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With the success of the CounterDataFlow Pipeline microarchitecture developed by Oregon State University, there is increasing demand for a highly flexible high-level simulator modeling tool to support the further expansions and studies of the Counterflow pipeline processors family. This work examines the implementation of a Java-based execution-driven simulator modeling tool, bBlocks, which gains flexibility by identifying the independent parts in a micro system and partitioning them into reusable blocks. Two simulators have been constructed to demonstrate the possibility of bBlocks. / Graduation date: 2001

Pipelines from offshore petroleum fields must frequently pass overareas with uneven seafloor.  In such cases the pipeline may havefree spans when crossing depressions. Hence, if dynamic loads canoccur, the free span may oscillate and time varying stresses maygive unacceptable fatigue damage. A major source for dynamicstresses in free span pipelines is vortex induced vibrations (VIV)caused by steady current. This effect is in fact dominating ondeep water pipelines since wave induced velocities andaccelerations will decay with increasing water depth. Thechallenge for the industry is then to verify that such spans cansustain the influence from the environment throughout the lifetimeof the pipeline.\\\\The aim of the present project is to improve the understanding ofvortex induced vibrations (VIV) of free span pipelines, andthereby improve methods, existing computer programs and guidelinesneeded for design verification.  This will result in more costeffective and reliable offshore pipelines when laid on a veryrugged seafloor.\\\\VIV for multiple span pipeline is investigated and the dynamicalinteraction between adjacent spans has been shown. The interactionmay lead to increased or decreased response of each spansdepending on the current speed and the properties for the twospans. The extension of the contact zone between the spans andseafloor parameters will of course also be important for theinteraction effect.\\\\The influence from temperature variation on vortex inducedvibrations has been demonstrated. The response frequency isinfluenced through changes in pipe tension and sag. Both increaseand decrease of the response frequency may be experienced.Moreover, it is shown that the influence from snaking of the pipeon the temperature effect is small, at least for large diameterpipes.\\\\A free span pipeline will necessarily oscillate close to the seabed.The presence of the seabed will therefore have some influences onthe ambient flow profile and also on the flow pattern around thecylinder during oscillation. Hydrodynamic parameters may thereforevary when the pipe is close to the seabed. In the present work, theinfluence from spatial varying current profiles is investigated forboth single and multiple span pipeline. It is shown that thedifference between using uniform and spatial varying currentprofiles is significant for some current speeds. It is also shownthat use of spatial varying current profiles can be even moreimportant for multiple span pipeline.\\\\The comparison of VIVANA analysis results with MARINTEK testresults has been given. It shows VIVANA predicts the cross-flow responsegenerally much higher than the test measurements, especially for thehigher mode responses. To improve understanding of this phenomena, the VIVANA model was tuned tothe test model and results are compared in different cases. Attempts were made to obtain a better agreement by adjusting some of the input parameters to VIAVANA. The reference point is tuned by changing various hydrodynamic properties, i.e. $C_{L}$, $St$ and added mass. The response frequenciesare also tuned in order to have a better agreement on the results. It is been concluded that the method used here by VIVANA is not able to describe VIV for free spanning pipelines adequately. It is not possible to find a set of parameter in a rational way that will give reasonably correct results. The discrepancy between the analysis and test results are highlighted which confirms the interaction between the in-line and cross-flow vibrations.Discussions are given and addressed on different reasons which may cause this phenomena.\\\\An improved strategy for non-linear analysis of free span pipelineis outlined. Time domain analysis for free span pipeline hasbeen performed. The difference between time and frequency domainanalysis has also been investigated by varying boundary conditions,pipe properties and axial tension. A significant difference is shownbetween results from time and frequency domain analysis at each endof the span where the pipe is started to interact with the seafloor.Due to high fatigue at this point, the importance of usingnon-linear time domain analysis is therefor obvious and highlyrecommended.

Pipelines are one of the safest forms of transportation for oil and gas. However, pipelines may experience some defects, such as cracks, corrosion and cracks in corrosion, during service period. In this thesis, the current defect assessment methods for crack, corrosion and crack in corrosion defects are reviewed. The aim of this study was to evaluate the effect of the crack in corrosion defects on the failure pressure of natural gas transmission pipelines. Consequently, a series of burst tests with varying defect depths were undertaken on end-capped, seam-welded API 5L Grade X60 (433 MPa yield stress) pipeline steel of external diameter 508 mm (20 inch), 5.7 mm wall thickness. Defects were created by pre-fatiguing the pipe to create a crack. The number of cycles required to create a fatigue crack were varied between 75000 to 150000 cycles based on the desired final defect depth. For the (CIC) defects, the pipe was pre-fatigued to create a sharp crack, and the artificial corrosion defect was simulated by machining a rectangular groove over the fatigue crack. The rupture tests were conducted by pressurizing the pipe until failure occurred. Results were analyzed using various assessment methods. For the artificial corrosion defects, the predicted failure pressures based on RSTRENG were more reliable than those based on Modified B31G. This study revealed that CorLAS provided the least conservative prediction for crack defects, whereas the other methods provided more conservative estimates of failure pressure. Moreover, the predicted failure pressure of the level 3 FAD for API 579 cylinder equations had better agreement with experimental results in comparison with the other methods, i.e. BS7910 and NG-18. The failure pressure for CIC defects for pipes tested fell between corrosion defects (lower bound) and crack defects (upper bound). The transition to crack defect behavior only occurs when the crack defect depth is significant or vice versa. It should be noted that the crack to corrosion ratio is not the only parameter to evaluate a CIC defect. There are other parameters such as total defect depth and defect profile, which affect the failure behavior of a CIC defect.

Pipelines are one of the safest forms of transportation for oil and gas. However, pipelines may experience some defects, such as cracks, corrosion and cracks in corrosion, during service period. In this thesis, the current defect assessment methods for crack, corrosion and crack in corrosion defects are reviewed. The aim of this study was to evaluate the effect of the crack in corrosion defects on the failure pressure of natural gas transmission pipelines. Consequently, a series of burst tests with varying defect depths were undertaken on end-capped, seam-welded API 5L Grade X60 (433 MPa yield stress) pipeline steel of external diameter 508 mm (20 inch), 5.7 mm wall thickness. Defects were created by pre-fatiguing the pipe to create a crack. The number of cycles required to create a fatigue crack were varied between 75000 to 150000 cycles based on the desired final defect depth. For the (CIC) defects, the pipe was pre-fatigued to create a sharp crack, and the artificial corrosion defect was simulated by machining a rectangular groove over the fatigue crack. The rupture tests were conducted by pressurizing the pipe until failure occurred. Results were analyzed using various assessment methods. For the artificial corrosion defects, the predicted failure pressures based on RSTRENG were more reliable than those based on Modified B31G. This study revealed that CorLAS provided the least conservative prediction for crack defects, whereas the other methods provided more conservative estimates of failure pressure. Moreover, the predicted failure pressure of the level 3 FAD for API 579 cylinder equations had better agreement with experimental results in comparison with the other methods, i.e. BS7910 and NG-18. The failure pressure for CIC defects for pipes tested fell between corrosion defects (lower bound) and crack defects (upper bound). The transition to crack defect behavior only occurs when the crack defect depth is significant or vice versa. It should be noted that the crack to corrosion ratio is not the only parameter to evaluate a CIC defect. There are other parameters such as total defect depth and defect profile, which affect the failure behavior of a CIC defect.

The first topic of this thesis proposes an 8-bit, 20 MSample/s pipeline analog-to-digital converter (ADC). The sharing amplifiers technique is employed to reduce the overall number of the amplifiers wherein dynamic comparators are adopted to reduce the power consumption. The proposed design is implemented by 0.35 £gm CMOS technology. The simulation results show that maximum power consumption is 45 mW given a 3.3 V power supply, and the SFDR is 45 dB with a sinusoidal input at 5 MHz. The second topic is to describe a 5-bit, 2.4 MSample/s, low power analog-to-digital converter for ZigBee receiver using 868/915 MHz band. The converter uses the successive approximation architecture. By using 0.18 £gm CMOS technology, the simulation results show the worst-case power consumption is merely 449.6 £gW. The converter achieves the maximum differential nonlinearity of 0.3 LSB, the maximum integral nonlinearity of 0.5 LSB.

Thesis (Ph. D.)--University of Texas at Austin, 1999. / Vita. Includes bibliographical references (leaves 1103-1112). Available also in a digital version from Dissertation Abstracts.