浅议自由下落微粒流与环境空气的关系

研究微粒流在环境空气中的自由下落是气固两相流新的研究领域之一.在微粒流自由下降过程中,环境空气被下落运动的微粒流卷吸到微粒流场中形成微粒羽状流,并伴随着散射飘尘的产生,从而使得工作场合的空气被严重污染.本文介绍了目前国际学术界在该方面的研究进展,并讨论了微粒流的下降高度、质量流量、微粒粒径、微粒密度等物理参数的变化对在微粒流自由下落过程中所产生的卷吸空气量的影响,同时展示和分析了微粒粉尘和卷吸空气进行量化和模拟的一些方法.

乳糜微粒流对黄芩苷纳米乳动物体内组织分布的影响研究

目的探究乳糜微粒流对黄芩苷纳米乳大鼠体内淋巴组织的分布,初步阐明黄芩苷纳米乳具有淋巴靶向性的机制。方法利用高效液相色谱法测定生物样品中黄芩苷浓度;大鼠分别灌胃给予黄芩苷纳米乳和黄芩苷混悬液,剂量为144.0 mg/kg;建立大鼠乳糜微粒流阻断模型,考察乳糜微粒介导的跨膜转运对黄芩苷纳米乳在淋巴组织器官分布的影响。结果与未阻断组相比,大鼠体内乳糜微粒流的阻断,可影响黄芩苷纳米乳组大鼠体内脾、胸腺和淋巴结血药浓度-时间曲线下面积、药峰浓度等参数,但未对黄芩苷混悬剂组大鼠的体内药物代谢动力学参数产生影响。结论黄芩苷纳米乳刺激乳糜微粒的分泌,增加药物经淋巴途径的转运量,药物富集于淋巴器官,可能是黄芩苷纳米乳靶向淋巴器官的主要机制。

浅议自由下落微粒流与环境空气的关系

研究微粒流在环境空气中的自由下落是气固两相流新的研究领域之一。介绍了国际上在该方面的研究进展,讨论了微粒流的下降高度、质量流量、微粒粒径、微粒密度等物理参数的变化对在微粒流自由下落过程中所产生的卷吸空气量的影响,同时展示和分析了微粒粉尘和卷吸空气进行量化和模拟的一些方法。

自由下落微粒流中气固两相流的数值模拟

在微粒流的自由下落过程中,环境空气会被卷吸到微粒流中,形成微粒羽流,有关微粒羽流与环境空气关系的基础理论及数值模拟研究文献相对较少。本文通过RNGk-ε模型对二维微粒羽流中的微粒与环境空气的耦合进行数值模拟,并讨论了微粒羽流速度分布、微粒羽流密度与羽流的流速变化关系,以及微粒羽流质量流对羽流流速的影响。

微粒流特性参数对微粒浓度和免挂壁高度影响的研究

本文以有限空间内微粒羽流下落特性研究实验台为研究对象,采用四种直径的卸料口和四种微粒密度为实验变量,运用Fluent分析方法,探讨卸料口直径及微粒密度对有限空间内微粒自由下落特性的影响,避免微粒流在下落的过程中贴附在杀菌罐体表面导致杀菌效果减弱的现象。结果表明,卸料口处的浓度最大,在水平方向上,浓度值由轴心处向壁面处逐渐衰减;在竖直方向上,浓度值沿着粒子下落方向逐渐减小。在本文的研究范围内,当密度为471.88kg/m3,卸料口直径为35mm时,出现最小挂壁高度0.6m;当密度为727.28kg/m3,卸料口直径为20mm时,出现最大挂壁高度1.3m。为避免微粒流在下落的过程中贴附在杀菌罐体表面导致杀菌效果减弱的现象,光波杀菌装置安装在微粒挂壁高度略高一点的位置,即能保证微粒扩散达到一定的程度,能够达到杀菌效果,又能保证微粒没有黏附在壁面上,且能长期使用。

微粒羽流自由降落过程特性的探讨

根据自由下落微粒羽流的运动特征,对微粒羽流自由下落过程中卷吸空气的机理进行初步分析,应用Tomom i给出的混合微粒模型及Ogata给出的单微粒模型与环境空气卷吸量实验值进行对比分析.结果表明,混合微粒模型对环境空气卷吸量的模拟值与实验值有较好的吻合性,而Ogata给出的单微粒模型预测值低于实测值.实验结果表明,环境空气卷吸量随着微粒羽流下降高度的延伸而增加,随着微粒流中微粒的密度及粒径的增大而减小.

微粒羽流中粉尘的实验研究

通过实验观察和实验结果分析,研究了自由下落羽流产生的粉尘与物料本身的物理参数和工作参数的变化关系,并对实际生产操作过程中如何减少粉尘的产生提供了参考建议。

黄沙散料流自由下落速度的实验研究

指出了对工业生产、散料运输等过程中所产生的微粒粉尘运动特性进行研究,是人工环境控制的重要课题之一。利用专门搭建的实验装置,在静止环境空气中对黄沙散料的自由下落过程进行实验研究,探讨了黄沙散料在不同参数条件下下降速度的变化规律。实验结果表明:微粒瞬时下降速度随着下降高度的增加而增大;微粒速度在下落前期增长较快,下降高度达到0.06m后曲线趋于平缓。随着初始下落口径的增大,微粒束的下降速度增大;随着微粒粒径的增大,微粒束的下降速度增大。

评述近20年传统医学“气本质”的理论研究进展

整合近20年对"气学"理论的成果,提出气为不具固定形态,并通过渗透、聚散、出入等形式贯穿于一切事物之间的暗物质、信息流、势能力场以及生物电磁场。同时整合哲学、医学、现代生物学、物理学、信息领域相应之观点进行扼要概述,并肯定"气"的实质即诠释事物"生成-衍变-终结"过程的线索,同时医学领域之气亦为探究生命体自平衡、自稳态模式构建之纲领。

关于气的研究方法的探讨

当前,对中医“气”实质的认识颇不一致。有的认为,气是构成和维持人体生命活动的物质基础;有的认为,气是物质,也是功能;亦有认为,气仅是“功能”的表现;还有的认为,气既非物质,也非功能,而是一种信息调控过程。虽有如上几种不同的认识,但从哲学观点和医学实质上看,“气”应是在一定物质基础上产生的运动形式。

万物生长靠太阳———太阳活动对地球和人类的影响

○万○物○生○长○靠○太○阳———太阳活动对地球和人类的影响沈海璋（北京天文台）太阳和地球是与人类关系最为密切的两个天体。由于空间科学技术的发展，从而形成了一门边缘学科———日地物理学。太阳是个高温炽热的气体球，是个巨大的辐射源。太阳中心区的氢核聚变...

碱法合成纳米δ-MnO_2及其电化学性能

介绍了在改进的碱性条件下合成δ－MnO2，经XRO和TEM测试表明为晶型良好的纳米δ－MnO2，在9mol／LKOH和5mol／LLiNO3中进行放电和循环伏安测试，结果表明放电容量尚可，循环稳定性较好。

Application of Composite Ultrafine Particles in ER Fluids

Aim To obtain a kind of electrorheological (ER) flind with high comprehensive properties in order to satisfy the needs of engineering application. Methods A new type of dispersed phase── composite ultrafine particles (UFP) was obtained by the method of microemulsion, which was used to mix with silicon oil. aam electroinduced stress and apparent viscosity of the ER fluids with three different volume fractions were tested under the conditions of different temperatures, electric fields and shear rates. Results A series of systematic tests show that the new type of ER fluids with volume fraction of 30% possesses obvious ER effect. Conclusion The double layers polarization plays an important role in ER effect.

Motion and orientation of cylindrical and cubic particles in pipe flow with high concentration and high particle to pipe size ratio

Lattice Boltzmann method was used to numerically investigate the motion and orientation distribution of cylindrical and cubic particles in pipe flow with high concentration and high particle to pipe size ratio. The transient impulse model of 3D collisions between particles and between particle and wall is proposed. The numerical results are qualitatively in agreement with and quantitatively comparable to the experiment data. The results show that the increases of both the cylindrical particle to pipe size ratio and the particle aspect ratio decrease the rotation about all axes. All rotations of cubic particles decrease with increasing the particle concentration. The cubic particles, rotating more drastically in the flow with large Reynolds number, rotate faster than the cylindrical particles with the same size. The cylindrical particles align with the flow direction more obviously with decreasing Reynolds numbers. However, the orientations of cubic particles are spread all over the range with no significant difference in magnitude, and the Reynolds numbers have no obvious effect on the orientations of cubic particles.

Study on Character of Micro-Canal Deposit and Its Significance in Petroleum Geology——Case study of Tuo-147-well in north zone of Dongying depression

Exploration on reservoir of glutenite segment in steep slope zone of half graben-like basin is one of the hot spot targets at present and in the future for new reservoirs; And the study of sediment character of sandy-conglomerate bodies is the keystone and also the difficult problem. Taking Tuo-147-well area in north zone of Dongying depression as an example, the micro-canal sedimentation was researched. The result shows that many micro-canals exist at the end of slope grain-flow in steep slope zone of half graben-like basin; The micro-canals grow at the end of subaqueous grain-flow deposited bodies of 3rd member of the Shahejie formation. The main condition of micro-canal formation is the slope angle less than 18° and a long suitable sedimentary slope. These micro-canals may communicate the reservoir of glutenite segment in steep slope zone and the hydrocarbon stratum as a bridge role. Therefore, it is significant in theory and practice for discovering a series of micro-canals at the end of slope grain-flow in steep slope zone of half graben-like basin.

Effect of particle loading on heat transfer enhancement in a gas-solid suspension cross flow

Heat transfer between gas-solid multiphase flow and tubes occurs in many industry processes, such as circulating fluidized bed process, pneumatic conveying process, chemical process, drying process, etc. This paper focuses on the influence of the presence of particles on the heat transfer between a tube and gas-solid suspension. The presence of particles causes positive enhancement of heat transfer in the case of high solid loading ratio, but heat transfer reduction has been found for in the case of very low solid loading ratio (M s of less than 0.05 kg/kg). A useful correlation incorporating solid loading ratio, particle size and flow Reynolds number was derived from experimental data. In addition, the k-ε two-equation model and the Fluctuation-Spectrum- Random-Trajectory Model (FSRT Model) are used to simulate the flow field and heat transfer of the gas-phase and the solid-phase, respectively. Through coupling of the two phases the model can predict the local and total heat transfer characteristics of tube in gas-solid cross flow. For the total heat transfer enhancement due to particles loading the model predictions agreed well with experimental data.

Electro-rheological properties of montmorillonite particles coated with titania in methyl silicone oil

Montmorillonite particles coated with titania were synthesized by means of a sol-gel method to use with elec-tro-rheological material. The characteristics of these composite particles were studied by X-ray diffraction, scanning electron mi-croscopy (SEM) and Fourier transform infrared spectroscopy (FT-IR). The electro-rheological (ER) effects were measured after these particles were mixed with methyl-silicon oil by 20% and 30% (weight percent). The experimental results show that these montmorillonite/titania particles exhibit a marked ER effect compared with pure montmorillonite particles under a DC electric field. The highest static yield stress is up to 4.28 kPa, which is an increase of about 3.13 kPa over that of untreated montmorillonite pow-der under the electrical field strength of 3.2 kV/mm at room temperature.

Tracking Submicron Particles in Microchannel Flow by Microscopic Holography

Three-dimensional tracking of submicron particles in flows in a micro-channel was carried out using in-line holographic microscopy.A fixed single 0.5 μm fluorescent particle was identified and isolated from dust particles or overlapped particle pair using the laser induced fluorescent(LIF) method.Then in-line microscopic holograms of the fixed single particle were obtained at different positions on the optical axis,i.e.the defocus distances.The holograms of the single particle were used as the model templates with the known defocus distances.The particles in the in-line microscopic holograms of flow in the microchannel were then identified and located to obtain their two-dimensional positions.The defocus distances of those particles were determined by matching each hologram pattern to one of the model templates obtained in the single particle test.Finally the three-dimensional position and velocity of each particle were obtained.

Effect of Working Temperature on the Resistance Characteristic of a Pleated Stainless Steel Woven Filter

Effect of working temperature on the resistance characteristic including the permeability coefficient and the pressure drop evolution of a pleated stainless steel woven filter with a nominal pore size of 0.5 μm has been studied. The permeability coefficient was obtained based on the pressure drop data and the Darcy＇s law. In three filtration experiments, pure carbon dioxide at 283 K, nitrogen at 85 K and liquid helium at 18 K are adopted, respectively. It is found that the permeability coefficient decreases at the working temperature due to the cold shrink of the filter element at cryogenic temperature. Then, two kinds of feed slurries, mixture of liquid nitrogen and solid carbon dioxide at 85 K, and mixture of liquid helium and solid nitrogen at 18 K, flow into the filter cell. The solid particles are deposited on the filter surface to form a filter cake and the purified liquid flows through the filter. It is found that the pressure drop evolution shows the same trend on these two temperatures, which can be divided into three stages with high filtration efficiency, indicating the feasibility of the filter for cryogenic application. However, variant cake resistances are obtained, which is resulted from the different interactions between solid particles in the feed slurry at lower working temperature.

Prediction of Thermophoretic Deposition Efficiency of Particles in a Laminar Gas Flow along a Concentric Annulus： A Comparison of Developing and Fully Developed Flows

Thermophoresis is an important mechanism of micro-particle transport due to temperature gradients in the surrounding medium.It has numerous applications,especially in the field of aerosol technology.This study has numerically investigated the thermophoretic deposition efficiency of particles in a laminar gas flow in a concentric annulus using the critical trajectory method.The governing equations are the momentum and energy equations for the gas and the particle equations of motion.The effects of the annulus size,particle diameter,the ratio of inner to outer radius of tube and wall temperature on the deposition efficiency were studied for both developing and fully-developed flows.Simulation results suggest that thermophoretic deposition increases by increasing thermal gradient,deposition distance,and the ratio of inner to outer radius,but decreases with increasing particle size.It has been found that by taking into account the effect of developing flow at the entrance region,higher deposition efficiency was obtained,than fully developed flow.