Band gap expansion, shear inversion phase change behaviour and low-voltage induced crystal oscillation in low-dimensional tin selenide crystals

Regulated by encapsulating nanotube diameter, SnSe forms ordered 2 × 2 or disordered 3 × 3 ‘phase change’ nanocrystals.

Study of Real-Time Measurement for Thickness of Coating Film Based on Quartz Crystal Oscillator

After the technologies of measurement for thin-film thickness were analyzed, the method of real-time measurement for coating thickness based on quartz crystal oscillation was proposed. The principle of the thickness measured by frequency shifting was analyzed on theory, the functional relationship between the resonant frequency shifting and the film thickness changing was deduced. Aim at the complicated working condition in coating machine, the structure of the measuring system for reducing the influence from external pressure and temperature was designed. The circuit for detecting the frequency shift was designed. Final, according to the experiment result, the resolution of thickness measurement can achieve sub-micrometer level.

Self-Correcting Time Synchronization Based on Cross Layer for Wireless Sensor Network

Due to energy restrictions, node distribution density and hardware computing power etc., the traditional time synchronization mechanism is not suitable for wireless sensor network. The paper discussed the main reason that caused asynchronization and proposed an improved time synchronization algorithm based on cross layer optimization for wireless sensor network. Considering the stability of crystal oscillation and the linearity of crystal deviation in the physical layer, the improved time synchronization mechanism implemented a self-correction by the cross-layer MAC protocol. Estimating the crystal oscillation drift, the crystal deviation had been self-corrected just by a few times data broadcast. The experiment on the MCU Si1000 physical layer platform has demonstrated the practicability of the algorithm. The synchronization algorithm is able to keep a stable network operation in the way of extending the synchronization period and reducing the synchronization cost. The synchronization mechanism is applicable to the active acquisition network, especially the realtime one.