A freestanding oscillator for resonant-ultrasound microscopy.

Resonant-ultrasound microscopy with a freestanding rod oscillator has been developed for mapping a material's elastic properties in a localized surface region, for the purpose of evaluating elastic stiffness through the resonance frequency of the oscillator contacting the specimen by its tip. A stronger biasing static magnetic field makes the ferritic steel oscillator plumb without any other mechanical support except tip-sample contact. For a noncontacting acoustical coupling, the longitudinal vibration of the oscillator is excited and detected with a surrounding solenoid coil by the magnetostrictive effect. This freestanding configuration realizes only a mechanical "point" contact between the oscillator and the sample surface, which yields accurate measurement of the local elastic stiffness. As an illustrated example, the new microscopy method is applied to an SCS- 6 SiCf/Ti-6Al-4V composite to visualize its elastic-stiffness distribution.

Estimation of Sensitive Proportion by Randomized Response Data in Successive Sampling.

This paper considers the problem of estimation for binomial proportions of sensitive or stigmatizing attributes in the population of interest. Randomized response techniques are suggested for protecting the privacy of respondents and reducing the response bias while eliciting information on sensitive attributes. In many sensitive question surveys, the same population is often sampled repeatedly on each occasion. In this paper, we apply successive sampling scheme to improve the estimation of the sensitive proportion on current occasion.

Dynamic-contact stiffness at the interface between a vibrating rigid sphere and a semi-infinite viscoelastic solid.

Vibration of a rigid sphere contacting a semiinfinite viscoelastic solid is studied theoretically. The rigid sphere is subjected to an oscillating force while being compressed in the vertical direction by a static force. The contact-pressure distribution and contact radius at the interface vary with the oscillation. Assuming sufficiently small oscillating force, we derive the dynamic-contact-pressure distribution with the constant contact radius, which establishes dynamic contact stiffness between the sphere and the viscoelastic solid. Numerical calculations show the influence of vibration frequency, contact radius, Poisson's ratio, and the damping characteristic of the solid.

Vibration analysis of an isotropic elastic sphere contacting a semi-infinite cubic solid.

Vibration analysis of an isotropic elastic-sphere oscillator contacting a semi-infinite cubic solid is investigated by considering dynamic deformation at the contact interface. Assuming sufficiently small oscillation amplitude of the sphere compared with the static indentation deformation, the dynamic maximum contact pressure and the variable contact radius yield a dynamic-contact pressure distribution of constant contact radius. The combination of the sphere oscillation and the solid motion at the contact interface through contact-displacement conditions gives resonance frequencies of the elastic sphere. Unlike the conventional quasi-static model, this dynamic contact model agrees well with the measurements, which will benefit the quantitative evaluation of the local Young's modulus and the orientation of micro-scaled anisotropic grains by the resonance-frequency shifts of a vibrating oscillator in resonance ultrasound microscopy and the efficient removal of micron or sub-micron particles from the substrate in the dry laser cleaning technique.

Vibration analysis on electromagnetic-resonance-ultrasound microscopy (ERUM) for determining localized elastic constants of solids.

In this paper we present a new acoustic-resonance microscopy, Electromagnetic-Resonance-Ultrasound Microscopy (ERUM), to measure the localized elastic stiffness of a solid material. It visualizes the resonance-frequency shift of vibrating piezoelectric crystal (langasite, La3Ga5SiO14) excited by an electric field from a solenoid coil. The acoustic coupling is made only at the tip of the crystal touching the specimen surface. Being based on the calibration for the specimen's effective stiffness, the local elasticity is determined from the resonance frequencies of the crystal with the Rayleigh-Ritz method. An approximate model for the specimen's effective stiffness predicts the shift of resonance frequencies, for which the conventional Hertz-contact model is improved. As an illustrating example, the mapping of Young's modulus of a duplex stainless steel is presented, which shows good agreement with the existing study.