525 research outputs found
Enhancing frequency stability by integrating nonconventional power sources through multi-terminal HVDC grid
The 2050 targets established by the EU will foster both larger penetration of renewable energy, especially wind power, and more cross–border interconnections. Moreover, this new framework requires the non-conventional power sources and power converter-based systems to be responsible for the duties traditionally carried out by conventional synchronous generators as frequency support. This paper presents how different power-electronic based technologies can provide frequency support individually and in a coordinated manner (with different priority given by the deadbands) ensuring a stable operation. The implemented scenarios push the system to the limits to exploit potential bottlenecks, and demonstrating how joint regulation of the power electronic based technologies enhances the frequency stability of the AC synchronous areas. The different control schemes and their interaction are investigated in Cigre DC grid benchmark adapted for frequency stability studies and implemented in Matlab/Simulink simulation tool. This modified grid includes 5-terminal HVDC grid with two offshore wind farms and three AC networks including battery and onshore wind farms
SO(10) unified models and soft leptogenesis
Motivated by the fact that, in some realistic models combining SO(10) GUTs
and flavour symmetries, it is not possible to achieve the required baryon
asymmetry through the CP asymmetry generated in the decay of right-handed
neutrinos, we take a fresh look on how deep this connection is in SO(10). The
common characteristics of these models are that they use the see-saw with
right-handed neutrinos, predict a normal hierarchy of masses for the neutrinos
observed in oscillating experiments and in the basis where the right-handed
Majorana mass is diagonal, the charged lepton mixings are tiny.
In addition these models link the up-quark Yukawa matrix to the neutrino
Yukawa matrix Y^\nu with the special feature of Y^\nu_{11}-> 0 Using this
condition, we find that the required baryon asymmetry of the Universe can be
explained by the soft leptogenesis using the soft B parameter of the second
lightest right-handed neutrino whose mass turns out to be around 10^8 GeV. It
is pointed out that a natural way to do so is to use no-scale supergravity
where the value of B ~1 GeV is set through gauge-loop corrections.Comment: 26 pages, 2 figures. Added references, new appendix of a relevant fit
and improved comment
Privacy by Design: From Technologies to Architectures (Position Paper)
Existing work on privacy by design mostly focus on technologies rather than
methodologies and on components rather than architectures. In this paper, we
advocate the idea that privacy by design should also be addressed at the
architectural level and be associated with suitable methodologies. Among other
benefits, architectural descriptions enable a more systematic exploration of
the design space. In addition, because privacy is intrinsically a complex
notion that can be in tension with other requirements, we believe that formal
methods should play a key role in this area. After presenting our position, we
provide some hints on how our approach can turn into practice based on ongoing
work on a privacy by design environment
Experimental evidence for 56Ni-core breaking from the low-spin structure of the N=Z nucleus 58Cu
Low-spin states in the odd-odd N=Z nucleus 58Cu were investigated with the
58Ni(p,n gamma)58Cu fusion evaporation reaction at the FN-tandem accelerator in
Cologne. Seventeen low spin states below 3.6 MeV and 17 new transitions were
observed. Ten multipole mixing ratios and 17 gamma-branching ratios were
determined for the first time. New detailed spectroscopic information on the
2+,2 state, the Isobaric Analogue State (IAS) of the 2+,1,T=1 state of 58Ni,
makes 58Cu the heaviest odd-odd N=Z nucleus with known B(E2;2+,T=1 --> 0+,T=1)
value. The 4^+ state at 2.751 MeV, observed here for the first time, is
identified as the IAS of the 4+,1,T=1 state in 58Ni. The new data are compared
to full pf-shell model calculations with the novel GXPF1 residual interaction
and to calculations within a pf5/2 configurational space with a residual
surface delta interaction. The role of the 56Ni core excitations for the
low-spin structure in 58Cu is discussed.Comment: 15 pages, 7 figures, submitted to Phys. Rev.
Heavy quarkonium: progress, puzzles, and opportunities
A golden age for heavy quarkonium physics dawned a decade ago, initiated by
the confluence of exciting advances in quantum chromodynamics (QCD) and an
explosion of related experimental activity. The early years of this period were
chronicled in the Quarkonium Working Group (QWG) CERN Yellow Report (YR) in
2004, which presented a comprehensive review of the status of the field at that
time and provided specific recommendations for further progress. However, the
broad spectrum of subsequent breakthroughs, surprises, and continuing puzzles
could only be partially anticipated. Since the release of the YR, the BESII
program concluded only to give birth to BESIII; the -factories and CLEO-c
flourished; quarkonium production and polarization measurements at HERA and the
Tevatron matured; and heavy-ion collisions at RHIC have opened a window on the
deconfinement regime. All these experiments leave legacies of quality,
precision, and unsolved mysteries for quarkonium physics, and therefore beg for
continuing investigations. The plethora of newly-found quarkonium-like states
unleashed a flood of theoretical investigations into new forms of matter such
as quark-gluon hybrids, mesonic molecules, and tetraquarks. Measurements of the
spectroscopy, decays, production, and in-medium behavior of c\bar{c}, b\bar{b},
and b\bar{c} bound states have been shown to validate some theoretical
approaches to QCD and highlight lack of quantitative success for others. The
intriguing details of quarkonium suppression in heavy-ion collisions that have
emerged from RHIC have elevated the importance of separating hot- and
cold-nuclear-matter effects in quark-gluon plasma studies. This review
systematically addresses all these matters and concludes by prioritizing
directions for ongoing and future efforts.Comment: 182 pages, 112 figures. Editors: N. Brambilla, S. Eidelman, B. K.
Heltsley, R. Vogt. Section Coordinators: G. T. Bodwin, E. Eichten, A. D.
Frawley, A. B. Meyer, R. E. Mitchell, V. Papadimitriou, P. Petreczky, A. A.
Petrov, P. Robbe, A. Vair
Shrinking a large dataset to identify variables associated with increased risk of Plasmodium falciparum infection in Western Kenya
Large datasets are often not amenable to analysis using traditional single-step approaches. Here, our general objective was to apply imputation techniques, principal component analysis (PCA), elastic net and generalized linear models to a large dataset in a systematic approach to extract the most meaningful predictors for a health outcome. We extracted predictors for Plasmodium falciparum infection, from a large covariate dataset while facing limited numbers of observations, using data from the People, Animals, and their Zoonoses (PAZ) project to demonstrate these techniques: data collected from 415 homesteads in western Kenya, contained over 1500 variables that describe the health, environment, and social factors of the humans, livestock, and the homesteads in which they reside. The wide, sparse dataset was simplified to 42 predictors of P. falciparum malaria infection and wealth rankings were produced for all homesteads. The 42 predictors make biological sense and are supported by previous studies. This systematic data-mining approach we used would make many large datasets more manageable and informative for decision-making processes and health policy prioritization
Global Search for New Physics with 2.0/fb at CDF
Data collected in Run II of the Fermilab Tevatron are searched for
indications of new electroweak-scale physics. Rather than focusing on
particular new physics scenarios, CDF data are analyzed for discrepancies with
the standard model prediction. A model-independent approach (Vista) considers
gross features of the data, and is sensitive to new large cross-section
physics. Further sensitivity to new physics is provided by two additional
algorithms: a Bump Hunter searches invariant mass distributions for "bumps"
that could indicate resonant production of new particles; and the Sleuth
procedure scans for data excesses at large summed transverse momentum. This
combined global search for new physics in 2.0/fb of ppbar collisions at
sqrt(s)=1.96 TeV reveals no indication of physics beyond the standard model.Comment: 8 pages, 7 figures. Final version which appeared in Physical Review D
Rapid Communication
Observation of Orbitally Excited B_s Mesons
We report the first observation of two narrow resonances consistent with
states of orbitally excited (L=1) B_s mesons using 1 fb^{-1} of ppbar
collisions at sqrt{s} = 1.96 TeV collected with the CDF II detector at the
Fermilab Tevatron. We use two-body decays into K^- and B^+ mesons reconstructed
as B^+ \to J/\psi K^+, J/\psi \to \mu^+ \mu^- or B^+ \to \bar{D}^0 \pi^+,
\bar{D}^0 \to K^+ \pi^-. We deduce the masses of the two states to be m(B_{s1})
= 5829.4 +- 0.7 MeV/c^2 and m(B_{s2}^*) = 5839.7 +- 0.7 MeV/c^2.Comment: Version accepted and published by Phys. Rev. Let
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