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Radial diffusion of resonant particles in tandem mirrors

Description: The radial diffusion of resonant particles in the banana regime and the plateau regime is derived in detail from kinetic theory. The plateau diffusion, calculated in the tau-approximation, confirms the result given by Ryutov--Stupakov without derivation. The banana diffusion also agrees with the R--S result provided the latter is corrected for some dependence of the collision frequency on epsilon and phi.
Date: December 4, 1978
Creator: Lee, Y.C.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Analytical theory of drift waves and drift Alfven waves in tokamaks

Description: The collisionless drift wave and drift Alfven wave instabilities in a sheared magnetic field are considered using the complex transformation technique of Antonsen. It is shown that no unstable bounded eigensolutions for the finite-..beta.. radial eigenmode equations exist. We also present a more general technique based on the wave-flux conservation and find, furthermore, that the convective amplification of drift waves in the electrostatic limit can be anomalously large, which could lead to enh… more
Date: January 1, 1979
Creator: Lee, Y.C. & Chen, L.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Energy confinement comparison of ohmically heated stellarators to tokamaks

Description: An empirical scaling prescribes that the energy confinement time in ohmically heated stellarators and tokamaks is proportional to the internal energy of the plasma and the minor radius, and inversely proportional to the current density. A thermal-conduction energy transport model, based on a heuristic assumption that the effective momentum transfer in the radial direction is proportional to the classical parallel momentum transfer which results in ohmic heating, is used to explain this scaling.
Date: December 1, 1979
Creator: Chu, T. K. & Lee, Y. C.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Stability of drift-wave eigenmodes with arbitrary radial wavelengths

Description: A general theory for the stability of collisionless drift-wave eigenmodes in sheared slab magnetic fields is developed using the S-matrix technique. The eigenmodes are described with the integral formulation which fully takes into account the nonlocal effects of finite ion gyro-orbits. The universal eigenmode is then shown to be absolutely stable for arbitrary radial wavelengths.
Date: May 1, 1979
Creator: Lee, Y. C.; Chen, L. & Nevins, W. M.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Stability analysis of a hot electron EBT plasma

Description: Previous theoretical studies have predicted that an EBT-confined plasma will have a stable equilibrium for beta values of the toroidal core plasma comparable to the beta value for the hot electron annulus. We show that, when the ring is allowed to be perturbed, there is a new physical effect, enhanced compression of the core plasma; that in the limit of negligible ..beta../sub core/, the interchange mode is stable for ..beta../sub ring/ greater than about 20%, as was found before; but that when… more
Date: December 1, 1979
Creator: Van Dam, J. W. & Lee, Y. C.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Improved input representation for enhancement of neural network performance

Description: The performance of an associate memory network depends significantly on the representation of the data. For example, it has already been recognized that bipolar representation of neurons with -1 and +1 states out- perform neurons with on and off states of +1 and 0 respectively. This paper will show that a simple modification of the pattern vector to have zero bias will provide even more significant increase for the performance of an associative memory network. The higher order algorithm is used… more
Date: January 1, 1987
Creator: Aldrich, C. H.; An, Z. G.; Lee, K. & Lee, Y. C.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Time series prediction using a rational fraction neural networks

Description: An efficient neural network based on a rational fraction representation has been trained to perform time series prediction. The network is a generalization of the Volterra-Wiener network while still retaining the computational efficiency of the latter. Because of the second order convergent nature of the learning algorithm, the rational net is computationally far more efficient than multilayer networks. The rational fractional representation is, however, more restrictive than the multilayer net… more
Date: January 1, 1988
Creator: Lee, K.; Lee, Y. C.; Barnes, C.; Aldrich, C. H. & Kindel, J.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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HIERtalker: A default hierarchy of high order neural networks that learns to read English aloud

Description: A new learning algorithm based on a default hierarchy of high order neural networks has been developed that is able to generalize as well as handle exceptions. It learns the ''building blocks'' or clusters of symbols in a stream that appear repeatedly and convey certain messages. The default hierarchy prevents a combinatoric explosion of rules. A simulator of such a hierarchy, HIERtalker, has been applied to the conversion of English words to phonemes. Achieved accuracy is 99% for trained words… more
Date: January 1, 1988
Creator: An, Z. G.; Mniszewski, S. M.; Lee, Y. C.; Papcun, G. & Doolen, G. D.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Machine learning using a higher order correlation network

Description: A high-order correlation tensor formalism for neural networks is described. The model can simulate auto associative, heteroassociative, as well as multiassociative memory. For the autoassociative model, simulation results show a drastic increase in the memory capacity and speed over that of the standard Hopfield-like correlation matrix methods. The possibility of using multiassociative memory for a learning universal inference network is also discussed. 9 refs., 5 figs.
Date: January 1, 1986
Creator: Lee, Y.C.; Doolen, G.; Chen, H.H.; Sun, G.Z.; Maxwell, T. & Lee, H.Y.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Information theoretic derivation of network architecture and learning algorithms

Description: Using variational techniques, we derive a feedforward network architecture that minimizes a least squares cost function with the soft constraint that the mutual information between input and output be maximized. This permits optimum generalization for a given accuracy. A set of learning algorithms are also obtained. The network and learning algorithms are tested on a set of test problems which emphasize time series prediction. 6 refs., 1 fig.
Date: January 1, 1991
Creator: Jones, R.D.; Barnes, C.W.; Lee, Y.C. & Mead, W.C.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Stability of drift waves with the integral eigenmode equation

Description: An analytical theory on the stability properties of drift-wave eigenmodes in a slab plasma with finite magnetic shear is presented. The corresponding eigenmode equation is the integral equation first given by Coppi, Rosenbluth, and Sagdeev (1967) and rederived here, in a relatively simpler fashion, via the gyrokinetic equation. It is then proved that the universal drift-wave eigenmodes remain absolutely stable and finite electron temperature gradients do not alter the stability.
Date: November 1, 1981
Creator: Chen, L.; Ke, F. J.; Xu, M. J.; Tsai, S. T.; Lee, Y. C. & Antonsen, T. M. Jr.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Applications of neural networks to process control and modeling

Description: Modeling and control of physical processes are universal parts of modern life, from control of chemical plants to riding a bicycle. Often, an effective model of the process is not known so that traditional control theory is of little use. If a process can be represented by a set of a data which captures it behavior over a range of parameter settings, a neural net can inductively model the process and form the basis of an optimization procedure. We present a neural network architecture which is … more
Date: January 1, 1991
Creator: Barnes, C.W.; Brown, S.K.; Flake, G.W.; Jones, R.D.; O'Rourke, M.K. & Lee, Y.C.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Using CNLS-net (Connectionist Normalized Local Spline-network) to predict the Mackey-Glass chaotic time series

Description: We use the Connectionist Normalized Local Spline (CNLS) network to learn the dynamics of the Mackey-Glass time-delay differential equation, for the case {tau} = 30. We show the optimum network operating mode and determine the accuracy and robustness of predictions. We obtain pedictions of varying accuracy using some 2--120 minutes of execution time on a Sun SPARC-1 workstation. CNLS-net is capable of very good performance in predicting the Mackey-Glass time series. 11 refs., 4 figs.
Date: January 1, 1991
Creator: Mead, W.C.; Jones, R.D.; Barnes, C.W.; Lee, L.A.; O'Rourke, M.K. (Los Alamos National Lab., NM (USA)); Lee, Y.C. et al.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Nonlinear adaptive networks: A little theory, a few applications

Description: We present the theory of nonlinear adaptive networks and discuss a few applications. In particular, we review the theory of feedforward backpropagation networks. We than present the theory of the Connectionist Normalized Linear Spline network in both its feedforward and iterated modes. Also, we briefly discuss the theory of stochastic cellular automata. We then discuss applications to chaotic time series tidal prediction in Venice Lagoon, sonar transient detection, control of nonlinear processe… more
Date: January 1, 1990
Creator: Jones, R.D.; Qian, S.; Barnes, C.W.; Bisset, K.R.; Bruce, G.M.; Lee, K. et al.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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