Optimization of the deposited power distribution inside a layeredlossy medium irradiated by a coupled system of concentrically placedwaveguide applicators

A method is proposed for controlling the deposited power distribution in a layered cylindrical lossy model, irradiated by a phased-array hyperthermia system consisting of four waveguide applicators. A rigorous electromagnetic model of the heated tissue, which takes into account coupling phenomena between system elements, is used for predicting the electric field at any point inside tissue. The relative amplitudes and relative phases of the array elements are optimized in order to attain desired specific absorption rate (SAR) distributions inside and outside malignant tissues. A constrained nonlinear optimization problem is solved by using the penalty function method and the resulting unconstrained minimization of the penalty function is carried out by the downhill simplex method. Two practical phased-array hyperthermia systems have been studied and numerical results are presented     

Optimization of the deposited power distribution inside a layered lossy medium irradiated by a coupled system of concentrically placed waveguide applicators

A method is proposed for controlling the deposited power distribution in a layered cylindrical lossy model, irradiated by a phased-array hyperthermia system consisting of four waveguide applicators. A rigorous electromagnetic model of the heated tissue, which takes into account coupling phenomena between system elements, is used for predicting the electric field at any point inside tissue. The relative amplitudes and relative phases of the array elements are optimized in order to attain desired specific absorption rate (SAR) distributions inside and outside malignant tissues. A constrained nonlinear optimization problem is solved by using the penalty function method and the resulting unconstrained minimization of the penalty function is carried out by the downhill simplex method. Two practical phased-array hyperthermia systems have been studied and numerical results are presented.     

Temporal processing of emotional stimuli: The capture and release of attention by angry faces.

Neuroimaging data suggest that emotional information, especially threatening faces, automatically captures attention and receives rapid processing. While this is consistent with the majority of behavioral data, behavioral studies of the attentional blink (AB) additionally reveal that aversive emotional first target (T1) stimuli are associated with prolonged attentional engagement or “dwell” time. One explanation for this difference is that few AB studies have utilized manipulations of facial emotion as the T1. To address this, schematic faces varying in expression (neutral, angry, happy) served as the T1 in the current research. Results revealed that the blink associated with an angry T1 face was, primarily, of greater magnitude than that associated with either a neutral or happy T1 face, and also that initial recovery from this processing bias was faster following angry, compared with happy, T1 faces. The current data therefore provide important information regarding the time-course of attentional capture by angry faces: Angry faces are associated with both the rapid capture and rapid release of attention. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Maximizing Power-System Loadability in the Presence of Multiple Binding Complementarity Constraints

In this paper, the problem of maximizing power-system loadability with multiple complementarity constraints representing generator limits is examined. The structure of the loadability surface is investigated, the various type of limits are classified and a general algorithm to optimize settings of control variables, in order to maximize loadability margin is developed. The importance of nonsmooth corner points (CPs) of the loadability surface that are due to the simultaneous occurrence of several loadability conditions is discussed. At such limits, maximization of loadability margin is performed based on techniques provided by nonlinear optimization theory. For this purpose an algorithm to identify multiple binding constraints on a CP is developed. Illustrative examples on small, but realistic systems are included.     

Optimal steady-state temperature distribution for a phased arrayhyperthermia system

A method is presented for the evaluation of optimal amplitude and phase excitations for the radiating elements of a phased array hyperthermia system, in order to achieve desired steady-state temperature distributions inside and outside of malignant tissues. Use is made of a detailed electromagnetic and thermal model of the heated tissue in order to predict the steady-state temperature at any point in tissue. Optimal excitations are obtained by minimizing the squared error between desired and model predicted temperatures inside the tumor volume, subject to the constraint that temperatures do not exceed an upper bound outside the tumor. The penalty function technique is used to solve the constrained optimization problem. Sequential unconstrained minima are obtained by a modified Newton method. Numerical results for a four element phased array hyperthermia system are presented     

A Nonfeasible Gradient Projection Recurrent Neural Network for Equality-Constrained Optimization Problems

In this paper, a recurrent neural network for both convex and nonconvex equality-constrained optimization problems is proposed, which makes use of a cost gradient projection onto the tangent space of the constraints. The proposed neural network constructs a generically nonfeasible trajectory, satisfying the constraints only as t rarr infin. Local convergence results are given that do not assume convexity of the optimization problem to be solved. Global convergence results are established for convex optimization problems. An exponential convergence rate is shown to hold both for the convex case and the nonconvex case. Numerical results indicate that the proposed method is efficient and accurate.     

Inverse electrocardiography by simultaneous imposition of multipleconstraints

The authors describe two new methods for the inverse problem of electrocardiography. Both employ regularization with multiple constraints, rather than the standard single-constraint regularization. In one method, multiple constraints on the spatial behavior of the solution are used simultaneously. In the other, spatial constraints are used simultaneously with constraints on the temporal behavior of the solution. The specific cases of two spatial constraints and one spatial and one temporal constraint are considered in detail. A new method, the L-Surface, is presented to guide the choice of the required pairs of regularization parameters. In the case when both spatial and temporal regularization are used simultaneously, there is an increased computational burden, and two methods are presented to compute solutions efficiently. The methods are verified by simulations using both dipole sources and measured canine epicardial data