Problem of distribution moments in statistical physics

Machine vision based particle size and size distribution determination of airborne dust particles of wood and bark pellets

This paper examines suspended minerogenic particle distributions in the near‐coastal ocean, Oceanside, California. The environment is dominated by resuspension of particles from a well‐sorted sandy sediment. We obtain information on the suspended mineral matter from the relocatable numerical sedimentation model, TRANS98. Inputs for the model include bottom particle size distribution, wind speed, wave period and height, and near‐bottom current speed. Model output is a vertical profile of mineral particle concentrations and size distributions at selected depths. The mineral particle size distribution allows the calculation of the total scattering coefficient of suspended minerogenic matter. The particle size distribution for the bed at Oceanside is approximately Gaussian lognormal in character. The predicted size distribution near bottom is a skewed Gaussian lognormal; then the distribution shifts toward the increasing importance of smaller size classes as we approach the water surface. Deeper stations maintain a lognormal character up into the surface layers while the shallower stations switch to a particle size distribution of the smallest size class being the modal class in the surface layers. Hyperbolic size distributions have been proposed for the Oceanside site from optical observations. These distributions would have a slope of 2.1 for coastal water which would decrease to as low as 1.3 for shallow nearshore stations and near the bottom. None of the proposed hyperbolic slopes provides an adequate approximation of the particle distributions predicted by TRANS98. The larger particle size classes are significantly overestimated by hyperbolic models, which causes the total scattering coefficient of the minerogenic matter to be overestimated. These results indicate that hyperbolic slope models cannot be used to retrieve particle size distributions by inversions involving the total scattering coefficient nor are they accurate estimators of the minerogenic scattering coefficient.

Change in size distribution of ultrafine aerosol particles undergoing Brownian coagulation

A physical insight into sonochemical emulsion polymerization with cavitation bubble dynamics

The performance of membrane electrode assembly (MEA) greatly depends on the structure of catalyst layers. Carbon particles with Pt nanoparticles sitting on its surface and Nafion ionomer network which bind the catalyst Pt/C particles together and provide the proton conduction path (proton transport to reaction sites) are two major components in a catalyst layer (1-3). A good catalyst/ionomer interface is important because such interface provides 3-phase reaction zone for oxygen reduction reaction (ORR). The ionomer coverage over carbon particles directly affects the catalyst utilization, consequently, the mass activity and the thickness of the ionomer layer over a carbon particle determines the O2 diffusion barrier. Hence, achieving the balanced catalyst/ionomer interface with appropriate H+conductivity and thin layer (low diffusion barrier) is critical step for a high performance MEA. The fabrication of MEA starts from the catalyst ink in which catalyst powder and Nafion ionomer are mixed in a solvent. It will be desired if the catalyst/ionomer interface can be formed in a catalyst ink. To study the formation of such an interface, the dispersion of catalyst powder and ionomer particles in an ink system needs to be studied to see if the particle size of carbon changes after Nafion ionomer addition—increased carbon particle size generally indicates the formation of the interface. Ultra-small angle X-ray scattering (USAXS) characterization had been proved to be a great method to investigate the particle size of aggregate system (4). We have developed a unique method (5) to characterize the catalyst dispersion in inks using the combined USAXS and Cryo-TEM by which USAXS can provide the geometry and size distribution of different particles in a ink while cryo-TEM can confirm the USAXS results with direct observation of geometry and size distribution of these particles (Cryo-TEM is usually used to characterize biology samples by fast freezing the liquid samples to form a very thin ice to lock all particles within the liquid to keep their original structure and size of these particle without interruption). In this work, we studied the interaction between Nafion ionomer and two carbon blacks which are NH2 functionalized carbon black (XC72-NH2) and SO3H functionalized carbon black (XC72-SO3H). By comparing the particle size change of carbon black particles before and after addition of Nafion ionomer in two ink systems, we can study the interaction between Nafion and carbon black aggregates. The USAXS results and corresponding Cryo-TEM images of four ink systems are shown in figure 1 and 2. The particle size from USAXS fitting is shown in Table 1. It can be seen in figure 1 and table 1 that the size of the aggregates of carbon black in NH2-CB ink system which is in the 2nd level of USAXS fitting increases a lot (87.1%) after adding Nafion ionomer. However, according to the observation from figure 2 and table 1, the size of the carbon black aggregates which is in the 2nd level of the USAXS fitting only decreased a little (13.5%). Nafion ionomer particles with negative charges (-SO3 -) on the surface attract the positively charged (-NH3 +) carbon particles via electrostatic forces to form larger aggregates. Opposite results can be found in XC72-SO3H ink system because XC72-SO3H particles with negative charges (-SO3 -) was repelled by the negatively charged (-SO3 -) Nafion ionomer particles. From the results above, it is clearly that the charged groups on carbon can effectively affect the formation of catalyst/ionomer interface which can be used as an effective tool to build the interface. Understanding the interaction between Nafion ionomer and catalyst support will lead to the rational design a high performance MEA. Reference 1. Z.-F. Li, L. Xin, F. Yang, Y. Liu, Y. Liu, H. Zhang, L. Stanciu and J. Xie, Nano Energy, 16, 281 (2015). 2. M. S. Wilson and S. Gottesfeld, Journal of Applied Electrochemistry, 22, 1 (1992). 3. L. Xin, F. Yang, S. Rasouli, Y. Qiu, Z.-F. Li, A. Uzunoglu, C.-J. Sun, Y. Liu, P. Ferreira, W. Li, Y. Ren, L. A. Stanciu and J. Xie, ACS Catalysis, 6, 2642 (2016). 4. H. K. Kammler, G. Beaucage, D. J. Kohls, N. Agashe and J. Ilavsky, Journal of Applied Physics, 97, 054309 (2005). 5. F. Xu, H. Zhang, J. Ilavsky, L. Stanciu, D. Ho, M. J. Justice, H. I. Petrache and J. Xie, Langmuir, 26, 19199 (2010). Figure 1

Factors affecting the characteristics of particles formed were investigated in such cases where the emulsion type was the same, W/O, but particle-forming components were added to the 0 phase in method 1 and to the W phase in method 2. The theoretical composition of particles was 80SiO 2 .20TiO 2 . It was necessary to use a complex alkoxide solution to obtain single-type spherical particles. In general, the size distribution of particles was smaller and the yield was lower in method 1 than in method 2. The mean size and size distribution decreased with increasing ratio of [H20]/ [M(OR) 4 ] in both methods. The size distribution was not greatly affected by the amount of surfactant in both methods. The oxide composition was closer to the theoretical value but more organic materials tended to be contained in particles formed by method 2. TiO2 content was always higher than the theoretical value in particles formed by method 1. In method 2, the mean size, size distribution, oxide composition and yield of particles were affected significantly by the time from the preparation of gelling solution up to the beginning of the particle-forming reaction.

Comparison of particle size distributions and volatile organic compounds exhaled by e-cigarette and cigarette users

The invention provides a method and an apparatus for measuring the size, concentration and size distribution of particles in a fluid by determining the characteristics of an acoustic speckle signal of the particles and relating these characteristics to the size and concentration characteristics of the particles. The method and the apparatus are especially useful for the measurement of the size distribution of small particles in optically opaque liquids.

SummaryA new microscopic principle based on radiometric stereo microscopy is presented, which is designed for investigating macro‐dispersion of filler in rubber. The image acquisition is combined with a stereological method of estimating the volume‐weighted size distribution of the filler particles. Experimental results for carbon black filler in rubber obtained by radiometric stereo microscopy are compared with those from microtomography using synchrotron radiation, and, furthermore, a simulation study is used for evaluation. It turns out that using the new three‐dimensional microscopic method, the size distribution of the filler particles can be estimated from fresh cuts of rubber with high accuracy, and thus it is an interesting alternative to well‐established dark field microscopy.Lay DescriptionMacro‐dispersion of globular filler particles in a rubber matrix is an important quantity that depends on manufacturing parameters and influences various rubber properties. Therefore, it must be carefully adjusted during the incorporation process and investigated by industrial quality control (ASTM D7723‐18). Quality control is usually based on freshly made planar sections so‐called fresh cuts through rubber specimen. After stress retention of the rubber one obtains a rough cutting surface in which the filler particles appear as imprints or bumps, called nodges. These nodges can be made visible by classical light microscopy under dark field (DFM) illumination. The systems disperGRADER+ or the disperGRADER Alpha View were specifically designed for rubber inspection. However, it has proved to be very difficult estimating the size distribution of the filler particles from the observed white spots in the DFM image. In any case it is still necessary to compute the size distribution of the filler particles from an estimated size distribution of the section profiles. The latter is numerically unstable, i.e. small errors of the estimated size distribution of the section profiles lead to large errors of the computed filler size distribution.Applying DFM combined with filler dispersion estimation as described in ASTM D7723‐18 appears to be a fingerprint method only. For this reason, the new microscope nSPEC 3D was applied for rubber inspection. The principle used for surface imaging is based on radiometric stereo allowing for perfect three‐dimensional reconstruction of curved surfaces of fresh cuts. From this reconstruction it is possible to measure the height of particle nodges as well as their volumes. Furthermore, we present a new stereological method for estimating the filler size distribution from samples of the height and the volume of the nodges. Finally, microtomography with synchrotron radiation and computer simulation are applied to evaluate accuracy of the presented method.

The Nested Air Quality Prediction Modeling System (NAQPMS) is a new-generation fully coupled Eulerian model independently developed by the Institute of Atmospheric Physics, CAS. It can simulate the behavior and predict the values of various air pollutants, including PM2.5. This study coupled NAQPMS with an aerosol microphysics module—advanced particle microphysics (APM) to form a category model of NAQPMS + APM, which can simulate the microdynamics of multi-scale aerosols. This model used a high resolution classification method to characterize the size distribution of aerosol particles, which not only shows the mass concentration of aerosol particles, but also the number concentration, its spectral distribution, and the mixing state of particles. The NAQPMS + APM model can provide data for detailed analysis of the microdynamics mechanisms of fine particle pollution.

While it is well known that particle size reduction impacts the performance of bioprocessing such as anaerobic digestion or composting, there is a relative lack of knowledge about particle size distribution (PSD) in pre-treated organic material, i.e., the distribution of particles across different size ranges. PSD in municipal solid waste (MSW) pre-treated for bioprocessing in mechanical–biological treatment (MBT) was researched. In the first part of this study, the PSD in pre-treated waste at two full-scale MBT plants in the UK was determined. The main part of the study consisted of experimental trials to reduce particle sizes in MSW destined for bioprocessing and to explore the obtained PSD patterns. Shredders and a macerating grinder were used. For shear shredders, a jaw opening of 20 mm was found favourable for effective reduction of particle sizes, while a smaller jaw opening rather compressed the wet organic waste into balls. Setting the shredder jaw opening to 20 mm does not mean that in the output all particles will be 20 mm or below. PSD profiles revealed that different particle sizes were present in each trial. Using different types of equipment in series was effective in reducing the presence of larger particles. Maceration yielded a PSD dominated by very fine particles, which is unsuitable for composting and potentially also for anaerobic digestion. It was concluded that shredding, where equipment is well selected, is effective in delivering a material well suited for anaerobic digestion or composting.

The production of ultra-fine particles of alloys and metal-nitride mixtures was attempted by the pulsed Nd:YAG laser heating-evaporation of various Ni-Ti, Fe-Ti or Cu-Ni target alloys or partly Fe-Ti-powder mixtures in Argon or Nitrogen atmosphere. Especially, characteristics of particle morphology and size distribution, and compositions and lattice structures of alloy particles or the metal:nitride ratio of mixture particles were examined and compared with the properties of target materials. As a result, ultra-fine alloy particles of less than 150 nm in maximum size could be produced in spherical or polyhedral shape from their target alloys or powder mixtures in Ar atmosphere at 0.1 MPa (1 atm). The chemical compositions and structures were generally different from those of target materials, and the reason was interpreted in terms of the fact that the volatile element was enriched in the evaporated particles. Moreover, in N2 atmosphere, ultra-fine particles of metal-nitride mixtures such as Ni and TiN or Fe and TiN were formed from Ni-Ti or Fe-Ti alloys, respectively. The mixture ratio appeared controllable by selecting alloy compositions.

Blockchain technology, as a revolutionary concept, born with Bitcoin, is triggering the start of a new era on information. It is generally recognized that the blockchain-based systems achieve high security in the process of information sharing in a distributed network, at the cost of low efficiency in terms of data throughput or high costs in consuming computational resources. A natural question we are interested in is whether there exists a trade-off principle between different performances of a blockchain system, which is also regarded as blockchain impossibility triangle (BIT) problem. In this paper, we propose an analysis method which can be used to verify the existence of the BIT. Our analysis method is composed of two layers. In the first layer the basic and core attributes are abstracted by building a consensus model, and in the second layer the analysis approach is designed to verify the existence of a BIT. Specifically, in the first layer, we firstly define a leaderless consensus model to quantitatively abstract the basic parameters in the process of system consensus, then three core attributes are justified to serve as the three vertices of the discussed triangle problem, namely security, cost, and efficiency. Based on the core attributes, we propose the credibility metric which measures the difficulty of achieving credible consensus for a given blockchain system. In the second layer, we analyze the existence of BIT, where we have demonstrated the conditions that a BIT exists and the conditions that the triangle does not exist. Finally, the proposed analysis method is applied in analyzing PoW based blockchain systems, where we have shown that there is no BIT problem in PoW based systems. Furthermore, the proposed analysis method can also help the blockchain developers in finding the promising directions of a new blockchain consensus mechanism.

Changes in the spatial distributions of platelet Al3Ti particles in an Al-Al3Ti alloy by equal-channel angular pressing

The size distribution of the mass concentration of some water soluble materials was measured by an impactor of three stages and membrane filters. It was found that about the half of the mass of sulfate and ammonium particles is in the range of Aitken nuclei. The size distribution of sulfate particles depends on the relative humidity of the air: more nuclei are in the Aitken size range if the relative humidity is smaller. The size distribution of chloride particles is rather different from that of sulfate and ammonium particles: only a small fraction of the total mass is in the Aitken range. Considering the stoichiometric proportion of the ammonium sulfate, it is an ammonium excess, which is greater in the case of smaller particles. It is not impossible that this ammonium excess is caused by the presence of ammonium hydroxide. It follows from these results that in the Aitken size range there are many sulfate and ammonium particles which may be active cloud nuclei even over the continents. DOI: 10.1111/j.2153-3490.1968.tb00385.x