Papers by Keyword: Size Distribution

Abstract: Sand samplers were laid out in the grassland in the northern foot of Yinshan Mountain for collecting soil flux samples from 0 to 1.5m height above the surface from Mar, 1, 2008 to Feb,29,2009.Grain size parameters proposed by Folk and Ward, including average, SD, skewness and kurtosis of grain size were used. The vertical distribution of grain size characteristic of sediments trapped by sand samplers in different seasons was analyzed by using electrical mirror technology. The results indicated that size of aeolian sand in desert steppe is mainly sand and silt. The content of coarse silt, very fine sand and medium sand are 20~60%,10~30% and 10~20%,respectively,in the sediment–for all seasons. As height increased, the content of sand decreased while silt increased and the mean size of particle changed from fine sand to very fine sand. The mean diameter of particle ranged from 2.4~4.2and standard deviation ranged from 0.7~1.5Skewness is positive with the value ranges from 0 to 0.2,while Kurtosis mainly concentrated on 0.7 to 1.3.

Abstract: Superfine ground calcium carbonate (GCC) produced by carbonate minerals is a widely used inorganic powder material. In order to get a finer GCC powder with narrow distribution span, the effect of rotational speed and media density on ground GCC were studied by dry grinding GCC in a planetary ball mill under different rotational speed and various media density. The grinding limit-particle size and distribution of grinding calcium carbonate were measured by centrifugal sedimentation granulometer. The structure of GCC was measured by X-ray diffraction. The result shows that low rotational speed and high-density media is conducive to get a product with smaller particle size and narrow size distribution; crystal plane (012) and (122) are more stable than (018) and (116).

Abstract: Aimed at detecting the particulate size distributions in the typical air pollution city of Shijiazhuang, China, this research collected samples in haze episode and non-haze episode separately and found the difference between the two situations. In non-haze episode, the average size distribution is a U-shape curve both lifting at the size minimum and maximum, with slightly higher frequency in the size below 0.65μm (grade 1 and grade 2); but in haze episode, the frequency of 0.43~0.65μm (grade 2) and 0.65~1.1μm (grade 3) increase evidently. By the correlation coefficient calculation, the mass concentration of PM_0.43~0.65 has strong negative relationship with visibility range, which should be responsible for the low visibility formation. The fitting function demonstrates that the mass concentration of PM_0.43~0.65 must be limited below 0.117 mg/m³ if the visibility range reaches 10km (“medium”), and below 0.006 mg/m³ over 19km (“good”). And there is a inflection point around 0.01 mg/m³ of PM_0.43~0.65 as for the visiblity variation, in which the visiblity range decreases rapidly with slight increase of PM_0.43~0.65 when below 0.001 mg/m³. PM_0.43~0.65 is conclusively regarded as the feature size of particulate responsible for the haze formation in Shijiazhuang, China.

Abstract: Mesophase microbeads were prepared by thermal condensation in the presence of heterogeneous and homogeneous systems. Morphologies and sizes of mesophase microbeads are characterized by scanning electronic microcopy (SEM), polarized light optical microphotography (PLOM) and laser particle size analyzer. SEM and PLOM results exhibit that mesophase microbeads have a narrow size distribution and many large particle in heterogeneous system. In homogeneous system, there are a great deal of smaller mesophase microbeads and a very little of larger mesophase microbeads. The laser particle size analysis results show that size distribution of mesophase microbeads in heterogeneous system is quite different from that in homogeneous system. There are multi-peaks on volume distribution curve in heterogeneous system. Larger mesophase microbeads are mainly in tens micron peak of size distribution curve. In homogeneous system, particle size of mesophase microbeads has a wide distribution and only single peak on size distribution curve. Moreover, sulfur concentration in reaction system makes the size of mesophase microbeads increase and the size distribution curve move to larger particle diameter. But sulfur concentration can not affect the curve pattern of size distribution.

Abstract: Vertical mill grinding system is one of the important cement grinding equipments developed in recent years. In this paper, through the industry vertical mill grinding GGBS carried out a detailed analysis of particle size, on this basis, using the attached to the sample preparation method, obtained the typical SEM images of GGBS through industrial vertical mill, and using particle image analysis software for slag microstructure has carried on the qualitative analysis, obtained the change rule of microstructure of the grinding process. Meanwhile, using shape index, roundness coefficient, flat degree, angularity and surface roughness quantitative characterization of the microstructure of slag powders.

Abstract: The smoke particle size distribution of cotton rope smoldering fire were measured with DMS500 Fast Particulate Spectrometer under different temperature and humidity. Through the experiments, we prove that the temperature and humidity of environment have a great influence on cotton rope smoldering smoke particle size distribution. Cotton rope smoldering smoke particle size distribution at an elevated temperature will migrate to small size. Nevertheless, the effect of humidity is more complicated that need a more depth research. Additionally, Fire smoke aerosol is a non-steady-state.

Abstract: In the present study, Zn-hydroxyapatite (Zn-HA) was synthesized, the powder was thermally treated at different temperatures and then characterized. The Zn-HA powder was characterized mainly by FTIR and XRD, but have been performed investigations like SEM, BET and size distribution. The addition of ZnO in hydroxyapatite causes alleged interactions with the existing groups in HA, which amend the corresponding signals to these groups in the IR spectra. X-ray diffractograms for samples (untreated and heat-treated) have been recorded and microstructural parameters for the all samples have been calculated. The obtained average sizes of the crystallites and the network tensions support the idea that Zn-HA powders are nanostructured. The SEM images and size distributions for Zn-HA indicate a cluster of crystals with nanometer-scale of the population-base. Was determined the adsorption-desorption isotherms for Zn-HA powder at 100 o C and 800 o C. The dates obtained from the analysis of particle size distribution indicates for the Zn-HA powder an size distribution for granules in the range from 0.05 to 0.3μm

Abstract: Basing on fractal geometry theory, establish fractal calculation model in effective stress, analyze and discuss the relationship between microstructure of porous medium and effective stress, reveal the influence law of the latter on the former. The results of the study show that the fractal calculation model of effective stress can describe the relationship between them. With the increase of effective stress, the fractal dimension of porous medium increases exponentially, porosity and pore number in porous medium decrease exponentially and mean radius of pore decreases.

Abstract: The particles of smoke generated by flaming n-heptane was measured by Fast Particulate Spectrometer (DMS500), and the particle number concentration and size distribution were recorded and analyzed for investigating the smoke dynamic characteristics. The experimental results indicated that the particle number concentrations of buoyant plume above the flame approximately decrease with the height. At the center of ceiling, there is an approximate linear relationship between the particle number concentration and heat release rate. The count median diameter (CMD) varies with time and the change rate of CMD varies with particle concentration. In these experiments, the CMD is a constant in a few minutes after burning extinction.

Abstract: In this article, calcium carbonate filled linear low density polyethylene (LLDPE) was prepared and the influences of particle size and size distribution on the rheological and mechanical properties of the composites were investigated. The results showed that the glass transition and thermal decomposition temperatures of LLDPE phase in LLDPE/CaCO₃ composites were shifted toward higher temperatures by the restriction of CaCO₃ particles on the segmental and long-range chain mobility of the LLDPE phase. The composites showed shear thinning behaviors and the viscosity decreased with the rational size and size distribution. Additionally, the elongation at break notably improved to some extent.