Narrow Results

Faced with environmental and economic challenges, the transition to renewable energies is a priority, particularly in the maritime transport sector, which is subject to increasingly strict regulations. For ships, this adaptation remains complex due to space constraints and the rapid pace of technological advances, sometimes making certain solutions quickly obsolete and generating losses for shipowners. This work explores the use of rotating cylinders, based on the Magnus effect, as an auxiliary propulsion solution for ships. This effect occurs when air circulating around a rotating object creates a pressure difference, generating a force perpendicular to the airflow and the cylinder’s axis of rotation. Compared to other wind technologies, this method has promising potential to reduce emissions and improve energy efficiency. The results of this study highlight the economic and environmental benefits of rotating cylinders, positioning them as a clean and renewable energy for ship propulsion. These findings, consistent with previous work, highlight the rationale of this technology, already adopted by some modern commercial vessels, such as bulk carriers, oil tankers and cruise ships, which seek to optimize their energy efficiency. Thus, despite the challenges, the benefits related to fuel savings and reduced emissions make Flettner cylinders a promising solution for the future of maritime transport.

UHF flows are the flows obtained as inductive limits of flows on full matrix algebras. We will revisit universal UHF flows and give an explicit construction of such flows on a UHF algebra M_k^∞ for any k and also present a characterization of such flows. Those flows are UHF flows whose cocycle perturbations are almost conjugate to themselves.

Pore-scale simulations of fluid flow and mass transport offer a direct means to reproduce and verify laboratory measurements in porous media. We have compared lattice-Boltzmann (LB) flow simulations with the results of NMR spectroscopy from several published flow experiments. Although there is qualitative agreement, the differences highlight numerical and experimental issues, including the rate of spatial convergence, and the effect of signal attenuation near solid surfaces. For the range of Reynolds numbers relevant to groundwater investigations, the normalized distribution of fluid velocities in random sphere packings collapse onto a single curve, when scaled with the mean velocity. Random-walk particle simulations in the LB flow fields have also been performed to study the dispersion of an ideal tracer. These simulations show an encouraging degree of quantitative agreement with published NMR measurements of hydrodynamic and molecular dispersion, and the simulated dispersivities scale in accordance with published experimental and theoretical results for the Peclet number rangek 1 ≤Pe≤1500. Experience with the random-walk method indicates that the mean properties of conservative transport, such as the first and second moments of the particle displacement distribution, can be estimated with a number of particles comparable to the spatial discretization of the velocity field. However, the accurate approximation of local concentrations, at a resolution comparable to that of the velocity field, requires significantly more particles. This requirement presents a significant computational burden and hence a numerical challenge to the simulation of non-conservative transport processes.

Study of strange particles produced at (sub)threshold energies in nucleus-nucleus collisions can deliver insights into fundamental questions about the in-medium properties of hadrons in dense baryonic matter. Many theoretical calculations for the production and propagation of strangeness at SIS energies lead to various predictions concerning the existence and the magnitude of in-medium effects for strange particles in nuclear matter. FOPI measured the flow of strange particles in Ni + Ni collisions at 1.93A GeV and the results are compared with transport models which are favorable to in-medium effect.

By considering the 12-dimensional superalgebra, inferences are drawn about the finiteness of the 12-dimensional theory unifying the superstring models. The dimensional reduction of the nonsupersymmetric theory in four dimensions to a supersymmetric action in three dimensions is established for the bosonic sector. It is found to be the quotient by ${\mathbb{Z}}_2$ of the integration over the fiber coordinate of a theory with $N=1$ supersymmetry. Consequently, a flow on the moduli space of Spin(7) manifolds from a $G_2$ structure with $N=1$ supersymmetry yielding a phenomelogically realistic particle spectrum to a $G_2$ holonomy manifold compatible with supersymmetry in three dimensions and a nonsupersymmetric action in four dimensions, solving the quantum cosmological constant problem, is proven to exist. The projection of the representations of the $(10,2)$ superalgebra of the 12-dimensional theory to four dimensions include nonperturbative string solitons that are more stable because the dynamics is described by supersymmetric theory with a higher degree of finiteness.

Studies of $J/\psi$$v_2$ at RHIC and LHC energies have provided important elements toward the understanding on the production mechanisms and thermalization of charm quarks. Bottomonia has an advantage since it is a cleaner probe. A brief discussion has been provided for $\mathrm{{\rm Y}}(1S)$$v_2$, which can become the new probe for QGP, including the necessity of studies for small systems.

Friction stir welding (FSW) experiments were conducted, using a work hardened aluminium alloy and a cast aluminium alloy followed by examination focusing on the upper weld zone. The examination has revealed the feature of the major forward flow due to the forward motion of the shoulder. A thin shear layer was identified between the tool shoulder and the workpiece with a distinctive shear flow direction. The thickness of the shear layer was alloy dependent. An embedded layer in the upper weld zone has also been identified. The flow phenomena leading to this will be discussed. A velocity profile in the shear layer, based on the apparent alignment of Si particles in the cast alloy after FSW, has suggested a dominant sliding contact condition.

We characterize topologically ω-limit sets of nonrecurrent orbits for continuous flows on the n-sphere . Namely, it is shown that if Ω is the ω-limit set of some nonrecurrent orbit of a continuous flow on then it is the boundary of a region with connected complementary. Conversely, if Ω is the boundary of a region with connected complementary then there is a (C^∞) smooth flow on having Ω as the ω-limit set of one of its nonrecurrent orbits.

We consider an equivalence relation for a given free mapping f of the plane. Under the assumption that f is embeddable in a flow {f^t : t ∈ R} we describe the structure of equivalence classes of the relation. Finally, we prove that f restricted to each equivalence class is a Sperner homeomorphism.

In this paper we characterize topologically the empty interior subsets of a compact surface S which can be ω-limit sets of recurrent orbits (but not of nonrecurrent ones) of continuous flows on S. This culminates the classification of ω-limit sets for surface flows initiated in [Jiménez & Soler, 2001; Soler, 2003; Jiménez & Soler, 2004a, 2004b].

We also show that this type of ω-limit sets can always be realized (up to topological equivalence) by smooth flows but cannot be realized by analytic flows.

In this work, we show that the bailout embedding method is responsible for creating different dynamical behaviors and for destroying intrinsic features present in mixed phase spaces of the area-preserving Hamiltonian maps, where the sticking to regular (or resonant) islands degrades chaotic properties. In particular, the base map chosen for the study is the two-dimensional (2D) Web Map (WM). The four-dimensional (4D) embedded Web Map dynamics is governed by four-parameters: ($K,q$) in the WM control the nonlinearity and the type of symmetry structures (crystalline or quasi-crystalline) in phase space, respectively; ($\alpha ,\gamma$) in the embedding equations determine the mass density ratio and dissipation, respectively. For specific parameter combinations we explore the existence of transient chaos phenomenon, hyperchaotic dynamics and control the degradation of the underlying diffusive behaviors observed in phase space of the WM. If the WM is subjected to large enough dissipation through the embedding equations, stable periodic points (inside resonance islands) become sinks attracting almost all the surrounding orbits, destroying all invariant curves which divide the phase space into chaotic and regular domains. As area-preserving maps obtained from Hamiltonian flows usually share the crucial property that resonance islands can be found immersed in chaotic sea (characterizing the mixed phase space) for appropriated parameter combinations, the results obtained here for the 4D embedded WM should be considered generic for such whole class of nonlinear systems.

This paper investigates unbiased directed transport, known as the ratchet effect, within a system coupled to a fluid modeled by the bailout embedding technique. The system dynamics under the fluid influence are described by a four-dimensional mapping governed by parameters such as dissipation ($\gamma$), ratchet kicking (K), and the relationship between fluid and particle densities ($\alpha$). We explore the behavior of the Ratchet Current (RC) in the parameter spaces $K\times \gamma$ and $K\times \alpha$, particularly focusing on the aerosol case ($\alpha <1$). Our findings reveal a complex interplay of parameters, with larger RCs observed for parameter pairs that induce periodic dynamics in the ratchet system. Furthermore, we observe RC reversal as a function of $\gamma$ and $\alpha$, and identify coexisting attractors (multistability) at higher $\gamma$ values. These results shed light on the intriguing phenomenon of directed transport in fluid dynamics, offering insights that may contribute to understanding particle transport in nature, especially in the aerosol regime.

We introduce a condition that establishes a symmetry for diagrams associated with a class of dynamical systems (flows) which are induced by weighted points in the plane. This symmetry is known from weighted Delaunay- and power diagrams where it always holds. Under this condition the combinatorial and worst case algorithmic complexities of the flow diagrams are lower than in the general case. The condition is natural in the sense that it is automatically fulfilled for sets of unweighted points.

Collective phenomena in ion–ion collisions are well-known, but the research in small systems, like proton–proton and proton-lead, is starting both from the experimental and theoretical side. In this paper, we present a short review of the most important observables related to flow, as well as phenomenological results to explain the Relativistic Heavy Ion Collider and Large Hadron Collider results. Different variables and their relations to collectivity in small systems are discussed.

In high energy heavy-ion collisions, the final anisotropic flow coefficients and their corresponding event–plane correlations are considered as the medium evolutional response to the initial geometrical eccentricities and their corresponding participant–plane correlations. We formulate a systematic theoretical analysis to study the hydrodynamical responses concerning higher-order effects in $\mathrm{\text{Pb}}+\mathrm{\text{Pb}}$ collisions at $\sqrt{s_{\mathrm{\text{NN}}}}=2.76$TeV by using Monte Carlo (MC) Glauber model. To further understand the transformations of the initial participant–plane correlation, we construct a new set of events which randomize the directions of the initial participant–planes of the original events. Our results indicate that the final strong event–plane correlations are mainly transformed from the large initial eccentricities, rather than the strong participant–plane correlations. However, the large flow coefficients and the discrepancies between the flow coefficients calculated by the single-shot and event-by-event simulations in peripheral collisions are relevant to those strong initial participant–plane correlations.

Heavy flavor production is a sensitive probe of the initial gluon density in the nucleon and is modified by the entire evolution of the hot quark and gluon medium created in high-energy nucleus–nucleus collisions. Besides, it is a process that can be calculated by perturbative QCD because of their large mass. The PHENIX experiment at RHIC studied the heavy flavor productions for a broad momentum and rapidity ranges using single leptons from the semileptonic decay of charm and bottom hadrons, and dileptons from $J/\psi$ decays in $p+p$, $p+$A, and Au$+$Au collisions at $\sqrt{s_{NN}}$$=$200GeV. In these proceedings, the recent experimental results in $p+p$, Au$+$Au, and the small collision systems are presented and the heavy flavor productions and their modifications are discussed.

Baryonic Matter at Nuclotron (BM@N) is a fixed-target experiment designed to probe the properties of the strongly interacting matter in the region of high baryon densities. In the beginning of 2023, BM@N has conducted the first physical experiment collecting several hundred millions of $\mathrm{\text{Xe}}+\mathrm{\text{CsI}}$ collisions at the beam energy of 3.8AGeV ($\sqrt{s_{NN}}=3.28$GeV). We report the preliminary results for the directed flow $v_1$ of protons with respect to the spectator symmetry plane from the first physics run at the BM@N facility. The results were compared with the existing data from previous measurements of directed flow in heavy-ion collisions at the beam energies of several GeV.

In this work we are study the Fuzzy Initial Value Problem (FIVP) with parameters and/or initial conditions given by fuzzy sets. Starting from the flow equation of the deterministic Initial Value Problem (IVP) associates to FIVP, we obtain the FIVP flow, through the principle of Zadeh. Follow, we introduce the concept of fuzzy equilibrium stability of FIVP and some examples are given.

The phase opposition of velocity waveforms between coronary arteries (predominantly diastolic) and veins (systolic) is the most prominent characteristic of coronary hemodynamics. The phase opposition indicates the importance of intramyocardial capacitance vessels, as a determinant of phasic coronary arterial and venous flows. To investigate the functional characteristics of the intramyocardial capacitance vessels and its physiological significance, we analyzed the change in venous flow following changes in coronary arterial inflow. It was shown that during diastole the intramyocardial capacitance vessels have two functional components, unstressed volume and ordinary capacitance. Unstressed volume is defined as the volume of blood in a vessel at zero transmural pressure, and it was ~5% of the volume of the myocardium. The systolic coronary venous outflow showed a significant, positive correlation with the total displaceable blood volume stored in the intramyocardial unstressed volume and ordinary capacitance. When the unstressed volume was saturated, the coronary inflow was decreased significantly, compared with that for the unsaturated condition. Thus, the increase in intramyocardial blood volume decreases the coronary arterial inflow, whereas it enhances coronary venous outflow. The latter is an interesting analogy to the Starling's law of the heart.

Vortices in flow past a heart valve, in streams and behind an arrow were realized, sketched and discussed by Leonardo da Vinci. The forced resonance and collapse of the Tacoma Narrows Bridge under 64 km/h. wind in 1940 and the Kármán vortex street are classic examples of dynamic interaction between fluid flow and solid motion. There are similar and dissimilar characteristics of vortices between biological and physical flow processes. They can be analyzed by numerical solutions of the Navier–Stokes equations with moving boundaries. One approach is to transform the time-dependent domain to a fixed domain with the geometric, kinematic and dynamic parameters as forcing functions in the Navier–Stokes equations.