61,469 research outputs found
Economic implications of current systems
The primary goals of this study are to estimate the value of R&D to photovoltaic (PV) metallization systems cost, and to provide a method for selecting an optimal metallization method for any given PV system. The value-added cost and relative electrical performance of 25 state-of-the-art (SOA) and advanced metallization system techniques are compared
Solar water heating system for a lunar base
An investigation of the feasibility of using a solar water heater for a lunar base is described. During the investigation, computer codes were developed to model the lunar base configuration, lunar orbit, and heating systems. Numerous collector geometries, orientation variations, and system options were identified and analyzed. The results indicate that the recommended solar water heater could provide 88 percent of the design load and would not require changes in the overall lunar base design. The system would give a 'safe-haven' water heating capability and use only 7 percent to 10 percent as much electricity as an electric heating system. As a result, a fixed position photovoltaic array can be reduced by 21 sq m
Identification of a high-velocity compact nebular filament 2.2 arcsec south of the Galactic Centre
The central parsec of the Milky Way is a very special region of our Galaxy;
it contains the supermassive black hole associated with Sgr A* as well as a
significant number of early-type stars and a complex structure of streamers of
neutral and ionized gas, within two parsecs from the centre, representing a
unique laboratory. We report the identification of a high velocity compact
nebular filament 2.2 arcsec south of Sgr A*. The structure extends over ~1
arcsec and presents a strong velocity gradient of ~200 km s^{-1} arcsec^{-1}.
The peak of maximum emission, seen in [Fe III] and He I lines, is located at
d{\alpha} = +0.20 +/- 0.06 arcsec and d{\delta} = -2.20 +/- 0.06 arcsec with
respect to Sgr A*. This position is near the star IRS 33N. The velocity at the
emission peak is Vr = -267 km s^{-1}. The filament has a position angle of PA =
115{\degr} +/- 10{\degr}, similar to that of the Bar and of the Eastern Arm at
that position. The peak position is located 0.7 arcsec north of the binary
X-ray and radio transient CXOGX J174540.0-290031, a low-mass X-ray binary with
an orbital period of 7.9 hr. The [Fe III] line emission is strong in the
filament and its vicinity. These lines are probably produced by shock heating
but we cannot exclude some X-ray photoionization from the low-mass X-ray
binary. Although we cannot rule out the idea of a compact nebular jet, we
interpret this filament as a possible shock between the Northern and the
Eastern Arm or between the Northern Arm and the mini-spiral "Bar".Comment: 7 pages, 4 figures, published online in MNRA
Standard environmental testing practices
Manual on procedural requirements for performing certain environmental tests on space flight equipment provides information for test equipment designers, quality control and production engineers. Contents of manual are summarized
A self-consistent Hartree-Fock approach for interacting bosons in optical lattices
A theoretical study of interacting bosons in a periodic optical lattice is
presented. Instead of the commonly used tight-binding approach (applicable near
the Mott insulating regime of the phase diagram), the present work starts from
the exact single-particle states of bosons in a cubic optical lattice,
satisfying the Mathieu equation, an approach that can be particularly useful at
large boson fillings. The effects of short-range interactions are incorporated
using a self-consistent Hartree-Fock approximation, and predictions for
experimental observables such as the superfluid transition temperature,
condensate fraction, and boson momentum distribution are presented.Comment: 12 pages, 15 figure file
Elusive Codes in Hamming Graphs
We consider a code to be a subset of the vertex set of a Hamming graph. We
examine elusive pairs, code-group pairs where the code is not determined by
knowledge of its set of neighbours. We construct a new infinite family of
elusive pairs, where the group in question acts transitively on the set of
neighbours of the code. In our examples, we find that the alphabet size always
divides the length of the code, and prove that there is no elusive pair for the
smallest set of parameters for which this is not the case. We also pose several
questions regarding elusive pairs
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