3 research outputs found
Ant colony optimization for controller and sensor-actuator location in active vibration control
No full textDeveloping light weight yet stronger and more flexible panels in aircraft structure to with stand from failure due to vibration has been the interest of many researchers nowadays. Piezoelectric material has been the popular choice to attenuate vibration actively and numerous techniques of optimal control and actuator placement have been proposed. This paper discusseson active vibration control of a simply supported thin plate excited and actuated by piezoelectric patches. Mathematical model of the simply supported plate with piezoelectric patches is derived using Euler-Bernoulli model. The main focus is to find the optimal location of the collocated sensor-actuatorand controller gains using a swarm intelligent algorithm called Ant Colony Optimization (ACO) which later verified with Genetic Algorithm (GA). A simply supported plate is taken as a benchmark model to perform simulation study
Estimating ensemble average power delivered by a piezoelectric patch actuator to a non-deterministic subsystem
No full textEngineering systems such as aircraft, ships and automotive are considered built-up structures. Dynamically they are taught of as being fabricated from many components that are classified as deterministic subsystems (DS) and non-deterministic subsystems (Non-DS). Structures’ response of the DS is deterministic in nature and analysed using deterministic modelling methods such as finite element method (FEM). The response of Non-DS is statistical in nature and estimated using statistical modelling technique such as statistical energy analysis (SEA). SEA method uses power balance equation, in which any external input to the subsystem must be represented in terms of power. Often, input force is taken as point force and ensemble average power delivered by point force is already well-established. However, the external input can also be applied in the form of moments exerted by a piezoelectric (PZT) patch actuator. In order to be able to apply SEA method for input moments, a mathematical representation for moment generated by PZT patch in the form of average power is needed, which is attempted in this paper. A simply-supported plate with attached PZT patch is taken as a benchmark model. Analytical solution to estimate average power is derived using mobility approach. Ensemble average of power given by the PZT patch actuator to the benchmark model when subjected to structural uncertainties is also simulated using Lagrangian method. These two results are compared and presented in this paper. The effects of size and location of the PZT actuators on the power delivered to the plate are later investigated
An evaluation of the writing component of the higher secondary English syllabus in Bangladesh
No full textThis evaluation study sets out to investigate the effectiveness of the writing component
of the Higher Secondary Certificate (HSC) English syllabus in Bangladesh. The aims of
the research were (i) to discover the needs and problems of students with regard to
writing; and the purposes for which they need to communicate in writing in English;
(ii) to identify their strengths and weaknesses in different aspects of writing; (iii) to
gather perceptions of teachers and students on the writing process and to compare
these with actual classroom practice with a view to characterising the approach to the
teaching of writing in the Bangladeshi HSC context; (iv) to collect views on the
syllabus and textbook and to determine if there was a match between student
needs and the syllabus; and (v) to suggest
recommendations for improving writing skills in the classroom.
This thesis is divided into nine chapters. Chapter 1 sets the context of the study by
presenting its objectives, significance and research questions. A brief account of the
history of the Revised English Syllabus is also presented. Chapters 2 and 3 contain
reviews of the literature relevant to the field of writing and evaluation. Chapter 2
examines writing as 'composing' and 'text' and the different approaches to writing
pedagogy. Findings from a couple of studies on the implementation of the process
approach in different contexts are also presented. Chapter 3 explores the different
approaches to evaluation and provides the framework for this evaluation study. The
design features and the procedures employed in the study are given in chapter 4. To
achieve methodological triangulation a series of instruments was used as well as data
collected from a range of stakeholders. For the purposes of this study a marking
scheme was designed to analyse the writing samples of students. Chapters 5 to 7
present and analyse the data. More specifically chapter 5 deals with the analysis of
findings about the writing process, i.e. the collation of perceptions and the actual
practice of writing in class. Chapter 6 examines the purposes, needs and problems of
learners with regard to writing and also concentrates on the evaluation of the HSC
writing syllabus. The analysis of students' Writing Tasks and the Examination
Compositions are dealt with in chapter 7. Chapter 8 focuses on the discussion of the
findings, followed by recommendations. In addition, a discussion on the socio-cultural
appropriateness of borrowing western methodologies for local contexts is also
highlighted. Finally, a summary of the main results from the empirical evaluation study
and their implications are presented in chapter 9. The limitations of the study
are also acknowledged in this last chapter.
The findings of the study revealed a disparity between students needs and what the
HSC writing syllabus contains, and its actual implementation in the classroom. The
teachers adopted an approach to writing which was overridingly form-focused and
hence, product oriented. They performed roles which were traditional e.g. the teacher
as purveyor of knowledge and evaluator. Teachers lack training in areas specific to the
development of writing skills and are unaware of recent developments in writing
approaches. There was no evidence in this study of promoting or encouraging the
strategies of skilled writers in the classes observed.
This study has contributed to the documentation of curriculum evaluation studies in the
context of Bangladesh, as well as frameworks for the assessment of writing skills for
use in this context. An awareness has been raised about the hindering and helpful
factors in bringing about change and general caution is suggested in the making of
foreign methodologies appropriate to the local Bangladeshi situation. Based on the
findings of this study, recommendations are also made in relation to curriculum
development and pedagogy
