EULER CHARACTERISTIC OF TANGO BUNDLES

We are interested in a vector bundle constructed by Tango (1976). The Tango bundle is an indecomposable vector bundle of rank n-1 on the complex projective space P^n. In particular, we show that the Euler characteristic of the Tango bundle on P^n is equal to 2n-1

A characterization of the algebraic degree in semidefinite programming

In this article, we show that the algebraic degree in semidefinite programming can be expressed in terms of the coefficient of a certain monomial in a doubly symmetric polynomial. This characterization of the algebraic degree allows us to use the theory of symmetric polynomials to obtain many interesting results of Nie, Ranestad and Sturmfels in a simpler way.Comment: 14 page

Experimental and Numerical Evaluation of Concentrically Loaded RC Columns Strengthening by Textile Reinforced Concrete Jacketing

Nowadays, Textile Reinforced Concrete (TRC) has become a very popular strengthening technique for concrete structures. This paper presents an investigation on the applicability of TRC for strengthening reinforced concrete column. Both experimental and numerical studies are conducted to evaluate the confinement effects of various TRC strengthening schemes. The experimental study is performed on a series of six reinforced concrete square columns tested to failure. Two of them were un-strengthened as references, the other four were strengthened by one or two layers of Carbon Textile Reinforced Concrete (CTRC). The results indicated that the application of carbon TRC enhanced the ductility and ultimate strength of the specimens. Failure of all strengthened columns was together with tensile rupture of textile reinforcements at the corners of column. Finite element models of the CTRC strengthened columns based on ATENA software package were developed and verified with the experimental results. The analytical results show that in the specimen corner areas, textile reinforcements are subjected to a 3D complicated stress state and this may be the cause of their premature failure

The experience of using e-commerce platforms affects the online purchase intention of customers in the FMCG (Fast moving consumer goods) sector in Hanoi city

In recent times, the Vietnamese e-commerce market is in a period of strong development, in addition, to the sharp increase in people’s demands to join e-commerce platforms after the epidemic. The research group started with an overview study, then research hypotheses and models were proposed. After conducting preliminary qualitative and quantitative research to adjust the appropriate scales, the research group created a questionnaire and collected data in online forms with a sample size of 350. Next, the data was entered into the software for SEM analysis. The results of the study indicate that the quality of the e-commerce platform has an indirect impact on the purchase intention through the positive impact on the trust and the negative impact on the perceived risk. Attitudes towards information, trust, perceived risk, and perceived usefulness have direct influences on purchase intention. Attitude towards information, trust, and perceived usefulness have positive effects on purchase intention, while perceived risk harms purchase intention. In addition, purchase intention is relatively strongly influenced by trust and perceived usefulness. Perceived risk and attitude towards information have little influence on purchase intention. Finally, the research team proposes some solutions for businesses to increase the purchase intention of consumers through e-commerce platforms. &nbsp

Penetrating Keratoplasty for Keratoconus in Vietnamese Patients

BACKGROUND: Keratoconus is an ectatic corneal disorder that can impair the visual acuity. Up to now, penetrating keratoplasty (PK) remains the most common surgical procedure to treat severe keratoconus. In Vietnam, most keratoconus patients come to visit doctor at severe stage and were treated by PK, so we conduct this study. AIM: To evaluate the results of PK for keratoconus in Vietnamese patients. METHODS: This was a retrospective study of 31 eyes with keratoconus who underwent PK in VNIO from January 2005 to December 2014. RESULTS: The average visual acuity was 0.86 ± 0.37 logMAR (20/145). In the group of patients without amblyopia, best spectacle-corrected visual acuity of 20/60 or better was recorded in 75.9% of eyes and 93.1% of eyes achieved a best corrected visual acuity with hard contact lenses of 20/40 or better. Mean postoperative corneal power was 43.8 ± 4.5D. Mean corneal astigmatism was 5.9 ± 2.7D. 94.6% of grafts remained clear. Posterior subcapsular cataract developed in 22.6% of eyes. Graft rejection was recognized in 12.9% of eyes. CONCLUSION: PK is an effective procedure with high rate of graft survival for keratoconus patients. However, patients should be aware of the necessary of optical correction to gain the best VA after surgery