Remarks on the extension of the Ricci flow

We present two new conditions to extend the Ricci flow on a compact manifold over a finite time, which are improvements of some known extension theorems.Comment: 9 pages, to appear in Journal of Geometric Analysi

Evidence for SU(3) symmetry breaking from hyperon production

We examine the SU(3) symmetry breaking in hyperon semileptonic decays (HSD) by considering two typical sets of quark contributions to the spin content of the octet baryons: Set-1 with SU(3) flavor symmetry and Set-2 with SU(3) flavor symmetry breaking in HSD. The quark distributions of the octet baryons are calculated with a successful statistical model. Using an approximate relation between the quark fragmentation functions and the quark distributions, we predict polarizations of the octet baryons produced in $e^+e^-$ annihilation and semi-inclusive deeply lepton-nucleon scattering in order to reveal the SU(3) symmetry breaking effect on the spin structure of the octet baryons. We find that the SU(3) symmetry breaking significantly affects the hyperon polarization. The available experimental data on the $\Lambda$ polarization seem to favor the theoretical predictions with SU(3) symmetry breaking. We conclude that there is a possibility to get a collateral evidence for SU(3) symmetry breaking from hyperon production. The theoretical errors for our predictions are discussed.Comment: 3 tables, 14 figure

Principle of Balance and the Sea Content of the Proton

In this study, the proton is taken as an ensemble of quark-gluon Fock states. Using the principle of balance that every Fock state should be balanced with all of the nearby Fock states (denoted as the balance model), instead of the principle of detailed balance that any two nearby Fock states should be balanced with each other (denoted as the detailed balance model), the probabilities of finding every Fock state of the proton are obtained. The balance model can be taken as a revised version of the detailed balance model, which can give an excellent description of the light flavor sea asymmetry (i.e., $\bar{u}\not= \bar{d}$) without any parameter. In case of $g\Leftrightarrow gg$ sub-processes not considered, the balance model and the detailed balance model give the same results. In case of $g\Leftrightarrow gg$ sub-processes considered, there is about 10 percent difference between the results of these models. We also calculate the strange content of the proton using the balance model under the equal probability assumption.Comment: 32 latex pages, 4 ps figures, to appear in PR

Coupled KdV equations of Hirota-Satsuma type

It is shown that the system of two coupled Korteweg-de Vries equations passes the Painlev\'e test for integrability in nine distinct cases of its coefficients. The integrability of eight cases is verified by direct construction of Lax pairs, whereas for one case it remains unknown

The validity and reliability of the exposure index as a metric for estimating the radiation dose to the patient

Introduction With the introduction of digital radiography, the feedback between image quality and over-exposure has been partly lost which in some cases has led to a steady increase in dose. Over the years the introduction of exposure index (EI) has been used to resolve this phenomenon referred to as ‘dose creep’. Even though EI is often vendor specific it is always a related of the radiation exposure to the detector. Due to the nature of this relationship EI can also be used as a patient dose indicator, however this is not widely investigated in literature. Methods A total of 420 dose-area-product (DAP) and EI measurements were taken whilst varying kVp, mAs and body habitus on two different anthropomorphic phantoms (pelvis and chest). Using linear regression, the correlation between EI and DAP were examined. Additionally, two separate region of interest (ROI) placements/per phantom where examined in order to research any effect on EI. Results When dividing the data into subsets, a strong correlation between EI and DAP was shown with all R-squared values > 0.987. Comparison between the ROI placements showed a significant difference between EIs for both placements. Conclusion This research shows a clear relationship between EI and radiation dose which is dependent on a wide variety of factors such as ROI placement, body habitus. In addition, pathology and manufacturer specific EI’s are likely to be of influence as well. Implications for practice The combination of DAP and EI might be used as a patient dose indicator. However, the influencing factors as mentioned in the conclusion should be considered and examined before implementation

The Ricci flow on noncommutative two-tori

In this paper we construct a version of Ricci flow for noncommutative 2-tori, based on a spectral formulation in terms of the eigenvalues and eigenfunction of the Laplacian and recent results on the Gauss-Bonnet theorem for noncommutative tori.Comment: 18 pages, LaTe

Friction and wear of Cu-15 wt%Ni-8 wt%Sn bronze lubricated by grease at room and elevated temperature

Cu-15 wt%Ni-8 wt%Sn (CuNiSn) bronze alloy shows promising bearing performance when used in tribological applications and has attracted increasing research interest. In this work, the tribological performance of CuNiSn in terms of friction and wear were investigated in a ball-on-disc contact configuration, sliding against a Al2O3 ball under varying normal loads (1 and 4 N) and environmental temperatures (room temperature (~18 °C) and 110 °C). Post-test characterization techniques, including optical profilometry, scanning electron microscopy (SEM), energy dispersive X-ray (EDX) and transmission electron microscopy (TEM) were adopted to characterize the wear track on the CuNiSn surface after 13,500 cycles of reciprocating sliding. Both friction and wear behaviour was found to depend on the load and temperature whilst wear resistance reduced with increased temperature. A mechanically mixed layer (MML) and plastic deformation layer (PDL) were characterized by TEM micrographs of the cross-section from the wear track. Under 4 N load, a 1–1.5 μm thick tribolayer was developed during sliding at room temperature compared with a 200–300 nm tribolayer at 110 °C. The friction and wear mechanisms were largely dominated by properties of the tribolayers which were initially associated with and affected by load and temperature

Darboux Transformations for a Lax Integrable System in 2n2n-Dimensions

A $2n$-dimensional Lax integrable system is proposed by a set of specific spectral problems. It contains Takasaki equations, the self-dual Yang-Mills equations and its integrable hierarchy as examples. An explicit formulation of Darboux transformations is established for this Lax integrable system. The Vandermonde and generalized Cauchy determinant formulas lead to a description for deriving explicit solutions and thus some rational and analytic solutions are obtained.Comment: Latex, 14 pages, to be published in Lett. Math. Phy

Computer analysis of objects’ movement in image sequences: methods and applications

Computer analysis of objects’ movement in image sequences is a very complex problem, considering that it usually involves tasks for automatic detection, matching, tracking, motion analysis and deformation estimation. In spite of its complexity, this computational analysis has a wide range of important applications; for instance, in surveillance systems, clinical analysis of human gait, objects recognition, pose estimation and deformation analysis. Due to the extent of the purposes, several difficulties arise, such as the simultaneous tracking of manifold objects, their possible temporary occlusion or definitive disappearance from the image scene, changes of the viewpoints considered in images acquisition or of the illumination conditions, or even nonrigid deformations that objects may suffer in image sequences. In this paper, we present an overview of several methods that may be considered to analyze objects’ movement; namely, for their segmentation, tracking and matching in images, and for estimation of the deformation involved between images.This paper was partially done in the scope of project “Segmentation, Tracking and Motion Analysis of Deformable (2D/3D) Objects using Physical Principles”, with reference POSC/EEA-SRI/55386/2004, financially supported by FCT -Fundação para a Ciência e a Tecnologia from Portugal. The fourth, fifth and seventh authors would like to thank also the support of their PhD grants from FCT with references SFRH/BD/29012/2006, SFRH/BD/28817/2006 and SFRH/BD/12834/2003, respectively

Improving emergency plans management with SAGA

[EN] Emergency plans are the tangible result of the preparedness activities of the emergency management lifecycle. In many countries, public service organizations have the legal obligation to develop and maintain emergency plans covering all possible hazards relative to their areas of operation. However, little support is provided to planners in the development and use of plans. Often, advances in software technology have not been exploited, and plans remain as text documents whose accessibility is very limited. In this paper, we advocate for the definition and implementation of plan management processes as the first step to better produce and manage emergency plans. The main contribution of our work is to raise the need for IT-enabled planning environments, either at the national or organization-specific levels, which can lead to more uniform plans that are easier to evaluate and share, with support to stakeholders other than responders, among other advantages. To illustrate our proposal, we introduce SAGA, a framework that supports the full lifecycle of emergency plan management. SAGA provides all the actors involved in plan management with a number of tools to support all the stages of the plan lifecycle. We outline the architecture of the system, and show with a case study how planning processes can benefit from a system like SAGA.We thank J. Marzal and R. Garrido, from the UPV Prevention Service, for their cooperation in the early design of SAGA. The work of J.H. Canós, M.C. Penadés, M. Llavador and A. Gómez is partially funded by the Spanish Ministerio de Educación y Ciencia (MEC) under grant TIPEx (TIN2010-19859-C03-03). The work of M.R.S. Borges is partially supported by grant nos. 560223/2010-2 and 308003/2011-0 from CNPq (Brazil) and grant no. E-26/103.076/2011 from FAPERJ (Brazil). The cooperation between the Brazilian and the Spanish research groups was partially sponsored by the CAPES/MECD Cooperation Program, Project #169/PHB2007-0064-PC.Canos Cerda, JH.; Borges, M.; Penadés Gramage, MC.; Gómez Llana, A.; Llavador Campos, M. (2013). Improving emergency plans management with SAGA. Technological Forecasting and Social Change. 80(9):1868-1876. https://doi.org/10.1016/j.techfore.2013.02.014S1868187680