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Southeastcon '94. Creative Technology Transfer - A Global Affair., Proceedings of the 1994 IEEE

Date 10-13 April 1994

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Displaying Results 1 - 25 of 112
  • Proceedings of SOUTHEASTCON '94

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    Freely Available from IEEE
  • Effect of system optical configuration on visibility profiles for circularly polarized backscattered laser beam

    Page(s): 60 - 63
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    Based on the laser Doppler anemometry technique and Mie scattering theory, the visibility-particle size relationship (visibility profile) is computed for spherical particles of complex index of refraction. The analysis is restricted to the backscatter direction, for incident light that is circularly polarized. It is observed that the shape of the visibility profile is greatly influenced by the index of refraction of the particle and the optical parameters of the system. The effect that the optical parameters, such as beam angular separations (Ψ), collecting aperture size (R), and off-axis collecting angle (Φ0 ), have on the visibility profiles is examined. It is established that the visibility technique is useful for particle sizing under limited values of the optical parameters. It is found that particle sizing is feasible for values of Ψ ranging from 9.5° to 1.0°, and for values of R ranging from 4.0° to 14.0°. It is observed, in many cases, that moving the collecting aperture slightly off-axis improves the quality of the visibility profile for particle sizing View full abstract»

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  • Modeling three-dimensional acoustic waves in the ocean

    Page(s): 455 - 459
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    Conventional three-dimensional ocean acoustic modeling ignores Earth flattening, while this effect, as has been shown by Munk et. al. (J. Phys. Oceanogr, 18, 1988, 1876-1898), can not be ignored for long-range transmissions. To take into account the Earth flattening, a new three-dimensional wave equation is derived, in the paper, in terms of a new coordinate system: the ellipsoidal coordinates (geographic latitude, longitude, and depth). From the wave equation, a set of three-dimensional ray equations is then obtained. Both the wave equation and the ray equations account for Earth flattening and Earth curvature, so that they are very useful for solving long-range problems in ocean acoustics and in seismology. The derivations of these new equations are presented in the paper View full abstract»

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  • Modeling and simulation of the data communication network at the ASRM facility

    Page(s): 258 - 264
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    This paper describes the modeling and simulation of the communication network for the NASA Advanced Solid Rocket Motor (ASRM) facility under construction at Yellow Creek near Iuka, Mississippi. Manufacturing, testing, and operations at the ASRM site will be performed in different buildings scattered over a 1800 acre site. These buildings are interconnected through a local area network (LAN), which will contain one logical Fiber Distributed Data Interface (FDDI) ring acting as a backbone for the whole complex. The network contains approximately 700 multi-vendor workstations, 22 multi-vendor workcells, and 3 VAX clusters interconnected via Ethernet and FDDI. The different devices produce appreciably different traffic patterns, each pattern will be highly variable, and some patterns will be very bursty. Most traffic is between the VAX clusters and the other devices. Comdisco's Block Oriented Network Simulator (BONeS) has been used for network simulation. The two primary evaluation parameters used to judge the expected network performance are throughput and delay View full abstract»

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  • Comparison of measured and calculated CFO voltages for 115 kV and 230 kV substations

    Page(s): 285 - 287
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    This paper presents both experimental results and calculations of CFO voltages for 115 kV and 230 kV substations. Several different methods are used to calculate the CFO voltage. The accuracy of specific equations and a graphical method used for the evaluation of CFO voltages for HV substations are discussed. The paper concludes with a discussion and analysis of equations used for the estimation of air clearances in HV substations based on CFO voltages View full abstract»

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  • Solution of the waveguide problem by a method based on the integral definition of the curl operator

    Page(s): 209 - 211
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    The definition of the curl operator in terms of an integral is shown to lead to a method for numerical solutions. In the paper, the derivation of this method, as well as examples for waveguides are presented View full abstract»

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  • Evolution of multi-valley electron distributions in GaAs

    Page(s): 447 - 449
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    An approach based on the physical evolution of the distribution function in the energy relaxation scale is used to study multi-valley distribution functions of electrons in GaAs subjected to a rapid change in electric field. This approach, which assumes the distribution can be determined by mean energy, is able to describe transport phenomena, including inter-valley transitions, in the scale as small as the energy relaxation time. Results show that, near the peak of velocity overshoot and bottom of undershoot in the Γ valley, the energy-dependent distribution cannot respond as fast as the distribution obtained from Monte Carlo method. This results in less pronounced overshoot and undershoot in the Γ valley when using the introduced approach than using the Monte Carlo method. However, in the L valley, overshoot and undershoot are not pronounced, and these two approaches are in very good agreement View full abstract»

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  • Quasi-static characteristic of a shielded cylindrical coupled microstrip transmission line by finite-element method

    Page(s): 170 - 174
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    This paper presents a finite-element method of numerical analysis for a system of a shielded cylindrical coupled microstrip transmission lines. The complete polynomial field of the high order element up to fourth is used in this study. The microstrip line consists of two coupled dielectric circular cylinders characterized by permittivity ε1 and ε2 and partially embedded in the ground plane. The two infinitesimally thin strips with arbitrary size are clad on the coupled dielectric circular cylinders. The coupling between the two conducting strips of the coupled microstrip line is investigated. The first and higher order elements are used in the finite-element method to calculate for the quasi-static potential and the corresponding field distribution in the microstrip line. The capacitance per unit length of the line is obtained from a variational expression and the effective dielectric constant, characteristic impedance, and phase velocity are also computed. A perturbational method is used to calculate the losses due to conductor and dielectric dissipation View full abstract»

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  • Computer-based temperature controller in an energy-conservative manner

    Page(s): 465 - 469
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    The purpose of this work is to develop a computer-based temperature controller for use on board the NASA Space Shuttle for micro-gravity experiments. To meet the requirement of energy conservation and other system specifications, an improved ON-OFF type control scheme which includes a proportional-integral (PI) controller and a pulse-width modulator has been investigated. The comparison of the authors' control algorithm, signal transfer technique and power conversion analysis with that of a conventional controller are presented. Computer implementation, including system hardware and software, are described in this paper. Finally the system performance is illustrated through experiment results View full abstract»

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  • Digital processing for non-stationary narrow-band interference suppression in fading channels

    Page(s): 408 - 412
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    The suppression of narrow-band interference has long been a concern in direct-sequence spread spectrum (DS-SS) communication systems. Recently, transform domain processing (TDP) approaches have been used to suppress intentional interference. This paper extends previous work done in the area of TDP utilizing non-linear rank order filters, namely conditional median filters (CMFs). The paper confronts problems incurred in Rayleigh distributed fading channels. A solution is suggested by introducing a normalized adaptive median filter. This adaptive approach considers each received bit independently and uses a normalization metric to compensate for fading. The paper also presents bit error rates (BER) for a DS-SS receiver employing the proposed approach. Using Monte-Carlo simulations the BER of the fading channel was determined for various jammer and fading scenarios, and results are presented View full abstract»

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  • Visualization of two and three dimensional antenna patterns

    Page(s): 270 - 272
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    An educational software package (APV) is developed for the analysis and design for different types of antenna and antenna arrays. The software is interactive and provides three and two dimensional views for the computed far field patterns. Different plane cuts, in the three dimensional representation are immediately accessible after generating the far field pattern. The two dimensional patterns can be displayed in rectangular or polar format with relative or dB scales. Other relevant antenna parameters such as input impedance, radiation resistance and power, and directivity are also computed and displayed for user information. The APV software runs on IBM or compatible personal computers View full abstract»

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  • The use of wavelet transform as a preprocessor for the neural network detection of EEG spikes

    Page(s): 1 - 3
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    In this study, the wavelet transform is used to process EEG data as input to a feed forward neural network for the detection of epileptogenic transient waveforms. The compression capability of wavelet transform provided the inclusion of data before and after the spike for contextual information without increasing input size of the neural network. The network is trained for the detection of spikes and non-spikes. The results show that wavelet transform can be used to provide more relevant information for improving the detection of epileptogenic spikes for automated EEG monitoring of seizure patients View full abstract»

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  • A genetic algorithm-based approach to economic dispatch of power systems

    Page(s): 212 - 216
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    In view of the Clean Air Act (CAA) of 1990, the economic dispatch problem considering the compensating generation plan provided in the Act is nonlinear, ill-structured and multimodal. This paper presents a genetic algorithm (GA) based approach to solve this problem. Test results show that the genetic algorithm-based approach produces significantly better solutions compared against those obtained using the standard economic dispatch approach. It also proves the robustness of this algorithm in solving this type of optimization problem View full abstract»

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  • Stationary and cyclostationary random process models

    Page(s): 450 - 454
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    Cyclostationary random process modeling is an area of signal processing that has been the subject of numerous journal papers. W.A. Gardner (1988) devoted half of a book to cyclic spectral analysis. Cyclostationarity, however, has not received very much attention at regional conferences in the recent past, which implies that it is not being utilized by many practising engineers. Therefore, this paper reviews both stationary and cyclostationary random process models. It will be seen that cyclostationary models are more complete than stationary random process models for many manmade signals. Since these signals are best modeled as cyclostationary random processes, signal processors that exploit cyclostationarity can, in principle, have performance superior to traditional processors that utilize only stationary statistical models View full abstract»

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  • A neural network-based text independent voice recognition system

    Page(s): 131 - 135
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    A text-independent voice recognition experiment was conducted using an artificial neural network. The speech data were collected from three different speakers uttering thirteen different words. Each word was repeated ten times. The speech data were then pre-processed for signal conditioning. A total of 12 feature parameters were obtained from Cepstral coefficients via a linear predictive coding (LPC). These feature parameters then served as inputs to the neural network for speaker classification. A standard two-layer feedforward neural network was trained to identify different feature sets associated with the corresponding speakers. The network was tested for the remaining unseen words in text-independent mode. The results were very promising with a voice recognition accuracy of more than 90%. The success rate could be increased by adding more utterances from each speaker View full abstract»

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  • DSP controller for a permanent magnet synchronous motor drive

    Page(s): 413 - 417
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    The drives industry is steadily moving towards digital implementation of controllers for variable speed drives. This paper discusses the implementation of a DSP controller for controlling a permanent magnet synchronous motor (PMSM). It discusses the theory of operation of a PMSM drive and shows how a DSP controller has been designed to perform the vector and current control functions. The design criteria is presented and advantages and disadvantages of the DSP selected to perform the vector and current control functions is discussed. The techniques used in software development are also discussed View full abstract»

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  • Boost derived topology as a power factor correction circuit

    Page(s): 175 - 179
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    This paper proposes a novel PWM converter which is a modified version of the conventional boost topology with output electrical isolation and zero-voltage switching (ZVS). The steady-state analysis and the control characteristic curves are presented. Also, the authors present a closed loop system for the converter as a power factor correction circuit (PFCC) application. The system uses voltage referencing and current sensing. This is achieved by implementing the commercially available chip ML4821 (average current mode controller) in the closed loop system. Circuit simulation based on PSPICE of the proposed topology is given. It is shown that the simulation and theoretical results are in agreement View full abstract»

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  • The prospect and exploration of higher electronics education in the 21st century

    Page(s): 301 - 303
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    The technology of electronic information is coming to the fore in the world of advanced science and technology. It is widely applied not only in the economic field, but also in social life. In the 21st century, our world will become an information and intelligence society. It is also the critical period for the realization of China's modernization. China needs enough qualified professionals in electronic information science. Professionals in all the other specialities need to be equiped with the required knowledge and skills of electronic information science and technology. So the knowledge of the professionals specializing in electronics needs to be renewed, too. The paper discusses how China's higher electronics education (HEE) will reform and develops some tentative ideas and measures of HEE in the 21st century in China; it also discusses training high quality applied personnel and points out how these may serve the economic construction and social development better View full abstract»

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  • Voltage maps simplify electric circuit analysis

    Page(s): 185 - 189
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    The pioneering work over 50 years ago by M.I.T. faculty who wrote textbooks for the study of electrical sciences set the pattern for the study of electric circuits in the United States. Authors who developed textbooks after those early works largely followed the techniques advanced there. This paper extends the analytical procedures adopted for identifying current direction and voltage polarities in a circuit. While the M.I.T. works adopted an arrow to indicate current direction, a similar arrow symbol for voltage was not adopted. Double subscript notation identifying nodes and relative polarity was used instead. This notation has contributed to confusion of students who are learning electric circuits. A simpler designation of voltage polarity by an open-head arrow promotes a better understanding of electric circuit operation. This paper proposes the use of a closed-head arrow for current direction, and an open-head arrow for a voltage rise between nodes. In this method all voltages are rises only. All voltages can be drawn in a voltage map of a circuit, using open-head arrows to show both voltage rises from sources of emf and voltage rises across resistors caused by Ohm's law relationships. This proposed method for identifying voltages corresponds with the node voltage polarity terminology used to interpret results from computer software programs such as PSPICE. A consistent conformity with symbols in circuit analysis is an enhancement to learning for the beginning student of electric circuit analysis. The voltage map is such a learning enhancement View full abstract»

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  • Application of three dimensional image analysis to the mammalian cell nucleus

    Page(s): 98 - 100
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    A three dimensional image segmentation and analysis system is proposed to study the confocal microscopy images of DNA replication sites in cell nuclei. The algorithm presented here includes detection of replication sites in 2D slices in the image and reconstructing 3D objects from 2D data. We also present a user interface to allow easy interaction with both the segmentation algorithm and the 3D segmented data View full abstract»

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  • Learning control applied to feedforward compensator tuning

    Page(s): 470 - 474
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    When a robot performs the same task repeatedly, a learning controller can enhance the performance of the system significantly. The function of the learning controller is to update the feedforward compensator which cancels the dynamics of robot manipulators and friction of each joints. The feedforward compensator especially plays an important role in the contact force control of robot manipulators with a rigid workpiece. In this paper, the learning algorithm which guarantees the asymptotic stability is studied and used to refine the feedforward compensator. Experiments with a two degree of freedom direct drive robot confirms the effectiveness of the algorithm View full abstract»

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  • An approach to independent joint adaptive control for the TUMA I

    Page(s): 316 - 320
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    The design of an independent joint adaptive controller for the robotic manipulator TUMA I is outlined in this paper. The TUMA I is a four-degree-of-freedom planar redundant arm built as a testbed at Tulane University. The development of an adaptive independent joint control for a robotic manipulator is outlined when the mathematical model parameters of the manipulator system may not be available and an alternative to the well-known computed torque adaptive control approach can be found useful. The controller design presented is based on heuristic adaptive control methods for servomechanisms using the Diophantine equation as the designing principle View full abstract»

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  • Statistical circuit simulation and yield analysis for IC's

    Page(s): 128 - 130
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    The importance of running statistically based process, device and circuit simulations is becoming critical to IC design for manufacturing techniques. Thus arises the need for software-based packages that couple statistical techniques to conventional simulators. Monte Carlo techniques have been implemented in various such packages, but the nature of Monte Carlo designs often lead to time-consuming and inefficient techniques. This paper concentrates on coupling more efficient statistical techniques (based on a Design of Experiments methodology) and conventional simulators with the aid of software tools for the purpose of characterizing circuit performances in terms of equipment and material variables View full abstract»

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  • Spectral domain analysis of coupled microstrip transmission lines

    Page(s): 201 - 203
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    A full-wave spectral-domain integral equation formulation is used to analyze coupled open boundary microstrip transmission lines. A general rigorous formulation is specialized to the case of two identical uniform lines and a method of moments (MOM) solution is implemented. In contrast with earlier subdomain basis MOM solutions, entire-domain basis functions which incorporate appropriate edge conditions for transverse and longitudinal current components are utilized. This allows closed-term evaluation of relevant spatial integrals and results in improved accuracy using far fewer terms. Extensions of earlier results, including characteristic impedances, propagation constants and current distributions are presented for the dominant and first two higher-order coupled modes, and compare favorably to results of other techniques View full abstract»

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  • Lightning performance tests on 115 kV transmission line models with spline ball ionizers

    Page(s): 288 - 291
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    This paper presents the results of an investigation of the lightning performance of a transmission line with spline ball ionizers. An experimental investigation was conducted to determine the critical flashover (CFO) voltage between a scale model of a charged cloud and a transmission line with spline ball ionizers. The CFO voltages for the standard lightning impulses were measured for both positive and negative polarity View full abstract»

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