超细颗粒在声场流化床中的流化特性

在内径为130mm的声场流化床中,以原生纳米级SiO2超细颗粒为物料,在声压水平为0～140dB、声波频率为0～500Hz范围内系统地考察了声波对超细颗粒流化特性的影响。结果表明：当声波频率为100～150Hz、声压大于130dB时,声波可以有效地消除节涌、抑制沟流、降低临界流化速度,显著地改善纳米SiO2颗粒的流化质量。在频率一定的情况下,声压越高,超细颗粒的临界流化速度越低,流化质量越好。当频率低于100Hz或高于150Hz时,随着频率的进一步降低或增加,超细颗粒的临界流化速度都增大,甚至又出现节涌和沟流。声波的效果减弱甚至消失。     

Systemic Immune Effects of Titanium Dioxide Nanoparticles after Repeated Intratracheal Instillation in Rat

The potential immune effects of titanium dioxide nanoparticles (nano-TiO₂) are raising concern. Our previous study verified that nano-TiO₂ induce local immune response in lung tissue followed by intratracheal instillation administration. In this study, we aim to evaluate the systemic immune effects of nano-TiO₂. Sprague Dawley rats were treated by intratracheal instillation with nano-TiO₂ at doses of 0.5, 4, and 32 mg/kg body weight, micro-TiO₂ with 32 mg/kg body weight and 0.9% NaCl, respectively. The exposure was conducted twice a week, for four consecutive weeks. Histopathological immune organs from exposed animals showed slight congestion in spleen, generally brown particulate deposition in cervical and axillary lymph node. Furthermore, immune function response was characterized by increased proliferation of T cells and B cells following mitogen stimulation and enhanced natural killer (NK) cell killing activity in spleen, accompanying by increased number of B cells in blood. No significant changes of Th1-type cytokines (IL-2 and INF-γ) and Th2-type cytokines (TNF-α and IL-6) were observed. Intratracheal exposure to nano-TiO₂ may be one of triggers to be responsible for the systemic immune response. Further study is needed to confirm long-lasting lymphocyte responses and the potential mechanisms.     

滤饼颗粒物性对滤饼特性影响的分析

介绍颗粒的物性及滤饼的特性,通过对形成滤饼的颗粒物性的分析,论述了颗粒的尺寸、颗粒尺寸分布、颗粒密度、颗粒形状和颗粒间附着力对滤饼特性的影响,证实了滤饼的特性与其颗粒物性之间有着密不可分的联系,不同的颗粒物性将直接影响滤饼的特性（尤其是对滤饼比阻）的不同,从而影响过滤的效果。     

TFT玻璃基板中的铂金粒子研究

通过分析玻璃基板制造中存在的铂金粒子的产生机理,为玻璃基板制造中控制铂金粒子的产生提供参考依据,从而降低玻璃基板生产中铂金粒子的发生率。     

RESS法制备微细颗粒的喷嘴内流动特性的数值模拟

为了对RESS法制备微细颗粒过程中喷嘴内流体规律进行研究,通过对超临界流体快速膨胀法（rapid expansion of supercritical solution,RESS）流动过程的研究与分析,建立了喷嘴内超临界流体流动数学模型。对喷嘴内流场和温度场进行研究,考察了预膨胀压力、预膨胀温度、长径比等操作参数对RESS过程的影响,模拟结果表明,喷嘴内部的密度曲线在喷嘴入口段,几乎没有发生变化,而在直管段和出口膨胀段超临界流体密度发生急剧下降;随着长径比的增大,喷嘴内密度曲线变陡;随着长径比的增大,喷嘴出口处流体的温度都变小,过饱和度变大,结晶颗粒使得更为细小。该模型和模拟过程能够为实现制备均一微细颗粒的实际操作条件和优化过程参数奠定基础。     

Separation Characteristics of Inorganic Particles from Rainfalls in Dissolved Air Flotation: A Korean Perspective

Abstract

Many reservoirs have been constructed in Korea to store water resources utilizing the terrain of the land. In general, dam source waters contain algae species that have densities close to that of water. Consequently algae are difficult to remove by conventional gravity sedimentation (CGS), while dissolved air flotation (DAF) is known to be an effective process for the purpose. The same source waters usually also have high turbidities due to mineral soil particles in the wet summer season. Systematic studies on the effect of high turbidity on the DAF process are very limited. In this work, DAF and CGS experiments were carried out to investigate water treatment characteristics and removal efficiencies under various COD/SS and chlorophyll‐a/SS ratios. A kinetic DAF process model was employed to describe bubble‐floc collision and agglomeration, as well as the rising velocity of bubble‐floc agglomerate. Our results showed that the initial collision‐attachment efficiency for the clay floc size range of 100?400 µm was a relatively low value of 0.3. The removal efficiency by DAF was greater than by CGS when chlorophyll‐a/SS ratio was high. It was also found that sedimentation prior to flotation is required for the effective separation of large clay flocs caused by runoff. Our experimental and theoretical results also suggest that the DAF process requires carefully operation in Korea, especially, in the rainy summer season.     

多喷嘴对置式气化炉内气固两相流动与炉壁的颗粒捕捉特性

对多喷嘴对置式气化炉内复杂的气固两相流动与炉壁的颗粒捕捉特性进行三维数值模拟。应用Euler-Lagrange模型模拟气固两相流动,采用Realizable k-ε湍流模型计算炉内气相湍流流场,颗粒轨迹跟踪采用随机轨道模型。模拟结果与冷模测试数据吻合,且流场与热模实验现象一致,壁面捕捉颗粒平均粒径与热态水煤浆气化实验数据吻合。工业规模模拟结果表明,壁面捕捉的颗粒平均粒径呈现一定的规律性,存在两个极大值位置,分别在喷嘴平面下方0.2 m及上方2.8 m处,在喷嘴平面上方,壁面捕捉颗粒粒径随颗粒密度的增大而减小;颗粒沉积能基本覆盖整个炉膛内壁,颗粒在撞击流股作用下在喷嘴平面上方1.8 m及下方1.9 m处沉积量最大;缩短喷嘴上方直段高度将影响炉内流场,拱顶对撞击流股产生一定的限制作用,使其变短变宽,并且使拱顶捕捉颗粒粒径增加,颗粒沉积速率增加。     

浅谈纳米粒子在生物学和医学中的应用

介绍了纳米粒子的基本特征及其在生物学和医学中的应用。     

荷能粒子在类金刚石膜形成中的作用

类金刚石膜由于其优异性能和广泛应用已引起越来越多的研究兴趣。尽管各种化学和等离子体辅助ＣＶＤ和ＰＶＤ技术已用来沉积类金刚石膜（ＤＬＣ膜）,但其形成机理仍不清楚。本文通过分析荷能离子的作用,应用热峰效应和离子刻蚀效应来解释ＤＬＣ膜的形成     

纳米粒子抑制软质聚氯乙烯中增塑剂迁移的研究

使用Brabender塑化仪,通过熔融共混制备了软质聚氯乙烯/无机纳米粒子复合材料;利用加热失重法和傅立叶红外光谱法研究了增塑剂在该材料中的迁移规律。实验结果表明:在软质聚氯乙烯中添加少量无机纳米粒子起到了抑制增塑剂迁移的作用。     

北京市城乡结合部大气可吸入颗粒物中正构烷烃的分析

分不同季节采集分析北京市城乡结合部的大气可吸入颗粒物。用气相色谱-质谱技术分析了北京市城乡结合部大气可吸入颗粒物中饱和烃组分,检测出C11～C37的正构烷烃及其它烃类化合物。正构烷烃分布主要可分为3种类型:前峰型、后峰型、单峰型。利用地球化学的相关参数,同时结合正构烷烃的分布特征,对正构烷烃的污染来源进行分析。前峰型,主要来源于汽车尾气和化石燃料燃烧。后峰型,主要来源于植物蜡。单峰型,既有植物蜡的输入,也有尾气和化石燃料燃烧的输入。对正构烷烃在不同季节大气可吸入颗粒物中分布情况的比较,表明正构烷烃分布随季节有较明显的变化。     

Heterogeneous Structures in the Synthesis of Hydrophobic Lauryl Acrylate-Styrene-Ethylene Glycol Dimethacrylate Copolymer Particles

Novel crosslinked hydrophobic lauryl acrylate-styrene-ethylene glycol dimethacrylate copolymer particles were synthesized with heterogeneous structures by radical suspension copolymerization with benzoyl peroxide as the initiator. Ethylene glycol dimethacrylate was used as a crosslinking agent; toluene, cyclohexanol, 1-octanol and liquid paraffin were used as porogens. The effects of the crosslinking monomer and porogens on the morphologies of the copolymer microspheres were investigated. The copolymers were characterized by FTIR, SEM and swelling in toluene. Permanent pores remained in the dried polymeric particles prepared with nonsolvating porogens at certain crosslink densities as indicated by SEM pictures. The results of swelling revealed that 1-octanol was the most effective porogen, leading to the LA-S-EGDMA copolymer particles with maximum porosity and optimized spheric morphology. Furthermore, lower crosslink density and higher porogen contents promote the formation of porous morphology.     

微乳反胶团体系在纳米超微颗粒制备中的应用

综述了微乳状液体系的应用现状,对微乳反胶团反应器的原理,形成与结构进行了研究与探讨,并进一步阐述了微乳反应器在纳米超微颗粒制备领域中的应用现状。     

团聚硼颗粒在HTPB富燃料推进剂中的流变特性

为了探索球形团聚硼颗粒的制备效果,对端羟基聚丁二烯(HTPB)黏合剂、不同类型的团聚硼颗粒与HTPB黏合剂以一定质量配比形成的悬浮液,以及含团聚硼颗粒HTPB富燃料推进剂流变特性进行了对比研究。结果表明,HTPB黏合剂的表观黏度随温度的升高而降低,最终趋于某一定值;在一定温度下,无定形硼粉经团聚改性后,团聚硼颗粒与HTPB形成悬浮液的表观黏度和屈服值较团聚前降低,且两者均随时间的增加而增加;采用含团聚硼颗粒的富燃料推进剂药浆的流变特性大大改善,有利于含硼富燃料推进剂能量的提高和燃烧性能的改善。     

Influence of Operating Conditions on the Freeze-Drying of Frozen Particles in a Fixed Bed and Modeling Data

Experimental runs have been carried out to investigate the influence of shelf temperature and total gas pressure in the chamber on the primary drying sublimation kinetics of a packed bed of frozen spherical particles of a model 16.6% (w/w) sucrose solution. Sublimation kinetics determined, in situ and on line, by weighing continuously the freeze-dried sample, were observed to increase with the total gas pressures and with the shelf temperatures. A physical model, based on the hypothesis that two “sublimation fronts” advancing at the same time from the bottom of the bed, due to the contact heat flux, and from the top of the bed, due to radiation heat flux, was proposed. Fair agreement was found between simulated and experimental data.     

液固循环流化床中颗粒轴向速度的实验研究

利用超声多普勒测速仪实验测量了液固循环流化床中不同径向位置处颗粒瞬态轴向速度,研究了其概率密度分布特征。采用瞬态速度的标准偏差衡量瞬态速度的波动程度,考察了不同操作形式下的颗粒时均轴向速度的径向分布以及表观液速和颗粒循环速率等操作条件对速度波动程度和速度均衡径向分布的影响,利用相间作用力对两种分布的特点进行了机理分析,并对液固和气固循环流化床中颗粒的流动行为进行了比较。     

在离子液体[BMIM]BF4-水中制备Cu2O粒子

以CuCl2.2H2O和NaOH为原料,离子液体1-丁基-3-甲基咪唑四氟硼酸盐[BMIM]BF4-水混合溶剂为介质,利用化学还原法在112℃反应12 h合成了Cu2O粒子,考察了[BMIM]BF4对产物的影响。用XRD、ESEM/EDS和TEM/SAED对Cu2O粒子进行了结构和形貌表征;用FTIR和TG/DSC证实了离子液体修饰在Cu2O粒子的表面,从而有效地阻止了Cu2O粒子的氧化和团聚;用紫外-可见吸收光谱估测了Cu2O粒子的带隙能量为2.38 eV。离子液体在反应中发挥了还原剂、稳定剂、分散剂和模板剂的多重作用。     

Interactions Between Micron-sized Glass Particles and Poly(dimethyl siloxane) in the Absence and Presence of Applied Load

A technique using a scanning electron microscope to view a fine particle in contact with a flat substrate whilst under load and during its removal is described. The particle is attached to an atomic force microscope cantilever so that the magnitude of the load can be estimated directly from the imaged deflection. Interactions between 5 to 60 μm spherical glass particles and cross-linked poly(dimethyl siloxane) were studied in the presence and absence of load. W_A was estimated to be 74 mJ/m² from the size of the contact area in the absence of load. Using highly flexible cantilevers to apply load resulted in large shear displacements and forces, which distorted the contact area and assisted in particle removal. These shear effects were eliminated by using a more rigid cantilever to measure a normal pull-off force for which the interface toughness, G_c , exceeded 950 mJ/m². The large adhesion hysteresis indicated the presence of chemical bonding, presumed to occur between silanol and siloxane groups. The mode of particle detachment varied significantly with the choice of cantilever, showing evidence of both cohesive failure and interfacial crack propagation. The relevance of these results to the interpretation of AFM data is discussed.     

Porcine Adipose-Derived Mesenchymal Stem Cells Retain Their Stem Cell Characteristics and Cell Activities While Enhancing the Expression of Liver-Specific Genes after Acute Liver Failure

Acute liver failure (ALF) is a kind of complicated syndrome. Furthermore, adipose-derived mesenchymal stem cells (ADMSCs) can serve as a useful cell resource for autotransplantation due to their abundance and micro-invasive accessability. However, it is unknown how ALF will influence the characteristics of ADMSCs and whether ADMSCs from patients suffering from end-stage liver diseases are potential candidates for autotransplantation. This study was designed to compare various properties of ALF-derived ADMSCs with normal ADMSCs in pig models, with regard to their cellular morphology, cell proliferative ability, cell apoptosis, expression of surface antigens, mitochondrial and lysosomal activities, multilineage potency, and expression of liver-specific genes. Our results showed that ALF does not influence the stem cell characteristics and cell activities of ADMSCs. Intriguingly, the expression levels of several liver-specific genes in ALF-derived ADMSCs are higher than in normal ADMSCs. In conclusion, our findings indicate that the stem cell characteristics and cell activities of ADMSCs were not altered by ALF and these cells can serve as a new source for regenerative medicine.     

Possible Ignition of Particles Ejected into the Gap in Explosive Welding of Titanium

Processes that occur in the welding gap during explosive welding are analyzed. It is shown that metal particles flying out into the gap due to the jetformation effect can ignite in shockcompressed air. For most metals, the energy released thereby is small and has no significant influence on weld formation. In titanium welding on large areas, surface sections located far from the place of detonation initiation, which experience a longterm action of a hot air flow, can dissolve a large amount of oxygen and nitrogen. If particles from these sections enter the gap, it can lead to chemical reactions with formation of TiO₂ and TiN by the mechanism of internal combustion. The energy released in the gap per unit area is commensurable with and even greater than the kinetic energy of the accelerated (flyer) plate. Local bulging and rupture of metal observed in practice can be explained by ignition and combustion of gassaturated titanium particles in the welding gap.