769 research outputs found

    The Feedback Control Strategy of the Takagi-Sugeno Fuzzy Car-Following Model with Two Delays

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    Considering the driver’s sensing the headway and velocity the different time-varying delays exist, respectively, and the sensitivity of drivers changes with headway and speed. Introducing the fuzzy control theory, a new fuzzy car-following model with two delays is presented, and the feedback control strategy of the new fuzzy car-following model is studied. Based on the Lyapunov function theory and linear matrix inequality (LMI) approach, the sufficient condition that the existence of the fuzzy controller is given making the closed-loop system is asymptotic, stable; namely, traffic congestion phenomenon can effectively be suppressed, and the controller gain matrix can be obtained via solving linear matrix inequality. Finally, the simulation examples verify that the method which suppresses traffic congestion and reduces fuel consumption and exhaust emissions is effective

    A study of monitor functions for two dimensional adaptive mesh generation

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    This is the published version, also available here: http://dx.doi.org/10.1137/S1064827597327656.In this paper we study the problem of two-dimensional adaptive mesh generation using a variational approach and, specifically, the effect that the monitor function has on the resulting mesh behavior. The basic theoretical tools employed are Green's function for elliptic problems and the eigendecomposition of symmetric positive definite matrices. Based upon this study, a general strategy is suggested for how to choose the monitor function, and numerical results are presented for illustrative purposes.The three-dimensional case is also briefly discussed. It is noted that the strategy used here can be applied to other elliptic mesh generation techniques as well

    A Moving Mesh Method Based on the Geometric Conservation Law

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    This is the published version, also available here: http://dx.doi.org/10.1137/S1064827501384925.A new adaptive mesh movement strategy is presented, which, unlike many existing moving mesh methods, targets the mesh velocities rather than the mesh coordinates. The mesh velocities are determined in a least squares framework by using the geometric conservation law, specifying a form for the Jacobian determinant of the coordinate transformation defining the mesh, and employing a curl condition. By relating the Jacobian to a monitor function, one is able to directly control the mesh concentration. The geometric conservation law, an identity satisfied by any nonsingular coordinate transformation, is an important tool which has been used for many years in the engineering community to develop cell-volume-preserving finite-volume schemes. It is used here to transform the algebraic expression specifying the Jacobian into an equivalent differential relation which is the key formula for the new mesh movement strategy. It is shown that the resulting method bears a close relation with the Lagrangian method. Advantages of the new approach include the ease of controlling the cell volumes (and therefore mesh adaption) and a theoretical guarantee for existence and nonsingularity of the coordinate transformation. It is shown that the method may suffer from the mesh skewness, a consequence resulting from its close relation with the Lagrangian method. Numerical results are presented to demonstrate various features of the new method

    Rhodopsin‐based light‐harvesting system for sustainable synthetic biology

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    Rhodopsins, a diverse class of light‐sensitive proteins found in various life domains, have attracted considerable interest for their potential applications in sustainable synthetic biology. These proteins exhibit remarkable photochemical properties, undergoing conformational changes upon light absorption that drive a variety of biological processes. Exploiting rhodopsin's natural properties could pave the way for creating sustainable and energy‐efficient technologies. Rhodopsin‐based light‐harvesting systems offer innovative solutions to a few key challenges in sustainable engineering, from bioproduction to renewable energy conversion. In this opinion article, we explore the recent advancements and future possibilities of employing rhodopsins for sustainable engineering, underscoring the transformative potential of these biomolecules

    SwG-former: Sliding-window Graph Convolutional Network Integrated with Conformer for Sound Event Localization and Detection

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    Sound event localization and detection (SELD) is a joint task of sound event detection (SED) and direction of arrival (DoA) estimation. SED mainly relies on temporal dependencies to distinguish different sound classes, while DoA estimation depends on spatial correlations to estimate source directions. To jointly optimize two subtasks, the SELD system should extract spatial correlations and model temporal dependencies simultaneously. However, numerous models mainly extract spatial correlations and model temporal dependencies separately. In this paper, the interdependence of spatial-temporal information in audio signals is exploited for simultaneous extraction to enhance the model performance. In response, a novel graph representation leveraging graph convolutional network (GCN) in non-Euclidean space is developed to extract spatial-temporal information concurrently. A sliding-window graph (SwG) module is designed based on the graph representation. It exploits sliding-windows with different sizes to learn temporal context information and dynamically constructs graph vertices in the frequency-channel (F-C) domain to capture spatial correlations. Furthermore, as the cornerstone of message passing, a robust Conv2dAgg function is proposed and embedded into the SwG module to aggregate the features of neighbor vertices. To improve the performance of SELD in a natural spatial acoustic environment, a general and efficient SwG-former model is proposed by integrating the SwG module with the Conformer. It exhibits superior performance in comparison to recent advanced SELD models. To further validate the generality and efficiency of the SwG-former, it is seamlessly integrated into the event-independent network version 2 (EINV2) called SwG-EINV2. The SwG-EINV2 surpasses the state-of-the-art (SOTA) methods under the same acoustic environment

    Variational Mesh Adaptation Methods for Axisymmetrical Problems

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    This is the published version, also available here: http://dx.doi.org/10.1137/S0036142902401591.We study variational mesh adaptation for axially symmetric solutions to two-dimensional problems. The study is focused on the relationship between the mesh density distribution and the monitor function and is carried out for a traditional functional that includes several widely used variational methods as special cases and a recently proposed functional that allows for a weighting between mesh isotropy (or regularity) and global equidistribution of the monitor function. The main results are stated in Theorems \ref{thm4.1} and \ref{thm4.2}. For axially symmetric problems, it is natural to choose axially symmetric mesh adaptation. To this end, it is reasonable to use the monitor function in the form G = \lambda_1(r) {\mbox{\boldmath {e}}}_r {\mbox{\boldmath {e}}}_r^T + \lambda_2(r) {\mbox{\boldmath {e}}} _\theta {\mbox{\boldmath {e}}}_\theta^T , where {\mbox{\boldmath {e}}}_r and {\mbox{\boldmath {e}}}_\theta are the radial and angular unit vectors. It is shown that when higher mesh concentration at the origin is desired, a choice of λ1\lambda_1 and λ2\lambda_2 satisfying λ1(0)0\lambda_1(0) 0 by choosing λ1\lambda_1 and λ2\lambda_2. In contrast, numerical results show that the new functional provides better control of the mesh concentration through the monitor function. Two-dimensional numerical results are presented to support the analysis
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