identifier: Hoddinott, Terry Keith <https://research.library.mun.ca/view/creator_az/Hoddinott=3ATerry_Keith=3A=3A.html>   (1986) Stochastic finite element analysis applied to soil media with uncertain material properties.  Masters thesis, Memorial University of Newfoundland.

abstract: This thesis examines how material uncertainty influences the short term settlements and stresses of foundations.  Expressing the uncertainty of material strength in terms of elastic modulus, the foundation and layered-soil-medium interaction is analyzed.  Two soil models are examined: (i) an elastic, single phase, layered soil medium with undrained material properties and (ii) a piecewise linear elastic, single phase, layered soil medium approximating the nonlinear behaviour of soil.  For the piecewise linear approximation, two shear-strain-dependent soil modulus relationships are included to differentiate between clays and sands. -- Utilizing a two-dimensional plane strain triangular element, a stochastic finite element solution is formulated.  The procedure incorporates the elastic modulus variation by considering a linear two term Taylor series expansion of the equilibrium equations. -- To limit the extent of errors induced by the omission of second order terms, the coefficient of variation (C.O.V.) for elastic modulus is assumed to be less than 30%.  To model the degree of interdependence between finite elements, a decaying exponential correlation distance function in terms of the scalar distance between elements is used.  Based on the definition of covariance combined with the linear two-term expansion for elastic modulus, the covariance of nodal displacements and the variance of element stresses are derived. -- To model the stochastic finite element procedure, a FORTRAN computer code is developed for both linear and piecewise linear material elasticity.  The displacements and stresses obtained from the plane strain analysis are considered as the mean values.  Using the covariance of displacements and variance of stresses computed for selected nodes and elements, the resulting coefficients of variation are determined for actual displacements, relative displacements and stresses.  A parametric analysis is carried out to establish the sensitivity of the stochastic finite element procedure to correlation distance, modulus C.O.V. and soil models.  This type of analysis is defined as an upper bound due to its maximizing the material uncertainty.  Also the random variation of material properties and its influence on displacements and stresses are examined by including a procedure to randomly vary the modulus C.O.V. from zero to maximum. -- Two ocean structure cases are examined to verify the stochastic finite element formulation, viz., (i) the Ekofisk Tank and (ii) the Mobile Arctic Caisson (M.A.C.).  The Ekofisk Tank is examined for gravitational loads and guasistatic wave loads representative of an actual storm.  Gravitational forces and design ice forces are applied to the M.A.C. structure.  In both cases, numerical results compare very well with those published in literature for the prototype structures, differing by less than 10% for most conditions. -- The main conclusions from the parametric study of the stochastic finite element procedure for soil-structure interaction are: -- (i) The effect of elastic modulus uncertainty is more pronounced in the uncertainty of stresses than the displacements. -- (ii) As the correlation distance factor becomes large (greater than 10), the variation of displacements or stresses attributed to local material uncertainty is smaller.  Under this condition the soil continuum is highly correlated. -- (iii) The proportion of uncertainty in results are insensitive to the varying loading conditions. -- (iv) The piecewise linear soil model provides closer agreement with the published data for prototype structures and yields lower coefficients of variation for displacements and stresses than the elastic model.


identifier: Raman-Nair, Wayne <https://research.library.mun.ca/view/creator_az/Raman-Nair=3AWayne=3A=3A.html>   (1984) Stress analysis of a porous deformable seabed under wave loading.  Masters thesis, Memorial University of Newfoundland.

type: Thesis NonPeerReviewed

format: application/pdf application/pdf

abstract: Wave-induced pore pressure and effective stresses in sea beds of finite and infinite depth are computed using the Biot theory of deformation of porous media (1962).  The Biot theory is simplified to a quasi-static case and the sea bed response is determined using the Papkovich-Neuber technique of the theory of elasticity.  The general theory (Biot, 1962) is compared with the quasi-static theory. -- The results are used to determine the depth of liquefaction and the depth of sliding failure, the latter being investigated via the Mohr-Coulomb failure criterion.


identifier: Nasr, Nagwa Hamed Mohamed <https://research.library.mun.ca/view/creator_az/Nasr=3ANagwa_Hamed_Mohamed=3A=3A.html>   (1979) The effect of different weighting functions when using the method of moments in linear antenna analysis : a different approach.  Masters thesis, Memorial University of Newfoundland.

abstract: It is the purpose of the present investigation to obtain and  study mathematical expressions for the currents of a center-fed linear antenna subjected to a known incident electrical field. In the analysis process the direct solution of an integral equation for the current expression is replaced by the solution of an integral equation for a certain intermediate function. This method which is discussed by Walsh²⁷⁻³⁰ eliminates the need for applying boundary conditions to an integral operator. The proposed method has been examined using the moment method in conjunction with three different weighting functions for solving the integral equation and a comparative study of the results is made. A set of Walsh functions is used for the basis functions. The use of Walsh functions for weighting functions allows efficient calculations of the matrix elements, and yields accurate results for certain antenna lengths. However, for other lengths the use of cosine functions for weighting functions is found to be more efficient. The third set of weighting functions used ispiece-wise sinusoidal functions, which yields the most complicated calculations. Several examples are given to illustrate the application of the proposed method, when the moment method is used in conjunction with three different weighting functions. The method has a rate of convergence which is in general much faster than the methods used by Srivastava²⁴ and Thiele²⁵. The results obtained by Srivastava are based on the same method of analysis, with the same basis functions used in this thesis, but in conjunction with point-matching, while Thiele's results are based on solving Pocklington's equation  using point-matching in conjunction with different basis functions. It is of interest to note that, the proposed method has the same flexibility as Pocklington's equation, but is better behaved numerically. Furthermore, the use of the moment method in conjunction with different weighting functions rather than using the point-matching technique, yields a smaller matrix to be inverted. In general, the results are in good agreement with the results obtained by other researchers.


identifier: Ragab, Ahmed Mahmoud <https://research.library.mun.ca/view/creator_az/Ragab=3AAhmed_Mahmoud=3A=3A.html>   (1978) The dynamical behaviour of fixed offshore structures using the Wittrick-Williams algorithm (nonlinear eigenvalve solution).  Masters thesis, Memorial University of Newfoundland.

abstract: The dynamical behaviour of fixed offshore framed structures is studied using the Wittrick-Williams algorithm which considers the nonlinear eigenvalue problem.  The effects of i) shear deformation and rotary inertia and ii) axial static loading (accounting for the self-weight of the structural members) are considered in this study of nonlinear free vibration and forced response to wave forces.  The algorithm is also used for analysis of offshore structure by Modal Synthesis.  The problem of rigid body modes in the modal synthesis is handled by vertical sectioning.  The eigenvalue and eigenvectors obtained from using the algorithm (nonlinear free vibration values) are used to determine the linear forced response to ice forces; taking into account the non-proportionality of the damping matrix and the response quantities are obtained by a step-by-step integration method. -- The members are assumed to be rigidly connected and the added water mass is assumed equal to the mass of the water displaced.  The structural modelling is based on a two-dimensional representation of the three-dimensional tower assuming a constant dimension equal to the base length perpendicular to the plane.  The distributed masses of the members in the plane of the frame are computed by summing up the structural mass, the mass of the water contained in the tube and the mass of the water displaced.  The member masses in the plane perpendicualr to the frame are assumed to be lumped at the horizontal cross-brace levels. -- The results of the study indicate that while the first two frequencies obtained from the Wittrick-Williams algorithm formulation and linear eigenvalue agree closely, the effect of the algorithm is significant for the higher frequencies.  Modal Synthesis enables solutions of large systems due to the reduced size matrices, partitioning and partial modal coupling.  The results also highlight the significant effects of the axial static force in the dynamic tangent stiffness matrix in the response study of the offshore structure.  Neglect of the off-diagonal terms in the non-proportional damping matrix does not affect the dynamic response values.  Fields for further research include i) soil-structure interaction studies for gravity offshore structures, buried pipelines and ii) nuclear power plant structures.


identifier: Dawe, C. Roy <https://research.library.mun.ca/view/creator_az/Dawe=3AC=2E_Roy=3A=3A.html>   (1984) Wave-soil tank calibration and geotechnical studies of seafloor instability.  Masters thesis, Memorial University of Newfoundland.

abstract: The general scope of this research is to understand the problem of seafloor instability due to ocean surface waves with particular reference to the offshore activities on the Canadian east coast.  An evaluation of the wave effects on seabed stability is necessary in the determination of the long term stability of bottom-founded offshore production platforms and transportation systems for the Grand Banks and Sable Island regions. -- A wave tank was designed and built for the purpose of conducting laboratory tests with sediments similar to those found on the east coast.  The tank is 8.5 m long, 0.76 m wide and 1.0 m deep, with a capability of generating regular waves of maximum heights of about 0.12 m.  The wave length can be varied from 0.5 m to 4 m.  The representative seafloor was a bed of sand about 0.4 m deep, underlying a water column up to 0.5 m deep.  The tank can be tilted so that slopes of up to 1:10 may be formed at the water-soil interface to represent seabed slopes.  A beach was designed and built to absorb the wave energy and to minimize the effect of reflected waves.  Reflection coefficients of less than 10% were obtained for the frequently used wave types.  Reflection coefficients as low as 5% can be obtained for some specific sets of wave characteristics. -- Waves with a steepness between 0.04 and 0.1 caused failure of the test bed of fine sand when it was in a loose state.  Porewater pressure was measured by embedding pressure transducers inside the soil.  Soil failure by liquefaction was confirmed by the measured pressures.  However, the sand always stabilized again after about 10 to 20 cycles resulting in a denser soil.  The soil failure appears to be the result of transient wave effects rather than porewater pressure buildup.  This is more pronounced when the soil is sloped. -- In a parallel theoretical research of the same problem, solutions have been reported using Biot’s equations.  Comparison of the measured wave induced porewater pressures with the reported theoretical values show a good correlation in some cases. -- The present studies show that the seabed will be subjected to mass movement under specific wave conditions.  This failure depends on the seafloor sediment type and its initial insitu state.  In combination with the bottom currents, the effect of the waves on the seabed could be quite severe.


identifier: Gao, Zhi <https://research.library.mun.ca/view/creator_az/Gao=3AZhi=3A=3A.html>   (1994) The influence of design quality on productivity in construction.  Masters thesis, Memorial University of Newfoundland.

abstract: In many countries, the productivity in the design office has been a neglected field compared with the outpourings of research and theory on productivity in construction.  It may thus be useful to review the state of the art in construction research, as there are parallels to be drawn with the design environment.  The author used ten construction projects to research the influence of design quality on the productivity in construction.  The ten projects were all designed by the author.  The data were collected after the construction phase and the direct costs were identified with rework(including redesign), repair, and replacement.  Finally the author gives four equations for forecasting quality problems related to design in construction.  The methods of analysis used are statistical, optimization, simulation and fuzzy logic.  Analysis of the data indicates that in construction the deviations on projects accounted for an average of 12.4% of the total project cost.  Furthermore, design deviation average 78% of the total number of deviations, 79% of the total deviation costs, and 9.5% of the total project cost.  Since design cost is a small percentage of total costs, and an increase in design expenditure can frequently reduce total life cycle costs, it is important to research the influence of design quality on productivity in construction.


identifier: Steel, M. Abigail <https://research.library.mun.ca/view/creator_az/Steel=3AM=2E_Abigail=3A=3A.html>   (1989) The formation of spray-ice and a selection of its constitutive properties with comparisons to ice and snow.  Masters thesis, Memorial University of Newfoundland.

abstract: This thesis examines the production of the material spray-ice, and several of its constitutive properties with comparisons drawn to existing spray-ice data as well as snow, ice and soil.  Consideration was given as to how spray-ice was best represented as an engineering material and what factors effect its behavior.  It was also important to add to the limited existing data base on spray-ice and to review the methods of production. -- After a fairly extensive literature review on spray-ice, solid ice, granular ice and snow and a brief overview of the pressuremeter, the experimental results are presented.  A total of thirty-seven pressuremeter tests were performed on first year ice and spray-ice.  The production of spray-ice was evaluated through a large-scale test program and laboratory simulation.  Finally a series of triaxial tests were performed on the laboratory made spray-ice. -- From these experiments it was found that spray-ice behaved in a manner similar to granular ice or loose sand.  However, its failure envelope has a shape that agrees with solid ice or snow.  The cohesive properties of spray-ice plays an important role in determining its behaviour.  It was found that spray-ice strength and failure type was highly dependent on the confining pressure and consolidation time as well as being affected by the test temperature, strain rate and sample density.  The strength trends found in this study do not entirely agree with the results of others on spray-ice, but the strength values and stress-strain curves are similar.  The behaviour was comparable in some cases to that of solid, granular ice and snow.  The pressuremeter tests performed on spray-ice did not compare well with values in the literature but, in general, agreed with the derived triaxial results.  Generally, these tests were effective in evaluating spray-ice but additional work is required to understand this interesting and important material.


identifier: Ryan, Joseph P. (Joseph Patrick) <https://research.library.mun.ca/view/creator_az/Ryan=3AJoseph_P=2E_=28Joseph_Patrick=29=3A=3A.html>   (1983) The electromagnetic scattering from a vertical discontinuity with application to ice hazard detection : an operator expansion approach.  Masters thesis, Memorial University of Newfoundland.

abstract: The long range detection of ice hazards such as multi-year ice, pressure ridges and icebergs will allow for more efficient planning of Arctic navigation routes and exploration in ice infested waters.  An analysis of the electromagnetic scattering from a vertical discontinuity representing the transition from sea water or first-year ice to a multi- year ice sheet has been carried out.  The analysis is based on a method of Space/Field decomposition where two Heaviside functions are used to decompose a three dimensional space into three regions each having different electrical properties.  Maxwell's equations are used to derive a partial differential field equation for the complete space.  Making use of a field decomposition, this differential equation may be decomposed into three field equations, one for each region, and a boundary equation.  A spherical Green's function is taken as the fundamental solution and the spatial Fourier transform is used to simplify the equations to a single integral equation.  Selecting a vertical electric dipole as the source field the solution for the vertical component of the surface field is obtained by writing this resultant integral equation in an operator form and expanding the inverse operator in a Neumann series.  Using the Laplace transform and stationary phase integration this series solution may be summed to provide expressions for both the backscattered field and the field propagated past the boundary separating the two media.  The solution for the propagated field agrees with that of both Bremmer and Wait.  The technique differs from that of previous investigators in that it is possible to obtain an expression for the backscattered field and thereby the radar cross-section of the vertical discontinuity.  The results of this analysis indicate that radar operating in the High Frequency range (3 - 30 MHz) should provide a significant improvement over present methods for the detection of this type of hazard.


identifier: Smith, David A. (David Abram) <https://research.library.mun.ca/view/creator_az/Smith=3ADavid_A=2E_=28David_Abram=29=3A=3A.html>   (1986) Trawl gear performance and net drag analysis with application to small trawls and vessels.  Masters thesis, Memorial University of Newfoundland.

abstract: In the following thesis a procedure is developed to determine the engineering performance of an inshore trawling system from an analysis of the forces acting on the towing warps and bridle system.  Equilibrium force balance equations are derived for each warp and solved using a fourth-order Runge kutta numerical analysis method.  The procedure is then applied to an inshore trawl and the results are used in the comparison of vessel power and gear drag. -- In addition towing tank drag measurements were made on small polyethylene nets.  The effect of the development of turbulent flow around the net on the drag of the net is investigated.  Empirical drag coefficients are also derived for polyethylene netting from these measurements.  The coefficients are then used in empirical trawl net drag calculations using methods developed by Dickson, Kowalski and Fridman.  In addition the relationship between the orientation of a mesh and the drag of the net is investigated.  It is shown how mesh orientation can explain the reduced drag of a square mesh net as compared to a diamond mesh net.


identifier: Khan, Zille Ahmad <https://research.library.mun.ca/view/creator_az/Khan=3AZille_Ahmad=3A=3A.html>   (1985) Triaxial testing on soils from Newfoundland areas : results of monotonic and cyclic tests.  Masters thesis, Memorial University of Newfoundland.

abstract: The study presents the laboratory testing of various types of soils using triaxial equipment recently established at Memorial University of Newfoundland.  Sand from Hibernia area, Clayey Silt from Placentia Bay area and Silty Clay from West Coast of Newfoundland were submitted to standard monotonic triaxial tests.  Isotropically consolidated undrained (CIU) compression tests, isotropically consolidated drained (CID) compression tests were performed as well as several extension tests or pore pressure controlled tests.  Cyclic triaxial tests were also carried out on Sand and Clayey Silt. -- Results showed that, despite known limitations, the equipment was adequate in providing reliable geotechnical parameters.  A discussion of these results and a comparison with earlier work by other researchers are presented.


identifier: Ahmad, Mohamed Fouad Abdel Meneim <https://research.library.mun.ca/view/creator_az/Ahmad=3AMohamed_Fouad_Abdel_Meneim=3A=3A.html>   (1979) Ultimate load behaviour of internally pressurized 'cut-and-cover' orthotropic reactor containment.  Masters thesis, Memorial University of Newfoundland.

abstract: Nonlinear static and dynamic analyses are presented for 'cut-and-cover’ type underground reinforced concrete nuclear reactor containments subjected to internal pressurization.  A nonlinear anisotropic model has been adapted and incorporated into a general linear and nonlinear, static and dynamic finite element analysis programme, NONSAP, to account for the orthotropic behaviour of reinforced concrete.  The load increment required in elastoplastic static analysis, and the time interval, as well as the boundary simulation of infinite or semi-infinite continuum in dynamic analysis, are adequately taken into account in this study.  Numerical investigations of the stability of equilibrium iteration procedure to reduce the divergence of the incremental solution from the true solution, are also presented. -- Parametric studies for the static response of the containment are carried out for:  1) stiffness of backfill (original and stabilized sandy loam fill with different cement ratios, 2%, 6%, and 10%); 2) thickness of backfill (2.5, 7.5, 12.5, and 18.5m);  3) percentage of reinforcing steel (#18 bars @ .25m, #18 bars @ .35m, #14 bars @ .35m, and plain concrete); 4) thickness of containment (1.25, 1.5, 2, and 2.5m) and; 5) different types of surrounding medium (sandy loam, clay, sand stone, and silty clay).  The response values determined are:  i) maximum positive vertical displacement, ii) maximum negative vertical displacement, iii) vertical and horizontal displacement, iv) stress-displacement relation at the point of maximum stress concentration.  The results confirm the effect of the different parameters on the response of the containment.  The stiffness of backfill and the containment thickness have the greatest effect.  The reinforcement effect is amplified when plastic flow commences. -- Dynamic analysis is carried out to study the response of a containment to a typical pressure-time function following a Loss-of-Coolant-Accident (LOCA).  A disturbance in displacements and stresses, is observed immediately after pressure decreases for two seconds after which the response becomes steadystate.


identifier: Poon, Martin Wai Yee <https://research.library.mun.ca/view/creator_az/Poon=3AMartin_Wai_Yee=3A=3A.html>   (1991) A clutter suppression scheme for high frequenccy (HF) radar.  Masters thesis, Memorial University of Newfoundland.

abstract: A clutter suppression scheme for high frequency (HF) radar is presented in this thesis.  The HF radar has been developed for coastal surveillance and the remote sensing of the ocean.  When the HF electromagnetic waves propagate over the ocean, the backscatter from the ocean surface has well defined frequencies, known as “Bragg" frequencies, shifted from the radar frequency.  One of the characteristics of the HF backscatter is the high level of ocean clutter which hampers target detection.  It is desirable to suppress the ocean clutter before target detection operation.  The proposed scheme is developed based on the recognition of the time-varying behaviour of the ocean clutter that can be simply characterized by two narrowband frequency-modulated sinusoidal signals with their centre frequencies equal to the "Bragg" frequencies.  The scheme consists of two parts.  First, a time-varying technique referred to as Hankel rank reduction method is used to estimate the instantaneous frequencies of the clutter signals.  The method states that a Hankel matrix of a time series data consisting of a finite number of sinusoids can be approximated to, via Singular Value Decomposition (SVD), a lower rank matrix defined by the finite number of the principal singular values, even if the frequencies of the sinusoids are varying slowly with time.  The instantaneous frequencies are estimated from those principal singular values.  The use of SVD is to decompose the Hankel matrix into a signal and a noise vector subspace.  The signal subspace is identified by the largest singular values.  Second, a process in which the frequency component of the clutter signals is removed from the reduced rank Hankel matrix instantaneously is developed to suppress the ocean clutter.  Subsequently, another reduced rank Hankel matrix is constructed from which the target signal can be extracted. -- The performance of the scheme has been evaluated on computer-synthesized data and on some real data collected from a recently developed HF radar.  The results from both cases showed that the instantaneous frequencies of the ocean clutter signals and the target signal were properly tracked by the Hankel rank reduction method and that a substantial level of the ocean clutter, in the range of 20 to 50 dB, could be suppressed by the scheme proposed.


identifier: Choi, Jose <https://research.library.mun.ca/view/creator_az/Choi=3AJose=3A=3A.html>   (1989) A message priority local area network for substation protection and control.  Masters thesis, Memorial University of Newfoundland.

abstract: A specialized microcomputer network is developed to meet the real-time processing requirements of a digitally protected substation.  This application has strict timing constraints and requires a fast communication response.  The network is based on the principle that direct access to channel is granted exclusively to the ready message with the current highest priority. -- The network requirements of the digitally protected substation are defined.  The data flow of the substation resembles the message priority in nature.  To implement the message priority scheme, a totally distributed network is employed. -- A simulation model is developed to predict the performance of the network.  Results from the simulation indicate that the network is capable of meeting the timing constraints of the real-time application.


identifier: Oancea, Marius-Adrian <https://research.library.mun.ca/view/creator_az/Oancea=3AMarius-Adrian=3A=3A.html>   (1991) A comparative assessment of mechanistic load equivalence factors for flexible pavements.  Masters thesis, Memorial University of Newfoundland.

abstract: This study deals with mechanistic Load Equivalence Factors (LEF) for flexible pavements. It addresses two sets of objectives. First, a theoretical investigation of cycle counting methodologies used for mechanistic LEF's calculation was carried out. Second, a number of these methods were used for calculating LEF's from in-situ strains. -- The study includes an extensive literature review, starting with the empirical approach proposed by the  AASHO Road Test (AASH0, 1961). Mechanistic methods for LEF's  calculation are subsequently introduced and discussed. -- Next, the concept of fatigue cycle, as defined by the ASTM standard E 1049-85, is introduced and its applicability to flexible pavements is investigated. As a result of the comparison of all the fatigue cycle counting methods proposed by the standard, the Range-Pair Counting Method was  selected for LEF's calculation. -- The experiment undertaken  in order to obtain strain versus time histories included two  experimental trucks, namely a 3-axle configuration and a 5-axle configuration. The experiment involved 3 levels of speed, 3 levels of loading and 2 replicate runs of the experimental vehicles for each speed and load combination. Each set of 2 replicate runs of the experimental trucks were  followed by an equal speed run of the Benkelman Beam truck. -- Resulting strain versus time histories were evaluated in terms of the quality of the lateral placement. Those corresponding to the best lateral placements were processed by the proposed ASTM Range-Pair Cycle Counting method, by the mechanistic method employed during the RTAC 1986 study, and the results were compared to the empirical AASHO LEF's. A new integral approach, based on the cycle definition provided by the selected ASTM method for cycle counting, was  also introduced. -- Comparative assessment of LEF's calculated by different methods was made in order to validate numerically and investigate the suitability of each  method for LEF's calculation.


identifier: Picco, Robert C. <https://research.library.mun.ca/view/creator_az/Picco=3ARobert_C=2E=3A=3A.html>   (1997) A comparative study of flow forecasting in the Humber River Basin using a deterministic hydrologic model and a dynamic regression statistical model.  Masters thesis, Memorial University of Newfoundland.

abstract: Since 1995 the Water Resources Management Division of the Department of Environment and Labour has generated flow forecasts for the Humber River Basin. These forecasts are required to provide a flood warning for residents living in the downstream sections of the basin. Information is also useful to the Deer Lake Power Company for the safe and efficient operation of the hydroelectric development that controls over two thirds of the basin. -- Flow forecasts for  river systems can be generated using two approaches. One approach is to use a deterministic model that tries to construct a mathematical model by accounting for some, or all of, hydrologic factors responsible for runoff in the basin. The second approach is to develop a statistically based model that uses the historic flows and climate data from the basin to generate a forecast. For any model to be effective in an operational environment, it must be compatible with hydrometeorologic input data collected in near real time. -- The current method of generating forecasts uses the SSARR (Streamflow Synthesis and Reservoir  Regulation) hydrologic model, a continuous simulation model that has reservoir routing capabilities, plus the ability to  account for the areal distribution of meteorologic inputs, including snowmelt. This model defines the water budget using hydrometeorological inputs. -- In this study a forecast method based on the dynamic regression technique was developed to produce one, two and three day forecasts for the five gauged sub basins results. Also, forecasts for the same time periods were produced using the SSARR model. The results of both methods were compared using the mean absolute percentage error (MAPE) criterion. -- The results of the comparison showed that the dynamic regression performed better than the SSARR model for all basins, particularly for the larger basins.


identifier: Kadarisman <https://research.library.mun.ca/view/creator_az/Kadarisman=3A=3A=3A.html>   (1993) A comparative study of the application of two catchment models to the Babak River Basin Lombok Island - Indonesia.  Masters thesis, Memorial University of Newfoundland.

abstract: A common problem in water resources planning in Eastern Indonesia, particularly in the Province of West Nusa Tenggara (NTB), is the lack of streamflow data. In general the available runoff data do not cover periods of more than one decade and are often insufficient for design purposes. Rainfall data, however, can have records that are two or three decades in length. To extend the length of the streamflow records, rainfall data may be transformed into streamflows using a catchment rainfall-runoff model. Two conceptual catchment models, the Tank Model and Mock's Model, are proposed for this transformation of rainfall into  runoff. Both models require mean areal precipitation and evapotranspiration as inputs. The Tank Model requires daily inputs values, while Mock's Model requires monthly input values. Two variations of the Tank Model (configurations with three and four tank components) were studied. -- Three year data periods (1973-1975) were employed for calibration,  and the subsequent three year periods (1976-1979) were used for verification. By a trial and error method, a set of parameters for the four component Tank Model were obtained and suggested for modelling daily runoff of the Babak River.  The model with three tanks did not give a good representation of low flows. By the same method, a set of parameters for the Mock Model were obtained; these are considered satisfactory for monthly flow modelling. Mock's Model is considered suitable for preliminary water resources   studies, where monthly time steps are appropriate. The choice of a suitable model varies with the purposes and the availability of data. Additional rain gauges in the basin are recommended to improve the results of the model. For basins located near the Babak River basin and for basins with similar catchment characteristics, the obtained parameters for both the Tank Model and Mock's Model can be used as initial values.


identifier: Pike, Darryl Scott <https://research.library.mun.ca/view/creator_az/Pike=3ADarryl_Scott=3A=3A.html>   (1994) An investigation of programmable compliance during robot/environment interactions.  Masters thesis, Memorial University of Newfoundland.

abstract: This thesis explores the effects of changing the effective damping and stiffness coefficients on the dynamic operating characteristics of a single degree of freedom direct-drive robot during "making" contact with a rigid environment. Altering these two coefficients ultimately implies changing the compliance of the robot/environment interaction. Since the compliance is changed dynamically and in real-time, the approach is referred to as Active Compliance. The thesis provides insight into the fundamental contact dynamics of a single robotic link such that the results can be used to describe the dynamics of more complex multi-degree of freedom manipulator architectures. -- Active compliance requires real-time control of the damping and stiffness characteristics and is fundamentally a dynamic force control  scheme allowing the robot to conform to the natural constraints imposed by the environment. To investigate this interaction in this thesis a software simulation program and  a single degree of freedom direct-drive robot arm are developed. The thesis also clearly defines five distinct phases associated with the process of making contact. These contact phases are generic and apply to both mobile and fixed robots. -- This study highlighted the following conclusions (1) Both mobile and fixed robots can benefit from controlled active compliance, (2) Altering these coefficients in real-time during the contact process is achievable, (3) The distance from the environment is not a necessary piece of information for contact under a force controlled contact scheme, (4) Compliance can be implemented  based on a force constraint imposed upon the robot and the environment, (5) Sensors provide control information and must be strategically selected and mounted, (6) Ideal Damping and Stiffness laws are developed and proven functional, (7) Friction is a significant impedance factor which effects all aspects of the contact cycle.


identifier: Bahree, Rajeeve <https://research.library.mun.ca/view/creator_az/Bahree=3ARajeeve=3A=3A.html>   (1987) Analysis and design of rotor blades due to the transient thermal and vibratory loads.  Masters thesis, Memorial University of Newfoundland.

abstract: The research work carried out in this thesis deals with the transient thermal and vibratory analysis of a gas turbine rotor blade. The design criteria of a rotor blade is suggested after studying the combined effects of the vibratory and thermal stresses on the turbine blade. -- The non-linear equations for the transient temperature distribution within the airfoil cross-section of the blade are derived using the finite element analysis. The non-linearity in these equations is due to the radiative heat transfer and-also due to the variation of the material properties of the blade with temperature. The non-linear differential equations are transformed to the non-linear algebraic equations in the time domain using a finite difference scheme. The temperature gradients and the thermal  stresses are calculated from the transient temperatures obtained from the heat transfer analysis. -- The mathematical model for the vibratory analysis is formulated using solid, quadratic, isoparametric finite element's. The stiffness and mass matrices are integrated using Gaussian quadrature. A dynamic matrix reduction technique is used to condense the global stiffness and mass matrices of the blade. The free vibration analysis of the blade is carried out using the condensed system matrices. The effects of the transient temperature distribution and the angle of pre-twist on the undamped natural frequencies of the rotor blade  are studied. -- The vibratory stresses are calculated due to  nozzle excitation and centrifugal forces. The nozzle excitation forces are modelled as a series of impulses using  the kinematic equations. The principal stresses are obtained  from the vibratory stress vector and the design of the rotor  blades is based on the distortion energy stress.


identifier: Batstone, Paul S. <https://research.library.mun.ca/view/creator_az/Batstone=3APaul_S=2E=3A=3A.html>   (1990) Analysis of inbound freight to Newfoundland.  Masters thesis, Memorial University of Newfoundland.

abstract:
The prime purpose of this research was to analyze the historical patterns of inbound general freight to Newfoundland by mode of transport, to identify the socio-economic factors which chiefly influence the inbound traffic, and to develop and test a forecasting model. A secondary objective was to investigate and test several non-causal forecasting techniques whose results could be compared with those of the model tested. -- The approach to this transportation planning topic was guided by the well developed method of analysis used in traffic engineering and  urban transportation planning. Having reviewed the literature and collected a suitable data set, a preliminary statistical analysis was conducted. This was followed by the  application of linear regression with the appropriate testing of the underlying assumptions using the t-test, the F-test and the Bartlett's test. Other methods used included the calculation of simple ratios of traffic volume to the various socio-economic factors, and time series and smoothing techniques. -- The historical pattern of general freight to Newfoundland has demonstrated constant growth over the last 20 years with considerable variability in the split between the rail, truck and direct shipping modes. Current inbound traffic by all modes is in the order of 1 million tonnes annually. Using multiple linear regression, the combination of population and the value of retail trade was found to influence the inbound traffic to the greatest extent. Simple ratios of inbound traffic to selected socio-economic employment ratio demonstrated the least difference between forecast and actual value. -- The best straight line  fit was found to be the combination of population and the value of retail trade with the use of regression analysis. The resulting equation had an R-Square of 80%, which is considered an acceptable degree of accuracy for the industry, and intuitively made sense. The predictions calculated from non-causal techniques resulted in similar orders of accuracy. -- In a broader vein, it was also concluded that the analysis of freight transportation issues  has been inhibited in the past by the lack of data at the regional and national levels. -- A logical extension of this  research is further application of the classical transportation planning process; that being the analysis of modal choice and traffic assignment. The use of one or more of the qualitative methods of forecasting should also be investigated. This was felt to be particularly important since the rail mode in Newfoundland has been eliminated and a newly regulated transportation environment is evolving. --
Key Words: freight; freight demand; freight forecasting; freight transportation; general freight; modal choice of shipping; modal split; mathematical modelling; operations research; regression analysis; statistical applications; time series; transportation engineering and transportation planning.


identifier: Warikoo, Raman <https://research.library.mun.ca/view/creator_az/Warikoo=3ARaman=3A=3A.html>   (1989) Analysis of propeller shaft transverse vibrations.  Masters thesis, Memorial University of Newfoundland.

abstract:
The aim of this project was to find a simple, practical and sufficiently accurate method for finding the natural frequencies of a propeller shaft assembly. The need for such  methods is felt at the early design stages when sufficient data about the system is not available and the need to restrict the cost of analysis is of importance. Due to these  facts it is clear that the methods based on the discretization of the continuum, which can estimate the natural frequencies accurately may not be advisable to go in  for in the initial stages. -- In the class of approximate methods, to which this work belongs, investigations done so far have crudely modelled the propeller, which was avoided in the present work. The propeller was considered to be a flexible rotor mounted with blades. -- To solve the problem analysis was carried out in three parts. First the blade was  studied for the natural frequencies, mode shapes, static deflections and the steady state stresses. The blade was assumed to be a cantilever and the results were cross-checked by a preliminary finite element analysis using beam elements. The assumption was found to be quite valid after doing the finite element analysis using 3-D isoparametric 20  noded elements. For the airfoil blade effects of rotation, shear deflection, rotary inertia, pitch setting angle were taken into consideration. Second the shaft-rotor system was studied and the equation for the transverse vibrations was derived in the complex plane which was solved for the natural frequencies. Effects of forward and reverse whirl, fixed and simply supported forward bearing end conditions, tail shaft length variation, rotary inertia and shear deflection were investigated. Lastly the natural frequencies  of the blades and the shaft-rotor system were coupled to give the resultant natural frequency of the propeller shaft assembly. The hydrodynamic effect has been taken into consideration by incorporating the added mass effects for the propeller. Two approximations for the natural frequency
of the assembly were arrived at, the zeroth order and the first order. The true value of the frequency is supposed to lie in between the two limits. Effects due to change in the number of blades, blade geometry and the shaft parameters on  the propeller shaft assembly were checked for. Agreement between the results obtained from the present work and with those available in the literature was found to be excellent.  Finite element analysis comparisons also were very satisfactory.


identifier: Yingming, Xiao <https://research.library.mun.ca/view/creator_az/Yingming=3AXiao=3A=3A.html>   (1995) An experimental study of crack detection in a rotating shaft.  Masters thesis, Memorial University of Newfoundland.

abstract: This thesis investigated the dynamic characteristics of a rotating shaft by using modal experimental method and an experimental model has been developed for crack detection. -- In this study, an imitation crack, which simulates the characteristic of a transverse crack, in the middle span of a rotating shaft, is designed and the rotating shaft experiment setup is made up. Experiments are carried out in different crack parameters and different size rotors in forward and backward rotation. -- It is found that the natural frequency of the rotating shaft decreases and frequency response amplitude increases with increasing crack  parameter. The maximum difference of natural frequency between cracked and uncracked shaft is 14.7%, and the maximum difference of frequency response amplitude with a crack is 4 times as high as that without crack. It is also found that the rotating shaft in backward rotation has the same vibration response as that in forward rotation. -- The experiment results show that the critical speed of the rotating shaft is sensitive to cracks. Therefore, the method  may be used in industrial application for detection crack in  rotating shafts.


identifier: Cross, John F. <https://research.library.mun.ca/view/creator_az/Cross=3AJohn_F=2E=3A=3A.html>   (1992) An experimental study of the dynamics of catenary mooring lines.  Masters thesis, Memorial University of Newfoundland.

abstract: This work examines the dynamic forces that are generated in catenary mooring lines when the top part of the line is subjected to a forcing function. The forcing function consists of a sinusoidal motion of fixed amplitude but varying frequency and varying angle in the vertical plane. The effect of changes in the pretension in the chain is also  examined. -- Four different areas of response are classified  by the response of the line and the characteristics of the force in the line observed over time. The force in each area  is examined and the mechanism that generates these forces is  discussed. The change of these forces with changes in the forcing function at the top end of the line is also examined. -- The model parameters for the catenary mooring system are identified and model tests performed. From these model tests it is possible to conclude that large structures  such as oil rigs and large vessels will cause mooring lines to respond in a range where dynamic forces need not be taken  into account. However, smaller objects such as buoys will suffer significant dynamic forces.


identifier: Thiagarajan, Krishnaprasad <https://research.library.mun.ca/view/creator_az/Thiagarajan=3AKrishnaprasad=3A=3A.html>   (1989) An experimental study on higher order waves and hydrodynamic loading on vertical surface piercing cylinders.  Masters thesis, Memorial University of Newfoundland.

abstract: Estimation of second order wave loading on offshore structures has attracted recent attention in research. This thesis presents the results of an experimental study carried  out to quantify second order wave forces on a vertical cylinder in a wave tank. The initial part of this thesis is directed towards formulating and analyzing the wave field present in the laboratory. These results formed part of the input for further studies on wave forces. Due to the physical limitations of the wave tank, it was found that several waves coexist with the progressive wave of interest in the tank. An analysis procedure was developed using a Fast Fourier Transform technique and a least squares curve fitting method to separate the wave of interest from the side effects and identify its principal parameters. Several side effects were quantified in the process. Wave forces on a vertical cylinder to second order were theoretically formulated from a literature survey. Analysis of the measured wave forces in the wave tank involved using a fast fourier transform to identify the first and second order force components. Towards the end of the study, it was found  that the proposed formulations for the total wave field in the tank and the wave forces on a cylinder were adequate. There exist many phenomena in a wave tank whose effects on measurements requires further research. It is emphasized that systematic experimental studies of higher order waves form an important part of offshore research development.


identifier: Shu, Zhiqin <https://research.library.mun.ca/view/creator_az/Shu=3AZhiqin=3A=3A.html>   (1992) A PWM current-fed inverter for induction heating.  Masters thesis, Memorial University of Newfoundland.

abstract: This thesis presents the description, analysis and implementation of a medium freqnency PWM current-fed inverter for induction heating applications. The feasibility  of the application of a PWM scheme to the current-fed inverter in this particular field is investigated. The steady-state performance of the system is evaluated by a simulation program which is based on the state-space method of analysis. The analytical results by simulation are verified experimentally on a laboratory set-up of a power level of 100 watts at about 1 kHz. -- The current-fed PWM inverter is designed to achieve the goal of using a simpler control scheme to reduce the power losses and overall maintenance cost. It does not use a stage of controlled rectifier for the output regulation, which has the drawback of injecting large harmonics into the utility system. The overall control strategy is relatively simple, because the control loop does not include the input circuit of the system. The current-fed PWM inverter presented in this thesis shows the possibility of achieving output power regulation by means of both the swept-frequency method and the PWM scheme. A simple IC-based triggering circuit has been developed which can provide the required stable PWM signals in a range wide enough to achieve the goal of control.


identifier: Yan, Bing <https://research.library.mun.ca/view/creator_az/Yan=3ABing=3A=3A.html>   (1997) A low cost planar near-field / far-field antenna measurement system.  Masters thesis, Memorial University of Newfoundland.

abstract: In this thesis, a low cost planar near-field/far-field (NF/FF) antenna measurement system is designed, built and validated in Center for Cold Ocean Research Engineering (C-CORE), Memorial University of Newfoundland. The design of the system is presented in detail, a faster technique is used to speed the determination of the far-field radiation pattern. The basic theory of near-field antenna measurements  is reviewed. A software package has been designed which has a user friendly interface. Details of the NF/FF transformation using fourier transform are presented. Far-field radiation patterns calculated from near-field measurements have been compared with the far-field patterns measured directly inside C-CORE's RF anechoic chamber, and reasonably accurate results are observed for a number of antennas. Based on the cost of the system ($2,000), the reasonably accurate results are quite acceptable. This NF/FF  measurement system is an addition to the Memorial University  electromagnetic measurement facility.


identifier: Zhou, Hao <https://research.library.mun.ca/view/creator_az/Zhou=3AHao=3A=3A.html>   (1997) A mass-weighted upwind-based control volume finite-element method for steady two-dimensional viscous compressible flows.  Masters thesis, Memorial University of Newfoundland.

abstract: The formulation and implementation of a mass-weighted upwind-based control volume finite element method (CVFEM) for steady, two-dimensional, viscous compressible internal flows is reported in this thesis. In the development of this  method, a CVFEM for steady, quasi-one-dimensional, viscous compressible flows was also formulated. The proposed method is a colocated shock capturing formulation. Polygonal control volumes are constructed around each node in the finite-element mesh, and discretized forms of the governing equations are obtained by deriving algebraic approximations to integral conservation equations for each control volume. -- The proposed methods are formulated using the velocity components, pressure, and temperature as the dependent variables: density is calculated from an equation of state. Linear interpolation is applied to pressure and diffused scalars, and a mass weighted upwind function is applied to the convected scalars. An interpolation function incorporating a pseudo-velocity and a pressure gradient is used to represent mass conserving velocities; this allows the development of a colocated method valid for compressible  flows. The discretized forms of the governing equations are solved using an iterative algorithm. In this algorithm, linearized forms of the discretized momentum and continuity equations are solved in a segregated manner by using a tridiagonal matrix algorithm. -- The proposed quasi-one- and  two-dimensional CVFEM's are applied to several inviscid and viscous compressible fluid flow problems, and the solutions generated are compared with theoretical, numerical, and experimental results available in the literature. This comparison shows that the proposed CVFEM's can generate solutions that are in agreement with the expected physical behaviour of some compressible flows and with the available results. The results suggest further research is required in  the evaluation and enhancement of the mass-weighted interpolation functions currently used, however, as the shock smearing in the proposed method is excessive, and the accuracy of solution is not satisfactory.


identifier: Tully, Susan Hentschel <https://research.library.mun.ca/view/creator_az/Tully=3ASusan_Hentschel=3A=3A.html>   (1997) A neural network approach for predicting the structural behavior of concrete slabs.  Masters thesis, Memorial University of Newfoundland.

abstract: Reinforced concrete slabs exhibit complexities in their structural behavior due to the composite nature of the material and the multitude and variety of factors that affect such behavior. As such, current methods for the design and analysis of reinforced concrete slabs are limited  in scope and are approximate at best as they must rely on the results of experimental tests, which are both costly and  time-consuming to perform. The research embodied by this document investigates the use of a branch of artificial intelligence known as Neural Networks (NN) as a quick and reliable alternative to such experimental testing. -- Four neural network models are developed to predict the following  aspects of the overall behavior of a concrete slab: 1) load-deflection behavior; 2) crack pattern at failure; 3) concrete strain distribution; and 4) reinforcing steel strain distribution. Results from experimental tests on thirty-four full scale slabs are utilized to develop these four models, incorporating all of the parameters that govern  their behavior. The rationale behind and the details involved are explained for the setup, computer implementation and selection of each optimum neural network model. Results show that the neural network technique can perform as a satisfactory alternative to experimental testing or detailed calculations to provide speedy predictions of all four aspects of the structural behavior of concrete slabs. A comprehensive spreadsheet tool is next created to incorporate all four of the optimum neural networks. The spreadsheet uses readily available software and can be used by structural engineers for instantaneous access to the prediction of any or all of the four aspects of a concrete slab's behavior given minimal data to describe  the slab and the loading conditions. This tool, combined with the results for the four neural network models, demonstrates the powerful capabilities and success of neural  networks in the realm of civil and structural engineering in  general and reinforced concrete design in particular. This approach could readily be expanded to include the same predictions for other structural concrete elements such as beams and shear walls.


identifier: Zhu, Xia <https://research.library.mun.ca/view/creator_az/Zhu=3AXia=3A=3A.html>   (1997) A new class of unbalanced CAST ciphers and its security analysis.  Masters thesis, Memorial University of Newfoundland.

abstract: The original CAST cipher is an efficient and secure private-key block cipher designed to be an alternative to the Data Encryption Standard (DES). In this thesis, we present a new class of unbalanced CAST ciphers which employs the same structure of S-box and round function of the original CAST cipher but has a lower memory requirement. Unbalanced CAST ciphers with one or two 8x32 S-boxes in the round function require only 1/4 or 1/2 the memory of the original CAST cipher, respectively. -- This thesis examines the application of differential and linear cryptanalysis, two of  the most powerful methodologies for attacking private-key block ciphers, to the unbalanced CAST ciphers. The results of analysis show that a 48-round unbalanced CAST cipher with  one 8 x 32 S-box and a 24-round unbalanced CAST cipher with two 8 x 32 S-boxes, both of which are equivalent to a 12-round original CAST cipher in efficiency, are resistant to both differential and linear cryptanalysis. -- We also investigate the unbalanced CAST ciphers from the perspective  of information theory. The results suggest that the maximum static and dynamic input-output bit information leakages for  the unbalanced CAST ciphers constructed by 8 x 32 S-boxes are much smaller than for DES. -- The conclusion reached by the thesis is that unbalanced CAST ciphers can be considered  to be efficient, secure ciphers which require less memory than the original CAST cipher.


identifier: Turpin, Arden E. <https://research.library.mun.ca/view/creator_az/Turpin=3AArden_E=2E=3A=3A.html>   (1991) Balancing of flexible rotors supported on bearings having non-linear flexibility.  Masters thesis, Memorial University of Newfoundland.

abstract: In real-life applications, multi-disk-rotor systems are supported on bearings which have non-linear flexibility. The  balancing of such systems at high speeds is a challenging task. This thesis presents a method of balancing such systems. The dynamic equations of motion of the non-linear system are derived using the influence coefficient method as  well as the Lagrangian equations. An equivalent linear system is found using the optimization principles. Finally, the correct balance weights for the non-linear system are obtained based on the equivalent linear system. The results thus obtained establish the utility of such a method of balancing of nonlinear systems.


identifier: Hussein, Amgad Ahmed <https://research.library.mun.ca/view/creator_az/Hussein=3AAmgad_Ahmed=3A=3A.html>   (1990) Behaviour of reinforced concrete slabs made with high-strength concrete.  Masters thesis, Memorial University of Newfoundland.

abstract: The present research investigation deals with the structural behaviour of two-way slabs made with high-strength concrete subjected to punching shear. -- A high-strength concrete mix, suitable for offshore applications, was developed using conventional cement and aggregates available in Newfoundland. The incorporation of silica fume and high-range water reducing agent made it possible to achieve high strengths at early ages. A compressive strength of 70 MPa at 28 days was achieved for concrete mix incorporating 12% class F fly ash, 8% condensed silica fume and a high-range water reducing agent of naphthalene formaldehyde base. The relevant rheological and mechanical properties of the mix were examined. In addition, an experimental program was carried out to study the effect of cold ocean water, simulated under laboratory conditions, on the mechanical properties of green high-strength concrete containing silica fume and fly ash. -- Seventeen slabs were tested in the structural laboratory at M.U.N. The effect of the reinforcement ratio, concrete strength, slab depth and column size on the behaviour of the slabs was investigated. The structural behaviour of the tested slabs with regard to deformations, strains, ultimate capacity, and modes of failure was examined. Test results revealed that the present North American Codes are unsafe for high-strength concrete slabs, since they overestimate the influence of the concrete strength, as a factor, on the ultimate capacity of two-way slabs. -- Based on the test results, a mechanical model was adopted. The formulation takes into account the actual behaviour of the high-strength concrete and steel. The proposed model gave a fairly good agreement between the predicted and experimental punching loads.


identifier: Gowda, Siddappa Shankare <https://research.library.mun.ca/view/creator_az/Gowda=3ASiddappa_Shankare=3A=3A.html>   (1983) Analytical and experimental investigation on the fatigue behaviour of tubular joints for offshore monopod structures.  Doctoral (PhD) thesis, Memorial University of Newfoundland.

abstract: This study is concerned with the analytical and experimental investigation of fatigue behaviour of monopod tubular joints in air and cold seawater environments. A total of seven joints were tested under cyclic loading. Two specimens - one in air and the other in water - were subjected to pseudo-random loadings. The remaining five specimens - two in air and three in seawater - were tested under constant amplitude sinusoidal loadings. The joints were tested both in as-welded and weld tow ground conditions. The corrosion tests were carried out in natural seawater at 0°C to simulate the cold ocean environment. -- From the measured strains during static loading at critical hot spot locations, strain and stress concentration factors were determined and compared with the finite element analysis. The MSC/NASTRAN finite element computer code was used using triangular and quadrilateral flat shell elements. Each element has five degrees of freedom consisting of two in-plane displacements, a normal displacement and bending rotations. -- The effect of seawater, weld toe grinding, the nature of applied loads and crack growth characteristics are studied in detail. The fatigue lives of the joints for crack initiation, propagation and final failure are determined and compared with those of T or Y-joints from the published literature. For the three joints tested in seawater, the fatigue life for wall penetration are compared with the analytical life estimation using fracture mechanics approach. The fatigue results of all the joints tested are compared with the relevant U.K. DD 55 Q and AWS-XX S-N curves.


identifier: Ma, Zhongyun <https://research.library.mun.ca/view/creator_az/Ma=3AZhongyun=3A=3A.html>   (1998) Bioremediation of petroleum hydrocarbon contaminated soil using indigenous cultures.  Masters thesis, Memorial University of Newfoundland.

abstract: This research consisted of studying the biodegradation potential of Total Petroleum Hydrocarbons (TPH) in a diesel contaminated soil using indigenous cultures. From a site investigation conducted on a polluted site in Argentia (Newfoundland, Canada), typical soil profiles and contaminants were determined for helping in setting up an Environmental Test Facility. The potential for bioremediation of soils in that area was studied in the laboratory. Four lands of cultures were isolated from the petroleum hydrocarbon (diesel) contaminated soil, enriched in the laboratory and injected into the soil as a seed to increase the population of cultures. The contaminated soils were incubated in closed reactors at temperatures ranging from 25 to 5°C and pH values from 6 to 8. The addition of mineral salts as nutrients was also included. Surfactants were used as additional chemicals to enhance the rate of bioremediation. -- The degradation of TPH was evaluated by concentration monitoring (Gas Chromatography) and bacteria counting. Temperature effects study showed that biotreatability markedly decreased with decreasing temperature. The optimal rate of bioactivity was obtained in a neutral or slight acid condition, and surfactant Triton X-100 showed an enhancement of degradation of petroleum hydrocarbon, while the surfactant Tween 60 did not improve degradation. Nutrient requirement was also clearly identified. Under optimal condition, the TPH removal efficiency reached 50% of the initial value. It was also observed that bacteria seeding is possible and echances the remediation rate. -- Surfactants were used to wash diesel out of the contaminated soils in column tests. Distilled water, 0.5% (w/w) aqueous solution of surfactant Tween 60 and 0.5% (w/w) aqueous solution of surfactant Triton X-100 were used as leaching solutions. Corresponding TPH removals were obtained as 5.3%, 21.7%, and 67.8% respectively, demonstrating potential efficiency of combining physical and biological remediation methods.


identifier: Vallabhan, Satish. C. <https://research.library.mun.ca/view/creator_az/Vallabhan=3ASatish=2E_C=2E=3A=3A.html>   (1995) Application of artificial neural networks for voltage stability evaluation of power systems.  Masters thesis, Memorial University of Newfoundland.

abstract: Voltage instability has emerged as one of the most important areas of concern to modern power utilities. Once associated with weak power systems and long transmission lines, voltage instability problems are now acutely felt in highly developed networks. This is because many utilities are loading their bulk transmission networks to their maximum capacity to avoid the enormous capital costs of building new lines, In recent years, voltage instability has been responsible for several system collapses in Europe, Asia and North America. -- Voltage instability is concerned with the ability of a power system to maintain acceptable voltage at all buses in the system under normal loading conditions and after being subjected to a disturbance. A system enters a state of voltage instability when a disturbance, increase in load demand, or change in system condition causes a progressive and uncontrollable decline in voltage. The main reason causing voltage instability is the inability of the power system to meet the demand for reactive power. The other factors contributing to voltage instability are generator reactive power/voltage control limits, load characteristics, characteristics of static var compensators, and action of on load transformer tap changers. -- The study of voltage instability has become an important area of research in the field of power system engineering. The main thrust of research has been to arrive at an accurate and reliable indicator of the proximity of a system to voltage collapse. Such an indicator would be useful to utilities in operating their systems with maximum economy and security. However, for such voltage stability indices to be truly useful to utilities from an operations point of view, they should be implemented on-line in the Energy Management System (EMS). The Energy Management System has become a very important tool in modern power system control and operation and has versatile capabilities for power system control, analysis and monitoring. The major hurdle in the on-line implementation of voltage stability indices in an EMS would be the heavy computational costs involved in terms of time, memory and hardware costs. This is because most methods for voltage stability analysis need repeated solutions of power flows and associated calculations. Thus, for on-line applications, there is a need for tools which can quickly identify potentially dangerous conditions and provide the operator with guidance to steer the system from voltage collapse. Also, in view of the large size of modem power networks, it is important that the memory requirements of the computational tools be as low as possible. -- In recent years, there has been considerable interest in the application of Artificial Neural Networks (ANN) to power system problems. Artificial Neural Networks have the ability to identify and classify complex relationships, which are nonlinear and result from large mathematical models. The main feature of an ANN is the ability to achieve complicated input-output mappings through a learning process, without explicit programming. Once an ANN has been trained, it can classify new data much faster than would be possible by solving the model analytically. ANNs have the potential to play an important role in Energy Management Systems by providing system operators with a fast and reliable indication of the voltage stability of a power system. -- This thesis presents the application of ANNs for evaluation of power system voltage instability. Two popular voltage stability indices are studied and simulations are carried out on the IEEE 24 Bus system and the 39 Bus New England system. The effect of contingencies on the voltage stability of the above two systems was investigated. ANN models were designed to evaluate the voltage stability indices using the system parameters available from the EMS as inputs. For the energy margin based voltage stability index, separate ANN models were used for each contingency. However, for the load margin index, a single ANN model which takes into account the network topology, was used to evaluate the voltage stability. This single ANN model is able to evaluate the voltage stability of a system under normal operating condition (i.e., all lines in service) and also in the event of a line outage. Simulation results are presented on the application of the above indices to both power systems. The performance of the ANN models are presented, which compares the predicted accuracy to the expected value. The thesis also proposes a scheme for integrating the ANN based system into the EMS environment.


identifier: Balasubramanian, Raghu <https://research.library.mun.ca/view/creator_az/Balasubramanian=3ARaghu=3A=3A.html>   (1993) Application of neural networks in robotic control and design of mechanisms.  Masters thesis, Memorial University of Newfoundland.

abstract: Neural network has been widely used in various fields of robotics. In this work, the neural network analysis using backpropagation algorithm is applied to the inverse velocity analysis of robotic manipulators near the singularity points accounting for the tracking error and feasibility of joint velocities. The inverse computations using the pseudo-inverse of the Jacobian matrix are compared with those obtained by the neural network analysis. The results illustrated using examples of two well known manipulators show the advantages of using the present work. A new learning algorithm called LP-neuro method is then developed to solve neural network problems, in this algorithm, the weights are obtained by a combination of Linear Programming having a sparse coefficient matrix and a single variable non-linear optimization method. The results are illustrated by solving three different problems, two of which are useful in the on-line control of robotic manipulators. The designs of a function generator and a four-bar mechanism whose coupler curve passes through nine specified points, have been carried out using neural network methods. The design problem has been solved using non-linear techniques which yield a weight matrix in each of the cases. The accuracy of the methods is also discussed. Finally, gain parameters required for the trajectory control are evaluated using non- linear optimization method. Neural network is then trained to evaluate the gain parameters based on error history of different trajectories.


identifier: Doucet, J. Michael <https://research.library.mun.ca/view/creator_az/Doucet=3AJ=2E_Michael=3A=3A.html>   (1996) Cavitation erosion experiments in blocked flow with two ice-class propeller models.  Masters thesis, Memorial University of Newfoundland.

abstract: Ships that operate in ice-infested waters often experience momentary increased propeller cavitation because ice pieces can block the How into the propeller. Model tests have shown that the presence of blockages in the flow field can lead to regions of violent cloud cavitation. For ducted propellers, this additional cavitation is more significant than it is for open propellers: ice pieces may become lodged against and within the duct and subject the propeller to longer periods of increased cavitation due to the blocked How. Associated with this cavitation is the possibility of cavitation erosion. -- The extent and severity of cavitation erosion that a marine propeller may experience cannot presently be determined theoretically. To gain an understanding of how this phenomenon affects a full scale propeller, it is necessary to perform model tests. -- This thesis presents the results of an erosion study that was completed in the cavitation tunnel at the Institute for Marine Dynamics (IMD), a facility of the National Research Council (NRC) of Canada. Paint tests provided the medium through which the erosion was studied. A limited number of tests were attempted with pressure sensitive films to estimate the intensity of the cavitation. Two model propellers, both having a diameter of 200 mm, were used. The first model, an open, fixed pitch propeller, was of the type that is fitted to the Canadian Coast Guard (CCG) R-CIass (1200-Scries) icebreakers. The second model, a variable pitch ducted propeller, was of the type that is fitted to the Canadian Marine Drilling (CANMAR) Lid. vessel MV Robert LeMeur. -- During testing, a simulated ice blockage was installed upstream of the model such that the nominal blade/blockage clearance was approximately I nun. Experiments were completed over a range of advance coefficients for various test conditions, including tests at reduced pressure and at atmospheric pressure. The effects of changes in the proximity of the blockage were also examined. A lest was performed in open flow for each propeller to provide a baseline for the erosion results. For each experiment, the resulting types of cavitation and the erosion patterns were recorded. V7/.V video equipment and }5 mm still photography were used lo document both the experiments and the results. In subsequent analysis, the areas of erosion were estimated using an image analysis program and comparisons between each test were made.  -- Generally, given the same test conditions, the dueled propeller experienced more erosion than the open propeller. Cavitation persisted longer on the ducted propeller due to the influence of the nozzle. -- For both propellers, the amount of face erosion increased with increasing advance coefficient. Back erosion was minimally affected by changes in the advance coefficient. -- Concerning proximity effects, erosion increased, for both propellers, as the blade/block clearance was increased, until it reached a peak. This peak occurred at a gap of 5 mm. Further increases in clearance resulted in reduced erosion. -- Pressure sensitive film tests were unsuccessful as the films were torn from the blades by the violent cavitation. For future tests under such adverse conditions, a more robust fastening system is required.


identifier: Hynes, Frank <https://research.library.mun.ca/view/creator_az/Hynes=3AFrank=3A=3A.html>   (1996) Centrifuge modelling of ice scour in sand.  Masters thesis, Memorial University of Newfoundland.

abstract: The interaction of icebergs (of glacial origin) and pressure ridge ice keels (formed from frozen sea water) with the seabed is recognized as an important consideration in the development of hydrocarbon resources in both the arctic and eastern offshore regions of Canada. To understand the detrimental effect of a scouring ice mass upon the integrity of seafloor facilities such as wellheads, pipelines and submarine cables, a large amount of analytical, experimental and phenomenological research into ice keel scour has been undertaken. -- Concerns related to the ice keel scour phenomenon are currently being addressed within a joint industry and government sponsored research program entitled the Pressure Ridge Ice Scour Experiment (PRISE). The objective of this program is to develop the expertise and understanding required for the safe and economical engineering of offshore pipelines in regions prone to ice keel scour. Under the auspices of the PRISE program, a series of centrifuge modelling tests involving ice keel scour were undertaken. The centrifuge modelling program involved towing an instrumented model ice keel of set geometry across a model testbed at a set scour depth while under the influence of a centrifugal force. The objective of the tests was to measure scour-induced stresses and pore pressures, horizontal and vertical loads and model keel/ soil interface pressures. -- The results obtained during the experimental program involving ice keel scour in sand highlighted the importance of the static soil "dead wedge" beneath the model ice keel with respect to variation in scour loads and subscour soil displacements. Analysis of the results served to support Been's (1990) shear dragging hypothesis. The results also suggest that a linear relationship can be used to describe the variation of scour loads with depth.


identifier: Subramaniam, Kavitha <https://research.library.mun.ca/view/creator_az/Subramaniam=3AKavitha=3A=3A.html>   (1996) Changes in physical, hydraulic and microstructural properties of clays exposed to organics.  Masters thesis, Memorial University of Newfoundland.

abstract: The use of engineered clay liners for containing landfill wastes and protecting groundwater quality is based on the adsorption capacity and impermeability of the clay fabric. Excessive leachate through clay barriers is mainly due to changes in the intrinsic permeability of the clay material when exposed to contaminants. The compatibility of clay barriers with leachate is also evaluated through an assessment, of changes in the index properties and/or internal structure of the soil. One of the major factors that can affect the clay performance is the presence of organic chemicals in the leachate that typically constitute more than 55% of the total leachate generated in landfills. -- The goals of this work are to provide a better understanding of the effects of various organic fluids on clay minerals and to provide a database for clay-organic fluid interactions, so that the results may be used for the evaluation and prediction of clay barrier performance in waste containment applications. -- Three clay minerals; kaolinite, illite and smectite are investigated in this study. The chemicals used as permeants cover a wide range of dielectric constants and aqueous solubilities. These include acetic acid (acidic), aniline (basic), methanol and acetone1 (neutral polar), and carbon tetrachloride, trichloroethylene and xylene (neutral nonpolar). Permeability measurements have been carried out on the clays using a rigid wall permeameter. Microstructures have been observed using Scanning Electron Microscopy to determine the effects of these organic chemicals on the internal structure of the clays. This study also attempts to correlate in dex property tests and sediment at ion analyses with observed changes in intrinsic permeability and microstructure of the clays. Electrical properties of the permeant appear to control hydraulic conductivity and microstructure, especially for smectitic clay.


identifier: Baker, W. Roland B. (William Roland Boyd), 1953- <https://research.library.mun.ca/view/creator_az/Baker=3AW=2E_Roland_B=2E_=28William_Roland_Boyd=29,_1953-=3A=3A.html>   (1992) Computational models in wave analyses.  Masters thesis, Memorial University of Newfoundland.

title: Computational models in wave analyses

abstract: The use of microcomputer technology to solve many of the iterative and tedious computations encountered in the engineering field is becoming prominent. Coastal Engineering is one of the many fields in engineering where the presence of the microcomputer is being felt. The need to compete efficiently and economically in the engineering market requires the accessibility to and use of computer software to speed up some of the menial tasks. This thesis presents the development and demonstrated use of three (3) such software packages. The data encryption software, CADGRID, water wave refraction and diffraction software, MUNWAVE, and the water basin response software, LONGWAVE, were developed using the Microsoft, QuickBasic program development software on a 80386 CPU based microcomputer system with 80387 coprocessor. The plotting routines were written using the Hewlett Packard Graphics Language (HPGL). The programs CADGRID and LONGWAVE will work in either EGA, VGA, CGA or Hercules monochrome graphics mode with VGA recommended. The program MUNWAVE will only operate in EGA graphics mode.


identifier: Zhang, Yifei <https://research.library.mun.ca/view/creator_az/Zhang=3AYifei=3A=3A.html>   (1994) Control of an hydraulic subsea robot.  Masters thesis, Memorial University of Newfoundland.

title: Control of an hydraulic subsea robot

abstract: Remotely operated vehicles (ROVs) and underwater robots have been greatly involved in scientific related research and commercial utilization of underwater resources for the past few decades. They are operated at scenes where conditions are beyond the physical limitation of human divers or are too hazardous for them. -- To gain experience with the design, fabrication, control and operation of subsea robot, an hydraulic subsea robot is being developed at Faculty of Engineering and Applied Science of Memorial University of Newfoundland. This uses a plunger/waterjet device to control depth. When operating with the plunger, variation of displaced volume generates a positive or a negative buoyancy and thus controls the robot's vertical movement and depth. When operating with water- jet, movement is controlled by the combination of the buoyancy and the thrust generated from the waterjet squeeze. -- This thesis explains in detail the development of the control system of the robot, from simulation to test in a water tank, and reviews the systems stability, time response and frequency response performance.


identifier: Tang, Zhuo-hua <https://research.library.mun.ca/view/creator_az/Tang=3AZhuo-hua=3A=3A.html>   (1993) Laboratory measurement of shear strength and related acoustic properties.  Masters thesis, Memorial University of Newfoundland.

abstract: The general purpose of this research is to pursue the correlationship between acoustic properties and strength properties of sands. Conventional methods for correlating these characteristics rely on in-situ measurements of the wave velocity and shear strength. These measurements are subject to error from contamination by many unknown influences. A combined laboratory acoustic-triaxial testing equipment was developed to study reliably the interrelationship between shear strength and shear wave velocity by using piezoelectric ceramic benders to measure shear wave velocity in the triaxial tests. In processing the wave signals, the Hilbert transform technique was applied to precisely determine the wave propagation time. -- An unified stress-strain model is proposed for predicating sand behavior under loading conditions. It is found that the popular hyperbolic equation is a special case of the new model that can be applied to sands with a wide range of relative densities. --  Shear wave velocity increases with increasing confining pressure but decreases with increasing void ratio. It is found that shear wave velocity increases with increasing axial strain until reaching its peak strength and then drops. The rate of decrease depends on the type of sand and confining pressure. -- The microstructural analyses and experimental results indicate that the shear wave velocity-axial strain relationship follows the same mechanism controlling stress-strain behavior of sands. Therefore the new stress-strain model is modified further according to experimental results to correlate shear wave velocity and shear strength. Unambiguous results in shear wave velocity have been established as a function of stress ratio and axial strain. The comparisons between model and measured data indicate that the proposed equation can describe well wave velocity changes with stress and strain.


identifier: Bhattacharya, Dipankar <https://research.library.mun.ca/view/creator_az/Bhattacharya=3ADipankar=3A=3A.html>   (1991) Design and analysis of auto scaling pulsed analog neural circuits.  Masters thesis, Memorial University of Newfoundland.

abstract: Minimization of synaptic area is important in a neural network with a high synapse to neuron ratio. Consequently one has to optimize the synapse rather than the neuron. A pulsed analog network with amplitude modulation results in a very compact and efficient synapse. Charge summation is used which leads to a single bus as the summer. Membrane capacitance has been distributed to the synapses allowing the network to be perfectly scaled. Like the biological neuron, the neuron fires a single output pulse when the activation exceeds the threshold. A discharge pulse is generated to discharge the membrane capacitances via discharge transistors which have also been distributed to synapses for scaling purposes. Circuit design and detailed analysis has been included along with simulation results. Standard cells have also been presented. As the proposed architecture behaves quite differently from existing architectures, simulation of some of the standard examples of neural networks have been included. Two chips have also been designed using 3μm design rules.


identifier: Greening, David L. <https://research.library.mun.ca/view/creator_az/Greening=3ADavid_L=2E=3A=3A.html>   (1996) Design and commissioning of a computer controlled oscillating hydrofoil dynamometer.  Masters thesis, Memorial University of Newfoundland.

abstract: High propulsive efficiencies can be realised from oscillating foil propulsors. Information on these propulsors can be obtained by systematically studying the geometry's and motions of manufactured foils and the fins and flukes of cetacean mammals and fast swimming fish, which propel themselves through oscillations of a high aspect ratio lunate fin or fluke. -- The development of a dynamometer for studying the flow patterns and propulsive characteristics of oscillating foil propulsors is described. The dynamometer was designed to measure the effect of variations in foil parameters such as planform, sweep back, foil section, pitching axis location, and foil flexibility for a series of oscillating motions. It was designed primarily for use in a cavitation tunnel, to study the flow over the foils and their cavitational characteristics and, secondarily, for use in a towing/wave tank, to study the propulsion efficiency of the foils. Two foils were mounted in a central mounting pod which in turn was connected to the drive system. Mounting the foils in this manner did not disturb the flow over the tips of the foils which are thought to play a prime role in the propulsive performance of the foils. The drive system consisted of two numerically controlled direct current servo motors connected to a 80286 computer through a Unidex 14 series multi-axis motion controller. The system was programmed to produce a small sine wave oscillating motion and to allow the oscillating motion to be modified easily. -- The dynamometer was capable of producing a series of motions which were obtained by modifying the motion subroutine in the Unidex control program. The first motion programmed for use with the dynamometer was a small pitch angle sine wave motion with a constant phase angle of 90° between pitch and heave. -- This thesis project was the first in a series of thesis projects aimed at developing a fully functional oscillating foil dynamometer to 1) Oscillate test foils with a substantial variety of oscillating motions; 2) Study the development of the flow over the test foils; 3) study the formation of cavitation on the test foils; and 4) To determine the propulsion efficiency of the test foils. The aim of this thesis was 1) design and fabricate the prototype dynamometer, 2) program its control system to produce the initial oscillating motion, 3) conduct a series of tests to determine the systems abilities and limitations, and 4) make recommendations on how to overcome its limitations. The implementation of the recommendations is left as part of the next thesis project in this series. -- The performance and evaluation of the dynamometer in a series of preliminary tests is described. These tests were aimed at evaluating the performance of the dynamometer and its computer control system and not as a complete study of the foils. The foils which were used in the initial tests had a rectangular planform with an aspect ratio of six and a NACA 0019 section (this section is similar to the section through the flukes of a fin whale). -- The initial test consisted of running the dynamometer with a sine wave motion for a series of pitch and heave amplitudes, pitching axis locations, oscillating frequencies, and water flow velocities. These tests demonstrated the operational capabilities of the dynamometer, the accuracy of the obtained motion compared with the requested motion and the quality of the data retrieved from the data acquisition system.


identifier: Hermanto, Ivi <https://research.library.mun.ca/view/creator_az/Hermanto=3AIvi=3A=3A.html>   (1990) Design development and testing of microprocessor-based prototype relay for power transformer protection.  Masters thesis, Memorial University of Newfoundland.

abstract: The digital protection of electrical power apparatus has been an active area of research for the past twenty years. These research results are being utilized in some of the digital relay designs. The digital protection of power transformers requires complex calculations and logic, hence the use of a digital processor seems to be natural and attractive. -- A stand-alone prototype digital protective relay for power transformer protection has been designed, implemented and tested successfully. The prototype digital relay integrates up to three different relaying functions in  a single relay. Any changes to the relay operating characteristic can be carried out simply in the software without tampering with the hardware. The relay hardware is designed in two different boards namely, the data acquisition and the digital processing boards. The data acquisition board consists of seven identical circuits each having a scaling circuit, a sixth order Chebyshev anti-aliasing filter and a sample-and-hold circuit. All the seven  signals are then multiplexed and connected to an A/D converter. The digital processing board consists of a TMS320E15 digital signal processor. -- The relay software program is developed for the complete three phase percentage  differential relay with second harmonic restraint for inrush  and fifth harmonic restraint for overexcitation. The primary  and secondary ground fault protection is also provided. The software is written in modular form such that any relay algorithm can be used by simply changing only one subroutine. The present relay design utilizes the Discrete Fourier Transform (DFT) to extract the current harmonics. -- The prototype digital relay was tested extensively in the laboratory for a duration of three months. The results of these tests show that the relay always cleared all the faults that were applied on the transformer and the relay never maloperated.


identifier: Wang, Li <https://research.library.mun.ca/view/creator_az/Wang=3ALi=3A=3A.html>   (1990) Determination of permanent magnet synchronous motor parameters.  Masters thesis, Memorial University of Newfoundland.

abstract: Permanent magnet (P.M.) excited synchronous machines have shown increasing popularity in recent years for industrial drive applications. However, the limitation imposed by permanent magnet excitation causes some difficulties in evaluating the machine parameters. This thesis presents the experimental procedure of the determination of the P.M. synchronous motor parameters. The work is intended to evaluate the d- and q-axis reactances and the permanent magnet generated voltage under load condition. -- The air gap fields of the P.M. synchronous motor are evaluated for specific rotor and magnet configurations. An analog simulation of the interaction of these field quantities in the air gap is developed. A practical implementation of the digital measurement technique for determining motor torque angles is realized. A number of different test methods are developed and applied to a 3-phase, 60 Hz, 4-pole, 1 horsepower P.M. synchronous motor. Conventional test methods  are modified for use on this type of the motor. A search coil test developed to locate variation of the generated voltage with increasing load. The influence of the armature reaction is also investigated. -- A flux linkage test is developed to measure the static inductance of the machine and the search coils inserted in the stator slots of the motor are used to measure air gap flux distribution. Calculation of the d- and q-axis reactances is based on the flux and the current measured. The measurement methods come from the transformation of the two-axis theory.


identifier: Perchard, Derek Rex <https://research.library.mun.ca/view/creator_az/Perchard=3ADerek_Rex=3A=3A.html>   (1993) Crack detection in slender cantilever plates using modal analysis.  Masters thesis, Memorial University of Newfoundland.

abstract: Research over the past decade or so, has found a new application for modal analysis theory and experimentation. It involves non-destructive evaluation, with the primary intent of detecting and locating structural faults (cracks, voids, etc.) in structures such as off-shore oil platforms which are vulnerable to fatigue and other forms of inconspicuous damage. -- This current research program was conducted in an attempt to add to the existing body of knowledge on this subject. It illustrates through analytical  and experimental modelling, the effect that a simulated crack has on the modal characteristics of a simple structure, ie., a cantilever plate, with 5 levels of damage.  -- The assessment involved creating a finite element model of the structure using an integrated software package. SDRC - I-DEAS, to estimate the changes in various modal parameters, caused by a notch type crack. Additionally, a series of tests were carried out using response measurement equipment to experimentally determine the effect of the imposed defect. This was accomplished via measurement of dynamic response, using both accelerometers and strain gauges, and subsequent test data analysis using I-DEAS. -- Results obtained from both phases of analysts showed that the crack could be detected, primarily through observation of reduction in natural frequency for a number of modes. The  analytical model, in particular, provided a useful technique  of crack location via observed inconsistencies in the plots derived from differences in both displacement and rotation mode shapes for cracked plates, with respect to a reference plate. The experimentation performed verified the analytical  results, and provided additional insight into changes in damping, residue, and amplitude of dynamic response for frequency values at, and offset from those associated with the natural modes. This latter phenomena proved to be very sensitive and correlated well with observed changes in frequency. The measurement of strain response also proved to  be a good indicator of crack existence with major increases in response magnitude, far exceeding the corresponding acceleration response.


identifier: Hamza, Hany El-sayed <https://research.library.mun.ca/view/creator_az/Hamza=3AHany_El-sayed=3A=3A.html>   (1981) Creep, failure and fracture of ice.  Doctoral (PhD) thesis, Memorial University of Newfoundland.

title: Creep, failure and fracture of ice

abstract: A finite element creep bending model has been developed using thick plate theory. The model agrees very well with numerical creep models and with field data collected during a load bearing capacity test of fresh-water ice. A simple numerical formula is derived which can predict the time of the onset of failure using the critical strain energy as a failure criterion. This formula agrees very well with available field data. -- An algorithm has been developed which is able to predict the viscoelastic response of ice under different uniaxial loading conditions. This algorithm has been generalized using the finite element method to predict the viscoelastic response due to multiaxial loading.  The general finite element model is capable of solving the ice cover - offshore structure interaction problem. A similar procedure has been used to predict the viscoelastic response of the cracked three-point bend test specimen due to constant cross-head speed loading. -- The linear and non-linear fracture toughness of artificially grown fresh-water ice has been determined during a small-scale experimental program. The effect of rate of loading, test temperature, specimen dimensions, and grain size on fracture toughness has been investigated. -- Finally, the strain rate dependent, critical strain energy per unit volume has been proposed as a failure criterion for ice under different loading rates. The criterion is applicable to ice failure during a laboratory test and failure of ice covers due to interaction with an offshore structure or due to supporting a load for short or long periods of time.