含有奇异位势和临界指数的拟线性椭圆方程的G-对称解

本文讨论一类奇异拟线性椭圆型方程
-div(|x|^-ap|▽u|^p-2▽u)=μ+h(x)/|x|^(a+1)p|u|^p-2u+k(x)|u|^p-2u/|x|^bq,x∈R^N,
其中1 < p < N, 0 ≤ a < N-p/p, a ≤ b < a + 1, 0 ≤ μ < μ = (N-p/p-a)^p, q=p^*(a, b) = Np/N-(1+a-b)p,h 和k 是R^N上的连续有界函数, 且关于O(N) 的闭子群G满足某些对称性条件. 应用变分方法和Caffarelli-Kohn-Nirenberg 不等式, 在h与k满足适当条件下, 证得了一些G-对称解的存在性和多重性结果.     

一类拟线性椭圆方程非平凡广义解的存在性

该文讨论了下列拟线性椭圆方程的Dirichlet问题在一类Orlicz-Sobolev 空间中非平凡解的存在性 { -div(a(| u(x)|) u(x))=g(x, u), x∈Ω, u(x)=0,x∈∂Ω. 其中Ω 是 Rⁿ 中光滑的有界区域.Φ 和 g 满足一定条件时, 利用推广的山路引理证明了上述Dirichlet 问题存在广义的非平凡解的存在性.     

Littlewood—Paley算子及Marcinkiewicz积分在Campanato空间εa,p上的有界性

我们证明了下述结果:若f∈ε^a,p,则适当限制参数值时,有g(f)(x)(S(f)(x),g_λ^*(f)(x),μ(f)(x))<∞a.e.,或者g(f)(x)(S(f)(x),g_λ^*(f)(x),μ(f)(x))<∞a.e.;并且在前者成立时,有g(f)(S(f),g_λ^*(f),μ(f))∈ε^a,p,以及‖g(f)‖_a,p     

具临界指数及奇异性的双调和方程解的存在性

文中考虑了下面带奇异项的双调和方程 {?²u-μ/|x|^αμ =λg(x)μ+k(x)|μ|^q-2μ+|μ|^2*-2μ,x∈Ω, μ∈D₀^2,2(Ω), x∈∂Ω, 其中0∈Ω为R^N, N≥5中的有界区域, 0≤α, s < 4,2 < q < 2*(s) = 2(N-s)/N-4}, g(x), k(x) 为非负函数, 借助变分方法及嵌入映射D^2,2(R^N)→ L²*(R^N)的达到函数, 通过较精密的计算, 得到了上面方程解的存在性结果.     

一类带反应项的 Othmer-Stevens型趋化模型解的存在性

该文讨论了一类带反应项的Othmer-Stevens 型趋化模型的初边值问题 {∂u/∂t=D∨(u∨lnu/Φ(x, t, w))+ f(x, t, u), ∂w/∂t=g(x, t, u, w), u∨lnu/Φ(x, t, w) ?n^→=0. 证明了: 如果边界∂Ω ∈C^2+β, 函数Φ(x, t , w), f(x, t, u) 和 g(x, t, u, w)充分光滑,则该系统存在唯一解.     

类渐近线性p&q-Laplace方程弱解的全局衰减性

该文研究椭圆型方程 {Δ_pu+m|u|^p-2u-Δ_qu+n|u|^q-2u=g(x, u), x∈R^N, u∈ W^{1, p}(R^N)∩W^{1, q}(R^N) 弱解在全空间R^N上的衰减性, 其中m, n ≥ 0, N≥3, 1 < q < p < N, g(x, u)关于u满足类渐近线性. 证明了该方程的 弱解在无穷远处关于|x|呈指数衰减性.     

一类次P-Laplace方程非负解的不存在性

该文得到了在Ω上以下问题 {L_p,_ku+f(u)=0, , u|∂Ω=0 非负解的不存在性结果. 其中Ω为Heisenberg型群G中的区域(有界或无界), L_{p, k}u=divX (| _X u|^p-2 _X u)为对应于Greiner型向量场 X 的一类次P-Laplace算子.     

二阶抛物方程组解的Lp-正则性和Hölder连续性

在可控和自然增长条件下,非线性抛物组 u''_t-D_aA_i^a(x,t,u,Du)= B_i(x,t,u,Du),i=1,…,N,(x,t)∈Q之解。u∈L²(0,T;H¹(Ω,R^N))∩L^∞(0,T;L²(Ω,R^N))(或∩L^∞(Q,R^N))的空间导数D_au事实上属于L_loc^p(Q,R^N),p>2;拟线性抛物组 u''_t-Dα[A_ij^αβ(x,t,u)D_βu^j+a_j^a(x,t,u)]=B_i(x,t,u,Du),i=1,…,N的每一个解都在一开集 Q₁?Q上 Holder连续,且H^n+2-p(Q\Q₁)=0;若当j>i时A_ij^αβ=0,且B_i(x,t,u,p)关于|p|的增长阶小于2,则Q₁=Q;若A_ij^αβ和a_i^a都Holder连续,则D_au也在Q₁上 Holdler连续.     

关于g-函数的一些性质

本文得到的主要结果是:当f(x)∈BMO(Rⁿ)时,f的g-函数或者几乎处处发散,或者几乎处处取有限值;如属后者,则g(f)∈BMO(Rⁿ),且||g(f)||_*c||f||_*,而c只与空间维数有关。     

一类拟线性椭圆方程组的Dirichlet问题

The homogeneous Dirichlet problem(1) for quasilinear elliptic system in a bounded domain Ω is investigated in this paper. The existence of generalized solutions in [H₀¹(Ω)]^N is obtained by using the contructive Galerkin method. For the case of a_ij^lm=0 when i≠j, it is estatablished that such generalized solutions have bounded [L_∞(Ω)]N norm and possess Holeler continuity. Even in the particular case that f_i are independent of Du, our results have improved those of A. V. Lair [Ann. Mat. Pura Appl., 116(1978)], allowing b_i¹(x,u) and f_i(x,u) to have a growth in u arbitrarily close to 1.     

颤振分析中的特征值排序问题

颤振分析中判断颤振临界速度的重要依据是系统V-g和V-f图,即系统特征值随参数的变化曲线.在几乎所有商用软件及自编程序的输出结果中,有时会出现所谓的"窜支"现象,这给颤振临界速度和颤振穿越分支及耦合形式的判断带来很大不便.通过隐函数定理可以证明,除重特征值点以外,系统特征值连续依赖于系统参数变化.依据多元向量值函数连续性,建立对特征值的排列算法,给出系统特征根轨迹的正确曲线,再输出V-g和V-f图数据,从而避免"窜支"现象.编制应用程序,通过几个典型算例对算法进行了验证.该工作能够有效简化颤振分析的后处理工作,提高分析效率.     

On the hyperbolicity of the period-doubling fixed point

We give a new proof of the hyperbolicity of the fixed point for the period-doubling renormalization operator using the local dynamics near a semi-attractive fixed point (in a Banach space) and the theory of holomorphic motions. We also give a new proof of the exponential contraction of the Feigenbaum renormalization operator in the hybrid class of the period-doubling fixed point: our proof uses the non-existence of invariant line fields in the period-doubling tower (C. McMullen), the topological convergence (D. Sullivan), and a new infinitesimal argument.

     

考虑服务和退货的双渠道供应链定价问题研究

在考虑零售服务和消费者退货情况下,运用两阶段优化方法分别探究了集中式和分散式两种双渠道供应链的最优定价策略。研究发现零售服务有助于提高零售商的渠道权力,并始终使制造商获益,但只有当服务水平小于某一临界值时,才使制造商和零售商同时得到帕累托改进。零售价格和直销价格与退货率正相关,而与服务水平的关系受渠道结构的影响。服务水平的提高加剧了供应链的“双重边际化”效应,制造商通过生产与消费者需求相匹配的产品来降低退货风险可以减弱这种效应,从而提高供应链效率。     

树脂基复合材料粘接的优化设计

本文在试验数据和理论分析的基础上,提出树脂基复合材料单搭接的优化设计的原则,胶粘剂的选择、被粘物的设计,粘接长度的选择、胶层厚度的选择等.认为通过优化设计可以提高粘接强度,减轻产品的重量,提高其质量.     

Creep of polymer concrete in the nonlinear region

Two polyester-based polymer concretes with various volume content of diabase as an extender and aggregate are tested in creep under compression at different stress levels. The phenomenological and structural approaches are both used to analyze the experimental data. Common features of changes in the instantaneous and creep compliances are clarified, and a phenomenological creep model which accounts for the changes in the instantaneous compliance and in the retardation spectrum depending on the stress level is developed. It is shown that the model can be used to describe the experimental results of stress relaxation and creep under repeated loading. Modeling of the composite structure and subsequent solution of the optimization problem confirm the possibility of the existence of an interphase layer more compliant than the binder. A direct correlation between the interphase volume content and the instantaneous compliance of the composite is revealed. It is found that the distinction in nonlinearity of the viscoelastic behavior of the two polymer concretes under investigation can be due to the difference in their porosity. Submitted to the 11th International Conference on Mechanics of Composite Materials (Riga, June 11–15, 2000.) Translated from Mekhanika Kompozitnykh Materialov, Vol. 36, No. 2, pp. 147–164, 2000.     

Stress intensity factors for a finite plate with an inclined crack by boundary collocation

In this paper, we combine the Muskhelishvili＇s complex variable method and boundary collocation method, and choose a set of new stress function based on the stress boundary condition of crack surface, the higher precision and less computation are reached. This method is applied to calculating the stress intensity factor for a finite plate with an inclined crack. The influence of θ （the obliquity of crack） on the stress intensity factors, as well as the number of summation terms on the stress intensity factor are studied and graphically represented.     

拍卖机制设计在区块链中的应用与挑战

区块链是新一代信息技术的重要组成部分,是分布式网络、加密技术、智能合约等多种技术集成的新型数据库软件。过去的十多年,区块链技术在全球范围内产生广泛影响。如今的区块链技术,已从最初的关注于解决货币和支付的去中心化问题,转入到解决市场的去中心化问题。智能合约的出现使得基于区块链技术的去中心化金融进入高速发展状态,也涌现出区块链环境下的各类拍卖场景。本文首次从机制设计角度,以区块链交易费机制,非同质化代币(Non-Fungible Token,NFT)拍卖和矿工可提取价值(Miner-Extractable Value,MEV)交易位置拍卖为主要对象,总结和剖析近些年来区块链上特有的拍卖机制;并针对区块链特性,提出区块链上拍卖机制设计所面临的挑战和未来亟待解决的问题。     

Variation of the structure and permeability of tensioned fiber layers during impregnation with a thermoplastic polymer melt

The influence of displacements of tensioned fibers on the impregnation of fibrous layers with a polymer melt and on the final composite structure is studied. Using computer simulation, it is shown that, during impregnation, the structure of tensioned fibrous layers changes considerably depending on the initial arrangement and tensioning of fibers. The consolidated regions formed under the melt front move inside the impregnated layer with the advancing melt front. Displacement of the tensioned fibers as well as the formation of “washouts” favors the impregnation of internal layers, but cause significant inhomogeneity of the polymer structure. The surface (on the side of the melt flow) regions are more saturated with the polymer than the internal ones. A difference in the melt percolation mechanisms at various impregnation regimes is revealed. The effective permeability coefficients of a tensioned fiber layer are not constant but depend on the conditions and regimes of impregnation. Submitted to the 11th Conference on the Mechanics of Composite Materials (Riga, June 11–15, 2000). Translated from Mekhanika Kompozitnykh Materialov, Vol. 36, No. 2, pp. 259–270, March–April, 2000.     

Adiabatic divergence of the chaotic layer width and acceleration of chaotic and noise-induced transport

We show that, in spatially periodic Hamiltonian systems driven by a time-periodic coordinate-independent (AC) force, the upper energy of the chaotic layer grows unlimitedly as the frequency of the force goes to zero. This remarkable effect is absent in any other physically significant systems. It gives rise to the divergence of the rate of the spatial chaotic transport. We also generalize this phenomenon for the presence of a weak noise and weak dissipation. We demonstrate for the latter case that the adiabatic AC force may greatly accelerate the spatial diffusion and the reset rate at a given threshold.     

Numerical study on the dynamics of a jet-vortex interaction

The interaction of a vortex and a jet plays an important role for many industrial processes such as carbon black formation or combustion in diesel engines. The knowledge of physics of these phenomena is crucial for engineers, but also for scientists who wish to study this complex flow pattern. In this research, we numerically investigate cases where a cylindrical reactor is charged with gas injected through five ports. The first one is located along the main axis of the cylinder and this leads to the formation of the main jet. The other four ports are situated along the side walls such that the gas entering the cylinder tangentially through them causes a vortex to be formed. The objective of this paper is to show the fundamental physical phenomena and also how the initial and boundary conditions influence the results. It is shown how the process is influenced not only by modifying the velocity of injected gas, but also by the orientation and position of the vortex inlet nozzles.