A Control Systems Perspective to Condition Monitoring and Fault Diagnosis

Modern industrial processors, engineering systems and structures, have grown significantly in complexity and in scale during the recent years. Therefore, there is an increase in the demand for automatic processors, to avoid faults and severe break downs, through predictive maintenance. In this context, the research into nonlinear systems analysis has attained much interest in recent years as linear models cannot be used to represent some of these systems. In the field of control systems, the analysis of such systems is conducted in the frequency domain using methods of Frequency Response Analysis. Generalised Frequency Response Functions (GFRFs) and the Nonlinear Output Frequency Response Functions (NOFRFs) are Frequency Response Analysis techniques used for the analysis of nonlinear dynamical behaviour in the frequency domain. The problem of Condition Monitoring and Fault Diagnosis has been investigated in the perspective of modelling, signal processing and multivariate statistical analysis, data-driven methods such as neural networks have gained significant popularity. This is because possible faulty conditions related to complex systems are often difficult to interpret. In such a background, recently, a new data-driven approach based on a systems perspective has been proposed. This approach uses a controls systems analysis method of System Identification and Frequency Response Analysis and has been shown before as a potential technique. However, this approach has certain practical concerns regarding real-world applications. Motivated by these concerns in this thesis, the following contributions are put forward: 1. The method of evaluating NOFRFs, using input-output data of a nonlinear system may experience numerical errors. This is a major concern, hence the development of a method to overcome these numerical issues effectively. 2. Frequency Response Analysis cannot be used in its current state for nonlinear systems that exhibit severe nonlinear behaviour. Although theoretically, it has been argued that this is possible, even though, it has been impossible in a practical point of view. Therefore, the possibility and the manner in which Frequency Response Analysis can be conducted for these types of systems is presented. 3. Development of a System Identification methodology to overcome the issues of inadequately exciting inputs and appropriately capturing system dynamics under general circumstances of Condition Monitoring and Fault Diagnosis. In addition to the above, the novel implementation of a control systems analysis approach is implemented in characterising corrosion, crack depth and crack length on metal samples. The approach is applied to the data collected, using a newly proposed non-invasive Structural Health Monitoring method called RFID (Radio Frequency IDentification) wireless eddy current probing. The control systems analysis approach along with the RFID wireless eddy current probing method shows the clear potential of being a new technology in non-invasive Structural Health Monitoring systems

Perceived Causes and Effects of Project Delays: A Study of Government Building Construction Projects in the Central Province of Sri Lanka

The problem of delays in the construction industry is a global phenomenon, and Sri Lanka is no exception. The key objectives of this study are to identify and rank the factors that cause project delays in government construction projects and their effects as perceived by the three primary industry participants, namely the clients, consultants and contractors and assess the differences. A questionnaire survey was conducted to solicit the perceived causes and effects of project delays from clients, consultants and contractors responsible for government building construction projects in the Central province of Sri Lanka. Perceived delay factors of the said primary stakeholders were measured using a five-point Likert scale type statements. The causes and effects were ranked according to their Relative Importance Index (the product of Severity Index and Frequency Index). The Spearman Correlation method and Kruskal-Wallis tests were used to test the difference in the perception among the three primary stakeholders. Data were collected from 32 consultants, 49 contractors and 16 clients. This study identified improper project management by the contractor as the leading cause of project delay. The other main causes in the ranked order are shortage of labour, financial problems of the clients, improper day work planning by contractor, delay in payment process, scope changes, delays in drawings submission, delays in approvals, financial difficulties of the contractor and lack of communication. The highest level of agreement on causes of project delays was observed between clients and contractors whereas the lowest level of agreement was observed between clients and consultants. The main perceived effects of project delays are cost overrun, poor quality of the work, disputes, arbitration, litigation and total abandonment. In relation to the effects of project delays, a high level of agreement was observed among clients, consultants and contractors. Each party had a positive correlation for both causes and effects of project delays with the other two parties, while contractors and clients showed the highest agreement on delays causes. There was a very high correlation for ranked effects between any two parties. Keywords: Construction Projects, Delay Causes, Delay Effects, Clients, Contractors, Consultants, Correlational Analysi

Distribution and Conservation Awareness of Grey Slender Loris (Loris lydekkerianus nordicus) at Sampopham’s Arboretum, Dambulla, Sri Lanka

Lorises are very unique creatures that live on trees. As a result of habitat destruction, they have become a rarity and are on the verge of extinction. Sam Popham’s Arboretum, Dambulla is Sri Lanka’s only dry zone Arboretum where an amazing spectrum of trees, birds, butterflies, dragonflies, and mammals can be observed in their natural setting. The slow Lorises are now identified as a heavily threaten group of animals and declared as threatened species in Sri Lanka. Therefore, it is an urgent necessity to take measures to protect them in their habitats. There are no studies reported so far on different habitats and the distribution pattern of the Loris population at Sam Popham’s Arboretum. The main objective of this research is to study the distribution pattern and population estimation of Grey Slender Loris in different habitats at Sam Popham's Arboretum. The number of Lorises, its gender, maturity (adult/juvenile) and the species of tree (with the height) which Lorises were spotted were recorded and tagged. The data was collected for a period of seven months from January 2019 to July 2019. The results obtained so far showed that Lorises are restricted to certain specific tree species. Although the forest is rich with large no trees belonging to several families, they commonly occupied species such as Pamburu (Pamburus missionis), Daduwa (E. bracteata), Welan (P. suberifolium), Elapath Habarala (Diospyros ferrea), and Ahatu (Ficus tinctoria). Furthermore, the Lorises were sighted at a height of 5 feet and above. According to the results, 31 Grey Slender Lorises were found and 14 of them were adult males, six were adult females and 11 were juveniles. Out of the tree species, Daduwa (E. bracteats) has the highest number of loris sightings consisting of 4 adult Lorises all were male adults. Elapath Habarala (D. ferrea), Ahatu (Ficus tinctoria) and Velan (P. suberifolium) each consist 3 Grey Slender Lorises which were 3 adults males, 1 female and 4 juveniles. As per the present study, during the full moon, the Loris sighting was relatively low compared to other days due to the moonlight. However, during the study, an average of 3 Lorises can be observed within a period of 2 hours. This indicates that there is a good population of Lorises within the Arboretum. Therefore, the establishment of similar Arboretums and enhancing the knowledge of the general public will help to uplift the rapidly declining Loris populations in the area.Keywords: Loris, Arboretum, Dambulla, Distributio

The horofunction boundary of the Hilbert geometry

We investigate the horofunction boundary of the Hilbert geometry defined on an arbitrary finite-dimensional bounded convex domain D. We determine its set of Busemann points, which are those points that are the limits of `almost-geodesics'. In addition, we show that any sequence of points converging to a point in the horofunction boundary also converges in the usual sense to a point in the Euclidean boundary of D. We prove that all horofunctions are Busemann points if and only if the set of extreme sets of the polar of D is closed in the Painleve-Kuratowski topology.Comment: 24 pages, 2 figures; minor changes, examples adde

Valuing the Hikkaduwa Coral Reef: An Application of the Zonal Travel Cost Method

Hikkaduwa marine ecosystem is one of the major attractions among the recreationists for its fringing coral reef and the beach. However, a rapid degradation of the coral reef and the beach pollution are the main influences on the sustainable tourism. In this context, valuing the Hikkaduwa Marine National Park is important in order to draw the attention for the protection of the ecosystem. The objectives of this research were to estimate the economic values derived by the local visitors and to derive an optimal entrance fee. This research also aimed at investigating factors that influence visitation rates. Data collected from an onsite survey carried out among a sample of 231 visitors from 16 districts in Sri Lanka were analysed, using the Zonal Travel Cost Method to estimate the recreational value derived by the local visitors. The travel cost function showed that visitation rate is significantly and positively influenced by recreational experience and urban population fraction. The explanatory power of the estimated model was strong with an adjusted R2 value of 0.752. In the second stage, these significant explanatory variables were used to construct the demand curve. The estimated local recreational value of the park is around 380 times the income from the local visitors per year, which is worth about Rs. 1,300 per local visitor. As this site does not have a proper entrance fee, the calculated entrance fee which maximises the total revenue was around Rs.1,100. However, the current level of visitors will be reduced by more than 50%, if this entrance fee is imposed implying intragenerational equity issues. The outcomes of this research are useful in the management decision making for the protection of the Hikkaduwa coral reef and the surrounding environment.Keywords: Consumer surplus, Hikkaduwa coral reef, Tourism, Zonal Travel Cost Metho

Trace Spaces: an Efficient New Technique for State-Space Reduction

State-space reduction techniques, used primarily in model-checkers, all rely on the idea that some actions are independent, hence could be taken in any (respective) order while put in parallel, without changing the semantics. It is thus not necessary to consider all execution paths in the interleaving semantics of a concurrent program, but rather some equivalence classes. The purpose of this paper is to describe a new algorithm to compute such equivalence classes, and a representative per class, which is based on ideas originating in algebraic topology. We introduce a geometric semantics of concurrent languages, where programs are interpreted as directed topological spaces, and study its properties in order to devise an algorithm for computing dihomotopy classes of execution paths. In particular, our algorithm is able to compute a control-flow graph for concurrent programs, possibly containing loops, which is "as reduced as possible" in the sense that it generates traces modulo equivalence. A preliminary implementation was achieved, showing promising results towards efficient methods to analyze concurrent programs, with very promising results compared to partial-order reduction techniques

Percutaneous Coronary Intervention in the Elderly: Are Drug-coated Balloons the Future?

Balloon angioplasty revolutionised percutaneous treatment for coronary artery disease four decades ago, but vessel-threatening dissections, elastic recoil and restenosis were major drawbacks to an otherwise successful long-lasting intervention. Subsequent advances with bare metal stents and then drug eluting stents followed, aiming to mitigate the risks of acute vessel closure and restenosis. However, stent implantation often necessitates dual antiplatelet therapy for a prolonged period of time, which in itself can lead to adverse outcomes, especially in the frail elderly population at higher risk of bleeding. More recently, bioabsorbable stents have been implemented in clinical practice enabling earlier intimal coverage of the stent and apposition. However, another addition to the armamentarium of percutaneous coronary intervention is the use of drug-coated balloons without the need for deploying any coronary stents or scaffolds. Drug-coated balloons are semi-compliant balloons coated with an antiproliferative agent that is rapidly released on contact with the vessel intima exerting an anti-restenotic effect. The absence of a metallic scaffold means that the need for antiplatelet therapy can potentially be negated in the longer term if required. In this article, we will review the history of percutaneous coronary intervention and the available evidence for the appropriate use of drug-coated balloons especially in the elderly population. We will conclude this review by demonstrating the potential use of drug-coated balloon rather percutaneous stenting through case examples

A discourse analysis of trainee teacher identity in online discussion forums

Teacher education involves an identity transformation for trainees from being a student to being a teacher. This discourse analysis examined the online discussion board communications of a cohort of trainee teachers to better understand the situated identities of the trainees and how they were presented online. Their discussion board posts were the primary method of communication during placement periods and, as such, provided insight into how the trainees situated their identities in terms of being a student or being a teacher. During the analysis, the community boundaries, language and culture were explored along with the tutor's power and role in the identity transformation process. This involved looking at the lexis used by the students, the use of pronouns to refer to themselves and others such as teachers and pupils, the types of messages allowed in the community and the effect of the tutor's messages on their communication. The research found that the trainees felt comfortable with teaching but did not feel like teachers during the course. Tutors and school teachers need to develop an awareness of the dual nature of trainees' identities and help promote the transition from student to teacher. In the beginning of the course, trainees should be familiarised with teacher vocabulary and practical concepts in addition to pedagogical theory. Towards the end of the course, trainee identity as teachers could be promoted through the use of authentic assessments that mirror real teacher tasks and requirements

Rapid onset of action of costus speciosus leaf extracts on insulin resistance in experimental wistar rats

Objectives: To evaluate the effect of Costus speciosusleaf methanol and water extracts on insulin resistance. Methods: Male rats were divided into five groups (n=6) and IR was induced by high fat diet (19.13% fats). CS leaf methanol extract (CSlmex) and water extract (CSlwex) were prepared using standard methods. Rats were treated daily for 30 days. Group1: 0.5% Carboxy methyl cellulose (CMC) 1ml, Group2: 500 mg/kg/day CSlmex in CMC, Group3: 500 mg/kg/day CSlwex, Group4: 1500 mg/kg/day CSlwex, Group5: Pioglitazone 10mg/kg/day. Serum was analysed for glucose, triglycerides and insulin at baseline and after one month. IR was calculated using indirect indices; HOMA, QUICKI and McAuley (McA). Results: All CS extracts significantly reduced the IR (p<0.05). 500mg/kg CSlmex reduced IR by HOMA, QUICKI, McA by 61.3%, 15.6%, 39.8% while 1500mg/kg CSlwex reduced HOMA by 66.6%, QUICKI by 16.1% and McA by 36.5% respectively. There was no significant change of IR in CMC group (p>0.05).IR had been reduced by pioglitazone (HOMA 32.4%, QUICKI 12.5%, McA 10%) after one month but not statistically significant (p>0.05). Conclusion: CS leaf water and methanol extracts are effective on reducing IR in rats. Pioglitazone was used as the positive control. Previous scientists had shown that pioglitazone needs minimum of three months to make a significant therapeutic effect on IR although pharmacological effect appears after one month. Our finding shows that CS may have a rapid onset of action on IR based on our biochemical evidence compared to pioglitazone. Therefore, pharmacodynamic studies are recommended to evaluate the dose response relationship.