Abstract: A method of obtaining a parameter of a synchronous motor is disclosed and includes: setting an operating current of the motor; providing a positive fixed voltage to the motor and monitoring a feedback current from the motor; recording a triggering time for the feedback current to reach the operating current; providing a negative fixed voltage to the motor for the triggering time; obtaining a square-wave voltage with a fixed frequency based on the positive fixed voltage and the negative fixed voltage being provided; providing the square-wave voltage with the fixed frequency to one axis of the motor; transforming three-phase current from the motor into an axial current; computing an inductance value of this axis based on the fixed frequency, the square-wave voltage and the axial current; and, creating an inductance-current parameter table based on a plurality of the inductance values and the axial currents correspondingly.

Abstract: A non-return valve includes a flap and a valve body. The flap has one side formed with a pivot connector pivotally connected with the valve body and the other side formed integral with a weight. After the flap is pushed open by the pushing force of fluid and the pushing force of the fluid vanishes, the flap without being pressed by any force will be actuated by its own weight to quickly move down and tightly close the valve port of the valve body, having excellent effect of stopping fluid from flowing reversely and leaking out of the port.

Abstract: There is disclosed a process for producing an optical waveguide comprising contacting at least one optically smooth surface of a single crystal of K.sub.1-x Rb.sub.x TiOMO.sub.4 wherein x is from 0 to 1 and M is P or As with a specified molten salt of at least one of Rb, Cs and Tl at a temperature of from about 200.degree. C. to about 600.degree. C. for a time sufficient to increase the surface index of refraction at least about 0.00025 with respect to the index of refraction of the starting crystal, and cooling the resulting crystal. The product made thereby and a waveguide device using the same are also disclosed.