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Data-mining based machine learning (ML) method is emerging as a strategy to predict aluminium (Al) alloy properties with the promise of less intensive experimental work. However, ML models for wrought Al alloys are limited due to the difficulty in feature digitalization of the variety of manufacturing processes. Hence, most previous studies were constrained to specific alloy designations, which impeded the applicability of those ML models to broader wrought Al alloys. In the present work, we propose a novel feature engineering, called procedure-oriented decomposition (POD), assisting prediction framework to address the complexity introduced by manufacturing processes for wrought Al alloys. In this model, both chemical compositions and manufacturing processes are integrated as features. Correlation mapping of these features to the wrought Al alloys mechanical properties is established using the support vector regressor (SVR) model. The prediction framework demonstrates a high prediction accuracy and potential to design new alloys.

The exploration of cheap and efficient electrodes for hydrogen evolution reactions (HER) is extremely challenging. Herein, we report a newly-designed V2O3@Ni hybrid grown in situ on nickel foam as an efficient HER catalyst. The nickel foam not only promoted the electron transfer rate as a supporting substrate, but also worked as the source of Ni to enhance the integration of catalyst components with abundant active sites. Moreover, benefitting from the synergistic effect of the interface between V2O3 and Ni, which accelerated the entire electrochemical kinetics and facilitated the electron transfer, the in situ V2O3@Ni hybrid catalysts afforded a small overpotential of 47 mV and 100 mV at a current density of 10 mA cm−2 in 1.0 M KOH and 1.0 M PBS, respectively, and with excellent long-term stability. In addition, this research provides a new route for the fabrication of noble-metal-free electrocatalysts with excellent HER performance over a broad range of pH values.

A new tetragonal carbon allotrope (named T-C64) is predicted by swarm structural searches combined with first principles calculation. It contains 64 carbon atoms in a Tetragonal unit cell with I41/amd symmetry and exhibits distinct topologies including C28 cages. This new carbon phase has an sp2-sp3 network with calculated hardness of 68.2 GPa. In order to examine the stability of T-C64 under ambient pressure, we calculated the properties of elastic constant and phonon spectrum. In addition, by calculating the electronic properties of the crystal, it is concluded that T-C64 is an indirect band gap semiconductor with a band gap of 2.23 eV.

High-throughput first principles calculations for 109 carbon allotropes were performed. The elastic constants and phonon calculations suggest that these new structures are mechanically and dynamically stable at ambient pressure. Seven direct band gap semiconductor carbon allotropes were uncovered. The Vickers hardness of all seven structures exceeds 40 GPa, indicating that these allotropes are potential superhard materials.

In this paper, we report an impregnated type of tungstate dispenser cathode prepared by Ba5Sr(WO6)2. The direct-current (dc) and pulsed-current (pc) emission properties and their evaporation rates have been investigated compared with the traditional Ba-W dispenser cathodes. Experimental results show that the current densities of the impregnated tungstate cathodes are twice larger than that of a typical 6-1-2 aluminate cathode, e.g., the dc and pc emission densities of the tungstate cathode can reach up to 10.6 and 56.6 A/cm2 at $1050~^{\circ }\text{C}_{{\text {br}}}$ , respectively. The evaporation rate of the impregnated tungstate cathode is $2.02\times 10^{-{9}}\text{g}\cdot $ cm $^{-2}\cdot \text{s}^{-1}$ at $1050~^{\circ }\text{C}_{{\text {br}}}$ , which is only 54% as much as that of the aluminate cathode, as measured by a quartz crystal oscillating method. The work function model of the tungstate cathode was studied by ab initio density functional theory (DFT) calculation. It is found that free Ba is preferentially adsorbed on the hollow site of ZrO2-W (001), and on BaZrO3 (001) in a more stable way during operation, resulting from its fine emitting and evaporation characteristics.

Silicon is a preferred material in solar cells, and most of silicon allotropes have an indirect band gap. Therefore, it is important to find new direct band gap silicon. In the present work, a new direct band gap silicon allotrope of o-Si32 is discovered. The elastic constants, elastic anisotropy, phonon spectra, and electronic structure of o-Si32 are obtained using first-principles calculations. The results show that o-Si32 is mechanically and dynamically stable and is a direct semiconductor material with a band gap of 1.261 eV.

A new all-sp3 hybridized orthorhombic superhard carbon phase Fmmm-C80 (space group: Fmmm) with direct band gap and low density is uncovered by using CALYPSO code and first-principles calculations. The unit cell of Fmmm-C80 phase contains 80 carbon atoms, and its thermodynamic stability is confirmed by the phonon and molecular dynamics simulations. The semiconducting nature of the Fmmm-C80 was revealed by the calculated direct band gap of 4.11 eV. Also, Fmmm-C80 is found to be a potential superhard carbon phase for its large Vickers hardness of 51 GPa.

As one of the largest energy consumers, the transport sector generated direct and indirect emissions which significantly affect the environment, accounting for approximately one-third of the total carbon emissions. While the major impacts are from transport energy use and emissions, very few studies attempted to examine the impacts from transport infrastructure, especially at a city or country level. This paper, taking Shenzhen in China (a fast developing megacity) as the case study, is specially designed to quantify the carbon footprint of the urban roads by using streamlined life cycle assessment method. For given years (ranged from 2004 to 2013), various activities of urban roads (e.g. newly planned road construction, maintenance of road in use, and road renovation and demolition) have been examined in this study. The results show that the total carbon footprint from urban roads in Shenzhen was 260 (±20) thousand tons CO2e in 2013. The major contributor was the materials use (embodied impact) from newly constructed roads, which accounts for 52.3% of the total carbon footprint, followed by the maintenance stage (24.3%). The eco-design process of road construction plays a vital role in achieving the effective carbon footprint reduction. These findings help to better understand the carbon footprint from urban roads in megacities, and provide useful inputs for policy making process in terms of identifying carbon reduction opportunities for the transport sector. In addition, the methodologies are useful for the quantification of carbon footprint in other cities of China and beyond.

In order to enhance the emission current, reduce the operating temperature and prolong the lifetime of the pure W filament cathode for application in high-power (i.e., more than 10KW) continuous wave magnetron tube, a novel Y2O 3 -Gd2O 3 -HfO 2 impregnated W base direct-heated cathode (Y-Gd-Hf-O impregnated cathode) has been developed. In this abstract, the thermionic emission mechanism of the Y-Gd-Hf-O impregnated cathode has been researched by SEM, EDS and AES.

A new superhard carbon allotrope oC48 is uncovered. The mechanical and electronic properties of oC48 were studied by using first principles calculations. The calculated results of elastic constants and phonon dispersion show that oC48 is mechanically and dynamically stable. The hardness of oC48 is predicted to be 73.3 GPa, which indicates the superhardness of oC48. The elastic anisotropy of oC48 were also analyzed in detail. The band structure of oC48 shows that it is an indirect band gap semiconductor with a band gap of 1.464 eV.

A new carbon allotrope orthorhombic oC240, is proposed by first principles calculation. The unit cell of oC240 is composed of 240 carbon atoms. The calculated elastic constants and phonon spectra c...

The urgent need to develop low carbon urban transport systems particularly in Asian megacities is facing the significant challenge of growing motorization following population increase and economic development. Sustainable urban public transport (UPT) plays a crucial role to fulfil the ambitious targets on carbon emission reduction. In this study, life cycle assessment was employed to quantify the environmental impacts (measured by carbon emissions) of UPT systems (including bus and subway) in Shenzhen, a leading megacity in South China, and then to examine corresponding carbon intensity reduction potentials. Results showed that the total carbon emissions from UPT in Shenzhen have increased rapidly from 0.70 Mt in 2005 to 1.74 Mt in 2015 due to the fast growth of the volume of transport turnover. However, current low-carbon UPT mode has only reduced 0.21 Mt CO2 e (cumulative value, from 2005 to 2015), and thus could not contribute proportionally to the city's overall emission reduction target. Three advanced scenarios (from conservative to optimistic) were further simulated to estimate carbon emissions and their intensity reduction potentials over the next 15 years (2016–2030). Compared to the business-as-usual scenario, all these three low-carbon transition scenarios could significantly mitigate the rapid growth of carbon emissions and consequently help achieve Shenzhen's carbon intensity reduction goal by 2030 (60%, compared to 2005 level). These findings could not only inform evidence-based policy making to facilitate the low-carbon transition of the urban transport sector in Shenzhen, but also shed light on sustainable urban transition in other megacities.

In order to enhance the emission current, reduce the operating temperature and prolong the lifetime of the pure W filament cathode for application in high-power (i.e., more than 10KW) continuous wave magnetron tube, a novel Y 2 O 3 -Gd 2 O 3 -HfO 2 impregnated W base direct-heated cathode (Y-Gd-Hf-O impregnated cathode) has been developed. At 1700°br, the dc emission density of the Y-Gd-Hf-O impregnated cathode can reach to 10.5A/cm2. After 3600 h operation of the cathode under 1600°br, the dc emission current density of it is still stable at the initial value of 1.5A/cm2.

In this paper we mainly describes the research progress in a kind of ammonium perrhenate impregnated W matrix Ba-W cathode, which includes the evaporation rate measuring and the lifetime testing of the cathode. The evaporation rate measuring results shows that the evaporation rate of the cathode is 8.66×10-10g.cm−2s−1 at 1000 °Cbr measured by a quartz crystal oscillating method. The lifetime testing results show that the emission current, after 22392h lifetime at a temperature of 1000 °Cbr, has still increased more than 6% of the initial 3.0 A/cm2 DC current density.

Tungstate cathodes have been prepared by impregnating a mixture of the barium-strontium tungstate and zirconium hydride at 1840 °C b . Emission characteristics and evaporation properties were tested. The result shows that the dc emission current density reaches 4.30A/cm2 at 1000 °C b , 7.54A/cm2 at 1050 °C b , 9.43A/cm2 at 1100 °C b . The evaporation rate of the cathode is lower than an uncoated aluminate cathode.

In this paper we mainly describes the research progress in a kind of ammonium perrhenate impregnated W matrix Ba-W cathode, which includes the preparation of W-Re matrix by impregnated ammonium perrhenate solution and the cathode properties testing. The lifetime testing results show that the emission current, after 16056h lifetime at a temperature of 1000 °Cbr, has still increased more than 8% with 3.0 A/cm2 DC current.