Mortar型有限元方法的一类Mortar条件

研究了mortar型有限元方法的逼近性,建立了一种mortar条件具备最优误差的标准,在满足该标准的基础上介绍了两个mortar条件。利用这两个mortar条件分别构建mortar型旋转Q1元与mortar型P1非协调元。通过检验mortar条件符合标准,证明了这两种mortar有限元方法对于椭圆问题有最优的误差估计。     

Filler effect of fine particle sand on the compressive strength of mortar

The river sand, which is a non-pozzolanic material, was ground into 3 different particle sizes. Portland cement type I was replaced by the ground river sands at 10wt%–40wt% of binder to cast mortar. Compressive strengths of mortar were investigated and the filler effect of different fine particles of sand on the compressive strength of mortar was evaluated. The results show that the compressive strength of mortar contributed from the filler effect of smaller particles is higher than that of the coarser ones. The difference in compressive strength of mortar tends to be greater as the difference in ground river sand fineness increases. The results also suggest that ASTM C618 specification is not practically suitable for specifying pozzolan in concrete since the strength activity index of mortar containing ground river sand (high crystalline phase) with 33.8wt% of particles retained on a 45-μm sieve can pass the strength requirement.     

Strength, porosity, and chloride resistance of mortar using the combination of two kinds of pozzolanic materials

This article presents a study on the resistance to chloride penetration, corrosion, porosity, and strength of mortar containing fine fly ash (FA), ground rice husk-bark ash (RB), and ground bagasse ash (BA). Ordinary Portland cement (CT) was blended with a single pozzolan and two pozzolans. Strength, porosity, rapid chloride penetration, immersion, and corrosion tests were performed to characterize the mortar. Test results showed that the use of ternary blends of CT, FA, and RB or BA decreased the porosity of the mortar, as compared with binary blended mortar containing CT and RB or BA. The resistance to chloride penetration of the mortar improved substantially with partial replacement of CT with FA, RB, and BA. The use of ternary blends of CT, FA and RB or BA produced the mortar with good strength and resistance to chloride penetration. The resistance to chloride penetration was higher with an increase in the replacement level due to the reduced calcium hydroxide.     

一类Mortar型旋转Q_1元的多重网格方法

研究了一种mortar型旋转Q1元的多重网格方法,证明了W循环多重网格算法的最优收敛性,即收敛率与网格层数和尺寸无关,数值仿真验证了理论分析.     

关于不定问题mortar元方法

在最小正则性假设下,对非自共轭不定两阶椭圆问题矩形网络剖分下使用Wilson元的mortar有限元方法,在给定的mortar条件下,证明了解的存在唯一性和一致收敛性;在H2正则性假设下给出了误差估计;构造了解离散问题的加性Schwarz预条件子,证明了使用GMRES迭代法求解时的收敛性,给出了收敛速度估计和一些数值实验结果。     

非对称不定问题Mortar型旋转Q_1元的多重网格方法

讨论了mortar型旋转Q_1元求解非对称不定问题,给出了求解离散问题的多重网格算法,证明了多重网格方法的最优收敛性,即收敛速度与网格大小和层数无关.最后,数值结果验证了本文的理论分析.     

Mortar型旋转Q1元的瀑布型多重网格方法

展现了mortar型旋转Q1元的瀑布型多重网格方法.证明了采用共轭梯度作为光滑子的瀑布型多重网格法是最优的,而采用其它传统迭代作光滑子的瀑布型多重网格法是拟最优的.并通过数值试验验证了我们的理论结果.     

Effect of grinding on chemical and physical properties of rice husk ash

The effect of grinding on the chemical and physical properties of rice husk ash was studied. Four rice husk ashes with different finenesses, i.e. coarse original rice husk ash (RHA0), RHA1, RHA2, and RHA3 were used for the study. Ordinary Portland cement (OPC) was partially replaced with rice husk ash at 20% by weight of binder. The water to binder ratio (W/B) of the mortar was maintained at 110%±5% with flow table test. Specific gravity, fineness, chemical properties, compressive strength, and porosity test of mortars were determined. The differences in chemical composition of the rice husk ashes with different finenesses from the same batch are small. The use of RHA3 produces the mortars with good strength and low porosity. The strength of the mortar improves with partial replacement of RHA3 in comparison with normal coarse rice husk ash. The use of RHA3 results in a strong and dense mortar, which is due to the better dispersion and filling effect, as well as an increase in the pozzolanic reaction.     

Strength and chloride resistance of blended Portland cement mortar containing palm oil fuel ash and fly ash

This paper presented a study on the strength and chloride resistance of mortars made with ternary blends of ordinary Portland cement (OPC), ground palm oil fuel ash (POA), and classified fly ash (FA). The mortar mixtures were made with Portland cement type I containing 0-40wt% FA and POA. FA and POA with 1wt%-3wt% retained on a sieve No.325 were used. The compressive strength and rapid chloride penetration depth of mortars were determined. The results reveal that the use of ternary blended cements produces good strength mortars. The use of the blend of FA and POA also produces high strength mortars and excellent resistance to chloride penetration owing to the synergic effect of FA and POA. A mathematical analysis and two-parameter polynomial model were presented to predict the compressive strength. The mathematical model correlated well with the experimental results. The computer 3-D graphics of strength of the ternary blended mortars were also constructed and could be used to aid the understanding and the proportioning of the blended system.     

Mortar型旋转Q_1元多重网格的网格转移算子

讨论了Mortar型旋转Q1元多重网格算法的收敛性.对于网格不嵌套的旋转Q1有限元空间提出了两种Mortar条件,针对这两种Mortar条件介绍了相应的多重网格的网格转移算子,并且建立了网格转移算子有效的一个标准,即只要网格转移算子符合标准,则多重网格算法收敛.理论证明和数值实验说明了该网格转移算子的多重网格算法收敛.     

P1非协调Mortar元的V循环多重网格方法

给出了求解偏微分方程的P1非协调Mortar元的一个V循环多重网格方法，并证明了此方法的一致收敛性，即收敛性与网格层数和网格尺寸无关。     

抛物积分微分方程的非协调元的收敛性分析

讨论了抛物积分微分方程带约束的旋转Q1非协调元的收敛性,在不需要Ritz-Volterra投影及任何修正格式情况下,利用该单元的特殊性质,通过新的技巧,得到了最优误差估计.     

Mortar型旋转Q1元的V循环多重网格

展现了一种Mortar类型的旋转Q1有限元的多重网格方法．通过定义一些算子证明了这种V循环的多重网格是一致收敛的,它的收敛率不依赖于网格的尺寸和层数,并通过数值实验验证了理论分析的正确性．     

拟线性粘弹性方程的非协调有限元分析

讨论了一类拟线性粘弹性方程在半离散和全离散格式下的带约束的旋转Q1非协调有限元逼近.通过运用该元的相容误差可达到O(h2)阶分别导出了L2模和H1模意义下的最优收敛阶和超逼近性.对于提出的全离散逼近格式,得到了最优误差估计.     

抛物积分-微分方程的Mortar型有限体积元方法H1-范数的误差估计

研究了二维抛物积分微分方程的基于Crouzeix Raviart非协调元的Mortar型有限体积元方法.为了得到误差估计,我们引进了Mortar型Ritz Volterra投影算子并得到了它在H1范数意义下的逼近性质.最后我们证明了微分方程的真解和Mortar型有限体积元方程的解在H1范数意义下的误差估计是最优的.