Fault recovery in process control

Fault Recovery in process control requires effective fault detection, diagnosis and recovery schemes, and a fault-tolPi-ant system design. Fault detection and diagnosis involves creating a realistic model of the process, and using this model to analyse for fault conditions. The fault detection principles include feature extraction and pattern recognition, and analogue value limits and rate cf change limits. Fault recovery scheme? cover the realisation of redundancy ana back-up sub-systems, and state restoration techniques in the form of complete shutdowns, backward and forward recovery to a safe operating state. System design concepts include for the development of process control systems towards *hierarchical, level based distribution of functions. The level-based discussion is used as the basis for effective fault tolerant system design. Two case studies are included to show how fault recovery schemes were effected in a single process computer and in a distributed control system. Abstrac

Algebraic approaches for coded caching and distributed computing

This dissertation examines the power of algebraic methods in two areas of modern interest: caching for large scale content distribution and straggler mitigation within distributed computation. Caching is a popular technique for facilitating large scale content delivery over the Internet. Traditionally, caching operates by storing popular content closer to the end users. Recent work within the domain of information theory demonstrates that allowing coding in the cache and coded transmission from the server (referred to as coded caching) to the end users can allow for significant reductions in the number of bits transmitted from the server to the end users. The first part of this dissertation examines problems within coded caching. The original formulation of the coded caching problem assumes that the server and the end users are connected via a single shared link. In Chapter 2, we consider a more general topology where there is a layer of relay nodes between the server and the users. We propose novel schemes for a class of such networks that satisfy a so-called resolvability property and demonstrate that the performance of our scheme is strictly better than previously proposed schemes. Moreover, the original coded caching scheme requires that each file hosted in the server be partitioned into a large number (i.e., the subpacketization level) of non-overlapping subfiles. From a practical perspective, this is problematic as it means that prior schemes are only applicable when the size of the files is extremely large. In Chapter 3, we propose a novel coded caching scheme that enjoys a significantly lower subpacketization level than prior schemes, while only suffering a marginal increase in the transmission rate. We demonstrate that several schemes with subpacketization levels that are exponentially smaller than the basic scheme can be obtained. The second half of this dissertation deals with large scale distributed matrix computations. Distributed matrix multiplication is an important problem, especially in domains such as deep learning of neural networks. It is well recognized that the computation times on distributed clusters are often dominated by the slowest workers (called stragglers). Recently, techniques from coding theory have found applications in straggler mitigation in the specific context of matrix-matrix and matrix-vector multiplication. The computation can be completed as long as a certain number of workers (called the recovery threshold) complete their assigned tasks. In Chapter 4, we consider matrix multiplication under the assumption that the absolute values of the matrix entries are sufficiently small. Under this condition, we present a method with a significantly smaller recovery threshold than prior work. Besides, the prior work suffers from serious numerical issues owing to the condition number of the corresponding real Vandermonde-structured recovery matrices; this condition number grows exponentially in the number of workers. In Chapter 5, we present a novel approach that leverages the properties of circulant permutation matrices and rotation matrices for coded matrix computation. In addition to having an optimal recovery threshold, we demonstrate an upper bound on the worst case condition number of our recovery matrices grows polynomially in the number of workers

Protocol-processing overhead on the performance of error recovery schemes in high-speed network environments

This paper investigates the effects of protocol-processing overhead on the performance of error recovery schemes in high-speed network environments. The investigated error recovery schemes are:• an edge-to-edge error recovery scheme, where retransmissions of erred packets only take place between source and destination nodes, and• a link-by-link error recovery scheme, where retransmissions only take place between adjacent switching nodes.For retransmission of erred packets, we consider both Go-Back-N and Selective-Repeat procedures in the analysis.The performance measures we obtain are the distribution of transfer delays and the loss probability of packets across a network. To obtain these measures, this paper develops a tandem queueing network model with feedbacks where each queue represents a protocol layer within a switching node, rather than a switching node as a whole.Numerical results show that for a network with very-high-speed/low-error-rate channels, an edge-to-edge scheme gives the smaller packet transmission delay than a link-by-link scheme for both Go-back-N and Selective-Repeat retransmission procedures, while keeping the packet loss probability sufficiently small

Compressive Sensing for Feedback Reduction in MIMO Broadcast Channels

We propose a generalized feedback model and compressive sensing based opportunistic feedback schemes for feedback resource reduction in MIMO Broadcast Channels under the assumption that both uplink and downlink channels undergo block Rayleigh fading. Feedback resources are shared and are opportunistically accessed by users who are strong, i.e. users whose channel quality information is above a certain fixed threshold. Strong users send same feedback information on all shared channels. They are identified by the base station via compressive sensing. Both analog and digital feedbacks are considered. The proposed analog & digital opportunistic feedback schemes are shown to achieve the same sum-rate throughput as that achieved by dedicated feedback schemes, but with feedback channels growing only logarithmically with number of users. Moreover, there is also a reduction in the feedback load. In the analog feedback case, we show that the propose scheme reduces the feedback noise which eventually results in better throughput, whereas in the digital feedback case the proposed scheme in a noisy scenario achieves almost the throughput obtained in a noiseless dedicated feedback scenario. We also show that for a fixed given budget of feedback bits, there exist a trade-off between the number of shared channels and thresholds accuracy of the feedback SINR.Comment: Submitted to IEEE Transactions on Wireless Communications, April 200

Developing Integrated Waste Management Systems: Information Needs and the Role of Locally Based Data

No abstract available

Minimising flood risk accumulation through effective private and public sector engagement

Flooding is a global problem affecting both developing and developed countries. Academics and practitioners in climate science frequently argue that changing climatic conditions are likely to worsen the length and severity of these flood events, which will have catastrophic consequences to economies and social lives of communities world over. Whilst the overall consequences affecting many regions have been established, effective and efficient strategies to cope with the effects of flooding and building up resilience strategies have not properly evolved. This paper examines this issue by exploring effective strategies undertaken in partnerships between private and public stakeholders. The paper details two case studies conducted in a developed and a developing country to investigate what global strategies for coping and resilience to flooding have worked in practice. The two case studies: Cockermouth in Cumbria, UK and Patuakhali in Bangladesh provide interesting insights on how some of the strategies work within the chosen developed and developing country contexts. The case study findings are mapped against UNISDR’s ten-point checklist under the “Making Cities Resilient Campaign”. In conclusion the paper examines how these findings can be incorporated within city development plans to develop stakeholder capacity and capability and eventually build up resilient cities

Equality of opportunity and student support schemes

Equality of opportunity or access to education has always been propagated as a good mechanism to reduce economic imbalances between the rich and the poor. This is due to the fact that there is a historic correlation between educational attainment and occupational opportunities. In meeting this objective, the Malaysian government has invested vast amount of fund through subsidization of education particularly in higher education. In Malaysia, public universities obtain 80-90% of their funds from government grants. Not only the government support the public higher education institutions but it also provides the student support scheme in terms of scholarships and student loans. However with the increasing costs and rapid expansion of higher education, pressure for reform in higher education financing has intensified. Heavy reliance on public funds to finance higher education no longer seems to be an ideal solution. In this regard many countries around the world resort to the concept known as cost recovery. Replacing scholarship by student loans is one of the ways on how cost recovery can be implemented. The introduction of student loans, however, if not properly formulated will discourage or deter less advantaged socio-economic groups from getting access to higher education. In this paper we will discuss some policy options with regard to student support schemes which taking into consideration both efficiency and equity issues

Minimising flood risk accumulation through effective private and public sector engagement

Flooding is a global problem affecting both developing and developed countries. Academics and practitioners in climate science frequently argue that changing climatic conditions are likely to worsen the length and severity of these flood events, which will have catastrophic consequences to economies and social lives of communities world over. Whilst the overall consequences affecting many regions have been established, effective and efficient strategies to cope with the effects of flooding and building up resilience strategies have not properly evolved. This paper examines this issue by exploring effective strategies undertaken in partnerships between private and public stakeholders. The paper details two case studies conducted in a developed and a developing country to investigate what global strategies for coping and resilience to flooding have worked in practice. The two case studies: Cockermouth in Cumbria, UK and Patuakhali in Bangladesh provide interesting insights on how some of the strategies work within the chosen developed and developing country contexts. The case study findings are mapped against UNISDR’s ten-point checklist under the “Making Cities Resilient Campaign”. In conclusion the paper examines how these findings can be incorporated within city development plans to develop stakeholder capacity and capability and eventually build up resilient cities