Enhanced mechanical properties of Mg-3Al-1Zn alloy sheets through slope extrusion

A novel extrusion approach,entitled slope extrusion(SE),was employed to manufacture AZ31(Mg-3Al-1 Zn,wt%)alloy sheets.The microstructures,textures,and mechanical properties were investigated,compared with those of the AZ31 sheet fabricated by conventional extrusion(CE).Through the combination of finite element simulation and actual experiment,the ultimate results indicated that significant grain refinement(from 9.1 to 7.7 and 5.6μm)and strong basal texture(from 12.6 to 17.6 and 19.5 mrd)were achieved by the SE process.The essence was associated with the additional introduced inclined interface in the process of SE,which could bring about more asymmetric deformation and stronger accumulated strain along the ND when compared with the process of CE.As a consequence,the SE sheets exhibited a higher yield strength(YS)and ultimate tensile strength(UTS)than the counterparts of the CE sheet,which was mainly assigned to the synergistic effects from grain refining and texture strengthening.

Grain size dependence of annealing strengthening of an extruded Mg-Gd-Zn alloy subjected to pre-compression deformation

In this work, pre-strain annealing strengthening(PSAS) effect was investigated in an extruded Mg-1.0Gd-1.5 Zn(wt.%) alloy with respect to different grain sizes. The evolution of microstructures was provided by scanning electron microscopy(SEM), electron backscattered diffraction(EBSD), transmission electron microscopy(TEM) and high-angle annular dark-field scanning transmission electron microscopy(HAADF-STEM) under the initial state, pre-compression, intermediate annealing and re-compression conditions. The obtained results showed a grain size-dependent PSAS effect in the alloy. The sample with larger grain sizes corresponded to a higher strengthening effect, which mainly resulted from a more remarkable hindrance for the growth of existing twins and a larger proportion of activation for the nucleation of new twins. This was closely associated with the increase of back stress and friction stress for twin boundary motion impeded by the larger restraint of dislocations, the higher stress field surrounding solutes and the more Zn segregation. In addition to twinning behavior, Guinier Preston(G.P.) zones on basaldislocations were found after intermediate annealing and provided an extra strengthening by inhibiting the motions of gilding pre-existing dislocations and newly formed ones, but it was independent on the grain size.

Hot-deformation kinetics analysis and extrusion parameter optimization of a dilute rare-earth free magnesium alloy

The fundamental research on thermo-mechanical conditions provides an experimental basis for high-performance Mg-Al-Ca-Mn alloys.However, there is a lack of systematical investigation for this series alloys on the hot-deformation kinetics and extrusion parameter optimization. Here, the flow behavior, constitutive model, dynamic recrystallization(DRX) kinetic model and processing map of a dilute rare-earth free Mg-1.3Al-0.4Ca-0.4Mn(AXM100, wt.%) alloy were studied under different hot-compressive conditions. In addition, the extrusion parameter optimization of this alloy was performed based on the hot-processing map. The results showed that the conventional Arrhenius-type strain-related constitutive model only worked well for the flow curves at high temperatures and low strain rates. In comparison, using the machine learning assisted model(support vector regression, SVR) could effectively improve the accuracy between the predicted and experimental values. The DRX kinetic model was established, and a typical necklace-shaped structure preferentially occurred at the original grain boundaries and the second phases. The DRX nucleation weakened the texture intensity, and the further growth caused the more scattered basal texture. The hot-processing maps at different strains were also measured and the optimal hot-processing range could be confirmed at the deformation temperatures of 600~723 K and the strain rates of 0.018~0.563 s^(-1). Based on the optimum hot-processing range, a suitable extrusion parameter was considered as 603 K and 0.1 mm/s and the as-extruded alloy in this parameter exhibited a good strength-ductility synergy(yield strength of ~ 232.1 MPa, ultimate strength of ~ 278.2 MPa and elongation-to-failure of ~ 20.1%). Finally, the strengthening-plasticizing mechanisms and the relationships between the DRXed grain size, yield strength and extrusion parameters were analyzed.

An experimental study on metal precipitation driven by fluid mixing: implications for genesis of carbonate-hosted lead–zinc ore deposits

A type of carbonate-hosted lead–zinc(Pb–Zn)ore deposits, known as Mississippi Valley Type(MVT)deposits, constitutes an important category of lead–zinc ore deposits. Previous studies proposed a fluid-mixing model to account for metal precipitation mechanism of the MVT ore deposits, in which fluids with metal-chloride complexes happen to mix with fluids with reduced sulfur, producing metal sulfide deposition. In this hypothesis, however, the detailed chemical kinetic process of mixing reactions, and especially the controlling factors on the metal precipitation are not yet clearly stated. In this paper, a series of mixing experiments under ambient temperature and pressure conditions were conducted to simulate the fluid mixing process, by titrating the metal-chloride solutions, doping withor without dolomite, and using NaHS solution. Experimental results, combined with the thermodynamic calculations, suggest that H_2S, rather than HS^-or S^(2-),dominated the reactions of Pb and/or Zn precipitation during the fluid mixing process, in which metal precipitation was influenced by the stability of metal complexes and the pH. Given the constant concentrations of metal and total S in fluids, the pH was a primary factor controlling the Pb and/or Zn metal precipitation. This is because neutralizing or neutralized processes for the ore-forming fluids can cause instabilities of Pb and/or Zn chloride complexes and re-distribution of sulfur species, and thus can facilitate the hydrolysis of Pb and Zn ions and precipitation of sulfides. Therefore, a weakly acidic to neutral fluid environment is most favorable for the precipitation of Pb and Zn sulfides associated with the carbonate-hosted Pb–Zn deposits.

TCMSTD 1.0: a systematic analysis of the traditional Chinese medicine system toxicology database

Dear Editor,The safety and modernization of traditional Chinese medicine (TCM) are significant concerns for users’ lives and health. Recently, the adverse effects caused by TCM and traditional nontoxic TCM have been frequently reported (Joo et al., 2020;Liu et al., 2021). As the safety of TCM continues to attract widespread attention, many researchers have been investigating the toxicity of TCM in regard to the toxic ingredients, effects, mechanisms, and detoxification strategies in TCM (Figure S1 in Supporting Information). Although some TCMs cause toxic reactions, they also play key roles in treating certain unignorable diseases (Fang et al., 2022).Therefore, toxicity research is crucial and urgently needed to develop and safely use TCM.

Evolution of China's Forestry Policies since 1949 and Experience and Implications

Since 1949,the Chinese Communist Party ( CPC) and government have formulated series of policies to promote construction and development of forestry. The evolution of forestry policies brings constant deepening of understanding of the Party and government about forestry development laws. Forestry policies evolve from emergency and provisional to systematic and overall functions,making them become more scientific,pertinent and prospective. Besides,formulation of forestry policies is gradually influenced by international factors. When formulating forestry policies,it is required to follow forestry development laws,keep pace with time,and make constant improvement in practice,to suit demands of times and social development,and prudently handle the relationship between economic benefits and ecological benefits of forestry.

农村社区IT基础设施改进策略

当前,我国农村社区建设处在一个至关重要的时期,农村社区建设在近些年取得了许多突破性的进展,但在IT基础设施建设方面仍然存在许多方面的不足。本课题旨在发现当前我国农村建设过程中存在的问题,并提出适当的改进方案。通过对多方面资料的查阅与分析发现我国农村社区存在的问题,并对问题进行整合,提出建设性的意见。在对诸多资料进行整合分析时,发现农村社区IT基础设施建设存在的绝大部分问题与其自身建设密切相关,所以,对于问题的解决也将从其根本入手,先治其根本再达其标准。这样对问题进行分析并提出解决方案才可以高效的解决问题,为我国的乡村振兴战略添一份力,帮助农村社区更好地进行IT基础设施建设。

Synthesis and electrochemical properties of Zn_3V_3O_8 as novel anode material

Zn_3V_3O_8 two-dimensional micro sheets are successfully synthesized by combination of solvothermal method and heat treatment. The X-ray diffraction(XRD) and field emission scanning electron microscopy(SEM) are used to characterize the structure and morphology of the samples, and the battery testing system is used to investigate its electrochemical performance. The results show that the Zn_3V_3O_8 is successfully obtained using mix solvent(water:ethylene glycol =1:1), and the sample takes on morphology of two-dimensional sheets. The initial discharge capacity for Zn_3V_3O_8 two-dimensional micro sheets is 752.0 mAh/g at 100 mA/g in the voltage range of 0.01-3 V. After heat treatment in a tube furnace at 550 ℃, the sample had the initial discharge capacity as 1152.0 mAh/g and maintained it at 901.4 mAh/g after 100 cycles. The good electrochemical performance for Zn_3V_3O_8 two-dimensional micro sheets make it possible to be used as novel anode for lithium ion battery application.

Robustness of ventilation systems in the control of walking-induced indoor fluctuations: Method development and case study

Walking-induced fluctuations have a significant influence on indoor airflow and pollutant dispersion.This study developed a method to quantify the robustness of ventilation systems in the control of walking-induced fluctuation control.Experiments were conducted in a full-scale chamber with four different kinds of ventilation systems:ceiling supply and side return(CS),ceiling supply and ceiling return(CC),side supply and ceiling return(SC),and side supply and side return(SS).The measured temperature,flow and pollutant field data was(1)denoised by FFT filtering or wavelet transform;(2)fitted by a Gaussian function;(3)feature-extracted for the range and time scale disturbance;and then(4)used to calculate the range scale and time scale robustness for different ventilation systems with dimensionless equations developed in this study.The selection processes for FFT filtering and wavelet transform,FFT filter cut-off frequency,wavelet function,and decomposition layers are also discussed,as well as the threshold for wavelet denoising,which can be adjusted accordingly if the walking frequency or sampling frequency differs from that in other studies.The results show that for the flow and pollutant fields,the use of a ventilation system can increase the range scale robustness by 19.7%-39.4% and 10.0%-38.8%,respectively;and the SS system was 7.0%-25.7% more robust than the other three ventilation systems.However,all four kinds of ventilation systems had a very limited effect in controlling the time scale disturbance.

Theoretical dissection of superconductivity in two-dimensional honeycomb borophene oxide B_(2)O crystal with a high stability

Atomically thin borophene has recently been synthesized experimentally,significantly enriching the boron chemistry and broadening the family of two-dimensional(2D)materials.Recently,oxides of 2D materials have been widely investigated for nextgeneration electronic devices.Based on the first-principles calculations,we predict the existence of the superconductivity in honeycomb borophene oxide(B_(2)O),which possesses a high stability and could be potentially prepared by intrinsically incorporating oxygen into the recently synthesized borophene.

Orbitally driven giant thermal conductance associated with abnormal strain dependence in hydrogenated graphene-like borophene

Heat energy in solids is carried by phonons and electrons.However,in most two-dimensional(2D)materials,the contribution from electrons to total thermal conduction is much lower than that for phonons.In this work,through first-principles calculations combined with non-equilibrium Green’s function theory,we studied electron and phonon thermal conductance in recently synthesized 2D hydrogen boride.The hexagonal boron network with bridging hydrogen atoms is suggested to exhibit comparable lattice thermal conductance(4.07 nWK−1 nm−2)as graphene(4.1 nWK−1 nm−2),and similar electron thermal conductance(3.6 nWK−1 nm−2),which is almost ten times that of graphene.As a result,total thermal conductance of 2D hydrogen boride is about two-fold of graphene,being the highest value in all known 2D materials.Moreover,tensile strain along the armchair direction leads to an increase in carrier density,significantly increasing electron thermal conductance.The increase in electron thermal conductance offsets the reduction in phonon thermal conductance,contributing to an abnormal increase in thermal conductance.We demonstrate that the high electron density governs extraordinarily high thermal conductance in 2D hydrogen boride,distinctive among 2D materials.

应用于深井脉冲源装备的有序堆积相变胶囊热防护数值研究

针对深井恶劣环境下脉冲功率源装备内电子元件的热防护问题,本文利用数值方法对比了多种有序堆积相变胶囊复合结构的热防护性能,探究了相变胶囊尺寸、堆积方式等对热防护性能的影响,提出了热流密度评价指标与内壁温度数学预测模型.结果表明,相变微胶囊-玻璃棉复合结构具有较好的热防护性能,内壁温上升速率相较于玻璃棉填充结构可降低13.8%,但相变材料的含量制约着热防护效果;使用大尺寸的相变胶囊,增大相变材料比例的同时可形成封闭气孔,相比于相变微胶囊-玻璃棉复合结构,内壁温升幅度进一步降低了19.3%.通过改善相变胶囊堆积结构,发现采用大尺寸相变胶囊单层阵列结构的热防护性能更优.最后,提出了相变胶囊单层阵列热防护结构下内壁温升预测公式,预测值与数值模拟结果的平均误差低于7%.

Relating Initial Texture to Deformation Behavior During Cold Rolling and Static Recrystallization Upon Subsequent Annealing of an Extruded WE43 Alloy

Deformation behaviors during cold rolling and static recrystallization behaviors upon subsequent annealing of an extruded WE43 alloys with different initial textures were investigated in this study.Three types of differently textured WE43 initial alloys were labeled as samplesⅠ,ⅡandⅢ.The results showed that multiple twinning modes and basal slip dominated the deformation of samples during cold rolling.Cold-rolled sampleⅠactivated the larger number of double twins with high strain energy,accompanied by the more uniform strain distribution,than cold-rolled samplesⅡandⅢ.During subsequent annealing,recrystallized grains preferentially occurred in double twins,twin-twin intersections and grain boundaries,thereby making cold-rolled sampleⅠhave the more rapid recrystallization rate.Similar recrystallization textures formed in three types of cold-rolled samples at the recrystallization nucleation stage,and they never largely changed with the annealing time due to the uniform grain growth induced by the solute drag and the precipitation pinning at grain boundaries.After full recrystallization,the grain growth was controlled by the solute drag,instead of precipitates which were re-dissolved into the matrix.Finally,the nucleation and growth kinetics of static recrystallization were calculated,and the effects of initial texture on activation energies of recrystallization nucleation and growth were discussed.