Rolling bearing is one of the most critical components in rotating machinery, so in order to efficiently select features, reduce feature dimensions and improve the correctness of fault diagnosis, a feature selection and fusion method based on weighted multi-dimensional feature fusion is proposed. Firstly, features are extracted from different domains to constitute the original high-dimensional feature set. Considering the large number of invalid and redundant features contained in such original feature set, a feature selection process that combines with support vector machine (SVM) single feature evaluation, correlation analysis and principal component analysis-weighted load evaluation (PCA-WLE) is put forward in this paper for selecting sensitive features. The selected features are weighted and fused according to their sensitivity so as to further weaken the interference of low important features. Finally, this process is applied to the data provided by the Case Western Reserve University Bearing Data Center and Xi'an Jiaotong University School of Mechanical Engineering, respectively, and the fault is diagnosed by using the particle swarm optimization-support vector machine (PSO-SVM). The results show that this method can accurately identify different fault categories and degrees of bearing, which is superior and practical than single-domain fault diagnosis with higher recognition ability. INDEX TERMS Features selection, feature weighting, sensitive features, fault diagnosis.

The degradation behaviors and mechanisms of nitrile butadiene rubber O-rings aged in air are investigated by accelerated aging tests at different temperatures. The compressive stress changes of nitrile butadiene rubber O-rings are monitored by using a self-designed test device during the degradation process. The aging samples under different conditions are evaluated by measuring attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy, crosslinking density, compressive stress relaxation, weight loss, mechanical properties, and fracture morphology. The results demonstrate that the compressive stress declines with aging time, and the higher the temperature is, the faster the stress decreases. The ATR-FTIR results indicate that amide groups and hydroxyl groups are formed during the degradation process. The elevated temperature plays a significant role in the surface chemical changes. The changes in the crosslinking density of the samples could be attributed to the competition between crosslinking and chain scission, and the crosslinking mainly predominates in the aging process. The results of mechanical properties show that the tensile strength, elongation at break, and hardness of samples changes significantly with aging time and temperature. In addition, the fracture morphology observation reveals that the formation of a hardened brittle outer layer, voids, and agglomerates lead to a further decrease in mechanical properties. These results are very important for evaluating the lifetime of rubber O-rings and can be utilized to improve the stability and durability of sealing systems.

Achieving a (⁹⁹m)Tc-labeled fluoroquinolone derivative as a single photon emission computed tomography (SPECT) tracer is considered to be of great interest. The norfloxacin dithiocarbamate (NFXDTC) was synthesized and radiolabeled with a [(⁹⁹m)TcN]²(+) intermediate to form the (⁹⁹m)TcN-NFXDTC complex in high yield. The radiochemical purity of (⁹⁹m)TcN-NFXDTC was over 90%, as measured by thin layer chromatography (TLC) and high performance liquid chromatography (HPLC), without any notable decomposition at room temperature over a period of 6 h. The partition coefficient and electrophoresis results indicated that (⁹⁹m)TcN-NFXDTC was lipophilic and neutral. The bacterial binding assay studies showed tht (⁹⁹m)TcN-NFXDTC had a good binding affinity. Biodistribution results in bacterial infected mice showed that (⁹⁹m)TcN-NFXDTC had a higher uptake at the sites of infection and better abscess/blood and abscess/muscle ratios than those of (⁹⁹m)Tc-ciprofloxacin and (⁹⁹m)TcN-CPFXDTC (CPFXDTC = ciprofloxacin dithiocarbamate). The biodistribution results of (⁹⁹m)TcN-NFXDTC in bacterially infected mice and in mice with turpentine-induced abscesses indicated that (⁹⁹m)TcN-NFXDTC was suited to be a bacteria-specific infection imaging agent. Single photon emission computed tomography (SPECT) image studies showed there was a visible accumulation in infection sites, suggesting that it would be a promising candidate for bacterial infection imaging.

Thermal barrier coating (TBC) is a critical material in the aerospace domain to increase the lifetime of gas turbine components subjected to thermal load. The properties of TBC are strongly related to the growth of thermally grown oxide (TGO) whose main constituent is Al 2 O 3 . However, the oxidation of Cr and Co can affect the growth of TGO, which is not studied sufficiently. In this paper, high-temperature exposure at 1000 • C was performed to investigate the effect of Cr and Co oxides on TGO growth. The morphology and composition analysis of the interface between the ceramic top coat and the bond coat (TC/BC) were investigated by using scanning electron microscopy (SEM) and the energy dispersion spectrum (EDS). The thermodynamics and kinetics of oxidation were analyzed. The results indicated that the oxidation kinetics basically followed the sub-parabolic law with exposure time. Additionally, the major factor affecting the formation of oxides was the diffusion rate at the initial stage of exposure, then oxides depended on thermodynamics, and the oxidation was influenced by both of them in the last stage. The major elements to be oxidized were different at different stages. Moreover, the replacement reaction of Cr 2 O 3 and the phase conversion of Al 2 O 3 resulted in thickness variations of the TGO and Al-depleted zone during high-temperature exposure.

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