Kind Of Coupling Research Articles

Diffusion Cascades and Mutually Coupled Diffusion Processes

In this paper, we define and investigate a system of coupled regular diffusion equations in which each concentration acts as a driving term in the next diffusion equation. Such systems can be understood as a kind of cascade process which appear in different fields of physics like diffusion and reaction processes or turbulence. As a solution, we apply the time-dependent self-similar Ansatz method, the obtained solutions can be expressed as the product of a Gaussian and a Kummer’s function. This model physically means that the first diffusion works as a catalyst in the second diffusion system. The coupling of these diffusion systems is only one way. In the second part of the study we investigate mutually coupled diffusion equations which also have the self-similar trial function. The derived solutions show some similarities to the former one. To make our investigation more complete, different kinds of couplings were examined like the linear, the power-law, and the Lorentzian. Finally, a special coupling was investigated which is capable of describing isomerization with temporal decay.

The enhancement detection method based on the Fabry–Pérot cavity using terahertz frequency-domain spectroscopy

This article demonstrates a simple, efficient, and low-cost gas detection method for gases with absorption peaks in the terahertz range. A modes-adjustable Fabry–Pérot cavity is designed. By adjusting the length of the cavity, the center resonant frequency of the cavity can be coupled to the gas absorption peak. This kind of coupling can greatly enhance gas detection. To detect gas absorption peaks, we choose terahertz frequency domain spectroscopy (THz-FDS), whose frequency resolution can be up to the MHz level. Vapor is selected to verify the coupling phenomenon. The resonant frequency of the cavity is modified to couple to 0.56 THz, the absorption peak of vapor. Experiments are conducted at different humidity levels, the humidity is controlled by the supersaturated salt solution. Results indicate that at a humidity level of 15%, the coupling effect can enhance the detectability of vapor by approximately 167%, and this enhancement effect diminishes as humidity increases. We analyze the effect of different modes on the coupling and find that the high modes can make the coupling easier, but have little effect on the enhancement. Furthermore, the method is used to detect biomolecule-α-tyrosine to ensure it has wide applicability. This method can be used to detect substances with absorption peaks in the THz regime, especially for low-concentration gas.

Scrutinizing coupled vector dark energy in light of data

Since current challenges faced by ΛCDM might be hinting at new unravelled physics, here we investigate a plausible cosmological model where a vector field acts as source of dark energy. In particular, we examine whether an energy-momentum exchange between dark energy and dark matter could provide an explanation for current discrepancies in cosmological parameters. We carefully work out equations governing background and linear order perturbations and implement them in a Boltzmann code. We found that a negative coupling makes the dark energy equation of state less negative and closer to a cosmological constant during the matter dominated epoch than an uncoupled vector dark energy model. While the effect of the coupling is hardly noticeable through its effect on matter density perturbations, matter velocity perturbations and gravitational potentials are enhanced at late-times when dark energy dominates. Therefore, data of redshift space distortions help to narrow down these kinds of couplings in the dark sector. We computed cosmological constraints and found common parameters also present in ΛCDM are in good agreement with the Planck collaboration baseline result. Our best fit for a negatively coupled vector field predicts a higher growth rate of matter perturbations at low redshift, thus exacerbating the disagreement with redshift space distortions data. While a positively coupled vector field can lead to power suppression of P m(k,z = 0) on small scales as well as a lower growth rate of matter perturbations than the standard model, it might compromise the goodness of fit to the CMB angular power spectrum on small scales. We conclude that our negatively coupled vector dark energy model does not solve current tensions (i.e., H 0 and σ 8). Moreover, having three additional parameters with respect to ΛCDM, the negatively coupled vector dark energy model is heavily disfavoured by Bayesian evidence.

Dynamical adaptation in photoreceptors with gain control

The retina hosts all processes needed to convert external visual stimuli into a neural code. Light phototransduction and its conversion into an electrical signal involve biochemical cascades, ionic regulations, and different kinds of coupling, among other relevant processes. These create a nonlinear processing scheme and light-dependent adaptive responses. The dynamical adaptation model formulated in recent years is an excellent phenomenological candidate to resume all these phenomena into a single feedforward processing scheme. In this work, we analyze this description in highly nonlinear conditions and find that responses do not match those resulting from a very detailed microscopic model, developed to reproduce electrophysiological recordings on horizontal cells. When a delayed light-dependent gain factor incorporates into the description, responses are in excellent agreement, even when spanning several orders of magnitude in light intensity, contrast, and duration, for simple and complex stimuli. This extended model may be instrumental for studies of the retinal function, enabling the linking of the microscopic domain to the understanding of signal processing properties, and further incorporated in spatially extended retinal networks.

Coherence behavior of strongly coupled bosonic modes

We study the effect of the intermode coupling in the generation of coherence when two bosonic modes are bilinearly coupled. We consider the case for which the two modes are weakly coupled and the rotating-wave approximation (RWA) applies and the case for which they are strongly coupled and the RWA does not apply. Then, in the regime of validity of the RWA, there is no coherence generation solely due to squeezing effects, which means there is an exchange of excitation between the modes and negligible squeezing. On the other hand, if the two modes are strongly coupled coherence is generated by the squeezing interaction. For the system of two bosonic modes weakly coupled with a Markovian bath at temperature $T$ the coherence decreases with $T$. In general, when both kinds of couplings (exchange of excitation and squeezing) are turned on the exchange of excitation contributes to generating more coherence in comparison with a purely squeezing coupling. Thus, the coherence decreases more slowly with the temperature when both couplings are present. Finally, we explore the case when only one of the two coupled modes interacts with a Markovian bath while the other one remains free from the environment. We observe that the intermode coupling induces oscillations in the coherence and fidelity dynamics similar to the behavior for the coupling with a non-Markovian environment.

Thermal and mechanical properties of poly(lactic acid) filled with modified silicon dioxide: importance of the surface area

In this research work, the effect of the change in the surface area of silicon dioxide nanoparticles of the same size on mechanical properties of poly(lactic acid) nanocomposites (PLA) was studied, as well as the role of coupling agent amount in the compatibility of these nanomaterials. We consider a spherical silicon dioxide with a surface area of 170–200 m2/g (labeled as S–SiO2) and another considered amorphous with a surface area of 180–600 m2/g (labeled as P-SiO2). This surface areas difference plays an important role in modifying of nanoparticles polarity by incorporating a coupling agent and its integration into partially polar polymers. According to obtained results, for nanomaterials with high surface area, it was observed while increasing coupling agent amount, the elasticity of the composite was observed to increase. In contrast, in nanomaterials with spherical nanoparticles, it was observed that as the amount of coupling agent decreases, the resistance of the material increases, reaching a maximum when a 10:2 ratio is used. It was observed that behaviors for both nanoparticles were different, which gives an idea that the incorporation of nanoparticles in polymers is not an issue of coupling agent or quantity only, it is more important as it is arranged on the surface. This kind of couplings does not only affect mechanical properties, since the thermal behavior of the material was also influenced, where it was observed that particles with low surface area modify the crystallization rate when they have different percentages of coupling agent on the surface. Furthermore, it is observed that the incorporation of nanoparticles with high surface areas area does not modify the crystallization rate significantly. Besides, in both cases, it was observed that the highest crystallization rate is reached when a 10:2 ratio is used. However, the energy required to form crystals remains unchanged. Therefore, it is considered that the incorporation of nanoparticles only affects the crystal formation rate without disturbing the energy requirement for crystal formation. Finally, a maximum in the 10:2 ratio was observed for the compatibility in both particles, which was manifested in an increase in the storage module through a dynamic mechanical analysis. The rate of crystal formation as well as the number of formed crystals have a considerable effect on mechanical properties of nanocomposites when the surface area is modified.

Dissipative coupling, dispersive coupling, and their combination in cavityless optomechanical systems

We apply strategy of variational measurement to simplest variant of dissipative coupling (test mass displacement change transitivity of a single mirror) and compare it with simplest dispersive coupling (a single mirror as a test mass, which position changes the phase of reflected wave). We compare a ponderomotive squeezing in this two kinds of coupling. Also we analyze simplest variant of combined coupling, in which both dissipative and dispersive couplings are used, and show that it creates stable optical rigidity even in case of single pump. We demonstrate that variational measurement can be applied for combined coupling.

Symmetries and cluster synchronization in multilayer networks

Real-world systems in epidemiology, social sciences, power transportation, economics and engineering are often described as multilayer networks. Here we first define and compute the symmetries of multilayer networks, and then study the emergence of cluster synchronization in these networks. We distinguish between independent layer symmetries, which occur in one layer and are independent of the other layers, and dependent layer symmetries, which involve nodes in different layers. We study stability of the cluster synchronous solution by decoupling the problem into a number of independent blocks and assessing stability of each block through a Master Stability Function. We see that blocks associated with dependent layer symmetries have a different structure to the other blocks, which affects the stability of clusters associated with these symmetries. Finally, we validate the theory in a fully analog experiment in which seven electronic oscillators of three kinds are connected with two kinds of coupling.

Morphological magnetostatic coupling in spin valves due to anisotropic self-affine interface roughness

In this paper, we investigated the dipolar magnetic coupling in ferromagnetic multi-layered structures. However, this kind of coupling has been extensively studied since the last few decades through the Néel model (orange peel coupling), but most of the analyses were based on mathematically modeling a simple sinusoidal rough interface that hides the details of such a coupling. Therefore, we add a generality to the Néel model via adapting the anisotropic morphological self-affine interfaces that can unravel the details of interesting effects that are technologically important to consider for future magnonic and spintronic devices. The tensorial coupling between the ferromagnetic (FM) layers has been obtained from the magnetostatic energy of a pseudo-spin valve structure (FM/NM/FM). Our findings show that the coupling strength is dependent not only on the roughness properties of the self-affine interfaces but also on the rotational angle between the patterned interfaces. The variation of this orientation angle along with the change of the interface correlation lengths can switch FM coupling to antiferromagnetic coupling and vice versa. These results are advantageous for the engineering and fabrication of magnonic waveguide circuits and spintronic devices specifically in spin valves, magnetoresistive elements, and magnetic tunneling junctions.

A new kind of coupling.

A new kind of coupling.

Embedding-Based Complex Feature Value Coupling Learning for Detecting Outliers in Non-IID Categorical Data

Non-IID categorical data is ubiquitous and common in realworld applications. Learning various kinds of couplings has been proved to be a reliable measure when detecting outliers in such non-IID data. However, it is a critical yet challenging problem to model, represent, and utilise high-order complex value couplings. Existing outlier detection methods normally only focus on pairwise primary value couplings and fail to uncover real relations that hide in complex couplings, resulting in suboptimal and unstable performance. This paper introduces a novel unsupervised embedding-based complex value coupling learning framework EMAC and its instance SCAN to address these issues. SCAN first models primary value couplings. Then, coupling bias is defined to capture complex value couplings with different granularities and highlight the essence of outliers. An embedding method is performed on the value network constructed via biased value couplings, which further learns high-order complex value couplings and embeds these couplings into a value representation matrix. Bidirectional selective value coupling learning is proposed to show how to estimate value and object outlierness through value couplings. Substantial experiments show that SCAN (i) significantly outperforms five state-of-the-art outlier detection methods on thirteen real-world datasets; and (ii) has much better resilience to noise than its competitors.

Phase synchronization and lock between memristive circuits under field coupling

The dynamics of nonlinear circuits becomes dependent on the initials setting when memristor is included to design nonlinear circuits, and this memristive circuits can cause distinct transition between periodical and chaotic states by resetting the initial-dependent variables even all the parameters are fixed. A memristive circuit is used to investigate the synchronization stability when the resistor, capacitor, induction coil is applied to connect two identical circuits, respectively. For resistor-based voltage coupling, single channel coupling can realize phase lock even the resistor has to consume more Joule heat with the increase of coupling intensity. In case of capacitor coupling, continuous pump of electric field energy in the coupling capacitor can trigger time-varying electric field and then the phase errors between two circuits are locked. When induction coil is applied to couple two circuits, time-varying magnetic field is triggered to save field energy pumped from the two coupling circuits and then phase errors can also be stabilized. The three kinds of coupling between nonlinear circuits can modulate synchronization via continuous energy exchange and pumping. The coupling resistor just consumes Joule heat while capacitor and induction coil coupling can pump and save field energy and it provide another scheme as field coupling.

Generation of squeezed states and single-phonon states via homodyne detection and photon subtraction on the filtered output of an optomechanical cavity

In this paper, we consider the generation of mechanical squeezed states and single-phonon Fock states, respectively, by homodyne detection and photon subtraction in a dissipative or dispersive optomechanical system under the situation that the cavity linewidth ${\ensuremath{\kappa}}_{c}$ is much larger than the mechanical frequency ${\ensuremath{\omega}}_{m}$. We at first show that strong mechanical squeezing beyond the 3-dB limit can be achieved by homodyning the filtered cavity output field in a purely dispersive or purely dissipative optomechanical system for ${\ensuremath{\kappa}}_{c}\ensuremath{\gg}{\ensuremath{\omega}}_{m}$, while the combination of the two kinds of coupling can also effectively enhance the mechanical squeezing. We next show that in these optomechanical systems, mechanical single-phonon states with high fidelity can be generated via photon subtraction on the filtered cavity output field in the regimes of weak optomechanical entanglement and ${\ensuremath{\kappa}}_{c}\ensuremath{\gg}{\ensuremath{\omega}}_{m}$. It is found that the single-phonon Fock state via purely dissipative optomechanical coupling is attainable in the blue-detuned regime, whereas it is present in the red-detuned regime by purely dispersive optomechanical coupling. In addition, the effects of thermal fluctuations on the mechanical squeezing and the negativity of the Wigner function of the mechanical single-phonon states are also studied. It is shown that the Gaussian squeezing is much more robust against decohering thermal fluctuations than the non-Gaussian nonclassicality.

Economic Dispatch for Regional Integrated Energy System With District Heating Network Under Stochastic Demand

The strong interdependency of heat and power supply restricts the operational flexibility of combined heat and power (CHP) units, especially in cold seasons. More than that, such kind of coupling can conventionally cause massive power curtailment of renewable energy sources (RES) under stochastic heat demands. In this paper, these issues are resolved by the cooperation between the district heating network (DHN) and load-side thermal storages in a regional integrated energy system (RIES) model. In which, the DHN is formulated as an energy-storage-like (ESL) model, based on the dynamic characteristics of temperature and time delay effect of the medium within the pipeline system. The potential benefits of the proposed model, in terms of increasing the integration of RES and the total revenue of the entire system, have been demonstrated by the case studies.

Predictability of Financial Crisis via Pair Coupling of Commodity Market and Stock Market

The complex interactions between stock market and commodity market in financial crisis has been investigated by many researchers, but there is less known about how useful the pair coupling of the two markets for predicting financial crisis, where the pair coupling is the hidden essence of market interactions. This article investigates three kinds of couplings, namely time coupling, frequency coupling and space coupling, which are the different aspects of the pair coupling. In addition, a two-layer model, namely CHMM-ANN, is proposed to investigate the couplings and evaluate the predicting abilities based on the couplings. Coupled Hidden Markov Model (CHMM) is adopted at the bottom level to capture the hidden couplings, and then the couplings are put as input to classical Artificial Neural Network (ANN) at the top level to predict financial crisis. The experiment results on real financial data confirm the advantages of the pair coupling in predicting financial crisis.

Localization of U(1) gauge vector field on flat branes with five-dimension (asymptotic) AdS5 spacetime

In order to localize U(1) gauge vector field on Randall-Sundrum-like braneworld model with infinite extra dimension, we propose a new kind of non-minimal coupling between the U(1) gauge field and the gravity. We propose three kinds of coupling methods and they all support the localization of zero mode. In addition, one of them can support the localization of massive modes. Moreover, the massive tachyonic modes can be excluded. And our method can be used not only in the thin braneword models but also in the thick ones.

Quantum probes for the cutoff frequency of Ohmic environments

Quantum probing consists of suitably exploiting a simple, small, and controllable quantum system to characterize a larger and more complex system. Here, we address the estimation of the cutoff frequency of the Ohmic spectral density of a harmonic reservoir by quantum probes. To this aim, we address the use of single-qubit and two-qubit systems and different kinds of coupling with the bath of oscillators. We assess the estimation precision by the quantum Fisher information of the sole quantum probe as well as the corresponding quantum signal-to-noise ratio. We prove that, for most of the values of the Ohmicity parameter, a simple probe such as a single qubit is already optimal for the precise estimation of the cutoff frequency. Indeed for those values, upon considering a two-qubit probe either in a Bell or in separable state, we do not find improvement to the estimation precision. However, we also showed that there exist few conditions where employing two qubits in a Bell state interacting with a common bath is more suitable for precisely estimating the cutoff frequency.

Thermal coupling and effect of subharmonic synchronization in a system of two VO2 based oscillators

We explore a prototype of an oscillatory neural network (ONN) based on vanadium dioxide switching devices. The model system under study represents two oscillators based on thermally coupled VO2 switches. Numerical simulation shows that the effective action radius RTC of coupling depends both on the total energy released during switching and on the average power. It is experimentally and numerically proved that the temperature change ΔT commences almost synchronously with the released power peak and T-coupling reveals itself up to a frequency of about 10 kHz. For the studied switching structure configuration, the RTC value varies over a wide range from 4 to 45 μm, depending on the external circuit capacitance C and resistance Ri, but the variation of Ri is more promising from the practical viewpoint. In the case of a “weak” coupling, synchronization is accompanied by attraction effect and decrease of the main spectra harmonics width. In the case of a “strong” coupling, the number of effects increases, synchronization can occur on subharmonics resulting in multilevel stable synchronization of two oscillators. An advanced algorithm for synchronization efficiency and subharmonic ratio calculation is proposed. It is shown that of the two oscillators the leading one is that with a higher main frequency, and, in addition, the frequency stabilization effect is observed. Also, in the case of a strong thermal coupling, the limit of the supply current parameters, for which the oscillations exist, expands by ∼10%. The obtained results have a universal character and open up a new kind of coupling in ONNs, namely, T-coupling, which allows for easy transition from 2D to 3D integration. The effect of subharmonic synchronization hold promise for application in classification and pattern recognition.

Inductively shunted transmon qubit with tunable transverse and longitudinal coupling

We present the design of an inductively shunted transmon qubit with flux-tunable coupling to an embedded harmonic mode. This circuit construction offers the possibility to flux-choose between pure transverse and pure longitudinal coupling, that is coupling to the $\sigma_x$ or $\sigma_z$ degree of freedom of the qubit. While transverse coupling is the coupling type that is most commonly used for superconducting qubits, the inherently different longitudinal coupling has some remarkable advantages both for readout and for the scalability of a circuit. Being able to choose between both kinds of coupling in the same circuit provides the flexibility to use one for coupling to the next qubit and one for readout, or vice versa. We provide a detailed analysis of the system's behavior using realistic parameters, along with a proposal for the physical implementation of a prototype device.

Visible neutrino decay in the light of appearance and disappearance long-baseline experiments

We investigate the present constraints from MINOS and T2K experiments for the neutrino decay scenario induced by non-diagonal couplings of Majorons to neutrinos. As novelty, on top of the typical invisible decay prescription, we add the contribution of visible decay, where final products can be observed. This new effect depends on the nature of the neutrino-Majoron coupling, which can be of scalar or pseudoscalar type. Using the combination of disappearance data from MINOS and disappearance and appearance data from T2K, for normal ordering, we constrain the decay parameter α ≡ E Γ for the heaviest neutrino, where E and Γ are the neutrino energy and width, respectively. We find that when considering visible decay within appearance data, one can improve current neutrino long-baseline constraints up to alpha <mathcal{O}left(1{0}^{-5}right) {mathrm{eV}}^2 , at 90% C.L., for both kinds of couplings, which is better by one order of magnitude compared to previous bounds.