Richard E. Byrd and the North Pole flight of 1926: fact, fiction as fact, and interpretation

pp. 363-37

Verification of Gyrokinetic codes: theoretical background and applications

In fusion plasmas the strong magnetic field allows the fast gyro-motion to be systematically removed from the description of the dynamics, resulting in a considerable model simplification and gain of computational time. Nowadays, the gyrokinetic (GK) codes play a major role in the understanding of the development and the saturation of turbulence and in the prediction of the subsequent transport. Naturally, these codes require thorough verification and validation. Here we present a new and generic theoretical framework and specific numerical applications to test the faithfulness of the implemented models to theory and to verify the domain of applicability of existing GK codes. For a sound verification process, the underlying theoretical GK model and the numerical scheme must be considered at the same time, which has rarely been done and therefore makes this approach pioneering. At the analytical level, the main novelty consists in using advanced mathematical tools such as variational formulation of dynamics for systematization of basic GK code's equations to access the limits of their applicability. The verification of numerical scheme is proposed via the benchmark effort. In this work, specific examples of code verification are presented for two GK codes: the multi-species electromagnetic ORB5 (PIC) and the radially global version of GENE (Eulerian). The proposed methodology can be applied to any existing GK code. We establish a hierarchy of reduced GK Vlasov-Maxwell equations implemented in the ORB5 and GENE codes using the Lagrangian variational formulation. At the computational level, detailed verifications of global electromagnetic test cases developed from the CYCLONE Base Case are considered, including a parametric $\beta$-scan covering the transition from ITG to KBM and the spectral properties at the nominal $\beta$ value.Comment: 16 pages, 2 Figures, APS DPP 2016 invited pape

Archives in Controversy: The Press, the Documentaries and the Byrd Archives

One of the major news stories of 1996 was the discovery and analysis of Richard Byrd's diary and notebook for his North Pole flight of 1926. Byrd's claim to be the first to fly to the North Pole was challenged by his contemporaries and by later historians. The diary provided new evidence, and the news of its existence and meaning fueled stories that reached every part of the globe. Interest in Byrd also inspired producers of three documentaries. The archivist who dealt with reporters and producers discusses the media coverage, the challenges of working with reporters and producers of documentaries, and the impact of the publicity on an archival program

Gyrokinetic studies of core turbulence features in ASDEX Upgrade H-mode plasmas

Gyrokinetic validation studies are crucial in developing confidence in the model incorporated in numerical simulations and thus improving their predictive capabilities. As one step in this direction, we simulate an ASDEX Upgrade discharge with the GENE code, and analyze various fluctuating quantities and compare them to experimental measurements. The approach taken is the following. First, linear simulations are performed in order to determine the turbulence regime. Second, the heat fluxes in nonlinear simulations are matched to experimental fluxes by varying the logarithmic ion temperature gradient within the expected experimental error bars. Finally, the dependence of various quantities with respect to the ion temperature gradient is analyzed in detail. It is found that density and temperature fluctuations can vary significantly with small changes in this parameter, thus making comparisons with experiments very sensitive to uncertainties in the experimental profiles. However, cross-phases are more robust, indicating that they are better observables for comparisons between gyrokinetic simulations and experimental measurements

To the Pole: the diary and notebook of Richard E. Byrd, 1925-1927

(print) 161 p. : ill. ; 24 cmIntroduction 1 -- The Making Of An Explorer : Richard Evelyn Byrd, 1888-1924 7 -- The Greenland Expedition Of 1925 17 -- The North Pole Flight Of 1926 41 -- The Transatlantic Flight Of 1927 97 -- Epilogue : Richard Evelyn Byrd, 1928-1957 119 -- Appendix A : Chronology Of Byrd's Life 133 -- Appendix B : Navigational Report Of Byrd's Flight To The North Pole, 1926 139 -- Additional Readings 15

Somatic development long after the Fontan operation: Factors influencing catch-up growth

ObjectiveAs mortality and morbidity after the Fontan operation has improved, long-term outcome, including developmental aspects, have become more important. To understand the long-term effects of this operation, we followed somatic development for up to 15 years.MethodsWe evaluated 90 patients who underwent the Fontan operation between 1984 and 2004 (mean follow-up, 11.8 ± 4.2 years). The modified Fontan operations were atriopulmonary anastomosis (n = 19) and total cavopulmonary connection (n = 71). Mean age at the time of surgical intervention was 5.5 ± 4.8 years. Weight, height, and body mass index were evaluated preoperatively and postoperatively and given as percentiles on a normal growth curve.ResultsPostoperative weight, height, and body mass index reached the 47.2 ± 35.6, 37.9 ± 30.4, and 41.6 ± 31.2 percentiles, which were significantly better than preoperative values (the 21.6 ± 25.9, 25.9 ± 25.7, and 20.0 ± 25.1 percentiles). Although neither early surgical intervention nor anatomic features affected postoperative growth, early Fontan completion demonstrated better somatic development in subgroups of tricuspid atresia. Prior bidirectional Glenn shunting provided better weight gain before the Fontan operation. Prior atrioseptectomy, central shunt, and pulmonary artery reconstruction were associated with impaired somatic development. Reoperation and catheter-based intervention improved somatic development.ConclusionsLong-term catch-up growth can be observed in patients after the Fontan operation. Early volume-unloading procedures might lead to better somatic growth. Prior atrioseptectomy, central shunt, and pulmonary artery reconstruction are associated with impaired weight and height gain, implying that the severity of the underlying diseases affects postoperative somatic development

Fast transport simulations with higher-fidelity surrogate models for ITER

A fast and accurate turbulence transport model based on quasilinear gyrokinetics is developed. The model consists of a set of neural networks trained on a bespoke quasilinear GENE dataset, with a saturation rule calibrated to dedicated nonlinear simulations. The resultant neural network is approximately eight orders of magnitude faster than the original GENE quasilinear calculations. ITER predictions with the new model project a fusion gain in line with ITER targets. While the dataset is currently limited to the ITER baseline regime, this approach illustrates a pathway to develop reduced-order turbulence models both faster and more accurate than the current state-of-the-art