Master of Science

thesisClay mineral particles such as kaolinite (<2 microns in size), can cause significant problems in flotation processes and tailings disposal, including the processing of Florida phosphate rock and Canadian oil sands. In this thesis research, the sedimentation and consolidation of flocculated kaolinite suspensions are examined. High resolution X-ray Microtomography is used to describe the structure of the consolidated sediment. With this tomographic information, the complex geometry of the pore network structure for the consolidated flocs was established for the first time. With the experimental pore network structure, permeabilities were estimated by Lattice Boltzmann Simulation. Results for kaolinite sediment with and without polymer were compared and discussed as well as the effect of centrifugal forces. Results for flocculated kaolinite sedimentation/consolidation in a gravitational field are presented and discussed; the results show that as the polymer dosage increases the permeability of the flocculated kaolinite sediment increases, and as the suspension pH increases, the permeability of the flocculated kaolinite sediment decreases. Results for flocculated kaolinite sedimentation/consolidation in a centrifugal field are presented and discussed as well; the results reveal that when the centrifugation time increases, the permeability of the flocculated kaolinite decreases. Finally, as expected when the centrifugal forces increase, the permeability of the flocculated kaolinite sediment decreases

Consolidation and permeability of flocculated kaolinite sediment

posterVast oil sand resources are located in the province of Alberta, Canada, where water-based oil sands extraction operations are found including extraction and separation of the bitumen from the clay, sand, and water. The production of each barrel of synthetic crude oil (SCO) requires 2 m3 of processed water and generates 1.8 tonnes of solid tailings[1]. While coarse solids (sands) settle quickly to form beaches along the tailings pond, the fines (mainly silts and clays) take a much longer time to settle. Kaolinite is a major clay mineral found in oil sand tailings and organic polymers have been used to flocculate kaolinite to enhance the dewatering rate and sediment compaction

Output Feedback Control and Optimal Bandwidth Allocation of Networked Control Systems

A networked control system (NCS) is a control system where sensors, actuators, and controllers are interconnected over a communication network. This dissertation presents a framework for modeling, stability analysis, optimal control, and bandwidth allocation of the NCS. A ball magnetic-levitation (maglev) system, four DC motor speed-control systems, and a wireless autonomous robotic wheelchair are employed as test beds to illustrate and verify the theoretical results of this dissertation. This dissertation first proposes an output feedback method to stabilize and control the NCSs. The random time delays in the controller-to-actuator and sensor-to-controller links are modeled with two time-homogeneous Markov chains while the packet losses are treated with Dirac delta functions. An asymptotic mean-square stability criterion is established to compensate for the network-induced random time delays and packet losses in the NCS. Then, an algorithm to implement the asymptotic mean-square stability criterion is presented. Experimental results illustrate effectiveness of the proposed output feedback method compared to conventional controllers. The proposed output feedback controller could reduce the errors of the NCS by 13% and 30–40% for the cases without and with data packet losses, respectively. The optimal bandwidth allocation and scheduling of the NCS with nonlinear-programming techniques is also presented in the dissertation. The bandwidth utilization (BU) of each client is defined in terms of its sampling frequency. Two nonlinear approximations, exponential and quadratic approximations, are formulated to describe the system performance governed by discrete-time integral absolute error (DIAE) versus sampling frequency. The optimal sampling frequencies are obtained by solving the approximations with Karush-Kuhn-Tucker (KKT) conditions. Simulation and experimental results are given to verify the effectiveness of the proposed approximations and the bandwidth allocation and scheduling algorithms. In simulations and experiments, the two approximations could maximize the total BU of the NCS up to about 98% of the total available network bandwidth

Performance Enhancement of Multipath TCP for Wireless Communications with Multiple Radio Interfaces

ArticleMultipath TCP (MPTCP) allows a TCP connection to operate across multiple paths simultaneously and becomes highly attractive to support the emerging mobile devices with various radio interfaces and to improve resource utilization as well as connection robustness. The existing multipath congestion control algorithms, however, are mainly loss-based and prefer the paths with lower drop rates, leading to severe performance degradation in wireless communication systems where random packet losses occur frequently. To address this challenge, this paper proposes a new mVeno algorithm, which makes full use of the congestion information of all the subflows belonging to a TCP connection in order to adaptively adjust the transmission rate of each subflow. Specifically, mVeno modifies the additive increase phase of Veno so as to effectively couple all subflows by dynamically varying the congestion window increment based on the receiving ACKs. The weighted parameter of each subflow for tuning the congestio