Counterfeit products, particularly pharmaceuticals, electronic devices, and apparels, are widespread. They threaten consumer safety and cause huge economic losses to licit supply chain partners and governments. Although a number of traditional anti-counterfeiting technologies, such as holograms and chemical tags, are available to combat counterfeiting, they are vulnerable to imitation or being reused. Besides, these technologies are intended to protect individual items, rather than to safeguard an entire supply chain. As such, fake products may likely be injected into the supply chain to hurt end-consumers. Track-and-trace technology based on Radio Frequency Identification (RFID) has recently emerged as a promising tool to combat counterfeiting, because of its automatic and non-line-of-sight capability to identify massive product items. By maintaining an electronic pedigree (e-pedigree) that records the transaction information of product items along the supply chain, this approach stands out for protecting the supply chain against infiltration, eliminating theft and fraud, facilitating recall of defective products, and supporting remote authentication. However, a number of technical and critical issues have yet to be solved for practical implementation of RFID-based track-and-trace anti-counterfeiting. These include generation of accurate initial product e-pedigree in fast moving manufacturing lines, precise e-pedigree updating in batch product distributing and receiving, and fast e- pedigree queries for remote and real-time product authentication from end-customers. Without fully addressing these issues, the accumulated product e-pedigree data would be untrustworthy, rendering any subsequent operations of track-and-trace and product authentication unreliable. This thesis investigates the crucial implementation issues in RFID-based track-and-trace anti-counterfeiting. It firstly presents an innovative track-and-trace anti-counterfeiting system, based on which a TDPS algorithm is proposed for generation of initial product e-pedigree in fast moving production lines. The TDPS overcomes many practical issues, such as tag writing error and tag locking failure, and helps identify the bottleneck of initial product e-pedigree generation. To tackle the bottleneck, the TDPS is further optimized by incorporating a block writing method to enhance the tag EPC writing efficiency and an integration method to balance the overhead of RFID equipment. In product distributing and receiving, a mechanized 3D scanning method is proposed to improve bulk item identification rate and enhance the accuracy and completeness of product e-pedigree. Indeed, RFID-based track-and-trace anti-counterfeiting mandates a relatively high bulk item identification rate for product authentication and e-pedigree updating. Experimental results demonstrate that the mechanized 3D scanning can achieve a bulk item reading rate of up to 98.9%, which largely outperforms the widely documented bulk reading rate (70%) in real applications. In retailing level, the efficiency of e-pedigree queries would hugely impact on customer shopping experience and the effectiveness of track-and-trace anti-counterfeiting. A partition-based method is therefore developed to cluster product e-pedigree data to improve the speed of e-pedigree queries. This approach partitions the accumulated e-pedigree data into fixed and dynamic groups, such that queries are conducted mainly on active data, rather than on the whole historical data sets. By addressing the above key issues, this thesis contributes to making implementation of RFID-based track-and-trace anti-counterfeiting practically viable and reliable. / published_or_final_version / Industrial and Manufacturing Systems Engineering / Master / Master of Philosophy

As increasing power requirement in more or all electric aircraft, electric power system is required to be more efficient and lower in weight. Among the current power generation technologies, 115V variable frequency (VF) system and 270VDC system are regarded as the two optimal options for future use in MEA or AEA. Therefore, it is very important to compare their relative merits in order to determine the optimal choice on the primary power type. As the reviewed literature mainly represents the comparison between 270VDC system and 115V constant frequency system, it is very necessary to conduct the comparison between 270VDC system and 115V/VF system. The aim of this study is to grasp the nature of these systems and evaluate these two systems in terms of some engineering aspects. Literature regarding the power generation technology is first investigated. Based on initial comparison, the 270VDC brushless generating system and 115V VF generating system are selected for this study. Before conducting system architecture design and wiring system design, the load requirement analysis and optimization are conducted. Finally, a comparison between these two systems will be made in terms of weight, power off take, minimum voltampere (VA) capacity requirement, voltage drop, reliability, life cycle cost and risk. The results show that the 270VDC system is superior to the115V/VF system in terms of weight and efficiency. With regards to system reliability, the 270VDC system can be designed as either an active parallel system or a standby system while the 115V/VF system can only be designed as a standby redundant system. As far as risk is concerned, the 270VDC is more dangerous than the 115V/VF system in terms of arcing risk and corona discharge. All in all, the 270VDC system can be considered as the optimal choice for future use in AEA or MEA.

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M. Tech. Electrical Engineering / The radio frequency (RF) spectrum is a natural resource used by wireless network operators to provide radio communication and transmission systems. The availability of RF spectrum to various wireless network operators using large bandwidth and more than one channel, as demanded by their offered services, is challenging, due to RF spectrum scarcity and lack of optimal channel selection. On the other hand, the under-utilisation of licensed spectrum by some primary users' (PU's) networks may be improved by the use of dynamic spectrum access (DSA) techniques. Recent research has shown that a large portion of the assigned spectrum is used irregularly, leading to under-utilisation and waste of valuable frequency resources. The notion of cognitive radio (CR) was introduced to increase the effectiveness and efficiency of spectrum consumption. In a cognitive radio network (CRN), each secondary user (SU) is expected to select the best RF spectrum band for opportunistic use when the PUs have temporarily vacated the spectrum allocated to them. The literature has proposed many spectrum selection methods for selecting vacant spectra in CRNs. However, most of these methods do not consider the channel usage pattern over time by PUs and also do not adequately consider the effect that frequent channel-switching might have on the quality of service requirements of the SUs and the throughput of the CR system. Thus, the proposed scheme, which is heuristic-based spectrum selection scheme for minimal channel switching (HBSSS-MCS) and heuristic-based spectrum selection scheme for maximum throughput (HBSSS-MT) addresses these issues. The main study objectives were as follows: 1) Minimise the frequent switching of channels using HBSS-MCS; 2) Maximise the throughput of the CR system using HBSSS-MT. To achieve the objectives of this research work, the following sub-problems were addressed: 1) To investigate the spectrum selection schemes in cognitive radio network (CRN); 2) To design a learning mechanism to facilitate the selection of a suitable channel in the primary network.

The frequency control in the Nordic grid is to a large extent delivered by hydropower plants. The hydropower plants deliver frequency control of varying quality, meaning that a remuneration method based on more than just the static gain of the power plant is called for. This thesis has examined how three remuneration methods based on the hydropower plant output and the grid frequency deviation affects the grid stability. Using frequency data, the remunerated work along with the bandwidth and phase-crossover frequency was plotted and compared for varying governor settings. The results show that all three remuneration methods examined need constructive technical specifications (for example based on the frequency response) to not decrease the grid stability. The first remuneration method, where the power plant is remunerated for being on the right side of the power set point value as the grid frequency deviates, gave incentives for increased bandwidth, but no particular incentives regarding the phase-crossover frequency. The second remuneration method, where the power plant is remunerated for how well it matches the output power from a plant with no dynamics using a proportional controller, gave incentives for moderately high bandwidth and phase-crossover frequency. The third remuneration method, which remunerates how well the plant power output matches the load disturbance that gave rise to the grid frequency deviation, needs to be investigated further, but the initial analysis show that it did neither give incentives for increased bandwidth nor phase-crossover frequency.

Practical issues concerning the implementation and application of genetic algorithms to a number of optimisation problems are the main subjects dealt with in this thesis. Genetic algorithms (GAs) are an attractive class of computational models that attempt to mimic the mechanisms of natural evolution to solve problems in a wide variety of domains. A general purpose genetic algorithm toolkit is developed and applied to the Steiner Problem in Graphs and the Radio Link Frequency Assignment Problem. The toolkit is then extended to cover a large number of parallel genetic algorithm models which are then compared. Solutions for the two case studies are presented with each of the parallel GAs. The thesis begins with a general introduction to genetic algorithms. Holland's original genetic algorithm is described and it's workings illustrated on a simple function minimisation problem. The notion of a schema or similarity template as a basic building block in genetic algorithms is introduced and the schema theory presented. A description of important theoretical results is given and the introduction to genetic algorithms continues with practical issues that are dealt with in the second chapter. The basic components of a modern genetic algorithm are outlined and examples for important components, as found in the Jiterature, are given. The second chapter concludes with the description of a number of applications of genetic algorithms to areas such as function optimisation, combinatorial optimisation, genetic programming, process control and classifier systems. In Chapter 3, the sequential GA toolkit, GAmeter, is described. The General Search paradigm around which the toolkit is implemented is introduced. Notable characteristics of the genetic algorithms kernel and the user interface are mentioned. A popular function optimisation problem is used to illustrate important aspects of genetic algorithms and aspects specific to the toolkit. The Steiner Tree problem in graphs is the first of two case studies examined in detail in this thesis. This is a popular NP-complete problem with a range of applications in areas such as communications, scheduling and printed circuit design. A survey of standard techniques, such as simplification methods, exact algorithms and heuristics is given. Two possible representations for solving it using genetic algorithms are described and applied to a well-known set of problems. Chapter 4 concludes with a comparison of the best GA technique with other heuristics for this problem. The Radio Link Frequency Assignment Problem, described in Chapter 5, is the second case study investigated in this thesis. Genetic algorithms were applied to this problem as part of a EUCLID (European Cooperation for the Long Term in Defence) funded multi-national study to compare exact and heuristic techniques for hard combinatorial problems associated with military applications. A number of approaches used to solve this highly constrained, hard problem for genetic algorithms are described. These include a range of new genetic operators and catalytic terms that are added to the fitness function. Apart from the direct approach to solving this problem using genetic algorithms, for which the majority of operators and catalytic terms apply, an indirect approach which combines genetic algorithms with backtracking is described. The possibility of using a meta genetic algorithm to chose the best of a multitude of options, e.g. genetic operators and parameter settings for a GA applied to the Radio Link Frequency Assignment Problem is investigated. Results are reported for two sets of problems that were used by all participants in this project. An overview of the techniques investigated for this project is given and the chapter concludes with comparisons between all these techniques. In Chapter 6, an overview of general aspects in parallel processing is given. Parallel computer architectures, parallel programming paradigms and performance measurement are the main subjects dealt with in this chapter. Special emphasis is given to material relevant to the investigation on parallel genetic algorithms, presented in the following chapter. In Chapter 7, parallel genetic algorithms are examined in some detail. A number of parallel GA models are described and classified according to whether they are designed around the sequential GA or around a more natural model. A ParallelSequential General Search paradigm is presented that unifies the various parallel models and is used to extend the GA toolkit into a parallel GA toolkit for a parallel system based on Transputers. The parallel GA models are applied to problems from both of the case studies considered in this thesis. A comparison between the various parallel GA models concludes this chapter. The thesis finishes with a summary of a number of conclusions drawn from this research together with some suggestions for how this work may be continued in the future.

Broadband voltage-controlled oscillators are critical to the design of millimeter wave frequency synthesizers. This thesis proposes a design technique that can be used to significantly extend the achievable frequency span of an oscillator. A dual-band oscillator topology is described that can be configured to operate in one of two modes, by an electrical reconfiguration of the negative resistance core around the resonant tank, without switching passive elements within the tank itself. The configuration helps to minimize the difference in phase noise performance between the two modes, while achieving a wide tuning range. To verify the concept, a mm-wave VCO that operates at 30-GHz is designed in a commercial 0.18-um CMOS technology, with an approximate simulated tuning range of 20%. A dual-mode oscillator is also designed in a 0.13-um technology at 60-GHz. / text

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