Technique to Investigate Pulverizing and Abrasive Performance of Coals in Mineral Processing Systems

The operating costs of breaking coal particles into fine powder, to achieve optimum combustion for the boilers in a power plant, are made up of power input to carry on an energy intensive comminution mechanism and to overcome friction losses within pulverising machines. The operating costs also include the cost of the replacement of the processing system’s components due to wear. This study presents the development and application of an attrition test machine that enables an investigation of the factors that influence pulverizing efficiency. The attrition tester simulates grinding conditions in real vertical spindle mills. In this kind of mill, as with the tester, the size reduction process results from a shearing action during the redistribution of the coal particles. The redistribution and attrition within the coal bed are forced by movement of the rollers (or by a disc rotation, in the case of the tester). The testing method was oriented toward mechanical properties, i.e., internal friction shear strength, abrasiveness and grindability. This method enables facilitated testing procedures and a more exact simulation of grinding in vertical spindle coal mills. Ball-race mills and Loesche roller mills were used.

Fragmentation of ring galaxies and transformation to clumpy galaxies

We study the fragmentation of collisional ring galaxies (CRGs) using a linear perturbation analysis that computes the physical conditions of gravitational instability, as determined by the balance of self-gravity of the ring against pressure and Coriolis forces. We adopt our formalism to simulations of CRGs and show that the analysis can accurately characterise the stability and onset of fragmentation, although the linear theory appears to under-predict the number of fragments of an unstable CRG by a factor of 2. In addition, since the orthodox ‘density-wave’ model is inapplicable to such self-gravitating rings, we devise a simple approach that describes the rings propagating as material waves. We find that the toy model can predict whether the simulated CRGs fragment or not using information from their pre-collision states. We also apply our instability analysis to a CRG discovered at a high redshift, z = 2.19. We find that a quite high velocity dispersion is required for the stability of the ring, and therefore the CRG should be unstable to ring fragmentation. CRGs are rarely observed at high redshifts, and this may be because CRGs are usually too faint. Since the fragmentation can induce active star formation and make the ring bright enough to observe, the instability could explain this rarity. An unstable CRG fragments into massive clumps retaining the initial disc rotation, and thus it would evolve into a clumpy galaxy with a low surface density in an inter-clump region.

EXPERIMENTAL INVESTIGATIONS ON THE SURFACE APPLICATION OF SUPERPHOSPHATE BY THE FERTILISER SPREADING TOOL WITH INCLINED AXIS

One of the possible ways to significantly increase the spreading distance of fertilisers (and, accordingly, efficiency) by the fertiliser spreading tools may be creation of a structure with an inclined axis of rotation. For experimental investigations an experimental setup was developed and a solid mineral superphosphate granular fertiliser was used as a material. Increasing the angle of inclination of the disc of the fertiliser sowing tool with an inclined axis in a horizontal plane from 0 to 30º at a disc rotation frequency of 1000 min-1 leads to an increase in the effective sieving distance of granulated superphosphate by 34.9. It has been established that the best indices of mineral fertilisation both in terms of the operating width and the irregularity of the fertiliser introduction are provided at the angles of inclination of the disc of the new fertiliser distributing tool in a horizontal plane within 25-30º.

The kinematics and dark matter fractions of TNG50 galaxies at z = 2 from an observational perspective

ABSTRACT We contrast the gas kinematics and dark matter contents of z = 2 star-forming galaxies (SFGs) from state-of-the-art cosmological simulations within the ΛCDM framework to observations. To this end, we create realistic mock observations of massive SFGs ($M_*\gt 4\times 10^{10} \, \mathrm{M}_{\odot}$, SFR >50 M⊙ yr−1) from the TNG50 simulation of the IllustrisTNG suite, resembling near-infrared, adaptive-optics assisted integral-field observations from the ground. Using observational line fitting and modelling techniques, we analyse in detail the kinematics of seven TNG50 galaxies from five different projections per galaxy, and compare them to observations of twelve massive SFGs by Genzel et al. (2020). The simulated galaxies show clear signs of disc rotation but mostly exhibit more asymmetric rotation curves, partly due to large intrinsic radial and vertical velocity components. At identical inclination angle, their 1D velocity profiles can vary along different lines of sight by up to Δv = 200 km s−1. From dynamical modelling we infer rotation speeds and velocity dispersions that are broadly consistent with observational results. We find low central dark matter fractions compatible with observations ($f_{\rm DM}^v(\lt R_e)=v_{\rm DM}^2(R_e)/v_{\rm circ}^2(R_e)\sim 0.32\pm 0.10$), however for disc effective radii Re that are mostly too small: at fixed Re the TNG50 dark matter fractions are too high by a factor of ∼2. We speculate that the differences in gas kinematics and dark matter content compared to the observations may be due to physical processes that are not resolved in sufficient detail with the numerical resolution available in current cosmological simulations.

GASP XXIX – unwinding the arms of spiral galaxies via ram-pressure stripping

ABSTRACT We present the first study of the effect of ram pressure ‘unwinding’ the spiral arms of cluster galaxies. We study 11 ram-pressure stripped galaxies from GASP (GAs Stripping Phenomena in galaxies) in which, in addition to more commonly observed ‘jellyfish’ features, dislodged material also appears to retain the original structure of the spiral arms. Gravitational influence from neighbours is ruled out and we compare the sample with a control group of undisturbed spiral galaxies and simulated stripped galaxies. We first confirm the unwinding nature, finding that the spiral arm pitch angle increases radially in 10 stripped galaxies and also simulated face-on and edge-on stripped galaxies. We find only younger stars in the unwound component, while older stars in the disc remain undisturbed. We compare the morphology and kinematics with simulated ram-pressure stripping galaxies, taking into account the estimated inclination with respect to the intracluster medium (ICM) and find that in edge-on stripping, unwinding can occur due to differential ram pressure caused by the disc rotation, causing stripped material to slow and ‘pile up’. In face-on cases, gas removed from the outer edges falls to higher orbits, appearing to ‘unwind’. The pattern is fairly short-lived (<0.5 Gyr) in the stripping process, occurring during first infall and eventually washed out by the ICM wind into the tail of the jellyfish galaxy. By comparing simulations with the observed sample, we find that a combination of face-on and edge-on ‘unwinding’ effects is likely to be occurring in our galaxies as they experience stripping with different inclinations with respect to the ICM.

Does the rotational direction of a wind turbine impact the wake in a stably stratified atmospheric boundary layer?

Stably stratified atmospheric boundary layers are often characterized by a veering wind profile, in which the wind direction changes clockwise with height in the Northern Hemisphere. Wind-turbine wakes respond to this veer in the incoming wind by stretching from a circular shape into an ellipsoid. We investigate the relationship between this stretching and the direction of the turbine rotation by means of large-eddy simulations. Clockwise rotating, counterclockwise rotating, and non-rotating actuator disc turbines are embedded in wind fields of a precursor simulation with no wind veer and in wind fields with a Northern Hemispheric Ekman spiral, resulting in six combinations of rotor rotation and inflow wind condition. The wake strength, extension, width, and deflection depend on the interaction of the meridional component of Ekman spiral with the rotational direction of the actuator disc, whereas the direction of the disc rotation only marginally modifies the wake if no veer is present. The differences result from the amplification or weakening/reversion of the spanwise and the vertical wind components due to the effect of the superposed disc rotation. They are also present in the streamwise wind component of the wake and in the total turbulence intensity. In the case of an counterclockwise rotating actuator disc, the spanwise and vertical wind components increase directly behind the rotor, resulting in the same rotational direction in the whole wake while its strength decreases downwind. In the case of a clockwise rotating actuator disc, however, the spanwise and vertical wind components of the near wake are weakened or even reversed in comparison to the inflow. This weakening/reversion results in a downwind increase in the strength of the flow rotation in the wake or even a different rotational direction in the near wake in comparison to the far wake. The physical mechanism responsible for this difference can be explained by a simple linear superposition of a veering inflow with a Rankine vortex.

The AGN fuelling/feedback cycle in nearby radio galaxies – III. 3D relative orientations of radio jets and CO discs and their interaction

ABSTRACT This is the third paper of a series exploring the multifrequency properties of a sample of eleven nearby low-excitation radio galaxies (LERGs) in the southern sky. We are conducting an extensive study of different galaxy components (stars, dust, warm and cold gas, radio jets) with the aim of better understanding the AGN fuelling/feedback cycle in LERGs. Here, we present new, deep, sub-kpc resolution Karl G. Jansky Very Large Array (JVLA) data for five sample sources at 10 GHz. Coupling these data with previously acquired Atacama Large Millimetre/submillimetre Array (ALMA) CO(2–1) observations and measurements of comparable quality from the literature, we carry out for the first time a full 3D analysis of the relative orientations of jet and disc rotation axes in six FR I LERGs. This analysis shows (albeit with significant uncertainties) that the relative orientation angles span a wide range (≈30○–60○). There is no case where both axes are accurately aligned and there is a marginally significant tendency for jets to avoid the disc plane. Our study also provides further evidence for the presence of a jet-CO disc interaction (already inferred from other observational indicators) in at least one source, NGC 3100. In this case, the limited extent of the radio jets, along with distortions in both the molecular gas and the jet components, suggest that the jets are young, interacting with the surrounding matter and rapidly decelerating.

Fatigue strength of disk cutting tool of robotic equipment

The spatial rotation of the robotic unit cutting disk model is considered. The connection between the stresses in the disk and the kinematics of spherical motion is established. A criterion for the fatigue strength of a disk of robotic equipment is proposed. Keywords circular saw, disc, rotation frequency, inertial forces. [email protected]

Association between morphological characteristics of the optic disc and other anatomical features of the fundus in highly myopic eyes

Purpose: To investigate associated factors with optic disc characteristics in high myopia patients. Methods: According to the meta-analysis of pathologic myopia study, patients were divided into groups from categories 1 (C1) to C4. The diameters, tilt ratio, and rotation degree of optic disc, and the diameters of parapapillary atrophy were measured among other morphometric variables. Results: Totally 147 eyes (84 patients) were included. Longer horizontal optic disc diameter was associated with smaller tilt ratio ( p < 0.001, unstandardized regression coefficient B: −0.59), greater rotation degree ( p < 0.001, B: 0.01), and longer horizontal delta zone diameter ( p < 0.001, B: 0.09). Longer vertical optic disc diameter was associated with smaller rotation degree ( p < 0.001, B: 0.01), longer vertical delta zone diameter ( p < 0.001, B: 0.16), and longer disc–fovea distance (DFD; p < 0.024, B: 0.14). Generally, the horizontal optic disc diameter of C3 and C4 groups was smaller than C1 and C2, while vertical diameter and tilt ratio was greater than in C1 and C2. After setting axial length (AL) as an independent variable, horizontal diameters and tilt ratio still showed significant differences, while vertical diameters did not show significant differences. Conclusion: Axial elongation was associated with an increase of vertical optic disc diameter that was correlated with an reduction of optic disc rotation degree. By contrast, horizontal optic disc diameter elongation was correlated with an reduction of optic disc tilt ratio and an increase of optic disc rotation degree, which was independent of axial elongation.