Fast iterative solvers for boundary value problems on a local spherical region

Boundary value problems on local spherical regions arise naturally in geophysics and oceanography when scientists model a physical quantity on large scales. Meshless methods using radial basis functions provide a simple way to construct numerical solutions with high accuracy. However, the linear systems arising from these methods are usually ill-conditioned, which poses a challenge for iterative solvers. We construct preconditioners based on an additive Schwarz method to accelerate the solution process for solving boundary value problems on local spherical regions. References D. Crowdy. Point vortex motion on the surface of a sphere with impenetrable boundaries. Physics of Fluids, 18:036602 (2006). doi:10.1063/1.2183627. A. E. Gill. Atmosphere-Ocean Dynamics, International Geophysics Series Volume 30. Academic, New York (1982). R. Kidambi and P. K. Newton. Point vortex motion on a sphere with solid boundaries. Physics of Fluids, 12:581 (2000). doi:10.1063/1.870263. Q. T. Le Gia, I. H. Sloan, and T. Tran. Overlapping additive Schwarz preconditioners for elliptic PDEs on the unit sphere. Math. Comp., 78:79--101 (2009). doi:10.1090/S0025-5718-08-02150-9. C. Muller. Spherical Harmonics, Vol. 17 of Lecture Notes in Mathematics. Springer-Verlag, Berlin (1966). M. V. Nezlin. Some remarks on coherent structures out of chaos in planetary atmospheres and oceans. Chaos, 4:109--111 (1994). doi:10.1063/1.165997. T. Tran, Q. T. Le Gia, I. H. Sloan, and E. P. Stephan. Preconditioners for pseudodifferential equations on the sphere with radial basis functions. Numer. Math., 115:141--163 (2009). doi:10.1007/s00211-009-0269-8

An Analysis of EFL Teachers’ Fear of Failure as Their Motivation for Pursuing Graduate Studies

Many studies have been conducted to clarify the impact of teachers’ motivation for participating in TPD activities; nevertheless, none of them has viewed teachers’ fear of failure as their motivation for TPD, especially for pursuing graduate programs in the Vietnamese context. That explains why this current qualitative study with the participation of nine EFL teacher interviewees was administered to fill in the abovementioned gap. Moreover, the study was conducted in a tertiary institution in the Mekong delta of Vietnam. Based on the data analysis, several teachers’ fears of failure as their motivation for following graduate programs were detected. Their fears included self-perceived inadequate qualifications in TEFL which resulted in their ineffective teaching performances. Participants were also much concerned about losing a job, failing to have opportunities to further their education and losing momentum for work due to routinized teaching.  Mid- age job crisis, negative effects of lacking role models on the growth of children and other younger people, lack of collegial support, and low self-confidence were found to be motivating fears which stimulated participants to make them pursue higher degree programs. The paper ends with discussions of the findings and pedagogical implication

Electroweak phase transition in the economical 3-3-1 model

We consider the EWPT in the economical 3-3-1 (E331) model. Our analysis shows that the EWPT in the model is a sequence of two first-order phase transitions, $SU(3) \rightarrow SU(2)$ at the TeV scale and $SU(2) \rightarrow U(1)$ at the $100$ GeV scale. The EWPT $SU(3) \rightarrow SU(2)$ is triggered by the new bosons and the exotic quarks; its strength is about $1 - 13$ if the mass ranges of these new particles are $10^2 \,\mathrm{GeV} - 10^3 \,\mathrm{GeV}$. The EWPT $SU(2) \rightarrow U(1)$ is strengthened by only the new bosons; its strength is about $1 - 1.15$ if the mass parts of $H^0_1$, $H^\pm_2$ and $Y^\pm$ are in the ranges $10 \,\mathrm{GeV} - 10^2 \,\mathrm{GeV}$. The contributions of $H^0_1$ and $H^{\pm}_2$ to the strengths of both EWPTs may make them sufficiently strong to provide large deviations from thermal equilibrium and B violation necessary for baryogenesis.Comment: 17 pages, 9 figure

Excellent luminous flux of WLEDs with flat dual-layer remote phosphor geometry

This paper focuses on the comparison of the luminous flux of two dual-remote phosphor structures named flat dual-remote phosphor (FDRP) and concave dual-remote phosphor (CDRP). These two configurations have different luminous flux values due to the disparity in scattering properties in white LEDs. However, the researched results showed that FDRP structure is more lucrative than the CDRP structure when it comes to the luminous flux effectiveness. To support the aforementioned idea, this article also presents the influence of the distance between two phosphor layers (d1) and the distance between the phosphor layer with the LED surface (d2) on the optical properties of the FDRP structure. Specifically, the scattering ability and absorption properties of the remote phosphor layer will vary sharply if d1 and d2 are adjusted into different values, which produces an immense impact on the chromatic homogeneity and illumination capability of WLEDs. Therefore, in order to stabilize the correlated color temperature (CCT) of WLEDs at 8500 K when there is a modification on d1 and d2, the concentration of YAG:Ce3+ phosphor also needs to be varied. Accordingly, the scattering process and absorption phenomenon in the remote phosphor layer will bottom out when d1 = d2 = 0,  leading to the worst color quality and luminous flux. The effect of the spectra generated as these distances are adjusted is obvious evidence for this point. In other words, the larger the d1 and d2, the larger the scattering surface, and thus the blending of blue and yellow light rays will become more homogeneous, yielding the smallest white light deflection and the lowest luminous flux at the same time. The paper's results indicated that the luminous flux will reach a peak at 1020 lm if d1 = 0.08 mm or d2 = 0.63 mm and the chromatic deflection will hit the lowest point as d1 = 0.64 mm or d2 = 1.35 mm. In the end, manufacturers can make their choice for the production of higher-standard WLEDs based on the general knowledge and helpful information that the article has provided and analyzed

Improving luminous flux and color homogeneity of dual-layer phosphor sctructure

In order to clarify the main purpose of the study, we put a green phosphor layer SrBaSiO4:Eu2+ on the yellow phosphorus layer YAG:Ce3+ through using only one WLEDs structure in different color temperatures like 5600 K, 6600 K, 7700K. Then, we find the suitable SrBaSiO4:Eu2+ concentration in order that the luminous flux could get the highest value. The results show that SrBaSiO4:Eu2+ brings great benefits to increase not only optical gain but also color uniformity. Specifically, the greater the SrBaSiO4:Eu2+ concentration, the greater the output of WLEDs because of the development of green light component in WLEDs. However, only if the SrBaSiO4:Eu2+ concentration exceeds the level, a slight decrease in color rendering index (CRI) can occur, which based on Monte Carlo simulation. In addition, the results of this paper have contributed significantly to the creation of higher-powered WLEDs

Biosynthesis of silver nanoparticles using curcumin against the bovine mastitis bacteria

Bovine mastitis is the most common disease and has greatly affected economies around the world. This study aimed to determine the antibacterial ability of bovine mastitis by curcumin - silver nanoparticles (Cur-AgNPs). The study included experiments on presenting a new process for synthesizing silver nanoparticles using curcumin from fresh turmeric as a reducing agent and stabilizer. UV visible spectroscopy of the samples revealed the localized surface plasmon resonance absorbance of the dispersion of silver nanoparticles at 430 nm. The prepared Cur-AgNPs has a spherical shape with an average size of 30 nm and a size distribution of 15–47 nm. FT-IR (Fourier transform infrared spectroscopy) measurements of the samples showed that silver nanopartilces has been encapsulated well by curcumin. Cur-AgNPs with a concentration of 50-200 μg/mL has very effect to Staphylococcus aureus, Pseudomonas aeruginosa causing bovine mastitis in vitro. The maximum inhibition zone formed was 15 ± 0.85 mm for Staphylococcus aureus and 14 ± 0.56 mm for Pseudomonas aeruginosa. Plant materials mediating for the synthesis of silver nanoparticles have relatively rapid, less expensive, and widespread applications for antimicrobial therapy in the livestock sector