Design of robust total site heat recovery loops via Monte Carlo simulation

For increased total site heat integration, the optimal sizing and robust operation of a heat recovery loop (HRL) are prerequisites for economic efficiency. However, sizing based on one representative time series, not considering the variability of process streams due to their discontinuous operation, often leads to oversizing. The sensitive evaluation of the performance of an HRL by Monte Carlo (MC) simulation requires sufficient historical data and performance models. Stochastic time series are generated by distribution functions of measured data. With these inputs, one can then model and reliably assess the benefits of installing a new HRL. A key element of the HRL is a stratified heat storage tank. Validation tests of a stratified tank (ST) showed sufficient accuracy with acceptable simulation time for the variable layer height (VLH) multi-node (MN) modelling approach. The results of the MC simulation of the HRL system show only minor yield losses in terms of heat recovery rate (HRR) for smaller tanks. In this way, costs due to oversizing equipment can be reduced by better understanding the energy-capital trade-off

Understanding the biases to sepsis surveillance and quality assurance caused by inaccurate coding in administrative health data

Purpose Timely and accurate data on the epidemiology of sepsis are essential to inform policy decisions and research priorities. We aimed to investigate the validity of inpatient administrative health data (IAHD) for surveillance and quality assurance of sepsis care. Methods We conducted a retrospective validation study in a disproportional stratified random sample of 10,334 inpatient cases of age ≥ 15 years treated in 2015–2017 in ten German hospitals. The accuracy of coding of sepsis and risk factors for mortality in IAHD was assessed compared to reference standard diagnoses obtained by a chart review. Hospital-level risk-adjusted mortality of sepsis as calculated from IAHD information was compared to mortality calculated from chart review information. Results ICD-coding of sepsis in IAHD showed high positive predictive value (76.9–85.7% depending on sepsis definition), but low sensitivity (26.8–38%), which led to an underestimation of sepsis incidence (1.4% vs. 3.3% for severe sepsis-1). Not naming sepsis in the chart was strongly associated with under-coding of sepsis. The frequency of correctly naming sepsis and ICD-coding of sepsis varied strongly between hospitals (range of sensitivity of naming: 29–71.7%, of ICD-diagnosis: 10.7–58.5%). Risk-adjusted mortality of sepsis per hospital calculated from coding in IAHD showed no substantial correlation to reference standard risk-adjusted mortality (r = 0.09). Conclusion Due to the under-coding of sepsis in IAHD, previous epidemiological studies underestimated the burden of sepsis in Germany. There is a large variability between hospitals in accuracy of diagnosing and coding of sepsis. Therefore, IAHD alone is not suited to assess quality of sepsis care

Lateral heterogeneity scales in regional and global upper mantle shear velocity models

International audienceWe analyse the lateral heterogeneity scales of recent upper mantle tomographic shear velocity (Vs) global and regional models. Our goal is to constrain the spherical harmonics power spectrum over the largest possible range of scales to get an estimate of the strength and statistical distribution of both long and small-scale structure. We use a spherical multitaper method to obtain high quality power spectral estimates from the regional models. After deconvolution of the employed taper functions, we combine global and regional spectral estimates from scales of 20 000 to around 200 km (degree 100). In contrast to previous studies that focus on linear power spectral densities, we interpret the logarithmic power per harmonic degree l as heterogeneity strength at a particular depth and horizontal scale. Throughout the mantle, we observe in recent global models, that their low degree spectrum is anisotropic with respect to Earth's rotation axis. We then constrain the uppermost mantle spectrum from global and regional models. Their power spectra transfer smoothly into each other in overlapping spectral bands, and model correlation is in general best in the uppermost 250 km (i.e. the `heterosphere'). In Europe, we see good correlation from the largest scales down to features of about 500 km. Detailed analysis and interpretation of spectral shape in this depth range shows that the heterosphere has several characteristic length scales and varying spectral decay rates. We interpret these as expressions of different physical processes. At larger depths, the correlation between different models drops, and the power spectrum exhibits strong small scale structure whose location and strength is not as well resolved at present. The spectrum also has bands with elevated power that likely correspond to length scales that are enhanced due to the inversion process

SHTools: Tools for Working with Spherical Harmonics

International audienceGeophysical analyses are often performed in spherical geometry and require the use of spherical harmonic functions to express observables or physical quantities. When expanded to high degree, the accuracy and speed of the spherical harmonic transforms and reconstructions are of paramount importance. SHTools is a time and user-tested open-source archive of both Fortran 95 and Python routines for performing spherical harmonic analyses. The routines support all spherical-harmonic normalization conventions used in the geosciences, including 4p-normalized, Schmidt seminormalized, orthonormalized, and unnormalized harmonics, along with the option of employing the Condon-Shortley phase factor of ð21Þ m. Data on the sphere can be sampled on a variety of grid formats, including equally spaced cylindrical grids and grids appropriate for integration by Gauss-Legendre quadrature. The spherical-harmonic transforms are proven to be fast and accurate for spherical harmonic degrees up to 2800. Several tools are provided for the geoscientist, including routines for performing localized spectral analyses and basic operations related to global gravity and magnetic fields. In the Python environment, operations are very simple to perform as a result of three class structures that encompass all operations on grids, spherical harmonic coefficients, and spatiospectral localization windows. SHTools is released under the unrestrictive BSD 3-clause license

Shtools: Version 3.1

This release of SHTOOLS adds improved documentation for all Fortran 95 and Python routines, fixes several bugs, adds new functionalities, and adds additional example scripts. 3.1 release notes: Added OSX installation support via brew. Added make install that copies files to /usr/local. Reformatted all Fortran documentation files and rewrote the Python documentation and man pages. Added the routines CilmMinus and CilmMinusRhoH, which are the counterparts to CilmPlus and CilmPlusRhoH. Removed the following routines from the fortran documentation and Python wrappers: DhAj, NGLQ, NGLQSH, NGLQSHN. Removed the following redundant routines from SHTOOLS: ComputeD0, SHMTVarOpt0, SHSjkPG0. Renamed the routine PreCompute to SHGLQ. Renamed the routine YilmIndex to YilmIndexVector. Renamed the routine Hilm to BAtoHilm, and HilmRhoH to BAtoHilmRhoH. Renamed the routine Wl to DownContFilterMA, and WlCurv toDownContFilterMC. Added minimal support for three python classes: SHGrid, SHCoeffs, and SHWindow.These will be expanded upon in the next release. Added the routine SHMTCouplingMatrix

SHTOOLS: Version 3.2

This release contains the following improvements: Added the optional argument centralmeridian to Curve2Mask that accounts for cases where the curve makes a complete circle in longitude about the planet. Fixed in bug in the python implementation where the outputs error and corr of SHAdmitCorr were switched. Added OpenMP support. When compiling with make fortran-mp,make fortran2-mp, or make fortran3-mp, saved variables in the subroutines are defined as being threadprivate. Optimized performance of the routines SHMultiTaperSE, SHMultiTaperCSE, and SHLocalizedAdmitCorr. Minor documentation fixes

Antipodal focusing of seismic waves due to large meteorite impacts on Earth

We examine focusing of seismic waves at the antipode of large terrestrial meteorite impacts, using the Chicxulub impact as our case study. Numerical simulations are based on a spectral-element method, representing the impact as a Gaussian force in time and space. Simulating the impact as a point source at the surface of a spherically symmetric earth model results in deceptively large peak displacements at the antipode. Earth’s ellipticity, lateral heterogeneity and a spatially distributed source limit high-frequency waves from constructively interfering at the antipode, thereby reducing peak displacement by a factor of 4. Nevertheless, for plausible impact parameters, we observe peak antipodal displacements of ∼4 m, dynamic stresses in excess of 15 bar, and strains of 2 × 10−5. Although these values are significantly lower than prior estimates, mainly based on a point source in a spherically symmetric earth model, wave interference en route to the antipode induces ‘channels’ of peak stress that are five times greater than in surrounding areas. Underneath the antipode, we observed ‘chimneys’ of peak stress, strain and velocity, with peak values exceeding 50 bar, 10−5 and 0.1 ms−1, respectively. Our results put quantitative constraints on the feasibility of impact-induced antipodal volcanism and seismicity, as well as mantle plume and hotspot formation

The Effect of Water-Column Resonance on the Spectra of Secondary Microseism P-waves

We compile and analyze a dataset of secondary microseismic P-wave spectra that were observed by North American seismic arrays. Two distinct frequency bands, 0.13–0.15Hz and 0.19–0.21Hz, with enhanced P-wave energy characterize the dataset. Cluster analysis allows to classify the spectra and to associate typical spectral shapes with geographical regions: Low frequency dominated spectra (0.13-0.15Hz) are mostly detected in shallower regions of the North Atlantic and the South Pacific, as well as along the Central and South American Pacific coast. High frequency dominated spectra (0.19-0.21Hz) are mostly detected in deeper regions of the North-Western Pacific and the South Pacific. For a selected subset of high quality sources, we compute synthetic spectra from an ocean wave hindcast. These synthetic spectra are able to reproduce amplitude and shape of the observed spectra, but only if P-wave resonance in the water column at the source site is included in the model. Our datasets therefore indicate that the spectral peaks at 0.13-0.15Hz and 0.19-0.21 Hz correspond to the first and second harmonics of P-wave resonance in the water column that occur in shallower ocean depths (<3000m) and in the deep ocean (∼5000m), respectively. This article demonstrates the important effect of water column resonance on the amplitude and frequency of P-waves that are generated by secondary microseisms, and that the amplitude of high quality sources can be predicted from ocean wave hindcasts within a factor of 0.4 − 6

The Effect of Water Column Resonance on the Spectra of Secondary Microseism P Waves

International audienceWe compile and analyze a data set of secondary microseismic P wave spectra that were observed by North American seismic arrays. Two distinct frequency bands, 0.13-0.15 Hz and 0.19-0.21 Hz, with enhanced P wave energy characterize the data set. Cluster analysis allows to classify the spectra and to associate typical spectral shapes with geographical regions: Low-frequency-dominated spectra (0.13-0.15 Hz) are mostly detected in shallower regions of the North Atlantic and the South Pacific, as well as along the Central and South American Pacific coast. High-frequency-dominated spectra (0.19-0.21 Hz) are mostly detected in deeper regions of the northwestern Pacific and the South Pacific. For a selected subset of high-quality sources, we compute synthetic spectra from an ocean wave hindcast. These synthetic spectra are able to reproduce amplitude and shape of the observed spectra, but only if P wave resonance in the water column at the source site is included in the model. Our data sets therefore indicate that the spectral peaks at 0.13-0.15 Hz and 0.19-0.21 Hz correspond to the first and second harmonics of P wave resonance in the water column that occur in shallower ocean depths (<3,000 m) and in the deep ocean (∼5,000 m), respectively. This article demonstrates the important effect of water column resonance on the amplitude and frequency of P waves that are generated by secondary microseisms and that the amplitude of high-quality sources can be predicted from ocean wave hindcasts within a factor of 0.4-6