Investigation on charge parameters of underwater contact explosion based on axisymmetric SPH method

This paper investigates the effects of charge parameters of the underwater contact explosion based on the axisymmetric smoothed particle hydrodynamics （SPH） method. The dynamic boundary particle is proposed to improve the pressure fluctuation and numerical accuracy near the symmetric axis. An in-depth study is carried out over the influence of charge shapes and detonation modes on the near-field loads in terms of the peak pressure and impulse of shock waves. For different charge shapes, the cylindrical charge with different length-diameter ratios may cause strong directivity of peak pressure and impulse in the near field. Compared with spherical charge, the peak pressure of cylindrical charge may be either weakened or enhanced in different directions. Within a certain range, the greater the length-diameter ratio is, the more obvious the effect will be. The weakened ratio near the detonation end may reach 25% approximately, while the enhanced ratio may reach around 20% in the opposite direction. However, the impulse in different directions seems to be uniform. For different detonation modes, compared with point-source explosion, the peak pressure of plane-source explosion is enhanced by about 5%. Besides, the impulse of plane-source explosion is enhanced by around 5% near the detonation end, but close to those of the point-source explosion in other directions. Based on the material constitutive relation in the axisymmetric coordinates, a simple case of underwater contact explosion is simulated to verify the above conclusions, showing that the charge parameters of underwater contact explosion should not be ignored.

Performance Enhancement in Dye-Sensitized Solar Cells with Composite Mixtures of TiO_2 Nanoparticles and TiO_2 Nanotubes

In the present investigation,a new composite nanostructured photoanodes were prepared using TiO_2 nanotubes（TNTs） with TiO_2 nanoparticles（TNPs）.TNPs were synthesized by sol-gel method,and TNTs were prepared through alkali hydrothermal method.Dye-sensitized solar cells（DSSCs） were fabricated with different photoanodes comprising of various ratios of TNTs ＋ TNPs,synthetic indigo dye as photosensitizer,PMII（l-propyl-3-methylimidazolium iodide） as ionic liquid electrolyte and cobalt sulfide as counter electrode.The structures and morphologies of TNPs and TNTs were analyzed through X-ray diffractometer,transmission electron microscope and scanning electron microscopes.The results of the investigation showed that the DSSC-4 made with composite photoanode structure（TNTs/TNPs）（90% of TNPs ＋ 10% of TNTs） had improved photocurrent efficiency（2.11%） than pure TNPs（1.00%） and TNT film（0.78%）.Electrochemical impedance spectra revealed that the composite TNTs/TNPs film-based DSSCs possessed the lowest charge-transfer resistances and longest electron lifetime.Hence,it could be concluded that the composite TNTs/TNPs photoanode facilitates the charge transport rate and enhances the efficiencies of DSSCs.