NONPARAMETRIC ESTIMATES OF OPTION PRICES AND RELATED QUANTITIES

We propose a new nonparametric technique to estimate the call function based on the superhedging principle. This approach requires minimal assumptions on absence of arbitrage and other market imperfections. The estimates so obtained are then combined with SNP estimates of the actual density of market returns. This permits to investigate the time behavior of the relative distance between the two densities obtained. Our empirical findings suggest that the more the two densities differ, the shorter is time to maturity, suggesting a major role of uncertainty over shorter than longer horizons.

Microstructure and Properties of Tungsten Copper Composite Material

The copper-tungsten system in the liquid and solid phase is completely immiscible. In this paper, the powder solid-phase sintering method was used to prepare the copper-tungsten composites of different compositions (CuxWy, x=63, 78, 84, 87, 90, 91, y=37, 22, 16, 13, 10, 9 (x+y=100)). By XRD and SEM analysis of the sample microstructure, the trend of the ratio of the conductivity, density and hardness of the samples with different ratio were determined. The results show that with the increasing tungsten content, the conductivity of the copper-tungsten composite increases, whereas the amplitude reduces. The actual density of the sample is smaller than its theoretical density. The more the tungsten content is, the smaller its hardness value.

Pseudo-Density Approach to the Solution of a Thin Rotating Turbine Engine Disk

This paper considers a rotating gas turbine engine disk. The governing equations lead to a non-linear, second order equation with thickness h as parameter. “Thin disk” assumption is made, implying plane stress conditions. In the present study, starting from the equations of equilibrium and compatibility, the author proposes the new approach of Pseudo Material Density. By introducing a pseudo material density, the problem is reduced to the Flat Disk Equation that can be solved easily. Introduction of pseudo density, however, throws up an additional equation — a fourth one — relating the pseudo density, actual density and the thickness parameter. The equation is solved to find the shape of the disk in terms of the actual density. This procedure allows modeling of the non-uniform profile disk as a disk with flat profile facilitating easier analysis. An unexpected, but important result that emerges from the present study pertains to the proof testing of rotating disks. It is shown that it is now possible to replace the external blade loading exactly with a radial extension of the disk itself.

Zero catch criteria for declaring eradication of tephritid fruit flies: the probabilities

We examine procedures for declaring an area free of pest fruit flies following an eradication campaign. To date, the acceptable period of trapping zero flies has been calculated without an estimate of the probability of being wrong. The zero trapping periods are usually shorter when declaring local ‘area freedom’ from an endemic fly, than when claiming eradication of an exotic species. We use a model to calculate the probability of zero trap captures and therefore the probability of trapping further flies. The latter probability is always finite. A zero trapping result does not indicate the absence of flies. There must also be evidence of what constitutes a non-viable density, as indicated by the trapping rate. The non-viable densities of certain pest fruit fly species are known from decades of managing small incursions in fly-free zones. There is no need for implementation of eradication procedures if the trapping rate is sufficiently low, in these areas. For a given density of flies (defined in terms of expected mean catch per trap per week), the probability of zero trap captures reduces with time and the number of traps employed. If the model calculations use a non-sustainable density (inferred from trapping rate) then we may declare the actual density of flies to be less if the trapping result is zero for a given number of weeks with a given number of traps when the model predicts the probability of such a result to be sufficiently low, according to a criterion that is selected at a level suited to the purpose of the declaration.

Double Sampling to Estimate Density and Population Trends in Birds

We present a method for estimating density of nesting birds based on double sampling. The approach involves surveying a large sample of plots using a rapid method such as uncorrected point counts, variable circular plot counts, or the recently suggested double-observer method. A subsample of those plots is also surveyed using intensive methods to determine actual density. The ratio of the mean count on those plots (using the rapid method) to the mean actual density (as determined by the intensive searches) is used to adjust results from the rapid method. The approach works well when results from the rapid method are highly correlated with actual density. We illustrate the method with three years of shorebird surveys from the tundra in northern Alaska. In the rapid method, surveyors covered ∼10 ha h–1 and surveyed each plot a single time. The intensive surveys involved three thorough searches, required ∼3 h ha–1, and took 20% of the study effort. Surveyors using the rapid method detected an average of 79% of birds present. That detection ratio was used to convert the index obtained in the rapid method into an essentially unbiased estimate of density. Trends estimated from several years of data would also be essentially unbiased. Other advantages of double sampling are that (1) the rapid method can be changed as new methods become available, (2) domains can be compared even if detection rates differ, (3) total population size can be estimated, and (4) valuable ancillary information (e.g. nest success) can be obtained on intensive plots with little additional effort. We suggest that double sampling be used to test the assumption that rapid methods, such as variable circular plot and double-observer methods, yield density estimates that are essentially unbiased. The feasibility of implementing double sampling in a range of habitats needs to be evaluated.

Random sequential packing in Euclidean spaces of dimensions three and four and a conjecture of Palásti

A conjecture of Palásti [11] that the limiting packing density β d in a space of dimension d equals β d where ß is the limiting packing density in one dimension continues to be studied, but with inconsistent results. Some recent correspondence in this journal [7], [8], [13], [14], [15], [16], [18], [19], [20] as well as some other papers indicate a lively interest in the subject. In a prior study [3], we demonstrated that the conjectured value in two dimensions was smaller than the actual density. Here we demonstrate that this is also so in three and four dimensions and that the discrepancy increases with dimension.