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《Journal of computational science》2014,5(4):675-683
Analytical processing on multi-dimensional data is performed over data warehouse. This, in general, is presented in the form of cuboids. The central theme of the data warehouse is represented in the form of fact table. A fact table is built from the related dimension tables. The cuboid that corresponds to the fact table is called base cuboid. All possible combination of the cuboids could be generated from base cuboid using successive roll-up operations and this corresponds to a lattice structure. Some of the dimensions may have a concept hierarchy in terms of multiple granularities of data. This means a dimension is represented in more than one abstract form. Typically, neither all the cuboids nor all the concept hierarchy are required for a specific business processing. These cuboids are resided in different layers of memory hierarchy like cache memory, primary memory, secondary memory, etc. This research work dynamically finds the most cost effective path from the lattice structure of cuboids based on concept hierarchy to minimize the query access time. The knowledge of location of cuboids at different memory elements is used for the purpose. 相似文献
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Icosahedral quasicrystals are the most important and thermodynamically stable in all about 200 kinds of quasicrystals currently observed. Beyond the scope of classical elasticity, apart from a phonon displacement field, there is a phason displacement field in the elasticity of the quasicrystal, which induces an important effect on the mechanical properties of the material and makes an analytical solution difficult to obtain. In this paper, a finite element algorithm for the static elasticity of icosahedral quasicrystals is developed by transforming the elastic boundary value problem of the icosahedral quasicrystals into an equivalent variational problem. Analytical and numerical solutions for an icosahedral A1-Pd-Mn quasicrystal cuboid subjected to a uniaxial tension with different phonon-phason coupling parameters are given to verify the validity of the numerical approach. A comparison between the analytical and numerical solutions of the specimen demonstrates the accuracy and efficiency of the present algorithm. Finally, in order to reveal the fracture behavior of the icosahedral A1-Pd-Mn quasicrystal, a cracked specimen with a finite size of matter is investigated, both with and without phonon-phason coupling. Meanwhile, the geometry factors are calculated, including the stress intensity factor and the crack opening displacement for the finite-size specimen. Computational results reveal the importance of pbonon-phason coupling effect on the icosahedral A1-Pd-Mn quasicrystal. Furthermore, the finite element procedure can be used to solve more complicated boundary value problems. 相似文献
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镧系元素配位化学新领域: 生理及更高pH下镧 系元素-羟基自组装多核配合物 研究 总被引:6,自引:0,他引:6
在生理及更高pH下以α-氨基酸或EDTA作为配体,抑制Ln(Ⅲ)水解得到了一类镧系元素-羟基自组装多核配合物。该类多核配合物以具有类立方烷结构的[Ln4(μ~3-OH)~4]^8^+为基本结构单元,可以单体{[Ln~4(μ~3-OH)~4]^8^+},共顶点的“环状四聚体”{[Ln~1~2(μ~3-OH)~1~6]^2^0^+}或“环状五聚体”{[Ln~1~5(μ~3-OH)~2~0]^2^5^+}的形式稳定存在。本文报道了该类配合物的合成、结构及性质,探讨了卤素离子对“环状四聚体”及“环状五聚体”形成的模板效应,并初步证明了类立方烷结构单体,“环状四聚体”及“环状五聚体”乃是生理及更高pH下镧系元素的稳定存在形式。同时还证明了直接水解镧系元素硝酸盐或高氯酸盐能得到一类以正八面体结构的[Ln~6(μ~6-O)(μ~3-OH)~8]^8^+]为骨架的多核配合物。磁性测定表明,室温下各配合物的类立方烷结构中的镧系离子间无明显磁交换。 相似文献
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含剩余对称平均的不等式及其应用 总被引:2,自引:0,他引:2
定义 n个正实数 x1,x2 ,… ,xn的剩余对称平均 ∑k ( x) ,借助于数学归纳法及优超理论证明当 x∈Rn+ + 时有 :∑2 ( x)≥ ∑3( x)≥…≥ ∑n ( x)≥ A( x) .并将此结果用于正定矩阵 ,n维长方体及单形 . 相似文献
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Icosahedral quasicrystals are the most important and thermodynamically stable in all about 200 kinds of quasicrystals currently observed. Beyond the scope of classical elasticity, apart from a phonon displacement field, there is a phason displacement field in the elasticity of the quasicrystal, which induces an important effect on the mechanical properties of the material and makes an analytical solution difficult to obtain. In this paper, a finite element algorithm for the static elasticity of icosahedral quasicrystals is developed by transforming the elastic boundary value problem of the icosahedral quasicrystals into an equivalent variational problem. Analytical and numerical solutions for an icosahedral Al–Pd–Mn quasicrystal cuboid subjected to a uniaxial tension with different phonon–phason coupling parameters are given to verify the validity of the numerical approach. A comparison between the analytical and numerical solutions of the specimen demonstrates the accuracy and efficiency of the present algorithm. Finally, in order to reveal the fracture behavior of the icosahedral Al–Pd–Mn quasicrystal, a cracked specimen with a finite size of matter is investigated, both with and without phonon–phason coupling. Meanwhile, the geometry factors are calculated, including the stress intensity factor and the crack opening displacement for the finite-size specimen. Computational results reveal the importance of phonon–phason coupling effect on the icosahedral Al–Pd–Mn quasicrystal. Furthermore, the finite element procedure can be used to solve more complicated boundary value problems. 相似文献
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陈光曙 《纯粹数学与应用数学》2009,25(4):721-724
讨论了长方体上均匀分布密度函数问题,得到了长方体体积的估计量、估计量的点估计及估计量的密度函数. 相似文献
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