Search

Tunable dielectric materials, serving as key components in microwave electronic application, require both high dielectric tunability and low dielectric loss. However, the trade-off between dielectric tunability and dielectric loss restricts the improvement of the overall dielectric tunability properties. In the present study, we proposed an effective approach to benefit both high tunability and low dielectric loss, i.e., improving intrinsic dielectric response from the lattice polarization and restricting the extrinsic dielectric response from the domain motions at the same time. Experimentally different acceptor dopants were employed, including the introduction of K at the A-site and Mn, Fe and Co at the B-site. On one hand, the different acceptor dopants could adjust the Curie temperature and consequently resulting in the enhanced intrinsic dielectric response at room temperature. On the other hand, the employment of acceptor dopant could introduce the oxygen vacancies and form the acceptor-oxygen vacancy dipoles which may restrict the reorientation of microdomains, resulting in the decrease of extrinsic dielectric response. Herein, both enhanced tunability and reduced dielectric loss were achieved in acceptor doped BZT ceramics at ambient temperature (27 °C). In particular, Fe doped BZT ceramics achieved both high dielectric tunability of 93.8 % and low dielectric loss of 0.0038. Such performance is competitive with that of previous reported dielectric tunable materials. In addition, the dielectric tunability of Fe doped BZT ceramics maintained over 60 % within the wide temperature range from −20 °C to 60 °C. [ABSTRACT FROM AUTHOR]

• Multi-state memory in BaTiO 3 ceramics was successfully realized by acceptor-doping. • Four independently addressed memory states were obtained in the double hysteresis loop. • The effect of dopants on memory effect was systematically studied by substitute site. • Pronounced memory effect in K-doped samples implies precise information recognition. • Better fatigue resistance in Fe-doped samples benefits the enhancement of service life. In the present study, acceptor-doped Ba 0.99 K 0.01 TiO 3 and BaTi 0.99 Fe 0.01 O 3 ceramic samples were prepared by the conventional solid-state reaction method. Antiferroelectric-like double hysteresis loops with four distinct memory states were realized in both A-site K-doped and B-site Fe-doped BaTiO 3 samples, providing a possibility to achieve multi-state memories. The practice feasibility of the memory effect was verified by write/read operations. The experimental results showed that the A-site K-doped sample demonstrated a pronounced memory effect, while the B-site Fe-doped sample showcased an enhanced fatigue resistance. Moreover, the differences in the shapes of hysteresis loops and related parameters of memory effect between K-doped and Fe-doped samples were systematically investigated from the view of acceptor-substitute site. All the results indicated that acceptor-doped BaTiO 3 ceramics were greatly promising for multi-state memory. [Display omitted] [ABSTRACT FROM AUTHOR]

Early intervention with food allergenic proteins is considered the most promising and effective approach in preventing the onset of food allergy (FA). However, the effects of oral administration of protein antigens from different food sources on specific FA outcomes and its regulatory mechanisms remain largely unclear. Here, the Balb/c mice were treated with 5 mg of egg ovalbumin (OVA) or cow's milk β-lactoglobulin (BLG) for 5 days prior to intraperitoneal sensitization with OVA/Alum and oral challenge with 20 mg OVA. The results indicated that oral administration of both OVA and BLG significantly increased the proportion of regulatory T cells. However, the introduction of OVA, but not the bystander antigen BLG, prevented the occurrence of allergic diarrhea (OT-OVA group: 0% vs OT-BLG group: 100%) and mitigated the decrease in body temperature (OT-OVA group: 0.11 °C vs OT-BLG group: 1.1 °C). Specifically, the levels of serum immunoglobulin-E and mast cell protease-1 were significantly reduced, and the expression of zonula occludens-1 , occludin , and claudin-1 was increased in the OVA-treated mice but not BLG-treated mice. Subsequently, transcriptome sequencing and Western blot analysis revealed that oral administration of OVA reduced the expression and cleavage of gasdermin C, which further decreased interleukin-33 secretion. Additionally, the dysregulation of the gut microbiota and short-chain fatty acid metabolism in the intestinal microenvironment caused by FA was reversed in OVA-treated mice but not BLG. In summary, our results presented a unique approach to ameliorate FA through targeting gasdermin C -mediated pyroptosis and dysbiosis of the gut microbiota in the intestinal microenvironment with OVA. [Display omitted] • Oral administration of allergenic proteins prevents the occurrence of food allergy. • Induing oral tolerance through the introduction of allergens is antigen-specific. • Allergen-induced immune tolerance is associated with GSDMC-mediated cell pyroptosis. • The gut microbiota and SCFAs are involved in the induction of immune tolerance. • Specific food proteins can serve as nutritional elements to modulate immune responses. [ABSTRACT FROM AUTHOR]

In the present study, the effects of Er 2 O 3 doping on the phase, microstructure, and electrical properties of ZnO–Bi 2 O 3 based varistors were systematically investigated. In particular, a correlation between the microstructure and electrical properties was established based on the quantitative analyses of grain size, grain size distribution, and porosity. It was found that appropriate Er 2 O 3 content of 0.4 mol% effectively decreased the grain size and improved the homogeneity of grain size distribution, contributing to a well-connected Bi 2 O 3 intergranular network. Thus, simultaneously enhanced voltage gradient of 280 V/mm and relatively high nonlinear coefficient of 46 were achieved in varistors. However, with further increasing Er 2 O 3 content, the excess Er 2 O 3 phases were generated and agglomerated at grain boundaries. This further caused coarse pores and seriously undermined the connectivity of Bi 2 O 3 networks, leading to the decrease in nonlinearity of varistors. Furthermore, such a correlation revealed in this study may provide valuable guidelines for developing high-performance ZnO–Bi 2 O 3 based varistors. [ABSTRACT FROM AUTHOR]

Graph convolutional networks (GCNs) have been widely used for representation learning on graph data, which can capture structural patterns on a graph via specifically designed convolution and readout operations. In many graph classification applications, GCN-based approaches have outperformed traditional methods. However, most of the existing GCNs are inefficient to preserve local information of graphs — a limitation that is especially problematic for graph classification. In this work, we propose a locality-preserving dense GCN with graph context-aware node representations. Specifically, our proposed model incorporates a local node feature reconstruction module to preserve initial node features into node representations, which is realized via a simple but effective encoder–decoder mechanism. To capture local structural patterns in neighborhoods representing different ranges of locality, dense connectivity is introduced to connect each convolutional layer and its corresponding readout with all previous convolutional layers. To enhance node representativeness, the output of each convolutional layer is concatenated with the output of the previous layer's readout to form a global context-aware node representation. In addition, a self-attention module is introduced to aggregate layer-wise representations to form the final graph-level representation. Experiments on benchmark datasets demonstrate the superiority of the proposed model over state-of-the-art methods in terms of classification accuracy. [ABSTRACT FROM AUTHOR]

In the present study, an industrially viable ceramics fabrication way based on solid-state reaction method–semi-solution method was used to improve the dielectric and ferroelectric properties of acceptor-donor co-doped BaTiO 3 ceramics. Unlike the conventional solid-state reaction method, additives in the semi-solution method were introduced in the form of the aqueous solution rather than oxide powders. Experiment results show that higher peak dielectric constant ε m a x (140–150%), larger maximum polarization P m a x (24 μ C cm−2), and less apparent aging phenomena were achieved by the semi-solution method. A comprehensive microscopic analysis was carried out to explore the origin of property enhancement. Results show that enhanced properties could be ascribed to the higher level of compositional homogeneity and lower content of oxygen vacancies. This study provides a new method to control aging phenomena and achieve property enhancement in acceptor-donor co-doped ceramics. Moreover, this simple and cost-effective method may also find its application in other extensive-doped ceramics. [ABSTRACT FROM AUTHOR]

3D hierarchical porous N-doped carbon nanosheets/MgFe 2 O 4 (MFO/NPC) was designed and synthesized successfully as the anode materials for lithium ion batteries by freeze-drying technology with dual salt templates and subsequent in-situ solvent thermal method. Its specific capacity rises steadily to 1337.7 mAh g−1 at the 260th cycle with the initial coulombic efficiency of 78.3% (0.5 A g−1). And the capacity remains at 534.1 mAh g−1 even after 1500 cycles at the current density of 5 A g−1. The excellent electrochemical performances can be attributed to the 3D conductive carbon skeleton and the chemical interaction between MFO and the doped N element. 3D hierarchical porous N-doped carbon nanosheets /MgFe 2 O 4 (MFO/NPC) was designed and synthesized successfully as the anode materials for lithium ion batteries by freeze-drying technology with dual templates (NaCl and Na 2 SiO 3) and subsequent in-situ solvent thermal method. Due to the compositing with the 3D hierarchical porous carbon nanosheets and the chemical interaction between MFO and the doped N, the obtained material shows excellent cycling stability, rate performance and relatively high initial coulombic efficiency. A reversible specific capacity still remains at 534.1 mAh•g−1 even after a long-cycle of 1500 cycles at the high current density of 5 A•g−1. Image, graphical abstract [ABSTRACT FROM AUTHOR]

Energy absorption properties of cellular materials have gained increasing interest due to their superior performance and immense design space. This paper introduces a novel lattice material with a Butterfly configuration that has controllable multi-stage crushing behavior and high specific energy absorption capacity. A theoretical model is developed to predict the plateau stress, elastic modulus and critical strain of each stage, in order to obtain the multi-stage stress-strain curve. Compression experiments and the finite element modelling are also carried out to validate the theoretical model. Theoretical and experimental results show that the Butterfly lattice material has more than two crushing stages and a specific energy absorption property comparable to the traditional stretching-dominated lattice material. Finally, effects of topology configuration, cell number, and geometrical parameter on the energy absorption behavior are analyzed. It is found that the length of the vertical beam dramatically influences the plateau load and deformation behavior of each stage. [ABSTRACT FROM AUTHOR]

Glass additive BaO-SrO-TiO 2 -Al 2 O 3 -SiO 2 -BaF 2 is employed to enhance the microstructures and energy storage properties of the Ba(Zr 0.2 Ti 0.8)O 3 -0.15(Ba 0.7 Ca 0.3)TiO 3 ceramics. To clarify the energy storage mechanism, the charge transportation and polarization process are investigated by thermally simulated depolarization current (TSDC). The dielectric breakdown strength increases from 4.3 kV/mm to 10.8 kV/mm for BZT-0.15BCT ceramics with 11 wt% glass additives, indicating that glasses could refine the grain size, uniform the structure, and decrease defects. Due to the micro-domain region, dielectric relaxation behavior is observed with a broadened and reduced dielectric constant peak at a large dielectric constant of about 3000 at room temperature. The largest charge energy density of 1.45 J/cm3 and discharge density of 0.17 J/cm3 are achieved for BZT-0.15BCT glass ceramics with 7 wt% glass additives. TSDC results demonstrate that dipole origin movement and charge transportation have an important effect on the dielectric properties and dielectric breakdown strength, respectively, which are largely influenced by the defects distribution state at the interfaces. Moderate domain walls could restrain the defects to inhibit the charge transportation and are harmful for the dielectric properties inversely. To achieve excellent energy storage performance, moderate domain walls are compromise of slightly degrading dielectric properties and greatly improving dielectric breakdown strength. [ABSTRACT FROM AUTHOR]

Abstract This paper develops a fixed effect model to evaluate the effect of renewable energy policy using a panel dataset covering 29 countries during the period of 2000–2015. The renewable energy policy system in this paper includes seven aggregate policies and twelve specific ones. The empirical results indicate that four of seven aggregate policies, including fiscal and financial incentives, market-based instruments, policy support, and research, development and deployment, are demonstrated to be significant to the improvement of renewable energy capacity. Meanwhile, three of twelve specific policies, including price policy, grants and subsidies, and strategic planning, have positive effects on renewable energy development. This paper assesses the aggregate and specific policies in the same analysis framework, and the empirical results determined that synergy effects existed among specific policies. The empirical results also indicate that the implementation of the Kyoto Protocol in 2005 has had positive impacts on renewable energy development in typical countries. Highlights • Panel data study on the effectiveness of RE policies to promote RE development. • Four of seven aggregate policies are positively significant to RE capacity increase especially Market-based instruments and RD&D. • Three of twelve specific policies have significant positive effects on RE capacity especially price policy. • Synergy effects do exist among specific policies in renewable energy increase. [ABSTRACT FROM AUTHOR]