Key Engineering Materials Vols. 428-429

Abstract: In this paper, some virtuallab experiments have been done, in which the we get extraordinary transmission phenomenon by adding dielectric coating in the subwavelength periodic metallic slits. It is proved that dielectric coatings on the metal films can excite a surface wave which is transmitted in the metal slits by dielectric waveguides, and the symmetric wrapped dielectric cladding around the metal gains almost 10 times as great transmission as two surfaces cladding does. The paper explores a preliminary physics mechanism of this extraordinary transmission, which gets some valuable results in the application fields.

Abstract: By controlling the temperature of chemical reaction, we synthesized four polyphenylacetylene samples, in which the percentages of cis configurations were determined to be 65, 75, 85 and 100%, respectively. Ultraviolet-visible and fluorescence studies show that the cis-configured backbones have posed significant effects on the optical absorption and fluorescence of the polyphenylacetylenes. Upon the 325-nm excitation, the dilute solutions of these cis-polyphenylacetylenes give off weak fluorescence with their peak located at about 390 nm, but the concentrated solutions of the polymer can give off strong orange-red fluorescence with their peak located at about 600 nm. With Hückel tight binding theory, both the E-k dispersion relations and the density of states were calculated for cis-polyphenylacetylene. Our results suggest that the blue photoluminescence of polyacetylenes origins from the backbone enhanced -conjugation of the phenyl chromophors in the polymer, and that intermolecular interactions can occur in the excited complex of the polymer.

Abstract: This thesis introduces a low cost and high precision temperature cycle measurement system with adoption of PT100 as temperature sensor, with single chip computer as the core. The method of sub-three-wire connection is proposed for engineering practice, then, can eliminate the effects of lead wire resistance and simplify the external cable connection. We discuss and research circuit component selection, circuit design, improving system reliability, and a software method of piecewise linearization process is adopted, thus we ensure exact and reliable measure and the system characteristic of low cost and high precision.

Abstract: Parametric six-wave mixing processes have been achieved in Rb and two parametric six-wave mixing channels, 5S→→5D→→6P→→S1/2→→P1/2→→5S and 5S→→5D →→P→→S1/2→→52P3/2→→5S, have been identified. Competition between the two channels is observed and, furthermore, phase matching conditions in the two channels are analyzed and calculated. The calculation results agree well with the experimental observations, indicating that the phase matching is the main factor governing the competition between the two parametric six-wave mixing channels.

Abstract: With four-probe technique, we investigated the effects of the mortar-pestle grinding on the conductivity of ferric chloride doped conducting polymer polypyrrole, which had been synthesized by in situ polymerizing the monomer pyrrole in aqueous solutions in the presence of the oxidant iron (III) chloride. As the mortar-pestle grinding duration increased from 0 to 4 hours, the conductivity of the synthesized polypyrrole was found to decrease from about 100 to 10 S/m. In the meantime, the sizes of the grinded polymeric particles were found to decrease from 40.6 to 3.36 m as the grinding duration increased from 0 to 4 hours. Our results demonstrated that the grinding shortened conjugation lengths of the polymeric chains should be responsible for the decrease in the conductivity of the polymer.

Abstract: In our paper, we induced the process of ZnO based thin film transistors (ZnO-TFTs) fabricated on the substrate of glass. The photolithographic plate designed for using in the ZnO-TFT devices fabrication process was shown in our paper. The ZnO-TFT devices were fabricated successfully, the Ion/off ratio is ~104.

Abstract: Analysing the characteristics of a television transmitter carefully, the paper compares the television-based bistatic radar with the conventional monostatic and bistatic radar on targets detecting beyond the horizon in some given direction. In the light of the effect of ground diffraction produced by electromagnetic wave propagation on different radar ranges, it is shown that television-based bistatic radar has a potential advantage over conventional radar in targets detecting beyond the horizon because of its particular advantages in height gain and diffracting efficiency. At the same time, we have an in-depth study which is the decisive factor on radar ranging, height gain or diffraction effect, conduct an effective method of how determine the optimal wavelength so as to get the maximum radar detecting range.

Abstract: Ultrafine NiFe2O4 particles with spinel structure were prepared in the system of water-in-oil microemulsion of water/Triton X–100/n-hexanol/cyclohexane. The effects of calcining temperature and the other operation conditions were systematically discussed based on the techniques of SEM, XRD, VSM and so on. The result showed that NiFe2O4 nanoparticles, with a narrow size distribution(30-70nm), could be obtained by microemulsion method. The crystal grain diameter of the ultrafine NiFe2O4 particles could be enhanced with the improvement of the calcining temperature, the molar ratio of water to surfactant (w=[H2O]/ [surfactant]) and the concentration of Fe3+(or Ni2+), respectively. The VSM plots showed that the ferrimagnetic behavior was expected for this type of magnetic material. The XRD patterns and DTA-TG curves revealed that the optimal calcining temperature of NiFe2O4 sample was at around 500°C. The relation between the average particle size (D) and the value of w could be expressed as D=13.911+0.2628w. Moreover, it was indicated that low concentration of Fe3+(or Ni2+) was beneficial to the formation of small and regular NiFe2O4 particles.

Abstract: The microstructures of electrochemically-deposited copper control electrode on semiconducting porous silicon films were investigated with scanning electron microscopy. Our results showed that smooth control electrode could be grown in areas far from the edge of porous silicon film while irregular electrode was formed on the circular edge of porous silicon films. The self-similarity of the electrochemically-deposited copper control electrode was analyzed in details.

Abstract: We present a multi-channel PCs polarization filter, which overcomes the disadvantage of the low channel numbers in the existing filters. The multi-channel PCs polarization filter is based on one dimensional photonic crystal with a defect layer. The simulation results by transfer matrix method show that the filter can realize more than four filtering channels with the separation degree better than 0.95 and the transmission rate more than 50%, and the channels are almost distributed evenly. We also analyze the influence factors of filter performance. The results show that defect layer thickness of photonic crystal determines the number of filter channels. The thickness and number of unit layers of photonic crystals does not affect the number of filter channels, however it can adjust the location of central wavelength for each filter channel.