3,709 research outputs found
Symmetrical Observability of Kinematic Parameters in Symmetrical Parallel Mechanisms
This article presents an application of symmetry group theory in kinematic identification of parallel mechanisms of nlegs legs -- Kinematic Identification implies the estimation of the actual geometrical parameters (as opposed to nominal ones) of a physical mechanism -- For a symmetric mechanism, KI requires configuring sets of leg positions with symmetrical observability – This article presents as main contributions: (i) a conjecture that allows mapping the symmetries of the mechanism into the active-joint workspace, (ii) a set of necessary conditions to express leg parameters in coordinate systems which allow symmetrical observability, and (iii) a procedure for exploiting symmetries in pose selection for kinematic identification of symmetrical parallel mechanisms -- For the kinematic identification itself, we adopt a divide-and-conquer (DC) identification protocol -discussed by us in another publication- in which each leg of the mechanism is independently identified by using the inverse calibration method -- In this article we emphasize how to exploit the symmetries existent in (nlegs − 1) legs of the parallel mechanism allowing to apply to other legs the symmetry-transformed sample protocol used for the kinematic identification of a reference leg -- The symmetrical observability of sets of leg parameters allows to reduce the costs of the pose selection procedure by a factor of (1/nlegs) compared to a complete DC procedure in which the poses of each leg are selected independently -- The pose selection is carried out only for the reference leg -- For the (nlegs−1) remaining legs the poses are dictated by symmetry operations performed onto the poses of the reference leg -- An application of the symmetrical observability is presented through the simulated kinematic identification of a 3RRR symmetrical parallel mechanismPolytechnic School of the University of São PauloSitio webIndicaciones, Associação Brasileira de Métodos Computacionais em Engenharia, International Association for Computational Mechanics, International Congress and Convention Association, Conheça o São Paulo é Tudo de Bom, Embratur, PETROBRA
Novel Higgs decay signals in R-parity violating models
In supersymmetric models the lightest Higgs boson may decay with a sizable
branching ratio into a pair of light neutralinos. We analyze such decays within
the context of the minimal supersymmetric standard model with R-parity
violation, where the neutralino itself is unstable and decays into Standard
Model fermions. We show that the R-parity violating couplings induce novel
Higgs decay signals that might facilitate the discovery of the Higgs boson at
colliders. At the LHC, the Higgs may be observed, for instance, through its
decay -via two neutralinos- into final states containing missing energy and
isolated charged leptons such as , and .
Another promising possibility is the search for the displaced vertices
associated with the neutralino decay. We also point out that Higgs searches at
the LHC might additionally provide the first evidence of R-parity violation.Comment: 15 pages, 7 figures. Corrected affiliation
Impact assessment of irrigation management transfer in the Alto Rio Lerma Irrigation District, Mexico
Irrigation managementPrivatizationAssessmentEconomic aspectsLegal aspectsData collectionWater rightsWater allocationWater distributionGroundwaterFinancingMaintenanceOperationsAgricultural productionWater users' associationsFarmer participation
Formación de cristales lÃquidos cromónicos a partir de colorantes y su confinamiento en emulsiones agua-en-aceite y agua-en-agua
Treballs Finals de Grau de QuÃmica, Facultat de QuÃmica, Universitat de Barcelona, Any: 2019, Tutors: Maria Sarret Pons, Carlos Rodriguez AbreuChromonics are an interesting class of lyotropic liquid crystals with several potential medical and technological applications. Their confinement in emulsions provides an opportunity to design advanced organic-based materials. In this work, 9 dyes are tested in order to establish chromonic behaviour. Their phases are characterized using Polarized Optical Microscopy and Small Angle X-Ray Scattering (SAXS). Some of them are used for the formulation of stable water-in-oil (W/O) and water-in-water (W/W) emulsions, which are characterized using rheological techniques. Mesogenic phases were observed in seven of the nine studied dyes. Acid red 27, Alcian blue (chloride and acetate salts), Congo red and Neutral red acetate formed chromonic nematic (Nc phase) and hexagonal (M phase) columnar phases. The structure of their phases was not characterized due to partial insolubility.
The representative chromonic phases are shown through the partial phase diagram of nickel (II) phthalocyanine tetra-sulfonic acid. This compound stacks in cylindrical columns in both Nc and M phases, with a diameter of one molecule.
Two of the studied dyes were used to formulate the emulsion confinement. Representative optical textures of these systems were observed, as star-like and tactoid forms. The chromonic nematic phase of pinacyanol acetate was confined in drops of W/O emulsions with polydimethylsiloxane, vinyldimethylsiloxy terminated as the oil phase. The drop size was highly polydisperse and above 2 [mi]m. This emulsion showed a Newtonian rheology behaviour. Nickel (II) phthalocyanine tetra-sulfonic acid chromonic nematic phase was confined in W/W emulsions with added polyvinylpirrolydone. The W/W emulsion presented a polydisperse drop size larger than 1 [mi]m and showed a Newtonian behaviour. Other oils, surfactants and polymers were tested
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Modification of the National Weather Service Distributed Hydrologic Model for subsurface water exchanges between grids
To account for spatial variability of precipitation, as well as basin physiographic properties, the National Weather Service (NWS) has developed a distributed version of its hydrologic component, termed the Hydrology Laboratory-Research Distributed Hydrologic Model (HL-RDHM). Because channels are the only source of water exchange between neighboring computational elements, the absence of such exchange has been identified as a weakness in the model. The primary objective of this paper is to modify the model structure to account for subsurface water exchanges without dramatically altering the conceptual framework of the water balance module. The subsurface exchanges are established by partitioning the slow response components released from the lower layer storages into two parts: the first part involves the grid's conceptual channel, while the second is added to the lower layer storages of the downstream pixel. Realizing the deficiency of the water balance module to locate the lower zone layers in sufficient depths, a complementary study is conducted to test the feasibility of further improvement in the modified model by equally shifting downward the lower zone layers of all pixels over the basin. The Baron Fork at Eldon, Oklahoma, is chosen as the test basin. Ten years of grid-based multisensor precipitation data are used to investigate the effects of the modification, plus shifting the lower zone layers on model performance. The results show that the modified-shifted HL-RDHM can markedly improve the streamflow simulations at the interior point, as well as very high peak-flow simulations at the basin's outlet. Copyright 2011 by the American Geophysical Union
On the connection of Gamma-rays, Dark Matter and Higgs searches at LHC
Motivated by the upcoming Higgs analyzes we investigate the importance of the
complementarity of the Higgs boson chase on the low mass WIMP search in direct
detection experiments and the gamma-ray emission from the Galactic Center
measured by the Fermi-LAT telescope in the context of the . We obtain the relic abundance, thermal cross section,
the WIMP-nucleon cross section in the low mass regime and network them with the
branching ratios of the Higgs boson in the model. We conclude that the Higgs
boson search has a profound connection to the dark matter problem in our model,
in particular for the case that ( GeV) the BR(
WIMPs) . This scenario could explain this plateau of any mild
excess regarding the Higgs search as well as explain the gamma-ray emission
from the galactic center through the channel with a WIMP in the mass
range of 25-45 GeV, while still being consistent with the current limits from
XENON100 and CDMSII. However, if the recent modest excesses measured at LHC and
TEVATRON are confirmed and consistent with a standard model Higgs boson this
would imply that GeV, consequently ruling out any attempt to
explain the Fermi-LAT observations.Comment: 8 pages, 9 figure
Dynamics and Pattern Formation in Large Systems of Spatially-Coupled Oscillators with Finite Response Times
We consider systems of many spatially distributed phase oscillators that
interact with their neighbors. Each oscillator is allowed to have a different
natural frequency, as well as a different response time to the signals it
receives from other oscillators in its neighborhood. Using the ansatz of Ott
and Antonsen (Ref. \cite{OA1}) and adopting a strategy similar to that employed
in the recent work of Laing (Ref. \cite{Laing2}), we reduce the microscopic
dynamics of these systems to a macroscopic partial-differential-equation
description. Using this macroscopic formulation, we numerically find that
finite oscillator response time leads to interesting spatio-temporal dynamical
behaviors including propagating fronts, spots, target patterns, chimerae,
spiral waves, etc., and we study interactions and evolutionary behaviors of
these spatio-temporal patterns
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