10218510
Neural Network Based Feedback Scheduler for Networked Control System with Flexible Workload
Most control applications closed over a shared network are suffering from the time-varying characteristics of flexible network workload. This gives rise to non-deterministic availability of communication resources and may significantly impact the control performance. In the context of integrating control and scheduling, a novel feedback scheduler based on neural networks is suggested. With a modular architecture, the proposed feedback scheduler mainly consists of a monitor, a predictor, a regulator and an actuator. An online learning Elman neural network is employed to predict the network conditions, and then the control period is dynamically adjusted in response to estimated available network utilization. A fast algorithm for period regulation is employed. Preliminary simulation results show that the proposed feedback scheduler is effective in managing workload variations and can provide runtime flexibility to networked control applications.
20338082
Guaranteed Cost Control of Networked Control Systems: An LMI Approach
In this paper, networked control systems (NCS) is modeled as a discrete-time linear state-delayed system with norm-bounded uncertainty. Inspired by the so-called descriptor model transformation, a delay-dependent sufficient condition for the existence of a guaranteed cost controller for NCS is presented by a set of linear matrix inequalities (LMIs). The resulting controller can not only asymptotically stabilize the system but also guarantee an adequate level of performance. Theoretical analysis and illustrative results show that the control strategy presented in this paper is effective and feasible.
15649278
Robust Fault Isolation Filter Design for Networked Control Systems
In this paper, the effect of network-induced delay introduced into the control loop is modelled as time-varying disturbance. Based on this model, a fault isolation filter (FIF) for fault detection of networked control systems (NCSs) with multiple faults is then parameterized. Directional residual generations decoupling from the disturbance ensure the treatment of multiple faults appearing simultaneously or sequentially. The remaining degrees of freedom in the design of the filter's gain are used to satisfy an Hinfin disturbance attenuation and poles assignment constraints in the frame of Markov jump linear systems (MJLS). The sufficient existence conditions of the free parameters are formulated as a convex optimization problem over a couple of linear matrix inequalities (LMIs). An illustrative example is given to show the efficiency of the proposed method for NCS
2426410
Network information flow
We introduce a new class of problems called network information flow which is inspired by computer network applications. Consider a point-to-point communication network on which a number of information sources are to be multicast to certain sets of destinations. We assume that the information sources are mutually independent. The problem is to characterize the admissible coding rate region. This model subsumes all previously studied models along the same line. We study the problem with one information source, and we have obtained a simple characterization of the admissible coding rate region. Our result can be regarded as the max-flow min-cut theorem for network information flow. Contrary to one's intuition, our work reveals that it is in general not optimal to regard the information to be multicast as a "fluid" which can simply be routed or replicated. Rather, by employing coding at the nodes, which we refer to as network coding, bandwidth can in general be saved. This finding may have significant impact on future design of switching systems.
18473631
Cryptanalysis of a Chaotic Neural Network Based Multimedia Encryption Scheme
Recently, Yen and Guo proposed a chaotic neural network (CNN) for signal encryption, which was suggested as a solution for protection of digital images and videos. The present paper evaluates the security of this CNN-based encryption scheme, and points out that it is not secure from the cryptographical point of view: 1) it can be easily broken by known/chosen-plaintext attacks; 2) its security against the brute-force attack was much over-estimated. Some experiments are shown to support the results given in this paper. It is also discussed how to improve the encryption scheme.
46006955
Improved algorithm for finding next-to-shortest paths
We study the problem of finding the next-to-shortest paths in a weighted undirected graph. A next-to-shortest (u, v)-path is a shortest (u, v)-path amongst (u, v)-paths with length strictly greater than the length of the shortest (u, v)-path. The first polynomial algorithm for this problem was presented in [I. Krasikov, S.D. Noble, Finding next-to-shortest paths in a graph, Inform. Process. Lett. 92 (2004) 117-119]. We improve the upper bound from O(n3m) to O(n3).
218270
Cryptanalysis of a multistage encryption system
This paper analyzes the security of a new multistage encryption system (MES) recently proposed in ISCAS'2004. It is found that MES is insecure against a differential chosen-plaintext/ciphertext attack. Experiments are given to support the proposed attack. It is also pointed out that the security of MES against brute-force attacks is not sufficiently high.
18279993
Mixed Preservation of Conditionally Nonblocking Switches under 2-stage Interconnection
The 2-stage interconnection network is conceivably the most compact design for interconnecting small switches into a large switch. When a certain class of switches is preserved under 2-stage interconnection, recursive application of 2-stage interconnection then builds indefinitely large switches in this class from atomic ones. The present paper studies switches that are not preserved under 2-stage interconnection but are yet constructive from atomic elements through recursive 2-stage interconnection. The principle is "mixed preservation" based on the following two properties: first, the 2-stage interconnection network constructs a class-A switch when switches at nodes on one stage belong to class A and switches at nodes on the other stage belong to class B; second, class-B switches are preserved under 2-stage interconnection. A class of conditionally nonblocking switches for such mixed preservation are identified, which are useful in the recursive construction of distribution networks