Relays can be used in wireless communication systems to provide cell coverage extension, reduce coverage holes and increase throughput. Full duplex (FD) relays, which transmit and receive in the same time slot, can have a higher transmission rate compared with half duplex (HD) relays. However, FD relays suffer from self interference (SI) problems, which are caused by the transmitted relay signal being received by the relay receiver. This can reduce the performance of FD relays. In the literature, the SI channel is commonly nulled and removed as it simplifies the problem considerably. In practice, complete nulling is impossible due to channel estimation errors. Therefore, in this thesis, we consider the leakage of the SI from the FD relay. Our goal is to reduce the SI and increase the signal to noise ratio (SNR) of the relay system. Hence, we propose different precoder and weight vector designs. These designs may increase the end to end (e2e) signal to interference and noise ratio (SINR) at the destination. Here, a precoder is multiplied to a signal before transmission and a weight vector is multiplied to the received signal after reception. Initially, we consider an academic example where it uses a two path FD multiple input and multiple output (MIMO) system. The analysis of the SINR with the implementation of precoders and weight vectors shows that the SI component has the same underlying signal as the source signal when a relay processing delay is not being considered. Hence, to simulate the SI problem more realistically, we alter our relay design and focus on a one path FD MIMO relay system with a relay processing delay. For the implementation of precoders and weight vectors, choosing the optimal scheme is numerically challenging. Thus, we design the precoders and weight vectors using ad-hoc and near-optimal schemes. The ad-hoc schemes for the precoders are singular value decomposition (SVD), minimising the signal to leakage plus noise ratio (SLNR) using the Rayleigh Ritz (RR) method and zero forcing (ZF). The ad-hoc schemes for the weight vectors are SVD, minimum mean squared error (MMSE) and ZF. The near-optimal scheme uses an iterative RR method to compute the source precoder and destination weight vector and the relay precoder and weight vector are computed using the ad-hoc methods which provide the best performance. The average power and the instantaneous power normalisations are the two methods to constrain the relay precoder power. The average power normalisation method uses a novel closed form covariance matrix with an optimisation approach to constrain the relay precoder. This closed form covariance matrix is mathematically derived using matrix vectorization techniques. For the instantaneous power normalisation method, the constraint process does not require an optimisation approach. However, using this method the e2e SINR is difficult to calculate, therefore we use symbol error rate (SER) as a measure of performance. The results from the different precoder and weight vector designs suggest that reducing the SI using the relay weight vector instead of the relay precoder results in a higher e2e SINR. Consequently, to increase the e2e SINR, performing complicated processing at the relay receiver is more effective than at the relay transmitter.

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Differential protection is the unit protection system which is applied to protect a particular unit of power systems. Unit is known as zone in protection terminology which is equivalent to simple electrical node. In recent time, low impedance current differential protection schemes based on percentage restrained characteristics are widely used in power systems to protect busbar systems. The main application issue of these schemes is mis-operation due to current transformer (CT) saturation during close-in external faults. Researchers have suggested various solution of this problem; however, individually they are not sufficient to puzzle out all mis-operational scenarios. This thesis presents a new bus differential algorithm by defining alternative partial operating current characteristics of a differential protection zone and investigating its performance for all practical bus faults. Mathematical model of partial operating current and operating principle of the proposed bus differential relay are described in details. A CT saturation detection algorithm which includes fast and late CT saturation detection techniques is incorporated in relay design to increase the sensitivity of partial operating current based internal-external fault discriminator for high impedance internal faults. Performance of the proposed relay is validated by an extensive test considering all possible fault scenarios.

Over time, wireless technology advancements in the field of communications have been attracting every individual to turn into a wireless user. To accommodate the increasing number of users and to avoid the problem of spectrum scarcity, the concept of Cognitive Radio Network (CRN) has been developed. Cognitive Radio (CR) is an intelligent radio which efficiently detects and allocates the spectrums of primary licensed users (PUs) to the secondary unlicensed users (SUs). The SUs can utilize these spectrums as long as they do not cause harmful interfere to the PUs. Interference may occur because of the following reasons: misdetection of spectrum availability, the high transmission power of SU when both SU and PU are present in the same channel at the same time. In order to avoid interference, the radio has to have a very accurate spectrum sensing method, transmit power at SU should be constrained by the peak interference power of PU and the CR should continuously sense the presence of PUs. To increase the wireless coverage area and reliability of CRN, a new technology called Cooperative Cognitive Radio Network (CCRN), which is a combination of CRN and cooperative communications was developed. A CCRN not only increases the reliability and wireless coverage area of CR but also improves the overall performance of the system. In this context, the main objective of this research work is to evaluate the outage performance of a CCRN in an environment where fading and shadowing also come into the picture and to study the importance of relay networks in CRN. To fulfill the objectives of this research work, a two-hop decode-and-forward CCRN is considered. The recently introduced κ − µ shadowed fading channel is employed over the CCRN to generate a realistic environment.  In order to implement such system as a whole, a deep literature study is performed beforehand. Analytical expressions for the Probability Density Function (PDF) and Cumulative Distribution Function (CDF) of the Signal-to-Noise Ratio (SNR) are obtained. The analytical expressions and simulation results for Outage Probability (OP) are obtained and compared under different fading parameters. The importance of a multiple-relay system in CRN is presented. From the results obtained in this research work, we can conclude that the OP decreases with increase in allowable peak interference power at the PU. The transmit power at SU should always be constrained by the peak interference power at the PU to avoid interference. The overall system performance increases with increasing number of relays.

This thesis presents a new approach to extend and reduce the transmission range in wireless systems. Conditioning is defined as purposeful electromagnetic interference that affects a wireless signal as it propagates through the air. This interference can be used constructively to enhance a signal and increase its energy, or destructively to reduce energy. The constraints and limitations of the technology are described as a system model, and a flow chart is used to describe the circuit process. Remaining theoretical in nature, practical circuit implementations are foregone in the interest of elementary simulations depicting the interactions of modulated signals as they experience phase mismatch. Amplitude modulation and frequency modulation are explored with using both positive and negative conditioning, and conclusions to whether one is more suitable than the other are made.

The dorsal lateral geniculate nucleus (dLGN) has become an important model for studying many aspects of visual system development. To date, studies have focused on the development of retinal projections and the role of activity in shaping the pattern of synaptic connections made with thalamocortical relay cells. By contrast, little is known about relay cells and the factors that regulate the growth and establishment of their dendritic architecture. In many systems, such growth seems consistent with the synaptotrophic hypothesis which states that synapse formation and dendritic growth work in a concerted fashion such that afferent input and the establishment of functional synapses are needed to shape the maturation of dendritic arbors. To address this, we characterized the development of relay cells in the dLGN of wild-type (WT) mouse. By adopting a loss of function approach, we assessed the manner in which growth and maturation of relay cells were affected by retinal innervation. For this, we made use of the math-null (math5-/-) mouse in which progenitors fail to differentiate into retinal ganglion cells (RGCs), and exhibit a >95% cell loss. Anterograde labeling of RGC axons with cholera toxin subunit B (CTB), immunolabeling of RGC-specific presynaptic machinery in dLGN (e.g. vesicular glutamate transporter 2), and ultrastructural analysis at the electron microscopy level demonstrated that the dLGN is devoid of retinal innervation. We examined the functional and morphological characteristics of relay cells in WT and math5-nulls during early postnatal life by conducting in vitro whole cell recordings in slices containing dLGN. Individual relay cells were labeled by intracellular injection of biocytin, and imaged by confocal microscopy to obtain the 3-D reconstructions of their dendritic trees. Morphometric analysis revealed that relay cells in WT undergo two growth spurts: an early one where cell class specification and dendritic complexity are established and a later one marked by an increase in dendritic field and length. Following the third week, relay cells growth was stabilized. In math5-nulls, relay cells maintained their morphological identity whereby cells could be classified in three groups (Y: spherical, X: bi-conical, W: hemi-spherical). However, the dLGN was highly reduced in size, and relay cells showed disrupted growth spurts. Relay cells had smaller somata and exhibited fluctuations in dendritic complexity and field extent compared to age-matched WTs. Exuberance in dendritic branching was noted in week 2, and by week 5, relay cells had significantly smaller surface area resulting from a loss of dendritic segments and a reduction in dendritic field extent. Control experiments using RT-PCR revealed that these changes were not due to the loss of math5 in the dLGN. Whole cell recordings and voltage responses to square wave current pulses showed that math5-nulls possess the full compliment of intrinsic membrane properties, such as relay cells displayed both burst and tonic firing modes. A cross of the math5-null with a transgenic mouse that expresses GFP in layer VI cortical neurons revealed a dense plexus of corticogeniculate terminals throughout the mature dLGN. However, the rate of corticogeniculate innervation was highly accelerated and was complete a week earlier than WT. Electric stimulation of cortical axons revealed that synapses are functional and responses were indistinguishable from WT. Taken altogether, these observations suggest that retinal innervation plays an important trophic role in the maturation of dLGN and is necessary for the continued maintenance of relay cells’ structural integrity. However, the general form and function of relay cells seem largely unaffected by the loss of retinal innervation.

Power system fault detection is conventionally achieved using current and potential measurements. An alternate and unconventional form of protective relaying is feasible using rigid bus conductor motion as the means of detection. The research presented focuses on the detection of power system faults using visual displacement of conductor spans. Substation rigid bus conductor motion is modeled using dual spring-mass systems for accurate representation of conductor response to electromagnetic forces generated during system faults. Bundled rigid conductors have advantages including detection independent of system load currents and improved ability to detect polyphase and single phase faults. The dynamic motion of the conductors during the fault is optically monitored with a laser detection system. Timeovercurrent characteristics are derived for the application of fault detection. The response time of the conductor detector system is slower than conventional relays due to the natural frequencies of the conductor span limiting the speed of its displacement. This response time makes the fault detection system using conductor displacement an ideal candidate for a backup relay in power system protection schemes.

A real-time simulator (RTS) with digital and analog input/output modules is used to conduct hardware-in-the-loop simulations to evaluate performance of power system equipment such as protective relays by exposing the equipment to the simulated realistic operating conditions. This work investigates the use of RTS to test relays with single-pole-switching (SPS) feature. Single-pole switching can cause misoperations due to fault arc during reclosing of the breakers. Through this investigation, a test procedure appropriate for the testing SPS relays has been developed. The test procedure includes power system modeling for real time simulation, relay test setup, and test plan. HYPERSIM real-time simulator was used to model an actual power system. Transmission lines, three-winding transformers, and induction motor were modeled with actual parameters. Models for fault arc in HYPERSIM real time simulator were developed. Test set-up for evaluating relay performance and wiring drawings for connecting relay in closed-loop to the simulator were developed.

Thesis advisor: Yvette D. Kuiper / The Hudson Valley fold-thrust belt (HVB) is a narrow belt of deformed Upper Ordovician to Middle Devonian clastic and carbonate strata exposed in the western Hudson Valley of New York State. Geologic mapping at a scale of 1:10,000 was carried out near the town of Catskill. The southern portion of the map area includes a large doubly-plunging structure which features a fault-dominated southern portion plunging towards 017° and a northern fold-dominated, 206° trending, southerly plunging segment. A relay structure between two major faults or fault systems is interpreted as existing between the two domains. Farther north, the HVB narrows and folds plunge shallowly towards 212°, and then widens with folds plunging shallowly towards 017°. The changes can be explained by a localized increase in slip on the Austin Glen Detachment in the center of the map area, and subsequent loss of slip towards the north. / Thesis (BA) — Boston College, 2010. / Submitted to: Boston College. College of Arts and Sciences. / Discipline: College Honors Program. / Discipline: Geology and Geophysics.

Transformadores de potência são dispositivos que requerem atenção especial devido a sua grande importância ao sistema elétrico de potência no qual ele está conectado. Geralmente relés diferenciais são utilizados como proteção primária em transformadores de potência. Nestes relés, a corrente diferencial é comparada com um nível de ajuste e caso ocorra uma falta interna, o transformador deverá ser desconectado do restante do sistema. Entretanto, a simples detecção da presença de uma corrente diferencial não é suficiente para distinguir faltas internas de outras situações que também podem produzir tal corrente. Tais situações surgem durante a energização dos transformadores, devido a saturação dos transformadores de corrente, entre outras, as quais podem resultar em uma incorreta atuação da proteção. Uma rápida e correta discriminação entre faltas internas e outras situações é um dos desafios da moderna proteção de transformadores de potência. A respeito da identificação de faltas internas ou situações de energização, além da mencionada lógica diferencial é acrescentado uma subrotina baseada na restrição de harmônicas. Neste método, a corrente de energização é reconhecida através da presença de uma segunda harmônica obtida por filtros de Fourier. No entanto, o método de filtragem pode algumas vezes retardar a operação da proteção. Além disto, uma componente de segunda harmônica pode também estar presente durante uma falta interna. Este trabalho propõe a utilização da transformada Wavelet - uma poderosa ferramenta matemática - empregada como um meio rápido e eficiente de analisar as formas de onda de transformadores de potência e como uma alternativa a tradicional transformada de Fourier. Os sinais das correntes diferenciais são processados pelas transformadas discretas Wavelet, visando obter uma discriminação entre ambas situações (energização e falta). Um nível de limiar é utilizado após a decomposição Wavelet do sinal para discriminar entre as situações descritas. A janela de dados utilizada para este propósito pode ser variada. Para testar o algoritmo proposto, as simulações de energização e falta foram implementadas, utilizando o programa ATP (\"Alternative Transient Program\"). Em situações onde a janela de dados é reduzida para 1/4 de ciclo o critério de discriminação pode ser otimizado utilizando a transformada discreta de Wavelet auxiliada com técnicas de reconhecimento de padrões. Este trabalho apresenta a utilização de redes neurais artificiais para tal finalidade como exemplo. Resultados encorajadores são apresentados sobre a capacidade de discriminação para as situações descritas assim como a rapidez de resposta quando comparados aos métodos tradicionais. / Power transformers are devices that require special maintenance and care due to their importance to the electrical system to which they are connected. Generally, differential relays are used for the primary protection of large transformers. In such relays, differential currents are compared to a threshold and in the case of an internal fault, the transformer should be disconnected from the rest of the system. However, a simple detection of a differential current is not sufficient to distinguish internal faults from other situations that also produce such a current. Some of these situations appear during transformer energization (inrush currents), CT (current transformer) saturation, among others, which can result in an incorrect trip. A correct and fast distinction of internal faults from the other situations mentioned is one of the challenges for modern protection of power transformers. Concerning the identification of internal faults as opposed to inrush currents, the approach tarditionally used is the aforementioned differential logic together with harmonic restraint. In this method, transformer inrush current due to energization is recognized on the basis of second harmonic components obtained by Fourier filters. However, the filtering method can sometimes delay the protection process. In addition to this, a second harmonic component can also be present during internal faults. This work proposes Wavelet transform - a powerful mathematical tool - employed as a fast and effective means of analyzing waveforms from power transformers, as an alternative to the traditional Fourier transform. The differential signals are processed by discrete Wavelet transform to obtain the discrimination between both situations (inrush and fault). A threshold level is utilized after the Wavelet decomposition to discriminate the situations describeb. The time window used for such purpose can be varied. In order to test proposed algorithm, simulations of fault and inrush currents in a power transformer were implemented using ATP ( \"Alternative Transient Program\") software. When the time window is reduced to only 1/4 of the cycle the discrimination criteria should be optimized using a pattern recognition technique to aid the Discrete Wavelet transform. This study shows as a sample for this purpose the use of artificial neural networks. Very encouraging results are presented concerning the capacity of discrimination of the described situations as well as the speed of response when compared to the traditional method.