Helmholtz solver with transparent influx boundary conditions and nonuniform exterior

Boundary conditions for a 2D finite element Helmholtz solver are derived, which allow scattered light to leave the calculation domain in the presence of outgoing waveguides. Influx of light, through a waveguide or otherwise, can be prescribed at any boundary

A combination of Dirichlet to Neumann operators and perfectly matched layers as boundary conditions for optical finite element simulations

By combining Dirichlet to Neumann (DtN) operators and Perfectly Matched Layers (PML’s) as boundary conditions on a rectangular domain on which the Helmholtz equation is solved, the disadvantages of both methods are greatly diminished. Due to the DtN operators, light may be accurately fluxed into the domain, while the PML’s absorb light that is reflected from the corners of the domain when only DtN boundaries are used

A Mixed Methods Approach to Identifying Administration Issues Pertinent in Interscholastic Sports

The purpose of this study was to investigate three propositions: a) What are the administration issues most pertinent to interscholastic sport today, as well as the next five years?, b) How important are those administration issues to athletic administrators?, and c) What are the potential implications of those pertinent administration issues to practicing athletic administrators? The literature provides a general overview of relevant issues surrounding interscholastic athletics. However, the importance and implications of relevant issues to practicing high school athletic administrators are difficult to discern. To answer the first proposition, the Minnesota State High School League (MSHSL) provided 10 contemporary administration issues that were most pertinent to interscholastic sport today, as well as the next five years. To answer the second proposition, a Likert-Scale was created so that practicing athletic administrators could rate each issue on a scale of 5 = extremely important to 1 = very little importance. A national study was conducted with athletic directors from the National Interscholastic Athletic Administrators Association (N = 170) annual conference. A one-tailed ANOVA was executed to determine significant differences among the 10 administration issues identified by the MSHSL. Four issues were found to be significant; Athletic Facilities, Athletic Training, Health Issues and Travel Teams. A Games-Howell post hoc was executed to determine significant differences across geographical regions of the United States. For the third proposition, semi-structured interviews were completed to provide insight on the implications for practicing athletic administrators. The results offer insight from which further investigations could be conducted to continue building on policies that influence interscholastic athletic administrators’ day-to-day accountability when overseeing their athletic programs

A Dispersive Treatment of Kℓ4K_{\ell4} Decays

$K_{\ell4}$ are for several reasons an especially interesting decay channel of $K$ mesons: $K_{\ell4}$ decays allow an accurate measurement of a combination of $S$-wave $\pi\pi$ scattering lengths, one form factor of the decay is connected to the chiral anomaly and the decay is the best source for the determination of some low energy constants of ChPT. We present a dispersive approach to $K_{\ell4}$ decays, which takes rescattering effects fully into account. Some fits to NA48/2 and E865 measurements and results of the matching to ChPT are shown.Comment: 4 pages, talk given by PS at MESON2012 - 12th International Workshop on Meson Production, Properties and Interaction, Krak\'ow, Poland, 31 May - 5 June 201

Adaptive Step Size for Hybrid Monte Carlo Algorithm

We implement an adaptive step size method for the Hybrid Monte Carlo a lgorithm. The adaptive step size is given by solving a symmetric error equation. An integr ator with such an adaptive step size is reversible. Although we observe appreciable variations of the step size, the overhead of the method exceeds its benefits. We propose an explanation for this phenomenon.Comment: 13 pages, 5 Postscript figures, late

Waveguiding properties of surface states in photonic crystals

We propose and analyze novel surface-state-based waveguides in bandgap photonic crystals. We discuss surface mode band structure, field localization and effect of imperfections on the waveguiding properties of the surface modes. We demonstrate that surface-state-based waveguides can be used to achieve directional emission out of the waveguide. We also discuss the application of the surface-state waveguides as efficient light couplers for conventional photonic crystal waveguides.Comment: 4 pages 5 figure

Endogenous Technological Change in Energy Systems Models: Synthesis of Experience with ERIS, MARKAL, and MESSAGE

Technological change is widely recognised as a key factor in economic progress, as it enhances the productivity of factor inputs. In recent years also the notion has developed that targeted technological development is a main means to reconcile economic ambitions with ecological considerations. This raises the issue that assessments of future trajectories of for example en-ergy systems should take into account context-specific technological progress. Rather than tak-ing characteristics of existing and emerging technologies as a given, their development should be a function of dedicated Research, Development and Demonstration (RD&D) and market de-ployment under varying external conditions. Endogenous technological learning has recently shown to be a very promising new feature in energy system models. A learning, or experience curve, describes the specific (investment) cost as a function of the cumulative capacity for a given technology. It reflects the fact that tech-nologies may experience declining costs as a result of its increasing adoption into the society due to the accumulation of knowledge through, among others, processes of learning-by-doing and learning-by-using. This report synthesises the results and findings from experiments with endogenous technologi-cal learning, as reported separately within the EU TEEM project. These experiments have been carried out by three TEEM partners using three models: ERIS (PSI), MARKAL (ECN and PSI), and MESSAGE (IIASA). The main objectives of this synthesis are: to derive common methodo-logical insights; to indicate and assess benefits of the new feature, but also its limitations and issues to solve; and to recommend further research to solve the main issues. This synthesis shows that all model applications are examples of successful first experiments to incorporate the learning-by-doing concept in energy system models. Incorporating the learning-by-doing concept makes an important difference. The experiments demonstrate and quantify the benefits of investing early in emerging technologies that are not competitive at the moment of their deployment. They also show that the long-term impact of policy instruments, such as CO2 taxes or emission limits and RD&D instruments, on technological development can be assessed adequately with models including technology learning. Adopting the concept of endogenous learning, several types of RD&D interventions can be addressed that aim at accelerating the market penetration of new technologies. The directions into which such interventions might lead have been illustrated in some of the experiments. However, quantitative relationships between R&D policy and learning data parameters are still unknow

Predicting atmospheric optical properties for radiative transfer computations using neural networks

The radiative transfer equations are well-known, but radiation parametrizations in atmospheric models are computationally expensive. A promising tool for accelerating parametrizations is the use of machine learning techniques. In this study, we develop a machine learning-based parametrization for the gaseous optical properties by training neural networks to emulate a modern radiation parameterization (RRTMGP). To minimize computational costs, we reduce the range of atmospheric conditions for which the neural networks are applicable and use machine-specific optimised BLAS functions to accelerate matrix computations. To generate training data, we use a set of randomly perturbed atmospheric profiles and calculate optical properties using RRTMGP. Predicted optical properties are highly accurate and the resulting radiative fluxes have average errors within \SI{0.5}{\flux} compared to RRTMGP. Our neural network-based gas optics parametrization is up to 4 times faster than RRTMGP, depending on the size of the neural networks. We further test the trade-off between speed and accuracy by training neural networks for the narrow range of atmospheric conditions of a single large-eddy simulation, so smaller and therefore faster networks can achieve a desired accuracy. We conclude that our machine learning-based parametrization can speed-up radiative transfer computations whilst retaining high accuracy.Comment: 13 pages,5 figures, submitted to Philosophical Transactions

Calculations on 2-dimensional waveguides in photonic crystals

Using 2 different numerical methods (FDTD and a novel pandirectional planar Helmholtz solver), we analyzed the waveguide behaviour of a channel in a 2-dimensional photonic crystal. We calculated the bandgap of the crystal and the dispersion of a waveguide that is formed by a missing row of rods in the crystal. The coupling to this waveguide of both a Gaussian beam and a dielectric slab waveguide could be modeled and coupling efficiencies calculate

Propagation of short lightpulses in microring resonators: ballistic transport versus interference in the frequency domain

The propagation of short lightpulses in waveguiding structures with optical feedback, in our case optical microresonators, has been studied theoretically and experimentally. It appears that, dependent on the measurement set-up, ballistic transport or interference in the time domain of fs and ps laser pulses can be observed. The experiments are analyzed in terms of characteristic time scales of the source, the waveguide device and the detector arrangement and are related to Heisenberg's uncertainty principle. Based on this analysis a criterion is given for the upper bitrate for error free data transmission through optical microresonators