High Collisions Research Articles

Anisotropic turbulence in relativistic plasmas

Signs of turbulence have been observed at the relativistic heavy ion collision at high collision energies. We study the signatures of turbulence in this system and find that there are significant departures from isotropic turbulence in the initial and the pre-equilibrium stages of the collision. As the anisotropic fluctuations are subleading to the isotropic fluctuations, the Kolmogorov spectrum can usually be obtained even for the initial stages. However, the energy spectrum and the temperature fluctuations indicate deviations from isotropic turbulence. Since a strong momentum anisotropy exists between the transverse and the longitudinal plane, we study the energy density spectrum in these two planes by slicing the sphere into different planes. The geometrical anisotropy is reflected in the anisotropic turbulence generated in the rotating plasma and we find that the scaling exponent is different in the two planes. We also obtain the temperature spectrum in the pre-equilibrium stages. The spectrum deviates from the Gaussian spectra expected for an isotropic turbulence. All these seem to indicate that the large scale momentum anisotropy persists in the smaller length scales for the relativistic heavy ion collisions.

Assessing potential conflicts between offshore wind farms and migration patterns of a threatened shorebird species

AbstractInstallation of offshore wind farms (OWFs) is becoming increasingly important to ensure a reduction in greenhouse gas emissions; however, OWFs also pose a threat to migrating birds and other wildlife. Informed marine spatial planning is therefore crucial, but individual‐based high‐resolution data on bird migration across the sea are currently lacking. We equipped 51 individuals of the near threatened Eurasian curlew Numenius arquata with GPS tags (118 flight tracks) across multiple years and countries to assess their four‐dimensional migration routes across the Baltic Sea (i.e. flight tracks, altitudes, phenology and diurnal patterns), to inform collision‐risk models and assess potential conflicts with current and future OWFs. Despite a broad‐front migration, we identified core migration areas in the south‐western Baltic Sea (and adjacent mainland), largely overlapping with already operating OWFs. Generalized linear models based on a resampling procedure to overcome autocorrelation of tracking data showed that flight altitudes across the sea and during autumn (median: 60 m) were significantly lower than those across land (median: 335 m) and during spring (median across sea: 150; median across land: 576 m). Across the sea, curlews spent 74.8% and 62.2% of their migration times below 300 m during autumn and spring, respectively, indicating a potentially high collision risk with OWFs. The mean flight speed was 56.3 km/h (±20.3 km/h). Migration intensity was highest at night over a 10‐day period during April, suggesting that restricted turbine operation for several days might be a possible management measure. Our study showed that, even for broad‐front migrants, it is possible to identify particularly sensitive sea areas deserving special protection enabling a sound marine spatial planning. This is a crucial finding also for various other shorebirds on the East Atlantic Flyway. Further studies are needed to assess the behavioural reactions of migrating birds with respect to OWFs using high‐resolution tracking data.

D-meson production in high energy pA collisions within the QCD color dipole transverse momentum representation

The D-meson production is investigated by considering the unintegrated gluon distribution within the dipole approach in the momentum representation. We analyze the D-meson spectrum accounting for the effects of nonlinear behavior of the QCD dynamics which can be accordingly addressed in the dipole framework. The unintegrated gluon distribution is obtained by using geometric scaling property and the results are compared to the Glauber–Gribov framework. The absolute transverse momentum spectra and the nuclear modification ratios are investigated. Predictions are compared with the experimental measurements by the ALICE and LHCb Collaborations in pA collisions for different rapidity bins.

Collisional interaction process between a bubble and particles with different hydrophobicity

The collisional interaction process between bubbles and particles is considered to play an important role in flotation. This paper aims to investigate the effect of particle hydrophobicity on the bubble-particle collision and subsequent interaction process. Four types of bubble-particle interaction behaviors were observed, namely the non-collision, the collision but without attachment, the attachment with jump-in after collision, and the attachment without jump-in after collision. The ‘jump-in’ event was interpreted as the rupture of the water film, providing the formation and growth of a ‘three-phase contact line’ (TPCL). The mildly hydrophobic particle could attach to the bubble surface without the rupture of the water film, whereas the highly hydrophobic particle had the higher collision and attachment probability. The significant effect of particle hydrophobicity was found in the observed particle trajectories and velocities. The distance between the bubble and the particle of weakly hydrophobicity and mildly hydrophobicity remained almost constant in the particle sliding process on the bubble surface. However, the highly hydrophobic particle was observed to jump in instantaneously after a short interaction time. Influenced by hydrodynamic drag, the maximum sliding velocity of any particles near the bubble’s equatorial plane was higher than the particle terminal velocity, and highly hydrophobic particle had a higher difference. The analysis of the individual force components of particle provides valuable insights into the kinematic properties of particle as it slides. The hydrodynamic drag coefficient decreased with an increase in the particle contact angle, implying the highly hydrophobic particle had a smaller hydrodynamic drag. Additionally, the reaction force was introduced for the first time to satisfy the radial force balance relationship, and explanations were proposed in terms of its source.

Triple high energy nuclear and hadron collisions - a new method to study QCD phase diagram at high baryonic densities

We propose an entirely new method to study the phase diagram of strongly interacting matter by means of scattering the two colliding beams at the fixed target. Here we present the results of simulations of the most central triple nuclear collisions with the UrQMD 3.4 model for the beam center-of-mass collision energies sqrt{s_{NN}} = 2.76 hbox {TeV} and sqrt{s_{NN}} = 200 hbox {GeV}. The main outcome of our modeling is that even at these very high collision energies the initial baryonic charge densities are about 3 times higher than the ones achieved in the ordinary binary nuclear collisions. As a result, for instance, the yields of protons and varLambda -hyperons are strongly enhanced in the triple nuclear collisions. The other prospective applications of this method are briefly discussed. Among them we consider the low energy collisions of three nuclei of lead, passing through an intermediate system with an electric charge of 246 units which exceeds essentially the critical value of 173 and, hence, this may be of crucial importance to study the spontaneous emission of positron-electron pairs from the vacuum. We present the convincing arguments that the triple nuclear collisions method will allow the high energy nuclear physics community to create a new frontier in the studies of the QCD phase diagram and to lift up these studies to an entirely new level.

Towards 20 T Hybrid Accelerator Dipole Magnets

The most effective way to achieve very high collision energies in a circular particle accelerator is to maximize the field strength of the main bending dipoles. In dipole magnets using Nb-Ti superconductor the practical field limit is considered to be 8-9 T. When Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn superconductor material is utilized, a field level of 15-16 T can be achieved. To further push the magnetic field beyond the Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn limits, High Temperature Superconductors (HTS) need to be considered in the magnet design. The most promising HTS materials for particle accelerator magnets are Bi2212 and REBCO. However, their outstanding performance comes with a significantly higher cost. Therefore, an economically viable option towards 20 T dipole magnets could consist in an “hybrid” solution, where both HTS and Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn materials are used. We discuss in this paper preliminary conceptual designs of various 20 T hybrid magnet concepts. After the definition of the overall design criteria, the coil dimensions and parameters are investigated with finite element models based on simple sector coils. Preliminary 2D cross-section computation results are then presented and three main layouts compared: cos-theta, block, and common-coil. Both traditional designs and more advanced stress-management options are considered.

Application of Different Data Analytics for Evaluation of Heavy Vehicle Vulnerability in Cold-Region Rural Highways

Understanding the impacts of different driving conditions on truck speed is critical to the development and maintenance of resilient highway freight transportation systems. This study attempts to evaluate the combined impact of road weather, travel lane, vehicle type, and truck payload conditions on drivers’ speed choice by modelling speed distributions as normal distributions. Two data analytics, a regression-based approach (RBA) and a central limit theorem (CLT)-based approach (CBA), are adapted to model context-specific speed distributions. The regression-based approach models population-level speed distributions by considering samples of individual speed data, whereas the CBA uses sampling distributions produced according to the CLT. A holistic approach is proposed to identify overall vehicle-specific collision risks imposed by different road-weather conditions, based on the speed distribution parameters estimated. Implications of the study results pertaining to the trucking industry are threefold. First, adapting different data analytics leads to different study results; yet, the CBA is recommended to model speed distributions. Second, truck speeds are significantly affected by the presence of adverse road-weather conditions, yet marginally varied under different loading conditions. Third, overall, tractor–trailer combinations (TTCs) entail high collision risks, particularly when transporting a freight load under adverse road-weather conditions. The study results would be useful to policymakers, particularly for effective speed management in extremely cold regions. Trucking companies may use the study results to identify the least risk-posing road-weather conditions to deploy safe freight transport operations. The resulting speed distribution models are also useful as input to calibrate traffic micro-simulation models.

Atom deposition and sputtering at normal incidence simulated by the Frenkel-Kontorova chain.

The impact of a molecule of N atoms with a speed of v_{0} on the free end of the Frenkel-Kontorova chain is numerically simulated. Depending on the values of N and v_{0}, different scenarios of the molecule-chain interaction are observed. Molecules with low speed stick to the chain. At somewhat higher speeds, the molecules bounce off the chain. Further increase in v_{0} results in bouncing off a molecule larger than the incident one. At even higher speed, bouncing of the molecule off the chain takes place simultaneously with the formation of a supersonic crowdion (antikink) propagating along the chain. A very high collision velocity leads to the sputtering of atoms from the chain and the formation of single and multiple supersonic crowdions. Interestingly, the sputtering yield Y as the function of v_{0} demonstrates a nonmonotonous dependence. This is explained by the fact that supersonic crowdions can have a discrete set of propagation velocities. When v_{0} is such that supersonic crowdions are effectively excited, the latter transfer energy deep into the chain, and the sputtering is minimal. For some v_{0} ranges, the formation of supersonic crowdions is suppressed. In these cases, the energy transferred from the impact of the molecule to the chain is spent mainly on the sputtering of atoms. The results obtained qualitatively explain the physics of bombardment of a crystal surface by atomic clusters with applications in physical vapor deposition, ion implantation, ion-beam sputtering, and similar experimental techniques.

A modified probabilistic roadmap algorithm for efficient mobile robot path planning

Aiming to address the shortcomings of conventional algorithms in mobile robot path planning, such as long paths, random sampling and high collision risk, a novel probabilistic roadmap algorithm, or node reduction-based search algorithm, is proposed. A decision-making strategy is developed to identify the suitable node, which depends on the distance error to the nearby obstacles and goal and the Gaussian cost function, which improves path efficiency by eliminating unwanted nodes. Then, an optimal path is selected based on the weight of the edges. The comparative analysis is conducted in five different test cases with differing complexity. Different performance parameters are measured to validate the effectiveness of the proposed algorithm. The outcomes acquired from the different test cases indicate that the proposed algorithm outperforms the state-of-the-art algorithms, with a maximum improvement of 13.51% in path length, 66.82% in execution time, 28.5% in smoothness and 38.05% in collision risk value.

Augmentation of MS/MS Libraries with Spectral Interpolation for Improved Identification.

Tandem mass spectrometry (MS/MS) is a primary tool for the identification of small molecules and metabolites where resultant spectra are most commonly identified by matching them with spectra in MS/MS reference libraries. The high degree of variability in MS/MS spectrum acquisition techniques and parameters creates a significant challenge for building standardized reference libraries. Here we present a method to improve the usefulness of existing MS/MS libraries by augmenting available experimental spectra data sets with statistically interpolated spectra at unreported collision energies. We find that highly accurate spectral approximations can be interpolated from as few as three experimental spectra and that the interpolated spectra will be consistent with true spectra gathered from the same instrument as the experimental spectra. Supplementing existing spectral databases with interpolated spectra yields consistent improvements to identification accuracy on a range of instruments and precursor types. Applying this method yields significant improvements (∼10% more spectra correctly identified) on large data sets (2000–10 000 spectra), indicating this is a quick yet adept tool for improving spectral matching in situations where available reference libraries are not yet sufficient. We also find improvements of matching spectra across instrument types (between an Agilent Q-TOF and an Orbitrap Elite), at high collision energies (50–90 eV), and with smaller data sets available through MassBank.

Evaporation of microwave-shielded polar molecules to quantum degeneracy

Ultracold polar molecules offer strong electric dipole moments and rich internal structure, which makes them ideal building blocks to explore exotic quantum matter1–9, implement quantum information schemes10–12 and test the fundamental symmetries of nature13. Realizing their full potential requires cooling interacting molecular gases deeply into the quantum-degenerate regime. However, the intrinsically unstable collisions between molecules at short range have so far prevented direct cooling through elastic collisions to quantum degeneracy in three dimensions. Here we demonstrate evaporative cooling of a three-dimensional gas of fermionic sodium–potassium molecules to well below the Fermi temperature using microwave shielding. The molecules are protected from reaching short range with a repulsive barrier engineered by coupling rotational states with a blue-detuned circularly polarized microwave. The microwave dressing induces strong tunable dipolar interactions between the molecules, leading to high elastic collision rates that can exceed the inelastic ones by at least a factor of 460. This large elastic-to-inelastic collision ratio allows us to cool the molecular gas to 21 nanokelvin, corresponding to 0.36 times the Fermi temperature. Such cold and dense samples of polar molecules open the path to the exploration of many-body phenomena with strong dipolar interactions.

Effect of the dried limes (Citrus aurantifolia) on the caffeine kinetic extraction in black tea leaves (kinetic and thermodynamic study)

ABSTRACT. The kinetic and thermodynamic parameters were studied for the extraction of caffeine in black tea leaves and tea leaves containing antioxidant dried limes (Citrus aurantifolia). Caffeine is widely used in human consumption and is present in any liquid suitable for drinking except water. However, the health and environmental demerits make it significant to reduce caffeine to much less concentration or decaffeination. Therefore, the effect of the dried antioxidant Citrus aurantifolia on caffeine concentration followed by pseudo-first-order reaction, kinetic parameters (pseudo-first-order rate constant (k), equilibrium absorbance (A∞)), and thermodynamic activation parameters, the activation energy (Ea), change in enthalpy of activation (ΔH#), the change in entropy of activation (ΔS#) and change in activation Gibbs free energy (ΔG#) was calculated at four different temperatures 30, 60, 80, and 100 °C. Using the spectroscopic method the activation energy of the caffeine concentration in free black tea leaves solution (Ea = 13.32 kJmol-1) was higher than the black tea leaves mixed with lime solution (Ea = 9.89 kJmol-1), the higher collision of molecules A-factor (1.96 min-1), and large correlation factor (R2 = 0.95). The thermodynamic activation parameters ΔH#, ΔS#, and ΔG# demonstrate less heat absorption, irreversible, and more spontaneous interaction of lime with caffeine.&#x0D; &#x0D; KEY WORDS: Caffeine, Tea leaves, Citrus aurantifolia, Thermodynamic parameters, Kinetic&#x0D; Bull. Chem. Soc. Ethiop. 2022, 36(3), 697-705. &#x0D; DOI: https://dx.doi.org/10.4314/bcse.v36i3.18

Gluon saturation in proton and its contribution to single inclusive soft gluon production in high energy proton-nucleus collisions

The leading order single inclusive soft gluon production in high energy proton-nucleus (pA) collisions has been studied by various approaches for more than two decades. The first correction due to the gluon saturation in proton was analytically attempted recently through a diagrammatic approach in which only partial results were obtained. An important feature of the first saturation correction is that it includes both initial state and final state interactions. In this paper, we present the complete result derived from the Color Glass Condensate framework. Our approach is to analytically solve the classical Yang-Mills equations in the dilute-dense regime and then use the Lehmann-Symanzik-Zimmermann (LSZ) reduction formula to obtain gluon production from classical gluon fields.

Recent results on Central Exclusive Production with the STAR detector

We present results on the Central Exclusive Production of charged particle pairs h^{+}h^{-}h+h− (h = \pi, K, ph=π,K,p), pp\to p^\prime+h^{+}h^{-}+p^\primepp→p′+h+h−+p′, obtained with the STAR experiment at RHIC in proton-proton collisions at a center-of-mass energy of \sqrt{s} = 200s=200~GeV. All final-state particles were reconstructed, including forward-scattered protons detected in the Roman Pot system. As a result, the Double Pomeron Exchange (DPE) events were selected and the non-exclusive backgrounds were efficiently rejected.Differential fiducial cross sections were measured as functions of observables related to the central hadronic final state and to the forward-scattered protons. The measured cross sections were compared to phenomenological model predictions based on the DPE.We also present preliminary results on the measurement of the same physics process at higher collision energy \sqrt{s} = 510s=510~GeV. The data demonstrate features similar to those observed at \sqrt{s} = 200s=200~GeV.

Measurement of splittings along a jet shower in $\sqrt{s} = 200$ GeV pp collisions at STAR

Jets are algorithmic proxies of hard scattered partons, i.e. quarks and gluons, in high energy particle collisions. The STAR collaboration presents the first measurements of substructure observables at the first, second and third splits in the jet clustering tree via the iterative SoftDrop procedure. For each of these splits, we measure the fully corrected groomed shared momentum fraction (z_gg) and groomed jet radius (R_gg). We discuss the evolution of jet substructure in both the angular and momentum scales which allows for a self-similarity test of the DGLAP splitting function. We compare the fully corrected data to Monte Carlo models, providing stringent constraints on model parameters related to the parton shower and non-perturbative effects such as hadronization.

Influence of beam waist radius on radiation characteristics of high energy electron and laser pulse collision

Influence of beam waist radius on radiation characteristics of high energy electron and laser pulse collision

DMLAR: Distributed Machine Learning-Based Anti-Collision Algorithm for RFID Readers in the Internet of Things

Radio Frequency Identification (RFID) is considered as one of the most widely used wireless identification technologies in the Internet of Things. Many application areas require a dense RFID network for efficient deployment and coverage, which causes interference between RFID tags and readers, and reduces the performance of the RFID system. Therefore, communication resource management is required to avoid such problems. In this paper, we propose an anti-collision protocol based on feed-forward Artificial Neural Network methodology for distributed learning between RFID readers to predict collisions and ensure efficient resource allocation (DMLAR) by considering the mobility of tags and readers. The evaluation of our anti-collision protocol is performed for different mobility scenarios in healthcare where the collected data are critical and must respect the terms of throughput, delay, overload, integrity and energy. The dataset created and distributed by the readers allows an efficient learning process and, therefore, a high collision detection to increase throughput and minimize data loss. In the application phase, the readers do not need to exchange control packets with each other to control the resource allocation, which avoids network overload and communication delay. Simulation results show the robustness and effectiveness of the anti-collision protocol by the number of readers and resources used. The model used allows a large number of readers to use the most suitable frequency and time resources for simultaneous and successful tag interrogation.

Advanced post‐impact safety and stability control for electric vehicles

In terms of the possible secondary or multiple events accidents (MEA) after an initial vehicle to vehicle (V2V) impact, this research proposes an active safety & stability controller for independent-driven electric vehicles towards recovering the vehicle to safety states after an impact. The controller aims to regulate the course angle and lateral deviation that enforce the vehicle back to its original driving path. The upper-level controller is derived based on sliding mode technique. And the low-level controller aims to solve a convex quadratic allocation problem, which inherently incorporates fault-tolerance property. The independent in-wheel-motor (IWM) fault is very likely to happen under a real V2V impact and it contributes much to the driving safety & stability. Two typical real-end-collision scenarios under low- and high longitudinal velocities are designed to verify the proposed controller performance. The low- and high velocities collisions aim to simulate the urban and highway accidents, respectively. Compared to other control methods, i.e. pure braking and static allocation, the RMSEs of safety (lateral deviation, course angle) and stability indexes (yaw rate, sideslip angle) under proposed controller reduce significantly both in urban and highway accidents. Moreover, the controller performs robust enough against the impact-induced IWM fault. It further supports the effectiveness at dealing with the safety and stability of the ego vehicle after an initial impact and prevent possible MEA.

Hadron production with collinearly-improved unintegrated gluon distributions in high energy proton-proton collisions * *Supported by the National Natural Science Foundation of China (12165004, 12061141008, 11975005), Guizhou Provincial Science and Technology Projects ([2019]5103, [2019]5653), the Education Department of Guizhou Province (KY[2021]131), the National Key Research and Development Program of China (2018YFE0104700, 2018YFE01014800)

The collinearly-improved Balitsky-Kovchegov (ciBK) equation evolved unintegrated gluon distribution (UGD) is used for the first time to study hadron production in high energy proton-proton collisions in order to improve the predictive power of the Color Glass Condensate effective theory. We show that the ciBK equation evolved UGD provides a relatively better description of LHC data on the transverse momentum and integrated multiplicity distributions of charged hadron and neutral pion production for several collision energies compared with the running coupling Balitsky-Kovchegov (rcBK) equation evolved UGD. This is because the ciBK evolved UGD has a sharper transverse momentum distribution than the rcBK UGD. The impact of running coupling prescriptions on hadron production is studied, and it is found that the parent dipole and smallest dipole running coupling prescriptions provide similar depictions of the data. Moreover, the scale dependence of the fragmentation function is investigated by taking three typical values of scale. We find that the differences resulting from the scale dependence of the fragmentation function can be fully absorbed into the normalization factor, which lumps higher order corrections.

Cervical spine characteristics differ in competitive combat athletes compared with active control participants

BackgroundInjury to the head and neck are common in combat sport athletes. Impairments of the cervical spine have been found in some athletes who participate in sports with high forces and collisions. There is a lack of research on the effects of combat sports on the cervical spine. ObjectiveThe primary study aim was to investigate differences in cervical spine characteristics between combat athletes and a similarly aged active control group. The secondary aim was to investigate the relationship between symptom-based outcome measures and characteristics of the cervical spine. DesignCross-sectional. Method40 male adult combat sport athletes and 40 male adult control participants were recruited from 4 combat sport clubs and a university campus, Australia. Cervical spine assessments were conducted at a private physiotherapy clinic. The Neck Disability Index and the Post-Concussion Symptom Scale were used as symptom-based outcome measures. ResultsCombat sport athletes had a reduced range of cervical motion, but greater isometric strength and endurance compared with a control group (p < 0.05). The Neck Disability Index and Post-Concussion Symptom Scale were negatively correlated with cervical spine range of motion and isometric strength, meaning that higher scores correlated with a reduction in function. ConclusionsDifferences were observed in characteristics of the cervical spine in combat sport athletes compared with a control group. Higher symptom-based outcome scores correlated with reduced range of motion and strength of cervical spine muscles. Further investigation to establish clinical cut-off scores for functional impairment may be warranted.