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Model-based state-of-charge (SOC) and state-of-health (SOH) estimation for lithium-ion batteries has been widely applied in electrified vehicles, while the SOC and SOH estimators are highly coupled and nonlinear in conventional techniques. This leads to a bulky design of observer network and complicates the stability analyses. In this article, a new reduced-decoupling SOC and SOH coestimation algorithm based on convex optimization is proposed. This scheme estimates the battery SOC from the battery model and does not require the classic Coulomb-counting method. Therefore, it can decouple the capacity estimation from the SOC estimator and reduce the strong interaction existing in conventional coestimation methods. Besides, all state variables can be solved together by one estimator, which is straightforward and avoids the complicated observer network. Owing to the decoupling design, the stability of the proposed method becomes more intuitive and can be always guaranteed according to the convexity analysis without using other stabilizing approaches. In consequence, a weak-interaction and robust coestimation algorithm of SOC and SOH can be realized by the proposed technique. The experiments on a 5.4-Ah lithium polymer battery are implemented to validate the feasibility of the algorithm.

The computational efficiency of traditional model order reduction (MOR) methods may degrade sharply for multi-input multi-output (MIMO) systems especially when the number of ports of MIMO systems is very large. During the concrete computation process, many input-output pairs can be ignored due to the weak interactions to each other, and hence the efficiency of reduction can be improved by reducing the number of ports. In this brief, we develop a dynamic relative gain array (DRGA) method to decide which inputs are important enough to an output in the MOR process. The DRGA method is based on the state feedback predictive control, and both the steady state information and the dynamic information are considered in the process of loop pairing. Multi-input single-output (MISO) subsystems can be obtained from decoupling the original large MIMO system. Experimental results on RLC networks show that the proposed DRGA based MOR method has higher accuracy compared with the passive reduced-order interconnect macromodeling (PRIMA) method, the decentralized model order reduction (DeMOR) method, and the balance truncation reduction (BTR) method.

For many dynamical systems, it is required to actively control individual modes, especially when these are lightly damped or even unstable. In order to achieve a maximum control performance, these systems are often augmented with a large number of control inputs and measurement outputs. To overcome the challenge of choosing an adequate combination of input and output signals for modal control, an $\mathcal {H}_{2}$ -optimal isolation of modes via blending of inputs and outputs is proposed in this brief. Enforcing an explicit mode decoupling, the approach enables controlling individual modes with simple single-input single-output controllers. A numerically efficient algorithm is derived for the joint computation of the interdependent input and output blending vectors. The effectiveness of the proposed approach is demonstrated by increasing the modal damping of an aeroelastic system.

This paper mainly investigates the problem of extended dissipative filter design for switched discrete-time systems where the variation of switching signals among subsystems is governed by the persistent dwell-time strategy. Considering that in practical applications, the congestion of the communication channels between systems and filters may cause data loss, therefore the packet dropouts are taken into account to make the issue under consideration more general. Meanwhile, it is generally known that the mode information of the system may sometimes not be accessed, so we consider the design of a unified filter including mode-dependent and mode-independent filters simultaneously. A white sequence that obeys the Bernoulli distribution is used to express the random switching of the filters. The main purpose of this paper is to find a suitable filter design method which ensures that the resulting error system is exponentially mean-square stable and extended dissipative. Sufficient conditions are established to make sure the solvability of the addressed problem. By using appropriate decoupling method, some conditions that could be readily solved are obtained. In order to explain the correctness and effectiveness of the proposed method, two illustrated examples are given in the final part of this paper.

Chemical shift anisotropy (CSA) and dipolar CODEX (Cenralband Only Detection of EXchange) experiments enable abundant quantitative information on the reorientation of the CSA and dipolar tensors to be obtained on millisecond–second timescales. At the same time, proper performance of the experiments and data analysis can often be a challenge since CODEX is prone to some interfering effects that may lead to incorrect interpretation of the experimental results. One of the most important such effects is RIDER (relaxation-induced dipolar exchange with recoupling). It appears due to the dipolar interaction of the observed X nuclei with some other nuclei, which causes an apparent decay in the mixing time dependence of the signal intensity reflecting not molecular motion, but spin flips of the adjacent nuclei. This may hamper obtaining correct values of the parameters of molecular mobility. In this contribution we consider in detail the reasons why the RIDER distortions remain even under decoupling conditions and propose measures to eliminate them. That is, we suggest (1) using an additional Z filter between the cross-polarization (CP) section and the CODEX recoupling blocks that suppresses the interfering anti-phase coherence responsible for the X-H RIDER and (2) recording only the cosine component of the CODEX signal since it is less prone to the RIDER distortions in comparison to the sine component. The experiments were conducted on rigid model substances as well as microcrystalline 2H ∕ 15N-enriched proteins (GB1 and SH3) with a partial back-exchange of labile protons. Standard CSA and dipolar CODEX experiments reveal a fast-decaying component in the mixing time dependence of 15N nuclei in proteins, which can be misinterpreted as a slow overall protein rocking motion. However, the RIDER-free experimental setup provides flat mixing time dependences, meaning that the studied proteins do not undergo global motions on the millisecond timescale.

The plate interface undergoes two transitions between seismogenic depths and subarc depths. A brittle-ductile transition at 20–50 km depth is followed by a transition to full viscous coupling to the overlying mantle wedge at ∼80 km depth. We review evidence for both transitions, focusing on heat-flow and seismic-attenuation constraints on the deeper transition. The intervening ductile shear zone likely weakens considerably as temperature increases, such that its rheology exerts a stronger control on subduction-zone thermal structure than does frictional shear heating. We evaluate its role through analytic approximations and two-dimensional finite-element models for both idealized subduction geometries and those resembling real subduction zones. We show that a temperature-buffering process exists in the shear zone that results in temperatures being tightly controlled by the rheological strength of that shear zone’s material for a wide range of shear-heating behaviors of the shallower brittle region. Higher temperatures result in weaker shear zones and hence less heat generation, so temperatures stop increasing and shear zones stop weakening. The net result for many rheologies are temperatures limited to ≤350–420 °C along the plate interface below the cold forearc of most subduction zones until the hot coupled mantle is approached. Very young incoming plates are the exception. This rheological buffering desensitizes subduction-zone thermal structure to many parameters and may help explain the global constancy of the 80 km coupling limit. We recalculate water fluxes to the forearc wedge and deep mantle and find that shear heating has little effect on global water circulation.

In the paper, we consider the local-in-time and the global-in-time infinity-ion-mass convergence of bipolar Euler-Maxwell systems by setting the mass of an electron me=1 and letting the mass of an ion mi→∞. We use the method of asymptotic expansions to handle the local-in-time convergence problem and find that the limiting process from bipolar models to unipolar models is actually decoupling, but not the vanishing of equations for the corresponding the other particle. Moreover, when the initial data is sufficiently close to the constant equilibrium state, we establish the global-in-time infinity-ion-mass convergence.

The local composition of heterogeneous catalysts can deviate from average values obtained by integral techniques. However, due to the difficulties in capturing nontranslational parts, they are ofte...

Due to elimination of horizontal and vertical tails, flying wing aircraft has poor longitudinal and directional dynamic characteristics. In addition, flying wing aircraft uses drag rudders for yaw control, which tends to generate strong three-axis control coupling. To overcome these problems, a flight control law design method that couples the longitudinal axis with the lateral-directional axes is proposed. First, the three-axis coupled control augmentation structure is specified. In the structure, a “soft/hard” cross-connection method is developed for three-axis dynamic decoupling and longitudinal control response decoupling from the drag rudders; maneuvering turn angular rate estimation and subtraction are used in the yaw axis to improve the directional damping. Besides, feedforward control is adopted to improve the maneuverability and control decoupling performance. Then, detailed design methods for feedback and feedforward control parameters are established using eigenstructure assignment and model following technique. Finally, the proposed design method is evaluated and compared with conventional method by numeric simulations. The influences of control derivatives variation of drag rudders on the method are also analyzed. It is demonstrated that the method can effectively improve the dynamic characteristics of flying wing aircraft, especially the directional damping characteristics, and decouple the longitudinal responses from the drag rudders.

The letter presents a trailer-maneuverability analysis for the N-trailer kinematic structures comprising a tractor and an arbitrary number of single-axle trailers equipped with steerable or fixed wheels. For an elliptically-shaped set of tractor's input-velocities, we derive a mobility-ellipse generated in a velocity space of the (last) trailer. We show that the on-axle type of hitching present in the N-trailer leads to a singularity of a trailer-mobility (at least one degree of mobility is lost). Furthermore, we provide some relations between kinematic parameters of the N-trailer and its control inputs which enable shaping the trailer-mobility ellipse and decoupling it from a joint-configuration of the vehicle.

In this paper, we propose a fast compact implicit integration factor (FcIIF) method with non-uniform time meshes for solving the two-dimensional nonlinear Riesz space-fractional reaction-diffusion equation. The weighted and shifted Gruwald-Letnikov (WSGD) approximation is employed to the spatial discretization of the equation, and a system of nonlinear ordinary differential equations (ODEs) in matrix form is obtained. Since the cIIF method can provide excellent stability properties with good efficiency by decoupling the treatment of the diffusion and reaction terms, a fast cIIF (FcIIF) method with non-uniform time meshes is developed to solve the resultant nonlinear system of ODEs. Compared with the cIIF method, the proposed FcIIF method avoids the direct calculation of dense exponential matrices and requires less computational cost. The stability, accuracy and effectiveness of the proposed method are verified by the linear stability analysis and various numerical experiments.

This article describes a method that decouples hydrodynamic and hydrostatic pressure from total pressure in a dry gas seal, and analyses their functions and evaluates their contributions. It is applied to the pressure distributions of three typical symmetrical-groove dry gas seals – in particular the “fir tree” groove design – and is used to analyse the relationship between sealing performance and rotational speed. By separating the hydrodynamic and hydrostatic pressure distributions, their effects on sealing performance can be evaluated respectively. The hydrodynamic pressure of a symmetrical-groove dry gas seal is very weak because of the symmetry of the groove, which means that sealing performance is determined mainly by hydrostatic pressure. Therefore, when optimising the groove structure of such a seal, performance is improved by making the groove more receptive to high pressure. The first instalment of this article appears in the September 2020 issue of Sealing Technology (pages 4–9).

In the standard model of cosmology, the Universe began its expansion with an anomalously low entropy, which then grew dramatically to much larger values consistent with the physical conditions at decoupling, roughly 380,000 years after the Big Bang. There does not appear to be a viable explanation for this `unnatural' history, other than via the generalized second law of thermodynamics (GSL), in which the entropy of the bulk, S_bulk, is combined with the entropy of the apparent (or gravitational) horizon, S_h. This is not completely satisfactory either, however, since this approach seems to require an inexplicable equilibrium between the bulk and horizon temperatures. In this paper, we explore the thermodynamics of an alternative cosmology known as the R_h=ct universe, which has thus far been highly successful in resolving many other problems or inconsistencies in LCDM. We find that S_bulk is constant in this model, eliminating the so-called initial entropy problem simply and elegantly. The GSL may still be relevant, however, principally in selecting the arrow of time, given that S_h ~ t^2 in this model., Comment: 12 pages, 1 Table. Accepted for publication in EPJ-C

Particle number size distribution (PNSD) is of importance for understanding the mechanisms of particle growth, haze formation and climate impacts. However, the measurements of PNSD aloft in megacities are very limited. Here we report the first simultaneous winter measurements of size-resolved particle number concentrations along with collocated gaseous species and aerosol composition at ground level and 260 m in Beijing. Our study showed that the vertical differences of particle number concentrations between ground level and aloft varied significantly as a function of particle size throughout the study. Further analysis illustrated the impacts of boundary dynamics and meteorological conditions on the vertical differences of PNSD. In particular, the temperature and relative humidity inversions were one of the most important factors by decoupling the boundary layer into different sources and processes. Positive matrix factorization analysis identified six sources of PNSD at both ground level and city aloft. The local source emissions dominantly contributed to Aitken-mode particles, and showed the largest vertical gradients in the city. Comparatively, the regional particles were highly correlated between ground level and city aloft, and the vertical differences were relatively stable throughout the day. Our results point to-wards a complex vertical evolution of PNSD due to the changes in boundary layer dynamics, meteorological con-ditions, sources, and processes in megacities. (c) 2021 Elsevier B.V. All rights reserved.

The main objective of a statistical mechanical calculation is drawing the phase diagram of a many-body system. In this respect, discrete systems offer the clear advantage over continuum systems of an easier enumeration of microstates, though at the cost of added abstraction. With this in mind, we examine a system of particles living on the vertices of the (biscribed) pentakis dodecahedron, using different couplings for first and second neighbor particles to induce a competition between icosahedral and dodecahedral orders. After working out the phases of the model at zero temperature, we carry out Metropolis Monte Carlo simulations at finite temperature, highlighting the existence of smooth transitions between distinct "phases", The sharpest of these crossovers are characterized by hysteretic behavior near zero temperature, which reveals a bottleneck issue for Metropolis dynamics in state space. Next, we introduce the quantum (Bose-Hubbard) counterpart of the previous model and calculate its phase diagram at zero and finite temperatures using the decoupling approximation. We thus uncover, in addition to Mott insulating "solids", also the existence of supersolid "phases" which progressively shrink as the system is heated up. We argue that a quantum system of the kind described here can be realized with programmable holographic optical tweezers., Comment: 30 pages, 11 figures

We discuss the basic ideas of relativistic transport models used for the interpretation and description of experimental data from heavy-ion collisions at high collision energies. We highlight selected results from microscopic simulations of these reactions with a main focus on the UrQMD and PHSD approaches. We also address the results of macroscopic approaches like hydrodynamics or coarse-grained dynamics used in different model combinations in comparison to experimental data. We address the results of such simulations for the description of QCD matter close to equilibrium in terms of transport coefficients like shear η and bulk viscosity ζ and discuss the connection of the radial flow to the equation of state and the transport properties. Then we turn to dileptons and photons as messengers from the hot and dense region before coming to the exploration of the decoupling stage. Generally, we find that microscopic simulations provide a good description of a large variety of observables over many orders of collision energies.

The so-called method of phase synchronization has been advocated in a number of papers as a way of decoupling a system of linear second-order differential equations by a linear transformation of coordinates and velocities. This is a rather unusual approach because velocity-dependent transformations in general do not preserve the second-order character of differential equations. Moreover, at least in the case of linear transformations, such a velocity-dependent one defines by itself a second-order system, which need not have anything to do, in principle, with the given system or its reformulation. This aspect, and the related questions of compatibility it raises, seem to have been overlooked in the existing literature. The purpose of this paper is to clarify this issue and to suggest topics for further research in conjunction with the general theory of decoupling in a differential geometric context., Comment: 17 pages, to appear in J Geometric Mechanics

Colloidal suspensions in confined geometries exhibit rich diffusion dynamics governed by particle shapes and particle-confinement interactions. Here, we propose a colloidal system, consisting of ellipsoids in periodic array of obstacles, to investigate the confined diffusion of anisotropic colloids. From the obstacle density-dependent diffusion, we discover a decoupling of translational and rotational diffusion in which only rotational motion is localized while translational motion remains diffusive. Moreover, by evaluating the probability distributions of displacements, we found Brownian but non-Gaussian diffusion behaviors with increasing the obstacle densities, which originates from the shape anisotropy of the colloid and the multiplicity of the local configurations of the ellipsoids with respect to the obstacle. Our results suggest that the shape anisotropy and spatial confinements play a vital role in the diffusion dynamics. It is important for understanding the transportations of anisotropic objects in complex environments.

This study aims to develop a universal, robust, and linear method to obtain an initial guess configuration for the multi-step finite element method (FEM) solver of sheet metal forming. Using the decoupling theory, the deformation at each step in the multi-step FEM solver of the sheet metal forming is decoupled into two independent deformation modes: bending-dominated deformation and stretching-dominated deformation. The configuration of the bending-dominated deformation constrained by the sliding constraint surface is considered as the initial guess configuration for the current step in multi-step FEM solver. To get an accurate initial configuration at each step, the method of Laplace-Beltrami operator (LBO) on a simplicial surface is employed to obtain the initial guess configuration effectively. Several numerical examples are provided for validation and verification of the proposed method through its applications for complicated sheet metal workpieces of finite element simulations. The results show that the proposed method on the simplicial surface for the initial guess configuration within a few iterations to be significantly effective.

The disturbance decoupling problem (DDP) whereby the system outputs become insensitive to exogenous signals or disturbances plays a vital role in systems engineering and biological systems. Notably, many biological signalling systems with multiple outputs are usually susceptible to external environmental changes. The authors investigate the DDP for Boolean control networks (BCNs) and present a novel technique based on Boolean algebra to solve the DDP. In particular, the results on the DDP solvability are derived by transforming the system dynamics to a simplified form called output-friendly form. Furthermore, a constructive procedure based on the Karnaugh map to design all possible feedback controllers such that the states affecting the outputs are free from disturbances is proposed. Moreover, the presented results are extended to switched BCNs, and design all possible mode-independent feedback controllers. Finally, some examples including a Boolean model of Escherichia coli are provided to validate the main findings.

The relationship between the economy and the environment is not straightforward and is influenced by a multitude of factors. Ideally, economic growth would not damage environmental quality and environmental protection would not hinder economic growth. Achieving this decoupling often requires environmental policy, but the analysis of specific policy instruments and their necessary levels to achieve it is rare. In this paper, we use a stylized equilibrium model to explore distinct policy instruments under which relative decoupling and absolute decoupling between economic growth and emissions occur. In our model, final-goods production uses polluting (non-renewable) and non-polluting (renewable) resources. The government taxes emissions and subsidizes renewables production. In the empirical application, we focus on the case of electricity generation. Results show that, with a growing subsidy, relative decoupling exists. Achieving absolute decoupling is harder, but it occurs for a certain interval of the subsidy growth rate. For that purpose, the choice of the tax and subsidy growth rates is more important than the choice of the initial levels for these instruments. The choice of the subsidy growth rate indicates the prioritization between the economy and the environment. A lower subsidy growth rate favors the environment, while a higher one favors the economy. The tax growth rate dictates the distance between the output growth rate and the emissions growth rate. The higher the tax growth rate, the higher the difference between them. In sum, the government can decide between attaining higher output growth rates, higher emissions decreasing rates, or an intermediate situation.

Stable quantum memories that capable of storing quantum information for long time scales are an essential building block for an array of potential applications. The long memory time are usually achieved via dynamical decoupling technique involving decoupling of the memory states from its local environment. However, because this process is strongly limited by the errors in the pulses, an noise-protected scheme remains challenging in the field of quantum memories. Here we propose a scheme to design a noise-resisted \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\pi$$\end{document}π pulse, which features high fidelity exceeding \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$99.9\%$$\end{document}99.9% under realistic situations. Using this \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\pi$$\end{document}π pulse we can generate different dynamical decoupling sequences that preserve high fidelity for long time scales. The versatility, robustness, and potential scalability of this method may allow for various applications in quantum memories technology.

Multilevel buck dc–dc converters have advantages of low switching voltage stress, small inductor size, and high power density. To take an advantage of these properties, the flying capacitor voltage must be balanced at appropriate voltage references value. However, the multilevel buck dc–dc converters are a multi-input multioutput nonlinear strongly coupled control system. To address the problems associated with the complexity of strongly coupled voltages while maintaining control, in this article we propose a decoupled optimal control strategy with an inverse system theory. On the basis of establishing a large signal average model, a universal method to choose the output function for full linearization is proposed with the help of the inverse system method. Furthermore, the linearization and decoupling of the system are achieved, and a number of single-input, single-output pseudolinear subsystems are obtained. Based on the linearized system, multiple optimal controllers are designed to control the subsystems, which significantly reduces the difficulty in controller design. Numerical simulation results show that compared to proportional integral control with linear decoupling, the proposed control strategy has better dynamic regulation performance and stronger robustness under a six-level buck dc–dc converter. Finally, the proposed approach is further verified with the experimental results of a three-level buck dc–dc converter prototype.

This article describes a method that decouples hydrodynamic and hydrostatic pressure from total pressure in a dry gas seal, and analyses their functions and evaluates their contributions. It is applied to the pressure distributions of three typical symmetrical-groove dry gas seals – in particular the “fir tree” groove design – and is used to analyse the relationship between sealing performance and rotational speed. By separating the hydrodynamic and hydrostatic pressure distributions, their effects on sealing performance can be evaluated respectively. The hydrodynamic pressure of a symmetrical-groove dry gas seal is very weak because of the symmetry of the groove, which means that sealing performance is determined mainly by hydrostatic pressure. Therefore, when optimising the groove structure of such a seal, performance is improved by making the groove more receptive to high pressure. The first instalment of this article, which appears here, provides the background and an introduction to the decoupling method and describes the numerical model. Part II will be published in the October 2020 issue of Sealing Technology.

Methods to decompose the elastic wavefield into compressional wave (P-wave) and shear wave (S-wave) components in heterogeneous media without wavefield distortions or energy leakage are the key issues in elastic imaging and inversion. We have introduced a decoupled P- and S-wave propagator to form an efficient elastic reverse time migration (RTM) framework, without assuming homogeneous Lamé parameters. Also, no wave-mode conversions occur using the proposed propagator in the presence of strong heterogeneities, which avoids the potential imaging artifacts caused by wave-mode conversions in the receiver-side backward extrapolation. In the proposed elastic RTM framework, the source-side forward wavefield is simulated with a P-wave propagator. The receiver-side wavefield is back extrapolated with the proposed propagator, using the recorded multicomponent seismic data as input. Compared to the conventional elastic RTM, the proposed framework reduces the computational complexity while preserving the imaging accuracy. We have determined its accuracy and efficiency using two synthetic examples.

Stochastic system state estimation subject to the unknown interference input widely exists in many fields, such as the control, communication, signal processing, and fault diagnosis. However, the research results are mostly limited to the stochastic system in which only the dynamic state model or the measurement model concerns the individual unknown interference input, and the state model and the measurement model are both with the same unknown interference input. State estimate of the stochastic systems where the state model and the measurement model contain dual Unknown Interference inputs (dual-UI) with different physical meanings and mathematical definitions is concerned here. Firstly, the decoupling condition with the Unknown Interference input in the State model (S-UI) is shown, which introduces the decoupled system with the adjacent Measurement concerned Unknown Interference inputs (M-UI) appearing in the state model and the measurement model. Then, through defining the Differential term of the adjacent M-UI (M-UID), the equivalent system with only M-UID in the state model is obtained. Finally, considering the design freedom of the equivalent system, the decoupling filter in the minimum mean square error sense and the adaptive minimum upper filter with different applicable conditions are represented to obtain the optimal and sub-optimal state estimate, respectively. Two simulation cases verify the effectiveness and superiority compared with the traditional methods.

Objective: In the electroencephalogram (EEG) the quadratic phase coupling (QPC) phenomenon indicates the presence of non-linear interactions among brain rhythms that could affect the interpretation of their physiological meaning. We propose the use of the bicoherence as a QPC quantification method to understand the nature of brain rhythm interplay. Methods: We firstly provide a simulation study to show under which condition of signal to noise ratio (SNR) the bicoherence is a reliable QPC quantifier and how to interpret the results. Secondly, in the light of the simulation results, we applied the bicoherence analysis to real EEG data acquired on thirteen volunteers during a cue-paced reaching motor task to quantify coupling and decoupling between mu and beta rhythms. An inter-trial averaging procedure was adopted in order to allow the correct calculation of the bicoherence during a motor task. Results : Simulations demonstrated that SNR has a strong impact on the correct quantification of bicoherence and that a reliable detection of QPC is possible when the SNR is favorable (>−5 dB). Results from EEG data demonstrated a QPC between mu and beta rhythms during the resting state and its fading during movement planning and execution, providing valuable information for the interpretation of their dynamics. Conclusion: The bicoherence was proven to be an effective tool for the investigation of coupling between the sensorimotor rhythms during all the phases of a motor task. This was assessed in relation to the physiological changing of the SNR characterizing the frequency components of interest.

This article tackles the problem of controlling articulated soft robots (ASRs), i.e., robots with either fixed or variable elasticity lumped at the joints. Classic control schemes rely on high-authority feedback actions, which have the drawback of altering the desired robot softness. The problem of accurate control of ASRs, without altering their inherent stiffness, is particularly challenging because of their complex and hard-to-model nonlinear dynamics. Leveraging a learned anticipatory action, iterative learning control (ILC) strategies do not suffer from these issues. Recently, ILC was adopted to perform position control of ASRs. However, the limitation of position-based ILC in controlling variable stiffness robots is that whenever the robot stiffness profile is changed, a different input action has to be learned. Our first contribution is to identify a wide class of ASRs, whose motion and stiffness adjusting dynamics can be proved to be decoupled. This class is described by two properties that we define: strong elastic coupling, relative to motors and links of the system and their connections; and homogeneity, relative to the characteristics of the motors. Furthermore, we design a torque-based ILC scheme that, starting from a rough estimation of the system parameters, refines the torque needed for the joint positions tracking. The resulting control scheme requires minimum knowledge of the system. Experiments on variable stiffness robots prove that the method effectively generalizes the iterative procedure with respect to the desired stiffness profile and allows good tracking performance. Finally, potential restrictions of the method, e.g., caused by friction phenomena, are discussed.

Controlling and maintaining the orientation of the balloon-borne gondola for high-altitude flight is a prerequisite for ensuring the pointing control of observation instruments. When the balloon-borne gondola is flying in the stratosphere of the atmosphere, the existing external interferences will be converted into the coupling moment to the azimuth control system. Meanwhile, those uncertain factors and the frictional nonlinearity of the control system will also cause a certain magnitude of coupling moment. The existence of such coupling moment largely impacts on the accuracy and stability of the orientation control for the angular momentum exchange devices of the balloon-borne gondola. To address such an issue, this paper proposes and implements a novel type of integrated decoupler device. With this decoupler adopted, the aziDmuth control system could sense the existence of coupling torque and azimuth fluctuations quickly and suppress the influences of external interference, uncertain factors, and system structure nonlinearity on the azimuth control effectively, thereby improving the control accuracy of the azimuth control system. Both simulations and experiments are conducted to verify the effectiveness of the proposed device. The results show that the integration of the decoupler and the controller of the azimuth control system provide the azimuth control of the balloon-borne gondola with high accuracy and stability. Such a decoupler device design has a broad potential and could not only be used for balloon-borne gondola control but also could be applied onto other control systems using angular momentum exchange devices as actuators.

The interplay of Mie’s multipole resonances provides a huge opportunity for discovering new phenomena in nanophotonics and developing nanophotonic devices of new functionalities. One of the keys to...

High-speed permanent magnet synchronous machine is often used as a starter generator for a single-shaft micro-gas turbine due to its high efficiency and high-power density. However, when the machine works in the starting mode, it usually needs a complex control system to start since the machine cannot realise self-starting. Therefore, here, a dual-purpose rotor sleeve is proposed for the machine to have the starting ability. Furthermore, the dynamic response speed of the machine also can be improved by optimising the electromagnetic characteristics of the sleeve. Taking a 40 kW, 20,000 r/min surface-mounted permanent magnet machine as an example, the two-dimensional finite element model of the machine is established. The start-up time and locked rotor parameters under different sleeve conductivities are studied by the finite element method. In order to find out the reason for the change of starting performance, the rotor eddy current distribution is studied. Furthermore, the starting torque of the machine is decoupling analyzed, and the influence of sleeve conductivity on various kinds of torques are found to reveal the influence mechanism of sleeve conductivity on starting performance. Finally, the correctness of the model is verified by experiments.

This paper is concerned with the problem of output feedback control for continuous-time T–S fuzzy systems. The aim is to reduce the conservatism of finding output feedback controller design conditions based on the Lyapunov function which depends on membership functions. Firstly, in order to improve the existing results, a new approach to bound the time derivatives of the membership functions is proposed. Secondly, based on the non-quadratic Lyapunov function and matrix decoupling techniques, the static-output feedback controller and the dynamic output feedback controller are designed to guarantee that the system is asymptotically stable, respectively. Finally, three examples are given to indicate the effectiveness of the approach.

In order to improve the precision positioning accuracy of image stabilization mechanism, a two-dimensional image stabilization mechanism with parallel decoupling was proposed. Firstly, according to the principle of lever-half-bridge hybrid amplification mechanism, the structure of two-dimensional image stabilization mechanism was designed, the working principle was analyzed, and natural frequency of the mechanism was calculated. Secondly, static analysis, modal analysis, and flexure hinge parameter optimization of the mechanism based on ANSYS were carried out. The simulation results show that two-dimensional image stabilization mechanism can realize the micro-displacement positioning function in the X and Y directions. The resonance phenomenon does not occur when the mechanism works. The thickness and width are the sensitive parameters of flexure hinge. Finally, the actuation performance of two-dimensional image stabilization mechanism was tested during the prototype, the relationship between the output displacement in the X and Y directions and the input voltage, frequency was tested, and the displacement coupling in the X and Y directions was tested. The experimental results show that the motion displacement of the mechanism is 103.9 × 104.8 μm, and the output displacement coupling does not exceed 7.5% of the stroke. The image stabilization mechanism can realize large stroke and precision positioning functions, and is feasible in engineering applications.

PurposeViscous dampers are commonly used in large span cable-stayed bridges to mitigate seismic effects and have achieved great success.Design/methodology/approachHowever, the nonlinear analysis on damper parameters is usually computational intensive and nonobjective. To address these issues, this paper proposes a simplified method to determine the viscous damper parameters for double-tower cable-stayed bridges. An empirical formula of the equivalent damping ratio of viscous dampers is established through decoupling nonclassical damping structures and linearization of nonlinear viscous dampers. Shaking table tests are conducted to verify the feasibility of the proposed method. Moreover, this simplified method has been proved in long-span cable-stayed bridges.FindingsThe feasibility of this method is verified by the simplified model shaking table test. This simplified method for determining the parameters of viscous dampers is verified in cable-stayed bridges with different spans.Originality/valueThis simplified method has been validated in cable-stayed bridges with various spans.

In this paper, to solve the surge speed loss problem generated by sway-yaw motion in the path-following control, a model-based decoupling (MBD) method for surge speed and heading control in vessel path following is proposed. The guidance law is designed independently in the kinematic level. In the kinetic level, the surge model and sway-yaw model can be decoupled by assuming that the surge speed varies slowly, and the heading controller and surge speed controller are designed under the framework of the MBD method. Commonly, the surge speed controller is ignored in the path following or designed separately. In the MBD method, the heading controller is designed first through the MPC method, and the coupling terms between the surge model and sway-yaw model are treated as time-varying disturbances, which can be predicted through the outcomes of the heading controller. Then, the time-varying disturbances are compensating in the surge speed controller so that the surge speed can be feedforward compensated to achieve better performance. The simulation results compared the surge speed performance in path following of the MBD method and usual approaches to illustrate the effectiveness of the MBD method.

The paper deals with the seismic response analysis of nonlinear secondary oscillators. Bilinear, sliding and rocking single-degree-of-freedom dynamic systems are analysed as representative of a wide spectrum of secondary structures and non-structural components. In a first stage, the equations governing their full dynamic interaction with linear multi-degree-of-freedom primary structures are formulated, and then conveniently simplified using primary-secondary two-degree-of-freedom systems and dimensionless coefficients. In a second stage, the cascade approximation is applied, whereby the feedback action of the secondary oscillator on the primary structure is neglected. Owing to the piecewise linearity of the secondary systems being considered, efficient semi-analytical and step-by-step numerical solutions are presented. The semi-analytical solutions allow the direct evaluation of the seismic response under pulse-type ground excitations and are also used to validate step-by-step numerical schemes, which in turn can be used for general-type seismic excitations. In a third stage, a set of decoupling criteria are proposed for the pulse-type base excitations, identifying the conditions under which a cascade analysis is admissible from an engineering standpoint. Finally, the influence and relative dependencies between the input parameters of the ground motion and the primary-secondary assembly are quantified on the response of the secondary systems through nonlinear floor response spectra, and general trends are identified and discussed.

Deep eutectic solvents (DESs) are new-generation media that can be fine-tuned to have desired properties circumventing economic and environmental issues. Typically, these are ionic, and only recently, nonionic DESs, having interesting properties, are being explored. In this report, we examined the structure and dynamics of a nonionic lauric acid/menthol (LA/Men) DES through steady-state emission, solvation dynamics, time-resolved fluorescence anisotropy, and translational diffusion dynamics. The zero shift in the emission spectra of coumarin 153 (a solvatochromic dye) as a function of the excitation wavelength suggests that LA/Men DES is spatially homogenous. Decoupling (p = 0.63) of the average solvation time, ⟨τs⟩, from medium viscosity suggests the presence of mild dynamic heterogeneity in the system. Rotational time, ⟨τr⟩, which reflects the nature of the first solvation shell, shows little decoupling (p = 0.81), suggesting it to be fairly dynamically homogeneous at a shorter length scale. An Arrhenius-type analysis also proves that rotation is mainly controlled by medium viscosity. Translational diffusion time, ⟨τD⟩, which provides information at a larger length scale, is strongly decoupled from medium viscosity (p = 0.29). This indicates that at a larger length scale, the DES is quite dynamically heterogeneous. The slow component of solvation time, which is believed to originate at a larger length scale, correlates well with the translational diffusion timescale having similar activation energies. This suggests that their origin is same. Expectedly, for the long component of solvation time, the decoupling is quite strong (p = 0.30). Overall, our result demonstrates the structure and dynamics of the nonionic LA/Men DES, and the existence of length scale-dependent heterogeneity has been proposed.

Rational prediction of future CO2 at the regional level is essential to the carbon emission reduction targets in China. The primary aim of this study is to examine the applicability of an up-to-date forecast algorithm, namely dynamic mode decomposition (DMD), in provincial CO2 emission prediction. The testing results validate the accuracy and application value of the DMD short-run forecast, which may provide method reference for relevant policy formulation and research areas. Moreover, the 2020 provincial economic situation and CO2 emissions in China are projected via DMD. On this basis, the unqualified provinces regarding CO2 emission reduction are identified considering the relative standard and absolute standard, and the corresponding mitigation paths are proposed through decoupling analysis and shadow price calculation. The results indicate that the unqualified provinces include Heilongjiang, Gansu, Shanxi, Hebei, Liaoning, Jilin, Shaanxi, and Inner Mongolia. The open-emission-reduction mechanism should be adopted in the first five provinces; the conservative one should be applied in the other provinces. Graphical abstract.

Doping through the incorporation of transition metal ions allows for the emergence of new optical, electrical, and magnetic properties in quantum dots (QDs). While dopants can be introduced into QDs through many synthetic methods, the control of dopant location and host-dopant (H-D) coupling through directional dopant movement is still largely unexplored. In this work, we have studied dopant behaviors in Mn:CdS/ZnS core/shell QDs and found that dopant transport behavior is very sensitive to the temperature and microenvironments within the QDs. The migration of Mn toward the alloyed interface of the core/shell QDs, below a temperature boundary (Tb) at ∼200 °C, weakens the H-D interactions. At temperatures higher than the Tb, however, dopant ejection and global alloying of CdS/ZnS QDs can occur, leading to stronger H-D coupling. The behavior of incorporated dopants inside QDs is fundamentally important for understanding doping mechanisms and the host-dopant interaction-dependent properties of doped nanomaterials.

The frequency nadir is a significant indicator for the primary frequency response monitoring and control. It is imperative to predict the maximum frequency deviation and the time at which the maximum occurs with high efficiency and accuracy following a major disturbance. To develop an analytical model for the frequency nadir prediction, the closed-loop is broken and a parabolic frequency deviation is input for decoupling the calculation of governor response and frequency deviation. Following which, the polynomial fitting is adopted to depict the primary frequency response characteristic of each governor. The iterative numerical solution for the frequency nadir prediction model is carried out based on the insight into the features of governor response. Case studies are presented to verify the performance of the analytical model over WSCC 9-bus system, New England 39-bus system and practical provincial power system, where the frequency nadir prediction model demonstrates its advantages of easy implementation, minimum computation, and high accuracy.

The structural vibration and dominant vibration characteristics of the machining process of machine tools have an important influence on the machining quality and efficiency. The dominant vibration characteristics are related to two factors: the dynamic characteristics of the machine tool structure and the excitation characteristics of the system. In the dynamic process of structural vibration, the participations of various modes in a certain frequency domain are often different in the vibration process; that is to say, not all modes can be excited equally, only a certain mode or some of the modes may play a major role in the specific processing conditions and dominate. Thus, these modes are called the dominant vibration modes. Therefore, this paper proposes a method of modal response signal prediction and dominant vibration mode identification under the cutting state of machine tool and studies the dominant vibration characteristics of the machine tool structure under cutting conditions. A dynamic system modeling method based on state space and modal decoupling theory is proposed. The Kalman filter algorithm is used to predict the modal response signal of the machine tool during cutting process, and the modal participation degree is analyzed based on the predicted modal response signal. In this way, the dominant vibration mode of the machine tool structure is analyzed.

It is more efficient to employ inductive power transfer (IPT) systems to charge automated guided vehicles (AGVs) than traditional plug-in systems. In order to provide independent and different charging power for the driven system and the control system of AGVs simultaneously, this letter proposes a coaxial dual-receiver structure and a decoupling circuit, which utilizes a passive component connected with two receiving coils to cancel out the mutual inductance between each other. By using this decoupling method, the two receiving coils could be treated as independent receivers without precise placement or additional transformers. First, the decoupling model is analyzed in detail, and the value of the decoupling component is given without any restriction of the ratio of their current. Then, the structure of the dual receiver is designed. Finally, an IPT system with one transmitter and dual receivers is built to verify the feasibility of the proposed method. Experimental results show that when one of the loads varies from 20 to 80 Ω, the voltage fluctuation of the other load is as small as 1.36% with decoupling, whereas 54.46% of voltage fluctuation without decoupling. The results validate that the proposed method is suitable for the application requiring dual independent outputs in the same equipment.

In this letter, a new coupling structure for dynamic wireless power transfer (DWPT) systems is proposed. Bipolar coils are symmetrically placed on the transmitter unipolar coils, resulting in natural decoupling between the bipolar coils and the unipolar coils. This special structure can mitigate the self-couplings between the adjacent unipolar transmitter coils and hence facilitate the design of the compensation circuit. Another remarkable advantage of this design is that it can lead to a stable mutual coupling between the transmitter array and the receiver when the receiver moves along the transmitter, making it a natural fit for DWPT applications. Furthermore, to reduce the electromagnetic interference and power loss, an automatic segmented control scheme is implemented, and a position detection method by monitoring the primary current is developed. The feasibility of the proposed coupling structure and the position detection method are verified on a laboratory prototype with 72-V output voltage. The experimental results show that the power fluctuation is within ±2.5%, and system efficiency is around 90%. (This letter is accompanied by a video demonstrating the experimental test).

This paper focuses on current control in a permanent-magnet synchronous motor (PMSM). This paper has two main objectives: the first objective is to develop a neural-network (NN) vector controller to overcome the decoupling inaccuracy problem associated with the conventional proportional-integral-based vector-control methods. The NN is developed using the full dynamic equation of a PMSM, and trained to implement optimal control based on approximate dynamic programming. The second objective is to evaluate the robust and adaptive performance of the NN controller against that of the conventional standard vector controller under motor parameter variation and dynamic control conditions by: 1) simulating the behavior of a PMSM typically used in realistic electric vehicle applications and 2) building an experimental system for hardware validation as well as combined hardware and simulation evaluation. The results demonstrate that the NN controller outperforms conventional vector controllers in both simulation and hardware implementation.

Objective: Accelerating the co-simulation method for the design of transmit array (TxArray) coils is studied using equivalent circuit models. Materials and methods: Although the co-simulation method dramatically reduces the complexity of the design of TxArray coils, finding the optimum solution is not trivial since there exist many local minima in the optimization problem. We propose to utilize an equivalent circuit model of the TxArray coil to obtain a proper initial guess for the optimization process of the co-simulation method. To prove the concept, six different TxArray coils (i.e., three degenerate birdcage coils (DBC), two dual-row head coils, and one elliptical body TxArray coil) with two different loading strategies (cylindrical phantom and human head/body model) at 3 T field strength are investigated theoretically; as an example study, an eight-channel head-DBC is constructed using the obtained values. Results: This approach accelerates the design process more than 20-fold for the coils that are investigated in this manuscript. Conclusion: A fast and accurate method for tuning and decoupling of a TxArray coil can be achieved using its equivalent circuit model combined with the co-simulation method.

We combine our force-based theory of activated segmental relaxation for glass-forming polymer melts, with our new formulation of how nm-scale effectively static structural fluctuations induce dynam...

Author(s): Slepian, Zachary | Abstract: Perturbation theory (PT) is often used to model statistical observables capturing the translation and rotation-invariant information in cosmological density fields. PT produces higher-order corrections by integration over linear statistics of the density fields weighted by kernels resulting from recursive solution of the fluid equations. These integrals quickly become high-dimensional and naively require increasing computational resources the higher the order of the corrections. Here we show how to decouple the integrands that often produce this issue, enabling PT corrections to be computed as a sum of products of independent 1-D integrals. Our approach is related to a commonly used method for calculating multi-loop Feynman integrals in Quantum Field Theory, the Gegenbauer Polynomial $x$-Space Technique (GPxT). We explicitly reduce the three terms entering the 2-loop power spectrum, formally requiring 9-D integrations, to sums over successive 1-D radial integrals. These 1-D integrals can further be performed as convolutions, rendering the scaling of this method $N_{\rm g} \log N_{\rm g}$ with $N_{\rm g}$ the number of grid points used for each Fast Fourier Transform. This method should be highly enabling for upcoming large-scale structure redshift surveys where model predictions at an enormous number of cosmological parameter combinations will be required by Monte Carlo Markov Chain searches for the best-fit values.

The economic and social development of a country rely heavily on transportation. In China, it has become the third largest energy consumption sector and generates substantial amounts of carbon emissions. In the present study, direct and indirect carbon emissions from the transportation industry throughout China's 30 provinces during 1997-2017 were calculated. Further, to reveal the spatio-temporal characteristics of the relationship between carbon emissions and economic growth, the standard deviational ellipse and Tapio decoupling method were employed. The main results are as follows. (1) The total carbon emissions from the transportation industry increased from 132.79 million tons (Mt) in 1997 to 849.64 Mt in 2017, with an average annual growth rate of 9.72%; direct carbon emissions accounted for approximately 86% of the total. (2) Carbon emissions as well as the added value of the transportation industry had the same spatial distribution characteristics, presenting a northeast-southwest pattern during 1997-2017. Although their spatial distribution patterns were mainly in the north-south direction, the development in the east-west direction became increasingly obvious. (3) The decoupling index in the transportation industry was greater than 0.8 for most years, with an expansive negative decoupling state or an expansive coupling state. The differences in carbon emissions and economic growth between various provinces showed a spatio-temporal disparity of the decoupling states in the transportation industry. The obtained results are of considerable interest for China's policymakers to set more reasonable carbon emission reduction goals and implement targeted policies according to the carbon emission situation at a local scale.

Owing to the uncertainty around the coupling and decoupling of oil and gas prices, this study re-examines the relationship between oil and gas markets by modeling the price of one energy source based on the price of the other, both linearly and nonlinearly. We present an autoregressive exogenous model and three nonlinear frameworks with different patterns of asymmetry. Based on daily data from January 7, 1997, to December 29, 2017, our analysis reaches two main findings. First, the nonlinear frameworks outperform the linear model (i.e., the autoregressive exogenous model) in modeling the relationship between oil and gas prices. Second, the nature of asymmetry varies based on market direction. We show that when oil prices exhibit an extreme movement (i.e., beyond a threshold value in absolute value), gas prices react nonlinearly, and that there is no relationship otherwise. Our results are robust for other frequencies, mainly weekly and monthly. These findings explain the conflicting results in the literature on the complex relationship between these markets. The results might serve investors in term of hedging, portfolio diversification, and asset allocation as we show that in the calm period, there is no relationship between oil and gas prices; however, the interaction between markets is more pronounced during periods of extreme movement. Similarly, policymakers’ awareness of the nonlinear dynamic under extreme movements could inform the regulation policy and/or adjustment in case oil (gas) prices increase or decrease.