Particle Loss Research Articles

Coupling effects of dielectric loss in N-doped carbon double-shelled hollow particles for high-performance microwave absorption

Microwave absorbing materials with lightweight and high-performance are of great significance for electronic technique, ecological environment and defense applications. The hollow structure of carbon microspheres is beneficial to achievement of high-performance microwave absorption due to high interfacial polarization. However, the key characteristic is still unclear to control interfacial polarization. Herein, double-shelled N-doped carbon hollow particles derived from polypyrrole by self-sacrifice template were synthesized. The polymerization process was controlled by the interface between solid and pyrrole acid liquid in Fe3O4 disperse system, subsequently, micro-nano structure of carbon was tuned. The N-doped carbon double-shelled hollow particles (DSHS) show a strong dielectric loss due to coupling effect of resistance loss and interfacial polarization owing to the double-shelled hollow structure. Thus, DSHS shows a high-performance microwave absorption with minimum reflection loss (RLmin) of −75.10 dB at a thickness of 2.48 mm and effective absorption bandwidth (RL ≤ -10 dB) of 6.08 GHz and 4.05 GHz covering the whole Ku band and almost the whole X with a thickness of 2.21 mm and 3.00 mm, respectively. This work provides a simple approach for synthesizing N-doped carbon particles with distinct micro-nano hierarchical structure, double-shelled hollow microspheres assembled by nanoparticles have potential application as a high-performance MAM.

Size-dependent depositional loss of inorganic, organic, and mixed composition particles to Teflon chamber walls under various environmental and chemical conditions

Size-dependent depositional loss of inorganic, organic, and mixed composition particles to Teflon chamber walls under various environmental and chemical conditions

The magnetic gradient scale length explains why certain plasmas require close external magnetic coils

The separation between the last closed flux surface of a plasma and the external coils that magnetically confine it is a limiting factor in the construction of fusion-capable plasma devices. This plasma-coil separation must be large enough so that components such as a breeding blanket and neutron shielding can fit between the plasma and the coils. Plasma-coil separation affects reactor size, engineering complexity, and particle loss due to field ripple. For some plasmas it can be difficult to produce the desired flux surface shaping with distant coils, and for other plasmas it is infeasible altogether. Here, we seek to understand the underlying physics that limits plasma-coil separation and explain why some configurations require close external coils. In this paper, we explore the hypothesis that the limiting plasma-coil separation is set by the shortest scale length of the magnetic field as expressed by the ∇B tensor. We tested this hypothesis on a database of > 40 stellarator and tokamak configurations. Within this database, the coil-to-plasma distance compared to the minor radius varies by over an order of magnitude. The magnetic scale length is well correlated to the coil-to-plasma distance of actual coil designs generated using the REGCOIL method (Landreman 2017 Nucl. Fusion 57 046003). Additionally, this correlation reveals a general trend that larger plasma-coil separation is possible with a small number of field periods.

Measurements of Penning-Malmberg trap patch potentials and associated performance degradation

Antiprotons created by laser ionization of antihydrogen are observed to rapidly escape the ALPHA trap. Further, positron plasmas heat more quickly after the trap is illuminated by laser light for several hours. These phenomena can be caused by patch potentials—variations in the electrical potential along metal surfaces. A simple model of the effects of patch potentials explains the particle loss, and an experimental technique using trapped electrons is developed for measuring the electric field produced by the patch potentials. The model is validated by controlled experiments and simulations. Published by the American Physical Society 2024

Comparison of aerosol spectrometers : accounting for evaporation and sampling losses

Measuring aerosol size distribution with precision is critical to understand the transmission of pathogens causing respiratory illnesses and to identify risk mitigation strategies. It is however a challenging task as the size of pathogen-carrying particles evolves over time due to evaporation. Although measurement techniques well established in the field of aerosol science are often used to characterize bioaerosols, their performance is seldom assessed with respect to evaporation and deposition in sampling lines. Four instruments providing aerosol size distribution were compared using oil and water-based particles. They each rely on different measurement principles: phase doppler anemometry, light scattering, electrical mobility and aerodynamic impaction. Size distributions of oil-based particles showed consistency across different measurement instruments, but significant discrepancies arose for water-based particles undergoing evaporation. These larger differences result from both evaporation and particle deposition in transit between the sampling point and the measurement inside the instrument. Phase doppler anemometry was best suited for precise size distribution measurement, as it eliminates the need for a sampling line, thereby preventing particle loss or evaporation during transit. With this instrument as a reference, empirical correction factors for evaporation and deposition were derived from dimensionless numbers and experimental data, enabling quantitative assessment of bioaerosol size distribution using different instruments. To obtain the size distribution at the source of the aerosol generation, complete drying of a salt solution was performed. Using the complete drying technique and accounting for losses, sampling instruments can reliably provide this critical information and allow for thorough risk assessment in the context of airborne transmission.

Elutriation of fine particles in a pulsed fluidized bed

This paper reported on fine particle elutriation for two different static bed heights of 25 cm and 30 cm in a pulsed fluidized bed. The effects of three types of flow including continuous airflow, on-off pulsed airflow, and pulsed airflow imposed on continuous airflow were investigated. Observations showed that the elutriation fraction extremely increased with gas temporal average velocity and static bed height for continuous airflow, while for pulsed and mixed flows at the same condition the increase was not considerable. The effect of pulse frequency from 0.033 Hz to 0.1 Hz as an optimum range led to an extreme reduction loss of particles for pulsed and mixed airflows compared to continuous airflow even at high gas temporal average velocities. The elutriation rate of mixed airflow at 0.033 Hz and 3Umf for 30 cm static bed height on average was 75% and 35.3% less than continuous and pulsed airflows, respectively.

Electron cloud build-up studies for FCC-ee

The Future Circular Collider (FCC) study is developing designs for a new research infrastructure to host the next generation of higher performance particle colliders to extend the research currently being conducted at the LHC. In particular, FCC-ee is an electron-positron collider, which is the first stage towards a 100 TeV proton-proton collider FCC-hh. FCC-ee may be affected by electron cloud (e-cloud) and the strongest effects are foreseen for the Z configuration, due to the highest number of bunches, which corresponds to the smallest bunch spacing. The presence of a large electron density in the beam pipe can limit the achievable performance of the accelerator through different effects like transverse instabilities, transverse emittance growth, particle losses, vacuum degradation and additional heat loads of the inner surface of the vacuum chambers. In the design phase, the goal is to suppress the e-cloud effects in FCC-ee and, therefore, a preliminary study to identify the parameters, which play a significant role in the e-cloud formation has been performed. In this paper, an extensive e-cloud simulation study is presented. In particular, the impact of the e-cloud is studied for different configurations, for example: for the electron and the positron beam; in the different elements of the particle accelerator; changing the beam chamber geometry; for different values of the Secondary Emission Yield (SEY); and for different beam parameters.

PENGGUNAAN MULSA PLASTIK SEBAGAI UPAYA KONSERVASI LAHAN UNTUK MENJAGA STABILITAS SIFAT FISIKA DAN KIMIA TANAH

Low nutrient availability and high soil bulk density are caused by the loss of fertile soil particles due to the kinetic energy of rain. Land management that does not apply conservation principles such as soil covering is one of the factors causing this to happen. This research was conducted to determine the impact of using plastic mulch as one of conservation actions. This research was conducted at the experimental field University of Siliwangi, Mugarsari. Soil samples were taken from mulched and without mulch lands as treatments. Soil samples were collected at 0-10 and 10-30 cm soil depths. Soil samples were taken to analyze the chemical properties of the soils (i.e., pH H2O, organic C, total N, available P, exchangeable K, Ca, Mg, Na) and physical properties (i.e., soil bulk density, porosity, water content, and texture). The results showed that the use of mulch had a significant effect (p<0.05) on pH H2O, organic C, total N, available P, exchangeable K, exchangeable Ca, bulk density, and water content. The results of the correlation showed that increasing organic C in mulched land had an effect on decreasing BD (r = -0.739). In addition, the organic C increased soil porosity (r = 0.612). Meanwhile, soil depth had no effect (p>0.05) on soil chemical and physical properties.

Wildfire plume ageing in the Photochemical Large Aerosol Chamber (PHOTO-LAC).

Plumes from wildfires are transported over large distances from remote to populated areas and threaten sensitive ecosystems. Dense wildfire plumes are processed by atmospheric oxidants and complex multiphase chemistry, differing from processes at typical ambient concentrations. For studying dense biomass burning plume chemistry in the laboratory, we establish a Photochemical Large Aerosol Chamber (PHOTO-LAC) being the world's largest aerosol chamber with a volume of 1800 m3 and provide its figures of merit. While the photolysis rate of NO2 (jNO2) is comparable to that of other chambers, the PHOTO-LAC and its associated low surface-to-volume ratio lead to exceptionally low losses of particles to the walls. Photochemical ageing of toluene under high-NOx conditions induces substantial formation of secondary organic aerosols (SOAs) and brown carbon (BrC). Several individual nitrophenolic compounds could be detected by high resolution mass spectrometry, demonstrating similar photochemistry to other environmental chambers. Biomass burning aerosols are generated from pine wood and debris under flaming and smouldering combustion conditions and subsequently aged under photochemical and dark ageing conditions, thus resembling day- and night-time atmospheric chemistry. In the unprecedented long ageing with alternating photochemical and dark ageing conditions, the temporal evolution of particulate matter and its chemical composition is shown by ultra-high resolution mass spectrometry. Due to the spacious cavity, the PHOTO-LAC may be used for applications requiring large amounts of particulate matter, such as comprehensive chemical aerosol characterisation or cell exposures under submersed conditions.

Experimental study on cylindircal particle movement in a slurry pump guide vane

To investigate the movement characteristics of cylindrical particles within a slurry pump, the particle trajectories, particle distributions, particle velocity, and passing time of particles in the guide vane are tested by high speed photography. The test results indicate that the pump performance decreases and the wear of the blade pressure side deteriorates with the increase of cylindrical particle densities. The particles primarily flow into the guide vanes from the suction side and flow out from the pressure side. The velocity loss of particles in the guide vanes increases, and the time for particles passing through the guide vanes increases with particle densities. As the cylindrical particle concentrations increase, the pump performance decreases, and the wear of the blade pressure side deteriorates. Additionally, the total velocity loss of particles in the guide vane increases, and the time for particles passing through the guide vane increases with concentrations. Compared with spherical particles, the pump performance is better when the pump conveys cylindrical particles, and the cylindrical particles are more likely to wear the middle of the guide vane flow channel. The particles mainly flow into the guide vanes from the suction side and flow out from the pressure side. The velocity loss of cylindrical particles in the guide vane is smaller than that of the spherical particles. The time of cylindrical particles passing through the guide vane is shorter than that of the spherical particles.

基于CFD-DEM耦合中小型气吸红枣捡拾机物料输送仿真试验与验证

To improve the quality of air suction jujube picker, the CFD-DEM coupled method is used to numerically simulate the conveying process of jujube particles and explore the motion state, particle collision and energy loss of jujube particles in the pipeline. The erosion rate is selected as an evaluation index to discuss the influence of wind velocity, bending angle and diameter on the conveying process. The simulation results show that the collisions between jujubes, as well as the collisions between jujubes and pipe wall have an impact on the conveying performance, and the latter is more significant. The erosion rate is positively correlated with the wind velocity, negatively correlated with the pipe diameter, and the bending angle first decreases and then increases. The influence degree of factors on the erosion rate is: wind velocity > bending angle > pipeline diameter. The optimal parameter combination is a wind velocity of 28 m•s-1, a bending angle of 105 °, and a pipe diameter of 130 mm. At this time, the value of erosion rate is the lowest and the number of collisions and energy loss between jujube particles are reduced by 37.3 % and 13.87 % year-on-year, and those between jujube particles and pipe wall are reduced by 17.45 % and 17.61 % year-on-year, respectively. The test results show that the conveying pipe with optimized structural parameters can reduce the jujube skin damage rate by 2.06 %. The results of this study can provide a reference for the design and optimization of the air suction jujube picker.

Seepage deformation characteristic of gap-graded coral sand in the South China Sea

Foundation settlement and collapse disasters resulting from seepage deformation in hydraulic-filled islands and reefs have been observed in the South China Sea, but the underlying failure mechanism and characteristic remain unclear. This study aims to investigate the influence of compactness and fine particle content on the seepage deformation of gap-graded coral sand and revel the characteristics and mechanism of seepage deformation of gap-graded coral sand through laboratory seepage deformation tests. The results indicate that the seepage deformation failure mode of gap-graded coral sand is influenced by the content of fine particles which undergo an evolution process from continuous piping to discontinuous piping to boiling. Particle loss is affected by the constraints between coarse particles, and the ability of different particle contact forms to restrict the loss of fine particles is different. Moreover, irregular particle morphology increases intergranular constraints, enhancing the coral sand's resistance to seepage deformation compared to standard quartz sand. Based on these findings, the instability coefficient was used to consider the influence of particle morphology and inter-particle contact on the seepage deformation. A hydraulic criterion for the internal stability of coral sand was established, demonstrating its versatility. Furthermore, the applicability of existing geometric criteria in evaluating coral sand was analyzed. The existing methods were found to be inaccurate in evaluating the internal stability of coral sand specimens with a fine particle content below 20 %.

SIMULACIÓN DE LA INYECCIÓN DE UN HAZ NEUTRO EN TOKAMAKS CONTRIANGULARIDAD POSITIVA Y NEGATIVA

In this paper the dynamics of high energy charged particles in negative and positive triangularity tokamaks is through the simulation of a neutral beam injection on analytical MHD equilibria using the exact orbit code FOCUS. It is observed that the negative triangularity configuration presents fewer losses of non-thermal particles, and an energy deposition more localized than its counterpart.

Comparison of the moisture resistance of a steel-slag stone mastic asphalt mixture modified with Ca(OH)2

Stone mastic asphalt is a type of hot mix asphalt that requires much coarse aggregate, so substitution waste aggregate, such as steel slag, will be an economic reason. The problem is that there are still many things that have not been consistent in various studies related to the moisture resistance of steel slag. The study aimed to compare the effect of Ca(OH)2 on the moisture resistance of the steel-slag stone mastic asphalt mixture and to determine the optimal Ca(OH)2 dosage for improving the mixture resistance. This study employs basalt aggregate, steel slag from Krakatau Steel Company, 60/70 penetration asphalt, a stabilizing substance made of bamboo fiber, and Ca(OH)2. The Texas boiling and the static immersed methods are used to test the adhesion on a loose mixture. The retained Marshall stability and indirect tensile strength are used to test the adhesion on the compacted mix. Testing result of Krakatau steel slag shows that steel slag has a much higher Fe2O3 content than steel slag in general and has low water absorption; a poor affinity for asphalt results from this. The result of the Texas boiling method showed a decrease in the percentage adhesion value between steel slag and asphalt compared to natural basalt aggregates and asphalt. Marshall Stability Ratio and Tensile Strength Ratio increased after mixing the asphalt with Ca(OH)2. Marshall test results show decreased stability in mixtures with steel slag substitution. Adding Ca(OH)2 increased stability and resistance to moisture significantly. This indicated that Ca(OH)2 enhances moisture resistance on stone mastic asphalt with modified steel slag. Stability, Marshall stability ratio, indirect tensile strength ratio, particle loss, and Texas boiling test significantly improved with adding Ca(OH)2

Modelling erosion and stability degradation of a reservoir slope under periodic water level fluctuations

Water level rise and fall can lead to changes in seepage flow in the bank slopes of reservoirs. Cyclic seepage flow can result in the redistribution and even loss of fine particles in the slope, which eventually influences the slope stability. In this study, numerical simulations were conducted based on a multispecies transport finite element method (FEM) to investigate the influence of periodic water level fluctuations on the reservoir bank slope. The unsaturated soil was treated as a five-constituent mixture, by which erosion and deposition behaviours were captured by phase transition between deposited and fluidized fines. A constitutive model for suffusion considering the hydraulic fluctuation effect was employed to quantify the erosion process. The change in the seepage field and the corresponding evolution of the erosion rate and fines eroded ratio in the slope during the fluctuation period were investigated. The influence of the water level fluctuation frequency on the fines redistribution in the slope was analysed. Furthermore, the evolution patterns of the slope stability under different fluctuation frequencies were compared. The numerical results indicated that a higher fluctuation frequency could promote fine particle loss in the zones near the slope surface, consequently inducing greater deterioration in the slope stability.

Effects of microtopography shaping on characteristics of eroded sediment particles of a dump slope in an opencast coal mine in China

AbstractThe properties of sediment particles are crucial research areas for understanding soil erosion on dump slopes. In this study, the slope of the southern dump of the ATB opencast coal mine in the Pingshuo mining area in Shanxi Province, China, was selected to conduct microtopographical shaping and artificial rainfall simulation experiments. Three different gradients of rainfall intensity, 20, 50, and 80 mm·h−1, were set. The main component of rainwater was water (chemistry H2O) by a rainfall duration of 30 min. A Microtrac S3500 laser particle size analyzer was used to measure the collected erosion sediment particles. This study conducted level benches and fish‐scale pits microtopography shaping on the slope of the waste dump. The dimensions of the level bench design were 1, 2, and 1 m for the step width, for the step length, and between each level bench, respectively. The fish‐scale pits were 60 cm (length), 40 cm (width), and 30 cm (depth). The horizontal and row spacing of each fish‐scale pit was 1 m, and an unshaped terrain was used as the control group. Through dynamic monitoring and statistical analysis of the data, the impacts of rainfall intensity and microtopography shaping mode on the features of the eroded sediment particles were analyzed. Fine silt particles (53%) were lost as a result of the surface erosion of the slope. The mean starting periods of sediment particle loss decreased with the increase in rainfall intensity (589 s > 402 s > 305 s). Additionally, the clay and silt particle enrichment ratios decreased (ER >1), whereas the sand particle enrichment ratios increased (ER <1). The level benches had a stronger interception effect on fine sediment, whereas the fish‐scale pits had a weaker interception effect on sediment particles under heavy rain. The distribution properties of erosion sediment particles on a slope can be assessed using fractal dimension as an index. This study is significant for understanding the erosion mechanism of eroded sediment particles on dump slopes and provides a scientific foundation for soil erosion control on opencast coal mine dump slopes in the Loess Plateau. These results highlight the potential for the level bench to effectively delay the occurrence of runoff and greatly enhance the interception of sediment particles.

Radiatsionnye poteri deytronov, tritonov i al'fa-chastits na ionakh vol'frama v plazme tokamakov-reaktorov ITER i EU–DEMO

Integral radiative losses of deuterons, tritons, and alpha particles on impurity tungsten ions have been calculated for the first time within the statistical theory of the atom for the designed operational regimes of the ITER and EU-DEMO tokamak reactors. It was previously shown within the statistical theory of the atom that specific radiative losses of this new ion channel are comparable with specific electron radiative losses, which also include losses due to bremsstrahlung, radiative and dielectron recombination. Integral radiative losses have been calculated within the numerical model of fusion power isolines, which was previously proposed to study the operational space and design regimes of tokamak reactors. Spatial distributions of the tungsten density with various degrees of peaking in the center of a plasma column have been considered to study the influence of the accumulation of the impurity on integral radiative losses. It has been found that the studied new channel adds about 20 and 30% to the total integral radiative losses on tungsten in the ITER and E-U‑DEMO tokamak reactors, respectively. Consequently, this channel of radiative losses should be taken into account to examine in more detail the working scenarios of these devices.

Assessing residential PM2.5 concentrations and infiltration factors with high spatiotemporal resolution using crowdsourced sensors.

Building conditions, outdoor climate, and human behavior influence residential concentrations of fine particulate matter (PM2.5). To study PM2.5 spatiotemporal variability in residences, we acquired paired indoor and outdoor PM2.5 measurements at 3,977 residences across the United States totaling >10,000 monitor-years of time-resolved data (10-min resolution) from the PurpleAir network. Time-series analysis and statistical modeling apportioned residential PM2.5 concentrations to outdoor sources (median residential contribution = 52% of total, coefficient of variation = 69%), episodic indoor emission events such as cooking (28%, CV = 210%) and persistent indoor sources (20%, CV = 112%). Residences in the temperate marine climate zone experienced higher infiltration factors, consistent with expectations for more time with open windows in milder climates. Likewise, for all climate zones, infiltration factors were highest in summer and lowest in winter, decreasing by approximately half in most climate zones. Large outdoor-indoor temperature differences were associated with lower infiltration factors, suggesting particle losses from active filtration occurred during heating and cooling. Absolute contributions from both outdoor and indoor sources increased during wildfire events. Infiltration factors decreased during periods of high outdoor PM2.5, such as during wildfires, reducing potential exposures from outdoor-origin particles but increasing potential exposures to indoor-origin particles. Time-of-day analysis reveals that episodic emission events are most frequent during mealtimes as well as on holidays (Thanksgiving and Christmas), indicating that cooking-related activities are a strong episodic emission source of indoor PM2.5 in monitored residences.

Surface-barrier detector with smoothly tunable thickness of depleted layer for study of ionization loss and dechanneling length of negatively charged particles channeling in a crystal

A new method for the experimental study of ionization loss of relativistic negatively charged particles moving in a crystal in the channeling regime using a semiconductor surface-barrier detector with smoothly tunable thickness of the depleted layer is proposed. The thickness of the depleted layer in a flat semiconductor detector can be smoothly regulated by the value of the bias voltage applied to the detector. Therefore, the energy distribution of the ionization loss of relativistic particles which cross the detector and move in the channeling regime in the detector crystal can be measured along the path of the particles by varying the bias voltage of the detector and the dechanneling length can be found. Available literature data on experimental and theoretical researches of the dechanneling length are reviewed. The significant disagreement between the experimental and theoretical data is noted. Comparison of experimental data obtained by the detector-target with smoothly tunable thickness of the depleted layer with calculations can help to develop theoretical description of the dynamics of motion of negatively charged particles channeling in a crystal. A better understanding of the dechanneling length properties can be useful in the production of positrons and other particles such as neutrons by an electron beam in crystals, as well as in the development of crystalline undulators, and in the crystal-based extraction of electron beams from a synchrotron.

Radiative Losses of Deuterons, Tritons, and Alpha Particles on Tungsten Ions in the Plasma of the ITER and EU-DEMO Tokamaks

Radiative Losses of Deuterons, Tritons, and Alpha Particles on Tungsten Ions in the Plasma of the ITER and EU-DEMO Tokamaks