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 the shock angle exceeds a certain value, the deflection achievable by a single reflected shock is insufficient to turn the flow back to a direction parallel to the wall and transition to Mach reflection is observed. Mach reflection consists of three shocks, namely the incident shock, the reflected shock and a Mach stem, as well as a slip plane. The point where the three shocks meet is known as the 'triple point' in two dimensions, or a shock-shock in three dimensions. The only type of Mach reflection possible in steady flow is direct-Mach reflection, in which the Mach stem is