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Abstract In this study, the lipophilic Cu nanoparticles were synthesized by surface modification method to improve their dispersion stability in hydrophobic organic media. The oil-based nanofluids were prepared with the lipophilic Cu nanoparticles. The transport properties, viscosity, and thermal conductivity of the nanofluids have been measured. The viscosities and thermal conductivities of the nanofluids with the surface-modified nanoparticles have higher values than the base fluids do. The composition has more significant effects on the thermal conductivity than on the viscosity. It is valuable to prepare an appropriate oil-based nanofluid for enhancing the heat-transfer capacity of a hydrophobic system. The effects of adding Cu nanoparticles on the thermal oxidation stability of the fluids were investigated by measuring the hydroperoxide concentration in the Cu/kerosene nanofluids. The hydroperoxide concentrations are observed to be clearly lower in the Cu nanofluids than in their base fluids. Appropriate amounts of metal nanoparticles added in a hydrocarbon fuel can enhance the thermal oxidation stability.

Improving the carrier separation efficiency plays a decisive role in designing and constructing a high‐efficiency photocatalysis reaction system. Derived from providing a directional transport channel for photogenerated carriers, three‐dimensional (3D) nanostructures greatly improve the charge separation efficiency. Herein, TiO2/ZnO (TZ)/g‐C3N4 3D hierarchical nanostructure was constructed to artificially simulate photosynthesis of green plants. The optimal TZ/g‐C3N4 photoanode exhibits a photocurrent density of 1.46 mA/cm2 at 1.23 V versus reversible hydrogen electrode potential, 1.6 times that of pure TiO2 (0.9 mA/cm2). Moreover, under constant illumination (100 mW/cm2), the hydrogen production reached 80 μmol/cm2 within 180 min. It is worth noting that the TZ/g‐C3N4 photoanode shows surprising stability, which is an important indicator for the practical application of the photoelectrode. The excellent photoelectrochemical performance benefits from the following two aspects: TZ nanotree structure provides a directional transport channel for photogenerated carriers, and the modification of TZ by g‐C3N4 extends the response range to the visible region. [ABSTRACT FROM AUTHOR]

A sinusoidal phase modulation laser interferometer is proposed to detect water surface acoustic waves excited by underwater acoustic radiation, and an improved PGC-Arctan demodulation algorithm that combines prenormalization and Lissajous ellipse fitting is proposed to demodulate detection signals. In this paper, the effects of phase modulation depth, carrier phase delay, and interference signal visibility on the Lissajous figure formed by quadrature interference components are analyzed. The demodulation algorithm first uses the amplitudes of multiple Fourier spectral components of an interference signal to calculate the phase modulation depth C, and calculation of the carrier phase delay Vc is achieved through the introduction of a quadrature carrier signal. Then, certain coefficients regarding C and Vc are constructed for prenormalization of the two quadrature interference signal components to eliminate the local nonuniform widening phenomenon of Lissajous ellipse. Next, the outer and the inner contours are extracted from a uniformly widened Lissajous ellipse resulting from light intensity disturbance, and the axial ratio of the ellipse is obtained, which is used to correct the ratio of the quadrature interference signal to eliminate the effect of filter gain coefficients. At last, through the combination of an Arctan algorithm and a phase-unwrapping algorithm, high-precision demodulation of the interference signal is realized. A sinusoidal phase modulation interferometer was set up to detect water surface acoustic waves, and a series of detection experiments were carried out. The experiment results show that the detection method and demodulation algorithm described in this paper can accurately realize the measurement of weak water surface acoustic waves. The proposed algorithm shows less distortion in demodulation results, and its signal-to-noise distortion ratio is less than 20 dB at 500 Hz, which is significantly better than traditional algorithms. The experimental results demonstrate the effectiveness and accuracy of water surface acoustic wave detection using sinusoidal phase modulation interferometer. [ABSTRACT FROM AUTHOR]