Razor to shave themselves more, the demand for barbers providing straight razor shaves decreased. In 1960, stainless steel blades which could be used more than once became available, reducing the cost of safety-razor shaving. The first such blades were made by the Wilkinson firm, famous maker of ceremonial swords, in Sheffield. Soon Gillette, Schick, and other manufacturers were making stainless-steel blades. These were followed by multiple-blade cartridges and disposable razors. For each type of replaceable blade, there is generally a disposable razor. In the 1930s, electric razors became available. These can rival the cost of a good straight razor, although the
Mach reflection convex away from the oncoming flow, and the slip plane slopes towards the reflecting surface. By new results there is a new configuration of shock waves - configuration with a negative angle of reflection in steady flow. In Pseudo-steady flows, the triple point moves away from the reflecting surface and the reflection is a direct-Mach reflection. In unsteady flows, it is also possible that the triple point remains stationary relative to the reflecting surface (stationary-Mach reflection), or moves toward the reflecting surface (inverse-Mach reflection). In inverse Mach reflection, the Mach stem is convex toward the oncoming flow, and the slip