acase@tulane.edu / Fault growth is often accomplished by linking a series of en echelon faults through relay ramps. A relay ramp is the area between two overlapping fault segments that tilts and deforms as the faults accrue displacement. The structural evolution of breached normal fault relay ramps remains poorly understood because of the difficulty in defining how slip is partitioned between the most basinward fault (known as the outboard fault, which includes the severed fault tip), the overlapping fault (inboard fault), and any ramp-breaching linking faults. Along the Warner Valley fault in south-central Oregon, two relay ramps displaying different fault linkage geometries are lined with a series of pluvial shorelines that record a Pleistocene paleolake regression. The inner edges of these shorelines act as paleo-horizontal datums that have been deformed by fault activity, and are used to measure relative slip variations across the relay ramp bounding faults. By measuring the elevation changes using a 10m digital elevation model (DEM) of shoreline inner edges, I estimate the amount of fault activity on severed fault tips. In order to attribute shoreline deformation to fault activity I identify shoreline elevation anomalies, where deformation exceeds a ± 0.3% window from normalized elevation values; this encompasses my conservative estimates of natural variability in the shoreline geomorphology and the error associated with the data collection. For each ramp-breaching fault style activity is concentrated near the fault linkage site. Even after a ramp is fully breached the severed fault tip temporarily retains some connectivity to the main fault segment. Severed fault tips along a mid-ramp breach tend to be more active than the severed fault tip at a footwall breach. Persistent fault activity along the entire severed fault tip is dependent on the position of the linkage. These results indicate that on the time scale of 104 years after linkage, severed fault tips persist as active structures and accommodate meaningful amounts of strain. / 1 / Christopher Samuel Young

<p>In wireless transmissions the communication is often degraded by random fades, noise and other performance reducing phenomena. One way of improving the stability and reducing the error rates is to use relaying techniques where several nodes cooperate in a transmission between two of them. This thesis analyzes some of the available Decode-and-Forward relaying schemes for wireless transmission. The investigated schemes are conventional repetition coding, partial repetition coding and non-collaborative direct transmission. I have developed a three-node communication system using an audio channel to test the performance of repetition coding and direct transmission. This audio communication system can also be used to demonstrate some basic phenomena in wireless transmissions and how different scenarios change the performance of the communication. A theoretical performance analysis and computer simulations of the schemes performance over a Rayleigh fading channel are done as a basis for comparison. As a result we see that in the audio communication system repetition coding actually degrades the performance, compared to direct transmission, when using a relatively slow data rate in comparison to the speed of the fading in the audio channel.</p>

published_or_final_version / abstract / toc / Linguistics / Master / Master of Arts in Applied Linguistics

In wireless networks, it has always been a challenge to satisfy high traffic throughput demands, due to limited spectrum resources. In past decades, various techniques, including cooperative communications, have been developed to achieve higher communication rates. This thesis addresses the challenges imposed by cooperative wireless networks, in particular focusing on practical code constructions and designs for wireless relay networks. The thesis is divided into the following four topics: 1) constructing and designing low-density parity-check (LDPC) codes for half-duplex three-phase two-way relay channels, 2) extending LDPC code constructions to half-duplex three-way relay channels, 3) proposing maximum-rate relay selection algorithms and LDPC code constructions for the broadcast problem in wireless relay networks, and 4) proposing an iterative hard interference cancellation decoder for LDPC codes in 2-user multiple-access channels. Under the first topic, we construct codes for half-duplex three-phase two-way relay channels where two terminal nodes exchange information with the help of a relay node. Constructing codes for such channels is challenging, especially when messages are encoded into multiple streams and a destination node receives signals from multiple nodes. We first prove an achievable rate region by random coding. Next, a systematic LDPC code is constructed at the relay node where relay bits are generated from two source codewords. At the terminal nodes, messages are decoded from signals of the source node and the relay node. To analyze the performance of the codes, discretized density evolution is derived. Based on the discretized density evolution, degree distributions are optimized by iterative linear programming in three steps. The optimized codes obtained are 26% longer than the theoretic ones. For the second topic, we extend LDPC code constructions from half-duplex three-phase two-way relay channels to half-duplex three-way relay channels. An achievable rate region of half-duplex three-way relay channels is first proved. Next, LDPC codes for each sub-region of the achievable rate region are constructed, where relay bits can be generated only from a received codeword or from both the source codeword and received codewords. Under the third topic, we study relay selection and code constructions for the broadcast problem in wireless relay networks. We start with the system model, followed by a theorem stating that a node can decode a message by jointly decoding multiple blocks of received signals. Next, the maximum rate is given when a message is decoded hop-by-hop or decoded by a set of nodes in a transmission phase. Furthermore, optimal relay selection algorithms are proposed for the two relay schemes. Finally, LDPC codes are constructed for the broadcast problem in wireless relay networks. For the fourth topic, an iterative hard interference cancellation decoder for LDPC codes in 2-user multiple-access channels is proposed. The decoder is based on log-likelihood ratios (LLRs). Interference is estimated, quantized and subtracted from channel outputs. To analyze the codes, density evolution is derived. We show that the required signal-to-noise ratio (SNR) for the proposed low-complexity decoder is 0.2 dB higher than that for an existing sub-optimal belief propagation decoder at code rate 1/3.

Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1991. / Vita. Abstract. Includes bibliographical references (leaves 151-153). Also available via the Internet.

Thesis (M.A.)--University of Hong Kong, 2000. / Includes bibliographical references (leaves 104-108).

Since the introduction of Complementary-Metal-Oxide-Semiconductor (CMOS) technology, the chip industry has enjoyed many benefits of transistor feature size scaling, including higher speed and device density and improved energy efficiency. However, in the recent years, the IC designers have encountered a few roadblocks, namely reaching the physical limits of scaling and also increased device leakage which has resulted in a slow-down of supply voltage and power density scaling. Therefore, there has been an extensive hunt for alternative circuit architectures and switching devices that can alleviate or eliminate the current crisis in the semiconductor industry. The Nano-Electro-Mechanical (NEM) relay is a promising alternative switch that offers zero leakage and abrupt turn-on behaviour. Even though these devices are intrinsically slower than CMOS transistors, new circuit design techniques tailored for the electromechanical properties of such devices can be leveraged to design medium performance, ultra-low power integrated circuits. In this thesis, we deal with a new generation of such devices that is built in the back end of line (BEOL) CMOS process and is an ideal option for full integration with current CMOS transistor technology. Simulation and verification at the circuit and system level is a critical step in the design flow of microelectronic circuits, and this is especially important for new technologies that lack the standard design infrastructure and well-known verification platforms. Although most of the physical and electrical properties of NEM structures can be simulated using standard electronic automation software, there is no report of a reliable behavioural model for NEMS switches that enable large circuit simulations. In this work, we present an optimised model of a BEOL nano relay that encompasses all the electromechanical characteristics of the device and is robust and lightweight enough for VLSI applications that require simulation of thousands of devices. To verify the performance of the proposed model, complex logic circuits built exclusively with relays, and also, hybrid CMOS-NEM circuits are simulated and verified. Finally, these novel topologies are reviewed and discussed as low-power alternatives to current CMOS topologies.

This thesis performs simulations of a relay supervisory system (RSS) that works passively in conjunction with the existing protective relaying system at a substation. During normal system operating conditions, the RSS supervises the relay system to prevent trips due to hidden failures. During wide area network disturbances, it adapts the relay system to increase security of the power system. The RSS works passively in the sense that it waits for events to occur in the existing relay system before taking any action. The simulation performed includes a model of the RSS, along with simplified models of existing relays, performed in Matlab. A power system model in EMTP provides inputs to the RSS model. Multiple faults are applied to the EMTP model, and the RSS is tested under each fault condition, and with a variety of relay hidden failures. For all tests performed, the simulation of the RSS successfully prevents relay hidden failure from removing circuit elements inadvertently, while allowing correct relay operations to remove circuit elements. / Master of Science

We study a two-way amplify and forward relay network with two transceivers which communicate through a network of nr relays while there is no direct link between the two transceivers. Each relay is equipped with a single antenna for transmitting and receiving. We study the minimization of the total transmit power that is used in all of the network nodes given the condition that the transceiver which calculates the optimal transmitting power has a full knowledge about the channels between itself and the relays and the variance with zero mean of the channels between the relays and the other transceiver. The total average power is minimized subject to a soft constraint which guarantees that the outage probability is below a certain level. The optimal solution is derived in closed form and leads to a single relay selection criterion. / UOIT

abstract: This dissertation considers two different kinds of two-hop multiple-input multiple-output (MIMO) relay networks with beamforming (BF). First, "one-way" amplify-and-forward (AF) and decode-and-forward (DF) MIMO BF relay networks are considered, in which the relay amplifies or decodes the received signal from the source and forwards it to the destination, respectively, where all nodes beamform with multiple antennas to obtain gains in performance with reduced power consumption. A direct link from source to destination is included in performance analysis. Novel systematic upper-bounds and lower-bounds to average bit or symbol error rates (BERs or SERs) are proposed. Second, "two-way" AF MIMO BF relay networks are investigated, in which two sources exchange their data through a relay, to improve the spectral efficiency compared with one-way relay networks. Novel unified performance analysis is carried out for five different relaying schemes using two, three, and four time slots in sum-BER, the sum of two BERs at both sources, in two-way relay networks with and without direct links. For both kinds of relay networks, when any node is beamforming simultaneously to two nodes (i.e. from source to relay and destination in one-way relay networks, and from relay to both sources in two-way relay networks), the selection of the BF coefficients at a beamforming node becomes a challenging problem since it has to balance the needs of both receiving nodes. Although this "BF optimization" is performed for BER, SER, and sum-BER in this dissertation, the solution for optimal BF coefficients not only is difficult to implement, it also does not lend itself to performance analysis because the optimal BF coefficients cannot be expressed in closed-form. Therefore, the performance of optimal schemes through bounds, as well as suboptimal ones such as strong-path BF, which beamforms to the stronger path of two links based on their received signal-to-noise ratios (SNRs), is provided for BERs or SERs, for the first time. Since different channel state information (CSI) assumptions at the source, relay, and destination provide different error performance, various CSI assumptions are also considered. / Dissertation/Thesis / Ph.D. Electrical Engineering 2012