Granular Distribution Research Articles

Investigating the effects of B-site Cr doping on the structural, magnetic and magnetocaloric properties of La1.4Ca1.6Mn2− x Cr x O7 (0 ⩽ x ⩽ 0.4) bilayer manganites

In this work, we describe the preparation of a series of Cr-substituted La1.4Ca1.6Mn2−x Cr x O7 (x = 0.0, 0.1, 0.2, 0.3, 0.4) double-layer perovskite compounds using a solid-state reaction method. The XRD patterns of all the samples are characterized by a tetragonal structure with a bilayer Ruddlesden–Popper phase. Scanning electron microscope micrographs of the doped samples display ambiguous granular variation and distribution, thereby establishing that the Cr content adversely influences the diffusion kinetics during the sintering process. Combined field-cooled moment vs temperature (M–T) and isothermal magnetization measurements establish the presence of a ferromagnetic to paramagnetic transition in all samples. Furthermore, the second-order nature of the transition is identified using the Arrott plots for these compounds. The maximum values of the change in isothermal entropy are found to be 2.98 J kgK−1, 2.39 J kgK−1, 1.48 J kgK−1, 1.29 J kgK−1, and 1.13 J kgK−1 for samples with x = 0.0, 0.1, 0.2, 0.3, and 0.4, respectively, when exposed to a field of 2.5 T. The entropy curves of the pristine sample are bounded within a narrow range of temperatures while the isothermal entropy curves are broadly expanded over a range of temperatures upon Cr-doping. The broad entropy profiles of the Cr-doped compounds versus temperature suggest a relatively high magnetocaloric potential, compared to the parent compound.

A Review on SAR Image and its Despeckling

The method of speckle reduction is widely used in synthetic aperture radar (SAR) imagery over the last three decades. The SAR images are inherently speckled in nature. Speckle noise is a granular pattern distribution, usually modeled as a multiplicative noise that affects the SAR images, as well as all coherent images. Other SAR related problems are also discussed in this paper. Therefore, despeckling approaches are needed to improve the quality of SAR images. However, there is a trade-off between speckle reduction and the preservation of fine details in the despeckled SAR image. The reduction of the speckle noise without losing the fine details of the SAR image is a diffucult task. However, many despeckling methods have been discussed to reduce the speckle noise from the SAR images. Each method has their own norms, advantages and disadvantages. This article contains a review of some major work in the field of SAR image despeckling. Often, scientists and scholars have faced the struggle to understand the pattern distribution of the speckle noise in SAR images. Hence, a brief details about radar, SAR imaging, speckle noise in SAR images and the prevalent approaches of SAR image despeckling are reviewed here. The advantages and disadvantages of SAR image despeckling approaches are also analysed and discussed.

Comparative evaluation of the effectiveness of methods for certification of transplanted cell lines

The article presents the results of certification of two trofovariants of MDVK cell lines with the help of traditional method and flow cytometry. Research object was the test cultures MDBK-E and MDBK-B, which passed 30 and 43 passages, respectively, after cryopreservation. The traditional method of attestation of transplanted cell lines, widely used in practice, is rather laborious and requires significant expenditures of labor, money and time. The flow cytometry method is based on a wide range of cytochemical and fluorescent methods for the analysis of sizes, granularity, phases of the cell cycle, structural components (DNA, RNA, protein), cell apoptosis and a number of other indicators. It was experimentally established that the sublines of MDBK-E and MDBK-B cells differed in cultural, cytomorphological and karyological parameters, as well as in contamination by foreign agents and sensitivity to parainfluenza-3 viruses and infectious rhinotracheitis in cattle. Analysis of histograms of cell distribution depending on the DNA content showed that the studied lines MDBK-E and MDBK-B did not exceed the standard indicator in terms of apoptosis and were at the level of 3,9 and 6,8%, respectively. Cells of the MDBK-E line did not contain viral and mycoplasma contamination, were characterized by a pronounced growth potential, retained the original cell morphology and were the most promising substrate for the production of antigens of parainfluenza-3, infectious rhinotracheitis in cattle. Analysis of granularity distribution results testified to the violation of the division processes and the appearance in the population of the subline MDBK-B of abnormal cells, as well as inadequate conditions for maintaining the test culture. It has been established that the flow cytometry method is objective and quite promising in the selection of culture models that meet the requirements of domestic and international standards. The revealed correlation between the magnitude of apoptosis, cultural properties and parameters of the cell cycle makes it possible to assess the biological properties of the producer culture as one of the leading factors in the change in programmed cell death. Changes the index of programmed cell death underlies a number of important pathological conditions and degenerative processes.

Composition-graded multilayer nanogranular films enabling broadband tunneling magneto-dielectric effect: Role of the granular distribution

The tunneling magneto-dielectric (TMD) effect, which causes a magnetic field-induced increase in the dielectric permittivity (ε′0) of nanogranular films, is promising for use in multifunctional devices. However, the frequency response of the TMD effect features a peak dielectric change (the TMD ratio, Δε′/ε′0) at a specific frequency, which inevitably limits the utility of the effect to within a narrow frequency range. To achieve the high TMD effect over a wider frequency band, we experimentally and theoretically report composition-graded multilayer (CGM) Co-MgF2 nanogranular films (i.e., with a step-varied granular Co content) with still high TMD ratios beyond this particular frequency range. Theoretical fittings of the experimental dielectric and TMD results indicate that the wide inter-granular spacing distribution in CGM films represents the origin of the broadband TMD effect. This study clarifies the critical role of the granular distribution in regulating the frequency response of the TMD properties. The proposed CGM structure, which can go beyond the limitations of conventional uniform nanogranular materials, will enable broadband magnetoelectric device applications of the TMD effect.

Alternative Method for Production of Pb Halide Perovskite with High Current Response for Photodetection Devices

To produce functional active layers for photodetector devices, thin films of organic–inorganic CH3NH3PbI3 perovskite semiconductor have been grown by a close-space sublimation procedure and a hybrid dipping technique. x-Ray diffraction analysis was used to evaluate the crystalline quality of the thin films, confirming the achievement of a tetragonal structure of perovskite type in space group I4/mcm. Morphological analysis by scanning electron microscopy revealed a homogeneous and compact granular surface distribution. Kubelka–Munk analysis of the optical response measured by ultraviolet–visible (UV–Vis) spectrophotometry yielded an energy bandgap of 1.57 eV for the thin films produced by the close-space sublimation technique and 1.59 eV for those obtained by dipping. Photoluminescence experiments corroborated these bandgap values. The I–V characteristics of both thin films obtained at different incident laser powers and a wavelength of 650 nm demonstrated their potential for use as active layers in photodetector devices.

Composition and processing of sulphide lead-zinc ores from Chaabet El-Hamra mine (Setif, Algeria)

Purpose. In order to fully exploit the metal and facilitate its method of processing, we need an accurate knowledge of its composition, granular distribution, and association with unimportant and penalizing elements that we would like to get rid of, compared to the distribution of the element to extract by flotation method. Methodology. The present experimental work proposes an approach to the mineralogical, chemical and particle size characterization, several analyzes have been carried out by Scanning Electron Microscopy with Energy Dispersive Spectroscopy (SEM/EDS), X-ray Diffraction (XRD), Optical Microscopy (OM), Particle Size-Fraction Analysis (PSFA), and X-ray Fluorescence (XRF). These analyzes were submitted on samples of lead-zinc of different sizes as well as well-prepared fine powder of this ore; the zinc content of the raw material is about 5% Zn. Findings. The results obtained by the mineralogical characterization and the particle size analysis reveal a very varied and irregular texture of the ore, consisting mainly of sulphides (sphalerite, galena, pyrite, marcasite), associated with carbonate gangue, mainly dolomite and calcite. The theoretical dimensions of the particles found in the fine grain size classes [-1 +0.053] mm. In addition, the conditions of the pulp using the following reagents: CuSO4 activator, PAX collector, CaO regulator and the pine oil foamed, along with a pH modifier between 10.5 and 12 (11.8 optimal), improve the content of sulphide minerals, and increased the concentrate of sphalerite (ZnS) by foam Flotation with a maximum recovery and economically appropriate content (54% Zn concentrate). Originality. Depending on the results of the analysis performed and the complete collection of data obtained in the laboratory, we aim to optimize the process of treating lead-zinc sulphide ore and give a more detailed reference source to specialists, researchers and metallurgists in field of mining in general and in the treatment of polymetallic lead-zinc ore in the area studied in particular. Practical value. Benefit the values of beneficial minerals (concentrate of zinc and others sulphide), from different types of raw materials. The latter focuses on flotation as the main successful technique in the extraction of this type of lead-zinc minerals, but it requires constant research and careful examination of its elements and values in order to excel in this field of polymetallic-sulphide ore processing.

The stability of aerobic granular sludge under low energy consumption: optimization of the granular size distribution by a novel internal component

An innovative and energy-saving reactor set-up can optimize the granule size distribution and achieve stable aerobic granular sludge.

Experimental and numerical investigations on the hydrodynamics of gas-solid fluidized bed with an inclined agitator

The effect of inclined agitation on the fluidization quality of a gas-solid fluidized bed is experimentally and numerically investigated. The pressure characteristics are characterized by the standard deviation of pressure drop and power spectra. The particle velocity, solid volume fraction and granular temperature distributions are investigated by numerical modeling. It is found that inclined agitation enhances the gross circulation of solid particles and enlarges the affect region of the agitator, improving the gas-solid fluidization quality. The increase in the agitation speed leads to higher frequency of collisions and more activity of particles, resulting in decreases of bubble sizes and a more homogeneous solid volume fraction distribution. Wide-blade agitator can also improve the fluidization performance.

Identification of sands of dune and concretes using a granular model - Case of arid region -

This work attempts to carry out a study based on the formulation of concrete according to the proportions of each concrete component. The main objective of this study is to use one of the physical parameters of the components, namely the aggregate and the cement included.Thus, this study aims at identifying the granular distribution of each component as well as that of dry concrete mixtures, using a granular model is the fractal dimension (DF). The results obtained make it possible to transform the particle size curve into a fractal line. In this study, experimental results made for execution projects were used.Knowing that the parameters such as the granular extent (d/D) and the fractal dimension (DF), depend on the exact determination of the cumulative size of the grains according to their size, are based on the results of the size of the analysis particles. Thanks to these two parameters (d/D) and DF, we can identify the granular distribution of certain materials related to projects carried out in the region of Adrar - Algeria, using results of projects already carried out. And we proposed a software to facilitate many calculations, and thus the transformation of the particle size curves into fractal lines for each granular mixture was obtained with its correlation coefficient R².

Multidomain Memristive Switching of Pt38Mn62/[Co/Ni]n Multilayers

We investigate the mechanism of analoglike switching of ${\mathrm{Pt}}_{38}{\mathrm{Mn}}_{62}$/[$\mathrm{Co}$/$\mathrm{Ni}$] multilayers induced by spin-orbit torques. X-ray photoemission microscopy performed during magnetization reversal driven by current pulses shows that sequential switching of reproducible domain patterns can be achieved. Switching proceeds by domain-wall displacement starting from the edges of blocked ferromagnetic domains, which do not switch for either direction of the current and represent up to 24% of the total ferromagnetic area. The antiferromagnetic ${\mathrm{Pt}}_{38}{\mathrm{Mn}}_{62}$ layer has a granular texture, with the majority of the domains being smaller than 100 nm, whereas the ferromagnetic domains in $\mathrm{Co}$/$\mathrm{Ni}$ are typically larger than 200 nm. The blocked domains and the granular distribution of exchange bias constrain the origin as well as the displacement of the domain walls, thus leading to highly reproducible switching patterns as a function of the applied current pulses. These measurements clarify the origin of the memristive behavior in antiferromagnet-ferromagnet structures and provide clues for further optimization of spin-orbit torque switching and memristivity in these systems.

Numerical and experimental investigations of instability in a spouted bed with non-spherical particles

A spouted bed containing non-spherical particles was investigated numerically using the non-spherical discrete hard-sphere method, and experimentally using particle image velocimetry. The experimental and simulated particle velocity distributions were in agreement. Different operating conditions were used to investigate the instability of the spouted bed. Certain conditions created an S-shaped gas channel in the center of the bed, which proved the instability of non-spherical particles. The motion of micro-scale particles and bubbles was studied to determine their potential relationship with instability. It was found that the granular temperature distribution of the particles and bubbles was associated with the gas channel region. The behaviors of bubbles differed from those of particles. These results contribute to an understanding of instability mechanisms in spouted beds.

Influence of segregation on the performance of self-compacting concrete in the fresh and hardened states

The granular mixture represents one of most important parameters in the formulation of self-compacting concretes in order to achieve a representative granular distribution. A good resistance to segregation results in a regular distribution of the different sizes of the aggregates in all parts of the element, with the same granule density. The granular mixture must be homogeneous and representative, and has to be able to flow in the absence of dynamic and static segregation.The main objective of the present research is to study the influence of segregation on the performance of Self-compacting concrete in the fresh and hardened state, by determining the static segregation index according to the percentage of aggregates of class G 8/15 and that of aggregates of class G 3/8 in order to obtain a homogeneous granular mixture, whatever the volume of self-compacting concrete to be prepared. It is well acknowledged that the threshold of the discontinuation of granular mixing represents a new element with respect to segregation in concrete. The obtained results showed that the percentage of large aggregates has a significant influence on the segregation index and the performance of self-compacting concrete (SCC) at 28 days.

Microstructure evolution and stress rupture properties of K4750 alloys with various B contents during long-term aging

The relationship among B content, microstructure evolution and stress rupture properties of K4750 alloy during long-term aging were investigated. After aging at 800 ℃ for 1000 h, the decomposition degree of MC carbides of K4750 alloys with 0B, 0.007 wt. % B and 0.010 wt. % B were basically identical, which indicated that B has no inhibition on MC carbide decomposition during long-term aging. The MC carbide decomposition was accompanied by the formation of M23C6 carbides and a small number of η phases, which was controlled by the outward diffusion of C and Ti combined with the inward diffusion of Ni and Cr from the γ matrix. In addition, M23C6 carbides in boron-free alloy were in continuous chain and needle-like η phases were precipitated near them, while M23C6 carbides in boron-containing alloys remained in granular distribution and no η phases precipitation around them. Adding B could delay the agglomeration and coarsening of M23C6 carbides during long-term aging, which was because the segregation of B at grain boundary retarded the diffusion of alloy elements, thus weakened the local fluctuation of chemical composition near grain boundary. The stress rupture samples of K4750 alloys with various B contents after aging at 800 ℃ for 1000 h were tested at 750 ℃/380 MPa. The results indicated that the stress rupture properties of boron-containing alloys were significantly better than that of boron-free alloy, which could be attributed to the increase of grain boundary cohesion strength and the optimization of M23C6 carbide distribution due to the addition of B.

Effect of topography on the motion parameters and deposition characteristics of deflection-type rock avalanches using the discrete element method

In this study, the deflection-type rock avalanches, a typical moving form of landslide in mountainous regions, were selected as the research object. Basing on the analysis of topography features of this type of rock avalanche, the discrete element method (DEM) was used to simulate the mass movement process of rock avalanche under different combinations of topographic factors for analyzing the effect of topography on rock avalanche. Sensitivity analysis for topography shows that the travel distance and the velocity difference are confined by the restraint of slope-toe and deflection effects. The slope inclination of deposition area and flow area are the most significant factors for the travel distance and velocity difference, respectively. In addition, a multivariate regression model was proposed to describe the relationship between motion parameters and main topographic factors. Regarding to the velocity distribution of granular particles inside granular body, the relationship between velocities of granular particles and deposit thickness follows a power law distribution under the different deposit width and length, but there are significant differences in power exponents. As for the granular particle distribution inside a deposit body, there is an obvious inverse-grading structure of granular particles inside the deposit body due to the separation of granular particles in their movement.

VGI VISUALISATION TO SUPPORT PARTICIPATORY LAKE MONITORING: THE CASE STUDY OF SIMILE PROJECT

Abstract. This study focuses on the role of VGI visualization in encouraging participation to environmental Citizen Science, taking as a case study the mobile application developed within SIMILE (Informative System for the Integrated Monitoring of Insubric Lakes and their Ecosystems) project activities. The main project goal is the protection of water quality for Lugano, Maggiore and Como lakes through a geoinformatics coordination of existing monitoring systems with new data collection methods (satellite images, high frequency sensors and citizen science). This tool enables the producers to perform a community-based monitoring side by side with local authorities and research bodies improving the efficiency of the current protocols.Referring to ontologies of geospatial data, the VGI samples are analysed under different aspects as their quality, quantity, variety, granularity, spatial and temporal distribution, highlighting their temporary, moving and changing nature. This analysis shows the presence of potential contradictions existing between the application use and the perceived lake water quality, to be mitigated mainly working on the user interface of the map view. So, a study of existing conventions, especially in terms of colours, is compared with the results coming from the application of consolidated survey methodologies to this specific context. Reflections on markers, symbols and attributes of features and maps are presented introducing geovisual analytical solutions for dynamic phenomena. The design solutions adopted are finally presented and validated with a combination of different usability evaluation methods like heuristics and field tests.

Blue-shift in the optical band gap of sol-gel derived Zn(1-x)SrxO nanoparticles

Zn(1-x)SrxO nanoparticles (x = 0.00, 00.01, 0.02, 0.03, 0.05) are prepared by sol-gel co-precipitation. Strontium (Sr) doping causes small but highly significant band gap enhancement that amounts 0.58%. This band gap engineering, following a quartic variation with respect to dopant concentration (x), may find potential applications in the fabrication of various devices based on heterojunctions. The structural analysis of the nanoparticles is done using XRD. The randomly oriented polycrystalline nanoparticles (NPs) notice a decrease in lattice parameters for initial two doping levels, thereafter an increment. The crystallite sizes range between 10.54 and 27.76 nm, along various crystallographic planes. Due to Sr doping, dislocations are also caused whose density vary between 1.2 × 1015 and 9.0 × 1015 lines/m2. FTIR analysis confirms the presence of Zn–O bond prominently in tetrahedral mode. UV–Vis spectra reveal a dip at the wavelength corresponding to the band gap of NPs with different Sr concentration. Tauc's plot yields the band gap of undoped ZnO as 3.281 eV which gets augmented up to 3.30 eV by 5 at.% Sr doping. This band gap enhancement is an outcome of infiltration of Sr into the ZnO matrix, rather than substitution. PL emission spectra contain the peaks in UV and visible (violet-blue) range. The UV peak, arising from band-to-band exciton recombination, gets blue-shifted with Sr incorporation into ZnO. Violet-blue emissions, mainly originating from defect levels, see the changes only in their intensities. The surface morphology, through FESEM, presents elongated spherical, hexagonal and platelet kind of structures with interlinking granular chains. Interlinks densify with initial doping, whose role has been comprehended in governing the violet-blue emission. Sr doping of 3 at.% is found to have larger voids in the granular distribution. For highest doping interlinkages appear to resume. For compositional analysis EDX is performed, which confirms the presence of Sr in all doped ZnO NPs.

A settling model for full-scale aerobic granular sludge

The settling behavior of aerobic granular sludge (AGS) in full-scale reactors is different from the settling of normal activated sludge. Current activated sludge models lack the features to describe the segregation of granules based on size during the settling process. This segregation plays an important role in the granulation process and therefore a better understanding of the settling is essential. The goal of this study was to model and evaluate the segregation of different granule sizes during settling and feeding in full-scale aerobic granular sludge reactors. Hereto the Patwardhan and Tien model was used. This model is an implementation of the Richardson and Zaki model, allowing for multiple classes of particles. To create the granular settling model, the most relevant parameters were identified using aerobic granular sludge from different full-scale Nereda® reactors. The settling properties of individual granules were measured as was the bulk behavior of granular sludge beds with uniform granular sludge particles. The obtained parameters were combined in a model containing multiple granule classes, which then was validated for granular sludge settling in a full-scale Nereda® reactor. In practice a hydraulic selection pressure is used to select for granular sludge. Under the same hydraulic selection pressure the model predicted that different stable granular size distributions can occur. This indicates that granular size distribution control would need a different mechanism then the hydraulic selection pressure alone. This model can be used to better understand and optimize operational parameters of AGS reactors that depend on granular sludge size, like biological nutrient removal. Furthermore insights from this model can also be used in the development of continuously fed AGS systems.

CISK: An interactive framework for conceptual inference based spatial keyword query

Spatial keyword query is an important technique for recommending users their desired POIs in self-driving services. Inferring query intention has been recognized as an important yet challenging issue for spatial keyword search. However, existing methods are inadequate to discover qualified results due to the inability to capture the intention of short-text input keywords. In this paper, we adopt a conceptual inference based method to deduce implicit intentions of users and thus are able to find more meaningful answers. Firstly, a locality-aware inference model is designed to generate concepts by considering typicality, granularity and spatial distribution, taking into account the hypernym–hyponym relationships in knowledge graphs. Afterwards, we propose a novel interactive framework to learn conceptual preferences for users, by using k-skyband to prune unpromising objects at the beginning and employing dense subgraph to select promising candidates in each interaction round. After a small number of rounds of learning, all objects can be rationally ordered by a user’s personalized ranking function which is unknown in advance. Empirical study on two real datasets demonstrates the effectiveness of our proposed conceptual inference and preference learning based methods.

Analysis of machining process and thermal conditions during vibration-assisted cortical bone drilling based on generated bone chip morphologies

When the temperature during bone drilling exceeds the safety threshold, the bone tissue surrounding the drilling site can be irreversibly damaged. To investigate the influence of vibration-assisted drilling (VAD) methods on the temperature increase during bone drilling and the causes for temperature increase, drilling experiments were performed on fresh bovine femur samples. The morphology and granularity distribution of the generated bone chips were innovatively used to directly compare the machining processes and thermal conditions of conventional drilling (CD), low-frequency vibration-assisted drilling (LFVAD), and ultrasonic vibration-assisted drilling (UVAD). The experimental results indicated that LFVAD produced the lowest temperature increase of 31.4°C, whereas UVAD produced the highest temperature increase of 44.1°C with the same drilling parameters. Additionally, the morphologies and granularity distributions of the bone chips significantly differed among these methods. We concluded that the smaller temperature increase in LFVAD was mainly attributed to the improved thermal conditions resulting from the periodic cutting/separation motion and the reliable geometric chip-breaking mechanism. In contrast, the unfavourable thermal conditions of UVAD were caused by the higher applied frequency, which created a significantly larger amount of friction heat. This was the main cause for the highest observed temperature increase, resulting in bone crushing processes that generated additional heat.

CRUSHED LIMESTONE SAND: AN EFFECTIVE ALTERNATIVE TO NATURAL SAND IN CONCRETE

Due to its scarcity and the detrimental environmental effect of its extraction, leading to governmental restrictions, the good quality natural rounded siliceous sand became less available in Lebanon. This national and international issue affects the construction industry through the cost and the quality of concrete. Currently, this sand, too fine to be used alone as fine aggregate in concrete mixes, is always mixed with an appropriate percentage of crushed limestone sand to meet the standard grading. The objective of the study is to assess the feasibility of total replacement of natural rounded siliceous sand by crushed limestone sand to avoid the dependency of the construction field on the quality and availability of this material in the Lebanese context. The research program consists of proposing various concrete mixes without natural sand and verifying, following a performance-based approach, that their behaviors can be maintained, at different ages of hardened states, compared to those of the reference concrete incorporating natural sand. The resulting comparisons allow identifying the influences on compressive and flexural strengths of natural sand substitution and of the variations of granular size distribution. At this stage of the study, some preliminary conclusions about the applicability of the solution of natural sand total substitution are proposed.