Symmetry guaranteed Dirac-line semimetals in two-dimensions against strong spin-orbit coupling

Several intriguing electronic phenomena and electric properties were discovered in three-dimensional Dirac nodal line semimetals (3D-DNLSM), which are, however, easy to be perturbed under strong spin-orbit coupling (SOC). While two-dimensional (2D) layers are an emerging material category with many advantages, 2D-DNLSM against SOC is yet to be uncovered. Here, we report a 2D-DNLSM in odd-atomic-layer Bi (the brick phase, another Bi allotrope), whose robustness against SOC is protected by the little co-group C_2v \times Z^T_2, the unique protecting symmetry we found in 2D.Specially, (4n+2) valence electrons fill the electronic bands in the brick phase, so that the Dirac nodal line with fourfold degeneracy locates across the Fermi level. There are almost no other low energy states close to the Fermi level; this allows to feasibly observe the neat DNLSM-induced phenomena in transport measurements without being affected by other bands. In contrast, Other VA-group elements also form the brick phases, but their DNL states are mixed with the extra states around the Fermi level. This unprecedented category of layered materials allows for exploring nearly isolated 2DDNL states in 2D.Comment: Totally 25 pages including main text, methods and supporting information, 4 figures, 8 SI figure

Influence of Ag micro-alloying on the thermal stability and ageing characteristics of a Cu–14Fe in-situ composite

This paper studied the influence of Ag micro-alloying on the thermal stability and ageing characteristics of a deformation-processed Cu–14Fe in-situ composite prepared by thermo-mechanical processing. Heat treatment caused (i) edge recession, longitudinal splitting, cylinderization, break-up and spheroidisation of the Fe fibres in the Ag micro-alloyed Cu–14Fe in-situ composite, and (ii) recovery, recrystallisation and precipitation in the Cu matrix. Ag micro-alloying caused these processes to occur at lower temperatures. The index Z (a combination figure of merit that assesses the service performance) reached the peak value of 3.3×10 MPa·% IACS after isothermal heat treatment at 500 °C for 1 h, where IACS is the International Annealed Copper Standard, a measure of conductivity. The optimum combinations of tensile strength and conductivity were 1033 MPa and 56.6% IACS; 931 MPa and 58.9% IACS; or 851 MPa and 60.6% IACS. The tensile strength and conductivity of Ag micro-alloyed Cu–14Fe in-situ composite at η=7.8 after isochronal heat treatments were higher than those of the Cu–14Fe in-situ composite at each temperature

Susceptibility Analysis on Landslide Triggering Factors During the 2008 Wenchuan Earthquake

The 2008 Wenchuan earthquake with Mw7.9 induced numerous landslides along the Longmen Mt. zone in Sichuan Province of China. The authors investigated into various influential factors on the slope stability of 119 landslides in Wenchuan County, such as horizontal peak ground acceleration, slope angle, slope height, rock materials and geological structures. The authors developed hanging wall and footwall‟s acceleration attenuation formulae from 115 seismic stations and the formulae confirmed hanging-foot wall effect had notable influence on landslide distribution density and occurrence probability. The results of multivariable analysis clarified that slope height, horizontal peak ground acceleration and geological structures were more influential to sliding area and volume than slope angle and rock materials

地震時における斜面の安定性と地すべりの運動特性に関する研究

早大学位記番号:新6497早稲田大

Collaborative Viewpoint Adjusting and Grasping via Deep Reinforcement Learning in Clutter Scenes

For the robotic grasping of randomly stacked objects in a cluttered environment, the active multiple viewpoints method can improve grasping performance by improving the environment perception ability. However, in many scenes, it is redundant to always use multiple viewpoints for grasping detection, which will reduce the robot’s grasping efficiency. To improve the robot’s grasping performance, we present a Viewpoint Adjusting and Grasping Synergy (VAGS) strategy based on deep reinforcement learning which coordinates the viewpoint adjusting and grasping directly. For the training efficiency of VAGS, we propose a Dynamic Action Exploration Space (DAES) method based on ε-greedy to reduce the training time. To address the sparse reward problem in reinforcement learning, a reward function is created to evaluate the impact of adjusting the camera pose on the grasping performance. According to experimental findings in simulation and the real world, the VAGS method can improve grasping success and scene clearing rate. Compared with only direct grasping, our proposed strategy increases the grasping success rate and the scene clearing rate by 10.49% and 11%

Collaborative Viewpoint Adjusting and Grasping via Deep Reinforcement Learning in Clutter Scenes

For the robotic grasping of randomly stacked objects in a cluttered environment, the active multiple viewpoints method can improve grasping performance by improving the environment perception ability. However, in many scenes, it is redundant to always use multiple viewpoints for grasping detection, which will reduce the robot’s grasping efficiency. To improve the robot’s grasping performance, we present a Viewpoint Adjusting and Grasping Synergy (VAGS) strategy based on deep reinforcement learning which coordinates the viewpoint adjusting and grasping directly. For the training efficiency of VAGS, we propose a Dynamic Action Exploration Space (DAES) method based on ε-greedy to reduce the training time. To address the sparse reward problem in reinforcement learning, a reward function is created to evaluate the impact of adjusting the camera pose on the grasping performance. According to experimental findings in simulation and the real world, the VAGS method can improve grasping success and scene clearing rate. Compared with only direct grasping, our proposed strategy increases the grasping success rate and the scene clearing rate by 10.49% and 11%

A coupled elastoplastic damage model for brittle rocks

Brittle rock contains an important plastic deformation, which causes microcracks when coupled with stress-induced damage. A new coupled elastoplastic damage model is established in order to discuss the damage behaviors found in brittle rock, based on theoretical analysis and experiments. Micromechanic considerations determine the effective elastic properties of anisotropic damaged geomaterials. An energy-based damage criterion is used to deduce the damage initiation and the damage evolution law of the brittle rocks. Moreover, the non-linear unified strength criterion is modified. It takes anisotropic damage and the effects of intermediate principal stress into account, in order to determine both the yield and plastic potential functions. The non-associated plastic flow rule is utilized. The consistency condition of plastic and damage is applied in the coupled process. The damage evolution rule and the coupled plastic damage of brittle rock are conceived within the framework of irreversible thermodynamics. By comparing the simulations and the experimental data from limestone that was subjected to various loading paths, a strong connection between the numerical simulations and experimental data is therefore obtained. The numerical results show that the new model is able to describe the main features of the mechanical properties observed in brittle rock

A coupled elastoplastic damage model for brittle rocks: elastoplastic damage model for brittle rocks

Brittle rock contains an important plastic deformation, which causes microcracks when coupled with stress-induced damage. A new coupled elastoplastic damage model is established in order to discuss the damage behaviors found in brittle rock, based on theoretical analysis and experiments. Micromechanic considerations determine the effective elastic properties of anisotropic damaged geomaterials. An energy-based damage criterion is used to deduce the damage initiation and the damage evolution law of the brittle rocks. Moreover, the non-linear unified strength criterion is modified. It takes anisotropic damage and the effects of intermediate principal stress into account, in order to determine both the yield and plastic potential functions. The non-associated plastic flow rule is utilized. The consistency condition of plastic and damage is applied in the coupled process. The damage evolution rule and the coupled plastic damage of brittle rock are conceived within the framework of irreversible thermodynamics. By comparing the simulations and the experimental data from limestone that was subjected to various loading paths, a strong connection between the numerical simulations and experimental data is therefore obtained. The numerical results show that the new model is able to describe the main features of the mechanical properties observed in brittle rock