28013231
Global stabilization of a class of time-delay nonlinear systems
This paper is concerned with the problem of global stabilization by state feedback and output feedback for a class of time-delay nonlinear systems that are dominated by a triangular system satisfying linear growth conditions. By solving the Lyapunov equation and constructing the appropriate Lyapunov-Krasovskii functionals (LKF), the linear and memoryless state feedback controller and output feedback controller making the closed-loop system globally asymptotically stable (GAS) are explicitly constructed respectively. Comparing our design scheme with the backstepping method which has been widely used to deal with strictly feedback nonlinear systems, our design scheme is much simpler and more efficient. An example is given to show that the proposed design procedures are very simple and efficient.
129266425
Scaling of impervious surface area and vegetation as indicators to urban land surface temperature using satellite data
Vegetation and impervious surface as indicators of urban land surface temperature (LST) across a spatial resolution from 30 to 960 m were investigated in this study. Enhanced thematic mapper plus (ETM+) data were used to retrieve LST in Nanjing, China. A land cover map was generated using a decision tree method from IKONOS imagery. Taking the normalized difference vegetation index (NDVI) and percent vegetation area (V) to present vegetated cover, and the normalized difference building index (NDBI) and percent impervious surface area (I) to present impervious surface, the correlation coefficients and linear regression models between the LST and the indicators were simulated. Comparison results indicated that vegetation had stronger correlation with the LST than the impervious surface at 30 and 60 m, a similar magnitude of correlation at 120 and 240 m, and a much lower correlation at 480 and 960 m. In total, the impervious surface area was a slightly better indicator to the LST than the vegetation because all of the correlation coefficients were relatively high (>0.5000) across the spatial resolution from 30 to 960 m. The indicators of LST, V and I are slightly better than the NDVI and NDBI, respectively, based on the correlation coefficients between the LST and the four indices. The strongest correlation of the LST and vegetation at the resolution of 120 m, and the strongest correlation between the LST and impervious surface at 120, 480 and 960 m, denoted the operational scales of LST variations.
15371796
ACTIVE: agile coordinator testbed integrated virtual environment
This paper describes the specification, design and development of ACTIVE, a testbed for the testing and simulation of large-scale agent-based systems. ACTIVE is being developed as part of DARPA's Coordinators program. The goal of the ACTIVE testbed is to support the simulation of large collections of distributed cooperating agents in solving constrained scheduling problems.
17523247
Artificial Innate Immune System: An Instant Defence Layer of Embryonics
Will mankind ever be able to construct the elusive ‘perpetuum mobile’? We are still far from being able to design systems with a guaranteed finite lifetime, let alone those that we can confidently expect to function unaided in the presence of faults. For example, the Beagle II Mars mission just failed due to malfunction and, worse, the Columbia Space Shuttle suffered the same fate with the loss of many lives. In this context, it is unsurprising that fault tolerance is an increasing emphasis of research into reliable systems. Perhaps if we learn from nature we could design systems, which are tolerant against faults and are able to function properly. Through millions of years of evolution, living things have developed such characteristics. They are cell-based systems that possess an immune system providing an unparalleled defence against faults caused by foreign invaders. It therefore seems intuitive that a generic fault-tolerant hardware system that is inspired by biology should therefore be cell-based and possess some of the immune defence characteristics found in nature. This paper extends the current work on Embryonics (embryological electronics) at the University of the West of England. It combines internal self-healing characteristics of embryonic cellular array based systems with an instant defence layer, inspired by nature’s innate immune system.
16742949
Evaluation of the matrix exponential function using finite elements in time
The evaluation of a matrix exponential function is a classic problem of computational linear algebra. Many different methods have been employed for its numerical evaluation (Moler C and van Loan C 1978 SIAM Review 20 4), none of which produce a definitive algorithm which is broadly applicable and sufficiently accurate, as well as being reasonably fast. Herein, we employ a method which evaulates a matrix exponential as the solution to a first-order initial value problem in a fictitious time variable. The new aspect of the present implementation of this method is to use finite elements in the fictitious time variable. (Weatherford C A, Red E, and Wynn A 2002 Journal of Molecular Structure 592 47) Then using an expansion in a properly chosen time basis, we are able to make accurate calculations of the exponential of any given matrix as the solution to a set of simultaneous equations.
34379910
Global asymptotic stabilization of feedforward nonlinear systems with a delay in the input
In this paper, by constructing appropriate Lyapunov–Krasovskii functionals (LKF) and applying the model transformation of time-delay systems, a design scheme of state feedback controller for a class of feedforward nonlinear systems with a delay in the input is proposed. The designed controllers have a very simple structure and do not involve any saturation or recursive computation, which is widely applied in designing a controller of feedforward nonlinear systems. Using the transformation of coordinates and the property of Hurwitz polynomial, the problem of designing controller can be converted into the problem of finding a parameter, which can be solved by solving the optimization problem with linear matrix inequalities (LMIs) constraints. A simulation example is given to show the effectiveness of the proposed design procedure.
11105544
Solving Computational Fluid Dynamics Problems on Unstructured Grids with Distributed Parallel Processing
This paper describes a distributed parallel implementation of a finite element method for simulating incompressible viscous flows. When applied to unstructured finite element meshes, a conventional implementation of this algorithm becomes particularly space demanding for the storage of system matrices. This parallel implementation not only results in a faster computation but is also potentially capable of solving much larger problems as data and system matrix blocks are distributed. Experimental results demonstrating these key features are presented.