The influence of ground conductivity on the structure of RF radiation from return strokes

The combination of the finite conductivity of the Earth plus the propagation of the return stroke current up the channel which results in an apparent time delay between the fast field changes and RF radiation for distant observers is shown. The time delay predicted from model return strokes is on the order of 20 micro and the received signal has the characteristics of the data observed in Virginia and Florida. A piecewise linear model for the return stroke channel and a transmission line model for current propagation on each segment was used. Radiation from each segment is calculated over a flat Earth with finite conductivity using asymptotics approximations for the Sommerfeld integrals. The radiation at the observer is processed by a model AM radio receiver. The output voltage was calculated for several frequencies between HF-UHF assuming a system bandwidth (300 kHz) characteristic of the system used to collect data in Florida and Virginia. Comparison with the theoretical fast field changes indicates a time delay of 20 microns

Implementation of electrical energy by paired half-centers as revealed by structure and function

No Abstract.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/49961/1/901010207_ftp.pd

Semi-robust static Hedging of Barrier Options

We explore how to put the theory on static hedges of barrier options into use. We discuss a polynomial expansion of the exact static hedge in a stationary diffusion model provided by [9] and we develop an explicit expression of an asymptotic static hedge, which is constructed to perform well for short maturities. We derive a semi-robust static hedge in a sense, that it is model independent and depends upon one's beliefs about the future values of implied volatility only

The Importance of Mapping to the Next Generation Retinal Prosthesis

Evolutionarily, human beings have come to rely on vision more than any other sense, and with the prevalence of visual-oriented stimuli and the necessity of computers and visual media in everyday activities, this can be problematic. Therefore, the development of an accurate and fast retinal prosthesis to restore the lost portions of the visual field for those with specific types of vision loss is vital, but current methodologies are extremely limited in scope. All current models use a spatio-temporal filter (ST), which uses a difference of Gaussian (DOG) to mimic the inner layers of the retina and a noisy leak and fire integrate (NLIF) unit to simulate the optical ganglion. None of these processes show how these filters are mapped to each other, and therefore simulate the interaction of cells with each other in the retina. The mapping is key to having a fast and efficient filtering method; one that will allow for higher-resolution images with significantly less hardware, and therefore power requirements. The focus of this thesis was streamlining this process: the first major portion involved was applying a pipelining system to the 3D-ADoG, which showed some significant improvement over the design by Eckmiller. The major contribution was the mapping process: three mapping schemes were tried, and there was a significant difference found between them. While none of the models met the timing requirements, the ratios for speedups seen between the methods was significant. Evolutionarily, human beings have come to rely on vision more than any other sense, and with the prevalence of visual-oriented stimuli and the necessity of computers and visual media in everyday activities, this can be problematic. Therefore, the development of an accurate and fast retinal prosthesis to restore the lost portions of the visual field for those with specific types of vision loss is vital, but current methodologies are extremely limited in scope. All current models use a spatio-temporal filter (ST), which uses a difference of Gaussian (DOG) to mimic the inner layers of the retina and a noisy leak and fire integrate (NLIF) unit to simulate the optical ganglion. None of these processes show how these filters are mapped to each other, and therefore simulate the interaction of cells with each other in the retina. The mapping is key to having a fast and efficient filtering method; one that will allow for higher-resolution images with significantly less hardware, and therefore power requirements. The focus of this thesis was streamlining this process: the first major portion involved was applying a pipelining system to the 3D-ADoG, which showed some significant improvement over the design by Eckmiller. The major contribution was the mapping process: three mapping schemes were tried, and there was a significant difference found between them. While none of the models met the timing requirements, the ratios for speedups seen between the methods was significant. Despite the speedups and potential power savings, none of the other papers made specific mention of using any mapping schemes, nor how they improve both the speed and quality of the output images. The closest reference: a very vague reference to the amount of overlap as a tunable feature. Nevertheless, this is a key feature to developing the next generation prosthesis, and the manner in which the output from the ST filter bank is mapped seems to have a significant effect on speed, quality, and efficiency of the entire system as a whole