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41.
Until recently, numerical simulations of discontinuities in highly super-Alfvénic plasmas have been severely limited by comparatively crude resolution and accuracy. Significant progress in the numerical simulation of such plasmas was achieved with the recently implemented Central Weighted Essentially Non-Oscillatory (CWENO) scheme. Combining this technique with that of adaptive mesh refinement (AMR), we have developed a third-order numerical scheme, which is able to efficiently capture strong gradients on spatial scales being small compared to the overall scale of the plasma system considered. Here, we first describe important algorithmic aspects of the scheme as well as the physics included in it. Second, we present the results of various performance tests. And, third, we illustrate its application to ‘real world problems’ using the example of the dynamics of a Sedov-type explosion. 相似文献
42.
J.S. Sánchez 《Pattern recognition》2004,37(7):1561-1564
Instance-based learning methods like the nearest neighbour classifier generally suffer from the indiscriminate storage of all training instances, resulting in large memory requirements and slow execution speed. In this paper, new training set size reduction methods based on prototype generation and space partitioning are proposed. Experimental results show that the new algorithms achieve a very high reduction rate with still an important classification accuracy. 相似文献
43.
M. Jayasankar 《Materials Letters》2007,61(3):790-793
Formation of aluminium titanate (AT) has been achieved at low temperature through sol-gel process using boehmite and titanium hydroxide as precursors by controlling the particle size at nanoscale followed by in-situ peptisation. The formations of AT phase, particle size distributions, sintering and thermal expansion characteristics, and microstructural features have been reported. DTA and XRD analysis have been performed to confirm the formation of AT. A 94% relative density was obtained for aluminium titanate sintered at 1550 °C with controlled grain size in the range of 2-3 μm. 相似文献
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We describe a Gauss–Seidel algorithm for optimizing a three‐dimensional unstructured grid so as to conform to a given metric. The objective function for the optimization process is based on the maximum value of an elemental residual measuring the distance of any simplex in the grid to the local target metric. We analyse different possible choices for the objective function, and we highlight their relative merits and deficiencies. Alternative strategies for conducting the optimization are compared and contrasted in terms of resulting grid quality and computational costs. Numerical simulations are used for demonstrating the features of the proposed methodology, and for studying some of its characteristics. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
46.
影响铁精矿K2O、Na2O、SiO2含量的因素分析 总被引:2,自引:0,他引:2
郭相玲 《冶金标准化与质量》2003,41(1):9-12
用统计分析方法 ,分析了影响精矿K2 O、Na2 O、SiO2 含量的因素 ,并根据分析结论提出了对生产工艺进行定向控制的条件 相似文献
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49.
机械合金化过程中Fe70B30粉末晶粒尺寸和微观应变的研究 总被引:2,自引:0,他引:2
用X射线和电镜研究了Fe_(70)B_(30)粉末经不同时间高能球磨后晶粒尺寸和微观应力的变化。在机械合金化过程中,粉末的X射线衍射谱的宽度随球磨时间的增加逐渐加宽,这是晶粒细化和内部微观应力共同作用的结果。X射线衍射结果表明:随着机械合金化的进行,粉末的晶粒尺寸逐渐减小,球磨初期晶粒尺寸下降较快,经15h球磨,晶粒尺寸为25nm,机械合金化进行到一定时间后晶粒尺寸下降缓慢,80h球磨后晶粒尺寸可达5nm。在机械合金化过程中球磨所造成的微观应变不大,球磨初期粉末的内应力随球磨时间增加而增加,当粉末粒子尺寸很小时,随球磨的进行粉末中的微观应变显著下降。 相似文献
50.
Mgidi Donald Dlamini 《Solar Energy Materials & Solar Cells》1996,43(4):353
In this paper results on surface photovoltage (SPV) and electron beam induced conductivity (EBIC) studies of edge-defined film-fed growth (EFG) and floating zone (FZ) silicon solar cell materials (both p-type) are presented. A systematic comparison based on minority carrier diffusion length and carrier recombination is made between: (i) samples contaminated with Ti and/or Fe, (ii) samples gettered by phosphorous diffusion, and (iii) as-received samples. Deep level transient spectroscopy (DLTS) measurements, together with the iron-boron (FeB) pairing kinetics [1] have successfully been used to detect the presence of Fe in the samples. Even though this process is effective in revealing Fe impurities in p-type FZ silicon it is evidently not suitable for Fe identification in p-type EFG silicon. Ti, like Fe, is found to be a prominent lifetime-limiting metallic impurity in both EFG and FZ silicon. Phosphorous diffusion is proven to be an effective external gettering technique for fast-diffusing impurities such as Fe, but not for Ti. 相似文献