Pore Structure Analysis of Porous Particles by Modelless and Micropore Method

The modelless (ML) and micropore (MP) methods for the pore structure analysis of porous particles have been studied. Concerning the ML method, it has been shown that the Kiselev equation can only be used to describe condensation and evaporation in capillaries, but cannot be used to describe the increase and decrease of the thickness of the adsorption layer. Strictly speaking, therefore, the ML method is not modelless even for the pore core size distribution. A comparison between the ML method and methods using an equivalent pore model is given. The results of using the ML method in conjunction with a certain pore model are little less accurate than those obtained by adopting the equivalent pore model straightaway. The parameters required for the calculation of both the pore core size and the pore size distribution as well as the conversion between these two calculations are given. Concerning the MP method, it has been shown that the three types of v-t curves, the theoretical foundation of the MP method, are not in one to one correspondance to the three kinds of adsorption mechanism. From the viewpoint of accuracy, the MP method has no advantage over the methods which are based on the condensation mechanism, both have their own merits.     

Fractal Analysis of Surface Roughness of Particles in Porous Media

A fractal dimension for roughness height （RH） is introduced to characterize the degree of roughness or disorder of particle surface characters which significantly influence physical-chimerical processes in porous media. An analytical expression for the fractal dimension of RH on statistically self-similar fractal surfaces is derived and is expressed as a function of roughness parameters. The specific surface area （SSA） of porous materials with spherical particles is also derived, and the proposed fractal model for the SSA of particles with rough surfaces is expressed as a function of fractal dimension for RH and fractal dimension for particle size distribution, relative roughness of particle surface, and ratio of the minimum to the maximum particle diameters of spherical particles.     

A Geometrical Model for Tortuosity of Tortuous Streamlines in Porous Media with Cylindrical Particles

We present a three-dimensional geometry model for tortuosity of streamlines in porous media with randomly placed cylindrical particles. The proposed model is expressed as functions of porosity and geometrical parameters with no empirical constant. This might be helpful for understanding the physical mechanism for tortuosity of streamlines in three-dimensional porous media. The model predictions are found to be in good agreement with the experimental data available.     

Compressibility and Fractal Dimension of Fine Coal Particles in Relation to Pore Structure Characterisation Using Mercury Porosimetry

Mercury porosimetry has been applied to characterize the pore structure of fine coals particles. Interparticle voids and compressibility effects on the mercury intrusion data were examined. It is found that coal compressibility has a significant effect on mercury porosimetry data when pressure P>20 MPa. The compressibility of the two coals used was determined to be 3.13×10⁻¹⁰ m² N⁻¹ and 2.50×10⁻¹⁰ m² N⁻¹ for CA and GO coals, respectively. Fractal dimension analysis provides a “fingerprint” to distinguish the effect of coal compression from the pore filling process during mercury intrusion. It is shown that fractal dimension can be evaluated from the compressibility corrected pore volume data. Results from the present study suggest that statistic self-similarity of the fractal dimension perspective is limited by certain artificial effects, such as crushing and grinding. Different surface irregularities exist over different pore size ranges, and a single fractal dimension value can only be used to describe the surface irregularity within a limited pore size range. The average fractal dimensions in the pore size range of 6–60 nm were found to be 2.71 and 2.43 for CA and GO coals, respectively.     

Penetration of Waves and Particles through Porous Structures

The penetration of quantum and classical charged particles through porous films is investigated. The passage of quantum particles is analyzed by numerically solving the Schrödinger equation. The force of polarization acting on a charge is calculated by means of classical electrodynamics. The possibility of perforating thin films is analyzed.     

Simultaneous Measurement of Velocity and Equivalent Diameter on Non-Spherical Particles

The performance of a laser-based optical technique to measure simultaneously the velocity and equivalent diameter of nonsphercial particles was evaluated. The size information was provided by the absolute intensity of diffractively scattered light by a particle crossing a single laser beam, which is concentric with a laser Doppler probe volume. The response curve (size-intensity relationship) of the technique was estimated by calculations using the Fraunhofer approximation. Experiments with spherical glass and polyethylene and non-spherical metal and ceramic particles ranging from 20 to 200 μm confirmed the operation of the technique and in all the measurements the maximum error of the average diameter was 10 μm as compared with size information provided by a microscope.     

吸湿性均匀混合气溶胶粒子等效吸收系数计算分析

以两种典型的吸湿性气溶胶组分(氯化钠和硫酸铵)为例,采用米氏散射程序,计算了粒子的吸收效率因子等光学参量,并分析了吸湿性气溶胶粒子加热的等效吸收系数随时间的变化规律,着重分析了忽略粒子自身吸收对等效吸收系数的影响,常规计算值与等效吸收系数在1μs时相对误差可达到234.7%和255.2%。同时,就不同相对湿度、不同波长对等效吸收系数含时变化规律的影响进行了对比分析,并讨论了采用均匀混合模型计算结果的相对误差,在1μs时实际值与计算值相对误差最大,分别小于3.62%和7.07%。     

A Spheroidal Model of Light Scattering by Nonspherical Particles

Optics and Spectroscopy - We have constructed a spheroidal model to solve the problem of light scattering by nonspherical particles. The semiaxes of the model spheroid are determined based on the...     

Analysis of Porous Nanosilicon by Raman Spectroscopy

Journal of Applied Spectroscopy - Technologies for the production of nanostructured silicon and porous nanosilicon are presented. A method for the synthesis of porous nanosilicon by electrochemical...     

Structure of Water Microemulsion Particles: Study by Optical Methods

Physics of Wave Phenomena - It is shown by optical methods using light scattering intensity and shift of the stimulated low- frequency Raman scattering line that emulsion particles of the Emulson...     

Strengthening Porous PVA with TiO_2 Structure by an Ice-Templating Method

A poly vinyl alcohol(PVA) scaffold with aligned porous is strengthened by in-situ combining with TiO_2. The increased freezing rate can be used to further increase the strength of aligned porous materials. The strengthened porous PVA exhibits aligned interconnected porous structures and shows a significant enhancement in tensile testing and compression strength testing.     

等效球模型模拟冰晶云反射的误差分析

用射线光学理论计算了具有一定尺度分布的六角冰晶粒子在可见和近红外光谱区一系列波长上(0.2～5μm)的单次散射特性.利用米氏(Mie)理论,计算了与六角冰晶具有相同截面积的球形粒子的单次散射特性.根据辐射传输理论,应用累加法,分别计算了由冰晶粒子和等效球形粒子构成的卷层云的多次散射特性,计算结果表明当入射波长λ≈3.0 μm时,等效球Mie理论可以很好地用于计算卷层云的反射特性,但是当λ＜2.8μm时,尤其在可见光区,将引起显著的误差.最后提出了计算冰云光学特性的两种方案.     

三维多孔吸液芯毛细特性孔隙尺度格子Boltzmann模拟

通过改进后的QSGS方法构造了三维复杂多孔吸液芯结构,采用格子Boltzmann方法和GPU并行算法,数值模拟了孔隙尺度下多孔吸液芯毛细抽吸两相传输动态特性,并探讨了表面润湿性和孔隙率对两相界面分布和毛细性能的影响.研究结果表明,对于三维复杂结构多孔吸液芯,毛细抽吸过程中两相界面不规则性、分布不均匀性程度较大,孔尺度效...     

Morphological Characterization of Flowing Particles by Image Analysis Techniques

The guidelines which are at the base of the definition of a system capable of operating on a slurry containing the solid particulate for its characterization are described. All the considerations have been developed with particular reference to the case of a granular heterogeneous material in particular, the different research problems, making a comparison with the case of static images, acquired under laboratory conditions, are pointed out. Attention was focused on problems of acquisition and digital image processing to obtain information which is clean from noise and errors. The considerations and procedures analysed show general validity and can be applied to a large number of problems linked to the “on-line” morphological characterization of particulate solids materials. Some results for morphological characteristics of lead sulphide (PbS) samples are reported.     

A Micro-Mechanism Model for Porous Media

Based on the tortuous-expanding path/channel model, a micro-mechanism model for porous media is de- veloped. The proposed model is expressed as a function of tortuosity, porosity, resistance coefficient, and fluid properties. Every parameter in the proposed model has clear physical meaning. The results show that the model predictions are in good agreement with those from the existing experimental data.     

A Micro-Mechanism Model for Porous Media

Based on the tortuous-expanding path/channel model, a micro-mechanism model for porous media is developed. The proposed model is expressed as a function of tortuosity, porosity, resistance coefficient, and fluid properties. Every parameter in the proposed model has clear physical meaning. The results show that the model predictions are in good agreement with those from the existing experimental data.     

Equivalent Model, Error Analysis, and Design Steps of AGC Loop for MM-Wave Receiver

Automatic Gain Controlled (AGC) Loops are used in MM-Wave receiver in wide-ranging. In this paper, the equivalent model and loop equation of AGC Loop are built, the loop errors are analyzed and then the design steps of AGC Loop are given out.