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Electron beam–directed energy deposition (EB–DED) has emerged as a promising wire-based metal additive manufacturing technique. However, the effects of EBs on pendant droplets at wire tips have not yet been determined. The aim of this study is to enhance the understanding of this action by analyzing the mechanism of droplet oscillation. The pendant droplet oscillation phenomenon hinders the stable transfer of droplets to the molten pool and limits the feasibility of manufacturing complex lattice structures by EB–DED. Hence, another aim of this study is to create an oscillation suppression method. An escalating asymmetric amplitude is the main characteristic of droplet oscillation. The primary oscillation-inducing force is the recoil force generated from the EB-acted local surface of the droplet. The physical mechanism of this force is the rapid increase and uneven distribution of the local surface temperature caused by the partial action of the EB. The prerequisites for droplet oscillation include vacuum conditions, high power densities, and bypass wire feeding processes. The proposed EB–dynamic surrounding melting (DSM) method can be applied to conveniently and effectively suppress oscillations, enable the accurate transfer of droplets to the molten pool, and achieve stable processes for preparing the strut elements of lattice structures. Lowering the temperature and improving the uniformity of its distribution are the mechanisms of oscillation suppression in EB–DSM. In this study, the physical basis for interpreting the mechanism by which EBs act on droplets and the technical basis for using EB–DED to prepare complex lattice structure parts are provided.

China’s oases are the center of human life and economic development for tens of millions of inhabitants in drylands. However, oases have experienced a significant expansion of cropland during the past three decades, which has resulted in rapidly increasing agricultural water demand and increasing water shortages in the region. Although crop switching is recognized as a promising strategy for improving the sustainability of agricultural production, little is known about how much it can improve the sustainability of oasis cropping systems and whether there are trade-offs among multiple sustainability goals. Here, we used a crop-water-use model, data on crop production and nutrient content, observational data on streamflow, and oasis land-use data to assess the impacts of different crop switching scenarios on water demand, nutrient supply, and income. The results showed that oasis agricultural water demand increased from 28.5 km3 to 41.1 km3 between 1987 and 2017, with 74.6 % of the oasis counties experiencing increasing agricultural water stress. By replacing all crops with those having the lowest water demand in each respective county, the demand for irrigation can be reduced by 23.1 %, and the demand for groundwater reduced by as much as 72.8 %. Crop switching scenarios that also consider crop species diversity, in which replacing the highest water demand crops with alternative crops (those with the lowest water demands, highest protein production, or highest calorie production) in each county can effectively reduce irrigation water demand (8.5–12.9 % for streamflow and 32.7–43.3 % for groundwater), while increasing protein (21.3–35.8 %) and calorie (27.5–42.7 %) production as well as income (1.4–2.4 %). Our research provides potential solutions to effectively alleviate the conflict between agricultural development and the environment in oasis regions.

In this study, four high-chromium wear-resistant steels with varying vanadium contents were prepared. Their mechanical properties, corrosion behaviour and impact–abrasion–corrosion behaviour were comprehensively investigated in a simulated corrosive slurry environment. The result indicated the effectiveness of vanadium in enhancing the impact toughness of the steel. Notably, high-chromium steel with 0.2% vanadium exhibited notable characteristics, including a Rockwell hardness of 56.2 HRC and an impact toughness of 113.5 J. Introducing vanadium enhanced the corrosion resistance of high-chromium steels in electrochemical experiments. In terms of impact–abrasion–corrosion performance, the high-chromium steel containing 0.2% vanadium exhibited the highest resistance to impact–abrasion–corrosion when subjected to both the impact energies of 3 J and 6 J. Comprehensive examinations of surface and cross-sectional damage, coupled with detailed microstructure and microhardness analyses, revealed that the development of a white etching layer on the material's surface is crucial to enhancing its resistance to impact–abrasion–corrosion.

The two-phase titanium alloy Ti–10 V–5Al-2.5Fe-0.1 B was taken as the experimental material, and thermal compression experiments were carried out at a deformation temperature of 770–920 °C and a strain rate of 0.0005–0.5 s−1. An Arrhenius model, a modified Johnson-Cook model, and an improved BP neural network model based on the sparrow search algorithm (SSA-BP) model were established to predict the high temperature rheological stress of the alloy. A comparison of the prediction accuracy of the three models was made. When the partial random data in the rheological curves was used for model building and relatively independent data were used for predicting the rheological stress, the SSA-BP model had higher prediction accuracy, which exhibits the highest mean square correlation coefficient (R2) value of 0.9992 and the lowest root mean square error (RMSE) and average absolute relative error (AARE) values of 1.3031, and 2.0947 %, respectively. The ability of three models to predict the rheological stress for the new process parameters was verified. Results show that the SSA-BP model still has better prediction ability, which exhibits the highest mean square correlation coefficient (R2) value of 0.9720 and the lowest root mean square error (RMSE) and average absolute relative error (AARE) values of 5.0099, and 6.0382 %, respectively. The predicted values of SSA-BP for the rheological stress were used to construct the hot processing map. Results show that the trend of the power dissipation factor (η) value from the hot processing map predicted by SSA-BP can well agree with the microstructure evolution of the alloy.

The residual bearing capacity after fire is of great significance for safety assessment and repair of building structures. To accurately evaluate the residual strength of corroded beam after natural cooling, this study investigated the residual bearing capacity of corroded beam considering the bond deterioration after fire exposure. First, the bond behavior and flexural-deformation capacity was conducted by pullout test and bending test after corrosion erosion and fire temperatures damage. The bond deterioration test shows that when the temperature rises above 200℃ and the corrosion level exceeds 4.3 %, the bond strength decreases by 16.5 %. At the temperature reaches 600℃ or the corrosion degree reaches 13.8 %, the bond behavior damage exceeds 50 %. The bending test indicates that corrosion and high temperature damage both decrease the bending bearing capacity of the beam, but the influence of high temperature damage on the residual bearing capacity is greater than that of corrosion. The bond property deterioration decreases the strain value of the tensile rebar during the bending process, and decreases the bending capacity of the beam. Finally, a bond-slip constitutive model suitable for corroded beams after fire is proposed, which is applied to the calculation of the ultimate moment of the beam. The modified value of beam bearing capacity considering bond deterioration has better collimation and higher safety margin. The bond-slip constitutive model and the modified calculation method of bending moment of beam are helpful to provide more accurate performance assessment of beam after the coupling effect of corrosion and fire damage.

Sodium carbonate solvent absorbent has been widely studied for CO2 reduction to deal with global warming because of its green, low cost, and non-corrosive advantages. However, in the application of sodium carbonate as an absorbent for CO2 capture, there is no unified cognition of the mass transfer process, which leads to the lack of guidance for the industrial large-scale process. Moreover, the mechanism of mass transfer enhancement of surfactants, which can effectively improve the mass transfer performance, has not been effectively explored in the literature. Based on this, this paper firstly adopts the molecular dynamics method to analyze the solution characteristics after surfactant addition and optimize the surfactant. Subsequently, a classical dissolved oxygen test method was used to measure the gas-liquid mass transfer coefficient for CO2 absorption into sodium carbonate solution. And based on this mass transfer coefficient measurement method, the mass transfer process of sodium carbonate solution with surfactant was analyzed. The results showed that the sodium carbonate solution with 5 wt% concentration and 10 wt% concentration at 30 °C did not satisfy the pseudo first-order fast chemical reaction kinetics assumption. To improve CO2 absorption mass transfer rate, dodecyl trimethyl ammonium chloride (DTAC) surfactant was introduced, which was improved by 119 % compared with non-enhanced solvent at 5 wt% concentration solution, and the assumption of pseudo first order fast chemical reaction was satisfied. After the introduction of surfactant, the barrier effect decreased the liquid phase mass transfer coefficient, but the Marangoni effect happened in the 5 wt% concentration of sodium carbonate solution, which enhanced the liquid-phase mass-transfer coefficient. This finding reveals the mechanism of mass transfer promotion of sodium carbonate by the surfactant DTAC, which is of great engineering significance for the application in the field of decarbonization after the introduction of surfactant.

As an important intermediate for dual carbon targets, catalytic CO oxidation under mild conditions has received sufficient attention, as the reaction mechanism is directly related to the type of employed catalyst. High performance computing is performed with density functional theory to elucidate the mechanism of CO oxidation catalyzed by sulfur doped fullerene (C60-xSx (x = 1 ∼ 3)). The total activation energy for the first CO oxidation on C59S, C58S2, and C57S3 increases gradually, as implies that the CO oxidation on C59S should be easier than those on the other two dopants. Distinct electrons (0.852 e and 1.479 e) are transferred to oxygen atoms (O2) from C59S with the adsorption of O2 and CO. There is no synergistic effect for the doping S atoms. All elementary reactions on C59S are exothermic processes. This means that C59S is a potential material for addressing environmental protection issues and H2 purification for fuel cell applications.

As the dominant waste disposal process, incineration is regarded as the main incentive for the “not-in-my-backyard” syndrome, and faces an inescapable pressures of ultra-low emissions (ULE). Establishing precise response relationships between emission factors (EFs) and full-process influencing factors can provide guidance for the synergistic mitigation of flue gas pollutants (FGPs). In this work, the multi-dimensional EFs of FGPs were identified by initially integrating FGPs concentration monitoring data of existing 1,226 processing lines in China, technologies applied and operational experience (OE), local economic and political characteristics. Significant regional imbalance performance was observed, which EFs in the coastal regions were 3.55–92.39 % lower than those of the inland areas. NOx, SO2, HCl were identified as critical components requiring further reduction under the ULE standards, with exceedance rates recorded at 73.07 %, 38.90 %, and 56.69 %, respectively. An indicative value of 20 mg/m3 for PM is recommended for the control of heavy metals of Cd + Tl and Sb + As + Pb + Cr + Co + Cu + Mn + Ni based on the correlation coefficients of r = 0.28 (p

Biochar is a very promising material for soil remediation. However, most studies mainly focus on the adsorption ability of biochar on one heavy metal, which is difficult to evaluate the actual remediation effect since soils were contaminated with multiple heavy metals. In order to improve the soil remediation efficiency, we used the joint remediation method of magnetically modified biochar and ryegrass to remediate the soil polluted by compound heavy metals (chromium, nickel, copper, zinc, arsenic and cadmium), and evaluate the effect on the process of organic carbon mineralization in polluted soils. It was found that magnetic biochar and ryegrass together decreased the concentrations of Cr, Ni, Cu, Zn, As, and Cd in soils by 24.12 %, 23.30 %, 22.01 %, 9.98 %, 14.83 %, and 15.08 %, respectively, and reduced the available fractions. Ryegrass roots were the main accumulation part of heavy metals, and the order of enrichment effect was ranked as Zn > As > Cr > Cu > Ni > Cd. In addition, magnetic biochar can maintained the stability of the organic carbon pool, and inhibited the emission of volatile organic compounds from ryegrass. Overall, this study indicates that magnetic biochar spheres combined with ryegrass is an effective method for heavy metals co-contaminated soils, and has the excellent remediation ability for actual co-contaminated soils.

The Gleeble-3800 thermomechanical simulator unit was used to perform single-pass hot compression tests of the single-phase BCC structure AlFeCoNiMo0.2 high-entropy alloy at the deformation temperature of 950–1150 °C and strain rate of 0.001-1s−1. The hot deformation behavior of the alloy was studied, and the dynamic recrystallization critical strain was determined by the work hardening rate. The dynamic recrystallization mechanism of the alloy was revealed with the microstructure characterization techcique. The study results showed: The dynamic recrystallization critical strain of AlFeCoNiMo0.2 high entropy alloy did not show any notable dependency on the deformation temperature and strain rate. Without reaching the recrystallization temperature, the massive generation of subgrain structures suppresses the formation of dynamic recrystallization grains. The nucleation mechanism of the high-entropy alloy is subgrain merging mechanism caused by dislocation motion.

Microstructure of novel high-strength metastable β titanium alloy, Ti–4Al–6Mo–2V–5Cr–2Zr, is extremely sensitive to both aging temperature and time length, which directly regulates their mechanical properties. Therefore, it is particularly important to clarify the roles of aging treatment in both microstructure and mechanical properties of Ti–4Al–6Mo–2V–5Cr–2Zr. Through varying the aging temperature from 520 to 640 °C and time from 2 h to 8 h, effects of aging technological parameters on the microstructure and tensile properties of Ti–4Al–6Mo–2V–5Cr–2Zr was systematically investigated. It is noted that the secondary α phase (αs) inside the β matrix coarsens as a function of the aging temperature and time length, and the shape of αs phase changes from fine needle to short rod. Moreover, lower aging temperature and longer aging time result in a higher volume fraction of αs phase. Combined with tensile test results, it is evident that volume fraction of αs phase leads to high strength. The volume fraction of αs phase in the alloy after aging at 520 °C for 6 h reaches 61.9% along with the highest ultimate tensile strength of 1367 MPa. In addition, the strengthening mechanism of reinforced phase αs was clarified with both SEM and TEM observations. Results show that the αs with the internal lattice distortion and HCP structure effectively prevent the dislocation slip. And the αs phase arranged in a triangular shape has a profound strengthening effect.

Flexible control of atomization pressure and bar material feeding speed was achieved during preparation of TC11 alloy 3D-printing spherical powder on basis of a vacuum-induced multistage atomization process. Collision at the metal drop atomization stage was effectively avoided and spherical powder quality was significantly enhanced while ensuring the high fine-powder yield. Under the optimized atomization process conditions, the powder with D90 of 59.2 μm, highest sphericity, O and N element increment below 0.04%, and 15–53 μm powder yield of 30% was obtained. These comprehensive mechanical properties meet the requirement for 3D printing.

As a novel metastable β titanium alloy, Ti-6Mo-5V-3Al-2Fe, it is essential to establish the correlation among its microstructure, strength and ductility. In this paper, transmission electron microscope (TEM) and scanning electron microscope (SEM) were used to observe the secondary α phase (αs) of the aged alloy. The strength and ductility of the alloy were characterized by a room temperature tensile test. The dependence of strength and ductility on the αs of the alloy was investigated. Results indicate that the minimum width and spacing of αs within β grains can be obtained after being aged at 470°C for 4h. As the increase of aging temperature and time, the average width and average spacing of αs increase. A relational equation among precipitation strengthening and spacing length of αs is established to analyze the strengthening mechanism. It is demonstrated that the average spacing length of αs plays a predominant role in the strengthening of the alloy. The aged alloy exhibits poor ductility due to the formation of continuous grain boundaries α phase (GB α). After being aged at 620°C for 4h, Widmansta¨tten α phase nucleates along β grain boundaries and grows toward β matrix (WGB α). The combination of αs spacing widening and WGB α formation obviously improves the ductility of the alloy.

To realize the triple functions of “roadway support, thermal insulation and heat regulation” of pumping wet shotcrete (PWS), the microencapsulated phase change material (MPCM) with poly (lauryl methacrylate) as shell and paraffin wax as core was synthetized by interfacial polymerization. The surface morphology, particle size distributions, core-shell compositions, the performances of the thermal stability and phase change of the MPCM were analyzed. The results show that the synthetized MPCM has excellent performances and can be applied in PWS. To obtain the optimal mixed proportions of the key materials (i.e., ceramsite, sand and MPCM) in PWS, the key performance indices were employed in the orthogonal experimental design to test the multiple performances of the PWS containing MPCMs. The results show that these performances are influenced by the dosages of the key materials and the recommended dosages were: 112.5 kg/m3 of ceramsite, 1250 kg/m3 of sand and 100 kg/m3 of MPCM. This study shows that the application of the MPCMs cannot only further reduce the thermal conductivity of PWS but also endow PWS with the function of heat regulation. A broad prospect of the application of MPCMs in underground cooling engineering can be expected.

The multiple functions and services provided by ecosystems that linked human-being are under threat with the global environment changes. Large-scale research of ecosystem multifunctionality (EMF), which include AN, AP, AK, CEC, SOM, SMC, SMN, AGB BGB and other indicators, can help us excavate ecosystems more comprehensively and strengthen protection awareness of biodiversity, but it remains scarce, especially for the Qinghai-Tibet Plateau (QTP). In this paper, evaluating EMF by the three calculation approaches–average approach, single threshold approach, and principal component analysis, we presented the spatial pattern of EMF over the QTP. We found that three approaches undergone the coincident spatial variation characteristic, with a decreasing gradient from southeast to northwest. Although the EMFs of forests (geometric mean of three indexes = 0.37) and alpine meadows (geometric mean of three indexes = 0.29) were significantly higher than those of alpine steppe (geometric mean of three indexes = 0.16) and alpine desert steppe (geometric mean of three indexes = 0.12) ecosystems, the EMFs jointly exhibited an inverted U-shaped distribution with altitudinal gradient in all ecosystems. For the correlation between EMF and precipitation, which first increases and then decreases along altitudinal gradient, with a turnaround around 4000–5000 m. Nevertheless, the correlation between EMF and temperature, which universally increases with altitudinal gradient. Our results emphasize that gradient change of EMF is attributed to elevation dependence of climate change throughout the QTP, and understanding transformation threshold that is beneficial for the protection and sustainable development of ecosystems.

Cytochalasans are an important class of fungal metabolites displaying remarkable structural diversity and significant biological activity. Historically, considerable effort has been devoted toward the synthesis of cytochalasans. Comparably, merocytochalasans, an array of more complicated molecules biosynthetically derived from cytochalasans and epicoccine through hetero-dimerization, -trimerization or -tetramerization, have been less explored. In recent years, our group has shown keen interest on cytochalasans and merocytochalasans, which has culminated in the collective syntheses of a variety of representative molecules of this family. To this end, we first developed a highly concise, efficient and modular approach to access 11/6/5 tricyclic cytochalasans, featuring an intermolecular Diels-Alder reaction and a ring-closing metathesis reaction as key steps. Based on this synthetic route, several cytochalasan monomers, including aspochalasin B, aspochalasin P, aspochalasin D and aspergillin PZ, have been synthesized within 11–14 longest linear steps. Subsequently, a couple of hetero-dimeric and -trimeric merocytochalasans, including asperchalasines A-E and asperflavipine B, have been accessed from aspochalasin B and the suitable epicoccine precursors through a series of intriguing bio-inspired transformations such as Diels-Alder reaction and formal [5 ​+ ​2] cycloaddition. Moreover, the full profile of the regio- and endo/exo selectivity of the Diels-Alder heterodimerization has been explored through computational study. The present study not only notably enriches the synthetic chemistry of cytochalasans and merocytochalasans, but also affords venerable clue to decipher the biosynthetic origins of the newly identified merocytochalasans.

As a challenging but promising technology, wire-based in-situ additive manufacturing shows great advantages in material preparation and part manufacturing integration. However, compared with single-wire AM technology, it faces a more complex droplet transition pattern, which is closely related to the feeding modes of the elemental wires. In the current work, the effect of wire feeding methods on the droplet transition mode, the morphology, composition, and mechanical properties is for the first time systematically studied. Three wire feeding methods, including double-side-feeding, single-side-feeding, and parallel-feeding, were adopted to fabricate the Ti-Al-Nb intermetallics in-situ. The results show that the TiNb wire and pure-Al wire enter the molten pool separately and with a totally inconsistent droplet transition mode in the double-side-feeding and single-side-feeding methods. This droplet transition results in poor morphology, macro-segregation, and inconsistent mechanical properties. While in the parallel-feeding method, the TiNb and Al droplet transfer to the molten pool after forming a common droplet, which provides a better guarantee for the morphology and performance of the deposited parts. As a research oriented to the deposition process, the current work is of great significance for enriching the fundamental theory and promoting the development of the wire-based in-situ AM technology.

Sprayed dust suppression techniques are widely used to reduce the dust concentration in mines, and evaporative cooling by water spray is increasingly used as an approach to enhance thermal comfort in built environments. In mines, the roadway under excavation, which is known as the development heading, has not yet been connected to through ventilation. Auxiliary ventilation is the most important but also the most difficult to achieve in this area. Operators face the dual threat of dust and high temperatures in the area, in particular at the end of the heading, that is, at the heading face. To improve the working environment in this area, the present study improved the load-haul-dump vehicle and installed an external spray system on the bucket of the vehicle. To verify the cooling and dust suppression effect of the system, a computational fluid dynamics simulation was adopted to simulate the velocity and temperature fields of the airflow and the dynamic distributions of the water droplets using the Euler–Lagrange approach. The study shows that the water droplets can completely cover the dust-producing area, and the water temperature of the spray system can significantly affect the temperature distribution on the airflow in the development heading.

Background: The International Agency for Research on Cancer (IARC) classifies diesel engine exhaust as carcinogenic to humans based on sufficient evidence for lung cancer. IARC noted, however, an increased risk of bladder cancer (based on limited evidence). Objective: To evaluate the association between quantitative, lifetime occupational diesel exhaust exposure and risk of urothelial cell carcinoma of the bladder (UBC) overall and according to pathological subtypes. Methods: Data from personal interviews with 1944 UBC cases, as well as formalin-fixed paraffin-embedded tumor tissue blocks, and 2135 controls were pooled from two case-control studies conducted in the U.S. and Spain. Lifetime occupational histories combined with exposure-oriented questions were used to estimate cumulative exposure to respirable elemental carbon (REC), a primary surrogate for diesel exhaust. Unconditional logistic regression and two-stage polytomous logistic regression were used to calculate odds ratios (ORs) and 95% confidence intervals (CIs), adjusting for smoking and other risk factors. Results: Exposure to cumulative REC was associated with an increased risk of UBC; workers with cumulative REC >396 μg/m3-years had an OR of 1.61 (95% CI, 1.08–2.40). At this level of cumulative exposure, similar results were observed in the U.S. and Spain, OR = 1.75 (95% CI, 0.97–3.15) and OR = 1.54 (95% CI, 0.89–2.68), respectively. In lagged analysis, we also observed a consistent increased risk among workers with cumulative REC >396 μg/m3-years (range of ORs = 1.52–1.93) for all lag intervals evaluated (5–40 years). When we accounted for tumor subtypes defined by stage and grade, a significant association between diesel exhaust exposure and UBC was apparent (global test for association p = 0.0019). Conclusions: Combining data from two large epidemiologic studies, our results provide further evidence that diesel exhaust exposure increases the risk of UBC. Keywords: Bladder cancer, Diesel exhaust, Occupation