Abstract: The type of acoustic absorber comprises a micro-perforated plate, a cavity behind the micro-perforated plate, a slender and curved main acoustic propagation passage communicating with the cavity, and a set of acoustic filters arranged along the main acoustic propagation passage. These acoustic filters have different cut-off frequencies and are arranged in the order of the cutoff frequencies from high to low from the open end to the closed end of the main acoustic propagation passage. The acoustic filter comprises a section of the main acoustic propagation passage and at least one cavity communicating with the main acoustic propagation passage. The type of acoustic absorber is characterized by adopting a main acoustic propagation passage to provide different phase delay for a micro-perforated plate to realize that a micro-perforated plate effectively absorbs broadband acoustic waves, and by combing the close arrangement of main acoustic propagation passage to achieve the ultra-thin structure.

Abstract: The present invention belongs to the technical field of alternating current induction servo motors, and particularly relates to a rotary-type induction servo motor with a constant-output-torque by using uniform magnetic fields and a linear-type induction servo motor with a constant-output-force by using uniform magnetic fields. The present invention has main features that the rotary-type induction servo motor or the linear-type induction servo motor is composed of N independent motor units; each independent motor unit has the same or similar structure, and is powered by single-phase alternating current; and the N independent motor units have an equal voltage magnitude of power supply, but voltage phases are different and form an arithmetic progression.

Abstract: The present invention discloses a ultrathin acoustic impedance converter belonging to the acoustic field, which is characterized by comprising one or a plurality of impedance conversion units, wherein each impedance conversion unit is composed of a frame, a plurality of prestressed membranes or prestressed string nets, and multiple layers of acoustic materials, wherein a through cavity is fabricated in the frame, the prestressed membranes or string nets and the acoustic materials are alternately arranged in the cavity, i.e., a prestressed membrane or string net is arranged, and then a layer of acoustic materials is arranged, and so on until the through cavity is fully filled. The cavity can be designed in different shapes either with a variable cross section or a uniform cross section.

Abstract: The present invention discloses a ultrathin acoustic impedance converter belonging to the acoustic field, which is characterized by comprising one or a plurality of impedance conversion units, wherein each impedance conversion unit is composed of a frame, a plurality of prestressed membranes or prestressed string nets, and multiple layers of acoustic material, wherein a permeable cavity is arranged in the frame, the prestressed membranes or string nets and the acoustic material are alternately arranged in the cavity, i.e., a prestressed membrane or string net is arranged, and then a layer of acoustic material is arranged, and so on until the cavity is fully filled. The cavity can be designed in different shapes, including a variable cross section and a uniform cross section. Each prestressed membrane or string net is required to be applied with prestress before being arranged in the cavity, and the magnitude of the prestress depends on the resistance value that the membrane or string net is expected to reach.

Abstract: The present invention belongs to the technical field of alternating current induction servo motors, and particularly relates to a rotary-type induction servo motor with a constant-output-torque by using uniform magnetic fields and a linear-type induction servo motor with a constant-output-force by using uniform magnetic fields. The present invention has main features that the rotary-type induction servo motor or the linear-type induction servo motor is composed of N independent motor units; each independent motor unit has the same or similar structure, and is powered by single-phase alternating current; and the N independent motor units have an equal voltage magnitude of power supply, but voltage phases are different and form an arithmetic progression.