The abandoned smelters present a substantial pollution threat to the nearby soil and *** this study,63 surface soil samples were collected from a zinc smelter to quantitatively describe the pollution characteristics,e...
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The abandoned smelters present a substantial pollution threat to the nearby soil and *** this study,63 surface soil samples were collected from a zinc smelter to quantitatively describe the pollution characteristics,ecological risks,and source apportionment of heavy metal(loid)s(HMs).The results revealed that the average contents of Zn,Cd,Pb,As,and Hg were 0.4,12.2,3.3,5.3,and 12.7 times higher than the risk screening values of the construction sites,***,the smelter was accumulated heavily with Cd and Hg,and the contribution of Cd(0.38)and Hg(0.53)to ecological risk was 91.58%.ZZ3 and ZZ7 were the most polluted workshops,accounting for 25.7%and 35.0%of the pollution load and ecological risk,*** influence of soil parent materials on pollution was minor compared to various workshops within the *** with PMF,APCS-MLR and GIS analysis,four sources of HMs were identified:P1(25.5%)and A3(18.4%)were atmospheric deposition from the electric defogging workshop and surface runoff from the smelter;P2(32.7%)and A2(20.9%)were surface runoff of As-Pb foul acid;P3(14.5%)and A4(49.8%)were atmospheric deposition from the leach slag drying workshop;P4(27.3%)and A1(10.8%)were the smelting process of zinc *** paper described the distribution characteristics and specific sources of HMs in different process workshops,providing a new perspective for the precise remediation of the smelter by determining the priority control factors.
In seed breeding, the vibrating screen used for pre-sowing grading parental seeds often has the problem of poor self-purification rate. Using elastic balls to clean the plugging seeds and ensure the self-purification ...
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In seed breeding, the vibrating screen used for pre-sowing grading parental seeds often has the problem of poor self-purification rate. Using elastic balls to clean the plugging seeds and ensure the self-purification of the screen is a viable technical solution. To clarify and improve the operating performance of the elastic ball particles, a DEM-MBD coupling simulation model of the elastic ball screen-cleaning device was established in this study, and a numerical simulation analysis of the complex motion process was carried out. The mechanism of action of the elastic ball was explained more completely from the aspects of excitation force and energy transfer. Through the Plackett-Burman test, it was determined that the vibration frequency has the most significant effect on the excitation force. Multiple linear regression analysis was performed on each factor and the mathematical relationship equation. It was found that when the maximum excitation force was greater than 7 N and the average excitation force was greater than 2 N, the self-purification rate was greater than 95%. The self-purification rate was then increased to 99.81% by variable frequency tests. The variable frequency achieved better self-purification effect.
NH_(3)-SCR is an effective mean of NOxremoval in the non-electric industry, however, the high activation temperature and poor H_(2)O resistance of SCR catalysts posed a barrier to its application. In this work, a seri...
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NH_(3)-SCR is an effective mean of NOxremoval in the non-electric industry, however, the high activation temperature and poor H_(2)O resistance of SCR catalysts posed a barrier to its application. In this work, a series of three-dimensionally ordered macroporous(3DOM) catalysts were synthesized via a colloidal crystal template(CCT) method, and various characterizations were carried out to explore the physicochemical property of catalysts. The experiment results reveal that Ce_(0.2)Mn_(0.2)/3DOM-TiO_(2) catalyst presents the excellent low-temperature catalytic activity of nearly 100% at 100℃. Furthermore, the enhanced H_(2)O resistance is achieved, certified by the unaffected NO remove at 150℃ in the participation of 15 vol% H_(2)O. The characterizations results exhibit that the improved dispersion of the active component and enhanced redox ability are conducive to the low-temperature catalytic activity. N_(2) adsorption and desorption experiments indicate that catalyst with 3DOM support possesses a larger pore diameter and specific surface area, which may weaken the condensation of H_(2)O in the microporosity of catalysts and improved the H_(2)O resistance of the catalyst. In situ DRIFTS results manifest that Ce_(0.2)Mn_(0.2)/3DOM-TiO_(2) catalyst could not only absorb more NH_(3) and generate more surface-active sites, but inhibit the competitive adsorption between H_(2)O and SCR reactants.
Composite filler metal refers to the traditional filler metal by adding a certain proportion of various forms of superalloy,carbon fiber and ceramic particles as reinforcement *** to the addition of the reinforcement ...
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Composite filler metal refers to the traditional filler metal by adding a certain proportion of various forms of superalloy,carbon fiber and ceramic particles as reinforcement *** to the addition of the reinforcement phase,the filler metal can have a suitable thermal expansion coefficient,which can effectively reduce the residual stress at the brazing joint caused by the different thermal expansion coefficients of the base metal and improve the comprehensive performance of the brazing *** recent years,with the progress of science and technology,the research on nanomaterials has been deepening,and nanomaterials are widely used in the modification of composite filler metals because of their special surface effect,small size effect,quantum size effect and macroscopic quantum tunneling *** modification performance of different composite solders by nanoparticles in recent years is reviewed,the advantages and disadvantages of nano-reinforced composite solders are analyzed,and the future research direction of composite solders is prospected.
The effect of rotation-curvature correction and inviscid spatial discretization scheme on the aerodynamic performance and flow characteristics of Darrieus H-type vertical axis wind turbine(VAWT)are investigated based ...
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The effect of rotation-curvature correction and inviscid spatial discretization scheme on the aerodynamic performance and flow characteristics of Darrieus H-type vertical axis wind turbine(VAWT)are investigated based on an in-house *** solver is developed on an in-house platform HRAPIF based on the finite volume method(FVM)with the elemental velocity vector transformation(EVVT)*** present solver adopts the density-based method with a low Mach preconditioning *** turbulence models are the Spalart-Allmaras(SA)model and the k-ωshear stress transport(SST)*** inviscid spatial discretization schemes are the third-order monotone upstream-centered schemes for conservation laws(MUSCL)scheme and the fifth-order modified weighted essentially non-oscillatory(WENO-Z)*** power coefficient,instantaneous torque of blades,blade wake,and turbine wake are compared and analyzed at different tip speed *** extensive analysis reveals that the density-based method can be applied in VAWT numerical simulation;the SST models perform better than the SA models in power coefficient prediction;the rotation-curvature correction is not necessary and the third-order MUSCL is enough for power coefficient prediction,the high-order WENO-Z scheme can capture more flow field details,the rotation-curvature correction and high-order WENO-Z scheme reduce the length of the velocity deficit region in the turbine wake.
The catalytic behavior of a catalyst for chlorine-containing volatile organic compounds(CVOCs) oxidation largely depends on the synergistic interaction between the oxidizing and acidic *** the present work,two catalys...
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The catalytic behavior of a catalyst for chlorine-containing volatile organic compounds(CVOCs) oxidation largely depends on the synergistic interaction between the oxidizing and acidic *** the present work,two catalysts with different distributions of CeO_(2) on the inner and outer surfaces of 4.0Ce-USY-ex and 4.0Ce-USY-dp(USY zeolite) were prepared respectively by ion exchange and deposition methods,with a purpose of finding out how the location of the oxidation sites(CeO_(2)) influence its synergistic effect with the acidic sites of *** results show that 4.0Ce-USY-ex is much more active for catalytic degradation of 1,2-dichloroethane(DCE),while 4.0Ce-USY-dp catalyst exhibit higher catalytic degradation activity for other structured CVOCs(dichloromethane(DCM),trichloroethylene(TCE),chlorobenzene(CB)).CeO_(2) in 4.0Ce-USY-ex catalyst mainly disperses in the pore channels of USY zeolite,and there are many strong acid centers on the surface,which is conducive to the dechlorination conversion of ***,CeO_(2) in 4.0Ce-USY-dp catalyst is mainly distributed on the outer surface of USY and has strong oxidation ability,which contributes to the deep oxidation of ***,the presence of a large number of strong acid centers on the catalyst surface of 4.0Ce-USY-ex catalysts leads to severe accumulation of surface carbon species and significantly decreases its stability towards ***,a large number of active oxygen species on the surface of 4.0Ce-USY-dp and CeO_(2) catalysts are beneficial to the deep oxidation of DCE,reducing the formation of surface carbon and thus improving the stability of the ***,the influence of the location of the oxidation sites on its synergistic effect with the acidic sites was established in the present work,which could provide some new ideas for the rational design of CVOCs degradation catalyst with appropriate distribution of active sites.
*** Halogens,including fluorine(F),chlorine(Cl),bromine(Br),and iodine(I),are highly mobile and water-soluble elements that can become significantly enriched in melts and *** fluids and melts,halogens react with nearl...
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*** Halogens,including fluorine(F),chlorine(Cl),bromine(Br),and iodine(I),are highly mobile and water-soluble elements that can become significantly enriched in melts and *** fluids and melts,halogens react with nearly all metals and readily form complexes with metal cations,significantly influencing the distribution of metal elements between different ***,halogens play a crucial role in the migration,enrichment,and mineralization of key metals in the lithosphere(Weis et al.,2012;Liu et al.,2024).
Realization of high performance satellite onboard clock is vital for various positioning, navigation, and timing applications. For further improvement of the synchronization-based satellite time and frequency referenc...
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Realization of high performance satellite onboard clock is vital for various positioning, navigation, and timing applications. For further improvement of the synchronization-based satellite time and frequency references, we propose a geosynchronous(GEO) satellite virtual clock concept based on ground–satellite synchronization and present a beacon transponder structure for its implementation(scheduled for launch in 2025), which does not require atomic clocks to be mounted on the satellite. Its high performance relies only on minor modifications to the existing transponder structure of GEO satellites. We carefully model the carrier phase link and analyze the factors causing link asymmetry within the special relativity. Considering that performance of such synchronization-based satellite clocks is primarily limited by the link's random phase noise, which cannot be adequately modeled, we design a closed-loop experiment based on commercial GEO satellites for pre-evaluation. This experiment aims at extracting the zero-means random part of the ground-satellite Ku-band carrier phase via a feedback loop. Ultimately, we obtain a 1σ value of 0.633 ps(two-way link), following the Gaussian distribution. From this result, we conclude that the proposed real-time Einstein-synchronization-defined satellite virtual clock can achieve picosecond-level replication of onboard time and frequency.
Commensal enterococci with pathogenic potential often facilitate the growth of diverse pathogens,thereby exacerbating ***,there are few effective therapeutic strategies to prevent and intervene in enterococci-mediated...
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Commensal enterococci with pathogenic potential often facilitate the growth of diverse pathogens,thereby exacerbating ***,there are few effective therapeutic strategies to prevent and intervene in enterococci-mediated polymicrobial ***,we find that enterococci at high density drive the expansion and pathogenicity of enteric Salmonella enterica serotype Typhimurium(***).Subsequently,we show that the driving role of enterococci in such infections is counteracted by dietary coumarin glycosides in ***,which are tolerant of iron-deficient environments,produceβ-glucosidases to hydrolyze coumarin glycosides into bioactive aglycones,inhibiting *** growth and ameliorating the severity of ***-induced symptoms by inducing iron ***,we demonstrate that coumarin glycosides as a common diet effectively reverse enterococci-facilitated enteric infections,providing an alternative intervention to combat polymicrobial infections.
A medium-carbon low-alloy steel with designed chemical composition was *** steel exhibits an excellent product of strength and elongation value of 31,832 MPa%through quenching and partitioning treatment,with a tensile...
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A medium-carbon low-alloy steel with designed chemical composition was *** steel exhibits an excellent product of strength and elongation value of 31,832 MPa%through quenching and partitioning treatment,with a tensile strength of 1413 MPa and elongation of 22%.X-ray diffraction analysis and transmission electron microscopy characterizations confirm that the retained austenite in the specimens undergoes stress-induced phase transformation to the martensite and hexagonal phases,namely the transformation-induced plasticity(TRIP)effect is *** TRIP effect,triggered by the stress-induced phase transition of retained austenite,is responsible for the excellent mechanical properties obtained in the *** further investigating the stress-induced phase transition mechanism,thermodynamic methods are *** free energy of face-centered cubic-Fe,ε-Fe,ω-Fe and body-centered cubic-Fe associated with the stress-induced phase transition was calculated using molecular dynamics simulations,and a calculation method of strain energy in thermodynamic units for the stress-induced martensitic transformation is *** final results reveal the process and thermodynamic mechanism of stress-induced martensitic transformation in medium-carbon steels,in which the hexagonal phase can participate in the process as an intermediate product.
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