| 1. |
|
|
| 2. |
- Ekman, Petter, 1988-
(författare)
-
Important Factors for Accurate Scale-Resolving Simulations of Automotive Aerodynamics
- 2020
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Road transports are responsible for almost 18 % of the greenhouse gas emission in Europe and are today the leading cause of air pollution in cities. Aerodynamic resistance has a significant effect on fuel consumption and hence the emission of vehicles. For electric vehicles, emissions are not affected by the aerodynamics as such but instead have a significant effect on the effective range of the vehicle.In 2017, a new measurement procedure was introduced, Worldwide Harmonized Light Vehicles Test Procedure (WLTP), for measuring emissions, fuel consumption, and range. This procedure includes a new test cycle with increased average driving speed compared to the former procedure, which thereby increases the importance of the aerodynamic resistance, as it drastically increases with speed. A second effect is that the exact car configuration sold to the customer needs to be certified in terms of fuel consumption and emissions. The result is that every possible combination of optional extras, which might affect the aerodynamic resistance, needs to be aerodynamically analyzed and possibly improved. From 2021, the European Commission will introduce stricter emission regulations for new passenger cars, with the fleet-wide average lowered to 95 grams CO2=km, which puts an even higher demand on achieving efficient aerodynamics.Virtual development of the aerodynamics of road vehicles is today used to a great extent, using Computational Fluid Dynamics, as it enables faster and cheaper development. However, achieving high accuracy for the prediction of the flow field and aerodynamic forces is challenging, especially given the complexity of both the vehicle geometry in itself and the surrounding flow field. Even for a simplified generic bluff body, accurately predicting the flow field and aerodynamic forces is a challenge. The main reason for this challenge of achieving results with high accuracy is the prediction of the complex behavior of turbulence. Scale-resolving simulation (SRS) methods, such as Large Eddy Simulation (LES), where most of the turbulent structures are resolved has in many studies shown high accuracy but unfortunately to a very high computational cost. It is primarily the small turbulent structures within the near-wall region that requires a _ne resolution in both space (the mesh) and in time. This fine resolution is the reason for the very high computational cost and makes LES unfeasible for practical use in industrial aerodynamic development at present and in the near future. By modeling the turbulent structures within the near-wall region using a Reynolds-Averaged Navier-Stokes (RANS) model, and resolving the turbulence outside the region with a LES model, a coarser resolution is possible to use, resulting in significantly lower computational cost. Which used RANS model is of high importance, and especially how much turbulent viscosity the model generates, as too high values can result in suppression of the resolved turbulence.The transitioning between the RANS and LES regions have a significant effect on the results. Faster transition enables more resolved turbulence, favorable for higher accuracy, but needs to be balanced with sufficient shielding of the RANS region. If resolving the turbulence occurs within the near-wall region, and the mesh is not sufficiently fine, it can result in poor accuracy.By increasing the time-step size and disregarding best-practice guides, the computational cost can be significantly reduced. The accuracy is reasonably insensitive to the larger time step sizes until a certain degree, thereby enabling computationally cheaper SRS to achieve high accuracy of aerodynamic predictions needed to meet present and future emission regulations.
|
|
| 3. |
- Karlsson, Adrian, et al.
(författare)
-
Extended treatment in cerebral ischemia score 2c or 3 as goal of successful endovascular treatment is associated with clinical benefit.
- 2024
-
Ingår i: Journal of neuroradiology = Journal de neuroradiologie. - 0150-9861. ; 51:2, s. 190-195
-
Tidskriftsartikel (refereegranskat)abstract
- Successful reperfusion, defined as a modified treatment in cerebral ischemia (mTICI) score 2b or 3, is an important goal for endovascular treatment (EVT) of stroke. Recently, an extension of the mTICI score with an additional grade 2c indicating near-complete reperfusion (expanded TICI, eTICI) and a revised definition of success as eTICI 2c or 3 were proposed. We evaluate whether eTICI 2c translates into improved clinical outcome compared to eTICI 2b.Consecutive patients with large vessel occlusion in the anterior circulation who underwent EVT between December 2013 and December 2020 were included. Clinical outcome measures were favorable functional outcome at 90 days (modified Rankin Scale [mRS] scores 0 to 2 or return to pre-stroke mRS) and early neurological improvement (National Institutes of Health Stroke Scale [NIHSS] improvement ≥4 points or a score of 0-1 at 24h).Of 1282 included patients (median age 76, median NIHSS 16), reperfusion was classified as eTICI 2b in 410 (32%), eTICI 2c in 242 (19%) and eTICI 3 in 464 (36%). eTICI 2c differed significally from 2b with respect to early neurological improvement (aOR=1.49, 95% CI=1.01-2.19). No statistically significant difference in favorable functional outcome at 90 days was found (eTICI 2c vs 2b, aOR=1.31, 95% CI=0.88-2.00).Our study indicates early clinical benefit at 24h of achieving eTICI 2c compared to eTICI 2b, but no significant difference was seen in favorable functional outcome at 90 days. Our results support eTICI 2c and 3 as the goal of a successful thrombectomy but do not exclude eTICI 2b as an acceptable result.
|
|
| 4. |
- Karlsson, Anders, et al.
(författare)
-
Numerical scattering simulations for estimating soot aggregate morphology from nephelometer scattering measurements
- 2022
-
Ingår i: Journal of Aerosol Science. - : Elsevier BV. - 0021-8502. ; 159
-
Tidskriftsartikel (refereegranskat)abstract
- Nephelometers are regularly used for air quality monitoring through scattering measurements of aerosols in the atmosphere. Less attention has been paid to the potential of estimating soot morphological parameters from nephelometer measurements in combination with scattering theory. In this work, we perform a fundamental laboratory study where an Ecotech Aurora 3000 nephelometer is used for measuring the scattering properties of soot with different characteristics. The nephelometer monitors the forward and backward scattering at three wavelengths (450 nm, 525 nm, and 635 nm) to retrieve information on the ratio of forward and backward scattering intensities, as well as the scattering wavelength dependence. An inverse scattering method, based on the Rayleigh–Debye–Gans theory, for determination of the equivalent fractal dimension (Df) and radius of gyration (Rg) of soot particles from the experimental scattering data was developed. It is shown that the inverse method can estimate Rg and Df when Rg<185nm and from the wavelength dependence, information on the relative amount of organic soot could be obtained. For validation, estimated parameters are compared with the morphological parameters of soot sampled from the mini-CAST soot generator and evaluated using transmission electron microscopy (TEM). Uncertainties and limitations of the procedure are discussed.
|
|
| 5. |
- Karlsson, Adrian, et al.
(författare)
-
Stent retriever versus aspiration based thrombectomy: impact on first pass reperfusion, procedure time, and clinical outcomes in large vessel occlusion. Nationwide registry based cohort study
- 2024
-
Ingår i: JOURNAL OF NEUROINTERVENTIONAL SURGERY. - 1759-8478 .- 1759-8486.
-
Tidskriftsartikel (refereegranskat)abstract
- Background First pass reperfusion (FPR), defined as near complete reperfusion (extended Treatment in Cerebral Ischemia (eTICI) score 2c/3) in a single attempt without rescue therapy has been proposed as a quality metric. However, it remains unclear if the thrombectomy method influences clinical outcome and FPR rate. This study evaluates whether stent retriever and aspiration based thrombectomy differ in FPR rate, technical and clinical outcomes in FPR, and multiple pass reperfusion (MPR).Methods This retrospective, nationwide, multicenter registry study included consecutive patients with proximal anterior or posterior circulation stroke, treated between 2018 and 2021 in Sweden. Outcome measures were FPR rate, procedure time, early neurological improvement (>= 4 points on National Institutes of Health Stroke Scale (NIHSS) or a score of 0-1 at 24 hours), favorable functional outcome (modified Rankin Scale score of 0-2 or no decline at 90 days), and mortality at 90 days.Results Of 3309 patients (median age 75, median NIHSS 16), 1990 underwent stent retriever and 1319 aspiration based thrombectomy as the firstline method. No difference in FPR rate was observed. Aspiration based thrombectomy showed a shorter procedure time in the FPR group (crude OR (cOR) 6.4 min (95% CI 3.4 to 9.3), adjusted OR (aOR) 8.7 min (95% CI 1.8 to 15.6)) and MPR group (cOR 9.7 min (95% CI 4.0 to 15.4), aOR 17.4 min (95% CI 9.6 to 25.2)), and association with early neurological improvement (cOR 1.21 (95% CI 1.03 to 1.42), aOR 1.40 (95% CI 1.18 to 1.67)) and favorable functional outcome (aOR 1.22 (95% CI 1.01 to 1.47)).Conclusions Our findings suggest that aspiration based thrombectomy was associated with a shorter procedure time and better clinical outcomes than treatment with a stent retriever. No difference was found in FPR rate.
|
|
| 6. |
- Marriott, Ross J., et al.
(författare)
-
Factors Associated With Circulating Sex Hormones in Men
- 2023
-
Ingår i: Annals of Internal Medicine. - 0003-4819. ; 176:9, s. 1221-1234
-
Forskningsöversikt (refereegranskat)abstract
- Background: Various factors modulate circulating testosterone in men, affecting interpretation of testosterone measurements. Purpose: To clarify factors associated with variations in sex hormone concentrations. Data Sources: Systematic literature searches (to July 2019). Study Selection: Prospective cohort studies of community-dwelling men with total testosterone measured using mass spectrometry. Data Extraction: Individual participant data (IPD) (9 studies; n = 21 074) and aggregate data (2 studies; n = 4075). Sociodemographic, lifestyle, and health factors and concentrations of total testosterone, sex hormone–binding globulin (SHBG), luteinizing hormone (LH), dihydrotestosterone, and estradiol were extracted. Data Synthesis: Two-stage random-effects IPD meta-analyses found a nonlinear association of testosterone with age, with negligible change among men aged 17 to 70 years (change per SD increase about the midpoint, -0.27 nmol/L [-7.8 ng/dL] [CI, -0.71 to 0.18 nmol/L {-20.5 to 5.2 ng/dL}]) and decreasing testosterone levels with age for men older than 70 years (-1.55 nmol/L [-44.7 ng/dL] [CI, -2.05 to -1.06 nmol/L {-59.1 to -30.6 ng/dL}]). Testosterone was inversely associated with body mass index (BMI) (change per SD increase, -2.42 nmol/L [-69.7 ng/dL] [CI, -2.70 to -2.13 nmol/L {-77.8 to -61.4 ng/dL}]). Testosterone concentrations were lower for men who were married (mean difference, -0.57 nmol/L [-16.4 ng/dL] [CI, -0.89 to -0.26 nmol/L {-25.6 to -7.5 ng/dL}]); undertook at most 75 minutes of vigorous physical activity per week (-0.51 nmol/L [-14.7 ng/dL] [CI, -0.90 to -0.13 nmol/L {-25.9 to -3.7 ng/dL}]); were former smokers (-0.34 nmol/L [-9.8 ng/dL] [CI, -0.55 to -0.12 nmol/L {-15.9 to -3.5 ng/dL}]); or had hypertension (-0.53 nmol/L [-15.3 ng/dL] [CI, -0.82 to -0.24 nmol/L {-23.6 to -6.9 ng/dL}]), cardiovascular disease (-0.35 nmol/L [-10.1 ng/dL] [CI, -0.55 to -0.15 nmol/L {-15.9 to -4.3 ng/dL}]), cancer (-1.39 nmol/L [-40.1 ng/dL] [CI, -1.79 to -0.99 nmol/L {-51.6 to -28.5 ng/dL}]), or diabetes (-1.43 nmol/L [-41.2 ng/dL] [CI, -1.65 to -1.22 nmol/L {-47.6 to -35.2 ng/dL}]). Sex hormone–binding globulin was directly associated with age and inversely associated with BMI. Luteinizing hormone was directly associated with age in men older than 70 years. Limitation: Cross-sectional analysis, heterogeneity between studies and in timing of blood sampling, and imputation for missing data. Conclusion: Multiple factors are associated with variation in male testosterone, SHBG, and LH concentrations. Reduced testosterone and increased LH concentrations may indicate impaired testicular function after age 70 years. Interpretation of individual testosterone measurements should account particularly for age older than 70 years, obesity, diabetes, and cancer.
|
|
| 7. |
- Marriott, Ross J, et al.
(författare)
-
Factors Associated With Circulating Sex Hormones in Men : Individual Participant Data Meta-analyses.
- 2023
-
Ingår i: Annals of internal medicine. - 1539-3704. ; 176:9, s. 1221-1234
-
Forskningsöversikt (refereegranskat)abstract
- Various factors modulate circulating testosterone in men, affecting interpretation of testosterone measurements.To clarify factors associated with variations in sex hormone concentrations.Systematic literature searches (to July 2019).Prospective cohort studies of community-dwelling men with total testosterone measured using mass spectrometry.Individual participant data (IPD) (9 studies; n= 21074) and aggregate data (2 studies; n= 4075). Sociodemographic, lifestyle, and health factors and concentrations of total testosterone, sex hormone-binding globulin (SHBG), luteinizing hormone (LH), dihydrotestosterone, and estradiol were extracted.Two-stage random-effects IPD meta-analyses found a nonlinear association of testosterone with age, with negligible change among men aged 17 to 70 years (change per SD increase about the midpoint, -0.27 nmol/L [-7.8 ng/dL] [CI, -0.71 to 0.18 nmol/L {-20.5 to 5.2 ng/dL}]) and decreasing testosterone levels with age for men older than 70 years (-1.55 nmol/L [-44.7 ng/dL] [CI, -2.05 to -1.06 nmol/L {-59.1 to -30.6 ng/dL}]). Testosterone was inversely associated with body mass index (BMI) (change per SD increase, -2.42 nmol/L [-69.7 ng/dL] [CI, -2.70 to -2.13 nmol/L {-77.8 to -61.4 ng/dL}]). Testosterone concentrations were lower for men who were married (mean difference, -0.57 nmol/L [-16.4 ng/dL] [CI, -0.89 to -0.26 nmol/L {-25.6 to -7.5 ng/dL}]); undertook at most 75 minutes of vigorous physical activity per week (-0.51 nmol/L [-14.7 ng/dL] [CI, -0.90 to -0.13 nmol/L {-25.9 to -3.7 ng/dL}]); were former smokers (-0.34 nmol/L [-9.8 ng/dL] [CI, -0.55 to -0.12 nmol/L {-15.9 to -3.5 ng/dL}]); or had hypertension (-0.53 nmol/L [-15.3 ng/dL] [CI, -0.82 to -0.24 nmol/L {-23.6 to -6.9 ng/dL}]), cardiovascular disease (-0.35 nmol/L [-10.1 ng/dL] [CI, -0.55 to -0.15 nmol/L {-15.9 to -4.3 ng/dL}]), cancer (-1.39 nmol/L [-40.1 ng/dL] [CI, -1.79 to -0.99 nmol/L {-51.6 to -28.5 ng/dL}]), or diabetes (-1.43 nmol/L [-41.2 ng/dL] [CI, -1.65 to -1.22 nmol/L {-47.6 to -35.2 ng/dL}]). Sex hormone-binding globulin was directly associated with age and inversely associated with BMI. Luteinizing hormone was directly associated with age in men older than 70 years.Cross-sectional analysis, heterogeneity between studies and in timing of blood sampling, and imputation for missing data.Multiple factors are associated with variation in male testosterone, SHBG, and LH concentrations. Reduced testosterone and increased LH concentrations may indicate impaired testicular function after age 70 years. Interpretation of individual testosterone measurements should account particularly for age older than 70 years, obesity, diabetes, and cancer.Medical Research Future Fund, Government of Western Australia, and Lawley Pharmaceuticals. (PROSPERO: CRD42019139668).
|
|
| 8. |
- Michelsen, Brigitte, et al.
(författare)
-
Differences and similarities between the EULAR/ASAS-EULAR and national recommendations for treatment of patients with psoriatic arthritis and axial spondyloarthritis across Europe
- 2023
-
Ingår i: The Lancet Regional Health - Europe. - 2666-7762. ; 33
-
Forskningsöversikt (refereegranskat)abstract
- This is the first report comparing EULAR and national treatment recommendations for PsA patients across Europe, and the first this decade to compare ASAS-EULAR and national treatment recommendations in axSpA patients. An electronic survey was completed from October 2021–April 2022 by rheumatologists in 15 European countries. One and four countries followed all EULAR and ASAS-EULAR recommendations, respectively. Five countries had no national treatment recommendations for PsA and/or axSpA, but followed other regulations. In several countries, national treatment recommendations predated the most recent EULAR/ASAS-EULAR recommendations. Entry criteria for starting biologic/targeted synthetic disease-modifying anti-rheumatic drugs varied considerably. In several countries, for PsA patients with significant skin involvement, interleukin-17 inhibitors were not given preference. The positioning of Janus Kinase inhibitors differed and Phosphodiesterase-4 inhibitors were not in use/reimbursed in most countries. This study may motivate European countries to update their national treatment recommendations, to align them better with the latest international recommendations.
|
|
| 9. |
- Pöppelwerth, Adrian, et al.
(författare)
-
Scale size estimation and flow pattern recognition around a magnetosheath jet
- 2024
-
Ingår i: Annales Geophysicae. - : Copernicus GmbH. - 0992-7689 .- 1432-0576. ; 42:1, s. 271-284
-
Tidskriftsartikel (refereegranskat)abstract
- Transient enhancements in the dynamic pressure, so-called magnetosheath jets or simply jets, are abundantly found in the magnetosheath. They travel from the bow shock through the magnetosheath towards the magnetopause. On their way through the magnetosheath, jets disturb the ambient plasma. Multiple studies already investigated their scale size perpendicular to their propagation direction, and almost exclusively in a statistical manner. In this paper, we use multi-point measurements from the Time History of Events and Macroscale Interactions during Substorms (THEMIS) mission to study the passage of a single jet. The method described here allows us to estimate the spatial distribution of the dynamic pressure within the jet. Furthermore, the size perpendicular to the propagation direction can be estimated for different cross sections. In the jet event investigated here, both the dynamic pressure and the perpendicular size increase along the propagation axis from the front part towards the center of the jet and decrease again towards the rear part, but neither monotonically nor symmetrically. We obtain a maximum diameter in the perpendicular direction of about 1 RE and a dynamic pressure of about 6 nPa at the jet center.
|
|
| 10. |
- Samuelsson, Jennifer, et al.
(författare)
-
Risk of de novo aneurysm formation in patients previously diagnosed with a ruptured or unruptured aneurysm: 18-year follow-up.
- 2023
-
Ingår i: Clinical neurology and neurosurgery. - 0303-8467 .- 1872-6968. ; 233
-
Tidskriftsartikel (refereegranskat)abstract
- Data on de novo aneurysm formation after treatment for intracranial aneurysms remains scarce. We studied the incidence of de novo aneurysm formation in patients who had undergone aneurysm treatment more than 18 years prior to follow-up. As it is a disease affecting a younger patient population more specific guidelines are needed when planning a follow-up regime.The rate of de novo aneurysm formation was assessed with Magnetic Resonance Angiography (MRA) follow-up >18 years after endovascular or microsurgical treatment for an intracranial aneurysm. Variables associated with de novo aneurysm formation were studied using logistic regression. Missing data were imputed using chained random forests. A data-driven model for the prediction of de novo aneurysm was created to calculate the relative variable importance of ten clinical features.De novo aneurysms were identified in 11/81 (13.6 %) patients, of whom 1 was male, over a median follow-up of 20 years. Sex was the most important variable associated with de novo aneurysm formation. Regarding the development of de novo aneurysm, men displayed an odds ratio (OR) of 0.16 (0.01-0.97), compared with women. OR for mRS score 2 or more was 0.20 (95 % CI 0.01-1.34), and OR for smokers was 3.70 (0.54-31.18). Six out of 11 patients (54.5 %) needed treatment; 1 underwent endovascular treatment (EVT) and 5 underwent microsurgical treatment (MST). The overall annual de novo aneurysm formation rate was 0.92 %.This study highlights the need for a longer follow-up imaging monitoring of patients that have previously undergone treatment for an intracranial aneurysm. These data are useful to take into consideration when planning a follow-up strategy.
|
|
| 11. |
- Schmidt, Bernard, 1981-, et al.
(författare)
-
Augmented Reality Approach for a User Interface in a Robotic Production System
- 2022
-
Ingår i: SPS2022. - Amsterdam; Berlin; Washington, DC : IOS Press. - 9781643682686 - 9781643682693 ; , s. 240-251
-
Konferensbidrag (refereegranskat)abstract
- In a Cyber-physical system, the information flow from the cyber part to the physical part plays a crucial role. This paper presents the work of development and initial testing of an augmented reality approach to provide a user interface for operators that could be a part of a robotic production system. The solution is distributed and includes a communication hub that allows the exchange of data and information between multiple clients e.g. robot controllers, an optimization platform, and visualization devices. The main contributions of the presented work are visualization of optimization results and visualization of information obtained from the robot controller and the integrated communication framework. The paper also presents challenges faced during the development work and opportunities related to the presented approach. The implemented interface uses HoloLens 2 mixed reality device to visualize in real-time information obtained from a robot controller as well as from simulation. Information regarding the placement of work objects and targets or currently executed lines of code can be useful for robotic cell programmers and commissioning teams to validate robot programs and to select more optimal solutions toward sustainable manufacturing. The operator can simulate the execution of the robot program and visualize it by overlying the robot cell with the 3D model of the simulated robot. Moreover, visualization of future robot motion could support human-robot collaboration. Furthermore, the interface allows providing the user with details from multi-objective optimization performed on a digital twin of the robotic cell with the aim to reduce cycle time and energy consumption. It allows visualizing selected scenarios to support decision-making by allowing comparison of proposed solutions and the initial one. The visualization includes cell layout, robot path, cycle time, robot energy consumption. The presented approach is demonstrated in industry-inspired cases and with the use of an industrial ABB robot.
|
|
| 12. |
- Tiensuu, Kiira, et al.
(författare)
-
RAVEN: a student rocket program at Luleå University of Technology, Sweden
- 2021
-
Ingår i: IAC 2021 Congress Proceedings, 72nd International Astronautical Congress (IAC), Dubai, United Arab Emirates. - : International Astronautical Federation (IAF).
-
Konferensbidrag (refereegranskat)abstract
- RAVEN, Rocketry and Aerospace Vehicle Engineering in Norrbotten, is the first rocket project at Luleå University of Technology (LTU), Sweden. The project started in early 2020, and it aims to design, build, test and launch a hybrid propulsion rocket. The initial objectives are to reach an altitude of 10 km with an accompanying payload of 10 kg. The RAVEN team is based at the Kiruna Space Campus and consists of approximately 30 graduate students. The main goal of the first RAVEN rocket is to demonstrate its technology. The team is designing the entire rocket from scratch, including the hybrid propulsion system that uses nitrous oxide as the oxidising agent and paraffin as the solid fuel component, to produce approximately 6 kN of thrust. A modular rocket structure will offer customisation, enabling simple design changes in future iterations. Thus, the layout allows individual subsystems to be re-designed without changes directly affecting others. The project is meant to create a foundation for future student and research rocket projects at LTU. The follow-up developments could further iterate on the first rocket design, increasing hands-on education and providing more collaboration opportunities between the university and the aerospace industry – and eventually provide an in-house platform for research and education at the university or even for commercial start-ups. The infrastructure and resources, such as the proximity to the Esrange Space Center launch facility and support from the university and industry, make Northern Sweden an ideal location to establish a continuous rocket program.
|
|
