Imaging phonon-mediated hydrodynamic flow in WTe2

In the presence of interactions, electrons in condensed-matter systems can behave hydrodynamically, exhibiting phenomena associated with classical fluids, such as vortices and Poiseuille flow. In most conductors, electron-electron interactions are minimized by screening effects, hindering the search for hydrodynamic materials; however, recently, a class of semimetals has been reported to exhibit prominent interactions. Here we study the current flow in the layered semimetal tungsten ditelluride by imaging the local magnetic field using a nitrogen-vacancy defect in a diamond. We image the spatial current profile within three-dimensional tungsten ditelluride and find that it exhibits non-uniform current density, indicating hydrodynamic flow. Our temperature-resolve current profile measurements reveal a non-monotonic temperature dependence, with the strongest hydrodynamic effects at approximately 20 K. We also report ab initio calculations showing that electron-electron interactions are not explained by the Coulomb interaction alone, but are predominantly mediated by phonons. This provides a promising avenue in the search for hydrodynamic flow and prominent electron interactions in high-carrier-density materials.Comment: 11 pages, 4 figures + supplementary materia

Lens Learning Sparrow Search Algorithm

In this paper, a lens learning sparrow search algorithm (LLSSA) is proposed to improve the defects of the new sparrow search algorithm, which is random and easy to fall into local optimum. The algorithm has achieved good results in function optimization and has planned a safer and less costly path to the three-dimensional UAV path planning. In the discoverer stage, the algorithm introduces the reverse learning strategy based on the lens principle to improve the search range of sparrow individuals and then proposes a variable spiral search strategy to make the follower's search more detailed and flexible. Finally, it combines the simulated annealing algorithm to judge and obtain the optimal solution. Through 15 standard test functions, it is verified that the improved algorithm has strong search ability and mining ability. At the same time, the improved algorithm is applied to the path planning of 3D complex terrain, and a clear, simple, and safe route is found, which verifies the effectiveness and practicability of the improved algorithm

The Effect of Yttrium on the Solution and Diffusion Behaviors of Helium in Tungsten: First-Principles Simulations

We systematically investigated the influence of yttrium (Y) on the evolution behavior of helium (He) in tungsten (W) by first-principles calculations. It is found that the addition of Y reduces the solution energy of He atoms in W. Interestingly, the solution energy of He decreases with decreasing distance between Y and He. The binding energies between Y and He are inversely correlated with the effective charge of He atoms, which can be attributed to the closed shell structure of He. In addition, compared with pure W, the diffusion barrier (0.033 eV) of He with Y is lower, calculated by the climbing-image nudged elastic band (CI-NEB) simulations, reflecting that the existence of Y contributes to the diffusion of He in W. The obtained results provide a theoretical direction for understanding the diffusion of He

Influence of size of graphene oxide on interfacial properties of carbon fiber/epoxy resin under damp and heat conditions

Two different sizes of graphene oxide (GO) produced by the Hummers method had been incorporated into epoxy resins and used to fabricate GO modified carbon fiber reinforced epoxy resin composites (GO/CF/EP) by compression molding method, and the composite material was processed under damp and heat conditions. The modification effects of dry and wet composite materials were investigated through interlayer shear performance, dynamic thermomechanical properties and microscopic morphology. The results indicate that GO has a good improvement on the interlaminar shear strength and glass transition temperature of composite materials. In the dry state at room temperature, two sizes of GO have basically the same improvement effect on the interlaminar shear strength of the composite. With the increase of GO content, the small size of GO makes the hygrothermal interlaminar shear strength of composites decrease faster. When the GO content is 0.1%(mass fraction, the same as below), the improvement of the interlaminar shear performance of the composite material is better, however, the glass transition temperature of the composite material is better when the GO content is 0.2%. With the increase of GO content, the exothermic peak of the GO-EP composite resin matrix shifts to low temperature, and the small size of GO shortens the gel time of the composite resin. The micro-morphology analysis shows the presence of GO is beneficial for increasing the crack propagation path during the failure of composite material, thereby more conducive to the dissipate the crack tip energy by the material

Preparation and certification of two freshwater sediments certified reference materials for polycyclic aromatic hydrocarbons

<div><p>Two freshwater sediments certified reference materials (CRMs) for 16 polycyclic aromatic hydrocarbons (PAHs) have been developed by the Institute for Environmental Reference Materials (IERM) of Ministry of Environmental Protection (MEP) in China. The methodology for preparing the CRMs of PAHs in sediments is described in this paper. The collected natural sediment samples were air-dried, ground, homogenised, packed, sterilised and tested on stability and homogeneity. Homogeneity results showed that the between-unit variation was confirmed to be below 4.5% for each compound. Stability was assessed after storage of samples for 16 months at temperature less than 30°C and in shade. The certification of the natural sediment matrix CRMs for PAHs was based on the agreement of results using different analytical techniques including gas chromatography/mass spectrometry (GC/MS) and reversed-phase liquid chromatography (LC) by no less than eight collaborating laboratories including IERM. Results of the homogeneity showed that the calculated <i>u</i>_bb′ was 0.9–2.5% for environmental river standard-4 (ERS-4) and 9–2.3% for environmental lake standard-1 (ELS-1), whereas stability results of total 16 PAHs indicated that the calculated <i>u</i>_rel,lts was 4.2% for ERS-4 and 2.2% for ELS-1. Certified values of 16 PAHs in ERS-4 varied from 8.5 to 167 μg/kg and ranged from 0.036 to 2.8 mg/kg in ELS-1.The good comparability, together with the independent confirmation of the assigned mass fraction by using different methods, confirmed that the CRMs are suitable for the method validation and quality control in soil or sediments analysis.</p></div

Achieving Invisibility of Homogeneous Cylindrically Anisotropic Cylinders

10.1007/s11468-010-9145-8Plasmonics53251-25

An All-Protein Multisensory Highly Bionic Skin

To achieve a highly realistic robot, closely mimicking human skin in terms of materials and functionality is essential. This paper presents an all-protein silk fibroin bionic skin (SFBS) that emulates both fast-adapting (FA) and slow-adapting (SA) receptors. The mechanically different silk film and hydrogel, which exhibited skin-like properties, such as stretchability (>140%), elasticity, low modulus (<10 kPa), biocompatibility, and degradability, were prepared through mesoscopic reconstruction engineering to mimic the epidermis and dermis. Our SFBS, incorporating SA and FA sensors, demonstrated a highly sensitive (1.083 kPa–1) static pressure sensing performance (in vitro and in vivo), showed the ability to sense high-frequency vibrations (50–400 Hz), could discriminate materials and sliding, and could even identify the fine morphological differences between objects. As proof of concept, an SFBS-integrated rehabilitation glove was synthesized, which could help stroke patients regain sensory feedback. In conclusion, this work provides a practical approach for developing skin equivalents, prostheses, and smart robots

An All-Protein Multisensory Highly Bionic Skin

To achieve a highly realistic robot, closely mimicking human skin in terms of materials and functionality is essential. This paper presents an all-protein silk fibroin bionic skin (SFBS) that emulates both fast-adapting (FA) and slow-adapting (SA) receptors. The mechanically different silk film and hydrogel, which exhibited skin-like properties, such as stretchability (>140%), elasticity, low modulus (<10 kPa), biocompatibility, and degradability, were prepared through mesoscopic reconstruction engineering to mimic the epidermis and dermis. Our SFBS, incorporating SA and FA sensors, demonstrated a highly sensitive (1.083 kPa–1) static pressure sensing performance (in vitro and in vivo), showed the ability to sense high-frequency vibrations (50–400 Hz), could discriminate materials and sliding, and could even identify the fine morphological differences between objects. As proof of concept, an SFBS-integrated rehabilitation glove was synthesized, which could help stroke patients regain sensory feedback. In conclusion, this work provides a practical approach for developing skin equivalents, prostheses, and smart robots

An All-Protein Multisensory Highly Bionic Skin

To achieve a highly realistic robot, closely mimicking human skin in terms of materials and functionality is essential. This paper presents an all-protein silk fibroin bionic skin (SFBS) that emulates both fast-adapting (FA) and slow-adapting (SA) receptors. The mechanically different silk film and hydrogel, which exhibited skin-like properties, such as stretchability (>140%), elasticity, low modulus (<10 kPa), biocompatibility, and degradability, were prepared through mesoscopic reconstruction engineering to mimic the epidermis and dermis. Our SFBS, incorporating SA and FA sensors, demonstrated a highly sensitive (1.083 kPa–1) static pressure sensing performance (in vitro and in vivo), showed the ability to sense high-frequency vibrations (50–400 Hz), could discriminate materials and sliding, and could even identify the fine morphological differences between objects. As proof of concept, an SFBS-integrated rehabilitation glove was synthesized, which could help stroke patients regain sensory feedback. In conclusion, this work provides a practical approach for developing skin equivalents, prostheses, and smart robots