Static Coupling Research Articles

On robust synchronization of heterogeneous linear multi-agent systems with static couplings

This paper addresses cooperative control problems in heterogeneous groups of linear dynamical agents that are coupled by diffusive links. We study networks with parameter uncertainties, resulting in heterogeneous agent dynamics, and we analyze the robustness of their output synchronization. The networks under consideration consist of non-identical double-integrators and harmonic oscillators. The geometric approach to linear control theory reveals structural requirements for non-trivial output synchronization in such networks. Furthermore, a clock synchronization problem and a circular motion coordination problem are discussed as applications corresponding to these two network types. The results are illustrated by numerical simulations.

Global Exponential Synchronization of Two Memristor-Based Recurrent Neural Networks With Time Delays via Static or Dynamic Coupling

This paper is concerned with the global exponential synchronization of two memristor-based recurrent neural networks (MRNNs) with time delays via static or dynamic coupling. First, four coupling rules (i.e., static state coupling, static output coupling, dynamic state coupling, and dynamic output coupling) are designed for the exponential synchronization of drive-response pair of MRNNs. Then, several global exponential synchronization criteria are derived by constructing suitable Lyapunov–Krasovskii functionals based on the Lyapunov stability theory. Compared with existing results on synchronization of MRNNs, the conditions herein are easy to be verified. Moreover, the designed dynamic state coupling and output coupling rules have good anti-interference capacity. Finally, two illustrative examples are presented to substantiate the effectiveness and characteristics of the presented theoretical results.

Network synchronization of time-delayed coupled nonlinear systems using predictor-based diffusive dynamic couplings.

We study the problem of controlled network synchronization of coupled semipassive systems in the case when the outputs (the coupling variables) and the inputs are subject to constant time-delay (as it is often the case in a networked context). Predictor-based dynamic output feedback controllers are proposed to interconnect the systems on a given network. Using Lyapunov-Krasovskii functional and the notion of semipassivity, we prove that under some mild assumptions, the solutions of the interconnected systems are globally ultimately bounded. Sufficient conditions on the systems to be interconnected, on the network topology, on the coupling dynamics, and on the time-delays that guarantee global state synchronization are derived. A local analysis is provided in which we compare the performance of our predictor-based control scheme against the existing static diffusive couplings available in the literature. We show (locally) that the time-delay that can be induced to the network may be increased by including the predictors in the loop. The results are illustrated by computer simulations of coupled Hindmarsh-Rose neurons.

Adaptive consensus tracking for linear multi‐agent systems with heterogeneous unknown nonlinear dynamics

SummaryThis paper considers the consensus tracking control problem for general linear multi‐agent systems with unknown dynamics in both the leader and all followers. Based on parameterizations of the unknown dynamics of all agents, two decentralized adaptive consensus tracking protocols, respectively, with dynamic and static coupling gains, are proposed to guarantee that the states of all followers converge to the state of the leader. Furthermore, this result is extended to the robust adaptive consensus tracking problem in which there exist parameter uncertainties and Lipschitz‐type disturbances in the network. It is also shown that the parameter estimation errors converge to zero based on contradiction method and Lyapunov function approach. Finally, a simulation example is provided to illustrate the theoretical results. Copyright © 2015 John Wiley & Sons, Ltd.

Magnetization dynamics in an exchange-coupled NiFe/CoFe bilayer studied by x-ray detected ferromagnetic resonance

Exchange-coupled hard and soft magnetic layers find extensive use in data storage applications, for which their dynamical response has great importance. With bulk techniques, such as ferromagnetic resonance (FMR), it is difficult to access the behaviour and precise influence of each individual layer. By contrast, the synchrotron radiation-based technique of x-ray detected ferromagnetic resonance (XFMR) allows element-specific and phase-resolved FMR measurements in the frequency range 0.5–11 GHz. Here, we report the study of the magnetization dynamics of an exchange-coupled Ni0.81Fe0.19 (43.5 nm)/Co0.5Fe0.5 (30 nm) bilayer system using magnetometry and vector network analyser FMR, combined with XFMR at the Ni and Co L2 x-ray absorption edges. The epitaxially grown bilayer exhibits two principal resonances denoted as the acoustic and optical modes. FMR experiments show that the Kittel curves of the two layers cannot be taken in isolation, but that their modelling needs to account for an interlayer exchange coupling. The angular dependence of FMR indicates a collective effect for the modes of the magnetically hard CoFe and soft NiFe layer. The XFMR precessional scans show that the acoustic mode is dominated by the Ni signal with the Co and Ni magnetization precessing in phase, whereas the optical mode is dominated by the Co signal with the Co and Ni magnetization precessing in anti-phase. The response of the Co signal at the Ni resonance, and vice versa, show induced changes in both amplitude and phase, which can be ascribed to the interface exchange coupling. An interesting aspect of phase-resolved XFMR is the ability to distinguish between static and dynamic exchange coupling. The element-specific precessional scans of the NiFe/CoFe bilayer clearly have the signature of static exchange coupling, in which the effective field in one layer is aligned along the magnetization direction of the other layer.

Characterization of the Static Thermal Coupling Between Emitter Fingers of Bipolar Transistors

A strategy for compact modeling the static thermal coupling between the emitter fingers of SiGe heterojunction bipolar transistors (SiGe-HBTs) is described. An extraction methodology that includes the nonlinear temperature dependence of the thermal conductivity is introduced and applied to suitable test structures. The experimental results are used for calibrating a 3-D numerical solution of the equation for heat conduction based on a Green's function approach. The latter can then be employed for generating thermal coupling networks for arbitrary transistor configurations.

Magnetic normal modes of bicomponent permalloy/cobalt structures in the parallel and antiparallel ground state

Two-dimensional arrays of bicomponent structures made of cobalt and permalloy elliptical dots with thickness of 25 nm, length 1 \ensuremath{\mu}m, and width of 225 nm, have been prepared by a self-aligned shadow deposition technique. Brillouin light scattering has been exploited to study the frequency dependence of thermally excited magnetic eigenmodes on the intensity of the external magnetic field, applied along the easy axis of the elements. Several modes have been observed while sweeping the field along the major and minor hysteresis loops, encompassing both the parallel and the antiparallel alignment of the magnetization in adjacent permalloy and cobalt dots. Micromagnetic simulations based on the dynamic matrix method enabled us to successfully reproduce the measured evolution of the frequencies with the field, as well as to identify the spatial profiles of the modes. A marked difference in the field dependence of the frequency of some modes has been observed for parallel and antiparallel magnetization configurations, suggesting the possibility of tuning the dynamic response in a reprogrammable way. The role of both static and dynamic magnetic coupling in determining the mode frequency is discussed in detail by studying the frequency evolution as a function of the gap size between the dots.

Synchronization of Identical Linear Systems and Diffusive Time-Delayed Couplings

We study the problem of controlled network synchronization for a class of identical linear systems. The systems are interconnected through static and dynamic diffusive couplings with time-delays. In particular, we derive conditions on the systems, on the couplings, on the time-delay, and on the network topology that guarantee global synchronization of the systems. Diffusive time-delayed dynamic couplings are constructed by combining linear observers and output feedback controllers. Using passivity properties, sufficient conditions for boundedness of the interconnected systems are derived. Moreover, predictor-based dynamic couplings are proposed in order to enhance robustness against time-delays in the network. The results are illustrated by numerical simulations.

Two Driven Coupled Qubits in a Time Varying Magnetic Field: Exact and Approximate Solutions

We study the dynamics of a two-qubit system coupled through time dependent anisotropic $XYZ$ Heisenberg interaction in presence of a time varying non-uniform external magnetic field. Exact results are presented for the time evolution of the system under certain integrability conditions. Furthermore, the corresponding entanglement of the system is studied for different values of the involved parameters. We found that the time evolution and different properties of entanglement such as amplitude, frequency and profile can be finely tuned by the interplay of the characteristics of the time-dependent magnetic field and exchange coupling. Also we show how the discrete symmetries of the system Hamiltonian, which splits its Hilbert space into two distinct subspaces, can be utilized to deduce the dynamics in one of its two distinct subspaces from the other one. Moreover, approximate results for the time evolution are provided utilizing the rotating wave as well as the perturbation approximations for the special case of either static magnetic field or exchange coupling. We compare the range of validity of the two approximation methods and their effectiveness in treating the considered system and determine their critical parameters.

Beam coupling in hybrid photorefractive inorganic-cholesteric liquid crystal cells: Impact of optical rotation

We develop a theoretical model to describe two-beam energy exchange in a hybrid photorefractive inorganic-cholesteric cell. A cholesteric layer is placed between two inorganic substrates. One of the substrates is photorefractive (Ce:SBN). Weak and strong light beams are incident on the hybrid cell. The interfering light beams induce a periodic space-charge field in the photorefractive window. This penetrates into the cholesteric liquid crystal (LC), inducing a diffraction grating written on the LC director. In the theory, the flexoelectric mechanism for electric field-director coupling is more important than the LC static dielectric anisotropy coupling. The LC optics is described in the Bragg regime. Each beam induces two circular polarized waves propagating in the cholesteric cell with different velocities. The model thus includes optical rotation in the cholesteric LC. The incident light beam wavelength can fall above, below, or inside the cholesteric gap. The theory calculates the energy gain of the weak beam, as a result of its interaction with the pump beam within the diffraction grating. Theoretical results for exponential gain coefficients are compared with experimental results for hybrid cells filled with cholesteric mixture BL038/CB15 at different concentrations of chiral agent CB15. Reconciliation between theory and experiment requires the inclusion of a phenomenological multiplier in the magnitude of the director grating. This multiplier is cubic in the space-charge field, and we provide a justification of the q-dependence of the multiplier. Within this paradigm, we are able to fit theory to experimental data for cholesteric mixtures with different spectral position of cholesteric gap relative to the wavelength of incident beams, subject to the use of some fitting parameters.

The implementation of a thermal bubble actuated microfluidic chip with microvalve, micropump and micromixer

This paper presents the implementation of a thermal bubble actuated microfluidic chip with microvalve, micropump and micromixer, based on a simple process with SOI wafer. Only two photolithography processes were required to provide an effective means of manufacturing the vertical bulk microheater and high-aspect-ratio microchannel for microfluidic applications. The static and dynamic electro-thermal coupling behaviors of the proposed resistive silicon-based microheater were evaluated by finite element analysis to provide an applicable design. The feasibility of each actuation element has also been verified by experiments. Experimental results show that the sizes of thermal bubbles, at flow rates less than 4.5μl/s, can be controlled steadily by applying the magnitude of direct current that meets the requirement of a microvalve to modulate flow rate. When applying an alternating current with high frequency to the microheater, thermal bubbles could grow cyclically and collapse rapidly, so the liquid stream could be regulated by the repeated volume change of thermal bubbles. A maximum volume flow rate of 4.5μl/s was obtained, under the driving voltage with a frequency of 60Hz and 30% duty ratio. The mixing test of the multi-layer fluidics with laminar flow also was successfully implemented by using the volume of thermal bubble to create turbulent flow in the fluids. With no moving parts, the proposed microfluidic chip is well designed with high performance and reliability.

Static magnetoelectric coupling of magnetoelectric laminated composites under combined temperature and stress loadings

For the tri-layer symmetric magnetoelectric (ME) laminated composites made of giant magnetostrictive materials and piezoelectric materials, we chose the nonlinear magnetostrictive constitutive with variable coefficients and the linear piezoelectric constitutive to obtain the vibration equation for the laminated composites. The surface force and displacement speed were equivalent to the circuit voltage and current in the equivalent circuit for the laminated composites. According to the equivalent circuit, a model of the static magnetoelectric field coefficient for the strong nonlinear thermo-magneto-electro-mechanical coupling was obtained. Without considering the pre-stress, the comparisons of the static ME coefficient versus temperature curves for the experimental and theoretical results were in good agreement both qualitatively and quantitatively for low and moderate magnetic fields. The theoretical results were smaller than the experimental results under high magnetic fields. This model was adopted to predict variations in the ME coefficients in the laminated composites under different bias magnetic fields, temperatures, and stresses. This showed that the laminated composites had the strongest magnetoelectric effect at 0 °C; a large compressive stress effectively suppressed the magnetoelectric effect attenuation caused by high temperatures; an appropriate tensile stress improved the maximum magnetoelectric coefficient and lowered its bias magnetic field near room temperature. These results provide a theoretical basis for the design and application of high-performance and miniaturized magnetoelectric devices, operating under extreme temperature conditions.

Empirical investigation into static and dynamic coupling metrics

Recent research in the field of object-oriented software engineering has been focusing on the usage of software metrics for the assessment of a product's quality. Software design coupling metrics include some of the most widely applicable metrics used in the modern software industry. Although static coupling metrics are used for analyzing the structural aspects of the object-oriented software systems, their inability to capture the behavioral aspects is well known and hence has given way to the evolution of their runtime counterparts i.e. the dynamic coupling metrics. Most of the dynamic coupling metrics proposed until now have not yet been empirically validated due to the high evaluation cost involved in the runtime metric data collection, hence limiting their practical application. This paper, as a part of our ongoing research on empirical validation of the dynamic coupling metrics, presents an empirical investigation into the static and dynamic CBO (Coupling Between Objects) metrics using some open source real world java applications. A set of criteria for the selection of sample benchmark applications required for the dynamic metrics validation has also been devised. A scenario based approach in combination with the appropriate statistical techniques has been used in an attempt to correlate the static and dynamic coupling metrics.

Dispersion potential between three-bodies with arbitrary electric multipole polarizabilities: molecular QED theory.

Molecular quantum electrodynamics is used to obtain an expression for the retarded dispersion energy shift between three arbitrarily electrically polarizable atoms or molecules. A generalized Craig-Power Hamiltonian that depends quadratically on the electric displacement field is employed together with third-order diagrammatic perturbation theory. This approach simplifies the calculation relative to the use of the usual multipolar coupling Hamiltonian that is linear in the displacement field. Specific higher multipole non-additive contributions are then extracted. These include dipole-dipole-quadrupole, dipole-quadrupole-quadrupole, and dipole-dipole-octupole potentials valid for oriented and isotropic species with arbitrary separation distances between particles, extending recent work in which these energy shifts were given for equilateral triangle and collinear geometries. Near-zone limiting forms are found to agree with earlier works in which static inter-particle couplings were used.

Numerical Calculation on Cavitation Pressure Pulsation in Centrifugal Pump

In order to study the internal flow in centrifugal pump when cavitation occurs, numerical calculation of the unsteady flow field in the WP7 automobile centrifugal pump is conducted based on the Navier-Stokes equations with the RNG k – ε turbulence model and Zwart-Gerber-Belamri cavitation model. The distributions of bubble volume fraction and pressure pulsation laws in the pump are analyzed when cavitation occurs. The conclusions are as follows: the bubble volume fraction is larger on the suction side of impeller blade near the inlet edge, which is consistent with the low-pressure region distribution. Bubble volume is determined by the growth rate and collapse rate of every bubble in the bubble group. The cavitation degree changes over time with the impeller rotation and the bubble growth and collapse coexist in the impeller flow channels. The main pulsation results from the cyclic and static coupling between the impeller and the tongue, while the fluctuating amplitude is increased by the cavitation.

T4有机染料敏化薄膜的超快动力学特性

Excited-state processes in T4 organic dye-sensitized Al2O3and TiO2films were studied by femtosecond transient absorption spectroscopy and femtosecond time-resolved photoluminescence dynamics based on up-conversion method.By multiexponential analysis,we obtained the electron injection efficiency of 93% in T4 dye-sensitized TiO2film.In addition,we further got the electron injection rate of1.17 ps-1in the T4 dye-sensitized TiO2film by a static inhomogeneous electronic coupling model.

Behavior of Inter-Core Crosstalk as a Noise and Its Effect on <i>Q</i>-Factor in Multi-Core Fiber

The stochastic behavior of inter-core crosstalk in multi-core fiber is discussed based on a theoretical model validated by measurements, and the effect of the crosstalk on the Q-factor in transmission systems, using multi-core fiber is investigated theoretically. The measurements show that the crosstalk rapidly changes with wavelength, and gradually changes with time, in obedience to the Gaussian distribution in I-Q planes. Therefore, the behavior of the crosstalk as a noise may depend on the bandwidth of the signal light. If the bandwidth is adequately broad, the crosstalk may behave as a virtual additive white Gaussian noise on I-Q planes, and the Q-penalty at the Q-factor of 9.8dB is less than 1dB when the statistical mean of the crosstalk from other cores is less than -16.7dB for PDM-QPSK, -23.7dB for PDM-16QAM, and -29.9dB for PDM-64QAM. If the bandwidth is adequately narrow, the crosstalk may behave as virtually static coupling that changes very gradually with time and heavily depends on the wavelength. To cope with a static crosstalk much higher than its statistical mean, a margin of several decibels from the mean crosstalk may be necessary for suppressing Q-penalty in the case of adequately narrow bandwidth.

Variational analysis of the coupling between a geometrically exact Cosserat rod and an elastic continuum

We formulate the static mechanical coupling of a geometrically exact Cosserat rod to a nonlinearly elastic continuum. In this setting, appropriate coupling conditions have to connect a one-dimensional model with director variables to a three-dimensional model without directors. Two alternative coupling conditions are proposed, which correspond to two different configuration trace spaces. For both, we show existence of solutions of the coupled problems, using the direct method of the calculus of variations. From the first-order optimality conditions, we also derive the corresponding conditions for the dual variables. These are then interpreted in mechanical terms.

The adaptive coupling scheme and the heterogeneity in intrinsic frequency and degree distributions of the complex networks

Abstract In the paper, we applied an adaptive principle to three kinds of complex networks as well as a random network within the context of the Kuramoto model. We found that the adaptive scheme could suppress the negative effect of the heterogeneity in the networks and the phase synchronization is enhanced obviously. The paper mainly investigates the adaptive coupling scheme in the small-world network, the scale-free network, and the modular network. Comparing with other weighted or unweighted static coupling schemes, the adaptive coupling scheme has a better performance in synchronization and communication efficiency, and provides a more realistic picture of synchronization in complex networks.

A self-decoupled three-axis force sensor for measuring the wheel force

The wheel force transducer is an important device in the automotive testing field which can measure the force or torque applied to the wheel. Because existing wheel force transducers are almost commercial products, they are too expensive and technical information about them has not been made public; this slows down the development of the wheel force transducer to a certain extent. Accordingly a three-axis wheel force transducer is presented in this paper which is self-decoupled without calculating the decoupling matrix in theory. Its elastic body has a spoke structure with eight elastic beams, which means that it is easy to fabricate. This paper first introduces the overall elastic body structure of the proposed wheel force transducer. Then the strain gauge arrangement, the principle of strain measurement, the connection modes of the bridge circuits and the rotation decoupling principle for Fx and Fz are analysed, and the self-decoupled characteristics are depicted in detail. Finally, to verify the validity of the designed wheel force transducer, three kinds of experiment are carried out. In the static experiments the static performance and the self-decoupled characteristics of the wheel force transducer are verified; in the dynamic tests, a vehicle dynamics test system is adopted to verify the accuracy of the wheel force transducer in the dynamic environment; in road tests, the sensor is installed in the vehicle to verify whether the output of the proposed wheel force transducer can reflect the variation in the force applied to the wheel in practical applications. The results shows the following: first, the maximum non-linearity error, the maximum hysteresis error and the maximum repeatability error of the proposed wheel force transducer are 0.9% of the full scale, 1.1% of the full scale and 0.5% of the full scale respectively; second, the static coupling rate is about 0.08%, which means that the designed wheel force transducer is self-decoupled in theory; third, the proposed wheel force transducer can measure Fx, Fz and My effectively in real applications.