KEYWORDS: Optical spheres, Refractive index, 3D modeling, Optical engineering, Particles, Chemical reactions, Monte Carlo methods, Computer simulations, Windows, Optical simulations
The high temperature around hypersonic vehicles due to aero-heating will result in air reactions. Considering how much is unknown about how these reactions’ three-dimensional effects may affect aero-optics, a direct simulation Monte Carlo (DSMC) method with a quantum–kinetic chemical reaction model is used to explore the relationship between aero-optical effects and different flying conditions of a three-dimensional sphere. Cases of inert or reactive flowfield, different incident angles of a beam, Mach numbers 7 to 20, and angles of attack −10 deg to 10 deg are simulated. By defining the boresight error and phase deviation, it is found that an error of about 14% will be introduced if real gas effects and three-dimensional effects are both neglected. The variation of aero-optical effects with Mach number in a broader range is slightly different from the existing conclusions.
In the present study, phosphorescent imaging technique was developed to achieve simultaneous measurements of droplet size, speed and temperature of dispersed droplets in spray flow ejected from an air-blast nozzle. By using phosphorescent molecules as the tracers excited by an ultraviolet laser sheet for the quantitative flow measurements, the detected images of tagged phosphorescent molecules at two successive times determine the dynamic and thermodynamic behaviors of dispersed particles. A PTV based method was used to analyze the droplets size, trajectory and speed, and a lifetime based approach was used to measure the cross-correlated droplets temperature. The experimental results demonstrated phosphorescent imaging technique behaves the potential to widely used and well suited for spray measurement and droplet characterization.
TiO2 nanotubes have been now an attractive nanostructured material due to their unique opto-electronic catalytic ability, compatibility to particle materials and feasibility to fabricate. However, these advantages were usually limited by morphological and structural defects from the electrochemical anodization method. More detailed understandings of the tube formation process are also needed. We have systematically investigated the tube formation with varying conditions. Beside discovery of new nanosphere structure, we have systematically investigated the spontaneous oscillating phenomena in potentiostatic anodization of TiO2 tubes. Consequently, we have established a novel comprehensive physical and chemical method that effectively influences the morphology and structural properties of TiO2 nanotubes. With assistance of periodical anodic voltage and moderate mechanical stirring, the efficiency of dye sensitized solar cells (DSSCs) can be significantly enhanced. For instance, the efficiency of DSSC with small TiO2 islands in the anode can be 114% higher than the control sample. This method has also turned the efficiency of DSSC with TiO2 nanotubes by low temperature current annealing into announceable value (from 2.05% to 3.51%).
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