Development and integration of the capillary pumped loop GAS and Hitchhiker flight experiments

The Capillary Pumped Loop (CPL) is a thermal control system with high density heat acquisition and transport capability. A small spaceflight version of the CPL was built and flown as a GAS experiment on STS 51-D in April 1985 and STS 51-G in June 1985, and as a Hitchhiker-G experiment on STS 61-C in January 1986. The purpose of the experiments was to demonstrate the capability of a capillary pumped system under microgravity conditions for use in the thermal control of large scientific instruments, advanced orbiting spacecraft, and space station components. The development, integration, and test activities of the CPL are described

OSS-1/contamination monitor

A 20-cm high, 18-cm wide, and 30-cm long (8x7x12 inch) box weighing about 7 kg (15 lbs) and consuming about 7 watts of power was carried on the OSS-1 pallet to monitor the mass build-up or accretion of condensible, volatile materials on surfaces in the shuttle bay during all phases of ascent, on-orbit, and descent. Passively thermally controlled, the box holds two witness samples and four actively temperature controlled quartz crystal microbalances (TQCM) whose temperature can vary from -60 C to +80 C. Graphs show the accretion indicated by the TQCM during the launch and early orbital phase. Conditions during tail to the Sun, nose to the Sun, and bay to the Sun attitudes of the shuttle during STS-3 are reflected in temperatures indicated by the OSS-1 thermistor. These temperatures influence outgassing rates of various materials as well as measurements made by the contamination monitor package. The parameters that bear on TQCM measurements data are shown in graphs and discussed

Characterisation and optimisation of PECVD SiNx as an antireflection coating and passivation layer for silicon solar cells

In this work, we investigate how the film properties of silicon nitride (SiNx) depend on its deposition conditions when formed by plasma enhanced chemical vapour deposition (PECVD). The examination is conducted with a Roth & Rau AK400 PECVD reactor, where the varied parameters are deposition temperature, pressure, gas flow ratio, total gas flow, microwave plasma power and radio-frequency bias voltage. The films are evaluated by Fourier transform infrared spectroscopy to determine structural properties, by spectrophotometry to determine optical properties, and by capacitance–voltage and photoconductance measurements to determine electronic properties. After reporting on the dependence of SiNx properties on deposition parameters, we determine the optimized deposition conditions that attain low absorption and low recombination. On the basis of SiNx growth models proposed in the literature and of our experimental results, we discuss how each process parameter affects the deposition rate and chemical bond density. We then focus on the effective surface recombination velocity S eff, which is of primary importance to solar cells. We find that for the SiNx prepared in this work, 1) S eff does not correlate universally with the bulk structural and optical properties such as chemical bond densities and refractive index, and 2) S eff depends primarily on the defect density at the SiNx-Si interface rather than the insulator charge. Finally, employing the optimized deposition condition, we achieve a relatively constant and low S eff,UL on low-resistivity (≤1.1 Ωcm) p- and n-type c-Si substrates over a broad range of n = 1.85–4.07. The results of this study demonstrate that the trade-off between optical transmission and surface passivation can be circumvented. Although we focus on photovoltaic applications, this study may be useful for any device for which it is desirable to maximize light transmission and surface passivation.This work was supported by an Australian Research Council Linkage between The Australian National University and Braggone Oy under Grant LP0989593

Effects of introduced trout predation on non-diadromous galaxiid fish populations across invaded riverscapes

Abstract We assessed the landscape-scale effect of predation pressure from trout on the population integrity and distributions of non-diadromous galaxiids in high-country streams of the South Island, New Zealand. The effects of trout (brown trout, Salmo trutta, and rainbow trout, Oncorhynchus mykiss) on two widespread species, the Canterbury galaxias (Galaxias vulgaris Stokell) and the alpine galaxias (G. paucispondylus Stokell) were assessed. Experiments confirmed that both species were vulnerable to trout predation and that habitat (size and disturbance regime) may be a factor in local co-occurrence. Quantitative electrofishing surveys indicated that G. paucispondylus distributions were less affected by trout than G. vulgaris distributions and that the species’ range was limited by temperature. Trout created demographic sinks for G. vulgaris across most invaded reaches, while refuge populations in streams above barriers to trout acted as demographic sources for this species. G. vulgaris was consistently absent from small, stable stream reaches far from sources, indicating that trout predation pressure and propagule pressure (driven by immigration from sources) interact to drive local G. vulgaris persistence in trout-invaded reaches. Predation pressure is likely to be highest in areas where infrequent flooding allows high densities of large trout (> 150 mm FL) to occur and where there are few refugia for galaxiids. A spatial model was developed to predict exclusion of galaxiids by trout across invaded networks. If used appropriately, the model could be used to find new refuge populations of non-diadromous galaxiids and to aid planning of active rehabilitation of trout-invaded river networks

On the nature of spectral line broadening in solar coronal dimmings

We analyze the profiles of iron emission lines observed in solar coronal dimmings associated with coronal mass ejections, using the EUV Imaging Spectrometer on board Hinode. We quantify line profile distortions with empirical coefficients (asymmetry and peakedness) that compare the fitted Gaussian to the data. We find that the apparent line broadenings reported in previous studies are likely to be caused by inhomogeneities of flow velocities along the line of sight, or at scales smaller than the resolution scale, or by velocity fluctuations during the exposure time. The increase in the amplitude of Alfv\'en waves cannot, alone, explain the observed features. A double-Gaussian fit of the line profiles shows that, both for dimmings and active region loops, one component is nearly at rest while the second component presents a larger Doppler shift than that derived from a single-Gaussian fit.Comment: 16 pages, 11 figures - Accepted for publication in Ap

Intertemporal Changes in the Riskiness of REITs

This study investigates the variability in the risk components of REITs over the 1973-1989 period using the cusum test, the cusum of squares test, and the Quandt's log-likelihood ratio method. Four REIT portfolios were formed: an all-REIT portfolio, an equity REIT portfolio, a hybrid REIT portfolio, and a mortgage REIT portfolio. The two-index model was employed and the results indicated that both the market beta and the interest-rate beta of the portfolios were time-varying. In addition, significant shifts in return-generating regimes over time were detected for all four portfolios.

A ground track control algorithm for the Topographic Mapping Laser Altimeter (TMLA)

The results of an analysis of an algorithm that will provide autonomous onboard orbit control using orbits determined with Global Positioning System (GPS) data. The algorithm uses the GPS data to (1) compute the ground track error relative to a fixed longitude grid, and (2) determine the altitude adjustment required to correct the longitude error. A program was written on a personal computer (PC) to test the concept for numerous altitudes and values of solar flux using a simplified orbit model including only the J sub 2 zonal harmonic and simple orbit decay computations. The algorithm was then implemented in a precision orbit propagation program having a full range of perturbations. The analysis showed that, even with all perturbations (including actual time histories of solar flux variation), the algorithm could effectively control the spacecraft ground track and yield more than 99 percent Earth coverage in the time required to complete one coverage cycle on the fixed grid (220 to 230 days depending on altitude and overlap allowance)