Summary of ISO/TC 201 International Standard ISO 18516:2019 Surface chemical analysis—Determination of lateral resolution and sharpness in beam-based methods with a range from nanometres to micrometres and its implementation for imaging laboratory X-ray photoelectron spectrometers (XPS)

ISO 18516:2019 Surface chemical analysis—Determination of lateral resolution and sharpness in beam-based methods with a range from nanometres to micrometres revises ISO 18516:2006 Surface chemical analysis—Auger electron spectroscopy and X-ray photoelectron spectroscopy—Determination of lateral resolution. It implements three different methods delivering parameters useful to express the lateral resolution: (1) the straight edge method, (2) the narrow line method and (3) the grating method. The theoretical background of these methods is introduced in ISO/TR 19319:2013 Surface chemical analysis—Fundamental approaches to determination of lateral resolution and sharpness in beam-based methods. The revised International Standard ISO 18516 delivers standardized procedures for the determination of the (1) effective lateral resolution by imaging of square-wave gratings, the (2) lateral resolution expressed as the parameter D12–88 characterizing the steepness of the sigmoidal edge spread function (ESF) determined by imaging a straight edge and (3) the lateral resolution expressed as the full width of half maximum of the line spread function (LSF), wLSF, determined by imaging a narrow line. The last method also delivers information on the shape of the LSF, which characterizes an individual imaging instrument. Finally, the implementation of all three standardized methods in the field of imaging laboratory X-ray photoelectron spectroscopy (XPS) is shortly presented. This part of the letter is based on the use of a new test sample developed at ETH Zurich, Switzerland. This test sample displays a micrometre scaled pattern motivated by the resolving power of recent imaging XPS instruments

Using LES to Study Reacting Flows and Instabilities in Annular Combustion Chambers

Great prominence is put on the design of aeronautical gas turbines due to increasingly stringent regulations and the need to tackle rising fuel prices. This drive towards innovation has resulted sometimes in new concepts being prone to combustion instabilities. In the particular field of annular combustion chambers, these instabilities often take the form of azimuthal modes. To predict these modes, one must compute the full combustion chamber, which remained out of reach until very recently and the development of massively parallel computers. Since one of the most limiting factors in performing Large Eddy Simulation (LES) of real combustors is estimating the adequate grid, the effects of mesh resolution are investigated by computing full annular LES of a realistic helicopter combustion chamber on three grids, respectively made of 38, 93 and 336 million elements. Results are compared in terms of mean and fluctuating fields. LES captures self-established azimuthal modes. The presence and structure of the modes is discussed. This study therefore highlights the potential of LES for studying combustion instabilities in annular gas turbine combustors

Calibration of multi-layered probes with low/high magnetic moments

We present a comprehensive method for visualisation and quantification of the magnetic stray field of magnetic force microscopy (MFM) probes, applied to the particular case of custom-made multi-layered probes with controllable high/low magnetic moment states. The probes consist of two decoupled magnetic layers separated by a non-magnetic interlayer, which results in four stable magnetic states: ±ferromagnetic (FM) and ±antiferromagnetic (A-FM). Direct visualisation of the stray field surrounding the probe apex using electron holography convincingly demonstrates a striking difference in the spatial distribution and strength of the magnetic flux in FM and A-FM states. In situ MFM studies of reference samples are used to determine the probe switching fields and spatial resolution. Furthermore, quantitative values of the probe magnetic moments are obtained by determining their real space tip transfer function (RSTTF). We also map the local Hall voltage in graphene Hall nanosensors induced by the probes in different states. The measured transport properties of nanosensors and RSTTF outcomes are introduced as an input in a numerical model of Hall devices to verify the probe magnetic moments. The modelling results fully match the experimental measurements, outlining an all-inclusive method for the calibration of complex magnetic probes with a controllable low/high magnetic moment

A novel ensemble-based conceptual-data-driven approach for improved streamflow simulations

A novel framework, an ensemble-based conceptual-data-driven approach (CDDA), is developed that integrates a hydrological model (HM) with a data-driven model (DDM) to simulate an ensemble of HM residuals. Thus, a CDDA delivers an ensemble of ‘residual-corrected’ streamflow simulations. This framework is beneficial because it respects hydrological processes via the HM and it profits from the DDM’s ability to simulate the complex relationship between residuals and input variables. The CDDA enables exploring different DDMs to identify the most suitable model. Eight DDMs are explored: Multiple Linear Regression (MLR), k Nearest Neighbours Regression (kNN), Second-Order Volterra Series Model, Artificial Neural Networks (ANN), and two variants of eXtreme Gradient Boosting (XGB) and Random Forests (RF). The proposed CDDA, tested on three Swiss catchments, was able to improve the mean continuous ranked probability score by 16-29% over the standalone HM. Based on these results, XGB and RF are recommended for simulating the HM residuals

Large-Eddy Simulation of Kerosene Spray Ignition in a Simplified Aeronautic Combustor

The current work presents the Large Eddy Simulation (LES) of a kerosene spray ignition phase in a simplified aeronautical combustor for which detailed experimental data are available. The carrier phase is simulated using an unstructured multi-species compressible Navier-Stokes solver while the dispersed liquid phase is modeled with a Lagrangian approach. An energy deposition model neglecting the presence of a plasma phase in the very first instants of the energy deposition process, a reduced kinetic scheme and a simplified spray injection model are combined to achieve both a reasonable computational expense and a satisfactory overall accuracy. Following a brief description of the validation of these models, non reactive gaseous and two-phase flow LES's of the target combustor are performed. Excellent agreement with experiments is observed for the non reactive gaseous simulations. The dispersed phase velocity fields are also well reproduced while discrepancies appear for the spatial size distribution of the particles. Finally, numerical snapshots of a successful ignition phase are shown and discussed