A see-saw scenario of an A4A_4 flavour symmetric standard model

A see-saw scenario for an $A_4$ flavour symmetric standard model is presented. The latter, compared with the standard model, has an extended field content adopting now an additional $A_4$ symmetry structure (along with the standard model symmetry). As before, the see-saw mechanism can be realized in several models of different types depending on different ways of neutrino mass generation corresponding to the introduction of new (heavy in general) fields with different symmetry structures. In the present paper, a general description of all these see-saw types is made with a more detailed investigation on type-I models, while for type-II and type-III models a similar strategy can be followed. As within the original see-saw mechanism, the symmetry structure of the standard model fields decides the number and the symmetry structure of the new fields. In a model considered here, the scalar sector consists of three standard-model-Higgs-like iso-doublets ($SU_L(2)$-doublets) forming together an $A_4$-triplet, and three iso-singlets transforming as three singlets (1,$1^{'}$ and $1^{''}$) of $A_4$. In the lepton sector, the three left-handed lepton iso-doublets form an $A_4$-triplet, while the three right-handed charged leptons are either $A_4$-singlets in one version of the model, or components of an $A_4$-triplet in another version. To generate neutrino masses through, say, the type-I see-saw mechanism, it is natural to add four right-handed neutrino multiplets, including one $A_4$-triplet and three $A_4$-singlets. For an interpretation, the model is applied to deriving some physics quantities such as neutrinoless double beta decay effective mass $|\langle m_{ee}\rangle|$, CP violation phase $\delta_{CP}$ and Jarlskog parameter $J_{CP}$, which can be verified experimentally.Comment: LaTeX, 31 pages, 12 figures, 6 tables. V3: some parts modifie

Innovation and Export of Vietnam’s SME Sector

Innovation has long been considered an important factor for creating and maintaining the competitiveness of nations and firms. The relationship between innovation and exporting has been investigated for many countries. However, there is a paucity of research in Vietnam with respect to this issue. In this paper we examine whether innovation performed by Vietnam’s small and medium enterprises (SMEs) enhances their exporting likelihood. Using the recently released Vietnam Small and Medium Enterprise Survey 2005, we find that innovation as measured directly by ‘new products’, ‘new production process’ and ‘improvement of existing products’ are important determinants of exports by Vietnamese SMEs.Vietnam; Export; Innovation; Small and Medium Enterprise

Model of neutrino effective masses

It is shown that an effective (nonrenormalizable) coupling of lepton multiplets to scalar triplets in the 331 model with sterile/exotic neutrinos, can be a good way for generating neutrino masses of different types. The method is simple and avoids radiative/loop calculations which, sometimes, are long and complicated. Basing on some astrophysical arguments it is also stated that the scale of SU(3)L symmetry breaking is at TeV scale, in agreement with earlier investigations. Or equivalently, starting from this symmetry breaking scale we could have sterile/exotic neutrinos with mass of a few keV's which could be used to explain several astrophysical and cosmological puzzles, such as the dark matter, the fast motion of the observed pulsars, the re-ionization of the Universe, etc

Quality comparison of Y-shape joints by tube hydroforming with and without counterforce

The design capability, strength, and structural rigidity provided by tube hydroforming (THF) are successfully used in many applications to produce high-strength parts and assemblies with improved mechanical properties, optimized service life, and weight features. In tubular metal forming, output parameters such as branch height, distribution of tube wall material thickness, distribution of damage factor, metal flow, effective stress, and effective strain significantly affect the quality of the product after the forming process. Therefore, this paper aims to evaluate the manufacturing quality of Y-shape joints from AISI304 material steel tube through output parameters of THF process with and without counter punch force on numerical simulation base. The Finite Element Method (FEM) has become an established feature of metal forming technology. The objective of FEM is to replace costly and elaborate experimental testing with fast, low-cost computer simulation. The simulation study uses finite element method-based virtual prototyping techniques to characterize output parameters, gain insight into strain mechanics, and predict mechanical properties of shaped components. The research results are presented clearly and unambiguously through the evaluation of 7 criteria to compare the quality of the specimens hydroformed by two surveyed cases and optimize the crucial input process parameters. And these data can be applied in experiments, more efficient product and process design, calculation, and control of input parameters avoiding costly trial and error in industrial production. The findings can help technologists optimize process parameters in the hydroforming process of products with protrusion from a tubular blan