Research on High Power Factor Single Tube Variable Structure Wireless Power Transmission

Aiming at the problems existing in the current radio energy transmission system, we propose a wireless power transmission (WPT) system with the parallel–parallel (PP)-compensated structure. The transmitter of the transmission system adopts a separate topological structure to suppress the current shock and noise. In order to improve the efficiency of the WPT, reduce the static loss, and reduce the current oscillation loss on the power side, the input current ripple can be improved by two parallel phase-shifting methods. In this paper, two topological theories are analyzed, and the simulation and experiment results verify the correctness of these theories under both static and on-load conditions. After the final two-way phase-shift, 61.99% of the ripple is reduced. It provides a new approach for the design of WPT systems with PP structure.

4.5kV FRD Development for high current power modules

A 4.5kV/100A FRD was designed by simulation, which had optimized carrier density distribute cell and ruggedness terminal. The cell was composed of P-body/N-sub/N+ layers, when the P-body doping concentration is lower, the carrier density distribution on the P-body/N-sub is lower; when carrier density di stribution on the P-body/N-sub side is lower than that on the N-sub/N+ side, the FRD has soft recovery but bad surge-current capability. So the P-body doping concentration needs trade-off consideration. Lifetime control technology was also used to optimize the carrier density distribution and trade-off characteristics. The terminal has high breakdown voltage, low electric field and large process window, which means more ruggedness and high reliability. The experiment results show that the design chip and competitor chip has nearly the same trade-off characteristics, the design chip has larger dynamic loss but lower static loss. The design chip has high surge current, the surge current is 13 times as much as the rate current.

SIMULTANEOUS CALIBRATION TO A RANGE OF PORTFOLIO CREDIT DERIVATIVES WITH A DYNAMIC DISCRETE-TIME MULTI-STEP MARKOV LOSS MODEL

This article describes a dynamic discrete-time multi-step Markov model for the losses experienced by a given credit portfolio, and develops a method for the simultaneous calibration of the model to all available relevant market prices (for CDO's, forward-start CDO's, options on CDO's, leveraged super-senior tranches with loss triggers, etc.) established on a given day. The implementation is via an efficient linear programming procedure, and examples are given. The approach represents an extension of previous work (Walker, 2005, 2006; Torresetti et al., 2006) on the static loss-surface model to a model containing the necessary underlying dynamics.

Dynamics of Two-Line Ship Towing/Mooring Systems: Bifurcations, Singularities of Stability Boundaries, Chaos

A methodology is developed for analysis and design of two-line towing and mooring (TLT/M) systems based on their nonlinear, horizontal-plane, slow-motion dynamics. The time evolution of the corresponding autonomous dynamical system is described in a six-dimensional state space. Branching diagrams identify supercritical pitchfork bifurcations and turning points which result in static loss of stability. TLT/ Ms also exhibit Hopf bifurcations which result in dynamic loss of stability and periodic solutions. Stability charts are developed to show catastrophe sets and regions of qualitatively different dynamics. Thus, regions of hazardous dynamics and line breaking—such as unstable equilibrium, unstable limit cycle, and chaotic dynamics—are identified. Theoretical conclusions are verified by numerical simulations of tanker and barge TLT/Ms. Based on this methodology, only a limited number of simulations is needed for analysis and design of TLT/Ms. Lines can be selected then to complement—rather than countereach other and allow the system to attain a safe equilibrium.