Investigations of the particle motion characteristics in the gas solid two phase wake of leeward side circular cylinder

This paper investigates the characteristics of the particle motion in circular cylinder wake flow of leeward side by simulating the micro particle flow around circular cylinder using Euler two fluid model combined with Reynolds stress model. It compares the particle velocity and concentration of different particle size in the leeward area. The results show that the vortex is formed after the gas flowed passing the cylinder, and the concentration and velocity of particles are affected by the turbulent intensity in the leeward side. Gas entrainment vortex and particles own inertia decide the flow form of fine particle around the cylinder. Both effects impact the particle concentration distribution of different size particles in the leeward area. With the increase of particle size, the particle concentration increases at the beginning and then decreases in the leeward area.     

弹性波作用下渗流多孔介质微粒运移分析

弹性波作用下渗流多孔介质微粒运移分析是对目前静态流体或稳态多相渗流中微粒运移/捕集的补充,通过分析弹性波对微粒剥离运移捕集过程的影响,建立弹性波作用下微粒运移模型,得到对微粒运移效果和储层物性变化的影响规律。由推导得到的弹性波作用下微粒剥离临界速度可知,当微粒与孔喉半径的比值越小时弹性波导致的振荡附加力影响越大,临界速度与流体粘度、微粒/孔喉半径比成负相关,与基质胶结程度、结构力、微粒半径、微粒密度成正相关。弹性波作用下微粒运移模型需同时考虑多孔介质渗流速度的变化,此时微粒剥离释放速率增加,但随着波衰减和时间延长而降低,微粒在孔隙表面沉积滞留速率先上升后下降,喉道堵塞的速率有所上升,说明弹性波作用下微粒的剥离和悬浮能力增加,但亦增加了微粒在微细孔喉"架桥"堵塞的可能性。研究结论对岩石物理学和工业化波动处理涉及的储层物性研究具有一定指导意义。     

Study on the Sedimentation Rule of the Particles in Debris Flow

In this paper, according to the study on a great number of experiments and data analyses, the sedimentation rule of solid particles in debris flow is set up. Three main factors that influence the particle sedimentation in debris flow were studied; the basic reasons to influence the particle sedimentation were analyzed. The particle sedimentation in debris flow could be divided into three stages,i, e. the starting stage, the quick sedimentation stage and the accumulation stage,and detailed analysis on the sedimentation process each stage was made. The liquid viscosity, particle quality and additional water pressure have an important role on the sedimentation rule of the particle in debris flow.     

Deformation Feature of the Particle Improved Roadbed of Qinghai-Tibetan Railway

The design idea and the spot experimental scheme of the particle improved roadbed are analysed in detail and deformed law with time of the particle improved roadbed in the cycle of freezing and thawing. The results indicate that the deformation of the particle improved roadbed presents the corresponding frost - heave deformation with the cycle of freezing and thawing. As compared with the ventilated embankment, the particle improved roadbed can, to some extent, shorten the freezing period and ease the frost-heave deformation.     

聚丙烯酰胺对沙化草场土壤颗粒组成的改良效果

为了探讨聚丙烯酰胺对防治北方农牧交错带草场沙化的效果,通过野外小区对比试验和室内分析,采用二因素完全随机设计,研究了在不同植被条件下施用不同剂量聚丙烯酰胺后土壤颗粒组成的变化。结果表明：在30~120kg/hm2的剂量范围内,聚丙烯酰胺能够有效地促进土壤砂粒（2~0.02mm）含量的减少和黏粉粒（<0.02mm）含量的增加,使土壤粗砾化现象得到明显改善。其中尤以30kg/hm2水平的聚丙烯酰胺剂量效果最为明显,砂粒含量的降低幅度比对照提高了6.95~11.29个百分点,黏粉粒含量的增加幅度比对照提高了6.91~12.54个百分点。     

Frost Heave Tests for the Bedding Materials of Face Rockfill Dam in Pushihe, P. R. China

To insure the safe performance of rockfill dam faces in cold seasons, frost tests were carried out at a consistent empirical freezing speed of 20mm/day to study the frost susceptibility of the bedding materials. The influence of gradation, fine particle content, water content, and surcharge of the bedding material on frost heaving were obtained. When fine particle content was below 12%, there was no or only weak frost heaving. Frost increased linearly as fine particle content rose. When the fine particle content was fixed, the linear relationship between the water content and the frost heaving changed with the gradations. Typical water content of 7.5%, fine particle content of 12%, and concrete face density of 59g/cm3 are suggested for the bedding material to avoid frost damage.     

Advance in Study of Theory and Method for Analyzing Characteristics of Particle Group of Binding Material System

The characteristic parameters of particle group, new test method, the theory and method of model formation and the relationship between characteristics of particle group and its essential quality are introduced on the basis of analyzing the research method and theory for characteristics of particle group. The trend of this area is also prospected.     

黄土高原层状云系发展阶段的云物理特征及降水机制分析

由于对复杂云结构特征认识与实时监测识别能力的限制,当前的人工增雨实际作业中,催化最佳时机、最佳部位的判定还是非常困难的,为充分发挥地基、空基和遥感等先进探测装备的作用,建立最佳作业潜力区的实时识别技术,利用2010年4月20日机载DMT云粒子测量、GPS、雷达和卫星等对山西省层状云系发展阶段的探测资料,分析云的微物理结构特征及降水机制,对提高人工影响天气催化作业的科学性具有重要意义,同时为短时临近预报提供新的依据。结果表明：本次探测层状云系发展阶段为多层结构,垂直方向上有3层云,云层之间夹有2个干层,云系厚度约为4500 m,较深厚,高层是冰云Cs,中低层是冷性的As和Ns,符合自然“播种—供水”的降水机制。垂直方向对应3个丰水区,在5400~5600 m高度的丰水区,对应温度为-9~-11.2℃左右,是云粒子快速增长区,凝华增长和冰晶聚合是该区的主要物理过程,3600 m附近大量过冷水存在为降水粒子的长大提供了较好的条件,2800~3200 m高度层（0℃层附近）为融化和碰并增长层。从高层至低层,云粒子谱型有较强的规律性。从本次飞机观测云的结果来看,层积云粒子谱型在降雨形成前,主要为单峰型,降雨形成初期为双峰型。大云滴和部分小冰晶粒子谱型均呈多峰分布,且在800 μm以下出现了明显的不连续现象。探测过程中云粒子浓度在较大的时空范围内起伏较小,而相应时空范围内冰晶粒子浓度均小于10 /L,该云区对于实施人工催化是非常有利的。     

基因枪转化技术在棉花遗传转化上的应用

将外源基因导入棉花的方法很多,目前,最受瞩目的是农杆菌介导法和基因枪转化法。本文对基因枪转化法的基本原理、发展情况、技术的优缺点、影响转化率的主要因素以及此方法在棉花遗传转化中的研究动态进行了分析。     

Submicron Particles Sizing Methods and Measurement Techniques

Due to a series of wonderful characteristics, submicron particles are of high value in national economy, defense modernization and high technology fields, with wide application prospects. Submicron particle sizing methods and techniques are difficult problems in particle research field. Modern methods for particle sizing are stated and analyzed. Some problems are discussed when these methods are used for submicron particles.     

CFD-DEM Simulation to Study the Filtration Characteristic of the Fine Particle in the Filter Media

The gas-solid two-phase flow characteristics of fine particles in the filter media were simulated based on CFD-DEM (Discrete Element Method) in this study, and the particle group, particle size distribution, and the rebound effect between particles, particle and fiber were taken into account the calculations. Additionally, the movement characteristics of the particle group and the deposition form of the fine particles in the fibrous filtration were analyzed. The results indicate that it is convenient and feasible to simulate the filtration process of the filter media as well as the deposition process and form of the fine particle on the media surface using CFD-DEM, and the simulation results are consistent with the experimental observations in the literature. The surface filtration has larger contribution to the filtration process, and most of the particles are captured by the media surface. Meanwhile, parts of smaller particles that enter into the media are captured by the depth filtration. A larger number of particles are collected by the particle-particle capture mechanism. The filtration efficiencies of the filter media are varied with the particle systems, and for the model of the filter media in this study, the filtration efficiency of the multi-particle system is about 20% higher than that of the single-particle one.     

中国冬播小麦面粉颗粒度分布及近红外透射光谱测试技术研究

面粉颗粒度是影响小麦食品加工品质的重要性状。以2001－2002年度来自北部冬麦区、黄淮冬麦区、长江中下游冬麦区和西南冬麦区的256份小麦品种（系）为材料，用激光散射颗粒度分析仪和近红外透射光谱技术对面粉颗粒度进行了研究。结果表明，我国小麦面粉颗粒度分布特点为从北向南，硬质麦分布比例逐渐减少，软质麦分布比例逐     

Analysis on the Temperature-control Effect of the Particle Improved Roadbed in Qinghai-Tibet Railway

Based on the observerd ground-temperature data of the particle improved roadbed in Beiluhe test site of Qinghai-Tibet railway, the characteristics of the ground temperature to the particle improved roadbed and its temperature-control effect are analyzed ,and compared with other frozen soil protecting means. The result indicated that the ground temperature of the particle improved roadbed changes with the seasons,and its characteristics present as a sinusoidal curve. Compared with the normal roadbed, the paticle improved roadbed has cooling roadbed and the effect of protecting frozen soil in mean annual ground temperature. Compared with the normal duct-ventilation embankment, the cooling effect of the particle improved roadbed in cold season is less than that of the duct-ventilation roadbed,and the thermal shield effect is better than that of the particle improved roadbed in warm season. The ground temperature curve has the better tendency of the frozen soil protection. It is an active means of frozen soil protecton.     

橡胶粒子束缚水分的生理功能初析

橡胶粒子是由半单位生物膜包裹的细胞器,表面带负电荷,能够吸附水分子;由于在细胞中橡胶粒子数量极多,故能形成较强束缚水分的能力。产胶植物通过增加橡胶粒子合成,来提高吸水能力,以抵御逆境胁迫;胁迫消除时,又融合小橡胶粒子为更大粒子,来减少橡     

The Application of Fractal to Submicron Particle Sizing

Brownian Motion is one of the important characteristics of submicron particles.On the basis of observatiorl for Brownian motion of particles,the authors present a medel to describethis physieal process by usin g fractal theory a nd this medel is proved to be valid in theory.Throughfurther an alyzing,we establish the relationship between fractal characteristics and particle sizeparameters.Combining image signal processing technique,particle size information can be obtainedby computing fractal dimension values,and then a new method for particle sking will be developedinfuture.     

DEM模拟解析二元混合颗粒粒径偏析分布规律

颗粒粒径偏析分布是高炉炉顶布料过程中不可避免的现象,易造成炉喉处局部料层的空隙度降低和压差升高,影响煤气流的均匀分布,继而间接影响炉况的顺行。通过DEM离散单元法模拟研究二元混合颗粒的偏析分布规律,同时,提出一个偏析指数T,用以表征粒径偏析分布的相对程度。研究结果表明：同一T值图中,相邻区域颗粒的T值相差越大,则该区域颗粒的粒径偏析程度越大;不同T值图中,所有相邻T值之差的平均绝对值越大,则颗粒堆积整体粒径偏析程度越为严重。     

Stability of Particle size Improved Roadbed in Permafrost

Roadbed stability, including thermal and strength stability, is the ability of roadbed to adapt to pavement settlement, slurry effusion, shear slide and haunching up of the roadbed resulting from moving vehicles and many natural influences. Thermal stability is the sensitivity of the thermal state of the roadbed to the external environmental condition. It is the key point of the roadbed stability in permafrost. Research concerning roadbed thermal stability in permafrost is analyzed, and the judgment principle of thermal stability is discussed. The regular change of the ground temperature and deformation of particle size improved roadbeds are analyzed by studying field observation data of the particle size improved roadbed after two freezing and thawing cycles. We conclude that the particle size improved roadbed can raise the upper limit of frozen soil. Based on the judgment principle, the particle size improved roadbed is regarded as a new type of stable structure.     

不同颗粒大小对高光谱估算土壤有机质含量的影响

研究旨在对不同颗粒大小的土样进行土壤有机质含量高光谱估算建模,以期得到土样制备时合适的土样颗粒大小,减少不必要的工作量。笔者对过10、20、60、100目筛的土样进行高光谱数据测量,并对光谱数据进行反射率(R)、反射率一阶导数(R’)和反射率倒数对数[Log(1/R)]3种光谱数据变换,然后运用偏最小二乘回归法(PLSR)、支持向量机法(SVM)和PLSR-SVM相结合的方法建立土壤有机质含量估算模型。研究结果表明：土壤颗粒大小对土壤光谱反射率有明显影响,颗粒越小,土壤光谱反射率越高;运用PLSR-SVM建立的SOM估算模型比只利用PLSR或SVM建立的模型精度高;当土壤颗粒大小＜0.25 mm时,对于SOM光谱估算模型精度的提高没有太大的帮助。该试验为进行土壤有机质含量高光谱估算制备土样提供指导。     

填充床中细小颗粒渗流行为的DEM模拟

为进一步探索COREX过程固体物料的运动状态,对COREX过程中涉及到的细小颗粒渗流行为进行了DEM模拟。考察不同颗粒直径比、阻尼系数及滑动摩擦系数对细小颗粒渗流行为的影响,特别是计算得到不同模拟参数下细小颗粒在填充床内的运动轨迹。模拟结果显示,渗流过程中细小颗粒的平均渗流速度为一定值。随着颗粒直径比的增加,颗粒竖直方向的渗流速度逐渐减小,停留时间与径向弥散逐渐变大。随着颗粒间阻尼系数的增加,颗粒渗流速度逐渐增加,停留时间逐渐减小,径向弥散逐渐变小。滑动摩擦系数对细小颗粒的渗流行为影响较小。从细小颗粒运动轨迹分析可知,颗粒直径比变大时,细小颗粒易在空隙中缓慢移动,易趋于静止床层中,导致颗粒沉积。随着颗粒间阻尼系数变小,颗粒运动轨迹向填充床边缘发展,偏离床层中心。     

不同土壤条件下山农12小麦籽粒HMW-GS积累及GMP粒度分布特征

在沙壤、中壤和黏壤3种质地土壤条件下,以优质强筋小麦品种山农12为材料研究了小麦强势与弱势籽粒高分子量谷蛋白亚基(HMW-GS)积累特征及其与谷蛋白大聚合体(GMP)粒度分布的关系。结果表明,3种质地土壤上,小麦强、弱势籽粒HMW-GS花后14 d均已形成,强势粒HMW-GS含量明显高于弱势粒,说明强势粒具有较强的HMW-GS积累能力。小麦籽粒HMW-GS含量和GMP含量均表现为黏壤土>中壤土>沙壤土,说明黏壤土有利于HMW-GS的积累。小麦GMP粒径分布范围在0.37~245 μm之间;数目分布呈单峰曲线,体积和表面积分布呈双峰曲线。小麦强势粒GMP>100 μm颗粒数目百分比和体积百分比均显著高于弱势粒,强势粒具有更多的大粒径GMP颗粒。小麦HMW-GS含量和GMP含量与<10 μm和<100 μm GMP 颗粒体积百分比均呈显著或极显著负相关,与>100 μm GMP颗粒体积百分比呈显著或极显著正相关,说明大粒径GMP颗粒具有较高的HMW-GS含量。