DEM investigation of the influence of particulate properties and operating conditions on the mixing process in rotary drums: Part 1-Determination of the DEM parameters and calibration process

This paper's goal was to select methods and a calibration procedure which would lead to the determination of relevant parameters of a discrete element method (DEM) and virtual material creation. Seven particulates were selected with respect to their shape (spherical and non-spherical), size and density. The first calibration experiment involved "packing test" to determine the shape accuracy and bulk density of virtual packed particulates. The series of simulations were compared with real experiments, and the size, shape and density of virtual particles were optimized. Using three apparatuses, the input parameter values were experimentally determined for a contact model that defines the behavior of particulates in DEM simulations. The research part of the paper examines the influence of factors such as particle number; pile formation method; and the method of evaluation of the angle of repose on the process of the calibration of virtual material. The most reproducible results were achieved by the "pilling" method and by the rotating drum-both evaluated by the geometric method. However, it is always advisable to make an overall visual comparison of the slope shape between the calibration simulation and the experimental curves. The bowl's diameter to particle size ratio should be greater than 25, and the calibration experiment should contain approximately 4000 particles to ensure representative results during angle of repose calibration experiment.Web of Science82art. no. 22

Scale-free Universal Spectrum for Atmospheric Aerosol Size Distribution for Davos, Mauna Loa and Izana

Atmospheric flows exhibit fractal fluctuations and inverse power law form for power spectra indicating an eddy continuum structure for the selfsimilar fluctuations. A general systems theory for fractal fluctuations developed by the author is based on the simple visualisation that large eddies form by space-time integration of enclosed turbulent eddies, a concept analogous to Kinetic Theory of Gases in Classical Statistical Physics. The ordered growth of atmospheric eddy continuum is in dynamical equilibrium and is associated with Maximum Entropy Production. The model predicts universal (scale-free) inverse power law form for fractal fluctuations expressed in terms of the golden mean. Atmospheric particulates are held in suspension in the fractal fluctuations of vertical wind velocity. The mass or radius (size) distribution for homogeneous suspended atmospheric particulates is expressed as a universal scale-independent function of the golden mean, the total number concentration and the mean volume radius. Model predicted spectrum is in agreement (within two standard deviations on either side of the mean) with total averaged radius size spectra for the AERONET (aerosol inversions) stations Davos and Mauna Loa for the year 2010 and Izana for the year 2009 daily averages. The general systems theory model for aerosol size distribution is scale free and is derived directly from atmospheric eddy dynamical concepts. At present empirical models such as the log normal distribution with arbitrary constants for the size distribution of atmospheric suspended particulates are used for quantitative estimation of earth-atmosphere radiation budget related to climate warming/cooling trends. The universal aerosol size spectrum will have applications in computations of radiation balance of earth-atmosphere system in climate models.Comment: 18 pages, 5 figures. arXiv admin note: substantial text overlap with arXiv:1105.0172, arXiv:1005.1336, arXiv:0908.2321, arXiv:1002.3230, arXiv:0704.211

Non-Einstein Viscosity Phenomenon of Acrylonitrile–Butadiene–Styrene Composites Containing Lignin–Polycaprolactone Particulates Highly Dispersed by High-Shear Stress

Lignin powder was modified via ring-opening polymerization of caprolactone to form a lignin–polycaprolactone (LPCL) particulate. The LPCL particulates were mixed with an acrylonitrile–butadiene–styrene (ABS) matrix at an extremely high rotational speed of up to 3000 rpm, which was achieved by a closed-loop screw mixer and in-line melt extruder. Using this high-shear extruding mixer, the LPCL particulate size was controlled in the range of 3395 nm (conventional twin-screw extrusion) down to 638 nm (high-shear mixer of 3000 rpm) by altering the mixing speed and time. The resulting LPCL/ABS composites clearly showed non-Einstein viscosity phenomena, exhibiting reduced viscosity (2130 Pa·s) compared to the general extruded composite one (4270 Pa·s) at 1 s–1 and 210 °C. This is due to the conformational rearrangement and the increased free volume of ABS molecular chains in the vicinity of LPCL particulates. This was supported by the decreased glass transition temperature (Tg, 83.7 °C) of the LPCL/ABS composite specimens, for example, giving a 21.8% decrement compared to that (107 °C) of the neat ABS by the incorporation of 10 wt % LPCL particulates in ABS. The LPCL particulate morphology, damping characteristics, and light transmittance of the developed composites were thoroughly investigated at various levels of applied shear rates and mixing conditions. The non-Einstein rheological phenomena stemming from the incorporation of LPCL particulates suggest an interesting plasticization methodology: to improve the processability of high-loading filler/polymer composites and ultra-high molecular weight polymers that are difficult to process because of their high viscosity

Theory and simulation of spectral line broadening by exoplanetary atmospheric haze

Atmospheric haze is the leading candidate for the flattening of expolanetary spectra, as it's also an important source of opacity in the atmospheres of solar system planets, satellites, and comets. Exoplanetary transmission spectra, which carry information about how the planetary atmospheres become opaque to stellar light in transit, show broad featureless absorption in the region of wavelengths corresponding to spectral lines of sodium, potassium and water. We develop a detailed atomistic model, describing interactions of atomic or molecular radiators with dust and atmospheric haze particulates. This model incorporates a realistic structure of haze particulates from small nano-size seed particles up to sub-micron irregularly shaped aggregates, accounting for both pairwise collisions between the radiator and haze perturbers, and quasi-static mean field shift of levels in haze environments. This formalism can explain large flattening of absorption and emission spectra in haze atmospheres and shows how the radiator - haze particle interaction affects the absorption spectral shape in the wings of spectral lines and near their centers. The theory can account for nearly all realistic structure, size and chemical composition of haze particulates and predict their influence on absorption and emission spectra in hazy environments. We illustrate the utility of the method by computing shift and broadening of the emission spectra of the sodium D line in an argon haze. The simplicity, elegance and generality of the proposed model should make it amenable to a broad community of users in astrophysics and chemistry.Comment: 16 pages, 4 figures, submitted to MNRA

Production and solidification analysis of titanium carbide particulates reinforced aluminium alloy matrix composite by vortex mixing - sand casting technique

In this study, production and solidification analysis of metal matrix composite (MMC) consisting of titanium carbide particulates reinforced aluminium-11.8% silicon alloy matrix are done. A combination of vortex mixing - sand casting technique is used as the manufacturing method to produce the specimens. Thermal measurement during the casting process is captured and solidification graphs are plotted to represent the solidification characteristic. The result shows that as volume fraction of particulates reinforcement is increased, solidification time becomes faster. Particulates reinforcement promotes solidification which will support finer grain size of the casting specimen and in turn produce better mechanical property. Hardness test is performed and it confirms that hardness number increases as more particulates are added to the MMC system

Methods for providing ceramic matrix composite components with increased thermal capacity

A method for enhancing the cooling capability of a turbine component made from a ceramic matrix composite. The method improves the thermal performance of the component by producing a surface having increased cooling capacity, thereby allowing the component to operate at a higher temperature. The method tailors the available surface area on the cooling surface of the composite component by depositing a particulate layer of coarse grained ceramic powders of preselected size onto the surface of the ceramic matrix composite component. The size of the particulate is selectively tailored to match the desired surface finish or surface roughness of the article. The article may be designed to have different surface finishes for different locations, so that the application of different sized powders can provide different cooling capabilities at different locations, if desired. The compositions of the particulates are chemically compatible with the ceramic material comprising the outer surface or portion of the ceramic matrix composite. The particulates are applied using a slurry and incorporated into the article by heating to an elevated temperature without melting the matrix, the particulates or the fiber reinforcement

The relevance of the evolution of experimental studies for the interpretation and evaluation of some trace physical evidence

In order for trace evidence to have a high evidential value, experimental studies which mimic the forensic reality are of fundamental importance. Such primary level experimentation is crucial to establish a coherent body of theory concerning the generation, transfer and persistence of different forms of trace physical evidence. We contend that the forensic context, at whatever scale, will be specific to each individual forensic case and this context in which a crime takes place will influence the properties of trace evidence. it will, therefore, be necessary in many forensic cases to undertake secondary level experimental studies that incorporate specific variables pertinent to a particular case and supplement the established theory presented in the published literature. Such studies enable a better understanding of the specific forensic context and thus allow More accurate collection, analysis and interpretation of the trace physical evidence to be achieved. This paper presents two cases where the findings of secondary level experimental studies undertaken to address specific issues particular to two forensic investigations proved to be important. Specific pre-, syn- and post-forensic event factors were incorporated into the experimental design and proved to be invaluable in the recovery, analysis and in achieving accurate interpretations of both soil evidence from footwear and glass trace evidence from a broken window.These Studies demonstrate that a fuller understanding of the specific context within which trace physical evidence is generated and subsequently collected, as well as an understanding of the behaviour of certain forms of trace physical evidence under specific conditions, can add evidentiary weight to the analysis and interpretation of that evidence and thus help a court with greater certainty where resources (time and cost) permit

The influence of physical and chemical linkage on the properties of nanocomposites

It has been shown by several groups that the mechanical and electrical behavior of composites changes quite substantially, and often beneficially, when the filler particle size is less than 100 nm in diameter. There is also good reason to believe that the interface between the embedded particulates and the polymer matrix holds the key to understanding the bulk phenomena observed. Materials based on an SiO2-polyolefin system have been formulated with functionalized particulates so as to affect the physical and chemical linkages. The agents used to achieve this include amino-silane, hexamethyl-disilazane and triethoxyvinylsilane. The emerging picture of the interface is supported by detailed dielectric spectroscopy and internal space charge assessment. The nature of the internal structure has been related to the bulk properties observed such as the breakdown strength, voltage endurance, and the measurement of internal charges resulting from interfacial polarization