Particle Size Distribution Patterns Research Articles

Improved models for fractal colloidal agglomeration: computationally efficient algorithms

A variety of modeling techniques for the population balances resulting from particle coagulation were examined. The simplified models using the non-uniform discretization scheme were compared to uniform discrete models. Further, new algorithms that incorporate a non-uniform discretization were developed. The uniform discrete population balance was used as the basis of comparison as it considers a continuous distribution of size classes of particles. Comparisons included the particle collision mechanisms of perikinetic, orthokinetic, and differential sedimentation with the inclusion of flow-induced break-up. Initial particle populations considered were both monodisperse and polydisperse. The analysis focused on the resulting population distribution and a statistical comparison to the uniform discrete model. In the course of the investigation, new algorithms were found to be substantial improvements in terms of computational time over the other models and compared favorably to the discrete/continuous model with respect to accuracy. New probability distribution functions for aggregates produced in non-uniform discrete coagulation modeling were derived and incorporated into the population balance equations. These new algorithms made it possible to simulate fractal aggregate coagulation with high accuracy, perfect mass conservation and exceptional computational efficiency. Parameter sensitivity analysis showed that a break-up kernel does not influence total particle concentration within the limited range of having the break-up coefficient less than collision efficiency, but does influence the particle size distribution and coagulation patterns. An aggregate break-up study with various kernel parameters indicated that break-up rate is more influenced by particle volume and not size class or diameter as previously suspected. The new probability distribution functions are found to be useful in fractal aggregation modeling via the higher numerical stability and accuracy. The new particle population model (Eq. (17)) is shown in the investigation to be superior to all of the other models, having mass conservation factor of over 0.99 and computation time of 3.125 × 10 −2 s, thus the new model of Eq. (17) can be used to develop predictive simulations for coagulation in computational fluid dynamics and reaction modeling.

Influence of gel-derived nanocrystalline spinel in a high alumina castable: Part 1

A newer class of spinel-alumina castable was fabricated by incorporating 8.0 wt.% of modified spinel additives synthesized via sol–gel and coprecipitation methods. These additives prepared by cheaper ingredients after optimum grinding and calcination, were characterized in terms of particle size distribution, infrared spectra and X-ray diffraction patterns. The properties of those spinel-alumina castables, with another prepared by the same amount of commercial preformed spinel fine, were studied and compared. Cold crushing strength, apparent porosity, hot modulus of rupture, pore size distribution, scanning electron microscopy, energy dispersive spectral analysis, thermal shock and slag corrosion resistance tests of selected samples were done to identify the immense prospect of sol–gel additive. Transmission electron microscope (with SAED facility) was also utilized to establish the nanocrystalline feature of the sol–gel additive.

Examination of the Phenomena Concerning Optical Particle Measurements Using the Direct Finite-Difference Solution of Maxwell's Equation(Influence of Multiple Scattering and Three-Dimensionality of Scatterer on Diffraction)

At first, the accuracy of the scattering patterns predicted for typical examples by a direct finite-difference solution technique was examined by comparing them with the analytical solutions. Comparisons with regard to the scattering patters formed by a single cylinder, a pair of cylinders or a single true sphere showed good agreement. Based on this confirmation of accuracy of the direct finite-difference solution method, the influence of multiple-scattering and three-dimensionality of scatterer on the diffraction was discussed. Even if the volume fraction of particles is same, larger number density of scatterers leads to more remarkable distortion of scattering pattern and subsequent erroneous measurement of particle size distribution. When a cylindrical scatterer is long in the direction of optical axis, its scattering pattern is remarkably different from that formed by a true sphere of the same diameter. That is, the diffraction pattern is affected by the three-dimensionality of scatterer.

How do the indoor size distributions of airborne submicron and ultrafine particles in the absence of significant indoor sources depend on outdoor distributions?

Although almost all epidemiological studies of smaller airborne particles only consider outdoor concentrations, people in Central Europe actually spend most of their time indoors. Yet indoor pollutants such as organic gases, allergens and dust are known to play a prominent role, often affecting human health more than outdoor ones. The aim of this study was to ascertain how the indoor particle size distributions of submicron and ultrafine particles correlate with the outdoor concentrations in the absence of significant indoor sources. A typical indoor particle size distribution pattern has one or two modes. In the absence of significant indoor activities such as smoking, cooking etc., outdoor particles were found to be a very important source of indoor particles. The study shows that in the absence of significant indoor sources, the number of indoor concentrations of particles in this size range are clearly lower than the outdoor concentrations. This difference is greater, the higher the number of outdoor concentrations. However, the drop in concentration is not uniform, with the decrease in concentration of smaller particles exceeding that of larger ones. By contrast, the findings with larger particle sizes (diameter > 1 microm) exhibit rather linear concentration decreases. The non-uniform drop in the number of concentrations from outdoors to indoors in our measurements considering smaller particles ( >0.01 microm) is accompanied by a shift of the concentration maxima to larger particle diameters.

日本で2002年春に採取した風送ダストについてその非水溶性成分の化学組成を粒径分布から見た特徴

2002年3月から5月にかけて、那覇、福岡、名古屋、つくばの4地点で風送ダスト試料を採取し、その非水溶性成分中の化学組成を測定した。ほとんどの元素は、その粒径分布の特徴として2.1～7.0μmの粒径に一つのピークを示すことから、主に鉱物エアロゾルに含まれていると考えられる。しかし、Cd, Sn, Sb, Pb, Biなどの元素は1μmよりも細かいダスト粒子に多く含まれ、人為起源の炭素エアロゾルに由来すると考えられた。 Al2O3濃度で各元素濃度を規格化した値の粒径分布の特徴から、風送ダスト中の鉱物組成は1μmを境に変化し、2μmより細かい粒子では人為起源物質の混入率が高くなることなどが明らかになった。次に、Al2O3規格値の空間的及び時系列的な変化に着目すると、一部の元素に系統的な地域差、すなわち観測点周辺からの物質の混入が認められた。しかし、一度ダストイベントが発生すると、ほぼすべての元素の濃度比は試料採取地点に関係なくほぼ一定の値を示し、非常に大量の風送ダストが東アジア地域から日本へ運ばれていることが明らかになった。

Effect of Protein-Polyphenol Ratio on the Size of Haze Particles

Various concentrations of the haze-active (HA) protein gliadin and the HA polyphenol tannic acid were combined in pH 4.5 buffer. The resulting hazes were measured by light scattering, and their particle size distribution patterns were examined with a laser diffraction particle size analyzer. The shape of the haze intensity response generally followed that seen in previous experiments, but haze intensity was noticeably greater with two particular gliadin-tannic acid ratios (2:1 and 5:1, w/w) than with other combinations. The size of the particles varied with the protein-polyphenol ratio, as previously hypothesized. In general, larger particles were seen with intermediate ratios, while both higher and lower proportions resulted in smaller particles. The data expressed as volume percent were highly quantized—essentially, only three particle sizes were seen. The proportions of these varied as the amounts of protein and polyphenol changed. The contributions of particles of each size to the haze intensity in different samples were estimated. The results suggested that the particles that contributed the most haze were typically in a narrow band, with diameters in the range of 10–20 μm. Variations in particle size induced by normal brewing practices are expected to have an impact on fining and filtration performance.

LDL particle size distribution is associated with carotid intima-media thickness in healthy 50-year-old men.

Results of cross-sectional and prospective studies have suggested that small, dense low-density lipoprotein (LDL) particles predispose to coronary heart disease. We investigated the relationships between plasma concentrations of LDL subfractions and intima-media thickness (IMT) of the common carotid artery (CCA), quantified by B-mode ultrasound, in 94 healthy, 50-year-old men, all of whom were homozygous for the apolipoprotein E3 allele. A novel 3% to 7.5% polyacrylamide gradient gel was developed to provide separation of LDL subfractions with high resolution, as was a procedure to quantify plasma concentrations of these LDL subspecies. The LDL particle size distribution pattern obtained by the gradient gel electrophoresis procedure was in good agreement with the one obtained by a well-established, single-spin density gradient ultracentrifugation technique. LDL-II (particle size, 23.5 to 25.0 nm) was the most abundant subfraction, and its plasma concentration correlated closely with the total LDL cholesterol concentration (r=0. 61, P<0.001) but not with CCA IMT (r=-0.13, NS). In contrast, the plasma concentration of the predominant small, dense LDL particle subfraction (LDL-III; particle size, 22.5 to 23.5 nm) correlated strongly with CCA IMT (r=0.42, P<0.001). In multivariate analysis, the plasma concentration of the LDL-III subfraction contributed significantly to the variation in CCA IMT (R(2)=0.19). When plasma triglycerides and LDL cholesterol were forced into the multivariate model, 10% of the variation in CCA IMT was still accounted for by the LDL-III subfraction. In summary, use of a novel and sensitive gradient gel electrophoresis method for evaluation of LDL heterogeneity provided the basis for demonstrating an independent relation between the plasma concentration of small LDL and IMT of the CCA in healthy, middle-aged men.

The use of a mathematical model to compare particle size data derived by dry-sieving and laser analysis

The results of sediment particle size determinations by dry-sieving and laser particle sizer are compared. When analysing the same samples the two techniques produce different results. The mean percentage similarity between replicate samples analysed by the two techniques was 79%. A computer based mathematical model is described, which converts dry-sieved data so that they are comparable to laser sizer data. The effectiveness of this conversion is tested on over 400 samples, with a wide range of particle size distribution patterns. It is concluded that the conversion model is effective; mean percentage similarity of replicate samples was improved to 91%.

Particle Size Design Using Computer Optimization Technique

AbstractThe effect of binder solution (amount and composition) on the mean particle size and its distribution of granule was investigated by using a computer optimization technique. The granules were manufactured by two continuous processes, granulating and sizing using a high-speed mixer granulator and a hammer mill, respectively. The particle size distribution pattern of granules was markedly varied with the change in the amount and composition of the binder solution. The distribution pattern could be well expressed by the log-normal distribution model. For designing the optimal particle, a computer optimization technique was applied to the experimental results obtained in this study. The technique was found to be useful for searching the optimal formula in the practical scale.

Particle Size Distribution of Airborne Trace Metals

Abstract Weekly samples of aerosol in seven size fractions were taken in the period from 13 October 1985 to 16 September 1986, and analyzed for cadmium, copper, manganese, sodium, lead, zinc and-partially-arsenic and vanadium. Sampling locations were south of Berne, Switzerland, at elevations of 515, 750, 940 and 1550 metres above sea level, respectively. First results indicate that the aerosol concentrations usually decrease with increasing elevation; the extent of this decrease is, however, largely controlled by the prevailing atmospheric stability. During some weeks in February 1986 unusually high aerosol concentrations were observed. The meteorologic situation and the observed element spectrum indicate that transport from Eastern Europe had occurred. Each component of the aerosol exhibits a typical pattern of particle size distribution which, for most elements, does not vary significantly with altitude.

Aerosol characterization and apportionment using cascade impactors and activation analysis

The use of particle-size distribution measurements and techniques for aerosol physical characterization, together with composition data for 30 elements, has led to useful deductions about the sources of airborne particulates. Collections with cascade impactors operated at three locations in Toronto, Canada, were analyzed by INAA and photonuclear activation (IPAA). The efficiency and reliability of impactors for aerosol size-distribution characterization was studied by scanning electron microscopy and calculating equivalent aerodynamic diameters; values obtained in this way were in close agreement with predicted values. Toronto aerosols exhibited both expected and unusual particle-size distribution patterns with many elements exhibiting either size distributions biased toward large (e.g. Al, Sc, Ti, Fe) or small particles (e.g. Br, Cl, Cu). Other elements (viz. Pb, Zn, As, Sb) exhibited different and unusual size distributions, presumably from different sources. Factor analysis and chemical mass balance (CMB) applied to data for a suburban site allowed emission source identification and aeorosol apportionment with a fair degree of certainty, and, preliminary results using factor analysis for size-fractionated samples, indicate a potential for relatively accurate source apportionment in more complex airsheds.

Quantification of human serum apolipoprotein A–I by zone immunoelectrophoresis assay and a procedure for the preparation of an A–I standard

A zone immunoelectrophoresis assay (ZIA) for human serum apolipoprotein A–I (Apo A–I) is described. In this immunologie technique, glass capillaries filled with agarose gel containing anti-Apo A–I are used. Apo A–I produces zones of immunoprecipitates with migration distances directly proportional to the apolipoprotein concentration. Two plasmas and their isolated high density lipoprotein (HDL) fractions, having different particle size distribution patterns have been analyzed for Apo A–I using rocket electroimmunoassay in parallel with ZIA. A good agreement between the two methods was obtained. With ZIA, Apo A–I complexed with lipids in HDL yielded concentration values that were unaffected by lipoprotein particle size and by delipidation. A standard curve, linear between 0.5 and 3.5 mg Apo A–I/l, was obtained with ZIA. A protocol for the preparation of an Apo A-I standard without prior purification of the apolipoprotein is presented. Using ZIA, 75 serum samples representing a heterogeneous study population were analyzed for Apo A–I. A mean value of 1.23 g/l with a relative standard deviation of 28% was obtained. The corresponding mean for total HDL cholesterol was 1.64 mmol/l ( RSD = 61%).

A distribution function for particle populations having a finite size range and a mode independent of the spread

A distribution function ▪and its cumulative form ▪ are described and their mathematical properties analyzed. Since f(0) = f(a) = 0, this function can be applied to real particle populations, having a definite size range 0 < x < a determined by physical considerations. Unlike most asymmetric distribution functions, the mode estimate μ can be varied independently of the spread measure C, thus being more consistent with real life situations where a process that affects one need not affect the other in a predetermined manner. The mathematical structure of f(x) allows for both symmetry around the mean and skewness to either right or left, depending on whether μ = a 2 , μ > a 2 or μ < a 2 , respectively. This permits the simulation of extreme changes in particle size distribution patterns without changing the model format. The parameter B is an arbitrary constant whose effect on the distribution curve shape is of little significance as long as its magnitude remains small relative to that of a. Although the integrals that appear in f(x) and F(x) cannot be easily solved analytically, their values can conveniently be computed by standard numerical methods employing a microcomputer.

Electron paramagnetic resonance linewidth of superparamagnetic particles

Superparamagnetic particles have been investigated by electron magnetic resonance. We have shown that the temperature dependence of the linewidth (above the freezing temperature) is sensitive to the pattern of particle size distribution. The behavior of the linewidth as a function of temperature is explained if we assume an anisotropic Dzyaloshinskii–Moriya type of interaction where the relaxation process occurs by a longitudinal component.

Study of magnetism in fine particles of ferric hydroxysulfate by Mössbauer spectroscopy

Experimental results of magnetization and Mössbauer measurements on ferric hydroxysulfate are presented. The method developed in the preparation and characterization of samples is discussed. In the present paper the magnetic properties are explained taking into account the pattern of particle size distribution of the samples in the region of superparamagnetism. The model is described in the molecular-field approximation for randomly dilute magnets.

Aeolian deposition and soil parent materials in northern Nigeria

The introduction considers the nature of the problem of “drift” soils in northern Nigeria. The physical environment of the survey area is described briefly and the percentages of silt, very fine sand and fine sand occurring in the soils are mapped. Textural belts are identified and the profile distribution frequencies within the belts are tabulated. Parent material origins are discussed and attempts are made to reconcile the apparently aeolian nature of the soil materials, in terms of the particle-size distribution pattern, with the various soil profile morphologies of today.