The permanent magnet synchronous machines have been attracting more and more attention due to the advantages of high torque density, outstanding efficiency and maturing technologies. Under the urges of mandatory energy efficiency requirements, they are considered as the most potential candidates to replace the comparatively low-efficient induction machines which dominate the industrial market. However, most of the high performance permanent magnet machines are based on high cost rare-earth materials. Thus, there will be huge demands for low-cost high-performance permanent magnet machines. Ferrite magnet is inexpensive and abundant in supply, and is considered as the most promising alternative to achieve the goal of low cost and high performance. In consideration of the low magnetic energy, this thesis explored the recent developments and possible ideas of ferrite machines, and proposed a novel multi-layer spoke-type interior permanent magnet configuration combining the advantages of flux focusing technique and multi-layer structure. With comparable material cost to induction machines, the proposed ferrite magnet design could deliver 27% higher power with 2-4% higher efficiency with exactly the same frame size. Based on the data base of International Energy Agency (IEA), electricity consumed by electric machines reached 7.1PWh in 2006 [1]. Considering that induction machines take up 90% of the overall industrial installation, the potential energy savings is enormous. This thesis contributes in five key aspects towards the investigation and design of low-cost high-performance ferrite permanent magnet machines. Firstly, accurate analytical models for the multi-layer configurations were developed with the consideration of spatial harmonics, and provided effective yet simple way for preliminary design. Secondly, the influence of key design parameters on performance of the multi-layer ferrite machines were comprehensively investigated, and optimal design could be carried out based on the insightful knowledge revealed. Thirdly, systematic investigation of the demagnetization mechanism was carried out, focusing on the three key factors: armature MMF, intrinsic coercivity and working temperature. Anti-demagnetization designs were presented accordingly to reduce the risk of performance degradation and guarantee the safe operation under various loading conditions. Then, comparative study was carried out with a commercial induction machine for verification of the superior performance of the proposed ferrite machine. Without loss of generality, the two machines had identical stator cores, same rotor diameter and stacking length. Under the operating condition of same stator copper loss, the results confirmed the superior performance of the ferrite machine in terms of torque density, power factor and efficiency. Lastly, mechanical design was discussed to reduce the cost of mass production, and the experimental effort on the prototype machine validates the advantageous performance as well as the analytical and FEA predictions.

Les travaux présentés dans cette thèse se focalisent sur des machines électriques fonctionnant sur le principe de la commutation du flux. Nous étudions des topologies excitées par des aimants permanents, des bobinages DC ou encore hybride (structure à double excitation). Dans une première partie, nous répondrons de manière directe à une problématique industrielle visant à réaliser une application « Alternateur DC » à faible coût. Une modélisation numérique de topologies à double excitation innovantes est tout d’abord proposée. Le modèle est ensuite couplé à un algorithme génétique afin de tendre vers un dimensionnement optimal de ces structures. La seconde partie de ce manuscrit est dédiée à la modélisation analytique de structures excitées par des aimants. Des modèles analytiques du champ d’entrefer suivant différentes approches sont proposés - soit par la théorie des fonctions de perméance, soit par la résolution formelle des équations de Maxwell. Par la suite, un modèle analytique du champ dans les parties ferromagnétiques est proposé. Il permet de déterminer le champ avec précision en tenant compte du caractère bidirectionnel des loci d’induction dans les culasses de ces structures. Ce modèle permet à posteriori d’évaluer les pertes fer dans ces structures. Nous proposons finalement une étude des performances optimales de ces structures en couplant le modèle avec un algorithme stochastique d’optimisation. L’influence du nombre de dents rotoriques ou encore des pertes fer sur les performances électromagnétiques sont mises en évidence. Finalement, la troisième et dernière partie de ce manuscrit détaille une approche originale d’exploration topologique. Après avoir présenté une extension du modèle analytique formel aux structures aimantées, nous exposons l’approche d’exploration topologique pour des structures à excitation statique avec des aimants permanents. / The work presented in this thesis focus on electrical machines based on flux-switching principle. We were studying topologies with permanent magnets, DC field coils or hybrid-excited (combining both PMs and DC coils) structures. In the first part of this manuscript, we are meeting industrial needs being set by our partner Leroy Somer. The aim is to design in an optimal way a low cost “DC Generator”. Numerical simulations of unconventional hybrid-excited structures are firstly proposed. Then, to carry out a global optimization of those topologies, the numerical model is coupled with a genetic algorithm. The second part of this work is dedicated to an analytical model to predict the airgap field in conventional and unconventional switched-flux machines with DC coils. Two approaches are proposed, either using the Magnetomotive force- Permeance theory or directly solving the field governing equations in the doubly-slotted airgap of those structures. After, an analytical model to determine the magnetic field in ferromagnetic parts is proposed. This model can account for bidirectional field in stator and rotor yokes. This model can be used a popsteriori to assess iron losses in the core. Finally, influences of the number of rotor teeth, or iron losses, on optimal electromagnetic performances are investigated using a stochastic algorithm. In the third and last part of this thesis, we detailed an original approach named topological exploration. We first derivate an analytical model capable to predict the airgap field in PM excited structure. Then, the topological exploration approach was applied to static PM excited machines.

<p>In both the chemical and mechanical pulping process, the logs are cut into wood chips by a disc chipper before fibre separation. To make the wood chipping process more efficient, one have to investigate in detail the coupling between theprocess parameters and the quality of the chips. The objective of this thesis is to obtain an understanding of the fundamental mechanisms behind the creation of wood chips. Both experimental and analytical/numerical approaches have been taken inthis work. The experimental investigations were performed with an in‐house developed equipment and a digital speckle photography equipment. The results from the experimental investigation showed that the friction between the log and chipping tool is probably one crucal factor for the chip formation. Further more it was found that the indentation process is approximately self‐similar, and that the stress field over the entire crack‐plane is critical for chip creation. The developed analytical model predicts the normal and shear strain distribution. The analytical distributions are in reasonable agreement with the corresponding distributions obtained from a finite element analysis.</p>

In both the chemical and mechanical pulping process, the logs are cut into wood chips by a disc chipper before fibre separation. To make the wood chipping process more efficient, one have to investigate in detail the coupling between theprocess parameters and the quality of the chips. The objective of this thesis is to obtain an understanding of the fundamental mechanisms behind the creation of wood chips. Both experimental and analytical/numerical approaches have been taken inthis work. The experimental investigations were performed with an in‐house developed equipment and a digital speckle photography equipment. The results from the experimental investigation showed that the friction between the log and chipping tool is probably one crucal factor for the chip formation. Further more it was found that the indentation process is approximately self‐similar, and that the stress field over the entire crack‐plane is critical for chip creation. The developed analytical model predicts the normal and shear strain distribution. The analytical distributions are in reasonable agreement with the corresponding distributions obtained from a finite element analysis.

The objective of the proposed research is to develop an analytical model that predicts performance and power for many-core architecture and further propose a mechanism, which leverages the analytical model, to enable energy-efficient execution of an application. The key insight of the model is to investigate and quantify a complex relationship that exists between the thread-level parallelism and memory-level parallelism for an application on a given many-core architecture. Two metrics are proposed: memory warp parallelism (MWP), which refers to the number of overlapping memory accesses per core, and computation warp parallelism (CWP), which characterizes an application type. By using these metrics in addition to the architectural and application parameters, the overall application performance is produced. The model uses statically-available parameters such as instruction-mixture information and input-data size, and the prediction accuracy is 13.3% for the GPU-computing benchmarks. Another important aspect of using many-core architecture is reducing peak power and achieving energy savings. By using the proposed integrated power and performance (IPP) framework, the results showed that different optimization points exist for GPU architecture depending on the application type. The work shows that by activating fewer cores, 10.99% of run-time energy consumption can be saved for the bandwidth-limited benchmarks, and a projection of 25.8% energy savings is predicted when power-gating at core level is employed. Finally, the model is shifted to throughput using OpenCL for targeting more variety of processors. First, multiple outputs relating to performance are predicted, including upper-bound and lower-bound values. Second, by using the model parameters, an application can be categorized into a different category, each with its own suggestions for improving performance and energy efficiency. Third, the bandwidth saturation point accuracy is significantly improved by considering independent memory accesses and updating the performance model. Furthermore, a trade-off analysis using architectural and application parameters is straightforward, which provides more insights to improve energy efficiency. In the future, a computer system will contain hundreds of heterogeneous cores. Hence, it is mandatory that a workload gets scheduled to an efficient core or distributed on both types of cores. A preliminary work by using the analytical model to do scheduling between CPU and GPU is demonstrated in the appendix. Since profiling phase is not required, the kernel code can be transformed to run more efficiently on the specific architecture. Another extension of the work regarding the relationship between the speed-up and energy efficiency is mathematically derived. Finally, future research ideas are presented regarding the usage of the model for programmer, compiler, and runtime for future heterogeneous systems.

This thesis amends some existing theoretical gaps and an overall lack of empirical studies regarding the ways R&amp;D managers can use Open Innovation during the management of the radical innovation processes’ early development phase.Using existing theories, an interview guide and an analytical model was created. These were later used during the gathering and analysis of empirical data. Our sampling involves three of Sweden’s largest companies, representing three distinct industry fields. Interviews took place during April 2010, and all the interviewees were R&amp;D managers with previous experience with Open Innovation and radical innovation.The results reveal that the managers do use Open Innovation when managing radical innovation, and point to both benefits and issues brought about by using Open Innovation during this process. The use of Open Innovation during the management of radical innovation can be divided into two main aspects; the actual extent to which it is used, and the ways the managers use it. Our results reveal that the extent varies from an early peak, an in between Open Innovation chasm and a final increase. Furthermore, our studies also show that the main ways the managers use OI are; exploitation and creation of revenue streams, knowledge leveraging and integration, and finally to create superior products using broad knowledge networks.

A generalized ejector model was successfully developed for gas ejector design and performance analysis. Previous 1-D analytical models can be derived from this new comprehensive model as particular cases. For the first time, this model shows the relationship between the cosntant-pressure and constant-area 1-D ejector models. The new model extends existing models and provides a high level of confidence in the understanding of ejector mechanics. “Off-design” operating conditions, such as the shock occurring in the primary stream, are included in the generalized ejector model. Additionally, this model has been applied to two-phase systems including the gas-liquid ejector designed for a Proton Exchange Membrane (PEM) fuel cell system. The equations of the constant-pressure and constant-area models were verified. A parametric study was performed on these widely adopted 1-D analytical ejector models. FLUENT, commercially available Computational Fluid Dynamics (CFD) software, was used to model gas ejectors. To validate the CFD simulation, the numerical predictions were compared to test data and good agreement was found between them. Based on this benchmark, FLUENT was applied to design ejectors with optimal geometry configurations.

It is an internationally acknowledged that marine protected area (MPA) is an important measure for maintaining biodiversity and rescuing endangered species. MPA can also effectively inhibit human interferences such as development and pollution discharge. The establishment of MPA is possible to fulfill the goal of sustainable management, which is to conserve marine habitat for an integrative ecosystem and a higher biodiversity. However, how to design an effective MPA remains an important research issue to be explored. In order to grasp the spatial distribution of the ecological data in the study area, the current research uses spatial interpolation tool, Kriging, provided by the Geographic information system (GIS) software. Then three spatial analytical models have been developed based on integer programming techniques. It is guarantee that all three models can find the global optimal solutions for the best protective area partitions. This quantitative approach is more efficient and effective compared to the qualitative methods in many aspects. The models are able to preserve the maximum ecological resources under the limited spatial area. Besides, the model formulation can be adjusted from different environmental impact factors to fulfill the requirements of users. The case study of the research is to design a MPA for Kaomei wetland. However the spatial analytical models developed in this research can also be applied to protected area design in land area.

Capacitive Micromachined Ultrasonic Transducers (CMUTs) have demonstrated significant potential to advance the state of medical ultrasound imaging beyond the capabilities of the currently employed piezoelectric technology. Because they rely on well-established micro-fabrication techniques, they can achieve complex geometries, densely populated arrays, and tight integration with electronics, all of which are required for advanced intravascular ultrasound (IVUS) applications such as high-frequency or forward-looking catheters. Moreover, they also offer higher bandwidth than their piezoelectric counterparts. Before CMUTs can be effectively used, they must be fully characterized and optimized through experimentation and modeling. Unfortunately, immersed transducer arrays are inherently difficult to simulate due to a phenomenon known as acoustic crosstalk, which refers to the fact that every membrane in an array affects the dynamic behavior of every other membrane in an array as their respective pressure fields interact with one another. In essence, it implies that modeling a single CMUT membrane is not sufficient; the entire array must be modeled for complete accuracy. Finite element models (FEMs) are the most accurate technique for simulating CMUT behavior, but they can become extremely large considering that most CMUT arrays contain hundreds of membranes. This thesis focuses on the development and application of a more efficient model for transducer arrays first introduced by Meynier et al. [1], which provides accuracy comparable to FEM, but with greatly decreased computation time. It models the stiffness of each membrane using a finite difference approximation of thin plate equations. This stiffness is incorporated into a force balance which accounts for effects from the electrostatic actuation, pressure forces from the fluid environment, mass and damping from the membrane, etc. For fluid coupling effects, a Boundary Element Matrix (BEM) is employed that is based on the Green's function for a baffled point source in a semi-infinite fluid. The BEM utilizes the nodal mesh created for the finite difference method, and relates the dynamic displacement of each node to the pressure at every node in the array. Use of the thin plate equations and the BEM implies that the entire CMUT array can be reduced to a 2D nodal mesh, allowing for a drastic improvement in computation time compared with FEM. After the model was developed, it was then validated through comparison with FEM. From these tests, it demonstrated a capability to accurately predict collapse voltage, center frequency, bandwidth, and pressure magnitudes to within 5% difference of FEM simulations. Further validation with experimental results revealed a close correlation with predicted impedance/admittance plots, radiation patterns, frequency responses, and noise current spectrums. More specifically, it accurately predicted how acoustic crosstalk would create sharp peaks and notches in the frequency responses, and enhance side lobes and nulls in the angular radiation pattern. Preliminary design studies with the model were also performed. They revealed that membranes with larger lateral dimensions effectively increased the bandwidth of isolated membranes. They also demonstrated potential for various crosstalk reduction techniques in array design such as disrupting array periodicity, optimizing inter-membrane pitch, and adjusting the number of membranes per element. It is expected that the model developed in this thesis will serve as a useful tool for future iterations of CMUT array optimizations.

An analytical model is presented for the analysis of pulse interference tests conducted in a fractured porous medium with connection to a free surface boundary at the water table. The solution is applicable to open borehole pulse interference tests due to the accommodation of multiple horizontal fractures intersecting each wellbore and a connection from the uppermost horizontal fracture to a free surface boundary. The solution is derived using the Laplace transform method and evaluation of the solution is performed by numerical inversion using the Talbot algorithm. Based on an informal sensitivity analysis, unique values for transmissivity, storativity, specific storage, vertical hydraulic conductivity and specific yield are predicted over a range of realistic values for these parameters. The analytical model is used to analyze slug tests and pulse interference tests conducted in a fractured gneiss formation. The results of these tests are compared to long-term pumping tests to identify the effect of measurement scale on transmissivity, storativity, vertical hydraulic conductivity and specific yield obtained in a fractured rock setting. Scale artefacts relating to measurement or analysis methods are minimized through the use of consistent well configurations in each of the applied hydraulic testing methods. The geometric mean estimates of transmissivity and storativity are shown to vary by less than an order of magnitude from local-scale tests to long-term pumping tests. The geometric mean specific yield result from a series of pulse interference tests that samples both highly fractured and poorly fractured portions of the rock formation approximates the long-term pumping test estimate of specific yield. The geometric mean result for vertical hydraulic conductivity decreases by approximately 1.5 orders of magnitude from the slug test to pumping test scale; however, pulse interference tests conducted on highly fractured portions of the formation produce vertical hydraulic conductivity estimates that are within a half order of magnitude of the long-term pumping test results. This suggests that the performance of pulse interference tests on a highly fractured portion of a rock formation may be a less time-intensive alternative to large-scale pumping tests in the determination of vertical hydraulic conductivity. / Thesis (Master, Civil Engineering) -- Queen's University, 2011-06-24 19:29:52.743