Abstract: An ultrasonic positioning system having multiple degrees of freedom of movement includes an array of piezoelectric ceramic elements grouped in pairs of adjacent ceramic elements of opposite deformation responses aligned in a first direction and also pairs aligned in a second direction, an elastic body bonded to the ceramic elements, and a moving body movably supported on the elastic body for movement in at least the two directions. The pairs of ceramic elements are activated with offset pairs of ceramic elements by electrical signals offset in phase to generate a traveling wave for driving the moving body. In a preferred embodiment, the ceramic elements have a length to width ratio of 2:1 with their lengths aligned in the X direction and widths aligned in the Y direction. When excitation signals having a frequency corresponding to either their length or width are applied, the ceramic elements can vibrate in two modes to drive the moving body in the X or Y direction.

Abstract: A threaded fastener has a standard part with a standard thread form characterized by thread walls with a standard included angle, and a modified part complementary to the standard part having a modified thread form characterized by thread walls which are symmetrically inclined with a modified included angle that is different from the standard included angle of the standard part's thread walls, such that the threads of one part make pre-loaded edge contact with the thread walls of the other part. The thread form of the modified part can have an included angle that is greater, less, or compound as compared to the included angle of the standard part. The standard part may be a bolt and the modified part a nut, or vice versa.