Homogeneous Coupling Research Articles

Ensemble learning for predicting average thermal extraction load of a hydrothermal geothermal field: A case study in Guanzhong Basin, China

Accurate prediction of the average thermal extraction load (ATEL) in hydrothermal heating systems optimizes energy recovery, though numerical models are constrained by modeling accuracy and computational time costs. Data-driven modeling can efficiently screen alternative production plans and enhance daily operational decisions. However, ensemble learning applications for forecasting ATEL lack comprehensive comparisons and appropriate algorithm selection. This study evaluates six ensemble learning algorithms: random forest (RF), adaptive boosting (AdaBoost), gradient boosting decision trees (GBDT), extreme gradient boosting (XGBoost), light gradient boosting machine (LightBGM) and categorical boosting (CatBoost) on 1159 data points from a homogeneous thermal-hydraulic coupling numerical model. The superior performance of the CatBoost is characterized by the highest accuracy (with the lowest root mean square error (RMSE) of 150.6 kW–170.7 kW, minimal mean absolute percentage error (MAPE) of 0.66%–0.73%, and exceptional R2 values of 0.999), commendable stability, reasonable computational cost and low uncertainty. LightGBM, XGBoost, and GBDT are identified as suitable substitutes, whereas RF is a possible substitute. Moreover, the production rate is identified as the most significant factor contributing to the ATEL, followed by the well spacing and injection temperature. While perforation depth has the least influence on heat recovery.

Precise synthesis of conjugated polymers via a scalable and homogeneous room-temperature Suzuki-Miyaura coupling

Precise synthesis of conjugated polymers via a scalable and homogeneous room-temperature Suzuki-Miyaura coupling

An experimental and modeling study on homogeneous oxidative coupling of methane utilizing N2O as oxidant

Experimental and kinetic modeling studies were performed to investigate the homogeneous oxidative coupling of methane utilizing nitrous oxide as the oxidant (N2O-OCM). The experiments were performed in a jet stirred reactor at atmospheric pressure and temperatures of 773–1173 K. Synchrotron vacuum ultraviolet photoionization mass spectrometry was used to achieve comprehensive and isomer-resolved identification of major products and nitrogenous, carbonyl and hydrocarbon intermediates. To interpret the experiments, a detailed kinetic model was developed by extending the widely used hydrocarbon growth mechanisms. Rate of production and sensitivity analyses were performed to provide a deep insight into the complex reaction network. The results demonstrate that N2O dissociation is the rate-controlling step, and the mild oxidation of N2O effectively reduces the production of CO2 as byproduct and meanwhile improves the selectivity of C2 species. In the presence of N2O, CH3 can actively participates in H-abstraction reactions of C2H6 and C2H4, besides the self-coupling reactions. Due to chain-propagation competition reactions (N2O+H=N2+OH and N2O+H=NH+NO), NH3 and NO exhibit low concentrations. The detailed formation pathways for NH3 and NO were elaborated, and the evolution routes of carbonyl intermediates in the presence of N2O were analyzed. Benzene formation is found mainly through C3 self-recombination and C5 ring reforming reactions. Finally, comparative analysis with O2-OCM reveals that the presence of oxygen promotes the conversion of CH3 to CH2O and deep oxidation of C2H3, explaining the lower C2 yield of O2-OCM. The inherent limitation of the C2 yield of N2O-OCM primarily arises from the reaction of C2H4 and O, as well as the subsequent reaction CH2(S)+N2O=CH2O+N2. The experiment observations confirmed the existence of C2 carbonyl intermediates such as ketene and acetaldehyde. The study highlights the notable role of O2 molecular and O atoms in the homogeneous OCM and offers kinetic support for the OCM reaction process with catalysts.

Bipartite leaderless synchronization of fractional-order coupled neural networks via edge-based adaptive pinning control

This paper introduces the signed graph into fractional-order coupled neural networks (FCNNs) and the bipartite synchronization is investigated for leaderless FCNNs. Instead of formulating leader’s state or isolated node’s state as the synchronization reference target, the bipartite synchronization of leaderless FCNNs is discussed by developing a direct error approach. First, an important fractional-order inequality is rigorously proved by contradiction. By virtue of fractional-order inequality, gauge transformation and several analytical tools, the criteria of bipartite leaderless synchronization are obtained for FCNNs with heterogeneous and homogeneous coupling weights. Specially, for the two types coupling weights, the adaptive pinning schemes are adopted which just rely on partial network information based on the spanning tree and connected dominating set, respectively. Eventually, the theoretical analysis is verified by two numerical simulations.

Using coupling imperfection to control amplitude death.

Previous studies of nonlinear oscillator networks have shown that amplitude death (AD) occurs after tuning oscillator parameters and coupling properties. Here, we identify regimes where the opposite occurs and show that a local defect (or impurity) in network connectivity leads to AD suppression in situations where identically coupled oscillators cannot. The critical impurity strength value leading to oscillation restoration is an explicit function of network size and system parameters. In contrast to homogeneous coupling, network size plays a crucial role in reducing this critical value. This behavior can be traced back to the steady-state destabilization through a Hopf's bifurcation, which occurs for impurity strengths below this threshold. This effect is illustrated across different mean-field coupled networks and is supported by simulations and theoretical analysis. Since local inhomogeneities are ubiquitous and often unavoidable, such imperfections can be an unexpected source of oscillation control.

The Effects of Viscosity and Capillarity on Nonequilibrium Distribution of Gas Bubbles in Swelling Liquid–Gas Solution

A detailed statistical description of the evolution of supersaturated-by-gas solution at degassing has been presented on the basis of finding the time-dependent distribution in radii of overcritical gas bubbles. The influence of solution viscosity and capillarity via internal pressure in the bubbles on this distribution has been considered until the moment when the gas supersaturation drops due to depletion and stops nucleation of new overcritical gas bubbles. This study is based on our previous results for the nonstationary growth rates of overcritical bubbles depending on gas supersaturation, diffusivity and solubility in solution, solution viscosity, and surface tension on bubble surface. Other important factors are linked with the initial rate of homogeneous gas bubble nucleation and coupling between diffusivity and viscosity in the solution. Here, we numerically studied how all these factors affect the time-dependent distribution function of overcritical bubbles in their radii, maximal and mean bubble radii, and the time-dependent swelling ratio of a supersaturated-by-gas solution in a wide range of solution viscosities.

Mechanistic Views on the Manganese Catalyzed Homogeneous Coupling Reactions

Abstract: The transition metal-catalyzed C-C and C-X (X=heteroatom) homo and crosscoupling reactions were pioneered as a momentous strategy for the total synthesis of natural products, agrochemicals, pharmaceuticals, etc. Among the various transition metal-catalyzed reactions, manganese catalysis held a distinctive identity owing to its earth-abundance and eco-friendliness apart from its unique characteristics. Despite having many synthetic advancements, exploiting manganese as a catalyst for coupling reactions has recently gained pivotal gravity. An in-depth comprehension of the molecular mechanism of the chemical reaction will provide further insight to optimize the reaction conditions. The mechanisms adopted by Mn-catalyzed couplings are found to differ from other first-row transition metal counterparts. Hence in this article, we provide the state-of-the-art on the detailed theoretical aspects of manganese-catalyzed carbon-carbon (C-C) and carbon-heteroatom (C-X; X=Si) coupling reactions.

Editorial for the special issue “Control‐theoretic approaches for systems in the life sciences”

Editorial for the special issue “Control<scp>‐theoretic</scp> approaches for systems in the life sciences”

Synchronization dynamics of phase oscillators with generic adaptive coupling

Adaptive coupling schemes among interacting elements are ubiquitous in real systems ranging from physics and chemistry to neuroscience and have attracted much attention in recent years. Here, we extend the Kuramoto model by considering a particular adaptive scheme in a system of globally coupled oscillators. The homogeneous coupling is correlated with the global coherence of the population that is weighted by the generic nonlinear feedback function of the amplitude of the order parameter. The studied model is analytically tractable that generalizes the theory of Kuramoto for synchronization transition. We develop a mean-field theory by establishing the self-consistent equation describing the stationary dynamics in the thermodynamic limit. Importantly, the Landau damping effect, which turns out to be far more generic, is revealed in the framework of the linear stability analysis of the resonant pole theory. Furthermore, the relaxation rate of the order parameter in the subcritical region is obtained from a universal formula. Our study can deepen the understanding of synchronization transitions and other related collective dynamics in networked oscillators with adaptive interaction schemes.

Relaxation dynamics of phase oscillators with generic heterogeneous coupling.

The coupled phase oscillator model serves as a paradigm that has been successfully used to shed light on the collective dynamics occurring in large ensembles of interacting units. It was widely known that the system experiences a continuous (second-order) phase transition to synchronization by gradually increasing the homogeneous coupling among the oscillators. As the interest in exploring synchronized dynamics continues to grow, the heterogeneous patterns between phase oscillators have received ample attention during the past years. Here, we consider a variant of the Kuramoto model with quenched disorder in their natural frequencies and coupling. Correlating these two types of heterogeneity via a generic weighted function, we systematically investigate the impacts of the heterogeneous strategies, the correlation function, and the natural frequency distribution on the emergent dynamics. Importantly, we develop an analytical treatment for capturing the essential dynamical properties of the equilibrium states. In particular, we uncover that the critical threshold corresponding to the onset of synchronization is unaffected by the location of the inhomogeneity, which, however, does depend crucially on the value of the correlation function at its center. Furthermore, we reveal that the relaxation dynamics of the incoherent state featuring the responses to external perturbations is significantly shaped by all the considered effects, thereby leading to various decaying mechanisms of the order parameters in the subcritical region. Moreover, we untangle that synchronization is facilitated by the out-coupling strategy in the supercritical region. Our study is a step forward in highlighting the potential importance of the inhomogeneous patterns involved in the complex systems, and could thus provide theoretical insights for profoundly understanding the generic statistical mechanical properties of the steady states toward synchronization.

How clock heterogeneity affects synchronization and can enhance stability.

The production process of integrated electronic circuitry inherently leads to large heterogeneities on the component level. For electronic clock networks this implies detuned intrinsic frequencies and differences in coupling strength and the characteristic time delays associated with signal transmission, processing, and feedback. Using a phase-model description, we study the effects of such component heterogeneity on the dynamical properties of synchronization in networks of mutually delay-coupled Kuramoto oscillators. We test the theory against experimental results and circuit-level simulations in a prototype system of mutually delay-coupled electronic clocks, so-called phase-locked loops. Interestingly, our results show that heterogeneity in the system can actually enhance the stability of synchronized states. That means that beyond the optimizations that can be achieved by tuning homogeneous coupling strengths, time delays, and loop-filter cut-off frequencies, heterogeneities in these system parameters enable much better optimization of perturbation decay rates, stabilization of synchronous states, and tuning of phase differences between the clocks. Our theory enables the design of custom-fit synchronization layers according to the specific requirements and properties of electronic systems, such as operational frequencies, phase relations, and, e.g., transmission delays. These results are not restricted to electronic systems, because signal transmission, processing, and feedback delays are common to networks of spatially distributed and coupled autonomous oscillators.

Reduced transfer operators for singular difference equations

For tridiagonal block Jacobi operators, the standard transfer operator techniques only work if the off-diagonal entries are invertible. Under suitable assumptions on the range and kernel of these off-diagonal operators which assure a homogeneous minimal coupling between the blocks, it is shown how to construct reduced transfer operators that have the usual Krein space unitarity property and also a crucial monotonicity in the energy variable. This allows to extend the results of oscillation theory to such systems.

Synchronization dynamics of phase oscillator populations with generalized heterogeneous coupling

The Kuramoto model, serving as a paradigmatic tool, has been used to shed light on the collective behaviors in large ensembles of coupled dynamic agents. It is well known that the model displays a second-order(continuous) phase transition towards synchrony by increasing the homogeneous(uniform) global coupling strength. Recently, there is a great interest in investigating the effects of the heterogeneous patterns on the collective dynamics of coupled oscillator systems. Here, we consider a generalized Kuramoto model of globally coupled phase oscillators with quenched disorder in their natural frequencies and coupling strength. By correlating these two types of inhomogeneity, we systematically explore the impacts of heterogeneous structure, the correlation exponent, and the intrinsic frequency distribution on the synchronized dynamics. We develop an analytic framework for capturing the essential dynamic properties involved in synchronization transition. In particular, we demonstrate that the forward critical threshold describing the onset of synchronization is unaffected by the location of heterogeneity, which, however, does depend crucially on the correlation exponent and the form of frequency distribution. Furthermore, we reveal that the backward critical points featuring the desynchronization transition are significantly shaped by all the considered effects, thereby enhancing or weakening the ability of synchronization transition (bifurcation). Our investigation is a step forward in highlighting the importance of heterogeneous pattern presented in the complex systems, and could, thus, provide significant insights for designing the strategy of inducing and controlling synchronization.

Rotational state specific dissociation dynamics of D2O via the C̃(010) state: The effect of bending vibrational excitation.

The rotational state resolved photodissociation dynamics of D2O via the C̃(010) state has been investigated by using the D-atom Rydberg tagging time-of-flight technique combined with a tunable vacuum ultraviolet light source. The D-atom action spectrum of the C̃(010) ← X̃(000) band and the corresponding time-of-flight (TOF) spectra of D-atom photoproducts formed following the excitation of D2O to individual rotational transition have been measured. By comparison with the action spectrum of the C̃(000) ← X̃(000) band, the bending vibrational constant of the C̃ state for D2O can be determined to be v2 = 1041.37 ± 0.71cm-1. From the TOF spectra, the product kinetic energy spectra, the vibrational state distributions of OD products, and the state resolved anisotropy parameters have been determined. The experimental results indicate a dramatic variation in the OD product state distributions for different rotational excitations. This illuminates that there are two distinctive coupling channels from the C̃(010) state to the low-lying electronic states: the homogeneous electronic coupling to the Ã1B1 state, resulting in vibrationally hot OD(X) products, and the Coriolis-type coupling to the B̃1A1 state, producing vibrationally cold but rotationally hot OD(X) and OD(A) products. Furthermore, the three-body dissociation channel is confirmed, which is attributed to the C̃ → 1A2 or C̃ → Ã pathway. In comparison with the previous results of D2O photolysis via the C̃(000) state, it is found that the v2 vibration of the parent molecule enhances both the vibrational and rotational excitations of OD products.

Collective states in a ring network of theta neurons.

We consider a ring network of theta neurons with non-local homogeneous coupling. We analyse the corresponding continuum evolution equation, analytically describing all possible steady states and their stability. By considering a number of different parameter sets, we determine the typical bifurcation scenarios of the network, and put on a rigorous footing some previously observed numerical results.

Weak synchronization and convergence in coupled genetic regulatory networks: Applications to damped oscillators and multistable circuits

AbstractThe study of synchronization in coupled genetic networks is a very challenging topic that is usually analyzed on a case‐by‐case basis. Here we consider a general model of genetic networks and examine two forms of interconnection, either homogeneous or heterogeneous coupling, corresponding to coupling functions that are either equal or different from those governing the individual dynamics. In the case of individual subsystems having unique but different steady states, we prove that the homogeneous coupled system has a unique globally asymptotically stable steady state. Moreover, in the case of large coupling strength, we show that under suitable assumptions the network achieves weak synchronization in the sense that the individual steady states become arbitrarily close. In the heterogeneous case, stability conditions are more intricate and some stronger assumptions on the individual dynamics have to be made, under which we prove a similar weak synchronization result in the case of large coupling strength. We apply the results to the synchronization of damped oscillators and to the control of multistable systems.

Kinetic modeling of total oxidation of propane over rhodium

The heat release rates of fuel-lean propane/air mixtures over a rhodium wire catalyst were measured with microcalorimetry experiments and simulated with a 2D reactive code. Based on these studies, global reaction parameters of the total oxidation of C3H8 over Rh were extracted and a full catalytic reaction mechanism was developed. Wire microcalorimetry experiments were performed at atmospheric pressure and temperatures up to 900 K, while surface kinetic data was determined within the kinetic-controlled regime below 630 K. The dissociative adsorption of C3H8 on Rh and its subsequent decomposition reaction were fitted based on the global reaction parameters, and a thermodynamically consistent reaction mechanism for the total oxidation of C3H8 on Rh was constructed by incorporating these two fitted steps into a CH4-Rh surface mechanism. The constructed catalytic reaction mechanism well reproduced the measured heat release rates in the wire microcalorimeter and was further validated against 2D Raman measurements of major gas-phase species concentrations in an Rh-coated planar channel. Moreover, when working in conjunction with a recently reported pressure dependence of catalytic reactivity and a detailed gas-phase chemistry, the developed catalytic reaction mechanism excellently captured the catalytic reactivity and the homogeneous ignition during hetero-/homogeneous combustion in the planar channel at pressures up to 6 bar. The hetero-/homogeneous coupling of the intermediate species (such as CO) appreciably affected the onset of homogeneous ignition, while the corresponding coupling via radical (O, H and OH) reactions was very weak. Finally, the key reactions controlling catalytic ignition and homogeneous ignition during hetero-/homogeneous combustion were identified.

A Homogeneous Label-Free Electrochemical microRNA Biosensor Coupling With G-Triplex/Methylene Blue Complex and λ-Exonuclease-Assisted Recycling Amplification.

A novel homogeneous label-free electrochemical biosensor using G-triplex/methylene blue (G3/MB) complex as the signal generator together with an amplification assisted by the λ-exonuclease (λ-Exo) has been successfully constructed for ultrasensitive microRNA (miRNA) detection. An integrated microelectrode was designed to realize the miniaturization of the homogeneous electrochemical assay. Taking advantage of G3, that can specifically bind with MB and decrease its diffusion current, a single-stranded functional DNA hairpin structure was designed as the bio-recognition probe. The probe consisted of G3, eight bases to block G3, and the complementary sequences of the target miRNA. Here we chose miRNA141—a potentially diagnostic biomarker of prostate cancer as the model target. The presence of miRNA141 could hybridize with the probe DNA to form a double-stranded structure with a 5′-phosphorylated terminus. Then λ-Exo was adopted to digest mononucleotides from the 5′-end, leading to the release of G3 part and miRNA141. The released miRNA could hybridize with another probe to trigger the cycling process, while the released G3 could therefore interact with MB to cause a detectable decrease of diffusion current. The proposed strategy showed a low detection limit of 16 fM and an excellent specificity to discriminate single-base mismatches. Furthermore, this sensor was applied to detect miRNA141 from diluted human serum samples, indicating that it has great potential in the application of nucleic acid detection in real samples.

Optimal resilience of modular interacting networks

Coupling between networks is widely prevalent in real systems and has dramatic effects on their resilience and functional properties. However, current theoretical models tend to assume homogeneous coupling where all the various subcomponents interact with one another, whereas real-world systems tend to have various different coupling patterns. We develop two frameworks to explore the resilience of such modular networks, including specific deterministic coupling patterns and coupling patterns where specific subnetworks are connected randomly. We find both analytically and numerically that the location of the percolation phase transition varies nonmonotonically with the fraction of interconnected nodes when the total number of interconnecting links remains fixed. Furthermore, there exists an optimal fraction [Formula: see text] of interconnected nodes where the system becomes optimally resilient and is able to withstand more damage. Our results suggest that, although the exact location of the optimal [Formula: see text] varies based on the coupling patterns, for all coupling patterns, there exists such an optimal point. Our findings provide a deeper understanding of network resilience and show how networks can be optimized based on their specific coupling patterns.

Kinetic approach to nuclear-spin polaron formation

Under optical cooling of nuclei, a strongly correlated nuclear-spin polaron state can form in semiconductor nanostructures with localized charge carriers due to the strong hyperfine interaction of the localized electron spin with the surrounding nuclear spins. Here we develop a kinetic-equation formalism describing the nuclear-spin polaron formation. We present a derivation of the kinetic equations for an electron-nuclear spin system coupled to reservoirs of different electron and nuclear spin temperatures which generate the exact thermodynamic steady state for equal temperatures independent of the system size. We illustrate our approach using the analytical solution of the central spin model in the limit of an Ising form of the hyperfine coupling. For homogeneous hyperfine coupling constants, i.e., the box model, the model is reduced to an analytically solvable form. Based on the analysis of the nuclear-spin distribution function and the electron-nuclear spin correlators, we derive a relation between the electron and nuclear spin temperatures, where the correlated nuclear-spin polaron state is formed. In the limit of large nuclear baths, this temperature line coincides with the critical temperature of the mean-field theory for polaron formation. The criteria of the polaron formation in a finite-size system are discussed. We demonstrate that the system's behavior at the transition temperature does not depend on details of the hyperfine-coupling distribution function but only on the effective number of coupled bath spins. In addition, the kinetic equations enable the analysis of the temporal formation of the nuclear-polaron state, where we find the build-up process predominated by the nuclear spin-flip dynamics.