Computational Fluid Dynamics (cfd) Modeling of a Laboratory Scale Coal Gasifier

Furthering gasification technology is an essential part of advancing clean coal technologies. In order to seek insight into the appropriate operations for the formation of synthetic gas (syngas) a numerical simulation was performed to predict the phenomena of coal gasification in a laboratory scale entrained-flow coal gasifier. The mesh for the model was developed with ICEM CFD software and the chemical and physical phenomena were modeled using the fluid flow solver ANSYS FLUENT. Mesh independence was verified. The model was validated with experimental data from several studies performed on a laboratory scale gasifier. Systematic examination of the model was performed by varying primary and secondary inlet concentrations of steam and oxygen in regular intervals. Studies were also performed to investigate the effects of coal particle size and steam preheat temperatures. The effect of the turbulence model was also investigated by employing two turbulence models. Of the two turbulence models used the standard k-ε model showed the best agreement with experimental data. Model predictions found that increasing the steam concentration or preheat temperatures in the secondary inlet generally decreases production, while increasing and concentrations. Increasing the steam content in the secondary inlet showed no signifigants effects on predicted temperatures in the gasifier. Increasing the oxygen concentration in the primary inlet generally increases exit temperatures, , and production, while decreasing concentrations.It was found that decreasing the particle size increases the , , and concentration, while decreasing the concentrations

Dissipation characteristics of quantized spin waves in nano-scaled magnetic ring structures

The spatial profiles and the dissipation characteristics of spin-wave quasi-eigenmodes are investigated in small magnetic Ni$_{81}$Fe$_{19}$ ring structures using Brillouin light scattering microscopy. It is found, that the decay constant of a mode decreases with increasing mode frequency. Indications for a contribution of three-magnon processes to the dissipation of higher-order spin-wave quasi-eigenmodes are found

Mesenchymal Stem Cells and Inflammatory Cardiomyopathy: Cardiac Homing and Beyond

Under conventional heart failure therapy, inflammatory cardiomyopathy usually has a progressive course, merging for alternative interventional strategies. There is accumulating support for the application of cellular transplantation as a strategy to improve myocardial function. Mesenchymal stem cells (MSCs) have the advantage over other stem cells that they possess immunomodulatory features, making them attractive candidates for the treatment of inflammatory cardiomyopathy. Studies in experimental models of inflammatory cardiomyopathy have consistently demonstrated the potential of MSCs to reduce cardiac injury and to improve cardiac function. This paper gives an overview about how inflammation triggers the functionality of MSCs and how it induces cardiac homing. Finally, the potential of intravenous application of MSCs by inflammatory cardiomyopathy is discussed

Direct observation of domain wall structures in curved permalloy wires containing an antinotch

The formation and field response of head-to-head domain walls in curved permalloy wires, fabricated to contain a single antinotch, have been investigated using Lorentz microscopy. High spatial resolution maps of the vector induction distribution in domain walls close to the antinotch have been derived and compared with micromagnetic simulations. In wires of 10 nm thickness the walls are typically of a modified asymmetric transverse wall type. Their response to applied fields tangential to the wire at the antinotch location was studied. The way the wall structure changes depends on whether the field moves the wall away from or further into the notch. Higher fields are needed and much more distorted wall structures are observed in the latter case, indicating that the antinotch acts as an energy barrier for the domain wal

Spin-wave propagation in a microstructured magnonic crystal

Transmission of microwave spin waves through a microstructured magnonic crystal in the form of a permalloy waveguide of a periodically varying width was studied experimentally and theoretically. The spin wave characteristics were measured by spatially-resolved Brillouin light scattering microscopy. A rejection frequency band was clearly observed. The band gap frequency was controlled by the applied magnetic field. The measured spin-wave intensity as a function of frequency and propagation distance is in good agreement with a model calculation.Comment: 4 pages, 3 figure

Optics in Curved Space

We experimentally study the impact of intrinsic and extrinsic curvature of space on the evolution of light. We show that the topology of a surface matters for radii of curvature comparable with the wavelength, whereas for macroscopically curved surfaces only intrinsic curvature is relevant. On a surface with constant positive Gaussian curvature we observe periodic refocusing, self-imaging, and diffractionless propagation. In contrast, light spreads exponentially on surfaces with constant negative Gaussian curvature. For the first time we realized two beam interference in negatively curved space

Direct current control of three magnon scattering processes in spin-valve nanocontacts

We have investigated the generation of spin waves in the free layer of an extended spin-valve structure with a nano-scaled point contact driven by both microwave and direct electric current using Brillouin light scattering microscopy. Simultaneously with the directly excited spin waves, strong nonlinear effects are observed, namely the generation of eigenmodes with integer multiple frequencies (2 \emph{f}, 3 \emph{f}, 4 \emph{f}) and modes with non-integer factors (0.5 \emph{f}, 1.5 \emph{f}) with respect to the excitation frequency \emph{f}. The origin of these nonlinear modes is traced back to three magnon scattering processes. The direct current influence on the generation of the fundamental mode at frequency \emph{f} can be related to the spin-transfer torque, while the efficiency of three-magnon-scattering processes is controlled by the Oersted field as an additional effect of the direct current