排序方式： 共有17条查询结果，搜索用时 129 毫秒
1.
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
2.
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
3.
Paulo Blikstein Tamar Fuhrmann Shima Salehi 《Journal of Science Education and Technology》2016,25(4):513-526
In this paper, we investigate an approach to supporting students’ learning in science through a combination of physical experimentation and virtual modeling. We present a study that utilizes a scientific inquiry framework, which we call “bifocal modeling,” to link student-designed experiments and computer models in real time. In this study, a group of high school students designed computer models of bacterial growth with reference to a simultaneous physical experiment they were conducting, and were able to validate the correctness of their model against the results of their experiment. Our findings suggest that as the students compared their virtual models with physical experiments, they encountered “discrepant events” that contradicted their existing conceptions and elicited a state of cognitive disequilibrium. This experience of conflict encouraged students to further examine their ideas and to seek more accurate explanations of the observed natural phenomena, improving the design of their computer models. 相似文献
4.
5.
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
6.
7.
Mohammad Salehi Mohammad Soltani Hadis Tamleh Shohreh Teimournezhad 《Learned Publishing》2020,33(2):89-95
The proliferation of predatory or bogus journals has been recognized as a threat to academic research, and this study was conducted to discover the experiences of authors published in these journals. Eighty authors who had published in journals identified as predatory were surveyed. We asked how the authors learnt about these journals, what they thought about the reputation of the journals, their experiences of peer review and the quality of feedback provided, and whether publication was driven by PhD or job requirements. Our results showed that a third of authors discovered the journals by web searches or responding to email invitations. Over half said the reputation and name of the journal were important in selecting a journal, although a third admitted that the journal they published in did not have a good reputation. The main reason for selecting the journals was the promise of fast publication (31.2% respondents). Only half of the respondents said that publication was driven by PhD or job requirements. Just over a third reported that peer review was good or excellent, and only 17.5% said that peer review was poor or non‐existent – over 70% thought they had received good feedback from the journals. Although the research was somewhat limited, it does indicate general satisfaction with the journals in which the authors published. Fast publication coupled with good feedback and encouragement to submit can make publishing in predatory journals so tempting that few authors can resist. 相似文献
8.
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
9.
Mohammad Sadegh Cheri Hamidreza Shahraki Jalal Sadeghi Mohammadreza Salehi Moghaddam Hamid Latifi 《Biomicrofluidics》2014,8(5)
Measurement and control of pressure-driven flow (PDF) has a great potential to enhance the performance of chemical and biological experiments in Lab on a Chip technology. In this paper, we present an optofluidic flow sensor for real-time measurement and control of PDF. The optofluidic flow sensor consists of an on-chip micro Venturi and two optical Fabry-Pérot (FP) interferometers. Flow rate was measured from the fringe shift of FP interferometers resulted from movement fluid in the on-chip micro Venturi. The experimental results show that the optofluidic flow sensor has a minimum detectable flow change of 5 nl/min that is suitable for real time monitoring and control of fluids in many chemical and biological experiments. A Finite Element Method is used to solve the three dimensional (3D) Navier–Stokes and continuity equations to validate the experimental results. 相似文献
10.
Karimian Zahra Farrokhi Majid Reza Moghadami Mohsen Zarifsanaiey Nahid Mehrabi Manoosh Khojasteh Laleh Salehi Nasim 《Education and Information Technologies》2022,27(3):3299-3320
Education and Information Technologies - The COVID-19 crisis has had a profound effect on higher education, especially medical education due to its sensitive nature, dealing with people’s... 相似文献