In this article, the H∞ optimization design of a hybrid vibration absorber (HVA), including both passive and active elements, for the minimization of the resonant vibration amplitude of a single degree-of-freedom (SDOF) vibrating structure is derived by using the fixed-points theory. The optimum tuning parameters are the feedback gain, the tuning frequency, damping and mass ratios of the absorb...

I report the discovery of blueshifted broad absorption line (BAL) troughs in at least six transitions of the Balmer series of hydrogen (Hβ to H9) and in Ca II, Mg II and excited Fe II in the quasar SDSS J125942.80+121312.6. This is only the fourth active galactic nucleus known to exhibit Balmer absorption, all four in conjunction with low-ionization BAL systems containing excited Fe II. The sub...

In a single-degree-of-freedom weakly nonlinear oscillator subjected to periodic external excitation, a small-amplitude excitation may produce a relatively large-amplitude response under primary resonance conditions. Jump and hysteresis phenomena that result from saddle-node bifurcations may occur in the steady-state response of the forced nonlinear oscillator. A simple mass-spring-damper vibrat...

Graphene, whose absorbance is approximately independent of wavelength, allows broadband light-matter interactions with ultrafast responses. The interband optical absorption of graphene can be saturated readily under strong excitation, thereby enabling scientists to exploit the photonic properties of graphene to realize ultrafast lasers. The evanescent field interaction scheme of the propagating...

Sub-picosecond optical pulses have been successfully generated using a novel monolithic passive colliding pulse mode-locked (CPM)l semiconductor multiple quantum-well (MQW) laser. Transform-limited pulse width of 830 femto-seconds is achieved at a wavelength of 1.5pm and a repetition rate of 80 GHz. The measured timebandwidth product is 0.31. A record high repetition rate of 350 GHz is also dem...

Few nonsurgical treatment options are available to the patient with debilitating knee osteoarthritis (OA) that is refractory to conservative care. The KineSpring® System joint unloading implant is a unique device that reduces the load carried by the medial compartment of the knee joint by up to 13 kilograms during the stance phase of gait. We report a case of a male patient who underwent implan...

The study of ideal absorbers, which can efficiently absorb light over a broad range of wavelengths, is of fundamental importance, as well as critical for many applications from solar steam generation and thermophotovoltaics to light/thermal detectors. As a result of recent advances in plasmonics, plasmonic absorbers have attracted a lot of attention. However, the performance and scalability of ...

Flue gas desulfurization (FGD) systems are employed to remove SO(x) gasses that are produced by the combustion of coal for electric power generation, and consequently limit acid rain associated with these activities. Wet FGDs represent a physicochemically extreme environment due to the high operating temperatures and total dissolved solids (TDS) of fluids in the interior of the FGD units. Despi...

Recently, techniques involving random patterns have made it possible to control the light trapping of microstructures over broad spectral and angular ranges, which provides a powerful approach for photon management in energy efficiency technologies. Here, we demonstrate a simple method to create a wideband near-unity light absorber by introducing a dense and random pattern of metal-capped monod...

The design and validation of a dual polarization source for waveguide-coupled millimeter and sub-millimeter wave cryogenic sensors is presented. The thermal source is a waveguide mounted absorbing conical dielectric taper. The absorber is thermally isolated with a kinematic suspension that allows the guide to be heat sunk to the lowest bath temperature of the cryogenic system. This approach ena...