| 1. |
- Kumsars, Indulis, et al.
(författare)
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Randomised comparison of provisional side branch stenting versus a two-stent strategy for treatment of true coronary bifurcation lesions involving a large side branch : the Nordic-Baltic Bifurcation Study IV
- 2020
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Ingår i: Open heart. - : BMJ Publishing Group Ltd. - 2053-3624. ; 7:1
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Tidskriftsartikel (refereegranskat)abstract
- Background: It is still uncertain whether coronary bifurcations with lesions involving a large side branch (SB) should be treated by stenting the main vessel and provisional stenting of the SB (simple) or by routine two-stent techniques (complex). We aimed to compare clinical outcome after treatment of lesions in large bifurcations by simple or complex stent implantation.Methods: The study was a randomised, superiority trial. Enrolment required a SB >= 2.75 mm, >= 50% diameter stenosis in both vessels, and allowed SB lesion length up to 15 mm. The primary endpoint was a composite of cardiac death, non-procedural myocardial infarction and target lesion revascularisation at 6 months. Two-year clinical follow-up was included in this primary reporting due to lower than expected event rates.Results: A total of 450 patients were assigned to simple stenting (n = 221) or complex stenting (n=229) in 14 Nordic and Baltic centres. Two-year follow-up was available in 218 (98.6%) and 228 (99.5%) patients, respectively. The primary endpoint of major adverse cardiac events (MACE) at 6 months was 5.5% vs 2.2% (risk differences 3.2%, 95% CI -0.2 to 6.8, p=0.07) and at 2 years 12.9% vs 8.4% (HR 0.63, 95% CI 0.35 to 1.13, p = 0.12) after simple versus complex treatment. In the subgroup treated by newer generation drug-eluting stents, MACE was 12.0% vs 5.6% (HR 0.45, 95% CI 0.17 to 1.17, p = 0.10) after simple versus complex treatment.Conclusion: In the treatment of bifurcation lesions involving a large SB with ostial stenosis, routine two-stent techniques did not improve outcome significantly compared with treatment by the simpler main vessel stenting technique after 2 years.
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| 2. |
- Remouit, Flore, 1988-
(författare)
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Underwater Electrical Connections and Remotely Operated Vehicles
- 2016
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Remotely Operated Vehicles (ROVs) are underwater robots that perform different kind of operations, from observation to heavier tasks like drilling, carrying and pulling cables, etc. Those ROVs are costly and require skilled personal to operate it as well as equipment for transportation and deployment (boats, cranes, etc.).The division for electricity at Uppsala University, is developing a wave energy converter (WEC) concept. The concept is based on a point-absorbing buoy with a directly driven linear generator placed on the seabed. Several units are connected to a marine substation that is located on the seabed, whose role is to collect and smooth the power absorbed from the waves and then bring it to the shore through one single cable.Cable connection is a big challenge in the project because the WEC concept is small and many units are necessary to create a rentable farm. Nowadays this operation is performed by divers but using Observation Class ROV (OCROV) could be an interesting alternative since they are affordable at lower costs and easier to operate. Cable connection is however a heavy task and requires force that an OCROV does not have. It will need a docking system from which the vehicle will take its force. It would then go to the station, dock itself to this support plate, grab the cables and connect them together. This procedure cannot be done by the ROV operator because it requires accurate displacement and quick adjustment of the robot’s behavior.An autopilot was created in Matlab Simulink that consists of three units: the path following, the ROV, and the positioning unit. The first one uses the vehicle’s position and computes the speed and heading to be applied on the ROV in order to guide it on the desired path. The second one contains a controller that will adapt the thrust of each propeller to the force needed to reach the desired heading and speed from the path following unit. It also contains the model of the ROV that computes its position and speed. The last unit consists of a Kalman filter that estimates the ROV position and will be used in case of delay or failure in the communication with the positioning sensors.The autopilot model is used with a positioning system that utilizes green lasers and image processing. Two green lasers are used as fixed points in each camera picture and from their distance on the image, the actual distance between the ROV and the docking platform can be computed. In addition, optical odometry is used. The idea behind is to estimate how the ROV is behaving by evaluating the changes between two pictures of the camera. Those two systems, laser and odometry, work together in order to get more accurate results.The laser system has so far been tested in air. The distance measurements gave interesting results with an error inferior to 3%, and angle measurements gave less than 10% error for a distance of one meter. One advantage with the system is that it gets more accurate as the vehicle gets closer to the docking point.In addition to the ROV project, a review study was conducted on the variability of wave energy compared with other resources such as tidal, solar, and wind power. An analysis of the different tools and models that are used to forecast the power generation of those sources was done. There is a need for collaboration between the different areas because the future will aggregate those different sources to the grid and requires a unification of the models and methods.
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| 3. |
- Alzuhairi, Karam Sadoon, et al.
(författare)
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Sub-acute cardiac magnetic resonance to predict irreversible reduction in left ventricular ejection fraction after ST-segment elevation myocardial infarction : A DANAMI-3 sub-study
- 2020
-
Ingår i: International Journal of Cardiology. - : Elsevier BV. - 0167-5273. ; 301, s. 215-219
-
Tidskriftsartikel (refereegranskat)abstract
- Aims: To predict irreversible reduction in left ventricular ejection fraction (LVEF) during admission for ST-segment elevation myocardial infarction (STEMI) using cardiac magnetic resonance (CMR) in addition to classical clinical parameters. Irreversible reduction in LVEF is an important prognostic factor after STEMI which necessitates medical therapy and implantation of prophylactic implantable cardioverter defibrillator (ICD). Methods and results: A post-hoc analysis of DANAMI-3 trial program (Third DANish Study of Optimal Acute Treatment of Patients With ST-elevation Myocardial Infarction) which recruited 649 patients who had CMR performed during index hospitalization and after 3 months. Patients were divided into two groups according to CMR-LVEF at 3 months: Group 1 with LVEF≤35% and Group 2 with LVEF>35%. Group 1 included 15 patients (2.3%) while Group 2 included 634 patients (97.7%). A multivariate analysis showed that: Killip class >1 (OR 7.39; CI:1.47–36.21, P = 0.01), symptom onset-to-wire ≥6 h (OR 7.19; CI 1.07–50.91, P = 0.04), LVEF≤35% using index echocardiography (OR 7.11; CI: 1.27–47.43, P = 0.03), and infarct size ≥40% of LV on index CMR (OR 42.62; CI:7.83–328.29, P < 0.001) independently correlated with a final LVEF≤35%. Clinical models consisted of these parameters could identify 7 out of 15 patients in Group 1 with 100% positive predictive value. Conclusion: Together with other clinical measurements, the assessment of infarct size using late Gadolinium enhancement by CMR during hospitalization is a strong predictor of irreversible reduction in CMR_LVEF ≤35. That could potentially, after validation with future research, aids the selection and treatment of high-risk patients after STEMI, including implantation of prophylactic ICD during index hospitalization.
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| 4. |
- Ayob, Mohd Nasir, et al.
(författare)
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Small-Scale Renewable Energy Converters for Battery Charging
- 2018
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Ingår i: Journal of Marine Science and Engineering. - : MDPI. - 2077-1312. ; 6:1
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents two wave energy concepts for small-scale electricity generation. In the presented case, these concepts are installed on the buoy of a heaving, point-absorbing wave energy converter (WEC) for large scale electricity production. In the studied WEC, developed by Uppsala University, small-scale electricity generation in the buoy is needed to power a tidal compensating system designed to increase the performance of the WEC in areas with high tides. The two considered and modeled concepts are an oscillating water column (OWC) and a heaving point absorber. The results indicate that the OWC is too small for the task and does not produce enough energy. On the other hand, the results show that a hybrid system composed of a small heaving point absorber combined with a solar energy system would be able to provide a requested minimum power of around 37.7W on average year around. The WEC and solar panel complement each other, as the WEC produces enough energy by itself during wintertime (but not in the summer), while the solar panel produces enough energy in the summer (but not in the winter).
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| 5. |
- Boström, Cecilia, et al.
(författare)
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Design proposal of electrical system for linear generator wave power plants
- 2009
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Ingår i: 35TH ANNUAL CONFERENCE OF IEEE INDUSTRIAL ELECTRONICS. - : IEEE. - 9781424446483 - 9781424446506 ; , s. 4180-4185
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Konferensbidrag (refereegranskat)abstract
- This paper describes an electrical system layout for a wave power plant connecting linear generators to the grid. The electrical power out from the wave energy converters must be converted before they can be connected to the grid. The conversion is carried out in marine substations that will be placed on the seabed.The paper presents experimental power data from a wave energy converter that has been in operation at the Lysekil research site since March 2006. Moreover, results and analyses from experiments and simulations from tests with the generator connected to a rectifier and filter are presented. A simulation is made to show the difference between having the generator connected to a linear load and a nonlinear load, which would be the case when the generator is connected to the grid.
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| 6. |
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| 7. |
- Carlsbecker, Annelie, et al.
(författare)
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Molecular control of normal and acrocona mutant seed cone development in Norway spruce (Picea abies) and the evolution of conifer ovule-bearing organs
- 2013
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Ingår i: New Phytologist. - : Wiley. - 0028-646X .- 1469-8137. ; 200:1, s. 261-275
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Tidskriftsartikel (refereegranskat)abstract
- Reproductive organs in seed plants are morphologically divergent and their evolutionary history is often unclear. The mechanisms controlling their development have been extensively studied in angiosperms but are poorly understood in conifers and other gymnosperms. Here, we address the molecular control of seed cone development in Norway spruce, Picea abies. We present expression analyses of five novel MADS-box genes in comparison with previously identified MADS and LEAFY genes at distinct developmental stages. In addition, we have characterized the homeotic transformation from vegetative shoot to female cone and associated changes in regulatory gene expression patterns occurring in the acrocona mutant. The analyses identified genes active at the onset of ovuliferous and ovule development and identified expression patterns marking distinct domains of the ovuliferous scale. The reproductive transformation in acrocona involves the activation of all tested genes normally active in early cone development, except for an AGAMOUS-LIKE6/SEPALLATA (AGL6/SEP) homologue. This absence may be functionally associated with the nondeterminate development of the acrocona ovule-bearing scales. Our morphological and gene expression analyses give support to the hypothesis that the modern cone is a complex structure, and the ovuliferous scale the result of reductions and compactions of an ovule-bearing axillary short shoot in cones of Paleozoic conifers.
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| 8. |
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| 9. |
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| 10. |
- Crespo, Alejandro J., et al.
(författare)
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On the state-of-the-art of CFD simulations for wave energy converters within the open-source numerical framework of DualSPHysics
- 2023
-
Ingår i: Proceedings of the 15th European Wave and Tidal Energy Conference, Bilbao, 3-7 September 2023. - : European Wave and Tidal Energy Conference.
-
Konferensbidrag (refereegranskat)abstract
- There are currently several types of devices capable of harnessing wave energy, exploiting a broad variety of physical transformation processes. These devices – known as Wave Energy Converters (WECs) – are developed to maximize their power output. However, there are still uncertainties about their response and survivability to loads induced by adverse environmental conditions, with a consequent increase of the Levelized Cost of Energy (LCOE), which prevents in fact their commercial diffusion. As evidenced by a large body of research, marine renewable energy devices need to have more robust design practices. To address this issue, we propose the CFD-based DualSPHysics toolbox as a support in the design stages. DualSPHysics is high-fidelity software inherently suited to numerically address most challenges posed by multiphysics simulations, which are required to reliably predict WEC response in situations well beyond operational conditions. It should be noted that WECs, generally, may be connected to the seabed and comprise mechanical systems named Power Take-Offs (PTO) used to convert the energy from waves into electricity or other usable energies. To reproduce these features, DualSPHysics benefits from coupling with the multiphysics library Project Chrono and the dynamic mooring model Moordyn+. In this work, the augmented DualSPHysics framework is utilised to simulate a range of very different types of WECs with a variety of elements, such as catenary connections, taut mooring lines, or linear and nonlinear PTO actuators. Version 5.2 of the open-source licensed code was recently released, making the numerical framework publicly available as one unit. This work aims to provide a numerical review of past applications, and to demonstrate how the same open-source code is able to simulate very different technologies.Specifically, this paper proposes routine modeling and validation procedures using the SPH-based solver DualSPHysics applied to five different WEC types: i) a moored point absorber (PA); ii) an oscillating wave surge converter (OWSC); iii) a floating OWSC (so called FOSWEC); iv) a wave energy hyperbaric converter (WEHC); and v) a multi-body attenuator (so called Multi-float M4). For each device listed above, we provide validation proof against physical model data for various components of the floater(s) and PTO related quantities, performed under specific sea conditions that aim to challenge their survivability. Within the scope of this research, we present the WEC response with respect to the degrees of freedom that really matter for each of the floatings due to hydrodynamic interactions (i.e., heave, surge, and pitch), along with quantities more intimately connected to the anchoring systems (e.g., line tension) or the mechanical apparatus (e.g., end-stopper force). The quality of the results, the discussion built upon them and the demonstrated solver exploitability to a wide range of WECs show that one software model can run all cases using the exact same methodology, which is of great value for the marine energy R&D community. Finally, we discuss future research objectives, which include the implementation of automation to apply open control systems and possible applications to subsets of WEC farm arrays and other floating energy harnessing devices.
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| 11. |
- Danfors, Torsten, 1964-
(författare)
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11C Molecular Imaging in Focal Epilepsy
- 2012
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Epilepsy is a common neurological disease affecting 6 million people in Europe. Early prevention and accurate diagnosis and treatment are of importance to obtain seizure freedom. In this thesis new applications of carbon-11-labelled tracers in PET and autoradiographic studies were explored in focal epilepsy.Patients with low-grade gliomas often experience epileptic seizures. A retrospective PET-study assessing seizure activity, metabolic rate measured with 11C-methionine and other known prognostic factors was performed in patients with glioma. No correlation was found between seizure activity and uptake of methionine. The presence and termination of early seizures was a favourable prognostic factor.Activation of the neurokinin-1 (NK1) receptor by substance P (SP) induces epileptic activity. PET with the NK1 receptor antagonist GR205171 was performed in patients with temporal lobe epilepsy (TLE) and healthy controls. In TLE patients an increased NK1 receptor availability was found in both hemispheres, most pronounced in anterior cingulate gyrus ipsilateral to seizure onset. A positive correlation between NK1 receptors and seizure frequency was observed in ipsilateral medial structures consistent with an intrinsic network using the NK1-SP receptor system for transmission of seizure activity.The uptake of 18F-fluoro-deoxy-glucose (FDG) is related to cerebral blood flow (CBF). Previously, methods to estimate blood flow from dynamic PET data have been described. A retrospective study was conducted in 15 patients undergoing epilepsy surgery investigation, including PET with 11C-FDG and 11C-Flumazenil (FMZ). The dynamic FMZ dataset and pharmacokinetic modeling with a multilinear reference tissue model were used to determine images of relative CBF. Agreement between data of FDG and CBF was analyzed showing a close association between interictal brain metabolism and relative CBF.Epilepsy often occurs after traumatic brain injuries. Changes in glia and inhibitory neuronal cells contribute to the chain of events leading to seizures. Autoradiography with 11C-PK11195, 11C-L-deprenyl and 11C-Flumazenil in an animal model of posttraumatic epilepsy studied the temporal and spatial distribution of microglia, astrocytes and GABAergic neurons. Results showed an instant increase in microglial activity that subsequently normalized, a late formation of astrogliosis and an instant and prolonged decease in GABA binding. The model can be used to visualize pathophysiological events during the epileptogenesis.
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| 12. |
- Ekberg, Tomas, et al.
(författare)
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Clinical impact of positron emission tomography (PET) with (18F)fluorodeoxyglucose (FDG) in head and neck tumours
- 2007
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Ingår i: Acta Oto-Laryngologica. - : Informa UK Limited. - 0001-6489 .- 1651-2251. ; 127:2, s. 186-193
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Tidskriftsartikel (refereegranskat)abstract
- Conclusion. PET plays an important role in staging, on suspicion of recurrence and for detection of occult primary tumours in the head and neck. Objective: Since 1998 we have used positron emission tomography (PET) with (F-18)fluorodeoxyglucose (FDG) to assess selected patients. This procedure has often helped in making decisions on staging and treatment. Patients and methods. The case records of the first 80 patients (104 PET examinations) were studied retrospectively. Results. A total of 39 examinations were performed for staging. PET detected all primary tumours except two (stage T1), and staging was adjusted after 13%. In all, 33 PET examinations were performed on suspicion of recurrent tumour. In 52% of these PET determined further treatments; in 21% PET had a direct impact on the surgical planning. In 18 patients with metastases from an occult primary tumour, PET detected 39% of those tumours; in 22% it was the sole modality to do so. No recurrences or second primary tumours were detected when PET was used for follow-up of clinically cured patients. Results were similar when squamous cell carcinomas (SCCs) were considered alone as compared to the complete material. The mean standardized uptake value (SUV) was higher for cases deemed tumour-positive than in negative cases.
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| 13. |
- Engström, Jens, et al.
(författare)
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A resonant Two Body System for a point absorbing Wave Energy Converter with direct-driven linear generator
- 2011
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 110:12, s. 124904-
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Tidskriftsartikel (refereegranskat)abstract
- Based on an earlier conceptual model of a two body system point absorbing wave energy converter tuned to resonance in Swedish west coast sea states, an extended coupled hydrodynamic, mechanic, and electromagnetic model has been developed. The hydrodynamic characteristics of the two body system are studied in the frequency and time domain, while its response to real Swedish west coast sea states are studied in the time domain, by using a wave energy converter model with two independently moving bodies connected to a direct driven linear generator with non-linear damping. The two body system wave energy converter gives nearly 80% power capture ratio in irregular waves. The resonant behaviour is shown to be sensitive to the shape of the spectrum, and the distance between the two bodies is shown to have a large effect on the power absorption.
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| 14. |
- Engström, Jens, et al.
(författare)
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Buoy geometry and its influence on survivability for apoint absorbing wave energy converter : Scaleexperiment and CFD simulations
- 2017
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Konferensbidrag (refereegranskat)abstract
- For wave energy to be an economically viable energysource, the technology has to withstand power levelsduring storms that can be close to 50 times higher thanduring normal operating conditions, and withstandmany years of wear. The impact of high wave loads isstudied not only within the field of wave energy, buthas long been a subject of study for ships, platformsand other offshore structures.To model the force on the device under extreme and/orovertopping waves is a difficult task. Experiments areexpensive and difficult to implement, and numerical meth-ods are either very computationally demanding CFD-methods, or less accurate approximative methods. Inaddition, the performance and experienced forces during extreme waves are model dependent, and differentoffshore structures must be studied independently.Here, a 1:20 scale model of the Uppsala Universitypoint-absorber type wave energy converter (WEC) has been tested in extreme wave conditions at the COASTLaboratory Ocean Basin at Plymouth University. The WEC consists of a linear generator connected to a buoyat the sea surface, and performance of two differentbuoys is studied: a cylinder and cylinder with moon-pool. Two types of wave sets have been used: focusedwaves embedded into regular waves, and irregular waves. The focus of this paperis on comparing the performance of the two buoys, and on analysing the experimental data using a numerical model. A fully non-linear computational fluid dynamics(CFD) model based on OpenFOAM is presented and validated.
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| 15. |
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| 16. |
- Engström, Jens, et al.
(författare)
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Energy absorption from parks of point-absorbing wave energy converters in the Swedish exclusive economic zone
- 2020
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Ingår i: Energy Science & Engineering. - : John Wiley & Sons. - 2050-0505. ; 8:1, s. 38-49
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Tidskriftsartikel (refereegranskat)abstract
- In a future energy system based on renewable energy sources, wave energy will most likely play a role due to its high energy potential and low intermittency. The power production from parks of wave energy converters of point absorber type has been extensively studied. This is also the case for the wave energy resource at many coastal areas around the globe. Wave energy has not yet reached a commercial level, and a large variety of technologies exist; therefore, an established method to calculate the technical potential for wave energy has still not been established. To estimate the technical potential of wave energy conversion, some approximations inevitably need to be taken due to the systems high complexity. In this study, a detailed mapping of the wave climate and simulation of large arrays of hydrodynamically cross‐coupled wave energy converters are combined to calculate the technical potential for wave energy conversion in the Swedish exclusive economic zone. A 16‐year wave data set distributed in a 1.1 km × 1.1 km grid is used to calculate the absorbed energy from a park of 200 generic point absorbers. The areas with best potential have an average annual energy absorption of 16 GWh for the selected wave energy park adapted to 1 km2 when using a constant damping, while the theoretical upper bound is 63 GWh for the same area.
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| 17. |
- Engström, Jens
(författare)
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Hydrodynamic Modeling of the Energy Conversion from Ocean Waves to Electricity
- 2009
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Research within wave energy conversion has seen a large increase during the last years. Several concepts are now taking the final steps towards commercialization. Conversion from wave energy for grid connection is a multi disciplinary task involving many challenges; one being the fact that the device has to be dimensioned for a nominal power and still be able to withstand the extreme powers in some of the harshest conditions on earth. The research and development of a concept based on a point absorber converting wave energy to a direct driven linear generator were initiated in 2002 at Uppsala University. Theoretical simulations have now been compared to offshore full scale experiments at the research test site. This thesis focuses on the hydrodynamic wave/device interaction for a Wave Energy Converter subjected to Swedish west coast wave climate. First conclusions on the Wave Energy Converters dynamics and energy absorption have been drawn based on earlier results. A thorough study of the sea state of Skagerrak and Kattegat has been made to asses the potential and get design parameters for the Wave Energy Converter. Based on that, a Wave Energy Converter model using potential linear wave theory and with the generator as a linear damper, has been developed to simulate the dynamics and power capture ratio. The model has also been used to simulate how biomass accumulated on the buoy will affect the dynamics. As a next step, the model has been further developed to simulate a two component system having optimum amplitude response at frequencies coinciding with Swedish west coast conditions. Results are presented for time series of real ocean wave data collected at the research test site as well as for empirical spectra. An enhanced amplitude response for the two component system is achieved by adding supplementary inertia by use of the added mass from a submerged body. Simulations show that the increased velocity in the two component system gives an increased power capture ratio by a factor of two compared to the regular system of a point absorber. The increased velocity also leads to a decrease in optimal damping for energy absorption with 60 %. The main weakness of the hydrodynamical modeling is thought to be the neglected viscosity that might lead to unpredicted energy losses, pointing out the direction for improvement and future work.
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| 18. |
- Engström, Jens, 1977-
(författare)
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Hydrodynamic Modelling for a Point Absorbing Wave Energy Converter
- 2011
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Surface gravity waves in the world’s oceans contain a renewable source of free power on the order of terawatts that has to this date not been commercially utilized. The division of Electricity at Uppsala University is developing a technology to harvest this energy. The technology is a point absorber type wave energy converter based on a direct-driven linear generator placed on the sea bed connected via a line to a buoy on the surface. The work in this thesis is focused mainly on the energy transport of ocean waves and on increasing the transfer of energy from the waves to the generator and load. Potential linear wave theory is used to describe the ocean waves and to derive the hydrodynamic forces that are exerted on the buoy. Expressions for the energy transport in polychromatic waves travelling over waters of finite depth are derived and extracted from measured time series of wave elevation collected at the Lysekil test site. The results are compared to existing solutions that uses the simpler deep water approximation. A Two-Body system wave energy converter model tuned to resonance in Swedish west coast sea states is developed based on the Lysekil project concept. The first indicative results are derived by using a linear resistive load. The concept is further extended by a coupled hydrodynamic and electromagnetic model with two more realistic non-linear load conditions. Results show that the use of the deep water approximation gives a too low energy transport in the time averaged as well as in the total instantaneous energy transport. Around the resonance frequency, a Two-Body System gives a power capture ratio of up to 80 percent. For more energetic sea states the power capture ratio decreases rapidly, indicating a smoother power output. The currents in the generator when using the Two-Body system is shown to be more evenly distributed compared to the conventional system, indicating a better utilization of the electrical equipment. Although the resonant nature of the system makes it sensitive to the shape of the wave spectrum, results indicate a threefold increase in annual power production compared to the conventional system.
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| 19. |
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| 20. |
- Engström, Jens, et al.
(författare)
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Offshore Measurements and Numerical Validation of the Mooring Forces on a 1:5 Scale Buoy
- 2023
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Ingår i: Journal of Marine Science and Engineering. - : MDPI. - 2077-1312. ; 11:1
-
Tidskriftsartikel (refereegranskat)abstract
- Wave energy conversion is a renewable energy technology with a promising potential. Although it has been developed for more than 200 years, the technology is still far from mature. The survivability in extreme weather conditions is a key parameter halting its development. We present here results from two weeks of measurement with a force measurement buoy deployed at Uppsala University’s test site for wave energy research at the west coast of Sweden. The collected data have been used to investigate the reliability for two typical numerical wave energy converter models: one low fidelity model based on linear wave theory and one high fidelity Reynolds-Averaged Navier–Stokes model. The line force data is also analysed by extreme value theory using the peak-over-threshold method to study the statistical distribution of extreme forces and to predict the return period. The high fidelity model shows rather good agreement for the smaller waves, but overestimates the forces for larger waves, which can be attributed to uncertainties related to field measurements and numerical modelling uncertainties. The peak-over-threshold method gives a rather satisfying result for this data set. A significant deviation is observed in the measured force for sea states with the same significant wave height. This indicates that it will be difficult to calculate the force based on the significant wave height only, which points out the importance of more offshore experiments. © 2023 by the authors.
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| 21. |
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| 22. |
- Engström, Jens, et al.
(författare)
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Performance of large arrays of point absorbing direct-driven wave energy converters
- 2013
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 114:20, s. 204502-
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Tidskriftsartikel (refereegranskat)abstract
- Future commercial installation of wave energy plants using point absorber technology will require clusters of tens up to several hundred devices, in order to reach a viable electricity production. Interconnected devices also serve the purpose of power smoothing, which is especially important for devices using direct-driven power take off. The scope of this paper is to evaluate a method to optimize wave energy farms in terms of power production, economic viability and resources. In particular, the paper deals with the power variation in a large array of point-absorbing direct-driven wave energy converters, and the smoothing effect due to the number of devices and their hydrodynamic interactions. A few array geometries are compared and 34 sea states measured at the Lysekil research site at the Swedish west coast are used in the simulations. Potential linear flow theory are used with full hydrodynamic interactions between the buoys. It is shown that the variance in power production depends crucially on the geometry of the array and the number of interacting devices, but not significantly on the energy period of the waves.
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| 23. |
- Engström, Jens, et al.
(författare)
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Properties of the Energy Transport for Plane-Parallel Polychromatic Surface Gravity Waves in Waters of Arbitrary Depth
- 2015
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Ingår i: IEEE Journal of Oceanic Engineering. - 0364-9059 .- 1558-1691. ; 40:2, s. 408-416
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Tidskriftsartikel (refereegranskat)abstract
- It is well known that the energy transport of ocean waves propagates with the group velocity and that the energy decreases exponentially with depth. Expanding this theory, we will derive expressions for the energy transport as a function of depth and the total instantaneous transport's development over time for waves in waters of finite depth. Solutions to the Laplace equation are found for plane-parallel polychromatic waves with linearized boundary conditions. A time series of wave elevation collected at Uppsala University's wave energy research test site is chosen to present the results. Solutions for waters of both infinite and arbitrary depths are presented and compared. The solutions are convolution-type integrals with the wave elevation where we have found efficient ways to calculate the kernels. The difference in group velocity between finite depth and infinite depth and its impact on the energy transport is clearly seen in the results. The use of the deep-water approximation gives a too low energy transport in the time averaged as well as in the total instantaneous energy transport. We further show that the total instantaneous energy transport can actually have a direction that is opposite to the direction of the waves as observed from a reference frame fixed to the seabed.
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| 24. |
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| 25. |
- Engström, Jens, et al.
(författare)
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Total instantaneous energy transport in polychromatic fluid gravity waves at finite depth
- 2012
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Ingår i: Journal of Renewable and Sustainable Energy. - : AIP Publishing. - 1941-7012. ; 4:3, s. 033108-1-033108-8
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Tidskriftsartikel (refereegranskat)abstract
- The total instantaneous energy transport can be found for polychromatic waves when using the deep water approximation. Expanding this theory to waves in waters of finite depth, we derive an expression for the total instantaneous energy transport for polychromatic fluid gravity waves based on potential theory with linearized free surface boundary conditions. We present the results for time series of wave elevation measured at the Uppsala University wave energy research test site. We show that a significant proportion of the total instantaneous energy transport is not accounted for when using the deep water theory. This is important since many wave energy conversion devices under development will operate in waters that do not fulfil the deep water criteria.
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| 26. |
- Engström, Jens, et al.
(författare)
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Wave energy converter with enhanced amplitude response at frequencies coinciding with Swedish west coast sea states by use of a supplementary submerged body
- 2009
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Ingår i: Journal of Applied Physics. - USA : American Institute of Physics. - 0021-8979 .- 1089-7550. ; 106:6
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Tidskriftsartikel (refereegranskat)abstract
- The full-scale direct-driven wave energy converter developed at Uppsala University has been in offshore operation at the Swedish west coast since 2006. Earlier simulations have now been validated by full-scale experiment with good agreement. Based on that, a theoretical model for a passive system having optimum amplitude response at frequencies coinciding with Swedish west coast conditions has been developed. The amplitude response is increased by adding supplementary inertia by use of the additional mass from a submerged body. A sphere with neutral buoyancy is chosen as the submerged body and modeled as being below the motion of the waves. The model is based on potential linear wave theory and the power capture ratio is studied for real ocean wave data collected at the research test site. It is found that the power capture ratio for the two body system can be increased from 30% to 60% compared to a single body system. Increased velocity in the system also decreases the value for optimal load damping from the generator, opening up the possibility to design smaller units.
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| 27. |
- Engström, Märet, et al.
(författare)
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Elfiskerapport
- 2012
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Mellan år 2006 och 2009 elfiskades totalt 197 lokaler. Huvuddelen av dessa ingick ilänsstyrelsens program för kalkeffektuppföljning och biologisk återställning.En mindre del utgjordes av elfisken i okalkade vattendrag. År 2006 fiskades 10 okalkadelokaler, 2007 2 lokaler, 2008 8 lokaler, och slutligen 2009 7 lokaler, där 4 lokaler tillkom föratt undersöka förutsättningar för eventuell framtida kalkning i Halån. Då några av de okalkadelokalerna återkommit under åren, är antalet okalkade lokaler 19 st.Merparten av de 197 lokalerna har fiskats vartannat år, flera gånger tidigare. Undersökninghar sin tonvikt lagd på skyddsvärda bestånd av öring, lax och flodkräfta.Det tycks inte finnas någon generell trend över hela länet att fångsterna ökat eller minskatunder de år elfiskena utförts men medelfångsten är högre under 2000 –talet än under 1990-talet.Produktionen av laxfisk påverkas stort av flödena under året. Vissa undersökningar tyder påatt nyproduktionen av laxfisk blir lägre året efter låga höstflöden pga. av att fisken haftsvårare att vandra upp till sina lekplatser. Fångsterna blir också lägre om man tvingas fiskavid höga vattenflöden.En trendanalys med hjälp av regression visar att trenden är positiv (dvs. en ihållande ökningav öringtätheten) i 77 lokaler och negativ i 81. I resten av lokalerna kan ingen analys göras dåde är fiskade mindre än 3 gånger. En statistisk analys, där man använder ett R2-värde medgräns >=0,5 (dvs. en förklaringsgrad där åtminstone 50% av variationen inte är slumpmässig)blir dock trenderna signifikant positiva i endast 17 lokaler och signifikant negativa i 13lokaler. I kvarvarande 39 lokaler kan ingen analys göras, då de antingen inte fiskats 3 gånger,eller att ingen fisk fångats.Trendanalysen fångar dock inte upp snabba, stora förändringar i populationstätheter, då detinte blir signifikant med mycket låga fångster ett antal år, men en ökning på kanske flerahundra procent det sista året. I sådana fall hänvisas till kommentarer för just det enskildavattendraget/lokalen.I täthetsbedömingar av öringbestånden med hjälp av jämförelsevärden från det nationellaelfiskeregistret och det senast utförda elfisket är antalet lokaler som anses ha låga tätheter 93st, normala tätheter 98 st och höga tätheter 6.
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| 28. |
- Engström-Ruud, Linda, et al.
(författare)
-
Activation of GFRAL+ neurons induces hypothermia and glucoregulatory responses associated with nausea and torpor.
- 2024
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Ingår i: Cell reports. - 2211-1247. ; 43:4
-
Tidskriftsartikel (refereegranskat)abstract
- GFRAL-expressing neurons actuate aversion and nausea, are targets for obesity treatment, and may mediate metformin effects by long-term GDF15-GFRAL agonism. Whether GFRAL+ neurons acutely regulate glucose and energy homeostasis is, however, underexplored. Here, we report that cell-specific activation of GFRAL+ neurons using a variety of techniques causes a torpor-like state, including hypothermia, the release of stress hormones, a shift from glucose to lipid oxidation, and impaired insulin sensitivity, glucose tolerance, and skeletal muscle glucose uptake but augmented glucose uptake in visceral fat. Metabolomic analysis of blood and transcriptomics of muscle and fat indicate alterations in ketogenesis, insulin signaling, adipose tissue differentiation and mitogenesis, and energy fluxes. Our findings indicate that acute GFRAL+ neuron activation induces endocrine and gluco- and thermoregulatory responses associated with nausea and torpor. While chronic activation of GFRAL signaling promotes weight loss in obesity, these results show that acute activation of GFRAL+ neurons causes hypothermia and hyperglycemia.
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| 29. |
- Engstrøm, Thomas, et al.
(författare)
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Danegaptide for primary percutaneous coronary intervention in acute myocardial infarction patients : A phase 2 randomised clinical trial
- 2018
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Ingår i: Heart. - : BMJ. - 1355-6037 .- 1468-201X. ; 104:19, s. 1593-1599
-
Tidskriftsartikel (refereegranskat)abstract
- Objectives: Reperfusion immediately after reopening of the infarct-related artery in ST-segment elevation myocardial infarction (STEMI) may cause myocardial damage in addition to the ischaemic insult (reperfusion injury). The gap junction modulating peptide danegaptide has in animal models reduced this injury. We evaluated the effect of danegaptide on myocardial salvage in patients with STEMI. Methods: In addition to primary percutaneous coronary intervention in STEMI patients with thrombolysis in myocardial infarction flow 0-1, single vessel disease and ischaemia time less than 6 hours, we tested, in a clinical proof-of-concept study, the therapeutic potential of danegaptide at two-dose levels. Primary outcome was myocardial salvage evaluated by cardiac MRI after 3 months. Results: From November 2013 to August 2015, a total of 585 patients were randomly enrolled in the trial. Imaging criteria were fulfilled for 79 (high dose), 80 (low dose) and 84 (placebo) patients eligible for the per-protocol analysis. Danegaptide did not affect the myocardial salvage index (danegaptide high (63.9±14.9), danegaptide low (65.6±15.6) and control (66.7±11.7), P=0.40), final infarct size (danegaptide high (19.6±11.4 g), danegaptide low (18.6±9.6 g) and control (21.4±15.0 g), P=0.88) or left ventricular ejection fraction (danegaptide high (53.9%±9.5%), danegaptide low (52.7%±10.3%) and control (52.1%±10.9%), P=0.64). There was no difference between groups with regard to clinical outcome. Conclusions: Administration of danegaptide to patients with STEMI did not improve myocardial salvage. Trial registration number: NCT01977755; Pre-results.
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| 30. |
- Francisco, Francisco, 1985-, et al.
(författare)
-
Wave Power as Solution for Off-Grid Water Desalination Systems : Resource Characterization for Kilifi-Kenya
- 2018
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Ingår i: Energies. - : MDPI. - 1996-1073. ; 11:4
-
Tidskriftsartikel (refereegranskat)abstract
- Freshwater scarcity is one of humanity's reoccurring problems that hamper socio-economic development in many regions across the globe. In coastal areas, seawater can be desalinated through reverse osmosis (RO) and transformed into freshwater for human use. Desalination requires large amounts of energy, mostly in the form of a reliable electricity supply, which in many cases is supplied by diesel generators. The objective of this work is to analyze the wave power resource availability in Kilifi-Kenya and evaluate the possible use of wave power converter (WEC) to power desalination plants. A particular focus is given use of WECs developed by Uppsala University (UU-WEC). The results here presented were achieved using reanalysis-wave data revealed that the local wave climate has an approximate annual mean of 7 kW/m and mode of 5 kW/m. Significant wave height and wave mean period are within 0.8-2 m and 7-8 s respectively, with a predominant wave mean direction from southeast. The seasonal cycle appeared to be the most relevant for energy conversion, having the highest difference of 6 kW/m, in which April is the lowest (3.8 kW/m) and August is the peak (10.5 kW/m). In such mild wave climates, the UU-WEC and similar devices can be suitable for ocean energy harvesting for water desalination systems. Technically, with a capacity factor of 30% and energy consumption of 3 kWh/m(3), a coastal community of about five thousand inhabitants can be provided of freshwater by only ten WECs with installed capacity of 20 kW.
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| 31. |
- Giannini, Gianmaria, et al.
(författare)
-
Wave Energy Converter Power Take-Off System Scaling and Physical Modelling
- 2020
-
Ingår i: Journal of Marine Science and Engineering. - : MDPI. - 2077-1312. ; 8:9
-
Tidskriftsartikel (refereegranskat)abstract
- Absorbing wave power from oceans for producing a usable form of energy represents an attractive challenge, which for the most part concerns the development and integration, in a wave energy device, of a reliable, efficient and cost-effective power take-off mechanism. During the various stages of progress, for assessing a wave energy device, it is convenient to carry out experimental testing that, opportunely, takes into account the realistic behaviour of the power take-off mechanism at a small scale. To successfully replicate and assess the power take-off, good practices need to be implemented aiming to correctly scale and evaluate the power take-off mechanism and its behaviour. The present paper aims to explore and propose solutions that can be applied for reproducing and assessing the power take-off element during experimental studies, namely experimental set-ups enhancements, calibration practices, and error estimation methods. A series of recommendations on how to practically organize and carry out experiments were identified and three case studies are briefly covered. It was found that, despite specific options that can be strictly technology-dependent, various recommendations could be universally applicable.
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| 32. |
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| 33. |
- Giassi, Marianna, et al.
(författare)
-
Capturing the experimental behaviour of a point-absorber WEC by simplified numerical models
- 2020
-
Ingår i: Journal of Fluids and Structures. - : Elsevier BV. - 0889-9746 .- 1095-8622. ; 99
-
Tidskriftsartikel (refereegranskat)abstract
- The paper presents a wave basin experiment of a direct-driven point-absorber wave energy converter moving in six degrees of freedom. The goal of the work is to study the dynamics and energy absorption of the wave energy converter, and to verify under which conditions numerical models restricted to heave can capture the behaviour of a point-absorber moving in six degrees of freedom. Several regular and irregular long-crested waves and different damping values of the power take-off system have been tested. We collected data in terms of power output, device motion in six degrees of freedom and wave elevation at different points of the wave basin. A single-body numerical model in the frequency domain and a two-body model in the time domain are used in the study. Motion instabilities due to parametric resonance observed during the experiments are discussed and analysis of the buoy motion in terms of the Mathieu instability is also presented. Our results show that the simplified models can reproduce the body dynamics of the studied converter as long as the transverse non-linear instabilities are not excited, which typically is the case in irregular waves. The performance of the more complex time domain model is able to reproduce both the buoy and PTO dynamics, while the simpler frequency domain model can only reproduce the PTO dynamics for specific cases. Finally, we show that the two-body dynamics of the studied wave energy converter affects the power absorption significantly, and that common assumptions in the numerical models, such as stiff mooring line or that the float moves only in heave, may lead to incorrect predictions for certain sea states.
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| 34. |
- Giassi, Marianna, et al.
(författare)
-
Comparison of wave energy park layouts by experimental and numerical methods
- 2020
-
Ingår i: Journal of Marine Science and Engineering. - : MDPI AG. - 2077-1312. ; 8:10
-
Tidskriftsartikel (refereegranskat)abstract
- An experimental campaign of arrays with direct-driven wave energy converters of point-absorbing type is presented. The arrays consist of six identical floats, moving in six degrees of freedom, and six rotating power take-off systems, based on the design developed at Uppsala University. The goals of the work were to study and compare the performances of three different array layouts under several regular and irregular long-crested waves, and in addition, to determine whether the numerical predictions of the best performing array layouts were confirmed by experimental data. The simulations were executed with a frequency domain model restricted to heave, which is a computationally fast approach that was merged into a genetic algorithm optimization routine and used to find optimal array configurations. The results show that good agreement between experiments and simulations is achieved when the test conditions do not induce phenomena of parametric resonance, slack line and wave breaking. Specific non-linear dynamics or extensive sway motion are not captured by the used model, and in such cases the simulation predictions are not accurate, but can nevertheless be used to get an estimate of the power output.
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| 35. |
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| 36. |
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| 37. |
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| 38. |
- Gravråkmo, Halvar, et al.
(författare)
-
Toroidal Buoy for Point Absorver WEC with Focus on Added Mass and Overloads
-
Tidskriftsartikel (refereegranskat)abstract
- In order for a wave energy converter (WEC) to produce electricity at competitive prices, the generator must not be over dimensioned in order to save money on production, transport and installation, but the WEC, in this case a point absorber, must also be dimensioned to withstand harsh sea states. High added mass will in some cases create severe inertia forces on the generator and might shorten the service life of the system. The magnitude of the overload forces can be reduced by choosing a buoy geometry with small added mass. Measurements of snap loads produced by a toroidal buoy and calculations of buoy intertia forces causing overloads on a generator with a toroidal buoy and an equal generator with a cylindrical buoy are investigated in order to compare the two shapes numerically. A toroidal buoy was found to have less added mass than a vertical cylindrical buoy with similar excitation force, which caused reduced overloads at short wave periods, thus reducing the overloads on the generator. Snap loads were found to not cause much greater loads than other forces found during operation.
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| 39. |
- Göteman, Malin, 1980-, et al.
(författare)
-
Advances and Challenges in Wave Energy Park Optimization : A Review
- 2020
-
Ingår i: Frontiers in Energy Research. - : Frontiers Media SA. - 2296-598X. ; 8
-
Forskningsöversikt (refereegranskat)abstract
- A commercial wave energy system will typically consist of many interacting wave energy converters installed in a park. The performance of the park depends on many parameters such as array layout and number of devices, and may be evaluated based on different measures such as energy absorption, electricity quality, or cost of the produced electricity. As wave energy is currently at the stage where several large-scale installations are being planned, optimizing the park performance is an active research area, with many important contributions in the past few years. Here, this research is reviewed, with a focus on identifying the current state of the art, analyzing how realistic, reliable, and relevant the methods and the results are, and outlining directions for future research.
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| 40. |
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| 41. |
- Göteman, Malin, 1980-, et al.
(författare)
-
Arrays of Point-Absorbing Wave Energy Converters in Short-Crested Irregular Waves
- 2018
-
Ingår i: Energies. - : MDPI AG. - 1996-1073. ; 11:4
-
Tidskriftsartikel (refereegranskat)abstract
- For most wave energy technology concepts, large-scale electricity production and cost-efficiency require that the devices are installed together in parks. The hydrodynamical interactions between the devices will affect the total performance of the park, and the optimization of the park layout and other park design parameters is a topic of active research. Most studies have considered wave energy parks in long-crested, unidirectional waves. However, real ocean waves can be short-crested, with waves propagating simultaneously in several directions, and some studies have indicated that the wave energy park performance might change in short-crested waves. Here, theory for short-crested waves is integrated in an analytical multiple scattering method, and used to evaluate wave energy park performance in irregular, short-crested waves with different number of wave directions and directional spreading parameters. The results show that the energy absorption is comparable to the situation in long-crested waves, but that the power fluctuations are significantly lower.
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| 42. |
- Göteman, Malin, 1980-, et al.
(författare)
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Fast modeling of large wave energy farms using interaction distance cut-off
- 2015
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Ingår i: Energies. - : MDPI AG. - 1996-1073. ; 8:12, s. 13741-13757
-
Tidskriftsartikel (refereegranskat)abstract
- In many wave energy concepts, power output in the MW range requires the simultaneous operation of many wave energy converters. In particular, this is true for small point-absorbers, where a wave energy farm may contain several hundred devices. The total performance of the farm is affected by the hydrodynamic interactions between the individual devices, and reliable tools that can model full farms are needed to study power output and find optimal design parameters. This paper presents a novel method to model the hydrodynamic interactions and power output of very large wave energy farms. The method is based on analytical multiple scattering theory and uses time series of irregular wave amplitudes to compute the instantaneous power of each device. An interaction distance cut-off is introduced to improve the computational cost with acceptable accuracy. As an application of the method, wave energy farms with over 100 devices are studied in the MW range using one month of wave data measured at an off-shore site.
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| 43. |
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| 44. |
- Göteman, Malin, 1980-, et al.
(författare)
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Methods of reducing power fluctuations in wave energy parks
- 2014
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Ingår i: Journal of Renewable and Sustainable Energy. - : AIP Publishing. - 1941-7012. ; 6, s. 043103-
-
Tidskriftsartikel (refereegranskat)abstract
- One of the major challenges in constructing effective and economically viable wave energy parks is to reduce the large fluctuations in power output. In this paper, we study different methods of reducing the fluctuations and improve the output power quality. The parameters studied include the number of devices, the separating distance between units, the global and local geometries of the array, sea state and incoming wave direction, and the impact of including buoys of different radii in an array. Our results show that, e. g., the fluctuations as well as power per device decrease strictly with the number of interacting units, when the separating distance is kept constant. However, including more devices in a park with fixed area will not necessarily result in lowered power fluctuations. We also show that varying the distance between units affects the power fluctuations to a much larger extent than it affects the magnitude of the absorbed power. The fluctuations are slightly lower in more realistic, randomized geometries where the buoys tend to drift slightly off their mean positions, and significantly lower in semi-circular geometries as opposed to rectangular geometries.
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| 45. |
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| 46. |
- Göteman, Malin, 1980-, et al.
(författare)
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Optimizing wave energy parks with over 1000 interacting point-absorbers using an approximate analytical method
- 2015
-
Ingår i: International Journal of Marine Energy. - : Elsevier BV. - 2214-1669. ; 10, s. 113-126
-
Tidskriftsartikel (refereegranskat)abstract
- Large arrays of wave energy converters of point-absorber type are studied using an approximate analytical model. The model is validated against a numerical method that takes into account full hydrodynamic interactions based on linear potential flow theory. The low computational cost of the analytical model enables parameter studies of parks in the MW range and includes up to over 1000 interacting devices. The model is actuated by irregular wave data obtained at the Swedish west coast. In particular, focus is on comparing park geometries and improving park configurations to minimize the power fluctuations.
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| 47. |
- Göteman, Malin, 1980-, et al.
(författare)
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Resilience of wave energy farms using metocean dependent failure rates and repair operations
- 2023
-
Ingår i: Ocean Engineering. - : Elsevier. - 0029-8018 .- 1873-5258. ; 280
-
Tidskriftsartikel (refereegranskat)abstract
- Emerging offshore renewable energy technologies are expected to become an important part of the futureenergy system, and reliability for these new technologies in different metocean scenarios must be guaranteed.This poses a challenge in extreme weather scenarios like storms, in particular for less mature technologiessuch as wave energy. Not only the offshore survivability must be controlled; the restoration after disruptiveevents and failures should be addressed and optimized. Offshore operations are costly and cannot be carriedout if the weather is too harsh, and the resulting downtime after failures may be financially devastating forprojects. In this paper, the resilience of large wave energy systems is studied with respect to wave conditions,metocean dependent failure rates, and weather windows available for offshore repair operations. A metocean-and time-dependent failure rate is derived based on a Weibull distribution, which is a novelty of the paper.The performance of the farm is assessed using the varying failure rates and metocean data at different offshoresites. Critical metocean thresholds for different offshore vessels are considered, and the resilience is quantifiedusing relevant measures such as unavailability and expected energy not supplied. The resilience analysis iscoupled to an economic assessment of the wave farm and different repair strategies. Our results show thatthe commonly used assumption of constant failure rates is seen to overestimate the annual energy productionthan when a more realistic varying failure rate is used. Two offshore sites are compared, and the availabilityis found to be higher at the calmer site. Most of the evaluated repair strategies cannot be considered to beeconomically justified, when compared to the cost of the energy not supplied.
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| 48. |
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| 49. |
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| 50. |
- Haraldsson, André, et al.
(författare)
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A Helical tomotherapy as a robust low-dose treatment alternative for total skin irradiation
- 2019
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Ingår i: Journal of Applied Clinical Medical Physics. - : Wiley. - 1526-9914. ; 20:5, s. 44-54
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Tidskriftsartikel (refereegranskat)abstract
- Mycosis fungoides is a disease with manifestation of the skin that has traditionally been treated with electron therapy. In this paper, we present a method of treating the entire skin with megavoltage photons using helical tomotherapy (HT), verified through a phantom study and clinical dosimetric data from our first two treated patients. A whole body phantom was fitted with a wetsuit as bolus, and scanned with computer tomography. We accounted for variations in daily setup using virtual bolus in the treatment plan optimization. Positioning robustness was tested by moving the phantom, and recalculating the dose at different positions. Patient treatments were verified with in vivo film dosimetry and dose reconstruction from daily imaging. Reconstruction of the actual delivered dose to the patients showed similar target dose as the robustness test of the phantom shifted 10 mm in all directions, indicating an appropriate approximation of the anticipated setup variation. In vivo film measurements agreed well with the calculated dose confirming the choice of both virtual and physical bolus parameters. Despite the complexity of the treatment, HT was shown to be a robust and feasible technique for total skin irradiation. We believe that this technique can provide a viable option for Tomotherapy centers without electron beam capability.
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