S-doped TiO2 nanoparticles were fabricated by hydrothermal process and post-calcination, and their morphology, crystalline phase and chemical composition were characterized with transmission electron microscopy, powder X-ray diffraction and selected area electron diffraction. The results showed that S was successfully doped into the TiO2. We investigated the photocatalytic reactions in a simulated environment in tandem with thermal desorption-gas chromatography-mass spectrometry determinations. The catalytic activity of S-doped TiO2 was evaluated by monitoring the photodegradation of BTEX from wood-based panels, and 95% degradation rate in 75 min demonstrated efficient visible-light catalytic performance.
Aluminum nitride (AlN) power was successfully synthesized by direct nitridization method heating for 4h at 950°C with magnesium (Mg) and ammonium chloride (NH4Cl) as additives. The morphology and microstructure of nitride product were done by XRD and SEM. Result reveals that the nitride producs was pure hexagonal phase. In addiation, whiskers in the power which diameter is at the nanoscale and length ranging from a few microns were also observed, and EDS test displays the component of whiskers is AlN.
We demonstrate ultrafast amorphization in a Ge2Sb2Te5 (GST) film through a nonthermal process by femtosecond pump-probe experiments. A strong absorption peak in 532 nm is founded during the amorphization and the energy level corresponded is about 0.65~3.82 eV by calculations. First-Principles Calculations simulation experiments are used to prove the results of experiment and then explain the mechanism of amorphization of GST. Also, results of experiments show that the time to reach the absorption peak is decided by pulse width and wavelength but not the laser influence.
The dynamic positioning (DP) vessel maintains its position and heading by active thrusters. For safety reasons, DP vessels are typically designed with redundancy thrusters more than needed for motion control. Optimization theories are useful in finding thrust allocation solutions that minimize fuel consumption and reduce “wear and tear” on a thruster. But several challenges exist such as uncertain thruster model, thruster dynamics characters and the individual limitations of the thrusters. In this paper, a dynamic thrust allocation scheme is presented based on model predictive control (MPC) that directly takes thrusters with dynamics characters and various constraints into account. It is shown in simulations that the MPC dynamic thrust allocation scheme performs better in comparison with an existing static allocation method. Its main advantage is the ability to handle thruster dynamics characters and various constraints.
A femtosecond laser pulse duration is shorter than many physical/chemical characteristic times, which makes it possible to control electron dynamics such as ionizations and electron densities. This study expermetally investigtes the effects of laser fluence on sub-wavelength periodic surface structuring based on ultrafast laser electron dynamics control. A quantum model for the sub-wavelength periodic surface structuring is also proposed, which considers both the wave properties in the photon particle-properties based plasma model for photon-electron interactions and transient localized changes of material properties. It shows that the laser fluence strongly affects the ablation crater shapes. The prediction of ablation crater shape and periodicity is in agreement with experimental data.
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