Combustion of fine aluminum and magnesium powders in water

Micron-sized metal powders carried by a nitrogen flow were fed along the axis of a cylindrical hydrogen/oxygen diffusion flame. The particles ignited and burned in the water vapor at approximately 2500 K. Experiments were performed at atmospheric pressure. The environment in which particles burned was characterized in detail using computational fluid dynamics. The computations confirmed that the metal powders burned in water while the effect of oxygen and other oxidizing species could be neglected. Combustion was characterized experimentally for micron-sized powders of both aluminum and magnesium. Particle size distributions were measured using low-angle laser light scattering. Optical emission of the burning particles was recorded using filtered photomultiplier tubes. Measured durations of individual particle emission pulses were assumed to represent their burn times; these data were classified into logarithmically spaced time bins. The distribution of the particle burn times was correlated with their size distributions assuming that larger size particles burned longer. It was observed that correlation between the burn times, t, and particle diameters, D, can be approximately described as t ∼ D^0.64 and t ∼ D^0.68 for aluminum and magnesium powders, respectively. The results were compared to previous reports and possible reasons for discrepancies between the present and earlier results were discussed.     

pH值与温度对中空聚合物微球的影响

在高压釜中,以单分散的聚苯乙烯-甲基丙烯酸(P(St-MAA))为种子微球,采用碱中和冷却法制备中空聚合物微球,研究了pH值与温度对中空微球的影响。扫描电子显微镜、透射电子显微镜等测试分析表明,pH值与温度对中空微球的体积变化分数ΔV、中空孔径DHTEM、中空度A影响明显;随着pH值的增大或反应温度的升高,ΔV增大。当反应温度一定时(t=140℃),pH=10.5的乳液制备的中空微球DHTEM约为184 nm,A为17.3%;当乳液的pH一定(pH=12.5),碱中和反应温度以125℃为宜,此时DHTEM约为210 nm,A为24.6%。     

三聚氰胺基螯合树脂的超声合成及在镍离子传感器中的应用

采用超声法制备了三聚氰胺-甲醛-乙二胺四草酰乙酸螯合树脂(MFT)。利用MFT/纳米碳管复合物修饰充蜡石墨电极WGE(MFT/MWCNTs/WGE)制备了一种镍离子传感器。采用场发射扫描电镜及电化学等技术表征了该修饰电极的特性。结果显示,羧基化纳米碳管对MFT螯合树脂具有较强的粘合力,可使该螯合树脂有效地分散,并均匀地吸附在纳米碳管上。MFT/MWCNTs/WGE对镍离子检测效果较好,在1.0×10-11mol/L～1.0×10-10mol/L的浓度范围内,Ni(II)的溶出峰电流与其浓度呈良好的线性增长关系,其线性方程为i(μA)=9.58438+1.07753C x(1×10-11mol/L),R=0.991,检测限为1×10-13mol/L(3σ)。     

旋转/牵引速度比对旋转挤出聚乙烯管结构和性能的影响

采用自行研制的聚合物管旋转挤出装置,研究了旋转挤出过程中旋转/牵引速度比对聚乙烯(PE)管结构和性能的影响。扫描电镜(SEM)和热收缩实验结果表明,通过控制旋转/牵引速度比,可有效调节PE管内串晶偏离轴向的角度,降低轴向取向度,提高PE管的力学性能。当旋转/牵引速度比为0.6时,旋转挤出PE管的环向拉伸强度从常规挤出管的19.4MPa提高到33.5MPa,提高了72.7%。     

Solution of the plane problem for anisotropic media containing an elliptic inhomogeneity with dislocation-like interface

A general form solution of the plane problem for anisotropic media containing an elliptic inhomogeneity with a dislocation-like interface is presented. It is based on the complex series expansion of the stress functions. A general procedure for the determination of coefficients in the series using a continuity condition for the stresses at the imperfect interface and a discontinuity condition for a jump in the normal or tangential displacements at the interface is illustrated. The jump in the displacement components is described by the dislocation-like model based on the assumption that discontinuity of displacement across the interface is linearly proportional to the elastic displacement at the interface in the inhomogeneity. The model can reasonably characterize the imperfect interface from perfect bonding to complete debonding due to separate or combined effect of eigenstrains and far-field tension. Convergence of the results is obtained by truncating a finite number of terms in the series. The present solution is verified with available analytical results for the case of a perfect interface. In this paper, the pattern for the stresses in the heterogeneous anisotropic materials is shown. The effect of imperfect parameters on the distributions of stresses is also discussed. The method and procedure proposed in the paper are useful in analyzing the strength and failure of anisotropic materials containing an inhomogeneity with imperfect interface.     

Interval-parameter robust quadratic programming for water quality management under uncertainty

Effective planning of water quality management is important for facilitating sustainable socio-economic development in watershed systems. An interval-parameter robust quadratic programming (IRQP) method is developed by incorporating techniques of robust programming and interval quadratic programming within a general optimization framework. The IRQP improves upon existing quadratic programming methods, and can tackle uncertainties presented as interval numbers and fuzzy sets as well as their combinations. Moreover, it can deal with nonlinearities in the objective function such that economies-of-scale effects can be reflected. The developed method is applied to a case study of a water quality management under uncertainty. A number of decision alternatives are generated based on the interval solutions as well as the projected applicable conditions. They represent multiple decision options with various environmental and economic considerations. Willingness to accept a low economic revenue will guarantee satisfying the water quality requirements. A strong desire to acquire a high benefit will run the risk of violating environmental criteria.     

IFQP: A hybrid optimization method for filter management in fluid power systems under uncertainty

An interval-fuzzy quadratic programming (IFQP) method is developed for the assessment of filter allocation and replacement strategies in fluid power systems (FPS) under uncertainty. It can directly handle uncertainties expressed as interval values and/or fuzzy sets that exist in the left-hand and right-hand sides of constraints, as well as in the objective function. Multiple control variables are used to tackle independent uncertainties in the model's right-hand sides and thus optimize the overall satisfaction of the system performance. The IFQP method is applied to a case of planning filter allocation and replacement strategies under uncertainty for an FPS with a single circuit. A piecewise linearization approach is firstly employed to convert the nonlinear FPS problem into a linear one. The generated decision alternatives can help decision makers to identify desired policies for contamination control under various total costs, satisfaction degrees, and system-failure risks under different contaminant-ingression/generation rates.     

An interval-parameter two-stage stochastic integer programming model for environmental systems planning under uncertainty

An interval-parameter two-stage stochastic mixed integer programming (ITMILP) technique is developed for waste management under uncertainty. It is a hybrid of inexact two-stage stochastic programming and mixed integer linear programming methods. The ITMILP method can directly handle uncertainties expressed not only as probability density functions but also as discrete intervals. It can be used to analyse various policy scenarios that are associated with different levels of economic penalties when the promised policy targets are violated. More importantly, it can facilitate dynamic analysis of decisions on capacity expansion planning within a multi-region, multi-facility, multi-period, and multi-option context. The results will help to generate a range of decision alternatives under various system conditions, and thus offer insight into the trade-offs between environmental and economic objectives. The ITMILP method is applied to planning facility expansion and waste flow allocation within a waste management system. The results indicate that reasonable solutions have been generated for both binary and continuous variables. The binary-variable solutions represent the decisions of facility expansion, while the continuous-variable solutions are related to decisions on waste flow allocation.     

ECR结合磁控溅射——制备DLC薄膜的新方法

介绍了新型的结合电子回旋共振(ECR)微波等离子体气相沉积与磁控溅射镀膜特点的ECR-650型镀膜系统,并利用该系统通过溅射石墨靶和金属钛靶在不锈钢基底上制备了具有Ti/TiNx/TiNxCy中间层结构的C薄膜。由于镀膜工艺问题,得到的薄膜主要由石墨构成。研究了制备时不同的气压和氩气分压对薄膜表面形貌、硬度等的影响。     

溶液相制备Ⅱ-Ⅵ族半导体纳米材料研究新进展

Ⅱ-Ⅵ族半导体纳米材料具有特殊的物理化学性质,在光学、电学和光电子等领域都有着巨大的应用前景,因此是纳米材料制备领域的研究热点之一。文章主要综述了近年来溶液相中Ⅱ-Ⅵ族半导体纳米材料制备方法的若干进展情况,并展望了其发展趋势。