The manipulation of locked intrinsic localized modes/discrete breathers is studied experimentally in nonlinear electric transmission line arrays. Introducing a static lattice impurity in the form of a capacitor, resistor or inductor has been used both to seed or destroy and attract or repel these localized excitations. In a nonlinear di-element array counter propagating short electrical pulses traveling in the acoustic branch are used to generate a stationary intrinsic localized mode in the optic branch at any particular lattice site. By changing the pulse polarity the same localized excitation can be eliminated demonstrating that the dynamical impurity associated with the propagating electrical pulse in the acoustic branch can trigger optical localized mode behavior.

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We report on the photopolymerization dynamics and the volume holographic recording properties of a thiol-ene based nanoparticle-polymer composite (NPC) doped with a blue-sensitive photoinitiator, Darocur V R TPO, by using a highly coherent blue diode laser operating at a wavelength of 404 nm. Our study indicates that volume gratings recorded in the NPC amount to meeting the material requirements of refractive index modulation and material recording sensitivity for holographic data storage media. It is also found that polymerization shrinkage of recorded NPC gratings is higher than that of the same thiol-ene based NPC with a green (523 nm)-sensitive photoinitiator, Irgacure V R 784/BzO 2 . We attribute such a difference in shrinkage to the photopolymerization dynamics at these recording wavelengths. We show that this shrinkage increase at 404 nm can be mitigated to some extent by controlling the thiol-ene stoichiometry in the NPC. V C 2015 AIP Publishing LLC. [http://dx.

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Flow-induced in-line oscillation of two tandem circular cylinders has been experimentally studied by free-oscillation tests in a wind tunnel. Only one of the two cylinders was elastically supported easily to move in the in-line direction for reduced mass-damping parameter Cn ≈ 1; the other of the tandem cylinders was fixed to the tunnel sidewalls. The gap between upstream and downstream cylinders was changed from s = 0.3 to 3. We measured the response amplitudes of the oscillatory cylinder in the in-line direction and the vortex-shedding frequency in the wake. The flow around the tandem cylinders was visualized by the smoke-wire method. As a result of the upstream cylinder, there was a wide excitation region of reduced velocity, Vr = 1.5 to 2.5 in all ranges of gap ratios of s = 0.3 to 3. This excited oscillation was mainly induced by symmetric vortex shedding; the other excitation of Vr = 3 to 3.5 at wide gap ratios of s = 2 to 3, was induced by alternate Karman vortex shedding, as with the in-line oscillation of a single cylinder. The downstream cylinder had an excitation region in a wide range of Vr = 2 to 4 for the narrow gap distance of s = 0.3 to 0.75, which seems to be induced by alternate Karman vortex shedding. The other excitation regions due to symmetrical vortices were limited to the regions of gap distances of s = 0.75 to 2. Furthermore, the downstream cylinder oscillated as a buffeting phenomenon influenced by wake-fluctuation of the upstream cylinder, when gap distance was greater than s = 2.5.