scholarly journals ESTABLISHING THE ROTATION SPEED VARIATION RANGE LIMITS FOR AUTO-EXCITATION OF SELF-OSCILLATING GRINDING IN A TUMBLING MILL

2020 ◽  
Vol 4 ◽  
pp. 32-35
Author(s):  
Kateryna Deineka ◽  
Yurii Naumenko
Keyword(s):  
Visual Analysis ◽  
Rotation Speed ◽  
Relative Size ◽  
Fine Fraction ◽  
Coarse Fraction ◽  
The Self ◽  
Cement Clinker ◽  
Crushed Material ◽  
Degree Of Filling ◽  
Tumbling Mill

The influence of the structure of a two-fraction polygranular feed of the chamber on the value of the drum rotation speed at auto-excitation of self-excited oscillations with a maximum swing is considered. Such a pulsating mode of movement of the charge is used in the self-oscillating process of grinding in a tumbling mill. The coarse fraction simulated the grinding bodies was steel bullets with a relative size ψdb=0.026. The fine fraction, simulated the particles of the crushed material, was a cement clinker with a relative particle size ψdm=0.00013. Variable factors of experimental studies were: the degree of filling the chamber in the state of rest κbr=0.25; 0.29; 0.33 and the degree of filling the gaps between the particles of the coarse fraction with particles of the fine fraction κmbgr=0.0625; 0.375; 0.6875; 1. The method of visual analysis of transient processes of self-oscillating modes of feed behavior in the cross section of the rotating drum chamber is applied. Measurements of the speed limits of the drum rotation were carried out with auto-excitation of self-oscillations of the filling. The magnitude of the self-oscillation swing was estimated by the increase in the difference between the maximum and minimum values of the filling dilatancy for one period of pulsations. An increase in the upper limit of the speed range ψω2 with a decrease in κbr and κmbgr was established. The growth rate of ψω2 increases at low values of κbr and κmbgr. Some increase in the lower limit of the ψω1 range with a decrease in κbr and κmbgr was revealed. An increase in the range of speeds of rotation was recorded at the maximum range of self-oscillations ψω1–ψω2 with a decrease in the connected interaction of the intra-mill filling. This coherent interaction is due to an increase in κbr and κmbgr. The value of the ψω1–ψω2 range varies from 1.01–1.03 at κbr=0.33 and κmbg=1 to 1.22–1.66 at κbr=0.25 and κmbgr=0.0625. The range gets its maximum value with fine and superfine grinding

scholarly journals The effect of the filling degree of the tumbling mill chamber on the bifurcation value of the froude number

2021 ◽  
pp. 21-24
Author(s):  
Kateryna Deineka ◽  
Yurii Naumenko ◽  
Tamara Myronenko
Keyword(s):  
Froude Number ◽  
Visual Analysis ◽  
Relative Size ◽  
Experimental Studies ◽  
Fine Fraction ◽  
Coarse Fraction ◽  
Spherical Particles ◽  
Charge Movement ◽  
Filling Degree ◽  
Tumbling Mill

The influence of the filling degree of the drum chamber on the bifurcation value of the Froude number in the case of self-excitation of self-oscillations of a two-fraction granular charge with a minimum swing is considered. Such a pulsating mode of the charge movement is used in the self-oscillating grinding process in a tumbling mill. The coarse fraction that simulated the milling bodies consisted of spherical particles of an incoherent granular material with a relative size in the chamber ψb=0.00733. The fine fraction, simulating the material to be ground, was cement with a relative particle size ψm≈0.092∙10-3. The value of the adopted analogue of the kinematic viscosity of the two-fraction granular loading approached the value of 10-3 m2/s. The main variable factor in experimental studies was the filling degree of the drum chamber with loading at rest κb=0.25, 0.35, and 0.45. An additional factor was the degree of filling the gaps between the spherical particles of the coarse fraction with particles of the fine fraction κb=0, 0.25, 0.5, and 1. The method of visual analysis through the transparent end wall of the chamber of transient processes of the loading behavior with a smooth change and fixation of the velocity was applied. The bifurcation minimum value of the rotation speed was recorded, at which the steady-state circulation mode of the load movement turns into a transient pulsation one with a minimum swing. A decrease in the bifurcation values of the Froude number Frb on the cylindrical surface of the chamber with an increase in κb has been established. An increase in the intensity of the decrease in Frb with an increase in κm was revealed. The recorded effect is due to an increase in the connected properties of a two-fraction loading during self-excitation of self-excited oscillations with an increase in κb and κm. The numerical values of the boundaries of the range of bifurcation values of the Froude number for a tumbling mill Frb=0.0484–1.17 have been determined. The obtained Frb range corresponds to the Reynolds value in the range Re=40–197. The maximum Frb value is obtained with coarse grinding. An increase in the likelihood of self-excitation of self-oscillations of the intra-chamber loading with a decrease in the fineness of grinding was revealed

scholarly journals INFLUENCE OF SMALL FRACTION OF POLYGRANULAR FILL OF ROTATING DRUM ON SELF-OSCILLATION SWING

2019 ◽  
pp. 31-37
Author(s):  
Deineka Kateryna
Keyword(s):  
Visual Analysis ◽  
Large Fraction ◽  
Relative Size ◽  
The Self ◽  
Spherical Particles ◽  
Rotating Drum ◽  
Crushed Material ◽  
Maximum Range ◽  
Size Of Particles ◽  
Degree Of Filling

The influence of the structure of two-fractional polygranular fill of a rotating drum on the self-oscillation swing is considered. The pulsating mode of flow of such intrachamber fill is used in the self-oscillating grinding process in a tumbling mill. Spherical particles of non-coherent granular material of 2.2 mm size were used as a large fraction modeling the grinding bodies. Cement was used as the small fraction modeling the particles of the crushed material. The factors of experimental studies were accepted: the gaps between particles of large fraction degree of filling at rest dispersed particles of small fraction 0, 25, 50 and 100%, the relative size of particles of large fraction in the drum chamber 0.519, 0.733, 1.04, 1.47, 2.08, 2.93, 4.15 and 5.87% (drum chamber radius 212, 150, 106, 75, 53, 37.5, 26.5 and 18.75 mm), the chamber degree of filling at rest 25, 35 and 45%. The method of visual analysis of fill motion patterns in the cross section of a rotating chamber and measurement of dilatation was applied.Video of the fill pulsating flow was taken. The magnitude of the self-oscillation swing was estimated by the increase in the difference of the maximum and minimum values of the fill dilatation over one period of pulsating. The maximum range of self-oscillation swing reached the value of 1.36. The change of the self-oscillation swing from zero at the beginning of self-excitation of pulsations to the maximum value with the greatest increase of dilatation was revealed. The effect of a decrease in the maximum range of self-oscillation swing with enhanced fill coherent properties has been registered. The attenuation of the spray of particles of large fraction in the chamber due to the coherent effect of the small fraction was established. An increase in the self-oscillation swing of single-grain fill was found with a decrease in the relative particle size and the chamber degree of filling. A decrease in the self-oscillation swing of two-fractional fill was found with an increase in the content of small fraction, a decrease in the relative size of particles of a large fraction, and an increase in the chamber degree of filling.

scholarly journals THE DRUM ROTATION VELOCITY VALUE WHEN AUTO-OSCILLATION SELF-EXCITATION WITH MAXIMUM SWING OF A POLYGRANULAR INTRACHAMBER FILL

2020 ◽  
pp. 61-69
Author(s):  
Kateryna Deineka ◽  
Yurii Naumenko ◽  
Anatolii Zmiievskyi
Keyword(s):  
Visual Analysis ◽  
Large Fraction ◽  
Relative Size ◽  
Experimental Studies ◽  
Rotation Velocity ◽  
The Self ◽  
Spherical Particles ◽  
Crushed Material ◽  
Fill Fraction ◽  
Degree Of Filling

The influences of the structure of two-fractional polygranular intrachamber fill on the drum rotation velocity value when auto-oscillation self-excitation with maximum swing is considered. The pulsating mode of flow of such intrachamber fill is used in the self-oscillating grinding process in a tumbling mill. Spherical particles of non-coherent granular material of 2.2 mm size were used as a large fraction modeling the grinding bodies. Cement was used as the small fraction modeling the particles of the crushed material. The factors of experimental studies were accepted: the gaps between particles of large fraction degree of filling at rest dispersed particles of small fraction 0, 25, 50 and 100%, the relative size of particles of large fraction in the drum chamber 0.519, 0.733, 1.04, 1.47, 2.08, 2.93, 4.15 and 5.87% (drum chamber radius 212, 150, 106, 75, 53, 37.5, 26.5 and 18.75 mm), the chamber degree of filling at rest 25, 35 and 45%. The method of visual analysis of transient processes of self-oscillating fill flow modes in the cross section of a rotating chamber was applied. Measurements of the drum rotation velocity during fill self-excited self-oscillations were performed. The magnitude of the self-oscillation swing was estimated by the increase in the difference of the maximum and minimum values of the fill dilatation over one period of pulsating. The magnitude of the relative drum rotation velocity at the maximum range of fill self-oscillation swing varied within 0.777-1.4. The effect of a decrease in the relative drum rotation velocity value, when the maximum polygranular intrachamber fill self-oscillations swing, with enhanced fill coherent properties has been registered. A decrease in the relative rotational velocity was established with a decrease in the relative particle size of large fill fraction and an increase in the content of small fill fraction and an increase in the chamber degree of filling. A sharp intensification of the decrease in the relative rotation velocity at a value of the relative size of large particles of less than 0.015 is revealed.

scholarly journals Establishing the effect of a simultaneous reduction in the filling load inside a chamber and in the content of the crushed material on the energy intensity of self-oscillatory grinding in a tumbling mill

2021 ◽  
Vol 1 (1 (109)) ◽  
pp. 77-87
Author(s):  
Kateryna Deineka ◽  
Yuriy Naumenko
Keyword(s):  
Energy Intensity ◽  
Large Fraction ◽  
Fine Fraction ◽  
Sharp Decrease ◽  
Dynamic Effect ◽  
The Self ◽  
Cement Clinker ◽  
Solid Loading ◽  
Oscillatory Process ◽  
Crushed Material

The effect of a simultaneous change in the degree of filling a chamber with load κbr and in the content of the crushed material κmbgr on the efficiency of the self-oscillatory grinding process has been estimated. Using a method of numerical modeling based on the results of experimental visualization of the flow has helped establish an emergent dynamic effect of the sharp increase in the self-oscillatory action of two-faction loading at a joint reduction in κbr and κmbgr. A significant decrease in the passive quasi-solid loading motion zone has been detected, as well as an increase in the active pulsation zone and a growth of dilatancy. The manifestation of the effect is enhanced by the simultaneous interaction of increasing the scope of self-oscillations and weakening the coherent properties of particles in a loose large fraction under the influence of the particles of fine fraction. A significant decrease in the values of the inertial loading parameters has been established: maximum dilatancy υmax, the relative scale of self-oscillations ψRυ, the maximum share of the active part of κfammax, and the generalized complex degree of dynamic activation Ka. A 2.65-time growth of υmax was detected, ψRυ increased by 5 times, κfammax ‒ by 4.36 times, Ka ‒ by 18.4 times, at a joint decrease in κbr from 0.45 to 0.25, in κmbgr ‒ from 1 to 0. The synergistic technological effect of a sharp decrease in the specific energy intensity Еo/Еs has been established, as well as an increase in the relative performance Co/Cs in the self-oscillatory grinding, due to a significant increase in the dynamic action of loading, which is exacerbated by the joint interaction of reduced κbr and κmbgr. The process of the self-oscillatory grinding of cement clinker has been investigated. A 62 % reduction in Еo/Еs and a 125 % increase in Co/Cs were detected at a joint decrease in κbr from 0.45 to 0.25, in κmbgr ‒ from 1 to 0.125. The established effects make it possible to substantiate the parameters for the energy-efficient self-oscillatory process of grinding in tumbling mills with a conventional structure

Long-term variations in individual particle types in the aerosol of Phoenix, Arizona, as determined using automated electron microprobe analysis and multivariate statistical techniques

1993 ◽  
Vol 51 ◽  
pp. 742-743
Author(s):  
Karen A. Katrinak ◽  
James R. Anderson ◽  
Peter R. Buseck
Keyword(s):  
Electron Microprobe ◽  
Fine Fraction ◽  
Coarse Fraction ◽  
Motor Vehicles ◽  
Multivariate Statistical Methods ◽  
Multivariate Statistical ◽  
X Ray ◽  
Mineral Particles ◽  
Anthropogenic Air Pollutants

Aerosol samples were collected in Phoenix, Arizona on eleven dates between July 1989 and April 1990. Elemental compositions were determined for approximately 1000 particles per sample using an electron microprobe with an energy-dispersive x-ray spectrometer. Fine-fraction samples (particle cut size of 1 to 2 μm) were analyzed for each date; coarse-fraction samples were also analyzed for four of the dates.The data were reduced using multivariate statistical methods. Cluster analysis was first used to define 35 particle types. 81% of all fine-fraction particles and 84% of the coarse-fraction particles were assigned to these types, which include mineral, metal-rich, sulfur-rich, and salt categories. "Zero-count" particles, consisting entirely of elements lighter than Na, constitute an additional category and dominate the fine fraction, reflecting the importance of anthropogenic air pollutants such as those emitted by motor vehicles. Si- and Ca-rich mineral particles dominate the coarse fraction and are also numerous in the fine fraction.

scholarly journals Political Storytelling on Instagram: Key Aspects of Alexander Van der Bellen’s Successful 2016 Presidential Election Campaign

2017 ◽  
Vol 5 (4) ◽  
pp. 15-25 ◽  
Author(s):  
Karin Liebhart ◽  
Petra Bernhardt
Keyword(s):  
Political Communication ◽  
Presidential Election ◽  
Digital Storytelling ◽  
Visual Analysis ◽  
The Self ◽  
Election Campaigns ◽  
Relevant Factor ◽  
One Year ◽  
Key Aspects ◽  
Presidential Election Campaign

This article addresses the strategic use of Instagram in election campaigns for the office of the Austrian Federal President in 2016. Based on a comprehensive visual analysis of 504 Instagram posts from Green-backed but independent presidential candidate Alexander Van der Bellen, who resulted as winner after almost one year of campaigning, this contribution reconstructs key aspects of digital storytelling on Instagram. By identifying relevant image types central to the self-representation of the candidate, this article shows how a politician makes use of a digital platform in order to project and manage desired images. The salience of image types allows for the reconstruction of underlying visual strategies: (1) the highlighting of the candidate’s biography (<em>biographical strategy</em>), (2) the presentation of his campaign team (<em>team strategy</em>), and (3) the presentation of the candidate as a legitimate office holder (<em>incumbent strategy</em>). The article thus sheds light on visual aspects of digital storytelling as relevant factor of political communication.

scholarly journals Aerosol characterisation including oxidative potential as a proxy of health impact

2019 ◽  
Vol 29 (2) ◽  
Author(s):  
Miroslav Josipovic ◽  
Catherine Leal-Liousse ◽  
Belinda Crobeddu ◽  
Armelle Baeza-Squiban ◽  
C. Keitumetse Segakweng ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Black Carbon ◽  
Fine Fraction ◽  
Health Impact ◽  
Coarse Fraction ◽  
Dry Season ◽  
Wet Season ◽  
Oxidative Potential ◽  
Ionic Content ◽  
Vaal Triangle

This study aimed to characterise aerosols sampled in the vicinity of a major industrialised area, i.e. the Vaal Triangle. It included thedetermination of oxidative potential as a predictive indicator of particle toxicity. Aerosol samples were collated through the cascadefiltering during an eight-month period (12 h over three days in one week). Three size fractions were analysed for organic carbon(OC), black carbon (BC) and oxidative potential (OP), while ionic content was presented as monthly and seasonal concentrations. Thecontinuous measurement of black carbon by an optical attenuation instrument was collated concurrently with cascade filtering. Thecarbonaceous content was low compared to the ionic one. Within the carbonaceous concentrations, the organic carbon was higherthan concentrations of black carbon in both seasons in the ultra-fine fraction; the opposite was the case for the fine fraction, whilethe coarse fraction concentrations of organic carbon in the dry season had higher concentrations than black carbon in the wet seasonand organic carbon in the wet season. The OP tended to increase as the size was decreasing for wet season aerosols, whereas, forthe dry season, the highest OP was exerted by the fine fraction. The ultrafine fraction was the one showing the most contrasting OPbetween the two seasons. Continuous monitoring indicated that the higher BC concentrations were recorded in the dry/winter partof the year, with the daily pattern of concentrations being typically bimodal, having both the morning and evening peaks in bothseasons. Within the ionic content, the dominance of sulphate, nitrate and ammonium was evident. Multiple linear correlations wereperformed between all determined compounds. Strong correlations of carboxylic acids with other organic compounds were revealed.These acids point to emissions of VOC, both anthropogenic and biogenic. Since they were equally present in both seasons, a mixtureof sources was responsible, both present in the wider area and throughout the year.

scholarly journals Investigating Subantarctic 14C Ages of Different Peat Components: Site and Sample Selection for Developing Robust Age Models in Dynamic Landscapes

Radiocarbon ◽  
2019 ◽  
Vol 61 (4) ◽  
pp. 1009-1027 ◽  
Author(s):  
Zoë A Thomas ◽  
Chris S M Turney ◽  
Alan Hogg ◽  
Alan N Williams ◽  
Chris J Fogwill
Keyword(s):  
Bulk Material ◽  
Sample Selection ◽  
Fine Fraction ◽  
Systematic Difference ◽  
Coarse Fraction ◽  
Sedimentary Sequences ◽  
Subantarctic Islands ◽  
Dynamic Landscapes ◽  
Age Model ◽  
Selection For

ABSTRACTPrecise radiocarbon (14C) dating of sedimentary sequences is important for developing robust chronologies of environmental change, but sampling of suitable components can be challenging in highly dynamic landscapes. Here we investigate radiocarbon determinations of different peat size fractions from six peat sites, representing a range of geomorphological contexts on the South Atlantic subantarctic islands of the Falklands and South Georgia. To investigate the most suitable fraction for dating, 112 measurements were obtained from three components within selected horizons: a fine fraction <0.2 mm, a coarse fraction >0.2 mm, and bulk material. We find site selection is critical, with locations surrounded by high-ground and/or relatively slowly accumulating sites more susceptible to the translocation of older carbon. Importantly, in locations with reduced potential for redeposition of material, our results show that there is no significant or systematic difference between ages derived from bulk material, fine or coarse (plant macrofossil) material, providing confidence in the resulting age model. Crucially, in areas comprising complex terrain with extreme relief, we recommend dating macrofossils or bulk carbon rather than a fine fraction, or employing comprehensive dating of multiple sedimentary fractions to determine the most reliable fraction(s) for developing a robust chronological framework.

scholarly journals In situ physical and chemical characterisation of the Eyjafjallajökull aerosol plume in the free troposphere over Italy

2014 ◽  
Vol 14 (2) ◽  
pp. 1075-1092 ◽  
Author(s):  
S. Sandrini ◽  
L. Giulianelli ◽  
S. Decesari ◽  
S. Fuzzi ◽  
P. Cristofanelli ◽  
...  
Keyword(s):  
Inductively Coupled Plasma ◽  
Gamma Ray ◽  
Fine Fraction ◽  
Chemical Properties ◽  
Analytical Techniques ◽  
Ground Level ◽  
Coarse Fraction ◽  
Volcanic Plume ◽  
Physical And Chemical ◽  
Aerosol Plume

Abstract. Continuous measurements of physical and chemical properties at the Mt. Cimone (Italy) GAW-WMO (Global Atmosphere Watch, World Meteorological Organization) Global Station (2165 m a.s.l.) have allowed the detection of the volcanic aerosol plume resulting from the Eyjafjallajökull (Iceland) eruption of spring 2010. The event affected the Mt. Cimone site after a transport over a distance of more than 3000 km. Two main transport episodes were detected during the eruption period, showing a volcanic fingerprint discernible against the free tropospheric background conditions typical of the site, the first from April 19 to 21 and the second from 18 to 20 May 2010. This paper reports the modification of aerosol characteristics observed during the two episodes, both characterised by an abrupt increase in fine and, especially, coarse mode particle number. Analysis of major, minor and trace elements by different analytical techniques (ionic chromatography, particle induced X-ray emission–particle induced gamma-ray emission (PIXE–PIGE) and inductively coupled plasma mass spectrometry (ICP-MS)) were performed on aerosols collected by ground-level discrete sampling. The resulting database allows the characterisation of aerosol chemical composition during the volcanic plume transport and in background conditions. During the passage of the volcanic plume, the fine fraction was dominated by sulphates, denoting the secondary origin of this mode, mainly resulting from in-plume oxidation of volcanic SO2. By contrast, the coarse fraction was characterised by increased concentration of numerous elements of crustal origin, such as Fe, Ti, Mn, Ca, Na, and Mg, which enter the composition of silicate minerals. Data analysis of selected elements (Ti, Al, Fe, Mn) allowed the estimation of the volcanic plume's contribution to total PM10, resulting in a local enhancement of up to 9.5 μg m−3, i.e. 40% of total PM10 on 18 May, which was the most intense of the two episodes. These results appear significant, especially in light of the huge distance of Mt. Cimone from the source, confirming the widespread diffusion of the Eyjafjallajökull ashes over Europe.

Masculine Bodies, Selfies, and the (Re)configurations of Intimacy

2017 ◽  
Vol 21 (1) ◽  
pp. 112-130 ◽  
Author(s):  
Begonya Enguix ◽  
Erick Gómez-Narváez
Keyword(s):  
Qualitative Data ◽  
Visual Analysis ◽  
The Self ◽  
Self Management ◽  
Body Parts ◽  
Structured Interviews

This article is part of a research about the use of selfies in two different apps, Grindr and Instagram. We are interested in exploring how selfies relate to masculine bodies and produce different negotiations of intimacy. Selfies are personal, bodily centered, and highly visible. Understanding their production can contribute to the discussion on the digital exposure of intimacy and on the (self) management of masculine bodies. We consider selfies as discursive media that merge the visual and the discursive. Through their practice, users actively negotiate their masculine bodies and their intimacies and question and/or affirm hegemonies. Based on visual analysis and qualitative data obtained from observation and structured interviews, our results point out to the active production of selfies in relation to the different apps and to different styles of bodies that (in)visibilize different body parts and/or emotional traits. Selfies (re)present hegemonic, resistant, and emergent bodies with different understandings of intimacy.

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