Diversity effects in long distance high frequency radio pulse propagation

1961 ◽  
Vol 65D (3) ◽  
pp. 213 ◽  
Author(s):  
S.A. Bowhill
Keyword(s):  
High Frequency ◽  
Pulse Propagation ◽  
Radio Pulse ◽  
Long Distance ◽  
Diversity Effects

Efficient simulation of unidirectional pulse propagation in high-contrast nonlinear nanowaveguides

2013 ◽  
Vol 2 (1) ◽  
Author(s):  
Jonathan Andreasen ◽  
Miroslav Kolesik
Keyword(s):  
Total Internal Reflection ◽  
Femtosecond Pulse ◽  
Transverse Direction ◽  
Pulse Propagation ◽  
Improved Method ◽  
Long Distance ◽  
Efficient Simulation ◽  
Index Contrast ◽  
Propagation Methods ◽  
Beam Propagation Methods

AbstractThis work demonstrates an improved method to simulate long-distance femtosecond pulse propagation in highcontrast nanowaveguides. Different from typical beam propagation methods, the foundational tool here is capable of simulating strong spatiotemporal waveform reshaping and extreme spectral dynamics. Meanwhile, the ability to fully capture effects due to index contrast in the transverse direction is retained, without requiring a decomposition of the electric field in terms of waveguide modes. These simulations can be computationally expensive, however, so cost is reduced in the improved method by considering only the waveguide core. Fields in the cladding are then properly accounted for through a boundary condition suitable for the case of total internal reflection.

scholarly journals Fast reconfiguration of high-frequency brain networks in response to surprising changes in auditory input

2012 ◽  
Vol 107 (5) ◽  
pp. 1421-1430 ◽  
Author(s):  
Ruth M. Nicol ◽  
Sandra C. Chapman ◽  
Petra E. Vértes ◽  
Pradeep J. Nathan ◽  
Marie L. Smith ◽  
...  
Keyword(s):  
High Frequency ◽  
Brain Networks ◽  
Small World ◽  
Brain Network ◽  
Auditory Presentation ◽  
Long Distance ◽  
Sensory Environment ◽  
Response Network ◽  
Rapid Changes ◽  
Measure Synchronization

How do human brain networks react to dynamic changes in the sensory environment? We measured rapid changes in brain network organization in response to brief, discrete, salient auditory stimuli. We estimated network topology and distance parameters in the immediate central response period, <1 s following auditory presentation of standard tones interspersed with occasional deviant tones in a mismatch-negativity (MMN) paradigm, using magnetoencephalography (MEG) to measure synchronization of high-frequency (gamma band; 33–64 Hz) oscillations in healthy volunteers. We found that global small-world parameters of the networks were conserved between the standard and deviant stimuli. However, surprising or unexpected auditory changes were associated with local changes in clustering of connections between temporal and frontal cortical areas and with increased interlobar, long-distance synchronization during the 120- to 250-ms epoch (coinciding with the MMN-evoked response). Network analysis of human MEG data can resolve fast local topological reconfiguration and more long-range synchronization of high-frequency networks as a systems-level representation of the brain's immediate response to salient stimuli in the dynamically changing sensory environment.

scholarly journals Development of superluminal pulse propagation in a serial array of high-Q ring resonators

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Yuma Morita ◽  
Makoto Tomita
Keyword(s):  
Pulse Propagation ◽  
Propagation Distance ◽  
Pulse Velocity ◽  
Ring Resonators ◽  
Saddle Point Method ◽  
Long Distance ◽  
Traditional Group ◽  
Gaussian Shape ◽  
High Q ◽  
Good Agreement

Abstract We experimentally examined the development of superluminal pulse propagation through a serial array of high-Q ring resonators that provides a dynamic recurrent loop. As the propagation distance, i.e., the number of ring resonators that the pulses passed through increased, the pulse advancement increased linearly, largely maintaining its Gaussian shape. The sharp edge encoded at the front of the pulse was, however, neither advanced nor delayed, in good accordance with the idea that information propagates at the speed of light. We also carried out a numerical simulation on the superluminal to subluminal transition of the pulse velocity, which appeared after the pulse had propagated a long distance. The time delays, which we calculated using the saddle point method and based on the net delay, were in good agreement with our results, even when predictions based on the traditional group delay failed completely. This demonstrates the superluminal to subluminal transition of the propagation velocity.

scholarly journals The Utility of Satellites and Autonomous Remote Sensing Platforms for Monitoring Offshore Aquaculture Farms: A Case Study for Canopy Forming Kelps

2020 ◽  
Vol 7 ◽  
Author(s):  
Tom W. Bell ◽  
Nick J. Nidzieko ◽  
David A. Siegel ◽  
Robert J. Miller ◽  
Kyle C. Cavanaugh ◽  
...  
Keyword(s):  
Remote Sensing ◽  
Optical Sensors ◽  
High Frequency ◽  
Autonomous Vehicles ◽  
Energy Demand ◽  
Spatial Scales ◽  
Long Distance ◽  
Decadal Scale ◽  
Canopy Area ◽  
Kelp Aquaculture

The emerging sector of offshore kelp aquaculture represents an opportunity to produce biofuel feedstock to help meet growing energy demand. Giant kelp represents an attractive aquaculture crop due to its rapid growth and production, however precision farming over large scales is required to make this crop economically viable. These demands necessitate high frequency monitoring to ensure outplant success, maximum production, and optimum quality of harvested biomass, while the long distance from shore and large necessary scales of production makes in person monitoring impractical. Remote sensing offers a practical monitoring solution and nascent imaging technologies could be leveraged to provide daily products of the kelp canopy and subsurface structures over unprecedented spatial scales. Here, we evaluate the efficacy of remote sensing from satellites and aerial and underwater autonomous vehicles as potential monitoring platforms for offshore kelp aquaculture farms. Decadal-scale analyses of the Southern California Bight showed that high offshore summertime cloud cover restricts the ability of satellite sensors to provide high frequency direct monitoring of these farms. By contrast, daily monitoring of offshore farms using sensors mounted to aerial and underwater drones seems promising. Small Unoccupied Aircraft Systems (sUAS) carrying lightweight optical sensors can provide estimates of canopy area, density, and tissue nitrogen content on the time and space scales necessary for observing changes in this highly dynamic species. Underwater color imagery can be rapidly classified using deep learning models to identify kelp outplants on a longline farm and high acoustic returns of kelp pneumatocysts from side scan sonar imagery signal an ability to monitor the subsurface development of kelp fronds. Current sensing technologies can be used to develop additional machine learning and spectral algorithms to monitor outplant health and canopy macromolecular content, however future developments in vehicle and infrastructure technologies are necessary to reduce costs and transcend operational limitations for continuous deployment in an offshore setting.

Key Issues on Train Line Planning for Beijing-Shanghai High Speed Railway

2010 ◽  
Author(s):  
L. Nie ◽  
D. B. Fei ◽  
S. D. Zhou ◽  
H. L. Fu ◽  
L. Tong
Keyword(s):  
High Frequency ◽  
High Speed ◽  
Travel Demand ◽  
Time Window ◽  
Long Distance ◽  
Line Planning ◽  
High Speed Railway ◽  
Passenger Flow ◽  
Train Operation ◽  
Service Plan

The Beijing-Shanghai High speed railway line (Hereinafter referred to as “Jing-Hu HSL”) is one of the most important railway lines in the Chinese rapid passenger transportation network and will be put into operation at the end of 2011. Train line planning directly reflects the quality and competition ability of train services. The characteristics of operational conditions and passenger flow of this corridor HSL bring about a few new issues on train line planning like night train operation, train OD sets, cyclic operation, and train stop schedule. For the first issue, a large amount of long distance travel demand put forward the demand for night services, which causes great conflict with the time-window for maintenance work. The confliction can be solved by harmoniously utilizing the parallel lines. For the second one, in view of the differences of technical and economic factors between HSL and conventional railways, high frequency and medium-long distance train will dominate HSL’s train service plan rather than low frequency and long distance trains on conventional railways. Thus, part of long-distance passenger flow has to transfer at some stations. Considering the whole possible ODs over Jing-Hu HSL and the transfer condition of related stations, the optimal OD sets and corresponding transfer plan is suggested. High frequency makes HSL possible to operate trains cyclically to improve service quality. However, with too many train ODs and some special trains, e.g. night train, an incomplete cyclic train operation mode is more practical. The ODs which can provide cyclic service for Jing-Hu HSL need to be identified. For the last issue, although non-stop long-distance train is a very popular kind of service in China, it should be reconsidered for Jing-Hu HSL line because of massive intercity travel demand and regular stops required. Each of the above issues is very complex. What is more, they have close relationship between each other. Due to limited space, the methods used to solve these issues are given in conceptual way rather than detailed description of mathematical model. The research paves the way for future integration study to design an efficient, economic, convenient, and regular train service plan for Jing-Hu HSL.

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