<p> General theory of nuclear reactor kinetics is discussed, with emphasis on CANDU* reactors. The numerical solution of the group diffusion equations using the IQS+ method is presented. Several important numerical parameters are studied with reference to a one-dimensional slab reactor undergoing a LOC° accident. These parameters are: number of mesh points in the region of solution, frequency of shape calculations, and convergence criteria. * Canada - Deuterium - Uranium + Improved Quasi-Static o Loss of Coolant / Thesis / Master of Engineering (MEngr)

<p> In this report, the theory for the Improved Quasistatic (IQS) method of solving the three-dimensional, two-neutron-energy group, time-dependent neutron diffusion equations is developed, and approximations appropriate to the CANDU-PHW reactor system are introduced. The theory is extended to a numerical formulation of the problem. The TM-2 computer program (written in FORTRAN 5), which employs the IQS method to numerically solve a two-dimensional form of the diffusion equations (with a correction to account for axial leakage), is outlined. Input and output descriptions for the TM-2 code are provided.</p> / Thesis / Master of Engineering (MEngr)

We consider the flow of nonlinear Maxwell fluids in the unsteady quasistatic case, where the effect of inertia is neglected. We study the well-posedness of the resulting PDE initial-boundary value problem. This well-posedness depends on the unique solvability of an elliptic boundary value problem. We first present results for the 3D case, locally and globally in time, with sufficiently small initial data, and for a simple shear flow problem, locally in time with arbitrary initial data; after that we extend our results to some 3D flow problems, locally in time, with large initial data. Additionally, we present results for models of White-Metzner type in 3D flow, locally and globally in time, with sufficiently small initial data. We solve our problem using an iteration between elliptic and hyperbolic linear subproblems. The limit of the iteration provides the solution of our original problem. / Ph. D.

This thesis is devoted to the theoretical study of slow thermodynamic processes in non-equilibrium stochastic systems. Its main result is a physically and mathematically consistent construction of relevant thermodynamic quantities in the quasistatic limit for a large class of non-equilibrium models. As an application of general methods a natural non-equilibrium generalization of heat capacity is introduced and its properties are analyzed in detail, including an anomalous far-from-equilibrium behavior. The developed methods are further applied to the related problem of time-scale separation where they enable to describe the effective dynamics of both slow and fast degrees of freedom in a more precise way. Powered by TCPDF (www.tcpdf.org)

Frontal Protection Systems (FPS) have become a popular accessory for passenger vehicles. They are used to protect the front of a vehicle during minor impacts, and to attenuate the impact energy during major impacts. With the increased safety of modern passenger vehicles, the fitment of a FPS to a vehicle requires careful consideration to the design and installation of the FPS as they may modify vehicle crush characteristics. This is particularly important in vehicles fitted with air bags. These community and industry concerns triggered the research discussed in this thesis, which is the first comprehensive project undertaken in this particular area. This project generated comprehensive research knowledge on the impact response and energy absorption of FPS in order to evaluate performance. This involved a range of experimental testing supplemented by finite element analysis. Experimental testing was conducted using quasi-static and dynamic techniques to assess the overall performance of current FPS available. Finite element models were then generated and analysed using both implicit and explicit techniques, and calibrated against the experimental testing results. These models were used throughout the project to assess the FPS response, in particular the energy absorbed, to changes in impact characteristics. FPS assessment guidelines were developed from the knowledge generated from the numerous FPS tests and analyses carried out in this research project. These guidelines have been used in the design and evaluation of a number of FPS for airbag compatibility. The real life performance of vehicles fitted with these FPS, have given confidence to the assessment criteria developed in this research project. This project has demonstrated that FPS can be designed to complement the safety systems of modern passenger vehicles, and thus passenger safety. This would not have been possible without the comprehensive research carried out in this project.

This thesis is concerned with the theoretical and computational aspects of generating solutions to problems involving materials with fading memory, known as viscoelastic materials. Viscoelastic materials can be loosely described as those whose current stress configuration depends on their recent past. Viscoelastic constitutive laws for stress typically take the form of a sum of an instantaneous response term and an integral over their past responses. Such laws are called hereditary integral constitutive laws. The main purpose of this study is to analyse adaptive finite element algorithms for the numerical solution of the quasistatic equations governing the small displacement of a viscoelastic body subjected to prescribed body forces and tractions. Such algorithms for the hereditary integral formulation have appeared in the literature. However the approach here is to consider an equivalent formulation based on the introduction of a set of unobservable interval variables. In the linear viscoelastic case we exploit the structure of the quasistatic problem to remove the displacement from the equations governing the internal variables. This results in an elliptic problem with right hand side dependent on the internal variables, and a separate independent system of ordinary differential equations in a Hilbert space. We consider a continuous in space and time Galerkin finite element approximation to the reformulated problem for which we derive optimal order a priori error estimates. We then apply the techniques of the theory of adaptive finite element methods for elliptic boundary value problems and ordinary differential equations, deriving reliable and efficient a posteriori error estimates and detailing adaptive algorithms. We consider the idea of splitting the error into space and time portions and present results regarding a splitting for space time projections. The ideas for splitting the error in projections is applied to the finite element approximation and a further set of a posteriori error estimates derived. Numerical studies confirm the theoretical properties of all of the estimators and we show how they can be used to drive adaptive in space and time solution algorithms. We consider the extension of our results for the linear case to the constitutively nonlinear case. A model problem is formulated and the general techniques for dealing with a posterior error estimation for nonlinear space time problems are considered.

No description available.

In this dissertation, a group of vehicle dynamics simulation tools is developed with two primary goals: to accurately represent vehicle behavior and to provide insight that improves the understanding of vehicle performance. Three tools are developed that focus on tire modeling, vehicle modeling and lap time simulation. Tire modeling is based on Nondimensional Tire Theory, which is extended to provide a flexible model structure that allows arbitrary inputs to be included. For example, rim width is incorporated as a continuous variable in addition to vertical load, inclination angle and inflation pressure. Model order is determined statistically and only significant effects are included. The fitting process is shown to provide satisfactory fits while fit parameters clearly demonstrate characteristic behavior of the tire. To represent the behavior of a complete vehicle, a Nondimensional Tire Model is used, along with a three degree of freedom vehicle model, to create Milliken Moment Diagrams (MMD) at different speeds, longitudinal accelerations, and under various yaw rate conditions. In addition to the normal utility of MMDs for understanding vehicle performance, they are used to develop Limit Acceleration Surfaces that represent the longitudinal, lateral and yaw acceleration limits of the vehicle. Quasi-transient lap time simulation is developed that simulates the performance of a vehicle on a predetermined path based on the Limit Acceleration Surfaces described above. The method improves on the quasi-static simulation method by representing yaw dynamics and indicating the vehicle's stability and controllability over the lap. These improvements are accomplished while maintaining the simplicity and computational efficiency of the two degree of freedom method. / Graduation date: 2013

This dissertation concerns quasistatic torsional mirror's for optical applications. The intended main area of application is the use as switch in optical network's, replacing the conventional optical-electro-optical conversation. With these actuator's a new concept of electrostatic actuation has been realised. While the drive electrodes are integrated into the deflectable mirror, the whole counter electrode below the mirror plate remains at equal ground potential. The device is manufactured out of two parts using method's of silicon bulk mikro machining. A deflectable mirror plate, torsional spring's and the surrounding support structure are fabricated within the thin device layer at the top of BSOI material. The counter electrode is manufactured out of a highly doped silicon wafer. Both part's are assembled together by adhesive bonding at die level at the end. Since the driving potential is supplied to the mirror plate and the counter electrode is at ground level, lateral tolerances because of device assembly mismatches does not appear with the use of the new concept. In detail the mirror plate itself is divided into two seperate electrodes by a parallel arrangement of filled isolating trenches. The highly doped device layer provides electrical connection via the torsional spring's to the mirror electrodes. A quasistatic torsional actuation is performed if a dc-voltage is applied between one mirror side and the counter electrode. Several design's have been fabricated. The lateral dimension of the torsional mirror plate vary from 0,5 mm to 2,0 mm. The designed characteristic frequencies vary from 0,5 to 3 kHz. For quasistatic actuation the pull in angle vary from 1 to 5 degree and the pull in voltage goes up to several hundred volts. Accessorily the mirror plate is enclosed by a comb drive structure. So that the device could be used for low voltage resonant actuation or an capacitive position read out becomes feasible. Within this thesis the new concept has been verified and functionality has been demonstrated. Depending on their characteristic frequency, devices are suitable to perform quasistatic actuation within 10 ms. Experiments indicated that the electrical isolation damages irreversible at drive voltage's above 400 volt. It limits the maximum deflection of nearly all design's. At prototype actuators repeatability has been studied. No drift was observed in the static characteristic within several cycles for certain designs. Closed-loop position control is not mandatory for the actuators fabricated within this thesis. Mechanical stress inside the mirror plate causes deformation of the reflective surface larger than permitted by optical criteria. This paves the way for further device optimization, yield improvement and system integration.

Baigiamajame magistro darbe nagrinėjama dalelių mišinio dinaminė elgsena kvazistatiniame pusiausvyros būvyje. Pagrindinis dėmesys skiriamas mišinio makro- ir mikrobūsenai charakterizuoti. Darbo tikslas – ištirti betono užpildams būdingomis fizinėmis-mechaninėmis savybėmis pasižyminčio sferinių dalelių mišinio struktūrą ir elgseną fliuktuojančioje aplinkoje kvazistatinio pusiausvyros būvio sąlygomis. Dalelių mišinio elgsenos dinaminis modeliavimas atliktas diskrečiųjų elementų metodu (DEM). Modeliuoti viendispersis ir daugiadispersis mišiniai. Pagal gautus rezultatus, mišinio makrobūsena charakterizuojama struktūros užimama tūrio dalimi (tankumu), dalelių kontaktinėmis jėgomis bei koordinacijos skaičiumi. Atskirų mišinio dalelių mikrobūsena charakterizuojama taikant unikalų geometrinį metodą, sukurtą pagal Hamiltono mechanikos, bendrosios reliatyvumo teorijos ir kvantinės gravitacijos teorijų principus. Metodui realizuoti parengtas kompiuterinis algoritmas patvirtino iškeltas hipotezes. / In the Master Thesis an investigation of dynamical behavior of the mixture of particles under quasistatic equilibrium conditions was performed. It focuses on a characterization of the macro- and microstate of the mixture. The purpose of the research is to explore structure and behavior of the mixture of spherical particles, characterized by the typical physical-mechanical properties of concrete aggregates, in a fluctuating environment under quasistatic equilibrium conditions. Dynamic simulation of the behavior of the particles was performed via the discrete element method (DEM). According to the results obtained, the macrostate of the mixture was investigated in view of a volume fraction, contact forces of particles and a coordination number. A characterization of the microstate of distinct particle was done using the unique geometrical method which had been created according to Hamiltonian mechanics, the theory of relativity and the principles of quantum gravity. The developed computer algorithm allowed to confirm the hypotheses of the method.