Heavy-tailed Distributions In Stochastic Dynamical Models

Heavy-tailed distributions are found throughout many naturally occurring phenomena. We have reviewed the models of stochastic dynamics that lead to heavy-tailed distributions (and power law distributions, in particular) including the multiplicative noise models, the models subjected to the Degree-Mass-Action principle (the generalized preferential attachment principle), the intermittent behavior occurring in complex physical systems near a bifurcation point, queuing systems, and the models of Self-organized criticality. Heavy-tailed distributions appear in them as the emergent phenomena sensitive for coupling rules essential for the entire dynamics

Labor Supply Effects of Social Insurance

This chapter examines the labor supply effects of social insurance programs. We argue that this topic deserves separate treatment from the rest of the labor supply literature because individuals may be imperfectly informed as to the rules of the programs and because key parameters are likely to differ for those who are eligible for social insurance programs, such as the disabled. Furthermore, differences in social insurance programs often provide natural experiments with exogenous changes in wages or incomes that can be used to estimate labor supply responses. Finally, social insurance often affects different margins of labor supply. For example, the labor supply literature deals mostly with adjustments in the number of hours worked, whereas the incentives of social insurance programs frequently affect the decision of whether to work at all. The empirical work on unemployment insurance (UI) and workers' compensation (WC) insurance finds that the programs tend to increase the length of time employees spend out of work. Most of the estimates of the elasticities of lost work time that incorporate both the incidence and duration of claims are close to 1.0 for unemployment insurance and between 0.5 and 1.0 for workers' compensation. These elasticities are substantially larger than the labor supply elasticities typically found for men in studies of the effects of wages or taxes on hours of work. The evidence on disability insurance and (especially) social security retirement suggests much smaller and less conclusively established labor supply effects. Part of the explanation for this difference probably lies in the fact that UI and WC lead to short-run variation in wages with mostly a substitution effect. Our review suggest that it would be misleading to apply a universal set of labor supply elasticities to these diverse problems and populations.

Small World Graphs by the iterated "My Friends are Your Friends'' Principle

We study graphs obtained by successive creation and destruction of edges into small neighborhoods of the vertices. Starting with a circle graph of large diameter we obtain small world graphs with logarithmic diameter, high clustering coefficients and a fat tail distribution for the degree. Only local edge formation processes are involved and no preferential attachment was used. Furthermore we found an interesting phase transition with respect to the initial conditions.Comment: Latex, 12 pages with 10 figure

Coupled Cluster Treatment of the XY model

We study quantum spin systems in the 1D, 2D square and 3D cubic lattices with nearest-neighbour XY exchange. We use the coupled-cluster method (CCM) to calculate the ground-state energy, the T=0 sublattice magnetisation and the excited state energies, all as functions of the anisotropy parameter $\gamma$. We consider $S=1/2$ in detail and give some results for higher $S$. In 1D these results are compared with the exact $S=1/2$ results and in 2D with Monte-Carlo and series expansions. We obtain critical points close to the expected value $\gamma=0$ and our extrapolated LSUBn results for the ground-state energy are well converged for all $\gamma$ except very close to the critical point.Comment: 11 pages, Latex, 4 postscript figure, accepted by J.Phys.: Condens. Matte

"Valuing the Visual Disamenity of Offshore Wind Projects at Varying Distances from the Shore: An Application on the Delaware Shoreline"

Several offshore wind power projects are under consideration in the United States. A concern with any wind power project is the visual disamenity it may create. Using a stated preference choice model, we estimated the external costs to residents of the State of Delaware for offshore wind turbines located at different distances from the coast. The annual costs to inland residents was $19,$9, $1, and$0 (2006$) for turbines located at 1, 3.6, 6, and 9 miles offshore. The cost to residents living on the ocean was$80, $69,$35, and $27 for the same increments.Windfarms, View Disamenity, Valuation

Influence of a solar proton event on stratospheric ozone

Ozone depletion in the stratosphere associated with the solar proton event of August 4, 1972, was observed with the backscattered ultraviolet experiment on the Nimbus 4 satellite. An abrupt ozone decrease in the 75-80 deg N zone of about 0.002 atm-cm above 4 mb was observed to persist throughout the month of August. A decrease was noted in the 55-65 deg N zone on days 219 and 220, but recovery occurred on day 221. Thereafter, a more gradual decrease was observed. The equatorial zone also showed gradual decrease after day 218, but these were not uniquely distinguished from seasonal variations. The observed change in total ozone following the event was -0.003 atm-cm for the 75-80 deg N zone, corresponding to a 1.3 percent reduction in the 0.305 atm-cm zonal average, but within the 0.019 atm-cm standard deviation. Above the 10 mb surface in the 75-80 deg N zone however, a decrease of 0.004 atm-cm may be compared with a standard deviation of 0.001 atm-cm

Cumulative sum techniques

Call number: LD2668 .R4 1967 K7

Evaluation of WRF-Sfire Performance with Field Observations from the FireFlux experiment

This study uses in-situ measurements collected during the FireFlux field experiment to evaluate and improve the performance of coupled atmosphere-fire model WRF-Sfire. The simulation by WRF-Sfire of the experimental burn shows that WRF-Sfire is capable of providing realistic head fire rate-of-spread and the vertical temperature structure of the fire plume, and, up to 10 m above ground level, fire-induced surface flow and vertical velocities within the plume. The model captured the changes in wind speed and direction before, during, and after fire front passage, along with arrival times of wind speed, temperature, and updraft maximae, at the two instrumented flux towers used in FireFlux. The model overestimated vertical velocities and underestimated horizontal wind speeds measured at tower heights above the 10 m, and it is hypothesized that the limited model resolution over estimated the fire front depth, leading to too high a heat release and, subsequently, too strong an updraft. However, on the whole, WRF-Sfire fire plume behavior is consistent with the interpretation of FireFlux observations. The study suggests optimal experimental pre-planning, design, and execution of future field campaigns that are needed for further coupled atmosphere-fire model development and evaluation

Total ozone changes in the 1987 Antarctic ozone hole

The development of the Antarctic ozone minimum was observed in 1987 with the Nimbus 7 Total Ozone Mapping Spectrometer (TOMS) instrument. In the first half of August the near-polar (60 and 70 deg S) ozone levels were similar to those of recent years. By September, however, the ozone at 70 and 80 deg S was clearly lower than any previous year including 1985, the prior record low year. The levels continued to decrease throughout September until October 5 when a new record low of 109 DU was established at a point near the South Pole. This value is 29 DU less than the lowest observed in 1985 and 48 DU less than the 1986 low. The zonal mean total ozone at 60 deg S remained constant throughout the time of ozone hole formation. The ozone decline was punctuated by local minima formed away from the polar night boundary at about 75 deg S. The first of these, on August 15 to 17, formed just east of the Palmer Peninsula and appears to be a mountain wave. The second major minimum formed on September 5 to 7 again downwind of the Palmer Peninsula. This event was larger in scale than the August minimum and initiated the decline of ozone across the polar region. The 1987 ozone hole was nearly circular and pole centered for its entire life. In previous years the hole was perturbed by intrusions of the circumpolar maximum into the polar regions, thus causing the hole to be elliptical. The 1987 hole also remained in place until the end of November, a few days longer than in 1985, and this persistence resulted in the latest time for recovery to normal values yet observed