Stationary Expansion Shocks for a Regularized Boussinesq System

Stationary expansion shocks have been identified recently as a new type of solution to hyperbolic conservation laws regularized by nonlocal dispersive terms that naturally arise in shallow‐water theory. These expansion shocks were studied previously for the Benjamin‐Bona‐Mahony (BBM) equation using matched asymptotic expansions. In this paper, we extend the BBM analysis to the regularized Boussinesq system by using Riemann invariants of the underlying dispersionless shallow‐water equations. The extension for a system is nontrivial, requiring a combination of small amplitude, long‐wave expansions with high order matched asymptotics. The constructed asymptotic solution is shown to be in excellent agreement with accurate numerical simulations of the Boussinesq system for a range of appropriately smoothed Riemann data.     

Error Bounds of Regularized Gap Functions for Nonsmooth Variational Inequality Problems

We study the Clarke–Rockafellar directional derivatives of the regularized gap functions (and of some modified ones) for the variational inequality problem (VIP) defined by a locally Lipschitz but not necessarily differentiable function on a closed convex set in an Euclidean space. As applications we show that, under the strong monotonicity assumption, the regularized gap functions have fractional exponent error bounds and consequently that the sequences provided by an algorithm of Armijo type converge to the solution of the (VIP). The research of this author was supported by an Earmarked Grant from the Research Council of Hong Kong.     

A Short Proof of the Large Time Energy Growth for the Boussinesq System

We give a direct proof of the fact that the \(L^p\)-norms of global solutions of the Boussinesq system in \({\mathbb {R}}^3\) grow large as \(t\rightarrow \infty \) for \(1<p<3\) and decay to zero for \(3<p\le \infty \), providing exact estimates from below and above using a suitable decomposition of the space–time space \({\mathbb {R}}^{+}\times {\mathbb {R}}^{3}\). In particular, the kinetic energy blows up as \(\Vert u(t)\Vert _2^2\sim ct^{1/2}\) for large time. This contrasts with the case of the Navier–Stokes equations.     

Singular Solutions of a Boussinesq System for Water Waves

Studied here is the Boussinesq system $$η_t+u_x+(ηu)_x+au_{xxx}-bη_{xxt}=0,$$ $$u_t+η_x+\frac{1}{2}(u²)_x+cη_{xxx}-du_{xxt}=0,$$of partial differential equations. This system has been used in theory and practice as a model for small-amplitude, long-crested water waves. The issue addressed is whether or not the initial-value problem for this system of equations is globally well posed.The investigation proceeds by way of numerical simulations using a computer code based on a a semi-implicit, pseudo-spectral code. It turns out that larger amplitudes or velocities do seem to lead to singularity formation in finite time, indicating that the problem is not globally well posed.     

Boussinesq方程组弱解的衰减下界

本文利用Fourier分解方法研究Boussinesq方程组Cauchy问题弱解的L2衰减下界估计.     

Solitary Water Waves for a 2D Boussinesq Type System

We prove the existence of solitons （finite energy solitary wave） for a Boussi- nesq system that arise in the study of the evolution of small amplitude long water waves including surface tension. This Boussinesq system reduces to the generalized Benney-Luke equation and to the generalized Kadomtsev-Petviashivili equation in appropriate limits. The existence of solitons follows by a variational approach involving the Mountain Pass Theorem without the Palais-Smale condition. For surface tension sufficiently strong, we show that a suitable renormalized family of solitons of this model converges to a nontrivial soliton for the generalized KP-I equation.     

A Hessian Regularized Nonlinear Time Series Model

We introduce a nonparametric nonlinear time series model. The novel idea is to fit a model via penalization, where the penalty term is an unbiased estimator of the integrated Hessian of the underlying function. The underlying model assumption is very general: it has Hessian almost everywhere in its domain. Numerical experiments demonstrate that our model has better predictive power: if the underlying model complies with an existing parametric/semiparametric form (e.g., a threshold autoregressive model (TAR), an additive autoregressive model (AAR), or a functional coefficient autoregressive model (FAR)), our model performs comparably; if the underlying model does not comply with any preexisting form, our model outperforms in nearly all simulations. We name our model a Hessian regularized nonlinear model for time series (HRM). We conjecture on theoretical properties and use simulations to verify. Our method can be viewed as a way to generalize splines to high dimensions (when the number of variates is more than three), under which an analogous analytical derivation cannot work due to the curse of dimensionality. Supplemental materials are provided, and will help readers reproduce all results in the article.     

A Singular Expansion of Solution for a Regularized Compressible Stokes System

A compressible Stokes system is considered in a sector of the plane. The continuity equation is regularized by adding the diffusion term . We give a high-order expansion of corner singularities for the regularized system when the corner singularities for the Laplacian are implemented. A solution formula is constructed in an abstract way, and new associate singular functions are introduced for extracting high-order corner singularities. In the expansion, the smoother parts of the associate singular functions are used. Communicated by Rafael D. Benguriasubmitted 14/11/02, revised 12/08/03, accepted 04/10/03     

一类反应扩散方程的爆破时间下界估计

该文讨论了一类反应项为非线性非局部热源且热汇具有时间系数的反应扩散方程,分别在Dirichlet、Neu-mann或Robin边界条件下,在有界区域中的爆破行为.若解可能在有限时间发生爆破,通过构造合适的辅助函数,对时间系数给出适当的条件,利用Sobolev、H?lder不等式及Payne和Schaefer积分不等式等...     

一个非线性色散波方程的惟一连续性

该文证明:和如下耦合色散系统相联系的初值问题的充分光滑的解$(u,v)=(u(x,t),v(x,t))$, 如果在两个时刻有半线支集那么它们全为零. {∂ _tu+∂³_x u+∂ _x(u^p v^p+1)=0, ∂ _tv+∂³_x v+∂_x(u^p+1v^p)=0,x∈R,t≥ 0     

Jacobi Elliptic Numerical Solutions for the Time Fractional Variant Boussinesq Equations

The fractional derivatives in the sense of Caputo, and the homotopy perturbation method are used to construct the approximate solutions for nonlinear variant Boussinesq equations with respect to time fractional derivative. This method is efficient and powerful in solving wide classes of nonlinear evolution fractional order equations.     

On the Sharp Time Decay Rates for the 2D Generalized Quasi-geostrophic Equation and the Boussinesq System

Journal of Nonlinear Science - We compute the sharp time decay rates of the solutions of the IVP for quasi-geostrophic equation and the Boussinesq model, subject to fractional dissipation....     

Explicit Bounds for Some Special Integral Inequalities on Time Scales

In this paper, we investigate some nonlinear integral inequalities on time scales, which provide explicit bounds on unknown functions. Our results, which can be used as handy tools to study the properties of certain dynamic equations on time scales, unify and extend some integral inequalities and their corresponding discrete analogues.     

Hitting Time and Convergence Rate Bounds for Symmetric Langevin Diffusions

Methodology and Computing in Applied Probability - We provide quantitative bounds on the convergence to stationarity of real-valued Langevin diffusions with symmetric target densities.     

一类二维空间中广义Boussinesq水波系统解的渐近性

在二维空间中，讨论了一类Boussinesq水波系统并用初值中出现的小参数的级数形式表示了此系统的确切解，得到了此解的长时间渐近行为按指数衰减．     

一类变式Boussinesq系统的行波解

本文研究—类变式Boussinesq系统ηt+((1+αη)w)x-β/6wxxx=0, wt+αwwx+ηx-β/2wxxt=0,其中α和β都是正常数.许多逼近模型都能从此系统中被推导出,比如Boussinesq系统和两分量Camassa-Holm系统等.本文利用平面动力系统方法研究它的行波解及相图,得到了孤立波解,广义扭波解,广义反扭波解,紧孤立波解和周期波解,并给出了这些解的数值模拟.     

The Asymptotic Limit for the 3D Boussinesq System

In this paper, we show the asymptotic limit for the 3D Boussinesq system with zero viscosity limit or zero diffusivity limit. By the classical energy method, we prove that as viscosity(or diffusivity) coefficient goes to zero the solutions of the fully viscous equations converges to those of zero viscosity(or zero diffusivity) equations, which extend the previous results on the asymptotic limit under the conditions of the zero parameter(zero viscosity ν = 0 or zero diffusivity η = 0) in 2D case separately.     

Cauchy problem for a higher-order Boussinesq equation

In this study we establish global well-posedness of the Cauchy problem for a higher-order Boussinesq equation. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)