基于步冷试验的2.25Cr-1Mo-0.25V钢母材及焊缝回火脆化研究

对原始态、步冷态、脱脆态和脱脆步冷态2.25Cr-1Mo-0.25V钢母材及焊缝冲击试验结果进行分析,得到了母材和焊缝在不同状态下的韧脆转变温度vTr54.2和FATT以及脆化度ΔvTr54.2和ΔFATT。试验结果表明,步冷试验之后,母材发生较低程度脆化或脱脆现象,但是脆化度或脱脆度较低,表明母材具有良好的抗回火脆化性能;经脱脆试验后,母材和焊缝都发生较高程度的脱脆,表明材料的脆化主要是由于回火脆化引起的,脱脆试验使得材料的韧脆转变温度降低;脱脆步冷试验后,焊缝发生较高程度的脆化,焊缝对脱脆步冷试验的敏感性较高,脱脆步冷试验有效促进了焊缝的脆化。在相同脆化条件下,母材的脆化敏感性低于焊缝,焊缝更易发生脆化。     

Improving weld formability by a novel dual-rotation bobbin tool friction stir welding

A novel dual-rotation bobbin tool friction stir welding (DBT-FSW) was developed, in which the upper shoulder (US) and lower shoulder (LS) have different rotational speeds. This process was tried to weld 3.2 mm thick aluminum-lithium alloy sheets. The metallographic analysis and torque measurement were carried out to characterize the weld formability. Experimental results show that compared to conventional bobbin tool friction stir welding, the DBT-FSW has an excellent process stability, and can produce the defect-free joints in a wider range of welding parameters. These can be attributed to the significant improvement of material flow caused by the formation of a staggered layer structure and the unbalanced force between the US and LS during the DBT-FSW process.     

The Propagation Background in Social Networks: Simulating and Modeling

Machine Intelligence Research - Recent years have witnessed the booming of online social network and social media platforms, which leads to a state of information explosion. Though extensive...     

Tribological and corrosion behaviors of fluorocarbon coating reinforced with sodium iron titanate platelets and whiskers

A series of sodium iron titanate (NFTO)–fluorocarbon composite coatings have been prepared with the liquid-phase blending method. The effects of two types of NFTO, NFTO platelets, and NFTO whiskers, on the tribological and corrosion behaviors of the composite coatings, are systematically studied. The results show that the addition of NFTO can significantly enhance the friction-reducing and wear resistance performances of the fluorocarbon coating. Under dry sliding, the minimum specific wear rate is 1.67 × 10⁻⁴ mm³/Nm for the platelet-filled composite coatings and 1.15 × 10⁻⁴ mm³/Nm for the whisker-filled composite coatings, respectively, showing a decrease of 83.5 and 88.6% than that of pure coating. Under a simulated seawater environment, the minimum specific wear rate is 5.44 × 10⁻⁵ mm³/Nm for the platelet-filled composite coatings and 0.84 × 10⁻⁵ mm³/Nm for the whisker-filled composite coatings, respectively, showing a decrease of 90.5 and 98.5% than that of pure coating. The morphologies of worn surfaces, wear debris, and transfer films are analyzed, and the corresponding wear resistance mechanisms are discussed. The electrochemical impedance spectroscopy certifies a remarkably improved corrosion resistance of the composite coatings which have been immersed in 3.5 wt % NaCl solution for 30 days. The composite coating reinforced with 7.5 wt % platelets shows the highest resistance of 256.3 × 10⁶ Ω·cm², approximately two orders of magnitude higher than that of pure coating. © 2020 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48936.     

A Dual Inhibitor of DYRK1A and GSK3β for β-Cell Proliferation: Aminopyrazine Derivative GNF4877

Loss of β-cell mass and function can lead to insufficient insulin levels and ultimately to hyperglycemia and diabetes mellitus. The mainstream treatment approach involves regulation of insulin levels; however, approaches intended to increase β-cell mass are less developed. Promoting β-cell proliferation with low-molecular-weight inhibitors of dual-specificity tyrosine-regulated kinase 1A (DYRK1A) offers the potential to treat diabetes with oral therapies by restoring β-cell mass, insulin content and glycemic control. GNF4877, a potent dual inhibitor of DYRK1A and glycogen synthase kinase 3β (GSK3β) was previously reported to induce primary human β-cell proliferation in vitro and in vivo. Herein, we describe the lead optimization that lead to the identification of GNF4877 from an aminopyrazine hit identified in a phenotypic high-throughput screening campaign measuring β-cell proliferation.     

煤矿新型让压锚杆研究及应用

针对高应力软岩巷道围岩的大变形特征,设计了一种煤矿新型让压锚杆,主要运用钢套管内部约束热固性聚氨酯弹性材料来达到大变形让压的目的。试验表明,该锚杆与传统让压锚杆相比,具有让压距离大(为传统让压锚杆的3倍)、让压后承载性能稳定的显著特点。工程应用表明,该锚杆对深部高应力软岩巷道围岩稳定性能起到较好的控制作用。     

综掘工作面智能化开采技术的实践

针对煤矿开采深度的增加引起的采掘和衔接问题,山西长平煤业公司通过技术引进,设计了基于信息自动化的智能化开采技术,为实现该矿安全高效生产奠定了基础。     

Stable Organic Titanium Catalysts and Reactive Distillation Used for the Transesterification of Dimethyl Carbonate with Phenol

The transesterification of dimethyl carbonate with phenol to methyl phenyl carbonate (MPC) was investigated on novel catalysts such as titanium diisopropoxide bis(ethyl acetoacetate) and titanium dibutoxide bis(ethyl acetoacetate) in a closed batch reactor at 185–206 °C under high pressure. The produced methanol could be removed efficiently by reactive distillation in order to overcome the equilibrium. The prepared catalysts have higher resistance to water than titanium alkoxides. Phenol conversion as high as 86.4 % with an MPC selectivity of 99.4 % was achieved under optimal reaction conditions within 9 h. Most of the catalytic activity was retained after repeated use for ten times.     

Polymer hydrogel cross-linked by inorganic nanoparticles for removing trace metal ions

Hydrogels for absorbing metal ions in wastewater have attracted more attentions in the environmental field especially for recent years. The removal efficiency of hydrogel adsorbents for eliminating metal ions is highly related with the effective contact between adsorbents and adsorbates. However, poor water absorption capacity of the hydrogel adsorbents would restrict on the expose of adsorption sites to the targeted subjects, causing undesirable removal ratio (RR) especially for metal ions at trace level. Thereby, the reported hydrogel adsorbents mainly focus on the removal of high content but not the trace level of metal ions so far. In this work, poly(acrylamide) (PAM)/poly(acrylic acid) (PAA)/Ca(OH)₂ composite hydrogel is applied to adsorb trace metal ions. Swelling ratio of such PAM/PAA/Ca(OH)₂ gel reaches 2,530 g/g, resulting in effective exposure of active sites and further expected RR for trace metal ions. The RRs of such adsorbent for Cu²⁺ (initial concentration C₀ = 0.064 mg/L), Al³⁺ (C₀ = 0.27 mg/L), Co²⁺ (C₀ = 0.59 mg/L), Cr⁶⁺ (C₀ = 0.52 mg/L), Mn²⁺ (C₀ = 0.55 mg/L), Ni²⁺ (C₀ = 0.59 mg/L), Zn²⁺ (C₀ = 0.65 mg/L), Ag⁺ (C₀ = 1.08 mg/L), and La³⁺ (C₀ = 1.39 mg/L) are 56.6, 80.8, 41.3, 29.3, 34.6, 44.6, 55.9, 45.8, and 35.5%, respectively. This work broadens the application of hydrogel adsorbent for eliminating trace metal ions from polluted water.