Abstract: A coating fault locating technique transmits a base electric signal from a power source to a buried metal pipe. A location of a coating fault in the buried pipe is detected by detecting a gradient of a changing magnetic field between two points spaced along the buried pipe. The gradient is detected based upon the output differential of at least one pair of search coils. The gradient is caused by a leakage of current that occurs at the coating fault. In particular, the at least one pair of search coils are provided in a mobile unit that is located above ground. The at least one pair of search coils are spaced apart from one another and have their axes arranged so as to have a low sensitivity to a magnetic field generated by the base electric signal running through the buried pipe. The at least one pair of coils are spaced apart from each other such that a line drawn between midpoints of the search coils' axes crosses a plane normal to the axis of the buried pipe.

Abstract: A substrate serving as a heat sink for a semiconductor efficiently radiates heat from a semiconductor element mounted thereon. The substrate consists of a composite alloy metal which consists of a sintered body of a metal powder having a high melting point such as W and Mo impregnated with a filling metal such as Cu and Ag, wherein the sintered body of a metal powder having a high melting point has a grain size composition of a combination of a plurality of powder groups having statistically different average grain sizes from group to group, and the powder of each group is dispersed uniformly.