Switching control systems and their design automation via genetic algorithms

The objective of this work is to provide a simple and effective nonlinear controller. Our strategy involves switching the underlying strategies in order to maintain a robust control. If a disturbance moves the system outside the region of stability or the domain of attraction, it will be guided back onto the desired course by the application of a different control strategy. In the context of switching control, the common types of controller present in the literature are based either on fuzzy logic or sliding mode. Both of them are easy to implement and provide efficient control for non-linear systems, their actions being based on the observed input/output behaviour of the system. In the field of fuzzy logic control (FLC) using error feedback variables there are two main problems. The first is the poor transient response (jerking) encountered by the conventional 2-dimensional rule-base fuzzy PI controller. Secondly, conventional 3-D rule-base fuzzy PID control design is both computationally intensive and suffers from prolonged design times caused by a large dimensional rule-base. The size of the rule base will increase exponentially with the increase of the number of fuzzy sets used for each input decision variable. Hence, a reduced rule-base is needed for the 3-term fuzzy controller. In this thesis a direct implementation method is developed that allows the size of the rule-base to be reduced exponentially without losing the features of the PID structure. This direct implementation method, when applied to the reduced rule-base fuzzy PI controller, gives a good transient response with no jerking

The insidious nature of ‘hard core’ alternative conceptions: Implications for the constructivist research programme of patterns in high school students' and pre-service teachers' thinking about ionisation energy

The present study contributes to the constructivist research programme (RP) into learning science by comparing patterns in responses from two groups of learners - senior high schools students and pre-service teachers - in the same educational context (Singapore), to a diagnostic instrument relating to the topic of ionisation energies. This topic is currently included in the curriculum for 16-19 year-old students studying chemistry in Singapore (and elsewhere). The comparison shows that although (a) graduate pre-service teachers offered some types of incorrect responses less frequently than high school students; (b) they retained high levels of alternative conceptions commonly found among high school students; and - of particular note - (c) certain alternative conceptions were found to be more common among the graduates. This suggest the intuitive appeal of certain alternative conceptions is such that they can readily be reproduced down ‘generations’ of learners. The findings are explored in terms of a range of conceptual resources that have been developed within the constructivist RP. The analysis suggests that the curriculum sets out inappropriate target knowledge for senior high school students, given the nature of the subject matter and the prior learning of the students. It is also suggested that it may be fruitful to consider conceptual learning in terms analogous to the RP found in science, and that from this perspective certain insidious alternative conceptions can be understood as derived from commitments that are taken-for-granted and protected from explicit challenge by a protective belt of refutable auxiliary conceptions

Understanding the Rate of Acid Reactions: Comparison Between Pre-Service Teachers and Grade 10 Students

A two-tier multiple choice diagnostic instrument on the stoichiometry and rate of acid reactions was administered to 611 Grade 10 students and 171 pre-service teachers. The results showed that the Grade 10 students and preservice teachers held alternative conceptions related to the properties of different acids affecting their rates of reaction, and the particles in the resulting mixtures at the end of the reactions. The study stresses the importance of identifying and clarifying the pre-service teachers' understanding of the concepts that they will teach as this may have consequences on their future students' learning of chemistry

Skin models for cutaneous melioidosis reveal Burkholderia infection dynamics at wound's edge with inflammasome activation, keratinocyte extrusion and epidermal detachment.

Funder: Research Centre of Excellence, Mechanobiology InstituteFunder: National Research FoundationFunder: Cambridge-NUS Global Alliance FundABSTRACTMelioidosis is a serious infectious disease endemic in Southeast Asia, Northern Australia and has been increasingly reported in other tropical and subtropical regions in the world. Percutaneous inoculation through cuts and wounds on the skin is one of the major modes of natural transmission. Despite cuts in skin being a major route of entry, very little is known about how the causative bacterium Burkholderia pseudomallei initiates an infection at the skin and the disease manifestation at the skin known as cutaneous melioidosis. One key issue is the lack of suitable and relevant infection models. Employing an in vitro 2D keratinocyte cell culture, a 3D skin equivalent fibroblast-keratinocyte co-culture and ex vivo organ culture from human skin, we developed infection models utilizing surrogate model organism Burkholderia thailandensis to investigate Burkholderia-skin interactions. Collectively, these models show that the bacterial infection was largely limited at the wound's edge. Infection impedes wound closure, triggers inflammasome activation and cellular extrusion in the keratinocytes as a potential way to control bacterial infectious load at the skin. However, extensive infection over time could result in the epidermal layer being sloughed off, potentially contributing to formation of skin lesions

Measuring Islamisation in Indonesia: The Practice of Islam in Central Java and West Sumatra During Reformasi

This thesis explores a proposed method for measuring the degree of Islamisation within a community, where Islamisation is defined as the extent to which Islam and religious concepts and rationale are used to organise and decide within the community at the political, social, cultural and personal levels. This proposed method involves the aggregation and analysis of measurements from different aspects by which a community could be Islamised, in order to obtain an assessment of the general state of Islamisation within that community. To assess the method’s feasibility, this thesis deploys it in two case studies of the Indonesian provinces of Central Java and West Sumatra during the Reformasi era. These case studies demonstrate that this method can be used to derive substantiated broad assessments about Islamisation. These assessments suggest West Sumatra is more Islamised than Central Java, although both provinces have experienced Islamisation during Reformasi

DEALIENATION : SOCIAL LIVING IN PUBLIC HOUSING

Master'sMASTER OF ARCHITECTURE (M.ARCH

APPLICATION OF COST-BENEFIT ANALYSIS IN PLANNING

Bachelor'sBACHELOR OF SCIENC

AMINO SUGAR-SCHIFF'S BASE COMPLEXES

Bachelor'sBACHELOR OF SCIENCE (HONOURS

Design of sophisticated fuzzy logic controllers using genetic algorithms

Abshct- Design of fuzzy logic controllers encounters difficulties in the selection of optimized membership functions and fuzzy rule base, which is traditionally achieved by a tedious trial-and error process. This paper develops genetic algorithms for automatic design of high performance fuzzy logic controllers using sophisticated membership functions that intrinsically reflect the nonlinearities encounter in many engineering control applications. The controller design space is coded in base7 strings (chromosomes), where each bit (gene) matches the 7 discrete fuzzy value. The developed approach is subsequently applied to design of a proportional plus integral type fuzzy controller for a nonlinear water level control system. The performance of this control system is demonstrated higher than that of a conventional PID controller. For further comparison, a fuzzy proportional plus derivative controller is also developed using this approach, the response of which is shown to present no steady-state error. I

Design of Sophisticated Fuzzy Logic Controllers Using . . .

Design of fuzzy logic controllers encounters difficulties in the selection of optimized membership functions and fuzzy rule base, which is traditionally achieved by a tedious trial-and-error process. This paper develops genetic algorithms for automatic design of high performance fuzzy logic controllers using sophisticated membership functions that intrinsically reflect the nonlinearities encountered in many engineering control applications. The controller design space is coded in base-7 strings (chromosomes), where each bit (gene) matches the 7 discrete fuzzy value. The developed approach is subsequently applied to the design of a proportional plus integral type fuzzy controller for a nonlinear water level control system. The performance of this control system is demonstrated higher than that of a conventional PID controller. For further comparison, a fuzzy proportional plus derivative controller is also developed using this approach, the response of which is shown to present no steady..