Power Generation of Pure Sine Wave in Batteryless Solar System using Advanced Control

A novel technique for conversion of DC power to AC power is introduced using solar powered sine wave generation system is presented. DC power extracted from solar system is made utilitarian for driving the BLDC (brushless DC) motor with constant speed constraints. The back EMF signals of each phase of the BLDC motor facilitated the development of technique for the sine wave generation from solar system without battery backup. This motor is coupled with AC generator, which yields the AC power on demand. The constant speed constraint indispensable for fixed electrical frequency at the output of generator. A new control technique is rendered for reference tracking speed control of BLDC motor using Lyapunov theory by changing switching frequency, and also maintaining the voltage level at the output of converter driving BLDC by regulating the switching frequency of the zeta converter. The proposed methodology for generation of AC power from solar power system is also tested on prototype. The comparison of conventional technique for generation of sine wave power and proposed scheme is mentioned at later section of this paper for describing the efficacy of newly presented scheme.

Exploring Metaphors of Teachers Practices and Perceptions for Assessing Creative Writing Skills

The world is becoming a "Global village" in which English has become a tool to communicate across the borders. To maintain effective communication, it becomes necessary for the teaching and learning process to take account of language skills. When taking into account language skills, it becomes pertinent for teachers to keep an accountability check of a child's progress from the early years of schooling. Moreover, it is also significant to gain teachers' perceptions about assessment. For that the purpose of this study was to explore teachers' practices and perceptions for assessing creative writing skills in an EFL classroom at grades one and two in a private school through metaphors. Two teachers were selected as research participants along with work samples of six students, three samples from each class. Metaphors were used as a tool in this study to get teachers' insights about the assessment of creative writing skill through interviews. Along with that document analysis and classroom observations sufficed the data collection. Metaphors shared by teachers, were cooking and floating. Metaphors helped in extracting teachers' sub-conscious meaning which were evident in their practices. It was evident from the interpretation of teachers' metaphors; they had ambiguous ideas about continuous assessment. Teachers used a variety of continuous assessment tools such as observation, asking questions to name a few but without any developed insights. It was also revealed from the data gathered that teachers focused more on grammatical aspects of language. Though teachers practiced creative writing with students they were of a view that students are not creative. As a result, they took up the role of a transmitter and gave less space to students to be imaginative. This study suggests that English language teachers should be aware of the purposes and uses of continuous assessment in order to help students in an appropriate way for their effective learning.