In this thesis, a new proactive coordinated ramp metering approach is developed based on speed data obtained from vehicle probe technology (or in future from IntelliDrive). The objective function formulated in this approach minimizes the total vehicular travel time and delay experienced by vehicles on the freeway and on-ramps. A rolling horizon framework is formulated to obtain the optimum ramp metering rates for the next time interval. In addition, the developed approach employs a dynamic weighting scheme that gives different weights in the objective function to different freeway sections and the on-ramps. The developed approach is tested using Quadstone PARAMICS’ microsimulation software package. This probe-based adaptive ramp metering approach has been compared with a detector-based algorithm and pre-timed ramp metering algorithms. The comparative analysis of the three ramp metering approaches was conducted on an 8 km freeway section on Highway 2 in Calgary, Alberta, Canada with Quadstone PARAMICS’ microsimulation. The performances of the algorithms were examined and compared, in terms of freeway and system delays, densities and speeds. A sensitivity analysis has also been conducted to compare the performance of the developed probe-based approach for different percentages of market share of probe data (i.e. number of vehicles acting as probes). The results of the analysis indicate that the probe-based algorithm consistently outperformed the two other approaches in terms of all performance measures. The probe-based approach is shown to exceed the performance of the detector-based approach with a market share of vehicle probes as low as 3%. The results of the analysis are promising and show the effectiveness of developing ramp metering control algorithms taking as main input parameters speed data from vehicle probes on the freeway.
Mar
13
Hydration and Hydrolysis with Water Tolerant Lewis Acid Catalysis in High Temperature Water
The purpose of this work was to develop the technique of performing organic reactions in high temperature water HTW) with water-tolerant Lewis acids WTLAs). We define high temperature water, or superheated water, as liquid water above its normal boiling point. A water-tolerant Lewis acid is a Lewis acid that is not deactivated in the presence of water. Our work is the first application of WTLAs to HTW reaction media. We studied two basic reactions in HTW with WTLA catalysis: alkyne hydration to form ketones, and ether hydrolysis to form alcohols. We used a model aryl alkyne, 1-phenyl-1-propyne to carry out a catalyst comparison study. InOTf)3 was the best catalyst of those tested: InOTf)3, InCl3, ScOTf)3, YbOTf)3, HCl, and H2SO4. Reactions at different temperatures 150, 175, 200, and 225°；C) allowed us to determine activation energy and frequency factor to be 21.4 ＋/- 0.6 kcal/mol and 108.8＋/-0.3 L mol-1 s-1, respectively. We tested additional aryl and alkyl alkyne systems to help define the scope and limitations of the general method. Anisole served as our model alkyl aryl ether for the hydrolysis reactions. We tested the same acid catalysts as above and again found InOTf)3 to be the best catalyst of those tested. Experiments at different temperatures 200, 225, 250, 275, and 300°；C) allowed us to determine that activation energy and frequency factor were 31 ＋/- 1 kcal/mol and 1010.6＋/-0.5 L mol-1 s-1, respectively. We tested additional ethers toward hydrolysis to gain mechanistic insight and determine the limitations of the procedure. We tested the effects that our reactor vessel may be exerting upon the reaction. For alkyne hydration, we found that the use of a capillary quartz reactor slowed the reaction dramatically, likely due to transport limitations. For ether hydrolysis, we found that the presence of any surface tested—quartz or statinless steel—decreased reaction progress. We hypothesize that this phenomenon is due to interaction between the surface and the InOTf) 3 catalyst. These experimental results identify an important phenomenon that had previously gone unrecognized in the field. The overall significance of our work is our demonstration that the use of WTLAs in HTW presents potential as a novel medium for organic synthesis. For hydration and hydrolysis, this previously unexplored reaction medium can be competitive with traditional techniques in terms of rate and yield.
Mar
13
Synthesis and optical properties of silicon-gold core-shell nanowires
In this study, silicon nanowires (SiNWs) were used as the templates to synthesize Si-Au core-shell nanowires through multi-steps wet chemistry method. The use of SiNWs permitted precise control of core diameter and wire length and the wet chemistry method allowed control of shell thickness. Far-field optical scanning microscopy study showed that the Si-Au core-shell nanowires emit two photon luminescence (TPL) signals under near infrared (NIR) excitation. Furthermore, the TPL along the Si-Au core-shell nanowires demonstrated interference pattern which might be due to the plasma field enhancement. The TPL pattern along the Si-Au core-shell nanowires might be used as a read-out of plasma wave and provide a new insight of one dimension metallic nanostructure.
Mar
13
Fluid flow related phenomena and inclusion motion in continuous casting strands
To improve the efficiency of the continuous casting process and the quality of its products, this dissertation mainly investigated fluid flow related phenomena and inclusion motion in continuous casting. Mathematical simulation was performed for this purpose. Both a slab caster and a billet caster were investigated. In the study of the slab caster, the application of electromagnetic brake field on the slab mold was evaluated. The results indicated that the magnetic force decelerated the high speed steel jet, stabilized the top fluctuation, and prevented the bias flow inside the mold. The other study of this slab caster involved the fluid flow features during the transient casting process. It included casting start, casting speed variation, and temperature fluctuation. Especially for the casting start, the entire process was simulated using the volume of fluid multiphase model and dynamic mesh method. The results indicated the serious entrainment of air during the filling process and large fluctuations in the top surface level at the beginning of dummy bar moving. In the billet caster study, billet samples were collected from an industrial trial. The features of the nonmetallic inclusions were characterized by automated particle analysis and the size and spatial distribution of nonmetallic inclusions were determined. Mathematical models were developed to predict the entrapment locations of inclusions in the solidifying shell and compared to the industrial results. The distribution of inclusions predicted through mathematical modeling in the cross section of billet was in good agreement with the sample measurements.
Mar
13
Studies on weathered waterborne treated wood: Leaching of metals during service and metals based sorting upon recycle
Weathered waterborne treated wood is believed to behave differently than new wood during service regarding the loss of its metallic-based preservatives. Also, weathered preserved wood should be separated from the unpreserved wood upon recycle. The first objective of this dissertation was to evaluate losses from weathered CCA-treated wood samples at different retention levels under normal field conditions and to compare leaching to new ACQ as alternative to CCA). Results showed that arsenic leached at a higher rate than chromium and copper in all CCA treated wood samples, while copper leached the highest from the ACQ sample. Overall results suggest that the leaching rate of metals on a percent basis from in-service pressure treated wood may increase as the wood weathers； however due to lower retention levels of the metals in the wood as it ages the yearly mass of metals lost would be at similar or at lower quantities in comparison to new treated wood. The second objective was to evaluate the use of automated X-ray fluorescence XRF) systems for identifying and removing As-based and Cu-based treated wood within the recovered wood waste stream. A full-scale online automated XRF-detection, conveyance and diversion system was used for experimentation. At the different applied feeding rates and belt speeds, online sorting efficiencies of waste wood by XRF technology were high ＞70% for both treated wood and untreated wood). The incorrectly diverted pieces of wood were attributed to deficiencies in the wood conveyance systems and not to deficiencies in the XRF-based detection. Online sorting was shown to sort wood which would meet the residential soil cleanup target levels in Florida when an infeed is composed of 5% of treated wood pieces. Comparisons with other sorting methods show that XRF technology can potentially fulfill the need for cost-effective processing at large wood recycling facilities ＞30 tons per day). Management of weathered CCA-preserved wood, due to its continuity of leaching metals and the need to remove it upon the recycle of wood, will likely continue until complete banning and removal from the environment, a process that may extend up to the next century.
Mar
13
Vector control of multiphase permanent magnet synchronous motors
This thesis describes the modeling, the simulation and the implementation of vector control for a variable speed drive system of multiphase permanent magnet synchronous machines. The considered machines have non salient surface-mounted rotors. After a review of the classical theory of vector control, we adapt this method to control a machine that has an odd number of stator winding phases greater than three. A simplified model in Simulink/MATLAB is developed to study this control method. After having illustrated this method, we present a test bench implemented with a DSP. We carry out validations for two machines； the first with a three-phase stator and the other with a seven-phase stator. To illustrate the advantage of the presented control method, we show that the use of a harmonic of EMF of a multiphase machine can produce a constant torque. We analyze also the operation with one phase open without modifying the control strategy in order to show the fault tolerance of multiphase machines.
Mar
13
Flow and Acoustics of Jets from Practical Nozzles for High- Performance Military Aircraft
This research project examines supersonic jets from nozzles representative of the practical variable-geometry convergent-divergent nozzles used on high-performance military aircraft. The nozzles employed have conical convergent sections, sharp throats and conical divergent sections. Nozzles with design Mach numbers of 1.3, 1.5, 1.56 and 1.65 are tested and the flow and acoustics examined. Such nozzles are found to produce a double-diamond shock structure consisting of two overlapping sets of shock cells, one cast from the nozzle lip and one cast from the nozzle throat. These nozzles are found to produce no shock-free condition at or near the design condition. As a result they produce shock-associated noise at all supersonic conditions. The shock cell spacing, broad-band shock-associated noise peak frequency and screech frequency all match those of more traditional nearly isentropic convergent-divergent nozzles. A correlation is proposed which improves upon the Prandtl-Pack relation for shock cell spacing in that it accounts for differences in nozzle design Mach number which the Prandtl-Pack relation does not. This proposed relation reverts to the Prandtl-Pack equation for the case of a design Mach number of 1.0. Chevrons are applied to the nozzles with design Mach numbers of 1.5 and 1.56. The effective penetration of the chevrons is found to be a function of the jet Mach number. Increasing jet Mach number increases effective penetration of the chevrons and increases the magnitude of all chevron effects. Chevrons on supersonic jets are found to reduce shock cell length, increase mixing and spreading, decrease turbulent kinetic energy at the end of the potential core and increase it near the nozzle. Chevrons corrugate the shear layer but not the shock structures inside the jet which remain axisymmetric. Chevrons thicken the shear layer, reducing the sonic diameter and reducing the diameter of the shock cells. By reducing their diameter they also reduce the shock cell spacing. Chevrons reduce low-frequency mixing noise near the end of the potential core, increase high-frequency noise near the nozzle exit. They eliminate screech and reduce broad-band shock-associated noise and shift it to higher frequencies. Fluidic injection is applied to the nozzle with design Mach number of 1.5. Fluidic injection corrugates the shear layer, increases mixing and spreading, reduces low frequency mixing noise, increases high frequency noise, reduces broad-band shock-associated noise and shifts its peak to higher frequency.
Mar
13
Modeling and analysis of process complexity and performance in mixed model assembly systems
Increasing global competition demands that the manufacturing industry move from mass production into mass customization production in order to provide more varieties of products and thus satisfy customer demands. It has been shown that the increase of product variety has a negative impact on manufacturing system performance. Therefore, it is essential to understand how product variety complicates an assembly system, affecting its operation performance. Such knowledge, once validated, can be further used to improve manufacturing system design and operation. The objective of this dissertation is to develop an enhanced general methodology for modeling and analyzing process complexity for mixed model assembly systems. The following fundamental research has been conducted: 1) A set of complexity metrics are proposed for measuring the complexity of various elements in a manufacturing system. These metrics are proposed by constructing a linkage with the communication system framework. Unlike the existing complexity measures defined in the literature, this research is the first effort to include production quality into the measurement of how well a manufacturing system can handle the process complexity induced by the input demand variety. 2) A systematic method is developed for efficiently and explicitly representing complex hybrid assembly system configurations by the use of algebraic expressions, which can overcome drawbacks of two widely used representation methods: block diagrams and adjacency matrices. By further extending the algebraic configuration operators, the algebraic performance operators are defined for the first time for the systematic evaluation of system performance metrics； these metrics include quality conforming rates for individual product types at each station, process capability for handling complexity, and production cycle time for various product types. Therefore, when compared to other methods, the proposed algebraic expression modeling method also has a unique merit in providing computational capability for automatically evaluating various system performance metrics. 3) An integrated model is introduced for the first time to describe the effect of operators factors on the process operation performance. The model includes intrinsic factors such as the operators thinking time and experience； and extrinsic factors such as the choice task complexity induced by the product variety in mixed model assembly systems.
Mar
13
Low temperature constrained sintering of cerium gadolinium oxide films for solid oxide fuel cell applications
Cerium gadolinium oxide CGO) has been identified as an acceptable solid oxide fuel cell SOFC) electrolyte at temperatures 500-700°；C) where cheap, rigid, stainless steel interconnect substrates can be used. Unfortunately, both the high sintering temperature of pure CGO, ＞1200°；C, and the fact that constraint during sintering often results in cracked, low density ceramic films, have complicated development of metal supported CGO SOFCs. The aim of this work was to find new sintering aids for Ce0.9Gd 0.1O1.95, and to evaluate whether they could be used to produce dense, constrained Ce0.9Gd0.1O1.95 films at temperatures below 1000°；C. To find the optimal sintering aid, Ce 0.9Gd0.1O1.95 was doped with a variety of elements, of which lithium was found to be the most effective. Dilatometric studies indicated that by doping CGO with 3mol% lithium nitrate, it was possible to sinter pellets to a relative density of 98.5% at 800°；C—a full one hundred degrees below the previous low temperature sintering record for CGO. Further, it was also found that a sintering aids effectiveness could be explained in terms of its size, charge and high temperature mobility. A closer examination of lithium doped Ce0.9Gd0.1O 1.95 indicated that lithium affects sintering by producing a Li 2O-Gd2O3-CeO2 liquid at the CGO grain boundaries. Due to this liquid phase sintering, it was possible to produce dense, crack-free constrained films of CGO at the record low temperature of 950°；C using cheap, colloidal spray deposition processes. This is the first time dense constrained CGO films have been produced below 1000°；C and could help commercialise metal supported ceria based solid oxide fuel cells.
Mar
13
Strategic targeting of outliers for expert review
In the era of massive data sets, it is difficult for domain scientists to interact directly with their own data. Because the analysis of single examples may yield insights in the research process, it is important to use automated methods to highlight potentially interesting phenomena when hand inspection is not possible. This dissertation examines a particular sub-case of this problem: the use of machine learning to direct an experts attention to potentially informative outliers. Outliers warrant study in both a positive and negative sense. In the positive sense, outliers might be indicative of new scientific phenomena, whose study may pave the road to scientific discovery. In the negative sense, outliers might be worthy of elimination or alteration, in order to move forward with the original research objectives. This dissertation explores two novel manifestations of the anomaly detection problem that are motivated by domain scientists need to mine their data sets for single outlying examples. The first is the unsupervised detection of anomalies in large sets of unsynchronized time series data for the purpose of aiding scientific discovery. This work is applied to astrophysics time series data. The second is the detection of label noise in training data in order to improve the supervised learning process. This work is applied to problems in remote sensing, medical text mining, and volcanology. This thesis makes four contributions. First, we introduce a method called PCAD, for the discovery of local and global outliers on large sets of unsynchronized time series data. Second, we perform a comprehensive review of methods for the detection of label noise in training data, and introduce a new method called PWEM. Third, we introduce an interactive framework, called ICCN, that cleans training sets of label noise with help from a domain expert. Finally, we introduce a semi-supervised learning method, called collaborative learning, that synthesizes ideas from our research on label noise detection and uses them to minimize label noise during training data generation.