增量式块主成分分析的焊缝图像特征提取算法北大核心CSCD

针对焊缝图像特征提取的实时性问题,该文提出一种增量式块主成分分析(incremental block principal component analysis,IBlockPCA)算法,用于焊缝特征主成分的提取。该算法先将焊缝表面图像分割成子图像块并对其进行重构,然后利用提出的IBlockPCA算法对局部块图像进行增量式特征提取,并采用KNN算法对提取的特征主成分进行分类识别;最后在焊缝数据集上进行了算法的性能对比。实验结果表明,该算法在收敛率、分类率及复杂度等方面均优于其他主成分分析(principal component analysis,PCA)算法,其分类识别率为97.5%,其平均处理速度可达50 frame/s,能够满足焊缝表面图像的实时性处理需求。     

Phase Separation Derived Core/Shell Structured Cu11V6O26/V2O5 Microspheres: First Synthesis and Excellent Lithium‐Ion Anode Performance with Outstanding Capacity Self‐Restoration

Novel amorphous vanadium oxide coated copper vanadium oxide (Cu₁₁V₆O₂₆/V₂O₅) microspheres with 3D hierarchical architecture have been successfully prepared via a microwave‐assisted solution method and subsequent annealing induced phase separation process. Pure Cu₁₁V₆O₂₆ microspheres without V₂O₅ coating are also obtained by an H₂O₂ solution dissolving treatment. When evaluated as an anode material for lithium‐ion batteries (LIBs), the as‐synthesized hybrid exhibits large reversible capacity, excellent rate capability, and outstanding capacity self‐recovery. Under the condition of high current density of 1 A g^?1, the 3D hierarchical Cu₁₁V₆O₂₆/V₂O₅ hybrid maintains a reversible capacity of ≈1110 mA h g^?1. Combined electrochemical analysis and high‐resolution transmission electron microscopy observation during cycling reveals that the amorphous V₂O₅ coating plays an important role on enhancing the electrochemical performances and capacity self‐recovery, which provides an active amorphous protective layer and abundant grain interfaces for efficient inserting and extracting of Li‐ion. As a result, this new copper vanadium oxide hybrid is proposed as a promising anode material for LIBs.     

Rechargeable Aluminum‐Ion Batteries Based on an Open‐Tunnel Framework

Rechargeable batteries based on an abundant metal such as aluminum with a three‐electron transfer per atom are promising for large‐scale electrochemical energy storage. Aluminum can be handled in air, thus offering superior safety, easy fabrication, and low cost. However, the development of Al‐ion batteries has been challenging due to the difficulties in identifying suitable cathode materials. This study presents the use of a highly open framework Mo_{2.5 + y} VO_{9 + z} as a cathode for Al‐ion batteries. The open‐tunnel oxide allows a facile diffusion of the guest species and provides sufficient redox centers to help redistribute the charge within the local host lattice during the multivalent‐ion insertion, thus leading to good rate capability with a specific capacity among the highest reported in the literature for Al‐based batteries. This study also presents the use of Mo_{2.5 + y} VO_{9 + z} as a model host to develop a novel ultrafast technique for chemical insertion of Al ions into host structures. The microwave‐assisted method employing diethylene glycol and aluminum diacetate (Al(OH)(C₂H₃O₂)₂) can be performed in air in as little as 30 min, which is far superior to the traditional chemical insertion techniques involving moisture‐sensitive organometallic reagents. The Al‐inserted Al _x Mo_{2.5 + y} VO_{9 + z} obtained by the microwave‐assisted chemical insertion can be used in Al‐based rechargeable batteries.     

Sandwiched Thin‐Film Anode of Chemically Bonded Black Phosphorus/Graphene Hybrid for Lithium‐Ion Battery

A facile vacuum filtration method is applied for the first time to construct sandwich‐structure anode. Two layers of graphene stacks sandwich a composite of black phosphorus (BP), which not only protect BP from quickly degenerating but also serve as current collector instead of copper foil. The BP composite, reduced graphene oxide coated on BP via chemical bonding, is simply synthesized by solvothermal reaction at 140 °C. The sandwiched film anode used for lithium‐ion battery exhibits reversible capacities of 1401 mAh g^?1 during the 200th cycle at current density of 100 mA g^?1 indicating superior cycle performance. Besides, this facile vacuum filtration method may also be available for other anode material with well dispersion in N‐methyl pyrrolidone (NMP).     

Large‐Scale Fabrication of Core–Shell Structured C/SnO2 Hollow Spheres as Anode Materials with Improved Lithium Storage Performance

Due to the high theoretical capacity as high as 1494 mAh g^?1, SnO₂ is considered as a potential anode material for high‐capacity lithium–ion batteries (LIBs). Therefore, the simple but effective method focused on fabrication of SnO₂ is imperative. To meet this, a facile and efficient strategy to fabricate core–shell structured C/SnO₂ hollow spheres by a solvothermal method is reported. Herein, the solid and hollow structure as well as the carbon content can be controlled. Very importantly, high‐yield C/SnO₂ spheres can be produced by this method, which suggest potential business applications in LIBs field. Owing to the dual buffer effect of the carbon layer and hollow structures, the core–shell structured C/SnO₂ hollow spheres deliver a high reversible discharge capacity of 1007 mAh g^?1 at a current density of 100 mA g^?1 after 300 cycles and a superior discharge capacity of 915 mAh g^?1 at 500 mA g^?1 after 500 cycles. Even at a high current density of 1 and 2 A g^?1, the core–shell structured C/SnO₂ hollow spheres electrode still exhibits excellent discharge capacity in the long life cycles. Consideration of the superior performance and high yield, the core–shell structured C/SnO₂ hollow spheres are of great interest for the next‐generation LIBs.     

Fabrication of Fe3O4 Dots Embedded in 3D Honeycomb‐Like Carbon Based on Metallo–Organic Molecule with Superior Lithium Storage Performance

A novel metallo–organic molecule, ferrocene, is selected as building block to construct Fe₃O₄ dots embedded in 3D honeycomb‐like carbon (Fe₃O₄ dots/3DHC) by using SiO₂ nanospheres as template. Unlike previously used inorganic Fe₃O₄ sources, ferrocene simultaneously contains organic cyclopentadienyl groups and inorganic Fe atoms, which can be converted to carbon and Fe₃O₄, respectively. Atomic‐scale Fe distribution in started building block leads to the formation of ultrasmall Fe₃O₄ dots (≈3 nm). In addition, by well controlling the feed amount of ferrocene, Fe₃O₄ dots/3DHC with well‐defined honeycomb‐like meso/macropore structure and ultrathin carbon wall can be obtained. Owing to unique structural features, Fe₃O₄ dots/3DHC presents impressive lithium storage performance. The initial discharge and reversible capacities can reach 2047 and 1280 mAh g^?1 at 0.05 A g^?1. With increasing the current density to 1 and 3 A g^?1, remarkable capacities of 963 and 731 mAh g^?1 remain. Moreover, Fe₃O₄ dots/3DHC also has superior cycling stability, after a long‐term charge/discharge for 200 times, a high capacity of 1082 mAh g^?1 can be maintained (80% against the capacity of the 2nd cycle).     

Mesoporous NiS2 Nanospheres Anode with Pseudocapacitance for High‐Rate and Long‐Life Sodium‐Ion Battery

It is of great importance to exploit electrode materials for sodium‐ion batteries (SIBs) with low cost, long life, and high‐rate capability. However, achieving quick charge and high power density is still a major challenge for most SIBs electrodes because of the sluggish sodiation kinetics. Herein, uniform and mesoporous NiS₂ nanospheres are synthesized via a facile one‐step polyvinylpyrrolidone assisted method. By controlling the voltage window, the mesoporous NiS₂ nanospheres present excellent electrochemical performance in SIBs. It delivers a high reversible specific capacity of 692 mA h g^?1. The NiS₂ anode also exhibits excellent high‐rate capability (253 mA h g^?1 at 5 A g^?1) and long‐term cycling performance (319 mA h g^?1 capacity remained even after 1000 cycles at 0.5 A g^?1). A dominant pseudocapacitance contribution is identified and verified by kinetics analysis. In addition, the amorphization and conversion reactions during the electrochemical process of the mesoporous NiS₂ nanospheres is also investigated by in situ X‐ray diffraction. The impressive electrochemical performance reveals that the NiS₂ offers great potential toward the development of next generation large scale energy storage.     

Simple synthesis of a porous Sb/Sb2O3 nanocomposite for a high-capacity anode material in Na-ion batteries

High-capacity anode materials are highly desirable for sodium ion batteries.Here,a porous Sb/Sb2O3 nanocomposite is successfully synthesized by the mild oxidization of Sb nanocrystals in air.In the composite,Sb contributes good conductivity and Sb2O3 improves cycling stability,particularly within the voltage window of 0.02-1.5 V.It remains at a reversible capacity of 540 mAh·g-1 after 180 cycles at 0.66 A·g-L Even at 10 A·g-1,the reversible capacity is still preserved at 412 mAh.g-1,equivalent to 71.6％ of that at 0.066 A.g-1.These results are much better than Sb nanocrystals with a similar size and structure.Expanding the voltage window to 0.02-2.5 V includes the conversion reaction between Sb2O3 and Sb into the discharge/charge profiles.This would induce a large volume change and high structure strain/stress,deteriorating the cycling stability.The identification of a proper voltage window for Sb/Sb2O3 paves the way for its development in sodium ion batteries.     

Irregular Time‐Varying Stress Degradation Path Modeling: a Case Study on Lithium‐ion Cell Degradation

The aim of this paper is to investigate the issue of degradation modeling and reliability assessment for products under irregular time‐varying stresses. Conventional degradation models have been extensively used in the relevant literature to characterize degradation processes under deterministic stresses. However, the time‐varying stress, which may affect degradation processes, widely exists in field conditions. This paper extends the general degradation‐path model by considering the effects of time‐varying stresses. The new degradation‐path model captures influences of varying stresses on performance characteristics. A nonlinear least square method is used to estimate the unknown parameters of the proposed model. A bootstrap algorithm is adopted for computing the confidence intervals of the mean time to failure and percentiles of the failure‐time distribution. Finally, a case study of lithium‐ion cells is presented to validate the proposed method. Copyright © 2015 John Wiley & Sons, Ltd.