14,666 research outputs found
Buffer thermal energy storage for an air Brayton solar engine
The application of latent-heat buffer thermal energy storage to a point-focusing solar receiver equipped with an air Brayton engine was studied. To demonstrate the effect of buffer thermal energy storage on engine operation, a computer program was written which models the recuperator, receiver, and thermal storage device as finite-element thermal masses. Actual operating or predicted performance data are used for all components, including the rotating equipment. Based on insolation input and a specified control scheme, the program predicts the Brayton engine operation, including flows, temperatures, and pressures for the various components, along with the engine output power. An economic parametric study indicates that the economic viability of buffer thermal energy storage is largely a function of the achievable engine life
Natural Gauge Hierarchy in SO(10)
It is shown that a natural gauge hierarchy and doublet-triplet splitting can
be achieved in SO(10) using the Dimopoulos-Wilczek mechanism. Artificial
cancellations (fine-tuning) and arbitrary forms of the superpotential are
avoided, the superpotential being the most general compatible with a symmetry.
It is shown by example that the Dimopoulos-Wilczek mechanism can be protected
against the effects of higher-dimension operators possibly induced by
Planck-scale physics. Natural implementation of the mechanism leads to an
automatic Peccei-Quinn symmetry. The same local symmetries that would protect
the gauge hierarchy against Planck-scale effects tend to protect the axion
also. It is shown how realistic quark and lepton masses might arise in this
framework. It is also argued that ``weak suppression'' of proton decay can be
implemented more economically than can ``strong suppression'', offering some
grounds to hope (in the context of SO(10)) that proton decay could be seen at
Superkamiokande.Comment: 26 pages in plain LaTeX, 5 figures available on request, BA-94-0
Simulating Impacts of Extreme Weather Events on Urban Transport Infrastructure in the UK
Urban areas face many risks from future climate change and their infrastructure will be placed under more pressure
due to changes in climate extremes. Using the Tyndall Centre Urban Integrated Assessment Framework, this paper
describes a methodology used to assess the impacts of future climate extremes on transport infrastructure in
London. Utilising high-resolution projections for future climate in the UK, alongside stochastic weather generators
for downscaling, urban temperature and flooding models are used to provide information on the likelihood of future
extremes. These are then coupled with spatial network models of urban transport infrastructure and, using thresholds
to define the point at which systems cease to function normally, disruption to the networks can be simulated.
Results are shown for both extreme heat and urban surface water flooding events and the impacts on the travelling
population, in terms of both disruption time and monetary cost
A Simple Grand Unified Relation between Neutrino Mixing and Quark Mixing
It is proposed that all flavor mixing is caused by the mixing of the three
quark and lepton families with vectorlike fermions in 5 + 5-bar multiplets of
SU(5). This simple assumption implies that both V_{CKM} and U_{MNS} are
generated by a single matrix. The entire 3-by-3 complex mass matrix of the
neutrinos M_{nu} is then found to have a simple expression in terms of two
complex parameters and an overall scale. Thus, all the presently unknown
neutrino parameters are predicted. The best fits are for theta_{atm} less than
or approximately 40 degrees. The leptonic Dirac CP phase is found to be
somewhat greater than pi radians.Comment: 10 pages, 4 figures, one table. Typos correcte
Soil moisture detection by Skylab's microwave sensors
The author has identified the following significant results. Terrain microwave backscatter and emission response to soil moisture variations were investigated using Skylab's 13.9 GHz RADSCAT (radiometer/scatterometer) system. Data acquired on June 5, 1973, over a test site in west-central Texas indicated a fair degree of correlation with composite rainfall. The scan made was cross-track contiguous (CTC) with a pitch of 29.4 deg and no roll effect. Vertical polarization was employed with both radiometer and scatterometer. The composite rainfall was computed according to the flood prediction technique using rainfall data supplied by weather reporting stations
System integration report
Several areas that arise from the system integration issue were examined. Intersystem analysis is discussed as it relates to software development, shared data bases and interfaces between TEMPUS and PLAID, shaded graphics rendering systems, object design (BUILD), the TEMPUS animation system, anthropometric lab integration, ongoing TEMPUS support and maintenance, and the impact of UNIX and local workstations on the OSDS environment
Eliminating the d=5 proton decay operators from SUSY GUTs
A general analysis is made of the question whether the d=5 proton decay
operators coming from exchange of colored Higgsinos can be completely
eliminated in a natural way in supersymmetric grand unified models. It is shown
that they can indeed be in SO(10) while at the same time naturally solving the
doublet-triplet splitting problem, having only two light Higgs doublets, and
using no more than a single adjoint Higgs field. Accomplishing all of this
requires that the vacuum expectation value of the adjoint Higgs field be
proportional to the generator I_{3R} rather than to B-L, as is usually assumed.
It is shown that such models can give realistic quark and lepton masses. We
also point out a new mechanism for solving the \mu problem in the context of
SO(10) SUSY GUTs.Comment: 24 pages in LaTeX, with 3 figure
Simple supersymmetric solution to the strong CP problem
It is shown that the minimal supersymmetric left-right model can provide a
natural solution to the strong {\it CP} problem without the need for an axion,
nor any additional symmetries beyond supersymmetry and parity.Comment: Plain Latex. 10 pages, including two figures which are part of the
Latex file. Shortened version, to appear in Phys. Rev. Lett. 7
Higgs-Mediated tau -> 3 mu in the Supersymmetric Seesaw Model
Recent observations of neutrino oscillations imply non-zero neutrino masses
and flavor violation in the lepton sector, most economically explained by the
seesaw mechanism. Within the context of supersymmetry, lepton flavor violation
(LFV) among the neutrinos can be communicated by renormalization group flow to
the sleptons and from there to the charged leptons. We show that LFV can appear
in the couplings of the neutral Higgs bosons, an effect that is strongly
enhanced at large tan(beta). In particular, we calculate the branching fraction
for tau -> 3 mu and mu -> 3 e mediated by Higgs and find that they can be as
large as 10^{-7} and 5x10^{-14} respectively. These modes, along with B^0 -> mu
mu, can provide important evidence for supersymmetry before direct discovery of
supersymmetric partners occurs. Along with tau -> mu gamma and mu -> e gamma,
they can also provide key insights into the form of the neutrino Yukawa mass
matrix.Comment: 9 pages LaTeX, 2 figures. Added a discussion of mu -> 3e and its
ramifications for probing neutrino mass matrix. Also added references, fixed
typos, and made one notational chang
Direct CP violation in neutral kaon decays
The final result is presented of the NA48 Experiment performed at CERN SPS
neutral kaon beams on the direct CP violation parameter Re(epsilon'/epsilon),
as maesured from the decay rates of neutral kaons into two pions. The data
collected in years 1997-2001 yield the evidence for direct CP violation with
Re(epsilon'/epsilon)=(14.7+-2.2)10^-4. Description of expermental method and
systematics, comparison with world data and some discussion of implications for
theory are given.Comment: 5 pp., 3 figs, presented on behalf of NA48 Collaboration at PASCOS
2003 Conference, Mumbai, India, 2-8 Jan 2003, to appear in Praman
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