| 1. |
- Bergström, Ulf, et al.
(author)
-
Long-term effects of no-take zones in Swedish waters
- 2022
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Reports (other academic/artistic)abstract
- Marine protected areas (MPAs) are increasingly established worldwide to protect and restore degraded ecosystems. However, the level of protection varies among MPAs and has been found to affect the outcome of the closure. In no-take zones (NTZs), no fishing or extraction of marine organisms is allowed. The EU Commission recently committed to protect 30% of European waters by 2030 through the updated Biodiversity Strategy. Importantly, one third of these 30% should be of strict protection. Exactly what is meant by strict protection is not entirely clear, but fishing would likely have to be fully or largely prohibited in these areas. This new target for strictly protected areas highlights the need to evaluate the ecological effects of NTZs, particularly in regions like northern Europe where such evaluations are scarce. The Swedish NTZs made up approximately two thirds of the total areal extent of NTZs in Europe a decade ago. Given that these areas have been closed for at least 10 years and can provide insights into long-term effects of NTZs on fish and ecosystems, they are of broad interest in light of the new 10% strict protection by 2030 commitment by EU member states.In total, eight NTZs in Swedish coastal and offshore waters were evaluated in the current report, with respect to primarily the responses of focal species for the conservation measure, but in some of the areas also ecosystem responses. Five of the NTZs were established in 2009-2011, as part of a government commission, while the other three had been established earlier. The results of the evaluations are presented in a synthesis and also in separate, more detailed chapters for each of the eight NTZs. Overall, the results suggest that NTZs can increase abundances and biomasses of fish and decapod crustaceans, given that the closed areas are strategically placed and of an appropriate size in relation to the life cycle of the focal species. A meta-regression of the effects on focal species of the NTZs showed that CPUE was on average 2.6 times higher after three years of protection, and 3.8 times higher than in the fished reference areas after six years of protection. The proportion of old and large individuals increased in most NTZs, and thereby also the reproductive potential of populations. The increase in abundance of large predatory fish also likely contributed to restoring ecosystem functions, such as top-down control. These effects appeared after a 5-year period and in many cases remained and continued to increase in the longer term (>10 years). In the two areas where cod was the focal species of the NTZs, positive responses were weak, likely as an effect of long-term past, and in the Kattegat still present, recruitment overfishing. In the Baltic Sea, predation by grey seal and cormorant was in some cases so high that it likely counteracted the positive effects of removing fisheries and led to stock declines in the NTZs. In most cases, the introduction of the NTZs has likely decreased the total fishing effort rather than displacing it to adjacent areas. In the Kattegat NTZ, however, the purpose was explicitly to displace an unselective coastal mixed bottom-trawl fishery targeting Norway lobster and flatfish to areas where the bycatches of mature cod were smaller. In two areas that were reopened to fishing after 5 years, the positive effects of the NTZs on fish stocks eroded quickly to pre-closure levels despite that the areas remained closed during the spawning period, highlighting that permanent closures may be necessary to maintain positive effects.We conclude from the Swedish case studies that NTZs may well function as a complement to other fisheries management measures, such as catch, effort and gear regulations. The experiences from the current evaluation show that NTZs can be an important tool for fisheries management especially for local coastal fish populations and areas with mixed fisheries, as well as in cases where there is a need to counteract adverse ecosystem effects of fishing. NTZs are also needed as reference for marine environmental management, and for understanding the effects of fishing on fish populations and other ecosystem components in relation to other pressures. MPAs where the protection of both fish and their habitats is combined may be an important instrument for ecosystembased management, where the recovery of large predatory fish may lead to a restoration of important ecosystem functions and contribute to improving decayed habitats.With the new Biodiversity Strategy, EUs level of ambition for marine conservation increases significantly, with the goal of 30% of coastal and marine waters protected by 2030, and, importantly, one third of these areas being strictly protected. From a conservation perspective, rare, sensitive and/or charismatic species or habitats are often in focus when designating MPAs, and displacement of fisheries is then considered an unwanted side effect. However, if the establishment of strictly protected areas also aims to rebuild fish stocks, these MPAs should be placed in heavily fished areas and designed to protect depleted populations by accounting for their home ranges to generate positive outcomes. Thus, extensive displacement of fisheries is required to reach benefits for depleted populations, and need to be accounted for e.g. by specific regulations outside the strictly protected areas. These new extensive EU goals for MPA establishment pose a challenge for management, but at the same time offer an opportunity to bridge the current gap between conservation and fisheries management.
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| 2. |
- Bryhn, Andreas, et al.
(author)
-
Fisk- och skaldjursbestånd i hav och sötvatten 2019 : Resursöversikt
- 2020
-
Reports (other academic/artistic)abstract
- Fisken i havet är en resurs som rör sig fritt över nationella gränser. EU har därför en gemensam fiskeripolitik (GFP). Många arter som är viktiga för Sverige regleras inte i GFP och förvaltas därför nationellt.Denna rapport syftar till att:beskriva utvecklingen av fiskeripolitikenförklara den nuvarande politikens mål och regelverk och dess relation till mål och regler på miljöområdetförklara politikens nationella genomförande och det nationella handlingsutrymmetexemplifiera hur Havs- och vattenmyndigheten arbetat med att reglera fisket.
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| 3. |
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| 4. |
- Jönsson, Håkan, et al.
(author)
-
Svensk Mjölk
- 2005
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In: Mat Genealogi och gestaltning. - 9144045549 ; , s. 71-84
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Book chapter (other academic/artistic)
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| 5. |
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| 6. |
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| 7. |
- Andric, Jelena, 1979, et al.
(author)
-
A study of a flexible fiber model and its behavior in DNS of turbulent channel flow
- 2013
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In: Acta Mechanica. - : Springer Science and Business Media LLC. - 0001-5970 .- 1619-6937. ; 224:10, s. 2359-2374
-
Journal article (peer-reviewed)abstract
- The dynamics of individual flexible fibers in a turbulent flow field have been analyzed, varying their initial position, density and length. A particlelevel fiber model has been integrated into a general-purpose, open source Computational Fluid Dynamics (CFD) code. The fibers are modeled as chains of cylindrical segments connected by ball and socket joints. The equations of motion of the fibers contain the inertia of the segments, the contributions from hydrodynamic forces and torques, and the connectivity forces at the joints. Direct Numerical Simulation (DNS) of the incompressible Navier–Stokes equations is used to describe the fluid flow in a plane channel and a one-way coupling is considered between the fibers and the fluid phase. We investigate the translational motion of fibers by considering the mean square displacement of their trajectories. We find that the fiber motion is primarily governed by velocity correlations of the flow fluctuations. In addition, we show that there is a clear tendency of the thread-like fibers to evolve into complex geometrical configurations in a turbulent flow field, in fashion similar to random conformations of polymer strands subjected to thermal fluctuations in a suspension. Finally, we show that fiber inertia has a significant impact on reorientation time-scales of fibers suspended in a turbulent flow field.
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| 8. |
- Bergström, Ulf, et al.
(author)
-
Stickleback increase in the Baltic Sea - A thorny issue for coastal predatory fish
- 2015
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In: Estuarine, Coastal and Shelf Science. - : Elsevier BV. - 0272-7714 .- 1096-0015. ; 163, s. 134-142
-
Journal article (peer-reviewed)abstract
- In the Baltic Sea, the mesopredator three-spined stickleback (Gasterosteus aculeatus) spends a large part of its life cycle in the open sea, but reproduces in shallow coastal habitats. In coastal waters, it may occur in high abundances, is a potent predator on eggs and larvae of fish, and has been shown to induce trophic cascades with resulting eutrophication symptoms through regulation of invertebrate grazers. Despite its potential significance for the coastal food web, little is known about its life history and population ecology. This paper provides a description of life history traits, migration patterns and spatiotemporal development of the species in the Baltic Sea during the past decades, and tests the hypothesis that stickleback may have a negative impact on populations of coastal predatory fish. Offshore and coastal data during the last 30 years show that stickleback has increased fourfold in the Bothnian Sea, 45-fold in the Central Baltic Sea and sevenfold in the Southern Baltic Sea. The abundances are similar in the two northern basins, and two orders of magnitude lower in the Southern Baltic Sea. The coastward spawning migration of sticklebacks from offshore areas peaks in early May, with most spawners being two years of age at a mean length of 65 mm. The early juvenile stage is spent at the coast, whereafter sticklebacks perform a seaward feeding migration in early autumn at a size of around 35 mm. A negative spatial relation between the abundance of stickleback and early life stages of perch and pike at coastal spawning areas was observed in spatial survey data, indicating strong interactions between the species. A negative temporal relationship was observed also between adult perch and stickleback in coastal fish monitoring programmes supporting the hypothesis that stickleback may have negative population level effects on coastal fish predators. The recent increase in stickleback populations in different basins of the Baltic Sea in combination with negative spatiotemporal patterns and previously observed interactions between stickleback and coastal predatory fish suggests that this species may have gained a key role in the coastal food webs of the Baltic Sea. Through its migrations, stickleback may also constitute an important vector linking coastal and open sea ecosystem dynamics. (c) 2015 Elsevier Ltd. All rights reserved.
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| 9. |
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| 10. |
- Bryhn, Andreas, et al.
(author)
-
Fisk- och skaldjursbestånd i hav och sötvatten 2020 : Resursöversikt
- 2021
-
Reports (other academic/artistic)abstract
- I rapporten kan du ta del av bedömningen som görs av situationen för bestånd som regleras inom ramen för EU:s gemensamma fiskeripolitik (GFP). Bedömningarna baseras på det forskningssamarbete och den rådgivning som sker inom det Internationella Havsforskningsrådet (ICES). Totalt redovisas underlag och råd för 48 fisk- och skaldjursarter.De bestånd som förvaltas nationellt baseras på de biologiska underlagen, och rådgivningen i huvudsak på den forskning och övervakning samt analys som bedrivs av Institutionen för akvatiska resurser vid Sveriges lantbruksuniversitet (SLU Aqua) samt yrkesfiskets rapportering.
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| 11. |
- Burstedt, Anna, et al.
(author)
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Inledning
- 2006
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In: Mat. - Lund : Studentlitteratur. ; , s. 5-19
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Book chapter (other academic/artistic)
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| 12. |
- Duffy, Stephen W., et al.
(author)
-
Mammography screening reduces rates of advanced and fatal breast cancers : Results in 549,091 women
- 2020
-
In: Cancer. - : John Wiley & Sons. - 0008-543X .- 1097-0142. ; 126:13, s. 2971-2979
-
Journal article (peer-reviewed)abstract
- Background: It is of paramount importance to evaluate the impact of participation in organized mammography service screening independently from changes in breast cancer treatment. This can be done by measuring the incidence of fatal breast cancer, which is based on the date of diagnosis and not on the date of death.Methods: Among 549,091 women, covering approximately 30% of the Swedish screening‐eligible population, the authors calculated the incidence rates of 2473 breast cancers that were fatal within 10 years after diagnosis and the incidence rates of 9737 advanced breast cancers. Data regarding each breast cancer diagnosis and the cause and date of death of each breast cancer case were gathered from national Swedish registries. Tumor characteristics were collected from regional cancer centers. Aggregated data concerning invitation and participation were provided by Sectra Medical Systems AB. Incidence rates were analyzed using Poisson regression.Results: Women who participated in mammography screening had a statistically significant 41% reduction in their risk of dying of breast cancer within 10 years (relative risk, 0.59; 95% CI, 0.51‐0.68 [P < .001]) and a 25% reduction in the rate of advanced breast cancers (relative risk, 0.75; 95% CI, 0.66‐0.84 [P < .001]).Conclusions: Substantial reductions in the incidence rate of breast cancers that were fatal within 10 years after diagnosis and in the advanced breast cancer rate were found in this contemporaneous comparison of women participating versus those not participating in screening. These benefits appeared to be independent of recent changes in treatment regimens.
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| 13. |
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| 14. |
- Dåderman, Anna Maria, 1953-, et al.
(author)
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Violent behavior, impulsive decision-making, and anterograde amnesia while intoxicated with Flunitrazepam and alcohol or other drugs : A case study in forensic psychiatric patients
- 2002
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In: The journal of the American Academy of Psychiatry and the Law. - Bloomfield, CT, USA. - 1093-6793 .- 1943-3662. ; 30:2, s. 238-251
-
Journal article (peer-reviewed)abstract
- It is known that many male juvenile delinquents commit violent crimes while intoxicated with flunitrazepam (FZ), often in combination with alcohol or other drugs. We have also noted the combined abuse of FZ with, for example, alcohol in male forensic psychiatric patients. Our objective was to study violent behavior, impulsive decision making, and amnesia in male forensic psychiatric patients who were intoxicated predominantly with FZ, to increase knowledge of the abuse of FZ in vulnerable subjects. We studied five forensic psychiatric patients, all of whom were assessed in 1998. All of the subjects reported earlier reactions to FZ, including hostility and anterograde amnesia. At the time of their crimes they were all intoxicated with FZ, often in combination with alcohol or other drugs, such as amphetamine or cannabis. In contrast to their behavior based on their ordinary psychological characteristics, their crimes were extremely violent, and the subjects lacked both the ability to think clearly and to have empathy with their victims. Our observations support the view that FZ abuse can lead to serious violent behavior in subjects characterized by vulnerable personality traits, and that this effect is confounded by the concurrent use of alcohol or other drugs. It is evident that FZ causes anterograde amnesia. Previous research and the results presented herein allow us to draw the following conclusion: on the basis of the neuropsychopharmacologic properties of FZ, legal decisions, such as declaring FZ an illegal drug, are needed in countries where it is now legal.
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| 15. |
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ETN:JOB
- 2008
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Editorial collection (other academic/artistic)
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| 16. |
- Fredriksson, Håkan
(author)
-
Aktivitet: Robotar är heta i kalla biltester
- 2011
-
Other publication (pop. science, debate, etc.)abstract
- Nu startar ett treårigt forskningsprojekt om förarlösa bilar i testbranschen. Varje vinter kommer tusentals biltestare till Norrbotten för att testköra nya bilmodeller och komponenter i kyla. Men snart kanske körrobotar tar över i alla fall inne på testbanorna.
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| 17. |
- Fredriksson, Håkan
(author)
-
Aktivitet: Robotförare testas i Malå
- 2013
-
Other publication (pop. science, debate, etc.)abstract
- En förarlös bil utan ratt, kan det vara framtiden? Just nu testas en så kallad styrrobot i Malå. Inslaget visades i Västerbottensnytt och Rapport i Februari 2013.
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| 18. |
- Fredriksson, Håkan, et al.
(author)
-
Automotive winter testing with path-following steering robot
- 2015
-
In: International Journal of Vehicle Systems Modelling and Testing. - 1745-6436 .- 1745-6444. ; 10:1, s. 29-52
-
Journal article (peer-reviewed)abstract
- When testing modern active safety systems on cars, it is essential to test vehicle response to steering inputs. This paper highlights the use of a path-following steering robot for repetitive car testing in winter conditions. Experiments have been made with commonly used test sequences, e.g., lane-change, double lane-change, constant radius circle, and handling circuit. The steering input from the human driver is replaced by a steering robot and a path-following algorithm. The main focus for this paper is to describe what happens when one pushes the path-following system to, and beyond, the physical limitations of road grip when cornering at high vehicle speed. It shows that, with an appropriate tuning of the path-following parameters, the system performs predictably and satisfactorily. The overall conclusion is that a path-following steering robot is indeed useful for repetitive test in winter conditions with poor road grip.
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| 19. |
- Fredriksson, Håkan, et al.
(author)
-
GIMnet on the MICA wheelchair
- 2010
-
Conference paper (other academic/artistic)abstract
- This paper describes the implementation of GIMnet on the MICA wheelchair.
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| 20. |
- Fredriksson, Håkan, et al.
(author)
-
Gyro feedback of a hydraulic steering system
- 2011
-
In: International Journal of Vehicle Autonomous Systems. - 1471-0226 .- 1741-5306. ; 9:3/4, s. 189-202
-
Journal article (peer-reviewed)abstract
- We study the problem to steer, teleoperated as well as autonomously, a tractor that is to operate on a rough and slippery surface. The main idea is to control the effective steering angle of the vehicle. A benefit with this approach is that the vehicle will strive to move in a predefined way irrespective of the surface conditions. To test if the approach is usable we implemented a straight forward p-controller in combination with an estimator of the effective steering angle of the tractor. Our tests indicates that the approach can be useful. Future work would include studies on more advanced control strategies and estimators to reduce some of the problems that we address.
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| 21. |
- Fredriksson, Håkan
(author)
-
Laser on kinetic operator
- 2010
-
Doctoral thesis (other academic/artistic)abstract
- This thesis highlights a variety of aspects within the field of mobile robots. The hinge is system architecture for mobile robots. For a mobile robot to be put into operation all necessary systems have to be functioning and control mechanisms have to be established. The robot may be set to operate autonomously as well as remotely controlled. Either way, different sensors and algorithms may be needed for navigation, obstacle detection, and other functionalities. In this thesis, a methodology to design a flash for illuminating retroreflective beacons is proposed. The flash is used in a navigation system based on CMOS cameras. Furthermore, a method to create a 3D environment model from 2D range data is presented. The result is used in a vehicle simulation software. Two different methods for a vehicle to find its way in an environment are proposed. The first method is intended for use in a winter environment. The idea is to make the vehicle drive between the snow banks on the sides of a road, created when removing the snow from the road with a snow plough. The snow banks are detected using an algorithm working on data from a range measuring laser. The other method finds the free space where the vehicle may move without running into any obstacle. Vehicle modelling and control are discussed. The problem to steer a tractor that is to operate on a rough and slippery surface is studied and a method to compensate for the slippage of the front wheels is presented. An implemented and tested kinematic model for a teleoperated track loader is also presented. Finally, a method for smooth path-following is suggested. The method utilises motion control to force the vehicle to behave smoothly, combined with continual re-routing to, if possible, let the vehicle "cut corners" and take the shortest possible path. The overall goal, to put a mobile robot into operation, may be reached by combining the different aspects discussed in this thesis.
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| 22. |
- Fredriksson, Henrik, et al.
(author)
-
Modeling of road traffic flows in the neighboring regions
- 2021
-
In: Procedia Computer Science. - : Elsevier. ; 198, s. 43-50
-
Conference paper (peer-reviewed)abstract
- Traffic flows play a very important role in transportation engineering. In particular, link flows are a source of information about the traffic state, which is usually available from the authorities that manage road networks. Link flows are commonly used in both short-term and long-term planning models for operation and maintenance, and to forecast the future needs of transportation infrastructure. In this paper, we propose a model to study how traffic flow in one location can be expected to reflect the traffic flow in a nearby region. The statistical basis of the model is derived from link flows to find estimates of the distribution of traffic flows in junctions. The model is evaluated in a numerical study, which uses real link flow data from a transportation network in southern Sweden. The results indicate that the model may be useful for studying how large departing flows from a node reflect the link flows in a neighboring geographic region.
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| 23. |
- Fredriksson, Håkan, et al.
(author)
-
Multisource flash system for retroreflective beacon detection in CMOS cameras
- 2008
-
In: Optical Engineering. - : SPIE-Intl Soc Optical Eng. - 0091-3286 .- 1560-2303. ; 47, s. 103001-
-
Journal article (peer-reviewed)abstract
- We present a method for improving a flash system for retroreflective beacon detection in CMOS cameras. Generally, flash systems are designed in such a manner that makes them suited for beacon detection in a small range interval. We strive to increase the flash system range interval by exploiting the directional properties of the retroreflector. Thus, light sources placed relatively far away from the optical axis of the camera will contribute only when the retroreflector is far away. This fact can be used to compensate for the 1/distance2 dependency of optical power. We present underlying theory and formulae, then describe a flash system consisting of several light-emitting diodes that was designed by considering the presented method. Simulations show that the usable flash range of the improved system can be almost doubled compared to a general flash system. Tests were performed indicating that the presented method works according to theory and simulations.
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| 24. |
- Fredriksson, Håkan
(author)
-
Navigation sensors for mobile robots
- 2007
-
Licentiate thesis (other academic/artistic)abstract
- In mobile robot applications navigation systems are of great importance. Automation of mobile robots demands robust navigation systems. This thesis deals with a few solutions on how to help a mobile robot navigate in an environment. Navigation systems using retroreflective beacons and applications relying on laser range finders are two different solutions to aid a mobile robot. The first type of system provides very robust navigation, with the use of extra infrastructure in the environment. The latter has no need for any extra infrastructure as it can use the structure in the surrounding environment. Navigation using dead reckoning and GPS systems are also discussed. Furthermore, some of the mobile robot platforms available at Luleå University of Technology, and their application are presented.
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| 25. |
- Fredriksson, Håkan, et al.
(author)
-
Range data in vehicle dynamic simulation
- 2009
-
Conference paper (peer-reviewed)abstract
- This paper presents a way to merge range data into the vehicle dynamic simulation software CarSim7.1. The range data consists of measurements describing the surface of a road, and thus, creates a close to reallife 3D simulation environment. This reduces the discrepancy between the real life tests and simulation ofvehicle suspension systems, dampers, springs, etc. It is important for the vehicle industry to represent a reallife environment in the simulation software in order to increase the validity of the simulations and to studythe effects that uneven roads have on the systems. Furthermore, a 3D environment based on real life data isalso useful in driving simulators, when for example, analysing driver behaviour, testing driver response, andtraining for various driving conditions. To measure and collect data, a car was equipped with instruments anda computer. On top of the car, a SICK LMS200 2D lidar was mounted tilted downwards, facing the roadin front of the car. To create the 3D environment, all the individual measurements were transformed to aglobal coordinate system using the pose (position and orientation) information from a high-class navigationsystem. The pose information made it possible to compensate for the vehicle motion during data collection.The navigation system consisted of a GPS/IMU system from NovAtel. To reach high navigation performance,the raw GPS/IMU data were post-processed and fused with data from three different fixed GPS base stations.The range data were modified with a Matlab script in order to parse the data into a file that could be read byCarSim software. This created the 3D road used in the vehicle dynamic simulations. The measurements werecollected at a go-kart track in Lule°a, Sweden. Finally, tests have been performed to compare simulation resultsbetween using a 2D surface (i.e. flat) and a 3D surface (close to real life). It is seen that the simulation resultsusing the 2D surface is clearly different from the 3D surface simulation.
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| 26. |
- Fredriksson, Håkan, et al.
(author)
-
snowBOTS: a mobile robot on snow covered ice
- 2007
-
In: Proceedings of the 13th IASTED International Conference on Robotics and Applications. - Anaheim, Calif. : ACTA Press. - 9780889866850 ; , s. 222-228
-
Conference paper (peer-reviewed)abstract
- We introduce snowBOTs as a generic name for robots working in snow. This paper is a study on using scan ning range measuring lasers towards an autonomous snow cleaning robot, working in an environment consisting al most entirely of snow and ice. The problem addressed here is using lasers for detecting the edges generated by "the snow meeting the road". First the laser data were filtered using his togram/median to discriminate against falling snowflakes and small objects. Then the road surface was extracted us ing the range weighted Hough/Radon transform. Finally the left and right edges of the road was detected by thresh olding. Tests have been made with a laser on top of a car driven in an automobile test range just south of the Arctic Circle. Moreover, in the campus area, the algorithms were tested in closed loop with the laser on board a robotized wheelchair.
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| 27. |
- Fredriksson, Håkan, et al.
(author)
-
snowBOTs: Gyro guided steering of a teleoperated tractor during winter conditions
- 2008
-
Conference paper (other academic/artistic)abstract
- This article describes the steering system implemented on the tractor IceMaker I. No direct position feedback is used for the steering angle of the front wheels. Instead, the steering angle is estimated by a motion model of the vehicle using gyro and odometer information. This estimated angle is used as feedback to a regulator that controls the steering system. The operator sets the requested steering angle and the regulator controls the hydraulic steering system to maintain the requested steering angle. Within certain limits, the tractor can be expected to behave according to the motion model irrespective of the surface conditions. The tractor can be teleoperated from a remote computer through a wireless network, WLAN. To enable teleoperation, the tractor has been equipped with a computer, some sensors, and other necessary equipment. During teleoperation, the operator controls the steering angle of the front wheels and the speed of the tractor using a joystick. The steering system has been tested both during winter conditions on a low friction surface and also on dry asphalt. The results indicates good performance when teleoperating the tractor. When driving carefully it is possible to operate the tractor up to full speed (25km/h). However, the steering regulator tends to exaggerate the real steering angle during sharp turns when driving on very slippery surface.
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| 28. |
- Fredriksson, Håkan, et al.
(author)
-
Track loader kinematics
- 2010
-
In: Preprints. - Timisoara : Ed. Politehnica. ; , s. 139-142
-
Conference paper (peer-reviewed)abstract
- We study the problem to teleoperate a Caterpillar 973c track loader. The track loader and a system for teleoperation are described. A tested and working kinematic model used for dead reckoning is also presented. Track speed sensors combined with a rate gyro are used as input to the model. The model shows good results when tested and compared to a GPS navigation system.
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| 29. |
- Fredriksson, Håkan, et al.
(author)
-
Winter test of ABD steering robot
- 2013
-
Reports (other academic/artistic)abstract
- This report highlights the use of a steering robot with path-following for car testing in winter conditions. The steering robot was provided from Anthony Best Dynamics. Experiments have been made with a couple of commonly used test sequences (lane change, dual lane change, constant radius circle, handling), the result from these test are shown and discussed. The path-following algorithm gives steering commands to the car (replace the human driver), these commands affect how the car will move; hence, the car performance is affected by the behaviour of the path-following algorithm. The settings of the path-following algorithm greatly affect the car response in different situations. This is especially noticeable when the car starts to slide, a situation common when driving on a slippery winter road. The main focus for this report is to describe what happens when you push the path-following system to, and beyond, the physical limitations concerning road grip and vehicle speed. A theoretical analysis of the path-following algorithm and how it reacts on large lateral errors and high sideslip angles was done. As shown in the results, the evaluated path-following test sequences in general did work out well. Some characteristics of the algorithm, especially noticeable when driving in winter condition, were found and discussed. The overall impression is that the ABD steering robot with path-following can indeed be useful for repetitive test in winter conditions with bad road grip.
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| 30. |
- Fredriksson, Sam, 1966, et al.
(author)
-
An evaluation of gas transfer velocity parameterizations during natural convection using DNS
- 2016
-
In: Journal of Geophysical Research - Oceans. - 0148-0227 .- 2156-2202. ; 121:2, s. 1400-1423
-
Journal article (peer-reviewed)abstract
- Direct numerical simulations (DNS) of free surface flows driven by natural convection are used to evaluate different methods of estimating air-water gas exchange at no-wind conditions. These methods estimate the transfer velocity as a function of either the horizontal flow divergence at the surface, the turbulent kinetic energy dissipation beneath the surface, the heat flux through the surface, or the wind speed above the surface. The gas transfer is modeled via a passive scalar. The Schmidt number dependence is studied for Schmidt numbers of 7, 150 and 600. The methods using divergence, dissipation and heat flux estimate the transfer velocity well for a range of varying surface heat flux values, and domain depths. The two evaluated empirical methods using wind (in the limit of no wind) give reasonable estimates of the transfer velocity, depending however on the surface heat flux and surfactant saturation. The transfer velocity is shown to be well represented by the expression, k(s) = A (Bv)(1/4) Sc2(n), where A is a constant, B is the buoyancy flux, m is the kinematic viscosity, Sc is the Schmidt number, and the exponent n depends on the water surface characteristics. The results suggest that A = 0.39 and n approximate to 1/2 and n approximate to 2/3 for slip and no-slip boundary conditions at the surface, respectively. It is further shown that slip and no-slip boundary conditions predict the heat transfer velocity corresponding to the limits of clean and highly surfactant contaminated surfaces, respectively.
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| 31. |
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| 32. |
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| 33. |
- Fredriksson, Sam, 1966, et al.
(author)
-
Large eddy simulation of the tidal power plant Deep Green using the actuator line method
- 2017
-
In: IOP Conference Series: Materials Science and Engineering. - 1757-8981 .- 1757-899X. ; 276:1
-
Conference paper (peer-reviewed)abstract
- Tidal energy has the potential to provide asubstantial part of the sustainable electric power generation. Thetidal power plant developed by Minesto, called Deep Green, is anovel technology using a ‘flying’ kite with an attached turbine,moving at a speed several times higher than the mean flow.Multiple Deep Green power plants will eventually form arrays,which requires knowledge of both flow interactions betweenindividual devices and how the array influences the surroundingenvironment. The present study uses large eddy simulations(LES) and an actuator line model (ALM) to analyze theoscillating turbulent boundary layer flow in tidal currentswithout and with a Deep Green power plant. We present themodeling technique and preliminary results so far.
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| 34. |
- Fredriksson, Sam, 1966, et al.
(author)
-
MODEL TIDAL POWER IN A TURBULENT OCEAN
- 2018
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In: Oceanera-Net Final Conference, Edinburg, Scotland, 30-31 January 2018..
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Conference paper (other academic/artistic)
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| 35. |
- Fredriksson, Sam, 1966, et al.
(author)
-
Modelling Deep Green tidal power plant using large eddy simulations and the actuator line method
- 2021
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In: Renewable Energy. - : Elsevier BV. - 0960-1481 .- 1879-0682. ; 179, s. 1140-1155
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Journal article (peer-reviewed)abstract
- The Deep Green technique for tidal power generation is suitable for moderate flows which is attractive since larger areas for tidal energy generation hereby can be used. It operates typically at mid-depth and can be seen as a "flying" kite with a turbine and generator attached underneath. It moves in a lying figure-eight path almost perpendicular to the tidal flow. Large eddy simulations and an adaption of the actuator line method (in order to describe arbitrary paths) are used to study the turbulent flow with and without Deep Green for a specific site. This methodology can in later studies be used for e.g. array analysis that include Deep Green interaction. It is seen that Deep Green creates a unique wake composed of two velocity deficit zones with increased velocity in each wake core. The flow has a tendency to be directed downwards which results in locally increased bottom shear. The persistence of flow disturbances of Deep Green can be scaled with its horizontal path width, D-y, with a velocity deficit of 5% at approximately 8-10D(y) downstream of the power plant. The turbulence intensity and power deficit are approximately two times the undisturbed value and 10%, respectively, at 10D(y). (C) 2021 The Authors. Published by Elsevier Ltd.
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| 36. |
- Fredriksson, Sam, 1966, et al.
(author)
-
Near-surface physics during convection affecting air-water gas transfer
- 2016
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In: IOP Conference Series: Earth and Environmental Science. - : IOP Publishing. - 1755-1307 .- 1755-1315. ; 35:1, s. 012007-
-
Conference paper (peer-reviewed)abstract
- The gas flux at the water surface is affected by physical processes including turbulence from wind shear, microscale wave breaking, large-scale breaking, and convection due to heat loss at the surface. The main route in the parameterizations of the gas flux has been to use the wind speed as a proxy for the gas flux velocity, indirectly taking into account the dependency of the wind shear and the wave processes. The interest in the contributions from convection processes has increased as the gas flux from inland waters (with typically lower wind and sheltered conditions) now is believed to play a substantial role in the air-water gas flux budget. The gas flux is enhanced by convection through the mixing of the mixed layer as well as by decreasing the diffusive boundary layer thickness. The direct numerical simulations performed in this study are shown to be a valuable tool to enhance the understanding of this flow configuration often present in nature.
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| 37. |
- Fredriksson, Sam, 1966, et al.
(author)
-
Surface shear stress dependence of gas transfer velocity parameterizations using DNS
- 2016
-
In: Journal of Geophysical Research: Oceans. - 2169-9275 .- 2169-9291 .- 0148-0227 .- 2156-2202. ; 121:10, s. 7369-7389
-
Journal article (peer-reviewed)abstract
- Air-water gas-exchange is studied in direct numerical simulations (DNS) of free-surface flows driven by natural convection and weak winds. The wind is modeled as a constant surface-shear-stress and the gas-transfer is modeled via a passive scalar. The simulations are characterized via a Richardson number Ri=Bν/u*4 where B, ν, and u* are the buoyancy flux, kinematic viscosity, and friction velocity respectively. The simulations comprise 0Ric or kg=Ashearu*Sc-n, Ri
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| 38. |
- Fredriksson, Sam T, et al.
(author)
-
Estimating air-water gas transfer velocity during low wind condition with and without buoyancy
- 2018
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Conference paper (other academic/artistic)abstract
- This work aims at refining the gas transfer velocity parameterization during low wind conditions with and withoutbuoyancy, to be used in regional and global climate models. This parameterization and the enhanced understanding of the smallscale processes present in the vicinity of the air-water interfaces can of course be used for other purposes as well such as chemical and environmental engineering.
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| 39. |
- Fredriksson, Sam T, et al.
(author)
-
Tidal power plant simulations using large eddy simulation (LES) and the actuator line method (ALM)
- 2018
-
Conference paper (other academic/artistic)abstract
- The share of the renewable energy in the gobal energy mix is to be increased according to the sustainable development goals of the UN. Tidal energy can here potentially play a substantial role for the electric power generation. The tidal power plant Deep Green developed by Minesto uses a novel technology with a “flying” kite that, with its attached turbine, sweeps the tidal stream with a velocity several times higher than he mean flow. Eventually these power plants will form arrays requiring knowledge of (1) the interaction between individual power plants as well as (2) how the power plants and the arrays will influence the surrounding environment. The tidally oscillating turbulent boundary layer flow is in the present study analyzed using Large Eddy Simulations (LES) utilizing two different modeling techniques (pseudo-spectral and finite volume method). The boundary layer flow is analyzed both undisturbed and with a sweeping tidal power plant. The power plant is modeled using the Actuator Line Method (ALM). This method has been reformulated in order to be able to take arbitrary pathways of the actuator line into account. The results for the undisturbed flow simulations show, e.g., variations of the turbulence intensity depending on pre- or post-tidal peak flow for equivalent volume mean flow. The results for the modeled power plant show, e.g., how the wake flow downstream of the power plant that can be related to the size of the pathway size.
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| 40. |
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| 41. |
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| 42. |
- Fredriksson, Sam, 1966, et al.
(author)
-
Turbulence Characteristics in Tidal Flows Using LES and ALM to Model the Tidal Power Plant Deep Green
- 2018
-
In: 4th AWTEC, Taipei, Taiwan, 2018.
-
Conference paper (peer-reviewed)abstract
- The turbulence in tidal flows affects the design and operation of tidal plants, e.g., through control system and dynamical loads. Present work is focused on a specific site west of Holy Island along the north west cost of Wales and a specific tidal power plant, Deep Green. Although, specific and applied, the work is generally applicable regarding findings and modelling techniques for other sites and designs. Large Eddy Simulations (LES) are used to study first the undisturbed tidal flow and then the flow with a power plant in operation. The undisturbed tidal flow simulations show that the turbulence characteristics differ between the acceleration and deceleration phase of the tidal cycle. The turbulence statistics are also used to estimate dynamical loads on the tidal plant with respect to, e.g., fatigue. Secondly, a novel Actuator Line Method (ALM) tidal power plant model, that e.g., takes the arbitrary trajectories of the power plant wing into account, is used. It’s used to study how the power plants affect the environment, available power downstream, and turbulence characteristics affecting other power plants in possible power plant arrays. It is shown that the width of the trajectory can be used as a measure to estimate the wake extent.
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| 43. |
- Han, Yilin, et al.
(author)
-
Effects of microgravity on neural crest stem cells
- 2024
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In: Frontiers in Neuroscience. - : Frontiers Media S.A.. - 1662-4548 .- 1662-453X. ; 18
-
Journal article (peer-reviewed)abstract
- Exposure to microgravity (μg) results in a range of systemic changes in the organism, but may also have beneficial cellular effects. In a previous study we detected increased proliferation capacity and upregulation of genes related to proliferation and survival in boundary cap neural crest stem cells (BC) after MASER14 sounding rocket flight compared to ground-based controls. However, whether these changes were due to μg or hypergravity was not clarified. In the current MASER15 experiment BCs were exposed simultaneously to μg and 1 g conditions provided by an onboard centrifuge. BCs exposed to μg displayed a markedly increased proliferation capacity compared to 1 g on board controls, and genetic analysis of BCs harvested 5 h after flight revealed an upregulation, specifically in μg-exposed BCs, of Zfp462 transcription factor, a key regulator of cell pluripotency and neuronal fate. This was associated with alterations in exosome microRNA content between μg and 1 g exposed MASER15 specimens. Since the specimens from MASER14 were obtained for analysis with 1 week’s delay, we examined whether gene expression and exosome content were different compared to the current MASER15 experiments, in which specimens were harvested 5 h after flight. The overall pattern of gene expression was different and Zfp462 expression was down-regulated in MASER14 BC μg compared to directly harvested specimens (MASER15). MicroRNA exosome content was markedly altered in medium harvested with delay compared to directly collected samples. In conclusion, our analysis indicates that even short exposure to μg alters gene expression, leading to increased BC capacity for proliferation and survival, lasting for a long time after μg exposure. With delayed harvest of specimens, a situation which may occur due to special post-flight circumstances, the exosome microRNA content is modified compared to fast specimen harvest, and the direct effects from μg exposure may be partially attenuated, whereas other effects can last for a long time after return to ground conditions.
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| 44. |
- Hoeber, Jan, 1986-, et al.
(author)
-
A Combinatorial Approach to Induce Sensory Axon Regeneration into the Dorsal Root Avulsed Spinal Cord
- 2017
-
In: Stem Cells and Development. - : Mary Ann Liebert Inc. - 1547-3287 .- 1557-8534. ; 26:14, s. 1065-1077
-
Journal article (peer-reviewed)abstract
- Spinal root injuries result in newly formed glial scar formation, which prevents regeneration of sensory axons causing permanent sensory loss. Previous studies showed that delivery of trophic factors or implantation of human neural progenitor cells supports sensory axon regeneration and partly restores sensory functions. In this study, we elucidate mechanisms underlying stem cell-mediated ingrowth of sensory axons after dorsal root avulsion (DRA). We show that human spinal cord neural stem/progenitor cells (hscNSPC), and also, mesoporous silica particles loaded with growth factor mimetics (MesoMIM), supported sensory axon regeneration. However, when hscNSPC and MesoMIM were combined, sensory axon regeneration failed. Morphological and tracing analysis showed that sensory axons grow through the newly established glial scar along "bridges" formed by migrating stem cells. Coimplantation of MesoMIM prevented stem cell migration, "bridges" were not formed, and sensory axons failed to enter the spinal cord. MesoMIM applied alone supported sensory axons ingrowth, but without affecting glial scar formation. In vitro, the presence of MesoMIM significantly impaired migration of hscNSPC without affecting their level of differentiation. Our data show that (1) the ability of stem cells to migrate into the spinal cord and organize cellular "bridges" in the newly formed interface is crucial for successful sensory axon regeneration, (2) trophic factor mimetics delivered by mesoporous silica may be a convenient alternative way to induce sensory axon regeneration, and (3) a combinatorial approach of individually beneficial components is not necessarily additive, but can be counterproductive for axonal growth.
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| 45. |
- Hoffstedt, Caroline, et al.
(author)
-
When do people choose to be informed? : Predictors of information-seeking in the choice of primary care provider in Sweden
- 2020
-
In: Health Economics, Policy and Law. - Cambridge : Cambridge University Press. - 1744-1331 .- 1744-134X. ; 15:2, s. 210-224
-
Journal article (peer-reviewed)abstract
- Improving the ability of patients to make informed choices of health care provider can give providers more incentive to compete based on quality. Still, it is not evident to what extent and when people search for information when choosing a provider. The aim of this study is to identify under what circumstances individuals seek information when choosing a primary care provider. Research to date has mostly focused on individuals’ demographic and socio-economic characteristics and the poor availability of information as barriers to information-seeking and use. Our results highlight the importance of taking individuals’ personal motivations and situational context into account when studying information-seeking behavior. Overall, these results suggest that not even individuals who are likely to search for information since they switched or considered switching primary care provider, do so to any greater extent. However, those motivated to change providers by internal factors such as dissatisfaction or a belief that other providers may provide superior services actively sought out information to a greater extent than those motivated by external factors such as the closure of their current provider, or by moving house. Gender, employment status, place of residence and education level was also significantly associated with information-seeking.
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| 46. |
- Hultman, Johan, et al.
(author)
-
Från jord till ord: Skånsk mat
- 2006
-
In: Mat. genealogi och gestaltning. - 9144045549 ; , s. 35-54
-
Book chapter (other academic/artistic)abstract
- Texten analyserar hur lokal och regional matkultur används och skapas som ett redskap för att marknadsföra Skåne. Speciell vikt läggs vid att visa hur "kultur" inte är något som finns a priori i en plats eller region, utan hur "kultur" istället skapas i marknadsföringssammanhang.
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| 47. |
- Hultman, Martin, 1992-, et al.
(author)
-
Comprehensive imaging of microcirculatory changes in the foot during endovascular intervention - A technical feasibility study
- 2022
-
In: Microvascular Research. - Maryland Heights, MO, United States : Academic Press. - 0026-2862 .- 1095-9319. ; 141
-
Journal article (peer-reviewed)abstract
- Chronic limb-threatening ischemia (CLTI) has a major impact on patient's lives and is associated with a heavy health care burden with high morbidity and mortality. Treatment by endovascular intervention is mostly based on macrocirculatory information from angiography and does not consider the microcirculation. Despite successful endovascular intervention according to angiographic criteria, a proportion of patients fail to heal ischemic lesions. This might be due to impaired microvascular perfusion and variations in the supply to different angiosomes. Non-invasive optical techniques for microcirculatory perfusion and oxygen saturation imaging have the potential to provide the interventionist with additional information in real-time, supporting clinical decisions during the intervention. This study presents a novel multimodal imaging system, based on multi-exposure laser speckle contrast imaging and multi-spectral imaging, for continuous use during endovascular intervention. The results during intervention display spatiotemporal changes in the microcirculation compatible with expected physiological reactions during balloon dilation, with initially induced ischemia followed by a restored perfusion, and local administration of a vasodilator inducing hyperemia. We also present perioperative and postoperative follow-up measurements with a pulsatile microcirculation perfusion. Finally, cases of spatial heterogeneity in the observed oxygen saturation and perfusion are discussed. In conclusion, this technical feasibility study shows the potential of the methodology to characterize changes in microcirculation before, during, and after endovascular intervention.
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| 48. |
- Hyyppä, Kalevi, et al.
(author)
-
Projekt: Seende rullstol
- 2012
-
Other publication (pop. science, debate, etc.)abstract
- Projektet syftar till att göra det möjligt för personer med funktionsnedsättning, som inte själva har full förmåga att styra en rullstol, att ändå nyttja den. Sensorer på rullstolen upptäcker automatiskt hinder i omgivningen och ger därmed den rörelsehindrade hjälp med styrningen.En virtuell blindkäpp som består av en haptisk robotarm kopplad till en laser som mäter avstånd till föremål i omgivningen har även tagits fram. Utifrån informationen skapas en 3D-bild som brukaren av den virtuella blindkäppen kan känna på med robotarmen.Fortsatt forskning kommer att fokusera på den virtuella vita käppen som kommer att ha en mycket längre räckvidd än en vanlig vit käpp. Vi avser att göra den handhållen så att rullstolen inte behövs som bärare av laserskanner och haptisk robot. En mycket viktig del i vår forskning är att åstadkomma en bra användarupplevelse. Synskadade, som har stor erfarenhet av den vanlig vita käppen, skall snabbt lära sig att använda den virtuella vita käppen.
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| 49. |
- Innala Ahlmark, Daniel, et al.
(author)
-
Den seende rullstolen
- 2011
-
Conference paper (other academic/artistic)abstract
- In its current form, the white cane has been used by visually impaired people for almost a hundred years. It is an intuitive device that helps visually impaired people navigate independently. For people who, in addition to a visual impairment, also have impaired movement, this independence is not as certain. If a wheelchair or a walker is needed, human assistance might be a necessity.MICA (Mobile Internet Connected Assistant) is a computerized wheelchair that has been equipped with a laser rangefinder that can measure the distance to obstacles in the environment. This information has been used to make the wheelhair able to drive on its own, avoiding obstacles, so that users unable to drive a wheelchair themselves are able to use it.The latest addition to MICA - a virtual white cane - allows visually impaired wheelchair users to virtually touch obstacles in their environment, and thus navigate in a similar way to those using a regular white cane. This is accomplished by generating a simplified 3D model based on the data acquired from the laser rangefinder, and sending this data to a haptic device, allowing users to feel the 3D model.The virtual white cane is still in an early development stage. The first test drive of MICA with the virtual white cane (together known as "The Sighted Wheelchair") was performed on 2011-05-10. A short video called "The Sighted Wheelchair" can be found on YouTube.Future work will focus on developing the software that communicates with the laser rangefinder and the haptic device to improve the user experience. Efforts will also be made to overcome the limitations of the laser rangefinder, improving the 3D model.
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| 50. |
- Innala Ahlmark, Daniel, et al.
(author)
-
Obstacle Avoidance Using Haptics and a Laser Rangefinder
- 2013
-
In: 2013 IEEE Workshop on Advanced Robotics and its Social Impacts. - Piscataway, NJ : IEEE Communications Society. - 9781479923687 ; , s. 76-81
-
Conference paper (peer-reviewed)abstract
- In its current form, the white cane has been used by visually impaired people for almost a century. It is one of the most basic yet useful navigation aids, mainly because of its simplicity and intuitive usage. For people who have a motion impairment in addition to a visual one, requiring a wheelchair or a walker, the white cane is impractical, leading to human assistance being a necessity. This paper presents the prototype of a virtual white cane using a laser rangefinder to scan the environment and a haptic interface to present this information to the user. Using the virtual white cane, the user is able to "poke" at obstacles several meters ahead and without physical contact with the obstacle. By using a haptic interface, the interaction is very similar to how a regular white cane is used. This paper also presents the results from an initial field trial conducted with six people with a visual impairment.
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