Compound Particles Research Articles

A fault diagnosis method combined with compound multiscale permutation entropy and particle swarm optimization–support vector machine for roller bearings diagnosis

A method based on compound multiscale permutation entropy, support vector machine, and particle swarm optimization for roller bearings fault diagnosis was presented in this study. Firstly, the roller bearings vibration signals under different conditions were decomposed into permutation entropy values by the multiscale permutation entropy and compound multiscale permutation entropy methods. The compound multiscale permutation entropy model combined the different graining sequence information under each scale factor. The average value of each scale factor was regarded as the final entropy value in the compound multiscale permutation entropy model. The compound multiscale permutation entropy model suppressed the shortcomings of poor stability caused by the length of the original signals in the multiscale permutation entropy model. Validity and accuracy are considered in the numerical experiments, and then compared with the computational efficiency of the multiscale permutation entropy method. Secondly, the entropy values of the multiscale permutation entropy/compound multiscale permutation entropy under different scales are regarded as the input of the particle swarm optimization–support vector machine models for fulfilling the fault identification, the classification accuracy is used to verify the effectiveness of the multiscale permutation entropy/compound multiscale permutation entropy with particle swarm optimization–support vector machine. Finally, the experimental results show that the classification accuracy of the compound multiscale permutation entropy model is higher than that of the multiscale permutation entropy.

Thermal aging effects on microstructure, elastic property and damping characteristic of a eutectic Sn–3.5Ag solder

The present work describes the microstructural changes and their impacts on the electrical resistivity, elastic modulus and damping property of a eutectic Sn–3.5wt% Ag solder material when exposed to high temperature. A detail microstructural study was conducted through the scanning electron microscopy with energy-dispersive spectroscopy analysis and electron backscattered diffraction technique. In as-cast eutectic Sn–Ag solder alloy, sub-micrometer size Ag3Sn intermetallic compound (IMC) particles and bamboo-like dendritic structure with a dimension of length 20–30 µm and width 3–5 µm formed during solidification. However, after thermal aging treatment at 150 °C for 60 days, the fine Ag3Sn IMC particles and β-Sn grain appeared with coarse microstructure with the formation of twinning having the twin axis and 60° rotation. As a result, microstructure and Sn-crystal orientation of Sn–Ag solder greatly impact on its overall properties and turned inferior. From material properties evaluation, it was confirmed that the electrical resistivity, elastic and shear moduli values were significantly reduced with aging time. Consequently, the values of damping capacity improved due to the reduction of moduli.

Finished plasma strengthening and restoration of fuel equipment details

The results of the investigation of the physical and mechanical properties of diamond-like coatings of the DLCPateks type (a-C: H / a-SiOCN) obtained on friction surfaces by transporting the atomic and molecular flux of vapor particles of liquid chemical compounds by a plasma jet of an arc plasma torch of atmospheric pressure are presented. The layer formed on the working surfaces is a non-metallic amorphous multilayer coating with a low coefficient of friction, increased microhardness, chemical inertness, hydrophilicity, high heat resistance and dielectric characteristics. To minimize the possible defectiveness of the main material, it is proposed to apply thin-film coatings to them at the final stage of manufacturing fuel equipment parts.

Bilayer-rich graphene suspension from electrochemical exfoliation of graphite

The superior electronic properties of graphene change with number of layers, making different layered flakes suitable for different applications. Bilayer has a tunable band gap and is promising material for electronic applications. Liquid phase synthesis methods are scalable, can provide flakes with size suitable for microelectronic fabrication technologies and allow easy, defect-free transfer of flakes to the application substrate. However, these methods yield flakes with different number of layers. Here, we show a modified electrochemical exfoliation of graphite that gives a bilayer-rich graphene suspension. The method first obtains particles of stage-2 graphite intercalation compound. These particles have alternating weak and strong attraction between the two nearest neighboring layers which allowed the tuning of ultrasonic agitation intensity, such that cleavages occurred at weak attraction sites yielding primarily bilayer graphene flakes. Graphene flakes were produced only on ultrasonic cleaving and were done in DMF, a medium favorable for graphene dispersion thus avoiding aggregation of the freshly generated bilayer flakes. In principle, our method can be tuned for the liquid phase synthesis of layer-specific graphene flakes for any given number of layers. The method could therefore provide a general synthesis process for graphene required in different end-use.

Ἄτλας ἀστεμφής: Traces of local particles in Greek compounds and the origins of intensive alpha

Ἄτλας ἀστεμφής: Traces of local particles in Greek compounds and the origins of intensive alpha

Mesoscopic Phase Transition Kinetics in Secondary Particles of Electrode-Active Materials in Lithium-Ion Batteries

Many compounds used as battery storage electrodes undergo large composition changes during use that are accompanied by a first-order phase transition. Most studies of these phase transitions have focused on the unit cell to single-crystallite scale, whereas real battery electrodes are typically composed of mesoscopic assemblies of nanocrystallites, for which phase transformation mechanisms are poorly understood. In this work, a systematic study is conducted of the potentiostatic (constant driving force) kinetics of phase transition in secondary particles of representative intercalation compounds: LiFePO4, LiMn1–xFexPO4, and Li4Ti5O7. Storage kinetics are studied as a function of overpotential, material composition, primary particle size, and temperature. We find that in regimes where phase transformation occurs, the results can be self-consistently explained as nucleation and growth kinetics within the framework of the Johnson–Mehl–Avrami–Kolmogorov model. This implies that despite the common secondary particle topology, the electrochemically driven phase transformations occur by nucleation and growth with little apparent resistance to phase propagation across the grain boundaries. Growth appears to be one-dimensional in nature, consistent with a hybrid growth model in which rapid surface propagation is followed by slower growth into particles.

Simple Determination of Gaseous and Particulate Compounds Generated from Heated Tobacco Products.

As a new form of cigarettes, heated tobacco products (HTPs) have been rapidly distributed worldwide. In this study, an improved method for analyzing gaseous and particulate compounds generated from HTPs is described. Smoke is collected using a GF-CX572 sorbent cartridge with 300 mg of carbon molecular sieves, that is, Carboxen 572 (CX572), and a 9 mm glass-fiber filter (GF). After collection, the CX572 particles from the cartridge are transferred along with the GF and deposited into a vial containing two phases of carbon disulfide and methanol. The CX572 particles settle into the lower carbon disulfide phase, while nonpolar compounds are desorbed. After the sample is allowed to stand, the solution is slowly stirred. The two-phase mixture of carbon disulfide and methanol is combined into a homogeneous solution. Polar compounds are then desorbed, while the desorbed nonpolar compounds remain in solution. For the analysis of carbonyl compounds, an enriched 2,4-dinitrophenylhydrazine solution is added to a portion of the combined solution for derivatization and subsequent high-performance liquid chromatography analysis. For the analysis of volatile organic compounds and water, a portion of the combined solution is analyzed by gas chromatography-mass spectrometry or equipped with a thermal conductivity detector. By applying the proposed GF-CX572 one-cartridge method to the analysis of the mainstream smoke generated from HTPs and traditional cigarettes, several chemical compounds are detected, and the chemical composition of smoke is revealed. The GF-CX572 one-cartridge method can analyze gaseous and particulate chemical compounds from the HTP smoke by utilizing not only the entire puff volume but also one puff volume because the GF-CX-572 cartridge can be replaced with a new cartridge within 3 s. An overview of the chemicals generated from HTPs is obtained in detail by one-puff volume sampling. In addition, the generated chemical compounds strongly depend on the temperature of tobacco leaves in HTPs.

Radiative characteristics of a particle using a bump and pit sphere model

Using the particle superposition method, we constructed a bump and pit sphere model that randomly distributes bumps and pits onto the surface of a wavelength-sized host sphere to simulate a rough particle. We studied both the influence of the imaginary part of the refractive index and the number of dusted grains on the particle's radiative properties and found that the linear polarization and phase function of the particle were sensitive to these two parameters. Changes in the imaginary part of the refractive index caused a regular change in the linear polarization, which was reflected in the number of positive peaks and negative troughs. In addition, the number of dusted grains on the surface of the particle changed the absolute value of the linear polarization, because the linear polarization of a particle with many grains on its surface has a smaller absolute value than a particle with few grains. The backward-scattering region of the phase function became significantly smoother for non-dielectric particles than for dielectric particles. Finally, we analyzed the radiative characteristics of polydisperse compound particles. We found that the optical effects of the ratio of pit number to bump number on the polydisperse compound particles are rather weak, if not negligible.

Could portable powered respirators help us avoid the exposure to air pollution?

Atmospheric pollution has become a persistent threat to human health. Consequently, the effects of breathing polluted air in large cities are being assessed for given risk groups and different indoor and outdoor activities. This work delves into the study of the possibility to develop individual portable air-purifying respirators to avoid the exposure to atmospheric pollution when carrying out common daily activities at home or outdoors. Samples of known concentrations of the criteria pollutants (except for lead) have been monitored before and after passing through a powered occupational respirator which has been also tested carrying out physical activities mainly under outdoor conditions. The results show that the system is not effective against carbon monoxide but it does provide protection against particulate matter, SO2, NOx, O3, and volatile organic compounds, that is, most of the main pollutants found in outdoor air. Thus, individual powered respirators are technologically viable based on the current occupational devices and by providing them with additional suggested improvements. Being affordable, this kind of systems may become very helpful not only for assistive applications but also for healthy people willing to reduce exposure to air pollution.

Spatiotemporal Variation in Composition of Submicron Particles in Santiago Metropolitan Region, Chile

The chemical composition of submicron particles (aerodynamic diameter Da < 1.0 μm) was investigated at three locations in the Santiago Metropolitan Region (SMR), Chile. Measurements campaigns were conducted in winter and spring 2016, at representative sites of a rural, urban and urban receptor environment. Instrumentation consisted of an optical analyzer to determine Black Carbon (BC) and the Aerosol Chemical Speciation Monitor (ACSM) to measure concentrations of particulate chloride (Cl-), nitrate (NO3-), sulfate (SO42-), ammonium (NH4+) and non-refractory carbonaceous species (organics). Complementary data, such as ozone concentration and meteorological parameters were obtained from the public air quality network. Results showed that in both the winter and spring seasons the organics predominated in the mass of submicron particles. This fraction was followed in decreasing order by NO3-, NH4+, BC, SO42- and Cl-. The highest average organics concentrations were measured in winter at the urban (32.2 µg m–3) and urban receptor sites (20.1 µg m–3). In winter, average concentrations of both NO3- and NH4+ were higher at the urban receptor site (12.3 and 4.5 µg m–3, respectively) when compared to the urban site (6.4 and 3.1 µg m–3, respectively). In general, all the measured species were present in higher concentrations during winter, excepting SO42-, which was the only one that increased during spring. The transition towards spring was also associated with an acidification of the aerosol at the rural and urban receptor site, while at the urban site the aerosol was observed alkaline. The highest average ozone concentration during both the winter and spring seasons were recorded at the urban receptor site (7.2 and 24.0 ppb, respectively). The study reports data showing that the atmosphere in the SRM has a considerable load of particulate organic compounds, NO3- and NH4+, which are in higher concentrations at urban sites during the winter season. Based on wind patterns and the hourly profiles of chemical species, the study suggests that during daytime the polluted air masses from the urban center can move to the northeast part of the region (namely urban receptor site) leading to the formation of submicron particles as well as photochemical ozone.

Impact of particulate sediment, bentonite and barite (oil-drilling waste) on net fluxes of oxygen and nitrogen in Arctic-boreal sponges

To meet the increasing global energy demand, expanding exploration for oil and gas reserves as well as associated drilling activities are expected in the Arctic-boreal region where sponge aggregations contribute to up to 90% of benthic biomass. These deep-water sponges along with their microbial endobionts play key roles in the nitrogen cycling in Arctic-boreal ecosystems. This study aimed to investigate the effects of drilling discharges and associated sediment resuspension events on net fluxes of oxygen, ammonium, nitrate and nitrite in three common deep-water sponge species in the form of explants. Sponges were exposed to suspended bentonite and barite, the primary particulate compounds in drilling waste, as well as suspended natural sediment particles for a period of 33 days (on average 10 mg L−1 for 12 h day−1). The exposure period was followed by a pollution abatement period for a further 33 days. No sponge mortality was observed during the experiment. However, exposure to these particles, especially to barite, led to reduced oxygen consumption by up to 33% that was linearly correlated with reduced nitrite/nitrate release by the sponges. The changes in net fluxes were accompanied by decreased tissue oxygenation by up to 54% within the sponges. These findings reveal the effects of fine particles on sponge metabolic processes by reducing aerobic respiration and microbial nitrification, and possibly by favouring anaerobic processes such as microbial denitrification. Most of the sponge responses recovered to their control levels upon the pollution abatement period, but the effects caused by barite may not be reversible. Our findings provide the first insight into the ecological consequences of oil and gas drilling activities on sponge-mediated nitrogen cycling in the Arctic-boreal region.

Study of Indoor PM2.5 and Volatile Organic Compounds Concentration in Selected Rural and Urban Areas of Zambia

Background: High levels of household air pollution (HAP) occur in houses of many developing countries due to combustion of biomass fuels (wood, charcoal, cow dung, crop residues) in the households in open fires or inefficient stoves. Particulate Matter (PM2.5) and Volatile Organic Compounds (VOCs) are among the significant pollutants that are generated and can adversely affect the health of the exposed. Therefore, we monitored PM2.5 and VOC in selected rural and urban areas of the Copperbelt province of Zambia in order to measure the magnitude and correlates of HAP concentration levels. Methods: Indoor PM2.5 particles Results: Biomass fuel use in our study area was the dominant source of household energy for cooking. Mean indoor PM 2.5 varied greatly between households depending on fuel and kitchen type while the variations in VOC were not that much. Concentration levels for PM2.5 varied between 79 µg/m3 and 921 µg/m3, with an overall mean (SD) for daily average of 444.5 µg/m3 (170.2) while for VOC concentration levels ranged from 245 ppb to 393 ppb with an overall mean (SD) for daily average of 342 ppb (25.3). The median (Q1, Q2) indoor PM2.5 during cooking time was 501(411,686) µg/m3 and daily average 393(303,578) µg/m3 while VOC daily average was 343(320, 363) ppb concentrations in the entire study population. Conclusion: Household air pollution mean concentrations in rural and urban settings of Ndola and Masaiti excessively exceed the WHO guidelines; hence continued efforts through research and advocacy are needed to mitigate the health damaging levels of household air pollution.

27p-YC-10 ガス中蒸発法による有機化合物微粒子ペリレンの生成

27p-YC-10 ガス中蒸発法による有機化合物微粒子ペリレンの生成

Preparation of silybum marianum seeds extract nanoparticles by supercritical solution expansion

Nanoparticles containing silymarin derivatives were prepared from de-oiled silybum marianum seeds extract using supercritical CO2 (SC-CO2) and DMSO. All steps including lipophilic compounds removal, extraction, and particle production were carried out using SC-CO2. In This method, SC-CO2 was saturated with the solution of the extract at higher pressure. Then, depressurization of the supercritical solution led to a decrease in solvation power and particle formation while pressures at both conditions (pre- and post-expansion) were above the critical pressure.Characterization using LC–MS demonstrated that the extract and nanoparticles contained silymarin derivatives. Optimum conditions were obtained at a pressure of 350 bar, pressure drop of 230 bar, equilibration time of 30 min, collection time of 60 min, the extract volume of 20 μL, and the temperature range of 55–60 °C. The average particle size was 70 ± 20 nm at both conditions.

High-strength and free-cutting silicon brasses designed via the zinc equivalent rule

This study reports on the formation of high-strength and free-cutting silicon brasses designed and adjusted via the zinc equivalent rule by adding Pb replacers (Si and Al elements). Microstructure analysis indicates that phase components of the designed silicon brasses transform from α+β to β and further to β+γ with the increased zinc equivalent induced by increased Si and Al contents, respectively. Meanwhile, many ultrafine intermetallic compound particles are distributed along the grain boundaries of the α and β phases and embedded into the β-phase matrix along with high densities of nanoscale intermetallic compounds distributed in the β-phase matrix close to the grain boundaries. With the increased zinc equivalent, β-phase microhardness and Brinell hardness of the designed silicon brasses increase gradually accompanied by an increase in ultimate tensile strength and a decrease in elongation. Evaluation of chip morphology and machining surface quality imply that α+β brass has good abilities for chip breakage and free-cutting machinability. These results provide significant insight into the microstructural design of high-strength and free-cutting brass alloys.

An experimental and numerical study of the light scattering properties of ice crystals with black carbon inclusions

We investigate the optical properties of ice crystals nucleated on atmospheric black carbon (BC). The parameters examined in this study are the shape of the ice crystal, the volume fraction of the BC inclusion, and its location inside the crystal. We report on new spectrometer measurements of forward scattering and backward polarization from ice crystals nucleated on BC particles and grown under laboratory-controlled conditions. Data from the Cloud and Aerosol Spectrometer with Polarization (CASPOL) are used for direct comparison with single-particle calculations of the scattering phase matrix. Geometrical optics and discrete dipole approximation techniques are jointly used to provide the best compromise of flexibility and accuracy over a broad range of size parameters. Together with the interpretation of the trends revealed by the CASPOL measurements, the numerical results confirm previous reports on absorption cross-section magnification in the visible light range. Even taking into account effects of crystal shape and inclusion position, the ratio between absorption cross-section of the compound particle and the absorption cross-section of the BC inclusion alone (the absorption magnification) has a lower bound of 1.5; this value increases to 1.7 if the inclusion is centered with respect to the crystal. The simple model of BC-ice particle presented here also offers new insights on the effect of the relative position of the BC inclusion with respect to the crystal's outer surfaces, the shape of the crystal, and its size.

An in-situ method to estimate the tip temperature and phase selection of secondary Fe-rich intermetallics using synchrotron X-ray radiography

A method was developed based on synchrotron X-ray radiography to estimate tip temperatures of 203 Fe-rich intermetallic compound (IMC) particles during directional solidification of Al-Cu-Fe alloys. Tip temperatures showed two distinct IMC populations corresponding to Al6(Fe,Cu) and Al7Cu2Fe, validated by post-solidification microscopy. The IMC tip undercooling of each growing IMC was estimated by comparison with its equilibrium formation temperature. The effect of Fe concentration, cooling rate and grain refiner additions on the IMC tip undercooling was studied. With a large number of IMC particles measured, we show the relationship between solidification parameters, secondary IMC selection and tip undercooling.

Theoretical Insight into the Biodegradation of Solitary Oil Microdroplets Moving through a Water Column.

In the aftermath of oil spills in the sea, clouds of droplets drift into the seawater column and are carried away by sea currents. The fate of the drifting droplets is determined by natural attenuation processes, mainly dissolution into the seawater and biodegradation by oil-degrading microbial communities. Specifically, microbes have developed three fundamental strategies for accessing and assimilating oily substrates. Depending on their affinity for the oily phase and ability to proliferate in multicellular structures, microbes might either attach to the oil surface and directly uptake compounds from the oily phase, or grow suspended in the aqueous phase consuming solubilized oil, or form three-dimensional biofilms over the oil–water interface. In this work, a compound particle model that accounts for all three microbial strategies is developed for the biodegradation of solitary oil microdroplets moving through a water column. Under a set of educated hypotheses, the hydrodynamics and solute transport problems are amenable to analytical solutions and a closed-form correlation is established for the overall dissolution rate as a function of the Thiele modulus, the Biot number and other key parameters. Moreover, two coupled ordinary differential equations are formulated for the evolution of the particle size and used to investigate the impact of the dissolution and biodegradation processes on the droplet shrinking rate.

Exposure to firework chemicals from production factories in pregnant women and risk of preterm birth occurrence in Liuyang, China

ABSTRACTIn the production of fireworks, various pollutants including particles of metals and organic compounds are released into the environment. Although the adverse effects of these air pollutants are known, the impact on pregnant women residing in this area remains to be determined. The aim of this study was to examine the association between maternal exposure to fireworks production chemicals and frequency of preterm birth in Liuyang, China. Maternal exposure to fireworks production was estimated at the residential district level and assessed using factory density, which was defined as the number of fireworks factories per 1000 residents in each district. The association of maternal exposure to particulates released from fireworks production plants with frequency of preterm birth was determined using data obtained from a cohort study conducted in Liuyang, China. Data were analyzed utilizing linear regression and logistic regression. There was no significant association between factory density and spontaneous preterm or medically induced preterm birth. Unexpectedly, pregnant women residing in areas with higher density of fireworks factories were at a reduced risk of preterm premature rupture of membranes (PPROM). Data demonstrated that residential density of fireworks factories appeared to be negatively correlated with preterm birth rate as evidenced by PPROM. At present, it is difficult to reconcile the inverse relationship between firework chemical exposure and frequency of preterm births as ambient particulate inhalation is known to adversely affect preterm birth occurrence.

Microwave-shielding behavior of silanized Cu and Cu–Fe3O4 compound particle-reinforced epoxy resin composite in E-, F-, I-, and J-band frequencies

In this work, microwave-shielding behavior of epoxy thermosetting plastic reinforced with silanized Cu and Cu–Fe3O4 compound particles were studied in frequency bands E, F, I, and J. The principal aim of this work is to evaluate the significant advantage of surface-modified magnetic and conductive fillers over as-received fillers in microwave shielding. The conductive and magnetic properties of epoxy resin were improved by additions of Cu and Fe3O4 particles. Compound particles of Cu–Fe3O4 were produced by mechanical alloying process (ball milling). The compound particles were surface treated by 3-Aminopropyltrimethoxysilane (APTMS) for better dispersion in epoxy resin matrix. Functional groups on particle’s surface after silane surface treatment were confirmed by FT-IR spectra analysis. The TEM images revealed that effective Cu–Fe3O4 particle compounding was formed at 1 h milling time. The maximum dielectric constant of 6.8 and magnetization of 675E−6 were observed for surface-modified compound particle-reinforced epoxy composite designation RCF2. Similarly, maximum microwave attenuation of 35% (44 dB) was observed for surface-modified compound particle-reinforced composite designation RCF2 in ‘J’-band frequency.