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In this paper a new integrated observer-based fault estimation and accommodation strategy for discrete-time piecewise linear (PWL) systems subject to actuator faults is proposed. A robust estimator is designed to simultaneously estimate the state of the system and the actuator fault. Then, the estimate of fault is used to compensate for the effect of the fault. By using the estimate of fault and the states, a fault tolerant controller using a PWL state feedback is designed. The observer-based fault-tolerant controller is obtained by the interconnection of the estimator and the state feedback controller. We show that separate design of the state feedback and the estimator results in the stability of the overall closed-loop system. In addition, the input-to-state stability (ISS) gain for the closed-loop system is obtained and a procedure for minimizing it is given. All of the design conditions are formulated in terms of linear matrix inequalities (LMI) which can be solved efficiently. Also, performance of the estimator and the state feedback controller are minimized by solving convex optimization problems. The efficiency of the method is demonstrated by means of a numerical example. 相似文献
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Seyed Mohammad Ali Taghavi 《Culture, Theory & Critique》2013,54(2):123-138
Although Richard Rorty's controversial thought has been the subject of many works, there has not been much discussion about his approach to cultural difference. The purpose of this article is to examine how Rorty sees cultural differences philosophically and how he deals with them politically. For him, rationality, morality and even the scope of moral responsibility towards others are defined in terms of solidarity with a particular community and ‘ethnocentrism’, rather than in terms of a universal and metaphysically derived set of criteria. It can be argued that since language, language games and values are mainly components of culture, the latter is one of the most significant communities with which Rorty is concerned, though he is not explicit about it. Nevertheless, Rorty does not think that the moral and philosophical significance of communities, particularly cultural communities, should be reflected in politics. The main argument of the article is that there is an unresolved tension in Rorty's thought between philosophical, moral and emotional attribution of significance to communities and arguably cultural communities, and a disregard for them in the political sphere. This paves the way for outlining an approach to cultural difference that is more just and even more in harmony with Rorty's own philosophy. 相似文献
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Mojtaba Soltanlou Andra Coldea Christina Artemenko Ann‐Christine Ehlis Andreas J. Fallgatter Hans‐Christoph Nuerk Thomas Dresler 《Mind, Brain, and Education》2019,13(4):313-325
It is under debate whether the neural representation of numbers and letters might rely on distinct neural correlates, or on a mostly shared neural network. In the present study, a total of 47 children in fifth grade (Experiment 1) and sixth grade (Experiment 2) simply copied numbers and letters on a touch screen while brain activation changes were recorded by means of functional near‐infrared spectroscopy (fNIRS). fNIRS data of both experiments and a joint analysis revealed that a shared neural network, particularly in the left hemisphere, was activated in response to both number and letter copying. Interestingly, no difference was observed in brain activation patterns between these two stimuli, as revealed by Bayesian analysis. Our findings indicate that both number and letter copying lead to similar brain activation in children. We further suggest methodological and applied applications of these findings in the frame of educational neuroscience. 相似文献
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Bahram Vazirnezhad Farshad Almasganj Seyed Mohammad Ahadi Ari Chanen 《浙江大学学报(A卷英文版)》2009,10(10):1461-1475
Speaker variability is an important source of speech variations which makes continuous speech recognition a difficult task. Adapting automatic speech recognition （ASR） models to the speaker variations is a well-known strategy to cope with the challenge, Almost all such techniques focus on developing adaptation solutions within the acoustic models of the ASR systems. Although variations of the acoustic features constitute an important portion of the inter-speaker variations, they do not cover variations at the phonetic level. Phonetic variations are known to form an important part of variations which are influenced by both micro-segmental and suprasegmental factors. Inter-speaker phonetic variations are influenced by the structure and anatomy of a speaker＇s articulatory system and also his/her speaking style which is driven by many speaker background characteristics such as accent, gender, age, socioeconomic and educational class. The effect of inter-speaker variations in the feature space may cause explicit phone recognition errors. These errors can be compensated later by having appropriate pronunciation variants for the lexicon entries which consider likely phone misclassifications besides pronunciation. In this paper, we introduce speaker adaptive dynamic pronunciation models, which generate different lexicons for various speaker clusters and different ranges of speech rate. The models are hybrids of speaker adapted contextual rules and dynamic generalized decision trees, which take into account word phonological structures, rate of speech, unigram probabilities and stress to generate pronunciation variants of words. Employing the set of speaker adapted dynamic lexicons in a Farsi （Persian） continuous speech recognition task results in word error rate reductions of as much as 10.1% in a speaker-dependent scenario and 7.4% in a speaker-independent scenario. 相似文献
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In this study, the efficiency of bitumen and asphalt mixtures modified with crumb rubber （CR） and recycled glass powder （RGP） is evaluated. From an environmental point of view, the application of RGP in asphalt mixtures is considered beneficial since it prevents accumulation of waste glass in the natural environment. Rheological and mechanical properties of modified bitumen samples were investigated by laboratory methods such as bitumen conventional tests and dynamic shear rheometer （DSR）, and also by asphalt mixture performance tests including Marshall stability, indirect tensile strength （ITS）, compressive strength, and indirect tensile stiffness modulus. The results showed that the application of RGP in place of CR has no negative impact on the efficiency of bitumen and asphalt mixtures and even improves their engineering properties except for the toughness index （TI）. Moreover, a modification with 5% CR and 5% RGP in asphalt mixtures results in the best overall performance. 相似文献
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Seyed Amin Mirlohi Falavarjani Fattane Zarrinkalam Jelena Jovanovic Ebrahim Bagheri Ali A. Ghorbani 《Information processing & management》2019,56(6):102070
The ever increasing presence of online social networks in users’ daily lives has led to the interplay between users’ online and offline activities. There have already been several works that have studied the impact of users’ online activities on their offline behavior, e.g., the impact of interaction with friends on an exercise social network on the number of daily steps. In this paper, we consider the inverse to what has already been studied and report on our extensive study that explores the potential causal effects of users’ offline activities on their online social behavior. The objective of our work is to understand whether the activities that users are involved with in their real daily life, which place them within or away from social situations, have any direct causal impact on their behavior in online social networks. Our work is motivated by the theory of normative social influence, which argues that individuals may show behaviors or express opinions that conform to those of the community for the sake of being accepted or from fear of rejection or isolation. We have collected data from two online social networks, namely Twitter and Foursquare, and systematically aligned user content on both social networks. On this basis, we have performed a natural experiment that took the form of an interrupted time series with a comparison group design to study whether users’ socially situated offline activities exhibited through their Foursquare check-ins impact their online behavior captured through the content they share on Twitter. Our main findings can be summarised as follows (1) a change in users’ offline behavior that affects the level of users’ exposure to social situations, e.g., starting to go to the gym or discontinuing frequenting bars, can have a causal impact on users’ online topical interests and sentiment; and (2) the causal relations between users’ socially situated offline activities and their online social behavior can be used to build effective predictive models of users’ online topical interests and sentiments. 相似文献
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Mojtaba Salehi Isa Nakhai Kamalabadi Mohammad Bagher Ghaznavi Ghoushchi 《Education and Information Technologies》2014,19(4):713-735
Material recommender system is a significant part of e-learning systems for personalization and recommendation of appropriate materials to learners. However, in the existing recommendation algorithms, dynamic interests and multi-preference of learners and multidimensional-attribute of materials are not fully considered simultaneously. Moreover, these algorithms cannot effectively use the learner’s historical sequential patterns of material accessing in recommendation. For addressing these problems and improving the accuracy and quality of recommendation, a new material recommender system framework based on sequential pattern mining and multidimensional attribute-based collaborative filtering (CF) is proposed. In the sequential pattern based approach, modified Apriori and PrefixSpan algorithms are implemented to discover latent patterns in accessing of materials and use them for recommendation. Leaner Preference Tree (LPT) is introduced to take into account multidimensional-attribute of materials, and learners’ rating and model dynamic and multi-preference of learners in the multidimensional attribute-based CF approach. Finally, the recommendation results of two approaches are combined using cascade, weighted and mixed methods. The proposed method outperforms the previous algorithms on the classification accuracy measures and the learner’s real learning preference can be satisfied accurately according to the real-time up dated contextual information. 相似文献