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Bridge bearing is an essential component with the function of connecting the superstructure and substructure of the bridge, transmitting load and providing movability to the superstructure. Under dynamic conditions, the internal friction of bridge bearing dissipates the vibration energy and therefore reduces the dynamic response of the bridge. Meanwhile, bearing friction is considered to have possible contribution to some nonlinear dynamic behaviour of the bridge structure, which requires further investigation.However, bearing friction, in most cases, are ignored or considered roughly and implicitly as part of structural damping in current bridge designing codes and methods. Most previous research was also focusing on bearing friction’s effect under high-amplitude vibration conditions, such as earthquake or heavy wind load. Bearing friction’s effect under common low-amplitude vibration in SLS such as train-induced vibration and vehicle-induced vibration is less attended. Although the effect of such low-amplitude vibration is less significant to structural safety, it plays an essential role to the bridge’s traffic safety and comfort. Meanwhile, the cumulative effect of such vibration can significantly influence the life and durability of bridge bearings due to its high occurring frequency. Hence, a clearer understanding of bearing dynamic behaviour is required to improve the understanding of bridge and bearing dynamics.In this thesis, an advanced numerical tool is developed for dynamic analysis of bearing friction. A 3D pot bearing finite element that can be implemented in commercial FE software ABAQUS, is programmed based on the mathematical friction models developed in previous research and the Bouc-Wen hysteretic model. Numerical results that accord with the results of relevant friction tests are produced by the calibrated and validated bearing finite element, giving proof that the element is capable to reflect the dynamic friction response of bridge pot bearing in reality.The 3D shell numerical model of Banafjäl bridge located on the Bothnia Line in Norrland, Sweden, is built as a study case of bridge dynamic analysis in this thesis, with implementation of the newly developed bearing element. The feasibility of implementing the bearing element in bridge dynamic analysis is proven by the numerical results. The nonlinear influence of bearing friction on the dynamic response of bridge structure, especially the influence on structural damping properties, is discussed preliminarily. The analysis results show that with the consideration of bearing friction, the damping presents a clear amplitude-dependency, which accords the phenomenon reported in previous research.

Planing hull is one solution to break the speed barrier of conventional hull, but as the boat reaches a high speed, massive whisker spray will be developed and attached to the hull, which causes a notable resistance increase. A Swedish company Peterstep invented an innovative spray deflector that can deflect the spray backwards and harvest kinetic energy from the spray.In the 2019 spray deflector project, many tests were done in Davison Laboratory Towing Tank, and there is a trim angle difference between plated and non-plated hulls. To investigate possible reasons, more tests are implemented in this project. According to the test results, the reason is determined as the different roughness of the hull and bottom due to differences in materials. Also, the tape for sealing the seam between hull and bottom plate affects the sharpness of the hard chine, thereby hindering the flow separation.The model used in previous experiments is no longer suitable for the further investigation. The modular design caused the different running position of plated and non-plated hull. In addition, the hull is too slender for the wave test. Therefore, a new model is needed to satisfy the new objectives of experiments. In this paper, the detailed design is surrounded by design aims and restrictions, such as increase spray resistance and avoid porpoising.There are few researches on HSC free running model test. To investigate the performance of the spray deflector in the test environment more similar to reality, a free running model with propulsion and steering system is necessary. The preliminary design, component selection and testing plan are outlined in this paper. / Planande skrov är en lösning för att bryta hastighetsbarriären hos ett konventionellt skrov, men när båten når hög hastighet kommer omfattande whisker spray att utvecklas på skrovet, vilket orsakar en anmärkningsvärd ökning av motståndet. Ett svenskt företag Peterstep har utvecklat en innovativ sprutdeflektor som kan avleda sprayen bakåt och skörda kinetisk energi från sprayen.Under sprutdeflektorprojektet 2019 gjordes många tester i Davison Laboratorys släpränna och det noterades en oönskad trimvinkelskillnad mellan modeller där skrovet byggts i en del eller med ett steg som fyllts igen med en bottenplatta. För att undersöka möjliga skäl till detta implementeras nya tester i detta projekt. Enligt testresultaten bestäms orsaken som skrovets och bottenplattans olika jämnhet på grund av materialskillnader. Även tejpen för tätning av sömmen mellan skrov och bottenplatta påverkar skärpan i slaget och hindrar därmed flödets avlösning.Modellen som använts i tidigare experiment är inte lämplig för fortsatt utredningen. Den modulära designen orsakade olika gångläge beroende på hur skroven hade byggts upp. Dessutom är skrovet för smalt för vågproven. Det behövs därför en ny modell för att uppfylla målen med experimenten.I det här arbetet har designen ytterligare designmål och begränsningar, som att mäta sprutmotståndet och att undvika porpoising.Det finns få undersökningar om HSC-test med frigående modeller. För att undersöka sprutdeflektorers prestanda i testmiljö som liknar verkligheten är det nödvändigt med en frigående modell med eget framdrivnings- och styrsystem. Den preliminära designen, komponentvalet och testplanen beskrivs i detta dokument.

<p>Nanofluids are engineered colloidal dispersions of nanoparticles in a liquid. The field of nanofluids has seen much interest due to reported heat transfer enhancements over the corresponding pure fluids at low particle concentrations. Particularly, a large increase in critical heat flux (CHF) has been widely reported along with modification of the boiling interface. Inconsistencies in reported impact on nucleate boiling heat transfer and the degree of CHF enhancement illustrate the need for further study.</p> <p>A pool boiling experiment has been designed and constructed at McMaster University to allow for the study the boiling of water-based nanofluids. The facility has been commissioned with saturated distilled water tests at atmospheric pressure, heat flux levels up to 1200 kW·m^-2, and at wall superheat levels up to 19.5^oC. Wall superheat and heat flux uncertainties were estimated to be ±0.6^oC and ±20 kW∙m^-2, respectively. For the installed test section, heat flux is limited to 2.62 ± 0.06 MW·m^-2. A high speed video system for the analysis of bubble dynamics was tested and used for qualitative comparisons between experimental runs. This system was tested at 2500 FPS and an imaging resolution of 39 pixels per mm, but is capable of up to 10 000 FPS at the same spatial resolution. Heat flux versus wall superheat data was compared to the Rohsenow correlation and found to qualitatively agree using surface factor <em>C_sf</em> = 0.011. Results were found to have a high degree of repeatability at heat flux levels higher than 600 kW·m^-2.</p> <p>The new facility will be used to conduct studies into the pool boiling of saturated water-based nanofluids at atmospheric pressure. Additional work will involve the control and characterization of heater surface conditions before and after boiling. Quantitative analysis of bubble dynamics will be possible using high speed video and particle image velocimetry.</p> / Master of Applied Science (MASc)

Switched reluctance machines (SRMs) are well known for their simple and robust structure, facilitating their increasing application in many sectors, for example vacuum cleaners, where domestic machines operate at high-speed, 50,000 RPM being typical. Conventional SRMs (CSRMs) use a decoupled concentrated phase winding so that torque is predominantly only generated due to the self-inductance, which limits utilization of the machine electrical circuits. In this thesis, the toroidal winding SRM (TSRM) is introduced, which operates based on the variation of mutual inductance between different phases. The toroidal winding introduces additional winding space, and the winding is practically easy to implement, both features that lead to a relatively higher copper filling factor. The toroidal winding also benefits the machine thermal performance, as the winding is directly exposed on the machine periphery and thus accessible to cooling. All these make TSRMs interesting and meaningful for further study. Following a comprehensive comparison of CSRM and TSRM characteristics, a general torque equation is presented that is applicable to both CSRM and TSRM. Two 12-switch converters are proposed to drive three-phase TSRMs. Moreover, sinusoidal current excitation with a commercial three-phase half-bridge converter has been suggested as an alternative converter solution for TSRMs. Accordingly, a three-phase six-stator-pole, four-rotor-pole CSRM is designed and optimized with a speed of up to 50,000 rpm in this thesis. A TSRM is resized to achieve the same envelope dimension as a benchmark CSRM. Thus, a comparative study between high-speed CSRM and TSRMs has been carried out. They have both been prototyped and tested. The findings suggest that the TSRM is superior, considering machine mass and wire temperature management. The TSRM has a better torque output at lower speeds because copper losses are dominant. However, the CSRM has more advantages at higher speeds due to lower iron losses and lower DC voltage requirements. / Thesis / Doctor of Philosophy (PhD)

The ever-increasing bandwidth requirements to support telecommunications infrastructure necessitates large-scale fabrication of low-cost and scalable silicon photonic integrated circuits. Wavelength-division multiplexing (WDM) schemes are fundamentally limited in the number of channels supported in long-haul transmission by the erbium doped fiber amplifier (EDFA). To address this, researchers have turned focus toward the thulium doped fiber amplifier (TDFA), which provides 3× more bandwidth. This thesis describes the development of high-speed silicon-on-insulator (SOI) micro-ring resonator (MRR) modulators optimized for wavelengths in the TDFA band. Chapter 2 presents a theoretical performance comparison between MRR modulators designed for optimized use at EDFA and TDFA wavelengths. Chapter 3 presents an experimental study of optical loss mechanisms at extended wavelengths which suggests reduced waveguide scattering and enhanced divacancy defect absorption as well as larger bending and substrate leakage losses when compared with shorter wavelengths. An electronic variable optical attenuator is characterized in Chapter 4 to experimentally verify the predicted 1.7× TDFA-band free-carrier effect enhancement over EDFA-band wavelengths. The first steady-state operation of an MMR modulator near a central wavelength of 1.97 µm is also demonstrated under the enhanced free-carrier effect. Chapter 5 demonstrates the first high-speed reverse bias operation of an MRR modulator with a measured bandwidth of 12.5 GHz, and an on-chip optical link consisting of a modulator followed by a defectmediated detector with open eye-diagrams up to data rates of 12.5 Gbps. Chapter 6 introduces an electrically-driven post-fabrication defect-assisted resonance trimming technique via local annealing for use in MRR devices. Chapter 7 presents a Monte Carlo simulation of resonance alignment in multi-MRR systems subjected to spatially-correlated wafer variation created through the Virtual Wafer Model process to predict thermal power consumption and power reduction through resonance trimming. / Thesis / Doctor of Philosophy (PhD)

This research addresses the critical need for precise two-phase flow data in the development of computer simulation models, with a specific focus on the annular flow regime's droplet behavior. The study aims to contribute to the evaluation of safety and efficiency in nuclear reactors that handle fluids transitioning between liquid and gas states for thermal energy transport. Central to the investigation is the collection and analysis of droplet size and velocity distribution data, particularly to help with developing models for the water-cooled nuclear power plants. The experimental setup employs advanced tools, including a high-speed camera, lens, teleconverter, and a selected light source, to capture high-resolution images of droplets. Calibration procedures, incorporating depth of field testing, are implemented to ensure accurate droplet size measurements. A critical component of the research is the introduction of a droplet identification program, developed using Matlab, which facilitates efficient processing of experimental data. Preliminary results from the Virginia Tech test facility demonstrate the system's capability to eliminate out-of-focus droplets and obtain precise droplet data in a reasonable amount of time. Experimental results from the Rensselaer Polytechnic Institute test facility provide droplet size and velocity distributions for a variety of annular flow conditions. This facility has a concurrent two-flow system that pumps air and water at different rates through a 9.525 mm inner diameter tube. The conditions tested include gas superficial velocities ranging from 22 to 40 m/s and liquid superficial velocities ranging from 0.09 to 0.44 m/s. The measured flow has a temperature of 21°C and a pressure of 1 atm. / Master of Science / This research explores the behavior of small droplets as fluids transition between liquid and gas states, particularly within the context of the cooling water in nuclear power plants. The overarching goal is to collect data on these droplets to improve computer simulations that help design nuclear reactors and assess their safety. This is important because it is often infeasible due to safety, monetary, or time restrictions to physically test some nuclear reactor equipment. The study employs state-of-the-art technology, including high-speed cameras and specialized imaging tools, to capture and analyze droplet size distribution data. This investigation is pivotal in ensuring the fuel in nuclear reactors remain adequately cooled during part of the boiling process. The research methodology includes the development of a droplet identification program using Matlab, ensuring efficient processing of experimental data. Preliminary findings from experimental tests at Virginia Tech showcase the program's capability to filter out irrelevant data and provide accurate droplet information. Experimental results from the Rensselaer Polytechnic Institute annular flow test facility provide droplet size and velocity data for a range of conditions that cooling water may face. Beyond its contributions to nuclear engineering, this research holds promise for influencing advancements in various applications that involve liquid droplets, opening avenues for innovation in the broader scientific and engineering communities.

In the last few years, scientific consensus is that emission of greenhouse gases (GHGs) into the atmosphere is contributing to changes in the earth's climate. While uncertainty remains over the pace and dimensions of the change, a consensus on the need for action has grown among the public and elected officials. In part, this shift has been accelerated by concern over energy security and rising fuel prices. The new political landscape has led many cities, states, and regions to institute policies aimed at reducing GHG emissions. These policies and emerging initiatives have significant implications for the transportation planning process. The transportation sector accounts for approximately 27% of GHG production in the U.S. (as of 2003) and while the U.S. accounts for only roughly 5% of the world's population, it is estimated that it produces over 20% of the world's GHG emissions. Note that this does not include "lifecycle" emissions that result from the processes undertaken to extract, manufacture, and transport fuel. Carbon dioxide represents approximately 96% of the transportation sector's radiative forcing effects. Unlike conventional air pollutants, carbon dioxide emissions are directly tied to the amount of fuel consumed and its carbon intensity. Therefore, emissions reductions can be achieved by increasing the use of low-carbon fuels, improving fuel economy, or reducing total vehicle miles of travel - often called the three legged stool. (A fourth leg is congestion reduction, at certain optimal speeds). These same factors are related to our use of imported oil, so actions taken to reduce GHG emissions may actually produce benefits in both policy areas. The climatic risks of additional emissions associated with capacity projects must be balanced against the mobility, safety, and economic needs of a community or region. Consequently, this dissertation attempts to quantify the impacts of high-emitting vehicles on the environment and to propose solutions to enhance the currently-used high-emitting vehicle detection procedures. In addition, fuel consumption and emission models for high-speed vehicles are developed in order to provide more reliable estimates of vehicle emissions and study the impact of vehicle speeds on vehicle emissions. The dissertation extends the state-of-the-art analysis of high emitting vehicles (HEVs) by quantifying the network-wide environmental impact of HEVs. The literature reports that 7% to 12% of HEVs account for somewhere between 41% to 63% of the total CO emissions, and 10% are responsible for 47% to 65% of HC emissions, and 10% are responsible for 32% of NOx emissions. These studies, however, are based on spot measurements and do not necessarily reflect network-wide impacts. Consequently, the research presented in this dissertation extends the state-of-knowledge by quantifying HEV contributions on a network level. The study uses microscopic vehicle emission models (CMEM and VT-Micro model) along with pre-defined drive cycles (under the assumption that the composite HEV and VT-LDV3 represent HEVs and NEVs, respectively) in addition to the simulation of two transportation networks (freeway and arterial) to quantify the contributions of HEVs. The study demonstrates that HEVs are responsible for 67% to 87% of HC emissions, 51% to 78% of CO emissions, and 32% to 62% of the NOX emissions for HEV percentages ranging from 5% to 20%. Additionally, the traffic simulation results demonstrate that 10% of the HEVs are responsible for 50% to 66% of the I-81 HC and 59% to 78% of the Columbia Pike HC emissions, 35% to 67% of the I-81 CO and 38% to 69% of the Columbia Pike CO emissions, and 35% to 44% of the I-81 NOX and 35% to 60% of the Columbia Pike NOX emissions depending on the percentage of the normal-emitting LDTs to the total NEVs. HEV emission contributions to total HC and CO emissions appear to be consistent with what is reported in the literature. However, the contribution of NOX emissions is greater than what is reported in the literature. The study demonstrates that the contribution of HEVs to the total vehicle emissions is dependent on the type of roadway facility (arterials vs. highways), the background normal vehicle composition, and the composition of HEVs. Consequently, these results are network and roadway specific. Finally, considering that emission control technologies in new vehicles are advancing, the contribution of HEVs will increase given that the background emission contribution will decrease. Given that HEVs are responsible for a large portion of on-road vehicle emissions, the dissertation proposes solutions to the HEV screening procedures. First, a new approach is proposed for estimating vehicle mass emissions from concentration remote sensing emission measurements using the carbon balance equation in conjunction with either the VT-Micro or PERE fuel consumption rates for the enhancement of current state-of-the-art HEV screening procedures using RSD technology. The study demonstrates that the proposed approach produces reliable mass emission estimates for different vehicle types including sedans, station wagons, full size vans, mini vans, pickup trucks, and SUVs. Second, a procedure is proposed for constructing on-road RS emission standards sensitive to vehicle speed and acceleration levels. The proposed procedure is broadly divided into three sub-processes. In the first process, HE cut points in grams per second are developed as a function of a vehicle's speed and acceleration levels using the VT-Micro and CMEM emission models. Subsequently, the HE cut points in grams per second are converted to concentration emissions cut points in parts per million using the carbon balance equation. Finally, the scale factors are computed using either ASM ETW- and model-year-based standards or engine-displacement-based standards. Given the RS emissions standards, the study demonstrated that the use of on-road RS cut points sensitive to speed and acceleration levels is required in order to enhance the effectiveness of RS. Finally, the dissertation conducted a study to develop fuel consumption and emissions models for high-speed vehicles to overcome the shortcomings of state-of-practice models. The research effort gathered field data and developed models for the estimation of fuel consumption, CO₂, CO, NO, NO2, NOx, HC, and PM emissions at high speeds. A total of nine vehicles including three semi-trucks, three pick-up trucks, and three passenger cars were tested on a nine-mile test track in Pecos, Texas. The fuel consumption and emission rates were measured using two portable emission measurement systems. Models were developed using these data producing minimum errors for fuel consumption, CO₂, NO2, HC, and PM emissions. Alternatively, the NO and NOx emission models produced the highest errors with a least degree of correlation. Given the models, the study demonstrated that the newly constructed models overcome the shortcomings of the state-of-practice models and can be utilized to evaluate the environmental impacts of high speed driving. / Ph. D.

With the ever increasing deployment and usage of gigabit networks, traditional network anomaly detection based intrusion detection systems have not scaled accordingly. Most, if not all, systems deployed assume the availability of complete and clean data for the purpose of intrusion detection. We contend that this assumption is not valid. Factors like noise in the audit data, mobility of the nodes, and the large amount of data generated by the network make it difficult to build a normal traffic profile of the network for the purpose of anomaly detection. From this perspective, the leitmotif of the research effort described in this dissertation is the design of a novel intrusion detection system that has the capability to detect intrusions with high accuracy even when complete audit data is not available. In this dissertation, we take a holistic approach to anomaly detection to address the threats posed by network based denial-of-service attacks by proposing improvements in every step of the intrusion detection process. At the data collection phase, we have implemented an adaptive sampling scheme that intelligently samples incoming network data to reduce the volume of traffic sampled, while maintaining the intrinsic characteristics of the network traffic. A Bloom filters based fast flow aggregation scheme is employed at the data pre-processing stage to further reduce the response time of the anomaly detection scheme. Lastly, this dissertation also proposes an expectation-maximization algorithm based anomaly detection scheme that uses the sampled audit data to detect intrusions in the incoming network traffic. / Ph. D.