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- 2019
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Tidskriftsartikel (refereegranskat)
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| 2. |
- Allison, Robert S., et al.
(författare)
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Perspectives on the definition of visually lossless quality for mobile and large format displays
- 2018
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Ingår i: Journal of Electronic Imaging (JEI). - 1017-9909 .- 1560-229X. ; 27:5, s. 1-23
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Tidskriftsartikel (refereegranskat)abstract
- Advances in imaging and display engineering have given rise to new and improved image and videoapplications that aim to maximize visual quality under given resource constraints (e.g., power, bandwidth).Because the human visual system is an imperfect sensor, the images/videos can be represented in a mathematicallylossy fashion but with enough fidelity that the losses are visually imperceptible—commonly termed“visually lossless.” Although a great deal of research has focused on gaining a better understanding ofthe limits of human vision when viewing natural images/video, a universally or even largely accepted definitionof visually lossless remains elusive. Differences in testing methodologies, research objectives, and targetapplications have led to multiple ad-hoc definitions that are often difficult to compare to or otherwise employ inother settings. We present a compendium of technical experiments relating to both vision science and visualquality testing that together explore the research and business perspectives of visually lossless image quality,as well as review recent scientific advances. Together, the studies presented in this paper suggest that a singledefinition of visually lossless quality might not be appropriate; rather, a better goal would be to establish varyinglevels of visually lossless quality that can be quantified in terms of the testing paradigm.
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| 3. |
- Dong, Jiankai, et al.
(författare)
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An experimental study on a novel radiant-convective heating system based on air source heat pump
- 2018
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Ingår i: Energy and Buildings. - : Elsevier BV. - 0378-7788 .- 1872-6178. ; 158, s. 812-821
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Tidskriftsartikel (refereegranskat)abstract
- Air source heat pump (ASHP) has been widely applied to many parts of the world due to its simple structure and low initial cost. To save energy consumed for spacing heating and enhance the indoor thermal environment, improving the performances of ASHP has become one of the research focus in the relevant field. Currently, the most conventional heating terminal of ASHP system for spacing heating is finned tube heat exchanger coupled with air fan, which may cause strong draught sensation and dry eye problem and make users feel uncomfortable during convective heating. On the other hand, radiant heating is attracting more and more attention due to its comfortable indoor thermal environment. In this paper, a novel radiant-convective heating terminal was presented and coupled into an ASHP system. Both the operating characteristics and heating performances of the novel system were experimentally investigated. The experimental results showed that the novel system took about 28 min to enter a steady operating stage, during which the radiant panel surface temperature and outlet air temperature for the novel heating terminal, and COP of the novel system were 40.9 degrees C, 32.1 degrees C, and 3.11, respectively, under a standard heating condition. In addition, all parameters mentioned above saw a linear increase when the outdoor air temperature increased from -4.0 to 10.0 degrees C, and their respective rising rates were 0.41 degrees C, 0.28 degrees C and 0.04 per increased outdoor air temperature. Furthermore, the experimental results also demonstrated that adjusting the indoor air flow rate could effectively allocate the amount of heat generated by different heat transfer modes, which may have significant effects on the indoor thermal environment.
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| 4. |
- Frazier-Wood, Alexis C., et al.
(författare)
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Genetic variants associated with subjective well-being, depressive symptoms, and neuroticism identified through genome-wide analyses
- 2016
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Ingår i: Nature Genetics. - : Nature Research (part of Springer Nature). - 1061-4036 .- 1546-1718. ; 48, s. 624-
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Tidskriftsartikel (refereegranskat)abstract
- Very few genetic variants have been associated with depression and neuroticism, likely because of limitations on sample size in previous studies. Subjective well-being, a phenotype that is genetically correlated with both of these traits, has not yet been studied with genome-wide data. We conducted genome-wide association studies of three phenotypes: subjective well-being (n = 298,420), depressive symptoms (n = 161,460), and neuroticism (n = 170,911). We identify 3 variants associated with subjective well-being, 2 variants associated with depressive symptoms, and 11 variants associated with neuroticism, including 2 inversion polymorphisms. The two loci associated with depressive symptoms replicate in an independent depression sample. Joint analyses that exploit the high genetic correlations between the phenotypes (vertical bar(p) over cap vertical bar approximate to 0.8) strengthen the overall credibility of the findings and allow us to identify additional variants. Across our phenotypes, loci regulating expression in central nervous system and adrenal or pancreas tissues are strongly enriched for association.
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| 5. |
- Kuznecovs, Artjoms, 1990, et al.
(författare)
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A methodology for design and fatigue analysis of power cables for wave energy converters
- 2019
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Ingår i: International Journal of Fatigue. - : Elsevier BV. - 0142-1123 .- 1879-3452. ; 122, s. 61-71
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Tidskriftsartikel (refereegranskat)abstract
- The recent development of subsea power cables for various offshore marine renewable energy technologies has identified the need for new cables that have low structural stiffness properties. This type of cable is referred to as dynamic cable because of its high bending flexibility compared to static cables. The current study presents a cable design model and simulation models that were developed for the design and fatigue analysis of dynamic cables. These models were applied on a subsea dynamic power cable with a design that is suitable for a floating point-absorbing wave energy converter (WEC), where the cable must withstand cyclic loads imposed by the motions of the WEC, the waves and the ocean currents. The cable design model is presented with its detailed design and dimensioning methodology for cables with multiorder helical structures, with respect to desired (target) mechanical properties. The cable design model is verified against a verification study in the literature. A simulation model of a fatigue test rig for accelerated rotational bending is presented. The results from the numerical simulations and the subsequent fatigue analyses are compared against results from experiments using the test rig. The influence of the dynamic effects and mechanical properties on the fatigue life of the cable is discussed. This study contributes to a better understanding of the fatigue failure mechanisms of the cable, and it also highlights the importance of further development of numerical models.
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| 6. |
- Lang, Xiao, 1992, et al.
(författare)
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Comparison between full-scale measurements and numerical simulations of mooring forces in a floating point-absorbing wec system
- 2019
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Ingår i: Advances in Renewable Energies Offshore - Proceedings of the 3rd International Conference on Renewable Energies Offshore, RENEW 2018. ; , s. 865-873
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Konferensbidrag (refereegranskat)abstract
- The design of functional elastic mooring systems for floating point-absorbing Wave Energy Converters (WECs) is important for the WEC’s power capture, the durability and reliability of the mooring system. This study presents results from the OCEANERA-NET project ELASTMOOR where Waves4Power’s WEC WaveEL 3.0 is used as a reference case for full-scale measurements of mooring line forces. The elastic mooring system consists of three mooring legs, where each leg is divided into two mooring lines with an intermediate submerged floater. The WaveEL 3.0 WEC is installed outside Runde in Norway and its mooring forces have been measured continuously between June and November, 2017. A numerical simulation model of the full-scale installation has been developed in the DNV GL software SESAM. The study presents a comparison between the mooring forces from full-scale measurements and simulations for various environmental load conditions. The results are discussed with regards to uncertainties and the prediction capacity of the numerical model.
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| 7. |
- Liu, Yingyi, et al.
(författare)
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Response characteristics of the DeepCwind floating wind turbine moored by a Single-Point Mooring system
- 2018
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Ingår i: Applied Sciences (Switzerland). - : MDPI AG. - 2076-3417. ; 8:11
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Tidskriftsartikel (refereegranskat)abstract
- In recent years, the SPM (Single-Point Mooring) concept has been widely employed in several branches of the naval architecture and marine engineering field, such as FPSOs (Floating Production, Storage and Offloading units), offshore oil rigs, etc., but not yet popular in the offshore wind energy. To investigate the response characteristics of an SPM-moored FWT (Floating Wind Turbine), in the present work, we perform a numerical study on the DeepCwind semisubmersible wind turbine, using the state-of-the-art open-source tool FAST. The free-decay test results show that the SPM layout affects the natural periods of the wind turbine in rotational modes, as well as the mooring stiffness of the diagonal rotational and crossing rotational-translational terms, especially in relation to the yaw mode. Comparisons of the RAOs (Response Amplitude Operators) elucidate that the presence of wind influences significantly the sway, roll and yaw motions of the SPM layout. Finally, the weathervane test shows that an asymmetry exists in the free-yaw motion response when the semisubmersible wind turbine is moored by an SPM system.
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| 8. |
- Ringsberg, Jonas, 1971, et al.
(författare)
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Comparison of mooring solutions and array systems for point absorbing wave energy devices
- 2018
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Ingår i: Proceedings of the International Conference on Offshore Mechanics and Arctic Engineering - OMAE. - 9780791851326 ; 11A, s. 1-11
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Konferensbidrag (refereegranskat)abstract
- Most of the ocean energy technologies are considered to be ina pre-commercial phase and need technical development. Thisstudy focuses on design of mooring solutions and comparesarray systems of a specific floating point-absorbing waveenergy converter (WEC) developed by the companyWaves4Power. A full-scale prototype of the WEC is installedin Runde (Norway) where it is moored with three polyestermooring lines, each having one floater and one gravity anchor.Based on this reference installation, the method of systemsengineering was used to propose twenty-two conceptualmooring solutions for different array systems. They werecompared and reduced to four top concepts in a systematicelimination procedure using Pugh and Kesselring matrices. Thetop concepts were assessed in detail by means of LCOE(levelised cost of energy), LCA (life cycle analysis) and riskanalyses. The fatigue life of the mooring lines and the energycapture were calculated using results obtained from coupledhydrodynamic and structure response analyses in the DNV-GLDeepC software. Two final concepts were proposed for thewater depths 75 and 200 m.
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| 9. |
- Ringsberg, Jonas, 1971, et al.
(författare)
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Models for design and fatigue analysis of dynamic power cables for wave energy converters
- 2019
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Ingår i: Trends in the Analysis and Design of Marine Structures - Proceedings of the 7th International Conference on Marine Structures, MARSTRUCT 2019. - : CRC Press/Balkema. - 9780367278090 ; , s. 488-497
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Konferensbidrag (refereegranskat)abstract
- The current study presents a brief overview of a cable design model and simulation models that were developed for the design and fatigue analysis of dynamic cables. These models were applied on a subsea dynamic power cable with a design that is suitable for a floating point-absorbing Wave Energy Converter (WEC), where the cable must withstand cyclic loads imposed by the motions of the WEC, the waves and the ocean currents. An example of a verification study of the cable design model is presented where data from experiments in the literature was used. Further, a simulation model of a fatigue test rig for accelerated rotational bending is also presented. The results from the numerical simulations and the subsequent fatigue analyses are compared against results from experiments using the test rig. The influence of the dynamic effects and mechanical properties on the fatigue life of the cable is discussed.
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| 10. |
- Vance, Charlene, et al.
(författare)
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Making effective WEC design choices based on simulation and analysis
- 2019
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Ingår i: Proceedings of the International Conference on Offshore Mechanics and Arctic Engineering - OMAE. - : American Society of Mechanical Engineers. - 9780791858899 ; 10
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Konferensbidrag (refereegranskat)abstract
- The study presents analyses of key parameters that affect the performance of the point absorbing wave energy converter (WEC). Performance is assessed by running hydrodynamic and structural response simulations and calculating the power absorption of the WEC and fatigue damage in the mooring lines from the output data. The baseline model of the WEC input to the simulation is modelled after the WaveEL 3.0 device, designed by Waves4Power and installed in Runde, Norway. Simulations are run for single buoy and small array configurations, varying environmental conditions, mooring system, and WEC buoy shaft length. Environmental conditions are chosen to reflect locations studied as potential future installation sites. Select configurations are further analyzed through an analysis of LCOE and LCA. The results show that optimal mooring line geometry depends on water depth, and that optimal shaft length depends on the average sea conditions at the location. The array simulations show that small WEC separating distances will limit the mooring line length, which will result in lower power absorption and lower fatigue lives in the mooring lines. The LCOE shows that the four-buoy array configuration is the most profitable, and both the LCOE and LCA show that the main process contribution to climate change and the total product cost is the manufacturing of the WEC buoy itself. The research in this study demonstrates the importance of using simulations to make effective WEC design choices for a given environment.
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