Investigating the effects of effective stress on pore-dependent permeability measurements of crushed coal

The accurate determination of permeability is one of the parameters essential for the study of fluid flow and transport state. However, a large number of fractured coal bodies are faced during the production of coal mines. The study of permeability of these special media composed of grains of a certain size, whose structure is different from that of raw coal, has been in the exploratory stage. In this paper, inspired by the calculation method of median particle size and the calculation principle of KC’s equation, we calculate the permeability parameters of broken coal particles. It is considered that its permeability is closely related to the compaction and re-crushing process of skeletal grains. The lateral limit compression test of the crushed coal body was designed, and the pore-dominated permeability calculation method was given to reveal the mechanism of the action of the effective stress. The dependence relationship between the effective stress and the pore-correlation permeability is obtained by data analysis, and the force and deformation process of the crushed coal grain media is described. In contrast to the conventional Darcy series of permeability discussions, our approach excludes the influence of fluid factors on the permeability of porous media. The permeability of porous media is considered to be determined only by its own pore structure.

Experimental Study on Factors Influencing the Strength Distribution of In Situ Cemented Tailings Backfill

Previous studies have found that the strength of in situ cemented tailings backfill usually presents an S-shaped distribution, which decreases first, then increases, and decreases thereafter along the direction of slurry flow. In this study, to explore the factors determining the distribution, a similar model test of cemented tailings backfill was carried out. The distribution law of grain size composition and the cement content of backfill materials along the flow direction were experimentally studied, and the comprehensive factor influencing the strength distribution was analyzed. The results show that, firstly, near the feeding point, there are more coarse particles, whereas the content of fine particles is higher farther away. The measured maximum median particle size can be more than three times the minimum value. Secondly, the cement content increases gradually along the flow direction and reaches the peak at the end of the model, which can be more than twice the minimum value, indicating that the degree of segregation is significant. Thirdly, the strength distribution of cemented backfills is comprehensively determined by both the particle size distribution (PSD) and the cement content. The maximum value appears neither at the point with peak median particle size, nor at the point with the highest cement content. Lastly, there is a strong linear correlation between the strength of cemented backfills and the strength factor (SF), which is defined as the product of the uniformity coefficient and cement content of filling materials, indicating that the SF can be used to quantitatively reflect the comprehensive effects of PSD and cement content on the strength. As SF is a comprehensive quantitative index reflecting the distribution of strength, it will be further studied in later research to acquire more experimental results of the relationship between sample strength and SF, which will be meaningful for the quality evaluation of in situ cemented backfills, and the optimization of backfill system.

Influence of the particle size distribution of monomodal 316L powder on its flowability and processability in powder bed fusion

Powder bed fusion (PBF) is the most commonly adopted additive manufacturing process for fabricating complex metal parts via the layer-wise melting of a powder bed using a laser beam. However, the qualification of PBF-manufactured parts remains challenging and expensive, thereby limiting the broader industrialization of the technology. Powder characteristics significantly influence part properties, and understanding the influencing factors contributes to effective quality standards for PBF. In this study, the influence of the particle size distribution (PSD) median and width on powder flowability and part properties is investigated. Seven gas-atomized SS316L powders with monomodal PSDs, a median particle size ranging from 10 μm to 60 μm, and a distribution width of 15 μm and 30 μm were analyzed and subsequently processed. The PBF-manufactured parts were analyzed in terms of density and melt pool dimensions. Although powder flowability was inversely related to the median particle size, it was unrelated to the distribution width. An inverse relationship between the median particle size and the part density was observed; however, no link was found to the distribution width. Likely, the melt pool depth and width fluctuation significantly influence the part density. The melt pool depth decreases and the width fluctuation increases with an increasing median particle size.

Obtaining and research of pharmaceutical properties of antiemetics in a form of powder for inhalation

Samples of antiemetic drugs (ondansetronum, palonosetronum, metoclopramidum) in the form of powder for inhalation have been developed by the method of spray drying. The granulometric composition, hygroscopicity and aerodynamic distribution of aerosol particles of the drugs have been investigated. The dosage form of the powder for inhalation of antiemetics (ondansetronum and palonosetronum) in terms of its particle size distribution, hygroscopicity and content of the agent corresponds to those for inhalation using dry powder inhalers. In the study of the phase-dispersed composition of aerosol, ondansetronum and palonosetronum in the dosage form of powder for inhalation as part of the HandiHaler inhaler (at a flow rate of 60 l / min) showed high rates of the released dose up to 72-76%, respirable particle fraction (up to 5 m) up to 54 -56% and a mass median particle size of about 3 microns. Obtaining the inhaled form of metoclopramide requires optimization of the production method for receiving the product with acceptable pharmaceutical properties.

Mechanically activated mine tailings for use as supplementary cementitious materials

Two mine tailings are evaluated for their potential as supplementary cementitious materials. The mine tailings were milled using two different methods – ball milling for 30 minutes and disc milling for durations ranging from 1 to 15 minutes. The modified R3 test was carried out on the mine tailings to quantify their reactivity. The reactivity of the disc milled tailings is greater than those of the ball milled tailings. Strong correlations are obtained between milling duration, median particle size, amorphous content, dissolved aluminum and silicon, and reactivity of the mine tailings. The milling energy results in an increase in the fineness and the amorphous content, which do not appreciably increase beyond a disc milling duration of 8 minutes. The reactivity increases significantly beyond a certain threshold fineness and amorphous content. Cementitious pastes were prepared at 30% supplementary cementitious materials replacement level at a water-to-cementitious materials ratio of 0.40. No negative effects of the mine tailings were observed at early ages in cement pastes based on isothermal calorimetry and thermogravimetric analysis, demonstrating the potential for these materials to be used as supplementary cementitious materials.

The use of ground glass in red glazes: structural 3D imaging and mechanical behaviour using optical coherence tomography and nanoindentation

In this study we investigate the impact of the addition of colourless glass particles to red glazes, as seen in many 15th-17th-century easel paintings. With the use of reconstructions, we examined the influence of the paint preparation process on the morphological and mechanical properties of the paint film. Three sets of reconstructions were made, a control without ground glass, reconstructions with coarse or fine ground glass mixed in, and reconstructions where fine ground glass was ground jointly with the pigment oil mixture. The latter gave the desired consistency and colour based on visual inspection. The dried reconstructions were non-invasively imaged using optical coherence tomography (OCT). A data-analysis pipeline was developed for both the segmentation of the OCT images and the measurement of the size and spatial distributions of the glass particles within the glaze layer. Moreover, we used a nanoindentation protocol to measure the viscoelastic properties of the dried red glaze film. The OCT results show an expected decrease in median particle size with longer grinding-time, for which the additional grinding with pigment/oil resulted in a more narrow size distribution and a homogenous spatial distribution of the glass particles. The nanoindentation results indicate that the addition of glass particles increases the elastic and viscous moduli of the red glaze layers. The homogeneous size distribution, obtained by grinding the oil, pigment, and glass together, induces higher elastic and viscous moduli. Our imaging and analyses approach, combining OCT and nanoindentation, provides a non-invasive and quantitative investigation of glass particles in (semi-) transparent paint layers, and their effect on the mechanical properties of the glaze. The results of this study contribute to a better understanding of the artists’ addition of ground glass in paint layers.

Natural Ventilation Characterization in a Classroom under Different Scenarios

The COVID-19 pandemic has pointed to the need to increase our knowledge in fields related to human breathing. In the present study, temperature, relative humidity, carbon dioxide (CO2) concentration, and median particle size diameter measurements were taken into account. These parameters were analyzed in a computer classroom with 15 subjects during a normal 90-minute class; all the subjects wore surgical masks. For measurements, Arduino YUN, Arduino UNO, and APS-3321 devices were used. Natural ventilation efficiency was checked in two different ventilation scenarios: only windows open and windows and doors open. The results show how ventilation affects the temperature, CO2 concentration, and median particle diameter size parameters. By contrast, the relative humidity depends more on the outdoor meteorological conditions. Both ventilation scenarios tend to create the same room conditions in terms of temperature, humidity, CO2 concentration, and particle size. Additionally, the evolution of CO2 concentration as well as the particle size distribution along the time was studied. Finally, the particulate matter (PM2.5) was investigated together with particle concentration. Both parameters showed a similar trend during the time of the experiments.

Aeolian sediments in paleowetland deposits of the Las Vegas Formation

The Las Vegas Formation (LVF) is a well-characterized sequence of groundwater discharge (GWD) deposits exposed in and around the Las Vegas Valley in southern Nevada. Nearly monolithologic bedrock surrounds the valley, which provides an excellent opportunity to test the hypothesis that GWD deposits include an aeolian component. Mineralogical data indicate that the LVF sediments are dominated by carbonate minerals, similar to the local bedrock, but silicate minerals are also present. The median particle size is ~35 μm, consistent with modern dust in the region, and magnetic properties contrast strongly with local bedrock, implying an extralocal origin. By combining geochemical data from the LVF sediments and modern dust, we found that an average of ~25% of the LVF deposits were introduced by aeolian processes. The remainder consists primarily of authigenic groundwater carbonate as well as minor amounts of alluvial material and soil carbonate. Our data also show that the aeolian sediments accumulated in spring ecosystems in the Las Vegas Valley in a manner that was independent of both time and the specific hydrologic environment. These results have broad implications for investigations of GWD deposits located elsewhere in the southwestern U.S. and worldwide.

Improved Formulation of 224Ra-Labeled Calcium Carbonate Microparticles by Surface Layer Encapsulation and Addition of EDTMP

Radium-224-labeled CaCO3 microparticles have been developed to treat peritoneal carcinomatosis. The microparticles function as carriers of 224Ra, facilitating intraperitoneal retention of the alpha-emitting radionuclide. It was necessary to control the size of microparticles in suspension over time and introduce a sterilization process for the clinical use of the radiopharmaceutical. Ethylenediamine tetra(methylene phosphonic acid) (EDTMP) was investigated as a stabilizing additive. The possibility of encapsulating the radiolabeled microparticles with an outer surface layer of CaCO3 for the improved retention of radioactivity by the carrier was studied. This work evaluated these steps of optimization and their effect on radiochemical purity, the biodistribution of radionuclides, and therapeutic efficacy. An EDTMP concentration of >1% (w/w) relative to CaCO3 stabilized the particle size for at least one week. Without EDTMP, the median particle size increased from ~5 µm to ~25 µm immediately after sterilization by autoclaving, and the larger microparticles sedimented rapidly in suspension. The percentage of adsorbed 224Ra progeny 212Pb increased from 56% to 94% at 2.4–2.5% (w/w) EDTMP when the 224Ra-labeled microparticles were layer-encapsulated. The improved formulation also resulted in a suitable biodistribution of radionuclides in mice, as well as a survival benefit for mice with intraperitoneal ovarian or colorectal tumors.

Enhanced Sunlight Photocatalytic Activity and Biosafety of Marine-Driven Synthesized Cerium Oxide Nanoparticles: A Future prospect

This contribution presents the biosynthesis, physiochemical properties, and biological activity of biogenic CeO2 NPs using, for the first time, marine oyster extract as an effective and rich source of bioreducing and capping/stabilizing agents in a one-pot recipe. CeO2 NPs formation was initially confirmed through the color change from light green to pale yellow and subsequently, their corresponding absorption peak was spectroscopically observed at 310 nm with an optical band-gap of 4.67 eV using the DR-UV technique. Further, XRD and Raman analyses indicated that nanoceria possessed face-centered cubic arrangements without any impurities, having an average crystallite size of 10 nm. TEM and histogram results revealed that biogenic CeO2 NPs was approximately spherical in shape with a median particle size of 15±1 nm. The presence of various bioorganic substances on the surface of nanoparticles was deduced by FTIR and TGA results. It is found that marine-based nanoceria shows no cytotoxic effect on the cell, thus indicating their enhanced biocompatibility and biosafety to living organisms. In contrast, nanoceria demonstrated as an effective bactericidal agent toward pathogens. Visible light-activated CeO2 nanocatalyst revealed rapid photodegradation of methylene blue. Owing to simplicity, cost-effectiveness, and environmentally friendly nature, this novel marine biosynthetic route paves the way for prospective applications of nanoparticles in various areas of bioscience.