1,863 research outputs found
Risk assessment for the installation and maintenance activities of a low-speed tidal energy converter
The study presented in this paper, is part of the Deep Green project, which includes the development of a power converter/device for employment in low-speed tidal currents. It mainly focuses on the initial steps to investigate the ways on how to minimize the risks during handling, operation and maintenance (O&M) activities of the full-scale device particularly in offshore operations. As a first tep, the full-scale device offshore installation and O&M tasks are considered. The overall risk analysis and decision making methodology is presented including the Hazard Identification (HAZID) approach which is complemented with a risk matrix for various consequence categories including personnel Safety (S), Environmental impact (E), Asset integrity (A) and Operation (O). In this way, all the major risks involved in the mentioned activities are identified and actions to prevent or mitigate them are presented. The results of the HAZID analysis are also demonstrated. Finally, the last section of this paper presents the discussion, conclusions and future actions for the above-mentioned activities regarding the full-scale device
Collider Effects of Unparticle Interactions in Multiphoton Signals
A new model of physics, with a hidden conformal sector which manifests itself
as an unparticle coupling to Standard Model particles effectively through
higher dimensional operators, predicts strong collider signals due to
unparticle self-interactions. We perform a complete analysis of the most
spectacular of these signals at the hadron collider, pp -> 4photon and pp
->2photon,2gluon. These processes can go through the three-point unparticle
self interactions as well as through some s and t channel diagrams with one
and/or two unparticle exchanges. We study the contributions of individual
diagrams classified with respect to the number of unparticle exchanges and
discuss their effect on the cross sections at the Tevatron and the LHC. We also
restrict the Tevatron bound on the unknown coefficient of the three-point
unparticle correlator. With the availability of data from Tevatron, and the
advent of the data emerging from the LHC, these interactions can provide a
clear and strong indication of unparticle physics and distinguish this model
from other beyond the standard model scenarios.Comment: 28 pages, 16 figure
Constraints on Dark Photon from Neutrino-Electron Scattering Experiments
A possible manifestation of an additional light gauge boson , named
as Dark Photon, associated with a group is studied in neutrino
electron scattering experiments. The exclusion plot on the coupling constant
and the dark photon mass is obtained. It is shown
that contributions of interference term between the dark photon and the
Standard Model are important. The interference effects are studied and compared
with for data sets from TEXONO, GEMMA, BOREXINO, LSND as well as CHARM II
experiments. Our results provide more stringent bounds to some regions of
parameter space.Comment: 22 pages, 6 figures, 2 tables, text improved, fig.6 updated,
references adde
CP Asymmetry in Charged Higgs Decays to Chargino-Neutralino
We analyze the charge-parity (CP) asymmetry in the charged Higgs boson decays
to chargino-neutralino pairs, H^- -> chargino_i + neutralino_j. We show first
that these modes have a large branching ratio for m_H^- > 600 GeV. We use
Cutkosky rules to obtain the analytical formulas needed for the evaluation of
the asymmetry under consideration. We then calculate the CP asymmetry in
chargino-neutralino decays by including supersymmetric mass bounds, as well as
constraints from b -> s gamma, (g-2)_mu, Delta\rho and electric dipole moments.
Finally, we discuss observability of the asymmetry at the LHC by calculating
the number of required charged Higgs events to observe the asymmetry for each
decay channel. We show that the inclusion of constraints considerably reduces
the projected CP asymmetry, and that the optimal channel for observing the
asymmetry is H^- -> chargino_1 + neutralino_2.Comment: 23 pages, 8 figures, one tabl
Rare Decay of the Top t -> cgg in the Standard Model
We calculate the one-loop flavor changing neutral current top quark decay t
-> cgg in the Standard Model. We demonstrate that the rate for t -> cgg exceeds
the rate for a single gluon emission t -> cg by about two orders of magnitude,
while the rate for t -> cq barq (q=u) is slightly smaller than for t -> cg.Comment: 22 pages, 4 figures and 2 tables. Typo in Eq.2.1 corrected, text
slightly modified, references added. Version to appear in Phys.Rev.
Rare B_s -> \gamma \nu \bar{\nu} decay with polarized photon and new physics effects
Using the most general, model independent effective Hamiltonian, the rare B_s
->\gamma \nu \bar{\nu} decay with polarized photon is studied. The sensitivity
of the branching ratio and photon polarization to the new Wilson coefficients
are investigated. It is shown that these physical observables are sensitive to
the vector and tensor type interactions, which would be useful in search of new
physics.Comment: 9 pages, 5 figure
CP Asymmetry in Charged Higgs Decays in MSSM
We discuss and compare the charge-parity (CP) asymmetry in the charged Higgs
boson decays H -> \bar{u}_i d_j for the second and third generation quarks in
the minimal supersymmetric standard model. As part of the analysis, we derive
some general analytical formulas for the imaginary parts of two-point and
three-point scalar one-loop integrals and use them for calculating vectorial
and tensorial type integrals needed for the problem under consideration. We
find that, even though each decay mode has a potential to yield a CP asymmetry
larger than 10%, further analysis based on the number of required charged Higgs
events at colliders favors the \bar{t}b, \bar{c}b, and \bar{c}s channels, whose
asymmetry could reach 10-15% in certain parts of the parameter space.Comment: 25 pages, 9 figures. Discussion about charged Higgs observability
added, typos corrected, accepted for publication in PR
Impact of Sb degrees of freedom on the charge density wave phase diagram of the kagome metal CsVSb
Elucidating the microscopic mechanisms responsible for the charge density
wave (CDW) instability of the AVSb (A=Cs, K, Rb) family of kagome
metals is critical for understanding their unique properties, including
superconductivity. In these compounds, distinct CDW phases with wave-vectors at
the and points are energetically favorable, opening the possibility of
tuning the type of CDW order by appropriate external parameters. Here, we shed
light on the CDW landscape of CsVSb via a combination of
first-principles calculations and phenomenology, which consists of extracting
the coefficients of the CDW Landau free-energy expansion from density
functional theory. We find that while the main structural distortions of the
kagome lattice in the staggered tri-hexagonal CDW phase are along the
nearest-neighbor V-V bonds, distortions associated with the Sb ions play a
defining role in the energy gain in this and all other CDW states. Moreover,
the coupling between ionic displacements from different unit cells is small,
thus explaining the existence of multiple CDW instabilities with different
modulations along the c-axis. We also investigate how pressure and temperature
impact the CDW phase of CsVSb. Increasing pressure does not change the
staggered tri-hexagonal CDW ground state, even though the -point CDW
instability disappears before the -point one, a behavior that we attribute
to the large nonlinear coupling between the order parameters. Upon changing the
temperature, we find a narrow regime in which another transition can take
place, toward a tri-hexagonal Star-of-David CDW phase. We discuss the
implications of our results by comparing them with experiments on this
compound
An application of fuzzy-AHP to ship operational energy efficiency measures
Lowering fuel consumption of ships has gained a great deal of attention in maritime industry with regards to both environmental and economic concerns. The potential for fuel economy in shipping ranging between 25% to 75% is possible by using existing technology and practices and technical improvements in the design of new ship. Despite the existence of many technology and design-based approaches, limitations of emerging these measures has led to discussions about the potential energy savings through operational changes. In this study, operational measures were examined within the scope of Ship Energy Efficiency Management Plan (SEEMP) adopted by International Maritime Organization (IMO). We applied the Analytic Hierarchy Process (Fuzzy-AHP) approach, one of multi-criteria decision making (MCDM) techniques, to prioritize the weight of each measure. Fuzzy AHP effectively reflects the vagueness of human thinking with interval values, and shows the relative importance of operational measures - which can be the fundamental decision making data for decision makers (ships' masters, operating companies and ship owners) - by providing a strategic approach to identify energy efficient solutions
The Casimir Force in Randall Sundrum Models
We discuss and compare the effects of one extra dimension in the Randall
Sundrum models on the evaluation of the Casimir force between two parallel
plates. We impose the condition that the result reproduce the experimental
measurements within the known uncertainties in the force and the plate
separation, and get an upper bound kR < 20 if the curvature parameter k of
AdS_5 is equal to the Planck scale. Although the upper bound decreases as k
decreases, kR ~ 12, which is the required value for solving the hierarchy
problem, is consistent with the Casimir force measurements. For the case where
the 5th dimension is infinite, the correction to the Casimir force is very
small and negligible.Comment: 16 pages, 2 figures, references added, text improved, accepted for
publication in PR
- …