Charge-mass Ratio Research Articles

Numerical analysis of the local damage of RC beams under close‐in explosions based on the calibrated Karagozian & Case (K&C) concrete model

AbstractLimited research has been carried out to investigate the local damage features of reinforced concrete (RC) beams under close‐in explosions. To better capture the local damage features of rectangular cross‐sectional RC beams, a numerical study on the RC beams subjected to close‐in explosions based on the calibrated Karagozian & Case (K&C) concrete model was conducted in LSDYNA. First, a systematic calibration of the K&C model for concrete was performed in the single‐element numerical analysis. Calibration of the K&C model consists of parameter determination for the new strength surfaces, modification of the damage function to better feature the tensile behavior of concrete, elimination of the element size effect by introducing an element size factor and determination of the scaled damage factors. The new strength surfaces are verified and determined through both the approximation calculation method and the parameter fitting method. And the damage function was modified by reducing the termination of λ to better characterize the brittleness of concrete and feature the tensile failure. A comparison between the numerical results and the corresponding experimental results demonstrates that the calibrated K&C model and established FEM model of RC beams subjected to close‐in explosions can well characterize the local damage features of RC beams. On this basis, a further parameter analysis on the factors influencing the local damage response of RC beams was conducted by considering reinforcement details (stirrup spacing and longitudinal reinforcement diameter) and charge details (charge mass and aspect ratio). Results show that the close‐in explosions destroyed the concrete corners in the blast surface with shear stress first and the side shear failure of concrete corners weakens the concrete core strength and contributes to the greater loss of concrete core. Rear spalling damage was initially caused by the bond failure between the tensile longitudinal reinforcement and the surrounding concrete. Furthermore, increasing stirrup spacing, tensile longitudinal reinforcement diameter, and charge mass contribute to the increase in local damage sizes.

Multispecies Ion Acceleration in 3D Magnetic Reconnection with Hybrid-Kinetic Simulations.

Magnetic reconnection drives multispecies particle acceleration broadly in space and astrophysics. We perform the first 3D hybrid simulations (fluid electrons, kinetic ions) that contain sufficient scale separation to produce nonthermal heavy-ion acceleration, with fragmented flux ropes critical for accelerating all species. We demonstrate the acceleration of all ion species (up to Fe) into power-law spectra with similar indices, by a common Fermi acceleration mechanism. The upstream ion velocities influence the first Fermi reflection for injection. The subsequent onsets of Fermi acceleration are delayed for ions with lower charge-mass ratios (Q/M), until growing flux ropes magnetize them. This leads to a species-dependent maximum energy/nucleon ∝(Q/M)^{α}. These findings are consistent with insitu observations in reconnection regions, suggesting Fermi acceleration as the dominant multispecies ion acceleration mechanism.

Particle dynamics on test papapetrou fields of vacuum spacetimes

In this paper we examine the dynamics of test particles subjected to Papapetrou fields which emerge from vacuum spacetimes isometries. Assuming that the background geometry is described by a Kerr metric whose timelike Killing vector satisfies Maxwell equations, we evaluate the electromagnetic fields—Papapetrou fields—by fixing a locally non-rotating (LNR) frame of reference. We also evaluate such the electromagnetic fields for a vanishing rotation parameter assuming a timelike frame of reference for a Schwarzschild background. In order to probe for the effect of the test Papapetrou fields we study the motion of charged particles in a Kerr background. Restricting ourselves to orbits in the equatorial plane with LNR initial conditions we show that there is an explicit deviation between orbits of neutral and charged particles in the case of repulsive electromagnetic configurations. For critical charge-mass ratios ζ * test particles can be found in the Kerr retrograde photon sphere. For static configurations we show that massive/charged test particles may populate the unstable Schwarzschild photon sphere for given domain of the parameter space.

The influence of ball collision charging on carbon recovery of fly ash triboelectrostatic separation

ABSTRACT The recovery of unburned carbon particles from fly ash by triboelectrostatic separation can realize energy conservation and solid waste recycling. Collision charging by metal ball has been proposed to enhance the particle charging and improve the unburned carbon recovery efficiency. It can increase the particle contact area, shorten the contact time, and improve the charge–mass ratio of particles. The charging model of ball collision was established. The collision charging process between particles and ball was simulated by CFD-DEM coupling method. The influence of ball material and gas velocity on the charge–mass ratio was studied, and that of gas velocity and voltage on separation was evaluated by experiments. The results showed that the collision charge between particles and metal ball was greater than that between particles. With the gas velocity of 30 m/s, Cu ball collisions obtained a relative maximum charge–mass ratio of 0.393nC/g and 0.275nC/g for carbon and ash particles, respectively. The reasonable experimental conditions were gas velocity of 20 m/s and voltage of 15kV. The loss on ignition of 14.3% and carbon recovery of 90.36% were obtained. Compared with the no-ball system, the ball collision improved the carbon recovery rate by 55.20%.

Investigation of the Rayleigh–Taylor instability in charged fluids

The present study shows that the Rayleigh–Taylor (RT) instability and its growth rate are strongly dependent on the charge-mass ratio of charged particles in a charged fluid. A higher charge-mass ratio of the charged fluid appears to result in a stronger effect of the magnetic field to suppress the RT instability. We study the RT instabilities for both dusty plasma (small charge-mass ratio of charged particles) and ion-electron plasma (large charge-mass ratio of charged particles). It is found that the impact of the external magnetic field to suppress the RT instability for ion-electron plasma is much greater than that for dusty plasma. It is also shown that, for a dusty plasma, in addition to region parameters such as the external magnetic field, region length, its gradient, as well as dust particle parameters such as number density, mass, and charge of dust particles, the growth rate of the RT instability in a dusty plasma also depends on parameters of both electrons and ions such as the number densities and temperatures of both electrons and ions.

No-go theorem for static configurations of two charged dust species

We consider static spacetimes with no specific spacial symmetry where the matter content consists of two charged dust species. This comes motivated by the fact that static configurations are possible with one dust, but only if it is electrically counterpoised dust (ECD). In order to have such dust, the quotient between electric charge density and mass density needs to be fine-tuned to a value that is far less than the charge-mass quotient for any known particle. Here we prove that there are no static configurations with two dust species unless each one is ECD. This shows that ECD spacetimes cannot be made with matter that has on average the correct charge-mass ratio, but that the underlying particles must have such ratio.

Experimental study on DC corona charging characteristics of powder particles with different properties

In this paper, the charging characteristics of powder particles with different properties under DC discharge corona conditions were studied experimentally. The influence of different charging voltages and different charging structures on the charge-mass ratio of particles was analyzed through ELPI measurement. The experimental results show that the far-field charging structure of the electrode can effectively charge powder materials like Graphite micro powder, copper sulfide, talcum powder, and porous material (Si Al) within the particle size range of 0.1 μm−10 μm; When there is no streamer or spark between the charging electrode and the grounding electrode of the charging device, the higher the charging voltage is, the higher the degree of air ionization is, and the better the charging effect on particles is; Under the same charge condition, the charge-mass ratio of particles decreases with the increase of particle size.

The theory on thing's limits. Part 2: A brief analysis of the new knowledge of Newton's first law

According to the norm of identifying truth in this theory, and Newton's first law which is a basis that can look at the overall situation, and by virtue of the electron storage ring as an experimental fact, it is pointed out: Only in reality can there be inertia. Inertia represents the continuity of the development of thing. As the speed gradually approaches to the c, the particle's mass also approaches to zero along with its static mass due to the impact of electromagnetic radiation, which is exactly the root where the energy shrinkage effect of high-speed particles comes from, and also the primary factor causing the spectrum redshift. Therefore, the Big Bang theory is wrong. All photons are produced from the high-density particles through electromagnetic radiations. Wherever there is fluctuation, there must be mass, and vice versa. This is the correct understanding of "wave-particle duality". No matter the high-speed electrons or the photons produced by them all have different static masses, but their charge-mass ratio is always the same physical constant, and not affected by relativistic effects and electromagnetic radiations. This is the true internal mechanism to constitute the uncertainty principle, and conforms to the experimental facts related to it. It can be proved that in a constant magnetic field, the high-speed electron or photon of having a relatively large curvature radius, which has a high moving speed and less mass, energy and wave frequency. Since Einstein used the absolute space-time established by Newton as the criterion and came to the conclusion that the relative space-time was curved, then he should no longer make circular arguments, that was, used the relative space-time as the criterion, to change the unit length and time established by the absolute space-time.

Numerical Simulation of the Trajectory of UAVs Electrostatic Droplets Based on VOF-UDF Electro-Hydraulic Coupling and High-Speed Camera Technology

The electrostatic spray technology can significantly improve the utilization rate of liquid medicine under the operation characteristics of unmanned aerial vehicles (UAVs) with small load and low spray volume. To explore the settlement law of electrostatic droplets, further improve the amount of droplets deposited in target crops, and reduce the loss of missing target, this study adopted the method of combining numerical simulation and high-speed photography to study the movement characteristics of electrostatic droplets of UAV induction conical electrostatic nozzle. Based on the droplet spatial dynamics theory, a user-defined function and volume of fluid (UDF-VOF) multiphase spray model is established to simulate the trajectory of electrostatic droplet. TEMA software is used to analyze the droplet motion image under electrostatic field, and the characteristic parameters, such as trajectory and velocity are obtained. Theoretical analysis and spray test results show that the main factors affecting electrostatic droplet settlement are charging voltage, droplet falling distance, and airflow velocity. The optimal charging voltage of electrostatic droplet is 14 kv, the maximum charge-mass ratio is 1.04 mC/kg, and the average particle size is 209.77 μm. The numerical simulation results show that spray height, charging voltage, and lateral wind speed have significant effects on droplet sedimentation. The results of high-speed camera analysis show that the induced electric field causes the droplet to adsorb the target crop, resulting in the droplet movement trajectory deflection.

Forces and charge analysis of a water droplet dragged by an electric field

Droplet removal from solid surfaces is particularly important for heat and mass transfer, corrosion protection, and certain technological requirements in production. In this study, we investigate droplet removal from a solid surface using an electric field. First, a visual platform was established to capture a video of the droplet deforming and jumping motion in an electric field, and a deformed ellipse equation was applied to fit the liquid droplet profiles. Second, the electric charge distribution was obtained, and the electric forces on the droplet surface before and after jumping were calculated. The result indicates that the charge only accumulates on the upper surface of the droplet, mostly at the top point, and the maximum charge of the 7 μl droplet is about 2 × 10−4 μC in this experiment. The forces on the droplet are almost constant and maintain a constant acceleration (greater than 10 m/s2) after leaving the surface. Third, the effects of droplet volume, electric field intensity, and electrode plate distance on droplet jumping were quantitatively studied. The experiments show that the electric field intensity required for droplet jumping is independent of the droplet volume but positive with the distance between the plates, when the distance between plates increases from 10 to 18 mm, the critical jumping electric field intensity increases by 0.1 kV/mm. The droplet acceleration decreases by about 20% with the increase in volume (5–10 μl) but increases with the increase in electric field intensity. The charge increases with the increase in electric field intensity, but the charge–mass ratio decreases by about 30% with the increase in volume (5–10 μl). Finally, the results show that a small volume and plate distance are more favorable to stimulating the droplets jumping under the electric field.

Purity prediction of the two‐stage high voltage electrostatic separation of a mixture of three polymers

AbstractClean and efficient separation is an important requirement for the high‐value‐added recycling of end‐of‐life automobile polymers. In this study, polymer particles for vehicles were considered as research objects, and a two‐stage electrostatic separation device was designed to separate a mixture of three polymer particles. A kinematic model of friction‐charged particles in a two‐stage free‐fall separator was established. Then, a suitable time period for triboelectrostatic charging with regard to electrostatic separation was determined, and a charge–mass ratio distribution of mixed‐polymer particles, that is, polyamide (PA), polypropylene (PP), and polyethylene (PE), was measured using a Faraday cage based on the triboelectrostatic charging experiment of three types of particles in a friction barrel‐type tribocharger. The theoretical purities of PA, PP, and PE were calculated using the motion and particle charge–mass ratio distribution models were 100.00%, 89.51%, and 92.95% respectively. The experimental purities of PA, PP, and PE were 94.68%, 80.76%, and 84.27%, respectively, which is consistent with the theoretical purity. Results of the study can provide a theoretical and experimental reference for one‐pass electrostatic separation of three kinds of plastic particles.

Tidal effects in AdS charged torus-like black hole

In this paper, we analyze the tidal effects of anti-de Sitter charged black holes. The tidal force components are obtained by Riemann tensor on tetrad basis and geodesic deviation equation. The radial components of tidal force have the same changes outside the horizon if the charge mass ratio is closer to each other, unlike in Reissner–Nordström BHs. The angular tidal forces increase infinitely with increase of charge and [Formula: see text]. We derive the geodesic deviation equation on a neutral body for anti-de Sitter torus like charged black hole. We find the radial and angular tidal forces on the neutral body. Furthermore, we express the graphical behavior of radial and angular components for the most suitable initial conditions.

Chaos bound and its violation in charged Kiselev black hole

The chaos bound in the near-horizon regions has been studied through the expansions of the metric functions on the horizon. In this paper, we investigate the chaos bound in the near-horizon region and at a certain distance from the horizon of a charged Kiselev black hole. The value of the Lyapunov exponent is accurately calculated by a Jacobian matrix. The angular momentum of a charged particle around the black hole affects not only the exponent, but also the position of the equilibrium orbit. This position gradually moves away from the horizon with the increase of the angular momentum. We find that the bound is violated at a certain distance from the horizon and there is no violation in the near-horizon region when the charge mass ratio of the particle is fixed. The small value of the normalization factor is more likely to cause the violation.

Dust Removal Mechanism of the Vibrating String Filter with Charged Water Mist

The traditional dust removal technology is difficult to meet the strict requirements of environmental protection, so it is of practical significance and research value to study how to purify fine dust in workshop. Fine dust can be suspended in the atmosphere, while reducing the air quality. Excessive inhalation of dust may result in disease. So it should be paid close attention to dust control. The water mist charging process has experienced three stages: induction charge, corona charge transition, and corona charge. When the discharge distance is 80 mm, the charge-mass ratio of droplet and the current of water mist are most affected by corona voltage. The significant impact analysis of orthogonal experiment is studied. The result of the orthogonal experiment is analyzed by the variance method. It is noted that the inlet wind speed has the highest influence, and the discharge distance has a least influence on the dust removal efficiency. The discharge distance is 80 mm, and the voltage working band is suitable for the normal voltage regulation of the electrostatic precipitator. The condensation efficiency of charged droplets on dust is beneficial to reduce the negative effect of excessive wind speed on wet vibrating string grid and to improve the effective handling volume of dust collector. The charge-mass ratio of water mist is improved effectively, and the dust removal efficiency is increased in the vibrating string filter with charged water mist. Theoretical analysis and experimental studies showed that the vibrating string filter with charged water mist is as a new composite efficient dust removal technology that can effectively deal with the purification of fine dust particles in the gas stream, especially in respiratory dust removal.

Experimental study on rotary triboelectric separation of low-rank coal macerals with surface modification

The enrichment of vitrinite can enhance the oil yield and conversion rate in low-rank coal liquefaction. The work evaluated the effects of surface modification on the rotary triboelectric separation of macerals. Permittivity and charge–mass ratio analysis of vitrinite and inertinite under various modified conditions demonstrated that kerosene and diesel were excellent modifiers since they keep the permittivity of macerals at a low level. The largest difference in triboelectric charge of vitrinite and inertinite was obtained when 3.0 kg/t kerosene was adopted as modifier. Rotary triboelectric separation of untreated low-rank coal indicated that the optimal separation, i.e., a vitrinite content of 65.45% and a recovery of 69.89%, was obtained at a feed rate of 1.5 g/s, a friction wheel speed of 3000 rpm, and a separation voltage of 30 kV. Under the optimum operating conditions, the optimal rotary triboelectric separation under surface modification, i.e., a vitrinite content of 69.78% and a recovery of 73.52%, was achieved when the coal was treated by 3.0 kg/t kerosene. The results demonstrated that surface modification significantly improved the rotary triboelectric separation by changing the surface electrical properties of macerals, while the excessive dosage of the modified reagent was unfavorable to achieving optimal separation.

Lubrication-enhanced mechanisms of titanium alloy grinding using lecithin biolubricant

As a dielectric, biolubricant (vegetable oil) cannot maximize the efficiency of electrostatic atomization minimum quantity lubrication (EMQL). The lecithin-enhanced technology is expected to solve this technical bottleneck. The effects of lecithin on the electrophysiological properties of biolubricant (soybean oil) were investigated. Lecithin can increase the conductivity, viscosity, and charge mass ratio and reduce the surface tension of soybean oil. Comparative experiments show that the maximum average temperature rise of workpiece surface with MQL is 241.6 °C. The value under flooding, EMQL, and L+EMQL is reduced by 28.97%, 42.8%, and 48.92%, respectively, compared with MQL. The influence of lecithin mixing ratio on grinding performance was discussed. The minimum surface roughness value (0.49 µm) is obtained at the mixing ratio of 2:10.

A 16-parts-per-trillion measurement of the antiproton-to-proton charge-mass ratio.

The standard model of particle physics is both incredibly successful and glaringly incomplete. Among the questions left open is the striking imbalance of matter and antimatter in the observable universe1, which inspires experiments to compare the fundamental properties of matter/antimatter conjugates with high precision2-5. Our experiments deal with direct investigations of the fundamental properties of protons and antiprotons, performing spectroscopy in advanced cryogenic Penning trap systems6. For instance, we previously compared the proton/antiproton magnetic moments with 1.5 parts per billion fractional precision7,8, which improved upon previous best measurements9 by a factor of greater than 3,000. Here we report on a new comparison of the proton/antiproton charge-to-mass ratios with a fractional uncertainty of 16 parts per trillion. Our result is based on the combination of four independent long-term studies, recorded in a total time span of 1.5 years. We use different measurement methods and experimental set-ups incorporating different systematic effects. The final result, [Formula: see text], is consistent with the fundamental charge-parity-time reversal invariance, and improves the precision of our previous best measurement6 by a factor of 4.3. The measurement tests the standard model at an energy scale of 1.96 × 10-27 gigaelectronvolts (confidence level 0.68), and improves ten coefficients of the standard model extension10. Our cyclotron clock study also constrains hypothetical interactions mediating violations of the clock weak equivalence principle (WEPcc) for antimatter to less than 1.8 × 10-7, and enables the first differential test of the WEPcc using antiprotons11. From this interpretation we constrain the differential WEPcc-violating coefficient to less than 0.030.

Effect of plasma properties on magnetic bubbles

In this work, a three-dimensional hybrid simulation program is used to investigate the process of the explosion and expansion of a large number of thermal debris ions in a low density background plasma. By quantitatively calculating the variation of the magnetic bubble and the bubble constraint in the motion of the debris cloud, studied are the influences of the background plasma charge density, the background ion atomic weight, and the charge-mass ratio of the fragment ion on the magnetic bubble. The results show that the background charge density has an important effect on the motion of the bubble and debris cloud. In the early stage of the debris cloud expansion, the background ion atomic weight has little effect on the bubble expansion, but it affects the movement of debris cloud at a later time. When the charge-mass ratio of the debris ion is small, the radius of the ion gyration is larger than the bubble radius, and the bubble radius is small so that it cannot restrain the debris cloud. When the charge-mass ratio of the debris ion is large, the radius of the ion gyration is smaller than the bubble radius. If the background charge density is low in this condition, the early expansion of the bubble and the debris cloud are slightly affected by the charge-mass ratio of the fragment ions, and only the subsequent evolution of the system is influenced. If the background charge density is large in this condition, the charge-mass ratio of the fragment ion has a prominent influence on the motion of the bubble and the debris cloud.

Effect of combined blast and fragmentation load on the dynamic response of reinforced concrete structures

The current paper presents an improved model for the dynamic response of RC wall to a combined load of blast and fragmentation, as a result of a cased charge detonation. The model considers the damage inflicted by the fragments and their additional momentum, as well as the more realistic blast load. The main aim of the study is to compare the more realistic structural response to existing design methodologies that neglect the fragmentation effects or treat them in a simplified manner. After the model validation, this comparison is done through a parametric study to investigate the effects of various parameters on the results. It is found that the concrete compressive strength, reinforcement ratio, and charge height are not dominant factors for studying the level of the conservativeness of existing methodologies. The standoff distance, cross-section thickness, and casing to charge mass ratio were found to strongly influence the differences between the design methodologies.

Discrete element numerical simulation of fly ash triboelectrostatic separation in a nonlinear electric field

Fly ash is solid waste produced by thermal power generation, and its carbon content is a key factor affecting its recycling. Due to the large difference in fly ash quality and insufficient tribocharging, the parallel plate electric field with constant electric field strength cannot meet the practical needs of efficient decarbonization of fly ash particles with wide charge range or small charge to mass ratio (CMR). Therefore, a nonlinear electric field structure is proposed. The separation process of fly ash particles in the nonlinear electric field is explored through the establishment of geometric model and the application of CFD-DEM coupled calculation method, and the main influencing factors of fly ash electrostatic dry separation are studied. The results show that the nonlinear electric field structure is feasible to achieve high efficiency decarbonization of fly ash. With the increase of air flow velocity, the loss on ignition of positive electrode first increases and then decreases. The loss on ignition (LOI) of positive electrode products is directly proportional to the voltage and the CMR of the input, but inversely proportional to the feed quantity. Air flow velocity of 20 m/s, voltage of 30 kV, charge-mass ratio of 1.1–1.2 nC/g and feed quantity of 5000/s are suitable conditions for efficient decarbonization of fly ash. Compared with parallel plates, hyperbolic nonlinear electric field has higher decarbonization efficiency and lower energy consumption in experiment.