We have fabricated the first optical quality polymer films of aromatic ladder polymers having an unbroken conjugated backbone, and find third-order nonlinear susceptibilities two orders of magnitude larger than CS2. The nonlinearities respond in less than 6 ps. Although we find their space symmetry to agree with that expected for a nonresonant electronic nonlinearity, the mechanism may well depend on lattice motion. The polymers are stable and rugged at room temperature. We also develop and analyze a simple form of degenerate four-wave mixing for the measurements, finding expressions for the effects of uncertainties in the spatial and temporal pulse profiles.

New polymers incorporating a variety of electroactive moeities with defined π-electron conjugation lengths have been synthesized and characterized by degenerate four wave mixing (DFWM) techniques. The χ(3)/α values for these materials varied from 10−12 to 10−13 esu cm. This work has identified several promising structures with nonlinear optical activity including organometallic and purely organic materials. The preparation of composite materials has also permitted the measurement of χ(3)/α as a function of the electroactive unit concentration.

Both the aerospace and marine industry have widely relied on a honeycomb sandwich structure (HSS) because of its high strength-to-weight ratio. However, the intrinsic nature of an adhesively bonded multi-layer structure increases the risk of debonding when the structure is under strain or exposed to varying temperatures. Such defects are normally concealed under the surface but can significantly compromise the strength and stiffness of a structure. In this paper, the guided wave method is used to detect debondings which are located between the skin and the honeycomb in sandwich plates. The propagation of guided waves in honeycomb plates is investigated via numerical techniques, with emphasis placed on demonstrating the behavior of structure-based wave interactions (SWIs). The SWI technique is effective to distinguish heterogeneous structures from homogeneous structures. The excitation frequency is necessary to generate obvious SWIs in HSSs; accordingly, a novel strategy is proposed to select the optimal excitation frequencies. A series of experiments are conducted, the results of which show that the presented procedure can be used to effectively detect the locations and the sizes of single- and multi-damage zones in HSSs.

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The optimal condition of polysilicon ferric chloride (PFSC) flocculant was established by thinking of the factors , such as Si/Fe molar ratios,the reaction temperature and the pH value of the solution. When the molar ratio of Si and Fe = 1, pH value = 0.6, curing temperature at 30 ~40 °C, poly ferric chloride dosage of 0.75mg/L, the rate of turbidity removal of seawater is up to 96.5%. Experimental results show that poly ferric chloride seawater turbidity removal effect is obvious.