Spin-star environment assisted entanglement generation in weakly coupled bipartite systems

We study the entanglement evolution in a weakly coupled bipartite system with a large energy level difference under the influence of spin-star environments. The subsystems can be coupled to a pure state or a thermal equilibrium state spin-star environment. Our results show that, in the case of the coupling strength being less than the energy level difference of the subsystems （weakly coupled）, the spin-star environment can always be used to assist the entanglement generation of the bipartite system.

Characterization of forced localization of disordered weakly coupled micromechanical resonators

The mode localization phenomenon of disordered weakly coupled resonators(WCRs)is being used as a novel transduction scheme to further enhance the sensitivity of micromechanical resonant sensors.In this paper,two novel characteristics of mode localization are described.First,we found that the anti-resonance loci behave as a linear function of the stiffness perturbation.The antiresonance behavior can be regarded as a new manifestation of mode localization in the frequency domain,and mode localization occurs at a deeper level as the anti-resonance approaches closer to the resonance.The anti-resonance loci can be used to identify the symmetry of the WCRs and the locations of the perturbation.Second,by comparing the forced localization responses of the WCRs under both the single-resonator-driven(SRD)scheme and the double-resonator-driven(DRD)scheme,we demonstrated that the DRD scheme extends the linear measurement scale while sacrificing a certain amount of sensitivity.We also demonstrated experimentally that the amplitude ratio-based sensitivity under the DRD scheme is approximately an order of magnitude lower than that under the SRD scheme,that is,the amplitude ratio-based sensitivity is−70.44%(Nm^(−1))^(−1) under the DRD scheme,while it is−785.6%(Nm^(−)1)^(−1) under the SRD scheme.These characteristics of mode localization are valuable for the design and control of WCR-based sensors.

Euler-type schemes for weakly coupled forward-backward stochastic differential equations and optimal convergence analysis

We introduce a new Euler-type scheme and its iterative algorithm for solving weakly coupled forward-backward stochastic differential equations （FBSDEs）. Although the schemes share some common features with the ones proposed by C. Bender and J. Zhang [Ann. Appl. Probab., 2008, 18： 143-177], less computational work is needed for our method. For both our schemes and the ones proposed by Bender and Zhang, we rigorously obtain first-order error estimates, which improve the half-order error estimates of Bender and Zhang. Moreover, numerical tests are given to demonstrate the first-order accuracy of the schemes.

Algorithm Selection Method Based on Coupling Strength for Partitioned Analysis of Structure-Piezoelectric-Circuit Coupling

In this study, we propose an algorithm selection method based on coupling strength for the partitioned analysis ofstructure-piezoelectric-circuit coupling, which includes two types of coupling or inverse and direct piezoelectriccoupling and direct piezoelectric and circuit coupling. In the proposed method, implicit and explicit formulationsare used for strong and weak coupling, respectively. Three feasible partitioned algorithms are generated, namely(1) a strongly coupled algorithm that uses a fully implicit formulation for both types of coupling, (2) a weaklycoupled algorithm that uses a fully explicit formulation for both types of coupling, and (3) a partially stronglycoupled and partially weakly coupled algorithm that uses an implicit formulation and an explicit formulation forthe two types of coupling, respectively.Numerical examples using a piezoelectric energy harvester,which is a typicalstructure-piezoelectric-circuit coupling problem, demonstrate that the proposed method selects the most costeffectivealgorithm.

Importance of Three-Dimensional Piezoelectric Coupling Modeling in Quantitative Analysis of Piezoelectric Actuators

This paper demonstrates the importance of three-dimensional(3-D)piezoelectric coupling in the electromechanical behavior of piezoelectric devices using three-dimensional finite element analyses based on weak and strong coupling models for a thin cantilevered piezoelectric bimorph actuator.It is found that there is a significant difference between the strong and weak coupling solutions given by coupling direct and inverse piezoelectric effects(i.e.,piezoelectric coupling effect).In addition,there is significant longitudinal bending caused by the constraint of the inverse piezoelectric effect in the width direction at the fixed end(i.e.,3-D effect).Hence,modeling of these effects or 3-D piezoelectric coupling modeling is an electromechanical basis for the piezoelectric devices,which contributes to the accurate prediction of their behavior.

Study on a Gas Plunger Lift Model for Shale Gas Wells and Its Effective Application

The problem of efficient gas lift for gas well annulus packers that rely on their own energy plungers is considered.The complex related gas-liquid problem is addressed in the frame of model where the gas inflow dynamics and liquid inflow dynamics of the considered shale gas wells are weakly coupled.On this basis,and with the aiding support of indoor simulation experimental data,a new gas plunger lift design taking into account liquid leakage is obtained.Finally,a dedicated software relying on this approach is developed and used to verify the reliability of the model by means of field examples.

Effect of wind fluctuating on self-starting aerodynamics characteristics of VAWT

The present work deals with an investigation of the self-starting aerodynamic characteristics of VAWT under fluctuating wind. In contrast to the previous studies, the rotational speed of the turbine is not fixed, the rotation of the turbine is determined by the dynamic interaction between the fluctuating wind and turbine. A weak coupling method is developed to simulate the dynamic interaction between the fluctuating wind and passive rotation turbine, and the results show that if the fluctuating wind with appropriate fluctuation amplitude and frequency, the self-starting aerodynamic characteristics of VAWT will be enhanced. It is also found that compared with the fluctuation amplitude, the fluctuation frequency of the variation in wind velocity is shown to have a minor effect on the performance of the turbine. The analysis will provide straightforward physical insight into the self-starting aerodynamic characteristics of VAWT under fluctuating wind.

Control schemes for synchronizing two subnetworks with weak couplings

In this paper, we propose a well-designed network model with a parameter and study full and partial synchronization of the network model based on the stability analysis. The network model is composed of a star-coupled subnetwork and a globally coupled subnetwork. By analyzing the special coupling configuration, three control schemes are obtained for synchronizing the network model. Further analysis indicates that even if the inner couplings in each subnetwork are very weak, two of the control schemes are still valid. In particular, if the outer coupling weight parameter 0 is larger than （n2 - 2n）/4, or the subnetwork size n is larger than 02, the two subnetworks with weak inner couplings can achieve synchronization. In addition, the synchronizability is independent of the network size in case of 0 〈 0 〈 n/（n ＋ 1 ）. Finally, we carry out some numerical simulations to confirm the validity of the obtained control schemes. It is worth noting that the main idea of this paper also applies to any network consisting of a dense subnetwork and a sparse network.

Reduction of interfacial thermal resistance of overlapped graphene by bonding carbon chains

Exploring the mechanism of interfacial thermal transport and reducing the interfacial thermal resistance are of great importance for thermal management and modulation.Herein,the interfacial thermal resistance between overlapped graphene nanoribbons is largely reduced by adding bonded carbon chains as shown by molecular dynamics simulations.And the analytical model(phonon weak couplings model,PWCM)is utilized to analyze and explain the two-dimensional thermal transport mechanism at the cross-interface.An order of magnitude reduction of the interfacial thermal resistance is found as the graphene nanoribbons are bonded by just one carbon chain.Interestingly,the decreasing rate of the interfacial thermal resistance slows down gradually with the increasing number of carbon chains,which can be explained by the proposed theoretical relationship based on analytical model.Moreover,by the comparison of PWCM and the traditional simplified model,the accuracy of PWCM is demonstrated in the overlapped graphene nanoribbons.This work provides a new way to improve the interfacial thermal transport and reveal the essential mechanism for low-dimensional materials applied in thermal management.

Coupling Interactions and Trapped Effects for a Triple-Well Potential

Weak and strong coupling interactions and trapped effects have always played a significant role in understanding physical and chemical properties of materials. Triple-well anharmonic potential may be modeled for interpretation of energy spectra from the nuclear to macro molecular systems, and also crystalline systems. Exact periods of a trapped particle in each well of the potential are explicitly derived. For the extended Duffing system, it is predicted that infinite series of both frequency and spatial trajectory approach to exact results in the limit of weak-coupling cases (g→0).

Convergence of the deep BSDE method for coupled FBSDEs

The recently proposed numerical algorithm,deep BSDE method,has shown remarkable performance in solving high-dimensional forward-backward stochastic differential equations(FBSDEs)and parabolic partial differential equations(PDEs).This article lays a theoretical foundation for the deep BSDE method in the general case of coupled FBSDEs.In particular,a posteriori error estimation of the solution is provided and it is proved that the error converges to zero given the universal approximation capability of neural networks.Numerical results are presented to demonstrate the accuracy of the analyzed algorithm in solving high-dimensional coupled FBSDEs.

A KAM Theorem for Reversible Systems of Infinite Dimension

For reversible systems of infinite dimension we prove an infinitely dimensional KAM theorem with an application to the network of weakly coupled oscillators of friction. The KAM theorem shows that there are many invariant tori of infinite dimension, and thus many almost periodic solutions, for the reversible systems.

Numerical analysis of shell-side flow-induced vibration of elastic tube bundle in heat exchanger

The responses of the flow-induced vibration of an elastic tube bundle subjected to the shell-side cross flow are investigated in this paper. The weak coupling method and the fluid solid interface are used to solve the fluid-structure interaction problem with consideration of the geometry and physical natures. The effects of the shell-side fluid flow velocity and the structural parameters on the flow-induced vibration are discussed. Numerical results demonstrate that the vibration frequency and amplitude at the monitor points increase with the increase of the shell-side water inlet velocity in all directions. The wall thickness and the external diameter of the elastic tube bundle have significant effects on the responses of the flow-induced vibration. The structural parameters affect the vibration frequency and amplitude, and the vibration equilibrium position in the water flow direction. The vibration frequency decreases with the increase of the tube external diameter. In addition, the vibration in the water flow direction has a lower equilibrium position when the elastic tube bundle has a larger wall thickness or smaller external diameter.

Characteristic Analysis of UHVAC/DC Hybrid Power Grids and Construction of Power System Protection

Strong DC coupling with weak AC and large-scale renewable energy integration are the two significant characteristics of ultra-high-voltage AC/DC(UHVAC/DC)hybrid power grids in China.Strong coupling between AC and DC grids and the different integration performance of renewable energy sources have profoundly changed the stability characteristics of the power system.The traditional stability control system is inadequate for the stability control of UHVAC/DC power grids.This paper analyzes the requirements for constructing an integrated defense system in a UHVAC/DC hybrid power grid(i.e.power system protection).The definition,connotation,and designing principles of power system protection are put forward.The relationship between the power system protection and the traditional three-defense lines is investigated.The design principles,general hardware structure and main functions of a power system protection are presented.Key problems and technologies are specified in the construction of the power system protection.

Measurement of PV asymmetry in +p→d+γ and ■+d→n+p

The measurement of parity-violating （PV） observables in few-nucleon system can shed light on our current understanding of the weak interaction between nucleons.Theoretical models describe the nucleonnucleon weak interaction at low energies use a series of undetermined parameters.Two parity violating measurements have been considered： the capture of polarized slow neutrons on hydrogen （n ＋ p → d ＋ γ） at Los Alamos National Laboratory for first phase and Oka Ridge National Laboratory for second phase and the helicity dependence of the deuteron photodisintegration cross section using circularly polarized photons （γ ＋ d → n ＋ p） at Shanghai Institute of Applied Physics.The goal of both experiments is to constraint the weak meson-nucleon couplings to a precision of 1 ×10^-8 .The introduction of both experiments is presented.