666 research outputs found
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Control and supervision of a complex production process using hybrid systems techniques
New processing activities for the decommissioning of the Experimental Breeder Reactor 2 are being carried out at Argonne National Laboratory. The task addressed in this paper is a process to convert metallic sodium to sodium carbonate. The main idea is to characterize this sodium operation as a system that integrates real-time continuous and discrete-event components and then apply hybrid system techniques to design and implement the control and supervisory policies. This paper introduces the research in progress at ANL on this conversion process, the flow of material, and the hybrid control solution
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State-space supervision of reconfigurable discrete event systems
The Discrete Event Systems (DES) theory of supervisory and state feedback control offers many advantages for implementing supervisory systems. Algorithmic concepts have been introduced to assure that the supervising algorithms are correct and meet the specifications. It is often assumed that the supervisory specifications are invariant or, at least, until a given supervisory task is completed. However, there are many practical applications where the supervising specifications update at real time. For example, in a Reconfigurable Discrete Event System (RDES) architecture, a bank of supervisors is defined to accommodate each identified operational condition or different supervisory specifications. This adaptive supervisory control system changes the supervisory configuration to accept coordinating commands or to adjust for changes in the controlled process. This paper addresses reconfiguration at the supervisory level of hybrid systems along with a RDES underlying architecture. It reviews the state-based supervisory control theory and extends it to the paradigm of RDES and in view of process control applications. The paper addresses theoretical issues with a limited number of practical examples. This control approach is particularly suitable for hierarchical reconfigurable hybrid implementations
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Planning and supervision of reactor defueling using discrete event techniques
New fuel handling and conditioning activities for the defueling of the Experimental Breeder Reactor II are being performed at Argonne National Laboratory. Research is being conducted to investigate the use of discrete event simulation, analysis, and optimization techniques to plan, supervise, and perform these activities in such a way that productivity can be improved. The central idea is to characterize this defueling operation as a collection of interconnected serving cells, and then apply operational research techniques to identify appropriate planning schedules for given scenarios. In addition, a supervisory system is being developed to provide personnel with on-line information on the progress of fueling tasks and to suggest courses of action to accommodate changing operational conditions. This paper provides an introduction to the research in progress at ANL. In particular, it briefly describes the fuel handling configuration for reactor defueling at ANL, presenting the flow of material from the reactor grid to the interim storage location, and the expected contributions of this work. As an example of the studies being conducted for planning and supervision of fuel handling activities at ANL, an application of discrete event simulation techniques to evaluate different fuel cask transfer strategies is given at the end of the paper
The one-loop renormalization of the MSSM Higgs sector and its application to the neutral scalar Higgs masses
The structure of the Higgs sector in the minimal supersymmetric standard
model is reviewed at the one-loop level. An on-shell renormalization scheme of
the MSSM Higgs sector is presented in detail together with the complete list of
formulae for the neutral Higgs masses at the one-loop level. The results of a
complete one- loop calculation for the mass spectrum of the neutral MSSM Higgs
bosons and the quality of simpler Born-like approximations are discussed for
sfermion and gaugino masses in the range of the electroweak scale.Comment: 32 pages, report KA-THEP-5-199
Homocysteine-Lowering Treatment and the Risk of Fracture: Secondary Analysis of a Randomized Controlled Trial and an Updated Meta-Analysis
High plasma homocysteine is a risk factor for osteoporotic fractures. Several studies have assessed the possible preventive effect of homocysteine-lowering B-vitamin treatment on the risk of fracture with inconclusive results. In the current study, we include new results from the Aspirin Folate Polyp Prevention Study (AFPPS) together with an updated meta-analysis of randomized controlled trials (RCTs). Our objective was to determine whether there is an association between homocysteine-lowering B-vitamin treatment and the risk of fracture. The AFPPS trial was performed between 1994 and 2004 in nine clinical centers in the United States, and 1021 participants were randomized to a daily folic acid dose of 1 mg (n = 516) or placebo (n = 505). The main outcome was fracture of any type. In addition, we analyzed the risk of hip fracture. In the meta-analysis, studies were identified following a search strategy in electronic database and by hand searching. Risk ratio with 95% confidence interval (CI) was chosen for pooled analyses. In the AFPPS, no statistically significant association was found between folic acid treatment and fractures of any type (risk ratio [RR] = 0.95; 95% CI 0.61–1.48) or hip fracture (RR = 0.98; 95% CI 0.25–3.89). In the meta-analysis, six RCTs were included with a total of 36,527 participants. For interventions including folic acid and/or vitamin B12, the pooled RR for treatment was 0.97 (95% CI 0.87–1.09) for fractures of any type (n = 1199) and 1.00 (95% CI 0.81–1.23) for hip fractures (n = 335). In conclusion, no association was found between homocysteine-lowering treatment with B vitamins (folic acid and vitamin B12) and the risk of fracture
Interaction of strontium chloride solution with calcium aluminate phosphate (CAP) system
Processing of contaminated water in Fukushima Daiichi Power Plant results in various aqueous secondary wastes. A significant strontium ( 90 Sr) contamination represents one of the key challenges for their management, and we have been developing a new cementing matrix based on calcium aluminate phosphate (CAP) system with reduced water content for such aqueous secondary wastes. In the present study, the interaction of CAP with SrCl2 was investigated to gain insight into the capability of CAP system in Sr immobilisation. It was found that the immobilisation is possible, and the incorporation of Sr appears to be associated with the formation of insoluble phosphate salts. The obtained results also suggest that 1 kg of CAP powders can incorporate 200 g of Sr under tested condition
The SUSY seesaw model and lepton-flavor violation at a future electron-positron linear collider
We study lepton-flavor violating slepton production and decay at a future
e^+e^- linear collider in context with the seesaw mechanism in mSUGRA post-LEP
benchmark scenarios. The present knowledge in the neutrino sector as well as
improved future measurements are taken into account. We calculate the signal
cross-sections \sigma(e^{+/-}e^- -> l_{\beta}^{+/-} l_{\alpha}^-
\tilde{\chi}_b^0 \tilde{\chi}_a^0); l_{\delta}=e, \mu, \tau; \alpha =|= \beta
and estimate the main background processes. Furthermore, we investigate the
correlations of these signals with the corresponding lepton-flavor violating
rare decays l_{\alpha} -> l_{\beta} \gamma. It is shown that these correlations
are relatively weakly affected by uncertainties in the neutrino data, but very
sensitive to the model parameters. Hence, they are particularly suited for
probing the origin of lepton-flavor violation.Comment: 31 pages, 10 figures, version published in Phys. Rev.
Fermionic decays of sfermions: a complete discussion at one-loop order
We present a definition of an on-shell renormalization scheme for the
sfermion and chargino-neutralino sector of the Minimal Supersymmetric Standard
Model (MSSM). Then, apply this renormalization framework to the interaction
between charginos/neutralinos and sfermions. A kind of universal corrections is
identified, which allow to define effective chargino/neutralino coupling
matrices. In turn, these interactions generate (universal) non-decoupling terms
that grow as the logarithm of the heavy mass. Therefore the full MSSM spectrum
must be taken into account in the computation of radiative corrections to
observables involving these interactions. As an application we analyze the full
one-loop electroweak radiative corrections to the partial decay widths
\Gamma(\tilde{f} -> f\neut) and \Gamma(\tilde{f} -> f'\cplus) for all sfermion
flavours and generations. These are combined with the QCD corrections to
compute the corrected branching ratios of sfermions. It turns out that the
electroweak corrections can have an important impact on the partial decay
widths, as well as the branching ratios, in wide regions of the parameter
space. The precise value of the corrections is strongly dependent on the
correlation between the different particle masses.Comment: LaTeX 53 pages, 22 figures, 3 tables. Typos correcte
A Quantitative Model of Energy Release and Heating by Time-dependent, Localized Reconnection in a Flare with a Thermal Loop-top X-ray Source
We present a quantitative model of the magnetic energy stored and then
released through magnetic reconnection for a flare on 26 Feb 2004. This flare,
well observed by RHESSI and TRACE, shows evidence of non-thermal electrons only
for a brief, early phase. Throughout the main period of energy release there is
a super-hot (T>30 MK) plasma emitting thermal bremsstrahlung atop the flare
loops. Our model describes the heating and compression of such a source by
localized, transient magnetic reconnection. It is a three-dimensional
generalization of the Petschek model whereby Alfven-speed retraction following
reconnection drives supersonic inflows parallel to the field lines, which form
shocks heating, compressing, and confining a loop-top plasma plug. The
confining inflows provide longer life than a freely-expanding or
conductively-cooling plasma of similar size and temperature. Superposition of
successive transient episodes of localized reconnection across a current sheet
produces an apparently persistent, localized source of high-temperature
emission. The temperature of the source decreases smoothly on a time scale
consistent with observations, far longer than the cooling time of a single
plug. Built from a disordered collection of small plugs, the source need not
have the coherent jet-like structure predicted by steady-state reconnection
models. This new model predicts temperatures and emission measure consistent
with the observations of 26 Feb 2004. Furthermore, the total energy released by
the flare is found to be roughly consistent with that predicted by the model.
Only a small fraction of the energy released appears in the super-hot source at
any one time, but roughly a quarter of the flare energy is thermalized by the
reconnection shocks over the course of the flare. All energy is presumed to
ultimately appear in the lower-temperature T<20 MK, post-flare loops
Supersymmetric effects in top quark decay into polarized W-boson
We investigate the one-loop supersymmetric QCD (SUSY-QCD) and electroweak
(SUSY-EW) corrections to the top quark decay into a b-quark and a longitudinal
or transverse W-boson. The corrections are presented in terms of the
longitudinal ratio \Gamma(t-->W_L b)/\Gamma(t--> W b) and the transverse ratio
\Gamma(t-->W_- b)/\Gamma(t--> W b). In most of the parameter space, both
SUSY-QCD and SUSY-EW corrections to these ratios are found to be less than 1%
in magnitude and they tend to have opposite signs. The corrections to the total
width \Gamma(t-->W b) are also presented for comparison with the existing
results in the literature. We find that our SUSY-EW corrections to the total
width differ significantly from previous studies: the previous studies give a
large correction of more than 10% in magnitude for a large part of the
parameter space while our results reach only few percent at most.Comment: Version in PRD (explanation and refs added
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