Dynamical Point Of View Research Articles

Measurement of CO2 Emissions Efficiency and Analysis of Influencing Factors of the Logistics Industry in Nine Coastal Provinces of China

The surge in CO2 emissions affects global climate change and the development of society. The logistics industry, being a swiftly advancing industry, demonstrates an escalating trend in CO2 emissions. Therefore, this paper selects the more developed coastal provinces (districts) in China’s logistics industry and takes 2011–2020 as the research period. Using the Super-SBM model and the Malmquist index model, the article analyzes the changes in the carbon emission efficiency of the logistics industry from the static and dynamic perspectives and then explores the factors affecting it using the panel model and the mediating effect model. Findings from research indicate that: (1) The CO2 emission efficiency of the logistics industry is generally moderate when viewed from a static perspective. (2) Taking a dynamic viewpoint, there is a slight declining trend in the overall CO2 emission efficiency. (3) As environmental regulations become more stringent, the CO2 emission efficiency follows the “U”-shaped pattern, initially declining and then rising. Environmental regulations can influence CO2 emission efficiency by affecting technological innovation. Additionally, energy efficiency plays a positive role in promoting CO2 emission efficiency. Recommendations: Implement differentiated environmental regulations tailored to local conditions. Emphasize technological innovations. Enhance the energy efficiency.

Dynamical systems insights on cyclonic compound “wet” and “windy” extremes in the Eastern Mediterranean

AbstractExtreme weather, such as heavy precipitation and strong winds, can co‐occur, resulting in larger socio‐economic impacts than the linear sum of their components. These are termed “compound extremes” and are challenging to forecast even a few days before. With this aim, we investigate the “wet” and “windy” extremes associated with Eastern Mediterranean cyclones in winter. We combine insights from a synoptic classification algorithm, traditional atmospheric analysis techniques, and dynamical systems theory. In phase space, the latter quantifies atmospheric states' co‐recurrence ratio (α) and persistence (Θ−1). We base the analysis on ERA5 at various pressure levels and time lags. Our analysis is two‐fold; first, we define compound dynamical extremes (CDE) based on upper and lower deciles of α and Θ−1, linking them to the synoptic patterns. We find that CDEs are related to the depth and location of the surface cyclone and upper‐level trough. Then, we show that high co‐recurrence and persistence are associated with heavier precipitation and stronger wind speed. Second, we define compound extremes (CE), the upper 5% of precipitation intensity and wind velocity co‐occurring simultaneously. We link these back to the dynamical system metrics anomalies. Finally, we compare CEs with individual extremes and cyclone climatology. We find that CEs display significantly higher co‐recurrence and persistence than individual extremes. Indeed, days with high co‐recurrence and persistence anomalies are ∼2–18 times more likely to be allied with extreme weather, depending on the extreme type, than low co‐recurrence and persistence. Moreover, we show that the upper levels are significantly more persistent than the surface flow during a CE. The mid‐February 2012 “wet” and “windy” CE case‐study strengthened the abovementioned climatological findings. To conclude, the dynamical systems viewpoint is a valuable complement to understanding the dynamics of CEs in the Eastern Mediterranean. We foresee it to be fruitfully applied to other CEs and regions.

Influence of obstruction’s unilateral length on flow and heat transfer performance of micro-channel heat sinks with flow obstructions

As the density and integration of electronic equipment continue to increase, it becomes necessary to build micro-channel heat sinks with more efficient cooling effects to solve the heat removal issue. This paper proposes a series of obstructions established on a smooth water-cooled micro-channel and analyzes the heat transfer and flow performance from the viewpoint of fluid dynamics. By adjusting the unilateral side length of the obstructions, the simulation conducted a comparative analysis between the seven different obstruction shapes and smooth micro-channel heat sinks, focusing on Nusselt number, thermal resistance, and pressure loss across a range of Reynolds numbers. The findings demonstrate that the heat dissipation capacity of micro-channel heat sinks with obstructions is consistently superior to that of the smooth heat sink, and the performance of these heat sinks is affected by the length of unilateral side of the obstructions. With no consideration of pumping power, the paper argues that the heat sink with obstructions, specifically those with a unilateral side length of 0.06 mm, has the best heat dissipation capacity at Reynolds numbers below 460. At this Reynolds number, the Nusselt number increases by 99% and the thermal resistance decreases by 33% compared to a smooth micro-channel heat sink. However, when the pumping power is considered, the heat sink with obstructions whose unilateral sides are the shortest has the best performance due to its minimal pressure loss. While meeting the thermal resistance requirement of 0.033, it requires only one-fourth of the pumping power needed by a heat sink with obstructions whose unilateral sides are longest.

Stationarity of quantum statistical ensembles at first-order phase transition points

We study the dynamics of quantum statistical ensembles at first-order phase transition points of finite macroscopic systems. First, we show that at the first-order phase transition point of the system, with an order parameter that does not commute with the Hamiltonian, any quantum state with an order parameter that has a nonzero value always evolves towards a macroscopically distinct state after a sufficiently long time. From this result, we argue that the stationarity required for statistical ensembles should be interpreted as stationarity on a sufficiently long but finite timescale. Finally, we prove that the density matrix of the squeezed ensemble, a class of generalized statistical ensembles proposed as the only concrete method of constructing phase coexistence states applicable to general quantum systems, is locally stationary on timescales diverging in the thermodynamic limit. Our results support the validity of the squeezed ensemble from a dynamical point of view and open the door to nonequilibrium statistical physics at the first-order phase transition point.

Dynamic state of low-Reynolds-number turbulent channel flow.

We numerically study the dynamic state of a low-Reynolds-number turbulent channel flow from the viewpoints of symbolic dynamics and nonlinear forecasting. A low-dimensionally (high-dimensionally) chaotic state of the streamwise velocity fluctuations emerges at a viscous sublayer (logarithmic layer). The possible presence of the chaotic states is clearly identified by orbital instability-based nonlinear forecasting and ordinal partition transition network entropy in combination with the surrogate data method.

Quantum dynamics of the internal motion of biphenyl-based molecular junctions.

Single molecule junctions based on selected 4,4'-biphenyldithiol and 4,4'-dicyanobiphenyl derivatives bonded to gold electrodes are analyzed from a dynamical point of view. A fully quantum mechanical description of the internal rotation of the biphenyl moiety is carried out in terms of the nuclear wavepacket dynamics obtained by the solution of the time-dependent Schrödinger equation expressed in terms of the torsion angle between the phenyl rings. The required potential energy surfaces are computed using abinitio electronic structure methods. The nature and positions of the substituents on the phenyl rings determine the features of the potential energy surfaces. The effect of the initial conditions on the time propagation of the nuclear wavepackets and, as a consequence, on the evolution of the conformational distribution is also analyzed. In addition, the conductances at zero bias for the nanojunctions were computed for different conformations of the biphenyl fragments. Weighted by the wavepacket amplitudes, non-stationary conductance expectation values, and time-averaged torsion angles and conductances for the entire simulation are obtained. The consequences of using the time-averaged values to perform a linear regression between the conductance and the square of the cosine of the dihedral angle between the phenyl rings are analyzed and compared to the usual static approach based only on the information for equilibrium geometries. The study of the time dependent conformational variations of the biphenyl moieties in the nanojunctions allows for a better understanding of the quantum chemical phenomena that affect their transport properties.

Suppression and frequency control of repetitive spiking in the FitzHugh-Nagumo model.

The FitzHugh-Nagumo equationis a simple model equationthat exhibits spiking. The output signal of a neuron is represented in the spiking frequency or firing rate. We consider a few control methods for spiking from the viewpoint of nonlinear dynamics. The repetitive spiking can be suppressed in the FitzHugh-Nagumo model by the periodic sinusoidal force with high frequency. We study the transition to the suppressed state numerically and perform a linear stability analysis to understand the suppression of the spiking. Next, we study coupled FitzHugh-Nagumo equations. We find that the periodic forcing makes the system chaotic, and the desynchronization induced by chaos weakens the total output of spiking in a certain parameter range. Finally, we propose a method of feedback control for the spiking frequency. We can get the desired spiking and bursting frequency using this feedback control. The feedback control method is analyzed using a mapping for the input.

Beyond neurons and spikes: cognon, the hierarchical dynamical unit of thought

AbstractFrom the dynamical point of view, most cognitive phenomena are hierarchical, transient and sequential. Such cognitive spatio-temporal processes can be represented by a set of sequential metastable dynamical states together with their associated transitions: The state is quasi-stationary close to one metastable state before a rapid transition to another state. Hence, we postulate that metastable states are the central players in cognitive information processing. Based on the analogy of quasiparticles as elementary units in physics, we introduce here the quantum of cognitive information dynamics, which we term “cognon”. A cognon, or dynamical unit of thought, is represented by a robust finite chain of metastable neural states. Cognons can be organized at multiple hierarchical levels and coordinate complex cognitive information representations. Since a cognon is an abstract conceptualization, we link this abstraction to brain sequential dynamics that can be measured using common modalities and argue that cognons and brain rhythms form binding spatiotemporal complexes to keep simultaneous dynamical information which relate the ‘what’, ‘where’ and ‘when’.

Interfacial Proton Supply/Filtration Regulates the Dynamics of Electrocatalytic Nitrogen Reduction Reaction: A Perspective

AbstractAs a promising energy carrier, ammonia synthesis by electrocatalytic nitrogen reduction reaction (eNRR) is a promising green and low‐carbon ammonia synthesis strategy that can replace the traditional Haber–Bosch process. However, the development of eNRR processes is mainly severely constrained by competitive hydrogen evolution reaction (HER), and the corresponding strategies to inhibit this adverse side reaction to obtain high eNRR selectivity are still limited. In addition, for this complex reaction involving gas–liquid–solid three‐phase interface and proton/electron transfer, it is great significance to analyze and summarize the existing inhibition HER strategies from the viewpoint of dynamics. In view of this, this work reviews proton supply/filtration regulation strategy in catalytic system, allowing a systematic survey of the literature focusing on interface membrane regulation (inorganic membrane and organic membrane), electrolyte regulation (metal‐mediated strategy and electrolyte ion regulation strategy) and system device design (electrode structure design and electrolytic cell device design). Constructive catalytic system design guidance is also suggested to inhibit hydrogen evolution and improve NH3 selectivity, aiming for scalable and economically feasible applications.

Hydration of Alkali Metal and Halide Ions from Static and Dynamic Viewpoints.

Ion hydration in aqueous solutions plays a paramount role in many fields. Despite many studies on ion hydration, the nature of ion hydration is not consistently understood at the molecular level. Combining neutron scattering (NS), wide-angle X-ray scattering (WAXS), and molecular dynamics (MD), we quantify the ionic hydration degree (hydration ability) systematically for a series of alkali metal and halide ions based on static and dynamic hydration numbers. The former is based on the orientational correlation of water molecules bound to an ion derived from the positional information from NS and WAXS. The latter is defined as the mean number of water molecules remaining in the first coordination shell of an ion over a residence time of bound water molecules around the ion from MD. The static and dynamic hydration numbers distinguish hydration from coordination and quantify the ionic hydration degree, which provides a valuable reference for understanding various phenomena in nature.

Wada boundaries on a hyperbolic pair of pants

In this paper, the geodesics of an open multiply connected hyperbolic manifold are presented from the dynamical system point of view. The approach is completely numerical. Similar to the closed hyperbolic case there is a zero-measure set of periodic orbits. The difference is that now, most of the geodesics escape to infinity through one of the topologically distinct channels, and initial conditions are identified to which channel the orbit escapes. The initial condition mesh reveals basins of attraction to each channel. We verified that the basin boundary points are of the Wada type by two independent methods. We have also calculated the basin entropy of the system and verified that it depends on the opening angle of the escape channels. The manifold chosen is the pair of pants together with the leaves, so there are 3 distinct exit channels.

Variational Principles on Geometric Rough Paths and the Lévy Area Correction

In this paper, we describe two effects of the L\'evy area correction on the invariant measure of stochastic rigid body dynamics on geometric rough paths. From the viewpoint of dynamics, the L\'evy area correction introduces an additional deterministic torque into the rigid body motion equation on geometric rough paths. When the dynamics is driven by coloured noise, and for rigid body dynamics with double-bracket dissipation, theoretical and numerical results show that this additional deterministic torque shifts the centre of the probability distribution function by shifting the Hamiltonian function in the exponent of the Gibbsian invariant measure.

The Alignment of Circular Economy Business Models (CEBM) with the Strategies of Small and Micro Enterprises Operating in Malta

This paper sets out preliminary findings for research investigating, from a dynamic viewpoint, how small and micro enterprises operating in the small island state of Malta align their business strategies with Circular Economy Business Models (CEBM). The aim is to establish an analytical framework evaluating their process of alignment. These businesses are a major economic driver for the island. In 2021, out of the 55,950 registered businesses in Malta, 52,674 were micro-firms and 2,686 were small businesses (NSO 2021). The study applies grounded theory methodology, using Corbin and Strausss conditional matrix (2015) and Charmazs constructivist approach (2006). To understand their implementation of circular practices, interpretative, in-depth interviews were carried out with five owners-managers in the service, logistics, manufacturing, retail, and wholesale sectors. The research postulates an early conceptual model showing how a set of contextual conditions influences the alignment of CEBM with the strategies of businesses in Malta. Factors influencing CEBM adoption include owner-managers personal traits, organisational factors, and external factors. The findings presented are part of a larger study mapping common alignment paths pursued by firms in the circular economic shift. It offers recommendations to owners-managers, policymakers, and academic researchers. Few studies have yet focused on the alignment between CEBM and the business strategy of firms in small island states. Generally, studies concentrate on larger businesses in bigger countries. This research study adds significantly to existing knowledge and academic literature.

Analysis of the spatial layout and influencing factors of pollution-intensive industries based on enterprise dynamics

The studies of the spatial layout and impact mechanism of pollution-intensive industries have become one of the research hot spots for regional sustainable development. From the viewpoint of enterprise dynamics, this study used a spatial econometric model and kernel density analysis methods to analyze the spatial layout characteristics of pollution-intensive industries in the urban agglomeration in the middle reaches of the Yangtze River (UAMRYR) in 2010, 2015, and 2020, and to explore the reasons for the formation of the spatial divergence of different sub-industries. The results showed that (1) in the past decade, the pollution-intensive industries in the UAMRYR have spatial shift characteristics, basically presenting a “core-edge” pattern from central cities to peripheral cities, and an “agglomeration-diffusion-agglomeration” spatial trend. (2) Different sub-industries had obvious differences in their agglomeration and diffusion trends. The proliferation trend of the non-metallic mineral products industry and the agricultural and sideline foodstuffs processing industry were obvious, which made environmental management difficult. The manufacture of raw chemical materials and chemical products presented the trend of agglomeration, then diffusion, followed by agglomeration, and transferred to areas outside the urban agglomeration, which reduced the pollution to the environment to a certain extent. The spatial pattern of the electricity, heating power production and supply industry were relatively stable, with little overall change. (3) The spatial layout of pollution-intensive industries was mostly driven by the level of economic development and the degree of industrial agglomeration. Innovation capacity and labor cost promoted the spatial diffusion of industries, and the degree of trade openness intensified the agglomeration of pollution-intensive industries in space. The results of the study provided a more microscopic perspective for understanding the changes in the spatial pattern of pollution-intensive industries and served as a reference for the government to formulate industrial and environmental policies.

Distinctly Different Dynamical Processes in Maintaining the Intraseasonal NAO+ and NAO−

AbstractPositive feedback between high‐frequency eddies and low‐frequency processes is believed to play an essential role in the NAO evolution. In this study, however, it is found that the previously well‐studied upscale forcing to the intraseasonal scale window is mostly limited during the phase NAO−, but almost disappears during NAO+. The maintenance of the intraseasonal NAO+ is by a strong barotropic instability of the basic flow, which has been overlooked previously. The divergence of the Reynolds stress tensor that decelerates the basic flow is found to account for this asymmetry. For NAO−, there also exist strong interactions between the basic flow and the intraseasonal component, but the energy transfer is in a dipolar form, which, if integrated over space, contributes insignificantly as a whole. These new findings from a dynamics viewpoint shed insight deeper into NAO, a climate mode playing a key role in the Northern Hemisphere warming.

A hyper-parameterization method for comprehensive ocean models: Advection of the image point

Idealized and comprehensive ocean models at low resolutions cannot reproduce nominally-resolved flow structures similar to those presented in the high-resolution solution. Although there are various underlying physical reasons for this, from the dynamical system point of view all these reasons manifest themselves as a low-resolution trajectory avoiding the phase space occupied by the reference solution (the high-resolution solution projected onto the coarse grid). In order to solve this problem, a set of hyper-parameterization methods has recently been proposed and successfully tested on idealized ocean models. In this work, for the first time we apply one of hyper-parameterization methods (Advection of the image point) to a comprehensive, rather than idealized, general circulation model of the North Atlantic.The results show that the hyper-parameterization method significantly outperforms the coarse-grid ocean model by reproducing both the large- and small-scale features of the Gulf Stream flow. The proposed method is much faster than even a single run of the coarse-grid ocean model, requires no modification of the model, and is easy to implement. Moreover, the method can take not only the reference solution as input data but also real measurements from different sources (drifters, weather stations, etc.), or combination of both. All this offers a great flexibility to ocean modellers working with mathematical models and/or measurements.

Interfacial Hole-Charge-Transfer Dynamics in Organic Solar Cells: A Dynamic Viewpoint

The energy loss of hole-charge transfer in nonfullerene-acceptor (NFA) organic solar cells has been significantly reduced by minimizing their interfacial energy offset to near-zero and negative values. However, the physical mechanism of highly efficient hole-charge transfer in these conditions has not been fully addressed. In this work, we theoretically clarify that a moving hole charge along the polymer-donor and NFA interface, generated from the spontaneous dissociation of NFA molecular excited states, tends to transfer from NFA molecules to polymer-donor to keep moving, even their interfacial energy offset is chosen as a negative value. This dynamic viewpoint revises the conventional static viewpoint about the dependence of hole-charge transfer upon the interfacial energy offset. In addition, considering the polaron effect in organic molecules with a hole charge generated, we redefine the interfacial energy offset and further consider the effects of the NFA molecular electron-lattice interaction and lattice elastic constant on the hole-charge transfer.

Stability in mechanics and dynamics; a brief historical tour from Newton to modern tools, including Riemannian structures and entropy

AbstractThis article presents some historical developments in the theory of stability in mechanics from a dynamical systems point of view, focusing on mathematical methods from the earliest developments (Newton) and explaining some classical and some recent methods used, including Riemannian structures, entropy and notions of stability in dynamics.

A review of symbolic dynamics and symbolic reconstruction of dynamical systems

Discretizing a nonlinear time series enables us to calculate its statistics fast and rigorously. Before the turn of the century, the approach using partitions was dominant. In the last two decades, discretization via permutations has been developed to a powerful methodology, while recurrence plots have recently begun to be recognized as a method of discretization. In the meantime, horizontal visibility graphs have also been proposed to discretize time series. In this review, we summarize these methods and compare them from the viewpoint of symbolic dynamics, which is the right framework to study the symbolic representation of nonlinear time series and the inverse process: the symbolic reconstruction of dynamical systems. As we will show, symbolic dynamics is currently a very active research field with interesting applications.

Two-dimensional T[formula omitted]-phase MA[formula omitted]N[formula omitted] (M=Mo/W, A=Si/Ge) nanosheets: First-principles insights into the structural stability, electronic property and catalytic performance for hydrogen evolution reaction

For the emerging MA2Z4 materials, most researches focus on their perfect trigonal-prismatic (H-phase) and octahedral (T-phase) geometries, while the distorted octahedral (T′-phase) one is rarely studied. In this work, we perform a first-principles study on the T′-phase MA2N4 (M=Mo/W, A=Si/Ge) nanosheets to investigate their structural, mechanical, electronic and catalytic properties. As a metastable phase, the T′-MA2N4 nanosheets still possess sufficient stability from the energetic, dynamical, thermal and mechanical points of view. Unlike the semiconducting H-phase counterparts, the T′-MA2N4 nanosheets display a semimetallic or metallic behaviour depending on the lattice constants. Interestingly, these T′-MA2N4 nanosheets exhibit highly efficient catalytic performance for hydrogen evolution reaction (HER). The Gibbs free energy of hydrogen adsorption on the T′-MoGe2N4 nanosheet is close to zero, which is even superior to the well-known Pt catalyst. Furthermore, all the surface N atoms behave as active sites, giving rise to excellent basal HER activity. For these MA2N4 systems, the T′-phase will become more favourable than the H-phase via a combined effect of electron injection and tensile strain. Our study demonstrates that the T′-phase MA2N4 nanosheets possess peculiar electronic properties and promising HER activity, opening up potential applications in nano-devices and renewable energy.