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- Jiang, Bin, et al.
(författare)
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Topological structure of urban street networks from the perspective of degree correlations
- 2014
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Ingår i: Environment and Planning, B. - : SAGE Publications. - 0265-8135 .- 1472-3417. ; 41:5, s. 813-828
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Tidskriftsartikel (refereegranskat)abstract
- Many complex networks demonstrate a phenomenon of striking degree correlations: that is, a node tends to link to other nodes with similar (or dissimilar) degrees. From the perspective of degree correlations, in this paper we attempt to characterize topological structures of urban street networks. We adopted six urban street networks (three European and three North American), and converted them into network topologies in which nodes and edges represent individual streets and street intersections, respectively, and compared the network topologies with three reference network topologies (biological, technological, and social). The urban street network topologies (with the exception of Manhattan) showed a consistent pattern that distinctly differs from the three reference networks. The topologies of urban street networks lack striking degree correlations in general. Through reshuffling the network topologies towards, for example, maximum or minimum degree correlations while retaining the initial degree distributions, we found that all the surrogate topologies of the urban street networks, as well as the reference ones, tended to deviate from small-world properties. This implies that the initial degree correlations do not have any positive or negative effect on the networks’ performance or functions.
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| 2. |
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| 3. |
- Liu, Shaohua, et al.
(författare)
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Synthesis of chiral TiO2 nanofibre with electron transition-based optical activity
- 2012
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Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 3, s. 1215-
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Tidskriftsartikel (refereegranskat)abstract
- The optical chirality induced at the absorption bands due to electronic exciton coupling of the transition dipole moments between chromophores in close proximity is ubiquitous in helical organic materials. However, inorganic materials with optical activity resulting from electronic transitions have not been explored. Here we report the synthesis of chiral TiO2 fibres via transcription of the helical structure of amino acid-derived amphiphile fibres through coordination bonding interactions between the organics and the TiO2 source. Upon calcination, the as-prepared amorphous TiO2 double-helical fibres with a pitch length of ~100 nm were converted to double-helical crystalline fibres with stacks of anatase nanocrystals in an epitaxial helical relationship. Both the amorphous and anatase crystalline helical TiO2 fibres exhibited optical response to circularly polarized light at the absorption edge around ~350 nm. This was attributed to the semiconductor TiO2-based electronic transitions from the valence band to the conduction band under an asymmetric electric field.
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| 4. |
- Yin, Xiaojun, et al.
(författare)
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In-depth comparison of methanol port and direct injection strategies in a methanol/diesel dual fuel engine
- 2023
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Ingår i: Fuel Processing Technology. - : Elsevier BV. - 0378-3820. ; 241
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Tidskriftsartikel (refereegranskat)abstract
- For methanol/diesel dual-fuel combustion, there are two different methanol injection implementations: port injection into the intake manifold and direct injection into cylinder. In this work, an experimental comparison was conducted for the two methanol injection strategies to study the effects of the methanol-energy-substation ratio (ESR) and diesel injection timing on the fuel-air mixing and combustion characteristics. The results showed that the ignition delay was increased with ESR due to the cooling effect of methanol evaporation in the cylinder. The combustion duration under methanol direct injection condition was much shorter than that of the methanol port injection strategy. The methanol direct injection strategy had a more controllable and stable heat release than that of methanol port injection strategy. The maximum ESR could reach up to 96.0% in the methanol direct injection strategy. The methanol direct injection strategy had a better fuel economy, and its maximum indicated thermal efficiency could reach up to 41.55% at 50% ESR. The methanol direct injection strategy yielded higher NOx emissions than that with the port injection strategy, accompanied by a mild increase of soot emissions. Compared with methanol port injection, the methanol direct injection strategy exhibits lower CO emissions, however, it suffers from higher HC emissions.
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