High-frequency structural-acoustic analysis using an unstructured zero-order energy FEM formulation

Based on the governing equations of energy flow analysis in plate and acoustic domain, an unstructured zero-order energy finite element method (uEFEM0) formulation is presented to simulate the high-frequency behavior of plate structures in contact with acoustic cavities. The new formulation is derived using EFEM0, in which the energy primary variable is conserved in each element. The bending, longitudinal, and shear wave fields in the plates are all included. By meshing plates with triangular grids and cavities with tetrahedral grids, this new formulation can be easily used for modeling structures with arbitrary shape. The formulation is validated by comparing the results obtained from uEFEM0 with those from statistical energy analysis and literature. Good correlations are observed, and the advantages of the uEFEM0 formulation are identified

A γ\gamma-ray Quasi-Periodic modulation in the Blazar PKS 0301−-243?

We report a nominally high-confidence $\gamma$-ray quasi-periodic modulation in the blazar PKS 0301$-$243. For this target, we analyze its \emph{Fermi}-LAT Pass 8 data covering from 2008 August to 2017 May. Two techniques, i.e., the maximum likelihood optimization and the exposure-weighted aperture photometry, are used to build the $\gamma$-ray light curves. Then both the Lomb-Scargle Periodogram and the Weighted Wavelet Z-transform are applied to the light curves to search for period signals. A quasi-periodicity with a period of $2.1\pm0.3$ yr appears at the significance level of $\sim5\sigma$, although it should be noted that this putative quasi-period variability is seen in a data set barely four times longer. We speculate that this $\gamma$-ray quasi-periodic modulation might be evidence of a binary supermassive black hole.Comment: 9 pages, 8 figures; Accepted for publication in Ap

(E)-N′-(3,4-Dichloro­benzyl­idene)nicotino­hydrazide monohydrate

In the title compound, C13H9Cl2N3O·H2O, the 3,4-dichloro­benzene ring is nearly coplanar with the pyridine ring, making a dihedral angle of 4.78 (8)°. Inter­molecular O—H⋯O, O—H⋯N, N—H⋯O and weak C—H⋯O hydrogen bonding is present in the crystal structure