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

Advanced SOM & K Mean Method for Load Curve Clustering

From the load curve classification for one customer, the main features such as the seasonal factors, the weekday factors influencing on the electricity consumption may be extracted. By this way some utilities can make decision on the tariff by seasons or by day in week. The popular clustering techniques are the SOM & K-mean or Fuzzy K-mean. SOM &Kmean is a prominent approach for clustering with a two-level approach: first, the data set will be clustered using the SOM and in the second level, the SOM will be clustered by K-mean. In the first level, two training algorithms were examined: sequential and batch training. For the second level, the K-mean has the results that are strongly depended on the initial values of the centers. To overcome this, this paper used the subtractive clustering approach proposed by Chiu in 1994 to determine the centers. Because the effective radius in Chiu’s method has some influence on the number of centers, the paper applied the PSO technique to find the optimum radius. To valid the proposed approach, the test on well-known data samples is carried out. The applications for daily load curves of one Southern utility are presented

MEDICAL STUDENTS’ EVALUATION OF AN ENGLISH FOR SPECIFIC PURPOSES COURSEBOOK: A CASE IN VIETNAM

The current study investigates students’ evaluation of the English for Specific Purposes (ESP) coursebook taught at a medical college in the Mekong Delta, Vietnam. After using it for a year, the users, including medical students and their teachers, have given some unofficial feedback on the book. This study provided insightful official information about how its student users perceive the coursebook they were adopting. Data on the evaluations of the ESP coursebook were gained from questionnaires administered to 166 students majoring in nursing and pharmacy in charge of ESP programs. Semi-structured interviews were employed with four students to get more specific apprehension. The results of this study indicated that students were satisfied with the ESP coursebook in terms of the covering of four skills, the presence of vocabulary and grammar, relevant content, understandable social and cultural context, suitability for mix-level students. In addition, participants perceived that communicative skills were not sufficiently presented, examples in grammar were not more interesting, the illustrations were not diverse and enough, and the cover was simple but not appealing. Suggestions regarding the pedagogical implications for the adoption and evaluation of the coursebook were discussed

MODELO DE CONSULTA ESCOLAR NO VIETNÃ: ESTUDO DE CASO DE PROFESSORES EM TEMPO PARCIAL

The school consultation model in Vietnam currently being implemented according to Circular No. 31/2017/TT-BGDDT effective from February 2, 2018, is the “Part-time teacher” model. The purpose of this exploratory study is to test the awareness of officials and teachers about the effectiveness of elements in the “part-time teacher” school consultation model in high schools in Ho Chi Minh City, Vietnam. The research sample was randomly selected from 4 high school heads and from teacher pedagogical training courses and management training classes, with 538 participants, of which teachers (69.0%), and managers (31.0%); in the study sample, there were (36.2%) participating in the school’s psychology team. Research subjects (28.6%) were trained in psychological consultation capacity by topic; (8.9%) training in psychological counseling capacity and granting training certificates; (5.4%) training for bachelor of psychology and master of psychology; (57.1%) had not studied through the psychological counseling competency program. The instrument’s validity and reliability were verified through the evaluation of Cronbach alpha analysis, and exploratory factor analysis (EFA). When analyzing the EFA factor, the results of the factors in the model have a positive correlation of 76.2% (R2 = 1.00), in the factors of personnel conducting consultations, policies for personnel participating in consultations, and policies for consulting personnel. Joining the school counseling team, the consultation process and the consultation room have not been paying attention.O modelo de consulta escolar no Vietname que está atualmente a ser implementado de acordo com a Circular n.º 31/2017/TT-BGDDT, em vigor a partir de 2 de fevereiro de 2018, é o modelo “Professor a tempo parcial”. O objectivo deste estudo exploratório é testar a sensibilização de funcionários e professores sobre a eficácia dos elementos do modelo de consulta escolar de “professores a tempo parcial” em escolas secundárias na cidade de Ho Chi Minh, Vietname. A amostra da pesquisa foi selecionada aleatoriamente entre 4 diretores de escolas de ensino médio e de cursos de formação pedagógica de professores e turmas de formação gerencial, com 538 participantes, sendo professores (69,0%) e gestores (31,0%); na amostra do estudo havia (36,2%) participantes da equipe de psicologia da escola. Os sujeitos da pesquisa (28,6%) foram capacitados em capacidade de consulta psicológica por tema; (8,9%) formação em capacidade de aconselhamento psicológico e concessão de certificados de formação; (5,4%) formação para bacharel em psicologia e mestre em psicologia; (57,1%) não haviam cursado o programa de competência em aconselhamento psicológico. A validade e a confiabilidade do instrumento foram verificadas por meio da avaliação da análise alfa de Cronbach e da análise fatorial exploratória (AFE). Ao analisar o fator AFE, os resultados dos fatores do modelo apresentam correlação positiva de 76,2% (R2 = 1,00), nos fatores pessoal que realiza consultas, políticas para pessoal participante de consultas e políticas para pessoal consultor. Juntando-se à equipe de aconselhamento escolar, o processo de consulta e o consultório não têm prestado atenção

Corona based air-flow using parallel discharge electrodes

A novel air-flow generator based on the effect of ion wind has been developed by the simultaneous generation of both positive and negative ions using two electrodes of opposite polarity placed in parallel. Unlike the conventional unipolar-generators, this bipolar configuration creates an ion wind, which moves away from both electrodes and yields a very low net charge on the device. The electro-hydrodynamic behavior of air-flow has been experimentally and numerically studied. The velocity of ion wind reaches values up to 1.25 m/s using low discharge current 5 mu-A with the kinetic conversion efficiency of 0.65% and the released net charge of �30 fA, 8 orders of magnitude smaller compared with the discharge current. Due to easy scalability and low net charge, the present configuration is beneficial to applications with space constraints and/or where neutralized discharge process is required, such as inertial fluidic units, circulatory flow heat transfer, electrospun polymer nanofiber to overcome the intrinsically instability of the process, or the formation of low charged aerosol