after springs production, different residual stresses are created in the inner and outer surfaces of spring wires. some of these stresses for example compressive residual stresses are useful and some are harmful. the effects of vareation of these stresses are caused spring relaxation and decrising in their free length when they are loaded intermittently. for review this phenomena in this resear...

cellulose sulfuric acid as a bio-polymer based solid catalyst efficiently catalyzes the selectively oxidation of sulfides to sulfoxides and thiols to disulfides using hydrogen peroxide as a green oxidant with good yields at room temperature. the developed method offers a number of advantages such as high selectivity, mild reaction conditions, simple operation, cleaner reaction profiles, low cos...

the paper presents results of experimental studies on the methane and propane ignition process in various volumetric compositions of oxidizers heated to temperatures higher than ignition point of analyzed fuels (htac conditions–high temperature air combustion conditions). the increment of temperature dt and the ignition delay time tig are parameters characterizing the process of ignition under ...

nano sulfated titania was tested as solid acid heterogeneous catalyst for the synthesis of 4-(trifluoromethyl) coumarin and coumarin derivatives under solvent-free condition. factorial design evidenced a positive effect of reaction temperature, amount of catalyst, and solvents.  this nano-sized sulfated titania has been prepared by a sol-gel hydrothermal process. the prepared sulfated titania s...