Phase Space Diagram Research Articles

Evaluation of SPARC divertor conditions in H-mode operation using SOLPS-ITER

Abstract The predicted divertor conditions for the SPARC tokamak are calculated using SOLPS-ITER for a range of scrape-off-layer (SOL) heat flux widths $\lamq$, input powers, and particle fuelling locations. Under H-mode scenario conditions with an upstream separatrix density of 1\e20 m$^{-3}$, the most conservative range of $\lamq$ extrapolations ($\approx$ 0.15 mm) results in extremely high unmitigated particle and energy fluxes to the divertor, both under full field (12.2 T) and power ($P_{SOL}$ = 29 MW) conditions, and 2/3 field with $P_{SOL}$ = 10 MW. Increasing the cross-field SOL diffusivities by 2-10x reduces the magnitude of the mitigation challenge, however strategies such as impurity seeding or strike-point-sweeping will likely still be required. 

A combination of steady-state and time-dependent SOLPS-ITER simulations are used to map out phase space diagrams of upstream and divertor conditions. At low upstream density the inner and outer divertor conditions are highly asymmetric, with a large temperature difference and significant heat fluxes driven by parallel currents. The solution has sharp bifurcations with a region of hysteresis, depending on whether the initial state is at a low or high density. This behavior is observed even when the fuelling location, cross-field diffusivity, and impurity level is changed, although the density window with asymmetry is reduced.

The addition of neon impurity seeding reduces the divertor heat fluxes, but also causes a drop in the upstream electron density with fixed particle throughput. This drop can be counteracted by increased main ion throughput, however too much neon results in a back transition into the asymmetric divertor regimes suggesting a need for control of both main ion and impurity seeding levels to achieve a desired divertor state.

Constraining [formula omitted] gravity by dynamical system analysis

In this paper, we have studied the different phases of the evolution of the Universe through the dynamical system analysis. Here we explored the f(T,B,TG,BG) gravity, where T, B, TG, and BG respectively represent torsion, boundary term, teleparallel Gauss–Bonnet term, and Gauss–Bonnet boundary term. The transformation f(T,B,TG,BG)=−T+F(T,B,TG,BG) has been incorporated to get the deviation from the Teleparallel Equivalent of General Relativity. Two well motivated cosmological models (i) F(T,B,TG,BG)=f0TmBnTGk and (ii) F(T,B,TG,BG)=b0B+g0TGk have been studied. The critical points representing different phases of evolution have been studied in details. Further with the help of the eigenvalues and phase space diagrams, the stability and attractor nature of the accelerating solutions have been explored. The evolution plots have been analysed for the corresponding cosmology. The compatibility of the evolution plots has been checked with standard density parameters at present time.

Constructing a Galaxy Cluster Catalog in IllustrisTNG300 Using the Mulguisin Algorithm

We present a new simulated galaxy cluster catalog based on the IllustrisTNG simulation. We use the Mulguisin (MGS) algorithm to identify galaxy overdensities. Our cluster identification differs from the previous friends-of-friends (FoF) cluster identification in two aspects: (1) we identify cluster halos based on the galaxy subhalos instead of unobservable dark matter particles, and (2) we use the MGS algorithm, which separates galaxy overdensities hosted by massive galaxies. Our approach provides a cluster catalog constructed in a way similar to the construction of observed cluster catalogs using spectroscopic surveys. The MGS cluster catalog lists 303 halos with M 200 > 1014 M ⊙, including ∼10% more than the FoF catalog. The MGS catalog includes more systems because we separate some independent massive MGS cluster halos that are bundled into a single FoF halo. These independent MGS halos are apparently distinguishable in the galaxy spatial distribution and the phase-space diagram. Because we construct a refined cluster catalog that identifies local galaxy overdensities, we evaluate the effect of MGS clusters on the evolution of galaxies better than when using the FoF cluster catalog. The MGS halo identification also enables effective identifications of merging clusters by selecting systems with neighboring galaxy overdensities. We thus highlight the fact that the MGS cluster catalog is a useful tool for studying clusters in cosmological simulations and for comparing with observed cluster samples.

Analysis of stability and bifurcation and design of optimal control for phytoplankton–zooplankton–fish model with additional food and fish harvesting

ABSTRACT This paper investigates the dynamics of a four-dimensional plankton-fish system that contains three communities of plankton: non-toxic phytoplankton, toxic-producing phytoplankton, and zooplankton. The zooplankton consumes both non-toxic and toxic-producing phytoplankton. First, the positivity and boundedness of the solutions in the plankton-fish model are evaluated. Then, we derive the conditions for the existence of ecologically possible equilibria and their local and global asymptotic nature. Furthermore, we evaluate the criteria for the existence of Hopf-bifurcation and transcritical bifurcation. By applying Pontryagin’s maximum principle, we investigate the optimal control of fish harvesting, where fishing effort is taken as a control parameter. By using phase-space diagrams, time responses, bifurcation diagrams, and numerical analyses validate the theoretical results. The numerical results including maximum Lyapunov exponent verify chaotic dynamics of the system. We notice that a suitable choice of harvesting, phytoplankton growth rate, and additional food parameters can control the chaotic behavior of the presented model. The proposed novel mathematical model gives deeper insights to theoretical ecologists on how toxic-producing phytoplankton affects zooplankton and fish populations in aquatic systems. Furthermore, the proposed model is more appropriate for fish harvesting to maximize profit as well as species conversion in the presence of toxic phytoplankton.

Teleparallel gravity and quintessence: The role of nonminimal boundary couplings

In this paper, we have outlined the development of an autonomous dynamical system within a general scalar-tensor gravity framework. This framework encompasses the overall structure of the non-minimally coupled scalar field functions for both the torsion scalar (T) and the boundary term (B). We have examined three well-motivated forms of potential functions and constrained the model parameters through dynamical system analysis. This analysis has played a crucial role in identifying cosmologically viable models. We have analysed the behaviour of dynamical parameters such as equation-of-state parameters, as well all the standard density parameters for radiation, matter, and dark energy to assess their compatibility with current observational data. The phase space diagrams are presented to support the stability conditions of the corresponding critical points. The Universe is apparent in its late-time cosmic acceleration phase via the dark energy-dominated critical points. Additionally, we compare our findings with the most prevailing ΛCDM model. The outcomes are further inspected using the cosmological data sets of Supernovae Ia and the Hubble rate H(z).

Exploration of microscopic physical processes of Z-pinch by a modified electrostatic direct implicit particle-in-cell algorithm

Abstract For investigating efficiently the stagnation kinetic-process of Z-pinch, we develop a novel modified electrostatic implicit particle-in-cell algorithm in radial one-dimension for Z-pinch simulation in which a small-angle cumulative binary collision algorithm is used. In our algorithm, the electric field in z-direction is solved by a parallel electrode-plate model, the azimuthal magnetic field is obtained by Ampere’s law, and the term for charged particle gyromotion is approximated by the cross product of the averaged velocity and magnetic field. In simulation results of 2 MA deuterium plasma shell Z-pinch, the mass-center implosion trajectory agrees generally with that obtained by one-dimensional MHD simulation, and the plasma current also closely aligns with the external current. The phase space diagrams and radial-velocity probability distributions of ions and electrons are obtained. The main kinetic characteristic of electron motion is thermal equilibrium and oscillation, which should be oscillated around the ions, while that of ion motion is implosion inwards. In the region of stagnation radius, the radial-velocity probability distribution of ions transits from the non-equilibrium to equilibrium state with the current increasing, while of electrons is basically the equilibrium state. When the initial ion density and current peak are not high enough, the ions may not reach their thermal equilibrium state through collisions even in its stagnation phase.

Distinct propagating and standing modes of tropical intraseasonal variability as represented by the two principal oscillation patterns

Although the tropical intraseaonal variability (TISV), as the most important predictability sources for subseasonal-to-seasonal (S2S) prediction, is dominated by Madden-Julian oscillation (MJO), its significant fraction does not always share the canonical MJO features, especially when the convective activity arrives at Maritime Continent. In this study, using principal oscillation pattern (POP) analysis on the combined fields of daily equatorial convection and zonal wind, two distinct leading TISV modes with relatively slower e-folding decay rates are identified. One is an oscillatory mode with the period of 51 days and e-folding time of 19 days, capturing the eastward propagating (EP) feature of the canonical MJO. The other is a non-oscillatory damping mode with e-folding time of 13.6 days, capturing a standing dipole (SD) with convection anomalies centered over the Maritime Continent and tropical central Pacific, respectively. Compared to the EP mode, the leading moisture anomalies at low level to the east of convection center are diminish for the SD mode, and instead, the strong negative anomalies of moisture and subsidence motion emerge in the tropical central Pacific area, which may be responsible for the distinct propagation features. Without filtering methods used, timeseries of the two POPs could be applied to the real-time monitoring of EP and SD events in the phase-space diagram. The two modes can serve as the simple and objective approach for a better characterization for diverse natures of TISV beyond the canonical MJO description, which may further shed light on dynamics of the TISV and its predictability.

Supersymmetric smooth distributions of M2-branes as AdS solitons

We show that the singularities of certain distributions of M2-branes can be removed by adding a Wilson loop around a compact direction along the brane. The holographic coordinate naturally ends up before the singularity and the resulting spacetime provides an AdS soliton configuration, albeit possibly supersymmetric. We study the phase space diagram of these M2-branes distributions endowed with Wilson loops and show that different distributions are interconnected, providing a rich structure of phase transitions at zero temperature.

Distribution of Merging and Post-merger Galaxies in Nearby Galaxy Clusters

We study the incidence and spatial distribution of galaxies that are currently undergoing gravitational merging (M) or that have signs of being post-merger (PM) in six galaxy clusters (A754, A2399, A2670, A3558, A3562, and A3716) within the redshift range of 0.05 ≲ z ≲0.08. To this aim, we obtained Dark Energy Camera mosaics in the u′ , g′ , and r′ bands covering up to 3 × R 200 of the clusters, reaching 28 mag arcsec−2 surface brightness limits. We visually inspect u′ g′ r′ color-composite images of volume-limited (M r < −20) cluster member galaxies to identify whether galaxies are of M or PM type. We find 4% M-type and 7% PM-type galaxies in the galaxy clusters studied. By adding spectroscopic data and studying the projected phase-space diagram (PPSD) of the projected clustocentric radius and the line-of-sight velocity, we find that PM-type galaxies are more virialized than M-type galaxies, having a 1%–5% higher fraction within the escape-velocity region, while the fraction of M-type was ∼10% higher than the PM type in the intermediate environment. Similarly, on a substructure analysis, M types were found in groups in the outskirts, while PM-type populated groups were found in ubiquitous regions of the PPSD. Adopting literature-derived dynamical state indicator values, we observed a higher abundance of M types in dynamically relaxed clusters. This finding suggests that galaxies displaying post-merger features within clusters likely merged in low-velocity environments, including clusters outskirts and dynamically relaxed clusters.

Mathematical Modelling and Computational Dynamics of the impact of Quasi-Lockdown Policy in Control of COVID-19 in Akwa Ibom State, Nigeria

Determining the impact of a local control strategy, implemented to curtail the spread of COVID-19 has become obligatory to enable policy makers to combat the so-called long covid. This research used a deterministic SEIAHR-model, incorporating a logistic function to investigate the effect of quasi-lockdown policy during reemergence of corona virus pandemic. The notion of uniform convergence and fixed point theory were used to establish positive invariant region, ultimate boundedness, and existence of unique solution of the model. Nonlinear dynamical behaviours of the model such as stability and oscillating flows occurred at the disease free, and endemic equilibrium points. Using centre manifold theory, a trans-critical bifurcation with hysteresis effect were established, when quasi-lockdown policy was used as a control parameter in the model. A forward sensitivity analysis was conducted to unfold parameters that contributed significantly towards the spread and control of the infection. These parameters were estimated and fitted using least square technique, comparative to the observed real datasets adapted from the Nigeria Centre for Disease Control (NCDC). The polynomial regression model fitted the observed datasets with an average coefficient of determination given as R2 = 0.94. Simulations in form of phase space diagrams were used to validate the theoretic results. Epidemiologically, the model demonstrated that quasi-lockdown policy was necessarily a strategic policy to curb the spread of the infection, but not sufficient to eradicate the disease as the disease persisted endemically. It was shown that the basic reproduction number of the infection was within the critical threshold (R0 \(\le\) 1), when the lockdown policy was enforced strictly, but otherwise on relaxation of the lockdown policy (R0 \(\ge\) 1) Thus a relaxation of the quasi-lockdown policy leads to increase in susceptibility of the populace as the infection risk ratio increases in the model. Similarly, the model predicted that a pre-mature lifting of the lockdown policy could have led to high infectivity on the susceptible class and disastrous to healthy living of the citizens.

Granular roll waves on a μ (J) rheology model: A dynamical systems perspective

This paper focuses on the formation and the unique characteristics of granular roll waves generated by utilizing the depth-averaged dynamic model recently introduced by Fei et al. [Appl. Math. Modell. 119, 763–781 (2023)], which employs μ(J) rheology. Notably, the symmetrical shape of the generated roll waves deviates from the typical pattern observed in both dry granular and water roll waves, which demonstrate a gradually rising flank followed by a sudden drop. Through a dynamical systems analysis and the associated phase space diagrams, which provide a comprehensive geometrical overview, we reveal the mathematical properties associated with the stable-uniform flow and the emergence of the granular roll waves. We then delve into the correlation between the shape of these roll waves and the nullclines of the dynamical system, whose analytical expression is presented. Additionally, we highlight the qualitative similarities and differences between the aforementioned model for liquid-immersed flowing granular matter and its well-established counterpart for dry granular flows based on the μ(I) rheology.

A new four-dimensional hyperchaotic system with hidden attractors and multistablity

This paper proposes a novel 4D hyperchaotic system with hidden attractors and coexisting attractors, which have no equilibrium points. The dynamic behavior of the system and five groups of coexisting attractors are analyzed by applying phase space diagrams, bifurcation diagrams and the Lyapunov exponents spectrum. Additionally, the system’s stable limit cycles and unstable periodic orbits were calculated through the variational method and then encoded using symbolic dynamics. The numerical results were verified via a circuit simulation, confirming the realizability of the novel hyperchaotic system in hardware facilities. Finally, we applied the active synchronization control method to the new system with remarkable results.

The Evolution of the Cold Gas Fraction in Nearby Clusters’ Ram-pressure-stripped Galaxies

Cluster galaxies are affected by the surrounding environment, which influences, in particular, their gas, stellar content, and morphology. In particular, the ram pressure exerted by the intracluster medium promotes the formation of multiphase tails of stripped gas detectable both at optical wavelengths and in the submillimeter and radio regimes, tracing the cold molecular and atomic gas components, respectively. In this work we analyze a sample of 16 galaxies belonging to clusters at redshift ∼0.05 showing evidence of an asymmetric H i morphology (based on MeerKAT observations) with and without a star-forming tail. To this sample we add three galaxies with evidence of a star-forming tail and no H i detection. Here we present the galaxies’ H2 gas content from APEX observations of the CO (2–1) emission. We find that in most galaxies with a star-forming tail the H2 global content is enhanced with respect to undisturbed field galaxies with similar stellar masses, suggesting an evolutionary path driven by the ram pressure stripping. As galaxies enter into the clusters, their H i is displaced but also partially converted into H2, so that they are H2 enriched when they pass close to the pericenter, that is, when they also develop the star-forming tails that are well visible in UV or B broad bands and in Hα emission. An inspection of the phase-space diagram for our sample suggests an anticorrelation between the H i and H2 gas phases as galaxies fall into the cluster potential. This peculiar behavior is a key signature of the ram pressure stripping in action.

Free stream turbulence intensity effects on the flow over a circular cylinder at [formula omitted]: bifurcation, attractors and Lyapunov metric

Varying the free-stream turbulence intensity (Ti= 0%, 5%, 10%) the flow over a circular cylinder for Re=3900 is examined using high fidelity eddy-resolving simulations. Results show that with growth of the turbulence intensity, the drag coefficient increases and the pressure base coefficient drops, as well as the flow bifurcation in the near wake occurs, when the length of the separation zone is reduced by about two, and the stream velocity profile is reshaped from U-shaped to V-shaped. The flow transformation is accompanied by the separation of the wall stress scales. At the same time, dynamics of the vortex shedding (Strouhal number) remains unchanged. The flow bifurcation, confirmed experimentally in practice, and the phase transition are examined using the Lyapunov metric (predictability time and phase-space diagrams). The predictability times, i.e. the phase transition between the two states Ti = 0% → 5% and Ti = 0% → 10% are estimated at one half and one of the characteristic convective time, after which the saturation occurs when both dynamical systems reach a statistical stationary state. Finally, phase-space states are visualized in 2D and 3D, and shown that related attractors can be bounded by simple geometrical ellipsoids.

Synchronization Analysis of a Master-Slave BEC System via Active Control

This paper will focus on theoretical treatment of the dynamic of the Bose-Einstein Condensate (BEC) systems contained different external trapping potentials. We construct the phase space diagrams and Lyapunov Characteristic Exponents (LCEs) for master and slave systems depended on the system parameters and propose a nonlinear control for the synchronization of systems in their chaotic states. The synchronization is obtained in master-slave scheme for different initial values. Numerical results are also given to show the efficiency of the used control technique.

ENSO phase space dynamics with an improved estimate of the thermocline depth

The recharge oscillator model of the El Niño Southern Oscillation (ENSO) describes the ENSO dynamics as an interaction between the eastern tropical Pacific sea surface temperatures (T) and subsurface heat content (thermocline depth; h), defining a dynamical cycle with different phases. h is often approximated on the basis of the depth of the 20 °C isotherm (Z20). In this study we will address how the estimation of h affects the representation of ENSO dynamics. We will compare the ENSO phase space with h estimated based on Z20 and based on the maximum gradient in the temperature profile (Zmxg). The results illustrate that the ENSO phase space is much closer to the idealised recharge oscillator model if based on Zmxg than if based on Z20. Using linear and non-linear recharge oscillator models fitted to the observed data illustrates that the Z20 estimate leads to artificial phase dependent structures in the ENSO phase space, which result from an in-phase correlation between h and T. Based on the Zmxg estimate the ENSO phase space diagram show very clear non-linear aspects in growth rates and phase speeds. Based on this estimate we can describe the ENSO cycle dynamics as a non-linear cycle that grows during the recharge and El Nino state, and decays during the La Nina states. The most extreme ENSO states are during the El Nino and discharge states, while the La Nina and recharge states do not have extreme states. It further has faster phase speeds after the El Nino state and slower phase speeds during and after the La Nina states. The analysis suggests that the ENSO phase speed is significantly positive in all phases, suggesting that ENSO is indeed a cycle. However, the phase speeds are closest to zero during and after the La Nina state, indicating that the ENSO cycle is most likely to stall in these states.

A Blueprint for the Milky Way’s Stellar Populations. IV. A String of Pearls—the Galactic Starburst Sequence

We continue our series of papers on phase-space distributions of stars in the Milky Way based on photometrically derived metallicities and Gaia astrometry, with a focus on the halo−disk interface in the local volume. To exploit various photometric databases, we develop a method of empirically calibrating synthetic stellar spectra based on a comparison with observations of stellar sequences and individual stars in the Sloan Digital Sky Survey, the SkyMapper Sky Survey, and the Pan-STARRS1 surveys, overcoming band-specific corrections employed in our previous work. In addition, photometric zero-point corrections are derived to provide an internally consistent photometric system with a spatially uniform metallicity zero-point. Using our phase-space diagrams, we find a remarkably narrow sequence in the rotational velocity (v ϕ ) versus metallicity ([Fe/H]) space for a sample of high proper-motion stars (>25 mas yr−1), which runs along Gaia Sausage/Enceladus (GSE) and the Splash substructures and is linked to the disk, spanning nearly 2 dex in [Fe/H]. Notably, a rapid increase of v ϕ from a nearly zero net rotation to ∼180 km s−1 in a narrow metallicity interval (−0.6 ≲ [Fe/H] ≲ −0.4) suggests that some of these stars emerged quickly on a short gas-depletion timescale. Through measurements of a scale height and length, we argue that these stars are distinct from those heated dynamically by mergers. This chain of high proper-motion stars provides additional support for recent discoveries suggesting that a starburst took place when the young Milky Way encountered the gas-rich GSE progenitor, which eventually led to the settling of metal-enriched gas onto the disk.

The cross-correlation-based analysis to digest the conformational dynamics of the mitoBK channels in terms of their modulation by flavonoids.

The activity of mitochondrial large-conductance voltage- and [Formula: see text]-activated [Formula: see text] channels (mitoBK) is regulated by a number of biochemical factors, including flavonoids. In particular, naringenin (Nar) and quercetin (Que) reached reasonable scientific attention due to their well-pronounced channel-activating effects. The open-reinforcing outcomes of Nar and Que on the mitoBK channel gating have been already reported. Nevertheless, the molecular picture of the corresponding channel-ligand interactions remains still to be revealed. In this work, we investigate the effects of the Nar and Que on the conformational dynamics of the mitoBK channel. In this aim, the cross-correlation-based analysis of the single-channel signals recorded by the patch-clamp method is performed. The obtained results in the form of phase space diagrams enable us to visually monitor the effects exerted by the considered flavonoids at the level of temporal characteristics of repetitive sequences of channel conformations. It turns out that the mitoBK channel activation by naringenin and quercetin does not lead to the change in the number of clusters within the phase space diagrams, which can be related to the constant number of available channel macroconformations regardless of the flavonoid administration. The localization and occupancy of the clusters of cross-correlated sequences suggest that mitoBK channel stimulation by flavonoids affects the relative stability of channel conformations and the kinetics of switching between them. For most clusters, greater net effects are observed in terms of quercetin administration in comparison with naringenin. It indicates stronger channel interaction with Que than Nar.

Diselenide Dianion’s Dual Powers: PdSe2Polymorph Control and Pd3Se10Superatomic Crystal Creation

There is a diverse family of palladium selenide compounds, including semiconducting orthorhombic PdSe2 (O-PdSe2) and monoclinic PdSe2 (M-PdSe2), which are unusual among transition-metal dichalcogenides as they are composed of diselenide dianions Se22–. Thus far, the solution syntheses of materials with Se–Se bonds typically require the in situ reduction of Se precursors. Here, we explore the use of electrochemically precise reactions between Na2Se2 and a Pd2+ source, Na2PdCl4, as a solution-phase route to selectively form different PdSe2 polymorphs in the absence of surfactants. By altering the reactant molar ratios and time, we map out a synthetic phase space diagram that shows how to create a wide variety of palladium selenide phases. With increasing Se22–/Pd2+ molar ratios, regions are identified where Pd17Se15, M-PdSe2, and O-PdSe2 exist as the dominant or exclusive thermodynamic product. Additionally, we discover Pd3Se10, a superatomic crystal composed of Pd6Se20 cube-shaped clusters held together by van der Waals forces, which forms as a kinetic product under short reaction times. In total, the use of the diselenide dianion precursor allows for the selective solution-phase synthesis of M-PdSe2 or O-PdSe2, as well as the discovery of a previously unreported palladium selenide phase.

Investigating the impact of sea surface temperature on the development of the Mediterranean tropical-like cyclone “Ianos” in 2020

This study aims to unravel and quantify the impact of sea surface temperature (SST) on the formation, intensity, structure and track of the Mediterranean tropical-like cyclone (medicane) Ianos occurred on 15–20 September 2020 at the central Mediterranean. This study, thus, demonstrates how Ianos would be in past and future climate conditions, assuming that SST changes over the years, but preserving the same atmospheric conditions. To investigate the SST impact, the medicane was simulated using the Advanced Weather and Research Forecasting (WRF-ARW) model. The numerical experiments were initialized either with SST analysis data (control experiment) or applying a uniform decrease and increase to SST analysis by 1 °C and 2 °C (four sensitivity experiments). In this way, the past and future climatic SSTs were concisely approximated. Analysis of various thermodynamic parameters in combination with phase space diagrams, revealing the thermal symmetry and the warm core structure of the cyclone, indicated that Ianos was very sensitive on SST. Thus, SST changes especially by ±2 °C had significant impact on its intensity, changing the period of tropical features while also determining the track and the landfall location. Overall, the average enthalpy flux (i.e., the sum of sensible and latent heat fluxes) in Ianos changed by approximately −39% and + 50% when SST changed by −2 °C and + 2 °C, respectively. This, in turn, affected the characteristics of Ianos causing changes for example in the average wind speed (approximately −15% and + 15%) and the average precipitation (approximately −56% and + 44%). This study quantifies the impacts of SST on Ianos medicane that have important research and socioeconomic implications with a view to a changing future. Therefore, it could support scientists, decision-makers and civil protection in the adaptation to extreme weather phenomena by building climate resilience and sustainability.