Search Results (22)

The introduction of polymers has significantly altered the properties of sand particles in shale oil production fluids, leading to a more complex sedimentation mechanism. However, the specific ways in which polymers influence sand sedimentation dynamics remain poorly understood. In this study, Soxhlet extraction and supercritical water oxidation techniques were employed to compare the particle size distribution of polymer-containing sand with that of actual sand. The results show that sand sedimentation in polymer-containing shale oil production fluids involves two mechanisms: gravity-dominated single-particle sedimentation and polymer-induced multi-particle flocculation–sedimentation. Additionally, polymers induce both flocculation–sedimentation and hindering effects. Specifically, the water content and temperature can promote single-particle sedimentation and flocculation–sedimentation of the sand particle group by adjusting the rheology, polymer content, and stability of the production fluid. In this experimental study, the sedimentation rates of the two processes were increased by 38.05% and 54.76%, respectively. Based on these findings, the sedimentation characteristics of sand particles in production fluids under the influence of polymers were obtained, offering valuable insights for the management and control of sand in polymer-containing shale oil production fluids. Full article

Analysis of the (i) charge balance function and (ii) fluctuations of the net electric charge of hadrons in $Pb$+$Pb$ collisions at center-of-mass energy 2.76 TeV per nucleon pair was performed within a two-component hydjet++ model. It is shown that neither the widths of the balance function nor the strongly intensive quantities, D and Σ, used to describe the net-charge fluctuations, can be reproduced within the model based on a grand canonical ensemble approach for generating multiparticle production. To solve this problem, it is necessary to take into account exact charge conservation in an event-by-event basis. The corresponding procedure was developed and implemented in the modified hydjet++ model. It provides a fair description of the experimental data. Full article

Enzyme-powered nanomotors have attracted significant attention in materials science and biomedicine for their biocompatibility, versatility, and the use of biofuels in biological environments. Here, we employ a hybrid mesoscale method combining molecular dynamics and multi-particle collision dynamics (MD–MPC) to study the dynamics of nanomotors powered by enzyme reactions. Two cascade enzymes are constructed to be layered on the same surface of a Janus colloid, providing a confined space that greatly enhances reaction efficiency. Simulations indicate that such a configuration significantly improves the utilization of intermediate products and, consequently, increases the self-propulsion of the Janus motor. By presenting the gradient fields of substrates and products, as well as the hydrodynamics surrounding the motor, we explore the underlying mechanism behind the enhanced autonomous velocity. Additionally, we discuss the improvements in environmental safety of the modified motor, which may shed light on the fabrication of biocatalytic nano-machines in experiments. Full article

The multiplicity distributions of charged particles and their combinants for pp collisions at LHC energies are studied within the Multipomeron Exchange Model (MEM) that takes into account the phenomenon of string fusion. It is shown that the use of Gaussian-type distributions for multiplicity distributions at a fixed number of pomerons allows, within the MEM framework, the reproduction of the resulting multiplicity distributions and the oscillatory behavior of combinants, found in the ALICE and CMS pp collision data at LHC energies. It is important that in the proposed approach, the parameters of these Gaussian-type distributions are not considered free, but are calculated from the two-particle correlation function of a single string. Full article

A new method for studying two-particle transverse momentum ($P_T$) correlations in soft hadronic interactions is proposed. It is shown that Monte Carlo models: PYTHIA 6 and Geant4 FTF (FRITIOF), give different predictions for the correlations in proton–proton interactions. The correlations are connected with Schwinger’s mechanism of particle creation. These correlations can be studied in current and future experiments in high energy physics, in particular, at the Nuclotron-based Ion Collider fAcility (NICA). Full article

In this paper, using the concept of multi-pomeron exchange, we develope a Monte Carlo model of interacting quark–gluon strings acting as particle-emitting sources aimed at describing inelastic proton–proton interactions at high energies. The implemented 3D (three-dimensional) dynamics of colour string formation resulted in their finite length in the rapidity space and in the fluctuating event-by-event spatial density. Thus, this results in string cluster formation because of the fusion mechanism and the appearance of long-range multiplicity and mean transverse momentum (mean-$p_T$) correlations in rapidity. We study, via the pseudorapidity dependence, the sensitivity to the details of the 3D dynamical formation of strings for several observables such as the forward–backward correlation coefficient value, strongly intensive quantity, $\mathrm{\Sigma }$, and the “almost” strongly intensive observable, the variance, ${\sigma }_C^2$, of the distribution of the asymmetry coefficient, C. The strongly intensive quantity $\mathrm{\Sigma }$ is used in this study to suppress trivial statistical fluctuations in the number of particles emitting similar types of sources and to reveal the intrinsic fluctuations of a single source. We demonstrate the connection between $\mathrm{\Sigma }$ and such often used observables as cumulants, factorial cumulants, and ${\sigma }_C^2$. We stress the importance of the contribution of “short” strings and the event asymmetry of the initial conditions on the long-range correlation measures. We argue that string cluster formation because of the fusion mechanism explains the collective effects seen in multiplicity and transverse momentum–multiplicity, $⟨p_T⟩$–N, long-range correlation functions. Full article

Non-additive (or non-extensive) entropies have long been intensively studied and used in various fields of scientific research. This was due to the desire to describe the commonly observed quasi-power rather than the exponential nature of various distributions of the variables of interest when considered in the full available space of their variability. In this work we will concentrate on the example of high energy multiparticle production processes and will limit ourselves to only one form of non-extensive entropy, namely the Tsallis entropy. We will discuss some points not yet fully clarified and present some non-obvious consequences of non-extensiveness of entropy when applied to production processes. Full article

We celebrate the legacies of our friend and mentor Professor Lianshou Liu who was one of the pioneers for the phenomenology of multi-particle interactions and initiated the physics of relativistic heavy-ion collisions in China. In this article, we discuss some of the recent exciting experimental observations on the collective phenomena including collectivity, chirality, criticality, strangeness production, and thermal equilibrium in high-energy nuclear collisions. Future directions, especially the physics at high baryon density, will be discussed with a focus on the first-order phase boundary and hyperon–nucleon interactions. Full article

Within the framework of the model with quark-gluon strings (color flux tubes) as sources, the properties of the strongly intense variable $\Sigma$, which characterizes the correlations between the number of particles in two observation windows separated in rapidity, are studied. It is shown that, in pp collisions at LHC energies, string fusion effects leading to the formation of string clusters have a significant effect on the behavior of this observable. The experimentally observed changes in this variable with the initial energy and centrality of the pp collision can only be explained by taking into account the formation of string clusters consisting of an increasing number of merged strings. It is demonstrated that the study of the behavior of the $\Sigma$ observable as a function of the rapidity distance between the centers of the observation windows and the width of these windows with variable experimental conditions using different energies and centralities of pp-collisions makes it possible to extract the parameters of string clusters from the experimental data. Full article

In this paper, the nuclear modification factors, $R_{xA}$, are investigated for pion production in small system collisions, measured by PHENIX experiment at RHIC (Relativistic Heavy Ion Collider). The theoretical framework is the parton transverse momentum $k_T$-factorization formalism for hard processes at small momentum fraction, x. Evidence for collective expansion and thermal effects for pions, produced at equilibrium, is studied based on phenomenological parametrization of blast-wave type in the relaxation time approximation. The dependencies on the centrality and on the projectile species are discussed in terms of the behavior of Cronin peak and the suppression of $R_{xA}$ at large transverse momentum, $p_T$. The multiplicity of produced particles, which is sensitive to the soft sector of the spectra, is also included in the present analysis. Full article

The present paper reports on the methods of the systematic analysis of the high-energy collision distributions—in particular, those adopted by Jean Cleymans. The analysis of data on high-energy collisions, using non-extensive statistics, represents an important part of Jean Cleymans scientific activity in the last decade. The methods of analysis, developed and employed by Cleymans, are discussed and compared with other similar methods. As an example, analyses of a set of the data of proton-proton collisions at the center-of-mass energies, $\sqrt{s}=0.9$ and 7 TeV, are provided applying different methods and the results obtained are discussed. This line of research has the potential to enlarge our understanding of strongly interacting systems and to be continued in the future. Full article

The Unruh effect can be considered a source of particle production. The idea has been widely employed in order to explain multiparticle production in hadronic and heavy-ion collisions at ultrarelativistic energies. The attractive feature of the application of the Unruh effect as a possible mechanism of the multiparticle production is the thermalized spectra of newly produced particles. In the present paper, the total entropy generated by the Unruh effect is calculated within the framework of information theory. In contrast to previous studies, here the calculations are conducted for the finite time of existence of the non-inertial reference frame. In this case, only a finite number of particles are produced. The dependence on the mass of the emitted particles is taken into account. Analytic expression for the entropy of radiated boson and fermion spectra is derived. We study also its asymptotics corresponding to low- and high-acceleration limiting cases. The obtained results can be further generalized to other intrinsic degrees of freedom of the emitted particles, such as spin and electric charge. Full article

Selective laser sintering (SLS) is one of the most commonly used methods in additive manufacturing, due to its high prototyping speed and applicability to various materials. In the present work, molecular dynamics (MD) simulations were performed to study the thermodynamic behaviors of the planar stacked nanoparticles (NPs) model and explore the potential capability of the SLS process with nano-sized metal powders in the zero-gravity space environment. A multi-particle model of titanium–aluminum (Ti–Al) core–shell NP with a particle radius of 50 Å was constructed to investigate the characteristics of the melted pattern during sintering. Two patterns with different spatial densities were considered to study the influence of particle stacking on the melting process. Various core volume fractions and heating rates were examined to investigate their effects on the quality of the final sintered product. The stacked-NPs models with core volume fractions (CVFs) of 3%, 12%, and 30% were linearly heated up to 1100 K from room temperature (298 K) with heating rates of 0.04, 0.2, 0.5, and 1.0 K ps⁻¹. The initial fusion temperature and final sintering temperature for each stacking pattern were obtained via the validation from the radial distribution function, mean squared displacement, and the radius of the gyration analysis. The 30% CVF yields the largest neck size before the melting point, while beyond the melting point, a larger core helps delay the formation of the fully-melted products. It is observed that using the close-packed stacked-NPs model under a slow heating rate (long melting duration) would help form a stable, completely sintered product with a relatively low final sintering temperature. Full article

We propose the generalized multipomeron exchange model for multiparticle production in high-energy proton–proton, proton–nucleus and heavy-ion collisions. For all of these systems, we consider collectivity effects based on the quark–gluon string fusion concept, where new types of particle-emitting sources—strings with higher tension—are produced. We obtained the model parameters using the data on the multiplicity dependence of the mean transverse momentum of charged particles in $pp$ and $p\overline{p}$ collisions over a wide energy range (from ISR to LHC). We calculated the yields of strange, multi-strange and charm particles as a function of multiplicity for $pp$, p-$Pb$ and $Pb$-$Pb$ collisions at the LHC energy and compared the results with the experimental data. Full article

We construct a simple toy model and explicitly demonstrate that the balance function (BF) can become negative for some values of the rapidity separation and hence cannot have any probabilistic interpretation. In particular, the BF cannot be interpreted as the probability density for the balancing charges to occur separated by the given rapidity interval. Full article