Localized Birkhoff average in beta dynamical systems
Bo Tan Bao-Wei Wang Jun Wu Jian Xu
In this note, we investigate the localized multifractal spectrum of Birkhoff average in the beta-dynamical system $([0,1], T_{\beta})$ for general $\beta>1$, namely the dimension of the following level sets $$ \Big\{x\in [0,1]: \lim_{n\to \infty}\frac{1}{n}\sum_{j=0}^{n-1}\psi(T^jx)=f(x)\Big\}, $$ where $f$ and $\psi$ are two continuous functions defined on the unit interval $[0,1]$. Instead of a constant function in the classical multifractal cases, the function $f$ here varies with $x$. The method adopted in the proof indicates that the multifractal analysis of Birkhoff average in a general $\beta$-dynamical system can be achieved by approximating the system by its subsystems.
keywords: $\beta$-expansion Hausdorff dimension. localized Birkhoff average
Time-varying delayed feedback control for an internet congestion control model
Shu Zhang Jian Xu
A proportionally-fair controller with time delay is considered to control Internet congestion. The time delay is chosen to be a controllable parameter. To represent the relation between the delay and congestion analytically, the method of multiple scales is employed to obtain the periodic solution arising from the Hopf bifurcation in the congestion control model. A new control method is proposed by perturbing the delay periodically. The strength of the perturbation is predicted analytically in order that the oscillation may disappear gradually. It implies that the proved control scheme may decrease the possibility of the congestion derived from the oscillation. The proposed control scheme is verified by the numerical simulation.
keywords: delayed differential equation time-varying delay. Internet congestion control method of multiple scales Hopf bifurcation
Zero-electron-mass limit of Euler-Poisson equations
Jiang Xu Ting Zhang
We study the limit of vanishing ratio of the electron mass to the ion mass (zero-electron-mass limit) in the scaled Euler-Poisson equations. As the first step of this justification, we construct the uniform global classical solutions in critical Besov spaces with the aid of ``Shizuta-Kawashima" skew-symmetry. Then we establish frequency-localization estimates of Strichartz-type for the equation of acoustics according to the semigroup formulation. Finally, it is shown that the uniform classical solutions converge towards that of the incompressible Euler equations (for ill-preparedinitial data) in a refined way as the scaled electron-mass tends to zero. In comparison with the classical zero-mach-number limit in [7,23], we obtain different dispersive estimates due to the coupled electric field.
keywords: Zero-electron-mass limits Euler-Poisson equations Strichartz-type estimate. critical Besov spaces skew-symmetry
Modeling and prediction of HIV in China: transmission rates structured by infection ages
Yicang Zhou Yiming Shao Yuhua Ruan Jianqing Xu Zhien Ma Changlin Mei Jianhong Wu
HIV transmission process involves a long incubation and infection period, and the transmission rate varies greatly with infection stage. Conse- quently, modeling analysis based on the assumption of a constant transmission rate during the entire infection period yields an inaccurate description of HIV transmission dynamics and long-term projections. Here we develop a general framework of mathematical modeling that takes into account this heterogeneity of transmission rate and permits rigorous estimation of important parameters using a regression analysis of the twenty-year reported HIV infection data in China. Despite the large variation in this statistical data attributable to the knowledge of HIV, surveillance efforts, and uncertain events, and although the reported data counts individuals who might have been infected many years ago, our analysis shows that the model structured on infection age can assist us in extracting from this data set very useful information about transmission trends and about effectiveness of various control measures.
keywords: compartmental models stability. HIV/AIDS infection age
Some properties of positive solutions for an integral system with the double weighted Riesz potentials
Jiankai Xu Song Jiang Huoxiong Wu
In this paper, we study some important properties of positive solutions for a nonlinear integral system. With the help of the method of moving planes in an integral form, we show that under certain integrable conditions, all of positive solutions to this system are radially symmetric and decreasing with respect to the origin. Meanwhile, using the regularity lifting lemma, which was recently introduced by Chen and Li in [1], we obtain the optimal integrable intervals and sharp asymptotic behaviors for such positive solutions, which characterize the closeness of system to some extent.
keywords: Integral system regularity lifting lemma moving plane method radially symmetry solution weighted-Hardy-Littlewood-Sobolev inequality.
Single-machine scheduling with past-sequence-dependent delivery times and a linear deterioration
Yunqiang Yin T. C. E. Cheng Jianyou Xu Shuenn-Ren Cheng Chin-Chia Wu
In many real-life scheduling environments, the jobs deteriorate at a certain rate while waiting to be processed. This paper addresses some single-machine scheduling problems with past-sequence-dependent (p-s-d) delivery times and a linear deterioration. The p-s-d delivery time of a job is proportional to the job's waiting time. It is assumed that the deterioration process is reflected in the job processing times being an increasing function of their starting times. We consider the following objectives: the makespan, total completion time, total weighted completion time, maximum lateness, and total absolute differences in completion times. We seek the optimal schedules for the problems to minimize the makespan and total completion time. Despite that the computational complexities of the problems to minimize the total weighted completion time and maximum lateness remain open, we present heuristics and analyze their worst-case performance ratios, and show that some special cases of the problems are polynomially solvable. We also show that the optimal schedule for the problem to minimize the total absolute differences in completion times is $V$-shaped with respect to the normal job processing times.
keywords: deterioration Scheduling past-sequence-dependent delivery times.
Asymptotic theory for disc-like crystal growth (II): interfacial instability and pattern formation at early stage of growth
Jian-Jun Xu Junichiro Shimizu
This paper is a continuation of the paper ([1] ), which is called paper (I) afterward. In the present paper, which we shall call paper (II), we study the interfacial instability property of the side interface of a growing disc-like crystal at the early stage of growth by using the approach developed in the interfacial wave (IFW) theory of dendritic growth. Our analysis show that the system allows two types of unstable modes over the side-interface: (1). The axi-symmetric $(m=0)$ modes. The most dangerous axi-symmetric mode is the base mode $A_0$, which is responsible for formation of the axi-symmetric pattern over the side-interface, anti-symmetric about the central plane of the disc; (2). The non-axi-symmetric modes, which are responsible for non-axi-symmetric pattern formation around the edge of the disc. The growth rates of these non-axi-symmetric modes are much smaller than the growth rate of the base mode $A_0$. During the course of disc growth, the unstable $A_0$-mode merges first. It leads to the formation of anti-symmetric pattern about the central plane over the side-interface. Following the onset of unstable base mode $A_0$, a set of non-axi-symmetric growing modes also appear. However, due to the smallness of growth rate of these unstable modes, the non-axi-symmetric pattern around the edge of the disc becomes observable, only after a sufficiently long time. Our theoretical predictions are in good agreement with the available experimental data.
keywords: Interfacial Instability quantization condition surface tension unstable eigen-modes kinetic attachment. disc-like crystal growth
Well-posedness and stability of classical solutions to the multidimensional full hydrodynamic model for semiconductors
Jiang Xu
This paper is concerned with the global well-posedness and stability of classical solutions to the Cauchy problem for the multidimensional full hydrodynamic model in semiconductors on the framework of Besov space. By using the high- and low- frequency decomposition method, we obtain the exponential decay of classical solutions (close to equilibrium). Moreover, it is also shown that the vorticity decays to zero exponentially in the 2D and 3D space. The work weakens the regularity requirement of the initial data and improves some known results in Sobolev space.
keywords: Exponential stability classical solutions hydrodynamic model.
Duplicating in batch scheduling
Yuzhong Zhang Chunsong Bai Qingguo Bai Jianteng Xu
In this paper, we firstly propose a technique named Duplicating , which duplicates machines in batch scheduling environment. Then we discuss several applications of Duplicating in solving batch scheduling problems. For the batch scheduling problem on unrelated parallel machines to minimize makespan, we give a $(4 - \frac{2}{B})$- approximation algorithm and a $(2 - \frac{1}{B} + \epsilon)$ algorithm when $m$ is fixed. We also present a $4(2 - \frac{1}{B} + \epsilon)$-competitive algorithm for the on-line scheduling problem on identical machines to minimize total weighted completion time by another technique-$\rho-dual$, which is proposed originally by Hall et al.(1997).
keywords: Duplicating Parallel machines. Integer programming Batch scheduling
Zero-relaxation limit of non-isentropic hydrodynamic models for semiconductors
Jiang Xu Wen-An Yong
This paper deals with non-isentropic hydrodynamic models for semiconductors with short momentum and energy relaxation times. With the help of the Maxwell iteration, we construct a new approximation and show that periodic initial-value problems of certain scaled non-isentropic hydrodynamic models have unique smooth solutions in a time interval independent of the two relaxation times. Furthermore, it is proved that as the two relaxation times both tend to zero, the smooth solutions converge to solutions of the corresponding semilinear drift-diffusion models.
keywords: relaxation limit continuation principle Non-isentropic hydrodynamic model energy estimates. Maxwell iteration

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