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In this paper, we investigate the rotation-dominant three-scale singular limit of the initial-value problem to the inviscid rotating stratified Boussinesq equations. We first prove a dispersive decay estimate for the linear propagator of that limit regime, which requires novel techniques involving an elaborate frequency cut-off since the phase function is degenerate on both horizontal and vertical directions in some areas. Using the dispersive decay estimate, we then investigate rigorously the rotation-dominant limit of local strong solutions to Boussinesq equations with ill-prepared initial data. The limiting system is shown to be the two-dimensional incompressible Euler equations coupled with a two-dimensional transport equation but in three spatial dimensions. [ABSTRACT FROM AUTHOR]

In this paper, we investigate the incompressible limit of the compressible primitive equations with the effect of gravity. First we prove that the estimates of the local strong solutions to the compressible primitive equations with γ = 2 are uniform to the Mach number. Then we show that the local strong solutions of the system with well-prepared initial data, as well as their time derivatives, converge to those of the inhomogeneous incompressible primitive equations as the Mach number tends to zero. The convergence rates are shown to be identical to the Mach number. [ABSTRACT FROM AUTHOR]

A dispersive decay estimate is proven for the linear propagator of the three-scale rotating stratified Boussinesq equations in the stratification-dominant regime. Because the phase function of that propagator is both singular and degenerate, obtaining the estimate requires novel techniques involving cutting phase-space shells into several pieces and using different methods in each region. Using the decay estimate, we prove the long-time existence of solutions to the initial-value problem for the nonlinear equations and obtain a rate of convergence to the limit system and intermediate asymptotics. [ABSTRACT FROM AUTHOR]

In this paper, we consider the motion of two compressible fluid flows under the interaction of magnetic field in bounded domain. With the help of spectral analysis, we prove the low Mach number limit from global weak solutions of the rescaled system to global weak solutions of the limit system, with ill-prepared initial data. [ABSTRACT FROM AUTHOR]

Singular limits of the rotating stratified Boussinesq equations are considered as the Froude number and Rossby number tend to zero at different rates. The limiting dynamics are validated for the rotation-dominant and the stratification-dominant cases, respectively. Furthermore, the convergence rate estimates are obtained. [ABSTRACT FROM AUTHOR]

We are concerned with two kinds of singular limits of the Cauchy problem to the two-layer rotating shallow water equations as the Rossby number and the Froude number tend to zero. First we construct the uniform estimates for the strong solutions to the system under the condition that the Froude number is small enough. Different from the previously studied cases, the large operator of this model is not skew-symmetric. One of the key new ideas in this paper is to obtain the uniform estimates using the special structure of the system rather than the antisymmetry of the large operator. After that the convergence of the equations with ill-prepared data to a two-layer incompressible Navier-Stokes system is proved with the help of Strichartz estimates constructed in this paper. [ABSTRACT FROM AUTHOR]

In low-earth-orbit (LEO) satellite-to-ground communication, the size of satellite antennae is limited and the satellite motion trajectory is predictable, which makes the channel state information (CSI) of the satellite-to-ground channel easy to leak and impossible to use to generate a physical layer key. To solve these problems, we propose a key generation method based on multi-satellite cooperation and random perturbation. On the one hand, we use multi-satellite cooperation to form a constellation that services users, in order to increase the equivalent aperture of satellite antennae and reduce the correlation between the legal channel and the wiretap channel. On the other hand, according to the endogenous characteristics of satellite motion, a random perturbation factor is proposed, which reflects the randomness of the actual channel and ensures that the CSI of the legal channel is not leaked due to the predictability of satellite motion trajectory. Simulation results show that the proposed method can effectively reduce the leakage of the legal channel's CSI, which makes the method of physical layer key generation safe and feasible in the LEO satellite-to-ground communication scene. [ABSTRACT FROM AUTHOR]

Accurate navigation and localization are essential for Autonomous Underwater Vehicles (AUVs). However, the unknown modeling errors and nonlinear errors will affect the AUV positioning accuracy. Meanwhile, the marine environment changes may not be accurately sensed by AUV. Therefore, this paper proposes a Hybrid Model (HM) navigation methodology for AUV to reduce the impact of unknown errors and better predict the future states simultaneously. Firstly, an error correction sub-model based on Sequence to Sequence (Seq2Seq) predicts AUV pseudo displacements. The pseudo displacements are augmented to the observation vector to correct the unknown errors in the state estimation. Secondly, a state regression sub-model based on Gaussian Process Regression (GPR) is utilized to capture the motion trends from the historical data and regress the state variation, which is used to resist the unknown disturbances in the changeable marine environment. The sub-models work parallel with the master model, benefiting from the Interacting Multiple Model (IMM). We compare the performance of the proposed HM to Extended Kalman Filter (EKF), Unscented Kalman Filter (UKF), and IMM-EKF by using the actual experimental data of Sailfish 210 AUV. The experimental results show that the proposed HM algorithm achieves superior navigation accuracy and good fault tolerance capability. • A HM navigation method is proposed to improve AUV navigation accuracy. • An error correction sub-model predicts AUV pseudo displacements. • A state regression sub-model captures the motion trends from historical data. [ABSTRACT FROM AUTHOR]

Autonomous Underwater Vehicle (AUV) navigation and localization in the complex and changeable marine environment is crucial and challenging. The inaccurate noise covariance matrix may result in significant prediction errors or even filtering divergence for traditional navigation algorithms. Meanwhile, the outliers in sensor observations also have a substantial adverse effect on the AUV positioning accuracy. Therefore, in this paper, we propose an Improved Interacting Multiple Model-Unscented Kalman Filter (IIMM-UKF) with both adaptivity and robustness for AUV navigation. Firstly, the Variational Bayesian (VB) based UKF algorithm is proposed as adaptive sub-models of IIMM to estimate the time-varying measurement noise covariance adaptively. Secondly, an outliers detector sub-model is proposed to enhance the robustness of IIMM. Gaussian Process Regression (GPR) is used to regress state pseudo values for each sub-model as estimations of the filtering process when the outliers are detected by the residual χ 2 detector. Multiple models work in parallel to achieve high-precision and robust AUV navigation. The performance of the IIMM-UKF algorithm has been evaluated on AUV with simulation and actual experimental data. In sea trials, the average AUV navigation accuracy of the IIMM-UKF is improved by 61.02% compared to EKF, 43.44% compared to UKF, and 35.54% compared to the IMM-UKF. • Multiple models work in parallel to improve the AUV navigation accuracy and robustness. • Adaptive sub-model based on Variational Bayesian. • Outliers detector sub-model based on residual χ 2 and GPR. [ABSTRACT FROM AUTHOR]

• Shoot bending, an effective agronomic measure can promote flowering in apple trees. • The 1,060 up- and 1,079 down-regulated proteins after shoot bending. • Differentially expressed proteins involved in fatty acid and lipid pathways were up-regulated by shoot bending. • Starch synthesis related proteins were down-regulated by shoot bending. • Circadian rhythm- and flowering-related genes were up-regulated by shoot bending. Flowering is an important life cycle stage in apple trees, and young 'Nagafu No. 2' produce limited inferior flower buds. Shoot bending, an effective agronomic measure, is widely used to promote flowering but little is known regarding the underlying molecular mechanisms. Using isobaric tags for relative and absolute quantification LC−MS/MS, 8,585 proteins expressed in buds during flower bud differentiation were identified. The 1,060 up- and 1,079 down-regulated proteins after shoot bending were divided into 7 pattern-based groups: I (22/5), II (30/57), III (34/21), IV (77/61), V (381/452), VI (218/170), and VII (298/313) types. Number of proteins were associated with carbohydrate, fatty acid, and lipid metabolism, as well as hormone, transcription factor, circadian rhythm, and photoperiod and flowering pathways. The differentially expressed proteins involved in fatty acid and lipid pathways were up-regulated by shoot bending, while other proteins that were involved in starch synthesis were down-regulated. In addition, circadian rhythm- and flowering-related genes were up-regulated by shoot bending. This research provides a valuable inventory of proteins involved in floral bud development and contributes to the understanding of the regulatory mechanisms of flower bud differentiation caused by shoot bending in apple trees. [ABSTRACT FROM AUTHOR]