B-BBM方程解的Gevrey类正则性

研究了周期边界条件下B-BBM方程解的性态．在二维情况下证明了解在关于空间变量的Gevrey函数类中关于时间是解析的．这个结果说明解关于空间变量是实解析函数．     

关于拟微分算子方程Gevrey解的新探

鹿立江教授在1983年数学学报第1期上研究了一类拟微分算子Cauchy问题的L~2存在性,本文限制非齐次项在Gevrey 函数空间中,得到相应的解也在Gevrey 函数空间中,从而使解更加精确化了;另一方面,本文还继续了Paul R.Wenston 的工作,Paul R.Wenston 在空间L_2([0,T],H_s(R~n))中讨论了一类双曲型拟微分算子方程解的适定性,得到了在Gevrey 函数空间中这类算子的解是存在唯一的.     

拟周期Gevrey势能下Jacobi算子的Lyapunov指数的全域连续性

Lyapunov指数一直是动力系统中的核心概念与研究热点.本文中研究拟周期Jacobi算子模型所对应的Lyapunov指数.我们使用解析逼近,次调和函数,Birkhoff遍历定理,大偏差定理和雪崩原理等方法和理论,证明在势能为s-Gevrey函数(s<2)的条件下,若频率是强Diophantine数,Lyapunov指数关于能量是全域连续的.     

分数阶漂移-扩散模型解的Gevrey解析性和衰减率

目的 研究一类分数阶漂移-扩散模型整体解的Gevrey解析性和衰减率，该模型是半导体中经典模型Poisson-Nernst-Planck方程组的推广模型，数学形式上表现为分数阶非线性抛物型和椭圆型偏微分方程耦合而成的混合型方程组。方法 利用多线性奇异积分算子理论和Fourier微局部分析技术进行研究。结果与结论证明了分数阶漂移-扩散模型在临界Fourier-Besov空间中的整体解是Gevrey解析的，并得到了此整体解的衰减率。     

不可压流在Fourier-Besov空间中的Gevrey正则性及时间衰减

利用多线性奇异积分和频率分析技术,得到分数次不可压流方程在Fourier-Besov空间中的全局适度解的适定性和Gevrey正则性,进而得到全局解在Fourier-Besov空间中的时间衰减率.     

Gevrey势能的离散拟周期 Schrodinger算子的非扰动Anderson局域化

考虑一类具有Gevrey势能的离散拟周期Schrodinger算子, 其中其势能可写成一维环面上的大值解析函数加上Gevrey小扰动. 用大偏差定理和半代数理论证明在大系数下, 对任意的固定相位以及对几乎所有的频率, 该算子满足非扰动的Anderson局域化.     

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.     

气体扩散层集流体对Ni(OH)2纳米结构电化学性能的影响

We report the electrochemical performance of Ni(OH)₂ on a gas diffusion layer (GDL). The Ni(OH)₂ working electrode was successfully prepared via a simple method, and its electrochemical performance in 1 M NaOH electrolyte was investigated. The electrochemical results showed that the Ni(OH)₂/GDL provided the maximum specific capacitance value (418.11 F·g?1) at 1 A·g?1. Furthermore, the Ni(OH)₂ electrode delivered a high specific energy of 17.25 Wh·kg?1 at a specific power of 272.5 W·kg?1 and retained about 81% of the capacitance after 1000 cycles of galvanostatic charge–discharge (GCD) measurements. The results of scanning electron microscopy (SEM) coupled with energy-dispersive X-ray spectroscopy (EDS) revealed the occurrence of sodium deposition after long-time cycling, which caused the reduction in the specific capacitance. This study results suggest that the light-weight GDL, which can help overcome the problem of the oxide layer on metal–foam substrates, is a promising current collector to be used with Ni-based electroactive materials for energy storage applications.     

全尾砂膏体充填材料早期强度、性能改善及稳定性分析

High-density tailings, small cementitious materials, and additives are used for backfill materials with poor early compressive strength (ECS), which may greatly affect the mining and backfill cycle, to prepare paste backfill materials (PBMs) with a high ECS. The effects and mechanisms of different early strength agents on the property of PBM are investigated. The action mechanism of additives on the properties of PBM is also analyzed through X-ray diffraction, scanning electron microscope, and energy dispersive spectrometry. Results show that the effects of single-component additives 1, 3, and 6 are better than those of the other additives, and their optimal dosages are 3wt%, 1wt%, and 3wt%, respectively. The optimum multicomponent combinations are 1wt% of additive 1 and 1.5wt% of additive 6. The ECS of the paste with additive 10 increases to a greater extent than that of the other pastes because of the synergistic action of additive 1 with additive 6. The hydration product of Ca(OH)₂ is consumed, and more C–S–H gels are generated with the addition of additives to paste. Tailings particles, ettringite crystals, and gels intertwined with one another form a dense net-like structure that fills the pores. This structure can significantly improve the ECS of PBM.     

低能质子对辐照富镍TiNi合金薄膜显微组织、马氏体转变和力学性能的影响

Ni–48.5at%Ti thin films were irradiated in the austenite phase by different energy-level protons at a dose rate of 1.85 × 1012 p/(cm2·s), and the total dose was 2.0 × 1016 p/cm2. The microstructures of the thin films before and after irradiation were evaluated by transmission electron microscopy (TEM) and grazing-incidence X-ray diffraction (GIXRD), which showed that the volume fraction of Ti₃Ni₄ phase elevated with proton energy level. The influence of proton irradiation on the transformation behavior of the TiNi thin films was investigated by differential scanning calorimetry (DSC). Compared with the unirradiation film, the reverse transformation start temperatures (A_s) decreased by about 3°C after 120 keV proton-irradiation. The proton irradiation also had a significant effect on the mechanical properties of the TiNi thin films. After 120 keV energy proton-irradiation, the fracture strength increased by 8.44%, and the critical stress increased by 21.1%. In addition, the nanoindenter measurement image showed that the hardness of the thin films increased with the increase of proton-irradiation energy. This may be due to the defects caused by irradiation, which strengthen the matrix.