| 1. |
- Khorsandi, Bahare M., et al.
(author)
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6G E2E Architecture Framework with Sustainability and Security Considerations
- 2022
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In: 2022 IEEE GLOBECOM Workshops, GC Wkshps 2022 - Proceedings. ; , s. 832-837
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Conference paper (peer-reviewed)abstract
- The research on 6G in the EU-funded flagship project Hexa-X started with the investigation of the most important technology enablers and the evaluation of relevant 6G use cases. The next step is to integrate these enablers in a 6G E2E architecture that fulfills all use case-based Key Performance (KPI) and Key Value Indicators (KVI) and that follows the guidelines of general architectural principles. In addition, the main focus of an E2E 6G architecture must be on security and sustainability which both will have increased importance for future communication networks and society.
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| 2. |
- Adolfsson, Stefan, et al.
(author)
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Automatic Detection of Burn-through in GMA Welding Using a Parametric Model
- 1996
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In: Mechanical Systems & Signal Processing. - London : Academic Press. - 0888-3270. ; 10:5, s. 633-651
-
Journal article (peer-reviewed)abstract
- This paper addresses the problem of automatic detection of burn-through in weld joints. Gas metal are (GMA) welding with pulsed current is used, and welding voltage and current are recorded. As short-circuitings are common between the welding electrode and the work piece during burn-through, a short-circuit detector is developed to detect these events. To detect another specific characteristic of burn-through-a broadband long-lasting voltage component-this detector is combined with a square-law detector. This second detector is based on a non-linear modification of an autoregressive model with extra input (ARX-model) of the welding process. The results obtained from this compound detector indicate that it is possible to detect burn-through in the welds automatically. The work also indicates that it is possible to design an on-line monitoring system for robotic GMA welding.
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| 3. |
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| 4. |
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| 5. |
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| 6. |
- Axberg, Stefan, et al.
(author)
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Lärobok i Militärteknik, vol. 9 : Teori och metod
- 2013. - 1
-
Book (other academic/artistic)abstract
- Ämnet militärteknik utgår från att tekniska system är officerens arbetsredskap och att en förståelse för och kunskap om dessa verktyg är central för att kunna utöva professionen framgångsrikt. Denna nionde volym av Lärobok i Militärteknik, benämnd Teori och Metod, behandlar centrala begrepp, teorier och postulat samt metoder för värdering av teknik och består av ett antal texter författade av 16 forskare och lärare vid den militärtekniska avdelningen. Volymen riktar sig främst till de som inlett sin officersutbildning och utgörs till stora delar av ett kompilat av publicerade och opublicerade militärtekniska texter och kan sägas utgöra militärteknikens ”state of the art”.
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| 7. |
- Backe, Stefan, et al.
(author)
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Injuries in rock climbing : An epidemiological study of the Swedish climber population
- 2008
-
Conference paper (peer-reviewed)abstract
- Objective.The popularity of rock climbing is increasing worldwide, both as a recreational physical activity and as a competitive sport. By its nature, rock climbing is associated with injury risks. We aimed to examine typical injury patterns in a representative sample from a total population of climbers.Material and methods.A mail survey was distributed to a random sample consisting of 10 % of the Swedish Climbing Association membership (597/6067 persons). Self-reported information about climbing history, safety practices, and retrospective accounts of injury events were obtained.Results.The annual incidence of overuse injuries was 280/1000 climber years. Inflammatory tissue damage to the fingers and wrists were most common injury types. Men and climbers practising bouldering or sport climbing reported more overuse injuries. The incidence of acute injuries was considerably lower (25/1000 climber years). Men were represented twice as often as women in this group. Twenty-four percent of climbers reporting overuse injuries also suffered an incident or acute injury that same year. The largest number of acute injuries occurred during traditional climbing. These injuries were commonly localised to the feet and ankles. The most frequent cause reported to explain the acute injuries was the human factor, i.e. mistakes or lapses.Discussion and conclusions.Overuse injuries are common among climbers, while acute injuries are less common but can lead to long absence from climbing. Both types of injuries can be reduced by focussed prevention programs. While overuse injuries can be reduced by a better balance between climbing activity and rest, systematic information about safety practices and participation in mandatory first aid and climbing rescue courses can reduce acute injuries and their consequences.
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| 8. |
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| 9. |
- Backe, Stefan, et al.
(author)
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Rock climbing injury rates and associated risk factors in a general climbing population
- 2009
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In: SCANDINAVIAN JOURNAL OF MEDICINE and SCIENCE IN SPORTS. - : Wiley. - 0905-7188 .- 1600-0838. ; 19:6, s. 850-856
-
Journal article (peer-reviewed)abstract
- The objective was to examine injury rates and associated risk factors in a representative sample of climbers. A random sample (n=606) of the Swedish Climbing Association members was sent a postal survey, with an effective response rate of 63%. Self-reported data regarding climbing history, safety practices and retrospective accounts of injury events (recall period 1.5 years) were obtained. Descriptive statistical methods were used to calculate injury incidences, and a two-step method including zero-inflated Poissons regression analysis of re-injuries was used to determine the combination of risk factors that best explained individual injury rates. Overall, 4.2 injuries per 1000 climbing hours were reported, overuse injuries accounting for 93% of all injuries. Inflammatory tissue damages to fingers and wrists were the most common injury types. The multivariate analysis showed that overweight and practicing bouldering generally implied an increased primary injury risk, while there was a higher re-injury risk among male climbers and a lower risk among the older climbers. The high percentage of overuse injuries implies that climbing hours and loads should be gradually and systematically increased, and climbers regularly controlled for signs and symptoms of overuse. Further study of the association between body mass index and climbing injury is warranted.
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| 10. |
- Berg, Anna, 1975-, et al.
(author)
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Effect of nitric oxide on histamine-induced cytological transformations in parietal cells in isolated human gastric glands
- 2007
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In: Digestive Diseases and Sciences. - : Springer Science and Business Media LLC. - 0163-2116 .- 1573-2568. ; 52:1, s. 126-136
-
Journal article (peer-reviewed)abstract
- Previous studies have shown that nitric oxide (NO) inhibits histamine-induced gastric acid secretion in isolated human gastric glands. NO synthase has been found to be present in the human oxyntic mucosa and has been suggested to serve as a paracrine regulator of gastric acid secretion. Histamine stimulation of parietal cells induces cytoskeletal rearrangements, recruitment of H +/K +-ATPase-rich tubulovesicles to the apical membrane and expansion of intracellular canaliculi. The aim of the present study was thus to investigate (i) the effect of an NO donor on histamine-induced cytological transformations and (ii) the influence of increased [Ca 2+] i on NO-induced morphological changes in human parietal cells. Human gastric glands were isolated and subjected to the NO donor SNAP prior to histamine administration. [Ca 2+] i was increased by photolysis of the caged Ca 2+ compound NP-EGTA. The distribution of F-actin, ezrin, and H +/K +-ATPase was assessed by confocal microscopy. Ultrastructural analysis was performed using transmission electron microscopy. SNAP did not influence the histamine-induced translocation of F-actin, ezrin, and H +/K +-ATPase but prevented an increase in the canalicular size. Elevation of [Ca 2+] i in resting cells was found to mimic histamine-induced intraparietal cell transformations; however, NO-induced parietal cell morphology was unaffected by a rise in [Ca 2+] i. These results indicate that NO inhibits secretion of fluid into the canalicular lumen without affecting membrane recruitment and that this effect is Ca 2+-insensitive. © 2006 Springer Science+Business Media, Inc.
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| 11. |
- Berg, Anna, 1975-, et al.
(author)
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Nitric oxide-an endogenous inhibitor of gastric acid secretion in isolated human gastric glands
- 2004
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In: BMC Gastroenterology. - 1471-230X. ; 4:16
-
Journal article (peer-reviewed)abstract
- BackgroundEndothelial nitric oxide synthase (eNOS) has previously been detected in the glandular part of the human gastric mucosa. Furthermore, nitric oxide (NO) has been shown to influence gastric secretion in various animal models. The present study was conducted to investigate the influence of exogenously and endogenously derived NO on histamine- and cAMP-stimulated gastric acid secretion in isolated human oxyntic glands.MethodsOxyntic glands were isolated from human gastric biopsies and were subsequently pre-treated with NO donors and nitric oxide synthase inhibitors and then exposed to histamine or dibutyryl-cAMP (db-cAMP). The secretory response of the glands was determined as accumulation of [14C]aminopyrine.ResultsThe histamine- or db-cAMP-induced acid secretion was attenuated by L-arginine, a known source of endogenous NO, and also by the NO-donors sodium nitroprusside (SNP) and S-nitroso-N-acetyl-penicillamine (SNAP). Pre-treatment with either of the NOS inhibitors NG-nitro-L-arginine methyl ester (L-NAME) or NG-nitro-L-arginine (L-NNA) enhanced the secretory response.ConclusionOur results show that NO inhibits gastric acid secretion in isolated human gastric glands, and that there is endogenous formation of NO within the glandular epithelium in the vicinity of the parietal cells.
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| 12. |
- Berg, Anna, 1975-, et al.
(author)
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Nitric oxide inhibits gastric acid secretion by increasing intraparietal cell levels of cGMP in isolated human gastric glands
- 2005
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In: American Journal of Physiology - Gastrointestinal and Liver Physiology. - : American Physiological Society. - 0193-1857 .- 1522-1547. ; 289:6, s. G1061-G1066
-
Journal article (peer-reviewed)abstract
- We have previously identified cells containing the enzyme nitric oxide (NO) synthase (NOS) in the human gastric mucosa. Moreover, we have demonstrated that endogenous and exogenous NO has been shown to decrease histamine-stimulated acid secretion in isolated human gastric glands. The present investigation aimed to further determine whether this action of NO was mediated by the activation of guanylyl cyclase (GC) and subsequent production of cGMP. Isolated gastric glands were obtained after enzymatic digestion of biopsies taken from the oxyntic mucosa of healthy volunteers. Acid secretion was assessed by measuring [14C]aminopyrine accumulation, and the concentration of cGMP was determined by radioimmunoassay. In addition, immunohistochemistry was used to examine the localization of cGMP in mucosal preparations after stimulation with the NO donor S-nitroso-N-acetylpenicillamine (SNAP). SNAP (0.1 mM) was shown to decrease acid secretion stimulated by histamine (50 μM); this effect was accompanied by an increase in cGMP production, which was histologically localized to parietal cells. The membrane-permeable cGMP analog dibuturyl-cGMP (db-cGMP; 0.1–1 mM) dose dependently inhibited acid secretion. Additionally, the effect of SNAP was prevented by preincubating the glands with the GC inhibitor 4H-8-bromo-1,2,4-oxadiazolo[3,4-d]benz[b][1,4]oxazin-1-one (10 μM). We therefore suggest that NO in the human gastric mucosa is of physiological importance in regulating acid secretion. Furthermore, the results show that NO-induced inhibition of gastric acid secretion is a cGMP-dependent mechanism in the parietal cell involving the activation of GC.
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| 13. |
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| 14. |
- Börjesson, Stefan, 1979-
(author)
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Antibiotic Resistance in Wastewater : Methicillin-resistant Staphylococcus aureus (MRSA)and antibiotic resistance genes
- 2009
-
Doctoral thesis (other academic/artistic)abstract
- A large part of the antibiotics consumed ends up in wastewater, and in the wastewater the antibiotics may exert selective pressure for or maintain resistance among microorganisms. Antibiotic resistant bacteria and genes encoding antibiotic resistance are commonly detected in wastewater, often at higher rates and concentrations compared to surface water. Wastewater can also provide favourable conditions for the growth of a diverse bacterial community, which constitutes a basis for the selection and spread of antibiotic resistance. Therefore, wastewater treatment plants have been suggested to play a role in the dissemination and development of antibiotic resistant bacteria. Methicillin-resistant Staphylococcus aureus (MRSA) is a large problem worldwide as a nosocomial pathogen, but knowledge is limited about occurrence in non-clinical environments, such as wastewater, and what role wastewater plays in dissemination and development of MRSA. In this thesis we investigated the occurrence of MRSA in a full-scale wastewater treatment plant (WWTP). We also investigated the concentration of genes encoding resistance to aminoglycosides (aac(6’)-Ie+aph(2’’)), β-lactam antibiotics (mecA) and tetracyclines (tetA and tetB) in three wastewater-associated environments: (1) soil from an overland flow area treating landfill leachates, (2) biofilm from a municipal wastewater treatment plant, and (3) sludge from a hospital wastewater pipeline. In addition, concentrations of mecA, tetA and tetB were investigated over the treatment process in the WWTP. These investigations were performed to determine how the prevalence and concentration of MRSA and the antibiotic resistence genes are affected in wastewater and wastewater treatment processes over time. The occurrence of MRSA was investigated by cultivation and a commercially available real-time PCR assay. In order to determine concentrations of the genes aac(6’)-Ie+aph(2’’), mecA, tetA and tetB in wastewater we developed a LUXTM real-time PCR assay for each gene. Using cultivation and real-time PCR we could for the first time describe the occurrence of MRSA in wastewater and show that it had a stable occurrence over time in a WWTP. MRSA could mainly be detected in the early treatment steps in the WWTP, and the wastewater treatment process reduced the number and diversity of cultivated MRSA. However, our results also indicate that the treatment process selects for strains with more extensive resistance and possibly higher virulence. The isolated wastewater MRSA strains were shown to have a close genetic relationship to clinical isolates, and no specific wastewater lineages could be detected, indicating that they are a reflection of carriage in the community. Taken together, these data indicate that wastewater may be a potential reservoir for MRSA and that MRSA are more prevalent in wastewater than was previously thought. The real-time PCR assays, for aac(6’)-Ie+aph(2’’), mecA, tetA, and tetB that we developed, were shown to be sensitive, fast, and reproducible methods for detection and quantification of these genes in wastewater environments. The highest concentrations of all genes were observed in the hospital pipeline, and the lowest in the overland flow system, with tetA and aac(6´)-Ie+aph(2´´) detected in all three environments. In the full-scale WWTP, we continuously detected mecA, tetA and tetB over the treatment process and over time. In addition, it was shown that the treatment process reduces concentrations of all three genes. The data presented in this thesis also indicate that the reduction for all three genes may be connected to the removal of biomass, and in the reduction of tetA and tetB, sedimentation and precipitation appear to play an important role.
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| 15. |
- Ericson, Amanda, et al.
(author)
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IIoT Intrusion Detection using Lightweight Deep Learning Models on Edge Devices
- 2024
-
In: 2024 IEEE 20th International Conference on Factory Communication Systems (WFCS). - : IEEE conference proceedings. - 9798350319347
-
Conference paper (peer-reviewed)abstract
- In the rapidly evolving cybersecurity landscape, detecting and preventing network attacks has become crucial within the industrial sector. This study aims to explore the potential of intrusion detection by employing deep learning within edge computing, especially for the Industrial Internet of Things. Specifically, TinyML converted CNN, LSTM, Transformer-LSTM, and GCN models on the UNSW-NB15 dataset. A comprehensive dataset analysis gained insights into the nature of attack behavior data. Subsequently, a comparative analysis in an edge computing setup using Raspberry Pi units revealed that the GCN model, with its accuracy of 97.5%, was the best suited of the compared models for this application. However, the study also explored variables like time consumption, where the CNN model was the fastest out of the compared models. This research also highlights the need for continued exploration, especially in addressing dataset imbalances and enhancing model generalizability. By recognizing each model's strengths and areas of improvement, this research serves as a step toward bolstering digital safety and security in an increasingly interconnected industrial world.
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| 16. |
- Ericson, Marten, et al.
(author)
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Architecture landscape
- 2023
-
In: Towards Sustainable and Trustworthy 6G: Challenges, Enablers, and Architectural Design. - 9781638282396 ; , s. 11-39
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Book chapter (other academic/artistic)abstract
- The network architecture evolution journey will carry on in the years ahead, driving a large scale adoption of 5th Generation (5G) and 5G-Advanced use cases with significantly decreased deployment and operational costs, and enabling new and innovative use-case-driven solutions towards 6th Generation (6G) with higher economic and societal values. The goal of this chapter, thus, is to present the envisioned societal impact, use cases and the End-to-End (E2E) 6G architecture. The E2E 6G architecture includes summarization of the various technical enablers as well as the system and functional views of the architecture.
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| 17. |
- Ericson, Stefan, et al.
(author)
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A vision-guided mobile robot for precision agriculture
- 2009
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In: Proceedings of 7th European Conference on Precision Agriculture. - Wageningen : Wageningen Academic Publishers. - 9789086861132 - 9789086866649 ; , s. 623-630
-
Conference paper (peer-reviewed)abstract
- In this paper we have developed a mobile robot which is able to perform crop-scale operations using vision as only sensor. The system consists of a row-following system and a visual odometry system. The row following system captures images from a front looking camera on the robot and the crop rows are extracted using Hough transform. Both distance to the rows and heading angle is provided which both are used to control the steering. The visual odometry system uses two cameras in a stereo setup pointing perpendicular to the ground. This system measures the travelled distance by measuring the ground movement and compensate for height variation. Experiments are performed on an artificial field due to the season. The result shows that the visual odometry have accuracy better than 2.1% of travelled distance.
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| 18. |
- Ericson, Stefan, et al.
(author)
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Algorithms for Visual Odometry in Outdoor Field Environment
- 2007
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In: Proceedings of the 13th IASTED International Conference on Robotics and Applications. - Anaheim, Calif. : ACTA Press. - 9780889866850 - 9780889866867 ; , s. 287-292
-
Conference paper (peer-reviewed)abstract
- In this paper different algorithms for visual odometry are evaluated for navigating an agricultural weeding robot in outdoor field environment. Today there is an encoder wheel that keeps track of the weeding tools position relative the camera, but the system suffers from wheel slippage and errors caused by the uneven terrain. To overcome these difficulties the aim is to replace the encoders with visual odometry using the plant recognition camera. Four different optical flow algorithms are tested on four different surfaces, indoor carpet, outdoor asphalt, grass and soil. The tests are performed on an experimental platform. The result shows that the errors consist mainly of dropouts caused by overriding maximum speed, and of calibration error due to uneven ground. The number of dropouts can be reduced by limiting the maximum speed and detection of missing frames. The calibration problem can be solved using stereo cameras. This gives a height measurement and the calibration will be given by camera mounting. The algorithm using normalized cross-correlation shows the best result concerning number of dropouts, accuracy and calculation time.
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| 19. |
- Ericson, Stefan, et al.
(author)
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Information Fusion for Autonomous Robotic Weeding
- 2009
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In: INFORMATIK 2009. - : Köllen Druck + Verlag GmbH. - 9783885792482 ; , s. 2461-2473
-
Conference paper (peer-reviewed)abstract
- Information fusion has a potential applicability to a multitude of differentapplications. Still, the JDL model is mostly used to describe defense applications.This paper describes the information fusion process for a robot removing weed ina field. We analyze the robotic system by relating it to the JDL model functions.The civilian application we consider here has some properties which differ from thetypical defense applications: (1) indifferent environment and (2) a predictable andstructured process to achieve its objectives. As a consequence, situation estimatestend to deal with internal properties of the robot and its mission progress (throughmission state transition) rather than external entities and their relations. Nevertheless, the JDL model appears useful for describing the fusion activities of the weeding robot system. We provide an example of how state transitions may be detected and exploited using information fusion and report on some initial results. An additional finding is that process refinement for this type of application can be expressed in terms of a finite state machine.
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| 20. |
- Ericson, Stefan K., 1974-, et al.
(author)
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Analysis of two visual odometry systems for use in an agricultural field environment
- 2018
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In: Biosystems Engineering. - London : Elsevier. - 1537-5110 .- 1537-5129. ; 166, s. 116-125
-
Journal article (peer-reviewed)abstract
- This paper analyses two visual odometry systems for use in an agricultural field environment. The impact of various design parameters and camera setups are evaluated in a simulation environment. Four real field experiments were conducted using a mobile robot operating in an agricultural field. The robot was controlled to travel in a regular back-and-forth pattern with headland turns. The experimental runs were 1.8–3.1 km long and consisted of 32–63,000 frames. The results indicate that a camera angle of 75° gives the best results with the least error. An increased camera resolution only improves the result slightly. The algorithm must be able to reduce error accumulation by adapting the frame rate to minimise error. The results also illustrate the difficulties of estimating roll and pitch using a downward-facing camera. The best results for full 6-DOF position estimation were obtained on a 1.8-km run using 6680 frames captured from the forward-facing cameras. The translation error (x,y,z) is 3.76% and the rotational error (i.e., roll, pitch, and yaw) is 0.0482 deg m−1. The main contributions of this paper are an analysis of design option impacts on visual odometry results and a comparison of two state-of-the-art visual odometry algorithms, applied to agricultural field data.
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| 21. |
- Ericson, Stefan, et al.
(author)
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Row-detection on an agricultural field using omnidirectional camera
- 2010
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In: 2010 IEEE/RSJ international conference on intelligent robots and systems. - Piscataway, N.J. : IEEE Press. - 9781424466740 - 9781424466764 - 9781424466757 ; , s. 4982-4987
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Conference paper (peer-reviewed)abstract
- This paper describes a method of detecting parallel rows on an agricultural field using an omnidirectional camera. The method works both on cameras with a fisheye lens and cameras with a catadioptric lens. A combination of an edge based method and a Hough transform method is suggested to find the rows. The vanishing point of several parallel rows is estimated using a second Hough transform. The method is evaluated on synthetic images generated with calibration data from real lenses. Scenes with several rows are produced, where each plant is positioned with a specified error. Experiments are performed on these synthetic images and on real field images. The result shows that good accuracy is obtained on the vanishing point once it is detected correctly. Further it shows that the edge based method works best when the rows consists of solid lines, and the Hough method works best when the rows consists of individual plants. The experiments also show that the combined method provides better detection than using the methods separately.
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| 22. |
- Ericson, Stefan, et al.
(author)
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Stereo Visual Odometry for Mobile Robots on Uneven Terrain
- 2008
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In: WCECS '08 Proceedings of the Advances in Electrical and Electronics Engineering - IAENG Special Edition of the World Congress on Engineering and Computer Science 2008. - Washington : IEEE Computer Society. - 9780769535555 - 9781424435456 ; , s. 150-157
-
Conference paper (peer-reviewed)abstract
- In this paper we present a stereo visual odometry system for mobile robots that is not sensitive to uneven terrain. Two cameras is mounted perpendicular to the ground and height and traveled distance are calculated using normalized cross correlation. A method for evaluating the system is developed, where flower boxes containing representative surfaces are placed in a metal-working lathe. The cameras are mounted on the carriage which can be positioned manually with 0.1 mm accuracy. Images are captured every 10 mm over 700 mm. The tests are performed on eight different surfaces representing real world situations. The resulting error is less than 0.6% of traveled distance on surfaces where the maximum height variation is measured to 96 mm. The variance is measured for eight test runs, total 5.6 m, to 0.040 mm. This accuracy is sufficient for crop-scale agricultural operations.
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| 23. |
- Ericson, Stefan
(author)
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Vision-Based Perception for Localization of Autonomous Agricultural Robots
- 2017
-
Doctoral thesis (other academic/artistic)abstract
- In this thesis Stefan investigates how cameras can be used for localization of an agricultural mobile robot. He focuses on relative measurement that can be used to determine where a weeding tool is operating relative a weed detection sensor. It incorporates downward-facing perspective cameras, forward-facing perspective cameras and omnidirectional cameras. Stefan shows how the camera’s ego-motion can be estimated to obtain not only the position in 3D but also the orientation. He also shows how line structures in the field can be used to navigate a robot along the rows.
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| 24. |
- Ericson, Stefan, et al.
(author)
-
Visual Odometry System for Agricultural Field Robots
- 2008
-
In: Proceedings of the World Congress on Engineering and Computer Science 2008, WCECS 2008, October 22 - 24, 2008, San Francisco, USA. - Hong Kong : International Association of Engineers. - 9789889867102 ; , s. 619-624
-
Conference paper (peer-reviewed)abstract
- In this paper we present a visual odometry system for agricultural field robots that is not sensitive to uneven terrain. A stereo camera system is mounted perpendicular to the ground and height and traveled distance are calculated using normalized cross correlation. A method for evaluating the system is developed, where flower boxes containing representative surfaces are placed in a metal-working lathe. The cameras are mounted on the carriage which can be positioned manually with 0.1 mm accuracy. Images are captured every 10 mm over 700 mm. The tests are performed on eight different surfaces representing real world situations. The resulting error is less than 0.6% of traveled distance on surfaces where the maximum height variation is measured to 96 mm. The variance is measured for eight test runs, total 5.6 m, to 0.040 mm. This accuracy is sufficient for crop-scale agricultural operations.
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| 25. |
- Huang, Rui, et al.
(author)
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An Efficient Way to Estimate the Focus of Expansion
- 2018
-
In: 2018 3rd IEEE International Conference on Image, Vision and Computing (ICIVC 2018). - : IEEE. - 9781538649923 - 9781538649916 - 9781538649909 ; , s. 691-695
-
Conference paper (peer-reviewed)abstract
- Detecting independent motion from a single camera is a difficult task in computer vision. It is because the captured image sequences are the combinations of the objects' movements and the camera's ego-motion. One major branch is to find the focus of expansion (FOE) instead as the goal. This is ideal for the situation commonly seen in UAV's camera system. In this case, the translation is dominant in camera's motion while the rotation is relatively small. To separate the ego motion and scene structure, many researchers used the directional flow as the theoretic basis and extracted its properties related to FOE. In this paper, we formulate finding FOE as an optimizing problem. The position of FOE has the minimal standard deviation for the directional flow in all directions, which is also subjected to the introduced constraint. The experiments show the proposed methods out-perform the previous method.
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| 26. |
- Höst, Stefan, et al.
(author)
-
Low complexity computation of the BT0 Hilbert twisted pair cable model
- 2010
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In: [Host publication title missing]. ; , s. 195-199
-
Conference paper (peer-reviewed)abstract
- By use of the Hilbert transform the standardized BT0 twisted pair cable model can be rederived as a causal model with lower order, denoted BT0$_H$. In the present contribution the computational complexity of the BT0$_H$ model is decreased as the Hilbert transform is approximated with a look-up table implemented as a polynomial approximation. This results in a model of lower complexity than BT0$_H$ and lower order than the original BT0 model. Finally a comparison on causality of the considered models is presented.
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| 27. |
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| 28. |
- Knaust, Stefan
(author)
-
Microsystems for Harsh Environments
- 2015
-
Doctoral thesis (other academic/artistic)abstract
- When operating microsystems in harsh environments, many conventionally used techniques are limiting. Further, depending on if the demands arise from the environment or the conditions inside the system, different approaches have to be used. This thesis deals with the challenges encountered when microsystems are used at high pressures and high temperatures.For microsystems operating at harsh conditions, many parameters will vary extensively with both temperature and pressure, and to maintain control, these variations needs to be well understood. Covered within this thesis is the to-date strongest membrane micropump, demonstrated to pump against back-pressures up to 13 MPa, and a gas-tight high pressure valve that manages pressures beyond 20 MPa.With the ability to manipulate fluids at high pressures in microsystems at elevated temperatures, opportunities are created to use green solvents like supercritical fluids like CO2. To allow for a reliable and predictable operation in systems using more than one fluid, the behavior of the multiphase flow needs to be controlled. Therefore, the effect of varying temperature and pressure, as well as flow conditions were investigated for multiphase flows of CO2 and H2O around and above the critical point of CO2. Also, the influence of channel surface and geometry was investigated.Although supercritical CO2 only requires moderate temperatures, other supercritical fluids or reactions require much higher temperatures. The study how increasing temperature affects a system, a high-temperature testbed inside an electron microscope was created.One of the challenges for high-temperature systems is the interface towards room temperature components. To circumvent the need of wires, high temperature wireless systems were studied together with a wireless pressure sensing system operating at temperatures up to 1,000 °C for pressures up to 0.3 MPa.To further extend the capabilities of microsystems and combine high temperatures and high pressures, it is necessary to consider that the requirements differs fundamentally. Therefore, combining high pressures and high temperatures in microsystems results in great challenges, which requires trade-offs and compromises. Here, steel and HTCC based microsystems may prove interesting alternatives for future high performance microsystems.
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| 29. |
- Lidell, Anton, et al.
(author)
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The Current and Future Challenges for Virtual Commissioning and Digital Twins of Production Lines
- 2022
-
In: SPS2022. - Amsterdam; Berlin; Washington, DC : IOS Press. - 9781643682686 - 9781643682693 ; , s. 508-519
-
Conference paper (peer-reviewed)abstract
- The use of virtual commissioning has increased in the last decade, but there are still challenges before the software code validation method is widespread in use. One of the extensions to virtual commissioning is the digital twin technology to allow for further improved accuracy. The aim of this paper is to review existing standards and approaches to developing virtual commissioning, through a literature review and interviews with experts in the industry. First, the definitions and classifications related to virtual commissioning and digital twins are reviewed, followed by, the approaches for the development of virtual commissioning and digital twins reported in the literature are explored. Then, in three interviews with experts of varying backgrounds and competencies, the views of the virtual technologies are assessed to provide new insight for the industry. The findings of the literature review and interviews are, among others, the apparent need for standardisation in the field and that a sought-after standard in the form of ISO 23247-1 is underway. The key finding of this paper is that digital twin is a concept with a promising future in combination with other technologies of Industry 4.0. We also outline the challenges and possibilities of virtual commissioning and the digital twin and could be used as a starting point for further research in standardisations and improvements sprung from the new standard.
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| 30. |
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| 31. |
- Nergård, Henrik, et al.
(author)
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Functional product development : discussing knowledge enabling technologies
- 2006
-
In: Proceedings of Design 2006. - Zagreb : University of Zagreb. - 9536313790 ; , s. 587-593
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Conference paper (peer-reviewed)abstract
- The concept of functional products affects the business as a whole. The hardware will be offered to customers as one part incorporated in a total offer. The offer as a whole compromise services related to and/or designed into that hardware. The product development level will be affected, this emerging development process is called Functional Product Development (FPD). Computer tools to support decisions in engineering design are commonly used by design teams. Today, these tools are considered to be internal and support engineering specific knowledge. However, FPD insists on collaboration between companies to achieve additional knowledge. The purpose in this paper is to discuss new demands on computer tools to support decisions in FPD.
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| 32. |
- Nergård, Henrik, et al.
(author)
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Functional product development - discussing knowledge enabling technologies
- 2006
-
Conference paper (peer-reviewed)abstract
- The purpose in this paper is to discuss new demands on computer tools to support decisions in functional product development. To do that, a tentative picture of changes in product development motivated by the concept of functional products has to be outlined to serve as a basis for the discussions. The concept of functional products affects the business as a whole. The hardware will be offered to customers as one part incorporated in a total offer. The offer as a whole compromise services related to and/or designed into that hardware. Accordingly, the product development level will be affected. But, to meet the expectations the concept of functional products has to affect the design phase of the hardware in particular. Global collaboration in product development puts new demands on knowledge enabling technologies. Computer tools to support decisions in engineering design are commonly used by design teams. Today, these tools are considered to be internal and support engineering specific knowledge. However, the concept of functional products in global design teams insists on collaboration between companies to achieve additional knowledge. Engineering design activities in functional product development need collaboration on a day-to-day basis despite distance.
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| 33. |
- Noumonvi, Koffi Dodji, et al.
(author)
-
The Kulbäcksliden research infrastructure : a unique setting for northern peatland studies
- 2023
-
In: Frontiers in Earth Science. - : Frontiers Media S.A.. - 2296-6463. ; 11
-
Research review (peer-reviewed)abstract
- Boreal peatlands represent a biogeochemically unique and diverse environment in high-latitude landscape. They represent a long-term globally significant sink for carbon dioxide and a source of methane, hence playing an important role in regulating the global climate. There is an increasing interest in deciphering peatland biogeochemical processes to improve our understanding of how anthropogenic and climate change effects regulate the peatland biogeochemistry and greenhouse gas balances. At present, most studies investigating land-atmosphere exchanges of peatland ecosystems are commonly based on single-tower setups, which require the assumption of homogeneous conditions during upscaling to the landscape. However, the spatial organization of peatland complexes might feature large heterogeneity due to its varying underlying topography and vegetation composition. Little is known about how well single site studies represent the spatial variations of biogeochemical processes across entire peatland complexes. The recently established Kulbäcksliden Research Infrastructure (KRI) includes five peatland study sites located less than 3 km apart, thus providing a unique opportunity to explore the spatial variation in ecosystem-scale processes across a typical boreal peatland complex. All KRI sites are equipped with eddy covariance flux towers combined with installations for detailed monitoring of biotic and abiotic variables, as well as catchment-scale hydrology and hydrochemistry. Here, we review studies that were conducted in the Kulbäcksliden area and provide a description of the site characteristics as well as the instrumentation available at the KRI. We highlight the value of long-term infrastructures with ecosystem-scale and replicated experimental sites to advance our understanding of peatland biogeochemistry, hydrology, ecology, and its feedbacks on the environment and climate system.
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| 34. |
- Prost, Stefan, et al.
(author)
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Comparative analyses identify genomic features potentially involved in the evolution of birds-of-paradise
- 2019
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In: GigaScience. - : OXFORD UNIV PRESS. - 2047-217X. ; 8:5
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Journal article (peer-reviewed)abstract
- The diverse array of phenotypes and courtship displays exhibited by birds-of-paradise have long fascinated scientists and nonscientists alike. Remarkably, almost nothing is known about the genomics of this iconic radiation. There are 41 species in 16 genera currently recognized within the birds-of-paradise family (Paradisaeidae), most of which are endemic to the island of New Guinea. In this study, we sequenced genomes of representatives from all five major clades within this family to characterize genomic changes that may have played a role in the evolution of the group's extensive phenotypic diversity. We found genes important for coloration, morphology, and feather and eye development to be under positive selection. In birds-of-paradise with complex lekking systems and strong sexual dimorphism, the core birds-of-paradise, we found Gene Ontology categories for "startle response" and "olfactory receptor activity" to be enriched among the gene families expanding significantly faster compared to the other birds in our study. Furthermore, we found novel families of retrovirus-like retrotransposons active in all three de novo genomes since the early diversification of the birds-of-paradise group, which might have played a role in the evolution of this fascinating group of birds.
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| 35. |
- Svensson, Stefan, 1985-, et al.
(author)
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ESEM as a Tool for Studying High Temperature Electronics
- 2011
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In: IMAPS High Temperature Electronics Network (HiTEN 2011), July 18-20, 2011 ,Oxford, UK.
-
Conference paper (peer-reviewed)abstract
- Researchers studying materials and processes at high temperatures are often restricted to do evaluation afterwards and at room temperature using e.g. scanning electron microscopy (SEM). Limited by high vacuum, outgassing and non-conducting samples are difficult to study with SEM. For such samples, environmental scanning electron microscope (ESEM) is an alternative that is particularly suited also for high temperature in-situ studies. The electron detector in the ESEM make use of otherwise unwanted scattering of electrons as an amplifier of the signal, and by using differential pumping, it is possible to introduce several mbar of either oxygen, water vapor, or a gas of choice into the sample chamber while still maintaining the high-vacuum in the electron column. The auxiliary gas neutralizes surface charges built up by the electron beam, which makes it possible to image non-conductive and outgassing samples, thus making it possible to study e.g. polymeric and high temperature materials. Our ESEM, FEI XL30, have a heating stage making it possible to reach temperatures up to 1500°C. Equipped with electrical feed- throughs, the instrument can be used to study high temperature phenomena on electrically activated components.ESEM is an instrument that has found its use for biological and organic samples. However, less work has been done using it for high temperature processes. Here, we show real-time imaging of the sintering of dielectric and Ag thick-film prints on AlN substrates. The use of the electrical feed-throughs to activate electrical components and study them at high temperatures is also demonstrated. ESEM is a versatile tool for high temperature studies and in-situ analysis of electrical components, solder processes and different die-attach materials.
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| 36. |
- Törngren, Martin, 1963-, et al.
(author)
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Competence Networks in the Era of CPS : Lessons Learnt in the ICES Cross-Disciplinary and Multi-domain Center
- 2019
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In: Proceedings of the International Workshop on Design, Modeling, and Evaluation of Cyber Physical Systems, CyPhy 2019. - Cham : Springer International Publishing. - 9783030411305 - 9783030411312 ; , s. 264-283
-
Conference paper (peer-reviewed)abstract
- Cyber-Physical Systems (CPS) are evolving to become more intelligent, autonomous and collaborating, playing an important role in societal infrastructure. The amount of knowledge required in developing and managing future CPS will be unprecedented, leading to stronger needs for collaboration, competence provisioning, continuous learning and renewal of education. This is where “competence” (or learning) “networks” involving academia and industry play an important role. We elaborate and discuss needs, lessons learnt and challenges for such competence networks in the context of CPS. We draw upon our experiences gained from ICES - the KTH-industry cross-disciplinary and multi-domain competence network which in 2019 has been operational for 11 years, growing from 6 to more than 30 participating organizations. The ICES network focuses on activities to support students, industrial engineers and managers, and academic faculty, acting as a network, catalyst and competence provider directed towards these stakeholders. We elaborate challenges faced during the operation of ICES including the lack of prioritization of competence networks and education, the paradox with strong needs for competence networks but perceived lack of time, the challenges of reaching out to stakeholders, and fragmented efforts addressing competence provisioning. We finally discuss ways forward. In conclusion, we believe that the ICES type of network could be relevant in many other areas characterized by complex systems.
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| 37. |
- Zeiske, Stefan, et al.
(author)
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On the Impact of Cadmium Sulfide Layer Thickness on Kesterite Photodetector Performance
- 2023
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In: Advanced Photonics Research. - : Wiley-VCH Verlagsgesellschaft. - 2699-9293. ; 4:9
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Journal article (peer-reviewed)abstract
- Kesterites are currently viewed as one of the most promising candidates for earth abundant and benign elements to substitute critical raw materials in photovoltaic technologies and may also be suitable for low-noise, room-temperature, self-powered photodetectors. However, while the impact of buffer layers on kesterite solar cell efficiency has been an active area of investigation, links between photodetector performance and intermediate layers are yet to be addressed. Herein, the impact of cadmium sulfide buffer layers on the performance of kesterite (Cu2ZnSnS4) photodetectors is probed. Specifically, the effect of buffer layer thickness on various photodetector performance metrices is clarified, including noise current, spectral responsivity, noise equivalent power, frequency response, and specific detectivity. Devices with a 100 nm cadmium sulfide layer perform the best, achieving a linear dynamic range of 180 dB and frequency responses in the range of tens of kHz. The key loss mechanisms are identified, and it is found that the photodetector performance to be primarily limited by shunt resistance-induced thermal noise and defect-induced nonradiative losses. Furthermore, we estimate the upper radiative limit of specific detectivity to be approximately 1019 Jones. Our results highlight the potential of kesterites to be used as an interesting earth abundant candidate for photodetection applications.
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