| 1. |
- Blohm, My, et al.
(författare)
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Learning by doing : an observational study of the learning curve for ultrasonic fundus-first dissection in elective cholecystectomy
- 2022
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Ingår i: Surgical Endoscopy. - : Springer. - 0930-2794 .- 1432-2218. ; 36, s. 4602-4613
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Surgical safety and patient-related outcomes are important considerations when introducing new surgical techniques. Studies about the learning curves for different surgical procedures are sparse. The aim of this observational study was to evaluate the learning curve for ultrasonic fundus-first (FF) dissection in elective laparoscopic cholecystectomy (LC).METHODS: The study was conducted at eight hospitals in Sweden between 2017 and 2019. The primary endpoint was dissection time, with secondary endpoints being intra- and postoperative complication rates and the surgeon's self-assessed performance level. Participating surgeons (n = 16) were residents or specialists who performed LC individually but who had no previous experience in ultrasonic FF dissection. Each surgeon performed fifteen procedures. Video recordings from five of the procedures were analysed by two external surgeons. Patient characteristics and data on complications were retrieved from the Swedish Registry of Gallstone Surgery and Endoscopic Retrograde Cholangiopancreatography (GallRiks).RESULTS: Dissection time decreased as experience increased (p = 0.001). Surgeons with limited experience showed more rapid progress. The overall complication rate was 14 (5.8%), including 3 (1.3%) potentially technique-related complications. Video assessment scores showed no correlation with the number of procedures performed. The self-assessed performance level was rated lower when the operation was more complicated (p < 0.001).CONCLUSIONS: Our results show that dissection time decreased with increasing experience. Most surgeons identified both favourable and unfavourable aspects of the ultrasonic FF technique. The ultrasonic device is considered well suited for gallbladder surgery, but most participating surgeons preferred to dissect the gallbladder the traditional way, beginning in the triangle of Calot. Nevertheless, LC with ultrasonic FF dissection can be considered easy to learn with a low complication rate during the initial learning curve, for both residents and specialists.
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| 3. |
- Capek, Miloslav, et al.
(författare)
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Characteristic Mode Decomposition of Scattering Dyadic
- 2022
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Ingår i: 2022 IEEE International Symposium on Antennas and Propagation and USNC-URSI Radio Science Meeting, AP-S/URSI 2022 - Proceedings. - 9781665496582 ; , s. 283-284
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Konferensbidrag (refereegranskat)abstract
- This abstract describes the decomposition of a matrix representing a scattering dyadic into characteristic modes. Scattering dyadic, as compared to conventionally used impedance matrices, are independent of numerical method used to compute them and the same characteristic mode formulation can be used for decomposition of composite and inhomogeneous materials. The utilization of scattering dyadic makes it possible to synthesize characteristic modes which are orthogonal over prescribed portions of the far-field sphere, or ex-post decomposition of measured data. The theory is demonstrated on a simple example and its features are discussed.
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| 4. |
- Capek, Miloslav, et al.
(författare)
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Cloaking Synthesis Based on Exact Re-analysis
- 2022
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Ingår i: 2022 IEEE International Symposium on Antennas and Propagation and USNC-URSI Radio Science Meeting, AP-S/URSI 2022 - Proceedings. - 9781665496582 ; , s. 293-294
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Konferensbidrag (refereegranskat)abstract
- A novel synthesizing procedure is introduced and employed to extract locally-optimal cloaking devices. Their performance is compared with fundamental bounds found using a convex optimization approach. The optimization method is based on a method-of-moments paradigm utilizing rank-1 updates of the structure iteratively performed based on a greedy algorithm. This approach produces locally optimal shapes and its incorporation into a global search strategy is described and applied. As compared to classical topology optimization schemes, no post-processing is required. Two canonical problems are solved and presented.
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| 5. |
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| 6. |
- Cordova, Stephanie, et al.
(författare)
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Potential for the valorization of carbon dioxide from biogas production in Sweden
- 2022
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Ingår i: Journal of Cleaner Production. - : Elsevier Science Ltd. - 0959-6526 .- 1879-1786. ; 370
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Tidskriftsartikel (refereegranskat)abstract
- Biogas solutions offer many advantages to improve sustainable development, but there is still untapped potential in its environmental performance. During biogas upgrading, CO2 is separated from the gas to deliver a flow with high methane concentration and thus high energy content. In this practice, CO2 is commonly emitted to the atmosphere without contributing to a net addition of climate gases because of its biological origin, being a missed opportunity for carbon capture. In this paper, CO2 valorization is an option that has been evaluated using a qualitative and quantitative approach, taking Sweden as an example. Results showed that around 140 kt of CO2 can potentially be captured and utilized from biogas upgrading, which can significantly increase in future scenarios. If CO2 were turned into methane using power-to-gas technology, an additional 35% of biogas could be produced in the short term, meaning up to additional 0.7 TWh in 2020. By 2050, around 600 to 1600 kt of CO2 could be available, depending on how well the biogas production develops and how much of the biogas is upgraded, resulting in up to 6.2 TWh of biomethane. The qualitative assessment suggested that only minor modifications in the upgrading process are required for this practice. Biogas actors are interested in getting involved in valorization projects that enhance their circular business and avoid carbon lock-in mainly to improve the environmental performance of biomethane. Moreover, the application of CO2 valorization requires collaboration with different actors to integrate current CO2 demand or innovative transformation technologies.
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| 7. |
- Fussell, Julia C., et al.
(författare)
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A Review of Road Traffic-Derived Non-Exhaust Particles : Emissions, Physicochemical Characteristics, Health Risks, and Mitigation Measures
- 2022
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Ingår i: Environmental Science and Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 56:11, s. 6813-6835
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Forskningsöversikt (refereegranskat)abstract
- Implementation of regulatory standards has reduced exhaust emissions of particulate matter from road traffic substantially in the developed world. However, nonexhaust particle emissions arising from the wear of brakes, tires, and the road surface, together with the resuspension of road dust, are unregulated and exceed exhaust emissions in many jurisdictions. While knowledge of the sources of nonexhaust particles is fairly good, source-specific measurements of airborne concentrations are few, and studies of the toxicology and epidemiology do not give a clear picture of the health risk posed. This paper reviews the current state of knowledge, with a strong focus on health-related research, highlighting areas where further research is an essential prerequisite for developing focused policy responses to nonexhaust particles.
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| 8. |
- Gustafsson, Mats, 1966-, et al.
(författare)
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Effekt på dammförråd och PM10-halter av tunnelstädning
- 2022
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Driftmetoder mot höga partikelhalter orsakade av vägdamm i gatu- och vägmiljöer har under lång tid utvärderats i vanlig gatumiljö. Resultaten är dock ofta förhållandevis svårtolkade på grund av inverkan av meteorologi och omfattande inblandning från andra partikelkällor än just den gata som studeras. För att komma vidare med mer detaljerade studier av metodik och strategi och för att få mer lättolkade resultat, kan studierna förflyttas in i vägtunnlar. Dessa har en mer kontrollerad miljö med små meteorologiska variationer och en tydlig och helt dominerande partikelkälla – trafiken. Projektet ”Utvärdering av tekniker och strategier för damningsminimerad väg- och gatudrift i tunnelmiljö” avsåg att utvärdera olika varianter av damningsminimerande åtgärder i Södra länken, med fokus på dammbindningsstrategier och städning. På grund av säkerhetsmotiv fick vi inte möjlighet att testa olika dammbindningsstrategier varför projektet har fokuserat enbart på städning och i föreliggande rapport presenteras resultatet från två utvärderingar; en genomförd i januari, då partikelkällorna är starka och dammförrådet stort och en i juni, då källorna är svaga och dammförrådet litet. I januari städade först den så kallade supersugen och sedan Disa-Clean och i juni städade maskinerna i omvänd ordning. För utvärdering av effekterna användes VTI:s vägdammsprovtagare WDS II och luftkvalitetsdata från den mätstation i tunneln som testerna genomfördes vid. Resultaten visar att dammförrådet minskas mer i kombinationen i januari, det vill säga av högtryckstvätt följt av vakuumsug, än tvärtom, som i juni. Även om PM10-data är mer svårtolkade finns indikationer på att halterna i januari minskar något, medan halterna i juni snarare ökar efter städinsatsen. Resultatet att högtryckstvätt följt av vakuumsug fungerar väl för att städa bort vägdamm styrks av snarlika studier genomförda i Norge med samma utvärderingsteknik (WDS).
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| 9. |
- Gustafsson, Mats, et al.
(författare)
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Unified Theory of Characteristic Modes : Part I: Fundamentals
- 2022
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Ingår i: IEEE Transactions on Antennas and Propagation. - 0018-926X. ; , s. 11801-11813
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Tidskriftsartikel (refereegranskat)abstract
- A unification of characteristic mode decomposition for all method-of-moment formulations of field integral equations describing free-space scattering is derived. The work is based on an algebraic link between impedance and transition matrices, the latter of which was used in early definitions of characteristic modes and is uniquely defined for all scattering scenarios. This also makes it possible to extend the known application domain of characteristic mode decomposition to any other frequency-domain solver capable of generating transition matrices, such as finite difference or finite element methods. The formulation of characteristic modes using a transition matrix allows for the decomposition of induced currents and scattered fields from arbitrarily shaped objects, providing high numerical dynamics and increased stability, removing the issue of spurious modes, and offering good control of convergence. This first part of a two-part paper introduces the entire theory, extensively discusses its properties and offers its basic numerical validation.
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| 10. |
- Gustafsson, Mats, et al.
(författare)
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Unified Theory of Characteristic Modes : Part II - Tracking, Losses, and FEM Evaluation
- 2022
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Ingår i: IEEE Transactions on Antennas and Propagation. - 0018-926X. ; 70:12, s. 11814-11824
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Tidskriftsartikel (refereegranskat)abstract
- This is the second component of a two-part paper dealing with a unification of characteristic mode decomposition. This second part addresses modal tracking, interpolation, the role of ohmic losses, and presents several numerical examples for surface-based method-of-moment formulations. A new tracking algorithm based on algebraic properties of the transition matrix is developed, achieving excellent precision and requiring a very low number of frequency samples as compared to procedures previously reported in the literature. The transition matrix is further utilized to show that characteristic mode decomposition of lossy objects fails to deliver orthogonal far fields and to demonstrate how characteristic modes can be evaluated using the finite element method.
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