Strong Collision Research Articles

Three-dimensional FSI simulation of cell entrapment utilizing acoustic interparticle force in a standing acoustic field

Abstract In recent years, there has been significant development in microfluidic devices for cell separation and sorting using acoustic methods in biomedical applications. The acoustic interparticle force (AIF) arises from particle interactions with the scattered field of other particles, influencing particle motion at close ranges and facilitating optimal trapping and separation. This study analyzes a two-particle system consisting of a fixed particle and a white blood cell (WBC) within a standing acoustic field and creeping flow using fluid-structure interaction (FSI). To reduce computational costs by decoupling the acoustics and FSI, the acoustic pressure equation (AcPr) was solved on the frequency domain to calculate the total acoustic radiation force in each time step. Model accuracy was assessed by evaluating interparticle (AIF) and primary acoustic radiation forces (ARF) on a polystyrene particle and comparing simulation results to analytical and experimental data. Results demonstrate precise ARF performance, with discrepancies in acoustic interparticle force attributed to viscous losses near the particle surface. Moreover, the higher density of the fixed particle compared to WBCs induces significant acoustic interparticle attraction at close distances. Consequently, cell entrapment occurs through strong attraction and collision with fixed aluminum and silicon particles in creeping flow in all three Reynolds numbers 1.4E-3, 2.1E-3, and 3E-3. Increasing Reynolds numbers augment the likelihood of cell separation from the fixed particle. These findings contribute to optimizing cell isolation and entrapment strategies.

A phenomenological study of the evolution of shock-induced O i emission lines in the spectrum of nova V2891 Cygni

ABSTRACT The eruption of Nova V2891 Cygni in 2019 offers a rare opportunity to explore the shock-induced processes in novae ejecta. The spectral evolution shows noticeable differences in the evolution of various oxygen emission lines such as O i 7773 Å, O i 8446 Å, O i 1.1286 μm, O i 1.3164 μm, etc. Here, we use spectral synthesis code cloudy to study the temporal evolution of these oxygen emission lines. Our photoionization model requires the introduction of a component with a very high density ($n \sim 10^{11}$ cm$^{-3}$) and an enhanced oxygen abundance (O/H $\sim$ 28) to produce the O i 7773 Å emission line, suggesting a stratification of material with high oxygen abundance within the ejecta. An important outcome is the behaviour of the O i 1.3164 μm line, which could only be generated by invoking the collisional ionization models in cloudy. Our phenomenological analysis suggests that O i 1.3164 μm emission originates from a thin, dense shell characterized by a high density of about $10^{12.5}\!-\!10^{12.8}$ cm$^{-3}$, which is most likely formed due to the strong internal collisions. If such is the case, the O i 1.3164 μm emission presents itself as a tracer of shock-induced dust formation in V2891 Cyg. The collisional ionization models have also been successful in creating the high-temperature conditions ($\sim 7.07\!-\!7.49 \times 10^5$ K) required to reproduce the observed high ionization potential coronal lines, which coincide with the epoch of dust formation and evolution of the O i 1.3164 μm emission line.

Effects of cross flow on the launching process of submarine-launched vehicle considering the 6-DOF motion at barrel-exit stage

Submarine-launched vehicle (SLV) is a research hotspot due to its strong strike capability, among which underwater launching technology is a key issue hindering its development. In this paper, a numerical model is proposed to simulate the launching problem of SLV. The high nonlinearity induced by the coupling of multi-degree-of-freedom motions and the interaction between fluid and structure is solved. Specifically, the 6-DOF motion model of structure considering its strong added-mass effect, cavitation model and collision model are adopted. This numerical model is firstly validated by simulating the launching of SLV in still water. And then, the applicability of this model is discussed, as well as the effect of cross flow and initial launching velocity on the launching process. The results indicate that proposed numerical model could be used under both low-speed and high-speed cross flow situations. Cross flow changes the attitude and locomotion state of SLV. When flow velocity exceeds 1.25 m/s, the collision occurs between SLV (with the initial launching velocity of 40 m/s) and its barrel. This obtained locomotion of SLV after leaving its barrel causes the launching failure. Besides, a method of increasing launching velocity is introduced to promote the success rate of launching in high-speed cross flow situation.

Development and application of a three-dimensional pseudo-Voigt function for muon spin relaxation analysis of weakly magnetic materials.

We present a three-dimensional pseudo-Voigt function to analyze muon spin relaxation (μSR) in weakly magnetic materials. Our approach approximates the Voigt function by superimposing Gaussian and Lorentzian functions using a one-dimensional method proposed by Di Rocco and Cruzado [Acta Phys. Pol., A 122, 666 (2012)]. We derive the peak of the Voigt function analytically and express the Half Width at Half Maximum (HWHM) of the Voigt function as a function of the HWHMs of the Gaussian and Lorentzian functions. We compare the pseudo-Voigt function to the exact Voigt function and find a maximum normalized discrepancy of ∼20% at the tail of the distribution function, depending on the ratio of Lorentzian to Gaussian HWHMs and internal magnetic field. We apply the derived three-dimensional pseudo-Voigt function to calculate μSR functions for zero- and longitudinal-field experiments and use them to fit μSR time spectra of La2-xSrxCuO4 with 2.4% Sr, employing a strong collision model with the static-based pseudo-Voigt muon spin relaxation function as the initial condition. Our results show that the Gaussian- and Lorentzian-fitted parameters and fluctuation rate are in good agreement with results from the exact Voigt function for a temperature range of 30-200K, with the deviation of Gaussian and Lorentzian width parameters reaching ∼0.15G below 30K.

Study on the flow and collision characteristics of catalyst particles in FCC reactor

Fluid Catalytic Cracking (FCC), a typical fluidization technology, faces serious issues of catalyst particle attrition and loss. Attrition is an important cause of catalyst loss. Due to the small particle size and complex flow process inside the reactor，it is difficult to conduct experimental research on it. The flow, collision and attrition characteristics of catalyst in the reactor are still unclear. This study established a geometric model of a catalytic cracking unit and used CFD-DEM bidirectional coupling numerical simulation method to study the flow and collision characteristics of catalyst particles in the catalytic cracking unit. The result indicate that particles collide with the wall most frequently， with an average collision frequency of 141,501.89 Hz. The particle wall collision frequencies above the nozzle, at the top of the riser, and in the cyclone separator are the highest, with an average collision frequency of 244.90 Hz, 1441.2 Hz, and 3571.15 Hz, respectively. Strong single collisions and slight continuous collisions of large size particles often occurred in the device. For small particles, the difference in strength between each collision within the device is not significant.

Stable and ultralong room-temperature phosphorescent copolymers with excellent adhesion, resistance, and toughness.

Developing stable room-temperature phosphorescence (RTP) emission without being affected by moisture and mechanical force remains a great challenge for purely organic systems, due to their triplet states sensitive to the infinitesimal motion of phosphors and the oxygen quencher. We report a kind of highly robust phosphorescent systems, by doping a rigid phosphor into a copolymer (polyvinyl butyral resin) matrix with a balance of mutually exclusive features, including a rigidly hydrophilic hydrogen bond network and elastically hydrophobic constituent. Impressively, these RTP polymeric films have superior adhesive ability on various surfaces and showed reversible photoactivated RTP with lifetimes up to 5.82 seconds, which can be used as in situ modulated anticounterfeit labels. They can maintain a bright afterglow for over 25.0 seconds under various practical conditions, such as storage in refrigerators, soaking in natural water for a month, or even being subjected to strong collisions and impacts. These findings provide deep insights for developing stable ultralong RTP materials with desirable comprehensive performance.

Increasing Efficiency and Reliability in Multicast Routing based V2V Communication for Direction-Aware Cooperative Collision Avoidance

Mobile ad hoc networks (MANETs), which are a promising method for the intelligent transportation system, include vehicular ad hoc networks (VANETs) (ITS). Developing reliable and strong cooperative collision avoidance (CCA) strategy to mitigate the growing number of road fatalities each year is one of the main difficulties facing vehicular ad hoc networks (VANETs).A proper and successful routing method aids in the successful expansion of vehicular ad hoc networks. This study explains the architecture, interface layers, safety features, and implementation of a novel priority-based direction-aware collision avoidance system (P-DVCA). It distinguishes our study in the collision area of VANETs by accounting for realistic bi-directional traffic. The scheme begins with the development of dynamic clusters, which is difficult because of the bi-directional diverse traffic and the need to avoid collisions within and between clusters. The target node is sent an early warning message that includes the safe speed and the likelihood of a collision in order to notify it of an impending danger. To determine the least expensive, shortest one with the fewest hops between the source and the endpoint. A crucial problem with VANETs is the transmission of data from a source node to the base station. Cross-layer issues must be solved for a robust and stable collision avoidance programme to function properly in a VANET communication architecture. The results of the simulation show that the suggested scheme significantly outperforms CCM and C-RACCA in terms of cluster stability, fewer collisions, low latency, and low communication overhead. According to the findings, P-DVCA offers stable clustering, minimises network congestion, and lowers communication overhead and latency.

Performance analysis of hydraulic excavators in complex excavation environments and different bucket trajectories

Simulations of excavation operations not only help understand how excavators perform in specific environments but also can be used to optimise operating parameters. In this work, we explore the performance of hydraulic excavators under conditions of cohesive and size-dispersed materials and different bucket trajectories. The results indicate that with the cohesion increasing, the spillage of particles from the bucket is reduced, but the hydraulic power fluctuates greatly due to the strong collision of particle aggregates on the bucket. As the particle size distribution turns wider, small particles exert an intensive interaction force on the bucket, and the stress distribution on the bucket becomes wider. Therefore, some suggestions are given for practical excavation operations in different stockpile scenarios. Additionally, the bucket can be initially placed close to the base of the stockpile to achieve low specific energy consumption and high productivity.

Influence of laser-induced Au-plasma plume collision on the efficiency of x-ray radiations and the energy-transport process relevant to ICF

Experiments and simulations have been carried out to study the colliding process by two lasers irradiating a gold half-hohlraum. Via analyzing the evolutionary x-ray images, radiation fluxes and self-emission spectrum of tracers, influence on the x-ray conversion efficiency and the local plasma temperature Te,i from two gold-plasma plumes have been investigated deeply, which is similar as the configuration in Inertial Confinement Fusion (ICF). Experimental results confirm a region with high electron and ion temperatures Te,i are induced, satisfying the strong collision condition of λi<ΔL , where λ i and ΔL are respectively the ion mean-free path and the gradient length of Te . It leads to almost 30% increasing of M-band component compared to that from a single laser-irradiation case. Meanwhile ion temperature in this region increases more rapidly than electrons, reaching about Ti≈(16±4) keV ( Te≈(2±0.2) keV). Thus, our studies provide the experimental evidence of quantitative x-ray enhancement and a non-equilibrium evolution simultaneously due to the plasma collision for the first time. Besides, two-dimensional simulation results reveal that this process can not be precisely described by the traditional shock-heating model by dissipating the shock energy only to ions. But by distributing the viscous heating between both electrons and ions as theoretically discussed by Miller (2020 Comput. Fluids 210 104672), numerical results can match experiments better. This discovery will be of great importance to improve the precision of prediction for ICF.

Investigating the Chemical Stability of Electrospray Plumes During Particle Collisions

Electrospray thrusters fulfill the main propulsion requirements for long-term small-satellite missions. However, the molecules present in the plume are susceptible to collisions, chemical reactions, and fragmentation, which may introduce different new species with various mass-to-charge ratios inside the plume. Prediction of the byproducts that appear upon collisions is of prime importance to predicting the evolution of the plume and estimating the performance and the lifetime expectancy of the thruster. In this work, we use molecular dynamics simulations to investigate monomer–neutral collisions at different impact configurations, impact energies, and impact parameters, and we provide the mass spectra of the resulting species. We predict that 1) collisions within a center-of-mass distance of 6 Å can result in momentum exchange and molecular fragmentation, 2) higher-energy impacts produce more byproducts, and 3) heavy molecules (e.g., 1-ethyl-3-methylimidazolium [EMI] and BF4) are more likely to result from weak collisions (<30 eV), whereas light molecules (e.g., H, F, and CH3) are more likely to result from strong collisions. Collisional fragmentation is shown to negatively affect key performance indicators, including reductions in thrust, specific impulse, and propulsive efficiency. This phenomenon potentially accounts for the observed discrepancies in experimental measurements of current and mass loss rates.

A path planning method for compliant jointing of weakly rigid helicopter fuselage

PurposeThe purpose of this paper is to propose a strategy for the final assembly of helicopter fuselage with weak rigidity parts and mismatched jointing butt ends.Design/methodology/approachThe strategy is based on path planning methods. Compared with traditional path planning methods, the configuration-space and collision detection in the method are different. The obstacles in the configuration-space are weakly rigid and allow continuous contact with the robot. The collision detection is based on interference magnitudes, and the result is divided into no collision, weak collision and strong collision. Only strong collision is unacceptable. Then a compliant jointing path planning algorithm based on RRT is designed, combined with some improvements in search efficiency.FindingsA series of planning results show that the efficiency of this method is higher than original RRT under the same conditions. The effectiveness of the method is verified by a series of simulations and experiments on two sets of systems.Originality/valueThere are few reports on the automation technology of helicopter fuselage assembly. This paper analyzes the problem and provides a solution from the perspective of path planning. This method contains a new configuration-space and collision detection method adapted to this problem and could be intuitive for the jointing of other weakly rigid parts.

Sequential two photon absorption induced optical limiting action of oxide upconverter based MoS2 heterostructures

Lanthanide ions (Yb, Er) doped cerium oxide (CeO2) and yttrium oxide (Y2O3) upconverter nanoparticles were prepared by sol-gel synthesis technique. And the upconverter nanoparticles (CeO2: Yb, Er and Y2O3: Yb, Er) were made us heterostructure with MoS2 by hydrothermal synthesis. XRD confirms the formation of cubic phase of CeO2, cubic phase of Y2O3, hexagonal phase of MoS2 and their coexistence in heterostructures. Further, the observation of characteristic Raman peaks between 400 and 700 cm−1 (Raman modes of CeO2, Y2O3) and 300–400 cm−1 (Raman modes of MoS2) assured the formation of heterostructures. FESEM exposes that in heterostructures nanospheres (CeO2: Yb, Er) and nanospindle (Y2O3: Yb, Er) were dispersed on MoS2 nanoplatelets. Furthermore, when forming the heterostructure with MoS2, the diameter of the CeO2 nanosphere got increased (90 nm) whereas, the length of the Y2O3 nanospindle was decreased (166 nm). The maximum absorption band occurred at UV region due to the charge transition from O2− to Ce ion or Y ion for CeO2 (340 nm) and Y2O3 (274 nm) respectively. Both upconverters exhibits interesting luminescence behaviour with green emission (537 nm, 588 nm), blue emission (497 nm) and red emission (621 nm). Nonlinear absorption induced optical limiting action were examined by open aperture Z-scan technique using nanosecond pulse laser. All the prepared nanoparticles exhibit a reverse saturable absorption pattern ascribed due to sequential two photon absorption. Among, all the samples, MoS2–CeO2: Yb, Er and MoS2–Y2O3: Yb, Er heterostructure possess a high nonlinear absorption coefficient (16.76 × 10−10 m/W, 13.61 × 10−10 m/W) and low limiting threshold (0.33 × 1012 W/m2, 0.51 × 1012 W/m2) due to the strong inter-band collision between of MoS2 and upconverters. The absorption of high number of photons and low limiting threshold behaviour make MoS2–CeO2: Yb, Er and MoS2–Y2O3: Yb, Er heterostructures as potential candidate for the fabrication of optical limiter based laser safety devices.

Combined denoising method of acceleration signal during mobile robot collision

Collision safety of mobile robot is one of the important indexes of robot safety evaluation. The acceleration signal of the robot can completely feed-back the state of the collision process, but it is also vulnerable to noise interference such as vibration and impact, which is difficult to be used for direct analysis. In order to solve the problem of mixing acceleration signal with impact noise and periodic vibration noise during robot collision, a combined filtering noise reduction method based on empirical mode decomposition (EMD), improved wavelet threshold method and dynamic sliding window is proposed. And a wavelet adaptive threshold function is constructed. The wavelet coefficients are automatically adjusted using the information of decomposition degree and noise level, and a dynamic adjustment strategy of sliding window length is designed. The acceleration information of robot can be effectively extracted in the process of strong noise collision. The experimental results show that this method has better noise reduction effect than other methods.

The Truths of Space-time Contractions of Special Relativity

This paper points out that there is no any experimental evidence for the length contraction of a moving object in special relativity. It is just a theoretical prediction based on the Lorentz transformation formula. Einstein put forward the concept of simultaneous relativity in order to explain the length contraction. In this paper, an example called Ji Hao's bridge-breaking paradox is provided to prove that this kind of paradoxes cannot be explained by simultaneous relativity. A completely symmetric method is introduced to prove that the famous twin paradox is unsolvable. The time delay experiments of special relativity, such as the life time of μ meson and the atomic clocks moving around the Earth are discussed. It is proved that time slows down of a moving clock does not exist too. It is a misunderstanding to use the lifetime of μ mesons to prove the time delay of special relativity because μ mesons decay prematurely due to strong collisions with other nuclei in the Earth's surface atmosphere. What calculated in theory is the time difference between two atomic clocks flying east and west observed in the stationary reference frame of the Earth's mass center. But the measurement of time difference is on the surface of the Earth. Because of the symmetry of motion speed, there is no time difference caused by the motion speed between the two atomic clocks observed on the Earth’s surface, so the experiment of atomic clocks moving around the Earth is invalid. The experiment is also suspected of fabricating experimental data. The conclusion of this paper is that the space-time contraction of special relativity and its relativity cannot happen in real nature, time and space are absolute concepts, and the Lorentz transformation cannot be correct.

Investigation of bionic composite laminates inspired by the natural impact-resistant helicoidal structure in the mandibles of trap-jaw ants.

Many living organisms exhibit exceptional capabilities and have evolved effective strategies to synthesize impact-resistant and damage-tolerant structures. One such example can be observed in the rapid mandible strikes ofOdontomachus monticola, a species of trap-jaw ants from the ponerine subfamily. During trap-jaw strikes, the mandibles can achieve peak speeds of 35.42 m s-1, and the maximum acceleration can reach 71 729 g within an average duration of 0.18 ms. The extreme acceleration results in instantaneous mandible strike forces that can exceed 330 times the ant's body weight, withstanding thousands of impacts. A natural impact-resistant fibrous helicoidal structure is found in the mandibles of trap-jaw ants. This microstructure is characterized by periodic modulus oscillations that increase energy absorption and improve stress redistribution, offering added protection against damage from impact loading. A carbon fiber reinforced helicoidal composite is fabricated based on the microstructure of the trap-jaw ant's mandibles. The results show that the helicoidal composite with a 12° helical-fiber exhibits higher residual strength, making it more capable of withstanding strong collisions. The catastrophic propagation of damage along the thickness direction is prevented by in-plane spreading and redirection of cracks. This research provides useful references for fabricating bionic impact-resistant composites.

Microwave-activated Cu-doped zirconium metal-organic framework for a highly effective combination of microwave dynamic and thermal therapy

Percutaneous microwave ablation (PMA) is a thermoablative method used as a minimally invasive treatment for liver cancer. However, the application of PMA is limited by its insufficient ROS generation efficiency and thermal effects. Herein, a new microwave-activated Cu-doped zirconium metal-organic framework (MOF) (CuZr MOF) used for enhanced PMA has a significantly improved microwave sensitizing effect. Owing to the strong inelastic collisions between ions confined in numerous micropores, CuZr MOF has strong microwave sensitivity and high thermal conversion efficiency, which can significantly improve microwave thermal therapy (MTT). Moreover, because of the existence of Cu2+ ions, a further benefit of CuZr MOF is their Fenton-like activity, in particular, microwaves used as an excitation source for microwave dynamic therapy (MDT) can improve the Fenton-like reaction to maximize the synergistic effectiveness of cancer therapy. Importantly, CuZr MOF can inhibit the production of heat shock proteins (HSPs) by producing abundant ROS to enhance tumor destruction. Mechanistically, we found that CuZr MOF + MW treatment modulates ferroptosis-mediated tumor cell death by targeting the HMOX1/GPX4 axis. In summary, this study develops a novel CuZr MOF microwave sensitizer with great potential for synergistic treatment of liver cancer by MTT and MDT.

A modified projection approach to line mixing

This paper presents a simple approach to combine the high-resolution narrowband features of some desired isolated line models together with the far wing behavior of the projection based strong collision (SC) method to line mixing which was introduced by Bulanin, Dokuchaev, Tonkov and Filippov. The method can be viewed in terms of a small diagonal perturbation of the SC relaxation matrix providing the required narrowband accuracy close to the line centers at the same time as the SC line coupling transfer rates are retained and can be optimally scaled to thermalize the radiator after impact. The method can conveniently be placed in the framework of the Boltzmann–Liouville transport equation where a rigorous diagonalization of the line mixing problem requires that molecular phase and velocity changes are assumed to be uncorrelated. A detailed analysis for the general Doppler case is given based on the first order Rosenkranz approximation, and which also provides the possibility to incorporate quadratically speed dependent parameters. Exact solutions for pure pressure broadening and explicit Rosenkranz approximations are given in the case with velocity independent parameters (line frequency, strength, width and shift) which can readily be retrieved from databases such as HITRAN for a large number of species. Numerical examples including comparisons to published measured data are provided in two specific cases concerning the absorption of carbon dioxide in its infrared band of asymmetric stretching, as well as of atmospheric water vapor and oxygen in relevant millimeter bands.

Improving dynamic collision frequencies: Impacts on dynamic structure factors and stopping powers in warm dense matter

Simulations and diagnostics of high-energy-density plasmas and warm dense matter rely on models of material response properties, both static and dynamic (frequency-dependent). Here, we systematically investigate variations in dynamic electron–ion collision frequencies ν(ω) in warm dense matter using data from a self-consistent-field average-atom model. We show that including the full quantum density of states, strong collisions, and inelastic collisions lead to significant changes in ν(ω). These changes result in red shifts and broadening of the plasmon peak in the dynamic structure factor, an effect observable in x-ray Thomson scattering spectra, and modify stopping powers around the Bragg peak. These changes improve the agreement of computationally efficient average-atom models with first-principles time-dependent density functional theory in warm dense aluminum, carbon, and deuterium.

Molecular mechanism in the solubility reduction of elemental sulfur in H2S/CH4 mixtures: A molecular modeling study

The solubility evolution of elemental sulfur in sour gas is key to study the occurrence and inhibition of sulfur deposition in the exploitation of high-sulfur gas reservoirs. Elemental sulfur mainly dissolves in H2S, and its solubility decreases dramatically in the presence of methane. As both methane and H2S are the main components in high-sulfur gas, it is essential to understand the molecular mechanism of the solubility reduction in H2S/CH4 mixtures. Molecular dynamics simulations are carried out for the S8, H2S and CH4 mixtures to reproduce the solubility reduction upon methane addition, and then used to reveal the reduction mechanism at the level of intermolecular interaction. The simulations reveal that both the strong competitiveness and high collision probability of H2S–CH4 pairs reduce the average densities of H2S–S(S8) and H2S–H2S pairs, which reduce the sulfur solubility in a direct/indirect but cooperative way. The role of methane in the solubility reduction is then discussed and the molecular mechanism of sulfur dissolution and precipitation in the sour gasses is addressed.

Petrogenesis of the Qiongduojiang Gabbro in Tethys Himalaya and Its Metallogenetic Implication

With the northward subduction and final closure of the Neo-Tethyan oceanic crust, the Indian and Eurasian plates finally collided together and underwent a strong collision orogenic event, resulting in large-scale crust–mantle magmatic interactions. In order to clarify the controversies about tectono-magmatic activities after the Indian–Eurasian continental collision, we report the newly dated Eocene Qiongduojiang gabbro explored in the Tethyan–Himalaya belt, southern Tibet. LA-ICP-MS zircon U-Pb dating shows that the crystallization age of the Qiongduojiang gabbro is 46.1 ± 1.7 Ma. The whole-rock major and trace elements, as well as Rb-Sr, Sm-Nd, and Pb isotopic data results, show that the Qiongduojiang gabbro is apparently depleted in Nd isotopes, is enriched in Pb isotopes, and has maintained a consistent 87Sr/86Sr(t) value. This paper argues that the E-MORB-like Qiongduojiang gabbro originated from asthenosphere upwelling caused by slab breakoff of the Neo-Tethyan oceanic plate. This event caused large-scale magmatic activities, a magmatic mixing process between ancient crust and deep mantle, and wild distribution of Eocene Gangdese plutons along the Yarlung–Tsangpo Suture Zone, and it rendered the subduction-modified Tibetan lithosphere fertile from the Gangdese porphyry Cu deposits.