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This paper discusses the problem of the fuzzy sliding mode control for a class of disturbed systems. First, a fuzzy auxiliary controller is constructed based on a feedback signal not only to estimate the unknown control term, but also participates in the sliding mode control due to the fuzzy rule employed. Then, we extend our theory into the cases, where some kind of system information can not be obtained, for better use of our theoretical results in real engineering. Finally, some typical numerical examples are included to demonstrate the effectiveness and advantage of the designed sliding mode controller. 相似文献
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This paper deals with the problem of adaptive output feedback neural network controller design for a SISO non-affine nonlinear system. Since in practice all system states are not available in output measurement, an observer is designed to estimate these states. In comparison with the existing approaches, the current method does not require any information about the sign of control gain. In order to handle the unknown sign of the control direction, the Nussbaum-type function is utilized. In order to approximate the unknown nonlinear function, neural network is firstly exploited, and then to compensate the approximation error and external disturbance a robustifying term is employed. The proposed controller is designed based on strict-positive-real (SPR) Lyapunov stability theory to ensure the asymptotic stability of the closed-loop system. Finally, two simulation studies are presented to demonstrate the effectiveness of the developed scheme. 相似文献
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Zuolong Wei Kjell G. Robbersmyr Hamid R. Karimi 《Journal of The Franklin Institute》2017,354(12):4896-4912
As a complex process, vehicle crash is challenging to be described and estimated mathematically. Although different mathematical models are developed, it is still difficult to balance the complexity of models and the performance of estimation. The aim of this work is to propose a novel scheme to model and estimate the processes of vehicle-barrier frontal crashes. In this work, a piecewise model structure is predefined to represent the accelerations of vehicle in frontal crashes. Each segment in the model is corresponding to the energy absorbing component in the crashworthiness structure. With the help of Ensemble Empirical Mode Decomposition (EEMD), a robust scheme is proposed for parameter identification. By adjusting the model structure and parameters according to the initial velocity, crash processes in different conditions are estimated effectively. The estimation results exhibit good agreement with finite element (FE) simulations in three different cases. It is shown that, the proposed model keeps low complexity. Furthermore, the structure information of vehicle is involved in improving the accuracy and ability of crash estimation. 相似文献
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Shixiang Sun Xinjiang Wei Huifeng Zhang Hamid Reza Karimi Jian Han 《Journal of The Franklin Institute》2018,355(12):4897-4915
In this paper, a composite fault tolerant control (CFTC) with disturbance observer scheme is considered for a class of stochastic systems with faults and multiple disturbances. The disturbances are divided into two parts. One represents the stochastic disturbance with partial known information which is formulated by an exogenous system. The other is independent Wiener process. A stochastic disturbance observer is designed to estimate exogenous disturbance. To make the first type of disturbance can be rejected and the fault can be diagnosed, a composite fault diagnosis observer with disturbance observer is constructed. Furthermore, a composite fault-tolerant controller is proposed to compensate disturbances and faults. Finally, simulation examples are given to demonstrate the feasibility and effectiveness of the proposed scheme. 相似文献
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Yueyang Li Hamid Reza Karimi Choon Ki Ahn Yuan Xu Dong Zhao 《Journal of The Franklin Institute》2018,355(7):3330-3353
This work deals with the problem of optimal residual generation for fault detection (FD) in linear discrete time-varying (LDTV) systems subject to uncertain observations. By introducing a generalized fault detection filter (FDF) with four parameter matrices as the residual generator, a novel FDF design scheme is formulated as two bi-objective optimization problems such that the sensitivity of residual to fault is enhanced and the robustness of residual to unknown input is simultaneously strengthened. A generalized operator based optimization approach is proposed to deduce solutions to the corresponding optimization problems in operator forms, where the related H∞/H∞ or FD performance index is maximized. With the aid of the addressed methods, the connections among the derived solutions are explicitly announced. The parameter matrices of the FDF are analytically derived via solving simple matrix equations recursively. It is revealed that our proposed results establish an operator-based framework of optimal residual generation for some kinds of linear discrete-time systems. Illustrative examples are given to show the applicability and effectiveness of the proposed methods. 相似文献
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Mozhgan Karimi Dietmar Jannach Michael Jugovac 《Information processing & management》2018,54(6):1203-1227
More and more people read the news online, e.g., by visiting the websites of their favorite newspapers or by navigating the sites of news aggregators. However, the abundance of news information that is published online every day through different channels can make it challenging for readers to locate the content they are interested in. The goal of News Recommender Systems (NRS) is to make reading suggestions to users in a personalized way. Due to their practical relevance, a variety of technical approaches to build such systems have been proposed over the last two decades. In this work, we review the state-of-the-art of designing and evaluating news recommender systems over the last ten years. One main goal of the work is to analyze which particular challenges of news recommendation (e.g., short item life times and recency aspects) have been well explored and which areas still require more work. Furthermore, in contrast to previous surveys, the paper specifically discusses methodological questions and today’s academic practice of evaluating and comparing different algorithmic news recommendation approaches based on accuracy measures. 相似文献
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Alireza Karimi Reza Razaghi Mahdi Navidbakhsh Toshihiro Sera Susumu Kudo 《Sports Engineering》2016,19(2):105-115
Although it might be believed that the eye only comprised a very small area of the face, its injury due to the ball impacts in different sports seems to be severe enough to entice many researchers to determine the level of injury and then attempt to minimize it. Sports-related eye injuries, especially tennis, pose a substantial and preventable problem to the eye due to the high speed of the tennis ball (69 m/s). This is why many ophthalmologists provide a wide range of information for their patients regarding the risks of eye injuries in tennis to prevent the injury to well over 100,000 eyes each year. However, so far although there are some general information regarding the injury to the human eye components due to the tennis ball impact, the details of the stresses and deformations have not been well determined. Therefore, the goal of this study was to determine the stresses and deformations of the eye components, including cornea, aqueous body, iris, ciliary body, lens, vitreous body, retina, sclera, optic nerve, extra and intraconal fats, and muscles, attributable to the tennis ball impact via a Lagrangian–Eulerian computational coupling model. Magnetic resonance imaging was employed to establish a finite element model of the human eye according to a normal human eye. The numerical results revealed the highest amount of stress in the iris (19.2 MPa), whereas the lowest one was observed in the vitreous body (1.77 Pa). The cornea also experienced the stress of 8.27 MPa which might be high enough to invoke rupture in this delicate material. In addition, the results exhibited a decreasing and increasing of the radius of curvature for the cornea and lens, respectively. Finally, the collision of the tennis ball to the eye triggered the resultant displacement of 0.045 µm in the optic nerve which may imply a non-significant injury to that. The findings of this study may have implications not only for understating the values of stresses and deformations in the human eye components but also for helping the ophthalmologists to have a more precise diagnosis about the injury position in the eye due to the tennis ball impact. 相似文献
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In ad hoc querying of document collections, current approaches to ranking primarily rely on identifying the documents that contain the query terms. Methods such as query expansion, based on thesaural information or automatic feedback, are used to add further terms, and can yield significant though usually small gains in effectiveness. Another approach to adding terms, which we investigate in this paper, is to use natural language technology to annotate - and thus disambiguate - key terms by the concept they represent. Using biomedical research documents, we quantify the potential benefits of tagging users’ targeted concepts in queries and documents in domain-specific information retrieval. Our experiments, based on the TREC Genomics track data, both on passage and full-text retrieval, found no evidence that automatic concept recognition in general is of significant value for this task. Moreover, the issues raised by these results suggest that it is difficult for such disambiguation to be effective. 相似文献
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Manjima Dhar Jessica Wong Armin Karimi James Che Corinne Renier Melissa Matsumoto Melanie Triboulet Edward B. Garon Jonathan W. Goldman Matthew B. Rettig Stefanie S. Jeffrey Rajan P. Kulkarni Elodie Sollier Dino Di Carlo 《Biomicrofluidics》2015,9(6)
Circulating tumor cells (CTCs) are important biomarkers for monitoring tumor dynamics and efficacy of cancer therapy. Several technologies have been demonstrated to isolate CTCs with high efficiency but achieve a low purity from a large background of blood cells. We have previously shown the ability to enrich CTCs with high purity from large volumes of blood through selective capture in microvortices using the Vortex Chip. The device consists of a narrow channel followed by a series of expansion regions called reservoirs. Fast flow in the narrow entry channel gives rise to inertial forces, which direct larger cells into trapping vortices in the reservoirs where they remain circulating in orbits. By studying the entry and stability of particles following entry into reservoirs, we discover that channel cross sectional area plays an important role in controlling the size of trapped particles, not just the orbital trajectories. Using these design modifications, we demonstrate a new device that is able to capture a wider size range of CTCs from clinical samples, uncovering further heterogeneity. This simple biophysical method opens doors for a range of downstream interventions, including genetic analysis, cell culture, and ultimately personalized cancer therapy. 相似文献