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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
241

New multilateral well architecture in heterogeneous reservoirs

Jia, Hongqiao 30 September 2004 (has links)
Multilateral well technology has been widely used in the world oil fields. There still has technical limitation of these kinds of well structure. This thesis presents a new multilateral well architecture which is more flexible and economical. The performance of new multilateral well in heterogeneous reservoirs is studied, and that is compared with vertical well architecture also. In order to study the productivity of new multilateral wells, we use a numerical simulation method to set up heterogeneous reservoir models. The three reservoir models included anisotropic permeability, shale multi-layer, and flow units. Under a pseudo-steady-state, the productivities of horizontal laterals and deviated laterals are calculated and compared. We find that new multilateral well architecture has good performance in heterogeneous reservoir. The heterogeneous properties of reservoirs influence the productivity of horizontal laterals more than deviated laterals. The shale multi-layer and flow units that dominate the fluid flow in reservoirs are important for reservoir characterization.
242

Numerical simulation of the truss spar 'Horn Mountain' using COUPLE

Theckum Purath, Basil 16 August 2006 (has links)
A truss spar, named as Horn Mountain, was deployed in the Gulf of Mexico in 1,650 m of water, approximately 150 km southeast of New Orleans in June 2002. Horn Mountain is operated by British Petroleum (B.P.). Extensive field measurements were made using an integrated marine monitoring system attached to the truss spar. In this study, dynamic analysis of the truss spar interacting with its mooring and riser system was performed using a time-domain numerical code, known as ‘COUPLE’. The simulated results were then compared with the corresponding field measurements made during Hurricane Isidore. During the numerical study, various hydrodynamic parameters which were crucial to the accuracy of predicting the global motions of the truss spar and tensions in mooring lines and risers were scrutinized, such as the drag and added-mass coefficients of heave plates, hard tank and truss beams. Satisfactory agreement between the simulation and corresponding measurements was reached, indicating that the numerical code, COUPLE, can be used to conduct the time-domain analysis of a truss spar interacting with its mooring and riser system under severe storm impact. A comparative study was also conducted to analyze the significance of interaction of risers with the hull structure. Three different cases of coupled analysis are simulated, namely (i) coupled analysis of truss spar interacting with mooring lines, (ii) coupled analysis of truss spar interacting with the mooring lines and the steel catenary risers, (iii) coupled analysis of truss spar interacting with the mooring lines, the steel catenary risers and top tension risers. Major statistical parameters of the global motions of the truss spar and the mooring line tensions for the three cases are compared with the field measurements.
243

Framework for a visual energy use system

McDonald, Christopher Ernest 02 June 2009 (has links)
The goals of this research include developing and identifying software technologies, which facilitate the use of buildings described in Building Information Modeling (BIM) tools in both a simulation and visualization. The study focused on the development of a tool to fulfill the visualization needs of a Visual Energy Use System. To accomplish this, the study identified an open BIM file standard, the Industry Foundation Classes (IFC). The study also identified a video game based 3D virtual environment, the Doom 3 Engine. A tool developed during the study, IFCtoMAP, converts IFC data into the .MAP file format understood by the Doom 3 Engine. Finally, the study identified the IFCtoIDF utility, which translates IFC data into a format understood by the building energy simulation program EnergyPlus. Data from the Building Information Modeling tool Revit Building exports to the .IFC file format, which in turn drives the two conversion utilities IFCtoMAP and IFCtoIDF. The output of the IFCtoIDF tool consists of an .IDF file that EnergyPlus uses to perform an energy simulation. The output of the IFCtoMAP tool consists of a .MAP file, which the Doom 3 game engine uses to display three dimensional first person perspective visualization. The result of the study was the successful creation of an automated tool that converts building geometry found in .IFC files into the .MAP file format understood by Doom 3 game engine. This document details the methods employed by the IFCtoMAP software along with a brief discussion of the IFCtoIDF conversion utility.
244

Electro-Optical Property Study of Novel Discotic Liquid Crystals Containing 9-{11-[2,3,6,7-Tetrakis(hexyloxy)dibenzo[a,c] phenazinylcarbonyloxyalkyl]}carbazol Moiety

Chuang, Yao-wei 27 July 2007 (has links)
Discotic liquid crystals(DLCs) in this research absorb the light in visible region of spectrum, this characteristic is not found in rod-like liquid crystals. A majority of discotic liquid crystals form columnar mesophases probably due to intense £k-£k interactions of polyaromatic cores. £k-£k interactions are caused by intermolecular overlapping of p-orbitals in £k-conjugated systems, so they become stronger as the number of £k-electrons increases. Three new hexagonal columnar disctic liquid crystals 9-{11-[2,3,6,7-tetrakis(hexyloxy)dibenzo[a,c]phenazinylcarboxyalkyl]} have been successfully synthesized by covalently attaching carbazole moiety to a tetrakis (hexyloxy)dibenzo[a,c]phenazinyl core with an ester group containing different lengths of alkyl spacer having 3,6,and 11 carbon atoms. In order to set up a basic data base, we measure and analyze the discotic liquid crystals via various instruments.In addition, we also utilize both simulation systems of MMM and QMM to predict several molecular dynamics and properties such as: vibration, rotation, motion and heat of formation and so on.So we can see more depth inside how the concentration effects on the geometry structure arrangement of the discotic liquid crystals.
245

Truncation rules in simulation analysis : effect of batch size, time scale and input distribution on the application of Schriber's rule

Baxter, Lori K. 04 June 1990 (has links)
The objective of many simulations is to study the steady-state behavior of a nonterminating system. The initial conditions of the system are often atypical because of the complexity of the system. Simulators often start the simulation with the system empty and idle, and truncate, or delete, some quantity of the initial observations to reduce the initialization bias. This paper studies the application of Schriber's truncation rule to a queueing model, and the effects of parameter selection. Schriber's rule requires the simulator to select the parameters of batch size, number of batches, and a measure of precision. In addition, Schriber's rule assumes the output is a time series of discrete observations. Previous studies of Schriber's rule have not considered the effect of variation in the time scale (time between observations). The performance measures for comparison are the mean squared error and the half-length of the confidence interval. The results indicate that the time scale and batch size are significant parameters, and that the number of batches has little effect on the output. A change in the distribution of service time did not alter the results. In addition, it was determined that multiple replicates should be used in establishing the truncation point instead of a single run, and the simulator should carefully consider the choice of time scale for the output series and the batch size. / Graduation date: 1991
246

Industrial scheduling with evolutionary algorithms using a hybrid representation

Andersson, Martin January 2011 (has links)
Scheduling problems have been studied extensively in the literature but because they are so hard to solve, especially real-world problems, it is still interesting to find ways of solving them more efficiently. This thesis aims to efficiently solve a real-world scheduling problem by using a hybrid representation together with an optimisation algorithm. The aim of the hybrid representation is to allow the optimisation to focus on the parts of the scheduling problem where it can make the most improvement. The new approach used in this thesis to accomplish this goal, is the combination of simulation-based optimisation using genetic algorithms and dispatching rules. By using this approach, it is possible to investigate the effect of putting specified job sequences in certain machines and using dispatching rules in the other. The hypothesis is that the optimisation can use dispatching rules on non-bottleneck machines that have little impact on the overall performance of the line and some specified job sequences on bottleneck machines that are hard to be scheduled efficiently with dispatching rules. This would allow the optimisation to focus on the bottleneck machines and that would produce a more efficient search. The results from the case study shows it is a viable approach exceeding or equalling existing techniques. The hypothesis that the optimisation can focus its efforts is supported by a bottleneck analysis which corresponds with the experimental results from optimisations.
247

Fundamental studies of atomic diffusion by computer simulation of atomic processes on the giga event scale and multiple PC's in parallel

Zhang, Qiongshan 11 June 1992 (has links)
The classic treatment of diffusion by Einstein and by Chandrasekhar assumed conservative boundary conditions; mobile species were neither created nor destroyed on the sample surface. It is normal to assume that vacancies and host interstitials are created and annihilated on incoherent interfaces or free surfaces; i.e., these are assumed to be perfect sources and sinks. Impurities may also be gained or lost at an interface. It seems that no analytic solutions are available for diffusion with annihilating boundary conditions. In this thesis, the author presents massive data obtained by giga event Monte Carlo simulation of the macro-consequence of atomic level assumptions using VIDSIM, a computer simulation program for the simulation of point defect diffusion and interaction in diamond and zinc-blend structure crystals. The author contrasts these results with the error function complement (ERFC) forms obtained with conservative boundary conditions. An empirical formula is proposed with the help of DF_FIT, a fitting program developed by the author to conduct the statistical analysis and fitting the experimental data to certain functions typical for diffusion processes. Investigations on the redistributions of impurities in an atomiclayer- doped (ALD) host materials such as Si is reported. Asymmetric diffusion of ALD impurities is observed and demonstrated. / Graduation date: 1993
248

Using optimized computer simulation to facilitate the learning process of the free throw in wheelchair basketball

Hamilton, Brianne Nicole 05 January 2006
A computer simulation program was previously developed by the researcher which determines a theoretically optimal movement pattern for the free throw in wheelchair basketball. The purpose of this study was to evaluate the external validity of the optimization program by examining whether the knowledge of the optimal movement pattern facilitates performance of the free throw in wheelchair basketball. </p><p>In a pilot study, four able-bodied players from the Saskatchewan Wheelchair Basketball Mens Team were invited to participate on one occasion. These participants were videotaped shooting free throws to provide knowledge of an expert wheelchair free throw movement pattern. Using video analysis, it was found that the release conditions used by this group were very similar to those predicted to be optimal. This lent support to the predicted optimal movement pattern being an actual optimal movement pattern for the free throw in wheelchair basketball. In the primary study, thirty-three able-bodied male participants were randomly assigned to three groups: a no-feedback group; a video-feedback group; and an optimal pattern feedback group. The participants performed wheelchair basketball free throw training for three days over one week. The no-feedback group simply shot free throws from a wheelchair, whereas the video-feedback group viewed video of their previous free throws, and the optimal pattern group viewed video of their previous free throws with an optimal free throw pattern superimposed. The participants also completed a pretest one week before and a retention test one week after the training period. </p> <p>A repeated measures ANOVA was used to test for significant differences between the three training groups in free throw success in wheelchair basketball over each testing occasion. The statistical analyses indicated that there were no differences in free throw success between the group that had knowledge of their personalized optimal movement pattern when compared to the groups that received either no-feedback or video-feedback (p<0.05). </p> <p>Video analysis revealed that the wheelchair free throw movement pattern of participants in the optimal pattern group changed substantially from the pretest to the post-test. This suggests that the participants in the optimal pattern group were making progress towards their optimal movement patterns, but had not yet mastered the movement pattern.
249

Ground-based Simulation of Airplane Upset Using an Enhanced Flight Model

Liu, Stacey Fangfei 31 May 2011 (has links)
Loss-of-control resulting from airplane upset is a leading cause of worldwide commercial aircraft accidents. One of the upset prevention and recovery strategies currently being considered is to provide pilot upset recovery training using ground-based flight simulators. However, to simulate the large amplitude and highly dynamic motions seen in upset conditions, both the flight model and the simulator motion need improvement. In this thesis, an enhanced flight model is developed to better represent the aircraft dynamics in upset conditions. In particular, extension is made to the aerodynamic database of an existing Boeing 747-100 (B-747) model to cover large angle of attack, sideslip and angular rates. The enhanced B-747 model is then used to conduct a set of upset recovery experiments in a flight simulator without motion. The experimental results can be used to identify and potentially correct major motion cueing errors caused by the conventional motion drive algorithm in upset conditions.
250

Ground-based Simulation of Airplane Upset Using an Enhanced Flight Model

Liu, Stacey Fangfei 31 May 2011 (has links)
Loss-of-control resulting from airplane upset is a leading cause of worldwide commercial aircraft accidents. One of the upset prevention and recovery strategies currently being considered is to provide pilot upset recovery training using ground-based flight simulators. However, to simulate the large amplitude and highly dynamic motions seen in upset conditions, both the flight model and the simulator motion need improvement. In this thesis, an enhanced flight model is developed to better represent the aircraft dynamics in upset conditions. In particular, extension is made to the aerodynamic database of an existing Boeing 747-100 (B-747) model to cover large angle of attack, sideslip and angular rates. The enhanced B-747 model is then used to conduct a set of upset recovery experiments in a flight simulator without motion. The experimental results can be used to identify and potentially correct major motion cueing errors caused by the conventional motion drive algorithm in upset conditions.

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