Stimulated Raman Scattering for All Optical Switches

We theoretically and experimentally investigate an all optical switch based on stimulated Raman scattering in optical fibers. The experimental setup consists of a Raman circuit of two stages connected in series through a bandpass filter. In the first stage, we have a saturated amplifier, in this stage the pump pulses are saturated when pump and signal are launched to the input or the pump pulses remain without saturation when pump only is launched at the input. The second stage works as the Raman amplifier; for this stage amplification is directly dependent on the pump power entering from the first stage. For the case when pump pulse only is launched at the input pass to the second stage without saturation and amplifies the signal entering in the second stage, very intense signal pulses appear at the output of this stage. For the case when both pump and signal pulses are launched to the input, the pump pulse is saturated in the first stage and the filter rejected the amplified signal, so that only low power pump enters the second stage and consequently no signal pulses appear at the output. We show that the contrast can be improved when using fibers with normal and anomalous dispersion connected in series in the first stage. The best contrast (the ratio of energies) obtained was 15 dB at 6 W pump peak power

Thermocatalytic degradation of lignin monomer coniferyl aldehyde by aluminum–boron oxide catalysts

Two aluminum–boron oxide catalysts were produced via a sol–gel method at pH 3 and 4 during the solution mixing step of the synthesis, these materials were employed in thermocatalytic degradation of coniferyl aldehyde (CA), which was used as a probe molecule of the lignin polymeric molecule and is comprised of the repetitive monomers coniferyl, sinapyl, and paracoumaryl. The two synthesized catalysts were mostly amorphous and mesoporous, aiding in permeability and percolation of CA. A commercial catalyst was compared (Pt/alumina at 1 wt%) with both catalysts synthesized in this work by kinetic tests by varying the CA concentration and inlet temperature. Under the same reaction conditions, the commercial catalyst showed higher activity than the aluminum–boron oxide catalysts, but the synthetic catalysts presented a wider variety of organic products than the commercial catalyst. In particular, two high-value products, isomers of eugenol and isoeugenol, were yielded in higher percentages. The experimental reaction rate data was fit to a Langmuir–Hinshelwood model, and kinetic parameters were analyzed, revealing how the adsorbed CA molecules on the catalytic surface had higher mobility with the synthesized catalyst compared with the commercial catalyst, the value of $\Delta S_{\mathrm{ads}}^{0}$ for the synthetic catalysts were $-$5.48 and $-$4.31 J/mol-K and for the commercial catalyst $-$37.17 J/mol-K

Thermocatalytic degradation of lignin monomer coniferyl aldehyde by aluminum–boron oxide catalysts

Two aluminum–boron oxide catalysts were produced via a sol–gel method at pH 3 and 4 during the solution mixing step of the synthesis, these materials were employed in thermocatalytic degradation of coniferyl aldehyde (CA), which was used as a probe molecule of the lignin polymeric molecule and is comprised of the repetitive monomers coniferyl, sinapyl, and paracoumaryl. The two synthesized catalysts were mostly amorphous and mesoporous, aiding in permeability and percolation of CA. A commercial catalyst was compared (Pt/alumina at 1 wt%) with both catalysts synthesized in this work by kinetic tests by varying the CA concentration and inlet temperature. Under the same reaction conditions, the commercial catalyst showed higher activity than the aluminum–boron oxide catalysts, but the synthetic catalysts presented a wider variety of organic products than the commercial catalyst. In particular, two high-value products, isomers of eugenol and isoeugenol, were yielded in higher percentages. The experimental reaction rate data was fit to a Langmuir–Hinshelwood model, and kinetic parameters were analyzed, revealing how the adsorbed CA molecules on the catalytic surface had higher mobility with the synthesized catalyst compared with the commercial catalyst, the value of $\Delta S_{\mathrm{ads}}^{0}$ for the synthetic catalysts were $-$5.48 and $-$4.31 J/mol-K and for the commercial catalyst $-$37.17 J/mol-K

Thermophysical Properties of Biodiesel with Ethyl Levulinate, Ethyl Acetoacetate, and Ethyl Pyruvate + MgO Mixtures from 288.15 to 338.15 K

Thermophysical properties are important to design the fuel system components and to evaluate new alternative fuels in diesel engine tests. Also, experimental properties allow us to understand the type of interactions present in the studied mixtures. Densities, viscosities, and refractive indices of biodiesel + ethyl levulinate, + ethyl acetoacetate, and + ethyl pyruvate with MgO mixtures have been measured from 288.15 to 338.15 K at 0.1 MPa over the whole composition range and at a constant concentration of 5 × 10–6 in mass fraction for MgO. Our experimental properties for the pure ketoesters agree with data reported in the literature within an average absolute percentage deviation of 0.056, 3.140, and 0.027 % for density, viscosity, and refractive index, respectively. Vibrating tube densimeter, glass capillary viscosimeter, and Abbemat refractometer have been used to measure the properties. Densities and viscosities of the biodiesel mixtures have been compared with the biodiesel fuel standard EN 14214. Flash point, cetane index, and calorific value of the biodiesel mixtures that meet the EN 14214 norm have been measured. Excess molar volume, viscosity deviation, and refractive index deviation are obtained from experimental data and correlated using the Redlich–Kister equation. Equations reported in the literature are used to correlate the thermophysical properties of the investigated mixtures