Small cells are low-powered radio access nodes that operate in licensed and unlicensed spectrum that have a range of 10 meters to 200 meters, compared to a mobile macrocell which might have a range of a few kilometres. This dissertation proposes algorithms for the enhancement of small cells installed in high speed rails. The thesis addresses two main points: the link between the small cell and the base station, and the link between the end-users and the small cell. The channel between the small cell and the base station is a fast fading channel due to the mobility of the high speed rail. The first part of the thesis proposes methods to enhance the link between the small cell and the base station using Low-Density Parity-Check codes (LDPC) for fast fading channels. The proposed uses nonuniform reconstruction methods based on the soft output log-likelihood ratio (LLR) provided by the LDPC decoder. The LLRs provide information about the location of the symbols with high probability of being correct. The grid formed under the assumption of a correlated Rayleigh channel affecting the transmitted data is highly nonuniform. Reconstruction of the channel under such assumptions is highly unstable. A signal-to-noise- ratio dependent regularization method is implemented to enhance the performance under imperfect Doppler spread estimation. The second part of the thesis proposes algorithms for the link between the end-user and the small cell. Since power efficiency is a major factor for end-users employing battery powered devices, we propose a Linear Programming (LP) algorithm for signal shaping to minimize the average transmitted power. The other problem the thesis addresses is the minimization of Peak-to-Average Power-Ratio (PAPR) of Orthogonal Frequency Division Multiplexing (OFDM) signals. The PAPR is minimized using a set of phase shifts for the constituting subcarriers of the OFDM signal. The set of phase shifts is determined using a LP approach that minimizes the complexity when the block length is high. A real-time implementation of some of the algorithms is carried out using the TMS320C6713 Texas Instruments board. The results for fixed-point versus floating-point implementation is shown for a different number of precision bits. / Thesis (Ph.D, Electrical & Computer Engineering) -- Queen's University, 2013-04-27 16:54:32.464

A special work evolution was performed at Los Alamos National Laboratory (LANL) with a particular 73As/74As source but the worker’s extremity dosimeter did not appear to provide appropriate dosimetric information for the tasks performed. This prompted a reconstruction of the dose to the worker’s hands. The computer code MCNP was chosen to model the tasks that the worker performed to evaluate the potential nonuniform hand dose distribution. A model was constructed similar to the worker’s hands to represent the performed handling tasks. The model included the thumb, index finger, middle finger, and the palm. The dose was calculated at the 7 mg cm-2 skin depth. To comply with the Code of Federal Regulations, 10 CFR 835, the 100 cm2 area that received the highest dose must be calculated. It could be determined if the dose received by the worker exceeded any regulatory limit. The computer code VARSKIN was also used to provide results to compare with those from MCNP where applicable. The results from the MCNP calculations showed that the dose to the worker’s hands did not exceed the regulatory limit of 0.5 Sv (50 rem). The equivalent nonuniform dose was 0.126 Sv (12.6 rem) to the right hand and 0.082 Sv (8.2 rem) to the left hand.

Hemodialysis is a renal replacement therapy that removes waste solutes from the blood stream using concentration gradients across a membrane. In order to overcome several shortcomings and increase the waste removal rate, a new dialyzer (filter) design is proposed in this study. In the new dialyzer design, the blood concurrently flows with a sheath fluid in a micro-fluidic channel. Because the blood stream directly contacts the sheath stream, it is important to prevent blood cell migration from the blood stream to the sheath stream while providing enough time for the waste solutes to diffuse into the sheath stream. This research was intended to understand the migration behavior of red blood cells (RBC) and platelets in non-uniform suspension flow, where the blood and sheath flows in direct contact, and apply the results to identify the feasible design space of the proposed dialyzer. The effect of different flow conditions and channel geometry on the blood cell extraction ratios (ER), the ratio of cells lost into the sheath stream, in non-uniform suspension flows was parametrically studied using Lattice Boltzmann and Spectrin Link (LB-SL) method based direct numerical simulation (DNS). Analyzing ER over the flow distance showed that the channel size and the area ratio of sheath to channel are the main variables that affect the ER. Based on the relationship found, a meta-model of RBC ER was created, although platelet ERs showed only a general trend. Based on the study, feasible conditions that will retain blood cells in the blood stream were identified. Then, the DNS results of blood cell ER were used with a molecule diffusion model and a hemodialysis system model to study the feasibility of the proposed dialyzer design that maximizes middle molecule filtration with limited blood cell and protein loss. No feasible design was found in the studied range suggesting that relying purely on the diffusion based on the direct contact for the removal of middle molecules is not a feasible solution with the small channel size (~700 µm) due to the loss of protein. It suggested that in order to increase the middle molecule removal while maintain the protein level, clearance ratio of middle molecule to protein should be increased using large channel size, small sheath stream thickness, long tubule length, and slow blood flow velocity. The intellectual merit of this research lies in understanding the migration behavior of blood cells in a non-uniform suspension. This knowledge helped to establish the feasibility of the proposed dialyzer design and can be applied in a variety of applications for the manipulation of cells in a micro-fluidic channel.

In this thesis, the problem of overvoltage calculation on multiconductor transmission lines due to nonuniform external electromagnetic field excitations, such as lightning, is investigated by introducing a field-voltage macromodel. The main purpose of this thesis is to find a fast and efficient algorithm to model the effect of the radiated electromagnetic fields on transmission lines. This is done by replacing distributed voltage and current sources along the transmission line which are as a result of external electromagnetic field radiation, by voltage and current sources at the terminals of the transmission line. For this purpose, the knowledge of electromagnetic field at every point on the transmission line is required. A transfer function based pole-residue tracing technique will be introduced in this thesis. By using the proposed algorithm, a closed form solution for the lumped sources at the terminals of transmission line in the frequency domain is obtainable. This approach will enable us to bridge the software working in frequency domain with those working in the time domain. The effect of different parameters on calculated overvoltage such as finite conductivity of the ground and lightning return stroke channel (RSC) specifications are studied. The theoretical background and extent of validity of the proposed algorithm are reviewed in this thesis.

In this thesis, the problem of overvoltage calculation on multiconductor transmission lines due to nonuniform external electromagnetic field excitations, such as lightning, is investigated by introducing a field-voltage macromodel. The main purpose of this thesis is to find a fast and efficient algorithm to model the effect of the radiated electromagnetic fields on transmission lines. This is done by replacing distributed voltage and current sources along the transmission line which are as a result of external electromagnetic field radiation, by voltage and current sources at the terminals of the transmission line. For this purpose, the knowledge of electromagnetic field at every point on the transmission line is required. A transfer function based pole-residue tracing technique will be introduced in this thesis. By using the proposed algorithm, a closed form solution for the lumped sources at the terminals of transmission line in the frequency domain is obtainable. This approach will enable us to bridge the software working in frequency domain with those working in the time domain. The effect of different parameters on calculated overvoltage such as finite conductivity of the ground and lightning return stroke channel (RSC) specifications are studied. The theoretical background and extent of validity of the proposed algorithm are reviewed in this thesis.

The finite-difference time-domain (FDTD) method has been widely and effectively used for analysis in many kinds of electromagnetic problems. Generally, the computational space can be divided into many lattices with rectangular; and the length on each of these meshs is equivalent in unitary aspect. In some of those problems, a greatly improved accuracy of the solution can be obtained if a finer discretization is used in specific regions of the computational space. There are limitations of the present form of uniform FDTD. It must increase the computational cost (memory and CPU time). Concerning the impression, we are trying to find more efficient ways of utilizing nonuniform grids. Coarser mesh for uncomplicated structure and finer mesh for complicated structure in nonuniform grids. However, this way can use in part of cutting area only. There are two edges connects the truncation of computational space. A similar scheme has been used with nonuniform FDTD method by a modification to the mesh scheme. The subcell method is a very general approach, capable of analyzing arbitrarily-shaped structures. In local area the mesh change from rectangular to irregular. Subgridding method is dissimilar to the both methods. Furthermore, the anisotropic PML to decrease the electromagnetic wave from nonuniform mesh of the computational space. It have replaced Mur¡¦s first-order absorbing boundary conditions and Berenger¡¦s PML for improving computationally efficient. Finally, compare them with the anisotropic PML in the essay.

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This dissertation deals with some computational and analytic challenges for dynamic process operations using first-principles models. For processes with significant spatial variations, spatially distributed first-principles models can provide accurate physical descriptions, which are crucial for offline dynamic simulation and optimization. However, the large amount of time required to solve these detailed models limits their use for online applications such as nonlinear model predictive control (NMPC). To cope with the computational challenge, we develop computationally efficient and accurate dynamic reduced order models which are tractable for NMPC using temporal and spatial model reduction techniques. Then we introduce an input and state blocking strategy for NMPC to further enhance computational efficiency. To improve the overall economic performance of process systems, one promising solution is to use economic NMPC which directly optimizes the economic performance based on first-principles dynamic models. However, complex process models bring challenges for the analysis and design of stable economic NMPC controllers. To solve this issue, we develop a simple and less conservative regularization strategy with focuses on a reduced set of states to design stable economic NMPC controllers. In this thesis, we study the operation problems of a solid sorbent-based CO2 capture system with bubbling fluidized bed (BFB) reactors as key components, which are described by a large-scale nonlinear system of partial-differential algebraic equations. By integrating dynamic reduced models and blocking strategy, the computational cost of NMPC can be reduced by an order of magnitude, with almost no compromise in control performance. In addition, a sensitivity based fast NMPC algorithm is utilized to enable the online control of the BFB reactor. For economic NMPC study, compared with full space regularization, the reduced regularization strategy is simpler to implement and lead to less conservative regularization weights. We analyze the stability properties of the reduced regularization strategy and demonstrate its performance in the economic NMPC case study for the CO2 capture system.

Reverse-flow combustors have been used in heavy land-based gas turbines for many decades. A sheath is typically installed to provide cooling at an expense of large pressure losses, through small jet impingement cooling and strong forced convention channel flow. With the modern advancement in metallurgy and thermal-barrier coating technologies, it may become possible to remove this sheath to recover the pressure losses without melting the combustor chamber. However, without the sheath, the flow inside the dump diffuser may exert nonuniform cooling on the combustion chamber. Therefore, the objective of this project is to investigate the flow pattern, pressure drop, and heat transfer in the dump-diffuser reverse-flow combustor with and without sheath to determine if the sheath could be removed. The investigation was conducted through both experimental and computational simulation. The results show that 3.3% pressure losses could be recovered and the highest wall temperature will increase 18% without the sheath.