Thesis (M. Phil.)--University of Hong Kong, 1999. / Includes bibliographical references (leaves 124-127).

A leak-off test is one of the most common procedures to test the fracture pressure of the exposed formations. After cementing and drilling out of the casing shoe, the LOT is run to verify that the casing, cement, and formation can withstand the pressure needed to safely drill the next section of the well. The equivalent mud weight obtained from the test is recorded and reported to government agencies as the strength of the casing shoe. Drilling engineers also rely on the reading from the LOT and use it as the maximum pressure that may be imposed on the formation to avoid fracturing. Exceeding the maximum pressure may result in serious consequences such as lost circulation, one of the most costly events in drilling operations. Therefore, accurate determination of formation fracture gradient is critical and can avoid a variety of well control problems. Considerable efforts to model LOT and leak-off behaviors have been done in the past. Altun (2001) and Paknejad (2007) each presented a unique method to estimate leak-off volume by dividing the pressurized system into four sub-systems: mud compression, casing expansion, fluid leakage, and borehole expansion. The volume response from each sub-system is then combined to represent the total volume pumped during a LOT. However, neither model included the expansion volumes of cement sheath and formation rock outside of the casing; these volumes are not trivial and should not be neglected. In addition, both models use only pump pressure to calculate volumes generated during a LOT. The actual downhole pressure and the pressure acting from the outside are ignored. In this study, the volume contributions from cement sheath expansion and formation rock expansion are calculated using single cylinder Lame’s equation. The results are added with Altun’s borehole expansion volume, mud compression volume, and fluid leakage volume to represent the total volume for the enhanced Altun model. Secondly, a Wider Windows mechanical expansion model is developed based on the concentric cylinder theory. This model simulates the compounded effect of casing, cement, and formation expansion along the cased hole based on pressures inside the wellbore and out in the far-field stress region. The volume generated from concentric cylinder expansion is then combined with Altun’s mud compression volume and fluid leakage volume to simulate the total volume pumped during a LOT. The developed models were verified using three sets of field LOT data obtained from literature and compared with the original Altun model. The results confirmed that leak-off volume along the cased hole should be analyzed as a compounded effect of casing, cement, and formation expansion. Overall, the WW models accurately simulate both leak-off volume and leak-off behaviors. / text

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In this research it was shown that the electroless plated palladium deposited as large number of randomly oriented grains, which were separated by grain boundaries (GB). The nano-scale dimensions of these grain boundaries allowed the diffusion of helium through the palladium membrane. This implied that in a dense palladium membrane, the grain boundary network was so convoluted that helium flux could be neglected. The transmission electron microscope (TEM) images of the palladium at room temperature showed grains of about 50 nm in size and nuclei of about 5 nm in size. The TEM images of a pre-annealed Pd sample at 500ºC in hydrogen atmosphere for 48 hours, showed big grains of 100 to 200 nm in size and most of the grain boundary intersections had dihedral angles very close to 120°. However, the pre-annealed Pd sample at 500ºC in helium atmosphere for 48 hours, showed grains of the size of 70 to 100 nm and many of the grain boundary intersections did not show dihedral angles of 120°. This proved that high temperature annealing not only caused significant grain growth and grain boundary (straightening) migration, but also the grain boundary migration was faster in hydrogen than in helium atmosphere. Also, the hydrogen and helium characterization of the palladium membranes showed that the leak formed faster in hydrogen than in helium. Thus, combining the TEM observations with the membrane characterization results, it is possible to conclude that grain boundary migration is one of the most probable reasons for leak formation in palladium composite membranes. The TEM images of the pre-annealed Pd sample also showed that the grain boundaries can achieve an equilibrium configuration within 48 hours of annealing at 500°C in hydrogen. This research helped in better understanding of the role of grain boundary migration on the leak formation in the composite palladium membranes and this information can be useful for the production of leak resistant stable membranes in the future.

Immunotherapy with IL-2 is accompanied by severe toxicity leading to development of vascular leak syndrome (VLS). Previous studies from our laboratory demonstrated that CD44 knockout mice exhibit marked decrease in IL-2 induced VLS, thereby suggesting a role for CD44 in VLS. In the current study we tested whether use of mAbs against CD44 or hyaluronic acid (HA), the ligand for CD44, can abrogate IL-2 induced VLS. Administration of IL-2 (75,000 U/mouse, three times a day for 4 days) into C57BL/6 mice triggered significant VLS in the lungs and liver. Interestingly, HA caused a marked increase in IL-2-induced VLS in the lungs and liver. In contrast, use of anti-CD44 mAbs reduced IL-2-induced VLS in the lungs and liver. The change in VLS seen following HA or anti-CD44 mAbs treatment was not due to any defect in lymphocyte migration or homing to various organs because histopathological studies in these mice demonstrated significant and often greater perivascular infiltration of lymphocytes when compared to mice treated with IL-2 alone. However, HA treatment exhibited a marked increase in IL-2-induced lymphokine-activated killer (LAK) cell activity while anti-CD44 mAbs treatment led to a significant decrease in IL-2-induced LAK cell activity. These studies demonstrate that HA or anti CD44 mAbs may serve as a useful tool to selectively alter the LAK activity as well as to prevent the toxicity induced by IL-2. Altering CD44-HA interactions in vivo may offer a novel therapeutic approach to prevent endothelial cell injury by cytotoxic lymphocytes in a variety of clinical diseases. / Master of Science

In addition to the antigen-specific receptors, the T and B cells also express a variety of adhesion molecules, which are known to participate in cell-cell interaction, migration, homing and signal transduction. CD44 is a widely distributed cell surface glycoprotein whose principal ligand has been identified as hyaluronic acid (HA), a major component of the extracellular matrix. In the current study, we investigated whether HA or mAbs against CD44 would induce a proliferative response in mouse lymphocytes. Spleen cells from normal and nude but not severe combined immunodeficient mice, exhibited strong proliferative responsiveness to stimulation with soluble HA or anti-CD44 mAbs. Furthermore, purified B cells but not T cells were found to respond to HA. These data demonstrated that interaction between HA and CD44 can regulate murine B cell effector functions and that such interactions may play a critical role during normal or autoimmune responsiveness of B cells. Endothelial cell injury resulting in vascular leak syndrome (VLS) is one of the most widely noted phenomenons in a variety of clinical diseases, however, the underlying reason for which remains unclear. We used interleukin-2 induced VLS as a model to investigate the role of cytolytic lymphocytes in the direct cytotoxicity of endothelial cells. BL/6 wild-type mice developed significant VLS in the lungs, liver and spleen following IL-2 administration. Interestingly, perforin-knockout mice exhibited marked decrease in VLS in all three organs tested. Also, FasL-defective (gld) mice and Fas-deficient (lpr) mice exhibited decreased VLS in the liver and spleen, but not in the lungs. These results demonstrated for the first time that perforin and FasL may actively participate in endothelial cell injury and induction of VLS in a variety of organs. Inasmuch as, CD44 also plays a major role in the lymphocyte adhesion to the endothelial cells, we used CD44-knockout mice and observed that such mice exhibited markedly diminished VLS following IL-2-treatment. Our data also suggested that blocking CD44 helps in reducing the IL-2-induced VLS and therefore such an approach may serve as a useful tool to prevent endothelial cell damage seen in a variety of clinical disorders. / Ph. D.

A model-based estimation process is implemented in simulation of a water transmission line for the purpose of leak detection. The objective of this thesis is aimed at determining, through simulation results, the effectiveness of the Extended Kalman Filter for leak detection. Water distribution systems often contain large amounts of unknown losses. The range in magnitude of losses varies from 10 to over 50 percent of the total volume of water pumped. The result is a loss of product, including water and the chemicals used to treat it, environmental damage, demand shortfalls, increased energy usage and unneeded pump capacity expansions. It is clear that more control efforts need to be implemented on these systems to reduce losses and increase energy efficiencies. The problems of demand shortfalls, resulting from lost product, are worsened by the limited availability of water resources and a growing population and economy. The repair of leakage zones as they occur is not a simple problem since the vast majority of leaks, not considered to be major faults, go undetected. The leak detection process described in the work of this thesis is model based. A transient model of a transmission line is developed using the Method of Characteristics. This method provides the most accurate results of all finite-difference solutions to the two partial differential equations of continuity and momentum that describe pipe flow. Simulations are run with leakage within the system and small transients are added as random perturbations in the upstream reservoir head. The head measurements at the two pipe extremes are used as inputs into the filter estimation process. The Extended Kalman Filter is used for state estimation of leakage within the transmission line. The filter model places two artificial leakage states within the system. The estimates of these fictitious leakage states are then used to locate the actual position and magnitude of leakage within the transmission line. This method is capable of locating one leak within the line. The results of the Extended Kalman Filter (EKF) process show that it is capable of locating the position and magnitude of small leaks within the line. It was concluded that the EKF could be used for leak detection, but field tests need to be done to better quantify the ability of these methods. It is recommended that a multiple filtering method be implemented that may be able to locate the occurrence of multiple leakage.

A model based algorithm of pipeline flow is developed and tested to determine if the model is capable of detecting a leak in a pipeline. The overall objective of this research is to determine the feasibility of applying the Extended Kalman Filter and a new technique defined as the Extended Boundary Approach to the detection of leakages in a physical water distribution system. <p>The demands on the water supply system increase as the human population grows and expands throughout the world. Water conservation is required to ensure an adequate supply of water remains for future generations. One way to conserve this water is by reducing the leakages in underground water distribution systems. Currently between 10 to 50 percent of the pumped water is lost due to unrecognized leakages. This results in a huge revenue loss of water, chemicals and energy that is required for transporting the water. The detection of underground leakages is a very complex problem because many leakages are small and go unnoticed by todays leak detection technology. <p>A model based leak detection technique is developed and tested in this thesis. The Method of Characteristics is used to develop a model of a single pipeline. This method is extensively used and provides the most accurate results of the two partial differential equations of continuity and momentum that describe pipe flow. The Extended Kalman Filter is used to estimate two fictitious leakages at known locations along the pipeline. In order to ensure the model is observable four pressure measurements are needed at equally spaced nodes along the pipeline. With the development of the Extended Boundary Approach only the upstream and downstream pressure measurements are required, however; the upstream and downstream flow measurements are also required. Using the information from the two fictitious leaks the actual leak location and magnitude can be determined. This method is only capable of detecting one leak in a single pipeline. <p>The results of the developed model show that the approach is capable of theoretically determining the leak location and magnitude in a pipeline. However, at this time, the feasibility of implementing the proposed leak detection method is limited by the required level of accuracy of the sensors which is beyond that found in todays technology. It was also found that the EKF used primarily steady state information to predict the leakage. It is recommended that further research explore alternate models which might better enhance the EKF approach using transient information from the pipeline. This may allow implementation on a real pipeline.

A model-based estimation process is implemented in simulation of a water transmission line for the purpose of leak detection. The objective of this thesis is aimed at determining, through simulation results, the effectiveness of the Extended Kalman Filter for leak detection. Water distribution systems often contain large amounts of unknown losses. The range in magnitude of losses varies from 10 to over 50 percent of the total volume of water pumped. The result is a loss of product, including water and the chemicals used to treat it, environmental damage, demand shortfalls, increased energy usage and unneeded pump capacity expansions. It is clear that more control efforts need to be implemented on these systems to reduce losses and increase energy efficiencies. The problems of demand shortfalls, resulting from lost product, are worsened by the limited availability of water resources and a growing population and economy. The repair of leakage zones as they occur is not a simple problem since the vast majority of leaks, not considered to be major faults, go undetected. The leak detection process described in the work of this thesis is model based. A transient model of a transmission line is developed using the Method of Characteristics. This method provides the most accurate results of all finite-difference solutions to the two partial differential equations of continuity and momentum that describe pipe flow. Simulations are run with leakage within the system and small transients are added as random perturbations in the upstream reservoir head. The head measurements at the two pipe extremes are used as inputs into the filter estimation process. The Extended Kalman Filter is used for state estimation of leakage within the transmission line. The filter model places two artificial leakage states within the system. The estimates of these fictitious leakage states are then used to locate the actual position and magnitude of leakage within the transmission line. This method is capable of locating one leak within the line. The results of the Extended Kalman Filter (EKF) process show that it is capable of locating the position and magnitude of small leaks within the line. It was concluded that the EKF could be used for leak detection, but field tests need to be done to better quantify the ability of these methods. It is recommended that a multiple filtering method be implemented that may be able to locate the occurrence of multiple leakage.

A model based algorithm of pipeline flow is developed and tested to determine if the model is capable of detecting a leak in a pipeline. The overall objective of this research is to determine the feasibility of applying the Extended Kalman Filter and a new technique defined as the Extended Boundary Approach to the detection of leakages in a physical water distribution system. <p>The demands on the water supply system increase as the human population grows and expands throughout the world. Water conservation is required to ensure an adequate supply of water remains for future generations. One way to conserve this water is by reducing the leakages in underground water distribution systems. Currently between 10 to 50 percent of the pumped water is lost due to unrecognized leakages. This results in a huge revenue loss of water, chemicals and energy that is required for transporting the water. The detection of underground leakages is a very complex problem because many leakages are small and go unnoticed by todays leak detection technology. <p>A model based leak detection technique is developed and tested in this thesis. The Method of Characteristics is used to develop a model of a single pipeline. This method is extensively used and provides the most accurate results of the two partial differential equations of continuity and momentum that describe pipe flow. The Extended Kalman Filter is used to estimate two fictitious leakages at known locations along the pipeline. In order to ensure the model is observable four pressure measurements are needed at equally spaced nodes along the pipeline. With the development of the Extended Boundary Approach only the upstream and downstream pressure measurements are required, however; the upstream and downstream flow measurements are also required. Using the information from the two fictitious leaks the actual leak location and magnitude can be determined. This method is only capable of detecting one leak in a single pipeline. <p>The results of the developed model show that the approach is capable of theoretically determining the leak location and magnitude in a pipeline. However, at this time, the feasibility of implementing the proposed leak detection method is limited by the required level of accuracy of the sensors which is beyond that found in todays technology. It was also found that the EKF used primarily steady state information to predict the leakage. It is recommended that further research explore alternate models which might better enhance the EKF approach using transient information from the pipeline. This may allow implementation on a real pipeline.