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The effects of polymorphic form and particle size of SiO2 fillers on the dielectric, mechanical and thermal properties of SiO2–Polyetheretherketone (SiO2–PEEK) composites were investigated in this paper. Strong low frequency (

A simple method to achieve multi-focus and pattern manipulation in antenna near field (NF) is proposed in this study, whose effectiveness is then validated by measurements based on different transmit-array antennas. The radiating aperture is divided into several regions and each region corresponds to one assigned focal point, thus achieving multi-focusing performance. Then, the superposition principle is employed and constrains the multiple foci into a certain area to get a contoured pattern. Three examples are investigated. Ant-A presents four balanced focal spots simultaneously, while Ant-B presents two unbalanced foci. A square flat-top field pattern is obtained for Ant-C. Three-dimensional printing technology is employed to fabricate these lenses, resulting in a low cost and light weight. Measured results coincide well with the numerical design and simulation. The proposed method provides a simple and effective alternative for NF power redistribution and owns great value in such applications as radio-frequency identification, wireless power transmission, millimetre-wave imaging etc. [ABSTRACT FROM AUTHOR]

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Photoinduced chemical reaction between thioxanthen-9-one (TX) and diphenylamine (DPA) were investigated by the nanosecond laser flash photolysis. With photolysis at 355 nm, the triplet TX (3TX*) is produced via a Franck-Condon excitation and intersystem crossing. In the transient absorption spectra of the reduction of 3TX* by DPA in pure and aqueous CH3CN, four bands are clearly observed and assigned to absorption of 3TX*, TXH., TX.- and DPA.+, respectively. With the increase of solvent polarity, the blue-shift was observed for all absorption bands of the intermediates. With the aid of dynamic decay curves, an electron transfer followed by a protonation process is confirmed for the reduction of 3TX* by DPA. The quenching rate constants of 3TX* by DPA very slightly decrease from 9.7×109 L/(mol·s) in pure CH3CN, to 8.7×109 L/(mol·s) in CH3CN:H2O (9:1), 8.0×109 L/(mol·s) in CH3CN:H2O (4:1) and 7.5×109 L/(mol·s) in CH3CN:H2O (1:1). Therefore water plays a minor role in the title reaction, and moreover no obvious medium effect of solvent polarity is observed for the electron transfer between 3TX* and DPA, indicating that the 3nπ* and 3ππ* states of TX have the approximate ability to attract an electron from DPA. [ABSTRACT FROM AUTHOR]

Combining Raman spectroscopy with density functional theory, the populations of the trans-and gauche-ethanol conformers are investigated in carbon tetrachloride (CCl4) and carbon disulfide (CS2). The spectral contributions of two ethanol conformers are identified in OH stretching region. The energy difference between both conformers is estimated with the aid of the calculated Raman cross sections. It can be seen that the trans-ethanol is more stable in CCl4 and CS2 solutions. The spectra are also obtained at different temperatures, and it is found the van't Hoff analysis is invalid in these solutions. By taking accounts of the Boltzmann distribution and theoretical Raman cross section, the energy difference is found to be increased with temperature, which shows the weak intermolecular interactions can enhance the population of trans-ethanol. [ABSTRACT FROM AUTHOR]

The Raman depolarization ratios of gaseous CO2 in the spectral range of 1240-1430 cm-1 are determined with a sensitive photoacoustic Raman spectroscopy, and more accurate data compared to the literature results are presented. The precision of the obtained depolarization ratio is achieved by measuring and fitting the dependence of the PARS signal intensity on the cross angle between the polarizations of two incident laser beams. [ABSTRACT FROM AUTHOR]

The performance of seed laser source will have a great impact on the output pulse quality of the master oscillator power amplifier (MOPA) system. Here, we report the influence of the soliton vector features on the pulse uniformity in an all-fiber MOPA configuration. We demonstrated that, although the intensity of the dissipative soliton seed source is uniform, the intensity of the output pulse train from the MOPA will show fluctuations if the soliton polarization state is not locked, i.e., polarization-rotating vector soliton. It is found that the appearance of non-uniform pulse intensity is caused by the combination of the polarization instability and the polarization dependent gain in the polarization maintaining fiber amplifier. The obtained results indicate that the polarization evolution of seed pulsed source is critical to generation of stable pulse train from the MOPA, and also might be useful to the communities dealing with solitons and high-power pulsed fiber lasers.