62,343 research outputs found
On-board processing concepts for future satellite communications systems
The initial definition of on-board processing for an advanced satellite communications system to service domestic markets in the 1990's is discussed. An exemplar system with both RF on-board switching and demodulation/remodulation baseband processing is used to identify important issues related to system implementation, cost, and technology development. Analyses of spectrum-efficient modulation, coding, and system control techniques are summarized. Implementations for an RF switch and baseband processor are described. Among the major conclusions listed is the need for high gain satellites capable of handling tens of simultaneous beams for the efficient reuse of the 2.5 GHz 30/20 frequency band. Several scanning beams are recommended in addition to the fixed beams. Low power solid state 20 GHz GaAs FET power amplifiers in the 5W range and a general purpose digital baseband processor with gigahertz logic speeds and megabits of memory are also recommended
Database Analysis to Support Nutrient Criteria Development (Phase I)
The intent of this publication of the Arkansas Water Resources Center is to provide a location whereby a final report on water research to a funding agency can be archived. The Texas Commission on Environmental Quality (TCEQ) contracted with University of Arkansas researchers for a multiple year project titled “Database Analysis to Support Nutrient Criteria Development”. This publication covers the first of three phases of that project and has maintained the original format of the report as submitted to TCEQ. This report can be cited either as an AWRC publication (see below) or directly as the final report to TCEQ
Database Analysis to Support Nutrient Criteria Development (Phase II)
The intent of this publication of the Arkansas Water Resources Center is to provide a location whereby a final report on water research to a funding agency can be archived. The Texas Commission on Environmental Quality (TCEQ) contracted with University of Arkansas researchers for a multiple year project titled “Database Analysis to Support Nutrient Criteria Development”. This publication covers the second of three phases of that project and has maintained the original format of the report as submitted to TCEQ. This report can be cited either as an AWRC publication (see below) or directly as the final report to TCEQ
Crystal growth in fused solvent systems
The successful nucleation of bismuth germanate, B12GeO20 on a high quality seed and the growth of regions of single crystals of the same orientation of the seed are reported. Lead germanate, Pb5Ge3O11 was also identified as a ferroelectric crystal with large electrooptic and nonlinear optic constants. Solvent criteria, solvent/development, and crystal growth are discussed, and recommendations for future studies are included
Singular Schrodinger operators in one dimension
We consider a class of singular Schr\"odinger operators that act in
, each of which is constructed from a positive function
on . Our analysis is direct and elementary. In particular it does
not mention the potential directly or make any assumptions about the magnitudes
of the first derivatives or the existence of second derivatives of . For
a large class of that have discrete spectrum, we prove that the eigenvalue
asymptotics of does not depend on rapid oscillations of or of the
potential. Similar comments apply to our treatment of the existence and
completeness of the wave operators.Comment: 23 page
Is Cosmology Solved?
We have fossil evidence from the thermal background radiation that our
universe expanded from a considerably hotter denser state. We have a well
defined and testable description of the expansion, the relativistic
Friedmann-Lemaitre model. Its observational successes are impressive but I
think hardly enough for a convincing scientific case. The lists of
observational constraints and free hypotheses within the model have similar
lengths. The scorecard on the search for concordant measures of the mass
density parameter and the cosmological constant shows that the high density
Einstein-de Sitter model is challenged, but that we cannot choose between low
density models with and without a cosmological constant. That is, the
relativistic model is not strongly overconstrained, the usual test of a mature
theory. Work in progress will greatly improve the situation and may at last
yield a compelling test. If so, and the relativistic model survives, it will
close one line of research in cosmology: we will know the outlines of what
happened as our universe expanded and cooled from high density. It will not end
research: some of us will occupy ourselves with the details of how galaxies and
other large-scale structures came to be the way they are, others with the issue
of what our universe was doing before it was expanding. The former is being
driven by rapid observational advances. The latter is being driven mainly by
theory, but there are hints of observational guidance.Comment: 13 pages, 3 figures. To be published in PASP as part of the
proceedings of the Smithsonian debate, Is Cosmology Solved
The Politics of Accumulation in Small?town India
Summaries Using the analytical framework of social structures of accumulation, the economic politics of local urban civil?social organisations and their impact on capital, class and the business economy is examined. Although such organisations are structured through many dimensions, notably occupation, commodity, party politics, religion, gender and locality, the most prominent single category comprises caste — and closely?related, finely?defined occupational associations. In the town's societal corporatist form of accumulation, the political, cultural and ideological hegemony of a single social group — the capitalist class — imposes itself, supported by a strong ideology based on transformations of the institution of caste. Due to the reinforcement of caste, patriarchy and the rhetoric of town unity, economic interests and ideological factors overlap in exactly the manner Gramsci thought to be the essence of civil society. Furthermore, through the caste system and through patriarchy, ideology comes to form a significant component in the local social structures of accumulation
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