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排序方式: 共有1608条查询结果,搜索用时 31 毫秒
1.
Induction of decision trees   总被引:322,自引:2,他引:320  
The technology for building knowledge-based systems by inductive inference from examples has been demonstrated successfully in several practical applications. This paper summarizes an approach to synthesizing decision trees that has been used in a variety of systems, and it describes one such system, ID3, in detail. Results from recent studies show ways in which the methodology can be modified to deal with information that is noisy and/or incomplete. A reported shortcoming of the basic algorithm is discussed and two means of overcoming it are compared. The paper concludes with illustrations of current research directions.  相似文献
2.
Learning Logical Definitions from Relations   总被引:41,自引:11,他引:30  
This paper describes FOIL, a system that learns Horn clauses from data expressed as relations. FOIL is based on ideas that have proved effective in attribute-value learning systems, but extends them to a first-order formalism. This new system has been applied successfully to several tasks taken from the machine learning literature.  相似文献
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4.
Salinization is a major cause of soil degradation in the Murray–Darling Basin of Australia. The objective of this research is to evaluate the utility of field-derived spectra of saline soils and related vegetation for characterizing and mapping the spatial distribution of irrigation-induced soil salinization. A FieldSpec FR hand-held spectrometer was used to measure the spectra of a range of salinized soils and associated vegetation. Strategies for mapping field-derived spectra using hyperspectral (HyMap) imagery were assessed, and a continuum-removed Spectral-Feature-Fitting (SFF) approach adopted. Field-derived spectra of the vegetation comprising of samphire, sea blite, and native grass species are also useful indicators of salinization; however, their absence is not necessarily an indicator of healthy soils. Distribution maps created using the SFF method and a restricted wavelength range of field-derived spectra provide an accurate record of the distribution of both vegetation and soil indicators of salinization at the time of image acquisition. Salinized soil and vegetation indicator class maps show a similar spatial distribution to soil salinization as mapped by ground-based geophysical surveys.  相似文献
5.
Evolutionary structural optimization for dynamic problems   总被引:22,自引:0,他引:22  
This paper presents a simple method for structural optimization with frequency constraints. The structure is modelled by a fine mesh of finite elements. At the end of each eigenvalue analysis, part of the material is removed from the structure so that the frequencies of the resulting structure will be shifted towards a desired direction. A sensitivity number indicating the optimum locations for such material elimination is derived. This sensitivity number can be easily calculated for each element using the information of the eigenvalue solution. The significance of such an evolutionary structural optimization (ESO) method lies in its simplicity in achieving shape and topology optimization for both static and dynamic problems. In this paper, the ESO method is applied to a wide range of frequency optimization problems, which include maximizing or minimizing a chosen frequency of a structure, keeping a chosen frequency constant, maximizing the gap of arbitrarily given two frequencies, as well as considerations of multiple frequency constraints. The proposed ESO method is verified through several examples whose solutions may be obtained by other methods.  相似文献
6.
查询扩展技术进展与展望   总被引:17,自引:0,他引:17  
查询扩展技术是改善信息检索中查全率和查准率的关键技术之一,并成为近年来研究的热点.以查询扩展技术的发展为主线,将目前的研究方法归纳为三类:关键词查询扩展技术、查询词权重调整技术和语义概念查询扩展技术.对这三类扩展技术进行了整体性阐述和比较性研究,对一些关键性问题进行了探讨,并展望未来的发展趋势.  相似文献
7.
SLOM: a new measure for local spatial outliers   总被引:11,自引:0,他引:11  
We propose a measure, spatial local outlier measure (SLOM), which captures the local behaviour of datum in their spatial neighbourhood. With the help of SLOM, we are able to discern local spatial outliers that are usually missed by global techniques, like “three standard deviations away from the mean”. Furthermore, the measure takes into account the local stability around a data point and suppresses the reporting of outliers in highly unstable areas, where data are too heterogeneous and the notion of outliers is not meaningful. We prove several properties of SLOM and report experiments on synthetic and real data sets that show that our approach is novel and scalable to large datasets. Sanjay Chawla is a Senior Lecturer in the School of Information Technologies at the University of Sydney. His research interests span the area of data mining and spatial database management. He is a co-author of the textbook “Spatial Databases: A Tour”, which is published by Prentice Hall. His research work has appeared in leading publications, including IEEE Transaction on Knowledge and Data Engineering and GeoInformatica. He received his Ph.D. in Mathematics from the University of Tennessee, USA. Pei Sun is currently a Ph.D. student in the School of Information Technology, Sydney University, Australia. His research interests include data mining and spatial database. He received his M.E. degree from the University of New South Wales, Sydney, Australia, in 2002 and a B.E. degree from Beijing Forestry University, China, in 1990.  相似文献
8.
Stability analysis of fuzzy control systems   总被引:10,自引:0,他引:10  
A discrete-time fuzzy control system which is composed of a dynamic fuzzy model and a fuzzy state feedback controller is proposed. Stability of the fuzzy control system is discussed and a sufficient condition to guarantee the stability of the system is given in terms of uncertain linear system theory. The results in this paper improve our previous stability results. An example is used to show the proposed method.  相似文献
9.
INS algorithm using quaternion model for low cost IMU   总被引:10,自引:0,他引:10  
This paper presents a generic inertial navigation system (INS) error propagation model that does not rely on small misalignment angles assumption. The modelling uses quaternions in the computer frame approach. Based on this model, an INS algorithm is developed for low cost inertial measurement unit (IMU) to solve the initial attitudes uncertainty using in-motion alignment. The distribution approximation filter (DAF) is used to implement the non-linear data fusion algorithm.  相似文献
10.
In a finite element analysis (FEA), the contours of element von Mises stress and stiffness sensitivity number are found to be very similar. This paper shows there to be an equivalence between the von Mises stress criterion and the stiffness criterion for element elimination or addition in evolutionary structural optimization. The examples presented demonstrate the same resulting topologies during the evolving process using the two different criteria. The effect of numerical errors on topology is also investigated. It is concluded that the optimized topologies of a structure using the fully stressed criterion and the minimum compliance or maximum stiffness criterion are equivalent.  相似文献
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