Media Of Different Densities Research Articles

Optimization and Experimental Study of Iron Ore Grinding Medium Parameters Using EDEM Discrete Element Software.

Energy savings and consumption reduction of ball mills are crucial for industrial production. The grinding medium is an important component of a ball mill. In theory, using higher-density grinding media can yield better grinding results. However, for materials with varying grindability, employing grinding media of different densities can reduce energy consumption while maintaining the same grinding effect. This study simulates the motion of the grinding media in the mill using three different densities of balls and the same material (iron ore). The results reveal that balls with densities of 5.8 g/cm3 and 7.8 g/cm3 achieve faster grinding of materials into finer particles, but balls with a density of 5.8 g/cm3 consume less energy. Therefore, replacing a ball with a density of 5.8 g/cm3 in a ball mill can significantly reduce energy consumption. This study will assist in selecting the optimal grinding medium density for different materials, ultimately contributing to energy savings and reduced carbon emissions.

Richtmyer-Meshkov Instability of Laminar Flame

A slow laminar flame which is a thin (less than 1 mm thick) gas layer separating media of different densities is proposed as the interface between gaseous media for laboratory studies of Richtmyer-Meshkov and Rayleigh-Taylor instabilities. The potential of the proposed approach to produce the interface is shown by the example of shock wave interaction with a laminar flame in a lean hydrogen-air mixture (6 vol.% hydrogen). The development of Richtmyer-Meshkov instability at the interface between a heavy (cold) mixture and a light (hot) mixture was recorded by shadowgraphy.

Effects of liquid property on onset velocity of circulating fluidization in liquid-solid systems: A CFD-DEM simulation

Knowledge on regime transition from conventional to circulating fluidization is important to scale-up and operation of liquid-solid fluidized systems in industrial applications. Previous experimental studies reported that the onset velocity measured by bed empty time test is pertinent to the physical properties of particle and liquid, and independent of solid inventory, bed geometry, and configuration. The effect of liquid properties is, however, not clear yet since tap water is usually used as the working fluid in laboratory test for convenience. To address this problem, a Computational Fluid Dynamics-Discrete Element Method (CFD-DEM) model is applied to numerically measure the onset velocity of particles in different liquid media. The model is first validated in terms of the experimental data of bed expansion in literature. Then several kinds of particles and three kinds of liquid media of different densities and viscosities are further simulated. We find that the Reynolds number based on onset velocity and Archimedes number follows a power-law relationship. With the decrease of Archimedes number, the discrepancy of Reynolds number based on onset velocity and that on particle terminal velocity becomes highly significant. The ratio of the onset velocity to particle terminal velocity for various particles in one liquid medium is not a constant, and instead dependent on both the particle and liquid properties.

Permanent Fiber-Optic System Monitors Oil-Rim Movement

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 188868, “Development and Field Application of a Permanent Fiber-Optic Wellbore-Fluid-Level Monitoring System,” by C. Staveley, SPE, C. Doyle, and C. Coetzee, Smart Fibres; A. Franzen, H. Den Boer, A. van Rooyen, and W. Birch, Shell; and A.B. Biderkab and E. Moes, Petroleum Development Oman, prepared for the 2017 Abu Dhabi International Petroleum Exhibition and Conference, Abu Dhabi, 13–16 November. The paper has not been peer reviewed. In highly fractured carbonate reservoirs, the conventional method of monitoring oil-rim movement is running wireline gradiometric surveys periodically. However, some operators have found that this method is inconclusive and is unable to provide information in a manner timely enough to influence operations because the gradiometric surveys are only run a few times a year. In this paper, the authors describe a project to design, field trial, and qualify an alternative solution for real-time monitoring of the oil rim in carbonate reservoirs that overcomes these disadvantages. Current Methodology The methodology of performing gradiometric surveys can be applied in reservoirs successfully where the permeability of the formation is high and where the formation is fractured such that good communication exists between fluid within the formation and within the observation well (given that the well casing is highly perforated across the full length of the reservoir section). Under these conditions, the fluid levels measured by the gradiometric surveys give the operator enough information about the oil rim within the reservoir to adopt an active smart-field production method. The term “smart field” is used by the operator to describe oilfield operations where surface decisions are supported by measurements from within the reservoirs. While the use of gradiometric surveys for production optimization is helpful, it does have disadvantages. Each survey requires a well intervention; as can be imagined, the process is relatively expensive and introduces health, safety, and environmental (HSE) risks while the well is open. Consequently, gradiometric surveys are generally commissioned at a low frequency, perhaps only one or two measurements per year within key observation wells. New Methodology In the early 2000s, a potential was recognized to provide an array of permanently deployed pressure gauges in the wellbore to measure the density of the media between adjacent gauges. From this measurement, the interfaces between the media of different densities could be derived accurately. The idea of measuring pressure within a well is not new; pressure transducers based on numerous electronic measurement principles have been used by the industry for decades. However, these electronic gauges are not optimal for use in the described application because of their relatively short service life at the elevated temperatures found in wellbores and be-cause of the logistical difficulties and high cost associated with deploying a string of multiple electronic gauges in a single well. The operator’s in-well technology team examined the emerging use of optical-fiber Bragg gratings (FBGs) for pressure metrology applications in extreme environments. The gauges used in this technology required no downhole electronics and offered long service at elevated downhole temperatures. The technology offered the long-term stability required to detect the subtle pressure changes resulting from small fluid-level changes. Dozens of such gauges could be deployed in a series on one optical cable connected to a single surface-acquisition unit (interrogator).

On the Structure of the Mixing Zone at an Unstable Contact Boundary

The interface between two media of different densities (contact boundary) moving with an acceleration directed from the less dense medium to the more dense one is unstable (Rayleigh–Taylor instability) [1, 2]. The initial perturbations of the interface grow indefinitely and, as a result, a medium mixing zone growing with time is formed at the interface. The structure of such a mixing zone at gas–gas and gas–liquid interfaces is discussed on the basis of laboratory experiments on shock tubes of various types. It is concluded that the regions of turbulent and laminar flows are combined in the mixing zone.

2. Entropic closure for MRI-guided radiotherapy

Introduction The majority of patients affected by cancer are nowadays treated by radiotherapy, which consists in delivering a homogeneous dose with energetic particles. Magnetic Resonance Imaging (MRI)-guided radiotherapy shows precisely the tumor position in real time and allows to direct the photon beams to the tumor while sparing organs at risks. Our work consists in the validation of a new model developped to simulate the energy deposition of the particles used in radiotherapy (electrons, photons and protons) in the presence of strong magnetic field, within human tissues, and its adaptation to this new technology. Material and methods This model is based on a kinetic entropic closure of the linearized Boltzmann equation [1] , which describes the transport of energetic particles in the matter. This equation takes a lot of computation time to be solved due to the high number of variables. To simplify this, we replace fluences by angular moments, which allows getting rid of the angular variables and improve the calculation time. We obtain a set of angular moments equations, and we close this set using the Boltzmann’s principle of entropy maximization on the two first equations of the set. This model has an accuracy comparable to references Monte-Carlo (MC) codes [2] (Geant4, MCNPx, Penelope), and is less time-consuming than these ones. We added the Lorentz force into our code to study the influence of a magnetic field on the dose deposition, and compared it to the reference full MC code FLUKA. To further validate our model, we have carried out an experimental campaign in which we irradiated a composition of materials of different mass densities, with 6 and 18 MV photon beams of a Varian Clinac 21Ex accelerator, without and with the influence of a 0.87 T magnetic field of amplitude induced by a permanent magnet. Results We show a good agreement between our model and the FLUKA code ( Fig. 1 ). We highlight the effects that occur on the propagation of particles in the matter in presence of a magnetic field of a few Tesla. Indeed, it modifies the dose deposition by shifting the deposition of energy, leading to an increased diffusion depending on the orientation of the magnetic field. Moreover, it also leads to an increase or decrease of the dose deposited at the interfaces between materials depending on their difference between mass densities. The results of our experiments lead to the same conclusions. These effects have to be taken into account in order to prevent creation of hot spots or a spread of energy distribution in a human body, within computation times compatible with the clinical environment. Conclusion Our model is a good candidate for future Treatment Planning Systems since it allows a faster and efficient way to plan a viable treatment for a patient in presence of strong magnetic fields. A magnetic field modifies the profile of the dose deposition such as it has to be taken into account in calculations to prevent the dramatic changes which occur at interfaces between media of different density. This work takes place in the framework of POPRA (Programme Optique Physique et Radiotherapie en Aquitaine), which involves several laboratories around problematics on the topic of cancer treatment.

Full-Wave Electromagnetic Scattering From Rough Surfaces With Buried Inhomogeneities

We develop a methodology for modeling coherent electromagnetic scattering from rough surfaces with buried inhomogeneities in three dimensions. The inhomogeneities considered in this paper include random spherical media, random cylindrical media, and root-like cylindrical clusters. They are used to simulate rocks, ice particles, and vegetation roots buried beneath the ground surface that can be seen by the low-frequency radars in Earth remote sensing applications. The approach we develop first calculates volumetric scattering from the media using coherent approaches, including both the conventional recursive transition matrix (T-matrix) method as well as a new generalized iterative extended boundary condition method we developed for tilted finite cylinders, and then transforms the T-matrix to the scattering matrix, which is then used to form the full scattered field of layered structures with rough surface and subsurfaces. We validate the methodology by comparing with other numerical solutions for special cases, and show sensitivity results for scattering from rough surface with buried random spherical media and random cylindrical media of different densities. We also construct a basic root model and calculate the scattering cross sections from single and multiple root clusters with or without a subsurface interface underneath. With the approach developed in this paper, we are able to study the sensitivity of radar signals to subsurface scatterers. For example, our simulations show that, depending on their density and water content, buried roots could enhance the backscatter from a single rough surface by as much as 5 dB in co-pol components, and substantially more in cross-pol components. The results of this model are expected to enable more accurate geophysical retrievals of soil moisture as well as soil organic content.

Time-resolved whole field investigation of plasma plume-induced shock wave in liquid media of different densities

Laser-produced plasma-induced shock wave in liquid media of different densities has been experimentally studied using non-intrusive diagnostics. A time-resolved Mach–Zehnder interferometer is setup to track the shock wave and subsequent density perturbations in the medium. Two-dimensional spatial distributions for both, ambient medium density and plasma (electron) density have been obtained by employing customised inversion technique and algorithm on the recorded interferograms. It has been observed that the nature of the shock-induced density perturbation in liquid medium is significantly different as compared to that in the gaseous medium. The observed density perturbations have been correlated with the primary shock wave and stress waves reflected from within the target and travelling back in the medium. The trend in the variation of electronic charge density in the plume region has also been studied.

Application of cone-beam micro-CT on high-speed Diesel flows and quantitative cavitation measurements

X-ray computed tomography (CT) is well-known and widely used in the medical sector for diagnosis of various illnesses. The technique is based on the absorption (i.e. attenuation) of the ionising electromagnetic radiation by the object. The amount of energy to be absorbed depends on the density and its thickness; the transmitted radiation through the object is then compared to the incident radiation that leads to a reconstruction of attenuation coefficients versus spatial position in the object. Thus, the resulting three-dimensional slices of the object are used (a) to identify internal geometric features of objects, and (b) to distinguish between media of different densities, i.e. liquid and air/vapour. In this study, the geometry extraction capability has been applied on time-averaged cavitation pocket shapes, as well as, the capability of density differentiation measurements on Diesel fuel flows. Results appear promising and pose a challenge in providing quantitative measurements of cavitation vapour fraction inside an injection hole.

SU-E-T-131: Dosimetric Impact and Evaluation of Different Heterogenity Algorithm in Volumetric Modulated Arc Therapy Plan for Stereotactic Ablative Radiotherapy Lung Treatment with the Flattening Filter Free Beam

Purpose: The present study aimed to investigate the dosimetric impacts of the anisotropic analytic algorithm (AAA) and the Acuros XB (AXB) plan for lung stereotactic ablative radiation therapy using flattening filter-free (FFF) beam. We retrospectively analyzed 10 patients. Methods: We retrospectively analyzed 10 patients. The dosimetric parameters for the target and organs at risk (OARs) from the treatment plans calculated with these dose calculation algorithms were compared. The technical parameters, such as the computation times and the total monitor units (MUs), were also evaluated. Results: A comparison of DVHs from AXB and AAA showed that the AXB plan produced a high maximum PTV dose by average 4.40% with a statistical significance but slightly lower mean PTV dose by average 5.20% compared to the AAA plans. The maximum dose to the lung was slightly higher in the AXB compared to the AAA. For both algorithms, the values of V5, V10 and V20 for ipsilateral lung were higher in the AXB plan more than those of AAA. However, these parameters for contralateral lung were comparable. The differences of maximum dose for the spinal cord and heart were also small. The computation time of AXB was found fast with the relative difference of 13.7% than those of AAA. The average of monitor units (MUs) for all patients was higher in AXB plans than in the AAA plans. These results indicated that the difference between AXB and AAA are large in heterogeneous region with low density. Conclusion: The AXB provided the advantages such as the accuracy of calculations and the reduction of the computation time in lung stereotactic ablative radiotherapy (SABR) with using FFF beam, especially for VMAT planning. In dose calculation with the media of different density, therefore, the careful attention should be taken regarding the impacts of different heterogeneity correction algorithms. The authors report no conflicts of interest

Nanosecond electric explosion of a tungsten wire in different media

The effect of surrounding media of different densities and electric strengths on the heating dynamics of a micron wire during its nanosecond electric explosion is investigated. Tungsten wires with diameters of d = 25–50 μm were exploded in air and water at a current rise time of (dI/dt) ∼ 1010 A/s. The diagnostic complex is described.

The Effect of Different Isolation Procedures on Canine Leucocyte Populations and on Lectin‐induced Lymphocyte Proliferation

Proliferation assays performed on peripheral blood mononuclear cells (PBMC) are commonly used in experimental and clinical immunology. A prerequisite for an in vitro assay is the ability to obtain relatively pure populations of mononuclear cells from whole blood, as contaminating polymorphonuclear cells may affect the proliferation of lymphocytes. Purification of canine leucocytes from whole blood is associated with difficulties in obtaining pure lymphocytes in high yields. The aim of this study was to optimize the lymphocyte purification from canine whole blood in terms of total cell recovery and purity, while not influencing the proliferation capacity of the isolated cells. To acquire optimal isolation of canine lymphocytes several density gradient media of different densities and osmolalities were examined. For optimal phagocyte removal, pre-treatment of whole blood with carbonyl iron/arabic gum and/or adherence to fibrinogen pre-coated polystyrene tissue flasks were examined. Lectin-induced proliferation was used as measurement of cell activity of the obtained cell fractions after the different separation procedures. Canine blood pre-treated with carbonyl iron/arabic gum followed by density gradient centrifugation with medium 'G' (density: 1.079 g/cm(3), osmolality: 256 mOsm) and adherence to pre-coated polystyrene tissue flask obtained the best PBMC cultures with a median lymphocyte purity of 88% and a median yield of recovered lymphocytes of 54%. This culture also resulted in the highest proliferation and subsequently the highest stimulation index upon lectin stimulation.

On the construction of stable iterative methods for solving ill-posed nonlinear equations with nondifferentiable operators

In this paper we present a general scheme of constructing stable iterative methods for solving nonlinear operator equations free of standard differentiability and regularity assumptions on the whole of the solution space. Equations of this type are of frequent occurrence in modern studies of inverse problems in mathematical physics and engineering. In the work we relax the classical smoothness and regularity assumptions and replace them by similar conditions on an appropriate finite dimensional affine subspace of the original solution space. In the framework of the developed scheme, we propose several implementable iterative processes for stable approximation of solutions to nondifferentiable irregular operator equations. One of the methods has been applied to a 3D inverse problem of reconstruction of the interface between two media of different densities from measurements of the gravity field on the plane outside the dividing surface. Numerical experiment confirm stability of the method relative to the noise in gravimetric data.

On the construction of stable iterative methods for solving ill-posed nonlinear equations with nondifferentiable operators

In this paper we present a general scheme of constructing stable iterative methods for solving nonlinear operator equations free of standard differentiability and regularity assumptions on the whole of the solution space. Equations of this type are of frequent occurrence in modern studies of inverse problems in mathematical physics and engineering. In the work we relax the classical smoothness and regularity assumptions and replace them by similar conditions on an appropriate finite dimensional affine subspace of the original solution space. In the framework of the developed scheme, we propose several implementable iterative processes for stable approximation of solutions to nondifferentiable irregular operator equations. One of the methods has been applied to a 3D inverse problem of reconstruction of the interface between two media of different densities from measurements of the gravity field on the plane outside the dividing surface. Numerical experiment confirm stability of the method relative to the noise in gravimetric data.

Theoretical and experimental dissection of gravity-dependent mechanical orientation in gravitactic microorganisms.

Mechanisms of gravitactic behaviors of aquatic microorganisms were investigated in terms of their mechanical basis of gravity-dependent orientation. Two mechanical mechanisms have been considered as possible sources of the orientation torque generated on the inert body. One results from the differential density within an organism (the gravity-buoyancy model) and the other from the geometrical asymmetry of an organism (the drag-gravity model). We first introduced a simple theory that distinguishes between these models by measuring sedimentation of immobilized organisms in a medium of higher density than that of the organisms. Ni2+-immobilized cells of Paramecium caudatum oriented downwards while floating upwards in the Percoll-containing hyper-density medium but oriented upwards while sinking in the hypo-density control medium. This means that the orientation of Paramecium is mechanically biased by the torque generated mainly due to the anterior location of the reaction center of hydrodynamic stress relative to those of buoyancy and gravity; thus the torque results from the geometrical fore-aft asymmetry and is described by the drag-gravity model. The same mechanical property was demonstrated in gastrula larvae of the sea urchin by observing the orientation during sedimentation of the KCN-immobilized larvae in media of different density: like the paramecia, the gastrulae oriented upwards in hypo-density medium and downwards in hyper-density medium. Immobilized pluteus larvae, however, oriented upwards regardless of the density of the medium. This indicates that the orientation of the pluteus is biased by the torque generated mainly due to the posterior location of the reaction center of gravity relative to those of buoyancy and hydrodynamic stress; thus the torque results from the fore-aft asymmetry of the density distribution and is described by the gravity-buoyancy model. These observations indicate that, during development, sea urchin larvae change the mechanical mechanism for the gravitactic orientation. Evidence presented in the present paper demonstrates a definite relationship between the morphology and the gravitactic behavior of microorganisms.

Two-color excitation fluorescence microscopy through highly scattering media

We study the performance of two-color excitation (2CE) fluorescence microscopy [Opt. Lett. 24, 1505 (1999)] in turbid media of different densities and anisotropy. Excitation is achieved with two confocal excitation beams of wavelengths lambda(1) and lambda(2), which are separated by an angular displacement theta, where lambda(1) not equal lambda(2), 1/lambda(e) = 1/lambda(1) + 1/lambda(2), and lambda(e) is the single-photon excitation wavelength of the sample. 2CE fluorescence is generated only in regions of the sample where the two excitation beams overlap. The 2CE fluorescence intensity is proportional to the product of the two excitation intensities and could be detected with a large-area photodetector. The requirement of spatiotemporal simultaneity for the two excitation beams makes 2CE fluorescence imaging a promising tool for observing microscopic objects in a highly scattering medium. Optical scattering asymmetrically broadens the excitation point-spread function and toward the side of the focusing lens that leads to the contrast deterioration of the fluorescence image in single- or two-photon (lambda(1) = lambda(2)) excitation. Image degradation is caused by the decrease in the excitation energy density at the geometrical focus and by the increase in background fluorescence from the out-of-focus planes. In a beam configuration with theta not equal 0, 2CE fluorescence imaging is robust against the deleterious effects of scattering on the excitation-beam distribution. Scattering only decreases the available energy density at the geometrical focus and does not increase the background noise. For both isotropic and anisotropic scattering media the performance of 2CE imaging is studied with a Monte Carlo simulation for theta = 0, pi/2, and pi, and at different h/d(s) values where h is the scattering depth and d(s) is the mean-free path of the scattering medium.

On the evolution and stability of interfacial ripples on and off the critical frequency

Under consideration are interfaces between two media of different densities and which arise from the interaction between the Mth and Nth harmonics of the motion where 1 ≤ N < M. By means of the method of multiple scales in both space and time a pair of nonlinear coupled partial differential equations is derived which model the progression of the interface. The equations contain a detuning parameter [sgrave] which allow imperfections in the resonance to be taken into account. Stokes-type sinusoidal solutions to the equations were sought. It was found that solutions exist for all values of the interaction ratio M/N. In some situations interfaces exist at both exact and near resonance; while in others they are destroyed by amplifications in the detuning. In yet others, a quantity of detuning is actually necessary for the profiles to exist. In all cases, even when the parameters are fixed, a very large class of interface profiles is possible. Finally, the stability of the profiles is studied. It is found that some are quite stable, even to perturbations with wavenumbers close to the main flow.

Legends of echoes linked through acoustics to prehistoric art

A new area for acoustic research has arisen from a previously unsuspected relationship between ancient legends of echoes, and prehistoric rock art. This art includes Ice Age deep cave paintings, and Native American petroglyphs typically found high on canyon walls. This acoustic connection is important because there has been no satisfactory explanation of the motivation for the production of rock art (neither the unusual locations nor the subject matter the artists chose). Yet producing rock art clearly was a major preoccupation for early Homo sapiens sapiens over a span of tens of thousands of years. The concept of sound wave propagation and reflection is a modern paradigm, and is based on the abstraction of invisible pressure waves being diverted by boundaries between media of different densities. In ancient times, however, the causes for many natural phenomena were explained by personification or animism, including attributing echoes to be the responses of spirits. Could echoes have motivated the ancient artists? Acoustic studies at rock art sites may be starting to answer this important question.

Investigation of interaction between reflected shocks and growing perturbation on an interface

This paper reports the result of investigation into Richtmyer–Meshkov instability (RMI) resulting from multiple interactions of shock waves with the interface between two media of different densities. The instability growth rates were measured after the interactions of the mixing zone with the refracted shock and the first and the second shocks reflected from the endwall. It was shown that for the contribution of separate shock–interface interactions to the instability growth rate, the condition of additivity is not realized. The values of the factor \(\psi\), accounting for the decrease in the RMI growth rate due to the thickening of the mixing zone, have been determined for a continuous interface and for a turbulent mixing zone.

High-Resolution, Submicron Particle Size Distribution Analysis Using Gravitational-Sweep Sedimentation

Sedimentation velocity is a powerful tool for the analysis of complex solutions of macromolecules. However, sample turbidity imposes an upper limit to the size of molecular complexes currently amenable to such analysis. Furthermore, the breadth of the particle size distribution, combined with possible variations in the density of different particles, makes it difficult to analyze extremely complex mixtures. These same problems are faced in the polymer industry, where dispersions of latices, pigments, lacquers, and emulsions must be characterized. There is a rich history of methods developed for the polymer industry finding use in the biochemical sciences. Two such methods are presented. These use analytical ultracentrifugation to determine the density and size distributions for submicron-sized particles. Both methods rely on Stokes’ equations to estimate particle size and density, whereas turbidity, corrected using Mie’s theory, provides the concentration measurement. The first method uses the sedimentation time in dispersion media of different densities to evaluate the particle density and size distribution. This method works provided the sample is chemically homogeneous. The second method splices together data gathered at different sample concentrations, thus permitting the high-resolution determination of the size distribution of particle diameters ranging from 10 to 3000 nm. By increasing the rotor speed exponentially from 0 to 40,000 rpm over a 1-h period, size distributions may be measured for extremely broadly distributed dispersions. Presented here is a short history of particle size distribution analysis using the ultracentrifuge, along with a description of the newest experimental methods. Several applications of the methods are provided that demonstrate the breadth of its utility, including extensions to samples containing nonspherical and chromophoric particles.