Inter-system Coupling Research Articles

Hydrodynamization in hybrid Bjorken flow attractors

Hybrid fluid models, consisting of two sectors with more weakly and more strongly self-interacting degrees of freedom coupled consistently as in the semi-holographic framework, have been shown to exhibit an attractor surface for Bjorken flow. Retaining only the simple viscid fluid descriptions of both sectors, we find that, on the attractor surface, the hydrodynamization times of both subsectors decrease with increasing total energy density at the respective point of hydrodynamization following a conformal scaling, reach their minimum values, and subsequently rise rapidly. The minimum values are obtained when the respective energy densities are of the order of the inverse of the dimensionful inter-system coupling. Restricting to attractor curves which can be matched to glasma models at a time set by the saturation scale for both p-p and Pb-Pb collisions, we find that the more weakly coupled sector hydrodynamizes much later, and the strongly coupled sector hydrodynamizes earlier in p-p collisions, since the total energy densities at the respective hydrodynamization times of these sectors fall inside and outside of the conformal window. This holds true also for phenomenologically relevant solutions that are significantly away from the attractor surface at the time we match to glasma models.

Robustness assessment of weakly coupled cyber-physical power systems under multi-stage attacks

Evaluating the robustness of cyber-physical system (CPS) under multi-stage attacks is fundamental to enhancing CPS resilience. Currently, many models inadequately consider information flow, which is not aligned with reality. The initial focus of this paper is on introducing a weakly coupled interdependent model for CPS. This model considers probabilistic line outage rules, cyber flow transmission characteristics, and the probabilities of inter-system coupling failures. Subsequently, the multi-stage attack strategies are presented and employed by the proposed model during disaster scenarios, along with the proposed robustness assessment indicators. The numerical results illustrate the robustness of the weakly-coupled CPS model under multi-stage attacks. This lays a modeling and simulation foundation for repair crew to enhance the CPS resilience.

Exploration of Urban Subsystem Coupling Coordination Based on Resilience in Luohe City

With urbanization, the uncertainties faced by urban areas continue to increase, and in response, China's urban planning is transitioning from a focus on quantity to quality. Promoting system coupling and coordination helps to make urban areas more resilient to risk. This paper uses data from Luohe City (China) in 2022 as an example to calculate the inter-system coupling coordination degree (CCD), find the factors that obstruct resilience construction, and further explore the spatial heterogeneity of the obstacle factors. The synthetic evaluation model, coupling evaluation model, and obstacle diagnosis model are used to evaluate and analyze each subsystem. The results are as follows: According to the synthetic evaluation, the mean urban development value is 0.48, with high-value regions clustered in the Southeastern built-up zone. Mean value of urban coupling coordination is 0.66, the coordination level is 7 (Moderate Coordination). Urban development degree is positively correlated with CCD. Globally, the economy is the main factor obstructing resilient growth, but the core obstacle areas of the ecosystem are larger and have a wider impact. This study contributes to understanding the internal action of urban systems and provides data for balance development and urban resilience enhancement.

Effect of Inter-System Coupling on Heat Transport in a Microscopic Collision Model

In this paper we consider a bipartite system composed of two subsystems each coupled to its own thermal environment. Based on a collision model, we mainly study whether the approximation (i.e., the inter-system coupling is ignored when modeling the system–environment interaction) is valid or not. We also address the problem of heat transport unitedly for both excitation-conserving system–environment interactions and non-excitation-conserving system–environment interactions. For the former interaction, as the inter-system interaction strength increases, at first this approximation gets worse as expected, but then counter-intuitively gets better even for a stronger inter-system coupling. For the latter interaction with asymmetry, this approximation gets progressively worse. In this case we realize a perfect thermal rectification, and we cannot find an apparent rectification effect for the former interaction. Finally and more importantly, our results show that whether this approximation is valid or not is closely related to the quantum correlations between the subsystems, i.e., the weaker the quantum correlations, the more justified the approximation and vice versa.

Local versus global master equation with common and separate baths: superiority of the global approach in partial secular approximation

Open systems of coupled qubits are ubiquitous in quantum physics. Finding a suitable master equation to describe their dynamics is therefore a crucial task that must be addressed with utmost attention. In the recent past, many efforts have been made toward the possibility of employing local master equations, which compute the interaction with the environment neglecting the direct coupling between the qubits, and for this reason may be easier to solve. Here, we provide a detailed derivation of the Markovian master equation for two coupled qubits interacting with common and separate baths, considering pure dephasing as well as dissipation. Then, we explore the differences between the local and global master equation, showing that they intrinsically depend on the way we apply the secular approximation. Our results prove that the global approach with partial secular approximation always provides the most accurate choice for the master equation when Born–Markov approximations hold, even for small inter-system coupling constants. Using different master equations we compute the stationary heat current between two separate baths, the entanglement dynamics generated by a common bath, and the emergence of spontaneous synchronization, showing the importance of the accurate choice of approach.

Corner states in a second-order acoustic topological insulator as bound states in the continuum

A second-order topological insulator is designed on a platform of a two-dimensional (2D) square lattice with all coupling coefficients having the same sign. Simulated results show the existence of two types of nontrivial corner states in this system, with one type being identified as bound states in the continuum (BIC). The non-BIC corner states are also found by surrounding a nontrivial sample by a trivial one, and interestingly, these perfectly confined corner states can be gradually delocalized and merge into edge states by tuning the intersystem coupling coefficient. Both BIC and non-BIC corner states originate from bulk dipole moments rather than quantized quadrupole moments, with the corresponding topological invariant being the 2D Zak phase. Full wave simulations based on realistic acoustic waveguide structures are demonstrated. Our proposal provides an experimentally feasible platform for the study of the interplay between BIC and a high-order topological insulator, and the evolution from corner states to edge states.

Putting the "dynamic" back into dynamic functional connectivity.

The study of fluctuations in time-resolved functional connectivity is a topic of substantial current interest. As the term “dynamic functional connectivity” implies, such fluctuations are believed to arise from dynamics in the neuronal systems generating these signals. While considerable activity currently attends to methodological and statistical issues regarding dynamic functional connectivity, less attention has been paid toward its candidate causes. Here, we review candidate scenarios for dynamic (functional) connectivity that arise in dynamical systems with two or more subsystems; generalized synchronization, itinerancy (a form of metastability), and multistability. Each of these scenarios arises under different configurations of local dynamics and intersystem coupling: We show how they generate time series data with nonlinear and/or nonstationary multivariate statistics. The key issue is that time series generated by coupled nonlinear systems contain a richer temporal structure than matched multivariate (linear) stochastic processes. In turn, this temporal structure yields many of the phenomena proposed as important to large-scale communication and computation in the brain, such as phase-amplitude coupling, complexity, and flexibility. The code for simulating these dynamics is available in a freeware software platform, the Brain Dynamics Toolbox.

Dynamical Pattern Representation of Cardiovascular Couplings Evoked by Head-up Tilt Test.

Shannon entropy (ShE) is a recognised tool for the quantization of the temporal organization of time series. Transfer entropy (TE) provides insight into the dependence between coupled systems. Here, signals are analysed that were produced by the cardiovascular system when a healthy human underwent a provocation test using the head-up tilt (HUT) protocol. The information provided by ShE and TE is evaluated from two aspects: that of the algorithmic stability and that of the recognised physiology of the cardiovascular response to the HUT test. To address both of these aspects, two types of symbolization of three-element subsequent values of a signal are considered: one, well established in heart rate research, referring to the variability in a signal, and a novel one, revealing primarily the dynamical trends. The interpretation of ShE shows a strong dependence on the method that was used in signal pre-processing. In particular, results obtained from normalized signals turn out to be less conclusive than results obtained from non-normalized signals. Systematic investigations based on surrogate data tests are employed to discriminate between genuine properties—in particular inter-system coupling—and random, incidental fluctuations. These properties appear to determine the occurrence of a high percentage of zero values of TE, which strongly limits the reliability of the couplings measured. Nevertheless, supported by statistical corroboration, we identify distinct timings when: (i) evoking cardiac impact on the vascular system, and (ii) evoking vascular impact on the cardiac system, within both the principal sub-systems of the baroreflex loop.

Markovian master equations for quantum thermal machines: local versus global approach

The study of quantum thermal machines, and more generally of open quantum systems, often relies on master equations. Two approaches are mainly followed. On the one hand, there is the widely used, but often criticized, local approach, where machine sub-systems locally couple to thermal baths. On the other hand, in the more established global approach, thermal baths couple to global degrees of freedom of the machine. There has been debate as to which of these two conceptually different approaches should be used in situations out of thermal equilibrium. Here we compare the local and global approaches against an exact solution for a particular class of thermal machines. We consider thermodynamically relevant observables, such as heat currents, as well as the quantum state of the machine. Our results show that the use of a local master equation is generally well justified. In particular, for weak inter-system coupling, the local approach agrees with the exact solution, whereas the global approach fails for non-equilibrium situations. For intermediate coupling, the local and the global approach both agree with the exact solution and for strong coupling, the global approach is preferable. These results are backed by detailed derivations of the regimes of validity for the respective approaches.

Bath-induced coherence and the secular approximation

Finding efficient descriptions of how an environment affects a collection of discrete quantum systems would lead to new insights into many areas of modern physics. Markovian, or time-local, methods work well for individual systems, but for groups a question arises: Does system-bath or intersystem coupling dominate the dissipative dynamics? The answer has profound consequences for the long-time quantum correlations within the system. We consider two bosonic modes coupled to a bath. By comparing an exact solution against different Markovian master equations, we find that a smooth crossover of the equations of motion between dominant intersystem and system-bath coupling exists---but it requires a nonsecular master equation. We predict singular behavior of the dynamics and show that the ultimate failure of nonsecular equations of motion is essentially a failure of the Markov approximation. Our findings support the use of time-local theories throughout the crossover between system-bath-dominated and intersystem-coupling-dominated dynamics.

Integrated application of hospital information based on enterprise service bus

The present hospital information systems are analyzed,with finding that hospital information isolated island phenomenon getting worse due to failure of interconnection of various systems and equipment vendors with different technologies.An integrated platform based on an enterprise service bus is proposed for hospital information,which can be connected into these heterogeneous systems,effectively minimizing the inter-system coupling,and achieving data and service interconnection,enabling an integrated and intelligent hospital architecture. Key words: Hospital informationization; Isolated island; System integration; Enterprise service bus

Entanglement entropy of coupled conformal field theories and Fermi liquids

In this paper, we calculate the entanglement R\'enyi entropy of two coupled gapless systems in general spatial dimension $d$. The gapless systems can be either conformal field theories or Fermi liquids. We assume the two systems are coupled uniformly in an $h$-dimensional submanifold of the space, with $0\ensuremath{\le}h\ensuremath{\le}d$. We will focus on the scaling of the R\'enyi entropy with the size of the system, and its scaling with the intersystem coupling constant $g$. Three approaches will be used for our calculation: (1) exact calculation with ground-state wave functional, (2) perturbative calculation with functional path integral, and (3) scaling argument.

Identifying topology of general dynamical networks from noisy data

The reverse engineering problem of identifying the topology of dynamical networks withtime varying intersystem coupling delays from noisy observation data is treated in thispaper. A three-stage approach is adopted to solve this identification problem: first,feedback control is applied to the network and it is driven to its equilibrium state; then, theinformation obtained from the observed steady state responses is explored and theidentification problem is converted into a mixed integer optimization problem; finally, aninference algorithm is applied to obtain all elements of the connectivity matrix.Several dynamical network examples are provided for illustration. Identificationresults show that the proposed method is robust to noise and computationallyefficient.

Antiferromagnetic exchange in two-leg spin-1/2 ladders.

Extraction of antiferromagnetic (AF) exchange constants J and J\ensuremath{'} in two-leg spin-1/2 nearest-neighbor (NN) Heisenberg ladders from experimental magnetic spin susceptibility \ensuremath{\chi}(T) data is studied, where J\ensuremath{'} is the NN exchange constant in the rungs and J is that in the legs. Two low-T (T\ensuremath{\ll}J/${\mathit{k}}_{\mathit{B}}$) approximations of Troyer, Tsunetsugu, and W\"urtz [Phys. Rev. B 50, 13 515 (1994)] for \ensuremath{\chi}(T) of the isolated spin-1/2 two-leg ladder with J\ensuremath{'}/J=1 are shown to be accurate to \ensuremath{\sim}10% when extrapolated to T\ensuremath{\sim}J\ensuremath{'}/${\mathit{k}}_{\mathit{B}}$. The variations in the magnetic excitation dispersion relation parameters [which enter the low-T expression of Troyer et al. for \ensuremath{\chi}(T)] for J\ensuremath{'}/J1 are inferred from previous theoretical results. Next, the values of the maxima in \ensuremath{\chi}(T)\ensuremath{\equiv}${\mathrm{\ensuremath{\chi}}}^{\mathrm{max}}$ from many numerical calculations in the literature for various nonfrustrated spin-1/2 NN Heisenberg antiferromagnets are considered. The values of the product ${\mathrm{\ensuremath{\chi}}}^{\mathrm{max}}$${\mathit{z}}_{\mathrm{eff}}$ are found to depend systematically and almost uniqely on an effective magnetic coordination number ${\mathit{z}}_{\mathrm{eff}}$, defined in the text, but are nearly independent of the dimensionality of the spin lattice and of the magnitude of any gap in the magnetic excitation spectrum. This observation allows accurate bounds on the exchange coupling constants in arbitrary quasi-low-dimensional spin-1/2 antiferromagnets to be inferred from experimental ${\mathrm{\ensuremath{\chi}}}^{\mathrm{max}}$ values. Finally, a mean-field-type expression for \ensuremath{\chi}(T) for arbitrary quasi-low-dimensional spin-1/2 Heisenberg antiferromagnets is derived, using the above ${\mathrm{\ensuremath{\chi}}}^{\mathrm{max}}$ phenomenology as input, which allows the influence of intersystem coupling on \ensuremath{\chi}(T) to be evaluated. These results, and the \ensuremath{\chi}(T) calculations of Barnes and Riera [Phys. Rev. B 50, 6817 (1994)] for isolated two-leg spin-1/2 Heisenberg ladders, are used to analyze the experimental \ensuremath{\chi}(T) data of Azuma et al. [Phys. Rev. Lett. 73, 3463 (1994)] for the spin-1/2 two-leg ladder compound ${\mathrm{SrCu}}_{2}$${\mathrm{O}}_{3}$. The analyses together suggest that J\ensuremath{'}/J\ensuremath{\sim}0.5, contrary to the expectation that J\ensuremath{'}/J\ensuremath{\approxeq}1, and that J is very large (\ensuremath{\sim}2000 K), similar to the value of J in the linear-chain cuprate ${\mathrm{Sr}}_{2}$${\mathrm{CuO}}_{3}$. \textcopyright{} 1996 The American Physical Society.

On coupling many small systems for transaction processing

The prospect of coupling a large number of small inexpensive microprocessor based systems to deliver the performance of a large transaction processing system at lower cost has not been realized, to date. Inter-system interference, multi-system coupling protocol overhead and the increased processing time for smaller systems can cause considerable degradation. A methodology is developed to determine the number of processors needed to satisfy transaction throughput and response time requirements for processors of different MIPS (sizes). The minimum MIPS per processor required to satisfy response time, throughput and utilization constraints in a transaction processing complex of N coupled systems is also determined, by using an approximate analytical model driven by measured workload parameters. Despite large assumed cost advantages on a per MIPS basis we find that small systems do not match up to the cost/performance of some larger systems. Besides multi-system's coupling degradation, there is a small system effect. Because of the increased transaction execution time in smaller systems, transaction hold on to resources longer, thereby causing increased inter-system interference. Our cost criterion indicates that there is an optimum processor size below which total system costs would increase appreciably. Ways to reduce the inter-system interference and coupling protocol overheads are investigated and shown to shift this optimum.

Role of Larger Herbivores in Seagrass Communities

The nutritional ecology of macroherbivores in seagrass meadows and the roles of grazing by urchins, fishes and green turtles in tropical systems and waterfowl in temperate systems are discussed in this review. Only a few species of animals graze on living seagrasses, and apparently only a small portion of the energy and nutrients in seagrasses is usually channeled through these herbivores. The general paucity of direct seagrass grazers may be a function of several factors in the composition of seagrasses, including availability of nitrogen compounds, presence of relatively high amounts of structural cell walls, and presence of toxic or inhibitory substances. The macroherbivores, however, can have a profound effect on the seagrass plants, on other grazers and fauna associated with the meadow, and on chemical and decompositional processes occurring within the meadow. Grazing can alter the nutrient content and digestibility of the plant, as well as its productivity. Removal of leaf material can influence interrelations among permanent and transient faunal residents. Grazing also interrupts the detritus cycle. Possible consequences of this disruption, either through acceleration or through decreased source input, and the enhancement of intersystem coupling by increased export and offsite fecal production, are discussed. The extent and magnitude of these effects and their ecological significance in the overall functioning of seagrass meadows only can be speculated, and probably are not uniform or of similar importance in both tropical and temperate seagrass systems. However, areas grazed by large herbivores provide natural experiments in which to test hypotheses on many functional relations in seagrass meadows.

Electron paramagnetic resonance in exchange-coupled systems with unlike spins. II. The intermediate-coupling regime

We analyze the transverse dynamic magnetic susceptibility of an isotropic exchange-coupled system with unlike spins in a uniform external field. An approximate theory for the susceptibility is developed which interpolates between results obtained previously in the limits of strong and weak intersystem coupling. The expression for the susceptibility involves both thermodynamic and relaxation parameters, both of which are shown to be related to various spin-spin correlation functions. When the equal-time correlation functions are evaluated by treating the intersystem interactions in the molecular-field approximation, the resulting expression for the susceptibility is equivalent in form to that obtained from Bloch equations derived by Barnes and Zitcova-Wilcox in their analysis of the resonance of magnetic impurities in metallic hosts.

ChemInform Abstract: SINGLET‐TRIPLET INTERSYSTEM COUPLING IN FORMALDEHYDE

Chemischer InformationsdienstVolume 6, Issue 1 Physical Organic Chemistry ChemInform Abstract: SINGLET-TRIPLET INTERSYSTEM COUPLING IN FORMALDEHYDE J. C. D. BRAND, J. C. D. BRANDSearch for more papers by this authorD. S. LIU, D. S. LIUSearch for more papers by this author J. C. D. BRAND, J. C. D. BRANDSearch for more papers by this authorD. S. LIU, D. S. LIUSearch for more papers by this author First published: January 7, 1975 https://doi.org/10.1002/chin.197501054AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume6, Issue1January 7, 1975 RelatedInformation

System identification in large scale systems with hierarchical structures

Due to its systems control orientation, the theory of multilevel hierarchical control developed by Mesarovic and others appears especially promising for identification and modeling of large scale systems consisting of relatively independent subsystems with strong and weak intersystem coupling. Standard techniques of optimum systems control and estimation theory may be used to resolve system problems described in this format. Determination of system structure and identification of system parameters form an inherent part of this procedure. To achieve advantages by hierarchical system concepts, it is necessary to decompose a large scale system into a number of smaller parts in such a manner that individual subsystem estimation, identification and control is feasible and to coordinate the subsystems in order to obtain the overall system goal. While decomposition is in theory easy, in practice it must be accomplished such that subsystem structure preserves constraints, information structures and acceptable authority structures. The success of coordination will thus, in practice, be affected by the particular system decomposition chosen. This paper presents the results of an investigation of system identification, using the maximum a posteriori criterion, of system parameters within a hierarchical structure. Examples demonstrate the use of the system identification algorithms.

On stochastic control system design methods for weakly coupled large scale linear systems

Abstract : The paper considers the problem of decentralized control of two weakly coupled linear stochastic systems, using quadratic performance indices. The basic idea is to have each controller control independently his own system, based upon noisy measurements of his own output. To compensate for the effects of weak coupling upon the resultant performance, fake white plant noise is introduced to each system. The appropriate intensity of the fake plant noise is obtained through the solution of an offline deterministic matrix optimal control problem. The effects of this design method upon the overall system performance are analyzed as a function of the degree of intersystem coupling. (Author)