1,976 research outputs found
Energy balance of different organic biogas farming systems
The ecological impact of biogas plants depends on their integration into a given farming system. Therefore only farm-specific and no general statements are possible. In this paper, two different concepts of biogas production for an organic cash crop farm have been energetically balanced using a model software. The analysis of input and efficient use of fossil energy carriers provides information on the environmental relevance of the farm operations. Apart from this, renewable energy production in the farming systems is compared to food production, and changes in the farm output are described. It turns out that organically run cash crop farms can benefit from a reasonable integration of a biogas plant, both in food crop and energy production. An increased orientation on the growing of energy crops, however, leads to worse utilization of fossil energy carriers and reduced food production
Fast Automated Analysis and Classification of Color Pictures by Signature and Pattern Recognition Using a Color Scanner
A commercial color scanner with high resolution is used for picture processing. The scanner is modified and additional electronic instruments are connected to the built-in color computer. The operations are carried out in an on-line process, simultaneously with the scan of the picture a processed picture is recorded on a special scanner film. Because there is no storage of image datas short processing times are obtained. The image datas are handled in a color computer, a gradation processor, an operational amplifier and a comparator to realize various\u27 procedures of picture operations.
The procedures are classified here in global, local and point operations. Global operations refer to the whole picture, these are for instance rectification, enlargement, density transformations. Local operations are mostly used for texture and pattern recognition and are related to the scanned picture element and its surrounding area. Point operations manipulate the information of a single picture element. The scanner generates three color signals from each picture element, which are handled in the color computer for color and signature recognition.
Several operations may be carried out in the same scan. The processed picture is displayed on a b/w transparency or on a color film. A suitable display for thematic mapping is essential for a correct interpretation of the processed picture
Redshifts of the Gravitational Lenses MG0414+0534 and MG0751+2716
We report redshifts in two gravitational lens systems, MG0414+0534 and
MG0751+2716. The lens galaxy in MG0414+0534 lies at z_l=0.9584+/-0.0002. The
luminosity and extreme red color of the lens are then typical of a passively
evolving, early-type, ~2L* galaxy. The galaxy cannot have a significant global
mean extinction without being anomalously luminous. The lens galaxy in
MG0751+2716 has a redshift of z_l=0.3502+/-0.0003 and it is a member of a small
group. The group includes the nearby, bright companion galaxy whose redshift we
confirmed to be z=0.3501+/-0.0001 and a nearby emission line galaxy with
z=0.3505+/-0.0003. A second emission line galaxy with z=0.5216+/-0.0001 was
found nearly superposed on the first emission line galaxy. The source in
MG0751+2716 is a z_s=3.200+/-0.001 radio quasar. For flat universes with
Omega_0=1.0 (0.3), 96% (87%) of lenses like MG0414+0534 and 7% (3%) of lenses
like MG0751+2716 are expected to have lower lens redshifts than observed.Comment: 9 pages, AASTeX Latex, including 5 Postscript figures, submitted to
Astronomical Journa
C-MOS array design techniques: SUMC multiprocessor system study
The current capabilities of LSI techniques for speed and reliability, plus the possibilities of assembling large configurations of LSI logic and storage elements, have demanded the study of multiprocessors and multiprocessing techniques, problems, and potentialities. Evaluated are three previous systems studies for a space ultrareliable modular computer multiprocessing system, and a new multiprocessing system is proposed that is flexibly configured with up to four central processors, four 1/0 processors, and 16 main memory units, plus auxiliary memory and peripheral devices. This multiprocessor system features a multilevel interrupt, qualified S/360 compatibility for ground-based generation of programs, virtual memory management of a storage hierarchy through 1/0 processors, and multiport access to multiple and shared memory units
Tropical analogues of a Dempe-Franke bilevel optimization problem
We consider the tropical analogues of a particular bilevel optimization
problem studied by Dempe and Franke and suggest some methods of solving these
new tropical bilevel optimization problems. In particular, it is found that the
algorithm developed by Dempe and Franke can be formulated and its validity can
be proved in a more general setting, which includes the tropical bilevel
optimization problems in question. We also show how the feasible set can be
decomposed into a finite number of tropical polyhedra, to which the tropical
linear programming solvers can be applied.Comment: 11 pages, 1 figur
Exchange-correlation orbital functionals in current-density-functional theory: Application to a quantum dot in magnetic fields
The description of interacting many-electron systems in external magnetic
fields is considered in the framework of the optimized effective potential
method extended to current-spin-density functional theory. As a case study, a
two-dimensional quantum dot in external magnetic fields is investigated.
Excellent agreement with quantum Monte Carlo results is obtained when
self-interaction corrected correlation energies from the standard local
spin-density approximation are added to exact-exchange results. Full
self-consistency within the complete current-spin-density-functional framework
is found to be of minor importance.Comment: 5 pages, 2 figures, submitted to PR
Optimized Effective Potential Method in Current-Spin Density Functional Theory
Current-spin density functional theory (CSDFT) provides a framework to
describe interacting many-electron systems in a magnetic field which couples to
both spin- and orbital-degrees of freedom. Unlike in usual (spin-) density
functional theory, approximations to the exchange-correlation energy based on
the model of the uniform electron gas face problems in practical applications.
In this work, explicitly orbital-dependent functionals are used and a
generalization of the Optimized Effective Potential (OEP) method to the CSDFT
framework is presented. A simplifying approximation to the resulting integral
equations for the exchange-correlation potentials is suggested. A detailed
analysis of these equations is carried out for the case of open-shell atoms and
numerical results are given using the exact-exchange energy functional. For
zero external magnetic field, a small systematic lowering of the total energy
for current-carrying states is observed due to the inclusion of the current in
the Kohn-Sham scheme. For states without current, CSDFT results coincide with
those of spin density functional theory.Comment: 11 pages, 3 figure
Exchange-energy functionals for finite two-dimensional systems
Implicit and explicit density functionals for the exchange energy in finite
two-dimensional systems are developed following the approach of Becke and
Roussel [Phys. Rev. A 39, 3761 (1989)]. Excellent agreement for the
exchange-hole potentials and exchange energies is found when compared with the
exact-exchange reference data for the two-dimensional uniform electron gas and
few-electron quantum dots, respectively. Thereby, this work significantly
improves the availability of approximate density functionals for dealing with
electrons in quasi-two-dimensional structures, which have various applications
in semiconductor nanotechnology.Comment: 5 pages, 3 figure
Quantifying morphological variability within extant mammalian species
Main articleIn this study we attempt to establish a baseline for measuring species variability in the
palaeontological record by using linear regression analysis on sets of measurements from extant
mammalian species (males and females within species). In particular, this study explores the
standard error of the m-coefficient (s.e.m) , derived from linear regression analyses associated with
equations of the form y = mx + c, to quantify the degree of morphological variability within extant
mammalian species. The slope m generally centres around 1.00. Even though the species in this
study range in size from small rodents to large ungulates, s.e'm values show a normal distribution
around a mean of 0.035 . The approach outlined here has potential application in palaeontological
contexts where there is uncertainty about any two specimens being conspecific.Foundation for Research Development
Introgressive hybridization and the evolutionary history of the herring gull complex revealed by mitochondrial and nuclear DNA
<p>Abstract</p> <p>Background</p> <p>Based on extensive mitochondrial DNA (mtDNA) sequence data, we previously showed that the model of speciation among species of herring gull (<it>Larus argentatus</it>) complex was not that of a ring species, but most likely due more complex speciation scenario's. We also found that two species, herring gull and glaucous gull (<it>L. hyperboreus</it>) displayed an unexpected biphyletic distribution of their mtDNA haplotypes. It was evident that mtDNA sequence data alone were far from sufficient to obtain a more accurate and detailed insight into the demographic processes that underlie speciation of this complex, and that extensive autosomal genetic analysis was warranted.</p> <p>Results</p> <p>For this reason, the present study focuses on the reconstruction of the phylogeographic history of a limited number of gull species by means of a combined approach of mtDNA sequence data and 230 autosomal amplified fragment length polymorphism (AFLP) loci. At the species level, the mtDNA and AFLP genetic data were largely congruent. Not only for <it>argentatus </it>and <it>hyperboreus</it>, but also among a third species, great black-backed gull (<it>L. marinus</it>) we observed two distinct groups of mtDNA sequence haplotypes. Based on the AFLP data we were also able to detect distinct genetic subgroups among the various <it>argentatus</it>, <it>hyperboreus</it>, and <it>marinus </it>populations, supporting our initial hypothesis that complex demographic scenario's underlie speciation in the herring gull complex.</p> <p>Conclusions</p> <p>We present evidence that for each of these three biphyletic gull species, extensive mtDNA introgression could have taken place among the various geographically distinct subpopulations, or even among current species. Moreover, based on a large number of autosomal AFLP loci, we found evidence for distinct and complex demographic scenario's for each of the three species we studied. A more refined insight into the exact phylogeographic history within the herring gull complex is still impossible, and requires detailed autosomal sequence information, a topic of our future studies.</p
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