Papers by Chaouki Abdallah
Lecture Notes in Control and Information Sciences, 2004
In large-scale distributed-computing environments, there are a number of inherent time-delay fact... more In large-scale distributed-computing environments, there are a number of inherent time-delay factors that can seriously alter the expected performance of load-balancing (or scheduling) policies that do not account for such delays. This situation arises, for example, in systems for which each computational element (CE) is connected by means of a shared broadband communication medium. The delays, in addition to being large, fluctuate randomly as a result of uncertainties in the network condition and uncertainty in the size of the loads to be transferred between the CEs. The performance of such distributed systems under any load-balancing policy is therefore stochastic in nature and must be assessed in a probabilistic sense. Moreover, the design of load-balancing policies that best suit such delay-infested environments must also be carried out in a statistical framework. Indeed, it has been observed in recent simulation-based and experimental studies that the delay, especially that corresponding to transferring large loads between CEs, can cause the system to fall into a mode whereby CEs unnecessarily exchange loads back and forth. This results in an undesirable situation where loads continue to be in transit. It has been observed that the notion of limiting the number of balancing instants in scheduling algorithms can be used to customize certain load-balancing policies to random-delay environments. But the effectiveness of this strategy depends on the decision as to when and how often such load-balancing cycles are to be executed. If a system starts from a certain unbalanced state, we would expect that there would be an optimal time at which balancing must be executed so as to minimize the overall completion time of a workload. In particular, the load-balancing instant should be large enough to ensure that all CEs have updated knowledge of the state of the system. Yet, the balancing instant should be soon enough so that the system does not remain in an unbalanced state for an excessively prolonged time whereby allowing some of the CEs to be idle. It has also been noticed that an additional strategy for mitigating the effects of delay in load balancing is to reduce the gain, or strength, of the load-balancing policy. That is, for each overloaded CE, only a fraction of the load to be transferred is actually transferred to other CEs. Thus, in view of these unique phenomena that occur in load balancing in delay-infested networks, optimizing the performance over the inter-balancing times and the load-Authors Suppressed Due to Excessive Length balancing gains becomes an important problem. In this Chapter, the performance of a single-instant load-balancing strategy on a distributed physical system is studied both theoretically and experimentally. The experiments are performed on an inhouse wireless distributed testbed as well as a Monte-Carlo simulation tool. The theoretical analysis is carried out based on the concept of regeneration in stochastic processes. In particular, a probabilistic analysis of the queuing system which models the distributed system is developed and studied.
Lecture Notes in Control and Information Sciences, 2004
Congestion control in the Available Bit Rate (ABR) class of Asynchronous Transfer Mode (ATM) netw... more Congestion control in the Available Bit Rate (ABR) class of Asynchronous Transfer Mode (ATM) networks poses interesting challenges due to the presence of delays, magnitude and rate constraints on the inputs and additive disturbances. In this paper, we consider a discrete-time fixed-structure controller for an ATM/ABR switch, also modeled in discrete-time, and solve a robust tracking control problem in which the target is a threshold on the queue level.
Quantifier elimination approach to frequency domain design
Lecture Notes in Control and Information Sciences, 2000
Preface: Special Issue on New Advances in Nonlinear and Optimal Controls of Robotic and Autonomous Systems
International Journal of Robotics and Automation, 2011
Eprint Arxiv Cs 0610087, Oct 13, 2006
We introduce an application of a mobile transient network architecture on top of the current Inte... more We introduce an application of a mobile transient network architecture on top of the current Internet. This paper is an application extension to a conceptual mobile network architecture. It attempts to specifically reinforce some of the powerful notions exposed by the architecture from an application perspective. Of these notions, we explore the network expansion layer, an overlay of components and services, that enables a persistent identification network and other required services. The overlay abstraction introduces several benefits of which mobility and communication across heterogenous network structures are of interest to this paper. We present implementations of several components and protocols including gateways, Agents and the Open Device Access Protocol. Our present identification network implementation exploits the current implementation of the Handle System through the use of distributed, global and persistent identifiers called handles. Handles are used to identify and locate devices and services abstracting any physical location or network association from the communicating ends. A communication framework is finally demonstrated that would allow for mobile devices on the public Internet to have persistent identifiers and thus be persistently accessible either directly or indirectly. This application expands IP inter-operability beyond its current boundaries.
WEB-based education tools that incorporate static content, video-on-demand, live synchronized v... more WEB-based education tools that incorporate static content, video-on-demand, live synchronized video, as well as collaboration research spaces, often present information as isolated and diffuse topics compromising the integral learning and research experience. The Ibero-American Science & Technology Consortium (ISTEC) "ChipsnSalsa" WEB project addresses this problem by integrating content into structured but flexible information maps and contextual databases. It enables students to take advantage of the content, and turns the WEB portal/gateway into a diligent information provider that orders the information optimally for their particular needs. Similarly, it enables researchers to have specific and accurate access to the most relevant information in their research, while establishing knowledge bases, real-time peer review, and repositories for future work and long haul ongoing projects. It also provides them with virtual labs and real-time online publishing. Double indexing with full text index and metadata information, and relating the content in a common structured metadata organization.
Control of Robot Manipulators
382 Appendix A / Review of Robot Kinematics and Jacobians (d) FIGURE A.1-1 (Cont.) (à) cylindrica... more 382 Appendix A / Review of Robot Kinematics and Jacobians (d) FIGURE A.1-1 (Cont.) (à) cylindrical coordinates (RPP); (e) Cartesian arm, rectangular coordinates (PPP). compliant articulated robot for assembly) arm. It has quite a different struc-ture than the RRP spherical arm shown in ...
In this article, we introduce a robust non-fragile state feedback controller which is also optima... more In this article, we introduce a robust non-fragile state feedback controller which is also optimal with respect to a performance measure, using Linear Matrix Inequalities (LMIs). The uncertainties are assumed to be polytopic, both in the controller gains and the system dynamics. A numerical example is presented to demonstrate the e ciency of this method, and the controller turns out to be robust with respect to the uncertainties in the plant and the controller.
Robust Control of Particle Accelerators
1990 American Control Conference, 1990
We consider a game-theoretic power control algorithm for wireless data realistic channels. We stu... more We consider a game-theoretic power control algorithm for wireless data realistic channels. We study the performance of the algorithm for wireless data in the fast, flat-fading channel mobile users encounter in accessing the cellular system. The game-theoretic power control algorithm depends on an average utility function that assigns a numerical value to the quality of service (QoS) of users. The fading coefficients under this channel model are studied for two appropriate channel models that are used in CDMA cellular systems: Rayleigh fast flat fading channel and Rician fast flat fading channel.
We have observed that many neural network models can be written as a bilinear system with a speci... more We have observed that many neural network models can be written as a bilinear system with a speci c form of nonlinear state-to-input feedback. This framework includes the ART architecture among others. There are two signi cant results which follow from this observation. First, the parameters of the model determine the controllability of the system. A system is controllable if there exists some input which transfers any initial state to any desired nal state in a nite time. If for a given set of these parameters the system is not controllable, then there are regions of the state space which the system can never enter in a nite time for any input. Because of this restriction the learning ability of the system may be severely limited. Second, the multiplicative equation is linear in all of the parameters, and all of the adjustable weights. This means that a provably convergent learning algorithm can be devised for all of these quantities. This does not however circumvent the learning limitation since the learning algorithm is not guaranteed to converge in a nite time. In the paper, we will study these issues as they apply to the ART architecture.
Experimental Investigation of Active Feedback Control of Turbulent Transport in a Magnetized Laboratory Plasma
Attempts to date at controlling turbulent transport in magnetic confinement devices have largely ... more Attempts to date at controlling turbulent transport in magnetic confinement devices have largely focused on physically minimizing the transport. However, in a fusion device, minimal particle transport is not necessarily desirable, since it can lead to core impurity accumulation, or alpha particle buildup. Ideally, active control over the transport, rather than simple minimization, could be obtained. To this effect, research is now underway at the UNM to actively control particle transport. Turbulence and transport dynamics are, of course, strongly nonlinear, and apparently not deterministic. However, modern nonlinear control methods now exist, such as chaotic control and fuzzy control, which do not rely on a model of the system dynamics to be able to affect stable control. Experiments will take place in a 1 m long hot cathode linear plasma device that has recently begun operation. This device will be upgraded to 3 m, with axial field up to 0.2 Tesla in the next 18 months. Sheared flows, generated via biased concentric rings, will be utilized to modify the transport. Fluctuations and flux will be monitored with probe arrays. Research will focus on exploring possible methods for the nonlinear control of transport.
A generalization of Benford's law and its application to images
2007 European Control Conference, Jul 1, 2007
... [14] Ch. Schaefer, JP Schrapler, JP Muller, and GG Wag-ner, Automatic identification of fake... more ... [14] Ch. Schaefer, JP Schrapler, JP Muller, and GG Wag-ner, Automatic identification of faked and fraudulent interviews in the german SOEP, Journal of Applied Social Science Studies, vol. 125, pp. ... [16] JR Hernández, M. Amado, and F. Pérez-González, DCT-domain ...
Employing Markov Networks on Curriculum Graphs to Predict Student Performance
2014 13th International Conference on Machine Learning and Applications, Dec 1, 2014
Robust control of accelerators
A Synthesis of Gradient and Hamiltonian Dynamics Applied to Learning in Neural Networks
Online Student Support Services for STEM Courses in New Mexico: A Cross-Institutional Approach
Multidimension Syst Sign Proc, 1994
In this paper, we find necessary and sufficient conditions for the stability of a family of annul... more In this paper, we find necessary and sufficient conditions for the stability of a family of annular, complex polynomials with the possibility of including a center polynomial. The proposed results can be modified to solve the disk problem by simply equating the inner radius of the annuli to zero. These results have applications in the communications arena and some signal processing problems.
Statistical Learning Applied to the Energy Management in a Fuel Cell Electric Vehicle
... M. Cavalletti ∗ J. Piovesan ∗∗ CT Abdallah ∗∗ S. Longhi ∗ P. Dorato ∗∗ G. Ippoliti ∗ ... cont... more ... M. Cavalletti ∗ J. Piovesan ∗∗ CT Abdallah ∗∗ S. Longhi ∗ P. Dorato ∗∗ G. Ippoliti ∗ ... controllers, based on Boolean of fuzzy logic rules, are used to minimize the fuel consumption using different vehicular variables such as torque demand or car speed (N. Jalil and Salman ...
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Papers by Chaouki Abdallah