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The authors have developed a method for optimizing nonlinear physiologically based pharmacokinetic (PBPK) models using Lagrangian-based or genetic algorithms. The optimization method is demonstrated using PBPK models for pharmacokinetics of nicotine, in which parameters that are not well established can be systematically varied to obtain optimized solutions based on experimental data. The method provides valuable guidance in the determination of these model parameters. The PBPK model for nicotine was developed in C and linked with the ordinary differential equation package, CVODE. The model can be run either stand-alone or under the control of an optimization package. The optimization is performed using SuperCode, running either a Lagrangian-based (VMCON) or a genetic algorithm-based (GALIB) optimizer. To reduce computational time, SuperCode can carry out the optimization in parallel, utilizing the Parallel Virtual Machine (PVM) message-passing software. Both the VMCON and GALIB optimizing algorithms have...

The Compact Ignition Tokamak is a high-performance device designed to study the physics of burning plasmas. Key physics aspects of the design are described, including plasma performance, disruption...

A human simulation environment, the Virtual Human (VH), is under development at the Oak Ridge National Laboratory (ORNL). Virtual Human connects three-dimensional (3D) anatomical models of the body with dynamic physiological models to investigate a wide range of human biological and physical responses to stimuli. The authors have utilized the Java programming language to develop a flexible user interface to the VH. The Java prototype interface has been designed to display dynamic results from selected physiological models, with user control of the initial model parameters and ability to steer the simulation as it is proceeding. Taking advantage of Java's Remote Method Invocation (RMI) features, the interface runs as a Java client that connects to a Java RMI server process running on a remote server machine. The RMI server can couple to physiological models written in Java, or in other programming languages, including C and FORTRAN. Future versions of the interface will be linked to 3D anatomical models of the human body to complete the development of the VH.

Compact stellarators have the potential to make steady-state, disruption-free magnetic fusion systems with beta approximately 5% and relatively low aspect ratio (R/ < 4.5) compared to most drift-optimized stellarators. Magnetic quasi-symmetry can be used to reduce orbit losses. The National Compact Stellarator Experiment (NCSX) is designed to test compact stellarator physics in a high-beta quasi-axisymmetric configuration and to determine the conditions for high-beta disruption-free operation. It is designed around a reference plasma with low ripple, good magnetic surfaces, and stability to the important ideal instabilities at beta approximately 4%. The device size, available heating power, and pulse lengths provide access to a high-beta target plasma state. The NCSX has magnetic flexibility to explore a wide range of equilibrium conditions and has operational flexibility to achieve a wide range of beta and collisionality values. The design provides space to accommodate plasma-facing components for divertor operation and ports for an extensive array of diagnostics.

The Tokamak Simulation Code and the TWIR postprocessor code have been used to develop credible plasma disruption scenarios for the Compact Ignition Tokamak (CIT) in order to predict the evolution of forces on CIT conducting structures and to provide results required for detailed structural design analysis. The extreme values of net radial and vertical vacuum vessel (VV) forces were found to be F{sub R}={minus}12.0 MN/rad and F{sub Z}={minus}3.0 MN/rad, respectively, for the CIT 2.1-m, 11-MA design. Net VV force evolution was found to be altered significantly by two mechanisms not noted previously. The first, due to poloidal VV currents arising from increased plasma paramagnetism during thermal quench, reduces the magnitude of the extreme F{sub R} by 15-50{percent} and modifies the distribution of forces substantially. The second effect is that slower plasma current decay rates give more severe net vertical VV loads because the current decay occurs when the plasma has moved farther from midplane than is the case for faster decay rates. 7 refs., 9 figs., 1 tab.

The relative dependence of ideal ballooning instability on the pressure profile is studied in a flux-conserving sequence of equilibria with parameters representative of the Fusion Engineering Device (FED). The instability region based on a pressure profile with an exponential dependence on the poloidal flux suggests an improved profile through which a significant increase in the stable beta value is realized. The corresponding change in the pressure function appears to be relatively small in real space. Computational results indicate that the design value of beta in the FED may be achieved and suggest that for sufficiently optimized pressure profiles, ideal high-n MHD stability limits may not have been exceeded in present tokamaks.