Based on the concept of an access control matrix, a new dynamic access control scheme for frequently inserted or deleted users and files is proposed. The main idea of this paper is inspired by the mechanism of key-loc...
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In this paper, the parallel implementations of two well-known linear state-space filtering algorithms, namely the Kalman and the Lainiotis filters, in MIMD machines are studied from a computational standpoint. The ana...
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In this paper, the parallel implementations of two well-known linear state-space filtering algorithms, namely the Kalman and the Lainiotis filters, in MIMD machines are studied from a computational standpoint. The analysis assumes both time invariant and time varying system models and uses precedence graphs and critical paths. The parallelism efficiency of the implementations is also defined and studied. Results indicate that these algorithms can be implemented in parallel using a comparatively small number of processors. Furthermore, the efficiency of the parallel implementations can be very high or very low, depending on the state and measurement vector dimensions.
QFT is an engineering design theory devoted to the practical design of feedback control systems. The foundation of QFT is that feedback is needed in control only when plant (P), parameter and/or disturbance (D) uncert...
QFT is an engineering design theory devoted to the practical design of feedback control systems. The foundation of QFT is that feedback is needed in control only when plant (P), parameter and/or disturbance (D) uncertainties (sets P; = {P}, D = {D}) exceed the acceptable (A) system performance uncertainty (set A ={A}). The principal properties of QFT are as follows. (1) The amount of feedback needed is tuned to the (P,D,A); sets. If A/ 'exceeds’ (P,D)feedback is not needed at all. (2) The simplest modelling is used: (a) command, disturbance and sensor noise inputs, and (b) the available sensing points and the defined outputs. No special controllability test is needed in either linear or non-linear plants. It is inherent in the design procedure. There is no observability problem because uncertainty is included. The number of independent sensors determines the number of independent loop transmissions (Li,,), the functions which provide the benefits of feedback. (3) The simplest mathematical tools have been found most useful—primarily frequency response. The uncertainties are expressed as sets in the complex plane. The need for the larger P,D sets to be squeezed into the smaller A set results in bounds on the Li(jω)in the complex plane. In the more complex systems a key problem is the division of the 'feedback burden’ among the available L^jco). Point-by-point frequency synthesis tremendously simplifies this problem. This is also true for highly uncertain non-linear and time-varying plants which are converted into rigorously equivalent linear time invariant plant sets and A or disturbance sets with respect to the acceptable output set si. Fixed points theory justifies the equivalence. (4) Design trade-offs are highly transparent in the frequency domain, between design complexity and cost of feedback (primarily bandwidth), sensor noise levels, plant saturation levels, number of sensors needed, relative sizes of P,A and cost of feedback. The de
This work concerns the problem of broadcasting a large message efficiently when each processor has partial prior knowledge about the contents of the broadcast message. The partial information held by the processors mi...
Scheduling packets to be forwarded over a link is an important subtask of the routing process both in parallel computing and in communication networks. This paper investigates the simple class of greedy scheduling alg...
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Finding a shortest network interconnecting a given set of points in the Euclidean plane (a Steiner minimum tree) is known to be NP-hard. It is shown that there exists a polynomial-time heuristic with a performance rat...
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Finding a shortest network interconnecting a given set of points in the Euclidean plane (a Steiner minimum tree) is known to be NP-hard. It is shown that there exists a polynomial-time heuristic with a performance ratio bigger than square root 3/2.< >
This article is concerned with the structure and stability properties of a combustion front that propagates in the axial direction along the surface of a cylindrical solid fuel element. The fuel consists of a mixture ...
Positive systems are a class of discrete-time systems that provide effective mathematical models in many fields of applications and for which the theory of non-negative matrices plays a key role in investigating model...
The Command Support At-Sea Experiment (CS@SE) provides experimental advanced graphics display systems consisting of large screen color displays and operator console color displays in the combat information center (CIC...
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The Command Support At-Sea Experiment (CS@SE) provides experimental advanced graphics display systems consisting of large screen color displays and operator console color displays in the combat information center (CIC) of an Aegis cruiser and in the tactical flag command center (TFCC) of an aircraft carrier. CS@SE systems are designed to prototype potential command support capabilities in an at-sea environment to validate and refine requirements for planned production system upgrades. These systems use sophisticated color graphics techniques to provide real-time tactical displays that improve the availability of information to an operator by reducing clutter through the use of color, area fill, transparen overlays and intensity coding of track symbols. Interfaces wen developed with the Aegis Display System (ADS), Shipboarc Gridlock System with Auto-correlation (SGS/AC), Flag Dats Display System (FDDS) and Tomahawk Engagement Planning and Exercise Evaluation System (TEPEE) that provided the data for the presentation of a tactical display. Display elements included both real-time and over-the-horizon (OTH) surface track data, velocity leaders, tags, uncertainty ellipses, and history trails. The display also included filled land masses, country boundaries, commercial airways, cities, graphics overlays (i.e., operational areas), weapon system missile performance contours, and engagement plans. This paper describes the experiment, its installation and integration into the shipboard environments of an Aegis cruiser (USS Leyte Gulf ) and an aircraft carrier (USS America , its usage by the ships companies and embarked staffs, and the experiment result! and findings. Key conclusions of the experiment are: 1 Advanced graphics color displays can significantly enhance the ability of the warfighter to assimilate a complex tactical display. 2 Both ships reported a requirement for a correlated OTH and real-time track display with the ability to clearly differentiate the two types
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