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31.
Jiye Liang Feng Wang Chuangyin Dang Yuhua Qian 《International Journal of Approximate Reasoning》2012,53(6):912-926
Feature selection is a challenging problem in many areas such as pattern recognition, machine learning and data mining. Rough set theory, as a valid soft computing tool to analyze various types of data, has been widely applied to select helpful features (also called attribute reduction). In rough set theory, many feature selection algorithms have been developed in the literatures, however, they are very time-consuming when data sets are in a large scale. To overcome this limitation, we propose in this paper an efficient rough feature selection algorithm for large-scale data sets, which is stimulated from multi-granulation. A sub-table of a data set can be considered as a small granularity. Given a large-scale data set, the algorithm first selects different small granularities and then estimate on each small granularity the reduct of the original data set. Fusing all of the estimates on small granularities together, the algorithm can get an approximate reduct. Because of that the total time spent on computing reducts for sub-tables is much less than that for the original large-scale one, the algorithm yields in a much less amount of time a feature subset (the approximate reduct). According to several decision performance measures, experimental results show that the proposed algorithm is feasible and efficient for large-scale data sets. 相似文献
32.
Nguyen Huy Tuan Dang Duc TrongPham Hoang Quan 《Applied mathematics and computation》2011,217(12):5177-5185
The paper is concerned with the non-linear backward heat equation in the rectangle domain. The problem is severely ill-posed. We shall use a modified integral equation method to regularize the nonlinear problem. The error estimates of Hölder type of the regularized solutions are obtained. Numerical results are presented to illustrate the accuracy and efficiency of the method. This work is a generalization of many earlier papers, including the recent paper [D.D. Trong, N.H. Tuan, Regularization and error estimate for the nonlinear backward heat problem using a method of integral equation, Nonlinear Anal. 71 (9) (2009) 4167-4176]. 相似文献
33.
D.?P.?Kozlenko N.?T.?Dang S.?E.?KichanovEmail author E.?V.?Lukin K.?Knizek Z.?Jirák L.?S.?Dubrovinsky V.?I.?Voronin B.?N.?Savenko 《The European Physical Journal B - Condensed Matter and Complex Systems》2013,86(8):360
High pressure evolution of structural, vibrational and magnetic properties of La0.75Ca0.25MnO3 was studied by means of X-ray diffraction and Raman spectroscopy up to 39 GPa, and neutron diffraction up to 7.5 GPa. The stability of different magnetic ground states, orbital configurations and structural modifications were investigated by LDA + U electronic structure calculations. A change of octahedral tilts corresponding to the transformation of orthorhombic crystal structure from the Pnma symmetry to the Immaone occurs above P ~ 6 GPa. At the same time, the evolution of the orthorhombic lattice distortion evidences an appearance of the e g d x² ? z² orbital polarization at high pressures. The magnetic order in La0.75Ca0.25MnO3 undergoes a continuous transition from the ferromagnetic 3D metallic (FM) ground state to the A-type antiferromagnetic (AFM) state of assumedly 2D pseudo-metallic character under pressure, that starts at about 1 GPa and extends possibly to 20–30 GPa. 相似文献
34.
In this paper, for multiple attribute decision-making problem in which attribute values are interval grey numbers and some of them are null values, a decision model based on grey rough sets integration with incomplete information is proposed. We put forward incidence degree coefficient formula for grey interval, by information entropy theory and analysis technique, the method and principle is presented to fill up null values. We also establish the method of grey interval incidence cluster. Because grey system theory and Rough set theory are complementary each other, decision table with preference information is obtained by the result of grey incidence cluster. An algorithm for inducing decision rules based on rough set theory and the dominance relationship is presented. In some extent, this algorithm can deal with decision-making problem in which the attribute values are interval grey numbers and some of them are null values. Contrasted with classical model of cluster decision-making, the algorithm has an advantage of flexibility and compatibility to new information. 相似文献
35.
36.
Abstract
Highly substituted novel 4H-pyrimido[1,6-a] pyrimidines were prepared by a trifluoromethanesulfonic acid catalyzed one-pot three-component condensation of 4-aminopyrimidines, aldehydes, and β-ketoesters. A preliminary feasibility study was undertaken on these compounds, to assess the potential production of a library of further diversified compounds by nucleophilic replacement of Cl (R1) or by reaction of electrophiles with the NH2 (R2) group. 相似文献37.
N. T. Dang D. P. Kozlenko S. E. Kichanov Z. Jirák E. V. Lukin B. N. Savenko 《Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques》2012,6(5):817-820
The crystal and magnetic structure of Pr0.1Sr0.9MnO3 manganite has been studied by the neutron diffraction at high pressures up to 5 GPa in the temperature range 10?C295 K. At normal pressure and decreasing temperature the appearance of the C-type (T N = 220 K) and G-type (T N = 180 K) antiferromagnetic states occurs, which is accompanied by a structural phase transition from the cubic structure (Pm $ \bar 3 $ m space group) to the tetragonal structure (I4/mcm space group). It is shown that the temperature of the transition to the C-type antiferromagnetic phase increases with pressure with the pressure coefficient dT N/dP = 4.0(5) K/GPa and the temperature of the transition to the G-type antiferromagnetic phase weakly depends on pressure. 相似文献
38.
党亚茹 《新疆大学学报(理工版)》1996,13(3):43-50
本文以国际性评论、文摘刊物《MathematicsReviews》(美国数学会出版)在1984-1993年间摘录文南总量和摘录中国数学研究文献量为统计样本,从分支学科文献量分布的角度,比较了中外数学研究的现状.特别结合国家自然科学基金“七五”、“八五”数学重大项目的研究成果,探讨了目前数学研究的发展趋势. 相似文献
39.
二连通偶图的周长 总被引:2,自引:0,他引:2
党恺谦 《新疆大学学报(理工版)》1989,6(3):9-12
本文给出了二连通偶图 G 的周长的下界的新的形式及 G 为哈密尔顿的新的充分条件. 相似文献
40.
Dr. Shi Tang Dr. Zhi Wang Yanzi Xu Huili Ma Dr. Jia Wang Dr. Christian Larsen Prof. Dongfeng Dang Prof. Ergang Wang Prof. Ludvig Edman 《Angewandte Chemie (International ed. in English)》2023,62(23):e202302874
The emission efficiency of organic semiconductors (OSCs) often suffers from aggregation caused quenching (ACQ). An elegant solution is aggregation-induced emission (AIE), which constitutes the design of the OSC so that its morphology inhibits quenching π–π interactions and non-radiative motional deactivation. The light-emitting electrochemical cell (LEC) can be sustainably fabricated, but its function depends on motion of bulky ions in proximity of the OSC. It is therefore questionable whether the AIE morphology can be retained during LEC operation. Here, we synthesize two structurally similar OSCs, which are distinguished by that 1 features ACQ while 2 delivers AIE. Interestingly, we find that the AIE-LEC significantly outperforms the ACQ-LEC. We rationalize our finding by showing that the AIE morphology remains intact during LEC operation, and that it can feature appropriately sized free-volume voids for facile ion transport and suppressed non-radiative excitonic deactivation. 相似文献