Active attenuation of propeller blade passage noise

Acoustic measurements are presented to show that active cancellation can be used to achieve significant reduction of blade passage noise in a turboprop cabin. Simultaneous suppression of all blade passage frequencies was attained. The spatial volume over which cancellation occurred, however, is limited. Acoustic intensity maps are presented to show that the acoustic input to the fuselage was sufficiently non-localized so as to require more judicious selection of cancellation speaker location

Picosecond nonlinear optical features of ferroelectric A(6)M(2)M(8)O-30 large sized nanocrystallites

Second and third order nonlinear optical susceptibilities of A(6)M(2)M(8)O-30 ferroelectric crystallites 100 nm powders were studied. The measurements were carried out for powders and thin films of guest-host composites made of Poly(methyl methacrylate) (PMMA) matrix. The studies were carried out by Kurtz Perry method using a Q-switch 16 ps picosecond Nd:YAG laser with peak pulse power 25 MW operating at 1064 nm fundamental wavelength. We have established that Ba6Ti2Nb8O30 ferroelectric crystallites achieve the highest (among the studied materials) second order optical susceptibilities equal to about 8.12 pm/V. The use of picosecond laser pulses and of the crystallites with high monodispersion allow to obtain an information concerning the second order optical susceptibilities with the avoiding of the local thermoheating which may change the output susceptibilities

Nonlinear optical characterization of functionalized organometallic complexes using THG and Z-scan techniques

We report the measurements of third-order nonlinear optical (NLO) properties in picosecond regim of functionalized organometallic complexes using third harmonic generation (THG) and Z-scan techniques. We show the results obtained for solutions dissolved in dichloromethane with different concentrations. For each chromophore, we give the values of: the nonlinear absorption coefficient β, the nonlinear refractive index n2, the third-order nonlinear susceptibility χ 3 and the second-order nonlinear hyperpolarisability γ of individual molecules. This approach allowed us to determine also the electronic and rotational contributions of χ 3 by using a picosecond laser Nd:YAG at the fundamental wavelength 1064 nm

ACL 85. Nonlinear optical characterization of functionalized organometallic complexes using THG and Z-scan techniques

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