The reduction behaviour of wustite-type iron oxide scale on a low-carbon, low-silicon steel by dissolved carbon in the steel at 650–900 °C under pure nitrogen was studied. It was found that dissoved carbon in the steel examined was able to react with the wustite scale on the surface, leading to reduction of this scale. It was also found that the scale reduction rate was the most rapid within 750–800 °C, followed by that at 700 °C and then at 850 °C, whereas the rates were essentially zero at 650 and 900 °C. Decarburization occurred to the steel as a result of scale reduction, and the degree of decarburization at 750–800 °C was also the most severe. The rate of scale–carbon reaction was primarily controlled by carbon diffusion through the decarburization layer as the calculated carbon permeability, defined as the product of carbon diffusivity and the carbon concentration difference across the decarburization layer, also reached its maximum within 750–800 °C. Scale reduction led to the formation of pores at the scale–steel interface as a result of volume shrinkage when wustite was reduced to iron, but the porosity volume was smaller than calculated at 800–850 °C, which could have an inhibiting effect on the scale–carbon reaction. The calculated volume of CO + CO2 gases generated as a result of scale–carbon reactions was about 100 times the calculated porosity volume. It was believed that the wustite scale was permeable to CO and/or CO2, allowing the much larger volume of CO and CO2 gases to escape through the scale layer. 相似文献
Enantiodivergent catalyst systems were developed using metals with different ionic radii and a multifunctional brucine diol (BD) ligand. The catalytic use of purported 1:1 Cu‐BD complexes in the 1,3‐dipolar cycloaddition of azomethine ylides with chalcones resulted in the selective formation of endo‐pyrrolidines in 87–96% ees with an absolute stereochemical outcome of (2R,3S,4R,5S). In contrast, an opposite absolute stereochemical outcome was observed by using the catalysts derived from Ag(I) salts and BD. The demonstration of enantiodivergent approaches to a broad class of substrates/reaction types underlines their synthetic value in asymmetric synthesis.
Copper‐catalyzed aerobic coupling of thiols and alcohols affords sulfinates and thiosulfonates. These products are assumed to form via sulfinyl radicals which are not commonly found in oxidative coupling reactions of thiols. A reaction mechanism involving sulfinyl radicals is proposed, and mass and electron paramagnetic resonance (EPR) experimental results are provided.
We have designed, fabricated and measured electrically-driven active metamaterials which operate as external modulators for TeraHertz Quantum Cascade Lasers. The modulation is achieved by applying a voltage to the metamaterial layer which actively displaces carriers from the n-doped layer causing changes in damping and frequency location of the lowest metamaterial response. We demonstrate their operation at 2.4 and 2.8 TeraHertz and obtain a maximum modulation depth of ~60% with a large degree of modulation linearity. 相似文献
In a machine translation system, word sense disambiguation has an essential role in the proper translation of words when the target word can be translated differently depending on the context. Previous research on sense identification has mostly focused on adjacent words as context information. Therefore, in the case of nominal compounds, sense tagging of unit nouns mainly depended on other nouns surrounding the target word. In this paper, we present a practical method for the sense tagging of Korean unit nouns in a nominal compound. To overcome the weakness of traditional methods regarding the data sparseness problem, the proposed method adopts complement‐predicate relation knowledge that was constructed for machine translation systems. Our method is based on a sentential form recovery technique, which recognizes grammatical relationships between unit nouns. This technique makes use of the characteristics of Korean predicative nouns. To show that our method is effective on text in general domains, the experiments were performed on a test set randomly extracted from article titles in various newspaper sections. 相似文献
The fundamental transverse mode lasing of a hybrid laser diode is a prerequisite for efficient coupling to a single‐mode silicon waveguide, which is necessary for a wavelength‐division multiplexing silicon interconnection. We investigate the lasing mode profile for a hybrid laser diode consisting of silicon slab and InP/InGaAsP deep ridge waveguides. When the thickness of the top silicon is 220 nm, the fundamental transverse mode is lasing in spite of the wide waveguide width of 3.7µm. The threshold current is 40 mA, and the maximum output power is 5 mW under CW current operation. In the case of a thick top silicon layer (1 µm), the higher modes are lasing. There is no significant difference in the thermal resistance of the two devices. 相似文献
The study investigated differences in worker satisfaction and perceived job performance regarding privacy, interaction, and acoustic quality issues in personal workspaces between five office types in LEED-certified buildings. It finds that people in high cubicles showed significantly lower satisfaction and job performance in relation to visual privacy and interaction with co-workers than both enclosed private and enclosed shared office types. They also showed significantly lower satisfaction with noise level and sound privacy and lower job performance perceived by acoustic quality than enclosed private, enclosed shared, and bullpen types. The bullpen type, open-plan office without partitions, presented significantly higher satisfaction with noise level and higher performance perceived by acoustic quality than both high and low cubicles. Considering the bullpen type also showed higher satisfaction with sound privacy than the high cubicle type, high partitions don't seem to contribute to creating workspaces where people can have a secure conversation. The bullpen type didn't show any difference from the enclosed shared type in all privacy, interaction, and acoustic quality questions, indicating it may be a good option for a small office space instead of the enclosed shared type. 相似文献
This study evaluated the charging characteristics of a carbon fiber ionizer for PM2.5 and carried out particle capture laboratory tests after an ionizer was installed upstream of the media of an electret cabin air filter. When the ion concentration per particle (Ni) of the carbon fiber charger was 106 ions/cm3, the average charge numbers for each particle were 1.54, 0.88, and 0.49 at 0.6, 1.2, and 1.8 m/s of face velocity, respectively (the particle charging times, τ, were 167, 83, and 56 ms, respectively). For these face velocities, the PM2.5 removal efficiencies of the filter media were 69.3%, 65.2% and 62.2%, respectively, but increased to 80.4%, 71.2% and 65.5%, respectively, when the ionizer was turned on. The carbon fiber ionizer was then installed in front of an electret cabin filter in the air conditioning system of an automobile, after which field tests were performed at a roadside area. For the same Niτ used in the lab-scale tests, the effects of the carbon fiber ionizer on increasing PM2.5 %Reduction were mild as 9.4%, 4.0%, and 2.8% when the flow rates were at the second, fourth, and sixth levels, respectively (the face velocities were 0.6, 1.2, and 1.8 m/s, respectively). The PM2.5 %Reduction can be substantially increased by 20–21%, for a higher value of Niτ (=1.0×108 ions s/cm3), which is realized by increasing the power consumption of the carbon fiber ionizer. 相似文献