Abstract: The present disclosure provides a system and method for verifying alternating current (AC)/direct current (DC) conversion of an ultralow-frequency voltage. The system includes a quantum voltage generation system, a low-frequency signal source, a follower, three switches, a double-heater-strip thermoelectric converter, a nanovoltmeter, a clock source, a high-precision digital sampling system, and an upper computer. Based on DC and AC quantum voltage technologies and with reference to the double-heater-strip thermoelectric converter, an ultralow-frequency voltage is traced to a DC quantum voltage through AC/DC conversion, and a conversion result is compared with an AC quantum voltage to verify rationality of precision and an uncertainty evaluation result of AC/DC conversion of the ultralow-frequency voltage, so as to ensure reliability of AC/DC conversion of the ultralow-frequency voltage. This resolves a problem that the AC/DC conversion result of the ultralow-frequency voltage cannot be verified.

Abstract: An auxiliary string pressing device for guitar playing includes a bracket, wherein the bracket having a bracket mounting structure, the bracket is provided with elastic pieces, each elastic piece having a fixed end and a movable end, the fixed end of the each elastic piece and the bracket being connected by an elastic piece fast mounting structure, a front face of the movable end of the each elastic piece is provided with a key, and a back face of the movable end of the each elastic piece being provided with a string pressing block. The auxiliary string pressing device uses an elasticity of the elastic pieces to reset, wherein a structure is simplified. The elastic piece fast mounting structure of the elastic pieces and the bracket enable the elastic pieces to be replaced by such a mounting structure.

Abstract: An auxiliary string pressing device for guitar playing includes a bracket, wherein the bracket having a bracket mounting structure, the bracket is provided with elastic pieces, each elastic piece having a fixed end and a movable end, the fixed end of the each elastic piece and the bracket being connected by an elastic piece fast mounting structure, a front face of the movable end of the each elastic piece is provided with a key, and a back face of the movable end of the each elastic piece being provided with a string pressing block. The auxiliary string pressing device uses an elasticity of the elastic pieces to reset, wherein a structure is simplified. The elastic piece fast mounting structure of the elastic pieces and the bracket enable the elastic pieces to be replaced by such a mounting structure.