| 1. |
- Björklund, Andreas, et al.
(författare)
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Shortest Two Disjoint Paths in Polynomial Time
- 2014
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Ingår i: Lecture Notes in Computer Science. - Berlin, Heidelberg : Springer Berlin Heidelberg. - 1611-3349 .- 0302-9743. - 9783662439470 ; 8572, s. 211-222
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Konferensbidrag (refereegranskat)abstract
- Given an undirected graph and two pairs of vertices $(s_i,t_i)$ for $i\in\{1,2\}$ we show that there is a polynomial time Monte Carlo algorithm that finds disjoint paths of smallest total length joining $s_i$ and $t_i$ for $i\in\{1,2\}$ respectively, or concludes that there most likely are no such paths at all. Our algorithm applies to both the vertex- and edge-disjoint versions of the problem. Our algorithm is algebraic and uses permanents over the polynomial rings $Z_2[x]$ and $Z_4[x]$ in combination with Mulmuley, Vazirani and Vazirani's isolation lemma to detect a solution. We develop a fast algorithm for permanents over these rings by modifying Valiant's 1979 algorithm for the permanent over $Z_{2^l}$.
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| 2. |
- Kehoe, Laura, et al.
(författare)
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Make EU trade with Brazil sustainable
- 2019
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Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 364:6438, s. 341-
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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| 3. |
- Lauenstein, Åsa, et al.
(författare)
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Flexibla automationslösningar för 3D-printade sandkärnor
- 2021
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The purpose of the project was to develop solutions for automation of postprocessing of 3D-printed sand cores and the goal was to achieve the same production speed for 3D printed cores as for conventional production. Within three industrial demonstrators, communication solutions between printer, robot, and production systems were developed. Technical solutions were tested for adaption of manual work steps to robot. Preconditions for digitalization of the production flow via traceability was tested and the effect on the business models of the foundries were tested. In the making of these demonstrators, several technical issues have been solved, above all the fundamental aspects of data transfer and compatibility between different systems. Therefore, it is possible to motivate a robot investment already from increased efficiency of the first simple work steps.The project was a cooperation between robot manufacturer, machine supplier, producers of castings, and research institute. The representation of the entire value chain turned out to be a crucial success factor. The results include decision data for investments in a printer and other automation solutions associated w with core manufacturing in the individual foundry. The effect of these results is that Sweden's foundries will strengthen their position with respect to the international competition both short and long term since the results will lead to increased productivity. By evaluating the use of vision systems. The project has also generated inspiration of the development in automation and AI solutions, and further cooperation between the participating companies.
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| 4. |
- Ma, Yunpeng, et al.
(författare)
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Automated and Systematic Digital Twins Testing for Industrial Processes
- 2023
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Ingår i: Proceedings - 2023 IEEE 16th International Conference on Software Testing, Verification and Validation Workshops, ICSTW 2023. - : Institute of Electrical and Electronics Engineers Inc.. - 9798350333350 ; , s. 149-158
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Konferensbidrag (refereegranskat)abstract
- Digital twins (DT) of industrial processes have become increasingly important. They aim to digitally represent the physical world to help evaluate, optimize, and predict physical processes and behaviors. Therefore, DT is a vital tool to improve production automation through digitalization and becomes more sophisticated due to rapidly evolving simulation and modeling capabilities, integration of IoT sensors with DT, and high-capacity cloud/edge computing infrastructure. However, the fidelity and reliability of DT software are essential to represent the physical world. This paper shows an automated and systematic test architecture for DT that correlates DT states with real-time sensor data from a production line in the forging industry. Our evaluation shows that the architecture can significantly accelerate the automatic DT testing process and improve its reliability. A systematic online DT testing method can significantly detect the performance shift and continuously improve the DT's fidelity. The snapshot creation methodology and testing agent architecture can be an inspiration and can be generally applicable to other industrial processes that use DT to generalize their automated testing.
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| 5. |
- Ma, Yunpeng, et al.
(författare)
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Using Deep Reinforcement Learning for Zero Defect Smart Forging
- 2022
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Ingår i: Advances in Transdisciplinary Engineering. - : IOS Press. - 9781643682686 - 9781643682693 ; , s. 701-712
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Konferensbidrag (refereegranskat)abstract
- Defects during production may lead to material waste, which is a significant challenge for many companies as it reduces revenue and negatively impacts sustainability and the environment. An essential reason for material waste is a low degree of automation, especially in industries that currently have a low degree of digitalization, such as steel forging. Those industries typically rely on heavy and old machinery such as large induction ovens that are mostly controlled manually or using well-known recipes created by experts. However, standard recipes may fail when unforeseen events happen, such as an unplanned stop in production, which may lead to overheating and thus material degradation during the forging process. In this paper, we develop a digital twin-based optimization strategy for the heating process for a forging line to automate the development of an optimal control policy that adjusts the power for the heating coils in an induction oven based on temperature data observed from pyrometers. We design a digital twin-based deep reinforcement learning (DTRL) framework and train two different deep reinforcement learning (DRL) models for the heating phase using a digital twin of the forging line. The twin is based on a simulator that contains a heating transfer and movement model, which is used as an environment for the DRL training. Our evaluation shows that both models significantly reduce the temperature unevenness and can help to automate the traditional heating process.
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| 6. |
- Ma, Yunpeng, et al.
(författare)
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Using Deep Reinforcement Learning for Zero Defect Smart Forging
- 2022
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Ingår i: Advances in Transdisciplinary Engineering. - : IOS Press BV. - 9781614994398 ; , s. 701-712
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Konferensbidrag (refereegranskat)abstract
- Defects during production may lead to material waste, which is a significant challenge for many companies as it reduces revenue and negatively impacts sustainability and the environment. An essential reason for material waste is a low degree of automation, especially in industries that currently have a low degree of digitalization, such as steel forging. Those industries typically rely on heavy and old machinery such as large induction ovens that are mostly controlled manually or using well-known recipes created by experts. However, standard recipes may fail when unforeseen events happen, such as an unplanned stop in production, which may lead to overheating and thus material degradation during the forging process. In this paper, we develop a digital twin-based optimization strategy for the heating process for a forging line to automate the development of an optimal control policy that adjusts the power for the heating coils in an induction oven based on temperature data observed from pyrometers. We design a digital twin-based deep reinforcement learning (DTRL) framework and train two different deep reinforcement learning (DRL) models for the heating phase using a digital twin of the forging line. The twin is based on a simulator that contains a heating transfer and movement model, which is used as an environment for the DRL training. Our evaluation shows that both models significantly reduce the temperature unevenness and can help to automate the traditional heating process. © 2022 The authors
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| 7. |
- Bjorklund, Andreas, et al.
(författare)
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Fast Zeta Transforms for Lattices with Few Irreducibles
- 2016
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Ingår i: ACM Transactions on Algorithms. - : Association for Computing Machinery (ACM). - 1549-6325 .- 1549-6333. ; 12:1
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Tidskriftsartikel (refereegranskat)abstract
- We investigate fast algorithms for changing between the standard basis and an orthogonal basis of idempotents for Mobius algebras of finite lattices. We show that every lattice with v elements, n of which are nonzero and join-irreducible (or, by a dual result, nonzero and meet-irreducible), has arithmetic circuits of size O(vn) for computing the zeta transform and its inverse, thus enabling fast multiplication in the Mobius algebra. Furthermore, the circuit construction in fact gives optimal (up to constants) monotone circuits for several lattices of combinatorial and algebraic relevance, such as the lattice of subsets of a finite set, the lattice of set partitions of a finite set, the lattice of vector subspaces of a finite vector space, and the lattice of positive divisors of a positive integer.
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| 8. |
- Bjurling, Björn, et al.
(författare)
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Foreign Information Manipulation & Interference: A Large Language Model Perspective
- 2024
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- This report focus on the intersection ofForeign Information Manipulation andInterference and Large Language Models.The aim is to give a non-technicalcomprehensive understanding of howweaknesses in the language models canbe used for creating malicious content tobe used in FIMI.
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| 9. |
- Björklund, Andreas, et al.
(författare)
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Approximating longest directed paths and cycles
- 2004
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Ingår i: Lecture Notes in Computer Science. - Berlin, Heidelberg : Springer Berlin Heidelberg. - 1611-3349. ; 3142, s. 222-233
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Tidskriftsartikel (refereegranskat)abstract
- We investigate the hardness of approximating the longest path and the longest cycle in directed graphs on n vertices. We show that neither of these two problems can be polynomial time approximated within n(1-epsilon)for any epsilon > 0 unless P = NP. In particular, the result holds for digraphs of constant bounded outdegree that contain a Hamiltonian cycle. Assuming the stronger complexity conjecture that Satisfiability cannot be solved in subexponential time, we show that there is no polynomial time algorithm that finds a directed path of length Omega(f(n) log(2) n), or a directed cycle of length Omega(f(n) log n), for any nondecreasing, polynomial time computable function f in w(1). With a recent algorithm for undirected graphs by Gabow, this shows that long paths and cycles are harder to find in directed graphs than in undirected graphs. We also find a directed path of length Omega(log(2) n/log log n) in Hamiltonian digraphs with bounded outdegree. With our hardness results, this shows that long directed cycles are harder to find than a long directed paths. Furthermore, we present a simple polynomial time algorithm that finds paths of length Omega(n) in directed expanders of constant bounded outdegree.
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| 10. |
- Björklund, Andreas, et al.
(författare)
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Computing the permanent modulo a prime power
- 2017
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Ingår i: Information Processing Letters. - : Elsevier BV. - 0020-0190. ; 125, s. 20-25
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Tidskriftsartikel (refereegranskat)abstract
- We sPRThow how to compute the permanent of an n×n integer matrix modulo pk in time nk+O(1) if p=2 and in time 2n/exp{Ω(γ2n/plogp)} if p is an odd prime with kp0 we can compute the permanent of an n×n integer matrix in time 2n/exp{Ω(δ2n/β1/(1−δ)logβ)}, provided there exists a real number β such that |perA|≤βn and β≤(144δn)1−δ.
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