551 research outputs found
Ways of Transition to Clean Energy Use: Two Methodological Approaches
The combustion of fossil fuels for the production of energy has already resulted in significant modifications of the earth's environment, primarily through the emissions of carbon dioxide, sulfur dioxide, nitrogen oxides, and particulates.
The modern world primary energy consumption patterns and its trends lead to the utilization of dirtier and more expensive fossil fuels. The desire to protect the environment is contradictory Lo such structural changes in energy like the broader use of coal as substitution for liquid fuels, taking into account the depletion of coal deposits with low sulfur contents.
Previous studies carried out at IIASA, in the FRG, the US, the USSR and other countries, formulate one long-term technological strategy that might limit pollutant emissions sufficiently to permit an efficient and ecologically sustainable development of the world's energy consumption patterns. This technological strategy is based on the implementation of the so-called Integrated Energy Systems (IES) or Integrated Energy-Chemical Systems (IECS). The basic idea of IES incorporates the decomposition and purification of primary fossil energy inputs before combustion, the integration of these decomposed (clean) products and the allocation of them in line with the requirements for final energy. Thus, Integrated Energy Systems represent a concept for providing a flexible range of final energy forms from varying inputs of different primary energy sources. Other potential advantages include improved performance of the whole energy system, such as higher efficiencies and lower environmental impacts.
The joint report of the Kernforschungsanlage Julich (KFA), Julich, FRG and the Siberian Energy Institute (SEI), Irkutsk, USSR describes the concepts, methodological approaches, and preliminary results of the analysis of technological options and technoeconomic properties of the different types of integrated energy systems. The study of KFA and SEI, based on the cooperation with the International Institute for Applied Systems Analysis, emphasizes the common viewpoint that the idea of integrated energy systems constitutes an essential basis for new studies on energy systems with a high degree of utilizing primary energy sources and with low emissions
Confinement-Deconfinement Transition in 3-Dimensional QED
We argue that, at finite temperature, parity invariant non-compact
electrodynamics with massive electrons in 2+1 dimensions can exist in both
confined and deconfined phases. We show that an order parameter for the
confinement-deconfinement phase transition is the Polyakov loop operator whose
average measures the free energy of a test charge that is not an integral
multiple of the electron charge. The effective field theory for the Polyakov
loop operator is a 2-dimensional Euclidean scalar field theory with a global
discrete symmetry , the additive group of the integers. We argue that the
realization of this symmetry governs confinement and that the
confinement-deconfinement phase transition is of
Berezinskii-Kosterlitz-Thouless type. We compute the effective action to
one-loop order and argue that when the electron mass is much greater than
the temperature and dimensional coupling , the effective field theory
is the Sine-Gordon model. In this limit, we estimate the critical temperature,
.Comment: 11 pages, latex, no figure
Deuteron frozen spin polarized target for nd experiements at the VdG accelerator of Charles University
A frozen spin polarized deuteron target cooled by the 3He/4He dilution
refrigerator is described. Fully deuterated 1,2-propanediol was used as a
target material. Deuteron vector polarization about 40% was obtained for the
target in the shape of a cylinder of 2 cm diameter and 6 cm length. The target
is intended for a study of 3N interactions at the polarized neutron beam
generated by the Van de Graaff accelerator at the Charles University in Prague
Proximity effect at superconducting Sn-Bi2Se3 interface
We have investigated the conductance spectra of Sn-Bi2Se3 interface junctions
down to 250 mK and in different magnetic fields. A number of conductance
anomalies were observed below the superconducting transition temperature of Sn,
including a small gap different from that of Sn, and a zero-bias conductance
peak growing up at lower temperatures. We discussed the possible origins of the
smaller gap and the zero-bias conductance peak. These phenomena support that a
proximity-effect-induced chiral superconducting phase is formed at the
interface between the superconducting Sn and the strong spin-orbit coupling
material Bi2Se3.Comment: 7 pages, 8 figure
Centrality Dependence of the High p_T Charged Hadron Suppression in Au+Au collisions at sqrt(s_NN) = 130 GeV
PHENIX has measured the centrality dependence of charged hadron p_T spectra
from central Au+Au collisions at sqrt(s_NN)=130 GeV. The truncated mean p_T
decreases with centrality for p_T > 2 GeV/c, indicating an apparent reduction
of the contribution from hard scattering to high p_T hadron production. For
central collisions the yield at high p_T is shown to be suppressed compared to
binary nucleon-nucleon collision scaling of p+p data. This suppression is
monotonically increasing with centrality, but most of the change occurs below
30% centrality, i.e. for collisions with less than about 140 participating
nucleons. The observed p_T and centrality dependence is consistent with the
particle production predicted by models including hard scattering and
subsequent energy loss of the scattered partons in the dense matter created in
the collisions.Comment: 7 pages text, LaTeX, 6 figures, 2 tables, 307 authors, resubmitted to
Phys. Lett. B. Revised to address referee concerns. Plain text data tables
for the points plotted in figures for this and previous PHENIX publications
are publicly available at
http://www.phenix.bnl.gov/phenix/WWW/run/phenix/papers.htm
Evidence of Color Coherence Effects in W+jets Events from ppbar Collisions at sqrt(s) = 1.8 TeV
We report the results of a study of color coherence effects in ppbar
collisions based on data collected by the D0 detector during the 1994-1995 run
of the Fermilab Tevatron Collider, at a center of mass energy sqrt(s) = 1.8
TeV. Initial-to-final state color interference effects are studied by examining
particle distribution patterns in events with a W boson and at least one jet.
The data are compared to Monte Carlo simulations with different color coherence
implementations and to an analytic modified-leading-logarithm perturbative
calculation based on the local parton-hadron duality hypothesis.Comment: 13 pages, 6 figures. Submitted to Physics Letters
Formation of dense partonic matter in relativistic nucleus-nucleus collisions at RHIC: Experimental evaluation by the PHENIX collaboration
Extensive experimental data from high-energy nucleus-nucleus collisions were
recorded using the PHENIX detector at the Relativistic Heavy Ion Collider
(RHIC). The comprehensive set of measurements from the first three years of
RHIC operation includes charged particle multiplicities, transverse energy,
yield ratios and spectra of identified hadrons in a wide range of transverse
momenta (p_T), elliptic flow, two-particle correlations, non-statistical
fluctuations, and suppression of particle production at high p_T. The results
are examined with an emphasis on implications for the formation of a new state
of dense matter. We find that the state of matter created at RHIC cannot be
described in terms of ordinary color neutral hadrons.Comment: 510 authors, 127 pages text, 56 figures, 1 tables, LaTeX. Submitted
to Nuclear Physics A as a regular article; v3 has minor changes in response
to referee comments. Plain text data tables for the points plotted in figures
for this and previous PHENIX publications are (or will be) publicly available
at http://www.phenix.bnl.gov/papers.htm
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