Effect Of Collisions Research Articles

Unveiling the impact of heterogeneous driving behaviors on traffic flow: A mesoscale multi-agent modeling approach

There are fewer simulation studies that comprehensively consider the impact of collision events due to heterogeneous driving behaviour on multi-lane traffic flow. This comprehensive study utilized multi-agent modeling to simulate the driver-vehicle-road system at the mesoscale level, integrating the characteristics of heterogeneous driving behavior. We developed a traffic flow simulation model for a three-lane urban arterial road segment and used rule-based algorithms to simulate vehicle following, lane changing, and collision behavior. A visualization simulation program was developed using NetLogo software to observe and analyze vehicle behavior. The findings revealed that collision events were the leading cause of traffic bottlenecks, impacting the continuity and coherence of traffic flow. Even after the collision event subsided and congestion eased, the average vehicle speed could not fully recover to its original level, reaching only about 70% of the maximum vehicle speed. Aggressive drivers exhibited distinct speed control strategies compared to conservative and ordinary drivers. This study demonstrates the effectiveness of multi-agent modeling in capturing the relationship between traffic bottlenecks and collision events, highlighting the influence of dynamic traffic events on driving behavior.

Effect of secondary flow and wall collisions on particle-laden flows in 90° pipe bends

Fully developed, statistically stationary particle-laden turbulent flows in a 90° pipe bend at a moderate Reynolds number are studied using direct numerical simulation coupled to a Lagrangian particle tracking technique. Three populations of particles are studied which are two-way coupled with the carrier phase. The focus is the investigation of the effect of strong curvature on particle transport dynamics across a range of particle inertias. A validation of the carrier phase predictions is performed, with good agreement found with available experimental data. It is demonstrated that the presence of particles notably affects the turbulence statistics of the carrier phase, decreasing the mean fluid velocity in the outer bend while slightly increasing it in the inner bend. Two intriguing phenomena emerge: the presence of a particle void near the inner bend and reflection layers near the outer bend. Centrifugal forces are responsible for driving particles to the outer wall, with some rebounding back into the main body of the flow, and others, influenced by the secondary flow in the plane of the pipe cross-section, converging towards the inner wall before re-entering the central pipe region. These effects dictate the size and shape of the particle void region and the formation of reflection layers due to particle-wall collisions. These two phenomena have a significant influence on the particle distribution in the pipe bend, as well as on the first- and second-order moments of the velocity and acceleration of the particulate phase. Finally, a heat map of particle-wall collision statistics indicates that the effect of the secondary flow on particle distribution and particle-wall collisions is not negligible.

Identifying the influence of airbag structure on driver injury during a crash using a dummy model

This study undertakes the analysis of collision scenario using a car model with a dummy and airbags, in the event of a direct collision with a hard wall, one of the necessary studies of passive safety. To describe in detail, the input conditions, a simulation problem of the driver's seat displacements was performed and this displacements data was exported as boundary conditions for the collision simulation. The results simulation crash show that the calculated energy values and simulation results are approximately the same (7.381E+07 and 7.367E+07), energy is converted from kinetic energy into internal energy of the elements. The airbag deployment simulation results are similar to NHTSA's previous research, both in terms of graph shape and maximum value. The impact of the collision incident on the driver is not excessively large, as evidenced by surveys on head (HIC 300), thigh (F 2.8 kN), and neck (F3,098 kN; T 190 Nm) injuries. However, the study proceeds to further analyze and assess the airbag's structure, examining its influence on these metrics, concluding that changes in the exhaust valve size (increase from 1000 mm2 to 2000 mm2) lead to a reduction in the evaluated parameters. These results suggest changes to the airbag structure to enhance driver safety, as well as a simpler simulation model to save analysis time

Unveiling Nonsecular Collisional Dissipation of Molecular Alignment.

We conducted a joint theoretical and experimental study to investigate the collisional dissipation of molecular alignment. By comparing experimental measurements to the quantum simulations, the nonsecular effect in the collision dissipation of molecular alignment was unveiled from the gas-density-dependent decay rates of the molecular alignment revival signals. Different from the conventional perspective that the nonsecular collisional effect rapidly fades within the initial few picoseconds following laser excitation, our simulations of the time-dependent decoherence process demonstrated that this effect can last for tens of picoseconds in the low-pressure regime. This extended timescale allows for the distinct identification of the nonsecular effect from molecular alignment signals. Our findings present the pioneering evidence that nonsecular molecular collisional dissipation can endure over an extended temporal span, challenging established concepts and strengthening our understanding of molecular dynamics within dissipative environments.

The irreversibility of microscopic motions

People have long had a problem: the equations of motion that reflect the laws of physics are invariant under time inversion, while there always are irreversible processes for gases composed of microscopic particles. This article solves the problem. The point is that we should distinguish between the concepts of the equation of motion and concrete motion. We also need to distinguish between the concepts of time-inverse motion and reverse motion. The former is anticlockwise, which is a fictional motion, while the latter is clockwise. For the single-particle motions in classical mechanics and in quantum mechanics, we present mathematical expressions for time-inversion motion and reverse motion, respectively. We demonstrate that single-particle motion is irreversible. The definition of the reversibility of two-particle collisions is given. According to the definition, the two-particle collision as a microscopic motion process is irreversible. Consequently, for a gas consisting of a large number of particles colliding with each other, its movement should be irreversible, unless the condition of detailed balance is met. We provide a physical explanation for detailed balance, which does not concern the meaning of microscopic reversibility. The detailed balance means that after a pair of reciprocal collisions occur, the distribution function of the particles remains unchanged. Therefore, microscopic two-particle collision events are irreversible, but the statistical average of a large number of collision events makes it possible for the macroscopic process of a gas to be reversible. Conclusively, we clarify the microscopic mechanism of the irreversible process of gases.

Implementation of three-dimensional contact algorithm in numerical manifold method for the structural impact simulation

Structural impact often accompanies large amounts of contacts and leads to complex mechanical phenomena. In solid mechanics, the numerical manifold method (NMM) is proposed to address problems featuring continuous-discontinuous transitions by utilizing a dual coverage system encompassing both mathematical and physical covers. In the present work, a penalty contact algorithm for 3DNMM based on cover-based contact theory is programmed and applied to impact mechanics problems. The accuracy of the developed contact algorithm is firstly calibrated through free-falling blocks and collision blocks. The influence of contact parameters on contact convergence is systematically studied, and three preliminary criteria for how to set contact parameters are provided. The effectiveness of the contact algorithm is verified by conserving system momentum during block collisions. Subsequently, the contact algorithm is applied to Taylor rod and car-streetlight impact simulation, further confirming its effectiveness in modeling high-speed collisions, large displacements, and large deformations of structures. By comparing the 3DNMM results with those from Abaqus, the contact algorithm developed here performs exceptionally well in solving collision problems and produces results consistent with commercial software. The research results in the present work verify the applicability and accuracy of the proposed contact algorithm in solving structural dynamic impact problems. The present work also provides guidance for contact parameter setting in impact problems.

Upper limit on the chiral magnetic effect in isobar collisions at the Relativistic Heavy-Ion Collider

The chiral magnetic effect (CME) is a phenomenon that arises from the QCD anomaly in the presence of an external magnetic field. The experimental search for its evidence has been one of the key goals of the physics program of the Relativistic Heavy-Ion Collider. The STAR Collaboration has previously presented the results of a blind analysis of isobar collisions (Ru4496+Ru4496, Zr4096+Zr4096) in the search for the CME. The isobar ratio (Y) of CME-sensitive observable, charge separation scaled by elliptic anisotropy, is close to but systematically larger than the inverse multiplicity ratio, the naive background baseline. This indicates the potential existence of a CME signal and the presence of remaining nonflow background due to two- and three-particle correlations, which are different between the isobars. In this postblind analysis, we estimate the contributions from those nonflow correlations as a background baseline to Y, utilizing the isobar data as well as Heavy Ion Jet Interaction Generator simulations. This baseline is found consistent with the isobar ratio measurement, and an upper limit of 10% at 95% confidence level is extracted for the CME fraction in the charge separation measurement in isobar collisions at sNN=200 GeV. Published by the American Physical Society 2024

End-to-end simulation of particle physics events with flow matching and generator oversampling

The simulation of high-energy physics collision events is a key element for data analysis at present and future particle accelerators. The comparison of simulation predictions to data allows looking for rare deviations that can be due to new phenomena not previously observed. We show that novel machine learning algorithms, specifically Normalizing Flows and Flow Matching, can be used to replicate accurate simulations from traditional approaches with several orders of magnitude of speed-up. The classical simulation chain starts from a physics process of interest, computes energy deposits of particles and electronics response, and finally employs the same reconstruction algorithms used for data. Eventually, the data are reduced to some high-level analysis format. Instead, we propose an end-to-end approach, simulating the final data format directly from physical generator inputs, skipping any intermediate steps. We use particle jets simulation as a benchmark for comparing both discrete and continuous Normalizing Flows models. The models are validated across a variety of metrics to identify the most accurate. We discuss the scaling of performance with the increase in training data, as well as the generalization power of these models on physical processes different from the training one. We investigate sampling multiple times from the same physical generator inputs, a procedure we name oversampling, and we show that it can effectively reduce the statistical uncertainties of a dataset. This class of ML algorithms is found to be capable of learning the expected detector response independently of the physical input process. The speed and accuracy of the models, coupled with the stability of the training procedure, make them a compelling tool for the needs of current and future experiments.

Compact ultrafast neutron sources via bulk acceleration of deuteron ions in an optical trap

A scheme for a quasi-monoenergetic high-flux neutron source with femtosecond duration and highly anisotropic angular distribution is proposed. This scheme is based on bulk acceleration of deuteron ions in an optical trap or density grating formed by two counter-propagating laser pulses at an intensity of ∼1016W/cm2 in a near-critical-density plasma. The deuterons are first pre-accelerated to an energy of tens of keV in the ambipolar fields formed in the optical trap. Their energy is boosted to the MeV level by another one or two laser pulses at an intensity of ∼1020W/cm2, enabling fusion reactions to be triggered with high efficiency. In contrast to previously proposed pitcher–catcher configurations, our scheme can provide spatially periodic acceleration structures and effective collisions between deuterons inside the whole target volume. Subsequently, neutrons are generated directly inside the optical trap. Our simulations show that neutron pulses with energy 2–8 MeV, yield 1018–1019n/s, and total number 106–107 in a duration ∼400 fs can be obtained with a 25 μm target. Moreover, the neutron pulses exhibit unique angularly dependent energy spectra and flux distributions, predominantly along the axis of the energy-boosting lasers. Such microsize femtosecond neutron pulses may find many applications, such as high-resolution fast neutron imaging and nuclear physics research.

Continuous flow mechanochemical synthesis of Zr-MOF as effective catalyst for 4-nitrophenol reduction

Nitroaromatic compounds (NACs) are a group of organic chemicals containing one or more nitro functional groups attached to an aromatic ring. These compounds are considered emerging pollutants (EPs) in wastewater due to their potential environmental and human health impacts. These NACs can enter wastewater through various sources, including the production and use of explosives, dyes, pesticides, or pharmaceuticals. 4-nitrophenol (4-NP) is considered a priority pollutant due to its toxicity and potential environmental and health hazards. Thus, its removal is crucial. For that purpose, a novel strategy to carry out Zr-MOFs syntheses has been developed employing I-CHEM technology (Impact Continuous flow Heated Mechanochemistry), an improved wet-milling process. The resulting materials have demonstrated efficacy as catalysts in the reduction of 4-NP towards 4-aminophenol (4-AP), a precursor to paracetamol.Notably, the most promising outcomes were achieved with Zr-MOF prepared through continuous flow mechanochemical processes utilizing Zr-methacrylate clusters as precursor (Zr-MOF/2@RL). 4-NP removal was successfully carried out at room temperature, with an outstanding optimal time of removal of 14 min, 30% faster than with synthesized by conventional methodologies. These findings underscore the innovation brought about by the I-CHEM synthetic approach, where more effective collisions are reached, as well as opening avenues for broader applications of MOFs. The wet-mechanochemical procedure not only demonstrates its novelty, but also presents the potential for scalability under continuous flow conditions, further enhancing the feasibility of large-scale production.

External-magnetic-field-induced paramagnetic squeezing effect in heavy-ion collisions at energies available at the CERN Large Hadron Collider

External-magnetic-field-induced paramagnetic squeezing effect in heavy-ion collisions at energies available at the CERN Large Hadron Collider

A gyrokinetic simulation model for 2D equilibrium potential in the scrape-off layer of a field-reversed configuration

The equilibrium potential structure in the scrape-off layer (SOL) of the field-reversed configuration (FRC) can be affected by the penetration of edge biasing applied at the divertor ends. The primary focus of the paper is to establish a formulation that accurately captures both parallel and radial variations of the two-dimensional (2D) potential in SOL. The formulation mainly describes a quasi-neutral plasma with a logical sheath boundary. A full-f gyrokinetic ion model and a massless electron model are implemented in the GTC-X code to solve for the self-consistent equilibrium potential, given fixed radial potential profiles at the boundaries. The first essential point of this 2D model lies in its ability to couple radial and parallel dynamics stemming from resistive currents and drag force on ions. The model successfully recovers the fluid force balance and continuity equations. These collisional effects on 2D potential mainly appear through the density profile changes, modifying the potential through electron pressure gradient. This means an accurate prescription of electron density and temperature profiles is important in predicting the potential structure in the FRC SOL. The Debye sheath potential and the potential profiles applied at the boundaries can be additional factors contributing to the 2D variations in SOL. This comprehensive full-f scheme holds promise for future investigations into turbulent transport in the presence of the self-consistent 2D potential together with the non-Maxwellian distributions and open boundary conditions in the FRC SOL.

A self-sensing Al/aramid hybrid laminate for detection of MMOD collision with electrical resistance tomography

Aiming at the micrometeoroid/orbital debris (MMOD) collision problem for space structures, this paper proposes a self-sensing aluminum/aramid hybrid laminate for detection of MMOD collision event and identification of its associated damage. A co-curing method is used to fabricate the hybrid laminate while carbon nanotube (CNT) film and flexible printed circuit (FPC) are embedded in the laminate as sensing layer. By injecting tiny currents into the CNT film before and after MMOD collision and collecting the corresponding boundary voltages, electrical resistance tomography (ERT) is employed to reconstruct tomographic image of the conductivity change caused by MMOD collision and provide information about the damage. Experimental studies have conducted to perform ballistic high velocity impacts to simulate MMOD collision to three self-sensing hybrid laminates. The results have demonstrated that, the CNT film has good sensing performance, and the reconstructed image of conductivity changes can reflect the location and approximate size of the damage, validating the effectiveness of the proposed self-sensing hybrid laminate and providing a new way for space structures to detect MMOD collisions.

Millimeter to THz Spectroscopy of HC18O+ and HC17O+: Accurate Rest Frequencies for Astrophysical Studies

Heavy oxygen isotopic species of HCO+ are important optically thin astrophysical tracers. The ground-state rotational spectrum of HC18O+, DC18O+, HC17O+, and DC17O+ has been recorded in the laboratory in the frequency range from 85 GHz to 1.3 THz. The ions have been produced in the negative column of a glow-discharge plasma, and their spectrum has been recorded in absorption using a frequency-modulation submillimeter-wave spectrometer. Various sources of systematic error have been carefully accounted for in order to obtain highly accurate line-position measurements. Theoretical estimates of the molecular parameters and of the collision effects on the line shape have been obtained by high-level ab initio calculations. The analysis yielded much improved rotational and centrifugal distortion constants, thus bringing the spectroscopic characterization of these rare isotopic variants to the same level of the parent species. Also, the first experimental rotational data for DC17O+ have been provided. These results allow for the calculation of an updated set of rest frequencies to support current and future astrophysical studies. The derived data set for the widely used HC18O+ tracer reaches an accuracy of a few parts in 109 up to 1.5 THz. Such accuracy is important for the analysis of astrophysical objects targeted by Atacama Large Millimeter/submillimeter Array observations at the submillimeter regime.

Use of the Meta-Analysis and Kolmogorov Criteria in the Finding of Singularities of a Nuclear Matter Created in Ultra-Relativistic Nuclear Collisions

Published theoretical data from several models – PHSD/HSD both with and without chiral symmetry restoration (CSR), applied to experimental data on nuclear collisions from BEVALAC/SIS to LHC energies were analyzed using meta-analysis and Kolmogorov criteria. This made it possible to localize possible features of nuclear matter created in central nucleus-nucleus collisions. Ignition of a drop of quark-gluon plasma (QGP) begins already at an energy of about √s<SUB>NN</SUB> = 2 GeV. The assessment showed that this QGP droplet occupies a small fraction, 15% (average radius of about 5.3 fm, if the fireball radius is 10 fm), of the total volume of the fireball created at √s<SUB>NN</SUB> = 2.7 GeV. A drop of exotic matter undergoes a split phase transition – separated boundaries of sharp (1<sup>st</sup> order) crossover and CSR in chiral limit, between QGP and Quarkyonic matter at an energy about √s<SUB>NN</SUB> = 3.5 GeV. The critical endpoint of 2<sup>nd</sup> order probably cannot be reached in nuclear collisions. The triple phase area occupies interval from √s<SUB>NN</SUB> =12 GeV to 15 GeV, the critical endpoint of 1<sup>st</sup> order – at around √s<SUB>NN</SUB> = 20 GeV. The boundary of smooth (2<sup>nd</sup> order) crossover transition with CSR in chiral limit between Quarkyonic matter and QGP was localized between √s<SUB>NN</SUB> = 9.3 GeV and 12 GeV, and between Hadronic and QGP in the interval from √s<SUB>NN</SUB> = 15 GeV to 20 GeV, the boundary of sharp (1<sup>st</sup> order) crossover transition with CSR in chiral limit between Hadronic matter and QGP was localized after √s<SUB>NN</SUB> = 20 GeV. The phase trajectory of the hadronic corona, enveloping the exotic droplet, always remains in the hadronic phase. The possible phase diagram of nuclear matter created in mid-central heavy ion collisions is also presented in the same energy range as for central collisions. Taking into account the quantum nature of the fireball created in nuclear collisions, emphasis is on the existence of events in central nuclear collisions at energy range from √s<SUB>NN</SUB> = 2 GeV to 2.76 TeV, at which no exotic matter is created and nuclear matter in the fireball remains in the hadronic phase throughout its (fireball) evolution.

Evaluating deposited radiation energy amount and collision quantities of small-molecule radiosensitizers through Monte Carlo simulations

This study investigates the photon interaction mechanism of various small molecule radiosensitizers, including Hydrogen Peroxide, Nimorazole, 5-Fluorouracil, NVX-108, and others, using the MCNP 6.3 Monte Carlo simulation code. The simulations focused on quantifying the linear attenuation coefficients, mean free path, and accumulation factors of these radiosensitizers, as well as their interactions in a simulated spherical water phantom irradiated with a 100 keV mono-energetic X-ray source. Our findings reveal significant variations in deposited energy, collision events, and mean free path among the radiosensitizers, indicating different efficacy levels in enhancing radiation therapy. Notably, NVX-108 demonstrated the highest energy deposition, suggesting its potential as a highly effective radiosensitizer. The study also examined the individual attenuation properties of these radiosensitizers against energetic photons, with NVX-108 showing the highest attenuation coefficient and a shorter mean free path, further supporting its superior potential in effective radiosensitization. It can be concluded that NVX-108 has higher interaction tendency with the energetic photons comparing other small-molecules under investigation.

Функціональні характеристики системи RMS-R3 у третій серії фізичних вимірювань в експерименті LHCb

The upgraded LHCb detector allows the collection of data in the third physics run at instantaneous luminosity up to 2·1033 cm-2s-1 in proton-proton collisions at energy up to 14 TeV. A set of high-speed monitoring systems, including the RMS-R3 system, which monitors the nuclear interactions in the interaction region of the IP-8 (LHCb) experiment and the background, ensures the effective conduct of the experiment. An important functional characteristic of this system is the observation of luminosity stability over a wide dynamic range, which in its upper limit provides a linear response at ten times the nominal luminosity. This paper illustrates a new functionality feature of the RMS-R3, which is its ability to produce highly accurate data on the localization of the physical events of nuclear collisions in the interaction region of the experiment. The data measured in 2022 - 2023 allow us to observe the parameter variation impact of the nucleus-nucleus average number interactions in a single bunch crossing of the beams, the change of the state of the VELO detector and the injection of gaseous target SMOG2 by different gases.

Advances in Femtosecond Coherent Anti-Stokes Raman Scattering for Thermometry

The combustion process is complex and harsh, and the supersonic combustion flow field is also characterized by short duration and supersonic speed, which makes the real-time diagnostic technology for the transient environment extremely demanding. It is of great significance to realize high time-resolved accurate measurement of temperature, component concentration, and other parametric information of the combustion field to study the transient chemical reaction dynamics of the combustion field. Femtosecond CARS spectroscopy can effectively avoid the collision effect between particles in the measurement process and reduce the influence of the non-resonant background to improve the measurement accuracy and realize the time-resolved measurement on a millisecond scale. This paper introduces the development history of femtosecond CARS spectroscopy, points out its advantages and disadvantages, and looks forward to the future development trend to carry out high time-resolved measurements, establish a database of temperature changes in various complex combustion fields, and provide support for the study of engine mechanisms.

New type of UV cured low dielectric naphthalene resin: Structure-activity relationship of different substitution sites

UV-curing low dielectric materials exhibit wide applications in the field of additive manufacturing of electronic packaging, owing to their environmental protection, good thermal stability, low dielectric constant (Dk), and dielectric loss (Df). Wherein, one-step UV curing realizes process simplification of low dielectric materials gradually sparked widespread research. In this work, a series of novel naphthalene-based low dielectric materials were prepared for one-step UV curing. The double bond conversion rate of resins exceeds 90 % in a short time and the resins perform exceptional dielectric properties (Dk < 2.8, Df < 0.009, 110 MHz), high thermal stability (T5% > 270 °C), and hydrophobicity (water contact angle > 95°). Notably, 1,6-naphthalene dimethacrylate/Trihydroxymethylbutyl trimethylacrylate (1,6-NEA/TMPTA) suggests lowest dielectric performance (Dk = 2.19, Df = 0.005) with significant thermal stability (Tg = 190 °C, T5% = 367.4 °C) because the π-π conjugation of the asymmetric structure of 1,6-NEA, which allows for a greater variety of stacking patterns and increases the effective collisions between the reactive sites of the photosensitive monomer and the reactive diluent. This work has revealed the structure-activity relationship between the substituents on naphthalene derivatives and their photochemical properties, providing a novel methodology for the development of low dielectric electronic packaging materials through additive manufacturing techniques.

Cenozoic deformation of the Weihe Graben in central China: Insights from Analogue modeling

The Weihe Graben is located in the composite area of the Tethys-Himalayan tectonic and circum-pacific tectonic domains and is an essential structural feature related to Cenozoic intracontinental deformation. However, two different hypotheses, sinistral strike-slip, and extensional mechanism, are proposed for the origin of this graben. In this study, we designed crust-scale analog models based on fault kinematics to better understand the deformation and dynamic mechanisms of the Weihe Graben. Fault kinematics shows early sinistral strike-slip and NW-SE extensional deformation and late NE-SW, S-N, and NW-SE extensional deformation. Our experimental results reveal that Model C1 (sinistral strike-slip + NW-SE extension) is the most similar to the geological structure of the Weihe Graben in the Paleogene. Furthermore, the NE-SW extension results in two larger subsidence areas in the northeast and southwest of the basin, similar to the formation of the two depressions during the Miocene. The S-N extension causes the basin to expand southward and northward, consistent with the sedimentary characteristics of Weihe Graben in the Pliocene. The NW-SE extension leads to relatively strong fault activity in the northwest and southeast of the basin, resembling the active fault characteristics since the Quaternary. Therefore, we propose that the Weihe Graben formed by a strike-slip and extensional combined mechanism in the Eocene-Oligocene, influenced by the far-field effects of the Indian-Asian collision and crust-mantle processes triggered by the stagnant paleo-Pacific plate. Subsequently, during the Neogene-Quaternary, the graben’s development shifted towards an extensional regime under the influence of the eastward extrusion of the Tibetan Plateau.