Temperature control has been implemented in friction stir processing and has demonstrated the ability to give improved process control. In order to have optimal control of the process, the parameters of the system to be controlled must be accurately identified. The system parameters change with tool geometry and materials, workpiece materials, and temperature. This thesis presents the use of the relay feedback test to determine the system parameters. The relay feedback test is easy to use and promotes system stability during its use. The results from the relay feedback test can be used to determine controller gains for a PID controller. The use of this method, as well as the quality of the resulting control is demonstrated in this paper.

Yes / In this paper two novel antennas, suitable for access and backhaul links, are designed, fabricated and tested for a Relay Station in a WiMAX wireless network. A single modi¯ed E-shaped patch antenna is described, presenting 10 dB gain over 12.4% bandwidth. This antenna element is used for the design of a 4 £ 4 planar array which provides experimental gain of 21.2 dB. The antenna system on the Relay Station operates at 3.4 GHz and includes one single antenna element for access link realization and an antenna array for the backhaul link realization. These antennas are installed in two con¯guration arrangements and tested in terms of their radiation performances and coupling e®ects. The simulated and measured results are quite satisfactory and in good agreement at which the maximum coupling between the access and backhaul antennas is found below ¡25 dB for all tested cases.

Cal Poly San Luis Obispo’s Electrical Engineering Department and the Power Energy Institute have developed a microgrid laboratory with various generators, loads, and protection systems over the past several years. To improve and make the Cal Poly microgrid laboratory more realistic, this thesis outlines the process of improving the EE microgrid setup by adding a wind energy generation system via an induction generator, excitation capacitors, and a protection relay. By adding an induction generator, the microgrid system becomes more resilient to sudden power fluctuations by maintaining a stable voltage and frequency when the microgrid is islanded. To test this, a disturbance was introduced to the islanded microgrid by turning on and off the pump motor load for one second and by adding a torque load. Without the wind energy system, the system frequency drops below 59.7Hz causing the microgrid to collapse. However, with the wind energy system, the microgrid frequency is kept above 59.7Hz and can remain operational even if the pump motor is loaded to 2 lb•in. This is due to the large inertia the induction generator contains. This is further investigated by creating a Simulink model that models a wind turbine system with wind fluctuations. The model shows that by having a large rotating mass, the inertia keeps the output power stable even if there are rapid wind speed fluctuations.

The growth of Distributed Energy Resources is accelerating, causing significant changes in utility distribution systems due to the bidirectionality of power flow. As a result, protection systems will require upgrades to operate with these new requirements. The current-only directional relay (CODR) is a novel proposal that detects the direction of fault currents without the need for new devices, but instead upgrades the software logic of existing devices, making it a cost-effective solution. This work provides a complete description of how to implement a hardware testbed to review the CODR method. Findings show that CODR performs successfully in a real environment, but its algorithm needs to be upgraded if used in distribution systems where lines have a non-negligible resistive component. / Master of Science / The use of renewable energy sources, such as solar panels and wind turbines, is growing rapidly. This is causing changes in the way electricity is distributed, as power can now flow in both directions. To keep up with these changes, the systems that protect the electricity grid need to be updated. One cost-effective solution is to use a new type of relay, called the current-only directional relay (CODR), which can detect the direction of fault currents without the need for new devices. This work describes how to test the CODR method using a hardware testbed. The results show that the CODR performs well in a real environment, but its algorithm needs to be updated for use in certain types of distribution systems.

The realization of high data rate wireless communication and large-scale connectivity with seamless coverage has been enabled by the introduction of various advanced transmission technologies, such as multiple access (MAC) technology and relay-assisted communications. However, beyond the accurate representation and successful transmission of information, in many applications it is the semantic aspect of that information that is really of interest. This thesis makes contributions to both the technology of conventional wireless communications and the theory of semantic communication. The main work is summarized as follows: We first consider an uplink system with K single-antenna users and one base station equipped with a single antenna, where each user utilizes a binary constellation to carry data. By maximizing the minimum Euclidean distance of the received sum constellation, the optimal user constellations and sum constellation are obtained for K=3 users. Using the principle of lattice coding, that design is extended to the K-user case. In both settings, the sum constellation belongs to additively uniquely decomposable constellation group (AUDCG). That property enables us to reduce the maximum likelihood multi-user detector to a single-user quantization based receiver. The symbol error probability (SEP) formula is derived, showing that our proposed non-orthogonal multiple access (NOMA) scheme outperforms the existing time division multiple access (TDMA) designs for the same system. Our design also sheds light on the general complex constellation designs for the MAC channel with arbitrary user constellation size. Specifically, K-user constellations with any 2^Mk size can be obtained using combinations of the proposed binary constellations. Next we concentrate on a multi-hop relay network with two time slots, consisting of single-antenna source and amplify-and-forward relay nodes and a destination node with M antennas. We develop a novel uniquely-factorable constellation set (UFCS) based on a PSK constellation for such system to allow the source and relay nodes to transmit their own information concurrently at the symbol level. By taking advantage of the uniquely-factorable property, the optimal maximum likelihood (ML) detection was equivalently reduced to a symbol-by-symbol detection based on phase quantization. In addition, the SEP formula was given, while enable us to show that the diversity gain of the system is one. For semantic communication, a new source model is considered, which consists of an intrinsic state part and an extrinsic observation part. The intrinsic state corresponds to the semantic feature of the source. It is not observable, and can only be inferred from the extrinsic observation. As an instance of the general model, the case of Gaussian distributed extrinsic observations is studied, where we assume a linear relationship between the intrinsic and extrinsic parts. We derive the rate-distortion function (in both centralized encoding and distributed encoding) of semantic-aware source coding under quadratic distortion structure by converting the semantic distortion constraint of the source to a surrogate distortion constraint on the observations. With proposed AUDCG and UFCS-based designs, high data rates as well as low detection latency can be achieved. Our modulation division method will be one of the promising technologies for the next generation communication and the analysis of the source coding with semantic information constraints also provides some insights that will guide the future development of semantic communication systems. / Thesis / Doctor of Philosophy (PhD) / The proliferation of smart phones and electronic devices has spurred explosive growth in high-speed multimedia services over the next generation of wireless cellular networks. Indeed, high data rates and large-scale connectivity with seamless coverage are the dominant themes of wireless communication system design. Moreover, beyond the accurate representation and successful transmission of information, the interpretation of its meaning is being paid more attention nowadays, which requires the development of approaches to semantic communication. The goal of this thesis is to contribute to the development of both conventional and semantic communication systems. Two advanced transmission technologies, namely, multiple access and relay-assisted communications are considered. By taking advantage of the special structures of digital communication signals, new approaches to multiple access and relay-assisted communications are developed. These designs enable high data rates, while simultaneously facilitating low-latency detection. Since there has been very limited analysis of the source coding of a vector source subject to semantic information constraints, we also study the rate distortion to trade-off for vector sources in both the case of centralized encoding and the case of distributed encoding, and we establish some insights that will guide the future development of semantic communication systems.

Motivated by current applications in multihop transmission and ad hoc networks, the classical three-node relay channel consisting of a source-destination pair and a relay has received significant attention. One of the crucial aspects of the relay channel is the design of proper relaying protocols, i.e., how the relay should take part into transmission. The thesis addresses this problem and provides a partial answer to that. In this thesis, we propose and study two novel relaying protocols. The first one is based on constellation rearrangement (CR) and is suitable for higher-order modulation schemes. With CR, the relay uses a bit-symbol mapping that is different from the one used by the source. We find the optimal bit-symbol mappings for both the source and the relay and the associated optimal detectors, and show that the improvement over conventional relaying with Gray mapping at the source and the relay can amount to a power gain of several dB. This performance improvement comes at no additional power or bandwidth expense, and at virtually no increase in complexity. The second one is a half-duplex decode-and-forward (DF) relaying scheme based on partial repetition (PR) coding at the relay. With PR, if the relay decodes the received message successfully, it re-encodes the message using the same channel code as the one used at the source, but retransmits only a fraction of the codeword. We analyze the proposed scheme and optimize the cooperation level (i.e., the fraction of the message that the relay should transmit). We compare our scheme with conventional repetition in which the relay retransmits the entire decoded message, and with parallel coding, and additionally with dynamic DF. The finite SNR analysis reveals that the proposed partial repetition can provide a gain of several dB over conventional repetition. Surprisingly, the proposed scheme is able to achieve the same performance as that of parallel coding for some relay network configurations, but at a much lower complexity. Additionally, the thesis treats the problem of resource allocation for collaborative transmit diversity using DF protocols with different type of CSI feedback at the source. One interesting observation that emerges is that the joint powerbandwidth allocation only provides marginal gain over the relaying protocols with optimal bandwidth allocation. / QC 20101119

Yes / A novel beam-forming module based on Wilkinson power divider technology, including attenuators and phase shifter chips is designed, fabricated and evaluated to be incorporated in a Relay Station connecting it with the Base Station under a 4G network. The proposed module is a 1:8 port circuit, utilizing two substrates, providing approximately 700 MHz bandwidth over 3.5 GHz frequency band and less than −20 dB transmission line coupling. Moreover an external control unit that feeds the beam-forming module with code-words that define the proper amplitude/phase of the excitation currents is established and described. The presented module is connected to a planar array and tested for two beam-forming scenarios, providing satisfactory radiation patterns.

A measurement tool has been developed to estimate errors in relaying current transformers and voltage transformers. The tool has been developed to collect data in a substation and send it to a remote location over a telephone line. Different schemes were evaluated and tested in the laboratory. The final choice was made on the basis of the hardware and transmission cost constraints. The measurement unit was developed using hardware similar to that used in a computer relay. The signals from the current and voltage transducers were sampled using a microprocessor and an analog to digital converter in real-time. The measurement device has been installed in the field. The data from the field was collected remotely and analyzed in the Virginia Tech Power Systems laboratory. The analysis of the data is presented at the end. / Master of Science

Logic for an adaptive reclosing relay has been developed. The relay works correctly in a wide number of fault cases. The relay has the following distinguishing characteristics : (a) Reclosing into a three phase fault is avoided under all circumstances. (b) The logic is applicable only for circuit breakers which. have reclosing on individual phases. (c) The relay works correctly in the case of both (shunt) compensated and uncompensated lines. / Master of Science

Designers of low-power radio systems for use in urban areas would benefit from the capability for accurate computer-based predictions of signal loss due to shadowing. This thesis is intended to fill a need for prediction methods that exploit a building database and consider the three-dimensional profile of the radio path. Models are presented that allow the application of Fresnel-Kirchoff diffraction theory to arbitrarily oriented buildings of simple shapes. Building location information used by the diffraction models is in a form compatible with a geographic information systems (GIS) database. Diffraction screens are constructed at all building edges, including those of both horizontal and vertical orientations, in order to consider all possible diffractions and to compute field contributions often ignored. Multiple buildings and edges of the same building that introduce multiple successive diffractions are considered with a rigorous, recursive application of the diffraction theory that requires sampling the field distribution in each aperture. Robust and computationally efficient numerical methods are applied to solve the diffraction integrals. The software implementation of these methods is tested with example runs and comparisons with 914 MHz continuous-wave measurements taken on the Virginia Tech campus. / Master of Science