Mixed Particles Research Articles

Reconsideration of surface tension and phase state effects on cloud condensation nuclei activity based on the atomic force microscopy measurement

Abstract. Dicarboxylic acids are ubiquitous in atmospheric aerosol particles, but their roles as surfactants in cloud condensation nuclei (CCN) activity remain unclear. In this study, we investigated CCN activity of inorganic salt (sodium chloride and ammonium sulfate) and dicarboxylic acid (including malonic acid (MA), phenylmalonic acid (PhMA), succinic acid (SA), phenylsuccinic acid (PhSA), adipic acid (AA), pimelic acid (PA), and octanedioic acid (OA)), mixed particles with varied organic volume fractions (OVFs), and then directly determined their surface tension and phase state at high relative humidity (over 99.5 %) via atomic force microscopy (AFM). Our results show that CCN-derived κCCN of studied dicarboxylic acids ranged from 0.003 to 0.240. A linearly positive correlation between κCCN and solubility was obtained for slightly dissolved species, while negative correlation was found between κCCN and molecular volume for highly soluble species. For most inorganic salts and dicarboxylic acids (MA, PhMA, SA, PhSA and PA), a good closure within 30 % relative bias between κCCN and chemistry-derived κChem was obtained. However, κCCN values of inorganic salt–AA and inorganic salt–OA systems were surprisingly 0.3–3.0 times higher than κChem, which was attributed to surface tension reduction, as AFM results showed that their surface tensions were 20 %–42 % lower than that of water (72 mN m−1). Meanwhile, semisolid phase states were obtained for inorganic salt–AA and inorganic salt–OA and also affected hygroscopicity closure results. Our study highlights that surface tension reduction should be considered when investigating aerosol–cloud interactions.

Remote sensing of aerosol water fraction, dry size distribution and soluble fraction using multi-angle, multi-spectral polarimetry

Abstract. A framework to infer volume water fraction, soluble fraction and dry size distributions of fine-mode aerosol from multi-angle, multi-spectral polarimetry retrievals of column-averaged ambient aerosol properties is presented. The method is applied to observations of the Research Scanning Polarimeter (RSP) obtained during two NASA aircraft campaigns, namely the Aerosol Cloud meTeorology Interactions oVer the western ATlantic Experiment (ACTIVATE) and the Cloud, Aerosol, and Monsoon Processes Philippines Experiment (CAMP2Ex). All aerosol retrievals are statistically evaluated using in situ data. Volume water fraction is inferred from the retrieved ambient real part of the refractive index, assuming a dry refractive index of 1.54 and by applying a volume mixing rule to obtain the effective ambient refractive index. The uncertainties in inferred volume water fraction resulting from this simplified model are discussed and estimated to be lower than 0.2 and decreasing with increasing volume water fraction. The daily mean retrieved volume water fractions correlate well with the in situ values with a mean absolute difference of 0.09. Polarimeter-retrieved ambient effective radius for daily data is shown to increase as a function of volume water fraction as expected. Furthermore, the effective variance of the size distributions also increases with increasing effective radius, which we show is consistent with an external mixture of soluble and insoluble aerosol. The relative variations of effective radius and variance over an observation period are then used to estimate the soluble fraction of the aerosol. Daily results of soluble fraction correlate well with in situ-observed sulfate mass fraction with a correlation coefficient of 0.79. Subsequently, inferred water and soluble fractions are used to derive dry fine-mode size distributions from their ambient counterparts. While dry effective radii obtained in situ and from RSP show similar ranges, in situ values are generally substantially smaller during the ACTIVATE deployments, which may be due to biases in RSP retrievals or in the in situ observations, or both. Both RSP and in situ observations indicate the dominance of aerosol with low hygroscopicity during the ACTIVATE and CAMP2Ex campaigns. Furthermore, RSP indicates a high degree of external mixing of particles with low and high hygroscopicity. These retrievals of fine-mode water volume fraction and soluble fraction may be used for the evaluation of water uptake in atmospheric models. Furthermore, the framework allows us to estimate the variation in the concentration of fine-mode aerosol larger than a specific dry radius limit, which can be used as a proxy for the variation in cloud condensation nucleus concentrations. This framework may be applied to multi-angle, multi-spectral satellite data expected to be available in the near future.

Neutron-neutral particle mixing and its observable consequences

In this work, we explore the mixing between neutron ($n$) and elementary neutral particle ($\eta$), which violates both the baryon number ($\mathcal{B}$) and the lepton number ($\mathcal{L}$) by one unit but conserves their difference $(\mathcal{B}-\mathcal{L})$. Such mixing may give rise to non-trivial effects that are different from the Standard Model predictions. We organize our discussions based on two scenarios, roughly depending on whether an interference between oscillation and decay occurs, or whether the new-physics effects associated with the $n$-$\eta$ mixing contribute to the absorptive mixing amplitude. If an oscillation process is not accompanied by an interference between oscillation and decay, or the new-physics interactions do not contribute to the absorptive mixing amplitude, such a process can be classified as pure oscillation. Otherwise, it can be classified as impure oscillation. In the scenario of pure oscillation, CP-violation arising from the Majorana phase can manifest itself through the $n$-$\bar{n}$ oscillation process and may lead to observable effects. In the scenario of impure oscillation, we analyze the testable implications on the masses and lifetimes of the mass eigenstates formed as a result of the $n$-$\bar{n}$ oscillation mediated by $\eta$. In this scenario, we also suggest a unified interpretation of the neutron lifetime anomaly and the $n$-$\bar{n}$ oscillation measurements based on the $n$-$\eta$ mixing. In both scenarios, we present the lower bounds imposed by the experimental searches for $n$-$\bar{n}$ oscillations on the masses of the color multiplet bosons and point out that they could be within the reach of a direct detection at the LHC or future high-energy experiments.

An efficient and reliable scheduling algorithm for unit commitment scheme in microgrid systems using enhanced mixed integer particle swarm optimizer considering uncertainties

The use of an electrical energy storage system (EESS) in a microgrid (MG) is widely recognized as a feasible method for mitigating the unpredictability and stochastic nature of sustainable distributed generators and other intermittent energy sources. The battery energy storage (BES) system is the most effective of the several power storage methods available today. The unit commitment (UC) determines the number of dedicated dispatchable distributed generators, respective power, the amount of energy transferred to and absorbed from the microgrid, as well as the power and influence of EESSs, among other factors. The BES deterioration is considered in the UC conceptualization, and an enhanced mixed particle swarm optimizer (EMPSO) is suggested to solve UC in MGs with EESS. Compared to the traditional PSO, the acceleration constants in EMPSO are exponentially adapted, and the inertial weight in EMPSO decreases linearly during each iteration. The proposed EMPSO is a mixed integer optimization algorithm that can handle continuous, binary, and integer variables. A part of the decision variables in EMPSO is transformed into a binary variable by introducing the quadratic transfer function (TF). This paper also considers the uncertainties in renewable power generation, load demand, and electricity market prices. In addition, a case study with a multiobjective optimization function with MG operating cost and BES deterioration defines the additional UC problem discussed in this paper. The transformation of a single-objective model into a multiobjective optimization model is carried out using the weighted sum approach, and the impacts of different weights on the operating cost and lifespan of the BES are also analyzed. The performance of the EMPSO with quadratic TF (EMPSO-Q) is compared with EMPSO with V-shaped TF (EMPSO-V), EMPSO with S-shaped TF (EMPSO-S), and PSO with S-shaped TF (PSO-S). The performance of EMPSO-Q is 15%, 35%, and 45% better than EMPSO-V, EMPSO-S, and PSO-S, respectively. In addition, when uncertainties are considered, the operating cost falls from $8729.87 to $8986.98. Considering BES deterioration, the BES lifespan improves from 350 to 590, and the operating cost increases from $8729.87 to $8917.7. Therefore, the obtained results prove that the EMPSO-Q algorithm could effectively and efficiently handle the UC problem.

Fabrication and assessment of bifunctional electrospun poly(l-lactic acid) scaffolds with bioglass and zinc oxide nanoparticles for bone tissue engineering

Electrospun scaffolds based on poly(l-lactic acid) (PLLA) with bioglass (n-BG) and zinc oxide (n-ZnO), and mixture of both, were developed to design bifunctional biomaterials with enhanced bioactive and biocidal properties. The presence of n-BG increased the fiber diameter of the pure PLA from 1.5 ± 0.3 μm to 3.0 ± 0.8 μm for 20 wt%. ZnO and the mixed nanoparticles did not significantly affect the morphology. The mechanical properties decreased with the presence of nanoparticles. Scaffolds based on PLA/n-BG promoted hydroxyapatite (HA) formation in simulated body fluid (SBF) that was inhibited with the presence of ZnO. Notably, mixed particles produced bioactivity although at longer times. The incorporation of n-ZnO produced a biocidal capacity against S. aureus in the polymeric scaffold, reaching a viability reduction of 60 % after 6 h of exposure. When both types of nanoparticles were combined, the bacterial viability reduction was 30 %. Pure PLA scaffolds and the composites with n-BG showed good ST-2 bone marrow-derived cell line viability, scaffolds with n-BG (pure or mixture) presented lower viability. Results validated the use of both n-BG and n-ZnO fillers for the development of novel bifunctional PLA-based scaffolds with both bioactive and biocidal properties for bone tissue engineering applications.

Experimental study on coolability of mixed particle size debris bed under top flooding

During severe accident in reactor, a debris bed is formed after the core melt interacts with the coolant, this is the key stage to realize the melt retention in vessel and terminate the accident process. Studying the drying characteristics of such stacked particle beds can expand the safety margin of the In-Vessel Retention (IVR) strategy. In this paper, based on the debris bed's characteristics of prototype fuel coolant interaction (FCI) experiment, a one-dimensional cylindrical debris bed with irregular and multi-sized sand particles was constructed. At the uniformly stacked case, the typical characteristics were observed. Two vapor phase concentration areas appeared in the debris bed before and after drying, bubble blocking area was formed in the middle of the debris bed before drying, then a dry zone appeared at the bottom of the debris bed due to lack of liquid, the dry area extended first radially and then axially. Meanwhile, the influence of system pressure is significant, dryout heat flux (DHF) under 1.0 MPa is almost twice than normal pressure. At the sand particles layered case, it was found that DHF increased by 40%∼50% compared with uniformly stacked condition, the bubble blocked area and dry area coincided, and occurred in the middle of the debris bed. Finally, a DHF model based on Reed pressure drop model is established for one-dimensional uniform sand debris bed, and the calculated values are in good agreement with the experimental values.

Effect of Different Blades on Suspension Characteristics of Anaerobic Digestion Particles and Energy Consumption Optimization Analysis

In this study, a solid-liquid mixing system model was established to simulate the coexistence of floating particles (FP) and sinking particles (SP) in the early stage of anaerobic digestion, and the mixing effect and energy consumption of the system were investigated. Four typical blades were selected to compare the solid phase distribution of straw particles under different blade stirring, and the distribution of FP and SP in the coexistence system was clarified. Then the combination of full-factorial design and numerical simulation was applied to compare the effect of blade diameter and blade width on particle mixing, which was better than that of immersion depth. A comprehensive equation was further established to balance the weight between the particle mixing effect and energy consumption and improve the blade design. It provided theoretical support for the design and amplification of subsequent stirring equipment.

Serpentine and furrowed wavy channels-based enhancement in heat transfer for a rocket engine chamber

The thermal protection of the rocket engine combustion chamber is one of the fundamental challenges in supersonic flight. This paper investigates serpentine and furrowed wavy cooling channels with a rectangular cross-section to enhance heat transfer performance and hydrogen turbulent fluid flow characteristics. Ansys fluent was used to investigate the effects of configuration, wavy amplitude, and channel wavelength on the heat wall temperature, Nusselt number, coolant velocity, pressure drop, turbulent kinetic energy, and thermal stratification phenomena. Four different wave amplitudes and three wavelengths are compared to determine the optimal structure required to achieve the best heat transfer enhancement with acceptable pressure drop. Compared to the straight channel, the maximum temperature of the furrowed channel (Case 6) was decreased by 15.38% at an amplitude of 0.2 mm. Furthermore, the thermal performance factor is evaluated for eight furrowed wavy structures. The result is shown that the structure with an amplitude of 0.2 mm and a wavelength of 1 mm (Case 6) can demonstrate better thermal performance, which is increased by 31.55% compared to the straight channel. The wavy surfaces cause separation in diverging zones and secondary flows in converging zones, which disturbs the boundary layer, enhances particle mixing and improves convective heat transfer.

Insight into hydrodynamics and heat transfer characteristics in a gas–solid spout fluidized bed from a multiple zone view

In this work, the hydrodynamics and heat transfer characteristics within a gas–solid spout fluidized bed were investigated from a multiple-zone view by employing the coupled computational fluid dynamic and discrete element method. Results show that both the axial and radial particle mixing rates are accelerated with the axial particle mixing rate much faster than the radial one when increasing the spouting gas velocity. Besides, the particle-scale and the multiple-zone heat transfer analyses show that the annulus zone makes the major contribution to inter-particle conduction with the particle–particle conduction and the particle–fluid-particle conduction heat fluxes taking up about 64 % and 73 %, followed by the fountain zone taking up about 28 % and 22 %, respectively. As for the particle–fluid convective heat transfer, the spouting and annulus zones make almost the comparative contributions being about 38 %, followed by the fountain zone being less than 24 %. Moreover, the full-bed time-averaged heat transfer analysis shows that the particle–fluid convective heat transfer plays a dominant role in the heat transfer process in the spout fluidized bed with the particle–particle conductive and the particle–fluid-particle conductive heat fluxes being about 0.1 % and 1 % of the particle–fluid convective heat flux. The results of this study can provide an efficient theoretical reference for the gas–solid flow-mixing-heat transfer processes optimization and intensification of spout fluidized beds.

Reducing Particle Exposure and SARS-CoV-2 Risk in Built Environments through Accurate Virtual Twins and Computational Fluid Dynamics

The World Health Organization has pointed out that airborne transmission via aerosol particles can be a strong vector for the spread of SARS-CoV-2. Protecting occupants from infectious diseases or harmful particulate matter (PM) in general can be challenging. While experimentally outlining the detailed flow of PM in rooms may require complex setups, computational fluid dynamics (CFD) simulations can provide insights into improving the safety of the built environment and the most effective positioning of air-purifying devices. While previous studies have typically leveraged Reynolds-averaged Navier–Stokes (RANS) approaches for predicting particle propagation, the turbulence length scales accurately captured in these simulations may not be sufficient to provide a realistic spread and the mixing of particles under the effects of forced convection. In this paper, we experimentally validate a Lattice Boltzmann very large eddy simulation (VLES) approach including particle modeling. We also demonstrate how this simulation approach can be used to improve the effectiveness of air filtration devices in realistic office environments.

Heat transfer within dynamically structured bubbling fluidized beds subject to vibration: A two‐fluid modeling study

AbstractBubbling fluidized beds are often used to achieve a uniform particle temperature distribution in industrial processes involving gas and particles. However, the chaotic bubble dynamics pose significant challenges in scale‐up. Recent work (Guo et al., 2021, PNAS 118, e2108647118) has shown that using vibration can structure the bubbling pattern to a highly predictable manner with the characteristic bubble properties independent of system width, opening opportunities to address key issues associated with conventional bubbling fluidized beds. Herein, using two‐fluid modeling simulations, we studied heat transfer characteristics within the dynamically structured bubbling fluidized bed and compared to unstructured bubbling fluidized beds and packed beds. Simulations show that the structured bubbling fluidized bed can achieve the most uniform particle temperature distribution because it can achieve the best particle mixing while maintaining a global heat transfer coefficient similar to that of a freely bubbling fluidized bed.

A unified model of suspension concentration distribution in sediment mixed turbulent flows using generalized fractional advection-diffusion equation

The fractional operator in a space fractional advection-diffusion equation (FADE) plays a significant role in the mixing and vertical movement of sediment particles in a sediment-laden turbulent flow under non-local effects. Turbulent flow exhibits non-local mixing properties, which leads to the non-Fickian diffusion process that cannot be captured by the traditional diffusion equation. In this work, we present a generalized FADE that includes the generalized fractional differential operator in the Caputo sense. The full analytical solution is proposed utilizing the general Laplace transformation method. This generalized solution contains weight and scale functions and includes the effects of non-locality. It has been shown that several existing famous models of suspension concentration distribution for sediment particles (including both type-I and type-II distributions) in turbulent flows can be obtained from the proposed generalized solution with proper choices of the scale and weight functions in particular. Here a total of fourteen different types of concentration distribution equations including type-I and type-II profiles are derived from the general solution. Further possible generalizations of the model are also discussed which are more useful for practical applications. It is found that the several existing sediment distribution models are equivalent up to choices of weight and scale functions. Further, we found that the scale function could be physically related to the characteristic Lagrangian length of sediment mixing. The choice of the scale and weight function for both the type-I and type-II profiles are discussed and analyzed. Finally, the model is validated with experimental data as well as field data from the Missouri River, Mississippi River, and Rio Grande conveyance channels, and in each case, satisfactory agreements are obtained. These suggest the broader applicability of the present study.

Preparation and properties of CoCrMo-Ni@Al2O3 composite by selective laser melting

In this study, nickel coated alumina (Ni@Al 2 O 3 ) particles were prepared via electroless plating, and ball milled with CoCrMo alloy powder in the proportion of 0 wt% to 2 wt%. Then the Ni@Al 2 O 3 reinforced CoCrMo alloy were manufactured by selective laser melting (SLM) process. The microstructure, mechanical property and wear resistance performance of the CoCrMo alloy were characterized. By increasing the content of Ni@Al 2 O 3 particles from 0 wt% to 1.0 wt%, the CoCrMo alloy kept flawless with the highest hardness of 435 HV 1 and best abrasion performance, which could be attributed to the pinning dislocation slip effect of Al 2 O 3 phase and the metallurgical bonding of Ni phase with CoCrMo alloy during the SLM process. When the content of Ni@Al 2 O 3 increased to 2 wt%, the inconsistent fluidity between Ni@Al 2 O 3 and CoCrMo powders has led to the uneven distribution of mixed particles during the powder spreading process, which resulted in the lowest compressive strength and wear resistance. • In the field of joint replacement surgery, the SLM-processed CoCrMo alloy implants are gaining more popularity for their excellent mechanical properties. In order to promote the wear resistance and prolong the service life of implants, small amounts of ceramic particles can be added into the alloy matrix. • In this work, we have fabricated the uniformly core-shell structure of Ni coated Al 2 O 3 particle by electroless plating, and the CoCrMo composites with different amounts of Ni@Al 2 O 3 particles were prepared by SLM technology. As the Ni phase acted as a bridge during the melting process, the surface of CoCrMo-Ni@Al 2 O 3 composites were smooth without obvious cracks. Moreover, the CoCrMo composites demonstrated better wear resistance and stable coefficient of friction for the introduction of Al 2 O 3 .

Voltage stability assessment prediction using a guide strategy-based adaptive particle swarm optimisation-neural network algorithm

<span lang="EN-US">In this work, the indicators of electrical power network stability and voltage stability (VS) are discussed and developed with the aim of using a power transfer stability index (PTSI) indicator as a predictor for voltage stability (VS) in electrical power networks. The power transfer stability index (PTSI) was thus used to detect abnormally weak voltages in buses within such power system networks (weak). The target data are obtained using the Newton Raphson method (NR) and include magnitude, phase angle, and active and reactive power. A new adaptive particle swarm optimization-neural network algorithm based on a guiding strategy (GSAPSO-NN) was also used to achieve the goal of the paper by improving the mixed particle updates and the weightings of the neural network to decrease the search time. All results were then compared with actual values as calculated using the PTSI NR method. The final results show only simple differences or approximately the same values using both the proposed and the classical methods. The MATLAB-PSAT package was employed to obtain most of these results and the testing of the new method was done on the IEEE14 bus system as well as the Iraqi 24-bus power system. The effectiveness validation of the new hybrid method for assessing voltage stability was thus achieved.</span>

Drastically different restructuring of airborne and surface-anchored soot aggregates

Combustion soot particles are fractal aggregates of hydrophobic spherules. Mixing of soot particles with other chemicals during atmospheric processing may partially offset their hydrophobicity, promoting water uptake and structural compaction. We investigated morphological changes in fractal soot particles coated by sulfuric acid and then humidified, both in airborne and surface-bound states. Airborne soot was probed by tandem differential mobility analysis. Surface-bound soot was studied in a controlled microenvironment of a closed cell, using environmental transmission electron microscopy. After humidification, the airborne particles became fully compact, but the deposited particles showed only minor morphological changes despite significant water uptake. Although minor, those changes were detected during both water condensation and evaporation, indicating that condensation-evaporation cycles play an important role in atmospheric soot compaction. Lesser restructuring of deposited aggregates was caused by surface anchoring and coating loss, making anchoring an indispensable tool for preserving morphology of aggregates against changing experimental environment.

On the theory of the issue of cleaning the filtration surface from accumulated contaminants during the processing of unrefined vegetable oils by vibration and ultrasonic oscillatory movements

The article presents the results of a theoretical analysis of the issue of cleaning the filtration surface from the sediment of contaminants that prevent the passage of the cleaned oil through the adsorption layer in the installation for cleaning oil from oxidation products. Based on the classical theory of oscillatory motion, the conditions necessary for the floating and mixing of sediment particles by reducing their sidementation stability are considered.

Interaction between two car models with application to pollutant dispersion

Nowadays, air quality monitoring is a major concern. Among pollutants, exhaust UltraFine Particles (UFP) have a harmful effect on health due to their small size and to their ability to penetrate the bloodstream, the respiratory system, the brain as well as the placental barrier. Out of the industrial emissions, road traffic is a major source of air pollution. UFP emitted from the cars can infiltrate the car cabin through leakages and ventilation system leading to poor air quality in the passenger compartment. Improving the knowledge regarding the dispersion of exhaust UFP in the wake of a car considering road traffic is then mandatory. In this paper, the dispersion of UFP is studied in the wake of a leading vehicle (LV) followed by a second one. Two rear slant angles (φ) for LV and 6 inter-vehicle distances are considered. Velocities and UFP concentrations are collected in a wind tunnel. The influence of the rear slant angle of the leading vehicle is discussed on both wake dynamics and concentration fields. The results indicate that a critical inter-vehicle distance can be identified above which the recirculation region remains unchanged. Considering the concentration fields, for a leading vehicle with φ=0°, the large recirculation region tends to entrap the particles and to homogenize the particle mixing. For φ=25°, the attachment of the flow in the rear slant angle has a strong impact on the particle dispersion. It leads to a small recirculation region, which entraps particles leading to a non-homogeneous mixing. The Particle Concentration fields in Number (PNC) reveal high levels in the exhaust tailpipe plane that can contribute to lower PNC levels in the car cabin. Comparisons with previous studies are discussed and possible recommendations are suggested.

A Study on Optimal Location Selection and Semi-Finished Product Inventory Allocation in the Steel Industry

With the development of industrial production technologies and market economy, Postponement is increasingly being adopted by continuous production enterprise as a method that enables multi-product, mass customization production. In order to make use of the Postponement in manufacturing production enterprises need to achieve customized production and reduce enterprise costs. A modeling is conducted in the production process of Postponement in iron and steel enterprises in this paper. With the goal of minimizing total costs on a specific customer service level, mixed integer nonlinear programming and particle swarm algorithms are adopted for modeling and solving, to determine the optimal location and optimal semi-finished product inventory of PDP and CODP. Finally, taking an iron and steel enterprise as an example, the feasibility and effectiveness of the model and algorithm are verified. The study shows that the change of the optimal locations of PDP and CODP is affected by the change of customer service level and delay penalty coefficient, but the speed of change of the optimal location of PDP shows longer delays. In addition, the size of the capacity of semi-finished product inventory corresponding to CODP has a direct influence on whether the semi-finished product inventory corresponding to PDP participates in production, which in turn affects the optimal semi-finished product inventory on all levels. Through the analysis, it is found that the model constructed in this paper can better describe the overall situation and the influence relationship of the Postponement, and the study supplements the deficiency of the research on Postponement in the continuous manufacturing enterprises and enriches the content of the quantitative research on the Postponement.

Red Mud-Amended Soil as Highly Adsorptive Hybrid-Fill Materials for Controlling Heavy Metal Sewage Seepage in Industrial Zone.

With the rapid development of urbanization, the problem of environmental pollution is becoming more and more serious. As a major pollutant, heavy metals have caused serious contamination in soil and groundwater. In order to prevent the diffusion of heavy metals in the soil from industrial sewage, the concept of hybrid-fill layer construction improved by red mud was proposed in this study. This study examines the adsorption capacities of lead and zinc ions and engineering characteristics on red mud-amended soils by direct shear, permeability, adsorption, desorption batch and column tests. Two mixing methods, full particle size displacement mixing and partial particle size displacement mixing, were adopted. The results showed that red mud effectively increased the adsorption capacity of soil to heavy metal ions, and the desorption rate of ions after adsorption was less than 3%, which had good anti-desorption ability. The optimum content of red mud in hybrid-fill material can be determined as 20%. The direct shear test showed that the internal friction angle of hybrid-fill material was 38.9°, and the cohesive force was 30.3 kPa, which met the engineering strength requirements of foundation materials. Based on the test results, red mud can be used as a barrier material to prevent heavy metal contamination in industrial sewage from diffusion, which controls not only heavy metal contamination but also consumes industrial by-products.

Unsupervised Pharmaceutical Polymorph Identification and Multicomponent Particle Mapping of ToF-SIMS Data by Non-Negative Matrix Factorization.

Crystal polymorphism of pharmaceutical compounds directly impacts resulting physicochemical characteristics, a critical aspect in active pharmaceutical ingredient (API) production. Tools to characterize and chemically map these polymorphs at the single particle scale remain important to advancing directed manufacture of targeted polymorphs. Here, time-of-flight secondary ion mass spectrometry (ToF-SIMS) was employed for chemically imaging inkjet printed acetaminophen samples. ToF-SIMS generates large data sets of high spatial resolution images. Extracting relevant data and peaks of interest can be laborious for, and biased by, users. Advances in machine learning approaches have introduced many supervised and unsupervised methods for data analysis. In this study, we apply non-negative matrix factorization (NMF) for the unsupervised analysis of ToF-SIMS chemical image data. More specifically, an expanded variant of NMF, NMFk, was employed to determine the data set's latent dimensionality. NMFk combines the spectral unmixing of traditional NMF with k-means clustering of the resulting factors and an optimization of the reconstruction and clustering. The method was used to identify the number of polymorph phases-and their representative mass spectra-generated from inkjet printed acetaminophen samples. Amorphous, crystalline form I, and crystalline form II polymorphs were observed. The learned polymorph mass spectra were then used to map the learned polymorphs onto subsequent particle samples of acetaminophen. Finally, NMFk also enabled the decomposition of mixed particle samples (i.e., migraine medicine), learning the number of compounds and their composition. The extracted constituent phase mass spectra-representing single compounds-were searched against mass spectral libraries for identification.