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A novel optically transparent ultra-wideband (UWB) disc monopole antenna is proposed. The antenna is fed by a 50 Ω coplanar waveguide and its operational bandwidth is measured from 1 to 8.5 GHz. Gain and radiation patterns are also presented. The antenna exhibits omnidirectional and monopole-like radiation patterns at low frequencies for the H-plane and E-plane, respectively. The proposed antenna uses the highly conductive AgHT-4 transparent film, which makes the antenna suitable for inter-vehicle communication. 相似文献
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Terahertz time-domain spectroscopy measurements were made for vertically aligned multi-walled carbon nanotube (VACNT) films. We obtained the frequency dependent complex permittivity and conductivity (on the assumption that permeability μ = 1) of several samples exhibiting Drude behaviour for lossy metals. The obtained material properties of VACNT films provide information for potential microwave and terahertz applications. 相似文献
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Topalov AA Katsounaros I Meier JC Klemm SO Mayrhofer KJ 《The Review of scientific instruments》2011,82(11):114103
This paper describes a system for performing electrochemical catalyst testing where all hardware components are controlled simultaneously using a single LabVIEW-based software application. The software that we developed can be operated in both manual mode for exploratory investigations and automatic mode for routine measurements, by using predefined execution procedures. The latter enables the execution of high-throughput or combinatorial investigations, which decrease substantially the time and cost for catalyst testing. The software was constructed using a modular architecture which simplifies the modification or extension of the system, depending on future needs. The system was tested by performing stability tests of commercial fuel cell electrocatalysts, and the advantages of the developed system are discussed. 相似文献
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I. Katsounaros 《Electrochimica acta》2006,52(3):1329-1338
The electrochemical reduction of nitrate on tin cathode at very high cathodic potentials was studied in 0.1 M K2SO4, 0.05 M KNO3 electrolyte. A high rate of nitrate reduction (0.206 mmol min−1 cm−2) and a high selectivity (%S) of nitrogen (92%) was obtained at −2.9 V versus Ag/AgCl. The main by-products were ammonia (8%) and nitrite (<0.02%). Small amounts of N2O and traces of NO were also detected.As the cathodic potential increases, the %S of nitrogen increases, while that of ammonia displays a maximum at −2.2 V. The %S of nitrite decreases from 65% at −1.8 V to <0.02% at −2.4 V. The kinetic analysis indicated that the formation of nitrogen and ammonia proceeds through the intermediate nitrite.The reduction follows first order kinetics for both nitrate and nitrite at more cathodic potentials than −2.4 V, while at less negative potentials the kinetics is more complicated.The %Faradaic efficiency (%FE) of the reduction at −2.9 V was about 60% initially and decreased to 22% at 40 min.A cathodic corrosion of tin was observed, which was more intensive in the absence of nitrate. At potentials more negative than −2.4 V, small amounts of tin hydride were detected. 相似文献
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I. Katsounaros 《Electrochimica acta》2007,52(23):6412-6420
The influences of the potential, the concentration and the nature of the supporting electrolyte on the rate of the reduction of nitrate on tin were studied by both voltammetry and constant potential electrolytic experiments.Both the rate of the reduction of nitrate and the yield of nitrogen increase as the negative potential increases from −1.8 to −2.8 V versus Ag/AgCl, while the yield of nitrite decreases. The yield of ammonia displays a maximum at −2.4 V and consequently decreases.The rate of the reduction at −1.8 V versus Ag/AgCl increases significantly as the concentration of NaCl increases. The cation of the supporting electrolyte increases the rate of the reduction along the series Li+ < Na+ < K+ < Cs+. Higher rates than that of the alkalimetals have been obtained in the presence of ammonium as well as of multivalent cations such as Ca2+ and La3+. The anion of the supporting electrolyte decreases the rate of the reduction in the order I− > Br− > Cl− > F− at −1.8 V.The experimental results were qualitatively explained by the Frumkin theory and additionally by the theory of the formation of ion pairs between the cation of the supporting electrolyte and the reacting nitrate. 相似文献
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I. Katsounaros 《Electrochimica acta》2008,53(17):5477-5484
The influence of the concentration of nitrate in the range between 100 and 62,000 mg L−1 NaNO3 in NaCl solutions was studied under constant potential electrolysis at −2.8 V vs. Ag/AgCl. The rate of the reduction follows Langmuir-Hinshelwood kinetics, according to which zero order kinetics is followed at concentrations higher than 0.3 M whereas first order at lower concentrations.The selectivity to nitrogen increases from 70 to 83% as the concentration of nitrate increases from 100 to 1500 mg L−1 and it remains almost constant for higher nitrate concentrations, whereas that of ammonia exhibits the opposite trend decreasing from 25 to 11%. The % Faradaic Efficiency (%FE) increased with the increase of the concentration of nitrate from 25% at 0.1 M to 78% at 1 M when 95% of nitrate was reduced in both cases. At high concentrations of nitrate, hyponitrite and hydroxylamine were detected as intermediates of the reduction and a reaction scheme which is in agreement with the experimental results has been proposed.The hydrogen evolution in our conditions probably takes place through the discharge of the cation of the supporting electrolyte instead of the Volmer-Tafel mechanism and the reduction of nitrate proceeds through electrochemical hydrogenation. 相似文献
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