Implicit Quadrature-Free Direct Reconstruction Method for Efficient Scale-Resolving Simulations

The present study develops implicit physical domain-based discontinuous Galerkin(DG)methods for efficient scale-resolving simulations on mixed-curved meshes.Implicit methods are essential to handle stiff systems in many scale-resolving simulations of interests in computational science and engineering.The physical domain-based DGmethod can achieve high-order accuracy using the optimal bases set and preserve the required accuracy on non-affinemeshes.When using the quadraturebased DG method,these advantages are overshadowed by severe computational costs on mixed-curved meshes,making implicit scale-resolving simulations unaffordable.To address this issue,the quadrature-free direct reconstruction method(DRM)is extended to the implicit DG method.In this approach,the generalized reconstruction approximates non-linear flux functions directly in the physical domain,making the computing-intensive numerical integrations precomputable at a preprocessing step.The DRM operator is applied to the residual computation in the matrix-free method.The DRM operator can be further extended to the system matrix computation for the matrix-explicit Krylov subspace method and preconditioning.Finally,the A-stable Rosenbrock-type Runge–Kutta methods are adopted to achieve high-order accuracy in time.Extensive verification and validation from the manufactured solution to implicit large eddy simulations are conducted.The computed results confirm that the proposed method significantly improves computational efficiency compared to the quadrature-based method while accurately resolving detailed unsteady flow features that are hardly captured by scale-modeled simulations.

Measurement of the high energyγ-rays from heavy ion reactions usingČerenkov detector

The energetic bremsstrahlung photons up to 100 MeV produced in heavy ion collisions can be used as a sensitive probe for short-range correlation in atomic nuclei. The energy of the γ-rays can be measured by collecting the Čerenkov light in the medium induced by the fast electrons generated in the Compton scattering or electromagnetic shower of the incident γray. Two types of detectors based on pure water and lead glass as sensitive materials were designed for this purpose. The γresponse and optical photon propagation in the detectors were simulated based on electromagnetic and optical processes in Geant4. The inherent energy resolutions of 0.022(4) + 0.51(2)∕E^(1/2)_(γ) for water and 0.0026(3) + 0.446(3)∕E^(1/2)_(γ) for lead glass were obtained. The geometry sizes of the lead glass and water were optimized to 30 cm × 30 cm × 30 cm and 60 cm × 60 cm ×120 cm, respectively, to detect high-energy γ-rays at 160 MeV. The Hough transform method was applied to reconstruct the direction of the incident γ-rays, providing the ability to experimentally distinguish the high-energy γ-rays produced in the reactions on the target from random background cosmic-ray muons.

Stress Wave Propagation Analysis on Vortex-Induced Vibration of Marine Risers

To analyze the stress wave propagation associated with the vortex-induced vibration（VIV） of a marine riser, this paper employed a multi-signal complex exponential method. This method is an extension of the classical Prony＇s method which decomposes a complicated signal into a number of complex exponential components. Because the proposed method processes multiple signals simultaneously, it can estimate the “global” dominating frequencies（poles） shared by those signals.The complex amplitude（residues） corresponding to the estimated frequencies for those signals is also obtained in the process. As the signals were collected at different locations along the axial direction of a marine riser, the phenomena of the stress wave propagation could be analyzed through the obtained residues of those signals. The Norwegian Deepwater Program（NDP） high mode test data were utilized in the numerical studies, including data sets in both the in-line（IL） and cross-flow（CF） directions. It was found that the most dominant component in the IL direction has its stress wave propagation along the riser being dominated by a standing wave, while that in the CF direction dominated by a traveling wave.

Improving the energy resolution of the reactor antineutrino energy reconstruction with positron direction

Purpose Improving the energy resolution of the reactor antineutrino energy reconstruction.Methods Simulate the energy resolution of a liquid scintillator detector and reconstruct the antineutrino energy with the positron scattering angle,a simple positron direction reconstruction method is implemented in a toy liquid scintillator detector like the Taishan Antineutrino Observatory(TAO)with 4500 photoelectron yield per MeV.Results A 4%to 26%improvement of energy resolution can be achieved for 5 MeV reactor antineutrinos at TAO.Conclusion The emission direction of the produced positron in IBD reaction can be used to estimate the kinetic energy of neutron and thus the reconstructed antineutrino energy resolution can be improved.

Three-dimensional reconstruction for a large scene of integral imaging based on color-position characteristics

A new large-scale three-dimensional(3D) reconstruction technology based on integral imaging with color-position characteristics is presented.The color of the object point is similar to those of corresponding points.The corresponding point coordinates form arithmetic progressions because integral imaging captures information with a senior array which has similar pitches on x and y directions.This regular relationship is used to determine the corresponding point parameters for reconstructing 3D information from divided elemental images separated by color,which contain several corresponding points.The feasibility of the proposed method is demonstrated through an optical indoor experiment.A large-scale application of the proposed method is illustrated by the experiment with a corner of our school as its object.

Analysis of the spatial discrimination threshold of head-related transfer function magnitude

A binaural-loudness-model-based method for evaluating the spatial discrimination threshold of magnitudes of head-related transfer function（HRTF） is proposed.As the input of the binaural loudness model,the HRTF magnitude variations caused by spatial position variations were firstly calculated from a high-resolution HRTF dataset.Then,three perceptualrelevant parameters,namely interaural loudness level difference,binaural loudness level spectra,and total binaural loudness level,were derived from the binaural loudness model.Finally,the spatial discrimination thresholds of HRTF magnitude were evaluated according to just-noticedifference of the above-mentioned perceptual-relevant parameters.A series of psychoacoustic experiments was also conducted to obtain the spatial discrimination threshold of HRTF magnitudes.Results indicate that the threshold derived from the proposed binaural-loudness-modelbased method is consistent with that obtained from the traditional psychoacoustic experiment,validating the effectiveness of the proposed method.

Spatial-temporal variation characteristics of global evaporation revealed by eight reanalyses

On the basis of eight atmospheric reanalyses, we analyzed the spatial-temporal characteristics of global evaporation and also briefly evaluated the eight reanalyses. The results indicate that the long-term mean annual evaporation obtained from different reanalyses are consistent over most regions, with significant maritime-continental contrasts, as well as differences in meridional directions, and the land evaporation generally decreases with the increase of altitude. In addition, the temporal evolution of global evaporation varies significantly among the datasets, MERRA, ERA-Interim, NCEP-NCRA, and NCEP-DOE are very similar, whereas CFSR agrees best with ERA-40. Comparison of the inter-annual to inter-decadal variability of land evaporation reveals large differences among the reanalyses, whereas MERRA, CFSR, and NCEP-DOE are exactly similar. The temporal variation of evaporation over the oceans showed a relatively high consistency, which indicates that the quality of the reconstructed evaporation values over the oceans is higher, and even greater uncertainties lie in the estimates of evaporation over the land. In general, MERRA and NCEP-DOE may appropriately reflect the spatial-temporal characteristics of global evaporation, showing strong representativeness. The CFSR and ERA-40 are capable of revealing the characteristics of land evaporation, whereas ERA-Interim, NCEP-NCAR, OAFlux, and HOAPS are relatively applicable for research focused on the evaporation over the oceans. According to ERA-40, NCEP-NCAR, and OAFlux, global evaporation significantly decreased for the period of 1958–1978. In contrast, most of the eight reanalyses show a significant linear increase for the period of 1979–2011, and evaporation over the oceans was even more pronounced. Furthermore, the results are presented for the mean annual cycle of global evaporation, the changes at the low latitudes in the Northern Hemisphere are most distinct, and the monthly variation amplitude of the land evaporation was higher than that of the evaporation over the oceans.