Abstract: A method for multi-hop data transmission in an ad-hoc network comprising concealed nodes. A source node determines the probability of a collision-free transmission of data to the following nodes and if a high probability of collision-free transmission is present, transmits a data packet to a following node without coordinating transmission-channel allocation with concealed nodes disposed in the vicinity of the next node.

Abstract: A method and apparatus for friction stir welding that produces a weld of significantly reduced surface roughness at significantly higher welding rates, in materials that are difficult to weld, such as non-extrudable aluminum alloys. The method includes cooling the stir welding tool during the welding process, thereby reducing the tendency of softened metal to adhere to the rotating pin and shoulder of the tool. The apparatus includes a tool with internal spaces or an external jacket, through which coolant can be pumped to remove heat and cool the tool during welding operations. In another embodiment, the apparatus includes a device for spraying a coolant onto exterior surfaces of the distal end of the welding tool to thereby remove heat from the tool, and the surrounding workpiece, during welding.

Abstract: A collapsible hand truck (10) having storage and operative positions. The truck includes a back frame (12) having a back side, an upper end (16) and a lower end (18). Two wheels (44) are rotatably connected to the back frame lower end (18) at a position offset rearwardly and downwardly therefrom. The offset position is created by aft-extending arms (40). The truck (10) further includes a bail (14) having a front end (20) and an aft end (22). The aft end (22) is rotatably connected to the back frame lower end (18). A strap (50) is provided for maintaining the maximum angular distance between the back frame (14) and the bail (12) during use. In the operative position, the bail (14) is located substantially forward of the back frame (12) and the strap (50) is interconnected between the bail front end (20) and the back frame upper end (16). To reach the storage position, the bail (14) rotates downward and aftward to a location behind the back frame (12) and substantially adjacent to the back frame back side.