Bucket rotor wind-driven generator

As compared with the ordinary propeller type rotor, the bucket rotor is limited in rotational speed since the tip rotor speed can never exceed the wind speed. However, it does not present the blade fatigue problem that the ordinary rotor has, and it perhaps causes less sight pollution. The deflector vanes also provide a venturi passage to capture greater wind flow. The bucket rotors can be strung together end-to-end up to thousands of feet long to produce large amounts of power

Two-Wavelength Neodymium Based Lasers

A dual wavelength Q switched laser cavity has been successfully designed and assembled to evaluate the new neodymium (Nd) based materials. Initial characterization has been achieved for Nd:YAG and Nd:YLF. The results indicate that for a fixed pulse repetition frequency, the delay time can be used to adjust the relative energy between the 1.06 and 1.32 micrometer pulses. Any deficiency in the performance of one transition can be made up by performance in the other simply by changing the relative amount of time the population inversion is allowed to build up for each pulse. The best performance was obtained using a 13cm cavity length, the shortest possible cavity with the available equipment. The gain in the Nd:YLF 1.047 µm cavity was so high, the diffraction efficiency of the acoustooptic Q switch was insufficient to hold off lasing with a 5% output coupler. The transmission of the 1.047 micrometer output coupler used for dual wavelength operation of Nd:YLF was 30% whereas the transmission of the 1.06 micrometer output coupler necessary to achieve dual wavelength operation in Nd:YAG was 5%. At a pulse repetition frequency for each wavelength of 2kHz, and with 820mW of absorbed pump power, Nd:YLF produced pulse energies of 40±2 µJ and 15.3±0.6 µJ, and pulse lengths of 44±1 ns, and 410±10 ns at the wavelengths of 1.047 and 1.32 µm respectively. Nd:YAG produced pulse energies of 33±1 µJ and 27±1 µJ, and pulse widths of 32±0.4 ns and 183±1 ns at the wavelengths of 1.06 and 1.34 µm respectively. A separate set of dual wavelength data is also presented for Nd:YLF at 5.0kHz

Comparison of Forest Cover Prior To and Following Disturbance in Two Areas of the Great Smoky Mountains National Park

Prelogging forest cover and the nature and intensity of logging disturbance for two areas in the Great Smoky Mountains National Park were characterized using written records, photographs, interviews and, where available, virgin stands on similar sites. Present seral position and stand character were determined from fixed-area plots established on sties for which previous forest cover and intensity of disturbance had been determined. A low- to mid-elevation hardwood forest occupying a north-facing drainage on the Tennessee side of the Park was determined to have been mixed mesophytic in character prior to logging and was most intensively disturbed by skidder logging near drainage bottoms. succession reverted to early pioneer stages where logging was followed by gardening and where skidder damage was intensive, generally the most productive sites. Upper slope and higher-elevation sites were generally less disturbed and appear to be returning more rapidly to stable mid- to late-seral stages. Yellow-poplar was unusual among the species studied, in being one of the largest dominants in the original forests, while being the most aggressive pioneer on the best sites following intensive disturbance. In spruce-fir forests at upper elevations, spruce, although less tolerant than fir, was the dominant species in mixed, old-growth stands. This was due to the large size and longevity of spruce compared to the smaller size and shorter life span of fir. Logging disturbance appeared to favor spruce except on exposed sites and at higher elevation where climatic extremes favored fir

Likelihood Analysis of Cosmic Shear on Simulated and VIRMOS-DESCART Data

We present a maximum likelihood analysis of cosmological parameters from measurements of the aperture mass up to 35 arcmin, using simulated and real cosmic shear data. A four-dimensional parameter space is explored which examines the mean density \Omega_M, the mass power spectrum normalization \sigma_8, the shape parameter \Gamma and the redshift of the sources z_s. Constraints on \Omega_M and \sigma_8 (resp. \Gamma and z_s) are then given by marginalizing over \Gamma and z_s (resp. \Omega_M and \sigma_8). For a flat LCDM cosmologies, using a photometric redshift prior for the sources and \Gamma \in [0.1,0.4], we find \sigma_8=(0.57\pm0.04) \Omega_M^{(0.24\mp 0.18) \Omega_M-0.49} at the 68% confidence level (the error budget includes statistical noise, full cosmic variance and residual systematic). The estimate of \Gamma, marginalized over \Omega_M \in [0.1,0.4], \sigma_8 \in [0.7,1.3] and z_s constrained by photometric redshifts, gives \Gamma=0.25\pm 0.13 at 68% confidence. Adopting h=0.7, a flat universe, \Gamma=0.2 and \Omega_m=0.3 we find \sigma_8=0.98 \pm0.06 . Combined with CMB, our results suggest a non-zero cosmological constant and provide tight constraints on \Omega_M and \sigma_8. We finaly compare our results to the cluster abundance ones, and discuss the possible discrepancy with the latest determinations of the cluster method. In particular we point out the actual limitations of the mass power spectrum prediction in the non-linear regime, and the importance for its improvement.Comment: 11 pages, submitted to A&

The clustering properties of radio-selected AGN and star-forming galaxies up to redshifts z~3

We present the clustering properties of a complete sample of 968 radio sources detected at 1.4 GHz by the VLA-COSMOS survey with radio fluxes brighter than 0.15 mJy. 92% have redshift determinations from the Laigle et al. (2016) catalogue. Based on their radio-luminosity, these objects have been divided into two populations of 644 AGN and 247 star-forming galaxies. By fixing the slope of the auto-correlation function to gamma=2, we find r_0=11.7^{+1.0}_{-1.1} Mpc for the clustering length of the whole sample, while r_0=11.2^{+2.5}_{-3.3} Mpc and r_0=7.8^{+1.6}_{-2.1} Mpc (r_0=6.8^{+1.4}_{-1.8} Mpc if we restrict our analysis to z<0.9) are respectively obtained for AGN and star-forming galaxies. These values correspond to minimum masses for dark matter haloes of M_min=10^[13.6^{+0.3}_{-0.6}] M_sun for radio-selected AGN and M_min=10^[13.1^{+0.4}_{-1.6}] M_sun for radio-emitting star-forming galaxies (M_min=10^[12.7^{+0.7}_{-2.2}] M_sun for z<0.9). Comparisons with previous works imply an independence of the clustering properties of the AGN population with respect to both radio luminosity and redshift. We also investigate the relationship between dark and luminous matter in both populations. We obtain /M_halo/M_halo<~10^{-2.4} in the case of star-forming galaxies. Furthermore, if we restrict to z<~0.9 star-forming galaxies, we derive /M_halo<~10^{-2.1}, result which clearly indicates the cosmic process of stellar build-up as one moves towards the more local universe. Comparisons between the observed space density of radio-selected AGN and that of dark matter haloes shows that about one in two haloes is associated with a black hole in its radio-active phase. This suggests that the radio-active phase is a recurrent phenomenon.Comment: 11 pages, 7 figures, minor changes to match published version on MNRA