| 1. |
- Aspenberg, Per, 1949-, et al.
(författare)
-
Artrosskolan : evidensen måste stärkas
- 2018
-
Ingår i: Läkartidningen. - : Läkartidningen Förlag AB. - 0023-7205 .- 1652-7518. ; 115
-
Tidskriftsartikel (populärvet., debatt m.m.)
|
|
| 2. |
|
|
| 3. |
- Chen, WenChuang, et al.
(författare)
-
Numerical modelling of a point-absorbing wave energy converter in irregular and extreme waves
- 2017
-
Ingår i: Applied Ocean Research. - : Elsevier BV. - 0141-1187 .- 1879-1549. ; 63, s. 90-105
-
Tidskriftsartikel (refereegranskat)abstract
- Based on the Navier-Stokes (RANS) equations, a three-dimensional (3-D) mathematical model for the hydrodynamics and structural dynamics of a floating point-absorbing wave energy converter (WEC) with a stroke control system in irregular and extreme waves is presented. The model is validated by a comparison of the numerical results with the wave tank experiment results of other researchers. The validated model is then utilized to examine the effect of wave height on structure displacements and connection rope tension. In the examined cases, the differences in WEC’s performance exhibited by an inviscid fluid and a viscous fluid can be neglected. Our results also reveal that the differences in behavior predicted by boundary element method (BEM) and the RANS-based method can be significant and vary considerably, depending on wave height.
|
|
| 4. |
- Farhang, Mehdy, et al.
(författare)
-
The trend of radiological severity of hip fractures over a 30 years period : a cohort study
- 2019
-
Ingår i: BMC Musculoskeletal Disorders. - : Springer Science and Business Media LLC. - 1471-2474. ; 20:1
-
Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Despite advances in operative techniques and preoperative care, proximal femur fractures (PFF) still represent a great public health problem. Displacement and fracture stability have been assumed as important determinants of treatment modality and outcome in such fractures. Purpose of this study was to determine whether the radiological severity of PFF fractures has increased over time.METHODS: In a cohort study, the plain radiographs of all patients with PFF aged over 50 years who were admitted to Umeå University Hospital in 1981/82, 2002 and 2012 were recruited to examine the types of fractures.RESULTS: The ratio of undisplaced to displaced femoral neck (FN) fractures was 30 to 70% in 1981/82, 28 to 72% in 2002 and 25 to 75% in 2012. The ratio of stable to unstable intertrochanteric (IT) fractures was 64 to 36% in 1981/82, 68 to 32% in 2002 and 75 to 25% in 2012. The ratio of simple to comminute subtrochanteric fractures was 35 to 65% in 1981/82, 16 to 84% in 2002 and 12 to 88% in 2012. In both FN and IT fractures we found no statistical difference among these 3 study periods, p = 0.67 and p = 0.40. In subtrochanteric fractures we saw a tendency towards more comminute subtrochanteric fractures (1981/82 to 2012), p = 0.09.CONCLUSIONS: We found no significant increment in the radiological severity of FN and IT over a 30 years' period. However, there was tendency towards an increase in comminute subtrochanteric fractures.
|
|
| 5. |
- Hai, Ling, et al.
(författare)
-
Modelling a point absorbing wave energy converter by the equivalent electric circuit theory : A feasibility study
- 2015
-
Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 117
-
Tidskriftsartikel (refereegranskat)abstract
- There is a need to have a reliable tool to quickly assess wave energy converters (WECs). This paper explores whether it is possible to apply the equivalent electric circuit theory as an evaluation tool for point absorbing WEC system modelling. The circuits were developed starting from the force analysis, in which the hydrodynamic, mechanical, and electrical parameters were expressed by electrical components. A methodology on how to determine the parameters for electrical components has been explained. It is found that by using a multimeter, forces in the connection line and the absorbed electric power can be simulated and read directly from the electric circuit model. Finally, the circuit model has been validated against the full scale offshore experiment. The results indicated that the captured power could be predicted rather accurately and the line force could be estimated accurately near the designed working condition of the WEC.
|
|
| 6. |
- Hulsart Billström, Gry, 1982-
(författare)
-
Bone Regeneration with Cell-free Injectable Scaffolds
- 2017
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Bone is a remarkable multifunctional tissue with the ability to regenerate and remodel without generating any scar tissue. However, bone loss due to injury or diseases can be a great challenge and affect the patient significantly. Autologous bone grafting is commonly used throughout the world. Autograft both fills the void and is bone inductive, housing the particular cells that are needed for bone regeneration. However, a regenerative complement to autograft is of great interest as the use of biomaterials loaded with bioactive molecules can avoid donor site morbidity and the problem of a limited volume of material. Two such regenerative products that utilise bone morphogenetic protein (BMP)-7 and -2 have been used for more than a decade clinically. Unfortunately, several side effects have been reported, such as severe swelling due to inflammation and ectopic bone formation. Additionally, the products require open surgery and use of supra physiological doses of the BMPs due to poor localisation and retention of the growth factor. The purpose of this thesis was to harness the strong inductive capacity of the BMP-2 by optimising the carrier of this bioactive protein, thereby minimising the side effects that are associated with the clinical products and facilitating safe and localised bone regeneration. We focused on an injectable hyaluronan-based carrier developed through polymer chemistry at the University of Uppsala. The strategy was to use the body’s own regenerative pathway to stimulate and enhance bone healing in a manner similar to the natural bone-healing process. The hyaluronan-based carrier has a similar composition to the natural extracellular matrix and is degraded by resident enzymes. Earlier studies have shown improved properties when adding hydroxyapatite, a calcium phosphate that constitutes the inorganic part of the bone matrix. In Paper I, the aim was to improve the carrier by adding other forms of calcium phosphate. The results indicated that bone formation was enhanced when using nano-sized hydroxyapatite. In Paper II, we discovered the importance of crushing the material, thus enhancing permeability and enlarging the surface area. We wished to further develop the carrier system, but were lacking an animal model with relatively high throughput, facilitated access, paired data, and we were also committed to the 3Rs of refinement, reduction, and replacement. To meet these challenges, we developed and refined an animal model, and this is described in Paper III. In Paper IV, we sought to further optimise the biomaterial properties of the hydrogel through covalent bonding of bisphosphonates to the hyaluronan hydrogel. This resulted in exceptional retention of the growth factor BMP-2. In Paper V, SPECT/PET/µCT was combined as a tri-modal imaging method to allow visualisation of the biomaterial’s in situ action, in terms of drug retention, osteoblast activity and mineralisation. Finally, in Paper VI the correlation between existing in vitro results with in vivo outcomes was observed for an array of biomaterials. The study identified a surprisingly poor correlation between in vitro and in vivo assessment of biomaterials for osteogenesis.
|
|
| 7. |
- Li, Wei, et al.
(författare)
-
Bivariate joint distribution modeling of wave climate data using a copula method
- 2016
-
Ingår i: International Journal of Energy and Statistics. - World Scientific Publishing. - 2335-6812. ; 4:3
-
Tidskriftsartikel (refereegranskat)abstract
- The bivariate joint distribution of the significant wave height and the wave period is of great importance in characterizing the wave climate at a wave energy converter test site. In this paper, we investigate bivariate joint distribution modeling of the wave climate at the Lysekil wave energy converter test site off the Swedish west coast. This study is based on 9 years of wave observations at the test site from 2005 to 2013. Archimedean Copulas are used for the bivariate joint distribution modeling of the significant wave height and the wave period. Measured wave data is compared with simulated wave climate data for the Lysekil test site using three Archimedean Copula models, the Clayton, Frank and Gumbel copulas. The R-squared statistical test yields a better goodness of fit for the Gumbel copula compared to the other two copulas. In addition, the Archimedean Copula method is applied to the measured wave climate data from two other sites to illustrate the general applicability. It shows that the Archimedean Copulas exhibits stable performance with good accuracy in characterizing the wave climate and they can be employed for forecasting the wave energy resource and assessing the survivability of wave energy converters.
|
|
| 8. |
- Li, Wei, et al.
(författare)
-
Statistical Analysis of Wave Climate Data Using Mixed Distributions and Extreme Wave Prediction
- 2016
-
Ingår i: Energies. - : MDPI AG. - 1996-1073. ; 9:6
-
Tidskriftsartikel (refereegranskat)abstract
- The investigation of various aspects of the wave climate at a wave energy test site is essential for the development of reliable and efficient wave energy conversion technology. This paper presents studies of the wave climate based on nine years of wave observations from the 2005-2013 period measured with a wave measurement buoy at the Lysekil wave energy test site located off the west coast of Sweden. A detailed analysis of the wave statistics is investigated to reveal the characteristics of the wave climate at this specific test site. The long-term extreme waves are estimated from applying the Peak over Threshold (POT) method on the measured wave data. The significant wave height and the maximum wave height at the test site for different return periods are also compared. In this study, a new approach using a mixed-distribution model is proposed to describe the long-term behavior of the significant wave height and it shows an impressive goodness of fit to wave data from the test site. The mixed-distribution model is also applied to measured wave data from four other sites and it provides an illustration of the general applicability of the proposed model. The methodologies used in this paper can be applied to general wave climate analysis of wave energy test sites to estimate extreme waves for the survivability assessment of wave energy converters and characterize the long wave climate to forecast the wave energy resource of the test sites and the energy production of the wave energy converters.
|
|
| 9. |
- Parwal, Arvind, et al.
(författare)
-
A comparative analysis of linear and nonlinear control of wave energy converter for a force control application
- 2019
-
Ingår i: International Marine Energy Journal. - : European Wave and Tidal Energy Conference. - 2631-5548. ; 2:1, s. 39-50
-
Tidskriftsartikel (refereegranskat)abstract
- The aim of wave energy converters (WECs) is to harvest the energy from the ocean waves and convert into electricity. Optimizing the generator output is a vital point of research. A WEC behaves as a nonlinear system in real ocean waves and a control that approximates the behaviour of the system is required. In order to predict the behaviour of WEC, a controller is implemented with an aim to track the referenced trajectory for a force control application of the WEC. A neural model is implemented for the system identification and control of the nonlinear process with a neural nonlinear autoregressive moving average exogenous (NARMAX) model. The neural model updates the weights to reduce the error by using the Levenberg-Marquardt back-propagation algorithm for a single-input-single-output (SISO) nonlinear system. The performance of the system under the proposed scheme is compared to the same system under a PI-controller scheme, where the PI gains have been tuned accordingly, to verify the control capacity of the proposed controller. The results show a good tracking of dq (direct-quadrature) axes currents by regulating the stator currents, and hence a force control is achieved at different positions of the translator. The dynamic performance of the control is verified in a time domain analysis for the displacement of the translator.
|
|
| 10. |
- Parwal, Arvind, et al.
(författare)
-
Experimental Test of Grid Connected VSC to Improve the Power Quality in a Wave Power System
- 2018
-
Ingår i: 2018 5th International Conference on Electric Power and Energy Conversion Systems, EPECS 2018. - 9781538664575
-
Konferensbidrag (refereegranskat)abstract
- This paper provides an overview of electric power conversion system installed at the Lysekil research site, located at the west coast of Sweden. The electric power conversion system consists of rectifiers, rectifying the power from the wave energy converters, a DC-link and a grid-tied inverter. The paper focuses on the performance of the inverter and the filter and presents experimental results obtained during the grid integration.
|
|
