具有良好可再生性的新型二氧化硅磁性氧化石墨烯纳米复合材料

Graphene oxide (GO) wrapped Fe₃O₄ nanoparticles (NPs) were prepared by coating the Fe₃O₄ NPs with a SiO₂ layer, and then modifying by amino groups, which interact with the GO nanosheets to form covalent bonding. The SiO₂ coating layer plays a key role in integrating the magnetic nanoparticles with the GO nanosheets. The effect of the amount of SiO₂ on the morphology, structure, adsorption, and regenerability of the composites was studied in detail. An appropriate SiO₂ layer can effectively induce the GO nanosheets to completely wrap the Fe₃O₄ NPs, forming a core-shell Fe₃O₄@SiO₂@GO composite where Fe₃O₄@SiO₂ NPs are firmly encapsulated by GO nanosheets. The optimized Fe₃O₄@SiO₂@GO sample exhibits a high saturated adsorption capacity of 253 mg·g?1 Pb(II) cations from wastewater, and the adsorption process is well fitted by Langmuir adsorption model. Notably, the composite displays excellent regeneration, maintaining a ~90% adsorption capacity for five cycles, while other samples decrease their adsorption capacity rapidly. This work provides a theoretical guidance to improve the regeneration of the GO-based adsorbents.     

微波预处理对复杂铜矿磨矿及浮选动力学的影响

The effect of CaCO₃, Na₂CO₃, and CaF₂ on the reduction roasting and magnetic separation of high-phosphorus iron ore containing phosphorus in the form of Fe₃PO₇ and apatite was investigated. The results revealed that Na₂CO₃ had the most significant effect on iron recovery and dephosphorization, followed by CaCO₃, the effect of CaF₂ was negligible. The mechanisms of CaCO₃, Na₂CO₃, and CaF₂ were investigated using X-ray diffraction (XRD), scanning electron microscopy and energy dispersive spectrometry (SEM–EDS). Without additives, Fe₃PO₇ was reduced to elemental phosphorus and formed an iron–phosphorus alloy with metallic iron. The addition of CaCO₃ reacted with Fe₃PO₇ to generate an enormous amount of Ca₃(PO₄)₂ and promoted the reduction of iron oxides. However, the growth of iron particles was inhibited. With the addition of Na₂CO₃, the phosphorus in Fe₃PO₇ migrated to nepheline and Na₂CO₃ improved the reduction of iron oxides and growth of iron particles. Therefore, the recovery of iron and the separation of iron and phosphorus were the best. In contrast, CaF₂ reacted with Fe₃PO₇ to form fine Ca₃(PO₄)₂ particles scattered around the iron particles, making the separation of iron and phosphorus difficult.     

不同硅饱和系数水榴石的碳酸化分解动力学

Carbonated decomposition of hydrogarnet is one of the vital reactions of the calcification–carbonation method, which is designed to dispose of low-grade bauxite and Bayer red mud and is a novel eco-friendly method. In this study, the effect of the silica saturation coefficient (x) on the carbonation of hydrogarnet was investigated from the kinetic perspective. The results indicated that the carbonation of hydrogarnets with different x values (x = 0.27, 0.36, 0.70, and 0.73) underwent two stages with significantly different rates, and the kinetic mechanisms of the two stages can be described by the kinetic functions R3 and D3. The apparent activation energies at Stages 1 and 2 were 41.96–81.64 and 14.80–34.84 kJ/mol, respectively. Moreover, the corresponding limiting steps of the two stages were interfacial chemical reaction and diffusion.     

一种超重力燃烧合成制备高性能高熵合金的新方法

A new method of high-gravity combustion synthesis (HGCS) followed by post-treatment (PT) is reported for preparing high-performance high-entropy alloys (HEAs), Cr_0.9FeNi_2.5V_0.2Al_0.5 alloy, whereby cheap thermite powder is used as the raw material. In this process, the HEA melt and the ceramic melt are rapidly formed by a strong exothermic combustion synthesis reaction and completely separated under a high-gravity field. Then, the master alloy is obtained after cooling. Subsequently, the master alloy is sequentially subjected to conventional vacuum arc melting (VAM), homogenization treatment, cold rolling, and annealing treatment to realize a tensile strength, yield strength, and elongation of 1250 MPa, 1075 MPa, and 2.9%, respectively. The present method is increasingly attractive due to its low cost of raw materials and the intermediate product obtained without high-temperature heating. Based on the calculation of phase separation kinetics in the high-temperature melt, it is expected that the final alloys with high performance can be prepared directly across master alloys with higher high-gravity coefficients.     

窄板坯结晶器内连铸工艺参数对钢液流场的影响

Computational simulations and high-temperature measurements of velocities near the surface of a mold were carried out by using the rod deflection method to study the effects of various operating parameters on the flow field in slab continuous casting (CC) molds with narrow widths for the production of automobile exposed panels. Reasonable agreement between the calculated results and measured subsurface velocities of liquid steel was obtained under different operating parameters of the CC process. The simulation results reveal that the flow field in the horizontal plane located 50 mm from the meniscus can be used as the characteristic flow field to optimize the flow field of molten steel in the mold. Increases in casting speed can increase the subsurface velocity of molten steel and shift the position of the vortex core downward in the downward circulation zone. The flow field of liquid steel in a 1040 mm-wide slab CC mold can be improved by an Ar gas flow rate of 7 L·min?1 and casting speed of 1.7 m·min?1. Under the present experimental conditions, the double-roll flow pattern is generally stable at a submerged entry nozzle immersion depth of 170 mm.     

电渣重熔脱硫技术研究进展

Electroslag remelting (ESR) gives a combination of liquid metal refining and solidification structure control. One of the typical aspects of liquid metal refining during ESR for the advanced steel and alloy production is desulfurization. It involves two patterns, i.e., slag–metal reaction and gas–slag reaction (gasifying desulfurization). In this paper, the advances in desulfurization practices of ESR are reviewed. The effects of processing parameters, including the initial sulfur level of consumable electrode, remelting atmosphere, deoxidation schemes of ESR, slag composition, melting rate, and electrical parameters on the desulfurization in ESR are assessed. The interrelation between desulfurization and sulfide inclusion evolution during ESR is discussed, and advancements in the production of sulfur-bearing steel at a high-sulfur level during ESR are described. The remaining challenges for future work are also proposed.     

利用皮秒激光烧蚀制备非球形铝纳米颗粒

We report the picosecond laser ablation of aluminum targets immersed in a polar organic liquid (chloroform, CHCl₃) with ~2 ps laser pulses at an input energy of ~350 μJ. The synthesized aluminum nanoparticles exhibited a surface plasmon resonance peak at ~340 nm. Scanning electron microscopy images of Al nanoparticles demonstrated the spherical morphology with an average size of (27 ± 3.6) nm. The formation of smaller spherical Al nanoparticles and the diminished growth could be from the formation of electric double layers on the Al nanoparticles. In addition to spherical aluminum nanoparticles, triangular/pentagonal/hexagonal nanoparticles were also observed in the colloidal solution. Field emission scanning electron microscopy images of ablated Al targets demonstrated laser induced periodic surface structures (LIPSSs), which were the high spatial frequency LIPSSs (HSF-LIPSSs) since their grating period was ~280 nm. Additionally, coarse structures with a period of ~700 nm were observed.     

Mineral transition and formation mechanism of calcium aluminate compounds in CaO?Al2O3?Na2O system during high-temperature sintering

The mineral transition and formation mechanism of calcium aluminate compounds in CaO?Al₂O₃?Na₂O system during the high-temperature sintering process were systematically investigated using DSC?TG, XRD, SEM?EDS, FTIR, and Raman spectra, and the crystal structure of Na₄Ca₃(AlO₂)₁₀ was also simulated by Material Studio software. The results indicated that the minerals formed during the sintering process included Na₄Ca₃(AlO₂)₁₀, CaO·Al₂O₃, and 12CaO·7Al₂O₃, and the content of Na₄Ca₃(AlO₂)₁₀ could reach 92wt% when sintered at 1200°C for 30 min. The main formation stage of Na₄Ca₃(AlO₂)₁₀ occurred at temperatures from 970 to 1100°C, and the content could reach 82wt% when the reaction temperature increased to 1100°C. The crystal system of Na₄Ca₃(AlO₂)₁₀ was tetragonal, and the cells preferred to grow along crystal planes (110) and (210). The formation of Na₄Ca₃(AlO₂)₁₀ was an exothermic reaction that followed a secondary reaction model, and its activation energy was 223.97 kJ/mol.     

含细夹层的分矿充填层中流动特性的可视化

Ore particles, especially fine interlayers, commonly segregate in heap stacking, leading to undesirable flow paths and changeable flow velocity fields of packed beds. Computed tomography (CT), COMSOL Multiphysics, and MATLAB were utilized to quantify pore structures and visualize flow behavior inside packed beds with segregated fine interlayers. The formation of fine interlayers was accompanied with the segregation of particles in packed beds. Fine particles reached the upper position of the packed beds during stacking. CT revealed that the average porosity of fine interlayers (24.21%) was significantly lower than that of the heap packed by coarse ores (37.42%), which directly affected the formation of flow paths. Specifically, the potential flow paths in the internal regions of fine interlayers were undeveloped. Fluid flowed and bypassed the fine interlayers and along the sides of the packed beds. Flow velocity also indicated that the flow paths easily gathered in the pore throat where flow velocity (1.8 × 10?5 m/s) suddenly increased. Fluid stagnant regions with a flow velocity lower than 0.2 × 10?5 m/s appeared in flow paths with a large diameter.     

一种Buck-Boost直-交变换器的新控制策略的研究

高电能质量的直-交变换器在生产和研究领域越来越受到人们的重视.Buck-Boost直-交变换器具有较低的谐波分量,可以消除传统控制理论中的动态调整过程.变换器由两个完全相同的Buck-Boost直-直变换器反串联组成.两个变换器给定电压的幅值相同、相角相差180o,迭加后在输出端得到正弦电压.采用能量控制的方法,使每次从输入端传递到输出端的能量等于给定所要求的正弦波能量与负载所需能量的代数和.仿真结果证明了基于能量传递控制的Buck-Boost直-交变换器控制策略的正确性.     

"得"句中主语S的构成

从句法结构方面考察和分析“得”字句中“得”前的主语S。根据主语S是否出现,“得”句可分为主语未省略句和主语省略句两类,其中,主语省略的情况比较普遍。在主语未省略的情况下,主语大多由体词和体词性短语充当;在主语省略的情况下,主语承某一句省略占了相当的比例。     

审美救赎论:从"人生的艺术化"到"审美化生存"

在阐述审美救赎论时,不倚重被目前的学术界炒得很热的社会批判理论,把关注的重心投向被学界淡忘的朱光潜先生和宗白华先生的审美思想。与西方现代的学术思潮有着密切联系的朱光潜先生,其“人生艺术化”主张还是相当“古典”的,而学术取向颇具古典味的宗白华先生,其“审美化生存”思想则更具现代性。     

基于频响分析法的脉冲电源与容性负载间匹配电路设计

为克服传统的基于负载匹配法设计的匹配电路存在导致容性负载上脉冲电压上升率明显降低的不足,提高脉冲电源在容性负载下的应用效果,提出了将频响分析用于设计脉冲电源与容性负载问匹配电路的方法．基于此法设计了一种由电感（Lm）支路和与其并联的阻-容（Rm-Cm）串联支路构成的匹配电路,当Lm、Rm和Cm满足使容性负载上的脉冲电压（u2）与脉冲电源输出的脉冲电压（u1）之比（u2/u1）的频响特性,在脉冲电源输出的脉冲电压的有效频谱范围内接近不失真系统频响特性的条件时,可在容性负载上得到既无振荡,且上升率高的脉冲电压．实验验证该匹配电路是有效的．     

中频直流点焊机恒流控制方法研究与仿真

针对电阻点焊过程存在的负载电阻非线性变化而导致焊接电流不稳定的问题,提出了模糊控制和PI控制二者相结合的控制算法.利用模糊控制设计了比例系数和积分系数可以实时在线整定的PI控制器,构建了中频直流点焊电源的系统模型,使PI控制输出量通过PWM发生器产生4路占空比恒定而移相角实时变化的PWM波,实现对全桥逆变器的移相调压,...     

高校“80后”辅导员队伍“三化”建设途径探索

分析了高校"80后"辅导员队伍建设的各类挑战,对高校"80后"辅导员队伍实现"三化"的建设途径进行了探索,以期建设一支"专业化、职业化、专家化"、素质过硬、结构合理且相对稳定的高校"80后"辅导员队伍,实现高校人才的培养目标和稳定发展。     

倒"T"形叠合简支板的试验研究

利用实际工程中应用的倒"T"形板构件,根据叠合层和二次配筋的不同制作各种试验构件,采用普通标准粘土砖分级施加均布荷载的方法,进行了均布静荷载试验.研究结果表明:当倒"T"形板肋部面积合适且叠合面(构件翼缘)粗糙程度满足混凝土结构设计规范要求时,叠合面具有足够的粘结抗剪能力,能够保证叠合板的整体受力工作性能;叠合板后浇混凝土,通过二次配筋可以提高其跨中截面的受弯承载力,且可以较大幅度地提高叠合板的延性,从而增强建筑结构的抗震性能.     

逃禅绣佛长斋里,避世佳人锦瑟旁——论王士禄的"逃"情结

世论王士禄大多简单类比于乃弟渔洋，称为“神韵”理论的先驱或同路人，实则其人生形态、诗学倾向皆与渔洋颇有分别，其“时逃于贝叶，时逃于绮语”的“逃”情结更是我们可藉以窥探清初朝堂诗歌群体心态的一扇窗口。     

"可以"用法浅探

“可以”具有助动词和形容词两种用法:做助动词时一般能和除能愿动词以外的大多数动词搭配,还能和一些单音词形成较为固定的搭配;做形容词既可表示程度高,也可表示程度不高,其被动和消极色彩较浓。     

氧化钽/氧化铝薄膜的阻变特性和突触特性

通过微电子加工工艺,制备出具有ITO/TaO_x/AlO_x/Ti结构的双介质层阻变存储器.器件中引入的氧化铝介质层有效地减小了器件的运行电流,降低了高/低阻态间切换所需的功耗,并增大了高/低阻态电阻比值.研究表明,器件的高低态电阻与其切换电压均有良好的稳定性和均匀性,且器件表现出可靠的擦写性能与保持性能.进一步研究表明,器件高阻态导电受肖特基发射机制主导,低阻态导电受空间电荷限制机制主导.器件还具有连续可调的电阻渐变行为,利用反复电脉冲刺激下的器件电阻变化来表征突触的权值,可以模拟突触行为.