Discrete formulation of mixed finite element methods for vapor deposition chemical reaction equations

The vapor deposition chemical reaction processes, which are of extremely extensive applications, can be classified as a mathematical model by the following governing nonlinear partial differential equations containing velocity vector, temperature field, pressure field, and gas mass field. The mixed finite element (MFE) method is employed to study the system of equations for the vapor deposition chemical reaction processes. The semidiscrete and fully discrete MFE formulations are derived. And the existence and convergence (error estimate) of the semidiscrete and fully discrete MFE solutions are demonstrated. By employing MFE method to treat the system of equations for the vapor deposition chemical reaction processes, the numerical solutions of the velocity vector, the temperature field, the pressure field, and the gas mass field can be found out simultaneously. Thus, these researches are not only of important theoretical means, but also of extremely extensive applied vistas.     

MIXED FINITE ELEMENT METHODS FOR THE SHALLOW WATER EQUATIONS INCLUDING CURRENT AND SILT SEDIMENTATION (Ⅱ)——THE DISCRETE-TIME CASE ALONG CHARACTERISTICS

IntroductionThoughatransport_diffusion (orLagrange_Galerkin)method ,whichisalsocalledachar_acteristicsmethod ,isanoldone[1]andhasbeenextensivelyappliedtodealingwithPDEswithdiffusiontermand/orconvection ,ithadnotbeenmixedthefiniteelementmethodstotreatsuccessfullytheconvergenceofnumericalsolutionfortheNavier_Stokesequationsuntiltheearly198 0s[2 ].Intheearly 1 990s,Berm挷ｄｅｚｅｔａｌ.[3]appliedthismethodtodealingwiththeshallowwaterequationsonlyincludingthecurrentandthedepthofwaterandonlyderi…     

MIXED FINITE ELEMENT METHODS FOR THE SHALLOW WATER EQUATIONS INCLUDING CURRENT AND SILT SEDIMENTATION ( Ⅱ )-THE DISCRETE-TIME CASE ALONG CHARACTERISTICS

The mixed finite element (MFE) methods for a shallow water equation system consisting of water dynamics equations, silt transport equation, and the equation of bottom topography change were derived. A fully discrete MFE scheme for the discrete-time along characteristics is presented and error estimates are established. The existence and convergence of MFE solution of the discrete current velocity, elevation of the bottom topography, thickness of fluid column, and mass rate of sediment is demonstrated.     

Difference scheme and numerical simulation based on mixed finite element method for natural convection problem

ntroductionLetΩ R2 beaboundeddomain .Weconsiderthefollowingnon_stationarynaturalconvectionproblem :Problem (Ⅰ )　Findu =(u1,u2 ) ,p ,andTsuchthat,foranyt1>0 ,ut- μΔu +(u· )u + p=λjT　　 ((x ,y ,t) ∈Ω× (0 ,t1) ) ,divu =0　　　　　　　　　 ((x ,y,t) ∈Ω× (0 ,t1) ) ,Tt-ΔT +λu· T =0　　 ((x,y,t) ∈Ω× (0 ,t1) ) ,u =0 ,T =0　　　　　　 ((x,y,t)∈ Ω× (0 ,t1) ) ,u(x ,y ,0 ) =0 ,　T(x,y,0 ) =f(x,y)　　 ((x,y) ∈Ω) ,whereuisthefluidvelocityvectorfield ,pthepressurefield ,Tthet…     

课堂对话,让数学课堂精彩纷呈

雅思贝尔斯认为,对话是真理的敞亮和思想本身的实现.由此可见,我们的教学应该以对话的形式展开,在师生民主、平等和互相尊重的基础上,进行探讨和倾听,以达到师生共同发展的目的.然而,在传统数学教学中,教师更为关注知识的传授,在这样知识本位和教师主体的教学模式下,课堂对话形同虚设.随着新课程改革的深化,“课堂对话”已经成为数学课程改革共同关注和研究的内容.学生交流能力和思维能力的培养离不开课堂对话的实施,如何有效展开课堂对话,才能促进学生的交流和思考,造就精彩课堂呢?     

关于Meir-Keler型压缩映射的一点注记

本文举例说明了文［１，２］的结论不成立     

MIXED FINITE ELEMENT METHODS FOR THE SHALLOW WATER EQUATIONS INCLUDING CURRENT AND SILT SEDIMENTATION (Ⅰ)-THE CONTINUOUS-TIME CASE

An initial-boundary value problem for shallow equation system consisting of water dynamics equations, silt transport equation, the equation of bottom topography change, and of some boundary and initial conditions is studied, the existence of its generalized solution and semidiscrete mixed finite element (MFE) solution was discussed, and the error estimates of the semidiscrete MFE solution was derived. The error estimates are optimal.     

管材包裹混凝土柱轴压细观力学数值模拟

将不同模量管材包裹下的轴压混凝土圆柱构件内部混凝土看作由骨料、砂浆骨料过渡层、砂浆组成的三相复合材料,利用骨料随机投放程序确定骨料在试件中的随机位置,并考虑各相材料的弹塑性性质,建立了构件的三维非线性细观分析模型.通过对不同模量管材(PE,HDPE,PVC,钢)包裹下的轴压混凝土圆柱的内部细现力学性能进行分析,探讨不同材料外包下轴压混凝上柱破坏的开展与其内部各种材料(如骨料、过渡层、砂浆等)及外部包裹材料的细观受力状况的关系.     

从振动波形研究贝塞尔函数和勒让德函数的渐近关系

通过圆平面和球面上对称振动的分析,比较了零阶贝塞尔函数和勒让德函数曲线,发现两者形状有明显的相似性.在进行振幅变换后,两者曲线几乎重合.从数学和物理角度解释了圆平面和球面上振动波形相似的原因,导出了零阶贝塞尔函数和勒让德函数的渐近关系,并得到了贝塞尔函数零点的一个估计公式.     

测量温度传感器的时间响应特性

从理论上分析了温度传感器响应时间的物理机理,给出了测量温度传感器时间响应的实验方法,并测量了铠装铂电阻温度传感器的时间响应特性.