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- Brusich, S, et al.
(författare)
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Croatian National Data and Comparison with European Practice: Data from the Cardiac Resynchronization Therapy Survey II Multicenter Registry
- 2018
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Ingår i: Cardiology research and practice. - : Hindawi Limited. - 2090-8016 .- 2090-0597. ; 2018, s. 3479846-
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Tidskriftsartikel (refereegranskat)abstract
- Aims. The Cardiac Resynchronization Therapy (CRT) Survey II was conducted between October 2015 and December 2016 and included data from 11088 CRT implantations from 42 countries. The survey’s aim was to report on current European CRT practice. The aim of this study was to compare the Croatian national CRT practice with the European data. Methods. Five centres from Croatia recruited consecutive patients, in a 15-month period, who underwent CRT implantation, primary or an upgrade. Data were collected prospectively by using online database. Results. A total of 115 patients were included in Croatia, which is 33.2% of all CRT implants in Croatia during the study period (total n=346). Median age of the study population was 67 (61–73) years, and 21.2% were women. Primary heart failure (HF) aetiology was nonischemic in 61.1% of patients, and HF with wide QRS was the most common indication for the implantation (73.5%). 80% of patients had complete left bundle branch block, and over two-third had QRS ≥150 ms. Device-related adverse events were recorded in 4.3% of patients. When compared with European countries, Croatian patients were significantly younger (67 vs. 70 years, p=0.012), had similar rate of comorbidities with the exception of higher prevalence of hypertension. Croatian patients significantly more often received CRT-pacemaker when compared with European population (58.3 vs. 29.9%, OR 3.27, 95%CI 2.25–4.74, p<0.001). Conclusion. Our data indicate strict selection of patients among HF population and adherence to guidelines with exception of higher proportion of CRT-pacemaker implantation. This is likely to be influenced by healthcare organization and reimbursement issues in Croatia.
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- Basara, Branislav, 1964, et al.
(författare)
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Effects of convection schemes on hybrid RANS-LES calculations
- 2018
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Ingår i: Notes on Numerical Fluid Mechanics and Multidisciplinary Design. - Cham : Springer International Publishing. - 1612-2909 .- 1860-0824. ; 137, s. 145-155
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Tidskriftsartikel (refereegranskat)abstract
- Nowadays it is commonly accepted to report on convections schemes in the case of Large Eddy Simulations. However, this is still not mandatory for the hybrid Reynolds-Averaged Navier-Stokes (RANS)—LES calculations. Therefore, this paper intends to show that the effects of convection scheme is equally important for hybrid RANS-LES calculations as well as for LES runs. We choose here the Partially-Averaged Navier–Stokes (PANS) model as the representative hybrid RANS-LES model but the conclusions derived in this work are equally applicable to other methods. The aim of the paper is to provide a proper criterion from the employment of higher order differencing schemes. The paper will assess two approaches, namely step functions where central-differencing scheme is used in the regions with a lower unresolved turbulent kinetic energy and a continuous function which depends on the ratio between unresolved and total kinetic energy. The results will be presented for the flow around the square cylinder. Direct numerical simulation (DNS) data and measurements are available for comparisons.
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- Basara, Branislav, 1964, et al.
(författare)
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Scale-resolving simulations of the flow in internal combustion engines
- 2018
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Ingår i: Proceedings of the Thermal and Fluids Engineering Summer Conference. - 2379-1748. ; 2018-March, s. 245-248
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Konferensbidrag (refereegranskat)abstract
- The common practice in predicting engine flows is to use the Reynolds-averaged Navier-Stokes (RANS) models. However, the RANS models are single point closures relying on the assumption of self-similarity of the turbulence spectrum, the fact leading to only one characteristic turbulence length scale, defining the entire spectrum. Consequently, the complex physics of the flow in engines could not be captured well in such a way. In the case of running RANS model for multi-cycle engine calculations, calculation results will converge to one cycle results (the first 3-4 cycles are different due to different cycle starting fields, but then the results of the each next cycle will be the same) without predicting cycle-to cycle variations (CCV). Some of reported CCV results with RANS models, are probably due to numerical artefacts rather than physical background of the RANS models. In order to correctly capture all engine related flow phenomena, Large-Eddy Simulation (LES) has been recently more often used, but due to high computational costs, mainly as a research but not as a productive tool. An alternative approach could be found in the use of hybrid LES/RANS (HLR) models. Therefore, we use here a seamless HLR method denoted as Partial-Averaged Navier-Stokes (PANS) in conjunction with the universal wall treatment (Basara, 2006) in order to provide the optimum regarding the accuracy and computational costs. This turbulence bridging method, which supports any filter width or scale resolution, is derived from the Reynolds-Averaged Navier-Stokes (RANS) model equations. It inevitably improves results when compared with its corresponding RANS model if more scales of motions are resolved. The PANS (Girimaji, 2006) variant derived from the four equation near-wall eddy viscosity transport model (see Basara et al. 2011), namely k-ε-ζ-f turbulence model is used here (commercial software AVL FIRE®). This is done by varying the unresolved-to-total ratios of kinetic energy and dissipation given as (euqacation presented) This procedure is applied here on the full engine case. First, Figure 1 shows the resolution parameter fk which is based on RANS results and Eq. (2). This roughly shows that the mesh is in general coarse, for example for LES calculations, but fine enough to try PANS model (note that fk = 1 is in the 'RANS region' and fk = 0.4 is the minimum value). One could propose such mesh analysis prior to LES calculations in order to avoid long calculations, an assessment of the resolved energy and then again new meshing etc. Following the SSV approach applied on the same mesh, an instantaneous fk, which is different than one based on the RANS calculations, is shown in Figure 2, but overall, there are a lot of similarities. This is of course also due to different turbulence level predicted by two approaches. Calculations are performed here also by using spray and combustion modules. Predicted flame front propagation is shown in Figure 3, so the variations are visible for two neighbour cycles N and N+1. One can see that at the top most position of the piston towards head side of position (top dead center - TDC) and few degrees after TDC, the flame front is very different. This can be also seen at different cross-section as shown in Figure 4. This of course causes the pressure variations. It should be also reported that for this particular mesh, cycle to cycle variations obtained by LES are double larger than obtained with PANS calculations (20% vs. 10%) and measurements provided the value of 30%. However, having in mind Figures (1) and (2), and knowing that for proper LES calculations fk should be at least less than 0.2, those variations of 20% could be more addressed to the calculation error. The results presented here show the advantage of the variable resolution PANS method when compared to RANS models. With the help of the computational mesh and the resolution parameters incorporated used in PANS, cycle-to-cycle variations could be predicted. These results approve the PANS basic idea of providing the optimum fidelity on the given numerical mesh. It is also clear that in order to get the most accurate results, meshes should be further refine. However, many engine cases can be calculated with coarser meshes and the then last investigations could be made with refined meshes.
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| 7. |
- Linde, C, et al.
(författare)
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The Membership Committee of the ESC
- 2019
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Ingår i: Cardiovascular research. - : Oxford University Press (OUP). - 1755-3245 .- 0008-6363. ; 115:12, s. E130-E132
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Tidskriftsartikel (refereegranskat)
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- Pennells, Lisa, et al.
(författare)
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Equalization of four cardiovascular risk algorithms after systematic recalibration : individual-participant meta-analysis of 86 prospective studies
- 2019
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Ingår i: European Heart Journal. - : Oxford University Press (OUP). - 0195-668X .- 1522-9645. ; 40:7, s. 621-
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Tidskriftsartikel (refereegranskat)abstract
- Aims: There is debate about the optimum algorithm for cardiovascular disease (CVD) risk estimation. We conducted head-to-head comparisons of four algorithms recommended by primary prevention guidelines, before and after ‘recalibration’, a method that adapts risk algorithms to take account of differences in the risk characteristics of the populations being studied.Methods and results: Using individual-participant data on 360 737 participants without CVD at baseline in 86 prospective studies from 22 countries, we compared the Framingham risk score (FRS), Systematic COronary Risk Evaluation (SCORE), pooled cohort equations (PCE), and Reynolds risk score (RRS). We calculated measures of risk discrimination and calibration, and modelled clinical implications of initiating statin therapy in people judged to be at ‘high’ 10 year CVD risk. Original risk algorithms were recalibrated using the risk factor profile and CVD incidence of target populations. The four algorithms had similar risk discrimination. Before recalibration, FRS, SCORE, and PCE over-predicted CVD risk on average by 10%, 52%, and 41%, respectively, whereas RRS under-predicted by 10%. Original versions of algorithms classified 29–39% of individuals aged ≥40 years as high risk. By contrast, recalibration reduced this proportion to 22–24% for every algorithm. We estimated that to prevent one CVD event, it would be necessary to initiate statin therapy in 44–51 such individuals using original algorithms, in contrast to 37–39 individuals with recalibrated algorithms.Conclusion: Before recalibration, the clinical performance of four widely used CVD risk algorithms varied substantially. By contrast, simple recalibration nearly equalized their performance and improved modelled targeting of preventive action to clinical need.
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