Impact of Firefighting Sprays on the Fire Performance of Structural Steel Members

Fire Technology - The feasibility of coupled computational fluid dynamics (CFD) and finite element (FE) simulations to aid the planning of fire intervention tactics and the effectiveness of...     

Control of morphology and optical properties of PbS nanostructured thin films by deposition parameters: study of mechanism

PbS thin films were grown on glass substrates by chemical bath deposition (CBD) using lead nitrate, thiourea and sodium hydroxide in aqueous solutions at three different temperatures (22, 36 and 50?°C). The microstructure and morphology evolution of the films were investigated using X-ray diffraction, scanning electron microscopy and atomic force microscopy. Optical properties were studied using UV–Vis–IR spectroscopy. The results indicate that temperature plays an important role in controlling the morphology and optical properties of nanostructured PbS thin films through changing deposition mechanism. The active deposition mechanism changed from cluster to ion-by-ion mechanism with an increase in deposition temperature from 22 to 50?°C, and consequently, film properties such as morphology, optical absorption and preferred orientation changed completely.     

Details of a theoretical model for electronic structure of the diamond vacancies

A new model to calculate electronic states of the diamond vacancies has been developed using many body techniques. This model is based on physical assumptions of previous molecular models but does not use configuration interaction. Present model allows an accurate and unified treatment of electronic levels and related eigen functions for diamond vacancies, in addition to transition energies of the first dipole-allowed transitions in the neutral (V⁰) and negatively charged (V⁻) vacancies, GR1 and ND1 band. For the first time, we calculated their optical transition intensities. For obtaining these results, we solved a generalized form of the Hubbard Hamiltonian, which consists of all electron–electron interaction terms on atomic orbital basis. Spatial symmetry of the defect, T_d symmetry, is included in the form of the Hamiltonian, and the eigen states have automatically the correct spin and symmetry properties. We discuss the possibility of the reduction of the wide gap between theoretical and semiempirical wisdom by including deformation of the dangling orbital or delocalization of the vacancy electrons to the next nearest neighbor (NNN) atoms of the vacancies. Our prediction for low lying the ³T₁ level of the neutral vacancy in diamond is consistent with experimental expectations. We report the variation of the ground and excited states of the GR1 and ND1 lines with hopping parameter t and also the electronic configurations of these states.     

Relativistic effects, infrared intensities, diffusion and lithiation in InSb

We consider In₄Sb₄H₁₈ cluster with zinc-blend structure of InSb. The cohesive energy and band gap of InSb were calculated by Unrestricted Hartree–Fock (UHF) and Density Functional Theory (DFT) method and it was shown that underestimated values of band gap can be decreased by considering the relativistic effects and in some cases InSb crystal even to be a semimetal. By calculating time-dependent DFT (TDDFT), the first three singlet and triplet excited energies were calculated and it was shown the 0.23 eV (band gap of InSb at 77 K) is placed between them. The infrared intensities were calculated and it is shown that the 367 cm⁻¹ (294 cm⁻¹ experimentally) mode can be attributed to the LO(Γ) in InSb. Finally it was shown that the Cadmium (Cd) diffuses substantially as Cd_In and changes the first three singlet and triplet excited energies, but Lithium (Li) is placed in empty spaces of InSb crystal in the lithiation of InSb.