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The paper contains a summary of results obtained when researching demand for transporting dangerous goods of class 3 (oil and oil derivates) in the area of the city of Belgrade in 2007. Considering all transport modes used for carrying oil and oil derivates (road, rail and water transport), we present the total quantities of transported goods on a percentage basis. In light of road transport, the paper presents the features of demand for transport in terms of time and space that are a basis for the management of transporting dangerous goods and input to defining transportation routes to dangerous goods. Among the features of demand for transport in terms of time, the paper presents the quantities of goods transported within different months of the year, different week days and different periods of the day. The features of demand for transport in terms of space presented in the paper are goods flow features depending on their origin and the destination of movement in relation to the defined serviced area and the load of traffic network with goods flows.

Analysis of carrier transport in cascaded GaAs/AlGaAs, p-Si/SiGe and GaN/AlGaN terahertz structures is performed using self-consistent rate equations with kinetic energy-balance simulations. The electron transport in n-type structures is simulated using standard envelope function and nonparabolic effective mass approximations with all relevant electron–electron and electron–optical phonon scattering. In the case of GaAs-based structures the model is extended to include ionized impurity and interface roughness scattering as well. The hole subband structure in the p-type device is calculated using the 6 × 6 k · p model, and then used to find carrier relaxation rates due to the alloy disorder, acoustic and optical phonon scattering, as well as hole–hole scattering. The simulation accounts for the in-plane k-space anisotropy of both the hole subband structure and the scattering rates. Results are presented for the original GaAs/AlGaAs THz quantum cascade laser and prototypes of GaN/AlGaN and Si/SiGe THz quantum cascade structures. [ABSTRACT FROM AUTHOR]