Investigation of nickel hydrogen battery technology for the RADARSAT spacecraft

The low Earth orbit (LEO) operations of the RADARSAT spacecraft require high performance batteries to provide energy to the payload and platform during eclipse period. Nickel Hydrogen cells are currently competing with the more traditional Nickel Cadmium cells for high performance spacecraft applications at geostationary Earth orbit (GEO) and Leo. Nickel Hydrogen cells appear better suited for high power applications where high currents and high Depths of Discharge are required. Although a number of GEO missions have flown with Nickel Hydrogen batteries, it is not readily apparent that the LEO version of the Nickel Hydrogen cell is able to withstand the extended cycle lifetime (5 years) of the RADARSAT mission. The problems associated with Nickel Hydrogen cells are discussed in the contex of RADARSAT mission and a test program designed to characterize cell performance is presented

Photoluminescence-Based Current-Voltage Characterisation of Individual Subcells in Multi-Junction Devices

We demonstrate a photoluminescence based, contactless method to determine the current-voltage characteristics of the individual subcells in a multi-junction solar cell. The method, furthers known results for single junction devices and relies upon the reciprocity relation between the absorption and emission properties on a solar cell. Laser light with a suitable energy is used to excite carriers selectively in one junction and the internal voltages are deduced from the intensity of the resulting luminescence. The IV curves obtained this way on 1J, 2J and 6J devices are compared to those obtained using electroluminescence. Good agreement is obtained at high injection conditions while discrepancies at low injection are attributed to in-plane carrier transport

The solar flares of August 28 and 30, 1966

Observatory data correlation and evaluation on solar flares of Aug. 28 and 30, 196

Nb3Sn wire shape and cross sectional area inhomogeneity in Rutherford cables

During Rutherford cable production the wires are plastically deformed and their initially round shape is distorted. Using X-ray absorption tomography we have determined the 3D shape of an unreacted Nb3Sn 11 T dipole Rutherford cable, and of a reacted and impregnated Nb3Sn cable double stack. State-of-the-art image processing was applied to correct for tomographic artefacts caused by the large cable aspect ratio, for the segmentation of the individual wires and subelement bundles inside the wires, and for the calculation of the wire cross sectional area and shape variations. The 11 T dipole cable cross section oscillates by 2% with a frequency of 1.24 mm (1/80 of the transposition pitch length of the 40 wire cable). A comparatively stronger cross sectional area variation is observed in the individual wires at the thin edge of the keystoned cable where the wire aspect ratio is largest.Comment: 6 pages, 11 figures, presented at EUCAS 201

On rational delegations in liquid democracy

Liquid democracy is a proxy voting method where proxies are delegable. We propose and study a game-theoretic model of liquid democracy to address the following question: when is it rational for a voter to delegate her vote? We study the existence of pure-strategy Nash equilibria in this model, and how group accuracy is affected by them. We complement these theoretical results by means of agent-based simulations to study the effects of delegations on group's accuracy on variously structured social networks

On rational delegations in liquid democracy

Liquid democracy is a proxy voting method where proxies are delegable. We propose and study a game-theoretic model of liquid democracy to address the following question: when is it rational for a voter to delegate her vote? We study the existence of pure-strategy Nash equilibria in this model, and how group accuracy is affected by them. We complement these theoretical results by means of agent-based simulations to study the effects of delegations on group's accuracy on variously structured social networks

A Robust Strategy for Sustainable Energy

The known energy resource base is more than sufficient to provide a growing world population with energy on the scale to which the industrial countries have grown accustomed and to which the developing countries aspire. Environmental constraints exist but have promising solutions, provided farsighted policies are adopted in timely fashion. We illustrate the scale of the problem using a simple numerical scenario of world energy demand over the next century and calculating the implied increase in carbon emissions and atmospheric carbon concentrations. We conclude that action is needed soon to keep carbon concentrations below 500 parts per million as of 2050 and that the cost of mitigation will be less than 1 percent of gross world product as of 2050, assuming today’s promising technologies prove successful, but also that additional novel mitigation technologies will need to be developed and adopted after 2050.macroeconomics, Sustainable Energy

Radiation Rates for Low Z Impurities in Edge Plasmas

The role of impurity radiation in the reduction of heat loads on divertor plates in present experiments such as DIII-D, JET, JT-60, ASDEX, and Alcator C-Mod, and in planned experiments such as ITER and TPX places a new degree of importance on the accuracy of impurity radiation emission rates for electron temperatures below 250 eV for ITER and below 150 eV for present experiments. We have calculated the radiated power loss using a collisional radiative model for Be, B, C, Ne and Ar using a multiple configuration interaction model which includes density dependent effects, as well as a very detailed treatment of the energy levels and meta-stable levels. The "collisional radiative" effects are very important for Be at temperatures below 10 eV. The same effects are present for higher Z impurities, but not as strongly. For some of the lower Z elements, the new rates are about a factor of two lower than those from a widely used, simpler average-ion package (ADPAK) developed for high Z ions and for higher temperatures. Following the approach of Lengyel for the case where electron heat conduction is the dominant mechanism for heat transport along field lines, our analysis indicates that significant enhancements of the radiation losses above collisional radiative model rates due to such effects as rapid recycling and charge exchange recombination will be necessary for impurity radiation to reduce the peak heat loads on divertor plates for high heat flux experiments such as ITER.Comment: Preprint for the 11th PSI meeting, gzipped postscript with 11 figures, 14 page

Gold-Catalyzed Intramolecular Aminoarylation of Alkenes: C-C Bond Formation through Bimolecular Reductive Elimination

Gold-ilocks and the 3 mol % catalyst: Bimetallic gold bromides allow the room temperature aminoarylation of unactivated terminal olefins with aryl boronic acids using Selectfluor as an oxidant. A catalytic cycle involving gold(I)/gold(III) and a bimolecular reductive elimination for the key CC bond-forming step is proposed. dppm= bis(diphenylphosphanyl)methane

Detection of Damage in Operating Wind Turbines by Signature Distances

Wind turbines operate in the atmospheric boundary layer and are subject to complex random loading. This precludes using a deterministic response of healthy turbines as the baseline for identifying the effect of damage on the measured response of operating turbines. In the absence of such a deterministic response, the stochastic dynamic response of the tower to a shutdown maneuver is found to be affected distinctively by damage in contrast to wind. Such a dynamic response, however, cannot be established for the blades. As an alternative, the estimate of blade damage is sought through its effect on the third or fourth modal frequency, each found to be mostly unaffected by wind. To discern the effect of damage from the wind effect on these responses, a unified method of damage detection is introduced that accommodates different responses. In this method, the dynamic responses are transformed to surfaces via continuous wavelet transforms to accentuate the effect of wind or damage on the dynamic response. Regions of significant deviations between these surfaces are then isolated in their corresponding planes to capture the change signatures. The image distances between these change signatures are shown to produce consistent estimates of damage for both the tower and the blades in presence of varying wind field profiles