The work presented here provides a mathematical model for solving the problem of lubrication (calculation of efficiency) of worm gear drives, including a description of the engagement geometry and comprehensive modeling of the worm gear drive lubrication process based on the physical characteristics of the lubricant and the applied materials of contact bodies. The established mathematical model is based on the thermo-elasto-hydrodynamic (TEHD) lubrication theory that has proven to be successful in the analysis of journal bearings. The solution of the problem on hand by analyzing the loss of power in gearing, i.e. by analyzing the efficiency ratio of the gear, is basically reduced to the problem of mathematical modeling of local friction coefficients in the oil film along the contact line of the gears. The applicability of TEHD lubrication and the developed computer program were verified by comparing numerical results with experimental values obtained on a test bench using a real worm gear.

The field of self-assembled monolayers has grown rapidly since the discovery of these structures (1983) and their ability to modify physical and chemical properties of surfaces. The process of self-assembly consists of two distinct steps: (i) a fast adsorption of head group of an organic molecule on a specific substrate, and (ii) a slow organization of alkyl chains by intermolecular van der Waals interactions. These layers enable to tailor and to optimize surface properties for a variety of technological applications (chemical and biochemical sensors, biocompatibilization of metal surfaces, DNA immobilization, corrosion protection) as well as for fundamental studies of surface phenomena. In this study, the adsorption kinetics of 1-dodecanethiol on the gold substrate was studied in-situ using electrochemical impedance spectroscopy. The reason for the thiol adsorption on gold is based on two considerations: (i) gold is a relatively inert metal and does not form stable oxides on its surface, and (ii) there is a strong specific interaction with sulfur which allows the formation of a stable monolayer. Dependence of the surface coverage on the concentration was described by the Langmuir isotherm at all investigated concentrations of dodecanethiol, ranging from 3×10^(-6) to 1×10^(-3) M, in 0.1 M ethanolic solution of LiClO4. Parameters characterizing the adsorption thermodynamics, the adsorption coefficient, and the free energy of adsorption were determined. The thiol monolayers were characterized using contact angle measurements. The contact angle value (≈ 100°) has shown a high hydrophobicity. The electrochemical properties have been studied in a 0.1 M NaClO4 using cyclic voltammetry and electrochemical impedance spectroscopy. The thiol monolayer behaves as a barrier film, almost an ideal dielectric which effectively prevent electrolyte from contacting the gold substrate.