Influence of the Metal Particle Size on the Ignition of Energetic Materials

A theoretical study of multi‐particle ignition uses a hot spot model which calculates the temperature evolution of individual hot spots in an energetic material. It indicated that ultra‐fine hot particles would be very effective in igniting energetic materials if impinging and penetrating the solid propellant. Igniting mixtures were prepared containing ultra‐fine Ti particles which react fastest compared with coarse particle mixtures, standard B/KNO₃ and black powder. The ultra‐fine particles, however, are obviously oxidized or gasified too fast as to reach the energetic material to be initiated and longer ignition delays are found mainly compared with coarse particle mixtures. An optimized mixture of coarse and ultra‐fine particles would give an improvement of ignition delay times.     

烷基苯磺酸盐的生物降解性与其结构及降解时间的关系研究

运用拓扑指数研究方法，证明阴离子表面活性剂烷基苯磺酸盐系列化合物的生物降解性与其结构及降解时间之间具有明显的相关性，通过回归分析得到降解性（Y）与分子二阶连接性指数（2Xn)及降解时间（T）的相关模型方程式，其复相关系数R＞0．09，标准偏差E＝1．131，平均标准偏差D＝0．017，在传统的单变量QSBR－表面活性剂生物降解与其结构之间的定量关系研究中引入第二变量时间因子，是一种新的尝试，补充和完善了QSBR，提高了结果的合理性和准确性，也扩大了其适用范围，为众多的同名系列化合物生物降解性的预测和评价提供了一种新的方式和手段。     

考虑颗粒凝并情况下充分发展圆管湍流场中的纳米颗粒的迁移(英文)

Numerical simulations of nanoparticle migration in a fully developed turbulent pipe flow are performed.The evolution of particle number concentration,total particle mass,polydispersity,particle diameter and geometric standard deviation is obtained by using a moment method to approximate the particle general dynamic equation.The effects of Schmidt number and Damkhler number on the evolution of the particle parameters are analyzed.The results show that nanoparticles move to the pipe center.The particle number concentration and total particle mass are distributed non-uniformly along the radial direction.In an initially monodisperse particle field,the particle clusters with various sizes will be produced because of coagulation.As time progresses,the particle cluster diameter grows from an initial value at different rates depending on the radial position.The largest particle clusters are found in the pipe center.The particle cluster number concentration and total particle mass decrease with the increase of Schmidt number in the region near the pipe center,and the particles with lower Schmidt number are of many dif-ferent sizes,i.e.more polydispersity.The particle cluster diameter and geometric standard deviation increase with the increase of Damkhler number at the same radial position.The migration properties for nano-sized particles are different from that for micro-sized particles.     

Breakage probability of irregularly shaped particles

The investigation of breakage probability by compression of single particles was carried out. The spherical glass particles and irregularly shaped particles of NaCl, sugar, basalt and marble were subjected to a breakage test. The breakage test includes the compression up to breakage of 100 particles to obtain the distribution of the breakage probability depending on the breakage force or compression work. The breakage test was conducted for five particle size fractions from each individual material, at two stressing rates. Thus obtained 50 breakage force distributions and corresponding 50 breakage work distributions were fitted with log-normal distribution function.Usually, the breakage probability distribution can be found by means of stress or energy approach. The first one uses the stress to calculate the breakage probability distribution. The second approach uses the mass-related work done to break the particle. We prefer to use the breakage force and energy as essential variables. The correlation between the force and energy at their breakage points is obtained by integrating the characteristic force–displacement curve, i.e. the constitutive function of elastic–plastic mechanical behavior of the particle. The irregularly shaped particle is approximated by comparatively “large” hemispherical asperities. In terms of elastic–plastic deformation of the contacting asperities with the plate, a transition from elastic to inelastic deformation behavior was considered. Thus, one may apply the model of soft contact behavior of comparatively stiff hemispheres. Based on this model a relationship between the breakage force distributions and corresponding energy distributions was analyzed. Every tested material exhibits a linear relationship between average breakage energy and average breakage force calculated for every size fraction.For future consideration both force and energy distributions were normalized by division by average force or energy, consequently. The relationship between the fit parameters of normalized energy distribution and corresponding fit parameters of normalized force distribution was established. The mean value and standard deviation of normalized force distribution can be found from mean value and standard deviation of normalized energy distribution by means of system of two linear equations. The coefficients of those linear equations remain the same for all of the above tested materials; particle size fractions and stressing rates. As a result the simple transformation algorithm of distributions is developed. According to this algorithm the force distribution can be transformed into energy distribution and vice versa.     

铜基镀银层中镉含量的测定

将铜基镀银材料在120°C、10%(体积分数)的HNO3中退镀8~15min,然后采用电感耦合等离子体质谱仪(ICP-MS)测定退镀液中镉含量,根据退镀量及所测含量,计算出镀层的镉含量。此方法检出限为0.15mg/kg,实际样品分析的相对标准偏差小于4.8%,样品加权平均回收率为99.2%,能满足镀层有害物质检测的相关规定要求。     

The CREC-GS-Optiprobes and its focal region: Gas–solid flow measurements in down flow reactors

The Chemical Reactor Engineering Center – Gas Solid – Optiprobes (CREC-GS-Optiprobe) can be used to determine particle cluster properties in down flow reactors. These properties include solid hold-up, cluster size and cluster velocity. Critical to this task is the determination of the “focal region”. It is established in this study that the CREC-GS Optiprobes display an “effective focal region” smaller than the focal region calculated using geometrical and optical considerations. In this respect, an “effective focal region” of 118 μm with a standard deviation of 34 μm is established on the basis of different considerations including experimental observations. The existence of this “effective focal region” is most valuable in downer units given it makes the CREC-Optiprobe a suitable tool for measurements of clusters sizes with an average diameter of 84 μm FCC particles as well as local solid concentration.     

基于PLS快速剪枝法的RBF神经网络软测量模型建模方法和应用

提出一种从RBF神经网络隐含层的输出信息出发，通过PLS快速剪枝法，一次性剪去多余节点，生成最优规模的数学解析模型的方法。并用该方法建立了某化工企业精对苯二甲酸(PTA)晶体平均粒径的软测量模型，针对实际对象进行仿真研究，结果表明，该方法计算速度快，建立的模型精度高，适合实际工程应用的需求。     

Simulations and measurements of in‐mold melt flow during the injection molding of polystyrene

Simulations are often used to model polymer flow during injection molding to design molds and select processing parameters. It is difficult to determine the accuracy of these simulations due to a lack of experimentally measured in‐mold velocimetry and melt‐front progression data. This article compares the results from commercial mold‐filling simulation software to experimental data obtained via particle image velocimetry (PIV) in a special optical‐access mold with a rectangular cavity. Moldflow was used to simulate the mold filling by a polystyrene melt in the experimental configuration, and these simulated results are compared to the appropriately averaged time‐varying velocity field measurements. Simulated results for melt‐front progression are also compared with experimentally observed flow fronts. The ratio of the experimentally measured average velocity magnitudes to the simulation magnitudes was found on average to be 0.99 with a standard deviation of 0.25, and the difference in velocity orientations was found to be 0.9° with a standard deviation of 3.2°. The corner area opposite the gate was most problematic for the simulation. The region behind the front also had a relatively high simulation error, though not as severe as that in the corner. POLYM. ENG. SCI. 2013. © 2012 Society of Plastics Engineers     

多变量多时滞非方系统的解耦内模控制

多变量复杂控制系统不仅具有多耦合和多时滞性,还具有结构上的复杂性,即输入输出不等,传递函数为奇异矩阵。传统的多变量内模控制是基于对非奇异对象求逆来进行的,因此很难解决这类问题。针对该情况引入矩阵论中的广义逆概念,通过求对象的广义逆矩阵来设计解耦内模控制器,打破了内模控制只能对方系统进行控制的局限性,并利用泰勒近似很好地解决了多滞后的问题,最后通过设计特殊形式的滤波器,不仅能够消除由纯滞后近似引入的不稳定极点,保证系统的稳定性,且能够保证系统的正则性。仿真结果表明,该方法不仅跟踪迅速,且继承了内模控制的无余差和强鲁棒性,动态解耦效果良好,仅对时滞变化较为敏感。由于系统基于内模控制设计,故模型匹配度越高,系统响应越好。     

煤粉工业锅炉运行数据与供料参数的相关性研究

供料参数的定量测量是锅炉实现自动调节的重要前提。目前直接测量设备受浓度测量范围、成本等因素影响,对工业锅炉适用性有限,而锅炉现有各传感器的部分数据与供料系统关系密切。为了探究根据传感器数据计算供料参数的可行性,以1 Hz频率收集了天津华苑1台58 MW锅炉的传感器数据,在控制其他变量的条件下筛选中间仓重量、一次风总压、锁气阀转速、炉膛压力、烟气氧含量等与供料相关的数据,通过最小二乘法、决定系数等分析方法,定量计算变量绝对值、标准差与供料参数的关系。结果表明,当中间仓进料阀关闭时,可通过中间仓称重以高准确度计算供料器300 s内的平均供料量;使用供料锁气阀转速计算供料量,基于锁气阀填充率和填充密度为定值的假设,低转速下供料曲线符合该假设。但随着锁气阀转速提高,供料量随转速的增长速率以二次曲线规律边际递减,且递减规律存在个体差异;一次风总压计算供料量属于差压法,用于计算供料量时,调整后的决定系数RAdj2>0.98,具有较高的准确性,但需要根据每台设备的累计运行数据计算系数k;炉膛负压波动可较好反映供料波动,但准确性低于使用一次风总压,取样时间为30 s时,供料量标准差-炉膛压力标准差RAdj2达到最大值,为0.890 1;供料量-耗氧量的RAdj2在取样时间200 s时达到最大值0.296 1,供料量标准差-耗氧量标准差RAdj2在取样时间10 s时达到最大值0.640 8,说明耗氧量用于推断供料波动的可靠性中等,推断供料量的可靠性较差,这可能与该锅炉煤粉的掺混比例不稳定使单位质量煤粉热值波动较大有关。     

40%氰草津水悬浮剂的气相色谱分析

采用气相色谱法,内标物为邻苯二甲酸二环己酯,用内标法对40%氰草津水悬浮剂的有效成分进行分离和检验。本方法标准偏差≤0.24,变异系数<0.60%,平均回收率为100.38%。     

Floc breakage in agitated suspensions: Effect of agitation rate

A population balance equation that governs the floc size distribution in turbulent flow, incorporating both the splitting and erosion mechanisms of floc breakage has been presented in previous studies[6,7]. Experiments have been conducted in which transient floc size distributions of dilute suspensions of Kaolin-hydrous ferric-oxide flocs undergoing breakage in agitated batch system are obtained over turbulent microscale shear rates ranging from 60 to 400 sec^?1. Floc size distributions over a range of floc diameters from about 1 to 100 μ m are measured by overlapping techniques, including computerized optical scanning of photographs and rapid electronic sizing of individual flocs using a light blockage transducer. The experimentally determined size distributions are then fit to those computed from the population balance equation, using constrained nonlinear least squares. The splitting frequency of parent flocs is found to vary as the 0.33 power of the parent floc volume and 0.71 power of the shear rate. The average number of daughter fragments produced upon splitting of individual flocs is found to be about 2.5. The mean and standard deviation of the daughter fragments produced upon splitting are found to be in fixed ratio to one another, independent of the parent floc size and shear rate. An appropriately nondimensionalized coefficient characterizing floc erosion has been found to be independent of shear rate.     

Crystal Structure of Monoclinic Hafnia and Comparison with Monoclinic Zirconia

The crystal structure of monoclinic HfO₂ was determined using Weissenberg techniques. Data were obtained from a needlelike single crystal which was grown from a lithium molybdate melt. The crystal was rotated about the α axis, and reflection data were obtained for nine levels. A three-dimensional least-squares refinement confirms that monoclinic hafnia is isomorphous with monoclinic zirconia. The atomic coordinates in the structures agree within one standard deviation. Thus, the fractional coordinates for the metal atom differ by less than 0.0005 and those for the oxygen atoms by no more than 0.01. Whereas three of the seven Hf–O distances are larger than the corresponding Zr–O distances, the average value is approximately 0.01 Å smaller. The average metal-metal distance is approximately 0.02 Å less in HfO₂ than in ZrO₂.     

Statistical properties of interparticle/void distance for amorphous plastics toughening

Statistical properties of interparticle/void distance (ID) for various particle/void and dispersion types are studied in relation with toughening of plastics using computer‐generated three‐dimensional models. Particle/void size groups adopted were either of constant diameter or of log‐normal distribution. Particles/voids were dispersed at uniform‐random or flocculated with multiple clusters. It was found that IDs are (a) of approximately Gaussian distribution for particles/voids of either a constant diameter or a log‐normal distribution, when they are dispersed at uniform‐random, but (b) not of Gaussian distribution for particle/void sizes of bimodal log‐normal distribution, nor for flocculated log‐normal distribution of particles/voids dispersed with multiple clusters. It was also found that the degree of ID uniformity for a single group of log‐normally sized particles/voids is not sensitive to standard deviation of particle/void size. Mixing effect on ID properties using two groups of log‐normally distributed particles/voids with similar mean particle/void diameters was simulated. It was found that, when a significant amount (36 vol %) of particles/voids of a small mean and standard deviation of ID was mixed with a group of particles/voids of a large mean and standard deviation of ID, mean and standard deviation of ID for the mixture were not substantially lower than those of the group of particles/voids of the large mean and standard deviation of ID. It was also found that the degree of ID uniformity for the mixture of the two groups was lower than those of individual groups, indicating that the mixing has deleterious effect on toughening. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 4256–4262, 2006     

A comparative experimental study of the autoignition characteristics of alternative and conventional jet fuel/oxidizer mixtures

Autoignition characteristics of an alternative (non-petroleum) and two conventional jet fuels are investigated and compared using a heated rapid compression machine. The alternative jet fuel studied is known as “S-8”, which is a hydrocarbon mixture rich in C₇-C₁₈ linear and branched alkanes and is produced by Syntroleum via the Fischer-Tropsch process using synthesis gas derived from natural gas. Specifically, ignition delay times for S-8/oxidizer mixtures are measured at compressed charge pressures corresponding to 7, 15, and 30 bar, in the low-to-intermediate temperature region ranging from 615 to 933 K, and for equivalence ratios varying from 0.43 to 2.29. For the conditions investigated for S-8, two-stage ignition response is observed. The negative temperature coefficient (NTC) behavior of the ignition delay time, typical of higher order hydrocarbons, is also noted. Further, the dependences of both the first-stage and the overall ignition delays on parameters such as pressure, temperature, and mixture composition are reported. A comparison between the autoignition responses obtained using S-8 and two petroleum-derived jet fuels, Jet-A and JP-8, is also conducted to establish an understanding of the relative reactivity of the three jet fuels. It is found that under the same operating conditions, while the three jet fuels share the common features of two-stage ignition characteristics and a NTC trend for ignition delays over a similar temperature range, S-8 has the shortest overall ignition delay times, followed by Jet-A and JP-8. The difference in ignition propensity signifies the effect of fuel composition and structure on autoignition characteristics.     

苏嵯输油管道混合原油凝点计算方法

对呼伦贝尔与塔木察格原油不同混合比例下进行凝点测试实验,并根据已有的混合原油凝点模型进行计算,优选了凝点计算模型。通过分析实验数据,采用曲线拟合和最小二乘法进行模型修正两种方法得出苏嵯输油管道混合原油凝点计算公式,并对修正后模型和拟合出的曲线进行验证。实验数据表明修正后的模型较曲线拟合公式对于计算混合原油凝点结果更精准,可使原油的凝点较已有模型计算值的最小平均绝对偏差减小75%,较最大平均绝对偏差减小99%,较最小标准偏差减小45.77%,较最大标准偏差减小75.26%。     

分光光度法测定油井岩芯的吸蓝量

介绍一种确定吸蓝反应终点的新方法。与通常采用的晕环法相比,该方法具有更高的准确性。与普通的分光光度法相比,该方法的优点是不需要用标准蒙脱石样品作标准曲线。根据所建立的方法测定蒙脱石的质量分数时,可以减小由于样品的不均匀性而产生的误差。对于某一油井岩芯样品,经过６ 次平行测定,蒙脱石质量分数的平均值为１５ ．１ ％ ,相对标准偏差为０ ．１ ％ 。     

Injection-Compression Molded Part Shrinkage Uniformity Comparison between Semicrystalline and Amorphous Plastics

Both semicrystalline polypropylene (PP) and amorphous polystyrene (PS) parts were molded by injection-compression molding. The Taguchi method was utilized to investigate the effects of six processing parameters, including mold temperature, compression speed, compression time, compression distance, delay time, and compression force, on part shrinkage uniformity (SU), which was represented by standard deviation of shrinkage. Analyses of means and variance showed that the compression force is the most important parameter for SU of both parts. The compression distance is the second most significant parameter of SU on the PS parts, but it is the least important parameter on the PP part. The optimal processing parameters for improving the SU of both parts were found and verified experimentally.     

Influence of plasticizer on Poisson's ratio of epoxy polymers

A series of simultaneous isothermal tensile creep measurements of the longitudinal extension and the lateral contraction in standard thin tension specimens yielded individual curves for the variation of the lateral contraction ratio (Poisson's ratio) at different loading and temperature steps throughout the viscoelastic spectrum for a series of pure and plasticized cold-setting epoxy polymers. By applying the principle of reduced variables and shifting the isothermal creep curves along the log(time) scale, composite curves were obtained for Poisson's ratio which have the shape of sigmoid curves, thus proving the dependence of this viscoelastic function on time and temperature. It was shown that the corresponding transition regions were shifted towards the origin (t = 0) as the amount of plasticizer was increased, while the shape of the corresponding composite curves did not change and the variation of the logarithmic time factor remained essentially the same but with steeper gradients for increasing amounts of plasticizer. Comparison of the viscoelastic spectra for this function with the corresponding spectra for creep extension, shear and bulk compliances found previously indicated that the spectrum of this function is broader than the others and while it starts to appear earlier than the shear compliance spectrum it disappears after the corresponding bulk compliance spectrum. Finally, glass transition temperatures for the various mixtures were found to be lower by 5° to 10°C than those obtained from measurements using a thermal analyser.     

颗粒形状对包衣设备内药片颗粒运动特性影响的数值模拟

为研究颗粒形状对包衣设备内药片颗粒运动特性的影响,基于离散单元法及自行编写的喷雾区颗粒检测算法,采用数值模拟的方法对五种不同形状(棒状、长椭球、扁椭球、双凸形和球形)的药片颗粒在包衣设备内的运动行为规律进行了研究。分析了颗粒形状对颗粒系统的能量、床面颗粒平动速度、颗粒温度及颗粒流在喷雾区域停留时间的分布及其相对标准差的影响。结果表明,颗粒形状对颗粒的平均动能、颗粒床面速度、颗粒温度、喷雾区域停留时间分布及颗粒间包衣均匀性有重要影响。除双凸形颗粒系统外,对于其他四种形状的颗粒系统,随着颗粒球形度增大,颗粒系统具有的动能、床面速度和颗粒温度均呈减小趋势。除棒状颗粒系统外,对于其余四种形状的颗粒系统,随着颗粒球形度增大,颗粒系统在包衣喷雾区域内平均停留时间减小,平均停留时间的相对标准差增大,包衣均匀性变差。与球形颗粒系统相比,非球形颗粒系统的包衣均匀性更好;药片颗粒形状对包衣设备内颗粒运动特性及颗粒之间的包衣均匀性有重要影响。