Passive optical wind and turbulence detection system Patent

Passive optical wind and turbulence remote detection syste

Transport coefficients for the shear dynamo problem at small Reynolds numbers

We build on the formulation developed in Sridhar & Singh (JFM, 664, 265, 2010), and present a theory of the \emph{shear dynamo problem} for small magnetic and fluid Reynolds numbers, but for arbitrary values of the shear parameter. Specializing to the case of a mean magnetic field that is slowly varying in time, explicit expressions for the transport coefficients, $\alpha_{il}$ and $\eta_{iml}$, are derived. We prove that, when the velocity field is non helical, the transport coefficient $\alpha_{il}$ vanishes. We then consider forced, stochastic dynamics for the incompressible velocity field at low Reynolds number. An exact, explicit solution for the velocity field is derived, and the velocity spectrum tensor is calculated in terms of the Galilean--invariant forcing statistics. We consider forcing statistics that is non helical, isotropic and delta-correlated-in-time, and specialize to the case when the mean-field is a function only of the spatial coordinate $X_3$ and time $\tau\,$; this reduction is necessary for comparison with the numerical experiments of Brandenburg, R{\"a}dler, Rheinhardt & K\"apyl\"a (ApJ, 676, 740, 2008). Explicit expressions are derived for all four components of the magnetic diffusivity tensor, $\eta_{ij}(\tau)\,$. These are used to prove that the shear-current effect cannot be responsible for dynamo action at small \re and \rem, but for all values of the shear parameter.Comment: 27 pages, 5 figures, Published in Physical Review

Applications of remote sensing to stream discharge predictions

A feasibility study has been initiated on the use of remote earth observations for augmenting stream discharge prediction for the design and/or operation of major reservoir systems, pumping systems and irrigation systems. The near-term objectives are the interpolation of sparsely instrumented precipitation surveillance networks and the direct measurement of water loss by evaporation. The first steps of the study covered a survey of existing reservoir systems, stream discharge prediction methods, gage networks and the development of a self-adaptive variation of the Kentucky Watershed model, SNOPSET, that includes snowmelt. As a result of these studies, a special three channel scanner is being built for a small aircraft, which should provide snow, temperature and water vapor maps for the spatial and temporal interpolation of stream gages

Late growth stages and post-growth diffusion in organic epitaxy: PTCDA on Ag(111)

The late growth stages and the post-growth diffusion of crystalline organic thin films have been investigated for 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA) on Ag(111), a model system in organic epitaxy. In situ x-ray measurements at the anti-Bragg point during the growth show intensity oscillations followed by a time-independent intensity which is independent of the growth temperature. At T > 350 K, the intensity increases after growth up to a temperature-dependent saturation value due to a post-growth diffusion process. The time-independent intensity and the subsequent intensity recovery have been reproduced by models based on the morphology change as a function of the growth temperature. The morphology found after the post-growth diffusion processes has been studied by specular rod measurements.Comment: 9 pages, 8 figures, accepted for publication in Surface Scienc

Optical crossed-beam investigation of local sound generation in jets

Cross correlation of optical signals from two light beam sound detectors for jet noise source localizatio

Noise elimination by piecewise cross correlation of photometer outputs

A piecewise cross correlation technique has been developed to analyze the outputs of remote detection devices. The purpose of this technique is to eliminate the noise from optical background fluctuations, from transmission fluctuations and from detectors by calculating the instantaneous product of the detector output and a reference signal. Each noise component causes positive and negative oscillations of the instantaneous product and may thus be cancelled by an integration of the instantaneous product. The resultant product mean values will then contain the desired information on the spatial and temporal variation of emission, absorption and scattering processes in the atmosphere

Reservation Wages of First and Second Generation Migrants

This paper analyzes the reservation wages of first and second generation migrants. Based on recently collected and rich survey data of a representative inflow sample into unemployment in Germany, we empirically test the hypothesis that reservation wages increase from first to second generation migrants. Two extensions of the basic job search model, namely an unknown wage offer distribution and different reference standards, provide theoretical justifications for this conjecture. In both extensions, changing frames of reference are identified as a channel through which the phenomenon of increasing reservation wages may arise. In as far as language skills or self-evaluated returns to characteristics reflect a person's frames of reference, we find empirical support for this mechanism to be present.migration, ethnic identity, ethnosizer, Germany, unemployment, job search, reservation wages

Study of hot wire techniques in low density flows with high turbulence levels

Prediction of heat, mass, species, and momentum fluxes in a space vehicle and aerodynamic noise production by supersonic jet and rocket exhausts requires a predictability of the associated turbulence fields. The hot wire is a technique that will allow an experimental determination of turbulent properties

Economic Preferences and Attitudes of the Unemployed: Are Natives and Second Generation Migrants Alike?

In this paper we study the economic effects of risk attitudes, time preferences, trust and reciprocity while we compare natives and second generation migrants. We analyze an inflow sample into unemployment in Germany, and find differences between the two groups mainly in terms of risk attitudes and positive reciprocity. Second generation migrants have a significantly higher willingness to take risks and they are less likely to have a low amount of positive reciprocity when compared to natives. We also find that these differences matter in terms of economic outcomes, and more specifically in terms of the employment probability about two months after unemployment entry. We observe a significantly lower employment probability for individuals with a high willingness to take risks. Some evidence suggests that this result is channeled through reservation wages and search intensity.Unemployment, Migration, Personality Traits, Risk Attitudes, Time Preferences, Trust, Reciprocity