Two-dimensional antiferroelectric tunnel junction

Ferroelectric tunnel junctions (FTJs), which consist of two metal electrodes separated by a thin ferroelectric barrier, have recently aroused significant interest for technological applications as nanoscale resistive switching devices. So far, most of existing FTJs have been based on perovskite-oxide barrier layers. The recent discovery of the two-dimensional (2D) van der Waals ferroelectric materials opens a new route to realize tunnel junctions with new functionalities and nm-scale dimensions. Due to the weak coupling between the atomic layers in these materials, the relative dipole alignment between them can be controlled by applied voltage. This allows transitions between ferroelectric and antiferroelectric orderings, resulting in significant changes of the electronic structure. Here, we propose to realize 2D antiferroelectric tunnel junctions (AFTJs), which exploit this new functionality, based on bilayer In$_2$X$_3$ (X = S, Se, Te) barriers and different 2D electrodes. Using first-principles density functional theory calculations, we demonstrate that the In$_2$X$_3$ bilayers exhibit stable ferroelectric and antiferroelectric states separated by sizable energy barriers, thus supporting a non-volatile switching between these states. Using quantum-mechanical modeling of the electronic transport, we explore in-plane and out-of-plane tunneling across the In$_2$S$_3$ van der Waals bilayers, and predict giant tunneling electroresistance (TER) effects and multiple non-volatile resistance states driven by ferroelectric-antiferroelectric order transitions. Our proposal opens a new route to realize nanoscale memory devices with ultrahigh storage density using 2D AFTJs

Two-Dimensional Antiferroelectric Tunnel Junction

Ferroelectric tunnel junctions (FTJs), which consist of two metal electrodes separated by a thin ferroelectric barrier, have recently aroused significant interest for technological applications as nanoscale resistive switching devices. So far, most existing FTJs have been based on perovskite-oxide barrier layers. The recent discovery of the two-dimensional (2D) van der Waals ferroelectric materials opens a new route to realize tunnel junctions with new functionalities and nm-scale dimensions. Because of the weak coupling between the atomic layers in these materials, the relative dipole alignment between them can be controlled by applied voltage. This allows transitions between ferroelectric and antiferroelectric orderings, resulting in significant changes of the electronic structure. Here, we propose to realize 2D antiferroelectric tunnel junctions (AFTJs), which exploit this new functionality, based on bilayer In2X3 (X = S, Se, Te) barriers and different 2D electrodes. Using first-principles density functional theory calculations, we demonstrate that the In2X3 bilayers exhibit stable ferroelectric and antiferroelectric states separated by sizable energy barriers, thus supporting a nonvolatile switching between these states. Using quantum-mechanical modeling of the electronic transport, we explore in-plane and out-of-plane tunneling across the In2S3 van der Waals bilayers, and predict giant tunneling electroresistance effects and multiple nonvolatile resistance states driven by ferroelectric-antiferroelectric order transitions. Our proposal opens a new route to realize nanoscale memory devices with ultrahigh storage density using 2D AFTJs

In Situ Production of Copper Oxide Nanoparticles in a Binary Molten Salt for Concentrated Solar Power Plant Applications

Seeding nanoparticles in molten salts has been shown recently as a promising way to improve their thermo-physical properties. The prospect of such technology is of interest to both academic and industrial sectors in order to enhance the specific heat capacity of molten salt. The latter is used in concentrated solar power plants as both heat transfer fluid and sensible storage. This work explores the feasibility of producing and dispersing nanoparticles with a novel one pot synthesis method. Using such a method, CuO nanoparticles were produced in situ via the decomposition of copper sulphate pentahydrate in a KNO3-NaNO3 binary salt. Analyses of the results suggested preferential disposition of atoms around produced nanoparticles in the molten salt. Thermal characterization of the produced nano-salt suspension indicated the dependence of the specific heat enhancement on particle morphology and distribution within the salts

Position Based Balloon Angioplasty

Balloon angioplasty is an endovascular procedure to widen narrowed or obstructed blood vessels, typically to treat arterial atherosclerosis. Simulating angioplasty procedure in the complex vascular structures is a challenge task since the balloon and vessels are both flexible bodies. In this paper, we proposed a position based balloon physical model to solve nonlinear physical deformation in the process of balloon inflation. Firstly, the balloon is discrete modeled by the closed triangle mesh, and the hyperelastic membrane material and continuum based formulation are combined to compute the mechanical properties in the process of balloon inflation. Then, an adaptive air mesh generation algorithm is proposed as a preprocessing procedure for accelerating the coming collision process between balloon and blood vessel according to the characteristic of collision area which is relative fixed. The experiment results show that this physical model is feasible, which could simulate the contact and deformation process between the inflation balloon and the diseased blood vessel wall with good robustness and in realtime

A modified Euler-Lagrange-Euler approach for modelling homogeneous and heterogeneous condensing droplets and films in supersonic flows

This is the final version. Available from Elsevier via the DOI in this record.Data availability: No data was used for the research described in the article.The phase change in supersonic flows is of great interest in many industrial applications including steam turbines, nozzles, ejectors and aircraft. However, the phase change phenomenon is still not fully understood due to the completed flow behavior including nucleation, condensation, film generation and shock waves in supersonic flows. In the present study, we proposed a modified Euler-Lagrange-Euler model to explore the internal flow mechanism within supersonic separators. The mutual heat and mass transfer of the gaseous phase, droplets, and liquid film were simulated in supersonic flows. The homogeneous nucleation and growth model was innovatively added to ensure the model’s comprehensiveness. The feasibility of the proposed model was validated by experiments. Then, the interaction of heterogeneous and homogeneous condensation in supersonic condensation flow was excavated for the first time. The results show the heterogeneous droplet diameter’s decrease or concentration’s increase had a significant inhibitory effect on homogeneous condensation. Subsequently, the supersonic swirl field’s generation, the dynamic evolution of the homogeneous/heterogeneous droplet condensation and deposition, the liquid film development, and the heat-mass transfer between them in the supersonic separator were analyzed using the proposed model. Furthermore, the separation capacity of the supersonic separator was evaluated considering the co-action of homogeneous and heterogeneous condensation. Results show that increasing inlet droplet concentration from 0.0001 kg/s to 0.0025 kg/s can increase vapor separation efficiency and dew point depression from 61.39 % to 84.74 % and 19.03 K to 28.28 K, respectively.National Natural Science Foundation of ChinaNational Natural Science Foundation of ChinaNational Natural Science Foundation of Chin

Nonlinear Anomalous Hall Effect for Néel Vector Detection

Antiferromagnetic (AFM) spintronics exploits the Néel vector as a state variable for novel spintronic devices. Recent studies have shown that the fieldlike and antidamping spin-orbit torques (SOTs) can be used to switch the Néel vector in antiferromagnets with proper symmetries. However, the precise detection of the Néel vector remains a challenging problem. In this Letter, we predict that the nonlinear anomalous Hall effect (AHE) can be used to detect the Néel vector in most compensated antiferromagnets supporting the antidamping SOT. We show that the magnetic crystal group symmetry of these antiferromagnets combined with spin-orbit coupling produce a sizable Berry curvature dipole and hence the nonlinear AHE. As a specific example, we consider the half-Heusler alloy CuMnSb, in which the Néel vector can be switched by the antidamping SOT. Based on density-functional theory calculations, we show that the nonlinear AHE in CuMnSb results in a measurable Hall voltage under conventional experimental conditions. The strong dependence of the Berry curvature dipole on the Néel vector orientation provides a new detection scheme of the Néel vector based on the nonlinear AHE. Our predictions enrich the material platform for studying nontrivial phenomena associated with the Berry curvature and broaden the range of materials useful for AFM spintronics

Energy efficiency assessment of hydrogen recirculation ejectors for proton exchange membrane fuel cell (PEMFC) system

This is the final version. Available from Elsevier via the DOI in this record. Data availability statement: The research data supporting this publication are provided within this paper.The ejector is the core component for hydrogen recirculation in a proton exchange membrane fuel cell (PEMFC) system. However, in the past, the computational fluid dynamics (CFD) simulation of the ejector mainly focused on the influence of the change of the structural parameters on its performance, while the research on phase change condensation was lacking. Here, we proposed a two-phase flow model integrating the non-equilibrium phase change conservation equations and four categories of entropy transport equations, which analysed the phase change characteristics and the influence of different primary pressures on the property of ejector and internal entropy and exergy under the dry and wet gas models. We validated that the wet gas model has a good prediction ability with an MRE of only 2.53%. There was a significant difference between the dry and wet gas models, for example, the dry gas model predicted a larger Mach number and entrainment ratio, while the temperature and pressure were less than that of the wet gas model. Finally, the entropy and exergy were analysed, and the dry gas model overestimated the entropy generation, i.e, when the pressure of the primary inlet raised to 5.0 bar, the entropy generation overestimated by the dry gas model had reached 138.66 J kg-1K− 1 . The exergy destruction and exergy destruction ratio both increased with the rise of primary pressure. The dry gas model overestimated the exergy destruction and exergy destruction ratio, and the maximum overestimated values can reach 41.83 kJ/kg and 15.83%, respectively.National Natural Science Foundation of ChinaNational Natural Science Foundation of Chin

Scale-free download network for publications

The scale-free power-law behavior of the statistics of the download frequency of publications has been, for the first time, reported. The data of the download frequency of publications are taken from a well-constructed web page in the field of economic physics (http://www.unifr.ch/econophysics/). The Zipf-law analysis and the Tsallis entropy method were used to fit the download frequency. It was found that the power-law exponent of rank-ordered frequency distribution is $\gamma \sim 0.38 \pm 0.04$ which is consistent with the power-law exponent $\alpha \sim 3.37 \pm 0.45$ for the cumulated frequency distributions. Preferential attachment model of Barabasi and Albert network has been used to explain the download network.Comment: 3 pages, 2 figure