AA/MA/AMPS/St分散剂的制备及对钛白粉悬浮稳定性能研究

以丙烯酸(AA)、顺丁烯二酸酐(MA)、2-丙烯酰胺-2-甲基丙磺酸(AMPS)和苯乙烯(St)为单体,通过自由基聚合反应,制备得到了具有两亲结构的聚合物分散剂.将该聚合物分散剂应用于钛白粉在水中的分散,考察了其对钛白粉悬浮稳定性、Zeta电位和粘度性能等的影响.同时,还对该聚合物的结构进行了FT-IR、TGA和XRD分析.结果表明,此聚合物能显著地改善钛白粉在水中的分散情况.     

Experimental Study of Machinability in Millgrinding of SiCp/Al Composites

An attempt was made to investigate the machinability of Si Cp/Al composites based on the experimental study using mill-grinding processing method. The experiments were carried out on a high-speed CNC machining center using integrated abrasive cutting tool. The effects of combined machining parameters, e g, cutting speed(vs), feed rate(vf), and depth of cut(ap), with the same change of material removal rate(MRR) on the mill-grinding force and surface roughness(Ra) were investigated. The formation mechanism of typical machined surface defects was analyzed by SEM. The experimental results reveal that with the same change of material removal rate, lower mill-grinding force values can be gained by increasing depth of cut and feed rate simultaneously at higher cutting speed. With the same change of MRR value, lower surface roughness values can be gained by increasing the feed rate at higher cutting speed, rather than just increasing the depth of cut, or increasing the feed rate and depth of cut simultaneously. The machined surface of Si Cp/Al composites reveals typical defects which can influence surface integrity.     

基于解析解的四阶PDE曲面裁剪方法

该文提出了一种可以广泛应用于四阶PDE曲面的裁剪方法。利用PDE的参数域内的曲线在曲面上投影,得到所求裁剪曲面的边界曲线,然后通过边界曲线的导矢与曲面在边界曲线处的法向量得到边界曲线处的跨界导矢,最后以求得的裁剪曲面的边界曲线以及裁剪曲面在边界曲线处的跨界导矢为PDE曲面的边界条件,用四阶的PDE曲面方程求得PDE裁剪曲面。     

基于弯矩影响面方法的单向板移动荷载最不利位置研究

采用影响面的方法,运用matlab数值分析软件对移动荷载下板的弯矩变化进行了模拟分析。通过控制板的长短边比例,得出不同工况下移动荷载的最不利位置,同时对影响最不利位置的因素进行了相关的模拟研究,得出了长宽比越大的板,其受移动荷载的影响越小的结论。对今后具体的工程计算具有一定的参考意义。     

气雾射流动态传热实验研究

设计搭建了气雾射流动态传热实验装置,建立了二维非稳态导热反问题模型,研究了表面温度和表面热流密度的时间分布.结果表明在冷却过程中缸体穿越喷射区与淌水区历经了几个不同的换热阶段,温度曲线出现了明显的周期性的特点,成功的模拟了连铸二冷气雾冷却周期性换热的特征.     

Non-complete relief method for measuring surface stresses in surrounding rocks

The measurement of surface stresses in surrounding rocks with the use of a relief method of annular hole-drilling was studied by numerical analysis. The stress relief process by hole-drilling was then simulated with the use of finite element method. The influences of the borehole diameter（d）, the initial stresses and the ratio of the initial principle stresses on the variations of the remained stress and the released stress in function of the relief depth（h） were discussed. The relation between the non-dimensional ratio of the released principle strains and that of the initial principle stresses, and the effect of the elastic modulus and the Poisson ratio of the rock mass on the stress relief curves were studied. The results show that the stress relief behavior formulated with the non-dimensional ratio of the released stress and the ratio of h/d is only sensitive to the ratio of the initial principle stresses and the Poisson ratio. The stresses are completely released when h equals 1.6d, and the tensile stresses take place on the bore core surface in the relief measurement process. Finally, a non-complete relief method of annular hole-drilling for measuring surface stress in surrounding rocks is proposed and the procedure is presented.     

Selective removal of heavy metal ions from aqueous solutions with surface functionalized silica nanoparticles by different functional groups

The industrial silica fume pretreated by nitric acid at 80 °C was re-used in this work. Then, the obtained silica nanoparticles were surface functionalized by silane coupling agents, such as（3-Mercaptopropyl） triethoxysilane（MPTES） and（3-Amincpropyl） trithoxysilane（APTES）. Some further modifications were studied by chloroaceetyl choride and 1,8-Diaminoaphalene for amino modified silica. The surface functionalized silica nanoparticles were characterized by Fourier transform infrared（FI-IR） and X-ray photoelectron spectroscopy（XPS）. The prepared adsorbent of surface functionalized silica nanoparticles with differential function groups were investigated in the selective adsorption about Pb2＋, Cu2＋, Hg2＋, Cd2＋ and Zn2＋ions in aqueous solutions. The results show that the（3-Mercaptopropyl） triethoxysilane functionalized silica nanoparticles（SiO2-MPTES） play an important role in the selective adsorption of Cu2＋ and Hg2＋, the（3-Amincpropyl） trithoxysilane（APTES） functionalized silica nanoparticles（SiO2-APTES） exhibited maximum removal efficiency towards Pb2＋ and Hg2＋, the 1,8-Diaminoaphalene functionalized silica nanoparticles was excellent for removal of Hg2＋ at room temperature, respectively.     

Optimizing crashworthiness design of square honeycomb structure简

To provide theoretical basis for square honeycombs used as crashworthy structures, energy-absorption properties of metal square honeycombs and the size optimization were performed. Specific energy absorption （SEA） was defined as the energy absorbed by the honeycomb structure per unit volume. This parameter was often used for determining the crashworthiness of thin-walled structures. In order to find the most optimized metal square honeycomb structure with the maximum SEA and the lowest peak stress, the cell length and the foil thickness of the metal honeycombs were optimized, with a low peak stress and a high SEA set as the two primary objectives. The pre-processing software Patran was used to build FE models, and the explicit solver LS-DYNA was employed to perform the crashworthiness analyses. The results show that the square honeycomb exhibits good energy absorption performance in some cases. The geometry is effective using 16.8% less buffer structure volume than the hexagonal honeycombs with a peak stress limitation of 1.21 MPa.     

Surface resistivity of carbonaceous fiber/PTFE antistatic coatings

Abstract： PAN （Polyacrylonitrile）-based carbonaceous fibers were prepared at the heat treatment temperature （HTT） range of 650 to 900 ℃. The relationships among HTT, carbon content and volume resistivity of the carbonaceous fibers were investigated. The carbonaceous fibers/PTFE （Polytetrafluoroethylene） antistatic coatings were prepared by the spraying technology and the effects of carbonaceous fibers and pigments on surface resistivity of the coatings were systematically discussed. Micrographs provide insight into the antistatic mechanism of the coating. The results show that carbon content of the carbonaceous fibers increases from 68.8% to 74.8% （mass fraction） and the volume resistivity decreases drastically from 1.94× 10^-3 to 8.27× 10 ^-2.cm. The surface resistivity of the antistatic coating is adjustable between 10^5 and 10^8Ω2 to fit the different antistatic materials. Static is dissipated by a conductive network of short fibers and the tunneling effect between the neighboring fibers and conductive pigments. Conductive pigments make the conductive network more perfect and improve the antistatic ability, but insulating pigments acting as barriers for the formation of conductive channel increases the surface resistivity of the coatings. The influence of pigments on the surface resistivity drops gradually with the decrease of the carbonaceous fibers volume resistivity.     

Orthogonal design and numerical simulation of room and pillar configurations in fractured stopes

Room and pillar sizes are key factors for safe mining and ore recovery in open-stope mining. To investigate the influence of room and pillar configurations on stope stability in highly fractured and weakened areas, an orthogonal design with two factors, three levels and nine runs was proposed, followed by three-dimensional numerical simulation using ANSYS and FLAC3~. Results show that surface settlement after excavation is concentrically ringed, and increases with the decrease of pillar width and distances to stope gobs. In the meantime, the ore-control fault at the ore-rock boundary and the fractured argillaceous dolomite with intercalated slate at the hanging wall deteriorate the roof settlement. Additionally, stope stability is challenged due to pillar rheological yield and stress concentration, and both are induced by redistribution of stress and plastic zones after mining. Following an objective function and a constraint function, room and pillar configuration with widths of 14 m and 16 m, respectively, is presented as the optimization for improving the ore recovery rate while maintaining a safe working environment.