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System Theory, 2004. Proceedings of the Thirty-Sixth Southeastern Symposium on

Date 2004

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Displaying Results 1 - 25 of 128
  • Robustness of a class of controlled Petri nets

    Publication Year: 2004 , Page(s): 92 - 96
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1621 KB) |  | HTML iconHTML  

    In our previous works, we have unveiled the fault tolerant properties of several subclasses of controlled Petri nets, including CPPN, MG-refined nets and CAPN. In this paper, we extend the results to a class of controlled Petri net with uncertainties and flexible routes (CPNU-FR). By exploiting the routing flexibility of a CPNU-FR, we characterize a feasible condition to maintain production for a certain type of products by keeping the liveness of a cyclic production route. Based on this condition, we propose a structural decomposition method to test the feasibility of production routes. Based on the liveness condition for the nominal CPN, we characterize a condition to test whether a certain type of resource failures is tolerable. View full abstract»

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  • Neural network-based modeling and design of on-chip spiral inductors

    Publication Year: 2004 , Page(s): 561 - 564
    Cited by:  Papers (1)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1556 KB) |  | HTML iconHTML  

    A neural network approach is presented for the modeling and re-design of high-Q on-chip spiral inductors. The approach involves the creation of neural network models to map 3D multi-level spiral inductor geometric and material characteristics to SPICE equivalent circuit parameters. The neural network replaces computationally expensive FEM-based extraction and field solution. The approach is especially attractive because it is capable of accurately and efficiently predicting important inductor characteristics such as self-inductance, Q-factor, self-resonant frequency and parasitic resistance and capacitance. It also offers substantial computational savings over field solution-evaluation of neural model required on average 2% of the cpu time required for field solution. The neural approach served not only as a basis for fast spiral inductor circuit extraction but also permits fast spiral layout design refinement from post-optimization inductor circuit-level parameters. View full abstract»

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  • Mobile agents for computer intrusion detection

    Publication Year: 2004 , Page(s): 517 - 521
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1896 KB) |  | HTML iconHTML  

    In the age of the Internet, computer intrusion detections are at best a black art. The science to perceive, track, and understand intrusions is still at its infancy. Many different technologies and topologies are under investigation to see which model provides adequate data for intrusion detection. In this paper, we present a platform independent Java-based mobile agent intrusion detection system (IDS). In our prototype mobile agent IDS, the focus is on port scanning and file integrity checking. The mobile agents are implemented using the Concordia mobile agent development kit. The performance and memory resources required to run these mobile agents are discussed. View full abstract»

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  • Measuring enterprise reuse in large corporate environment

    Publication Year: 2004 , Page(s): 565 - 569
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1605 KB) |  | HTML iconHTML  

    Reuse continues to be an important topic in most IT organizations. In a previous article, the author (2003) identifies the top obstacles in enterprise reuse as: lack of awareness of software available for reuse (repository), level of effort required to design software for reuse (education and lessons learned) and programmer lack of intent to actually reuse other organizational assets (education and executive support). This paper reviews a methodology utilized in a large telecommunications organization to measure reuse at the enterprise level. The paper reviews the different type of assets available for reuse, repository methodology, and specific metrics of reuse. View full abstract»

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  • Blind separation of signals from piece-wise constant gain mixtures using independent component analysis

    Publication Year: 2004 , Page(s): 462 - 466
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1803 KB) |  | HTML iconHTML  

    An algorithm is developed to separate signals mixed with piecewise constant matrices. Independent component analysis technique is employed to separate the signals. Algorithms are presented to identify the lengths of the segments and remove order, scaling and sign ambiguities present in the independent component analysis of consecutive segments. View full abstract»

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  • Fifth-order sigma delta modulator with decimation

    Publication Year: 2004 , Page(s): 522 - 526
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1655 KB) |  | HTML iconHTML  

    This paper describes the use of very high precision noise shaping sigma delta modulation techniques for high fidelity audio applications that require a signal-to-noise ratio (SNR) of at least +80 dB. This paper discusses the implementation of a fifth-order sigma delta modulator with an oversampling frequency of 5.68 MHz. Specifically this paper is a comparative study of Matlab and Pspice implementations of our fifth order sigma delta modulator with a VHDL-based finite impulse response (FIR) filter. View full abstract»

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  • Web proxy analysis in distributed iSCSI RAIDs

    Publication Year: 2004 , Page(s): 225 - 229
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1613 KB) |  | HTML iconHTML  

    With the popularity of Web services and e-commerce, we have a high demand on data storage. Because of the development of the Internet infrastructure and the low cost of deployment, implementing storage over IP has become a trend. While networked storage brings economy, it also raises performance concern. In a typical distributed Web system, I/O requests from clients users may be satisfied by many different parties along the I/O path from front-end clients to back-end storage systems via proxy and Web servers. To improve the performance, we need to identify the I/O distribution pattern along the path. This paper analyzes the I/O distribution along the I/O path of a distributed iSCSI RAID system by using kernel counters and profiles how the I/O requests are satisfied at different levels of the proxy server and storage system, which is useful to identify the performance bottleneck. View full abstract»

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  • Performance analysis of the adjusted step size NLMS algorithm

    Publication Year: 2004 , Page(s): 467 - 471
    Cited by:  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1540 KB) |  | HTML iconHTML  

    An adaptive noise canceller is a well-known method for removing noise from noise-corrupted speech. The problem arises in many situations such as airplane cockpits and automobiles. Tire adjusted step size NLMS (normalized least mean squares) algorithm incorporating a variable step size parameter whose values are based on the ratio of signal-to-noise power has very good convergence speed and low steady-state misadjustment. This paper extends the results of the adjusted step size NLMS algorithm [J. Kim et al., 2003] by investigating the adjusted step size NLMS algorithm approaches when large and abrupt changes of the desired signal as well as the noise signal are present. Simulation results are presented to compare the performance of the adjusted step size NLMS algorithm with the fixed step size LMS algorithm and other commonly used variable step size LMS algorithms. View full abstract»

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  • The solution to the Lyapunov equation in constant gain filtering and some of its applications

    Publication Year: 2004 , Page(s): 21 - 25
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1487 KB) |  | HTML iconHTML  

    Presented in this paper is a solution to the Lyapunov equation in constant gain filtering. A specific method for deriving the noise reduction ratios for the alpha-beta and alpha-beta-gamma filters are explored using the Lyapunov equation. This enables us to simplify the computation drastically. For a 2 × 2 matrix, one has to solve for one unknown instead of two. For a 3 × 3 matrix, one has to solve for three unknowns instead of six and so on. Thus reduction in the number of variables has considerable advantage for higher dimensional filters such as the alpha-beta-gamma filter. View full abstract»

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  • Darboux transformations and linear parabolic partial differential equations

    Publication Year: 2004 , Page(s): 527 - 530
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1447 KB) |  | HTML iconHTML  

    A method is provided to solve boundary value problems to parabolic partial differential equations of the form: ut = uxx + f(x)u, provided f(x) is obtained as twice the second derivative of the logarithm of the wronskian of separable solutions to the heat equation and the boundary conditions result in a regular Sturm Liouville problem upon doing separation of variables. Darboux transformations are used to obtain a complete set of eigenfunctions for the boundary value problem allowing for a solution in terms of an eigenfunction expansion. View full abstract»

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  • Contingency selection and static security enhancement in power systems using heuristics-based genetic algorithms

    Publication Year: 2004 , Page(s): 556 - 560
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1590 KB) |  | HTML iconHTML  

    This paper proposes a technique to identify critical double-line outages and enhance static security by optimal placement of FACTS devices using heuristics-based genetic algorithm (GA). Two indices have been used for contingency screening: double-line contingency index (DCI), based on line overflows, and voltage sensitivity index (VSI), based on bus voltage violations. Contingency screening is treated as the primary optimization problem with an objective of finding all double-line outages with maximal DCI and VSI. Security enhancement is treated as a constrained secondary optimization problem. The objective is to reduce transmission losses through the branches of the system and reduce or remove the overflows and voltage violations present. The voltage magnitude at each bus and the line flow through each branch for all the buses and branches have been considered as inequality and equality constraints. The technique is demonstrated using IEEE 14 bus and IEEE 30 bus systems. View full abstract»

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  • Pattern synthesis and performance of conical arrays

    Publication Year: 2004 , Page(s): 145 - 149
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1728 KB) |  | HTML iconHTML  

    This paper extends a beam pattern synthesis algorithm based on the maximization of directivity subject to constraints on sidelobes, to a conformal array geometry. The expressions required for implementation of the algorithm are derived for an arbitrary set of elements and then evaluated for the specific case of an array of radiating slot elements on the surface of a right circular cone. The cone array geometry, chosen for its similarity to an aircraft or missile nosecone, is considered for several important performance parameters including scan volume, sidelobe control, and cross-polarization. View full abstract»

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  • A generalized acceleration model for Kalman filter trackers

    Publication Year: 2004 , Page(s): 31 - 35
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1567 KB) |  | HTML iconHTML  

    Kalman filter trackers used for radar tracking typically model target accelerations as plant noises that are assumed to last for the entire sample interval. That assumption is so ubiquitous that it is rarely stated explicitly. In this paper we present a generalized model in which accelerations endure less than the sample interval, and derive a new formula for plant noise covariance that is a function of the interval length and the acceleration's endurance and start time. We explore the limiting behavior of this formula as acceleration endurance vanishes, and also show that position and velocity gains can be traded off by simply moving the acceleration earlier or later in the sample interval. View full abstract»

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  • Hybrid active/passive interaction control for robot manipulators

    Publication Year: 2004 , Page(s): 441 - 445
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1702 KB) |  | HTML iconHTML  

    Motion control of robot manipulators is typically accomplished by sensing and regulating the positions of the joint actuators to cause the end-effector to follow a programmed trajectory. Unfortunately, position control schemes usually fail for tasks that require significant physical interaction between the robot and a workpiece. This restriction severely limits the scope of work that robots are able to do. A solution to this problem is to incorporate some form of compliance into the manipulator to compensate for positioning errors. Researchers have been focused on two principal methods of achieving manipulator compliance - passive mechanism synthesis and active force control - both of which have advantages and disadvantages. In this paper, the authors present recent advances in passive mechanism synthesis algorithms, and investigate the utility of combining a simple, passive mechanism with an active force control scheme to obtain a compliant manipulator with desirable characteristics for interaction control. View full abstract»

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  • Dynamic simulation of a linear variable reluctance motor using coupled network models

    Publication Year: 2004 , Page(s): 160 - 164
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1592 KB) |  | HTML iconHTML  

    The objective of this paper is to simulate and study the dynamics of a linear variable reluctance motor using coupled network models. The need for an explicit functional expression to describe flux linkage has been eliminated, since the magnetic subsystem is coupled to, and simultaneously solved with, the dynamics of the electrical and mechanical subsystems. This paper focuses on the development of a coupled network model that incorporates the effects of magnetic saturation and spatial harmonics, and also includes the application of position control software interacting with the physical system. View full abstract»

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  • Performance analysis of UNIX user datagram protocol implementations

    Publication Year: 2004 , Page(s): 230 - 235
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1725 KB) |  | HTML iconHTML  

    As wired and wireless networks grow, underlying protocols need to be evaluated so that heterogeneous networks can be linked in an efficient manner. Among the transport layer protocols, user datagram protocol UDP is the only protocol that offers a fast and efficient mechanism to handle voice and video data traffic because it is a message based, connectionless service operating on the IP layer. In addition to the network conditions, it is observed that the performance also depends upon the implementation of the protocol. UNIX is one of the most widely used operating system in the networking world and different UNIX flavors have different UDP stack implementation. In this research work the performance of different UDP implementations were compared under different network conditions. It is observed that no UDP implementation dominates in all the tested network conditions. It is also observed that the selection of an appropriate datagram size had large impact on the overall performance. View full abstract»

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  • An optimal measure for camera focus and exposure

    Publication Year: 2004 , Page(s): 472 - 475
    Cited by:  Papers (7)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1463 KB) |  | HTML iconHTML  

    Consistent image quality is one of the most important requirements for a camera system. This applies to application systems in industrial inspection, consumer photography and microscopy. The quality of an image can be measured in terms of two components: sharpness and contrast. These can be directly translated to the camera system control variables: focus and exposure. A number of measures have been developed to adjust the focus and exposure independently. In this paper, an optimal statistical measure of image quality is developed and tested. This measure allows the simultaneous optimization of both the focus and exposure settings during system calibration or operation. The performance of this measure is demonstrated using a series of test patterns and compared to other popular measures. View full abstract»

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  • Multiple target tracking with symmetric measurement equations using unscented Kalman and particle filters

    Publication Year: 2004 , Page(s): 195 - 199
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1573 KB) |  | HTML iconHTML  

    The symmetric measurement equation approach to multiple target tracking is revisited using unscented Kalman and particle filters. The characteristics and performance of these filters are compared to the original symmetric measurement equation implementation relying upon an extended Kalman filter. Counter-intuitive results are presented and explained for two sets of symmetric measurement equations, including a previously unknown limitation of the unscented Kalman filter. The point is made that the performance of the SME approach is dependent on the interaction of the set of SME equations and the filter used. View full abstract»

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  • A feasibility study on using neural networks in performance analysis of coal-fired power plants

    Publication Year: 2004 , Page(s): 541 - 545
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1607 KB) |  | HTML iconHTML  

    Coal-fired power plants are highly complex nonlinear systems. Several performance-monitoring techniques based on linearization and empirical estimations have been developed. However, there is a need for nonlinear modeling for the power plant performance analysis in order to meet the growing demands of economic and operational requirements. In the present research neural networks are used to model the thermodynamic process of a coal-fired power plant, based on actual plant data and simulated data obtained from mathematical models that provide information that is currently not directly available. A sensitivity analysis study is performed to determine the effect of various plant variables on an essential performance parameter, namely, coal flow rate. The safe operation of a coal-fired power plant also requires correct operation of plant instrumentation. Failed instruments provide inaccurate information on the state of a process, which can lead to undesirable or inefficient operation of the power plant. Artificial neural networks are used to develop the analytical redundancy to infer the state of important plant parameters. A sensitivity analysis study is performed to determine the critical parameters influencing the estimated plant parameters. View full abstract»

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  • Input band-pass limiting in a PLL: its influence on interference-induced bifurcation

    Publication Year: 2004 , Page(s): 328 - 332
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1568 KB) |  | HTML iconHTML  

    The sum of a desired tone and an interfering, offset in frequency by v radians/second, tone is considered as the input reference signal for a system comprised of an ideal band-pass limiter and first-order PLL combination. Parameter y denotes the ratio of interfering signal to desired signal amplitudes. In the first of two cases, this two-tone reference signal is supplied directly to the PLL. In the second case, the two-tone reference is band-pass limited before application to the loop. In both cases, if ratio y is sufficiently small (i.e., the interference is relatively weak), the PLL can phase lock to the desired tone, and the interfering tone causes a closed-loop, (2π/v)-periodic phase error (i.e., a periodic beat note within the loop). However, as y increases, a point y = yb is reached where the periodic phase error bifurcates (yb is the bifurcation point), and the PLL breaks phase lock. A metric of interference rejection ability, the value yb, is a function of tone frequency spacing v, PLL closed loop bandwidth G, loop detuning wΔ and whether or not input band-pass limiting is employed. Two different algorithms are described for calculating the bifurcation point yb. The first is based on a numerical solution of the equation that describes the PLL; the second is based on harmonic balance methods. These two algorithms are used to show that, depending on the value of v relative to the PLL closed-loop bandwidth G, input band-pass limiting may, or may not, increase the bifurcation point yb. Specifically, for detuning wΔ = 0, input band-pass limiting decreases the bifurcation point yb for a range of v within the PLL closed-loop bandwidth. View full abstract»

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  • A variable step-size adaptive noise canceller using signal to noise ratio as the controlling factor

    Publication Year: 2004 , Page(s): 456 - 461
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1597 KB) |  | HTML iconHTML  

    This paper introduces an adaptive noise canceller (ANC) using a proposed variable step size least mean-square (LMS) algorithm. The step size varies between two hard limits based on a predetermined nonlinear decreasing function of signal to noise ratio (SNR) estimated at every iteration of the algorithm. The performance of the proposed algorithm is studied for different power levels of both stationary and nonstationary Gaussian noise added to the original speech. Compared with other several variable step size algorithms, computer simulations show performance superiority of the proposed algorithm in decreasing excess mean square error (EMSE) in both stationary and nonstationary noise environments. Simulations of the proposed method also show substantial improvements in decreasing misadjustment and reverberation. View full abstract»

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  • Analysis of fuel cell based power systems using EMTDC electrical power simulator

    Publication Year: 2004 , Page(s): 270 - 274
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1588 KB) |  | HTML iconHTML  

    Current demands for alternative power generation have expanded beyond the utility industry into advanced transportation. Electrical and hybrid automobiles have long been developed utilizing fuel cell technology, and all-electric aircraft someday becomes a reality. To facilitate such work in electrical power simulators such as PSCAD/EMTDC and later in real-time power simulators like RSCAD/RTDS, accurate models of the transient behavior of all system components must be developed. Although the current state of power system models sufficiently encompasses most conventional systems for detailed simulations, fuel cell models for such studies are underdeveloped for power system analysis. This paper presents the integration of a proton exchange membrane fuel cell model into proposed electrical power system architecture. The fuel cell and support system for power delivery, including the appropriate power electronics and energy storage devices, are simulated and presented. The fuel cell model includes both electrical and thermal components to better capture transient behavior. View full abstract»

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  • On continuous-time stochastic systems in a new approach to system theory

    Publication Year: 2004 , Page(s): 482 - 487
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1708 KB) |  | HTML iconHTML  

    This paper deals with an alterative definition of continuous-time models of discrete-time causal systems in a new approach to system theory, namely with the definition of continuous-time stochastic systems. Despite the general system theory has been intensively studied since 1960s, none of the developed theories has been fully accepted by professional community as sufficiently comprehensive up to now. The alternative system theory is based on quite new system paradigms consequent upon attentive observations and results in an axiomatic system theory with correctly and unambiguously defined notions. View full abstract»

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  • Clutter complexity analysis of hyper-spectral bands

    Publication Year: 2004 , Page(s): 531 - 535
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1835 KB) |  | HTML iconHTML  

    This work investigates the use of a clutter complexity measure for the selection of bands for a detector operating over forward looking hyper-spectral image cubes. By clutter complexity, we mean an aggregation of statistical image features that predict the "degree of difficulty" to detect and/or identify a target object in an image. We show that clutter complexity correlates well with single-band automatic target recognition (ATR) performance. We also show the performance of the multi-band ATR when the bands are selected based on clutter complexity. To baseline this ATR performance, we consider a uniform band ordering strategy and an "optimal" ordering strategy determined by an exhaustive search. Our results show that the ordering by clutter complexity results in an improvement of the ATR performance when compared to the uniform ordering strategy. This improved performance is however not as good as the performance obtained for the optimal ordering. View full abstract»

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  • PCF vs DCF: a performance comparison

    Publication Year: 2004 , Page(s): 215 - 219
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2173 KB) |  | HTML iconHTML  

    Wireless LANs are gaining importance at a very rapid pace. The idea of being mobile and connected to the Internet is driving new innovations in this area. With the recent innovations in the field of multimedia networks, the requirements of QoS support over wireless LANs are becoming more stringent. Quality of service in a wireless LAN is affected by a number of parameters like channel access method, physical/environmental conditions, number of nodes, distance etc. A proper selection of protocols/topology helps in maintaining/improving the QoS support of a wireless network. In this paper, the authors analyze the effect of channel access methods on the multimedia (voice) traffic. Two channel access methods, namely point coordinate function (PCF) and distributed coordinated function are considered for their support for QoS. The simulation results indicate that using PCF for multimedia traffic results in better performance. View full abstract»

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