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971.
A pattern is a model or a template used to summarize and describe the behavior (or the trend) of data having generally some recurrent events. Patterns have received a considerable attention in recent years and were widely studied in the data mining field. Various pattern mining approaches have been proposed and used for different applications such as network monitoring, moving object tracking, financial or medical data analysis, scientific data processing, etc. In these different contexts, discovered patterns were useful to detect anomalies, to predict data behavior (or trend) or, more generally, to simplify data processing or to improve system performance. However, to the best of our knowledge, patterns have never been used in the context of Web archiving. Web archiving is the process of continuously collecting and preserving portions of the World Wide Web for future generations. In this paper, we show how patterns of page changes can be useful tools to efficiently archive Websites. We first define our pattern model that describes the importance of page changes. Then, we present the strategy used to (i) extract the temporal evolution of page changes, (ii) discover patterns, to (iii) exploit them to improve Web archives. The archive of French public TV channels France Télévisions is chosen as a case study to validate our approach. Our experimental evaluation based on real Web pages shows the utility of patterns to improve archive quality and to optimize indexing or storing. 相似文献
972.
A K-nearest neighbours method based on imprecise probabilities 总被引:1,自引:1,他引:0
Sebastien Destercke 《Soft Computing - A Fusion of Foundations, Methodologies and Applications》2012,16(5):833-844
K-nearest neighbours algorithms are among the most popular existing classification methods, due to their simplicity and good
performances. Over the years, several extensions of the initial method have been proposed. In this paper, we propose a K-nearest
neighbours approach that uses the theory of imprecise probabilities, and more specifically lower previsions. We show that
the proposed approach has several assets: it can handle uncertain data in a very generic way, and decision rules developed
within this theory allow us to deal with conflicting information between neighbours or with the absence of close neighbour
to the instance to classify. We show that results of the basic k-NN and weighted k-NN methods can be retrieved by the proposed approach. We end with some experiments on the classical data sets. 相似文献
973.
Julián Luengo José A. Sáez Francisco Herrera 《Soft Computing - A Fusion of Foundations, Methodologies and Applications》2012,16(5):863-881
Fuzzy rule-based classification systems (FRBCSs) are known due to their ability to treat with low quality data and obtain
good results in these scenarios. However, their application in problems with missing data are uncommon while in real-life
data, information is frequently incomplete in data mining, caused by the presence of missing values in attributes. Several
schemes have been studied to overcome the drawbacks produced by missing values in data mining tasks; one of the most well
known is based on preprocessing, formerly known as imputation. In this work, we focus on FRBCSs considering 14 different approaches
to missing attribute values treatment that are presented and analyzed. The analysis involves three different methods, in which
we distinguish between Mamdani and TSK models. From the obtained results, the convenience of using imputation methods for
FRBCSs with missing values is stated. The analysis suggests that each type behaves differently while the use of determined
missing values imputation methods could improve the accuracy obtained for these methods. Thus, the use of particular imputation
methods conditioned to the type of FRBCSs is required. 相似文献
974.
Yiqiao Cai Jiahai Wang Jian Yin 《Soft Computing - A Fusion of Foundations, Methodologies and Applications》2012,16(2):303-330
Differential evolution (DE) is a simple and powerful population-based search algorithm, successfully used in various scientific
and engineering fields. However, DE is not free from the problems of stagnation and premature convergence. Hence, designing
more effective search strategies to enhance the performance of DE is one of the most salient and active topics. This paper
proposes a new method, called learning-enhanced DE (LeDE) that promotes individuals to exchange information systematically.
Distinct from the existing DE variants, LeDE adopts a novel learning strategy, namely clustering-based learning strategy (CLS).
In CLS, there are two levels of learning strategies, intra-cluster learning strategy and inter-cluster learning strategy.
They are adopted for exchanging information within the same cluster and between different clusters, respectively. Experimental
studies over 23 benchmark functions show that LeDE significantly outperforms the conventional DE. Compared with other clustering-based
DE algorithms, LeDE can obtain better solutions. In addition, LeDE is also shown to be significantly better than or at least
comparable to several state-of-art DE variants as well as some other evolutionary algorithms. 相似文献
975.
Ramon Jansana Umberto Rivieccio 《Soft Computing - A Fusion of Foundations, Methodologies and Applications》2012,16(3):493-504
We introduce a new product bilattice construction that generalizes the well-known one for interlaced bilattices and others
that were developed more recently, allowing to obtain a bilattice with two residuated pairs as a certain kind of power of
an arbitrary residuated lattice. We prove that the class of bilattices thus obtained is a variety, give a finite axiomatization
for it and characterize the congruences of its members in terms of those of their lattice factors. Finally, we show how to
employ our product construction to define first-order definable classes of bilattices corresponding to any first-order definable
subclass of residuated lattices. 相似文献
976.
José M. Cecilia José M. García Ginés D. Guerrero Miguel A. Martínez-del-Amor Mario J. Pérez-Jiménez Manuel Ujaldón 《Soft Computing - A Fusion of Foundations, Methodologies and Applications》2012,16(2):231-246
Membrane Computing is a discipline aiming to abstract formal computing models, called membrane systems or P systems, from the structure and functioning of the living cells as well as from the cooperation of cells in tissues, organs, and
other higher order structures. This framework provides polynomial time solutions to NP-complete problems by trading space
for time, and whose efficient simulation poses challenges in three different aspects: an intrinsic massively parallelism of
P systems, an exponential computational workspace, and a non-intensive floating point nature. In this paper, we analyze the
simulation of a family of recognizer P systems with active membranes that solves the Satisfiability problem in linear time
on different instances of Graphics Processing Units (GPUs). For an efficient handling of the exponential workspace created
by the P systems computation, we enable different data policies to increase memory bandwidth and exploit data locality through
tiling and dynamic queues. Parallelism inherent to the target P system is also managed to demonstrate that GPUs offer a valid
alternative for high-performance computing at a considerably lower cost. Furthermore, scalability is demonstrated on the way
to the largest problem size we were able to run, and considering the new hardware generation from Nvidia, Fermi, for a total
speed-up exceeding four orders of magnitude when running our simulations on the Tesla S2050 server. 相似文献
977.
Zhibin Wu Jiuping Xu 《Soft Computing - A Fusion of Foundations, Methodologies and Applications》2012,16(4):577-589
In group decision making (GDM) using linguistic preference relations to obtain the maximum degree of agreement, it is desirable
to develop a consensus process prior to the selection process. This paper proposes two consensus models with linguistic information
to support the GDM consensus reaching process. Two different distance functions between linguistic preference relations are
introduced to measure both individual consistency and group consensus. Based on these measures, the consensus reaching models
are developed. The two models presented have the same concept that the expert whose preference is farthest from the group
preference needs to update their opinion according to the group preference relation. In addition, the convergence of the models
is proved. After achieving the predefined consensus level, each expert’s consistency indexes are still acceptable under the
condition that the initial preference relations are of satisfactory consistency. Finally, an example is given to show the
effectiveness of the models and to verify the theoretical results. 相似文献
978.
Daniel Camps-Mur Manil Dev Gomony Xavier Pérez-Costa Sebastià Sallent-Ribes 《Computer Networks》2012,56(12):2896-2911
The Wi-Fi technology, driven by its tremendous success, is expanding into a wide variety of devices and applications. However, many of these new devices, like handheld devices, pose new challenges in terms of QoS and energy efficiency. In order to address these challenges, in this paper we study how the novel MAC aggregation mechanisms developed in the 802.11n standard can be used to enhance the current 802.11 QoS and power saving protocols. Our contribution is twofold. First, we present a simulation study that illustrates the interactions between 802.11n and the current 802.11 QoS and power saving protocols. This study reveals that the 802.11n MAC aggregation mechanisms perform better when combined with the power save mode included in the original 802.11 standard than with the 802.11e U-APSD protocol. Second, we design CA-DFA, an algorithm that, using only information available at layer two, adapts the amount of 802.11n aggregation used by a Wi-Fi station according to the level of congestion in the network. A detailed performance evaluation demonstrates the benefits of CA-DFA in terms of QoS, energy efficiency and network capacity with respect to state of the art alternatives. 相似文献
979.
Sergio Herrerı´a-Alonso Miguel Rodrı´guez-Pérez Manuel Fernández-Veiga Cándido López-Garcı´a 《Computer Networks》2012,56(10):2456-2467
The IEEE 802.3az standard provides a new low power mode that Ethernet network interfaces can use to save energy when there is no traffic to transmit. Simultaneously with the final standard approval, several algorithms were proposed to govern the physical interface state transition between the normal active mode and the new low power mode. In fact, the standard leaves this sleeping algorithm unspecified to spur competition among different vendors and achieve the greatest energy savings. In this paper, we try to bring some light to the most well known sleeping algorithms, providing mathematical models for the expected energy savings and the average packet delay inflicted on outgoing traffic. We will then use the models to derive optimum configuration parameters for them under given efficiency constraints. 相似文献
980.
The paper focuses on a control design for a vehicle suspension system in which a balance between different performance demands is achieved. The starting point of the control design is a full–car model which contains nonlinear components, i.e. the dynamics of the dampers and springs and nonlinear actuator dynamics. In order to handle the high complexity of the problem this paper proposes the design of a two‐level controller of an active suspension system. The required control force is computed by applying a high‐level controller, which is designed using a linear parameter varying (LPV) method. For the control design the model is augmented with weighting functions specified by the performance demands and the uncertainty assumptions. The actuator generating the necessary control force is modelled as a nonlinear system for which a low‐level force‐tracking controller is designed. To obtain the low‐level controller a backstepping method is proposed. As an alternative solution a feedback linearization method is also presented. The operation of the controller is illustrated through simulation examples. Copyright © 2011 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society 相似文献