Low Collision Research Articles

Experimental Investigation on the Drift and Collision of Containers Induced by Tsunami Action on a Wave Absorbing Revetment

<i>This study examined the collision dynamics between tsunami-driven drifting containers and port cranes, prompted by risks from the recent 7.6 magnitude earthquake and tsunami off Noto Peninsula, Japan. Hydraulic experiments were conducted to analyze container drift and collision forces using motion analysis software (DIPP-Motion) and a load cell installed on a crane leg model. The key parameters included the tsunami wave height, container weight (empty and loaded), initial position, and revetment type. The results suggested that higher tsunami wave heights led to more extraordinary inundation, allowing containers to float more efficiently, reducing bottom friction, and increasing drift speed and collision forces. The collision speeds ranged from 1.59 to 2.48 m/s, with collision forces of 45.18 to 77.68 N, representing increases of 6.45 to 15.58 times than no object. Heavier containers required deeper water to float, resulting in lower drift and collision speeds (0.88–0.89 times that of lighter containers). The wave-absorbing revetment caused higher flow velocities, producing collision speeds and forces 1.32–1.48 times greater than the vertical revetment. These findings highlight the importance of considering the tsunami magnitude, container weight, initial position, and revetment type in design, with face-to-face contact conditions crucial for estimating the maximum collision forces and preventing future tsunami damage.</i>

Mixed quantum/classical theory for rotationally inelastic scattering of identical collision partners revised.

Mixed quantum/classical theory (MQCT) for the treatment of rotationally inelastic transitions during collisions of two identical molecules, described either as indistinguishable or distinguishable partners, is reviewed. The treatment of two molecules as indistinguishable includes symmetrization of rotational wavefunctions, introduces exchange parity, and leads to state-to-state transition matrix elements different from those in the straightforward treatment of molecules as distinguishable. Moreover, the treatment of collision partners as indistinguishable is eight times faster. Numerical results presented herein for H2 + H2, CO + CO and H2O + H2O systems indicate good agreement of MQCT calculations with full-quantum calculations from the literature and show that an a posteriori correction, applied after treatment of the collision partners as distinguishable, generally produces good results that agree well with the rigorous treatment of collision partners as indistinguishable. This correction for the cross section includes either multiplication by 2 or a summation over physically indistinguishable processes, depending on the transition type. After this correction, the results of the two treatments agree within 5% for most but may reach 10-20% for some transitions. At low collision energies dominated by scattering resonances, these differences can be larger, but they tend to decrease as collision energy is increased. It is also shown that if the system is artificially forced to follow the same collision path in the indistinguishable and distinguishable treatments, then all differences between the results of the two treatments disappear. This interesting finding gives new insight into the collision process and indicates that the indistinguishability of identical collision partners comes into play through the collision path itself, rather than through matrix elements of inelastic transitions.

State-resolved quantum dynamics and reaction mechanisms of the Ne + HD+(v = 1) reaction

In the work, accurate converged theoretical simulations of the Ne + HD + ( v = 1 ) reaction are presented with the time-dependent wave packet (TDWP) method using the accurate potential energy surface by Lv (J. Chem. Phys. 2010, 132, 014303). In particular, the effect of intramolecular substitution and the translational collision energy on the reactive dynamics is investigated in detail to discern the reaction mechanisms. Total and state-to-state integral cross sections (ICSs) and differential cross sections (DCSs) of the two channels are derived and compared over a wide range of collision energies up to 1.2 eV. The analysis of the ICSs in terms of the total angular momentum contributions shows that the contribution of the J partial wave varies in the two reactive channels at different collision energies. The product state-resolved DCSs reveal that two opposite mechanisms co-exist in the two reactive channels with different ratios at low and high collision energies. Overall, NeH + + D channel appears to form the products via collision complex formation, which survives long enough leading to a forward–backward symmetric total DCS at low collision energies. In comparison, the NeD + + H proceeds through a direct stripping reaction, with predominantly forward scattering in the DCSs.

Ortho-Para Conversion for H+ + H2 Collision in Low Temperature: A Fully Close-Coupled Time-Dependent Wave Packet Study.

The collision-induced rate coefficients of ortho-para conversion for the H+ + H2 reaction provide accurate information to probe the lifetime of cold environments in interstellar media. Rotationally resolved reaction probabilities are calculated at the low collision energy regime (0 < Ecol ≤ 0.3 eV) by employing the coupled three-dimensional (3D) time-dependent wave packet (TDWP) formalism in hyperspherical coordinates on a recently constructed ab initio ground adiabatic potential energy surface of H3+ [J. Chem. Phys. 2014, 141, 204306] for the process H+ + H2 (v = 0, j = 0-5) → H+ + H2 (v' = 0, j'). Cross-sections are then computed from the converged reaction probabilities as a function of total angular momentum (J) over the same energy regime and subsequently employed to obtain the rate constants for the ortho-to-para (O-P) and para-to-ortho (P-O) conversions and their ratio. The ratio of ortho-para conversion shows (a) appropriate convergence with the inclusion of a higher number of initial rotational states as well as a reasonable agreement with the results from a quantum statistical method and (b) a peak at lower temperature that could be due to the available collision energy for transitions involving lower rotational states (j = 0 → j' = 1).

Impact of attitude, behaviour and opinion of e-scooter and e-bike riders on collision risk in Singapore

Active Mobility Devices (AMDs) such as electric scooters (e-scooters) and electric bikes (e-bikes) are increasingly used on shared paths and Park Connector Networks (PCNs) in Singapore, leading to frequent interactions between AMD riders, pedestrians, and cyclists. To ensure safety, it is crucial to understand the factors associated with collision risk related to these AMDs. To gain insights into the riders’ perspectives on the risk-taking behaviours and attitudes towards safety and sharing paths, a survey was conducted with 369 e-bike and 133 e-scooter riders across Singapore. The collected data was analysed to identify critical features of behaviour, attitudes, and opinions of e-scooters/e-bikes riders and their impact on perceived collision risk. Logistic Regression was used to select the most important behavioural features linked to collision risk, and significance of each was quantified by using the odds ratios in the chosen model. The results reveal that e-bike riders who regularly brake hard to avoid obstacles and highly value capacity of e-bike to carry goods face an increase in collision risk by 49.1% and 43.48% respectively. Those preferring quieter AMDs face 33.31% lower collision risk. Additionally, e-bike riders advocating for more traffic enforcement or the importance of slowing down when overtaking pedestrians face 20.69% and 38.84% lower collision risk respectively. E-scooter riders who manoeuvre quickly to dodge collisions or prioritize passenger-carrying capacity encounter a 142.25% and 67.43% higher collision risk, respectively. Furthermore, e-scooter riders willing to bend rules when not causing inconvenience to others face an increase in collision risk by 123.00%. These outcomes offer significant insights for the design and regulation of active mobility to safeguard all road users in a multi-modal transport environment.

Hybrid vehicular access protocol and message prioritization for real-time safety messaging

Real-time safety services rely on the exchange of messages to enhance the operations of connected and automated vehicles (CAVs). These safety messages convey vital information about traffic conditions, enabling drivers to take necessary measures to prevent accidents. The timely and reliable delivery of these messages is essential, necessitating efficient channel access. Vehicular Deterministic Access (VDA) is employed as a channel access scheme with distinct priorities and stringent timing guidelines, particularly for urgent safety warnings. In this paper, we propose a hybrid approach that combines VDA and Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) protocols, along with a message prioritization algorithm, to ensure efficient and reliable communication of safety messages in vehicular networks. Our approach leverages the strengths of both VDA and CSMA/CA to avoid message collisions; VDA is more efficient under high traffic loads, while CSMA/CA is better suited for low traffic loads. Additionally, the incorporation of the message prioritization algorithm ensures strict deadline guarantees for high-priority messages, such as Decentralized Environmental Notification Messages (DENMs). We evaluate our proposed solution using the Artery simulation framework. Our results show over a 93% delivery rate for DENM exchanges while maintaining low collision probability across various traffic loads. This research provides practical guidance for the development of efficient and reliable communication systems for CAVs. It also offers a detailed analysis of the trade-offs among different access protocols and message prioritization strategies in vehicular networks.

Reliability analysis and uncertainty evaluation for assessing low velocity car impacted cosmetic damage of prototyped RC bridge pier

Crashworthiness of low velocity vehicles with reinforced concrete (RC) bridge pier has become widespread scenario that warrants a continuous threat on the structural viability. Even, low velocity small car collisions creates a short duration quasi-static to dynamic effect in different damage levels from low and cosmetic to collapse, depending on energy dissipation, not generally considered in design practices, making the piers susceptible to various level of damage. Bridge piers do not always collapse upon impact, and some are kept in service without pertinent health examinations that warrant serviceability. Unfortunately, little attention has been provided to keep the post impact low to medium distressed piers in service. Medium to higher damage need a complete replacement, whereas the low to cosmetic damage needs an additional meticulous investigation. This study is an attempt to assess cosmetic damage and residual capacities of RC pier via pendulum impacts to replicate low velocity car crash scenarios. To investigate post impact performance, experimental results are captured and transformed into realistic crash scenarios. Deterministic analysis via dynamic increase factor (DIF) approach to evaluate damage index (λ) and probabilistic method via resistance reduction method (RRM) to capture the uncertainties are performed in determining residual and reduced capacity of the representative pier. To identify damage incurred from collision and identify the probability of failure (Pf), a limit state (LS) equation has been developed comprising impact load and resistance and utilized as a model to estimate reliability index (β). Both the models used are able to precisely capture reduced capacities providing a good agreement between the shear and the axial capacity which control primary resistance of the impact loads and principal serviceability respectively. This study will provide an aid to forensic structural engineers.

Multiagent trajectory decision‐making for complex systems based on transformer large model structure

AbstractThe article explores the application of transformer‐based large models for trajectory decision‐making in complex decision systems, focusing on multiagent nodes in a topological structure. By leveraging the capabilities of large models, the proposed approach enhances decision‐making in model‐free control environments characterized by numerous agents, diverse internal tasks, and unknown conditions. The proposed framework integrates advanced transformer models with a sophisticated decision‐making framework to enhance the efficiency, safety, and reliability of multiagent operations in dynamic environments. The results demonstrate the superior performance of the transformer model, achieving a trajectory decision‐making accuracy of 97.8%, significantly outperforming other models such as long short‐term memory (LSTM), gate recurrent unit (GRU), and traditional approaches. The visualizations highlight the close alignment between the true and predicted outcomes of complex decision‐making systems, showcasing the model's ability to capture complex dependencies and interactions within the multiagent environment. High task completion rates and low collision rates further underscore the effectiveness of the decision‐making framework in optimizing agent coordination and ensuring safe operations.

Laser-assisted deuterium-tritium fusion: A quantum dynamical model

Deuterium-tritium (D-T) fusion is a key to generating safe, clean, and limitless energy on Earth in future fusion power plants. Its understanding at low collision energies is incomplete, as D-T fusion is a quantum tunneling process affected by resonances whose origin is linked to properties of not fully understood nuclear forces. Simplified quantum dynamical calculations of laser-assisted D-T fusion are presented, suggesting that laser-nucleus interaction can enhance the average D-T fusion probability by 7–70% at deep subbarrier energies using laser fields of intensity 1027–1029 Wcm−2 and a photon energy of 1 eV. Published by the American Physical Society 2024

Research on Obstacle Avoidance Strategy of Automated Heavy Vehicle Platoon in High-Speed Scenarios

Amidst the rapid progression of the road transport industry, the safety and efficiency of heavy-vehicle platoons have garnered significant attention. The study tackles the challenge of obstacle avoidance presented by vehicles owing to their considerable mass, delayed response times, and line-of-sight impediments, by introducing a cooperative obstacle avoidance system for heavy-vehicle platoons based on deep reinforcement learning. The system comprises three primary modules: perception, decision-making, and control. Initially, the perception module acquires real-time environmental data. Subsequently, the decision-making module formulates obstacle avoidance decisions based on the acquired data. Specifically, it implements a two-stage braking obstacle avoidance strategy under low collision risk scenarios, while employing a fifth-degree polynomial for planning and tracking obstacle avoidance paths under high collision risk conditions suitable for steering maneuvers. The control module utilizes the local multi-agent deep deterministic policy gradient (LADDPG) algorithm to train the heavy-vehicle platoon agents, ensuring the formation’s maintenance while mitigating collisions with other vehicles and obstacles. The effectiveness of the proposed system is substantiated through simulation experiments, demonstrating its adaptability to various traffic conditions, selection of suitable obstacle avoidance strategies, and significant enhancement of obstacle avoidance performance and heavy-vehicle platoon stability.

Metamorphic and chronological records of early Permian continental collision in Beni Bousera granulites (Internal Rif belt): implications for the tectonic evolution of northern Morocco during Pangea construction

This work presents petrological data obtained from shielded mineral inclusions within large garnets from the Beni Bousera metamorphic unit (internal Rif belt, northern Morocco) combined with in situ U‒Th‒Pb dating of monazite inclusions. In the considered Beni Bousera metapelites, the occurrence of mineral inclusions of kyanite + rutile + plagioclase + K-feldspar + quartz ± graphite trapped in garnet cores is diagnostic of high-pressure granulite-facies metamorphism. Geothermobarometry combined with thermodynamic modelling yields minimal P ‒ T conditions of approximately 1.37–1.5 GPa and 780–795°C, consistent with the development of palaeogradients during crustal thickening in collision belts. A concordant U/Pb age of 281 ± 3 Ma is obtained from associated monazite inclusions in the same garnet cores. These new petrochronological data attest to the early Permian continental collision in northern Morocco. The obtained dataset is constrained with petrological and geochronological parameters available on other neighbouring segments of the Variscan belt. Within the framework of recently unified full plate reconstruction models, the presented tectonic scenario suggests that all these orogenic segments were built during the late Carboniferous–early Permian crustal thickening at the northwestern Gondwana margin in response to the convergence of Laurentia and Gondwana during the late stages of Pangaea construction.

Decentralized human-like control strategy of mixed-flow multi-vehicle interactions at uncontrolled intersections: A game-theoretic approach

A critical challenge that future autonomous driving systems face is improving the ability to cope with complex real-world interaction scenarios such as uncontrolled intersections. In the near future, a mixed traffic flow of human-driven vehicles (HDVs) and connected autonomous vehicles (CAVs) will coexist in transport networks, which motivates us to explore the interaction between HDVs and CAVs to improve traffic efficiency and safety. To help CAVs better interact with HDVs and adapt to the mixed-flow environment, we propose a human-like decentralized control strategy for CAVs. First, a game-theoretic framework is proposed to model multi-vehicle interactions (including HDV-CAV, CAV-CAV interactions) in the mixed-flow environment. The existence of solutions is proven to ensure the feasibility of the proposed game-theoretic model. Next, a driving style recognition algorithm is embedded into the proposed model to help CAVs understand and predict human drivers’ actions. The proposed model is calibrated via a real-world dataset and used to simulate traffic in several testing scenarios. Real-world vehicle trajectories are used to verify the accuracy of generated vehicle trajectories in simulations. Experimental results indicate that 1) CAVs can take more reasonable actions to determine whether to yield while ensuring safety when competing for the right of way with HDVs using the proposed method compared with conservative driving strategies, 2) a higher penetration rate of CAVs can significantly enhance travel efficiency and lower collision risk at uncontrolled intersections.

Drivers’ situational awareness of surrounding vehicles during takeovers: Evidence from a driving simulator study

This study aimed to understand the influence of surrounding vehicle configuration, driving lane, and traffic density on drivers’ situational awareness (SA), takeover performance, and eye-tracking behaviors in conditionally automated driving. An experiment was conducted with the participation of 40 university students using a fixed-base driving simulator configured to simulate SAE Level 3 automation. During the experiment, participants were engaged in playing Tetris on a tablet as a non-driving related task in automated driving mode. Upon hearing an auditory takeover request, participants were instructed to take control of the vehicle, and then complete a scene reconstruction task to report their SA after transferring control back to the automated driving system. Our findings showed that drivers often neglected vehicles at their sides and rear during the takeover, which was associated with higher collision risks. Higher oncoming traffic density led to drivers’ worse SA of surrounding vehicles but more cautious driving behavior. Driving in the right lane generally resulted in smoother takeovers with lower collision risks. Interestingly, while SA did moderate the impacts of driving conditions on safety margins, a higher level of SA did not consistently relate to improved performance, especially in complex scenarios. This suggests the need for support systems that guide drivers to focus on safety–critical objects rather than simply amplifying SA in general. These insights have significant implications for the design of driver monitoring and support systems in automated vehicles.

The imprint of conservation laws on correlated particle production

The study of event-by-event fluctuations of net-baryon number in a subspace of full phase space is a promising direction for deciphering the structure of strongly interacting matter created in collisions of relativistic heavy nuclei. Such fluctuations are generally suppressed by exact baryon number conservation. Moreover, the suppression is stronger if baryon number is conserved locally. In this report we present a conceptually new approach to quantify correlations in rapidity space between baryon-antibaryon, baryon-baryon, and antibaryon-antibaryon pairs and demonstrate their impact on net-baryon number fluctuations. For the special case of Gaussian rapidity distributions, we use the Cholesky factorization of the covariance matrix, while the general case is introduced by exploiting the well-known Metropolis and Simulated Annealing methods. The approach is based on the use of the canonical ensemble of statistical mechanics for baryon number and can be applied to study correlations between baryons as well as strange and/or charm hadrons. It can also be applied to describe relativistic nuclear collisions leading to the production of multi-particle final states. One application of our method is the search for formation of proton clusters at low collision energies emerging as a harbinger of the anticipated first-order chiral phase transition. In a first step, the results obtained are compared to the recent measurements from the CERN ALICE collaboration. Such investigations are key to explore the phase diagram of strongly interacting matter and baryon production mechanisms at energy scales from several GeV to several TeV.

Traffic navigation via reinforcement learning with episodic-guided prioritized experience replay

Deep Reinforcement Learning (DRL) models play a fundamental role in autonomous driving applications; however, they typically suffer from sample inefficiency because they often require many interactions with the environment to learn effective policies. This makes the training process time-consuming. To address this shortcoming, Prioritized Experience Replay (PER) has proven to be effective by prioritizing samples with high Temporal-Difference (TD) error for learning. In this context, this study contributes to artificial intelligence by proposing a sample-efficient DRL algorithm called Episodic-Guided Prioritized Experience Replay (EPER). The core innovation of EPER lies in the utilization of an episodic memory, dedicated to storing successful training episodes. Within this memory, expected returns for each state–action pair are extracted. These returns, combined with TD error-based prioritization, form a novel objective function for deep Q-network training. To prevent excessive determinism, EPER introduces exploration into the learning process by incorporating a regularization term into the objective function that allows exploration of state-space regions with diverse Q-values. The proposed EPER algorithm is suitable to train a DRL agent for handling episodic tasks, and it can be integrated into off-policy DRL models. EPER is employed for traffic navigation through scenarios such as highway driving, merging, roundabout, and intersection to showcase its application in engineering. The attained results denote that, compared with the PER and an additional state-of-the-art training technique, EPER is superior in expediting the training of the agent and learning a more optimal policy that leads to lower collision rates within the constructed navigation scenarios.

Construction of diabatic potential energy surfaces for the SiH2+ system and dynamics studies of the Si+(2P1/2, 3/2) + H2 reaction.

The construction of diabatic potential energy surfaces (PESs) for the SiH2+ system, related to the ground (12A') and excited states (22A'), has been successfully achieved. This was accomplished by utilizing high-level abinitio energy points, employing a neural network fitting method in conjunction with a specifically designed function. The newly constructed diabatic PESs are carefully examined for dynamics calculations of the Si+(2P1/2, 3/2) + H2 reaction. Through time-dependent quantum wave packet calculations, the reaction probabilities, integral cross sections (ICSs), and differential cross sections (DCSs) of the Si+(2P1/2, 3/2) + H2 reaction were reported. The dynamics results indicate that the total ICS is in excellent agreement with experimental data within the collision energy range studied. The results also indicate that the SiH+ ion is hardly formed via the Si+(2P3/2) + H2 reaction. The results from the DCSs suggest that the "complex-forming" reaction mechanism predominates in the low collision energy region. Conversely, the forward abstraction reaction mechanism is dominant in the high collision energy region.

A Globally Accurate Neural Network Potential Energy Surface and Quantum Dynamics Studies on Be+(2S) + H2/D2 → BeH+/BeD+ + H/D Reactions.

Chemical reactions between Be+ ions and H2 molecules have significance in the fields of ultracold chemistry and astrophysics, but the corresponding dynamics studies on the ground-state reaction have not been reported because of the lack of a global potential energy surface (PES). Herein, a globally accurate ground-state BeH2+ PES is constructed using the neural network model based on 18,657 ab initio points calculated by the multi-reference configuration interaction method with the aug-cc-PVQZ basis set. On the newly constructed PES, the state-to-state quantum dynamics calculations of the Be+(2S) + H2(v0 = 0; j0 = 0) and Be+(2S) + D2(v0 = 0; j0 = 0) reactions are performed using the time-dependent wave packet method. The calculated results suggest that the two reactions are dominated by the complex-forming mechanism and the direct abstraction process at relatively low and high collision energies, respectively, and the isotope substitution has little effect on the reaction dynamics characteristics. The new PES can be used to further study the reaction dynamics of the BeH2+ system, such as the effects of rovibrational excitations and alignment of reactant molecules, and the present dynamics data could provide an important reference for further experimental studies at a finer level.

Impact of an enhanced sobriety checkpoints programme and publicity campaign on motor vehicle collisions, injuries and deaths in Leon, MX: a synthetic control study

ObjectiveDrunk driving is a major cause of road traffic injuries and deaths in Latin America. We evaluated the impact of a drunk driving intervention in Leon, Mexico on road traffic...

Full quantum calculations of the line shape for H2O perturbed by Ar at temperatures from 20 to 300 K.

This work theoretically studied the spectral line shape of H2O perturbed by Ar in the temperature range of 20-300K for the pure rotational lines below 360cm-1, as well as three lines (31, 2 ← 44, 1, 54, 2 ← 41, 3, and 73, 5 ← 60, 6) in the v2 band. In order to perform precise dynamical calculations at low collision energies, a full-dimensional long-range potential energy surface was constructed for the H2O-Ar system for the first time to correct the long range of our newly developed intermolecular potential energy surface. Subsequently, the six line-shape parameters (pressure-broadening and -shifting parameters, their speed dependencies, and the complex Dicke parameters) were determined from the generalized spectroscopic cross section by the full quantum time-independent close-coupling approach on this new potential energy surface. Our theoretical results are in good agreement with the available experimental observations. Furthermore, the influence of the speed-dependence and Dicke narrowing effects on the line contour was revealed by comparing the differences among the Hartmann-Tran, quadratic-speed-dependent Voigt, and Voigt profiles. The temperature dependence of each line-shape parameter was further parameterized using the triplet-power-law for three pure rotational 61, 6 ← 52, 3, 41, 4 ← 32, 1, and 31, 3 ← 22, 0 lines. These line-shape parameters will provide a comprehensive set of theoretical references for subsequent experimental measurements.

Controlling volume fluctuations for studies of critical phenomena in nuclear collisions

We generalize and extend the recently proposed method [1] to account for contributions of system size (or volume/participant) fluctuations to the experimentally measured moments of particle multiplicity distributions. We find that in the general case there are additional biases which are not directly accessible to experiment. These biases are, however, parametrically suppressed if the multiplicity of the particles of interest is small compared to the total charged-particle multiplicity, e.g., in the case of proton number fluctuations at top RHIC and LHC energies. They are also small if the multiplicity distribution of charged particles per wounded nucleon is close to the Poissonian limit, which is the case at low energy nuclear collisions, e.g., at GSI/SIS18. We further find that mixed events are not necessarily needed to extract the correction for volume fluctuations. We provide the formulas to correct pure and mixed cumulants of particle multiplicity distributions up to any order together with their associated biases.