PurposeTrade and environment are essential issues closely related to the development of the national economy and the improvement of people’s livelihood in the new era. The Report to the 19th National ...Congress of the Communist Party of China (CPC) listed the construction of a strong trading power as an important part of building a modern economic system and pollution prevention and treatment as one of the three key battles to win the decisive victory of building a moderately prosperous society in all respects. However, the relationship between trade and environmental pollution is still very controversial in the existing literature, and there is a paucity of literature on the relationship between trade and environmental pollution based on micro data.Design/methodology/approachThis paper merged China’s Firm-Level Pollution Database with China’s Industrial Enterprise Database and China’s industry tariff rates. Additionally, by virtue of the quasi-natural experiment of China’s accession to the World Trade Organization (WTO), a difference in difference (DID) model was constructed to alleviate the endogeneity issue.FindingsAccording to the results, the trade barrier decrease (trade liberalization) significantly reduces the intensity of SO2 emissions, a major pollutant of enterprises, as the intensity of SO2 emissions decreased 2.16% for each unit decrease of the trade barrier. The analysis of the mechanisms shows that the SO2 emission intensity of enterprises is mainly due to the decrease of enterprises’ pollution emission rather than the decrease of output, and the decrease of enterprises’ pollution emission is mainly caused by the enterprises’ cleaner production process rather than the end treatment of pollution emission. The decrease of coal use intensity is an important mechanism of the decrease of SO2 emission intensity caused by the decrease of trade barriers. Among the technical effects of the change of the trade barrier affecting enterprises’ pollution emission, biased technical change rather than neutral technical change dominates.Originality/valueThe findings of this paper imply that expanding openness can enhance China’s social welfare not only through the economic growth mechanisms identified in the classical literature, but also through environmental improvements. This provides useful policy insights for promoting the construction of a strong trading power and winning the battle against pollution in the new era.
High-entropy alloys are a class of materials that contain five or more elements in near-equiatomic proportions
. Their unconventional compositions and chemical structures hold promise for achieving ...unprecedented combinations of mechanical properties
. Rational design of such alloys hinges on an understanding of the composition-structure-property relationships in a near-infinite compositional space
. Here we use atomic-resolution chemical mapping to reveal the element distribution of the widely studied face-centred cubic CrMnFeCoNi Cantor alloy
and of a new face-centred cubic alloy, CrFeCoNiPd. In the Cantor alloy, the distribution of the five constituent elements is relatively random and uniform. By contrast, in the CrFeCoNiPd alloy, in which the palladium atoms have a markedly different atomic size and electronegativity from the other elements, the homogeneity decreases considerably; all five elements tend to show greater aggregation, with a wavelength of incipient concentration waves
as small as 1 to 3 nanometres. The resulting nanoscale alternating tensile and compressive strain fields lead to considerable resistance to dislocation glide. In situ transmission electron microscopy during straining experiments reveals massive dislocation cross-slip from the early stage of plastic deformation, resulting in strong dislocation interactions between multiple slip systems. These deformation mechanisms in the CrFeCoNiPd alloy, which differ markedly from those in the Cantor alloy and other face-centred cubic high-entropy alloys, are promoted by pronounced fluctuations in composition and an increase in stacking-fault energy, leading to higher yield strength without compromising strain hardening and tensile ductility. Mapping atomic-scale element distributions opens opportunities for understanding chemical structures and thus providing a basis for tuning composition and atomic configurations to obtain outstanding mechanical properties.
In this paper, we empirically investigate the impact of energy regulation on manufacturing firms' energy intensity and energy structure during 2003–2009. The identification uses the energy regulation ...of the 11th Five-Year Plan implemented in 2006. We show that tighter energy regulation leads to a significant energy intensity decrease and that firms switch their energy structure from using dirty fossil energy to a cleaner one. We also examine the mechanisms behind this phenomenon and find that the rising R&D inputs and increasing energy consumption ratio of high energy efficient firms are the mainly two reasons.
•Tighter energy regulation leads to significant energy efficiency improvement and firms switch to a cleaner energy structure.•The rising R&D inputs and increasing energy share for high energy efficient firms are the main two mechanisms behind.•We find that the decline of energy intensity is driven mainly by non-stated-owned firms and energy intensive firms.
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Technologically important mechanical properties of engineering materials often degrade at low temperatures. One class of materials that defy this trend are CrCoNi-based medium- and ...high-entropy alloys, as they display enhanced strength, ductility, and toughness with decreasing temperature. Here we show, using in situ straining in the transmission electron microscope at 93 K (−180 °C) that their exceptional damage tolerance involves a synergy of deformation mechanisms, including twinning, glide of partials and full dislocations, extensive cross-slip, and multiple slip activated by dislocation and grain-boundary interactions. In particular, massive cross-slip occurs at the early stages of plastic deformation, thereby promoting multiple slip and dislocation interactions. These results indicate that the reduced intensity of thermal activation of defects at low temperatures and the required increase of applied stress for continued plastic flow, together with high lattice resistance, play a pivotal role in promoting the concurrent operation of multiple deformation mechanisms, which collectively enable the outstanding mechanical properties of these alloys.
Twin nucleation in a face-centered cubic crystal is believed to be accomplished through the formation of twinning partial dislocations on consecutive atomic planes. Twinning should thus be highly ...unfavorable in face-centered cubic metals with high twin-fault energy barriers, such as Al, Ni, and Pt, but instead is often observed. Here, we report an in situ atomic-scale observation of twin nucleation in nanocrystalline Pt. Unlike the classical twinning route, deformation twinning initiated through the formation of two stacking faults separated by a single atomic layer, and proceeded with the emission of a partial dislocation in between these two stacking faults. Through this route, a three-layer twin was nucleated without a mandatory layer-by-layer twinning process. This route is facilitated by grain boundaries, abundant in nanocrystalline metals, that promote the nucleation of separated but closely spaced partial dislocations, thus enabling an effective bypassing of the high twin-fault energy barrier.
Cross-slip of screw dislocations plays an important role in the plastic deformation of face-centered cubic (FCC) metals and alloys. Here we use the free-end nudged elastic band (FENEB) method to ...determine the atomistic reaction pathways and energy barriers of cross-slip in an FCC single crystal of Ni. We focus on the cross-slip process mediated by an array of pinning vacancy clusters in the form of stacking fault tetrahedra. We also study a competing process of screw glide by direct cutting of those pinning obstacles on the original slip plane. The activation energies of both cross-slip and obstacle-cutting are determined for different stresses, obstacle spacings and sizes. Using FENEB-calculated energy barriers, we construct dislocation mechanism maps to reveal the effects of resolved shear stress, obstacle spacing and size on the rate-controlling dislocation process for plastic deformation. We further evaluate the activation volumes of cross-slip and obstacle-cutting. The latter result emphasizes the notion of finite strength of the atomically sized pinning obstacles to dislocation motion and also validates the Nabarro scaling law of the linear dependence of activation volume on obstacle spacing.
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•The new anti-icing/de-icing strategy combined active de-icing and passive anti-icing methods was proposed.•The multifunctional coating had both passive slippery and active ...electro-/photo-thermal properties.•This coating showed high-efficient dynamic and static anti-icing/de-icing behaviors.
Icing formation can cause tremendous economic losses and pose a severe threat to equipment safety. To mitigate icing problems, both active de-icing and passive anti-icing materials have been utilized. Traditional active electro-thermal methods suffer from energy consumption, low efficiency, while passive slippery liquid-infused porous surfaces meet the challenges of stability during icing/de-icing cycles. In this study, a bilayer anti-icing/deicing coating combined with active photo-/electro-thermal and passive slippery properties was proposed. The prepared coating exhibited ultra-slippery, reducing ice adhesion and stability properties benefit by covalently grafting polydimethylsiloxane (PDMS) brushes in a cross-linked skeleton of epoxy. Moreover, both electricity and solar energy can be adopted for heating the surface, showing high efficient electro-thermal/photo-thermal promoted anti-icing/de-icing properties. The composite coating can reduce 29% electricity consumption and 47% de-icing time by virtue of slippery and photo-thermal properties. This functional slippery electro-/photo thermal coating with high-efficient anti-icing and de-icing performances may have broad application prospects in various industry fields.
•Effects of initial void geometry on plastic deformation of metallic solids are studied.•Growth of a void with an increasing void ellipticity converges to that of a crack.•Influence of void ...ellipticity is more pronounced for a larger orientation angle.
Molecular dynamics simulations are performed to study the plastic deformation of Cu single crystals containing an elliptic cylindrical void. The effects of initial void geometry including void ellipticity and void orientation angle on plastic deformation are examined by considering the stress–strain response, dislocation nucleation from the void surface, and porosity/void cross-sectional shape evolution. It is found that (i) the initial void geometry plays an important role and (ii) the growth of voids with an increasing initial ellipticity converges to that of a crack. Our results reveal the underlying mechanisms of initial void ellipticity- and orientation angle-dependent plastic deformation of metallic solids, and provide direct evidence that there is no dividing line between a void and a crack in terms of the mechanical responses of these solids.
This paper uses numerical simulation to investigate the effects of diluents on the flame structure and NO generation of H2/CO micromixing flames. The results show that under the same thermal power ...condition, the diluents reduce the flame temperature and decrease the combustion reaction rate and flame propagation velocity. In addition, the diluents downsize the flame and force it downstream. With an increase in the diluent fraction, these trends are amplified. The NO production decreases due to the diluents, and the NO is lowest when H2O is added. When the diluents are CO2 and H2O, the NO generation is dominated by the reactants’ concentration. This results in the lowest temperature not corresponding to the lowest NO production. The diluents also reduce the sensitivity of the NO production to the temperature, and the CO2 diluent highly weakens the sensitivity.
The excellent hydrodynamic properties of fishes enable them to respond rapidly to exterior excitation in water. In this study, three types of bionic surfaces were designed and manufactured based on ...the construction and mechanical properties of the tuna skin. The surface and coating features of these bionic surfaces were analyzed, and their drag reduction performance was investigated in a circulating water tunnel. The results revealed that the drag reduction effect was proportional to the flexible coating thickness, and a maximum drag reduction of 7.22% was achieved for the dual-structure coupling surface with a flexible coating thickness of 140 µm. The simulation results indicated that the “vortex stretching” effect formed near the fish scale wall further decreased the high-velocity regions, leading to low- and high-velocity streaks inside the boundary layer close to the bionic fish scale surface along the streamwise direction. As the flexible coatings could absorb turbulent fluctuations, they formed larger low-pressure areas near the surface, enabling a better drag reduction effect. The drag reduction mechanism for the dual-structure coupling surfaces arose from the combined actions of the flexible coatings and fan-shaped imbricated fish scales. This study may provide an ideal alternative for drag reduction and antifouling properties in underwater vehicle planning.
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