3,164 research outputs found
Telecommunications and data acquisition systems support for Voyager missions to Jupiter and Saturn, 1972-1981, prelaunch through Saturn encounter
The Deep Space Network has supported the Voyager Project for approximately nine years, during which time implementation, testing, and operational support was provided. Four years of this time involved testing prior to launch; the final five years included network operations support and additional network implementation. Intensive and critical support intervals included launch and four planetary encounters. The telecommunications and data acquisition support for the Voyager Missions to Jupiter and Saturn are summarized
Cost reductions in nickel-hydrogen battery
Significant progress was made toward the development of a commercially marketable hydrogen nickel oxide battery. The costs projected for this battery are remarkably low when one considers where the learning curve is for commercialization of this system. Further developmental efforts on this project are warranted as the H2/NiO battery is already cost competitive with other battery systems
The Future Of Master Limited Partnerships
Master limited partnerships have grown in size, number, and economic importance over the past fifteen years. They now represent a stable and healthy component of many investment portfolios. MLPs have generated impressive risk-adjusted performance compared to that of other equity investments. This performance is the result of their fee-based, low risk business structure that produces a steady cash distribution to investors. The future to these traditional MLPs and similar new entrants is quite positive. However, new entrants that potentially deviate from this successful operating structure are entering the MLP market. This raises major questions regarding the sustainability of these firms as MLPs. This study examines the future of MLP markets within the context of traditional and non-traditional new entrants. Furthermore, the emergence of institutional investors on MLP markets is discussed
User benefits and funding strategies
The justification, economic and technological benefits of NASA Space Programs (aside from pure scientific objectives), in improving the quality of life in the United States is discussed and outlined. Specifically, a three-step, systematic method is described for selecting relevant and highly beneficial payloads and instruments for the Interim Upper Stage (IUS) that will be used with the space shuttle until the space tug becomes available. Viable Government and private industry cost-sharing strategies which would maximize the number of IUS payloads, and the benefits obtainable under a limited NASA budget were also determined. Charts are shown which list the payload instruments, and their relevance in contributing to such areas as earth resources management, agriculture, weather forecasting, and many others
Exploratory development and services for preparing and examining ultrathin polished sections of lunar rocks and particulates, part 1
Development of improved procedures is reported for three classes of lunar materials: dense rocks, breccias, and particulates. High quality ultrathin sections of these materials are obtained. Lists of equipment and supplies, procedures, photomicrographic documentation, and training are provided. Advantages of ultrathin polished sections for conventional and unconventional optical microscopy methods are described. Recommendations are provided for use of ultrathin sections in lunar rock studies, for further refinement of ultrathinning procedures, and for additional training efforts to establish a capability at the Manned Space Center. For Part 2, See N72-50754
A Comprehensive Spectroscopic Analysis of DB White Dwarfs
We present a detailed analysis of 108 helium-line (DB) white dwarfs based on
model atmosphere fits to high signal-to-noise optical spectroscopy. We derive a
mean mass of 0.67 Mo for our sample, with a dispersion of only 0.09 Mo. White
dwarfs also showing hydrogen lines, the DBA stars, comprise 44% of our sample,
and their mass distribution appears similar to that of DB stars. As in our
previous investigation, we find no evidence for the existence of low-mass (M <
0.5 Mo) DB white dwarfs. We derive a luminosity function based on a subset of
DB white dwarfs identified in the Palomar-Green survey. We show that 20% of all
white dwarfs in the temperature range of interest are DB stars, although the
fraction drops to half this value above Teff ~ 20,000 K. We also show that the
persistence of DB stars with no hydrogen features at low temperatures is
difficult to reconcile with a scenario involving accretion from the
interstellar medium, often invoked to account for the observed hydrogen
abundances in DBA stars. We present evidence for the existence of two different
evolutionary channels that produce DB white dwarfs: the standard model where DA
stars are transformed into DB stars through the convective dilution of a thin
hydrogen layer, and a second channel where DB stars retain a helium-atmosphere
throughout their evolution. We finally demonstrate that the instability strip
of pulsating V777 Her white dwarfs contains no nonvariables, if the hydrogen
content of these stars is properly accounted for.Comment: 74 pages including 30 figures, accepted for publication in the
Astrophysical Journa
Multiwavelength Observations of the Hot DB Star PG 0112+104
We present a comprehensive multiwavelength analysis of the hot DB white dwarf
PG 0112+104. Our analysis relies on newly-acquired FUSE observations, on
medium-resolution FOS and GHRS data, on archival high-resolution GHRS
observations, on optical spectrophotometry both in the blue and around Halpha,
as well as on time-resolved photometry. From the optical data, we derive a
self-consistent effective temperature of 31,300+-500 K, a surface gravity of
log g = 7.8 +- 0.1 (M=0.52 Msun), and a hydrogen abundance of log N(H)/N(He) <
-4.0. The FUSE spectra reveal the presence of CII and CIII lines that
complement the previous detection of CII transitions with the GHRS. The
improved carbon abundance in this hot object is log N(C)/N(He) = -6.15 +- 0.23.
No photospheric features associated with other heavy elements are detected. We
reconsider the role of PG 0112+104 in the definition of the blue edge of the
V777 Her instability strip in light of our high-speed photometry, and contrast
our results with those of previous observations carried out at the McDonald
Observatory.Comment: 10 pages in emulateapj, 9 figures, accepted for publication in Ap
Teaching Sodium Fast Reactors in CEA
International audienceAmong the Fast Neutron Reactor Systems, the SFR has the most comprehensive technological basis as result of the experience gained from worldwide operation of several experimental, prototype, and commercial size reactors since the 1940s. This experience corresponds to about 402 years of operation by end of 2010. Six reactors are in operation BOR60, BN600 and BN800 in Russia, Joyo in Japan, FBTR in India and CEFR in China. One reactor is being commissioned PFBR (500MWe) in India and several projects are currently developed FBR1 and 2 in India, BN1200 in Russia, JSFR in Japan, PGSFR in Korea, CFR-600 in China and ASTRID in France. In order to support operation of existing reactors, design activities for new projects and decommissioning of old reactors, it is mandatory to develop skills, more particularly among the young generation, who will operate these new reactors. In addition, education and training is also essential to share the knowledge among the teams involved in Research and Development. Several strategies are developed at the national level, or within multilateral framework, like EU or IAEA to support development of Fast Reactors.In France, to answer to this increasing demand of Education and Training, four sessions are proposed, within the frame of INSTN (French National Institute for Nuclear Science and Technology)-SFR History, main options, design and operational feedback-SFR Functional analysis and design-SFR Safety and operation-SFR Sodium structures interactionsThe French Na School (ESML) provides since 1975 also several sessions dedicated to Na facilities design, safe operation, handling, and also decommissioning and sodium treatment. Beside courses, practical exercises are organized during each session. 10 different modules are available, ranging in length from 1 to 5 days. CEA contributes also to the organization of European Sessions dedicated to Sodium Fast Reactors, organized within the frame of the European Commission (CP-ESFR, ESNII+ , ESFR-SMART) This Education and Training strategy is a key element for the future of the development of Sodium Fast Reactors, and more particularly ASTRID project. CEA is ready to share training experience and to collaborate with other foreign Education and Training Entities
Characterizing stellar populations in spiral disks
It is now possible to measure detailed spectral indices for stellar
populations in spiral disks. We propose to interpret these data using
evolutionary synthesis models computed from the Star Formation Histories
obtained from chemical evolutionary models. We find that this technique is a
powerful tool to discriminate between old and young stellar populations. We
show an example of the power of Integral Field spectroscopy in unveiling the
spatial distribution of populations in a barred galaxy.Comment: 5 pages, to be published in "Science Perspectives for 3D
Spectroscopy", Eds. M. Kissler-Patig, M.M. Roth and J.R. Walsh
(Springer-Verlag, ESO astrophysics symposia series
Reaction of Cr + , Mn + , Fe + , Co + , and Ni + with O2 and N2O. Examination of the translational energy dependence of the cross sections of endothermic reactions
Reactions of Cr + , Mn + , Fe + , Co + , and Ni + with O2 and N2O to yield metal oxide ions are examined using an ion beam apparatus. Reaction cross sections sigma as a function of ion translational energy E are reported. With one exception, Fe + +N2O, the cross sections exhibit an energy threshold Eo. Several models are used to interpret the excitation functions for the O2 reactions and it is concluded that the classical line-of-centers form sigma alpha (1–Eo/E) is most useful. Bond energies derived in this manner are D°(CrO + ) = 3.45±0.1 eV, D°(MnO + ) = 2.48±0.1 eV, D°(FeO + ) = 3.01±0.1 eV, D°(CoO + ) = 2.76±0.1 eV, and D°(NiO + ) = 1.95±0.1 eV. Since these bond energies are all greater than D°(N2–O) = 1.7 eV, the observation of energy thresholds for the reactions with N2O are surprising. These results are explained in terms of a qualitative view of the electronic potential energy surfaces involved
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