风化岩石的破碎分形及其工程地质意义

利用分形统计的方法,对风化花岗岩矿物成分的粒度分布特征进行了分析和统计,并根据分析的结果指出,岩石的风化破碎过程具有分形特征。其粒度分布的双对数曲线为多段折线,不同斜率的折线段对应不同的分形维。因此,分形维至少有2个数值,一为结晶颗粒粒度分形维,一为碎裂颗粒粒度分形维。同时,根据试验结果和理论分析得到,碎裂粒子的累积频率分布也符合指数分布,并给出了用指数分布系数求解碎块的碎裂概率的理论计算公式。随后,讨论了碎裂分形维和岩石强度与颗粒结构的关系,并以岩石的降维碎裂演化,得到以分形维描述的岩石风化速率。     

玄麦甘桔颗粒不同厂家质量比较

目的:比较不同厂家玄麦甘桔颗粒质量差异。方法:依照2015年版《中国药典》一部玄麦甘桔颗粒质量标准对本院以及9个不同市售厂家18批次的样品进行含量、性状、溶化性以及粒度检查,考察其质量。结果:18批次样品性状、溶化性以及粒度检查均符合规定,但是不同厂家、不同批次之间含量差异较大。结论:不同厂家、不同批次玄麦甘桔颗粒质量均存在显著差异,各厂家需进一步做好质量控制。     

基于回归正交设计的沉砂池细砂分离特性分析

悬浮颗粒粒度特性是影响旋流沉砂池设计与运行效能的重要因素之一,我国城镇污水中无机物粒径细微,不宜直接采用常规参数取值进行设计。针对城镇污水中无机悬浮颗粒的粒度分布特征,构建了比氏旋流沉砂池模型,以回归正交试验设计为手段,开展了数值模拟与实际物理模型相结合的研究。基于悬浮颗粒不同粒径范围(0～100、100～200、200μm),建立了分离效率与影响因素之间的多元回归模型,明确了各因素对不同粒径颗粒去除率的影响规律及优化运行参数。不同粒度范围悬浮颗粒去除的各最优工况中,搅拌桨转速和水力停留时间各不相同,适当增加水力停留时间和转速,可以在一定程度上提高对细微无机颗粒的分离去除效能,但对粒径100μm的颗粒去除率提升空间较低。在优化工况条件下,物理模型试验结果与回归模型分析的误差为1.86%～4.20%,具有良好可信度。     

粉煤灰的粒度分形评价及颗粒特征分析

针对不同细度的粉煤灰,引入分形理论探讨了粉煤灰的粒度分布特征,在激光粒度分析试验的基础上,计算了其各自相应的分形维数,证明了其不失为一种较好的评价粉体粒度特征的理论方法;同时对其颗粒性状如:在水泥基材料中的密实填充效应、颗粒形貌等进行了系统的试验研究,结果表明:70%水泥和30%超细粉煤灰颗粒混合相比于纯水泥颗粒能更好的满足Horsfield理想填充,而其特有的形貌特征使其在水泥基材料中具有较好的减水增强效应。     

粒度分布对胶结砂岩力学特性的影响

储层出砂过程中砂岩颗粒的离散与其细观结构性有密切关系。以胶结砂岩为研究对象,基于三维颗粒流数值模型(PFC3D)建立4种不同粒度分布的数值模型,模拟剪切过程的砂岩力学响应,研究不同粒度分布的砂岩体应力比、体应变、配位数和黏结破坏与轴应变之间的关系。结果表明:粒度分布对砂岩力学特性的影响较大,仅基于随机方法产生颗粒建立的数值模型不能完全代表实际砂岩的物理结构。须根据实测的砂岩粒度分布建立三维数值模型,才能准确描述储层砂岩的力学特性。粒径越小,连接的颗粒越少,自由度越大,开采中成为离散颗粒的可能性越大。     

仿刺参摄食砂砾粒度的选择性研究

在对自然海区和池塘养殖的仿刺参消化道内含物中砂砾粒度调查的基础上,选择不同粒度的砂砾作为试验材料,对苗种培育阶段不同规格仿刺参的摄食行为进行了研究。结果表明:仿刺参对摄食的砂砾粒度的选择性十分显著,自然海区仿刺参依生存环境的差异,其消化道内砂砾粒度组成比例略有差异,但其60%粒度组成区间为0.0625⁰.5 mm;池塘养殖仿刺参消化道内砂砾粒度组成60%粒度区间为<0.25mm;室内试验中,在各粒级砂砾比例相同的条件下各试验组仿刺参均表现出一致的粒度选择性,在其选择的砂砾颗粒粒度中,60%以上的颗粒粒径为0.1250.5 mm;池塘养殖仿刺参消化道内砂砾粒度组成60%粒度区间为<0.25mm;室内试验中,在各粒级砂砾比例相同的条件下各试验组仿刺参均表现出一致的粒度选择性,在其选择的砂砾颗粒粒度中,60%以上的颗粒粒径为0.125⁰.5 mm。因此可认为仿刺参摄食砂砾粒度的选择范围为0.1250.5 mm。因此可认为仿刺参摄食砂砾粒度的选择范围为0.125⁰.25 mm。     

基于不同质地土粒度测试方法的研究

土的粒度组成是土的基本物理属性之一,传统的土的粒度分析方法有移液管法和密度计法,激光法是近年来新兴的粒度分析方法。然而,这三种方法由于其测试原理的差异导致其测试结果存在定性及定量的差异。本文研究选取粉土和粉质黏土两种不同质地土,通过进行室内粒度分析试验,描述了移液管法、密度计法及激光法三种方法测得结果的粒径分布曲线特征,并讨论了三者之间的差异,结果表明:三种粒度分析方法中激光法精密度最高,移液管法次之,密度计法最低;粒径在2~0.1mm范围内时,对于粉质黏土和粉土两种不同质地土,三种测试方法测试结果均无显著差异;粒径小于0.1mm时,移液管法和密度计法对粉质黏土的测试结果没有显著差异,均显著高于激光法,而粉土的测试结果则为移液管法最高、密度计法次之、激光法最低。在测定土的粒度组成时,激光法与移液管法之间可建立相应的转换关系。     

集料粒度分布的概率研究

本文使用数字图像处理技术,利用颗粒群特性研究中取得的一些结论,分析了三种不同产地4.75～9.5 mm粒径范围的花岗岩颗粒粒度分布规律,为今后的碎石生产控制与精确级配设计进行理论铺垫.     

基于粒度熵概念的贝壳砂颗粒破碎特性描述

对取自福建莆田湄洲湾海域的贝壳砂进行了不同围压、不同相对密度下的三轴排水剪切试验,同时考虑了尺寸效应的影响。依据试样试验前后粒径分布资料,在统计熵概念基础上提出颗粒破碎粒度熵模型对其破碎率进行了度量,并与Hardin颗粒破碎模型进行了比较,结果表明：贝壳砂颗粒破碎率与围压、相对密度及试样尺寸均有关系,在相同试验条件下,贝壳砂颗粒破碎程度随着试样尺寸的增加而增大,随着围压的增加而增大;当相对密度较低时,颗粒破碎率呈增大趋势;相对密度增加到较高值时,颗粒破碎程度减弱;贝壳砂三轴压缩前后的级配曲线均可以通过粒度熵模型参数表征,其中相对基础熵参数（NB）较好地反映了颗粒破碎程度大小,破碎率愈高,NB值愈小,NB与Hardin破碎率存在显着的线性关系。贝壳砂颗粒破碎粒度熵参数能较好地描述其颗粒破碎行为,为岩土介质材料的颗粒破碎分析提供了一个新的量化指标。     

在自然状态下密度对无机渗透复合聚苯乙烯保温板的性能影响

为了研究AEPS板在自然状态下密度对其性能的影响,通过检测不同密度AEPS板的导热系数、垂直于板面的抗拉强度、抗压强度、燃烧性能,分析密度与四者之间的变化规律。结果表明:随着AEPS板的无机粉料填充量增加,其燃烧性能、导热系数、抗压强度得到了提高。聚苯颗粒之间的孔隙率以及聚苯颗粒的粒度在一定程度上影响了垂直于板面的抗拉强度,聚苯颗粒的粒度越大,垂直于板面的抗拉强度越小。     

pH值对工程废浆稳定、絮凝及固结特性的影响

在影响药剂真空预压法处理工程废弃泥浆效果的诸多因素中,pH值是其中最重要的因素之一。文中关于pH值对工程废弃泥浆稳定、絮凝和固结特性的影响进行了研究。首先探讨不同pH值时废浆中土颗粒Zeta电位的变化规律;然后研究泥浆不同pH时絮凝剂APAM的最佳添加量和不同pH值调节方式时废浆的絮凝效果;最后通过固结试验分析了在絮凝剂APAM添加量相同情况下不同pH值导致废浆的不同固结特性。研究结果表明：①土颗粒表面Zeta电位的绝对值随废浆pH值的增大而减小,颗粒粒径随pH值的减小呈增大趋势,特别是在酸性条件下,废浆中土颗粒更容易发生聚沉,小于0.01mm的土颗粒多变为0.01~0.02mm的土颗粒;②不同pH值的废浆在达到最佳絮凝状态时各条颗分曲线相差不大,但是APAM的最优添加量随着废浆的pH值变化而变化;③pH值的不同调节方式对废浆的絮凝效果有较大影响,相同pH值时,采用CaO调节方式得到的废浆絮体粒径要比采用NaOH调节方式得到的废浆絮体粒径要大;④固结试验表证明pH值接近中性泥浆絮体的固结系数最大,建议在药剂真空预压处理工程废弃泥浆时将pH值调节至中性。研究成果对药剂真空预压乃至压滤、离心法处理工程废弃泥浆实践均具有一定的实际指导意义。     

Grouping methods for MPS soot transport model and its application in large-scale enclosure fires

A soot transport model called Multi-Particle-Size model (MPS model) was developed to improve the prediction of soot movement by considering the uneven mass size distribution of soot particles and the influence of particle size on the gravitational settling. The model requires a sophisticated grouping method to divide the soot particles into several groups and determine the representative size for each group. In this paper, several soot particle grouping methods and the approach to calculate the representative sizes are developed with the aim of balancing the computational efficiency and the prediction accuracy of the model. The performance of the MPS model when different grouping methods are applied is investigated through the comparison of the predicted movement of soot particles generated from several materials. Based on this analysis a grouping method that results in the identification of three groups is shown to be sufficient to represent the influence of particle size on the gravitational settling for a variety of combustible materials and the computational cost of the extra governing equations for the transport of soot particles in the groups is acceptable. Furthermore, the efficiency of the model is demonstrated by simulating soot movement in a large-scale industrial building with a high ceiling.     

Size, number and chemical composition of nanosized particles in drinking water determined by analytical microscopy and LIBD

In this paper we comprehensively characterized particles in drinking water originating from a lake water source. We focused on particles smaller than a few hundred nm. Several analytical techniques were applied to obtain information on number concentration, size distribution, morphology and chemical composition of the particles. Morphological information was obtained by atomic force microscopy (AFM) analysis. Two types of particles, spherical aggregates up to a few tens of nm and elongated fibers were identified. Similar structures were also observed in transmission electron microscope (TEM) images. A size distribution of the particles was obtained by applying image analysis (IA) tools on the TEM images. IA results showed an exponential increase of the particle number concentration down to 40 nm, which is the lower detection limit of our setup. The total number of particles down to 10 nm and the average particle diameter were determined with the laser-induced breakdown detection (LIBD) method. The results were in good agreement with the TEM-IA data and showed a total number concentration of roughly 10(8) particles/mL in the purified water. The carbon of the particles was investigated with scanning transmission X-ray microscopy (STXM), which revealed that most particles were organic matter; the C-1s spectra were typical for dissolved organic matter. The methods were applied to characterize the particles from two different drinking waters treated with different methods (conventional vs. ultrafiltration (cut-off 100 kDa)). The results showed that the particle number density following ultrafiltration was lower by a factor of 5-10, compared to conventional treatment. However, the average particle diameter in the finished water of both treatment trains was roughly the same.     

纳米ZrO_2的应用及粒度测量分析

简要介绍了ZrO2及纳米ZrO2的应用,同时介绍了纳米ZrO2粒度表征的不同方法,如电子显微镜分析法、比表面积法和激光粒度法。对不同方法进行分析比较,不同的表征方法,各有侧重点,都不能测得实际粉末颗粒的绝对大小。所以纳米ZrO2在不同的应用领域,应采用不同的表征方法。     

密度计法颗粒分析试验后水筛法研究

通过对密度计法颗粒分析试验的后水筛法和先水筛法进行比较试验，综合分析两种模式下粒径分布曲线存在差异的原因，探寻后水筛法的可行性。试验结果表明：后水筛法中未滤出的大颗粒在悬液中下沉，影响1min时比重计读数，并夹带粘粒下沉，对试验结果造成误差；相同土样的两组粒径分布曲线具有很好的相关性，因此，后水筛法在经过准确的粘粒含量校正后，才能应用于生产性试验。     

Study on the real-time size distribution of smoke particles for each fire stage by using a steady-state tube furnace method

For the analysis of the adverse effects of smoke on health, it is essential to determine the amount and location of smoke particles deposited in the respiratory tract. However, the deposition characteristics of the particles are influenced by their morphology and size distribution. Moreover, the real-time particle size distribution during inhalation is important for determining smoke particle deposition in the lungs. Smoke particles generated under different fire conditions differ in their physical and chemical characteristics. Thus, there is a need to adopt international standard methods for characterizing the particles generated in fire. In the present study, the size distributions together with morphology of smoke particles were measured for each fire stage by using the steady-state tube furnace method given in ISO/TS 19700. The size distributions of smoke particles from wood and polypropylene (PP) were measured in real time by using an electric low-pressure impactor (ELPI⁺), and their morphologies were analyzed using transmission electron microscopy (TEM).     

Using portable particle sizing instrumentation to rapidly measure the penetration of fine and ultrafine particles in unoccupied residences

Much of human exposure to particulate matter of outdoor origin occurs inside buildings, particularly in residences. The particle penetration factor through leaks in a building's exterior enclosure assembly is a key parameter that governs the infiltration of outdoor particles. However, experimental data for size‐resolved particle penetration factors in real buildings, as well as penetration factors for fine particles less than 2.5 μm (PM_2.5) and ultrafine particles less than 100 nm (UFPs), remain limited, in part because of previous limitations in instrumentation and experimental methods. Here, we report on the development and application of a modified test method that utilizes portable particle sizing instrumentation to measure size‐resolved infiltration factors and envelope penetration factors for 0.01–2.5 μm particles, which are then used to estimate penetration factors for integral measures of UFPs and PM_2.5. Eleven replicate measurements were made in an unoccupied apartment unit in Chicago, IL to evaluate the accuracy and repeatability of the test procedure and solution methods. Mean estimates of size‐resolved penetration factors ranged from 0.41 ± 0.14 to 0.73 ± 0.05 across the range of measured particle sizes, while mean estimates of penetration factors for integral measures of UFPs and PM_2.5 were 0.67 ± 0.05 and 0.73 ± 0.05, respectively. Average relative uncertainties for all particle sizes/classes were less than 20%.     

3D Image Segmentation of Aggregates from Laser Profiling

Abstract: In digital imaging of discrete particles, such as stone aggregates, segmentation is one of the most important processes. Automated scanners of different designs use cameras or lasers to obtain digital images of groups of aggregate particles. To accurately determine particle size and shape parameters, each particle region in the image must be isolated and processed individually. Here, a method for segmenting a particle image acquired from laser profiling is developed using a Canny edge detector and a watershed transformation. Canny edges with rigorous and liberal threshold values are used to outline particle boundaries on a binary image and to check the validity of watersheds, respectively. To find appropriate regional minima in the watershed transformation, a varying search window method is used, where the number of neighboring pixels being compared with the pixel of interest is determined from the height value of the pixel. Test results with this method are promising. When implemented in automated systems that are designed to rapidly assess size and shape characteristics of stone particles, this technique can not only reduce the amount of time required for aggregate preparation, but also increase the accuracy of analysis results.     

Suspended particle size distribution and the performance of deep bed filters

The paper examines the importance of suspended particle size distribution in deep bed filtration. Experiments were conducted with suspensions of different size distributions. The changes in total concentration, concentrations of particles of different sizes and the headloss were observed. The suspension with the largest mean particle size gave the greatest removal. It was also observed that the size distribution changed with depth and time, and this was shown to be crucial in understanding filter behaviour. It was concluded that in modelling filter performance it is not sufficient to use the mean characteristics of the influent suspension. Some evidence was found for the interaction between particles of different sizes, and the particle size distribution also affects the distribution of deposit throughout the bed.     

Prediction of hydro-suction dredging depth using data-driven methods

In this study, data-driven methods (DDMs) including different kinds of group method of data handling (GMDH) hybrid models with particle swarm optimization (PSO) and Henry gas solubility optimization (HGSO) methods, and simple equations methods were applied to simulate the maximum hydro-suction dredging depth (h_s). Sixty-seven experiments were conducted under different hydraulic conditions to measure the h_s. Also, 33 data samples from three previous studies were used. The model input variables consisted of pipeline diameter (d), the distance between the pipe inlet and sediment level (Z), the velocity of flow passing through the pipeline (u₀), the water head (H), and the medium size of particles (D₅₀). Data-driven simulation results indicated that the HGSO algorithm accurately trains the GMDH methods better than the PSO algorithm, whereas the PSO algorithm trained simple simulation equations more precisely. Among all used DDMs, the integrative GMDH-HGSO algorithm provided the highest accuracy (RMSE = 7.086 mm). The results also showed that the integrative GMDHs enhance the accuracy of polynomial GMDHs by ~14.65% (based on the RMSE).