Transversal-rotational and zero group velocity modes in tunable magneto-granular phononic crystals

We report on the design and operation of a 1D magneto-granular phononic crystal composed of a chain of steel spherical beads on top of permanent magnets. The magnetic field of the permanent magnets induces forces in the granular structure. By changing its strength, we can tune the dynamic response of the granular structure. We present experimental results with evidence of coupled transversal-rotational modes, and zero group velocities modes. These observations are well supported by a proposed model taking into account the mechanical coupling between the beads and the magnets by linear stiffnesses and including all degrees of freedom in translations and rotations

New host record for \u3ci\u3eEntylia carinata\u3c/i\u3e (Forster) (Hemiptera: Membracidae)

Yacon, Smallanthus sonchifolius (Poepp.) H. Rob (Asteraceae), is recorded as a new host plant for Entylia carinata (Forster) (Hemiptera: Membracidae) in Mt. Holly, NC. Adults, nymphs, and attending ants were found on numerous plants

New host record for \u3ci\u3eEntylia carinata\u3c/i\u3e (Forster) (Hemiptera: Membracidae)

Yacon, Smallanthus sonchifolius (Poepp.) H. Rob (Asteraceae), is recorded as a new host plant for Entylia carinata (Forster) (Hemiptera: Membracidae) in Mt. Holly, NC. Adults, nymphs, and attending ants were found on numerous plants

Testing a bead-rod contact with a nonlinear resonance method

International audienceWe study the dynamics of an elastic structure composed of a cylindrical rod in contact with a bead at one extremity. Wave propagation within the cylindrical rod is considered linear and dispersionless while the bead-rod contact shows a highly nonlinear behavior as expected from the Hertz's model of contact. The resonance curves of the nonlinear contact depend on the excitation amplitude, where a downshift of the resonance frequency with increasing exci-tation amplitude is observed. The prediction of the resonance frequency shift by the Hertz's model is compared to the experimental results and shows a disagreement. A better agreement is found by considering the losses with a viscoelastic model, namely the Kuwabara and Kono or Brilliantov model. The observation of the nonlinear effects linked to the resonance of the mass-spring system can lead to the design of nonlinear elastic metamaterials, where the wave propagation is controlled by nonlinear isolated resonators

New host record for \u3ci\u3eEntylia carinata\u3c/i\u3e (Forster) (Hemiptera: Membracidae)

Yacon, Smallanthus sonchifolius (Poepp.) H. Rob (Asteraceae), is recorded as a new host plant for Entylia carinata (Forster) (Hemiptera: Membracidae) in Mt. Holly, NC. Adults, nymphs, and attending ants were found on numerous plants

New host record for Entylia carinata (Forster) (Hemiptera: Membracidae)

Yacon, Smallanthus sonchifolius (Poepp.) H. Rob (Asteraceae), is recorded as a new host plant for Entylia carinata (Forster) (Hemiptera: Membracidae) in Mt. Holly, NC. Adults, nymphs, and attending ants were found on numerous plants

New host record for Entylia carinata (Forster) (Hemiptera: Membracidae)

Yacon, Smallanthus sonchifolius (Poepp.) H. Rob (Asteraceae), is recorded as a new host plant for Entylia carinata (Forster) (Hemiptera: Membracidae) in Mt. Holly, NC. Adults, nymphs, and attending ants were found on numerous plants