This work utilized a combination of experimental evidence and fractal geometric method to assess the effect of crack extension concerning the thermal shock on residual strength of ceramics. Sintered alumina (Al ₂ O ₃ ) ceramic slabs were bundled and quenched in water under different thermal shock temperatures. The fractal dimension of thermal shock crack patterns on the interior surface and the cooled surface was calculated by the Box‐counting method. Fracture energy of a fractal pattern of microcracks in quasi‐brittle solids was employed to explain the relationship between crack length and fractal dimensions. The results show that if the crack propagation has the same crack length but a larger fractal dimension, it will absorb more fracture energy. The thermal shock crack patterns of Al ₂ O ₃ ceramics with different grain sizes were analyzed, and the smaller grain size ceramic had a higher fractal dimension of crack patterns than the larger one.

The microchannel heat sink (MCHS) has the advantages of small heat transfer resistance, high heat transfer efficiency and small size, which exhibits good heat transfer performance in the field of active heat dissipation of electronic devices integrated with high heat flux density. In this paper, the application of MCHS in thermal management is reviewed in recent years, and the research progress of microchannel topology on enhancing heat transfer performance is summarized. Firstly, the research progress on the cross-sectional shape of the microchannel shows that the heat transfer area and fluid flow dead zone of the microchannel is the keys to affecting the heat transfer performance; Secondly, the microchannel distribution and the bionic microchannel structure have a great role in enhancing heat transfer performance, especially in microchannel temperature uniformity; Thirdly, the disturbing effect caused by interrupted structures in microchannels such as ribs and concave cavities has become a hot topic of research because it can weaken the thermal boundary layer and increase heat dissipation. Finally, the commonly used MCHS materials and cooling media are summarized and introduced. Based on the above reviews of MCHS research and applications, the future trends of MCHS topologies are presented.

Fatigue assessment is especially important in long-term physical work and training to avoid injury caused by muscle fatigue. The surface electromyography (sEMG) signal has been widely used to detect muscle fatigue states. The purpose of this paper is to establish muscle functional networks and provide a comprehensive assessment of muscle fatigue using multi-channel sEMG signals from the back muscles. A muscle functional network is constructed based on the Pearson correlation coefficients between the channels of sEMG signals, and we explore how the economic properties and small-world properties of the muscle network change with cost. Then, the network threshold is determined by changes in small-world properties. We extract network parameters through complex network methods to quantify and analyze the differences in muscle functional networks under different fatigue states. The most significant results of this novel approach indicate that the economic and small-world properties of the muscle network gradually decrease with increasing fatigue, and network parameters decrease significantly after fatigue. The method presented in this paper provides a new foundation for assessing muscle fatigue.