When the traditional multi-motor speed synchronous control strategy is applied to the vacuum pump system, it is prone to the drawbacks of large synchronization error. In this paper, a simplified mathematical model of the motor for a vacuum pump is established and the transfer function is introduced, which weakens the multivariable, strong coupling and nonlinear characteristics of the motor system. According to the basic principle of the relative coupling control strategy, the neural network Proportion Integration Differentiation (PID) is introduced as a speed compensator in this system. It effectively improves the synchronization and anti-interference ability of the multi motor.

The first order variation of critical loads of thin-walled columns with bisymmetric open cross-sectiondue to some variations of the stiffness and location of bracing elements is derived. The con-siderations are based on the classical linear theory of thin-walled beams with non-deformablecross-section introduced by Vlasov [1]. Both lateral braces and braces that restraint warping andtorsion of the cross-section have been taken into account. In the numerical examples dealing withI-column, the functions describing the influence of location of the braces with unit stiffness on thecritical load of torsional and flexural buckling are derived. The linear approximation of the exactrelation of the critical load due to the variation of the stiffness and location of braces is determined.

Professor architect Juliusz Żórawski was for the author of this paper, a leading personality, during his period of studiea and assistantship. Author on the wider background of events of his life, draws a portrait of his mentor according to: creative Modern projecting, thinking, talking and writing about architecture – especially on the field of form. The teacher and his pupil had similar passions, e.g. expressing oneself by free hand sketching, sensibility towards a landscape, e.g. Tatra Mountains. This is why in spite that Żórawski was rather radical Modernist, the fan of abstraction, the author of this paper owes him his own views closer to the contextualism, and a creative, more “hot”expression, and at the first – his passion towards architecture and its creation.