Data-driven approach for modeling Reynolds stress tensor with invariance preservation

The present study represents a data-driven turbulent model with Galilean invariance preservation based on machine learning algorithm. The fully connected neural network (FCNN) and tensor basis neural network (TBNN) [Ling et al. (2016)] are established. The models are trained based on five kinds of flow cases with Reynolds Averaged Navier-Stokes (RANS) and high-fidelity data. The mappings between two invariant sets, mean strain rate tensor and mean rotation rate tensor as well as additional consideration of invariants of turbulent kinetic energy gradients, and the Reynolds stress anisotropy tensor are trained. The prediction of the Reynolds stress anisotropy tensor is treated as user's defined RANS turbulent model with a modified turbulent kinetic energy transport equation. The results show that both FCNN and TBNN models can provide more accurate predictions of the anisotropy tensor and turbulent state in square duct flow and periodic flow cases compared to the RANS model. The machine learning based turbulent model with turbulent kinetic energy gradient related invariants can improve the prediction precision compared with only mean strain rate tensor and mean rotation rate tensor based models. The TBNN model is able to predict a better flow velocity profile compared with FCNN model due to a prior physical knowledge.Comment: 23 page

Visualization of Sparus macrocephalus Infection by GFP- Labeled Edwardsiella tarda

Abstract Edwardsiella tarda is a fish pathogen that causes systemic infections in many marine and freshwater fish. The invasion pathway of E. tarda was studied in vivo in Sparus macrocephalus using a virulent strain of E. tarda, transformed with a plasmid encoding green fluorescent protein and sharing similar virulence characteristics as the parent strain. Fish were divided into six groups: (A) bacteria bath-challenged, unwounded fish, (B) bacteria bath-challenged fish, skin mucus layer partially removed by paper towel, (C) bacteria bath-challenged fish, skin artificially wounded by scalpel, (D) bacteria intramuscularly-challenged fish, (E) normal fish, and (F) phosphate-buffered saline intramuscularly-treated fish. The number of bacteria from blood, gills, kidney, muscle, spleen, liver, and intestine were determined 2, 4, 6, 12, 24, and 48 h post-challenge. High numbers of bacteria were observed in the gills and intestine, followed by the liver, kidney, spleen, and muscle of infected fish. The number of bacteria was significantly higher in groups B and C than in group A. The skin, intestine, and gills were likely the main routes of entry for E. tarda. The IJA appears exclusively as a peer-reviewed on-line open-access journal at http://www.siamb.org.il. Only registered persons are able to access full papers. To register free of charge, complete and return our registration form. 2 Wang et al

Efficient perpendicular magnetization switching by a magnetic spin Hall effect in a noncollinear antiferromagnet

Current induced spin-orbit torques driven by the conventional spin Hall effect are widely used to manipulate the magnetization. This approach, however, is nondeterministic and inefficient for the switching of magnets with perpendicular magnetic anisotropy that are demanded by the high-density magnetic storage and memory devices. Here, we demonstrate that this limitation can be overcome by exploiting a magnetic spin Hall effect in noncollinear antiferromagnets, such as Mn3Sn. The magnetic group symmetry of Mn3Sn allows generation of the out-of-plane spin current carrying spin polarization collinear to its direction induced by an in-plane charge current. This spin current drives an out-of-plane anti-damping torque providing the deterministic switching of the perpendicular magnetization of an adjacent Ni/Co multilayer. Due to being odd with respect to time reversal symmetry, the observed magnetic spin Hall effect and the resulting spin-orbit torque can be reversed with reversal of the antiferromagnetic order. Contrary to the conventional spin-orbit torque devices, the demonstrated magnetization switching does not need an external magnetic field and requires much lower current density which is useful for low power spintronics

Analysis of fine grained sand and shale sedimentary characteristics in estuary based on sediment dynamics

Due to the dual effects of fluvial and tides, the tidal sand bars in estuaries have complex sedimentary characteristics and complex internal structures, making them difficult to predict and describe. In this paper, the sedimentary dynamics numerical simulation method is used to establish a tidal-controlled estuary model. The effects of tidal range and sediment grain size on tidal sand bars are simulated. The length, width, and thickness of tidal sand bars, as well as the length and thickness of the internal shale layer, are also analyzed. The results show that in the environment of a tide-controlled estuary, the tidal range has a more significant effect on tidal sand bars compared to the sediment grain size under the specific conditions used in this study. The main effect of tidal range on tidal sand bars is that the greater the tidal range, the greater the length-to-width ratio of the sandbank, and the higher the degree of sandbank development. In a tidal-controlled estuary environment, the formation and distribution of shale layer structures are also affected by tides: the length of the shale layer increases as the tidal energy increases, but the changes in the thickness are not obvious. Numerical simulations of the development and distribution of the tidal sand bars and shale layers in estuaries based on sedimentary dynamics will provide a basis for the sedimentary evolution of tide-controlled estuaries and will provide guidance for the exploration and development of tidal estuaries

Comparative genomics reveals adaptive evolution of Asian tapeworm in switching to a new intermediate host

Taenia saginata, Taenia solium and Taenia asiatica (beef, pork and Asian tapeworms, respectively) are parasitic flatworms of major public health and food safety importance. Among them, T. asiatica is a newly recognized species that split from T. saginata via an intermediate host switch ∼1.14 Myr ago. Here we report the 169- and 168-Mb draft genomes of T. saginata and T. asiatica. Comparative analysis reveals that high rates of gene duplications and functional diversifications might have partially driven the divergence between T. asiatica and T. saginata. We observe accelerated evolutionary rates, adaptive evolutions in homeostasis regulation, tegument maintenance and lipid uptakes, and differential/specialized gene family expansions in T. asiatica that may favour its hepatotropism in the new intermediate host. We also identify potential targets for developing diagnostic or intervention tools against human tapeworms. These data provide new insights into the evolution of Taenia parasites, particularly the recent speciation of T. asiatica

Visualization of Sparus macrocephalus Infection by GFP-Labeled Edwardsiella tarda

Edwardsiella tarda is a fish pathogen that causes systemic infections in many marine and freshwater fish. The invasion pathway of E. tarda was studied in vivo in Sparus macrocephalus using a virulent strain of E. tarda, transformed with a plasmid encoding green fluorescent protein and sharing similar virulence characteristics as the parent strain. Fish were divided into six groups: (A) bacteria bath-challenged, unwounded fish, (B) bacteria bath-challenged fish, skin mucus layer partially removed by paper towel, (C) bacteria bath-challenged fish, skin artificially wounded by scalpel, (D) bacteria intramuscularly-challenged fish, (E) normal fish, and (F) phosphate-buffered saline intramuscularly-treated fish. The number of bacteria from blood, gills, kidney, muscle, spleen, liver, and intestine were determined 2, 4, 6, 12, 24, and 48 h post-challenge. High numbers of bacteria were observed in the gills and intestine, followed by the liver, kidney, spleen, and muscle of infected fish. The number of bacteria was significantly higher in groups B and C than in group A. The skin, intestine, and gills were likely the main routes of entry for E. tarda

Genetic Mechanism of Lower-Order Faults in Shale Formations in Rift Basins

The distribution of lower-order faults affects the development of oil and gas and the distribution of remaining oil, which is also the key to the development of fault block reservoirs in eastern China. The lower-order faults are characterized by short extension, small fault displacement, and difficult identification by traditional seismic interpretation methods. Therefore, it is necessary to predict the development law of faults in combination with the paleostress field during the fault formation period to improve the accuracy of fault seismic interpretation. In this paper, on the basis of reservoir structural analysis and rock mechanics experiments, the geological and mechanical model of the Sanduo period is established to predict the simulation of the paleostress field during the development of lower-order faults. The development of lower-order faults in rift basins is mainly controlled by the minimum principal stress and stress difference, and the shear stress in the profile controls the tendency of faults. Controlled by the paleostress field, the occurrence of lower-order faults in the Weizhuang area, Gaoyou Sag, and Subei Basin is very complex, and the strike of the fault is distributed as a tension shear broom on the plane. The prediction results can provide a reference for the excavation of remaining oil and the development of oil and gas

An Improved Peak Sidelobe Reduction Method for Subarrayed Beam Scanning

This paper focused on PSL (peak sidelobe level) reduction for subarrayed beam scanning in phased array radars. The desired GSP (Gaussian Subarray Patterns) are achieved by creating a subarray weighting network. The GSP-based method could reduce PSL of array pattern; compared with the method based on the desired subarray pattern which is defined by ideal space-domain filter, the PSL reduction performance is improved remarkably. Further, based on the concept adopting superelement patterns to approximately express original subarray patterns, the simplified GSP-based method is proposed. So the dimension of each matrix required for creating the weighting network, which was originally the same as the element number, could be reduced to the same as the subarray number. Consequently, we achieve remarkable reduction of the computation burden; simultaneously, the PSL mitigation performance is degraded slightly. Simulation results demonstrate the validity of the introduced methods