221 research outputs found

    Techniques for data pattern selection and abstraction

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    This thesis concerns the problem of prototype reduction in instance-based learning. In order to deal with problems such as storage requirements, sensitivity to noise and computational complexity, various algorithms have been presented that condense the number of stored prototypes, while maintaining competent classification accuracy. Instance selection, which recovers a smaller subset of the original training set, is the most widely used technique for instance reduction. But, prototype abstraction that generates new prototypes to replace the initial ones has also gained a lot of interest recently. The major contribution of this work is the proposal of four novel frameworks for performing prototype reduction, the Class Boundary Preserving algorithm (CBP), a hybrid method that uses both selection and generation of prototypes, Instance Seriation for Prototype Abstraction (ISPA), which is an abstraction algorithm, and two selective techniques, Spectral Instance Reduction (SIR) and Direct Weight Optimization (DWO). CBP is a multi-stage method based on a simple heuristic that is very effective in identifying samples close to class borders. Using a noise filter harmful instances are removed, while the powerful heuristic determines the geometrical distribution of patterns around every instance. Together with the concepts of nearest enemy pairs and mean shift clustering this algorithm decides on the final set of retained prototypes. DWO is a selection model whose output set of prototypes is decided by a set of binary weights. These weights are computed according to an objective function composed of the ratio between the nearest friend and nearest enemy of every sample. In order to obtain good quality results DWO is optimized using a genetic algorithm. ISPA is an abstraction technique that employs the concept of data seriation to organize instances in an arrangement that favours merging between them. As a result, a new set of prototypes is created. Results show that CBP, SIR and DWO, the three major algorithms presented in this thesis, are competent and efficient in terms of at least one of the two basic objectives, classification accuracy and condensation ratio. The comparison against other successful condensation algorithms illustrates the competitiveness of the proposed models. The SIR algorithm presents a set of border discriminating features (BDFs) that depicts the local distribution of friends and enemies of all samples. These are then used along with spectral graph theory to partition the training set in to border and internal instances

    Constructivism, epistemology and information processing

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    The author analyzes the main models of artificial intelligence which deal with the transition from one stage to another, a central problem in development. He describes the contributions of rule-based systems and connectionist systems to an explanation of this transition. He considers that Artificial Intelligence models, in spite of their limitations, establish fruitful points of contact with the constructivist position.El autor analiza los principales modelos de inteligencia artificial que dan cuenta del paso de la transición de un estudio a otro, problema central del desarrollo. Describe y señala las aportaciones de los sistemas basados en reglas así como de los sistemas conexionistas para explicar dicha transición. Considera que los modelos de inteligencia artificial, a pesar de sus limitaciones, permiten establecer puntos de contacto muy fructiferos con la posición constructivista

    Data granulation by the principles of uncertainty

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    Researches in granular modeling produced a variety of mathematical models, such as intervals, (higher-order) fuzzy sets, rough sets, and shadowed sets, which are all suitable to characterize the so-called information granules. Modeling of the input data uncertainty is recognized as a crucial aspect in information granulation. Moreover, the uncertainty is a well-studied concept in many mathematical settings, such as those of probability theory, fuzzy set theory, and possibility theory. This fact suggests that an appropriate quantification of the uncertainty expressed by the information granule model could be used to define an invariant property, to be exploited in practical situations of information granulation. In this perspective, a procedure of information granulation is effective if the uncertainty conveyed by the synthesized information granule is in a monotonically increasing relation with the uncertainty of the input data. In this paper, we present a data granulation framework that elaborates over the principles of uncertainty introduced by Klir. Being the uncertainty a mesoscopic descriptor of systems and data, it is possible to apply such principles regardless of the input data type and the specific mathematical setting adopted for the information granules. The proposed framework is conceived (i) to offer a guideline for the synthesis of information granules and (ii) to build a groundwork to compare and quantitatively judge over different data granulation procedures. To provide a suitable case study, we introduce a new data granulation technique based on the minimum sum of distances, which is designed to generate type-2 fuzzy sets. We analyze the procedure by performing different experiments on two distinct data types: feature vectors and labeled graphs. Results show that the uncertainty of the input data is suitably conveyed by the generated type-2 fuzzy set models.Comment: 16 pages, 9 figures, 52 reference

    Vwire: Digital Content Management through Spatial Arrangement - a Tool for Visual Argumentation in the Humanities

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    The Vwire project initiates an open source and extensible environment for producing, sharing and discussing visually ordered data sets in the humanities. Even those existing database tools that allow researchers to see multiple images simultaneously do not allow for the active and intuitive configuration of the images - like arranging snapshots on a table - that Vwire provides. Already implemented as an add-on module for Plone 4 (a mature and recently much improved Content Management System [CMS]), Vwire leverages existing technology and extends the visualization tools available to humanities researchers. We propose a test case using a small group of Teotihuacan stone masks, which are of archaeological and art historical importance, and we will elicit collaboration between experts from both fields to help refine and troubleshoot the existing tool

    Teaching addition and subtraction by the method of bidirectional translation: an empirical study

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    Bidirectional Translation, devised by the author, is a structured approach to the teaching of addition and subtraction which aims to give children greater understanding of arithmetical operations. The approach systematically involves both: the translation of numerical representations into hypothetical, real world contexts; and the extraction of the appropriate numerical operations from hypothetical, real world contexts. It is this emphasis on translation from and to both the numerical representation and realistic contexts which gives rise to the name, Bidirectional Translation. An experimental group of 90 primary one children were taught to add and subtract (within 10) by the method of Bidirectional Translation. Post-test comparison of the experimental subjects' performance with that of a control group showed significantly superior performance on the part of the experimental subjects in terms of the utilizability of addition, the evocability of addition, the utilizability of subtraction and the evocability of subtraction for five different classes of verbal context, namely: Part-Part Whole, Separating, Joining, Equalizing and Comparison contexts. In all instances the probability of the results being chance ones were less than 5% and in most, were less than 1%. In both the experimental and control groups, most children performed better when they were required to utilize concepts than when they were required to evoke concepts. Similarly they performed better when they were required to add than when they were required to subtract. The differences, however, were not always significant. It is suggested that the effectiveness of the methodology of Bidirectional Translation is rooted in a structure which allows the child to make his/her thinking explicit and which allows the teacher to monitor this

    Identity and the Cruciform Brooch in Early Anglo-Saxon England: An Investigation of Style, Mortuary Context, and Use

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    This thesis uses the cruciform brooch, a well-represented and highly decorative dress-fastener, as an entry point for looking at the construction of identities relating to ethnicity, gender, age, and power in the early Anglo-Saxon period. The examination of this artefact is holistic and multi-dimensional, and the major topics of consideration are: (a) typology and stylistic variability, (b) chronology, (c) distribution, (d) mortuary context, (e) use, repair and costume, and finally (f) iconography and symbolism. These threads come together to provide an understanding of why and how the cruciform brooch evolved as it did, how it was used in life and death (and by whom), and the complex social identity the artefact was used to construct and display.EThOS - Electronic Theses Online ServiceGBUnited Kingdo
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