat)abstract
- Estimation of kidney function is often part of daily clinical practice, mostly done by using the endogenous GFR-markers creatinine or cystatin C. A recommendation to use both markers in parallel in 2010 has resulted in new knowledge concerning the pathophysiology of kidney disorders by identification of a new set of kidney disorders, selective glomerular hypofiltration syndromes. These syndromes, connected to strong increases in mortality and morbidity, are characterised by a selective reduction in the glomerular filtration of 5-30 kDa molecules, such as cystatin C, compared to the filtration of small molecules < 1kDa dominating the glomerular filtrate e.g., water, urea, creatinine. At least two types of such disorders, shrunken or elongated pore syndrome, are possible according to the pore model for glomerular filtration. Selective glomerular hypofiltration syndromes are prevalent in investigated populations, and patients with these syndromes often display normal measured GFR or creatinine-based GFR-estimates. The syndromes are characterised by proteomic changes promoting the development of atherosclerosis, indicating antibodies and specific receptor-blocking substances as possible new treatment modalities. Presently, the KDIGO guidelines for diagnosing kidney disorders do not recommend cystatin C as a general marker of kidney function and will therefore not allow the identification of a considerable number of patients with selective glomerular hypofiltration syndromes. Furthermore, as cystatin C is uninfluenced by muscle mass, diet or variations in tubular secretion and cystatin C-based GFR-estimation equations do not require controversial race or sex terms, it is obvious that cystatin C should be a part of future KDIGO guidelines.
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| 7. |
- Ylikiiskilä, Johan, et al.
(författare)
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Improving Newton's method for Initialization of Modelica models
- 2011
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Konferensbidrag (refereegranskat)abstract
- Initializing a model written in Modelica translates to finding consistent initial values to the underlying DAE. Adding initial equations and conditions creates a system of non-linear equations that can be solved for the initial configuration. This paper reports an implementation of Newton's method to solve the non-linear initialization system. This implementation also uses a regularization method to deal with singular Jacobians as well as sparse solvers to exploit the sparsity structure of the Jacobian. The implementation is based on the open-source projects JModelica.org and Assimulo, KINSOL from the SUNDIALS suite and SuperLU.
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| 8. |
- Åkerberg, Johan, et al.
(författare)
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Future industrial networks in process automation : Goals, challenges, and future directions
- 2021
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Ingår i: Applied Sciences. - : MDPI AG. - 2076-3417. ; 11:8
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Tidskriftsartikel (refereegranskat)abstract
- There are many initiatives and technologies working towards implementing factories of the future. One consensus is that the classical hierarchical automation system design needs to be flattened while supporting the functionality of both Operation Technology (OT) and Information Technology (IT) within the same network infrastructure. To achieve the goal of IT/OT convergence in process automation, an evolutionary transition is preferred. Challenges are foreseen during the transition, mainly caused by the traditional automation architecture, and the main challenge is to identify the gap between the current and future network architectures. To address the challenges, in this paper, we describe one desired future scenario for process automation and carry out traffic measurements from a pulp and paper mill. The measured traffic is further analyzed, which reveals representative traffic characteristics in the process automation. Finally, the key challenges and future directions towards a system architecture for factories of the future are presented. © 2021 by the authors.
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| 9. |
- Åkesson, Johan, et al.
(författare)
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Manual Control and Stabilization of an Inverted Pendulum
- 2005
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Ingår i: Proceedings of the 16th IFAC World Congress. - 008045108X
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Konferensbidrag (refereegranskat)abstract
- The problem of stabilizing an inverted pendulum on a cart while enabling manual control of the cart velocity is treated. Introduction of an input saturation nonlinearity makes the problem challenging in the sense that the system may be driven to a state where recovery is not possible. A controller based on the controllability set of the inverted pendulum, which ensures stability and tracking of constant reference velocities for the cart is developed. The controller also offers a trade-off between performance and robustness.
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| 10. |
- Åkesson, Johan, et al.
(författare)
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Safe Manual Control of the Furuta Pendulum
- 2001
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Ingår i: Proceedings of the 2001 IEEE International Conference on Control Applications, 2001. (CCA '01).. - 0780367332 ; , s. 890-895
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Konferensbidrag (refereegranskat)abstract
- This paper deals with the manual control of unstable systems, subject to control signal saturation. In particular we consider the Furuta pendulum, where the problem is to control the orientation of the arm manually while stabilizing the inverted pendulum. This paper presents an analysis which leads to an insight into the problem as well as the control strategy. This control strategy has been implemented on the real Furuta pendulum. Aspects of the implementation as well as experimental results are discussed
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