Dielectric properties of TbMnO3 ceramics doped with Bi and Fe ions

AbstractThe ceramic composites of TbMnO3, Tb0.95Bi0.05MnO3, Tb0.9Bi0.1MnO3 and Tb0.9Bi0.1Mn0.95Fe0.05O3 were compounded by conventional solid-state reaction. Both dielectric constants (ɛ′) and loss tangent (tanδ) of composites have been measured and studied as a function of the temperature from 80 to 400K and the frequency from 100Hz to 1MHz. Interestingly, doping Bi makes dielectric constant decrease and the dielectric dissipation peaks disappear in the high temperature range. But the dielectric constant becomes larger and the dielectric dissipation peaks appear again in the high temperature range after Fe doping appropriately. Analysis indicates that the perovskite structures gradually vary with the increase of Bi replacing Tb, thus the dielectric properties could be enhanced with the small amount of Mn replacement with Fe

Mask DINO: Towards A Unified Transformer-based Framework for Object Detection and Segmentation

In this paper we present Mask DINO, a unified object detection and segmentation framework. Mask DINO extends DINO (DETR with Improved Denoising Anchor Boxes) by adding a mask prediction branch which supports all image segmentation tasks (instance, panoptic, and semantic). It makes use of the query embeddings from DINO to dot-product a high-resolution pixel embedding map to predict a set of binary masks. Some key components in DINO are extended for segmentation through a shared architecture and training process. Mask DINO is simple, efficient, and scalable, and it can benefit from joint large-scale detection and segmentation datasets. Our experiments show that Mask DINO significantly outperforms all existing specialized segmentation methods, both on a ResNet-50 backbone and a pre-trained model with SwinL backbone. Notably, Mask DINO establishes the best results to date on instance segmentation (54.5 AP on COCO), panoptic segmentation (59.4 PQ on COCO), and semantic segmentation (60.8 mIoU on ADE20K) among models under one billion parameters. Code is available at \url{https://github.com/IDEACVR/MaskDINO}

Electrical control of spin coherence in ZnO

Electric field enhanced electron spin coherence is characterized using time-resolved Faraday rotation spectroscopy in n-type ZnO epilayers grown by molecular beam epitaxy. An in-plane dc electric field E almost doubles the transverse spin lifetime at 20 K, without affecting the effective g-factor. This effect persists till high temperatures, but decreases with increasing carrier concentration. Comparisons of the variations in the spin lifetime, the carrier recombination lifetime and photoluminescence lifetimes indicate that the applied E enhances the radiative recombination rate. All observed effects are independent of crystal directionality and are performed at low magnetic fields (B < 0.2 T).Comment: 13 pages, 3 figure

Gap opening of single-layer graphene under the continuum model

Gap opening at the Dirac point of the single-layer graphene with periodic scalar and vector potentials has been theoretically investigated under the continuum model. The symmetry analysis indicates that the two-fold degeneracy at the Dirac point can be lifted when the potentials break both the chiral symmetry and the time-reversal symmetry. A gap equation at the Dirac point is obtained analytically with perturbation theory. It is shown that a mass term at the Dirac point would be generated by coupling of vector and scalar potentials. This gap equation could be considered as a criterion for gap opening at the Dirac point, which is confirmed by the numerical calculation. Furthermore, the bandgap from the gap equation agrees well with the exact result, when the applied potentials are weak.Comment: It contains 14 page in text written by MS word 2007, and 4 figure

Visual In-Context Prompting

In-context prompting in large language models (LLMs) has become a prevalent approach to improve zero-shot capabilities, but this idea is less explored in the vision domain. Existing visual prompting methods focus on referring segmentation to segment the most relevant object, falling short of addressing many generic vision tasks like open-set segmentation and detection. In this paper, we introduce a universal visual in-context prompting framework for both tasks. In particular, we build on top of an encoder-decoder architecture, and develop a versatile prompt encoder to support a variety of prompts like strokes, boxes, and points. We further enhance it to take an arbitrary number of reference image segments as the context. Our extensive explorations show that the proposed visual in-context prompting elicits extraordinary referring and generic segmentation capabilities to refer and detect, yielding competitive performance to close-set in-domain datasets and showing promising results on many open-set segmentation datasets. By joint training on COCO and SA-1B, our model achieves $57.7$ PQ on COCO and $23.2$ PQ on ADE20K. Code will be available at https://github.com/UX-Decoder/DINOv.Comment: technical repor

A theoretical study of resonant tunneling characteristics in triangular double-barrier diodes

Abstract Resonant tunneling characteristics of triangular double-barrier diodes have been investigated systematically in this Letter, using Airy function approach to solve time-independent Schrödinger function in triangular double-barrier structures. Originally, the exact analytic expressions of quasi-bound levels and quasi-level lifetime in symmetrical triangular double-barrier structures have been derived within the effective-mass approximation as a function of structure parameters including well width, slope width and barrier height. Based on our derived analytic expressions, numerical results show that quasi-bound levels and quasi-level lifetime vary nearly linearly with the structure parameters except that the second quasi-level lifetime changes parabolically with slope width. Furthermore, according to our improved transmission coefficient of triangular doublebarrier structures under external electric field, the current densities of triangular double-barrier diodes with different slope width at 0 K have been calculated numerically. The results show that the N-shaped negative differential resistance behaviors have been observed in current-voltage characteristics and current-voltage characteristics depend on the slope width

Oxocarbon-functionalized graphene as a lithium-ion battery cathode : a first-principles investigation

In recent years, organic-based, especially carbonyl-based, Li-ion battery electrode materials have attracted great attention due to their low-cost, environmentally friendly nature and strong Li-ion bonding abilities. However, new research is required to further increase the electron mobility and cycling performance of organic materials. The performance of a high-carbonyl C6O6 molecule-functionalized graphene electrode for Li-ion batteries is investigated using the density functional theory. The binding energy calculations indicate that the C6O6 molecule is adsorbed on graphene via physisorption. C6O6@graphene maintains excellent electronic conductivity with 1 to 6 Li ions. By our statistical method, the reduced voltage of the C6O6@graphene cathode displays a voltage between 2.6 V and 1.5 V with 2 phases from 1 to 6 Li ions with energy density of approximately 155 mA h g−1. The results obtained reveal that C6O6@graphene is a promising electrode material for renewable Li-ion batteries

Manipulating coupling state and magnetism of Mn-doped ZnO nanocrystals by changing the coordination environment of Mn via hydrogen annealing

Mn-doped ZnO nanocrystals are synthesized by a wet chemical route and treated in H2/Ar atmosphere with different H2/Ar ratios. It is found that hydrogen annealing could change the coordination environment of Mn in ZnO lattice and manipulate the magnetic properties of Mn-doped ZnO. Mn ions initially enter into interstitial sites and a Mn3+O6 octahedral coordination is produced in the prepared Mn-doped ZnO sample, in which the nearest neighbor Mn3+ and O2 ions could form a Mn3+-O2--Mn3+ complex. After H2 annealing, interstitial Mn ions can substitute for Zn to generate the Mn2+O4 tetrahedral coordination in the nanocrystals, in which neighboring Mn2+ ions and H atoms could form a Mn2+-O2--Mn2+ complex and Mn-H-Mn bridge structure. The magnetic measurement of the as-prepared sample shows room temperature paramagnetic behavior due to the Mn3+-O2--Mn3+ complex, while the annealed samples exhibit their ferromagnetism, which originates from the Mn-H-Mn bridge structure and the Mn-Mn exchange interaction in the Mn2+-O2--Mn2+ complex

MnO Nanoparticles Interdispersed in 3D Porous Carbon Framework for High Performance Lithium-Ion Batteries

Interdispersed MnO nanoparticles that are anchored and encapsulated in a three-dimensional (3D) porous carbon framework (MnO@CF) have been constructed, which display nanosphere architecture with rich porosity, well-defined carbon framework configuration, and excellent structure stability. When evaluated as an anode material, the MnO@CF exhibits relatively high specific capacity of 939 mA h g^–1 at current rate of 0.2 A g^–1 over 200 cycles and excellent rate capability of 560.2 mA h g^–1 at 4 A g^–1. By virtue of its mechanical stability and desirable ionic/electronic conductivity, the specific design can be a promising approach to fabricate high-performance lithium-ion batteries

Studia o Ksia·zce i Informacji

Zn1-xMnxO (x = 0.0005, 0.001, 0.005, 0.01, 0.02) nanocrystals are synthesized by using a wet chemical process. The coordination environment of Mn is characterized by X-ray photoelectron spectroscopy, Raman spectroscopy, and its X-ray absorption fine structure. It is found that the solubility of substitutional Mn in a ZnO lattice is very low, which is less than 0.4%. Mn ions first dissolve into the substitutional sites in the ZnO lattice, thereby forming Mn2+O4 tetrahedral coordination when x ≤ 0.001, then entering into the interstitial sites and forming Mn 3+O6 octahedral coordination when x ≥ 0.005. All the samples exhibit paramagnetic behaviors at room temperature, and antiferromagnetic coupling can be observed below 100 K