Multistage Transitions Research Articles

Entropy Engineering Constrain Phase Transitions Enable Ultralong-life Prussian Blue Analogs Cathodes.

Prussian blue analogs (PBAs) are considered as one of the most potential electrode materials in capacitive deionization (CDI) due to their unique 3D framework structure. However, their practical applications suffer from low desalination capacity and poor cyclic stability. Here, an entropy engineering strategy is proposed that incorporates high-entropy (HE) concept into PBAs to address the unfavorable multistage phase transitions during CDI desalination. By introducing five or more metals, which share N coordination site, high-entropy hexacyanoferrate (HE-HCF) is constructed, thereby increasing the configurational entropy of the system to above 1.5R and placing it into the high-entropy category. As a result, the developed HE-HCF demonstrates remarkable cycling performance, with a capacity retention rate of over 97% after undergoing 350 ultralong-life cycles of adsorption/desorption. Additionally, it exhibits a high desalination capacity of 77.24mg g-1 at 1.2V. Structural characterization and theoretical calculation reveal that high configurational entropy not only helps to restrain phase transition and strengthen structural stability, but also optimizes Na+ ions diffusion path and energy barrier, accelerates reaction kinetics and thus improves performance. This research introduces a new approach for designing electrodes with high performance, low cost, and long-lasting durability for capacitive deionization applications.

Research on switching control based sliding mode coordination strategy of hybrid electric vehicle

The transient mode transition from pure electric driving to hybrid driving in a hybrid electric vehicle (HEV) involves multiple stages, each characterized by different models and control objectives, demanding diverse levels of controller robustness and convergence performance. Addressing the complexities of multi-stage transitions in a parallel HEV, the paper proposes a dynamic coordination strategy based on the switched control system concept. Distinct sliding mode controllers (SMC) are designed for each transition stage, tailored to the specific characteristics of powertrain operation. At the engine starting and speed synchronization stages, the global integral sliding mode control (GISMC) is integrated with a novel anti-saturation reaching law to ensure the system resides in the sliding mode, enhancing global robustness. During the engine speed regulation stage, the nonsingular terminal sliding mode control (NTSMC) facilitates rapid engine speed tracking for reduced mode transition time. By combining GISMC for global robustness and NTSMC for accelerated convergence, the strategy is designed to enhance mode transition quality at different stages. Simulation results demonstrate a 7.3% reduction in mode transition time and a 60.7% decrease in jerk compared to the conventional SMC strategy. In hardware-in-the-loop tests, the proposed control strategy proves effective in improving mode transition quality.

Broadening the operating temperature span of the electrocaloric effect in lead-free ceramics via creating multi-stage phase transitions

The strategy of this study achieves a large electrocaloric response of ΔT > 1 K within a temperature span of 66 °C. The cooling performance exceeds 90% and 80% of the maximum for temperature spans of 44 °C and 67 °C, respectively.

RETRACTED: Data-driven model predictive control for real-time planned lead time optimization in a reconfigurable flow line

Mass customization has enabled smart manufacturing systems to develop reconfigurable machines and fixtures to fulfill customized products with high process variety. Coupled with these reconfigurable components, diversified design and operational problems should be dealt with such that the efficiency of reconfigurations can be maximized. This paper investigates a planned lead time (PLT) optimization problem after addressing the pre-determined reconfigurations and real-time disruptions in a flow line. A data-driven model predictive control (d-MPC) is developed for this problem such that the total expected cost for work-in-process inventory, final-product inventory, and tardiness penalty can be minimized. Considering the predictive multi-stage transitions and reconfigurable behaviors, d-MPC utilizes max-plus algebra to generate a time-varying state-space equation for a flow line. In this regard, a systematic method for permanent production loss identification can be formulated for real-time disruption diagnosis. This identification is useful in providing feedback signals for d-MPC and thus a closed-loop feedback control for PLT optimization can be achieved. A case study of an industrial welding line is reported to illustrate the operational benefits of d-MPC. The results demonstrate that d-MPC can efficiently cooperate with PLT optimization with machine reconfiguration such that the total expected cost can be minimized. Compared with continuous re-optimization, d-MPC adopts an event-driven mechanism to respond to real-time disruptions and can decrease the nervousness of flow lines with lower operational costs.

Stochastic Bifurcations and Multistage Order–Chaos Transitions in a 4D Eco-Epidemiological Model

A tritrophic “prey-intermediate predator-top predator” population system with disease in the intermediate predator is considered. For this 4D-model, the bifurcation analysis is performed. In this analysis, the rate of the disease transmission is used as a bifurcation parameter. A variety of mono-, bi- and tri-stable behaviors with regular and chaotic attractors are analyzed. It is shown how random disturbances of the bifurcation parameter cause multistage stochastic transformations, noise-induced excitement, and stochastic transitions from order to chaos and reversely. These noise-induced effects are studied in terms of stochastic P- and D-bifurcations.

Early warnings for multi-stage transitions in dynamics on networks.

Successfully anticipating sudden major changes in complex systems is a practical concern. Such complex systems often form a heterogeneous network, which may show multi-stage transitions in which some nodes experience a regime shift earlier than others as an environment gradually changes. Here we investigate early warning signals for networked systems undergoing a multi-stage transition. We found that knowledge of both the ongoing multi-stage transition and network structure enables us to calculate effective early warning signals for multi-stage transitions. Furthermore, we found that small subsets of nodes could anticipate transitions as well as or even better than using all the nodes. Even if we fix the network and dynamical system, no single best subset of nodes provides good early warning signals, and a good choice of sentinel nodes depends on the tipping direction and the current stage of the dynamics within a multi-stage transition, which we systematically characterize.

Provenance change in Carboniferous-early Permian sedimentary successions in the North Qaidam tectonic belt, northern Tibetan Plateau: Implications for the Kunlun oceanic plate subduction process

• The age of tuff layer from the lower Zhabusagaxiu Formation indicates that the North Qaidam tectonic belt has early Permian sedimentary succession. • The major provenance of the North Qaidam tectonic belt evolved southward from the North Qaidam tectonic belt to the East Kunlun Orogen during the Carboniferous to early Permian. • Carboniferous to Permian sedimentary successions in the North Qaidam tectonic belt were deposited in a retroarc setting. Late Paleozoic sedimentary successions are widespread in the North Qaidam tectonic belt (NQTB), providing an ideal window to constrain the coeval tectonic background of the NQTB to East Kunlun Orogen (EKO). However, little attention has been devoted to these sedimentary-related records. In this study, stratigraphic and detrital zircon U-Pb geochronologic investigations were undertaken on the late Paleozoic successions in the NQTB to reveal multistage tectonic transitions. A weighted mean age of 293±3 Ma was obtained for a tuff sample from the basal Zhabusagaxiu Formation, yielding a first-order time estimate that assigns an early Permian age. Stratigraphic correlation and paleocurrent reconstruction indicate that Carboniferous to early Permian sedimentation in the NQTB took place in a north-dipping neritic environment. Sandstone petrology and detrital zircon geochronology converge to reveal that the major provenance of the NQTB evolved southward from the North Qaidam Orogen in the early Carboniferous, via the EKO and the Qaidam Block in the late Carboniferous, to the EKO in the early Permian. Detrital zircons with crystallization ages of Carboniferous to early Permian in all samples implicate that Carboniferous to Permian magmatism should be common in the EKO. The north-dipping paleogeography and occurrence of syn-depositional magmatic zircons in the provenance further suggest that the tectonic evolution of the NQTB should occur in a retroarc portion, rather than a passive continental margin deepening southwards to the Kunlun Ocean.

Noise-Induced Transformations in a System of Two Coupled Equilibrium and Chaotic Subpopulations

We study the collective behavior of populations, coupling the equilibrium and chaotic subsystems by mutual migration. It is assumed that the dynamics of an isolated subsystem is modeled by the Ricker map, and the intensity of migrations within the metapopulation is subject to random perturbations. In the deterministic case, we specify parameter zones of mono- and birhythmicity with regular and chaotic attractors. Noise-induced multistage transitions from order to chaos and vice versa are investigated from an approach that combines direct numerical simulations, studies of chaotic transients, stochastic sensitivity, and confidence domains.

Multistage transitions in viscoelastic turbulent flow: Vortex structures and self-sustaining mechanisms

Viscoelastic dilute polymer solutions are known to display drag reduction in turbulent flows. At constant Re and as the fluid becomes more elastic (increasing Wi), the flow undergoes transitions between several stages of different behaviors. The first is the onset of drag reduction, before which the turbulent friction factor remains indistinguishable from its Newtonian limit. The second is the transition from low-extent (LDR) to high-extent drag reduction (HDR), which increasing evidences have shown to be a qualitative transition between different types of turbulent dynamics. The third is the convergence to the maximum drag reduction (MDR) asymptote, after which the friction factor becomes constant. Although increasing drag reduction with increasing Wi is intuitively expected, transitions between these stages are accompanied by drastic changes in flow statistics and structural patterns, indicating fundamental differences in the underlying turbulent dynamics. Mechanistic understanding into these transitions is far from complete. Our latest work has offered fresh insights into both the LDR-HDR and HDR-MDR transitions. For the former, we developed a new vortex analysis method, called VATIP, and applied it to analyze the differences between the conformation statistics in LDR and HDR regimes. The result links the occurrence of HDR to the dominance of a new turbulence self-sustaining mechanism. For the latter, although a full answer to the MDR problem remains elusive, our analysis of the so-called elastoinertial turbulence (EIT) challenges the long-held presumption of MDR being an ultimate flow state that is no longer affected by polymers. The finding calls for a new direction of thought in constructing a theoretical explanation for MDR.

Photoinduced multistage phase transitions in Ta2NiSe5

Ultrafast control of material physical properties represents a rapidly developing field in condensed matter physics. Yet, accessing the long-lived photoinduced electronic states is still in its early stages, especially with respect to an insulator to metal phase transition. Here, by combining transport measurement with ultrashort photoexcitation and coherent phonon spectroscopy, we report on photoinduced multistage phase transitions in Ta2NiSe5. Upon excitation by weak pulse intensity, the system is triggered to a short-lived state accompanied by a structural change. Further increasing the excitation intensity beyond a threshold, a photoinduced steady new state is achieved where the resistivity drops by more than four orders at temperature 50 K. This new state is thermally stable up to at least 350 K and exhibits a lattice structure different from any of the thermally accessible equilibrium states. Transmission electron microscopy reveals an in-chain Ta atom displacement in the photoinduced new structure phase. We also found that nano-sheet samples with the thickness less than the optical penetration depth are required for attaining a complete transition.

Observation of New Dynamics of Transitions among Intermediate Species in Crystal Evolution and Its Role in a Generic Model of Crystallization

The mass and phase transitions among intermediate species are unique dynamics in nonclassical crystallization that are under investigation. In this research, we used a pulsed laser to initiate crystallization in its early stages and observed the crystal evolution through transitions and interactions among the intermediate species. The crystal evolution was induced and observed in situ simultaneously by the same electron beam in a transmission electron microscope without a liquid cell environment, thereby eliminating the complexity introduced by the additional nucleation in the precursor solution. The observed mass diffusion among species in an anti-Ostwald ripening way indicated that crystallization systems were composed of intermediate species in various phases. We found that these intermediate species were not like rigid building blocks but kept changing in size and phase and evolving in multistage transitions. Considering the observations, we propose a generic model by extending the classical nucleation theories to describe the dynamics of intermediate transitions and all possible crystal evolution pathways, discovered or not.

Monitoring of spatial data coordinate basis integrity using coordinate transformations

The modern spatial data coordinate basis (SDCB) is built taking into account the variety of existing and used today geodetic networks, models of physical fields of the Earth, cartographic models, as well as coordinate systems (СS). One of the requirements for SDCB from the standpoint of system analysis is the requirement of integrity, which presupposes the unity of the determination of coordinates, that is, the consistency of the results of determining the coordinates of the same points in different CSs. The article is devoted to the monitoring of the accuracy characteristics of the available software for coordinate transformations in terms of single-stage and multi-stage transitions between ellipsoidal coordinates of different systems.

Noise-induced shifts in dynamics of multi-rhythmic population SIP-model

Motivated by important ecological applications, we investigate a three-dimensional population system describing mutual dynamics of predator (P) and prey divided into susceptible (S) and infected (I) species. In our study, we focus on a parameter zone with complex multi-rhythmic behavior where several oscillatory attractors coexist, both regular and chaotic. An effect of random disturbances in this SIP-model is investigated on the basis of direct numerical simulation and analytical stochastic sensitivity technique. It is revealed that random fluctuations in the rate of the infection spread result in the transitions between oscillatory modes with extinction of predator. It is shown that these noise-induced phenomena are accompanied by stochastic bifurcations and multi-stage order-chaos transitions.

Homocrystalline mesophase formation and multistage structural transitions in stereocomplexable racemic blends of block copolymers

Polymer crystallization is a multi-stage process and generally takes place through the metastable intermediate structure or mesophase. However, mesopahse is difficult to be experimentally detected during crystallization and its formation mechanism is not well understood. Herein, we find that the formation of mesopahse is facilitated in the crystallization of stereocomplexable block polymers. We use the poly(L-lactic acid)-poly(ethylene glycol)-poly(L-lactic acid) (PLLA-PEG-PLLA) and poly(D-lactic acid)-poly(ethylene glycol)-poly(D-lactic acid) (PDLA-PEG-PDLA) as the stereocomplexable pair and investigate the synergetic effects of copolymer composition and PLLA/PDLA stereocomplexation on the mesophase formation in the PLLA-PEG-PLLA/PDLA-PEG-PDLA 1/1 blends. Intriguingly, the stereocomplexable blend having the high PEG fraction forms the unique homocrystalline mesophase at the low crystallization temperature (Tc, 70–120 °C) but the usual α-form homocrystals (HCs) at high Tc (120–160 °C), except for the stereocomplexes (SCs). However, the crystalline structure of PLLA-PEG-PLLA/PDLA-PEG-PDLA blend with low PEG fraction is similar as the PLLA/PDLA blend; it crystallizes in the mixture of α(α′)-HCs + SCs at Tc = 70–160 °C. The homocrystalline mesophase formed in stereocomplexable blend is metastable and reorganizes into the more thermally-stable α-HCs and SCs during heating. We propose that the mesophase formation in enantiomeric blend is resulted by the constrained effects induced by the stereocomplexation and microphase separation of block copolymers.

Pressure-Controlled Migration of Paramagnetic Centers in a Heterospin Crystal.

A study of the single-crystal-to-single-crystal transformation induced by temperature variation for the chain polymer Cu(II) complex with nitronyl nitroxide showed that an increase in the hydrostatic pressure of up to ∼0.07 GPa completely changes the intracrystalline displacements of molecules relative to one another. This, in turn, significantly affects the interaction energy of the unpaired electrons of the paramagnetic centers and hence the form of the temperature dependence of the magnetic susceptibility χT. The cooling of crystals under normal conditions causes a rearrangement of the intrachain exchange clusters {>N-•O-Cu(II)-O•-N<} accompanied by a shortening of the distances between the paramagnetic centers. This changes the character of exchange interactions and generates multistage spin transitions. An increase in the hydrostatic pressure leads to a drastic change in the O···O distances between the nitroxyl fragments of adjacent chains, an increase in the antiferromagnetic exchange between them, and complete suppression of spin transitions.

Multistage electronic nematic transitions in cuprate superconductors: A functional-renormalization-group analysis

Recently, complex phase transitions accompanied by the rotational symmetry breaking have been discovered experimentally in cuprate superconductors. To find the realized order parameters, we study various charge susceptibilities in an unbiased way, by applying the functional-renormalization-group method to the realistic $d$-$p$ Hubbard model. Without assuming the wavevector of the order parameter, we reveal that the most dominant instability is the uniform ($q = 0$) charge modulation on the $p_x$ and $p_y$ orbitals, which possesses the d-symmetry. This uniform nematic order triggers another nematic p-orbital density wave along the axial (Cu-Cu) direction at $Q_a = (\pi/2,0)$. It is predicted that uniform nematic order is driven by the spin fluctuations in the pseudogap region, and another nematic density-wave order at $q = Q_a$ is triggered by the uniform order. The predicted multistage nematic transitions are caused by the Aslamazov-Larkin-type fluctuation-exchange processes.

Coherent structure dynamics and identification during the multistage transitions of polymeric turbulent channel flow

Drag reduction induced by polymer additives in wall-bounded turbulence has been studied for decades. A small dosage of polymer additives can drastically reduce the energy dissipation in turbulent flows and alter the flow structures at the same time. As the polymer-induced fluid elasticity increases, drag reduction goes through several stages of transition with drastically different flow statistics. While much attention in the area of polymer-turbulence interactions has been focused on the onset and the asymptotic stage of maximum drag reduction, the transition between the two intermediate stages – low-extent drag reduction (LDR) and high-extent drag reduction (HDR) – likely reflects a qualitative change in the underlying vortex dynamics according to our recent study [1]. In particular, we proposed that polymers start to suppress the lift-up and bursting of vortices at HDR, leading to the localization of turbulent structures. To test our hypothesis, a statistically robust conditional sampling algorithm, based on Jenong and Hussain [2]’s work, was adopted in this study. The comparison of conditional eddies between the Newtonian and the highly elastic turbulence shows that (i) the lifting “strength” of vortices is suppressed by polymers as reflected by the decreasing lifting angle of the conditional eddy and (ii) the curvature of vortices is also eliminated as the orientation of the head of the conditional eddy changes. In summary, the results of conditional sampling support our hypothesis of polymer-turbulence interactions during the LDR-HDR transition.

Beetle and plant arrow poisons of the Ju|'hoan and Hai||om San peoples of Namibia (Insecta, Coleoptera, Chrysomelidae; Plantae, Anacardiaceae, Apocynaceae, Burseraceae).

The use of archery to hunt appears relatively late in human history. It is poorly understood but the application of poisons to arrows to increase lethality must have occurred shortly after developing bow hunting methods; these early multi-stage transitions represent cognitive shifts in human evolution. This paper is a synthesis of widely-scattered literature in anthropology, entomology, and chemistry, dealing with San (“Bushmen”) arrow poisons. The term San (or Khoisan) covers many indigenous groups using so-called ‘click languages’ in southern Africa. Beetles are used for arrow poison by at least eight San groups and one non-San group. Fieldwork and interviews with Ju|’hoan and Hai||om hunters in Namibia revealed major differences in the nature and preparation of arrow poisons, bow and arrow construction, and poison antidote. Ju|’hoan hunters use leaf-beetle larvae of Diamphidia Gerstaecker and Polyclada Chevrolat (Chrysomelidae: Galerucinae: Alticini) collected from soil around the host plants Commiphora africana (A. Rich.) Engl. and Commiphora angolensis Engl. (Burseracaeae). In the Nyae Nyae area of Namibia, Ju|’hoan hunters use larvae of Diamphidia nigroornata Ståhl. Larvae and adults live above-ground on the plants and eat leaves, but the San collect the underground cocoons to extract the mature larvae. Larval hemolymph is mixed with saliva and applied to arrows. Hai||om hunters boil the milky plant sap of Adenium bohemianum Schinz (Apocynaceae) to reduce it to a thick paste that is applied to their arrows. The socio-cultural, historical, and ecological contexts of the various San groups may determine differences in the sources and preparation of poisons, bow and arrow technology, hunting behaviors, poison potency, and perhaps antidotes.

Turbulent drag reduction and multistage transitions in viscoelastic minimal flow units

The observation that addition of a minute amount of flexible polymers to fluid reduces turbulent friction drag is well known. However, many aspects of this drag reduction phenomenon are not well understood; in particular, the origin of the maximum drag reduction (MDR) asymptote, a universal upper limit on drag reduction by polymers, remains an open question. This study focuses on the drag reduction phenomenon in the plane Poiseuille geometry in a parameter regime close to the laminar–turbulent transition. By minimizing the size of the periodic simulation box to the lower limit for which turbulence persists, the essential self-sustaining turbulent motions are isolated. In these ‘minimal flow unit’ (MFU) solutions, a series of qualitatively different stages consistent with previous experiments is observed, including an MDR stage where the mean flow rate is found to be invariant with respect to changing polymer-related parameters. Before the MDR stage, an additional transition exists between a relatively low degree (LDR) and a high degree (HDR) of drag reduction. This transition occurs at about 13%–15% of drag reduction and is characterized by a sudden increase in the minimal box size, as well as many qualitative changes in flow statistics. The observation of LDR–HDR transition at less than 15% drag reduction shows for the first time that it is a qualitative transition instead of a quantitative effect of the amount of drag reduction. Spatio-temporal flow structures change substantially upon this transition, suggesting that two distinct types of self-sustaining turbulent dynamics are observed. In LDR, as in Newtonian turbulence, the self-sustaining process involves one low-speed streak and its surrounding streamwise vortices; after the LDR–HDR transition, multiple streaks are present in the self-sustaining structure and complex intermittent behaviour of the streaks is observed. This multistage scenario of LDR–HDR–MDR recovers all key transitions commonly observed and studied at much higher Reynolds numbers.

Elastic constants ofNi−Mn−Gamagnetic shape memory alloys

We have measured the adiabatic second order elastic constants of two $\mathrm{Ni}\text{\ensuremath{-}}\mathrm{Mn}\text{\ensuremath{-}}\mathrm{Ga}$ magnetic shape memory crystals with different martensitic transition temperatures, using ultrasonic methods. The temperature dependence of the elastic constants has been followed across the ferromagnetic transition and down to the martensitic transition temperature. Within experimental errors no noticeable change in any of the elastic constants has been observed at the Curie point. The temperature dependence of the shear elastic constant ${C}^{\ensuremath{'}}$ has been found to be very different for the two alloys. Such a different behavior is in agreement with recent theoretical predictions for systems undergoing multi-stage structural transitions.