Weak turbulence theory of the non-linear evolution of the ion ring distribution

The nonlinear evolution of an ion ring instability in a low-beta magnetospheric plasma is considered. The evolution of the two-dimensional ring distribution is essentially quasilinear. Ignoring nonlinear processes the time-scale for the quasilinear evolution is the same as for the linear instability 1/t_ql gamma_l. However, when nonlinear processes become important, a new time scale becomes relevant to the wave saturation mechanism. Induced nonlinear scattering of the lower-hybrid waves by plasma electrons is the dominant nonlinearity relevant for plasmas in the inner magnetosphere and typically occurs on the timescale 1/t_ql w(M/m)W/nT, where W is the wave energy density, nT is the thermal energy density of the background plasma, and M/m is the ion to electron mass ratio, which has the consequence that the wave amplitude saturates at a low level, and the timescale for quasilinear relaxation is extended by orders of magnitude

Plasticity in current-driven vortex lattices

We present a theoretical analysis of recent experiments on current-driven vortex dynamics in the Corbino disk geometry. This geometry introduces controlled spatial gradients in the driving force and allows the study of the onset of plasticity and tearing in clean vortex lattices. We describe plastic slip in terms of the stress-driven unbinding of dislocation pairs, which in turn contribute to the relaxation of the shear, yielding a nonlinear response. The steady state density of free dislocations induced by the applied stress is calculated as a function of the applied current and temperature. A criterion for the onset of plasticity at a radial location $r$ in the disk yields a temperature-dependent critical current that is in qualitative agreement with experiments.Comment: 11 pages, 4 figure

Oscillatory dynamics of a superconductor vortex lattice in high amplitude ac magnetic fields

In this work we study by ac susceptibility measurements the evolution of the solid vortex lattice mobility under oscillating forces. Previous work had already shown that in YBCO single crystals, below the melting transition, a temporarily symmetric magnetic ac field (e.g. sinusoidal, square, triangular) can heal the vortex lattice (VL) and increase its mobility, but a temporarily asymmetric one (e.g. sawtooth) of the same amplitude can tear the lattice into a more pinned disordered state. In this work we present evidence that the mobility of the VL is reduced for large vortex displacements, in agreement with predictions of recent simulations. We show that with large symmetric oscillating fields both an initially ordered or an initially disordered VL configuration evolve towards a less mobile lattice, supporting the scenario of plastic flow.Comment: 5 pages, 4 figures. To appear in Phys. Rev.

Survey of Effectiveness of Transportation Services

With increased emphasis on public accountability and program evaluation, the need for effectiveness measures to indicate the extent to which an agency\u27s goals and objectives are being met is increasingly apparent. A research study was undertaken to establish and implement a procedure for monitoring the effectiveness of transportation services in Kentucky. Quantitative data for many of the effectiveness measures were obtainable only through responses from the public. Surveys of licensed drivers and bus riders were selected as data sources. This report addresses the procedures and results of the two surveys. Responses were received from 35.5 percent of the 10,000 licensed drivers who were sent questionnaires and 26.0 percent of the 4,560 bus riders. Results from the surveys were summarized into the following areas: (l) survey response, (2) personal information, (3) satisfaction with transportation services, (4) inadequate transportation services, (5) drivers\u27 complaints and compliments, (6) future government spending for transportation, (7) problems getting to various destinations, (8) use of other modes of transportation, (9) opinions on laws or government regulations, and (10) bus rider survey

Problem Identification for Highway Safety Plan (FY 1983)

An annual highway safety program is proposed each year for the State of Kentucky in order to comply with Section 402, Title 23 of the United States code. This program includes the identification, programming, budgeting, and evaluation of safety projects. This report is the fourth in a series of annual reports which have been included as the problem identification portion of Kentucky\u27s Annual Highway Safety Plan. The approach used in this study involved identifying problem areas related to the 18 highway safety program standards with added emphasis placed on selected areas. This resulted in the analysis of 19 problem identification areas. Recommendations were made for programs which could serve as countermeasures for the highway safety problems identified and for studies to develop and evaluate such programs

Problem Identification for Highway Safety Plan

To comply with Section 402, Title 23 of the United States Code, each state is required to prepare an annual highway safety program. Kentucky\u27s program, which includes identification, programming, budgeting, and evaluation of highway safety projects, is intended to have a positive impact on the reduction of traffic accidents. The first step in the program, problem identification, requires systematic, statistical analyses of accident records. In-depth analyses of accident data were performed, and 29 problem areas were investigated. Accident rates were found for counties and cities in the following categories: total accidents; fatal accidents; accidents by driver age and sex; and speed-, alcohol-, and drug-related accidents. In addition, rates were reported for accidents involving pedestrians, bicycles, motorcycles, school buses, commercial buses, combination trucks, single-unit trucks, railroad trains, and emergency vehicles. This is the second report on problem identification prepared for the Office of Highway Safety Programs. Last year\u27s problem identification analysis was included in its entirety in Kentucky\u27s Annual Highway Safety Plan for Fiscal Year 1980

Safety Improvement Program for Toll Roads

This report presents proposed safety improvements for Kentucky\u27s toll roads. The primary methods of identifying needed improvements were an accident analysis and a field inventory. The accident analysis identified specific high-accident spots and sections. Also, accident rates were calculated for each toll road, and the types of accidents which had occurred in the 3-year period were summarized. A separate 10-year analysis of fatal accidents was made. The field inventory was used to identify roadway features which are now substandard and in need of upgrading. Also, high-accident spots and sections were investigated in the field. The benefits and costs for each improvement were estimated and used as input into a dynamic programming model used as a means of priority ranking the improvements. A total of 42 improvement alternatives were included in the analysis at an estimated cost of $58.5 million. Those alternatives with benefit-cost ratios greater than 1.0 totaled only$8.7 million