We report on a systematic correlation between the fine-structure splitting and polarization anisotropy of excitons in InAs/GaAs quantum dots, but with an unexpected reversal in order of the polarization eigenaxes. Such an anticorrelation is explained by a large valence-band-mixing induced splitting due to the shape and strain anisotropies. The strength and phase of valence band mixing are also found to play an important role in the tuning of fine structure splitting using an in-plane magnetic field.

A theoretical model for the electron-hole exchange interaction in three-dimensionally ͑3D͒ confining semiconductor nanostructures is presented to explain the observed decreasing tendency of the fine-structure splittings ͑FSSs͒ of small InGaAs/GaAs self-assembled quantum dots ͑QDs͒ with increasing the emission energies. The experimentally revealed FSS reduction is shown to be highly associated with the significant 3D spreading of electronic orbitals and reduced overlap of electron and hole wave functions in small and/or Ga-diffused QDs. The combination of quantum size and Ga-diffusion effects substantially reduces the averaged e-h exchange interaction and leads to the reduced FSSs in the regime of high emission energy.

Nowadays, sawdust has been widely regarded as a sand replacement material to produce sawdust concrete. This thesis uses orthogonal test to analyze the mechanical and heat preservation as well as heat insulation property with the sawdust replacement ratio of 0%, 3%, 5%, 7%, 10%, respectively, to get an optimal sawdust replacement ratio. Besides, it also discusses the deficiencies of this research.

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