Displacement Sensing of an Active String Actuator Using a Step-Index Multimode Optical Fiber Sensor.

A thin McKibben artificial muscle is a pneumatic actuator with an outer diameter of only 1.8 mm. We fabricated a string-shaped actuator called an "active string actuator," which achieves a high contractile displacement by accumulating thin McKibben artificial muscles. To control the displacement, the length of the active string actuator should be estimated. However, this is difficult because bulky and rigid sensors are unsuitable for the sensor element of the active string actuator. Therefore, in this study, we propose a new sensing method for estimating the length of an active string actuator. The proposed sensing system is simple and comprises only three components: a step-index multimode optical fiber, a light emitter, and a light receiver. A step-index multimode optical fiber was combined with the active string actuator, and the length was estimated from the change in the amount of light propagating in the optical fiber when the active string actuator was driven. Fundamental experiments were conducted in this study, and the results demonstrated that the optical fiber sensor value changed with the actuator length. This suggests that it is possible to estimate the displacement of an active string actuator using an optical fiber sensor.

Fermi surface in La-based cuprate superconductors from Compton scattering imaging.

Compton scattering provides invaluable information on the underlying Fermi surface (FS) and is a powerful tool complementary to angle-resolved photoemission spectroscopy and quantum oscillation measurements. Here we perform high-resolution Compton scattering measurements for La2-xSrxCuO4 with x = 0.08 (Tc = 20 K) at 300 K and 150 K, and image the momentum distribution function in the two-dimensional Brillouin zone. We find that the observed images cannot be reconciled with the conventional hole-like FS believed so far. Instead, our data imply that the FS is strongly deformed by the underlying nematicity in each CuO2 plane, but the bulk FSs recover the fourfold symmetry. We also find an unusually strong temperature dependence of the momentum distribution function, which may originate from the pseudogap formation in the presence of the reconstructed FSs due to the underlying nematicity. Additional measurements for x = 0.15 and 0.30 at 300 K suggest similar FS deformation with weaker nematicity, which nearly vanishes at x = 0.30.

Magnetoelectric effect driven by magnetic domain modification in LuFe2O4.

The magnetocapacitance effect was investigated using impedance spectroscopy on single crystals of LuFe(2)O(4). The intrinsic impedance response could be separated from the interfacial response and showed a clear hysteresis loop below T(Ferri)∼240 K under the magnetic field. The neutron diffraction experiment under the magnetic field proves the origin of the dielectric property related to the motion of the nanosized ferromagnetic domain boundary. These results imply that the modification of the microscopic domain structure is responsible for the magnetoelectric effect in LuFe(2)O(4).