Tunable transmission and harmonic generation in nonlinear metamaterials

We study the properties of a tunable nonlinear metamaterial operating at microwave frequencies. We fabricate the nonlinear metamaterial composed of double split-ring resonators and wires where a varactor diode is introduced into each resonator so that the magnetic resonance can be tuned dynamically by varying the input power. We show that at higher powers the transmission of the metamaterial becomes power dependent, and we demonstrate experimentally power-dependent transmission properties and selective generation of higher harmonics.This work has been supported by the Australian Research Council through the Discovery projects, by the Australian Academy of Science through a travel grant, and by the Air Force Office of Scientific Research AFOSR through the MURI program Grant No. F49620-03-1-0420

Effect of Thermal Gradients on the Electromigration Lifetime in Power Electronics

The combined effects of electromigration and thermomigration are studied. Significantly shorter electromigration lifetimes are observed in the presence of a temperature gradient. This cannot be explained by thermomigration only, but is attributed to the effect of temperature gradient on electromigration-induced failures

Tunable transmission and harmonic generation in nonlinear metamaterials

We study the properties of a tunable nonlinear metamaterial operating at microwave frequencies. We fabricate the nonlinear metamaterial composed of double split-ring resonators and wires where a varactor diode is introduced into each resonator so that the magnetic resonance can be tuned dynamically by varying the input power. We show that at higher powers the transmission of the metamaterial becomes power dependent, and we demonstrate experimentally power-dependent transmission properties and selective generation of higher harmonics.Comment: 3 page

Wave scattering and splitting by magnetic metamaterials

We study experimentally propagation of electromagnetic waves through a slab of uniaxial magnetic metamaterial. We observe a range of novel phenomena including partial focusing and splitting into multiple transmitted beams.We demonstrate that while some of these experimentally observed effects can be described within the approximation of an effective medium, a deeper understanding of the experimental results requires a rigorous study of internal eigenmodes of the lattice of resonators

A low-bias simulation scheme for the SABR stochastic volatility model

The Stochastic Alpha Beta Rho Stochastic Volatility (SABR-SV) model is widely used in the financial industry for the pricing of fixed income instruments. In this paper we develop an lowbias simulation scheme for the SABR-SV model, which deals efficiently with (undesired) possible negative values, the martingale property of the discrete scheme and the discretization bias of commonly used Euler discretization schemes. The proposed algorithm is based the analytic properties of the governing distribution. Experiments with realistic model parameters show that this scheme is robust for interest rate valuation

Nonlinear magnetic metamaterials

We study experimentally nonlinear tunable magnetic metamaterials operating at microwave frequencies. We fabricate the nonlinear metamaterial composed of double split-ring resonators where a varactor diode is introduced into each resonator so that the magnetic resonance can be tuned dynamically by varying the input power. We demonstrate that at higher powers the transmission of the metamaterial becomes power-dependent and, as a result, such metamaterial can demonstrate various nonlinear properties. In particular, we study experimentally the power-dependent shift of the transmission band and demonstrate nonlinearity-induced enhancement (or suppression) of wave transmission

Extensible Component Based Architecture for FLASH, A Massively Parallel, Multiphysics Simulation Code

FLASH is a publicly available high performance application code which has evolved into a modular, extensible software system from a collection of unconnected legacy codes. FLASH has been successful because its capabilities have been driven by the needs of scientific applications, without compromising maintainability, performance, and usability. In its newest incarnation, FLASH3 consists of inter-operable modules that can be combined to generate different applications. The FLASH architecture allows arbitrarily many alternative implementations of its components to co-exist and interchange with each other, resulting in greater flexibility. Further, a simple and elegant mechanism exists for customization of code functionality without the need to modify the core implementation of the source. A built-in unit test framework providing verifiability, combined with a rigorous software maintenance process, allow the code to operate simultaneously in the dual mode of production and development. In this paper we describe the FLASH3 architecture, with emphasis on solutions to the more challenging conflicts arising from solver complexity, portable performance requirements, and legacy codes. We also include results from user surveys conducted in 2005 and 2007, which highlight the success of the code.Comment: 33 pages, 7 figures; revised paper submitted to Parallel Computin

Salmonella choleraesuis live vaccine strain suisaloral: molecular characterization and differentiation from homologous field isolates

The Salmonella enterica subsp. enterica (S.) live vaccine Suisaloral represents an auxotrophic mutant of a S. Choleraesuis strain which is deficient in adenine synthesis. Based on this auxotrophic marker, an adenine-deficient medium is used to identifY this vaccine strain by its inability to grow in this diagnostic medium. However, the widespread application of a Salmonella live vaccine strain requires additional methods that enable a reliable identification of the vaccine strain, its differentiation from field isolates of the same serovar as well as the proof of its genetic stability during animal and environmental passages. Since molecular methods have proven to be very useful tools for the characterization of Salmonella field isolates (Olsen et al. 1993) but also of other Salmonella enterica subsp. enterica (S.) live vaccine strains such as the S. Typhimurium vaccine strain Zoosaloral H (Schwarz & Liebisch 1994a,b) and the S. Dublin vaccine strain Bovisaloral (Liebisch & Schwarz 1996), four independent molecular methods were used to characterize the S. Choleraesuis live vaccine strain Suisaloral and to differentiate this live vaccine strain from homologous field isolates