Abstract: Positive reference spiked in collected sample for use in qualitatively and quantitatively detecting viral RNA.

Abstract: A sound absorber is configured as a rectangular hexahedral box and forms a porous double-layer Helmholtz resonance sound absorbing structure, at the same time, the sound absorber in the form of a box forms a structural resonance sound absorbing device itself, and the first-order natural mode frequency of the device is identical to that of a wheel air chamber. When the box-type sound absorbing structure is assembled in a wheel, double functions of absorbing acoustic resonance of the wheel air chamber under the organic combination of Helmholtz resonance sound absorption and structural resonance sound absorption can be realized.

Abstract: The present application relates to a wheel with a sound absorber, the sound absorber being mounted in a wheel air chamber to reduce acoustic resonance, wherein the sound absorber is configured as a flat hexahedral box resonator and fastened to a wheel hub through a band, a first positioning mechanism is provided between the hub and the box resonator to fix the relative positions of the hub and the box resonator, and a second positioning mechanism is provided between the box resonator and the band to fix the relative positions of the box resonator and the band. According to the technical solution of the present disclosure, the resonator is positioned and fixed more reliably on the wheel, and the wheel is simple and economical in manufacturing, and convenient and controllable in installation and operation.

Abstract: The present disclosure relates to a sound absorber and a wheel having the same. The sound absorber is configured as a rectangular hexahedral box and forms a porous double-layer Helmholtz resonance sound absorbing structure, at the same time, the sound absorber in the form of a box forms a structural resonance sound absorbing device itself, and the first-order natural mode frequency of the device is identical to that of a wheel air chamber. When the box-type sound absorbing structure is assembled in a wheel, double functions of absorbing acoustic resonance of the wheel air chamber under the organic combination of Helmholtz resonance sound absorption and structural resonance sound absorption can be realized.

Abstract: The present application relates to a wheel with a sound absorber, the sound absorber being mounted in a wheel air chamber to reduce acoustic resonance, wherein the sound absorber is configured as a flat hexahedral box resonator and fastened to a wheel hub through a band, a first positioning mechanism is provided between the hub and the box resonator to fix the relative positions of the hub and the box resonator, and a second positioning mechanism is provided between the box resonator and the band to fix the relative positions of the box resonator and the band. According to the technical solution of the present disclosure, the resonator is positioned and fixed more reliably on the wheel, and the wheel is simple and economical in manufacturing, and convenient and controllable in installation and operation.