基于数据质量评价的目标估计

针对目标估计过程需要大量人工参与、自动化程度低的问题，提出了基于数据质量评价的目标估计方法。利用目标数据质量评价方法，对不同传感器得到的目标数据质量进行科学、有效的测度和评价，并根据质量得分动态调整各数据源在目标估计过程中所占的权重，从而减少人工干预，提高目标估计效能。仿真试验结果证明了该方法的有效性。     

Effect of organic solvent on the cold sintering processing of SrFe12O19 platelet-based permanent magnets

In this work we have investigated the effect of the solvent during the processing of SrFe₁₂O₁₉ platelet-based permanent magnets by cold sintering process (CSP) plus a post-thermal treatment. Several organic solvents: glacial acetic acid, oleic acid and oleylamine have been analyzed, optimizing the CSP temperatures at 190?270 °C, under pressures of 375?670 MPa and 6?50 wt% of solvent. Modifications in the morphological and structural properties are identified depending on the solvent, which impacts on the magnetic response. Independently of the solvent, the mechanical integrity of ferrite magnets obtained by CSP is improved by a post-annealing at 1100 °C for 2 h, resulting in relative densities around 92 % with an average grain size of 1 μm and a fraction of SrFe₁₂O₁₉ phase >91 %. H_C ≥ 2.1 kOe and M_S of 73 emu/g are obtained in the final sintered ceramic magnets, exhibiting the highest H_C value of 2.8 kOe for the magnet sintered using glacial acetic acid.     

Presentation attack detection based on two-stream vision transformers with self-attention fusion

Aiming at the performance degradation of the existing presentation attack detection methods due to the illumination variation, a two-stream vision transformers framework (TSViT) based on transfer learning in two complementary spaces is proposed in this paper. The face images of RGB color space and multi-scale retinex with color restoration (MSRCR) space are fed to TSViT to learn the distinguishing features of presentation attack detection. To effectively fuse features from two sources (RGB color space images and MSRCR images), a feature fusion method based on self-attention is built, which can effectively capture the complementarity of two features. Experiments and analysis on Oulu-NPU, CASIA-MFSD, and Replay-Attack databases show that it outperforms most existing methods in intra-database testing and achieves good generalization performance in cross-database testing.     

(Cu1/3Nb2/3)4+ ionic substituting effects,low-temperature sintering behaviors,and improved temperature stability of Ba3Nb4Ti4O21 microwave dielectric ceramics

In this study, (Cu_1/3Nb_2/3)⁴⁺ complex cation and BaO–ZnO–B₂O₃ glass frit were adopted to solve the high sintering temperature and poor temperature stability of Ba₃Nb₄Ti₄O₂₁ ceramics. It is shown that pure Ba₃Nb₄Ti₄O₂₁ phase was formed when Ti site was partially replaced by (Cu_1/3Nb_2/3)⁴⁺ cation. The increasing number of dopants decreases the dielectric polarizability, correspondingly, the dielectric constant and temperature coefficient of the resonance frequency values are reduced consistently. The variation of the Q × f value is determined by internal ionic packing fraction and external sintering densification. The (Cu_1/3Nb_2/3)⁴⁺ cation effectively decreases the suitable sintering temperature from 1200 to 1050 °C while greatly improving the temperature stability. BaO–ZnO–B₂O₃ glass was used to further improve the low-temperature sintering characteristics of Ba₃Nb₄Ti₄O₂₁ ceramics. It is proven that the addition of glass frits effectively decreases the temperature to 925 °C with combinational excellent microwave dielectric properties: ε_r ～55.6, Q × f ～5700 GHz, τ_f ～3 ppm/^°C, making the Ba₃Nb₄Ti₄O₂₁ ceramics promising in the applications of low-temperature cofired ceramic technology.     

Predictive process mapping for laser powder bed fusion: A review of existing analytical solutions

One of the main challenges in the laser powder bed fusion (LPBF) process is making dense and defect-free components. These porosity defects are dependent upon the melt pool geometry and the processing conditions. Power-velocity (PV) processing maps can aid in visualizing the effects of LPBF processing variables and mapping different defect regimes such as lack-of-fusion, under-melting, balling, and keyholing. This work presents an assessment of existing analytical equations and models that provide an estimate of the melt pool geometry as a function of material properties. The melt pool equations are then combined with defect criteria to provide a quick approximation of the PV processing maps for a variety of materials. Finally, the predictions of these processing maps are compared with experimental data from the literature. The predictive processing maps can be computed quickly and can be coupled with dimensionless numbers and high-throughput (HT) experiments for validation. The present work provides a boundary framework for designing the optimal processing parameters for new metals and alloys based on existing analytical solutions.     

Method for calculating horizontal drain induced non-linear and large strain degree of consolidation

Consolidating dredged clay slurries using a combination of vacuum pressure and prefabricated horizontal drains (PHDs) is widely used in practice. This is a large strain problem, but there is no existing large strain theory for PHD induced consolidation. A method with explicit equations has been proposed to consider both mechanical and geometrical non-linearities in analyzing PHD induced consolidation. The method considers stepwise variation of properties using imaginary time concept. An imaginary time is determined by the condition of continuity of degree of consolidation before and after changing the properties. Then the method was applied to analyze a large scale model test of vacuum consolidation with PHD. Two analyses were conducted. One considered both the mechanical and geometrical non-linearity (large strain), and another only considered mechanical non-linearity (small strain). The results of large strain analysis agree with the measured settlement curve and excess pore pressures well. While the small strain analysis under-estimated the rate of consolidation significantly. The results from this study indicate that for analyzing PHD induced consolidation of clay slurries considering the effect of large strain is important, and the proposed method can be a useful design tool.     

Consolidation considering increasing soil column radius for dredged slurries improved by vacuum preloading method

Soil column is often investigated in the improvement of dredged slurries. Different from the smear zone, the soil column forms gradually and has extremely low permeability. This study presents an analytical solution for soil consolidation considering the increasing radius of the soil column and time-dependent discharge capacity. Based on the solution, the influence of the radius' increase on the consolidation behavior is found significant when the soil column has low permeability and large final radius, and the increase of formation time can lead to the increase of consolidation speed and final consolidation degree.     

Fabrication and upconversion luminescence properties of Er:SrF2 transparent ceramics compared with Er:CaF2

SrF₂ transparent ceramic is a promising upconversion material due to the low phonon energy. The effect of different sintering temperatures on Er:SrF₂ transparent ceramics was investigated. The suitable sintering temperature for Er:SrF₂ transparent ceramics was 900 °C by hot-pressed sintering in this study. High quality of Er:SrF₂ transparent ceramics with different doping concentrations were obtained. The upconversion luminescence spectra and decay behavior were compared between Er:SrF₂ and Er:CaF₂ transparent ceramics with different Er³⁺ doping concentration. The green emission of 5 at.% Er:SrF₂ ceramic was much stronger than that of 5 at.% Er:CaF₂ ceramic, while the red emission of Er:SrF₂ ceramic was almost the same as that of Er:CaF₂ ceramic. The upconversion luminescence lifetime of Er:SrF₂ transparent ceramics was longer than that of Er:CaF₂.All the results indicated Er:SrF₂ transparent ceramics was a candidate for green fluorescent upconversion materials.     

Moderate temperature sintering of BaZr0.8Y0.2O3-δ protonic ceramics by A novel cold sintering pretreatment

The state-of-the-art protonic ceramic conductor BaZr_0.8Y_0.2O_3-δ (BZY20) requires an extremely high sintering temperature (≥1700 °C) to achieve the desired relative density and microstructure necessary to function as a proton conducting electrolyte. In this work, we developed a cold sintering pretreatment assisted moderate-temperature sintering method for the fabrication of high-quality pure BZY20 pellets. BZY20 pellets with high relative density of ~94% were fabricated with a final sintering temperature of 1500 °C (200 °C lower than the traditional sintering temperature). A comparison with BZY20 control samples indicated that the proper amount of BaCO₃ introduced on the BZY20 particle surface and the high green density achieved by cold sintering pretreatment were the main drivers for lowering the sintering temperature. The electrical conductivity measurement by electrochemical impedance spectroscopy showed that the as-prepared BZY20 pellets have a proton conductivity comparable to the state-of-the-art values. The cold sintering pretreatment outlined in this work has the potential to lower the sintering temperatures for similar types of protonic ceramic materials under consideration for a wide range of energy conversion and storage applications.