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Although the light-emitting diode (LED) has been developed into relative maturity, thermal management remains an important problem for high-power LEDs. To obtain the temperature distribution and improve the heat dissipation of high-power LED systems, an $N$ -layer model which is flexibly applied to different LED packaging structures is proposed, where the equivalent method of heatsinks is also included. The corresponding analytical solutions to temperature field and thermal resistance are generalized to Nth to adapt to the model. The method is proved to be accurate and time-saving in comparison with finite element method (FEM) simulations. In particular, it has obvious advantages in dealing with the thin layer analysis where the target region is much smaller than the entire model. By calculating the junction temperature and thermal resistance of an example LED module, the method is demonstrated in detail. Effects of printed circuit board (PCB) composition and heatsink on heat dissipation are analyzed, and the related thermo-mechanisms are revealed in terms of thermal resistance. This work may have significance for the design work of high-power LED systems.

To realize continuous real-time monitoring of the large-scale internal strain field of coal and rock mass, a bidirectional strain sensor based on FBGs encapsulated using a hollow cylindrical steel tube was designed. The sensor’s structural parameters were optimized through unidirectional loading, and the strain change laws of the sensor were analyzed under unidirectional and bidirectional loading conditions, in which the stress-strain fitting curves of the sensor and the relationships of the strain in the vertical and horizontal directions were obtained under different lateral pressure loading conditions. A similar theoretical model was established to verify the accuracy of the linear relationship between the surrounding rock stress and the strain measured by the sensor system.