In this paper a three-dimensional model for determination of a microreactor's length is presented and discussed. The reaction of thermocatalytic decomposition has been implemented on the base of experimental data. Simplified Reynolds-Maxwell formula for the slip velocity boundary condition has been analysed and validated. The influence of the Knudsen diffusion on the microreactor's performance has also been verified. It was revealed that with a given operating conditions and a given geometry of the microreactor, there is no need for application of slip boundary conditions and the Knudsen diffusion in further analysis. It has also been shown that the microreactor's length could be practically estimated using standard models.

The paper presents an approach for evaluation of the likelihood of damage to the transportation infrastructure in the context of the terrorist attacks on the example of a number of bridges located in Wrocław (Poland). Assuming that there will be only one bridge destroyed in a given area, in order to determine the probability of damage to one of the objects, there was one of multi-criteria optimi-zation methods used, i.e. the method of Analytical Hierarchy Process (AHP). The main advantage of the analysis carried out was that the accepted hierarchy of decision-making options could be easily explained in a scientifi c manner, not only with reference to personal knowledge, experience, and intuition.