The Open Systems Interconnect Model (OSI) is a conceptual model of networking thatcategorizes network functions into seven layers. It is defined in this model that how layerscommunicate with each other. In this thesis, we address common Layer 2 attacks and theirsolutions. Layer 2 is considered a very weak link in a secure network. If the data is compromisedat Layer 2, it cannot be detected at other layers because each layer works without the knowledgeof other layers. We discuss Layer 2 weakness and vulnerability exploitation tools briefly. It isexplained how an attacker can exploit network by using different attack tools. Our results showthat these attacks are very productive if a network administrator does not implement propersecurity at Layer 2 in the OSI model. We propose solutions to secure Layer 2 devices and thesesolutions are implemented by using attack tools. Security configurations are deployed to combatagainst attacks and protect the integrity, confidentiality, and availability of the network traffic.

In order to achieve the ambitious decarbonisation targets of the UK government, up to 30GW of wind generation could be connected to the GB transmission system by 2020. The challenges imposed when incorporating this volume of renewable energy are significant, introducing new technical challenges for National Grid as the system operator for the Great Britain transmission system. The majority of this new renewable generation will be connecting in Scotland and offshore in the UK as a whole. This results in greater uncertainty in the system from significant changes to the direction and volume of power flows across the network. In addition this implies a higher power transfer capacity requirement on the AC transmission lines, which are currently stability-limited, connecting SPT (Scottish Power Transmission) and National Grid networks. The required power transfer capability increases every year because of the large-scale increase in wind generation. Therefore, there is insufficient transmission capacity in the existing network to accommodate the increasing power transfer without constraining output of some generation plants. A range of new state of art technologies such as embedded HVDC link and Thyristor Controlled Series Compensation (TCSC) are planned to be added to the GB system in order to provide additional capacity and consequently facilitate the integration of large-scale renewable generation. It is, therefore essential that National Grid explores new ways of operating the transmission network and new devices to gain additional benefit from the HVDC link and the TCSC capabilities with regard to the system stability enhancement. This thesis investigates the effectiveness of the HVDC link and the TCSC with a view to system stability enhancement. A hierarchical stability control system to enhance the stability limit and achieve the best transient and dynamic performance using the HVDC link and the TCSCs as actuators in the feedback control system is proposed. In addition, a stability control system, using a robust and stabilising Sample Regulator multivariable control design method , to guarantee the system robustness and stability is proposed and designed. The performance and capability of the designed controller in co-ordinated control of the forthcoming power flow control devices are demonstrated on benchmark networks as well as full dynamic models of the GB transmission system using various study cases. Finally, the effectiveness of the West Coast HVDC link in improving the inter-area oscillation damping is presented using the developed model of the future GB transmission system.

The notation of t/i numbers is used to describe knots and links on the double torus in two different ways, as a step toward the eventual classification of double-torus links.

A highly survivable communication network is desirable, as service disruption is usually not tolerated. In this thesis we mainly investigate and discuss the survivability of two specific communication networks, termed topology 1 and 2, under usual network failures. The survivability of the networks mainly comes from their structure. Both topologies have different routes between all source-destination pairs, which gives the networks high route diversity. In fact, both topologies considered are regular networks with connectivity 3. Discussion starts by defining several network properties, such as average route-length and link and node utilization, for the fault-free condition. Alterations of these properties are investigated when a network failure takes place. Using the results for fault-free and faulty situations, a comparison is made between the topologies. Topologies 1 and 2 are also compared with other standard topologies like full ring, square grid and star topologies. Another regular network topology called the star-ring topology is also introduced and investigated for the same properties. Enough insight is given to devise an optimal re-routing strategy when a network failure takes place. A new idea of static routing strategy called the Static Disjoint Routing Strategy is introduced. This disjoint routing strategy is proven to be close in performance to that of traditional Dynamic Shortest Routing with a considerable gain in ease of operation. The disjoint routing table is used to investigate whether any link or node becomes over utilized in faulty situations. On the whole both topologies were found to be highly survivable structures with reasonable cost. / Master of Science

The development of protype applications with sensors and actuators in the automation industry requires tools that are independent of manufacturer, and are flexible enough to be modified or extended for any specific requirements. Currently, developing prototypes with industrial sensors and actuators is not straightforward. First of all, the exchange of information depends on the industrial protocol that these devices have. Second, a specific configuration and installation is done based on the hardware that is used, such as automation controllers or industrial gateways. This means that the development for a specific industrial protocol, highly depends on the hardware and the software that vendors provide. In this work we propose a rapid-prototyping framework based on Arduino to solve this problem. For this project we have focused to work with the IO-Link protocol. The framework consists of an Arduino shield that acts as the physical layer, and a software that implements the IO-Link Master protocol. The main advantage of such framework is that an application with industrial devices can be rapid-prototyped with ease as its vendor independent, open-source and can be ported easily to other Arduino compatible boards. In comparison, a typical approach requires proprietary hardware, is not easy to port to another system and is closed-source.

Motor drives represent electric equipment used for speed control of electric motors. Varieties of industrial applications, such as assembly, pumps, fans etc., require motors and they consume huge amount of electric energy. Compared with traditional motor drives, which can only send energy from grid to motor, a regenerative motor drive can achieve bi-directional power flow control between motors and utility grid. Regenerative motor drives are excellent candidates for reducing power loss in motor-related applications. One of the most essential parts of a regenerative motor drive power cell is dc-link capacitors. They create suitable dc-link voltages and smooth the voltage waveforms. Reliability, or lifetime of dc-link capacitors highly affect power cell lifetime, and power loss in dc-link capacitor is also another issue that worth noticing. This thesis focuses on the lifetime modeling and lifetime improvement of dc-link capacitors in a regenerative cascaded H-bridge medium-voltage motor drive. The lifetime modeling bases itself on the mechanisms of dominant lifetime stresses in practical operations. A proposed method is used to reduce a dominant current harmonic component in dc-link capacitors. With the proposed lifetime model and harmonic-reduction method, dc-link capacitor lifetime improvement can be anticipated in this motor drive model. Less power losses in those dc-link capacitor banks can also be achieved. / Thesis / Master of Applied Science (MASc)

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Part A of two parts. Part B titled: "The Processing and Evaluation of Long Lived GaA1As Channeled Substrate Planar Lasers". / <p> The design and fabrication of a low cost optical communications link is described. The evaluation of this system shows that it can transmit bipolar analog signals in a bandwidth of O to 17 kHz with less than 0.1% non-linearity, Combined with an autoranging capability, the linear link is demonstrated to be useful for high accuracy remote data acquisiton. </p> / Thesis / Master of Engineering (MEngr)

This work demonstrates the design and implementation of a digitally encoded Sinusoidal Pulse Width Modulation strategy for the switching of bi-directional secondary side power switches of an AC-link. Through this method, high frequency (200 kHz) half sinusoid or haversine voltage pulses produced by the Parallel Loaded Resonant converter working in discontinuous mode at primary side are converted to low frequency (400/60/50 Hz) waveforms at the output. This control strategy allows the converter to operate at high power density, as soft switching (ZCS/ZVS) is possible at both the turn-on and turn-off of switches. Also through this strategy the output waveform at load will have low Total Harmonic Distortion (THD).

No description available.