Utilization of texture, contrast and color homogeneity for detecting and recognizing text from video frames

It is possible to index and manage large video archives in a more efficient manner by detecting and recognizing text within video frames. There are some inherent properties of videotext, such as distinguishing texture, higher contrast against background, and uniform color, making it detectable. By employing these properties, it is possible to detect text regions and binarize the image for character recognition. In this paper, a complete framework for detection and recognition of videotext is presented. The results from Gabor-based texture analysis, contrast-based segmentation and color homogeneity are merged to obtain minimum number of candidate regions before binarization. The performance of the system is tested for its recognition rate for various combinations and it is observed that the results give recognition rates, reasonable for most practical purposes

Output-feedback control of linear time-varying and nonlinear systems using the forward propagating Riccati equation

For output-feedback control of linear time-varying (LTV) and nonlinear systems, this paper focuses on control based on the forward propagating Riccati equation (FPRE). FPRE control uses dual difference (or differential) Riccati equations that are solved forward in time. Unlike the standard regulator Riccati equation, which propagates backward in time, forward propagation facilitates output-feedback control of both LTV and nonlinear systems expressed in terms of a state-dependent coefficient (SDC). To investigate the strengths and weaknesses of this approach, this paper considers several nonlinear systems under full-state-feedback and output-feedback control. The internal model principle is used to follow and reject step, ramp, and harmonic commands and disturbances. The Mathieu equation, Van der Pol oscillator, rotational-translational actuator, and ball and beam are considered. All examples are considered in discrete time in order to remove the effect of integration accuracy. The performance of FPRE is investigated numerically by considering the effect of state and control weightings, the initial conditions of the difference Riccati equations, the domain of attraction, and the choice of SDC

A numerical comparison of frozen-time and forward-propagating Riccati equations for stabilization of periodically time-varying systems

Feedback control of linear time-varying systems arises in numerous applications. In this paper we numerically investigate and compare the performance of two heuristic techniques. The first technique is the frozen-time Riccati equation, which is analogous to the state-dependent Riccati equation, where the instantaneous dynamics matrix is used within an algebraic Riccati equation solved at each time step. The second technique is the forward-propagating Riccati equation, which solves the differential algebraic Riccati equation forward in time rather than backward in time as in optimal control. Both techniques are heuristic and suboptimal in the sense that neither stability nor optimal performance is guaranteed. To assess the performance of these methods, we construct Pareto efficiency curves that illustrate the state and control cost tradeoffs. Three examples involving periodically time-varying dynamics are considered, including a second-order exponentially unstable Mathieu equation, a fourth-order rotating disk with rigid body unstable modes, and a 10th-order parametrically forced beam with exponentially unstable dynamics. The first two examples assume full-state feedback, while the last example uses a scalar displacement measurement with state estimation performed by a dual Riccati technique

Faux-Riccati Synthesis of Nonlinear Observer-Based Compensators for Discrete-Time Nonlinear Systems

Pseudo-linear models of nonlinear systems use either a state-dependent coefficient or the Jacobian of the vector field to facilitate the use of Riccati techniques. In this paper we use the state-dependent Riccati equation (SDRE) and the forward propagating Riccati equation (FPRE) with pseudo-linear models to construct nonlinear observer-based compensators for output-feedback control of nonlinear discrete-time systems. While attractive due to their simplicity and potentially wide applicability, these techniques remain largely heuristic. The goal of this paper is thus to present numerical experiments to assess the performance of these "faux" Riccati techniques on representative nonlinear systems. The goal is to compare the performance of SDRE and FPRE when used with either a state-dependent coefficient or the Jacobian of the vector field. Stabilization and performance are considered, along with integral control for step command following

Infinite-Horizon Linear-Quadratic Control by Forward Propagation of the Differential Riccati Equation

One of the foundational principles of optimal control theory is that optimal control laws are propagated backward in time. For linear-quadratic control, this means that the solution of the Riccati equation must be obtained from backward integration from a final-time condition. These features are a direct consequence of the transversality conditions of optimal control, which imply that a free final state corresponds to a fixed final adjoint state [1], [2]. In addition, the principle of dynamic programming and the associated Hamilton-Jacobi-Bellman equation is an inherently backward-propagating methodology [3]

Serum malondialdehyde concentration in babies with hyperbilirubinaemia

AIM—To determine lipid peroxide concentrations in the first 10 days of life.
METHODS—Malondialdehyde concentrations were investigated in neonates with or without hyperbilirubinaemia during the first 10 days of life.
RESULTS—Serum malondialdehyde concentrations were higher in infants with hyperbilirubinaemia than in controls. A positive correlation was found between malondialdehyde and bilirubin concentrations in the study group. When the study group was categorised according to the presence of haemolysis, a significant correlation was found between malondialdehyde and bilirubin concentrations in those infants with hyperbilirubinaemia due to haemolysis. There was no such correlation in those without haemolysis.
CONCLUSION—Exchange transfusion rapidly produces variable changes in pro-oxidant and antioxidant plasma concentrations in neonates, which may be responsible for free radical metabolism. The fall in malondialdehyde concentration is probably directly related to its exogenous removal by exchange transfusion.