6,475 research outputs found
Recharge unit provides for optimum recharging of battery cells
Percent recharge unit permits each cell of a rechargeable battery to be charged to a preset capacity of the cell. The unit automatically monitors and controls a rechargeable battery subjected to charge-discharge cycling tests
Assessment of flywheel energy storage for spacecraft power systems
The feasibility of inertial energy storage in a spacecraft power system is evaluated on the basis of a conceptual integrated design that encompasses a composite rotor, magnetic suspension, and a permanent magnet (PM) motor/generator for a 3-kW orbital average payload at a bus distribution voltage of 250 volts dc. The conceptual design, which evolved at the Goddard Space Flight Center (GSFC), is referred to as a Mechanical Capacitor. The baseline power system configuration selected is a series system employing peak-power-tracking for a Low Earth-Orbiting application. Power processing, required in the motor/generator, provides a potential alternative configurations that can only be achieved in systems with electrochemical energy storage by the addition of power processing components. One such alternative configuration provides for peak-power-tracking of the solar array and still maintains a regulated bus, without the expense of additional power processing components. Precise speed control of the two counterrotating wheels is required to reduce interaction with the attitude control system (ACS) or alternatively, used to perform attitude control functions. Critical technologies identified are those pertaining to the energy storage element and are prioritized as composite wheel development, magnetic suspension, motor/generator, containment, and momentum control. Comparison with a 3-kW, 250-Vdc power system using either NiCd or NiH2 for energy storage results in a system in which inertial energy storage offers potential advantages in lifetime, operating temperature, voltage regulation, energy density, charge control, and overall system weight reduction
Multi-parameter approach to R-parity violating SUSY couplings
We introduce and implement a new, extended approach to placing bounds on
trilinear R-parity violating couplings. We focus on a limited set of leptonic
and semi-leptonic processes involving neutrinos, combining multidimensional
plotting and cross-checking constraints from different experiments. This allows
us to explore new regions of parameter space and to relax a number of bounds
given in the literature. We look for qualitatively different results compared
to those obtained previously using the assumption that a single coupling
dominates the R-parity violating contributions to a process (SCD). By combining
results from several experiments, we identify regions in parameter space where
two or more parameters approach their maximally allowed values. In the same
vein, we show a circumstance where consistency between independent bounds on
the same combinations of trilinear coupling parameters implies mass constraints
among slepton or squark masses. Though our new bounds are in most cases weaker
than the SCD bounds, the largest deviations we find on individual parameters
are factors of two, thus indicating that a conservative, order of magnitude
bound on an individual coupling is reliably estimated by making the SCD
assumption.Comment: 30 pages, 8 figures, 2 tables. Typos fixed, two references added and
references updated. Eq. (41) removed, Eq. (40) and text modified. Published
versio
WMAPing the Universe: Supersymmetry, Dark Matter, Dark Energy, Proton Decay and Collider Physics
In this review we discuss constraints on minimal supersymmetric models of
particle physics implied by the recent astrophysical observations of WMAP.
Although the prospects of detecting supersymmetry increase and 90 percent of
the available MSSM parameter space can safely be reached by the sensitivity of
future colliders, nevertheless we pay particular emphasis on discussing regions
of the appropriate phase diagrams, which -if realized - would imply that
detection of supersymmetry, at least in the context of minimal models, could be
out of colliders reach. We also discuss the importance of a precise
determination of the radiative corrections to the muon anomalous magnetic
moment, both theoretically and experimentally. Finally, we briefly commend upon
recent evidence, supported by observations, on a dark energy component of the
Universe, of as yet unknown origin, covering 73 percent of its energy content.Comment: Review paper, 69 pages Latex, 35 eps figures incorporate
The design and implementation of a meaning driven data query language
We present the design and implementation of a Meaning Driven Data Query Language - MDDQL - which aims at the construction of queries through system made suggestions
of natural language based query terms for both scientific
application domain terms and operator/operation ones. A query construction blackboard is used where query language
terms are suggested to the user in its preferred natural
language and in a name centered way, together with their connotation. This helps in understanding the meaning of the terms and/or operators or operations to be included in the query. Furthermore, the construction of the query turns out to be an incremental refinement of the query under construction through semantic constraints, where only those domain language terms and/or operators/operations are suggested which result into meaningful combinations of query terms as related to the scientific application domain
semantics. Therefore, semantically meaningless queries can be prevented during the query construction. Such a semantics aware mechanism is not available in conventional database query languages such as SQL, where one is allowed to execute a query calculating, for example, the average of numerical data values whereas they represent the codes of categorical values. Moreover, no familiarity with the semantics of complex database schemes or interpretation
of the symbols (names of classes/tables/attributes, value codes) underlying the storage model, as well as familiarity with the syntax of a database specific query language are needed by the end-user. The constructed query can be submitted to the MDDQL query interpretation and transformation engine, where the corresponding SQL-query
is generated and delegated to a DBMS (e.g., Oracle, MSAccess, SQL-Server). Generation of SQL-statements addressing NF2 data models such as those provided by the
object-relational Oracle DBMS is also enabled. The query
result is presented in a table based form where all storage
model symbols are interpreted and can be exported for the
usage with statistical software packages (e.g., SPSS)
Target dark matter detection rates in models with a well-tempered neutralino
In the post-LEP2 era, and in light of recent measurements of the cosmic
abundance of cold dark matter (CDM) in the universe from WMAP, many
supersymmetric models tend to predict 1. an overabundance of CDM and 2.
pessimistically low rates for direct detection of neutralino dark matter.
However, in models with a ``well-tempered neutralino'', where the neutralino
composition is adjusted to give the measured abundance of CDM, the neutralino
is typically of the mixed bino-wino or mixed bino-higgsino state. Along with
the necessary enhancement to neutralino annihilation rates, these models tend
to give elevated direct detection scattering rates compared to predictions from
SUSY models with universal soft breaking terms. We present neutralino direct
detection cross sections from a variety of models containing a well-tempered
neutralino, and find cross section asymptotes with detectable scattering rates.
These asymptotic rates provide targets that various direct CDM detection
experiments should aim for. In contrast, in models where the neutralino mass
rather than its composition is varied to give the WMAP relic density via either
resonance annihilation or co-annihilation, the neutralino remains essentially
bino-like, and direct detection rates may be below the projected reaches of all
proposed experiments.Comment: 13 pages including 1 EPS figur
Trileptons from Chargino-Neutralino Production at the CERN Large Hadron Collider
We study direct production of charginos and neutralinos at the CERN Large
Hadron Collider. We simulate all channels of chargino and neutralino production
using ISAJET 7.07. The best mode for observing such processes appears to be
pp\to\tw_1\tz_2\to 3\ell +\eslt. We evaluate signal expectations and
background levels, and suggest cuts to optimize the signal. The trilepton mode
should be viable provided m_{\tg}\alt 500-600~GeV; above this mass, the decay
modes \tz_2\to\tz_1 Z and \tz_2\to H_{\ell}\tz_1 become dominant, spoiling
the signal. In the first case, the leptonic branching fraction for decay is
small and additional background from is present, while in the second case,
the trilepton signal is essentially absent. For smaller values of ,
the trilepton signal should be visible above background, especially if
and m_{\tell}\ll m_{\tq}, in which case the leptonic
decays of \tz_2 are enhanced. Distributions in dilepton mass
can yield direct information on neutralino masses due to
the distribution cutoff at m_{\tz_2}-m_{\tz_1}. Other distributions that may
lead to an additional constraint amongst the chargino and neutralino masses are
also examined.Comment: preprint nos. FSU-HEP-940310 and UH-511-786-94, 13 pages (REVTEX)
plus 7 uuencoded figures attache
MDDQL-Stat: data querying and analysis through integration of intentional and extensional semantics
We would like to present a prototype system enabling a
rather empirical than a formal approach to the problem
of posing queries to a semantically rich (quality aspects,
semantic distance, etc.) data integration system {G,S,M} (Global schema, Sources, Mediation) through integration
not only of intensional but also of extensional semantics.
While the first is provided by an alphabet Ag, as given by
an ontology based global schema G, and a high level query
language (conjunction/disjunction + inequalities + statistical operations), the latter enables synthesizing of data source specific and previously transformed query results according to well-defined set operations for heterogeneous, distributed data sources. Our approach contrasts with other GAV (Global-As-View) related architectures for mediation of integrated read-only views, in that it simplifies query processing while preserving flexibility when adding new data sources, despite the inherited complexity of mappings due to enhanced semantic description of data (semantic distance, quality parameters, etc.) such that statistical results and comparisons become more meaningful
The Reach of the Fermilab Tevatron and CERN LHC for Gaugino Mediated SUSY Breaking Models
In supersymmetric models with gaugino mediated SUSY breaking (inoMSB), it is
assumed that SUSY breaking on a hidden brane is communicated to the visible
brane via gauge superfields which propagate in the bulk. This leads to GUT
models where the common gaugino mass is the only soft SUSY breaking
term to receive contributions at tree level. To obtain a viable phenomenology,
it is assumed that the gaugino mass is induced at some scale beyond the
GUT scale, and that additional renormalization group running takes place
between and as in a SUSY GUT. We assume an SU(5) SUSY GUT above
the GUT scale, and compute the SUSY particle spectrum expected in models with
inoMSB. We use the Monte Carlo program ISAJET to simulate signals within the
inoMSB model, and compute the SUSY reach including cuts and triggers approriate
to Fermilab Tevatron and CERN LHC experiments. We find no reach for SUSY by the
Tevatron collider in the trilepton channel. %either with or without %identified
tau leptons. At the CERN LHC, values of (1160) GeV can be probed
with 10 (100) fb of integrated luminosity, corresponding to a reach in
terms of of 2150 (2500) GeV. The inoMSB model and mSUGRA can likely
only be differentiated at a linear collider with sufficient energy to
produce sleptons and charginos.Comment: 17 page revtex file with 9 PS figure
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