Tunable Unidirectional Sound Propagation through a Sonic-Crystal-Based Acoustic Diode

Nonreciprocal wave propagation typically requires strong nonlinear materials to break time reversal symmetry. Here, we utilized a sonic-crystal-based acoustic diode that had broken spatial inversion symmetry and experimentally realized sound unidirectional transmission in this acoustic diode. These novel phenomena are attributed to different mode transitions as well as their associated different energy conversion efficiencies among different diffraction orders at two sides of the diode. This nonreciprocal sound transmission could be systematically controlled by simply mechanically rotating the square rods of the sonic crystal. Different from nonreciprocity due to the nonlinear acoustic effect and broken time reversal symmetry, this new model leads to a one-way effect with higher efficiency, broader bandwidth, and much less power consumption, showing promising applications in various sound devices

Seismic Performance Investigation of Cold-Formed Steel Framed Shear Walls with Steel Sheathing

Cold-formed steel (CFS) framed shear walls with steel sheet sheathing can achieve higher shear resistance compared to conventional CFS framed shear walls. Experimental and numerical investigation of seismic behavior was present on two CFS shear walls sheathed with steel sheet for the base layer combined with gypsum wallboards for the face layer on both sides. Monotonic shear and cyclic loading tests were conducted on wall specimens. The failure mechanism, bearing capacity, stiffness and ductility of specimens were obtained. On the basis of rational simplification of CFS framed shear walls, the finite element software ABAQUS was used to simulate the monotonic behavior of CFS shear walls and the structural analysis software OpenSees was used in developing and calibrating 2D models of reversed cyclic shear wall test. A comparison between the numerical simulations and the test results showed a good agreement between the results of the numerical studies and the test results. The conclusions of this study can be applied to the seismic design of CFS framed shear walls

N,N-Bis(diphenyl­phosphan­yl)benzyl­amine

In the title compound, C31H27NP2, the diphenyl­phosphanyl groups are staggered relative to the PNP backbone. The N atom is displaced by 0.219 (2) Å from the plane formed by the two P atoms and the methylene C atom. The angles around the N atom are 120.84 (16), 113.29 (16) and 120.57 (12)°, indicating that it exhibits a distorted trigonal–pyramidal geometry. There are no classical inter­molecular inter­actions

Dyonic Reissner-Nordstrom Black Holes and Superradiant Stability

Black holes immersed in magnetic fields are believed to be important systems in astrophysics. One interesting topic on these systems is their superradiant stability property. In the present paper, we analytically obtain the superradiantly stable regime for the asymptotically flat dyonic Reissner-Nordstrom black holes with charged massive scalar perturbation. The effective potential experienced by the scalar perturbation in the dyonic black hole background is obtained and analyzed. It is found that the dyonic black hole is superradiantly stable in the regime $0<r_{-}/r_{+}<2/3$, where $r_\pm$ are the event horizons of the dyonic black hole. Compared with the purely electrically charged Reissner-Nordstrom black hole case, our result indicates that the additional coupling of the charged scalar perturbation with the magnetic field makes the black hole and scalar perturbation system more superradiantly unstable, which provides further evidence on the instability induced by magnetic field in black hole superradiance process