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AS-Index: A Structure for String Search Using n-Grams and Algebraic Signatures 被引量:1
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作者 Camelia Constantin Cedric du Mouza +2 位作者 Witold Litwin Philippe Rigaux Thomas Schwarz 《Journal of Computer Science & Technology》 SCIE EI CSCD 2016年第1期147-166,共20页
We present the AS-Index, a new index structure for exact string search in disk resident databases. AS-Index relies on a classical inverted file structure, whose main innovation is a probabilistic search based on the p... We present the AS-Index, a new index structure for exact string search in disk resident databases. AS-Index relies on a classical inverted file structure, whose main innovation is a probabilistic search based on the properties of algebraic signatures used for both n-grams hashing and pattern search. Specifically, the properties of our signatures allow to carry out a search by inspecting only two of the posting lists. The algorithm thus enjoys the unique feature of requiring a constant number of disk accesses, independently from both the pattern size and the database size. We conduct extensive experiments on large datasets to evaluate our index behavior. They confirm that it steadily provides a search performance proportional to the two disk accesses necessary to obtain the posting lists. This makes our structure a choice of interest for the class of applications that require very fast lookups in large textual databases. We describe the index structure, our use of algebraic signatures, and the search algorithm. We discuss the operational trade-offs based on the parameters that affect the behavior of our structure, and present the theoretical and experimental performance analysis. We next compare the AS-Index with the state-of-the-art alternatives and show that 1) its construction time matches that of its competitors, due to the similarity of structures, 2) as for search time, it constantly outperforms the standard approach, thanks to the economical access to data complemented by signature calculations, which is at the core of our search method. 展开更多
关键词 full text indexing large-scale indexing algebraic signature
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Optimization techniques in deep convolutional neuronal networks applied to olive diseases classification
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作者 El Mehdi Raouhi Mohamed Lachgar a +1 位作者 Hamid Hrimech Ali Kartit 《Artificial Intelligence in Agriculture》 2022年第1期77-89,共13页
Plants diseases have a detrimental effect on the quality but also on the quantity of agricultural production.However,the prediction of these diseases is proving the effect on crop quality and on reducing the risk of p... Plants diseases have a detrimental effect on the quality but also on the quantity of agricultural production.However,the prediction of these diseases is proving the effect on crop quality and on reducing the risk of production losses.Indeed,the detection of plant diseases-either with a naked eye or using traditional methods-is largely a cumbersome process in terms of time,availability and results with a high-risk error.The present work introduces a depth study of various CNN architectures with different optimization algorithms carried out for olive disease detection using classification techniques that recommend the best model for constructing an effective disease detector.This study presents a dataset of 5571 olive leaf images collected manually on real conditions from different regions of Morocco,that also includes healthy class to detect olive diseases.Further,one of the goals of this research was to study the correlation effects between CNN architectures and optimization algorithms evaluated by the accuracy and other performance metrics.The highest rate in trained models was 100%,while the highest rate in experiments without data augmentation was 92,59%.Another subject of this study is the influence of the optimization algorithms on neuronal network performance.As a result of the experiments carried out,the MobileNet architecture using Rmsprop algorithms outperformed the others combinations in terms of performance and efficiency of disease detector. 展开更多
关键词 Convolutional neuronal networks(CNN) Classification Optimization Gradient descent Plant diseases Olive dataset diseases(ODD)
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