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.     

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.     

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.     

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.     

向量优化中真有效点之间的联系

对几种主要的真有效点间的关系进行研究.研究结果表明:严有效点是Henig真有效点;强有效点是Borwein真有效点;强有效点是Henig真有效点;强有效点是Hartley真有效点.     

高维自治Birkhoff系统奇点类型及其稳定性

研究了高维自治Birkhoff系统的奇点类型及其稳定性,首先由奇点方程得到系统的奇点及其性质,然后研究了奇点处Fréchet导数的特征根性质,从而判断出高维自治Birkhoff系统的奇点不存在汇和源,只存在双曲奇点.并给出判断奇点稳定性的相关定理.     

二维移动网格方法中边界网格点移动的数值研究

本文对二维移动网格方法中边界网格点移动处理方法进行了探讨,一种做法是把边界上的网格点的移动速度等同于和它相邻的内部点的移动速度,另一种做法是将边界上的网格移动看作一维情形,结合数值算例分析和比较了两种处理方法的效果。     

综合不规则三角网和区域生长的建筑物提取方法

应用激光雷达探测技术(LiDAR)进行建筑物提取其效率一直是工程应用的关键,针对现有先滤波后提取建筑物一类方法效率低下的问题,提出一种综合不规则三角网和区域生长的从原始机载激光雷达数据中直接提取建筑物的方法。首先利用原始点云数据建立不规则三角网,利用三角网中突起物边缘点所在三角形的法向量、边长及高程特征,提取突起物边缘点;然后以提取出的边缘点为种子点,根据三角网连接关系进行区域生长,提取突起物点集合;最后删除集合中点数量较少的非建筑物点集,得到建筑物点集。该方法可直接从原始点云数据中提取出不同建筑物的点集,无需经过滤波操作。通过仿真实验证明该方法在保证建筑物提取准确度的情况下效率有明显提高并且具有一定的适用性。     

一种基于标记点的近景摄影测量系统

给出了一种基于标记点的鲁棒三维重建摄影测量系统;采用编码点和非编码点等标记点方式.为了减少不同图像间误匹配的概率,采用一种新的基于编码点的匹配方法,不同图像间非编码点的匹配从编码点开始,并通过相似性准则、模糊度准则和距离误差准则来剔除误匹配,可获得非常高的正确匹配率.采用一种新的基于标记点的加权迭代特征算法,用编码点恢复相机的投影矩阵,从而可以确定相机的外部姿态参数;用非编码点恢复3D坐标.与已有的加权迭代特征算法比较,该算法避免了所有点参与计算相机的投影矩阵,运算速度更快.由于采用标记点的亚像素定位方法,提高了3D重建精度.实验结果表明,在3D重建方面,该系统是强壮和精确的.     

广义梯度与超有效解

全文先通过引进了超有效,超有效点的定义,并说明了他们的包含关系,然后再定义它们在超有效,超有效点意义下的广义梯度,证明他们在一定条件下的存在性,最后讨论广义梯度与集值向量优化超有效点与超有效点最优性条件的关系。     

歌手比赛评分中的一个概率问题

本文计算出了ｎ个裁判为某名歌手所评ｎ个分中的最高分与最低分是奇异分的概率。为歌手比赛现行评分法中，去掉一个和最氏分的评分方法的合理性找到了理论上的依据。     

对双线铁路开行组合列车中间越行点改建问题的探讨

本文论述了目前我国开行以组合列车为主的重载运输中中间越行点改建的若干重要问题,其中包括设置越行点的必要性、影响越行点数量和设置地点诸因素的分析、越行点股道有效长的确定、越行点图型的选择以及越行点合设与分设等问题。     

三维数据拼接中编码标志点的设计与检测

提出了一种编码标志点的设计与检测方法,以满足三维扫描测量中对大面积物体进行全场检测的编码标志点拼接法的要求。编码标志点由编码点和标志点组成,其中标志点提供位置信息,编码信息被编译储存在编码点的排布中。研究了编码点的数量和编码标志点方案总数的对应关系以及标志点的编码方法。对编码标志点的检测以及偏心误差进行了分析。实验证明,该编码标志点方案简洁、严密,容易识别,达到了设计要求。     

地价监测点空间配置模式研究——以重庆市主城区为例

地价监测点的配置是地价动态监测体系建立中最基本、最关键的一个环节，在对地价监测点内涵分析的基础上，结合了重庆市主城区的实际情况划分地价监测区域，分别建立地价监测点的定量和定位配置模型对重庆市主城区地价监测点进行配置，力求为重庆市乃至全国范围内地价监测点的空间配置在理论和技术上有所帮助。