Solar power absorption in a glass tube

The optics of a glass tube to be used in near-Earth space at the focus of a solar concentrator has been examined, and an equation for the power absorbed from multiple-reflected light beams in the tube wall has been developed. The equation has been used to calculate the power absorbed by a highly transmissive form of fused silica. The equilibrium temperature reached by the tube with only radiative cooling has also been examined, and it shows a significant rise with large solar concentrations. The results apply specifically to cylindrical containment vessels for space-based solar-pumped lasers and generally to any similarly irradiated tubes

Dividends, stock repurchases and signaling: evidence from U.S. panel data

This paper exploits yearly accounting data from 1977 to 1994 to test the relative signaling power of dividends and net stock repurchases. The specification controls for potential agency cost and asset dissipation effects. Specifically, we regress changes in future income before extraordinary items on changes in dividends, changes in net stock repurchases, and a host of control variables. We also split the sample at 1981 to measure the impact of changes in the relative taxation of distribution methods. For the full twenty-year sample, only dividend changes are correlated with changes in future income. Moreover, the dividend coefficient and the repurchases coefficient differ statistically different in every future income equation. Splitting the sample reveals that the pre-1981 subsample drives the full-sample results. Put another way, the empirical link between changes in dividends and changes in future income vanishes just as a revision of the tax law reduced the tax disadvantage of dividend distributions. This evidence supports the notion that, at least for a period in time, firms deliberately exposed shareholders to punitive taxation to signal favorable prospects.Corporate governance

Wind Tunnel Analysis and Flight Test of a Wing Fence on a T-38

A low-speed wind tunnel study and flight tests were performed to examine the effects of a wing fence on the T-38A. Wind tunnel results were based upon force and moment data collected with a six-component balance and flow visualization at Reynolds numbers up to 0.3 x 106, based on mean aerodynamic chord. The model did not include the last 7.79 feet of the aircraft, and the engine and exhaust were modeled as through-holes. Five fence geometries, placed at wing station 125 (± 0.825 semispan), were compared. The best performer of these designs, based on drag polar, was the fence that wrapped the leading edge and extended 84.6 percent of the local chord length along the wing\u27s upper surface. Wind tunnel data showed that this fence increased the lift coefficient by up to 6.3 ± 0.6 percent and reduced spanwise and separated flow outboard the fence. The flight-tested fence was based on the best performing fence design from the wind tunnel study. The results were based on aircraft instrumentation and flow visualization at Reynolds numbers up to 9.98 x 106. It was inconclusive whether the fence caused an increase in lift coefficient. The fence reduced the roll-off tendency and wing rock during approaches to stall. Tuft visualization on the aircraft wing suggested that the fence reduced spanwise and separated flow outboard the fence, which agreed with the wind tunnel results

Age-related shifts in bacterial diversity in a reef coral

This study investigated the relationship between microbial communities in differently sized colonies of the massive coral Coelastrea aspera at Phuket, Thailand where colony size could be used as a proxy for age. Results indicated significant differences between the bacterial diversity (ANOSIM, R = 0.76, p = 0.001) of differently sized colonies from the same intertidal reef habitat. Juvenile and small colonies (28 cm mean diam). Bacterial diversity increased in a step-wise pattern from juvenilessmallmedium colonies, which was then followed by a slight decrease in the two largest size classes. These changes appear to resemble a successional process which occurs over time, similar to that observed in the ageing human gut. Furthermore, the dominant bacterial ribotypes present in the tissues of medium and large sized colonies of C. aspera, (such as Halomicronema, an Oscillospira and an unidentified cyanobacterium) were also the dominant ribotypes found within the endolithic algal band of the coral skeleton; a result providing some support for the hypothesis that the endolithic algae of corals may directly influence the bacterial community present in coral tissues.Barbara Brown recieved funding from the Leverhulme Trust [www.leverhulme.ac.uk]; Grant number: EM-2013-058. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript

Searching for Clean Observables in B−3˘eD∗/tau−νˉτB -\u3e D* /tau- \bar{\nu}_{\tau} Decays

In this thesis, the clean angular observables in the $\bar{B} \to D^{*+} \ell^- \bar{\nu}_{\ell}$ angular distribution is studied. Similar angular observables are widely studied in $B \to K^* \mu^+ \mu^-$ decays. We believed that these angular observables may have different sensitivities to different new physics structures