Marked particle size and support effect of Pd catalysts upon the direct decomposition of nitric oxide

The catalytic behavior of beryllia-supported Pd catalyst for the direct decomposition of NO was compared with that of silica supported one. The TOF of NO decomposition was one order of magnitude larger in the case of Pd/BeO. Over Pd/SiO₂, the TOF was increased with the increase of the Pd particle size. On the contrary, over Pd/BeO smaller Pd particles exhibited higher TOF for NO decomposition suggesting some strong electronic or structural interaction between Pd and beryllia. TPD spectra of NO(a) over reduced catalysts indicated that NO was adsorbed on Pd/SiO₂ more strongly than on Pd/BeO, and dissociation of NO(a) was easier on the former catalyst. FT-IR spectra of adsorbed NO at room temperature followed by the evacuation at elevated temperatures confirmed this. TPD spectra of O₂ desorbed from oxidized surface indicated that adsorption strength of O(a) is one of the most important factors to determine the catalytic activity of NO decomposition over supported Pd catalysts.     

Optical-transmission experiment at 400 mb/s using a graded-index fibre

An optical-transmission error-rate experiment is described in which a graded-index fibre up to 5 km long is used as a transmission medium. It is shown that impairments in the transmission are mainly determined by the total frequency response of the transmission medium, including the fibre and its connection.     

Mechanism of formation of C2-oxygenated compounds from CO + H2 reaction over SiO2-supported Rh catalysts

The mechanism of acetaldehyde and ethanol formation from the CO + H₂ reaction below atmospheric pressure has been investigated by combining infrared spectroscopic measurement and ¹³CO and C¹⁸O isotopic tracer studies with reaction kinetics. The rates of acetaldehyde and ethanol formation are markedly dependent on the nature of metal precursors employed. The addition of sodium cations depresses the total catalytic activity, while the selectivity for ethanol is increased by the addition of manganese cations. From the behavior of surface species under reaction conditions, it is concluded that acetaldehyde is formed through the following two steps: (i) CO insertion into C₁ species which are reaction intermediates for not only hydrocarbons but also for the methyl group in acetaldehyde, and (ii) subsequent formation of acetate ions whose one oxygen atom is supplied from the support, finally producing acetaldehyde. Differences in ¹⁸O distribution in acetaldehyde and ethanol during the C¹⁸O + H₂ reaction indicate that ethanol is not produced via direct hydrogenation of acetaldehyde.     

Development of a 275-kV liquid cooling-type gas-insulated transformer

Construction of 275-kV and 500-kV substations in densely populated areas is thought to be necessary in the future to maintain a stable supply of electricity. The use of gas-insulated transformers is now considered for substations because such transformers are non-flammable and nonexplosive. Since the completion of the 77-kV gas-insulated transformer in 1979, we have continued research to develop gas-insulated transformers applicable to a higher voltage level up to 500 kV. As the results of the research, 275-kV, 300-MVA a liquid cooling-type gas-insulated transformer has been developed.     

Modulation characteristics of 1.3 ?m buried-stripe InGaAsP laser up to 2 Gbit/s data rates

Modulation experimenting on a buried-stripe (b.s.) InGaAsP laser emitting at 1.3 ?m was carried out up to 2 Gbit/s. The b.s. laser is free from relaxation oscillation, which degrades modulated optical pube waveforms, especially at high data rates. The repeater gain of 1.6 Gbit/s transmission systems is improved by 9 dB compared with previously reported experiments. Modulation characteristics up to 2 Gbit/s are reported.     

Dispersion-free single-mode fibre transmission experiments up to 1.6 Gbit/s

Long-span single-mode fibre transmission experiments at 1.3 ?m have been refined toward higher digit rate and longer fibre span. Error-rate against receiving optical level characteristics showed that optical power penalties at 100 Mbit/s, 1.2 Gbit/s and 1.6 Gbit/s are negligible, even after 30 km, 23 km and 13 km fibre transmission, respectively.     

On the expected behaviors of the Dijkstra's shortest path algorithm for complete graphs

Shortest path, shortest spanning tree, complete graph, number of comparisons, expected complexity     

An 800 Mbit/s optical transmission experiment using a single-mode fiber

It has been confirmed by a preliminary transmission experiment that a repeater spacing at 800 Mbits/s can be lengthened up to 7.3 km, by using a combination of a low-loss single-mode fiber and a well designed AlGaAs laser. The laser is modulated by a signal current superimposed on a dc bias current above the threshold. This modulation scheme avoids the spectrum broadening of the laser at the cost of extinction ratio degradation. A discrepancy of about 13 dB exists between the measured and the calculated error-rate performance curves. The major part of the discrepancy, 10 dB, is due to the extinction ratio degradation.     

Synthesis and characterization of europium(II)-holoborates,Eu2B5O9Cl and Eu2B5O9Br

Europium(II)-haloborates, Eu₂B₅O₉Cl and Eu₂B₅O₉Br, were synthesized and characterized by X-ray analysis, magnetic susceptibility and luminescent spectral measurements. The chloroborate Eu₂B₅O₉Cl crystallizes in the tetragonal system, D⁶₄-P4₂2₁2, with cell dimensions: a=11.349(4), $\text{c}\text{=6.500(4)}\text{A}\text{?}$ and Z=4, and Eu₂B₅O₉Br in the orthorhombic system, C¹⁰_2v-Pnn2 or D¹²_2h-Pnnm, with cell dimensions: a=11.503(3), b=11.382(3), $\text{c}\text{=6.484(2)}\text{A}\text{?}$ and Z=4. Both of them were paramagnets with paramagnetic Curie temperature at about ?1 K, and band emissions peaking at about 430 and 435 nm which were based on a 4f⁷-4f⁶5d transition of Eu²⁺ ion were observed on Eu₂B₅O₉Cl and Eu₂B₅O₉Br, respectively.