This paper presents the cooperative preview control method for continuous-time multi-agent systems with a time-invariant directed communication topology. First, the cooperative tracking preview control problem is transformed into the optimal regulation problem of an augmented system. Next, by applying the results of the standard optimal preview control of continuous-time linear systems, a controller of the augmented system is obtained. Furthermore, the stabilisability and detectability of the augmented system are studied under the fixed digraph and the prescribed leader. Then, we derive the controller of multi-agent systems with error integral and preview action that can guarantee the achievement of cooperative optimal preview tracking. Finally, the effectiveness of the controller is shown by numerical simulations. 相似文献
In this study, an arid grassland was selected, and the chlorophyll content of the leaf and canopy level was estimated based on Landsat-8 Operational Land Imager (OLI) data using the PROSAIL radiative transfer (RT) model. Two vegetation indices (green chlorophyll index, CIgreen, and greenness index, G) were selected to estimate the leaf and canopy chlorophyll content (LCC and CCC). By analysing the effect of soil background on the two indices, the LCC was divided into low and moderate-to-high levels. A different combination of the two indices was adopted at each level to improve the chlorophyll content estimation accuracy. The results suggested that the chlorophyll content estimated using the proposed method yielded a higher accuracy with coefficient of determination, R2 = 0.84, root-mean-square error, RMSE = 9.67 μg cm?2 for LCC and R2 = 0.85, RMSE = 0.43 g m?2 for CCC than that using CIgreen alone with R2 = 0.62, RMSE = 20.04 μg cm?2 for LCC and R2 = 0.85, RMSE = 0.71 g m?2 for CCC. The results also confirmed the validity of this approach to estimate the chlorophyll content in arid areas. 相似文献
Feature extraction from images, which are typical of high dimensionality, is crucial to the recognition performance. To explore the discriminative information while depressing the intra-class variations due to variable illumination and view conditions, we propose a factor analysis framework for separate “content” from “style,” identifying a familiar face seen under unfamiliar viewing conditions, classifying familiar poses presented in an unfamiliar face, estimating age across unfamiliar faces. The framework applies efficient algorithms derived from objective factor separating functions and space mapping functions, which can produce sufficiently expressive representations of feature extraction and dimensionality reduction. We report promising results on three different tasks in the high-dimensional image perceptual domains: face identification with two benchmark face databases, facial pose classification with a benchmark facial pose database, extrapolation of age to unseen facial image. Experimental results show that our approach produced higher classification performance when compared to classical LDA, WLDA, LPP, MFA, and DLA algorithms. 相似文献
Cardiovascular diseases are currently the major causes of mortality in the world, especially in developed nations. As a predominant one, thrombosis is the platelet aggregation induced by a high shear rate. Platelet aggregation assay can clarify the occurrence mechanism of thrombosis, as well as be used as an important tool in the clinical diagnosis, personalized treatment, and screening of anticoagulants. Thus, relevant studies attracted considerable attention. As an important step in platelet aggregation, platelet adhesion and its detection also attract intensive concern. Thus, some analytical methods have been developed for platelet adhesion assay, and the impact of shear rate is one of the focuses. Compared with other devices, biosensors can give a more accurate result within a shorter time. Furthermore, some biosensors can achieve real-time analysis. However, only one or several shear rates can be tested at the same time, which may decrease the analytical efficiency. Meanwhile, in most cases, only the average platelet adhesion effect within a reactor is detected, and the impact of the distribution of shear rates is improperly neglected. In this study, a microfluidic device with a single channel is designed and fabricated for platelet adhesion assay. When the platelet-rich plasma flows through the collagen-modified sensing surface of the channel bottom, the interaction between platelets and collagen molecules on the entire surface can be simultaneously monitored by using a surface plasmon resonance imaging (SPRi) system. A gradient of the shear rate (0–546 s-1) could be formed within the channel by choosing a suitable depth-to-width ratio (1:5), so platelet adhesion at multiple shear rates could be monitored simultaneously. This method enables the measurement of the adhesion process of unlabeled platelets on the entire sensing surface, in vitro, at multiple shear rates. Such a system can obtain more accurate platelet adhesion result at a given shear rate than traditional methods. Furthermore, in an individual operation, platelet adhesion can be repeatedly tested at multiple points with an equal shear rate, so a much higher analytical efficiency can also be achieved. 相似文献
This study provides evidence supporting the use of the update strategies for the support vector regression (SVR) model. Firstly, the fitting and interpolation method (FIM) is presented to select SVR parameters, and three infill strategies are adopted to search for update points. Secondly, the infill strategy and parameter selection method are illustrated by test functions that illustrate their dependability. The distribution of update points, the sample density and the proportion of update points are discussed. Finally, the adaptive SVR surrogate model is applied to optimize the protective effect of railway wind barriers. The result shows that the parameter selection method has high stability. On the whole, the accuracy of the adaptive SVR model using a suitable infill strategy will be improved with an increasing proportion of update points if the final number of training points is identical. The optimization result shows an optimal porosity of 0.117 when the height of the railway wind barrier is 2.05 m (full scale).
Hexahedral mesh has obvious mechanical advantages over tetrahedral mesh, but it is no trivial task to generate hexahedral mesh for complex object shapes such as individual faces. This paper presents a novel method to generate patient-specific hexahedral meshes of facial soft tissue models, based on a volumetric cross-parameterization mapping from a standard hexahedral mesh to the individual model. The volumetric parameterization is constructed based on triple of the volumetric harmonic fields, which are adapted to be as close to mutually orthogonal as possible, to achieve some quasi-conformal effect. In addition, some piecewise constraints on the harmonic fields are added to ensure anatomical feature correspondence. Experimental results show that our approach works efficiently for facial soft tissue modeling, avoids element flipping and preserves mesh element angles to a significant extent. 相似文献
This paper presents an intuitive nose surgery planning and simulation system, using 3D laser scan image and lateral X-ray image, to provide high quality prediction of the postoperative appearance, and design the patient specific prosthesis model automatically. After initial registration, the internal surface of soft tissue at the nose region was generated by the statistical data for soft tissue thickness adapted by the individual thickness information from the X-ray image. Then, the sketch contour of the 3D scan data on the lateral X-ray image was modified manually or adjusted automatically according to some aesthetic statistical data, to drive the simulation in real time by the state-of-the-art Laplacian surface deformation method. When satisfied with the 3D postoperative appearance, the deformation was mapped to the internal surface of soft tissue, and the change before and after simulation was utilized to generate the patient specific prosthesis model automatically. The surgeons who used the system confirmed that this planning system is attractive and has potential for daily clinical practice. 相似文献