Design of Predictive Controllers by Dynamic Programming and Neural Networks

This paper proposes a method for the design of predictive controllers for nonlinear systems. The method consists of two phases, a solution phase and a learning phase. In the solution phase, dynamic programming is applied to obtain a closed-loop control law. In the learning phase, neural networks are used to simulate the control law. This phase overcomes the curse of dimensionality problem that has often hindered the implementation of control laws generated by dynamic programming. Experimental results demonstrate the effectiveness of the metho

On the Halo Occupation of Dark Baryons

We introduce a new technique that adopts the halo occupation framework for understanding the origin of QSO absorption-line systems. Our initial study focuses specifically on MgII absorbers. We construct a model of the gaseous content in which the absorption equivalent width W_r is determined by the the amount of cold gas, in the form of discrete clouds, along a sightline through a halo. The two quantities that we specify per halo in the model are (1) the mean absorption strength per unit surface mass density A_W(M), and (2) the mean covering factor kappa_g(M) of the gaseous clouds. These parameters determine the conditional probability distribution of W_r as a function of halo mass, P(W_r|M). Two empirical measurements are applied to constrain the model: (i) the absorber frequency distribution function and (ii) the W_r-dependent clustering amplitude. We find that the data demand a rapid transition in the gas content of halos at ~10^11.5 Msol/h, below which halos contain predominantly cold gas and beyond which gas becomes predominantly hot. In order to reproduce the observed overall strong clustering of the absorbers and the anti-correlation between W_r and halo mass M, roughly 5% of gas in halos up to 10^14 Msol/h is required to be cold. The gas covering factor is near unity over a wide range of halo mass, supporting that Mg II systems probe an unbiased sample of typical galaxies. We discuss the implications of our study in the contexts of mass assembly of distant galaxies and the origin of QSO absorption line systems.Comment: 15 emulateapj pages, 7 figures, replaced with revised version incorporating referee's comment

A False Acceptance Error Controlling Method for Hyperspherical Classifiers

Controlling false acceptance errors is of critical importance in many pattern recognition applications, including signature and speaker verification problems. Toward this goal, this paper presents two post-processing methods to improve the performance of hyperspherical classifiers in rejecting patterns from unknown classes. The first method uses a self-organizational approach to design minimum radius hyperspheres, reducing the redundancy of the class region defined by the hyperspherical classifiers. The second method removes additional redundant class regions from the hyperspheres by using a clustering technique to generate a number of smaller hyperspheres. Simulation and experimental results demonstrate that by removing redundant regions these two post-processing methods can reduce the false acceptance error without significantly increasing the false rejection error

A Training Sample Sequence Planning Method for Pattern Recognition Problems

In solving pattern recognition problems, many classification methods, such as the nearest-neighbor (NN) rule, need to determine prototypes from a training set. To improve the performance of these classifiers in finding an efficient set of prototypes, this paper introduces a training sample sequence planning method. In particular, by estimating the relative nearness of the training samples to the decision boundary, the approach proposed here incrementally increases the number of prototypes until the desired classification accuracy has been reached. This approach has been tested with a NN classification method and a neural network training approach. Studies based on both artificial and real data demonstrate that higher classification accuracy can be achieved with fewer prototypes

MathRun: An Adaptive Mental Arithmetic Game Using A Quantitative Performance Model

Pedagogy and the way children learn are changing rapidly with the introduction of widely accessible computer technologies, from mobile apps to interactive educational games. Digital games have the capacity to embed many learning supports using the widely accredited VARK (visual, auditory, reading, and kinaesthetic) learning style. In this paper, we present a mathematics educational game MathRun for children age between 7-11 years old to practice mental arithmetic. We build the game as an interactive learning environment that fuses game mechanics with learning and uses the popular game genre “infinite runner” as the game mode. The game consists of an automatically generated infinite game map and mathematical questions also procedurally generated with varied levels of difficulty and complexity. A novel real-time performance evaluation method is developed for quantitative modeling the performance of the player. The model evaluates the performance in each primitive map block of the game map and level progression is automatically carried out based on the result of the evaluation. Therefore, the proposed game-based learning environment is adaptive to players with dynamic level progressions based on the combination of not only mathematics ability, but also gameplay skills of the player to facilitate learning processes through gameplay and appropriate adaptive progression of maths ability

Nuclear matter symmetry energy and the neutron skin thickness of heavy nuclei

Correlations between the thickness of the neutron skin in finite nuclei and the nuclear matter symmetry energy are studied in the Skyrme Hartree-Fock model. From the most recent analysis of the isospin diffusion data in heavy-ion collisions based on an isospin- and momentum-dependent transport model with in-medium nucleon-nucleon cross sections, a value of $L=88\pm 25$ MeV for the slope of the nuclear symmetry energy at saturation density is extracted, and this imposes stringent constraints on both the parameters in the Skyrme effective interactions and the neutron skin thickness of heavy nuclei. Predicted thickness of the neutron skin is $0.22\pm 0.04$ fm for $$Pb, $0.29\pm 0.04$ fm for $^{132}$Sn, and $0.22\pm 0.04$ fm for $$Sn.Comment: 6 pages, 4 figures, 1 table, revised version, to appear in PR

Triton-3He relative and differential flows and the high density behavior of nuclear symmetry energy

Using a transport model coupled with a phase-space coalescence after-burner we study the triton-3He relative and differential transverse flows in semi-central 132Sn+124Sn reactions at a beam energy of 400 MeV/nucleon. We find that the triton-3He pairs carry interesting information about the density dependence of the nuclear symmetry energy. The t-3He relative flow can be used as a particularly powerful probe of the high-density behavior of the nuclear symmetry energy.Comment: 6 pages, 2 figures, Proceeding of The International Workshop on Nuclear Dynamics in Heavy-Ion Reactions and the Symmetry Energ

The Last Eight-Billion Years of Intergalactic SiIV Evolution

We identified 24 SiIV absorption systems with z <~ 1 from a blind survey of 49 low-redshift quasars with archival Hubble Space Telescope ultraviolet spectra. We relied solely on the characteristic wavelength separation of the doublet to automatically detect candidates. After visual inspection, we defined a sample of 20 definite (group G = 1) and 4 "highly-likely" (G = 2) doublets with rest equivalent widths W_r for both lines detected at > 3 sigma. The absorber line density of the G = 1 doublets was dN_SiIV/dX = 1.4+0.4/-0.3 for log N(Si+3) > 12.9. The best-fit power law to the G = 1 frequency distribution of column densities f(N(Si+3)) had normalization k = (1.2+0.5/-0.4) x 10^-14 cm2 and slope alpha = -1.6+0.3/-0.3. Using the power-law model of f(N(Si+3)), we measured the Si+3 mass density relative to the critical density: Omega(Si+3) = (3.7+2.8/-1.7) x 10^-8 for 13 < log N(Si+3) < 15. From Monte Carlo sampling of the distributions, we estimated our value to be a factor of 4.8+3.0/-1.9 higher than the 2 . From a simple linear fit to Omega(Si+3) over the age of the Universe, we estimated a slow and steady increase from z = 5.5 --> 0 with dOmega/dt_age = (0.61+/-0.23) x 10^-8 Gyr^-1. We compared our ionic ratios N(Si+3)/N(C+3) to a 2 < z < 4.5 sample and concluded, from survival analysis, that the two populations are similar, with median = 0.16.Comment: 18 pages, 9 figures, 4 tables, added figures and new analysis, results have changed, accepted to Ap