Razor and blades model the disposable safety razor and founder of Gillette Safety Razor Company, Gillette did not originate this model. The urban legend about Gillette is that he realized that a disposable razor blade would not only be convenient, but also generate a continuous revenue stream. To foster that stream, he sold razors at an artificially low price to create the market for the blades. But Gillette razors were expensive when they were first introduced and the price only went down after his patents expired: it was his competitors who invented the razors-and-blades model. This model has been used in several businesses for
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