A Vlasov-Poisson plasma of infinite mass with a point charge
Gang Li Xianwen Zhang

We study the time evolution of the three dimensional Vlasov-Poisson plasma interacting with a positive point charge in the case of infinite mass. We prove the existence and uniqueness of the classical solution to the system by assuming that the initial density slightly decays in space, but not integrable. This result extends a previous theorem for Yukawa potential obtained in [10] to the case of Coulomb interaction.

keywords: Vlasov-Poisson plasma point charge infinite mass Coulomb interaction classical solution
General decay for a viscoelastic Kirchhoff equation with Balakrishnan-Taylor damping, dynamic boundary conditions and a time-varying delay term
Wenjun Liu Biqing Zhu Gang Li Danhua Wang

In this paper, we consider a viscoelastic Kirchhoff equation with Balakrishnan-Taylor damping, dynamic boundary conditions and a time-varying delay term acting on the boundary. By using the Faedo-Galerkin approximation method, we first prove the well-posedness of the solutions. By introducing suitable energy and perturbed Lyapunov functionals, we then prove the general decay results, from which the usual exponential and polynomial decay rates are only special cases. To achieve these results, we consider the following two cases according to the coefficient α of the strong damping term: for the presence of the strong damping term (α>0), we use the strong damping term to control the time-varying delay term, under a restriction of the size between the time-varying delay term and the strong damping term; for the absence of the strong damping term (α=0), we use the viscoelasticity term to control the time-varying delay term, under a restriction of the size between the time-varying delay term and the kernel function.

keywords: Viscoelastic Kirchhoff equation Balakrishnan-Taylor damping dynamic boundary conditions time-varying delay
Stable strong and total parametrized dualities for DC optimization problems in locally convex spaces
Gang Li Xiaoqi Yang Yuying Zhou
By using properties of dualizing parametrization functions, Lagrangian functions and the epigraph technique, some sufficient and necessary conditions of the stable strong duality and strong total duality for a class of DC optimization problems are established.
keywords: epigraph Conjugate functions DC programming.
Time consistent policy of multi-period mean-variance problem in stochastic markets
Zhiping Chen Jia Liu Gang Li
Due to the non-separability of the variance operator, the optimal investment policy of the multi-period mean-variance model in Markovian markets doesn't satisfy the time consistency. We propose a new weak time consistency in stochastic markets and show that the pre-commitment optimal policy satisfies the weak time consistency at any intermediate period as long as the investor's wealth is no more than a specific threshold. When the investor's wealth exceeds the threshold, the weak time consistency no longer holds. In this case, by modifying the pre-commitment optimal policy, we derive a wealth interval, from which we determine a more efficient revised policy. The terminal wealth obtained under this revised policy can achieve the same mean as, but not greater variance than those of the terminal wealth obtained under the pre-commitment optimal policy; a series of superior investment policies can be obtained depending on the degree the investor wants the conditional variance to decrease. It is shown that, in the above revising process, a positive cash flow can be taken out of the market. Finally, an empirical example illustrates our theoretical results. Our results generalize existing conclusions for the multi-period mean-variance model in deterministic markets.
keywords: policy revision. Markovian markets Bellman's optimality principle mean-variance Time inconsistency
The stable duality of DC programs for composite convex functions
Gang Li Lipu Zhang Zhe Liu

In this paper, we consider a composite DC optimization problem with a cone-convex system in locally convex Hausdorff topological vector spaces. By using the properties of the epigraph of the conjugate functions, some necessary and sufficient conditions which characterize the strong Fenchel-Lagrange duality and the stable strong Fenchel-Lagrange duality are given. We apply the results obtained to study the minmax optimization problem and $l_1$ penalty problem.

keywords: Strong Fenchel-Lagrange duality DC programming stable duality
The coordination of single-machine scheduling with availability constraints and delivery
Ganggang Li Xiwen Lu Peihai Liu
Single-machine scheduling problems with production and delivery are studied in this paper. There is only one delivery vehicle with capacity $z$. Jobs are not allowed to resume. The $P \rightarrow D$ system and $D \rightarrow P$ system are considered, respectively. For the machine with an availability constraint, we present two $4/3$-approximation algorithms and show that the bounds are tight. For the machine with periodic availability constraints, we provide two polynomial time approximation algorithms which are the best possible.
keywords: algorithm. Scheduling availability constraint delivery
Two-machine scheduling with periodic availability constraints to minimize makespan
Ganggang Li Xiwen Lu
A two-machine scheduling problem where one machine has periodic availability constraints has been studied. The objective is to minimize makepan. For the nonresumable version, we give a better approximation algorithm with performance ratio of $4/3$. For the resumable version, we provide an offline $4/3$-approximation algorithm and an optimal online algorithm, respectively.
keywords: availability constraint nonresumable Scheduling resumable algorithm.
The Toland-Fenchel-Lagrange duality of DC programs for composite convex functions
Yuying Zhou Gang Li
In this paper, by virtue of the epigraph technique, we construct a new kind of closedness-type constraint qualification, which is the sufficient and necessary condition to guarantee the strong duality between a cone constraint composite optimization problem and its dual problem holds. Under this closedness-type constraint qualification condition, we obtain a formula of subdifferential for composite functions and study a cone constraint composite DC optimization problem in locally convex Hausdorff topological vector spaces.
keywords: constraint qualification. duality Epigraph composite

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